Antibacterial performance of a novel photocatalytic-coated cordierite foam for use in air cleaners

Yanyan Yao; Tsuyoshi Ochiai; Hitoshi Ishiguro; Ryuichi Nakano; Yoshinobu Kubota

doi:10.1016/j.apcatb.2011.06.020

Antibacterial performance of a novel photocatalytic-coated cordierite foam for use in air cleaners

Appl Catal B. 2011 Aug 11;106(3):592-599. doi: 10.1016/j.apcatb.2011.06.020. Epub 2011 Jun 23.

Authors

Yanyan Yao^{1

2}, Tsuyoshi Ochiai^{1

3}, Hitoshi Ishiguro^{1

2}, Ryuichi Nakano^{1

4}, Yoshinobu Kubota^{2

1}

Affiliations

¹ Kanagawa Academy of Science and Technology, KSP Bldg. West 6F, 3-2-1 Sakado, Takatsu-ku, Kawasaki, Kanagawa 213-0012, Japan.
² Department of Urology, Graduate School of Medicine, Yokohama City University, 3-9 Fukuura, Kanazawa-ku, Yokohama, Kanagawa 236-0004, Japan.
³ Division of Photocatalyst for Energy and Environment, Research Institute for Science and Technology, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan.
⁴ Kitasato Research Center for Environment Science, 1-15-1, Kitasato, Minami-ku, Sagamihara, Kanagawa 252-0329, Japan.

Abstract

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 5-6 log 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 0.25 mW cm^-2 of UV-A irradiation for 24 h, 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.

Keywords: Air-cleaning filters; Airborne pathogens; Photocatalytic degradation; TiO2-coated cordierite foam.