Absorption and mobility of molecules of water and organic substances in carbon adsorbents. Communication 2. Study of mobility of molecules of methanol on activated carbons differing in micropore structure, by means of pulse gradient NMR

Abstract

1. The self-diffusion coefficients (SDC) of water molecules on activated carbons are lower than in bulk water by a factor of 5–100, occupying an intermediate position between the SDC of water molecules on type A hydrophilic zeolite and on ZSM-5 hydrophobic zeolite. 2. In the range of adsorption levels that was investigated, the SDC of water molecules on activated carbons is independent of the coverage of the adsorbent. 3. For carbons with a high mobility of water molecules, the activation energy of diffusion is approximately the same as in bulk water. 4. The lowest value of the SDC is obtained for ultramicroporous activated carbons AU-11 and AU-14, and the highest value for activated carbon AU-42, which has the largest pores. In a series of carbons with molecular-sieve properties (MSC-4A, MSC-5A, and MSC-6A), the SDC of water molecules is higher for the adsorbents with large pores.