Research Group in Advanced Oxidation Processes (AdOx), Chemical Systems Engineering Center, Department of Chemical Engineering, University of São Paulo, Av. Prof. Luciano Gualberto, tr. 3, São Paulo, SP, 380, Brazil.
Department of Energy Engineering, São Paulo State University (UNESP), Av. Barrageiros, Rosana, SP, 1881, Brazil.
Environ Sci Pollut Res Int. 2019 Feb;26(5):4337-4347. doi: 10.1007/s11356-018-2555-4. Epub 2018 Jun 21.
The purpose of this study was to investigate the aqueous phase photochemical behavior of enoxacin (ENO), an antibiotic selected as a model pollutant of emerging concern. The second-order reaction rate constants of ENO with hydroxyl radicals (HO) and singlet oxygen (O) were determined at pH 3, 7, and 9. Also, the rate constants of the electron transfer reaction between ENO and triplet states of chromophoric dissolved organic matter (CDOM*) are reported for the first time, based on anthraquinone-2-sulfonate (AQ2S) as CDOM proxy. The sunlight-driven direct and indirect ENO degradation in the presence of dissolved organic matter (DOM) is also discussed. The results show that direct photolysis, which occurs more rapidly at higher pH, along with the reactions with HO and AQ2S*, is the key pathway involved in ENO degradation. The ENO zwitterions, prevailing at pH 7, show k HO, k, and k of (14.0 ± 0.8) × 10, (3.9 ± 0.2) × 10, and (61.5 ± 0.7) × 10 L mol s, respectively, whose differences at pH 3, 7, and 9 are due to ENO pH-dependent speciation and reactivity. These k values, along with the experimental ENO photolysis quantum yield, were used in mathematical simulations for predicting ENO persistence in sunlit natural waters. According to the simulations, dissolved organic matter and water depth are expected to have the highest impacts on ENO half-life, varying from a few hours to days in summertime, depending on the concentrations of relevant waterborne species (organic matter, NO, NO, HCO).
本研究旨在探究依诺沙星（ENO）在水相中的光化学行为。ENO 是一种新兴关注污染物的抗生素模型化合物。在 pH 值为 3、7 和 9 时，测定了 ENO 与羟基自由基（HO）和单线态氧（O）的二级反应速率常数。此外，还首次报道了 ENO 与发色溶解有机物（CDOM*）三重态之间电子转移反应的速率常数，以蒽醌-2-磺酸盐（AQ2S）作为 CDOM 探针。还讨论了在溶解有机物（DOM）存在下阳光驱动的直接和间接 ENO 降解。结果表明，直接光解（在较高 pH 值下更快发生）以及与 HO 和 AQ2S*的反应是 ENO 降解的关键途径。在 pH 值为 7 时占主导地位的 ENO 两性离子，具有较高的 kHO、k 和 k 值（分别为（14.0±0.8）×10、（3.9±0.2）×10 和（61.5±0.7）×10 L mol s），其在 pH 值为 3、7 和 9 时的差异归因于 ENO 随 pH 值变化的形态和反应性。这些 k 值，以及实验测定的 ENO 光解量子产率，被用于数学模拟，以预测 ENO 在阳光照射下的自然水中的持久性。根据模拟结果，溶解有机物和水深预计对 ENO 的半衰期影响最大，在夏季，根据相关水相物种（有机物、NO、NO、HCO）的浓度，半衰期从数小时到数天不等。
