Photocatalyst, its manufacture and applications

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a photocatalyst body in which photocatalyst particles are immobilized on a substrate of hollow glass particles, a method for producing the same, and an application thereof.

【0002】

[Conventional technology]

When photocatalyst particles are irradiated with light of a wavelength equal to or greater than the band gap, electrons are generated in the conduction band and holes are generated in the valence band by photoexcitation, and the strong reducing power of electrons and the strong oxidizing power of holes are used in various reactions. It is well known that it is available. At this time, since the photocatalyst particles themselves are fine particles and it is difficult to separate the solid air and the solid liquid after the reaction if they are used as they are as a photocatalyst, an attempt has been made to fix the photocatalyst particles on a substrate larger than the photocatalyst particles. There is.

【0003】

For example, the following methods have been proposed as a method for fixing the photocatalytic particles on the substrate.

【0004】

(1) Fine titanium oxide powder adheres to a film-like, bead-like, board-like, fibrous-like, etc. substrate made of a light-transmitting material such as nitrocellulose, glass, polyvinyl chloride, nylon, methacrylic resin, and polypropylene. Method of making (Japanese Patent Laid-Open No. 62-66861).

【0005】

(2) A method of impregnating a porous glass support with an alcohol solution of titanium (IV) tetrabutoxyoxide and heating it to form anatase-type titanium oxide to hold and fix it to the porous glass support. 2-50154).

【0006】

(3) The semiconductor catalyst powder is held and fixed in a porous polymer membrane (for example, polyfluoroethylene resin) having a photosensitizer such as a dye or a metal complex as a side chain by press-fitting, impregnating, adhering, or the like. Method (Japanese Patent Laid-Open No. 58-125602).

【0007】

(4) A method of fixing titanium oxide to a filtration filter made of polypropylene fiber or ceramics (Japanese Patent Laid-Open No. 2-68190).

【0008】

(5) A method of holding and fixing titanium oxide powder in the entanglement of quartz, glass, and plastic fibers, and holding both sides with light-transmitting glass (US Patent 4888101).

【0009】

(6) Platinum is fixed to an alumina substrate by a sputtering method, and a mixed dispersion of anatase-type titanium oxide powder and an organic solvent solution of methyl methacrylate is applied thereto by a spin coating method, and then a binder is applied. (Robert E. Hetric, Applied Physics Communications, 5, (3), 177-187 (1985)).

【0010】

(7) A method of spraying and fixing titanium oxide on the surface of polyester cloth by a low-temperature spraying method (Tsukasa Sakurada, Surface Technology Vol. 41, No. 10, P60 (1990)).

【0011】

However, each of the above-mentioned known methods for fixing the photocatalytic particles to the substrate has the following drawbacks.

【0012】

First, in fixing using organic substances such as (1), (3), (4), and (5) as binders, most of the organic substances are decomposed by the photocatalytic action of the photocatalytic particles. Not reliable. Further, the method (2) uses an expensive organic titanium compound as a raw material and is directly fixed to fragile glass, so that the reliability of the strength is low. On the other hand, the methods (6) and (7) are not preferable because the temperature becomes very high during fixing and the high photocatalytic activity of the photocatalytic particles is lost.

【0013】

Other commonly used methods include a method of simply impregnating and fixing a slurry-like titanium oxide in an inorganic porous body, and a binder obtained by hydrolyzing or heating and melting an alkali salt such as silica-based or alumina-based. There are methods to use, but in the former, titanium oxide particles are not fixed, so they easily fall off due to vibration or impact, and in the latter, the catalyst surface is covered with a binder for fixing the catalyst and is active. There was a problem that most of it was lost.

【0014】

Further, since these methods are difficult to process, there is a problem that the light energy cannot be sufficiently utilized while the cost is high.

【0015】

Furthermore, in recent years, the range of application of photocatalytic particles has increased dramatically in relation to the prevention of environmental pollution. In connection with this, there is a demand for a method of fixing the photocatalyst function inexpensively, firmly and for a long period of time without impairing its photocatalytic function, but the conventional method has not always been satisfactory. Further, the substrate of the photocatalyst is also required to be inexpensive, have excellent fixing property with the photocatalyst particles, and facilitate the separation operation from the object to be treated, but the conventional ones do not fully satisfy these requirements. There wasn't.

【0016】

On the other hand, in relation to the prevention of environmental pollution, photocatalytic particles are used to decompose and remove harmful gases such as aldehydes, mercaptans, and ammonia, and to purify sewage such as industrial wastewater, mining wastewater, lakes, and seawater. , There is a demand for a simple method for sterilizing a hydroponic culture solution.

【0017】

In particular, hydroponics is one of the vegetable and flower production methods aimed at saving resources, saving energy and increasing production in agriculture, and has rapidly become widespread in recent years.

【0018】

In hydroponics, after harvesting crops, the used culture solution is discarded, which causes groundwater pollution and eutrophication of rivers and lakes. Therefore, establishing the above-mentioned culture solution recycling technology is an effective method from the viewpoint of resource saving and prevention of environmental pollution. When considering the recycling of culture broth, it is most important to remove phytopathogens mixed during cultivation in addition to adjusting fertilizer components.

【0019】

Conventional hydroponic culture removal techniques include (1) drug administration, (2) ultraviolet irradiation, (3) ozone, (4) heating method, (5) ultrasonic method, etc., but (1) The use registration to mix the drug with the culture solution is not permitted, (2) is high running cost such as power supply and lamp replacement, and (3) is low running cost, but in the culture solution necessary for growing crops. Iron and manganese are insolubilized in (4), the total processing time (heating and cooling) is long, the running cost is high, and (5) has the disadvantages that the effect is not clear.

【0020】

[Problems to be Solved by the Invention]

The present invention has been made in view of the above problems, has excellent fixability to a substrate without deteriorating the activity of photocatalytic particles, is inexpensive, can be used for both gas and aqueous solutions, and these objects to be treated. It is an object of the present invention to provide a photocatalyst having excellent separation and workability from the above and a method for producing the same, and to provide a simple method for preventing environmental pollution using the photocatalyst.

【0021】

[Means for solving problems]

As a result of diligent research from the above viewpoint and first repeated research on the suitability of the substrate, the present inventors have found that hollow glass particles are a suitable material, and a hollow shirasu balloon, which will be described later, is a more preferable material. Further, a binding agent having a good compatibility for binding the hollow shirasu balloon and the photocatalyst particles was found, and the present invention was completed based on these findings.

【0022】

That is, the photocatalyst of the present invention is characterized in that the photocatalyst particles are fixed on the surface of the hollow glass particle substrate using an inorganic substance as a binder.

【0023】

Further, the hollow glass is SiO₂The average particle size of the glass particles can be 10 to 500 μm, and the bulk specific gravity can be 0.13 to 0.70.

【0024】

Further, the hollow glass particle substrate can be a hollow shirasu balloon and / or a granulated product thereof.

【0025】

Further, the average particle size of the hollow shirasu balloon granulated product can be set to 1 to 50 mm.

【0026】

Further, the photocatalytic particles can be at least one selected from the group consisting of titanium oxide, zinc oxide, iron oxide, potassium titanate, strontium titanate, molybdenum sulfide, and indium oxide.

【0027】

Further, the inorganic substance can be at least one selected from the group consisting of silica, alumina, clay, and frit.

【0028】

Further, the raw material of the frit can be a phosphorus-containing compound.

【0029】

On the other hand, in the method for producing a photocatalyst of the present invention, a hollow glass particle substrate is dipped in a paint in which photocatalyst particles are dispersed in silicic acid ester and water, and the paint is adhered to the surface thereof, and then 100 to 900. It is characterized by heat treatment at ° C.

【0030】

Further, in the method for producing a photocatalyst of the present invention, a hollow glass particle substrate is dipped in a paint in which photocatalyst particles are dispersed in a silicate ester, water and an organic solvent, and the paint is adhered to the surface thereof. It is characterized by heat treatment at ~ 900 ° C.

【0031】

Further, the method for producing a photocatalyst of the present invention is characterized in that a paste containing frit and photocatalyst particles is attached to a hollow glass particle substrate and then heat-treated at 450 to 1000 ° C.

【0032】

On the other hand, the method for decomposing and removing harmful gas of the present invention is characterized in that the harmful gas is passed through the container containing the photocatalyst and the container is irradiated with light containing ultraviolet rays.

【0033】

Further, the water purification method of the present invention is characterized in that water is passed through the photocatalyst whose specific gravity is adjusted so as to float and / or settle in water, and light containing ultraviolet rays is irradiated.

【0034】

Further, in the method for sterilizing a hydroponic culture solution of the present invention, the culture solution is passed through the photocatalyst whose specific gravity is adjusted so as to float and / or settle in water, and the culture solution is irradiated with light containing ultraviolet rays. It is characterized by.

【0035】

BEST MODE FOR CARRYING OUT THE INVENTION

As the hollow glass particle substrate used in the present invention, not only those artificially produced by using silicate glass powder or the like, but also those obtained by heat-treating a natural product such as shirasu balloon can be used.

【0036】

Here, the shirasu balloon is a fine vitreous material (Si0) obtained by heat-treating volcanic glass fine particles contained in shirasu at around 1000 ° C for a short time.₂It is a spherical hollow particle having an average particle size of 10 to 500 μm and a bulk specific gravity of 0.13 to 0.70 (60 to 80%). Shirasu balloon has extremely small volume specific gravity, is nonflammable, and has a high melting point, so it is inactive even at high temperatures, does not generate toxic gas, is lightweight, and has excellent properties such as heat insulation, sound insulation, and heat resistance. It is a material with.

【0037】

As a raw material for the shirasu balloon, among the volcanic glass contained in the shirasu, one containing a large amount of thick massive volcanic glass having a transparent and smooth surface is desirable in terms of the shape, specific gravity and strength of the balloon.

【0038】

A photocatalyst in which photocatalyst particles are attached to the porous volcanic ejecta itself, instead of a hollow silas balloon, does not completely cover the pores, so when this is used for wastewater treatment, the liquid permeates inside the photocatalyst. However, it is not preferable because it may not be sufficiently processed. On the other hand, the hollow shirasu balloon has a high surface smoothness, so such a concern is far less.

【0039】

Further, as will be described later, in order to facilitate the separation of the photocatalyst and the object to be treated of the gas and the aqueous solution, and for the convenience of using the shirasu balloon in the column, the shirasu balloon is granulated. Is more preferable as a substrate.

【0040】

As the photocatalyst particles, at least one of titanium oxide, zinc oxide, iron oxide, potassium titanate, strontium titanate, molybdenum sulfide, and indium oxide can be used, and among them, titanium oxide, zinc oxide, and strontium titanate are preferable. Titanium oxide is particularly preferable. Further, a titanium acid fiber made of potassium titanate or the like can also be used. Further, those obtained by adding an appropriate dopant to those photocatalytic particles can also be used.

【0041】

When the photocatalytic particles are titanium oxide, the anatase type is preferable, and the specific surface area is 20 m.²/ g ~ 500m²/ g is preferred, especially 100m²/ g ~ 400m²/ g is more preferred. The titanium oxide particle size is preferably 0.01 μm to 1 μm, more preferably 0.02 μm to 0.1 μm in terms of primary particle size, and may be a granulated product or a sintered body thereof. When the particle size is increased by making a granulated product or a sintered body, when the film thickness of the inorganic substance is relatively large depending on the application, the photocatalytic activity is effectively exhibited because the cue is cueed from the film.

【0042】

It is also preferable that the titanium oxide contains a metal oxide such as W, Sn, S, Mo, V, Mn and Zn that improves the catalytic activity.

【0043】

As with titanium oxide, the purity of other photocatalytic particles is not particularly specified, and if necessary, appropriate impurities can be added and used for the purpose of adjusting the band gap.

【0044】

Further, the photocatalyst of the present invention may contain an antibacterial substance such as Ag, Cu and Zn and a functional substance that adsorbs a harmful substance such as activated carbon and zeolite.

【0045】

The inorganic substances are preferably silica, alumina, clay, and frit, and among them, silica, frit, and clay are preferable, and silica is most preferable.

【0046】

In the photocatalyst of the present invention, when the substrate is a hollow shirasu balloon and the inorganic substance as a binder is silica, the silica film containing photocatalyst particles on the surface of the substrate shirasu balloon and the silica-based silas balloon. The fixation is particularly good. When the film thickness becomes thick, it is useless for the photocatalytic effect, and the film strength tends to decrease. Therefore, the film thickness is preferably 50 μm or less. On the other hand, when the film thickness is thinner than 0.1 μm, it does not play a role as a binder, so the film thickness is preferably 0.1 μm or more, and more preferably 1 μm or more. The proportion of the photocatalyst particles in the silica film containing the photocatalyst particles is preferably 10 to 90% by weight, more preferably 20 to 85% by weight, and most preferably 40 to 80% by weight.

【0047】

On the other hand, as the silicate ester used in the method for producing a photocatalyst of the present invention, any known silicate ester can be used, but methyl silicate, ethyl silicate and butyl silicate are preferable, and ethyl silicate is most preferable.

【0048】

In the production method according to the present invention, the viscosity, dispersibility, and drying rate of the paint can be improved by adding an organic solvent to the silica sol and alcohol obtained by hydrolyzing the silicic acid ester. Typical types of organic solvents include alcohols such as cellosolves and carbitols. Among the cellosolves, those having an alkyl group are preferable, and butyl cellosolve having a butyl group is particularly preferable. Among the carbitols, carbitol and carbitol acetate are preferable. As alcohols, ethanol and butanol are preferable.

【0049】

The water added to the paint is used for hydrolysis of silicate ester, but the pH of the paint is preferably acidic in order to increase the dispersibility of titanium oxide in the paint and the strength of the paint film, and pH 4 or less is more preferable. It is preferable, and pH 2 or less is particularly preferable. As a method for lowering the paint pH, it is preferable to attach sulfate roots to the surface of the titanium oxide particles or, when the acidity of titanium oxide itself is weak, add a small amount of acid to water to lower the paint pH. As the acid added to water, hydrochloric acid, sulfuric acid, nitric acid and the like can be used.

【0050】

In the above-mentioned production method, a silica film containing photocatalytic particles is formed on the surface of a hollow glass particle substrate to be a substrate. When ethyl silicate is used as the silicate ester with respect to 100 parts by weight of the photocatalyst particles, the blending ratio of the coating material for producing the silica film is 30 to 3200 parts by weight, preferably 60 to 1400 parts by weight. Parts, more preferably 80 to 520 parts by weight, and when methyl silicate and butyl silicate are used as the silicate ester, the preferred amount is the coefficient corresponding to the ratio of each molecular weight, 0.73 and 1.54 with ethyl silicate. It is the value multiplied by the numerical value of. The solvent is 0 to 1000 parts by weight, preferably 0 to 500 parts by weight, and the water is 10 to 1100 parts by weight, preferably 20 to 500 parts by weight, and more preferably 30 to 200 parts by weight.

【0051】

In the above blending ratio, if the number of photocatalytic particles is less than the blending ratio, the photocatalytic activity as a film is lowered, and if it is more than the blending ratio, the adhesion and strength of the silica film are deteriorated, which is not preferable.

【0052】

Generally, the heat treatment after fixing is preferably 100 to 900 ° C, but if it is less than 100 ° C, it takes a long time to gel the silica sol and it is difficult to obtain film strength, so 100 to 500 ° C is particularly preferable. ..

【0053】

When the binder of the photocatalyst of the present invention was silica, it was included in the silica film which became porous by dehydration from the silica sol produced by hydrolysis of silicic acid ester, evaporation of alcohol, and evaporation of organic solvent. Since the photocatalyst particles easily come into contact with atmospheric gas, bacteria adhering to the surface, etc., these can be efficiently decomposed and sterilized.

【0054】

Further, at least one kind of binder of clay and frit can be used from the viewpoint of excellent fixing property to the substrate and low cost without lowering the activity of the photocatalytic particles.

【0055】

That is, clay, frit and photocatalytic particles, or powder consisting of frit and photocatalyst particles are mixed, kneaded into a paste using water or an organic solvent, taken in a bat, and a hollow glass particle substrate (particularly hollow) is contained therein. An appropriate amount of silas balloon and / or its granules) is added and lateral vibration is applied to promote the fixation of the photocatalytic particles on the surface of the substrate, which is set at 450 to 1000 ° C, preferably 450 to 800 ° C, and further. Preferably, it can be heated at 450 to 600 ° C. The frit is preferably a compound containing phosphorus, and is typically Li because of the advantage that the melting point can be lowered.₂O-Na₂OB₂O₃-Al₂O₃-P₂O₅Those having the composition of are more preferable. Further, when the heating temperature is lower than 450 ° C, the temperature becomes lower than the melting point of the frit, so that the photocatalytic particles are not fixed on the substrate, and when the heating temperature is higher than 1000 ° C, the activity of the photocatalytic particles is lowered, which is not preferable. The clay is not particularly limited, but when clay is added, the paste can be easily prepared.

【0056】

The present invention also relates to a method for decomposing and removing harmful gas using the photocatalyst, and the harmful gas referred to here is aldehyde, mercaptan, ammonia, and NO._XEtc. are included.

【0057】

Since the photocatalyst body exhibits yellow, brown, and white depending on the type of photocatalyst particles, it can be used as it is in an appropriate place such as a park or a roadside tree without spoiling the aesthetic appearance. In addition, in order to facilitate the replacement of the photocatalyst and to prevent the photocatalyst from moving due to the wind, put the photocatalyst in a container or bag that transmits ultraviolet rays, and place it in an appropriate position for use. You can also do it. Further, in order to decompose and remove harmful gas efficiently, simply and inexpensively, it is preferable to put a photocatalyst in a column and use it. That is, a method of decomposing and removing harmful gas by putting a photocatalyst in a column made of a material that transmits ultraviolet rays, forcing or allowing harmful gas to pass through it, and irradiating a lamp containing sunlight or ultraviolet rays. is there. When the photocatalyst uses a shirasu balloon as a substrate, it is lightweight, so that the gas can easily flow even when used in a column, and the photocatalyst can be easily replaced. When a column is used, a photocatalyst based on a granulated shirasu balloon is more preferable. If the photocatalyst is based on a granulated shirasu balloon, the photocatalyst emission prevention filter from the column does not require a special filter, and a mesh with an opening of about 0.5 mm is sufficient.

【0058】

Further, the photocatalyst can be used by putting it in a frame or the like made of a material that transmits ultraviolet rays. These are characterized by being easy to carry, easy to install, and easy to replace the photocatalyst.

【0059】

Furthermore, since the photocatalyst of the present invention can have an apparent specific gravity larger or smaller than that of water depending on the amount of inorganic substances and photocatalytic particles, it can float and / or settle in water, purifying water and hydroponic cultivation. It can be widely used for sterilizing culture solutions. In addition, by using it in a column, preferably in a column made of a material that transmits ultraviolet rays, the flow of gas or aqueous solution is easy, or because it is lightweight, it is suspended near the liquid surface to allow the sun to flow. Light can be used effectively.

【0060】

When a lightweight hollow silas balloon is used as a substrate in the photocatalyst of the present invention, the apparent specific gravity of the photocatalyst can be arbitrarily adjusted by appropriately selecting and obtaining the amount of the photocatalyst particles containing the binder. can do. If the apparent specific gravity is greater than 1, the photocatalyst sinks to the bottom of the water, whereas if it is 1 or less, it is necessary to put a net at the outlet of the water to prevent the photocatalyst from flowing out. The body floats or floats to improve contact with the liquid, leading to an improvement in the photocatalytic function. The properties of the hollow shirasu balloon handled in the present invention are suitable for this purpose.

【0061】

Further, the water referred to here includes factory wastewater, mining wastewater, industrial water, agricultural water, drinking water, lakes and marshes, river water, seawater and the like. When purifying water using the photocatalyst of the present invention in the lake shore, river shore, coast, running channel, water tank, filter, sewer, or aquatic organism breeding area where these exist, contact with these waters. The photocatalyst is installed at a possible location, or the photocatalyst is placed in water. Next, the arranged photocatalyst is irradiated with light containing ultraviolet rays to purify the water. Examples of the light containing ultraviolet rays include light from sunlight, fluorescent lamps, black lamps, xenon flash lamps, mercury lamps, and the like.

【0062】

In particular, light containing ultraviolet rays of 300 to 400 nm is preferable. The irradiation amount and irradiation time of light containing ultraviolet rays can be appropriately set depending on the degree of pollution of sewage. The method of irradiating the photocatalyst with light containing ultraviolet rays can be appropriately selected. For example, when irradiating from the upper part of the water surface, installing a light source in the sewage to irradiate, or purifying the sewage in the aquarium. , It is also possible to irradiate from the side surface of the water tank. Further, when the photocatalyst of the present invention is placed in a place where it can come into contact with sewage and then the photocatalyst is irradiated with light containing ultraviolet rays, the sewage is purified by the photocatalytic function of the photocatalyst at the irradiated place. In addition, at a location in the same reaction system that is not irradiated with light containing ultraviolet rays, purification by the microorganism can be performed by adhering a microorganism having a water purification function to the photocatalyst in advance.

【0063】

Speaking of the target treated products in the sewage purification method, it is possible to decompose and remove organic substances such as free chlorine and trihalomethane remaining in the water, and mining wastewater whose regulations have been strengthened by the revision of the Water Pollution Control Law. It can also be used to remove selenium contained in it.

【0064】

In the latter case, a photocatalyst is put into the mining wastewater to utilize sunlight, or a photocatalyst of the present invention is put into a column, the mining wastewater is passed through the photocatalyst, and an ultraviolet irradiation lamp is applied to the photocatalyst. , 6-valent selenium is reduced to 4-valent or 0-valent and recovered.

【0065】

Further, as an application of the method for purifying sewage using the photocatalyst of the present invention, the harmful gas can be decomposed by immersing the pipe in the water into which the photocatalyst is put and allowing the harmful gas to pass through and bubbling.

【0066】

Furthermore, in terms of equipment, in order to improve the irradiation efficiency of light containing ultraviolet rays to the photocatalyst, a light reflector is provided, the inner wall surface of the container is mirror-finished, and a mirror or the like is installed on the inner wall surface of the container. You can also do it.

【0067】

Further, in the method for sterilizing a hydroponic culture solution of the present invention, an ultraviolet lamp is desirable as a light source for promoting photocatalytic activity, but conventional strength is not required, and running costs can be reduced. Further, if the photocatalyst of the present invention is provided in a container separate from the culture solution container together with the ultraviolet irradiation device, combined with the culture solution container and circulated by a pump, the bactericidal effect is more efficient and the maintenance of the culture solution container is maintained. Also improves. The apparatus of FIG. 1 is shown as a specific example of a method for sterilizing a hydroponic culture solution using the photocatalyst of the present invention.

【0068】

In the apparatus of FIG. 1, a hydroponic cultivation tank 7 having a culture solution tank 1, a circulation pump 2, a sterilization tank 3, and a plant 8 is provided from the upstream side to the downstream side, respectively. The sterilization tank 3 is filled with a culture solution to be sterilized, and the photocatalyst 5 is suspended / settled in the culture solution. Further, in the sterilization tank 3, ultraviolet germicidal lamps 4 are provided horizontally at substantially equal intervals in the vertical direction, and filters 6 are provided at the inlet and outlet of the tank 3.

【0069】

In the apparatus of FIG. 1, the culture solution is sent from the culture solution tank 1 to the sterilization tank 3 by the circulation pump 2, and the culture solution is produced by the photocatalytic effect of the photocatalyst body 5 irradiated with ultraviolet rays by the ultraviolet germicidal lamp 4 in the sterilization tank 3. Is sterilized. The sterilized culture solution is sent to the hydroponic cultivation tank 7 having the plant 8 through the filter 6. The solution containing the phytopathogens produced by hydroponics is circulated and sent to the culture solution tank 1, and the process is repeated.

【0070】

With this device, the running cost is low, sterilization can be performed efficiently, and the maintenance of the culture solution container is improved.

【0071】

The contents of the present invention will be described in more detail with reference to Examples below, but these Examples are merely examples, and the scope of the present invention is not limited thereto.

【0072】

[Example]

Example 1 Titanium oxide (anatase type specific surface area 330m²/ g) 6 g, 9 g of ethyl silicate, 3 g of water with 0.5 mol of hydrochloric acid, 0.12 g of boric acid and 6 g of butyl cellosolve in a 120 ml mayonnaise bottle with 90 g of 3 mm glass beads for 10 minutes with a paint conditioner manufactured by Red Devil. It was dispersed and mixed to obtain a coating material containing silica sol.

【0073】

Using a granulated shirasu balloon having an average particle size of 5 mm as a substrate, the paint was dipped in the paint, and the paint and the granulated shirasu balloon to which the photocatalytic particles were fixed were separated by a sieve.

【0074】

After air-drying for a whole day and night, it was baked at 150 ° C. to immobilize a silica film containing photocatalytic particles on a substrate, and then washed with warm water at 90 ° C. to remove boric acid. This was dried at 110 ° C. and then heat-treated at 400 ° C. for 1 hour to obtain a photocatalyst.

【0075】

Example 2 In Example 1, the same procedure was carried out except that the amount of titanium oxide in the paint was 2.6 g.

【0076】

Example 3 In Example 1, the same procedure was carried out except that the photocatalytic particles were zinc oxide.

【0077】

Example 4 In Example 1, the same procedure was carried out except that the photocatalytic particles were strontium titanate.

【0078】

Example 5 The procedure was carried out in the same manner except that a shirasu balloon having an average particle size of 180 μm was used as the substrate in Example 1.

【0079】

Example 6 After mixing 6 g of titanium oxide powder of Example 1 and 4 g of phosphate ester-based frit with a coffee mill, this mixed powder was spread on a bat. A granulated silas balloon having an average particle size of about 2 mm, which was a substrate, was placed in a vat, and water was sprayed by spraying to advance the fixation of the titanium oxide powder to the substrate while rolling. The titanium oxide-fixed granulated shirasu balloon was dried at 110 ° C. for 1 hour and then heat-treated at 550 ° C. for 2 hours to obtain a photocatalyst.

【0080】

Comparative example 1 The procedure was the same as in Example 1 except that the granulated shirasu balloon of Example 1 was replaced with soil for the horticultural pumice stone.

【0081】

Comparative example 2 Granulated shirasu balloon only [0082]

Comparative example 3 A coating material in which titanium oxide of Example 1 was dispersed in acrylic, acrylic-melamine and urethane resin was applied to a substrate.

【0083】

Test example 1. Peeling test After confirming the immobilization of the photocatalyst particles on the surface of the substrate by the scanning electron microscope observation, the photocatalyst was placed in water and ultrasonically applied for 10 minutes to separate the photocatalyst from water, and then water. The transmittance was measured. A transmittance of 95% or more is marked with , and a transmittance of less than 95% is marked with x.

【0084】

2. Acetaldehyde decomposition test Put 0.37 g of photocatalyst in a 100 ml Bayer bottle, inject acetaldehyde in an amount that makes the gas concentration in the bottle 2000 ppm, and inject ultraviolet rays with a wavelength of 350 nm from the outside of the bottle at 6.3 mW / cm.²After irradiation for 1 hour, the air in the bottle was measured with a gas chromatograph G3800 (detector FID) manufactured by Yanagimoto Seisakusho.

【0085】

3. Algae development test A photocatalyst and 20 ml of water were placed in a glass examiner and left outdoors for a week to observe the presence or absence of algae growth.

【0086】

4. Photocatalyst weather resistance test After irradiating the photocatalyst with ultraviolet rays for 500 hours using a Dew panel optical control weather meter manufactured by Suga Test Instruments Co., Ltd., the change in color tone on the surface of the photocatalyst was examined, and according to the peeling test conditions described in 1. A peeling test was performed and the transmittance was measured. The case where no discoloration is visually observed and the transmittance in the peeling test is 95% or more is evaluated as , and the case where discoloration is observed or the transmittance in the peeling test is less than 95% is evaluated as x.

【0087】

5. Se in water⁶⁺Reduction test Na₂SeO₄Was dissolved in distilled water to prepare a 100 mg Se / l selenic acid solution. 50 ml of the prepared selenic acid solution was dispensed into a 100 ml Erlenmeyer flask, and 2.5 mM hydrazine sulfate was added. After inserting the rotor, add about 0.30 g of the photocatalyst sample, and while stirring with a magnetic stirrer, emit ultraviolet rays of 350 nm from the top at 10.0 mW / cm.²After irradiating for 10 hours, the metal selenium reduced to 0 valence is filtered through a millipore filter, and Se in the solution.⁶⁺Concentration was measured with ICAP-575 manufactured by Nippon Jarrel Ash Co., Ltd. The test results of 1 to 5 are shown in Table 1.

【0088】

[table 1]

<img file="JPH10249210A_D0001.tif" />【0089】

According to the results in Table 1, the samples of the examples had higher transmittance, no algae growth, better weather resistance, acetaldehyde, and Se than those of the comparative examples.⁶⁺The concentration was also found to be low.

【0090】

[Effect of the invention]

In the photocatalyst of the present invention, since the photocatalyst particles are fixed on the surface of the hollow glass particle substrate by using an inorganic substance as a binder, the matching between the glass and the inorganic substance is good, so that the photocatalyst particles are firmly formed. The photocatalytic particles can be fixed for a long period of time at low cost without losing the high photocatalytic activity of the photocatalytic particles.

【0091】

When a hollow silas balloon is used as the hollow glass particle substrate and the inorganic substance as a binder is silica, a silica film containing photocatalytic particles on the surface of the silas balloon which is the substrate and silica containing silica as a main component are used. The fixability with the balloon is particularly good, and the photocatalytic particles can be fixed even better. Further, the effective surface area of the photocatalyst can be increased by fixing the photocatalyst particles on the surface of the hollow shirasu balloon using an inorganic substance as a binder.

【0092】

Furthermore, by using a granulated shirasu balloon obtained by granulating a shirasu balloon as a substrate, it is possible to facilitate the separation of the photocatalyst and the object to be treated with gas and aqueous solution, and it is easy to operate when used in a column. It will be excellent in sex.

【0093】

On the other hand, according to the method for producing a photocatalyst of the present invention, a photocatalyst contained in a silica film made porous by dehydration from a silica sol produced by hydrolysis of a silicic acid ester, evaporation of alcohol, and evaporation of an organic solvent. Since the particles easily come into contact with atmospheric gas, bacteria adhering to the surface, etc., these can be efficiently decomposed and sterilized.

【0094】

Further, in the method for producing a photocatalyst of the present invention, by using a frit, it is possible to peel off from the surface of the photocatalyst during use and make solid-gas or solid-liquid separation difficult without deteriorating the photocatalytic ability. Absent.

【0095】

Further, the photocatalyst of the present invention exhibits an excellent effect of removing malodorous gases such as aldehydes and mercaptans and bactericidal property by the photocatalytic effect of irradiation with ultraviolet rays, and at the same time, the photocatalyst has processability, weather resistance and the object to be treated. It is suitable for decomposing and removing harmful gases because it has excellent separation operability.

【0096】

Further, in the photocatalyst of the present invention, since the apparent specific gravity of the photocatalyst can be arbitrarily adjusted, the photocatalyst may be submerged in the bottom of the water by making the apparent specific gravity larger than 1, or the photocatalyst may be set to 1 or less in the treated water. The body can be floated or floated to further improve the contact with the liquid, and the photocatalytic function can be improved.

【0097】

Furthermore, when titanium oxide or zinc oxide is used as the photocatalytic particles, it has a bactericidal effect on various fungi, so by adjusting the apparent specific gravity, it can be present at an arbitrary position in the culture solution tank. It can efficiently sterilize phytopathogens.

[Simple explanation of drawings]

[Figure 1]

It is an apparatus which shows an example of the sterilization method of the hydroponic culture solution of this invention.

[Explanation of symbols]

1 Culture solution tank 4 UV germicidal lamp 5 Photocatalyst