Removal of basic dye methylene blue in aqueous solution by Safi clay

This study reports the adsorption of methylene blue dye, a cationic dye used in dyeing cotton, wood and silk, on the crude and purified clay from Safi (Morocco). The adsorption experiments demonstrated that adsorption equilibrium is established after 20 minutes. Various experimental parameters were analyzed: pH, adsorbent mass, initial dye concentration. The experimental results showed that adsorption of methylene blue onto crude and purified clay is related to the pH of the solution and the initial dye concentration. The adsorption capacity was determined using the Langmuir and Freundlich isotherms. The monolayer adsorption capacity for methylene blue dye is 50 mg per g of crude clay while the monolayer adsorption capacity on purified clay is 68,5 mg per g clay. The adsorption kinetics of methylene blue were studied using the equations of the pseudo-first-order and pseudo-second-order reactions. The kinetics of adsorption of methylene blue dye onto the crude and purified clay can be described by a pseudo-second-order model. The effect of temperature on the adsorption of the dye was also evaluated and the thermodynamic parameters were determined.