Using local IAST with micropore size distribution to predict multicomponent adsorption equilibrium of gases in activated carbon

A mathematical model is proposed to predict multicomponent adsorption equilibrium of gases in a heterogeneous activated carbon. The model, called MPSD-IAST, assumes a micropore size distribution (MPSD) to represent the energetic heterogeneity of adsorbent and uses the ideal adsorbed solution theory (IAST) to describe the local multicomponent adsorption equilibrium within a given pore. The overall adsorption isotherm is the integral of the local adsorbed-phase concentration over the complete pore size distribution range accessible to the adsorbate molecule. The adsorbate-adsorbent interaction energy is related to micropore size via the Lennard-Jones potential theory, and the size exclusion effect is taken into account in the competitive adsorption of different species for a given pore. The MPSD-IAST model predictions are examined with the equilibrium data of mixed gases measured on two commercial activated carbons (Ajax and Norit). The results are compared with those obtained using a MPSD-EL model where the local adsorption isotherm is described by an extended Langmuir equation.