Efficient degradation of tetrabromobisphenol A via electrochemical sequential reduction-oxidation: Degradation...

Tetrabromobisphenol A (TBBPA), a toxic persistent pollutant, should be effectively removed from the environment. In this study, an electrochemical sequential reduction-oxidation system was proposed by controlling reaction atmosphere with Pd-Fe nanoparticles modified Ni foam (Pd-Fe/Ni) electrode as cathode for TBBPA degradation. To obtain an efficient Pd-Fe/Ni electrode for TBBPA degradation, various factors, like Pd loading, Fe²⁺ adding amounts, were examined. The Pd-Fe/Ni electrode exhibited higher TBBPA conversion and debromination than the counterparts, due to the synergism of Fe⁰ and electrochemical reduction. Similar TBBPA conversions and debromination ratios were observed for the cases of sparging N₂ only and sparging N₂ followed by air, which were higher than those of aeration. Reductive debromination occurred while first bubbling N₂, forming tri-BBPA, di-BBPA, mono-BBPA and BPA; and these intermediates were likely to be further oxidized by OH generated from H₂O₂ together with Pd-Fe/Ni electrode under aeration. Reductive and oxidative intermediates (including aromatic ring-opened product) were identified by HPLC and UPLC-QTOF-MS. Based on the intermediates, the possible TBBPA degradation mechanism and pathway were proposed. This study demonstrates that sequential reduction-oxidation process tuned by N₂ and air bubbling was favored for TBBPA degradation, thus, it should be a promising process for HOCs degradation.