Copper extraction from chloride solutions by evaporation and reduction with hydrogen

Abstract

In order to obtain a metallic product from the CuCl2-HCl solution purified by anion-exchange separation, the straightforward method of evaporation to dryness and reduction with H2 was investigated. Thermodynamic study of the probable reactions in the Cu-Cl-H-O system pointed out the feasibility of the direct reduction of CuCl2. In order to find out the practical reduction rates and effective recoveries, the process was tested under different conditions. The first step of reduction, which results in the conversion of CuCl2 to CuCl, is readily executable at temperatures slightly below the CuCl-CuCl2 eutectic point. The second step, which results in the metallic product, requires higher temperatures, though safely below the melting point of CuCl. Kinetic analysis of the critical second step provided an activation energy of 138 kJ mol-1 which could be interpreted in terms of a chemical reaction dominated mixed mechanism.