Study on the Visible-Light Photocatalytic Performance and Degradation Mechanism of Diclofenac Sodium under the System of Hetero-Structural CuBi₂O₄/Ag₃PO₄ with H₂O₂.

Two kinds of CuBi₂O₄/Ag₃PO₄ with different heterojunction structures were prepared based on the combination of hydrothermal and in-situ precipitation methods with surfactant additives (sodium citrate and sodium stearate), and their characteristics were systematically resolved by X-ray Diffraction (XRD), Brunauer-Emmett-Teller (BET), X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscope (SEM)/ High-resolution Transmission Electron Microscopy (HRTEM), UV-vis Diffuse Reflectance Spectra (DRS) and Photoluminescence (PL). Meanwhile, the photocatalytic properties of the catalysts were determined for diclofenac sodium (DS) degradation and the photocatalytic mechanism was also explored. The results indicate that both of the two kinds of CuBi₂O₄/Ag₃PO₄ exhibit higher photocatalytic efficiency, mineralization rate, and stability than that of pure CuBi₂O₄ or Ag₃PO₄. Moreover, the catalytic activity of CuBi₂O₄/Ag₃PO₄ can be further enhanced by adding H₂O₂. The free radical capture experiments show that in the pure CuBi₂O₄/Ag₃PO₄ photocatalytic system, the OH• and O₂•- are the main species participating in DS degradation; however, in the CuBi₂O₄/Ag₃PO₄ photocatalytic system with H₂O₂, all OH•, h⁺, and O₂•- take part in the DS degradation, and the contribution order is OH• > h⁺ > O₂•-. Accordingly, the photocatalytic mechanism of CuBi₂O₄/Ag₃PO₄ could be explained by the Z-Scheme theory, while the catalysis of CuBi₂O₄/Ag₃PO₄ with H₂O₂ follows the heterojunction energy band theory.