title: Comparative studies of operational parameters of degradation of azo dyes in visible light by highly efficient WOx/TiO2 photocatalyst.
abstract: The multidimensional aspects of the photocatalytic activity were investigated in a systematic way by employing the dyes Acid Orange 7 (AO7) and Methyl Orange (MO) as substrates in terms of their degradation or conversion rates. 4.0% WO(x)/TiO(2) nanocomposite demonstrated the best reactivity under visible light, allowing more efficient usage of solar light. The reduced form of W decreased the band gap and inhibited electron hole recombination efficiently. This composite was characterized by X-ray diffraction spectroscopy (XRD), UV-vis diffuse reflectance spectroscopy (DRS), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX). A series of experiments were conducted to investigate the operational parameters under visible light irradiation such as optimization of nanocomposites wt%, change of pH, reuse of catalyst and initial dye concentration. The kinetics of the dyes degradation was found to follow the Langmuir-Hinshelwood model. Decomposition or mineralization was investigated with the changes of absorption spectra, pH, degradation efficiency and TOC removal in visible irradiation systems. FT-IR spectroscopy of these adsorbed dyes on WO(x)/TiO(2) powder provided an insight to the mode of its adsorption on WO(x)/TiO(2). It was found that the dye adsorbed on WO(x)/TiO(2) underwent a series of oxidation steps which lead to decolorization and formation of a number of intermediates mainly aromatic and aliphatic acids. These intermediates were quantified by GC/GC-MS.
authors.affiliation: Key Laboratory for Advanced Materials and Institute of Fine Chemicals, East China University of Science and Technology, Shanghai 200237, PR China.
authors.forename: Ahmed Khan Leghari
authors.initials: AK
authors.lastname: Sajjad
authors.forename: Sajjad
authors.initials: S
authors.lastname: Shamaila
authors.forename: Baozhu
authors.initials: B
authors.lastname: Tian
authors.forename: Feng
authors.initials: F
authors.lastname: Chen
authors.forename: Jinlong
authors.initials: J
authors.lastname: Zhang
mesh_terms: D001391:Azo Compounds / Q000737:chemistry* / Q000528:radiation effects; D001557:Benzenesulfonates / Q000737:chemistry / Q000528:radiation effects; D002264:Carboxylic Acids; D004396:Coloring Agents / Q000737:chemistry* / Q000528:radiation effects; D007700:Kinetics; D008027:Light; D053761:Nanocomposites; D010087:Oxides / Q000737:chemistry*; D014025:Titanium / Q000737:chemistry*; D014414:Tungsten / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D001391:Azo Compounds; D001557:Benzenesulfonates; D002264:Carboxylic Acids; D004396:Coloring Agents; D010087:Oxides; D014874:Water Pollutants, Chemical; C009495:titanium dioxide; C100258:methyl orange; C511604:tungsten oxide; D014025:Titanium; C014722:2-naphthol orange; D014414:Tungsten