Diffuse reflectance infrared spectra of kaolinite and kaolinite/alkali halide mixtures. Curve-fitting of the OH stretching region

Diffuse reflectance infrared spectra of kaolinite and binary mixtures of this clay with alkali halides have been analysed using curve-fitting and deconvolution. For caesium chloride and caesium bromide, decomposition of the hydroxyl stretching region has made it possible to correlate the positions and intensities of bands due to structural hydroxyl groups of kaolinite, or to intercalated water, with the degree of intercalation. One of these bands, arising from uncoupled inner surface OH stretching in kaolinite, is not identifiable in spectra of the uncomplexed clay or mixtures where intercalation did not occur. A new band revealed by curve-fitting spectra of intercalated samples is attributed either to water at the interface between the clay and the alkali halide, or to an FeO—H impurity in the kaolinite. Key words: kaolinite, infrared, curve-fitting.