Liquid-liquid extraction studies on Zn(II) and Cd(II) using phosphonium ionic liquid (Cyphos IL 104) and recovery of zinc from zinc plating mud

The present study describes partition behavior of Zn(II) and Cd(II) from acidic chloride medium using Cyphos IL 104 [trihexyl(tetradecyl)phosphonium bis 2,4,4-(trimethylpentyl)phosphinate] diluted in toluene. Factors affecting the extraction such as concentration of extractant and H+, nature of diluent, equilibration time and temperature have been evaluated. Loading and regeneration capacity along with the stability of extractant have also been assessed. The data obtained have been used to determine the stoichiometry of the extracted complex that was found to be 1:2 i.e., two moles of extractant per mole of Zn(II)/Cd(II). Effect of temperature on distribution suggested the process to be exothermic and spontaneous with ΔG° values of −39.63 ± 4.27 kJ/mol and −65.91 ± 0.4 kJ/mol for zinc and cadmium, respectively. The extraction behavior of associated metal ions namely Cu(II), Ni(II), Co(II), Fe(II)/(III) and Mn(II) has been studied and conditions for their separation from zinc and cadmium have been optimized. Based on the extraction data a separation scheme was designed and applied to a synthetic multi element mixture for the recovery of zinc and cadmium. The potential of the extractant for the recovery of zinc from zinc plating mud is assessed.