Water in silicate glass:: 17O NMR of hydrous silica, albite, and Na2Si4O9 glasses

The mechanism of incorporation of water in silica (SiO2), albite (NaAlSi3O8), and Na2Si4O9 composition glass has been studied by H-1, O-17, Na-23, Al-27, and Si-29 NMR spectroscopy. Hydrated samples were prepared by quenching the melt from high pressure and high temperature with use of solid-media apparatus with a O-17-enriched starting material. Water content of the hydrated glasses was estimated from H-1 NMR peak intensities compared with reference materials. For SiO2 glass, the O-17 NMR spectrum has a sharp resonance line at the position corresponding to the chemical shift of molecular water. O-17 NMR of both dry and hydrous (50 mol % H2O) albite glasses shows two environments with peaks for Si-O-Si and Si-O-Al. No significant difference was seen between dry and hydrated glasses. For the Na2S4O9 glass, H-1 and Si-29 NMR results are consistent with each other and suggest the formation of Si-OH and molecular water in this glass. O-17 NMR of this glass shows significant differences between dry and hydrated glass. The intensity of the nonbridging oxygen peak for the hydrated sample decreased considerably with added water. The intensity change of the nonbridging oxygen peak could be quantitatively explained by a formation of a complex with equal molar amounts of Na+ and H2O.