采用DZ988N从复杂硫酸盐溶液中高效选择性萃取铜

时间：TIME\@"yyyy'年'M'月'd'日'"2022年3月29日学海无涯页码：第1-页共1页采用DZ988N从复杂硫酸盐溶液中高效选择性萃取铜1Introduction

Withtherapideconomicgrowthandsocialdevelopment,thetotaldemandforcopperhasbeenrisingsteadily,andwillexceedcopperreservesby2050accordingtothecurrentconsumptionofcopper[1-2].Duetothedepletionofhigh-gradecoppermineralresources,growingattentionispaidtorecoveringcopperfromlow-gradeoresandindustrialwastes[3-5].However,duringtheleachingprocessofcoppermaterials,impuritieswillbeleachedintosolutionalongwiththemainmetal.So,furthertreatmentsincludingprecipitation[6],ionexchange[7],membraneseparation[8],selectiveadsorption[9],andsolventextractionarerequiredtorecovervaluablemetalsandremoveimpuritiesfromthesolution[10].Amongthem,solventextractionisoneofthemostcommonmethodstoseparateandconcentratemetalsinanaqueoussolution.SRIVASTAVAetal[11]investigatedtheliquid-liquidextractionofchromiumfromindustrialeffluentwithtributylphosphateasapotentialextractant.ILYASetal[12]studiedtheextractionofnickelandcobaltfromammonialeachingsolutionofNi-lateriteoreaftercarbon-thermalreductionroastingby10vol%LIX84-Iandconcludedthattheselectiveextractionrateofnickelwasmorethan97%overCoattheorganic-to-aqueousratioof1.ISHFAQetal[13]investigatedtheextractionofCr(VI)andFe(III)fromelectroplatingwasteliquidcontainingCr,Fe,Zn,andfreeacidofchloridemediumbyTBP,andconvertedthecarcinogenicmetalCr(VI)toless-toxicmetalCr(III)aftertreatmentwithascorbicacid.

Acidicextractantandhydroximehydroxyoximeextractantaretwomaintypesofcopperextractants.Ifanacidicextractantisusedtoobtainapurecoppersolution,theironshouldberemovedandthealkalinewillbeaddedtoneutralizeH+inthesolutionbeforecopperextractionatahighequilibriumpH.However,hydroxyoximeextractants,suchasLIX63,LIX64,LIX65N,LIX622,LIX70,LIX860,LIX622,LIX864,LIX984,andLIX984N,werewidelystudiedandusedforcopperextractionfromacidicsolutionsduetotheirgreatextractioncapacity,excellentseparationefficiencyfromironandlowerextractionequilibriumpH[14-15].ASGHARIetal[16]evaluatedtheeffectofimpurityionssuchasZn(II),Mn(II),Fe(III)andFe(II)onthecopperextractionbyusing18%LIX®984Ninkerosene,and93.9%copperwasextractedatpHof2andextractiontimeof600s.JUNetal[17]optimizedthekeyexperimentalparametersofLIX84-Iforextractingcopper,suchastemperature,equilibriumpHandextractantconcentration,andconfirmedthatLIX84-Ihasastrongaffinitywithcooperduetotheemergenceofspontaneousinner-spherecoordinationwithdisruptedhydration.BARIKetal[18]recoveredcopperfromawasteheatboilerdustleachingliquorbyusingLIX84-IandLIX622NataphasevolumeratioO/A(A:aqueousphase;O:organicphase)of1.5/1andextractantconcentrationof30%,andachieved98.64%and99.95%efficiencywithathree-stagescounter-currentextraction,respectively.POSPIECH[19]recoveredCu(II)fromsulphatesolutioncontainingCo(II),Ni(II)andMn(II)withamixtureof5%Kelex100and10%LIX70atpHof2,and99%copperwasextractedalongwith10%ofothermetals.KUMARetal[20]selectivelyextractedCu(II)fromitsmixturewithNi(II)atpHof2,andcopperseparationcoefficientreached6000with40%LIX664N.AlthoughmanystudiesonhydroxyoximeextractantswerecarriedouttoseparateCu(II)fromothermetals,DZ988NhasnotbeenappliedtoextractcopperfromthesulfuricacidleachingsolutioncontainingCu(II),Co(II),Fe(II)andZn(II).

Thisworkaimedtoinvestigatetheextractionandseparationofcopper,cobalt,ironandzincfromthesulfuricacidleachingsolutionofapolymetallicresidue.ThereactivefunctionalgroupsofDZ988Nwereidentified,andthechelatingmechanismforcopperextractionwasinvestigated.Theinfluencefactorsonmetalextractionefficiency(ηM)andseparationcoefficient(βA/B)werestudiedandtheoptimalextractionconditionswereexplored.Meanwhile,McCabe-Thieleisothermdiagramswerebuilttodeterminethenumberofstagesatdifferentphaseratios.

2Materialsandmethods

2.1Materials

ThepolymetallicresiduefromawetzincsmelterinGuangdong,China,wasleachedwithsulfuricacid,andtheproducedsolutionwasusedasthefeedintheexperiments.Theconcentrationofthemajormetalcomponentsintheleachingsolutionwere:c(Cu(II))=5.25g/L,c(Co(II))=1.27g/L,c(Fe(II))=2.16g/Landc(Zn(II))=11.19g/L.

TheextractantDZ988Nisamixtureof5-nonylsalicylaldoximeand2-hydroxy-5-nonylacetophenoneoximeatavolumeratioof1:1,andtheeffectivecomponentsofextractantareLIX84andLIX860N,similartoLIX984N[21].DZ988N,abrownliquidwithadensityof0.91-0.93g/cm3,waspurchasedfromZhengzhouDeyuanFineChemicalsCo.,Ltd.,China.SolventoilNo.260wasemployedasdiluentforextractant,whichwasprovidedbyShanghaiRare-EarthChemicalCo.,Ltd.,China.

2.2Methods

2.2.1Copperextraction

Whentheaqueousphasewasmixedwiththeorganicphase,DZ988Nwillchelatewithcopper,andwillnotreactwithothermetalsincludingcobalt,ironandzinc[22-23].Thechelatecompoundsformedduringextractionwereinsolubleinwaterbutsolubleinorganic,andthuscopperwasseparatedfromsulfuricacidleachingsolution.TheabovereactionprocesscanbedescribedasEq.(1)[15,24].

2HRorg+Cu2+aq⇔R2Cuorg+2H+aq

(1)

TheflowsheetofcopperextractionisshowninFigure1.Aqueousandorganicphasewereaddedinasealabletesttubeatachosenphasevolumeratio,andtwophasescompletelymixedintheSHZ-82Thermostaticwaterbathoscillator(ChangzhouXiangtianExperimentalInstrumentFactory,China)forapresettime.ThenthemixedfluidswerecentrifugedtotwoindividualphasesintheTD6MCentrifuge(HunanXiangliScientificInstrumentCo.,Ltd.,China)andseparatedbyaseparatoryfunnel.

Figure1Flowsheetofcopperextraction

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ThepHvalueofsolutionwasadjustedwithdilutesulfuricacid,anddeterminedwiththePHS-3CpHmeter(ShanghaiPrecisionScienceInstrumentCo.,Ltd.,China).ThefunctionalgroupsoforganicphaseweredetectedbyNicolet6700Fouriertransforminfraredspectroscopy(FT-IR,ThrmoFisherScientific,USA),andtheconcentrationsofmetalsinaqueousphaseweredeterminedwithICAP7400radialinductivelycoupledplasmaemissionspectroscope(ICP,ThrmoFisherScientific,USA).

Themetalextractionefficiency(ηM)iscalculatedaccordingtoEq.(2)[25]:

ηM=c0MV0−c1MV1c0MV0×100%

(2)

wherec0Mandc1MaretheconcentrationsofmetalMinaqueousphasebeforeandafterextraction,respectively;V0andV1arethevolumesofaqueousphasebeforeandafterextraction,respectively.

Themetaldistributionratio(DM)wascalculatedaccordingtoEq.(3)[26]:

DM=[M]org[M]aq

(3)

where[M]aqand[M]orgaretheconcentrationsofmetalinaqueousphaseandorganicphaseatextractionequilibrium,respectively.

Theseparationcoefficient(βA/B)oftwodifferentmetals(AandB)iscalculatedaccordingtoEq.(4)[27]:

βA/B=DADB=[A]org/[A]aq[B]org/[B]aq

(4)

2.2.2Counter-currentextraction

Tocompletelyextractcopperfromtheaqueous,counter-currentextractionprocesswasemployed.AstheoperationprocessshowninFigure2,theaqueousphasemovedinoppositedirectiontotheorganicphase.Whentheaqueousphasewasaddedinthefirststage,theraffinatemovedbackward;whentheorganicphasewasaddedinthelaststage,theloadingorganicphasemovedforward.

Figure2Operationprocessofcounter-currentextraction(aq:Aqueousphase;org:Organicphase;m:Extractionstage;X0:[Cu2+]aqofinletaqueousphase;Y1:[Cu2+]orgofoutletorganicphase;Xm:[Cu2+]aqafterthemthstageextraction;Ym+1:[Cu2+]orgafterthemthstageextraction)

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IfthevolumesofaqueousphaseV(A)andorganicphaseV(O)remainedunchangedduringthecounter-currentextractionprocess,thefollowingrelationshipisdefinedbyEq.(5)withreferenceofmaterialbalanceprinciple.

(X0−Xm)⋅V(A)=(Y1−Ym+1)⋅V(O)

(5)

Todeterminetheneedednumberofstagesduringcounter-currentextractionprocess,theextractionisothermdiagram(McCabe-Thielediagram)includingequilibriumisothermandoperationline,wasbuiltatachosenphasevolumeratioO/A[28].Theequilibriumisothermdescribedthecopperdistributionintwophases,whichwasobtainedunderthechosenextractionconditions,continuouslycontactingfreshaqueousphasewithloadingorganicphaseuntiltheextractantsaturation.Inaddition,accordingtoEq.(5),theoperationlinewasdefinedbyEq.(6),passingthroughtwopoints(X0,Y1)and(Xm,Ym+1)withaslope1/R.Risthephasevolumeratiooforganictoaqeousphase.

Y1=V(O)V(A)(X0−Xm)+Ym+1=R(X0−Xm)+Ym+1

(6)

3Resultsanddiscussion

3.1Chelatingmechanismofextractionprocess

TheFT-IRpatternoffreshandloadingorganicphasesbothcontaining20%DZ988NareshowninFigure3.Thebandsat2850,2920and2955cm-1correspondedtothealkaneC—Hstretchingvibrationsof—CH2and—CH3,andtheirbendingvibrationswereassociatedtothebandsat1460and1375cm-1,respectively.Thebandsat721and829cm-1wereassignedto—CHexternalbendingvibrationsonthearomaticring[29].Thebandsat1020and1640cm-1wereassignedtotheN—OstretchingvibrationandtheC=Nstretchingvibration,intheoximegroup(—C=NOH),respectively[30,31].Thebandat1543cm-1attributedtotheN—Hbendingvibrationwithhydrogenbonding(N…H—O).TheN—Hstretchingvibrationisassociatedtothebandat3421cm-1,whichisoverlappedwithawideabsorptionpeakofO—Hstretchingvibrationinthehydroxylgroup(—OH)[32,33].Thebandsof—C=NOHandR—OHgroupsappearedinFigure3,indicatingthateffectivecomponentsofextractantDZ988Nexistintheorganicphase.

Figure3FT-IRpatternoffreshorganicphaseandloadingorganicphase

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ComparingFT-IRcurvesoffreshandloadingorganicphasesinFigure3,therearesignificantchangesofseveralabsorptionpeaks.ThebandofN—Hbendingvibrationwithhydrogenbonding(N…H—O)at1543cm-1disappearsafterextraction,whilethebandof—OHstretchingvibrationat3421cm-1isweakened.Thetwodonoratomsofnitrogeninthe—C=NOHgroupandoxygenintheR—OHgrouparesimultaneouslycoordinatedtotheCu(II)toformaredundantbond,andthehydrogenofthe—C=NOHgroupformsaninternalhydrogenbondwiththeoxygenoftheR—OHgroup,thusformingthecomplexshowninFigure4[34-35].

Figure4ComplexstructureoforganicphaseandCu(II)

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3.2Extractionefficiencyandseparationcoefficient

3.2.1EffectofDZ988Nconcentration

TheeffectofDZ988Nconcentrationontheextractionefficiencyandseparationcoefficientwasstudiedunderthefollowingconditions:pHofaqueousphaseof2.0,extractiontemperatureof25°C,extractiontimeof5min,phaseratioO/Aof1/1.TheDZ988Nconcentrationincreasedfrom5%to35%,withtheresultsshowninFigure5.

Figure5EffectofDZ988Nconcentration(v/v)on(a)extractionefficiencyand(b)separationfactor

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Figure5(a)illustratedthattheCu(II)extractionefficiencyincreasedfrom65.50%to97.06%withDZ988Nconcentrationincreasedfrom5%to25%.NofurtherobviousraisewasdetectedwhenDZ988Nconcentrationexceeded25%.TheextractionefficienciesofCo(II),Fe(II)andZn(II)hadaslightlyincreasebyabout1.7%,2.2%and1.1%,respectively.InFigure5(b),theseparationcoefficients,βCu/Zn,βCu/FeandβCu/CoshowedagrowthtrendsimilarwithCu(II)extractionefficiency,andreached2112,1595and2998,respectively,atDZ988Nconcentrationof25%.Therefore,toensureahighercopperextractionefficiencywithalowerconsumptionofextractant,DZ988Nconcentrationof25%wasappropriatetoextractcopperfromthesulfuricacidleachingsolution.

3.2.2EffectofpHvalueofaqueousphase

TheinfluenceofpHvalueofaqueousphaseontheextractionefficiencyandseparationcoefficientwasinvestigatedunderaconditionwithDZ988Nconcentrationof20%,extractiontemperatureof25°C,extractiontimeof5min,phaseratioO/Aof1/1.ThepHvalueofaqueousphaseincreasedfrom0.4to2.8,withtheresultspresentedinFigure6.

Figure6EffectofpHvalueofaqueousphaseon(a)extractionefficiencyand(b)separationfactor

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Figure6(a)indicatesthattheCu(II)extractionefficiencyfirstincreasedfrom49.8%to95.55%withpHvalueincreasedfrom0.4to2.0,andthenremainedunchangedwhenpHvaluehascontinuouslyrisento2.8.ThepHvaluehadalimitedeffectontheextractionefficiencyofZn(II)andCo(II).However,whenpHreached2.8,asignificantincreasewasdetectedinironextractionefficiency.AsmallamountofFe(II)wasoxidizedtoFe(III),thenhydrolyzedandprecipitatedatpH2.8,sothattheconcentrationofironintheraffinatedecreasedandtheironextractionefficiencycalculatedbyEq.(2)washigherthantheactualone.Figure6(b)furtherillustratesthattheseparationcoefficientsβCu/Co,βCu/FeandβCu/Znfirstlyincreasedfrom67,53and106to1351,1037and1904,respectively,withthepHvalueincreasedfrom0.4to2.0,andthendecreasedwhenpHvalueexceeded2.0.Consideringbothcopperextractionefficiencyandseparationcoefficient,2.0wasselectedasthepreferredpHvalueofaqueousphase.

3.2.3Effectofextractiontemperature

Figure7illustratestheeffectofextractiontemperatureontheextractionefficiencyandseparationcoefficientwithDZ988Nconcentrationof20%,initialpHofaqueousphaseof2.0,extractiontimeof5min,phaseratioO/Aof1/1,andextractiontemperatureintherangeof25℃to75℃.

Figure7Effectofextractiontemperatureon(a)extractionefficiencyand(b)separationfactor

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Theextractionprocesswasperformedinasealedtesttube.AstheresultsshowninFigure7,boththecopperextractionefficiencyandseparationcoefficientincreasedalongwithtemperaturefrom25℃to75℃.Thehightemperaturecanfacilitatethemasstransferbetweenthetwophases;therefore,theearlyincreaseintemperaturewillpromotecopperextractionefficiency[36].However,excessivetemperaturerisewillhindertheextractionreactiontosomeextentduetotheexothermicreactionofcopperextraction,whichwouldplayamoredominantrolethanmasstransfer[37].Theaqueousphaseandorganicphasewillvolatileathightemperatureinanopenextractionenvironment.After5minextraction,thelossoftwophaseswas4%at25℃,and46%at75℃,respectively.Consideringboththecopperextractionefficiencyandthevolatilizationloss,25℃wassuggestedastheoptimalextractiontemperaturewherethecopperextractionefficiencycanreach95.59%withalmostnovolatilizationlossintwophases,andβCu/Co,βCu/Fe,βCu/Znwere1385,1088,1941,respectively.

3.2.4Effectofextractiontime

Theextractiontimeoftwophasesintherangeof1to10minwasselectedasthefactortoinvestigateitseffectontheextractionefficiencyandseparationcoefficient(βA/B)underfixedconditionsofDZ988Nconcentrationof20%,pHofaqueousphaseof2.0,extractiontemperatureof25℃,andphaseratioO/Aof1/1.TheresultsareshowninFigure8.

Figure8Effectofextractiontimeon(a)extractionefficiencyand(b)separationfactor

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ItwasobservedinFigure8(a)thatthemetals’extractionefficiencyincreasedwithextractiontimeincreasingfrom1to6min,andkeptconstantwhenextractiontimecontinuouslyrose.After6minextraction,theextractioncapacityofDZ988Nalmostachievedequilibrium,andtheextractionefficienciesofCo(II),Fe(II),Cu(II)andZn(II)were1.70%,2.12%,97.50%and1.11%,respectively.InFigure8(b),theseparationcoefficientsβCu/Co,βCu/Fe,andβCu/Znkeptgrowthwithanincreaseinextractiontime,andreached2255,1797and3468attheextractiontimeof6min,respectively,whileβCu/Zndecreasedat3minduetothegrowthofDZngreaterthanthatofDCu.Therefore,6minwasselectedasthesuitableextractiontimetoachieveanacceptablecopperextraction.

3.2.5EffectofphasevolumeratioO/A

ThephasevolumeratioO/Aalsohasasignificantinfluenceonthecopperextractionprocess.TheexperimentswerecarriedoutundertheconditionsofDZ988Nconcentrationof20%,pHofaqueousphaseof2.0,extractiontemperatureof25℃,extractiontimeof5min.ThephasevolumeratioO/Adecreasedfrom3.0/1to1/4.0,andtheresultswerepresentedinFigure9.

Figure9EffectofphaseratioO/Aon(a)extractionefficiencyand(b)separationvolumefactor

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Figure9showsthatboththeextractionefficiencyandseparationfactorgenerallypresentedadownwardtrendwiththephaseratioO/Arising.WhenO/Adecreasedfrom3.0/1to1/1.5,Cu(II)extractionefficiencydecreasedslowlyfrom98.44%to95.06%.However,asignificantdropinseparationcoefficientsβCu/Co,βCu/FeandβCu/Zn,decreasingfrom2477,2091and3030to1450,1056and1867,respectively,weredetected.WhenO/Adecreasedto1/4.0,copperextractiondecreasedobviouslyto57.94%,becauseofthelimitedextractioncapacityofDZ988Nforcopper.ExtractionatalowO/Awillleadtoahighdepletionoftheextractant,therefore,1/1.5wasconsideredasasuitablephasevolumeratioO/A.

Aone-stageextractionwascarriedoutundertheoptimalconditionsachievedfromaboveexperiments,andtheextractionefficienciesofCo(II),Fe(II),Cu(II)andZn(II)were1.56%,2.03%,97.53%and1.08%,respectively;theseparationcoefficientsβCu/Zn,βCu/FeandβCu/Co,were2492,1905and3306,respectively,indicateingthatDZ988Nhadahighextractionforcopperinsulfuricacidsolution,whilecobalt,ironandzincwerehardlyextractedandcanbeseparatedwellwithcopper.

3.3Counter-currentextraction

TheMcCabe-Thielediagramsincludingequilibriumisothermandoperationline,werebuilttodeterminethestagesofcounter-currentextraction.TheextractionswereperformedundertheconditionsofDZ988Nconcentrationof25%,pHofaqueousphaseof2,extractiontemperatureof25°C,extractiontimeof6min.ThephasevolumeratiosO/Aof1/1.0,1/1.5and1/2.0wereinvestigated,respectively.ThecopperequilibriumconcentrationsinthetwophasesarepresentedinTable1,andtheparametersofoperationlinedefinedbyEq.(6)withanaimof[Cu2+]aqlessthan0.005g/L,arepresentedinTable2.

Table1Copperequilibriumconcentrationsintwophases

mV(O)/V(A)=1/1.0V(O)/V(A)=1/1.5V(O)/V(A)=1/2.0

Xm/

(g·L-1)

Ym+1/

(g·L-1)

Xm/

(g·L-1)

Ym+1/

(g·L-1)

Xm/

(g·L-1)

Ym+1/

(g·L-1)

10.11145.13910.21477.55380.46679.5677

21.34509.04461.838512.67183.023114.0226

32.417511.87764.422513.91384.919514.6846

44.360512.76765.109514.12535.161014.8636

55.130512.88765.223014.16655.224514.9156

65.196512.94165.250514.16655.250514.9156

75.250512.9416————

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Table2ParametersofoperationlinesatdifferentO/A

V(O)/V(A)X0/(g·L-1)Xm/(g·L-1)Y1/(g·L-1)Ym+1/(g·L-1)

1/15.25050.0055.24550

1/1.55.25050.0057.86830

1/25.25050.00510.4910

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AccordingtothedatainTables1and2,theequilibriumisothermandtheoperationlineateachphasevolumeratioO/AaregraphicallypresentedinFigure10.Thenumberofstepsdrawnbetweenequilibriumisothermandoperationlineweredefinedastheneededstagesofcounter-currentextraction.Figure10illustratesthatwhentheO/Awas1/1.0,1/1.5and1/2.0,therequiredstageswere2,2and3,respectively.AccordingtoFigure9(a),copperextractionefficiencydecreasedwithincreasingO/A.Therefore,morestagesofcounter-currentextractionweresuggestedtoachievetheacceptablecopperconcentrationinraffinate.

Figure10McCabe-Thielediagramsforcopperextractionunderdifferentphasevolumeratios:(a)V(O)/V(A)=1/1.0;(b)V(O)/V(A)=1/1.5;(c)V(O)/V(A)=1/2.0

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Undertheoptimalextractionconditionsachievedfromthesinglefactorexperiments,atwo-stagecounter-currentextractionprocesswascarriedout.Thecopperextractionefficiencywas99.92%,and[Cu2+]aq=0.0044g/L≤0.005g/L.Obviously,thecounter-currentextractionimprovedcopperextractioncomparedwiththesingle-stageextraction.

3.4Extraction-stripping

UsingacidicwaterofpH=3.0canwashawaymostimpurityionscarriedintheextractionprocess,andtheremovalrateofeachmetalionwas:Cu0.23%,Co93.24%,Fe94.267%andZn92.384%.Then,forefficientstrippingofcopperalongwithloadedorganic,theconcentrationofH2SO4variedintherangeof0.5to3.0mol/LunderconditionsofphaseratioO/A1:1.0,temperature25°Candcontacttime5min.

TheresultspresentedinFigure11showthatonly68.21%Cuwasstrippedwith0.5mol/LH2SO4.Furtherincreaseintheacidconcentrationto1.5mol/L