| With the constant development of industrial course, people's life has been improveddramatically, while meantime it also has brought about devastating influence in ourenvironment where all of us live on. Every year, large numbers of wastewaters containinghigh concentration poisonous organic compounds are discharged into surface water,which menace not only the health of human being but also the living condition of otherlife-form. The elimination of toxic and hazardous chemical substances such as organicdye compounds, surfactant, pesticide remains and so on from waste effluents andpreviously contaminated sites has become a major concern. In order to address thissignificant problem, extensive research is underway to develop advanced biochemical,physical adsorb, semiconductor catalysis and many other physicochemical methods forthe characterization and elimination of hazardous chemical compounds from wastewaters.However, such organic pollutants cannot be decomposed easily and completely usingordinary chemical and biological methods, since the structures of these organic dyecompounds in wastewaters usually contain one or several benzene rings. In recent years,many attentions have been paid to the method of semiconductor-based photocatalyticdegradation to treat these dye wastewaters.In these semiconductor materials, titanium dioxide (TiO2) as photocatalyst is widelyused to photodegradate many organic pollutants for its relatively high catalytic reactivity,physical and chemical stability, avirulence and cheapness and so on. Even so, only underirradiation of ultraviolet light (λ< 387 nm) TiO2 catalyst can effectively destroy theorganic pollutants in wastewaters because of its broad band-gap (Eg = 3.2~4.5 eV). Ingeneral, the sunlight only contains 3 % ~5 % ultraviolet light, so it is impossible to utilizesunlight directly for activating TiO2 photocatalyst effectively. Hence, the photocatalyticdegradation method treating wastewaters needs costly equipments and large numbers ofenergies as light source. This is a big burden for many countries, especially for thosedeveloping countries. In order to utilize sunlight, we have considered whether there aresome substances those can turn visible lights into ultraviolet lights to satisfy therequirement of TiO2 photocatalysts. Fortunately, the upconversion luminescencematerials containing rare earth metal ions are just what we want to adulterate to generalTiO2 photocatalysts.In this work, a new upconversion luminescence agent containing Erbium (Er)element was synthesized and then mixed into TiO2 powder by ultrasonic dispersion andthen a novel doped TiO2 photocatalyst utilizing visible light was firstly prepared and itsphotocatalytic activity was checked through the photocatalytic degradation reaction ofvarious hazardous componds as model compound under the visible light irradiationemitted by six three basic color lamps. Otherwise, in order to compare the photocatalyticactivities the same experiment was carried out for undoped TiO2 powder. Thisupconversion luminescence agent can emit five upconversion fluorescent peaks shown inthe fluorescent spectrum whose wavelengths are all below 387 nm under the excitation of488 nm visible light;Doped and undoped TiO2 powder was charactered by XRD andTEM;Process of degradation was detected by UV-Visible spectrum. The degradationratio of hazardous compounds in the presence of doped TiO2 powder under visible lightirradiation within certain time period was obviously higher than the correspondingdegradation ratio in the presence of undoped TiO2 powder. It indicates that theupconversion luminescence agent prepared as dopant can effectively turn visible lights toultraviolet lights that are absorbed by TiO2 particles to produce the electron-cavity pairs.All the results show that the TiO2 powder doped with upconversion luminescence agentis a promising photocatalyst using sunlight for treating the industry dye wastewater ingreat force. |
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