Preparation and characterization of activated carbon from corncob by chemical activation with H3PO4 for 2,4-dichlorophenoxyacetic acid adsorption

Corncob activated carbon (CCAC) was prepared and its ability to remove 2,4-dichlorophenoxyacetic acid (2,4-D) from aqueous solutions was studied. The BET surface area, Langmuir surface area and cumulative pore volume of CCAC were 1273.91 m/g, 2010.12 m2/g and 0.900 cm3/g, respectively. The adsorption kinetics was best represented by the pseudo-second-order model. The superiority of the Freundlich isotherm model in describing the equilibrium adsorption data was shown by the adjusted correlation coefficients (R2adj) and root-mean squared error (RMSE) values. High percent removal of 69.10, 69.58 and 73.86% were achieved for 2,4-D initial concentration of 400 mg/L at 30, 40 and 50 °C, respectively. Activation energy, Ea for the adsorption was determined to be 39.87 kJ/mol and a diffusion-controlled process indicating physisorption mechanism was proposed. From the thermodynamic parameters determined, the adsorption was found to be spontaneous and endothermic in nature. Intraparticle diffusion and Boyd kinetic models confirmed film diffusion as the rate-controlling step. A single-stage batch adsorber was designed to obtain the mass of CCAC required to achieve desired percent removal of 2,4-D from effluent solutions of different volumes using the Freundlich equation.

► Corncob was a suitable precursor for the production of activated carbon.
► The corncob activated carbon (CCAC) was produced by chemical activation with H3PO4.
► High percent removal of 2,4-D from aqueous solutions was obtained with CCAC.
► Kinetic and isotherm models were used to interpret adsorption mechanisms.
► The adsorption was found to be spontaneous and endothermic in nature.
► A diffusion-controlled process indicating physisorption mechanism was inferred.