Degradation of antibiotic chloramphenicol in water by pulsed discharge plasma combined with TiO2/WO3 composites: mechanism and degradation pathway

Pulsed discharge plasma (PDP) combined with TiO2/WO3 composites for chloramphenicol (CAP) degradation was investigated. The prepared TiO2/WO3 composites were characterized by scanning electron microscope, transmission electron microscope, nitrogen adsorption apparatus, zeta sizer, X-ray diffraction, Raman spectra, UV–Vis absorption spectroscopy, X-ray photoelectron spectroscopy, photocurrent and electrochemical impedance spectroscopy. The degradation performance showed that the addition of TiO2/WO3 composites significantly enhanced the removal efficiency of CAP in PDP system. At a peak voltage of 18 kV, the highest removal efficiency of CAP could reach 88.1% in PDP system with 4 wt% TiO2/WO3, which was 36.8% and 26.0% higher than that in sole PDP system and PDP/TiO2 system, respectively. The TiO2/WO3 composites significantly accelerated interfacial charge transfer process compared to the pure TiO2. Besides, the effect of catalyst dosage and peak voltage on CAP removal was evaluated. OH, O3 O2−, h+ and high-energy electrons contributed to CAP degradation in PDP-TiO2/WO3 system. Addition of TiO2/WO3 composites can decompose O3 and produce more OH and H2O2. The degradation intermediates were measured by liquid chromatography-mass spectrometry (LC–MS) and ion chromatography (IC). The cycling degradation experiment showed that the TiO2/WO3 composites have good reusability as well as stability.