Adsorption thermodynamics of Methylene Blue onto bentonite

The effect of temperature on the equilibrium adsorption of Methylene Blue dye from aqueous solution using bentonite was investigated. The equilibrium adsorption data were analyzed using three widely applied isotherms: Langmuir, Freundlich, and Redlich-Peterson. A non-linear method was used for comparing the best fit of the isotherms. Best fit was found to be Redlich-Peterson isotherm. Thermodynamic parameters, such as Delta G degrees, Delta H degrees, and Delta S degrees, were calculated using adsorption equilibrium constant obtained from the Langmuir isotherm. Results suggested that the Methylene Blue adsorption on bentonite was a spontaneous and endothermic process. (C) 2009 Elsevier B.V. All rights reserved.