Construction of a novel Mn3O4/NiCo2S4 composite catalyst for enhanced peroxymonosulfate activation toward rapid degradation of ofloxacin: Mechanistic and toxicity assessment.

Ofloxacin (OFX) represents a significant threat to aquatic ecosystems and human health due to its environmental persistence, antimicrobial activity, and potential to promote drug resistance. However, how to achieve its efficient and environmentally friendly removal remains a challenge. In this study, a novel Mn3O4/NiCo2S4 composite catalyst was constructed for the first time via a hydrothermal method to activate peroxymonosulfate (PMS) for the rapid removal of OFX. Under optimal conditions, the NM-2/PMS system achieved 90.5 % removal within 20 min and exhibits excellent catalytic performance and cycling stability across various water matrices, highlighting its promising practical applicability. Quenching experiments, EPR analysis, and reactive species contribution calculations revealed that singlet oxygen (1O2) plays a dominant role in PMS activation for OFX degradation, while sulfate radicals (SO4·-), hydroxyl radicals (·OH), and superoxide radicals (O2·-) contribute synergistically. Mechanistic investigations further demonstrated that redox cycling among Ni2+/Ni3+, Co2+/Co3+, and Mn2+/Mn3+/Mn4+, in concert with synergistic interactions with sulfur species, collectively promoting the efficient activation of PMS. Moreover, potential OFX degradation pathways were elucidated using ESP mapping, DFT calculations, and LC-MS analysis, with toxicity evaluations performed for the intermediates. Therefore, based on the design concept of high efficiency, environmental friendliness and stability, this study developed a novel heterogeneous catalyst (NM-2), providing a promising strategy for the effective removal of recalcitrant organic pollutants from real water matrices.