title: Thermal degradation of polybrominated diphenyl ethers over as-prepared Fe3O4 micro/nano-material and hypothesized mechanism.
abstract: The thermal degradation of decabromodiphenyl ether (BDE-209) featuring fully substituted bromines was investigated over an as-prepared Fe3O4 micro/nano-material at 300 °C. Degradation followed pseudo-first-order kinetics with kobs = 0.15 min(-1) higher than that for decachlorobiphenyl (CB-209). Twenty-six newly produced polybrominated diphenyl ether (PBDE) congeners were identified using the available PBDE standards, while four PBDE congener products were predicted using third-order polynomial regression equation. Analysis of the products indicated that BDE-209 underwent stepwise hydrodebromination over as-prepared Fe3O4. Similar to the case for CB-209, two initial hydrodebromination steps are favored at the BDE-209 meta-positions, giving the major products BDE-207 and BDE-197. However, the variance about the preferred products began to emerge from the start of heptabromodiphenyl ethers (hepta-BDEs). The majorly produced hepta-BDE isomer with BDE-183 is unbrominated at one ortho-position. However, this is different from the reported degradation of CB-209, which always produced the products chlorinated at all four ortho-positions until the ortho-position had to be removed for the formation of trichlorobiphenyls and dichlorobiphenyl still majorly chlorinated at three or two ortho-positions. The early BDE-209 hydrodebromination steps appear to be strongly influenced by steric effects, whereas subsequent hydrodebromination steps, as more bromine atoms are removed, will be gradually governed more by thermodynamics.
authors.affiliation: State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P.O. Box 2871, Beijing, 100085, China.
authors.forename: Qianqian
authors.initials: Q
authors.lastname: Li
authors.affiliation: State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P.O. Box 2871, Beijing, 100085, China.
authors.forename: Fan
authors.initials: F
authors.lastname: Yang
authors.affiliation: State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P.O. Box 2871, Beijing, 100085, China. gjsu@rcees.ac.cn.
authors.forename: Guijin
authors.initials: G
authors.lastname: Su
authors.affiliation: State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P.O. Box 2871, Beijing, 100085, China.
authors.forename: Linyan
authors.initials: L
authors.lastname: Huang
authors.affiliation: State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P.O. Box 2871, Beijing, 100085, China.
authors.forename: Huijie
authors.initials: H
authors.lastname: Lu
authors.affiliation: State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P.O. Box 2871, Beijing, 100085, China.
authors.forename: Yuyang
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P.O. Box 2871, Beijing, 100085, China.
authors.forename: Minghui
authors.initials: M
authors.lastname: Zheng
mesh_terms: D001966:Bromine / Q000737:chemistry; D055768:Halogenated Diphenyl Ethers / Q000737:chemistry*; D049329:Nanostructures; D011075:Polybrominated Biphenyls / Q000737:chemistry*
chemical_list: D055768:Halogenated Diphenyl Ethers; D011075:Polybrominated Biphenyls; C511855:2,2',3,3',4,4',6,6'-octabromodiphenyl ether; C483839:2,2',3,4,4',5',6-heptabromodiphenyl ether; C512045:2,2',3,3',4,4',5,6,6'-nonabromodiphenyl ether; C010902:decabromobiphenyl ether; D001966:Bromine
keywords: Degradation pathway; Fe3O4 micro/nano-material; Hydrodebromination products; Polybrominated diphenyl ether; Steric effect; Thermodynamics