NAS-NS-3050.txt

LOS ALAMOS NATIONAL

i

 

LABORATORY

I

- JD

|

8 00054 9948

3 933

National_
| Academy
of

   

Sciences

National Research Council

NUCLEAR SCIENCE SERIES

The Radiochemistry
of Uranium

U

- Atomic

N 1. A
Commission

 
COMMITTEE ON NUCLEAR SCIENCE

D. A. Bromley, Chairman
Yals University

Martin J. Barger
National Bursau of Standards

Victor P. Bond
Brookhasven National Laboratory

Gregory R. Choppin
Florida Stats Univenity

W. A. Fowler
California Institute of Technology

Q. C. Phillips
Rics University

Geaorge A. Kolstad
U. 8. Atomic Energy Commission

John McElhinney
Naval Ressarch Laboratory

Robley D. Evamme, Vice Chairman
Massschusetts |nstitute of Technology

C. K. Resd, Exscutive Secratary
National Acsdemy of Sciences

Herman Feshbech
Msssachusetts Institute of Technology

F. 8. Goulding
Lawrence Radistion Laborstory

Bemd Kshn ;
Ngticnal Canter for Radiological Health

Members-at-Large

Lisison Members

Qeorge Wetherill
University of Callfornia

Alexander Zucksr
Oak Ridgs Nstional Laborstory

Walter 8. Rodney
National Sciancs Foundation

Lowls Slack
Amarican Instituts of Physics

Subcommittes on Radlochemistry

Gregory R. Choppin, Chairman
Floride Stats University

Herbert M. Clark
Renmssiser Polytechnic Institute

Raymond Devls, Jr.
Brookhaven National Laboratory

Bruce Dropesky
Los Alamos Scientific Laborstory

Rolfe Herber
Rutgers University

John A. Miskel
Lawvrencs Radintion Laboratory

Jullan M. Nisisen
Pacitioc Northwest Laboratory

Q. D. O'Kelley
Osk Ridge National Laboratory

Andrew F. Stshney
Argonne National Laboratory

John W. Winchester
University of Michigan

Membership as of January 1972
I

I

AEC Category NAS-NS-3050

uc-4

The Radiochemisiry of Uranium

JAMES E. GINDLER

Argomne Nalional Laboralory
Argonne, Illinois

Iséua.nce Date: March 1962

LOS ALAMOS
SCIENTIFIC LABORATORY

MOV 7 1978

LIBRARIES
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Subcommittee on Radiochemistry
National Academy of Sciences —National Research Council
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Printed In the United Statss of America

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1962; latast printing 1972
FOREWORD

The Subcommlttee on Radlochemlstry 1s one of a number of
subcommlttees working under the Commlttee on Nuclear Science
within the Natlonal Academy of Sclences - Natlonal Research
Councll. Its members represent government, industrial, and
unilverslty laboratorlies In the areas of nuclear chemlstry and
analytical chemlstry

The Subcommlttee has concerned ltself wlith those areas of
nuclear sclence which involve the chemist, such as the collec-
tion and distributlion of radiochemlcal procedures, the estab-
lishment of speciflcations for radlochemlically pure reagents,
avallabllity of cyclotron time for service lrradlationas, the
place of radlochemlstry 1n the undergraduate college program,
etec.

Thlis serles of monographs hag grown out of the need for
up-to~date compllatlions of radlochemical informatlon and pro-
cedures. The Subcommlttee hap endeavored to present a serles
which wlll be of maximum use to0 the worklng sclentlset and
which contalne the latest avallable informatlion. Each mono-
graph collecte In one volume the pertinent Information required
for radlochemical work with an indlividual element or a group of
closely related elements,.

Anh expert in the radliochemlstry of the particular element
has wrltten the monograph, followlng a standard format developed
by the Subcommittee. The Atomle Energy Commission has sponsored
the printing of the serles.

The Subcommittee 18 confldent these publlcations wlll be
useful not only to the radiochemlset but also to the research
worker in other flelds such as phyelcs, blochemlistry or medliclne
who wishes to use radlochemlcal techniques to solve a epeciflc
problem.

W. Wayne Melnke, Chalrman
Subcomnlttee on Redlochemlstry

111
INTRODUCTION

This volume which deals wlth the radiochemistry of
uranium l1s one of a serles of monographa on radiochemlstry
of the elements. There 18 Included a revlew of the nuclear
and chemlcal features of partlcular interest to the radilo-
chemist, a discusslon of problems of dissclutlion of a sample
and countling technlques, and flnally, a cocllection of radio-
chemlical procedures for the element as found in the litera-
ture.

The seriles of monographs willl cover all elements for
which radiochemlcal procedures are pertinent. Plans include
revision of the monograph perlodlcally as new technlques and
procedures warrant. The reader 1s therefore encouraged to
call to the attentlion of the author any published or unpub-
lished materlial on the radlcchemlstry of uranium whlch mlght
be included in a revised versaion of the monograph.

iv
CONTENTS

Y. GOeneral Revliews of the Inorganlc and Analytical Chemlstry
of Uranlum

II. General Revliews of the Radlochemlistry of Uranium
ITI. Table of Isotopes of Uranlum 3

IV. Review of Those Features of Uranlum Chemistry of Chief
Interest to the Radlochemist

5
A. Metallic Uranium 5
l. Preparation 5

2. Physlicael properties 6

3. Chemlcal properties 6

T

B. Compounds of Uranium

C. The Chemistry of Uranium in Solution 14
1. Oxidation states 153
2. Complex ion formatlon 21
3. Non-aqueous solutlons of uranium 30
D. Separation of Uranium 39
1. Precipitation 40
2. 8olvent extraction 60
Ethers, esters, ketones, and alcohols 63
Organophosphorua compounds 122 .
Amines and quaternary ammonlum salts 169
Carboxylic aclds 180
Chelatlng agents 182
3. TIon exchange 202 -
Anlion exchange 204
Catlon exohange 222 .
4. Chromatography 227
5. Volatillization , 231
6. Eleotrochemlcal methods 232
T. Pyrometallurglcal processes 235
E. Determination of Uranlum 236
1. Counting techniques 236
. 2. Sample preparation 241

3. Activation analysis 248
F. Dissolution of Uranium Samplea

1. Metalllo uranium

2. Alloys of uranium

3. Compounds of uranium

4., Meteorites, minerals, and ores
5. Blologlcal samples

6. Ailr dust samples

V. Collection of Detalled Procedures

252

252
254

- 254

255
256
257
The Radiochemistry of Uranium

JAMES E. GINDLER
Argonne National Laboratory
Argonne, Illinois

General Revlews of the Inorgenlc and Analytical Chemistry of

Uranilum.

1'

J. W. Mellor, "Uranium" in "A Comprehensilve Treatlise on
Inorgenic and Theoretical Chemistry," Volume XII, Chapter
ILXIII, pp. 1-138, Longmans Green and Company, London, 1932.
R. J. Meyer and E. Pletsch, "Gmeline Handbuch der Anorgan-
ischen Chemile," 8th Editlon, Syétem No. 55, Verlag Chemle,
G.m.b.H., Berlin, 1936.

N. V. Sidgwick, "Uranium" 1in "The Chemlical Elements and
Thelr Compounds," PP- 1069-1086, Clarendon Press, Oxford,
1950.

C. J. Rodden and J. C, Warf, "Uranlum" in "Analytical
Chemistry of the Manhattan ProJject," National MNuclear
Energy Serles, Divlision VIII, Volume 1, Chepter 1, pp. 3-
159, C. J. Rodden, Ed., McGraw-H1ll Book Co., Inec., New
York, 1950.

., J. J. Katz and E. Rablnowitz, "The Chemistry of Uranium,"

Natlional Nuclear Energy Series, Division VIII, Volume 5,
McGraw-H111l Book Co., Inc., New York, 1951.
G. T. Seaborg, "The Actinide Seriles" in "Comprehensive

Inorganic Chemistry," Volume I, Chapter 3, pp. 161-223,
10.

11.

12,

13.

14,

15,

16.

17.

M. C. Sneed, J. L. Maynard, and R. C. Brasted, Ed., D.

van Nostrand Company, Inc., New York, 1953.

H. R. Hoekstra and J. J. Katz, "The Chemistry of Uranlum"
in "The Actinide Elements," National Nuclear Energy Serles,
Divislon IV, Volume 14A, Chapter 6, pp. 130-188, G. T.
Seaborg and J. J. Katz, Ed., McOGraw-H1ll Book Co., Inc.,
New York, 195%4.

" J. J. Katz and G. T. Seaborg, "The Chemlstry of the Actinide

Elements, " Chapter V, pp. 94-203, John Wiley and Sons,
Inc., New York, 1957.

"Urenium, " R. Calllat and J. Elston, Directors, in "Nouvesau
Tralte de Chemtle Minerale," Part I, Volume XV, P. Pascal,
Director, Masson et Cle, Parls, 1960. Part II, 1961.

G. Meister, "Uranium" 1n "Rare Metals Handbook," Chapter
26, pp. 501-571, C. A. Hampel, Ed., Reinhold Publishing
Corp., New York, 1954.

L. Gralnger, "Uranlum and Thorilum," George Newnes Limited,
London, 1958,

A. N, Holden, "Physical Metallurgy of Uranium," Addison-
Wealey Publishing Company, Inc., Readlng, Mass., 1958.
"Uranium Ore Processing," J. W. Clegg and D. D. Foley, Ed.,
Addison-Wesley Publishing Company, Inc., Reading, Mass.,
1958.

"Uranium" in "Scott's Standard Methods of Chemlcal Analy-
gis," Volume I, pp. 1017-1027, N. H. Furman, Ed., D. van
Nostrand Co., Inc., New York, 1939.

TID-5223, Production end Separation of U233, Collected
Papera, Part 1 and Part 2, L. I. Katzin, Ed., 1952.
TID-5290, Chemistry of Uranium, Collected Papersa, Book 1
and Book 2, J. J. Katz and E. Rablnowltz, Ed., 1958.

G. H. Morrison and H. Freiser, "Solvent Extrection in
Analytical Chemistry," John Wiley and Sons, Inc., New
York, 1957.
IT. General Revliews of the Radlochemlstry of Uranium.

1.

E. K, Hyde,

"Radlochemical Separetlion of the Actinilde

Elements" in "The Actinlde Elements," Natlonal Nuclear

Energy Series, Divielon IV, Volume 1l4A, Chapter 15, pp.

542-595, G. T. Seaborg and J. J. Katz, Ed., McGraw-Hill Book

Co., Inc., New York, 1954.

E. K. Hyde, Paper P/728 "Radlochemical Separations Methods

for the Actinide Elements," Volume 7, pp. 281-303, Pro-

ceedings of the International Conference in Geneva,

August, 1955, on the Peaceful Uses of Atomlc Energy,

United Nations, New York, 1956,

IIT. Teble of Isotopes of Uranium® ,

Isotope

U227

U228

229

230

231

232

Half-Life

1.3 min
9.3 min

58 min

20.8 day

L.3 day

74 year

Type and Ener
of Radlation %fiev)

o 6.8

a (~80%) 6.67

EC(~20%)

EC(~80%)

a (~20%) 6.42

o 5.884 (67.2%)
5.813 (32.1%)

5.658 { 0.7%)

EC (99+%)
«(5.5x1073%) 5.45

a 5.318 (68%)
5.261 (32%)
5.134 (0.32%)

Method of
Preparation

Th?32(a,9n)
T™h23%(a,8n); ~2%
daughter 36 min Pu232

Th®3%(a,7n); ~0.1%

daughter 20 min Pu233
Th®32(a,6n); ~15%
daughter 17.7 day
Pa23o;

~6% daughter 9.0
hour Pu234
™h?32(a,5n);
pa®3!(a,2n);

3 x 1073% daughter
26 min Pu°3°
™he32(q, in) ;
daughter 1.31 day

232

Pa ;s daughter

2.85 year Pu236:

U233(n,2n)
Table of -Isotopes of Uranium (Continued)

Type and Ene
of Radiationr?fiev)

Isotope Half-Life

ye33 1.626 x 10°
: _year®
U234(UII) 2.48 x 10° year

g235m 26.5 min

U235(acU) 7.1 x 10% year

236 2.39 x 107 year

ye37 6.75 day

a 4.816
4.773
h.717
k.655
4.582

a 4.768
4,717

IT

a 4.559
4.520
4.370
4. 354
%.333
4,318
4,117

a 4.499

g~ 0.248

(83.5%)
(14.9%)
( 1.6%)
(0.07%)
(0.04%)

(T2%)
(28%)

(6.7%)
(2.7%)
(25%)
(35%)
(14%)
( B8%)
(5.8%)

Method of
Preparation

daughter 27.0 day
Pa233

natural radloactivlity
0.0056%;

daughter 1.175 mln
Pa?3¥M(vx,,) ;

daughter 6.66 hour
pa23%(uz);

daughter 86.4 year
Pu238; y233 (n,9)
daughter 24,360

year Pu239
natural radioactivity
0.720%;

daughter 26.5 min
U235m; daughter

410 day Np=3°;
daughter 23.7 min
Ppo32

51% dsughter

Np236~£;

daughter 6,580 year
Pu2*0; 1235 (n, )
daughter 11 min

pa237 g,

fifi%fllf% daughter

U238 (n, 2n) ;
v236(n, )
Table of Isotopes of Uranium (Contilnued)

Isotope Half-Life Type and Energy Method of
of Radilation (Mev) Preparation

U238(UI) 4. 51 x 109 year a 4.195 natural radio-

actlvity
| 99, 276%
U239 23.54% min BT 1.21 U238(n:7)5
: 2
u?38(q,p)
240 . -

107 yesar
Puauu; 2nd order

neutron capture

on U238

2 Data concerning half-lives, radlations and branching ratlos, unleas
othefwise noted has been obtalned from the "Table of Isotopes" by
D. Strominger, J. M. Hollander and G. T. Seaborg, Revlews of
Modern Physics, 30, No. 2, Part II, Aprlil, 1958. This compilla-
tion may be consulted for more complete information on the

isotopes and for references to the orlginal llterature.

o

Ya. P. Dokuchayev and I. S. Oslpov, Atomnaya Energiya, 6, 73 (1959).

|o

J. E. Gindler and R. K. Sjoblom, J. Inorg. Nuclear Chem., 12, 8

(1959).
The half-11fe of Pa237 has been reported recently to be 39 = 3

j

min, K. Takahashl and H, Morinaga, Nuclear Physilce, 15, 66k

(1960).

IV. Revlew of Those Features of Uranium Chemistry of Chief

Interest to the Radlochemlst.

A, Metallle Uranium

1. Preparation. Uranium metal may be prepared by several methods:l
the reduction of uranlum oxldes with carbon 1in an arc-melting
furnace; reductlon of uranlum oxldes with magneslum, aluminum,
calclum or calclum hydride; the reductlon of uranlum halldes
wilith alkali or alkaline-earth metals; electrolytic reduction
of uranium halides; and the thermal decomposifion of uranium.

iocdide.
2., Physical properties. Metallle uranlum exlsts 1n three allo-

 

tropic for-rnes:-g-’-:i the orthorhomblc alpha form, stable below
6£63°C; the tetragonal beta form which exists between 663°C and
770°C; and the body-centered cuble form which exlists at higher
temperatures (> 770°C). The physlical properties of the metal
as complled by Graingeri'are given 1n Table X. Because of the
method of preparation, impurlties may be contalned 1n the

metal which alter 1te propertiles. Also, a number of the physl-
cal characterlstics depend upon anisotropic and structural
effects, eg. thermal expansion. Therefore, 1f physical proper-
tles are pertinent to an experiment or design, 1t is besat to
determine them 1ndividuslly for the metal used.

The changes wrought 1n metallic uranium by radletion and
thermal cyclling may be considerable. The results of reactor radla-
tion on the metal are: dimensional 1nstabllity, surface roughening
and plmpling, warplng, high hardness, extreme brittleness, cracks
and poroslty, broadened x-rey diffraction llnes, and decreased

thermal and electwlcal conductivity.é- Thermal cycling growth 1s

elmllar in many respects to that caused by radlation damage.
However, dlfferences exlst, the fundamental difference belng
in the mechanism of growth. (The reader 1s directed to reference

3 for more detalled discusalon of this subject.)

3. Chemlcal propertles. Uranlum 18 8 highly reactive metal. A
potential of +1.80 volts for the half-cell reaction, U - U3 + 3e,
places 1t below beryllium and above hafnium and aluminum in the
electromotive force series.-2 The metal forms 1ntermetallic
compounds with Al, Be, B1, Co, Cu, Ga, Au, Fe, Pb, Mn, Hg, Ni,

Sn, Ge, In, Ir, Pd, Pt, T1, and Zn;= solid solutlons with Mo, Ti,
Zr, and Nb.2 It reacts at varying temperatures with H,, B, C, Si,
N C1 Br

P, As, O,., S, Se, F

27 2’ 2! 2’
Neoq, CHH’ Co, COE' 1,2 In alr, at room temperature, massive

o2 I2, HQO’ HF(g): HE'_S’ NH3: NOJ HCl(g)

uranium tarnlshes to form a yellow and. eventually a black oxide
coating. TFinely divided powder may burn spontaneocusly. In boilling
water, massive uranlum corrodes slowly wlth the formation of uran-
lum dioxilde and hydrogen. The reaction products with steam are
uranium oxide and hydride. The diseolutlion of uranium metal 1s

discussed 1n sectlon IV-F.

Table I. Physlcal Properties of Uranium Metall

Density (high purity) 19.05 + 0.02 gm/cm3
Density (industrial uranium) 18.85 * 0.20 gm/cm>
Melting point 1.132 £ 1°C.

Bolling point 3,818°C.

Heat of fusion 4.7 kecal/mole

Vapor pressure (1,600°C.) 10'1‘L mm

Thermal conductivity (70°C.) 0.071 cal/cm-sec-°C.

Electrical reslstivity (25°C.) 35 x 10° ohm/'cm3

Mean coefflcient of linear 16 x 10’6/”01
thermal expanaion (random
orientation 25-100°C.)

Specific heat (25°C.) 6.65
Enthalpy (25°C.) 1,520 cal/mole
Entropy (25°C.) 12,0 cal/mole/°C,

2 1. Gralnger, reference &.

Iv-B. Compoundes of Uranium

Uranium comblnea with most elements to form a large number
and varlety of compounds. "Gmelins Handbuch der Anorganischen
Chemie,ӎ which surveys the llterature through the year 1935,
deacrlbes seversl hundred compounds. Ketz and Seaborgg describe
some of the more recently prepared compounds, princlpally of

organlc character, such as chelates, alkoxldes, amldes, mercap-

fides, and w-cyclopentadlenyl compounds.
The oxldatlion states of uranium in the comblned form vary
from IT to VI. Divalent uranium compounds reported are U0 and
US. Trivalent uranium compounds are more numerous and include

the hydride, nitride, seaqulsulfide, halides and borohydride.

Uranium (III) sulfate UH(SOu)2 has also been reported.-I A

large number of tetravalent compounds are known varylng in
complexlty from the oxide and simple blnary salts to more com-
plicated organic structures. Complex salts such as 3(CN3H6)2003-

U(CO3) 4H20 and E(NH4)2C204 . U(caou)2 * 6H,0 form an impor-

2
tant group of uranium (IV) compounds. Complex salts are formed

also with halide, sBulfite, sulfate, and phoephate lona. Inorgeanic

compounds of pentavalent uranium are UF5, UCl5, fi015 . 80012, 8

UCl5 . PCls,é and UF5 ' xHF.é UOCl3 has been reported as an lnter-

nmedlate compound 1in the chlorination of uranium oxlides with
carbon tetrachloride.l Uranium (V) alkoxldes have been pre-
and UOCl, - EtOH

5 3
have been reported.g- Hexavalent uranlum 1p represented by

pared.g Also, the compounds (C5H6N)2 Uocl

UF6, UCl6, U03, uranates, and uranyl (UoS*) compounds, Uranyl
compofinds are the moet numerous uranlum compounds and vary in

type from simple salts to complex organic arrangemente. Complex
salts are formed with hallde, lodate, nitrate, carbonate, cyanide,
acetate, oxalate, sulfate, phosphate, arsenate, chromate and

vanadate lons. Tripie acetate salts of the form

I
MM (00,) 5(CH4CO,) g + 6H,O,

where ML 13 an alkall metal (L1, Na, or K) and ML 18 a divalent

metal (Mg, N1, Zn, ete.), are used in analytical separatlions of

uranium. Addltion compounds, such as U02(NO 2CH,COCyH

3)2 3
repregent a large number of uranyl compounds.

9.'

Uranatesa and peruranates are lmporftant in the analytical

chemlistry of uranium. Uranates have the general formula xMIO .

2
yUo., or xMIIO . yU03. They may be prepared by different me‘chods.—s-’--l-9

3

However, in usual analytlcal procedures, they are preclpitated
from a uranyl solution by the addltlion of a soluable metal hydrox-
ide, NH40H, NaOH, Ca(OH)E, etc., The uranates are insoluble in
water but dlssolve 1n acids.

Per'ura.natea§ are formed when uranyl sclutlions contalnling
hydrogen peroxlde are made alkallne. The composltion of the
peruranates depends upon the concentratlon of the slkall and
peroxide. The following groups have been ldentifled:

M2U2010 . xHEO, M2U06 . xHEO, M6U2013 . xHEO, and M4UOB . xHEO.
The peruranates are generally socluble in water. The least soluble
are those of the M2U2010 . xH20 group. The peruranates are
soluble 1n dilute mineral aclds.

Table II liste a number of uranium compounds togéther with
thelir behavior in different solvents. The compounds listed are
primarily bilnary compounds or slmple salts. The order in which
they appear 1s the order in which they may be found in "Gmelins

Handbuch der Anorganischen Chemile." 6

Table II. Uranlum Compounds and Thelr Sclvents.

Compound Solvent

UH3 . 8. HNO3(vigorous), cone. HC1Oy, hot

conao. HESOH’ a. +H,0, 1. alk., 1liq. NH

2°2 3

U02 B. HNO3, aq. reg., conec. Hasou, slowly
converted to U({IV)-salts in hot fum. HC1

U308 8. HNOB; heated to redness U308 1a only
v. 8l. s. dil. HCl and H,S0,, more 8. conc. -
2., 8. hot conec. Hesou; HF forms s. U02F2
and 1, UF4

UO3 8. mineral a.

UO2'xH2Q[U(OH)4'(x-2)H20] 8. dill. a.

U3OB . xH2O 8. 4.
UO3 . 2H20 8. 4., converted to UO3-H20 i1n bolling
HEO
Table II. - Continued

Compound

Solvent

U03-H20,[H2U04,002(0H)21 8. a., warm conc. UOe(NO3)2 aoln.

UO"_ - 2H20

U3N4

U0, (NOg), - 6HyO a

UFy,
UF5, U2F9' U4F17
UFg

U02F2

UCl
UClu
UCl
UClG
UoC1

Uo,Cl

UBr3

solubility in H,0: 20° C-.0006 g/100 ml,
90°¢-.008 g/100 ml; d. HCl; alk.
hydroxides form UO3 and B. peruranates
a. HN03; i. cone, HCl, Hasou

solubility in H,0: 0°C-170.3 g/100 ml,
60°C=goluble in all proportions; a. al.,
ether, acptone, daill. a.

s. h. HC10y, h. HNOg, h. Hy30,, H,B0, +
mineral a.

i. H20; 8. fum. HGlOu, HNO3 + H3BOB;
metatheslzed to U(IV)-hydroxide by
heating with NaOH

d. Hao forms s. anF2 and 1. UFu

B. H20-visoroun reaoction, cclu, GHCls;
v, 8. CEHECIu; d. alcohol, ether

B. H20, alcohol; 1. ether, amyl alcohol
s. Hao, HC1l, glec. acetlic a.; 1. 0014,
GH013, ecetone, pyridine

8. HEO, CEHBOH’ acetone, ethyl acetate,

ethyl beneoate; 1. ether, CHCl benzene

3!
.. Hzo(d.); abmsolute alcohol, ethyl
benzoate, trichloracetliec acid, ethyl

acetate, benzonitrite, 052, S0C1

2
d. H20; 8. 0014, CHCl3
8. H20
8. H20: 18°C=320 g/100 ml; 8. alcohol,
ether
a. H20

8 41- and tri-hydrates are also well established.

10
Table II. - Continued

Compound

uo » H,0

2( 3)2 2

us

U2S3

Us
Uo,S

U02803 . 4H20

U(SOu)e * 9H,O
U(sou)2 * 8H,0

U(sou)z ’ 4H20

U0304 . EHEO

UOESO4 . 3H20

U02504 . HEO

USe2

UOESe

Solvent

B. HEO, acetone, methyl- and ethyl-acetate,

pyrldine; 1. ether

B. HEO

8. HEO‘ alcohol, ether

8. H20

8. H20

v. 8l. 8. H.0: 18°C-a form, 0.1049

2
g/100 ml, B form, 0.1214 g/100 ml;

cold ppt. B. HNO3 and H3P04, 1. a.

after previously heating to boliling
temp.; 8. alk. carbonates

v. difficultly B. cone., HCl, dil. HNO3

+0 aq. reg., conc. HNO3

d. steam, HNO3; B. hot conc. HCL

gl. s. H,0; 8. dil. a., alcohol, (NH4)2003;

1. abBolute alcohol
1. H20; B. 8q. or alcohollic SO2 solution

hydrolyzee 1n H,0 wlth separation of

2

basglc sulfate, UOSOu . 2H20; 8. dil.

mineral a., acetlc a.

hydrolyzes in H,0(d.); B. dil. H,S50,,
HC1

8. a. _

s. Hy0: 15.5°C-20.5 g/100'ml, 100°C-
22.2 g/100 ml; s. mineral a.

8, H20

lgnites wlth HNO3; chemical propertles

gimilar to U82

4. H20; g. cold HC1l - forma U02012

11
Table II. - Contlnued

Compound

UC,5e0, * 2H,C
UB

12

U(BHu)u
UcC

U02003

er(Hcoe)2 " H,0

U02(H002)2 » U0 3H,,0

G

U02(0H3002)2 " 2H,0

U(0204)2 . 6H20

U020204 : 3H20

U(04H406)2 - 2H,0

U02(04H406) . 4H20
er(CNs)2 * 8H,0

Solvent
and HESe; reacts violently wlth HNO3 -
Se 18 first -formed and 1s then oxldlzed

1. H.O0; s, HC1

2

8. aq. reg., HNO HF

3!
8. cold HF, cold HC1, HN03, cone. H2 Y

reduces conec. Hesou
1. hot cone. HCl, HF; slowly B. hot conc.
HESOH

d. H20, alcohol

d. H,0, dil. HC1l, d411. HNO dil. H2804;

2 3’
reacts vigorously wlth heated conc. a.
8. a.

8. H20:
alcohol; 8l1. a. formle a.; 1. ethyl

15°C-420 g/100 ml; a. methyl

glcohol, ether, acetone, CS 0014,

o2
CH013, benzene, petroleum ether
less 3. HEO than neutral salt; more
8. formlc a. than neutral salt

s. Hy0: 15°C-7.69% g/100 mi; v. 8.
alcohol; 1. ether

1. HEO’ dil., a.; 8. warm conc. HC1,

conc. HNO3

sl. 8. H,0: 14°C-0.8 g/100 ml, 100°C-
3.3 g/100 ml; s. mineral a., H,C,0, and
alk. oxalate solutlons

1. H20, organic solventsa; s. tartaric a.,
tartrates, conc. =a.

sl. 8. H,0: 17°C-3.28 g&/100 cc solutiomn
8. H,0, ethyl and amyl alcohol, acefione,

ether

12
Table II. - Sontinued

Compound

USi2

U(H2P02)4 - xH,.0

2
U0, (HyP05) 5
U(HP03)2 ’ 4H20
UO,HPO,
US(P04)lL

UH2(P04)2 * 2H,0
(U02)3(P04)2 » XH,0
UOHPOy - xH,0

UPEOT

(U0,)Pp0, + 5H 0

U(Pos)4
UOE(POB)

U3Asu

UB(Asou)llL
UHE(A504)2 * 3H,0

2

UHE(A304)2 - 2H,0

UO HABO) - HHy0
(U02)2 A0,

5U0, * 38b,05 * 15H0
. v295 + XH,0

UO3

U0y ¢ Vp05 * HLO
200, « V,05
TVOLCrO, + XH0

Solvent

1. cold or hot conc.: EHCI1, HNO3, Hesou,

ag. reg.; 8. conc. HF; converted to
gilicate and uranate by molten alk. and
alk. carbonatea at red heat

d. bolling conc. HN03, aq. reg., alk.

hydroxide

1. H20, dil. a.; 8. conc. a., 50% H3PO2
1. H20, ail. H25045 8. HNO3

1. H,0, 411. a.; 8. conc. &., 50% H3PO3
1. HEO’ dil. a.; B. conc. a.

i. H20; attacked by a., €8D. HNO3

8. conc. HC1
1. HEO, acetlec a.; 8. mlneral &a.

1. H,0; 8. mineral a., xs.(NHu)ECO3

1. H.0, cold a.

1. H.0, alcohol, ether; =. XB. N34P207,

1. H, 0, HCI, HN03, H2504

1. H.0; 8. dil. a., esp. arsenlc a.

1. H,.0, acetle a.

8. aq. reg., hot cone. HELl, d. HNO3

13
Table II. - Contlnued

Compound Solvent

U(M004)2 8. HC1

U02M004 1. H20, CHCl3, benzene, toluene, ether,

alcohol, acetlc a.; 8. HC1, H,S0y,
HNQ3, H28207

3UO3 . ','r'MoO3 1. H20; 8. minersal ga.
. ' . HN

UO3 8Moo3 13H20 8 03

UO2 . 3WO3 . 6H20 8. HCl; 4. HN03; 1. H2804

UO3 * 3W‘03 . 5H20 8. H20

UO3 ’ WO3 . 2H20 sl. 8. H20

Abbreviations uesed:
a. - acld fum. - fumling
alk. - alkalil h. - hot
aq. - agqueous 1. - Insoluble
ag. reg. - aqua reglas 1. - liquid
cone. concentrated 8. - soluble
d. decomposes sl. - 8lightly
dil. dilute V. - very
esap. eapeclelly X8. - excess
Iv-C. The Chemletry of Uranlum 1n Solution

1. Oxidatlon states.

Four oxldation states are known for uranium

ilons 1n aqueous solution: the trl-, tetra-, penta-, and

hexapositive states.

sented as U+3, U+4,

UO2

+ 11+
and UO2

Ions 1n these states are usually repre-

2 s respectlvely. The

potentlals between the various oxidatlion states are glven

velow for aeldlc and basle solutions.2

Acldic solution:

yL:80 +3 0.61

1 M HC10, at 25°C

T

-0.33%4 l

14
Baslc solutilon: .
y2e17 U(OH)3§LL& U(oH)ugiég U02(0H)2

Triposltive uranium, U+3. Evlidence for the existence of
U*3 comes from the reversibllity of the U(III)/U(IV) couple.
Solutlons mey be prepared by the dissolution of a uranium
trihalide or by the electrolytic reduction of a uranium (IV)
or (VI) solution. Chloride, bromide, 1lodide, perchlorsate
arid sulfate solutions of uranium(III) have been reported.ll
They are deep red 1fi color and unstable, wlth oxidatlion of U+3
to U+4 occurring and hydrogen being evolved. Strongly acidi-
fled Bolutionulg or those kept at low temperaturealg appear
to be more stable.

Tetraposltive uranium, U+4. The exlistence of the T

+i

ion 1n solution has been confirmed by measurement of the

acid lliberated on dlssolving UClu i3 and by solvent extraction
studies of U(IV) with thenoyltrifluoroacetoneli& and
acetylacetone.IEB Uranous sclutions may be prepared by dle-
solution of a water-soluble salt: the chloride, bramide,
lodide, or sulfate; by dlssolutlionh of uranium or a uranium
compound 1n an approprlate solvent, e.g., uranium metel in
gulfuric or phosphorlic acid; or by reduction of a uranyl
solution by chemical, electroochemical or photochemical means.
The Bolutions are green in color. They are stable 1n the
qbsenca of alr but are oxidlzed by oxygen. Uranlum(IV) under-
goes hydrolysis with evidence 1n the flrst stages for the
formation of the mononuclear specles, U0H+3. 13,15-18 Poly-
merlc specles also are formed which apparently are not 1n
equilibrium with the monamer.23:12:19 mietanenil found that

in addition to the monomerlc specles, e polymer of the type
U[(OH)lefi"'n could account for the hydrolyseils of urenium(IV)
to good approximation. Table IIT, based primarlly upon the

date complled by Bjerrum, Schwarzenbach, and S111én,22

15
Ion Method

nagnet
ap
ap
Bp

8p

sol

8p

U02 gh
gl

aol

24+
uoz" qh
gl
qh, gl

gl, fp, Bp

gl, fp, BP

p(H,0)

80l

- 8p
dist
gl
gl

2+
UO2
gh, 81

gh, 8l

25
10-43
10-43

15-25
25
25
25

25

25-26
20-25

25

B &

8 3

257

25%

25

25

25

25

25
25-49

25
25

25

 

Table II1. Hydrolysis of U

Medlum
ar
€(NaC10y)
0.5(NaC10,)
-0

0.19(HC10, )

" 0 oorr

3(Na)01ou

0 oorr

2(0104')

0 corr
var

vaT

0 corr
c[Ba(NoB)EJ
1(Na)c10,
1(Na)c10,
1(Na)c1o4
0.15(KNaC10,)

©.1 Cl0y

2U02(010#)
+U03
0 aorr

var

0.1(Na)C10,

0 corr
0.3#7[Ba(c1ou)2]
0.0347[Ba(c1ou)2]

0.0347[31(010;)2]
1(Na)C10,,

2+
0.4U03
3(Na)Cl0,,
1.4003*

M and UoS*  roms?

‘-Iog of equilibrium constant, remarka

¥ -2.30

-1.63(C=2), -1,56(C=1), -1:50({C=0,5)
-1.90{10°), -1.47(25°), ~1.00(%3°)
-1.12(10°), -0.68(25°), ~0.18(k3°)

= 11.7, a%8; = 36(25°)

-1.38(15.2°}, -1.12{2%.7°)

"

R

*
» o

o

-

A'E; = 10.7, A'Sl = 33, 43, = 52
*xl -2,0, tflgfi,n+1 «l.2-==3.4n
Ksg -3.770"u(on), (5)"]

7

-1.68, fK -1.73%

R LA H\0 g UOHSY 4 Ht

$x, : U+ 00 2 vop®t 4 bt

"6, : UM + 250 3 U(0R)2F 4 ow
*Ban,pay ¢ ()M + 30,0 = UL (0H) IR 4 3oR*
'K, -h3

"By -5.87

"L, -1.50, *B,, -4.95

ev U0,N040H, U0, (KO,),0H°"

*x, k.09

*Boy -5.97(0=0.6), -5.72(C=0.06)

'Kl ~4.70(?, Bee rer. 43}, ev polyn opx

'_F*

)3

'*52n,n+1 0.30---6.35n

*flan_n+1 0.30--=6. 40n

"Bop -5:9%, "Byy -14.29

K, [030g(0M)2™) : -3.55(n=0), -6.5(n=1),
-7.4%(n=2), -11.0(n=3), -11.4(n=4)

*Bap -5.94, '543 ~12.90

v (U0 0K)2*, not vo,08*

6.08, "%, 1.90, X, -3.60, X, -3.
'xso 5 0 33 - 8y 317

'Kl -%.14%, ev polyn opx
K, -k.19
K, -4.2, fxa -5.20
'fl22 -5.06, lbza_ -1.26
-
", -5.40, "8,, -5.82
™, -5.82(25°), -5.10(20°), A"H,=20.8 -
*8op -6.15(25°), -5.92(40°), a’n322-5.7
* -
A Sl - 1.3, A”8 - -6
* % " Ba
512 -3.606, fi22 ~£.02
'fllz - 3-68' '522 = 6.3, *343 I-lE.G(qh),
*Byy - 12.9(a1)
*Bon,par T (041)I02Y + 2n0 e
U0, [{0R),00,15% + 2nk* ete.

a
~ After J. Bjerrum, G. Schwarzenbach, and L. @. Sillfin, raference 20.

18

Refarence

21
13
22
13,21

16
16
17
23

18

49
37
38

25¢
39,52,53
32

L2, eri3y
42, arsh
Lo

L4

4B

50
51
45
46
16

46
&7

47
-0

0.1
1 Moo,

1(rat10,)

I(mo._)

1{m)c10,

Takls IIT (Contined)

The notation ussd Iin this amd in the tahles on aoxplex iam
formaticn 1 mabtternoed wiber that used by Bjearrum, Bolmmresenbach,

fimfi.m-n The sxplzsation of e tabls which

follows ia taken primarily from pard IT of referwnds 20 and this
shonld bé conmlted for fariher details eonoarning petation,
Fart I of reference 20 mxy he oansultsd for a Assoription of tha
varicos swthods by whiach equilibrizns oconstarbs ere debarerined.

Oolusn ana, "Yem," refars to the canirul ion N about whioh

the camplex is formmd.

Oaloem two, "Method," refars to e awbthod Wy whish the
omoatants were measured. The abbreviations ussd are:

al ex anion exthinge

ombrifugs or ultrecantrifogs

calarinebkry

sondustiviby

digtibutiss between wo phasen

aal, oot spaalfied

fresaing paint

glass algotrods

1on exchangs

t mgmatio sussspbibility

p{E0) partisl pressure af substanse
indleated

o ihERE

Oolumn thres, "T," gplves tha tamparaturs in “C,

’555.‘.193.!"

Agy0o0y
?

A mathod, not speoifisd
polarography

premrative waork

quinhyirors electrods

axf with redox slechrode
lnlu‘bfllhl"

speatrophotomatry

I-ray diffraction

sombinabion of tharmedynewis.data
axf mmsoremant with P4 alsatrods
wnf cpaguresmmb with Ag,0.0, eleatrods
mathod oot knawn to empllers

" 1ndi-

oxbes room temperatmre, ind "t" is wsed if the bemparmture is um-

nom o the oampllers.

Oolomn feur, "Kedizm, " dsnotes the mture of the msdium to
wbich thw squilibtcium ooostents refer. T caooantiretlons glven
in tarms of mnles par libar or males par idlogram are not dis-

tingol s
Symbols nasd e
omstants axbtrapolated to mare lanlo strangth.
constants ocrrected Eo wero lopnis stremgth by
application of scme thaoretiocal ar s=pirieal
Tormala.
an ianie stremgih af 0.1 mols par litar.
consba=t emomntrution of the subrhancs
stated (1 mole per liter NaClQ,).
laonio stremgth hald canstant abt walus ptated
(1 mole par litar) by sddition of the inert
salt Indieated.
peasurensnts made at & sariss of lonie
strengths (I) with BaCl0, as the inert malt.
camuentration af the anian (010") hald

sanstant at tte valus stated () male par liter)

0(010._")

ater is tha salvent unless otharwiss ntated.

with the lon shown in parenthases as She
inart u.t.‘l_.m.

meamresstbs mads ot & sariss of porohlorats
oonoentratlions.

dilute solution, oconéanbrebion usually not
more than 0.01 mole par litaer.

lonio msdice varied, and in some cases mo
spacial attemph was mmdse b0 oconiral the ionis
abrength.

tha madizm was minly sqwecusy EC1 ab varicas
concantrations.

sthanol as solvent.

wvarious organis salvemts.

508 mathancl-wntar as solvent.

Calumr five, "Log of emilibriom constamt, resmvis.” Tha

K, &" mans "log) I, = 6%

‘l2 5 3" maans fln;lol! > 3% 1.9., the "log® and "=" mymbols are
axitted. Capesnbtrations [ 1 are usually expressed as mnles par
litsr, bot is not disticgnished from wolss par kilogrem. Presmures p

Following oonventicns are used )

ars in smospheres.

Tha equilibrive conatarmks refer.to varioos types of reantions

indicased ar the naxt page.

17
Table IIT {Qontimued)

1. Conasocutive or mtap-wles conatantmi K
a. Addltion of ligend {L)

(M, ]
Wi+ e Mg B o

" by 35
b, Addition of protonated ligend (HL) with slimipation
of protan
tr, 1 1]
(M, 5 1(EL]
6. Addition of protonated ligam? (EPI.)

+ *
ML, +HL 2 ML +E Txo-

[n(E I.)n]

(N(BL)y o R D

W(E_L)

plna + Bl = FHL), HLXK-
4. addi‘ion of cantrul stom (M)

[HnI-]

LiNea N
" % D, L10

En-

2. Cumilatlive or gross conatantm: p
In B, and B the subscripts n end m denots tha
camposition of the complex M I, formed. UWhen ll- 1l, the
Bacond mubdoript 1a omitted,
a. Additlan of gemtral atams (N) end ligands (L)
(L

=™ + al. Fb lI:lI'I.'l [H]n[L]n

Pop =
b. Addition of centmal atoms (M) end protonated ligands
(HL) with sliminatioen of Protons
DE, 1 (R
+ -
o + nHL = M L + oH Bm = W
3. Solubility constanta: I.
a. Solid "aI*b in squlilibrium with frees icnes in solublan
MLy (8) e a + b Koy - ot n®
b. So0lid M;I, in equilibrium with couplex M I snd ligand
L in solution

T Maly(8) o Moty + (2 - nlr
E, = [u‘LnJ[L]"-iE - 2]
"m
tha subsoripts n ard @ dencte ths composition of
M
the camplex Han formad in solutlon. When m = 1, the seoomd
mabsoript s omitted.

In K,

¢. Protoneted ligand resots with ths elimiratian of proten
Do) + (B - nE @ang, + (3R n)m
mb
o r 11 G 2
o Dl
m [H+] (T -l.'l)
4. Aoidio and bhaslec gonstants:
n. When L ia hydroxide (0E7), M, 1@ water mmd 'l[n is

the nth aoid dlasscelation constant for tha hydrolysis of

A mevailic lon.

b. The use of H' as tha cantral ston to repressnt pro-
tolytle constants is illustrated by 1.d. above. -

0. Other acidic oanstants Are deroted by K., followsd >
by parenthessas ancloaing the formula of tha specied domating
the protom.

d. Basioc oonstants are denoted Wy “b follow, 1f nacessary,
by parenthases enclosing the formula of tha spaoiass accepting
the proton-

5. BSpesolal oonwtantm:s

a. X (equation] )

The eguation definas the reactien to which K refers.

v ', tx

™a oorrespanding reaction is given in parentheses
arter tha oonrtant when the latter is riret used for a
particular ligard or cantrel atom, or the reaction is
siven immediataly below the egullibriun constants for &
particular ligand or ceptral atom.

o. (formula)

Tha formula gives the ocomposltiaon of tha cqlple: in
terns of the speciss frow which it 1a formed. Specias with
nagative subsoripts are eliminated in the rformation of tha omm-
plex.

4. K, (foraula)

The formula gives thd composition of the solid phass
in terms of ths species with which it is in equilibrium in
aolution. Speciss with negative subsoripts are sliminated
in the formatilon of the solla.

Heat ocntent and entropy ohanges sre included in column
fMve. AH 1s ususlly written in idloocalories and AS in oalories
par dagres. Thay ire related to the corresponding cumulative
a:u.uimm conatants as follows: B, AEBn; Brm* AEBm; 'flm.
A fl_- Wnere the symbol X is uped for the sfuilibrium constant,
Eor 8 lu given tha pane sumPMaaript or subsaript aa ths corre=

eponding K: e.g., K, afy) Ky, 8E, 0 "l(m, n*l\lnfls eto.

Other abbreviations ussd In column five are:

[ Kan evidence for the existemos of the vomplex H“I.:l
opk scmplax

ont cationic

enl anianig

unsh uncharged

pelyn polymiolear

¥ mathors' doubt sxprepssd in referencs glven
(1) compilars' doubt

Columnh six, "Hslerences,™list the references as they arm
A reference such as "5,af.95"
indicates that calouwlations have pesn mads in relerensce 25 based

fourd at the and of this work.

upon data in referense 6.

18
sumarizea the results of several studies on the hydrolysils
of the uranium(IV) ion.

Pentapositive uranium, UOS . The existence of uranium(V)

 

ion 1n solution has been.conflrmed by polarographlce measure-

24-26

ments. Support for the U02+ 1ion comes from the reverai-

bility of the U(V)/U(VI) coupleZl and from infrared2S and
crystallographicggiig studles of uranlum and transuranlc ele-
mente, Solutions of U02+ may be prepared by dissolution of
U015§£ or by reduction of a uranyl solutlon, electrolytilcally
or with U(IV) 1ons, hydrogen, or zinc ar.l:l;.algam.l‘i The formation
of U(V) 18 an ihtermediate process 1n the photochemlcal reduction
of U(VI) in a sucrose solutlon.=2 The solutlons are unstable
and dlsproportionate to U{VI) and U(IV). The rate of dis-
proportionation is second order 1n urenium(V) concentration
"and first order in acid concentration.ifiili The U02+ lon 18
most stable 1n the pH range of 2 to 4,22 Tt is oxidized to
the uranyl lon by molecular oxygen, Fe(III) and Ce(IV).lé

+2

Hexapositlve uranlium, UO2 A number of phyeical-cheml-

 

cal measurements as well as cryastallographle, infrared and
Raman spectra studles support the exlstence of U{(VI) 1on as
Uozafngg Uranyl solutions are easlly prepared by dls-
solutlion of water-soluble salts: the niltrate, fluoride,
chloride, bromlde, lodlde, sulfate, and acetete. Other water-
goluble uranyl ealts Include thoee of other organlc acids:
the formate, propionste, butyrate, and valgrate; and certaln
double salts such as potasslum uranyl sulfate, sodlum uranyl
carbonate, sodlium uranyl chromate, etc. Uranyl solutlons

may be prepared also by diasolution of a uranium(VI) compound
in an approprilate solvent, by dissolutlon of a lower valence
uranium compound 1n an oxldilzling medium, or by oxlidatlion

of lower valence uranlium lons already 1n solutlon. TUranyl
8olutions are yellow 1n color. They are the most atable of

uranlum aolutlons. As 1ndicated 1n preceding paragraphs, the

19
uranyl lon may be reduced by reducing agent&ii or by electro-
chemical or photochemical means. The degree of dissoclatlion
of uranyl salts 1n aqueoue solution varies. Uranyl perchlorate
ie apparently completely d:l.slsoc:‘l.at‘,ed;-:-L-9 whereas, uranyl
fluoride 18 undlssociated and tends to form dimers (see section
on complex lon formation - IV-C2).3§L§§ Hydrolysle of the
uranyl lon has been the subJect of extensive 1nvestigatlon.
Conalderable evldence has been adduced for the formation of
polymeric species of the type Uoz(Uo3)§+.3kEZ According

to Sutton,flg formation of polymers beyond the trimer U3082+
is negliglble. However, the trimer itself may undergo
further hydrolysis with the formation of U308(0H)"', U50g(OH) 5,
and eventuelly anlonlc species.flg&il Ah]:-land,-ltg in hils
origlnal paper, proposed the formation of the monomer UOE(OH)+
as wall as peolynuclear species. In a reappralsal of the

work, Arhland, Hietanen, and S1114n23 stated that there was
no cartain indicatlion of mononuclear complexes being formed.
Rather, the experlmental data was explalned on the basis

that complex lons of the type U02[(OH)2U02]$1+ were formed.
From the data 1t was not possible to distingulsh between a
limited mechanism in which n variled from 1 to 3 or 4 or an
unlimited mechanism in whlch n assumed all integral values.
The authors were lnclined to prefer the latter. I‘&'.r-a'us--:l-'-2
suggesated that reactlons leadlng to the formatlion of polymers
mey have & less poeltive value of AH than the reactlion
leading to the formation of the monomer. Consequently, the
latter process mlight be ldentlfied more readlly at high
temperatures than at room temperature. Thls is apparently

the case as was shown by Hearne and 1.'u'hitc-:-i‘l-g who determilned

the enthalpy change to be 20.8 kecal/mole for the monomerilc
reaction (UO,OH' formed) and 6.7 kcal/mole for the dimeric

+

reaction (U20 formed). Table III summarlzes much of the

2
5

20
data avallable on the hydrolysls of the uranyl lon. Included

in the table are values of the equllibrium constant K., the

12
constant for the formatlion of the monomerlc species. Thils
constant has been evaluated by at least seven groups of
:I.n\'reE;’c.’Lgator's--aégféfiiflg?fig:él excluslve of Hearmne and Whiteié.
The values obtalned agree very well (log *Kl = -4.09 to -4.70).
However, the experimental c:ondj.til.ons-g-és-ng-’-é9 and assump-
tionsgé&iig'used in some of the evaluatlons have been

42

questioned.fié Algo, the re-evaluatlon of Ahrland's— work
already has been mentlioned, and Rydbergil has proposed an
explanation for not detectlng polynuclear gpecles in hils
experiments. None-the-less, one must concur wlth R:grdber'gél
who wrote, "---1t seems remarkable that the same constants
should be obtalned for a filictlve mononuclear hydrolysls
product with different U(VI) concentrations and so different
methods of investigation---."

Complex lon formatlon. The abllity of uranlum to form complex
ions 1n solutionse 1s of conslderable importance 1n its analytlcal
peparation and determination. Hydrolysis, mentloned 1n the
previous section, is but a speclal case of complex ion formatlon.
Numerous complexes have been r-eported.z’-i However, the amount

of quantitative data for the varlous ligands 1s rather llmited

and often contradictory.

Tripositlve uranium. Evldence has been reported for

 

uranium(III) cupfer'rate-éi and uranium(IIT) chloroié complexen.

Tetrapositive uranium. Inorganic complexes of uranium(IV)

 

wnlch have been recognlzed through the Tormation of ccmplex salts
include the fluorlde, chloride, sulfate, sulflte, and phoe;pl'l.'sate.z’-E
Table IV llsts the equilibrlum constants and thermodynamlc

data avallable for some of the uranium(IV) complexes in aqueous
6=

solution. In additlon, a carbonate complex, posslbly U(COB)B s

has been found to be stable in solutlone of excems carbonate

or blcarbonate ions.éi

21
b+

Table IV. Complex Formation with U Ions - Inorganic _1'.u:I.sn.m‘.|s.E

Complexing agant Method T Medium Log of equilibrium constant,remarkas Reference
Thiocyenate; red 20 1(NaCl0y), 0.68' K  1.39, K, 0.A6, K; 0.23 57
SCN” atst 10  2(Ra)C1q, 18" K 1.78, K, 0.52 58
" 25 n K 1.49, K, 0.62 58
ARy= -5.7, ABy= -1.8, AS;= -10, A3,= 9.7
" ko " K, 1.30, K, 0.68 58
Phosphate, sol 35  var v UAIS(HL)g+br TAlg (D)3 2* 59
Pog "
Sulfate, 505~ atet 25  2(HC105) :‘i 2.53, ::2 ~0.13 12a
n " " X 2.4, 'K, 1.32 1%a,cf.
60
" n " K, 3.2%, K, 2.18[K (§)1.125](%) 1%a,0f.
60, 61
n 10 2(Na)Cl0,, 1H* x 2.63, 'K, 1.3 58
- " 'x, 2.52, 'K, 1.35 58
8H)~ -3.2, ARy= 0.9, AS;= 0.7, AS,~ 9.3
" %0 n *x, 2.38, 'K, 1.38 58
Fluoride, F~ ast 25  2(Kac10,), iE* 'K 36, "B, 38 58
Chloride, C1~ Bp 25 0.5(H3010') K, -0.20 13
" 25 0 corr K, 0.85 13
red 20  1Na)clo,, 0.6H7 K, 0.30 57
atst 10  2(NaCloy), 18" K o.52 58
" ' 25 " K 0.26; or K, 0.08, K, -0.02 58
" 40 " K, 016; or K, -0.0%, K, -0.06 58
anl ex 25 HC1 var ev ani opx in >5.5M HC1 62
Bromide, Br~ red 20 1(Na)c1o,, 0.6H* K 0.18 57

 

a
TAfter J. Bjerrum, G. Schwarzenbach, and L. G. $1116n, reference 20.
Column one denotes the complexing ligand (L). The notation 1s explained following Table III,

Numeroué organic complexes are formed with the uranium(IV)
lon: the acetate, oxalate, tartrate, malate, citrate,.lactate,
glycolate, etc.ifi However, the amount of quantltative data
available on thelr formatlon 18 very meager. Tishkoff-éi has
calculated dlssoclation constants for acetate complexes on the

basis of the oxygenated uranium(IV) ion UO2+

being formed. The
formatlon constanis measured for acetylacetone, thenoyltrlfluoro-
acetone and ethylenedlamine tetraacetic acld complexes are glven
in Teble V.

Pentapositive uranium. Although it appears that uranium(V)

complexes should be formed 1n the reduction of uranium(VI) ions

22
in complexing.media,éi little data 1s avallable.

Hexaposltive uranium. Inorganic uranlum(VI) complexes

 

which have been identified through the formation of crystalline
saltts Include the fluorildes, chlorides, nltrates, sulfates,
carbonates, cyanldes, and phoaphates.Qi Uranyl solutlons with
these anlone present have been studled. The results are listed
in Table VI. A number of dlscrepanciee appear 1n the deta. For
example, evlidence for some complexing of the uranyl ion wilth

nitratezflizgizz and chlofidcsT’Ts’77’105_107ions hes been reported

 

by some 1investigators; but a complete lack of evidence'has been
reported by o‘chers.ég Day and Powerszz have polnted out that the
constants calculated by them are concentration constants rather than
activity constants. Consequently, the small complexing effect may
be caused by. the varlatlon of actlvity coefflclents with a change
in medium. Other investigators, however, who have corrected
their resulta to apply to pure aqueous solutlona have found some
complexing to occur with the chloride ion.éz-"-lgéfl'-gz

The type of complex formed between uranyl and fluoride lone
also 1ls subjJect to some questlon. Ahrland and co-workerslggiigi
have determlined equllibrium constants for the formation of

complexes U02F+, Uo,F U0, F, , and UOEFME_ and found no evidence

2 2’ 273

for the dimerlzation of U02F2 for uranyl ion concentrations less
than 0.1M. Day and Powers,ZI however, found no evlidence for the
formatlion of complexes beyond U02F+; and Johnson, Kraus and
Young:’lé have reported the dimerization of U02F2 in solutions

not very different from those lnvestigated by Ahrland, gE_gl.lgfl

Numerous organlic complexee have been reported.-:'-"-i Much of
the quantitative data 1s summarized in Table VII,

There 18 often dleagreement between different 1lnvestligators
csncerning the nature of the complexing ligand. Uranyl-oxalate
complexes serve as an example. The oxelate 1lon, 02042', has been
propoeed by some :l.nvee.’t:iga‘t:oralflé&&2 88 the complexing ligand;

the bioxalate lon, HC,0,, by othersi*l:116; ang He1at*2 nas

(Text continues on pege 30.)
23
Tables V. Complex Formation with ‘IJA"" Ione - Urganic Ligandsd

Complexing agent Methad T Hedlumn pK of HPL Log of equilibrium constant, Raferance
remarks
c:5rlao2 diat 25 0.1(010,") B.82 K, 8.6, X, 8.4, % 6. b 14b, 111
acetylacetone: HL Ky 6.1
n " n B.B2 K, 9.02, K, B.25, 13 6.52 14b, eof. 112,
Ky 5.98, Py 17.27, B3 23.79 113
By 29.77 '
CgHl50pF5S Bp 25 - 0.1 K 7.2 114
thenoyltrifluoro-
acetone HL
C; oM 6% Ya. : L 2.21 K 25.6 115
Sy Lo e a0l 25  (Fy80,)(1) EL7  2.77 pRIEGE®* &2 KL + 28N 1.0
L EL?" 6.16
w3~ 10.26

 

a
TAfter Bjerrum, Schwarrenbach, end 51116m, .reference 20,

The data, wilth the exceptlon of reference 111, has been camplled by J. Gindler.
Column one liste the empirical formula, the name of the ligand, and a formula of thea type HPL
which defines the entity L in terms of which the equilibrium conatanta are exprassed.
The ligands are placsd in order of thelr emplirical formula according to Dellstein's sysatem.
Column flve li_nta the pK valuen (-103101() of the mcld-base equilibria involving the liganda
and fer to the dlssoclat : b+l-p)=

= HFL(\"'P)-' :nflp_ll,(b"'l'l’)' +at ; Km w

[HpL(b-p) 'J

The notation 1s sxplained following Table III.

Tablé VI, Complex Formatlon with Uog"' Ions - Inorganio _T.isa.nd#

Complexing agent Method T Medium Log of equllibrium constant, remaris Refarance
Cyanoferrate{II),
Fe(cfl)g' sol a5 var Eflo -13.15 65
Thiocyanate, ap 20 1(Nac10,) K, 0.76, K, ~0.02, X, 0.4 66
SCN” Bp 25 -0 K, 0.93 ) 67
Carbonate, prap aolid av U‘OzL_.l,t" 63 .
coZ- sol sp? 25¢ O corr Ky 3.78 69 quoted in
3 ref. TO
mol ap 257 O corr K[00,(0H) H,0(8) + CO,(g) wet TO,C0,(8) 63
+ 2112o1a
+ +
_ x.zfxpoxf (8% 1.82, xa/xpor.i-‘ wth) 1.1 63
AG 25 0 corr By 1h4.6, fl3 18.3 63
mp- ~2 Ey -3.5, ev (U’Oa)z_(OH)aL' 70
aol -0 X [Raf(vo ) 12,8 o -2.0 70

26
_ K.E/xpoxg(n*') : U0,C0,(n) + 2HCO] e uoe(coa)g" + Co,(g) + H,0

Ry/Rp E5(E') 1 D0, (00,)5" + znoo; W,(0,)3" + Co,(g) + B0

sol 25  1(ng,C1) By 22.77 n
ap 0.3(kN05) . TEIDO,(00,)3" + B0, =2 U0,(00,) 0083 72
+ Eco_;la.o

sp -0 % 2.2

8p var x[uozwoa)zoo"' + 8t & 10,(c0,), 00E>"110.6 73
Nitrate, NOj sp 25 5.38(NaCloy), oK' K, -0.68 74

sp 25 T(RaCl0,), 28" K, -0.57 h

X-ray so0lid av UOZL; in m:trozx..j(s) 75

qh 20 1({Nac10y) X, -0.3 T 16

dist 10-30 2(NaCl0,) K, -0.52(10°), -0.62(25°), -0.77(%0°) il

fl_.
Table VI. = Continued

Complexing agent

Phoaphate, FOj-

Methed T
ap ?
ap 22-28
8p

cond 25
oond 25
ap 25
so0l 25
aol 25
anl ex 20
s0l 19-20
ap 25
sp 25
dlast 25

anl ex 20

ap 25

Bp 25

Medium
var
org
M0200
EtoH
MeECO
:LHClou

1HCth_

1HC10)?
1H0104?
1HC1O),
1HC10,

]-!'3L vVar

E3L var

E3L dii

di
H3L 1

53L di1

]-%L 4a11

molid:

var

Q nsorr

yar
1.07(Na0104)
1.07{NaC10y)

0 aorr

1(010u')

0 Corr(%)

Log of equilibrium constant, remarks Referenca
no ev cpx: 150-fold exceag L 50
&v U0 Lq 78
Ky 3.6 in Me,CO : 79
12(?)3.15, K3(?)1.39 in EtOH 80
x2(7)3.96, xa(?)z.us in Me,CO 80
Itwog“ + HyL @ vogH,  I** + (2-x)E*11.58 81
KID0S* + KL 2 00, | ¥ + (2-x)K*11.57 82,83
T xwm]lor?2 of. 83

R[D0Z" + 2T = 0, (H,L), + 2HYIL.18
E[U05" + 3H,L = U0, (H L) HL + 2B*12.30S
K, (U0 HL(a) + 28% o wol* + H,11-2.65
K, [U0,EL(s) + x8" 2 voH, | 17%)-1.29
X=]1or?2
K [UofL(s) + HoL o= UOE(HEL)EJ-I.T
I(’[UDQHI-(u) + 2H3L = UOE(HzL)EHBL]-O-SE
R, [(00,)5L,(8) + 65" e 300EF + 2E.1]-6.15
K, [(U0,)gLy(8) + HyL + 3H' =3 300,H,L%)-2.50
Kp[(U0,) 3L, (8) + 4B L =2 300, (HyL),1-2.89
Eq[(00,)31,(8) + THyL = 300, (H L) H L1053

'*uoaflr.(u)“ - anrrro#(neo)q(g)

av UOEEQL"', UOE,H3L2+, o, (8,L), 84,85
HEL' : K 3.00, K, 2.43, K3 1.90 86
HL : K <1.88, B, 3.86, B, 5.23

K, [00, (H,1)371-0.53, -2.27, -1.%8

Ea[UOE(l'%L)g"'J-l.BE, -1.18
(gt - K14 2-12)
B, (V02 hr} 137)-26.36 a7
x (vo2*eL3)-23.11

24, 2- +
K, (U0Z "HL=")-10.6T, (5" : K 12.44, K, 6.71,
113 1.96

; 24 +

av U02H2L+, O H L2, 00, (ByL) s UOGH L, 88

p(voZ*al; HI)i.15% 89,90
+ o b
B{Uog"'H_e(!-LaL)ell-Bll— 89,90
fl[trog“l-lfz(}%l.)au.ofi
By, (003" + 1H,L = oS (1~gm L7 ezt 91

+ (108" : K, 098, K); < 1.8, Ky 1,38,
Kp1 2% Kpp 3-95 Ky 1.1, Ky 2.5%,
%2 J'I'-Bl K33 5'3

H,__.L' : X 3.0, B, 5.5, By 7.4
H3L : Ky ¢ 1.8, By 3-9, 53 5.3 (same aa

11+ Bopr Kgg)
(u* : K 4 2.10)
K:r.:] T Kig O:Ts 1(11 0.8, Kao 0.4, K 1.4 88,cf, 91
(xt - K5 1.68)
Kyy t K 1.1, Ky 1.2, Ky 1.3, Ky 2.2 88,cf. 91

(B : x4 2.10)

same equilibrium reectlon, different notation
mame equilibrium reaction, different notation
same @quillibrlum reazocotlion, different notation

le o l@
Table VI. ~ Contimed
Camplexing agent Method T Madium Log of equilibrium constant, remarks Reference
Polyphosphate, pH 25 Al n~5:K 3.0, or B, 6.0, or Py 9.5 92
[Pn°3n+1] (n-2)-
Arsenate, AsO3~  sol g1 20 var x,(voZt m2")-10.50, K (003"L1*L*")-18.82 g3
X, (v02*Na*13")-21.07
X, (vo2te*t3")-22.60, X (00Z*Nm,*L3")-23.77
(6" : K, 11.53, K, 6.77, K4 2.25)
Sulfite, sog' 8p ver ev T0,LS", strong epx 94
8ol 25 (m4)2m3var xao-a.'59 a5
By 7-10
Sulfate, 50§ 8P 25  2.65(Kkacioy), 28" K, 0.70 74
25  3.5(%), =8 K, 1.83[K, (¥9)1.125) 74, cf. 61
qh 20 1(NaC10) K, 1.70, K, 0.84, K 0.86 96
p(003 1% 207) 3.78
B(0031L3"20") .60
8p 20 1(NaC10y) K 1.75, K; 0.90 96
cond 25 0 corr Kl 3.23¢% g7
dist 10  2(KeC10,) K 1.80, K, 0.96[K, (E")1.01) 77
atet 25  2(NeCl0y) X, 1.88, K, 0.97[K (E1.08] 77
4H, = 2.3, AH, = -0.9, A8, = 16, A8, = 2
dist 40  2(Na010,) K, 1.93, K, 0.93[11(3*')1.17] 7
anl ex var ey UOELg", U205Lg' 93
ani ex 25  var ov UO,L, T0,L2", uozxg'. U205L;' 99
8p 25 -0 E, 2.96, 12 -1 67
Fluoride, F~ anl ex 25  HCl var 'k, 1.18 100
K 4.32 100, o£ 101
ap var K, 5.5, By =B 101
8p ~0  UOF, var "Ry (200,F, = (U0,R,),10.18 35
qh 20 1(RaC10,) K, 4.59, E; 3.34, X, 2.56, K, 1.36
(K, (Eh)2.94] 102
cond 25 0 aorr EE ~Lk. &k, gv other opx 103
dist  10-§0 2(NaClo,) K, 1.78(10°), 1.42(25%), 1.32(%0°) 77
25  2(NaC10,) A= 514, a'8,= -2 77
atst 25  C(NaCiOy) "k, i.32(c=2), 1.43(c=1), 1.38(0=0.5), 77
1.57(C=0.25), 1.71(C=0.05)
cfug 0-30 UO,F, var xyp 0.48(0%), 0.85(30°) 16
‘qh 20  1(Fa)Clo, K, 4.5% K, 3.3%, K 2.57, Ky 1.3% 102, 104
tK, (5%)2.93], no ev polyn opx for < 0.1-005"  of. 104
Chlerids, C1~ qh 20  1(Nacloy) X, -0.10 76
sp 20 1(NaC10,) K, -0.307 76
pol sp gl 25 0O oorr 1& Q.38 105
"dist  10-h0 2(HaCl0,) X,  -0.24(10°), -0.06(25°), 0.06(40°) 7
25  2(NaC10y) AR, = 3.8, AS; = 12 77
anl ex 25 HC1 var ev anl opx in > 0.5M - HCl 106
25 0O corr K, -0.1.°K, 0.82, K, -1.70 106,c£. 107
sp 25 -0 K 0.21 67
ap e var no ev opx : 150-fold exscaesa L~ 50
sp e, 00 ev UO,LY, UO,L,, 0,15 ' 108
Perchlorate, ClO;- ap 25 2-6 010; no ev c¢px 109
Bromide, Er~ gh 20  1(¥aCl0,) K, +0.30 76
Table VI. - Contlrued

Complexing agent

Todate, 0,

ap
8ol

gol

Mathod

Medium

25 -0
25 o.e(NHun)
60 q.z(mucl)

Log of equilibrium constant, remarkas Rafesrence
- K -0,20 67
X, -7.01, B, 2.73, 53 3.67 110
1!0-6.65, 52 2.74, flj 3.44 110

Z after Bjerrum, Sohwarsenbach, and 91llan, reference 20,

Dates which appeared in the literature prior to the middle of 1957 haa been campiled moatly

by the above authora.

The notation 1s explained following Table IIT.

Complexing agent

C2H20u

oxallc acid:HEL

C2H402
acestic acid:HE

02Hu03

giyeolie eeld:HL

C2H30201

Subfequent data has been campiled by J. Gindlep,

Table VII. Complex Frmation with Uog"‘ Ions - Organi¢ Ligands®

Methed

Pt

oat ex

cat ax

cat ex

22,050,

AgoCo0y

AECx0,

801

gol
sol

oat ex

oat ex

801

Bp gl
ap gl
sp gl
emf sp

pol

cat ex
1on ex
gl

cat ex

emf

T

25

25

20

20
20
25

25
25

20

25
RT

25
25
20

Medium PK of H I Log of equlillbrium oonstant, Reference
¥ remarics
0 eorr H,L 1.27 K, 5.82, X, 4.7%, HL : K 2.57 49
HL™ 4.29
0.16HC10;,  H,L 1.28 HL™: Ky 3.40, K, 2.56 116
HL™ 3.75
1HC10, HyL 1.28 HL™: K, 2.83, K, ~1.85 116
ZHC10, HyL 1.28 HL™: K 2.89, K, ~1.85 116
0.069 *KI'(UOE)ELE' + oL =
(U02)2L5']4.‘+2 117
0.022 *x 1.60, ¥&[(Uo )18 + I2°
’ 2 3
2(uo,L,)%711. 32 117
K[E(U02L2)2- I e (Uoz)zfig'ls--‘?fil
0.008 ¥ 0.lg 117
ver B,L 0.97 E 6.77, E, 5.23, B, 12 118
HL™ %.19 Klwo5t + AL = UoL + 21*11.60
24 2= -+
1':[11‘212 +22H2I'.' = UDELE + AF"31.68
HC10y, $1.54" X, [002*L ~(H,0)41-8.66 118
ANO;, > 1.5H" K, [uo3* L2'(l-220)3]-8.52 118
1HC10 K, 6.58 graphically, 6.%0 anmlyti-
4 1 116, af
cally, By 10.74 118
2HC10, K, 6.92 116,cf 118
=0 K 6.00, K, 5.08, 3. 44 (pre- 119
ferred value) !
0.312 Ky 2.1 1zo0 .
0.05 K[200L + Hy0, =2 (U0,L),(00)2" + 2nti-1.62 120
0.312 KI2U0,I3™ + HyOp i (U0,),(00)18™ + 28%]-3.66 120
121
1NaCloy 4 .59 K, 2.38, K, 1.98, 13 1.98 2
NaL-HL K, 2.63, K, 2.03, Ky 1.60 64
buffer
0.16({NaC1) K, 2.38, Pq €.36 122
. . 123
0.5(Nam3) 1% 1.22, B, 5.89 ,
1NaClo, 3.58 X 2.ha, K, 1.54, X 1.24 12
0.16(¥aC1) K, 2.78, K, 1.30 116
0.16-0.19 K, 2.75, K, 1.52 116
1
1NaClo, 2.66 K, 1.hg, K, 0.85, 1!3 0.51 25

a7
Table VII. - Continued

Complexing agent Method T Medlium pK of H L Log of equilibrium constant, Referance
P remarks
chlorovacetlic acid:HL sp 20 1Na0104 2.66 Kl 1.98, Ka 0.80, K, 0.37 125
C H 0N atet 25 0.45(NeCl) HLT 2.32 K 1.43 ) lee
glyolne:EL pH 1.90
C,AgON, pH 25 0.15-0.25 HL' 8.06 K, 5.15 126
glvolne amide:L
C4HgOy Bp RT ev U03*/L opx in retic 1/1 pf 3.5 127
laotio eeld:HL sp,pi RT av Uo,':,'*'/r. opx in ratio 1/1 pE 6; 128
presupposed dimerization
CH 05N diet 25 o.45(rac1) ELF 2.21 K o.67 116
serina:HL pH 2.05
CyHgOg Bp RT ey Uog"'/mu:l.a.te ofx in ratio 1/1 127
malic acid:H,L and 2/1 pH 3.5
ep,PE  RT ov U03*/malate opx in ratio 1/1 as 128
dimer poid solution; 3/3 and
3/2 pH ~8
CyFeO¢ 8D RT ov UOS*/tartrate epx in ratio 1/1, 127
tartaria acid:H L 2/1%, and 3/1 pH 3.5, 1.6
ap,pi  RT ev U05*/tartrate cpx in retic 1/1 as 128
dimer geid solutlon; 3/9 and /2
pE -8
C5HgO, gl 30 -+ 0 B.95 K, 7.74, X, 6.43 129
acetylacetone:HL. gl 10 -0 9,10 K, 7.94, 12 6.53 129
dist 25 0.1(c10;) 8.82 K, 6.8, X, 6.3 51, 111
K[005*+ 1™ + HL = voL(r) 8.7
K[D05*+ 217 + HL. ¢\ UO,L,(HL)114.8
ap 25 BtOH ‘HL : Ky 2.43 BO
CeEqOg op,pE  20-21 0.1(KaClo,) E,L ¥.07 HL™ : K 2.48 110
ascorbic acid:(HaL) pH 2-3
CgHgOy »p RT  (MaCl) ev U02¥/citrate opx in ratio 1.1
citric acld:HyL and 2/1 pH 2-6 131
pol 30 ev Uog"'/uitmte cpx in ratio 1/1
present as dimer pH 4.6 132
gp,pi AT : ev 005" /ottrate opx in retio 3/3
and 3/2 pH B 128
ap,pi ¥ var A3 K, 3.165 pE 4-7 ' 133
cond ev UOZHEL” & U0,IE™ + BY pi 3.6
av Uog"'/citmte epx in ratio 2/3 pE T7-9
g 25 0.15(%) HL 2.9% H27: K 8.5 134
1-13L' k.3h
112" 5.62
CeigOoNy pH 25 0.15-0.25 EIY6.17 K 7.17 . 126
histidine :HL HL 9.20
073602 ap ¥ 50% EtoH K, 1.81 urenyl acetate, 135
salicylaldehyds :HL acetlic acid present, pH 3
ver Bo 2.63 urenyl nitrate, pH 5
C:..’,J-ISO3 =p I'.I. 13. 4 136
sallcylic acld:H,L dist 25 0.1{NaC10,) H,L 2.82 HL™: K 2.2 138
HL™ 13 -X[003% + HL™ + OB @ U0,{HL) (0H)112.1
Table VII,- Contilnued

Complexing agent Method T Medium pX of HpL Log of equilibrium conastant, Refarenca
remarks

c.THEo4 gl 30 50% dioxan 9.40 K 10.1, x2 7.3 139
koJle acild:HL
Cg06S ep 25 =0.015 K L™ 2.86  HLZ": K, 3.89 130
5-gulfosalicylic
acid:HaL
071-:.?.02}: D 8.09 K, 6.40, X, L.g7 14
salicylamide :HL
CoHy10,N, pH 25 0.15-0.25 HL?* 5.38 K 5.76 126
histidine methyl 't 7.93
eater:L
CgHeON, gl 20 50% aloxan HL' 1.77 K, .68, K, 7.16 142
8-hydroxycinnoline :HL 0.3 NaClOu HL B.84
CqHEON, gl 20 50f dioxan EL' <2 X, 8.4, K, 7.51 142
5=hydroxyquinoxaline:HL 0.3 Na.C104 HL 9.29
CgTeON, gl 20 50% dloxan H2L+ 3.30 X, 8.99, K, 7.70 142
8-hydroxyqulnagoline:HL 0.3 Na.Cth_ HL 9.59
CaHgOs dist 25 0.1(NaC10y) 3.69 1c[uo§,+ + 17 + OE" &= Uo,(L)(0H)111.9 138
methaxybenzolio acid:HL
CgtON gl 20 50% dloxan H2L+ 4.4 K| 11.25, K, 9.6% 1y
8-hydro inolire 0.3 NaC10, KL 10.80

(oxine) :HL dist 25 0.1 fq 23.76 143
CgHgON, gl 20 50% dloxan 32L+ 2.59 K; 9.00, K, 7.30 132
B-hydroxy-4-methyleinnoline:HL. 0.3 NaCl0, HL 9.00
CgH, 0y NS PR, 8p 25 0.1 KNog HyL 3.84 K, 8.52, K, 7.16 14
8-hydroxyquinoline-5-sulphonic acid:H,L HL™ B.35 K[UOQ(OH)LE- + 5 - UozLa"] 6.68

K[(er(OH)La)g' + i g 200,127 111.7
K[200,(0H)L;" (UOE(OH)Lz)g'Jl.T

€y gHgOR g1 20 50% dloxan H,L' 5.01 X, ~9.4, K, -8 142
8-hydroxy-2-methylquinoline:HL 0.3 Na.Clou_ HL 11.01
C1 oHgON gl 20 50% dloxan I-I2L+ L.71 K 11.25, 9.52 12
8-hydroxy-5-methylquinoline:HL 0.3 NaCloq_ HL 11.11
01 gHgON g1 20 50% dioxen H,L® 4.76 K, 10.89, K, 9.26 142
6-hydroxy-5-methylquinolire:HL 0.3 NaC10, HL 10.71
0, gHlgON gl 20 50% dioxan H2L+ k.26 K 11.28, K, 9.78 142
B-hydroxy-T7-methylquinoline:HIL. 0.3 NaCqu_ HL 11.31
C1 ot o0, gl 20 50% dloxan H L' 3.15 K, 8.77, K, 7.33 142
8-hydroxy-2:L-dimethylquinazoline :HL HL 10.1%
€y gFy 50N gl 20 S5of dioxan H,LY 5.4 K 10.10, X, B8.20 142
1:2:3:4-tetravydro-9-hydroxy-

acrldine :HL 0.3 NnClOu HL 11.39
¢, oHy 5CN, g1 20 50% diaxan EL" < 1 K, 8.53, X, 7.85 142
8-hydroxy-4-methyl-2-

phernylquinagoline :HL 0.3 NaGlOu HL 11.33
CeaH23°9N3 ap 25 var (mh)z}fl' “(%): 5 L.77 145

ammonlum a.urintrio.a.rboxi’late
(eluminon reagent) :(N‘Eu)HEL

 

-2 pfter Bjerrum, S&hwarzenha.ch, and 311ltn, reference 20.

Date which appeared in the literature prior to 1956 has been compiled moatly by the
above authors. mbsequént data has been complled by J. Gindler.

The notatlon l1m expl_a.j.nad following Tablee TII and V.

29
atated that a complex 18 formed wlth undlasoclated oxalic acld,

Heceou. In more recent work, Moskvlin and Zakharovallg conclude

that complexes may be formed with both 02042 and Hcaou' 1ons and
that the amount of each formed will depend upon its stabllity and
the conditions of the experiment.

The compoaltlon of a complex 1s sometimes declded upon by
comparison with complexee having simllar liganda. For example,

I-Ic‘ilfc-BeJ:-ne.t'}:r'om-,;"--zg in her work with salicylic acld, H,A, and

2
methoxybenzolec acld, HB, wase able to show that complexes of the
type U0, (H,A) (HY) , UO2(H2A)(H+) _5» and U02(HB)(H+) _p Were
formed in the agqueous phase. (The negatlve subscripts indicate
that H™ was eliminated in the formation of the complex;) The
experimental data for methoxybenzolc acld was approximated by
asguming only the complex UOE(B)(OH). For sallcylic acid, the
complexes U02(HA)+ corresponding to U02(H2A)(H+)_1 and
UOE(HA)(OH) or UO,A corresponding to UOE(HEA)(H"')_2 were postulated.
It was not poeslble to distingulsh between the latter two.
However, from Cthe simllarity of the distribution curves found for the
two aclda, it was suggested that the sallcylate complexes are
formed by HA™ ligands.

A vast amount of work other than that listed in Table VII
has been done on the preparation and identificatlion of organic
uranyl complexes. Some of the complexing agenta studled recently
include dilhydroxy-malelc acid,lflg trioae-reductonelig#lég
(enoltartroneldehyde), reductic acld=2t (eyclopentene-2-dlol-2,3-
one-1), complexoneslfigiléi (1iminodlacetic acid and its derivatives),
xanthates and dithiocarbamates,lé& 1:>I-0'|:opor-phyr-:l.n,l—i2 o-cresotic
acid,léé miricitrine,lEI dialkylphosphoric acids,lég&lég and
pyrazolone derivat-ives.lég
3. Non-aqueous solutlions of uranium.

Solubility studles. A number of uranium salts are

 

soluble in orgenlc solvents. Uranyl nitrate 1s the'notable

example. Ag the hexahydrate, this salt 1s soluble in a

30
varlety of ethers, eaters, ketones, alcohola, aldehydes,

and substituted hydrocarbons.161'16 The followlng generall-

zatlons have been madeléé concerning 1ts solution 1n organlc

gsclvents:

(1) In a given homologous series, the solubllity decreases

as the molecular weight of the solvent -il.ncreaaea.161 16

(2) Solutions occur~w1thtl§2

Ethers: aliphsatlic
ethylene glycol
dlethylene glycol
saturated cyclie

Acetals
Ketones: aliphatic

aromatlc

alicyclic

mixed aliphatlic-aromatic
Alcohols: aliphatlc

allecycllce
Varlious esters

Nitrogen-contalning solvents: niltriles
aromatlc basea

(3) Solutione do not occur with:
Hydrocarbonsléi

Ethers:léé aromatlc
unsaturated cyclic

Sulfur-conteining solvents.lég

Glueckaufiéé has made the phenomenologlcal obeervation
that a plot of the solubllity of uranyl nltrate against the
oxygen-to-carbon ratio 1n the solvent molecule results 1n
a silngle curve for alcohols and ethers; but in a double curve
for ketones; one for symmetrlic and one for asymmetrlic ketones.

Tonization. The quantity (An/constant)* hae been used
by McKay and co-workersléz:lég to estlmate the degree of

lonization of uranyl salte 1n organlc sclvents. By this

criterion, uranyl nitrate 1n concentrations of 0.01 - 1M 1s

*
A = molar conductlvity. T = vlacoslty. The constant 60 1s
used for 1:1 - electrolytes; 120 for 1:2 - electrolytes.

31
substantially unionized 1n water-saturated solutlons of ethers,
ketones, alcoholes and tributyl phosphate? Only 1n saturated
diethyl cellosolve and 1n 1sobutyl alcochol is ilonizatlon 1n
excess of 10%. The large amount of water whilch dlssolves in
the latter solvent may account for this.

In tributyl phosphate, the dissociation of uranyl nitrate
increases as 1ts concentratlon 1n the organlc phase 1s de-
creased. At 10'5E-the salt 1s approximately 40 per cent
dissociated,lég i.e., An/120 = 0.4 Uranyl perchlorate at
this concentration is almost completely ionized.lég Lon
associatlon occurs at higher concentratibns, but elgnificaently
less than for uranyl nitrate. At approxlmately 0.01M, the
assoclation of uranyl perchlorate 1s maximum (An/120 has a
minimum value of —0.1) in the concentration range 107 to 1M,
The lonizatlion of this salt may well be assoclated wlth the
amount of water contalned withlin the tributyl phosphate since
the electrical conductivity 1s decreased by dehydration.lég

Jezowska - Trzeblatowskae and co-wc':rkersEg have measured
the molar conductivity of uranyl nitrate in organlc solvents
that contaln only water from the hexahydrated uranyl saltf*
The conductlvlity was found to be low and to decrease wilth a
decrease of the dlelectric constant of the solvent.

Conductivity measurements of UCl4 iIn methyl aleohol
indicated the salt to be somewhat dissociated.gg- The
‘dissociation was found to increase on additlon of tributyl
phosphate.

Kaplan, Hildebrandt, and Ader=lC have classified into

Solvents tested other than tributyl phosphate: diethyl
ether, dlethyl cellosolve, dlibutyl carbitol, methylisobutyl

-ketone, 1gobutyl alcohol, and lsocamyl alcohol.

**¥30lvents tested: methyl alcohol, ethyl alcochol, acetone,
ethyl-methyl ketone, methyl 1lsobutyl ketone, acetylacetone,
stannous chleoride 1n acetone.

32
types the abaorptlon spectra of uranyl nitrate in a number of
*

solvents and solvent mlxtures. Differences between types

were attrlibuted to a serles of hydrated and solvated nltrate

complexes, UOZY , UO N0, UOL(NO The

2773 ° 3)2’ 3)3-'

relative concentrations of the complexea depend upon the nature

and er(No

of the solvent, its water content, and the concentration of
added nitrates. It 18 1lnteresting to note that the absorp-
tion Bpectrum of uranyl nitrate in tributyl phosphate (0.016 -
1.6 M) is characteristic of the complex UOE(NOB)Q and indicates
1lttle ionizationjlég A simllar spectrum 18 glven by uranyl
nitrate 1n methyl 1sobutyl ketone (0.02 fl)fzg Uranyl perchlor-
ate 1n methyl 1sobutyl ketone (0.02 M), however, exhibite a

spectrum characterigtic of the uranyl ion, UO‘%+ . These
results appear to be 1n general agreement wlth those obtalned
through conductivity-viscoslty measurements.léz:lég

The trinltratouranyl complex UOE(NO3)3- hes been studled
by a number of workersZgiIgi&Zl;lZi It 18 formed by the
additlion of a second soluble nitrate to a solutilon of uranyl
nitrate in a non-aqueous solvent such as anhydrous nitrilc
&s.ciLd_,-:I—'Zl dinltrogen tetroxide,llg acetone,zg---’—Ig methyl
l1sobutyl ketone,Ig dibutyl ether,lZi etc. Kaplan and co-
workeraIg also report that the complex 1s formed in 16 M
nitric gcid, but that 1td formation 1s far from complete.
The negative character of the complex has been demonstrated
by electrolytlc transference exper-iment:st.—'?-g Its composition
has been deduced by the 1lsolation of solld compounds from
golutlons of the type descrlbed abovez-g--’—-JlZl’—Ezg end by the
gimilarity of the abeorption spectrum of such solutlions with

that of erystalline cesalum uranyl nitrate,CsUOz(N03)31§112

*Spectra clasgifled: uranyl .nltrate in water, acetone-water,
dioxane-water, n-propanol-watér, ethanol, chloroform + 0.7%
ethanol, pyridlne, acetlc acld, ethylacetate, tetraethylene
glycol dlbutyl ether, nitroethane, methyl isobutyl ketone,
cyclohexanone; uranyl perchlorate 1n methyl 1sobutyl ketone.

33
The stahllity of the complex depends upon the nature of the
essociated cation as well as the nature of the solvent and
the prepence of water 1n the solvent. The general order of
the solvents with respect to stabillity of the trinitrate
complex 1s: ketone > ether > alcohol > water£1§

The formatlion of chlorouranyl complexes 1n neon-&queous
solvents has been reported by Vdovenko, Lipovskii, and
NikitinssC® The complexes U0201+, U0,CL,, U02013‘ were
formed by the additlion of-pyridine hydrochloride or hydro-
xylamine hydrochlorlide to a solution of uranyl perchlorate
or uranyl chlorlde in dcetone. The Btablllity of the tri-
chlorouranyl complex wae found to be dependent upon the
amount of water present 1n the solvent. A compound wae
separated and ldentifled es (C5H5NH)2U02014.

Hydration. In partltion studles of uranyl nitrate
between aqueous solutlion and organilc solvent (alcohols,
eatera, ethers and ketones) 1t 18 generally found that the
water content of the organlc phase lncreases with uranyl

*
nitrate concentration.16 167

For alcohols, the relation
between the water content Mw and uranyl nltrate concentration
Mu appears to be a complex function.** For esters, ethers,
and ketones the relation 1s linear except posslbly at high
values of Mu. This reletlon may be expressed

M, o= Mo+ hM .
The quantitles are expressed in terms of molallties of the

dry solvent. M; 18 the solubillity of water in the pure

gsolvent; h 1is a conatant. The siope of the line, h, repre-

*

The water content of alcohole may decrease Inltlally as the
uranyl E%trate concentration is 1ncreased from O to 0.1-0.2
molal,1067 .

* % .

" Katzin and Sulliva.nz‘-§1 report a linear relation.bfg een
M _and M; for lsobutyl alcohol. McKay and Mathleso point
oUt that If the deta of Katzin and Sulllvan at low M, are glven
significance, then & more compllicated relationshlp between the
two quantltles exlets.

34
sents the degree of hydration. For many of the linear

solventa h is very nearly 4.0.16. 167 This hae been inter-

oreted by Katzin®l* to mean that the specles U0, (H#,0),, (NO

is extracted. McKay,lZé however, conslders thls to be a

3)2

nean hydration number; that a serles of hydrates are presént
ranging from the dl- to the hexahydrate; that these hydrates
are 1n equllibrlum wlith each other-and'are of comparable
stabillty. The latter view ls supported by 1isoplestic
neasurements.izg

Infrared measurements on ethereal and ketonle solutions*
of uranyl nitrate, lndicate two moleculea of water to be
strongly bound to the uranyl nlitrate and the remainihg
water molecules to be more weakly bound.lZZiEIQ

The extraction of uranyl nltrate from an agqueous system
into tributyl phosphate (TBP) causes the displacement of

water from the organle phase.lég The displacement 13 roughly

linear with h being -2.l§§ This 1e 1n agreement with the

formulae TBP'H,O and UOE(NO3)2'2TBP.E§§ Uranyl perchlorate,
however, apparently does carry some water into tributyl
phosphate.lég Whether thls water 1ip assoclated with free
uranyl lone or unionized U02(0104)2 1s undetermined.
Solvation. The isolatlon of solvated uranium salts,
in particular uranyl nitrate,ls reported 1n the 1iterature.§9
163,180-182 In phase studies of ternary syetema: uranyl
nitrate, water, organic splvent, Katzln and Sullivanléi_
have concluded that uranyl- nitrate 1n aqueous solution is
largely hexasolvated, subject to the sctlivity. As organiec
melecules are dissolved, 2,3,4 and perhaps 6 water molecules
may be displeced, depending upon the electron-donor capabllities
of the orgenlc moleculea. The total solvation 1e a functlon

of the actlvity levels of the water and organlc molecules,

 

* Solvente studled: diethyl ether, acetone, methylethyl ketone.

35
If a particular confilguration is stable enough, 1t may survive
as a crystalllne sollid. The particular stabllity of the final
two water molecules 18 in agreemept with the resulta of Ryskin
and co-workerslzz&lzg obtalned through infrared abporptlon
meapurements. The abllity of solvents to dlsplace water 1s
in the order: alcohols > ethers > ketonee.lgi This general
order of solvate stablllty 1s confirmed by heat of soletion
measurements.léfi It 18 in gsgreement also wlth the order of
base (electron-donor) strengths of the solvents determined by
other means.léé&lgi' Methyl isobutyl ketone 18 anomalous 1n
that 1t behaves stronger toward uranyl nltrate than its base
strength would indicate.83:183 Priputyl phosphate, according
to heat measurements, competes with water almost as well as
dlethyl ether and 1sobutyl a100h01el§§

The order of solvents with respect to solvate stabllity
1s opposite to that with respect to the stability of the
ftrinltratouranyl complex. Thls Buggests a competitlion be-~
tween solvent molecule and nitrate lon for coordlnatlon

wlth the uranyl 1on.lI;

Feder, Ross and V‘cvgellgi have studled the stabllity of
molecular addltion compounds wlth uranyl nltrate. The com-
pounds were prepared by shaking uranyl nitrate dehydrate wlth
varioug addenda in an lnert solvent: benzene and/or 1,2-
dlchlorcethane. 1l:1 moiecular addlition compounds were found
with uranyl nitrate and ethyl aleohol, n-dodecyl alcohol,
tetrahydrofuran, propylene oxide, mesltyl oxide, tributyl
phoaphate, and N,N-dibutylacetamide. 1:2 compounds were
observaed with uranyl nitrate and acetone, methyl lsobutyl
ketone, cyclohexanoné, ethjl acetate, 2,4-dimethyltetrahydro-
thiopene 1,1-dloxide, B-chloroethylacetate, ethyl chloroacetate,
ethyl cyanoacetate, dlethyl ether, allyl alcohol, ethylene
chlorohydrin, and acetonltrile. Formation constants were

determined from changes 1n the aolubllity of urenyl nitrate.

36
It was shown that the stabllity of the addltlion molecules,
for those addenda having simllar functional groups, was 1in
agreement w%th the base strength of the addend; l.e., the

more s8table the molecule, the greater the base atréngth

df the addend.

The average number of solvate molecules n assoclated
wlth uranyl nitrate 1n 1ts partition between water and
varicus organlec Bolvents* has been Btudled by McKaylgéngg
and co-workere. The value of n was found to vary wlth the
uranyl nitrate concentration of the organic phase. For
most of the solventa studled, n varled between 1 and 4.
For cyclohexane, considerably larger velues were found for
low uranyl nltrate concentratlions.

A saturated Bolution of uranyl nitrate hexahydrate
i1n trlbutyl phosphate corresponds closely to the unhydrated
3)2'2TBP.£§-§J—-]-'gI Evldence for

the exlstence of the Blngle specles 15:168 18

disolvated compound UOE(NO

(1) The solubility is not appreclably temperature
dependent over the range 0-50°C.

(2) On freezing and rewarming a saturated solutlon, a
sharp melting-point of -6.0 = 0.5°C 1g observed.

(3) The mole ratio of uranyl nitrate to TBP approaches
the value 1:2 asymptotically under a varlety of condltions.

(1) The effect of inert dlluents for the TBP on uranyl
nitrate partltion coefficlents supports a 1:2 formula? l.e.,
the partltion coefflclent of uranyl nitrate varles as the
square of the TBP concentration. |

The experimentel conditlionsa under whlch Feder, Rosa

184

and Vogel—— reported the formation of UOQ(NO *TBP were

32
congiderably different from those of Healy and McKay.lég

»*

Organlec solvents studled: diethyl ether, diisopropyl ether,
dlethyl cellosolve, dlbutyl cellosolve, dlbutyl carbitol,
penta-ether, lsoamylacetate, methyl 1sobutyl ketone, cyclo-
hexanone,

37
Jezowska - Trzeblatowska, 33_5129 report that the
absorptlon spectrum of uranyl nitrate 1n tributyl phosphate
glves no 1ndication of the formatlon of a stable complex.
Attempts to ldentlfy a complex specles in the concentration
range 0.02-0.06M were unsuccessful.

Heaford and McKay-1§2 report evidence for the formatilon
of U02(CIM)232TBP under certain conditions. From & 10.3M
aqueoul perchloric acld solutlon, the partitlon coefficlent
of uranium varles as the square of the TBP concentration 1n
benzene. Under other conditlions, other solvates may be formed.
Jezowska - Trzeblatowska, gg_glgg report the formation of a
1:1 complex between U014 and TBP in methyl alecchol.

Tributyl phoBphlne oxide, 1like tributyl phosphate,
forms an anhydrous disolvate wlth uranyl nitrate.lgl Healy
and Kennedylgg report & number of other neutral organophoa-
phorus solvents which form solvates with uranyl nitrate.
Most, but not all, of the solvates reported are anhydrous.
A1l of the solvents extract uranium from aqueous solutlon
in proportlion to the square of the solvent concentratlon
(in benzene). However, not &ll solutions of the soclvent in
benzene and saturated in uranyl nitrate give mole ratios of
solvent to uranium of 2:1. For the two diphosphanates and
one pyrophosphate studled the mole ratlos were l1l:1. This
may be indlcatlve of chelation or polymer formation. The
mole ratio 1n triphenyl phosphate wag ~22:1. This 18
probably the result of the solvent belng unfible to.displace
water from the coordination sphere of the uranyl 1on.l§§

Solvate formatlon. between uranyl salts and acld organo-
phosphorug compounds, eg. mono- and dl-alkyl phosphorlc acids
hes been the subJect of Bome investigation.ao 158,1 188
1:1 complexea between uranyl nitrate and mono- and di-butyl

phosphate and mono- and dl-amyl phosphate 1n ethyl alcohol

have been reported.ég In explanation of diatributlon data

38
in conjunctlon with 1soplestic and vliscoslty measurements,
| Baea, Zlngaro and Colemanlég have hypotheslzed that uranlum

(VI) 18 extracted from aqueous perchlorate solutlone into
n-hexane solutions of di-{2-ethylhexyl)-phosphate, HL, as
the specles U02(HL)2L2. As the uranium concentration of
the organic phase 1s Increased, there 1s strong evidence
that polymerlzation occurs.lfig Similar-conclusions have been
made by Dyrssenlig on the basls of the distribution of uranlum
(VI) between agueous perchlorate solutilon and dibutyl phos-
phate, HK, in chloroform. In hexone, the species UOE(HK)EK2

and U02K2 have been 1dent1fied.l§2 The extraction of
uranium (VI) by dibutyl phosphate from aqueous niltrate
solutions into benzene has been studled by Healy and Kennedy.-]:gg
In addiflion to the specilesa UOE(HK)2K2, the polyuranyl specles
(UOEKE)erK and the nitrated speciles UOE(NO3)2 + 2HK have been
postulated to explaln the shape of the extraction curve as a
function of nitric acid concentration.

It has been postulated that the formatlon of mixed sol-

vates or solvated chelates enhances the extractlon of uranium
into certaln solvent mixtures. These systems are dlscussed

in a lzfer section on solvent extraction.

IV-D Separation of Uranium

 

A number of review articles have been written on the analyti-
cal chemistry of u::-:amium.é-f-flai-'-iggz-g-99 These, together with many
texts on chemlcal analysels (see, for example, references 201-209),
gerve well a3 guldes to the separatlon and purlfication of the ele-
ment. More specislized surveys have been made by Hechfiglg on the
quantitative micro-analjsis of uranium-bearing minerals, and
by Law:r*c»lwEsbcfll.g-ll on separation processes for the recovery of
nuclear fuels.

Two general technlques are avallable for the separatlon of

uranium. {1) Uranlum 18 removed from solution in the presence

39
of contamlnants by preclpltation, solvent -extractlon or some
alternative method. (2) Uranium 18 kept 1n solutlon and contam-
inants are removed. These techniquee are facllitated by the
fact that uranium i1s reasonably stable 1n two oxidation states,
(Iv) and (VI), and that complex formatlon may be effected to
prevent the removal of elther uranium or contaminant from solutilon.
In the fellowlng paragraphs, the Beparatlon of uranium by
precipitation, solvent extraction, and ion exchange are deacribed
1n zome detall. Reference 18 made also to other methods of separa-
tion: chromatography, electrodeposition, volatilizatlon and

pyrometéllurgy.

1. Precipitation. In classical syetems of analysis, uranlum
18 & member of the third group of elements.* That 1s,
1t 18 not precilpitated by hydrochloric acld or by hydrogen
sulfide in an acidiec solutdon, but 1t 18 preclpitated by
ammonium hydroxide or ammonlum sulfide (see references 204,
206, 208, 213). Unfortunately, for the separation of
uranlum, many other elements also are preclpltated by the
same reagents. However, there exlate a large number of
reagents capable of preclpltating uranlum over a wlde range
of pH. These, combined wlth Judiclous use of the two oxidation
states and/or the complexing abiiity of uranium, mey be used
to provlide reasonably pure uranium deposita.

Preciplitants. With the advent of nuclear energy as a
source of power, numerous preclpltants have been investl-
gated 1n an effort to find one speciflc for the separation
and/or determination of uranium. None have been found to

date. Waregli hag summarlized early work using organlc rea-

* ~

In the system outllined by Noyes and Bray 292 yranium is
precipltated 1n the sixth group wlth ammonium hydroxide and
18 converted to the sulfide wlith hydrogen sulflde. In the
system of West and Parks,2l?2 uranium 18 precipltated in the
fifth (basic benzoate)group.

40
gents a8 preclplitants. Shegli and Baileygié have investigated

aome of the more promlslng onea. Rodden and Warf-ii have
discussed the use of many reagents, both inorganic and organic,
and have descrilbed procedurea for the use of many of them. The
latter preclpitants, 1.e., those for which proceduree have been
given by Rodden and Wa::-f,--?fi are denoted by a dagger (t) 1n the

foliowing discusslon.

 

Inorganlic preclpltants. The reagents are 1isted-alpha-

 

betleally according to anlon.

Arsenates.* Argenlce acld and ammonlium, sodium and
potasslium arsenate preclpltate uranium as uranyl metal arsenate.
Silver, tltanium, zirzonlum, thorlum and lead interfere.
Separation 1s made from the alkall metals, alkallne earthes,
aluminum, 1ron (TI), and rare earths, including trivalent
cer:l.um.ii

Carbonates.G’63;201,204,206:217-224

 

Precipitation of
uranium with ammonium, sodlum, or potasslum carbonates 18 not
very satlsfactory. Highly soluble carbonate-uranyl complexes
are formed. Under proper conditions,the metal uranyl -tricarbon=
ate saltse MuUOéC03§are formed. The solubllitles of the
respective ammonium, sodium, and potasslum salts Iin water
are 50(15°c),2—2£ 150(RT),@5 and 71(18"0)2—1§ grame per
1liter. The solubllity of the potassium salt in a 50% solu-
tion of potasslium carbonate 1s 0.200 grams per liter.ggl
The solubllity of the sodlum salt 1ls decreased by lncreaslng
temperature and by lncreaslng sodlum salt coneentration,ggi
Te¥ak2il has studled the precipltetion of uranium by
ammonium and sodium carbonate. From a 0.043N uranyl nitrate
solution, preclpltetion was obBerved to be maxlmum 1n the
region of 0.1N precipitant concentration. Two maxima were
observed for ammonlum carbonate; one for sodium carbonate.

Above and below these falrly narrow reglons of precifiitant

concentration, uranium enters into solutilon.

4]
The uranium (IV) salt, NaGU(CO3)5 * 11H,0 1s preclpltated
from reduced carbonate solutions at hlgh uranlum and carbonate
concentrations.éé

Barium uranyl carbonate salts are reported to be very
1|.m5=.olub1e.-6---:'1 However, 1ln the presence of carbonate solutions
the alkallne earth salts are unstable according to fthe

reaction,éfl

MaU0,(C05) 5 (5 + 2co§' = [002(003)3]4‘ + MCOZ (..
Tezakgll has found the preclpltation of uranium to be nearly
complete when the barium:uranium ratio is greater than 600
and the excess carbonate 1s leas than four times the barium
concentratlion.

A suspenslon of barium carbonate may be used to pre-
clpltate uraniumrgfliggé Ammonium salts 1nterfere. A
suspension of baslc¢ zin¢ carbonate may be simllarly used.éfliggz
Iron, alumlnum and thorium also precipiltate.

Cyanides. Alkall cyanides form a yellow preclpltate
when added_to uranyl solutiona.éi

Ferrocxanides.T The addltlon of potassium ferrocyanide
to a uranyl salt solution causes the formation of a deep-
red preclpltate or suspension, depending upon the concentratlon
of uranium. The reaction 18 used much in qualitative anal-
ysils for the identlfication of uranium. However, it 1s

little used for quantitatiye separation. The separation 1s

poor and there are many :I.n‘l:er-ii'el:'encses.-ai Separation can be

made from beryllium in a weakly acldlc sulfate solution.22S

Fluorides. ' Hydrogen fluorilde preclpitates uranium (IV)
as the tetrafluoride. The preclpitate is gelatlnous and
difflicult to filter.ifi Separation 1s made from metals com-
plexed by fluoride ilons, eg., tantalum and zirconlum. Uran-
1um may be reduced to the (IV)-state with zinec in a solution

made sllightiy acidic.}—9—6—

42
The double fluorldes, eg., NaUFS, are pparingly soluble
even 1ln the presence of atrong acids.igé Separatlon can be
made under these condltions from Mo, Ti, Ni, Co, Mn, Cu, Fe
(1I), and Vv (III). Alumlnum preclpitates as the double salt,
Na,AlF¢. Iron (IIT) precilpltates in part. Reductlon to
uranlum (IV) may be done 1n the presence of fluorldes wlth
tron (Ir).220:222 Rongalite (N H,S,0, * 2CH,0 - 4H,0) also
hasa been used to effect-reduction.gig _

Hydroxides. The additiofi of a metal hydroxide to a
seolution of uranyl ealts results 1n the formatlon of the
metal uranate. It has commonly been assumed that the metal
diurante, M2U207, 1s precipltated by ammonlum, sodium, or
potasasium hydroxlde. However, experimentsl evlidence 1ndi-
cates that the composltlon of the preclpltate depends upon
the coridltlons which exist during precipltation and upon
the subsequent treatment, such as washlng, whlch 1t re-
ceives.23:7237

Armonlum hydroxideT preclpltates uranlum quantitatively
atpH 4 or grea’cer.-a-lt The presence of ammonium salts and
macerated fllter paper facllitate precipltation. Separation
1s mede from alkall meftale, alkallne eartha, and cations '
forming ammonla complexee. Repeated precipltations may be
necessary to glve sufficlent separation. Phosphorus, vana-
dium, ellicon, boron, alumlinum, lron and other elements of
the ammonium hydroxide analytical group alsoc are precipitated.glg—
Complexing agents: carbonate, oxalate, cltrate, tartrate,
fluoride, etec., interfere.

Preclpitation with alkall metal hydroxldes is slmllar to
that with ammonlum hydroxlde. Uranlum may be preclpltated
In the presence of carbonate wlth sodium or potasslum hydroxide
of sufficlent concentratlon. Carbonate lon lnterference may

be removed by heating.

43
Pale green gelatlinous UO2 . H20 18 precipltated from
uranium (IV) solutions by ammonium and alkall metal hydroxides.
Todates.  Uranium (IV) 18 precipltated from an acid

solutlon by potassium 1oda.te.gi Separatlion can be mede from

copper, molybdenum, and reduced vanad.1.1.:.111.g-3-g Aluminum 1n
amounts up to fifty times that of uranium does not 1lnterfere.
Larger amounts of aluminum and divalent iron 1n any concen-
tration cause lncomplete precipltation. Titanlum, zlrconlum,
cerlum (IV), and thorium preclpitate with 1odate. 32

Mercuric oxide. Uranium 1 preclplitated when a
suspension of mercurlc oxide is bolled 1n an aqueous solution
contalning ammonium chlo::-ide.ii Separatlon 1s made from
alkell metals and alkelline eartha. Hydroxy aclds 1nterfere.

Peroxides.* Hydrogen peroxide preciplitates uranium
peroxlde, U04 . xHEO, from sllghtly acldic solutions. The
reaction occurs in the pH range 0.5-3.5. The optimum range
1s 2.0-2.5, Hydrogen lons released wlth the formatlon of
uranium peroxlde are neutrallzed with ammonia or ammonium
acetate. Complete preclpltation requires an excess of
hydrogen peroxlide. Quantlitative separatlon may be effected
by freezing the solutlon, allowling 1t to ptand, and filtering
at 2°C. The separation from most elements 18 good slnce 1t
18 done from an acldilc aolution.ii&g}g Plutonium, thorium,
hafnium, zlreconlum, and vanadlium also preclpltate. Iron
dnterferes by catalytlecally decomposing hydrogen peroxide.
Small quantities of 1ron may be complexed wlth acetlc, lactle,
or malonle acid. Low ylelds may result from the use of
malonic acld. Ammorium, pofasslum, and alkaline earths re-
tard the rate of precipltation. Complexlhg lons such as
oxalate, tartrate,lsulfate, and fluoride 1n large quantitles,

also interfere. Fluorlde lon may be camplexed with aluml-
num . 2328

44

19
Phosphates. Phoephorlc acld and sodlum monohydrogen
phosphate,precipitate.anHPou from uranyl solutions. Uranyl
ammonium phosphgte, UO,NH),POy, 1s precipitated by (1~11+14)2HP01l
or NaeHPou in the presence of ammonlium acetate.* Preciplitation
‘is made in the pH range 1.2-2.3, 1.7 belng optimum. It ie
not very eelectlive. Zirconlum, bilemith, and thorlium pre-
cipltate under similar conditlons. Alksll metals are retalned.
Separatlon 18 made from vanadlum. Both UOéHPOu and UOQNH4P04
are poluble in mineral acida.3E

Phosphate precipitation of uranium (IV) 1s more selec-
tlve. 1t 1s made from dllute hydrochlorlec or perchloric
acld solutlons. Separatlion is made from manganese, lron,
vanadlum and most other elements. Zlrconlum, thorium, and,
to a emaller extent, titanium and tin precipitate.lgé:lg&
Aluminum interferes by the formatlon of soluble complexes with
uranium and phoaphate 1ons.22 With sulfate and aluminum
present, uranium l1e precipltated in a narrow pH-range around
one. At higher pH, the soluble aluminum-uranlium-phosphate
complex 18 formed; at lower pH, the soluble uranium-sulfate
complex. Chromlum in excees of 0.2 gram per 100 milliters
ceueeg Incomplete precipita.t—ion.lgé Large amounts of fluorlde
ion prevent precipitation.lgé

Sodlum hexametephosphate [(NaP03)6] also precipltates
uranium (IV) from acid solutiona.gfig Adherence to fsirly
stringent condltlone allows for complete preciplitation., A
3N. B0, solution of uranium (IV) 1s heated to 60-70°C. If
more than 2 mg. of uranium are to be precipita%ed, a freshly
prepared 2% hexametaphosphate solution 1s added until its
concentration in the precipltating medium 1s 0.30-0.35 per
 cent. To preclpltate smaller amounts of uranium, 'a 0.5
per cent solution of thorium chloride ls added as carrier

and the hexametaphoephete added until it 1s in excess 25 per

cent with respect to the thorium, 1.e., molar ratlo of Th:PO3

45
is 1:5. Coagulation 1s improved by heating in a water=-bath
for ten to fifteen mlnutes after precipitatlion. Under these
conditlons separation 1s made from V (1) and (IV), Fe, du,
and other di- and tri-valent metals. Incomplete precipitation
occurse wlth 1Increased or decreased acldlty -- probably because
of enhanced solubllity of the compound and complex formation,
respectively. Precipltation from sulfurlc acld 1s incomplete
Pecause of urafiium-sulfate ¢omplex formation. Under certaln
conditions both uranium (IV) and (VI) form complexes with
hexametaphosphate.

Hypophosphoric -acid (H4P206), eodlum dihydrogen hypo-
2P207)
precipitate uranium (IV) from acld solutions.' Other

phosphate (Na2H2P206), and sodium pyrophoaphate (Na

tetrevalent metals, T1, Zr, and Th, also preclpltate. Separa-
tion is made from uranium (VI) and trivalent metals-in-general.ifl

Phosphites. Sodium hypophosphite (NaHePOE) and ammonium
thiosulfate or sulfurous acld preclpitate uranium from a
bolling, dilute acid solut-ion.gfll Zirconium and tltanium
precipitate under similar condltlonse. These elemente may
be separated prior to uranlum by bolling with sodium hypo-
sulfite alone. Elements forming acld-~lnsoluble sulfides
are removed wlth hydrogen sulfide before adding sodium hypo-
~phosphlte and ammonium thilosulfate.

Sulfetes. Uranium (IV) sulfate 1s practically insoluble
in 47 per cent perchlorilc acid. Precipltation is made 1n a
sulfuric acid medium. Uranium is reduced on a mercury cathode
and concentrated perchloric acid 18 then added.

Sulfldes. Ammonlum sulfidef or polysulfide precipitates
brown, amorphous uranyl sulfide. Numerous other elemente are
preclpltated under similar cc::onclit:iona.?-ii Complexing agente
such as carbonate, pyrophosphate, and citrate 1nterfere.3fi
Uranium (IV) salts are precipiltated as U0, * H,0 by ammonium

sulfide.222

46
Hydrogen sulfide bubbled through a nearly neutral solu-
tion of uranyl salts contalning hexamethylene tetramine pre-
cipltates uranium 1n a readily fllterable, crystelline form
of "uranium red."’ Separation 1s made from alkall metals end
alkallne ea.r-th-s.ifl--’-lgz

Vanadates. Ammonlum metavanadate firecipitates ammonlum
uranyl vanadate from uranyl soluftions buffered with ammonlum

'acetate.éfi- Uranovanadlc aclds are preclpitated at pH 2.2-

6.5.gflg Wlithin thepe limltas, the compoeltion doea not depend
upon the hydrogen lon concentration. It does depend upon the
vanadium : uranlum ratlo present'in solution. Compounds
correspondlng to the formulae

H[UOE(OH)2V03]-H20, H[UOQ(OH)(V03)2]'2H 0, and H[UOE(VO3)3]'4H20

2

have been-identified.gfig Ammonlum esalts of These aclde have

been syntheslzed 1n the presence of ammonlium chloride.gflg
Ammonilum uranyltrimetavanadete 18 the least soluble. However,
itse formatlon 18 a long processa at room temperature. Heatlng

greatly accelerates 1te rate of formatlon.

Organlc preclpltants. Organlc preclpltating reagents

 

 

are llisted alphabetically.

3-Acetyl-d-hydroxycoumarin (3-acetyl benzotetronic acild).
An alcoholle solutlon of the reagent added to a uranyl salt
solution forme & pPale yellow preclpitate insoluble 1n ethano%%i
Precipitation occurs between pH 1.5 and 7. Below pH 1.5 the
reagent precipitates. The thorium complex 1s soluble in
alcohol, but precilpitates from an agqueous solution at pH 2-4.
Lanthanum and cerium (III) do not interfere when present in
amounts ten times that of uranium. Cerlum (IV) interferes
even in small amounts.

Acradine. Uranium (IV) and (VI) are preclpltated by
the reagent With the addition of ammonium thiocyanate.gli
Iron (III), cobalt, copper, zinc, cadmlum, mercury, and bils-

mith precipltate.2it2216

47
Aldehyde ammonla precipltates an.glé

Alizarin and Allzarin Red S (sodium alizarin sulfonaete).
Uranium 1s preclplitated slowly by the reagents when the
uranyl ion concentratlon 1s less than 20 mlicrograms per
m111111ter.212

Aluminon (ammonium selt of aurintricarboxylilec acid).

The reagent precipltates both uranium (IV) and (VI) from
sulfate solutlone at pH 3_5_§l§

Amines. Ammine salts, generally of the form U02(Am1ne)2 X5,
where X is an acld radical such as acetate, chlorilde,
nitrate, etc. have been prepared from acetanilide, anti-
pyrene, bromoantipyrine, dilethylaniline, exalgin, nitroso-
antlipyrine, p-nitrosodimethylanilline, phenacetln, pyramidon,
pyrldine, qulnaldine, and quinollne. Mono-, trl- and tetra-
ammine Bglts also have been formed. The salts are generally
prepared 1ln anhydrous chloroform or amyl alcohol solutiona.
However, some of the more stable salts may be precipltated

from agqueous or alcohollc solutions;glfligii_

2-Amino pyridine precipltates UO3.glé

Ammonilum benzoate. Uranyl lon 18 precipltated by the

 

reagent from slightly acidic solutions heated to bolllng.
A 0.05 N solution of the reagent contalning about 2.5%
NHuOH 1s bolled separately and added 1ln an excess of three
to four times the uranlum present. Carbonate lon prevents
quantitative prfi_-c:fi.p:l;t-a.t:-il.c>n.-1-§2Lgflz

Ammonium dithlocarbonate precipitates uranium (VI).
Derivatives also are formed with Al, Mn(II), Fe(II), Co,
Ni, Cu(II), Zn, Ag, Sn(IV), Pb, and p1,246

Anthragallol forma brown precipitates or solutions with

o, vodt , Fe3t, cu?t, and Moofi' . 212

Anthranilic acid. Uranium (IV) is precipitated from a

solution of the reagent buffered with ammonium acetate. The

reagent added to a 0.1gL02(N03)2 solution forme a heavy

48
yellow preclpltate. The amount of preclpltate 1ls lncreased
by the additlon of 1M acetlc aclid; decreased by the addltlon
of 1M sodium acetate. Fifty micrograms of uranyl ion per
drofi of solutlion glves no obaservable preclplitate. In acetilc
acid-sodlum acetate buffered scolutlionas, slightly soluble
Balts are formed with the reagent and Mn, Co, Ni, Cu, 2Zn,
cd, Hg(II),and Pb.232

Areonlic acide. Benzenearsonic acidf preclpltates
uranium (IV) in a weakly ecldic solution, pH 1-3. Titanlum
and cerlum (IV) are partially precipitated. Thorium, zir-
conlum, hafnlum, tin (IV), nlobilum, and tantalum are
quantitatively precipitated.l”

Arsonilic acid (p-aminobenzenesrsamic acid) precipitates
uranium (VI) in 2 weakly acidic solution, pH 1-4 or great%%;
At pH 2.1 or greater the preclpltetlon 1s quantlitatlive as
evlidenced by negative ferrocyanlde teste of the flltrate.
Other lons which precipitate from neutral or alightly acidlce

2+ 2+ 2+ 4+
’ »

solutions 1nclude Cu™ ', Zn Ca™', end U With the

addition of sodlum acetate, aluminum and ferrlc lons also
precipitate.glé

Qther substituted arsonlic aclds which glve difficulty
soluble uranyl salts are 3-nitro-4-hydroxybenzene- and
methane-arsonlc acj.dsl.:j-E

Bis-benzenephosphonlc acid. Tests on 50-150 mg/i
uranium (VI) in sulfurlc acld solutions in the presence of
approximately 100- to 1l000-fold excess ferrous, sulfate,
aluminum, magnesilum, and phosphate lone gave nearly 99%
preclpitation with the reagent. Optimum condltions for
precipitation are pH 1 25°C, and 10/1 molar ratio of reagent
to uranium.g&-El

Benzenesulfinlc acld precipitates uranium (IV) in
acldic solutions. Iron (III) and the tetravalent lons Ti,

Sn, Ce, and Th &also precipit—a.te.gli

49
Benzopurpin precipitates uranium (IV) and (VI).glé.

Bengoylacetone precipltates uranium (VI).glé
5=-Bromo-7-carboxy-8-hydroxyquinoline precipltates

uranlum {VI), copper, zine, cadmium, mercury, and 1ead.gflg
5-Carboxy-8-hydroxyquiholine precipltates uranium (VTI)

i1n solutions buffered with acetic acld and sodium acetate.

Iron, copper, zlnc, cadmlum, mercury, and lead precipitate.gflg
7-Carboxy-B8-hydroxyqulnoline preclpltates urenium (VI)

In ammonlacal tartrate aolutlons.
Catechol forms compounds with tetravalent uranium, sillcon,

titanlum, zirconium, and thorium.gli Catechol comblned wlth

pyrldine preclpltates hexavalent uranium.gli—
Cresotinlec .acld 1n the presence of sodlum acetate pre-
eipltates uranium (IV) from solution. Aluminum end iron

(III) also precipitate. Separetion 1s made from Cr, Fe(II),
Co, N1, Cu, Zn, Cd, and Mo.2t3.210

Cupferron (ammonium nitrosophenylhydroxylamine).f

Uranium (IV) 13 precipltated from acidic solutlons by the
reagent. Good separation i1s made from other elements 1f this
precipltation follows one in which uranium was kept 1n the
hexavalent atate. Ions whlch are preclpitated by cupferron
from acldiec solutione lneclude T1, V, Fe, Ga, Zr, Nb, Sn, Sb,
Hf, and Ta. Ions which are not preclpltated under such
conditions include the alkall metals, alkalline earths, Be,

B a8 borate or fludborate, Al, P, Cr, Mn, Ni, Zn,and U(VI).
Precipitation 1s usuelly made in a sulfuric acid medlum

but hydrochloric or organic aclids may be used. Nltric acld
should be avolded; also perchloric acld 1f the precipitate

1s to be 1lgnited. The presence of a reduclng agent, hydrcx-
ylamine or sodlum hydrosulfite, facllitates complete pre-
clpitation of uranium (IV). The cupférrate may be filteréd
or extracted with an organlic solvent puch as chlorof'orm.-3-&--'-gfig .

50
Hexavalent uranium ls preciplteted by cupfefron from
neutral solutiona.gég

Dibenzoyl methane forme & yellow preclplitate with

uranium (VI) flé

3,5-Dibromosallcylaldoxime precipitatea U(VI), Co, Ni,

Hg(II), and Pb.22%

4,4'-D1hydroxy-3,5,3',5'-tetra(hydroxymethyi)'-diphenylmethane
precipltates U(VI), Mn, Fe(III), Cu(II), and Hg(II).glg

Dimethylammonium dimethyldlthiocarbomate forms & red

precipitate with uranium (vI).2L8

Diphenyl thiocarbgzlde precipitates uranium (VI) from

neutral solutions. Copper (II), silver, lead, and bilsmuth also

preciplitate with the reagent.glé

Dipropylamine forms a yellow preclpitate with ura.n:l.um.glé

Digalicylalethylene dilmine precipltates uranium (IV)

and (VI). Most heavy metals are precipltated by the 1:'ea.gen1;.3i
216

3.

Ethylenedlamine and uranyl nitrate form an Ilnsoluble

Ethanolemine precipitates UO

double salt, U0,S0) (H,S0) ), NH,CH.CH, N, 1n-alcoholic-sulfuriec
aclad Bolution.gég Double salts of the same type are formed
wilth plperazine and dimethylpiperazine. Sieam‘aslen:?-23 observed
that a solutlon of ethylénediamine added to & uranium solutilon
£Zlves a bright yellow crystalline preclipitate that le soluble
In excess reagent.

Ethylenedlaemine tetracetic acid. Uranium 1s precipitated
when a uranyl acetate solutlon 1s bolled wlth so0lid reagent.gfifl
‘ Gallic acid precipitates U(IV), U(VI), Fe(iII), Cu(II),
and Zn.gié

Gualacel. A brown preclpltate resulta from the reactlon of
the potasslum salt of gualacol and uranyl acetate in an
aqueous solution.gié

Hexamethylene tetramine (urdtropine)* 18 o weaker base

than ammonlum hydroxlde and does not absorb carbon dloxide.

51
This reduces the llkellhood of carbonate interference and of
alkaline earth carbonate precipitation. Uranium l1s preclpl-
tated when the reegent 1B .bolled 1n a uranyl solutlion that
contalns ammonlum lion and no excess ao:::l.d.-3£ Ions that form
stable complexes with uranium interfere. Separation can be
made from alkeli metals, alkaline earths, Mn, Co, Ni, and
Zn. Zr, M, Fe, Al, Ce(IV), Th, and some other elements
preclpltate.

A double salt, U0,S50,-H,S0)*(CH,)Ny, 1s formed with the
reagent and an excess of sulfuriec acld and uranyl aalt.géé

a-Hydroxyacetophenone forms a whlte precipitate with
hexavalent uranium.g:—L-é

1-Hydroxyecridine (1l-acridol or benzoxine) precipitates
uranium (VI) in neutral solutlons. Calcium precipitates from
neutral solutions; Mg,Ca, and Ba from alkallne solutlions;
Cr(III), Mn(II), Fe(II and III), Cu(II), Zn, Cd, Hg(I and II),
Te(II), and Pb from eolutions contelning acetic acld and
sodlum acetate. Al, Sn{II), and Bl do not p]:-ecipil.tate.giI

1l-Hydroxyanthraquindne forme elightly soluble complexes
wlth uranyl, cobalt, cupric, nickel, maghesium, and man-
ganeae ions.gli

l-Hydroxy-3-methoxyxanthone may be used to separate
uranium, thorium, cerlc salte and cerlte earths.gig The
ceric salte and cerite earths are not precipltated by the
reagent. Thorium 1s precipitated at pH 2.6-4.0. Uranium
(uranyl ion) precipitates at higher pH.

8-Hydroxyquinaldine. Tetravalent uranium 1s preclipitated
by the reagent wlth the addltlon of ammonlum acetate. The
precipltatibn of hexavalent uranium is almost quantitative
in the pH range T7-9 from carbonate-free ammonlum acetate
'%buffer.gég Iron, cobalt, nlokel, copper, cadmlum, and
chromlum are precipltated by the 1:'eahgen1:,.-g-lé

8-Hydroxyquilnollne (oxine).T Hexavalent uranlum is

52
preclpitated as 1102(09}161\10)2 . CQI-L_(NO from weekly ecldlic or
basic solutions.fii Quantitative recovery has been reported
over the pH range 4.1-13.5. A large number of other elements
are preclpitated by oxlne including Mg, Al, Cr, Fe, Co, N1,
Cu, Zn, Cd, Mo, B1, and Th.glfiigég:ggi Uranium can be pre-
clpltated 1n the presence of small amounta of complexing
agente: fluorlde, hydroxylamine, oxalate,lactate, end ter-
t-ra.’c-e.;ii Separation from small amounts of phoephate also can
be made at pH 10-12 using an excess of oxine. Ammonlum
carbonate interferes. Tetravalent uranlum and oxlne form
a8 brownish-yellow deposit.gli

Isatin-B-oxime (fi—isatoxime).f Uranyl and mercurlc
ione are precipitated by the reagent from weakly acldile
solution. Precipltatlon 1s incomplete but can be made
quantitatlive by 1ncreasing the pH wlth sodlum acetate. A
number of other elements precipltate under these conditlions
including Fe(II), Co, Ni, Ag, Hg(I), and Pb.gé£ Separation
can be madé from Mn(II), Zn, and alkaline earth-ions.géé
In alkali tartrate polutions, uranium can be separated from
cobalt and nickel.géé

Isojuglone. The sodlum salt of thls reagent and uranyl
acetate form a carmine-red precipltate after washlng wilth
ethancl. Iron, cobalt, nickel, zine, cadmlum, mercury, eand
lead are precilpitated by the reagent.géz

Isonitroso-N-phenyl-3-methylpyrazolone. Uranyl nltrate or
acetate forms a reddish-orange preclpltate with a 1% solution
of the reagent 1ln a 50% alcoholle solutlon. Precipltation is
quantitative with the addition of sodlum acetate. Mercury (I)
and (II), copper (I) and (II) and uranyl lons preclpitate
in acidic medla (nitrate or sulfate). In acetate solutions,
'Ag, Cd, Ni, Co, Zn, Cu(II), and U022+ lons precipltate. By
reducing the acidlty wilth sodlium acetate, salts of Ag, Pb, Bi,

Cd, Mn, N1, Co, Fe(II), and Fe(III) can be precipitated from

53
nitrate solutlona. Salts of T1(I), Sb(III), Sn(II), A1,

Cr(III), and the elkaline earths do not precipitate.28

Lguramidine hydrochlorlide. This reagent has been

 

tested for the separatlon of uranium from phosphate solutionsfggg

At pH 2.45, 75% of the uranlum was preclpltated.
N-Lauryl-lauramidine. Thls reagent also has been tested

 

for the separatlon of uranium from phosphate sclutlona. At
pH 2.45, 85% of the uranium was preclipltated.

Meroapto-acetic acld forms a greenish-white precipltate

 

wlth tetravalent uran:l.u.m.-gzl'-é-!--‘?-!'-é

Methylamine precipltatee uranium (VI).E;E

Methyl red causes uranium (VI) and aluminum to pre-
cipitate.gli

Morpholine precipitates uranium (IV) and (VI) as well
as a number of other metal ions.glé A 1l mg per ml solution
of uranyl nitrate shows only a yellow color with the reagent.
No precipltate 1s formed.glé

p~-Naphthoguinollne 1n the presence of thlocyanate 1ion

 

precipltates uranium (VI), mercury, bismuth, copper, cadmium,
nickel, cobalt, zine, and iron (III) from sulfuric or nitric
acld faolut:l.ons.‘?’—z-§2

Neo-cupferron (ammonium a-nitrosonaphthyl hydroxylamine)
18 gimllar to cupferron 1n 1ts application. Uranlum (IV) is
preclpltated by the J:'eagen‘r:,.g-:!‘--l£ |

Nitrilotriacetic acld forms derivatives with uranium (VI),

 

iron (III), nickel, and copper (II).EIQ
m-Nitrobenzolc acld precipltates uranium (IV).QE
o~Nitrosohydroxylamlnophenyl p-toluenesulfonate forma a
yellow precipifiate wlth hexavalent uranium. Many other me-
tallic 1ons are preclplftated by the reagent including Al{ Cr,
Fe(III), Co, Ni, Cu(TI), cd, Ia, Ce, Hg(II), Bi, Pb, and Th.2L:
a-N1ltroso-f-naphthol 1 deposits uranium (VI) as & very
fine, yellow-orangeii to b]:'curm-?:li precipltate. Precipitation

54
1s made in the pH range 4_0_9_4,212

Metals such as 1iron,
cobalt, nickel, and.copper are precipitfated from elightly acid
solutions. Molybdenum as molybdate ion, zine, and uranium (IV)
form colored Boll'rb-ions.gli Aluminum, chromlum, and cadmium
give no visible reaction.gli The uranlum compound can be
extracted wlth amyl alcohol.§£

B-Nitroso-a-naphthol preclpitates uranyl ion from slightly
acidle solution. Iron, cobalt, nickel, copper, zine, and
molybdate lons also are preclpltated by the reagent. Alumi-~
num, chromium, cadmium, and uranium (IV) give no vislble
reactlons. The precipitation of uranium (VI) 1s most nearly
complete 1n an acetate buffered solution.gli

Oleic acid 18 a precipltant of uranium (VI). 216

Oxalic acid' precipltates uranium (IV) from aéidic
solution.éi Strongly complexing organlc compounds and
fluoride, sulfafe, and large amounts of phopphate 1lons inter-
fere. Uranlum 1s preclpltated from 2-3N hydrochlorlic acld
media. At lower aclditles other metal oxalates preclpltate,
eg., Fe(II), Zn, Cu. At higher acidities the solubllity of
uranium (IV) oxalate lncreases. Immediate filtration of the
preclipltate may result 1n losses up to 1% of the uranium to
the filltrate. _Recovery of uranium may be made more quantl-
tatlve by chllling the solutlon and allowlng it to steand.
Small amounts of menganese, 1ron, and nlckel may be carriled
wlth the preclpitate. Nlobium, the rare earths, and thorium
precipitate under eimilar conditions. If uranium 1la reduced
on a mercury cathode prior to preclpltatlon, no cations in
moderate amounts interfere except rare earths and thorium.

Precipltation of uranium can be made 1n cold 1N nitric
acld solutions.gég The uranium content should belless than
70 grams per liter. Enough oxallc acld 1s added to glve a
10% exceas of the smount theoretically required to precipitate
U(cgou)e. The uranium then 1s reduced to the (IV)-state by

55
5
adding sufficlent rongalite (Na2H 04-20H20'4H20) to glve a

255
7-10% excess of 1 mole of rongalite per mole of uranium.

Phenanthrene quinone monoxime preciplitates uranlum (1Iv)

 

and (VI), aluminum, iron, cobalt, nickel,copper, &and zinc.glé

Phenoxarslnlc acld preclpltates hexavalent ura.nium.gflg

2+

 

Phthlocol precipltates U4+, Udg+ s 4N

ions.glé

, and Mo0§~

Picrolonlc acid precipltates tetra- and hexa-valent
uranium and most other metallic 1on-s.gli

Piperazine. (See ethylenediamine).

gzridinef does nof absorb carbon dloxide like ammonium
hydroiide does. Thle reduces the-possibility of carbonate
interference or of alkaline earth precipitation 1n a uranium
separation. Ammonium nitrate facilitates uranlum precipltation,
Sulfate lon hinders 1t. Separation can be made from elkall
metals, alkaline eartha, Mn, Co, Ni, Cu,and Zn. 2Zr, Ti, Fe,

Cr, Al,and othérs are preclpltated by the reagent.gfl

Pyrogallol and pyridine comblne to form & derivative with
hexavalent uranium.gl&

Quinaldlce acidT forme & yellow, amorphous preclpltate
wilth uranyl ion.glé Preclpltation 48 made from a neutral or
weakly acidic (pH 2-3) solution 1n the presence of ammonium
chloride. The reagept preclpltates a number of metals Including
copper, 2zlne, cadmiumgzi and uranlum (I\J").—E-!'-2 Uranyl ion
18 not precipitated in the presence of alkall tartrategZE or
& high concentratlion of acetate 1on.'glz

Quinizarin (1,4-dihydroxy-anthraquinone) precipitates
uranium (IV) and (VI), iron and copper.glé—

Rhodizonle acld forme a blue-black preclpltate wlth
tetravalent uranium. In neutral solutions, Ag, Hg(I and II),
T1, Pb, Cu(II), Cd, Bi, Zn, Sr, Ba, Fe(II), and UO,(II) lona
are precipitated. At pH 2.8, Ag, Hg(I), Ti, Pb, Cd, Ba, and Su(II)
are precipitated.gzi

56
Salicyellic acld. The sodium salt of the reagent forms
a greenlsh-whilte preclpitate with uranium (IV). Under con-
aitions tested, Al, Cr, Fe, Co, Ni, Zn, Cd, Moch , and UG
lons were not precipitated.gli

Sebaale acid precipitates uranium (IV).fiE

Sodlum- acetate preclipltates sodium uranyl acetate from
fieubral or weekly acldic solutions of uranyl salta.lgg The
- method l1s not very useful for the precipitatioh of traces of
uranlum. The solubllity of sodlum uranyl acetate in a
solutlon 5M 1n sodlum nitrate, 1M in acetic acid, and 0.5M
In sodium acetate 1s about 100 mg per liter.gzg Neptunlum
(VI) and plutonium (VI) also precipitate under these condi-
tions. The additlion of sodlum acetate and zlnc acetate to
a neutral or weakly acldlc uranyl salt solution preciplitates
the triple salt, sodium zinec uranyl aceta.te.122

Sodium diethyldithiocarbamate preclpltates tetravalent
uranium, aluminum, iron, cobalt, nickel, copper, and cadmium.gli
Hexavalent uranium may be preéipitated when both uranyl and
reagent concentrations are suffilclently large.giéigzz

Scdlum ethyl xanthate forme an orange precipltate
wilth uranium (VI).glé

Strychnine 1n the presence of fluoride lon precipiltates
hexavalent uranium as 7(C,;H,,0,N,HF) * 6(UO2F2) " 2HF. The
solubllity of the preclpltaete. in water at 25°C 1s 47.5 mg/100
ml; in 60% alcohollc solution at 25°C, 30 mg/100 ml.2(8

Tannic acid (digallic acid)f and tannin (a glucose ester
of tanniec acid)* react with uranium (VI) to glve a deep-brown
.precipit-ad;e.3-E Elements arranged according to decreasing
ease of precipltatlion by tannin are Te, Ti, Nb, V, Fe, Zr, Hf,
Th, U, Al.’gzg The posltlion of chromlum 1n this series 1s
uncertaln. Tantalum, titanlum, and nloblum may be separated
by tannin in‘a slightly acidic oxalate solution. Uranium and

others are preclpitated by adding more tannln and by makilng

57
"the solutilon ammoniacal.. Uranium mey be preclpltated from
such solutions in the presence of mrbonate, acetate, or tartrate
1on£t.-g92

Thioslnamine. Uranium and cadmium are preclpltated when
‘an alkaline solution containing these elements 1s bolled with
the reagent.-a-gg

Carriera. Trace amounts of uranlium may be removed from
solutlon by the use of gatherlng agents or carrlers. The
cholce of a particular agent depends upon the conditions
under which precipltation 18 to be made and upon subsequent
chemiatry to which the precipltate is8 to be subJected.
Rodden and Warfifi have deseribed the applicatlon of several
carrlers: ferric, aluminum, and calclum hydroxide. The use
of barium carbonate and thorium hexametaphosphate has been
mentioned in the Bec¢tlon on lnorganlc precipltanta. Mag-
negium oxlde and thorium peroxlde have been used.ifi The
oxlde and salts of antimony,ggliggg calcium fluo:r:*icie,ill
and the phoephates of zirconium,lgz bismuth,ggi and thoriumlgz’
240 have been used to carry uranium from reduced solutions.
Uranium (IV), in general, should behave simllarly as nep-
tunium (IV) and plutonium (IV). These are carried by
lanthanum fluoride, cerlc and zlrconlum lodates, cerlic and
thorium oxalates, barium sulfate, zlrconlum phosphate, and
bismith a!raonate.gzé Uranlum (VI) does not carry wlth these
agents provliding the concentration of either carrier or

uranlum 13 not too large.

Complexes. The preclipltation of uranium in normally

 

precipltating medla is inhibited by the formation of

sBoluble complexea.ii Carbonate ion 1e a very efficlent
complexing agent of uranyl ion. In ammonium hydroxlde

solution, uranium can be Beparated from iron,_titanium,
zirconilum, and alumlnum with carbonate lon present. In ammonium

sulfide solutlions, carbonate lon makes possible the separation

58
of uranium from manganese, lron, cobalt, zlnc, and titanium.
Ammonium carbonate prevents the preclpltatlion of uranium with
phosphate. Preclpltatlion with sodilum carbonate makes posaible.
the separation of uranlium from berylllium, menganese, lron, cobalt,
nickel, zine, tltanlum; zlrconium, and the alkallne earths.

SodIum peroxide faclllitates the separation of uranium and
other metals with sodium carbonate. The addltlon of the per-
oxide alone to acld solutlions of 1iron, cobalt, rare earths,
titanium, zlrconium, hafnium, and thorium causes thelr precil-
pitation while uranium, 1f present, remalns 1n solution.

Uranium dces not preclipltate with tannlec acld 1n gelightly
acldic solution wlth oxalate lon present. Titanlum, nloblum,
tin, tantalum, and tungeten .are preclpitated under such con-
ditlons. Oxsalate lon also ilnterferes 1ln the precipitation
of uranium by ammonla. |

Tartrate, cltrate, and melate lons prevent the precipl-
tatlon of uranium by ammonium hydroxlde or suli‘:l.dea.i-li

Sallcylic acid and hydroxylamlne have both been used to
complex uranium in separations from rare earth elements.fii
Hydroxylamlne has been used In separations between uranium and
beryllium, aluminum, Ilron, and ’cnor-:I.ul:n..-3--i

Complexing agents that form weak complexes with uranium
and relatively strong complexes wlth other metallle lons meke
geparatlon posslble between the two: uranlum lg preclpltated
by a sultable reagent; the other lons remaln in solutilon.
Ethylenediaminetetrapetic acld (complexone II) and 1ts
disodium salt (complexone III) hafie been used successfully
in this respect. TUranlum has been preclpltated with
emmonla in the presence of complexonea wlthout interference
from Al, Cr, Mn, Fe, Co, N1, Cu, 2n, C4, La, Ce, Hg, Pb, Bi,
' ahd the alkallne ean:-ths.g§£ The recovery of uranium l1s not
entirely quantitative slnce the complexling agent 1lncresaaes

the solubllity of the ammonlum uranate.196 28 The abesorp-

59
tion of lmpurlities 1n the precipltate may necessltate
dissclution and repreclplitation of the uranium3l2§ Berylil
and titanlum follow the uranium chemistry;ggg | -

Quantitative recovery of uranium from the aforementloned
cations: Al, Cr, Mn, Fe, etc., can be made with ammonium
monohydrogen phosphate, (NHA)QHPOM’ in the presence of
ethyle nedlaminetetracetic acid.ggé&ggz Beryllium and
titanium agaln interfere. Small amounts of tltanlum may be
complexed wlith hydrogen peroxide before the addition of
other rea.gents.ggz _

Sen Serma and Ma1111288 have studied the separation
of uranium from other elements using 8-hydroxyquinoline (oxine)
as preclpltant and complexone III as complexlng or masklng
agent. It was found that complexone had no maskling actlion
on uranium in the pH range 5-9. In a solution buffered with
acetle dacld and ammonlium acetate et pH ~5.3 quantitative
separation was reported between uranium and Al, Mn, Fe(III),
Co, Ni, Cu, 2n, Zr, Cd, rare earths, Pb, Bi, Th, and P205.
In ammoniscal medium at pH ~8.4, & sinllar separation was made
from Vé05, M003, and W03: Steele and Taverner,lgg however,
were unable to duplicate the above results.

Solvent extraction. The solubllity of uranyl nitrate in

 

organlic solvents has long been recognized.lgé The ability
of dlethyl ether to extract thils salt has been used 1in
gystems of anelysis for many years. However, 1t 1s only
within recent yeare (starting in the 1940's) that widespread
use has been made of solvent techniques as a means of
geparating and purlfylng lnorganlc substances in general 289-299
and uranium in particular.191’192’194’197'192’3903305
The conditions under which uranium may be extracted are
many and varled. In the present paper, extraction from
aqueocus solutlon 1a consldered. However, extractlion from

8olid phasesigi::gz and slurriesigi has been lnvestigated

60
and a favorable uranium partition has been found. Conditlons
whlch affect the extraction of uranium from aqueous solutilon
by organic solvent are the composltion of the aqueous phase,
the nature of the organlc phase, the temperature, and the
time of equillbration. In the aqueous phase, such factors
ag uranium, acld, cocmmon anlon, forelgn anlon, and forelign
catlon concentratlon must be considered. The nature of the
organic phase depends upon the type and concentratlon of
solvent and dlluent. If the organlec phase 1s not initlally
barren, lts concentration of uranium, acld, ete., affects
partition.

Becauge of the number of varlables and the large number
of uranlum solvents, one cannot conslder, in a volume of thils
glze, each Bolvent 1n the l1light of each varlable. Indeed,
the behavlioral relatlon between solvent and the afore-men-
tloned varlables 18 known for only a few well-studled solvents.
The purpose of the present paper 1B to provide information
on the condltions best-sulted for the quantitatifie extraction
of uranium or for the separation of uranium from interfering
elements. Thls 18 done as much as possible in graphle or
tabular form.

The solvente are dlvlided l1lnto flve general classlfications:
1) ethers, esters, ketonea, and alcohols; 2) organo-phosphorous
compounds; 3) amlnes and quaternary ammonium selts; 4) carboxylic
aclds; 5) chelating agents. Dialkylphosphoric aclds, eg.,
dibutyl phosphate, are classified as organophosphorusa com-
pounds rather than chelatling agents. Carboxylic aclde are
classifled g8 such,although gome may aleo be conslidered
chelating agente, eg., sallcyllc acid. A number of extrac-
tants may serve also as dlluents or secondary solvents for
other extractants. Such systems are descrlbed under the
primary extractant. For example, a cupferron-hexone system

is described under "cupferron" rather than under "hexone!

61
In the discusslon, the terms "extractant" and "solvent"
are often used Interchangeably. "Diluent" 1s used to describe
a secondary solvent rather than the term "inert solvent." The
cholce of dlluent may appreclably affect the partition of
uranlum. A number of terms that are frequently used are
defined below.

Partltion or -extractlon coefflclent:
a = o2 = concentration of a substance i1n the organic phase
T, ~ concentration of the same substance in the agueous
phase
Percentage extracted:
a
P = Tha X 100, when equal volumes of both phases are present

after shaklng.

 

Mass ratlo:
- Mo _ amount of a substance in the organic phase _ . Yo
K fi; ~ amount of the same subsftance 1n the aqueous V;

phabse
Separation factor:
concentratlion of substance A in the organlc¢ phase
concentration of substance B iIn the organlc phese

B = concentration of subgtance A in the aqueous phase
concentratlon of' substarice B 1n the aqueous phase

Equilibrlum laws. The physlcal chemlcal principles

Involved in the solvent extraction of uranyl nitrate have

 

o [+

been summarized in references 308-312. Detalled methods
of treating the varlous equlllbria involved have been
dev:{_:aed.l;l?‘-fil;’:—:ili A more slimple approach,adapted from a
paper by Carleson;;l 18 herewlth presented.

It may be assumed that within a certaln concentration
range an average uranlum complex 18 extracted. The complex
is represenftative of a whole set of complexes and may be
written H{M("'x)L(x_'_y)(HzO)h - (8),- M®. in this case,
may be Ut or UOEE. L, as written, ig a slngly, negatlvely
charged ligand. It may be more highly charged. & represents
a solvent molecule. The subacripts y, h, and n need not be
Integers. The reactlion for the extraction mechanism may be

wrltten !

62
M¥aq + yiTaq + (x+y)L7aq + nS org =
HyML(x+y)Sn(H20)h°rg + mH,,0.

The thermodynamic equllibrium constant for the reactlon is
m
‘ [HyML(x+y)Sn(H20)hJ org {H26Y
> [t 1Y) [818ng - £(7)

 

where {i}-and [ 1, respectively, represent the actlvity and
concentration of a quantlty in the agqueous phase unless
otherwise identified by the symbol "org.fi f(7) represents
the product of the actlvlty coeffleienta. The partitlion
coefficlent is approxlmeted by

[HyML(K+Il$n(H20)h]org

.o [ ¥]
The relaticn between the partlitilon coefficlent and equilibrium
constant 1s

log a == y loglHTlag + (x+y)loglL”Jag + n logl[Slorg

-m 1og {§2§} + log f(vy) + log K.

Information concernlng the extracted specles may be obtalned
by measurling the partition coeffilclent whille varying the
concentration of only one of the quantitles. A knowledge of
the activity coefficients islthen requlred or the product of
the activity coefficlents 1n both phases muet be kept constant.

As gtated previously, the above approach to solvent
extraction is a simplified verslon. It represents only an
average extracted species. Among other things, 1t does not
conslder the effect of water activity 1In tfie organlc phase,
Bolvent activity in the aqueous phase, complex formatlion be-
tween the varlous components 1in elther phase, or the formatilon
of polynuclear species. These effects may be large or small
depending upon the solvent, aqueous medlium, and uranium con-

centration inveolved.

ETHERS, ESTERS, KETONES, AND ATCOHOILS. Uranyl nltrate

 

18 extracted by many polar solvents whlich contalin donor

oxygen atoms such as ethers, esters, ketones, and alcohols.ilg:igg—

A

63
Extractlon from water solutlons 1s small unless the uranium
concentration 1a appreclable. This 18 shown in figures 1-5
in which the data of McKay and co-workers,lzéilgz Wla.l:-ner-,-a-gl--f-igg
and Vesely, et 81323 are plotted. In general, it has been
observed-igl that: |

1) the extraction coefficlent of uranium decreases when
the number of carbon atoms 1ncreases for a glven homologous
peries of organlc solvents, '

2) for a molecule with a given number of carbon atoms
and a glyen chemical functional group, solvents wlth strailght
chalns are more efflclent extractants than those wlth
branched chains,

3) one or more double bonds in a molecule increases the
efficlency,

4) primary alcohols are more efficlent than secondary
ones, '

5) the coefficlent of extractlon increases with the
solubllity; but there 1s no well-defined relatlon between
the two. | |

Evldence consldered 1iIn the sectlon on non-aqueous sol-
utlone indicates that uranium 1s extracted from agqueous
nltrate solutions ae hydrated, solvated uranyl nitrate,
UOE(Noa)E(H2O)hSh' Under approprilate conditions, the
hydrated, sgolvated trinitrate-uranyl complex may be extracted.
The relatlonship between partitlion coefficlent and equllibrlum
constant for the extraction mechanism shows the extraction of
the former species to be favored by ~ large free nitrate and
free solvent concentrations and b& small water actlvity.

Effect of nltric acld. The addition of nitric acld to

 

the aqueous phase favors the extraction of uranlum by pre-
venting or decreasing the hydrolysls of uranyl 1lon and by
increasing the nltrate lon concentration.ig& Nitric acid

1s extracted also by the organic solvents. This requilres

64
59

URANYL MOLALITY (organic phase)

 

 

 

 

        

 

 

   

 

 

 

T ! 1 !
0.5 | _=0 -
. “’ .
- 'a‘
a 7
1 I | mg 0.4 ’p =
L - D
g I "
i < o &
o o
4 Z s
50 d
28 ¢
;g o.2r =
™
5|
Joz 6
g O —
q O
. -
© <P
| 0 I == 7 et e A
0 00 02 03 04 05 06
q GRAM OF URANYL NITRATE per
URANYL MOLALITY (oqueous phase) GRAM OF AQUEOUS PHASE
@A) ' (B)

Figure 1. Partitlon of uranyl nitrate between water and simple ethers. O,-diethyl ether. A,

ethyl-n-propyl ether. 0O, ethyl-n-butyl ether. V¥V, di-lsopropyl ether. 9, dl-n-butyl ether. a,
dl-n-hexyl ether. 0O, 2,2’ -dichlorethyl ether.

1-A. After E. Glueckauf, H. McKay, and A. Mathleson, reference 185. Temperature, 25°C except for
dlethyl ether: first three points at 259C, last polnt at 20°C, remainder at 18°C.

1-B. After R. K. Warner, reference 321. Dashed curve represents the partltion of uranyl nitrate
between diethyl ether and a saturated ammonium nitrate sclution. Temperature, 20°C,
URANYL MOLALITY (organic phase)

 

 

 

 

0s |

 

 

 

 

 

 

o
o w

0
M a

I
s Q i

i |:9 0.3 |
“z
= © i
0.2
20 ]
x
35
w — -
O'E 0.1
g @
® A
o 0 L ' =
0 0.1 0.2 0.3 0.4 0.5 0.6
4 GRAM OF URANYL NITRATE per
URANYL MOLALITY (oqueous phase) GRAM OF AQUEOQUS PHASE

(a) (B)

Figure 2. Partlitlon of uranyl nitrate between water and complex ethers. O, phenyl cellosolve,
A, dlbutyl cellosolve. V,V, dlbutyl carbitol. a,0, pentaether.

2-A. Open symbols, after E. Gleuckauf, H. McKay, and A. Mathleson, reference 185, 8Solild symbols,
after A. Gardner, H. McKay, and D. Warren, reference 176. Temperature, 25°C,
2-B. After R. K. Warner, reference 321. Temperature 20°C,.
 

URANYL MOLALITY
(organic phase)

 

 

 

0O ] ]
0 | 2 3 q
URANYL MOLALITY (oqueous phase)

Figure 3-A. Partltlon of uranyl nitrate between water and 1soamyl
acetate. After E. Glueckauf, H. McKay, and A. Mathleson, reference
185. Temperature, 25°C.

 

 

 

 

 

- 0.4 T | 1 |
Q.
»
e < |
g T 0.3 -
=
z
> o 0.2~ ~-
>«
2o
= o
S
© oa —
L =
o
= a‘-‘
$° ol e
o 0 0.l 0.2 0.3 0.4 0.5 0.6

GRAM OF URANYL NITRATE per
GRAM OF AQUEOUS PHASE

Flgure 3-B. Partitlion of uranyl nltrate between water and nitro-
methane and saturated ammonium nitrate (dashed curve) and nitro-
methane. After R. K. Warner, reference 322. Temperature, 20°C.
89

 

 

 

    

 

  

 

 

 

 

 

4 | T T
— 0.5 -
o ~
% a
W i
© T e ‘2 0.4 -
s &T
o |: Q.
S Zo _
z 0.3 ~

> - Sd
- 290
= Sc _
I x O |
- Sw 0.2
O o

w
E C)E
= a & 0.l J
] @
q O
@ 4
S A5 ] iy

0 v ‘.—‘J‘ Prre
H-nfYS o 0.l 0.2 03 - 0.4 0.8 0.6
0 | 2 3 4 GRAM OF URANYL NITRATE per
URANYL MOLALITY (aqueous phase) GRAM OF AQUEOUS PHASE
() ®)

Figure 4. Partitilon of uranyl riltrate between water and ketones. O, methyl ethyl ketone. @,
methyl 1sobutyl ketone. A, methyl n-amyl ketone. A, dl-lsobutyl ketone. 0O, cyclohexanone, MHC,
methyl cyclohexanone.

h-A. After E. Glueckauf, H. McKay, and A, Mathieson, reference 185, Temperature, 25°C.

4-B, MHC curves, after V. Vesely, H. Beranovd, J. Maly, reference 323. Dashed curve--aqueous
solution, 6M NH 4NO3. Remaining curves, after R. K. Warner, reference 321. Temperature, 20°C.
Dashed curve--aqueous soclutlon, saturated ammonium nitrate.
 

 

 

 

 

 

  

 

 

 

 

s 3 =T T 1
&®
Q
gL
o
(4]
.g |
E T fl
>
=
=
<
4 | F =
O
=
- |
3
> P P
> o | 2 3 4
URANYL MOLALITY (aoqueous phase)
(a)
T T I ! T
a, 04} ' .
o
o
& o i
|: o 0.3 I
<z
22 el
2 . -
§c:o
53
L -
0§ 0.1 -
e
Z
<X
0 0.\ 0.2 0.3 0.4 0.5 0.6

GRAM OF URANYL NITRATE per
GRAM OF AQUEOUS PHASE

(B)

Flgure 5. Partition of uranyl nitrate between water and alcohols.
O, n-butanol. ®, n-pentanol. A, n-hexanol. V, methyl isocbutyl
carbinol. 0O, 1scamyl alcohol. @8, sec-octyl alcohol

5-A. After E, Glueckauf, H. McKay, and A. Mathleson, reference 185.
Temperature, 25°C.

' 5-B. After R. K. Warner, reference 321, Temperature, 20°C.

69
that it be replaced 1n continuous or multlcontact extractlon
process. Large concentrations of nltric acld are generally
not deslrable, The formation of HNO3 . Sn complexes reduces
the amount of free Bsolvent, the extractlon of other elements
1s enhanced, and the danger of an explosive reactlon between
solvent and acid 1s increased. The formation of HM(N03)x+1
specles, which may be more easilly extracted than M(NO3)X,
is promoted by the eddition of nltric acld. For uranium,

however, the formatilon of the trinltrate-uranyl complex 183
8

3.

Effect of nitrate salts. The nltrate lon concentration

far from complete, even in 16 M HNO

 

may be lncreased by the additlon of fietal nltrates of signiflcant
solubllity to the aqueous phase. Thls not only promotes the
extractlion of uranium but also the extractlon of other elements
whose nitrates are soluble 1ln the organlc solvent. In some
cases, nitrates whlch Berve as Baltlng-out agents, eg. thorlum
may also be extracted 1n significant-amounts. The extractlon
of other salting-out agents, eg., ceslum, may be enhanced

by the formation of uranyl trinitrate complexes, I\*IUO_E,(I~103)3.§22
The ability of varlous nitrates to salt-out uranlum has been
related to the hydratlon of the cation,igé the actlvlty
coefflelent of the pure nltrate saa.lt,g’-g-I and the radlus

and charge of the cation.igg A salting-out agent which 1s
hlghly hydrated facilitates extractlion of uranium by reducing
the water activity. In filgure 6, the partition coefficient

of uranium 18 plotted as a functlion of aluminum nitrate

for several asolvents. The partltion of uranlum between
saturated ammonlium niltrate solutions and diethyl ether,
nitromethane, and methyl ethyl ketone 1s shown by the dashed
curves 1n flgures 1B, 3B, and 4B, 1:=espec=1:1veil.3,r.-32:—L-L3-gg
Ammonlum nitrate is wldely used as a salting agent in splte

of 1ts relatively poor salting-out ablllity. The ease wlth

which 1t 18 removed from solution or from heated samples

70
 

103

] IIlLIII

|TIIII—I_I_'

-1

IilllLL-

“ |‘|—rr||

A

10

 

PARTITION COEFFIGIENT OF URANIUM, &,

F
A

 

 

 

1.0 L1y
0 l 2 3 4 5 6 T 8 o 0 1l 12

EQUIVALENTS OF AI(NOg)g per 1000 cc OF HgO

 

Figure 6. Effect of aluminum nitrate as salting-out sgent on the
extractlion of uranium by varlous solvents.

Curve 1, dibutoxytetraethylene glycol (pentaether); Curve 2, dibu-
toxytriethylene glycol; Curve 3, dibutoxydilethylene glycol (dibutyl
carbitol); Curve 4, methyl isobutyl ketone (hexone); Curve 5, diethyl
ether; and Curve 6, dibutylmonoethylene glycol (dibutyl cellosolve).

Data adapted from E. Evers and C. Kraus, reference 332.

Conditlons: Aqueous phase - 2.0 to 6.0 grams of U per 100 cc of solu-
tlon containlng ajuminum nitrate. Organilc phage - solvent represented
by curve. Equal phase volumes* equllibrated at 27°C.

e ey b

*HEqual or approximately equal phase volumes were employed 1n distribu-
tion experiments with dlbutyl carbitol (C. A. Kraus, A-2322(1945)) and
with hexone (C. A. Kraus, A-2324(1945)). It ie assumed that the same
volume ratio was used for other experlments.

71
mekes 1ts use advantageous.

The presence of nltrate salts which are sufficlently
soluble in the organic solvent facllitates the extractlon
of uranium by formation of the trinltratouranyl complex,
RUOE(N03)3
Effect of other salte. Anlons that complex uranium

.Zfi This 1s discussed further under "Hexone."

in the agueous phase may serlously Ilnterfere with the ex-
traction of the latter. Chloride, fluoride, sulfate, phos-
phate, and several organlc¢ anions have been studled for
thelr interference. The adverse effecta of these ions may

be minimized by removing them from solution prior to uranium ex-
traction, by complexling the anlons wlth cations of salting-
out agents, or by using an excess of an efflclent salting-
out agent to over-ride the anlon interference. The inorganic
anlons may be precipitated as silver chloride, lenthanum
fluorlde, barium sulfate, zirconlum phosphate, or ammonlium
phoaphomolybdate. Fluoride lon ls complexed by alumlnum

and calcium. Sulfate ion 18 complexed by ferric ion. Large
amounts of sulfate lon are also precipitatefi by calclum
nitrate. Phosphate l1on 18 complexed by ferrlic and alumlnum
lons. Calclum nitrate has been used to counteract the effect
of acetate and oxalate. The effect of chloride on the
partition of uranlum may be reduced in the presence of a
Btrong saltling-out agent. Chloride ilon 1s more obJectionable
from the fact that it promotes the extractlion of other elements,
notably iron. In the presence of large amounts of interfering
dona, particularly sulfate and phoephate, 1t 18 advisable to
separate the uranlum from solution prlor to extraction. This
may be done by preclipitation with carbonate-free armonium
hydroxide. The preclpltate 18 dissolved in niltric acld and
the extraction 18 1nltilated. Ferric hydroxlde may be used

to carry trace amounts of uranium. |

Uranium may be extracted from aqueous medie other than

72
nitrate. Thilocyanate solutlons have been found satisfactory.
The extractilon, hoyever, i8 less Belective from thiocyanéte
than from nitrate solutlons.

Solvent actlon. The partltion of uranyl nltrate ls
dependent upon the free solvent concentratlon. This 1B
reflected in the coeffliclents of extraction of micro ahd
macro amountg of uranlum from highly salted aqueous solutlions.
The partition coefflclent of trace amounts 1s larger than
thaet of large amounts a3 a result of more avallable solvent.
A3 mentioned previously, macro amounts of uranium extract
more readlly from water solutlons or less highly salted
aqueous solutlions than do mlcro amounts. This effect may
be a2ttributed to the saltlng-out abllity of uranyl nltrate
itself.

The extractlon of other elements 1s affected also by
the uranium concentratlon. Hlgh loadlng of the solvent
by uranium reduces the extrafition of less preferred complex.
specles. High uranium loading may be achleved by diluting
the solvent with a secondary solvent 1n which uranyl nitrate
1s 1nsoluble or slgnifilcantly less soluble than in the primary
extractant. Solvenfi dilution, 1n general, causes a deorease
1n the partition coeff‘ic:l.ent.43l-g-r'--zgl-‘--agifii9 Wohlhuter and
Sauterongii have llsted a rumber of aromatlc and chlorine-
substltuted dlluents ln order of lncreasing harmfulness to
uranlum extractlion: benzene, toluene, xylene, carbon tetra-
chlorlde and dichloroethylene, chloroform. Solvent dllution
may be used also to Iimprove upon the phyesical propertiles
of the organic phase, eg., density, vliscoslity, etc.

The sultabllity of mixtures of oxygen-contalning
solvents as extractants for uranyl nitrate has been
studled 328-320,329,330 giover and co-workers322 reported
that none of tThe mlxtures they investligated were better than

the pure solvent. Recently, however, Fomln and I\"Im'*gunc:vég--2

73
and Vdovenko and_Krivokhatflkiiiag'have reported enhanced
uranyl nitrate partition coefflclents from solvent mixtures.
Vdovenko and Krivokhétskii repoft that over ten sfich mixtures
have been found. Among them are: di-lsopropyl ether and B,B'-
&iéhiérodiethyl ether, dibutjl ether and a,ai-diohlofodiethyl
.ether, diethyl ether and acetophenone, 1soamyl alcohol and
fiethyl 1sobutyl ketone. The enhanced extraction by solvent
mixtures has been attributed to the formatlon of mixed so0l-
vates of uranyl nitfafie.igg&aag _

Effect of temggraturé. The.extraction-of firanyl niltrate
1a decreased by a témperature inorease. Thg partition co-
efficlent of uranlum 18 plotted as a funotlion of temperature

for several solvents 1n flgure 7.§3g

 

 

 

 

 

— T 1 r T T 1T T T

s 1000 |-
- -
Tz -
E -l
Q -
T8
u p—
Ww
8

' 100 |~
z -
o C
t =
= i
o » -
g
a | -

10 1 | 3 | 2 | 1 1 ] L
0 6 i2 1] 24 30 36

TEMPERATURE, °C

Figure 7. The effect or temperature on the extraction of uranium by
organic solvents. O, dlbutyl carbltol. 0O, hexone. @, dlethyl ether.
A, pentaether. : '

Af'ter E. C. Evers and C. A. Kraue, reference 332. .
The tri les represent aqueous solutions palted with 36.6 grams
of Al(NO 3 ber 100 cc of water. All other symhols represent solu-
tions salted with 58 grams of Al1(NO3)3 per 100 cc of water. 2 to 6
grams of uranlum per 100 cc of solution were extracted.

74
Re-extraction. Uranium is re-sxtracted from the or-
ganle solvents conslidered in thils Bectiofi by contact wlth
water. Several water contacts may be required 1f large
amounts of uranlum or niltric acid have beefi extracted. Water-
soluble.salts whose anlons complex uranyl ion, eg., ammonlum
gulfate, facllltate re-extraction, '

.Extraction of other elements. A number of elements
other than uranium are extracted by oxygen-containins'sol-
vents. Those commonly found with irradlated uranium are
hexavalent Np and Pu*; pentavalent Pa; tetravalent Th, Np,
Pu, Zr(+Nb), and Ce; and ruthenlum complexes. Neptfinium,
plutonium, and cerium &re made less extractable by reduction
to lower oxidation states. Favorable separation of uranium
from the other elements may be achleved by control of the
nitriec acid and salting-out agent concentrations. Free
halogens are extracted. These elements may be sllimlnated
from solutlion prlor to uranium extraction. The fialogens
also comblne chemlcally with a number of solventa; eg,,
lodine and hexone. The cpmbined halogefi 1a not re-extracted
by water contacts. |

General survey. The extractlion of uranyl nitrate by
polar oxygen-contalnling solvents has been lnveastligated under
-a varlety of conditliona. The results of three surveya;lgzigg
in which the experlmental condltione were all different;are

gilven 1n Table VIIIT.

* Am{VI) forme an extractable nitrate. Strong oxidizing
condltions are necessary, however, for americium to be -
present in the (VI)-state. It 18 generally found in
golution as Am(III). _

75
Table VIIT. Distributlion of Uranyl Nitrate Between Varicus Oxygen-containing Solvents
and_Aqueous Nitrate Solutionm -

 

 

Survey 12 # Total Survey EE Survey 3%
Solvent Peroent extraoted volume in , Percent extracted :
T Th HNO, org. layen U Th Fa %y

Ethers
Diethyl ether 96 60 - 62.5 35 0.0 0.19" 0.09
n-Propyl ethesr T8 '1.d b4 55 2.2 0.0 0.10 )
Isopropyl ether es 20 &6.5 58 0.00
Dibutyl ether T c1| =5 53.5 1.6 | o.0 0.05 0.00
Ethyl n-butyl ether a5 <1 kg 55
Banzyl methyl ether 85 8 k1 55
p-g-Dichlorocethyl ether ¥5 <1 37 53.5
Diethyl celloaolve 55 24 - 0.29
Bthyl butyl cellosolve | 95 60 57T 61.5 59 T
Divutyl ocallosolve 90 17 ao 56.5 0.01
Fhenoyl collosolve C.00
Benzyl cellosolve 21
Dibutyl oarbitol 95 8k | 100 63.3 59 g.7| o0.15% 0.09
Dibutpxytetra-athylena 0.5k
glycol (pentamther) - - 99 100 66.6
Dimethyldiloxane 33 3.8
Esters . :
Ethylacetate (88 |77 - 65 13 | 0.6 0.26' |
n-Propyl acetate 95 46 92 60 50 1.3 9.1
ILsopropyl acetete . 54 1.2 11.9
n-Butyl acaetate B89 26 - 58 39 0.06 10.6
sec-Batyl ana'tate 39 é2.2
Ieobutyl acetate 21 0.02 0.18

Amyl acetate 86(7)| 16 - 56.5 11 |o.3 9"
2-Ethylbutyl acetate _ 9 0.02
2-Ethyl hexylacetate T2 <1 95 54
Butyl ocarbitol acetatel 93 B85 - &7
Qlycol dlacetate ‘ 0.25
Ethylacetoacetate Q.11
Methyl proprionate 10-20 | 0.2 0.06
Ethyl propricnate a2 0.03 0
Ethyl btutyrate ea 6, 75 57.5 10 o
Ethyl a-bromobutyrate 35 <1 o Bh
Methyl benzoate T.5] 0
Ethyl bensoate -80 1-3 54 56.5
Ethyl caproate a0 3 60 55
Diathyl maleats 0.07
Diathyl malonate 22
Ketonese
e s ane a7 |20
Methyl n-propyl ketone 53 11
Metrwlh:rul;h;tyl ketone 57 . r 0.00k%
Methyl n-amyl ketonse a7 0.9 | 30t 0.02
Methyl n-hexyl ketone 0.01
Dlethyl ketone 0.08
Diisopropyl ketone 56 0.3 | 38.77

 

 

 

 

 

70

 

 

 

 
Table VIIT. - Contirued

 

 

 

 

 

 

 

 

 

 

 

 

Solvent i Peruente'gx‘]fiimtad gomin » Per?‘e::eyextayz:n: ted Survey 3E
2Dt exiraoctec -ved
U | ™ HHO org. layer v h Pa o,
Acetophenone ) 0.05
Cyclopeantanone ' 0.80
Cyclohexancne 11 - 0.53
Kethyl oyclohexancne large
m-Methyl cyelohexanone -1
p-Mothyl oyclohexanone 0.30
Meaityl oxlde a3 T7.6 - 63 12.7 0.24
Tsophorone 27
JAlcohols
n~Butanol L 5.2
2-Fthyl butanol 0.01
gec-Butyl carbinol 30 0.6 0.01,""
tert-Amyl aloohol 68 €3 - 61
Dietnyl carbineol 2k 0.7
D:L:Laopré;wl ocarbinol 11.# 0.0
Tri-n-butyl carbinel g 5.6 51 54
2-Ethyl hexanol T5 lo T7.5 56.5 0.0 T2.1
Faptanol 24 0.65 | T1. 5*
Methyl r-amyl carbincl 36-50 3,7
n-Qotancl ’ 0.5 | 748
Heptadaoanol 0.0 .7
|2-Ethylnexanediol-1,3 0.09
Migcellansoun
Nitromethane 60 32 - | 62 54
1-Nitropropane Q.00
2—N1troi:mpane 3.5 Trace | 0.25
Nitrobenzens 2.1 Trace | 0.10
o=Nitroanlgole 3.5 Trace 0
Triochlorsethane 0 0 o
Trichlorcethylene 1.5 0.2
Chloroform 0
Jimethylsulfalons 1,68
2o, A Johnson end A. 3. Newton, reference 318.
Equel volumes of o ¢ solvent and aqueous solution (3¥ HNO., 3!4 Ca.(NO C. 635!4 Th(no Yn»
0.045 gm/Aml o, [§:10] mixed 10 mimtes. Ko extraction was 4 tected with ih 3

brampahimsoled p-fir@mphenetol aniscle, lsoamyl nitrita, ohlorobemene, :r.v'lune. ethyl 1041ds,
Eutyl bromide, and trilchleroethylene.

* Indiocates mutual 5o1ub:|.11ty of agueous Bolution and organic solvent.

b

= E.'K. Hyde and M. J. Wolf, reference 319.

Equal volumes of organie solvent and sguecus solution (1N ]-DiD3 3N mhmy 2N Th(mj)ll’
5 x 102 - 10 c/min 233 at 52 counting yield) mixed 5 mrimiten.

t Aquecus phase ; 1N ENO,, 2N NH,NO,, 2N Th(N0,),, 10" ~ 3 x 10° o/ Pa®33 at 1
counting ylald. 3 L 3w /n o%

¥ Aqueous phase : IN HNO,, 2N A1(NO), 3N Th(NOy)y, 10% - 3 x 10% c/m Pe®33 at 10%
counting yield. .

S ¢. n Stover, Jr., H. W. cr'a.nfla.ll, D. C. Stewart, aml P. Mapyer, referencs 320.

Bqual volumes of © ¢ golvent and agueous sclution (o 3kM HNO3, O. 501\!'002(1103)2 61120)
mixed 2 hours at 25 C.

"“Solvent identified as methyl isobutyl carbinol; formila given am CH,CH,CH(CH,)CH,OR
(een-tutyl carbincl).

77 .
_ ETHERS

Dlethyl ether

-éQEEQEE_EEEEEEE_EZEEEPE' The extractlon of uranyl nitrate
by diethyl ether 18 widely used in radiochemical separations.
because of the Be;ecfiivity of the extraction. Dlsadvantages
of the method are the high volatility and low flash point
of the solvent and the relatively low dlstribution of
uranium into the solvent.

The fiartition of uranyl nltrate between dlethyl ether
and water 1s illustrated in figure 1.282:321 yith bothn
. phases saturated with uranyl nltrate at 25-26°C, the dis-~
tribution coefficlent 1s about Q.68.3§§ The effect of nitric
acid'upon the partition of uraniumiiiiii& and nitric acidégg’
333-332 1tself 18 represented in figure 8. Furfian, Mundy,
and Morrison§g§ report that the pH'of the aqueous phase
should'be 4 or less for complete extraction of uranium to
occur. The influence of ammonium nitrate and calcium nitrate
upon the extractlion of nitric acld 1s also shown 1n flgure
g.326

Figurea 9 and 10 demonstrate the influence of various
salting-out agents on fhe distributlion of uranyl nitrate.igé&agg
The nitrate concentratlon plotted 1n figure 9 includes that
of the salting-out agent plus that of uranyl nltrate left
after extraction by an equal volume of ether. The latter
contributes only a few percent to the total nitrate concen-
tration in most cases. A notable exceptlon is the iron (III)
point at -1.18M nltrate concentration. In this-instance,.
0.82M nitrate lon 13 attributable to ferrlc nitrate and
the remainder to uranyl nltrate. The niltrate concentration
of the saltling-out agent 1s plotted 1n figure 10, Uranyl
nitrate contributes 1little to the nitrate concentration since
only one gram of uranyl nltrate was used per 100 grams of

initial aqueous solution. Furman, Mundy, and Morrisonagé

78
 

1 | | I | { l { l !

   

10 |— , S
E S HNOz - Ca(NOx)g ]
S _ , ' _
= . HNOa;- NH4NO3
o 3 }uog(NOz),
Eé IJ){—v" HNO+ 3
T 2
f N -
) - i
o - ) _
=
2 - T
=
;E 0. & f ’?
< - 3
o - :
0.0l L L1 111 1 |1

 

 

 

l 2 3 4 5 6 7T 8 9 10 11 12
INITIAL AQUEOUS NITRIG ACID GONOENTRA_TlON,H.

Figure B. The extractlon of uranyl niltrate and nitric acid by
dlethyl ether.

Uranyl nltrate extractilon:
O, after R, Bock and E. Bock, reference 333, Initlal U concentra-
tion, 0.1M; Temperature, 20° + 1°C; Vo/Vg = 1. Dashed and dotted
curves, after J. Kool, reference 334. Temperature, 25°C; Vo/Vgq = 1;
Inltlal U concentration, --—=—--—---~ 50, 150, 450 mg uranyl nitrate

(hexahydrate) per 15 ml} ...cveeeuas 1350 mg uranyl nitrate (hexahy-
drate) per 15 ml.

Nltric acld extraction:
O, after R. Bock and E. Bock, reference 333. Temperature, 19° +
10C; Vo/Vg = 1. @, after J. Kool, reference 334. Temperature,
25.0 + 0.1°C; Vo/Vg = 1. 0O, after A, Grinberg and G. Lozhklna,
reference 335. Temperature, 20°C; Vo/V5 = 1. A,V,V, after
N. Furmsr, R. Mundy, and G. Morrigon, reference Vo/Vy = 1; HNO3 -
Ca(NOa% , 100 g. of Ca(NO3%2 . 4Ho0 per 100 ml of 1nitial solugion

03; Ce

plus _HNOEN— NHyNO3, . of NH4NO3 per 100 mi of initial
solutlon plus 03. '

79
 

000 —r——T——T7T—T"TT7T T TTT

500

ll|l
lllll

200

I
|

100

Qy
o
o

1 Illllll
l_l_[ll.lll

- N
O O

ll |IIIII| I
]

(8 [

1 lIllIlI

N
I

PARTITION COEFFIC_IENT,

L bl 1

O
O
T T [ 7rIT]

0.2
0.1
0.05

 

1 Illllll
1 _I_IIIJJI

0.02

 

 

L L L L1
o I 2 3 4 5 6 7 8 ¢S 10 !l 12

NITRATE CONGCENTRATION OF AQUEOUS PHASE, M

 

0.0l

(See facing page for legend.)

80
Flgure 9.

117.

Effect of varlous nitrates upon the partlitlon coefflcient of

uranium wlth dlethyl ether.

After N. Furman, R. Mundy, and G. Morrison, reference 326.

The nitrate concentration plotted as the absclesa
Includes that attrilbutable to the equillibrium
concentrations of uranyl nitrate in additlion to
that of the 1nltlal concentration of salting-out

agent.
Conditions:
Salting-out Agent
NH4N03

NaNO
3

LiNO
3

Ca(NO3)2

Mg(NO, ),
Zn(NO3)2
Cu(NO3)2

Fe(NO3)3
AL(NO, )4

Th(No3)4

[(U)l, g/1
25
(25)
(25)
(25-100)
(25-100)
(50)
(~8->600)
(~8->200)
(25-100)
(50)

T.°C
25-6
2Uh-6

25-29

27-28
28-31

29

Vo/ Ve

H o R B R

The urenlum concentrations 1n paréntheses have been
estimated by roughly adding the equilibrium uranilum
concentratione of both esquecus and solvent phase.

81
 

    
    

 

 

 

T I o 1 | I | [ |
)

B Fatili) |

10 g snLi _

- g ]

C B Ca .

i i

= Y No

S - 7 NHeg ]

b N —

> 1.0 E 3

L E :

0 E ]

w i 4

ui : :
o
O

0.1 3

Z R

o 3

= -
—

> _
<
a

0.0l 3

0.00! L1y )
O ! 2 3 4 535 6 7T 8 9 10 i

GRAM EQUIVALENTS OF NITRATE per
iI000 g OF IN!TIAL AQUEOUS SOLUTION

Figure 10, Effect of varlious nltrates upon the partition coefficlent
of uranium wlth dlethyl ether.

After V, Vdovenko and T. V. Kovaleva, reference 328.

Conditions: 1 g. U02(N03)2 1n 100 g. of initlal aqueous solutlons;
Temperature, 25°C; and Vo/Va = 1.

82
observed that the saltlng action of a mlxture of nltrates
could be reasonably predlicted by the followlng method:

The logarithm of a_ for each salt at a glven total

nitrate molarity 1% divided by the total nltrate

molarity. These indlvidual quotlents are then mul-

tiplied by the nltrate molarity of the respectilve

Balts. The sum of the resultling products 1s then

equal to the logarlthm of the predicted partition

coefficlent. .
Hellman and Wolffiafi have studled the saltling action of
varlous nitrates 1n the presence of nitrlc acld and thorium
nitrate. Some of thelr results are listed 1n Table IX.
From the data 1t may be observed that (1) thorium nitrate
18 generally & less effectlve saltlng-out agent on a
normality basis than other metal nitrates and (2) the
extractlon of uranlum becomes less efflclent as the amount
of extracted thorium becomes appreclable.

The effect of several forelgn anlons on the extraction
of uranyl nitrate by dlethyl ether 1s glven 1n figure 11331
and Table X.igé Arsenate, molyhbdate, and vandate lons alao
interfere with the extractlon of uranlum. The effect of
these ione may be offset by the addition of ferrlc n;trate
to the solution.33§

The partitlon of a large number of elements between
various aqueous nitrate systems and dlethyl ether 1a8 given
in Table XI and illuetrated 1n filgures 12-14. The lncreased
dlstribution of heavy elements and fiesion product elements wilth
increased niltric acld concentratlion should be noted. For a
selective uranium extraction the nitrlc acld concentration
should be minimal. H;srdeg--32 has recommended an aqueous
phase 0.5-1M 1n nltric acld and 2.5M 1n magneslum nitrate
for the quantitative extraction of uranium by diethyl ether.
Mbre gelective extractlion of uranyl nitrate may be made from
a saturated ammonium nitrate-solution, 0.05-0.1M in nitrlec
acld. The extractlon can be made quanhtitatlive by repeated

contacts with ether.

83 (Text continues on page 92.)
Table IX. Distribution of Uranlum and Thorlum between Dlethyl Ether and Aquecus
Solutione Containing Verlous Amounts of Metal N:I.trntan?

 

 

 

Salting Total nitrate Composition of inltial aguascua Iuolution
agent normality 0.5N HNO; + salting agent 0.5N HKO, + 1K T™(R0,),
+ aplting agent
U extracted, ¥ U_axtracted, ¥ Th extraected, & .
HNO, 3 23 10 0.1
5 52 ko 3.3
7 62 RG 21
T T
LiN0, 2 10 22 0
3.5 36
5 31
5.5 T4 25 2
7 66 19
7.5 81 53
NH, KO 3 8 0.0
43 5 30 0.1
5.5 25
7 AT 0.5
9 57 0.8
10 59
12 59 1.2
Ca(fl03)2 2,37 13
2.75 11 0.0
3.62 32
.0 25
4.87 63
5.25 59 0.1
7.50 99 96 1.2
Mg(No,} 1.50 3
372 2.17 . 9 0.0
2,58 18
3.15
5 e o
- by 0.00
5.5 29 9 0.31
Mn(No.) 2.5 18 - :
372
3.5
5.0 75 2l.0 0.0
6.0 5.5
7.0 65
T.5 87
8.5 70
8.5 T2 43
Cu(No, ), a.5 12
3 g.g 6 12 0.0
g_g o 50 0.5
10.5 87 62 15
11.0 18 52
La(RO.) 2.5 14
-5
6.0 93 18 0.2
6.5 39 2.1
M(N03)3 g:g 18 3
h;o 54 0.0
5.5 €3 2.8
6.0 96
T5 57 17.6
'1'11(1«03)1L 3.0 8 0.0
5.0 32 0.1%
9.0 58 8.0
11.0 52 11.%

 

& Atter N. N. Hillman end M. J. Wolf, refersnce 336.

Five ml of ether were shaken 10 mirutes with 5 ml of the agueocus phase of appropriate
composition. 5,000 to 8,000 o/m of U233 tracer (52% counting yleld) wers supplied to
the aquemu’phaue. Variation of the trecer from 100 to 100,000 o/- in 5 ml did not

change the extracted.
 

 

 

 

 

 

 

 

100 1 ) — I
a
wJ .
b
kS \ _ —J
é Ci
— CeO4" g
» _
(a3
§ . -
= F- ]
2z -
g
o
D il
o s0§"
2 o
-
= -
W
0 ——
o
L .
2 POJ"
10 )| : 1 1
0 0.5 t.0 1.5 2.0

MOLARITY OF INTERFERING ION

Figure 11. The effect of various anions on the extraction of uranyl
nitrate by diethyl ether.

After T. R. Scott, reference 337.

Conditions: Aqueous phase - varylng amount of anlon, 3N HNO3, 1M
Fe(NO3) ; aqueous phage and organic phase shaken 1 minufe at room
tempera ure

85
Teble X. The Effects of Variocus Acids and Anions upon the Vistribution Coefficlent of

Acid or ealt

Urenyl Nitrate to Diethyl Ether.2

Compoalition of agquecus phase

 

 

resent .
P 4.23M c.-;n(uoa)2 4H,0 8M N‘HuNO? 6.86M NH, N0,
(1000 g/1) (640 g/1 (549 g/1)
None 19.95 0.645 0.364
HC1l, 1N 10.24 0.336
HC1, 2N 6.34 0.182
HNO5, 1N 43.56 1.162
HNOg, 2N 71.2 1.95
CH3COH, 1N 15.7 0.662, 0.616
CH4COH, 2N 10.52 0.720, 0.762
H,S0,, 0.0039% 0.613
H,S0y, 1N 29.6 0.024
H,50),, 2N 23.5 0.019
H,POy, 0.0058N 0.609
HyPOy, 1N 0.01 0.01
HyPOy, 2N 0.01 0.01
H,PC), 1N
37k 0= 3.98 0.067
HNOg, 2N _
(NH,‘L)Ecao4 * Hy0, 0.7 /100 ml 0.0847
HyC,0) - 2H,0, 0.7 /100 ml 0.0800

 

2 After Furman, Mundy and Morrison, reference 326.

The 1nitlal volumes of ether and Aqueous Bolutlon were equal. Room temperature,

86
 

100 | { | ol

  

LI LA

   

 

  
  
 

 

 

 

* Ge(lV)
3
- i
Z -
w
o Th(1V) J_
w 3
b -
ISI 4
S ]
> 4
o
3 3
= C 3
o C ]
g - -
a 5 4
F -
0.0! -
- 3
: ]
- 4
0.00I | ] | ] ] 1 1 L1 1 | I
0 |1 2 3 4 5 6 T 8 9 101 12 13

INITIAL AQUEOUS NITRIC AGID GONGENTRATION, M

Figure 12. The extractlon of varlocus metal nltrates by diethyl
ether.

After R. Bock and E. Bock, reference 333. Condltlons: equal
phase volumes.

Metal nitrate Initlal aqueous Temperature
concentration
Th 0.1M 20 + 1°C
Saturated LiNO3, Ca(N03)2, or Zn(NOg)Q solutions
Ce(IV) 1M + 1°c
Au(ITI O 1M room
Sc(III 0.1 20°0C

 

Saturated LANO3 solutilon

a7
 

Table XI. Distribution Goefficlenta of Elementa batwesn Diethyl Ethar and Variocue Nitrate
Solutlons.
Hament H 0% o.gmmot o0.8MmoS  umwo 2 1m0 N0 ewmmo.2 1.immo.d 1.3mmNo S
10MNH, NO 4.a_qca(m3)2 watdNE NO; 8atdLiNO, BHNH, NO, 611.4\1(:103)3
Al €0,001 ¢0.001 €0.001 0.0006 €0.0001
Am(VI) 0.6%2
5b{¥) <0.01
As 0.0015"0. 007" 0.o%8" 0.168
Ba €©-0005 «0.0005 <0.0005 <€0.0001
Be 0.01k 0.002
Bi 0.0001 0.0003 0.007 . 0.073 0.00031 ©0.021
B o.01" 0.033-0.39
cd <0. 00001 «0.00001 0.00001 0.003 <0.0001 0.0002
Ca 0.0003 0.0005 0.0005 <0 .0001
Ce(TIT) . <0.0009
Ce(IV) 27 0.095 0.714 30.3(29.3)
Cr(III) «©.0001 <0.0001 <C. 0001 €0.0001
cr(vI) <17
Co €0.0001 <0.0001 <€0.001 0.002 €0.0001
Cu 0.0004 ©.0002 0.0004 0.005 <0.0001  -0.00082
Dy 0.0004 ©.0003 0.002
ad 0.0001 0.00001 0.00076
Qe < 0.002
e 0.022
Aa(IIT) 32.3(36.5-50)
H 0.72(0.71)
In <0.000% <0.0004 0.0003 0.001
Fe 0.0005 0.0005 0.001 0.0013 <0.0001 0.0017
La €0.0001
Fb 0.0037 <0.0002 <€0.0002 0.005
11 <€0.00002 0.0001 0.0002 0.0003
Mg 0.0002 0.0001 0.0002 <0.0001
Mn(II) €0.0001 <0.0001 <0, 0001 0.002 €0.0001
Mn{VII) €0.005
Hg 0.003 <0.0001 ~ <0.0001 0.049 €0.0001 0.0003
Mo €O 0QLeEus 0.0065
Nd <0.0009
N1 <0.0001 <0.0001 <0.0001 0.0006 <€0.0001
Np(IV) 0.2
Np(V) 1.1
Np(VT) §
P 0.256
Pu(III) <0.001
Pu({IV) 10.3
Pu(VI) 2.4 1.5
K 0.0005 0.0002 0.002% <0.0001
Ra €0.00025 <0.00025 <0.00025
Rara
earths 0.00076 <€A 0O0Q05 <0.0031
Re <0.015%* <0.CQl5% «<0.015%+
Rb 0.00014%
Sm <0.0009
S 0.013 0.1%6 0,001
Ag 0.025 €0.0001  0.001
Table XI. - Contimed

Mement H,0  0.BMNO% o.gMENO.S  LMmvo.® 1m0 ® BMENO,.2 BMHNO. S 1. xyEwo, 2 1, 3y

 

 

3 T
10MHH, NO, 4.2210:1(1@03)2 satdNHNG, aa.tdLilGO3 BMNE, NO, 6!_0.1(1103)3
Na <0.0001 <0.0001 <0.0001 <0.0001
sr €0.0008 <0.0008 <0 .0009 <0.0001
(I} <o.oo‘3?5'<0.00'35 <o.005§' <€0.005
TL(IIT) 0.083
Th Q.001* 0.0036 1.20 0.528(0.531) 0.5 0.00%% 0.32
T <€0-005
U(vI) 0.68+ 1,31% 165" 2.09 73.8  1.86(1.78) 1.85 2.3 208
v(Iv) 0.0006-0:001" 0.004-0.008+% .
v{v) <0.0005* 0.019+ 0.0ko* 0.02
¥ 0.001 €0.0009
Zn <0.0005 <0.0005 <0.0005 0.001 <0.0001
Zr 0.001* ~0.087 0.0011 0.011
a

*

After FPurman, Murdy, and Merriscn, reference 326.

Conditlons werse a ed, 1n general, so thet approximately 5gz. of U oa ware racovared
from the ether extract prior to spectographic examinatlion. In genaral survey studles,
0.1 g. of eaoch of the elemants: Ag, Al, B, Pa, Bl, Ca, Cd, Co, Cr, Cu, Me, Hg, K, Li,
Mg, Mn, Ka, Ni, Pb, 8Sr, Ti, Zn, and Q.05 g. each of In & Re was present along with
uranyl nitrete and a salting agent, 80 g. per 100 ml of ammonium nitrete and 100 g.
per 100 ml of calcium nitrate. (The latter is equivalent to k.23 M if the salt ia
conaidered to be Ca(NDg)p - 4Hp0, #.58 M if it is considered to be Ca(N03),). The
desoription of the axpdriment gliven in reference 326 glves the nitric scld concentra-
tlon as 5 ml of concentrated acld per 100 ml. A table of the partitlon ocefficlaents
glves the noild oconcentratlon as 5 g. of HNI per 100 m1. If the conoentrated acld
concentration is conslderad to be approximately 1&j, both of the above velues glve
a2 nitrioc acid concantration of the agquecus solution as 0.8M. The agueoue eolutionm
were phaken to equilibrlum with an equal volume of ethar af 20°C.

The u.t)-a.rum partition sesfflclents are the maximum values determined (sme, also,
f 9).
i@nfi-e earths were present In amcunts such that only limlitlng velues could be given
for individual elements VWY Apsctrographic means axcept fur Dy and 01.

Large amounte of clements werw uUped: ¥V 1-2g, A8 or Cr 16-20g, Na or Ce niltrate T0-100g,
Fe 1g, Mo 0.3g per 100 ml. Analysis of the ether phape made by maans other than
apectrographic.

-

+4

Limit set by lack of smenslitivity of spectrographic test; e probably much smaller.
* Valence mtate not deslgnated.

+E¥E

b

@ 18 much gregtsr for Mo present as a heteropoly aold.

— After Book and 3Bock, refersnce 333,

Values of a for BM HNDg solutlene have been caloulated from P-values glven by Bock
and Bock. Those valuea l?h parentheses are a-valuea giver directly by Bock and Bock
or interppiated fram thelr data.

Concentration of element oconcerned in initiel solution: 0.1M with the axception of
Al 0.94%, Sb, Bl 0.2M, Ge 0.03M, H EM HN:_I;,, Fe(III) 0.4M, La 0.Z7H, Fb 0.075M, So 0.2M
for M D3, Zn 0.4M. - - - = -

E].?nen B were preae:ng anAthe hitrate with the following exceptione: Ge am dels,
P as (NH HPOy, A8 a8 Na ady, V am VOz, Cr aa cr s Mo as -molybdate,

The S%%G) uglution hydgly:‘;d atrongN?#.o—jThe la;-gl:gt ggz't of them&timorw vaa
precipltated as hydroxide and only traces were detected In the sther phase.

Cr(VI) extracted well but an exaot value could not be determined bscause of
reduction of the chromlum.

Mn({VII) was reduced with the meparation of MnOp from the ether mo that practleally
no Mn was axtracted, :

Temperature: 20° for the saturated NAyNO3 and LiNO3 solutions. Room temperature
for the X 1-}1:5 aolutiona.

Rll—fimpre.ry, Stephanon and Penneman, reference 343.

L

|~

An(YI) was prepared by peroxydlpsulPate oxidation.

After Kool, refersnce 334,

The values glven in this column are values teken from curves given in this reference
(nea, almo, figures 8 and 13).

Concentrations of the varlcus elements in the initlal aqueous solution: Th, 22 mg
per ml of Th(KOq)y - #Hp0; U, 3.3, 10, 30 amd 90 mg per ml of U02(NO3)s - 6Hz0; Np and
Pu, tracer quantities. No detectable difference was observed in the partition deta for
the first three quantities of U 1listed; & lower a (1.7) waB observed for the latter
concentratlon..

. Snekihg times for the Np and Pu experiments were -kept short (15 sec to 3 min) to
mirimiee dlasproportlonation to other oxlidation statea. The shaklng time for U solutlons
wae never less than 5 mlrutes. An Inordase to two hours dild not make a difference in
the repults.

After Vdovenke, reference 34},

The 1nitial aquscus layer contalned, in addition to the acid and salting agent, abeut
0.1M of the nitrate examined. Equel volumes of the agquecus solutlon and diethyl ather
wers shaken for 5 mirmutes. Alter 12 hours equilibration a sample of the organic
golution was taken for analysais.

89
PARTITION COEFFICIENT

 

 

 

 

 

i 1 1 | 1 | I I 1 1 I
10 | Pu(IV)
. Np(VI)
i Pu(Vl):

" Np(V)

1.0 =
- Th(iv) 3
i Np(IV) -
O.l — =
- ]
- | T

0.0l L L Ll L 11 |

 

o 1 2 3 4 B8 8 7 @ -9 i0 il )2
INITIAL AQUEQUS RNITRIC ACID CONGENTRATION, M

Figure 13.
The extractlon of actinide niltrates by dlethyl ether.
After J. Kool, reference 334,
Conditions:

Tracer amounts of Np239 and Pu239 in aqueous solutions
were equllibrated with an equal volume of diethyl ether
at 25°C and room temperature, respectlvely. 330 mg of
Th(NO3)y + 4Hp0 per 15 ml of initial aqueous solution
was equilibra%ed with an equel volume of ether.

The oxidatiog_gta.tes of neptunlum have been the subject of
some quesation. 45

%20
 

        

 

 

1.0 1 I - ]
- Ce (IV) ]
i i
- Zr -
l()-l — '3
- ;
o] n .
- r N
- [ .
o
o 1072 - Ce(lil) Nb —
s ;
Ll E i
O B i
O
z '
— -3 —
0 F -
| C ]
& . _
<X
o - i
|0_4 = —
[ i
10-3 | | |

 

0 l 2 3 4
INITIAL AQUEOUS NITRIC ACID CONGENTRATION, M

Flgure 14, Partitlon coeffilclents of fisslon producte between
diethyl ether and agueous sclutlon contalning Ca(NO3)> and different
initial acliditles. After V, Vdovenko, reference 343. Conditions:
Aqueous solutlon--required amounts of niltrle acld and radloactlve
material added to 3.5M solutlon of Ca(NO3)p; Vo/Va, 1.

91
Aqueous_thiocyanate systems. Uranium may be extracted
from aqueous thiocyanate solutiona by diethyl ether.ifigii&l
Table XII listse the fi&rtition coefficients of several
elements from aqueous soclutlons of various thlocyanate con-
centretiore fi A number of substances not -11sted in the
table glve negligible distributions or dlstributions of
only & few percent under the conditions tested: NH), , Sb(III),

As(TII), As(V), Bl, Cd, Cu(I), Cr(III), Ge(IV), Ii, Hg(II),

Teble XII. - Partition Coefficlents of Varlous Elements between Dlethyl
Ether and Aqueous Thlocyanate Solutions.2
Composltion of the inltlal aqueous solutlon

 

HC1 ot' ' NH4 SCN concentration

M c M 3M oM ™
0.1M a1l 0.5 20 0.011 0.099 0.275%
0.2M BeCl, 0.5 RT 0.039 0.987 5.29 11.9 |
0.1M CoCl, 0.5 RT 0.037 1.39 2.98 3.04
0.1M Gall, 0.5 RT 1.89 9.56 152

HC1 0.5 20 2.67 12.7 31.1 59.4

0.1M InCl, 0.5 RT 1.06 3.05 2.15 0.908
0.1M FeCl, 0.5 RT 8.00 5.13 3.08 1.14
0.1M MoOCl, ~0.5 RT 140 34.9 36. 42
0.1M ScClg 0.5 RT 0.145 3.95 8,06
0.1M(NHy)oSnClg 0.5 RT 144 950 > 1000 > 1000
0.1M T1Cl, 0.5 RT 1.43 5.25 3.94 3.22
0.1M TiCl, 0.5 RT ~0.15
0.1M U0,CL, 0.5 RT 0.821 0.117 0.160 0.072
0.1M VOC1, 0.5 RT 0.176 0.095 0.022
0.1M 2nCl, 0.5 RT 23.7 37.8 18.3 12.9

2 After R. Bock, reference 341.
L as a101,7
£ 6.2M
4 6.6

Equal phase volumes equllibrated at room temperature.

92
N1, PA(II). Figure 15 represents the change in a, with
thlocyanate concentration for aqueous solutions of different
aciditiieei:E Anglysils of the ammonlum, uranium, thiocyanate
concentration of the ether phase indicates that uranium 1s
extracted as U02.(SCN)2:3El

by dilethyl ether from aqueocus fluoride solutiona.ifig Table
XIII lists the partition coefficlents of a number of elements
from aqueous solutions of varlous hydrofluoric acld concen-
trations.

Dibutyl ether

ether as an extractant far uranium has been Investigated
extenslvely by workers 1ln the Soviet Union;ifi&ii&éziig Di-
butyl ether offers several advantages over dlethyl ether.

It 18 less soluble in water, lees volatile, and has a hlgher
flash point. The dietributlion coefflclent of uranyl nitrate
is, however, less for dibutyl ether than for diethyllether.
The partitlon of uranium between water and dlbutyl ether ds
represented in figure 1.222:32L Mo dqigtribution of uranyl
nlitrate and nitric acld 1s plotted as a functlon of agqueous
nitric acld concentration in flgure 16.§£§ Karpacheva,
Khorkhovina, and Agashkin&iig have 8tudled the effect of
varlous salting-out agents on the distributlon of uranyl
nitrate. The salting-out actlon was found to lnerease wilth
increasling valence of the catlon. The partlition coefflclent
of -uranium from an aqueous solution initially 0.5M fiOE(Noj)a,
4.5M Cca(WNO

o» and 0.5M HNO, into an organic phase 85% (by

3) 3
volume) dibutyl ether and 15% carbon tetrachloride is 0.70;
%py (VT) is 0.42.331 Zireonlum, nioblum, and ruthenium are
the main flsslon product elements ext::fla,n:-..ted.—efi&ij&g Heyn
and Ba.ne::"jee;a-29 have studled the extractlon of blsmzth

nitrate by dibutyl ether and several other solvents.

93
URANIUM PARTITION COEFFICIENT

 

 

 

 

 

1.0 I I I 1T I !
I .
I | ]
A < -
" )
H.QE&
X Q,
Q, ¢
: 6b
: .404, 7/ _
0.1 | "o -
- g ]
-
0.02 —
| —l ] 1 l_. ]
O ! 2 3 4 9 6 ¥
INITIAL AQUEOUS NH4qSCN GONCENTRATION, M

Flgure 15.

The extractlon of uranyl thlocyanate by dilethyl ether at

various inlitilal NHusCN and HC1 concentrations.

After R. Bock, reference 341,

Conditlions:

Aqueous phase--initially 0.1M, U0O,Cl., and NH,CNS and
= 4

HC1l concentratlion indlcated. 272

Equal phase volumes equilibrated at room temperature.

94
Table XIII.- Partition Coefficlents of Varlous Elemente between Aqueous.
HF Solutions and Diethyl EtherZ

HF concentration of the stertlng aqueous solutlon

 

Element— 1.OMHF 5. OMHF 10.0MHF 15.0MHF 20. OMHF
Sb(T1L) <0.0005 0.003 ' 0.019 5,000 0.0067
As(IIT) 0.111 0.227 0.432 0.530 0.605
As(V) <0.001 0.017 0.048 0.121 0.157
Be <0.0005 <0.0005 0.005 0.019 0.042
cd <0.0005 0.002 0.006 - 0.009 0.014
Co <0.002 - €0.002 <0.002 0.005 0.017
Cu(II) <0.001 <0.001 <0.001 0.010 0.013
Ge(IV) <0.002 <€0.002 0.005 0.028 0.072
Mn(IT) <0.0005 <0.0005 0.002 0.005 0.013
Hg(IT) <0.0005 <0.0005 <0.0005 0.009 0.028
Mo(VT) 0.007 0.018 0.031 0.062 0.103
M <0.0005 ¢0.0005 <0.0005 0.005 0.007
Nb(V) 0.006 0.04% 0.480 1.08 1.92

P(V) <0.001 0.011 0.032 0.110 0.173
Re(VII) 0.0005 0.121 1.58 1.78 1.62

Se{IV) 0.0006 0.022 0.080 0.131 .0.148
Ta 0.012 0.774 - 3,80 3.82 3.84

Te (IV) 0.0001 0.020 0,071 0.237 0.298
Sn(II) 0.020 0.029 0.052
Sn{IV) 0.006% 0.0062 0.053% 0.055
U(v1) <0.002 <0.002 <0.002 0.005 0.011
v(IIT) <0.0005 0.003 0.03 0.10 0.13

v(V) <0.001 0.004 0.017 0.056 0.093
Zn €0.001 <0.001 <0.001 0.002 0.009
Zr 0.004 0.005 0.005 0.012 0.030

& After Bock and Herrmann, reference 342.
Equal phase volumes equilibrated at 20.0 * 0.5°C.

E-The concentration in the 1nitlal aqueous solution of the lonlic specles
of the element listed in the table was 0.1M in each case with the
exception of Re(VII) which was 0.05M.

Fluoride stock solutlons were prepared 1n the following menner:
carbonates (Cd, Co, Cu, Mn(II), Ni, 2Zn), oxides (Sb(III), Ge(IV),
Hg(II), Nb(V), Se(IV), Ta(V), Te(IV), V{III)) or hydroxides or
hydrated oxides (SN(IV), Zr) were dissolved in an excess of HF;
As 03 was dilssolved in a known volume of O.1N NaOH and the calculated

amount of HF added to the solutlon; BeF2 and SnF2 were dissolved; K HAsOu,
Na2HP04, KReou, ammonium vanadate, ammonlum molybdate, and sodlium uranate
were dissolved 1n HF. '

5.4 M HF
£ 10.4 M HF

95
 

 

     
     

 

 

 

 

1.0 — -3
z - :
w [ HNO3 -
) =
@ o
TR
uw B {
o
O
z O. UOp(NO3)e _
o ]
e
-
o
g
a

oo L—1L 1 1 1 ¥ 1 1 1 1 '}

4 3 @8 7 8 © 10 1 12 13 14 15 16
INITIAL AQUEOUS NITRIC ACID CONCENTRATION, M

Figure 16.
Partitlon of urenyl. nltrate and nitric acid between dibutyl
ether and aqueous solutlon.
After V. Vdovenko, A. Ilpovskll, M. Kugzina, reference 346,
Conditions:

Equal phase volumesa equlllbrated at room temperature for
both UOo({NO3)o and HNO, extractions. For nitric acid,
polnte corr&aponding tg an acld content In the aqueous
golution of greater than 13.4M were obtained by the ex-
traction of previously aclidified dibutyl ether wlth con-
centrated nitric acld. For uranyl nitrete, polnts greater
than -12.0M HNO7 were simllarly obtalned. The uranlum
concentration ¥%as 78 mg/ml. :

Dibutyl "Cellosolve" (Dibutoxymonoethyleneglyocol)

Aqueous nitrate systems. A number of cellosolve
derivatives have been lnvestligated for the extraction of
uranium (Table VIII). Diethyl cellosolve 18 an excellent
extractant;iig Unfortunately 1ts solubllity 1in water 1s
large (21% by welght at 20°C). Dibutyl cellosolve 1s less
soluble in water (0.2% by welght at 20°C). However, 1t does

not extraot uranium as well as dliethyl ether, either from water

96
solutlon (figure 2l§543§l) or from aqueous alumirum nitrate
solution (figure 6112). The partition coefficlent of uranium
into dibutyl cellosolve from nearly satureted solutlona of
ammonlum, calcium, or ferrlic nltrate 1s 1, 50, and 20,

:n-.e.-apectil.\rely.-332

Dibutyl "Carbitol" (Dibutoxydlethyleneglycol)
Aqueous nitrete systems. Dibutyl carbitol (Butex) is

used in the recovery of irradiated fuel material.fiil As a
Bsolvent, 1t has ‘been subject to conslderable st:udy.a:g-'-352
The partition of urenium between water solution and soclvent
18 glven 1n figure E.EIQngilfigl The partition of uranlum
between nitric acld solution and dibutyl carbltol 1s
11lustrated in figure 17.353 For aqueous solutlons in this
range ol acld concentration, the partition coefficient 1s
observed to 1lncrease with increased uranyl nitrate concen-
tration. The partition coefficlent of nitric acld 1s plotted
as a function df acld concentration in figure 18.-33’—4'-"-353-'-3-5-i
In figures 19 and 20, the partlitlon coeffliclentes of uranlium
and several other heavy elements are plotted against nitric
acld concentration. The 1nitiel acld concentration of the
aqueous phase 18 plotted 1n figure 19.33& The equllibrium
acld concentration of the aqueous phase 1s glven in figure
20.3£E Best, et hl-352 have observed that the ateephess of
the extractlion ocurves (figure 20) 1s compatible with the
formetlion of the specles HM62(N03)3 and H2H(N03?6 in the
organic phase rather than Just Hoa(Nos;)2 and M(NO3)4. The
curves glven 1n figures 19 end 20 are 1n general agreement
consldering the dlfference ln acld concentration plotted.
There 18 a large discrepancy between Np(IV) data. The
abllity to malntaln neptunium 1ln the pentavelent state during
extractlion mey be subJect to question. The partitlion of some
fisslon product elements 18 given 1n figure 21 fop various

97
 

 

 

 

 

 

1.0 2
>
u -
s
E D.I —:
o j
w -
u —
S .
O ! Flgure 17. Distribution of uranyl nitrate
J between dlibutyl carbltol and nltrlc acld
g golution. Adapted from C. A. Kraus,
- reference 353. Conditlons: Approxlmately
- 0.01 b _ equal volumes of organlc and agueousg
- v ; - phase, 1lnitlaelly at the uranium and nitrlc
nq"' - acld concentrations 1indlcated, equlllbrated
o 7] at about 27°C.
-
fi
0.00lI
T | L I i I I r 1 !
&
o llo ' .
> -
T _ -g
o - -
. 4

 

 

 

h-

> -
w

9 L.
W

W Q.

o * 3
o ]
2 -
° -
- -
&

o " ]
a

0.0l | | 1 ] ] ] ] 1 ] 1

 

o I e 3 4 85 8 7 8 9 10 Il
INITIAL AQUEOUS 'NITRIC ACID CONCENTRATION, M

Figure 18. Distribution of nitric acild between dibutyl carbitol and
aqueous solutlon,

O, After C. A. Kraus, reference 353. 0, After J. Kooil, rfiferfince 334,
A, After D. G. Tuck, reference 354. Conditions: Equal334,35% or ap-
proximately equa.1355 volume portions of solvent and agueous solutilon
equilibrated at ~27°¢,353 250C,334 and ~21°C.354
 

100 T | ! I 1 ] | | I 1

 
   

 

 

 

 

; ———-- Pu(IV')':
] :

. 9F NptV)
e C Pu(VI) ]
w = -
O - u(vI) 7
L - 4
e i ™av)/

3 g NP(V) 3

Z - i

O -

_ T Np(1V)

- i

@ |

a C.l = 'E
r :
I ;

|
O I 2 3 4 5 6 78 9 10 11 I2
INITIAL [HNOgloq, M

_ Flgure 19.
The extreotlion of actinlde nitrates by dibutyl carbltol.
After J. Kool, reference 33L4,
Conditlions:

Tracer -amounta of Np239 or Pu239, 330 mg of Th(No3)4
4Ho0 per 15 ml, or 300 mg of UO2(NO3)o (hexahydrate) per
15 ml in aqueous nitric aclid solution equlllbrated wilth
an equal volume of dibutyl carbitol at 25°C or room tem-
peraturs.

The oxidatigfl states of neptunilum have been the subject of
some question.33D

99
 

OO —r——T——T7T—TT1T T T T T T

T T Tirl
O
=
oy
&

L1l

a
o
T
2
9
s
L1

/ Np{Vi)

A Pe(Vi)

  

1

LUV

T

1/ Th{IV)

 

PARTITION GOEFFICIENT,
o

o

I 1 IIIIII
] IJJIIII-

 

 

| | | | ]
6 7 8 9 10 1l
[HNOz]sq. M

Flgure 20.

 

o.o0 L4 LI

Pt 1
O I 2 3 4 5

The distribution of actinide elements between dibutyl carbiltol
_and aqueous Bolutlon as a function of equilibrium aqueous nitrie
acld concentration.

After G. Best, E. Hesford, and H. McKay, reference 345.
Conditions:

Tracer concentretions (~10'3§) of actinide. Temperature, 25°C..

100
G

PARTITION COEFFIGCIENT,

 

 

 

 

 

 

1.0 T— T 1T T T T T 1 T 1 3
- 3
[ 1

107 = A Ce(IV) 5
r -
i )

0% |- 3
: A Ge(lll) ]
i Y

|(y-3 = —
- .
- ]

o4 L—L 1 111
0 | 2 3 4 5 6 7T 8 9 10 11 12

[HNO3Joq. M

Flgure 21.
The partlitlion of tracer samounts of yttrium, cerium, and
zlrconlum between dlbutyl carbltol and aqueous solutlon
as 8 functlion of aqueous niltrlc acld concentration.

After H. McKay, K. Alcock, and D, Scarglll, reference 355.

101
 

 

10000 c—1T——T—7——T—T T T T T T T T 3
=.
© 1000 |
- -
2 -
wl
G ]
E b
W
o -
Z _
o i
~ |
=
< 10 |
o F
_
o b—1 0y

 

 

 

4 5 6 7T 8 9 1011 12 13 14 15 16 17
EQUIVALENTS OF METAL NITRATE
per 1000 ¢¢ OF WATER

Figure 22. The effect of salting-out agente on the extractlon of
uranium by dibutyl carbitol. @ Cu(N03)p, ®Ca(NO3)2, & Zn(NO3)z,
0 A1(NO3)3, l:l_Fe(NOg)g, A 1a(NO3)3. After E. Evers and C. Kfaus,
reference 332, Condifions: Urdnlum concentration, 2-6 g/100 cc
of phase. Temperature, 279C; Vo/Va = 1. X Al(N0353. After D. Lee,
R. Woodward, G. Clewett, reference 358. Conditlona: Trace amounts
of uranium. Temperature, 27°C; V,/Va, variled.
aqueous nltrlc acld c:onr:s.-ni;zz-e.i:.ti.onisl.-3"22 The dlatribution of
iron into dibutyl carbitol 1s increased by an lncreage 1n
a.c::l_d:l1‘:y.§-5—g Chloride ion promotes the extraction of iron.
Boron 18 extracted by butex, especlally 1in the presence of
copper nitrate as salting-out agent.aaig Vanadlum and molyp-
dermum are extracted to several per c:en‘v:,.-a-2 The extractlon

of cadmlum. chronlum, nlckel and tltanlum 1s small.d32

102
The effect of Ba;ting-out-agenta on the distrlbution
of uranium into 4ibutyl carbltol has been Butdied.iigiiég’
356-358 Some of the results are presented in filgure 22.

Aqueous_chloride systems. Uranium (IV) and (VI) and
thorlum are poorly extracted by dibutyl carbitel from
aqueous solutiofia 2-6M in hydrochloric acid.§§2 The extrac-
tlon of protactinlum 1s Increased as the acld concentratlion
18 1ncreased. From 6M HC1, ap, 18 10. The extraction of
_hydrochlorie acid 1s negliglble from agueous solutions less
than-fifl i1n hydrochloric acld. A thlird phase 1s formed upon
equilibration with 7.5M HC1l. The third phase containe a

large amount of the aclid., One phase resulte upon equlllbra-

tion with 8.5M HC1.

Pentaether (Dibutoxytetraethyleneglycol)

mich of the data pertinent to the extractlion of uranlum by
pentaether. The distrlbution of uranyl niltrate between
solvent and water 1is glven in figure EAlzéiigi The partl-
tlon coefflclent of uranyl nitrate from varlous nitrate

medla ls plotted in flgure 23.—3-§g The dlstributlon of

nltric acid as a function of aqueous acld concentration 1s
also shown 1n flgure 23.§§£ The effect of palting-out agents
on the partition of uranium is 1ilustrated In filgure 24,532
Table XIV 1lists the partition coefflcients of a number of
elements other than uranium between pentaether and various
aqueous med:!.a..—3--ég Uranium 1s éxtracted by pentaether from
aqueous solutions contalning ammonium nitrate and/or nitrilc
aclid in the presence of sulfate, phoaphate, or sillcate 1::m&1.4§§g
Phosphate 1lon, in large quantity, and soluble sllicate lons
are extracted by the solvent.iég Fluoride ion, in signifi-
cant quantity, lnterferes with uranyl nitrate extraction.

This effect may be overcome by compiexing the fluoride ion
with calclium or aluminum n:Ltz"::aLte.-:?:é2

103
 

       

    

o
llllflli

o~
| UOg(NOa)z:
5¢ NHqNOz /10 mli|

—t_ -0 HN03

IJ_lllll

 

0.1

PARTITION COEFFIGIENT, a

_I_l_l_llLlI

  

: ] ] I | L 1 1 ! ]
o | g 3 4 % &8 T @ € 10 H 12

INITIAL AQUEOUS NITRIC ACID GONGENTRATION, M

 

Flgure 23. The partition coefflclents of uranyl nitrate and nitric
acld between pentaether and agueoue solution. A UOQ(NO3)2 : 1.0 g.
Ugoa dlssolved in I-]N‘O'i;, dlluted to 50 ml with acid of depilred
strength, and shaken 1l minute wlth an equal volume of pentaether.
D_UOZ%NO3)2 + NHyNOg : 1.0 g. U308 dipsolved in 10 ml of ENO3 of
deslred strength af%er addition of 5 g. NH4N03; shaken with an equal
volume of pentaether for 1 minute at room temperature. Adapted from
D. Musser, D. Krause, and R. Smellle, Jr., reference 360. OHNO3 :
equal volumes of nltrle acld solutlon and pentaether equilibrateé
f‘gr 1 hour at 259C. After C. Stover, Jr. and H. Crandall, reference
361.

Cyclic ethers.

A number of cycllc ethers have been investigated as ex-
tractants for urand.um.M Those solventls that contaln
the furane nucleue have been found to glve good extractlons
of uranyl nitrate from aqueous solutions. Solvents of the
hydrocarbor substltuted tetrahydrofurane type have been
found to be eppeclally good.-lsj- The extractlon of uranium
and thorifim by four cyclic ethers 1s 1llustrated 1in figure

25 a8 a function of acld concentration 1in the agueous phase.is—lt

104
 

 

10000 c—T— T T 1
o

P-

z

W 1000

S

u

1R

ad

o

o

z

o

= 100

-

e

Lo

a.

ob—L 1 1o b

 

 

 

3 4 5 6 7 8 9 10 Il 12 13 14 1%

EQUIVALENTS OF METAL NITRATE per 1000cc OF WATER
Flgure 24. Effect of salting-out agents on the extraction of uranium
by pentaether. AN‘aNOgr V NH4yNO3, ®Ca(N03)p, OA1(NO3)3, QFe(NO3)3.
After E. Evers and C. aue, refeéerence 332 Condltions: Uranlum con-

centration, 2-6 g/100 ce of phase. Temperature, 279C or room tempera-
ture. '

From figure 254, 1t can be seen that uranyl nitrate 18 ex-
tracted more efficlently by the varlous solvents than ls
uranyl perchlorate. Better separation of uranlium and

thorium 18 also sachieved from nlitrate solutlion rather than

perchlorate.

ESTERS
Information 18 leas complete or less readlly available
for the extractlion of uranlum by esters than by ethers.
The dletributlion of uranyl nitrate between ilso-amyl
acetate and #ater 1 represented 1n f.’igu::'e_'}-fl..l-a-2
Karpacheva, et a1,iflg have found the extraction capaclty
of butyl acetate to be Intermedlate between dlethyl ether

and dibutyl ether. Hyde and Wolf,ilé in addition to thelr

105
 

Table XIV. Partitlon Coefficlents of Elemente between Penta-ether and
Various Aqueous Medial
Element Concentration in Aqueous m:nlut—:tonE
agqueous phase
before extraction Nitrate Nitrate + Sulfate Sulfate
(mg/25 m1) Chloride + Chloride
Al 500 0.003. 0.003 0.000 0.003
Ba 362 0.02
" 7 0.35
cd 501 0.024 0.003
" 500 0.026
n 10 0.053 0.01
" 10.5 0.004
Ca 521 0.011 _ - c
" 500 0.0001 —c
" 10.4 0.020 0.00
cl 496 0.026
n 4ol 0.02
" 10.3 0.025
" 9.9 0.03
Ccr(III) 500 0.003 0.004 0.0001
n 10 0.0023 0.013 0.000%
Co 555 0.007
" 500 0.002 0.00013
" 11 0.012
n 10 0.009 0.0065
Cu(II) 500 0.026 0.024 0.000
" 10 0.017 0.018 0.000
Fe(III) 515 0.031 0.003
" 500 1,2
" 10.3 0.035 0.002
" 10.0 0.046
Pb 500 0.017 --c
" 10 0.007 0.005
Mn(II) 500 0.0011 0.00006
n 10 0.0014 0.00075
Hg(II) ha7 ' 0.21 0.015
" 127 0.19 0.036
" 10 0.41 0.176 0.23 0.03
Mo (VI) 500 0.028 0.10 0.001 0.001
n 10 0.10 0.015

106
 

Teble XIV. - Continued
Element Concentratlon in Aqueous 8011.1'|.'.-:|.on'-E
agueous phase
before extraction Nitrate Nitrate + Sulfate Sulfate
(mg/25 ml) Chloride + Chloride
N1 516 0.0001
" 500 0.0018
" 10.3 0.0008
" 10 0.0032 0.00064
P(P0}" ) 500 0.00005 0.00001
" 10 0.00024 0.00
Ag 500 0.09 0.005
" 10 0.32 0.005
sof* (aa(NHu)asou) 500 0.00
" 10 0.00
Th 500 9.12 11.5 0.0001 0.0001
" 10 87.5 0.005
Sn{IV) 500 0.0024% 0.37 0.00015 0.000
" 10 0,019 0.0006
T1(IV) 11 0.003 0.00 0.035
W 10 0.081 0.0025
v(V) 140 Q.22
" 107 0.11
" 14 0.12
" 8.5 0.07 0.009
Zn gy 0.15
n by 0.018
n 10 0.14 --c
" 8.9 0.022 0.000
Zr 10 0.04o 0.013

2 Adapted from A. G. Jones, C-4.360.3(1945).
Equal volume portiona of aqueous solution and pentaether,

2 Niltrate
Sulfate

Chloride:

present.

: 3/4 saturated ammonium nitrate solution.
: paturated ammonium sulfate solutlon.
chloride added as ammonium chlorlde equlvalent to the metsal

L Preclpitates of insoluble sulfate obtalned 1n ammonium sulfate layer.

107
 

10 | | | ] ] 1 | ] |

‘Uronium ]

  
  
  

1 lIlIlI

L

 

 

 

 

- 3
z -
w -
2 ]
= T

w

o

o

z 1 T
° Thorium 2
« = == HCIO4]
q L
o

1 IILlLI

 

 

 

0.01 =
! i
Py

0 | 2 3 4 5 6 T 8 9 10 H
INITIAL AICD CONCENTRATION, M
(B)

Flgure 25. The effect of inltlial nltric and perchlorilc acid concentra-
tlon on the extraction of uranyl salts (Fig. 25-A) and thorium salts
(Flg. 25-B) by tetrahydrosylvane (THS), tetrahydropyrane (THP), 2-
ethyltetrahydrofurane (ETHF), and 2,5-dimethyltetrahydrofurane (MTHS).
After M. Branlca and E, Bona, reference 364, Conditlons: Uranium
concentration, 2 x 10_—3@. Thorlum concentration, tracer UX;. Tempera-
ture, 25 + 0,20C. Vo/Vg, 1. o

108
general survey work (Table VIII), have studled the extrac-
tlon of thorlum and uranium by ethyl acetate, n-propyl
acetate, and l1lso-propyl acetate as a function of the

nitrate concentration of the agueoue phase. It was the
observatlion of the latter groupglé that the extractilon of
uranlum tends to decrease wlth 1ncreasing molecular welight

of the esater. Therefore, only acetates and proplonates
need To be consldered serlously. Increased protactinum
extraction was observed wlth incfeasing length of the

alcohol portion of the ester.ilg It was further observed
that hydrolysls of the ester tends to lncrease the extractilon
of both thorlium and uranium.ilé It was not determined whether
the addition of alcohol or organic acild causes the 1ncreased

extractlon.

Ethyl acetate

nltrate between ethyl acetate and water has been studled by

deKeyser, Cypres, and Hermann.lé& The partition coeffiliclent

was found to vary from 0.17 at 22% UOE(NO3)2 . 6H20 in the
aqueous phase to 0.78 at 43% aqueous concentration. In
laboratory practlce, uranium 1s extracted by the solvent
from aqueous nitrate medla. The followlng conditlons have

been ueed by varlous groups to extract uranium:

Grimaldl and Levine3®2: 9.5 g. of AL(NOg)5 - 9HLO
are added to 5 ml of solutlon approximately 2.4N
in HNOS. 10 ml of ethyl acetate are added and
shaken at least 30 seconds.

Rodden and Tregonningiéé: Uranium preclipltated 1n the
presence of aluminum (20 mg) wilth NHMOH l1s dlssolved
in 1 ml of HN03(1 to 1). 8 g. of Mg(N03)2 . 6H20
18 added and the volume adJusted to 10 ml with water.
5 ml of ethyl acetate are added and vigorously shaken
for 2 minutes. (Used with 20-400 mg samples of U308')

109
Nietzel and DeSesa32l2368. approximately 15 ml of sat-
urated alumlnum nltrate solutlon are added to 3 ml
or leas of sample containing 0.30 to 15 g. of U308
per lliter. 20 ml of ethyl acetate are added and
sahaken for 1 mihute.

Guest and Zimmermanfiég: To 5 ml of sample contalning
5% concentrated HNO3 by volume, 6.5 ml of hot alumil-
num nitrate solution, having a bolling point of 130°C,,
are added. The resulting solution 1s cooled, 20 ml
of ethyl acetate are added, and the mlixture shaken
for 45 to 60 seconds.

Steele and Tavernerlgg: Approximately 5 ml of aqueous
golution are saturated with alumlinum nitrate. The
resulting solution 1s shaken with 10 ml of ethyl
acetate for 1-2 minutes.

In the procedure of Rodden and Tregonning,iég aluminum ni-
trate 1s used lnatead of magneslum niltrate 1f extractlion

i1s to be made 1n the presence of phoasphate. DeSesa and
NkfizeliéZLiég found that 1 molar concentratione of phos-
phate, sulfate, or carbonate ion could he tolerated with

no 111 effect on uranium extractlon. Small amounts of
godlum phosphate have been used to suppress the extractlon
of thorlum wlthout affectlng the extraction of uran:l.um.-l-2§
Steele and Ta.ver'nerlgg report the extractlon of apprecilable
amounts of thorium and zirconium and small amounts of
vanadium, molybdenum, and platlinum by ethyl acetate.
Grimaldl and Lev:l.ne,iéflli Guest and Zimmerman,§§2 and Nletzel
and DeSes&iéILiég have lnvesatigated the effect of a number
of elements on the recovery and/or determination of uranium
according to thelr respective procedures. Nletgel and
DeSes&iéZLzég-found vanadium, present in 100 mg amounts, was
precipltated and uranium was occluded 1n the preclpitatate.
Titanium was observed to partially extract. This was pre-
vented by preclpltatlion of titanlum wlth p-hydroxyphenylarsonilc

acld before extraction.
procedure in which uranium is extracted by ethyl acetate from
an aqueous phase contalning an excess of ammonium thlocyanate.
Dizdar and O‘I:I-enov:chl'?-'l have'also Inveatlgated the extraction

of the uranyl-thlocyanate complex by ethyl acetate,

KETONES
Methyl ethyl ketone.

nitrate between methyl ethyl ketone and water and between
methyl ethyl ketone and saturated ammonium nitrate solutlon
is glven in figure -, 321 E’ale::l.-]:gé reports a uranium
partition coeffleclent of approximately 25 between methyl
ethyl ketone and an aqueous solution of 60% NH4N03 and

1N HN03. Methyl ethyl ketone is not as selecfive as
diethyl ether'.—3-gl Homogeneous sclutlons are formed be-
tween the ketone and an equal wlume of saturated ferrilc or

cupric nitrate at 20°C.BgL

clent of uranium between methyl ethyl ketone and an aqueocus
GO%INH4N03, 3% NH,SCN solutlon 1s about 2000.i2§ Iron 18
extracted.

Milner and ‘Woocl—-?iZg report the separation of tantalum
and nioblum from uranium by extracting the fluorldes of

the former elements wilth methyl ethyl ketone.

Hexone (Methyl iso-butyl ketone).

between hexone and water 18 represented 1n figure 4.18 321

The partltion coefflcients of uranium, nitrlc acld, and
several other actinlde elements are plotted as a function
of aqueous nitric aeid concentratlion 1n flgure 26.—3-3-E The

effect of several salting-out agents on the partlition coeffl-

111
PARTITION COEFFICIENT, a

 

 

 

 

 

 

10 — T T T T T T T T T T 3

- _ Pu(IV) 3

l e Np(V) -

~ Pu(VI) 7

- U{vl) 7

1.0 . —

" " . 0 o SR HNOaf

- Th(IV)

] X Np(Iv) T

0.1 :— "-l. —
0.01 l l I | | 1 i | ] | |

0 ! 2 3 4 S5 8 T e 9 IiC 11 12

INITIAL NITRIGC AGCID GCONCENTRATION, M

Flgure 26.
The extractlon of nitriec acid and actinide nitrates, Th, U,
Np,and Pu, by methyl isobutyl ketone (hexone).
After J. Kool, reference 33i4.
Conditions:
Tracer amounta of Np232 or Pu239, ?30 mg of Th(NOg), °
4Ho0 per 15 ml, or 300 mg of U02(NO3 )5 (hexahydrate§
per 15 ml in nltric acld solutlon of nitric acid alone

equllibrated with an equal volume of hexone at 25°C or
room temperature.

The oxidatlion atfitea of neptunium have been thé subject
of some question.3%5

112
clent of uranlum 1s given 1n f:l_gu're.e'r.-—i12 Vdovenko and
co—workerazgé have obsBerved an increase 1n the partltion
coefficlents of ceslum, calclum, strontium, and lanthanum
when the uranyl nitrate concentratlon 1n the 1nitilal

aqueous solutlon 1le increased. This has been related to

the extraction of the elements as metal uranyl trinltrate
salts. The partition coefflcient of uranium from a highly
palted aqueous solutlon is decreased by an 1lncrease 1n
uranium concentration. Kra.us311 observed a, to decrease
from 153 to 78.3 aB the 1Inltlal uranlum concentration was
increased from 5 to 100 grams 1n an equeous solutlon con-
taining 580 grams of aluminum nitrate. Jenkins and IWIcKa.y-iI-'!i
found a. to decrease from 1.58 to 1.28 as the Initlal uranium
concentration was increased from 144 to 348 grams per liter

in an aqueous solution 8M in NH4N03 and 0.3N 1n HNO In

3
the latter case, commerclal hexone adJuated to 0.15N HNO3
was used as the extractant. Flgure 28 represents the ex-
tractlon of uranlium by hexone from aqueous solutions contalning
various amounts of nitric acid and calclum or ssod:!.um'n:L‘c,raLte.:’-Zi
The distribution of U(VI), Pu(VI), Pu(IV), Th, La, Ca, Na,

and HNO3 by hexone from aqueous solutions contalinlng nltrilc

acld and calclum nltrate has been lnvestlgated by Rydberg and

Bernstrgm.§Z§ Hyde and co-workers have studled the extraction

of uraniumiié and thorlumélélizz by hexone as a function of
the total nltrate concentration of the aqueous phase. Dlistri-
bution curves (a or P versus nitrilc acld or total nitrate
concentration of the agueous phase) are presented for the
varlious elements in the different papers. The effect of
alumlnum nitrate concentratlon on the extraction of fiaslon
product gamma-actlivity 1n general and zirconlum-nioblum,
cerlum, and ruthenium in particular 1s shown in flgure
29.§I§— Increased extractlon is effected by an increase

in salting-out agent. An increase 1n nitric acld concentra-

113
 

1000

 

 

[ ]
o -
100 -
- ;]
n 3
= ™ S
o - i
_ i
= . -
o
5 10k 3
w - ;
L. L =
w | i
- .
o [
g A
e L —_
- 1.0 = 3
= C ]
‘é - .
a. L .
- .
0.1 — =
s .
| a
oot b—d 1 1 1 111 )11 1|

 

 

o1 2 3 4 5 6 7 8 S 101 12 13
NITRATE CONCENTRATION, M

Flgure 27. The effect of varilous saltlng-out agents on the extractlon
of uranium by hexone. V NO3, mNaNO3, DCa(NOi)g, A Co(NO3)2, &
Mg (NO3 )2, oBe(NOi-;)g, O Al( 03?2. After W. H. Baldwin, referénce 319.
Condltlions: Egual volumes of pure hexone used to extract aqueous con-
talning 30 g U/liter.
ay

PARTITION COEFFICIENT,

 

o
1 1T 11hi
_
]
\\\ —
W)
W\
v\
v N
] |

 
 
  

 

 

 

 

 

>
o ” 1;4-
.0 -
NaNOy ;
NO3
e

-1 |
107 = | | | | 1 3
0 I 2 3 4 5 6

NITRATE GCONCENTRATION, M, OF SALTING-OUT AGENT

Figure 28.
The partition coefficlent of urdnium as a function of the
nitrate concentration of the salting-out agents, Ca(N03)é
and NaN03, for an 1nitlal concentratlon In the aqueous
phase of 100 g/1 of uranium and 1,2,3, or i4M HN03.
After A. Cacclari, R. Deleone, C. Flzzottl, and M. Gabaglio,

reference 375.

tion also causes an lncreased extractlon of fisslon products
(figure 29).§Z§

The extractlon of uranium by hexone is facilitated by
the presence of substltuted ammonlum nitrates whlch are
sufflclently soluble in the organlc solvent. A number of
these salts and thelr effect on the extractlion of uranium
are listed In Table XV.Z2 Tri-n-butylamine, 2-hexyl pyridine,
and dlbenzoyl methane lncrease the extraction of fission
products.izg Maeck,lgg;gl.ilg have lnvestligated the extrac-
tlon of uranium by hexone from an aqueous solutlion con-
taining aluminum nitrate and tetrapropylammonium nitrate.

The extractlon condltlons adapted as a result of the

115
 

 

 

 

 

 

10 l | I " oapM HRO 3
- 0.3M HNO3 :
| / QEE s ]
y / |
S .
F‘ —
=

Ll -
o C.1 E
i 3
m 1
Q -
o —

> Fission
o * Product _
= 0.0 y-Activity]
E - 0.0M HNO, .
o - “””f‘f’ ]
o | i
0.00I | 0.1 Bass | =
- Zr-Nb / ]

I ] 1 i ] 1
. |
0.000 o l 2 3 4 5 6

ALU' INUM NITRATE CONGENTRATION, N

Figure 29, The effect of salting-out agent, A1(NO3)3, on the ex-
tractlon of uranium and fission products by hexone fPom aqueous
solution at varlous nitric acild concentratlons. After F. R. Bruge,
reference 378.

Conditlions:

The results on uranilum and gross flssion product activity
were obtalned using G.P. A1(NO3); as sdlting-out agent and
pretreated hexone as solvent. Rn lrradlated uranlum slug,
cooled 144 daye and dissolved in HN03, was used as activity
source. Extractions were made at 30°C from an aqueous
phase oxidized 1 hour wilth 0.1M NasCr O7 at this tempera-
ture. The nitric acld 1s the sum of %hat-in the -aqueous
and organic phases, expressed as moles of nitric acid per
liter of aqueous phase,

Ruthenlum extraction:aqueous phase--0,1M K,Cry07, 0.2M
I-]INO3, Al(N03)3.

Cerlum extractlion:aqueous phase--o.oesfl Na,
HNO,, AJ.(NO3)3.

Zirconlum-nioblum extraction:aqueous phaae--O.lfl_KQC
0.25E'HN03, 8 g U per liter.

20T 0,, 0.5M

116
Table XV. Effect of 3ubstituted Ammonium Nltretes (RNOB) on the
Rxtraction of Tlranyl Nitrate by-Hexone-E

Catlion, R Total RNO3 o
- concentratlion
(mol/1 x 103)

 

None 0 2.62
(C,H,) NH 2.1 6.2
479’3 4.2 10.7
11.0 32.4
21.0 68
(C.H,. ). NH, 2 2.5 6.0
8717’2 5.0 g.u
10.0 15.5
' 20.0 33
c Ng £ 2.0 5,4
11%5" 5.0 13.4
10.0 26.7
20.0 57
Cq H.,N.H 2.1 5.5
1272472 10.5 25.6
(¢, H,) N 10.0 a7
479k 10.0 gl
C gH, NH & 10.0 2.8
(02H5)3NH 10.0 4.0
(CH20H2OH)4N 10.0 2.67

After Kaplan, Hlldebrandt, and Ader, reference 78.
Condltions:

equal volumes of hexone and of an aqueous solution. 8M i1n
NHyNO3, 0.4M in HNOg, and about 0.02M in uranyl nitrate.

o

o

dl-2-ethylhexylammonium

o

2-n-hexylpyridinium

[=1

methyl isobutyl ketazinlium

[]

2-methylpyridinium

investigation were 4.0 ml of 2.8M alumirum nitrate, 1N
acld-deficient, contalning 0.1%(weight/boiume) tetra-~
propylammonium nitrate; 2.0 ml hexone; and a sample slze

of 6.5 ml (~2 mg of uranium). These conditions provide

a good separatlion of uranium from many lones. The separatlion

from zlrconlum-nicbium 1s particularly good. The recovery

117
of uranium is excellent even 1n the presence of foreign
anions (10 to 1 mole ratlo of anion to uranium). Of those
aniona tested, tungstate lon lnterferes most seriously

(only 64.28% uranium extracted). Chloride, sulfate, phos-
phate, acetate, oxalate, etc., in the amounts tested, exhibilt
no appreclable interference in the extraction of uranium.
Chloride doesa promote the extraction of those ions which
form anlonlic chloride complexes, eg. gold (III)}. Certain
other anlons enhance the extractlon of fisslon producte, eg.

dichromate and thiosulfate lncrease cerium extraction.

by hexone from aqueous thiocyanate solution.zziiigg Reas3§9
has investligated the separation of firanium and thorium by thils
means. Some of hls results are given 1n Table XVI. The
effect of sulfate ion (experimental conditions B) 18 to
hinder the extractlion of both thorium and uranium. The
effect, however, l1ls greater for thorium than for uranium.
Consequently, greater separation of thorlum and uranium

can be made 1n the presence of the complexing sulfate i1on.

The extraction of protactinium from an aqueocus solutilon 1.2M
in NHyNO;, 0.20M in HNOg, about 0.01M in Th(NO;),, O.00987M
in Naesou, and 0.501M 1n KSCN by an equal volume of hexone

was < 4.4%. Decontamination from fission products is not

too good. Equllibration of equal volumes of hexone and

an aqueous solution approximately 0.04M in UOE(N03)E’

0.504M 1in Th(NO,),, 0.485M in Na,S0,, and 1M in HNO; resulted
in a beta decontamination factor of about 6.6 and a soft
gamma decontamlinatlon factor of about 1.5. Zlrconlum was

found to be the principal filssion product extracted.

Methylcyclohexanone

 

égueous nitrate systems. This solvent has been studied

118
Table XVI. Separatlon of U(VI) from Th(IV) by Thlocyanate Systems,2

 

Experimental condltions KSM U extracted Th extracted
M % : %
A 0.27 64.5 1.03-1.6
A 0.54 82 1.5-1.8
A. 0-9‘? 89-5 2-1-3.1
A 1.62 95 5.2-6.2
A 0.32 + 0.11M 79 3.3
antipyrine
*
0.501 63 0.14
B 0.25 35 0.015"

& After W. H. Reas, reference 380.
Experimental condltlons: :

A: 0.16M U02(NO3)p, 0.81M Th(NO3)Ly, volume of aqueous
phase = %.2 ml, volume of hexone = 10 ml.

B: 0.0974M UOp(NO3)o, 0.252M Th(NO3)y, O.2M HNOg, O.224M
NaoSOy, volume o% aqueous phase = 10 ml, volume of
hexone = 10 ml.

The thorium extractlion was performed under slightly
different conditlons 1n that NHyNOq was substituted
for U0p(NO3)p. An lonium (Th230) Tracer was added
to the solutlion and the dlstribution was measured
by the determination of lonium in each phase.

by workers 1ln Czechoslovakla as a means of separatlng uranlum
from thoriumigi and fission products.égfiiigg The extracta-
bility of uranium by methylcyclohexancne from sodium nltrate
solution (6-8M) is considerably better than that of thoriumsot
From nitric acld solution (BM), the extractabillity of uranium
18 only two- to three-fold greater than that of ‘r:ho::-:"u.lm.zgl
Ammonlum nitrate 1s comparable to sodium nltrate as a salting-
out agent for uranium.ggi Alumlinum nltrate l1s more effectilive
than elther. However, the order of salting-out agents 1ln
causlng lncreased flssion product extractabllity 1s Al > Na >
NHu. The hest separatlion of uranlum from fisslon products

13 achleved wlth ammonium nitrate as the saltlng-out

agent.igi Methylcyclohexanol present in commercial methyl-

cyclohexanone suppressea the extractlon of uranlum and fisslon

119
products. The separatlon factor between the two actlvitles,
however, 1lg lncreased slnce the partitlon coefflclent of
fisslon producte 18 decreased more than that of m."an-il.u.m.—3-?-1
The partitlon of uranlum between methylcyclohexanone and
water and methylecyclohexanone and 6M ammonium nltrate solutlon

18 given 1n figure 4-B.223

Other ketonle solvents

dee and W‘olf-ilé have studled the extractlon of uranium
and thorium by methyl n-amyl ketone and dlilsopropyl ketone
as a function of total nitrate concentration 1n the aqueocus
phase. In both casee, uranlum was better extracted than
thorlum. The extraction of thorium did not become appreclable
(¢5%) until the aqueous nitrate concentration was greater
than 5M.. Dililsopropyl ketone was found to be -an excellent
extractant of pr-ota.c'ls-:l.nil.um.-3l§

VEBelf, Beranové, and Mal{rzgg have 1nvestlgated the
extractlon of uranlium and fisslon products by several
methylalkyl ketones: methylhexyl, methylamyl, methlbutyl,
and methylpropyl In addltion to methyl isobutyl and methyl-
cyclohexanone. The partitlon coefflelents of both uranlum
and flsslon product actilvlty 'vere measured as a function of
acid concentration in the range of -0.4 to 3M nitric acid.
In thla acldity range, fisslon product extraction was found
to be maximum in the O-1M nitric acld region. The partition
coeffleient, Apps i1n this region was greatest wlth methyl-
propyl ketone (22 x 1073 at 0.61M) and least with methyl-
hexyl ketone (2.4 x 1073 at 0.03M). In the acid-deflclent
reglon, Opp Increased as the acid-defilclency was decreaaéd
(the solutilon was made more acidilc). After the maximum
Gpp Was reached 1n the 0-1M acid.region, the partition
coefflicient was décreased and then increased as the aqueous

solution was made more acldiec up to 3-4M. The partition

120
coefflcient of uranlum, 0,5 increased as the nltric acid
concentration was Ilncreased over the entire range. At 3M
nltrlc acld, o, varied from about 0.7 for methylhexyl
ketone to about 2 for methylpropyl ketone and 3 for methyl-
cyclohexanone. The greatest separation, B, of uranlum
from fisslon products was found 1n the 0.1M acld deficlent
reglon (-0.1M). For methylhexyl ketong B was found to be
>1500; for methylpropyl ketone f was about 400. The extraction
coefflcients of uranium were ¢ 0.2 for methylhexyl ketone
afid about 0.5 for methylpropyl ketone at thils acid concentration.
Allenigi has tested dilisobufyl ketone, dilsopropyl
ketone, and methylhexyl ketone as solvents for the purifil-
catlion of uranlum from iron, copper, chromium, and nickel.
Diisobutyl ketone was found most satlafactory under the
conditions tested. Dilsopropyl extracted some iron and
chromlum. Methylhexyl ketone extracted 1lron, chromlum,
end copper.
Uranlum and thorlum may be extracted quantlitatively

384

from a nitrate medium by mesityl oxlide. Under the condl-

tlons tested girconlum 1ls extracted to a large extent;

vanadlum and yttrium to a lesser extent; cerlum only slightly.

AT.COHOLS

316

Hyde and Wolf="— found alcohols to be only falr ex-

tractanta of uranlum and the extractlon capaclty to decrease

rapldly wlth the length of the carbon chaln. This 18 borne
385

out by the work of Poston, et al. who measured the ex-~-

tractlon coefflecients of uranlum and ruthenlium as a functilon

of alumlinum nltrate concentratlion of the aqueous phase for

Experimental conditions: A salt of the elements tested was
dissolved in 10 ml of HNO (15 + 85). DNineteen grams of alum-
1num nltrate crystals Were added and dissolved. The solutlon
was shaken for 15 seconds wilth 20 ml of mesltyl oxlide. The
extract was washed once wilth 20 ml of alumlnum nitrate solutlon
and analyzed.

121
hexone and several tertlary alcohols: tertlary amyl alcohol,
2-methyl 2-pentanol; 2-methyl 2-hexanol, 2-methyl 2-heptanol.
Only tertlary amyl alcohol extracted uranium better than
hexone (0.5 - 1.5M Al(N03)3, o.e_n;fmoB) and all four alcohole
extracted ruthenium better than hexone. Ruthenlum was
extracted as well or nearly as well as uranium by the al-
cohols. -

Dilsobutylecarbinol extracts ruthenlum nearly as well
as uranium.igé Thorium and zlrconium-mobium are poorly ex-
tracted. Protactinlum 1as extracted much more efficlently

than uranium.

MISCELLANEOUS SOLVENTS

Nitromethane has been recommended by.Warner-'igg as an
extractant for uranium. It 1s reslistant to oxldation,
Btable to hlgh concentratione of nitric :acid, and highly
Belectlive. The dilstributlon of uranyl nitrate between
nltromethane and water and nitromethane and saturated ammon-
lum nitrate solutlon 1s given 1n figure 3-B. The extractilon
of thorium nitrate by nltromethane from aqueous solution 1is
mich less than that of uranlum. Color tests indilcate that
neither copper, cobalt, iron III), nor chromium nitrate 1s
extracted by the solvent. With dlethyl ether, considerable
amounts of copper nitrate end trace-amounts_of ferrlic nitrate
are extracted. Nitrilc acld enhances the extractlion of uranyl
nitrate by nitromethane. However, above a critical acild
concentration (~5§ Initlal acid concentration with equal
phase volumes at 20°C) only one liquid phase 18 formed.

ORGANOPHOSPHORUS COMPQUNDS. Within recent years, a
large number of organophosphorous compounds have been developed
and investigated as extractants for uranium. These compounds
have-beefi gubdivided in the present paper into neutral and

acldic organophosphorus compounds.

122
NEUTRAL ORGANOPHOSPHORUS COMPOUNDS

Solvents 1lncluded 1n thls category are trlalkylphosphates,
(RO) ;P - O; dlalkyl alkylphosphonates, (RO)RE -» 0; alkyl
dialkylphosphlnates, (RO)REP-a 0; and %rialkylphosphlne oxides
RBP-e 0. The abllity of the solvents to extraédt uranium is
1n the order

(RO)3P-4 0 < (RO,)RP—> 0 < (RO)R,P— O <.RgP- 0.
This 18 also the order of lncreaslng base strengths of the
phosphoryl nygenfigg In Table XVII, the four types of
compounds are compared as extractants of uranium (VI),
plutonium (IV), thorium, fission products, and acids.§§1
It should be noted that although uranium is extracted almost
quantitatively by tributylphosphine oxide (Table XVII), other
elements are also hlghly extracted. 1In fact, in spite of
lower extractlion coeffliclents, tributyl phosphate affords a
better separation of uranium from thorium, plutonium (IV),
and fieslon products under the conditlons listed In Table
XVII than does trihutylphosphine oxide.

Tebles XvItT200:3%9 ong x1x320 115t the atstribution co-
=fficients of uranium and some assoclated elements for a number
of neutral organophosphorus extractants. Simllar informetion
on other solvents may be found 1n papers by Burser,égl Healy
and Kennedy,lgg and 1n numerous ORNL reports. The latter have
peen summarized by Blake, et al.322 and Brown, et alecs2392

The mechanlsm of extractlion by neutral organophosphorus
reagents appears to be simllar to that of tributyl phosphate,égg’
302,387 From nitrate systems, the extractlon of uranium by
tributyl phosphate and trioctylphoaphlne oxlde 18 descrilbed

fairly well by the equilibrium reactlon

25 -
UOy™ + 2NOg5™ + 28 = UOE(NO3)2 (3)2,
where S represents the solvent molecule.égg- Extraction may

be made by tributyl phosphate from chlorilde solution. Stronger

123
¥l

Table XVII. Comparlson of the Extractive Capaclties of Various Types of Organophosphorug

 

 

 

 

 

 

 

Compound&g
Extraction of U02(NO ) Extraction of U, Pu, and Fisslon !Exgpaction of
3’2 Productaé lTh—
Nitric acld concentratlon
oM 0.6M 3M No added HNO3 0.6M HN03
U U - Acld — Acld | U Pu | Gross Uross Pu Gross| Grosa | Th
ext'd| ext'q ext'd|ext'd| ext'd EVI) SIV) B T {VI}?IV) B axt'd
() |(#) | () [(®) |(%) %) (&) (&) |(B) [(B)|(®) [ (%) '(%) (%)
Tributyl -
phosphate 11 56 4 96.5 |8 17.4|o,7 |0.01 |(0.01 |58 |6.6 |0.07 |0.08 3.5
Dibutyl _
butylprhos- , '
phonate 55 o7 6 99.4 111 64 1.13/0.05 ]0.13 |97 54 _0.72 1.0 18
Butyl .
dibutylphos- ' ' '
phinate 98.5 | 99.9 | 15 99.9 |14 o4 (20 (1.9 |7.9 1{9%.4! 98 |23 38 T4
Tributyl
phosphine
oxlde 99.7°192.9 139 99.9 | 17 99.9|97.3{ 37 64 9989 99.8 12 |77 98.7

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

& pfter Higgins, Baldwin, and Ruth, veference 387.

Experimental conditions: equal phase volumes equllibrated 30 minutes at 25 0.2°C; organiec
phase - 0.75 M phosphorus compound dissolved in CCly; aqueous phase - 0.1M uranyl salt with
or without salting agent.

b Aqueous phase - 0.1M UOp(NO3)p from dissolving irradlated U slugs in HNOg - 6 monthe cooling.
£ Aqueous phase - 0.1M Th(Nog)lp
621

£

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Extraotiog l Extraction Extraotion of aoclds~
of UQaS0u~- 1 of UOaClo
H,80) concen- | HCl concen- % extracted
. tration tration '
oM oM oM 1M Aced cit-| Tar- | mNO so, | H,PO, | HEL
- — tic | ric ] tarie 3 250 3T
U U U U
ext'd ext'd ext'd ext'd
Tributyl (%) (%) (%) (%)
phosphate 0.001 | 0.001 | 0.3 0.8 25 |0 0 7 0 0 0
Dibutyl
butylphos- 0.1 0.03 |1 26
phonate
Butyl
dibutyl-
phosphinate 16 48 4o 92 49 |20 |20 27 2 3 0
Tributyl
phosphine .
oxlde 95 96.82 | 90 all pre- |58 |39 [23 39 {0 10 7
gome ppt. clplitated
formed
a

|

|

Aqueous phase - 0.1M ansou; acld as indicated.

Aqueous phase ~ approximately 1N acld.

Three phases wWere present, two of which were largely aqueous.
921

Teble XVIII. Extraction of Actinides and Zlirconlum by Phosphates and Phosphonates at 30°0$

 

Solvent b o Extractiog Goefficignt
o Th Np(IVv)— Pu(IV)= U(VI) Np(VI)& Pu(vIi)d Zr
Trilalkyl phosphate=
n-butyl 2-3 3.2 16.1 26 15.6 3.5 0.22
lscbutyl 2. 2.7 11.8 22 15.9 3.4
n-amyl 2.9 4,2 15.6 32 19.3 L.l
1go-amyl 4,2 .7 17.8 34 18.9 4.4 0.12
n-hexyl 3.0 3.6 15.6 38 20,0 4.5 0.14
n-octyl 2.4 3.4 15.3 3 15.7 3.9 0.1k
2-ethylhexyl 2.5 4.3 2 5 23 5.7 <14
2-butyl 0.45 4.9 2 o 20 4,6
3-amyl 0.22 3,5 18.1 4o 22 5.0
3-methyl-2-butyl 0.18 3.0 2L hr 25 5.4
4-mathyl-2-amyl 0.047 3.5 22 3 24 h.9
cyclohexyl 3.5 106 0.64
Dlalkyl alkylphosphonate£
dli-n-butyl n-butyl 24 92 O.lI
dl=n-butyl cyclohexyl 17 125 0.1
4l -n-amyl n-amyl 3 133 0.092
di-n-hexyl n-hexyl 2 89 0.070&
dl-2-ethylhexyl 2-ethyl-
hexyl 10.6 176 0.12
& pfter T. H. Siddall III, references 388 and 389.
E-Aqueous phase contalned 0.01M ferrous sulfamite.
E-Aqueous phase oontalned 0.01§.N3N02.
El--Aqueeus phase contalned 0.0lM ceric ammonlum sulfate.
g-1-.09M trialkyl phosphate in n-dodecane; extractants washed with 1M NaOH, water, and nitric
aold before use; aqueous phase 3.0M HNO3 at equllibrium; tracer concentration of element.

I

1.09M phosphonate in n-dodecane;aquecus phase 0.8M HN03 at equllibrium; tracer oconcentration
of element.

E-Ettrapolated value.
extractants may extract uranlum from sulfate and phosphate
solutlone, especlally 1f a small amount of nitrate 1s added

to the soliutlon.

Tributyl phosphate (TBP)

Aqueous nitrate systems. Inveatigations on the ex-
traetion of metal nitrates by TBP 1ndlcate the catlons are
extracted as single, well-defined specles: M(NO3)3(TBP)3,
M(NO,), (TBP),, and MOE(N03)2(TBP)2.@21—81ML323- This
differs from the extractlon of ethers, esters, and other
oxygen-contalning solvents, consldered previously, in which
a whole serles of complexes contalning varyling numbers of
nitrate, solvate, and water molecurles lg extracted. The
atabllity of the TBP-solvate molecules lncreases 1in the orderfill
HEO(‘I‘BP) < Pu(N03)3(TBP)3 < Pa.(NO3)5(TBP)3 < HN03(TBP),
HNOS(TBP)(HZO) <& Th(N03)4(TBP)2 < PL102(N03)2(TBP)2 <
Pu(N03)4(TBP)2 < U02(N03)2(TBP)2.

The unexpectedly large extractlon of nitric acld, thoriunh and
zirconium at very high acid concentratione indicates higher
complexes may be extracted.éll'

The dlstribution of uranyl nitrate betweén_TBP end water
ig represented in filgure 30.—3'-—9--lk The extraction coefficilent
of uranlum 18 plotted as a functlon of acld concentration for
varlous concentrations of TBP 1n filgure 31.322 The obsBerved
affects of (1) decreased @, with increased acid comncentration
and (2) Llncreased a, with increased TBP concentration, may
be explalned on the basis of free solvent concentration.
Flrst, as the acld concentration 1s increased, more nitrie
acld ls extracted resultlng in less free solvent. Second,
more free sblvent ls obviously avallable as a result of in-
creasing the solvent concentration. Since the partition
coefficlent of uranlum depends upon the second power of the

free solvent concentratilon, %, wlll decrease in the first case

127
Bzl

Table XIX. Extraotive Power of Tributyl Phosphate, Alkyl Fhosphonates, Diphosphonates, and FPhosphine Oxidee.-fi.

 

 

 

0
(cquo)eP‘\‘ 03H7-n
0

 

 

 

 

Initial concentration of HNOg,N l 0.5 1 2 0.5 1 2 | 0.5 1 2 } 0.5 1 2
Dlstribution goefflclents
Solvent U Pu(IV) ILZr-Nb Nb
(cuugo)apo 0.68 1.4 3.,65{ 0.19 0.67 2.73| .64 b6 105 .011 .0l .010
(CuH90)2P§H3 4.50 10.35 21.50f 5.46 11,15 14.907 .0058 .0040 .,015 | .0OOL .0020 .017
0 i
(1-051{110)2?-01{3 6.95 21.10 70.60| 1.53 T7.43 16.90| .15 .22 .33 .52 .34 .20
*
0
(C6H130)2_P\\-CH3 5.72 18.45 u45.70] 3.51 11.65 18.95| .10 .053 .13 .0050 - 012  .021
N .
(CTH150)EPQCH3 21.30 7.1 131 3.25 10.95 17.15| .0078 .04%0 .12 . 0000 .ol 00080
N
0
(cafll.ro)ap\— CH3_ 22.10 50.70 178.0 5.71 13.65 19.45| .037 .14 .28 .0061 019 .ok
(09H190)2P90H3 27.60 32.60 61.L0| 23.25 24%.15 21.70| .97 .67 .55 .013 014k 017
Y
(0101'[210)2P\\' GH3 6.73 14.65 34.30} 16.60 21.65 21.50| .38 40 54 . O0U3 L0043  .00%0
0 .
(c>-c51i110)2?-cn:_l 17.45 44,10 101.0| L4.47 17.35 25.15 .020 .061 .30 .015 013  .00B7
; 2
0
(CGHSO)EP—CP% 0.08 0.053 0.15| 1.8% 1.34 1.71{1.31 L42 .86 4o .15 .086
%
0
224:9"’;;?-0}13 13.43 28.80 69.90| 3.80 11.60 19.60| .24 .16 .24 | .0056 .0053 0062
67137 N\
0
('°4H9°)\1=-cu3 12.20 36.3 65.8 | 7.89 17.85 24.50 | .80 .47 .47 .0038 .0041 .0051
(c'(Hlso)/\\
0
- - 4.97 13.05 4k.20} 2.58 7.58 14.B5] .031 .091 .33 - - -
(n c,\Lfigo)aP%cEH5
0
(1_04[{90)5._03 7.58 22.50 57.30| 2.53 7.67 14.85| .0085 .018 .11 .0021 .0089 ,039
‘ 2\\ 275
10.435 22.20 T4.70]| 2.58 B.65 16.75)| .0039 .020 .10 |<.00@6 .0028 .0063
621

(1—05H110)2§§- CHy-n
0
(C4H90)2P - G4H9
*%
(C4H90)2PQ; C5H11
0
(i'°5H11°)23$' C5H1a
(1-CeH,10),p 2 G H. - -1
5711772 Bz 211
0
(1-05}1110)21:\ - CBHJT
0
(GUHBO)E%%; CHaCeHs
(04H90)2§;CH200H3

0
(04H90)2{(CH200235

0
(CMHQO)2%4350H2004H9

o
(c4H90)2§ifH(0H3)c52§-oc4flg
CyH,0),P ~ CH,CH,CO0C

(459)2\\0321*20 4
{cyH,0) P - CH, - P(C,H,0)
4“92\052 g%

0
(1-C5H110)23§: CH, - P(OC5H11-1)2

(CyHg) 5PO
(1-04H9)3P0

 

9.40 22.30
8.98 24.00
8.26 25.75
13.65 28.40
7.68 21.10
9.60 11.50

2.45 6,34

1.13 3.09
1.31 3.11

3.15 B.68

2.30 6.35

2.14 5.57
1.73 12.55
1.32 2.98

1880 1360
5.33 7.26

73.80
65.30

103.5

58.40

30.95
85.4
21.10
7.79
8.86
42,20
3%.50
16.46
17.26
9.60

352
7.19

 

 

 

2,02 7.3 14,15 - .013
2.82 9.4 17.50[ .003% .02
2.45 8.91 17.65( .0032 .024
2.50 9.00 15.75 I.012 .036
2,18 7.69 13.05 .011 .031
2.65 B8.92 17.00| .016 .038
0.47 1,91 6.00| .0034% .0084
0.26 1.16 4.24} .029 .075
0.3% 1.50 5.03] .43 u2
0.80 3.26 10.95( .031 .O77
0.15 2.35 6.39] .021 .025
0.79 2.38  6.24 .ot% .12
2.71  6.72 19.24| .23 .28
3.33 8.5 24,70| .41 41
365 299 83,2 !1.00 1.8%
B.lp 21.85 22.55 ..61 .55

 

.099

.097

Jd1

.13

13

.13

.022

.12

.42

.062

.043

.057

.29

A2

2.45
.55

 

 

. 0022
<, 001
.0035
011
.0017
»0012

.92
.0029

.0046
.0050
.0031
.0056
.011
.032

.6}
3.95

.0028

.010

022

0024

011

.0011

.0046
-0057
.0060
.0041
.0080
.011

.031

.60
1,40

.0022

.025

.032

074

.0031

.029

.0012
. 0061

.0067

012

.0058

.011

.031

A7
2.15

 

e After Petrov, et al., reference 390.

Organlc
1 e¢/1 Nb

1 =180; c = ayclo.

e - 0.5M phosphorus compound in CCl
, nitrilo acld as indicated.
Temperature, 20° = 1°C,

Volume r&tio

Initial sgueaus phase - 50 g/1 U, 1 g/1 Pu(IV), 1 o/1 2r + NpP°

(organic

aqueous), 2.

Time of shaking and of settling, 30 minutes.
 

 

 

 

 

Io = I N s IIIT ¥ v -0 |—I_I'IIII 1 1 1 v It
: .
. O —
o - ]
E _
> - -
E - i
-
q [~ -
-
S
d B -
0o - :
0.0| 1 L1 1.1 IIII 1 1 L1l ILII 1 L1l
0.0l 0.1 1.0 10

MOLALITY (aq)

Figure 30.
The partltion of uranyl nitrate between 100% TBP and water at 25°C.

After T. Healy, J. Kennedy, @. Waind, reference 394.

and increase 1n the second. The effect of uranium concentratlion
on a, is glven also as a funcilon of nltrlec acid concentration
in flgure 32.32§ The decreased extrectlion with lncreased
uranium concenfiration may agaln be lnterpreted 1ln terms of

the seclvent avallable. The partition coefflceclents of other
metal nltrates are aleo decreased, ln general, by 1ncréfiaed
uranium ccneentration. More efflc¢lent separatlon may there-
fore be achleved by lneresased uranium loading of the solvent.
For small amounts of uranium, a high uranium concentration may

be attalned 1n an organlc phase sultable for handling by

130
 

000 1T T T T T T T T T

    

 

 

 

-
L -
100 =
> _
© ™.
&_fl b
o
s °F E
- C -
w L. -
o - .1
S L 83% TBP
s 1OF & 39% TBP 3
= - o 9% T8P ]
g - ~
ol + -
o
-
0.1 ~
0.0l et Ly y g -

o1 2 3 4 5 6 7 8 9 01

INITIAL AQUEOUS NITRIC AGID
CONCENTRATION, M

Figure 31. The extractlon of uranyl nitrate by various concentra-
ticng of TBP in kerosene as a functlon of initial aguecus acid
concentration. After 7. Sato, reference 395. C(Condilitliona: Organic
phase - volume % TBP 1n kercsene as indicated. Aqueocus phase - 5 g.
uranyl nitrate per liter, nitrlc acld concentration indicated.
Temperature, 200C; Vo/Vg, 1.

131
2y

PARTITION COEFFICIENT,

 

 

 

 

 

 

 

'00 . Al | I 1T 11 IIII 1 m 1 1 l.lTll | 1 1 l‘l.'lr.
- 0.0l |4 } ]
- 0.005 M I
i 0.025 M c .
0.05 M S
- 0.0l M § -
0.2 M e
I0 | o -
C & .
C 0.3 M . ]
- > ]
| T 1
- D
05 M o8 T
S
1.0 E‘ > '?
- 1.0 M S )
. D -
1.5 M .
I J
o.l ] 1 M | 1 I]J_Il L1 ) IJ_llII i ] 1 1 1 1
0.1 1.0 10 100
INITIAL AQUEOUS NITRIG AGCID CONCENTRATION, M

Flgure 32.

The effect of 1lnitlal uranium concentration on the extraction
of uranyl nltrate by 20 volume per cent TBP in 0014 8B A&
function of 1nitial agqueous nltrlc acld concentration.

After R. L, Moore, reference 396.

Conditlons:
Equal volumes of phases shaken in a water bath at 25°C.

dilution of the sclvent. Duncan and Holburt321 have measured
the distrlbution of uranium,initlally present in 1.2 to 1200
micrograms per liter between 20% TBP in kerosene and nitric
acid solution. Although the results were somewhat erratic,

1t was generally shown that the partition coefficlent 18 nearly

constant over this range of uranium concentrations.

132
The extractive cepaclty of TBP is affected considerably
by the cholce of dlluent. Tanbe3 extracted U(v1), Np(1IV),
Np(VI), and Pu(VI) from 5M HNO; aqueous solutions with 0.15M
TBP dlssolved 1ln a number of solvents,;including benzene and
chloroform. Larger extractlion coefficlents were obtalned for
all the elements tested wilth benzene rather than chloroform
a8 dlluent. In the case of uranium, the difference in a, wes
- greater than ten-fold. Llttle difference 1n extractlve
capaclty was observed wlith TBP diluted by benzene or carbon
tetrachloride. Simllar results were obtalned by Dizdar, et
al.§22 Uranyl nitrate (0,00BBfl) was extracted from 2M nitriec
acld solutions by varlous concentratlons of TBP dlluted wlth
carbon tetrachloride, xylene, kerosene, hexane, dlbutyl ethef,
diethyl ether, and isopropyl ether. The partlition coefficient
was found to 1lncrease with lncreaslng TBP concentration to a
maxlmum for pure TBP. For carbon tetrachlorlde and xylene
the maximum value was already attalned at 40 mole per cent
TBP. The other dlluents are listed above 1n the approxlimate
order in which they inhiblt the extractlon of uranium by TBP.
Differences in a,,for various dlluents, were found to become
smailer wlth increased uranium concentration. Bruce§I§~ has
found that the extractlion of flsslon products 1ls also affected
by the cholce of diluent.

The extraction of uranlum by TBP is considerably en-
hanced by the presence of salting-out‘agents iln the aqueous
phaiaae.!—"g-g:fip-é The resulte of Sato&gé are given 1n Table XX
and figure 33.

The extractlon of uranlum by TBP decreases wlth increased
1:s-:m.lznsn:'a't:u:c'e.E—QIZE-:Ll

Phosphate, sulfate, and fluoride lons reduce the extrac-
tion of uranium by TBP from nitrate media.figg Uranium 1s
-extraected from ehlorlde solutlon but less efficiently than.

from nltrate solution. Slllica causes poor phase separation

133
Table XX. Extraotion of Uranyl Nitrate by TBP Uslng Varioug Niltrate
Salting-out Agents.fi

 

 

Jalting-out agent Percentage extracted
OM HNO4 1M HNO, 3M HNO, &M HNO4

(HNO,) 2.96 82.10 95.52 97.10
NH),NOg 70.00 92.30 96.50 97.40
L1NOg 73.05 94.60 97 .50 97.95
NaNO, 72.50 93.00 97.10 97.80
KNOg 65.00 90.50 96.00 97.10
Cu(N03)2 86.02 97 .50 97.70 99.00
Mg(N03)2 84.35 97 .20 97 .50 99.40
Ca(N03)2 82.48 96.60 96.60 97.50
Zn(No3)2 79.75 98.05 98.10 99.40
Al(NO3)3 99.90 99.60 98.20 99.50
Fe(N03)3 99.80 99.50 98.20 98.90

 

2 After T. Sato, reference 406.
Organic phase - 19% TBP in kerosene.
Aqueous phase -~ 5 g/1 uranyl nitrate, 1M salting-out agent, initial

gcld concentratlion indicated. _
Equal phase volumes shaken together for 30 minutes at 20°C.

and the formation of emulslons.

Uranlum may be re-extracted from TBP by contact with
sodium carbonate sol_ut:l.on.igg Ammonium sulfate, sodium sul-
fate, and urea solutlons have been used satisfactorily.fig2
Water or hydrogen peroxlide is Iineffectlve for TBP contalning
conslderable nltric acid.flg2

The distribution of nitrile acld between aqueocus solution
and 100% TBP i1s demonstrated in figure 34.E1g The. distri-

butlon of various metal nitrates bhetween TBP and nitrate

134
% EXTRACTED

 

 

 

 

 

rarmnim s gemg Erar s

; | L | !
Q ' 2 3
AMQUNT OF NITRATE SALTING-OUT AGENTS, M

80

Flgure 33.

Effect of niltrate selting-out agents upon the extraction of
uranyl nitrate at 1M inltlal nitrlec acld concentration.
After 'T. Sato, reference 406.
sonditions:
Organlc phass ~ 19% TBP in kerosene.
Aqueous phase - 5 g/l uranyl nitrate, 1M HN03, salting-
out agent concentratlon lndlcated.

Equal phase volumes shalien together for 30 minutes at
20°C, :

135
M

TBP PHASE,

ACID GONGENTRATION,

 

 

 

 

 

Io I I T 1T 1il I T 1 1 nm T avi I " T T T i
N Symbol Acid
t X HF
N v HCI o A% /"JO
a HNO3 X% ' o~ -_.-'.;':."
.0 = c HeS04 . gl / -
n / , & v %
[ ‘ , -
- X 8 #
0.l 7} i
J‘l T
0.01 L '—'—L"'“-ll L L 'l.—lllll 1 L L1111
0.0l Q.l 1.0 10

ACID CONCENTRATION, AQUEOUS PHASE, M
Figure 34.

The distribution of mineral aclds between 1004 TBP and agueous
solution at 25°C.
After E. Heafbrd and H. A. C. McKay, reference 412.

solutions has been extenslvely investigated. The extractilion
ooefficients of some actinide elements are plotted agalnst
aquéous nitric aold concentration im figures 35 and 36.£l§:£i§
Ishlmor] and Nhkamurafllz have also measured the partition co-
efficlents of Hf, Th, Pa, U(VI), Np(IV)(V)(VI), and Pu(IV){VI)
at varlous aqueous nitric acld concentrations. Filgure 37
represents the partition coefficlent of several fission pro-

ducts as a function of the nitric acid concentration.ti8-%20

136
 

   

 

 

 
 

00 71717 T T T T T T T 3
IO \a

v}
Y /A s,
=z
L)
o 1.0 -
o ]
L -
5 ¢ uvn
© A Pu(Vi) |
= 4 Pu(lV)
c 0.1 v Pu (ill) _
= o Np (V1) ]
= @ Np(lV) -
< 1 o Th(IV) i

¥
1

0.0l

 

 

P 11§
2 3 4 5 6 7 8 9 10 11 12

[HNOa] aq

Flgure 35. The partltlon coefflclent of actlnlde nitrates between
19% TBP in kerosene and aqueous solutlon as a function of equilil-
brium nitric acid concentration. @U (VI), ONp (VI), mNp (IV),
APu (VI) at 20°-23°C,, after K. Alcock, G. F.-Best, E. Hesford,
H. A. C. McKay, reference 413. A4APu (IV), VPu (III), at 25°C. or
20-23°C., after G. F. Best, H. A. C. McKay, P. R. Woodgate, ref-
erence 414. OTh (IV) at 25°C., after E, Hesford, H. A. C. McKay,
D. Scarglll, reference 415,

 

137
 

10

 

 

 

 

=1 | | | | | | T T 1
LA Pu(y) ® Bk{il)
S - & Am({ll} g Cf(ill)
. . o Cm{in) Es (i)
-
=z
W0
O
i
A
d
o
QO
2
o
= 0.
E._
a
<,
a
0.01 l i | 1 | I l l I I l
o | 2 3 4 3 €6 T B8 9 10 1l 12
[HNOg]aq
Figure 36.

The dlstribution of trivalent ectinides between 100% TBP and
aqueous solution as a functlion of equllibrium nitrie acld
concentration at 25°C.

After G. F. Best, E. Hesford, and H. A. C. McKay, reference 416.

The extractlion of rare earths, Y, Zr, Sc¢, Th,and Am by TBP
from aqueous nltric acid solutlon has been investigated by
Peppard and co-workers.flgi&&gg Jodine 18 extracted. It

forms addition compounds wlith carbon-unsaturated compounds

in the solvent. The extractlion of lodline is minimlzed by
keeping 1t In a2 reduced gtate and by careful selection of

TBP diluents.ézg- Rufhenium 1s.also extracted by TBP. Its
extractlon may be reduced by lncereased solvent saturation with

uranium, by dlgestion in a nitrate solution of very high lonic

138
 

 

 

 

 

o0 F—r—T1T—T7T— 717" 71T T~ T T T T T T
- © Eu-100% TBP :
L v Ce({lll)-100 % TBP -
O F © Nb-100% TBP X
C X Zr—-199% TBP ) :
- _ o Y-I19% TBP B E
- . &
E ' ___.-'_' s ,
O 1.0 Ff e )
8 [~ ) _"' | = g | / / o | :
z y . ? ' . . F ' ]
= 0.1 =9/~ D4 v*-w---w A3
= My T :
o / i i :
@ £ -
<1 : ..
a s . _
0.0l - ' —:
0-00! |11 b
c | 2 3 4 5 6 7 8 9 10 Il 12
[HNO3]ag.

Figure 37. The distribution of flsslon product elements between
TBP of several concentrations and agqueous solutlon as a functlon of
equilibrium nitrlc acld concentratlon. Z2r, after K. Alcock, F. C.
Bedford, W. H. Hardwick, and H. A. C. McKay, reference 418. v, Ia,
Ce, Eu, after D. Secarglll, K. Alcock, J. M. Fletcher, E. Hesford,
and H. A. C. McKay, reference 419. Nb, after C. J. Hardy and

D. Scargill, reference 420. Conditions: Tracer, carrlier-free or
with less than 1 g/1 of carrler, used 1n all cases, Zr equllibra-
tions made at 20-23°C,; Nb,r~206C.; all otherpg at 250C. TBP diluted
wlth kerosene.

139
strength, or by treatment with a reducing agent.fizg Suslc

and Jelic-—-—3 and Sato— 406

have studled the TBP extraction of
metal nitrates that may be used as ssglting-out agents. The
order of extraction of 0.1 mg per ml concentratlons of metal
from 2N HNO3 solutions by 20% TBR/kefoBene wlth no uranilum
present 1s B1 > Co > Cu > Fe > Zn } cda > Pl:l..‘-tgi The partition
coefficlient of blamth under such condltlons, wlth equal phase
volumes, is about 0.1l. The results of Satoi‘-(-)-§ are listed 1n
Table XXT,.

The partitlion of uranlum and other metal nitrates be=
tween tributyl phofiphate and aqueous solution ls affected

greatly by the presence of hydrolysis producte 1n the organilc

 

 

Table XXI. Extraction of Metal Nitrates by TBP.&
Metal nltrate Percentage extracted
OM HNOB 1M HN03

L:LN03 - -
Na.NOB - -
ICN03 - -
Cu(NOg), 0.050 0.025
MS(N03)2 - =
Ca(N03)2 0.118 0.064
213(1.*503)2 0.005 -
Al1(nNO )3 0.004 0.003
Fe(NOB 3 0.010 0.008

 

& After T. 8Ssto, reference 406.

nitric acild concentration indlcated.
Organio phase - 19% TBP dlluted in kerosene.
Equal phase volmmee shaken together for 30 minutes at 20°C.

Aqueocus phase ~ 5 g/l uranyl nitrate and 1M matnl nitrete at initlal
phase, eg., mono- and di-butyl phosphates. These products
may be elimlnated by washing or bolling the solvent with an
alkaline solution. Two procedures for the removal of TBP

Impuritles are gilven.

Procedure 142}: TBP is purified by boiling with a dilute

caustic soda solution. Add 500 ml of
0.4% NaOH solution to 100 ml of impure
TBP. Disetlll at atmospheric pressure un-
til 200 ml of distlllate have been collected.
The remaining TBP is washed repeatedly with
water. It may be drled by warming under
vaguum.

Procedure 235l: TBP 18 stlrred with an equal volume of
6M HCl at 60°C for 12 hours. The separated
TBP ie cooled to room temperature and
scrubbed wlth two equal-volume portlions
of water, three equal volume portions of
5% aqueous sodlum carbonate solutilon, and
three equal volume portlons of water. The
resultant TBP 1s dried by heating to 30°C
under reduced pressure.

Aqueous chloride systems. Uranium is extracted from

chloride sclution as U02012 « 2TBP although hlgher uranyl
chloride complexes may also be em;rza.c‘cet:'i.-E—Q—é-"—'—ltgg The par-
tltion of uranium between TBP and aqueous hydrochloric acid
solution 18 shown in figures 38%22:%29 4ng 39,230 Mo effect
of uranlum concentratlion on the dlstribution 1s given in

figure 4O;fl§§ the effect of TBP concentratlon, in figure
MI.EEQLEEI In Table XXII, the influence of salting-out

agents on the extraction of uranyl chlorlde by 30% TBP in
dibutyl ether 1s recorded.fiil The dlstribution of hydro-
chlorlec acld between TBP and aqueous solution is shown in
figuré 34.513 In figure 37, the partition coefficients of

Pa, Th, Zr, and Sc¢ are plotted as funetions of aqueous HCl
concentration.flggl&gfi In flgure 39, the partitlon coefflclents
of Ni, Mn, Cu, Co, Zn, In, and Fe (IIT) are similarly plotted.330
Ishimorl and Nakamura&ll have measured the partition coeffil-
clents of Hf, Th, Pa, U (VI), and Np (IV)(V)(VI) as functions

of aqueous acld concentration. Gal and P.uva.m-c-JEil have similarly

141
 

T riuri
)
X

o
o
T

)

t— ]

&

Rl

s ok

! C :\?
S - DY
— 1.0 f

- C ; 4
& C )
P - /
a

-l L_ ; f:
IOE .

I_I_Llllll

 

 

 

 

IO-E L i
1 2

ro

Figure 3B. The extraction coefficient of U, Pa, Th, Zr, and Sc
between pre-equilibrated 100% TBP and agqueous hydrochlorlc acid
at 220 + 20C. After D. F. Peppard, G. W. Mason, and M. V. Qergel,
reference 429, and D. F, Peppard, G. W. Mason, and J. L. Maier,
reference 422, :

142
 

 

 

 

 

1000 —r——T——T1T——T7T—T—T1T—T 1T 71T 1 7
[ Fe(ll) __g=="""
F §ee=mmtSmmTTY 3
100 NG -
o C .
- ! | -
Z
wl
o 10F 3
W C 7
(1 = -
wl L -
o _ i
o
™ =
5
= 0F 3
—_ - - o
- - ]
m - -
<
a - -
0.0l L1 a1 N I ||
O | 2 3 4 5 6 7 9 I0C Il 2

[Heilgq., M

Figure 39. The extractlon coefficients of U, In, Zn, Cu, Co, Fe,
and Mn between pre-equilibrated 100% TBP and aqueous HCl solution
at 21 + 0.1°C. . After H. Irving and D. N. Edgington, reference

430, TCondltione: TBP and HC1l pre-equllibrated by stirring equal
volumes together for about 10 minutes. Tracer concentrations or
about 0.02M U and Cu used. Equal volumes of pre-equllbrated phases
stirred together about 5 minutes.

143
 

 

 

 

 

Iq ] \.l .l e III T l I ¥ T lll 1 L | v )
| 2-initial U _
100 L concentration .
o .
@
LN ]
L s '
! N i
= “w
o - N -
w . * .
ui .
10 — —
8 [ . \@\ :
- l—equilibrium U ™ i
Z : N d
S - concentration N
= - ® 4
= I i
|—
@ L -
o
a.
(I -
[ 1 i 1 1 r_0 lll a1 [ ] 1 3 | ' | lll - 1 i 3 | I ll-
0.0l 0.l 1.0 10

[UO2Cis)aq, M

Flgure 40,.
The distribution of U0,Cl, between 100% TBP and aqueous HC1
solution as & function of uranium concentration of the aqueous
phase. Curve 1 represents the partition with the equilibrium
aqueous uranium concentration plotted as absclssa; curve 2,
the partltion with 1nitlal agqueous uranium concentratlon as
abscissa. .

After A. S. Kertes, and M. Halpern, reference 428.

Condltlons:

Conatant HC1l acid concentration of 8.83M; equal
phase volumes eguilibrated for 15 minutes at room
temperature, 18° - 22°C.

144.
 

i00

 

 

 

 

 

= -
<
o _
= .
Ll
o |0 =
L [
- L
C _
o
=
O -
=
b—
ez 1.0
q b
Q. _
o I 1 1 1
o-I l

% TBP

Figure 41. Partltlon coefficlent of uranium as a functlon of TBP
concentration for various initial aqueous HC1l concentrations.
10.7M, 6.75M, and 1.02M HCl curves, after V, M. Vdovenko, A. A.
Lipovskil, and S. A. Nlkitina, reference 426. Conditions: TBP
dlsgolved 1n benzene. Extraction made at rcom temperature using
U233, 4.6M, 5.9M and T7.6M HCl curves, after V. B. Shevchenko,

I. G. Slepchenko, V. S. Sechmidt, and E. A. Nenarokomov, reference
427. Conditions: TBP dlssolved in CClh. Equal phage volumes
(10 m1) mixed together for 30 minutes and allowed to stand for
12-15 hours.

examined the partition coefficients of Fe (II)(1rIr), U (VvI),
ca (11), Sr (II).Zr (IV), Ce (III), Ru (IV),and V (V).
Agueous _perchlorate systems. The distribution of uranyl
perchlorate between TBP and water at 25°C is shown in figure
42.;§2- Figure 43 gives the partiltlon coeffilclient of uranium

as a function of the aqueous perbhloric acid conc:em:r-f.xt_:T.on.lé2

145
Shevcheriko gg_gl,fizg-have studied the extractlon of uranyl
perchlorate ln the presence of HClOu, LiClOu, and NaClOu.

The saltlng-out capaoity of these salts increases 1n the order
listed. The choice of TBP diluen; also affects the extraction
of uranyl perchloraté. From.an agqueous solution of 0.065&
HC10, and 1M Na0104, the extractlon of uranlum by 2.20M TBP
wae found to decorease In the following order of d:I.lue:r:i:s:E-3-g

isoamyl acetate > n-butyl acetate > 1socamyl alcohol >
toluene > Xylene > benzene > carbon tetrachloride.

The distribution of perchloric acld between TBP and aqueous
solution is glven in figure 34_fll§ The partition coefflclents
of Th, Zn, Pm, Y, and Ce are plotted against aqueous per-

chloric acid concentration in figure 44.231 Ishimori and

Table XXII. Effect of Saltlng-out Agents on the Extraction
of Uranyl Chloride by TBP.2

 

Salting-out agent . a,
- 0.03
NaCl, sat'd 2.85
KCl, sat'd 0.38
NH)C1, 5M 0.71
LiCl, 5M 0.90
HC1l, 5M 17.6
CaClE, 2.5M ' 5.06
Mgcla, 2.5M 11.7
AlClB, 1.6TM 23.8

 

& After Gal and Ruvarec, reference 431.

Initial composition of organic phase - 30% (v/v)
TBP 1n dlbutyl ether, sat'd with 1.225M HC1l.

Initial compositlion of aqueous phase - 1.225M HC1,
0.1M UO 012, salting-out agent at concentratlion
1ndToat®d.

146
URANIUM GCONGENTRATION, ORGANIC, M

 

1 IIJII

 

 

 

 

1 -I - | III 1 1 111 |]I L 1 1 .I L 11
0.001 ;
0.0l 0.1 1.0 10

URANIUM CONGENTRATION, AQUEOUS, M

Figure 42.
The partition of uranyl perchlorate between 100% TBP and
water at 25°C,
After E. Hesford and H. A. C. McKay, reference 169.

.Nakamuraiiz have studied the extraction of Pa, and Np (IV)
(V)‘(VI) by TBP as a function of perchlorate concentration.

Aqueous sulfate systems. Sulfate lon 1s normally con-
gldered an interferlng ion in the extraction of uranium from
aqueous solutlion by TBP. Veereswarara.o,Eii however, found
that significant amounts of uranium may be extracted from
sulfuric acid solution and that the extraction i1s inecreased

as the acid concentration is increased (filgure 45).53&

147
10%

 

ey
o
o
1

lJIIIII

o
o

PARTITION COEFFICIENT,
o

 

 

 

Figure 43.

The extraction coeffleclent of trace amounts of uranium between
100% TBP and aqueous solution as a funetlon of equilibrium
aqueous HC10, concentration. 25°C.

After E. Hesford and H. A. C. McKay, reference 169,

148
 

 

 

 

- .

0% | =
s i ]
— L i
Z
E .
o 0F 3
TH C -
[T - -
w L -
o L -
O
=
o 1.0 —=
= - ]
- C ]
o - _
<L _ -
a

0.! F =

C .
0.0\ L fi I

 

| | :
O I 2 3 4 5 7 8 9 10 Il 12
[HCIO4]aq.. M

Figure 44. The distribution of Th, Pm, Ce, Zr, and Y between 100%
TBP and aqueous solutlon as a fu.nction of Initlal equllibrium aque-
ous HC1l0Oy concentration. After S. Sieklerskl, reference 433, Con-
ditions: Egqual phase volumes (15 ml) shaken together for about 20
minutes at 21°9-250C.

149
 

 

 

 

 

| I 1 T T T ]
: .
o 1.0 =
= - .
Z C B
W i B
O L -
w
W L -
11
Eg .
0.1 =
Z - 3
e - .
F C i
—

x - 7
g | i
0.0l | 1 l |1 ] | i

0 i .2 3 a 5 6 T 8 9

[He so.,].,q, M
Flgure 45.
The partition coefficlent of uranium between 30% TBP (v/v)
in.kerésene and aqueous solution &s a functlion of equllibrium
aqueous Hésou concentration. _
After U. Veereswararao, reference 43i.

Conditlons: _
Equal phase volumes (10 ml) equllibrated by shaldng

for 5 minutes at 18° + 1°C.

-The presence of sodlum chloride in sulfuric aseld solutiown
gugments fthe extractlon of uranium by 'I‘.‘BP.‘—Jrfii Molybdenum
and iron (III) are well extracted from such solutions.
Vanadium and iron (1II) fire poorly extracted compared to
urantum.23% The distribution of sulfuric acld between

TBP and aqueous solution 18 represented in figure 34.212

have studled the effect of thilocyanate lon on the extraction
of uranium from sulfate llquors by TBP. From an aqueous

solution contalning 1.5 g/1 of U3°B as uranyl sulfate and.

150
2.1 g/1 total sulfate ooncentration at pH 1.5, the partition
coefficlent of uranium varied from 3.5 to 100 as the thlo-
eyanate to uranyl molar ratlo was lncreased from 2 to 6.
Twenty per cefit TBP dissolved In kerosene wag used as ex-

tractant. The partition coefficient, o _, lncreases with

u?
lncreased TBP concentration, lncreases wlth incressed pH,
and decreases Wwlth incregsed sulfate concentratlon. Vanadlum
and -iron (III) are appreclably extracted by TBP from thio-
cyanate solutione. Copper, titanlum, cobalt are weakly
extracted. Iron (II), cadmium, molybdenum, magnesium and
aluminum are essentially not extracted. Phosphate lon may
cause the preclpltatlion of uranium or complex formation when
present in large amounts. Okada, et al.fiifi report the ex-
traction of uranium by TBP, mesltyl oxlde, and methyl ethyl

ketone from phosphoric acld solutions havling 20 tlmea as much

ammonium thilocyanate as uranium.

Tri-n-octylphosphine oxide (TOPO)

Much of the work on thils solvent haa been reported by
White and co—workers.flil:&ii Uranium 1ls extracted by TOPO
from nitrate and chlorlde solutlons and tc a smaller extent
from sulfate and perchlorate solutions. It is essentlally not
extraocted from phosphate asaolut:lons.—l'fll The extraction of U,
Th, Bi, Mo, Zn, and Cr by 0.1lM TOPO from aqueous solutlons
1s given as a function of nitric acld concentration 1ln filgure
46; ag a funetion of hydrochloric acld concentration in

flgure 47°fl£9!flfll

Iron and titanium extraction curves are
also included in figure 47. The extractlon of over 40 ions
by 0.1M TOPO from hydrochloric, sulfurlc, perchloric, and
nitric acid solutions is qualiltatively indicated 1in Table
x¥111.238  The extraction of mineral acids by 0.1M TOPO as
g functlon of acld concentratlon 1s glven in flgure 48.££l

Uranlum mey be stripped from TOPO solutlons by contact

151
PARTITION COEFFIGIENT,

 

 

 

 

 

U

- :

3 -

10% & -

C J

0% F =

10 F E

- 7

- -

1.0 -

- ._ -
0.1 Lo N Ny

O ! 2 3 4 5 6 7 8 9 10 I 12

NITRIC ACID, molarity
Figure 46.
Extrection of some metal ions by 0.1M tri-n-octylphosphine
oxide from nltric acld solutlons.

After J. C. White, references 440 and 4Xil.

152
PARTITION COEFFICIENT,

 

104 T T T T T T T T T 71

 

 

 

 

 

 

 

- § (- —Q 3
:E | Molybdenum -
n '.-' pltmenm— e e, e, o~ _+
i Uranium W e a
0% & E
- ]
_ -
0% = 4 4
10 / 0\ _
T i N2 ]
- g . -
- = g ,-; -
|.0 = 4 _,-"f ) ==
. @ E"'*-a i
o.i ) T8 o0
o I 2 3 4 5 6 7 8 9 10 1! i2
HYDROCHLORIG ACGCID, molarity

Figure U7.
Extraction of metal lons by 0.1lM trl-n-octylphosphine oxilde
from hydrochloric acid solutions.
After J, C. White, references 440 and 441.

153
HNO3

.1M TOPO in

HClOu

H2304

i

Gyclohexane.E

Extractlion of Ions from Acid Solufions with O
HC1

Table XXIIT.

Ton

M_

TN

m_

 

N

 

a1 *3
sp+3
As+5
Bafz
Be+2
pyt3
gt3
Cd+2
cate
Ce+3
Cr+6
CO+2
Cu+2
Dy*3
Ert3
Eut3
aat3
Gat3
Ge+4

M

Au

N

154

Ho+3
In+3
Fe+3
nat3
ppte
Mo+6

Mg+2
Hg+2
Table XXIIT.-Contlnued.

Ion

1M

HC1

2

I

H 304

HC10, -

I

-
I=

2

 

Ng*3

nite

Pd+2

Pt+2

ppt3

Ru+2

Sm.'"3

Ag+

Sr+2
mpt3
Tt

Tm+3

Sn"'4

E =

Z =2 2 9" =2 =2 =2

=2 =

H n = =2 =2 @B o= H =

Z 1 = o= =2 W= = = E;

H o2 2 B . B oBEH E

s =2 =2 w5 =z =

=

H =2 =2 2 2 @# w @ =

2 o= oW W OE =

= =2 =2 = =

=)

w B 7 =2 =E =2 = = = =2 o=

F =2 =2 2 2 #H w BH =

complete extractlon P = partlal extraction

2 =2 2 =2 2 2 =2 =2 =2 =

-3

H 2 2 2 =2 +H @B +3 =

2 w2 = =2 =2 2 &2 9Z2 929 2 =

H =2 =2 2 =2 t« w H

2

2 =2 = 7z =z 5

H =2 =2 2 2 @#H w '\ 2 w =2 2 =

N = no extraction

 

2 After J. C. White, reference 438.

Equal phase volumes equllibrated 10 minutes.

155
 

10 T I ] I 1 | r

  

 

 

 

: .
- ]
o . B
O L
E ’
g 1.0 = =
c - ]
i u -
-
2 L —
o - T
x
a 0y ]
O -
S Fd 1
0.0! | i 1 | L ] |

ot 2 3 4 5 6 T 8
ACID CONCENTRATION OF
EXTRACTED SOLUTION (M)
Figure 48.
Extractlon of mineral aclds by trl-n-octylphosphlne oxlde.
After J. C. white,-reference 4y,
Conditlons:
Agueous phases - acid solutlion of i1lndicated molarity.
Organic phase - 10 ml of O0.1M TOPO in cyclohexane.
v Vfi - 1.
wilth acld (HF, H3P04, or concgentrated (NH4)2304 solutions
at pH 2), hydroxide (NaOH or NH40H), or oarbonateE(NH4)2003
or Na2003] solutions.flfli Sodium carbonate 1s the most
effectlive stripping agent.
Tetraphenylphosphonium chloride (TPPC)
A recent study has been réported In whieh uranlum was
extracted 1lnto chloroform as the tetraphenylphosphonium uranyl

156
" trlbenzoate complax.fiflg- Uranyl 1on was converted to an anlonilc

form by benzolc aclid. Tetraphenylphosphonium chloride was used
ag extractant. The extraction of uranlum was found to depend
fiéon pH, TPPC concentratlion, and uranlum concentratlon. At
~£H 3-9, the extraction of uranlum w&s nearly quantitative.
Thé partltion eoeffigiéfit; afi, was increased wlth Ilncreased
TPPC concentration and was decreased wlth increased uranium
fioncentration. The decrease 1ln 2, wlth increased uranium

' concentration was observed with a constant urhnium—to-TPPc
molar ratio. At 25°Q.and bH 5.2, zine, zirconium (niobium),
and ruthenlum were appreclably extracted (~10-20% compared

to 100% for uranlum). The extractlon of zino and zirconium
may be depreflsed by the use of a complexing agent, EDTA, 1n

golutlcn.

ACIDIC ORGANOPHOSPHORUB COMPQUNDS

Uranium 1ls efficlently extracted by acldic organo-
phosphorus compounds whioh lnclude di- and mono- alkylphosphorlc
aclds, (HO)(RO)EP—D 0 and (HO)Q(RO)P—) 0; dlalkylphosphinie
acids, (HO)R2P-+ 0; alkylphosphonic aclds, (HO)ERP-é 0; and
dialkylpyrophosphoric aclds, HR,P,07. The latter aclds are
dlscussed separately.

Table XXIV comp#res the extfactive capaclties of several
dialkylphosphoric, dlalkylphosphinlc, and monoalkylphosphorilc
aclds for uranium.égg The abllity to extract uranium, within
a given class, appears to decrease wlth lnereased branchlng
of-the a2llkyl chaln near the phosphate group. The acldity ol
the reagent deoreases roughly in the pame ordef.figg- Where
comparlsons can be made for the same alkyl group between classes
of reagent, the extraction coefflclent of uranlum increases in
the order

dizalkylphosphoric acld < dialkylphosphinic aeld <
monoalkylphosphoric acid.

The cholce of dlluent affects the extractlion of uranium. For

157
. Table XXIV. Extractlon of Ursnium by Acldlc Organophosphorus

 

Heagents.5
Reagent Uranium extractlon coefflcient, a
- —_ Carbon fefrachlorlide Kerosene

 

Dlialkylphosphoric aclds

n-octyl EO 450
3,5,5-trimethylhexyl ? 260
1

2~ethylhexyl 135

2-athyl-4-methylpentyl _ - 90
2-propyl-4-methylpentyl ' - 60
octyl-2 11 -
dliscobutylmethyl 2 10
Dialkylphoephlnic acilds
v-phenylpropyl 300 -
phenyl-2-ethylhexyl 300 -
n-decyl 180 -
n-octyl 160 -
3,5,5-trimethylhexyl 120 -
2-ethylhexyl 30 -
Monoalkylphosphorlc aclds
n-octyl 580 -
3,5,5-trimethylhexyl >1000 £>1ooo;
2-ethylhexyl >1000 >1000
dlisobutylmethyl : 450 -
2,6,8-trimethylnonyl-4 - 650
1-isobutyl~l4-ethyloctyl - 600
3,9-diethyltridecanol-6 - 550

2 pfter C. A, Blake, Jr., C. F. Baes, Jr., K. B. Brown, C. F. Coleman,
J. C. White, reference 302.

Aqueous phase: 0.5M SO5~, pH 1, 0.004M U(VI) initially.
Organic phase: 0.1M reagent in solvent indloated.
Temperature, 25°.; VO/Va, 1.

dialkylphosphoric and dialkylphosphinic aclds, @ generally
lnereases as the dlelectrlc constant of the solvent increaaes.ggg
For monoalkylphosphorlic acids, a reverse trend 1s indicated.39§

The mechanlsm of extraction of uranlum by dlalkylphos-
phoric aclds has been studled by various groups.lfigi;ig&igg&&&l
At low uranlum concentrations, the extraotion mechanlsm appears
to be consistent with the reactlon

2
2

where HDAP represents & dialkylphosphoric acld. However, 1n

vost aq + 2(HDAP} org= UO,(DAP) org + 2H" aq,

158
organic solvents, dlalkylphosphoric acids are largely asso-
clated as d:I.mers.LLQ@&HQS&E&§ On this basis, the reaection

UGt aq + 2(HDAP), 18 = UO,(DAP),(HDAP), org + 2u* (1)

is fl.ncli.c:al.tecl.-:-L»-*rig-"-lég The number of dialkylphosphate groups
assoclated with the uranyl ion in equation (1) may be accounted
for by a chelate structure 12§;§Q§

 

 

feRz O
/P \
U02+/ 0 OH
2 1™~ o o
:
0

At higher uranium concentratlons, lsopiestlc and viscoslty
measurements indlcate that polymeric uranyl-dlalkylphogphate
chalns are formed.}ég

The extraction coeffilclent of uranium by dilbutylphosphoric
aclid, HDBP, is given in filgure 49 as a functlon of nitric

acid concentrationfigé The shape of the curve has been

explalned by Healy and Kennedy 1ln the followlng manner:l§§

The initlal decrease ln o; between 0.1M and 3M

HNO45 is expected on the basls of hydrogen ilon
rep?acement by UOB+ lon. However, for o, greater
than 10 not enough HDBP ls present in the organlc
phase to give the monomeric specles UOp (DBP),(HDBP)o
demanded by equation (1). In this reglon, the ex-
tractlon mechanlem is llkely to be governed by the
reactlon

x005* aq + (x+1)(HDBR), org = [UO,(DBP),] 2HDBP org + 2xH' aq. (2)

E]x

The shape of the extraction curve from 3M to 10M
HNO=z 15 simllar to that obtained with TBF and
ind?categ & change Iin extractlion mechanism. The
likely reaction is

U0§+ aq + 2NOJ agq + (HDBP), org = UO,(NO),2HDBP org. (3)

The decrease 1ln o; above TM HNO3 is probably due
to the competing reaction

(HDBP)2 org + 2HNO; aq = 2HDBP - HNo3 Orge. (4).

It is 1likely that mechanlsms (2) and/or}(3) also
ocour to zome extent at high acld concentratlons.

159
The extraction mechanism of dialkylphosphinic aclds 18
expected to be eimilar to that of dlalkylphosphoric aecids.
The former are often found as dimers 1n organic solvents
and the partition coeffilcient of uranium, @, exhiblte a
power dependence on extractant ooncentration at low uranium:
levels simllar to that of dialkylphosphoric aclds.=22 Mono-
alkylphosphoric and monoalkylphosphonic acilds havelfieen found
in larger polymeric aggregatea.figgl&&g" Partition coefficlents
for these extractants exhiblt first to second powsr depen- .
‘dencles ofi.extractant conoentration.ggg

Interference 0 uranium extraction by anions increases
< POP” .
Stripping 1is essentiallj the Inverse process of extraction.

in the order €10, < Cl™ < SOy

Uranium may be stripped from dlalkylphosphoric aelds by con-
tact with hydrofluorig sulfuric, phosphorilo,or even hydrochloric
aclds., The stripping efflclency 1s generally lncreased wlth
increased acid conc:emi'.l?a.t.:l.on.-lfltg Ammonium or sodlum carbonate
stripping 1s efficient.fiflg-

Szgergigglf In a search for reagents to modify kerosene as
the dlluent for dialkylphosphoric aoids,** 1t was dlscovered
that neutral organophosphorus compounds provided a synerglstic
enhancement of the uranium partitlon coefficient. The en-
hancement 1s increased in the following order of neutral
reagent:

trialkylphosphaté < alkyl dlalkylphosphonate < dialkyl al-
kylphosphinate < trlalkylphosphine oxlde.

Table XXV lists @, for several synergistic systems.igg‘ The

reason for the enhanced partition coeffiocilent, @, has been

* Co=-operative action of discrete agencles such that the total
effect 1s greater than the sum of the two effects taken 1in-
dependently. _ :

**Kerosene la modified to prevent separatlon of a dialkylphosphate
salt as a separate phase wheh alkaline stripplng is uscu. Long
chain alcohols have been used as chemical modifiers. These,
however, depress the extractlon coefficlent of uranium and

other metals,

160
ay

PARTITION COEFFICIENT,

 

 

 

— T T T T T T T T T7T
- -
100 —
.
10 -
:

1O ooy L Lt L1

 

 

O I 2 3 4 5 6 7T 8 9 10 11
NITRIC ACID NORMALITY
Flgure 49.

Variation of a, with nitric acid concentratlions for 0.1iM
dlbutylphosphorlic aclid In benzene using 20 ml organhic phase,
and 50 ml aqueous phase, and an lnitial firanium concentratlion
of 0,018M.
After T. V. Healy and J. Kennedy, reference 188.

explalned on the basls of (1) the additlion of neutral reagent
to the uranyl-hialkylphosphate complex through hydrogei. bond-
1ng§9g or of (2) eliminating the need of monomerizing a mole
of dimeric extractantflép in the extraction mechanism (see
equation (1)). A recent study of the synergistic system,
thenoyltrifluoroacetone-neutral organophosphorus compound,

indlcates that more lnvestligation 18 nebessary for a more’
451

 

precise explanatlon of synerglatlic effects. Much of the
work done on synerglstlc systems lnvolving dlalkylphosphoric

aclds is summarlzed.in reference 452.

161
Table XXV. Synerglstic Enhancement of Uranium Extraction Coefficient.2

 

 

@y
: R tic
Organophosphorus reagent Conc.,M Aififignt igmgifiiififi.iith
0.1M F2EHPA
Di(2-ethylhexyl) phosphoric
acid (D2EHPA) 0.1 135 -
Phoaphafes
trl-n=butyl 0.1 0.0002 k70
tri-2-ethylhexyl 0.1 .0.0002 - 270
Phosphonates
di-n-butyl n-butyl 0.1 0.0002 1700
dl-n-amyl n-amyl 0.1 0.0003 2000
di-n-hexyl n-hexyl 0.1 0.0004 2200
dl-2~ethylhexyl 2-ethylhexyl 0.1 0.0002 870
Phosphlnates
n-butyl dl-n-butyl 0.1 0.002 3500
n-butyl di-n-hexyl 0.1 0.002 3500
Phosphlne oxldes
tri-n-butyl 0.05 - 0.0025 7000
tri-n-octyl 0.1 0.06 3500
tri-2-ethylhexyl 0.1 0.02 650

 

& After C. A. Blake, Jr., C. F. Baes, Jr., K. B. Brown, C. F. Coleman,

J. C. White, reference 302.

Aqueous phase: 0.5M sofi pH 1, CLOO#M U(VI) initlally.
Organic phase: Reagents in kerosene diluent.

Temperature, 25°C.; Vb/v s l.

Di(2-ethylhexyl) phosphoric acid (D2EHPA, HDEHP)

This reagent may also be known by a less descriptilve

name, dioctylphosphate (DOF).
D2EHPA 18 reviewed in reference 453.

The extractlon of uranium by

The effect of acid

concentration on the extractlon of uranium by D2EHPA is

shown in flgure 50.£§§ The uwranlum extractlon curve for

D2EHPA from nitric acid is similar 1in shape, for the few

points given, to that for dibutylphosphoric acld given in

figure 49, Flgure 5l lllustrates the effect of nltrate ion

on the extractlon of uranium by D2EHPA.Efii The presence of

a small amount of nitrate in an aqueous sulfate solution 1n-

creasesa the extractlon of uranium slgnlflcantly.

An Increase

in temperature causes a decrease in uranium extraction.flzé

162
 

100

 

 

 

 

- | -

10 — -

> _ i

o C -

= - 1

= - -
w

O - .
w
w

E§ 1.0 — —

O - :

2 B ]

o - i

= 3 i
—

o i i
<
o

0.l — —

00N b—L 1 1 11111
0O 1 2 3 4 5 6 7 8 _ 9 10 Il 12 13 14

AGCID NORMALITY

Figure 50. Extractlion of uranium by di(2-ethylhexyl) phosphoric
acld in kercsene from mineral acid solutlons. After C. A. Blake,
K. B. Brown, and C. F. Coleman, reference 453. Conditions:
Organic phase - 0.1M D2EHPA 1n kerosene, 2% (w/v) 2-ethylhexanol.
Aqueous phase - 1 gU/1 for a2ll acld solutlons except H3PO4 in
which cage the U concentratlon was 100 ppm. Agitation time - 2
minutes. Vgp/Vz = 1 for all aclds but HNO3 in which Vo/Vgy = 2.

163
 

t000 T T T I 1 ' I

T 1T 1Tt

S—o>
L1l

@y

100

PARTITION GCOEFFICIENT,
o

       

 

 

I 1 I 1 ] I
0 | 2 3 4 5 6 7

NITRATE CONGCENTRATION, M

 

Figure 51, The effect of nltrate lon on the extractlon of uranium
by dli(2-ethylhexyl) phosphoric acid. Curve 1 - initial pH= 1.5 -
1.85; Qurve 2 - initial pH = 0.5 - 0.75. Conditlions: 0.0lM D2EHPA
in kerosene (1.3% 2-ethylhexanol), 1 g U/1 1n agueous phase, Vo/Vy =
2, 2 min, contact time. Curve 3 - 0.5M SO4, pH = 1.2. Conditions:
0.05M D2EHPA in CCly, 1 g U/1 in aqueous phase, Vg/Va = 1, 20 min.
contact time. After C. A. Blake, K, B. Brown, and C. F. Coleman,
reference 453,

The effect of diluent on q is given in Table VI 223 The
enhanced extractlon of uranium by D2HPA in synerglstic com-
bination with neutral organophosphorus reagents has already
been noted (Table XXV).égg The extent %o which other lons

are extracted 1s indicated qualitatively 1n Tables XXVII and
]‘CKVIII.EE}£

164
Table XXVI. Cholce of Diluent wita Di{2-ethylhexyl)
Fhosphoric Aéidné

Blluent s
Kerosene 1235
HeXane 110
Carbon tetrachloride 20
Isopropyl ether 17
Benzene 13
Chlorcform 3
2-Ethylhexanol 0.1
Cctanol-2 (capryl alcohol) 0.08

B aAfter C. A. Blake, K. B. Brown, and C. F. Coleman, reference
453.

0.1M D2EHPA, 0.004M U (VI), 0.5M SO§ ™, pH = 1.1,
Vb/v =1, agitation time = 10 min. (wrilst- action shaker) .

Dialkylpyrophosphoric aclds

Dlalkylpyrophosphoric acids are used ln the recovery of
uranium from low-grade phosphate oreg. Much of the work that
has been feported in projJect literature has been summarized
by Ellis, 222 by Long, Ellls, and Bailespfléé'and by Brown and
Golemancigi :The aclds are prepared Jjust prlor to use by
gdding alcohol to a slurry of P205 in kercsene wilth stirring
and coeling. A concentration of about 0.1 g P205 per ml of
kerosene 1s optimum.%55 A 2:1 mole ratio of alecchol: P205
is used to form the dialkylpyrophosphoric acid. A 3:1 mole
ratio should glve about equal mole quantities of mono- and
di-alkyl orthophosphorlc acidsufiéé The reactlons are com-
plex and mixtures of varlous phosphorlc aclds are formed.
With pyrophosphorlc acids, uranifim extraction lncreases

wlth carbon chaln length from butyl tc cctylnfifii Nonyl and

165
Table XXVII. Extractlon of Metal Ions from Acidic Soluticns with
- 0.1M Di(2-ethylhexyl) Phosphoric Acid in Cjclohexane.é

Metal Sodium Chloride (1M) Ammonium Sulfate (1M) Sodium Nitrate

Ion pH O pH 0.5 pH 1.5 pH 1.5

H I5

5B

a1ts3
As+5
Bate _ ]
pet2
g3

N
N

o

=1

>
e
I
'
Z "l =z=2 2=+

HH
3
+
w
2w 2 W
Z "= W
= 2 bR 2 2 nE s =

2 = M

o= ams

j=s
=
1
1

1
1
Wg o R BEEREZ2EZ 22022290kl 22229E22w222
1
EEHEEE ==

v
+
w
H =2 2 =28 60 B3 &
=22 HHEREAHR
H=zbHBEHHEHERZMH

o W O

=
[}

complete extraction, P = partial extraction, N = no extraction,
no test was conducted.

o

After W. J. Ross and J. C. White, reference 454.

Agueous phase: 1-2 mg of ion, salt at concentration I1ndicated,
PH indlcated.

Organic phase: 0.1M D2HPA in cyclohexane. 5 ml portions of each
phase shaken together for one hour.

166
Table XXVIII. Extrectlon of Rare Earths from Chlorlde Solutions

with Di(2-ethylhexyl) Phosphoric Acld in Cyclohexane.2
Ion pH1.9 pH1.0 pH1.02 pHO.5 pHO5®  pHO

y*3

La+3
cot3
prt3
Na*3

E

|

o

Sl
w
BEEEHEREEE oD

o]
=
o
=
Hd

HHEHE®BE A2 2 2 22
H & EHEEHEEHRE~N D2 2
H & EHEBEBHE -2 222
HEEEHDEZ2 2222 2 2
W =2 2 22 E s e

= complete extraction, P = partial extractlon, N = no extractilon.

After W. J. Ross and J. C. White, reference i454.
Aqueous phase' stgndargssoluiéon of 2 mg/ml cet3;

1 mg/ml Pr+3, Nat Ho+3; 0.5 mg/ml 7p+3,
0.2 mg/ml Y+ , La*3, Eu+3 H +3, Er*3; 0.1 mg/ml Yv¥ ;

1 ml of standard solutlon, 1 ml 5M Nacl NaOH or HCl to
glve desired pH in 5 ml of solution.-

Organlic phase: 5 ml of 0.1lM D2EHPA in oyclohexane extraction
ror 1 hour.

Without NaCl.

decyl glive about the same extractlion as oetyl.EQQ No appre-
clable dlfference in extractlng ablllity was observed between
pyrophosphorlc acldes pr epared with octanol-l or t'.>c‘c:5!.nol—2.-%§5—é
Most of the studlies have been made wlth octylpyrophosphoric
acld (OPPA). Pyrophosphoric aclds deterlorate fairly rapidly
wlth tlme at room temperature. At elevated temperatures,

the rate of deterloration 1s even greater. Contact with
mineral acld causes pyrophosaphoric acids to hydrolyze to
orthophosphoric acids. The rate of hydrolysls ls slower
with basic sblutions.izi

167
Kerosene 1s a satlsfactory dlluent for OPPA.EEE The
acld is used in 1-10% concentration.

The partitlon coefflclent of uranlum, &, 1s considera-
bly higher wlth OPPA than with the corresponding mixture of
orthophosphoric aclde, OPA. The partitlon coeffleclent 1s a
function of fthe oxidatlon potentlal of the acld. With OPPA,
satilsfactory uranium recovery can be made {f the e.m.f. 1s
-0.250 volts or greater.fiéé Reduction of the acld increases
the extraction of uranium conslderably. At zero to +100

volts.au 1s about twenty tlmes that at =300 to -200 volts.ffizé

The extractlon of iron 1s decreased in reduced solution, 1l.e.
%pe(11) < %Pe(III)"

Uranlum is stripped from the organic solvent by precipl-

tatlion as uranous fluoride.

| ‘Several papers have recently appeared 1ln open llterature
publicatlons concernlng the extrfiction of uranium by pyro-
phosphorle acids. Zangenfiéz has shown that OPFA prepared by
the alecoholysls of P205 1s a mixture of several components.
OPfA prepared in thls manner was found to be more effectlve in
the extraction of uranium than pure dloctylphosphoric acld by
two orderr of magnlftude. The pure acld was prepared by syn-
thesls, starting from POClB;

In an effort to determine the uranium specles extracted
by OPPA, Grdenic and Korparflég have 1solated the species
U(Oct2P207)2. The specles, however, was insoluble in ligroin,
the OPPA dlluent. It was soluble 1n ligroin containing OFPPA
in a ratio- of one mole of U(IV)-salt and 2 moles of OPPA.
This indlcates U(OctEHP207)4 1s the extractable specles. The
same formule was obtalned by determlnation of the uranium
content 1n a saturated ligroln phase.

Habashifiég has Investigated the extraction of uranium
and other metals by OPPA from phosphoric acid solutions.

Uranium (VI) was found to be more highly extracted than uranium

168
(IV). This is surprising in view of the increased extractlon
of uranium from reduced acld solution mentioned previously.
Also, cerium (III) was found to extract more resdlly than
cerium (IV). The partition coeffilcients of several metal lons

are glven for various phosphoric acld concentrations in Tabls

XXIX. The partlitlon coeffliclentgdecrease with H3P04 concen-
tration for all the metal lons tested except cerium. The
extraction coefflclents of both cerium (IV) and (III) pass
through maxima in the reglon of 4M H3P04. The partition
coefflcient of uranium ls decreased by lncreased initial
uranlum concentration. The addltlon of Na3P04 to the soclution
gauses a tc increase greatly--apparently by decreasing %the
hydrogen lon concentration 1n the aqueous phase. Fluoride
1lon interferes most seriously with the extractlon of uranium
by OFPPA.

Zangeniég has studled the extraction of uranium (IV)
from phosphoric acid by di{2-butyloctyl) pyrophosphate, BOPPA.

AMINES AND QUATERNARY AMMONIUM SALTS. A large number of
amlnes, quaternary ammonium salts, and other organonltrogen
compounds have been 1lnvestigated as posslble extractants of
ur.-e.nimn.il'éi:Eéi The physical chemlstry of uranlum extractlon
by amines has been studled by Mcwaell, Baes, and Allenflé&zgég
and Boi::-emlt—6-2-fl-£[9 Much of the above work has been summarilzed
by Coleman, et al.égi More recently, Mooreflz;-has reviewed
the extractlion of a large number of elements, lncluding
uranium, by amlnes.

The reactlons involved 1ln the extraction of uranium by
amines have been revlewed by Coleman, EE_élrégi Organic solu-
tlons of amines extract aclds from agqueous solution to form
alkylammonlum salts

R3N org + HX aq < R, NHK org. (5)

3
The amine salt 1n the organlc phase can exchange its lon for

another in the aqueous phase

169
Table XXiX. Partitlon Coefficients of Several Metal Ions
Between OPPA and H3P01.r.-a'-

 

. Partitlon coerficient

Ton® H3POy concentration

2M 4 &M M
U(v1) 190 46 - 23 20
U(Iv) 18.6 14,2 13.5
Th{IV) | 24 23 18 13
Fe(III) 18 8 5
Fe(II) | 1 <1 <1
v(Iv)e 2 0.8 0.1
Ce(IV) - 5 8 3 1
Ce(ILII) | T 22 4 2

After F. Habashl, reference 459.

1
i

The coefflclents, with the exceptlon of G (1v)s Were
determined from flgures which appear in reference 459.

|o

0.4 mg metal lon per ml; 24 OPPA in n-hexane; Vo/Va = 0.1.

Vb/Va = l.

le

R NHX org + Y aq = R3NHY org + X aq. (6)

The order of preferences for anions in the organic amine
solution s C10,” > HO™ > €17 > HS0, > F~. 3%
In this anion exchange representatlon, metals are then ex-
tracted from aqueous solutionsin which they are present
as anlons or anlonlc complexes. For example,
U03* ag + 3X” ag & UOXs" aq. (7a)
RSNHX org + U02X3'a.q <"-5 RNHUO X3 org + X". (7b)
This mechanlism, however, 1ls indistinguishable from one in
which a neutral complex 18 extracted.
oSt ag + 2% ag = UOLX, ag. (8a)
R3NHX org + UO,X, ac = RSNHU02K3 Org. . (*‘Bb_)

170
The factors that influence uranium extractlon have been
studlied most extensively for amine-sulfate Es§¢f.'s:’cem1&'>.§9~1£ The
effect of amine structure on the extraction of uranium and
other metal lone 1s 1llustrated in Table X}C}{.:?-O---li Uranium
(IV) 1s efficlently extracted by primary amines. The effi-
clency decreases with secondary and tertlary amines. With
uranium (VI) there does not seem to be much correlation be=
tween a, and amine class. Wlth primary, sscondary, -and ter=
tlary laurylamlnes, au(VI)’ under the condltlons given in
Table XXX, is < 0.1, 80, and 140, respectively.égfl With
primary laurylamine an emulslon 1s formed.égfl The extraction
of uranium 1s also affected by carbon chaln branching near
the niltrogen atom 1n tertlary amines (Table XXX). Certain
n=benzyl-branched-alkyl secondary amlnes have been found to

extract uranium extremely well.="" The uranium (VI) partition

coefficients of N-benzylheptadecylaminé, N-benzyltetradecyl-
amine, N-benzyldodecylamine, and N-(2-naphthylmethyl) dodecyl-
amlne, under the ccndltlons outlined in Table XXX, are 2000,

51000, > 1000, ~1000, respectively.3%® The partition coeffi-
clent depends upon the amlne-dlluent comblnatlon. The effect
of dlluent on Uu(VI) is indlecated in Table XXX.QQ&

The partition coefficient, Gu(VI)’ 1s iInfluenced by
uranium concentratlon in that 1t changes the amount of free
amine sulfate concentration.§9£ In sulfate solution, bisul-
fate complexes the amlne more strongly than does sulfate. The
uranium partitlon coeffleclent, therefore, decreases wlth in-
creaséd-acidity.égi ExXcess agueous su;fate causes a decrease
in GU(VI)°§9£ The partitlon coeffliclent 1ls also decreased
by increased temperature.ég& Extraction lsotherms 1ndlecate
that four to slx amine molecules are assoclated wlth each
uranium (VI) 1on.§9£ The number depends upon fhe partlcular
amine used. 1th vigoroue shaking, the partition coefficlent,

Qs varies approrximately as the flrst power of the free amine

171
2Ll

Table XXX, Effect of Amline Structure on the Extractlon of Metal Sulfates.>

 

 

Metal lon Partition coeffilclent, a
Prlmary Amlnes Secondary Amines Tertiary Amines
Amlne,  Primepe Di(tri- Aming Methyl- Tri-iso- Tris(2-
21F81— JM-EZ deoyl) 8-244 di-n- octylamine ethylhexyl)
amine decyl~- amine
emne
, Ga, Al
v(Iv), cr(III),
Mn(II), Fesn , _
Co(II), Ni(II),
C‘u II 9 Zn <0c1 <0¢01 <0-01 <0-01 <°l°l
v(III) yaE 0.1528
Fe(III) 40 0.5 0.1 <0,01
‘R.E.{III) 20 0,1 <0.01 <0,01
CeEIV} >50 15548 <€0.01 0,01
TL(IV 10Oo 0.2 <0.1
zZr >1000 350 . . 200 a
£ f £ £
Th(0,5M 80y) >5000= »>500 >5004- c <0402
u(1v) 3000 S5000548 55%1-5 ai
v'{v; o <l <1 <l
V(V)(pH2 )= ~20 ~20 ~20 ~20
MoEVI}E e 150 300 400 150 3
Mo (VI){pH2)= >1000 51000  >1000 >1000
U(vI 40 1 12 20 50 90 0.2
U{v:ti 258 3% 8 108
U(vI 50= 90~ 30 et

 

a

After C. F. Coleman, K. B. Brown, J. G. Moore, K. A. Allen, reference 30%4.

1M S04, pH 1, ~1 g metal lon per liter except as noted. Vo/Vy = 1, 0.1M amine in aromatlc
hydrocarbon diluent.
ELT

o

10

I

: H
1-(3-ethylpentyl)-lt=ethyloctylamine TN

t

. J ' oy a4 H
trialkylmethylamlne, homologous mixture, 18-24 carbon atoms I EEES |
. ! 1 s s ‘¢ ¥ H
bis-(l-iaébutyl—3,5—d1methylhexy1) anlne ."H':
Y
. -:O' .I....
Goefficlents at loadings of ~5 g Vor ~3 g Mo per liter of extractant. Extraction

coefficlents of these metals decrcase as thelr concentratlon decreases.
Extraction from 0.5M 304 solution.
Diluent kerosene instead of aromatlc hydrocarbon.

Diluent chloroform instead of aromatic hydrocarbon.
sulfate concentration,

Ty(vI) " k [M (2 amine) - nM (U (VI}) orgl,
where n has a-value between 4 and 6, characteristlic of the
amine.2%% With slow equilibration, in which the liquid-liquid
interfacial aree 1s strongly limited and interfaclal turbu-
lence is prevented, nearly theoretically 1deal resultg have
been obtained;fiég i.e.,

Cuivy) = k [M (& amlne) - nM (U (VI)) orgll.

Small amounts of foreign anlons added to sulfate solu-
tions hinder the extraction of uranium more than similar
amounts of added sulfate. The order of increasing interference
is SOu < P04 < Cl LF K N03.§9£

Effectlive separations between uranlum and other metal lons
may be made by cholce of amine and/or diluent (Table xxx).figfi
Modlficatlon of the diluent with long-chaln alcohols or other
modifiers affects the extractlve powers of the organlc solvent
phase. A possible syneprgilstic enhancament of au(VI) has been
found with 3,9-dlethyltridecyl-6 amine and di(2-ethylhéxyl)
phosphorice acid.flég _

The amine extraction of uranium (VI) from aqueous phosphate
or fluoride solutions 1s qualitatlvely simllar to that from
sulfate solution. Uranium is extracted from relatively low
anion concentrations. As the latter concentration i1s 1ln-
creased, a, is decreafled.gg& The opposlte 1ls true for chlorlde
or niltrate solutions. Uranlum extraction 1s Inecreased as the
concentratlon of elther of the latter two anions 1is 1ncreased§9£

Uranilum may be stripped from the aminé,solvent phase by
a number of methods. Uranium extracted as the. amlne~sulfate
complex may be strlipped by eontacfi wlith a nltrate or chlorilde
solutlion. Alkaline strilpping with ao&ium carbonate results
In an agqueous uranyl tricarbonate solution. Ammonium or so-

dium hydroxlide forms preclpltates that are difficult to handle.

A slurry of magneslum oxlde causes uranium to precilpitate

174
as a magnesium polyuranate.§g§

Tri-n-octylamine (TnOA)

The partitlon coefficlents obtalned by Keder, EE_EE:EIEJ
373 for the extraction of actlnide metals from niltric acid
solutiomsby 10 volume percent TnOA 1n Xxylene are glven in
flgure 52. Carswell§§2 has studled the extractlion of uranium
and thorlum by 0.2M TnOA 1n toluene, also, from nitrlc acid
" solution. Thorium appeers to be more strongly extracted than
uranium In the latter system. Uranlum, however, 18 extracted
practleoally to the same extent in both systems for acid . con=
centrations up to 6M.

The extraction of uranium from hydrochlorle acld solu-
tions by TnOA in CClu'haa been studled by Blzct and Tremillon&zi
The extraction curve aé a functlon of HC1l concentration is
gelmilar 1in shepe and magnlitude to that for trlilsococtylamine
plotted in figure 53.

Allen and co-workersfigi:&gg have made fundamental studles
ofi the extractlon of uranlum from sulfate solutlon by TnCA.

Extractlon of uranium from acetlc acld solution by TnOA
1n Amsco D=85 gppears to be lntermedlate between extraction
from sulfuric and phosphoric acids on one side and hydrochloric
and nitrle acids on the other.ig&

Triisooctylamine (Ti0A)

The results of Mocnreizi for the extractlon of uranlum
(VI), thorium, and fission products from hydrochloric acid
solution by 5% Ti0A in xylene are presented in figure 53.

The extraction of strontium-85 1s negliglble from 2~11M HCl.
Americium (III) and curium (III) are not extracted. Elements
which are extracted lnclude Fe(III), Co(II), Zn(II), HE(IV),
v(Vv), Pa(V), Ccr(vI), Mo(VI), u(Iv), Np(VI,V,IV), and Pu(Vvi,IV)
in addition to those shown 1n flgure 53. The extractlon of
iron, vanadium; and chromlum may be suppressed by reductlon

to & lower oxldatlon state. Ruthenlum remalns In the organlc

175
 

|03 1 1 1 I I I I 1 1 I I

   
  
  

 

  

 

 

 

 

i o i
i ] Pu(IVv) T
P
t - -
“F  Nouvi s :
- " Np(V){a x 10®) ]
= i
(1]
G 10 E' 2
w -
[ = =0
J 5
8 - Np(VI)
z UvI) Y
o 1.0 | o
= F Ao YV NG
E [ o ‘ 3 ;
= - —Pa(V) A S
Pu (1)
0.1 - a
- —_— Am (Ill) (a x 102)
ey
oo' ] 1 L ] ] 1 1 1 1 1 1
0 1 2 3 4 5 6 7T 8 9 101 12

HNO3 CONCENTRATION, M

Filgure 52. The extractlion of actinlde 1lons by ten volume percerit
trli-n-octylamine in xylene from aqueous nitric acld solution. After
l; W. E. Keder, J. C. Sheppard, and A. S. Wileon, reference 472 and
2) A. S. Wilson ahd W. E. Keder, reference 473.

Conditlons:

(1) Ten volume percent TnOA in xylene were stirred with
an equal velume of nitric acid of the deslred composi-
tion for 3-5 minutee at room temperature (~25°C.). Phases
were separated by centrifugation after contactlng.

(2) Uranium (IV) data only. Agqueous solutlons were pre-
pared at each nitric acld concentration by dilution of
a stock solution which was ~1M U(IV), 0.1M H310y, and
~1M Zn(IX). Solutions for extraction experiments were
0.015M U(IV). TnOA was contacted by an equal volume of
12M HNO3 followed by three contacts of one volume each
of' the nitric acld concentration used. Equal volumes
of agqueous and amine solutlons were contacted at room
femperature for 5 minutes. Phases were Beparated by
centrifugation. . - -

176
 

 

 

 

 

l

OOb

10
a -
tad _
—
O L
< L
o
<
w 1.0 = =
— _ i
< - -
i - -
E o
L
-
. 0.1 =
- _
Z -
m b
O L
&
m o
.

0.Gi -
0.001 | | | | | | | } | I |
o I 2 3 4 5 & 7 8 ¢S 10 1l 12

HCI CONGCENTRATION, M

Figure 53. The extraction of U233, Th230, and fissilon prcducte by 5%
(w/v) triisccctylamine in xylene as a functlon of HC1l concentration.
After F. L. Moore, reference 475. Conditlons: Equal phase volumes
extracted for two minutes at room temperature (24°C.).

177
phase when washed with 0.1M HC1l solutlon. Uranlum 1s stripped
into the aqueous phase. Excellent extraction (>90%) of macro
amounts of uranium (60.4 mg U/ml initial aqueous concentration)
can be obtalned from 9M HC1l with 20% TiOA in hexone.

Mooreizg has also Iinvestigated the extractlon of uranlum
(VI) from acetlic acld solution by TiOA. Extractlons were
carried out 1n the same manner as those from hydrochlorilec
acid solution (figure 53). Aqueous solutions of varying
acetlc acid concentratlon contalning 2 x 104 alpha counts
per mlinute per ml of U233 tracer were extracted with equal
volumes of 5% {(w/v) T10A In xylene. It wae found that maxi-
mum uranium extraction (>90%) is obtained from 0.5M to 1M
acetic acld solutions. The additlon of 3%(v/v) butyl cello-
solve to the Ti10A-xylene solution lnhilbits foaming during
the extractlon process. By lncreasing the T10A concentration,
macro amounts of uranium are efflclently extracted. Greater
than 95% stripping may be achieved by contactlng the amine-
xylene phase wilith an equal volume of 0.5M HNO3, 3M Hgsou,
6M H,50y, 1M NH,HCOg, concentrated NH),OH, or 0.25M HF-~0.25M
HNO3 golution. From 0.5M-1M acetilc acld solutilon, ruthenium
(11.5%), zirconium (27.9%), and niobium (11.1%) are extracted.
Separation 1s made from strontium (alkaline earths), ceslum
and europlum (rare earths), plutonium (III) (trivalent actin-
ides), thorilum, protactinium, hafnium, tantalum, lron, lead,
nickel, cobalt, manganese, chranium (III), aluminum, copper,
zinc, blsmuth, tin,and antimony.izl&&zé The selectlvity may
be improved 1f the uranium 1s flrst precipitated by hydroxlde,
dissolved with 1M acetlc acid, and then extracted as pre-
viously described. Iron hydroxlide 1s used to carry trace

amounts of uranlum 1in the precipltation step.fizg _

Other amine extractants.

 

A stated at the beglnnlng of this sectlon, many organc-

nitrogen compounds have been investlgated as extractants of

178
uranium. A large number of these investlgatione are reported
in ORNL reports (eg., ORNL-IQEEEIZ, ORNL-EOQQEZQ). - For
further information, one may refer to these reporte, the
summariesig&l&él:iéi previously mentloned, or the review by
Mqore.fizl- '

Quaternary ammonium Salts.

Thé enhanced extraction of uranlium by hexone contalning
tetrabutylammonium nitratezg or tetrapropylammonilum n‘.l.tra.1:e§12
has already been noted {see Hexone). Haeffner, Nilsson,and
Hultgrenflzg have also used tetrabutylammonlium nitrate to
extract uranyl nitrate with chloroform.

Quaternary ammonium galte, unllike amlnes, may be used to

extract uranium from alkallne carbonate Esolut:tonxa.&-u:-'-i'@-fl-ig9
The Rohin and Haas compound Quatsernary B-104* converted to the
carbonate form has been used successfully to extract uranlium
from agqueous solutlons having carbonate concentratlons up to
one mfi:ula.rafl§9 Amsco G alone or modifled wlth a long-ochaln
aloohol, tridecanol, and kerosene modifled with tridecanol
have been used asg dlluents. The alechol modifler improves

both the phase separatlon tline and the extractlon coefficient.figg

The partition coefflclent exhlbits a negative two power

dependence on carbonate concentrationigg in accord with

the 1:'eazo.c~,’cion§-(-)-2
b= aq
2(R4N)2003 org + U02(CO3)3 aq T__(R4N)4U02(003)3 org
+ zcog’ aq.  (9)
The extractilon coeffilcient 1s virtually independent of the
blecarbonate concentration wlth the carbonate-blcarbonate

total concentration held constant.flég The coefficient is

decreased by an lncrease 1n temperature.Eég Uranium may
be stripped from the organlc phase by solutions of HC1,

HC1-NH,C1, HNOj, and HNO3-NH4NO3.4 8,480 Mitrate solutions

* An lsopropanol solution of dilmethyldiodecylammonlum chloride.

179
are more effective than chloride.~lS Sodium hydrozide (2M-
3M) may also be used as a stripping agent.flgg

Clifford, gz_ggyfléi report the extractlion of uranium
from aqueous carbonate solutions by (1) forming a singly
charged anion, Uogxé,with a complexing agent, and (2) ex-
tracting this anion into an organlc solvent with a singly
charged catlon. Extractlons were obtained with benzoln 2-
oxlne, cupferron, hydroxylamine, peroxide, pyrogallol, and
8-quinolinol (oxine). The latter was used for further study.
Arquad 2C, R%N(CH3)201, where R 1is about a 16-carbon chain,
was found to be the most effective extractant tested. Hexone
was found to be the most effective solvent tested. Kerosene
gave no extractlon. With oxine as complexlng agent, the
extracted specles was ildentified as RuNUoz(Ox)3. The ex-
tractlon coefflcient of uranlum was found to lncrease with
increased pH; to Increase with lncreased oxine concentration

and with increased R4N01 concentration (to an optimum value);

to decrease wlth 1ncreased carbonate concentration. An ex=~
tractlion coefflclent, Qs of 10.9 was obtalned by extracting
two volumes of an aqueous solution contalning 0.01K UOE(NO3)2,
0.92M Na2CO3, 0.04M NaOH, and 0.02M Arquad 2C with one volume
of hexone contalnling 0.lO0OM oxine. DBoth uranium and oxine were
removed from the organle phase by etrong acids. S8Sodium bl-
carbonate was found the most effliclent strlpplng agent on a
counter-current basls.

CARBOXYLIC ACIDS.

HHk-Bernstromlggl&gg has studled the extraction of
uranium (VI), thorium, and lanthanum by several earboxylic
aclds: sallcylie, methoxybenzoic, 3,5-dinltrobenzoic, and
¢lnnamie. Table XXXI 1lists the pH at which 50 percent of
the metal lons are extracted from perchlorate solutions by
0.1M solutions of the carboxylic acld In hexone. Chloro-

form was found to be a poor solvent for the extraction of

180
Table XXXI. pH for 50 Percent Extraction of U(VI), Th, la
by Carboxylic Ac1d.2

 

Acid pH50

U0§+  H Lot
salicylic 3.12 3.332 4,935
Methoxybenzoic 3.42 3.82
3,5=Dinitrobenzolic 2.752 2,852 4,385
Cilnnamic 3.60% 3.072 6.13%

2 After B. HBk-Bernstrom, references 138, 482.
Aqueous phase: metal concentratilon, 107°M Th or La, 10'3§ U;
ionic strength, 0.1M adjusted by the addltion of NaCl0,;
pH adjusted with NalH and HC10,,.
Organic phase: 0.1M carboxylic acld in hexone.
Vb/va’ 1; temperature, 25°C.

— Log a = 0, reference 138,

[

Calculated from data glven 1n reference 482.

the metals by The carboxylic aclds studled.

Cole and BJ:'o1.'«m£5‘3-i have atudled the extraction of U(VI),
Th, Hf and Zr from agueous nltrate solutlons by sallcyllc
acid in furfural. Satisfactory separatlons between uranium
and thorilum were obtalned, depending largely upon the two
metal concentrations.

Sudarikov, gg_éi.flgi have studled the extractlon of U
(VI), T™h, Ce, La, ¥, and Sc from aqueous solutions by sali-
cylic acld in 1socamyl alcohol. The uranium complex was Qb-
gerved to extract at pH 1.5 and to be completely extracted at
pH 2.5 to 5.0. Up to pH 6.5, «, was found to decrease from

100 to 0.3=0.4 and to remaln unchanged at higher pH values.

Mills and Whetselfigé have extracted uraniuml(VI) with

. perfluorobutyrlc acid dissolved in dlethyl ether.

181
CHELATING AGENTS. The chelating agents described below are
listed in the same general order as they may be found in the
book by Morrison and Freiser,ggg

0 0
Acetylacetone, CH3 - Q - CHé -C - CH3

The extraction of both uranium (VI) and (IV) from per-
chlorate solutions with acetylacetone as chelating agent has
been investigated by Rydberg. The percentage extracted 1s
glven as a function of equilibrium pH in figures 54A,-B, and
-C for the three solvents, chloroform, benzene, énd hexone,
respectively. The extraectlion of other aotinides, fisslon
products, and hafnium 1s also included in the figures.lflh&il'
£§§:£§§ Strontium and potassium are poorly extracted by

acetylacetone l1nto chloroformmfigl Lanthanum and samarium

are poorly extracted by the chelating agent into all three
solvents,fléz

K:-fl.:slhen&§2 has 1nvestigated the extraction of uranium
(VI) wlth acetylacetone used both as chelating agent and
solvent. The results are glven in figure 554 together wlth
the extractlion ourves of several other metals. The eifect
of masking agents, ethylenediaminetetraacetate, fluorilde,
and tartrate, on the extractlon of these metals 1s glven in

figures 55-B,-C and -D, respectively.figg

The extractlon of uranlum by acetylacetone-chloroform
1n the presence of sodium chlorlde and EDTA has been
studled by Tabushi.flgg Sodium chloride Increases the eXx-
traction yield and broadens the favorable pH range. EDTA
permits the separation of uranium from thorium and filssion
products by more effectlve masking of the latter. Uranium

has also been extracted with acetylacetane using butylacetate
as flolvent.-li-s-;--:L

182
 

100 |-

80 |-
HiQv) 4

100a
I+a

=
r

40 |

20

 

 

 

ot L1 1 1
-t O I 2 3 &4 B8 6 7 8 9 101 12 13 14
EQUILIBRIUM pH

 

Figure 54-A. The extractlon of various elemente from 0.1M NaClOy
solutlions by an equal volume of acetylacetone-chloroform solution
at 25°C. Acetylacetone concsntrations used: TU(VI), 0.0210M

[HAa] aq; U(IV), 0.50M [HAa]Y org; Pu(IV), 1.00M [HAa] init; Th(IV),
0.04B9M [HAa] init; Hf'gIV), 0.050M [HA8]O org. After J. Rydberg,
references 51, 485-488,

 

 

 

 

1 T T I 1 I | 1 1 1 1 1
100 |- -
80 I Pu{lv) -
U - -
3+
=T 680 | -
n
a A
40 | -
20 | -
0 1 ] 1 1 ] ] ] ] | 1

 

 

-l O 1 2 3 4 5 6 7T 8 9 10 I
EQUILIBRIUM pH

Figure 54-B. The extraction of various elements from 0.1M NaClOy
solutione by an equal volume of acetylacetone-benzene polution at
2500, Acetylacetone concentrations used: U(VI), 0.0210M [HAz]aq;
U(Iv), 0.072M [HAa]aqg; Pu(IV), 1.00M [HAa]init; Th(IV), 0.0673M
[HAa]éorg; F.P.,0.70M [HAa]QOorg. F.P. irradilation time = cooling
time = 1 year. After J. Rydberg, references 51, 487, 488, 492 and
J. Rydberg and B. Rydberg, reference 1l4b.

183
 

 

 

 

I I I [ L L 1 1 { 1 1 T I
100 |- -
X Pu(IV) -
80 F ' jé\u(vn ]
Oy
8': 60 - -
“ a0 | il
20 - : HT(Iv) -
o 1 1 L1 1 1 1 1 11 1
-l O1I 2 3 4 58 8 7 8 9 10 1l I2 13 14

EQUILIBRIUM pH

Figure 54-C. The extraction of various elements from 0.1M NaCl0y
solutions by an equal volume of acetylacetone-hexone polution at
250C. Acetylacetone concentrations used: U(VI), 0.0210M [ HAa]aq;
Pu(IV), 1.00M [HAalinit; HF, 0.050M [HAa]Qorg. After J. Rydberg,
references 51, 487, 488,

0 0
1 n
Benzoylacetone, 9 - C - CHé =C - CH3.
-493

Stary has determined the stabllity constants of
uranyl acetate, oxslate, tartrate, and EDTA complexes. The
effect of these lons was obaserved on the extraction of uranium
(VI) from 0.1M NaCl0, solutions by 0.1M benzoylacetone in
benzene.

. 0 0
o I o n
2-Acetoacetylpyr1dine,'(;, -C - CH2 -C - GH3.

The extraction of uranium from a O0.2N NaOH, 0.2N acetic
acid solution at pH 5.0 to 6.5 by 0.12% acetoacetylpyridine
in butylacetate 1s reported by Hara.figi

3 g
Dlbenzoylmethane, ? -C - CH2 -C -0,

Uranium (VI) (0.05 - 0.5 mg) is extracted from aqueous
solution by a 0.5% solution of dlbenzoylmethane in ethyl ace-
1:.a1:e.—22 In the presence of other cations, the extraction is
made more selective by the addition of complexoreIII (EDTA

sodlum salt). Excess complexoneis complexed by a 1% Ca(N03)2

184
 

  
 

 

 

 

 

1 1 I I I 1 1 1 I i I 1 1 1 1
100 | -
- o s ’ -
w 80 |- -
B y’ Pb
< I -
£ 6ol i
*
i - 4
40 - -
E; —Qriginally in
w L i aqueous layer 4
O i 8 . .
@ 20 I 7 == = Originally in -
L 17 acetylacetatie
o A _ l
0 ey V1 o1y o0y
4 5 6 T 8 9 10 Il 12 13 14

EQUILIBRIUM pH

Flgure 55-A, The extraction of varlous metals from agueous solutlon
by an equal volume of acetylacetone at 259C. Solid lines 1ndicate
the metal was origlnally contalned 1n the aqueous phase. The dashed
lines 1ndicate the metal was origlnally in the organlc phase. The
PH was adJusted to the deslred value b{ gulfuric acld or sodium hy-
droxlde. After A. Krishen, reference 489,

 

   
  

 

 

 

 

T 1T 17 T T 1T 17 T T T T T T
100 |- -
- -" -
”'—_
o g EDTA
5 ' Metal : EDTA = 1:30
¢
= 60 0 ~ == Metal : EDTA= 1:10 ]
! cesdoee : H
e ! H Metal: EDTA = 115
40 - ’ E ’I Pb —
z ! ! 7
w [~ s g s .
& 20 ! !
o , —
[ U g T eeanen IT
o ese csasfomoso 'ql 1 1 1 1
-l O I 2 3 4 5% 6 T B8 9 101 12 13 14

EQUILIBRIUM pH

Flgure 55-B. The effect of ethylenediaminetetraacetate (EDTA) on the
extractlon of varlous metals from agueous solutlon by an equal volume
of acetylacetone at 250C., The mole ratio of metal to EDTA 1s shown
by the line texture. After A. Krishen, reference 489,

185
 

 

 

 

 

 

-t 15 1715+~ 175r+°C 7517+ T7TTq7rrTrT
100 |- -
L Cu d
pey--x ¥ ¥ N X N ) &
w ol 27 Po _
- é
O 5 . J
< #
e .
- 60 § Fluoride -
% 0 '
w I : Motali F~ = 18 )
8 - am e tF- s
; 40 | 8 mtol. F= o |10 _
w 8
o r ¢ 4
5 8
4 2
0 } ] 1 ] ) ] 1 1 ] 1 L 1 1 ] 1 L
-1 O 1 2 3 4 5 6 7T B8 92 101U 12 13 14

EQUILIBRIUM pH

Figure 55-C. The effect of fluoride on the extraction of varlous
metals from agqueous solution by an equal volume of acetylacetone at
2500, The mole ratio of metal to fluoride 1s shown by the line
texture. After A. Krishen, reference 489,

 

     
 

 

 

 

 

 

T T T T 1 1 1 1 T T 1 T 1 T T
100 | Feo -
- o U
a [ -L-—---------c“ )
. 02 g = Hf
2 g0 ¢ Pb
o :f ¢ Tartrate
- ¢
x 60 [ T P T - 1:30
w g Metal: Tartrate :
— [ - e = Matal: Tarfrate =1:10
fi 40 | -
o [ g Zr 7
[+ 4
L w 20 -
a
o 1 1 1 1 1 1 1
-1 O 1 2 3 4 B 86 7T 8 © 101 12 13 14

EQUILIBRIUM pH

Figure 55-D. The effect of tartrate on the extractlon of varlous
metals from aqueous solutlon by an equal volume of acetylacetone at
250C, The mole ratlio of metal to tartrate is shown by the line
texture. After A. Krishen, reference 489.

186
gsolution. The resulting solution 1is neutralized wilith ammonia
to pH 7 and 1s then contacted several times wilith the extract-
ing solutilon.

The dibenzoylmethane extraction of uranium with chloroform,

benzene, and carbon tetrachloride has been investigated by

7
Moucka and Stary.igé

 

Thenoyltrifluoroacetone (TTA), ’[;]l— C~CH, -C - CF
n B

3.
0 0
Considerable effort has been expended in the study of
TTA a8 an extractant for uranium. King,&gl Orr,Egg Helslg

and Crandall,flgg-Walton, et .'sl.l.,ég9 and Petersonégl-have

made fundamental studies on the extraction of uranium (VI)
from aqueous perchloratefigz&&gg and niltrat 49 00 medla by

TTA dlssolved in benzen 4 498,500,501 hexone,igg cyelo-

he:mnone,&22 and pentaether.Egg The partitlon coefficilent,
“u(VI)’ is increased by lnereased TTA concentration 1n the
organlce phase; decreased by lncreased initial uranium con-
centrat:l_on.ég-g The effect of pH and varlous salting agents
on the extraction of uranium (VI) and thorium from nitrate
solutions by 0.2M TTA 1in benzene 1ls shown 1n filgure 56.29g
Salting agents 1lncrease the extractlon of uranlium by TTA-
benzene from low pH solutlons. There 18 no apparent effect
on the extraction of thorium with or wlthout IE_AI(NO3)3.

A 4fl NH4N03 concentration in the aqueous phase (not shown),

in fact, depresaes the extractlion of thorium.égg The effect

of forelgn anions on the extractlon of U(VI)II and U(I‘U")-5—§

from aqueous perchlorate solutions by O0.5M TTA in benzene

1s shown in filgures 57%&A and 57-B, respectlvely. Poskanzer

and li‘o:l:'emz.:.n-s-p-i have recently revliewed the extraction of

elements throughout the perlodlc table by TTA. The pHvalues for

50 percent extraction into an equal volume of 0.2M TTA 1n

benzene at room temperature or 25°C. listed hy these authors

187
 

 

 

{ I 1 T T

100

a 80
il
-
.
&

= 860
3
l

E 40
L
o
@
w

e 90

0

 

 

 

Flgure 56. The effect of pH and salting-out agents on the extraction
of uranium (VI) and thorium by TTA-benzene solutlons. After E. K.
Hyde and J. Tolmach, reference 502. Condltlons: An egqual volume of
0.2M TTA in benzene was stirred vigorously for 20 minutes wlth an
aqueous solution containing 0.003M thorium or trace amounts of
uranlum-233 with or wlthout the esalting-out agent indicated at the
pPH gliven.

are: for U(VI) from dilute nitric acid,2%2 PHz = 1.97;
for U(VI) from HC10, + LiClOu,&gg b =2, Py = 1.79; for
U(IV) from HC1O, + Na0104,;£5 k=2, pHgg = -0.58; for U(IV)

from HNOg,2%% pH_( = -0.31.

3

Irving and Edg:l.ngtonilél have observed a synerglstlc en-
hancement of the uranlum partition coeffilclent with tributyl-
phosphate (TBP) - or tributylphosphine oxide (TBPO) - TTA
mixtures. The results, a,, versus percent TBP or TBPO 1n the
extractant mixture, are given in figure 58.

The analysls. of metals with TTA has been reviewed by
‘Moore, 222 Sheperd and Meinke2%® have published, with references,

the extraction curves of a large number of elements with TTA.

188
 

   

 

- vy
c I 2 3 4 5 6 7T 8 9 1i0

NORMALITY COMPLEXING AGENT

Figure 57-A. The effect of forelgn anfons on the extractlon of
uranium (VI) from aqueous perchlorate solution by TTA-benzene. After
R, A. Day, Jr. and R. M. Powers, reference 77. Condltionas: Organic
phage - 0.50M TTA in benzene pre-treated by shaking with dllute per-
chloric acld overnight. Aquecus phase - ~10-5M U233, anion at con-
centration indlcated, 0.05M HC104, plus sufficient NaClOy to maintain
an lonic strength of 2,0. Equal phase volumes shaken together for 2
hours at 25°C,

 

 

IJ)'% N G-
£3 A, .
0 -
LN
]E \“ -—
a R a ¥ = . F
v S _a Figure 57-B. The effect of foreign anilons
Ha—SCN -| on the extraction of uranium (IV) from
8 aqueous perchlorate solutlion by TTA-benzene.
& After R. A. Day, Jr., R. N. Wilhite, F. D.
C.; X — Hamilton, reference 58. Conditlons: Organic
o J Phase - 0.05M TTA in benzene pre-treated with
3 - dilute acld. Aquecus phase - 0,0016M - 0.0037M
i soZ- J U(IV), anlon at concentration indicafed, 1.000W
fi & 'H+ (HC10) used for all experiments except chlo-—
7 ride in which HC1l was used), plus sufficient
<% NaClOjy to maintailn an lonlc strength of 2.0.
Equal phase volumes shaken together for 30 min-
b = utes.
'.d.
t__;_L___aL___J
0.0i

o l 2 3

NORMALITY
COMPLEXING AGENT

189
 

 

l03 I ——0 Rél I |

 

 

= ST TTA-TBPO 0 O~
- 7 N
L @

102 |- e
> f ;
u . -
- _ -
G
s 'OF 3
™ : :
m C -
= :

Q - -
O I .
<

o LOF 3
= - .
e | 1
o L -

0™ |- E

|0-2 l I 1 l | ] ] ] l |

 

 

 

 

O 10 20 30 40 50 60 70 80 90 100
% TBP OR TBPO

Figure 58. The synergistlic enhancement of the uranium (VI) parti-
tlon coefflclent between agqueous nltrate solutions and mixtures of
TTA and TBP or TBPO 1n cyclohexane, After H, Irving, D. N. Edging-
ton, reference 451. Conditions: Organic phase - 0.02M mixture flf
TTA and TBP or TBPO in cyclohexane. Aqueous phase - 1.025 x 10-%M
U233, 0.01N HNO3. ual phase volumes shaken together for 24 hours
at room tefibera%ureE?21° - 230C.)

190
Substituted l-phenyl-3-methyl-4-acyl-pyrazolones-5,

1
CH3-S-CH-C=O
N C=0
e/
&t

Skytte Jens.enlé9 has studled the posgibllity of using

gsubstltuted l-phenyl-3-methyl-4-acyl-pyrazolones-5 as extrac-
tants for a number of elements including uranium (VI), thorium,
and lanthanum. The pH for 50% extractlon of trace amounts of
these elements by a lfllaolution of chelating agent 1n chlorof

form ls given ln Table XXXII. The pH5O-for TTA is glven for

 

comparison.
5 4
" '\
8—Quinolinol (8-hydroxyquinoline, oxine)’ 7 o
18 A -
A

OH
H
Hok,égl and Dyrssen and Dahlberglfii have studied the ex-

traction of uranlum (VI) from aqueous perchlorate solutilons
by oxine dlssolved in chloroform or hexone. Results of the
latter group,lfii percent extracted versus flnal aqueous pH,
are shown 1n figure 59. These results are 1n agreement with
those of Hok2CL (0.,1M oxine - CHC1, 10'3& U, aqueous per-
chlorate solution, ¢ = 0.1M, 25°C.). No apprecisble differ-

4am110_3fl

ence was observed with uranium concentrations of 10~
(open and solild circles, respectively, in figure 53). Chloro-
form 1s shown to be a sllghtly better solvent for the uranyl-
oxlne complex than hexone. The extractlon curves for Th,§g§
La and Smggg are alsc shown In the figure. A tabulation of
pH for 50% extractlon of various metal oxinates by chloro-
form has been made by Dyrssen and Dahlbergifii and ls repro-
duced 1n Table XXXXTIIT.

The extraction of uranium (VI) by solutione of 1% oxine

in chloroform from huffered aqueous solutions 18 shown in

figure 60 as a functlon of agueous pH.élg

191
Table XXXII. pH for 50% Extraction of Tracer Amounts of Uranlum (VI),
Thorium, and Lanthanum by 1M Solutions of Substlituted (R) 1-Phenyl-3-

methyl-4-acyl-pyrazolones-5 in Chloroform.2

 

 

R pfiso.of Metal Ion

uos" 't 1e3*
acetyl -0.15 0.10 2.60
proplonyl 0.05 0.05 2.65
butyryl 0.52 0.42 2.47
valleryl 0.24 0.24 2.84
capronyl o.7 -0.25 3.15
ethoxycarbonyl 1.00 not meas. 2.50
chloroacetyl 0.65 0.05 2.28
trifluoracetyl 0.8 not meas. not meas.
benzoyl _ 1.0 0.4 2.45
p-bromobenzoyl 0.9 0.30 2.3

p~niltrobenzoyl - - -

TTA : 0.70 -0.30 3.75

2 vValues for pH50 were calculated from data presented by B. Skytte
Jensen, reference 160. |

Aqueous perchlorate medla.

192
 

 
 
 
     
  

 

 

 

 

 

100 |- -
F 3 & ;: fi
80 - U(VII-GHGI, ¢ \ ]
Eflu | iy @ g -

o|*+ U (V1) —hexong |} -Sm-CHGl3 U(VI)-GHCI
o A 3-
. 0T 8 . ,4
a - .
40 | —La—-CHCl3 -
q
A 1

20
§ |
o l . ol offe L 11 1L 11

-1 O I 2 3 4 5§ 6 7 8 9 10 il 12 13 14 15

EQUILIBRIUM pH
Filgure 59, The extraction of tracer amounts of uranium (VI), thorium,
samarium, and lanthanum from perchlorate solutlon by solutlions of
oxlne-chloroform or oxine-hexone. After D. Dyrssen and V. Dahlberg,
reference 1433 D. Dyrssen, references 508 and 509. Conditions: Aque-
ous phase - lonic strength = 0.1M with NaOH, HC104, and NaClQy; for
uranium, open clrcles represent U.OOOlfl U concentrations, solid
clreclea and trilangles, 0.001M U. Organlc phase - oxlne concentrations:
for U, 0.100M; for Th, 0.050M; for La and Sm, 0.5M; solvent indicated.
Equal phase volumes equllibrated at 25°9C.

Substltuted qulnolinols.

Rulfs, et 81923 and Dyrssen, et al.2:* have studled the
extraction of uranlum by dlhalogen derivatives of 3-quinol-
inol. The uranium extraction curves with 1% solutlons of
5,7=-dlchloro- and 5,7~dibromo-8-quinolinol in chloroform
are shown as functions of final aqueous pH in figure 60.2lg
Use of the halogen-subetltuted oxines permits extraction of
uranium from more acldic aqueous solutions. Similar ocurves
for uranium, fhorium, and lanthanum are given in figure 61 -
for extractlon wlth 0.05M 5,7-dichloro-oxine in chloroformréli

Hynekélé-has g8tudled the extractlon of varlous metals
by 8-~hydroxyquinaldine (2-methyl-8-quinolincl). The uranium
complex was found to be extracted, but notquantitatively,

193
. Table XXXIII. pH for 50% Extraction of Metal Oxlnates wlth Chloroform.2

 

 

 

 

Metal lon pH Procedure Reference
Ga3t 1.0 V ag =V org, 0.1M total oxine. 511
In3* 2.1 Anions in aqueocus solution: chloride,
a3t 3.4
Fe3+ 1.6 Four successlve extractlons with 512
cust 2.0 0.01M solution of oxine in CHClafl
In3+ 2.2 Anions in aqueous solutlon: sulfate,
B13+ 3.0 acetate, nitrate, chlorilde.
3+
Al 4,2
N12+ 6.1
cot 6.5
sn*t 0.0 V ag = 5V org, 0.0TM oxine. 513
Mo 1.0 Anions in aqueous solutlon:
Fe3t 2,0 acetate, chloride, tartrate.
Cu 2.1
Ni 3.7
Al 3.8
Mot 6.4
by u '
Hf 1.3 V ag = V org, 0.1M total oxine. 143
UO%+ 2.6 Anions in aqueous solution:
Th4+ 3.1 perchlorate.
sm+ 5.7
La3"' 6.5

 

2 pfter D. Dyrssen and V. Dahlberg, reference 143.

*

pH = =log[H'] + 0.1.

by chloroform from an aqueous phase at pH 9.5 contalning

tartrate and acetate ions. Cyanlde or H202 prevented ex-

 

traction.
N=0
1-Nitroso-2-naphthol, "Ny -0H .
NN

Alimarin and Zoloi-.cwé-:-l'-g have inveatligated the extractlon
of uranium (VI) by organiec solutions of l-nitroso-2-naphthol.
It was found that a mole ratio of naphthol to U308 of 125

194
 

10C

== @0 |

20 |-

20 -

 

 

 

 

o Loy L1 1
-t Ot 2 3 4 5 6 7 8 © 10 1 12 13

EQU!LIBRIUM pH

Filgure 60.
The extraction of uranium (VI) by oxine and its 5,7 -dichloro-
and 5,7-dibromo~-derivatives. The percent extracted, P, was
‘calculeted from the values of the distributlion coefflclent
glven in the paper by C. L. Rulfs, A. K. De, Jr., J. Lakritz,
and P. J. Elving, reference 510.
Conditlions:
2.1 mg of uranium 1n 10 ml and 25 ml of an spproximately
1M buffer solution were shaken 6 to 8 minutes with 20 ml
of 2 1% oxine-chloroform sclution. The aqueous phase was

rinsed twice with 5 ml of ahloroform. The pH of the flpal
"aqueous phase was measured.

195
 

100 -

_éi;;_ 0 |

40 r

20 -

 

 

 

 

 

EQUILIBRIUM pH

Figure 61.
The extraction of tracer amounts of U (VI), Th, and La
by 0.05M 5,7-dichloro-oxine dissolved in chloroform
from 0.1M HC10, - Na0104 solutions at 25°C.
After D. Dyrseen, M. Dyrssen, and E. Johansson, reference

514.

and a volume phase ratio of organlo to aqueous of 0.25 1is
more than adequate to glve quantitatlive extractlion of uranium
into lsoamyl aloohol at a pH of 5 to 6. Two minute shaking
is sufficlent for quantitative uranium extraction. Ethyl
acetate, n=butanol, dlethyl ether, amyl acetate, benzene, and
chloroform also extract the uranium-naphthdlite complex,
Quantitative extraction 1s obtalned with ethyl acetate and n-
butanol at a pH of 3.0 to 8.5; with isoamyl alcohol at pH

4,5 to 7.5. Quantitative extraction can be achileved at tem-

peratures of 0° to 100°C. Chloride or nitrate ions at con-

196
centrations up to 0.2M do not serlously lnterfere with the

extraction of uranium. Iron (III) 1s completely extracted;

vanadium (IV) and (V) and thorium are partlally extracted.

The extractlon of all four metal ions 1s conzlderably

suppressed by complexling with complexore ITI (sodium salt

of EDTA). The pH range for quantitative separation of u-

rmanium with isoamyl alcohol 15 Increased in the pfesence of

complexone ITI (~25 mg complexore per mg of metal) to 6.5 = 9.

Aluminum and zlnc are not extracted with l-nitroso-2-naphthol.
Dyrssen, gg_g;,éll-have studled the extractlion of uranium

and thorium from aqueous perchlorate solutions (k = 0.1M)

by 0.1M l-nitroso-2-naphthol in chloroform. Fifty percent

of the uranlum was extracted at pH 3.07 and fifty percent

of .the thorium at pH 1.66. ILanthanum and samarium were not

extracted. Other metals that have been extracted as nitroso-

naphtholates include Mn(II), Fe(II), Co, Ni, pu(II), Pa(II),

Ag, Cd, Hg(II), Pu(IV)2LL ang Np(v).218

Ammonium salt N-nitrosophenylhydroxylamine (cupferron),

70
N - 07, NHf.

Cupferron ls an lmportant reagent in the analytical
geparation of uranlum. The reagent preclpitates uranium
(IV) from acidic (H2804 or HC1l) solution but not uranium
(VI). By converting uranium to its two 6x1dat10n states, -
geparatlon can be made alternatlvely from elements not pre-
cipitated by cupferron and ffom thoée preclpitated by the
reagent., The uranium (IV) cupferrate complex, U(Cup)u,
was found by Auge::é-]-'2 to be gsoluble 1n chloroform and neufral
organlc solvents., Furman, gg_gg,gég found milligram amounts
of uranium {IV) to be incompletely extracted from agueous
acid solution by hydrogen cupferrate 1ln chloroform but to

be almost completely extrscted by ethereal hydrogen cup-

197
ferrate; 1.e., ocupferron extracted by ether from an acld
solution. Ethereal hydrogen cupferrate was also found to
extract quantltatively macroamounts of urahium {IV) from
(1 + 19) sulfuric acid containing hydroxylamlne hydrochloride
and submilligram amounts from (1 + 19) sulfuric acid in the |
presence of saturated mercury-zinc amalgamegig The partition -
coefflcient, qu(IV)’ 18 Inoressed wlth lnereased cupferrate
concentration and 18 decreased wlth lncreased acid concen-
tration.gég

A uranium (VI) cupferrate complex is precipiteted by
the reagent from neutral solutibns° There appear to be two
forms, one of which 1s soluble in ethyl ether;gfig From
(1 + 9) sulfuric aeild, milligram amounts of uranium (VI)
are extracted by an equal volume of chloroform with an ex=
cess of cupferrdn presentngfig

The extraction of urantium (VI) cupferrate from aqueous
perchlorate selution by hexone and chloroform is given in
figure 62 as a functlon of the pH of the final aqueous
solution.lfl; Chloroform 1s a poor solvent for the complex.
Hexone 13 better, but quantitative extraction ls not achieved
by a single contact of the solvent with an equal volume of
the aqueous seolutlon. The extraction curves for Th,égg Sm,
and Laégg are also glven 1in the filgure.

The propertles of other metal cupferrates have been
reviewed by Furman, Mason, and Pekolaogig

N-Benzoylphenylhydroxylamine, @- C=0
|

Dyrssenégg-has studled the extraction of uranium (v1)
~with N-benzoylphenylhydroxylamine in chlnfioform from aquecus
perchlorate solutions. The results, P ?ersus PH, are shown

in figure 63 together with those for thorium and lanthanum.

198
 

 

 

 

 

! i 1 I ! P ! I' ¥ g i L L
loo _Th-hefione .;:,_:;_'-.-_':._. T T T o] ) B S ) -
80 -
B
60 ; T
i 1
8
40 ¢ -
b
' -
[ :
20 -
0 ] 1 1

X .
-1 Ol 2 3 4 5 6 7 B8 9 10 Il 12 13
EQUILIBRIUM pH

Figure 62.
The extraction of tracer amounts of uranium (VI}, thorilum,
samarium, and lanthanum cupferrates from perchlorate solu=
tlone by hexone or chloroform.
After D. Dyrssen and V. Dazhlberg, reference 143; D. Dyrasen,
references 508 and 509,
Conditions:

Aqueous phagse - lonle strength = 0.1M with NaOH, HC10
and NaCl0y. Na cupferrate added to aqueous phase: for
0.01M, for Th, Sm, and La, 0.005M.

Equal volumes of aqueous and organlc solvent indlcated
equlllbrated at 25°C.

y

 

2 Z N\
1-(2-Pyridylazo)-2-naphthol (PAN), LI\:P' ~N=N O
HO :

1-(2-Pyridylazo)~2-naphthol forms colored complexes
(generally red) with a large number of polyvalent metal
1ons.égi The uranyl-PAN complex 13 ineocluble in alcohols,

carbon tetrachlorlde, chloroform, and ethers.égg Ortho-

199
 

 

 

 

 

 

vk i 1 f ! ! i i 1 i ' I
100 |- 7
- .
80 7
60 =
r ]
40 i -
20 - .
! ]
o i

41 01| 2 3 &4 8 6 7 8 © i0 I 12
EQUILIBRIUM pH

Figure 63.

The extraction of tracer amounts of uranium (VI), thorium,
and lanthanum from perchlorate solutions by N-benzoyl-
phenylhydroxylamine dlssolved in chloroform.

After D. Dyrssen, reference 520.

Conditions:

Agqueous phase - lonic strength = 0. 1M with HC1Ox, NaOH,
and NaClOy. The aqueous phase was sometimes buffered with
1 ml of 0.1M anilinium perchlorate, sodium acetate, or
hydrozinium perchlorate per 15 ml.

Organic phase - 0, 1M N-benzoylphenylhydroxylamlne in
chloroform.

Temperature, 25°C.

or meta=dlchlorobenzene and bromobenzene are excellent sol-

vents for the complex. The maximum color of the uranyl-PAN

complex 18 developed at pH 10. At pH less than 5 or greater

than 12 little complex formation occurs.égg UOranium may be

selectively separated from a large number of elements by

PAN-dichlorobenzene extraction in the presence of masking

200
agents (EDTA, trinitrllotriscetlc acld, cyanide) and with
proper pH control.

29
Sodium diethyldithiocarbomate (DDTC), (CoHg)N - C Nat.
\S"
Bode223 reports that the U(VI) - DDTC complex, unlike

 

other heavy metals, 18 soluble 1in water. A precipitate 18
formed only with high concentrations of uranium and reagent.
The uranyl-DDTC complex ls practlcally inextractable by
carbon tetrachloride but is readlly extracted by isoamyl
alcohol, dlethyl ether, and amyl at:e1;.sa.1:e.-5-gi Others have
~used hexone,ég&-ethyl ace't:ate,-igi chloroform,égé and ben-
zene'—‘z'-gl to extract the complex. Employlng the above sol-
vents, the U(VI)-~DDTC complex has been extracted from
aqueous solutlons having a wlde range of pH, e.g., pH 1-5221
and pH 6.5-8.3.225- Sodlum tartrate has been used to prevent
hydrolysis at higher pH values.222 The U(VI)-DDTC complex
13 extracted In the presence of EDTA. Uranlum may then be
geparated from elements such as thorlum,that form strong EDTA
complexes.figfllégz&égg Uranium may be further separated from
those elements extracted as DDTC complexes by strlpping the
former 1lnto an ammonium carbonate solution.lgélégé.
CH=N—CHéCH2-N=CH=-

N A~ 0H HO
Dyrssen222 reports that uranium (VI) 1s somewhat

Digalicylethylenedlimine,

 

extractable (60-90%) with solutions of disalicylethylenc-
dllmine 1in chloroform. Hafnlium and thorlum are extracted
(90-99%) from weakly acldic solutlons (pH 1.5) with a 0.1-
0.5M chloroform solutlon of the reagent. Lanthanum and

samarlum are hot extracted.

Antipyrine, CH====T - CH3
I
O0=—C N -~ CH
~N 3
|
06H5

201
Roddenlgl has mentloned that chloroform extracts uranyl .
complexes with antipyrine. Reaa322 has reported that both
uranium {VI) and uranium (IV) are almost completely extracted
with antipyrlne-chloroform sdlutions from perchlorate medla.
Uranium may be separated from thorlum using the antlpyrine-
chloroform system. From an aqueous golution of 20.6 ml
containing 5 mmoles of Th(NOB),“ 1 mmole of U02(1503)2 and
48,6 mmoles of HCl, 93-94% of the uranium and only 5% of
the thorium was found to extract with 36 mmoles of antipy-
rine 1n chloroform. The uranyl-antipyrine complex is

soluble in niltrobenzene, but not very soluble 1n hexone.

P
7\
Tropolone, 'Q§
s *0
OH

The extraction of U(VI) and Th from 0.1M perchlorate
solutions by 0.05M tropolone 1n chloroform i1s given as a
function of pH in figure 64.23% The pH of 50% extraction
for U(VI), Th, and Y under the above condltions 18 approxi-
mately 0.9, 1.1, and 4.0, respectively. Iess than 50%
lanthanum 1s extracted at pH 6.5¢232

DyrssenEal reports the extraction of a uranium (VI)-

beta-lsopropyl tropolone complex with chloroform and hexone.

Ton Exchange. A number of articlea are avallable 1n
which the behavior of uranium toward lon exchange resins
s reviewed and in which reference to much of the litera-
ture 1s glven. Hyde,éég Katz and .':'.eaa.bor'g,g-(:!hcu::pin,é;’:g
Palei,lgz and Ruznetsov, gg_gg,ggg- have reviewed the lon
exchange of a number of the actlinlde elements lIncluding
uranlum. Steele and Tavernerlgg have outlined several
anlon exchange separatlons of uranium. Clegg and Foleyééé
have descrlbed the use of 1lon exchange resins in the pro=

cessling of uranium ores.

202
 

100

80

— 80

 

 

 

 

40 ~
“ w
20 ~
}- -
0o . 1 1 - 1111 ] L 1 1
-1 O I 2 3 4 5 6 7T 8 9 101 12 13 14
PH
Filgure 64.

The extraction of trace amounts of uranium (VI) and thorium
from 0.1M perchlorate solution by 0.05M tropolone in chloro-
form at 25°C.

After D. Dyrasen, reference 530.

In the followlng paragraphs, the dlstrlbution of
uranium (and of other elements) between an ion exchange
resln and a particular solutlon ls described in terms of
the distribution coefficlents, D and Dv' These are defilned

as
D = amount Mff[gram dry resin
amount M™/m? solution
and
p = amount M"*/ml resin bed

vV  amount M™/ml solution
The two coefflclents are related by the density of the
resln bed, Dv = pD. The coefflclent D 1s referred to as
KD_by many authora.

203
EEEEE~§EEE§E§E° Anion exchsnge resins commonly used
1n the radlochemical laboratory are the strong base resins
such as Dowex-1l and-2 and Amberlite JRA-410 and IRA-~400.
The capaclty of these resins 1a approximately 2.5 mllli-
equlvalents per gram of resin. Wealk base reslns are also

avallable. However, thelr use is more limlted. These

regins have capacltles ranging from about 6 to 10 milli-
equlvalents per gram of resin.

sSplvey, 95_3;,233 have lnvestlgated varlous factors
such as resin capaclty, resin phase volume anion adsorptilon,
etc, shat affect the sorption of uranium. Trivisonno232
has made a literature survey of factors that influence the
adsorption and elution of uranium by and from strong base
anion exchange reslns. These are similar to the factors
influencing solvent extraction and include, other than
those already mentloned, uranlum concentration, anlon con=-
centration, pH, the presence of other metallic lons and
forelgn anlons, temperature, resln size, poroslty, cross-
linkage, etc.

The varlous systems from which uranium may be adsorbed
by anlon exchange resine are descrlibed below. The resln
may be converted to a particular anionic form by washing
wlth an approprlate solution.

Chloride systems.

Kraus and Nelsonfiz’-é have measured the distribution
coefficlents for a number of elements between a strong base
anion exchange resin (Dowex~1l, 10% DVB, ~200 mesh) and
hydrochlorlc acld sclutlionsa of varylng molarlty. Thelr
repults are shown in figure 65. The results of Marcus,§§1
obtained under conditions simllar to those used by Kraus
and Nelson,é-aé are glven in figure 66, The concentrations
of the various elements used in the study by Marcus were

puch that the oxldatlon states could be determined spectro-

204
Go¢

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

    

 

 

 

 

 

 

 

 

 

 

 

 

 

 

_L e B“I T T 1 T T T o 1 |F ¥
| | 1] e T
N0 ADS.||NO ADB] w | ELEMENT i q i
gq. AND —] 1L ] It 1L
L ; | OXIDATION | NO ADS.~NO ADSORPTION O.i<M HCI <2 B e =
—_— @ BTATE = R TTEL T T
(Na " | {[Mg" [ ] e BL. ADG.- BLIGHT ADSORPTION IN I2M HCI I 4k 1S  Cl
| | 2 (0.3<Dx 1) —1I
NO ADB.NO ADS.. § i ny STR. ADS. - STRONG ADBORPTION D,»| NO ADS] 1 r T
[ O 4 & e [ 10 10 [
Aot MOLARITY Hel' el 1
"|[Ca |. c | JLTil ] ‘lfl_figll n | |Fe | |l "1Ss ' [ liBr
P T m | Hm
| NG A vo ADB.]| H JlsL. apsjiSL. aD3. 1L 7 | 1L
71I8L. ADS. | ml -
A - el v _?kn__‘_
5 4} - IZAH JIBTR. ADS{| - 3 L =, \Br
1 1 il 1 1 L I[ L el 1y A 1
1 1_3‘ T T T
_+m__
[STR. ADS] )
| IE
L A
OII 1 A+ T
|
1[sTR.ADS|[
1 L A -l

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Flgure 65, Adsorption of elements from hydrochloric acld solution wilth anlon exchange
resin (quaternary amine polystyrene divinyl benzene resin,—~200 mesh, 10% DVB) After
K. A. Kraus and F. Nelson, reference 536.
 

1C0

Dv.
I i lllllI
2
o
<
Sy
L Illllll

!
L
]

o
B

   
   

e
Z

s

5

& - U(Vl) ,-' ]
Q C a
O B l';.-':." N
Z - 7 7
s | No(y) f} -
=

-— ! .0 o - / B -
o= - _;:* :
L C M~ -
® L & -

B

e

0.1 1 | 1 i l ] }
0 ! 2 3 4 5 6 7 @

HC! CONCENTRATION, ™M

 

 

 

Figure 66.
Adsorption of elemente from hydrochloric acid solution with
Dowex=-1 anlon exchange resin (10% DVB).
After Y. Marcus, reference 537.

206
photometrically. No adsorption of Np(V), Pu(III), or Am(III)
was found. The data presented by W1sh§§§ for the adsorption
of various elemenrts by Dowex-2 ( x8,200-400 mesh) 1s repre-
sented in figure 67. Ward and Welch222 have studled the
distribution of neptunium In varlous oxidation etates be-
tween Amberlite IRA-U00 and hydrochloric acid solutions of
varying concentration. Thelr results show that Np(VI) 1s
atrongly adsorbed at >6§ HCl, Np(V) 1s exponentially
adsorbed from 3M to 6M HC1l (D increases from 1 to 10), and
Np(IV) is simllarly adsorbed from about 6M to 10M HC1 (D
increases from about 2 to 400). Prevot, gg_g;,éflg have
investigated the adsorption of U, Pu, Th;,; Pe, Ce,and Zr
" by anlon exchange resin A300D from hydrochlorilc acld solu-
tions ranging in molarity from & to 7. Quantitlies of 7 mg
Pu, 6.9 mg U and 5.9 mg Fe per ml of solutlon and 2 grams
of resln were used 1ln the determination of D. Thelir results
are conslderably different than those shown in flgures 65-67.
The dilstribution coefficlents of U(VI), and Fe{III) are lower
roughly by an order of magnitude. The dlstrlibution coefflcient
of Pu(IV) 1s almost an order of magnitude higher. For Pu(III),
D 1s about 0.1 at 4M HC1l and about 1 at 7TM HCl. Zirconium
adsorptlon 1s simllar to that shown In the figures. Thopium
and cerlum are poorly or not at all adsorbed.

Korkisch, et al.2+222*2 ngve found the distribution
coefficlent of uranium between Dowex-1l and hydrochlorilc acld
sBolutions to lncrease wlth lncreased alcohol concentration

. *»
of the solution. With 80% ethanol, D 18 i1ncreased from about

40 to 6000 as the HC1l concentration is increased from 0.2M
to E.EEyQEl The dilstribution coefficient at 2.4M HC1l without
aleochol is about 40. Alecohol also lnoreases the adsorption

of thorlum, titanlum, and zirconium. The distribution co-
* 95% alcohol denatured with benzene 18 consldered 100% alcohol.

207
 

 
 
     
 

103

D

g

 

 

 

 

 

Ty
<
L
9 |02 S — Mo (1) _
[T s 3
m fl ;
0 -
S \ o]
Lt /
= ' / i
o . ,’ Zr(IE)
= l = ’
IS 10 = i ’( -
@ - 2 ]
-— - z ~
o - 2 4
5 f / :
o o |
1.0 -é
|0-| I 1 I -} I ]
8 10 12 14
HC! CONCENTRATION, M

Figure 67.
Adsorption of elements from hydrochlorlec acid solutlon with
Dowex-2 anlon exchange resin (x8, 200-400 mesh).
After L. Wish, reference 538.

208
efficlents of these elements vary roughly between 1 and 10
from 80% alcohol solutions contalning HC1l in the range of
0.2M to 2.4M.2%2

Numerous peparations of uranlum from other elements
are poselble using hydrochloric acld systems. The more ob-
vious ones are those 1in which uranium 1s adsorbed and the
other element is not. Conslderatlon of figure 65, indicates
that uranium can be separated from alkali metals, alkallne
earths, aluminum, yttrium, rare earths, actinium, and thorium
by adsorption as uranium (VI) on a strong base anlon ex-
change resin from a concentrated hydrochloric acid solution.
Trilvalent actinide elements are not adsorbed from hydro-
chloric acld sclutions. Plutonlum 18 eluted as Pu (III) with
12M HC1l eontalining hydroxylamine hydrochlorlde and NH4I,
NHuI alone, or HI. Separatlons may be made by adsorption of
the contamlnating element and elution of uranlium with dilute
hydrochloric acld. For exsample, molybdenum 18 adsorbed ffom
0..1;Il;!I_HCl.,§Ei Bismuth is also adsorbed from dilute (<1M)
HCl.éE&Lé&é Other elemente that show strong adsorption from
dilute HC1l include many of the transition metals, tin,
tellurlium, and polonium.éié Kraus and Mooreiité have effected
the separation of protastinlum and uranium by adsorblng them
from 8M HC1 on a column of Dowex A-1 reein and developing
_the column with 3.8M HCl. Protactinium appeared first in
the eluent, separated from uranium. The uranlum fractlon
contalned; however, a falr amount of protactinium 'tailing'}

Advantage may be taken of the different distribution
coefficients exhiblted by lons 1ln varlous oxidatlon states
to effect thelr separatlon from uranlum. Iron reduced to
ferrous lon by hydrogen 1odide§£1 or ascorblc a.c:Lc:lEl—-|~§ 1s
separated by elution with 4M HCl. U(IV) may be separated
from Pa(IV) and Th(IV). U(IV) 18 adsorbed by Amberlite
IRA-401 (100 mesh) and Dowex-1 (100-200 mesh) from >8M HCI.

209
Nelther Pa(IV) nor Th(IV) 1s adsorbed from 6M - 12.6M ne1.249
The elutlon of Pu(III) by 12M HC1l from strong base anion
exchange resln has already been mentloned. Wish and Rowelléég
have effected the separation of Th, Pu, Zr, and Np from U
by elutlon with hydrochloric acld in a sequence of concen-
trations. The elements are adsorbed on the resin (Dowex-2)
from 12M HCl.  Thorium does not adsorb. Plutonlum 1s eluted
in the trivalent atate wlth 12M HCl saturated with hydroxyl-
amine hydrochlorlde and ammonium lodide. Zirconium is eluted
with 7.5M HC1; neptunium (IV) with a 6M HCl - 5% NH,OH - HC1
solution. Uranium 1s flnally eluted with O0.1N HC1.

Korkisch, gg_g;,fiél have separated uranium from tung-
sten by means of anlon exchange. The uranium is adsorbed
on Dowex <1 resin from a solution containing 20% 4M HCI and
80% ethanol (volume %#). Ascorbic acid is used to reduce
any 1iron present. The resin 1s washed with a similar solu-
tion and uranium 1s elufed wilth an ether-saturated 0.1M HCl

solution. No tungsten 1s observed in the final eluate.

Fluoride systems.
'F'a.::':T.sé-lig has reported the adsorptlion of elements from

hydrofluoric acld solutions wlth Dowex-1 anlon exchange
resin (x10, 200 mesh). His resulte are shown in figure

68. Uranlum (VI) adsorption 1s strong from dilute HF
solutions and decreases with lnoreased acld concentratlon.
Separation from elements exhiblting no or strong adsorptlon
from HF solutions may be achleved by.proper salectlon of the
aold concentration. Elements such as Be, B, Se¢, Ti, Zr, Mo,
8Sn, Te, Hf, Ta, W, Re, and Hg have adsorptién curves slmllar
in shape to that of uranium (VI). Separation from these
elements using an HF system should prove difflicult to almost
Impossible, dependling upon the distribution coefficlents 1n-

volved.

210
NO ADS. — NO ADSORPTION FROM IM-2&8M HF
SL ADS. - SLIGHT AD3SORPTION
9TR. ADS.—~ STRONG ADBORPTION: LOG DIST. COEFF. >2

 

LOG DISTR. COEFF.
o u

O

 

10
MOLARITE"\)" HF ROMAN NUMERALS REFER TO OXIDIZATION STATE
] IN INITIAL SOLUTION.

  

NGO ADS.[INO

112

 

Flgure 68. Adsorption of elements from hydrofluoric acid solutlon with Dowex-1 anilon
exchange resin (x10, 200 mesh). After J. P. Farls, reference 552,
Bhat and Gokh.s,leénr'23 have found evlidence for the ad-

sorption of the anionic apecles U02F3 with Amberllte IRA-300.
. HC1-HF szs;ems.

Certaln elements are effilclently separated from uranlium
by anlon exchange when a comblned HCl-HF eluting system 1s
used. Such systems have been studied by a number of work-
ers.éég-&éél—*:222 The results of Nelson, Rush, and Krausgég-
are shown 1n figure 69. Faris and Brody522 have examined
the distribution coeffleclent D of uranlum as a function of
HC1 concentration in the presence of O, 1, and 8M HF and as.
a functlon of HF concentration in the presence of O and 0.2M
HCl. The former three curves are plmlilar 1n shape but decrease
in megnltude as the HF concentration 1s increased. The pre-
sence of 0.2M HC1l also ocauses a decrease 1n magnitude of
the D ve.[HF] curve. However, the shapes of the O and 0.2M
HC1l ourves for varylng HF concentration are dlssimllar for
HF concentrations less than 4M. ~

Table XXXIV lists a number of separations of U from
other elements uslng HCl-HF elutiné golutions.

Nitrate systems.

The distribution of uranium between anlon exchange resins
and nitric acld solutlons has been reported by a number of
workers.-53élfiflg&fi&fi&fiég&éfi!&éfig:éég The results of Buchanan
and Fa:r-:i.fi';égg are glven in figure 70. From the non=- or only
slight adsorption of most of the elements from nitric acid
media, 1t appears that anlon exchange affords an excellent
means for purlfying uranium. Uranium 1s adsorbed more strongly
from nitrate salt solutions than from nitric aecld solutilona
alone.égé&éfizlfigg&éé; Wlth DeAcldlte FF resln, the adsorption
of uranium (VI) 1s greatest from Al(N03)3 solutions and de-
creases 1ln the order Ga(Nq92.> LiNO3 > NH4N03.§§§ Et?anol
Increases the dlstribution of uranium to the resin ph;se.éii
With an 80% alcoholle solution, the dilstribution coefficient

212
Table XXXIV. Separation of Uranlum from Various Elements by Anion

Exchange Using HC1l-HF Eluting Solutions.2&

 

& Dowex-l or -2 anion exchange resin used.

213

Elemental mixture Element eluted Eluting solution Reference
W, U W TM HC1-1M HF 555
U 0.1M HC1
U, W, Mo U 0.5M HC1 555
W 7TM HC1-1M HF
Mo 1M HC1
W, Nb, Ti, V, Zr, U, Ta W, T1, V, Zr TM HC1-4M HF 559
Nb TM HC1-0.2M HF
U 1M HC1-4M HF
Ta 24M HF or 4M NH)Cl-
1M NH,F
Fe(III), U Fe(IIT) 1M HF-0.01M HC1 555
U 1M HC1
R.E. as Eu(III),u(Iv), R.E. 8M HC1 556
u(vI), Zn(I1I) u(Iv) 8M HC1-0.1M HF
u(vI) 0.5M HC1
Zn(II) 0.01M HC1
Te(IV), U(VI) U(VvI) 3M HC1-1M(to 8M)HF 559
Te(IV) 1M HC1
Th(IV), Pa(V), U(VI) Th(IV) 10M HC1 556
Pa(V) OM HCl-1M HF
u(vI) 0.1M HC1
Pa, U 9M HC1 551
Pa TM HC1-0.11M HF
U 0.5M HC1
‘Zr, Np, Nb, U, Mo, Tec Zr 12M HG1-0.06M HF 538
' Np 6.5M HC1-0.004M HF
'Nb 6.0M HC1-0.06M HF
alr dry column and alcohol wash
U 0.1M HC1-0.06M HF
Mo, Te 12M HNO4
¥ie

 

Ba ]~ "

 

 

 

 

Dy<1 in HCL

S

[ IE

L Dyl _

[ In HGI—]
ad

| a
HEI- I M HF ]

 

 

 

 

 

  
   

 

 

 

 

Dy=<! In HCI
and
HGI- M HF

      

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

LEGEND:
2 T e ]
.6 T
u ! [
W ELEMENT j e (T T
Q 4/— AND [ Dy<ila HEI ]
c | oxipaTion - o per g LI:
th 2F— STATE —
5 |

0 q a 12

MOLARITY HCI

Figure 69. Adsorption of elements from HCl and HC1-HF solutions with ‘ahlon exchange
resln. _____ Distribution coefflcients 1n absence of HF. mwmmwr~w Distribution
coefficients in HC1-HF mixturee (usually 1M HF except Zr(IV), Hf(IV), Nb(V), Ta(V),
ang Pa(V) where M HF = 0.5). After F. Nelson, R. M. Rush, and K. A. Kraus, reference
558. _
Sie

  

Flgur
(x10, 200-400 mesh). After R. F. Buchanan and J. P. Faris, reference 562,

 

NO ADS. - NO ADSORPTION FROM [-14HM HN@y
SL. ADS.- BLIGHT ADSORPTION

 
    

   

LOG DISTR. COEFF.

Q —
o
p

2
1@

    

   

=
o
=

A

   

HNOy

 

 

I
. |INO ADS. ||NO

 

 

 

 

 

 

 

 

 
 

 

 

 

   

 

 

 

 

 

 

 

 

 

  

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

™| ||[Pa] F"E
7 Rl 7‘m
(&AIAR
IIl L L
e 70. The adsorption of elements from nitric acid solutlons wlth Dowex-1 anlon exchange resln
Table

XXXV. Separatlon of Uranium from Various Elements by

 

Anion Exchange Using Nitriec Acid Solutions.
Elemental Resln Element Eluting Solution  Reference
Mixture Eluted
Eu(III), U(VI) Dowex=l Eu(III) 8M HNO4 557
- : u({vr) 0.2M HNO,
U, Ru Dowex-2 U LE.HNO3 543
Zr, U, Th Dowex~2 Zr Column developed 543
U with 8M HN03. Zr
Th elutes first, followed
by U and then Th.
U, Th DeAcildite FF 6M HNO4 560
(77°C) U 4M HNO
Th Héo
U, Th Dowex-1 U 90% methanol-1M HNO3 564
Th 1M HNO3
U, Np Dowex~1 or U 6M HNO?-ferrous sulfamate - 565
Dowex-21K hydre.zine or semlcarbazide
Np 0-35EIHN03
Th, R.E., Dowex-2 Th, R.E., conc.HCl-trace HNO3 550
trana-Pu, trana-Pu
Pu, U, Zr, Np Pu conc.HC1l sat'd wlth
NH,,OH.HC1 and NH, I
- conc.HCl(BO%)-conc,HNOB(EO%)
U, 2r 12M HNOg
- conc. HC1
Np 4M HC1l with 5% NH20H-H01

for uranlum is about 12 between Dowex-l resin and 1.2M HNO3
solutlon; for a 40# alcohollic solution, D is about 7.

Table XXXV 1ists a number of separations of U from other
elements uslng nitrate media. The last procedure listed in
the table may be revised to include Pa separation. Following
the elution of U with 125_HN03, in which a small amount of

Pa 18 eluted; the remalnlng Pa is eluted«q&t? 12§_HN03-0.1fl
HF.220

216
Sulfate systems.

The recovery of uranium from sulfate liguors by anilon
exchange methods 1ls important lndustrlally. Laboratory-wise,
a number of procedurses have been:developed for the determlnatlon
of uranlum that make use of the adsorbablllty of the anioniec
uranyl sulfate complexes. The nature of these complexes has also
recelved considerable studygg&ééé&ééz-(see section on complex ions)-
The distribution of uranlum between anlon exchange reslns and
sulfate mediaz has been reported by a number of 1nvest1gatora.§§§&
5231529L25112§l129§-The results of Bunney, gg_gi,éii are given
In flgure 7l. Strontlum, yttrium, cerlum, and americlum do not
show any slgniflcant adsorption by the resin (Dowex-2) at any
acld concentration.éfii The distribution coeffilcient of Pu(IV)
is approximately twlce that of U(VI) in the acid range of O
to 10N st()ll_.-5-29 The adsorption of uranium (and thorium) from
solutions of (NH4)2504 1s simllar to that from H,S0),. The
decrease in adsorption is lese rapld, however, with lncreased
ammonium sulfate concentratlon than wlth sulfurle acid.éfié&éfil’
568 The adsorptlon of uranium from sulfate solutlon exhibits
a pH dependence (D 1lncreases a8 the pH 1s lncreased from 1 to
L} which decreases as the sulfate concentration is decreased.égi
The distribution coefficlent of uranium between Dowex-1 resin
and O to 1.2N sulfurlc acid solutions 1s one to three orders of
magnlitude greater from 80% ethanol solutions than from aqueous
aaolutil.onaa'..é-lkl

A number of procedures have been developed for the separa-
tlon of uranlum from various elements by anlon exchange in
saulfate solution. These generally lnvolve the adsorptlon of
the uranyl complex from a sulfate solutlion at pH 1 to 2 from
which the foreign element is not adsorbed. After thoroughly
wagshing the resin bed to remove 1lmpurities, urahium is eluted
wilth a dilute solutlon of hydrochlorle, nltrlec, or perchloric

acid. Mixtures of elements that have been or may be separsated

217
     

 

. v lll1ll'| 1 Illlllll 1 I T rIrl

Il .ee..OM O m

°”
L L i i1l

IIIILLLI i

1

  
 

 

 

 

t00 i ?_
D ;
h e -
10 & =
1.0 — —
_ )y & Z
\ a
., * @
O.I i LA {11 III \'l'u.l_.l.fl{u;\ | L A Lilll
0.1 1.0 10 100
N HpSO0,4
Flgure 71.

The adsorption of elements from sulfuric acld soclutions with
Dowex-2 anlon exchange resin (x8, 200-400 mesh).

After L. R. Bunney, N. E. Ballou, J. Pascual, S. Fotl, feference
543, |

218
from firanium by procedures similar to the one descrilbed 1lnclude
am, Th;2%3 re, a1, Mg;2%2 pe, v;212 2n, N1, Co, G4, Mn, Cu, Fe,
alkall metals;2LL Zr, Ce, Cs, Ag, Cd, V;2L2 p1;203 §.g. ;243,571,574
and metals contalned 1n ores.élifiézg-The literature references

should be congulted for exact experimental condltions.

Carbonate systems.

 

Uranium 18 recovered from carbonate leach llquors by anlon
exchange 1in lndustrial operations. Its anlon exchange behavior
1s simllar 1n carbonate solutlon to that in sulfate solutlon.
That 1s, the distribution coefflclent ls decreased with lncreased
carbonate concentration. Thls is i1llustrated 1n flgure 72 for
ammonlum carbonate Bolutions.ézi A Blmllar decrease in D i1s
observed for 1increased sodium carbonate concentration.éég The
distribution coefficlent 1s also decreased by a decrease 1n pH
of the solutlon. The lncrease ln blcarbonate concentration at
the lower pH lnterferes with uranium adsorptlon. Other anlons
such as sulfate, nitrate, and chlorilde may also lnterfere with
uranium adsorption from carbonate solutlon. To prevent gessing
with carbon dloxide, uranium 1s eluted with salt solutiomsrather
than aclds. 1

Vanadiumézg and phosphate and molybdateézg have been separated
from uranium in carbonate solutiona by anion exchange. The im-
purities are adsorbed on the resin together with uranium and
eluted with a 10% Na,CO4 solution. Uranium is eluted with a 5%
NaCl solution.

Phosphate systems.

The distribution of uranium and other elements between Dowex-
2 anion exchange resin and phosphoric acid solutlons 1s represented
1n figure 73.512 Marcusgl-has 8tudled the Dowex l-uranyl phosphate
system. His distribution coefflcients are lower by factors of 2

to 50 at 0.1M H3P04 and 3M H3P04, respectively,ézg than those shown
in figure 73.

219
 

Log D

 

 

 

o | | L | |
O 02 04 06 08 10 12

CONCENTRATION OF AMMONIUM
CARBONATE (M)

 

Flgure 72. The adsorption of elements from ammonium carbonate solu-
tions with Dowex-1 anion exchange resin (x8, 50-100 mesh). After

S. Migpuml, T. Taketatsu reference 575. Condltlons: Amounts taken,
Begj:, 11,7 mg (Be0); Cel+, 7.3 mg (Cedn); ThH, 26.9 mg (Thop); and

61.0 mg (U308 1 gram of resin and 200 ml of solution 1n con-
taB% 12-20 pouna ot 200¢

220
 

¢ l_l'llll'lll 1 1 Illllll L] rF Trrrry

     
   
    
    
     
 
   

Illlllll 1 ||||Il.|.l 1 |||||||_|

lJ_LIIIII'

O\ g \\
2 7 0 b
10 aTTA \ |

v NHeOH-HCI Mg \ %) Y
No(l¥) 4 ¢ so:o \ AW

A H3PO04

D (ml/g of oven-dried re'ain)

i

 

Figure 73.
The adsorption of elements from phosphoric acid solutions with

Dowex=-2 anion exchange resin (x8, 200 mesh).
After E. C. Frelling, J. Pascusl, and A. A. Delucchi, reference 579.

221
Separatlons between uranlum and the rare earths (Ce3+,
ce™), alkaline earths (Sro*), alkall metals (Cs*), and tellurium

are posslble uslng Dowex 2-H3P04 syétems. The 1atter.separation
has been used by Wiahégg who loaded a column of Dowex-2 resin
from a 0.1§.H3P04 solution. Tellurium passed through and
uranium was adsorbed. The column was then converted to the
chloride form W1fh cqnéentrated hydrochloric acld and uranium
was eluted with O.1M HCl - 0.06M HF. An alternative method
involved loading the column from cbncentrated HCl. Tellurium
was eluted with 1.ON H;PO, after washing the column with an
alcoholic phosphoric solutlon. The coluhn was then washed wlth
an alcoholic HCl gas solution. Uranium was eluted with a 0.1M
HCl - 0.06M HF solution and.molybdenum with 12M HNO,.
Miscellaneous systems.

Uranyl ion forms an anhlonic complex with acetate 1lons at
pH %4.25 to 5.25. The complex has been adsorbed on Amberlite
IRA-400 strong base resin 1in the determination of small amounts
of uranium 1n atones and natural waterspégliégg—-

Uranium 1s also adsorbed on Amberlite IRA-400 resin as an
ascorbate complex.ég;lég& Thorium, tltanium, zlrconlum, tungsten,
and molybdenum are also adsorbed.

Uranium complexed with sulfosallcylic acld has been
separated from Z2n, Cu, Ni, and Cd.ééé- The latter are complexed
with EDTA. The pH of the solution is kept between 8 and 10.
Separation has been made on Amberlite IRA-401 and Dowex-l resins.

The uranyl cyanate complex formed by adding potassium |
ceyanate aolqtion to a uranyl salt 1s adsorbed by Dowex=1 anién
exchange rewa;:l.n.-駧 Uranium 1is eluted by a dllute hydrochloric

acld solution.

Catlon exchange. Although a number of separations of
uranium from various elements have been reported in the litera-
ture, the amount of quantitative data reported 1s rather meager.

Hardyégz has sumarized much of the data avallable on the dis-

222
tribution of uranlum between cation exchange resins and nitric
and hydrochloric acld solutlong. HIs curves are reproduced in
figure T4. Distripution coefficient curves for other actinide
elements: Th, Pa, Np, Pu, are glven for comparison. Prevot,
Eg_glféig have published the distributilon curve for uranium
between catlion exchange resin C.50 and nitric acid solution.
Its shape and magnitude are simllar to that shown for the Zeokarb-
225-HN03 gystem in figure T4. Ishimori and Okunoiég have found
that 1ncreasing amounts of methancl in niltrie acid solution
(0.18M) increase the distributlon coefficient of uranium for
Dowex=50 regin.

The elutlon peak positions of a number of lons including
uranium {(IV) and (VI) are given in figure 75 for varlous hydro-
chloric acid concentrationge. The conditlons under which the
peak posltlons were determined are described in the figure
captlion. Ionescu, et al.§§§ have studled the effect of acetone
on the dlstrilbution of eeveral elemente between catlon exchange
reslns, KU-2 and R-21, and dllute hydrochloric acid solutions.
For fized hydrochloric acld concentrations of 1, 2, and 3%,
maximum uranyl distribution coefficients were found between
60 and BOZ acetone solutions. For 4 and 5% acid solutions, D
was found to be conslderably lower than for the more dilute
acld solutilons.

Ishlmorl and Okun'ofi§§ have investlgated a number of catlon
exchange systems other than those already noted. Some of thelr
results, D versus sodlum sulfate, sodium scetate, and oxallc .
acld concentration, are 1llustrated in filgure 76. The adsorp-
tlon of uranium by Dowex-50 from solutions of hydroxylamine
was found to be pH depenhdent. Ap the pH of the Bolutlon was
Increased, a sharp decrease ln D was obgerved between pH 5 and
6. Uranyl ion was not adsorbed by Dowex-50 resin from carbonate
soluftilon.

Khopkar and Deégg have lnvestigated the behavior of

223
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

4 8 q
10 T T 10 T T T 10 1 1 T
ZEOKARB 225 AMBERLITE IR 120 FRENCH C 50
pull
0° |- 4 103 i
D
it Np*
loE u Thm |°2 F -
10 N2 -
| 1 1 1 ] l | 1 1 I 1
0O 2 4 6 8 10 0O 2 4 6 8 8 10
M, HNO, M, HNO3
'04 1 | ! T |°4 T T T T '04 T T =T T
U¥l DOWEX 50 DOWEX 50 DOWEX S50
b4
3| Th™Y AMBERLITE | 3 3| ]
10 IR 120 10 - 10
D D
108 4 102 2 102 |- i
NHI' Punt
Th pull
10 - 10 4 10 | -
Um Np? pum
| 1 \ 1 1 1 "'l-—;N;E 1 l 1 L\— 1
0O 2 4 6 @8 10 O 2 4 6 8 10 O 2 4 6 8 10
M, HCI M, HCI M, MGl
Figure Ti.

The adsorptlon of uranlum and other actinlde elements by cation
exchange resins from nltric and hydrochloriec acild solutlions.
After C. J. Hardy, reference 587.

The curves present the data of the following investlgators:

€. J. Hardy, D. Scarglll, J. M. Fletoher, J. Inorg. Nuclear Chem.
7, 257 (1958): Th(IV), Pa(V), U(VI)-ENOg.

K. F. Sculz, M. J. Herak, Croat. Chem. Acta 29, 49 (1957):

Th{IV)-HC1.

R. M. Diamond, K. Street, Jr., G. T. Seaborg,.d. Am. Chem. Soc.
6, 1461 (1954): u(vI), Np(Iv), (V),(VI), PulrII),(Iv),(VI)-HCl.
. Ward, G. A. Welch, Unpublished data, U.K.A.E.A., Winddcale:

Np(V), (VI)-HNO3.
I. Prevot

377 (1958): Pu(TII

), LIV)

224

P. Régnaut, Progress 1in Nuclear Energy
-I'INO3 o

» Serles III, 2,
32M HCI

 

 

 

 

 

| 1 i 1
Np(V) Pu(VI)lU(\II) Cs YbSry cmlpuce La Ra Ac
Ev Ba
Np({VI) Am
62 M HCI
Lo e ey
Np(V) IU(VI) Ca YD Y cmlPu(III)GaLuBulflu I Ac
PU(V“ Sr{Eu U(N)
Am Pu(lV) Np(IV)
93M HCI
Ly ooy
Mp(V) Cs Pu(lV)YDb Y Pu(im) |Eu SrCe Ac
Uvl1) Np(IV
Pu{vl) Am  U{v)
122 M HCI
LW ouowouly
Mp(V) Cs Pu(lV)NpQV)AmCm Yb Ra¥Y EuBa OsLaSr Ac
v Pu{lll) ’
Pu(VIl)
1 1 vl | Lol I gl

 

10 100 1000
VOLUME OF ELUTRIANT

Filgure 75.

Elution peak positions of various ilons with 3.2, 6.2, 9.3,
and 12.2M HC1l from Dowex~50 catlon exchange resin. Elutrient
volume glven in drops.
After R. M, Diamond, K. Street, Jr., and G. T. Seaborg, rerefenoe
501.
Conditlions:

Dowex-50 resin, HR form, 250-500 mesh, settling rate

gpproximately 0.5 cm/min.

Column, 10 cem long x 1 mm dlameter,

Flow rate, approximately 0.1 cm/min.
Room temperature.

225
 

 

 

 

 

 

 

 

 

 

100 T I =
= - —
> 50 g-g }
w =
o w 7
w 20 - _
w £
O o
° o S -
& = n
o o ]
- 5 - -
S = -
o o i
£ s
@ ’r 1 o -
Q o

l 1 l n i b 1 |
O 0.l 0.2 O 0.l 0.2
SULFATE CONCENTRATICN, ¥ ACETATE CONCENTRATION, N

 

1 I!IJII

   

DISTRIBUTION COEFFICIENT, D
ro
I

 

 

| 1 t
O 1 28 3 4 B
HpGCgOs CONCENTRATION, %

 

Figure 76. The adsorption of uranium by Dowex-50 cation exchange
resln from solutlons of sodium sulfate; sodlum acetate, and oxallec
acld, After T. Ishimori and H. Okuno, reference 568.

Conditlonsa:

Sulfate - 0.5 g resin, NaR form; 5.4 mg U/25 ml; NapoSOy-
NaNO3 mixed solution, {Nal = 0.30N. -
Acetate -~ 0.5 g resin, NaR form; 5.4 mg U/25 ml; NaOAc-
NaNO3 mixed solution, [Nal = 0.16N.

Oxallec acid - 0.5 g resin, HR form; 10.8 mg U/25 ml.

226
uranium (VI) on Amberlite IR-120 catlion exchange resin with
hydrochloric, nltric, sulfurle, acetle, cltric, and perchloric
acids. Uranlum (1.7 mg) adsorbed on a resin bed (1.4 x 14.5
em) was eluted with 200 ml of various eluante. Uranium was
quantltatively recovered with 2-4M HC1l, 2-4M HN03, and 1-2M
Hasoq. Uranlum was incompletely recovered with 1M HCl, 1M
HNO5, 2M HC10,, 2M acetic acld, and 2-5% citric acld.

" Sullivan, et al1.22% have investigated the distribution of
uranium between Dowex-50 lon exchange resin and perchloric acld
medla as a functlon of tlme and blsulfate lon concentration.

Table XXXVI 11sts a number of separations of uranium from

various elements that have been achleved by catlon exchange.

4, Chromatosraggxw The subJeot of paper and cellulose chromatography

for the separatlon of uranlum has been reviewed by Rn:)dden:-L-gg and

198

by Steele and Taverner.—=— Work of Soviet sclentlstas in the

fleld heaa been reviewed by Palei-121 and by Seny&wln..élg References

to much of the literature may be found 1n the review article by

Kuznetsov, Savvin, and Mikha.ilov.ggg Books by Pollardglé-and by

Blasiuséli include chromatographlc separations of uranium.

One of the most successful separations of uranium by filter-
paper chromatography makes use of the solvent, 2-methyltetrahydro-
furan.éli Of thirty-one metals tested, only ruthenium and rho-

106 106

dlum, measured as Ru™~ - Rh™ -, and tungsten (W185) were in-

completely separated from uranlium (U233). The results for tin

(Snll3) and antimony (E’:blzj1L

) were 1nconclusive and the behavior
of mercury (H3203) was 8imllar to that of uranium.

An example of the use of celluloge columns in comblnation
wlth organilc solvent for the separatlon of uranlium is that given
by Burstall and Wealls.élé An ethereal solution contalnlng 5
per cent v/v of nitric acld i1s used to extract uranium from a
cellulose column. The nitrates of the alkall metals, alkallne

earths, rare earths, Cu, Ag, Zn, Cd, Al, In, T1, Ti, Hf, Ge, Sn, Y,

227
BZZ

Table XXXVT.

Elemental mixture

u,

b

U
U
U

s &

g & &

G

-

-

Qc dad g d

O

F.P.{(Cs,8r,Y,Ce)
F.P., Pu

F.P.
La

Eu

Ce, Eu, Y

R.E.

R.E.

Fe, Cu, 04, N1,
Mn

Element eluted <+ eluting agent

U-1.TOM HOl; Th-1.1M (NH4)2003

U, Th-90% acetone, 5% HCl, H,0 (U eluted first)
U=-1M HC1; Th-3M H,SO,

U-dil. HC1l; Th-complexing agent (Hso;)

U-2M HC1; 0.5M H,C,0,
dilute HNO,

U=dil. HC1l; Np(IV)-complexing agent

gasorb from 1M HNO3; eluted Np ahead of U with
2M HN03

Sr-0.1M HC1; Ce,Y=1M HC1; U-6M HC1l; Cs=5M NH),C1

adgord from uranyl nltrate sclutlon at pH 1-3;
0-0.2 €0 0.3M HoS0y; F.P.-phosphoric aeld and
1M HNO5; Pui-0.8H H3E04 and 1M HNO

F.P.=3% Ne,EDTA ; U=-3% NaOAc, 0.25M Na2003

La-0.06% Na EDTA, pH 4.0; U-3% NaOAs, 0.25M Na.2003

U-0.75M H,80,; Eu-6M HC1
U-1M H,C,0;; Ce, Eu, Y-5N HCl
R.E.~Na, EDTA

U-2, 5M HF

U, Fe,Cu-0.5N HpCoOh; Cd,N1,Co,Mn-3N HC1;
R.E.-5% ammonium cltrate

Separation of Uranium from Various Elemente by Catlon Exohange.

Resln
Amberllte IR-120
KUo-2

Amberlite IR-120

Reference

592
588

589

phenol formaldehyde 593

type

Wofatit KS
Amberlite IR-100

alginliq acld
Wofatlt KS

Amberlite IR-120
Amberlite IR=120

594
595

596
597

597

zirconium phosphate 598

sulfonated phenol
formzldehyde type

godliunm dialkyl
phosphate

sodium dialkyl
phosphate

Dowex-50
Amberlite IR-120
Amberlite IRC=50
Dowex-50
Amberlite IR-120

599

660

600

601,602

603
604
605
606
6272

U, FegIII), Co(II),
Cu(II

U,Fe(III)

U, Co, Cu, Ca

U, Ccd
U,Th,Ac,B1,Ra,Pb
U, many lons

U, many lons

U, Zr, CegIII),Cu,
Ni, Hg(II

U, phosphate

Fe,Co,Cu~2% Na EDTA, pH 3.0; U-3% NaOAe, 0.25M

NaECO
U,Fe-0.8M HC1 (U eluted first)
adsorb from O.1M HNO3; Co, Cu,

Ca=0.2M HNO4;

U-resin removed from~column and washed wit

0.25M Na.2003
Cd-0.5N HC1
U,Th,Ac,Bl-5% HyC,0y

forelgn lons-EDTA (Na salt)%. PH 7 U-H,S0,

forel

U-3N H,50,

Zr as anlonic oxalate complex
anionic EDTA complexes, Hg(II

ions-EDTA (Na salt;, (a)p. L1.T-1.9
or (b} pH 5.5=7.0 following Fe(OH.)3 precipitation;

Ce(III), Cu, Ni as
as anionle lodlde

complex are not adsorbed; U-4M HC1
phosphate (NaEHPou) not adsorbed; U-4M HC1

F.P. [=] fisslon products.
R.E. [=] rare earth elements.
EDTA [=] ethylenediaminetetraacetic acid.

godlum dlalkyl
phosphate

Lewatlt 3100

dlalkyl-
phosphoric acld

Dowex=-50
KUu-2
Amberlite IRC-50

(a)KU-2 or (b)
Amberlite IRC=50

Amberlite TR-120

Amberlite IR-120

600

607
600

608
609 -
610
611

589

589
Pb, Nb, Ta, Cr, W, Te, Mn, Fe, Co, and N1 remaln statlonary or
move only sllghtly. Gold reduced with_FeSOu 18 retalned by the
column. Mercury (II), selenlum, arsenic, antimony, and bilasmuth
move less rapidiy through the column than uranium. Cerlc nltrate
1s extracted as are thorlum, zirconium, and scandium nitrates.
Cerium in the III-state 1s not extracted. Thorlum extractlon
ip sensiltlive to the acld concentration. Zirconlum extractlon 1s
inhibited by phosphate, sulfate, ocxalate, and tartrate lons.
Scandium extraction 1s also inhlblted by tartrate lon. Tin 1s
precipltated as meta=-stannlic acld. Large amounts of tin may be
first removed by volatlllzation as the lodlde. Vanadlum 1ls re=
talned 1f peroxldes are absent. Ferrous sulfate reduces vana-
dium to an lmmoblle sglt. Phosphoric acld is extracted. Ferrilc
nitrate 1lnhlbits the extractlon of this acld. The behavior of
molybdenum ie complex. Irldlum and rhodlum are not extracted.
Traces of ruthenium and platinum may be found in the eluent.
Palladlum 1s extracted. Reduction of platinum and palladium
with FeSOu results 1In retention of bulk amounts by the column.
Small amounts of sulfate do net lnterfere with the extraction of
uranium. Sulfuric acld is retalned by the column under normal
conditions. Halldes increase the extractlon of other elements,
€.g2.,Au, Sn. Under normal conditlons, HC1l 1s retalned 1n the
columm; HBr, HI, bromine and lodine move slowly down the column.
Molybdenum and arsenlc may be adsorbed by the use of activated
alumina 1ln conjunctlon with celluloseoélz

The use of sllica gel columns comblned wilth organle solvents,
dibutyl carbltol and trlbutyl phosphates and nltric acid have
been used for the separation of uranlum and plu‘l:on:[um.él-a-&élg

A non-lonic phosphorylated resin, dlethyl polystyrene-
methylenephosphonate, may be used to separate uranium (VI) from
1ron {III), ianthanum, zirconium, niobium, thorium,and mixed
fission pr-c>dut3tfl.-§--2-g Uranium is adsorbed by the resin from 2

per cent solutlons of dilbutyl phosphorlc acld. The other elements

230
are not absorbed. Uranium 1ls eluted with a dimethyl formamide=
benzene solution.

The feasibility of using tributyl phosphate gels for the
separation of uranium from iron (IXI) and thorlum has recently

been demonstrated.égl

5. Volatilizatlon. Uranium may be separated from many elements by
fractional distlllatlon of the volatile compound, uranium hexa-
fluoride. This method of separation has been applied to the
recovery of uranium from lrradiated fuel elements. Katz and
Rabinowitzl have reviewed many of the early methods for the pre-
paratlon of UF6: fluorination of various uranlium compounds with
elemental fluorlne or cobalt trifluoride, dlsproportionation of
UF5 whlch results in both UFu and UF6, and the reaoction between
UF, and dry oxygen which results in U02F2 and UF6. The latter
two methods are not very practical from an analytlcal standpolint.
Other fluorlnating agentas that form UF6 Include ceric fluorlde,
manganic fluoride, silver difluoride, halogen fluorides (e.g.,

BrF., and ClF3) and fused metallle fluorides. Moat elements

3
form fluorides under the condltlons that UF6 1s obtalned. How-
ever, ohly a small number of these fluorides are volatile. Hyman,
gfi_g&,g have published a table of some 26 elements having fluorides
with boiling or sublimation points of 550°C or less. Included in
thls group are the fluorides of boron, sllicon, phosphorus,
vanadium, sulfur, tungsten, bismuth, plutonlum, and the fission
products, germanium, arsenlc; selenium, niobium, molybdenum,
ruthenium, antimony, tellurium, and iodine. The bolling point
ofIUFs is 54.6°C. Non-volatile fluorides from which uranium is
readlly separated Include those of the alkali metals, alkaline
earths, rare earths, Fe, Co, N1, Ag, Al, B¢, Mn, T1, Pb, 2n, Cu,
Hg, Cd, and ZP.QE;QEE

Uranium does not form a volatlle compound by interactlon

wlth anhydrous hydrogen fiuoride. Materlals such as Nb, Ta, As,

231
Sb, 51, Te, Se, eotc. do.éi The oxides of titanlum, tungsten,
and molybdenum regct slowly wlth HF. Vé05 and VN also react
elowly. VO, VéOu and V203 are not vola.til:_l.zed.ii Rodden and
\«ha.r-f-;i desoribe a procedure that makes use of both anhydrous
hydrogen fluoride and fluorine In the peparatlon of uranilum.
Posslble contamlnants of the separated UF6 include Cr, Ta, W, Mo,
or V.

Uranium hexachloride and uranium (IV) borohydfiide_are
volatlle compounds for which procedures might be developed for
the separatlon of uranium.

Uranium may be separated from arsenlc, antimony, bismuth,
selenlum, and tin by volatilization of the latter elements with
a mixture of hydrobromlec acld and ‘DJ:'omine.l-2§

6. Electrochemlecal methods. The electrolysle of dilute sulfuric acild
solutioné with a mercury cathode results 1n the quantitative
deposition of Cr, Fg, Co, N1, Cu, Zn, Ga, Ge, Mo, Rh, P4, Ag, C4,
In, Sn, Re, Ir, Pt, Au, Hg, and T1 in the cathode.213 Arsenic,
selenium, tellurium, osmlum, and lead are quantitatively separated
from the electrolyte, but are not quantitatively reposited in
the catl'acrder.-?-li Manganese, ruthenium, and antimony are incom-
pletely separated.glg- Uranium and the remalnlng actinlde elements,
rare earth elements, the alkall and alkaline eerth metals,
alunminum, vanadium, zirconium, niobium, ete. remaln in solu-
tionfgig- Cas’.f:.oég-i and Rodden and Warfléi have reviewed the effects
of many variables in the electrolytic separatlon of the above~
named elements from uranium. According to Rodden and Wa.r'f‘,.-afl
optlmm condltlionas for the purificatlon of uranium 1n sulffiric
acld solutlons wlth a mercury cathode are: electrolyte volume,

50 ml; free sulfuric acld ooncentratlon, 1N; current density,
as high as practicable with the given acid concentration (about
10 amp maxlmum); anode, flat platinum spiral or grid just

making contact wlth the surface of the electrolyte; cathode ares,

232
a8 large as practlcable; stirring, surface of the mercury cathode
18 stirred rather rapldly; temperature of electrolyte, between
25° and 40°C; mercury for the cathode, pure; anlons, chloride,
nitrate, and phosphate i1ons should be absent, or present in
only small amounts.

Uranium may be deposlted electrolytically at the cathode
of a cell from aeetate,ég&ié;l czau.J:'bona.te,-éég--oxa.ls.q.te,gi::-@ig
formate,éig-phosphate,éfig fluoride,éfig&éfll and chlo::-:l.de-s-j—{'g
solutions.  Many of the uranlum electrodeposltlon procedures
have been developed 1m an effort to prepare thin, uniform fllms
for alpha and fission counting rather than to separate the ele-
ment from any particular impurity. However, in the work of
Smith and cv:>-‘wor']rcel"E}é-g-l--‘L-"-égg and Coomanségl'uranium was separated
from alkall and alkaline earth metals and zlnc. Ga.s.tt;ég-3 and
Rodden and ‘.r\Ta.]:'f.‘-Z‘--ll review much of the material pertlnent to the

electrodeposition of uranium.
Electrodialyslis has achleved & certain amount of lmportance
in the recovery of uranlium from leach llquors. In a review ar-

ticle by Kunin,éfi; the followlng cells are preegented for con-

 

glderation:

(-) cathode anlon permeable membrane anode {+) (1)
U0, (No4) 5 NH,,NO4
NH4N03

(-) cathode anion permeable membrane anode (+) (2)
U0,S0y, H,S0,
H,y80,

(-) cathode anion permeable membrane anode (+) (3)
U0,Cl, NaC1l
NaCl
H,yS50)

 

233
(-) cathode | anlon membrane| NaCl Ication membrane| anode (+) (4)

U04C1, H,80,
NaCl -

oS0y

 

(=) cathode cation permeable membrane anode (+) (5)
2+
Uo,™, Ney €0 Na,CO4
NaHCO,

In acid systems (oells 1, 2, 3, and &), the transport of sulfate,
nitrate, and chloride ions to the anode results 1ln a removal of
acid and a subsequent increase in pH in the cathode compartment.
The uranium, reduced during electrolysis, 1s precipitated as

U0, or U(HP04)2o In the alkallne system, the transport of so-

2
dium lons 1s also accompanled by a rise in pH in the cathode
compartment and uranlum is again preclpltated as the dloxide or
as a mixture of dloxide and sodlum polyuranate.

The electrodlalytic separatlon of uranium from metals 1n
a complex mlxture has been demonstrated by Willard and F:Lnley.gfli
An ammonium blearbonate solution contalning U, Fe, N1, Cu, Cr,
Zn, Al, Mo, Mg, and Na salts, and traoces of other elements was
electrolyzed in a two-compartment cell having a catlon permeable
membrane and a mercury cathode. The solutlon was firset made
the catholyte (electrolyte in the cathode compartment) and elec-
trolyzed. Iron (80%), nickel and copper (95%8), tin, and zinec
were removed from solution by deposition. The blcarhonate solu=
tion was then made the anolyte and electrolyzed at a platinum
anode. All aluminum, molybdenum, ammonium, and sllicon, and some
sodium and megnesium were separated from the uranium by migra-
tlon. Uranium was retalned as the carbonate complex and was
recovered as the oxlde by evaporation of the anolyte.

Other features of the slectrodialytic behavior of uranium
that may be useful in 1ts separation and purification are (1)

the retention of uranium during electrodialysis from & perchloric

234
catholyte ueing an anion selective membrane, (2) the dissolution

and separation of impure UF,, and (3) the feasibllity of .electro-

dlalysis 1n organic solutions. ot

T. Pyrometallu;sicalAprocgsses. Although pyrometallurglical or high
temperature processes have been designed primarily for large
scale recovery of fertlle material from irradiated fuel elements,
some of the methods may find épplication In the radlochemistry
laboratory. Types of pyrometallurgleasl operations that have
received considerable attention are(l) distillation,(Z.) salt

extraction, (3.) molten metal extraction,(d ) oxidative slagging,

(5 ) electro~refining, and(6 ) decomposition of uranium iodide.

These methods have been revlewed by L&l.'.»n:-oe.]rc'.'l.og-:l-'l

l. Plutonium 18 concentrated by vacuum distillation
from molten uranium at 1500-1800°C.

2. Plutonlum la extracted from molten uranlum by salts
such as UF, or MgCl,. Uranium remalns in the metallic
gtate. Plfltonium 15 recovered as a hallde salt.

3. Plutonium ls extracted by molten metals, such as
gllver or magneslium, that are immlscible with molten
uranium. Fleslon products are also extracted.

4. Oxldative slagging involves the preferential formation
of the most stable oxldes by a molten irradiated fuel
element 1n a limlted oxygen environment. These oxldes
(rare earths) float to the surface of the molten ma=-
terlal and are skimmed off. Other oxldes diffuse 1into
the crucible and through the slag layer.

5. In electro-refining, uranlum is dissolved anodically
1n a fused salt bath of alkzll or alkaline earth halides
that contaln a uranium compound. Noble metals do not
dlssolve and are deposlted as anode sludge. Uranium
and chemically similar materials are deposited at the
cathode. Alkall, alkallne earth, and rare earth fission
products concentrate ln the salt bath..

6. Uranium 1is recovered as the metal from the thermal de-
composition of UIA. Zirconlum and nlobium are the principal
contamlnants.

" It 18 not the purpose of this sectlon to describe the
techniques involved in pyrometallurglcal processes. The lnterested
reader may consult The many papers presented in "Progress in
Nuclear Energy, Serles IITI, Process Chemistry,” volumes 1(1956)

and 2(1958), and in the "Proceedings of the International Con-

235
ference on Peaceful Uses of Atomic Energy,” volumes 9(1956) and

17(1958).
IV=E Determlnation of Urarilum

The amount of uranium 1n a sample may be determined by
atandard methods of analysls: gravimetric, volumetrie, colori-
metrie, spectrophotometric, e*l:c-,.31LL191"19_5’197’198'200'6)'&5
.Because of 1ts natural radiocactlivity, uranlum may also be deterw=
mined by counting technlques. The appllcablility, ln terms of
mass range, of varlous methods for the determination of uranium
1s glven in Table XxxvIr.222
1. Counting techniques. Principles of alpha, beta, and gamma

counting are considered 1ln review articles by Steinberg,éig

Hanna,éiz Deutach and Kofold-Hansen,éflg Crouthamel,éi& and

 

J'a.i‘i‘e:r.g59 All three methods of countlng are appllcable to
the radiometric determination of uranium since both alpha- and
beta-emitting i1sotopes exist (Section IIX). Spontaneous fissilon
half=11ves have been determined for several uranium isotopes:
U232, U234, U235, U236, 0238. These 1sotopes are too long-lived,
however, to make fisslon counting a practlcal method for thelr
determlination. |

Ionization chambers are most commonly used for the detection
of alpha particles. In figures 77 and 78 are shown the alpha
spectra of U235 and U233, respectlively. The spectra were obtalned
with a parallel plate, Frilsch grid ionlzation chamber using P-10
(90% argon, 10% methane) gas. A multl-channel analyzer was used
ln conJunction with the lonization chamber. Both U235 and U233
samples were prepared by volatilizatlon. Filgure 79 represents
the U233 alpha spectrum obtained with a surfacse barfier slllcon
s8olid state detector. Data for this flgure was taken from the
same sample as that for figure 78. It 1s readily apparent from
the.two figures that the solld state detector glves much better

resolution of the alpha groups than does the lonlzatlion chamber.

236
Table XXXVII. Range of Application of Various Methods for the

Determination of Ur'a.nium.-E

Method Ran?e of applicatlon Range of error
mlcrograms) %per cent)
Neutron actlvatlon 10')+ - 104 2 to 5
Fluoroscopy 1077 -2 ' +5 to 50
Emission spectroscopy 5 X 1072 - 50 +]1 to 10
Visual chromatography -1 o
on paper 10 = 10

Volumetric (1lncluding 5

microvolumetric) methods 1-5x10 0.5 to 5
Autoradlography (o emiselon) L

counting of tracks l1-10 +1 to 10
Colorlimetry N

dibenzoylmethane 10 - 10 +1 to 3

thlogyanate 50 - 5 x 104 tl to 3

H,0, - HC10, 103 - 107 1 to 5
Alphe counting = 50 - 5 x 103 +1 to 10
Polarography 102 - 104 2 to 5
Potentiometry 2 x 10° - 10" +1 to 5
Gravlimetric methods 5 x 101L - 0.1 to 2
a

— Adapted from a table glven by A. Simenauer, reference 199,

b 50 pg of U238 gives about 20 cpm at 52%4 geometry. Uranlum-

238 may be detected 1n samples having much lower counting

rates than thls, dependlng upon the physlcal condition of

the sample and the presence of extraneous alpha activlity. For
a thin gource wlth low alpha backggggnd, 1 alpha cpm of uranium
should be readily detected. For U this 1s the equlvalent

cf about 2 ug; for other uranium leotopes, the masa 18 even
less.

The data for flgure 79, however, was taken 1in 1000 minutes. The.
data for flgure 78 was taken in 10 minutes.

Alpha partlcles may be counted also by gaseous, llquld,
plastic, and crystalline scintlllation detectore. The resolu-
tion of these detectors is, 1ln general, less than lonlzation

chambers and their applicatlon more limited. Nuclear emilsions

are used to record alpha activity. Such devices as c¢loud chambers

are generally not used in the radloehemistry laboratory.
Geiger-Mfiller counters, proportlonal counters, and liquid,
_plastlc, and crystalline scintillation detectors are sultable

. for the counting of B -emitting lsotopes, U237, U23% and U240.

237
 

 

 

 

 

 

 

 

 

 

 

Iolooo rrTrrirrryrvyrrnrnvial rrritrrrrrrirrrinril r:
I { >} ]
F @ ¥
i 2 1
py ¢
0
< .
1000 2 —
- = $ B -
b " m . -t
o - g N o1 ¢ -
w - D l ': .
- L Y- P > | R -
> - § ! 5 2 ) ! -
Z [ £ I [3
= - ., = g I g -
g O o ¢ .
3 < < fal
2 100 — o g i = P
- - F ™~ §
a C '&.’5 S ™ 8 :
o s f o )
oD ‘_.-':- (\l: i
'.'
U235 71 x108 ye. |
10 Ionization Chamber o
- Detector |
_ | Div. = 28.6 kev ]
- ‘
|_0 L4y ety vl vt

ENERGY ——

Plgure 77-
Alpha spectrum of a volatilized source of U235 obtalned with
a parallel plate, Frisch grid lonizatlon chamber using 90%
argon - 1l0% methane gas.

D. J. Henderfion, Argonne National Laboratory, Unpublished data.

238
 

Q000 - M T T T T T I T T T T T T T T T T T T T T T T TT T T T T

—_—t 1 11 111

 

 

 

 

 

 

 

 

1000 -
0 _
W i
5 ]
< i
=
o
= 100 _
9 -
< )
» .
= _
2 :

o o~ --'; -1
© 233 5 '-
1 U233 162 x 109 yr.
10 - Ionization Chamber o\ 3
:. Detector D -
= | Div. = 20.0 kev ]
3 1
l.oII_LI_LI_L]_I_IJ_ll_lIIIIIJllll_IlIIIIJIJ_I
ENERGY —=
Figure 78.

Alpha sapectrum of a volatillzed source of U233 obtalned wlth

a parallel plate, Frisch grid lonization chamber using 90%
argon - 104 methane gas'.

D. J. Henderson, Argonne Natlonal Laboratory, Unpubllshed data.

239
 

    
  

 
   
       

 

 

 

 

 

 

 

 

 

 

Ioo;Ooo_[IIII.IIIITIIIIIIIlIIIIIIIIIIIIIIII
- i i
¥y © % _
n 24
I | © b -
. E..
7 1\ < _
10,000 |- = 4| & | :
L y o> 3 { .
v [~ t A g ‘ -
_ i~ g -
|_|-l_-| n fl: m -
D ~ i
z - | ~ |
= : T ] i
o 2 |
3
— 1000 o 3
- " E -
o -
* u 0 .
wn - © i
- - < -
2
o i i
o
o
100 ‘ 3
U233 1.62 x 109 yr. -
o o . Solid Stote Detector -
S | Div. = 7.8 kev e o
|o iyttt ek
ENERGY —
Figure 79.

Alpha spectrum of a volatilized source of U233 obtalned wilth

a surface barrier silicon detector.

P. W. Engelkemelir, Argonne National Laboratory, Unpublished data.

240
Sodium lodlde-thallium actlvated cryatals have galned wlde-
spread acceptance as detectors of gamma radiatlion. The gamna-
ray spectra of U239, U237, U235, U233, dand a uranium are from
the Belgilan Congo are illustrated 1n figures 80-8B4%,. The speotra
were measured by Crouthamel, Gatrousils, and Goalov:'f.ch-—s-—lt2 wilth a
Y-inch dlameter x 4-inch thick oylindrical NaI(Tl) crystal.

Not only can the amount of uranium in a sample be determined
directly by measuring the dlsintegratlon rates of the various
1sotopes, 1t can also be measured indirectly by determining the
activity of daughter products. For such a measurement to be
meaningful, however, the equllibrium conditlon between the
uranium lsotope and 1ts daughter must be known.

Information on the radicactive decay of the uranium isotopes
1le glven ln Section III. Further information on these isotopes
and thelr daughter products may be obtalned by consultlng the
"Table of.Iaotopes" complled by Stromminger, Hollander, and
Seaborgéél and the references given therein. Volumes 8 (1956),

3 (1958), and 28 (1958) of the "Proceedings of the Internatilonal

Conference on the Peaceful Uses of Atomlc Energy"” contaln a

number of articles on the radlometrlc determinatlon of uranium.

Reference to many more articles 1s made in the revliew papers

by Meinkenéég

2. Sanple preparatlon. One of the most lmportant problems to

overcome 1n the detection of alpha partlcles and 1n direct
fisslon counting 18 the preparation of thin folls or sample

| depoelite. Thls subject has recelved conslderable attention

and hag been reviewed by several authors.63?’647'650’653’654

Several techniques are avallable. The simplest and most quanti-

tatlive 1s the direct evaporation of an aliquot of a sample. The

dietribution of such deposlts are generally not very uniform.

Thie may be improved upon by the addltlon of a spreadlng agent

such as tetraethyleneglycol, TEG. Palntling technlques may be

uged to bulld up falrly uniform depcsits of several mllligrems

241
RELATIVE COUNTING RATE

per square centimeter.éééi-éEg Uranyl nitrate le dlssolved ln
alcohol and added to a dilute solution of Zapon in Zapon thinner
or cellulose In emyl acetate. This solutlon 1s painted over a
metal backing, allowed to dry, and then baked or ignited at a
sultable témperature. For aluminum backing, temperfitures of
550° to 600°C are satisfactory. For platinum, higher tempera-
tures (800°C) are preferresd. The.thickness of the uranium
deposlt 1B increased by repeatedly palnting and baking the

 

foll.
100
U239 23.5 min.
0 No auternat absorbar
Geomstry = 48%
i Dlv.» 2,95 tev
60
TO
60
g 3
50 = a
x 2
s S
40 c 3
3 8
z ©
30 3 g
~
20
10
0
ENERGY —
Figure 80.

Gamma-ray spectrum of U239 obtalned with a 4-inch dlameter x
Y-inch thick eylindrical NaI(Tl) crystal.
After C. E. Crouthamel, C. Gauvrousis, S. J. Goslovich, reference

649.

242
£ve

RELATIVE COUNTING RATE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

100 T T T T T T T T T I T T T T T T T T T T} T T T T T T T TV T T I T T T T 7T
90 fl
u%37 g 7 da.
80 1 No axtarnal absorbsr
fl Geometry I0%
70 [l‘ Ifi I Div,= B.0 hgv
R
o
g 3 8 ~
- . J 1 } j l
T Uy | :
. o\
o™
20 g 8
RV ERYE A
°
' Hk,dfr o *2 g ‘flm;\Huff
Tyt v et iy i i i it e s i s i gyt 4 g it g gttty

 

ENERGQY e

Figure 81. Gamma-ray spectrum of U237 obtained with a 4-inch diameter x 4-~inch thilck
eylindrical NaI(Tl) crystal. After C. E. Crouthamel, C. Gatrousis, S. J. Goslowvich,

reference 649,

 
¥¥e

RELATIVE COUNTING RATE

100

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

   

 

 

 

 

 

 

 

 

 

 

 

[TTT T T I TTTTTTITI T FTI T T T T T T T I T T T T rTrer T T rrITTI T I T T
90 |— UE‘-'35 7.Ix|0°yt.
T No external absorber
80 Go?metry 10%
| Div. = 6.6 kev
4 counted 30min, after
0 saparotion from
- n daughters, 10mgs. U
60 ° <
= - 234
x 2 o v .07 % isotopic
50 & _c:: = Ut3%93.41% content
z of 9 ues8 559
40 n ==
|z a
__J‘,': - = >
30 M a 3 3 2 2
2 > = o >
E ~ ® ® ll] o o
> - » < o a
20 12 o n—®a - o
- mn o o N /\
© 0 =
j Lnd. \_f/ x64
o ] | Lyt v e g et gt Pi 4t 1 bt
ENERGY —
Flgure 82. QGamma-ray spectrum of U232 obtained with a 4-inch diameter x UY-inch thick

cylindrical NaI(Tl) crystal.
reference

649,

After C. E. Crouthamel, C. Gatrousls, S. J. Goslovich,

 
S¥¢

RELATIVE COUNTING RATE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

i0o0 T TI T I T T T I it r i rTyTr T T T T T T T T T T T T T T T T i T T T T I T T T I T iTTrrd
80
" w U233 | 62 x10%yr.
80 3 :g:::tcm! Sr(NOz),
gtry 10%
a I Div. = 6.4 kev
70 3 —— :
2 Mass Anolysis
o 7.4 ppm 236
€0 S < | ppm 236
E PI. < | ppm 235
50 a < 2ppm 234
x jl[ < | ppm 232
alz 2
40 —z+Inl=—=
| (¥ S A 3
n — Q@ >
- : » 3 J‘:
£ o |13 o g g 3
_’ l’; gg °—‘ o N,/l\n
20 s -+ :
10 n8 o x 32
o|||| Lid i e et e e e i ettty s
ENERGY —=

Figure 83. Gamma-ray spectrum of U233 obtalned wilth a 4-inch diameter x 4-inch thick

cylindrical NaI(Tl) crystal.
reference 649.

After C. E. Crouthamel, C. Gatrousls, S. J. Gaslovich,

 
 

loo I I T I | I I I ' ' I ‘ 1 P10 1 1 1 1 I | ! ]/ |

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

I -
a o Uranium Ore J
& a {Belgium Congo-hand picke
20 < g < 580 mg/cm® Ba
wa 2 |& o t
80 2l é 2 | Dlv. = 78.5 hev
O 3 a =
~0 .
mm 0 ] E ~
w oo P_; 2 - E
g o A5
o« n . ™ ’ 2
© Sep|le v & z
: i T s &
z (|3 4
3 50 —4 1 0 £ @
.o v g < l.‘-? !——
w )1 "Lk 3 e
> 40 T, {i—A 2
. : ~
< z +
™
} : =
ng = o
20 §—3
l W K a i
10 } %
o |||4111||||1||||l|||||¢|_\L<\'f3=4,.u
ENERGY —
Figure 8.

Gamma-ray spectrum of uranium ore from the Belglan Congo obtalned
with a 4~inch ditameter x 4=inch thick cylindrical NeI(Tl) crystal.
After C. E. Grouthhmel, C. Gatrousis, 8. J. Goslovich, referenocs
649,

Samples of the metastable 0235 l1somer have been prepared
by electrostatically collectlng the recoll atoms of Pu239 in
air.m A negative potentlzal of several hundred volts was
applled to the metalllc collectlion plate.

Carswell and Hilstedgég have succeeded in preparing thin
sources by a spraying technique. The materlal to be deposited
1s dissolved as the nitrate in an organic solvent (alcohol or

acetone). The solutlon 1s drawn into a fine glass caplllary

246
tube and sprayed onto the backing material by applylng an
electric fileld.

Electrodeposltion 1ls a generally satlsfactory method for
preparing uniform samples wlth quantitative or nearly quantita-

tive ylelds. Uranium has been plated from a varlety of solu-

tionse: acetate,lu.LM formate’s_Bg_ Oxalate,62316'§§'638
carbonate,éfiiéég fluoride,62 632,61 and chlopide_éflg A satig=

factory electrolyte for the deposition of uranium is 0.4M
gmmonium o:\::aLlaau.i:e.é--s-i A rotating platinum anode 18 used to stir
the solutlion placed 1n a vertical cylindrical cell. The cell
is made of glass, luclte, or scme other chemically inert material.
The cathode on whlech the uranium 1s to be depaslted is thoroughly
cleansed and made the bottom of the cell. The assembled cell
i1s placed 1n a hot water bath and the temperature kept at about
80°C. A current denslty of approximately 0.1 a.mp/cm2 18 used.
The deposition 1s influenced strongly by the rate of stirring,
current denslty, and presence of forelgn ions.ftfit

Vacuum sublimation preovides an excellent means for the
preparation of thin depoelts of uranium. The sublimation of
uranlum acetylacetonate, U(05H702)4, has been used. A more
convenlent method 1s the sublimation of uranlum oxldes. A
uranium salt solutlon 1ls placed on a tungsten or tantalum ribbon
supported between two electrodes. The solution 18 dried by a
heat lamp or by passling a low current through the metal ribbon.
The sample backling materlal is suspended at a sultable helght
above the metal ribbon. A bell Jar 1s placed over the assembled
unit and evacuated. The uranlum 1z volatlilized by increasing
the current through the matal ribbon. The unlformity of the
deposlt depends upon the dlstance between the rilbbon and the
backling plate. The collection efficlency also depends upon
thls distance but in an inverse manner to that of deposit uni-
formity. Usually a compromlse is made between collection

d
efflclency and sample uniformity. Much of the uranium that 1s

247
not collected on the sample plate can be recovered from maskling
pPlates and glass chimneys placed between the filament and backing
fiaterial. The collection efflclency may also be improved by
subliming from furnaces so that the beam of uranium molecules

158 directed toward the backing plate. . The furnace 1s heated
lby'electron.bombardment or induction heating.

3. Activation Analysls. In activatiop-analysis, a nuclide

 

irradlated by neutrons, gamma raye, or charged particles 1s
transformed infto a radloactlve nucllde more easlly detected than
the origlnal one. The amount of orlginal materlal may be deter=
mined elther absolutely or comparatively. For an absolute deter-
mination, the crose sectlon of the reaction, the lrradlation flux,
and the disintegration rate of the reaction product must be known
or determlned. For comparatlive analysis, a substance of unknown
‘mass is irradiated simultaneously with & similar substance of
known mass. The positions ol these two subatahces are elther
8ide by slde or, 1f meparated, 1in positlons of like fiux. The
reactlon product actlvities of the two samples are compared to
glve the relative masses of the starting materlala. The com-
pqrative technique 1s, 1n general, much easler to apply. The
uncertalnties of many varlables are elimlnated by relative
measurements. .

Activatlon with thermal -neutrons may be successfully
employed as a method-of analysie for--natural uraniuvm, uranium-
236, and the fissionable isotopes of uranium. Nstural uranium
consists of U238(99.3¢), 123%(0.72%), and U23*(0.0057%).85L The

prinecipal reactiomof thepe nuclides with thermal neutrons are:*

38 1 39 gf ) 239 g- | 239 _a 35
U2 +n-+U2 - Np - Pu lea,

 

% .
Half-lives glven below the arrow are taken from the "Table of
Isotopes,"” reference 651, The value of V for the fisslon of
U235 15 taken from "Neutron Cross Sections," reference 660.

248
y233 + nl - Fission Products + 2.47 neutrons,
1]234 + nl —3 U2350

The amount of natural uranium present in a sample may then be
determlned from the amount of U239, Np23% or Pu239 activity -
formed after 1rradlation. Measurement of the Pu232 activity,
however, requlres elther a fairly large amount of U238, a long
irradiation perlod, or a comblnatlon of the two. The amount of
natural uranium may also be determlned from the flsslon of
uranium-235 elther by (1) fissilon counting the sample, (2) iso-

140 or T6132*’

lating and counting a fisslion product such as Ba
or fi3) measuring the total gamma actlvity 1nduced in the sample
by a short neutron irradiation-éfii Thermal neutron lrradiatilon
of U23* results tn U232 and 1s of little value in the determina-

tion of natural uranium.

Neutron lrradilatlion of U236 glves U237, a beta-emmiter
having a half-life of 6.75 da:,r:s.éél It is readlly 1ldentifiled
through its beta decay, assoclated gamma rays, and half-life.
Uranlum-238 irradiated with fast neutrons also produces U237,
U238(n,2n)U237. The cross sectlon for thls reactlon has been
determined with incldent neutron energles from 6 to 10 Mev
and at 16 Mev.éél

Actlvation analysls by flsslon countling 1s of wvalue only
if one fisslonlng nucllide 1s present or if the amounts of other
fissionling nuclides present are known and correctlons can be
made for them. The same 18 true for the lsolation and deter-
mination of fieslon products. Uranlum i1sotopes that are
fissionable with thermal neutrons fiogether wlth their thermal

660

neutron fisslon cross sectlicns are:——

y230 25 + 10 barns
ye3l 400 = 300 barns
*The fisslon product nuclldes Ba140 and Te132 are chosen since

they are free from lnterfering reactions and are produced 1n
good ylelds.

249
=32 80 + 20 barns

7233 527 = 4 barns
235 582 + 6 barns
0239 14 + 3 barns*

Other than U235, U233 is the best uranium isotope to determine
by fission counting or flsslon product analysls. Uranlum-232
may posslbly be determined in thie manner. The other lsotopes
are of such short half-=11fe that analysis of thelr own radla-
tions 1s a much better means for their ldentifilcatlon.

Excitatlion functions have been determined for a number of
reactliona wlth charged partlcles or gemma rays incldent on
uranlum lsotopes. These reactlons may be used for activation
analysls. For absolute analysis, 1t should be pointed out that
(1) the cross sections reported are sometimes subJect to con-
slderable error; (2) energy determinations of the incoming
particle or ray are also subject to error; and (3) the reaction
product can often be produced by a number of reactlons. Com-
parative analysls appears to be a much better method for the
determination of uranium. For gamma-ray (bremsstrahlung) activation,
slmiltaneous irradiations in a like flux are falrly easy to
accomplish. The two samples,; unknown and standard, are mechani-
cally rotated In the gamma-ray beam. For charged particle
activatlion, the simultaneous irradiation of twd samples in a
like flux may require some 1lngenuity on the part of the ex-
perimenter.**

A partlal list of reactions between uranium isotopes and

charged particles or gamma raye for which excitation functions

*
Plle neutrons.

*'Because of the short range of charged particlea, irradiations
are generally made with targets attached to or within the
vacuum system of the accelerator. To maintaln the system's
vacuum requlrements, to coql the samples properly, and to
lrradlate the mamples elmultaneously in a like flux may pre-
gent some dAiffioulty in equipment design.

250
or 1ndivlidual croes sections have been determined 1s gilven

below:
Protons
1?30 (p, 530?30 802

Deuterons

U238(d’2n)Np238 663,664
U238(d,4n)Np236 663,664
123%(q,p)u?39 804563
12384, t;4, pon)u237 664
U238(d,t)U237 662

U’235(d,n)Np236 §.6_"L'_6_6§

1235(4, 2n)Np235 664,666

1235 (a. 3n)np23t 664,666
u235(q, 4n)Np=33 566

Alpha particles

U238(c.',n)Pu241

u23%(q,n)np?35 666
U234(d,2n)Np234 666
*(a, 3n)np233 288

1233(q,n)np23% 86T
1233(4,2n)Np2 3B EEL
U233(4,3n)Np2 32 56T
u233(4,an)pa?30 06T
1233 (q,F)zALEL

1235(a,5m) 3% €69

+ 1238 (a,p)Np2tl B, p2Hl O 235(q pyNy230 669

U238(a,2n)Pu240 g6l
1230 (a, 30) pu?39 E64
U238(a,4n)Pu238 664,668
1230 (a, pn)np? 0 £69

U238(a,p2n Np239.§§2
)23 869

U236(a,4n)Pu236 668

235(q. ) pu238 664,669
1235(q,2n) pu237 69
235 (. 3n) pu236 661,669
235 (q, kn) pu235 882

Carbon lons

123812 yp)cp2t6 OIL
v238(c12, gn)cr2tt E1L
U238(012,a4n)0m242 571

Gamma, rays, bremsstrahlun

0238y, n)u237 672,673
v238(y,n) 1%

0235(a,p2n%Np236 £69
U235(a,F) 669

(233, n) 236 669
233(a.2n)pa23 669
1233(4, 3n) pu23% 669
233(a kn)pu33 669
U233 (4. 5n)pu33 669
7233(a, pn)Np232 569
33(q, pan)Np23* 882
1°33(a, p3n) Np®33 882
1233(q,r) 262

U233('YJN) ngl'.
The analysls of uranlum by actlivation methods 18 reviewed

by Koch,§1§ who also glves references to much of the lilterature.

IV-F. Diasolutlon of Uranlum Samples

l. Metallle uranium,.

 

EEEE. Uranium metal dissolves 1n nitric acld to form uranyl
nltrate. W1lth massive amounts of uranlum the rate of dissolu-
tion 1s moderately rapid.EII The reaction between uranium
turnings, powder, or sintered metal and nitrlc acid vapors or
nitrogen dloxlde may occur with exploslve violence.ézz Oxldes

of nltrogen are the principal gaseous products in the dlssolutilon

of the metal by HNO The presence of oxygen 1n the dissolver

gyatem tends to redzce the emlssion of these oxides.ézg The
rate of dissolution of large amounts of metallic uranium may

be Increased by the addition of small amounts of .=.’.uli’u1:-ic,§12
phosphoric,ézg&égg or perchloriaégl acld to the nitric acid.
HESO4. Hot concentrated sulfuric acld attacks uranium metal
slowly forming uranium (IV) sulfate.ézz Sulfurlec acid~hydrogen
peroxide mixtures react slowly with the metal at 75°C forming
uranyl Bulfate.égg The addition of small amounts of chlorlde
or fluorilde to HéSO4 - H202 Pixtures lncreases the dissolution
rate.égg

H3P04. Cold 85% phosphoric acld attacks uranium metal slowly.ézz
Egg;ghtration of the acld by heatlng produces a falrly rapld
reaction in which uranium (IV) phosphate 1s formed. If heated
too long, a chemically lnert, glassy subetance 18 formed.

HClOu. Uranium metal is Ilnert toward cold, dilute perchlorilc acid.

 

As the concentratlon 18 lncreased by heating a point 1s reached
at which the reactlon proceeds with violence.ézz&égg Oxlidlzling
agents added to dllute perchlorle acld dlssolve the metal.ézz
HCl. Concentrated hydrochloric acld vigorously attacks uranium
metal. Dllution of the acld dimlnlshee the attack. But even

with 4M HC1l there is a rapld evolution of hydrosen.égg A

252
finely dilvided, black preclpitate zoon formas after dissolution
begins. This preclpltate 1s not dissolved by heating. Only by
the additlon of oxldilzing agents (hydrogen peroxide, bromine,
chlorate, nltrate, persulfate, dlchromate, or ferrig ions) does
the precipltate dlssolve. Gaseoup chlorlne, aldéed by small
amounts of iro; or lodine, also oxldizes and solublllzes the
uranium preclpitate. The addition of small amounts of fluosiliecic
acl 682,68 or large amounts o¢f phosphorilc :;1.0.1(:]‘:—6--6-g to the hydro-
chlorlec acid prevents formation of the black preclpitate during
the dissolutlon of uranium metal.
HF. The reactlon of hydrofluoric acld wlth uranium metal 1ls slow
even at temperatures of 800_90°c,§11 The reaction 1 iInhibited
by the formetlon of 1nsoluble UF4 on the surface of the metal.
HBr. Hydrobromic acld attacks metalllc uranium in manner
similar to, but slower than, hydrochlorilc acid.éll The black
preclpitate 1s formed.
HI. The reaction between uranium metal and hydricdlc acid ls
slow.ézl
Organlc acides. Acetlec, formic, proplonlc, and butyrlec aclds
react rapldly wlth uranlum 1n the presence of hydrogen chloride.ézz
Benzole acld in ether reacts wlth the metal, forming the ben-
zoate,ézl Acetyl chlorlde and acetle anhydride react to form.
uyranous acetate.2LL
Mlscellaneous solvents. Uranium 1s dlssolved In a number of
medla other tfian acids:gfiléll&éfig solutlons of heavy metal salts
685

(silver perchlor'a.te‘,-§§-ll cupric ammonium chloride—= or ace=

tate§§§), alkaline peroxide solutions (NaOH-H202 or Na,0,-H,0
solutionségz), golutions of bromine and ethyl acetate,§§§L§§§

hydrogen chloride and ethyl aoetate,682

682

 

hydrogen chlorlde and

 

acetone, and nitrogen dloxlde 'and hydroger. fluoride.2§2

Table XXXVIII denotes qualiltatively some solutions that
satisfactdrily dissolve uranium.égg

Anodlc dlssclutlon. Metallic uranlum may be dlssolved elec-

 

253
trolytically by anode oxidation. A varilety of electrolytes
have been_used.égg:égg Satisfactory dlesolutions have been
made wlth sulfurle acid,682 nitric acid;égl tartarle acid,égl

 

phosphorlc acld contalning n:l.1:z'ate,-§gg and sodlium bicarbonate.égl

2. Alloys of uranlum. The ease with which uranium slloys are

 

dissolved depends largely upon the chemlcal behavlor of the
alloylng metal. Larsenégg-has reviewed the dlssolution of

some of the more common uranlum alloys. Table XXXVIII summarlzes
the effect of various reagents on these alloys.

3« Compounds of uranium. Table II lists solvents for a number

 

of uranium compounds. - General Review references 2, 4, 5, and
T (Section I) cover the chemlcal properties of these and other

compounds more fully.

Table XXXVIII. Reagente for the Dissolutlon of Uranium and Its Alloys.-E

 

S = gatisfactory N = unsatisfactory
Descriptilon HNO3 figgia Nig;ic- Hgi + %géic Bra- NaOH=-
EtOAc H,0,

U S S s S S s S
U-Zr N N 8 N N S N
U-Nb N N s N N s S
U-Fe 3 S S S S S N
U-Cr N N N S S s N
U-Ru N S N N N N N
U-Mo N S N S N S s
U-Fissium® N sS N N N N N
r-g12 s s

U-Pu s< 3 N S S S N

2 R. P. Larsen, reference 682.

b Alloyse containing from 1 to 3% Zr, Mo, Ru, Rh, Pd, and Ce.

L Fluoride must be added to dissolve Zr.

4 Nitric acld dissolutions leave 381 resldue, but nitric-hydro-
fluorlc acld dissolutlons can easlly lead to volatilization of

fluosllicice acid.

£ Pu itself 1is not reaedlly dissolved in nitric acld, hydrochloric
acld belng preferable.

254
The dlssolution of uranium oxldes 1s of conslderable
interest slnce uranlium samples prepared as accelerator targets,
for neutron irradlations;, or samples found 1n the natufal gtate
are frequently 1n the form of oxldes. Also, many compofinds of
uranium may be transformed to the oxlde by heating, hydrolysis,

or fusion. All of the oxldes, UO 08’ and UOé, are soluble

U
37 73
In nitric acld, formlng uranyl nltrate. UO3 1s soluble 1n other
minersl acida. U 08 and UO

2
perchlorilc acid;é— They are slowly dissolved in hot concentrated

are dlssolved by fumlng wlth

gulfurie acida§£ The presence of fluoride accelerates this
dissolution.égi Alkallne peroxides react wlth uranium oxides
to form soluble peruranates.éfliégl
4, Meteorites, minerals, and ores. The extraction of uranium
from natural deposlts may be accomplished by decompositlon and
diesolution of the entlre sample 1ncludlng uranlum or by leach=-
ing the uranlum from the pample. Grinding and roasting faclll-
tate the recovery. Roastling removes organic material. It also
helps form soluble uranlum compounds. |

Decompositlon of the sample may be accompllshed by acild
attack, by fuslon,or by a comblnatlon of the two. Mlneral aclds,
indlvidually or in comblnatlon, may be used. The presence of
hydrofluoric acld generally alds in dlssolution. Ores, sand,
etc. may be fused with sodlium carbonate, so@ium hydroxilde,
so&ium peroxlde, sodlum blsulfate, sodium chlorlide and sodium
hydroxide, ammonium sulfate, potassium bifluoride, and mag=
neslum oxide.ll;fi&ég& The melt ls solublllzed in water orlacid
and the separation of uranium made by procedures outlined in

Seetlon IV=-D. Rodden and 1.'Ja.r-f.'--:'3‘--ll have described a number of

procedures ln whlch uranium was made soluble by acld attack or
by fusion methods. The recovery of uranlum from monazite sands
hae been reported by Calklns, gg_géfégi

Acld and alkallne leaching &'¢ used on an industrial scale

' for the recovery of uranium from its ores. In acld leachilng,

255
hydrochloric, nitric, or sulfuric aold may be uaedel Indus-

trially, sulfuric acld is used because of itq economy. Oxidizing
agents (Fe(III), MnO,
uranium (VI). A separation of uranium and thorium with an oxalie

acld-nitric aocld leach solutlon has been raported.'§2§

» eta.) are used to convert uranium (IV) to

In alkaline leaching, various ocombinations of alkaline
carbonates, hydroxides, and peroxides have been used.: Indus-
trially, uranium is dissolved by alkalline ocarbonates as the
U02(003lg' complex. - Oxygen or other sultable oxidants are used-
to oonvert uranium (IV) to uranium (VI). Hydroxyl lons are
formed by the dissolution of uranium in carbonate solutions. The
presence of bloarbonate lon in the disaolvins'solution prevents
the preciplitation of uranium. The recovery of uranlum by acid
and alkaline leaching 18 reviewed in General Review reference
13 (Section I).

5. Blologlcal samples. The determination of uranium in blolo-
g;cfil fiamples 18 reviewed by Steadman.égé- Uranlum may he ex=
traocoted and determined directly from liquld samples. The sample
may also be ashed, as are solid samples, prior to uranium ex-
traction. Ashling fiay be carried cut as a wet or dry process.
Wet-ashlng 18 commonly done wlth a nitric acld solutiocn. Ashlng
may be completed wlth perchloric acld. However, extreme cautlon
must be exerclsed when heating organic materials with perchlorilc
acid. The ashed residue 1s dissolved in aocild and the uranium
determination continued from there. Wet=ashling need not be
‘carrled to completion. Analysis may be made upon the sample
after 1t has been thoroughly digested in acid.

6. Alr dust samples. Samples of alr dust are commonly collected
on filter papera. The uranium may be dissolved by digeating
the sample in nitrlc acld solution or the sample may be ashed

and the residue dlssolved 1n aold.

256
V. Collectlon of Detalled
Procedures

A prodedure for the determination of uranium may entail
one or more purificatlion steps a8 outllined 1n the preceding
sections. For ex#mple, uranium may be separated from Impuritles
by a serles of solvent extractions with one or more different
solvents. These may be interspersed wlth precipitation and/or
lon exchange methods. The procedures described hereln have
been gathered from .projeet reports, the.open literature, and
by private communicatlon. Only a limlted number are presented.
They have been selected.because they represent many of the
Beparation methode already descrlibed or because they represent
different problems in handling samples: problems of dissolution,
extrfiction in the presence of hlgh beta=gamma activity, etc.
A number of the procedures described do not make use of the ra-
diometrlc determination of uranlum. The method of separation
in these procedures, however, 1s applicable to radlochemlcal
~analysls and is, therefore,; included. A number of papers and
reports describe, in detall, procedures for the determinatiofi
of uraniuym. Thése 8should be noted. The work of Rodden end
Warfgi has frequently been mentloned in this paper. In addl-
tion to procedures for the precipitatlion, solvent extractlon,
volatilizatlon, and electrodeposition of uranium, these authors
have presented a number of selected procedures for the solutlon
of ores and minerals and the separation and determlnation of
uranium. Procedures for the anélyticalldetermination in naturally
occurring materlials have also been described by Rodden and
Trggonning,ééé'Grimaldi, May, Fletcher, and Titcomb,égz Schoeller
emd"P-m»,'ell,i?-92 and in the "Handbook of Chemical Determination

of Uranium in Minerals and Ores."§2§

The recent publlcatlon by
HooreEzl on extraction with amines contalne a collectlon of pro-

cedures, many of whlch have to do with the separation of uranium.

257
IROCEDURE 1: Uranilum-237-.

Source: B. Warren, LA-1567 (1953) p. 18.

Editort's note: Uranlum-237 may be separated from fission pro-
ducts, neptunium, and plutonium more easlly by lon exchange and/or
solvent extractlion techniques (see, for example, Procedure 7).

The following procedure 1s, however, an excellent example of
uranium purification by precipltation methods.

l. Introductilon

The significant steps 1n the determinatilon of U237 in ma-
terlials contalning flasslon products, neptunium and plutonium are
the following. Rare-earth, neptunium, and plutonlum actlvities
are removed by appropriate lanthanum fluoride scavenglng steps
in the presence of hydroxylamlne hydrochloride. The latter
reagent serves to reduce both neptunium and plutonlum so that
they may be carried down, and also to complex uranium and pre-~
vent 1ts later removal in lron scavenglng steps. Barlum and
Zlrconlum are preclpltated by barium fluozlirconate scavenglng.
followlng a cycle of ferric hydroxide scavenging and ammonium
dluranate precipltatlion steps, uranium 18 reduced by zlnc metal
in hydrochloric acld medium and precipltated, presumably as
U(OH)u,_with ammonlum hydroxlide. The uranium 1s further purifiled
by alternate conversilons to tetrafluoride and hydroxide. 24.1d
Th234(Ux1) which has grown in from =38 is removed by a zirconium
lodate scavenge and the uranlum 1s converted to ammonium dluranate.
Uranium 1s finally plated from nitric acld hedium onto a platinum
foll. \After flaming of the foll and welghlng, uranium is beta;
counted as U308' Chemlcal ylelds average 50 to 65%. Quadrupli-

cate determinations require approximately 8 hours.

2. Reagents
U238 carrier: 1 ml containing 10 mg of (5000/1) uranium. Pre-
paration: Welgh out 1 gm of U metal, dlssolve in
cone, HNO3, transfer to a 100-ml volumetrlc flask.
Make up to volume, adjusting the flnal solutilon

258
PROCEDURE 1 (Continued)

to 3M in HN03. The carrler 1s standardized by

plpeting 1 ml aliquots lnto a 000=Coors procelaln

cruclble, evaporating to dryness, 1gniting at 800°

for 45 min, and welghing as U308'

La carrier: 10 mg Le/ml (added as La(N03)3 . 6H20 in H20)

Ba carrler: 10 mg Ba/ml (added as Ba(No3)2 in H20)

Zr carrier: 10 mg 2r/ml (added as ZrO(N03)2 . 2Hé0 in 1M HNO

Fe carrier: 10 mg Fe/ml (added as Fe(NO3)3 * 9H,0 in very dilute

HN03)

HCl: conc.

HN03: 1M
HN03: BE
HNO3: conc.

HF: conec.

HESOM: cOone.

HI03: 0.35M

NHuoH: conc.

NH,OH - HCl: 5M

4% aqueous (NHy),C50y

Bry: liquid

Zn metal: 20 mesh, granular

Methanol: anhydrous

Methyl red indicator solution: 0.1% in 90% ethanol.

3. Equipment
Flsher burner

Centrifuge
Block for holding centrifuge tubes
Lo-m1l centrifuge tubes: Pyrex 8140 (10 per sample)

000-Coorse porcelain crucibles (one per standardization)

Pt-tipped tweezers
Plpets: assorted slzesa

259
PROCEDURE 1 (Continued)

Stirring rods
Plating assembly: 1 cell per allquot of sample

Source of current - Fisher Powerhouse (D.C.)
with varlable resistance in series wlth cells.

Cell - Brasé base (3" x 3") for holding
Pt cathode; 5-mil Pt circular 2" diameter disk (cathode);
gasket (Koroseal-Upholstery 36681) to seal cathode and chimney;
glass chimney, 2" diameter, 4" high, with 4 ears at helght of
3"; 1 1/4" steel springs for holding chimney to base; rotating
Pt anode. The cell is heated for 1 3/4 hours at 105° after

assembly to insure formation of s8eal between glass and Pt.

Water bath for cell - Autemp heater; 6"
crystallizing dish (for water bath); rubber pad for holding
cell.

4, Procedure

Step 1. Add 1 ml of sfandard U carrier to an allquot of
sample in a 40-ml long taper centrifuge tube. Dilute to about
10 ml, heat to bolllng, and preclpitate (NH1|_)2U207 by the drop-
wlse additlon of conec. NH40H.

Step 2. Centrifuge and dlscard the supernate.

Step 3. Dissolve the preelpltate in 1 to 2 ml of 1M HN03,
add 5.4 ml of H,0, 3 drops of La carrier, and 10 drops of 5M
NHEOH « HCl. Allow to stand for 5 min.

Step 4. Add 3 drops of conc. HF and allow to stand for 5
" min. Centrifuge for 5 min, transfer supernaté to a 4%0-ml
centrifuge tube, and dliscerd the preclpitate.

Step 5.. Add 3 dPOps of 1a carrlier and let stand for 5 min.
Centrifuge for 5 min, transfer supernate to a 40-ml centrifuge
tube, and discard the precipitate.

Step 6. Add 3 drops of Zr carrler and 15 drops of Ba

260
PROCEDURE 1 (Continued)

carrier. Centrifuge for 5 min and trensfer the supernate to a
40-ml1 centrifuge tube, dilscarding the precipltate.

Step 7. Add 4 drops of conc. H,80, and centrifuge for 5 min.
Transfer the supernate to a 4#0-ml centrifuge tube and dlscard
the precipiltate.

Step 8. Add 2 drops of Fe carrler, heat the solution to
bolling, and preclpltate Fe(OH)3 by the addition of conc. NH,OH.
Cool the tube under cold HEO’ centrifuge for 2;1/2 min, and
transfer the supernate to a 40-ml centrifuge tube, discarding
the precipiltate.

Step 9. Add O.% to 0.5 ml of 1llquid Br, (Note 1) slowly to
slighf excese and boll the solution to a light yellow color.

Add conc. NH,OH until (NH4)2U20

T
der cold water, centrlfuge, and save the precilpltate.

preclpltate forms. Cool un-

Step 10. Add 1 to 2 ml of 1M HNO, and 10 ml of H,O, heat

3 2
the solutlon to bolling, and add conc. NH40H to repreclpiltate

(NH4)2U207. Centrifuge and save the precipiltate.

Step 11. Add 1 to 2 ml of 1M HNO 10 ml1 of H,O0, 10 dropse

37 2

of 5M NH,OH * HCl, and 2 drops of Fe carrler. Let stand for

2
5 min. Heat the solutlon to boiling and precipitate Fe(OH)3
by addltlon of conc, NHuoH. Cool the tube under cold HQO,
centrifuge for 2-1/2 mln, and transfer the supernate to a 40-
ml centrifuge tube, dlscardlng the preclpltate.

Step 12. Repeat Step 9.

Step 13. Add 1 ml of conec. HC1l, 10 ml of H20, heat the
solution to boililng and precifiitate (NH4)2U'207 with conc. NH,OH.
Cool the tube, centrifuge, and save the preclpltate.

Step 14%. Dlssolve the precipltate in 1 ml of conc. HC1l and
10 ml of H,0. Add 2 gm of Zn metal (20 mesh, granular), and
heat the mixture untll the solution turns brown. Heat 1 addi-

tlonal minute.

261
PROCEDURE 1 (Continued)

Step 15. Let etand untll the vigorous gas evolutlon subsldes
and decant iInto a 40-ml centrifuge tube. Discard the Zn.

Step 16. Heat the solutlion to bolling and preclpiltate
U(OH)4 (?) with conec. NH),OH. (The precipitate will be greenish-
black.) Centrifuge and save the precipitate.

Step 17. Dissolve the preclpltate 1n 10 drops of conc. HCI.
Add 5 ml of Héo and 4 drops of conc. HF; Stir vigorously until
UF), precipltates, add 7 drops of conc. NH40H and stir. Cen-
trifuge 5 min and save the precipitate.

Step 18. Add 1 ml of cone. HC1l, heat slightly, add 10 ml of
H20, and heat the solution.to bolling (the precipitate should
dissolve). Add conc. NH)OH and precipitate U(OH)u (?) (greenish-
black precipitate).

Step 19. Repeat Step 17, except that 4 ml of H,0 are added
Instead of 5.

Step 20, Add 1 ml of conc. HNO3 and heat until NO, ceases
to be evolved. Add 10 ml of H,0 and precipitate (NH4)2U207
wilth cone. NH40H. Centrilfuge, discard the supernate, and
dissolve the precipltate In 1 ml of conc. HNOB.

Step 21. Add 10 ml of H2O, 4 drops of Zr cerrler, and 1 ml
of 0.35M HI03. Centrifuge, transfer the supernate to a 40-ml
centrifuge tube, and dlscard the preclpltate.

Step 22. Heat the solutlon to bolling and preclpltate
(NH4)2Ué07 with cone. NH),OH. Centrifuge and discard the supernate.

Step 23. Dissolve the precilpltate in 1 to 2 ml of lfl_HNOS,
dllute with 10 ml of Héo, and centrifuge. Transfer the super=
nate to a 40-ml centrifuge tube and discard the precipltate.

Step 24. Reprecipitate (NH4)2U'207 by bolling the solution
and adding conc. NHAOH. Centrifuge and save the precipltate.

Step 25. Add 5 drops of 8M HNO; and transfer to the plating
- cell which contains 10 ml of H,0 and 3 drops of 8M HNOB. Rinse

the centrifuge tube with three washes each conflisting of 5

262
PROCEDURE 1 (Continued)

drops of 8M HNO3 and 0.5 ml of B,0, transferring the washingfi
to the plating cell.

Step 26. Add 10 ml of 4% (NH4)20204 and wash the cell walls
down wlth approximately 5 ml of Héo. The total volume 1n the
cell should be about 40 ml.

Step 27. Add 5 drops of methyl red solutlion, and conc.
NH40H drop-wise until the solution turns yellow. Add BEHNO3
until the solution turns red or orange (one drop 1s usually
required); then add 3 drops of HN03 in excess.

Step 28. Plate for 1-1/2 hours at 1.5 amp and 8 volte at
80 to 90°. For the first 30 min, at 10-min intervals add
sufficienf 8M HNO5 to make the solution red to methyl red. At
40 min, add 3 drops of conc. NH40H, or enough to make the solu-
tion yellow to the 1ndicator.

Step 29. Wash down the cell walls with H20 to replenish that
lost by evaporation, and continue electrolysls for ah addltional
50 miln.

Step 30. Remove plate, wash with H20 and methanol. Flame
plate for 1 min. Cool, welgh as U308’ mount, and count. Correct
for Th234 (le) activity (see accompanying figure).

Notes

1. Liquid Br, destroys NH,OH and also the uranium-hydroxylamine

2
complex.

263
COUNTS /MINUTE

1.0

PROCEDURE 1 (Continued)

 

 

 

 

1 1r 1 vr 1 v rt
- n
— -]
e -
_ o -9
. o 0 © c =
~ o ° J
o -
~ O
L 0 -
_ o _
O
O
I—o —_
~ -
|.o —f
r—- -
L o b L by gy :
O 2 4 e 8 10 12 |14

DAYS

CORRECTION FOR UX; ACTIVITY/mg U3Qq

ON PLATE. Procedure |.

264
PROOCEDURE 2: Purification of Uranlum-240.

Source: E. K. Hyde and M. H. Studler, ANL-4182 (1948).
EE&Sor's note: The followlng procedure was uged toUngify

U formed by the second order neutron capture of « The
principal decontamlnating etep 18 the ether extractlon of
urenlum from a reduclng agueous solution. Uranium la further

purified by a number of precipltatlons that are not described
In detall. These, however, are falrly easy to perform.

Irradiation and Chemlcal Procedure

Two grams of depleted uranium (1 part 0235 per 30,000 parts
U238) &as U308 in a small 2g alumlnum capsule was lrradiated 1n
the Hanford plle for 12 hours including time for startup and
shutdown. B81x hours after the end of the irradiation the cap-
sule and 1lts contents were dissolved In nltrlc acld, using
mercuric ion as catalyst for dlssolving the alumlnum. The
uranlum was eXtracted batchwlse, the dlssolved aluminum serving
a8 a salting agent. The ether contalning the uranlum was then
passed through two statlc wash columns packed with 3/32 inch
stalnless steel helices and filled with a solution 10M in
ammonium nitrate, 0.1 M in nitric acid, 0.0l N in ferrous ilon
and 0.1 M in urea. Neptunlum was reduced by the aluminum 1n
the dissolver and by the ferrous lon 1n the wash colummg to an
unextractable oxldation state (Np IV and Np V). Additional
ether was passed through the columns to strip out the uranium.
These operatlone wWere carried out by remote control behind
lead shielding. The lnltial dissolver solution measured roughly
50 roentgens per hour at 8 i1nches. The ether solution emerging
from the second column and contalning the uranlum measured only
about 3 mr per hour at the surface, and most of thils was ether-
soluble iodine fileslon product activity. The uranium was ex-
tracted from the ether into an aqueocus ammonium sulfate solu-
tion and washed several times wlth ether to remove lodlne
actlvity. LaF3 was preclplitated from the uranjl nitrate solu=-
tion after reduction wlth sulfur dloxide to remove any traces

of Np239 which might have come through the ether extractlon.

265
PROCEDURE 2 (Continued)

r

The uranium was further purified by precipitation as dluranate,
sodium uranyl acetate, and peroxide and by a final ether ex-
traotion. Throughout this final serles of purlflcatlons there
was no detectable decrease 1n p-activity; thie 1indicates that
the uranlum was radioactivg}y pure.

Small aliquots of thelfinal uranium solutlon were evaporated
on platinum dises and ignited to U308 to study changes 1in
activity. The remaining uranium solutlon was used for extractlon

of neptunium daughter fractlons.

PROCEDURE 3: Purification of Irradiated U23°,

Source: S. Fried and H. Selig, Private communlcation.

Editor's note: The present procedure was used 1n an experliment
deséfig?d to measure the 525 mal neutron fisslon cross sectlon

of The amount of that can be tolerated 1n such an
experiment 1ls very small.

Two criterla were used in selectlng the purification steps

in the followlng procedure:

1) To obtaln uranium free of fission products and other
extraneous activitles wilithout 1ntroducing contamlnant
normal uranium 1in the procedure.f _

2) The initial part should lend itself easlly to remote

control manipulation.

*The reagents used were carefully purlfied. Thus, the niltriec
acld and perchloric acid were redistilled In a quartz still.

The NH4N0 was prepared from gaseous ammonia and distllied HNO3.

3
The HCl was prepared by passing HC1l gas into triply distllled

H20, etec.

266
PROCEDURE 3 (Continued)

Procedure:
A. In Cave
The irradiated uranium oxide (~0.3 mg) was dlssolved in
concentrated HNO, and made up to 2 M 1n HNO; with distilled H,0
to give total volume of about 15 ml. Some Fe'T was added to
keep Pu and Np in +%4 étate; The solutlon was saturated with
NH4N03 and contacted four times with 10 ml portions of ether.
Each contact was scrubbed twlce with 2 L‘.[_HNO3 saturated with
NH4N03o The comblned ether extracts were back extracted three
times wlth 5 ml portions of H20. The'HEO strip wae evaporated to
dryneas and trested with HCl to destroy NH4N03 carried over.
B. Outsilde Cave

The sample could now be handled easlly outslde the cave
wlth a minimum ‘of shielding, moat of the actlvity being dus to
U237. A mass spectrometrlc analysls showed 1t contalned 0.5
welght % of U3/, A flsslon count showed that additional purl-
238

fication was necessary to remove Np formed by (n,y) on Np237
whlch had bullt up during lrradiation.

The sample was taken up 1ln about 0.5 ml 6 N HC1l and put
on a small Dowex-1l column and washed. The Np comes off 1n
6 N HCl. Finally the uranium was eluted with 0.5 M HCl. The
eluate was evaporated to dryness and taken up in 0.2 ml of 5 M
HCl, 0.1 M KI and 0.05 M N2H40H » 2HCl. This was heated at 90°
for 2 minutes, diluted to 0.5 M in HCl and TTA extracted twice
for 15 minutee. The crilginal fraction was washed twice with
benzene and evaporated to drynese. |

In order to clean up the uranium for a mass apectrometric
analysils, 1t was subJected to another ether extraction as in
the first fitep. After the NH4N03 was destroyed the sample was
fumed with HGlOu to destroy any organic resldue from the ether
extraction.

~

267
PROCEDURE 4: Uranlum and Plutonium Analysis

Source: B. F. Rlder, J. L. Rusesell, Jr., D. W. Harris, J. P.

Peterson, Jr., GEAP-3373 (1960).

Samples of dissolved lrradlated fuel contaln highly

radloactlve fission products. For thls reason, uranlum and

plutonium are separated prior to analysis. The followlng pro-

cedure glves a good yleld together with a good deéontamination

factor.

Reagents:

1. Distilled cone. HNO3.

2. 2 M HNO3 - dlstlilled cone., HN03, double dilstllled H20.

3 U-~-233 solutlion, standardized.

4, Pu-236 solution, standardized.

5. KBr03 - Crystals, Reagent Grade. Low natural U blank.
6. 8 M NH4N03 in2 M HNO3 - Place 200 ml distilled 16 M HNO

7
8.
9.
10.
1.

12.
13.
14,
15.

3
+ 100 ml double distilled H20 in a large beaker. Bubble

NH3 gas through sclution until basic to pH paper. DBoil
off excess NH3 (solution neutral). Transfer to mixing

eylinder, add 50 ml of distllled 16 M HNO dilute to 400

3.
ml. Check density of solution (1.31 * 0.0l at 20°C.).
Hexone - distilled.

HC1 - C.P. reagent. Low natural U blank.

1 M HNO, - distllled conc. HN03, doub;e distilled H20°

304 H2OZ - meets A.C.S. specification, low natural U blank.
0.2 M T.T.A. in xylene - 4.44 gm T.T.A. dissolved in 100 ml
distilled xylene.

Xylene = distilled.

Efher - distllled.

0.05 EHNO3 - distilled conc. HNO3, double distilled H20.

H20 ~ double distilled.

Glassware:

All glassaware used 1s Pyrex which hae been soaked overnight 1in

268
PROCEDURE 4 (Continued)

50% HNO3 and rineed with double dlstllled water. Plpets are

rinsed with 50% HNO

3 and double distilled water before uslng.

Separation and Decontamination Procedure:

 

1.

" 1mlof 8 M NH4N0

Place the allquot for analysis in a 15 ml cone and evaporate
to about 1 ml. Add a sultable U-233 and Pu-236 spike, one
drop conc. nitric aceld, and several KBrO3 cryatals. Allow

to stand for 1 hour to allow oxldatlon of Pu to Pu02++.

Add 1.5ml 8 M NH4NO3 in 2 E.HNos, and evaporate to about

2 ml.

Prepare 2 scrub solutions ln separate 15 ml cones, contalning
3 in 2 _]fl_HNO3 and about 10 mge KBr03.
Preoxidlze about 10 ml hexone with 2 ml of 2 M HNO3 and
KBr03. Keep covered untll ready for use,

Extract the U and Pu four times for flve minutes with 2 ml
portions of hexone (methyl ilsobutyl ketone), adding 1 drop
of 16'§ HNO3 to the orilgilnal solutlon after each extractlon.

Scrub each extraet 1n turn with the two solutions prepared

In step 3.'

Strlp the comblned hexone extracts with five 2 ml portlons

of H20° Evaporate the comblned aquecus portions to dryness,

add a few drops of HNO. and HCl, take to dryness. Evaporate

to dryness wilth HNO3 uider a8 gentle stream of pure nltrogen
on a bolllng water bath.

Prepare 3 ml of 1 E_I.HNO3 and 1 drop of 30% H202, add 1 ml to
the Pu and U resldue from step 5 and two 1 ml portions to
separate 15 ml cones.

Extract 1mmedlately the Pu 2 times for 20 mln. with 2 ml
portions of 0.2 M T.T.A. (thenoyltrifluoroacetone) in xylene.
Scrub each in turn with solutions prepared in step 6. Save

the aqueous phase for uranium. Combine the T.T.A. extracts

and add a few crystals of trichloroacetic acid.

269
10.

1l.

12,

13.

1L,

15.

PROCEDURE 4 (Continued)

Mount the combined T.T.A. extracts on a platinum plate
for alpha pulse analysls.

After pulse analysis, remove the Pu for mass analysls as
follows: Cover disc wlth HF. Evaporate to dryness under
a heat lamp. Agaln cover dilsc with HF and evaporate to
dryneses. Cover dlsc wlth cono. HNO3 and evaporate to dryness.
Repeat 3 or 4 timee. Cover disc wilth cone. nitric, re-
flux a few seconds, and transfer with a plpet to a 15 ml
cone. Repeat 3 ar U4 times.

Evaporate the comblned conc. HNO3 refluxes to dryness.
Treat resldue wlth aqua regla and evaporate to dryness.
Evaporate to dryness with conec. HNO3 on a bolling water

bath several times. Add 50 * of 0.01 M HNO, to the evapor-

3
ated sample and submlt sample for mass epectrographic
analysis.

Wash the original 1 M HNO_ uranium fraction (Step 7) with

3

xylene. Add 1 drop of HNO_, and 3 drops of HCl to the

washed 1 M HNO3 and reflux3for about one-half hour to de-
setroy the organic present. Evaporate to dryness, flame
gontly to destroy organic-matter and dlesoclve the resldue
wlth 2 drops HNO3 and evaporate to dryness on a water tath.
Pipette three 1 ml portlons.of 8 M NH,NO; in 2 M HNO,,
dlssolve the evaporated U fraetlion 1n one 1 ml portion.
Place the other 2 portions ln two 15 ml cones for scrub
solutions.,

Extract the U with four 2 ml portlons of dlethyl ether, add~
ing 100 X of conec. HNO3 before each extractilon. Sorub each
extract In turn with 2 serub solutilons prepared in Step 12.
Evaporate the comblned ether extracts over 1 ml of HEO in

a 15 ml econe, Evaporate.to dryness.

Add 3 drops of HC1l and 1 drop of HN03, and evaporate to dry-

270
PROCEDURE 4 (Continued)

ness repeatedly untll the organlc ls destroyed. Flame gently
to expell ammonlum salte. Then dlssolve 1n HNO3 and evap=
orgte to dryness on a water bath. Add 50 : of 0,05 l\_d.HNO3
to the dry cone and submlt sample for masse spectrographic

analysls.

Plutonlum Calculatlon:

To determine the amount of Pu in the origlnal sample, 1t
13 necessary to measure 1ln a Frilach chamber the alpha spectrum
of the plate prepared in Step 8. The ratio of Pu-239 and Pu-240
activity to Pu-236 activity is calculated. If the ratio 1s mul-
tiplied by the original activity of Pu-236 fidded, the original
activity of Pu-239 plus Pu-240 can be obtalned. From the mass
anslysis a Pu-239 to Pu=-240 atom retlo 1s obtained. The speci-
fic actlivity of the mixture 1s calculated from that of the indl-
vidual isotopes. The Pu-239 plus Pu-240 activity can be con-
verted to Pu-239 plus Pu-240 welght by dividing this activity
by the speclfic activity of the mixture.

Uranlum Calculation:

The ratio of the various U lsotopes o U-233 from the mass
spectrometer data 1s multiplled by the amount of U-233 splke
originally added to the sample to obtaln the amount of each

uranlum isctope present 1ln the original sample.

PROCEDURE 5: Spectrophotometrlec Exftraction Methods Specifilo

for Uranium.

Source: W. J. Maeck, G. L. Booman, M. C. Elliott, and J. E.
Rein, Anals Chem. 31, 1130 (1959).

Abstract

Uranium as tetrapropylammonium uranyl trinltrate 1s quan-

271
PROCEDURE 5 (Continued)

tltatively separated from largé quantities of dlverse ions by
extraction into methyl 1sobutyl ketone (4-methyl-2-pentanone)
from an acld-deflcient aluminum nltrate salting solutlon. Milll-
gram levels are determined by a direct absofbance measurement
of the trinitrate complex 1ln the separated organic phase at
352 my. Mlerogram amounts are determined by adding dibenzoyl-
methane (1,3-diphenyl-l,3-propanedione) in an ethyl alcohol-
pyridine mixture to the separated organic phase and measuring
the absorbance of the chelate at 415 mu. The coefficlent of
variation 18 less than 1% at the 10-mg. and 25-y levels. The
1imit of sensitivity 1s 0.8 v for the dlbenzoylmethane method.

Apparatus and Reagents

Absorbance measurements of the tetrapropylammonlium uranyl
trinitrate complex were made wilth a Cary Model 14 recording
Bpectrophotometer and l-cm. Corex cellg. A Teflon 9 x 9 x 6 mm.
spacer placed in the bottom of the cells permlits absorbance
measurements wlith 2 ml. of sample. Abaorbance measurgments of
‘the dlbenzoylmethane complex were made wlth a Beckman DU spec=
trophotometer and 5-c¢m. Corex cells.

Extractions were made 1in 125 x 15 mm. teat tubes with
polyethylene stoppers. A mechanlcal extraction device? was
used for agltatlon.

Reagent grade inorganic and Eastman Kodak Co. White Label
organlc chemlcala were used without purlficatlon. Dilstilled
water was used throughout. The uranlum solutions were pfepared
by dlasolving purlfled black oxlde; U308‘ in a slight excees of
nitric acid, and making to volume with water.

The dibenzoylmethahe reagent 1s prepared by dlssolving
0.1140 gram'of dibenzoylmethane in 500 ml. of a 5% solution
(ve/v.) of ethyl alecohol in pyridine.

Salting and Scrub Solutions. A. 0.005M Tetrapropylammonium

272
PROCEDURE 5 (Continued)

Nitrate, 1N Acld-Deflclent Salting Solutlon. Place 1050 grams
of aluminum nltrate nonahydfate in a 2=l1liter beaker and add
water to a volume of 850 mi. Heabt, and after dissolutlion add
67.5 ml. of concentrated ammonium hydroxide. Stir for several
minutes until the hydroxlde preclpitate dilssolves. Cool to less
than 50°C.,add 10 ml. of 10# tetrapropylammonium hydroxide,
and stir untll dilssolved. - Transfer to a l=llter volumetrlc
flaek and make to volume wlith water. A prellminary extractlon
with methyi lsocbutyl ketone 1ls suggested to remove uranlum
contaminatlon in whlch case tetrapropylammonium hydroxide will
have to be re-added.

B. 0.025M Tetrapropylammonium Nitrate, 1N Acld-Defilolent
Salting Solutlon. Same as A except that 50 ml. of 10% tetra=-
propylammonium hydroxide 1s used.

C. 0.25M Tetrapropylammonium Nitrate, 1N Acld-Deficlent
Salting Solutilon. Neutralize 100 ml. of 10% tetrapropylammonium
hydroxlde to pH 7 with 5N nitric acld. Transfer to a large
evaporating dish and let stand untll a thlck crystal slurry
forms (which may take as long as 4 days). Place 210 grams of
aluminum nitrate nonahydrate in a 400-ml. beaker and transfer
the tetrapropylammonlum nitrate cryetals Into the beaker wlth
20 ml. of water. Stilr and add water to a volume of approximately
180 mi. Add 13.5 ml. of concentrated ammonium hydroxide and
fstir until dissolution 1s complete {which may require several
hours). Transfer to a 200-ml. volumetric flask and make to
volume wlth water.

D. Scrub Solutlon for Dibenzoylmethane Method. Add 940
grams of aluminum nltrate nonahydrate, 33 grams of tartarilc acld,
31 grams of oxalic acld, and 64 grams of (ethylenedinitrilo)-

-~ tetraacetic aclid to 100 ml. of water and 150 ml. of concentrated

ammonium hydroxlide. Heat with stirring until dissolved. Cool,

273
PROCEDURE 5 (Continued)

filter, transfer to a l-llter volumetric flask, and make to
volume wlth water. Remove uranium contamlnation by a methyl
1sobutyl ketone extractlon.

E. Speclal Solutlions. The following salting and scrudb
golutlone are used in the dibenzoylmethane method for samples
containing cerium(IV) or thorium.

1. Prepare an alumlnum nitrate saltling solutlon as A, but
omlt the tetrapropylemmonlum hydroxilde.

2. Prepare a sc¢rub solution by dissolving 154 grams of
ammonlum acetate and 20 grams of the sodlum salt of dlethyldi-
thlocarbamate In water to a volume of approximately 900 ml.
AdJust to pH 7, fllter, and make to a l-liter volume wlth water.

3. Prepare a mercurlc nltrate solution by dissblving 0.063
gram of mercurlc nitrate in 90 ml. of 1N nitric acld and making
to a2 100-ml. volume wlth 1N nitrlc acld.

Procedures

Milligrafi Amounts of Uranium. Wlth aqueoua samples of 0.5
ml. or less and contalning up to 2 meq. of acld, 0.5 to 12 mg.
of uranium can be extracted from a saltling solution whilch is
0.025M in tetrapropylammonlium nltrate and 1N acid—deficient.
Samples of hlgh acldlty should be neutrallzed to less than 2 meq.
of free acld, or a salting solution which 1s 2N acid-deficiefit
can be used for samples contalning up to 6 meq. of acild. If
cerium(IV) and thorium are present, the absorbance from uranium
will be maximum 1f the combined uranium(VI), thorium, and cer=
1um(IV) do not exceed 0.05 mmole in the sample aliguot. Samples
that contain more than 0.05 mmole of comblned uranium, cerium-
(Iv), and/or thorium can be analyzed after dilutlon, provided
the resulting sample aliquot contalns more than 0.5 mg. of
uranium. If this condltlon cannot he met, the 0.25M tetrapro-

pylammonlum nltrate salting solutlon 1s used, which can accommo-

274
PROCEDURE 5 (Continued)

date up to 0.5 mmole of comblned uranium, cerium(IV), and
thorlum.

Pipet a sample of 0.500 ml. or less, contalning from 0.5
to 12 mg. of uranium, into a test tube contalning 4.0 ml. of
salting solution B or C. Add 2.0 ml. of methyl lsobutyl ketone,
stopper, and extract for 3 mlmutes. Centrifuge to facllitate
phase separation. Transfer as much as possible of the organlec
phase with a micropipet to a l-om. cell contalning the Teflon
spacer. Measure the absorbance at 452 mu agalnst & blank pre-
pared by substituting 1N nitric acid for the sample.

Microgram Amounts of Uranium. Aqueous sample allquote
containing up to 2 mg. of uranium and as much as &E in acid can
be quantitatively extracted from a salting solution 0.005M in
tetrapropylammonium nitrate? . Neutrallze samples of higher
acldity to less than 8N before extractlon.

SAMPLES WITHOUT CERIUM(IV) AND THORTUM. Pipet a sample
of 0.500 ml. or less, containing from 0.8 to 75 ¥ of uranium,
into 2 test tube contalnlng 5.0 ml. of salting solutlon A.

Add 2.0 ml. of methyl 1sobutyl ketone, stopper, and extract for
3 minutes. Centrifuge to facllitate phase separation. Transfer
as much as possible of the organic phase to a test tube con-
taining 5.0 ml. of scrub solution D, stopper, and mix for 3
minutee. Centrifuge to facllitate phase separatlon. Remove

a 1.00-ml. aliguot of the organlc phase and transfer to a 25-
ml. flask. Add 15 ml. of the dibenzoylmethane-pyridlne reagent
and théroughly mix. Allow to stand 15 mlnutee, tranasfer to a
5-cm. Corex cell, and measure the absorbance at 415 mp oompared
to a blank prepared by substituting 1N nltric acld for the sam-
ple aliquot.

SAMPLES CONTAINING CERIUM(IV) OR THORIUM. Pilpet a sample

of 0.500 ml. or less, contalning from 0.8 to 75 v of uranium,

275
PROCEDURE 5 (Continued)

into a test tube contalning 5.0 ml. of the salting solutlon E-1.
Add 4.0 ml. of methyl isobutyl ketone, stopper, and extract for
3 mlnutes., Centrifuge to facllltate phase separatlion. Transfer
as much as poaslble of the organlc phase to another tube cone
taining 5.0 ml. of scrub solutlon E-2, stopper, and mix for 20
minutes. Centrlfuge as before. Tranafer at least 3 ml. of the
organlc phase to a fest tube contalnlng 5.0 ml. of saltlng solu-
tion E-1. Add 0.5 ml. of scrub solutlon E-3, stopper; mix for
10 minutes, and centrifuge. Remove a 2.00-ml. allquot of the
organlc phase and transfer to a 25-ml. flask. Add 15 ml. of the
dibenzoylmethane-pyrldine reagent and thoroughly mix. Let stand
15 minutes, transfer to a 5.0-cm. Corex cell, and measure the
absorbance at 415 mp compéred to a blank prepared by substitute

ing 1N nitrilc acid for the sample allquot,
Calibration. Two different standards contalning levels of

uranium sequlvalent to approximately 0.1 and 0.7 absorbance are
processed. The concentration of samples 1s establlshed by the
average absorptivity of these standards provlded agreement

within statlstical 1imits (95% confidence level) 1s obtained.

2 . J. Maeck, ¢. L, Booman, M. C. Elllott, J. E. Rein, Anal.
Chem. 30, 1902 (1958).

PROCEDURE 6: Determination of Uranium in Uranium Concentrates.
Source: R. J. Guest and J. B. Zimmerman, Anal. Chem. 27, 931 (1955).

Abstract
A method 1s described for the determinatlion of uranium in high grade
uranium material. Uranium ls peparated from contamlnants by means
of an ethyl acetate extraction using aluminum nitrate as a salting

agent. After the uranium hase been strlipped from the ethyl acetate

276
PROCEDURE 6 (Continued)

layer by means of water, colorlmetrlc determination of the uranium
is carrled out by the sodlum hydroxlde-hydrogen peroxlde method.
The procedure 1B accurate, rapld, and easlly adaptable to routine

work.

Reagents and Apparatus

Reagents. Ethyl acetate (Merck, reagent grade).

ALUMINUM NITRATE SALTING SOLUTION. Place approximately 450
grams of reagent grade (Mallinckrodt) alumlnum-nitrate [Al(NO3)3-
9H201 in a 600-ml. beaker and add 25 to 50 ml. of distillled water.
Cover the beaker and heat the mixture on a hot plate. If & clear
solutlon does not result after 5 to 10 minutes of bolling, add 20
ml. of water, and contlinue the bolling for 5 more mlinutea. Repeat
this step untll a clear solutlon 1s obtalned after bolling. Remove
the cover glass and concentrate the solutlon by bollling untll a
bolling point of 130°C. 18 reached. Cover the beaker with a watch
glass and elther transfer the solution to a conatant temperature
apparatus or keep the solutlon warm, finally heating to just under
boiling before use. If the solutlion 13 allowed to cool to approxi-
mately 60°C., recrystallizatlon of aluminum nitrate willl take place.
It is neceassary, therefore, to dllute the salting agent solutlon by
about one third ln order to prevent recrystalllization 1f the solu-
tion cools to room temperature. Accordingly, 1f the solutlon 18 to
stand overnight, add 35 ml. of dlstlilled water per 100 ml. of salt-
inz agent solutlion, mlx well, and cover.

If the salting agent solutlon 1s. to be atored, the following
procedure has been found convenlent. AdJjust the solutlon to the
proper concentration (boiling poilnt, 130°C.) and tranafer to a 100-
ml. three-necked reaction flask set on a heating mantle. AdJust the
heating so that the temperature of the solutlon 1e kept at about
110°C. In one of the necks place a water condenser, in another neck

a. thermometer, and Iin the third neck a removable ground-glass stop-

277
PROCEDURE, 6 (Continued)

per. Thlse third neck 1s utilized for plpetting the ealting agent
solutilon. |

ATLUMINUM NITRATE WASH SOLUTION. Add 100 ml. of alumlnum nltrate
salting solution (boiling point, 130°C.) to 73 ml. of distilled
water and 4 ml. of concentrated niltric acid.

Apparatus. Beckman DU spectrophotometer.

Heating'mantle. .

Three-necked reaction flask (1000 ml.).

Water condenser.

No. O rubber stoppers. Boil twlce 1n ethyl acétate before use.

Sixty-milliliter separatory funnels (Squibb, pear-shaped).

Procedure

Sample Dissolution. Place an appropriate quantity (1 to
5 grams) of the sample in a tared welghing bottle, stopper the
bottle, and welgh the bottle and contents immediately. Carry
out a molature determination on a separate sample 1f uranilum
1s to be calculated on a dpy welght basis.

Bring the sample into solutlon iIn one of three ways: (1)
nitric acid treatment, (2) multiacid treatment, or (3) sugar
carbon-godium peroxide fusion.

For the nltric acld tfeatment, dlssolve the sample in a
sultable quantity of nltric acld and transfer the solution and
insoluble resldue into an appropriate volumetric flask and make
up to volume. Regulate the dllutlon so that the aliquot chosen
for extractlion will contaln between 10 and 30 mg. of uranium
oxlde if the final dllutlon for the colorimetric finish is to
be 250 ml. AdJjust the acldlty of the sample solution to about
5% in nitric acid. |

If nitric scld treatment 1s not sufficient, treat the
Sample wlth hydrochlorilc acld, nltrlc acid, perchloric acld,
and finally sulfurle acid. If necessary, add a few mllliliters

278
PROCEDURE 6 (Continued)

of hydrofluoric acld. Fume the sample to dryness and leach
the resldue wilth nltrle aclid, finally transferring the solution
and resldue to an appropriate volumetric flask and adjusting
to 5% in nitric acld a8 in the glngle acld treatment.

If the sample 1B refrgctory, use the sugar carbon-sodium
peroxlde fusion method described by Muehlbergi. After dilssolu-
tion of the sample 1n thls manner, transfer the acldified solu-

tlon to an approprilate volumetrilc flask and dllute so that the
final solutlon 1s 5% in nltrilc acid.

Allquot solution samples dlrectly or dllute as required for
an gkthyl acetate extraction. If the sample 18 aliquoted di-
rectly for an extraetlon, add 5 drops of concentrated nitriec acild
per 5-ml allquot of sample and standards before extraction. Where
gamples are dlluted before aliquots are taken for extractlon,
adjust the acidlty so that the final volume 1s 5% in nitric ecid.

Ethyl Acetate Extractlon. Place an appropriate aliquot

 

(usually 5 ml.) in a 60-ml. separatory funnel, the stopcock of
which has been lubrlcated wlth sllicone grease. Add, by means
of a graduated pipet, 6.5 ml. of alumlnum nitrate solutlon per
5 ml. of sample solutlon. The aluminum nitrate saltlng solu-
tion should be added while hot (above 110°C.). Cool the solu-
tlon to room temperature and add 20 ml. of ethyl acetate.
Stopper the separatory funnels with pretreated rubber stoppers.
Shake the mixture for U5 to 60 seconds. Occaslonally erystalll-
‘zatlion will take place In the separatory funnel near the stop-
cock. In such a case place the lower part of the separatory
funnel 1n a beaker of hot water untll the solidifled portion
dissolves.

After the layers have separated, draln off the aqueous
(lower) layer. Occaslonally a cloudiness will appear at the
boundary of the aqueous and organlc layer. Thls cloudy portlon
should not be dralned off. Add 10 ml. of zlumlnum nitrate wash

279
PROCEDURE 6 (Continued)

solution to the funnel and agaln shake the mixture for 45 to 60
seéonds. Draln off the aqueouB layer, once again belng careful
to retaln the cloudy portion at the boundary In the funnel.
Rinse Inslde the stem of the separatory funnel with a stream of
water from a wash bottle.

Water Stripplng of Uranlum from Ethyl Acetate Layer Followed
by Sodium Hydroxlde=Hydrogen Peroxlde Colorimetric Finlsh. Add
15-ml. of water to the separatory funnel contalning the ethyl
acetate, stopper the flask, and shake the mlixture for about
1 minute. After washlng off the stopper with water, drain the
aqueous layer Ilnto a volumetrle flask of sultable slze and wash
the Beparatory funnel and ethyl acetate layer 4 or 5 times with
5=ml. portlons of water by means of a wash bottle. Combine the
aqueous fractions.

Add enough 20% sodium hydroxide solution (w./v.) to neu-
tralize the solution and dlssolve any preclpltated aluminum
hydroxide, then add 10 ml. in excess per 100 ml. of final
volume. Add 1 ml. of 30% hydrogen peroxide per 100 ml. of final
volume and make up the volume to the mark wlth distilled water.
Read the absorbahce after 20 minutes on the Beckman DU spectro=
photometer at 370 mp agalnst a reagent blank, using l-cm. Corex
cells and a ellt wldth of 0.2 mm. Compare the absorbances of
the samples agalnst the absorbances of astandard uranium solu-
tlons which ha#e been carriled through the procedure at the same
time. Choose the standards so that they cover the range 1nto
whlch fhe samples are expected to fall, using a ratio of one
standard to six samples. In practlce 1t 18 customary to work
between the limits of 10 and 30 mg. of uranlum oxide. This 1ia
arranged by estlmating the requlred sample welghts and diluting
and samplling accordingly. The final volume for colorimetric
reading 1s usually 250 ml.

280
PROCEDURE 6 (Continued)

Double Extraction of Uranium wlth Ethyl Acetate Followed
by Appllcatlon of Differentlal Colorimetry. Urafiium determina-
tions requiring the highest accuracy may be carrled out by a
double extraction of uranium with ethyl aceftate followed by the
applicatlon of differentilal colorlmetry as desoribed by Hiskey
and o‘i:he::'Es.E:£ In such a case 1t 1ls recommended that between
100 and 150 mg. of uranium oxlde be extracted, and a wave length
of 400 me be used durilng the colorimetric finish. The procedure
described below has been found satisfactory.

Extract an approprlate allquot of the sample solution with
20 mi. of ethyl acetate aB descrlibed above. Draw off the a-
quecus layer into a second separatory funnel contalning 10 ml.
of ethyl acetate. Stopper the funnels and shake the mlixture for
45 to 60 seconds. Draln off and discard the agueous layer. Add
10 ml. of aluminum nitrate wash solution to the flrst ethyl ace=
tate extract, stopper, and shake the mlixture for 45 to 60 seconds.
Drailn off the aqueous layer Into the separatory funnel containing
the second ethyl acetate extract, stopper, and shake the mixture
" for U5 to 60 seconds. Draln off and discard the aqueous layer.
Combine the ethyl acetate fractions. Rinse the second separa-
tory funnel wilth 20 ml. of water, dralning the washlngs 1lntc the
separatory funnel containlng the comblned ethyl acetate frac-
tions. Shake the mixture for 1 minute. Continue the water
stripplng as descrlbed above, collectling the fractions 1n an
approprlate volumetrlc flask. Finish colorlmetrlcally as de=-
scribed previously, allowing the strongly colored solutlon to
stand 1 to 2 hours to ensure stablllty before reading as a fading
effect of about 0.005 absorbance (optical density) has some-
times been noted on freshly prepared samples.

Read the absorbance of the sample solution on the Beckman

DU spectrophotometer at 400 mp agalnst a reference solutlon

281
PROCEDURE 6 (Continued)

whilch containse a known amount of uranium end hfis been carried
through the extractlon and color development procedure 1ln the
same manner as the sample. Alao carry along other standards
contalning slightly higher and lower amounts of uranlum than
the sample. Determine the concentratlion of uranium in the
aafiple elther by the callbration-curve method or the correction
method, as described by Neal€. If the amount of uranium in the
sample 1s not known, make a tesat run by taking an aliquot of the
sample solutlon and assaylng for uranium by the more rapid sin-
gle extractlion method. The standard solutlons to be used can
then be chosen according to the result obtained.

Removal of Interfering Thorium. After an ethyl acetate ex-
traction, strlp the uranium Iin water from the ethyl acetate and
collect the uranium fractlon 1n a 250-ml. beaker. Add snough
| 20% (w./v.) sodium hydroxide solution to neutralize the solution
and redissolve precipitdted aluminum hydroxlde. Then add 10-
ml. excess of 20% sodium hydroxide solutlon and 1 ml. of 30%
hydrogen peroxide per 100 ml. of final volume. Filtef the golu=
tion through an ll-cm. 41H filter paper (Whatman), collecting
the flltrate in a volumetrlc flask of sultable slze. Wash the
paper and precilpltate once with 5 ml. of a solution of 2% sodium
hydroxide contalning 0.1 ml. of 30% hydrogen peroxide. Re-
dlssolve the preclpltate by washing the paper wlth 10 ml. of
10% nitric acld solution, collecting the washings 1n the original
beaker. Neutrallze the solutlon with 20% sodium hydroxide
solution, and add 2 ml. in excess. Add 0.5 ml. of 30% hydro-
gen peroxlde, and filter off the precipltate on the origlnal
filter paper, washing as before and collecting the filltrates
in the original volumetric flask. If the precipltate on the
paper 1s colored yellow, repeat thls step. Make the solution

in the volumetrlc flask up to volume and read the absorbance

282
PROCEDURE 6 (Continued)

on the spectrophotometer. Carry standards through the same

procedure as the samples.

2 W. L. Muehlberg, Ind. Eng. Chem. 17, 690 (1925).

o

C. F. Hiskey, Anal. Chem. 21, 1440 (1949).

lo

C. F. Hliskey, J. Rabinowitz, and I. G. Young, Anal. Chem.
22, 1164 (1950).

e

G. Wo C. Mllner and A. A. Smales; Analyst 79, 414 (1954).

|

W, T. L. Neal, Analyst 79, 403 (195%).

[

I. G. Young, C. F. Hiskey, Anal. Chem. 23, 506 (1951).

PROCEDURE T7: Uranium-237.
Source: B. Warren, LA-1721 (Rev) (1956).

l. Introduction

In the carrler-free method for the determlnation of U237,
the principal decontamination step {which is preceded by a
La(OH)3 scavenge and partlal removal of plutonlum as the cup-
ferron complex) 18 the extraction of uranium into 30% TBP
(tertiary butyl phosphate) in benzene. Addltlional decontam~
ination 18 effected by adsorptlon of uranlum, firgt on an anlon
and then on a catlon exchange resin. The uranlum 1ls finally
electroplated on platinum. The chemical yleld is 40 to 60%
and 18 determined through the use of U233 tracer. The U237
18 BP-counted in a proportional counter with a 2.61—mg/cm2 Al
abgorber, and from the number of counts the number of atoms
of the lsotope 18 calculated. Four samples can be run in

about 6 hours.

283
PROCEDURE 7 (Continued)

2. Reagentsa
U233 tracer: amount determined by the c-countlng technlque

employed

La carrier: 10 mg La/ml [added as.La(N03)3 . 6320]

Fe carrier: 10 mg Fe/ml [added as Fe(N03)3 + 9H,0 in very
dilute HN03]

HC1: 0.1M

HC1: 5M

HC1l: 10M

HCl: conc.

HNO3: 3M
HNO: 5M
HN03: conac.
NH40H: conc.

NH,OH - HCl: SM

2
(NH4)20204 in H,01 L

TBP (teriary butyl phosphate): 30% by volume in benzene (Note 1)
Aqueous cupferron reagent: 6%

Methyl red indicator solution: 0.1% 1n 90% ethanol

Methanol: anhydroue

Chloroform
NHE: gas
012: gas
3. Equipment
Centrifuge

Fisher burner

Block for holdlng centrifuge tubes
Pt-tipped tweezers

Steam bath

S5-ml syringe and tranafer plpets
Mounting plates L

284
PROCEDURE 7 (Continued)

40-ml centrifuge tubes: Pyrex 8140 (three per aliquot of sample)
Jon exchange columns:

8 om x 3 mm tublng attached to bottom of 15-ml centrifuge

tube

Anilon resin: 5 cm Dowex A2-X8, 400 mesh, (Note 2)

Cation resin: 5 cm Dowex 50-X8, 100 to 200 mesh, (Note 2)
Stlirring rods
Motor-driven glass stirrers
Plating set-up: same as that used 1n Procedure 1 except that
the Pt cathode is a 1" dlsk and the glass chimney has a 7/8"
1.d4.

4, Procedure

Step 1. To an aliquot of sample not exceeding 20 ml 1n
a 30-ml 6entr1fuae tube, add 1 ml of U233 tracer and 3 drops

of La carrier, and bubble 1n NH, gas untll the preclpltate

which forms coagulates. Digest3for 15 min on a2 steam bath,
centrifuge, and discard the supernate.

Step 2. Diseolve the precipltate in 0.6 ml of conc. HCl
and dilute to 10 ml with H,0. Add 5 drops of 5M NH,OH + HCl
and 2 drops of Fe carrier (if this element 1s not already pre-
sent), and allow to stand for 10 min. Add 4 ml of chloroform,
6 ml of 6% oupferron,land extract the Pu(IV)-cupferron complex
by Btirring for 2 min. Remove the chloroform layer by means
of a transfer plpet and diacard. Extract the aqueous phase.
three addltlonal times with chloroform. To the aqueous layer
2add 3 drops of La carrier and bubble iIn NH3 gas until the pre-
clpitate formed coagulates. Dlgest for 15 min on a steam bath,
centrifuge, and dlscard the supernate.

Step 3. Diseolve the precipitate in 1.6 ml of conc. HNOB,
dilpte $0 5 ml with H20, add 2 ml of TBP solution, and stin

for 2 min. Draw off the TBP layer and transfer to a clean 40-

285
PROCEDURE 7 (Continued)

ml centrifuge tube. Extract again with 2 ml of TBP solution
and comblne wilth the previous extract. Add 1 ml of TBP solu-
tion to the original tube, draw it off, and comblne wlth the
other extracts.

Step 4, Wash the TBP extracts with two 3-ml portions of

5M HNO discarding the washings. Bubble 1n'Cl2 gas for 5 mln

’
at a vfgorous rate.

Step 5. Tranefer the solution to a Dowex A2 anlon ex-
change column. Permlt one-half of the solutlon to pass through
the resin under 8 to 10 1lb pressure. Add 1 ml of conc. HC1l to
the column and allow the remalnder of the solutlon to pass
through under pressure. Wash the column twice with 2-1/2 ml
of 10M ACl and then twice with 5M HC1l, dlscarding the washilngs.
Elute the U with two 2=1/2-ml portlons of 0.1M HCl, catching
the eluate 1n a clean 40-ml centrifuge tube.

Step 6. Dilute the eluate to 10 ml with H,0 and pass
through a Dowex 50 catlon exchange columm under 1 to 2 1b
pressure. Wash the resin three times with 2-1/2-ml portions
of 0.1M HCl and discard the washings. Elute the U wlth two
2-1/2-ml portions of 3M HNO3 into the plating cell.

Step 7. Add 5 ml of 4% (NH4)20204, 3 drops of methyl
red indicator solution, and make basic by the dropwlse addition
of conec. NH40H. Make the solution Just red to the indilcator
by the dropwise addition of 6M HN03, and add 3 drops 1ln ex-
cess. Plate at 1.1 amp and 8 volts for 1% hr at 80°C, At the
end of the flrst 10 min, add 3 drops of methyl red solution

and make acld with 6M HNO Check acldity at two additional

3.
10-min intervals, and at the end of 40 min add 3 drops of
cone. NH40H. At 10-min Intervale thereafter check to see that
the plating solution 1ls Just baslc to the indlecator. Remove

the cell from the water bath; wash three tlimes with methanol,

286
PROCEDURE 7 (Continued)

and dismantle the cell, carefully keeping the Pt dlsk flat.
Flame the disk over a burner. a-count the U233, mount, and
B-count in & proportlonal counter wilth a 2.61-mg/cm2 Al ab=-
sorber.

Notes

1. The TBP is purified before use by washing first with
1M NaOH and then with 5M HN03.

2. Before use, both the anion and cation resin are
washed alternately at least flve tlmes each wlth H20 and HC1,
and are then stored in H20.

3. See Procedure 1 for the correctlon for le actlvity

per mg U308 on plate.

PROCEDURE 8: Radloassay of Uranium and Plutonium in Vegeta-
tion, Soll and Water.

Source: E. L. Gelger, Health Physics 1, 405 (1959).
Abstract

A method 1s dlscussed for the separation of uranium
and plutonium from vegetatlon, soll and water. The method
is based on the extractlion of uranium and plutonium from 4
to 6 N nitric acid into 50% tri-n-butyl phosphate in n-tetra=-
decane dlluent. Uranlum and plutonlum are recovered together
with sufficient reduction 1n total sollds to allow a-counting
and pulse heilght analysis. Data from several hundred "spiked"
gsamples to which uranium and plutonium were added 1ndlcate a
nearly equal recovery of uranlum and plutonium. Average re-
coveries are 76 * 14 per cent for vegetation, 76 + 16 per
cent for soll, and 82 + 15 per cent for water. The procgdure

1s designed for samples that may be collected and analyzed

287
PROCEDURE 8 (Continued)

for radloactivity as a part of a health physics reglonal

monltoring program.

Procedures
Preparation of samples

Vegetatlon. Cut oven-dried vegetatlon into small pleces
and welgh 10.0 g into a 150 ml beaker. Heat the sample at
600°C, starting with a cold muffle furnace. When only white
ash remalns, remove fthe beéker from the muffle furnace and
allow to cool. Carefully add 2 ml of water, then add 10 ml
of 8 N HN03—O.5 E_Al(N03)3 solution. Cover the beaker with
a watch glase and boll the solutilon for 5 min. Allow to cool,
add 1 ml of 2 M__KNO2 golutlon and transfer the sample to a
100 ml centrifuge tube. Use 4 fl_HN03 to complete the transfer.
Centrifuge and decant the supernate lnto a 125 ml cylindrilcal
geparatory funnel graduasted at 30 ml. Wash the residue with
4y N HN03, centrifuge, and decant the wash solutlon to the
separatory funnel. The acid normality of the combined solu-
tions at this point 1s 4-6 N and the total volume should not
exceed 29 ml. Proceed to the extractlon procedure.

Soll. Grind 5 g of oven-dried soll with a mortar and
peatle untll the entlre sample ocan pase through a 200-mesh
sleve. Welgh 1.0 g of the 200-mesh soll into a 50 ml platinum
cruclble and heat the sample at 600°C for 4 hr. Remove the
gample from the muffle furnace and allow to cool. Add 3 ml of
T0% HNO3 and 10 ml of 48% HF then stir the sample for 2-3
min wlth a platlnum rod. Beat the sample 1ln a 200°C sand
bath untlil all tracees of molsture are removed. Repeat thls
HN03—HF treatment belng careful that the sample 18 completely
dry before proceedling to the next step. Allow the sample to
cool and then add 15 ml of 6 N HNO3-O.25 M Al(NO3)3 solution.

Cover wlth a watch glass and heat 1n the sand bath for 5 miln.

288
PROCEDURE 8 (Continued)

Allow to cool and decant the solution through a fllter, such
as Whatman no. 40, into a 125 ml e¢ylindricel separatory funnel
graduated at 30 ml. Leave as much of the resldue as possible
in the orucible and repeat the hot 6 N HNO4-0.25 M Al(NO3)3
treatment. Allow to cool and then fllter. Proceed to the ex-
traction procedure. |

Water. Place 1 1. of the sample 1n a 1.5 1. beaker and 1if
basic, neutralize with nitric acid. Add 15 ml of TO% HNO3 and
evaporate to 30-40 ml. Decant the solution through a filter,
such as Whatman no. 40, into a 100 ml beaker. Wash the 1.5 1.
beaker, the residue and the filter with 4 N HNOB. Evaporate the
combined solutlon in the 100 ml beaker to 5 ml. Add 20 ml of 4 N
HNOB, cover with a watch glass, and heat for 5 min. Transfer the
sample to a 125 ml cylindrical separatory funnel graduated at 30
ml. Wash the beaker with % g_HNO3 and transfer to the separatory
funnel, belng careful that the total volume 1In the separatory

funnel doea not exceed 29 ml. Proceed to the extractlon procedura.

Extraction

Add 1 .ml of 2 M KNO, to the sample in the 125 ml cyllndrilcal

2
geparatory funnel. Dilute to the 30 ml mark with 4 I‘_I_HNO3 and
stir the solution briefly. Add 30 ml of 504 TBF in n-tetradecane.
Agitate the solution vigorously for 4 min with an ailr-driven
stlrrer. Discard the acid portion (lower layer). Wash the TBP
portion with 4 Ij_.HNO3 and agaln dlscard the aclid portion. Back
extract with seven 15 ml portions of distilled water, collecting
the strilp solution 1n a 150 ml beaker. Evaporate the comblned
aqueous portlons to 10-~15 ml, then quantitatlively transfer the
solution to a flamed stalnless steel planchet. Allow to dry under
a hest lamp, flame the plancfiet to burn off organlec residue, end

count on an a-counter. Retaln for pulse-helght analysls 1f the

a-count exceeds a speclfled level.

289
PROCEDURE 9: Separation of Uranlum by Solvent Extraction with
Tril-n-octylphosphlne Oxlde.
Source: C. A. Horton and J. C. White, Anal. Chem. 30, 1779 (1958).

Abstract

A slmple, rapld method for the determination of uranium in
impure aqueous solutlons was developed. Uranium(VI) 1s extracted
by 0.1M trl-n-octylphoaphine oxlde 1n cyeclohexane from a nitrie
acid solutlion. A yellow color ls formed In an aligquot of the or-
ganlc extract by additlon of dlbenzoylmethane and pyridine in ethyl
alcohol. Interference by catlons 1s mlnlimized or eliminated by
selectlive reduoction, by fluoride complexatlon, or by absorbance
measurement at 416 mp rather than 405 mu, the wave length of
maxlmum absorbance, Interference by excess fluorlde or phosphate
18 eliminated by addition of aluminum nitrate before extractlon.
The range of the method 1ls 20 to 3000 ¢ of uranium ln the origlnal
golution, and the standard deviatlon is +2%.

Apparatus and Reagents

 

Absorbance measurements were made with a Beckman DU gpectro-
photometer;, using 1.00-cm. Corex or sllica cells.

Phase equlllbration for moat extractions was carrilied out in
the bottom portion of the apparatus (see accompanying figure).
Phase separatlon and removal of allquots of the upper organic
phage occurred after inverting the apparatus so that the solutlon
was 1ln the portlon of thls apparatus shown on top 1n the figure.

Some extractions were carrled out in 60- or 125-m]. separatory funnels.
STANDARD URANIUM SOLUTIONS. A stock solutlon of 24.0 mg. of

uranium(VI) per ml. was prepared by heating 7.10 gram of uranium
(Iv-VI) oxide (U308), prepared from pure uranium(VI) oxide (UO3),
in 10 ml. of perchloric acld to dlssolve 1t, and then dlluting
the resultant solutlon to 250 ml. with water. Dilutions of this
solution were made as required. Another standard sclutlon in 5%
sulfurilc acld was also used 1In checklng the spectrophotometric

callbration curve.

290
PROCEDURE 9 (Continued)

DIBENZOYIMETHANE. A solutlon that contalned 1 gram of
dibenzoylmethaene (1,3-diphenyl-1,3-propanedione), obtained from
Eastman Kodak Co., in 100 ml. of 95% ethyl alcohol was prepared
for use as the chromogenlc agent.

PYRIDINE. For most of the work, a solution prepared by
mlxing 1 volume of redilstllled reagent grade pyridine and 1 volume
of 95% ethyl alcohol was used.

TRI-n=-0CTYLPHOSPHINE OXIDE. A 0.10M solution of thls material,
prepared 1in the authors! laboratory, 1n cyclohexane, Eastman 702
or 7025, was used. Thls phosphlne oxlde 1s now avallable commer-
clally from Eastman (EK T440).

Sodium bisulfite, 10 (w./v.} % in water, stored at about 10°C.

Hydroxylamine sulfate, 2M 1n water.

Potassium fluorlde, 1M in water, stored 1n a polyethylene
bottle,

Procedure

Preliminary Treatment .A. Samples which do not contain inter-
fering lons. Pipet a 0.5- to 8-ml. aliquot of a solution in nitric,
perchloric, or sulfuric acld, estlmated to contain 15 to 2500 ¥y
of uranium(VI), into the bottom portion of the extraction vessel.
By the addltion of strong 10M sodlum hydroxide, nitric acld, or
sodium nitrate, adjust the solutlon so that a total aqueous volume
of 10 ml. will be 12 to 3N in hydrogen lon and 2 to 4M in nitrate
ion. For almost neutral solutlens, 2 ml. of concentrated nitric
acid wlll give the correct concentrations for a 10-ml. aqueocus-
volume. AdJust the total volume to 10 ml. Up to 12 ml. of aqueous
solution can be shaken with 5 or 10 ml. of extractant in the ap-
paratus wlthout undue splashing. If the total aqueous volume i1s
greater than 12 ml. after adJusting the acldlty and nitrate con-
Ltent, perform the extractlon ln a separatory funnel instead of the

speclal extractlon veasel.

291
PROCEDURE 9 (Contlnued)

B. Semples containing ilron(III), chromlum(VI), or vana-
dium(V). Pipet a 0.5- to 6-ml. aliquot of a solution in dilute
perchloric or sulfurlc medlum, estlimated to contaln 15 to 2500 vy
of uranium(VI), Into the bottom portlon of the extractlon vessel.
Reduce the iron(III) to iron(II), the chromium(VI) to chromium(III),
and the vanadium(V) to vapadium(IV or III) without reducing the
uranium(VI) to uranium(IV). Sodium bisulfite 1s a satisfactory
reductant 1f the solutlons are bolled to remove excess sulfur
dloxlde. Hydroxylamlne sulfate is also a satlsfactory reductant,
but amalgamated zinc 1s unsuitable. Add sufficlent nltriec acld or
sodium nitrate and water so that the final agueous volume of 8 to
12 ml. wlll be 1 to 3N 1in hydrogen lon and 2 to 4M in nltrate ion.

C. Samples contalning tiltanlum, thorlum, hafnium, zirconlum,
or iron(III), but only traces of alumirmum. Plpet a 0.5- to 6-ml.
aliguot of a solutlion in dilute niltrle, perchloric, or sulfurlo
acld, estimated to contaln 15 to 2500 v of uranium, into the
bottom of an extractlion vessel. Add sufficient base or acid, nltrate,
end water to glve 2 volume of about 8 ml., such that the solution
18 1 to 3N in hydrogen ion and 2 to 4M in nitrate lons. Add up to
e maxlmum of 2.5 ml. of 1M potasslum fluorlde when the concentra-
tlons of interfering lons are unknown. If hligh concentrations of
these lons are known to be present, additlional fluoride can be
tolerated.

D. Samples contalning excessive fluoride or phosphate.

Pipet an allquot 1nto an extractlon vessel, and adjust the acld
and nitrate contents aB in Treatment C. Add sufficlent aluminum
nitrate to complex the fluoride and phosphate estimated to be
present. The total volume should be 12 ml. or less.

Extraction. For amounts of uranium estimated to be under
about 1400 vy, pilpet 5 ml. of 0.1M tri-n-cctylphosphine oxlde in

cyclohexane 1nto the extractlion veasel contalning the treated

292
PROCEDURE 9 (Continued)

sample. For 1400 to 3000 v of uranlum, use 10 ml. of extractant.
Attach the top of the vessel and shake for 10 minutee on a re=
clprocating shaker. Invert the extractlion apparatus for separa-
tlon of the phases and removal of allquots of the upper organic

phase.

14mm.

A T

OS5 mm.

 

 

"'_f

$ 40/50

‘f

67mm.

_L
ST

EXTRACTION APPARATUS
USED IN Procedure 9.

 

- Color Development. Transfer by plpet a 1-, 2-, or 3-ml.
aliquot of the organlc extract into a 10- or 25-ml. volumetric
flask such that the final solutlon wlll contaln between 0.5 and
10 v of uranium per mi. For 10-ml., volumes, add 1.0 ml. of 50%

293
PROCEDURE 9 (Continued)

pyridine in ethyl alcohol, 2 ml. of 1% (w./v.) % dibenzoylmethane
in ethyl alcohol, and 95% ethyl alcohol to volume., For 25-ml.
volumes, use 2.5 ml. of pyridine and 5 ml. of dlbenzoylmethane.
After 5 or more minutes, measure the absorbance at 405 mp in l-om.
cells, using 95% ethyl alecohol a8 a reference solution. For sam-~
ples recelving Treatment C, also measure the absorbance at 416 mu.
A blank should be carrled through the enfire procedure dally.
Calculate the uranium content using the factors obtalned by ex-
tracting standard pure uranium solutlons as dlrected in Treatment

A, and measured at both 405 and 416 mu.

PROCEDURE 10: Radiochemlcal Determlnation of Uranium-237.
Source: F. L. Moore and S. A. Reynolds, Anal. Chem. 31, 1080 (1959).

Abstract
A radiochemical method for the determinatlon of uranium-237
1s based on complexling the uranyl lon in alkaline sclution with
hydroxylamine hydrochloride, followed by scavenglng wlith zlrconlum
hydroxlde and extraction of the uranlum from hydrochlorle acld
solutlon with trllsococtylamine-xylene. The technlque has been
applled successfully to the determinatlon of uranlum-237 1ln

homogeneous reactor fuel solutions.

Preparation and 3tandardlzatlion of Uranlum Carrier
Welgh ocut approximately 50 grams of uranyl nltrate hexshydrate.

Dissolve and make to 1 liter with 2 M nitrilc acld. Standardize

the carrier by plpetting 5-ml. alliquote into 50-ml. glase centrl-
fuge conesa and preclpltating ammonium dluranate by addlng concen=-
trated ammonium hydroxide. Fillter quantitatively through No. 42
Whatman fllter paper and lgnite 1ln porcelaln cruclbles at 800°cC.

for 30 minutes. Welgh as U308.

294
PROCEDURE 10 .{Continued)

Procedure

In a 40-ml. tapered centrifuge tube add 1 ml. of uranium
carrier and 0.2 ml. of zirconium carrier (approximately 10 mg. per
ml. of zirconium) to a sultable aliquot of the sample solution.
Dilute to approximately 10 ml., mlx well, afid precilpltate ammonium
dluranate by the additlon of conecentrated ammonlum hydroxlde.
Centrifuge for 2 minutes and dlscard the supernatant solutlon.
Wash the precipltate once with 15 ml: of ammonium hydroxide (1 to 1).

Dissolve the precipltate 1n 1 to 2 ml. of concentrated hydro-
chloric acld solutlon, dllute to about 10 ml., add 1 ml. of
hydroxylamine hydrochloride (5 M), and mix well. Precipitate
zlreconium hydroxlde by the addltion of concentrated ammonilum
hydroxide. Centrifuge for 2 minutes, add 0.2 ml. of zirconium
carrler, and etlr the supernatant solution, belng careful not to
disturb the precipltate. Centrifuge for 2 minutes. Add 0.2 ml.
of zirconlum carrler and repsat.

Transfer the supernatant solution to another 40-ml. centri-
fuge tuve, add several drops of phenolphthaleln, and adjust the
pH to approximately 8 by adding concentrated hydrochloric acid
solution dropwlse. Add an equal volume of concentrated hydro=-
chloric acid solutlon and extract for approximately 0.5 minute
wltha one-half volume portion of 5% (w./v.) trilsooctylamine-
xylene. Dilscard the aqueous phase. Wash the organlc phase by
mixing for 0.5 minute with an equal volume portion of 5 M hydro-
chloric acld solution. Repeat the wash step. Strip the uranium
from the orgenlc phase by mlxlng thoroughly with an equal volume
portion of 0.1 M hydrochlorie acld solution for 0.5 minute. Dlscard
the organlc phase.

Add 0.2 ml. of zirconlum carriler, mix well, and repeat the
" above procedure, beginning with the precipltation of ammonium

diuranate.

295
PROCEDURE 1C (Continued)

Flnally, precipltate ammonlum dluranate by the addltion. of
concentrated ammonium hydroxide. Centrifuge for 2 mlnutes. De-
cant and discard the supernatant solution. Filter on No. 42 What-
man fiiter paper and lgnite at 800°C. for 30 minutes.

Weligh the ufanium-oxide on a tared aluminum foll (0.0009
inoh), fold, and place in a 10 x 75 mm. culture tube. Insert a
sultable cork and count the uranium-237 gamma radloactivity in a
well-type sclntillstlion counter. Count the same day of the last
chemical separation.

Apply a blank correction 1f very low uranium-237 levels are
being determined. Determlne this correction by takling the pame
aliquot of uranium carrier through the exact procedure described
above. The blank correction 1s due primarily to the gamma radlo-

actlivlity assoclated wilth the uranium-235 1n the uranlum carrier.

PROCEDURE 11: Separatlion of Uranlum and Blsmuth.

Source: A. Krishen and H. Frelser, Anal. Chem. 29, 288 (1957).
Edltor'™a note: Uranlum has been geparated from a 5000=fold
excess of bismuth by the followlng method. Uranlum is, however,
not completely extracted (only 98.48% at pH values greater than
6.5). If this correction is applied, uranium 1s quantitatively

detergined by polarographlic means withln an experlmental error
of +1%,

" Reagenta
Acetylacetone. Commerclal acetylacetone was purilfied by
the method described by Stelnbach and Freisercé

Procedure
Analysis. The method of Souchay and Faucherre,E-uaing 0.1M
EDTA and 2M sodium acetate as a supporting electrolyte, was found
to be suitable in the presence of dissolved acetylacetone. The
half-wave potentlal was shifted to -0.47 volt but the wave helght .

was not affected.

296
PROCEDURE 11 (Continued)

Separatlon. Solutlions of uranyl sulfate contalning 0.1 and
1.0 mg. of uranium were mixgd with different amounts of bismuth
trichloride solutlion. A solutlon of the dlsodium salt of EDTA was
added to give a bismuth to EDTA ratio of 1 to 30. The pH of the
mixture was ralsed to 7.5 by careful additlon of 1§Isod1um hydroxide.
Then approximately 10 ml. of acetylacetone was added and the mix-
ture shaken for 10 minutes. The acetylacetone phase was separated,
filtered, and made up to a volume of 10 ml., of which 2 ml. was
wlthdrawn by a plpet iInto a 10-ml, boroslllicate glass volumetric
flask. The flask was very gently warmed untll the liquid was re-
duced in volume to about 0.5 ml. Then the supporting electrolyte
was added and the resulting solutlon deaerated for 5 minutes in
a 10-ml, Lingane-Lalitlinen H-type polarographlc electrolysis cell.
The polarogram was then recorded and the concentration of uranium

found from sultable callbration curves.

£ J. F, Steinbach, H. Freiser, Anal. Chem. 26, 375 (195%).

b p, Souchay, J. Faucherre, Anal. Chim. Acta 3, 252 (1949).

PROCEDURE 12: Isclatlon and Measurement of Uranlum at the
Microgram Level.
Source: C. L. Rulfs, A. K. De, and P. J. Elving, Anal. Chem.
28, 1139 (1956).
Abstract

A double cupferron separatlon of uranium using extractlon
has been adapted to the mlcro level. Uranium(VI).does not extract
in the first stage, which removee many potentially interfering
elements. Uranium(IV), obtained in the residual aqueous solutlon
by reduction at a mercury cathode, 18 simultaneously extracted as

the cupferrate into ether, from which 1t can be re-extracted lnto

297
PROCEDURE 12 (Continued)

nitric acid. A relatively simple one-plece glass apparatus is
used for all operations. The uranlum recoverfi at the milligram
level in an initisl 30-ml. sample wfia defiermined colorimetrically
as 94%. ¥ith 0.03 to0 0.13 7 of radioactive uranium-233 tracer

and 20 ¥ of natural uranium as carrier, the récovery is B86%;

the latter includes the addltional step of electrodeposltion of
the uranium onto a platinum planchet prilor to measurement by alpha
counting, which 18 only 94% complete. The decontamination possible
with this procedure was checked with 0.07 v quantities of uranlum-
233 in the presence of high mixed fisslon product activities; 85%
recovery. was obtained, contelning only 0.9% of the fission product
alpha activity (assumed to be uranium).

Apparatus
The reaction cell and simple eleotrical circult used 1s

shown 1n the aocompanying figure.

The electrolysls vessel, C, 18 protected from mercury lons
diffusiné from the working reference calomel electrode, A, by a
medium glase frit between B and C, and a fine frit backed with
en agar plug between B and A, Between runs, cell C 13 kept filled
wlth saturated potassium ohloride solution.

The apparafus for the electrodeposlitlon of uranium onto
platinum disks or planchets and for alpha-countlng measurement
of the resulting uranium plates have been deseribed.£ Beta
activity was measured by a chlorine-quenched argon=filled Gelger-
RMuller counter (1.4 mg. per sq. cm. of window) with a Model 165
scaler; a scintillation well counter with a thallium-activated
godium iodide erystal and a Model 162 scaler was used for gamma-
activity measurement of solutions (ca. 5 ml.) contained in a 13
x 150 mm. test.tube. The scalers and counters are made by the
Nuclear Inptrument and Chemlcal Corp. For examlnation of the

gamma-rey spectrum, a gamma-ray sclntillation spectrometer (bullt

298
PROCEDURE 12 (Continued)

| in the Department of Chemlstry, University of Michigan) was used
through the courteasy of W. Wayne Melnke.

Reggents
All chemlcals used were of C.P. or reagent grade unless

otherwise speclfied. The ethereal cupferron solution used (200
to 300 mg. of cupferron per 50 ml.) was actually a hydrogen oup-
ferrate solution; the ether and cupferron were mixed ln s mixing
eylinder with 5 to 10 ml. of 10 to 20% sulfuric acid and shaken

until dissolution was complete.

Procedures

Reductlve Extractlon. At the commencement of a run, bhrildge
B 18 flushed through stopcock 2 by filling B with fresh potasslum
chloride solution from the funnel through 1. € is dralined and
rinsed; 1 18 left open for a time to flush the frit. With 3 cloeed,
4 to 5 ml. of triple-distlilled mercury 1s placed in C. About 30 ml.
of uranyl sulfate solution (0.5 to 5 mg. of uranium and 0.5 to 1.5%
in sulfuric acld) is added and a potential of -0.35 volt vs.
S.C.E. 18 applled to the mercury. About 15 to 20 ml. of the
ether cupferron solution lg added. Stirring 1s adjusted at Just
over the minimal rate for efficlent current flow (usually about
0.2 ma. flows without stirring and 1.2 to 2.6 ma. with stirring).

Stopcock 1 is opened for about 30 seconds at approximately
S-minute .intervals throughout the run to minimlze any loss of
uranium into the bridge. A% 15- or 20-minute intervals, stirring
18 interrupted, the ether extract 1s bled through stopcock 4 into
cell D, and 15 to 20 ml. of fresh ether-cupferron solution 1s added.
Runs of 40- to 55-minute total duration appear %o be adequate.
Three increments of ether-cupferron solutlon were usually used,
' followed by a 5= to 10-ml. pure ether rinse at the conclusion of
“the run. (See Note 1.)

299
PROCEDURE 12 (Continued)

Stirrer

 

 

 

 

 

 

 

 

 

O SR

 

 

Potentio-
meter |

 

 

 

 

 

 

% 5ma‘.-

 

 

ELECTRICAL CIRCUIT FOR ELECTROGCHEMICAL
REDUGCTION OF URANIUM FOR Procedure 12.

Extraction and Measurement at Microgram Uranium Level. A
gslution of uranium-233 (10'7 to 10'8 gram) together with about
20 v of natural uranium (as sulfate) was submitted to reductive
extraction with cupferron for about 50 to 60 minutes. The
uranium (IV/III) cupferrate was then re-extracted in cell D from

the ether solution into three sucecesslve 15-ml. porti,onia’of ™

300
PROCEDURE 12 (Continued)

nitric acld. The comblned nltrilc acld extract was evaporated to
about 5 ml., treated with 25 to 30 ml. of concentrated nitric and
2 ml. of perchloric acid, and then evaporated to dryness. The
residue was digested with 10 ml. of 0.1M nitric acid for a few
minutes; the solutlon obtalned, after addition of about 10 vy more
of natural uranium (as sulfate), was used for electrodeposition
of the uranium onto a platinum planchet from an oxalate medium.2
A windowlees flow counter wlth Q-gas was used for counting the
alpha emisslon from the electrodeposited uranium.2
The whole operation took about 4 to 5 hours. Each méasure-
ment of alphas from the samples was callbrated by counting a

uranium oxlide standard (Natlonal Bureau of Standards No. 836-5).

Note 1. In some rune the current dropped to a low level soon
after the requisite number of eoulombs had passed for about a 3-
electron reduction of the uranium present. In other cases, the
current dld not deorease, but dlscontinuance of the run beyond
any pcint where twlce the theoretical ourrent had passed gave
patisefactory uranium recovery. In the latter cases, a gray ether-
insoluble, but alcohol=-soluble precipltate (apparently a merocury
cupferrate), was usually evident in the agueous phase. The cur=
rent efflclericy for the deslred process appeared to be good 1n
most runs.

The comblned ether extracts may be re=sxtracted 1ln cell D by
lnserting a clean stirrer, or they may be tranaferred witfl.rinsing
into a ¢lean separatory funnel. Three extractions with 20 to 30
ml. each of 0.5M, 4M; and 0.5M nitric acld were adequate to re-

extract uranium into aqueous sclution.

2 0. L. Rulfs, A. K. De, P. J. Elving, J. Electrochem. Soac. 10%,
80 {1957)-

301
PROCEDURE 13: The Determination of Uranhium by Solvent Extraction.
Source: R. F. Clayton, W. H. Hardwick, M. Moreton-Smith and R.
Todd, Analyst 83, 13 (1958).

Abstrect

The development of solvent-extraotlon methods for deter-
mining trace amounts of uranium-233 in 1rradiated thorium is
described. Thorium and 1ts alpha-emitting daughters are com-
pPlexed with EDTA, and, when uranium-233 ls extracted as 1ts di-
ethyldithleocarbamate complex, only blsmuth-212 accompanies 1it.
This 1s Immaterlal for colorimetrie or fluorimetric finlshes, but,
for determlnation of the uranium-233 by alpha counting, the
bismuth~212 must first be allowed to decay. If, however, the
uranium-233 1p extracted gs 1ts 8-hydroxyquinoline ocomplex, no
alpha emitter accompanles 1t and concentratlions of uranlum-233
ranging from 100 pg per ml down to 0.0l ug per ml in 0.7 M
thorium solutlon have been determined in this way.

METHOD FOR DETERMINING URANIUM-233 IN THORIUM NITRATE SOLUTIONS
BY EXTHACTION WITH OXINE
REAGENTS =~

Oxine solution A--A 10 per cent w/v solution of B-hydroxj-
qulnoline in isobutyl methyl ketone.

Oxline solution B--A 2.5 per cent w/v solution of 8-hydroxy-
quinoline 1n lsobutyl methyl ketone,

EDTA solutlon-~Dissolve 372.9 g of the disodium salt of
ethylenedlaminetetra-~acetic acid in 500 ml of water containing
80 g of sodium hydroxlide and make up to 1 1liter.

lml 323 mg of thorium.

Nitric aold, N.

Ammonia solution, sp. gr. 0.880.

Ammonla solutlon, 0.2 N.

Bromothymol blue indleator solution.

Anti-creeping solution--A 20 per cent solution of ammonlum

302
PROCEDURE 13 (Continued)

chloride contalning 2 per cent of a water-soluble glue (Stephen's

Stefix was found to be sultable).

PROCEDURE FOR 0.01 TO 1 pg OF URANIUM-233 PER ml--

With a plpette place a sultable volume of sample solution,
containing not more than 600 mg of thorium, in a 40-ml centrifuge
tube fitted with a8 glass stirrer. Add EDTA esolution to give about
a 10 per cent excess over the thorlum equivalent and then add 3
drops of bromothymol blue indlcator solution.

Add ammonia solution, sp. gr. 0.880, until the indiocator
turns blue. Return the color of the indicator to yellow by adding.
N nitric acid and then add 0.2 N ammonia solutlon until the color
of the indicator Just turns back to blue (pH 7). Add 2 ml of
oxine solution A, stir for 5 minutes, s8pln in a centrifuge to
separate the phases and then stopper the tube.

Evaporate duplicate 0.25-ml portions of the solvent phase
slowly on stalnless-ateel counting trays that have had 1 drop of
anti-creeping solutlon evaporated at their centers.®2 Heat the
trays to redness 1n the flame of a Meker burner, cool and count.
PROCEDURE FOR 1 TC 100 ug OF URANIUM-233 PER ml--

With & pilpette place a sultable volume of sample solutlon,
contalning about 10 pg of uranium-233, 1nla 40-ml centrifuge tube
and dilute to 3 ml with water. Add EDTA solution to give a 10
per cent excesas over fthe thorium_equivalent. Add 2 drops of
bromothymol blue indlcator solution and edjust the pH to 7 as
previously descrilbed.

Add 5 ml of oxline solution B, stir for 5 minutes, spin in
a centrifuge to separate the phases and then stopper the tube.
Evahofate duplicate 0.1 or 0.25-ml portlons of the solvent phase
for cofinting, as before.

Note that for a fluorimetric finlsh to elther procedure,

sultable dupllicate portlions of the solvent phase should be

303
PROCEDURE 13 (Continued)

avaporated in platinum fluorlmeter dlshes before fuslon with

sodium fluoride.

METHOD FOR DETERMINING URANIUM-233 IN THORIUM NITRATE SOLUTIONS
BY EXTRACTION WITH SODIUM DIETHYLDITHIOCARBAMATE
REAGENTS--

Hexone.

Sodlum dlethyldithlocarbamate solutlon--A freshly prepared
and filtered 20 per cent w/v aqueous solution.

EDTA solution--Prepared as described in reagents list, p. 377.

Ammonium nitrate solution, 2 M .

Ammonia solution, sp. gr. 6.880.

Nltric acid, concentrated and N.

Screened methyl orange 1lndicator solutlon.

Antl-creepling solution--A 20 per cent solution of ammonium
chlorlde contalning 1 per cent of a water=soluble glue.
PROCEDURE FOR 1 TO 100 pg OF URANIUM-233 PER ml--

With a plpette place a suitable volume of sample solution,
containing about 10 ug of uranium-233, in a2 40-ml centrifuge tube
fitted with a glass stirrer. Dillute to 4-ml with 2 M ammonlum
nltrate and add EDTA solutlon to glve a 10 per cent excess over
the thorlium equivalent. Stir and make Just alkaline to screened
methyl orange by adding ammonls solution and then add 0.5 ml of
sodlium dlethyldlthiocarbamate solutlon.

Stir and add N nitric acid untll the solution is mauve (not
red). Add 5 ml of hexone, stlr for 5 minutes and add more acild
to maintaln the mauve color 1f necessary. Spln 1n a centrifuge
to separate the phases and then stopper the tube.

Evaporate sultable duplicate portions of the solvent phase
on stalnless=-eteel counting trays that have had 1 drop of anti-
creeping solutlon evaporated at thelr centers. Heat the trays

to redness in the flame of a Meker burner, allow the bismuth-212

304
PROCEDURE 13 (Contilnued)

to decay, and then count. Alternatively, for a fluorimetrilec
finish, evaporate duplicate portione of the solvent phase in platin-
um fluorimeter dishes for fuslon with sodlum fluorilde.

Note that greater sensltivity can be obtalned by starting
wlth a larger volume of sample or by evaporating larger portlons

of the solvent phase.

2 w. H. Hardwick, M. Moreton-Smith, Analyst 83, 9 (1958).

PROCEDURE 14:; Uranium Radiochefiical Procedure Used at the
Unlverslty of Californla Radlation Laboratory at Iilvermore.

Source: E. K. Hulet, UCRL-4377 (195%4).

12 Atoms of U237 1solated from a 3-day-

14

Decontamlnation: 3 x 10
0ld mixture contalning 10" fisslone showed no
evldence of contamination when decay was followed

through three half lilves.

Yleld: 30 to 50 percent.
Separation time: About four hours.
Reagents: Dowex A-1 resin (fall rate of 5=-30 em/min).

Zinc dust, lsopropyl ether.
2M Mg(N03)2 with 1M HNO,.
2M HC1 with 2M HF.

l. To the solution contalning the activity in HCl in an Erlen-
meyer flask, add uranlum tracer in HC1l, 1 ml of conc. formlc
acld and several ml of conc. HCl.

2. Boil gently until volume 1s ~2-3 ml, replenishing the solu-
tion with several ml of formlc acld during the bolling.

3. Transfer to 20-ml Lusterold centrifuge cone, rinsing flask
twice with 1-2 ml of water and add 2-3 mg of La*tT. add 1
ml of conc. HF, gtir, heat, and centrifuge.

305
g.

10,

PROCEDURE 14 (Continued)}

Transefer supernatant to 20-ml Lusterold centrifuge cone, add

2=3 mg La+++, stir, heat, and centrifuge.

Transfer supernatant to 20-ml Lusteroid, add 5-10 mg Lat'T,

1/2 m1 of ceonoc. HCl and heat in a water bath. When the solu-
tion 1s hot, add small portions of zinc dust and stir. About
three small addltions of zinc duat should be made over a half-
hour perlod wlth vigorous stirring after each addition. If

the zinc dust tends to ball and sink to the bottom of the

tube at any tlme, addition of more conec. HCl wlll solve thils
problem. When all the zine from the last addition has dissolved,
add 4 or 5 ml of water and lfimi of conc. HF. 8tir, cool, and
centrifuge, retalning the LaF3 precipitate. Wash.precipitate
with 2 ml of 2M HC1l + 2M HF.

Dissolve the precipitate with 6M HNO, saturated with H3BOg,
stirring and heating. Trangfer the solutlon to a 40-ml glass
centrlfuge cone, washlng out the Lusterold cone with water.

Add several drops of H202 and etir and heat. Add 2 mg Fe+++

and make solutlon baslec with NHAQH and some NaOH. Heat, stir,
and céntrifuge.. Wash the precipltate with 2 ml of water.
Dissolve the precipltate 1in one to two drops of econe. HNO3 and
heat. Cool, add 10 ml QE_HQ(NOB)e + 1M HNOg saturated with
ether. Equillbrate twlce with 10-15 ml of dllsopropyl ether.
Pipet the ether phase into a clean 40-ml cone and equilibrate
ether layer with 3 ml of com. HCl. Pipet off and discard
ether layer. Heat HCl for ~30 seconds and again pipet off
the ether layer.

Pass the HCl solution through a Dowex~l anlon resin bed (2

‘em x 3 mm) by pushing the solution through the column with

air pressure. Rinse the centrifuge tube once with 1 ml of
conc. HC1 and push this solution through the column. Wash
resin with ~1 ml of conc. HCl. Discard effluent.

306
PROCEDURE 14 (Continued)

11. To colurm, add ~3/4 ml of O.5M HCl. Collect the eluate and

evaporate to a small volume and plate on a platinum dlsc.

PROCEDURE 15: Use of Ion Exchange Resins for the Determinatilon
of Uranlum 1in Ores and Solutlons.

Source. 8. Fisher and R. Kunin, Anal. Chem. 29, %00 (195T).

Abstract

The separation of uranlum from the lons interferlng wlth 1ts
analysls 1s accomplished by the adsorptlion of the uranium(VI) sul-
fate complex on a quaternary ammonium anion exchange resin._ Intef-
ference of such lons &8 1ron(III) and vanadium(V) is avolded by
thelr preferentlal reduction wlth sulfurous acid so that they, as
well a8 other cations, are not retained by the resin., Uranium is
eluted for analysls by dllute perchlorilic acid. The methed is

applicabie to both solutlons and ores.

Ore Solutlon

Two methods for the opening of_uranium-bearing ores were
investigated in conJunction with the lon exchange separatlion. The
flret 1s the standard digestlon wlth hydrofluoric and nltrlc aclds,
with subsequent evaporatlon to dryneass followed by a sodium car-
bonate fusion.2 The carbonate melt 1s dissolved in 5% sulfuric
acld to form a solution for the separation. A second method for
routine enalysls, designed to eliminate the need for hood facili-
tles and platinum vessels; lnvelves an oxldatlive leach with an
acidic manganese(IV) oxlde syatem. This procedure 18 given in
detail below. Other workersE, using the auvthors' separation
procedure, have recommended solutlon of the ore by treatment with

12M hydrochloric aclid plus 162 nitric acld followed by fuming'

307
PROCEDURE 15 (Continued)

wilth sulfurlce aecld to produce a sultable uranium solution for the
column influent.

Procedure. Welgh out samples of ore estimated to contaln
an amount of uranium oxlde less than 100 mg. but sufficient to be
detected by the chosen method of analysis. Add 20 ml. of 20% by
volume sulfuric acid and 2 grams of manganese(IV) oxide. Heat
the mixture to bolling. Allow to cool to room temperature. Dilute
with approximately 50 ml. of water. AdJust to a pH between 1.0
and 1.5 by the dropwlss addition of 20% sodium hydroxide. Filter
through fine-pore filter paper using two 10;m1. portions of water

to wash the residue on the paper.

Ton Exchange Separation

Apparatus. Tubes 0.5 inch in dlameter with high-porosity
sintered glass fllter disks fused to the lower end are used to
contaln the resin, The rafte of flow of solutlons through the
tube 18 regulated by a Bcrew elamp on rubber tubing below the
filter. Small separatory funnels are attached to the top of the
column to feed the sample and reagents.

Procedure. Convert a portion of quaternary ammonium anion
exchange resin (Amberlite XE-117, Type 2) of mesh size %0 to 60
{U.S. soreene) to the sulfate form by treating a column of it with
IQ% sulfurio acld, using 3 volumes per volume of resln. Rinse the
acld=treated resin with delonigzed water until the effluent 1s
neutral to methyl red. Draln the resin so prepared free of excess
water and store 1n a bottle. A 5-ml. portion of thils resin 1s used
for a single analysls. The resln 1s loaded into the filter tube and
the bed so formed 18 backwashed with enough water to free 1t of
alr. After the resln has settled the excess water is drained off
to within 1 cm. of the top of the bed prior to the passage of the
sample through the bed.

Add 5 drops of 0.1% methylene blue to the partially neu-

308
PROCEDURE 15 (Continued)

tralized (pH 1.0 to 1l.5) solution from the dissolved sodium car-
bonate melt or from the flltered manganese(IV) oxide leach. Add
6% sulfurous acid dropwise until the methylene blue is decolorized
and then add a 5-ml. excesB. Pass the reduced sample through the
resin bed at a rate not exceeding 2 ml. per minute. Wash the sam-
ple contalner with two 10-ml. portions of water, passing the
washing through the resih bed at the same flow rate. Elute the
uranium with 50 ml. of 1M perchloric acid. Determlne the uranium
content of the perchlorioc acld fractlon colorlimetrically by the
standard sodium hydroxide-hydrogen peroxide methodZ o# volumetri-
callyg. For colorlimetric analysis standard uranium solutlons
containing perchloric acld should be used 1n establishing the

qurve.

2 p. S. Grimaldl, I. May, M. H. Fletcher, J. Titcomb, U. S. Gecl.
Survey Bull. 1006 (195%).

D H. 7. Seim, R. J. Morris, D. W. Prew, U. 8. Atomic Energy Comm.
Document UN-TR-5 (1956).

£ 0. J. Rodden, "Analytical Chemistry of the Manhattan Project,”
McGraw-H11l, New York, 1950.

PROCEDURE 16: The Use of a "Compound" Column of Alumina and
Cellulose for the Determlnation of Uranium in Minerals and Ores
Containing Arsenlc and Molybdenum.
Souroce: W. Ryan and A. F. Willieme, Analyst 77, 293 (1952).
Abstract

A technlque 1n inorganic chromatogrephy, with alumina and
cellulose adsorbents 1ln the same extraotion column, 1s described
for the separation of uranium from minerals and orea. The pur-

pose of the alumina 1s to retain arsenic and molybdenum, which

309
PROCEDURE 16 (Continued)

are not readlly retalned by cellulose alone when ether containing
5 per cent v/v of concentrated nitric acid, sp.gr. 1.42, 18 used
as the extraction solvent.

METHOD FOR SAMPLES CONTAINING MOLYBDENUM OR ARSENIC OR BO'TH
Solvent--Add 5 ml of concentrated nitrlec acld, sp.gr« 1.42, to
each 95 ml of ether.

PREFARATION OF ALUMINA-CELLULOSE COLUMN--

The adsorptlon tube for the praparation.of the colum 1z a
glass tube about 25 cm long and 1.8 em in dlameter. The upper
end 18 flared to a dlameter of gbout 8 em to form a funnel that
permlts easy transfer of the sample. The lower end terminates
in a short length of narrow tubling and 1ls closed by a short
length of polyvinyl chloride tublng carrylng a screw cllip. The
inslde surface of the glass tube 1s coated wlth a slllicone in
the manner described by Burstall and Wells.2

Welgh 5 or 6 g of cellulose pulp* into a stoppered flask and
cover 1t with ether-nltric acld solvent. Pour the suspenslon ln-
to the glass tube, agltate gently and then gently press'down-the
cellulose to form a homogeneocus column. Wash the column wlth
about 100 ml of ether-nltric acld solvent and finally allow the
level of the solvent to fall to the top of the cellulose. Next
pour about 15 g of activated alumintum oxide* on top of the
cellulose, pour on 30 ml of ether-nlitric acld solvent and vig-
orously agilitate the alumina with a glass plunger. Allow the
packing to settle.. Allow the level of the ether to fall to the

surface of the alumina and the column 1s ready for use.

* Whatman's Standard Grade cellulose powder 1ls sultable.

t Type H, Chromatographic Alumina, 200 mesh. Supplled by Peter

Spence Ltd.

310
PROCEDURE 16 (Continued)

PREPARATION OF SAMPLE SOLUTION FROM MINERAL OR ORE=-

Welgh 1nto a platinum dish sufficlent of the sample to gilve
100 to 150 mg of U303, which 1s a convenient amount for a volu-
metric determinatlon. Decompose the sample by treatment with
nitric and hydrofluoric aclds in the manner describaed by Burstall
and Wells.® Finally remove hydrofluoric acid by repeated evapora-
tilons with nitrlc acld and take the sample to dryness. If the
addition of dilute nitrlc acid indicates the presence of undecom-
poeed materlal, fllter the insoluble residue on to a filter-paper
and ignite and fuse 1t 1In a nickel orucible with a few pellets
of potasslium hydroxide. Then add the melt to the filtrate and
take the whole to dryness.

Add 4 ml of diluted nitric aecid, 25 per cent v/v, to the
dry residue, gently warm to dlssolve the mixture and then ecol
the solution, which 1s then ready for chromatography.

EXTRACTION OF URANIUM—

Transfer the sample on a wad of dry cellulose pulp to the
top of the prepared alumina-aellulose columm? and extract the
uranium with 200 to 250 ml of ether-ni@ric acld solvent if ar-
senlc or molybdenum and arsenle is present in the origlnal samplae.
If molybdenum alone 18 present, the amount of solvent can he
reduced to 150 ml. Screen the column from direot sunlight. After
removal of ether from the eluate, determine the uranium volume-
trically. 2l

2 F. H. Buretall, R. A. Wells, Analyst 76, 396 (1951).

D p. H. Burstall, A. P. Williems, "Handbook of Chemical Methods

for the Determination of Uranium in Minerals and Ores," H. M.
Stetlonery Office, London, 1950.

311
PROCEDURE 17: Determination of Uranium-235 1n Mixtures of
Naturally Occurring Uranlum Isotopes by Radioactivation.
Source: A. P. Seyfang and A. A. Smales, Analyst 78, 394% (1953).

Abstract

A method previously used® for determlning uranlum in mlnerals
by neutron irradiation followed by measurement of the separated
fisslon-product barium has been extended to the determination
of uranium-235 in admixture with uranium-234 and uranium-238.

With microgram amounts of uranium-235, short irradlations
in the Harwell plle glve ample Bensitivity. Preclsion and
accuracy of better than +2 per cent have been achleved for a
range of uranium-235 contents covered by a factor of more than
10°.

| Method

REAGENTS -=

Magnesium oxlde--Analytical reagent grade.

Nitric acid, sp. gr. l.42.

Barium chloride solution--Dissolve 18 g of BaCl,-2H,0 in
water find malkte up toc 500 ml.

Lanthamum nitrate solution--A 1 per cent w/v solution of
.La(N03)'3 °6H20. ' |

Ammonium hydroxide, sp. gr. 0.880.

Strontium carbonate solution--A 2 per cent w/v solution.

Hydrochlorlc acld-diethyl ether reagent--A mixture of 5 parts
of concentrated hydrochloric aeid, sp. gr. 1.18, and 1 part of
dlethyl ether.

Sodium tellurate solution--A 0.4 per cent w/v solution.

Zine metal powder.

Methyl orange lndloator.

Potassium lodide solution~-A 1 per cent w/v solution.

Sodlum hypochlorite sclutlion--A commercilal aoiution containling

10 per cent of avallsble chlorine.

312
" about 50 mg of U

PROCEDURE 17 (Continued)

Hydroxylamlne hydrochloride.. _
Ferrile chloride solutlon--A 1 per cent w/v solution.
Sulfuriec acid--A 20 per cent v/v solutilon.

IRRADIATION--

Solids-- Samples contalnlng not much more uranium-éjs than
natural urgnium (say, up to three times more or 2 per cent) may
be Ilrradiated as polld; thils 1s usually U308° For these cut a
B=cm length of 2-mm polythene tubing and seal one end bylwarming
and pressing. Introduce freshly lgnited analytical reagent grade
magnesium oxlde to form a compact layer 4 to 5 mm in helght at
the sealed end of thé tube. Welgh the tube and contents, add
308 and re-welgh. Add a further simllar layer
of magneslum oxide on top of the U3°8 and then seal the open end.
Leave a free space about 1 cm long between the top of the mag-
nesium oxlde layer and the seal, for ease of opening. Treat
standard aend samples similarly. Place the tubes elther 1n.a
"special polythene bottle for irradilation in the pneumatic "rabbit"
of the pille or in a 3-inch aluminum can for irradiation 1n'£he
Yaself-perve"” holes in the pille. Irradiation 1s carried out for
any requlred time; usually 1t is about. .5 minutes. After irra-
dlating, place the contalners in lead shleldlng for about 15
hours. After thie perlod, tap down the ocontents of the polythene

tube away from one end and carefully ocut off the top. Empty the
contents into & 50-ml centrifuge tube. (The plug of magnesium
oxlde serves to "rinee” the sample tube as it ls emptied.) Add
2 ml of concentrated nitric acid (sp.gr. 1.42), gently warm to
"dissolve, and finally boll off the nltroue fumes. Add 5.00-m1
of a barium solution to act as carrier (a solution of 18 g of
barium chloride, BaCl,*2H,;0, in 500 ml of water).

Ligulds--For more hlghly enriehgd samples or when the amognt

-of sample avallable 1s small, solutions contalning welghed

313
PROCEDURE 17 (Continued)

quantitlies of solld sample must he lrradiated 1n small sillica
ampoules. The ampoules, whlch have a capaclty of about 1 ml,
are prepared from sillica tubing. After one end of each has been
sealed, the ampdules are welghed, the sample solution added from
a flne-pointed glass dropplng-tube and the ampoules re-welghed.
Pack the ampoules, after sealing the open ends, 1in cotton wool 1n
a 3-inch aluminium can and irradiate them in the "self-serve"
posltlon of the plle. The time of lrradlation necessary can be
calculated from the usual activation formulé; as an example, 1
pg of uranium-235 irradiated for 24 hours 1n a flux of 1012 neu-
trones per sq. cm per second glves about 5000 counts per minute
of barium-140 at 5 per cent counting efficlency, 24 hours after
the 1rradiation.

After removing them from the pile,'place the samples and
gptandards in lead shlelding for about 15 hours; the maln actlvity
1s due to silicon-31l. Transfer the ampoules to 100-ml tall-form
beakers contalning a few milliliters of water and 5.00 ml of
barlum carrier solutlon, carefully break off both ends of each
ampoule and warm to ensure thorough mixing. Decant into centrl-
fuge tubes and wash out the ampoules and beakers with further
small portions of water.

CHEMICAL SEPARATION--

Evaporate the solutlon contalning the lrradlated uranium
and barium carrier to 5 to 6 ml and add two drops of 1 per cent
lanthanum nltrate solution. Warm 1f necessary to dilssolve any
barium nitrate that may have crystallized, add concentrated
ammonium hydroxlde dropwlse untll a permanent preclpltate 1s
obtalned and then two drops 1n excess. Centrifuge and decant
Into another centrlfuge tube. Add methyl orange indlecator, and
then hydrochloric acid-until the solutlon 18 acid. Add 2 drops
of 2 per cent strontium solutlon, about 25 ml of hydrochloric

314
PROCEDURE 17 (Continued)

acid - dlethyl ether reagent, mix thoroughly, centrifuge and
decant. Wash the preciplitate with 5 ml of reagent, centrifuge

and decant. Disgolve the barium chloride precipitate in 3 to %

ml of water, re-preclpltate 1t by adding 20 ml of reagent, centri-
fuge and decant. Wash with 5 ml of reagent, centrifuge and decant.

Dlssolve the precilpltate in about 5 ml of water, add 6 drops
of lanthanum solution and 6 drops of the 4 per cent tellurate
solution and then about 3 mg of zlnc metal powder. When the
effervescence ceases, make the éolution Just ammonlacal to methyl
orange, centrifuge and decant into another tube. Add % drops of
1 per cent potasslum ilodlde solutlon and 2 drops of sodium hypo-
chlorite solution. Warm and set aside for 2 minutes. Acldify
wlth about 1 ml of hydrochloric acld, and add about 0.1l g of
hydroxylamlne hydrochloride. Boll under & hoad until all the
iodine appeare to be removed and the volume 1s reduced to 5 to
6 ml. Add 2 drops of strontlum solution and 2 drops of lanthanum
solutlion and repeat thé double barlum chlorlde preclpltation and
washlng, as above.

Dissolve the precipitate in about 5 ml of water, add 6 drops
of lanthanum solution, and 6 drops of 1 per cent ferrie chloride
gsolution. Make ammonlacal to methyl orange, add half a crumbled
Whatman accelerator tablet, and heat Just to bolling. 'Filter
through a 7-cm Whatman No. 30 fllter-paper 1nto a centrifuge tube,
wash twlce wlth 2 fo 3-ml portions of water. Dillute the flltrate
to about 20 ml and meke slightly acld with hydrochlorlc acid.
Heat nearly tc boiling and add dropwise 2 ml of 20 per cent v/v
sulfuric acld. Allow the precipltate to settle, decant, wash
with 10 ml of water, centrifuge, decant and repeat the washing
procedure to complete removal of the excess of acld.

Transfer ae mich as posslble of the preclpltate, by means

of a dropplng tube and a few drops of water, to a tared aluminium

315
PROCEDURE 17 (Continued)

counting tray. Dry under an infra-red lamp and finally heat in.
4 muffle furnace at 500°C for 15 minutes. Cool, weigh and re-
serve for counting.

COUNTING TECHNIQUE-- )

The counting equipment for this work consists of (1) a
power unilt (type 1082A or 200 is sultable), (11) scaling unit
(type 200 or 1009B), (11i) time accessory unit {type 1003B),
(1v) probe unit (type 200B or 1014A). Time pulses can be ob=-
talned from a master elsotrlc clock serving several unlts. A mica
end-window Geiger-Mfiller cgounter (2 mg per sg. cm.), of type
EHM2, 18 suitable; 1t is mounted in a lead castle with a Perspex
linlng and shelves.

Check the counting equipment in the normal fashlon wlth a
sultable beta-~emlttfer, such as natural uranlum oxide in equilib-
rlum wlth UXl and sz. Place the sample to be counted 1In a
Perspex carrler and insert it in a shelf at a Buifable distance
from the Geigen-Mflller tube to attalin a counting rate of 2000 to
3000 counts per mlnute. Count for a sufflcient time to obtailn
at least 10,000 counts for each barlum sulfate precipltate,
counting the preclpltates one after another without undue delay.
Correctlon for growth of lanthanum-l40 1s unnecessary if samples
and standards are counted within, say, 60 minutes of each other
provided the barium sulate precilpltatlons are carried out on
each nearly simultaneocusly.

CALCULATION OF RESULTS--

Correct all counts for background, colncldence loss and

chemlcal yleld and express as the resulta in counts per minute.

Welght of UP3° 1q standard _  Corrected count of standard

 

 

 

Then 23;; - -
Welght of U™~ 1in sample Corrected count of sample
35
and Welght °f“U2 in sample X 100 = percentage of uranlum-235
Weight of sample in sample.,
8,
= A. A. Smales, Analyst 77, T78 (1952).

316
PROCEDURE 18: Determination of Mlecrogram and Submicrogram
Quantities of Uranium by Neutron Actlvation Analysls.

Source: H. A. Mahlman end G. W. Ledlcotte, Anal. Chem. 27, 823
(1955).

Abstract

Miorogram and submlcrogram quantities of uranium have been
determined in synthetlic samples, ores, and solls by neutron
radloactivation analysis. The principles of the actlvation
analysip method used in this determination and the processing of
1rrddlated samples are dlscussed. Thils method of analysis 18 a
sensitive and specific method for determinling uranium 1in concen-
trations as small as 0.1l ¥ per gram with a probable rélative
standard error of 10#. Concentrations of uranium in quantities
as small as 0.0001 ¥ per gram can be determined by neutron activ=
atlor analysils.

Radloactivatlion Analysis of Samples thgt Contaln

Uranium

Nuclear Irradiation of Sample. Welghed portions of the
samples and the comparative standard are put into small quartz
tubas. The tubems are closed with cork stoppers that are wrapped
in gluminum. They are then irradlated in the reactor. After
irradiation, the samples are allowed to decay about 4 hours and
are then chemically processed as described below. The synthetle
samples used 1in thls laboratory had been processed by a fllter
paper partitlion chromatography technligue. After the separation,
the paper was convenlently 1irradlated in short pleces of quartz
tubing whoee openings were plugged by meana of cork stoppers.

Chemlcal Separatlion of Neptunlum=-239. In most neutron
activatlon analyses, é chemlcal separatlon 1s made to lsclate
the radiocactivity of the element from all other radloactlve
apecies in the sample. Usually an "isotople carrier"--a khown

amount of the natural inactive element--13 added to the solutions

317
PROCEDURE 18 (Continued)

of both the 1rradilated specimen and the comparison samples. The
golutions are then processed chemlcally to lsolate the carrler
and deslred radloelement from other elements and contamlnant
radloactivitles. 3mall amounts of other elements are added as
holdback or socavenging carrlers to asslst In the decontamlination
process.

Although neptunium-239 has a convenlent half l1life, 1t does
not have a stable 1sotope that can be used a8 an'lsotoplc carriler.
However, Seaborgi has shown that trace quantities of neptunium-
239 can be quantitatively carried on a nonlsotople carrler, such
as cerilum. The method of analyals reported below uees lanthanum
as a nonlsotoplc carrler for the neptunium-239 radiocactivity.

(See Note 1.)

Chemlcal Separation Procedure. PREPARATION. The lrradiated
ore and soll specimens are dissolved by digestion in a mixture of
concentrated nitric, hydrofluoric, perchloric, and sulfuric
acids. (Additional hydrofluoric acid can be added 1f a residue
of sllica remains 1n the bottom of the crucible.) After dissolu-
tion, the sample 1s concentrated to heavy sulfuric acid fumes,
cooled, and transferred to a 15-ml. centrifuge tube. If a residue
(sulfate salts) remains after the transfer, the solutlon is cen-
trifuged for 5 minutes, the supernatant transferred to another
tube, and the resldue washed with 1 ml. of 1M nitrlc acid. The
wash 1ls added to the supernatant and the residue discarded.
(Centrifugation is always for the stipulated time and at full
speed.) The sample 1s then further processed by the procedure
reported herein.

The irradiated synthetlc samples (paper chromstograms) are
processed by carefully igniting the paper contained in a porcelain
cruclble in a muffle furnace. The resildue 1s dilssolved in about

0.5 ml. of concentrated nitrlc acld. After dissolution, the

318
PROCEDURE 18 (Continued)

sample 1s transferred to a 15-ml. centrifuge tube and the process-
Ing continued wlth the procedure reported herein.

PROCEDURE. Three (3.0} milligrams of lanthanum and 0.250
ml. of 5M hydroxylamine hydrochlorlde solutlon are added to the
supernatant solutlon and the mixture digested for 5 mihutes wlth
occaslonal stlrring. The solution is cautiously neutralized with
concentrated ammonium hydroxlde to precipitate lanthanum hydroxide,
after which the mixture 18 centrifuged and the supernatant liquid
discarded.

The precipltate of lanthanum hydroxide is dissolved in 2 ml.
of 2M hydrochloric acld, and 1.0 mg. of strontlium (added as a
solution of strontium niltrate to serve as a holdback or scavenglng
carrier) and 0.250 ml. of 5M hydroxylamine hydrochloride solution
are added to the solution. The solutlon ls agaln digested for
5 minutes wlith Ilntermittent stirring, and 0.200 ml. of concentrated
hydrofluorlc acld 1s added dropwlse to the solutlon to precipiltate
lanthanum fluoride. After centrlfugation, the supernatant liquild
1s discarded and the preclpitete washed wlth 0.5 ml. of 1M hydro-
fluorie acld-1M nitric acld solution.

After washlng, the lanthanum fluorlde precipltete ls dissolved
ln 0.5 ml. of saturated borlc acld solution and 1.0 ml. of 6M
nitriec acld. One (1.0) mllliliter each of 10% potassium perman-
ganate solutlon and water are added to thlse solutlon, and the
resulting mixture ls agltated well and digested for 5 minutea.
Lanthanum fluoride 1s agaln precipltated wilth 0.250 ml. of con-
centrated hydrofluoric acld; the solution 1ls centrifuged and the
supernatant llquld transferred to another centrifuge tube. The
preclpitate is washed with 0.5 ml. of 1M hydrofluoric acid-1M nitriec
aclid solutlion and the wash comblined with the supernatant liquid.
The preclpltate 1ls dlscarded.

Three milligrams of lanthanum are added to the supernatant

319
PROCEDURE 18 (Continued)

liquid, and the solutlon 18 digested for 5 minutes and ¢entrifuged.
An additional 3.0 mg. of lanthanum are added to the supernatant
11quid and the solutlon agitated and digested for 5 minutes wilthout
disturbing the first precipltate on the bottom of the tube; then
the solution is centrifuged and the supernatant liquild transferred
to another centrifuge tube. The preclpltate 138 washed with 0.5

ml. of 1M hydrofluoric acild-1M nitric acild solution; centrifuged,
and the wash comblined wlth the supernatant liquid. The precipl-
tate 1s discarded.

One milligram of zirconium (added as a solution of zirconium
nitrate to serve as a holdback or scavenglng carrier) and 0.250 ml.
of 5M hydroxylamine hydrochloride are added to the solution and
the mixture agitated and digested 5 minutes. Three (3.0) milli-
grams of lanthanum and 2 ml. of 2M hydrofluoric acld are added
to the solutilon, and the solutlion 1s digested for 20 minutes and
then centrifuged. The supernatant liquid i1s dlecarded. The pre=-
clpltate 1s washed with 0.5 ml. of 1M hydrofluorlc acid-1M nitric
acld solution, and the resulting mlxture 1s centrifuged. The
wash 8olution 1s dlscarded after the centrifugation.

The precipitate 1s slurried in a small amount of 1M nitric
acid (about 0.5 ml.) and transferred to a small borosilicate glass
culture tube by means of a transfer pipet. The centrifuge cone
18 ringed wlth three 0.5-ml. portlions of 1M nitrie acld and the
rinses transferred to the ceculture tube. The tube 1s stoppered
wlth a cork stopper and the ¥ radiocesctivity measured by a well-
type gamma scintlllatlon counter.

The standard sample of uranium oxide (U308) is dissolved
in nitric acld and an aliquot of the solution processed under
the same condltions as the specimen samples. The uranium content
of the sample 1n question 1s dqyermined by equating the ratio of
the corrected neptunium-239 radioactlivity count in the unknown

320
. PROCEDURE 18 (Continued)

and the corrected neptunium-239 radloactivity count in the standard
sample.
b 237
Note 1. Hamaguchl and co-workers— have used Np tracer

to determine the chemlcal yleld..

2 ga. T. Seaborg and co-workers, Metallurglcal ProJect Rept. CN-
2689,41 (Feb. 15, 1945) (classified).

P-H. Hamaguchl, G. W. Reed, A. Turkevich, Geochlim. et Cosmochim.

Acta 12, 337 (1957).

Acknowledgements

It 18 a pleasure to acknowledge the aselstance of Miss M.
Tippet, Mliss R. Cushlng, Mr. N. Zaichick and others of the
Argonne National Laboratory lidbrary staff 1n locating t+the many
references used 1n wrilting thls paper; Dr. E. K. Hyde, who
kindly made avallable hls flle on the radlochemlstry of uranlum;
Mrs. D. E. Williams, who typed most of the manuscript; Miss F.
Taylor, for preparing the final flgures; Dr. C. E. Crouthamel,
who furnished the flgures of gamma-ray spectra; Dr. D. W.
Engelkemelr and Mr. D. J. Henderson, who supplled the data for.
the alpha spectra; and finally, Miss B. Lore and Mr. C. Ahlberg,
wlthout whom the completlon of thls paper would have been much,

much later.

321
10.

11.

12.
13.
1ha,.
14D,
15.

16.

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303.

304,

305.

306.
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310.

311.
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326.
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331.

332.
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336.

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339.
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341.
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352.
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356.
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361.
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337
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374,
375.

376.
377
378.

379.

380.
381.

382.

383.
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385.
386.
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389.
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391.
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339
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4ol
426,
427.
428.
4og,
430.
431,
432,

433,
13y,

435.
436,

437.
438.
439.

L4o,
441,

k2,
143,
iy,
15,
116,

i,
448,

M. V. Susic, N. Jelic, Bull. Inst. Nuclear Sci., "Borils Kidrich,"
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K. Alcock, S. 8. Grimley, T. V. Healy, J. Kennedy, H. A. C.
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V. M. Vdovenko, A. A. Lipovskll, S. A. Nikitlna, Zhur. Neorg.
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V. B. Shevchenko, I. G. Slepchenko, V. S. Schmidt, E. A.
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340
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450.
451.

452,
y53.
454,
455,
456.

457.
458.
459,
460.

461.

462,
163,
164,
165,
166.
467,
468.
169,
470.
171,

L2,

473.

47l
475.
476.
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‘A. D. Kelmers, ORNL-2172

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%. Zg?gen, Bull. Research Council Israel, Sect. A, 7A, 153
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BNL-583 (1959); NSA 14, 17642 (1960).
W. Sborgl, Z. Elektrochem. 19, 115 (1913).

Jo A. McLaren, D. W. Clline, H. 8. Clinton
J. Ho Goode, J. A. Westbrook, K-587-(19505.

?iggg%odney, U. 8. Patent 2,872,387 (1959); NSA 13, 13320

British Patent 829,090 (1960); NSA 14, 944 (1960).

C. D. Calkine, R. B. Filbert, Jr., A. E. Bearse, J. W. Clegg,
BMI-2434 (1950).

J« d« Flnley,

E. W. ChristoRherson, H. R. Grady, R. W. Woodard, C. E. Larson,
AECD-4181 (1946); NSA 10, 107h0 (1956).

L. Steadman, "The Pharmacology and Toxicology of Uranium
Compounds,” C. Voegtlin, H. C. Hodge, edltors, NNES, Division
VI, Volume 1, Chapter 19, Sectilon 4, McOGraw-Hlll Book Co.,
New York, 1953.

F. S. Grimaldl, I. May, M. H. Fletcher, J. Titcomb, Geol.
Survey Bull. 1006 (1954).

"Handbook of Chemical Methods for the Determination of Uranium

in Minerals and Ores,”™ His MajJesty's Stationery Office, London,
1950.

350
NUCLEAR SCIENCE SERIES: MONOGRAPHS ON RADIOCHEMISTRY
AND RADIOCHEMICAL TECHNIQUES

See the back of the title page for availability information

ELEMENTS

Aluminum and Gallium, NAS-NS-3032 [1961]

Americium and Curium, NAS-NS-3006 [1960]

Antimony, NAS-NS-3033 [1961]

Arssnic, NAS-NS-3002 (Rev.) [1965]

Astatine, NAS-NS-3012 [1960]

Barium, Calcium, and Strontium,
NAS-NS-3010 [1960]

Baryllium, NAS-NS-3013 [1960]

Cadmium, NAS-NS-3001 [1960]

Carbon, Nitrogen, and Oxygen,
NAS-NS-3019 [1960]

Cesium, NAS-NS-3035 [1961]

Chromium, NAS-NS-3007 (Rev.) [1963]

Cobalt, NAS-NS-3041 [1961]

Copper, NAS-NS-3027 [1961]

Fluorine, Chlorine, Bromine, and lodine,
NAS-NS-3005 [1960]

Francium, NAS-NS-3003 [1960]

Germanium, NAS-NS5-3043,[1961]

Gold, NAS-NS-3036 [1961]

Indium, NAS-NS-3014 [1960]

Iridium, NAS-NS-3045 [1961]

Iron, NAS-NS-3017 [1960]

Lead, NAS-NS-3040 [1961]

Magnesium, NAS-NS-3024 [1961]

Manganese, NAS-NS-3018 (Raev.)[1971]

Mercury, NAS-NS-3026 (Rev.) [1970]

Molybdenum, NAS-NS-3009 [1860]

Nickel, NAS-NS-3051 [1961]

Niobium and Tantalum, NAS-NS-3039 [1961]

Osmium, NAS-NS-3046 [1961] -

Palladium, NAS-NS-3052 [1961]

Phosphorus, NAS-NS-3056 [1962]

Platinum, NAS-NS-3044 [1961]

Plutonium, NAS-NS-3058 [1965]

Polonium, NAS-NS-3037 [1961]

Potassium, NAS-NS-3048 [1961]

Protactinium, NAS-N5-3016 [1959]

Radium, NAS-NS-3057 [1964]

Rare Earths— Scandium, Y ttrium, and
Actinium, NAS-NS-3020 [1961]

Rare Gases, NAS-NS-3025 {1960]

Rhenium, NAS-NS-3028 [1961]

Rhodium, NAS-NS-3008 (Rev.) [1965]

Rubidium, NAS-NS-3053 {1962]

Ruthenium, NAS-NS-3029 [1961]

Selenium, NAS-NS-3030 (Rev.) [1965]

Silicon, NAS-NS-3049 (Rev.) (1968]

Silver, NAS-NS-3047 [1961]

Sodium, NAS-NS-3055 [1962]

Sulfur, NAS-NS-3054 [1961]

Technetium, NAS-NS-3021 [1960]
Tollurium, NAS-NS-3038 [1960]

Thorium, NAS-NS-3004 [1960]

Tin, NAS-NS-3023 [1960]

Titanium, NAS-NS-3034 (Rav.) [1971]
Transcurium Elements, NAS-NS-3031 [1960]
Tungstan, NAS-NS-3042 [1961]

Uranium, NAS-NS-3050 [1961]

Vanadium, NAS-NS-3022 [1860]

Zinc, NAS-NS-3015 [1960]

Zirconium and Hafnium, NAS-NS-3011 [1860]

TECHNIQUES

Absolute Measurement of Alpha Emission
and Spontaneous Fission, NAS-NS-3112
[1968]

Activation Analysis with Charged Particles,
NAS-NS-3110 [1966]

Applications of Computers to Nuclear and
Radiochemistry, NAS-NS-3107 [1962]

Application of Distillation Techniquas to
Radiochemical Separations, NAS-NS-3108
(1962]

Cation-Exchange Techniques in Radio-
chemistry, NAS-NS-3113 [1971]

Chemical Yield Determinations in Radio-
chemistry, NAS-NS-3111 [1967]

Detection and Measurement of Nuclear
Radiation, NAS-NS-3105 [1861]

Liquid-Liquid Extraction with High-
Molecular-Weight Amines, NAS-NS-3101
[1960] _

Low-Level Radiochemical Separations,
NAS-NS-3103 [1961]

Paper Chromatographic and Electromigration
Techniques in Radiochemistry, NAS-NS-
3106 [1962]

Processing of Counting Data, NAS-NS-3108
[1965]

Rapid Radiochemical Separations, NAS-NS-
3104 [1961]

Separations by Solvent Extraction with
Tri-n-octylphosphine Oxide, NAS-NS-3102
[1961]

Current as of January 1972
Radiochemistry of Uranium . NAS-NS-3050 - USAEC