Study Of Photocatalytic Properties Of Polyoxometalates And The Novel Composites Materials Pom/TiO₂

In this paper, Sodium decatungstate was synthesized and(?)characterized by UV-Vis and FT-IR spectra. Took Na₄W₁₀O₃₂, H₃PW₁₂O(40)(?)and H₄ SiW₁₂O₄₀ as catalyst, photocatalytic properties, reaction kineticsland mechanism of polyoxometalates (abbreviated as POM) for thedecolorization of methyl orange dye solutions were studied inhomogeneous phase under near-UV irradiation. The results showed thatthe as-prepared compound remained the structures of Na₄W₁₀ O(32), thephotocatalytic properties was influenced by initial pH value of thesolution, the catalyst quantity and the initial concentration of the methylorange solution. The optimum catalytic conditions respectively were: theacidity of the solution being pH=2, pH=2 and pH=1, the dosage ofcatalyst being 0.6g/L, 0.6g/L and 0.4g/L, the concentration of methylorange being 20mg/L. The reaction could be described byLangmuir-Hinshelwood equation, and was a pseudo-first-order. The reaction was different from TiO2. There was a direct photocatalysis of methyl orange with POM.Then, three types of the solid photocatalytic materials such as Na4WI0O32/TiO2, H3PW,204o/Ti02 and H4SiW1204o/Ti02 were prepared by the sol-gel and programmed temperature hydrothermal methods. FT-IR, UV/DRS, XRD and TEM were used to characterize the composition, structure and morphology. Photocatalytic properties, reaction kinetics and the mechanism of them for the degradation of dimethyl phthalate (abbreviated as DMP) were studied in unhomogeneous phase under near-UV irradiation. The results showed that the POM/TiO2 particles exhibited a uniform anatase structure, programmed temperature hydrothermal methods were an important assurance of the result. POM infiltrating through the crystal lattice of TiO2, the primary POM structure remained intact in as-prepared composites, and there were intensive absorption in the near-UV spectra band. The photocatalytic properties were influenced by initial pH value of the solution, the catalyst quantity and the initial concentration of the DMP solution. The optimum catalytic conditions respectively were: the acidity of the solution being pH=6, the dosage the catalyst being 0.5g/L, l.Og/L and l.Og/L. The reaction could be described by Langmuir-Hinshelwood equation, the reaction was a pseudo-first-order. The POM/TiO2 had ahigher photocatalytic activity than TiO2, there was a synergistic effect yielded by the combination of POM and TiC>2.The study on degradation of the DMP solution with the novel composites materials POM/TiO2 had not been reported on the relative domestic researches. Therefore, the work of this paper provided to some extent the references to the researches of photocatalytic degradation of organic pollutants in water by polyoxometalates, the exploiture of higher photocatalytic activity unhomogeneous materials and their applications on the photocatalytic degradation of environmental hormone pollutants in the future.