A model of the two-stage condensation mechanism of water adsorption on nonporous carbon adsorbents

The mechanism of adsorption of water molecules on nonporous carbon adsorben ts has been suggested in terms of two different states of adsorbed water: s tretched liquid water and water that occupies an intermediate state between the liquid and vapor. Two stages of adsorption were distinguished: condens ation and pre-condensation that assumes the formation of molecular associat es. The BET model was used to describe the pre-condensation stage. The equa tions of the adsorption isotherm for water vapor in the region of condensat ion process and the expression for the determination of the specific hydrop hilic surface of adsorbents were found. Examination of the experimental dat a on adsorption of water vapor on nongraphitized samples of carbon adsorben ts shows that in the region of polymolecular adsorption, all isotherms fall into a common curve determined by the equation of the stretched liquid fil m and can be calculated regardless of the properties of individual liquid w ater. The equation for adsorption of water vapor on the hydrophobic surface was obtained.