Photodegradation of 2,2',4,4'-tetrabromodiphenyl ether in nonionic surfactant solutions

Recently, polybrominated diphenyl ethers (PBDEs) contaminated soils in electronic waste (e-waste) disposal sites of China have been reported and aroused concern. Since surfactant-aided soil washing followed by photodestruction has been suggested as a promising technology for soil remediation, the photodegradation of 2,2',4,4'-terabromodiphenyl ether (BDE-47) in nonionic surfactant solutions under UV-irradiation at 253.7 m was studied in the present work. The investigation was carried out on the effect of the type and concentration of surfactants, initial pH, and the addition of cations and acetone on BDE-47 photodecay. BDE-47 photodegradation all well followed pseudo-first-order kinetics under various conditions, and the decay rate was 0.4-1.3 times greater in the presence of surfactants than that in water alone. It was found that BDE-47 photodegradation was hardly affected through varying initial pH levels and retarded due to the presence of cations and acetone. The primary decay pathways in all surfactant micelles were shown to be reductive photodebromination, in which tri- to mono-BDEs were formed through a consecutive loss of bromine atoms. 2,4,4'-tribromodiphenyl ether (BDE-28), 4,4'-dibromodiphenyl ether (BDE-15), and 4-monobromodiphenyl ether (BDE-3) appeared sequentially as the predominant photoproducts over reaction time. Polybrominated dibenzofurans (mono- to tri-) were tentatively identified as additional intermediates for BDE-47 photodegradation in surfactant micelles.