[Study on the surface hydroxyl species of diatomite using DRIFT spectroscopy]

Using DRIFT spectroscopy, we detected surface hydroxyl structure of diatomite in this study. There were either isolated hydroxyl groups or H-bonded hydroxyl groups on the surface of the diatomite. At room temperature, the diatomite surface was predominantly covered by weakly adsorbed water in cavity and water bonded to surface hydroxyl groups via H-bonds. There appeared a broad band with middle wavenumber at 3,400-3,500 cm-1 as a result in the corresponding DRIFT spectra. With driving off adsorbed water by heating the sample from 200 degrees C to 1000 degrees C, the broad band fade away gradually, and a single band at about 3,745 cm-1, which is attributed to both isolated hydroxyl groups and partial H-bonded hydroxyl groups, became more and more intense with increasing temperature. Under the heat treatment conditions of 1,100 degrees C for one hour, the isolated hydroxyl groups were mostly desorbed from the surface, and the H-bonded hydroxyl groups that existed above the inner wall of micropores with diameter of circa 10 nm, however, had not yet condensed thoroughly. The thermal behavior was supposed to be a speciality of diatomite.