To investigate the thermal behavior of the coal-derived pyrite, the thermogravimetry and derivate thermogravimetric (TG-DTG) analyses of the sample is presented in Fig. 2, which shows the TG-DTG curves for the sample. The thermal decomposition of the coal-derived pyrite is discussed in details as followed. There are six main mass losses in TG curve of this sample. The first mass loss of 2.77% is observed at below 100 ◦C. This mass loss is attributed to be the elimination of adsorbed water molecules on the external surfaces of the sample. The second mass loss is observed at 124 ◦C with a mass loss of 3.02%, which is assigned to the loss of interparticle water for the sample. The third mass loss of 4.0% between 200 and 300 ◦C is assigned to the evolution of sulfur on the pyrite surface. It is reported that the existence of elemental sulfur at pyrite
surface have also been confirmed by other authors using Raman spectroscopy and X-ray photoeletron spectroscopy analysis [3]. The three mass losses for the sample, which correspond to mass losses of 8.92% (430–460 ◦C), 5.21% (460–515 ◦C) and 8.42% (520–590 ◦C),are assigned to the thermal reaction process for the coal-derived pyrite. The process can be represented by the following reaction