Photocatalytic reduction of Cr(VI) on nanosized Fe2O3 supported on natural Algerian clay: Characteristics, kinetic and thermodynamic study

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Vol. 200-202; pp. 611 - 618
• Main Authors: Mekatel, H., Amokrane, S., Bellal, B., Trari, M., Nibou, D.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier B.V 15.08.2012; Elsevier
• Subjects: Algerian clay; Applied sciences; Catalysis; Catalytic reactions; Chemical engineering; Chemistry; Chromate photo reduction; clay; energy; Exact sciences and technology; General and physical chemistry; Gibbs free energy; heat production; hematite; illite; Impregnation; Reactors; scanning electron microscopy; solar radiation; spectroscopy; surface area; temperature; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; X-ray diffraction; α-Fe2O3; α-Fe2O3; Impregnation; Chromate photo reduction; Algerian clay; Scanning electron microscopy; Enthalpy; Photocatalysis; Specific surface area; Dispersive spectrometry; X ray diffraction; Free energy; O; Chemical reduction; α-Fe; First order; Visible radiation; pH; Kinetics; Thermodynamic properties; Solar radiation; Catalyst
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2012.06.121

► The work deals with the Cr(VI) reduction on Fe2O3 loaded clay under visible light. ► The conduction band of Fe2O3 (−1.08V) is more negative than the HCrO4-/Cr3+ level. ► The Fe2O3/clay hetero-system is synthesized by impregnation. ► The Cr(VI) reduction follows a pseudo first order kinetic with of oxalic acid. Nanosized α-Fe2O3 (hematite) supported on Algerian clay (Fe2O3/clay), by impregnation is successfully used for the chromate reduction under visible light. The hetero-system is investigated by X-ray diffraction, FT-IR, scanning electron microscopy and energy dispersive spectroscopy (EDS) analysis. The microscopic observation shows that the supported hematite α-Fe2O3 is uniformly spread on the clay which consists mainly of ∼80% illite. The BET measurement gives a specific surface area of 140m2g−1. The photo-electrochemical characterization is undertaken to assess the photoactivity. The sensitizer Fe2O3 has a conduction band (−0.76VSCE) more cathodic than the chromate level (∼0.1VSCE). As application, the reduction is optimized with respect to catalyst dosage, Cr(VI) concentration, pH and temperature. A remarkable performance is obtained in less than 3h for a concentration of 50ppm at pH∼2 with a dosage of 1mg/mL. The chromate removal obeys to a pseudo first order kinetic with an apparent constant of 0.013min−1. The negative enthalpy and free energy indicate a spontaneous and exothermic process. Upon solar irradiation, the reduction of 100ppm Cr(VI) solution is completed after only 50min.