Modelling the kinetics of chalcocite leaching in acidified ferric chloride media under fully controlled pH and potential

The availability and efficiency of water use is now a major concern for the global minerals industry. Seawater is a potential water source for mineral beneficiation and metal extraction processes. With a focus on using seawater for heap leaching, we investigated and modelled the kinetics of chalcocite leaching with ferric chloride. To this end, a series of leaching tests were carried out in jacketed reactors under fully controlled pH and solution potential at ambient temperature using pure chalcocite as the model mineral. The effects of key parameters, including chloride concentration, ferric concentration, ferrous concentration, ferric/ferrous ratio, temperature, and particle size, were determined on the first and second stages of chalcocite leaching. The first stage leaching rate was sensitive to ferric concentration, temperature, and particle size, whereas it was insensitive to ferrous and chloride concentration. The second stage leaching rate was independent of chloride concentration but sensitive to solution potential, temperature, and particle size. A distinct kinetic model was obtained for each stage of chalcocite leaching. Based on the kinetic models, it is concluded that the leaching rate of the first stage was controlled by the diffusion of ferric ions, while a mixed kinetics governed the second stage kinetics, i.e., a combination of mineral decomposition and ferric reduction. The findings of this research are important for prediction of copper extraction performance when seawater is being applied to heap leaching of chalcocite to replace fresh water.