Photodegradation of Organic Pollutants in Wastewater under Free of Dissolved Oxygen

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Photodegradation of several organic substances by UV irradiation was demonstrated in the presence and absence of dissolved oxygen (DO). The degradation rate constants were determined to evaluate the effect of DO on the photodegradation.(1)Photodegradation of several benzene derivatives in the absence of dissolved oxygen was performed. The effect of substituent on the degradation rate was, NH_2<OH<CH_3<H<Cl>Br>COOH>NO_2. The Cl, Br, COOH derivatives produced benzene as an intermediate compound. On the other hand, NH_2, OH, CH_3 did not give benzene in their degradation processes. It is clear that the degradation mechanisms are quit different between the two derivative groups. The groups of Cl and Br drastically promoted their degradation rate, about 3 times, in the absence of DO.(2)The UV irradiation method was not effective for the degradation of EDTA and EDTA-Mn, Zn, Ni chelates in the presence and absence of DO.(3)It was found that inorganic salts, such as Na_2SO_4, K_2SO_4 promote the photo-degradation of organic materials by UV.