JP2517874B2 - Method for producing titanium oxide thin film photocatalyst - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a titanium oxide thin film photocatalyst used as an environmental purification material for wastewater treatment, water purification treatment and the like.

[0002]

2. Description of the Related Art In recent years, water pollution caused by domestic wastewater, industrial wastewater, etc., especially water sources such as organic chlorine solvents and golf course pesticides, which are difficult to treat with the currently used water treatment methods such as activated sludge method, Pollution is a serious problem. In addition, odors in living spaces and work spaces and contamination by resistant bacteria and mold represented by MRSA are also widespread.
Environmental pollution has become a serious social problem.

When the semiconductor is irradiated with light, electrons having a strong reducing action and holes having a strong oxidizing action are generated, and the molecular species in contact with the semiconductor are decomposed by the redox action. By utilizing such an action of the semiconductor, that is, a photocatalytic action, it is possible to decompose and remove environmental pollutants such as organic solvents, pesticides, and surfactants dissolved in water.
This method uses only semiconductors and light, and has less restrictions on reaction conditions such as temperature, PH, gas atmosphere, and toxicity as compared with methods such as biological treatment using microorganisms, and is difficult to treat with biological treatment methods. It has the advantage that even compounds such as organic halogen compounds and organic phosphorus compounds can be easily decomposed and removed. However, in the past research on decomposition and removal of organic substances by photocatalysts, semiconductor powders have been used as photocatalysts (for example, AL Pru).
den and D.D. F. Ollis, Journal
of Catalysis, Vol. 82,404
(1983), H .; Hidaka, H .; Jou, K .; N
ohara, J .; Zhao, Chemosphere,
Vol. 25, 1589 (1992), Teruaki Kuninaga, Kenji Harada, Keiichi Tanaka, Industrial Water, No. 379, 12 (199).
0)). Therefore, there is a drawback that it is difficult to separate and collect the object to be treated and the photocatalyst, and it is difficult to handle and use the photocatalyst. In order to collect the photocatalyst powder in the water treatment process, the treated water must be filtered, but since the photocatalyst is a fine powder, it causes clogging, and filtration is not easy and continuous water treatment is required. There was a problem that I could not.

[0004]

SUMMARY OF THE INVENTION In view of the above points, the present invention is capable of continuously performing wastewater treatment, water purification treatment, and the like, and has an effect of decomposing and removing environmental pollutants and its sustainability as an environmental purification material. Excellent, economical, safe, water resistant,
It is an object of the present invention to provide a method for producing a titanium oxide thin film photocatalyst having excellent properties in terms of heat resistance, light resistance, weather resistance and stability.

[0005]

Means for Solving the Problems The present inventor has conducted extensive studies in order to achieve the above object. As a result, after coating a substrate with titania sol, the temperature is gradually increased from room temperature to a final temperature of 600 ° C. to 700 ° C. Titanium oxide thin film produced by heating and heating and heating contaminates the environment such as organic solvents and pesticides dissolved in water by the redox action of electrons and holes generated by light irradiation. The inventors have found that the organic compound can be effectively decomposed and removed, and that the effect can be maintained without maintenance, and the present invention has been completed.

That is, according to the present invention, after coating a substrate with a titania sol prepared from titanium alkoxide and alcohol amines, the temperature is gradually increased from room temperature to 600.
In the method for producing a titanium oxide thin film photocatalyst, the temperature is raised to 750 ° C. to a final temperature of 700 ° C. and baked.

The titania sol used in the present invention is obtained by suspending ultrafine titanium oxide in water or hydrolyzing an alkoxide of titanium obtained by a reaction between alcohol, titanium tetrachloride, and titanium metal. Prepared. At that time, by adding alcohol amines such as diethanolamine and triethanolamine, a uniform and transparent titania sol can be obtained, and by using it, a high performance titanium oxide thin film photocatalyst can be manufactured.

In the titanium oxide thin film photocatalyst of the present invention, the titania sol thus obtained is coated on a substrate by a dip coating method, a spin coating method, a coating method, a spray method or the like, and then gradually heated and heated from room temperature to calcination. It is obtained by doing. The final temperature of the heating at this time, that is, the firing temperature is preferably 600 ° C to 700 ° C. By this operation, the titania sol coated on the substrate is converted into a titanium oxide thin film having a high performance as a photocatalyst and a crystalline form of anatase. At this time, directly 6
Baking at a temperature of 00 ° C to 700 ° C or a baking temperature of 6
When the temperature is lower than 00 ° C. or higher than 700 ° C., only a titanium oxide thin film containing rutile or amorphous having low activity as a photocatalyst can be obtained. In order to obtain a strong and high-performance titanium oxide thin film, the titanium oxide sol can be thinly and evenly applied or sprayed or spin-coated, or the dip coating can be used to slow down the pulling speed and pull up the titanium oxide thin film. It is desirable to prepare a multi-layered film by heating, calcining it, and repeating this operation. This makes it possible to obtain a thick and durable transparent and porous titanium oxide film having a large photocatalytic action.

Any substrate can be used for producing the titanium oxide thin film photocatalyst of the present invention, such as glass, ceramics, concrete or metal, as long as it can withstand firing at a temperature of 600 ° C to 700 ° C. It may be a material. Also, its shape is plate, cylindrical, prismatic, conical,
It may have any shape such as a spherical shape, a gourd shape, or a rugby ball shape. Also. The substrate may have a closed shape, may or may not have a lid, and may have a circular or square tubular shape, a fiber shape, or a hollow spherical shape such as a microballoon.

In order to further improve the performance of the titanium oxide thin film photocatalyst of the present invention, its surface may be coated with a metal film of platinum, rhodium, ruthenium, palladium, silver, copper, zinc or the like. Examples of the method for coating the surface with these metal films include a photoelectric deposition method, a CVD method, and a PVD method such as sputtering and vacuum deposition. In this case, if the thickness of the metal film is too thick, it will be costly and it will be difficult for light to reach the titanium oxide thin film. Therefore, it is preferable that the thickness of the metal film is as thin as possible.

The titanium oxide thin film photocatalyst according to the present invention thus obtained is used for sunlight, fluorescent lamps, black lights, U
V lamp, mercury lamp, xenon lamp, halogen lamp,
By the redox action of electrons and holes generated in the titanium oxide thin film by irradiation of artificial light from a metal halide lamp, etc., organic compounds that are polluting the environment such as organic solvents and pesticides dissolved in water can be easily It can be continuously decomposed and removed. Moreover, it has many advantages that it can be used at low cost, energy saving, and maintenance-free simply by irradiating light. Then, when a metal film of platinum or rhodium, ruthenium, palladium, silver, copper, zinc is coated on the titanium oxide film,
The catalytic action further increases the effect of decomposing and removing the organic compound.

Further, the titanium oxide thin film photocatalyst according to the present invention has a redox effect of electrons and holes generated in the titanium oxide thin film by irradiation of light, not only the organic compounds dissolved in water but also the bad odor in the air. It is possible to effectively decompose and remove environmental pollutants such as substances and prevent the reproduction of fungi and mold. When a metal film of platinum, rhodium, ruthenium, palladium, silver, copper, zinc, etc. is coated on the titanium oxide film, the metal film has an antibacterial and antifungal action due to its catalytic action. It is possible to effectively prevent the above-mentioned various bacteria and mold from propagating.

[0013]

EXAMPLES Among the examples of the present invention, particularly representative ones are shown below.

Example 1 Titanium tetraisopropoxide was diluted with isopropanol, hydrochloric acid and diisopropanolamine were added with stirring to prepare a transparent sol solution, which was prepared by dip coating to have a diameter of 8 mm, a length of 60 mm and a thickness of 60 mm. The surface of a 1 mm thick quartz glass tube was coated with a titanium oxide film.
That is, a quartz glass plate was immersed in this sol solution, pulled up, dried, and then heated and gradually heated from room temperature to 630 ° C. and fired. This was repeated 7 times to form a titanium oxide film of 0.2 μm on the surface of the quartz glass plate. As a result of examining the crystal structure of the obtained titanium oxide film by X-ray diffraction,
It was 100% anatase. This titanium oxide thin film photocatalyst was used to decompose tetrachlorethylene, which is now widely used as a solvent and a cleaning agent in the high-tech industry and cleaning industry and contaminates groundwater and soil. 18 ml of an aqueous solution of tetrachloroethylene having a concentration of 100 ppm (0.01% by weight) was put into a test tube made of hard glass, and the titanium oxide thin film photocatalyst obtained was immersed therein,
After bubbling oxygen, light from a 300 W xenon lamp was irradiated for 1 hour and 15 minutes. As a result of analyzing the amount of tetrachlorethylene contained in the obtained reaction liquid using a gas chromatograph, the amount of tetrachlorethylene was 95%.
It was decreasing. When the titanium oxide thin film photocatalyst was not used, the amount of tetrachloroethylene contained in the reaction solution was hardly reduced.

Comparative Example Titanium tetraisopropoxide was diluted with isopropanol, hydrochloric acid and diisopropanolamine were added with stirring to prepare a transparent sol solution, which was prepared by dip coating to have a diameter of 8 mm, a length of 60 mm and a thickness of 60 mm. The surface of a 1 mm quartz glass tube was coated with a titanium oxide film.
That is, a quartz glass plate was immersed in this sol liquid, pulled up, dried, and then heated and gradually heated from room temperature to 400 ° C. to be fired. This was repeated 7 times to form a titanium oxide film of 0.2 μm on the surface of the quartz glass plate. As a result of examining the crystal structure of the obtained titanium oxide film by X-ray diffraction,
Anatase was 20% and the rest was amorphous. Using this titanium oxide thin film photocatalyst, tetrachloroethylene was decomposed in the same manner as in Example 1. As a result of irradiating the light of a 300 W xenon lamp for 1 hour and 15 minutes, the amount of tetrachloroethylene was reduced by only 10%.

Example 2 Titanium tetraethoxide was diluted with methanol, nitric acid and triethanolamine were added with stirring to prepare a transparent sol solution, and a diameter of 1 was obtained by dip coating.
The surface of a quartz glass tube having a length of 0 mm, a length of 60 mm and a thickness of 1 mm was coated with a titanium oxide film. That is, a quartz glass tube was immersed in this sol solution, pulled up, dried, and then heated and gradually heated from room temperature to a temperature of 670 ° C. and fired. This was repeated 13 times to form a 0.4 μm titanium oxide film on the surface of the quartz glass plate. As a result of examining the crystal structure of the obtained titanium oxide film by X-ray diffraction, it was found to be 100% anatase. Using this titanium oxide thin film photocatalyst, trichlorethylene, which is widely used as a solvent and a cleaning agent in the high-tech industry and cleaning industry and contaminates groundwater and soil, has been decomposed. 500p
18 ml of an aqueous solution of trichlorethylene having a concentration of pm (0.05% by weight) was placed in a quartz glass test tube, the titanium oxide thin film photocatalyst obtained was immersed therein, and oxygen was bubbled through it. Was irradiated for 30 minutes. As a result of analyzing the amount of trichlorethylene contained in the obtained reaction solution using a gas chromatograph, the amount of trichlorethylene was reduced by 99%. When the titanium oxide thin film photocatalyst was not used, the amount of trichlorethylene contained in the reaction solution hardly decreased.

Comparative Example Titanium tetraethoxide was diluted with methanol, nitric acid and triethanolamine were added with stirring to prepare a transparent sol solution, and a diameter of 1 was obtained by a dip coating method.
The surface of a quartz glass tube having a length of 0 mm, a length of 60 mm and a thickness of 1 mm was coated with a titanium oxide film. That is, a quartz glass tube was immersed in this sol liquid, pulled up, dried, and then heated and gradually heated from room temperature to 750 ° C. and fired. This was repeated 13 times and the surface of the quartz glass tube was exposed to 0.
A 4 μm titanium oxide film was made. As a result of examining the crystal structure of the obtained titanium oxide film by X-ray diffraction, it was found that the film was anatase 50% and rutile 50%. Using this titanium oxide thin film photocatalyst, trichlorethylene was decomposed in the same manner as in Example 2. As a result of irradiating light from a high-pressure mercury lamp of 500 W for 30 minutes, the amount of trichlorethylene was 2
There was only a 0% reduction.

Example 3 Titanium tetraisopropoxide was diluted with absolute ethanol, hydrochloric acid and diethanolamine were added with stirring to prepare a transparent sol solution, and a quartz glass having a 20 mm square and a thickness of 1 mm was prepared by a dip coating method. The surface of the plate was coated with a titanium oxide film. That is, a quartz glass plate was immersed in this sol solution, pulled up, dried, and then heated and gradually heated from room temperature to a temperature of 650 ° C. and fired.
Repeat this 10 times to make 0.3μ on the surface of the quartz glass plate.
m titanium oxide film was made. As a result of examining the crystal structure of the obtained titanium oxide film by X-ray diffraction, anatase 10
It was 0%. Using this titanium oxide thin film photocatalyst, acetic acid was decomposed. 120 ppm (0.012% by weight)
20 ml in width and 30 m in length with 1 ml of aqueous solution of acetic acid
m into a quartz cell with a thickness of 3 mm, and the titanium oxide thin film photocatalyst obtained was immersed in the quartz cell and bubbled with oxygen.
The light of a 100 W high pressure mercury lamp was irradiated for 1 hour and 30 minutes. As a result of analyzing the amount of acetic acid contained in the obtained reaction liquid using a gas chromatograph, the amount of acetic acid was reduced by 80%. When the titanium oxide thin film photocatalyst was not used, the amount of acetic acid contained in the reaction solution hardly decreased.

Comparative Example Titanium tetraisopropoxide was diluted with absolute ethanol, hydrochloric acid and diethanolamine were added with stirring to prepare a transparent sol solution, and a quartz glass plate 20 mm square and 1 mm thick was prepared by the dip coating method. The surface of the was coated with a titanium oxide film. That is, a quartz glass plate was immersed in this sol solution, pulled up, dried, and immediately heated and baked at a temperature of 650 ° C. This was repeated 10 times to form a 0.3 μm titanium oxide film on the surface of the quartz glass plate. As a result of examining the crystal structure of the obtained titanium oxide film by X-ray diffraction, the anatase was 60% and the rutile was 40%. Using this titanium oxide thin film photocatalyst, acetic acid was decomposed in the same manner as in Example 3. As a result of irradiating the light of a 100 W high pressure mercury lamp for 1 hour and 30 minutes, the amount of acetic acid was 3
There was only a 0% reduction.

[0020]

INDUSTRIAL APPLICABILITY As described above, the present invention is excellent in the effect of decomposing and removing environmental pollutants such as organic compounds dissolved in water and malodorous substances in the air, and preventing the growth of fungi and mold and their sustainability. Moreover, it is an object of the present invention to provide a method for producing a titanium oxide thin film photocatalyst having excellent properties in terms of economy, safety, water resistance, heat resistance, light resistance, weather resistance, and stability. The titanium oxide used in the present invention is also used in paints, cosmetics, toothpaste, etc., and has many advantages such as excellent weather resistance and durability, nontoxicity, and safety.
The crystal form is anatase, which is produced by coating a substrate with titania sol prepared from titanium alkoxide and alcohol amines, and then gradually heating it from room temperature to a final temperature of 600 ° C. to 700 ° C. and firing it. The titanium oxide thin film photocatalyst is a redox effect of electrons and holes generated in the titanium oxide thin film upon receiving light from the outside such as an electric lamp or sunlight, and not only organic compounds dissolved in water but also air. It is possible to effectively and continuously prevent the decomposition and removal of environmental pollutants such as malodorous substances and the prevention of the growth of fungi and mold. Then, platinum or rhodium, ruthenium, palladium,
When coated with silver, copper, zinc, etc., its catalytic action further increases the effect of decomposing and removing and preventing the growth of bacteria and mold, and the effect is maintained without maintenance. The titanium oxide thin film photocatalyst according to the present invention can be applied not only to wastewater treatment but also to purification of pools and stored water, and is safer because it does not use toxic substances than conventional methods such as chlorine sterilization, and because it uses sunlight. Low cost, maintenance free and can be used semi-permanently. Furthermore, since it can be applied to various uses such as deodorization and antibacterial and antifungal in automobiles, living rooms, kitchens, toilets, etc., it has a great ripple effect.

Claims (2)

(57) [Claims] 1. A method for producing a titanium oxide thin film photocatalyst, which comprises coating a substrate with a titania sol and then gradually heating the temperature from a room temperature to a final temperature of 600 ° C. to 700 ° C. and firing the film. 2. The method for producing a titanium oxide thin film photocatalyst according to claim 1, wherein the titania sol is prepared from a titanium alkoxide and an alcohol amine.