Debromination of Polybrominated Diphenyl Ethers by Nanoscale Zerovalent Iron: Pathways, Kinetics, and Reactivity

Abstract

The debromination of selected polybrominated diphenyl ethers (PBDEs) by nanoscale zerovalent iron particles (nZVI) was studied to investigate the degradation pathways and the reaction kinetics of the PBDEs. The primary PBDE investigated was 2,3,4-tribromo diphenyl ether (BDE 21) to assess degradation pathways. nZVI could effectively debrominate the selected PBDEs into lower brominated compounds and diphenyl ether, a completely debrominated form of PBDEs. The susceptibility of the meta-bromine by nZVI was observed from the debromination tests for PBDEs with single-flanked (2,3-diBDE and 3,4-diBDE) and unflanked (three monoBDEs) bromines. The stepwise debromination from n-bromo-to (n-1)-bromodiphenyl ether was observed as the dominant reaction process, although simultaneous multistep debromination seemed to be plausible for di-BDEs having two bromines adjacent on the same phenyl ring. The reaction rate constants were estimated by assuming the reaction between PBDEs and nZVI was a pseudo-first order reaction and the rates decreased with fewer bromine substituents. The reaction rate constants were correlated with the heat of formation and the energy of the lowest unoccupied molecular orbital of the corresponding compounds, and these appear to be useful descriptors of relative reaction rates among PBDE homologue groups.

An integrated two-stage process for effective dechlorination of polychlorinated biphenyls in subcritical water in the presence of hydrogen donors

“…The first stage was mainly used for conducting Fe 0 corrosion and generation of hydrogen species. It has been reported that the relative resistance of positional isomers increased from para-to meta-to ortho-positions, which resulted in chlorines in the paraand meta-position were predominantly removed over chlorines in the ortho-position during the dechlorination process [7,[30][31][32][33]. Therefore the total conversion ratio of 46.5% with only residency at first stage in Fig.…”

“…As electron donor, Fe 0 provides electron via corrosion to reduce H + to molecular hydrogen which was used for subsequent hydrodehalogenation. Hence, corrosion of Fe 0 and generation of hydrogen species are always considered as the key steps during the whole dehalogenation process [6,7]. However, the low utility efficiency of Fe 0 due to the low H + concentration and formation of passivation layer always presents as obstacle to effective dehalogenation, especially in the case of complicated composition of PCBs mixture, such as commercial Aroclor [5,8].…”

Thermal degradation of polybrominated diphenyl ethers over as-prepared Fe3O4 micro/nano-material and hypothesized mechanism

“…1). The debromination of BDE-209 in the presence of zerovalent iron microparticles (Zhuang et al 2010) and resin-bound iron nanoparticles (Li et al 2007) also followed pseudo-first-order kinetics, with rate constants of 9.79×10 −5 min −1 (0.14 day −1 ) and 4.7×10 (Su et al 2014). The degradation behaviors of different halogenated compounds might vary in ways that are strongly dependent on the halogen substituents and chemical properties of the compounds.…”

Removing polybrominated diphenyl ethers in pure water using Fe/Pd bimetallic nanoparticles

“…BDE209 (water solubility < 0.1 μg$L -1 ) is less water soluble, but it is highly soluble in organic solvents such as tetrahydrofuran (THF) and acetone [9,10]. For this reason, most studies have focused on removal of BDE209 in the presence of organic solvents [9,10].…”

“…Nanoscale zero-valent iron (nZVI) has been used as an effective reductant for treating many halogenated organic compounds including TCE, PCBs, and PBDEs [11][12][13][14][15]. However, nZVI alone was not effective for removing PBDEs [10]. Iron (Fe)-based bimetallic nanoparticles have been tested to degrade PBDEs in the presence of organic solvents [9,[16][17][18].…”