Work

Effects and mechanisms of solution anions on the conversion of phlogopite to vermiculite

Year: 2026

Type: article

Abstract: The investigation of the weathering and alteration of phyllosilicate minerals is crucial for understanding chemical cycles, soil development and environmental fluctuations on the Earth’s surface. This study employs phlogopite extracted from Yuli County, Xinjiang, due to its property of transforming easily into interstratified phlogopite-vermiculite or vermiculite under an acidic oxidizing environment. The preparation of vermiculite is governed by the anion type, pH, oxidizing environment, reaction time and other related factors. Advanced analytical and characterization techniques, such as X-ray powder diffraction, thermogravimetric analysis, differential scanning calorimetry, Fourier-transform infrared spectroscopy, scanning electron microscopy, inductively coupled plasma spectroscopy and X-ray fluorescence were employed to study the phase, spectral characteristics, thermal behaviour, microstructure and compositional modifications of the product before, during and after conversion. The compositional variations before, during and after conversion were also examined. Phlogopite can be converted to vermiculite with the assistance of sulfate and chloride ions under acidic oxidation conditions. Moreover, a higher concentration of SO 4 2– in solutions resulted in elevated SO 4 2– adsorption on the surface of phlogopite in comparison to solutions with Cl – . This accelerates the destruction of the tetrahedra and octahedra in phlogopite, resulting in the release of additional ions (Si 4+ ,Al 3+ , K + , Mg 2+ ) from the phlogopite framework. This ultimately speeds up the conversion of phlogopite to vermiculite.

Source: Clay Minerals

DOI: 10.1180/clm.2026.10056