Photocatalytic oxidation of monuron in the suspension of WO3 under the irradiation of UV–visible light

• Published in: Chemosphere (Oxford) Vol. 86; no. 11; pp. 1079 - 1086
• Main Authors: Chu, W., Rao, Y.F.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.03.2012; Elsevier
• Subjects: Applied sciences; benzene; Decay pathway; dechlorination; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Exact sciences and technology; Global environmental pollution; Herbicides - analysis; Herbicides - chemistry; Hydrogen-Ion Concentration; hydroxyl radicals; hydroxylation; irradiation; Kinetics; Methylurea Compounds - analysis; Methylurea Compounds - chemistry; Monuron; oxidants; oxidation; Oxidation mechanism; Oxides - chemistry; Photochemical Processes - drug effects; photolysis; Pollution; Pollution, environment geology; Tungsten - chemistry; Ultraviolet Rays; WO3; WO3; Monuron; Oxidation mechanism; Decay pathway; Agricultural chemical product; Pollutant behavior; Photocatalysis; Pesticides; Herbicide; Chemical pollution; Ultraviolet radiation; Decontamination; Phenylureas; Visible radiation; WO; Oxidation; Photooxidation; Organic compounds; Photochemical degradation
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2011.11.062

► We investigated the photodegradation of monuron in UV–Vis/WO3 system. ► Hydroxyl radicals are believed to play a major role in this system. ► The generation of hydroxyl radicals mainly proceeds through the oxidation path. ► The influence of inorganic oxidants on the performance of this system was studied. ► Comparison between monuron decay pathways by UV–Vis/WO3 and UV/TiO2 was also conducted. A comprehensive study of the degradation of monuron, one of the phenylurea herbicides, was conducted by UV–Vis/WO3 process. It was found that hydroxyl radicals played a major role in the decay of monuron while other radicals (e.g. superoxide) and hole might also contribute to the decomposition of monuron. The oxidation path likely plays a major role in the generation of hydroxyl radicals. The effects of initial pH level, initial concentration of monuron, and inorganic oxidants on the performance of UV–Vis/WO3 process were also investigated and optimized. Comparison between monuron decay pathways by UV–Vis/WO3 and UV/TiO2 was conducted. The decay mechanisms, including N-terminus demethylation, dechlorination and direct hydroxylation on benzene ring, were observed to be involved in the oxidation of monuron in these two processes. Sixteen intermediates were identified during the photodegradation of monuron and degradation pathways were proposed accordingly.