Stable carbon isotope fractionation associated with oxidative degradation of decabromodiphenyl ether in water by heated activated sodium persulfate

Persulfate-based oxidation is an efficient method for BDE-209 degradation in the contaminated sites, however, the underlying oxidation mechanisms remained elusive. In this study, BDE-209 oxidation by heated activated sodium persulfate in water was comprehensively studied based on analysis of compound -specific stable isotope and radial quenching. BDE-209 oxidation followed the pseudo -first -order kinetic, and SO4 center dot - and center dot OH were involved into oxidation, with SO4 center dot - as the dominant radical. Normal isotope effects with enrichment in 13C were observed at activation temperature of 25 C and 45 C. However, two degradation stages were found for BDE-209 oxidation at 65 C, with normal carbon isotope fractionation for first stage and inverse carbon isotope fractionation for second stage. Carbon apparent kinetic isotope effect (C-13-AKIE) of BDE-209 was calculated to be 1.015-1.028, indicating that cleavage of C-Br was the rate -limiting step for BDE-209 oxidation. The results of degradation products, radical quenching and stable carbon isotope implied that OH-PBDEs were generated from the homolytic cleavage of C-Br bond of BDE-209 by the attack of SO4 center dot (-) and then combination with center dot OH during the oxidation by heated activated sodium persulfate. These findings could significantly promote the understanding on the oxidation mechanism of organic pollutants by the heated activated persulfate.