Nan Wang,1* Lihua Zhu,1 Ming Lei,2 Heqing Tang2*
1Shenzhen Institute of Huazhong University of Science and Technology, 518000, Shenzhen, China
2College of Resources and Environmental Science, South-Central University for Nationalities, 430074, Wuhan, China
Nano-Micro Conference, 2017, 1, 01044
Published Online: 27 October 2017 (Abstract)
Polybrominated diphenyl ethers (PBDEs) are widely used as flame retardants, and become a new class of global contaminants. Because PBDEs possess typical characteristics of persistent organic pollutants (POPs) like persistent, bioaccumulation, and biotoxicity, their elimination therefore attracts much attention of researchers.
The reductive debromination is a common strategy to treat PBDEs. Among various reductive methods, the photogenerated electron of TiO2 is considered to be highly efficient to reduce decabromodiphenyl ether (BDE209) . However, this leads to accumulation of brominated intermediates, but the debromination products with less bromine atoms are much more difficult to get further reductive debromination.
To promote the photocatalytic reductive debromination, we developed several TiO2-based composites including reduced grapheme oxide (RGO) loaded TiO2 (RGO/TiO2), Ag/TiO2, and CuO/TiO2 to reduce BDE209 and/or 2,2’,4,4’-tetrabromodiphenyl ether (BDE47) [2-4]. These heterosturctured photocatalysts have two beneficial roles: charge separation in space, and enhanced adsorption of PBDEs. Thus, the photocatalytic reduction of PBDEs was greatly improved. However, the complete debromination of PBDEs to diphenyl ether through the photocatalytic reduction process is rather difficult. For example, although all the added BDE47 was rapidly reduced, the debromination efficiency was still less than 50% over Ag/TiO2 and CuO/TiO2 [3,4]. This is because that the reduction of low-brominated PBDEs is rather difficult, due to their weak electron affinity.
Although most studies indicate that BDE209 is strongly resistant to oxidation, we firstly demonstrated that the h+/•OH-involved oxidative degradation of BDE209 took place slowly in the UV-irradiated TiO2 aqueous dispersions . We also noted that the oxidation of BDE209 is much slower than the following oxidation of the less-brominated organic intermediates. Since the highly brominated PBDEs are more easily reduced, and the lower brominated PBDEs become more susceptible to the oxidation, we then developed an effective “one-pot” photocatalytic system for driving concurrently the pre-reduction and consecutive oxidation of BDE47.
The authors acknowledge the financial supports from the National Natural Science Foundation (Grants No. 21477043), Shenzhen Knowledge Innovation Plan of Shenzhen City Technology Innovation Committee (No. JCYJ20150616144425374).
 Sun C; Zhao D; Chen C; W. Ma; J. Zhao, TiO2-mediated photocatalytic debromination of decabromodiphenyl ether: kinetics and intermediates. Environmental Science & Technology. 43, 157-162 (2009). doi:10.1021/es801929a
 M. Lei; N. Wang; L. Zhu; C. Xie; H. Tang, A peculiar mechanism for the photocatalytic reduction of decabromodiphenyl ether over reduced graphene oxide-TiO2 photocatalyst. Chemical Engineering Journal. 241, 207-215 (2014). doi:10.1016/j.cej.2013.12.032
 M. Lei; N. Wang; L. Zhu; Q. Zhou; G. Nie; H. Tang, Photocatalytic reductive degradation of polybrominated diphenyl ethers on CuO/TiO2 nanocomposites: A mechanism based on the switching of photocatalytic reduction potential being controlled by the valence state of copper. Applied Catalysis B: Environmental. 182, 414-423 (2016). doi:10.1016/j.apcatb.2015.09.031
 M. Lei; N. Wang; L. Zhu; H. Tang, Peculiar and rapid photocatalytic degradation of tetrabromodiphenyl ethers over Ag/TiO2 induced by interaction between silver nanoparticles and bromine atoms in the target. Chemosphere. 150, 536-544 (2016). doi:10.1016/j.chemosphere.2015.10.048
 Huang A; M. Lei; N. Wang; L. Zhu; Y. Zhang; Z. Lin; D, Ying; H. Tang, Efficient oxidative debromination of decabromodiphenyl ether by TiO2-mediated photocatalysis in aqueous environment. Environmental Science & Technology. 47, 518-525 (2013). doi:10.1021/es302935e
This article is licensed under a Creative Commons Attribution 4.0 International License. (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
© The Author(s) 2017