Insights on the intercalation mechanism of the coal-bearing kaolinite intercalation based on experimental investigation and molecular dynamics simulations

Cetyltrimethylammonium chloride (CTAC) was intercalated into the layers of coal-bearing kaolinite by using the intermediate of wet methanol intercalation composite that was obtained by the displacement intercalation reaction of dimethyl sulfoxide (DMSO) intercalation composite. The basal spacing of coal-bearing kaolinite was increased from 0.72 nm to 3.79 nm due to the intercalation of CTAC by X-ray diffraction (XRD). The remarkable change of characteristic peaks in the Fourier transform infrared spectroscopy (FTIR) spectra of intercalated coal-bearing kaolinite and the mass loss results of thermogravimetric analysis (TG) indicate that CTAC molecules have been successfully intercalated into its layers. Images of scanning electron microscopy (SEM) indicate that the significant separation of the kaolinite sheets was found and the rolling occurred at the lamellar edges after CTAC intercalation. Furthermore, the intercalation mechanism in the process was explored through the molecular dynamics simulation of CTAC intercalation system combined with theoretical calculations and experimental data. The approximate intercalation process is proposed that CTAC molecules may be presented in bilayer structures near the silica tetrahedron surface and alumina octahedron surface and then may be presented in inclined monolayers and inclined pseudo-trilayers into the interlayer space of kaolinite.