Photodegradation of 1,3,5-Tris-(2,3-dibromopropyl)-1,3,5-triazine-2,4,6-trione and decabromodiphenyl ethane flame retardants: Kinetics, Main products, and environmental implications

Abstract

Photodegradation has been demonstrated as one of the important environmental factors affecting the fate of contaminants such as brominated flame retardants (BFRs). However, a number of emerging BFRs, particularly those with high bromine substitution, have rarely been investigated for their photodegradation kinetics. Our study evaluated photodegradation of two highly brominated FRs, 1,3,5-tris-(2,3-dibromopropyl)-1,3,5-triazine-2,4,6-trione (TDBP-TAZTO) and decabromodiphenyl ethane (DBDPE), under various conditions. The results indicated that the degradation kinetics was affected by UV irradiation wavelength, intensity, solvent type, as well as the structural characteristics. TDBP-TAZTO exhibited degradation half-lives (t1/2) of 23.5–6931 min under various UV irradiation conditions and 91.2 days under natural sunlight. Its degradation was much slower than that of DBDPE which exhibited t1/2 of 0.8–101.9 min under UV and 41.3 min under natural sunlight. A variety of degradation products were detected as a result of different breakdown pathways. This indicated that photodegradation could substantially influence the fate of these highly brominated FRs, resulting in a cocktail of degradation products as environmentally occurring contaminants. This could also complicate the evaluation of the ecological risks of these target flame retardants, given that degradation products generally possess physicochemical properties and biological effects different from their parent chemicals.