Abstract

In chloride leaching of copper sulfide ores, dissolution of sulfide minerals occurs under the oxidative action of both ferric and cupric chloride species. Both oxidants are continuously regenerated by oxidation of ferrous and cuprous species with oxygen, which acts as a final electron acceptor. The rate of copper dissolution is very dependent on the electrochemical mechanisms of oxidation of copper sulfide species by these two oxidants. However, in an ore particle copper sulfide minerals are embedded in a matrix of gangue species that endure physical and chemical transformations during leaching. These transformations can enhance or inhibit the diffusion of reagents inside the ore particle, becoming a factor controlling the rate of copper dissolution. The present work reports some findings obtained in our laboratories of research of some fundamental aspects of chloride leaching: the kinetics of the simultaneous oxidation of ferrous and cuprous ion, which compete for the added oxygen; the kinetics and stoichiometry of leaching of chalcopyrite with ferric and cupric ions, which compete for electrons released from the sulfides; the role of transformations of gangue species on copper leaching kinetics and the influence of chloride ions presence. The relevance of these findings on the implementation of chloride leaching is discussed