Microstructural characteristic of montmorillonite and its thermal treatment products

Abstract

The montmorillonite was studied by different methods, such as chemical analysis, DAT, TG, XRD, IR, AFM and MAS NMR. The experimental results show that the hydroxyl in octahedra sheets begins dehydrating when the thermal treatment temperature reaches 659°C, but the layer structure remains the same, and the corresponding Al(VI) is turned into Al(IV) in octahedra sheets. When the temperature reaches 900°C, the layer structure of montmorillontite is destroyed, and the new mineral phase μ-cordierite is found. When the temperature reaches 1200°C, the μ-cordierite phase loses its stability, and decomposes into cristobalite phase and mullite phase. Meanwhile, the recrystallization phenomenon in thermal treatment products is obvious. There is a small quantity of Al^VI signal in MAS NMR spectrum, corresponding to Al of mullite. When the temperature reaches 1350°C, the cristobalite and mullite phases reduce slightly, and more Fe-cordierite phase appears, corresponding to Fe-cordierite spectrum in XRD and MAS NMR.

Keywords

montmorillonite / thermal treatment product / microstructure / μ-cordierite

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