Cu and Fe chalcopyrite leach activation energies and the effect of added Fe3+

XPS examination of leached chalcopyrite showed that the surface concentration of polysulfide and sulfate was significantly increased when Fe3+ was added to the leach liquor. Complementary SEM analysis revealed the surface features of chalcopyrite, most likely due to the nature of the polysulfide formed, are subtly different with greater surface roughness upon leaching in the absence of added Fe3+ as compared to a continuous smooth surface layer formed in the presence of added Fe3+. These observations suggest that the effect of Fe3+ addition on the rate of leaching is not due to the change in the chemical reaction controlled mechanism but due to a change in the available surface area for reaction.