Enhancement of manganese sand activation for PMS degradation of levofloxacin using Co₃O₄ quantum dots: Mechanism and application

The advancement of environmentally friendly, cost-effective and efficient persulfate catalysts represents a pivotal step in the evolution of advanced oxidation technology involving persulfate. In this study, manganese sand composites modified with Co 3 O 4 quantum dots were prepared by isovolumetric impregnation and employed to activate persulfate (PMS) for levofloxacin (LVF) degradation. The resulting materials were characterized, and the results demonstrated that the Co 3 O 4 quantum dots enhanced the electron transfer ability of the materials, which in turn improved the catalytic ability. The degradation rate of levofloxacin was 99 % within 60 min, and the total organic carbon mineralization rate was 46 % at dosages of 0.4 g/L and 0.3 g/L of catalyst and PMS, respectively. The results of probe experiments demonstrated that •OH, SO 4 •- , and non-radicals were responsible for 11.8 %, 6.6 % and 81.6 % of the observed degradation, respectively. Potential degradation pathways of levofloxacin were proposed based on HPLC-MS and Fukui index analysis, and the toxicity changes of the degradation products were investigated. Cycling experiments and ionic dissolution tests demonstrated the stability of the material, which exhibited 94 % degradation and a markedly reduced ionic dissolution at the fifth cycle. Subsequently, the Co 3 O 4 quantum dots‑manganese sand composite system was evaluated in extended continuous flow device experiments for the treatment of real medical wastewater. The mineralization rate of the medical wastewater was 77 % in 48 h of operation, demonstrating the feasibility of the reaction system for the treatment of real medical wastewater and providing technical references for the future treatment of difficult-to-degrade organic wastewater.