Papers by Keyword: TiO₂ Photocatalyst

Abstract: Nanocrystalline rutile TiO₂ particles were prepared via hydrothermal treatment of Ti-containing precursors obtained by low-temperature aging for a transparent diluted HCl solution of amorphous TiO₂. The products were modified with FeO_x and phosphoric acid, and the photocatalytic activities of the obtained catalysts under visible-light irradiation were examined. By the addition of FeO_x or phosphoric acid, the photocatalytic activity of the rutile TiO₂ was slightly increased. On the contrary, by the FeO_x loading and subsequent addition of phosphoric acid, significant increases in the photocatalytic activity were attained. Results of UV-vis suggest that the iron oxides formed on the surface of rutile TiO₂ were changed into highly dispersed iron phosphate species by the addition of phosphoric acid. It was presumed that these species effectively suppress the recombination reaction between the photogenerated electrons and holes and contribute to the high photocatalytic activity of the rutile TiO₂ photocatalysts modified with FeO_x and phosphoric acid.

Abstract: Photodegradation emerged as an effective technology for elimination of phenol and phenolic compound contaminants. In this paper, we developed an facile and scaled-up synthesis method for production of nanoscaled titanium dioxide (TiO₂) photocatalysts doped with inorganic metallic ions of Sn, Zn, Fe, Cr, Mo, W, V, Ce, Au, Ag, Pt, and Pd. The obtained photocatalysts show relatively small sizes around 10 nm with highly crystallinity and narrow size distribution, and their efficiencies for photocatalytic degradation of phenol are greatly enhanced by doping the metallic ions. The photocatalytic efficiencies of nanoscaled TiO₂ photocatalysts for phenol degradation could be improved to 93.6%, 89% and 98% by doping 2 wt.% Cr, 10 wt.% Ce, and 10 wt.% Pd, respectively, compared with that of the undoped nanoscaled TiO₂ photocatalysts around 42.5%. The doped nanoscaled TiO₂ photocatalysts may find potential application in treatment of phenol and phenolic compounds contaminants in industrial waste water.

Abstract: The fluorine-modified mesoporous silica HMS(F20) was synthesized by using the mixture of TEFS(SiF(OC2H5)3) and TEOS(Si(OC2H5)4) as the silica source. The specific surface and pore size distribution were characterized by N2 adsorption and the hydrophilic-hydrophobic property was measured by water adsorption. The photocatalytic activities of TiO2 nanoparticles loaded on HMF(F20) and HMS were investigated for the degradation of iso-butanol diluted in water. The results show that the fluorine-modified mesoporous silica HMS(F20) has higher hydrophobic property than HMS and the TiO2/HMS(F20) exhibits the higher photocatalytic activity than TiO2/HMS. The hydrophobic mesopores benefit the condensation of hydrophobic organic compounds diluted in water, which results in higher photocatalytic degradation efficiency.

Abstract: We analyzed the effects of several process variables on removal efficiencies of NO and SO2 by the low temperature plasma process combined with photocatalysts. The cylinder-wire type, dielectric barrier discharge process for plasma generation was used. The photocatalysts were coated onto the glass beads by dip-coating method. As the voltage applied to the plasma reactor increases, or as the pulse frequency of applied voltage increases, the NO and SO2 removal efficiencies also increase. As the initial NO concentration decreases, or as the residence time increases, the NO and SO2 removal efficiencies increase.

Abstract: Sick house syndrome caused by volatile organic compound (VOC) in the room is a serious problem in Japan. A photocatalytic wall paper was developed which is a wall paper coated with a visible light type of photocatalyst. When irradiated by light, the photocatalyst generates strong oxidative potential and decomposes almost all organic substances to water, carbon dioxide, and others. As a result of our experiment using the photocatalytic wall paper, toluene and acetaldehyde were decomposed efficiently even under a fluorescent lamp, and the photocatalytic wall paper had also strong anti-bacterial effect under the fluorescent lamp.

Abstract: TiO2/SiC was prepared by oxidizing the TiC-SiC precursor obtained by carbothermic reduction process of TiO2-SiO2 binary oxide. An XRD analysis indicated the formation of the mixture of anatase and rutile phases of TiO2 crystalline after the oxidation of TiC-SiC sample. TiO2/SiC photocatalyst exhibited a higher photocatalytic reactivity than TiO2-SiO2 binary oxide prepared by the conventional sol-gel method. These results indicate the advantages of SiC nano powders as catalyst support of the TiO2 photocatalysts, and TiO2/SiC photocatalyst is effective for the degradation of organic compounds diluted in water.

Abstract: TiO2 photocatalysts prepared by a novel multi-gelation method showed good photocatalytic activity for the degradation of 2-propanol diluted in water by the control of parameters such as particle size, surface area, crystallinity, pore-volume, pore-diameter as well as anatase and rutile phase composition by changing the number of pH swings during preparation. In particular, with this method the phase transition from anatase to rutile at higher pH swing times can be controlled and high purity and uniformity of the TiO2 particles which leads to higher photocatalytic activity of the particles can be achieved. From our experimental results, it has been observed that TiO2 catalysts prepared by this unique multi-gelation method, i.e., adopting variations in the pH swing, significantly shows higher photocatalytic activity for the degradation of 2- propanol diluted in water. It can be considered a viable alternative over existing commercial methods for the preparation of photofunctional catalysts.

Abstract: Dioxins are extremely toxic, and it is difficult to treat them with the conventional method. When irradiated by light, photocatalysts generate strong oxidative potential and decomposes almost all organic substances containing dioxins to water, carbon dioxide and others. Silica-gel has high adsorptive activity as well as large surface area, and it is transparent to ultraviolet light. Photocatalytic silica-gel was prepared by a dip coating method using TiO2 sol obtained by hydrolyzing titanium tetraisopropoxide on silica-gel bead (about 3mm in diameter) and heat-treated at 550°C. Since the surface area of the photocatalytic silica-gel is 300m2/g, the reaction area is large and allows the highly efficient decomposition of harmful organic substances, unpleasant odors and colored matters contained in waste water. The photocatalytic apparatus for decomposition of dioxins in emission gas from waste incinerators is composed of the catalyst layer consisting of 95dm3 photocatalytic silica-gel and 16 units of UV lamp. The photocatalytic apparatus was connected to the bypass line led from the outlet duct of cyclone, and the concentration of dioxins in the exhaust gas was measured. Decomposition test of dioxins in scrubber water was also performed using a photocatalytic apparatus with 150g photocatalytic silica-gel and 8 units of UV lamp. After 0.5dm3 of scrubber water containing dioxins was circulated in the photocatalytic apparatus for 1, 2 and 24 hour, each concentration of dioxins in the water was measured. As a result, the removal efficiency over 99% of dioxins in emission gas and scrubber water from waste incinerators has been obtained.