Adsorption of resorcinol and catechol on granular activated carbon: Equilibrium and kinetics

Investigations were conducted in the batch mode for studying the adsorption behavior of resorcinol and catechol on granular activated carbon from a basic salt medium (BSM) at pHapproximate to7.1 and temperature 30 degreesC. The isotherm data were correlated with six isotherm models, namely Langmuir, Freundlich, Redlich-Peterson, Radke-Prausnitz, Toth, and Fritz-Schlunder's using a nonlinear regression technique. It is observed that the catechol isotherm data may be represented by Redlich-Peterson, Radke-Prausnitz, Toth, and Fritz-Schlunder models with similar accuracy (max. dev. 12%). And the resorcinol data may be represented by Freundlich, Redlich-Peterson, Radke-Prausnitz, and Fritz-Schlunder models equally well (max. dev. 15%). Freudlich being a simple model is recommended for resorcinol. At the conditions investigated in this study, catechol is adsorbed to a greater extent than resorcinol. This is due to the compound's solubility and position of the -OH group on the benzene aromatic ring. The kinetics of adsorption have been found to be diffusion controlled and the value of effective particle diffusion coefficients is of the order of 10(-13) m(2)/s. Three distinct phases of kinetics-rapid, medium, and slow-have been observed. These results should be useful for the design of adsorbers for removing these pollutants. (C) 2003 Elsevier Ltd. All rights reserved.