Papers by Author: Eiji Watanabe

Abstract: Because bromic acid ion generated by the ozone processing of drinking water for sterilization is strong carcinogenic, there is a high possibility in persons health hazard. The titanium dioxide was reduced at 900-degree Centigrade by the gas atmosphere (CO or H₂). It was found that the concentration of the bromic acid ion in water was decreased at time when the reduced titanium oxide was added to water including the bromic acid ion. The bromic acid ion in water could be adsorbed by the titanium oxide reduced. In addition, it was suggested that the bromic acid ion could be decomposed into the bromide ion with low carcinogenic by using the photocatalitic function of titanium oxide under UV irradiation.

Abstract: Relationship of the adsorption behaviors of phosphorus with several natural materials and artificial HAS-clay with various chemical compositions was investigated. The amounts of phosphorus adsorbed by them were closely related with the contents of aluminum in the material. It was found that the higher the aluminum contents of material, larger the amount of phosphorus were adsorbed.

Abstract: Titanium dioxide photocatalyst films were prepared by dip-coating method using titanium dioxide sol solution in order to research the H₂O addition effect on the photocatalytic activities. The sol solution was prepared with titanium tetra-isopropoxide, urea and 2-methoxyethanol, then irradiated ultraviolet light and added distilled H₂O. The substrates for the dip-coating were fused silica plates and as-prepared films were dried at 100 °C then annealed at 650 °C. The films prepared by these methods showed visible light absorption in wavelengths longer than 380 nm and accelerated photodegradation of methylene blue by visible light irradiation. Furthermore, the photocatalytic activities of these films were depending on the H₂O additions to the sol solution.

Abstract: Phosphorus was one of the causative materials of eutrophication that was widely generated in the water system, for instance, the rivers, lakes, and marshes all over the world. The removal method using the phosphorus adsorption ability of volcanic ash fall deposits contained especially the amorphous alumino-silicate mineral was examined. To improve the practicality of durability and the adsorption ability of the volcanic ash fall deposits was heated within the range from 100 to 1100degrees. It was found that the phosphorus adsorption ability of the material was increased as the calcinating temperature was raised, and reached the maximum value at about 600degrees. The amount of adsorption of phosphorus had decreased rapidly when the material was heating to 600degrees or more.

Abstract: To obtain porous TiO2 film, the precursor sol was prepared by hydrolysis of Ti isopropoxide and then complexed with trehalose dihydrate. The porous TiO2 film was fabricated by dip-coating method on quartz glass substrates using this sol. The TiO2 films were calcined at 500-900 °C. The photocatalytic activities of the films were evaluated by examining decomposition of methylene blue in aqueous solution under UV light irradiation. The photocatalytic activity of the porous TiO2 film showed a different tendency according to the irradiation wavelength of UV light. The activity of the film evaluated under UV light irradiation with a wavelength of 254 nm was not affected a great deal by the clacination temperature. In the case of UV light irradiation with a wavelength of 365 nm, the activity of the film increased with increasing calcination temperature and that of the film calcined at 800 °C was the highest.

Abstract: Titanium dioxide sol solution was prepared using titanium tetra-isopropoxide, urea, 2-methoxyethanol. After that, ultraviolet light was irradiated to the sol solution, then, H2O was added to the solution. The prepared sol solution was dip-coated onto fused silica plates. The as-prepared films were dried at 100 °C and then annealed at 650 °C. The annealed films were anatase type titanium dioxides. Visible light absorption by the films was observed in wavelengths longer than 380 nm. Also, photodegradation of methylene blue by visible light irradiation was accelerated in the presence of the films prepared by these methods.

Abstract: To obtain porous and thick TiO2 film, the precursor sol was prepared by hydrolysis of Ti isopropoxide and then complexed with trehalose dihydrate. The porous TiO2 film was fabricated by dip-coating technique on quartz glass substrates using this sol. The TiO2 films were calcined at 500-700 °C. The photocatalytic activity of the films was evaluated by examining decomposition of methylene blue in aqueous solution under UV light irradiation. The TiO2 film prepared from the sol with trehalose was more active than TiO2 film prepared from the sol without trehalose. The trehalose addition to the dip-coating solution was effective in improving the photocatalytic activity of the TiO2 film.

Abstract: Two types of titanium dioxide sol solutions were prepared using titanium tetra-isopropoxide, urea, 2-methoxyethanol and water. The prepared sol solutions were dip-coated onto fused silica plates. These as-prepared films were dried at 100 °C and then annealed at 650 °C. The annealed films were anatase type titanium dioxides. Visible light absorption by the films was observed in wavelengths longer than 400 nm. Also, photodegradation of methylene blue by visible light irradiation was accelerated in the presence of the films prepared by these methods.

Abstract: The influence of the titania photocatalyst nano-particles to the skin is to be doubted. We studied the influence of different titania photocatalyst nanoparticles shape to the artificial skin like the human body under the UV light irradiation conditions. The decomposition degree of the artificial skin was evaluated from the monitoring of the amount of carbon dioxide generated from them by the titania photocatalyst nanoparticle activity. When spreading their titania nanoparticles on the skin sample, the carbon dioxide generated from the skin was not detected in the apatite coating titania nano-particle sample through was detected the sample coating no apatite. The result was considered not to have existed the influence on the skin samples because the titania nano-particle was not to touch the skin sample directly.

Abstract: To obtain porous TiO2 film, the precursor sol was prepared by hydrolysis of Ti isopropoxide and then complexed with trehalose dihydrate. The porous TiO2 film was fabricated by dip-coating technique on glass substrates using this solution. The TiO2 film was calcined at 500 °C. The maximum thickness of the film by one–run dip-coating was ca. 740 nm. The film was composed of nanosized particle and pore. The porosity of the TiO2 film was increased by the addition of trehalose dihydrate to the sol. The porous TiO2 films were calcined at various temperatures. The effects of the calcination temperature on the microstructure of the porous TiO2 film were investigated. The porous film prepared from sol containing trehalose still kept the porous structure for calcination at 950 °C. The phase transition temperature from anatase to rutile of the film was shifted from 650 to 700 °C by trehalose addition to the sol.