School of Energy and Environmental Engineering, Beijing Key Laboratory of Resource-oriented Treatment of Industrial Pollutants, International Science and Technology Cooperation Base for Environmental and Energy Technology of MOST, University of Science and Technology Beijing, Beijing 100083, China.
School of Environment, Tsinghua University, Beijing 100084, China.
Environ Sci Technol. 2024 Oct 1;58(39):17510-17519. doi: 10.1021/acs.est.4c07539. Epub 2024 Sep 19.
The application of 222 nm far-UVC irradiation for degrading organic micropollutants in water shows promise. Nitrate (NO), found in nearly all water bodies, can significantly impact the performance of 222 nm far-UVC-driven systems. This work was the first to investigate the effect of NO on sulfamethoxazole (SMX) photodegradation at 222 nm, finding that NO significantly enhances SMX degradation in different dissociated forms. Besides the hydroxyl radical (OH), reactive nitrogen species (RNS) also played important roles in SMX degradation. With increasing NO concentration, the RNS contribution to SMX degradation decreased from 25.7 to 8.6% at pH 3 but increased from 1.5 to 24.7% at pH 7, since the deprotonated SMX with electron-rich groups reacted more easily with RNS. The transformation mechanisms of SMX involving isomerization, bond cleavage, hydroxylation, nitrosation, and nitration processes were proposed. N isotope labeling experiments showed that the RNS-induced nitrated products even became the major products of SMX in the 222 nm far-UVC/NO system at pH 7 and exhibited a higher toxicity than SMX itself. Further research is necessary to avoid or eliminate these toxic byproducts. This study provides valuable insights for guiding the utilization of 222 nm far-UVC for treating antibiotics in NO-containing water.
222nm 远紫外线辐照在降解水中有机微量污染物方面具有广阔的应用前景。硝酸盐（NO）几乎存在于所有水体中，它会对 222nm 远紫外线驱动系统的性能产生重大影响。本研究首次考察了 NO 对 222nm 下磺胺甲恶唑（SMX）光降解的影响，结果表明，NO 以不同离解形式显著增强了 SMX 的降解。除了羟基自由基（OH）之外，活性氮物种（RNS）也在 SMX 降解中发挥了重要作用。随着 NO 浓度的增加，在 pH 值为 3 时，RNS 对 SMX 降解的贡献从 25.7%下降到 8.6%，而在 pH 值为 7 时，其贡献从 1.5%增加到 24.7%，这是因为具有富电子基团的去质子化 SMX 更容易与 RNS 反应。提出了涉及异构化、键断裂、羟化、亚硝化和硝化过程的 SMX 转化机制。N 同位素标记实验表明，在 pH 值为 7 的 222nm 远紫外线/NO 体系中，RNS 诱导的硝化产物甚至成为 SMX 的主要产物，其毒性比 SMX 本身更高。需要进一步研究以避免或消除这些有毒副产物。本研究为指导利用 222nm 远紫外线处理含氮水中的抗生素提供了有价值的见解。
