Photocatalytic auto-cleaning process of stains

Abstract

The present invention provides a process for photocatalytically treating stains of chilly and turmeric caused on kitchen tiles and platforms by coating a thin film of photocatalyst made of a semiconductor such as titanium dioxide uniformly dispersed in dilute silica sol thereon and using a light source such as a fluorescent lamp to irradiate and photoexcite the photo catalytic thin film by the small amount of UV radiation included in the fluorescent light, resulting in photo decomposition and auto-cleaning of the stains.

1 . A process for photocatalytically cleaning stains on a surface, the process comprising: 
 i) coating the surface with a thin film of a photo-catalytic semi-conductor material having a band gap energy;    ii) providing a fluorescent lamp emitting visible light of desired sufficient intensity, the lamp emitting light having wavelength greater 300 nm and UV radiation having band gap energy higher than the semi-conductor in order to photoexcite the semiconductor particulate;    iii) energizing the lamp to illuminate surrounding ambience of the surface and impinge UV radiation and visible light on the thin film;    iv) exposing the stain on the semiconductor coated surface to fluorescent light to photocatalytically decompose the stain.    
     
     
         2 . A method as claimed in  claim 1  wherein the surface is a fixture tile or a platform.  
     
     
         3 . A method a claimed in  claim 1  wherein the stain is caused by a spice selected from chilly and turmeric in emulsion with oil and water.  
     
     
         4 . A method as claimed in  claim 1  wherein the photo-catalytic semi-conductor material having a band gap energy is TiO 2 .  
     
     
         5 . A process is claimed in  claim 1 , wherein the ambience is a domestic kitchen, restaurant kitchen, hospital kitchen and a hotel kitchen.  
     
     
         6 . A process as claimed in  claim 1 , wherein the film is impinged by a fluorescent light having about 10% of UV radiation with an intensity of 100 to 350 lux.  
     
     
         7 . A process as claimed in  claim 1 , wherein the light source is a fluorescent lamp capable of emitting light including UV radiation having a wavelength of 300 to 700 nm.  
     
     
         8 . A process as claimed in  claim 1 , wherein the semiconductor material is anatase form of TiO 2 .  
     
     
         9 . A process as claimed in  claim 1 , wherein the film has a thickness of in the range of 0.5 to 5.0 micrometers.  
     
     
         10 . A process as claimed in  claim 1  wherein the surface is a glazed tile which is roughened prior to spraying and cheat curing.  
     
     
         11 . A process as claimed in  claim 1 , wherein the fluorescent lamp is mounted at a distance of 1 to 3 feet from the surface.  
     
     
         12 . A process as claimed in  claim 1 , wherein the contact time of stains on the surface with illumination is in the range of 2 to 6 hours.  
     
     
         13 . A process as claimed in  claim 1  wherein the semiconductor material is sprayed in the form of 2 to 5% of TiO 2  powder dispersed in 5 percent silica sol.  
     
     
         14 . A process as claimed in  claim 1  wherein the surface is dried and heated to a temperature in the range of 100 to 350° C. for 20 to 60 minutes after coating.  
     
     
         15 . A process as claimed in  claim 14  wherein the dried and heated tile is further sprayed with the semiconductor material and then dried and heated to a temperature in the range of 100 to 350° C. for 20 to 60 minutes.  
     
     
         16 . A process as claimed in  claim 1  wherein the photocatalyst is in powder form and contains at least 80% by weight of anatase type TiO 2  having a surface area in the range of 25 to 60 m 2 g−1 and X-ray diffraction peaks at 20=25.35 A °; 37.88 A ° and 48.15 A °.  
     
     
         17 . A process as claimed in  claim 1  wherein the surface is a ceramic tile, plane glass or a hard acrylic sheet.  
     
     
         18 . A process as claimed in  claim 1  wherein the stain is a chilly or turmeric stain in the form of a water dispersion or emulsion with oil with a concentration range of 1 to 5%.  
     
     
         19 . A process as claimed in  claim 1  wherein the fluorescent light is varied in the range of 50 to 350 lux.  
     
     
         20 . A process as claimed in  claim 1  wherein the irradiation time is varied in the range of 20 to 50 hours.