Efficient degradation of tetrabromobisphenol A by metal-organic framework-derived N-doped Fe/Fe3C@NC catalysts in sequential reduction-oxidation system

Tetrabromobisphenol A (TBBPA), a brominated flame retardant with environmental hazards poses challenges for degradation into less dangerous small molecule compounds using conventional single reduction or oxidation methods. In this study, N-doped Fe/Fe3C@NC was prepared as an efficient catalyst for TBBPA degradation in a sequential reduction–oxidation system (SROS). Nitrogen-doped carbon as support decelerated the oxidation of Fe0 and simultaneously accelerated electron transfer within the composites. After the reduction reaction, the Fe species in Fe/Fe3C@NC were converted to Fe2+, which activated peroxymonosulfate more efficiently. Thus, the degradation rate constant (kobs) of TBBPA reached 0.132 min−1, significantly higher than that of a single oxidation system (0.0464 min−1). In addition, the SROS generated more reactive oxygen species, especially O2•- and 1O2, which facilitated electron transport and consequently led to the rapid degradation of TBBPA. Degradation pathways of TBBPA in a SROS were initially proposed, with TBBPA being debrominated gradually during reduction and then directly oxidized by cleaving the central carbon. TBBPA mineralization percentage in the SROS reached 86 %, which was the result of the reduction initially increased the oxidizability of the pollutant and ring-opening susceptibility. Predicting the toxicity of the intermediates revealed that the intermediate products generated by the SROS during the TBBPA degradation had lower toxicity. This study provides insights into the efficient mineralization of organic pollutants for the remediation of aquatic environments.