Photocatalytic air treatment process under room light

• US 6,139,803 A
• Filed: 07/20/1998
• Issued: 10/31/2000
• Est. Priority Date: 11/10/1992
• Status: Expired due to Term

• Current Assignee: TOTO Company Limited (Toto Limited)
• Original Assignee: TOTO Company Limited (Toto Limited)
• Inventors: Kitamura, Atushi, Fujishima, Akira, Hashimoto, Kazuhito, Watanabe, Toshiya, Kojima, Eiichi
• Primary Examiner(s): MCKANE, ELIZABETH L
• Application Number:
  US09/119,050
• Time in Patent Office: 834 Days
• Field of Search: 422/121, 422/122, 428/702, 428/543, 428/904.4
• US Class Current: 422/121
• CPC Class Codes: A61L 9/16 using physical phenomena
• CPC Class Codes: A61L 9/205 using a photocatalyst or photosensitiser
• CPC Class Codes: B01D 2255/802 Photocatalytic
• CPC Class Codes: B01D 2259/804 UV light
• CPC Class Codes: B01D 53/86 Catalytic processes
• CPC Class Codes: B01D 53/8603 Removing sulfur compounds
• CPC Class Codes: B01D 53/8606 only one sulfur compound other than sulfur oxides or hydrogen sulfide
• CPC Class Codes: B01D 53/8621 Removing nitrogen compounds
• CPC Class Codes: B01D 53/8634 Ammonia
• CPC Class Codes: B01D 53/885 Devices in general for catalytic purification of waste gases
• CPC Class Codes: Y10T 428/8305 Miscellaneous [e.g., treated surfaces, etc.]

Abstract

A process for photocatalytically treating a hospital room contaminated by bacteria or an interior environment bearing airborne malodorous substances. A thin film of photocatalyst made of a semiconductor such as titanium dioxide is disposed on the inner wall of the hospital room or living space. The photocatalytic thin film is irradiated by a light source suitable for general lighting applications, such as a fluorescent lamp, and is photoexcited by the small amount of ultraviolet radiation included in the light of the fluorescent lamp. The wattage of the fluorescent lamp as well as the distance between the photocatalytic thin film and the lamp are selected such that the intensity of those UV wavelengths which have a higher energy than the band gap energy of the photo-catalyst is 0.001-1 mW/cm², preferably, 0.01-0.1 mW/cm². The bacteria and chemical compounds deposited on the photoexcited thin film are photodecomposed.

Claims

1. A room having a photocatalytic function, said room comprising:

enclosing surfaces including vertical walls, a floor and a ceiling defining an interior for the room;

a thin film of a photocatalytic semiconductor material having a band gap energy and covering at least a part of the enclosing surfaces of the room;

an electric lamp mounted on one of said enclosing surfaces in a position whereby said semiconductor material is in a light receiving relationship with said lamp, said lamp being an electric lamp for general lighting applications emitting a visible light for illumination and at least a small amount of ultraviolet radiation within the wavelength range between 300 nm and the wavelength corresponding to the band gap energy of said semiconductor material, the wattage of said electric lamp and the distance between said semiconductor material and said lamp being such that, when said lamp is energized, the total incident light intensity, impinging upon said semiconductor material, of said ultraviolet radiation within said wavelength range is 0.001 to 1 mW/cm².

2. A room according to claim 1, wherein said thin film is impinged by said ultraviolet radiation with an intensity of 0.1-0.01 mW/cm².

3. A room according to claim 1, wherein said electric lamp is mounted on said ceiling.

4. A room according to claim 1, which is a hospital room.

5. A room according to claim 1, wherein said electric lamp is a low-pressure mercury fluorescent lamp capable of emitting light including ultraviolet radiation having wavelengths of about 313 and 365 nm.

6. A room according to claim 1, wherein said electric lamp is a low-pressure mercury fluorescent lamp capable of emitting light including ultraviolet radiation having a wavelength of 350-360 nm.

7. A room according to claim 1, wherein said electric lamp is a high intensity discharge lamp.

8. A room according to claim 7, wherein said high intensity discharge lamp is a metal halide lamp.

9. A room according to claim 1, wherein said electric lamp is an incandescent lamp.

10. A room according to claim 1, wherein said semiconductor material comprises the anatase form of titanium dioxide.

11. A room according to claim 1, wherein the thickness of said thin film is about 0.3-10 micrometers.

12. A room according to claim 1, wherein said thin film of titanium dioxide is supported on a substrate affixed to at least said part of said enclosing surfaces.

13. A room according to claim 12, wherein said substrate is a glazed ceramic tile.

14. A room according to claim 1, wherein said semiconductor material comprises metalized particles of the rutile form of titanium dioxide.

15. A glazed ceramic bathroom fixture selected from the group consisting of urinals, wash basins and toilet bowls, said bathroom fixture having a surface at least partially covered with a thin film of a photocatalytic semiconductor material.

16. A glazed ceramic article according to claim 15 wherein said semiconductor material comprises anatase titanium dioxide.

17. A glazed ceramic article according to claim 15 wherein the thickness of said thin film is about 0.3-10 micrometers.

18. A glazed ceramic tile having a surface at least partially covered with a thin film of a photocatalytic semiconductor material.

19. A glazed ceramic article according to claim 18 wherein said semiconductor material comprises anatase titanium dioxide.

20. A glazed ceramic article according to claim 18 wherein the thickness of said thin film is about 0.3-10 micrometers.