Kinetics and thermodynamics of methylene blue adsorption by cobalt-hectorite composite

The cobalt-hectorite composite is used for the removal of MB from aqueous solution. Research concerning the effects of pH, composite dose, initial dye concentration and temperature are presented and discussed. Experiment data was analyzed using pseudo-second-order kinetics, intra-particle diffusion, and film diffusion. The characteristic parameters for each model have been determined. Thermodynamic parameters such as activation (Ea), standard free energy (ΔGo), the enthalpy (ΔHo) and the entropy (ΔSo) were also evaluated. The negative value of ΔGo (kJ/mol) and ΔHo (kJ/mol) indicates the spontaneous and exothermic nature of the reactions. The data of Ea shows the physisorption process of MB adsorption on Co-hectorite composite.

► In this paper, we reported equilibrium models and kinetic for the adsorption of methylene blue on Co-Hectorites. The rate-limiting step was controlled by both intra-particle diffusion and film diffusion. ► The thermodynamics of the adsorption process was researched. The thermodynamic parameters evaluated reveal the spontaneous and exothermic process of MB adsorption on Co-Hectorite composite. Little work has been studied the adsorption thermodynamics of Co-Hectorite. ► The result would be useful for design of wastewater treatment plants for removal of dye.