MAGIC-ANGLE-SPINNING NMR-STUDY OF ADSORBATE REACTIONS ON ACTIVATED-CHARCOAL

Magic angle spinning (MAS) NMR can distinguish between molecules adsorbed in monolayers within the micropores (>20 Angstrom) of activated charcoal and those present in multilayers or capillary-condensed liquid in the mesopores (20-500 Angstrom). The differentiation is possible due to the NMR shifts to low frequency induced by the large, diamagnetic susceptibility of the graphitic surface of the micropores (upon which primary adsorption occurs) in combination with slow molecular exchange between the micropores and mesopores. This study uses MAS NMR to characterize the adsorption and oxidation of 2-chloroethyl phenyl sulfide (CEPS) on activated charcoal. Micropore-filling by solvents and solvent displacement of micropore-adsorbed CEPS are also demonstrated for charcoal using this technique.