Enhanced norfloxacin removal from sludge by dielectric barrier discharge plasma synthesis with Fe3O4/g-C3N4

Abstract

The excess sludge adsorbed with antibiotics poses a huge threat to the ecological environment and human health, and the removal of antibiotics from sludge was focused on. The dielectric barrier discharge (DBD) coupled with Fe3O4/g-C3N4 to degrade norfloxacin (NOR) in excess sludge of wastewater treatment plant was studied, where Fe3O4/g-C3N4 was prepared through high-temperature calcination. At an input voltage of 90 V and at a current of 0.5 A, NOR concentration of 100 mg/kg total suspended solids (TSS), Fe3O4/g-C3N4 dosing of 100 mg/g TSS, and pH 6.94, the NOR degradation efficiency was 89.2 %, the energy yield was 1.98 mg/kWh, and the synergy factor of DBD with Fe3O4/g-C3N4 was 1.85. In this system, •OH, •O2−, h+, H2O2 and O3 played an important role in the degradation of NOR in sludge, and Fe3O4/g-C3N4 induced Fenton-like reactions using H2O2 generated by DBD and facilitated photocatalytic reactions with ultraviolet and visible light. There was a positive correlation between the NOR degradation efficiency and the sludge disintegration, and the sludge disintegration process released NOR from the solid phase to the liquid phase. Three possible degradation pathways and the toxicity evaluation of the intermediates were proposed based on the results of DFT and HPLC-MS. Additionally, the DBD/Fe3O4/g-C3N4 system improved the sludge disintegration and dewatering performance effectively.