June, 1W
~ X T R A C T I O NO F URANYL S A L T S BY TEI-'&BUTYL
PlIOSPIiATE
939
THE &IECIIANISX OF THE EXTRACTION OF SEVEltilL URANYL SALTS BY TRI-n-UUTYL PHOSPHATE BY KEIJI NAITO' AND TOSIIIO SUZUKI~ Japan Atamic Energy Research Institute, 'I'olcai,Ibaraki-ken, Japan Rscstwd Julu 18, 1981
The extraction of several uranyl salts (nitrate, chloride, perchlorate, eulfate, acetate, and phosphate) by TBP was studied. The formation of the complexes U02(NO&(TBP)2, UOzCl*(TBP)2, UOz(OAc)t(TBP)z, and UOz(ClO&OBP)4 was confirmed by artition study and infrared study. The influence of acid concentration on uranium extraction was discussed, especially For the system U02(C10,)2-HC104-TBP. The order of the extractabilities of the uranyl salts was compared with that of the acids.
Introduction The extraction of uranyl nitrate by TBP (trin-butyl phosphate) has been studied by many workers' because of its importance in the chemical processing of nuclear fuels. The mechanism of the extraction of uranyl nitrate by TBP was studied by Moore12McKay, et u Z . , ~ - ~ and lu'aito," and was confirmed as
the samples with those of the standard sample by using the 256-channel pulse height analyser. A lioken DS Type 301 spectrometer equipped with a rock salt prism wi19 used in the infrared measurements.
Results and Discussion Distribution Equilibrium.-The measurement of tJhe distribution ratio, Kd, for the dilute solution of uranyl salts (nitrate, chloride, perchlorate, sulfate, phosphate, acetate) was made a t various acid U02+2(aq.)+ 2KOP-(ay.) + 2TBP(org.) concentrations. In the case of the uranyl phosU02(l\Os)2(TBl'h(org.) ( 1) phate-phosphoric acid system, uranyl nitrate was used as a solute. TBP was used without dilution. The ex traction behavior of uranyl chloride beThe results obtaincd are shown in Fig. 1. The tween the aqueous and TBP phase was reported equilibrium of uranium in the by Reilly7 and Ishimoris; howcver, the mechanism aqueous phaseconcentrations were maintained as low as possible; of the extraction remains uncertain. almost all the cases, less than M ; and in The extraction of uranyl perchlorate by TBP in , ~ con- the cases of chloride, phosphate, and sulfate, was studied recently by I-Iesford, et ~ l . who X 1 0 - ~ ~ 1 0M-. ~ The data for the high acid cluded the formation of a complex, U02(C104)2- 3conccntra tion region of the U02Clz-BCl system (TBP)*. were obtained by Ishimori, el aZ.8 The object of the present work is to survey the Mechanism of Extraction. (1) Partition Study. extraction behavior of several uranyl salts (nitrate, - -Siiice mechnnism of extraction of uranyl chloride, perchlorate, sulfate, acetate, and phos- nitrate bythc 'l'B1' w w confirnird as cq. 1, the niechaphate) between the aqueous and T B P phase, and nism of cxtrad ion of ur:wyl salts may be expressed to reveal the mechanism of the extraction. The role of the anion during the process of uranium by thc general equation pUO2+*(aq.) ( 2 / m ) pX:-"(aq ) vTBP(org.) extraction also is to be discussed.
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Experimental Reagents.-The TRP was purified by the usual metliod.' The uranyl salts used in this stud were prepared by YokozawB Chemicsls, Tokyo. The otler reagents used were all A . R. grad('. Equipment and Method.-The experimental techniques were essentially the same as described in the preceding paper.10 All measurements were made a t a constant temperature of 25'. The concentration of uranium was determined by the alkaline peroxide mcthodll with a Hitachi EPU-2 spectrophotonieter (at X = 400 m p ) . For the samples of low uranium concentration, the neutron activation method was adopted qnd the samplex were irradiated in the JRR-1 reactor. In this c a m , the uranium concentration was determined by comparing the 7-peak heights of za"Np a t 0.106 and 0.229 MeV. of (1) For example, R. I. Sniith, TID-3502. ( 2 ) R. 1,. Moore, AECD-319G (1951). (3) K. A. Aloock, ef d.,Trans. Faraday SOC., sa, 39 (1958). (4) T. V. llealy and 11. A. C. McKay. ibid., 82, 633 (195~3). ( 5 ) E. Iiesford and H. A. C. McKay, ibid., 84, 573 (1958).
(0) K. Naito, Bull. Chem. SOC.Japan, SS, 303, 894 (19GO). (7) E. Reilly, ANL5254 (19Tj4). (8) T. lshimori and E. Kakamura, Bull. Chem. Soc. Japan, Sa, 713 (1959). (9) E. Hesford and €I. A. C. McKay, J . Inorg. & Nuclear Chem., 19, lG5 (1960). (10) K. Naito and T.Suzuki, J . I'hys. Chem., 66, 083 (1962). ( 1 I ) C. J. Rodden and J. C. Warf, "Analytiral Chemistry of the ?Amhattan Project," (National Nuclear Energy Series VIII-1 (1950)).
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(UOzXz/m)a(TBP)y(ors.) ( 2 )
where X-m indicates an anion and p and v are integers. The mechanism can be confirmed by determining the values of p and v, respectively, according to the method of analysis shown in the Appendix of the prevcding papcr.l0 The determination of thc value of p in the presencc of salting agents is shown in Fig. 2, from which the values of p are determined as p = 1 for UOr (Sod2-TBP, T'O~C~Z-TBP, UO2 (Clod)TTBP, and UO~(OAC)Z-TBP systems. This also is confirmed by the fact that the valucs of & for these systems are nearly proportional to thc square of the acid concentration. For the systems of uranyl acetate, phosphate, and sulfate, it is suggcstcd that uranyl ion is complexcd with the anion in the aqueous phase since the Kd values in the low acid (,oncentration region are nearly consttlnt. The determination of thc value of v is shown in Fig. 3, where carbon tetrachloride is used as a diluent. The values of v arc dcterrnined as v = 4, 2, and 2 for U0,(C104)2-TBPl UO&12-TBP, and UO~(OAC)~-TRP systems, respectively. Accordingly it w a s confirmed by this analysis that the mechanisms of extraction by TBP for
KEIJI NAITO AND Tosriro Suzuitr
090
I 103
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I-
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I'O.LC~~(TI~P)Z, 7T0.L(C104)2('l'BP)4, and G02(0Ac)2('l'lW)*. Though the mechanism of extraction for t hr systcnis of ura~iylsulfatr and phosphate also arc cxpwted to hc expressed as eq. 2, the mechanism is not clearly confirmed to the present since thrir low Kd values make the analysis difficul t * IIcsford, et ~ l . have , ~ reported the formation of a disolvate, C02(C104)&l'BP)z, at very high €IC104 concentrations (10-12 1'1). This disagreement or1 the system 7T0L(C104)2-T13P will be discussed later. (2) Infrared Study.--lilthough the compositioii of the o o ~ n p lformed (~ can be dcterrriiiicd by part 11 1011 in(x\iiwrnmt as descrihd nbovc., wo tried to clrtcimiiic 11 dircctly by m w n s oi infrared s p r c trOs('0pJ'. I t is known that 1hc, absorption band due to the
l'=O group at 1280 cm.-l is shifted to the longer wave lciigth by the formation of a complex with the inorganic saIt.6f*2One can observe the fart that thc interisity of the band due to free TBP de( " Y A S ~ ~ Sas the colicwitration of iiraniuni in thc TBP phase i~icrcnwi. Rincc i h c dccwaw of th(3 coilrelit ration of frclcl T13P cvrresponds to the (*ompobition of the c o n i p l c ~forrnrtl, thc wmpositioii of the complcs car1 be drtcrmincd by plotting the decreascl of the c~onccntrationof free THI' against the incrcasc of thr caoricwit r:itioii of uraniiim in the '1'13P phast.. Tht: inf'rarcd spectra obtaiiied for the U O r (ClO,)~-TBP system are shown in Fig. 4. All of t'hc spectra were obtained by capillary samplcs and their thicknesses were adjusted so as to give a conatant, iritensit'y in the absorption band due to CHa and GI-12 dcformat'ion vibration nt 1470 em.-'. (12) .J. 11. l,'crraro, .I. Inorg. & .Vucleai. Chein., 10, 319 (19.>!)).
Wavc length, ti
Fig. 4.-Infrared
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8
p.
0
IO
11
speatrs for the system of UOJ(C104)~~;'Ll~P, THI' l00(,,. C o n m of i i m i i i i i n i in T U P phase (mole/l.): 0; , 0.0,30; -.--, 0.327; - - - -., 0.169.
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'I'hc: samples were prepared by dissolving uranyl perc:hloratc: crystals in thc rl'131' phasc, aiid tho coricc:nt,rat,ioiis were O.US0, O.X?i, and 0. lfj!) M , respectively. 'l'hc drcwuso of thc coiic,ctnt,rat,ion of free TH1' with t.hc incrcasc of thc conccntmtioii of uranium in thc orgaiiic phasn is shown in 1;ig. 5%. 'rhc initial slope is 3.8, so the solwtioii iiiiintxr, v, in this case can be dctermincd as v = 3.8. On the ot'her hand, l T702(r\;Os)z> UOZCl2> U02SOr. This order is in good agrcemcnt with the order for proton
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acids, and it also is in thc iiiversc order to thc hydration energy of the anions. lo The difference of extractabilities due to thc anions is useful in the extraction of uranium from sulfuric acid solution by TBP. By adding anioiis such as SCK-, c104-, and NOa-, which are weakly hydrated in the aqueous phase, uranium can be easily extracted from thc aqueous phasc, leaving the S04= ion. Thc addit,ion of SCNion for the extraction of uranium from sulfuric acid solution was tried by Ross.14 Though uranium is extracted well by this method, there is the disadvantage that Fe(II1) also is extracted easily and accompanies the uranium. On the other hand, the addition of NO3- ion gives a high separation factor for uranium. The addition of C104ion also is effective, if TRP is used without dilution. However, if a diluent is used, the Kd of uranium dccreases rapidly with dilution becausc of the high solvent depcndencc of K d ( v = 4) in this case. Acknowledgment.-The authors would likc to express their gratitude to Drs. K. Kimura, T. Nakai, T. Mukaibo, and K. Oshima for thoir invaluable assistance and advice in this work. They also arc grateful to Prof. S. IIakishima for his hclpfill discussion. (14) A.
AI. Ross, TID-7508(1955).
ION EXCHANGE KINETICS OF POLYELECTROI~YTESUXllKIt STl3SI)YSTATE ELECTROLYSIS ACROSS A POROUS FRIT1 BY STANLKY J. GILLAND GUYV. FERRY Departwient of Chemistry, University of C o l o r a h , Iloulder, Colorado Receiced August $8,1961
A theory is developcti for EL stcatfy-state eloctrolysis method to determine t.hc charactcristias of ion binding u.it,ti polyrlectrolytes. The solutions of continuity equations of frce and bound tagged ion elcctric current flow are giver1 for tht. cases of onc or two exchange constants. Thc boundary conditions simulato the porous frit rnct,hod for difhsiori stridics. The ratio of tagged ion flows toward cathode andanode suggests a design and analysis of cxperirnents which allow a drterinination of the fraction of ion binding and exchange rate constants.
Introduction free ions. This has been shown for the system The intcract’ion between small ions and many of partially neutralized sodium po1yacrylate.j These studics have indicatcd that t,he rate of naturally occurring polymers, such as proteins and nucleic acids, plays a significant, role in de- exchange bctween free and bound sodium ions is t’erminingthe configuration and chemistry of these relatively slow. Wall6 has discussed these results rnatcrials. Thc methods uscd t o study ionic intcr- in connectlion uith the formation of a high potcmtial :u:tions hct;n.cen macro and sniall ions havc includcd ion atmosphere about the polyioii. Harris alld tlirec:l, dct,crminations, such as dialysis, oonduc- Itice’ havc proposed a theory of ion binding t)ast:d t,ii.ity, and clccitrophoresis, as well ~ L Sthc indirect; upon a more specific intcract,ion bctwcon small ions and charged sites on the polyion. cffccts yivcn by viscosity and light, scattering.2 The electrical transference method, devclopcd In this papcr wvo wish to discuss a stciady-st,at.c. by Wall and co-workers,3is capable of yielding not electrolysis situation which might be used t,o design . ~ interprctJfurthcr cxperimcnts of polyelectrolyte only a measure of the extent of ion b i r ~ d i n g ~ and but also the rates of exchange between bound and ion exchangc. The proposcd steady-statc oxpericxpcrimentul (1) This work was supported in part by & research grant (C-$393) ment simplifies the correlation of from the United States Public Health Service. parameters with ratc constants and fraction of (2) I. M. Klotz, “The Proteins,” Vol. I , P a r t B, Edited b y I€. Neurath and K. Bailey, Academic Press. Inc., New York, N. Y., 1953, Chapter 8. ( 3 ) J. R. Hriiaenga, P.F.Grieger, and F. T.Wall, J . A m . Chem. Soc., 7 2 , 2OBG (1030). , L ’ h C V L . , 62, 20:$ (l$j58). ( 4 ) 11. 11. 1 ) O I . P I I I I I S i l l l < l 1’. ~ ~ l J ~ l l l S ~Jl .I lI’hY,9.
( 5 ) (a) F. T. Wull und P. 1:. Griegcr, .I. Chem. /’/L!/Y., 20, 1200 (1952): (b) F. T. Wall, 1’. 1:. (;ricuer, -1. R. Fhiiecnya, and I t . I t . Doreinus, i b i d . , 20, 1206 (1952). (6) I
