JP2001000828A - Decomposition method and device provided with adsorption electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently decompose while avoiding the secondary environmental pollution due to the compd. formed resulting from decomposition by adsorbing a subject material to be decomposed to an electrode and also decomposing the subject material to be decomposed under photoirradiation by using the functional water generated near the electrode by electrolysis. SOLUTION: An ion exchange membrane 13 is provided at the inside of a decomposition tank main body 11 consisting of a light-transmissive material such as glass. An adsorption electrode 12 consisting of an electrically conductive adsorptive material is disposed similarly and connected at the positive electrode side of a power source device 18 and used as an anode at the time of electrolysis. Moreover, a cathode 16 consisting of platinum or the like is disposed at the reverse side to the adsorption electrode 12 and connected at a negative electrode side of the power source device 18. Then the subject material to be decomposed is charge from a bubbler 15 disposed at the lower part of the adsorption electrode 12 immersed in an aq. soln. containing electrolyte and adsorbed to the electrically conductive adsorptive material in the adsorption electrode 12. Thereafter, light is applied from a light irradiation means 14 and simultaneously the electrolysis is executed by charging the power source of the power source device 18 to form the functional water and to decompose the material.

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 a halogenated aliphatic hydrocarbon compound and an apparatus used therefor.

[0002]

2. Description of the Related Art A variety of organic compounds, for example, halogenated aliphatic hydrocarbons, have been used enormously with the recent development of industrial technology, and their disposal has become a serious problem. In addition, various kinds of used halogenated aliphatic hydrocarbons cause environmental problems such as polluting the natural environment, and great efforts have been made to solve them.

[0003] For example, chlorinated aliphatic hydrocarbons such as trichlorethylene (TCE) and tetrachloroethylene (PCE) have been widely and widely used in various industries as cleaning solvents and reaction solvents for metal parts, semiconductor parts, and clothing. Was.

However, since the toxicity of these compounds to living organisms such as mutagenicity and carcinogenicity has been pointed out, it has been required to eliminate the use of these compounds and to treat the solvents used so far to render them harmless. . In addition, these compounds that have already leaked into the natural environment cause pollution of rivers, groundwater, and soil, and a technique for economically and efficiently purifying these pollutants that have diffused into the natural environment is desired. Various techniques have been proposed for that purpose.

[0005] For example, as an example of a method for decomposing chlorinated aliphatic hydrocarbon compounds, there is a method of burning. Although this method is relatively simple, the decomposition products of chlorinated aliphatic hydrocarbons, such as hydrogen chloride and chlorine, react with other organic substances during the combustion process, resulting in more toxic substances such as polychlorinated biphenyls and dioxins. There is a concern about the possibility of emissions.
High temperature treatment is a disadvantage even in terms of energy.

As another example of the apparatus for decomposing chlorinated aliphatic hydrocarbon compounds, there is a method using an oxidizing agent or a catalyst. Specifically, for example, a method of decomposing with ozone (JP-A-3-382)
No. 97), a method of wet oxidative decomposition under high temperature and high pressure, and a method of oxidative decomposition with hydrogen peroxide or iron salt (Japanese Patent Application Laid-Open No. 60-2).
No. 61590).

A method using sodium hypochlorite as an oxidizing agent has also been proposed (US Pat. No. 5,611,642).
No. 558), and a method of combining sodium hypochlorite with ultraviolet irradiation.
No. 2741).

A method is also known in which a photocatalyst comprising fine particles of an oxide semiconductor such as titanium oxide and a liquid chlorinated aliphatic hydrocarbon are suspended under alkaline conditions and decomposed by light irradiation (Japanese Patent Application Laid-Open No. 7-141373). ). In addition, a catalyst method of performing oxidative decomposition using an oxide such as a platinum-based, alumina-based, or zirconia-based oxide is also known (Hiroshi Ichimura et al .: Ditto: JP-A-6-31135).

Further, as a method for decomposing chlorinated aliphatic compounds, a photodecomposition method of irradiating ultraviolet rays in a gas phase without using an oxidizing agent has already been attempted (Sekihiro et al .: "Present state and countermeasures of groundwater and soil pollution"). Japan Society on Water Environment Kansai Chapter, Environmental Technology Research Association, 1955: JP-A-8-243351).

[0010] It is known that chlorinated aliphatic hydrocarbons such as TCE and PCE are decomposed aerobically or anaerobically by microorganisms. Have been.

A method for removing low boiling organic substances by adsorbing them on an adsorbent such as activated carbon or zeolite is disclosed in Japanese Patent Laid-Open No. 5-26.
No. 9346 and JP-A-5-068845. These methods do not mention the treatment of adsorbed contaminants, but JP-A-5-000290, 00 discloses a method in which an organic chlorine compound is adsorbed on an iron-based porous body to decompose the same.
Nos. 0291 and 000292. Here, hydrogen peroxide solution is added to wastewater containing an organic chlorine compound such as trichloroethylene, and the mixture is aerated while being circulated in a treatment apparatus provided with an iron-based porous body to perform adsorption oxidative decomposition.

Further, a method of treating waste water by using a porous catalyst is disclosed in Japanese Patent Application Laid-Open No. 5-317716. Here, a porous body obtained by firing an oxide of iron containing at least one element in cobalt, nickel, cerium, silver, gold, platinum, palladium, rhodium, ruthenium and iridium is used. Nitrogen-containing compounds, sulfur-containing compounds, and organic halogen compounds adsorbed on the catalyst are subjected to wet oxidation.

[0013]

The inventors of the present invention have studied the methods for decomposing various halogenated aliphatic hydrocarbon compounds as described above. As a result, a complicated apparatus for decomposition is required, All of them contain or are expected to contain problems, such as the need for further detoxification treatment, so there are fewer problems and environmentally friendly halogenated aliphatic hydrocarbons It was concluded that techniques for the decomposition of compounds and aromatics were needed.

[0014] The present invention has been made based on new findings by the present inventors, and its object is to be more environmentally friendly, and it is more likely that compounds generated by decomposition will cause new environmental pollution. An object of the present invention is to provide a method capable of efficiently decomposing halogenated aliphatic hydrocarbon compounds at a low cost and an apparatus used for the method.

Investigations were made to achieve the above-mentioned problems. As a result, a sterilizing effect (Japanese Patent Application Laid-Open No. 1-180293) and an effect of cleaning contaminants on a semiconductor wafer (Japanese Patent Application Laid-Open No.
Functional water obtained by electrolysis of water reported to have, for example, acidic water,
It has been found that irradiation of light significantly enhances the resolution of halogenated aliphatic hydrocarbon compounds.

Further, the rate of decomposition of the halogenated aliphatic hydrocarbon compound by the functional water irradiated with the light is very high, but as the decomposition reaction is a chemical reaction, as the concentration of the substance to be decomposed decreases. Focusing on the fact that the decomposition efficiency decreases, high efficiency can be maintained by once adsorbing and concentrating and then decomposing.Furthermore, the decomposition target substance is decomposed by performing electrolysis using the adsorbent itself to which the decomposition target substance is adsorbed as an electrode. It has been found that by desorbing and decomposing water and generating electrolytically functional water, it is possible to omit means necessary for desorption and to perform efficient decomposition, and have reached the present invention.

[0017]

That is, according to the present invention, an electrode having an adsorptive surface is brought into contact with a halogenated aliphatic hydrocarbon compound as a substance to be decomposed so that the substance to be decomposed is adsorbed on the electrode. An adsorption step of adsorbing the substance to be decomposed on the surface, an electrode on which the substance to be decomposed is adsorbed is disposed together with a counter electrode in an aqueous electrolyte solution in a decomposition tank, and the electrode is used as an anode; Perform disassembly,
Decomposing the substance to be decomposed adsorbed on the electrode into the aqueous electrolyte solution, and decomposing the substance to be decomposed under light irradiation by functional water generated near the electrode by the electrolysis. It is about the method of decomposing the characteristic decomposition target substance.

The present invention also has a cracking tank, means for supplying a halogenated aliphatic hydrocarbon compound as a substance to be decomposed to the cracking tank, and a porous surface capable of adsorbing and desorbing the substance to be decomposed. An electrode, which also serves as a means for generating functional water that decomposes the substance to be decomposed under light irradiation by electrolysis of an aqueous solution of an electrolyte and an electrolytic solution of an adsorbent,
An apparatus for decomposing a substance to be decomposed, comprising: means for irradiating light to cause a decomposition reaction by the functional water; and a counter electrode of the electrode for performing the electrolysis.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION (Conductive adsorbent) The electrode for adsorbing a substance to be decomposed which can be used in the present invention is a solid having a property of adsorbing the substance to be decomposed, having conductivity (preferably volume resistance). The rate may be 10 ⁻³ Ωm or less), as long as it has a surface made of a conductive adsorbent that is not corroded by chlorine ions generated by electrolysis and can detach and attach a decomposition target when necessary. As those having such properties, for example, activated carbon, activated carbon fiber, which is made by carbonizing a cellulosic substance or chitinous substance such as wood and is generally used for adsorption of hydrocarbon compounds, etc.
Porous metals and the like can be mentioned.

Activated carbon and graphite constituting activated carbon fibers have a volume resistivity of about 10 ⁻⁵ Ωm, which is inferior to metals, but does not pose any problem as an electrode for electrolysis. If these are processed into a ribbon shape or a column shape or filled into something and the electric resistance at both ends is 100Ω or less, they can be used as an adsorbent and at the same time as an electrode for generating functional water.

Among them, activated carbon generally used has a specific surface area of 300 to 3000 m ² / g and a pore diameter of about 30 to 300 angstroms, and it is said that TCE in a gas phase adsorbs about 10 times its own weight. Further, when the present inventors conducted an experiment, it was found that in the case of TCE dissolved in
If the amount of activated carbon is about twice as high, TC
The E concentration falls below the environmental standard of 0.03 mg / L. Further, the amount of adsorption did not change in the case of the aqueous solution of TCE alone or in the case of other impurities.

For this reason, activated carbon which has just started to be used is filled into a pipe having a cross-sectional area of about 1.5 cm ² so that about 10 g of the pipe is formed with as little gap as possible, and a TC of a concentration of several mg / L is used.
Even when the aqueous solution E is flowed at a rate of 10 mL / min, the concentration at the outflow side can be kept below the environmental standard value for several hundred hours. At this time, the electric resistance between the upper end and the lower end is about 10Ω.

At present, various activated carbon fibers have been developed, and there are activated carbon sheets obtained by processing them into a cloth shape or a nonwoven fabric shape, and those obtained in a cartridge shape.
These may be incorporated into the device. Halogenated aliphatic hydrocarbon compounds or aromatic compounds adsorbed on these adsorbents are desorbed by heat generated during electrolysis, but if the desorption rate is slow, a high-temperature medium that heats the adsorbent itself or functional water is used. There are methods such as contact and microwave irradiation.

As the porous metal, fired fine powder such as iron or alumina can be used. However, since the metal is directly exposed to chlorine gas and chlorine ions, cobalt, nickel, cerium, silver, It is more preferable to sinter a fine powder of a corrosion-resistant metal such as one containing elements such as gold, platinum and palladium.

These have a volume resistivity of 10 ⁻⁷ Ωm or less, which is not a problem as an electrode. In addition, when the inventors conducted experiments on porous stainless steel, it was found that TCE in the gas phase adsorbed to the same degree as its own weight, and desorbed when the temperature was increased to 100 ° C.

(Electrolytic functional water) Functional water generated by electrolysis of water is, for example, a water tank having an electrolyte (eg, sodium chloride, potassium chloride, etc.) dissolved in raw water and having a pair of electrodes for the electrolyte solution. It can be obtained in the vicinity of the anode by performing electrolysis in the reactor. The oxidation-reduction potential when the hydrogen ion concentration (pH value) is 1 or more and 4 or less, the working electrode is platinum, and the reference electrode is silver-silver chloride. Is 800mV or more and 1500mV or less, and chlorine concentration is 5mg
It refers to water having a property of not less than / L and not more than 150 mg / L.

When producing functional water having the above-mentioned characteristics, the concentration of the electrolyte in the raw water before electrolysis is desirably 20 mg / L to 2000 mg / L for sodium chloride, for example, and the electrolytic current value at that time is 2 A to 20 A. It is desirable that

When a diaphragm is disposed between the pair of electrodes at this time, it is possible to prevent mixing of the acidic water generated near the anode and the alkaline water generated near the cathode, and the halogenated aliphatic hydrocarbon compound Alternatively, it is possible to obtain acidic water that can more efficiently decompose the aromatic compound. As the diaphragm, for example, an ion exchange membrane is preferably used.

(Functional Water-Mixed Electrolyzed Water) In addition to the above-mentioned acidic electrolyzed water, the ratio of alkaline water obtained in the vicinity of the cathode at the time of electrolysis for producing acidic electrolyzed water to 1 or less per 1 acidic water is 1 or less. Hydrogen ion concentration (pH value) obtained by mixing
The oxidation-reduction potential when the working electrode is a platinum electrode and the reference electrode is silver-silver chloride is 300 mV or more and 1100 mV or less, and the chlorine concentration is 2 mg / L or more and 100 or less.
Mixed electrolyzed water having a property of not more than mg / L also exhibits resolution equivalent to acidic electrolyzed water.

(Decomposition target halogenated aliphatic hydrocarbon compound) The decomposition target substance in the present invention is a halogenated aliphatic hydrocarbon compound.

Examples of the halogenated aliphatic hydrocarbon compound include an aliphatic hydrocarbon compound substituted with a chlorine atom.

Specifically, trichloromethane, dichloromethane, 1,1-dichloroethylene, cis-1,2-dichloroethylene, trans-1,2-dichloroethylene, trichloroethylene, tetrachloroethylene, 1,1,1-trichloroethane and the like can be mentioned. .

In the functional water after the decomposition of the above-mentioned various compounds, no new generation of organic compounds which is considered to have a bad influence on the environment at present is not observed at all even by mass spectrometry.

(Regarding Light Source) As the light to be irradiated when the decomposition target substance is decomposed by the functional water, for example, a light having a wavelength of 300
Light of up to 500 nm, especially 350 to 450 nm, is particularly preferred for the decomposition of halogenated aliphatic hydrocarbon compounds.

The light irradiation intensity on a mixture of functional water or an aqueous solution of hypochlorous acid and a halogenated aliphatic hydrocarbon compound to be decomposed is 10 μW / c from the viewpoint of decomposition efficiency.
m ^{2 to} 10 mW / cm ² , especially 50 μW / cm ^{2 to 5} mW / c
m ² is preferred. Specifically, for example, a light source having a peak at a wavelength of 365 nm has a wavelength of several hundred μW / cm ² (300 nm to 400 nm).
(measured between m).

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

The irradiation of the mixture of the electrolysis functional water and the halogenated aliphatic hydrocarbon compound with light may be performed directly on the functional water, or may be performed through a transparent container made of glass or plastic. You may. Light irradiation may be performed in the process of generating functional water,
Irradiation may be performed after generation.

In any case, in order to remarkably accelerate the decomposition, it is desirable to perform light irradiation at the time of contact between the functional water and the halogenated aliphatic hydrocarbon compound. In this embodiment using functional water, light having a large effect on the human body as light is used.
There is no need to use 0 nm ultraviolet light.

The above-mentioned various functional waters are all decomposed by light irradiation. At this time, for example, functional water generated by electrolysis of water containing an electrolyte such as sodium chloride contains hypochlorous acid or hypochlorite ion, and this hypochlorous acid or hypochlorite ion is used as a light source. It is considered that the action induces a decomposition active component such as a chlorine radical, a hydroxyl radical, or superoxide, and promotes a decomposition reaction of the halogenated aliphatic hydrocarbon compound.

The amount of hypochlorous acid in the functional water, which is considered to contribute to the decomposition of the halogenated aliphatic hydrocarbon compound by the functional water generated near the anode by the electrolysis, is p
It can be determined from H and chlorine concentration. Further, the functional water generated by electrolysis, for example, diluted with pure water or the like, can be used for decomposition of the halogenated aliphatic hydrocarbon compound.

For example, for TCE-contaminated water of about 10 ppm, the pH is 2.1, the oxidation-reduction potential is 1150 mV, and the residual chlorine concentration is 54.
Even with functional water obtained by diluting functional water of mg / L 5 times or more with water, the decomposition proceeds to 0.03 ppm or less in 4 hours. Alternatively, functional water having the same properties as the diluted functional water may be directly generated.

(Specific Examples of Method and Apparatus) Hereinafter, an example of a method for decomposing a substance to be decomposed using functional water and an example of a decomposition apparatus used for the method will be described. In this embodiment, the contact between the functional water and the substance to be decomposed under light irradiation may be performed at normal temperature and normal pressure, and no special equipment or environment is required.

The structure of the decomposing device is, for example, 1)
And 2).

1) The decomposition device is filled with water containing an electrolyte, the adsorption electrode is submerged in this, and the gas containing the substance to be decomposed is contacted and adsorbed on the adsorption electrode. 1 to 2 to generate functional water and decompose the substance to be desorbed by the heat generated by the electrolysis. It is a schematic diagram. In FIG. 1, reference numeral 11 denotes a decomposition tank main body made of a light-transmitting material such as glass or plastic. FIG. 2 is a top view of the decomposition tank main body.

Inside the main body, the ion exchange membrane 1
3, a semi-cylindrical adsorption electrode having a slightly smaller inner diameter than the main body filled with an adsorbent such as a granular activated carbon or an activated carbon sheet as a conductive adsorbent is installed therein. It is connected to the positive side and becomes an anode during electrolysis.

A cathode 16 made of platinum or the like is installed on the opposite side of the decomposition tank 11 from the adsorption electrode, and is connected to the minus side of the power supply 18. The substance to be decomposed is introduced from a bubbler 15 provided below the adsorption electrode immersed in an aqueous solution containing an electrolyte, and is adsorbed by a conductive adsorbent in the adsorption electrode.

Before the substance to be decomposed is detected from the exhaust gas of the apparatus, the inflowing gas is stopped and the adsorption is terminated. Thereafter, light is irradiated by the light irradiation means 14 provided on the adsorption electrode side of the decomposition tank 11, and at the same time, the power of the power supply device 18 is turned on to perform electrolysis to generate functional water and decompose.

The decomposition tank 11 has a sealed structure so that the substance to be decomposed and the decomposing component of the functional water do not leak to the outside.

The power of the power supply device and the light irradiation means may be automatically turned off when the concentration of the substance to be decomposed in the decomposition tank 11 is measured and becomes lower than the detection limit.

2) Exposure of the adsorption electrode to a gas or liquid containing the substance to be decomposed causes the substance to be decomposed to be adsorbed, and the substance is submerged in a decomposition apparatus filled with water containing an electrolyte, and electrolysis is performed under light irradiation. A configuration in which the decomposition target substance desorbed by the heat generated by electrolysis by generating functional water is subjected to water splitting by an optical mechanism: a schematic diagram of an embodiment of the decomposition apparatus of the decomposition target substance according to the present invention is shown in FIGS. Is almost the same as

The adsorption electrode is taken out of the decomposition tank 11 and is attached to the middle of a pipe through which the gas containing the substance to be decomposed passes, or is placed in a container containing the gas or liquid containing the substance to be decomposed, and left for a predetermined time.

After the substance to be decomposed is sufficiently adsorbed, the adsorption electrode is set in the decomposition tank 11 as shown in FIGS.
At the same time, light is irradiated by the light irradiating means 14 installed on the side of the adsorption electrode 1 and the power of the power supply 18 is turned on to perform electrolysis to generate functional water and decompose.

A configuration may be adopted in which a plurality of adsorption electrodes are prepared, exchanged at fixed time intervals to perform adsorption continuously, inserted into the decomposition tank 11 after adsorption, desorbed and decomposed, and regenerated.

A configuration may be adopted in which the power of the power supply device and the light irradiation means is automatically turned off when the concentration of the substance to be decomposed in the decomposition tank 11 is measured below the detection limit.

[0055]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.

Example 1 Continuous Decomposition of TCE Contaminated Gas in which Adsorption and Desorption Decomposition are Performed by the Same Apparatus The TCE contaminated gas was decomposed using the decomposition apparatus shown in FIG. First, outer diameter 2.5cm, inner diameter 2.0cm, height 5
Ion exchange membrane is attached to the surface of the chord part of the 0 cm semi-cylindrical column, stainless steel mesh is attached to the lower semi-circular portion, and about 100 g of granular activated carbon (manufactured by Kanto Kagaku) is packed in it. A semicircular stainless steel mesh was attached to the adsorption electrode.

This and a ribbon-shaped platinum having a width of 1 cm and a length of 50 cm were inserted into a glass decomposition tank 11 having an inner diameter of 3 cm and a height of 100 cm as shown in FIGS. Next, 8
An aqueous sodium chloride solution having a concentration of 1000 mg / L was introduced until the water level reached 0 cm, and the adsorption electrode and the platinum electrode were completely submerged.

The pH and oxidation-reduction potential of the electrolyzed functional water generated by the decomposer are measured in advance by applying a voltage of 50 V with the adsorption electrode on the anode side and the platinum electrode on the cathode side.
(Toko Chemical Laboratory, TCX-90i and KP900-
2N) and conductivity meter (Toko Chemical Laboratory Co., Ltd., TC
X-90i and KM900-2N), and the chlorine concentration was measured with chlorine test paper (Advantech).
2.6, redox potential 900mV, residual chlorine concentration 35mg
/ L.

A pipe at the bottom of the decomposition tank 11 is connected to a permeator (manufactured by
Gas Tech, PB-1B), open the valve at the bottom of the decomposition tank 11 and generate 10.4 ppm (vo
l.) through the bubbler 15 to the adsorption electrode 1
2. Air was supplied from the lower part at a flow rate of 50 mL / min.

During this period, the gas discharged from the decomposition tank 11 is periodically sampled with a gas tight syringe, and the TCE concentration in the discharged gas is measured by gas chromatography (Shimadzu Corporation).
GC-14B with FID detector, column is J & W
DB-624).
It was confirmed that E was adsorbed on the adsorption electrode.

Approximately 1 m of TCE-containing gas was supplied for 6 hours.
When g was adsorbed on the adsorption electrode, while the TCE-containing gas was being supplied from the permeator, the power supply of the power supply device 18 was turned on, and two black light fluorescent lamps 14 as light irradiation means 14 were installed 5 cm above and below the decomposition tank 11. (Product name: FL
10BLB: Toshiba Corporation, 10W).
At this time, the current between the electrodes was 6 A, and the irradiation light amount was 0.1 to 0.4.
mW / m ² .

During the electrolysis and the light irradiation, the TCE concentration in the exhaust gas was measured by gas chromatography. The detection limit was always set to 0.05 ppm (vol.) 5 minutes after the start of the electrolysis. It was below.

After about 2 hours, the power supply and the fluorescent lamp were turned off. At this time, the water temperature in the decomposition tank was 75 ° C. After a while, the permeator is disconnected and T
Air containing no CE was supplied, and the TCE concentration of the exhaust gas was measured by gas chromatography. As a result, no TCE desorbed below the detection limit was always observed.

From this experiment, it was found that all TCE in the TCE-containing gas generated and supplied for 8 hours was adsorbed on the adsorption electrode and decomposed by operating the decomposition apparatus for 2 hours.

Comparative Example 1 The same experiment as in Example 1 was performed except that the black light fluorescent lamp was not turned on.
At this time, the exhaust gas exhausted for 6 hours during which the adsorption operation was performed.
Although CE was not detected, after the electrolysis was started at 6 hours, the TCE concentration in the exhaust gas increased as the water temperature increased, and 28.3p at 8 hours when the water temperature reached 73 ° C.
pm (vol.).

When the black light fluorescent lamp is not turned on and the photofunctional water decomposition cannot be performed, the TCE adsorbed on the adsorption electrode is desorbed by the electrolysis due to a rise in the water temperature and the temperature of the adsorption electrode, and is mixed into the exhaust gas. I found out.

Example 2 Continuous Decomposition of TCE Contaminated Gas Performed by Apparatus Using Activated Carbon Fiber Filled and adsorbed with activated carbon fiber (trade name: Carbon Paper, manufactured by Nippon Carbon Co., Ltd.) instead of activated carbon The same experiment as in Example 1 was performed except that the electrodes were formed. At this time, no TCE was detected in the same manner as in Example 1 during the adsorption operation, during the electrolysis, and when the air containing no TCE was supplied after the electrolysis was completed.

From this experiment, it was found that activated carbon fibers could be used instead of activated carbon as the conductive adsorbent for the adsorption electrode.

Example 3 Continuous Decomposition of TCE Contaminated Gas in Which Adsorption and Desorption Decomposition are Performed in Different Locations Two adsorption electrodes similar to those used in Example 1 were prepared, and one of them was first used (adsorption electrode A). ) Is inserted into a semi-cylindrical glass tube having an inner diameter of 3 cm and a length of 60 cm, one end of the glass tube is connected to a permeator, and a TC having a concentration of 10.4 ppm (vol.) Is used.
The E-containing gas was flowed at a flow rate of 50 mL / min for 8 hours. At this time, the TCE of the gas flowing out from the other end of the glass tube
The concentration was measured by gas chromatography, but it was always below the detection limit, and it was confirmed that all TCE in the gas was adsorbed on the adsorption electrode.

After 8 hours, the suction electrode A was removed and replaced with the suction electrode B. The adsorption electrode A is the same as in the first embodiment shown in FIG.
Then, a sodium chloride aqueous solution having a concentration of 1000 mg / L was put in a state where the valve at the lower part of the decomposition tank 11 was closed, and the adsorption electrode and the platinum electrode were completely submerged in the same manner as in Example 1. A voltage was applied to the electrodes to turn on the black light fluorescent lamp.

After about 2 hours, the power supply and the fluorescent lamp were turned off. At this time, the water temperature in the decomposition tank was 75 ° C. Thereafter, the adsorption electrode A was taken out of the decomposition tank 11 and lightly washed with water to remove thorium chloride, and then drained.

After performing the adsorption operation with the adsorption electrode B for 8 hours, the adsorption electrode A was replaced again with the previously drained adsorption electrode A, the adsorption electrode B was inserted into the decomposition tank 11, and desorption decomposition was performed for 2 hours.

The adsorption and desorption decomposition operations by both adsorption electrodes are performed in two steps.
Each time was performed for a total of 32 hours. During this period, the outflow gas from the adsorption electrode during the adsorption step and the TCE concentration in the upper gas phase of the decomposition tank 11 during the decomposition step were periodically measured by gas chromatography, but were always below the detection limit.

According to this experiment, if there were two adsorption electrodes, one of them was connected to a pipe from which the TCE-containing gas was discharged, and
It was found that CE can be adsorbed and the other can be desorbed and decomposed to regenerate in the meantime.

Example 4 Batch Decomposition of TCE-Contaminated Water in Which Adsorption and Desorption Decomposition are Performed in Different Locations An adsorption electrode similar to that used in Example 1 was prepared, and 0.5 was prepared.
A TCE aqueous solution having a concentration of mg / L was completely submerged in a glass tube containing 2 L, and a lid with Teflon packing was attached so that TCE did not volatilize.

After 8 hours, the adsorption electrode was removed, 10 mL of the liquid in the glass tube was sampled, placed in a 27 mL vial bottle, stoppered with Teflon-coated butyl rubber, left at 23.5 ° C. for 30 minutes, and then gas phase was released. Chromatography
(GC-14B with FID detector, column is J-W DB-624, manufactured by Shimadzu Corporation). TCE concentration was below the detection limit, and TCE in aqueous solution was adsorbed to the adsorption electrode. all right.

Next, the adsorption electrode was inserted into the decomposition tank 11 as shown in FIG. 1 in the same manner as in Example 1, and an aqueous solution of sodium chloride having a concentration of 1000 mg / L was charged with the valve at the bottom of the decomposition tank 11 closed. Then, the adsorption electrode and the platinum electrode were completely submerged, and a voltage was applied to the electrodes in the same manner as in Example 1 to turn on the black light fluorescent lamp.

After about 2 hours, the power supply and the fluorescent lamp were turned off. At this time, the water temperature in the decomposition tank was 75 ° C. After that, for a while, the lower valve of the decomposition tank 11 is opened, and air containing no TCE is supplied, and TCE of exhaust gas is supplied.
The concentration was measured by gas chromatography, and TCE was not always observed below the detection limit.

The adsorption electrode was submerged again in a glass tube containing a TCE aqueous solution, and was subjected to a decomposition step 8 hours later. The result was the same.

From this experiment, it was found that all the TCE was adsorbed on the adsorption electrode by submerging the adsorption electrode in the TCE aqueous solution, and the adsorbed TCE could be decomposed and the electrode regenerated by operating the decomposition device for 2 hours.

Example 5 Continuous Decomposition of TCE-Contaminated Water in Which Adsorption and Desorption Decomposition are Performed at Different Locations Two adsorption electrodes similar to those used in Example 1 were prepared, and one of them was first used (adsorption electrode A). ) Is inserted into a semi-cylindrical glass tube having an inner diameter of 3 cm and a length of 60 cm, and one end of the glass tube is connected to a tube through which a TCE aqueous solution having a concentration of 0.5 mg / L flows at a flow rate of 10 mL / min. Run for 4 hours. At this time, the aqueous solution flowing out from the other end of the glass tube was taken into a vial, and the TCE concentration in the gas phase was measured by gas chromatography.
It was confirmed that all E was adsorbed on the adsorption electrode.

After 4 hours, the suction electrode A was removed and replaced with the suction electrode B. The adsorption electrode A was inserted into the decomposition tank 11 as shown in FIG. 1 in the same manner as in Example 1, and a 1000 mg / L aqueous sodium chloride solution was charged with the valve at the bottom of the decomposition tank 11 closed, and the adsorption electrode and the platinum electrode Was completely submerged, a voltage was applied to the electrodes in the same manner as in Example 1, and the black light fluorescent lamp was turned on.

After about 2 hours, the power supply and the fluorescent lamp were turned off. At this time, the water temperature in the decomposition tank was 75 ° C. Thereafter, the adsorption electrode A was taken out of the decomposition tank 11 and lightly washed with water to remove sodium chloride, and then drained.

After performing the adsorption operation with the adsorption electrode B for 4 hours, the adsorption electrode A was replaced again with the previously drained adsorption electrode A, and the adsorption electrode B was inserted into the decomposition tank 11 and desorbed and decomposed for 2 hours.

The adsorption and desorption decomposition operations by both adsorption electrodes are
Each time was performed for a total of 32 hours. During this period, the effluent from the adsorption electrode during the adsorption step and the TCE concentration in the upper part of the decomposition tank 11 during the decomposition step were periodically measured by gas chromatography, but were always below the detection limit.

According to this experiment, if there were two adsorption electrodes, one of them was connected to a tube from which the TCE aqueous solution was discharged, and the TC
It was found that E could be adsorbed and the other could be desorbed and decomposed during that time to regenerate.

[0087]

According to the present invention, in the process of decomposing a substance to be decomposed, a costly and inefficient operation is required to further reduce the low-concentration substance to be decomposed in the exhaust gas or wastewater to below the environmental standard value. Without contaminating the polluting gas or polluted water into the adsorption electrode consisting of a conductive adsorbent without increasing the size of the decomposition tank, extending the residence time, or connecting similar processing equipment in multiple stages. By concentrating by adsorption, using this as an anode, electrolysis in an aqueous solution of sodium chloride, and irradiation with light, the concentration can be easily reduced to a level lower than the environmental standard value for drainage or exhaustion.

[Brief description of the drawings]

FIG. 1 is a schematic view of one embodiment of an apparatus for decomposing a substance to be decomposed according to the present invention.

FIG. 2 is a top view of the decomposition tank main body of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Decomposition tank 12 (Anode side) Adsorption electrode 13 Ion exchange membrane 14 Light irradiation means 15 (For aeration of gas containing decomposition target substances) Bubbler 16 Cathode (platinum electrode) 17 Electric wire 18 (Electrolysis) Power supply device

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (reference) C02F 1/463 C02F 1/46 102 1/465 C07B 37/06 F term (reference) 4D002 AA21 BA02 BA08 BA09 DA02 DA03 DA17 DA41 DA44 EA02 4D012 CA11 CB01 CB03 CG01 CG02 CG03 CG04 CH04 CH10 4D061 DA08 DB19 DC09 EA03 EA08 EB02 EB12 EB13 EB22 EB23 EB24 EB26 EB29 EB30 EB33 EB35 EB37 EB39 ED12 GA13 A23 GA13 A18 GA23

Claims (28)

[Claims] An adsorbing step of contacting an electrode having an adsorptive surface with a halogenated aliphatic hydrocarbon compound as a substance to be decomposed to adsorb the substance to be decomposed on the adsorptive surface of the electrode; The electrode on which the substance to be decomposed is adsorbed is disposed together with the counter electrode in the aqueous electrolyte solution in the decomposition tank, the electrode is used as an anode, and the counter electrode is used as a cathode to perform electrolysis of the aqueous electrolyte solution and adsorb to the electrode. Decomposing the substance to be decomposed into the aqueous electrolyte solution, and decomposing the substance to be decomposed under light irradiation by functional water generated near the electrode by the electrolysis. Decomposition method of the substance. 2. The decomposition method according to claim 1, wherein the adsorption step and the decomposition step are performed in the same decomposition tank. 3. The decomposition method according to claim 1, wherein the substance to be decomposed is supplied in contact with the adsorptive surface of the electrode in a state of being contained in a gas or a liquid. 4. The decomposition method according to claim 1, wherein the material of the conductive adsorbent has a volume resistivity of 10 ⁻³ Ωm or less. 5. The decomposition method according to claim 1, wherein the surface of the conductive adsorbent is porous. 6. The decomposition method according to claim 4, wherein the conductive adsorbent is at least one selected from activated carbon, activated carbon fiber, and porous metal. 7. The decomposition method according to claim 1, wherein the electrolyte is at least one of sodium chloride and potassium chloride. 8. The electrolyzed functional water has a hydrogen ion concentration (pH value).
The decomposition method according to any one of claims 1 to 7, wherein the oxidation-reduction potential (working electrode: platinum electrode, reference electrode: silver-silver chloride electrode) is 800 to 1500 mV, and the chlorine concentration is 5 to 150 mg / L. . 9. The functional water has a hydrogen ion concentration (pH value) of 4 to 9.
10. The decomposition method according to any one of claims 1 to 7, wherein the oxygen reduction potential (working electrode: platinum electrode, reference electrode: silver-silver chloride electrode) is 300 to 1100 mV, and the chlorine concentration is 2 to 100 mg / L. 10. The decomposition method according to claim 1, wherein the light is light containing light in a wavelength range of 300 to 500 nm. 11. The decomposition method according to claim 10, wherein the light is light in a wavelength range of 350 to 450 nm. 12. The light irradiation amount is 10 μW / cm ² -10
The decomposition method according to any one of claims 1 to 11, wherein the decomposition method is mW / cm ² . 13. The irradiation amount of the light is 50 μW / cm ^{2 to 5} m.
Decomposition method according to claim 12, which is a W / cm ^2. 14. The decomposition method according to claim 1, wherein the halogenated aliphatic hydrocarbon is an aliphatic hydrocarbon compound substituted with a chlorine atom. 15. The halogen aliphatic hydrocarbon may be trichloroethylene, 1,1,1-trichloroethane, tetrachloroethylene, 1,1-dichloroethylene, cis-1,2-dichloroethylene, trans-1,2-dichloroethylene, trichloromethane (chloroform ) And at least one of dichloromethane. 16. A decomposition tank, means for supplying a halogenated aliphatic hydrocarbon compound as a substance to be decomposed to the decomposition tank, adsorption means having an adsorptive surface capable of adsorbing and desorbing the substance to be decomposed, and An electrode, which also serves as means for generating functional water that decomposes the substance to be decomposed under light irradiation by electrolysis of an aqueous electrolyte solution, means for irradiating light to cause a decomposition reaction by the functional water, and performing the electrolysis And a counter electrode of the electrode for the decomposition. 17. The decomposition apparatus according to claim 16, wherein the adsorption and desorption using the electrode and the decomposition reaction are performed in the same decomposition tank. 18. The decomposition apparatus according to claim 16, wherein the supply of the substance to be decomposed to a portion in contact with the adsorptive surface of the electrode is performed in a state of being contained in a gas or a liquid. 19. The decomposition apparatus according to claim 16, wherein the material of the conductive adsorbent has a volume resistivity of 10 ⁻³ Ωm or less. 20. The decomposition apparatus according to claim 16, wherein the surface of the conductive adsorbent is porous. 21. The decomposition apparatus according to claim 19, wherein the conductive adsorbent is at least one selected from activated carbon, activated carbon fiber, and porous metal. 22. The decomposition apparatus according to claim 16, wherein the electrolyte is at least one of sodium chloride and potassium chloride. 23. The electrolyzed functional water has a hydrogen ion concentration (pH
23) The oxidation-reduction potential (working electrode: platinum electrode, reference electrode: silver-silver chloride electrode) of 800 to 1500 mV, and the chlorine concentration of 5 to 150 mg / L. Decomposition equipment. 24. The functional water has a hydrogen ion concentration (pH value) of 4.
23. The decomposition apparatus according to claim 16, wherein the oxidation-reduction potential (working electrode: platinum electrode, reference electrode: silver-silver chloride electrode) is 300 to 1100 mV, and the chlorine concentration is 2 to 100 mg / L. 25. The decomposition apparatus according to claim 16, wherein the light is light including light in a wavelength range of 300 to 500 nm. 26. The decomposition apparatus according to claim 25, wherein the light is light in a wavelength range of 350 to 450 nm. 27. An irradiation amount of said light of 10 μW / cm ² to 10
The decomposition apparatus according to any one of claims 16 to 26, wherein the decomposition power is mW / cm ² . 28. An irradiation amount of the light is 50 μW / cm ^{2 to 5} m.
Decomposing apparatus according to claim 27 which is a W / cm ^2.