Guangdong Key Laboratory of Environmental Catalysis and Health Risk Control, Guangzhou Key Laboratory of Environmental Catalysis and Pollution Control, School of Environmental Science and Engineering, Institute of Environmental Health and Pollution Control, Guangdong University of Technology, Guangzhou, 510006, China; State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, 510640, China.
Guangdong Key Laboratory of Environmental Catalysis and Health Risk Control, Guangzhou Key Laboratory of Environmental Catalysis and Pollution Control, School of Environmental Science and Engineering, Institute of Environmental Health and Pollution Control, Guangdong University of Technology, Guangzhou, 510006, China.
Chemosphere. 2020 Nov;258:127378. doi: 10.1016/j.chemosphere.2020.127378. Epub 2020 Jun 13.
Light driven degradation is very promising for pollutants remediation. In the present work, photochemical reaction of tetrabromobisphenol A (TBBPA) under LED white light (λ > 400 nm) irradiation system was investigated to figure out the TBBPA photochemical degradation pathways and isotope fractionation patterns associated with transformation mechanisms. Results indicated that photochemical degradation of TBBPA would happen only with addition to humic acid in air bubbling but not in N bubbling. For photochemical reaction of TBBPA, singlet oxygen (O) was found to be important reactive oxygen species for the photochemical degradation of TBBPA. 2,6-Dibromo-4-(propan-2-ylidene)cyclohexa-2,5-dienone and two isopropyl phenol derivatives were identified as the photochemical degradation intermediates by O. 2,6-Dibromo-4-(1-methoxy-ethyl)-phenol was determined as an intermediate via oxidative skeletal rearrangement, reduction and O-methylation. Hydrolysis product hydroxyl-tribromobisphenol A was also observed in the reductive debromination process. In addition, to deeply explore the mechanism, carbon and bromine isotope analysis were performed using gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) and gas chromatography-multicollector inductively coupled plasma mass spectrometry (GC/MC/ICPMS) during the photochemical degradation of TBBPA. The results showed that photochemical degradation could not result in statistically significant isotope fractionation, indicated that the bond cleavage of C-C and C-Br were not the rate controlling process. Stable isotope of carbon being not fractionated will be useful for distinguishing the pathways of TBBPA and tracing TBBPA fate in water systems. This work sheds light on photochemical degradation mechanisms of brominated organic contaminants.
光催化降解在污染物修复方面很有前景。本工作研究了四溴双酚 A（TBBPA）在 LED 白光（λ>400nm）辐照体系下的光化学反应，以阐明 TBBPA 的光化学降解途径和与转化机制相关的同位素分馏模式。结果表明，TBBPA 的光化学降解仅在空气鼓泡中添加腐殖酸时发生，而在氮气鼓泡中不发生。对于 TBBPA 的光化学反应，发现单线态氧（O）是 TBBPA 光化学降解的重要活性氧物种。通过 O，鉴定出 2,6-二溴-4-（异丙叉）环己-2,5-二烯酮和两种异丙基苯酚衍生物作为光化学降解中间体。通过氧化重排、还原和 O-甲基化，确定 2,6-二溴-4-（1-甲氧基乙基）-苯酚为中间体。在还原脱溴过程中，还观察到水解产物羟基-三溴双酚 A。此外，为了深入探讨机制，在 TBBPA 的光化学降解过程中使用气相色谱/燃烧/同位素比质谱（GC/C/IRMS）和气相色谱-多收集器电感耦合等离子体质谱（GC/MC/ICPMS）进行了碳和溴同位素分析。结果表明，光化学降解不能导致统计上显著的同位素分馏，表明 C-C 和 C-Br 键的断裂不是控制过程。碳的稳定同位素不分馏将有助于区分 TBBPA 的途径并追踪 TBBPA 在水系统中的命运。这项工作阐明了溴代有机污染物的光化学降解机制。
