Enhanced photocatalytic activity of novel α-Bi₂O₃@g-C₃N₄ composites for the degradation of endocrine-disrupting benzophenone-3 in water under visible light

The commonly used benzophenone-3 (BP-3) as ultraviolet filter ingredients is an endocrine-disrupting chemical that has received particular attention owing to its environmental ubiquity, and it poses a threat to aquatic biota and human health. In this study, novel α-Bi₂O₃@g-C₃N₄ nanocomposites with different α-Bi₂O₃ contents and enhanced photocatalytic activity were synthesized by a mixing calcination method. The as-synthesized photocatalysts were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, ultraviolet–visible diffuse reflectance spectroscopy, N₂ adsorption/desorption isotherm analysis, electrochemical impedance spectroscopy, photoluminescence spectroscopy and electron paramagnetic resonance (EPR) spectroscopy. The 1 wt% α-Bi₂O₃@g-C₃N₄ composite exhibited the highest rate constant of 0.42 h^-1 for photocatalytic degradation of BP-3, which was up to 6.3 times higher than that of g-C₃N₄ (0.07 h^-1). The enhanced photocatalytic activity might be due to the enhanced separation of photogenerated electron-hole (e^--h⁺) charge pairs and suppression of e^--h⁺ recombination. Scavenging experiments suggested that •OH, h⁺ and •O^2- worked together in the α-Bi₂O₃@g-C₃N₄ photocatalytic process. The EPR spectra demonstrated that the α-Bi₂O₃@g-C₃N₄ composites generated considerably more •O^2- and •OH than g-C₃N₄. Finally, cyclic degradation experiments showed the reusability of 1 wt% α-Bi₂O₃@g-C₃N₄ for BP-3 removal.