The kinetics of leaching chalcocite in a

This study investigates the kinetics of leaching chalcocite in acidic oxygenated sulphate-chloride solutions, focusing on the leaching process which occurs in two distinct stages. The primary objective was to understand the mechanisms involved in the copper extraction process. Synthetic chalcocite samples were utilized, and their leaching behavior was analyzed. The first stage of the leaching process is characterized by the rapid diffusion of cuprous ions to the surface where they are oxidized to a divalent state, resulting in copper-deficient intermediates, as confirmed through X-ray diffraction. The diffusion of oxygen through the liquid boundary layer was identified as the rate-limiting factor, with an activation energy of 33.5 kJ/mole observed for this stage. The second stage progresses more slowly and can be modeled by the shrinking core theory, where covellite is surrounded by elemental sulphur. Here, the copper leaching rate is initially hindered by surface reactions, transitioning to limitations imposed by diffusion processes as leaching progresses, with an apparent activation energy of 69.0 kJ/mole. Additionally, the presence of chloride ions plays a crucial role in preventing the formation of a passivating sulphur layer, thereby enhancing the leaching efficiency.