Photosensitized Oxidation of Tetrabromobisphenol A by Humic Acid in Aqueous Solution^†

Abstract

The brominated flame retardant 3,3',5,5'-tetrabromobisphenol A (TBBPA) may accumulate in the environment, including surface waters, and degrade there to potentially toxic products. We have previously shown that singlet oxygen (1O2), produced by irradiation of rose bengal with visible light, oxidizes Triton X-100-solubilized TBBPA to yield the 2,6-dibromo-p-benzosemiquinone anion radical while consuming oxygen (Environ. Sci. Technol.42, 166, 2008). Here, we report that a similar 1O2-induced oxidation can be initiated in aqueous solutions by the irradiation of TBBPA dissolved in a humic acid (HA) solution. HA is a known weak 1O2 photosensitizer and we indeed detected the infrared 1O2 phosphorescence from HA preparations in D2O. When an aqueous preparation of HA was irradiated (lambda > 400 nm) in the presence of TBBPA, oxygen was consumed, and the 2,6-dibromo-p-benzosemiquinone anion radical was generated and detected using electron paramagnetic resonance. Radical formation and oxygen consumption were inhibited by sodium azide, a singlet oxygen quencher. Our results suggest that solar radiation, in the presence of HA, may play an important role in the photodegradation of TBBPA in the aquatic environment.

Troubleshooting the dichlorofluorescein assay to avoid artifacts in measurement of toxicant-stimulated cellular production of reactive oxidant species

“…Specifically, MEHP did not significantly affect DCF fluorescence in either HBSS or RPMI assay solutions lacking serum when compared to the solvent control in the same type of assay solution. Additionally, similar to previous research demonstrating that type of assay solution can impact DCF fluorescence (Han, et al, 2008; Han, et al, 2009; Kalinich, et al, 1997; Korystov, et al, 2007), we observed significantly lower DCF fluorescence for all treatment groups when HBSS was used as the buffer compared to RPMI or RPMI + serum.…”

Mechanochemical degradation of tetrabromobisphenol A: Performance, products and pathway

“…Therefore the debromination accounted only for a part of the degradation mechanism and in addition another degradation mechanism was involved. These results are similar with the studies on the degradation of TBBPA by oxidation, photochemical transformation and catalytic degradation, in which the reactions were dominated by a radical mechanism [55][56][57].…”

Photolysis Kinetics, Mechanisms, and Pathways of Tetrabromobisphenol A in Water under Simulated Solar Light Irradiation

“…This pathway has been reported in the oxidative degradation of TBBPA by singlet oxygen. 28,29 Debromination products (2) and (5) of TBBPA were formed under N 2 atmosphere as identified by LC/MS (Scheme 1-A). The debromination products were also reported by others in different systems.…”

“…20−28 TBBPA could be degraded by UV irradiation, 20,21 photocatalytic oxidation (TiO 2 , 22,23 Ag/Bi 5 Nb 3 O 15 , 24 BiOBr, 25 titanomagnetite, 26 [Mn-(VII)] 27 ), and photosensitized oxidation. 28,29 In these photoreactions, photogenerated electrons and reactive oxygen species (ROS) were responsible for its degradation. Debromination and beta scission were proposed as two major pathways.…”