Key Laboratory for City Cluster Environmental Safety and Green Development of the Ministry of Education, Institute of Environmental and Ecological Engineering, Guangdong University of Technology, Guangzhou 510006, China; Southern Marine Science and Engineering Guangdong Laboratory, Guangzhou511458, China; State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin150090, China.
Key Laboratory for City Cluster Environmental Safety and Green Development of the Ministry of Education, Institute of Environmental and Ecological Engineering, Guangdong University of Technology, Guangzhou 510006, China; Southern Marine Science and Engineering Guangdong Laboratory, Guangzhou511458, China.
Water Res. 2020 Oct 15;185:116234. doi: 10.1016/j.watres.2020.116234. Epub 2020 Jul 25.
X-ray contrast media (ICM), as the most widely used intravascular pharmaceuticals, have been frequently detected in various environmental compartments. ICM have attracted increasingly scientific interest owing to their role as an iodine contributor, resulting in the high risk of forming toxic iodinated byproducts (I-BPs) during water treatment. In this review, we present the state-of-the-art findings relating to the removal efficiency as well as oxidation intermediates of ICM by conventional and advanced oxidation processes. Moreover, formation of specific small-molecular I-BPs (e.g., iodoacetic acid and iodoform) during these processes is also summarized. Conventional oxidants and disinfectants including chlorine (HOCl) and chloramine (NHCl) have low reactivities towards ICM with HOCl being more reactive. Iodinated/deiodinated intermediates are generated from reactions of HOCl/NHCl with ICM, and they can be further transformed into small-molecular I-BPs. Types of disinfectants and ICM as well as solution conditions (e.g., presence of bromide (Br) and natural organic matters (NOM)) display significant impact on formation of I-BPs during chlor(am)ination of ICM. Uncatalyzed advanced oxidation process (AOPs) involving ozone (O) and ferrate (Fe(VI)) exhibit slow to mild reactivities towards ICM, usually leading to their incomplete removal under typical water treatment conditions. In contrast, UV photolysis and catalyzed AOPs including hydroxyl radical (HO) and/or sulfate radical (SO) based AOPs (e.g., UV/hydrogen peroxide, UV/persulfate, UV/peroxymonosulfate (PMS), and CuO/PMS) and reactive chlorine species (RCS) involved AOPs (e.g., UV/HOCl and UV/NHCl) can effectively eliminate ICM under various conditions. Components of water matrix (e.g., chloride (Cl), Br, bicarbonate (HCO), and NOM) have great impact on oxidation efficiency of ICM by catalyzed AOPs. Generally, similar intermediates are formed from ICM oxidation by UV photolysis and AOPs, mainly resulting from a series reactions of the side chain and/or C-I groups (e.g. cleavage, dealkylation, oxidation, and rearrange). Further oxidation or disinfection of these intermediates leads to formation of small-molecular I-BPs. Pre-oxidation of ICM-containing waters by AOPs tends to increase formation of I-BPs during post-disinfection process, while this trend also depends on the oxidation processes applied and solution conditions. This review summarizes the latest research findings relating to ICM transformation and (by)products formation during disinfection and AOPs in water treatment, which has great implications for the practical applications of these technologies.
X 射线造影剂（ICM）作为最广泛使用的血管内药物，已在各种环境介质中频繁检出。由于其作为碘供体的作用，ICM 引起了越来越多的科学关注，导致在水处理过程中形成高风险的有毒碘化副产物（I-BPs）。在本综述中，我们介绍了有关传统和高级氧化工艺去除 ICM 效率以及氧化中间体的最新研究结果。此外，还总结了这些过程中特定小分子 I-BPs（例如，碘乙酸和碘仿）的形成。包括氯（HOCl）和氯胺（NHCl）在内的常规氧化剂和消毒剂对 ICM 的反应性较低，而 HOCl 的反应性更高。HOCl/NHCl 与 ICM 的反应会产生碘化/脱碘化中间体，它们可以进一步转化为小分子 I-BPs。消毒剂的类型和 ICM 以及溶液条件（例如，溴化物（Br）和天然有机物（NOM）的存在）对 ICM 在氯化（胺）过程中形成 I-BPs 有显著影响。涉及臭氧（O）和高铁酸盐（Fe（VI））的非催化高级氧化工艺（AOPs）对 ICM 的反应性缓慢至温和，通常导致在典型的水处理条件下无法完全去除它们。相比之下，UV 光解和催化 AOPs 包括基于羟基自由基（HO）和/或硫酸根自由基（SO）的 AOPs（例如，UV/过氧化氢，UV/过硫酸盐，UV/过单硫酸盐（PMS）和 CuO/PMS）和涉及活性氯物种（RCS）的 AOPs（例如，UV/HOCl 和 UV/NHCl）可以在各种条件下有效去除 ICM。水基质的成分（例如，氯（Cl），Br，碳酸氢盐（HCO）和 NOM）对催化 AOP 中 ICM 的氧化效率有很大影响。通常，UV 光解和 AOPs 氧化 ICM 会形成相似的中间体，主要是由于侧链和/或 C-I 基团的一系列反应（例如，裂解，脱烷基化，氧化和重排）。这些中间体的进一步氧化或消毒会导致小分子 I-BPs 的形成。AOPs 对含 ICM 水的预氧化往往会增加后消毒过程中 I-BPs 的形成，而这种趋势还取决于所应用的氧化过程和溶液条件。本综述总结了水处理过程中消毒和 AOP 中 ICM 转化和（副）产物形成的最新研究结果，这对这些技术的实际应用具有重要意义。
