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Equilibrium, kinetic and thermodynamic studies on the adsorption of m-cresol onto micro- and mesoporous carbon
, J.J. Vijaya, G. Sekaran, K. Kayalvizhi
Published in
PMID: 17509758
Volume: 149
Issue: 1
Pages: 134 - 143
Investigations were conducted in batch mode to study the adsorption behaviour of m-cresol on a porous carbon prepared from rice husk (RHAC) by varying the parameters such as agitation time, m-cresol concentration (50-300 mg/l), pH (2.5-10) and temperature (293-323 K). Studies showed that the adsorption decreased with increase in pH and temperature. The isotherm data were fitted to Langmuir, Freundlich, and Dubinin-Radushkevic (D-R) models. The kinetic models such as pseudo-first-order, pseudo-second-order and intraparticle diffusion models were selected to understand the reaction pathways and mechanism of adsorption process. The thermodynamic equilibrium coefficients obtained at different temperatures were used to evaluate the thermodynamic constants ΔG°, ΔH° and ΔS°. The sorption process was found to be exothermic in nature (ΔH°: -23.46 to -25.40 kJ/mol) with a decrease in entropy (ΔS°: -19.44 to -35.87 J/(mol K)). The negative value of Gibbs free energy, ΔG° indicates that the adsorption occurs via a spontaneous process. The decrease in the value of -ΔG° from 17.70 to 13.54 kJ/mol with increase in pH and temperature indicates that the adsorption of m-cresol onto activated carbon is less favourable at higher temperature and pH range. The influence of mesopore and a possible mechanism of adsorption is also suggested. © 2007 Elsevier B.V. All rights reserved.
About the journal
JournalJournal of Hazardous Materials