Photocatalytic ozonation of metronidazole by synthesized zinc oxide nanoparticles immobilized on montmorillonite

Released antibiotics in the aquatic environment have undesirable biological and ecotoxicological effects. In this work, photocatalytic ozonation process was used for removal of metronidazole (MET) as commonly used antibiotic from aqueous media. ZnO nanoparticles as an effective photocatalyst were immobilized on the surface of montmorillonite (MMT). The ZnO/MMT catalyst was characterized by X-ray diffraction (XRD), N₂ adsorption/desorption, Fourier transform infrared (FT-IR), scanning electron microscope (SEM), and high resolution transmission electron microscope (HR-TEM). The ZnO/MMT activity was examined in the degradation of metronidazole under ozone bubbling and UV-A irradiation through photocatalytic ozonation process. The main influence factors on the photocatalytic ozonation activity such as ZnO/MMT dosage, pH, metronidazole initial concentration and ozone flow rate were studied. The results indicated that the MET removal efficiency was increased with increasing all the investigated factors except initial MMT concentration. The effect of organic and inorganic radical scavengers on the photocatalytic ozonation of MET was studied. Finally, several by products were identified by GC–MS analysis, which allowed to depict a possible mechanism for the MET degradation.