Hydrometallurgy 95 (2009) 308–315

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Hydrometallurgy

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Simultaneous extraction and separation of Cu(II), Zn(II), Fe(III) and Ni(II) bypolystyrene microcapsules coated with Cyanex 272

Md Fazlul Bari a,⁎, Md Sohrab Hossain a, Iqbal M. Mujtaba b,Shamsul Baharin Jamaluddin a, Kamaruddin Hussin a

a School of Materials Engineering, University Malaysia Perlis (UniMAP), Taman Muhibbah, 02600 Arau, Perlis, Malaysiab School of Engineering, Design and Technology, University of Bradford, West Yorkshire BD7 1DP, UK

⁎ Corresponding author. Fax: +60 49798178.E-mail address: fazlul@unimap.edu.my (M.F. Bari).

0304-386X/$ – see front matter © 2008 Elsevier B.V. Adoi:10.1016/j.hydromet.2008.07.003

a b s t r a c t

a r t i c l e i n f o

Article history:

The preparation of polystyr Received 17 April 2008Received in revised form 15 July 2008Accepted 15 July 2008Available online 19 July 2008

Keywords:MicrocapsulesExtractionSeparationCyanex 272Packed column

ene microcapsules coated with Cyanex 272 (MC-Xs) have been investigated andsimultaneous extraction and separation behavior of Cu(II), Zn(II), Fe(III) and Ni(II) in both batch and packedcolumn process have been carried out. It has been found from the studies that the dispersion agent plays animportant role during preparation of microcapsules. Morphology studies show that higher amount of Cyanex272 makes the MC-Xs inferior quality, whereas absence of Cyanex 272 in the microcapsules also makes thesurface brittle. Mean diameter of MC-Xs are highly dependant on stirring speed and amount of polystyrenetaken during preparation. The ratio of Cyanex 272 to polystyrene in the dispersed phase in preparationprocess for the batch extraction system shows the effect on extraction performance. Selective separation ofCu(II), Zn(II), Fe(III) and Ni(II) can be possible using MC-Xs by selecting the aqueous pH. Packed columnoperation studies illustrated that separation of Cu(II) from Zn(II) and Ni(II) can be obtained by performingrepeated process. Almost 100% stripping from loaded MC-Xs have been obtained using 0.1 M and 0.5 MH2SO4 solution for Cu(II), 0.1 M H2SO4 solution for Zn(II) and 0.5 M H2SO4 solution for Fe(III). Good stability ofMC-X is demonstrated from regeneration investigation. Finally selective recovery of Cu(II), Zn(II) and Ni(II)from leach liquor obtained from PCB is achieved performing the extraction-stripping process using MC-Xs.

© 2008 Elsevier B.V. All rights reserved.

1. Introduction

Copper, zinc, iron and nickel are valuable metals, and play significantrole in our daily life. Copper has been used in electronic products,household products, building constructions, chemical and pharmaceu-tical machinery, piping, various alloys, electroplated protective coating,etc. Zinc has been used in electroplating, metal spraying, automotiveparts, dry cell batteries, etc. Iron is themost used of allmetals. It has beenused in automobiles, hulls, structural components of buildings, etc.Nickel has been used in many industrial and consumer products, inclu-ding stainless steel, magnets, coinage and special alloys. These metalsalways co-exit in environmental waste sample like printed circuit board(PCB) and sludge. Thus there is a need to find out suitable technique forthe simultaneously extraction, separation, and recovery of these valuablemetals. Usual techniques for the separation and recovery of thesemetalsare, for example, solvent extraction, precipitation, electrolysis and ionexchange (Barbette et al., 2004). Among these techniques, the solventextraction technique offers a superior separation performance thanothers, but it has some limitation due to the extracting solvents arelimited to those that are water immiscible (for aqueous sample), emu-lations tend to form when the solvent are shaken and relatively large

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volumes of solvents are used that generate a substantial waste disposalproblem. Butmost of thesedifficulties that arise in solvent extraction canbe avoided by the use of any solid phase in place of organic solvent, suchas supported liquid membrane (Sarangi and Das, 2004; Alguacil andAlonso, 2005), solvent impregnated resin (Trochimczuk et al., 2004) andextractant microcapsules (Yang et al., 2005a,b; Gong et al., 2006;Nishihama et al., 2002). Among these processes, extractant microcap-sules which are prepared following solvent evaporation method arehighly promising as themicrocapsules prepared using this method havesomepotential advantages suchaseasyphase separation, including largespecific interfacial area, minimal use of organic solvent, high selectivity,maximal solvent loading ratio, and especially more stability.

Although there are diverse methods to prepare excellent micro-capsules, but most are time and energy consuming; whereas, solventevaporation is an economical, simple method for preparing uniformextractant microcapsules (Yang et al., 2004). Microcapsules have beenwidely used in various fields for their potential applications such asmedicine, pharmacy, agriculture chemistry, food and chemical industryand specially their utility in the separation and recovery of metals bycoated extractants (Mimura et al., 2001; Nishihama et al., 2002; Kamioet al., 2002). Preparation of polysulfone microcapsules containing di-2-ethylhahyl phosphoric acid and polystyrene microcapsules containingAliquat 336 by solvent evaporation method have been optimized tostudy the extraction for the recovery of various metal ions (Yang et al.,

Fig. 1. Optical microscope images. Composition of disperse phase: PS: CH2Cl2: Cyanex272=4 g: 50 ml: 2 g; continuous phase: 1 wt.% gum arabic solution; agitation speed:400 rpm.

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2004, 2005a,b). Results show that the microcapsules have a sufficientloading capacity for recovery metal ions in dilute solution and have asufficient stability for repeated processing.

Metal recovery and recycling fromwaste materials are now a majorconcern of thepolicy-makers, environmentalists, and engineers in termsof the protection of the environment and metal resource as well aseconomic benefit. Among these waste materials, PCB contains 10–30%copper as well as plastics, fiberglass, and other metals like zinc, nickel,tin, iron, lead, silver, aluminium etc., depending on the source and typeof the circuit board. Therefore, recycling of PCB is an important subjectnot only for the treatment of waste but also for the recovery of valuablematerials. A hydrometallurgical copper recycling process for electronicscrap like PCBs has been studied (Alam et al., 2007; Oishi et al., 2006,2007) using ammonia–ammonium salt solution which form copper (I)and copper (II) amine complexes and consisted of three stages of lea-ching, purification and electrowinning. In this process copper has beenleached in an ammoniacal alkaline solution that dissolved low im-purities and the dissolved copper existed as a monovalent copper–amine complex in the electrolyte.

The extractant, Cyanex 272, is a technical grade solvent extractionreagent. Its active component is bis (2, 2, 4-trimethylpentyl) phosphinicacid. This technical grade extractant has been used since 1983 and foundvery effective for the extractive separation of Co(II) from Ni(II) (Danesiet al., 1984; Xun and Golding, 1987; Sole et al., 2005), and also has theability to separate of others cation pairs. (Saleh et al., 2002; Ready et al.,2004;Wang and Li,1994). Recently Cyanex 272 has been used to extractother transition and lanthanides metals under appropriate conditionsfor its several advantages including high selectivity, low aqueous acidityin extraction, stripping and high separation factor of rare earth ions(Xiong et al., 2006). Although Cyanex 272 is a well known solventextraction reagent andextensivelyused in solventextraction and relatedarea for the extraction and separation of metal ions (Rydberg et. al.,1992), but there is rare works on simultaneous metal ions extractionusing MC-Xs.

This study examines the extraction and separation behavior of Cu(II),Zn(II), Fe(III) and Ni(II) in batch and packed column system usingpolystyrene MC-Xs prepared in the optimized condition. A completeprocess for the separation and recovery of Cu(II), Zn(II) and Ni(II) fromthe leach liquor of PCB has been investigated. The investigation has beencarried out on PCB recycling, yet the results of this study are importantfrom the viewpoint of waste treatment, and also with respect to therecovery of valuable materials.

2. Experimental

2.1. Reagents

Cupric sulphate (CuSO4d 5H2O), Nickel sulphate (NiSO4d 2H2O) andferric sulphate (Fe2(SO4)3d 7H2O), and Zinc sulphate (ZnSO4d 7H2O), withthe purity above 99%, used have been obtained from Labjax chemical Ltd,India, LeSOL laboratoryandUni-chem, respectively. ExtractantCyanex272(92%), i.e. bis (2, 4, 4-trimethylpentyl) phosphinic acid has been obtainedfrom Cytec Industries Inc., Canada. All other chemicals used are of at leastreagent grade.

2.2. Preparation of extractant microcapsules

A certain amount of polystyrene and desired amount of Cyanex 272have been dissolved in dichloromethane (DCM) as a dispersed phase.The continuous phase has been prepared by adding 1.0 wt.% gumArabic in 500 ml deionized water. Then, the dispersed phase has beenadded to the continuous phase under high-speed agitation at roomtemperature for 2 h to get an organic/water emulsion. After 2 h, DCMhas been allowed to evaporate completely under the same conditionsand the polystyrene MC-Xs have been obtained. The obtained MC-Xshave been washed for three times with deionized water and then

desiccated at room temperature. The MC-Xs have been characterizedby FT-IR (PerkinElmer, Model-200), optical microscope equipped witha digital camera and scanning electron microscopy (JEOL JSM 6400,Model-6210).

2.3. Extraction and separation of metal ions

The batch extraction has been performed using MC-Xs at roomtemperature. Definite amount of aqueous sulphate solution containingmetal ions and desired amount of MC-Xs have been mixed together in100 ml stopped conical flasks. The mixture has been stirred using ahotplate magnetic stirrer for 30 min and then separated by filtration.

In the packed column studies, 3.0 g MC-Xs have been packed into acolumn of 0.5 cm in diameter and 15.0 cm in height.100ml of aqueousmetal sulphate solution has been passed through the column and theeffluent has been collected at appropriate intervals in 20 fractions.

The pH value of the aqueous solution has been adjustedwithH2SO4

or NaOH solution, and kept constant concentration of CH3COO−(Ac−) tobe 0.25 M by adding calculated amount of CH3COOH (Ac) as a bufferagent. The metal concentration of the aqueous phase has beenmeasured using an Atomic Absorption Spectrometry (AAS, PerkinElmer, Analyst -700), and the metal ions concentrations in the MC-Xshave been estimated by difference. The distribution ratio (D) has beencalculated as the amount of metal ions present in the MC-Xs to that ofin the aqueous phase at equilibrium.

Leaching studies have been conducted by taking 100ml ammoniacalalkaline solution [NH3–(NH4)2SO4] with 400 mg crashed printed circuitboard in a 500ml roundbottomflaskfittedwithwater cooled condenserand stirrer,which is immersed inoil bathmaintained at60±1 °C for 24h.Concentrations of Cu(II), Zn(II) and Ni(II) contents in the leach liquorhave been determined by AAS and found to be 501.94 ppm, 14.23 ppm

Fig. 2. Scanning electron micrographs. Composition of disperse phase: (a) PS: CH2Cl2:Cyanex 272=4 g: 50 ml:3 g; (b) PS: CH2Cl2: Cyanex 272=4 g: 50 ml:0 g; continuousphase: 1 wt.% gum arabic solution; agitation speed: 400 rpm.

Fig. 4. Influence of the agitation speed on diameter of MC-Xs. Composition of dispersedphase: PS: CH2Cl2: Cyanex 272=4 g: 50 ml: 2 g; continuous phase: 1.5 wt.% gum arabicsolution. Number of MC-XS used for counting=15.

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and 16.41 ppm, respectively. Later, the leach liquor has been used torecover and separate of Cu(II), Zn(II) and Ni(II) through the batchextraction-stripping process using MC-Xs.

3. Results and discussion

3.1. Preparation of MC-Xs

Dispersants play an important role to prepare microcapsules whilefollow solvent evaporation method (Yang et al, 2004). They can beadsorbed on the surface of the oil droplet, improving the viscosity ofthe aqueous solution and preventing the microcapsules aggregation.

Fig. 3. The infrared spectrum of MC-Xs and its components. Curve

To test this mechanism, it has been tried to prepare extractantmicrocapsules without dispersant. But, it is found that obtainingmicrocapsules is hard without dispersant. This is because of theserious adhesive aggregation caused by the high viscosity of thepolymer solution. Thus, dispersants are required to prepare micro-capsules. Therefore, gum arabic is used as a dispersion agent for oursystem. It has been tested different concentration of gum arabicsolution as a continuous phase and found ideal MC-Xs while used 1%gum arabic solution as a continuous phase (Fig. 1). This figure showsthat the MC-Xs are spherical with narrow size distribution.

MC-Xs have been prepared by adding various amounts of Cyanex272 (0–5 g) in the dispersed phase during preparation. It is found thatquality of MC-Xs depends on the amount of Cyanex 272 in thedispersed phase during preparation. Quality of MC-Xs decreases withincreasing of the amount of Cyanex 272. It also observes that MC-Xsprepared with more than 3 g Cyanex 272 are coagulated. However,microcapsules prepared without Cyanex 272 become brittle, thussome ofmicrocapsules obtainwith broken surface (Fig. 2b). Coating onthe surface by Cyanex 272 can be conferred by the morphologicalappearance of the microcapsules prepared with and without Cyanex272 (Fig. 2).

The infrared spectrum of theMC-Xs and its component is shown inFig. 3. Curve 1 is of Cyanex 272, curve 2 is of polystyrene and curve 3 isof MC-Xs. The peaks at 816.79, 962.71, 1169.92, 1372.56, 1470.33,1663.65, 2370.92 and 2953.95 cm−1 for the spectrum of Cyanex 272

1, Cyanex 272; curve 2, Polystyrene; curve 3, microcapsules.

Fig. 5. Effect of Cyanex 272 to polystyrene ratio in dispersed phase on the extractionpercentage in batch extraction of Cu(II). Initial aqueous phase, [Cu(II)]=484 ppm, [SO4

2−]=1M,[Ac−]=0.25M; amount of microcapsules=1 g; pH=5.0; aqueous solution=10ml, (■) amountof Cyanex 272 in dispersed phase=2 g, (●) amount of PS=4 g.

Fig. 7. Effect of equilibrium pH on the extraction percentage in simultaneous batchextraction of Cu(II), Zn(II), Fe(III) and Ni(II) using MC-Xs. Initial aqueous phase: [Cu(II)]=530.78 ppm; [Zn(II)]=10.36 ppm, [Fe(III)]=15.69 ppm; [Ni(II)]=39.56 ppm; [SO4

2−]=1 M;[Ac−]=0.25 M; Solid phase: amount of Cyanex 272 in dispersed phase=2 g amount ofmicrocapsules=2 g; aqueous solution=20 ml.

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and microcapsules demonstrate that the Cyanex 272 has been suc-cessfully coated on the surface of microcapsules.

MC-Xs have beenprepared by various agitation speeds at 4 g PS and2 g Cyanex 272 in 50ml DCM, and calculated the average diameter. Theaveragediameter is plotted as a function of agitation speed in Fig. 4. It isfound that the mean diameter of the MC-Xs decreases with increasingthe agitation speed. Thus, the mean diameter of the MC-Xs can beeasily controlled by adjusting the stirring speed. Small microcapsulessize benefits mass transfer performance, but raise the pressure toohigh of the packed column (Yang et al, 2005a). Therefore, the agitationspeed of 400 rpm is used for further MC-Xs preparation experimentswhere the mean diameter is 80.02 μm tominimize the pressure in thepacked column process. Similar results have been obtained in thepreparation of polystyrene microcapsules containing Aliquot 336(Yang et al., 2005a).

The effect of Cyanex 272 andpolystyrene ratio in the dispersedphaseduring MC-Xs preparation on the percentage of extraction of Cu(II) hasbeen investigated at pH 5(initial pH, pH), is shown in Fig. 5. The expe-riments have been conducted at various amount of Cyanex 272 bykeeping constant amount of polystyrene, and vice versa. It is found thatextraction percentage of Cu(II) increases with increasing the ratio ofpolystyrene to Cyanex272up to1.5, thereafter extractiondecreaseswithincreasing the ratio. Though highest extraction percentage is achieved

Fig. 6. Effect of contact time on the percentage of extraction in simultaneous batch extractionof Cu(II), Zn(II), Fe(III) and Ni(II). Initial aqueous phase: [Cu(II)]=456.26 ppm, [Zn(II)]=11.77 ppm, [Fe(III)]=12.28 ppm, [Ni(II)]=38.12 ppm, [SO4

2−]=1 M, [Ac-]=0.25 M; amount ofCyanex 272 in dispersed phase=2 g, amount of microcapsules=2 g, pH=4.98; aqueoussolution=20 ml.

when ratioof polystyrene toCyanex272 in thedispersedphase is 1.5, thesize of MC-Xs prepared in this condition is too small which make therecovery of MC-Xs from the continuous phase is very less, whereas therecovery of MC-Xs is easy and higher when the ratio is 2 in the MC-Xspreparation. Hence, ratio of polystyrene to Cyanex 272 of 2 used forsubsequent MC-Xs preparation is adopted. Besides, extraction percen-tage of Cu(II) increases with increasing the ratio of Cyanex 272 to poly-styrene in the dispersed phase. However, extraction is not significantlyincreased above the ratio of 0.75, due to the MC-Xs coating is saturatedbyCyanex272 above the ratio of 0.75 of Cyanex272 to polystyrene in thedispersed phase. Therefore, 0.50-0.75 Cyanex 272 to polystyrene ratiohas been used in dispersed phase during themicrocapsules preparationto carry out further extraction experiments.

3.2. Batch extraction with the MC-Xs

Batch extraction studies have been carried out from sulphate-acetato medium contained both mixed and single metal using MC-Xsas a function of contact time and equilibrium pH for simultaneous

Fig. 8. Dependence of distribution ratio on equilibriumpHinsimultaneous batch extractionof Cu(II), Zn(II), Fe(III) and Ni(II) using MC-Xs. Initial aqueous phase: [Cu(II)]=530.78 ppm,[Zn(II)]=10.36 ppm, [Fe(II)]=15.69 ppm, [Ni(II)]=39.56 ppm, [SO4

2−]=1 M, [Ac-]=0.25 M;Solid phase: amount of microcapsules=2 g, amount of Cyanex 272 in dispersed phase=2 g;aqueous solution=20ml; (●)S=0.06, 0.67 and 2.22; I=0.19, -2.19 and -10.66; (■)S=0.2,1.23and 0; I=0.45, -2.14 and 4.01; (ҳ)S=0.59, 0.1.12 and 0; I=0.16, -1.31 and 4.19; (▲)S=0.07;I=1.44.

Fig. 9. Adsorption isotherm of Cu(II) onto the MC-Xs and effect of amount of MC-Xs on theextractionpercentage insinglemetal batchextractionofCu(II). Initial aqueousphase:[SO4

2−]=1 M, [Ac−]=0.25 M; amount of Cyanex 272 in dispersed phase=2 g; pH=5.0; aqueoussolution=10 ml, (●) [Cu(II)]=484 ppm , (■) amount of microcapsules=1 g.

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extraction, and amount of MC-Xs and Cu(II) ions concentration in theaqueous phase for the single metal of the Cu(II) extraction.

The effect of contact time on the percentage of extraction for thesimultaneous batch extraction of Cu(II), Zn(II), Fe(III), and Ni(II) using

Fig. 10. Effect of simultaneousmetal ions uptake of Cu(II), Zn(II), Fe(III) andNi(II) by packed colu15.69 ppm, [Ni(II)]=39.56 ppm, [SO4

2−]=1 M, [Ac−]=0.25 M; amount of Cyanex 272 in dispe(b), pH=3.0; (c), pH=4.0 and (d), pH=5.0.

MC-Xs is shown in Fig. 6. For the extraction of Cu(II), it is found thatthe percentage of extraction increases with increasing the contact timeup to 10min after that the curve level off. For the extraction of Zn(II) andFe(III), almost 100% extraction is achieved before 5 min of equilibratingtime. However, Ni(II) is not extracted in this experimental condition. Insubsequent experiments, 30 min of contact time has been adopted toensure complete equilibration.

The effect of equilibrium pH on the extraction percentage forthe simultaneous batch extraction of Cu(II), Zn(II), Fe(III) and Ni(III)from sulphate-acetato medium using MC-Xs is shown in Fig. 7. Theresults show that the extraction percentage of metal ions dependson the equilibrium pH. The extraction of Zn(II) and Fe(III) are started atequilibrium pH 1.0 and reached almost 100% at equilibrium pH 4.0.Under this experimental condition (equilibrium pH 1.0–4.0) theextraction of Cu(II) is about 18% and Ni(II) is zero. The extraction ofCu(II) is started at equilibrium pH 1.0 and reached almost 100%at equilibrium pH 6.3. The extraction of Ni(II) is started at equilibriumpH 5.4 and reached about 22% at equilibrium pH 6.71. The pH0.5 valueis a value where 50% metal ion is extracted. The greater the ΔpH0.5

value between two metals, the higher the selectivity of the extrac-tant is showed, so that a better separation efficiency is obtained.The pH0.5 values of 4.75, 2.5, and 1.5 are obtained for Cu(II), Zn(II), andFe(III) extraction, respectively, suggests the efficiency of separationwith the order: Fe(III)NZn(II) over Cu(II), whereas separationefficiency of Zn(II) over Fe(III) is quite low. However, the pH0.5 forthe nickel extraction can not be determined since extraction percent-age is reached to the plateau when extraction of Ni(II) is about 20% atequilibrium pH 5.4.

mnusingMC-Xs. Initial aqueous phase: [Cu(II)]=530.78 ppm, [Zn(II)]=10.36 ppm, [Fe(II)]=rsed phase=3 g, amount of microcapsules=3 g, aqueous solution=100 ml; (a), pH=2.0;

Fig. 12. Effect of sulphuric acid concentration on the stripping percentage of Cu(II), Zn(II)and Fe(III) from loadedMC-Xs. In loadedMC-Xs, [Cu(II)]=411.78 ppm, [Zn(II)]=13.73 ppm;[Fe(II)]=12.28 ppm.

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The values of K2 and Kd for Cyanex 272 in kerosene-0.10M(N+,H+)Cl−

mediumare found to be5.52×10−4 and53, respectively,means that verylittle amountof Cyanex272 is soluble in the aqueous phase (Biswaset al.,2005). In the present study, Cyanex 272 coated onto the polystyrenemicrocapsules is used for the extraction. Therefore, solubility of Cyanex272 into the aqueous phase is likely to be negligible which does notaffect significantly to the extraction.

The plot of log D vs. equilibrium pH is given in Fig. 8. For theextraction of Cu (II), it is found that the distribution ratio increaseswith increasing equilibrium pH. But below pH 4.0 region, the increa-sing of distribution ratio with increasing pH is negligible. The slopevalues are 0.67, and 2.2 at the equilibrium pH range of 4.0–5.44, and5.44–6.71, respectively. These indicate that no H+ is liberated bellowpH 4.0 region, a mechanism of one H+ liberation is occurred with themechanism of no H+ liberation at the equilibrium pH range of 4.0–5.44, and two H+ are liberated at the equilibrium pH range of 5.44–6.71 during the extraction of Cu(II). For the extraction of Zn (II), it isfound that the distribution ratio is independent at lower pH region(1.0–2.0). Above pH 2, the distribution ratio increases with increasingequilibrium pH up to 4.97, gives the value of slope 1.23 and thereafterthe line level off. This indicates that in this pH range, one H+ ion isliberated during the extraction of Zn(II). For the extraction of Fe(III), itis found that the distribution ratio increases with increasingequilibrium pH up to pH 4.97 and thereafter there is no significantincrease is observed. The slope is 0.59 below pH 3.0 and 1.12 in therange of pH 3.0–4.97, indicates that one H+ ion liberation mechanismprocess is occurredwith the no H+ ion liberationmechanism belowpH3.0 and one H+ is liberated at pH range of 3.0–4.97 for Fe(III)extraction. For the extraction of Ni(II), increasing of the distributionratio with increasing pH is negligible at the equilibrium pH rang of5.44-6.71. However, it can be noted that below pH 5.44, Ni(II) extrac-tion is nil.

Copper adsorption isotherm is given in Fig. 9. The adsorption ofcopper onto the MC-Xs increases with the increasing of initial Cu(II)ion concentration in the aqueous phase and reached to maximum at2.18 mmol/l Cu(II)(unadsorbed). Saturation of MC-Xs may be occurredwhen the concentration of unabsorbed Cu((II) in the aqueous phasebecomes 2.18mmol/l. Maximum loading capacity of MC-Xs by Cu(II) isdetermined to be 0.055 mmol/g (3.50 mg/g). The maximum loadingcapacity of Cu(II)-ion imprinted polymers prepared using dual-ligandreagent for Cu(II) has been found to be 18.96 mg/g.(Zhai et al., 2007).The higher result has been obtained because of using dual ligandreagents in the imprinted polymer.

Fig. 11. Effect of pH on the percentage of simultaneous metal ions uptake. Initial aqueousphase, [Cu(II)]=530.78 ppm, [Zn(II)]=10.36 ppm, [Fe(II)]=15.69 ppm, [Ni(II)]=39.56 ppm,[SO4

2−]=1 M, [Ac−]=0.25 M; amount of Cyanex 272=3 g; amount of microcapsules=3 g,aqueous solution=100 ml.

Variation of MC-Xs on the extraction percentage of Cu(II) is alsogiven in Fig. 9. It is found that the extraction percentage of Cu (II)increases as the amount of MC-Xs increased. Almost 87% of extractionis found when the MC-Xs amount is 3.0 g. From the nature of theextraction curve, it is seen that the degree of increasing is higher atlower amountofMC-Xs region (b1.5 g) than that of at higher amount ofMC-Xs region (N1.5 g). This is happened due to the decreases of Cu(II)concentration in the aqueous phase for higher extraction of Cu(II) withhigher amount of MC-Xs.

3.3. Simultaneous metal ions uptake by the packed column

Effects of metal ions uptake have been evaluated using packedcolumn experiments at different pH (2–5), as shown in Fig. 10. Withinthis pH range, no Ni(II) uptake is observed. In the microcapsules,uptake rate of Cu(II) increment is higher than that of Zn(II) and Fe(III)at pH 2 to 5. It is observed that uptake becomes higher with increasingpH, while separation efficiency decreases.

Percentage of metal ions uptake after passing through 100 ml ofmixed solution, containing531.24ppmCu(II), 9.81ppmZn(II),16.20ppmFe(III) and 38.74 ppm Ni(II) at different pH is given in Fig. 11. It is foundthat the percentage of Cu(II), Zn(II) and Fe(III) uptake increases withincreasing of pH and becomes 100% above pH 3 for Zn(II) and Fe(III)uptake, and about 8% at pH 3 for Cu(II) uptake. Therefore copper can beselectively recovered at pH 5 with little loses by repeated passing thesolution through the microcapsules packed column, after separating ofZn(II) and Fe(III) at around pH 3.

Fig.13. Theeffectof repeatedprocessingon theextractionpercentage. Initial aqueousphase:[Cu(II)]=1038.98 ppm, [SO4

2−]=1 M, [Ac−]=0.25 M, pH=5.0; Solid phase: amount of Cyanex272 in dispersed phase=2 g; amount of microcapsules=3 g; aqueous solution=20 ml.

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3.4. Effect of H2SO4 concentration in stripping of metal ions from loadedmicrocapsules

The effect of sulfuric acid concentrations on the stripping percentageof metal ions is shown in Fig.12. Stripping of Cu(II), Zn(II), and Fe(III) hasbeen carried out from the metal ions loaded MC-Xs at an solid phase toliquid ratio (S:L) of 1:10. It is found that the stripping percentge of Cu(II)

Fig. 14. Process for separation of Cu(II), Ni(II) and Zn(

decreases with increasing the acid concentration in strip solution above0.5 M H2SO4. Stripping percentage of Zn(II) decreases with increasingacid concentration in strip solution. Stripping percentage of Fe(III)increases with increasing acid concentration in the strip solution up to0.5 M, and decreases thereafter. Almolst 100% stripping is obtained at0.1M and 0.5MH2SO4 solution for Cu(II), 0.1MH2SO4 solution for Zn(II)and 0.5MH2SO4 solution for Fe(III). Deionizedwater has also been used

II) from sulphate leach liquor of PCB using MC-X.

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as a stripping solution to strip Cu(II), Zn(II) and Fe(III) from the loadedMC-Xs and obatained 4.1% Cu(II) and 10.6% Zn(II) stripped whereasstripping of Fe(III) is nil.

3.5. Regeneration of the microcapsules

The regeneration of the MC-Xs following the extraction-strippingprocesses has been investigated through the batch extraction system.AtfirstMC-Xs are loadedwith Cu(II) fromaqueous solution of 1039 ppmCu(II). The Cu(II) is then stripped from loaded MC-Xs using 0.1 M H2SO4

solution. TheseMC-Xs, soobtained, arewashedwithdeionizedwater forthree times and then reused for repeated processing. Percentage extrac-tion of Cu(II) obtained by repeated processing of MC-Xs, is shown inFig. 13. It is found that the extraction percentage increases at 1st threestages, and then decreases thereafter. This is due to the MC-Xs surfacemodification occurred during the 1st three extraction-stripping stageswhich enhance the percentage of extraction. After three stages, theextraction performance of MC-Xs decreases with increasing theextraction-stripping stage, this is occurred due to the deterioration ofCyanex 272 coating on the surface of MC-Xs. The results indicate thattheMC-Xsdohave enough resistance to acid solution andhave sufficientstability for metal ions extraction. It has been found from the earlierliteratures that three repeated processing can prove the possible reus-ability of microcapsules in process. (Yang et al., 2004; Nishihama et al.,2002).

3.6. Separation and recovery of metals from the sulphate leach liquor ofPCB

A leach liquor of PCB containing 501.94 ppm Cu(II), 16.41 ppm Zn(II)and 14.23ppmNi(II), obtained from leachingoperationof printed circuitboardhas beenused to carryout the solidphase extractionprocessusingMC-Xs is given in Fig. 14. A seven stages solid phase extraction processhas been carried with the S:L ratio of 1:10. It can be shown in the flowchart that selective recovery of Cu(II), Ni(II) and Zn(II) is found to be99.22%, 100% and 77.57%, respectively.

4. Conclusions

Polystyrene MC-Xs have been prepared and found Cyanex 272 hasbeen coated successfully. Batch extraction of Cu(II)withpreparedMC-Xsis found be dependent on the ratio of Cyanex 272 to polystyrene in thedispersed phase during preparation, amount of MC-Xs and Cu(II)concentration in the aqueous phase. Simultaneous batch extraction ofCu(II), Zn(II), Fe(III) and Ni(II) with varying pH shows the possibleseparation of these metals. Packed column operation for mixed metalsuptake shows that separation and uptake is dependant on pH. Strippingof Cu(II), Zn(II), Fe(III) and Ni(II) from the loaded MC-Xs has been foundto be 100% using 0.1 and 0.5 M H2SO4 solution for Cu(II), 0.1 M H2SO4

solution for Zn(II) and 0.5 M H2SO4 solution for Fe(III). Regenerationstudies of MC-Xs indicate thatMC-Xs do have enough resistance to acidsolution and have sufficient stability for metal ions extraction. Selectiverecovery of Cu(II), Zn(II) and Ni(II) is achieved to be 99.22%, 100% and77.57%, respectively, from the leach liquor of PCB using MC-Xs.

Acknowledgement

One of authors expresses his sincere thanks to the Malaysia HigherEducation Ministry for providing the financial support through FRGSgrant during his MSc course.

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