JP2005103519A - Method and apparatus for decomposing pollutant - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pollutant decomposing apparatus for decomposing and removing a water soluble organochlorine compound such as a haloacetic acid or the like or a chlorine gas formed by decomposing an organochlorine compound by light (including ultraviolet rays), and a pollutant decomposing method using it. <P>SOLUTION: This pollutant decomposing apparatus has a metal as a means catalytically reacting with gas to be treated after the irradiation with light and further decomposing or adsorbing the optically decomposed product remaining in the gas to be treated to remove the same. The pollutant decomposing method using it is also disclosed. Further, the pollutant decomposing apparatus and the pollutant decomposing method have a means/process for supplying hydrogen peroxide to a mixture containing metal ions or their compounds eluted from the metal by the catalytic reaction of the metal and the gas to be treated and the optically decomposed product and/or the organochlorine compound to decompose the mixture to a harmless low-molecular substance or inorganic matter. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a technology for decomposing pollutants, particularly organochlorine compounds.

  With the development of industrial technology until recent years, organochlorine compounds such as chlorinated ethylene, chlorinated methane, etc. have been used enormously, and their disposal has become a serious problem. In addition, these pollutants that have been used have serious environmental problems such as contaminating soil and groundwater, and great efforts are being made to solve them.

  To describe a specific treatment method for pollutants collected from contaminated soil, groundwater, etc., particularly halogenated aliphatic hydrocarbon compounds, a photolysis method in which ultraviolet rays are irradiated in the gas phase has already been attempted. For example, an exhaust gas containing an organic halogen compound is irradiated with ultraviolet rays to form an acidic decomposition gas, and then washed with an alkali to be detoxified (Japanese Patent Laid-Open No. 62-191025 (Patent Document 1)), organic halogen An apparatus (Japanese Patent Laid-Open No. 62-191095 (Patent Document 2)) is proposed in which wastewater containing a chemical compound is aerated and irradiated with ultraviolet rays after being discharged.

  Further, as an example of photolysis different from the above, a gaseous halogenated fatty acid in which a gas containing chlorine gas and a gaseous halogenated aliphatic hydrocarbon compound to be decomposed are mixed, and the mixed gas is irradiated with light. An apparatus for decomposing aromatic hydrocarbon compounds has been proposed (Japanese Patent Laid-Open No. 2001-137697 (Patent Document 3)). This decomposition apparatus uses chlorine gas generated from a solution containing chlorine as a simple and safe means for obtaining a gas containing chlorine gas.

As a technique different from photolysis, a method of decomposing an organic halogen compound by using a Fenton reagent is known. (JP-A-5-345189 (Patent Document 4), JP-A-6-91276 (Patent Document 5)).
JP 62-191025 A JP 62-191095 A JP 2001-137697 JP-A-5-345189 JP-A-6-91276

  As described above, in the decomposition of an organic chlorine compound by light such as ultraviolet rays, mainly haloacetic acid and chlorine are generated as decomposition products. The present inventor arrived at the present invention from the idea that it is preferable to further remove or decompose this decomposition product.

  It is an object of the present invention to provide a pollutant decomposition method and apparatus for further removing or decomposing a product obtained by decomposing a pollutant.

  The present invention also provides a method and apparatus for decomposing a pollutant that obtains a reactant from a product obtained by decomposing the pollutant and further uses this reactant to decompose other pollutants. With the goal.

That is, the present invention
The present invention relates to a method for decomposing a pollutant that forms a gas and a metal compound that is separable from the gas by irradiating light with a contaminant to be treated to cause a decomposition reaction and then reacting with a metal.

More specifically,
In the method of decomposing pollutants, which targets organic chlorine compounds for decomposition,
Introducing a substance to be treated containing the organochlorine compound and performing light irradiation to decompose the organochlorine compound;
A method for decomposing a pollutant, comprising: bringing a gas generated by the light irradiation into contact with a metal; and reacting chlorine in the gas with the metal to remove chlorine from the gas. ,
Preferably, the reaction between the metal and the chlorine is included in the material to be treated, is generated by light irradiation decomposition, or is performed in the presence of treated water separately introduced into the apparatus. .

  Also preferably, the present invention relates to the pollutant decomposition method, wherein the metal is at least one selected from the group consisting of Fe, Mn, Co, Ni, Ti, and Cu.

  More preferably, the present invention relates to the pollutant decomposition method using a metal processed into a fiber shape.

Still further, preferably, the metal has a plurality of ionic valences different from each other, and the valence eluted from the metal by a contact reaction between the intermediate product organic substance generated by the photo-irradiation decomposition reaction of the substance to be treated and the metal and chlorine. Metal ions that decompose hydrogen peroxide into a mixture containing a smaller metal ion or a compound thereof to decompose the mixture into lower molecules and reduce the proportion of free chlorine and chlorine remaining in organic molecules. The pollutant decomposition method further comprising a decomposition reaction step;
Among these, the metal ion decomposition step further includes the step of decomposing the mixture into CO ₂ , hydrogen chloride, a metal ion having a higher valence and water,
Particularly preferably, in the metal ion decomposition step, the unreacted organochlorine compound is simultaneously decomposed, and the pollutant decomposition method described above,
Particularly preferably, an organochlorine compound separately provided with a metal ion having a lower valence eluted from the metal by contact reaction between the metal and chlorine or a mixture of the compound and hydrogen peroxide at a location away from the light irradiation means. The present invention relates to the pollutant decomposition method as described above, comprising a step of sending to the decomposition means and a step of performing the metal ion decomposition by mixing with an organochlorine compound supplied in advance to the decomposition means.

Also preferably, the pollutant decomposition method according to the above, wherein the metal ion having a higher valence is Fe ³⁺ ion.

  In addition, preferably, the organic chlorine compound is at least one selected from the group consisting of trichloroethylene, 1,1,1-trichloroethane, tetrachloroethylene, dichloroethylene, chloroform, and dichloromethane.

The present invention also provides:
The present invention relates to a pollutant decomposing apparatus having means for irradiating light to a treated pollutant and a means for forming a metal compound that is separable from the gas by reacting with a metal after causing a decomposition reaction. .

More specifically,
In the pollutant decomposition equipment, which is intended to decompose organochlorine compounds,
Means for introducing a substance to be treated containing the organic chlorine compound and irradiating with light to decompose the organic chlorine compound;
A pollutant decomposition apparatus characterized by having a metal as a means for reacting with chlorine in the gas generated by the light irradiation and removing chlorine from the gas,
Preferably, the reaction between the metal and the chlorine is performed in the presence of treated water that is contained in the material to be treated, is generated by light irradiation decomposition, or is separately introduced into the apparatus. Relates to the device.

  Further preferably, the present invention relates to the pollutant decomposition apparatus as described above, wherein the metal is at least one selected from the group consisting of Fe, Mn, Co, Ni, Ti, and Cu.

  More preferably, it relates to the pollutant decomposing apparatus as described above, wherein the metal is processed into a fiber shape.

More preferably, the metal has a plurality of ionic valences different from each other, and the valence eluted from the metal by the contact reaction between the metal and chlorine, and the intermediate product organic substance produced by the photo-irradiation decomposition reaction of the substance to be treated. Metal that decomposes the mixture into lower molecules by supplying hydrogen peroxide to a mixture containing a smaller metal ion or compound thereof, and reduces the proportion of chlorine remaining in free chlorine and organic molecules. The pollutant decomposition apparatus according to the above, further comprising ion decomposition reaction means,
Among these, the metal ion decomposition reaction means further includes means for decomposing the mixture into CO ₂ , hydrogen chloride, a metal ion having a higher valence and water,
Particularly preferably, the metal ion decomposition reaction means relates to the pollutant decomposition apparatus according to the above, wherein the unreacted organochlorine compound is also decomposed.
Particularly preferably, a metal ion having a lower valence eluted from the metal by the catalytic reaction between the metal and chlorine or a mixture of the compound and hydrogen peroxide is separately provided in a place away from the light irradiation means. The present invention relates to the pollutant decomposing apparatus as described above, wherein the apparatus decomposes metal ions by mixing with an organic chlorine compound supplied to the decomposing means in advance.

Also preferably, the pollutant decomposing apparatus as described above, wherein the metal ion having a higher valence is Fe ³⁺ ion.

  In addition, it is preferable that the organochlorine compound is at least one selected from the group consisting of trichloroethylene, 1,1,1-trichloroethane, tetrachloroethylene, dichloroethylene, chloroform, and dichloromethane.

  According to the pollutant decomposition / removal method and apparatus according to the present invention, the decomposition product after photolysis can be efficiently and simply processed.

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

  FIG. 1 shows a pollutant decomposition / removal apparatus according to an embodiment of the present invention.

  In FIG. 1, a pollutant gas containing an organic chlorine compound is sent to a photolysis tank 1 through an introduction pipe 2 and decomposed by irradiation with light. It is sent continuously to the liquid contact tower. The gas-liquid contact tower 3 is a sealed hollow shell structure, and the lower part 4 is filled with a circulating solution. A gas-liquid contact part 5 made of a filler having a high porosity and a small resistance to gas flow is built in the intermediate part, and the upper part of the gas-liquid contact part 5 is a spraying chamber 6 for spraying the absorbing liquid. The upper part of the spraying chamber 6 is connected through an exhaust pipe 7 to an absorption tower (not shown) as a secondary processing facility. 8 is a means for supplying an aqueous hydrogen peroxide solution to the circulating solution, and 9 is a circulating pump.

  For example, when the organic chlorine compound which is a pollutant is trichlorethylene, it is decomposed into dichloroacetic acid and chlorine when subjected to photolysis treatment with ultraviolet rays in one photolysis tank. The gas after this treatment is sent to the gas-liquid contact tower 3. When fibrous iron is used as the filler of the gas-liquid contact tower 3, chlorine in the process gas reacts with iron in the filler to produce iron chloride as a reactant. On the other hand, dichloroacetic acid easily moves into the circulating solution, and some of the chlorine dissolves in the solution, but as the solution circulates, most of the chlorine reacts with iron anyway, resulting in the circulating solution. Becomes a solution containing iron ions and dichloroacetic acid. Here, hydrogen peroxide is supplied from the hydrogen peroxide supply means 8. The concentration of the hydrogen peroxide solution is preferably 0.005% to 5%.

  A fenton reaction occurs between iron ions and hydrogen peroxide, and dichloroacetic acid, which is a decomposition product dissolved in the solution, is oxidized and mineralized by hydroxyl radicals generated by the fenton reaction.

  The Fenton reaction is an oxidation reaction by hydroxyl radicals (.OH) generated by the following metal ions and hydrogen peroxide.

M ²⁺ + H ₂ O ₂ → M ³⁺ + ・ OH + OH ⁻
M ′ ⁺ + H ₂ O ₂ → M ′ ²⁺ + ・ OH + OH ^{−
_{M "3+ + H 2 O 2}} → M" 4+ + · OH + OH -

  Chlorine, which is one of the decomposition products, is absorbed and removed in the gas-liquid contact tower 3 by reacting with iron. Although it is difficult to absorb completely, the load on the means (not shown) for chlorine absorption in the latter stage can be significantly reduced.

  The metal (element) causing the Fenton reaction can be suitably used as long as it is a transition metal typified by iron and has a plurality of valences and can repeat oxidation and reduction. Specifically, Mn, Co, Ni, Ti, and Cu can be mentioned in addition to Fe.

  Furthermore, dichloroacetic acid, which is another decomposition product, is decomposed into carbon dioxide gas and hydrogen chloride by the hydroxyl radical generated in the Fenton reaction in the absorption tower 3.

  That is, when the photodecomposed gas comes into contact with the metal, chlorine, which is one of the decomposition products, reacts with the metal, so that the chlorine is removed. Further, the reactant (for example, iron chloride) is used for a decomposition reaction (Fenton reaction) of haloacetic acid which is another decomposition product.

  In particular, since haloacetic acid flows into the reaction field, the pH of the reaction solution becomes low, which is a suitable condition for the Fenton reaction.

  Examples of organochlorine compounds to be decomposed by the Fenton reaction include haloacetic acids such as trichloroacetic acid and dichloroacetic acid, which are known to be generated when photo-degrading chloroethylene-based substances that are various chlorine substitution products of ethylene. And the present invention can be used to decompose the substance.

  In addition, the harmful substances that are subject to decomposition by the above photolysis were released from contaminated soil, contaminated groundwater, harmful substances obtained by aeration of contaminated water, and harmful substances adsorbed on activated carbon due to heat. It is contained in harmful substances and harmful substances in exhaust gas from factories and chemical processes. Examples of the substances other than the chloroethylene-based substances mentioned above include methane chlorine substitutes such as chloromethane, dichloromethane, trichloromethane, etc., or ethane chlorine substitutes.

  The contact between the gas and the metal after the photolysis treatment and the decomposition of the substance to be decomposed using the reactants may be carried out in an integrated manner using a gas-liquid contact tower or the like as described above. It is good also as a structure which isolate | separated the decomposition | disassembly of the decomposition target substance using the reaction substance and the contact of the gas after a process.

  For example, fibrous iron containing a reaction material generated by reacting with chlorine gas can be used for decomposition reaction and soil repair in other places. By mixing contaminated soil contaminated with an organic chlorine compound and the fibrous iron and adding hydrogen peroxide, the organic chlorine compound in the contaminated soil is decomposed. This is because the iron salt reacted with chlorine causes a Fenton reaction with hydrogen peroxide. That is, in this configuration, the iron in the filler serves as chlorine removal in the apparatus, and the iron salt generated there can be used for the decomposition reaction as it is.

  Further, fibrous iron or the like may be used only for the purpose of removing chlorine.

  Although the substance to be decomposed as a decomposition reaction in other places is not particularly limited, examples thereof include chlorinated ethylene and chlorinated methane. Specifically, examples of the chlorinated ethylene include 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 chlorinated methane include methane substituted chlorine, such as chloromethane, dichloromethane, trichloromethane, and tetrachloromethane. Among these, trichloroethylene, 1,1,1-trichloroethane, tetrachloroethylene, dichloroethylene, trichloromethane, and dichloromethane are more suitable for the decomposition method of the present invention.

  A configuration in which the reactants as described above are used to repair other places can also be used to repair the same contaminated soil. For example, when the concentration of the pollutant in the contaminated soil is high, suction or the like is performed from the contaminated soil to remove the pollutant, and this sucked gas is processed by an apparatus as shown in FIG. 1 to decompose the pollutant. When the concentration of pollutants has decreased to some extent, stop the suction and subsequent gas treatment, and mix the hydrogen peroxide with the reactants containing iron ions generated in the previous decomposition treatment in this contaminated soil. Can advance the Fenton reaction and further reduce the contamination concentration.

  The present invention can be used whether the substance to be decomposed is in a gaseous state or in a solution state.

  We have explained fibrous iron as an example of filler, but a material with a large surface area that can take a wide contact area is desirable and is not limited to a fibrous material. Sponge, powder, wire, wire woven Etc. can be used. Commercially available steel scrubbing and steel wool may be used as they are or after being processed.

  Further, the contact between the processing gas and the metal may use a part of a member such as a metal or a pipe in the reaction tank without using the filler. Any form may be used as long as the metal in the process gas and the chlorine in the process gas react with each other by the contact between the process gas and the metal, and iron ions necessary for the subsequent Fenton reaction are eluted into the reaction field.

  Moreover, although the material was explained about iron, any material may be used as long as it generates chlorine gas and chloride and causes a Fenton reaction. For example, at least one selected from the group of Fe, Mn, Co, Ni, Ti, and Cu can be used.

  Furthermore, although the organic chlorine compound and chlorine were demonstrated, the other component which shows the same behavior may be sufficient. That is, any substance can be used as long as it can react with a metal by decomposition by light irradiation to form a metal compound that can be separated from a gas.

  Examples of the present invention will be described in detail below.

[Example 1]
(Pollution gas purification system)
The pollutant decomposition according to the present invention was experimentally confirmed using a system configuration as shown in FIG. In this system, the contaminants in the photolysis reaction tank 5 are irradiated with light from the light irradiation means 6 to decompose the contaminants. The gas containing the decomposition product after the decomposition treatment is continuously sent into the gas-liquid contact tower 3.

  Chlorine, which is one of the decomposition products in the gas-liquid contact tower 3, reacts with the iron filler in the gas-liquid contact tower 3 to produce iron chloride. Further, another decomposition product, haloacetic acid, moves into the circulating solution. Hydrogen peroxide is added to the circulating solution, causing a Fenton reaction with iron ions, and haloacetic acid is decomposed.

  As a pollutant gas for the experiment, a gas diluted in the air to have a content of 100 ppmv (meaning volume ppm; the same applies hereinafter) is fed into the photolysis reactor as a contaminated gas for experiment, and a light source having a peak at 254 nm ( Using a germicidal lamp 5 (model name GL10: Toshiba Corporation, 10 W), the contaminated gas was irradiated with light. Sponge-like iron (Kishida, 60 mesh) was used as the iron filler for the gas-liquid contact tower 3.

  Contaminated gas was fed into the photolysis reaction tank so that the residence time was 1 minute.

  Hydrogen peroxide was supplied so that the concentration of hydrogen peroxide in the circulating liquid was 0.1%.

  When the trichlorethylene concentration was measured at the outlet of the discharge pipe 7 in order to confirm that trichlorethylene was decomposed in the photolysis reaction tank 5, it was 0.05 ppmv or less.

  The main photodegradation products of trichlorethylene are chlorine and dichloroacetic acid.

  In order to confirm the decomposition effect of dichloroacetic acid, which is a decomposition product, case-1 is an example in which circulating water added with hydrogen peroxide to 0.1% is added to the filler using iron of the present invention. As a comparative reference example, an experimental example using a filler made of a poorly reactive material without using an iron filler was designated as case-2, and hydrogen peroxide was added to 0.1%. An example is case-3.

  Under the above conditions, the polluted gas purification system was operated for 24 hours for case-1, case-2, and case-3 as examples of the present invention and reference experiments. After operating for 24 hours, the concentration of dichloroacetic acid in the circulating liquid in the gas-liquid contact tower 3 was compared, and in case-1 which is an experimental example of the present invention against the values of case-2 and case-3, It was found that more than 95% of the decomposition products were decomposed and mineralized by the Fenton reaction.

  It was also found that chlorine was absorbed almost 90% by iron filler.

[Example 2]
A 27.5 ml glass vial was prepared, 10 ml of tap water was added, and 10 g of the following contaminated soil was added.

Trichlorethylene concentration 11.3mg / kg
Tetrachlorethylene concentration 8.1mg / kg
Dichloromethane concentration 2.3mg / kg
1,1,1-trichloroethane concentration 8.3 mg / kg.

  Furthermore, a part of the iron filler containing the reactant used in Example 1, case-1 was added to a glass vial. To this was added 0.5 ml of 30% hydrogen peroxide (Wako) and sealed with a butyl rubber stopper with a Teflon liner and an aluminum seal.

  In addition, a sample not containing an iron filler containing a hydrogen peroxide solution or a reactive substance was prepared for comparison.

  After 24 hours, the concentration of the pollutant in the contaminated soil was measured, and only the sample containing the iron filler containing the hydrogen peroxide solution and the reactant was 0.01 mg / kg or less. There was no noticeable degradation in the other samples. As a result, it was confirmed that the contaminated soil was purified and the pollutants released from the contaminated soil were also decomposed.

[Example 3]
(Pollution gas purification system 2)
The light irradiation in the photolysis reaction tank 5 is a black light fluorescent lamp (model name: FL10BLB: Toshiba Corporation, 10 W) that does not contain a wavelength component of 300 nm or less, and the pollutant gases from the inlet tube 2 are 100ppmv and chlorine gas. An experiment similar to that of Example 1 was performed except that the pressure was 25 ppmv.

  By adding chlorine, chlorine radicals are generated with relatively low light energy, and a decomposition reaction proceeds between the chlorine radicals and trichlorethylene, and chlorine and dichloroacetic acid are detected in the treated gas after decomposition.

  When the trichlorethylene concentration was measured at the outlet of the discharge pipe 7 in order to confirm that trichlorethylene was decomposed in the photolysis reaction tank 5, it was 0.05 ppmv or less.

  More than 95% of dichloroacetic acid, a photolysis product of trichlorethylene, was decomposed and mineralized.

  It was also found that chlorine was absorbed almost 80% by iron filler.

It is the schematic of the contaminant decomposition | disassembly apparatus concerning one embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photolysis reaction tank 2 Introducing pipe 3 Gas-liquid contact tower 4 Electrode 5 Gas-liquid contact part 6 Spraying chamber 7 Discharge pipe 8 Hydrogen peroxide supply means 9 Pump

Claims (20)

In the method for decomposing pollutants, which targets organic chlorine compounds for decomposition,
Introducing a substance to be treated containing the organochlorine compound and performing light irradiation to decompose the organochlorine compound;
A method for decomposing a pollutant, comprising: bringing a gas generated by the light irradiation into contact with a metal, and reacting chlorine in the gas with the metal to remove chlorine from the gas.   The decomposition method according to claim 1, wherein the reaction between the metal and the chlorine is carried out in the presence of treated water that is contained in the material to be treated, is generated by light irradiation decomposition, or is separately introduced into the apparatus.   3. The pollutant decomposition method according to claim 1, wherein the metal is at least one selected from the group consisting of Fe, Mn, Co, Ni, Ti, and Cu.   The pollutant decomposition method according to claim 1, wherein the metal is processed into a fiber shape.   The metal having a plurality of ionic valences different from each other, and a metal ion having a smaller valence eluted from the metal by the contact reaction between the metal and chlorine, and an intermediate product organic substance generated by a light irradiation decomposition reaction of the substance to be treated A metal ion decomposition reaction step in which hydrogen peroxide is supplied to a mixture containing the compound to decompose the mixture to lower molecular weight and reduce the proportion of chlorine remaining in free chlorine and organic molecules. Furthermore, the contaminant decomposition | disassembly method in any one of Claims 1-4 which has. The pollutant decomposition method according to claim 5, wherein the metal ion decomposition step further includes a step of decomposing the mixture into CO ₂ , hydrogen chloride, a metal ion having a higher valence and water.   The pollutant decomposition method according to claim 5 or 6, wherein the unreacted organochlorine compound is simultaneously decomposed in the metal ion decomposition step.   A metal ion having a lower valence eluted from the metal by the contact reaction between the metal and chlorine or a mixture of the compound and hydrogen peroxide is added to the organic chlorine compound decomposition means separately provided at a location away from the light irradiation means. The pollutant decomposition method according to claim 7, further comprising a step of sending and a step of performing the metal ion decomposition by mixing with an organic chlorine compound supplied in advance to the decomposition means. The pollutant decomposition method according to any one of claims 5 to 8, wherein the metal ion having a higher valence is an Fe ³⁺ ion.   The pollutant decomposition method according to any one of claims 1 to 9, wherein the organic chlorine compound is at least one selected from the group consisting of trichloroethylene, 1,1,1-trichloroethane, tetrachloroethylene, dichloroethylene, trichloromethane, and dichloromethane. In the pollutant decomposition equipment, which is intended to decompose organochlorine compounds,
Means for introducing a substance to be treated containing the organic chlorine compound and irradiating with light to decompose the organic chlorine compound;
A pollutant decomposition apparatus comprising a metal as a means for reacting with chlorine in a gas generated by the light irradiation and removing chlorine from the gas.   12. The pollutant decomposition according to claim 11, wherein the reaction between the metal and the chlorine is carried out in the presence of treated water that is contained in the substance to be treated, is generated by light irradiation decomposition, or is separately introduced into the apparatus. apparatus.   13. The pollutant decomposing apparatus according to claim 11, wherein the metal is at least one selected from the group consisting of Fe, Mn, Co, Ni, Ti, and Cu.   14. The pollutant decomposition apparatus according to claim 11, wherein the metal is processed into a fiber shape.   The metal having a plurality of ionic valences different from each other, and a metal ion having a smaller valence eluted from the metal by the contact reaction between the metal and chlorine, and an intermediate product organic substance generated by a light irradiation decomposition reaction of the substance to be treated Metal ion decomposition reaction means for decomposing the mixture to lower molecular weight by supplying hydrogen peroxide to the mixture containing the compound and reducing the proportion of chlorine remaining in free chlorine and organic molecules. The pollutant decomposition apparatus according to any one of claims 11 to 14, further comprising: The metal ion decomposition reaction means, said mixture CO _2, pollutant decomposition apparatus according to any crab claims 11 to 14, further comprising hydrogen chloride, the means for decomposing to a larger metal ions and water valences .   17. The pollutant decomposition apparatus according to claim 15 or 16, wherein the metal ion decomposition reaction means also decomposes the unreacted organochlorine compound.   A metal ion having a lower valence eluted from the metal by the contact reaction between the metal and chlorine or a mixture of the compound and hydrogen peroxide is added to the organic chlorine compound decomposition means separately provided at a location away from the light irradiation means. 18. The pollutant decomposition apparatus according to claim 17, wherein the metal ion decomposition is performed by feeding and mixing with an organic chlorine compound supplied in advance to the decomposition means. 19. The pollutant decomposing apparatus according to claim 15, wherein the metal ion having a higher valence is Fe ³⁺ ion.   20. The pollutant decomposition apparatus according to any one of claims 9 to 19, wherein the organic chlorine compound is at least one selected from the group consisting of trichloroethylene, 1,1,1-trichloroethane, tetrachloroethylene, dichloroethylene, trichloromethane, and dichloromethane.

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