A simple isotherm equation for modeling the adsorption equilibria on porous solids over wide temperature ranges

A new isotherm equation is derived from the distribution of energetic heterogeneity of adsorbent surface. It is simple in form and is physically compatible with the mechanism of monolayer adsorption. The proposed equation is used to model the experimental adsorption equilibrium of methane on activated carbon for the range of 158-333 K. It successfully represents the whole set of data for both sides of the critical temperature. Compared with the Langmuir-Freundlich equation, it yields a parameter of saturation adsorption, which is in agreement with the fictitious limiting adsorption defined by the intersection of linear isotherms.