Preparation Of Immobilized And Visible Light Responsive Photocatalyst Er³⁺: YAlO₃/TiO₂-SAC And Its Photocatalytic Activity

With the rapid development of industrialization, the environment and energy issueshave become major issues facing humanity in the21st century and must be resolved. Dueto unique performance such as being directly drived by solar energy and pollution-free,photocatalysis become an ideal technology for enviromental pollution treatment, moreoverit has a broad application prospect and significant economic benefits in the fields ofenviromental protection, clean sources of energy, health and medical treatment, buildingmaterials and food fresh keeping and so on. Therefore, photocatalysis is regarded highly byscientific communities and enterprises.As a representative of the emerging photocatalyst, TiO₂is widely used tophotodegradate many organic pollutants for its relatively chemical stability, high catalyticefficiency, cheap and easily obtained and non-toxic and so on. Even so, only underirradiation of ultraviolet light （λ<387nm） TiO₂catalyst can effectively destroy the organicpollutants in wastewaters because of its broad band-gap （Eg=3.2eV）. In general, thesunlight only contains about5%ultraviolet light, hence, the photocatalytic degradationmethod treating wastewaters needs costly equipments and large numbers of energies aslight source. Other hand, the following defects are found in the practical application ofpowdered TiO₂. Firstly, the photocatalyst is difficult to effective recovery. Secondly,photocatalyst are prone to form aggregation and lose of its active ingredients in aqueoussolution. Thirdly, the photocatalyst in suspension will affect the depth of light because ofits absorption for light. The above two points greatly influence and limit the universalapplication of the TiO₂photocatalytsis in practice.In this paper, a new upconversion luminescence agent containing Er element wassynthesized and then mixed into TiO₂powder to prepare a novel doped TiO₂photocatalyst.The Er³⁺:YAlO₃inside could upconvert visible light to UV, then UV would excite TiO₂outside to produce high activity hole which used for the photocatalytic reaction. Thepreparation of immobilized and visible light responsive photocatalystEr³⁺:YAlO₃/TiO₂-SAC was loading Er³⁺:YAlO₃/TiO₂on the surface of SAC by four ways.Some conclusions were drawn by various characterization analysis and performanceexperimental study. With better ultraviolet-visible upconversion properties, theupconversion luminescence agents Er³⁺:YAlO₃excited by visible light could emit UV（λ<387nm）. The Er³⁺:YAlO₃/TiO₂calcined after700℃showed a higher photocatalyticactivity because of its anatase phase and the smaller size of grain. The synergistic effect ofadsorption and degradation between Er³⁺:YAlO₃/TiO₂and SAC greatly improved the photocatalytic degradation efficiency of pholocatalyst Er³⁺:YAlO₃/TiO₂-SAC in thephotocatalytic degradation experiments for methyl orange. Through comparing thephotocatalyst prepared by different manner of loading, we found that the weight ofEr³⁺:YAlO₃/TiO₂in photocatalyst loaded by sol-gel was increasing, and the catalyticactivity and the loading stability were also improved. The application of TiO₂was greatlyimproved by mixing upconversion luminescence agent into TiO₂and loading TiO₂on thesurface of SAC. On the one hand, it enhanced the availability for visible light ofphotocatalytic, and ensured its efficient photocatalytic activity. The other hand, the size ofphotocatalyst particles was bigger, and it was easy for recycling. This all would establishthe theoretical and practical basis for TiO₂photocatalyst in actual industrial application infuture.