Investigation of the kinetics of pyrite oxidation by hydrogen peroxide in hydrochloric acid solutions

The kinetics of pyrite oxidation by hydrogen peroxide in hydrochloric acid solutions were investigated. The effects of stirring, temperature, particle size as well as hydrogen peroxide and hydrochloric acid concentrations were studied. The effects of H+ and Cl− additions were also examined. The oxidation kinetics were found to follow a shrinking core model, with the surface chemical reaction as the rate-controlling step. This is in accord with an activation energy of 65 kJ/mol and a linear relationship between the rate constant and the reciprocal of the particle radius. The reaction order with respect to hydrogen peroxide concentration was found to be 1.32. The rate of pyrite oxidation was found to decrease as the hydrochloric acid concentration increases, most likely owing to the adsorption of chloride ions onto the surface of the pyrite particles. H+ ions had no effect on the rate, whereas Cl− ions had an effect similar to that of the hydrochloric acid.