Investigation on preparation of micro-sized hematite powder from hydrous ferrous sulfate using microwave and conventional heating

Microwave and conventional heating were employed to synthesize micro-sized hematite powder from hydrous ferrous sulfate, a by-product in the process of titanium pigment manufacture. The TG/DTG analysis was used to study thermal behavior of the industrial ferrous sulfate. Therefore the temperature which was significant to product was defined. The calcination experiments were carried out to assess the effect of calcination temperature covering three different temperatures (650°C, 750°C and 850°C, respectively). X-ray powder diffraction (XRD) was used to characterize the structure of the product, while the scanning electron microscopy (SEM) was utilized to characterize the morphology of the product. Microwave calcination process resulted in a mixture of hematite and minor magnetite while a considerable amount of magnesium sulfate was detected with the conventional calcination process. The transformation from periclase to magnesium was discussed during the calcinations as well. The conventional heating resulted in porous product while the microwave heating resulted in smaller particle size.