Self-Enhanced Reductive–Oxidative Cascade Enabled by In Situ Iodide Mediation: Synergistic Removal of MIAA and BPA over Pd–CoFe2O4

The remediation of aquatic environments cocontaminated with halogenated organics and phenolic pollutants poses a significant challenge to conventional single-mode treatment technologies. To address this, we engineered a bifunctional Pd–CoFe2O4 catalyst that orchestrates a synergistic reductive–oxidative (R–O) cascade for the simultaneous elimination of monoiodoacetic acid (MIAA) and bisphenol A (BPA). This system operates on a novel converting reduction byproducts into catalytic resources strategy: initially, favorable hydrodeiodization of MIAA occurs on Pd sites using NaBH4 as a hydrogen source, releasing iodide ions (I–). Crucially, rather than persisting as waste, these I– ions serve as in situ mediators that activate peroxymonosulfate (PMS) in the subsequent oxidative stage. The rapidly generated reactive iodine species (RIS, e.g., I•, IO3–) facilitate the ultrafast degradation of BPA within 5 min, significantly outperforming standalone advanced oxidation processes. Mechanistically, the Pd0/Pdn+ species determine the reductive efficiency, while the Co2+/Co3+ redox cycle on the spinel support amplifies PMS activation. Consequently, this integrated R–O system achieves a 67% total organic carbon (TOC) removal efficiency, far exceeding the 17% of the molecular oxidation alone. This work establishes a transformative paradigm for converting reduction byproducts into catalytic assets for the efficient treatment of complex wastewater.