Dehydration kinetics of an Indian clay

Abstract

Decomposition of clay from Garo Hills of Meghalaya (India) was studied by dynamic thermogravimetry. A fourteen kinetic equation procedure was applied for analysis of non-isothermal weight change upto a temperature of 1223 K. Two stages of decomposition were clearly distinguised i.e. the initial dehydration period at temperature 373 K to 673 K and the dehydroxylation period in the temperature range 723 K to 1073 K. First order decomposition mechanism was found to be applicable to both dehydration and dehydroxylation steps. Activation energies of 67 kJ/mol and 278 kJ/mol are estimated for the first and second steps with frequency factors of 16.3 s−1 and 5.16×106s−1 respectively. The weight loss relating to the steps in TG curves allows determination of the contents of the basic mineral in the clay. Percentages of Al2O3.SiO2 and total volatiles as calculated from weight loss data are in accordance with the results of classical chemical analysis.