A convenient adsorption kinetic equation has been offered for the modeling of adsorption kinetics in batch systems when diffusion taking parts to the rate-controlling step of adsorption. This model is suggested based on the Smoluchowski-Waite equation for diffusioncontrolled second-order reactions. The proposed new model has better performance (lower absolute values of the relative errors (AARE) %) respect to the pseudo-second-order. Results of this equation are in agreement with experiment data especially at the initial times of adsorption that diffusion contributes to the rate-controlling step of adsorption. KEYWORDS:
