Removal of basic dye using raw and acid activated bentonite samples

The adsorption behavior of crystal violet (CV(+)) from aqueous solution onto raw (RB) and acid activated (AAB) bentonite samples was investigated as a function of parameters such as initial CV(+) concentration, contact time and temperature. The Langmuir and Freundlich adsorption models were applied to describe the equilibrium isotherms. The adsorption rate was fast and more than half of the adsorbed-CV(+) was removed in the first 55 min for RB and 25 min for 0.2-AAB at the room temperature (C(0)=1.2 mmol/g). The pseudo-first order, and pseudo-second order kinetic models were used to describe the kinetic data and rate constants were evaluated. The results best fit the pseudo-second order kinetic model with the rate constant, k(2), in the range of 13.52 x 10(-2) to 5.53 x 10(-2)g/mmol and 52.70 x 10(-2) to 6.69 x 10(-2)mmol/g min for RB and 0.2-AAB sample, respectively (C(0)=0.1-1.2 mmol/g).