Chromatographic Characterization of Adsorption Properties of Carbon and Silica Adsorbents

Adsorption isotherms and specific retention volumes of benzene on MCM41C16 mesoporous silica and F4O porous carbon were determined at different temperatures by employing inverse gas chromatography. The differential isosteric enthalpies, -∆Hads , and entropies, -∆Sads , of adsorption were calculated from the retention time data and compared with the results obtained from the adsorption second virial coefficients. The relation between the -∆Hads and -∆Sads quantities and experimental data was derived through the Antoine-type equation, which enables the evaluation of both -∆Hads and -∆Sads from adsorption second virial coefficient, B2S, calculated on the basis of chromatographically determined adsorption isotherms [1]. The values of this virial coefficient were calculated by employing the parameters of the Tóth and Unilan equations. The adsorption second virial coefficient is a linear function of the reciprocal column temperature, T, akin to the specific retention volume. The three parameter equations employed, i.e., the Tóth and Unilan, appeared to be the best equations for the description of chromatographic data on the adsorbents studied. Their surface and structural properties were characterized by gravimetric and volumetric methods [2,3].