DFT simulation of S-species interaction with smithsonite (0 0 1) surface: Effect of water molecule adsorption position

Surface sulfidization is the key to achieving good flotation performance of smithsonite, but its reaction mechanism at the atomic level remains poorly understood. In this work, the interaction of two S-species, i.e., S2- and SH- with smithsonite (0 0 1) surface in presence of water molecule was investigated using the density functional theory (DFT). The results indicated that the initial adsorption position of H2O molecule on the smithsonite surface had an important influence on the sulfuration reaction. There was no chemical interaction between S-species and smithsonite surface when the H2O molecule was perpendicularly placed between the Sspecies and surface Zn atom. However, when the H2O molecule was placed nearby the surface Zn atom, S-species repelled the H2O molecule from the surface and took place chemical interaction with the Zn atom. DOS analysis showed that the interaction of S-species with smithsonite surface in presence of H2O molecule nearby Zn atom mainly involved the S3p orbital and Zn 3d 4 s orbitals. Despite the partial overlap of 3p orbital with Zn 3d 4 s orbitals confirmed the chemical interaction between S-species and surface Zn atom, such interaction was not well strong and stable in nature due to the presence of S 3p and Zn 3d orbitals at different energy levels, which made them inferior matched with each other. Compared with S2-, HS- repelled the H2O molecule from the surface more easily and interacted with surface Zn atom, as confirmed by the electron density analysis.