Steric hindrance effect on adsorption of xanthate on sphalerite surface: A DFT study

Abstract The influence of steric hindrance effect on xanthate adsorption on sphalerite surface has been studied by adopting density functional theory (DFT). On the relaxed sphalerite (1 1 0) surface, one surface zinc atom coordinates with three sulfur atoms and is located in the center of a planar triangular structure. The sulfur atom with a large atomic radius could spatially hinder the zinc atom, which subsequently results in steric hindrance effect. Consequently, the interaction of xanthate S atoms with surface Zn has to overcome a potential barrier caused by steric hindrance effect. In addition, the DFT simulation and LST search confirmed that the replacement of surface Zn atom by Cu atom could decrease the energy barrier caused by steric hindrance effect, which is favorable for the adsorption of xanthate. The results could explain why ethyl xanthate with short chain length is hard to adsorb on the clean sphalerite surface, but can strongly adsorb on the Cu-activated sphalerite surface.