The influence of structure order on the kinetics of dehydroxylation of kaolinite

The structural order of kaolinite is an important factor that shows a substantial effect on the processes which take place during the thermal treatment of kaolin. The influence of structural order on the dehydroxylation process was investigated by simultaneous thermogravimetry and differential thermal analysis (TG-DTA). The thermal analysis was performed on the samples with gradually decreasing structural order prepared by milling procedure. The apparent activation energy of dehydroxylation process decreases with decreasing structural order according to the exponential function. The extrapolation of experimental data leads to the estimation of apparent activation energy of 76.6 kJ mol−1 and of frequency factor of 0.12 × 104 s−1 related to completely disordered form of kaolinite, while the ordered form shows the apparent activation energy of 216.17 kJ mol−1 and the frequency factor of 9.26 × 104 s−1. The relationships between features such as the infrared pattern of treated material, the degree of structural order and the apparent activation energy were established.