Characterization of kaolinite intercalation compounds with benzylalkylammonium chlorides using XRD, TGA/DTA and CHNS elemental analysis

Abstract Kaolinite of high structural order was intercalated with selected ammonium salts containing a benzyl group: benzyltrimethylammonium (B1), benzyltributylammonium (B2), benzalkonium (B3), benzyldimethyltetradecylammonium (B4) and benzyldimethylhexadecylammonium (B5) chlorides. As a precursor, a methoxy-kaolinite was used which had OCH3 methoxyl groups attached to the octahedral sheet. Such change of the octahedral surface character enabled intercalation of the salts which was not possible using other precursors (e.g. kaolinite–dimethyl sulfoxide). The new intercalation compounds were characterized using XRD (X-ray diffraction), thermal analysis (TGA/DTA) and CHNS elemental analysis. The XRD revealed a significant shift of the kaolinite basal reflection to higher values range from ~ 14 A (B1 salt) to ~ 38 A (B5 salt) which confirmed the intercalation. The d values depended on the type of used salt as well as on its initial concentration. The estimated space occupied by each molecule enabled to calculate the maximal molar capacity of the kaolinite in relation to the salts. The results were compared with the chemical formulas of the materials calculated on the basis of CHNS measurements. The TGA/DTA analyses were helpful to confirm the successful intercalation of the selected salts as the thermal decomposition of the kaolinite derivatives took place at higher temperatures as compared to appropriate physical mixtures.