Enhanced ozonation of vanillin catalyzed by highly efficient magnetic MnFeO/ZIF-67 catalysts: Synergistic effects and mechanism insights.

In this study, we synthesized magnetic MnFeO/ZIF-67 composite catalysts using a straightforward method, yielding catalysts that exhibited outstanding performance in catalyzing the ozonation of vanillin. This exceptional catalytic efficiency arose from the synergistic interplay between MnFeO and ZIF-67. Comprehensive characterization via x-ray photoelectron spectroscopy (XPS), x-ray diffraction (XRD), Fourier transform infrared spectrometer (FT-IR), Brunauer-Emmett-Teller (BET), field emission scanning electron microscopy (FE-SEM), and energy dispersive spectroscopy (EDS) confirmed that the incorporation of MnFeO promoted the creation of oxygen vacancies, resulting in an increased presence of l adsorbed oxygen (O) and the generation of additional ·OH groups on the catalyst surface. Utilizing ZIF-67 as the carrier markedly enhanced the specific surface area of the catalyst, augmenting the exposure of active sites, thus improving the degradation efficiency and reducing the energy consumption. The effects of different experimental parameters (catalyst type, initial vanillin concentration, ozone dosage, initial pH value, and catalyst dosage) were also investigated, and the optimal experimental parameters (300 mg/L1.0-MnFeO/ZIF-67, vanillin concentration = 250 mg/L, O concentration = 12 mg/min, pH = 7) were obtained. The vanillin removal efficiency of MnFeO/ZIF-67 was increased from 74.95% to 99.54% after 30 min of reaction, and the magnetic separation of MnFeO/ZIF-67 was easy to be recycled and stable, and the vanillin removal efficiency of MnFeO/ZIF-67 was only decreased by about 8.92% after 5 cycles. Additionally, we delved into the synergistic effects and catalytic mechanism of the catalysts through kinetic fitting, reactive oxygen quenching experiments, and electron transfer analysis. This multifaceted approach provides a comprehensive understanding of the enhanced ozonation process catalyzed by MnFeO/ZIF-67 composite catalysts, shedding light on their potential applications in advanced oxidation processes. PRACTITIONER POINTS: A stable and recyclable magnetic composite MnFeO/ZIF-67 catalyst was synthesized through a simple method. The synergistic effect and catalytic mechanism of the MnFeO/ZIF-67 catalyst were comprehensively analyzed and discussed. A kinetic model for the catalytic ozone oxidation of vanillin was introduced, providing valuable insights into the reaction dynamics.