Extraction of Valuable Metals from High-Iron Zinc Sulfide Concentrate by Reductive Leaching

Abstract

This study was conducted as part of the development of a new process to recover valuable metals of zinc, copper and indium from high-iron zinc sulfide concentrate (HIZSC) by the reductive leaching of high-iron zinc neutral leaching residue (HIZNLR) with zinc concentrate precipitation of copper with iron powder, neutralization of free sulfuric acid with zinc calcine, precipitation of indium with zinc powder and hematite precipitation to reject iron. Among these stages, reductive leaching is the crucial step, which makes that valuable metals in the materials can be effectively leached and ferric iron in the solution is reduced to ferrous iron. The reductive leachate enables copper, indium and iron separation from the solution in the subsequent process. The results show that by increasing the sulfuric acid concentration, HIZSC addition and prolonging the reaction time, the leaching efficiency of zinc, copper, indium and iron in the sample materials was significantly increased. The maximum metal-leaching efficiency was obtained; 84.3% of the iron was in its soluble ferrous state, and zinc ferrite in the HIZNLR was almost entirely dissolved under the experimental conditions of an H2SO4-to-HIZNLR mass ratio of 1.6, a liquid-to-solid ratio of 11.34 mL/g, a temperature of 90°C, an HIZSC addition of 1.05 times of the stoichiometric amount and a reaction time of 5 h.