Competitive adsorption of heavy metals on local landfill clay

The aim of this study is to investigate the interaction of Cr-III and Cd-II ions in solution with the local landfill clay of Jebel Chakir (Ghorbel-Abid et al., 2009) located in the northwest of Tunis (Tunisia, North Africa). The adsorption properties of natural clay and the Na-purified clay in a chromium and cadmium rich aqueous solution have been studied by batch technique. The amount of adsorbed heavy metals ions, Q(e), was determined for the adsorption systems as a function of the contact time, the pH, and the metal ion concentration. The results show that the uptake of Cr-III by the purified clay is very fast. The quantity removed from the solution reached a maximum value 15 min after mixing, for the purified clay, and 1 h for the natural clay, although the latter removes greater quantities of Cr-III ions compared to the Na-purified clay. However, the uptake of Cd-II reached its maximum value approximately 2 h after mixing, for the purified clay, and 3.5 h for the natural clay, although the removed quantities of Cd-II ions are comparable in both the Na-purified and natural clay. The experimental data points have been fitted to the Langmuir and Freundlich models. The competitive adsorption isotherms of Cr-III and Cd-II ions in similar conditions have been studied by the batch technique. The amount of adsorbed ions, Qe was determined. The results show that the presence of Cd-II has an important effect on the uptake of Cr-III. (C) 2011 Production and hosting by Elsevier B.V. on behalf of King Saud University.