Insight into cobalt substitution in LaFeO3-based catalyst for enhanced activation of peracetic acid: Reactive species and catalytic mechanism

In this study, a hollow sphere-like Co-modified LaFeO3 perovskite catalyst (LFC73O) was developed for peracetic acid (PAA) activation to degrade sulfamethoxazole (SMX). Results indicated that the constructed heterogeneous system achieved a 99.7% abatement of SMX within 30 min, exhibiting preferable degradation performance. Chemical quenching experiments, probe experiments, and EPR techniques were adopted to elucidate the involved mechanism. It was revealed that the superior synergistic effect of electron transfer and oxygen defects in the LFC73O/PAA system enhanced the oxidation ability of PAA. The Co atoms doped into LaFeO3 as the main active site with the original Fe atoms as an auxiliary site exhibited high activity to mediate PAA activation via the Co(III)/Co(II) cycle, generating carbon-centered radicals (RO·) including CH3C(O)O· and CH3C(O)OO·. The oxygen vacancies induced by cobalt substitution also served as reaction sites, facilitating the dissociation of PAA and production of ROS. Furthermore, the degradation pathways were postulated by DFT calculation and intermediates identification, demonstrating that the electron-rich sites of SMX molecules such as amino group, aromatic ring, and S-N bond, were more susceptible to oxidation by reactive species. This study offers a novel perspective on developing catalysts with the coexistence of multiple active units for PAA activation in environmental remediation. Pharmaceuticals and personal care products (PPCPs) are ubiquitous in the aquatic environment and are recognized as contaminants of concern. Sulfonamides (SAs), as a class of antibiotics to treat bacterial infection, have been commonly detected in soil and aquatic environments worldwide, bringing about environmental residues and antibiotic resistance that seriously threaten the global health. Herein, a novel Co-modified LaFeO3 (LFC73O) catalyst was successfully synthesized to activate the eco-friendly oxidant of peracetic acid (PAA) for highly efficient SMX removal. The study comprehensively evaluated the degradation performance, mechanisms, pathways, and ecotoxicity to validate the effectiveness of the LFC73O/PAA system for SMX oxidation.