Fe(III) Alleviates pH Dependence of Iron-based Bimetallic/PMS System for Organic Pollutant Oxidation

This work delves into the mechanism enabling pH interference resistance in iron-based bimetallic oxides within the peroxymonosulfate (PMS) system. We employed MnFe2O4 spinel oxides as a catalyst for an in-depth comparison with monometallic analogs. We discovered that Fe(III) sites within the bimetallic oxide serve as sacrificial sites for hydroxyl ions as pH rises, stabilizing the cycling of active Mn sites. Elevated pH promotes the formation of surface hydroxyl groups, which enhance PMS and phenol adsorption via hydrogen bonding, thereby facilitating PMS activation by adjacent Mn sites and accelerating phenol degradation on the catalyst's surface. The cooperative effects of Fe(III) sacrifice and enhanced hydrogen bonding contribute significantly to the expanded pH tolerance of the iron-based bimetallic system, achieving nearly a 4.9-fold increase in kinetic efficiency at pH 6.2 relative to pH 3.2. This study deepens our understanding of sustainable Fenton-like systems and highlights their promising role in the degradation of pollutants.