Degradation of norfloxacin in aqueous solution by atmospheric-pressure non-thermal plasma: Mechanism and degradation pathways

Norfloxacin is a synthetic antibiotics drug which is widely used in the treatment of infectious diseases and also often carelessly released into natural environment resulting in antibiotics-contaminated wastewater. In this work, we employed atmospheric-pressure non-thermal dielectric barrier discharge (DBD) to treat norfloxacin-contaminated water and investigated the degradation efficiency and mechanism for the plasma treatments under different conditions with varied working gas atmospheres. Our results showed that the DBD efficiency for norfloxacin degradation depended on reactive oxygen/nitrogen species (RONS) produced in the plasma treatment, while the plasma-induced hydroxyl radical played a critical role in the norfloxacin degradation. For O2-DBD, except for the contribution from reactive oxygen species (ROS), ozone could also play an important role. For N2-DBD, reactive nitrogen species (RNS) could work synergistically with H2O2 to enhance the degradation effect. We also checked the plasma activated liquid (PAL) effect and analyzed the degradation products so that the degradation mechanism and pathways could be elucidated. This work may therefore provide the guidance for effective and feasible application of low-temperature plasma technology in treatment of antibiotics-contaminated wastewater.