Adsorption and sequential degradation of polybrominated diphenyl ethers with zerovalent iron

The widely used flame retardants, polybrominated diphenyl ethers (PBDEs), have been regulated owing to their persistence and toxicity. However, the high and increasing accumulation amount of PBDEs in the environment raises a big concern for public safety. In this study, the removal processes of decabromodiphenyl ether (BDE-209) and monobromodiphenyl ether (BDE-3) with microscale zerovalent iron (MZVI) were investigated to get better understandings for the removal mechanism based upon adsorption and degradation. The removal kinetics of both compounds was analyzed and revealed two-step kinetics: a fast removal step at the beginning of the reaction and a follow-up slow removal step. By-products generated during the entire process followed a stepwise sequence. The content of brominated compounds on the surface of MZVI was measured. About 10-20% of BDE-209 and 15-30% of BDE-3 were adsorbed on MZVI. The adsorption of BDE-209 and BDE-3 on MZVI was confirmed through the Fourier transform infrared spectroscopy. Surface adsorption of PBDEs on MZVI dominates the removal mechanism in the beginning and further debromination with MZVI was found. Finally, about 70% of BDE-209 and 60% of BDE-3 was degraded by MZVI within about one month. Our findings provide evidences for understanding the removal mechanism of PBDEs with MZVI and its great longevity on the PBDE degradation, which can facilitate the remediation design. (C) 2013 Elsevier B.V. All rights reserved.