The oxidation behavior of unactivated and mechanically activated sphalerite

The oxidation behaviors of unactivated and mechanically activated sphalerites were investigated using the thermogravimetry method (TG) in flowing highly pure oxygen at the heating rate of 10 K min⁻¹. It is found that the remaining mass between 400 and 873 K in the TG curves of mechanically activated sphalerites rises with increasing grinding time. The difference in oxidation reactivity of unactivated and mechanically activated sphalerites was also discussed. The specific granulometric surface area (S _G), the structural disorder, and the content of elemental sulfur of unactivated and mechanically activated sphalerites were determined by X-ray diffraction (XRD) laser particle size analysis, X-ray diffraction, and the gravimetric method, respectively. The results show that the specific granulometric surface areas of mechanically activated sphalerites remain almost constant after a certain grinding period. The elemental sulfur contents of unactivated and mechanically activated sphalerites were determined to be 0.5 mg/g, and the lattice distortions (ɛ) increase but the crystallite sizes (D) decrease with increasing grinding time. All the results imply that the mass increase between 400 and 873 K in the TG curves of mechanically activated sphalerites depends mainly on the increase of lattice distortions (ɛ) and the decrease of the crystallite sizes (D) with increasing grinding time. It was concluded that TG is a useful method for characterizing mechanically activated sphalerites.