The effect of thermal treatment on some physicochemical and mineralogical properties of Bardakçı / Van clay

The aim of this study was to investigate the change in mineralogical and physicochemical properties of a clay raw material taken from Bardakçı / Van region depending on the heat treatment temperature. Characterization of the sample; X-ray fluorescence spectroscopy (XRF), inductively coupled plasma-mass spectrometry (ICP-MS), X-ray diffraction (XRD), differential thermal analysis (DTA), thermogravimetric analysis (TGA), fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), cation exchange capacity (methylene blue adsorption), Brunauer, Emmett and Teller (BET) and potentiometric mass titration (pzc) methods were used. Clay and non-clay minerals such as quartz, calcite, smectite (montmorillonite), amorphous material, feldspar, kaolinite, serpentine group minerals, tridimite, illite, mica and mixed layered clay minerals were identified in the original sample. Heat treatment was applied to the raw sample at temperatures between 100-1000 °C and kinetic and thermodynamic investigations were performed. Dehydration and dehydroxylation degradation enthalpies of thermal decomposition were determined from the change of CEC by applied heat treatment temperature. The results show that the decomposition before 500 oC is physical and at temperatures above it is chemical. Activation energies and Arrhenius constants of dehydration and dehydroxylation were determined by using Coats-Redfern equations from thermal analysis data (TGA, DTA) of the original sample. It was observed that the surface areas determined by Brunauer-Emmett-Teller (BET) method of all heat-treated samples tended to decrease with temperature. Keywords: Heat treatment, Heat treatment kinetics, Clay, Clay minerals, Surface area,