Molybdenum substitution for enhanced activation of persulfate in LaFeO3-based catalysts: reaction species and catalytic mechanism

A molybdenum (Mo)-modified LaFeO₃ (LFMO) perovskite catalyst was synthesized to activate peroxymonosulfate (PMS) for the degradation of indole in solution. The catalyst was characterized by XRD, SEM, and XPS. Results indicate that LFMO possesses a higher specific surface area and more catalytic active sites compared to unmodified LaFeO₃. XPS analysis reveals that the activation of PMS is mediated by Fe²⁺/Fe³⁺ and Mo⁴⁺/Mo⁶⁺ reduction–oxidation cycles. Oxygen vacancies generated by molybdenum substitution serve as reaction sites, which accelerate the dissociation of PMS and the production of reactive oxygen species. Chemical quenching experiments and EPR spectroscopic analyses were employed to elucidate the mechanism, highlighting the significant role of non-radical species in the removal of indole. Under optimal reaction conditions, the degradation efficiency of indole reached 90.53% within 30 min, demonstrating strong anti-interference against inorganic anions and natural organic matter. LFMO particles exhibit sustained catalytic activity and stability over five consecutive cycles. This LFMO/PMS system provides valuable insights for the development of non-radical degradation pathways based on PMS.