Comprehensive Utilization of Copper Slag in a Pyro-Hydrometallurgical Process for Iron Phase Reconstruction and Valuable Metals Recovery

Abstract

Copper slag is a major waste produced in pyrometallurgical plants during the smelting and converting operations and has caused heavy environmental contamination. A pyro-hydrometallurgical process for the treatment of copper slag has been developed to accomplish recovery of nickel, cobalt, and copper and reuse of iron source. It was proved that the slag phase was reconstructed by sulfation-sulfate decomposition roasting followed by water leaching, over 95% iron existing as hematite was transferred into residues which were subsequently to produce iron concentrates. Nickel-cobalt mixed hydroxide precipitate was obtained from liquors after the separations of copper, iron, and aluminum step by step. By adding concentrated HCl to re-dissolve the precipitate, then cobalt was extracted over nickel using extraction agent N235 and the raffinate was subsequently crystallized to produce nickel chloride by introducing HCl gas. On the basis of the optimum conditions from a laboratory-scale test, about 70% of copper, nickel, and cobalt were recovered as respective product, indicating the feasibility of the process.