Modification of kaolinite by controlled hydrothermal deuteration - a DRIFT spectroscopic study

Kaolinites were modified by controlled hydrothermal deuteration. Both infrared and near infrared vibration spectra of deuterated kaolinite were investigated by Diffuse Reflectance Infrared Fourier Transform spectroscopy. The stretching vibrations (v) of deuteroxyl groups of the kaolinite were observed at 2726, 2709, 2697 and 2667 cm(-1), respectively. The overtone bands (2v) of the deuteroxyl groups were visible in NIR regions at 5454, 5419, 5388 and 5342 cm(-1), respectively. The lattice vibrations of the kaolinite taking part in deuteration included 937, 915, 792, 751 and 690 cm(-1) which are assigned to hydroxyl group-related deformation or translation-vibration mode. The hydroxyl band at 3435 cm(-1) with its deuteroxyl band at 2542 cm(-1) resulted from unevenly distributed structural defects, either due to the isomorphous substitution of foreign cations or the imperfections of the kaolinite lattice structure.