Role of pore size distribution in the binary adsorption kinetics of gases in activated carbon

Abstract

A heterogeneous multicomponent adsorption model is presented to study the adsorption equilibrium and kinetics of mixed gases in activated carbon (AC). The model utilizes a micropore size distribution concept to interpret the solid structural heterogeneity. The pore size is related to the adsorbate-adsorbent interaction energy by the Lennard-Jones potential. The size exclusion effect is taken into account in the competition of different species for a given pore. Both pore diffusion of free species and surface diffusion of adsorbed species are considered in the theory. The driving force for surface diffusion is the chemical potential gradient in the adsorbed phase. Isothermal acid kinetics parameters extracted from single-component data fittings are used to predict multicomponent adsorption kinetics. Single and binary experimental adsorption and desorption data of ethane and propane in Norit activated carbon are collected to validate the model. The agreement between the model results and experimental data is good in general.