Catalytic Ozonation over Ca2Fe2O5 for the Degradation of Quinoline in an Aqueous Solution

The treatment of industrial wastewater with various organic compounds was essential for the source control of water pollution. Catalytic ozonation process was widely used in wastewater treatment due to its higher efficiency and easy operation. In this work, Ca2Fe2O5 was prepared by the sol–gel method and used as a catalyst to remove quinoline effectively by the catalytic ozonation process. The physical and chemical properties of the catalyst have been well characterized by X-ray diffraction, Fourier transform infrared spectroscopy, N2 physical adsorption–desorption profiles, transmission electron microscopy, and X-ray photoelectron spectroscopy. The results have shown that calcium iron oxide has sheet micromorphology and good crystal structure. In addition, the Ca2Fe2O5 catalyst has more oxygen vacancies than the Fe2O3 catalyst, which can promote the decomposition of ozone molecules to produce active free radicals effectively. In this study, the Ca2Fe2O5 catalyst has shown higher catalytic activity than the other reported catalysts, which can remove quinoline and other organics from an aqueous solution effectively. In the Ca2Fe2O5/O3 system, more ozone molecules decomposed to generate •OH radicals, which inhibited the direct reaction of ozone and quinoline to produce NH4+-N. Meanwhile, •OH radicals generated in the catalytic ozonation process has increased the chemical oxygen demand removal rate efficiently. In addition, the intermediate products in the catalytic ozonation process were studied by electrospray ionization–mass spectrometry analysis. This research shows a promising way to prepare efficient catalysts for the treatment of quinoline by the catalytic ozonation process.