Theoretical studies of hydrocarbon homologous series adsorption on activated carbons: Adsorption equilibria and calorimetry

The effect of the surface heterogeneity and lateral interactions between admolecules on adsorption of homologous series of light n-alkanes on activated carbons (ACs) was studied. For alkanes, the possibility to occupy more than one adsorption site bz a molecule is taken into account, thus the multi-site occupancy adsorption was considered. The generalized form of the Dubinin–Astakhov isotherm equation has been applied, taking type of surface topography as well as interactions between the adsorbed molecules into consideration. Therefore, it is possible in terms of the assumed adsorption model to distinguish whether the AC surface in question can be better characterized by “patchwise”, “random” or “mediate” model of the surface topography. Isosteric heats of adsorption corresponding to the model of multi-site occupancy adsorption were calculated, because the heat of adsorption profile exhibits both the degree of energetic heterogeneity of the gas–solid system and the strength of the interactions between admolecules. The heat effects of single gases corresponding to the case of multi-site occupancy adsorption have not been studied yet. Our theoretical studies were extensively tested based on the experimental data taken from literature.