Reduction of seawater salinity by natural zeolite (Clinoptilolite): Adsorption isotherms, thermodynamics and kinetics

We have investigated the adsorption isotherms, thermodynamics and adsorption kinetics of salt onto zeolites. The adsorption isotherm was studied using Langmuir, Freundlich, Temkin and Dubinin-Radushkevich models. The separation factor, R-L = 0.588, indicates the nature of adsorption process is favorable. The adsorption is physical as indicated by high adsorption intensity (n > 1) and small mean free energy (E < 20 kj/mol). The negative AG (-13.33 to 13.44 kJ/mol) indicates the spontaneous nature of adsorption. The negative AH (-16.71 kJ/mol) confirms the exothermic nature of adsorption process, whereas the negative AS ( 0.0116 kJ/mol K) suggests the configuration of the adsorbate on the zeolite surface is less random. Pseudo-second-order kinetic model well fits to the experiment data. Based on the characteristics of the adsorption isotherms, thermodynamic and adsorption kinetics, zeolite is potential for seawater desalination process. (C) 2016 Published by Elsevier B.V.