Degradation of 2,2″,4,4″-tetrabromodiphenyl ether (BDE-47) by a nano zerovalent iron-activated persulfate process: The effect of metal ions

A nano zerovalent iron activated by persulfate process (nZVI-PS) was applied to degrade 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47), which is representative of the polybrominated diphenyl ethers (PBDEs) found in electronic waste (e-waste) sites. The influences of Cu(II), Zn(II), and Ni(II) ions, which are co-present in electronic wastes were evaluated on the degradation process. Electron paramagnetic resonance (EPR) and quenching studies indicates that sulfate radicals (SO₄^[rad]−) and hydroxyl radicals (HO^[rad]) were both responsible for the degradation of BDE-47 during the treatment. Zn(II) and Ni(II) inhibited BDE-47 degradation, possibly due to their negative reduction potentials leading to surface adsorption on or complexation with nZVI. Cu(II), however, enhanced the degradation of BDE-47. Characterization of the nZVI surface reveals that the catalytic activity of Cu(II) could be attributed to the synergistic effect of Cu(0)-Cu(III) and Fe(II)-Fe(III) redox pairs, which favored the continuous decomposition of PS and thus BDE-47 degradation. Overall, these findings indicate that nZVI can be used as an effective activator of PS for removal of the lower brominated BDEs (e.g., tetra-BDE) and the role of metal ions cannot be neglected, which provides a significant implication for the use of nZVI-PS system in e-waste contaminated site.