Adsorption-desorption and kinetics studies of Methylene Blue Dye on Na-bentonite from Aqueous Solution

Abstract

Bentonite, which is composed mainly of clay minerals belonging to the smectite group, has a great scope in chemistry and industry. This study was conducted with a sample collected from the region of Nador (northeastern Morocco, North Africa), which is changed and purified sodium. In this work, adsorption experiments were carried out for the blue using the homo- ion exchanged sodium bentonite . The adsorption isotherms are determined experimentally and analyzed by different models( Langmuir, Freundlich and Redlich - Peterson ). The experimental data were analyzed by the Freundlich and the Langmuir isotherm types for low values of equilibrium concentration. The rise of the isotherm in this range of concentrations was related to the affinity of Methylene Blue for clay sites, and the equilibrium data fitted well with the Freundlich model with maximum adsorption capacity of 309,677 mg/g for a ratio RS/L= 0.13%. Pseudo-first and pseudo-second-order kinetic models were tested with the experimental data and pseudo-second order kinetics was the best for the adsorption of Methylene Bleu with coefficients of correlation R² ≥ 1, and the adsorption was rapid with 96 % of the Methylene Blue adsorbed within the first 18 min.