Removal of Cd2+ from aqueous solution by adsorption using Fe-montmorillonite

Abstract Fe-montmorillonite (Fe-Mont.) is obtained by exchanging the original interlayer cations of montmorillonite by poly-hydroxyl ferric. In this paper, Fe-Mont. was synthesized by using Ca-montmorillonite (Ca-Mont.) directly under ultrasonic treatment with the aim to enhance the ability of removal of heavy metal ions from wastewater. The modified materials were characterized by X-ray diffraction (XRD) and Fourier transform infrared (FT-IR). Batch equilibrium experiments of Cd(II) ions (Cd 2+ ) adsorption on the Fe-Mont. were performed. Effects of the initial pH of the solution and contact time on the adsorption of Cd 2+ were studied. Four types of adsorption isotherms were applied to describe the adsorption isotherms of Cd 2+ by Fe-Mont. The relationship between adsorbing capacity ( q e ) and equilibrium mass concentration ( C e ) is in accordance with the isothermal adsorption equation of Langmuir. Three kinetic models, including pseudo-first-order, pseudo-second-order and the Elovich equation model, were used to analyze the Cd 2+ adsorption process. The pseudo-second-order chemical reaction kinetics provide the best correlation of the experimental data, therefore the adsorption dynamics follows the laws of pseudo-second-order kinetics.