Ozonation of dimethyl phthalate catalyzed by highly active CuxO-Fe3O4 nanoparticles prepared with zero-valent iron as the innovative precursor

- Excellent catalytic potential of CuxO-Fe3O4 NPs in the ozonation of DMP was confirmed.
- Galvanic reaction between ZVI and Cu(II) was crucial in obtaining optimal CuxO-Fe3O4 NPs.
- Structural Cu(I) could re-generate from Cu(II) by either O2- and structural Fe(II).
- It provided feasible strategy for the regulation of low-valent metal catalyst in nanoscale.

Heterogeneous catalytic ozonation provides a promising alternative in the degradation of recalcitrant contaminants. CuxO-Fe3O4 nanoparticles (CuxFeO NPs, both Cu(I) and Cu(II) were contained, about 70 nm) were creatively synthesized using Fe(0) as the precursor and subsequently employed as the ozonation catalyst for dimethyl phthalate (DMP) degradation. Results showed that DMP degradation by O3/CuxFeO was significantly faster than those ozonation catalyzed by CuO, Fe3O4, or mixture of CuO and Fe3O4 (1:1 M ratio), which was ascribed to the unique CuxFeO NPs that composed of abundant structural Cu(I) (≡Cu(I)). It was among the first revealing the synergistic effect between ≡Cu(I) and surface lattice oxygen (O2-) in HO· generation, resulting in rapid DMP degradation kinetics and high mineralization efficiency. Besides the generation of ≡Cu(I), galvanic corrosion between Fe(0) and Cu(II) also generated structural Fe(II), which could reduce the ≡Cu(II) back to ≡Cu(I), thus compensating the electron loss of ≡Cu(I) and finally obtaining a high-efficiency cycling between ≡Cu(II) and ≡Cu(I). The DMP degradation pathway was introduced based on the intermediates detected. By regulating the (re)-generation of low-valent metal (≡Cu(I)), this study provides an innovative strategy to significantly promote the generation of HO· in catalytic ozonation, which might be promising for advanced wastewater treatment.

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