[Spectra study on the influence of drying process on palygorskite structure].

There are four different types of molecules of hydroxyl groups of the natural attapulgite. The band at 3614 cm(-1) was attributed to the stretching modes of hydroxyls coordinated with the magnesium. The band at 3415 cm(-1) is associated with the hydroxyl stretching vibrations of absorbed water. The bands at 3581 and 3552 cm(-1) were attributed to the symmetric and antisymmetric stretching modes of molecular water coordinated with the magnesium at the edges of the channels. The band at 1653 cm(-1) is associated with the hydroxyl stretching vibrations of zeolitic water. The structures of the natural palygorskite and its products dried at different temperatures for 30 min were analysed by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The absorbed, zeolitic and co-ordinated water decreased during the drying process at the same time. The absorbed water was completely-dehydrated firstly, then the zeolitic water, and lastly the co-ordinated water. And the hydroxyl groups remained until about 600 degrees C. When the co-ordinated water was dehydrated completely at 450 degrees C, the crystalloid was destroyed. The mechanism of the palygorskite structure change was also discussed in detail.