The transient adsorption of catechol from aqueous solution (C-0 = 5 kg/m(3)) on activated carbon in an upflow fixed-bed column at 293 K was studied. The critical time at which the early breakthrough of the maximum admissible concentration (C-crit = 0.3 x 10(-3) kg/m(3)) occurs is deduced from a Homogeneous Surface Diffusion Model (HSDM) that accounts for adsorption equilibrium and mass-transfer kinetics. The mass-transfer coefficient is measured using a thin bed adsorption method and a correlation is proposed to account for its dependence with the flow rate. The sensitivity of the model for the prediction of the critical time to the different parameters is discussed and it is found to be mostly dependant upon the mass-transfer coefficient K-f and the adsorbant mean particle diameter d(P). In addition, the critical time has been proved to increase with the adsorption capacity q(max). The existence of an optimal flow of polluted effluent through the column to achieve the removal of the pollutant with the highest efficiency is observed. (C) 2010 Elsevier B.V. All rights reserved.