The comparative study of two kinds of β-Bi2O3/TiO2 binary composite and their removal of 17ɑ-ethynylestradiol

In this work, we used TiO2 nanobelts and P25 particles as titanium sources to combine with β-Bi2O3 to form β-Bi2O3/TiO2 and β-Bi2O3/P25 composites. The prepared samples were characterized by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), and UV-vis absorbance spectroscopy and fluorescence spectroscopy. The structure and performance of two composites were comparatively investigated, and the β-Bi2O3 molar ratios in them were optimized and their roles in them were studied. The results showed that the TiO2 nanobelts and commercial TiO2 (P25) particles combined with β-Bi2O3 nanosheets. The optimal molar ratios of Bi to Ti element in two kinds of composites are 1:1. The β-Bi2O3 in P25/β-Bi2O3 makes more contribution to the improvement of photocatalytic activity of them than that in β-Bi2O3/TiO2 because P25 particles are distributed on β-Bi2O3 nanosheet more uniformly. The photocatalytic activities of β-Bi2O3/TiO2 (0.02275 min-1) and β-Bi2O3/P25 (0.02382 min-1) are 3.72 times and 3.90 times than that of pure β-Bi2O3 (0.0061 min-1) for EE2 removal. The enhanced photocatalytic activities of two kinds of composites are ascribed to photo-induced interfacial charge transfer on the heterojunction between β-Bi2O3 and TiO2 or P25. From the economic view, β-Bi2O3/P25 composites are better than β-Bi2O3/TiO2 because TiO2 nanobelts in the β-Bi2O3/TiO2 composite are obtained from P25 via extra hydrothermal treatment in strong alkaline environment. The free radical capture experiment indicated that the dominant reactive species are h+ and •O-2 for EE2 removal by TiO2/β-Bi2O3 and P25/β-Bi2O3 composites.