title: Mechanism of enhanced removal of quinonic intermediates during electrochemical oxidation of Orange II under ultraviolet irradiation.
abstract: The effect of ultraviolet irradiation on generation of radicals and formation of intermediates was investigated in electrochemical oxidation of the azo-dye Orange II using a TiO2-modified β-PbO2 electrode. It was found that a characteristic absorbance of quinonic compounds at 255 nm, which is responsible for the rate-determining step during aromatics degradation, was formed only in electrocatalytic oxidation. The dye can be oxidized by either HO radicals or direct electron transfer. Quinonic compounds were produced concurrently. The removal of TOC by photo-assisted electrocatalytic oxidation was 1.56 times that of the sum of the other two processes, indicating a significant synergetic effect. In addition, once the ultraviolet irradiation was introduced into the process of electrocatalytic oxidation, the degradation rate of quinonic compounds was enhanced by as much as a factor of two. The more efficient generation of HO radicals resulted from the introduction of ultraviolet irradiation in electrocatalytic oxidation led to the significant synergetic effect as well as the inhibiting effect on the accumulation of quinonic compounds.
authors: Institute of Environmental and Municipal Engineering, North China University of Water Resources and Electric Power, Zhengzhou 450011, China. Electronic address: lifazhan2000@sina.com.
authors: Fazhan
authors: F
authors: Li
authors: Institute of Environmental and Municipal Engineering, North China University of Water Resources and Electric Power, Zhengzhou 450011, China. Electronic address: liguoting@ncwu.edu.cn.
authors: Guoting
authors: G
authors: Li
authors: Department of Chemical Engineering, Monash University, Clayton Vic 3800, Australia.
authors: Xiwang
authors: X
authors: Zhang
mesh_terms: D001391:Azo Compounds / Q000737:chemistry* / Q000528:radiation effects; D001557:Benzenesulfonates / Q000737:chemistry* / Q000528:radiation effects; D002384:Catalysis; D055664:Electrochemical Techniques; D017665:Hydroxyl Radical / Q000737:chemistry; D007854:Lead / Q000737:chemistry; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry; D017975:Ruthenium Compounds / Q000737:chemistry; D014025:Titanium / Q000737:chemistry; D014466:Ultraviolet Rays; D014874:Water Pollutants, Chemical / Q000737:chemistry* / Q000528:radiation effects
chemical_list: D001391:Azo Compounds; D001557:Benzenesulfonates; D010087:Oxides; D017975:Ruthenium Compounds; D014874:Water Pollutants, Chemical; C029017:ruthenium dioxide; C009495:titanium dioxide; D007854:Lead; D017665:Hydroxyl Radical; C047365:lead oxide; D014025:Titanium; C014722:2-naphthol orange
keywords: Orange II; electrocatalysis; photocatalysis; ultraviolet; β-PbO(2) electrode