چكيده به لاتين
In this study, titania-silica nanophotocatalysts were first synthesized by wet impregnation metho¬d (WI). To improve its photocatalytic activity, tungsten and bismuth metal oxides, which were deposited on titania-silica using(WI), were used as promoters. The presence of these metal oxide promoters shifted the absorption edge of the titania-silica Differential reflectance spectroscopy toward higher wavelengths (lower energy gap). Optimal nano-photocatalyst with 50% wt% of titania, 1% wt% of tungsten and 1% wt% of bismuth resulted in 100% degradation of Rhodamine B under UV irradiation after 180 min in a batch reactor and under visible light irradiation after 180 min and 90 min in the batch reactor and immersion well reactor, respectively. Characterization of the synthesized nano-photocatalysts was performed using infrared spectroscopy, X-ray diffraction, scanning electron microscopy, X-ray energy dispersive spectroscopy and Diffuse reflectance spectroscopy. The results show that by adding 1% wt% of tungsten and 1% wt% of bismuth, the optimum photocatalytic structure is mesoporous and the size of the titania crystals decreases, indicating improved dispersion and stability of the nanophotocatalysts. Ultraviolet-visible spectroscopy was used to study nano-photocatalysts in the degradation of rhodamine B in the model solution. By studying the Operating parameters affecting the optimum photocatalytic activity under optimum operating conditions (pH = 6, initial concentration of rhodamine B= 15 mg/L, catalyst value=1 g/L, volume of dye solution=100 mL, temperature of dye=25oC and oxygenated water concentration=30 mM), 100% degradation of the pollutant was achieved within 30 minutes under visible light irradiation In 6 continuous cycles, the optimum photocatalytic degradation efficiency was reduced to 30% in the 6th cycle. Also, using different Scavengers, different active species were identified in the degradation of rhodamine B and it was found that the holes (h¬+) and superoxide radicals (O2-•) were the major active species during the photocatalytic degradation process.
Keywords: Titania-Silica, Bismuth, Tungsten, Nanophotocatalyst, Rhodamine B, Organic Pollutant, Visible Light, Ultraviolet Light
