| Summary: | BACKGROUND The thermal stability of bentonite and the changes of microstructure and property during heat treatment directly affect the application of bentonite in the field of mineral materials. Therefore, it is important to study the evolution of the composition and structure, and the change of surface properties of bentonite during heat treatment. Currently, the research of bentonite is concentrated in sodium modification, organic modification and retrofit of the modified structure and performance. The study of the changes in microstructure and physicochemical properties during the heat treatment of bentonite needs to be strengthened. OBJECTIVES To investigate the microstructure and physicochemical property as a function of thermal treatment of bentonite from the Kerjian region in Xinjiang. METHODS Bentonite from the Kerjian region in Xinjiang was heated at various temperatures. The chemical constituents of the original soil were analyzed by X-ray Fluorescence Spectrometry. The phase analysis and structural characterization of the heat-treated products were carried out by simultaneous thermal analysis, X-ray Diffraction, Infrared Spectroscopy and Scanning Electron Microscopy. The changes of specific surface area, methylene blue value and the gelling value during the heating process were studied. RESULTS With the increase of heat treatment temperature, the specific surface area of Kerjian bentonite decreased gradually, and the phase composition and structure changed greatly. When heated to 600℃, the blue absorption and colloid value of bentonite decreased sharply, and the hydroxyl groups in the main component montmorillonite octahedron sheet began to break out, while the layered structure was damaged. The montmorillonite phase disappeared above 800℃. A new mineral phase cordierite was produced at 1000℃. Above 1200℃, the mineral was transformed into quartzite phase, the particles were completely melted, and the recrystallization was obvious. CONCLUSIONS It is concluded that the expansibility and dispersion of Kerjian bentonite are basically lost at 600℃, and the mineral physicochemical properties are invalid.
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