Kinetics of dehydroxylation and evaluation of the crystallinity of kaolinite

This study presents results on the kinetics of kaolinite dehydroxylation. The accuracy of various methods of determining the values for the kinetic parameters and their sensitivity in detecting the mechanism of reaction is investigated. In particular, the differential order of reaction method of Baker, the general method of Achar et al., the integral method of Boy and Bohme, and the method of Coats and Redfern as modified by Fong and Chen are considered.

Kaolinites from well-known sources are used to study the influence of crystallinity on the values of kinetic parameters. The statistical significance of the various mathematical methods for the assessment of the data obtained from non-isothermal thermogravimetry is determined by comparison with experimental and theoretical data using a computer programme developed for this purpose. The study demonstrates that the kinetic parameters can be used to quantify the degree of crystallinity of kaolinite and also confirms other findings that the dehydroxylation of kaolinite is a second-order reaction.