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

The use of seawater in heap leaching of secondary copper sulfide minerals is a feasible alternative to freshwater in regions with limited freshwater supply. Seawater contains high concentrations of chloride ions that facilitate the formation of cupric/cuprous chloride complexes. The cupric ions formed can serve as an oxidizing agent for chalcocite oxidation. Even though copper leaching in chloride media has been well studied, most of the kinetics data were collected under uncontrolled leaching conditions. In this study, we modelled chalcocite leaching kinetics in chloride media using leaching data collected under fully-controlled pH and solution potential. Specifically, we carried out leaching tests with high-purity chalcocite sample in jacketed reactors to quantify the effects of chloride concentration, cupric concentration, particle size, and temperature on the copper extraction rate. The experimental results show that increases in chloride concentration and temperature remarkably enhanced the leaching rate; chalcocite leaching was insensitive to the initial cupric chloride concentration. Using the leaching data collected, we derived two individual kinetic models to describe the first and second stage of chalcocite leaching. This study provides fundamental kinetic models for predicting the performance of chalcocite leaching in cupric chloride for heap leach operations that intend to use seawater. •Chalcocite leaching in cupric chloride media occurred in two stages.•Kinetics models were obtained for each stage of chalcocite leaching.•First stage leaching was controlled by chloride diffusion through the liquid film.•Second stage leaching was controlled by chemical reaction process.•Second stage leaching was sensitive to temperature with a high activation energy.