Removal of dyes and pigments from wastewaters of dying and printing industries is a major environmental issue. Sorption rate and equilibrium parameters of Methylene Blue on granular and powdered activated carbons were investigated in a batch adsorber. Due to the significance of pore diffusion resistance and partial closure of pore mouths by dissociatively chemisorbed dyes, both sorption rate and sorption capacity values evaluated for granular Carbon were lower than the corresponding values for powdered activated carbon. Concentration independent effective pore diffusivity values in the order of magnitude of 10(-9) cm(2)/s were obtained by the moment analysis of a proposed diffusion model (Model I). (c) 2008 Elsevier B.V. All rights reserved.