Thermal behaviors of mechanically activated pyrites by thermogravimetry (TG)

The thermal decompositions of mechanically activated and non-activated pyrites were studied by thermogravimetry (TG) at the heating rate of 10 K min−1 in argon. Results indicate that the initial temperature of thermal decomposition (Tdi) in TG curves for mechanically activated pyrites decreases gradually with increasing the grinding time. The specific granulometric surface area (SG), the structural disorder of mechanically activated pyrites were analyzed by X-ray diffraction laser particle size analyzer, and X-ray powder diffraction analysis (XRD), respectively. The results show that the SG of mechanically activated pyrites remains almost constant after a certain grinding time, and lattice distortions (ε) rise but the crystallite sizes (D) decrease with increasing the grinding time. All these results imply that the decrease of Tdi in TG curves of mechanically activated pyrites is mainly caused by the increase of lattice distortions ε and the decrease of the crystallite sizes D of mechanically activated pyrite with increasing the grinding time. The differences in the reactivity between non-activated and mechanically activated pyrites were observed using characterization of the products obtained from 1 h treatment of non-activated and mechanically activated pyrites at 713 K under inert atmosphere and characterization of non-activated and mechanically activated pyrites exposed to ambient air for a certain period.