Fe-MOFs-derived Fe3O4-doped biochar from waste chopsticks: a novel catalyst for tetrabromobisphenol a degradation via peroxymonosulfate activation

Biochar production has emerged as a highly effective strategy for waste-to-resource conversion. In this study, biochar derived from waste chopsticks was doped with Fe₃O₄ using MIL-100 (Fe)—a metal-organic framework (MOF)—was synthesized at various pyrolysis temperatures and designated as Fe₃O₄@BC. The catalyst was employed to activate peroxymonosulfate (PMS) for the removal of tetrabromobisphenol A (TBBPA), a widely used brominated flame retardant (BFR). Remarkably, the Fe₃O₄@BC/PMS system achieved 98 % TBBPA removal within 30 min. The exceptional catalytic performance of Fe₃O₄@BC was attributed to the uniform dispersion of iron oxides and the abundance of oxygen-containing functional groups on the biochar surface. The underlying mechanism of TBBPA degradation was systematically investigated, revealing two distinct degradation pathways and identifying 18 by-products using liquid chromatography-mass spectrometry (LC-MS) and density functional theory (DFT) analysis. Furthermore, scavenger tests and electron paramagnetic resonance (EPR) spectra demonstrated that superoxide radicals (${O_2}^{·-}$) played a critical role in TBBPA degradation within the catalyst/PMS system. This study highlights the immense potential of biochar derived from waste chopsticks as an eco-friendly and efficient catalyst. Key advantages include the utilization of solid waste, reduced toxicity of degradation intermediates, and effective PMS activation for the degradation of BFRs.