Department of Municipal Engineering, Southeast University, Nanjing 211189, China.
Department of Municipal Engineering, Southeast University, Nanjing 211189, China.
Water Res. 2024 Aug 1;259:121844. doi: 10.1016/j.watres.2024.121844. Epub 2024 May 28.
Trace iron ions (Fe(III)) are commonly found in water and wastewater, where free chlorine is very likely to coexist with Fe(III) affecting the disinfectant's stability and N-DBPs' fate during UV/chlorine disinfection, and yet current understanding of these mechanisms is limited. This study investigates the effects of Fe(III) on the formation and toxicity alteration of halonitromethanes (HNMs), dichloroacetonitrile (DCAN), and dichloroacetamide (DCAcAm) from polyethyleneimine (PEI) during UV/chlorine disinfection. Results reveal that the maxima concentrations of HNMs, DCAN, and DCAcAm during UV/chlorine disinfection with additional Fe(III) were 1.39, 1.38, and 1.29 times higher than those without additional Fe(III), instead of being similar to those of Fe(III) inhibited the formation of HNMs, DCAN and DCAcAm during chlorination disinfection. Meanwhile, higher Fe(III) concentration, acidic pH, and higher chlorine dose were more favorable for forming HNMs, DCAN, and DCAcAm during UV/chlorine disinfection, which were highly dependent on the involvement of HO· and Cl·. Fe(III) in the aquatic environment partially hydrolyzed to the photoactive Fe(III)‑hydroxyl complexes Fe(OH) and [Fe(HO)], which undergone UV photoactivation and coupling reactions with HOCl to achieve effective Fe(III)/Fe(II) interconversion, a process that facilitated the sustainable production of HO·. Extensive product analysis and comparison verified that the HO· production enhanced by the Fe(III)/Fe(II) internal cycle played a primary role in increasing HNMs, DCAN, and DCAcAm productions during UV/chlorine disinfection. Note that the incorporation of Fe(III) increased the cytotoxicity and genotoxicity of HNMs, DCAN, and DCAcAm formed during UV/chlorine disinfection, and yet Fe(III) did not have a significant effect on the acute toxicity of water samples before, during, and after UV/chlorine disinfection. The new findings broaden the knowledge of Fe(III) affecting HNMs, DCAN, and DCAcAm formation and toxicity alteration during UV/chlorine disinfection.
痕量铁离子 (Fe(III)) 在水中和废水中很常见，而自由氯很可能与 Fe(III) 共存，这会影响紫外线/氯气消毒过程中消毒剂的稳定性和 N-DBPs 的归宿，然而，目前对这些机制的理解有限。本研究考察了 Fe(III) 对聚乙烯亚胺（PEI）在紫外线/氯气消毒过程中形成哈龙硝基甲烷（HNMs）、二氯乙腈（DCAN）和二氯乙酰胺（DCAcAm）的影响以及毒性变化。结果表明，在有额外 Fe(III) 存在的情况下，紫外线/氯气消毒过程中 HNMs、DCAN 和 DCAcAm 的最大浓度比没有额外 Fe(III) 存在时分别高出 1.39、1.38 和 1.29 倍，而不是像在氯化消毒过程中那样抑制 HNMs、DCAN 和 DCAcAm 的形成。同时，较高的 Fe(III) 浓度、酸性 pH 值和较高的氯剂量更有利于在紫外线/氯气消毒过程中形成 HNMs、DCAN 和 DCAcAm，这高度依赖于 HO·和 Cl·的参与。Fe(III) 在水环境中部分水解为光活性 Fe(III)-羟基配合物 Fe(OH) 和 [Fe(HO)]，它们经历紫外线光激活和与 HOCl 的偶联反应，实现有效的 Fe(III)/Fe(II) 相互转化，这一过程促进了 HO·的持续产生。广泛的产物分析和比较证实，由 Fe(III)/Fe(II) 内循环产生的 HO·的产生在增加紫外线/氯气消毒过程中 HNMs、DCAN 和 DCAcAm 的产量方面起着主要作用。值得注意的是，Fe(III) 的加入增加了紫外线/氯气消毒过程中形成的 HNMs、DCAN 和 DCAcAm 的细胞毒性和遗传毒性，但 Fe(III) 对紫外线/氯气消毒前后水样的急性毒性没有显著影响。新的发现拓宽了 Fe(III) 对紫外线/氯气消毒过程中 HNMs、DCAN 和 DCAcAm 形成和毒性变化的影响的认识。
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