SBA-15 templated mesoporous carbons for 2,4-dichlorophenoxyacetic acid removal

The ordered mesoporous silica SBA-15 was synthesized and used as a template for obtaining mesoporous carbon replicas. Adsorptive removal of pesticide 2,4-dichlorophenoxyacetic acid (2,4-D) from aqueous solutions onto two carbon replicas was investigated. Batch adsorption experiments varied in initial adsorptive concentration, contacting times, solution pH, and adsorbent dosage. Pseudo-first order model, pseudo-second order model, and intraparticle diffusion model were selected to interpret the kinetics of adsorption. Kinetic parameters such as rate constants, equilibrium adsorption capacities and correlation coefficients were calculated and discussed for each model. Equilibrium data were linearly fitted to Langmuir, Freundlich, Tamkin, Dubinin-Radushkevich, Jovanovic, Hurkins-Jura and Halsey isotherm models. It was shown that adsorption of 2,4-D onto two carbon replicas well followed the pseudo-second order kinetic model. Langmuir isotherm represented experimental data in the best way since this model gave the best fit. Adsorption capacity strongly depends on the solution pH and increases at lower pH values. (C) 2012 Elsevier B.V. All rights reserved.