Insight into interface-mediated electron transfer nonradical oxidation of β-diketones in iron oxide heterogeneous Fenton systems

Iron oxide-based heterogeneous Fenton systems are pivotal advanced oxidation technologies. Current studies demonstrate that pollutants incapable of complexing with surface Fe(III) are degraded via the hydroxyl radical (HO•) pathway, while carboxylic compounds follow a non-radical direct electron transfer mechanism. However, pollutant structural evolution during electron transfer remains unclear, and conventional monocarboxylic model pollutants cannot fully reveal Fe(III)-organic bond cleavage and oxidation pathways after complexation. In this work, β‑diketones with strong iron‑complexing capacity were selected as target contaminants and degraded in a ferrihydrite (Fhy)/H2O2 system. β‑diketones exhibited excellent degradation efficiency; the pseudo‑first‑order kinetic constant of benzoylacetone (BzAc) was 12 times that of phenol and 8 times that of nitrobenzene. Reactive species tests verified that HO•, FeIV=O and 1O2 were not the dominant active species. Six BzAc oxidation products were identified, all generated via inner‑sphere electron transfer. Acidic/weakly alkaline conditions and common anions Cl- and NO3- exerted negligible impacts, while OH- and SO42- significantly inhibited degradation. Fhy catalytic activity declined after cycles but was effectively restored by H2O2 regeneration. This study advances the understanding of non‑radical oxidation mechanisms and structure‑dependent degradation pathways in iron‑based Fenton‑like systems.