Targeted cleavage of ether bond in BDE209 by microwave catalysis over S-doped iron-based materials without toxic...

Addressing the challenges of soil contamination by decabromodiphenyl ether (BDE209) and the limitations of conventional remediation techniques which often generate toxic byproducts, this study developed sulfur-doped iron-carbon composites (FCS-x) via a one-step pyrolysis method. The materials were evaluated for their efficiency and underlying mechanisms in the microwave-catalyzed degradation of BDE209. Characterization results confirmed that uniform sulfur doping induced a mesoporous structure and significantly improved the microwave absorption performance, achieving a maximum reflection loss of -16.7 dB. Under optimized conditions, an 83.3% degradation efficiency was achieved within 20 min without external oxidant. Based on combined experimental studies and density functional theory (DFT) calculations, O₂^•- was identified as the dominant active species, e^- serves as the essential precursor for O₂ activation. The "hot spot" effect and conductive carbon matrix facilitated electron transfer, promoting the activation of O₂ to O₂^•-. GC-MS and LC-MS analyses, in conjunction with DFT results, revealed that microwave irradiation weakens the ether bond in BDE209. This process leads to selective cleavage without generating toxic low-brominated intermediates, thereby significantly mitigating environmental risks. This work illustrates the synergistic interaction between microwave thermal and non-thermal effects, and provides an efficient and eco-friendly strategy for the remediation of BDE209-contaminated soils.