Photocatalytic degradation of cefazolin over TiO2 coated on the fixed bed under UVC and solar

The presence of antibiotics in the environment especially in aqueous environments is a major warning about health and the environment. In this study, the photocatalytic degradation of cefazolin antibiotics was studied on the TiO2 nanoparticles coated on the fixed bed, which was treated in two light sources including UVC (250 nm) and natural solar. The effects of the operational parameters such as the initial concentration of the cefazolin and two light sources were examined and compared in both systems. Characterization of the TiO2 samples was performed by field emission scanning electron microscopy, X-ray diffraction, UV-VIS spectrophotometer, and surface area Brunauer-Emmett-Teller measurements. The highest photocatalytic activity for the degradation of cefazolin was obtained for the TiO2/UVC and 99% efficiency in 120 min. Also, the highest photocatalytic activity for the degradation of cefazolin was obtained for the direct TiO2/solar and 84% efficiency in 120 min. The photocatalytic degradation reaction of cefazolin was monitored by high performance liquid chromatography, total oxygen demand, and gas chromatography-mass spectrometry (GC-MS) analyses. The GC-MS analysis results indicate that degradation of cefazolin occurs through by-products thiocarbamide acid, thiadiazole, propanone, tetrazole, and dihydrothiazine ring cleavages followed by subsequent reactions with OH radicals. Finally, these substances become more stable and turn to mineral materials containing sulfate nitrate, and ammonia.