Aqueous norfloxacin sonocatalytic degradation with multilayer flower-like ZnO in the presence of peroxydisulfate

Multilayer ZnO nanoflowers were synthesized through a simple precipitation method and characterized by field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), X-ray photoelectron spectra (XPS) and nitrogen absorption -desorption techniques. The FE-SEM images show the integrated morphology of an individual flower-like ZnO nanostructure, which is made of nano-platelets with uniform thickness (20-30 nm). The average pore size and Brunauer-Emmet-Teller (BET) surface area of the as-synthesized ZnO were 27.25 nm and 13.53 m(2)/g. The sonocatalytic ability of the prepared samples was evaluated through norfloxacin (NF) degradation in an aqueous system using ultrasound (US) irradiation. To improve degradation efficiency, peroxydisulfate (Na2S2O8) was introduced to develop a US/ZnO/peroxydisulfate system, which exhibited an excellent synergistic effect. The effects of ZnO dosage, Na2S2O8 concentration, pH, and initial NF concentration were studied to determine the performances of the US/ZnO/peroxydisulfate process. Corresponding results showed that NF degradation rate increased with the increase of ZnO dosage but decreased with the increase of initial NF concentration. Under the optimal Na2S2O8 concentration of 0.1 g L-1 at pH 9, the best degradation efficiency can be achieved. Moreover, based on the scavenging experiment results and literatures, NF degradation through US/ZnO/peroxydisulfate system is majorly induced by 'OH and SO4- radicals.