Highly efficient PMS activation by nZVI@MoS2 via Mo-Fe interfaces synergistic interaction for rapid degradation of ofloxacin

Abstract

In this paper, composite nZVI@MoS₂ with different proportions was prepared to activate peroxymonosulfate (PMS) for the effective removal of ofloxacin (OFL) from aqueous solutions. Under optimal conditions (0.1 g L⁻¹ nZVI@MoS₂, 0.2 mM PMS, Mo/Fe ratio of 0.2, pH 6.7), the removal efficiency of OFL attained 97.4% within 30 min (kobs = 0.1485 min⁻¹), and the total organic carbon (TOC) removal efficiency was approximately 63%. The system was still capable of maintaining a removal rate of approximately 90% in the presence of common anions. Moreover, it could achieve a removal rate of 84% in actual water bodies and 75% after four consecutive cycles, which highlighted environmental adaptability and stability. In addition to OFL, nZVI@MoS₂ demonstrated effective degradation activity toward a broader range of antibiotics and phenolic compounds. The synergistic effect of Mo - Fe enables the coupled redox cycles of Mo4⁺/Mo6⁺ and Fe2⁺/Fe3⁺ to drive PMS activation toward the generation of O₂•⁻ from HO₂· and its conversion to ¹O₂, which is confirmed by quenching experiments, thus forming a dominant non-radical oxidation pathway. Ecotoxicological assessment has verified that it can effectively detoxify the transformation products. Based on density functional theory (DFT) and the detected degradation intermediates, degradation pathways of OFL were proposed. This study offers a significant reference for the development of Fe- based catalysts for the removal of organic pollutants.