Pulsed discharge plasma induced WO3 catalysis for synergetic degradation of ciprofloxacin in water: Synergetic mechanism and degradation pathway.

Pulsed discharge plasma (PDP) was adopted to induce WO3 for synergetic degradation of ciprofloxacin (CIP) in water. WO3 was firstly characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (DRS), Photocurrents and Photoluminescence. The degradation results showed that PDP could induce WO3 photocatalysis successfully, and a synergetic effect was established in PDP/WO3 system. After 60 min treatment time, 0.16 g/L WO3 increased the CIP removal from 71.3% to 99.6%, with the enhancement of the first-order kinetic constant from 0.020 min-1 to 0.081 min-1. Then, the effect of peak voltage, air flow rate and pH on CIP removal was evaluated. Active species trapping test verified that ·OH and ·O2- played the major role for plasma-degradation of CIP degradation, whereas OH and h+ were conductive to catalytic degrade CIP. WO3 addition lead to the decline of O3 and enhancement of OH no matter in deionized water or CIP solution. The degradation process was explored using fluorescence spectrograph, liquid chromatography-mass spectrometry (LC-MS) and ion chromatography (IC). Finally, the possible degradation pathways of CIP degradation were proposed. The reuse test suggested WO3 possessed excellent catalytic performance as well as good stability.