LAUSR

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 s−1.