This work was motivated by the need to describe the adsorption of cadmium ions from aqueous solutions. The model for the adsorption process includes differential balances for both the fixed bed and the organo-ceramic pellets in the bed. For the highly nonlinear isotherm and the physical parameters of this system, there are steep concentration profiles within the pellets. Accurate solutions were obtained using the method of lines (MOL). There is good agreement between the numerical results and the experimental breakthrough curve when the adsorption is assumed to be controlled by a film/pore diffusion mechanism. (C) 2004 Elsevier Ltd. All rights reserved.