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.