Research On Synthesis, Characterization Of BiMO₃（M=Gd, Sm） Solid Solution And Photocatalytic Degradation Of Direct Dyes

Photocatalysis has many advantsges such as no secondary pollution, mild operation conditions, high efficiency, solar energy using and so on. Photocatalysis is considered to be the most efficient and has a market prospects for the degradation of persistent organic pollutants. Therefore, researches on all kinds of photocatalysts and phocatalytic mechanism for efficient photocatalysis have become a hot subject.Considering that compounds containing bismuth showed unique advantages under visible light irradiation, Bi2O3was selected as research object in this paper. BiGdO3and BiSmO3solid solution with the fluorite-type structure were synthesized by a solid-state reaction method. The samples were characterized by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) and UV-Vis diffuse reflectance spectroscopy (DRS). Results showed that with the two-steps treatment procedure, BiGdO3and BiSmO3were of high purity and well crystallized with a cubic crystal system, a space group Fm3m225. The two samples were all irregular-shaped particles with a small specific surface area. There was plenty of adsorbed oxygen on the surface of BiGdO3and BiSmO3. Both of the two showed a strong optical absorption in the visible light region, and the band gaps of BiGdO3and BiSmO3were2.25eV and2.05eV.The photocatalytic activities of the as-prepared BiGdO3and BiSmO3samples were evaluated by the degradation of direct dyes (Direct Orange26, Direct Red23and Direct violet102) under visible light irradiation. Results showed that the photocatalytic degradation activities of BiGdO3and BiSmO3were higher than that of S-TiO2and Bi2O3. Furthermore, the photocatalytic degradation activity of BiGdO3is higher than that of BiSmO3. The effect of catalyst loading, initial concentration, pH, light source and the effect of coexisting ions and oxidants on the photocatalytic degradation efficiency was studied in detail. Moreover, the stability of both material and performance of BiGdO3and BiSmO3as visible-light photocatalysts was also studied. Results showed that the structure of BiGdO3and BiSmO3was stable during the photocatalytic reactions and the photocatalytic activity of the repeated cycles was still excellent.