Adsorption of Cr (VI) and Cd (II) on chitosan grafted polyaniline-OMMT nanocomposite: isotherms, kinetics and thermodynamics studies

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A novel nanocomposite adsorbent chitosan grafted polyaniline-OMMT (CPOM) was synthesized by oxidative free radical polymerization of aniline in presence of montmorillonite and chitosan. The material was well characterized by FTIR, XRD, TGA, SEM and TEM and engaged for the removal of Cr (VI) and Cd (II) from aqueous solutions. Various parameters such as adsorbent dose, solution pH, metal ion concentration and temperature were studies to find the optimum conditions for adsorption reaction. The equilibrium data were applied to study the Langmuir, Freundlich, Flory-Huggins and Temkin models. On the basis of value of correlation coefficient, the applicability of Langmuir isotherm model was confirmed and maximum monolayer adsorption capacity was found to be 90.90 mg g –1 for Cr (VI) and 54.64 mg g –1 for Cd (II). The adsorption kinetics data were found to be best followed by pseudo-second-order reaction and the adsorption mechanism was well described by chemisorption. Thermodynamic studies showed that the adsorption process was endothermic and feasible. The results show that the material exhibit a high removal efficiency towards Cr (VI) and Cd (II).