Adsorption Performance and Mechanism in Binding of Azo Dye by Raw Bentonite

Abstract

The adsorption behavior of methyl orange (MO) from aqueous solution onto rawbentonite (RB) sample was investigated as a function of parameters such as pH, inor-ganic anion, contact time, and temperature. The Langmuir and Freundlich adsorptionmodels were applied to describe the equilibrium isotherms. Langmuir adsorptioncapacity was found to be 34.34 mg/g at pH 4.0. The pseudo-first-order, pseudo-second-order kinetic, and the intra-particle diffusion models were used to describe the kineticdata. The values of the energy (Ea), enthalpy (DH6¼), and entropy of activation (DS6¼) werecalculated as 38.62 kJ/mol, 36.04 kJ/mol, and 150.05 J/mol K, respectively, at pH 4.0.