Selective extraction and separation of Cu(II), Zn(II), Ni(II) and Fe(III) from the leach liquor of Printed Circuit Board using Cyanex 272 coated microcapsules
Md. Sohrab, Hossain
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The main purpose of this study was to recover and extract Cu(II) in presence of Zn(II), Fe(III) and Ni(II) from the leach liquor of Printed Circuit Board (PCB) using polystyrene microcapsules coated with Cyanex 272 (MCXs). MC-Xs were prepared following the solvent evaporation method at different conditions, and optimization conditions for the preparation of MC-Xs were evaluated. At first, the liquid-liquid extraction behavior of Cu(II) from acidic sulphate-acetate medium by Cyanex 272 diluted in hexane was investigated as a function of equilibrium pH, aqueous phase concentration of Cu2+, and Ac − Ο24 S -, and Cyanex 272 concentration in the organic phase. Results showed that the extraction performance was highly dependent on pH, Cyanex 272 concentration and Ac- concentration and suggested that the extracted species is [Cu(HA2)(Ac).2HA]. Batch extraction studies were carried out from the sulphate-acetate medium for both simultaneously and single metal extraction system using MC-Xs as a function of contact time and equilibrium pH for simultaneous extraction, and amount of MC-Xs, Cyanex 272 to Polystyrene ratio (Cyanex 272/PS) and PS to Cyanex 272 ratio (PS/Cyanex 272) in dispersed phase and Cu(II) ion concentration in aqueous phase for the single metal extraction. It was observed that the pH value of the feed solution played an important role for successful separation of the metal ions. Simultaneous metal ions uptake and separation efficiency of Cu(II), Zn(II), Fe(III) and Ni(II) were investigated using MC-Xs with packed column at different pH (2-5), illustrating that within this pH range, Ni(II) uptake was nil, almost 100% at pH 4 for the Zn(II) and Fe(III), whereas Cu(II) uptake was 26% at pH 5. The separation efficiency of Cu(II) was higher over other metal ions. But, the separation efficiency Zn(II) over Fe(III) was quite low. Stripping of Cu(II), Zn(II) and Fe(III) was carried out from the loaded MC-Xs using different concentration of sulphuric acid solution at solid to liquid ratio (S:L) of 1:10 showing that almost 100% stripping was obtained at 0.1 M H2SO4 solution for the Cu(II) and Zn(II) and 0.5 M H2SO4 solution for the Fe(III). The regeneration experiment showed that the microcapsules have sufficient stability for the metal ions extraction. Factorial design and Yates’ analysis of experiment was carried out for the optimization and evaluation of the main effects and interactions of the Cu(II) extraction factors in the presence of Zn(II), Fe(III) and Ni(II) using MC-Xs at two different experimental conditions. Factorial design and Yates’ analysis was also carried out in order to determine the optimum condition of stripping factor for the stripping of Cu(II) from loaded MC-Xs using sulphuric acid solution.). Finally, A complete process for the separation and recovery of Cu(II), Zn(II), Fe(III) and Ni(II) was carried out from the leach liquor of PCB following the batch extraction process based on the batch extraction using MC-Xs. The process showed the selective recovery of 99.22%, 77.57% and almost 100% for the Cu(II), Zn(II) and Ni(II), respectively.