Coupled Dissolution with Reprecipitation (CDR) Reactions and Their Impact on Copper Sulphide Mineral Surface Area and Dissolution Rates

Copper is a critical metal required for green energy technologies such as wind turbines and solar cells. However, copper supply is limited by copper recovery from primary copper sulphides (e.g., chalcopyrite-CuFeS₂) due to passivating reaction products. Therefore, this study examined surface ‘passivation’ of primary copper sulphide minerals undergoing coupled dissolution with reprecipitation (CDR) reactions and the associated mineral surface changes in acidic and chloride-rich lixiviants (FeCl₃-only, AlCl₃-rich, NaCl-rich, and CaCl₂-rich lixiviants). Acidic FeCl₃-only, NaCl-rich, and CaCl₂-rich lixiviants resulted in only bornite dissolution and the formation of a residual Cu-S phase and Fe-SO₄ phase on the chalcopyrite surface. In contrast, leaching with the AlCl₃-rich lixiviant resulted in both chalcopyrite and bornite dissolution with limited hydrolysis of Fe³⁺ to Fe-hydroxy sulphates and minimal Fe³⁺ flux inhibition to the copper sulphide minerals surface due to the ion exchange mechanism between Al³⁺ and Fe³⁺. Further, there was preferential formation of an Al-SO₄ phase at consistently high Eh and acidity, thereby a high availability of Fe³⁺ in solution for enhanced copper dissolution from both bornite and chalcopyrite. These findings could serve as a reference for coupled dissolution with reprecipitation reactions during copper sulphide leaching, offering a pathway to more efficient and sustainable copper extraction from low-grade ores.