DFT study on the influence of sulfur on the hydrophobicity of pyrite surfaces in the process of oxidation

Abstract

Using the first-principles method of density functional theory (DFT) and the plane-wave ultra-soft pseudopotential method, the adsorption process of water on a perfect pyrite surface and a surface with an adsorbed sulfur atom was calculated and simulated. The mechanistic role of sulfur formed during pyrite surface oxidation in the hydrophobicity of pyrite surfaces was explored. The simulation results showed that compared with the perfect pyrite surface, the surface with an adsorbed sulfur atom had an absorption energy that went from a negative to a positive value. The strong FeS covalent bond was formed first between the surface pyrite iron atom and the adsorbed sulfur atom. Following this, a weak SO bond was formed between the sulfur and oxygen atoms of the water molecule. The adsorption of H2O on the pyrite surface was hindered by the generation of sulfur so that the surface with an adsorbed sulfur atom became hydrophilic. The simulation results are consistent with the results of wetting heat. The influence of sulfur adsorption on pyrite hydrophobicity was mechanistically revealed from the view of quantum chemistry.