Effect of the composition and surface functional groups of Fe-Ni bimetal oxides catalysts in catalytic ozonation process

In this study, Fe-Ni bimetal oxides (Fe-NiO_x) catalysts were used to activate O₃ in a heterogeneous system. This research focuses on the degradation mechanism of dimethyl phthalate (DMP) by adding Fe-NiO_x catalysts which activated the O₃ decomposition to generate strong oxidative hydroxyl radicals (•OH). The experimental results showed that O₃/Fe-NiO_x catalyst calcinated under 500 °C achieved 47.75% higher DMP removal efficiency when compared with ozonation of DMP without the catalyst. Besides, control experimental data suggested that the adsorption of DMP was negligible (<4%) for Fe-NiO_x. Thus, it was concluded that the removal of DMP was due to the catalytic ability of Fe-NiO_x rather than the adsorption of DMP onto the catalysts. Moreover, the unsatisfactory performance of Fe-NiO_x catalysts calcinated in the presence of N₂ revealed that O₂ played an important part in affecting the crystalline degree of catalysts during the synthesis process. Meanwhile, the X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR) characterization analysis indicated that calcination temperature was an indispensable factor that influenced the relative content of Ni²⁺ and hydroxyl groups (−OH) in Fe-NiO_x catalysts. Furthermore, the relative content of Ni²⁺ had a greater effect on catalysts' activity because of the electron transfer between multivalent metal states.