Photochemical degradation of iodate by UV/H2O2 process: Kinetics, parameters and enhanced formation of iodo-trihalomethanes during chloramination. (April 2019)

• Record Type: Journal Article
• Authors: Tian, Fu-Xiang; Ma, Shi-Xu; Xu, Bin; Hu, Xiao-Jun; Xing, Hai-Bo; Liu, Jing; Wang, Juan; Li, Yuan-Yi; Wang, Bo; Jiang, Xia
• Is Part Of: Chemosphere. Volume 221(2019)
• Page Start: 292
• Page End: 300
• Publication Date: 2019-04
• Subjects: iodate (IO3−) -- UV/H2O2 -- Iodo-trihalomethanes (I-THMs) -- Chloramination; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2019.01.014
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: In this paper, it was demonstrated that UV/H2 O2 process can not only obviously promote the degradation rate of IO3 −, but also greatly enhance iodo-trihalomethanes (I-THMs) formation in sequential chloramination. UV/H2 O2 exhibited much faster IO3 − decomposition than either UV or H2 O2 treatment alone due to the contribution of highly reactive species including O −, OH and e aq − . The degradation rate of IO3 − was affected by H2 O2 dosages, pH, UV intensity as well as the presence of natural organic matter (NOM). The calculated pseudo-first order rate constant gradually increased with H2 O2 dosages and solution pH, but behaved directly proportional to the UV intensity. Although NOM remarkably reduced the degradation rate of IO3 − in UV/H2 O2 process, their presence greatly enhanced the formation of I-THMs during subsequent chloramination. The overwhelming majority of iodoform at high UV fluences was also observed, which indicated improved iodination degrees of the detected I-THMs. UV/H2 O2 was proved to be more capable on the evolution of IO3 − to I − as well as I-THMs than UV and thereby enhanced the toxicity of disinfected waters in the following chloramination process. This study was among the first to provide a comprehensive understanding on the transformation of IO3 − as the emerging iodine precursor to form I-THMs via diverse advanced oxidation process technologies like UV/H2 O2 . Highlights: UV/H2 O2 exhibited a much faster IO3 − removal than either UV or H2 O2 treatment alone. The degradation contributions of direct photolysis and radicals were quantified. Increase of H2 O2 dosages and pH both led to gradually faster degradation of IO3 − . The k o b s was directly proportional to UV intensity while depressed by NOM presence. UV/H2 O2 greatly facilitated evolution of IO3 − to I-THMs than UV with NOM present.