Electrochemical Investigation of the Mechanism of Aqueous Oxidation of Pyrite by Oxygen

The aqueous oxidation of pyrite in air-equilibrated HCl solutions was investigated at various temperatures (30 and 40 oC), pH values (2 to 5) and sulfate concentrations (0.001 to 0.5 M). It was found that the oxidation current densities (iox) increase when the temperature and sulfate concentration increase. The rate dependence on sulfate concentration indicates that during the oxidative dissolution of pyrite an activated complex of ionic nature is formed on mineral surface, and sulfate is not involved in the rate determining step of pyrite oxidative dissolution.