Activated carbon was prepared from banana stalk by potassium hydroxide (KOH) and carbon dioxide (CO2) activation and its ability to remove the pesticides, 2,4-dichlorophenoxyacetic acid (2,4-D) and bentazon was explored. The banana stalk activated carbon (BSAC) was characterized by Fourier transform infrared spectroscopy (FT-IR) analysis. The adsorption kinetic data were analyzed using two kinetic models: the pseudo-first-order and pseudo-second-order models. The adsorption kinetics was better represented by the pseudo-second-order model. The equilibrium adsorption data obtained at 30, 40 and 50 degrees C were analyzed by Langmuir and Freundlich isotherm models and results showed that it was better described by the Freundlich model. Higher adsorption capacity observed for 2,4-D than bentazon were attributed to the presence of electron-withdrawing -Cl groups on the aromatic ring and smaller molecular size of 2,4-D. The thermodynamic parameters, Delta G degrees, Delta H degrees and Delta S degrees determined, showed that the adsorption of 2,4-D and bentazon onto BSAC was feasible, spontaneous and exothermic. The results showed that BSAC is an efficient adsorbent for the adsorptive removal of 2,4-D and bentazon from aqueous solutions. (C) 2011 Elsevier B.V. All rights reserved.