Time-efficient preparation and mechanism of methoxy-grafted kaolinite via acid treatment and heating

The previous preparation time of methoxy-grafted kaolinite (Kaol) presents great challenges to the development of Kaol intercalated products. In this study, methoxy-grafted Kaol samples were synthesized via guest displacement of a Kaol-dimethyl sulfoxide intercalation compound (Kaol-DMSO) and a Kaol-urea intercalation compound (Kaol-U) by acid treatment and heating. In the proposed method, the preparation time was dramatically shortened from 7 d to less than 1 h. The prepared methoxy-grafted Kaol showed a basal spacing between 0.86 and 0.90 nm in the X-ray diffraction patterns and the appearance of a vibrational band near 1655 cm(-1) in the infrared spectra. These findings indicate that both an acid environment and heating can speed up the preparation of methoxy-grafted Kaol. Adsorbed cations at the edges of Kaol particles form an electrical double layer in solution, and the promoted collision of particles under heating and replacement of hydrogen ions for cations in an acid environment contribute to the degradation of this double layers; expansion of pathways through which methanol can enter the Kaol interlayer spaces also occurs. Further intercalation with dodecyl dimethyl ammonium chloride proved the versatility of the proposed preparation approach for further intercalation.