Water adsorption and small angle X-ray scattering studies on the effect of coal thermal treatment Original Research Article

The effect of thermal treatment, at a relatively high temperature (∼- 340 °C), on two highvolatile bituminous coals is examined by water adsorption and small angle X-ray scattering (SAXS). The results suggest that the mesopore structure in both samples undergoes a partial collapse. Furthermore, a strong hydrophobic effect, at the very early stages of the adsorption process, is noted for only one of them. This observation is attributed to differences in the rigidity of each of the structures. Analysis of the spectra in terms of fractal geometry is also performed. It is proposed that thermal treatment changes the coal matrices from a dilute to a dense configuration. Heating causes a breakage of some oxygen and sulphur bridges giving rise to these structural alterations.