Treatment of Waste Water Containing Nitrophenols by Combination of Electrolytic and Photocatalytic Oxidation

Youiti SANO*CShigeo KOBAYASHI, Toshiaki TURU, Masaru MATSUMOTO, Toshiyuki NAGAISHI and Shun-ichi YOSHINAGA

Faculty of Engineering, Kyushu Sangyou University; 2-3-1 Matsukadai, Higashiku, Fukuoka-shi 813-8503 Japan

This paper investigates processes for the wet oxidation of waste water containing environmental contaminants including each nitrophenols. In particular, the electrolysis, photocatalysis and combined electrolysis and photocatalysis methods are examined. The nitro group was eliminated by each method and a nitrate ion produced. Further, as the TOC reduced, the method of decomposition by oxidation of the raw materials was identified. The decomposition products were fatty acids. The level of TOC removal by the electrolysis method is low and the decomposition of the fatty acids is slower than with the other methods.
As the removal of the TOC by photocatalysis electrolysis methods decreased with time, it is suggested that the fatty acids are gradually oxidized. In contrast with the electrolysis and the photocatalysis methods, the raw materials were promptly decomposed by the electrolysis photocatalysis method. The rate of removal of TOC was at least 90%, and the nitro group produced the nitrate ions in proportion to the rate of removal of the TOC. It is suggested that the activity species produced by the electrolysis method participate in this process.
It is therefore concluded that the reaction of the produced electron or positive hole on the catalyst by the photocatalysis method is promoted by the function of various activity species.

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