Room Temperature Solid Surface Water with Tetrahedral Jumps of 2H Nuclei Detected in 2H2O-Hydrated Porous Silicates

Abstract

The nature of water adjacent to solid silicate surfaces in kanemite, rehydrated zeolite A, rehydrated highly porous glass, rehydrated high surface area silica gel, and the hydration products of tricalcium silicate has been investigated with 2H NMR techniques and calorimetry. The room temperature 2H NMR quadrupole echo spectra of all samples show a sharp central resonance that corresponds to 2H2O. The kanemite, porous glass, and silica gel spectra show in addition powder patterns that were assigned, based on previous findings for kanemite, to silanol −OH groups experiencing rapid 3-fold jumps or rotational diffusion about the Si−O bond. The spectrum of hydrated tricalcium silicate shows in addition to the aqueous peak a rigid powder pattern that is assigned to Ca(O2H)2. Spectra obtained at −120 and −150 °C for the kanemite sample show that the qcc values for the aqueous deuterons range from 180 to 210 kHz, as would be expected for the different water environments observed in the X-ray structure of kanemite...