The aqueous-phase adsorption and desorption of toluene in Filtrasorb-300 (F-300) activated carbon fixed-bed adsorbers at 25 degrees C were investigated under a wide range of operating conditions. Process dynamics were described successfully using a homogeneous surface diffusion model with external mass transfer and a surface diffusion coefficient that increases with surface coverage. The model also accounted for irreversible toluene adsorption on F-300. The adsorption isotherm parameters, the surface diffusion coefficient and its dependence on surface concentration were determined independently in batch adsorption studies. The value of the external mass transfer coefficient as a function of the Reynolds number was determined by fitting the adsorption breakthrough curves. The fraction of irreversible toluene adsorption as a function of initial surface loading was found from the desorption breakthrough curves. Use of these independently measured equilibrium and transport parameters in the model permitted the successful description of experimental rates of toluene adsorption and desorption in F-300 fixed beds under a variety of operating conditions.