Oxidation of ciprofloxacin by the synergistic effect of DBD plasma and persulfate: reactive species and influencing factors analysis

Abstract

Synergistic system of a water falling film dielectric barrier discharge (DBD) plasma and persulfate (PS) has been set up in this work and used for oxidizing the ciprofloxacin (CIP) in water. Results on the reactive species formation in the DBD alone system as well as the DBD/PS system verified the PS activation in the DBD system. Influencing factors on the CIP degradation and the degradation process have also been studied. The obtained results show that the presence of PS could greatly improve the degradation and mineralization of the CIP and the degradation efficiency could reach 97.73% only after 40 min treatment with 4 mM PS addition. The increase of PS concentration, the lower CIP concentration, the acidic solution pH and the addition of metal ions (Fe2+ and Cu2+) were favorable for the enhancement of the CIP degradation, while the existence of Cl− and HCO− 3had negative effect on the degradation. The experiments related to scavengers’ addition confirmed the contribution of the main reactive species on the CIP oxidation. Three probable degradation pathways were proposed by analyzing the inorganic ions and organic by-products formed during the CIP degradation. The toxicity evaluation results on the CIP and its intermediates confirmed the effectiveness of the DBD/PS synergistic system.