Iron-confined hierarchically porous biochar: Efficient BPA degradation via free radical/non-radical mechanisms from multiple active sites.

This study developed a self-sustaining oxygen activation system based on spatially confined Fe nanoparticles in hierarchical biochar (Fe@KMBC), which effectively mitigated persistent iron leaching (<0.1 mg/L), metal catalyst aggregation, and the need for stoichiometric chemical dosages of activator in advanced oxidation processes. The dual confinement mechanism-physical entrapment within 4.23 nm mesopores and electronic coupling with oxygen-functional groups-enabled the continuous generation of •O2- and 1O2 via molecular oxygen activation and electron cycling of Fe nanoparticles, allowing Fe@KMBC to achieve exceptional BPA removal (442.2 mg/g) via radical/non-radical mechanisms at multiple active sites. Notably, the pore-architecture-mediated reactant enrichment and electron transfer to generate •O2- and 1O2 maintains high efficiency and low iron leaching after five cycles. This activator-free system, which requires no addition of PMS or H2O2, significantly reduces energy consumption and ecotoxicity, establishing a promising eco-engineering blueprint for the remediation of endocrine disruptors.