Specific features of the adsorption and nuclear magnetic relaxation of water molecules in active carbons. 1. Relation between the spin-spin relaxation of adsorbed water molecules and structural parameters of microporous active carbons

Abstract

Relation between the spin-spin nuclear magnetic relaxation time T2 of adsorbed water molecules and parameters of microporous structure of carbon adsorbents is disclosed. The pattern of dependences of T2 on the relative pressure and the number of water molecules per one primary adsorption site (PAS) is governed by the pore sizes and the number and nature of PASs. At a complete micropore filling, the T2 value depends on the volume density of PASs in active carbons. In the absence of PASs in the micropores, T2 is equal approximately to 21 ms. The larger the volume density of PASs, the smaller the number of water molecules per one PAS at the complete filling of micropores; i.e., the looser the packing of water molecules. The results of studying active carbons by the pulsed 1H NMR method agree well with the data of the adsorption method.