Quantum chemical study of the mechanisms, kinetics, and ecotoxicity assessment of OH radical-initiated reactions of 2,2′,4,4′,5,5′ -hexabrominated diphenyl ether (BDE-153) in atmosphere and wastewater

[Display omitted] •The mechanisms of BDE-153 initiated by OH radical were theoretically studied.•OH addition intermediates of BDE-153 are more favorable.•The total rate constants were calculated in gas phase and aqueous phase.•Most of the transformation products are still toxic to aquatic organisms. 2,2′,4,4′,5,5′-hexabrominated diphenyl ether (BDE-153) and its OH radical addition products are considered potentially harmful to ecological systems. Therefore, the oxidation reactions mechanisms of BDE-153 initiated by OH radical, the reaction kinetics and the ecotoxicity of BDE-153 assessment in the gas and the aqueous phase were investigated using quantumchemicalmethods. It is more feasible for the OH radical to add at the nonbromine substituted carbon atoms of the aromatic ring in the BDE-153 molecule to create OH addition intermediates. The secondary reactions involving OH addition intermediates in the presence of O2/NO would generate preferred tribromophenol and OH-addition products. Most of the transformation products are still toxic to aquatic organisms. The total and individual rate constants were evaluated by using the KiSThelP program in a suitable temperature range (198–338 K) and a pressure of 1 atm. At 298 K and 1 atm, the total rate constants in atmosphere and wastewater are 2.90 × 10-13 cm3 molecule-1 s−1 and 9.61 × 106 M−1 s−1, and the half-lives are 39.9 days and 72.1–7.21 × 1010 s, respectively. The implicit and explicit solvent models were used to examine the solvent effect on the total reaction. These results clarify the transformation mechanism, atmospheric fate, and ecotoxicity of BDE-153 in advanced oxidation processes. The calculations provided a basis for designing experimental and industrial applications of BDE-153.