JPH06320010A - Photocatalyst for treatment of harmful substance and device for treating harmful substance - Google Patents

Abstract

PURPOSE:To obtain a photocatalyst for treatment of a harmful substance having high efficiency and easy to handle by dipping a woven fabric of glass fibers in a soln. prepd. by dissolving a precursor of titanium oxide and an org. resin, drying the fabric and forming an Si-O-Ti bonded layer by firing between each of the glass fibers and the resulting titanium oxide. CONSTITUTION:A woven fabric of glass fibers A is dipped in a soln. prepd. by dissolving a precursor convertible into titanium oxide by heating and an org. resin in compatible solvents, the fabric is dried and an Si-O-Ti bonded layer C is formed by firing between each of the glass fibers A and the resulting thin titanium oxide film B coating the fabric to obtain the objective photocatalyst for treatment of a harmful substance. In this case, a dehydration condensation reaction proceeds and the Si-O-Ti bonded layer C is formed at a relatively low temp. because only the surface of the fabric is locally heated by the heat of combustion generated by an oxidation degradation reaction of the org. resin and that of org. residues constituting the precursor. By the presence of the layer C, a decomposition reaction of a harmful substance is accelerated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an organic halogen compound such as trichlorethylene, chloroform or dioxin which is present in a liquid or a gas phase when irradiated with light,
A photocatalyst for treating harmful substances such as cyanide, pesticide components, etc. that can efficiently decompose and remove harmful substances, or sterilize and reduce bacteria present in liquid or gas phase, and a photocatalyst for treating harmful substances. The present invention relates to a hazardous substance processing device used.

[0002]

2. Description of the Related Art Conventionally, as a method of treating a harmful substance by using a photocatalyst, titanium oxide powder is dispersed in a liquid and a solution containing the harmful substance is poured into the liquid and decomposed by irradiation with light. Known is a method of disposing a glass rod or glass sphere coated with a titanium oxide film by a CVD method or a sol-gel method in a liquid, pouring a solution containing a harmful substance into this, and irradiating it with light to decompose it. Has been.

[0003]

However, in the conventional method for dispersing the titanium oxide powder in the liquid, it is necessary to provide a filtration membrane on the downstream side in order to separate the powder and the liquid, and therefore the pressure Higher losses. Further, when the powder is dispersed in the liquid, the light is absorbed only in the outermost layer, and it becomes difficult for the irradiation light to penetrate to the inside, resulting in a drawback that the processing efficiency is reduced. Further, the conventional method using a glass rod or a glass sphere coated with a titanium oxide film does not require the installation of a filtration film for recovering powder and transmits light, but has a small contact interface with water or a gas phase. However, it has the drawback of poor processing efficiency. Furthermore, when the titanium oxide film is coated by the conventional CVD method or sol-gel method, the titanium oxide should intervene the Si—O—Ti bonding layer between the glass fiber and the glass fiber as the base material. Since it is not present and is present alone, there is a problem that the film may come off as a result of long-term use. It is an object of the present invention to eliminate these drawbacks of the prior art and provide a photocatalyst for treating harmful substances with high efficiency and ease of use, and a harmful substance treating apparatus using the photocatalyst.

[0004]

Means for Solving the Problems As a result of intensive studies for solving the above-mentioned drawbacks, the present inventors have found that a solution obtained by dissolving a precursor that becomes titanium oxide by heating and an organic resin in a compatible solvent. After immersing the woven fabric made of glass fiber in
The present invention has been completed by finding that the defects of conventional products can be eliminated by drying and firing.

That is, the photocatalyst for treating harmful substances of the present invention is a photocatalyst for treating harmful substances in which a woven fabric made of glass fibers is coated with titanium oxide, and the woven fabric made of the glass fibers is transformed into titanium oxide by heating. After immersion in a solution prepared by dissolving the precursor and the organic resin in a compatible solvent,
It is characterized in that a Si—O—Ti bond layer is formed between the glass fiber and the titanium oxide by drying and firing.

Fabric weight of the above-mentioned glass fiber (g
/ M ² ) may be anything, but in view of handleability and decomposition efficiency, usually 100 to 900 g / m ² is used. Further, as the kind of glass fiber constituting the woven cloth, any composition may be used, such as quartz glass, high quartz glass, E glass, C glass, S glass, A glass, etc., as long as it allows light to pass through. From the viewpoint of properties, E glass fiber is preferable. Further, the average fiber diameter of the glass fibers is not particularly limited, but is preferably 5 to 20 μm in order to be manufacturable and to secure the contact area with the fluid to be treated to obtain efficiency. The weave may be any weave, such as plain weave, twill weave and satin weave, but plain weave is preferred from the viewpoint of light transmission. Further, the implantation density, thickness, and tensile strength are not particularly limited, but from the viewpoint of strength against the fluid to be treated, both vertical and horizontal are 10 to 80 /
25 mm, 0.01 to 2.0 mm, 5 kgf / 25 mm
It is preferably a width or more.

As the precursor which becomes titanium oxide by the heating, titanium alkoxide, titanium chloride, titanium sulfide, titanium acetate, etc. can be used, but alcohols are used because of their compatibility with organic resin. When a compatible solvent is used, titanium alkoxide is preferably selected, and when water is used as a compatible solvent, titanium chloride is preferably selected. However, if the precursor and the organic resin are compatible with each other, any combination may be selected.

The organic resin is generally an acrylic resin, an olefin resin or the like, but the decomposition temperature is 200 because it needs to be oxidized and decomposed in the firing step in the manufacturing process.
It is only necessary that the resin is a resin having a temperature of not less than 0 ° C. and not more than the firing temperature, and has compatibility with the titanium oxide precursor, and is not particularly limited depending on the type and molecular weight of the monomer.

The woven fabric is dipped in a solution of the organic resin and the titanium oxide precursor thus selected, and then dried. The drying temperature depends on the boiling point of the compatible solvent.
It is preferably carried out in the range of up to 150 ° C. Next, the dried film is baked to remove the organic residues constituting the organic resin and the titanium oxide precursor. By this firing, the titanium oxide precursor is changed to titanium oxide, and the organic resin is oxidatively decomposed to obtain a thin film having a Si—O—Ti bond.

The thickness of the titanium oxide film to be coated is preferably 1 μm or less in view of the adhesiveness and light transmittance of the film. If it exceeds 1 μm, peeling of the film occurs, resulting in turbidity of water and deterioration of decomposition efficiency. In addition, the light transmittance also deteriorates, and it becomes difficult for light to reach the inside of the woven fabric, which is not preferable in terms of decomposition efficiency. In addition, the thickness of titanium oxide can be changed by adjusting the concentration of the titanium oxide precursor in the solution or by repeating the above production process.

Considering the entire woven fabric, the ratio of the amount of the coated titanium oxide film to the entire woven fabric is preferably 40 wt% or less. Also in this case, if it exceeds 40 wt%, the light transmittance is deteriorated and the titanium oxide is also peeled off, which is not preferable.

[0012] Further, when the noble metal is supported on titanium oxide, platinum, palladium, rhodium, gold,
Silver or the like is preferable. The method of supporting is easy if a photodeposition method is used.

Further, the harmful substance treating apparatus of the present invention is characterized in that the photocatalyst is arranged in a container for passing a solution or gas containing the harmful substance and a light source for irradiating the photocatalyst with light is provided. . In the above apparatus, for example, the container may be a transparent container made of plastics, borosilicate glass, quartz glass, or the like, and light may be irradiated from the outside of the container, or the container may be a transparent container. Alternatively, the light source may be arranged in the container. As the light source, a low pressure mercury lamp, a black light fluorescent lamp, or the like is used.

[0014]

When a known CVD method or sol-gel method is used to form a bond of Si-O-Ti between the substrate and the thin film, a high temperature of 600 ° C or higher is required.
This is because the reaction is based on the Si-OH group on the substrate surface and the Ti
Because it is due to a dehydration condensation reaction between —OH groups,
Generally, this condensation reaction increases the degree of freedom of the —OH group 6
It is said to occur above 00 ° C. For this reason, it is impossible to coat A glass, C glass, E glass and the like, which have high versatility and low heat resistance, and the substrates to be coated have been limited. In the present invention, the formation of the Si—O—Ti bond is due to the dehydration condensation reaction between the Si—OH group on the surface of the substrate and the Ti—OH group on the thin film, as in the CVD method and the sol-gel method. Is. However, in the present invention, since only the surface can be locally heated by the combustion heat generated by the oxidative decomposition reaction of the organic residue constituting the organic resin and the precursor of the metal oxide, the dehydration condensation reaction proceeds relatively, Si-O-Ti bonds are formed at low temperatures. Therefore, even when a substrate such as glass having low heat resistance is used, Si-
It becomes possible to form a thin film having a layer having an O—Ti bond, and a strong titanium oxide film can be obtained. Furthermore, the presence of this Si—O—Ti bond accelerates the decomposition reaction of harmful substances. It is generally said that the decomposition of harmful substances in liquid or gas phase is caused by the OH radical generated by decomposition of coexisting H ₂ O. When a titanium oxide photocatalyst is used, the electrons filled in the valence band are excited to the conduction band by irradiation with light, and electron holes are generated on the surface of titanium oxide. At this time, if Si—O—Ti bonds are present, irregular disorder occurs in the arrangement of the titanium oxide layers on the surface,
This disorder causes sites where electron holes are easily pooled. This site behaves like a strong acid point in a general solid catalyst, and segregation of charges occurs to promote generation of OH radicals. Therefore, the decomposition of the harmful substance can be promoted. Further, it is preferable to support a noble metal on the surface of the titanium oxide, because the decomposition reaction of harmful substances is electrochemically promoted. Further, the photocatalyst is flexible and can be installed in a container of any shape.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of the harmful substance treating apparatus of the present invention. In the figure, reference numeral 1 denotes a container made of a transparent quartz tube, in which a photocatalyst 2 for treating harmful substances is arranged, and the container 1
A solution containing a harmful substance is circulated therein through a pump 3, and light is emitted from a light source 4 provided in the vicinity of the container 1 to treat the harmful substance. In the figure, 5 is a converging mirror, 6 is an outlet for taking out a solution treated with a harmful substance, and 7 is an inlet for supplying a solution containing a new harmful substance.

Next, a concrete embodiment will be described together with a comparative example in accordance with a usage example of the apparatus. (Example) A basis weight 50 formed by weaving a yarn made of E glass monofilament (single fiber) having an average fiber diameter of 7 μm
A glass woven fabric (glass cloth) of 0 g / m ² was immersed in a solution of 10 g of titanium isopropoxide as a titanium oxide precursor and 10 g of an acrylic resin in 180 g of ethyl alcohol. Remove this woven glass cloth from the solution,
After being dried at 60 ° C for 1 hour, the temperature was raised to 450 ° C at a rate of 1 ° C / min and kept at 450 ° C for 5 hours to completely oxidize and decompose the organic resin and at the same time convert titanium isopropoxide to TiO ₂ . Change the TiO _{2 on the} glass fiber surface.
A film was formed. At this time, the thickness of the TiO ₂ film is about 0.3.
It was μm and was firmly attached. In this case, the ratio of the coated titanium oxide to the entire glass woven fabric is 18%.
Met. EPMA (X-ray microanalyzer for measurement, JEM-2000FXII manufactured by JEOL Ltd.)
And ESCA (using an X-ray photoelectron spectrometer, XSAM800 manufactured by Shimadzu-Kraitos Co., Ltd.) for the measurement, the presence of Si—O—Ti bonds was confirmed. Here, FIG. 2 is a cross-sectional view of the film according to this embodiment, where A is glass fiber, B is a TiO ₂ thin film, and C is Si—O.
-Ti bond layer is shown. This glass woven fabric (catalyst) was packed in a transparent quartz tube having a diameter of 12 mm and a length of 500 mm, the reaction solution was passed through, and circulated by a pump. The reaction solution was an aqueous solution in which 200 mg / l of chloroform was dissolved in double-distilled water, and the solution was irradiated with light from a low-pressure mercury lamp at a solution temperature of 40 ° C. After irradiation with light for about 5 hours, 95% of chloroform was decomposed. In this case, there was no turbidity in the water. Next, the reaction solution was replaced, and the same test was performed with an aqueous solution in which the same amount of chloroform was dissolved. This test was repeated 50 times, but there was no turbidity in the water,
In addition, the decomposition efficiency of chloroform did not decrease from the initial value and kept high efficiency.

Comparative Example Using the glass woven cloth used in the examples, an attempt was made to form a TiO ₂ thin film by the conventional sol-gel method. The liquid in which the glass woven cloth is dipped is 10 g of titanium isopropoxide, 0.1 g of concentrated sulfuric acid and 19 of ethyl alcohol.
The same method as in Example was used except that 0 g was changed to a mixed solution. The resulting TiO ₂ film has a thickness of about 0.3 μm.
It was m, but peeled off easily due to weak adhesion. in this case,
The ratio of the amount of coated titanium oxide to the entire glass woven fabric was 18%. When this film was analyzed by EPMA and ESCA in the same manner as in the above example, S
The presence of i-O-Ti bond was not confirmed. here,
FIG. 3 is a cross-sectional view of a film according to this comparative example, where A is glass fiber and B is a TiO ₂ thin film. This glass woven fabric (catalyst) was packed in a transparent quartz tube having a diameter of 12 mm and a length of 500 mm, the reaction solution was passed through, and circulated by a pump. The reaction solution was an aqueous solution in which 200 mg / l of chloroform was dissolved in double-distilled water, and the solution was irradiated with light from a low-pressure mercury lamp at a solution temperature of 40 ° C. After irradiation with light for about 5 hours, 80% of chloroform was decomposed, but the water was considerably turbid due to the loss of titanium oxide. Next, the reaction solution was replaced, and the same test was performed with an aqueous solution in which the same amount of chloroform was dissolved. At the second time, 60% decomposed under the same conditions, and at the third time 50% decomposed. Titanium oxide fell out every time the reaction solution was replaced and the test was performed.
%, And the catalytic function was lost.

[0018]

As described above, since the woven fabric according to the present invention has good light transmittance and a large contact area with water or gas, it is possible to highly efficiently decompose harmful substances in liquid or gas phase. Have. Moreover, Si-O-
Since the titanium oxide film is firmly covered by the Ti bond, there is no peeling or dropping of titanium oxide, high efficiency is maintained for a long time, and there is no turbidity of water, so there is no need to collect powder or the like. Has the effect. Furthermore, since the Si-O-Ti bond is present, the charge on the surface of titanium oxide is segregated, and this has the effect of promoting the generation of OH radicals required for decomposition of harmful substances. Also, since it has flexibility, it can be applied to containers with complicated shapes,
It has an effect that it can be formed into a column.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an embodiment of a hazardous substance processing apparatus of the present invention.

FIG. 2 is an enlarged cross-sectional view showing a formation state of a coating film of the photocatalyst for treating harmful substances of the present invention.

FIG. 3 is an enlarged cross-sectional view showing a state of forming a coating film of a photocatalyst for treating harmful substances according to a comparative example.

[Explanation of symbols]

1 Container 2 Photocatalyst for Treating Hazardous Substances 3 Pump 4 Light Source 5 Converging Mirror 6 Inlet 7 Inlet A Glass Fiber B TiO ₂ Thin Film C Si-O-Ti Bonding Layer

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Masayuki Murabayashi 4-25-14 Sasanodai, Asahi-ku, Yokohama-shi, Kanagawa (72) Inventor Kiminori Ito 1-16-13-906, Meguro-hon, Meguro-ku, Tokyo

Claims (5)

[Claims] 1. A photocatalyst for treating harmful substances, comprising a woven cloth made of glass fibers coated with titanium oxide, wherein the woven cloth made of glass fibers is compatible with a precursor that becomes titanium oxide by heating and an organic resin. A photocatalyst for treating harmful substances, characterized in that a Si—O—Ti bond layer is formed between the glass fiber and the titanium oxide by immersing in a solution prepared by dissolving in a solvent, and then drying and firing. . 2. The photocatalyst for treating harmful substances according to claim 1, wherein noble metals are supported on the titanium oxide. 3. The photocatalyst for treating harmful substances according to claim 1, wherein the titanium oxide has a thickness of 1 μm or less. 4. The amount of the titanium oxide is 40 wt% or less with respect to the glass fiber woven fabric.
4. The photocatalyst for treating harmful substances according to any one of 3 to 3. 5. The photocatalyst according to any one of claims 1 to 4 is arranged in a container through which a solution or gas containing a harmful substance is passed, and a light source for irradiating the photocatalyst with light is provided. Characteristic hazardous substance processing equipment.