Separation of Co(II) from Zinc Plant Acidic Thiocyanate Leach Solutions Containing Co(II) and Ni(II) by Solvent Extraction Using Trioctylamine in Toluene

In this study, a zinc plant purification cake (CINKUR Co. Turkey) was leached with sulphuric acid and an acidic leach solution containing Zn(II), Fe(II), Pb(II), Al(III), Cu(II), Co(II) and Ni(II) ions was obtained. After purification, ammonium thiocyanate and water were added to the remaining leach solution containing Co(II) and Ni(II) ions to adjust the chemical media and ion concentration. The acidic thiocyanate leach solutions were used in solvent extraction experiments. The various parameters were studied to determine the extraction and striping behaviour of Co(II). These parameters were diluent type, feed solution pH, extractant concentration, mixing speed, phase ratio, stripping solution type and concentration and etc. Under optimum extraction conditions, the maximum extraction efficiency (99.9 %) was achieved when using 5.0 %(v/v) TOA in toluene within 5 min. The extracted Co(II) was stripped effectively from the organic phase using 5.0 M NH3 solution.