The formation mechanism of organoammonium-kaolinite by solid-solid reaction

Abstract

Solid-solid reactions and its corresponding solution method have been utilized to study the formation and intercalation mechanism of organoammonium-kaolinite formed from quaternary ammonium salt and kaolinite (Kaol) by using a methoxy-modified Kaol as an intermediate. The products were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetry and differential scanning calorimetry (TG–DSC) analysis. Results showed that butyl trimethylammonium and hexyl trimethylammonium ions were successfully intercalated into the silicate layers, while the larger ions (CnH2n+1N(CH3)3+, n≥8) were not. The intercalated alkylammonium ions were lying flat and poorly packed between the interlayer spaces of Kaol. In addition, a similar thermal behavior in the products obtained by both methods was also revealed. During the intercalation process, the alkylammonium ions were introduced by ion-dipole intercalation. In addition to the ion-dipole force, some other factors may contributed to these results, such as the geometrical constraint, the pH value of the mixed solution, the adsorbed water molecules, and the charge distribution at the external surfaces (the latter three will play a role if solutions are used). When solid-state reaction was used, the attraction caused by ion-dipole force was not strong enough to overcome the geometrical constraints, therefore larger alkylammonium ions were not intercalated.