Dehydration Kinetics of Natural Talc

The dehydration kinetics of natural talc were studied using thermogravimetric analyses (TGA). The dehydration rate of talc increases with decreasing grain size, but there is little effect on the dehydration rate when the grain size is less than 5 mu m. The dehydration reaction of talc occurs in the temperature range 1103-1323 K; the thermal decomposition of talc yields enstatite and quartz plus water. The probable reaction mechanism for the dehydration of talc is an approximately second order reaction, whose differential and integral rate expressions are f(alpha) = (1 - alpha)(n) and G(alpha) = (1 - (1 - alpha)((1-n)))/(1 - n), respectively. The value of the reaction order n is 1.7, the activation energy E is 344 kJ/mol, and the pre-exponential factor alpha is 4.9 E12 s(-1). This dehydration reaction is probably a one-step reaction. The dehydration reaction is controlled by a heterogeneous mechanism. The relationship between the conversion rate of talc and time at different temperatures was obtained using the parameters derived from non-isothermal studies, and was used to predict the stability of talc at different temperatures.