Preliminary study on the adsorption of the cationic dye astrazon red by a portuguese bentonite

Abstract

The adsorption of Astrazon Red (C.I. Basic Red 46) in aqueous solution by a bentonite clay from Benavila, Portugal, was studied. The bentonite sample was mainly composed of montmorillonite, Na-Feldspar and calcite (XRD analysis). The texture characteristics were determined by Hg and He porosimetry and the specific surface area by the methylene blue adsorption method. A kinetic experiment was carried out at 15 degrees C to determine the time required to reach equilibrium. Experimental data were well described by the pseudo-second order kinetic model. Adsorption equilibrium isotherms were determined at different temperatures and the results fitted to Langmuir and Freundlich models. According to Langmuir model, the adsorption capacities were 141.0, 148.7 and 157.8 mg/g at 15, 25 and 35 degrees C, respectively.