INFRARED STUDY OF THE INTERCALATION OF KAOLINITE BY CESIUM BROMIDE AND CESIUM IODIDE

CsBr- and CsI-kaolinite intercalation complexes were synthesized by gr adually heating caesium halide disks of the DMSO-kaolinite intermediat e up to 330 degrees C, Infrared spectroscopy revealed two types of com plexes with the caesium salts: almost nonhydrous, obtained during ther mal treatment of the DMSO complex, and hydrated, produced by regrindin g the disk in air. Comparison of band positions for CsBr-kaolinite and CsI-kaolinite with those for the CsCl complex (observed in a previous study) shows that the strength of the hydrogen bond between the inter calated halide and the inner surface hydroxyl decreases on the order C sCl > CsBr > CsI. The nonreactivity of CsI in mechanochemical intercal ation may arise from weak interaction between I- and inner surface hyd roxyl groups, resulting from the fact that caesium is a very soft acid and iodide is a very soft base. Consequently, the very strong interac tion between the two ions in the crystal is not disrupted during mecha nochemical treatment. (C) 1998 Academic Press and Minister of Natural Resources, Canada.