Deciphering Mn(II)/peroxymonosulfate system with nitrilotriacetic acid to degrade antibiotics: Roles of Mn species and interference of protein-like DOM

Aquaculture activities discharge large amounts of antibiotics, with protein-like dissolved organic matter (DOM) coexisting in wastewater, whose impact on FF degradation remains unclear. An efficient advanced oxidation process (AOP) was established by Mn(II), nitrilotriacetic acid (NTA), and peroxymonosulfate (PMS) for degrading the typical aquaculture antibiotic florfenicol (FF), achieving removal efficiency of (97.38±1.02)% within 20 min primarily via Mn(V)= O , in which •OH, •SO 4 - , and 1 O 2 made minor contributions. The inhibitory effects of fishery amino acids on FF degradation followed the order: poly lysine > tryptophan > methionine > lysine. Based on electrochemical measurements and density functional theory (DFT) calculations, tryptophan and methionine competed for PMS binding sites, with methionine being preferentially oxidized by Mn(V)= O , thereby delaying FF degradation. Primary degradation pathways involved defluorination, dechlorination, and aromatic ring hydroxylation, exhibiting a reduced toxicity. Overall, this study developed a sustainable strategy to remove typical fishery antibiotics, highlighting the critical role of Mn(V)= O and the interference mechanism of protein-like DOM.