The Radio Chemistry of Plutonium.us AEC

8/7/2019 The Radio Chemistry of Plutonium.us AEC

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The Radiochemistry of Plutonium.Geor ge H. Colem anSep tember 1 , 1965

UN1 7J ERS ITY OF CALIFORNIALawren ce Ra dia tion La bora tory

Liver mor e, Ca liforn iaAEC Con tra ct No. W-7405 -en g-48

S u b comm it t ee o n Ra d io ch em is t ryNa tion al Aca dem y of Scien cesNa tion al Rea ea rcb Cou n cil

P rfm tedin USA. F r ic e82 .00 . Ava il a bl e f r om th eC le s .r in - fm Fede r a lSciemUficondTechnical Information,National Bureauof Stand ards,U. S .Depnrbnen tof Commer cerSp ringfield,Virginia.

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FOREWORD

Th e Su bcommittee on Rsdioch em is try is on e of a n u mber ofsu bcomm ittees work in g u nder th e Committee on Nu clea r Scien cewith in th e Na tion a l Academy of Scien ces - Na tiom l I&aa rchcouncil. Its members repres en t governmen t, In du et r la l, an du n lver s lt .y let i=tor ies In th e a rea s of mm iloch em is t ry a n dn u cl-r ch em is try. Su pport for th e a ct ivit ies of th is a n doth er su bcomn lt t ees of th e Ccmu oit tee on Nu clea r Scien ce isprovided by a gmn t from th e Na tion a l Scien ce Fou n da tion .

Th e Su bcomn lt tee h a s con cern ed Its elf with prepa ra t ion ofpu b lica t ion s , en cou ragin g an d appotiin g a ct ivit ies in n u clea redu ca tion , 6pon sorin g sympo~ti on selected cum -en t top ics inrad loch em is t ry an d n u clea r ch em is try, a n d in ves t iga t in g specia lproblem s as th ey a r is e. A s er ies of monograph s on th e md io-ch em is try of es s en t ia lly a ll th e elemen ts an d on md ioclwn ica ltech n iqu es is bein g pu blish ed . In it ia t ion a n d en cou ra gemen tof pu blica t ion of a r t lcleB on n u clea r edu ca tion in va r iou ssu bject a rea s of ch em is try h ave occu rred , an d developmen t an dim provemen t of cer ta in edu ca t ion a l a ct ivit ies (e.g., laboreto~an d demon s tm tion experimen ts with m dioect ivity) h ave beenen cou raged an d as s is ted . Ra dioact ive con tam in a t ion of reagen tsan d m a ter ia ls h a s been in ves t iga ted a n d specific recommenda tion srmde .

Th is ser ies of monograph s h a s resu lted from th e n eed forcompreh en s ive compila t ion s of md ioch em ica l an d n u cla a r ch em ica ltifommtion. Each monogmph collects in on e volum e th e pert in en tIn forma t ion requ ired for md loch em lca l work with an t id it idu lelemen t or with a specia lized tech n iqu e. Th e U. S. Atom ic En ergyCommiss ion h as spon sored th e pr in t in g of th e ser ies .

Ccumn en ts an d su gges t ion s for fu r th er pu b lica t ion s an da ctivit ies of va lu e to person s work in g with rad ioa ct ivity a rewelcom ed b y th e S ub com mittee.

M. E. &llou , Ch a irmanS u bcomm it tee on Rs dioch em is tr y

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PREFACETh is repor t h a s been p repa red a s on e of a ser ies of mon ograph s on th e rad io-

ch em is t ry of th e elemen ts for th e Su bcommittee on Rad ioCh em is try of th e Committeeon IWmlea r Scien ce with in th e Na tion a l Aca demy of Scien ces . Th ere is in clu ded areview of th e n u clea r a n d ch ern ic~ fea tu res of p lu ton ium of pa r t icu la r in teres t toth e rad ioch em is t , a d is cu s s ion of sample d isa cilu t ion &d cou n tin g tech n iqu es , an dfin ally, a collect ion of ra d ioch em ica l procedu res for p lu ton iu m.

Th e litera tu re sea rch was comp leted apprm dm a tely th rou gh September 1964.It is h oped th a t th e b ib liogra ph y is su fficien t ly exten s ive to serve th e n eeds of th erad ioch em iet , bu t it is to be expected th a t im portan t referen ces were o~tted .Th e au th or wou ld app recia te bein g made awa re of su ch om is s ion s , th a t th ey m igh tbe in clu ded in poss ib le fu tu re edit ion s of th is m onograph .

Th e au th or wis h es to exp res s th a n ks to Dr. Ea rl Hyde, for th e loa n of h isexten s ive ca rd file on th e rm iioch em ietry of p lu ton iu m , to Ca rl Wen a ri&h an d th es ta ff of th e LRL Libra ry who grea t ly a aa is ted in th e lit er a tu re sea rch , to Mrs .Sh au n a Ness *O typed th e firs t dra ft , an d to Mra . Vivian R. Men den h a ll whocompeten tly edit ed th e fin al dra ft an d p repa red th e bib liograph y.

I%m lly th e au f.bor th an ks h is colleagu es a t th e Lawren ce Radia t ion Labora tory,es pecia lly Dr. R. W. Hoff, for read in g an d crit icizin g th e m anu s cr ip t , an d Dr.P. C. Steven son for h is con th u ed in teres t an d su ppor t du r in g th e writ in g of th ismonograph.

George H. Colem anLa wr en ce Ra dia tion La bor at or yUn iver sit y of Ca lt ior niaLiver mor e, Ca lifor n ia

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CONTENTS

I. Gen era l Reviews of th e In organ ic a n d An a lyt ica l Ch em is tryof Plu ton ium . . . . . . . . . . . .

II. Gen era l Reviews of th e Radioch em is t ry of Plu ton ium . . .III. Tab le of Isotopes of Plu ton ium . . . . . . .rv. Ch em is try of Plu ton iu m of Specia l In teres t to th e Rad ioch em is t

A. Meta llic Plu ton iu m . . . , .A. 1 Prepa ra t ion . . . . .A. 2 Ph ys ica l Proper t ies . . .A. 3 Ch em ica l Propert ies . . .

B. Compou nds of Pu . . . . .c. Plu ton ium Ion s in Solu t ion . . .

C. 1 Oxida t ion Sta tes . . . .C. 2 Oxida t ion Redu ction Reaction s .C. 3 Disp ropor t ion a t ion Rea ction s .C. 4 Rad iolyt ic Redu ction of Pu Solu tion sC. 5 Hydrolyt ic Reaction s of Plu ton iu mC. 6 Pu (IV) Polym er . . . .C. 7 Complex Ion Forma tion . . .

D. Sepa ra t ion Meth ods . . . . .D. 1 Co-precip it a t ion an d Precip ita t ionD. 2 Solven t Extra ct ion Meth ods . .D. 3 Ion Exch an ge . . . .,

v. Dis solu tion of Plu ton iu m Samples for An alys isA. Meta llic Plu ton ium . . . . .B. Oth er Compou nds . . . . .c. Biologica l an d En vironmen ta l Sam ples .

VI. Sou rce Prepa ra t ion a n d Cou n tin g Meth ods .A. Sou rce Prepa ra t ion . . . . .

A. 1 Direct Eva pora t ion . . . .A. 2 Electrodepos it ion . . . .A. 3 Oth er Meth ods . . . . .

B. Cou n tin g . . . . . . .VII. Sa fety Con s idera t ion s . . . . .

A. Rad ioact ive Sa fety . . , . .B. Cr it ica lity Sa fety . . . . .

VIII. Collect ion of P rocedu res . . . .A. In trodu ction . . . . . .B. Lis t in g of Con ten ts . . . . .

Procedu re 1 . Determ in a tion of Pu in solu t ion s con ta in in g la rgeam ou n ts of Fean d Cr . . , . . .

Procedu re 2 . Sepa ra t ion an d determ in a t ion of Pu by TTAextract ion . . . . . . .

1234444468899151516172424287596969696969697979999102102103105105105108112

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CONTENTS (Con tin u ed )Page No.

Proced ures (Con tin u ed )Procedu re 3 . Sepa ra t ion an d determ in a tion of Pu in

U fis s ion p rodu ct m ixtu res . . .Procedu re 4 . Plu ton iu m . . . . . . .Procedu re 5 . Plu ton iu m . . . . . . .Procedu re 6 . Sepa ra t ion of Plu ton iu m from Ura n iu m andFis s ion Produ cts in Irra d ia ted Reactor

Ta rgets . . . . . . . .Procedu re 7 . Determ in a tion of Pu . . . .Procedu re 8 . Ura n iu m an d Plu ton ium Ana lys is . .Procedu re 9a . Sepa ra t ion of Plu ton iu m from Irra d ia ted

Uran ium . . . . . . . .Procedu re 9b . Sepa ra t ion of Plu ton iu m from Ura n ium Meta lProcedu re 10 . Pu rifica t ion of Plu ton ium from Uran iu m andFis s ion Produ cts . . . . . .Procedu re 11 . Ura n iu m and Plu ton iu m from En viron men ta l

Samples of SO1l, Vegeta t ion an d Wa ter .Procedu re 12 . Plu ton iu m from Environmen ta l Wa ter

Samples . . . . .Procedu re 13 . Plu ton iu m from Environm en ta l Wa ter

Samples . . . .Procedu re 14 . Sepa ra t ion of Plu ton iu m in Ura n iu m-Plu ton iu mFis s ion Elem en t Alloys by TBP Extra ct ionfrom Ch lor ide Solu t ion s . . . . .Procedu re 15 . Sepa ra t ion of Pu before Spectrograph ic An a lys isof Lrn pu rit ies An ion Exch an ge Meth od . . .Procedu re 16 . Sepa ra t ion of Plu ton iu m Before Spectrograph icAn a lys is of Impu rit ies . Ext ra ct ion

Ch roma tograph y Meth od Us in g TBP . . .Procedu re 17 . Sepa ra t ion of Np an d Pu by An ion Exch a n ge .Procedu re 18 . Sepa ra t ion of Np an d Pu by Ca tion Exch an ge

Ch rom a tograph y . . . . . . .Procedu re 19 . Determ in a tion of Plu ton ium in Urin e . .Procedu re 20 . Determ in a tion of PU239 in Urin e (Sm a ll Area

Electrodepos it ion Procedu re) . . . .Procedu re 21 . Determ in a tion of Plu ton ium in Urin e . .Procedu re 22 . Determ in a tion of Americium in Urin e in th ePres en ce of Plu ton iu m . . . . . .Procedu re 23 . Determ in a t ion of Plu ton ium in Urin e by An ion

Exch an ge . . . . . . . . .Procedu re 24 . Determ in a tion of Plu ton ium in Urin e by Co-crys ta lliza t ion with Pota s s ium Rhod izon a te .Procedu re 25 . Determ in a tion of Plu ton ium in Urin e an d Bone

Ash by Extract ion with Pr im a ry Am in es . .Glos sa ry . . . . . . . . . . . . . . .Referen ces . . . . . . . . . . . . . .

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The Radiochemistry of PlutoniumGEORGE H. COLEMAh T

Lawren ce Radia t ion Labora tory, Un ivers ity of Ca liforn iaLiverm ore, Ca liforn ia

I. GENERAL REVIEWS OF THE INORGANIC AND ANALYTICALCHEMISTRY OF PLUTONIUM

J . J . Ka tz an d G. T. Seaborg, , Th e Ch em is try of th e Actin ide Elemen ts , Chap .VII, (J oh n Wiley an d Sons In c., New York , 1957), pp . 239-325 .Plu ton ium , in Nou veau Tra it e de Ch im ie Min era le, Pau l Pa sca l, Gen l. Ed . Vol.xv, Uran ium et Tran s u ran ien s (Masson et Cie, Pa r is , 1962) pp 324-864 .Th e Complex Compou nds of th e Tran s t ira n ium Elemen ts J A. D. Gellman ,A. I. Moskvin , L. M. Za its ev, an d M. P. Mefodeva (Con su ltan ts Bu reau , NewYork , 1962 tran s l. by C. N. an d T. I. Tu rton ).M. Tau be, Plu ton ium , (Macm illan Co., New York , 1964; tran s l. by E.Lepa an d Z. Nan owski) Ch ap. 2 , pp 39-84 .R. E. Conn ick , l l o ~ d a t i o n S t a t e a , p o t e n t i a l s , E qu ilib ria , a n d Oxid at ion -Red u ct ionReaction s of Plu ton ium , in Th e Act in ide Elemen ts , Na tl. Nu cl. En ergy Series , Div.IV, Plu ton ium Project Record Vol. 14A; Ch ap. 8, G. T. Seaborg an d J . J . Ka tz,Eds . (McGraw-Hill Book Co., In c., N-ew York , 1954) pp 221-300 .J . c. Hin dm a-n , llIon i~ an d Molecu la r Species of Plu tOn ium in Solution, in QeActin ide Elemen ts , Vol. 14A, Chap . 10 , pp 371-434 .B. B. Cu n tigh am ,rPrepa ra t ion an d Propert ies of th e Compo~ds of Plu ton ium , in The Actin ide Elemen ts , Vol. 14A, Ch ap . 10, pp 371-434 .C. F. Metz, Th e An a lyt ica l Ch em is try of Plu ton ium , An a l. Ch em . 29 , 1748 (1957).D. Nebel, Th e An a lyt ica l Ch em is try of Plu ton ium , J oin t Pu blica t ion s Resea rchService NYC, AEC Report J PRS - 11689. tran s l. from Chem. Tech . Leipzig, ~5 22 (1 96 1),P, N. Pa lei, An a lyt ica l Ch em is try of th e Actin ides , tran s l. by S. Botch arskyJAERE-LIB/ TRANS- 787. (See a lso J . An a l. Ch em . USSR ~ 663 (1957 ).)A. J . Moses , Th e An a lyt ica l Chem is try of th e Actin ide Elemen ts (Macm illanCo., New York , 1963).A. S ch iffe rs , Plu ton iu m, sein e ch emisch en u nd ph ys illilis ch en Eigen sch a ften , Ch em iker Zeit . 86 , 656 (1962).K. W. Bagn a ll, Th e Tra n su ran ium Elemen ts , Sci. Progr . (London ) 52 , 66-83(1964).V. I. Ku zn etsov, S. B. Sawin , an d V. A. Mikh a ilov, Progres s in th e An a lyt ica lCh em is try of Uran iu m , Thorium and Plu ton iu m , Ru ss . Ch em . Rev. 29 , 243 (1960).R. Kra ft , C. J . Wen s r ich an d A. L. Langh ors t , Ch em ica l An alys is of Plu ton iu mand Plu ton iu m Alloys : Meth ods an d Tech n iqu e s , Lawren ce Radia t ion Labora tory,Un iver sit y of Ca lifor nia , Livermore, Ca lif. UCRL-6873, 1962.

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IL GENEWL REVDZWS OF THE RADIWHEMISTRYOF PLUTONIUM

16. E. K. Hyde, Radioch em ica l Sepa ra t ion s of th e Actin id e Elemen tfi~ in Th eActh ide Elemen ts , Na tion a l Nu clea r En ergy Series , Div. IV, p lu ton iumProject Record Vol. 14 , G. T. Seaborg an d J . J . Ka tz, Eds . (McGraw-HillBook CO. , New York . 1954) Ch ap . 15.

17. E. K. Hyde, Radioch em ica l Sepa ra t ion s Meth ods for th e Actin ide Elemen ts , in Proc. of th e In tern a t ion a l Con feren ce on th e Peaceftd Uses of Atom ic En ergy,Gen eva , 1955 , A/ CONF. 8/ 7, (Un ited Na tion s , New York . 1956) pp 261-303 ,Paper 728 .

18 . M. P. Fa u geraa , Sepa ra t ion et Pu rifica t ion des Isotopee, (of Plu ton ium ), inNou veau Tra ite de Ch em ie Min era le} Pau l PaBca l, Gen . Ed., Vol. IV,Uran im n et !lh%su ra .n ien s , ( ~s son et Cie, Pa r is , 1962 ) PP 339-385 .

19 . M. Tau be, Plu ton ium (Macm illan Co. , New York , 1984; tran s l. by E. Lepa an dZ. Nanowd i) . Ra dioch em ica l Meth od s of An alys is , pp 78-84 .

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~ - TABLE OF ISOTOPES OF pLuTo~M*Specific a P ar ticleActivity Type of EnergyIsotope Ha lf Life (d / m / pg) Decay (MeV) Met hod of Pr ep ar at ion

~u232 36 m in --

PU2 3 3 20 m in --

~u234 9,0 h r .-

PU235 26 m in --

PU236 2.85 yr 1 .18X 109

~u237 45.6 da ys --

~u238 86.4 yr 3 .88 X 107

0270, 6.58EC 98$

U235 + 100 MeV aparticles~233 + 40 MeV Dao.lye, 6.30

EC99+70 particlesU233 , 235 + 40 MeV apa r t icles Dau gh ter ofCm238

0670, 6.19EC 9470

a3 x 10 -37 ., 5.85EC 99 + ~.

U233, 235 + 20 -30 MeVa p a rt ic le s~235 + 40 MeV a pa rt iclesDau gh ter Np23 6Dau gh ter Cm 240

c1 5 .7 63 (6 9~o)5 .7 16 (3 17 0 )U235 + 40 MeV Q part iclesa o. oo3 70 , 5 .3 6 (7 9 70 )EC 99+% 5 .6 5 (2 1 70 )., ~238 + d eu t er on sDau h ter Cm242$Pu 2 9 + h igh en ergyneut ronsNp237 + n eu tron s

a 5 .4 95 (7 2~0 )5 .4 52 (2 8%)

Pu 239 24,360 yr 1 .36 X 105 U238 + n eu tr on sa 5 .1 47 (7 37 0 )5 .1 34 (1 77 0)5 .0 96 (1 0~0 )PU240 6,580 yr 5 .00 x 105 ~238 + n eu tr on sPU2 39 + n eu tron s

Dau gh ter of Cm244c1 5 .1 62 (7 6%)5 .1 18 (2 4%)

PU241 13 ,0 y-r 2 .57 X 108 a4 X 10-370 , 4 .89,B-99+7OU238 + n eu tr on sDau h ter of Cm245i?u 23 + a pa rt icles

PU242

PU243PU244

~u245PU246

3,79 x 105 8.65 X 103w

U238 + n eu t ron sAm241 + n eu tron s(Y 4.898 (767 . )4 .8 58 (2 47 0)PU242 + n eu t ron a4 .98 h r -- P- ---

(2 -- -7 .6X107 42.8w-

PU244 + n eu t ron s~238 + n eu tron s (th er -

P- ---fl- ---

10.6 h r --10 .85 da ys --

%Th e da ta for th is tab le were taken from th e recen t review of Hyde. 192 Tfiis worksh ou ld be con su lted for fu r th er deta ils an d referen ces to th e litera tu re.

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IV. CHEMISTRY OF PLUTONIUM OF SPECIAL INTEREST TO THE RADIOCHEMISTA. Meta llic Plu ton iu m

A.1 Pr ep ar at ionPlu ton ium meta l is mos t common ly prepa re~8by th e redu ction ,of a h a lide by a more

electropos it ive meta l su ch a s ca lcium . Connor h as compa red va riou s com bin ation sof h a lide a n d redu cin g meta l a n d fou n d th a t th e on ly s a t is fa ctory rea ct ion s were Pu F3 ,Pu F , 164a n d PuC13 redu ced with Ca meta l. Ha rmon an d Reas an d 0rth 306 h avediscu s sed th e con vers ion of Pu s a lts to m eta l on a n in du s tr ia l s ca le, wh ile An selin ,et a l.3 0 descr ibe a meth od for th e con vers ion on a gram sca le.A.2 Ph ys ica l Propert ies

Pu is a typ ica lly s ilver-wh ite a ppea r in g m eta l wh ich h as a n umber of pecu lia rph ys ica l proper t ies . Th e m eta l u ndergoes a tota l of five a llotrop ic modifica t ion sbelow th e melt in g poin t , two of wh ich h ave n ega tive coefficien ts of th erma l expan s ion .Ta ble IV-1 s umma rizes th e more importan t ph ys ica l proper t ies .A.3 Ch em ica l Propert ies

Pu is a very react ive m eta l. Th e poten tia l for th e cou p le Pu = PU*+ + e- is2 .03 volts , wh ich places it between s can d ium (Se) an d th orium (Th ) in th e EMF seriesof elemen ts . Pu oxid izes more rea dily th an does U, sn d res embles cer ium (Cc) in it srea ct ion s in a ir . Su perficia l oxida t ion of a fresh ly prepa red su rfa ce occu rs in a fewhou rs in n orma l a ir . Th e oxide is more or les s adh eren t , an d in severa l d ays th eoxida t ion react ion a ccelera tes u n til fin a lly th e oxida t ion to PU02 is complete. However ,th e oxide coa tin g protect s th e u n der lyin g meta l in dry a ir . an d th e oxida t ion proceedsm ore s lowly. Pu m eta l is a t ta cked a t eleva ted tempera tu res by mos t ga s es ; Hz, N2,h a logen s , S02 , etc. Pu meta l d is s olves ea s ily a n d rap id ly in modera tely con cen tra tedHC1 an d oth er h alogen a cids .

Pu form s in termeta llic compou nds with in term edia te s olid solu t ion s with mos tmeta llic elem en ts . However , s im ple eu tect ic m ixtu res a re u s u a lly made with th e grou pVa an d VIa meta ls , a n d very lit t le volu b ility in eith er th e liqu id or solid s ta te is ex- :h ib it ed by a lka li an d a lka lin e ea r th meta ls .

Th e beh avior of Pu towa rd va r iou s solu t ion s is given in Table IV-2 .

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TABLE IV- 1 . Ph ys ica l Proper t ies of Plu \ on iu m Meta l: M=Na , K, Rb, CS, NH4PU(S04)2M4Pu (S04)4 , M=K, Rb, NH4P;(N03)4M2Pu (N03 ),6 , M=K, Rb,POP04PU(HP0 4)2 . XH2 0PU2 H(P0 4)3 . yH2 0PU3 (P0 4)4 . ZH2 0Pu t, PU2C3PUOC03K6[pu (co3)51 0 m H20K4[Pu (C03 )41 . m H20K12 [ pu (co3)d omH20M4[Pu 02 (C03 )3] , M=K,

HP UF e ( c ~ ) 6 xH20PuFe(CN)6Pu 3[Fe(CN)6 ] 4 . XH2 0

Cs , T1

NH4

(Pu02)3[Fe@)6] 2 H20PU2 (C2 04 )3 .xH2 0

PU(C2 04 )2 6 H2 0

PU02(C204)-3H20

NaPu02(C2H302)2

s . H20s . HN03, i. H2S04 -K103, exces smo3s. HN03, decomposed in H2S03s . s lowly in boilin g m in era l a cid s ;react ion speeded by fu s ion withNaHS04 or HF added to HN03;s olu bilit y is m ore cliff icu lt if ign it eda bove 500s . m in era l a cids . m in era l a cids . m in era l a cid , Ksp = 1 .8 X. 1 0 -23 264s , con e. HN03, H2S04i. M2S04 -H2S04 , S. H20 a lcoh ols . H20, i. a lcoh ols . H20, i. a lcoh ols . H O, colloida l Pu form s in3a qu e u s soln . s . HN03, eth er , a ceton ei. c on e . HTJ 0 3 , . H20 il a cidS. h ot con e. m in era l a cid ; s1 . S.H3P04, NaOH; i. HC2H302

i. m in era l a cid - H3P04

s . HC1, H2S04, i. cold con e HN03S . h ot con e. HN0 3-Na F2i. H20 , s1 . s . cold m in era l a cids

i. a lcoh ol

:: ~:::$a :~co,, d . s . H20,i. HC1i. HC1i. HC1i. HC1i. H20 , s . m in ers l a cid ; s1 . S. K2C204.(NH4)2C204i. H2Cl, s . H2S04, HN03, HC104 s 1- s .a cid -K2C204, NH2C 204 m in imum s .in 1 .5 ~ HN03 - 0 .025 M 2c204 264S . m in era l a cid ; s1 . s , a cid 2C 24s1 . s . h ot H20, s . a cid

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* Compiled p r im a r ily from th e reviews of Cu n n in gh am an d Fau gera s a nd Heu berger 128Un les s oth erwise specified , th e da ta a re taken from th es e reviews .** Th e followin g abb revia t ion s a re u s ed:s . s olu b lei. insolubleS1 . s . s ligh t ly solu b lecone. concentratedd il. d ilu te

C. Plu ton iu m Ion s in Solu t ionC.1 Oxida t ion Sta tes

Plu ton iu m in aqu eou s solu t ion exis ts in th e +3, +4 , +5, or +6 oxida t ion s ta tes ,res em b lin g both u ra n iu m (U), n ep tu n iu m (Np) and amer icillm (Am ) in th is respect ,

Th e forma l oxida tion poten t ia l d ia gram s for Pu in a cid an d ba s ic s olu t ion a reta ken from La tim er . 2 0

ACID SOLUTION

BAS IC SOLUTIONPu ~ ~(oH1 o 95

3 - PU(OH)4 u PU020H = PU02(OH)2-0.51

Forma l oxida tion poten t ia ls for Pu cou ples in va r iou s 1 ~ solu t ion s a re sh own inTab le IV-.4 . Th e d is p lacemen ts of th e poten tia ls a re du e to th e complex-form in gten den cies of th e an ion s with Pu .

TABLE PJ -4 . Forma l Poten tia ls for Pu Cou p les in Va r iou s 1 ~ Solu t ion s

PU(III)-PU(IV) Pu (IW)-PU(VI) Pu (fII)-Pu (VI) P u (v) - PU (VI)HC104 -0.982 -1.043 -1 .023 -0.92HC1 -0.970 -1.052 -1 .024 -0 .912HN03 -0.92 -1 .05 -1.04 ------H2S04 -0.74 -1 .2- 1 .4 ------ ------

Th e lower oxida t ion s ta tes becom e more s ta b le in th e a ct in ide s er ies from U toAm , an d correspon d in gly th e h igh er oxida t ion s ta tes become more d ifficu lt to a tta in .Th is effect is illu s t ra ted in Tab le IV-5, wh ich sh ows th e free en ergies of forma t ionof va r iou s a ct in ide ion s.


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TABLE IY-5. Free En ergy of Forma tion of Actin ide Ion s (kca l/ m ole)M +++ M +t++ MO; MO~

u -124.4 -138 .4 -237 .6 -236,4Np -128 .4 -124 .9 -221 .0 -194 ,5Pu -140.5 -118.2 -204 .9 -183 .5Am -160 .5 -110.2 (-194 .5 ) -156 .7

Th u s th e mos t s ta ble +3 ion in th is s eries is Am+ , wliie th e mos t s ta ble +6 ion isu o~. Pu is th e fir s t member of th is s er ies in wh ich th e tr ipos itive s ta te is s ta bleen ou gh in aqu eou s solu tion to be u sefu l in s epa ra t ion ch em is try.

Th is fa ct is of su preme importan ce in th e radioch em is t ry of Pu , s in ce Pu can bes electively ma in ta in ed in eith er th e +3 or +4 oxida tion s ta tes in s epa ra t ion sch emes .Advan tage is taken of th is ab ility in man y of th e collected procedu res in s ection VI.

Th e oxida tion -redu ction beh avior of Pu is complica ted by severa l fa ctors :(1 ) f/ 0~ d isp roport ion a tes in to PU+4 an d PuO~ an d u n der cer ta in con d ition s PU+3,Pu , Pu o;, ++ +4and PU02 can a ll exis t in equ ilib rium ; Pu . m a sm all, h igh lych a rged ion an d th erefore u n dergoes exten s ive hydrcdys is a t low acid ity an d form sman y s tab le complex ion s . Th is ten den cy is a dom inan t fea tu re of Pu (IV) ch em is try.Pu (IV) forms a lon g-ch a in compou nd or polym er by h ydrolytic rea ct ion s . Pu (IV)polymer is on e of th e more u np lea s an t a spects of Pu ch em is try from th e s tan dpoin t oft h e r a dio ch em is t .C. 2 Oxida tion -Redu ction Rea ction s

Tab le IV-6 lis ts reagen ts and con dition s to effect ch an ges in oxida tion s ta te forPu ion s . It mu s t be emph as ized th a t a rela tively sma ll ch ange in con d ition s mayprodu ce a la rge ch an ge in th e equ ilib r iu m, a nd th at som e of th e oxida tion -redu ctionreaction s m ay proceed beyon d those lis ted . Therefore, th e lis ted rea ct ion s sh ou ldbe taken a s a gu ide on ly.

In gen era l, th e ch an ge in oxida tion s ta te between +3 an d +4 is rap id , s in ce on ly++one electron is in va lved in th is ch an ge. Sim ila r ly PuO~ an d PU02 chan ges a re rap id .Ch an ges in th e oxida tion s ta te of Pu wh ich in volve th e makin g or break in g of a Pu -Obon d a re u su a lly s lower. However , Hindman , 18 4 m a gen era l review of th e k in et ics ofact in ide oxida tion -redu ction rea ct ion s , gives examples of rea ct ion s in volvin g M-Obonds wh ich proceed a s rap i~y a s some in volving on ly electron tran s fer . Newton an dRabideau302 h ave s ls o reviewed th e kin et ics of a ctin ide oxida tion -redu ction reaction s .C. 3 Dis proport ion ation Rea ct ion s

The poten tia ls of th e va r iou s Pu cou p les a re su ch th a t appreciab le qu an tit ies ofs evera l oxida tion s ta tes may exis t in equ ilib r iu m. Pu (IV) an d Pu (V) a re both u n s tablewith respect to d is proport ion a t ion in to h igh er an d lower oxida t ion s ta tes in weak lya cid , u ncompleted media . Th ere a re s evera l impor ta n t eqt iib r ia wh ich mu s t becon s idered for an u nders ta n d in g of Pu oxida tion -redu ction ch em is t ry,


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TABLE IV-6 . Oxida tion -Redu ction Reaction s of Plu ton ium Ion s*A. Pu (IH) - R(m )

Reagents Solution Temp. Ra te Referen ce

C1 2H202

cr207H103mo~02

NO;

Dilu te a cid1 ,5 ~HCl6 ~ HC1,d ilu te H2 S0 40 .5 &lHClR-6 ~ HC14-8 &l HC104Dilu te a cidDilu te a cidDilu te a cid115 ~ HC1

ITN030 .4 2 ~ HN03JF e(H ) S u lfam at e,0 .1 ~ HN02

R.T.**R.T.R.T.R.T.R.T.R.T.R.T.R.T.R.T.R.T.R.T.9 7 cR.T.R.T.

Very rap idVery rap idVery rap id 235Very rap id 23 5Slow (tllz >9 h r)Equ ilib r iu m a t 907Pu (N) in severa l h ou rs 145Equ ilib r iu m a t 80 - 90~0Pu (~) in severa l h ou rs 14 5Extrem ely rap idExtrem ely rapidExtremely rapid 79No oxida tion in 42 h r.2 . 5 ~ 0 oxid ized in 4 h r ,more rap id in h igh erVery rap id 63Complete in few m in u tes 63

Th is ta b le is an en la rged vers ion o~ th e one given by Ka tz and Seaborgl wh ich wascompiled from data given by Conn ick. Un less oth erwise specified , th e da ta were ob-ta in ed from th is sou rce.** R. T. = room tempera tu re.

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B. Pu (~)~ Pu (LU)

Reagen ts Solu t ion Temp. Ra te ReferenceHydroqu in on e mu te HN03 R.T. RapidH2 , Pt 0 .5 g - 4 . O~HCl R.T. > 9~0 redu ced in 40 m inI- 0 .1 yKI+ 0.4 ~ HC1 R.T. 1/ 2 =2minHso; 0 .05 ~ NH4HS03, R.T. 1/ 2 = -2 m in 650.3 ~ mo~NH30H+ 0.5 M HN03 + 0.1 ~ R.T. 1/ 2 -40 m inNH36H+

NH20H. HC1, HC1 ----Zn .0 .5 ~ HC1 R.T.S0 2 1 ~ HN03 R.T.Ti# 6 ~ HC1, R.T.

d ilu te H2 S0 4 R.T.1 ~ HN03 + 1 ~H2S04R.T.

Cr++ Dilu te HC1 or H2S04 R.T.Ascorb ic HN03Acid 0 .5 ~HN03, 0 .01 ~ R.T.As corb ic acid

6 MHN03 O.1~A s~orb ic acid , Fe(II)Su lf am at e R.T.

H202 7J~HCl R.T.

-----------------------Rapidtl] 2 < 1 m inVery rap id 235Very rap id 235Rapid 103Rapid 2 35 , 4 49Rapid 416,402Rapid 65

Rapid 65Complete in severa l h r 145

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c.. Pu (IV)+ Pu (VI)

Reagents Solution Temp. Ra te Referen ce

NaBi03

BrO~C e+4HOC1

H5106Ml-lo;

03

Ag*

c r207HN03

Clz

Electrolysis

5 M HN03 + 0.84 R.T.g/ Xt er0 :1 ~ BrO~, 8 5 c1 ~ HN030.1 ~ Ce+4, 0 .5 ~ R.T.HN03pH 4.5 , -8 ,2 , 8 0 c0 .1 ~ HOC145y K2C03 4@ c0.02 y H5106,o.22&JHN03

R.T.

l~HNo3, 0 ,001 y 2 5 CMnO~Ce+3 or Ag+ ca ta lys t @ C0.25 ~ HzSO+ no 19=Ccata lys t0 .25 ;M_H2S04, n o 6 5 Ccata lys t2 ~ HC1, n o ca ta lys t R.T.Ag+ + S20~, 1 .1 ~ 2 5 CHN030.5 N H2S04, Solid OAg(ti)0 .05 ~ HC104, 2 5 Cd ilu te H2 S0 4 R.T.0 .55 ~ HN03, 98 * 11X 10-3 MPu0.03 ~ H S04 +7 8 00 Csa tu ra te C120.1 ~ HC104, 0 .025 22 c~ Clz 0 .056 &l Cl-0 .5 ~ HC104 R. T.

Complete in les s th an5 m in99~0 oxid ized in 4 h r

Complete in 15 m inComplete in 15 rn inComplete in 5 -10 m int l/ 2 = 100 m in

t l/ 2 = 50 m in

Complete in 30 m inComplete in 15 h r 150

Complete in 1-1 / 2 h r 1502-8 h r depen din g on 275, 27 6con cen tra t ion of PuComplete in 1 rn in

361 , 39

1/ 2 = 15 m inComplete in 9 h r 1298CF7Lcom plete in 2 h r 301

1/ 2, = 35 rn in

t l/ 2 =2hr

Complete in 30 m in 454

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D. Pu (VI) s Pu (~)

Reagents Solu t ion Temp. Rate Reference

HCOOH HN03 R.T. slowC20; 0 .02 ~ H2C204 75 C t l/ 2 = 60 m .inI- 2 .3~EU, 3 .1 ~ ? RapidHN03Fe~ HC1 R.T. Rapid

2-6 ~ HN03. 1 ~ R.T. Rapid 75Ferrou s Su lfm ate2 -4 ~ H2S04 R.T. Fa ir ly fa s t 361 , 39

NO; HN03 ? ? 96H202 HN03 R.T. Fa s t , redu ct ion 295con tin u es to PU(III)

E . Pu (V) +Pu (IV)Rea gen t s Solu t ion Temp. Ra te Referen ceHN02 --------------- R.T. s lowNH30H+ 0,5 M HC1, 0 .015 ~ R.T. slowNH3mH+

F. Pu (VI)~ Pu (V)Reagents Solu t ion Temp. Rate ReferenceI- pH 2 R.T. Ins tan taneousNH2NHj 0 .5 M Cl.. 0 .05 ~

?2 5 C 1/ 2 = 180 m inNH2XH

S0 2 pH -2 25 C Complete in 5 m inFe+ 0.05 2 ~ HC104, 0-25 C --------------------- 301~=2.

Th e fir s t of th ese is th e d isproport ion a t ion of Pu (137) a ccord in g to th e react ion3PU+4 + 2H20 = 2Pu 3 + PU02++ + AH+

for wh ich th e con cen tra t ion equ ilib r iu m con s tan t may be wr it ten

~ . (Pu +3)2 (PuO~+) (H+)4c (Pu~)3Table IV-7 lis t s Kc for th is react ion u n der s im ila r con dit ion s of acid ity a n d ion ic

s tren gth for d ifferen t acid s .

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ofP~%EV~;kAcidm a t 25C*Con cen tra t ion Equ ilib r iu m Con stan t for th e Dis proport ion at ionAcid H+~ 1.0 M; ~=l.OHC104 9X1 O-3HC1 2x 10-3HN03 4x 10-7 **H2S04 Very low

*~Taken from Gel man ~. 3Appreciab le qu an tit ies of Pu (III), Pu (IV),a n d Pu (VI) can n ot efis t togeth er in H2S04

s o lu t ion9 .Thes e da ta sh ow th a t s t ron g in ilu en ce of th e an ion ic medium on th e equ ilib r ium .

The equ ilib r ium is sh ifted ma rked ly to th e left even a t th ese low ion ic s tren gth s by th es t ron g complexes form ed by Pu (IW). Con versely, th e equ ilib r ium is sh ifted to th e r igh t bylower in g th e concen t ra tion of th e a cid an d complex form in g an ion , a t lea s t u nt il th e on s et ofh ydrolys is a t pH 1-1 ,5 . The h ydrolytic rea ct ion s aga in s ta b ilize Pu (IV).

The dispropor tion a t ion rea ct ion probab ly occu rs a s a s eries of b im olecu la r rea ct ion s .Accord in g to Conn ick an d McVey, 100 th e rea ction pa th may be

2pu +4 . pu +3 + PU02+ (s low)Pu o; + PU+4 = PU02++ + Pu +3 (Fast)

Th e fira t react ion is s low becau s e Pu -O bond forma tion is in volved , wh ile th e s econ drea ction on ly requ ires electron tran s fer, The ra te of th e firs t rea ction is s econ d-order in Pu (IV) con cen tra t ion an d in vera e th ird -order in H+ con cen tra t ion . Thefollowin g react ion sequ en ce is con s is ten t with th es e d iscrepan cies

PU+4 + H2 0PuOH+3 + H20

PuOH+3 + Pu (OH)~

PuOH+3 + H+PU(OH)2H + H+PU+3 + PuOT+ H.O + H+

CrockerO determ in ed th e rela t ive amou n t of each oxida t ion s ta te p res en t over awide ran ge of tem pera tu re an d ~03 con cen tra t ion . He fou n d th a t th e m in imu mcon cen tra t ion of HN03 to preven t forma t ion of Pu (VI) in a 4 X 103 M Pu (IV) solu t ionia 1 .5 ~ wh ile a t 98 C th e requ ired con cen tra tion of a cid is 8 M.

Th e second im por ta n t equ ilib r ium is th e d iap roport ion a tion of Pu (V), wh ich isu n s ta b le in m odera tely a cid solu t ion with respect to th e rea ct ion

2 Pu (v) = Pu (rv) + PU(VI)Conrdckgg des cribes th is overa ll rea ction a s proceed in g by eith er of th e two s lowreactions

(A) 2 PuO~ + 4H+ = Pu+4 + PuO~ + 2H20

(B) PuO~ + Pu +3 + 4H+ = 2Pu +4 + 2H20

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followed by th e fa s t rea ct ion(c) Pu o; + PU+4 = PU02* + PU+3

Reaction s A an d B in volve th e break in g of Pu -O bon ds , wh ile C does n ot . React ion Ais p roba bly on ly im por tan t u n til su fficien t PU+3 is formed for rea ct ion B to occu r ,s in ce B is k in et ica lly more proba ble th an A.

Th ese dis propor t ion at ion react ion s m ay be in volved in oxida t ion -redu ctionreact ion s by oth er reagen ts . In s tea d of d ir ect oxida t ion or redu ction , th ed isproport ion a t ion react ion can occu r firs t , followed by d irect oxida t ion or redu ct ionof th e a pp ropria te produ ct .C.4 Rad iolyt ic Redu ct ion of Pu Solu tion s

Th e a lph a pa rt icles em it t ed in th e decay of Pu 239 s u pp ly en ou gh en ergy to th e m edi-239u rn to decompose solu t ion s of Pu by rad iolys is . Th e rad iolys is p rodu ct s th en oxid izeor redu ce th e Pu , depen d in g on th e n a tu re of th e s olu t ion a n d th e oxida t ion s ta te ofth e Pu . Th is effect was firs t d escr ib ed by Kash a a n d Sh elin e 215 wh o n oticed 0 .670redu ction of Pu (VI) to Pu (IV) per da y in perch lor ic acid s a lu tion wh ich was in depen den tof a cid ity over a ran ge 0 .1 to 2 ~. Th e ra te of redu ct ion h HC1 wa s con s idera b lyless. II-I both ca ses th e react ion is S1OW enot igh to a llow th e equ ilib r iu m qu an tit iesof th e va r iou s oxida t ion s ta tes to be presen t . Th e redu ction of Pu (VI) proba blyproceeds firs t to Pu (V), an d th e lower s ta tes ob ta in ed by d isproport ion a t ion of th ision.

Ra bid ea u ~.3 26 con firmed th e above qu alit a t ive res u lt s con cern in g th e rela t ivera tes of HC104 an d HC1 redu ction a n d fou n d th a t th e s itu a t ion is comp lica ted by th eprodu ction of Cl- in HC104 solu t ion s an d C12 in HC1 solu t ion s . Also, if Br - is addedto HC1 04 s olu tion s, a n et oxida t ion in s tead of redu ction occu r s if th e mean ofida t ionn umber is in it ia J ly a pproxima tely 4 .x308Pages 309a n d Page; a n d Ha is s in s ky fou nd th a t th e ra te of redu ction depen dedvery s tron gly on th e n a tu re of th e an ion in a s tu dy of extern a l gamma-ra d ia t ionin du ced redu ct ion of Pu (VI). Th e ra tes of redu ction decrea sed in th e orderclo~ ~ so~ > Cl- >> NO;. Th ese resu lts p res u mably a lso apply to a u to-r edu ct ionb y a lp ha p art icles .

Popov et a l. 320 on th e oth er h an d fou n d on ly oxida t ion by ir ra d ia t ion of HN03solu t ion s of Pu with extern a l x-r ad ia t ion . Th e ra te of oxida t ion decrea sed with a nin crea se of NO~ and tota l a cid ity.

Th e les son to th e rad ioch em is t is clea r : Th e s ta ted oxida t ion s ta tes of old Pus a lu t ion s , pa r t icu la r ly low acid ity HC104 a n d H2S04 solu t ion s , sh o~d be viewedwit h s u s pic ion .C, 5 Hyd rolyt ic Reaction s of Plu ton iu m

Pu in a ll of it s ot id a t ion s ta tes exis ts in aqu eou s solu t ion s a s h igh ly ch a rged ion sa n d th erefore u ndergoes h yd rolys is rea ct ion s in d ilu te a cid solu tion s . Th e ten den ciesfor th es e ion s to u n dergo h ydrolys is is depen den t on th e ch a rge an d ion ic ra d iu s . Th eten den cy th u s in crea ses with in crea s in g a tom ic n umber for a ll th e oxida t ion s ta tesof th e act it ide s er ies an d in th e ca se of Pu in crea ses in th e order PuO~ < Pu +++ +4


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PU+4 h as a pproxima tely th e sam e ten den cy to h yd rolyze a s Ce 4 bu t lea s th an th a t ofHf+4 +4an d Zr .

Th e con s tan t for th e firs t d isp la cemen t of a proton from th e h yd ra t ion sph ere,a lon g with th e volu b ility produ ct for th e h yd roxide of th e va r iou s Pu ion s , is given in+3Table IV- 8 . In th e ca s e of Pu +4a n d Pu , th e h yd rolys is rea ct ion m ay be writ ten

PU (H20)X+ + H20 = Pu OH (H20)$-~1)+ + H30+ ;-1 +or in th e ca s e of PU02

PU0 2 (H2 0)X2+ + H20 = PU020H (H20);- ~ + H30+ .

Puo;+ h yd rolyzes to a grea ter efien t th an a s imp le d ipos it ive ion of th e samera diu s , s h owin g th e effect of th e h igh ly ch a rged cen tr a l Pu ion

TABLE IV- 8 . Firs t Hyd rolys is Con s tan ts an d Volu bility Produ cts for Plu ton iu m Ion s .

Ion Hydroxide KH SP o f Hyd r ox ide Ref.PU+3 Pu (OH) s 7 .22 (u = 0.069 , HC104) 2x 10 -0 *

7 .37 @ = 0.034 , HC1) 7x 10 -6 *PU+4 PU(OH)4 1.27 (u = 2.0 )Pu o~ PU02 (OH)2 3 .33 (1 .86 X 10-4 ~HN03) (3 * 1 ) x 10-5 (244)*As qu oted in Gel! m an et a l. 3

C. 6 Pu (IV) PolymerBy fa r th e mos t im por tan t h yd rolyt ic rea ct ion from a rad ioch em ica l s ta n dpoin t

is th e forma tion of colloid a l a ggrega tes in Pu (IV) solu t ion s by su cces s ive h yd rolys isreac t ions . Th e polym er pres u rn a bl y form s with oxygen or h yd roxyl br idges an d th erea ct ion is a pp aren tly ir r evers ib le. PU(OH)4 form a wh en th e react ion p roceeds tocomplet ion . In in termedia te s tages , h owever , th e colloid rema in s in s olu t ion a n d h aspropert ies ma rked ly cliff eren t from th ose of th e free ion . In m acro con cen tra t ion s th ecolor of a 0 .3 M HN03 solu t ion ch an ges from brown to b righ t green wh en th e solu t ionis h ea ted . Th e ad sorp t ion s pectra of polym er h a s a n en tirely d ifferen t ch a racter th anm on om eric Pu (IV) solu tion s.

Th e polymer can be form ed from man y s olu t ion s . Th e forma tion of Pu (l_V)polym er is fa vored by a n in crea s e in th e Pu con cen t ra t ion an d tem pera tu re or by adecrea s e in th e acid i~. As th e tota l n itra te con cen tr a t ion in crea ses th e polymerp recip it a tes , u p to a maximum a t 2 -3 M N03-. 104 Th e presen ce of s tron g comp let in gan ion s in hib it th e form a tion of polymer . Neverth eles s , th e presen ce of polymeric Pus h ou ld be s u spected wh en ever th e a cid con cen tra t ion is below 0.5 M. 327 Polym er isformed wh en s olu t ion s a re d ilu ted with wa ter beca u se of th e exis ten ce of tra n s ien tregion s of h igh pH, even th ou gh th e fin a l a cid ity m ay be h igh en ou gh to preven t forma tionof th e p olym er. 327 , 64 Th e polym er is a ls o formed by a dd in g les s th an a s toich io-m etr ic qu a n tity of a cid in th e d is s olu tion of PU(OH)4 precip ita te. Fortu na tely, PU(OH)4

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can be precip ita ted from or igin a lly monomeric solu t ion s an d red is solved with ou tappreciab le forma tion of polymer by u s in g excess reagen ts . 239 Pu (IV) polymer lmaybe completely precip ita ted from solu tion by mu ch les s th an s toich iometric amou n ts(approxim a tely 0.15 equ iva len ts of an ion ) of oxa la te, ioda te, a n d ph osph a te, forexample. Th is ph en omen on in d ica tes th a t th e complex con ta in s few ch a rges . Th isfa ct wa s u t ilized by Ocken den an d Welch 305 to remove ion ic Pu from the colloida lform by mean s of ca t ion exch ange.Depolymer iza tion is very s low a t room tem pera tu re in modera te a cid con cen t ra -tion s . Th e ra te is in crea s ed by h ea t in g, s t ron ger a cid con cen t ra tion , a n d add ition ofs tron g complet in g agen ts su ch a s flu oride an d su lfa te.

Care m u s t be taken to preven t th e forma t ion of Pu (IV) polym er in rad io ch em ica ls epara t ion s becau se of th e very differen t ch em ica l p ropert ies of th e polymer. Theexample of n on -adsorp t ion on ca t ion exch an ge res in h as a lready been given Th ePu (IV) polym er does not extra ct in to t r i- n -bu tyl phospha te, (TBP), for exam ple, bu tdoes ext ra ct in to d i-n -bu tyl ph osph oric a cid , (DBP).46 Th e form at ion of polym er insolu tion s of d ieth ylen e glycol d ibu tyl eth er (bu tex) h as been observed . 407

Cos tan zo an d Biggers 104 h ave determ in ed th e ra te of polym eriza tion an d de-polymer iza t ion a s a fu n ct ion of a cid ity, tempera tu re, Pu con cen tra tion , an d s a lt con -centration. Miner278 h as su mmar ized in forma tion con cern in g th e form at ion ofpolym er in n itra te solu tion s. Both th e above referen ces give su gges t ion s for th eavoidan ce of polym er forma tion in h an d lin g an d sh ipp in g macro amou n ts of Pu .

Polymer ic Pu (IV) adsorbs s tron gly on to gla s s , paper , etc., in d ica t in g th a t it is78p os it ively ch ar ged . Sa tu ra tion on gla s s occu rs a t a pproxim a tely 1 ~g/ cm2.Samar tseva345 fou n d th a t th e adsorp tion is grea ter on s ilica th an on gla s s , th a t 5 to 8h ou rs wa s n eces s a ry to rea ch equ ilib r ium with 10 -8 to 5 X 10-10 M Pu (lV) s olu tion s,an d th a t adsorp tion on gla s s wa s revers ib le a t pH < 4 .

Th e adsorp t ion of Pu (IV) 399 an d (VI)346 on p la tin um (Pt) h a s been s tu d ied froma qu eou s s olu t ion . It wa s fou n d th a t from 17 . to 4~0 of th e Pu (IV) can adsorb on a Ptsu r fa ce from organ ic ext ra cta n ts su ch a s TBP, t r i-n -octylam in e, (TOA), etc. 399In crea s in g th e con cen tra t ion of th e ext ra cta n t or th e aqu eou s n it r ic a cid ph a s e inequ ilib r ium with th e organ ic ph a se decrea s ed th e adsorp t ion .

C. 7 Complex Ion Form a tionTh e forma tion of complex ion s in aqu eou s solu t ion s with an ion ic ligan ds is an

impor ta n t fea tu re of th e aqu eou s ch em is try of Pu . Com plex form ation an d h ydrolys isa re competin g react ion s an d m ay be looked u pon a s th e dis p la cem en t of th e H20molecu les in th e h ydra t ion sph ere by th e an ion ic ligan d or by OH-, respectively. Th eab ility of an ion to form complexes is depen den t on th e m agn itu de of th e ion ic poten tia lwh ich may be defin ed by th e equ at ion

d=zjr.z is th e ch a rge on th e ion an d r is th e ion ic rad iu s . Th e va lu es of th e ion ic poten t ia lsof Pu in d ifferen t oxida t ion s ta tes a re given in Tab le IV- 9 .

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TABLE IV- 9 . Ion ic Poten tia l of Plu ton ium in Va riou s Oxida t ioh Sta tes*Cation Ion ic rad iu s (~) Ch a rge Ion ic poten t ia lPU+4 , 0 .90 4+ 4.44PU+3 1.03 3+ 2.91+2PU02 0.81 2+ 2.47PU02+ 0.87 1+ 1.15

*After Gel! man et a l. 3

The rela tive ten den cy of Pu ion s to form complexes th en isPu (IV) > Pu (HI) > Pu (VI) > Pu (V)

Gel, m a & a lt 3 sh ow th a t th e an ion ic liga n d h a s some effect on th is s eries .For example, th e pos it ion s of Pu (HI) an d Pu (VI) a re in terch an ged in th e ca s e of on la tecomplexes.

Sin gly ch a rged an ion s form weaker complexes with a ctin ides gen era lly th an domu lt ip ly ch a rged an ion s . Th e order of complex form in g ab ility with some an ion s is

CO; > C20; > SO; > F-> NO; > Cl- > C1O; .Tab les IV- 10 , IW - 11 , an d IV-12 lis t a va ila b le s ta b ility con s tan ts for complexes ofPu (III), Pu (l_V), Pu (V), an d Pu (VI), respect ively, wh ich a re ba s ed on th e review ofGel! man ~. 3 Th e ch em is t ry of complex compou n ds an d ion s of th e a ct in ides wa s97a lso reviewed by Comyns . Tab le IV- 13 lis t s s ta b ility con s tan ts for some complexesof s evera l a ct in ides for compar is on .

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.-

TABLE IV-10 . Stab ility Con s tan ts u f Pu (III) Ion s *

Com plex-form ation react ion Ionics trength K Ref.PU+3 + N03- = ~0~2 5 .9 *0 .5PU+3 + 2NO; = PU(N03); 14.3 * 0 .8PU+3 + 3NO~ = PU(N03 )f 14 .4 * 0 .8PU+3 +2+ cl- = pu cl 0 .5 0.58

1 .0 1 .1PU+3 + S04 -2 = Pu so: 10PU+3 + 2 s0 4-2 = Pll(s o4 )2 - 50 *33.6 x 1011PU+3 -2 = PU(C 20 4 );+ 2 c2 04 2 .0 x 109

1.4 x 109+3Pu -32 = PU(C 20 4 )3+ 3c204 2.4 X 1094.5 x 1010

PU+3 + 4c20~2 = PU(C204 )4 -5 4 .2 X 1011PU+3 8.3 x 109 *3- = Pu (Hc2 04 )~+ 4 HC2 04 6.3 x 1012

1 .0 9 .1 X1 01OPU+3 -4 _+7 -Pu y -4** 1.OX 10 21=1.0 2 .3 X 10170.1 (1 .3-3 .9) x 1018

PU+3 + H7 -3 = P ll& 7.7x 1011*3

PU+3 -2 +2 + H++ %2 7 = ;% 1.0 1 .6 X 109Pu 3 + 4C6 H507 -93 = fi (C6H507 )4 lx 1011PU+3 -92 = PU(C 4H 40 6 )6+ 6 c4H4 0 6 5X1O5Pu 3 + 5C2H302 = Pu (C2H302 )~2 5X1016 511

*Baaed on th e review of Geli m an et a l. 3 Th e da ta a re *en from th is s ou rceu n les s oth erwis e s pecified .**7 -4 . m th e an ion of k th ylen ediam in et etra acd i c a cid .

*3Va lu es a t zero ion ic s tren gth

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TABLE IV- 11. Stab flity Con etan ts of Pu(IV) Comp l e x e s *IonicCom plex-form at ion r ea ction strength K Ref.

~u+4 + cl- = PUC1+3+2PU+4 + 2C1- = PUC12

PU+4 + NO; = PU(N03)+3

PU(N03) 3 + NO; +2u PU(N03)2PU(N03)2 2 + NO; = PU(N03):PU(N03); + NO; = PU(N03):PU(N03): + NO; = Pu(N03)-Pu (N03)~ + NO; = Pu (N03)~2PU+4 +HF=~+3+H+

PU+4 + 2= = PUF2 +2+ ~H+Pu +3 HF=~;+9H+Pu +4 HF=m 4+4H+PU+4 + S04-2 = PU(S04) +2

Pu -24+ 2s04 = Pu@04):PU+4 2 = PU(S0 4)3+ 3s04 -2

PUM + CO;2 = PU(C03)+2~+4 - 2 = PU (C 20 4 )+2+ c204Pu -24 + 2C204 = PU(C204):~+4 - 2 = PU(C2 04 );2+ 3c20 4P u 4 + 4C204-2 = R(C204);4

PU(HP04)2 + (n + 4 - 3m )H+u Pu (P04)mH;w - 3m +(2- m) H3P04 ,wh ere m=l,2, ..5andn= 0,1, 2 ,. .3m2Pu +4 + H202 + H20 = PU(OO)(OH)PU+5+ 3H+ (brown com plex)2Pu +4 + 2H202 = Pti (00)2 PU+4 + 4H+(red complex)

1

2. 06 .01. 06. 06 .0

12

1 .0

10.0

1 .0

1 .01 .0

1. 0

0 .5

0 .5

1.380.67

2 .9 + 0.64. 7

3 .46 + 0 .060.960.33

1 .7X 1041 .1X 104

4.6 X 103

9 .1 x 10461.3X 10 11 **3.6 X 1083.2 X 10 20 **6.3X10161 .OX 1 02 7**2.5X 10236 .0 X 1029**3 .OX 10279.1X1027

6.8 x 106

6 .3x 106

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TABLE IV- 11 . (Con t in u ed)Ionic

Com plex-form ation rea ct ion s t ren gth K Ref.Pu +4 +-f -4** = Pu y 0 0 .1 1.58X 1024

1.4 x 1026Pu ++ H27=; Pu 2y + H+Pu -34 + 4C6H507 = Pu (C6H507)~ 8 1.7 x 102PU+4 2 = Pu (C4H4 06 )~8+ 6 c4 H4 06 2 .0 x 103PU+4 + ACAC - *3 = PU(ACAC)+3 0.1 3 .16x 1010Pu (ACAc ) 3 + AC.AC- = PU(ACAC)2+2 0.1 1 .58X 109

2 i- AcAc-PU(ACAC)2 ;= PU(ACAC)3 0.1 2 .51X 108Pu (AcAc); + AcAc- %@cAc)/ 0.1 1 .0 x 106PU+4 + C2H30~ = PU(C2H302)+3 2 .0 x 105 359PU+4 + 2C2H30~ = Pu (C2H302)~2 1 x 109 359PU+4 +1+ 3 c2 H3 02 = PU(C2H302)3 8 X 1013 359PU+4 - = PU(C2H302)4+ 4 c2H3 02 2 X1018 359PU+4 22+ 5C2 H3 02 = PU(C2 H3 02 ):1 4X1O 359

NOTES:*Based on th e review of Geli man et a l. 3 Th e da ta a re ta ken from th is sou rce u n -

ies s ot herwis e s pecified .** Va lu es a t zero ion ic s t ren gtk*3 Abbrevia tion s a re:1 . y-b m th e an ion of eth ylen ed iam in etet ra a cet ic a cid .2 . AcAc - = [CH3COCHC~H3]-.

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TABLE IV- 12. Stab ility Con s tan ts of Pu (V) a t i Pu (VD complexes*Ionic

Com plex-form ation r ea ct ion strength KP.@; + cl- = PU02C10 0.67

+ -2 = Pu o2 c2 0~02 + c204 0,05 3.3 x 104-3- 2 = PU0 2(C2 04 )2o; + 2c204 0.05 2.4 X 107Pu o; + y-4 . P@27-4** 7.9 x 1010-

0.05 1.6 x 1010+2Pu 02 + NO; = Pu 02NO~ 72Pu 02NO~ + NO; = Pu 02(N03)~ 36 & 0.3

2 + cl- = mo2cl+~0 2 1.250.73 * 0.07

PUO;2 + 2C1- = PU02C1; 0.35PUO;2 + 7 -4 . ~027-2 1 .75X 1016

6.9 X 107*3

1 .0

PUO;2 + c20p = PU02C20: 4 .3 x 1065 .0 x 1012*3~o+2 z + 2C204 = PU02(C204)2 3.0 x 1011

PUO;2 + CH3C~- = Pu 02(CH3COO)+ 1 .9 x 103

1. 0

1 .0

PUO;2 + 2CH3COO- = Pu02(CH3COO): 2 .0 x 1062 + 3CH3C00- = Pu 02(CH3COO)3--2 2 .3 X 1072+ 2CO;2-2 s P@2(co3 )2-2 1 x 10 15*3

*Taken from th e review of Gel lman et a l.3**Y4 is th e an ion of ethylen ed iam in etet ra acet ic a cid.*3 Va lu es a t zero ion ic s tren gth .

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TABLE IV- 13 . Stab ility Con s tan ts of Complexes of Severa l Act in ides*Com plex-form ation reaction u Np Pu Am

~e+3+ ~c ~ 2 = Me(C2 04 )2 -24 11.55*3 11.46*3Me+3+ y -4 . ~q-4** 21.0*3 20.6*3Me+4 2 = Me(C204+ c204 r2 8.61 8.54 8.74Me+4 2 = Me(C204)20+ 2c20 4 16.9 17.54 16.9Me+4 2 = Me(C204)3 -2+ 3 c2 04 22.7 24.0 23 .4Me+4 2 = Me(C204)4 -4+ 4 c2 04 27.7 27.4 27 .5Me02+ + C20~2 = Me02(C204)- 5.04 4,52Me02+ -2 -3+ 2c20 4 = Me02(C204)2 7 .36 7.38Me02+2 + C!H3C00- = Me02(CH3COO)+ 2 .7 3 .31 3.27Me02+2 + 2 CH3 C0 0- = Me0 2(CH3 COO)2 0 5.10 5.83 6.29Me02+ 2 + 3CH3C00 - = Me02(CH3COC))3 - 6 .41 7 .90 7.36MeO~2 + C20~2 = Me02C20f 6.77 6.64Me02+2 + 2C20~2 = Me02(C204)~2 12.0 11.5

2 = Me0 2(C0 3)2MeO~2 + 2C03 -2 14.0 15.0* Taken from th e review by Gellman et a l.3** -4 .7 m th e an ion of ethylen ed iam in etetra acet ic acid .*3 Th ermodyn amic va lu es ca lcu la ted by A. I. Moskvin .

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D. Sepa ra tion Meth odsD. 1 Co-precip ita tion an d Precipita t ion

Co-precip ita t ion snd precipita t ion pres en t differen t p roblem s to th e rad ioch em is tbecau se, in gen era l, th e in solu ble compou nds of Pu wh ich h ave des irab le p roper tiesin precip ita t ion reaction s a re n ot th ose formed in co-p recip ita tion rea ction s . Of th ecommon reaction s , on ly precip ita tion of Pu F3 an d Pu F4 an d co-precip ita t ion of Pu (III)a n d Pu (IV) by LaF3 a re an a logou s . Sin ce th e radioch em is t is likely to h ave sm all ort ra ce qu an t it ies of Pu in a rela t ively la rge volume, co-p recip ita t ion rea ct ion s a re moreimportan t to h im , an d will be con s idered firs t .

Co-precipitationCo-precip ita tion rea ct ion s a re ext remely impor ta n t in th e rad ioch em is t ry

of Pu . Indeed , th e firs t s epa ra t ion an d isola t ion of th e elemen t wa s a ccomplish ed byco-p recip ita t ion with LaF3 . Th is method h as become th e cla s s ic rad ioch em ica lmethod for Pu an d is s t ill widely u sed .

Th e co-precip ita t ion behavior of Np an d Pu towa rd a n umber of p recip ita n t is16sh own in Tab le IV- 14 , taken from th e review of Hyde. The beh avior of th ese elemen tsis represen ta tive of th e a ct in ides in a given oxida t ion s ta te. Th e pos s ib ility of s epa ra -t ion a r is es wh en th e elemen ts can be ma in ta in ed t i s epa ra te ot ida t ion s ta tes , a n d as elective precip ita n t is u s ed . Th e review of Bon ner an d Kahn 49 .gives a th orou ghdiscu ss ion of th e mechan ism of co-p recip ita tion an d a good review of co-precip ita t ionda ta for a ll th e elemen ts th rou gh 1949. Th e co-precip ita t ion beh avior of Pu h as beendiscu ss ed by Leader. 253

Th e s epa ra t ion of Pu by co-precip ita tion u su a lly ta kes advan tage of th e afore-men tion ed oxida tion an d redu ct ion cycles to effect pu rifica t ion . Th e procedu re may beillu s tra ted with th e ca rryin g of Pu (III) an d Pu (IV) an d th e n on -ca r ryin g of Pu (VI) onLaF3. On ly those elemen ts with co-precip ita t ion an d oxida tion -redu ct ion beh aviorvery s im ila r to th a t of Pu in terfere. The oxida tion - redu ct ion cycle may be repea teda s many t imes a s n eeded to get an y des ired degree of pu rity. Th e u s e of LaF3 pre-cip ita t ion is a lso a va lu ab le grou p s epara t ion an d volume redu ct ion s tep , s in ce n otvery man y elemen ts h ave a cid -in solu ble flu or ides .

In man y rad ioch em ica l procedu res , LaF3 is mou n ted for a lph a cou n t in g todeterm in e th e Pu . 191 , 83 , 82 , 446 Ch en ley et a l. 83 repor t a 2.6 q. n ega tive bia s by th ismeth od becau se of absorpt ion of th e a lph a pa r ticles in th e LaF3 . Th is b ia s is afu n ct ion of th e th ickn ess of th e cou n t in g sample an d mu s t be determ in ed for ea ch pro-cedure.

Ca lcium is one of th e elemen ts wh ich in ter feres with LaF3 co-precip ita t ion ,s in ce th e flu or ide is modera tely in solu ble. One method of solving th e prob lem of h ighCa concen tra t ion s ( >200 mg/ 1 ) is reported by Sch eich au er and Mes s a in gu ira l. 351 ThePu is oxidized to Pu (VI) an d CaF2 is p recip ita ted away from the Pu . Followin g re-du ction , th e Pu can eith er be co-precipita ted or sepa ra ted by oth er mean s ,

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TABLE lV - 1 4 . Co-precip ita tion Behavior of Trace Amou n ts of Plu ton ium an dNeptu n ium in Pr in cipa l Va len ce Sta tes . 16Carr ier com pou nd Pu (III) Pu (rv) Pu (VI) NP(IV) hTp(V ) Np(VI)HydroxidesLa nt ha n um flu or id ePhospha tes :

Zir con iu m p hos ph ateTh or iu m p yr op hos ph at eTh or iu m h yp op hos ph at eU (IV ) h yp op h os p h a te

Oxalates:Th or iu m oxa la teU(IV ) oxa la teBis mu th oxa la teLa nth an um oxa la te

Iodates:Zircon iu m ioda teTh or iu m ioda teCer ic ioda te

Sod iu m u ra nyl a ceta teZir con iu m p hen yla rs on a teTh or iu m per oxid eBis mu th a rs on ate

C*c

NCNC

cccc

NCNC

cc

cccccccc

cccNCccc

c c c cNC** C c NC

NC c NCNCNCNC

NCNCNCNC

c

NC

NCNC c NCNCc NC Poor*3 CNC c Poor NC

cNC* Th e let ter C in d ica tes th a t th e co-p recip ita t ion ha s been observed to be n ea rlyqu an tita tive u nder p roper con dition s.** Th e letters NC mean th a t co-p recip ita teon may be made less th an 1 to 2 percen tu nder p roper con dition s.*3 Poor in d ica tes an in termed ia te percen tage of ca r ryin g.

Co-precip ita tion of Pu with LaF3 ia a common s tep in th e an a lys is of b iologica l360 , 349, 257, 125 , 208 , 53m a ter ia l for Pu .Bismu th ph osph a te. Th e ca r ryin g of Pu on BiP04 is anoth er of th e ea r ly,

widely u sed meth ods of s epa ra tin g Pu from U an d fis s ion produ cts . Th e d eve lo pmen tof th e proces s is reported by Th ompson an d Seaborg. 401 Like LaF3 , BiP04 ca r riesboth Pu (III) a nd Pu (IV ) wh en precip ita ted from modera tely concen t ra ted n it r ic a cid . Apecu lia r ity is th e fa ct th a t Pu (IV) is more efficien tly ca r r ied th an Pu (III). Th e opt imumcon d it ion s for th e co-p recip ita t ion of Pu h ave been repor ted by Adsmson . 20 Th ese a re:1 ) co-p recip ita tion a t th e m in imum BiP04 volu b ility, 2 ) th e absen ce of s tron g com -p let in g a gen ts , 3 ) s low precip ita t ion , a n d 4) m in imum diges t ion a fter p recip ita t ion iscomplete.

In add ition to bein g very su cces s fu l in th e la rge s ca le p rocess ing PUP BiP04 pre-cipita t ion s h ave been u sed in gen era l ra d ioch em ica l p rocedu res 341,415 to cone en tr a tePu from la rge volumes of wa ter 237 126an d to determ in e Pu in u r in e, Th e procedu re ofRydberg 341 u ses th e fam ilia r oxida tion -redu ction cycle to effect pu rifica t ion . Plutonium

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is firs t oxidized to Pu (VI) with sod ium bismu th a te, BiP04 precipita ted from 0.1 NHN03, th en redu ced with fer rou s ion , an d fin a lly p recip ita ted with BiP04 .

Zir con iu m ph os ph ate. Zircon ium ph osph a te is a specific co-p recip itan t forPu (IV), in con tras t to BiP04 and LaF3 , 16wh ich ca rry both Pu (III) a n d Pu (lV). Hydedes cr ibes a NP-Pu sepa ra t ion ba sed on th e redu ction to Pu (III) before precip ita tin gzir con iu m ph os ph ate.

Oth er in or 118gan ic co-precip ita n ts . Du pet it an d Aten des cribed th e co-p recip ita t ion of a ct in ides with th or iu m peroxide and u ran iu m peroxide. All th e elem en tswere in th e tet rava len t oxida tion s ta te. They fou n d, th a t in gen era l, th e crys ta l typemade lit t le d ifferen ce in th e co-precip ita tion of th es e elemen ts . For example, Pu ca r r iedequ ally well with th oriu m peroxide, wh ich h a s a s im ila r crys ta l s t ru ctu re to p lu ton iumperoxide, an d with u ran ium peroxide wh ich ha s a d ifferen t s t ru ctu re.

A m ixtu re of Pu (IH) an d Pu (IY ) h a s been ca r r ied on lan th an um ioda te from dilu teHC1 so lu t i on . 2 3

Plu ton ium can be s epara ted d irect ly from a u r in e s ample by co-p recip ita tion with1 02 , 7 4ca lciu m am mon iu m ph osph ate.Pu (fV) and Am(III) h ave been qu an tita t ively co-p recipita ted with K5La (S04)4 , 151

an d Pu (IV) an d Np(lV) h ave been s epa ra ted by precip ita t ion of th e Pu from solu t ion swh ich a re u n s a tu ra ted in K2S04 . Th e m in imum Pu volu b ility in th is s ys tem occu rs a to.7g.152

Organ ic co-precip ita n ts . Zircon ium ph en yla rs on a te is a specific ca r r ierfor Pu (IY) and h a s been u sed in an a lyt ica l p rocedu res to determ in e th e oxida tions ta te 193, 414 , 227 an d to s epa ra te Np an d Pu a fter redu ct ion with NH20H.392 227, Kingu sed 2 X 10-4 ~ NH20H to preven t th e redu ction of Pu (IY ) du r in g th e an a lys is , wh ile a tth e s ame time not oxid izin g th e Pu (III). Voigt et a l. 414 fou n d th a t th e precip ita t ion ofPu is n ea r ly qu an t ita t ive from , a formate bu ffer of pH approxima tely 2, an d s ligh t ly les sso from HC1 solu tion s . Ice 13 got qu an t ita tive recovery in precip ita tion s from 1 ~HC1 s olu t ion s .

Merz273 u sed mandelic a cid an d p-bromomsn delic a cid with Y(HI) to ca r ryPu (IH) qu an t ita t ively a t pH 2-4 an d above. Zircon ium was u s ed for Pu (IV ) a t h igh era cid it ies . Th e precip ita tion was abou t 85 ~. complete a t 1 ~ HC1 an d HN03 for p -b romoman delic acid, an d somewh a t lower th an th is for man delic a cid .

Weiss an d Sh ipman 422 qu an t ita tively recovered Fe, Pu , C e, an d Pr from solu tionby th e forma tion of oxin e h omogeneou s ly in solu t ion by th e h ydrolys is of 8 - a cetoxy-quinoline.

Th es e workers determ in ed Pu in u r in e by co-crys ta lliza t ion with pota ss iumrh od izon ate.421 374 Ku zn ets ov an d Akim ova 247 co-precip ita ted Pu (IV) from 3 ~HN-03 solu tion s with bu tyl rh oda min e. Th e meth od is qu an t ita t ive an d s epara tes froma ll elemen ts except Th (lV ) an d U(VI). Repea ted precip ita t ion s effect th e s epa ra tion .Oth er dyes were su cces s fu lly u s ed to s epa ra te Pu by th e same procedu re.

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PrecipitationPrecip ita t ion of macro qu an t it ies of Pu is n eces sa ry in many an a lytica l

a nd rad ioch em ica l procedu res . The precip ita tion rea ct ion s wh ich h ave been fou n du sefu l in pra ct ice will be reviewed in th is s ect ion . The u s e of va r iou s precip ita tes aspu rifica tion s teps for Pu is illu s tra ted by Tab le IV- 15, wh ich gives decon tam in a tionfa ctors for Pu from Fe, Co, Zr , Mo, Ru , and Ce. 431 As u su a l, Zr an d Ru give th em os t t rou ble.

TABLE IY - 15. Decon tam in a tion Factors for Plu ton ium by Precip ita tion Meth ods . 431Plu ton ium Plu ton ium (IH) Plu ton iu m (IV) Plu ton iu m (Hf)Elemen t peroxide oxalate oxa la te flu or ide

Fe 50 33 10 1 .4co 30 47 > 95 8.6Zr 1 3 .5 >44 1 .1Mo >140 > 13 > 15 1 .1Ru >14 > 38 33 36Ce 6 , 1 1 1 .1

Hydroxide. Both Pu (IIZ) an d Pu (IY ) may be precip ita ted from m in era l acidsolu tion by sodium , pota ss ium or ammon ium hydroxide a s h ydra ted h ydroxides orh ydrou s oxides . Ca re mu s t be taken in redis solvin g Pu (I17) h ydroxide in a cid to pre-ven t form ation of Pu (IY) polym er , by main ta in in g a h igh acid concen tra t ion du rin g th edissolu t ion . Once formed, th e polymer d is solves very s lowly in a cid solu tion s . Th issu b ject is t rea ted more fu lly in th e sect ion on polymeric Pu (IV).

Fluoride. Pu F3 and Pu F4 may be precipita ted from acid solu tion byadd it ion of excess HF. Prevot et a l. 325 fou n d th a t Pu F3 form s a more t ra cta ble,crys ta llin e precip ita te th an does Pu F4 . Th e compou n d is s tab le to oxida tion if th e323precip ita te is kep t s lu r r ied in th e su pern a tan t s olu t ion . Th e fres hly p recip it atedcompou nds d issolve read ily in reagen ts wh ich complex flu oride ion , su ch as H3B03,bu t if h ea ted to 500 d is solve on ly with d ifficu lty. Meta th es is to th e h ydroxide withsod ium or potas s ium hydroxide is anoth er meth od of solu t ion . J on es214 fou nd th atPu F3 was su ita b le for u s e as a gravim etr ic s ta n dard for Pu , a t lea s t for a per iod ofs evera l m on th s. Th is meth od h as n ot been widely u s ed , h owever . It is in teres th g ton ote th a t PU02 prepa red by ign ition of th is Pu F3 a t 500C in oxygen was read ily solu b lein n it r ic a cid, in con tra s t to th e fin dings of oth er workers . Th is volu bility is a tt r ib -u ted to th e ext remely fin e pa rt icle s ize of PU02 prepared in th is work .

Peroxides. Pu (IV) peroxide is formed wh en h ydrogen peroxide is added toa cid solu tion s of PU(III)J Pu (IV), Pu (V), an d Pu (VI), becau se H202 can act a s both anoxidan t an d a redu cta nt. Pu (IV) peroxide a lways in corpora tes some of th e an ion pres -en t in to th e crys ta llin e precipita te. It h a s been su gges ted7 th a t th e presen ce of th ean ion is du e to a more or les s random pla cemen t between sh eets of Pu and peroxide

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oxygen in th e ra tio 1 :3. If a n excess of peroxide is u s ed in th e precipita t ion , th era t io may be lower. The extra peroxide a lso serves to h old th e sh eets togeth er.

Precip ita t ion of p lu ton ium peroxide h as been u sed as a pu rifica tion s tep for Pufrom most oth er ca t ion s 72 , 158, 329 , 425 an d a s a s tep in th e prepa ra tion of h igh pu rityPu com pou nds and solu tion s. 329 Th is p recipita tion h as been u sed to separa te Pu fromAm, th e Am remain ing in th e su pern a tan t solu t ion , 72 277 ~and to s epara te Pu and U.th e la t ter p rocedu re th e Pu was oxid ized to Pu (VI) by potas s ium broma te wh ich servedas a hold in g oxidan t , a nd u ran yl peroxide precip ita ted . Separa t ion factors of 2 -4wer e ob ta in ed .

Oxa la tes . Precipita tion of plu ton ium oxa la te from dilu te a cid ic solu tionh as been u sed as a con cen tra tion s tep before convers ion to oxide or meta l. 265 Th es epa ra tion fa ctors from oth er elemen ts a re not so grea t in some cas es a s in th eperoxide precip ita t ion procedu re 431, 141 (Tab le W- 14), bu t th e precipita te is easy tofilter an d work with . Th e s e compou nds u n dergo decompos ition by th e a ct ion of th eir134, 389 , 216own a lp h a r a dioa ct ivit y. Th e oxa la te is decomposed in to carbona te and CO,an d th e CO may redu ce eith er Pu (VI) or Pu (IY).

Oth er compou nds . The precip ita tion of p lu ton ium (IV) su lfa te tet ra hydra teh as been u sed to prepa re a h igh pu rity Pu compotmd for u se a s a gravimetr ic s ta nda rdfor Pu .4 24 Sta r t in g with a gross ly impu re solu tion , a p rodu ct of 99 . 9 8~, pu rity wa sob ta in ed a fter five s ucces sive r ecr ys ta lliza tion . Th is compou n d is su itab ly s tab le a sa gravimetric s ta nda rd a t lea s t for 18-mon th s , 448

Dices ium plu ton ium (IV) h exach or ide h as a lso been proposed as a prima rygra vim et ric s ta nda rd .2 7g The compou nd can be prepared by precip ita tion from an 8~ HC1 solu tion of Pu (lY ) by addition of C sC1 in HC1.D. 2 Solven t Ext ra ction Meth ods

The la rge-s ca le p rocess in g of reactor ta rgets is la rgely done by liqu id -liqu idextraction. Th is is so becau se of a combin a t ion of des irab le p ropert ies of th ismeth od; for example, grea t s pecificity for U and Pu , easy adaptab ility to remoteh an dlin g fa cilit ies , etc. These advan tages a re eas ily ca r ried over to la bora torysepa ra tion s wh ere specificity and ease of h and lin g are equ a lly importa n t.

A very grea t dea l of resea rch on liqu id -liqu id extraction sys tem s for Pu h asbeen ca rr ied ou t in th e developmen t of la rge-sca le p rocess es , an d a la rge port ion ofth e solven t ext raction da ta reported in th is section was taken u n der th e spu r of th eseem ingly n ever -end in g qu es t for more specific extra cta n ts , better rad ia t ion s tab ility,a nd th e like. The ba s ic da ta on th e extra ct ive propert ies of a given solven t a re, ofcou rse, equ a lly applicable in th e labora tory or indu s tr ia l s itu a tion ,

Th e gen era l p rin cip les of solven t extraction h ave been pu t forth in th e book byMorr ison a nd Freis er , 292 26 7an d in a comprehen s ive review by Marcu s . Th e s olven textraction da ta for Pu have been thorou gh ly reviewed by Sm ith . 388 Carleson77 h aswr it ten a good gen era l s u rvey of th e proces s ing ch emis t ry of n u clea r fu el for Pu , wh ile

450a recen t s ym pos iu m con ta in ed mu ch of in teres t con cern in g th e n ewer extra ct ionsystems.

28


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In th is sectioncoefficien t D, wh ich

th e da ta will mos t often be given in term s of th e d is t r ibu t ionis defin ed by th e equ a tion

D. con cen t ra t ion of th e solu te in th e or~an ic ph as econ cen t ra tion of th e solu te in th e aqu eou s ph a seTo save space, th e nota tion Dx for th e d is t r ibu t ion coefficien t of species x willbe u s ed in th e text.

Orga no Ph os ph orou s Com pou ndsTh is la rge an d importa n t cla ss of ext ra ct a n ts in clu des th e n eu tra l an d

acid ic es ters of ortho ph osph oric acid an d rela ted compou nds , th e phosph on a tes ,phosph in a tes and phosph in e oxides . The cla ss d ividea n a tu ra lly in to n eu tra l an dacid ic compou n ds by th e d ifferen ces in ext ra ct ion mechan ism . Th e n eu tra l com pou ndsext ra ct by solva tion of a n eu tra l complex in th e organ ic pha se by th e phosph oryloxygen , wh ile th e a cid ic compoumds , in genera l, opera te by an ion -exchan ge rea ct ionto form an ext ra ctab le species . Fu r th er solva tion may occu r in th e organ ic ph a se insome extra ction sys tem s of th is type.

Neu tr al Com pou n dsTri-n -bu tylph osph a te (TBP), (C4H90)3P0, will serve as th e typ ica lcompou nd of th is type. A complete su rvey of th e litera tu re on TBP extraction of Pu

is beyond th e s cope of th is review. The more recen t papers will be emph as ized,a lth ou gh ea r lier p roject work will n eces sa r ily be in clu ded . A summary of ea r ly workon TBP ha s been given by Geary. 143 The ph ys ica l an d ch em ica l p~5~rties of TBPa s an extra ct in g agen t h ave been summarized by McKay and Hea ly. Th e TBP -n it ra t esys tem will be discu s s ed firs t , followed by oth er aqu eou s sys tem s , and fin a lly oth ern eu tra l orga no-ph osph orou s com pou nds .

TBP-n it ra te sys tems . Hesford an d McKay 178 have formu la ted th e ex-t ra ct ion rea ct ion of meta l n itra tes in to TBP a s

(1)M+p + p N03- + q TBP(0) = M (N03)P q TBP(0)wh ere p is th e ch a rge on th e meta l ion an d q is th e n umber of TBP molecu les solva t in gth e n it ra te molecu le in th e organ ic pha se. Th e su bscrip t (o) refers to species in th eorgan ic pha se, a n d species withofit s u bs cr ip ts a re in th e aqu eou s pha se. Th e e qu ilib -rium con s tan t, n eglectin g a ctivity coefficien ts , is th en

a nd th e dis tr ib ut ion coefficien t(2)

(3)Un der con stan t a qu eou s con dition s, an d a t a su fficien t d ilu tion of TBP in an in ertdilu en t to make Eq. (2 ) va lid , th e d is tr ibu tion will be proport ion a l to th e qth power of

29


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th e TBP con e en tra t ion . Solovk in 391 h as ca lcu la ted d is tr ibu tion coefficien ts for th iss ys tem on a sem i-emp ir ica l ba s is a n d ob ta in ed good agreemen t with experim en ta l d a ta .

Tetr a - a n d h exava len t Pu a s well a s oth er a ct in id es h a ve been sh own to be d i-s olva tes in th e organ ic ph ase. 44 Th e extra cted complexes a re th en PU(N03)4 r 2 TBPfor Pu (IV) an d PU02(N03)2 . 2 TBP for Pu (VI). Work with t r iva len t Pu h as sh own th a tth e extra cted com plex is tr i-solva ted , Pu (N03 )3 3 TBP. 372 Laxm in a ra yan an et a l. 252h ave sh own th a t Pu (IV) in 2 -4 ~ HTT03 is a s socia ted with an average of 2 .6 n it ra te ion sa n d does n ot exis t a s u n d is s ocia ted Pu (N03)4 by comb in in g solven t extr a ct ion da tafrom severa l solven ts . Th ere is d irect eviden ce th a t th e complexes a re u n -ion ized inth e orga n ic ph as e. 170

Typica l da ta for th e extr a ct ion of a n u mber of elemen ts a t tra ce con cen tra t ionin to 19 volu me ~. TBP in keros en e from n it r ic acid solu t ion of va r iou s con cen tra t ion sa re sh own in Fig. 1 . Th e d is tr ibu tion coefficien ts r is es s teep ly a t low n itr ic acidcon cen tr a t ion s becau se of th e s tron g s a lt in g-ou t effect of th e n itr a te ion (Eq. 1 ),pa s ses th rou gh a m axim u m, a n d th en fa lls a t h igh er a cid con cen tra t ion s. Someelemen ts (e. g. Th a n d Y) pas s th rou gh m in im a an d ris e a ga in .

I I II Zr I

,o-o&u+dLu+E(XJl LlBRi8M

HN03 CONCENTRATION, AQUEOUSJM)Fig. 1 , Ext ra ct ion of m t ra tes a t t ra cecon cen t ra t ion m t~ 19 volume ~0 TBP inkerosen e a t 25oC from n it r ic a ci

Taken from McKay an d Hea ly.2 58 s olu t ion sTh e in - -

d ividu al referen ces a re: ~ t r ium350;th oriu m 179. zircon ium 2 , u ra n iu m an dn eptu niu m2d: an d plu ton iu m44~ 258.

30

Severa l oth er s tu d ies of th e ex-t ra ct ion of Pu from n itr ic acid solu t ion sh ave been reported . Ca rles on 76 used40~. TBP in kerosen e a n d pa id pa r t ic-u la r a t t en t ion to requ irem en ts to m a in -ta in Pu in th e des ired oxida t ion s ta te.He fou n d th a t NaN03 wa s n eces sa ry top repa re pu re Pu (IY) from an equ ilib r iu mdis proport ion a ted m ixtu re. Figu re 2s h ows th e effect of HN03 con cen tra t ionon s evera l r edu cin g agen t s in th e ex-tr a ct ion of an equ ilib r iu m Pu solu tion ,an d th e extra ct ion cu rve for Pu (llI)a lon e. Ferrou s su lfama te with a ddedh yd roxylam in e effects complete re-du ction of Pu (IV ) to Pu (IH) a t u p to 2 ~HN03, bu t fa ils a t h igh er acid it ies .Ferrou s ion plu s h yd ra zin e a n d h yd rox-ylam in e fa il to complete th e redu ctiona t p rogres s ively lower a cid it ies .Ca rleson a lso fou nd th a t s olid KBr03d id n ot oxid ize Pu (IV) to Pu (VI) in 1 .55~ HN03 a t room tem pera tu re, bu t th a tth e oxida t ion wa s qu an tit a t ive in 0 .1 ~Br03- a fter h ea t in g to 95C for s evera lhour s .

Codd in g et a l.92 , 93

u sed 307 .TBP in kerosen e, Rozen a n d Moiseen ko 334


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/ 21. 0 / 3* -

/4 / I,I II i r!

! i ;/ I // ,110-1 1 / /

D

/// 1.2 and3I/

I PUUII)--2 0.005 MFe(ll) sulphOm GtO(+ 0.006M hydr,oxylamlne)

-.-3 0.005-o.02M Fe OTl+hydrazlne;,.-2! -..-4 0.005 -0.04Mhydroxyla mine.

/ 11

3M(HN03)\ 20

-0.02

Fig. 2. Dis t r ibu t ion of Pu (III) an d equ i-lib r ium Pu (lII), Pu (IV), an d Pu (VI), m ix-tu res in th e pres en ces of s evera l redu cin gagen ts in 40~0 TBP in kerosen e an d n itr ica cid ; a ft er Ca rles on .7 6

364a nd Sh evch en ko a nd Federov u sed 2 07 .TBP in keros en e, a n d Bern s trom an dRydberg 41 u sed 1007 . TBP. All th eabove workers measu red th e d is tr ibu tioncoefficien ts of Pu (IV ) an d Pu (VI) as afu nction of equ ilib r iu m aqu eou s, n itr ica cid con cen t ra tion with s im ila r resu lts ,a n d s evera l a ls o s tu d ied th e effect ofU(VI) competit ion on th e extraction ofPu (IV ) an d Pu (VI). Flan a ry 132 derivedequ ilib r ium con s tan ts (defin ed by Eq.(2 )) for U(VI), HN03, an d Pu (IY) of 22,0 .18 , an d 3 respectively, wh ile Rozenan d Mois een ko334 an d Coddinget a l 92 , 93 get abou t 1.5 for Pu (IY).Th es e va lu es illu st ra te th e effectivecompet it ion of macro U(VI) over t racePu (IV ) in th e s imu lta n eou s extra ct ion ofth es e species , resu lt in g in a la rge re-du ction of th e Pu d is tr ibu tion coefficien ts(see Fig. 5).

Th e order of ext ra cta b ility in toTBP from n it r ic a cid solu tion s for th ea ctin ides is M(IV) > M(VI)>> M(III)?4 25826 The ext ra cta b ilityof th e tetra va len t a ct in ides in crea ses

with a tom ic n umber , i. e., Th (lY) < Np(lY) < Pu (IV), wh ile th a t of th e h exava len ta ct in ides decrea s es with a tom ic n umber , i. e., Pu (VI) < Np(VI) < U(VI). 44

Mois een ko an d Rozen 281 mea su red th e effect of tempera tu re on th e ext ra ction ofPu (lV) a s a fu n ct ion of n it r ic a cid concen t ra tion an d u ran yl n it ra te concen t ra tion (Figs .3, 4 , a n d 5). In th e absen ce of u ran yl n it ra te th e d is t r ibu tion coefficien t decrea s es withtem pera tu re below 5 ~ HN03, wh ile a t h igh er a cid ities it in crea s es . Th is effect isexp la in ed by a decrea se in th e equ ilib r ium con s tan t for th e d is tr ibu t ion rea ct ion withtempera tu re, with a compen sa tin g in crea se in th e a ctivity coefficien t of Pu (IY) a t h igh era cid it ies . Th is in crea s e is a scr ibed to a decrea s ed a s :j:ia t ion of Pu (IW) with n it ra teion s a t h igh er tempera tu res . Sh evch en ko an d Federov have s tu died th e s ame sys tema t n itr ic a cid con cen tra t ion s below 4 ~ with s im ila r resu lt s .

Bes t e~.43 measu red th e d is t r ibu tion of s evera l tr ipo s it ive a ctin ides an dlan th an ides from n it r ic a cid solu t ion s in to 1007 . TBP. Some of th eir da ta a re sh ownin Fig. 6 p lotted as a fu n ct ion of a tom ic n umber, a lon g with th e lan th an ide da ta ofHes ford ~. 77 for compar ison . Th e cu rves for th e two h omologou s s eries a reapproxim ately su per im posab le if a d ju stm en t is made to compare ion s of th e s ame rad iu sTh is illu s t ra tes th e im por ta n ce of ion ic rad iu s on th e ch em ica l beh avior of th es eelements.

31


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l ?

Ic

D

n.

0 5 10Concentrationof HN03 In aqu eou s @ase, &

Fig. 3. Depen dence of d is t r ibu t ion co-efficien t of Pu (IV) in to TBP on con cen tra tionof n itr ic a cid in aqu eou s ph a s e (for 28 1solu tion s n ot con ta in in g u ran yl n itra te).Cu rve 1-20, cu rve 2-30. cu rve 3-50,a n d cu rve 4 -70

1. 0

D,

Tem per a t ur e, CFig. 5 . Depen dence of d is t r ibu t ion co-efficien t of Pu (lV) in to TBP on tem pera tu re

with a u ran ium con ten t of 0 .42 M in th eaqu eou a pha s e. 281 con cen tra ti~n ofHN03: cu rve 1-0 . 5N, cu rve 2-IN,cu rve 3-2N, cu rve 4-3N, cu rve 5-4N,cu rve 6-6N, cu rve 7-8N, an d cu rve8 -1 ON.

32

I

( )

n 3

.Ib20 30 40 50 60 70Tempera ture, C

Fig. 4. Depen den ce of d is t r ibu tion co-efficien t of Pu (IV) in to TBP on tem perin solu tion s not con ta in in g u ran iu m. tiYeConcen t ra tion of HNO : cu rve 1 - O .5N,

2cu rve 2- lh T, cu rve 3- N, cu rve 4-3N,cu rve 5-4N, cu rve 6-1 ON, cu rve 7-5N,and cu rve 8-6 to 8N.

IO LA NTHANIDESA TRIPOSITIVE #~ 5*I[02 ACTINIOES ~ HNO~##I:LLaCe Pr Ndpm-u GdTb Oy HoEr TmYb

Fig. 6. Dis tr ibu t ion coefficien t a s afu nction of pos ition in th e lan th an idean d actin ide s eries . 43 . 1770 Lan th an id esA Tr ipos it ive a ctin ides

n


40/192

,0 2

D10

Io 5 10Aq u eou s n lt rlc acid concentratlankJFig. 7. Effect of NaN03 on th e dis -tr ibu tion of Pu (IV) between lg~o TBP inkerosen e and n itr ic a cid solu tion s .44 . 258

Th e s alt in g-ou t effect of n on -extra ctab lesa lt s on th e extract ion of Pu an d U h as re-ceived con sidera ble a t ten tion . 1 65 , 4 3, 1 49 ,5 2Typica l resu lts a re sh own in Fig. 7 in wh ichNa(N03) is u s ed as th e sa lt in g agen t forPu (IV ). 44 , 258 At a con s tan t tota l n itra te con -cen tra tion th e dis t r ibu tion coefficien t decreas esa s th e proport ion of n it r ic a cid is in creas ed ,bu t th e d is t r ibu t ion coefficien t is a lwaysgrea ter th an th a t of pu re HN03. Th is effectis cau sed by th e redu ct ion of competit ion forTBP molecu les by th e lower in g of th e extract-a ble n it ric a cid con cen tra tion .

Alum inum n itra te h a s been u sed as as a ltin g- ou t agen t for Pu in s evera l TBP ex-t ra ct ion p roces ses . 149, 165, 52 , 354

Applica tion s of TBP-n itra te sys tems . Man y papers h ave been writ ten abou tth e app lica tion of TBP to th e proces s ing of irra d ia ted U forPU195 , 132, 93 , 148,325 , 114 , 202 ,365, 109, 133 Th e process involves ext ra ct in g Pu (IV )an d U(VI) away from fiss ion produ cts in to TBP-keros en e from n it ric a cid solu tion s ,s t r ipp ing th e Pu in to a rela t ively concen t ra ted n itr ic acid solu tion by redu ct ion to Pu (IIf),an d fin a lly s t r ipp ing th e U(VI) with wa ter. Nitrou s a cid is added to th e feed solu tion in76th e firs t extra ct ion to s tab ilize Pu (IV). Ferrou s su lfamate wa s firs t u sed a s a re -du ctan t in th e Pu s t ripp ing s ta ge, 335 , 195 , 132 a lth ou gh U(IV) as a redu ctan t h as been ex-ten sively s tu died. 209, 221 , 67 .385, 353 , 342, 38 Th is reagen t can be gen era ted fromU(VI) an d s tab ilized by vola tile redu ctan ts , with th e con s iderable advan tage in la rge-s ca le proces s ing p lan ts of not in t rodu cin g n on -vola t ile ma teria ls (e. g. iror r ) in to th ewas te s treams , th u s perm itt in g a sma ller wa s te volume. The beh avior of fis s ion pro-du cts and oth er elemen ts in th is p roces s h as received mu ch a tten tion , both in th e pr ima rypapers an d oth ers . 88,161,431,133,367 A va r ia n t h a s been des cr ibed in wh ich th e fis s ionprodu cts , Pu an d U, a re su cces s ively s tr ipped from th e TBP ph as e by s tepwis e lower-

20 3in g of th e a cid con cen tra tion .TBP was u sed in th e isola tion of n a tu ra lly occu r rin g Pu . 315Analytical 362 144 , 114and rad ioch em ica l p rocedu res for Pu ba sed on TBP ex-

traction from HN03 h ave been given .An in teres tin g applica t ion is th e u s e of TBP in reversed-ph as e ch roma tograph y for

va riou s h eavy elem en t sepa ra tion s, 124 156157190 and for th e separa t ion of Pu (IIT),Pu (IV) an d Pu (VI) in HN03 . 380

TBP oth er aqu eou s sys tems . Tet ra - an d hexava len t actin ides extract wellin to TBP from modera tely con cen tra ted HC1 solu tion s , wh ile t r iva len t species a re

33


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103 ~

,.2 _

D

10

I

/

Pu (m)

/

Pu(m)/pU(m)

Pj >U(m)

H,0 -1 ~AQUEOUS I-& CON:ENTR:TION ([j)

Fig. 8. Extract ion of U an d Pu bTBP in CC14 from HC1 solu t ion s .24 $3070

es sen tia lly u n ext ra ct ab le. La rs en an dSeils249 mea su red th e extra ct ion of Uan d Pu in to 30% TEIP in CC14 (Fig. 8 ),a n d u s ed th is s ys tem as th e ba s is of anan a lytica l p rocedu re for th ese elem en ts(Procedu re 15, Sect. VIII). Both Pu (IV)an d Pu (VI) ext ra ct bet ter a t a ll a cid it iesth an U(IV) an d U(VI). Th e qu adr iva len ta ctin ides h ave h igh er , d is tr ibu tion co-efficien ts th an th e h exava len t above 5-6~ HC1, wh ile th e reverse is tru e a tlower a cid it ies . Th ese au th ors repor t ad is t r ibu tion coefficien t of abou t 10 -3 forPu (III) a nd 10-4 for Am (III) in 8 ~ HC1u n der th e s ame con d ition s . Th e va lu efor Am is con s idered more relia b le be-cau se of poss ib le pa r t ia l oxida t ion ofth e Pu (III) to Pu (IV). HC1 is mu ch les sext ractab le th an HN03 in to TBP. La rs enan d Seils repor t D = 0 .01 a t 6 M HC1 an d0.12 a t 8&l HC1 in to 3070 TBP inCC14.24

Solovkin et a l. 390 fou n d th a t th eext ra ction of Pu (IV) in to 1 .1 &l (3070)TBP in CC14 from perch lor ic a cid wa sappreciable. The d is t r ibu tion co-efficien ts va ried from 0.0045 a t 0.4 M.HC104 to 0 .9 a t 6 .4 ~ HC104. Th e ex-tra cted complex was determ in ed to bed i-s olva ted by TBP dilu tion experim en ts .

Pu (IV) an d Pu (VI) ext ra ct wellin to TBP from tr ich loro - an d tr iflu oroa cet ic acids . 183 Th e d is tr ib u tion coefficien tsdecreas e with in crea s in g a cid ity, ra th er th an th e u su a l in crea se. Th e d is tr ibu t ion co-efficien ts for both Pu (IV) and Pu (VI) a re abou t 4 to 5 times a s grea t for CC13COOH asfor CF3COOH a t low acid con cen tra t ion s. For ext ra ction of Pu (IV) in to 30~0 TBP inAmsco- 125 (a keros en e type d ilu en t ) f> m an in it ia l con cen t ra tion of 0 .5 M CC13COOH,D = 21; for Pu (VI), D = 4 .

Th e effect of add ition of su lfu r ic a cid an d ph osphoric a cid to l%(~) or Pu (VI) n it r ic a cid TE3P sys tem s is in va r ia b ly to lower th e d is t r ibu tion coefficien t 4 38 , 4 40 >4 37sulfuric439

ph osph or ic. Th is effect is p resumably du e to th e forma tion of u n extra cta b le

su lfa te an d phosph a te complexes of Pu . The effect is m ore pron ou n ced in Pu (IV) th an inPu (VI), a n d a t lower n it r ic a cid con cen tra tion s . For example, mak in g th e aqu eou s ph as e0 .08 M in H2S04 lowered D for Pu (IY) from 16 to 9 .5 in 4 J YJHN03; in 2 ~ HN03 th e437correspon d in g decrea s e wa s from 9 to 1 .4 . On th e oth er h an d th e lower in g of D for

34


42/192

Pu (VI) by th e add it ion of en ou gh H2 SO ~ to 2 M HN03 to make th e solu tion O. 1 M inH2S04 was on ly from 2.6 to 2 .2.

Su lfu ric a cid a ls o decrea s es th e extra ction of Pu (lY) in to TBP from HC1solu t ion s .441 A solu t ion 1 ~ in H2S04 lowered Dpu approxim a tely a fa ctor of 10th rou gh ou t a ch an ge in HC1 con cen tra tion of 3 -8 M.

Oth er n eu tra l ph osph orou s compou nds . A wide va r iety of organ o-ph osph orou scompou nds h a s been s tu d ied in an a ttempt to fin d oth er ext ra ctan ts for Pu an d U,Higgin s et a l. 181 work in g with th e bu tyl s er ies fou n d th e order to be ph osph a te(( RO)3PO) < ph osph on a te (R(RO)2PO) < phosph in a te (R2(RO)PO) < ph osph in e oxide(R3PO). ThUS th e ext ra ct in g power in crea s es with th e n umber of C-P bonds .Burger 69 , 70 corr firmed th is s er ies an d correla ted th e ext ra ct in g power with th e ba s is ityof th e ph osph oryl oxygen a s mea su red by th e P-O s tretch in g frequ en cy. Bu rger , 69 , 70an d Petrov et a l? 18 fou nd th a t elect ron ega t ive su bs t itu en ts in th e a lkyl ch a in su ch as Cl an dph en yl s t ron gly depress ed th e ext ra ction . Sidda l~76 fou n d th a t in crea s in g th e len gth ofth e a lkyl ch a in in th e phospha te s er ies made lit t le differen ce u p to 8 ca rbon a toms forqu adr iva len t a nd h exa va len t act in ides . Th e effect of b ran ch in g th e a lkyl ch a in is to in -crea s e th e extra ct ion of U, Np , an d Pu , bu t to s t ron gly depres s th a t of Th . Th is effectis a t tr ibu ted to s ter ic effects an d pos s ib le t r i- solva t ion of th e Th complex a t h igh ex-t ra ct an t c on ce nt ra tion s .

Th e et ira ction m ech an ism of th es e compou n ds is gen era lly th e s am e a s th a t forTBP, bu t n ot n eces s a r ily with th e same solva t ion n umber for a ll elemen ts . 267 Tri-n-oct ylph osph in e oxide (!TOPO) and t ri-n -bu tylph osph in e oxide (TBPO) extra ct Pu (IV ) an dPu (VI) a s th e d i - s olva te. 2 69 , 4 08 Th e da ta of Ma r tin an d Ocken den 269 . 1s ~ven in Figs . 9 an d10 for ext ract ion of s evera l elemen ts in to O. 1 ~ TOPO in cycloh exan e from HN03 an dHC1 s olu t io n s. Pu (IV) an d U(VI) a re both ext ra cted well (D = 4-30) from 3 ~ H2S04by 0 .3 ~ TOP0.187 The extract ion of Pu (lV ) a s a fu n ct ion of n it r ic a cid con cen tra t ionis s im ila r to th a t for TBP, bu t very mu ch h igh er , wh ile th a t for U(VI) an d Pu (VI) sh owd ifferen t a cid dep en den cies . Wh ite an d ROSS427 h ave wr it ten a gen era l review of th eextra ct ive proper t ies of TOPO.

Tra ce qu an t it ies of U h ave been s epara ted from la rge amou n ts of Pu by ext ra ct in gth e U with TOPO u n der redu cin g con dition s from 2 ~ HN03. 34Tab le IV- 16 is a compila t ion of da ta for th e extra ct ion of Pu (IV) by a la rge n umber

of compou n ds of th is type. Th e extra ct ion coefficien ts were con verted to 1 M extract -an t by u s in g th e squ a re law, th a t is by a s sum in g th a t th e extra cted complex is d i-solva ted in every cas e. Th e d is t r ibu t ion coefficien ts were taken a t 1 ~ HN03 wh erepos s ib le, bu t ca s es in wh ich oth er ion s were pres en t or th e a cid ity wa s d ifferen t a ren oted . Th e ext ra ct ive power rela t ive to TBP was ca lcu la ted by d irect com pa r is on in th esame series of exper im en ts wh ere poss ible, or by compa r is on to oth er TBP da ta ta ken

,. i u nder th e same s ta ted con d it ion s . Th e con vers ion of th e ph osph in e oxide da ta to 1 ~extra cta n t gen era lly requ ired la rge ext ra pola t ion s, s in ce th e experim en ts were don e a tlow ext ra ct an t con cen tr ation s. For th is reason th e n umer ica l va lu es of th e d is t r ib u tioncoefficien ts an d th e rela t ive ext ract ive power a re on ly approxima te.

35


43/192

100(

I0 (

1 (

D 1.(

0.

0 .0

0.00

100

Ic

I

D

1.

0

&

Hydrochloric acid molarltyFig. 10 . Ext ra ction of meta l ion s from

hydroch lor ic a cid by 0 .1 ~TOPO incyclohexane.269Nltrlc acid molarlty

Fig. 9. Ext ra ction of meta l ion s fromn itr i~ a cid by 0.1 ~ TOPO in cyclo -hexane.269

Acid ic Com pou n dsThese compou n dfi a re th e mono- an d d i - a cid ic es ters of phosph oric

a cid an d rela ted ph osph ona tes an d ph ospbin a tes . Th ey have recieved con s iderab lea tten t ion in recen t yea rs du r in g th e s ea rch for more vers a t ile or specific extracta n ts .In gen era l, th ese compou n ds extract by an ion exch ange type rea ction an a logou s toch ela tion . In many ca s es th e ch ela te compou n d th u s formed is fu rth er solva ted in th eorga nic ph as e. For example th e ext ra cted complex in th e ext ra ction of Th (IV) withh is - 2 - eth ylh exyl ph osphoric a cid from severa l a cids involves th e an ion s su ch a s N03-,cl-, a n d pos s ib ly C104- 312in extraction s from th e respect ive a cids .

Mon o-a cid ic compou n ds . Di-n -bu tyl ph osph oric a cid (DBP) an d b is -2 -eth ylh exyl ph osph oric a cid (HDEHP) a re th e compou n ds th a t h ave received mos tattention. They h ave been sh own to be dimer ic in th e organ ic ph a se in a n on -pola r310solven t su ch as benzen e. Th e dimer iza tion is p resum ably du e to h ydrogen bond in g toth e ph osph oryl oxygen . 130 Th e ext ra ct ion rea ct ion can be formu la ted a s

M - M(HA2)P(0) + PH+.p + P(HA)2(0) - (1)36


44/192

TABLE IV- 16 . Compiled Da ta on Extra ct ion of Pu (IV) by Neu tra l ~rgan o-ph osphorou s Compou ndsExtractant Extra ctan t Nitric Acid Pu Da tl M RelativeCon cen tra t ion Con cen tra t ion Cone. D Given Extra cta~t Ext ra ctab ilityPhosphatea Ililuent Vol. Y, (M) (M) (a) (M) in P ap er (b) (TBP = I. O)(c) Referen ce, .Tr ibu t yl (TBP) Kerosen e

Gu lf BT KeroseneKcroaeneBenzeneMesityleneHeptaneNonane------Xylenen -Dod ec a n e

D ib u t y l Carbonmethyl tc trachlorideD ib u t yl - d ec yl CarbontetrachlorideTriisobutyl n -Dod ec a n eTr i- n -a myl n -Dod ec a n eTr i-iaoamyl n -Dode can eTr i- n -h exyl n -Dod ec a n e

1 9 (0 .6 9 )3 0 (1 .0 9 )4 0 (1 .4 6)2 0 (0 .7 3 )2 0 (0 .7 3 )

1 0 0 (3 ,6 5 )(1)

3 0 (1 .0 9 )(o . 5 )(o . 5 )(1.09)(1.09)(1.09)(1.09)

1. 0

-3.0

1. 01. 03. 0

2 (in it i a l)2 (in it i a l)

3333

T(d)TT

.9X1 O-4

TTT

0.0038

0.0036TTTTT

1. 53. 03. 51.36

14.16. 44.725.46

36 .3. 016.10.712. 311.815.617.815.6

3. 22. 51. 62. 6

26.311.98. 8

10.21, 03. 013.52. 8

9. 29. 9

13.115.013.1

1.0 4492 , 9 37628 136 4I 36 436 436 44118 737 6

0.45 691.26 690.73 37 60.97 37 61.10 3760.97 37 6

Tr i- n -oct yl n -Dod cc a n e (1,09) 3 15.3 12.9 0.95 37 6NOTES:(a ) Equ ilibr iu m agu eou s con cen tra t ion a re lis ted except a s n oted .(b ) Ca lcu la ted by aa au rn in g d i- solva t ion an d idea lity in th e organ ic ph aae; i. e., D1 ~ = Dfl ~ 2() wh ere x is th e con cen tra t ion oft h e e xt ra ct a nt .(c) Ca lcu la ted by compa rin g to TBP u nder th e same condit ion s u n der th e s ame ev~rime~a l con dit ion s wh ere poaa ib le. Oth er-wis e th e compa ris on is made in d irect ly. Th es e caaea a re n oted .(d ) T rep resen ta tra cer qu an tit ies of Pu .

8/7/2019 The

The Radio Chemistry of Plutonium.us AEC

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