JPH09299809A - Harmful substance removing agent, its preparation, and harmful substance removing method using the agent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve handling, to have high photocatalytic activity, to keep the activity over a long period of time, and to be used in a humid atmosphere. SOLUTION: A harmful substance removing agent is composed of at least photosemiconductor in which metal oxide which has constituted metal oxide sol is used as a binder and metal oxide. A mixture of the photosemiconductor and the metal oxide sol is pelletized or molded and dried to prepare the agent. The agent is brought into contact with fluids containing harmful substances, or the agent is is contacted with the fluid while being irradiated with light to remove the harmful substances.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a harmful substance removing agent for removing harmful substances, a method for producing the same, and a method for removing harmful substances using the same.

[0002]

2. Description of the Related Art With the increasing awareness of global environment and living environment problems in recent years, there has been developed a technology for removing harmful substances such as organic halides and hydrocarbons emitted from various factories and automobiles, and malodorous components in living spaces. Interest is growing. In addition, ethylene, which is emitted from fruits and vegetables, has the effect of accelerating the decay of these fruits and vegetables. As a method for removing such harmful substances, a method using an adsorbent such as activated carbon or zeolite is generally used. However, since this method simply adsorbs the harmful substance, when a large amount of the harmful substance is present, the saturation of adsorption is reached and the harmful substance is not adsorbed any more. Further, there is a problem that the adsorbed harmful substance is desorbed as the state changes. Therefore, a method has been proposed in which a harmful substance is oxidized and decomposed by the catalytic action of an optical semiconductor such as titanium oxide to render it harmless.

[0003]

The above-mentioned optical semiconductors such as titanium oxide can make harmful substances harmless by photocatalytic activity. However, since it is a powder, there is a problem that it becomes very difficult to separate and collect it from the fluid to be processed. In order to solve this problem, there has been proposed a granulated body comprising titanium oxide, which is an optical semiconductor, and high-purity bentonite, which has improved handleability while maintaining photocatalytic activity (Japanese Patent Application No. 7-129383). . However, since this granule uses bentonite, its shape tends to collapse due to moisture, and it tends to collapse. Therefore, it is difficult to use in an atmosphere where a large amount of water is present, and there is a problem that the application range is restricted. Further, a fixed optical semiconductor obtained by fixing an optical semiconductor on a substrate such as glass or ceramics is under study.
This product is easy to separate and collect, but there is a problem that the photo-semiconductor immobilized is separated from the carrier due to contact with the fluid to be treated and the photocatalytic activity cannot be maintained for a long time. Moreover, there is a problem in that high-temperature baking is required for the immobilization treatment, which lowers the photocatalytic activity of the photosemiconductor.

[0004]

Means for Solving the Problems The present inventors have developed a harmful substance removing agent which is easy to handle, has a high photocatalytic activity, and can maintain the photocatalytic activity for a long period of time, and which can be used even under wet conditions. As a result of various searches to obtain the above, it was found that the desired toxic substance removing agent can be obtained by using the metal oxide that constitutes the metal oxide sol as the binder, The present invention has been completed by finding that the harmful substance removing agent can be applied to various harmful substance removing treatments. That is, the present invention is to provide a harmful substance removing agent which has excellent ability to remove harmful substances such as malodorous components and is easy to handle. Another object of the present invention is to provide a method for easily and inexpensively producing the harmful substance removing agent. Furthermore, the present invention is to provide a method for removing harmful substances using the harmful substance removing agent.

The present invention is characterized in that it is a granulated body containing at least an optical semiconductor and the metal oxide or a molded body thereof using the metal oxide constituting the metal oxide sol as a binder. It is a harmful substance remover. The form of the harmful substance removing agent of the present invention can be appropriately designed according to the use scene, and examples thereof include a spherical shape, a cylindrical shape, a ring shape, a plate shape, and a honeycomb shape. Further, it may have an irregular shape obtained by crushing a granulated body or a molded body. In the present invention, a structure having a honeycomb shape is preferable because the contact area with a harmful substance can be increased and the pressure loss can be reduced. The honeycomb-shaped structure is a structure having a large number of through holes having a cross section of a triangle, a quadrangle, a hexagon, a circle, an ellipse, or the like.
The size of the granulated body or the molded body can be appropriately designed depending on the use scene.

The photo-semiconductor exhibits a so-called photocatalytic action, and can oxidize and decompose harmful substances and render them harmless by the strong oxidizing power that appears when light is irradiated. For example, known optical semiconductors such as titanium oxide, zinc oxide, tungsten oxide, iron oxide, strontium titanate, molybdenum sulfide, and cadmium sulfide can be used alone or in combination of two or more kinds. In particular, titanium oxide, which has a high photocatalytic action, is chemically stable, and is harmless, is preferable. Titanium oxide includes not only so-called titanium oxide but also hydrous titanium oxide, hydrated titanium oxide, titanium hydroxide, metatitanic acid and orthotitanic acid. Among them, titanium oxide having an anatase type crystal form has excellent photocatalytic activity, and more preferably, it has a small particle size of 1 to 50 nm. More preferable titanium oxide particle size is 1
３０30 nm. Further, the above optical semiconductor may contain another metal such as iron, cobalt, nickel, copper, zinc, ruthenium, rhodium, palladium, silver, gold or platinum, or a compound of the other metal, in particular, oxidation. Titanium oxide carrying zinc and / or zinc hydroxide has both the adsorption ability of harmful substances and the decomposition ability by photocatalysis, and is more preferable.

The optical semiconductor used in the present invention can be obtained by various methods. For example, for titanium oxide, (1) a method of thermally hydrolyzing a titanium compound such as titanyl sulfate, titanium sulfate, titanium chloride or an organic titanium compound. And (2) a method of adding an alkali to a titanium compound such as titanyl sulfate, titanium sulfate, titanium chloride, or an organic titanium compound to neutralize it,
(3) A method of vapor-phase oxidizing titanium chloride, an organic titanium compound, or the like, (4) A method of firing the titanium oxide obtained by the methods (1) and (2) above at a temperature of about 800 ° C. or less, and the like. Can be obtained.

In the harmful substance removing agent of the present invention, the metal oxide acting as a binder is a metal oxide sol dispersed in a dispersion medium such as water or alcohol.
In the present invention, the metal oxide sol, in addition to the so-called sol containing a metal oxide, a sol containing a hydrous metal oxide, a sol containing a hydrated metal oxide, or a sol containing a metal hydroxide. Also includes. Examples of the metal oxide that constitutes such a metal oxide sol include silicon,
Oxides of metals such as aluminum, titanium, iron, zinc, cobalt and nickel (including hydrous oxides, hydrated oxides or hydroxides) can be used, and particularly selected from silicon, aluminum and titanium. At least one oxide of the element (including hydrous oxide, hydrated oxide or hydroxide) is preferred. The content of the metal oxide is preferably 5 to 30% by weight, and more preferably 10 to 20% by weight, based on the harmful substance removing agent. When the content of the metal oxide is less than the above range, it is not preferable because the binding force is insufficient and the strength of the harmful substance removing agent becomes weak, and when it is more than the above range, adsorption of the optical semiconductor Performance and photocatalytic activity are less likely to be exhibited, which is not preferable. The particle size of the metal oxide is 1 to 1 from the viewpoint of binding property.
100 nm is preferable and 1-50 nm is more preferable.

In the present invention, when an organic binder is used as a binder in addition to the metal oxides which have constituted the metal oxide sol, it is possible to make a more robust harmful substance removing agent, and therefore in a preferable form. is there. As the organic binder, an organic substance generally called an organic binder can be used. For example, starchy substances such as kansho, potato, tapioca, wheat, and corn starch, fungi, galactan (agar), seaweeds such as sodium alginate, Plant mucilages such as troloalloy, tragacanth and acacia, microbial mucilages such as dextrin and levan, proteins such as glue, gelatin, casein and collagen, viscose, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, carboxy cellulose, etc. Cellulose, soluble starch, carboxymethyl starch, starch such as dialdehyde starch, polyvinyl alcohol, sodium polyacrylate, polyethylene oxide, urea-based polymer, phenol-based starch Water-soluble organic binders for synthetic products such as polymers, polyvinyl acetate, vinyl acetate / ethylene copolymers, vinyl acetate / acrylic copolymers, vinyl acetate / Veova copolymers, and other vinyl acetate / polymerizable vinyl monomers , Acrylic emulsion polyacrylic acid ester, acrylic-Veova copolymer,
Examples thereof include vinyl acetate / Veova / acrylic, ethylene / vinyl acetate / acrylic, acrylic / styrene-based, polyvinyl chloride, vinyl chloride / vinylidene chloride copolymer, and emulsion polymers such as synthetic rubber latex. In the present invention, it is more preferable to add an emulsion polymer, since it can be used as a harmful substance-removing agent that is less disintegratable by water. The content of the organic binder is preferably 0.5 to 20% by weight, and more preferably 1 to 10% by weight, based on the harmful substance removing agent. When the content of the organic binder is less than the above range,
It is not preferable because the effect of adding the organic binder is hard to be recognized, and when the amount is more than the above range, it is not preferable because the adsorption ability and photocatalytic activity of the optical semiconductor are difficult to be exhibited.

The harmful substance removing agent of the present invention may contain an adsorbent in addition to the optical semiconductor and the metal oxide, or in addition to the organic binder to be added. As the adsorbent, a normal adsorbent capable of adsorbing harmful substances can be used, and for example, activated carbon, activated alumina, silica gel, zeolite or the like can be used.

If desired, the harmful substance removing agent of the present invention may contain various reinforcing materials and fillers. As the reinforcing material, titanium oxide fiber, potassium titanate fiber, crystalline cellulose, or the like can be used.

To produce the harmful substance removing agent of the present invention,
A method in which a mixture of an optical semiconductor and a metal oxide sol is granulated or molded and then dried is preferable. This method includes adding a metal oxide sol when granulating and molding an optical semiconductor. Further, in order to produce the harmful substance removing agent of the present invention, a method in which a mixture of an optical semiconductor, a metal oxide sol and an organic binder is granulated or molded and then dried is preferable. This method involves granulating optical semiconductors,
It includes adding a metal oxide sol and an organic binder at the time of molding. If necessary, the metal oxide sol may contain various dispersion stabilizers. In order to carry out the above-mentioned granulation and molding, for example, a machine such as a rolling granulator, an extrusion granulator, a stirring granulator, a crusher, a compression molding machine, a spray granulator, a mold molding machine is used. A granulated product or molded product obtained by a tumbling granulator, an extrusion granulator or a compression molding machine is preferable because its strength is relatively high. The obtained granulated body or molded body is dried.
The drying temperature is preferably room temperature to 150 ° C. If necessary, the granulated product and the molded product obtained by drying may be added to 150 to
You may bake at the temperature of 0 degreeC. By this firing, the strength of the granulated body or the molded body can be increased. However, if the baking temperature is higher than 300 ° C., the photocatalytic activity of the photosemiconductor is lowered, which is not preferable. If necessary, the granulated product or the molded product before drying may be subjected to a rolling granulator such as a Roche type granulator or a marumerizer to form a spherical granulated product, and then dried.

Further, in order to produce the harmful substance removing agent of the present invention, a mixture of an optical semiconductor and a metal oxide sol is dried,
Then, a method of coarsely crushing may be used. Further, in order to produce the harmful substance removing agent of the present invention, a method of drying a mixture of an optical semiconductor, a metal oxide sol and an organic binder, and then coarsely pulverizing the mixture may be used. The drying temperature is preferably room temperature to 150 ° C. The coarse pulverization can be carried out using a commonly used pulverizer, and the obtained product may be sieved if necessary. The pulverized product thus obtained may be fired at a temperature of 150 to 300 ° C., if necessary.

Next, using the harmful substance removing agent of the present invention,
To remove harmful substances in fluids,
A harmful substance is adsorbed and removed by bringing it into contact with a fluid containing the harmful substance, or a fluid containing the harmful substance is brought into contact with the harmful substance removing agent while irradiating light, and the harmful substance is caused by photocatalysis. Can be decomposed, made harmless and removed. Therefore, the harmful substance removing agent of the present invention is, for example, at a place where a fluid containing a harmful substance is present,
It may be placed in contact with harmful substances in various factories or places adjacent to them, toilets, living rooms, kitchens, refrigerators, automobiles, shoe boxes, and other living spaces. Hazardous substances in the fluid include ammonia, aldehydes, mercaptans,
It is possible to target amines, hydrogen sulfide, malodorous components such as methyl sulfide, nitrogen oxides, hydrocarbons, organic halogen compounds, bacteria, fungi and the like. In particular, the harmful substance removing agent of the present invention can efficiently remove malodorous components. The light for irradiating the harmful substance removing agent may be ultraviolet light having a wavelength of 400 nm or less, and examples of the light source include a mercury lamp, a xenon lamp, a mercury-xenon lamp, a germicidal lamp, a black light, and a white light. An artificial light source such as a fluorescent lamp or natural light of sunlight can be used. Further, the artificial light source and natural light may be used in combination, or the light emitted from them may be condensed and used. The irradiation of the harmful substance removing agent does not necessarily have to be performed continuously, and may be performed intermittently. When a fluid containing a harmful substance is brought into contact with the harmful substance removing agent by using a blower or a pump, the fluid can be forcibly brought into contact with the harmful substance removing agent, so that the harmful substance can be removed more efficiently. Furthermore, the harmful substance removing agent of the present invention, a light source, and a blower may be incorporated to form an air cleaning device. Specifically, the harmful substance removing agent of the present invention is filled in a box of an arbitrary shape made of a reticulated base material, which is provided in a gas flow path in an air purifying device, and the harmful substance removing agent is exposed to light. The light source can be arranged so as to hit the light source to form an air cleaning device.

[0015]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to these examples.

1. Sample preparation

Example 1 Titanyl sulfate was thermally hydrolyzed, and the resulting precipitate was filtered, washed, dried and pulverized to obtain hydrous titanium oxide (Sample A). As a result of X-ray diffraction, Sample A was anatase-type titanium oxide, and the X-ray particle size was 7 nm. 80 parts by weight of this sample A and a commercially available silicon oxide sol (Cataloid S-20L manufactured by Catalyst Kasei Kogyo Co., Ltd., particle size: 10)
20 nm) as silicon oxide, 20 parts by weight and an appropriate amount of water are added, and the mixture is kneaded, then extruded and granulated, shaped into a 5 mmφ udon shape, and dried at a temperature of 110 ° C. to remove the harmful substance removing agent of the present invention. (Sample E) was obtained.

Example 2 The sample A described in Example 1 was dispersed in pure water, dissolved with zinc chloride, neutralized with an aqueous solution of sodium hydroxide, and subsequently filtered, washed, dried and pulverized. A hydrous titanium oxide supporting zinc hydroxide (Sample B) was obtained. The molar amount of zinc hydroxide supported was Zn: Ti = 15: 85. As a result of X-ray diffraction, Sample B contained anatase-type titanium oxide, and its X-ray particle size was 7 nm. Next, a harmful substance removing agent (Sample F) of the present invention was obtained in the same manner as in Example 1 except that this sample B was used in place of the sample A in Example 1.

Example 3 In Example 1, a commercially available titanium oxide sol (CS-N manufactured by Ishihara Sangyo, particle size: 5 to 10) was used instead of the silicon oxide sol.
nm) as titanium oxide, except that
In the same manner as in Example 1, a harmful substance removing agent of the present invention (Sample G) was obtained.

Example 4 In Example 1, a commercially available aluminum oxide sol (boehmite sol AS manufactured by Nissan Kagaku Co., Ltd.) was used in place of the silicon oxide sol.
-520, particle size: 10 to 20 nm) was used as aluminum oxide in an amount of 20 parts by weight to obtain a harmful substance removing agent (Sample H) of the present invention in the same manner as in Example 1.

Example 5 80 parts by weight of the hydrous titanium oxide (Sample A) obtained in Example 1 and a commercially available silicon oxide sol (Catalyst Kasei Kogyo Cat
Alloyd S-20L, particle diameter: 10 to 20 nm) as silicon oxide, 15 parts by weight, polyvinyl acetate emulsion is added to 5 parts by weight in terms of resin content and an appropriate amount of water, and after kneading, extrusion granulation is performed to obtain a 5 mmφ product. Udon-shaped, 1
The harmful substance removing agent of the present invention (Sample I) was obtained by drying at a temperature of 10 ° C.

Example 6 A harmful substance removing agent (Sample J) of the present invention was prepared in the same manner as in Example 5 except that an acrylic emulsion polyacrylic ester was used in place of the polyvinyl acetate emulsion. Obtained.

Example 7 80 parts by weight of the sample A described in Example 1 and a commercially available silicon oxide sol (Cataloid S-2 manufactured by Catalyst Kasei Kogyo Co., Ltd.) were used.
0L, particle size: 10 to 20 nm) as silicon oxide 2
A mixture was obtained by adding 0 part by weight and an appropriate amount of water. The obtained mixture is molded with a compression molding machine and dried at a temperature of 110 ° C. to obtain a thickness of 15 mm, a pore diameter of 1 mm, and a thickness of 200 mm.
A harmful substance removing agent (Sample K) of the present invention, which is a honeycomb formed body of mesh, was obtained.

Comparative Example 1 A comparative sample T was obtained by granulating the sample A in the same manner as in Example 1 except that the silicon oxide sol was not added.

Comparative Example 2 Sample A was granulated in the same manner as in Example 1 except that a clay mineral (bentonite SUPER CLAY manufactured by Toyojun Yoko) was used in place of the silicon oxide sol.
Comparative sample U was obtained.

2. Sample Strength The samples E, F, G, H, I, and J of the example and the comparative sample U all had less powder falling off, and did not collapse even when a force of about 1.5 kg was applied. On the other hand, the strength of the comparative sample T was weak, and it was pulverized to the extent that it was lightly pinched with a finger. From this result, it was found that the harmful substance removing agent of the present invention has high strength, is difficult to be pulverized, and can withstand long-term use.

3. Water Resistance of Samples Water resistance was evaluated by immersing the samples obtained in the examples in pure water. Example samples E, F, G, H, I,
Both J and K did not lose their shape when immersed in water and maintained their shapes. On the other hand, the comparative samples T and U disintegrated and powdered when immersed in water. From this result, it became clear that the harmful substance removing agent of the present invention has excellent water resistance.

4. Hazardous substance removing ability by adsorption To examine the harmful substance removing ability of the sample F of Example 2,
After crushing the sample F, a particle L of 0.5 to 1 mm was collected to obtain a sample L. 0.1 g of the sample L was placed in a Pyrex glass container having a capacity of 2.8 l, and ammonia and methyl mercaptan, which are typical examples of malodorous gas, were 500 ppm each.
A considerable amount was added, and the removal capacity after 1 hour was examined. As a comparative sample, a commercially available inorganic adsorbent Mizukanite (MZ, manufactured by Mizusawa Chemical Co., Ltd.) was used. The results obtained are shown in Table 1. Sample L
In comparison with the comparative sample, it was found that the adsorption power of ammonia and methyl mercaptan was larger, and that the harmful substance removing agent of the present invention has an excellent ability to remove harmful substances by the adsorption action.

[0029]

[Table 1]

5. Hazardous substance removing ability by photocatalytic action Sample F of Example 2, Sample E of Example 1, Sample G of Example 3, Sample H of Example 4, Sample I of Example 5, and Sample J of Example 6 are harmful. In order to examine the substance removing ability, each sample was crushed, and then 0.5 to 1 mm particles were collected to obtain samples M, N, O, P, Q, and R, respectively. Sample M,
N, O, P, Q, R 0.1g each 0.8g capacity
Was placed in a Pyrex glass container, and acetaldehyde, which is a typical example of malodorous gas, was added in an amount corresponding to 150 ppm. Light irradiation with black light was performed from the outside of the Pyrex glass container, and the time-dependent change in acetaldehyde concentration was traced by gas chromatography. The amount of light on the sample surface was 1.0 mW / cm ² . As a comparison, the change in the concentration of acetaldehyde was examined without the light irradiation by the black light. The results are shown in Table 2 together. A large difference was found in the acetaldehyde concentration depending on the presence or absence of ultraviolet irradiation, and the ability of the harmful substance removing agent of the present invention to remove harmful substances by the photocatalytic action was confirmed.

[0031]

[Table 2]

Sample K obtained in Examples 7 and 1
And E were respectively placed in a cylindrical container made of Pyrex glass, and acetaldehyde having a predetermined concentration was introduced. After the adsorption reached equilibrium, the harmful gas removing ability of the sample was evaluated by measuring the carbon dioxide concentration generated by the decomposition of acetaldehyde in the container while performing light irradiation with black light. Table 3 shows the obtained results.
From these results, it was found that the harmful substance removing agent of the present invention is excellent in the ability to remove harmful substances by photocatalytic action, and the performance is further improved particularly by forming a honeycomb shape. From the above results, it was found that the harmful substance removing agent of the present invention has an excellent harmful substance removing ability and can maintain the harmful substance removing ability for a long period of time.

[0033]

[Table 3]

[0034]

INDUSTRIAL APPLICABILITY The present invention is a granule containing at least an optical semiconductor and the metal oxide or a molded product thereof, which uses the metal oxide constituting the metal oxide sol as a binder. A toxic substance removing agent characterized by having excellent toxic substance removing ability, and capable of sustaining the toxic substance removing ability for a long period of time. Moreover, since it is easy to handle such as separation / recovery, it can be applied to a wide range of applications as a harmful substance remover, and can be applied not only to industrial applications but also to general households.

Furthermore, the production method of the present invention is a useful method in that the above-mentioned harmful substance removing agent can be produced simply and inexpensively.

Further, the method for removing harmful substances of the present invention is a simple method using the above-mentioned harmful substance removing agent, and is therefore applicable not only to industrial applications but also to general household applications.

Claims (16)

[Claims] 1. A granulated body containing at least an optical semiconductor and the metal oxide, or a molded body thereof, which uses a metal oxide constituting a metal oxide sol as a binder. Hazardous substance remover. 2. The harmful substance removing agent according to claim 1, wherein the particle size of the metal oxide is 1 to 100 nm. 3. The harmful substance removing agent according to claim 1, wherein the content of the metal oxide is 5 to 30% by weight. 4. The harmful substance removing agent according to claim 1, wherein the content of the metal oxide is 10 to 20% by weight. 5. The harmful substance removing agent according to claim 1, wherein the metal oxide is at least one oxide of an element selected from silicon, aluminum and titanium. 6. The harmful substance removing agent according to claim 1, wherein the optical semiconductor is titanium oxide having an anatase type crystal form, and the particle diameter thereof is 1 to 50 nm. 7. The harmful substance removing agent according to claim 1, wherein the optical semiconductor is titanium oxide carrying zinc oxide and / or zinc hydroxide. 8. The harmful substance removing agent according to claim 1, wherein the metal oxide constituting the metal oxide sol and the organic binder are used as a binder. 9. The harmful substance removing agent according to claim 8, wherein the content of the organic binder is 0.5 to 20% by weight. 10. The harmful substance removing agent according to claim 8, wherein the organic binder is an emulsion polymer. 11. A granulated body or a molded body thereof is a honeycomb-shaped structure.
Or the harmful substance removing agent according to 8. 12. A method for producing a harmful substance removing agent, which comprises granulating or molding a mixture of an optical semiconductor and a metal oxide sol, and then drying. 13. A method for producing a harmful substance removing agent, which comprises granulating or molding a mixture of an optical semiconductor, a metal oxide sol and an organic binder, and then drying. 14. The method for producing a harmful substance removing agent according to claim 12, wherein the granulation or molding is performed by an extrusion granulator, a rolling granulator or a compression molding machine. 15. A method for removing harmful substances, which comprises removing the harmful substances by bringing a fluid containing the harmful substances into contact with the harmful substance removing agent according to claim 1. 16. A method for removing a harmful substance, which comprises contacting a fluid containing a harmful substance while irradiating the harmful substance removing agent according to claim 1 with the fluid to remove the harmful substance.