Thermal Dehydroxylation Kinetics of Algerian Halloysite by Differential Thermal Analysis

Abstract

In this study, the dehydroxylation of Algerian halloysite (DD1) was studied using differential thermal analysis. Measurements of samples were performed between room temperature and 1400 • C, at different heating rates of 10, 20, 30, 40 and 50 • Cmin −1. The activation energy calculated from isothermal (using Johnson-Mehl-Avrami and Ligero methods) and non-isothermal treatments (using Kissinger-Akahira-Sunose) were 135 kJ/mol and 153 kJ/mol, respectively. The Avrami parameter obtained by method of Ligero and the m parameter (a numerical factor) obtained by Matusita method were 1.55 and 1.59, respectively. The results show that bulk nucleation was dominant in halloysite transformation, followed by three-dimensional growth of meta-halloysite. This growth is controlled by diffusion from a constant number of nuclei. The frequency factor calculated by the isothermal treatment is equal to 4.16 × 10 6 s −1 .