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 (O3) and peroxymonosulfate (PMS, HSO5-), and assessed its effect on the formation of iodinated trihalomethanes (I-THMs) during chlorination treatment. The degradation of IPM was accelerated by the O3/PMS process, and the hydroxyl (HO•) and sulfate (SO4•-) radicals were major contributors to the degradation. Using identification of the second order reaction rate between SO4•- and IPM (kSO4•-, IPM = 1.6 × 109 M-1 s-1), 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 O3/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 O3/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-1 to 3.3 μg L-1 during chlorination. Although the presence of NOM provided the precursor of I-THMs during chlorination of IPM, the O3/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.

中文翻译：

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臭氧/过一硫酸氢盐（O3 / PMS）工艺加速碘帕醇的氧化：动力学，机理，同时降低了碘化消毒副产物的形成潜力。

碘帕醇（IPM）是水消毒过程中潜在的有毒碘化副产物（I-DBP）的潜在来源。在这项工作中，我们确定了臭氧（O3）和过氧一硫酸盐（PMS，HSO5-）组合降解IPM的动力学和机理，并评估了其对氯化处理过程中碘代三卤甲烷（I-THMs）形成的影响。IPM的降解通过O3 / PMS工艺得以加速，其中羟基（HO•）和硫酸盐（SO4•-）自由基是降解的主要因素。通过确定SO4•-和IPM之间的二级反应速率（kSO4•-，IPM = 1.6×109 M-1 s-1），确定HO•对降解的贡献为78.3％。pH> 7有助于IPM的降解 天然有机物（NOM）和碱度对O3 / PMS过程中IPM降解的影响有限。通过QTOF-MS / MS确定并推导了IPM的转化产物，并阐明了降解途径。这些包括酰胺水解，氨基氧化，夺氢，脱碘和羟基自由基加成。有趣的是，O3 / PMS对IPM的氧化也降低了其形成I-THM的潜力。IPM氧化后，在氯化过程中，由5μMIPM形成的I-THM从14.7μgL-1降至3.3μgL-1。尽管NOM的存在在IPM氯化过程中提供了I-THMs的前体，但O3 / PMS工艺将I-THMs的形成减少了71％，因为释放的碘化物氧化成碘酸盐可有效抑制I-THMs的形成。