HT-XRD non-isothermal kinetics study of delamination of kaolinite from termite mound

• The activation energy of delamination of kaolinite is 417 ± 9 kJ·mol–1.
• The process is controlled by the rate of 2nd order chemical equation.
• The superposition of delamination with dehydroxylation decreases the activation energy.
• The degree of delamination and dehydroxylation of metakaolinite depend on heating rate.

The kinetics and mechanism of delamination including the destruction of kaolinite layered structure of kaolinite from termite nest were investigated by non-isothermal high-temperature X-ray diffraction analysis. The process is controlled by the rate of the 2nd order chemical equation described by the kinetic function F2: (g(α) = (1 − y)− 1 − 1). The apparent activation energy was assessed to be 417 ± 9 kJ·mol− 1. The delamination is considered as the first step of the thermal transformation of kaolinite into metakaolinite but the temperature at which the maximum rate of dehydroxylation was reached is lower than the temperature for the maximum rate of delamination if a heating rate of ≤ 5 °C·min− 1 was applied and higher for heating rates ≥ 15 °C·min− 1. The superposition of both processes within the heating rates of 5 to 15 °C·min− 1 led to a significant decrease of activation energy. This behavior provides an option to modify the degree of metakaolinite delamination during the thermal treatment.

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