Investigating the thermal behavior and dehydroxylation kinetics of bentonite: isothermal and non-isothermal study

Abstract

This paper aims to study the crystallization kinetics of local bentonite taken from the Maghnia region of Algeria after conducting the toasting process to powder with different temperature degrees 200, 400, 500, 700, 800, 900, 1000°C and 1100°C. The material was examined by differential thermal analysis (DTA) at different heating rates (10–50°C/min), and X ray diffraction (XRD). We used also Infrared Spectroscopy to detect the vibrations characteristic of the chemical bonds and to analyze the molecules forming the material. Scanning electron Microscopy (SEM) has been used to investigate the bentonite microstructure revealing granules shape and distribution. We have applied Non-isothermal crystallization kinetic methods to study the mechanism of crystallization in the bentonite. After a calcinations process at 200°C and 700°C of the bentonite, X-ray diffraction data showed a decrease in the basal spacing (d001) from 12.72 Å of room temperature to about 11.98 Å and 9.93 Å respectively. We also observed the disappearance of the diffraction peaks represented by the d001 interval, which expresses the montmorillonite phase after calcination of samples at 800°C. The average activation energy has been determined by Kissinger method (221.046 kJ/mol), Ozawa method (225.557 kJ/mol) and Boswell method (229.356 kJ/mol). Growth morphology parameters and the frequency factor for the reaction of the dehydroxylation at different temperatures have been measured.