JPH0576877A - Water treatment method - Google Patents

Abstract

PURPOSE:To provide an economical water treatment method capable of obtaining safe water by easily and rapidly treating agricultural chemicals, an org. solvent (especially, halocarbon) or a surfactant (especially having a side chain) hard to treat by a present activated sludge method under a mild condition corresponding to worldwise water pollution. CONSTITUTION:Water to be treated such as waste water is introduced into a container having a titanium oxide film applied to the inner surface thereof and hydrogen peroxide and an iron salt are added to the water to be treated and this water to be treated is irradiated with light such as solar rays under heating or non-heating or the water and hydrogen peroxide are introduced into a container having an iron ion added titanium oxide film applied to the inner surface thereof to be irradiated with light under heating or non-heating. By this method, the org. matter contained in the water to be treated is rapidly decomposed to be perfectly oxidized to carbon dioxide and water and purified water is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water treatment method such as tap water treatment or sewage treatment.

[0002]

2. Description of the Related Art In recent years, water pollution caused by domestic wastewater and industrial wastewater has become a global problem as one of global environmental problems. Even in Japan, where water resources are abundant, pollution of pesticides on golf courses, contamination of groundwater by organic solvents used in high-tech industries, and contamination of water sources by synthetic detergents (surfactants) have become major problems. Compared with this, it is said that the water quality of the water supply deteriorated and the water became poor. This is because a large amount of chlorine and disinfectants are used for water treatment due to pollution of water sources compared with the past, so that they remain or react with organic substances in raw water to form organic chlorine compounds, and lakes. The cause is algae, plankton, mold, etc. due to eutrophication.

A widely used water treatment method at present is an activated sludge method. This method decomposes the above-mentioned pesticides, organic solvents (especially halocarbons) and surfactants (especially those with side chains).・ It has the drawback of being difficult to remove and being powerless against them. Methods for treating such biologically difficult-to-decompose organic substances include activated carbon adsorption method, chemical oxidation method, and reverse osmosis method, but all of them have problems in terms of treatment effect and economical efficiency. There is. Chlorine and ozone are typical oxidizers used in the chemical oxidation method. However, chlorine has an oxidizing power, reactivity with ammonium ions, residual chlorine due to excessive injection, or chlorine in the water to be treated. There is a problem that it reacts with the contained organic substances to produce trihalomethane and organochlorine compounds that have carcinogenicity. In addition, ozone has the drawback that both equipment and operating costs are high (for example, Takamine Kitao, Ryosuke Yahashi, Water Treatment Technology, Vol.8, No.8, 35 (1976)).

The Fenton's reagent discovered by HJH Fenton in the 1890s is a hydrogen peroxide solution to which a ferrous salt is added and is known to have strong oxidizing power (HJH Fenton, J. Chem. Soc., Vol.65, 89
9 (1894)). Hydrogen peroxide has a great advantage in that the price per unit amount of available oxygen is considerably lower than that of ozone and expensive equipment is not required. However, research on Fenton treatment, which is a water treatment using Fenton's reagent, has been conducted until now, but in this method, the progress of the reaction is slow and the pH of the water to be treated must be high acidic conditions of 2 to 4, Had drawbacks such as. Further, in order to put the Fenton treatment into practical use, it was necessary to further reduce the treatment cost.

[0005]

SUMMARY OF THE INVENTION In view of the above points, the present invention addresses water pollution by treating pesticides and organic solvents (especially halocarbons) and surfactants (especially of side chains) that are difficult to treat by the activated sludge method. It is an object of the present invention to provide an economical water treatment method capable of easily and rapidly treating (e.g., the one attached) and mild water to obtain safe water.

[0006]

According to the present invention, the object of the invention is to put water to be treated such as waste water in a container coated with a titanium oxide film, and add hydrogen peroxide and iron salt to heat or not heat. It is achieved by irradiating light such as sunlight with, or by putting water to be treated and hydrogen peroxide in a container coated with an iron ion-added titanium oxide film inside and irradiating with or without heating. To be done.

The container used in the present invention may be made of any material such as concrete, glass, plastic, ceramics and metal as long as it has the required strength. The container used in the present invention may be transparent or opaque, but when the titanium oxide film coated on the inside of the container is colorless and transparent, the transparent container also allows light to pass through the wall from the outside. This is convenient because it can be incident on the titanium oxide film.

The container used in the present invention may have any shape such as a prismatic shape, a cylindrical shape, a spherical shape, a conical shape, a gourd shape or a rugby ball shape. Further, the container may be closed, may or may not have a lid, and may be in the shape of a circular tube or a rectangular tube so that the reaction liquid flows out.

The container coated with a titanium oxide film used in the present invention is prepared by a sol-gel method from a titanium alkoxide obtained by the reaction of titanium tetrachloride and alcohol, and is subjected to a dip coating method or a spin coating method. It may be manufactured by coating the inside of the container by a coating method or the like and then firing it, or by heating and oxidizing the inside of the container made of titanium with a gas flame or the like to form titanium oxide. Alternatively, it may be manufactured by coating the inside of the container with a suspension of ultrafine particles of titanium oxide by a dip coating method, a spin coating method, a coating method, or the like. The firing temperature at that time is most preferably about 500 ° C. Furthermore, by assembling a plate or titanium oxide plate coated with titanium oxide produced by the above method,
The container may be manufactured.

The water to be treated such as waste water is placed in the container thus obtained and coated with a titanium oxide film, and hydrogen peroxide and iron salts are added to the container to irradiate it with light such as sunlight. The contained organic matter is rapidly decomposed and completely oxidized into carbon dioxide gas and water. In the case of the Fenton's reagent, the ferrous salt must be added to the hydrogen peroxide solution, but in the method according to the present invention, not only the ferrous salt but also the ferric salt or the mixture of the ferrous salt and the ferric salt is used. Can be used. In this case, examples of the iron salt used include various salts such as a sulfate, a nitrate, a carbonate, an acetate, an ammonium salt, and a halide such as chloride and bromide, and a nitrate and a sulfate are particularly preferable. The iron salt used in the present invention may be an anhydrous salt or a hydrated salt. Iron salts such as ferric sulfate have the advantages of being inexpensive, harmless to the environment, and easy to handle.

The iron ions used in the present invention may be divalent ions or trivalent ions. The container used in the present invention, which is coated with an iron ion-added titanium oxide film on the inside, is obtained by the above-mentioned method, and the container coated with the titanium oxide film is a ferrous salt or ferric salt or those. It may be manufactured by immersing the mixture in an aqueous solution of the mixture and then drying. Further, iron salt or an aqueous solution thereof is added to a gel made by a sol-gel method from titanium alkoxide, and a dip coating method or a spin coating method,
It may be manufactured by coating on the inside of the container by a coating method or the like and then baking it, or by adding an iron salt or its aqueous solution to a suspension of ultrafine titanium oxide, dip coating method, spin coating method, coating It may be manufactured by coating the inside of the container by a method and then firing. The firing temperature at that time is most preferably about 500 ° C.

When water to be treated such as waste water is placed in a container obtained by coating the titanium oxide film to which iron ions have been added, the water to be treated is irradiated with light such as sunlight when hydrogen peroxide is added thereto. Organic substances contained in the treated water are rapidly decomposed and completely oxidized into carbon dioxide gas and water. In this case, iron ions are contained in the titanium oxide film, and hydrogen peroxide is finally converted into water, so that the treated water can be used as it is without any operation such as filtration.

Examples of light sources used in the present invention include the sun, incandescent lamps, fluorescent lamps, halogen lamps, xenon lamps, mercury lamps and UV lamps. The light to be irradiated may be light having a long wavelength such as visible light, but light including a large amount of light having a short wavelength such as ultraviolet light may be used to increase the treatment speed of water. The light irradiation is performed from the inside or the opening of the container in the case of an opaque container, and from the inside or the opening or the outside of the container in the case of a transparent container. At this time, the processing speed can be increased by heating at the same time as the irradiation of light, but the temperature is most preferably about 70 ° C.
Further, at that time, if stirring is performed, the processing speed can be further increased.

The addition amount of hydrogen peroxide used in the present invention is stoichiometrically determined from a reaction formula in which organic matter contained in water to be treated is mineralized into carbon dioxide gas or water. In the case of the Fenton treatment, since a large amount of hydrogen peroxide is lost by reaction in vain, a considerably excess amount of hydrogen peroxide is required, but in the method of the present invention using a titanium oxide film, the water to be treated is treated. Since the decomposition reaction of the organic substances contained in is efficiently performed, the amount of hydrogen peroxide added may be approximately stoichiometric. In order to further increase the reaction efficiency, a titanium oxide film doped with magnesium, niobium, titanium, iron or the like may be used, or a dye or a platinum film may be coated. Further, in the case of Fenton's reagent, the amount of ferrous salt added to the hydrogen peroxide solution is equimolar to the amount of hydrogen peroxide added, but in the method according to the present invention, the amount of iron salt added is considerably higher than that. It can be small. Since treated water such as waste water often already contains iron ions, it may not be necessary to add iron salts.

[0015]

EXAMPLES Among the examples of the present invention, particularly representative ones are shown below.

Example 1 An aqueous solution of diethylbenzylphosphonate, which is an organophosphorus pesticide, at a concentration of 5 mmol / l was placed in a Pyrex glass container having a titanium oxide film coated on the inside thereof.
While adding 2 mol / l hydrogen peroxide and 0.01 mol / l ferric nitrate, stirring with a magnetic stirrer,
The light of a 500 W xenon lamp was irradiated for 30 minutes. As a result of analyzing the TOC value of the obtained reaction solution using a total organic carbon meter, the TOC value of the reaction solution was reduced by 98%. When the Fenton's reagent was not used for light irradiation, the TOC value was reduced by only 40%. Other organophosphorus pesticides such as 4-nitrophenyl diethyl phosphate (paraoxon), diethyl-p-nitrophenyl thiophosphate (parathion), O, O-dimethyl-S-
Similar results were obtained with (1,2-dicarbetoxyethyl) phosphorodithioate (malathion).

Example 2 Pyrex glass having a titanium oxide film coated on the inside thereof with an aqueous solution of alkylbenzene sulfonic acid having a concentration of 70 ppm, which is a general concentration of a detergent (alkylbenzene sulfonic acid) contained in a cleaning waste liquid discharged from a cleaning company. The mixture was placed in a container, 110 ppm of hydrogen peroxide and 720 ppm of ferric sulfate were added, and sunlight was irradiated for 20 minutes while stirring with a magnetic stirrer. The TOC value (Total Organic Carbon) of the obtained reaction solution was analyzed using a total organic carbon meter, and the concentration of alkylbenzenesulfonic acid was analyzed by the methylene blue method. As a result, the concentration of alkylbenzene sulfonic acid in the reaction solution was 10
It was reduced to ppm and the TOC value was also reduced by 90%.

Example 3 A quartz glass circular tube coated with a titanium oxide film on the inside was dipped in a 10% ferrous ammonium sulfate solution and dried, and then, the content thereof was 2,4-dimethyl as a raw material for dye. While slowly flowing down a solution of aniline having a concentration of 5 mmol / l and 0.2 mol / l of hydrogen peroxide at 50 ° C., 500 W of a xenon lamp was irradiated from the outside. As a result of analyzing the TOC value of the obtained reaction solution using a total organic carbon meter, the TOC value of the reaction solution was reduced by 90%.

Example 4 A 1% solution of disodium ethylenediaminetetraacetate, which is difficult to treat with activated sludge, was placed in an alumina container whose inside was coated with a titanium oxide film containing ferrous nitrate. Was added, and with stirring, the light of a 500 W xenon lamp in which light having a wavelength shorter than 435 nm was removed by a cut filter was irradiated from above for 1 hour. The TOC value of the obtained reaction solution was analyzed by using a total organic carbon meter, and the COD value (chemical oxygen demand) was analyzed by a COD measuring device. As a result, the TOC value of the reaction solution was 85%, and the COD value was Also 95
% Had been reduced.

Example 5 A Pyrex glass container coated with a titanium oxide film on the inside was placed in a 2 g / l aqueous solution of potassium chloroplatinate in ethanol and stirred with a magnetic stirrer for 10 minutes.
The surface of the titanium oxide film was coated with platinum by irradiating it with light from a 0 W mercury lamp for 4 hours. An aqueous solution of chloroform, which is a type of trihalomethane, having a concentration of 100 ppm was placed in this container, 30 ppm of hydrogen peroxide and 20 ppm of ferric sulfate were added, and sunlight was irradiated for 15 minutes while stirring with a magnetic stirrer. TOC of the obtained reaction solution
As a result of analyzing the values using a total organic carbon meter, the TO
The C value was reduced by 95%.

[0021]

INDUSTRIAL APPLICABILITY As described above, the present invention copes with global water pollution, and pesticides and organic solvents (especially halocarbons) that are difficult to treat by the activated sludge method, and surfactants (especially those with side chains). The present invention provides an economical water treatment method capable of easily and quickly treating water) under mild conditions.
Put water to be treated such as waste water in a container coated with titanium oxide film inside, add hydrogen peroxide and iron salt and irradiate light such as sunlight with or without heating, or add iron ion Treated water and hydrogen peroxide are placed in a container coated with a titanium oxide film inside and irradiated with light with or without heating to quickly remove organic substances contained in the treated water such as carbon dioxide gas and water. It can be decomposed into water and purified water can be obtained. At present, water purification plants usually use chlorine to remove ammoniacal nitrogen contained in raw water.However, it reacts with organic substances contained in raw water to produce carcinogenic trihalomethanes and organochlorine compounds. Therefore, it is a big problem. In the method of the present invention,
The ammonia nitrogen contained in the raw water becomes nitrogen gas and scatters, so it is not necessary to add chlorine. Therefore, highly safe water containing no carcinogenic trihalomethane or organochlorine compound produced by the reaction of chlorine with the organic matter contained in the raw water can be obtained. The effect is large even if the water treatment process according to the present invention is carried out to decompose the hardly decomposable substance, and subsequently the water treatment by the activated sludge method is carried out.

Claims (3)

[Claims] 1. A water treatment method comprising irradiating light with water to be treated, hydrogen peroxide and iron salt being placed in a container having a titanium oxide film coated inside. 2. A water treatment method characterized in that water to be treated and hydrogen peroxide are placed in a container whose inside is coated with a titanium oxide film to which iron ions have been added, and the container is irradiated with light. 3. The water treatment method according to claim 1 or 2, wherein heating is performed at the same time as irradiation with light.