Deintercalation of dimethylsulphoxide intercalated kaolinites - a DTA/TGA and Raman spectroscopic study

The deintercalation of dimethylsulphoxide intercalated kaolinites was studied using a combination of thermal analysis techniques and Raman spectroscopy. Thermal analysis shows three endotherms at 77 degrees, 117 degrees and 173 degrees C attributed to the loss of water and the loss of DMSO in two stages, The use of a thermal stage enabled Raman spectra of the deintercalation process to be obtained in situ at elevated temperatures. The Raman spectra of the DMSO intercalated kaolinites show two bands at 3620 and 3660 cm(-1) for the DMSO intercalated low defect kaolinite and 3620 and 3664 cm(-1) for the high defect intercalated kaolinite. The 3620 cm(-1) band is attributed to the inner hydroxyl of the kaolinite and shows no change upon deintercalation. The 3660 and 3664 cm(-1) bands are attributed to the inner surface hydroxyls of the kaolinite hydrogen bonded to the DMSO. The intensity of these bands decreases upon thermal treatment and at the same time, the bands at 3695 and 3684 cm(-1) increase in intensity. These changes clearly shows that the 3660 cm(-1) band is attributable to the inner surface hydroxyls hydrogen bonded to the DMSO. Deintercalation may also be followed by the decrease in intensity of the CH-stretching bands, The application of the DTA/TGA patterns to determine the appropriate temperatures for Raman spectroscopy of the dimethylsulphoxide proved most useful. (C) 1999 Elsevier Science B.V. All rights reserved.