Study On The Effect Of Er³⁺:Y₃Al₅O (12) On Photocatalytic Activity Of Semiconductors And Composites

The wastewater draining from dyeing industry has its disadvantage, such as the complex ingredient, high concentration organic pollutant, chromaticity high, large quantity of emission, high toxicity, difficult to be degraded and so on. With the growing global environmental pollution, environmental governance problem is increasingly attention by people. In recent years, people studied a lot of methods and techniques to degrade the dye wastewater. Among them, photocatalytic degradation of organic pollutants is a very good method due to its broad-spectrum effects.This method has its disadvantage, such as simple equipment, could operate at room temperature under normal atmospheric pressure, organic pollutants could be degraded rapidly, thorough, no secondary pollution and so on.In heterogeneous photocatalysis research field, TiO₂ and ZnO is the most common semiconductor photocatalysis, due to their low cost, non-toxic nature, and chemical stability. However, because of the wide band gap of TiO₂ and ZnO, only a small ultraviolet fraction of solar light (3-5 %) could be absorbed. Therefore, the effective utilization of solar energy still remains a challenge in photocatalytic applications. More than that, TiO₂ and ZnO have lower quantum efficiency, the photogenerated electron-hole pairs are readily recombined. So, the application of pure TiO₂ and ZnO in photocatalytic field has some limitations. Therefore, in order to improve the photocatalytic activity of TiO₂ and ZnO, the most important is to expand the range of absorption wavelength and restrain combination of electron-hole pairs. In order to solve these two problems, the upconversion luminescence agent, Er³⁺:Y₃Al₅O₁₂ is synthesized, which can transform visible light into ultraviolet light and then excitated TiO₂ and ZnO. We use the method of coupled semiconductor photocatalyst to restrain combination of electron-hole pairs and then satisfy the need of TiO₂ and ZnO truly.In this paper, Er³⁺:Y₃Al₅O₁₂ was prepared by nitrate-citrate acid methed, then the Er³⁺:Y₃Al₅O₁₂/ZnO, Er³⁺:Y₃Al₅O₁₂/TiO₂-ZnO, Er³⁺:Y₃Al₅O₁₂/TiO₂-ZrO₂ and Er³⁺:Y₃Al₅O₁₂/TiO₂-CeO₂ composites were synthesized by ultrasonic dispersion and liquids boil method. In succession, the structural morphology of these composites was characterized by XRD and SEM, their photocatalytic activities through degrading the dyes wastewater under the solar light irradiation were also tested by UV-vis and IC. Azo dyes are the most important class of synthetic organic dyes used in the textile industry and are therefore common industrial pollutants. They are produced in large amounts and may enter the environment during the production and manufacturing process. In this paper, In order to inspect their photocatalytic activity, the Azo Fuchsine dye as target organic pollutant was degraded. In addition, the effects of Er³⁺:Y₃Al₅O₁₂ content, catalyst proportion, heat-treated temperature and heat-treated time on photocatalytic activities of these composites were investigated systematically. Otherwise, the key impact parameters on photocatalytic degradation of organic dye such as solar light irradiation time, dye initial concentration and catalyst amount were also studied. At last, it turned out that these photocatalysts have the universal applicability through the study on degradation of other organic dye. These experiments prove the mechanism which proposed in this paper, TiO₂ and ZnO were excited by the ultraviolet light that results from Er³⁺:Y₃Al₅O₁₂ produce the electron-hole pairs, and the semiconductor photocatalyst coupling restrain combination of electron-hole pairs, which can further improve the photocatalytic efficiency of TiO₂ and ZnO.