JP2002001335A - Pollutant decomposition apparatus and method - Google Patents

Abstract

(57) [Problem] To provide a simpler and more efficient method for decomposing pollutants and a contaminant decomposer used for the method. SOLUTION: A reaction vessel provided with a pair of electrodes and a power supply for applying a potential to the electrodes, means for supplying water having an electrolyte dissolved therein, and a solution containing a contaminant to be purified in the reaction vessel. Means for supplying, a means for aerating a solution obtained by electrolyzing a mixed solution of water containing the electrolyte in the reaction vessel and the contaminant, and a means for irradiating the reaction vessel with light. Pollutant decomposition equipment. Further, a step of supplying water in which an electrolyte is dissolved to a reaction vessel, a step of supplying a solution containing a contaminant to be purified to the reaction vessel, and a mixed solution of water containing the electrolyte and a solution containing the contaminant A method for decomposing contaminants, comprising: a step of electrolyzing; a step of aerating an electrolytic solution in the reaction vessel; and a step of irradiating the reaction vessel with light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for decomposing pollutants (particularly, organic chlorine compounds and the like) and a pollutant decomposer used for the method.

In particular, the present invention relates to the purification of groundwater containing pollutants such as organic chlorine compounds, the removal of desorbed water generated in the activated carbon regeneration step, and the like, and the purification of desorbed water.

[0003]

2. Description of the Related Art With the development of industrial technology to date, organochlorine compounds (eg, chlorinated ethylene, chlorinated methane, etc.) have been used enormously, and disposal thereof has become a serious problem. In addition, there is an environmental problem that these used pollutants pollute the natural environment, and great efforts have been made to solve the problem.

As a method for treating these, for example, there is a method in which chlorinated ethylene is decomposed using an oxidizing agent or a catalyst, and specifically, a method in which ozone is decomposed by using ozone (JP-A-3-38).
297) and a method of irradiating ultraviolet rays in the presence of hydrogen peroxide (Japanese Patent Application Laid-Open No. 63-218293). A method is also known in which a photocatalyst composed of oxide semiconductor fine particles such as titanium oxide and liquid chlorinated ethylene are suspended under alkaline conditions and decomposed by light irradiation.
(JP-A-7-144137).

[0005] In addition to the above, a photolysis method of irradiating ultraviolet rays in a gas phase without using an oxidizing agent has already been attempted. For example, a method in which an exhaust gas containing an organic halogen compound is subjected to ultraviolet irradiation treatment to make it into an acidic decomposition gas, and then washed with alkali to render it harmless (Japanese Patent Laid-Open No. 62-191 025), containing an organic halogen compound Equipment that aeration-processes wastewater, irradiates the discharged gas with ultraviolet light, and then performs alkali cleaning.
(Japanese Patent Application Laid-Open No. 62-190195) and the like have been proposed. Decomposition of chlorinated ethylene by iron powder is also known (Japanese Patent Laid-Open No. 8-257570), and in this case, it is presumed that probably reductive decomposition has occurred. In addition, tetrachloroethylene (hereinafter referred to as P
For the decomposition of CE (abbreviated as CE), reductive decomposition has also been reported.

In addition, trichlorethylene (hereinafter, TCE)
It is known that chlorinated aliphatic hydrocarbons such as PCE and chlorinated aliphatic hydrocarbons are aerobically or anaerobically decomposed by microorganisms. Attempted.

[0007]

As described above, various methods for decomposing organic chlorine compounds have been proposed. However, according to the study of the present inventors, a complicated apparatus for decomposition is required. And the need for high energy, which led to the conclusion that more environmentally friendly technology for decomposing pollutants (such as organic chlorine compounds) was needed.

[0008] That is, the object of the present invention is simpler,
It is an object of the present invention to provide a more efficient method for decomposing pollutants and a contaminant decomposer used for the method.

[0009]

According to the present invention, there is provided a contaminant decomposition apparatus according to the present invention, comprising: a reaction vessel having a pair of electrodes and a power supply for applying a potential to the electrodes; and dissolving an electrolyte in the reaction vessel. Means for supplying purified water to the reaction vessel, means for supplying a solution containing a contaminant to be purified, and electrolysis of a mixed solution of water containing the electrolyte and the solution containing the contaminant in the reaction vessel. A contaminant decomposition apparatus comprising: means for aerating a solution; and means for irradiating the reaction vessel with light.

In particular, the electrolyte is a chloride, preferably sodium chloride or potassium chloride, a contaminant decomposer for generating chlorine by electrolysis, and a part or all of the aerated gas is supplied to the reaction vessel. A contaminant decomposer having a means for returning the gas, and a contaminant decomposer having means for irradiating a part or all of the aerated gas with light.

In the method for decomposing contaminants according to the present invention, a step of supplying water having an electrolyte dissolved therein to a reaction vessel, a step of supplying a solution containing a contaminant to be purified to the reaction vessel, and a step of dissolving the electrolyte A step of electrolyzing a mixed solution of water and a solution containing the contaminant, a step of aerating the electrolytic solution in the reaction vessel, and a step of irradiating the reaction vessel with light. It is.

In particular, the electrolyte is a chloride, preferably sodium chloride or potassium chloride, a contaminant decomposer for generating chlorine in a step of electrolyzing the mixed solution, and a part or a portion of the aerated gas. A method for decomposing contaminants having a step of returning the whole to the reaction vessel,
Furthermore, this is a method for decomposing contaminants, which comprises a step of irradiating a part or all of the aerated gas with light.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The operation of the apparatus and method of the present invention is as follows.

In the method and apparatus for decomposing contaminants of the present invention, a solution containing contaminants is supplied together with an electrolyte to a container having a pair of electrodes. Electrolysis is performed in the container, and water containing chlorine is generated near the anode. By aeration and aeration of the water containing the contaminant and chlorine, the contaminant is diffused from the solution, and part of the chlorine is also transferred to the gas phase. When light irradiation is performed on a mixed gas of a pollutant and chlorine, the pollutant is decomposed. The contaminants are sequentially transferred to the gas phase by ventilation, and chlorine is continuously generated by continuing the electrolysis, so that the contaminants are completely decomposed and removed.

Although the details of the decomposition process are not clear, for example, the contaminated water generated near the anode by electrolysis of the contaminated water containing an electrolyte such as sodium chloride contains hypochlorous acid or hypochlorite ions. It is considered that water containing chloric acid or hypochlorous acid is acidic, and the abundance ratio of chlorine increases. By venting this solution, volatile contaminants and chlorine move into the gas phase. It is considered that chlorine radicals are probably induced by irradiating the gaseous mixture with light, and the decomposition reaction of pollutants proceeds. Therefore, it is presumed that most of the decomposition proceeds in the gas phase rather than the liquid phase.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

By placing a pair of electrodes in contaminated water containing an electrolyte and applying an electric potential between them, the above-mentioned solution containing chlorine can be generated in the vicinity of the anode. Figure 1
Generates gas containing chlorine gas by letting air flow through the solution generated near the anode by electrolysis of contaminated water,
At the same time, an outline of an apparatus configuration for transferring a contaminant from the contaminated water to the gas and decomposing the gas in the gas is shown. Here, 1 is a reaction vessel, and the lower part also serves as a water tank for electrolysis. The water tank has an anode 2 and a cathode 3, a power supply 4 connected to the electrodes, a pipe 5 and a pump 6 for supplying water containing an electrolyte into the water tank, and a contaminated water containing a substance to be decomposed. A pipe 7 and a pump 8, a pipe 9 for supplying gas to be ventilated into the water tank, and a pump 10 are provided, and the vented gas is returned again to be used for venting contaminated water. When power is supplied from the power supply 4 to the electrodes 2 and 3 for electrolysis, electrolyzed water containing contaminants is generated on the anode 2 side. When gas for aeration is continuously supplied at a desired flow rate from the pipe 9 to the anode 2 side of the water tank section of the reaction vessel 1, the gas containing chlorine and the pollutants in the contaminated water are discharged into the gas phase section of the reaction vessel 1. You. Then, the mixed gas is irradiated with the light of the black light fluorescent lamp 11 inside the reaction vessel 1 to cause a decomposition reaction, thereby purifying the contaminated water. The purified contaminated water is discharged from the discharge pipe 12.

FIG. 2 shows an embodiment in which a diaphragm 13 is provided between the electrodes. As the diaphragm, for example, the electrolyte solution on the anode 2 side and the cathode 3 side is not moved to the opposite sides, respectively, and the cathode of the cations (for example, Na ⁺ , Ca ²⁺ , Mg ²⁺ , K ⁺ ) existing on the anode side is used. An ion exchange membrane that allows irreversible transfer to the anode side and allows irreversible transfer of anions (eg, Cl ⁻ , SO ₄ ²⁻ , HCO ₃ ⁻ etc.) existing on the cathode side to the anode side. It is preferably used. That is, chlorine can be efficiently generated by using an ion exchange membrane. In this case, contaminated water containing an electrolyte is supplied to the anode side of the water tank, and a solution containing the electrolyte is supplied to the cathode side, and contaminated water is not supplied.

(Electrolysis Conditions and Chlorine Concentration of Gas Generated by Aeration) As a condition for performing electrolysis in the reaction vessel, when a diaphragm is not used, the chlorine concentration is 10 mg / L or more and 100 mg / L or more.
It is desirable that the pH be such that electrolysis water having a pH of 3 to 8 is produced. When a diaphragm is used, for example, a hydrogen ion concentration (pH value) of 1 to 4 and a chlorine concentration of It is preferable that water having a property of 5 mg / L or more and 150 mg / L or less be generated.

The above contaminants are ventilated, and the concentration of chlorine gas generated therefrom is 5 ppm or more.
It is preferable to adjust the concentration to be 000 ppm or less, and particularly, to adjust the chlorine gas concentration in the mixed gas from 20 ppm to 500 ppm.
It is advisable to control the air flow so as to be between 80 ppm and 300 ppm.

As means for obtaining electrolyzed water as the water containing chlorine, commercially available strongly acidic electrolyzed water generators (for example, trade name: Oasis Bio Half; Asahi Glass Engineering Co., Ltd.)
Company name, strong electrolyzed water generator (Model FW-200; manufactured by Amano Corporation) can be used.

(Light Irradiation Means) The light irradiation means that can be used in the present invention is, for example, a wavelength of 300 to 500 nm.
Is preferable, and the wavelength is more preferably 350 to 450 nm. The light irradiation intensity on the functional aqueous solution and the decomposition target is 10 μW / cm ^{2 to} 10 mW / cm ^2.
By weight, more and more preferably, ^{50μW / cm 2 ~5mW / cm 2} . For example, in a light source having a peak near a wavelength of 360 nm, practically sufficient decomposition proceeds at an intensity of several hundred μW / cm ² (measured between 300 nm to 400 nm).

In the present invention, 250n which has a great effect on the human body
There is no need to use ultraviolet light having a wavelength around m or less. This means that 300 modules
This means that an expensive material such as quartz that transmits light of nm or less is not required, and inexpensive glass or plastic can be used.

As a light source of such light, natural light is used.
(Eg, sunlight) or artificial light (mercury lamp, black light, color fluorescent lamp, etc.) can be used.

(Pollutants to be Decomposed) Examples of the pollutants to be decomposed include chlorinated ethylene and chlorinated methane. Specifically, as the chlorinated ethylene, 1 to 4 chlorine-substituted products of ethylene, that is, chloroethylene, dichloroethylene (DCE), trichloroethylene
(TCE) and tetrachloroethylene (PCE). Further, examples of dichloroethylene include 1,1-dichloroethylene (vinylidene chloride), cis-1,2-dichloroethylene, and trans-1,2-dichloroethylene. Examples of the chlorinated methane include chlorine-substituted methanes such as chloromethane, dichloromethane, and trichloromethane.

There is no particular limitation on the contaminants containing the organochlorine compound to be decomposed, and the present invention can be applied to the purification of drainage and groundwater from a coating plant or a dry cleaning plant. Activated carbon is used to remove gas generated during air stripping and contaminants contained in vacuum extracted gas from contaminated soil. The present invention can be used for purification of desorbed water generated at the time of carrying out.

The processing temperature is not particularly limited, but is between 4 ° C. and 50 ° C.
° C, preferably 10 ° C to 40 ° C.

The decomposition may be performed by continuous aeration while electrolysis is performed, or the aeration may be performed continuously by performing electrolysis intermittently. In addition, decomposition of a flow system that continuously supplies contaminated water may be performed, or treatment may be performed in a batch form.

The proportion of gas in the reaction tank and the mixed solution that is the subject of electrolysis and the supply source of chlorine gas should be large in the gas part, and the volume of the gas part in the reaction tank should be 50% of the reaction tank volume. 90%, especially 60% to 80% is desirable.

[0030]

[Example 1] A strong electrolyzed water generator (Model FW) in which a diaphragm between an anode and a cathode was removed as a water tank portion of a reaction vessel 1 was used.
-200; manufactured by Amano Co., Ltd.). The pH and oxidation-reduction potential of the acidic functional water obtained on the anode side were measured by changing the electrolyte concentration of the water to be electrolyzed in various ways (Toko Chemical Laboratory, TCX-9).
0i and KP900-2N) and conductivity meter (Co., Ltd.)
(Toko Chemical Research Laboratory, TCX-90i and KM900-2N)
And the chlorine concentration was measured with chlorine test paper (Advantech). As a result, depending on the concentration of sodium chloride as an electrolyte (standard concentration is 1000 mg / L), electrolysis current value, electrolysis time, etc., the pH of this functional water is 4.0 to 10.0, the oxidation-reduction potential is 300 mV to 800 mV, and the chlorine concentration is 2 mg. / L ~ 70mg /
Changed to L.

Therefore, in this embodiment, the operation is performed under the condition that functional water having a pH of 7.9, an oxidation-reduction potential of 570 mV, and a residual chlorine concentration of 15 mg / L is generated. During operation, ventilation is performed on the anode side as shown in FIG. The chlorine concentration of the gas from the gas was 50 to 200 ppm when measured with a detector tube.

A 100 mg / L trichloroethylene (TCE) solution was prepared as contaminated water, and salt was added to the final concentration of 0.1 mg / L.
It was added to 1% and supplied into the reaction vessel. While operating the present apparatus under the conditions described above, the inside of the reaction vessel was irradiated with a black light fluorescent lamp 4 (trade name: FL10BLB; manufactured by Toshiba Corporation, 10 W). The aerated air was circulated to continuously perform aeration. After running for 1 hour, the concentration of trichlorethylene in the solution was measured.99.
It turned out that it decomposed more than 5%. When pH and residual chlorine were operated under different conditions to evaluate the decomposition, a decrease in the concentration was observed in each case. From this, it was found that TCE can be decomposed by irradiating the mixed gas obtained by ventilating and aerating the above device with light. It was also confirmed that TCE could be decomposed for different light intensities.

[Example 2] Strong acid functional water generator (trade name:
Strong electrolyzed water generator (Model FW-200; manufactured by Amano Corporation)
An experiment was conducted in substantially the same manner as in Example 1 except that a mold having a diaphragm between the anode and the cathode was used.
This device is operated by varying the electrolyte concentration of the water to be electrolyzed and the electrolysis time, and as a result, acidic functional water obtained on the anode side.
The pH and oxidation-reduction potential were measured with a pH meter (Toko Chemical Laboratories, TCX-90i and KP900-2N) and a conductivity meter (Toko Chemical Laboratories, TCX-90i and KM900-2N). The concentration was measured with chlorine test paper (Advantech). As a result, the pH of this functional water is 1.0 to 1.0 depending on the concentration of sodium chloride as an electrolyte (standard concentration is 1000 mg / L), electrolytic current value, and electrolytic time.
4.0, the oxidation-reduction potential changed from 800 mV to 1500 mV, and the chlorine concentration changed from 5 mg / L to 150 mg / L. Therefore, in this embodiment, the pH is 2.1, the oxidation-reduction potential is 1150 mV, and the residual chlorine concentration is
The system was operated under the condition that 64 mg / L of functional water was generated. During operation, as shown in FIG. 2, ventilation was performed on the anode side, and the chlorine concentration of the gas from the anode side was measured with a detector tube.
It was 0 ppm.

A 200 mg / L trichlorethylene (TCE) solution was prepared as the contaminated water, and salt was added thereto at a final concentration of 0.1%.
It was added to 1% and supplied into the reaction vessel. The inside of the reaction vessel was irradiated with a black light fluorescent lamp 4 (trade name: FL10BLB; manufactured by Toshiba Corporation, 10 W) while the apparatus was operated under the conditions described above. The aerated air was circulated to continuously perform aeration. After running for 1 hour, the concentration of trichlorethylene in the solution was measured.99.
It turned out that it decomposed more than 5%. When pH and residual chlorine were operated under different conditions to evaluate the decomposition, a decrease in the concentration was observed in all cases. From this, it was found that TCE can be decomposed by irradiating the mixed gas obtained by ventilating and aerating the above device with light. It was also confirmed that TCE could be decomposed for different light intensities.

Example 3 The decomposition of the recovered solvent was experimentally confirmed using the apparatus shown in FIG.

Desorption water from activated carbon was used as a substance to be decomposed. This activated carbon adsorbs pollutants of pollutant gas extracted by vacuum extraction from soil pollution by organochlorine compounds, and when this is desorbed by steam, the desorbed water contains
Trichloroethylene 150mg / L, dichloromethane 80
mg / L, 40 mg / L of tetrachloroethylene, 30 mg / L of 1,1,1-trichloroethane, and 30 mg / L of cis-1,2-dichloroethylene.

This desorbed water was introduced into the reaction tank 1. Electrolysis was performed for 10 minutes under the same conditions as in Example 1. At the same time, the pump 10 was operated to perform aeration for 30 minutes. The air returns to the pump through the circulation pipe 14,
It is aerated again with contaminated water. During this time, the gas phase was irradiated with light through the glass surface inside the reaction tank 1. Irradiation of light is performed using a black light fluorescent lamp 11 (trade name: FL10
BLB; 10 W manufactured by Toshiba Corporation) was used.

After aeration and light irradiation for 30 minutes, electrolysis was performed again for 10 minutes under the same conditions as above.
Following this, after performing aeration and light irradiation for 30 minutes, the treated water is taken out and a part thereof is n-hexane 100 m
Put in a container containing L, stir for 10 minutes, and then n-hexane
The layers were separated, and the amounts of trichloroethylene, dichloromethane, tetrachloroethylene, 1,1,1-trichloroethane and cis-1,2-dichloroethylene were measured by ECD gas chromatography. The concentration of the contaminants in the gas phase is measured by sampling the gas phase of the reaction tank 1 with a gas tight syringe and performing gas chromatography (trade name: GC
-14B (with FID detector); measured by Shimadzu Corporation, column was DB-624 manufactured by J & W.

As a result, n of the sample into which the treated water was injected
No contaminants were detected from -hexane, and no contaminants were detected from the sample from the gas phase, indicating that the desorbed water containing the contaminants was purified.

[0040]

The method and apparatus for decomposing contaminants according to the present invention do not cause drainage problems and enable efficient decomposition of contaminants at normal temperature and pressure.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a pollutant decomposition apparatus according to one embodiment of the present invention.

FIG. 2 is a schematic view of a pollutant decomposition apparatus according to another embodiment of the present invention.

[Explanation of symbols]

 1: Reaction tank 2: Anode 3: Cathode 4: Power supply 5: Pipe 6: Pump 7: Pipe 8: Pump 9: Pipe 10: Air pump 11: Light irradiation means 12: Drain pipe 13: Circulation pipe 14: Partition wall

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) C07C 19/01 C07C 19/01 19/05 19/05 21/10 21/10 (72) Inventor Masahiro Kawaguchi Ota, Tokyo 3-30-2 Kushita Maruko F-term (reference) in Canon Inc.

Claims (28)

[Claims] 1. A reaction vessel provided with a pair of electrodes and a power supply for applying a potential to the electrodes, means for supplying water having an electrolyte dissolved therein, and a solution containing a contaminant to be purified in the reaction vessel Means for supplying water, a means for aerating a solution obtained by electrolyzing a mixed solution of water containing the electrolyte and a solution containing the contaminant in the reaction vessel, and a means for irradiating the reaction vessel with light. And pollutant decomposition equipment. 2. The pollutant decomposition apparatus according to claim 1, wherein the electrolyte is chloride and generates chlorine by electrolysis. 3. An apparatus according to claim 2, wherein said electrolyte is sodium chloride or potassium chloride. 4. The contaminant decomposition apparatus according to claim 1, further comprising means for returning part or all of the aerated gas to the reaction vessel. 5. The contaminant decomposition apparatus according to claim 1, further comprising means for irradiating a part or all of the aerated gas with light. 6. The contaminant decomposing apparatus according to claim 1, further comprising means for supplying a solution containing the contaminant to be purified to the anode side of the electrode. 7. The contaminant decomposition apparatus according to claim 1, wherein the light is light including light in a wavelength range of 300 to 500 nm. 8. The pollutant decomposer according to claim 1, wherein said pollutant is a halogenated aliphatic hydrocarbon compound. 9. The halogenated aliphatic hydrocarbon compound,
The pollutant decomposition apparatus according to claim 8, wherein the apparatus is an aliphatic hydrocarbon compound substituted with chlorine element. 10. The method according to claim 9, wherein the halogenated aliphatic hydrocarbon compound is at least one of trichloroethylene, 1,1,1-trichloroethane, tetrachloroethylene, cis-1,2-dichloroethylene, chloroform and dichloromethane. The contaminant decomposition apparatus according to the above. 11. The solution in the reaction vessel has a hydrogen ion concentration.
The pollutant decomposer according to any one of claims 1 to 10, which has characteristics of (pH value) 3 to 8 and chlorine concentration of 10 to 100 mg / L. 12. The pollutant decomposer according to claim 1, further comprising a diaphragm between said pair of electrodes. 13. The contaminant decomposition apparatus according to claim 12, wherein said means for aeration is provided on the anode side of said electrode. 14. The solution according to claim 13, wherein the solution on the anode side separated by the diaphragm in the reaction vessel has characteristics of a hydrogen ion concentration (pH value) of 1 to 4 and a chlorine concentration of 5 to 150 mg / L. Pollutant decomposition equipment. 15. A step of supplying water containing an electrolyte to a reaction vessel, a step of supplying a solution containing a pollutant to be purified to the reaction vessel, and a step of supplying a solution containing the water containing the electrolyte and the solution containing the pollutant. A method for decomposing contaminants, comprising: a step of electrolyzing a mixed solution; a step of aerating an electrolytic solution in the reaction vessel; and a step of irradiating the reaction vessel with light. 16. The method according to claim 15, wherein the electrolyte is chloride, and chlorine is generated in a step of electrolyzing the mixed solution. 17. The method according to claim 16, wherein the electrolyte is sodium chloride or potassium chloride. 18. The method for decomposing pollutants according to claim 15, further comprising a step of returning part or all of the aerated gas to the reaction vessel. 19. The method according to claim 15, further comprising a step of irradiating a part or all of the aerated gas with light. 20. The method for decomposing pollutants according to claim 15, further comprising a step of supplying a solution containing the pollutants to be purified to the anode side of the electrode. 21. The method for decomposing contaminants according to claim 15, wherein the light is light containing light in a wavelength range of 300 to 500 nm. 22. The method according to claim 15, wherein the contaminant is a halogenated aliphatic hydrocarbon compound. 23. The method according to claim 22, wherein the halogenated aliphatic hydrocarbon compound is an aliphatic hydrocarbon compound substituted with a chlorine element. 24. The method according to claim 23, wherein the halogenated aliphatic hydrocarbon compound is at least one of trichloroethylene, 1,1,1-trichloroethane, tetrachloroethylene, cis-1,2-dichloroethylene, chloroform and dichloromethane. The method for decomposing pollutants described in the above. 25. The solution in the reaction vessel has a hydrogen ion concentration
25. The method for decomposing pollutants according to any one of claims 15 to 24, which has characteristics of (pH value) 3 to 8 and chlorine concentration of 10 to 200 mg / L. 26. The method for decomposing contaminants according to claim 15, further comprising a diaphragm between the pair of electrodes. 27. The method for decomposing pollutants according to claim 26, wherein the means for aeration is provided on the anode side of the electrode. 28. The solution according to claim 27, wherein the solution on the anode side separated by the diaphragm in the reaction vessel has a property that the hydrogen ion concentration (pH value) is 1 to 4 and the chlorine concentration is 5 to 150 mg / L. Pollutant decomposition method.