School of Chemical and Environmental Engineering, Shanghai Institute of Technology, Shanghai 201418, PR China.
School of Chemical and Environmental Engineering, Shanghai Institute of Technology, Shanghai 201418, PR China.
J Hazard Mater. 2017 Mar 15;326:138-144. doi: 10.1016/j.jhazmat.2016.12.012. Epub 2016 Dec 6.
The photodegradation of IO at 254nm and the formation of iodinated trihalomethanes (I-THMs) during subsequent chlorination or chloramination in the presence of natural organic matter (NOM) were investigated in this study. The thermodynamically stable IO can be degraded by UV irradiation with pseudo-first order kinetics and the quantum yield was calculated as 0.0591moleinstein. Solution pH posed no remarkable influence on the photolysis rate of IO. The UV phototransformation of IO was evidenced by the determination of iodide (I) and hypoiodous acid (HOI) in solution. NOM sources not only enhanced the photodegradation rate of IO by photoejecting solvated electrons, but also greatly influenced the production I-THMs in subsequent chlor(am)ination processes. In UV irradiation and sequential oxidation processes by chlorine or chloramine, the I-THMs formation was susceptible to NOM sources, especially the two major fractions of aqueous humic substances (humic acid and fulvic acid). The toxicity of disinfected waters greatly increased in chloramination over chlorination of the UV photodecomposed IO, as far more I-THMs especially CHI, were formed. As "the fourth iodine source" of iodinated disinfection by-products, the occurrence, transportation and fate of IO in aquatic environment should be of concern instead of being considered a desired iodine sink.
本研究考察了 IO 在 254nm 下的光降解以及在天然有机物 (NOM) 存在下随后氯化或氯胺化过程中形成的碘代三卤甲烷 (I-THMs)。热力学稳定的 IO 可以通过具有准一级动力学的紫外线辐照降解，量子产率计算为 0.0591moleinstein。溶液 pH 对 IO 的光解速率没有显著影响。通过测定溶液中的碘化物 (I) 和次碘酸 (HOI)，证明了 IO 的 UV 光转化。NOM 源不仅通过光逐出溶剂化电子来增强 IO 的光降解速率，而且还极大地影响了随后氯化 (胺) 化过程中 I-THMs 的生成。在紫外线照射和后续由氯或氯胺进行的顺序氧化过程中，I-THMs 的形成易受 NOM 源的影响，特别是水中腐殖质的两个主要部分（腐殖酸和富里酸）。与紫外线分解的 IO 氯化相比，氯胺化消毒水中的毒性大大增加，因为形成了更多的 I-THMs，特别是 CHI。作为碘消毒副产物的“第四碘源”，IO 在水生环境中的存在、迁移和归宿应该引起关注，而不是被视为理想的碘汇。
