Study on photodegradation pathway and mechanism of 2,2′,4,4′-Tetrabromodiphenyl ether

This paper focuses on the pathway, the kinetic laws and the mechanisms of BDE-47 photo-degradation in the environment. By changing the degradation conditions (such as light sources, solvents, inorganic salts and free radical scavengers) and analyzing the degradation products using gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS), a better understanding of the fate of 2,2′,4,4′-Tetrabromodiphenyl ether (BDE-47) in the environment is obtained. Results show that (i) the degradation reactions of BDE-47 under four different types of light sources are well described by the first order kinetic equation (r ≥ 0.9995); (ii) hydrogen-donating ability and light absorption property of an organic solvent have a joint influence on the kinetics of degradation of BDE-47, which makes the degradation rate constants of BDE-47 different in different solvents (hexane 0.2735, methanol 0.2720, toluene 0.1280, methanol/water (1:1) 0.0673, acetonitrile 0.0471, acetone 0.0030) ; (iii) the types and quantities of detected degradation products of BDE-47 are different in different solvents, BDE-1 is found only in hexane solvent, BDE-3 is not found in toluene, the relative content of BDE-28 in toluene is the highest (91.3%); (iv) inorganic ions have different effects on the degradation of BDE-47, the half-life of 0.10 mmol Fe3+ is reduced by 46.1% compared with that without adding 0.10 mmol Fe3+, the half-life of 0.5 mmol NH4+ is reduced by 46.7% compared with that without 0.5 mmol NH4+, 50 mg/L TBA can increase the half-life by 5.1% compared with no addition.