U.S. patent application number 11/025676 was filed with the patent office on 2006-06-29 for photocatalytic auto-cleaning process of stains.
This patent application is currently assigned to Council of Scientific and Industrial Research. Invention is credited to Anjani K. Bhatt, Pushpito K. Ghosh, Raksh V. Jasra, Dipak B. Shukla, Rajesh J. Tayade.
Application Number | 20060137708 11/025676 |
Document ID | / |
Family ID | 36609990 |
Filed Date | 2006-06-29 |
United States Patent
Application |
20060137708 |
Kind Code |
A1 |
Ghosh; Pushpito K. ; et
al. |
June 29, 2006 |
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.
Inventors: |
Ghosh; Pushpito K.;
(Bhavnagar, IN) ; Jasra; Raksh V.; (Bhavnagar,
IN) ; Shukla; Dipak B.; (Bhavnagar, IN) ;
Bhatt; Anjani K.; (Bhavnagar, IN) ; Tayade; Rajesh
J.; (Bhavnagar, IN) |
Correspondence
Address: |
DARBY & DARBY P.C.
P. O. BOX 5257
NEW YORK
NY
10150-5257
US
|
Assignee: |
Council of Scientific and
Industrial Research
New Delhi
IN
|
Family ID: |
36609990 |
Appl. No.: |
11/025676 |
Filed: |
December 28, 2004 |
Current U.S.
Class: |
134/1 ;
134/19 |
Current CPC
Class: |
C04B 41/87 20130101;
C03C 2218/112 20130101; B08B 7/0057 20130101; C04B 41/5041
20130101; C03C 2217/213 20130101; C03C 2217/23 20130101; C03C
17/256 20130101; C03C 2217/212 20130101; C03C 2217/71 20130101;
B01J 19/123 20130101; B01J 2219/0892 20130101 |
Class at
Publication: |
134/001 ;
134/019 |
International
Class: |
B08B 3/12 20060101
B08B003/12; B08B 7/00 20060101 B08B007/00 |
Claims
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.sub.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.sub.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.sub.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.degree. 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.degree. 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.sub.2 having a surface area in the range of 25 to 60 m.sup.2g-1
and X-ray diffraction peaks at 20=25.35 A .degree.; 37.88 A
.degree. and 48.15 A .degree..
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.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to photocatalytic oxidation of
spices with titanium dioxide coated on ceramic tiles and in
particular relates to reliable and successful use of TiO.sub.2
coated ceramic tiles and in-house fluorescent light to degrade
persistent stains caused by splashing, spilling of chilies and
turmeric on the walls/platform of kitchens.
BACKGROUND OF THE INVENTION
[0002] Fluid streams such as water or effluents often include
contaminants such as dissolved halogenated or organic compounds,
nitrogen oxides, halocarbons, pesticides, organic dyes, etc.
Photocatalysts can be used to purify fluid streams by converting
these contaminants into less harmful materials or substances, which
may be more easily removed therefrom.
[0003] The conversion of contaminants occurs when the effluent or
toxic pollutant is brought in contact with the photocatalyst
illuminated by a nearly ultra-violet or fluorescent light source.
The photocatalyst is either in the coated form or in dispersed
form. Typically, photocatalyst is deposited on the surface of a
support structure to provide a stable photo catalytic surface and
to ensure that the flowing stream does not carry it away. To be
effective, the contaminants must be brought into contact with the
photocatalyst.
[0004] The photocatalytic oxidation reaction with TiO.sub.2 either
in coated or dispersed form has been known for some time. A
synthetic and commercially available TiO.sub.2 containing greater
than 75 percent of anatase can be used as a photocatalyst to
degrade various organic species to render it environmentally safe.
These TiO.sub.2 either coated on support material or dispersed in
aqueous solution have been found to have good photocatalytic
degradation efficiencies when it is desired to impact oxidation or
reduction properties to organic moieties. Titanium dioxide have
specific properties for its use as a photocatalyst such as (i)
oxidation of water-bound environmental contaminants, irradiated
with solar or simulated light; (ii) complete photo degradation of
halocarbons, viz. dibromo-ethane, trichloroethylene;
chloro-benzenes etc widely used as solvents in pesticides,
insecticides, herbicides; (iii) photo destruction of different
classes of organic dyes and biological stains from waste water;
(iv) oxidation of cyanide found in rinse water of steel industry,
electroplating, gold extraction, extraction in mines, to less toxic
oxidation products like OCN. The latter is further oxidized to
NO.sup.3- and CO.sub.3.sup.2-; (v) reduction of metal ions to
metallic state to remove toxic and noble metal ions from waste
water; (vi) photo destruction of anionic, cationic and non-ionic
surfactants under solar or simulated light using aqueous TiO.sub.2
suspensions.
[0005] The wide spectrum of surface properties such as
crystallinity, high percentage of anatase, surface charge state,
surface hydration/hydroxylation, combined with fine particle size
and high surface area, low density and chemical inertness make
titanium dioxide a potential industrial photocatalyst in the field
of photo/environmental chemistry. Such a TiO.sub.2 in its porous
state can be employed for the photo catalytic oxidation reaction
employing simple method described hereinto.
[0006] The inorganic molecules and ions, viz. CO.sub.2, SO.sub.2,
NO.sub.3, NH.sub.4.sup.+ are the reaction products of
photocatalytic oxidation reaction on TiO.sub.2 surfaces. Under
favourable conditions, the organic species present in (i) waste
water effluents (ii) halo carbons (iii) dyes and dye stuff (iv)
surfactants (v) toxic pollutants etc. undergoes photocatalytic
oxidation reaction, when the TiO.sub.2 surface is irradiated with
ultra violet or fluorescent tube-light.
[0007] U.S. Pat. No. 5,035,784 (1991) to M. A. Anderson et al. has
disclosed the preparation of a highly porous titanium ceramic
membrane and which have the propensity to absorb organic molecules,
and also to degrade the complex organic molecules under UV light.
The preparation involves hydrolysis of titanium alkoxide at room
temperature in organic alcohol. The addition of large amount of
water will precipitate titanium hydroxide, which is then peptized
with HNO.sub.3 at room temperature. The suspension is heated with
stirring at 85.degree. C. and maintained it for 12 hours, whereby
the colloid gel is solidified onto a support which on firing at
500.degree. C. results in a highly porous, continuous web of
sintered particles forming a rigid membrane. The drawback
associated with this processes are (i) tight control of pH of the
colloidal mixture; ii) any alcohol as solvent will not be adequate.
The alcohol solvent is preferably an alkyl alcohol different from
alkyl radical in titanium alkoxide and (iii) the firing temperature
is critical as it may cause as it may cause cracking into the
resulting ceramic.
[0008] U.S. Pat. No. 5,874,701 (1999) to T. Watanabe et al.
discloses a process for photo catalytically treating hospital room
or living space contaminated by bacteria or an interior space
bearing airborne malodorous substances. It comprises of a thin film
of TiO.sub.2 coated on the inner walls of the room, which is
irradiated by a fluorescent lamp and photo excited by small amount
of UV radiation included in the light of the lamp. The wattage of
fluorescent lamp, distance between the thin film and lamp,
intensity of UV light were studied to photo decompose the bacteria
and chemical compounds deposited on the photo excited thin film.
This process has the limitation that it can photo decompose
bacteria and hazardous chemical compounds (airborne) substances. It
does not claim anything about auto cleaning of stains caused by
spices on kitchen walls and platforms.
[0009] U.S. Pat. No. 5,779,912 (1998) to A Gonzalez Martin et al.
discloses a method and apparatus for mineralizing organic
contaminants in water or air by photocatalytic oxidation in a
unique two-phase or three-phase boundary system in a photocatalytic
reactor, which works effectively at ambient temperature and low
pressure. The semi-conductor TiO.sub.2 is coated by different
technique on porous substances viz. porous polymers; porous metal;
porous carbon or graphite; or porous ceramic in order to have
passage there through for different oxidant, used in different
proportion in the decomposition process. The drawback associated
with this process is that the system is effective when binary metal
oxides are selected as photocatalyst, and at low pressure. The
presence of oxidant is quintessential for photodecomposition.
[0010] Japanese Patent No. 9,276,694 (1997) to O. Taware discloses
a method which involves the preparation of a paste from TiO.sub.2,
glass powder and water and applying a thin film of this paste on
ceramic surface prior to calcinations, in order to obtain a stiff
and less porous TiO.sub.2 layer that has strong adherence to
substrate and long service life. The drawback associated with
method is that this photocatalyst is compatible for decomposition
of nitrogen and phosphorous compounds, for cleaning air, exhaust
gas and water.
OBJECTS OF THE INVENTION
[0011] The main object of the invention is to provide a method for
photocatalytic oxidation of spices with TiO.sub.2 coated on ceramic
tiles, which obviates the drawbacks and limitations as detailed
above.
[0012] Another object of the invention is auto-cleaning of stains
caused by spurting of spices on kitchen walls and platforms, where
it is not easily reachable manually.
[0013] Another object of the invention is to provide stable
deposition of photocatalyst on surface of substrate and to ensure
that photocatalyst is not removed by flowstream of effluent.
[0014] Another object of the invention is to make the degradation
of spices more effective even in the presence of fluorescent
light.
[0015] Another object of the invention is to use anatase type of
TiO.sub.2 and the like TiO.sub.2 as Photocatalysts.
[0016] Another object of the invention is to provide a simple and
efficient method of coating a support material, while avoiding
complexities involved of known coating techniques.
SUMMARY OF THE INVENTION
[0017] Accordingly the present invention provides a process for
degradation of stains caused by spices with TiO.sub.2 coated on
ceramic tiles, which comprises of (i) spraying of 2 to 5% of
TiO.sub.2 powder dispersed in 5 percent silica sol on rough surface
of ceramic title; (ii) drying and heating the tiles in the
temperature range of 100 to 350.degree. C. for 20 to 60 minutes;
(iii) again spraying and drying/heating the titles as in step (ii);
(iv) placing droplets of slurry containing dispersed chilly or
turmeric in water or an emulsion with oil containing dispersed
chilly or turmeric in the concentration range of 1 to 5 percent, on
the coated ceramic title; (v) exciting the TiO.sub.2 surface with
ordinary fluorescent light having an intensity in the range of 5 to
20 lux, for effective contact time in the range of 20 to 80
minutes.
[0018] In an embodiment of the invention, the photocatalyst such as
TiO.sub.2 is in powder form and contains at least 80% by weight of
anatase type TiO.sub.2; surface area in the range of 25 to 60 m2g-1
and X-ray diffraction peaks at 20=25.35 A .degree.; 37.88 A
.degree. and 48.15 A .degree..
[0019] In another embodiment of the invention, the support material
is a ceramic tile, plane glass or a hard acrylic sheet.
[0020] In yet another embodiment of the invention, TiO.sub.2 powder
in the range of 2 to 5% is dispersed in 5 to 10% silica sol and
then sprayed on support material.
[0021] In another embodiment of the invention, the coated ceramic
title is heated in the temperature range of 100 to 350.degree. C.
for 5 a period in the range of 20 to 60 minutes.
[0022] In another embodiment of the invention, the spices tested
are chilly and turmeric either in water dispersion or emulsion with
oil in the concentration range of 1 to 5%.
[0023] In another embodiment of the present invention, the
fluorescent light is varied in the range of 50 to 350 lux.
[0024] In another embodiment of the invention, the irradiation time
is varied in the range of 20 to 50 hours.
DESCRIPTION OF THE INVENTION
[0025] In the present investigation, titanium dioxide which is
useful in the practice of this invention and which is photo
catalytically more active belongs to a class known as anatase-type
TiO.sub.2. In general TiO.sub.2 exist as a mixture of anatase and
rutile, with rutile content in minor proportion. The anatase and
rutile-type titanium dioxide are characterized by a tetragonal type
crystal structure. The anatase-type TiO.sub.2 and rutile-type
TiO.sub.2 have lattice constant a=3.78 A and c=9.49 A and a=4.58 A
and c=2.95 A respectively. A particular desirable type of, from
which a stable coating as well as photo catalysis oxidation
reaction can be carried out, is the anatase-type of TiO.sub.2 and
the like TiO.sub.2. These TiO.sub.2, have fine particles wherein
100% particles are finer than 20 microns and has BET surface area
in the range of 30 to 60 m.sup.2g.sup.-1. Titanium dioxide is a
crystalline material and exhibits definite peak position at
20=25.35, 37.88 and 48.15 as seen from X-ray powder diffraction
pattern. A typical, synthetic and commercially available TiO.sub.2
has about 75 percent of anatase-type TiO2 with the remainder of its
composition being rutile-type TiO.sub.2.
[0026] The titanium dioxide of anatase type has a band gap energy
of 3.2 electron volts, which corresponds to ultra violet (UV) light
of 388-nanometer wavelength. The titanium dioxide of rutile type
has a band gap energy of 3.0 electron volts, which corresponds to
UV light of 413-nanometer wavelength. Therefore, this TiO.sub.2
possesses a band gap energy, which requires minimum energy of light
to produce conduction band electrons and valence band holes. The
holes developed on the TiO.sub.2 surfaces reacts with water to
provide highly reactive hydroxyl radical ('0H). The holes and the
hydroxyl radicals are powerful oxidants and are capable of
oxidizing most of the organic materials.
[0027] In addition to the TiO.sub.2 mentioned above, it has been
found in the course of this invention that TiO.sub.2 having
different origin and having different proportion of anatase and
rutile are also useful in the photocatalytic oxidation provided
that it possesses the inherent characteristics, viz. (i) promotion
of electron when irradiated with the available photons under normal
condition of illumination in a household, (ii) capable of for a
hydroxyl radical and super-oxide ions and (iii) formation of
colloidal dispersion for easy application and maximizing light
absorption efficiency. The TiO.sub.2 surfaces are positively
charged in acidic medium and negatively charged in alkaline medium.
These surfaces to varying degrees are capable of attraction or
repulsion with the oxidizing substrate.
[0028] The preparation of thin film TiO.sub.2 on ceramic tile, is
carried out by first dispersing the TiO.sub.2 powder in
demineralized waster to produce a dilute slurry. Prior to
coating/layer formation by spray technique the surfaces of ceramic
tiles are mechanically made rough. The layer ceramic tiles are
first heated in an electric oven to remove the adhering water and
then calcined in muffle furnace in order to obtain a strong
adherence of TiO.sub.2. Strength of adherence of TiO.sub.2 to the
surface of the tile was tested by 1) keeping the tile under waters
of different pH (4-10) and measuring the adhered TiO.sub.2 on the
tile 2) keeping the tile under water at different temperatures
(60-70.degree. C.) measuring the adhered TiO.sub.2 on the tile 3)
keeping the tile under flowing tap water for 2 hours and measuring
the adhered TiO.sub.2 on the tile 4) applying adhesive tape on the
tile and checking the removal of TiO.sub.2 from the tile.
[0029] Most of the titanium dioxide exhibit in their natural state
the photocatalytic activity when excited with UV light or
fluorescent light. Ordinary room light also comprises of a UV
component with requisite features. The rutile-type TiO.sub.2
depicts lower photocatalytic activity while a much higher activity
can be seen when anatase-type TiO.sub.2 is used as a photocatalyst.
It has been found that anatase-type TiO.sub.2 with higher photo
activity can be prepared by subjecting the TiO.sub.2 powder to
controlled thermal treatment prior to coating the ceramic
tiles.
[0030] In common practice, a coating/layer of TiO.sub.2 on support
material can be prepared by applying a smooth paste, removing the
excess TiO.sub.2 and heating/firing at higher temperature. Other
methods of thin layer formation are spray pyrolysis, chemical
vapour deposition, plasma enhanced vapour deposition. In the
practice of this invention, another simple method of preparing a
stable coating which can be employed is by spraying the particles
uniformly dispersed in demineralized water and subsequently heating
and firing at higher temperature. The photoactive agent can also be
incorporated under the file manufacturing process, particularly
during the glazing step.
[0031] In general, the photocatalytic reaction between the excited
surface and the organic spices present in turmeric and chilly
powder can be red out under the influence of a weak light in a
room. According to this invention, improved photocatalyic
properties, i.e., higher efficiency can be obtained when the thin
TiO.sub.2 layer is activated either by a fluorescent lamp, an
incandescent lamp, or sunlight through a window. It is understood
that higher efficiency of anatase-type TiO.sub.2 for degradation of
organic species depends significantly upon the energy band gap,
which is ca. 3.2 eV. The band gap energy for such TiO.sub.2
photocatalyst is the minimum energy of light required to make the
material electrically conductive. The photoreaction under
controlled light leads to surface excitation and simultaneously to
the destruction of chromophoric organic species present in turmeric
and chilly. The latter can be either in a mixture form with water
or can be an emulsion with oil and water as is normally the case
during cooking of a variety of dishes.
[0032] According to the present invention, there is provided a
process for photo-catalytically treating the stains caused by
spilling chilly and turmeric in water or emulsion in oil on kitchen
tiles and platforms.
[0033] The first feature of the photocatalytic process, according
to the invention is that photocatalyst is in the form of thin film
of a solid-state semiconductor material is provided on the entire
surface of the interior walls and platform to ensure that the
reaction surface is available for photo-catalysis. The tiles and
platform coated with thin film of photocatalyst and in the presence
of fluorescent light, may be regarded as a large photocatalytic
reactor. This is particularly advantageous when the process
according to the invention is carried out for the purpose of
auto-cleaning of stains caused by spilling of chilly and turmeric
either in water or emulsion in oil. Stains caused by chilly and
turmeric are auto cleaned in situ by the action of photocatalyst,
upon contact with the wall surface coated with the photocatalytic
thin film, cleaning effect via photo decomposition can be
efficaciously accomplished.
[0034] The second feature of this photodecomposition process
according to the present invention resides in that the
photocatalyst is excited by making use of an electric lamp, such as
fluorescent lamps, which is provided in the room. This fluorescent
lamp includes a small amount of UV radiation of a wavelength range
having the light energy higher than the band gap energy of the
semiconductor photocatalyst. Therefore, the fluorescent lamp may be
used for the purpose of photo excitation of the photocatalyst
(TiO.sub.2) in addition to its intended general purpose of
illumination. Since the fluorescent lamp includes small amount of
UV radiation, the process of photodecomposition dispenses the need
for a separate UV light source. Accordingly the thin film of
photocatalyst may be exposed to illumination for the purpose of
photo excitation as described hereinbefore to ensure that the
photocatalytic thin film be disposed on the tile surfaces which is
easily accessible to people.
[0035] The third feature of the present invention is related to the
quantum yield of the light energy absorbed by the semiconductor
photo catalyst. It is the ratio between the number of photons
absorbed by the photocatalyst and the number of molecules which
undergo photo-chemical reaction. According to the invention, the
wattage of the fluorescent lamp and the distance between the
photocatalytic thin film on the tiles and the lamp are fixed so
that the total incident light intensity of the lamp is 50 to 350
lux.
[0036] Since in the process of the invention a photocatalyst in the
form of a thin film is employed and this film presents increasing
quantum efficiency with decreasing UV intensity, the use of
fluorescent lamp, of limited UV intensity may be advantageously
used to photo-excite the photocatalyst. As the light source is
turned on, the thin film of photo catalyst is excited by the UV
light, the surface hydroxyl groups are oxidized into OH radical and
the surface oxygen is reduced to super oxide ions due to the redox
action of generated electrons and holes. These species are highly
active and when the stains of chilly or turmeric are brought into
contact with the surface, they are decomposed into smaller
molecules or ions. In this regards it is considered that chilly and
turmeric stains containing chromophoric organics species is
chemically decomposed by the active species generated in the
process.
[0037] The following examples are given by way of illustration and
therefore should not be construed to limit the scope of the present
invention.
EXAMPLE 1
[0038] 5 gm of photocatalyst TiO.sub.2 mixed with 100 ml of 2%
concentration of colloidal silica sol and stirred for 2 hours and
sonicated for 30 minutes. This mixture was uniformly sprayed on
rough surface of ceramic tile using sprayings machine. The tile was
calcined at 450.degree. C. for 3 hours with increase in temperature
at the rate of 3.degree. C. per minute.
[0039] In 25 ml of water, 0.5 gm of turmeric and 1.0 gm of chilly
was thoroughly mixed, heated to 50.degree. C. to get good
dispersion of the turmeric and chilly. The patch of above mixture
of 1 cm wide was applied on the ceramic tile coated with
photocatalyst horizontally and this tile was kept under fluorescent
light. The distance between photocatalyst coated tile and tube
light was 2 feet and the intensity of the light was 250 lux. The
75% colour was removed in 26 hours under the tube light.
EXAMPLE 2
[0040] 5 gm of photocatalyst TiO.sub.2 mixed with 100 ml of 4%
concentration of colloidal silica sol and stirred for 2 hours and
sonicated for 30 minutes. This mixture was uniformly sprayed on
rough surface of ceramic tile using sprayings machine. The tile was
calcined at 350.degree. C. for 3 hours with increase in temperature
at the rate of 3.degree. C. per minute.
[0041] In 20 ml of water, 5 ml of vegetable oil, 0.5 gm of turmeric
and 1 gm of chilly was thoroughly mixed, heated to 50.degree. C. to
get good dispersion of the turmeric and chilly. The patch of above
mixture of 1 cm wide was applied on the ceramic tile coated with
photocatalyst horizontally and this tile was kept under fluorescent
light. The distance between coated tile and fluorescent light was 3
feet and the intensity of the light was 250 lux. The 100% colour
was removed in 22 hours.
EXAMPLE 3
[0042] 7 gm of photocatalyst TiO.sub.2 mixed with 100 ml of 5%
concentration of colloidal silica sol and stirred for 2 hours and
sonicated for 30 minutes. This mixture was uniformly sprayed on
rough surface of ceramic tile using sprayings machine. The tile was
calcined at 450.degree. C. for 3 hours with increase in temperature
at the rate of 3.degree. C. per minute.
[0043] In 20 ml of water, 5 ml of vegetable oil, 1 gm of turmeric
and 2 gm of chilly was thoroughly mixed, heated to 50.degree. C. to
get good dispersion of the turmeric and chilly. The patch of above
mixture of 1 cm wide was applied on the ceramic tile coated with
photocatalyst horizontally and this tile was kept under fluorescent
light The distance between coated tile and fluorescent light was 2
feet and the intensity of light was 250 lux. The 100% colour was
removed in 26 hours.
EXAMPLE 4
[0044] 3 gm of photocatalyst TiO.sub.2 mixed with 100 ml of 5%
concentration of colloidal silica sol and stirred for 2 hours and
sonicated for 30 minutes This mixture was uniformly sprayed on
rough surface of ceramic tile using sprayings machine. The tile was
calcined at 450.degree. C. for 3 hours with increase in temperature
at the rate of 3.degree. C. per minute.
[0045] In 25 ml of water, 1 gm of turmeric and 2 gm of chilly was
thoroughly mixed, heated to 50.degree. C. to get good dispersion of
the turmeric and chilly. The patch of above mixture of 1 cm wide
was applied on the ceramic tile coated with photocatalyst
horizontally and this tile was kept under the fluorescent light.
The distance between coated tile and fluorescent light was 2 feet
and the intensity of light was 116 lux. The 70% colour was removed
in 42 hours.
EXAMPLE 5
[0046] 7 gm of photocatalyst TiO.sub.2 was mixed with 100 ml of 5%
concentration of colloidal silica sol and stirred for 2 hours and
sonicated for 30 minutes. This mixture was uniformly sprayed on
rough surface of ceramic tile using sprayings machine. Then tile
was calcined at 350.degree. C. for 3 hours with increase in
temperature at the rate of 3.degree. C. per minute.
[0047] In 20 ml of water, 5 ml of vegetable oil, and 5 gm of
turmeric was thoroughly mixed, heated to 50.degree.0 C. to get good
dispersion of the turmeric and chilly. The patch of above mixture
of 1 cm wide was applied on the ceramic tile coated with
photocatalyst horizontally and this tile was kept under the
fluorescent light. The distance between coated tile and fluorescent
light was 2 feet and the intensity of light was 116 lux. 100%
colour was removed in 21 hours.
EXAMPLE 6
[0048] 5 gm of photocatalyst TiO.sub.2 was mixed with 100 ml of 6%
concentration of colloidal silica sol and stirred for 2 hours and
sonicated for 30 minutes. This mixture was uniformly sprayed on
rough surface of ceramic tile using sprayings machine. Then tile
was calcined at 350.degree. C. for 3 hours with increase in
temperature at the rate of 3.degree. C. per minute.
[0049] In 20 ml of water 5 ml of vegetable oil and 5 gm of chilly
was thoroughly mixed, heated to 50.degree. C. to get good
dispersion of the turmeric and chilly. The patch of above mixture
of 1 cm wide was applied on the ceramic tile coated with
photocatalyst horizontally and this tile was kept under the
fluorescent light. The distance between photocatalyst coated tile
and tube light was 1 feet and the intensity of light was 116 lux.
The 100% colour was removed in 30 hours.
EXAMPLE 7
[0050] 10 gm of photocatalyst TiO.sub.2 was mixed with 100 ml of 7%
concentration of colloidal silica sol and stirred for 2 hours and
sonicated for 30 minutes. This mixture was uniformly sprayed on
rough surface of ceramic tile using sprayings machine. Then tile
was calcined at 450.degree. C. for 3 hours with increase in
temperature at the rate of 3.degree. C. per minute
[0051] In 20 ml of water, 5 ml of vegetable oil and 0.5 gm of
turmeric and 2 gm of chilli was thoroughly mixed, heated to
50.degree. C. to get good dispersion of the turmeric and chilly.
The patch of above mixture of 1 cm wide was applied on the ceramic
tile coated with photocatalyst horizontally and this tile was kept
under the fluorescent light. The distance between photocatalyst
coated tile and fluorescent light was 3 feet and the intensity of
light was 350 lux. The 100% colour was removed in 46 hours.
EXAMPLE 8
[0052] 10 gm of photocatalyst TiO.sub.2 was mixed wit 100 ml of 7%
concentration of sodium silicate and stirred for 2 hours and
sonicated for 30 minutes. This mixture was uniformly sprayed on
rough surface of ceramic tile using sprayings machine. Then tile
was calcined at 450.degree. C. for 3 hours with increase in
temperature at the rate of 3.degree. C. per minute.
[0053] In 20 ml of water, 5 ml of vegetable oil and 0.5 gm of
turmeric and 2 gm of chilli was thoroughly mixed, heated to
50.degree. C. to get good dispersion of the turmeric and chilly.
The patch of above mixture of 1 cm wide was applied on the ceramic
tile coated photocatalyst horizontally and this tile was kept under
the fluorescent light. The distance between photocatalyst coated
tile and fluorescent light was 3 feet and the intensity of light
was 350 lux. The 70% colour was removed in 76 hours.
EXAMPLE 9
[0054] 10 gm of photocatalyst TiO.sub.2 was mixed with 100 ml of 5%
concentration of sodium silicate and stirred for 2 hours and
sonicated for 30 minutes. This mixture was uniformly sprayed on
rough surface of ceramic tile using sprayings machine. Then tile
was calcined at 450.degree. C. for 3 hours with increase in
temperature at the rate of 3.degree. C. per minute.
[0055] In 20 ml of water, 0.5 gm of turmeric and 2 gm of chilli was
thoroughly mixed, heated to 50.degree. C. to get good dispersion of
the turmeric and chilly. The patch of above mixture of 1 cm wide
was applied on the ceramic tile coated with photocatalyst
horizontally and this tile was kept under the fluorescent light.
The distance between photocatalyst coated tile and fluorescent
light was 3 feet and the intensity of light was 350 lux. The 50%
colour was removed in 76 hours.
EXAMPLE 10
[0056] 10 gm of photocatalyst TiO.sub.2 was mixed with 100 ml of 3%
concentration of sodium silicate and stirred for 2 hours and
sonicated for 30 minutes. This mixture was uniformly sprayed on
rough surface of ceramic tile using sprayings machine. Then tile
was calcined at 450.degree. C. for 3 hours with increase in
temperature at the rate of 3.degree. C. per minute.
[0057] In 20 ml of water, 5 ml of vegetable oil and 1 gm of
turmeric and 3 gm of chilli was thoroughly mixed, heated to
50.degree. C. to get good dispersion of the turmeric and chilly.
The patch of above mixture of 1 cm wide was applied on the ceramic
tile coated with photocatalyst horizontally and this tie was kept
under the fluorescent light. The distance between photocatalyst
coated tile and fluorescent light was 3 feet and the intensity of
light was 350 lux. The 60% colour was removed in 76 hours.
* * * * *