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insertion reaction with Mg2Mn0.5Ti0.5O4 inverse spinel in the aqueous phase

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insertion reaction with Mg2Mn0.5Ti0.5O4 inverse spinel in the aqueous phase

    insertion reaction with Mg2Mn0.5Ti0.5O4

    inverse spinel in the aqueous phase RAREMETALS

    VoL26,No.Dec2007,P.536

    E.mail:rm@ustb.edu.ca

    Availableonlineat,^,,ln?.sciencedirect.com

    .,,

    '

    ?

    :,ScienceDirect

    Li+extraction/insertionreactionwitllMgaMno.

    sTio.

    504inversespinelin

    theaqueousphase

    JANGJinhe,DONGDianquan,CHENGuanghui,LIUJiaqiang,andLIJianlong DepartmentofChemicalEngineering,QingdaoUniversityofScience&Technology,Qingdao266042,China

    (Received2006-0817)

    Abstract:Aninversespinel

    typemetaloxide,magnesium-manganese-titaniumoxide(Mg2Mno.5Tio504),wereprepared

    usingthecoprecipitation/thermalcrystallizationmethod.Theextraction/insertionreactionwiththismaterialwasinvesti

    gatedbyX

    my,saturationcapacityofexchange,pHti~tion,anddistributioncoefficient(measurement.Theacidtreat-

    mentsofMg2Mno.

55O4causedMgextractionsofmorethan81%,whereasthedissolutionsofMn4+andTiwerel

    ess

    than10%.Theexperimentalresultsprovedthattheacid-treatedsamplehasacapacityofexcha

    nge56mg?g.forLiinthe

    solution.ThechemicalanalysisshowedthattheLi+extraction/insertionprogressedmainlyb

    yionexchangemechanismand

    surfaceadsorption.

    Keywords:extraction/insertionreaction;inversespineltypemetaloxides;ion

    exchangemechanism;Mg2Mno.

    5Tio.

    504

    1.Introduction

    einorganicionexchangepreparationhasthe

    advantagesofthermostabillty,radiationresistance, simplesynthesis,andgoodselectivity.Asidefrom that.theadvantagesalsoincludethefinespecialtyin dealingwithnuclearwaste,gatheringandseparation ofmetalions,andchromatogramanalysis.Therefore, after1980s,thefundamentalstudyandapplication investigationhavebeenrenewed171.

    Wi廿1theprogressofthestudyofionsievetype

    morganlcmaterials,themorganlcionexchangema

    terialshavingspecial''sievesites''structurecanbe obtainedbyinsertingspecificionsintheinorganic compoundandfixingtheionsinsertedusingapar

    ticularapproach.Thentheextractionofthespecific ionsisinthepremiseofmaintainingtheinitialcrys

    tallizationstructure.Inthisstudy,thecoprecipita

    tion/thermalcrystallizationmethodsynthesizedthe Mg2Mno5Ti0.

504ofinversespineltypeoxide,whose

    compositionandstructurealedifferentfromthosein thepublishedreports[817].Theexperimentalre

    suitsindicatedthattheinorganicmaterialhasbetter selectivityandhighercapacityofexchangeforLiin thepreviouslyremovedMgsolution.Moreover, thecostischeapanditsapplicationprospectis significant.

    2.Experimental

    2.1.Reagentandinstruments

    MgSO4,MnSO4,andTi(S04)2wereallanalytical reagentsandpurewaterwasusedintheexperiment. D/maxAtypeXmydiffractioninstrument,Dx170

    typeionchromatograminstrument,AA670atom

    absorptionspectruminstrument,andCentrifuge 5804cen~fugalseparationinstrumentwereusedin thisstudy.

    2.2.SynthesisandidentificationofMg2MIl05rri05o4 Theamrnomawasdroppedintoastandardmixed solutionofMgSO4,MnSO4,andTi(SO4)2witha Mg/Mnffimoleratioofl:0.5:0.5underthecondi

    tionofconstantratechurning.AfterthepHof moth~solutionreachedl1.0,theadditionofH,02 solutiontothesolutionoxidizedMnztoMn".After reactingfully,centrifugalseparatingandwashingin Correspondingauthor:LIJianlongE-mail:lijianlong@qingdaonews.corn

    如增H,Liextraction/insertionreactionwithMg2MIl0. 5Ti0.

    504inversespinelintheaqueousphase537

waterledtoMgMn.Ticoprecipitation.

    Thecoprecipitationwascamedoutforfewhours onanelectricheatingplate,air-driedfor48hat 70.Candcrushed.Theexchangerprecursorwas thusobtained.Theprecursorwasheat-treatedfor4h at700,800,900,and950.C,respectivelytoobtain theMg.Mn.Tioxide.whosetheoreticalformulawas Mg2Mn0.

    5T504.Thesampleobtainedbythermal

    crystallizationtreatmentof900.CwasMgMnTi900

    ThenitwasanalyzedbyX..raydiffractionandcorn.. paredwiththepublishedreports10,16171.

    Compositionanalysis:A0.2gportionofsample (MgMnTi900)wasdissolvedwithacid.Thedeter

    minationofMg,Mn,andTicontentswasbyatomic absorptionspectrometry.Thedeterminationofthe Mnvalencewasbythemethodinthepublishedre

    port10andtheMgMnTi900compositionwas

    calculatedfromthesevalues.

    2.3.Cationextraction'ofMgMnTioxideandacid modification

    Four0.200gportionsofsample(MgMnTi900

    oxides)wereimmersedinHNO1solution(50mL) OfO.O1,O.1O,1.00,and10.00moI/L,respectively withshakinginconstanttemperaturewaterat25.C. After3days,thesupematantsolutionwastestedfor thedeterminationofthecationconcentration,its acidproofability,andtheextractionrationofMg, Mn4+.andT.

A5gportionofsample(MgMnTi9001wasim

    mersedina1mol/LHNOsolution(500mL)with intermittentshakinginconstanttemperaturewaterat 25.C.After7days.thesupematantsolutionwas discardedandnewHNO1solutionwasadded.Re

    peatingthistwice,theinitialsamplewasthentrans

    formedtoHtypesample,washedwithwater,and airdried.Thesampleobtainedbythermalcrystalli

    zationat900.Candacidmodifiedwasdesignatedas MgMnTi?900(H),andXraydiffractionwascarded

    outtocomparethes~bilizationofthestructure.The compositionwasdeterminedbythemethodreferred inSection1.2.andtheHcontentwascalculatedby thesubtractionmethod.

    2.4.Saturationcapacityofexchange

    Five0.5gportionsofMgMnTi?900(H)were weighed,andtheneachportionwasimmersedina O.10mol/Lsolution(10mL),containingLi,Na+, ,Rb+,andCs,respectively.Itwasthendilutedto 100mL.shakeninconstanttemperaturewaterat 25.C.Aftersaturationexchange(namely.after10 daysaccordingtothepublishedreports10,1617])

    thesolutionswerefilteredthroughasubminiature aperturesieve,andthecationconcentrationwas determined.Atthesametime,vacantexperiment wasalsodone.Theinorganicexchangersaturation capacityofexchangeforalkali..meta1..ionswasob- tainedbydecreasingthequantity.

    2.5.pHtitrationcurve

AO.100gportionofMgMnTi900(H)sample

    wasimmersedinamixedsolution(10mL)of0.10 mol/LLiindifferentmolerationsofC|Q(the rationswereadjustedusingLiOHandLiClsolution) withintermittentshakinginwaterat25.C.Afterthe samplewasshakenfor7days,thepHofthefiltered solutionwasdeterminedusingaprecisepHmeter. ThepHtitrationcurveofLiwasobtainedfromthe pHandtheOH-concentrationinthesample.The pHtitrationcurveofMgMnTi?900(H)forNawas obtained.

    2.6.Distributioncoefficient)

    Afterweighingfour0.100gportionsof

    MgMnTi?900(H),eachportionofthesamplewas immersedina0.05moI/LmixedsolutionfO.200mL1 containingLi,Na,K,Rb,andCs(C1-/OH-ra. tionsaredifferentineachsolution,c(cn+C(OH-)= O.1mol/L,C=Li,Na,,Rb+,andCs).Thetotal concentrationofalkali.metalionswas1.O×1o_

    mol/Lbyadding9mLOfdistilledwater.Afterthe sampleswereshakenfor7daysinconstanttem

    peraturewaterat25.CfoUowedbyfiltration,andthe cationconcentrationineachsamplewasobtained. 3.Resultsanddiscussion

    3.1.Compoundandappraisementof

    Mg2,In0.sTi0.so4

    TheX?raydiffractionpatternsofcompound metaloxide(Mg2Mno5Tio.504),crystallizedatdif-

538

    ferenttemperatures.areshowninFig.1.Thepure spmeltypephaseiSformedbetween700and950.C Thediffractionpeaksbecomehigherandsharper withtheincreaseintemperature.Thestructureof compoundmetaloxideMgzMno.5Tio.504crystallized at900.Cwasperfect.

    :

    \

    C

    Q

    C

    20/(.)

    F.1.Powder'SX-raydiffractionpatternsatitl~el-- entcrystaltemperatures.

    Basedonchemicalanalysis,thecompositionof MgMnTi900isMg2.

    1zMno.

    n9Tio5104.

    06,whose

    chemicalcomponentcorrespondswiththecomposi

    tionofinversespineltypemetaloxides.

    3.2.Ca6Oilextractionofcombinedoxide MgMnTiandacidmOdifica6On

    TheextractionrationofMg.

    Mn4+.andT

    fromMgMnTi900indifferentconcentrationsof HN01SOlutionisshowninFig.2.AccordingtoFig. 2,theextractabilitiesofMgare4JD%81%.Mn4+

    are7%16%.andTare2-3%8.2%.Theseindi

    catethattheextractabilitiesofMgarehigherthan

    thoseofNil4+andTwhentheexchangerwas immersedin1mol/Lacidsolution.corresponding withtheexchangerinabettercondition(1N.Mg 77%,M_n"9%,T6%).

    XraydiffractionofMgMnTi.9o0(H),whichiS theacidmodificationproduct,iSshowninFig.1.As shown,thestructureofMgMnTi.9o0(H)iSnearly constant,whichisinversespineloxidetyDe.Itindi. catesthattheexchangerissteady.

    Theanalysisindicatesthatthecompositionof MgMnTi900(H)wasH326M.57Mno.45Tio.~O3.24, RAREMETALS,VoL26,No.6.Dec2007

    whosecomponentof77%Mgwassubstitutedby Hcomparedwiththecomposition

    Mg212gn049Tio.

    5104.

    06beforebeingacidtreated.The

    specificMgofexchangerwasextractedandre

    mainedHtypeandwasidentifiedbytheinitialtype. CH./(tool?L)

    Fig.2.Extractionrationofcationsfrom MgMnTi?9o0.mnitricaddsolution.

    3.3.Saturationcapacityofexchange

    11lerelationbetweenionradiusandsaturatedion exchangecapacityofMgMnTi900(H)foralkaliis

    showninFig.3.AccordingtoFig.3,thecapacityof exchangeforLi+wasmuchhigherthanforalkali ions.ThecapacityforLiis56mg-,whichis muchhigherthanthatinthepublishedreports10,

    1417].Itprovesthattheionexchangesynthesized hasahighercapacityofexchange,andabetterre

    memberingofexchangeforLi+.Theeffectfactorsof saturationcapacityofexchangeofMgMnTi900(H)

    areasfollows:(1)theMgintheexchangesolution mustberemoved,becauseMgexchangeswiththe exchangervacancysitewhenthereexiststoomuch ofMg;(2)theexperimentalresultsindicatethat theexchangecapacityofionexchangerflorLris muchhigherthanthoseforotheralkaliionsinthin solution,whichindicatesthattheionexchangereac

    tioniScarriedoutbetweenbareions.Hence.bare ionsdiameterofMgisnearlyclosetothatofLi: (3)atthetimeofexchange,anMgisreplacedby twoi-i+.

    Linotonlyenteredthevacancysiteof

    Mg.butalsoexchangedwiththei-i+Ofsurface. Therefore,MgMnTi900(H)hasahigherexchange

    capacityforLi+.

    l/c0.Ic0I1J1)(

JangJ.H.eta1.LireactionwithMg2Mno.

    sTio.

    sO4inversespinelintheaqueousphase539 Ionradius|am

    rig.3.Relationbetweenionradiusandsaturatedion exchangecapacityofMgMnTi-900(II)foralkaliions. 3.4.PHtitration

    ThepHtitrationcurvesofMgMnTi900(H)for

    LiandNaareshowninFig.4.BOththesamples showlithiumion--sieveproperties;theapparentca-- pacifiesforLiaresignificantlylargerthanforNa overthestudiedpHrange.ThiSindicatesthatLiiS exchangeablewithlatticeprotonsinthebulkcrystal, whereasNa+isnotexchangeable.ItiSwellknown tllattheacidityofhydrousmetaloxideshowsaten

    dencytoincreasewithanincreaseintheValenceof themetalf10].

    C0H/(mmol?L)

    Fig.4.pHtitrationcurveofMgMnTi-900(H). 3.5.Distributioncoefficient(Kd)

    valuescanbethetokenofexchangeselecfivity ofMgMnTi900(H1f0rthecorrelatedions.Ac

    cordingtoFig.5,thevaluesofMgMnTi900(H)

    f0ralkaliionsincreasewiththeincreasedpHover thestudiedpHrange.Theselectivitysequenceof MgMnTi900(H)foralkalimetalionsiSasfollows: Li>Cs>Rb>K>Na.

    ItindicatesthatMgMnTi900(H)hasbetterion

    selectivityforLi.Ionexchangereacfionisa

    reversiblereaction.Thereacfionof}{+ ionexchangerwithalkalimetalionsinsolutionisas follows(exampleforLi3:

    MgMnTi(2H)+2LiMgMnTi(2Li)+2H.

    Fig.5.DistributioncoefficientofMgMnTi-900. 4.Conclusion

    Theexperimentalresultsindicatethatthe Mg2Mno.

    5Tio.

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