JPS60118289A - Water purifying method - Google Patents

Abstract

PURPOSE:To efficiently decompose and remove the pollution substance in waste water, by irradiating water to be treated containing the pollution substance with ultraviolet rays in the presence of a photo-oxidation catalyst, which is obtained by baking an inorg. material molded body having organotitanate adhered thereto. CONSTITUTION:A flat plate shaped photo-oxidation catalyst molded body 2 coated with titanium oxide or titanium oxide supporting platinum is put in a reaction tank 3 and a light source 1 is arranged above said tank 3. The light source 1 emits light with a wavelength of about 420nm or less. For example, a high pressure mercury lamp, a low pressure mercury lamp or a black lamp is used. Water to be treated enters the reaction tank 3 from a water introducing port 6 by a pump 7 and air or oxygen is introduced into said tank 3 by an air diffusing tank 4 while water to be treated is irradiated with the light source 1 to oxidize impurities therein in the presence of the photo-oxidation catalyst and discharged from a discharge port 5 as treated water. If necessary, waste water is reciaculated to the reaction tank 3 by the pump 7.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention decomposes and removes pollutants contained in water to be treated by irradiating them with ultraviolet rays in the presence of dissolved oxygen and a photo-oxidation catalyst. Concerning water purification methods.

The substances targeted for decomposition and removal according to the present invention are organic components dissolved in water and are usually expressed as CODCr (Chemical Oxygen Demand) values.

Traditionally, based on wastewater regulations (for sewage treatment and wastewater reuse),
Coagulation-sedimentation methods, biological treatment methods, etc. are popular, but more advanced purification technology is being sought. Removal of soluble organic matter is one of the most difficult targets to undergo advanced purification treatment. Conventionally, removal methods such as activated carbon adsorption, membrane permeation, and ozone oxidation have been used, but recently, photo-oxidation has been used to remove soluble organic matter. Removal methods are also being developed.

The activated carbon adsorption method is the most common and widely used method, but when the molecular weight of soluble organic matter is 100 to 10.00,
If it is around 0, there is no practical problem, but the adsorption capacity is small for relatively low-molecular saturated compounds and high-molecular compounds such as humic acid, and a large amount of activated carbon is required to completely remove them. If this becomes necessary and it is actually attempted to implement it, it will be extremely expensive and uneconomical. Although the membrane permeation method is an excellent treatment method with low energy consumption, it is difficult to remove hydrophilic low-molecular compounds such as alcohol, and it may clog the permeable membrane and cause deterioration of the membrane due to microbial growth, or the loss of membrane components. It has problems such as elution. Since the ozone oxidation method does not completely oxidize soluble organic matter to carbon dioxide gas and water, additional treatment is required. No-Rhoden-based oxidizing agent-1 For example, the photo-oxidation method that uses sodium hypochlorite in combination produces trihalomethane, which is said to be carcinogenic, and at the same time results in an increase in chlorine ions, sodium ions, etc. in the treated water. Undesirable. Recently, a method using a photo-oxidation catalyst has been developed as a new method for removing dyed substances without the above-mentioned drawbacks. This photo-oxidation method uses a photo-oxidation catalyst consisting of titanium oxide particles or titanium oxide particles supporting platinum group metals in the presence of sufficient dissolved oxygen to decompose and remove pollutants contained in the water to be treated. This is done by contact water passage while irradiating ultraviolet rays.

In the photo-oxidation method for removing pollutants, holes and electrons are generated on the surface of a photo-oxidation catalyst using light energy, and the reaction between the holes and electrons generates hydrogizol radicals and spar, which are rich in oxidizing ability. Because Oxide (0?) utilizes the reaction that oxidizes pollutants, the pollutants are oxidized and decomposed into harmless carbon dioxide without adding an oxidizing agent to oxidize and decompose pollutants as in conventional methods. It can be converted into gas or water. The catalyst used is insoluble in water because it is composed of titanium oxide and platinum group metal.
Unlike conventional oxidation methods, the water to be treated containing dissolved oxygen is irradiated with ultraviolet rays without leaving any decomposition products of the oxidizing agent.
Contaminants can be removed simply by contacting with photo-oxidation catalyst particles. Therefore, it is an extremely advantageous method for purifying water. For this reason, several water purification methods using photo-oxidation catalysts have been proposed, but the photo-oxidation catalyst used in the proposed methods is in the form of powder. This is to reduce the rate of recombination of electrons and holes generated by ultraviolet irradiation on the surface of the photo-oxidation catalyst as described above. This is because by turning the photooxidation catalyst into powder, the oxidation efficiency of organic matter is greatly increased.

Therefore, it can be said that the finer the powder of the photo-oxidation catalyst used, the better the oxidation efficiency.

However, when titanium oxide powder is used to purify water by the conventional method, there are problems in separating the water and the photo-oxidation catalyst after purifying the water, and separation and recovery are difficult. Titanium oxide and platinum group metals are expensive, and recovery and reuse of the catalyst is essential for economical water purification. However, if the photooxidation catalyst is a powder, it is impossible to completely recover and reuse it.
It was recognized that reuse was impossible and would be a major practical difficulty.

The present invention has been made in view of the above, and provides a method for removing pollutants by irradiating wastewater containing pollutants with ultraviolet rays in the presence of sufficient dissolved oxygen using a photo-oxidation catalyst. The purpose of the present invention is to provide a water purification method that does not require separation and recovery of the photo-oxidation catalyst after use.

The water purification method according to the present invention will be explained below. When using titanium oxide as a catalyst, it is possible to form the titanium oxide into a compact in order to avoid the disadvantages of being a powder, but since titanium oxide does not easily cause sintering between particles at low temperatures, it cannot be It is difficult to obtain a molded body with mechanical strength, and on the other hand, if sintered at a high temperature, a molded body with mechanical strength can be obtained, but effective photocatalytic activity cannot be obtained. The present inventors conducted extensive research to overcome the drawbacks of titanium oxide photooxidation catalysts, and as a result, titanium oxide was firmly attached to the surface of a molded product made of an inorganic material using the method described below, and the result was a high photocatalytic activity. It was discovered that a molded body could be obtained, and it was confirmed that pollutants in wastewater can be efficiently removed by using this photooxidation catalyst.

! 1-The material is mainly one selected from glass, alumina, silica, titanium oxide, mullite, and cordierite, and these are used alone or as a mixture, and a small amount of binder is added, then molded and sintered. and form a molded body. “The molded body has a flat plate and two cylindrical shapes.

Choose any shape such as cylindrical, and make it porous or have an uneven surface so that the surface area of the light irradiation area is large, and the shape is compatible with the equipment used and allows for efficient use of the light irradiation area. It is preferable that In addition to the above-mentioned inorganic materials, pottery made of feldspar, clay, etc., unglazed diaphragms for electrolysis, earthenware such as roof glass, and pottery such as bricks and tiles can also be used if organic titanates are attached to them.

The photooxidation catalyst can be obtained by attaching an organic titanate to the surface of the above-mentioned inorganic material molding, treating it under certain firing conditions to form titanium oxide, and further supporting a platinum group metal if necessary. Next, the manufacturing method will be explained in detail. The organic titanates that are attached to the surface of inorganic materials are alkyl titanates and allyl titanates.

Among titanium anlate and titanium chelate, one or more selected from these are used as a mixture. These titanates include methanol, ethanol, propatool, butanol, benzene, toluene,
Hexane, tetramerized carbon J.

It is dissolved in a diluent such as methyl chloroform or acetic acid to form a solution, and when a titanium chelate such as dihydroxybis(lactato)titanium monoammonium salt is used, water is used as a diluent to form an aqueous solution and the solution is applied to the surface of the molded article. The method of adhesion is to immerse the molded body in an organic titanate solution and take it out, or to apply the organic titanate solution with a brush or the like.

Alternatively, a method such as spraying can be used. The inorganic material molded body with a deposited amount of organic titanate is 100
After drying at C to 110C, the firing temperature is in the range of 350C to 700C, preferably 400C to 5C in an oxidizing gas atmosphere.
Firing treatment is performed in the range of 00C. As a result, the organic titanate is oxidatively decomposed and a molded body covered with titanium oxide having high photooxidation catalytic activity is obtained. Titanium oxide with photooxidation catalytic activity begins to be obtained at a firing temperature of 350C.

At high temperatures of 700C or higher, photooxidation catalyst activity is lost.

In addition, if the amount of organic titanate coated on the surface of the inorganic material is large, cracks may occur during the drying or firing process and there is a risk of peeling from the surface of the molded product. In other words, by repeating the organic titanate coating-drying-baking process as many times as necessary, the desired thickness of the titanium oxide film can be obtained. Although the titanium oxide-attached molded product obtained in and can be used satisfactorily as a photo-oxidation catalyst molded product for water purification, even more efficient photo-oxidation catalyst molding can be achieved by supporting platinum group metals on the surface of this titanium oxide. You get a body. As the supported metal, one selected from platinum, palladium, rhodium, ruthenium, etc. or a mixture of two or more thereof can be used. A method for supporting these metals on a molded body to which titanium oxide is attached is to immerse the molded body in an aqueous solution containing these metals in the form of a water-soluble inorganic compound and irradiate the metal with ultraviolet rays. This is carried out by a method of supporting the metal, or a method of adding a reducing agent to support the metal.

The main purpose of supporting metal is to prevent recombination of electrons and holes generated on the surface of titanium oxide by ultraviolet irradiation. The smaller the coverage ratio of metal to the light irradiation area and the larger the number of metal spots per unit light irradiation area, the higher the photooxidation catalyst activity. Therefore, the amount and state of the metal deposited are controlled and the metal is supported. The amount of gold fan is 0.01 wt 4-1 wt% relative to titanium oxide
It is.

The figure is a diagram explaining the basic concept of a water purification device using the photo-oxidation catalyst of the present invention.

A reaction tank 3 has a flat photooxidation catalyst molded body 2 coated with titanium oxide or platinum-supported titanium oxide, and a light source 1 is installed above it. The light source may be a high-pressure mercury lamp, a low-pressure mercury lamp, a black lamp, a xenon lamp, etc. that emit light with a wavelength of about 420 parts m or less, and sunlight can also be used as a light source. When using the light source in a immersed state, insert it into a quartz tube to protect the light source. When using a high-pressure mercury lamp, Pyrex glass can also be used. The water to be treated enters the reaction tank 3 through the inlet 6 by the pump 7, air or oxygen is introduced through the aeration pipe 4, is irradiated by the light source 1, impurities are oxidized by the photo-oxidation catalyst, and the water is discharged as treated water through the drain port 5. be discharged. If necessary, the waste water is circulated to the reaction tank 3 again by Bonschiff.

According to this method of water purification, titanium oxide is not in powder form, so there is no need to separate or recover it, and because it is firmly attached to the molded object, it will not fall off even after long-term use. Since it maintains a highly active oxidizing ability, it is possible to efficiently treat contaminated water, and if a light source containing ultraviolet light is used as the irradiation light, it can also sterilize mold, bacteria, viruses, etc. at the same time, so the effect is Extremely large.

Examples are shown below.

Example 1 A 5×5 crn glass plate was immersed in a mixed solution consisting of 10 parts of di-inzoloboxy, bis(acetylacetonata) titanium, 90 parts of inpropyl alcohol, and 200 parts of methanol, then taken out and dried at 110C for 30 minutes. A glass plate coated with titanium oxide was obtained by firing at 500C for 30 minutes in an oxygen atmosphere. After immersing it in an aqueous palladium nitrate solution, ascorbic acid was added as a reducing agent and a heating treatment was performed to support palladium.

The photooxidation catalyst thus obtained was placed in a reaction tank together with 100 ml of dextran solution ((,'0Dcr concentration 5omp,'z), and after oxygen was blown in, it was irradiated with a 100W high-pressure mercury lamp for 12 hours. As a result, C0Dcr
The concentration was 14 mg/l.

Example 2 A porous cylindrical body (trade name: Kerami Tsuilter) made of alumina coated with glass and having a diameter of 4.3 cm, a thickness of 4 mm, and a length of 20.0 ffl was injected with inpropyl titanate 30 to 1 (in-propyl titanate). Zorobil alcohol 1
A molded body coated with titanium oxide was obtained by immersing it in a mixed solution consisting of 30 parts and 1 part of acetic acid, taking it out, drying it at 110C for 1 hour, and firing it at 400C in an air atmosphere for 5 hours. . After that, ultrasonic cleaning was performed to remove titanium oxide with weak adhesion strength, and then in an aqueous solution containing acetic acid, sodium acetate, and chloroplatinic acid.
While the titanium oxide-coated molded body was immersed, it was irradiated from inside using a 100 W high-pressure mercury lamp to support platinum.

The thus obtained photo-oxidation catalyst molded body was again subjected to ultrasonic cleaning, and then 500w of dextran solution (cut
) cr43my/l) and irradiated with a 100W high-pressure mercury lamp for 6 hours while blowing air. As a result, the C0Dcr concentration decreased to 7 rn9/l. At this time, generation of carbon dioxide gas was also observed.

Example 3 Using the photo-oxidation catalyst molded body used in Example 2, 500 m of an aqueous solution containing various organic substances was irradiated with light using a 6W ultraviolet germicidal lamp after air was blown into a reaction tank. The results are shown in the table below.

Hata Kao Soap Co., Ltd. kitchen detergent [trade name Cerina] Example 4 Diameter 4 made of mullite (2Az2o3・5Si02)
．． 0crnl 20 parts of hydroxytitanium stearate and 10 parts of phenyl titanate were prepared into a circular molded body having a thickness of 5 m.

The body was immersed in a mixed solution consisting of 130 parts of toluene, then taken out and dried at 110C for 1 hour, and then dried at 500C in an air atmosphere.
A molded body coated with titanium oxide was obtained by firing for 1 hour. Using this molded body as a photo-oxidation catalyst, 100 mJ of dextran solution (COpcr40mf//
1,) into a reaction tank, and while blowing air
The sample was irradiated with a 00W high-pressure mercury lamp for 15 hours.

As a result, the C0Dcr concentration decreased to 20 m9/l.

[Brief explanation of the drawing]

The drawing is an explanatory diagram of the basic concept of the water purification device using the photo-oxidation catalyst of the present invention. l... light source, 2... photo-oxidation catalyst, 3... reaction tank,
4... Diffuser pipe, 5... Drain port, 6... Inlet port, 7
···pump. Patent Applicant Giken Kogyo Co., Ltd. Representative Patent Attorney Takuya Hadano

Claims (1)

[Claims] 8. Water to be treated containing pollutants in the presence of a photo-oxidation catalyst,
In the method of oxidizing and removing contaminants by irradiating ultraviolet rays or light containing ultraviolet rays, organic titanate is attached to the surface of a molded object made of an inorganic material, and then titanium oxide is formed on the surface of the molded object by firing treatment. or further, a method for purifying water, characterized in that pollutants are oxidized and removed using a photo-oxidation catalyst obtained by supporting a platinum group metal on titanium oxide. K. The organic titanate is an alkyl titanate. The water purification method according to claim 1, wherein the water purification method is one or a mixture of two or more selected from among rutitanate, titanium acylate, and titanium chelate. 3. The firing process is performed in an oxidizing gas atmosphere at a firing temperature of 3.
The water purification method according to claim 1, which is carried out at a temperature in the range of 50C to 700C. Ge, the platinum group metal is one or two selected from platinum, palladium, rhodium, and ruthenium.
The method for purifying water according to claim 1, which is a mixture of more than one species. The molded body made of the inorganic material is glass, alumina,
The first claim is a molded body made of one selected from silica, titanium oxide, mullite, and cordierite, either singly or as a mixture, molded and sintered with the addition of a small amount of binder. Water purification method described in section.