Leaching studies of chalcopyrite and sphalerite with hypochlorous acid

Laboratory studies have been conducted on the leaching of chalcopyrite and sphalerite with hypochlorous acid. The effects of stirring speed, temperature, pH, and hypochlorous acid concentration on the leaching rates have been determined. In addition, the leaching mechanisms have been resolved by analyzing the concentrations of the reaction products. It has been found that more than 90 pct extraction of both chalcopyrite and sphalerite can be achieved in one hour using less than 0.3 molar hypochlorous acid at room temperature. The primary leach products of chalcopyrite and sphalerite were sulfur and sulfate in the mole ratios of 1 to 1 and 2 to 1, respectively. A mixed kinetic model was applied to explain the leaching rates of chalcopyrite while a diffusion model was applied to explain the leaching rates of sphalerite. The mixed kinetic model involved steady-state diffusion of hypochlorous acid through the sulfur layer by a chemical reaction at the reaction interface. Good agreement between these models and the leaching rates of both minerals was obtained.