FTIR spectroscopy study of the structure changes of palygorskite under heating

Progressive heat treatment was applied to palygorskite, and the changes of the position and intensity of its infrared vibrations, particularly those in the low wavenumber region, were monitored by use of Fourier transform infrared spectroscopy. Moreover, the responses of the impurities in palygorskite under heating were also examined. Palygorskite is characterized by two bands at 1196 and 647 cm(-1), which are attributed to the asymmetric stretching vibration of the Si-O-Si group that connects the adjacent inverse SiO(4) tetrahedrons and the H(2)O-Mg-H(2)O stretching vibration in the MgO(6) octahedra at the edges of the channels, respectively. The band at approximately 680 cm(-1) is attributed to the overlapping symmetric stretching vibrations of Si-O-Mg and Si-O-Al (VI). In addition, the 865 cm(-1) band corresponds to the amorphous carbonate impurity.