Poly (Methacrylic acid) grafted regenerated cellulose ions exchangers membranes for Cu(II) ion adsorption: Kinetic, isotherm, and thermodynamic studies

Abstract

Poly (methacrylic acid) grafted cellophane ions exchanger membranes have been developed for Cu2+ ions separation from synthetic metal solutions in this study. Factors affecting the adsorption process, namely the copper ions concentration, the adsorption time, the adsorption temperature, and the grafting percentage have been studied. It was found that the Cu2+ uptakes increase by increasing Cu2+ ions concentration and the grafting percentage. Equilibrium has been obtained after 30 min of adsorption while the temperature is found to be of neglectable effect. Moreover, the kinetics, isotherms and thermodynamics of the adsorption process have been monitored. Adsorption behavior was kinetically considered using the pseudo-first-order and the pseudo-second-order models. The experimental data mostly correlated with the pseudo-second-order model. Moreover, the diffusion mechanism of the Cu(II) ions through the adsorption process has been studied. Various kinetic models namely; intraparticle diffusion model, D-W diffusion model, and Boyd diffusion model used. The actual rate-controlling step for Cu(II) ions removal determined. The adsorption equilibrium was assessed by using the Langmuir and the Freundlich isotherm equations where the Freundlich model had greater constancy with the equilibrium data. Also, the maximum monolayer adsorption capacity based on the Langmuir isotherm was 4.016 mg/g. Thermodynamic parameters as enthalpy change (ΔH°), free energy change (ΔG°), and entropy change (ΔS°) also were calculated. It is revealed that the adsorption of Cu2+ ions is spontaneous, favorable, and exothermic. Fourier transforms infrared analysis, thermal gravimetric analysis, and energy dispersive X-ray analysis provided pieces of evidence of the grafting and the adsorption processes. Morphological changes have been followed using a scanning electron microscope. The membranes show excellent reusability. Minor reduction of the adsorption and regeneration processes has been detected after 10 cycles.