JPH08323346A - Method and device for treating dry cleaning waste water - Google Patents

Abstract

PURPOSE: To provide a highly efficient treating device capable of maintaining performance even if the device is used repeatedly for treating and also maintaining high efficiency over a long period of time by preventing a peeling and dropping of a photocatalyst by decomposing tetrachloroethylene with a photocatalyst supported on a woven textile to purify a waste water. CONSTITUTION: The woven textile 2 carrying the photocatalyst is placed in a reaction vessel 1 made of a transparent quartz glass, etc., and also tetrachloroethylene-containing waste water is enclosed in the vessel 1 to agitate with an agitating blade 3. Then, the tetrachloroethylene is decomposed by irradiating light from a light source 4 provided in the vicinity of the reaction vessel 1 to purify the waste water. At this time, titanium oxide is used as the photocatalyst. The photocatalyst is supported on the woven textile 2 consisting of an inorg. fiber containing silicon oxide by interposing a Ti-O-Si bonding layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a photocatalyst and decomposes tetrachloroethylene existing in wastewater with high efficiency by irradiating light, and purifies the wastewater. Regarding a processing device.

[0002]

2. Description of the Related Art In a so-called park-type dry cleaning machine using tetrachlorethylene, used tetrachlorethylene is generated as a mixed gas with water. This is liquefied by condenser cooling, etc., and separated by gravity separation into a tetrachloroethylene layer and an aqueous layer, and only tetrachloroethylene is recovered and regenerated. On the other hand, the water layer is discharged as waste water, and tetrachloroethylene is dissolved or emulsified and dispersed in the waste water at a high concentration of about 100 mg / l to 500 mg / l. Conventionally, an activated carbon adsorption method, an aeration treatment method, or a combination of these methods has been used as a method for treating the wastewater discharged from such a dry cleaning plant.

[0003]

However, in the activated carbon adsorption method, the concentration of tetrachloroethylene is several mg.
It does not fall below the discharge standard value of 0.1 mg / l according to the Water Pollution Control Law, and the groundwater pollution problem cannot be solved. In addition, there is a drawback that when the adsorption capacity of activated carbon reaches saturation, it must be replaced or washed.
In addition, it is difficult to grasp the deterioration time of the activated carbon, and there is a problem that the activated carbon that has been adsorbed is treated, and the apparatus becomes large. In addition, in the aeration treatment method, 0.1 m
It is possible to achieve a low concentration of g / l or less, but since tetrachloroethylene is released into the atmosphere, it ignores the effects of being accumulated in the environment due to carcinogenicity to the human body and persistent decomposition. There was a drawback that it could not be done. Further, as a means for solving the problems of the activated carbon adsorption method and the aeration treatment method, a photolysis method using a semiconductor as a catalyst, specifically, a solution containing a harmful substance in a titanium oxide powder dispersed in the liquid There is a method of irradiating with light to perform decomposition treatment, but this method has the drawback that it requires a filtration membrane on the downstream side to separate powder and liquid, resulting in high pressure loss. It has not been realized. An object of the present invention is to provide a dry cleaning wastewater treatment method and a treatment apparatus using the same, which eliminates these drawbacks of the prior art and decomposes tetrachloroethylene to purify wastewater.

[0004]

Means for Solving the Problems As a result of intensive studies for solving the above problems, the present inventors have found that tetrachloroethylene can be decomposed with high efficiency by utilizing an oxidation reaction using a photocatalyst carried on a woven cloth. Then, they have completed the present invention. That is, the dry cleaning wastewater treatment method of the present invention is characterized in that tetrachloroethylene in wastewater discharged from a dry cleaning machine using tetrachloroethylene is decomposed by a photocatalyst carried on a woven cloth to purify the wastewater. Further, the dry cleaning wastewater treatment device of the present invention is characterized in that a photocatalyst supported on a woven fabric is arranged in a container for enclosing or passing the tetrachloroethylene-containing wastewater, and a light source for irradiating the photocatalyst with light is provided. And

Many photocatalysts such as titanium oxide and zinc oxide have been proposed, but titanium oxide is preferred from the viewpoints of decomposition efficiency, safety and stability. The titanium oxide may be a rutile type, an anatase type, or a coexisting type thereof, but the rutile type is suitable for reacting with low-energy light, and the anatase type is preferable for increasing the activity of the reaction. Is suitable. As a method of supporting the photocatalyst, it is preferable to support the photocatalyst in the form of a film on the surface of the fibers constituting the woven fabric from the viewpoints of handleability and decomposition efficiency.

The photocatalyst may be platinum, palladium,
A noble metal such as rhodium, gold, silver or copper, or a nitrate, sulfate or acetate of these noble metals may be supported. As the method for supporting the noble metal, a photoprecipitation method, specifically, a method of spraying metal ion water or a method of irradiating light after dipping in metal ion water, or a method of irradiating light in a state of dipping in metal ion water It is easy to use the method of fixing by reduction plating.

Woven cloth was selected as the carrier for the photocatalyst in terms of handleability, water permeability, strength and the like. Among the woven cloth, a strong bond (Ti-
O-Si bond) and chemical resistance,
A woven fabric composed of inorganic fibers containing silicon oxide having excellent light resistance is preferable. The inorganic fiber containing silicon oxide as used herein is, for example, quartz glass, high quartz glass, E glass, C
Any composition such as glass, S glass, A glass, etc. may be used as long as it allows light to pass through, but E glass fiber is preferable from the economical viewpoint. The basis weight (g / m ² ) of the woven fabric may be any, but in view of handleability and decomposition efficiency, 100 to 900 g / m ² is usually used. The average fiber diameter of the constituent inorganic fibers is not particularly limited, but it is preferably 5 to 20 μm in order to be manufacturable and to secure the contact area with the waste water to be treated to obtain efficiency. Further, the driving density, thickness, and tensile strength of the woven fabric are not particularly limited, but from the viewpoint of strength against treated wastewater, both vertical and horizontal are 10 to 80 fibers / 25 m.
m, 0.01 to 2.0 mm, 5 kgf / 20 mm width or more are preferable.

The Ti-O-Si bond can be obtained by using a solution of a titanium oxide precursor which becomes titanium oxide by heating and an organic resin as a starting material. As the titanium oxide precursor, titanium alkoxide, titanium chloride, titanium sulfide, titanium acetate and the like can be used. However, when alcohols are used as a compatible solvent, titanium is used because of the compatibility with the organic resin. When alkoxide or water is used as a compatible solvent, titanium chloride, titanium sulfide or titanium acetate is preferably selected. However, when the precursor and the organic resin are compatible with each other, any combination may be selected.

As the organic resin, acrylic resin,
Olefin-based compounds are generally used, but the decomposition temperature is 2 because oxidative decomposition is required in the firing process during the manufacturing process.
It is only necessary for the resin to be at least 00 ° C. and not more than the firing temperature as long as it is compatible with the titanium oxide precursor, and is not limited by the type and molecular weight of the monomer. As described above, a solution obtained by dissolving the selected precursor and the organic resin in a compatible solvent is used as a starting material for producing a titanium oxide photocatalyst. That is, in order to obtain a photocatalyst from this starting raw material, a woven fabric composed of inorganic fibers containing silicon oxide such as glass fibers serving as a carrier is dipped in this raw material liquid, or this raw material liquid is woven. The composition may be applied, sprayed, or the like to dry and then baked. This drying is preferably performed at 150 ° C. or lower for 30 minutes or more. In addition, the rate of temperature increase from the liquid loading to the drying and the drying to the firing is preferably 10 ° C./min or less. Further, the final firing step needs to be performed in consideration of the heat resistance of the woven fabric, but it is preferable to perform firing at a temperature of 550 ° C. or lower.

The light source may be a low-pressure mercury lamp, a germicidal lamp, a black light fluorescent lamp, or the like, but a general fluorescent lamp may be used if the reaction speed is not taken into consideration.

The reaction vessel used in the wastewater treatment device may be an enclosed type for treating the wastewater in a batch type or a circulation type for treating the wastewater in a circulating type. In the former enclosed type, a device for stirring the wastewater is required. Moreover, in the case of the circulation type, it is desirable to equip a circulation pump or the like.

Further, as the structure of the waste water treatment apparatus, for example, a reaction vessel is a transparent vessel made of plastics, borosilicate glass, quartz glass, or the like, and a photocatalyst is disposed inside, and light is emitted from a light source installed outside the reaction vessel. May be a so-called external irradiation type, or may be a so-called internal irradiation type in which a light source and a photocatalyst are arranged in the reaction container without making the reaction container a transparent container.

[0013]

For example, the titanium oxide photocatalyst is easily excited by light having a wavelength of 400 nm or less. Here, the excited photocatalyst decomposes water to generate hydroxy radicals (.O).
H) is generated. This hydroxy radical has a high oxidizing power, and decomposes harmful tetrachloroethylene (C ₂ C 1 ₄ ) into harmless CO ₂ and HCl as shown in Formula 1. C ₂ C 1 ₄ +4 [.OH] → 2CO ₂ + 4HCl ... (Formula 1)

In the present invention, the Ti—O—Si bond-formed photocatalyst-supporting woven fabric has a strong bond between the titanium oxide and the inorganic fibers, so that the photocatalyst does not drop out and has a long life. It can be carried.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of the dry cleaning wastewater treatment apparatus of the present invention, which is an example of a sealed external irradiation type. In the figure, 1 indicates a reaction vessel made of transparent quartz glass,
A woven fabric 2 carrying a photocatalyst was placed in the reaction vessel 1, and tetrachloroethylene-containing wastewater was enclosed in the vessel 1 and stirred by a stirring blade 3. Further, light is emitted from a light source 4 provided in the vicinity of the reaction container 1 to decompose tetrachloroethylene and purify waste water.

FIG. 2 shows an example of a distribution type internal irradiation type dry cleaning wastewater treatment apparatus. Reference numeral 5 in the figure denotes a reaction container made of opaque stainless steel, in which a woven fabric 2 carrying a photocatalyst and a light source 4 are arranged, and a drainage storage tank is provided in the reaction container 5 via a supply path 6. The waste water containing tetrachloroethylene is supplied from 7, is returned to the waste water storage tank 7 through the drainage channel 8, and is configured to circulate. In the figure, 9 indicates a circulation pump.

Next, a concrete example will be described along with a comparative example in accordance with a usage example of the apparatus shown in FIG. (Example 1) E glass fiber woven fabric 2 in which 3% by weight of a photocatalyst consisting of anatase type titanium oxide was loaded in a reaction vessel 1
(Fiber diameter 7 μm, basis weight 490 g / m ² , driving density vertical 31/25 mm, width 24/25 mm, thickness 0.
30 mm (63 mm, mock weave) was placed, and further 450 ml of tetrachloroethylene-containing wastewater was enclosed. The concentration of tetrachloroethylene at this time is JIS K0125
It was 500 mg / l when measured by the solvent extraction / gas chromatograph method of “Testing method for low molecular weight halogenated hydrocarbon in water / wastewater”. As the light source 4, eight 20W germicidal lamps GL-20 manufactured by Matsushita Electric Industrial Co., Ltd. were arranged. Next, when light irradiation was carried out for about 2 hours while stirring with a magnetic stirrer, the concentration of tetrachloroethylene in the waste water was as low as 0.1 mg / l or less. Further, even if the drainage was changed at any time and this operation was repeated 10 times, the decomposition efficiency did not decrease and the same result was obtained.

Comparative Example 1 A test was conducted in the same manner as in Example 1 except that 30 g of activated carbon was added instead of the E glass fiber woven cloth 2 carrying 3% by weight of the photocatalyst used in the above example. As a result, the tetrachloroethylene concentration after about 2 hours was 8 mg / l. When this operation was repeated 10 times by changing the drainage at any time, the efficiency decreased as the number of times was repeated, and tetrachloroethylene could hardly be removed at the 10th time.

The test results of Example 1 and Comparative Example 1 are summarized in Table 1. The numbers in the table show the concentration of tetrachloroethylene in the waste water after the test in mg / l.

[0020]

[Table 1]

[0021]

As described above, the dry cleaning wastewater treatment method and treatment apparatus according to the present invention is a method for degrading tetrachlorethylene by a photocatalyst carried on a woven fabric to purify the wastewater, unlike the conventional method. Further, it has an effect that the performance is not deteriorated even if it is repeatedly processed. Further, when the titanium oxide of the photocatalyst is bonded to each of the fibers constituting the woven fabric uniformly and with a strong Ti—O—Si bond, the photocatalyst does not peel off or fall off, and high efficiency can be maintained for a long time. You can

[Brief description of drawings]

FIG. 1 is a model diagram of a sealed type external irradiation type of an example of a dry cleaning wastewater treatment device of the present invention.

FIG. 2 is a model diagram of a distribution type internal irradiation type of an example of the dry cleaning wastewater treatment apparatus of the present invention.

[Explanation of symbols]

 1 Transparent Quartz Glass Reaction Container 2 Woven Cloth 3 Stirring Blade 4 Light Source 5 Opaque Stainless Reaction Container 6 Supply Channel 7 Waste Water Storage Tank 8 Discharge Channel 9 Pump

Front page continuation (72) Inventor Koichi Kawashima 630 Tarui-cho, Fuwa-gun, Gifu Prefecture Japan Inorganic Stock Company Tarui factory

Claims (6)

[Claims] 1. A dry cleaning wastewater treatment method, characterized in that tetrachloroethylene in wastewater discharged from a dry cleaning machine using tetrachloroethylene is decomposed by a photocatalyst carried on a woven cloth to purify the wastewater. 2. The dry cleaning wastewater treatment method according to claim 1, wherein the photocatalyst is titanium oxide. 3. The dry cleaning wastewater treatment method according to claim 2, wherein the photocatalyst is supported on a woven fabric made of inorganic fibers containing silicon oxide through a Ti—O—Si bonding layer. . 4. A dry cleaning wastewater treatment apparatus comprising a photocatalyst supported on a woven cloth and a light source for irradiating the photocatalyst with light, in a container in which the tetrachlorethylene-containing wastewater is enclosed or passed. . 5. The dry cleaning wastewater treatment apparatus according to claim 4, wherein the photocatalyst is titanium oxide. 6. The dry cleaning wastewater treatment apparatus according to claim 5, wherein the photocatalyst is supported on a woven fabric made of inorganic fibers containing silicon oxide through a Ti—O—Si bonding layer. .