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Preparation And Properties Of Supported Photocatalyst Phosphotungstic Acid/SiO2

Posted on:2007-01-09Degree:MasterType:Thesis
Country:ChinaCandidate:H F LiuFull Text:PDF
GTID:2121360185489621Subject:Physical chemistry
Abstract/Summary:PDF Full Text Request
Heteropolyacid (HPA) as novel catalytic materials have attracted extensive attention role in catalysis field since 1970s, which are generic terms of oxygen-contained multinary acid made up with the central atoms(such as P, Si, Ge and Ti)and the addenda atoms(such as Mo, W and V) by the coordinate bridging action of oxygen atoms. Heteropolyacid catalysts possess the unique "pseudo-liquid phase" behavior and multifunction (strong acid, strong oxidizability, photoelectric catalysis) and some other excellences. However, catalyst was difficult to reclaim in homogeneous systems and it can also make some pollution in some extents. Its catalytic activities of the HPA are greatly limited due to their very low specific surface areas, which has greatly limited its application. Therefore, incorporating HPA into Porous materials effectively will be of fundamental and practical significance.In this paper, via dipping technique, PWA was immobilized into the supporter SiO2 with high specific surface, which is prepared by sol-gel method, and then they were characterized by FT - IR, XRD, BET, TG-DSC and UV-Vis DRS. The photocatalytic behaviors of the composites were evaluated by degradation of aqueous methyl orange solution under the irradiation of two UV lamps (254nm). The effect of loading quantity, sintering temperature, catalyst quantity, stirring rate and catalyst reused were investigated. Meanwhile, the reaction mechanism was preliminary discussed combining the experimental results.The results showed that the supporter prepared by sol-gel method has large specific surface areas. Immobilized PWA exhibited excellent photocatalytic activity. When the catalyst was irradiated 1.5h, under the optimum condition of the loading quantity 0.3g, calcining temperature at 350℃, the initial concentration of the methyl orange solution 4 ppm, catalyst quantity 4.2 g/L, stirring rate 900 r/min, the decoloring ratio of methyl orange was up to 98.8%. The supported catalysts can be reused 8 times and still keep well activity. So it takes on potential application value. At the same time, the reaction mechanism for the photocatalytic degradation of aqueous methyl orange by the PWA/SiO2 is proposed as follows: the active species in solid acid catalysts is excited to...
Keywords/Search Tags:photocatalyst, phosphotungstic acid, methyl orange, immobilization, influence factors, mechanism
PDF Full Text Request
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