The influence of Ag+ cation on elemental sulfur passive layer and adsorption behavior of chalcopyrite toward Fe3+ and Fe2+ ions: Insights from DFT calculations and molecular dynamics simulations

Abstract

It is commonly understood that elemental sulfur forms a passive layer on the chalcopyrite surface, preventing it from leaching. The silver cation (Ag+) induces the semiconducting property of the passive layer by generating Ag2S species or defects sites. In the present work, the influence of Ag+ cation on the elemental sulfur passive layer is investigated by density functional theory (DFT) calculations and molecular dynamics (MD) simulations. According to the DFT calculations, the passive layer is non-conductive and prevents Fe3+ ion interaction with the chalcopyrite surface. After the adsorption of Ag + cation and formation of Ag2S species, however, the layer becomes reactive, and electrons transfer between the surface and the Fe3+ ion. Studies of the thermodynamic and electronic properties suggest that the defective surface has a smaller energy gap and that its interaction with the Fe3+ is spontaneous. According to the MD simulations, the defective surface has the lowest shear modulus.