Use of ionic liquid in leaching process of brass wastes for copper and zinc recovery

International Journal of Minerals, Metallurgy and MaterialsVolume 21, Number 2, February 2014, Page 138DOI: 10.1007/s12613-014-0876-yUse of ionic liquid in leaching process of brass wastes for copper andzinc recoveryAyfer Kilicarslan", Muhlis Nezihi Saridede"), Srecko Stopic?), and Bernd Friedrich?)1) Department of Metallurgical and Materials Engineering (Davutpasa Campus), Yildiz Technical University, Istanbul 34210, Turkey2) Department of Process Mtallurgy and Metal Recyeling (IME), RWTH Aachen University, Inuestrasse 3, Aachen 52072. Germany(Received: 5 August 2013; revised: 2 October 2013; accepted: 8 November 2013)Abstract: Brass ash from the industrial brass manufacturer in Turkey was leached using the solutions of ionic liquid (IL) 1-butyl-3-methy)-imi-dazolium hydrogen sulfate (bmim]HSO4) at ambient pressure in the presence of hydrogen peroxide (H2O2) and potassium peroxymonosulfate(oxone) as the oxidants. Parameters affecting leaching efficiency, such as dissolution time, IL concentration, and oxidizing agent addition, wereinvestigated. The results show that [bmim]HSO4 is an efcient IL for the brass ash leaching, providing the dissolution efficiencies of 9% for Znand 24.82% for Cu at a concentration of 50vol% [bmim]HSO4 in the aqueous solution without any oxidant. However, more than 9% of zinc and82% of copper are leached by the addition of 50vol% H2O2 to the [bmim]HSO4 soluion. Nevteless, the oxone does not show the promisingoxidant behavior in leaching using [bmim]HSO4Keywords: leaching; recovery; copper; zinc; ionice liquids; oxidantsdeveloped. In recent years, ionic liquids (ILs) have been1. Introductionfound to be the most promising candidates for leachingagents with the aim of achieving a new yet green hydro-Utilization and recovery of copper and zinc from indus-metallurgical process. Room-temperature ILs (RTILs) aretrial wastes are particularly important from economic ancconsidered as the next-generation molten salts, which arenvironmental viewpoints [1-4]. Typically, the brass pro-generally composed of organic cations and organic or inor-duction generates large quantities of various wastes, conganic anions. These molten salts may be synthesized withtaining significant amounts of copper and zinc. Slag gener-different anion and cation combinations to obtain the desiredated during brass alloy melting is the main source of cop-physicochemical properties. This is a great opportunity toper-based wastes. The metallic and nomallic parts of slagobtain the task-specific ILs. Important properties of theseare separated by a series of processes, i.e., crushing, washing, ILs, such as low vapor pressure, nonflammability, low tox-natural drying, Wet grinding, and sieving, in that order. Then,icity, negligible volatility, and thermal stability, make themthe separated metallic parts are recycled in a melting furnace,useful for various applications, including separation tech-and the residual nonmetallic part, called “brass ash", isniques, biochemistry, catalytic reactions, and electrochemi-stored for the recovery of copper and zinc [5-6].cal applications [7-1 1]. Furthermore, it is possible to recoverStudies on the recovery of metals from brass ash are gen-certain types of ILs after using them for the further reuseerally focused on the hydrometallurgical treatments. Metalwithout any appreciable loss of their punity and activity [12-20].recovery by the conventional acid or alkali leaching tech-The acidic nature and water solubility of ILs allow theirniques may not be environmentally friendly because of theapplication to the dissolution of metals [21-22]. Leaching oflarge amounts of acid/alkali consumed and the generation ofsulfidic copper, gold, and silver ores in the IL 1-buty1-3-high amounts of waste water. Therefore, to mitigate thesemethyI- imidazolium hydrogen sulfate (bmim]HSO4) hasadverse effects, the altermative extractants are required to bebeen studied by Whitehead et al, who have reported theCorresponding author: Ayfer Kilicarslan E- mail: akilic@ yiliz.du.r◎University of Science and Technology Bejjing and Springer-Verlag Berlin Heidelberg 2014中国煤化工包SpringerMYHCNM HGA. Kilicarslan et al, Use of ionic liquid in leaching process of brass wastes for copper and zinc recovery139promising results for the extraction of these metals [23-24].brass manufacturing plant in Turkey. The chemical compo-Other researchers have also used this IL for leaching ofsition of brass ash was analyzed by inductively coupledchalcopyrite, and it has been found that pure IL and itplasma optical emission spectrometry (ICP-OES), and theaqueous solutions are more effective than the conventionalresults are presented in Table 1. The phases of brass ashacid solutions used for leaching [25].vere analyzed by X-ray diffraction analysis (XRD), aIn this study, the recovery of copper and zinc from theshown in Fig. 1. The brass ash exists mostly in the form ofindustrial brass ash was attempted using [bmim]HSO4 in themetal oxides. A significant amount of copper is also foundleaching process. Furthermore, the parameters affectingto be present as the metallic phase in brass ash. Chemicalleaching efficiency, such as dissolution time, IL concentra-and spectrometry analyses show that ZnO, CuO, and Cu aretion, and oxidizing agent addition, were evaluated.the major components of brass ash.2. ExperimentalTable 1. Chemical composition of brass ash wt%ZnCuCaAlMgNaKSClSi2.1. Brass ashThe brass ash used in the experiments was supplied by a53.92 22.00 5.81 3.40 031 0.30 0.35 0.32 0.35 12.1715000◆ZnO0CuO. sCuzZn。800000θ Zn2SiO,φ Al2O;三5000φ203056(70201(9)Fig.1. XRD spectra of the brass ash sample.[bmim]HSO4 The samples for analysis were obtained2.2. Reagentsthrough a pipette dipped into the top part of solution. Sub-The IL ([bmim]H]HSO4) and two analytical-grade oxidantssequently, the samples were filtered using filter paper, and(potassium peroxymonosulfate (oxone) and hydrogen per-the metal concentrations in the liquors were analyzed byoxide (H2O2) solution (30wt%)) were used in the experi-ICP-OES. The leaching efficiency for copper and zinc wasments. All aqueous IL leach solutions were prepared usingdetermined according to the following equation.deionized water.Dissolution efficiency = (Metal amount in theliquor/Metal amount in the brass ash) x 100%(12.3. Leaching testsThe leach residues were characterized by scanning electronThe vessel used in leaching tests was a closed glassmicroscopy (SEM). Prior to the leaching tests, the pH valuebeaker, which was placed in a temperature-controlled water and reduction oxidation potential (Eh) values ofbath. The leaching tests were carried out at pulp densities of[bmim]HSO4 solutions containing various concentrations of100 g/L using a constant volume of 100 mL of leach solu-H2O2 and oxone were measured using a pH meter and a po-tion at a temperature of 70°C. The solutions were stirredtentiometer, respectively.magnetically at 400 r/min during leaching. The IL concen-trations in aqueous solution were 10%, 30%, and 50% by3. Results and discussionvolume. To investigate the effect of oxidizing agent addition3.1. Evaluation of Eh-pH values of solutions and chemi-on the leaching process, varying amounts of H2O2 werecal dissolutionadded to aqueous leach solutions with a constant IL concen-tration (50vol%). As an alternative oxidant, the oxone wasAccording to the Pourbaix diagram of a Cu-H2O system,also added at the concentrations of 0.3 mol/L and 0.5 mol/Lcopper dissolutic中国煤化工wer than 6 andto the aqueous IL leach solution containing 50vol%oxidizing redox IYHCNMHGi2showsthe140Int. J. Miner. Metall. Mater, Vol. 21, No. 2, Feb. 2014Eh-pH diagram obtained from the measurement of and the Eh values range between 0.95 and 0.67 for various[bmim]HSO4 solutions containing various concentrations ofoxone concentrations in the aqueous IL solution. Therefore,H2O2 and oxone. It is obvious from Fig. 2(a) that, when in-it can be claimed that the Eh-pH values of solutions are increasing the H2O2 concentration from 0vol% to 50vol% ingood agreement with those from the Pourbaix diagram for athe aqueous IL solution, the pH values decrease from 1.1 toCu-H2O system. Furthermore, since zinc is easily soluble in0.31, whereas the Eh values increase from 0.67 to 0.683. Fig. aqueous solution, the evaluation of its Eh-pH diagram was2(b) shows that the pH values range between 1.1 and 0.89omitted in this study..2p(a)0.685(b)1.41.01.0-一1.20.680二0.8.8-0.8>告0.6-合吉0.6- 0.6卤0.670 .0.4-).4 tt 0.665).2 F0.2- pH-十Eh00.6600.1.3J0H2O2 concentration/ vol%xone concentration 1(mol.L)Fig.2. Variation of acidity and redox potentials of [bmim]HSO4 solutions containing H2O2 (a) and oxone (b) at 25°C.The IL solutions containing different concentrations ofalso known that [bmim]HSO4 acts as an acid in the aqueousoxidizing agents were able to dissolve both copper and zincsolutions [23-24]. Fig. 3 shows the effect of the selected ILaccording to their Eh-pH values. The possible dissolutionconcentrations on the percentage of dissolved copper as areactions of metallic copper and/or copper and zinc com-function of leaching time. It can be seen that no remarkablepounds in [bmim]HSO4 solution containing oxidizing agents,copper dissolution is achieved at the [bmim]HSO4 concen-such as H2O2 and oxone, are proposed as the followingtrations of 10vol% and 30vol% in a leaching time of 5 h.equations.However, when the [bmim]HSO4 concentration is increasedH2O2 may decompose into water and oxygen:to 50vol%, copper starts to dissolve gradually, and its dis-2H2O2 -→2H2O + 2[0].(2solution ratio becomes to 25% after 5 h. However, this dis-Oxone ions may decompose into sulfate and oxygen: .solution ratio is still insufficient in view of the expected2HSO5 - →H2O +2SO4 + [O].(3)dissolution ratio of 90% for copper. The main reason for thisAnodic and cathodic reactions occur among copper, dislimited solubility of copper in the aqueous IL solution maysolved oxygen, and the IL:be the fact that the metallie copper is present in greaterquantity than the oxidic copper in the brass ash.Cu-→Cu2+ + 2e,(42H* +[0]+2e- -→H2O.(530 rAlternatively, the IL and H2O2 molecules may react with the[bmim]HSO, concentrationmetallic copper directly as▲- . 10vol%20 t一■ - 30vol%2Cu + H2O2 +4H+ +[0]-→2Cu2+ + 3H2O.(6-50vol%Zinc oxide may dissolve in IL solution according to the fol-lowing reaction.鱼12ZnO +4H+ -→2Zn2+ + 2H2O(73.2. Effect of IL concentrationThe IL [bmim]HSO4 was selected as a leaching agentTime/hbecause of its advantages, such as solubility in water, lowFig. 3. Effet c中国煤化: I”cpper disocost, environmental friendliness, and easy availability. It is lution."TYHCNM HGA. Kilicarslan et al, Use of ionic liquid in leaching process of brass wastes for copper and zinc recovery141Fig.4 shows the dissolution ratio of zinc in aqueous IL oxidative, and the copper metal dissolves more easily with asolutions of different concentrations. As can be seen fromhigher leaching ratio than in experiments without H2O2.this figure, the percentage of dissolved zinc increases sig-The effect of H2O2 addition on zinc dissolution ratio isnificantly as the IL concentration is increased from 10vol%shown in Fig. 6. Since zinc is present in oxide form in brassto 30vol%. The leaching time has no significant effect onash, higher dissolution ratios are already achieved withoutthe dissolution ratio of zinc for both these IL concentrations.the presence of any oxidant in the IL solutions. However,Further, the increment in the dissolution ratio is not negligi-H2O2 addition results in the higher dissolution ratios inble when the IL concentration is increased from 30vol% to .shorter leaching times. Almost the entire amount of zinc50vol%. A dissolution ratio of 99% for zinc is achieved atdissolves at the end of 30 min when 30vol% H2O2 is added.the IL concentration of 50vol% at the end of 4 h of leaching.00 r50vol% H2O2: 80-80[bmim]HSO, concentration30vol% H2O2- 30vol%10vol% H2O24050vol%; 20Fr 0vol% HO2旨200|Time/hFig. 5. Effect of H2O2 addition on the dissolution ratio ofFig. 4. Efect of [bmim]HSO4 concentration on zinc dissolu-copper in [bmim]HSO4 solution.3.3. Effect of H2O2 addition; 90Although almost the entire amount of zinc in brass ashwas dissolved at the IL concentration of 50vol%, the disso-lution ratio for copper was unsatisfactory because of the0vol% HO2metallic form. Oxidizing agents were then added to the70leach liquor to increase the dissolution ratio of copper. As isknown from the literature, oxygen solubility in [bmim]HSO450 L0.is similar to that in water [23]. Because the oxygen-dis-solving ability of ILs is comparable with that of water, theseILs can easily be used when oxidant action is needed. Then,Fig. 6. Effect of H2O2 addition on the dissolution ratio of zinctwo different oxidizing agents, H2O2 and oxone, were usedin [bmim]HSO4 solution.to obtain a higher copper dissolution ratio. H2O2 is known to3.4. Effect of oxone additionbe one of the most powerful oxidizing agents in acidic solu-tions. To investigate the effect of H2O2 addition on theAs mentioned earlier, the potassium peroxymonosulfateleaching efficiency, different concentrations by volume of(oxone) was also examined as an altemnative oxidant. Its ad-H2O2 was added to an aqueous IL solution of constant con-dition to acidic solution causes it to decompose into oxygencentration (50vol%).and sulfate. Its nontoxic nature, low cost, and simple han-The effect of H2O2 addition on the copper dissolution ra-dling properties are other reasons for its preferred use as antio in neat and aqueous IL leach solutions is shown in Fig. 5.oxidant.It is clearly seen that the dissolution ratio of copper in-Oxone with the concentrations of 0.3 mol/L and 0.5creases from 24.82% to 34.58% when the concentration ofmol/L was added to the aqueous solution having a constantadded H2O2 is increased from 0vol% to 10vol% after 5 h. IL concentration of 50vol%. Figs. 7 and 8 show the effectsAdding a higher concentration of H2O2 (30vol%) to theof oxone addition on the dissolution ratio of copper and zinc,leach solution increases the dissolution ratio further to respectively. The dissolution ratios for both copper and zinc44.48%. More than 82% of copper is leached at the H2O2decrease with th中国煤化工.5 mo/L oxone.concentration of 50vol%. H2O2 makes the IL solution moreThis decreaseYHCN MH Gactors, such as142Int. J. Miner. Metall. Mater, Vol. 21, No.2, Feb. 2014chemical changes in the structure of [bmim]HSO4 in theafter leaching using [bmim]HSO4 in the absence of any oX-presence of oxone. Therefore, a further investigation is re-idant and in the presence of H2O2 From Figs. 9(c) and (d), .quired to better understand this negative impact of oxone onhe positive effect of H2O2 on copper dissolution is clear. Itleaching efficiency.appears as if some ash particles disintegrate into subparticles3(in the presence of H2O2. In particular, in the presence of30vol% H2O2, the particle size of the leach residue is small-er than that of the brass ash when H2O2 is not used.冒200 mol/L oxone00一落100.3 mol/L oxone80 t●0 mol/. oxoneg0.5 mo/L oxone50 t40 F0.3 mol/L oxone,Time/h20Fig. 7. Effet of oxone addition on the dissolution ratio of0.5 mol/L oxonecopper in aqueous [bmim]HSO4 solution.453.5. Characterization of residues of leaching processFig. 8. Effect of oxone addition on the dissolution ratio of zincFig. 9 shows the SEM images of brass ash and residuesin aqueous [bmim]HSO4 solution.(a500 um(cd) "Fig. 9. SEM images of brass ash and leach residues obtained after filtering: (a) bras中国煤化工lant; (c) residueafter leaching with 10vol% H2O2; (d) residue after leaching with 30vol% H2O2.YHCNMHGA. Kilicarslan et al, Use of ionic liquid in leaching process of brass wastes for copper and zinc recovery1434. ConclusionsPhase Equilib., 219(2004), No.1, p.93.[12] J.M. Lee, Extraction of noble metal ions from aqueous solu-(1) The IL [bmim]HSO4 can act as an efficient acidiction by ionic liquids, Fluid Phase Equilib., 319(2012), p. 30.leaching agent for leaching of brass ash. Almost the entire[13] J.M. Reyna-CGonzalez, R. Galicia-Perez, J.M. Reyes-Lopez,and M. Aguilar-Martinez, Extraction of copper(II) fromamount of zinc (99%) dissolves successfully in 50vol%aqueous solutions with the ionic liquid 3-butylpyridiniumaqueous [bmim]HSO4 solution without adding any oxidant.bisl(rifluoromethanesulfony)imide，Sep. Purif. Technol,(2) Though it iknown that oxygen-containing89(2012), p.320.[bmim]HSO4 plays the role of an oxidant in the leach solu- [14] M. Regel-Rosocka, Extractive removal of zinc(I) from chlo-tion, the dissolution ratio of metallic copper from brass ashride liquors with phosphonium ionic liquidstoluene mixturesin the absence of additional oxidant is unsatisfactory.as novel extractants, Sep. Purif. Technol., 662009), No. 1, p.(3) A copper dissolution ratio greater than 82% is achie-[15] H.C.N. Hsu, CJ. Su, FL. Yu, WJ. Chen, D.X. Zhuang. M.J.ved in the presence of H2O2 with a concentration of 50vol%Deng，I.W. Sun, and P.Y. Chen, Extracting Cu(I) fromin [bmim]HSO4 solution. H2O2 addition to [bmim]HSO4 al-aqueous solutions with hydrophobic room-temperature ionicso leads to a higher dissolution ratio of zinc in a shorter timeliquid in the presence of a pyridine -based ionophore tothan that in the case of IL solution without H2O2.attempt Cu recovery: a laboratory study, Electrochim. Acta,(4) Oxone addition to the leach solution decreases the54(2009), No. 6, p. 1744.dissolution ratios for both copper and zinc. However, a fur-16] G.T. Wei, Z. Yang, and CJ. Chen, Room temperature ionicther investigation is required to better understand this nega-liquid as a novel medium for liquid/iquid extraction of metalions, Anal. Chim. Acta, 488(2003), No. 2, p. 183.tive impact of oxone addition on the dissolution of copper[17] M. Regel-Rosocka and M. Wisniewski, Selective removal ofand zinc.zinc(II) from spent pickling solutions in the presence of ironvith phosphonium ionic liquid Cyphos IL 101,ReferencesHydrometallurgy, 110(2011), No. 1-4, p.85.[18] A. 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