Characterization of chalcopyrite leach residues produced during medium temperature leaching of chalcopyrite

In order to determine the distribution of unrecovered copper among different phases or fractions, a systematic characterization of 13 leach residues generated during the processing of a variety of chalcopyrite concentrates under CESL conditions was carried out. Ferrihydrite and crystalline iron oxide content of the residue samples was determined by a two stage sequential extraction method. In different residue samples, the ferrihydrite content was found to vary between 2 to 46. In all the residue samples, hematite and elemental sulfur were the principal mineral phases. Sequential extraction studies showed that copper is associated with both ferrihydrite and crystalline iron oxyhydroxide phases of the residues, and the amount of copper in the residues increased with increase in its ferrihydrite content. There was a five fold increase in the amount of copper associated with amorphous iron phases as compared to the crystalline phases. Thus the development of process conditions which will minimize the ferrihydrite and maximize the hematite formation may help in minimizing the loss of copper to the residue.