Infrared study of the intercalation of potassium halides in kaolinite

KCl-, KBr-, and KI-kaolinite intercalation complexes were synthesized by gr adually heating potassium-halide discs of the dimethylsulfoxide (DMSO)-kaol inite intermediate at temperatures to 330 degrees C. Two types of complexes were identified by infrared spectroscopy: almost non-hydrous, obtained dur ing thermal treatment of the DMSO complex: and hydrated, produced by regrin ding the disc in air. The former showed basal spacings with integral series of 00l reflections indicating ordered stacking of parallel 1:1 layers. Gri nding resulted in delamination and formation of a disordered "card-house" t ype structure. The frequencies of the kaolinite OH bands show that the stre ngth of the hydrogen bond between the intercalated halide and the inner-sur face hydroxyl group decreases as Cl > Br > I. The positions of the H2O band s imply that halide-H2O interaction decreases in the same order. Consequent ly, the strength of the hydrogen bond between H2O and the oxygen atom plane increases in the opposite sequence. In the non-hydrous KCl-kaolinite complex the inner hydroxyl band of kaolini te at 3620 cm(-1) is replaced by a new feature at 3562 cm(-1), indicating t hat these OH groups are perturbed. It is suggested that Cl ions penetrate t hrough the ditrigonal hole and form hydrogen bonds with the inner OH groups . In contrast, Br and I ions are too large to pass into the ditrigonal hole s and do not form hydrogen bonds with the inner hydroxyls.