HIGH-RESOLUTION H-2 SOLID-STATE NMR OF (H2O)-H-2 ADSORBED ONTO ACTIVATED CARBON

Adsorption of deuteriated water onto activated carbon has been studied using magic-angle spinning (MAS) H-2 NMR. At (H2O)-H-2 vapour concent rations below 80% relative humidity a single line of moderate width is observed. The peak is chemically shifted by 6-8 ppm to low frequency of the signal for bulk (H2O)-H-2. At high relative humidities (>80%) a further, sharper, H-2 NMR signal was observed close to the chemical s hift of bulk (H2O)-H-2. The observed chemical shifts and line widths a re discussed in terms of the adsorption of the (H2O)-H-2 into the poro us carbon substrate. Signal intensities were measured relative to a st andard sample and an adsorption isotherm plotted. The results are cons istent with the standard gravimetric isotherm method for the sample. H owever, NMR offers the advantage of the direct observation of the chem ical species present in various locations within the sample.