Retention of chromium (III) and cadmium (II) from aqueous solution by illitic clay as a low-cost adsorbent

The adsorption by clay, a low-cost material, is, among different physicochemical processes, an efficient way for treating water that contains a low or a moderate concentration of heavy elements. The aim of this study is to investigate the interaction of Cr (III) and Cd (II) ions in solution, with local clay. Local clay, from Jebel Tejra located South West of Tunisia in North Africa, has been characterized. The mineralogical and chemical compositions of the materials were determined by X-ray diffraction (XRD), infrared spectroscopy (IR) and inductively coupled plasma ICP. The cation exchange capacity (CEC) was obtained using the methylene blue adsorption isotherm and the surface area (SA) was determined by applying the BET equation to the nitrogen adsorption isotherm at 77 K. The natural clay removes greater quantities of Cr (III) ions compared to purified clay. The experimental data points have been fitted to the Langmuir and Freundlich models. The competitive adsorption equilibrium isotherms of Cr (III) and Cd (II) ions, in a rich aqueous solution on natural and purified clays have been studied by the batch technique. The amount of adsorbed ions. Q(e) was determined. The results show that the presence of Cd (II) has an important effect on the uptake of Cr (III). (C) 2010 Elsevier B.V. All rights reserved.