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Removal of trivalent iron and chromium from aqueous solution by local clay

I.Ghorbel-Abid, E.Mehouachi, M. Trabelsi-Ayadi

The ability of local clay fromJebelKebir (north of Tunisia) to remove heavy metal ions fromwastewater was tested. The original claywas characterized using several techniques such as X-ray diffraction (XRD), transmission electronmicroscopy (TEM) and infrared spectroscopy (IR). The cation exchange capacities (CEC) as well as the specific surface area (SSA) were determined using the adsorption isotherm obtained with methylene bleu in aqueous solution. Chemical compositions were determined by the inductively coupled plasma technique (ICP). The results showthat thematerial is a smectite with a small proportion of kaolinite. The CEC and SSAvalues for the rawclay sample (JKb) are respectively 25meq /100 g, 206m2 /g of fired clay; and 50 meq /100 g and 403 m2/g of fired clay for Na-purified clay. During the removal process, batch technique is used, and the effects of heavy metal concentration and agitation time on adsorption efficiency are studied. The adsorption mechanism of Cr (III) and Fe (III) ions onto adsorbentswas evaluated in terms of kinetics and equilibrium. The Langmuir and Freundlich isotherms are applied in order to determine the efficiency of raw and Na-purified clay used as an adsorbent. In all cases results show that both Fe (III) and Cr (III) adsorption isotherms have a positive retention. In addition, it is concluded that natural clay can be used as an effective adsorbent for removing Fe (III) and Cr (III) fromwastewater.