Photodecomposition of tetrabromobisphenol A in aqueous humic acid suspension by irradiation with light of various wavelengths

• TBBPA/HA decomposition was investigated using EPR and LC-MS.
• The reactive species at >400 and > 300 nm were singlet oxygen and
• OH, respectively.
• 2,6-DBSQ.
• − and tribromohydroxybisphenol A were formed on irradiation at >300 nm.

The reactive species generated in aqueous 3,3′,5,5′-tetrabromobisphenol A (TBBPA)/humic acid (HA) suspensions above the TBBPA pKa (∼7.4), under various light-irradiation conditions, namely ambient and ultraviolet light, were investigated using electron paramagnetic resonance (EPR) spectroscopy and liquid chromatography-mass spectrometry (LC-MS). We confirmed that singlet oxygen and OH radicals are the key reactive oxygen species generated at wavelengths greater than 400 and 300 nm, respectively. The amount of 2,6-dibromo-p-benzosemiquinone anion radicals (2,6-DBSQ
• −) formed under irradiation at 400 nm increased linearly with respect to irradiation time; the initial reaction rate was 7.03 × 10−9 mol g−1 HA s−1. The rate increased with increasing pH and light intensity. LC-MS and EPR spectroscopy showed that tribromohydroxybisphenol A was formed under irradiation at 300 nm via reaction of OH radicals with TBBPA. This study, for the first time, shows that the main byproducts formed during irradiation at wavelengths above 300 nm are 2,6-DBSQ
• − and tribromohydroxybisphenol A, generated from singlet oxygen (1O2) and OH radicals, respectively. Photodecomposition of TBBPA in the environment may occur by formation of 1O2 and OH radicals.

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