Research on non-isothermal lattice distortion mechanism of montmorillonite for coal gangue identification

Previous research on coal gangue identification based on X-ray transmission technology mainly focused on image processing. However, the relationship between the evolution of the crystallographic structure and mineral identification still requires further investigation. In this work, montmorillonite samples are heat-treated and the microstructures of montmorillonites at different heating temperatures are characterized, and a montmorillonite aberration model is constructed from the characterization results to be used in XAFS calculations. Heat treatment induces structural distortion in montmorillonite. While Al-O bonds rupture during this process, the intercalated Al groups become immobilized between silicate tetrahedra. This confinement mechanism effectively inhibits structural collapse and preserves the lamellar morphology. Characteristics such as coupled out-of-plane vibration bands of Al-O in FTIR patterns, (020), (102), and (022) reflections shift in XRD patterns, crystalline spacing increasing and then decreasing in TEM images, and regular variation of μ(E) and radial structural function can be traced in photoelectric separation to determine whether montmorillonite is present in the sample. The results may provide a valuable reference for the identification and classification of specific clay minerals in gangue photoelectric separation.