Characterization of pyrolytic properties of pyrite in the terahertz frequency band

A systematic terahertz spectroscopy study of the mineral phase transformation process of natural pyrite samples heated in a nitrogen atmosphere is conducted. In addition, the pyrolysis process of pyrite in the 400 °C–800 °C temperature range is analyzed and discussed. This study is based on X-ray diffraction (XRD) and thermogravimetric-derivative thermogravimetric (TG-DTG) analysis of the corresponding thermal transformation sequences of pyrite, magnetopyrite, and sulfurous pyrite as the desulfurization process proceeds. Terahertz time-domain spectroscopy is employed to characterize the optical properties of the pyrolysis products. The results show that pyrite, magnetopyrite and sulfurous pyrite exhibit different absorption coefficients and refractive indices in the terahertz frequency band. The different optical properties of these products provide useful information for the investigation of the pyrolysis process of pyrite and the magnetic properties of environmental sediments.