3. Results and discussion
3.1. Thermo-chemical behaviors of pyrite, hematite and their mixture
It has been confirmed by many studies that pyrite is desulfurized gradually during thermal treatment [14]. As shown in Fig. 2, the TG-DTA curves of pyrite under N2 atmosphere demonstrate that there were three weight-loss stages in the range of 500–750 °C in addition to the dehydration stage approximately at 120 °C. Each of these stages corresponded to one endothermic peak. It was calculated that there was about 23% of weight (besides the water desorption) loss at 800 °C.