Sorption kinetics for surface resistance controlled systems

A simple mathematical model is proposed to represent the kinetics of adsorption and desorption for a system in which surface resistance is rate controlling with a concentration dependent rate coefficient. Expressions for the transient adsorption and desorption curves are obtained in closed form. When the rate coefficient increases strongly with loading, as it does for many of the systems that have been studied experimentally, the adsorption and desorption curves show characteristically different shapes. It is shown that the model provides a good representation of the sorption kinetics for methanol in large crystals of ferrierite for which extensive experimental data are available.