JP3118558B2 - Water treatment catalyst and water treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water treatment catalyst and a water treatment method for performing wastewater treatment, water purification treatment, water sterilization and algicidal treatment.

[0002]

2. Description of the Related Art In recent years, water pollution due to domestic wastewater and industrial wastewater, especially, organic chlorine-based solvents, pesticides, synthetic detergents (surfactants) which are difficult to treat by water treatment methods such as the activated sludge method currently used. ), Pollution of water sources by various chemical substances such as synthetic dyes and the like has been widespread, and environmental pollution has become a serious social problem.

[0003] The wastewater treatment method widely used at present is the activated sludge method. However, since this method uses living organisms called microorganisms, the reaction conditions such as temperature, pH, gas atmosphere and toxicity are severe, and the above-mentioned pesticides and organic compounds are used. It has the disadvantage that it is difficult to decompose and remove solvents (especially halocarbons), surfactants (especially those with side chains), and synthetic dyes.

When a semiconductor is irradiated with light, electrons having a strong reducing action and holes having a strong oxidizing action are generated, and molecular species in contact with the semiconductor are decomposed by the redox action. By utilizing such an action of the semiconductor, that is, a photocatalytic action, it is possible to decompose and remove environmental pollutants such as organic solvents, pesticides, surfactants, and synthetic dyes dissolved in water. This method only utilizes semiconductors and light, and has less restrictions on reaction conditions such as temperature, pH, gas atmosphere, toxicity, and the like, and is difficult to process using a biological treatment method, as compared to methods such as biological treatment using microorganisms. Easily decomposes even compounds such as organic halogen compounds and organic phosphorus compounds.
It has the advantage that it can be removed. However, semiconductor powders have been used as photocatalysts in studies on decomposition and removal of organic substances using photocatalysts (for example, see AL Pruden and DF Ollis, Journal of Catal
ysis, Vol. 82, 404 (1983), H. Hidaka, H. Jou, K. No
hara, J. Zhao, Chemosphere, Vol. 25, 1589 (1992),
Teruaki Hisaga, Kenji Harada, Keiichi Tanaka, Industrial Water, No. 379, 1
2 (1990)). Therefore, it is difficult to handle and use as a photocatalyst.In the case of water treatment, the treated water must be filtered to recover the photocatalyst powder.However, since the photocatalyst is a fine powder, clogging may occur. However, there is a problem that it is difficult to separate and recover the treated product and the photocatalyst, and it is not possible to continuously treat water. In addition, there is a disadvantage that it takes too much time to treat high-concentration wastewater.

[0005]

SUMMARY OF THE INVENTION In view of the above, the present invention addresses water pollution and is difficult to treat by the activated sludge method for pesticides, organic solvents (particularly halocarbons), surfactants (particularly side chains). To provide a high-performance, easy-to-handle water treatment catalyst capable of easily and quickly treating and purifying water contaminated with synthetic dyes and the like under mild conditions, and an economical water purification method. It is assumed that.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in order to achieve the above object, and as a result, the surface is covered with a titanium oxide film and adsorbs oxidizing agents such as hydrogen peroxide, ozone and oxygen. By placing the porous body in water contaminated with a chemical substance and irradiating it with light, it was found that the chemical substance was quickly and efficiently oxidized and decomposed into carbon dioxide gas and the like and detoxified, thereby leading to the present invention. Was.

The present invention provides a water treatment catalyst in which the surface of a porous body is coated with a titanium oxide film and adsorbs hydrogen peroxide, ozone, and oxygen, and the catalyst is placed in water to be treated and irradiated with light. Water treatment method. In the present invention, porous
The porous body composed of the above materials is a porous material as a whole.
Fee is defined as
It does not include a substrate having fine irregularities formed on the surface.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The porous material used in the present invention is activated carbon, activated alumina, silica gel, zeolite, clay sintered body, porous glass, foam ceramic, foam metal,
Various materials such as foam plastics can be mentioned, and silica gel and porous glass are particularly preferable in terms of transmitting light.

The shape of the porous body used in the present invention may be any shape such as a granular shape, a plate shape, a cylindrical shape, a prism shape, a conical shape, a spherical shape, a gourd shape, and a rugby ball shape.

[0010] The titanium oxide film is coated on the surface of the porous body by various methods such as vapor deposition, PVD, CVD, sputtering, coating of titania sol by a sol-gel method, and fixing of ultrafine titanium oxide.

It is preferable that the titanium oxide film used in the present invention has a high performance as a photocatalyst and the crystal form is anatase. Rutile, brookite, and amorphous ones are not preferred because of their low photocatalytic activity.

The catalyst for water treatment of the present invention is prepared by adsorbing an oxidizing agent such as hydrogen peroxide, ozone, or oxygen on a porous body whose surface is covered with a titanium oxide film. The present invention
In the above, oxygen means oxygen alone (ie, pure oxygen)
I do.

The water treatment catalyst of the present invention thus obtained is placed in water contaminated with a chemical substance and irradiated with light, whereby the porous substance efficiently adsorbs the chemical substance dissolved in the water, and The electrons and holes generated in the titanium oxide film by the irradiation of hydrogen react with the oxidizing agent such as hydrogen peroxide, ozone, and oxygen that are adsorbed to generate active oxygen species having an extremely large oxidation potential. Due to the oxidizing power, the chemical substance is quickly and efficiently oxidized and decomposed into carbon dioxide gas and the like, thereby rendering it harmless. At this time, by stirring,
The processing speed can be greatly increased.

Further, when a metal such as platinum, rhodium, ruthenium, palladium, silver, copper, zinc or the like is carried on the surface of the titanium oxide film of the water treatment catalyst of the present invention, the oxidative decomposition rate of the chemical substance increases. It gets even bigger.

The porous photocatalyst according to the present invention thus obtained is porous and has a large specific surface area, so that it efficiently adsorbs organic compounds contaminating the environment such as organic solvents dissolved in water and agricultural chemicals, and Light, fluorescent lamp, incandescent lamp, black light, UV lamp, mercury lamp, xenon lamp, halogen lamp, metal halide lamp, etc. Due to the extremely strong oxidizing power of the active oxygen species generated by the reaction of hydrogen oxide, ozone and oxygen, it can be quickly and continuously decomposed and removed to carbon dioxide or the like.

Next, the present invention will be described based on examples, but the present invention is not limited to the examples.

【Example】

Example 1 Granular foamed polyethylene having a diameter of 3 mm (specific surface area: 15 m ²
/ G) was heated to melt the surface and coated with a slurry of ultrafine particles of titanium oxide of anatase having a particle size of 7 nm. This was placed in a beaker containing a 31% aqueous solution of hydrogen peroxide and sufficiently adsorbed. The obtained catalyst for water treatment was used to decompose trichlorethylene, which is widely used as a solvent and a cleaning agent in the high-tech industry and the cleaning industry, and has become a problem by contaminating groundwater and soil. 10 ppm
Was placed in a quartz glass test tube, and 0.1 g of the obtained water treatment catalyst was placed therein, followed by irradiation with light from a 500 W high-pressure mercury lamp. One hour later, as a result of measuring the amount of trichlorethylene contained in the reaction solution using a gas chromatograph,
Trichlorethylene was decomposed and not detected.

Example 2 A transparent sol solution was prepared by adding anhydrous ethanol, triethanolamine and water to titanium tetrabutoxide, and the surface of spherical silica gel was coated with a titanium oxide film by a dropping method. That is, a small amount of this sol solution, about 5 m in diameter
The resulting mixture was dropped onto the surface of a spherical silica gel having a specific surface area of 450 m (specific surface area: 450 m ² / g), dried after dropping an excess liquid, and then gradually heated from room temperature to 600 ° C. and calcined. This was repeated three times to form a titanium oxide film on the surface of the spherical silica gel. As a result of examining the crystal structure of the obtained titanium oxide film by X-ray diffraction, it was found to be 100% anatase. This was placed in a beaker containing a 31% aqueous solution of hydrogen peroxide and sufficiently adsorbed. The dyeing effluent was decolorized using the obtained water treatment catalyst. After putting 3 ml of an aqueous solution of eosin 100 ppm as a model drain into a quartz cell,
1.5 g of the obtained catalyst for water treatment was put therein, and irradiated with a xenon lamp of 300 W to measure a UV-visible absorption spectrum. As a result, after one hour, it was completely decolorized and became colorless and transparent.

Example 3 A transparent sol solution was prepared by adding isopropanol and diethanolamine to titanium tetraisopropoxide, and the surface of the granular zeolite was coated with a titanium oxide film by a spray method. That is, 2 mm in diameter and 3 mm in length
Was sprayed while rocking a granular zeolite (specific surface area: 30 m ² / g) on a fine wire mesh, dried, and then heated from room temperature to 620 ° C., and calcined. This operation was repeated four times to form a titanium oxide film on the surface of the granular zeolite. As a result of examining the crystal structure of the obtained titanium oxide film by X-ray diffraction, it was found to be 100% anatase. This was put in a vacuum desiccator, and ozone was injected from the outside to allow sufficient adsorption. The obtained catalyst for water treatment was used to decompose tetrachloroethylene, which is widely used as a solvent and a cleaning agent in the high-tech industry and the cleaning industry, and is a problem that pollutes groundwater and soil. 18 ml of an aqueous solution of tetrachloroethylene having a concentration of 10 ppm was placed in a quartz glass test tube, and 8 g of the obtained water treatment was immersed therein, and irradiated with light from a 200 W low-pressure mercury lamp. After 1.5 hours, the concentration of tetrachloroethylene contained in the reaction solution was measured using a gas chromatograph.
ppm.

Example 4 A transparent sol solution was prepared by adding ethanol and N-ethyldiethanolamine to titanium tetraisopropoxide, and the surface of the granular activated carbon was coated with a titanium oxide film by a dropping method. That is, a small amount of this sol solution is dropped on the surface of granular activated carbon (specific surface area: 250 m ² / g) having a diameter of about 3 mm and treated with a 10% aqueous nitric acid solution heated to 80 ° C. And calcined at a temperature of 300 ° C. This was repeated five times to form a titanium oxide film on the surface of the granular activated carbon. The crystal structure of the obtained titanium oxide film was examined by X-ray diffraction.
%Met. This was placed in a vacuum desiccator, and oxygen was injected from the outside to allow sufficient adsorption. Acetic acid was decomposed using the obtained water treatment catalyst and this porous photocatalyst. 10 ml of an aqueous solution of acetic acid having a concentration of 20 ppm
Into a quartz container, and 5 g of the water treatment catalyst obtained therein.
Was immersed and irradiated with light from a 500 W ultra-high pressure mercury lamp while stirring. One hour later, the concentration of acetic acid contained in the obtained reaction solution was measured using a gas chromatograph. As a result, acetic acid was decomposed to 0%.

Example 5 The surface of a spherical activated alumina having a diameter of 5 mm (specific surface area: 80 m)
² / g) was coated with a titanium oxide film by sputtering. Thereafter, the temperature was gradually increased from room temperature to a temperature of 550 ° C., followed by firing. The crystal structure of the obtained titanium oxide film was examined by X-ray diffraction.
It was 0%. This was immersed in a 2 g / l aqueous solution of potassium chloroplatinate in ethanol, irradiated with light from a 100 W mercury lamp for 1 hour while stirring with a magnetic stirrer, and the surface of the titanium oxide film was coated with platinum by a photoelectric deposition method. . After this was dried, it was placed in a beaker containing a 31% concentration of hydrogen peroxide solution and sufficiently adsorbed. Using the obtained catalyst for water treatment, 4-nitrophenylethylphenylphosphinate, which is an organic phosphorus-based pesticide, was decomposed. 18 ml of an aqueous solution of 4-nitrophenylethylphenylphosphinate at a concentration of 50 ppm was placed in a hard glass test tube, and 1 g of the obtained water treatment catalyst was placed therein, followed by irradiation with a 500 W xenon lamp. One hour later, the amount of 4-nitrophenylethylphenylphosphinate contained in the reaction solution was measured using a gas chromatograph. As a result, the concentration of 4-nitrophenylethylphenylphosphinate was reduced to 0% by decomposition. I was

Example 6 A transparent titania sol was prepared by adding water and nitric acid to titanium tetraisopropoxide, and the surface of the clay sintered body was coated with a titanium oxide film by an immersion method. That is, a clay sintered body (specific surface area: 10 m ² / g) having a diameter of about 8 mm is immersed in the titania sol, excess liquid is dropped and dried, and the temperature is gradually lowered from room temperature to 650 ° C. Then, the temperature was increased to sintering. This was repeated three times to form a titanium oxide film on the surface of the clay sintered body. As a result of examining the crystal structure of the obtained titanium oxide film by X-ray diffraction, it was found to be 100% anatase. This was immersed in an aqueous solution of copper sulfate, heated and gradually heated from room temperature to 650 ° C., calcined, and then placed in a beaker containing a 31% concentration of hydrogen peroxide solution to be sufficiently adsorbed. The dyeing effluent was decolorized using the obtained water treatment catalyst. After placing 3 ml of a 200 ppm aqueous solution of methyl orange as a model drain into a quartz cell, 2 g of the obtained catalyst for water treatment was placed therein, and irradiated with a 500 W ultrahigh pressure mercury lamp to measure a UV-visible absorption spectrum. As a result, after one hour, it was completely decolorized and became colorless and transparent.

Example 7 A titanium oxide film was coated on the surface of foamed aluminum (specific surface area: 8 m ² / g) having a diameter of about 7 mm by PVD. Thereafter, the temperature was gradually increased from room temperature to a temperature of 550 ° C., followed by firing. The crystal structure of the obtained titanium oxide film was examined by X-ray diffraction.
00%. Put this in a vacuum desiccator,
Ozone was injected from outside to allow sufficient adsorption. Ethanol was decomposed using the obtained water treatment catalyst. 3
15 ml of a 00 ppm aqueous ethanol solution was placed in a hard glass test tube, and 2 g of the obtained water treatment catalyst was placed therein.
A 00 W xenon lamp was irradiated. One hour later, the concentration of ethanol contained in the reaction solution was measured using a gas chromatograph, and as a result, it was reduced to 0%.

Example 8 A transparent sol solution was prepared by adding ethanol and triethanolamine to titanium tetrabutoxide, and the surface of a porous glass was coated with a titanium oxide film by an immersion method. That is, a porous glass (specific surface area: 150 m ² / g) having a diameter of about 8 mm is immersed in this sol solution, excess liquid is dropped and dried, and then heated from room temperature to 550 ° C. gradually. Heated and fired. This was repeated four times to form a titanium oxide film on the surface of the porous glass. As a result of examining the crystal structure of the obtained titanium oxide film by X-ray diffraction, it was found to be 100% anatase. This was placed in a vacuum desiccator, and oxygen was injected from the outside to allow sufficient adsorption. The obtained catalyst for water treatment was used to decompose trichloroethane, which is now widely used as a solvent and a cleaning agent in the high-tech industry and the cleaning industry, and has become a problem by contaminating groundwater and soil. 3 ml of an aqueous solution of trichloroethane having a concentration of 15 ppm was placed in a quartz cell, and 3 g of the obtained water treatment was immersed in the quartz cell.
The book was irradiated with light. Three hours later, the concentration of trichloroethane contained in the reaction solution was measured using a gas chromatograph. As a result, the concentration of trichloroethane was decomposed to 0 ppm.
Was decreasing.

Example 9 Ethanol and diethanolamine were added to titanium tetraisopropoxide to prepare a transparent sol solution, and a surface of a foam ceramic was coated with a titanium oxide film by a dip coating method. That is, the diameter 2c
m, foam ceramics 5cm in length (specific surface area 5m
² / g) was immersed in a sol solution, slowly raised, and then heated from room temperature to a temperature of 650 ° C. and calcined. As a result of examining the crystal structure of the obtained titanium oxide film by X-ray diffraction, it was found to be 100% anatase. This was placed in a beaker containing a 31% aqueous solution of hydrogen peroxide and sufficiently adsorbed. Using the obtained catalyst for water treatment, parathion, which is an organic phosphorus-based pesticide, was decomposed. 10pp
50 ml of an aqueous solution of parathion having a concentration of m was placed in a hard glass beaker, the obtained catalyst for water treatment was placed therein, and three 200 W high-pressure mercury lamps were irradiated from three sides. Two hours later, the amount of parathion contained in the reaction solution was measured using a liquid chromatograph.
Had become.

[0025]

As described above, the present invention has high performance and is easy to handle because it can easily and quickly treat and purify environmental pollutants such as organic compounds dissolved in water under mild conditions. The purpose of the present invention is to provide a catalyst for water treatment and an economical water purification method. The titanium oxide used in the present invention is also used in paints, cosmetics, toothpastes, etc.
It has many advantages such as excellent weather resistance and durability, and is non-toxic and safe. Therefore, the catalyst for water treatment according to the present invention, in which the porous body is coated with titanium oxide, has its defects improved even if the porous body of the base material is weak to water such as silica gel, and has water resistance, weather resistance, and durability. It shows excellent characteristics in properties and the like. And the water treatment catalyst according to the present invention, the electrons and holes generated in the titanium oxide film by receiving light from the outside such as an electric lamp or sunlight, the hydrogen peroxide that has been adsorbed,
Reacts with oxidants such as ozone and oxygen to generate reactive oxygen species with extremely high oxidation potential, and due to its strong oxidizing power, pollutes the environment such as organic solvents and pesticides dissolved in water. Organic compounds are decomposed, but since the photocatalyst is porous, even if the concentration of environmental pollutants is low, it can be quickly and effectively decomposed and removed by adsorption even when the concentration is low. In addition, platinum or rhodium, ruthenium, palladium, silver,
If copper, zinc or the like is coated, its catalytic action further increases the decomposition removal effect. In this case, since the photocatalyst is porous, the metal is well dispersed and covers the photocatalyst, so that the catalytic action of the metal can be particularly effectively brought out.

Further, the catalyst for water treatment according to the present invention can be applied to a wide range of uses such as not only wastewater treatment or purification of pools and stored water, but also effective prevention of propagation of bacteria and fungi. When a metal film such as platinum, rhodium, ruthenium, palladium, silver, copper, or zinc is coated on the titanium oxide film, the metal film has an antibacterial and antifungal effect due to its catalytic action. The propagation of the above germs and mold can be effectively prevented. The method for water treatment according to the present invention can be performed at low cost, energy saving and maintenance-free only by irradiating light, unlike hydrogen peroxide, ozone, and oxygen, which are simply added to a solution. Because it is adsorbed, less waste is consumed and it can be used effectively,
Great economic effect.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Eiji Watanabe 41st old stock of Zenta Nitta character, Sayacho, Kaifu-gun, Aichi prefecture (72) Inventor Kozo Iseda 4-1-1, Oyamada, Kuwana-shi, Mie (56) References JP-A-8-309202 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B01J 21/00-38/74 C02F 1/30-1/32 C02F 1/72- 1/78 JICST file (JOIS)

Claims (5)

(57) [Claims] 1. A method of oxidizing a porous body made of a porous material.
Step of forming a titanium film and adsorbing a specific oxidizing agent
Water treatment catalyst produced by the step of
A water treatment catalyst characterized in that the surface of a porous material is coated with a titanium oxide film and at least one oxidizing agent selected from hydrogen peroxide, ozone and pure oxygen is adsorbed. 2. The method according to claim 1, wherein the porous body is at least one selected from activated carbon, activated alumina, silica gel, zeolite, sintered clay, porous glass, foam ceramics, foam metal, and foam plastic. Item 7. The water treatment catalyst according to Item 1. 3. The catalyst for water treatment according to claim 1, wherein the crystal form of the titanium oxide film is anatase. 4. Use of the porous catalyst according to claim 1 to remove water.
A method of treating , the surface is covered with a titanium oxide film,
A water treatment method comprising: placing a porous body, which has adsorbed at least one oxidizing agent selected from hydrogen peroxide, ozone, and pure oxygen, in water to be treated, and irradiating the water with light. 5. A method for producing water using the porous catalyst according to claim 1.
A method of treating , the surface is covered with a titanium oxide film,
Water treatment characterized by placing a porous body adsorbing at least one oxidizing agent selected from hydrogen peroxide, ozone and pure oxygen in water to be treated, and irradiating light with stirring. Method.