An XPS Study on Surfaces of Common Sulfide Minerals

Surface mineralogy is a boundary science between mineralogy a nd surface sciences, and is also one of the important frontier branches of moder n mineralo gy. Research on mineral surface and mineral-liquid interface provides direct or indirect valuable reference not only for the theory of geosciences and environme ntal protection, but also for mineral-rock materials and other related fields. T he surface mineralogy study of sulfides as a common group of important minerals is limited at present. The surface composition and the surface chemical state of sulfides such as pyrite, pyrrhotite, galena, chalcopyrite, sphalerite and arsen opyrite have been studied in this paper by XPS. Some valuable and interesting re sults related to oxidation and secondary change on sulfide surfaces have been g ained from this study. They include: (1) Sulfide surfaces are easy to be oxidize d in air and the products of oxidation are very complex including their metal hi gh valence oxides, hydroxides and sulfates. (2) Pyrite is more stable as compare d with other common sulfides. (3) The atom ratios on sulfide surfaces show an excess sulfur after oxidation. (4) Among the iron-bearing sulfides, the iron o n arsenopyrite surface is relatively stable, besides the iron on pyrite surf ace. However the isomorphic iron on sphalerite surface is easily to be oxidized.