title: Visible light CrO4(2-) reduction using the new CuAlO2/CdS hetero-system.
abstract: In this study, 64% of hexavalent chromium Cr(VI) reduction from the initial concentration (10(-4) M) is reported under visible light using the (CuAlO(2)/CdS) hetero-system. In this new hetero-system, low doped CuAlO(2) delafossite, synthesized by sol-gel works as an electrons reservoir with a wide space charge region (440 nm). In this case, the electron transfer to chromate is mediated via the hexagonal CdS variety, whose conduction band level is at -1.08 V with respect to the saturated calomel electrode which is more negative than the CrO(4)(2-)/Cr(3+) level. This high reduction rate is achieved under optimized pH and CuAlO(2) percentage. Moreover, salicylic acid gives the best performance among hole scavengers and CuAlO(2) approaches 100% photostability at pH 7.5. The photo-catalytic process follows a pseudo first order kinetic with a half life of 2h. The reaction products are identified by UV-visible spectrophotometry and linear voltametry at a platinum rotating electrode. The results reveal the presence of Cr(3+) after irradiation.
authors.affiliation: Centre of Research in Physical and Chemical Analysis (CRAPC), Algiers, Algeria.
authors.forename: R
authors.initials: R
authors.lastname: Brahimi
authors.forename: Y
authors.initials: Y
authors.lastname: Bessekhouad
authors.forename: N
authors.initials: N
authors.lastname: Nasrallah
authors.forename: M
authors.initials: M
authors.lastname: Trari
mesh_terms: D019187:Cadmium Compounds / Q000737:chemistry*; D002384:Catalysis; D017608:Chromium Compounds / Q000737:chemistry*; D007700:Kinetics; D008027:Light; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry*; D055668:Photochemical Processes; D013440:Sulfides / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D019187:Cadmium Compounds; D017608:Chromium Compounds; C574001:CuAlO(2); D010087:Oxides; D013440:Sulfides; C034939:cadmium sulfide; C023600:chromic oxide