Adsorption of pesticides from aqueous solution onto banana stalk activated carbon

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.