Competitive adsorption of heavy metals on local landfill clay

The aim of this study is to investigate the interaction of CrIII and CdII 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, Qe, 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 CrIII 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 CrIII ions compared to the Na-purified clay. However, the uptake of CdII 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 CdII 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 CrIII and CdII 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 CdII has an important effect on the uptake of CrIII.