Effect of silica source on photocatalytic properties of Bi2O3/Bi2SiO5 heterostructure

The Bi₂O₃/Bi₂SiO₅ heterostructures were obtained with various samples of silica as a precursor: on the basis of biogenic silica isolated from rice husk and rice straw and the silica of mineral origin. A mixture of Bi(NO₃)₃ and SiO₂ with a mass content of 15% was used for synthesizing all the samples. Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscope (SEM), X-ray phase, X-ray fluorescence, and ultraviolet-visible diffused reflectance spectroscopy (UV-vis DRS) were used to systematically characterize as-obtained materials. Photodegradation of methyl orange in neutral aqueous solutions (pH = 6.8) under UV irradiation was studied to evaluate their photocatalytic activities. Morphology, bandgaps, the value of the zero charge point, and photocatalytic activity of the samples depended on the characteristics of the original silica. The degree of methyl orange degradation reached the maximum values (81%−85%) for samples based on precipitated silica from rice husks, straw, and the minimum value (16%) for a composite with thermal silica from rice straw. Composites based on thermal silica from rice husks and reagents from mineral raw materials did not statistically differ from each other in the degree of methyl orange degradation (67%−74%).