Adsorption of Acid Blue 193 from aqueous solutions onto BTMA-bentonite

The adsorption of Acid Blue 193 (AB193) onto benzyltrimethylammonium (BTMA)-bentonite was investigated in aqueous solution in a batch system with respect to contact time, pH and temperature. The surface modification of BTMA-bentonite was examined using the FTIR technique. The pseudo-first-order, pseudo-second-order kinetic models and the intraparticle diffusion model were used to describe the kinetic data and the rate constants were evaluated. The experimental data fitted very well the pseudo-second-order kinetic model and also followed the intraparticle diffusion model up to 60 min, whereas diffusion is not only the rate controlling step. The Langmuir, Freundlich and Dubinin-Radushkevich (D-R) adsorption models were applied to describe the equilibrium isotherms and the isotherm constants were also determined. The Langmuir, Freundlich and D-R models agree with experimental data well. The change of free energy, enthalpy and entropy of adsorption were also evaluated for the adsorption of AB 193 onto BTMA-bentonite. The results show that BTMA-bentonite could be employed as low-cost material for the removal of acid dyes from effluents. (c) 2005 Elsevier B.V. All rights reserved.