Bentazon and carbofuran adsorption onto date seed activated carbon: Kinetics and equilibrium

Date seed (DS), an abundant and inexpensive natural resource in Iraq, was used to prepare DS activated carbon (DSAC) by physiochemical activation with potassium hydroxide (KOH) and carbon dioxide (CO2) as the activating agents at 850 degrees C for 3 h and 37 min. The adsorption kinetics and equilibrium of bentazon and carbofuran onto DSAC were examined in batch process. Adsorption studies were conducted in the pesticides initial concentration range of 25-250 mg/L, temperature of 30 degrees C and pH of 5.5. The pH studies were undertaken in the pH range 2-12. The adsorption kinetic data were analyzed by non-linear fitting using the pseudo-first-order and pseudo-second-order models. The adsorption of bentazon and carbofuran was better described by the pseudo-second-order equation. The experimental equilibrium data were analyzed by non-linear fitting using Langmuir and Freundlich isotherm models. Equilibrium data fitted better with the Freundlich model for both pesticides. DSAC showed higher adsorption in the case of carbofuran than for bentazon. Desorption of the used DSAC was studied using ethanol as solvent and percent desorption efficiencies of 84.1 and 82.2% were obtained after three cycles for bentazon and carbofuran, respectively. The high adsorption capacity of DSAC obtained for both pesticides showed that DS is a good precursor for the preparation of activated carbon for the adsorptive removal of bentazon and carbofuran. (C) 2011 Elsevier B.V. All rights reserved.