Potential Improvement in Photo Reduction of Towards Cr(VI) Species from Aqueous Solutions onto a Heterogeneous Na-Clay/Fe2O3 Catalyst

Clays in the soils are a natural barrier against pollution. A representative sample of clay (illite) from Algeria is collected and analyzed by XRD. The results show that this sample is illite containing calcite and quartz as impurities. We also analyzed the clay by SEM, EDS, and BET, and modified it by chemical treatment with NaCl in order to increase its specific surface area with the insertion of Na+ cations into the inter-foliar space. The study of Cr(VI) ions adsorption onto Na-Clay was performed. The influence of Cr(VI) initial concentration, pH of the solution, temperature, and solid/liquid ratio was studied. Among the tested models, the equilibrium data are well-fitted by the Langmuir isotherm. The maximum Cr(VI) adsorption rate was 44% at 25°C with limited capacity adsorption of 10 mg/g. The adsorption kinetic is best described by the pseudo-second-order model. The Cr(VI) ions reduction onto Na-Clay/Fe2O3 and the effect of the same parameters were also performed. The maximum reduction (98%) was reached at pH = 2, T = 25°C, [Cr(VI)] = 50 mg/L, and S/L = 1 mg/mL. It was found that the reaction follows the pseudo-first-order rationalized well by the Langmuir-Hinshelwood (LH) model. The evaluation of the thermodynamic parameters (ΔG°, ΔH°, and ΔS°) revealed that chromium (VI) adsorption and reduction were endothermic and exothermic respectively.