Polybrominated diphenyl ethers(PBDEs) are a group of persistent organic pollutants which have attracted a lot of concern because of their unreasonable use and disposal. Efforts have been paid to developing techniques to rapidly degrade PBDEs, among which the application of zero-valent iron(ZVI) has been found effective because of the reducibility and the ability of activating advanced oxidation processes(AOPs). In this paper, the research on degradation of PBDEs by ZVI are summarized, and the mechanism, kinetics, influencing factors and degradation pathways are reviewed. Although ZVI can be effectively used as direct electron donors for debromination of highly-brominated DEs, the resultant lower brominated DEs are more toxic and generally need further treatment. On the other hand, recent studies indicate ZVI could be used as indirect electron donors by inducing heterogeneous Fenton systems or persulfate(PS) systems to produce reactive oxygen species (ROS), which could degrade lower brominated DEs through ring opening. Therefore, the integration of ZVI and Fenton systems or persulfate systems by constituting two-stage reduction/subsequent oxidation treatment may be a solution for complete ring-opening degradation of highly-brominated DEs. Besides, further research on PBDEs degradation based on ZVI technology is discussed.
Contents
1 Introduction
2 Mechanism of PBDEs reductive debromination by ZVI
2.1 Mechanism of PBDEs reduction by ZVI
2.2 Mechanism of PBDEs reduction by bimetallic systems
2.3 Products and pathways of PBDEs debromination in ZVI reaction system
3 PBDEs reductive debromination by modified-ZVI
3.1 nZVI
3.2 Surface stabilized-nZVI
4 Kinetics of PBDEs reductive debromination
5 Influencing factors of PBDEs reductive debromination
5.1 pH
5.2 Organic matters
5.3 Metal cation
6 Reduction and advanced oxidation of PBDEs based on ZVI
7 Conclusion