Dey, A. K.

Eusebius, Lalit C. T.

Ghose, Animesh K.

Mahan, Ashok

English

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Indi~ Journal of ChemistryVol. 15A, May 1977,pp. 438·442Cation ExchangeSorptionof SomeMetal Ions from AqueousAmmoniumAcetateMedium: Separationof Ce(IV) fromCe(III), La(III) & Other Metal IonsLALIT C. T. EUSEBIUS, ASHOK MAHAN, ANIMESH K. GHOSE & A. K. DEY*ChemistryDepartment,University of Allahabad, Allahabad 211002Received28 August 1975; accepted15 September1976Thecationexchange(Dowex50W-X8;NHt-form)characteristicsof 19metalionsin variousconcentrations(O·02-1·60M)ofNH40Ac arereported.At low[NH40Ac]thesorptionofcerium(IV)is lowwhereasothermetalionsshowappreciabh~sorption.Throughthedeterminationofdistri-butioncoefficientsandseparationfactorsasa functionof [NH40Ac],separationofCe(IV)fromitsbinarymixtureswithCe(III),La(III), Co(II),Ni(II), Cu(II),Zn(II) or Pb(lI) hasbeenachieved.Thepossibilityofseparationbycolumnchromatographyinanumberofternarymixtures uchasCe(IV)-UO,(VI)-Ba(lI)jHg(II)jAI(III) ; Ce(IV)jUO,(VI)-Ce(I1I)jLa(III)jCo(lI)jNi(lI)jCu(lI)jZn(II)/Pb(II)-Ba(II)/Hg(II)/AI(III),hasbeenindicated.Separationfactors,elutioncurves and theresultsof resolutionof syntheticbinarymixturesarepresented.... (1)INAMI and Ishimori1separatedBa(II) andPb(II) on R-NH4 type resin using aq.NH40Ac (PH =6·1), while Honda2 de-d the separationof Mg(II), Ca(II), Sr(II) andKhopkar and De3 studied the cationexchnge behaviourof Ba(II) on Dowex 50W-X8and btaineda highvaluefor the separationfactorwith respectto Pb(II). De and Majumdar4 re-porte the separationAg(I), Pb(II) and Hg(II)usingNH40Ac medium. The separationfactorsofCe(II), Pm(III), Eu(IlI), Tb(III), Tm(III) andY(III determinedby columnelution methodinthis ediumby Ward and Choppin5 showedthatsepartions were comparativelypoorer than inother complexingmedia. A systematicstudy ofthe c tion exchangebehaviourof metalsin nitricacid-,.H40Ac medium has been reported earlierfrom his laboratory6,andthis work hasnow beenexten edusingaqueousNH40Ac mediumto achieveanu berof usefulandquantitativecationexchangesepartions.Mate ials and MethodsDo ex 50W-X8 (H+form), 100-200mesh,wastreat in a columnalternatelywith IN HCI andIN aOH beforeuse. The resin was then con-verte to NH:;--formby treatingwith20%ammoniasoluti n, andwashingwith waterundersuctiontillthee uentwasfreefromalkali (negativetestwithphen phthalein). It was treated with ethanol,dried undersuctionand finally in an ovenat 60°for a out 4-5 hr, and stored. The watercontentof ths resin was found to be 9,2% (±0'3%) byheatig the samplesto a constantweightat 110°.Thec pacitywas4·12meqfgresin.All •the chemicalsused were of reagentgrade.Standrd solutionsof metal ions were preparedfrom· heir nitrates(BDH, analar),excepthoseof*To iwhom all correspondencemay be addressed.438Ce(IV) and Ce(III) whichwerepreparedfrom eerieammoniumnitrate (E. Merck) and cerouschloride(JohnsonMatthey), respectively.Solutionsof Ce(IV) and Hg(II) were preparedin aq. NH40Ac,while those of other reagentswere preparedindoublydistilledwater.The solutionsweremechanicallyshakenwith awrist-motionmicroidflaskshaker(Griffin& George)in glassstopperedpyrex flasks (100ml) in batchexperiments.A graduatedcolumn (65 em long,intodiam. 0·85em)was usedfor chromatographicseparations.Distribution coefficients- Distribution coefficients(D) wefe determinedby the batch equilibrationmethod. One gram portions of the resin wereshakenfor 1 hr (it waspreviouslyascertainedthatthis timewasadequateto attain equilibrium)withsuitableamountsof metalion solutionscontainingdifferent NH40Ac concentrations.The solutionswerefilteredandanalysedfor total metalcontents,irrespectiveof species,eithertitrimetricallyagainstEDTA or by colorimetry. The concentrationsofNH40Ac usedwerein the rangeof 0'02to 1·60M.All determinationsweremadeat leastin duplicate.The D valueswereobtainedby Eq. (1).D meqmetalion per g resinmeqmetalion per ml solutionThe metal concentrationsemployedwere around12% of the total exchangecapacityof the resin,to ensurecompleteequilibration. The total volumeof aq. phasewas 25 ml. The experimentswereperformedat 30°±2°. The relativeexperimentalerrorsin the determinationof the D valueswere± 10 and ±20% for low and high D values,respectively.Preparation and pretreatmentof resin bed- Theresin slurry (-----'5g) was preparedin water andtransferredto the column. The resin bed had ann ~ _EUSEBIUSet aI.: CATIONEXCHANGECHARACTERISTICSOF METALIONSlengthof ",7·5 cm and was treatedwith 0·10MNH40Ac solution.The feed,25 ml of 0·10M/0·06M NH40Ac, waspreparedby mixingan aliquotof standardsolutionof Ce(IV) and one of the other metalions to beseparated.It was passedthroughthe resin bedand the flow rate maintainedat 1·0±0·3 mIlminute. During this operationall the metalionswere sorbed on the resin except Ce(IV). Theeffluentwascollectedin 5 ml fractions.The columnwas washedwith 0'06M or 0·10MNH40Ac, andthen eluted with 0·50M or 0·80MNH40Ac.Chromatographicseparation- After sorption,thecolumnwaswashedwith 30 ml of 0·10M NH40Acand the effluentagaincollectedin 5 ml portions.The total (55 ml) eluentvolu.me(25 ml feed+30ml washingsolution)was sufficientto recoverCe(IV) quantitatively.SorbedCo(II), Ni(II), Cu(II),Zn(II), Pb(II) and U02(VI) wereelutedby passingabout 200 ml of O·50M NH40Ac solution,whileLa(III) and Ce(III) by 80 ml of 0·80M NH40Ac.Ba(II), Hg(II) and Al(III) wereretainedstronglyon the column,andthe breakthroughof theseionswasstill not observedafter the passageof 200 mlof 0·50M NH10Ac or of 80 ml of 0·80M NH40Ac.ResultsandDiscussionThe D values for 19 cations are reportedinTable 1. Ions known to hydrolyseunder theseconditionshave been omitted. In all the casessorptionof themetalion decreasedwith increasing[NH40Ac] as indicatedfrom the D values. Theprobablereactionoccurringin solution may begivenby Eq. (2).Mn++mOAc- ~ M(OAc)l:-m)+ ... (2)wherethe complexwill be cationicwhen n>m;neutral when n =m; and anionic when n<m.The sorptionwill be less, if the complexformedhas a small positive,zero, or a negativecharge.A negativechargeis not alwaysnecessaryfor aneffectivedecreasein sorption,andin facttheconcen-tration of negativelychargedmetal acetatecom-plexesin mostcases[exceptU02(VI)]in aq.solutionis negligible7•As [NH40Ac] is increased,acetateion replacesthe coordinatedwater moleculesresultingin theformationof complexspeciesof a small positivecharge,and consequentlyD is lowered. A furtherincreasein [NH40Ac] leads to the formationofneutralspeciesand this also resultsin a decreaseof D. When [NH40Ac] is higher,and a neutralmetalacetateis presentin solution,the predomi-nantspecies5,lOin theresinphasewill be MII(OAc)+or MIII(OAc)2+asthe casemaybe.A moredefiniteproofthatM(OAc)2+andM(OAc)aare the speciesinvolved in La(III) and Ce(III)systemsat higher [NH40Ac], is obtainedfrom acon!)iderationof the dependencyof the separationfactorson the stability constants5.It followsthatin 0·80M NH40Ac solution,the speciesM(OAc)2+and M(OAc)aare presentin resin and solutionrespectively.This implies that D =M(OAc)2+/M(OAch (barrepresentsthe resinphase)or D oc(K2Ka)-1, whereK2 andKa arethesecondandthirdstepstability constantsll,respectively.The samedependencyon (K2Ka)-1 shouldexistfor thesepara-tion factorssincethesearethe ratiosof D values.It has beenobservedthat the agreementbetweenexperimentaland theoreticalvaluesof separationfactors(Table2) isgoodonlyforM(OAch -M(OAc)asystem. Theorderof D valuesfor La(III), Al(III),Ce(III), andCr(III) followsthe orderof solubilityof the complexesof thesemetalionswith acetate.Ce(IV) inspite of its high charge,has a pooraffinity towardsthe resin. Similar behaviourhasalsobeenobservedfor U02(VI), wherea moderatesorptionin 0'02M NH40Ac mediumis noted,whichstartsfallingas [NH40Ac]increases,andat a high[NH40Ac] the sorptionis very poor or evenlessthan that of Ce(IV). The low D valuesof Ce(IV)and U02(VI) are dueto the pronouncedformationTABLE 1~ VALUES OF DISTRIBUTIONCOEFFICIENTS(D) IN NEUTRAL NH.OAcMetalAmmonium acetateconcentrations(M)ion 0·020·0610235,81 6Ag(I)112·77 ·041· 634,8275 989,96 5Mg(II)767 508·323 780 2845 42·75-Ca(II)109867 ·221-18Sr(II)84 ,62,4351 H'~ ' 7'39Ba(II)469 ·- 5Mn(II)39416Co I2370' 09Ni3 190'- 7Cu( I)6·Zn62 8Cd(II)9 5 044 ,8'Hgpptppt 1-4Pb(I )2Al(III)-5447 7r H4'L H )41519 9 ·9e II4 8-'( V·354· -U02( I)6 1--,Q()439/INDIAN J. CHEl\I., VOL. 15A, MAY 1977TABLE 2 - SEPARATION FACTORS (:x~il) EVALUATED AT SlllTABLE [NH40Ac]:\1aMISy~tem[NH,OAc]a~lISystem[NH.OAc]MII MMIlLa(l l)-Ag(l)0·10391'2Co(Il)-C ( V)0,0620 3La(l )-Mg(II)061 7Ni(I )-Ce(150II Cu(II)26u ·8·1La(II)-Zn(Il)2Zn Id.9·9d '4I)-pb(ll),%pb(II)- (IV)4 5. r l0Al ll Ag ) 103 8e IV1239Al(l Il)-Cr(Il I)267I U02( l1 83Al(II )-Ce(lV)6l\1g(I}Ce(l )l(III)-U02( l)Ca(I )- Ir(U I 1-Sr(II -Ce(IV)e II) (ISr(Il -U02(VI)38 ·Ce O,,( l)6B I )-Zn l85Hg ) Zn IT 8B (I Pb(l )57 -JI ] d Ia )-Ce(IV)Ph J)51 546Hg(II)-U ,(V]5Mn(I )-Ce(]V)TAil1LE 3- ELUTION CHARACTERISTICS OF METAL IONSBTVVEl'T VEluting(ml)(ml)age t[NH.OAc]MCe(r· )3,515450·06/0·10CellI )57,8La(I )80U02('1) 50·5Co(lI29 , 0Ni(IIu )33 ·Zn II1PhI.] 1Bal>200--0,50.>8-8Hg )Al(U·l,lI )RTV =breakthroughvolume.VEl' =volumeelution peak.TEV =terminal elution volume.of . mplexes of these ions with acetate. At[NHOAc] >0·20M, the sorption of U02(VI) abruptlyfalls, probably due to the formatien of an anieniccom lex7• At lower [NH40Ac] (0-02-0-lOM), Ag(I)has he lowest D values [except Ce(IV) and up tosam extent U02(VI) when compared with othermeta ions. Ag(I) exhibited a similar behaviour6inHN3-NH40Ac system, which was attributed to thepres 1ce of NH;t ions in the medium_ The beha-viou becamemore pronouncedin the present casesince the resin used was also in the ammonium-formTI remaining metal ions behavenormally as theD v lues are either guided by the complexationreact on with acetate7or by the competitionof NH!coun er ions. Precipitation of Hg(II) and Ce(IV)was bservedin certain concentrationsof NH40Ac.Th valuesof the separation factors (rt.l\}\Ih) (Table" II2) w,re calculated for a number of pairs of metal440ions on the basis of large differencesin D values.The hatch experimentdata on the effectof NH40Acon the sorption of Ce(IV), and of Ce(III) and La(III)showed that a medium of 0·06-0·30M NH4 OAcis most suitallie for the separation of Ce(IV)from Ce(III) and La(III). At higher concentrati'lns(0'80-1,602\;1)of NH40Ac, these ions have low Dvalues, showingalmost identical sorption behaviourleading to no p lssibility of separation. Similarbehaviour has also been observed in the cases ofCo(H), Ni(II), Cn(H), Zn(II) and Pb(II). When[NH10Ac] is ()'(162\1, U02(VI) has a high value ofD and is retained quantitatively on the resin,and, therefore, its separation frc,m Ce(IV) is pos-sible. But at 0·10M NH40Ac (as in other cases)a clearcut separation is not po~sible. At 0·80MNHiOAc. bl th Ba(lI) and Hg(II) have a higheraffinity [exceptCa(II) and Sr(II)J towards the resinthan the other investigatedions, and hencea largenumber of separaticns can be achievedwith metalions having verv low D values at this [NHiOAc].On the basis of these results seme actual separa-tions were carried out using suitable eluents foreffectingclean:utseparaticnsof Ce(IV) from Ce(III),La(III), and other metal ions.Among the systems where actual separationswere carried out, the conditions predictcd frombatch experiment ebta were found to be true forcolumn chrom;ltogrilJ)hicseparationsof Ce(IV) fromCe(III), La(III), and other metal ions. The elutioncharacteristics (f a number of metal ions inveoti-gated in these media are shown in Table 3. Ageneral procedure involves feeding a mixture (25ml) containing metal ions and NH40Ac (overallconcentratien 0-10M) through the resin beelat therate of 1-0 ± 0-3 mljminute. Ce(IV) is quantita-tively recoveredby washingthe column with 30 mlof 0·10M NH40Ac, while other ions are retained.O'SOM NHi)Ac wasnext used for the desorptionofCo(II), Ni(II), Cu(II), Zn(II) or Pb(II) (Fig. 1),and 0-80M KH40Ac for Ce(III) and La(III) (Fig. 2).·WhenU02(VI) was taken as one of the componentsof the feed (25 ml) the overall [NH.OAcl was kept0-06M; becausein 0·10M NH40Ac U02.(VI) is notn n __ ~ __ ~ _.EUSEBIUS et at.: CATION EXCHANGE CHARACTERISTICS OF METAL IONS(a)Mean of duplicateruns with calculatedstandarddeviation.II5040Otherelement45'15±0'6045'15±0'2832·07±0·5532·07±0·42120'12±0'9834·7±0·1027-77±0·1831'87±0'2630·46±0·5042·24±0·4042-42±0'3230Found(a)(mg)Ce(IV)35·05±0·1428·22±0·0835·13±0·1728'22±0'2021·11±0·1034·93±0·2935·08±0·1635·09±0·1835'23±0'2335·00±0·3028·00±0·1220OtherelementLa(III) 45·15La(III) 45·15Ce(III) 32·07Ce(III) 32·07UO.(VI) 120·12Co(II) 34·77Ni(II) 27·77Cu(II) 31·77Zn(lI) 30,46Pb(lI) 42-44Pb(II) 42-44Taken(mg)oCe(IV)35,0328·0235·0328·0221·0135,0335·0335·0335·0335,0328·0240 0 10 20Effluent(ml)Fig. 3- Elutioncurveof Ce(IV)-UO.(VI)(7'5±0'3ml) onDowex50W-X8resin(NH~-form)columnTABLE 4 - QUANTITATIVE SEPARATION OFSYNTHETIC MIXTURES --42440 eo 120 160 200Effluent (ml)Fig. 1- Elution curves of Ce(IV)-Co(I1)jNi(II)jCu(II)jZn(II)jPb(II) (7'5±0'3ml) on Dowex50W-X8resin(NH:-form)column9c.2-e-cQIUCoUc.2'Ei•...-CGIUCoU 26,retained quantitativelyon the resin and someU02(VI) passesalongwithCe(IV) in the effluentasalso evidencedfrom the batch experiments.Thewashing was followed with the same NH40Acsolution(30 ml). U02(VI) was elutedwith 50 mlof 0·50M NH40Ac (Fig.3). In Figs 1-3,thevolumeof effluentincludesthe volumewhichpassesout ofthe resin from the original feed. The results,presentedin Table4, indicatethatcompletesepara-tion of Ce(IV) from othermetalions can success-fully be achieved.The strongly sorbed Ba(II),Hg(II) , andAI(III) ionscanalsobeseparatedfromLa(III), Ce(III), U02(VI), Co(II), Ni(II), Cu(II),Zn(II), or Pb(II). Themetalion La(III) or Ce(III)retainedontheresinwaselutedwith80mlof 0'80MNH40Ac, whileU02(VI), Co(II), Ni(II), Cu(II) orPb(II) with O·50M NH40Ac. Ba(II) , Hg(II) orAI(III) wasthenelutedwith cone.HCI or HN03•The ternaryseparaticninvolvesa moredetailedcolumnchromatographicinvestigation,sincechangesin the degreeof loading,ionic strengthandfactorsconcerningthe columnoperationhave a markedeffect. In thepresentstudiesthecolumnchromato-graphicexperimentshavealsorevealedthepossibi-lity of a numberof ternaryseparations,incebreak-throughof Ba(II), Hg(II) or Al(III) wasnot reached441La(lI\JCe(lill45040M NH40Ac45o 20 40 0 20 40 60 eoEffluent(ml)2- Elutioncurvesof Ce(IV)-Ce(III)jLa(III) (7·5±0·3ml)onDowex50W-X8resin(NH:-form)columnco:g 3•...CQlg 2oU7et- 1\ O-SOM NH40AcFig..'INDIAN J. CHEM., VOL. 15A, MAY 1977afte the passageof about 200ml of O·SOM or 80 ml" of O· OM NH40Ac, though this volume of NH40Acis scient to complete the elution of other metalions in the respective experiments. Therefore,Ba(I ), Hg(II) or AI(III) can be separated fromternry mixtures. After the complete elution ofothe ions as described above, these ions can bestrip edoff with cone. mineral acids. The otherpos-sible ternary mixtures which can be separatedare:Ce(1 )-U02(VI)-Ba(II)jHg(II)jAl(III); Ce(IV)jU02(VI)- e(II!)j La(III) jCo(I!) fNi(II) jCu(II) jZn(I!) jFb(II)- a(I1) I Hg(II) I Al(III).A abnormal behaviour has been observed in theeluti n of Al(III). At or above O'SOM NH40Acthe atch distribution coefficient of Al(I1I) is ofthe ame order as that of La(III) or Ce(III), butthe ehaviour on column was different. It appearsthat amphoteric nature and the formation of basicsalts of polynuclear hydrolytic species8,9,and poly-meri ation of the hydroxopolynuclear species areamog factors responsible for this abnormal beha-vion of AI(III).442AcknowledgementThe authors are grateful to the CSIR, New Delhi,for financial assistance.References1. MINAMI, E. & ISHIMORI, T., J. chem.Soc. Japan, 74(1953),378.2. HONDA, M., Japan Analyst, 3 (1954),132.3. KHOPKAR, S. M. & DE, A. K., Analyt. chim. Acta, 23(1960),441.4. DE, A. K. & MAJUMDAR, S. K., Talanta,10 (1963), 201.5. WARD, E. H. & CHOPPIN, G. R., J. inorg. nucl. Chem.,27 (1965),459.6. MAHAN, A., GHOSE, A. K. & DEY, A. K., SeparationScience,6 (1971), 781.7. SILLEN, L. G. & MARTELL, A. E., Stability constantsofmetal ion comPlexes,Special publication No. 17 (TheChemicalSociety, London), 1964.8. AVESTON, J., J. chem.Soc., (1965),4438.9. MARIN SKY, J. A. & MARCUS, Y, Ion exchangeand solventextraction,Vol. 5 (MarcelDekker, New York), 1973,51.10. BRUCHER, E. & SZARRAS, P., J. inorg. nucl. Chem.,28(1966),2361.11. HOLM, L. W., CHOPPIN, G. R. & MaY, D., J. inorg.nucl.Chem.,19 (1961).251.

Cation Exchange Sorption of Some Metal Ions from Aqueous Ammonium Acetate Medium: Separation of Ce(IV) from Ce(III), La(III) & Other Metal Ions

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Cation Exchange Sorption of Some Metal Ions from Aqueous Ammonium Acetate Medium: Separation of Ce(IV) from Ce(III), La(III) & Other Metal Ions

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