Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, School of Environmental Science and Engineering, Sun Yat-Sen University, Guangzhou 510275, China.
Guangzhou Ecological Environmental Monitoring Center, Guangzhou 510006, China.
Environ Sci Technol. 2022 Jul 5;56(13):9712-9721. doi: 10.1021/acs.est.2c01495. Epub 2022 Jun 15.
The formation of disinfection byproducts (DBPs) during UV/chlorine treatment, especially nitrogenous DBPs, is not well understood. This study investigated the formation mechanisms for dichloroacetonitrile (DCAN) from typical amino compounds during UV/chlorine treatment. Compared to chlorination, the yields of DCAN increase by 88-240% during UV/chlorine treatment from real waters, while the yields of DCAN from amino compounds increase by 3.3-5724 times. Amino compounds with electron-withdrawing side chains show much higher DCAN formation than those with electron-donating side chains. Phenylethylamine, l- phenylalanine, and l-phenylalanyl-l-phenylalanine were selected to represent amines, amino acids, and peptides, respectively, to investigate the formation pathways for DCAN during UV/chlorine treatment. First, chlorination of amines, amino acids, and peptides rapidly forms -chloramines via chlorine substitution. Then, UV photolysis but not radicals promotes the transformation from -chloramines to -chloroaldimines and then to phenylacetonitrile, with yields of 5.4, 51.0, and 19.8% from chlorinated phenylethylamine, l-phenylalanine, and l-phenylalanyl-l-phenylalanine to phenylacetonitrile, respectively. Finally, phenylacetonitrile is transformed to DCAN with conversion ratios of 14.2-25.6%, which is attributed to radical oxidation, as indicated by scavenging experiments and density functional theory calculations. This study elucidates the pathways and mechanisms for DCAN formation from typical amino compounds during UV/chlorine treatment.
在 UV/氯处理过程中，特别是含氮消毒副产物（DBPs）的形成，其机制尚不完全清楚。本研究考察了典型氨基化合物在 UV/氯处理过程中形成二氯乙腈（DCAN）的机制。与氯化相比，实际水样中 UV/氯处理时 DCAN 的生成量增加了 88-240%，而氨基化合物生成 DCAN 的量增加了 3.3-5724 倍。具有吸电子侧链的氨基酸比具有供电子侧链的氨基酸具有更高的 DCAN 生成率。选择苯乙胺、L-苯丙氨酸和 L-苯丙氨酰-L-苯丙氨酸分别代表胺、氨基酸和肽，以研究 UV/氯处理过程中 DCAN 的形成途径。首先，胺、氨基酸和肽通过氯取代迅速氯化形成一氯胺。然后，UV 光解而不是自由基促进从一氯胺到一氯亚胺和苯乙腈的转化，氯代苯乙胺、L-苯丙氨酸和 L-苯丙氨酰-L-苯丙氨酸生成苯乙腈的产率分别为 5.4%、51.0%和 19.8%。最后，苯乙腈转化为 DCAN 的转化率为 14.2-25.6%，这归因于自由基氧化，这一点可以通过清除实验和密度泛函理论计算来证明。本研究阐明了典型氨基化合物在 UV/氯处理过程中形成 DCAN 的途径和机制。
