Removal of Cu(Ii) and Cd(Ii) Ions From Aqueous Solutions Using Local Raw Material as Adsorbent: a Study in Binary Systems

Abstract

The purpose of this study is to examine the interaction of Cu(II) and Cd(II) ions in solution with the local raw clayey material of Tilkitepe located in the eastern shore of Lake Van in East Anatolia (Turkey). This material was used as an adsorbent without any chemical or physical treatment and was characterized by X-ray fluorescence, X-ray diffraction, scanning electron microscope, Fourier transform infrared and differential thermal analysis-thermogravimetric analyses. Langmuir, Freundlich, Dubinin-Kaganer-Radushkevich, Temkin and Harkins-Jura non-linear adsorption isotherm models were applied to the experimentally obtained adsorption data and the isotherm constants were calculated. The highest R-2 values for adsorption of both ions in the binary system were obtained by applying the experimental data to the Freundlich isotherm model. In binary system, the experimental adsorption capacities for Cu(II) and Cd(II) ions obtained by kinetic data were 52.631 and 44..843 mg g(-1) at 600 mg L-1 initial metal ion concentrations, respectively In the competitive adsorption, the affinity of Cu(II) toward the adsorbent was much higher than that of the Cd(II). Adsorption kinetics was evaluated using the pseudo-first-order, pseudo-second-order, intraparticle diffusion, Avrami and mass transfer kinetic models. The experimental data proved a closer fit to the pseudo-second-order model. Thermodynamic parameters such as enthalpy (Delta H degrees), Gibbs free energy (Delta G degrees) and entropy (Delta S degrees) were calculated using adsorption isotherms obtained at different temperatures. The results show that the adsorption is spontaneous and controlled by a physical mechanism.