Xie Min, Zhang Chengyang, Zheng Hongcen, Zhang Guoyang, Zhang Shujuan
State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, China.
State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, China.
Water Res. 2022 Jun 15;217:118424. doi: 10.1016/j.watres.2022.118424. Epub 2022 Apr 6.
In surface waters, photogenerated transients (e.g., hydroxyl radicals, carbonate radicals, singlet oxygen and the triplet states of dissolved organic matter) are known to play a role in the transformation of biorecalcitrant carbamazepine (CBZ). Small diketones, such as acetylacetone (AcAc) and butanedione (BD), are naturally abundant and have been proven to be effective precursors of carbon and oxygen centered radicals. However, the photochemical kinetics and mechanisms of coexisting diketones and CBZ are barely known. Herein, the effects of AcAc and BD on the photochemical conversion of CBZ were investigated compared with HO which was the main ·OH precursor in the environment. An enhancing effect was observed for the degradation of CBZ by the addition of diketones. The enhancing effect of diketones was pH-dependent and much more significant than HO under simulated solar irradiation. On the basis of the identification of transient species and the competition kinetic model, organic peroxyl radicals were found to play a dominant role in CBZ photodegradation, and the second-order rate constants of the reaction between CBZ and peroxyl radicals were determined to be approximately 10-10 Ms. Furthermore, mutagenic acridine was found to be the major cumulative intermediate with a yield of > 30% in the presence of diketones, which might be an environmental concern. This work indicates that the coexistence of diketones and persistent organic pollutants might lead to some detrimental effects on aquatic environments if the water is exposed to sunlight.
在地表水中，光生瞬态物质（如羟基自由基、碳酸根自由基、单线态氧和溶解有机物的三线态）已知在生物难降解的卡马西平（CBZ）的转化过程中发挥作用。小分子二酮，如乙酰丙酮（AcAc）和丁二酮（BD），天然丰度较高，并且已被证明是碳中心自由基和氧中心自由基的有效前体。然而，共存二酮和CBZ的光化学动力学及机理却鲜为人知。在此，将AcAc和BD对CBZ光化学转化的影响与环境中主要的·OH前体HO进行了比较研究。通过添加二酮观察到对CBZ降解有增强作用。在模拟太阳辐射下，二酮的增强作用与pH有关，且比HO的增强作用更为显著。基于瞬态物种的鉴定和竞争动力学模型，发现有机过氧自由基在CBZ光降解中起主导作用，并且测定出CBZ与过氧自由基反应的二级速率常数约为10⁻¹⁰ M⁻¹s⁻¹。此外，发现诱变剂吖啶是在二酮存在下产率> 30%的主要累积中间体，这可能是一个环境问题。这项工作表明，如果水暴露在阳光下，二酮和持久性有机污染物的共存可能会对水生环境产生一些有害影响。
