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 Co3O4 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 Co3O4 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 center dot OH, SO4 center dot-, 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 Co3O4 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.