Beijing Key Laboratory for Source Control Technology of Water Pollution, Engineering Research Center for Water Pollution Source Control and Eco-remediation, Beijing Forestry University, Beijing, 100083, China.
Chinese Academy of Environment Planning, Beijing, 100012, China.
Water Res. 2019 Nov 1;164:114940. doi: 10.1016/j.watres.2019.114940. Epub 2019 Aug 1.
The ubiquitous algogenic extracellular organic matters (EOMs) could enhance solar photodegradation of antibiotics such as Chlortetracycline (CTC), however, the role of chemical constituents and structure in their photosensitizing process was not clear. In this paper, EOMs were extracted from chlorella vulgaris (CV-EOMs), scenedesmus meyen (SM-EOMs) and microcystis aeruginosa (MA-EOMs) to explore their photosensitive efficiencies and mechanisms. All of the EOMs showed higher photosensitive efficiencies than natural organic matter (NOM). The quenching assays and competitive kinetics experiments confirmed the dominant role of EOMs* in accelerating CTC photodegradation. The quantum yield coefficients of EOMs* (f) of CV-EOMs, SM-EOMs, MA-EOMs, NOM were 139.89 ± 5.46, 125.35 ± 4.69, 91.76 ± 3.53, and 72.84 ± 4.45 L/(mol-photon), respectively. Specific chemical constituents and structure of EOMs were characterized by nuclear magnetic resonance (NMR), fourier transform ion cyclotron resonance mass spectrometry (FT-CIR-MS) and X-ray photoelectron spectroscopy (XPS). The results showed the positive linear correlation of f with content of carbonyl groups in EOMs. In addition, reduction of carbonyl groups in EOMs by NaBH significantly decreased CTC photodegradation rate. Density Functional Theory (DFT) calculation suggested the susceptible excitation of carbonyl groups in EOMs under solar light was ascribed to the lowest required energy of electronic transition from HOMO to LUMO (assigned as n-π* transition). The energy of triplet excited-states benzophenone, p-methoxy acetophenone and acetophenone (the EOMs model compounds) was calculated to be 284.92, 288.85 and 265.50 kJ/mol, which were higher than that of CTC (i.e., 217.46 kJ/mol), indicating the energy transfer from excited triplet state to excited triplet state CTC was possible. This study provided mechanism insights into photosensitization effects of allogenic EOMs on photochemical fate of pollutants in aqueous environment.
无处不在的致痛细胞外有机物质 (EOMs) 可以增强抗生素（如金霉素）的太阳光降解，但它们在光敏过程中的化学组成和结构的作用尚不清楚。在本文中，从普通小球藻（CV-EOMs）、微拟球藻（SM-EOMs）和铜绿微囊藻（MA-EOMs）中提取了 EOMs，以探讨它们的光敏效率和机制。所有 EOMs 都显示出比天然有机物（NOM）更高的光敏效率。猝灭实验和竞争动力学实验证实了 EOMs在加速 CTC 光降解中的主导作用。CV-EOMs、SM-EOMs、MA-EOMs、NOM 的 EOMs量子产率系数 (f) 分别为 139.89±5.46、125.35±4.69、91.76±3.53 和 72.84±4.45 L/(mol-光子)。通过核磁共振（NMR）、傅里叶变换离子回旋共振质谱（FT-CIR-MS）和 X 射线光电子能谱（XPS）对 EOMs 的特定化学组成和结构进行了表征。结果表明，f 与 EOMs 中羰基含量呈正线性相关。此外，EOMs 中羰基的还原通过 NaBH 显著降低了 CTC 的光降解速率。密度泛函理论（DFT）计算表明，EOMs 中羰基在太阳光下的敏感激发归因于从 HOMO 到 LUMO 的最低电子跃迁所需能量（指定为 n-π*跃迁）。计算了二苯甲酮、对甲氧基苯乙酮和苯乙酮（EOMs 模型化合物）的三重态激发态能量分别为 284.92、288.85 和 265.50 kJ/mol，高于 CTC（即 217.46 kJ/mol），表明从激发三重态到激发三重态 CTC 的能量转移是可能的。本研究为异源 EOMs 对水环境污染中污染物光化学命运的光敏化效应提供了机制见解。
