Effect of solution composition on the optimum redox potential for chalcopyrite leaching in sulfuric acid solutions

The leaching rate of chalcopyrite (CuFeS2) by Fe3+ in H2SO4 solutions depends on the redox potential determined by the Fe3+/Fe2+ concentration ratio, and there is a maximum leaching rate at an optimum redox potential. The present study investigated the effects of solution composition on the optimum redox potential by electrochemical measurements using a CuFeS2 electrode and electrolyte solutions containing 0.01–1 kmol m− 3 of H2SO4, Fe2+, and Cu2+ at 298 K in nitrogen.Anodic-polarization curves of the CuFeS2 electrode showed that there was a current peak on the curves in the presence of Cu2+ and Fe2+, corresponding to the maximum leaching rate. The redox potential of the peak increased markedly with increasing Cu2+ concentration, while it was little affected by the H2SO4 and Fe2+ concentrations. These results agree with the results of leaching experiments reported previously, and indicate that the optimum redox potential for chalcopyrite leaching is a function of the Cu2+ concentration. An empirical equation for the optimum redox potential for CuFeS2 leaching is proposed.