Ciprofloxacin transformation in aqueous environments: Mechanism, kinetics, and toxicity assessment during •OH-mediated oxidation
Ciprofloxacin transformation in aqueous environments: Mechanism, kinetics, and toxicity assessment during •OH-mediated oxidation
复制标题
环丙沙星在水环境中的转化：OH 介导的氧化过程中的机制、动力学和毒性评估。
DOI：
10.1016/j.scitotenv.2019.134190
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发表时间：
2020-01-10
影响因子：
9.8
通讯作者：
Zhao, Zhen
中科院分区：
文献类型：
--
作者：
Bai, Feng-Yang;Ni, Shuang;Zhao, Zhen
有机物与(OH)-O-中心点的初始反应对于理解有机物在水相高级氧化过程中的转化和归宿具有重要意义。本文采用密度泛函和计算动力学方法，研究了氟喹诺酮类抗生素环丙沙星(CIP)在(OH)-O-中心点引发降解的动力学和机理。我们考虑了所有可行的机制，包括H-抽提、(OH)-O-中心点加成和顺序电子质子转移。结果表明，H-抽提是主要的反应途径，产物自由基P7-H、P9-H和P10-H是主要的中间体。计算了环丙沙星在273K~323K温度范围内的水相速率系数，得到的理论值为6.07×10~(9)M~(-1)S(-1)，与实验值相近。此外，中间体P7-H、P9-H和P10-H在O-2、HO2中心点和(OH)-O-中心点的存在下容易转化为几个稳定的产物。H-抽提产物自由基(P7-H、P9-H和P10-H)与O-2结合生成的过氧基倾向于通过直接协同消除而不是间接机制生成Ho(2)(中心点)到周围。另外，过氧自由基可以通过三重态和单重态途径与HO2中心点反应，前者由于其较小的势垒而更有利。羟基取代的CIP与(OH)-O-中心点的反应具有比母体化合物更高的活性，这是因为它的势垒较低，反应速度较快。此外，根据生态毒性评价计算，含-NHC(O)的化合物IM3-P10-H-4对水生鱼类是有害的，是富含(OH)-O-中心点的环境中的初级产物。这一研究有助于加深我们对复杂水环境中CIP转化的理解。(C)2019爱思唯尔B.V.保留所有权利。
The initial reactions of organics with (OH)-O-center dot are important to understand their transformations and fates in advanced oxidation processes in aqueous phase. Herein, the kinetics and mechanism of (OH)-O-center dot-initiated degradation of ciprofloxacin (CIP), an antibiotic of fluoroquinolone class, are obtained using density functional and computational kinetics methods. All feasible mechanisms are considered, including H-abstraction, (OH)-O-center dot-addition, and sequential electron proton transfer. Results showed that the H-abstraction is the dominant reaction pathway, and the product radicals P7-H, P9-H, and P10-H are the dominating intermediates. The aqueous phase rate coefficients for the (OH)-O-center dot-triggered reaction of ciprofloxacin are calculated from 273 K to 323 K to examine the temperature dependent effect, and the theoretical value of 6.07 x 10(9) M-1 s(-1) at 298 K is close to the corresponding experimental data. Moreover, the intermediates P7-H, P9-H, and P10-H could easily transform to several stable products in the presence of O-2, HO2 center dot, and (OH)-O-center dot. The peroxy radical, which is generated from the incorporation of H-abstraction product radicals (P7-H, P9-H, and P10-H) with O-2, prefers to produce HO(2)(center dot )into the surrounding through direct concerted elimination rather than the indirect mechanism. In addition, the peroxy radical could react with HO2 center dot via triplet and singlet routes, and the former is more favorable due to its smaller barrier compared with the latter. The hydroxyl-substituted CIP has higher activity than its parent compound in their reactions with (OH)-O-center dot due to its lower barrier and faster rate. In addition, the -NHC(O)-containing compound IM3-P10-H-4 is harmful to aquatic fish and is the primary product in the (OH)-O-center dot-rich environment according to the ecotoxicity assessment computations. This study can improve our comprehension on CIP transformation in complex water environments. (C) 2019 Elsevier B.V. All rights reserved.