X-ray study of the thermal intercalation of alkali halides into kaolinite

Abstract

Intercalation complexes of kaolinite with a series of alkali halides (NaCl (trace amounts), KCl, RbCl, CsCl, NaBr, KBr, CsBr, Kl, Rbl and Csl) were obtained by a thermal solid state reaction between the kaolinite-dimethylsulfoxide intercalation complex and the appropriate alkali halide. The ground mixtures (1∶1 weight ratio) were pressed into disks that were gradually heated up to 250 °C for different times. X-ray diffractograms of the disks were recorded after each thermal treatment. At the end of the thermal treatment the disks were ground and basal spacings of the powders obtained. As a result of thermal treatment, alkali halide ions diffuse into the interlayers, replacing the intercalated dimethylsulfoxide molecules. Such a replacement may take place only if the thermal diffusion of the penetrating species is faster than the evolution of the intercalated organic molecule. With increasing temperature the intercalated salt diffused outside the interlayer space or underwent a thermal hydrolysis which resulted in the evolution of hydrogen halides from the interlayer space. Consequently, the amounts of intercalation complexes decreased at elevated temperatures.