Mesoporous Na₄W₁₀O₃₂/TiO₂ Composite Photocatalyst: Properation And Visible-light Photocatalytic Activity

The anatase phase, nanosized Na₄W₁₀O₃₂/TiO₂ composite was prepared by a sol-gel technique coupled with programmed temperature hydrothermal treatment. UV-vis diffuse reflectance spectroscopy (UV/DRS), infrared (IR) spectroscopy, Raman spectroscopy, inductively coupled plasma atomic emission spectroscopy (ICP-AES), and powder X-ray diffraction (XRD) were used to characterize the composition, phase structure and the integrity of the starting Na₄W₁₀O₃₂ after formation of the composite. The morphology and surface physicochemical properties of as-prepared solid photocatalytic materials were analyzed by transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), and nitrogen adsorption-desorption analysis. The results indicated that as-prepared material exhibited mesoporous structures with average pore size of 3.9 nm. In addition, the particles of the composite are well-distributed although aggregation among particles occurred, and the estimated average particle size is 20 nm.Photocatalytic property of the composite was tested by the degradation of 4-nitrophenol (4-NP) and dyes like rhodamoine B (RB), methylene blue (MB), congo red (CR) and methyl orange (MO) under visible-light irradiation. Obvious decreases of the concentions of the above pollutants were determined after irradiation of the suspension of 4-NP/dyes and Na₄W₁₀O₃₂/TiO₂ with visible-light. At the same time, Na₄W₁₀O₃₂/TiO₂ exhibited much higher photocatalytic activity than that of anatase TiO₂ or H3PW12O40/TiO₂, attributing to synergistic effect due to the combination of Na₄W₁₀O₃₂ and TiO₂ and its porous structure. The above composite catalysts also had the advantages of easily being separated and recovered, and deactivation of the catalyst was hardly observed after three catalytic runs.