Mineralogical identification, spectroscopic characterization, and potential environmental use of natural clay materials on chromate removal from aqueous solutions

The first part of this study is a chemico-mineralogical characterization of two Cretaceous sedimentary clays taken from Aleg formation of Jebel M’rhila (Tunisia). The clay deposits were localised in different levels; the uppermost (C1) and the lowermost (C2). This research has been carried out by using X-ray diffraction (XRD), infrared spectroscopy (IR), thermal analysis (TG and DT), observations with scanning electron microscopy (SEM) and analytic techniques. The second part of this study consists in evaluating the adsorption capacity of the natural clays in order to facilitate their industrial or environmental applications. At 20 °C and at pH 5, the maximum Cr(VI) adsorption capacities were 10.9 and 4.5 mg g−1 for C1 and C2, respectively. Langmuir, Freundlich and Dubinin–Radushkevich (D–R) isotherm models were used to evaluate the equilibrium data. The Langmuir isotherms fit better the experimental data. The results which were obtained can be introduced in data base for designing an adsorption process using clay, as a low-cost adsorbent for the treatment of the Cr(VI) rich wastewater.