Key Laboratory of Drinking Water Science and Technology,Research Center for Eco-Environmental Sciences, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 18 Shuang-qing Road, Beijing, 100085, China; School of Chemical and Environmental Engineering, China University of Mining and Technology, Beijing, 100083, China.
Key Laboratory of Drinking Water Science and Technology,Research Center for Eco-Environmental Sciences, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 18 Shuang-qing Road, Beijing, 100085, China.
Water Res. 2020 Apr 15;173:115615. doi: 10.1016/j.watres.2020.115615. Epub 2020 Feb 12.
Iopamidol (IPM) is a potential source of toxic iodinated byproducts (I-DBPs) during water disinfection. In this work, we determined the kinetics and mechanism of degradation of IPM by a combination of ozone (O) and peroxymonosulfate (PMS, HSO), and assessed its effect on the formation of iodinated trihalomethanes (I-THMs) during chlorination treatment. The degradation of IPM was accelerated by the O/PMS process, and the hydroxyl (HO) and sulfate (SO) radicals were major contributors to the degradation. Using identification of the second order reaction rate between SO and IPM (k = 1.6 × 10 M s), the contribution of HO to the degradation was determined to be 78.3%. The degradation of IPM was facilitated by pH > 7, and natural organic matter (NOM) and alkalinity had limited effects on the degradation of IPM in the O/PMS process. The transformation products of IPM were determined and inferred by QTOF-MS/MS, and the degradation pathways were elucidated. These include amide hydrolysis, amino oxidation, hydrogen abstraction, deiodination, and hydroxyl radical addition. Interestingly, oxidation of IPM by O/PMS also decreased its potential for formation of I-THMs. After oxidation of IPM, the I-THMs formed from 5-μΜ IPM decreased from 14.7 μg L to 3.3 μg L during chlorination. Although the presence of NOM provided the precursor of I-THMs during chlorination of IPM, the O/PMS process decreased I-THMs formation by 71%, because oxidation of released iodide into iodate effectively inhibited I-THMs formation. This study provides a new approach for the accelerated degradation of IPM and control of the formation of I-DBPs.
碘海醇（IPM）是水消毒过程中产生有毒碘代副产物（I-DBPs）的潜在来源。在这项工作中，我们结合臭氧（O）和过一硫酸盐（PMS，HSO）确定了 IPM 的降解动力学和机制，并评估了其在氯化处理过程中形成碘三卤甲烷（I-THMs）的影响。O/PMS 工艺加速了 IPM 的降解，羟基（HO）和硫酸根（SO）自由基是降解的主要贡献者。通过确定 SO 和 IPM 之间的二级反应速率常数（k=1.6×10 M s），确定 HO 对降解的贡献为 78.3%。pH 值>7 有利于 IPM 的降解，天然有机物（NOM）和碱度对 O/PMS 过程中 IPM 的降解影响有限。通过 QTOF-MS/MS 确定并推断了 IPM 的转化产物，并阐明了降解途径。这些途径包括酰胺水解、氨基氧化、氢提取、脱碘和羟基自由基加成。有趣的是，O/PMS 氧化 IPM 也降低了其形成 I-THMs 的潜力。氧化 IPM 后，在氯代过程中，从 5 μΜ IPM 形成的 I-THMs 从 14.7μg L 降低到 3.3μg L。尽管 NOM 的存在为 IPM 氯化过程中 I-THMs 的形成提供了前体，但 O/PMS 过程将 I-THMs 的形成减少了 71%，因为释放的碘化物被氧化成碘酸盐，有效地抑制了 I-THMs 的形成。本研究为加速 IPM 的降解和控制 I-DBPs 的形成提供了一种新方法。
