A fundamental DFT study of chalcopyrite surface evolution due to impurity divalent ions during leaching process

Chalcopyrite leaching process is hindered predominantly due to the passivation layers formed on its surface. The impurity salts normally present in the leaching systems may influence chalcopyrite leaching process. In this work, density functional theory (DFT) was carried out to investigate the influence of Mg2+ and Ca2+ on chalcopyrite (0 0 1)-S surface using Materials Studio. The results indicated that the presence of CaSO4 contributed to the breakage of S-S bonds on chalcopyrite (0 0 1)-S surface. Although Ca2+ was not found to bond with any of the S atoms derived from broken S22− bond, a stable structure of Ca-SO4-Fe was formed. Similarly, the adsorption of MgSO4 on chalcopyrite (0 0 1)-S surface contributed to the breakage of S22− bond, forming a complex and stable structure of S-Mg-SO4-Fe as new passivation layers due to the bonding effects between Mg2+ and a S atom from the broken S22− bond. The formation of these new structures covered on chalcopyrite (0 0 1)-S surface, further reducing chalcopyrite leaching rates. This study, therefore for the first time, reveals the influencing mechanisms of Mg2+ and Ca2+ sulfates on chalcopyrite leaching at an atomic level.