Comparative studies of operational parameters of degradation of azo dyes in visible light by highly efficient WOx/TiO2 photocatalyst

• Published in: Journal of hazardous materials Vol. 177; no. 1-3; pp. 781 - 791
• Main Authors: AHMED KHAN LEGHARI SAJJAD, SHAMAILA, Sajjad, TIAN, Baozhu, CHEN, Feng, JINLONG ZHANG
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier 15.05.2010
• Subjects: Adsorption; Applied sciences; Azo Compounds - chemistry; Azo Compounds - radiation effects; Benzenesulfonates - chemistry; Benzenesulfonates - radiation effects; Carboxylic Acids; Catalysis; Catalytic reactions; Chemical engineering; Chemistry; Coloring Agents - chemistry; Coloring Agents - radiation effects; Exact sciences and technology; General and physical chemistry; Kinetics; Light; Nanocomposites; Oxides - chemistry; Pollution; Reactors; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Titanium - chemistry; Tungsten - chemistry; Water Pollutants, Chemical - chemistry; Discoloration; Conversion rate; AO7; Modeling; Composite material; Optimization; Powder; Mineralization; Azo dye; Visible radiation; pH; WO; Aromatic compound; Nanocomposite; Oxidation; TiO; Solar radiation; Chemical reactivity; Photochemical degradation; MO; Hydrocarbon; Aliphatic compound; Photocatalysis; Reuse; Operational parameters; X ray diffraction; Ultraviolet radiation; Transmission electron microscopy; Adsorption; Physicochemical purification; Kinetics; Titanium oxide; Catalyst; Comparative study; Reflectance
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2009.12.102

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.