WATER-ADSORPTION IN CARBONS DESCRIBED BY THE DUBININ-ASTAKHOV AND DUBININ-SERPINSKI EQUATIONS

It is shown that the water adsorption isotherm of type IV, observed for a number of carbons near room temperature, can be decomposed into two contributions of types I and V. The corresponding isotherms can be treated as Dubinin-Astakhov equations. The initial section suggests the presence of sites with characteristic energies, E, in the range of 5-8 kJ mol(-1) and similar contributions to the molar enthalpy of immersion of the carbons into water. Similar values are obtained from the analysis of earlier data of Dubinin. The second part of the isotherm, of type V, is compatible with the earlier model of Dubinin and Serpinski. A satisfactory agreement is also found in most cases between the enthalpies of immersion calculated on the basis of the DA model and the experimental values.