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 AB193 onto BTMA-bentonite. The results show that BTMA-bentonite could be employed as low-cost material for the removal of acid dyes from effluents.