Fabrication of Ag2O/TiO2-Zeolite composite and its enhanced solar light photocatalytic performance and mechanism for degradation of norfloxacin

Norfloxacin, as an antimicrobial drug, has frequently been detected in municipal plants, which is predicted to be potential risk on human beings and the environment. In the present study, zeolite immobilizes silver oxide decorated titanium dioxide (Ag2O/TiO2-Zeolite) composite has been fabricated through modified sol-gel method. Afterwards, physicochemical properties of the as-fabricated Ag2O/TiO2-Zeolite sample are systematically studied by scanning electron microscope, X-ray diffraction, X-ray photoelectron microscopy, ultraviolet visible diffuse reflectance spectroscopy and surface photovoltage spectra measurements. Besides these, photocatalytic (PC) performance of Ag2O/TiO2-Zeolite composite is evaluated by photodecomposition of norfloxacin under simulated solar light illumination and generation of active hydroxyl ((OH)-O-center dot) radicals. Results indicate that the decorated Ag species exists in the form of Ag2O, which can greatly enhance the visible light absorbance and charge separation efficiency. Furthermore, Ag2O/TiO2-Zeolite composite displays superior PC performance, which is mainly ascribed to the intense light absorbance in visible region, narrow band gap level and high charge separation efficiency. In addition, the solar light PC degradation pathways of norfloxacin are proposed according to the HPLC-MS/MS measurements, including hydroxylation addition to parent compound, decarboxylation and defluorination of side chain from the norfloxacin. Moreover, the as-fabricated Ag2O/TiO2-Zeolite composite exhibits high stability after consecutive utilization for seven times. (C) 2016 Elsevier B.V. All rights reserved.