Enhanced degradation of tetrabromobisphenol A by magnetic Fe3O4@ZIF-67 composites as a heterogeneous Fenton-like catalyst

Magnetic Fe3O4@ZIF-67 composites were prepared, characterized, and used as heterogeneous catalysts to activate peroxymonosulfate (PMS) for the degradation of tetrabromobisphenol A (TBBPA). It was observed that all the added TBBPA (40 mg L−1) was completely degraded in 3 min in the Fe3O4@ZIF-67 (0.1 g L−1) + PMS (0.1 g L−1) system with a pseudo second-order degradation rate constant (k) of 110.3 L g−1 min−1, being nearly 10 times that (11.8 L g−1 min−1) in the ZIF-67 + PMS system and 2000 times that (0.06 L g−1 min−1) in the Fe3O4 + PMS system. The observed synergistic catalysis between Fe3O4 and ZIF-67 in Fe3O4@ZIF-67 enhanced not only the degradation of TBBPA, but also the TOC removal and the release of Br− during the degradation of TBBPA. Multiple reactive species including OH, SO4− and 1O2 were responsible for the degradation of TBBPA, but 1O2 was the dominant one. The synergistic catalytic mechanism of PMS activation by Fe3O4@ZIF-67 was proposed, which mainly involved the electron donating ability of Fe2+ in Fe3O4 for enhancing the Co3+/Co2+ cycle. Moreover, Fe3O4@ZIF-67 showed good recyclability and could be easily recycled by magnetic separation. This work provides an opportunity to construct highly efficient catalysts with magnetic recycling capability.