Kharbanda, J. L.

Singh, I. J.

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-~-_ .._----~~~---------------IndianJournal of ChemistryVol. 15A, May 1977,pp.403-405Coprecipitationof Radio Rutheniumwith Hydrous ManganeseDioxideJL L. KHARBANDA & 1. J. SINGHDesalinationandEffluentEngineeringDivision,BhabhaAtomicResearchCentre,Bombay400085Received9 August 1976;accepted15 September1976Removalof radioisotoperuthenium-106as nitrosylcomplexspecies,from aqueousolu-tions,by coprecipitationon hydrousman~anesedioxidehas beenstudied under differentconditionsof pH. andamountsof Mn(IV) oxideprecipitated.Precipitationhas beencarriedoutbytheactionofhydro~enperoxideonpotassiumperman~anatein basicmediaandinfluenceof electrolytes,agingof rutheniumsolutionsin contactwithpermanganate,on coprecipitationyieldshasbeendiscussed.Conclusionsregardingthenatureof theprocessesresponsibleforcoprecipitationaredrawn anda mechanismis outlined.Coprecipitationyieldsto the extentof98%andmorehavebeenobtainedsugl1estingits usein the treatmentof radioactivewastewaters.NITROSYLRUTHENIUM(II) (RuNOs"') ian isthe mast cammonfarm af radiO'ruthenium(106Ru)presentin radiaactivewastewatersproduced during reprocessingof spent nuclearfuels. Decantaminationaf radiaactive nitrasyl-rutheniumcamplexesby caprecipitatiano.n somemetal sulphidesand lead periadatehave beenreported1-4,but theuseoJ formeris limitedto acidsolutionswhereasthe latter givespartial remaval.Hydrausmanganesediaxidewhichis knawnfar itsaffinityto' fix a numberaf metalians an its surface,has beenusedfar the eliminatianof radiumfromuraniummill effiuents5and concentratianaJ radia-nuclides fram sea water6. Coprecipitatianof anumberaf traceelementswith Mn(IV) oxide havebeenreportedandsameusefulseparatianspropased7.Eliminatian of nitrosylrutheniumcomplexspeciesfrom aqueaus solutians by coprecipitatiananhydrausMn(IV) axidehavebeenstudiedin detailandthe resultsarerepartedin this paper.Materialsand MethodsTracer-Stock solutionsaf nitrasylruthenium(II)nitratewerepreparedby distillingcarrierfreeruthe-niumtracer(106Ru)fromasalutianaf sulphuricacidand cerium(IV)sulphateand collectingthe valatilerutheniumtetraoxideintO'10%nitric acidsalution.Nitrogen(II) oxide was simultaneouslyintraducedin the collectingmedia8•9.Nitrasylrutheniumsalu-tion preparedin this mannerwas neutralizedwithsadiumhydraxideandfurtherdilutedwith distilledwater. The activity of the stack solutianwas ofthe arder af 10-2 (Joc/ml.TO' maintainunifarmity,samestocksolutianwasusedthraughout.Carrierfree106Ruin the formaf rutheniumchla-ridewasobtainedfromIsotopeDivisianof BhabhaAtomic ResearchCentre. All ather chemicalsusedwere6f analargrade.Procedure- TO' nitrosylrutheniumstock salutianknownvolumesof standardpotassiumpermanganatesolutian were introducedwith canstant stirring.Manganesediaxide was precipitatedby the drap-wise addition af hydrogenperqxide. pH adjust-mentsweremadeusingsadiumhydroxideOJ' nitricacid solutions. After allowingthe precipitatesto'settlefor about2 hr,a 5mlportionof thesupernatewasfilteredthroughWhatmanNo. 42 filter paper.The filtratewas countedfor gammaactivity in awell type NaI(TI) detectarcannectedto' a singlechannelanalyser. Errors dueto lossesof thetraceractivity by sorption on filter paper, increaseinvalume of the tracerdue to' the additionof patas-siumpermanganate,hydragenperoxide,alkali andacidsalutionsweretakenin to accaunt. Caprecipi-tatian yieldswerecomputedand are expressedintermsofpercentageof radianuclidein theprecipitate.Effectaf electralytesan thecoprecipitationyieldswas studiedby intrOducingknown amountsofsodiumsulphateto' the tracerstocksolutionbeforetreatingwith permanganateand precipitatingtheoxide.ResultsandDiscussionThe resultsareexpressedin termsof coprecipita-tion yield,Y (%) representedby the relationY= Is~Fs 100IswhereIs is the initial activity of the test sO'lutian,Fs is the residualactivity of the aqueousphaseafterprecipitatian.Caprecipitatianyield remainsunaffectedin thepH range8 to 10. Coprecipitationyieldsas highas 98% andmorewereobtainedunderthesecondi-tions. A gradualdecreasein coprecipitatianwasobservedwith the increasein pH beyand 10. Asthe low and mediumactivewastewatersare nearneutral2, only alkalinepH was studied.Aging of nitrosylrutheniumin contact withpermanganatepriar to precipitationhas significanteffecton its ultimateprecipitatianwith manganesedioxide(Fig. 1). At raom temperaturea minimumaf 4 hr contacttimeis faundnecessaryfar obtainingmaximumcoprecipitatianyields. Aging periad is.403-6·985·425·265·064·753,36D23·7825·6024·7725·7825'9626·2190,5094·8895,0095-6896·2998,48Tracerinprecipitate(%)A =log Initial tracer / log Initial carrierTracer in soin Carrier in solnD =(Trac.er) solid / (Tra~er) solnCarner / CarnerData in Table 1 show that within the limits ofexperimental errors, D values obtained are fairlyconstantin the wholerange.whenfraction of manga-nes~precipitated is varied. The constancy of Dvalues indicates that tracer is finally removed byway of isomorphousmixed crystal formation. Theoccurrence of isomorphism can be expected onlyfrom similar compoundsand is true in the case ofdioxides of the two elementsas Ru02 is reportedtoTABLE 1- DISTRIBUTION OF NITROSYLRUTHENIUM INHYDROUS Mn(IV) OXIDEManganeseprecipi-tated(%)28·6042·0043-4046·2050,0071·205--04INDIAN J. CHEM., VOL. 15A,MAY 1977has beentestedwith the help of ion~exchangeresin.A column of 2 g of dry deacidite FF-IP (NOi-form)was used for this purpose. Nitrosylrutheniumtracer stock solution (50 ml) was kept in contactwith KMn04 (equivalent to 100 mg/litre Mn) forabout 4 hr at room temperatureand then passedthrough the column at the rate corresponding tothe specificload of 5. Radio ruthf'nium tracer wascompletely retained by the column, indicating thequantitative changeo~nitrosylruthenium into nega-tively cha,ged speclCS. Ruthenates and perru-thenatesare analogousto the correspondingmanga-nese compounds and yield hydrous dioxide onreduction. Hydrogen peroxide would thus generateRu(IV) oxide together with Mn(IV) oxide fromsolutions containing mixture of permanganateandthe correspondingspeciesof the tracer. This im-plies that hydrous dioxide is the ultimate productderived from nitrosylruthenium through the oxida-tion-reduction cvcle and it is in this form thatruthenium is finally precipitated with manganese.To further understand the natureof processrespon-sible for the ultimate precipitation of the tracer,another series of experimentswere conducted. Inthese studies, after having allowed the nitrosyl-ruthenium tracer to age in contact with permanga-nate, the txtent of manganese precipitated wasvaried by varying the amountsof hydrogenperoxideadded and the correspondingamounts of the traceractivity removec[from the liquid phase was deter-mined. The values of I., the heterogeneousenrich-ment factor and D, the homogeneousdistributionfactors were calculated using following expres-sionsll,12.2 ;3'r(hrs)5060>=190~l~;~§;;180U••••a:Q.oU70Fig. 1t-Agingof nitrosylrutheniumin contactwithpotas-siump~rmaganate'T' timein hours [1,at 60°C empera-ture;2, at 28°Ctemperature]consi erably reduced with increase in temperature.At Ie st 100 mg of manganeseare required to beadded.as permanganateand subsequently precipi-tated .as oxide for the scavenging process to beeffecti e.The problem of mechanismof coprecipitation israther complex, there being only few methods fordistin uishing between the various mtchanisms ofsorpti. n of trace elementsboth on performed andprefor ed precipitates. One of the methods in-volve studying the influenceof electrolyteson thecopre ipitation yield. This method gives informa-tion n the probability of ion-exchangein sorptionor c precipitation. Added sodium sulphate ispraeti ally without effecton the extent of coprecipi-tation. For instance at sodium sulphate concen-tratio of 0'0005,0,001,0,005, 0,01, 0·1 and 1·0Mthe c precipitation yields are 97,1, 97'01, 96'81,96,12, 95,68 and 93'54% respectively, thus rulingout t e ion-exchange mechanism. Direct fixationof ni rosylruthenium complex species by surfaceadsor tion has been tested with the help of exter-nally ormed precipitates obtained by the action ofH202 on KMn04. Precipitates were centrifuged,washe with distilled water and then suspendedin nitosylruthenium tracer stock solution. Only asmall fraction (...••20%) of the total activity wastaken p by the precipitatedMn(IV) oxide, indicatingthe i ability of Mn(IV) oxide to directly fix thecompLx species on the surface. This implies thatperrna ganate plays an important role in theoveral processof coprecipitation. Role of perman-ganat may be considered as similar to theaction of sodium hypochlorite which has beenreport d to oxidize nitrosvlruthenium to ruthe-nates and perruthenates in alkaline media10.Oxida ion of nitrosylrutheru.umby permanganate404KHARBANDA & SINGH: COPRECIPITATION OF RADIO RUTHENIUMbehavesimilarlyto Mn02 (ref. 10). This supportsthE'formationof hydrousdioxideof the tracerviaruthenatesandperruthenatfs,as the ultimatepro-duct. Thusit maybeconcludedthatpermanganateplaysa dm.1role both as an oxidantas well as asourceof hydrousMn(IV) oxide. Nitrosylrutheniumon undergOIngoxidation-reductionprocessis ulti-matelyprecipitatedas hydrousdioxide.AcknowledgementThe authorswishto thankShri M. P. S. Ramanifor theencouragementandDr K. S. Venkateswarlufor usefulsuggestions.References1. MOORE, R. L., J. inorg.nucl. Chem.,14 (1960),38.2. AMPHLETT, C. B., Treatmentand disposalof radioactivewastes(Pergamon Press, Oxford), 1961, 147.3. KONECNY, C. & WAGNEROVA, D. M., CoUnCzech.chem.Commun.,26 (1961), 325.4. AUCHAPT, J., Proc. CoUoquefranco- Espagnol,Sur LetreatmentDes combustiblesirradies, 1967, 35.5. TYNTRTRINA, A. P., ZHAGIN, B. P. & BAKHUROV, V. G.,AtomicEnergy(U.S.S.R.), 18 (1965), 487.6. YAMAGATA, N. & IWASHlMA, K., Nature,200 (1963), 52.7. BIGLIOCCA, C., FRANCO, G. & SABBIONI, E., Analyt.Chem.,39 (1967), 1634.8. KEPAK, F., Colln Czech.chem.Commun.,31 (1966), 3500.9. ZVJAGINCEV, O. E. etat., Khimiya Ruteniya (Izd. NaukaMoscow), 1965, 75.10. WYATT, E. A. & RICKARD, R. R., The radio chemistryofruthenium,NAS-NS-3629 (1961).11. DOERNER, H. A. & HOSKINS, W. M., J. Am. chem.Soc.,.47 (1925), 662.12. HENDERSON, L. H. & KRACEK, C. F., J. Am. chem.Soc.,49 (1927).738,405. ,_,,,~.~~.~~_,J

Coprecipitation of Radio Ruthenium with Hydrous Manganese Dioxide

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Coprecipitation of Radio Ruthenium with Hydrous Manganese Dioxide

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