Uncovering the oxidation mechanism of sphalerite (ZnS) in the absence and presence of water: A first-principles investigation

Abstract

Herein, a first-principles investigation was innovatively conducted to research the surface oxidation of ZnS-like sphalerite in the absence and presence of H₂O. The findings showed that single O₂ was preferred to be dissociated adsorption on sphalerite surface by generating SO and ZnO bonds, and the S atom on the surface was the most energy-supported site for O₂ adsorption, on which a ZnOSOZn structure will be formed. However, dissociated adsorption of single H₂O will not happen. It was preferred to be adsorbed on the top Zn atom on sphalerite surface in molecular form through ZnO bond. Besides, sphalerite oxidation can occur as if O₂ was present regardless of the presence of H₂O, and when H₂O and O₂ coexisted, the formation of sulfur oxide (SO₂) needed a lower energy barrier and it was easier to form on sphalerite surface than that only O₂ existed. In the absence of H₂O, when SO₂ was generated, further oxidation of which would form neutral zinc sulfate. In the presence of H₂O, the formation of SO₂ on sphalerite surface was easier and the rate of further oxidation to form sulfate was also greater. Consequently, the occurrence of sphalerite oxidation was accelerated.