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Solvent extraction of zinc from zinc sulfate solution

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Solvent extraction of zinc from zinc sulfate solutionof,zinc,from,Zinc

    Solvent extraction of zinc from zinc sulfate

    solution

    J.Cent.SouthUniv.Techno1.(2010,17:760764

    DoI:10.1007/sl1771-010-0553-x

    Solventextractionofzincfromzincsulfatesolution

    Springer

    LONGHuaizhong(J~怀中),CHAILi.yuan(柴立元),QINWen.qing(覃文

    ),TANGShuang-hua(唐双华)

    1.SchoolofMetallurgicalScienceandEngineering,CentralSouthUniversity,Changsha410083,China;

    2.SchoolofResourcesProcessingandBioengineering,CentralSouthUniversity,Changsha410083,China

    Abstract:Theextractionofzincfromzincsulfatesolutionwasinvestigated.using20%saponifiedD2EHPAasanextractantand

    260sulfonatekeroseneasadiluent.Thesolutionwasstirredfor8minatphaseratio(go/)of1.0:1.0,initialpHof2.0andstirring

    speedof200r/min.Theresultsshowthat75%zinccanbeextractedfromthezincsulfatesolutionwhentheconcentrationofzincis

    18.7g/Lafterbeingsettledfor10min.88.60%zinccanbestrippedby196g/Lsulfuricacid.andzincioncanbeseparatedfrom

    ferricion.

    Keywords:zincsulfatesolution;saponifiedbi(2

    ethylhexy1)phosphoricacid(D2EHPA);zinc;solventextraction

    1IntrOductiOn

    Atpresent,thepurificationofzinchydrometallurgy

    lixiviumisbasedonthechemicalprecipitationand

    replacementmethods.whichnotonlyconsumealarge

    amountofchemicalreagents,butalsoaredifficultto achievehighdegreeofpurification.Becauseoflarge differencebetweentheleachingprocessofthezincoxide oreandthetraditionalzinccalcininginthecycleof leachingsolutionandsolutionchemicalconditions.the traditionalpurificationprocessisnotsuitableforthe disposalofzincoxideoreleachingsolution1-2].

    However,theextractivepurificationofzincfromzinc oxideoreleachingsolutionisabetterselection3-5].

    Thestudiesaboutsolventextractionofzincfrom sulfatesolutionweremostlycarriedoutonthe backgroundofremovingtraceimpurityzinc[67].

    Becauseofthe1ackofeffectivezincextractionreagents andrelativelylowpricesofzincmeta1.theapplications ofsolventexactionofzincfromsulfatesolutionare limited[89].Organicphosphorusextractantsarewidely usedinthesolventextractionofzincfromzincsulfate solution10-131.However,onedisadvantageofthis processisthatferricionscanbeextractedsimultaneously 14-151.Inthiswork,thesolventextractionofzincfrom zincsulfatesolutionwasstudiedusingbi.f2ethylhexy1)

    phosphoricacid(D2EHPA)asanextractantand260 sulfonatekeroseneasadiluent.

    2Experimental

    2.1Materials

    AlowgradezincoxideorewasfromtheMengzi

    OreinYunnanProvince.China.Thechemical

    compositionoftheleachingsolutionofzincoxideoreis listedinTab1e1.Theconcenationsofzincionand

    ferricionintheleachingsolutionare18700.00and

30.00mg/L.respectively.

    Table1Chemicalcompositionofleachingsolutionofzinc oxideorer1n

    Inthisexperiment,theextractantwasD2EHPAand thediluentwas260sulfonatekerosene.Otherreagents includedH2504,NaOH,FeSO4.7H20,(NH4)2SO4,KC1, K2HPO4,Fe2(804)3'7H20,andZnSO4'6H20.

    2.2Principleofextraction

    AlkylphosphateextractantD2EHPAoftenexistsin dimerfornlinkerosenesolution.Zinccanbeextracted usingD2EHPA(expressedasHR)bythefollowing reactions:

    Zn2+(aq)+m

    2

    H2R2(.rg)

    ZnR2(2)HR(org)+2H(org)(1)

    Fe2+(aq)+m

    ,,

    H2R2(.)

    FeR2(2)HR(org)+2H(aq)(2)

    whereH2R2isthedimermoleculeofHR;andmisthe totalnumberofmoleculeofHR.Thistestwascarried Foundationitem:Project(50774094)supportedbytheNationalNaturalScienceFoundation

    ofChina

    Receiveddate:20100401;Accepteddate:20100520

    c0rrespondi?gauthor:LONGHuai?zhong,Doctoralcandidate;Tel:+86731

    88876765;E-mail:ysxblong@mail.CSU.edu.cn J.Cent.SouthUniv.Techno1.(2010)17:760764761

    outinaconstantinterfacialareacel1.Theschematic diagramoftheconstantinterfacialareacellisshownin

    Fig.1.Theleachingliquorwasaddedintheconstant interfacialareacel1.andtheconcentrationsofzincion andferricionwere18700.00and30.00mg/L.

    respectively.Then,theorganicphasewasslowlyadded totheaqueousphasealongtheinnerwall,andthemixer wasimmediatelytumedontocontrolthestirringspeed. Afterstirringforagivenperiodtheaqueousphaseand organicphasewerepouredintoaseparatingfunneland settledfor10min.Finally,theaqueousphasewas analyzed.

    Fig.1Schematicdiagramofconstantinterfacialareacell:1m Constanttemperaturewaterbath;2--Constantinterfacialarea cell;3--Thermometer;4Stirringpaddle;5--Sample;6

    Organicphase;7AqueOusphase

    3Resultsanddiscussion

    3.1Eflfect0fpHonextractionratioofzinc

    Hionsarereleasedintheextractionprocessusing acidicexactantD2EHPA.sotheexactionprocessis

    greatlyaffectedbypH.TheeffectofpHonthe

    extractionratioofzincwasinvestigatedwhenbeing extractedfor8minatvolumefractionofextractant D2EHPAof10%,phaseratio()of1.0:1.0,and

    stirringspeedof200r/min.TheresultsareshowninFig.2. ItcanbeseenfromFig.2thattheextractionratioof zincincreaseswithincreasingpH.Theextractionratioof zincislowbecauseoftheprotonationoftheextractant D2EHPAwhenpHis1essthan2.0.Theextractionratio ofzincincreasesto19.00%atpHOf2.0.WhenpH rangesfrom2.0to3.5,theextractionratioofzinc increasesto21.60%.Therefore.suitablepHofthe

extractionprocessis2.0.

    3.2EflfectOfvolumefractionofextractantD2EHPA onextractionratioofzinc

    Theeffectofthevolumefractionofextractant D2EHPAontheextractionratioofzincwasinvestigated undertheconditionsofpHofaqueousphaseof2.0, phaseratio(Za)of1.0:1.0,stirringspeedof200r/min andextractiontimeof8min.Fig.3showstheeffectof thevolumefractionofextractantD2EHPAonthe extractionratioofzinc.

    Fig.2EffectofpHonextractionratioofzinc VolumefractionofextractantD2EHPA/%

    Fig.3EffectofvolumefractionofextractantD2EHPAon extractionratioofzinc

    ItcanbeseenfromFig.3thattheextractionratioof zincincreaseswithincreasingvolumefractionof exactantD2EHPA.Theextractionratioreaches33.89% whenthevolumefractionoftheextractantD2EHPAis 30%.ThecurveslopeinFig.3isabout0.81atthe volumefractionofexactantD2EHPAlessthan20%.

    whilethecurveslopedecreasesto0-32whenthevolume fractionofexactantD2EHPAincreasesto30%.

    Generally.thegreatestvolumefractionofexactant

    D2EHPAshouldbe1essthan30%.otherwisetheorganic phasewillbecomeviscous.resultingindifficultphase separationandextractantD2EHPAwaste.Therefore,the optimumvolumefractionofextractantD2EHPAis20%. 3.3Effectofphaseratioonextractionratioofzinc Fig.4showstheeffectofphaseratioonthe

\0II_Z00=|.I0u-Io/n/.Il_IN00_.I0_【芑扫

    762

    :::!:!!!!

    So,theoptimalphasecontacttimeis8min.extractionratioofzinc aqueousphaseof2.0,

    undertheconditions

    volumefractionof

    D2EHPAof20%,phasecontacttimeof8

    stirringspeedof200r/rain.

    ofpHof

    extractant

    rain,and

    Zo/

    Fig.4Effectofphaseratio(Vo/)onextractionratioofzinc ItcanbeseenfromFig.4thattheextractionratioof zincincreaseswithincreasingphaseratio.Whenthe volumefractionofextractantD2EHPAis20%andphase ratioZaiS1.0:1.0,theextractionratiois36.10%.With increasingphaseratio,theviscosityoforganicphaseis accelerated.which1cadstodifficultphaseseparationand eventheaDpearanceofthethirdphase.

    3.4Effectofphasecontacttimeonextractionratioof zinc

    Fig.5showsthecurveofextractionratioofzincvs phasecontacttimeundertheconditionsofequilibrium pHofaqueousphaseof2.0,volumefractionof

    extractantD2EHPAof20%,phaseratio(/)of

    1.0:1.0.andstirringspeedof200r/min.

    Phasecontacttime/rain

    Fig.5Effectofphasecontacttimeonextractionratioofzinc

    ItcanbeseenfromFig.5thattheextractionratioof zincis37.88%whenthephasecontacttimeis10min. Afterwards,theextractionratioofzincincreasesslightly. 3.5Effectofstirringspeedonextractionratioofzinc Theeffectofstirringspeedontheextractionratioof zincwasinvestigatedundertheconditionsofequilibrium pHofaqueousphaseof2.0.volumefractionof

    extractantD2EHPAof20%,andphaseratio(/)of 1.0:1.0.TheresultsareshowninFig.6.

    Stirringspeed/(r?min)

    Fig.6Effectofstirringspeedonextractionratioofzinc Itcanbeseenthatthestirringspeedhassome

    impactonthereactionintheliquidliquidextraction

    process,andtheoptimumvalueis200r/min.

    3.6Ef_fectofc0ncentrati0nofmetalionsonextraction ratioofzinc

    Theeffectoftheconcentrationofmeta1ionsonthe exactionratioofzincwasinvestigatedunderthe conditionsofequilibriumpHof2.0.volumefractionof extractantD2EHPAof20%,phaseratio(pof

    1.0:1.0,phasecontacttimeof8min,andstirringspeed of200r/min.TheresultsareshowninFig.7.

    ItcanbeseenfromFig.7thattheextractionratioof zincdecreaseswithincreasingconcentrationofzincand ConcentrationofFe+/(mg?L1

    Fig.7Effectofconcentrationofferriciononextractionratioof zincatdifferentzincionconcen廿ations

    \0IIN00.II10u-I)(?

    /.口【700_=l.I10u矗暑

,.IIN00_II100J1

    ,.N00I10EJ

    J.Cent.SouthUniv.Techno1.(2010)17:760764763

    ferricions.Theextractionofmetalionusingorganic phaseD2EHPAassolventiscationexchangereaction. ThemetaljonsandHjonexchangeaccordingto Eqs.(1)and(2).Therefore,thenumberofHions participatinginexchangekeepsconstantwhenthe concentrationofextractantD2EHPAisinvariable.So. zincexactedfromthesolutionisinvariablebecausethe numberofHionsparticipatinginexchangekeeps constantwithincreasingconcentrationofmetalions. Therefore.theextractionratioofzincdeclines. 3.7Effectofinorganicagentsinaqueousphaseon extractionratioofzinc

    Theeffectofcomponentsofaqueousphaseon

    extractionratioofzincisshowninFig.8.Theextraction conditionsaredescribedasfollows:equilibriumPHof aqueousphaseof2.0.volumefractionofexactant

    D2EHPAof20%,phaseratio(Vo/)of1.0:1.0,phase contacttimeof8min,andstirringspeedof200r/min. Concentration/(g?L1

    Fig.8Effectofconcentrationoforganicagentinaqueousphase oilextractionratioofzinc

    Theexactionratioofzinccanbeaffectedbythe anionsinaqueousphase.WhenusingD2EHPAasan extractant,thecommonanionsimpactingonthe extractionratiocouldbearrangedas:SO>CO>

    Cl>NOl31.TheinvestigationontheeffectsofKC1, KH2PO4and(NH4)2S04ontheextractionofzincwas

    carriedout.Theresultsshowthattheorderofthethree kindsofsaltisKCl<KH2PO4~(NH4)2S04accordingto theirimpactontheextractionratioofzinc.The extractionratioofzincdecreasesfirstandthenincreases withincreasingCrconcentration.KH7PO4and (NH412S04acceleratetheextractionofzincbecause H2P0andNHintheextractionsystemhavea

    bufferactiontopHofextraction.TheequilibriumPHof extractionincreaseswithincreasingconcenationof

    KH2PO4orfNH4)2804,whichisconducivetothe extractionratioofzinc.

    3.8Eflfectofsaponifiersonextractionratioofzinc Saponifcationisaprocessinwhichthemetalions replaceHionsthroughacid.alkalineutralization reaction.CommonsaponifiersofD2EHPAareNaPH. NH40HandNa2CO,andtheorganicphaseisthe

    oil.wateremulsionaftersaponification14-151.

    Theeffectoftheorganicphasesaponifiedby differentconcentrationsofNaOHandNa,CO3onthe extractionratioofzincwasstudied.Theextraction conditionsareasfollows:concentrationofzincof l8.7L,equilibriumpHofaqueousphaseof2.0, volumefractionofextractantD2EHPAOf20%.phase ratio()0f1.0:1.0,phasecontacttimeof8min, stirringspeed200r/min.andsettlingtimeof10min.The resultsareshowninFig.9.

    Concentration/(g?L)

    Fig.9EffectofsaponificationconcentrationsofNa2CO3and NaPHonextractionratioofzinc

    ItcanbeseenfromFig.9thattheextractionabilitV

    ofexactantD2EHPAsaponifiedisenhanced.Andthe extractionratioofzincreaches75%whentheextractant issaponifiedbyNa2CO1.So.theexactionreactionis

    theexchangeprocessofsodiumionswithmeta1ions. whichacceleratestheexactionreactioninthealkaline

    environment.

    3.9Eflfectofstrippingspeedonextractionratioof zinc

    Thestrippingwascarriedoutusingsulfuricacid solutionasanextractantatacertainconcentration.In thisexperiment,theorganicphasecontains20% D2EHPA.260oi1solution.theconcentrationofzincion is18.7g/Landthatofferricionis30mg/Linthe organicphase.andthephaseratiois1.0:1.0.After stirringfor8minunderthestl'rringspeedof200r/min andthensettlingfor10min,thesamplewasanalyzed. TheresultsarelistedinTable2.

    Itisindicatedthatzinccanbeextractedabsolutely bythesulfuricacidwithhighconcentration.The strippingyieldofzincis87.55%(massfraction)when /nII00_-I0J1

    l/u_IN00_I-I00)(

    764J.Cent.SouthUniv.Techno1.(2010)17:760764

    Table2Effectofsulfuricacidconcentrationonstrippingyield ofzinc

    theconcentrationofsulfuricacidsolutionis120g/L. Ferricionisnotextracted.retainingintheorganicphase eveninthesulfuricacidwithhi2hconcentration.Whel1 theconcentrationofsulfuricacidis196g/L(2mol/L), 88.6O%zincionsandonly1.76%ferricionsarestripped.

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