Numerical modeling of adsorption on micropore adsorbents 2. Behavior of water molecules in the micropores of a carbon adsorbent

Abstract

1. The potential energy of the interaction of one water molecule with the walls of a micropore E(Zc) as a function of the distance to its lower surface has one or two minima, determined by the half-width of the micropore d. 2. The height of the barrier ΔU between the minima of E(Zc) and distance ΔR between these minima for a given model potential of the water-carbon interaction increase linearly with an increase in the slit half-width. The values of the coefficients of these linear dependences were obtained empirically. 3. The dependence of the transverse diffusion coefficient on d for one molecule of water has one distinct maximum at d ≈ 0.41 nm. For this micropore, the height of the barrier gDU between the minima of E(Zc) is kT. For a cluster of six water molecules, there is also a maximum, but at d ≈ 0.35 nm, which is due to the formation of hydrogen bonds between the molecules of water. 4. Note that with a micropore half-width of d > 0.375 nm, for a cluster of 19 molecules of water, the number of hydrogen bonds is ≈18 per cluster and increases monotonically with an increase in d from 0.36 to 0.46 nm. In the 0.47–0.5 nm region, the average number of hydrogen bonds is almost independent of d. 5. When d 0.425 nm, they favor localization of the water near the walls of the micropore.