Study The Degradation Of Dyestuff In The Water On Nanosize SnO₂ Based Coupled Semiconductor Photocatalysts

Photocatalytic degradation of dyestuff in water using semiconductors has attracted extensive attention in the past decades. Previous studies have proved that such photocatalysts can degrade most kinds of persistent organic pollutants, such as detergents, dyes, pesticides and volatile organic compounds, under UV-irradiation. However, the fast recombination rate of the photogenerated electron/hole pairs hinders the commercialization of this technology. It is of great interest to improve the photocatalytic activity of semiconductors for the degradation of organic compounds in water. In the paper, the method of improving the activity of nanophotocatalysts is studied.Using nanocomposite oxide photocatalysts is a good method to enhance the efficiency of light utilization. The oxide photocatalysts with different Sn contents are rarely studies recently. In this paper, the nanocomposite oxide photocatalysts are prepared using the co-precipitation method. The photocatalytic activities of the photocatalysts are evaluated using the photo degradation of acid blue 62 as a probe reaction under the irradiation of Xenon light. According to the lambert beer's law , A=εbc, the concentration of acid blue 62 solution can be attained from the absorption of the solution .The novel CuO-SnO₂ and Fe₂O₃-SnO₂ nanocomposite oxide photocatalysts have higher activity, and they display the photocatalytic activity with Acid Blue 62, and the removal efficiency reaches 95% within two hours. The removal efficiency of Acid Blue 62 is still over 70% when these photocatalysts have been used for five times, which is very important for their practical application.The novel CuO-SnO₂ and Fe₂O₃-SnO₂ nancomposite oxide photocatalysts, prepared by co-precipitation method, were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Energy Disperse Spectroscopy (EDS) and UV-Vis diffuse reflectance spectroscopy. The crystal, particle sizes, surface areas, the phase compositions and the optical absorption of the CuO-SnO₂ and Fe₂O₃-SnO₂ photocatalysts varied with the calcination temperatures and the molar ratios. The photocatalytic activities of CuO-SnO₂ and Fe₂O₃-SnO₂ photocatalysts, evaluated using the photo degradation of acid blue as a probe reaction under the irradiation of Xenon light, were also found to be related to the calcination temperature and the molar ratio. The maximum photo catalytic activities of CuO-SnO₂ and Fe₂O₃-SnO₂ photocatalysts were observed when the CuO-SnO₂ (the molar ratio is 1 : 1, amount of catalyst is 1.0g/l) nanocomposite oxide calcined at 500℃for 3h and Fe₂O₃-SnO₂ (the molar ratio is 1 : 2, amount of catalyst is 1.0g/l) nanocomposite oxide calcined at 400℃for 3h, due to the samples with good crystallization. The photocatalytic activities of CuO-SnO₂ and Fe₂O₃-SnO₂ photocatalysts are also studied when they are used for other dyeing waste water treatment. It can be observed from the experiments that the nanocomposite oxide photocatalysts are suitable for the low-concentration wastewater.Reaction kinetics for the degradation by the photocatalysts were studied based on the results of the experiments.Therefore, the work of this paper provided to some extent the references to the researches of photocatalytic degradation of organic pollutants in water by nanocomposite oxide photocatalysts, the exploiture of higher photocatalytic activity in heterogeneous materials and their applications on the photocatalytic degradation of environmental hormone pollutants in the future.