Separation of copper and indium from zinc hydrometallurgy solution

Abstract The separation and recovery of copper and indium from a solution arising from the reductive leaching of a zinc leaching residue was studied. Copper was enriched into a copper precipitate produced by iron powder precipitation; indium was hydrolyzed and enriched into a gypsum indium precipitate produced by limestone adjustment of pH. Separation and recovery of both copper and indium were achieved. The results showed that precipitation of copper(II) and arsenic(III) as Cu 2 O and Cu 3 As is thermodynamically feasible by adding iron powder to the reductive leach of a zinc leaching residue. Increasing the iron powder addition and reaction temperature promoted the formation of Cu 2 O and Cu 3 As. In the process of neutralizing and precipitating indium by adjusting the pH using limestone, indium was mainly concentrated in the precipitate by hydrolytic precipitation. The pH of the neutralization endpoint plays a decisive role in this hydrolytic enrichment. The extent of indium precipitation exceeded 98%, and the indium content of the precipitate reached 3.6 kg/t. Addition of limestone balances the acid across the entire production process. The main phase in the gypsum indium precipitate was CaSO 4 ·2H 2 O, the stable properties of which create favorable conditions for the recovery of indium in subsequent steps.