Dehalogenation apparatus and dehalogenation method

Abstract

This invention provides a technology for the dehalogenation of organic halogen compounds that can suppress the generation of secondary products while minimizing environmental impact. [Solution] The dehalogenation apparatus comprises an electrolytic cell 20, a processing liquid 22 contained in the electrolytic cell 20, an anode 40 and a cathode 30 immersed in the processing liquid 22. The processing liquid 22 contains an organic halogen compound having an unsaturated bond, an electrolyte, and vitamin B 12 or / and vitamin B 12 It contains derivatives. The pH of the treatment solution 22 is greater than 7 and less than or equal to 13.

Description

Technical Field

[0001] The present invention relates to a dehalogenation apparatus and a dehalogenation method.

Background Art

[0002] Organic halogen compounds such as organic chlorine compounds are known as substances that pollute soil and groundwater. There is a need for a technology to dehalogenate and detoxify or purify this organic halogen compound.

[0003] Non-Patent Document 1 (p587-590) discloses a bioremediation method (decomposition by microorganisms). In Non-Patent Document 1, a hydrogen donor is added and decomposing microorganisms are supplied to soil groundwater (bioaugmentation), or indigenous microorganisms are activated (biostimulation) to perform dechlorination under anaerobic conditions. Purifying agents such as lactic acid-based and yeast-based agents are known as hydrogen donors. Also, Non-Patent Document 1 (p587-590) discloses a method of adding a reducing agent and chemically performing dechlorination under anaerobic conditions. Iron powder is common as the reducing agent. The reaction pathway is the same as the above-described bioremediation method. Also, Non-Patent Document 1 (p587-590) discloses a method of adding an oxidizing agent and chemically performing oxidative decomposition. Examples of the oxidizing agent include ozone, hydrogen peroxide, persulfate, permanganate, and hydrogen peroxide and iron salts. The decomposition reaction pathway is different from the above-described bioremediation method and the method using a reducing agent, and is complex. Also, Non-Patent Document 2 discloses a method of installing an electrode in a medium and energizing it to dechlorinate a volatile organic compound (VOC) by an oxidation-reduction reaction at the electrode.

Prior Art Documents

Non-Patent Documents

[0004]

Non-Patent Document 1

[0005] In practical terms, bioremediation (decomposition by microorganisms) is suitable for in-situ remediation of contaminants up to a maximum concentration of approximately 10 mg / L (10 ppm), but depending on the decomposition activity of the microorganisms, remediation may take a considerable amount of time (several months to years). While decomposition using reducing agents is known to be applicable to higher concentrations and to have a faster decomposition reaction compared to bioremediation, its addition to the ground generally requires mechanical work involving stirring and mixing, which is costly and may alter the pH environment. Decomposition using oxidizing agents, like reducing agents, can be applied to high concentrations and often decomposes compounds in a shorter time than reducing agents. However, because they do not selectively decompose chlorine compounds, if many other organic substances are present, large amounts of chemicals must be used, which is not good from a cost or environmental perspective. Furthermore, the reaction pathway is complex, and the harmfulness of secondary products (such as chloroform and dichloromethane) must be taken into consideration. Electrolysis can be applied to high concentrations and decomposes substances in a short period of time, but it does not selectively decompose chlorine compounds, so if many other organic substances are present, it may consume a large amount of electricity. Furthermore, the reaction pathway is complex, and attention must be paid to the harmfulness of secondary products (such as chloroform and dichloromethane). In view of the above-mentioned problems, the present invention aims to provide a technology for the dehalogenation of organic halogen compounds that can suppress the generation of secondary products while reducing environmental impact. [Means for solving the problem]

[0006] One aspect of the present invention is a dehalogenation device. The dehalogenation device includes an electrolytic cell, a treatment liquid accommodated in the electrolytic cell, and an anode and a cathode immersed in the treatment liquid. The treatment liquid contains an organic halogen compound having an unsaturated bond and an electrolyte, and vitamin B is present on the surface of the cathode. 12 or a vitamin B 12 derivative is provided, or the treatment liquid contains vitamin B 12 or / and vitamin B 12 derivative, and the pH of the treatment liquid is greater than 7 and 13 or less. In the dehalogenation device of the above aspect, the organic halogen compound may be an organic chlorine compound. When vitamin B 12 or / and vitamin B 12 derivative is contained in the treatment liquid, the concentration of vitamin B 12 or / and vitamin B 12 derivative may be 0.05 to 0.50 mmol / L. The material of the anode may be a carbon material. The electrolyte may be one or more selected from sodium chloride, sodium sulfate, sodium hydroxide, barium hydroxide, sodium acetate, and ammonium chloride.

[0007] Another aspect of the present invention is a dehalogenation method. The dehalogenation method includes an electrolysis step of applying a constant voltage between an anode and a cathode immersed in a treatment liquid or applying a voltage so that a constant current flows between the anode and the cathode. The treatment liquid contains an organic halogen compound having an unsaturated bond and an electrolyte, and vitamin B is present on the surface of the cathode. 12 or a vitamin B 12 derivative is provided, or the treatment liquid contains vitamin B 12 or / and vitamin B 12 derivative, and the pH of the treatment liquid is greater than 7 and 13 or less. In the dehalogenation method of the above aspect, the organic halogen compound may be an organic chlorine compound. When vitamin B 12or / and vitamin B 12 When a derivative is included, vitamin B 12 or / and vitamin B 12 The concentration of the derivative may be 0.05 to 0.50 mmol / L. The material of the cathode may be a carbon material. The electrolyte may be one or more selected from sodium chloride, sodium sulfate, sodium hydroxide, barium hydroxide, sodium acetate, and ammonium chloride. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a technology for dehalogenating organic halogen compounds that can suppress the generation of secondary products while suppressing environmental impact. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a schematic diagram of a dehalogenation apparatus according to Embodiment 1. [Figure 2] Figure 2 is a schematic diagram illustrating the dehalogenation reaction that proceeds under an alkaline environment in the "dehalogenation apparatus or dehalogenation method" of Embodiment 1. [Figure 3] Figure 3 is a schematic diagram illustrating the pathway by which the C1 product is formed using NaCl as the supporting electrolyte. [Figure 4] Figure 4 shows the homocoupling reaction in the dechlorination process of tetrachloroethylene. [Figure 5] Figure 5 is a schematic diagram illustrating the dehalogenation reaction that proceeds under alkaline conditions in the dehalogenation apparatus 10 or dehalogenation method of Embodiment 2 (a schematic diagram illustrating the route in which PCE is dechlorinated to TCE and then the C1 product is formed). [Figure 6] Figure 6 shows the homocoupling reaction in the dechlorination process of trichloroethylene. [Figure 7] Figure 7 is a graph showing the time course of the PCE dechlorination reaction carried out under the same conditions as in Example 1. [Figure 8] Figure 8 is a graph showing the time course of the PCE dechlorination reaction carried out under the same conditions as in Example 6. [Figure 9] Figure 9 shows the cyclic voltammogram (CV) of a hydrophobic vitamin B12 / Nafion-modified carbon electrode. [Figure 10] Figure 10 is a graph showing the change over time when the initial concentration of tetrachloroethylene was biostimulated for 180 days under conditions similar to those in Examples 1 and 6. [Modes for carrying out the invention]

[0010] Embodiments of the present invention will be described in detail below. In this specification, unless otherwise specified, the notation "a~b" in the description of numerical ranges means a or greater and b or less.

[0011] (Embodiment 1) Figure 1 is a schematic diagram of a dehalogenation apparatus 10 according to Embodiment 1. The dehalogenation apparatus 10 comprises an electrolytic cell 20, a cathode 30, an anode 40, and a power supply 50.

[0012] The electrolytic cell 20 is a container for the processing solution 22. The processing solution 22 will be described later. The material of the electrolytic cell 20 is not particularly limited as long as it is alkali resistant, for example, glass or plastic.

[0013] The cathode 30 and anode 40 are immersed in the processing solution 22. The shapes of the cathode 30 and anode 40 are not particularly limited and may be, for example, rod-shaped or plate-shaped.

[0014] Carbon materials can be used as the materials for the cathode 30 and anode 40. Specifically, carbon materials include carbon nanotubes (CNTs), graphite, and glassy carbon.

[0015] The power supply 50 is electrically connected to the cathode 30 and the anode 40. The power supply 50 is a galvanostat that controls the voltage applied between the cathode 30 and the anode 40 and maintains a constant current flowing between the cathode 30 and the anode 40. Alternatively, a constant voltage may be applied between the cathode 30 and the anode 40.

[0016] <Processing solution> The treatment solution 22 contains organic halogen compounds having unsaturated bonds, electrolytes, and vitamin B 12 or / and vitamin B 12 It contains derivatives. The pH of the treatment solution 22 is preferably greater than 7 to 13, and more preferably 8 to 12. In other words, the treatment solution 22 is alkaline.

[0017] Examples of organic halogen compounds containing unsaturated bonds include organochlorine compounds such as tetrachloroethylene (PCE).

[0018] Examples of electrolytes include one or more selected from sodium chloride, sodium sulfate, sodium hydroxide, barium hydroxide, sodium acetate, and ammonium chloride.

[0019] <Vitamin B 12 or / and vitamin B 12 Derivatives> Vitamin B 12 or / and vitamin B 12 Derivatives are collectively called vitamin B 12 It is called a compound. Vitamin B 12 The compound is vitamin B 12 It is a compound with a skeleton, specifically a vitamin B compound having a structure in which a cobalt ion ligand is attached to a choline ring. 12 (Cyanocobalamin) is a common vitamin. 12 The compound is represented by the following chemical formula. [ka] In the above chemical formula, L is the cyano group (vitamin B) that is coordinated to the Co atom. 12 ) or water molecules (vitamin B12a (Aquacobalamin) represents

[0020] Vitamin B in processing solution 22 12 or / and vitamin B 12 Derivatives (Vitamin B 12 The concentration of the compound is preferably 0.05 to 0.50 mmol / L, and more preferably 0.10 to 0.20 mmol / L.

[0021] <Dehalogenation reaction> Figure 2 is a schematic diagram illustrating the dehalogenation reaction that proceeds under alkaline conditions in the dehalogenation apparatus 10 or dehalogenation method of Embodiment 1. In Figure 2, the case where the organic halogen compound is tetrachloroethylene (PCE) is illustrated as an example.

[0022] Figure 3 is a schematic diagram illustrating the pathway by which the C1 product is formed using NaCl as the supporting electrolyte. As shown in Figure 3, when NaCl is used as the supporting electrolyte under alkaline conditions, Cl derived from NaCl - Therefore, the electrolytic reaction of NaCl produces hypochlorite (ClO - ) occurs. The generated ClO - It adds to PCE to produce chlorohydrin. Chlorohydrin is Cl - It is eliminated and an acid chloride is formed, which hydrolyzes to produce trichloroacetic acid (TCA). TCA is deprotonated and oxidized to COO · While generating seeds, decarboxylation occurs. When decarboxylation occurs, the CC single bond is broken, · It produces CCl3 (a C1 compound). Under alkaline conditions, the reaction pathway with oxygen becomes dominant. · CCl3 reacts with oxygen to undergo a homocoupling reaction. The homocoupling reaction is shown in Figure 4. Subsequently, O2 decomposes, and Cl · It is eliminated, and then 2HCl is eliminated in the aqueous solution, producing CO2.

[0023] (Embodiment 2) Regarding the dehalogenation apparatus and dehalogenation method of Embodiment 2, the same configurations as in Embodiment 1 will be omitted, and the configurations that differ from Embodiment 1 will be described.

[0024] In this embodiment, the treatment solution 22 is vitamin B 12 or Vitamin B 12 Instead of including the derivative, vitamin B is placed on the surface of cathode 30. 12 or Vitamin B 12 A derivative is provided. In other words, at least a portion of the surface of the cathode 30 is vitamin B 12 or Vitamin B 12 It is coated or modified with a derivative.

[0025] Vitamin B at cathode 30 12 or Vitamin B 12 Methods for introducing derivatives include the spin coater method and the dipping method. By the spin coater method, vitamin B is added to cathode 30. 12 or Vitamin B 12 The specific method for providing derivatives will be described later. As a coating solution to modify cathode 30, hydrophobic vitamin B 12 It is preferable to use a coating solution which is a mixture of a compound and a polymer electrolyte. The polymer electrolyte is not limited, but an example is Nafion®. Hydrophobic vitamin B 12 An example of a compound is [Co(II)7C3ester]ClO4(C2), represented by the following formula. Note that the number of carbon atoms in the side-chain ester substituent in the following formula is not limited to 3; for example, it may have 1 to 8 carbon atoms. [ka]

[0026] <Dehalogenation reaction> Figure 5 is a schematic diagram illustrating the dehalogenation reaction that proceeds under alkaline conditions in the dehalogenation apparatus 10 or dehalogenation method of Embodiment 2. In Figure 5, the case where the organic halogen compound is tetrachloroethylene (PCE) is illustrated as an example.

[0027] As shown in Figure 5, in this embodiment, vitamin B is present on the cathode side. 12 The PCE is reduced and activated, and dechlorinated to TCE. Alternatively, TCE is produced by a direct reductive dechlorination reaction from the cathode. ClO derived from NaCl generated under alkaline conditions - It adds to TCE to produce chlorohydrin. Chlorohydrin is Cl - It is eliminated, and an acid chloride is formed, which hydrolyzes to produce dichloroacetic acid (DCA). DCA is deprotonated and oxidized to COO · While generating seeds, decarboxylation occurs. When decarboxylation occurs, the single bond between C and C breaks, producing ·CHCl2 (a C1 compound). Under alkaline conditions, the reaction pathway with oxygen becomes dominant. ·CHCl2 reacts with oxygen to undergo a homocoupling reaction. The homocoupling reaction is shown in Figure 6. Subsequently, O2 decomposes, and Cl · It is eliminated, and then 2HCl is eliminated in the aqueous solution to produce formic acid (HCOOH).

[0028] (Halogen-free method) The dehalogenation method of this disclosure includes an electrolytic step of applying a constant voltage between an anode and a cathode immersed in a processing solution, or applying a voltage such that a constant current flows between the anode and the cathode. This step can be carried out using the dehalogenation apparatus 10 described above. The treatment solution is as described above and contains an organic halogen compound having an unsaturated bond and an electrolyte. Examples of electrolytes include one or more selected from sodium sulfate, sodium chloride, sodium hydroxide, barium hydroxide, sodium acetate, and ammonium chloride. The pH of the treatment solution is preferably greater than 7 to 13. As in Embodiment 2, vitamin B is placed on the surface of the cathode. 12 or Vitamin B 12A derivative may be provided, and as in Embodiment 1, the processing solution may contain vitamin B 12 or / and vitamin B 12 Derivatives may also be included. Details of the organic halogen compound, treatment solution, and cathode are as described above.

[0029] The dehalogenation apparatus or dehalogenation method described above may produce the following effects. Vitamin B is a dehalogenation catalyst. 12 By using compounds and performing electrolysis in an alkaline environment, organic halogen compounds such as chloroethenes, which are soil and groundwater pollutants, can be dehalogenated, decomposed, and rendered harmless. By creating an alkaline environment in the treatment solution, the generation of secondary products produced by the decomposition of organic halogen compounds can be suppressed and decomposed. In particular, when the organic halogen compound is an organochlorine compound, the generation of harmful substances and precursors such as chloroform and dichloromethane can be suppressed and decomposed. Also, vitamin B 12 This improves the durability of the compound itself and enhances the persistence of the decomposition effect of organic halogen compounds. Vitamin B 12 The compound is of biological origin, non-toxic, and a water-soluble vitamin. Therefore, after dehalogenation treatment, vitamin B 12 Because it is biodegradable, the environmental burden can be reduced. Dehalogenation of highly concentrated treatment solutions containing organic halogen compounds with unsaturated bonds, which are contaminants, can be performed in a shorter time compared to biostimulation. Vitamin B 12 By using a compound as a catalyst, it is possible to accelerate the dehalogenation reaction while reducing power consumption. Based on the above effects, it is possible to effectively and efficiently decompose contamination by high concentrations of organic halogen compounds in soil and groundwater.

[0030] The embodiments of the present invention have been described above, but these are merely examples, and various other configurations can also be adopted. [Examples]

[0031] The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited thereto.

[0032] (Example 1) <Processing solution> A treatment solution with the following components and their respective concentrations was prepared. Water: 1L PCE: 0.166 mM (27.6 ppm, 27.6 mg) Vitamin B 12a (Aquacobalamin): 0.1 mM (134.8 mg) Na2SO4: 0.1M (14.2g) NaOH: 0.1M (4.0g)

[0033] The pH of the treatment solution in Example 1 was 13.193.

[0034] Dehalogenation treatment (electrolytic treatment) was performed under the following conditions. Constant current electrolysis: 20mA (current density = 0.5mA / cm 2 ) Cathode: Carbon rod Anode: Carbon rod Current flow: 1645C, 24h Experimental environment: Under air

[0035] <Analysis of the treated solution after dehalogenation treatment> After 24 hours, 0.2 mL of the dehalogenated treatment solution was taken and diluted in a vial containing 9.8 mL of distilled water to prepare the analytical solution. The content of tetrachloroethylene (PCE), trichloroethylene (TCE), cis-1,2-dichloroethylene, trans-1,2-dichloroethylene, vinyl chloride, ethylene, chloroform, and dichloromethane in the treatment solution was measured by headspace gas chromatography-mass spectrometry (HS-GCMS). The results are shown in Table 1. Vitamin B 12aIt can be seen that by performing electrolysis in an alkaline environment using [the specified method], the dechlorination of PCE proceeds, and C2 products are produced.

[0036] (Comparative Example 1) Vitamin B 12a Except for the absence of (aquacobalamin), the dehalogenation treatment was carried out in the same manner as in Example 1, and the treated solution sample was analyzed. The results obtained are shown in Table 1. Vitamin B 12a When the additive is not used, the yield of the C2 product is lower compared to Example 1, indicating that the dechlorination of PCE does not proceed easily.

[0037] (Example 2) Except for using 0.1M NaCl instead of Na2SO4 as the supporting electrolyte, the dehalogenation treatment was performed in the same manner as in Example 1, and a sample of the treated solution was analyzed. It was found that even when NaCl was used as the supporting electrolyte, the dechlorination of PCE proceeded in the same way as with Na2SO4.

[0038] (Example 3) Except for not using Na2SO4 as the supporting electrolyte, NaOH was used to adjust the environment to an alkaline state, and the dehalogenation treatment was carried out in the same manner as in Example 1, and a sample of the treated solution was analyzed. The results obtained are shown in Table 1. When only NaOH was used as the supporting electrolyte, the yield of the C2 product was lower compared to Example 1, and the dechlorination of PCE did not proceed well, indicating that a supporting electrolyte such as Na2SO4 is necessary.

[0039] (Example 4) The amount of NaOH added is 2.1 × 10 -2 Except for using mM (0.84 mg) and adjusting the pH of the treatment solution to 9.016 (weakly alkaline), the dehalogenation treatment was carried out in the same manner as in Example 1, and the sample of the treatment solution was analyzed. The results obtained are shown in Table 1. Vitamin B 12a It can be seen that dechlorination of PCE progresses when electrolysis is performed in a weakly alkaline environment using [the specified method].

[0040] [Table 1] "ND" indicates that the detection limit was not met. "<0.001%" indicates that the target compound was detected, but the yield was less than 0.001%. The values ​​in parentheses in the pH column indicate that the pH conditions are the same as in Example 1, and therefore the values ​​are considered equivalent.

[0041] (Example 5) Except for adding 0.132 mM (21.9 ppm, 21.9 mg) of TCE instead of PCE to the treatment solution, the dehalogenation treatment was carried out in the same manner as in Example 1, and a sample of the treatment solution was analyzed. The results obtained are shown in Table 2. Vitamin B 12a It can be seen that by performing electrolysis in an alkaline environment using [the specified method], dechlorination of TCE proceeds, similar to PCE, and C2 products are produced.

[0042] (Comparative Example 2) Except for not adding NaOH to the treatment solution and maintaining a pH near neutral (6.131), the dehalogenation treatment was carried out in the same manner as in Example 5, and a sample of the treatment solution was analyzed. The results are shown in Table 2. It can be seen that, in a non-alkaline environment, the dechlorination of TCE proceeds less smoothly compared to Example 5.

[0043] [Table 2] "ND" indicates that the detection limit was not met. The values ​​in parentheses in the pH column indicate that the pH conditions are the same as in Example 1, and therefore the values ​​are considered equivalent.

[0044] (Example 68: Hydrophobic Vitamin B 12 (Nafion-modified electrodes) <Processing of carbon electrodes> The surface of the carbon electrode (carbon plate, 10 cm long, 4 cm wide, 2 mm thick) was polished using abrasive paper (mesh=2000), and then the carbon electrode was washed with distilled water. Next, the surface of the carbon electrode was polished using alumina abrasive (BAS Corporation, 0.05 μm polishing alumina), and then the carbon electrode was washed with distilled water. The carbon electrode was immersed in anhydrous ethanol and ultrasonically cleaned for 5 minutes. After that, the surface of the carbon electrode was dried using a nitrogen gun.

[0045] <Preparation of coating solution> 0.1 mL of Nafion® dispersion (1-propanol (45.0% by mass), water (42.0% by mass), ethanol (4.0% by mass), Nafion (5.0% by mass)), 1.26 mL of ethanol, and 0.64 mL of distilled water were mixed and stirred by ultrasonic vibration for 5 minutes. Then, 7.14 mg of heptapropyl cobyrinate perchlorate ([Co(II)7C3ester]ClO4 (hydrophobic vitamin B) was added. 12 (2.68 mM) was added and stirred by ultrasonic vibration for 5 minutes to dissolve and obtain a coating solution. [ka]

[0046] <Modification of carbon electrodes> The carbon electrode was placed in a spin coater with one side facing upwards, and the coating solution described above was applied. It was then rotated at a speed of 500 rpm for 30 seconds. Afterward, it was rotated at a speed of 1000 rpm for 30 seconds to form a coating film on one surface of the carbon electrode. The resulting coating film was dried by natural drying. Next, the carbon electrode was placed in a spin coater with the other side facing upwards, and the coating solution was applied. It was then rotated at a speed of 500 rpm for 30 seconds. Afterward, it was rotated at a speed of 1000 rpm for 30 seconds to form a coating film on the other surface of the carbon electrode. The resulting coating film was dried by natural drying. Through these steps, the surface of the carbon electrode was treated with B 12 It was covered with it.

[0047] <Confirmation of carbon electrode modification> The working electrode (WE) is the hydrophobic vitamin B mentioned above. 12 A Nafion-modified carbon electrode was used, with a platinum wire as the counter electrode (CE) and Ag / AgCl as the reference electrode (RE). A solution of 0.71 g of 0.1 M Na2SO4 dissolved in 50 ml of water was used to obtain a cyclic voltammogram (CV) under a nitrogen atmosphere. The obtained CV is shown in Figure 9. Furthermore, a cyclic voltammogram (CV) was obtained under the same conditions as above, except that the above solution was saturated with PEC. The obtained CV is shown in Figure 9. Furthermore, a cyclic voltammogram (CV) was obtained under the same conditions as above, except that the working electrode (WE) was an unmodified carbon electrode (carbon plate). The obtained CV is shown in Figure 9. From the CV shown in Figure 9, hydrophobic vitamin B is present on the carbon electrode. 12 / Nafion has been modified (hydrophobic vitamin B 12 It was confirmed that the surface of the carbon electrode was coated with Nafion, and also hydrophobic vitamin B 12 The reactivity to PCE was confirmed.

[0048] <Processing solution> A treatment solution with the following components and their respective concentrations was prepared. Water: 1L PCE: 0.166 mM (27.6 ppm, 27.6 mg) Vitamin B 12a (Aquacobalamin): 0.1 mM (134.8 mg) (Used only in Example 7) Na2SO4: 0.1M (14.2g) NaOH: 0.1M (4.0g)

[0049] The pH of the treatment solution in Example 6 was 13.193.

[0050] Dehalogenation treatment (electrolytic treatment) was performed under the following conditions. Constant current electrolysis: 20mA (current density = 0.25mA / cm 2 ) Cathode: Hydrophobic vitamin B obtained by the method described above 12 Nafion-modified carbon electrode Anode: Carbon plate (10cm long, 4cm wide, 2mm thick) Current flow: 1645C, 24h Experimental environment: Under air

[0051] <Analysis of the treated solution after dehalogenation treatment> Similar to Example 1, after 24 hours, 0.2 mL of the treatment solution after dehalogenation treatment was collected and diluted in a vial containing 9.8 mL of distilled water to prepare the analytical solution. The content of tetrachloroethylene (PCE), trichloroethylene (TCE), cis-1,2-dichloroethylene, trans-1,2-dichloroethylene, chloroform, and dichloromethane in the treatment solution was measured by headspace gas chromatography-mass spectrometry (HS-GCMS). The results are shown in Table 3. Vitamin B 12 It can be seen that by performing electrolysis in an alkaline environment using a Nafion-modified electrode, the dechlorination of PCE proceeds and a C2 product is produced. Furthermore, sampling and analysis were performed at 1, 2, 3, 4, 6, 7, 8, 21, 23, and 24 hours after the start of the reaction. Figure 7 shows the changes in yield over time for tetrachloroethylene (PCE), trichloroethylene (TCE), cis-1,2-dichloroethylene, and trans-1,2-dichloroethylene.

[0052] (Comparative Example 3) Except for using an unmodified carbon electrode as the cathode, the dehalogenation treatment was carried out in the same manner as in Example 8, and a sample of the treated solution was analyzed. The results are shown in Table 3. Compared to Example 6, electrolysis using an unmodified carbon electrode yielded a lower yield of C2 products, indicating that dechlorination of PCE was less efficient.

[0053] (Example 7) Except for changing the carbon electrode from a carbon rod to a carbon plate, the dehalogenation treatment was performed in the same manner as in Example 1, and a sample of the treated solution was analyzed. The results are shown in Table 3. Even when the shape of the carbon electrode is a carbon plate, it can be seen that the dechlorination of PCE proceeds equivalently to that in Example 1 (where the carbon electrode is a carbon rod). Also, from Example 6 (hydrophobic vitamin B 12 -modified electrode) and Example 7 (homogeneous system), it can be seen that the dechlorination of PCE proceeds whether vitamin B 12 is modified on the electrode or dissolved in the treatment solution. In addition, since the amount of immobilized hydrophobic vitamin B 12 on the modified electrode in Example 6 is 1.34 mg (both sides of the cathode carbon plate), and the addition amount of vitamin B 12 to the treatment solution in Example 7 (homogeneous system) is 134.8 mg, it can be seen that the dechlorination of PCE using the modified electrode is more efficient than that of the homogeneous system.

[0054]

Table 3

[0055] (Time-course change of PCE dechlorination reaction) Under the same conditions as in Example 6, the treatment solution was sampled at each elapsed time shown in Table 4, and the treatment solution was analyzed. The obtained results are shown in Table 4. Figure 8 is a graph showing the time-course change of the PCE dechlorination reaction.

[0056]

Table 4

[0057] (Comparison of decomposition rates with biostimulation) To quantitatively evaluate the decomposition reaction rate of tetrachloroethylene (PCE) by biostimulation and Example 1 (homogeneous system where vitamin B 12a was dissolved in the treatment solution, alkaline environment) or Example 8 (hydrophobic vitamin B 12 / Nafion-modified electrode, alkaline environment), the first-order reaction rate constant was calculated. The following formula was used for the calculation formula.​​ C t =C0×e -λt λ: First-order reaction rate constant t: Number of days elapsed C t PCE concentration after t days from start C0: PCE concentration at the start of the test (t=0) (initial value) Furthermore, under conditions where the initial concentration of tetrachloroethylene was approximately the same as in Example 1 or Example 6 (30 ppm), biostimulation was performed using anaerobic microorganisms to which a hydrogen donor (polylactic acid polymer type) had been added, and the treated solution was analyzed at various time intervals. The results obtained for the first-order reaction rate constant are shown in Table 5. Furthermore, biostimulation was carried out for 180 days under conditions similar to those in Examples 1 and 6, with an initial concentration of tetrachloroethylene. Figure 10 shows the changes over time when biostimulation was carried out for 180 days with an initial concentration of tetrachloroethylene under conditions similar to those in Examples 1 and 6. Examples 1 and 6 show a first-order reaction rate constant 33.5 to 226 times higher than biostimulation, suggesting that early degradation can be expected.

[0058] [Table 5] [Industrial applicability]

[0059] The dehalogenation apparatus or dehalogenation method described herein can dehalogenate organic halogen compounds while suppressing environmental impact, and is expected to be used for the purification of soil and groundwater. [Explanation of symbols]

[0060] 10 Dehalogenation device, 20 Electrolytic cell, 22 Processing solution, 30 Cathode, 40 Anode, 50 Power supply

Claims

1. Electrolytic cell and The processing liquid contained in the electrolytic cell, an anode and a cathode immersed in the aforementioned processing liquid, Equipped with, The aforementioned treatment solution contains an organic halogen compound having an unsaturated bond, Electrolytes, Includes, The material of the cathode is a carbon material. Vitamin B １２ or Vitamin B １２ A derivative is provided, or the processing solution contains vitamin B １２ or / and vitamin B １２ A dehalogenation apparatus comprising a derivative, wherein the pH of the treatment solution is greater than 8 and less than or equal to 13.

2. The dehalogenation apparatus according to claim 1, wherein the organic halogen compound is an organic chlorine compound.

3. Vitamin B in the aforementioned processing solution １２ or / and vitamin B １２ When derivatives are included, vitamin B １２ or / and vitamin B １２ The dehalogenation apparatus according to claim 1, wherein the concentration of the derivative is 0.05 to 0.50 mmol / L.

4. The dehalogenation apparatus according to claim 1, wherein the electrolyte is one or more selected from sodium chloride, sodium sulfate, sodium hydroxide, barium hydroxide, sodium acetate, and ammonium chloride.

5. The process includes an electrolysis step of applying a constant voltage between an anode and a cathode immersed in a processing solution, or applying a voltage such that a constant current flows between the anode and the cathode. The aforementioned treatment solution contains an organic halogen compound having an unsaturated bond, Electrolytes, Includes, The material of the cathode is a carbon material. Vitamin B on the surface of the cathode １２ or a derivative of vitamin B １２ is provided, or the treatment liquid contains vitamin B １２ or / and a derivative of vitamin B １２ and the pH of the treatment liquid is greater than 8 and less than or equal to 13, a dehalogenation method.

6. The dehalogenation method according to claim 5, wherein the organic halogen compound is an organic chlorine compound.

7. Vitamin B in the aforementioned processing solution １２ or / and vitamin B １２ When derivatives are included, vitamin B １２ or / and vitamin B １２ The dehalogenation method according to claim 5, wherein the concentration of the derivative is 0.05 mmol / L to 0.50 mmol / L.

8. The dehalogenation method according to claim 5, wherein the electrolyte is one or more selected from sodium chloride, sodium sulfate, sodium hydroxide, barium hydroxide, sodium acetate, and ammonium chloride.

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