Removal of Cu (II) Ions from Aqueous Solution by Adsorption Using Natural Clays: Kinetic and Thermodynamic Studies

This study deals with adsorption kinetic, equilibrium and thermodynamic of Cu(II) ions from aqueous solution onto two natural local clays. The adsorbents were crushed, screened and characterized using different chemical and physical techniques like X-ray fluorescence, X-ray diffraction, Fourier transform infrared, etc. The effects of Cu (II) ion concentration, temperature, mass of adsorbents and pH of adsorption have been investigated. The maximum yield of adsorption was found in 90% and 30% of clay I and clay II respectively, at the conditions of initial concentration 500 mg. L^-1, adsorbent mass 3 g.L^-1, pH 6 and 298 K. They were explained by pseudo-second order in kinetic models. The experimental data of adsorption in equilibrium condition are tested by the isotherm equations like Freundlich, Langmuir and Dubinin-Radushkevich at different concentrations. Calculated thermodynamic quantities such as free energy (ΔG), the enthalpy (ΔH) and the entropy of adsorption (ΔS) indicate that the adsorption reaction was spontaneous, endothermic and controlled by physical mechanisms.