Isothermal kinetic analysis of the thermal decomposition of kaolinite: The thermogravimetric study

In this kinetic study, the dehydroxylation of the medium ordered kaolinite was investigated under isothermal conditions by the thermogravimetric analysis (TGA). The kinetic model function (mechanism) of the process and important kinetic parameters, i.e. overall activation energy (EA) and pre-exponential (frequency) factor (A), were evaluated from the series of the thermogravimetric experiments in the temperature range from 370 to 500 °C. The linearization procedure on measured data indicates that dehydroxylation of kaolinite and metakaolinite formation up to the temperature 410 °C is controlled by the rate of the second-order chemical reaction. The overall activation energy and frequency factor of dehydroxylation were determined as 257 kJ mol−1 and 1.9 × 1019 s−1, respectively. Above 410 °C, the course of thermal decomposition of kaolinite corresponds to a third-order reaction with the EA value of 202 kJ mol−1 and 2.9 × 1015 s−1, respectively.