Heavy metals in the environment. Part IV: An investigation into the solubility of metal chlorides in HCl-saturated solutions and the recycling of high-aluminium zinc residues in the zinc chloride process

An investigation into the use of high-copper zinc residues in the production of zinc chloride solution and the recovery of copper, as anhydrous copper(II) chloride, is reported. The process developed involves leaching of the high-copper zinc residues with concentrated hydrochloric acid to dissolve the zinc content leaving a residue which has a high copper content. Any copper dissolved in the primary leach is removed by electrodeposition to give a zinc chloride solution suitable for industrial use. The solid residue from the initial leach is trated with chlorine gas to solubilise the copper present, giving a solution of copper(II) chloride. This solution is purified to remove Zn²⁺ and Pb²⁺ by anion-exchange and Fe³⁺ and Al³⁺ by hydrolysis. The purified solution can then be converted to anhydrous copper(II) chloride with a purity of 99·6%.