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Yao Y.,Kanagawa Academy Of Science And Technology | Yao Y.,Yokohama City University | Ochiai T.,Kanagawa Academy Of Science And Technology | Ochiai T.,Tokyo University of Science | And 6 more authors.
Applied Catalysis B: Environmental | Year: 2011

A novel titanium dioxide-coated cordierite foam (TiO2/cordierite foam) was developed for use in air cleaners. By a simple impregnation procedure, TiO2 nanoparticles were immobilized firmly onto the surface of a cordierite foam substrate through high-temperature (500°C) calcination. The strong bactericidal performance of the fabricated foam was evaluated by a newly developed test method for complex three-dimensional through-pore structures. This method could trace 5-6log units of decrease in bacterial cell numbers in an air environment, thus meeting the criteria of both the JIS and ISO standard test methods. With 0.25mWcm-2 of UV-A irradiation for 24h, the bactericidal rate of the TiO2/cordierite foam exceeded 99.9% for five types of airborne or droplet-based infectious pathogens: Escherichia coli (E. coli), Pseudomonas aeruginosa (P. aeruginosa), Legionella pneumophila (L. pneumophila), Klebsiella pneumoniae (K. pneumoniae), and methicillin-resistant Staphylococcus aureus (MRSA). The results of repeat testing, where the same sample was used three times, revealed that the bactericidal rate for E. coli was maintained at 99.9% in the second and third use, indicating that the TiO2/cordierite foam possesses a long-term bactericidal action. The TiO2/cordierite foam also exhibited a high photocatalytic degradation capability on gaseous acetaldehyde, which is associated with sick building syndrome, and volatile organic compounds to generate CO2 and H2O. The results demonstrated that TiO2-coated cordierite foam has great potential for use in air-cleaning filters with not only high bactericidal performance to remove pathogens in the air and in droplets, but also strong decontaminating and deodorizing functionality. © 2011 Elsevier B.V.

Ishiguro H.,Kanagawa Academy Of Science And Technology | Ishiguro H.,Yokohama City University | Yao Y.,Kanagawa Academy Of Science And Technology | Yao Y.,Yokohama City University | And 11 more authors.
Applied Catalysis B: Environmental | Year: 2013

We investigated the antiviral activity of TiO2-coated cordierite foam used in air cleaners, as well as the evaluation methodology. Furthermore, we developed Cu2+/TiO2-coated cordierite foam and investigated the reduction in viral infection ratio. The method for evaluation of antibacterial activity of TiO2-coated cordierite foam could also be applied to evaluation of antiviral activity. We showed that Cu2+/TiO2-coated cordierite foam reduced the viral infection ratio to a greater extent than TiO2-coated cordierite foam. Our findings suggest that the infection risk by polluted air could be decreased using Cu2+/TiO2-coated cordierite foam in air cleaners. © 2012 Elsevier B.V.

Ochiai T.,Kanagawa Academy Of Science And Technology | Ochiai T.,Tokyo University of Science | Nanba H.,Kanagawa Academy Of Science And Technology | Nanba H.,Kanagawa University | And 15 more authors.
Catalysis Science and Technology | Year: 2012

An ozone-assisted photocatalytic water-purification unit using a TiO 2 modified titanium-mesh sheet (TMiP) was investigated. Significant decomposition of biological and chemical contaminants has been achieved by highly active intermediates formed by catalytic decomposition and photocatalysis.

Ochiai T.,Kanagawa Academy Of Science And Technology | Ochiai T.,Tokyo University of Science | Ochiai T.,Kitasato Research Center for Environment Science | Masuko K.,Tokyo University of Science | And 19 more authors.
Chemical Engineering Journal | Year: 2013

A versatile photocatalyst-excimer-lamp hybrid unit for both air- and water-purification at practical scale was investigated. The unit consisted of a xenon filled quartz tube (20mm i.d.×300mm length) and TiO2 nanoparticles-modified Ti-mesh sheet (TMiP™). Emission at 172nm from a xenon excimer (Xe2*) was able to produce reactive species by direct photolysis of water or air. At the same time, the emission was able to excite TiO2 on TMiP surface. Therefore, the unit decomposes organic contaminants by synergy of photocatalysis and photolysis. Air- and water-purification efficiency of the unit was examined by high concentration of acetaldehyde and phenol decomposition test, respectively. The disinfection activity of the units for waterborne pathogens was also investigated. For comparison, the purification units using excimer-lamp alone or UV lamps with TMiP and/or ozone treatment were evaluated in the same methods. The photocatalyst-excimer-lamp hybrid unit was able to decompose acetaldehyde and phenol effectively, compared with the other units. On the other hand, disinfection activity of the unit for waterborne pathogens was strongly affected by the kind of the waterborne pathogens. The difference of efficiency between organic pollutants and waterborne pathogens by the unit may be due to the molecular or bacterial size and the surface composition of bacteria and viruses, critical wavelength for disinfection, and the permeation ability of the outer wall of bacterial cells or virus particles for reactive species. Taken together, the photocatalyst-excimer-lamp hybrid unit has wide potentials for environmental purification by the synergy of photocatalysis and photolysis. These results would be attractive to develop a practical environmental purification system such as sewage water treatment. © 2012 Elsevier B.V.

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