The decomposition kinetics of mechanically activated alunite ore in air atmosphere by thermogravimetry

The thermal decompositions of both non-activated and mechanically activated alunite ore have been studied by thermogravimetry (TG). The ore was activated mechanically in an attritor for 15 min and amorphisation in the structure was studied by X-ray diffraction analysis. It can be verified that alunite decomposes in two steps, which are dehydration and desulphation. It was also established that the mechanical activation affected especially on the temperature range of dehydration reaction. The activation energies of dehydration and desulphation reactions have been calculated from the thermogravimetric data at heating rates of 5, 10, 15 and 20 K min−1 involving isoconversional methods of Ozawa and Kissenger–Akahira–Sunose (KAS).