Efficient degradation of Cu-Norfloxacin complexes in wastewater by electro-activated peroxymonosulfate coupled with electrocoagulation

Cu-Norfloxacin (Cu-NOR) complexes are ecotoxic, difficult to degrade naturally, and even increase the transmission of resistance genes. In this study, the electro-activated peroxymonosulfate (PMS) coupled with electrocoagulation (EC) system was innovatively constructed based on prepared MoSe2/CNC cathode and Al anode to degrade Cu-NOR complexes in wastewater. Various factors influencing Cu-NOR complexes removal were investigated. The results showed that the increase of the current was favorable to Cu-NOR removal, and it was suitable for a wider pH range, especially at pH 5-9. Compared with NaNO3 and NaSO4, NaCl as the electrolyte was more favorable for Cu-NOR removal due to the active chlorine substances which synergistically promoted the degradation of Cu-NOR. Response surface methodology (RSM) was performed to screen the significant factors and predict the optimal values. Under the optimal conditions, NOR, Cu and TOC removal reached 99.11 %, 100 %, and 91.54 %, respectively. Electron paramagnetic resonance (EPR) and quenching experiments indicated that O-1(2), center dot OH, SO4 center dot- and center dot O-2(-) were involved in the degradation of Cu-NOR complexes, and center dot O-2(-) played a major role. Besides, the ecotoxicity of the intermediates was evaluated and the flocs were characterized. Finally, the removal mechanism and degradation pathways of Cu-NOR complexes were proposed, involving breaking complexation, defluorination, carbonylation, ring opening of piperazine, etc., and finally mineralized into carbon dioxide, water and inorganic ions. Meanwhile, Cu2+ was removed through co-precipitation, adsorption, or flocculation by EC. This study provides a solution for efficient and green treatment of Cu-NOR complexes wastewater.