JP4621859B2 - Method for producing porous photocatalyst - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a porous photocatalyst used as an environmental purification material for decomposing and removing, for example, malodorous components and NOx environmental pollutants contained in the atmosphere, and performing wastewater treatment and purification treatment. In particular, the present invention relates to a method for producing a porous photocatalyst having structural features in which the surface of a porous carrier is coated with a titanium oxide film having titanium oxide particles in which calcium phosphate is supported in an island shape. It is.
[0002]
[Prior art]
In recent years, foul odors in living spaces and work spaces, air pollution due to harmful substances such as automobile exhaust gas, water pollution due to domestic wastewater and industrial wastewater, such as organic chlorine solvents that cannot be purified by the activated sludge method, especially Various environmental pollution problems such as water source pollution due to sprayed agricultural chemicals on golf courses are becoming apparent.
[0003]
Conventionally, as a method for preventing malodors or removing harmful substances in the atmosphere, absorption methods such as acids and alkalis, adsorbents, and soil absorption methods are often used. There is a risk of secondary pollution due to the problem of adsorbent and soil treatment.
[0004]
In addition, there is a method of concealing bad odors using a fragrance, and there is a problem of contamination due to the odor of the fragrance itself, and according to the activated sludge method, the processing capacity is low and the emission of sludge odor is inevitable. According to the Osson decomposition method, the Oson itself is toxic and costly (for example, Konosuke Nishida, Heibonsha "Daiten Encyclopedia", Volume 1, page 136 (published in 1984) ).
[0005]
By the way, when a semiconductor is irradiated with light, electrons having a strong reducing action and holes having a strong oxidizing action are generated on the surface, and molecular species in contact with the semiconductor are decomposed by the redox action. By utilizing such action of semiconductors, that is, photocatalytic action, it is possible to decompose and remove environmental pollutants such as organic solvents, pesticides and surfactants dissolved in water, and harmful substances in the atmosphere. . This method only uses semiconductors and light, and there are fewer restrictions on reaction conditions such as temperature, pH, gas atmosphere, and toxicity compared to biological treatment methods that use microorganisms. It has the advantage that even difficult organic halogen compounds and organophosphorus compounds can be easily decomposed and removed.
[0006]
[Problems to be solved by the invention]
However, studies on the decomposition and removal of organic substances using photocatalysts that have been conducted so far have used semiconductor powder as a photocatalyst (for example, ALPruden and DF Ollis, Journal of Catalysis, Vol. 82, 404 (1983), H. Hidaka). , H. Jou, K. Nohara, J. Zhao, Chemoshere, Vol. 25, 1589 (1992), Teruaki Hisanaga, Kenji Harada, Keiichi Tanaka, Industrial Water, No. 379, 12 (1990)), handling as a photocatalyst It is difficult to use, especially in the case of wastewater treatment and water purification, it is necessary to collect the photocatalyst powder by filtering the treated water, for example, because the photocatalyst is a fine powder, causing clogging. There is a tendency that it cannot be easily filtered. That is, there is a problem that continuous water treatment cannot be performed because it is difficult to separate and recover the photocatalyst.
[0007]
In order to remedy this drawback, immobilization of photocatalysts has been performed, and photocatalyst coating has been performed on the surface of a carrier such as a glass plate, but the photocatalytic reaction is a surface reaction, and the immobilized photocatalyst is Since the specific surface area was smaller than that of powder, there was a disadvantage that the performance was very poor.
[0008]
On the other hand, in order to improve the photocatalytic function of the photocatalyst, a porous titanium oxide fine powder and a water-soluble glucan are dispersed in water and dissolved, or a porous titanium oxide fine powder and a water-soluble glucan An air cleaning material (Japanese Patent Laid-Open No. 11-347407) obtained by immersing a carrier in a processing solution in which a fine powder of apatite is dispersed and dissolved in water, then drying and heat setting, or on the surface of spherical resin particles Spherical apatite composite particles (Japanese Patent Laid-Open No. 7-31964) coated with apatite composite particles composed of calcium phosphate and titanium oxide are known, and Japanese Patent Laid-Open No. 11-256472 discloses fibers and synthetic resin-made continuous particles. A technology in which a thin film made of calcium phosphate is provided on the surface of foam-type foam porous films, porous hollow fiber membranes, etc., and titanium oxide is supported on the surface of this thin film It has been disclosed.
[0009]
However, in order to increase the specific surface area of titanium oxide, although a porous titanium oxide fine powder is known, a porous photocatalyst formed by forming a titanium oxide film containing calcium phosphate on the surface of a porous carrier, particularly Is a porous photocatalyst in which a titanium oxide thin film is formed on the surface of a porous carrier and rose flower-shaped calcium phosphate is supported on the surface of the thin film, or rose flower-shaped calcium phosphate is island-shaped on the surface. There are no known porous photocatalysts comprising titanium oxide particles carried on the surface of a porous carrier, and titanium oxide particles carrying rose flower-shaped calcium phosphate in an island shape.
[0010]
The present invention has been intensively studied in view of the problems as described above, and its object is to continuously treat environmental pollutants such as malodorous components and NOx, wastewater treatment and water purification treatment in the atmosphere. To provide a method for producing a porous photocatalyst having excellent properties such as economy and safety, as well as excellent environmental degradation and antibacterial activity as an environmental purification material. There is a place to do.
[0011]
[Means for Solving the Problems]
Therefore, the gist of means adopted by the invention described in claim 1 of the present application is as described in the appended claims.
[0012]
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[0013]
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[0014]
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[0015]
According to the method for producing a porous photocatalyst according to claim 1, it is possible to produce a porous photocatalyst having a surface of an activated carbon honeycomb which is a porous carrier covered with a titanium oxide film containing calcium phosphate.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the method for producing a porous photocatalyst according to the present invention will be described. However, this is a representative one, and the present invention is limited by the following examples as long as the gist thereof is not exceeded. It is not something.
[0017]
In the present invention, a porous photocatalytic body, the surface of the activated carbon honeycomb as a porous carrier, Ru der that those coated with titanium oxide film containing titanium oxide particles and calcium phosphate. The shape of the porous support, granular, plate-like, cylindrical, prismatic, conical, spherical, or may be any shape such as a rugby ball shape.
[0018]
The photocatalyst is the excitation (photoexcitation) of electrons in the valence band when irradiated with light (excitation light) of energy (ie, short wavelength) larger than the energy gap between the conduction band and valence band of the crystal. It is a substance that can generate electric conductors and holes, such as titanium oxide, tin oxide, zinc oxide, vanadium oxide, dibismuth trioxide, tungsten trioxide, ferric oxide, strontium titanate, Examples thereof include cadmium sulfide, and one or more of these can be used. In view of exhibiting excellent photocatalytic action, it is preferable to use titanium oxide. In addition, as crystalline titanium oxide, there are anatase type, rutile type and brookite type, any of which can be used, but from the viewpoint of exhibiting the most excellent photocatalytic action, anatase type It is very preferable to use titanium oxide.
[0019]
When the photocatalyst is irradiated with ultraviolet rays and photoexcited, as described above, electron-hole pairs are generated on the surface of the photocatalyst. Among them, electrons reduce surface oxygen to generate superoxide ions (O ₂ ⁻ ), and holes oxidize surface hydroxyl groups to generate hydroxyl radicals (.OH), which are rich in reactivity. Both active species can treat odors and environmental pollutants very efficiently and reliably.
[0020]
By the way, in this specification, the term “titanium oxide” is a group consisting of titanium oxide, tin oxide, zinc oxide, vanadium oxide, dibismuth trioxide, tungsten trioxide, ferric oxide, strontium titanate, cadmium sulfide. Any one or a mixture of two or more selected more can be read.
[0021]
When the photocatalyst used in the embodiment of the present invention is titanium oxide, the photocatalyst is a mixture of titanium oxide particles and apatite, or titanium oxide particles supported on islands with, for example, rose flower-shaped apatite on the surface. A porous carrier surface coated with water or a binder, hydrolyzed titanium compound such as titanium alkoxide obtained by reaction of alcohol with titanium tetrachloride or metal titanium, etc., or amorphous titania When immersed in a simulated body fluid imitating human body fluid for about 10 to 30 days, more preferably in a simulated body fluid at 25 to 60 ° C. for about 20 minutes to 1 hour, calcium hydroxide and Calcium phosphate produced by reaction with phosphate ions is deposited and fixed to the surface of the porous carrier in the form of islands, forming a rose flower shape. It can be. If the time of immersion in the simulated body fluid is too long, calcium phosphate tends to adhere to the entire surface of the titanium oxide particles and hinder the surface reaction of the photocatalyst.
[0022]
By the way, in this specification, the “pseudo body fluid” refers to an isotonic aqueous solution containing at least Na and P ions. It preferably contains ions such as “Na”, “K”, “Cl”, “Ca”, “P”, “Mg”, and has a pH of 7-8, but has a pH of 7.3-7.7. Is particularly preferred.
[0023]
In addition, “calcium phosphate” indicates any one of hydroxyapatite, carbonate apatite, fluoride apatite, tricalcium phosphate, or octacalcium phosphate, or a mixture of two or more thereof.
[0024]
In addition, after forming a titanium oxide thin film in advance on the surface of the porous carrier, the surface of the thin film is immersed in an isotonic pseudo body fluid containing both calcium hydroxide and phosphate ions. It is also possible to carry calcium phosphate produced by the reaction between the calcium hydroxide and phosphate ions.
[0025]
In addition, on the surface of the titanium oxide film covering the surface of the porous carrier, a metal film such as platinum, rhodium, ruthenium, palladium, iron, silver, copper, zinc, etc. It can be coated by a PVD method such as a vacuum deposition method, thereby facilitating redox decomposition by photocatalysis by facilitating charge separation of electrons and holes, and oxidative decomposition and reductive decomposition by the metal catalyst. It can be introduced as an auxiliary means.
[0026]
As an artificial light source for exciting the photocatalyst, a sterilizing lamp, black light, fluorescent lamp, incandescent lamp, mercury lamp, UV light, xenon lamp, halogen lamp, metal halide lamp, or the like can be used. When a germicidal lamp that emits ultraviolet light having a maximum wavelength near 254 nm and a black light that emits ultraviolet light having a maximum wavelength near 380 nm are used in combination as a light source, the photocatalytic surface is irradiated with ultraviolet light emitted from the germicidal lamp. Since the ultraviolet rays emitted from the black light can pass through the photocatalyst and penetrate to the back surface of the photocatalyst particles, they can act synergistically. That is, sufficient excitation light can be irradiated to the photocatalyst, and the photocatalyst can be excited efficiently.
[0027]
The island-like calcium phosphate that constitutes the titanium oxide film covering the entire surface of the porous carrier is porous, and has affinity (biocompatibility) with proteins and carbohydrates that are biological components such as fungi and fungi. Because of its large size, it can efficiently adsorb microorganisms such as fungi and molds, and these can be rapidly and continuously redox-degraded by the active species rich in reactivity described above, and finally decomposes into carbon dioxide gas. It can be processed. That is, it is possible to completely prevent the generation of malodorous substances produced by life activities such as fungi and molds and released outside the cells.
[0028]
【Example】
Hereinafter, representative examples that further embody the present invention will be described, but the present invention is not limited to the following examples.
[0029]
Example 1: To a hydrolyzate of titanium tetraisopropoxide, an equivalent amount of titanium oxide particles (apatite amount with respect to titanium oxide, 5% by weight) having calcium phosphate supported on the surface in an island shape was added, and 20 g of that was 100 cm square and thick. It was applied to the surface of a 2 cm thick activated carbon honeycomb. This was heated and dried at 120 ° C. to produce a porous photocatalyst.
[0030]
Subsequently, NOx was decomposed and removed using the obtained porous photocatalyst. First, the obtained porous photocatalyst was placed in a sealed container with an internal volume of 50 liters set with a commercially available 100 W incandescent lamp inside, and after introducing 10 ppm of NOx with a syringe, the incandescent lamp was turned on. . After 1 hour, the NOx concentration contained in the air in the sealed container was measured by gas chromatography, and the reduced amount of NOx was injected. This operation was repeated every hour.
[0031]
As a result, it was found that when a porous photocatalyst was used, the concentration of residual NOx after 1 hour treatment was zero ppm each time, and NOx was completely removed by treatment for 1 hour.
[0032]
On the other hand, when the activated carbon honeycomb body was used instead of the porous photocatalyst body, the residual NOx concentration was zero ppm at the first time, but as the number of times increased, the residual concentration increased. The residual NOx concentration at the 10th time was 10 ppm, that is, the same concentration as that at the start, and it was found that no purification treatment was performed.
[0033]
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[0034]
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[0035]
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[0036]
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[0037]
【The invention's effect】
As described above, according to the present invention, it is excellent in the ability to decompose and remove various malodorous substances in the air and various environmental pollutants dissolved in water, and is excellent in the effect of preventing the growth of fungi and fungi, and is economical. The present invention provides a method for producing a porous photocatalyst having excellent safety and other characteristics. In particular, titanium oxide used in the present invention is also used in paints, cosmetics, toothpastes and the like, and has many advantages such as excellent weather resistance and durability, and harmless safety. Calcium phosphate is a biological component that forms animal bones and teeth, and is safe and harmless.
[0038]
When the porous photocatalyst produced by the method of the present invention is photoexcited by irradiating ultraviolet rays from the outside such as an electric lamp or sunlight, as described above, electron-hole pairs are generated on the surface of the photocatalyst. Of these, electrons reduce surface oxygen to generate superoxide ions (O ₂ ⁻ ), and holes oxidize surface hydroxyl groups to generate hydroxyl radicals (.OH). And, due to the oxidation-reduction reaction by these reactive species rich in reactivity, environmental pollutants in the atmosphere such as bad odor and NOx, SOx, or organic environmental pollutants such as organic solvents and agricultural chemicals dissolved in water. It can be quickly and efficiently decomposed and removed. In addition, compared to conventional methods such as ozone treatment, it does not use toxic substances such as Osong, and can be operated simply by irradiating light from the light or sunlight. Excellent, maintenance free and can be used for a long time. Furthermore, the porous photocatalyst produced by the method of the present invention not only deodorizes automobiles, living rooms, kitchens and toilets, treats wastewater, purifies pools and stored water, but also propagates microorganisms such as straw and mold. If it cannot be efficiently prevented, its application is versatile, and an effect that is extremely effective can be obtained.

Claims (1)

A method for producing a porous photocatalyst body in which the surface of an activated carbon honeycomb is coated with a titanium oxide film containing calcium phosphate,
No roses shape, coating containing titanium oxide particles apatite amount is 5% by weight of calcium phosphate is carried in an island shape on the surface for the titanium oxide, a hydrolyzate of titanium tetraisopropoxide to the surface of the activated carbon honeycomb And a method for producing a porous photocatalyst.