The structure of pumice: An XPS and 27Al MAS NMR study

In order to investigate the surface structure of pumice, an amorphous aluminosilicate, samples of pumice and of standards of silica and alumina have been studied by x‐ray photoelectron spectroscopy (XPS). The effect of a mild acid leaching was also considered. The analysis of the Si 2p, Al 2p and O 1s photoelectron peaks and the Si KLL and O KLL Auger peaks indicated that pumice is formed by tetrahedral silica with some units being replaced by aluminate, AlO2−. The acid treatment decreases the alkali and the aluminate ions. X‐ray photoelectron spectra of the valence band of pumices and of standards of Al2O3 and SiO2 agree with the core‐level results. To support the conclusions from the XPS study, magic angle spinning (MAS) 27Al nuclear magnetic resonance (NMR) of pumice was used. The spectrum is indicative of tetrahedrally coordinated aluminium.