Removal of pyridine derivatives from aqueous solution by activated carbons developed from agricultural waste materials

The paper investigates the ability of activated carbons developed from coconut shell to adsorb alpha-picoline, beta-picoline, and gamma-picolin from aqueous solution. The developed carbons are designated as SAC (activated carbon derived from coconut shells with out any treatment) and ATSAC (activated carbon derived from acid treated coconut shells). The carbons were, characterized and utilized for the sorption of alpha-picoline, beta-picoline, and gamma-picoline at different temperatures, particle size, pH and solid to liquid ratio. All the studies were performed by batch method to determine various equilibrium and kinetic parameters. The Langmuir and Freundlich isotherm models were applied and the Langmuir model was found to best report the equilibrium isotherm data. The adsorption of alpha-, beta-, and gamma-picoline followed the pseudo-second order rate kinetics. On the basis of kinetic studies, various rate and thermodynamic parameters such as effective diffusion coefficients, activation energy and activation entropy were evaluated. It was concluded that in majority of cases, the adsorption is controlled by particle diffusion at temperatures 10 degrees and 25 degrees C while at 40 degrees C it is controlled by film diffusion mechanism. Similarly at concentrations 25 and 50 mg/l the adsorption was governed by particle diffusion in most of the cases while at > 50 mg/l it was film diffusion controlled. The overall capacity of ATSAC was higher than SAC. The sorption capacity of gamma-picoline was found more followed by beta-picoline and alpha-picoline. (c) 2005 Elsevier Ltd. All rights reserved.