Copper recovery from ore by liquid–liquid extraction using aqueous two-phase system

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ContentslistsavailableatSciVerseScienceDirect

Journal

of

Hazardous

Materials

j o ur na l ho me p a g e : w w w . e l s e v i e r . c o m / l o ca t e / j h a z m a t

Copper

recovery

from

ore

by

liquid–liquid

extraction

using

aqueous

two-phase

system

Leandro

Rodrigues

de

Lemos, Igor

José

Boggione

Santos,

Guilherme

Dias

Rodrigues,

Luis

Henrique

Mendes

da

Silva,

Maria

C. Hespanhol

da

Silva

∗

GrupodeQuímicaVerdeColoidaleMacromolecular,DepartamentodeQuímica,CentrodeCiênciasExataseTecnológicas,UniversidadeFederaldeVic¸osa,Av.P.H.Rolfss/n,Vic¸osa, MG36560-000,Brazil

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AgreenmethodforCu(II)extraction oforeconcentratewasdeveloped. Selective separation of Cu(II) and

Zn(II), Co(II), Ni(II), Cd(II), Mn(II), Al(III)andFe(III)wasobtained. Themethod isenvironmental safe,

lowcostandeasyforscaleup. Theliquid–liquidextractionis

with-outuseoforganicsolvent.

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% E

Proportion PAN/Metal (mol/mol) Cu(II) Fe(III) Co(II) Ni(II) Zn(II)

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Articlehistory: Received14March2012

Receivedinrevisedform13August2012 Accepted14August2012

Available online 21 August 2012

Keywords: Greenchemistry Copper Ore

Liquid–liquidextraction Aqueoustwo-phasesystem

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WeinvestigatedtheextractionbehaviorofCu(II)intheaqueoustwo-phasesystem(ATPS)formedby (L35+MgSO4+H2O)or(L35+(NH4)2SO4+H2O)inthepresenceoftheextractingagent 1-(2-pyridylazo)-2-naphthol(PAN).AtpH=3andaPANconcentrationof0.285mmolkg−1,bothATPSleadtotheeffective separationofCu(II)fromothermetallicions(Zn(II),Co(II),Ni(II)andFe(III)).Highseparationfactorsrange between1000and10,000wereobtainedfortheextractionofCu(II)andconcomitantmetallicions.This ATPSwasusedfortheextractionofCu(II)fromaleachedoreconcentratewithaextractionpercentage of90.4±1.1%;othermetalsweremainlylocatedinthebottomphase.

1. Introduction

Copperiswidelyusedbecauseithasseveralessential proper-tiesfordifferenttechnologicalapplications,suchasuseinelectrical materialsandconstruction,transportation,andindustrial machin-ery parts, which are produced at a higher rate every year. At present, there are two main methods employed worldwide to processcopperorefor metalproduction:pyrometallurgicaland hydrometallurgicalmethods.

∗ Correspondingauthor.Tel.:+553138992175;fax:+553138992175. E-mailaddress:[email protected](M.C.H.daSilva).

Thepyrometallurgical methodcomprises numerous typesof shaft andflash technologies,includingcrushing,grinding, flota-tion,smelting-refiningandelectro-refining.Thepyrometallurgical method is used for sulfide flotation concentrates, and it is economicallyfeasibleforcopperrichfeedsandlarge-scale oper-ations[1].However,thisprocesshasseveraldrawbacks,including a high energy consumption and the production of hazardous gases.

Because ofan increasingworld demandfor copper, there is astrongincentivetodevelopenvironmentallyfriendlyprocesses for copper extraction from low-grade ores. Therefore, there is a considerable intensiﬁcation in theresearch and development of hydrometallurgical methods. These developments focus on

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by-productandconcentratetreatmentalternativestotraditional pyrometallurgicalmethodsfortheprocessingofsulﬁdeoresand concentrates,particularlyforsmall-scale productionandforthe processingof remotemetalresources thatare notamenableto pyrometallurgy[2].Hydrometallurgyconsistsofcrushing, leach-ing,solventextraction(SE)andelectrowinning.

TheSEstepisveryimportantbecauseitresultsinthe purifi-cationandpreconcentrationofthemetal.SEoffersaconvenient method for the extraction and separation of copper, and SE canbeefficiently appliedfor therecoveryofcopperfromleach liquorsand waste solutions using a variety of reagents [3].SE plantshavecriticalproblemsthatconsiderablyaffectthe extrac-tionefficiencyand selectivity,includingcrudformation,organic andaqueousphaseentrainments,andvariableandunpredictable phase separationtimes in settlers[4]. Furthermore,established SE methods involve organic solvents that are considered haz-ardousmaterialsbecausetheyaredetrimentaltotheenvironment and harmfulto humanhealth [5]. Therefore, it is importantto devisenovelextractionmethodsthatarecleanerandsafer.Hence, theaqueoustwo-phasesystem(ATPS)hasbeenintroducedasa promising liquid–liquid extraction systemfor metalseparation becauseitmostlyuseswaterandothernontoxicandnonflammable constituents[6–8].

ATPSisformedunderspeciﬁcthermodynamicconditionswhen onepolymerandoneelectrolytearemixed.Aphasesplitresultsin apolymer-enrichedtopphaseandanelectrolyte-enrichedbottom phase.Additionally,thesesystemshavea highcontentofwater inbothphases[9].TheATPShasseveraladvantages,includingits easyoperation, low-costand thepossibility torecycleits com-ponents[10].Thesesystemshave beenusedfortheseparation, preconcentration,puriﬁcationanddeterminationofbiomolecules [11–14], phenols [15,16], dyes [17] and metallic ions [6–8,18]. FactorssuchasthepH,thedesignofthesystem,theelectrolyte composition,the temperatureand the extractantconcentration strongly affect the partitioning behavior and the separation of analytes[19].

Inthedescribedwork,weseparatedcopperfromother metal-licionsusinganATPSformedbyatriblockcopolymercomposed ofpoly(ethylene oxide) (PEO)and poly(propyleneoxide) (PPO), MgSO4 and waterat 298K inthepresence of 1-(2-pyridylazo)-2-naphthol(PAN)asanextractingagent.Theinfluenceofcertain parametersonthemetalextractionyieldwasexamined,including theamountoftheaddedextractingagent,thepHofthesystem,the natureoftheATPSelectrolyte,aswellastheseparationfactorof thecoppercomparedtoseveralothermetallicions(Cd(II),Fe(III), Al(III),Mn(II),Ni(II),Co(II)andZn(II)).Theextractionmethodwas thenappliedfortheefficientextractionandpurificationofCu(II) fromtheleachateofacopperoreconcentrate.

2. Experimental

2.1. Materialsandchemicals

Allreagentswere ofanalytical grade quality and wereused as received without further puriﬁcation. The triblock copoly-merusedinthisstudywaspoly(ethyleneoxide)–poly(propylene oxide)–poly(ethylene oxide), L35, with an average molar mass (Mm) of 1900gmol−1 and 50% ethylene oxide, corresponding to a composition of (EO)11(PO)16(EO)11. The triblock copoly-mer,H2SO4 andHNO3 wereobtainedfromAldrich(Milwaukee, WI, USA). MgSO4·7H2O, (NH4)2SO4, NaOH, MnSO4·H2O, ZnSO4 andFeCl3 wereobtainedfromVETEC(Duque deCaxias, Rio de Janeiro,Brazil).PAN,HClO4,NH4Al(SO4)·12H2O,CoCl2,CdCl2·H2O, Ni(CH3COO)2·4H2O and CuSO4 were purchased from MERCK (Darmstadt,Germany).

2.2. Equipment

Deionizedwater (R≥18Mcm−1)wasused throughoutthe experiments.AMilli-QIIwaterdeionizer(MilliporeCorporation) wasusedforthefinalpurificationofthedistilledwater.ThepH measurementswereperformedusingaglasselectrodeconnected to a digital pH meter (Digicron Analítica Ltda, Digimed model DM-20).The experimentswereperformedonananalytical bal-ance(Shimadzu, AY220)withanuncertainty of_±0.0001g,and thetemperatureoftheATPSwasadjustedto25.0±0.1◦Cwitha temperature-controlledwaterbath(Microquímica,MQBTC99-20). A hot plate (Fisatom– 752A) and a centrifuge (Thermo Scien-tific,HeraeusMegafuge11R)werealsousedfortheexperiments. The metal concentrations were measured witha flame atomic absorptionspectrometer(VARIANAA240).Theoperations condi-tionswere:wavelength324.8nm,resolution0.5nm,currentlamp 4.0mA,air–acetyleneflame(airandacetylenefluxrates3.50and 1.50Lmin−1,respectively).

2.3. Aqueoustwo-phasesystemcomposition

Theaqueoustwo-phasesystemformedbyL35+MgSO4+H2O waspreparedby mixing2.00gof a57.19% (m/m)L35solution and2.00gofa19.88%(m/m)MgSO4 solution[20].Theaqueous two-phasesystemformedbyL35+(NH4)2SO4+H2Osystemwas preparedmixing2.00gofa54.22%(m/m)L35solutionand2.00g ofa18.71%(m/m)(NH4)2SO4solution[9].

2.4. InﬂuenceofthepHonextractionbehavior

The partitioning of each metallic ion in the biphasic sys-tem was performed to fix the global metal concentration at 0.0950mmolkg−1.TostudytheinfluenceofthepH,aPAN/metal ratioof3 wasused.Aconcentrated metalsolutionwitha con-centrationof 0.190mmolkg−1 wasprepared ina 19.88% (m/m) MgSO4 solution, and a concentrated PAN solutionwith a con-centrationof 0.570mmolkg−1 wasprepared ina 57.19% (m/m) L35solution.When2.00gofMgSO4 solutionis addedto2.00g ofL35solution,themetalandPANfinalconcentrationisreduced toahalfofinitialconcentration(0.0950mmolkg−1formetaland 0.285mmolkg−1 forPAN).ThepHofthewaterusedtoprepare theMgSO4andL35solutionshadbeenpreviouslyadjusted. Sul-furicacidwasusedtoadjust thepH=1.0,3.0 or5.0 andNaOH wasusedtoadjustpH=7.0,9.0or11.0.Inacentrifugetube2.00g of the metalsolution (0.190mmolkg−1) and 2.00g of the PAN solution(0.570mmolkg−1)wereweighed.Thetubewas manu-allystirredfor3min,centrifugedfor15minat3000rpm,andthen allowedtosettlefor1hat25.0±0.1◦C.Thetopphasewasthen col-lected,appropriatelydiluted,andthemetalconcentrationinthetop phasewasdeterminedwithaflameatomicabsorption spectrome-ter(FAAS).Theextractionpercentage(%E)ofthemetallicionswas calculatedbyEq.(1).

%E= (n₍Mm+)Top nMm+)T

×100 (1)

where (nMm+)Top istheamount(in mol)ofmetallic ionsinthe topphase,and(nMm+)Tisthetotalamountofmetallicionsinthe system.

2.5. InﬂuenceoftheamountofPANonextractionbehavior

AnATPS at pH=3.0 was used tostudy the inﬂuenceof the amountofPAN.Theprocedureforthisexperimentissimilartowhat wasdescribedinSection2.3,exceptthatthePANconcentrationin theL35solutionwasvariedfrom0.190to0.950mmolkg−1.

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Table1

Concentrationofpredominantmetallicionsinthesampleorecopperconcentrate.

Metal Concentration Copper 29.7%(m/m) Iron 12.0%(m/m) Nickel 1.03×103_mg_kg−1 Zinc 326mgkg−1 Chromium 134mgkg−1 Cobalt 98.8mgkg−1

2.6. InﬂuenceoftheATPScomponentnatureonextraction

behavior

TostudytheinﬂuenceoftheATPScomponentnature,aPAN

concentrationof0.570mmolkg−1andapHof3.0wereused.The

metalsolutionswerepreparedinaMgSO4solutionora(NH4)2SO4

solutiondependingontheexperiment.Thesubsequentstepswere

performedaccordingtowhatwasdescribedinSection2.3.

2.7. Copperoreconcentrate

Leachingoccurredafterincubationat25◦Cfor8hwith1.00gof thecopper(MineraçãoCaraíba–Jaguarari,Bahia,Brazil)in5.00mL ofHNO3(65%)and10.0mLofconcentratedHClO4.Theobtained leachatewasfilteredandtransferredtoa1.00Lflaskfilledwith deionizedwater.Theconcentrationofthemainmetalsinthe result-ingsolutionwasthendeterminedwithFAAS(Table1).

2.8. Copperextractionfromtheoreleachateandstripping experiments

Initially,thepHoftheleachatewasadjustedto3.0,resulting intheformationofaprecipitate.Theprecipitatewascentrifuged andtheconcentrationofthemainmetalsinthesupernatantwas determined with a ﬂame atomic absorption spectrometer. The supernatant was used toprepare solutions of L35 and MgSO4. ThePANsolution(14.7mmolkg−1)waspreparedintheL35 solu-tion.Inatube3.00gofthePANsolutionand3.00goftheMgSO4 solutionwereweighed.Thetubewasmanuallystirredfor3min, centrifugedfor15minat3000rpm,andthenallowedtosettlefor 1hat25.0±0.1◦C.Aftereachextractionstagethetopphaseand bottomphasewascollected,appropriatelydiluted,andthemetal concentrationinbothphasesweredeterminedwithaﬂameatomic absorptionspectrometer.

For both stripping stages of metal ion, 2.00g of loaded phase with metal ion (APTS top phase) was taken and con-tactedwith 2.00gof ATPS bottom phase added with HNO3 at different concentration, followed by vigorous shaking to reach equilibrium.

3. Resultsanddiscussion

3.1. InﬂuenceofthepHontheextractionbehaviorofmetallicions TheinﬂuenceofthepHontheextractionbehaviorofCu(II), Zn(II),Co(II)andNi(II)isshowninFig.1.Theseexperimentswere performedwiththeATPSformedfromL35+MgSO4+H2Oandwith aPANconcentrationof0.285mmolkg−1.

Theresultsshowedthatallmetalsareextractedataminimum efﬁciencyatapHof1.0becauseofthestrongprotonationofthePAN moleculeatthispHthathindersitscomplexationwithmetals.A highpHfavorstheionizationofPAN(pKa1=2.9andpKa2=11.6), whichfacilitatescomplexationandincreasestheextractionyield ofZn(II),Co(II)andNi(II).ForCu(II),theextractionyieldinitially increaseswithincreasingpHvaluesbecauseoftheionizationof PAN[21];however,forpHvaluesgreaterthan5.0,theamountof

12 10 8 6 4 2 0 0 20 40 60 80 100 Cu (II) Zn (II) Co (II) Ni (II) %E pH

Fig.1. TheeffectofthepHoftheATPSonthe%EofCu(II),Zn(II),Co(II)andNi(II)for theL35+MgSO4+H2OsystemwithaPANconcentrationof0.285mmolkg−1.

copperinthetopphasedecreases.Thisbehaviorisbecauseofthe increasedconcentrationofhydroxylgroupsinthemid-pHrange andthesubsequentformationofhydroxyl-complexeswithCu(II), reducingtheamountofCu(II)thatisavailabletointeractwithPAN. Thiseffectis lessdrasticfortheotheranalyzedmetals,without affectingthecomplexationwithPAN.

Themaximumextractionyieldswere103±2%forCu(II)atpH 3.0and70.2_±1.5%,61.2_±1.3%and45.0_±1.2%forZn(II),Co(II)and Ni(II),respectively,atpH12.However,mostinterestingly,atpH3.0 Cu(II)wascompletelyextractedtothetopphase,whereastheother metalsweremostlypresentinthelowerphase(%E≤7.69%).Thisis veryimportantforseparationprocessesthatrequiretheseparation ofCu(II)fromothermetallicions.Therefore,additionalstudieswere performedatthispH. 5 4 3 2 1 0 0 20 40 60 80 100 % E

Proportion PAN/Metal (mol/mol)

Co2+

Fe3+

Ni2+

Zn2+

Cu2+

Fig.2. TheeffectoftheamountofPANaddedtotheATPSonthe%EofCu(II),Zn(II), Co(II),Ni(II)andFe(III)fortheL35+MgSO4+H2OsystematpH=3.

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3.2. InﬂuenceoftheamountofPANontheextractionbehaviorof metallicions

Fig.2summarizesthe%EoftheCu(II),Co(II),Ni(II),Zn(II)and Fe(III)metallic ions added to the L35+MgSO4+H2O system at pH=3.0asafunctionoftheamountofPANinthetopphase.

IntheabsenceofPAN,themetalsaremainlyconcentratedinthe bottomphase(Fig.2)becausetherearestronginteractionsbetween thesulfate(ofthesaltintheATPSthatisprimarilylocalizedinthe bottomphase)andthechargedspeciesofthemetals(Eq.(2)).

Mm+_(aq)+xSO2−4(aq)M(SO4)

(2x−m)− x(aq) (2) K_M(SO 4)x(2x−m)−= _M(SO 4)x(2x−m)−·[M(SO4)x (2x−m)−_] Mm+·[Mm+]·SO42−·[SO4 2−_]x (3) InEq.(3),K M(SO4)x(2x−m)−

isthestandardthermodynamicconstant fortheformationofthemetal–sulfatecomplex,_M(SO

4)x(2x−m)− is theactivitycoefficientofthemetal–sulfatecomplexandMm+and _SO₄2− aretheactivitycoefficients ofthemetaland thesulfate, respectively.Thestabilityconstantdependsonthereaction con-ditionsandtheelectronicstructureofthecentralmetalion.The metal–sulfatecomplexesarepreferentiallyformedunderstandard conditionsinthefollowingorder:Cu ∼= Zn ∼= Ni ∼= Co<Fe[22].The metalextractionefficiencyisinverselyproportionaltothe forma-tionconstantofthecomplexifonlythemetal–sulfateinteraction isconsidered.

Ingeneral,theadditionof organicmoleculesascomplexants resultsinmuchlargeriondistributioncoefﬁcients,butthisaddition constrainstheapplicationofATPSbecausethecomplexantmustbe watersoluble[23].However,thecopolymerATPSenablestheuse ofthewater-insolubleextractant,PAN,becausethephaseenriched inmacromoleculesishighlyhydrophobicduetothepresenceof macromolecularaggregatedformedbyahydrophobiccoreanda hydrophilicshells.

TheadditionofPANtotheATPSinitiatescomplexformation betweenPANandthemetals.Fig.2showsthattheadditionofPAN resultsinanincreasein%Eforallmetals.Asthecomplexbetween PANandthemetalisformed,thecomplexmovesfromthebottom phasetothetopphasebecauseithasaspeciﬁcinteractionwiththe copolymermacromolecules.ThisPAN–metalcomplextransfer pro-cessresultsintheformationofadditionalcomplexesinthebottom phaseviaequilibriumdisplacement.Thisdisplacementequilibrium drivestheformationofcomplexeswhentheconcentrationofPAN isincreased,untilasaturationpointisreachedwhereadditional amountsofPANdonotaffecttheextractionyield.Theextraction ofcopperinthissystemisextremelyefﬁcient(%E ∼_{= 100)}compared totheextractionofothersmetalsthatlargelyremaininthebottom phase(%E≤45).

3.3. InﬂuenceoftheATPScomponentnatureontheextraction behaviorofmetallicions

The results of the inﬂuence of the ATPS salt nature on the extraction behavior of Cu(II) are shown in Fig. 3. These studies were performed with the ATPS formed by L35+MgSO4+H2OorL35+(NH4)2SO4+H2OandaPAN concentra-tionof0.285mmolkg−1atpH=3.0.

Fig.3 shows that the ATPSformed by L35+MgSO4+H2O is moreefficient for theextractionof Cu(II)at all pHvalues. The complexbetween Cu(II)and ammonium(logK=4.3)[22] has a higherformationconstantthanthecomplexbetweenCu(II)and sulfate(logK=2.4)[22],thusprovidingfortheammoniumATPS theleastamountofcopperforcomplexationwithPAN.Despiteits higherefficiencytheL35+MgSO4+H2OATPSextracted,inthefirst

10 8 6 4 2 0 0 20 40 60 80 100 % E

Proportion PAN/Metal (mol/mol)

MgSO4 pH = 3 (NH4)2SO4 pH = 3 MgSO4 pH = 7 (NH4)2SO4 pH = 7 MgSO4 pH = 11 (NH4)2SO4 pH = 11

Fig.3.TheeffectofATPS-formingelectrolytes(MgSO4or(NH4)2SO4)onthe%Eof

Cu(II)fordifferentamountsofPANatpH=3.0,6.0or11.0.

extractionstage,only82%(proportionPAN/metalequalto1.0).In ordertoimprovethepreviousresultsasecondextractionstagewas carriedoutforobtaining100%ofextraction.Thisresults demon-stratedthatwithonlytwoextractionprocessthisATPSiscapable toproduceacompletetransferenceofCu(II)fromthebottomphase tothetopphase.

3.4. Inﬂuenceofothersmetalsontheextractionbehaviorof copper

Table2liststheseparationfactors(SM,N)forCu(II)andother metalspresentconcomitantlyintheATPS(L35+MgSO4+H2O)and aPANconcentrationof0.285mmolkg−1atpH=3indifferent pro-portions. The separation factor expresses theefﬁciency for the separationoftwo species,MandN,inliquid–liquidextractions [24],andthevalueofSM,NcanbecalculatedbyEq.(4):

SM,N=DM DN

(4) whereDMandDNarethedistributioncoefﬁcientsofspeciesMand N,respectively.Thedistributioncoefﬁcientofanygivenspeciesis expressedbyEq.(5):

DM= %E

100−%E. (5)

SM,N values greater than 103 indicate an effective separation betweentwospecies.

Theseparationfactorofcopperishighcomparedtotheother analyzedmetallicions;theseparationfactorsaregreaterthan103 formostmetalconcentrations,evenreachingvaluesgreaterthan 104_._This_system_was_extremely_efﬁcient_for_the_separation_of cop-perfrommetalsconcomitant(Fe,Mn,Al,Ni,CoandZn)presentin Table2

Separationfactors(SCu,M)ofcopper(Cu)andseveralmetallicions(metal).

Proportion (metal/Cu)

SCu,Cd SCu,Fe SCu,Al SCu,Mn SCu,Ni SCu,Co SCu,Zn

1 1320 323 – 1600 1470 161 481

10 2560 1980 3720 5270 7040 12,000 872

50 4140 25,300 2230 6100 8400 27,500 979

100 3410 14,900 3020 31,800 11,500 2610 482

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1.2 1.0 0.8 0.6 0.4 0.2 0.0 0 20 40 60 80 100 HNO 3 concentration (mol L -1 ) 1st Stripping 2nd Stripping %S

Fig. 4.The stripping of Cu2+ _using _HNO3, _[PAN]₌_0.570_mmol_kg−1_, [Cu2+_]₌_0.190_mmol_kg−1_.

severaldifferentproportions.Thesecontaminantsareprevalentin

differentmatricessuchascopperoreandelectronicscrap.

3.5. Copperextractionfromtheoreleachate

Todeterminetheefﬁciencyoftheextractionsystem,ATPSwas

usedfor the separation and puriﬁcationof copperfrom a

cop-per oreleachate.The composition of themetals in thesample

wasdetermined(Table1).Thesamplewasleached,thepHwas

adjustedto3.0,themetallicionconcentrationinthesupernatant wasquantiﬁed([Cu]=306mgkg−1and[Fe]=54.4mgkg−1)andthe supernatantwasusedasasolventforthepreparationoftheATPS. TheconcentrationofPAN(14.7mmolkg−1)wasthreetimesgreater thantheconcentrationofcopperinthissystem.

The %E of copper was 90.4_±1.1%, demonstrating the efﬁ-ciencyofthisextractiontechniqueevenwithhighlyconcentrated metalsamplesandinthepresenceofseveralcontaminatingmetal species.Iron,themainmetalconcomitantinthissystem,was pre-dominantlyinthebottomphaseandhadalow%Eof16.3±0.5%. 3.6. Strippingproperty

AlthoughL35+MgSO4+H2OwithPANrevealshigherextraction abilitiesforCu2+_,_stripping_{characteristics}_are_important_factors_for evaluatingitspotentialapplication.StrippingofCu2+_was_carried outtwotimesusingHNO3solutionat25◦C.TostriptheloadedCu2+, aseriesofexperimentswascarriedoutwithvaryingHNO3 solu-tionconcentrationfrom0.20molL−1to1.2molL−1.Thestripping efﬁciency(%S)isdeﬁnedasfollows:

%S= [Cu]Bottom

[Cu]Top

(6) AsshowninFig.4,the%SvaluesofCu2+_using_L35₊_MgSO

4+H2O

withPANwere72%and90%intheﬁrstandsecondstrippingstages, respectively.

4. Conclusions

AnewandenvironmentallyfriendlyATPStechniquewas devel-opedfor liquid–liquidextractionandpuriﬁcationofCu(II)from orespretreatedbyhydrometallurgicalmethods.Thistechniqueis compatiblewiththeprinciplesofgreenchemistryandhasagood

efficiencyandeconomicalviability.TheATPSusedinthiswork con-sistedofL35+MgSO4+H2OorL35+(NH4)2SO4+H2O,andPANwas usedastheextractingagent.Theextractionefficiencyofthemetalis affectedbythepH,theamountofPAN,thenatureoftheelectrolyte andthepresenceofmetalconcomitants.Theresultsshowedthatall Cu(II)couldbeextractedtothetopphaseatpH=3.AtthispH,other metalsaremainlypresentinthelowerphase(%E≤7.69);thus,it ispossibletoseparateCu(II)atthispH.TheadditionofPANtothe systemresultsinanincreased%Eforallmetals,andaPAN con-centrationof0.285mmolkg−1resultedinthecompleteextraction ofCu(II)tothetopphase.TheATPSformedbyL35+MgSO4+H2O showedthehighest %Eandthehighestseparation factorvalues (SCu,M=1000–10,000)forCu(II)(comparedtoothermetal concomi-tants).Thissystemwasalsousedfortheextractionofcopperfroma leachedoreconcentrate.The%Evalueof90.4±1.1%demonstrated theefficiencyofthisextractiontechniquewithahighlycomplex samplewithtechnologicalapplications.

Acknowledgements

TheauthorsacknowledgetheFundaçãodeAmparoaPesquisa do Estado de Minas Gerais (FAPEMIG), Conselho Nacional de PesquisaeDesenvolvimentoTecnológico(CNPq)andtheInstituto NacionaldeCiênciaseTecnologiasAnalíticasAvançadas(INCTAA) forfinancialsupport.L.R.L.andG.D.R.acknowledgeresearch fel-lowships from CAPES and CNPq, respectively. The authors also acknowledgetheMineraçãoCaraíba(Jaguarari,Bahia,Brazil)for providingasampleofthecopperconcentrate.

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