The Influence of Impurity Monovalent Cations Adsorption on Reconstructed Chalcopyrite (001)-S Surface in Leaching Process

Hydrometallurgical processing of chalcopyrite is hindered predominantly due to the passivation layers formed on the chalcopyrite surface. However, the effects of impurity cations released from the gangue are not yet well understood. Density functional theory (DFT) calculations were carried out to investigate monovalent cations of Na+ and K+ on chalcopyrite (001)-S surface using Materials Studio. The results show that the 3d orbital of Fe and 3p orbital of S predominantly contribute to their activities during chalcopyrite oxidation and dissolution processes. In addition, SO42− is more likely to be adsorbed on one Fe site in the presence of Na+, while it is preferentially adsorbed on two Fe sites in the presence of K+. However, the adsorption of both Na2SO4 and K2SO4 on the chalcopyrite (001)-S surface contributes to the breakage of S–S bonds, indicating that the impurity cations of Na+ and K+ are beneficial to chalcopyrite leaching in a sulfuric environment. The adsorption energy and partial density of states (PDOS) analyses further indicate that the adsorption of Na2SO4 on chalcopyrite (001)-S surface is favored in both -BB (bidentate binuclear) and -BM (bidentate mononuclear) modes, compared to the adsorption of K2SO4.