Zinc-iron silicate for heterogeneous catalytic ozonation of acrylic acid: efficiency and mechanism

This research aimed at researching the degradation of acrylic acid (AA) in aqueous solution, by catalytic and non-catalytic ozonation processes performed in a semi-continuous reactor. Zinc-iron silicate was synthesized and characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) analysis, Fourier transformation infrared (FT-IR) and energy dispersive spectrometry (EDS). The characterization studies showed that Fe-Si binary oxide, Zn-Si binary oxide, ZnO and Fe₂O₃ deposits were formed on the surface of poor crystallinity zinc-iron silicate which contained abundant functional groups. Catalytic ozonation test results revealed that zinc-iron silicate exhibited high catalytic activity and stability in catalytic ozonation of AA in aqueous solution. The inclusion of zinc-iron silicate in the ozonation process enhanced AA decomposition by 28.7% and TOC removal by 20%, compared to the ozonation alone. The main AA removal mechanisms involved direct oxidation by ozone and indirect oxidation by hydroxyl radicals generated by the ozone chain reaction accelerated by zinc-iron silicate. The surface characteristics and chemical composition are significant factors determining the catalytic activity of zinc-iron silicate.