Heterogeneous catalytic ozonation of bisphenol a with oxygen vacancy-rich montmorillonite supported iron oxide

Heterogeneous catalytic ozonation is a promising technique for water purification, effectively addressing persistent organic pollutants. This study successfully synthesized oxygen-vacancy-rich Fe₂O₃/montmorillonite (Fe-MMT-400) nanocomposites via an integrated calcination strategy for enhanced catalytic ozonation of bisphenol A (BPA). Material characterization confirmed the effective structural integration and dispersion of acicular hematite on MMT substrates. XRD, FTIR, and XPS analyses verified the formation of oxygen vacancies (O_V), while BET measurements revealed an increased specific surface area, promoting ozone decomposition. In degradation experiments, the Fe-MMT-400/O₃ system demonstrated superior performance, achieving 89.9 % BPA removal within 15 min, significantly outperforming ozonation or catalyst-alone systems. Combined electron paramagnetic resonance (EPR) and radical quenching experiments identified surface oxygen atoms (O∗), hydroxyl radicals (^•OH), superoxide radicals (O₂^•-), and singlet oxygen (¹O₂) as the reactive oxygen species (ROS), with ^•OH being the dominant oxidative mediator. Furthermore, multidisciplinary characterization through XPS, DFT calculations, and TPD synergistically confirmed that the engineered O_Vs served as the primary active sites, crucially facilitating ozone adsorption and dissociation. This work ultimately establishes a comprehensive reaction mechanism framework, delineating the surface-mediated radical and non-radical pathways in the heterogeneous catalytic ozonation processes.