JP2009249705A - Electrode for electrolysis and use thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an poisoning-resistant electrode for electrolysis, which is, first, capable of reducing a nitrate nitrogen compound contained in a water liquid to be treated rapidly to an ammonia nitrogen compound and stably used in the presence of a corrosive material contained in the liquid to be treated without being corroded and second, capable of simply carrying out the sterilization or the degradation of bacteria or organic materials in the liquid to be treated without using excess chlorine and a treating method of a nitrate compound-containing waste using the same. <P>SOLUTION: The electrode for electrolysis is obtained by forming a conductive polymer layer on the surface of a metal or a carbon-made core material base body and the nitrogen compound contained in the water to be treated is electrolytically reduced using the same. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electrode for electrolysis for electrochemically treating nitrogen compounds contained in water to be treated, and more specifically, nitrate nitrogen compounds contained in water to be treated on one electrode. The present invention relates to a cathode electrode for electrolysis having a catalytic ability capable of reducing hydrogen to an ammoniacal nitrogen compound and capable of generating active oxygen for decomposing and sterilizing organic substances and bacteria contained in the water to be treated.

  In recent years, emission regulations on nitrogen compounds have been strengthened to prevent eutrophication in lakes and closed waters, and countermeasures have become an urgent issue at business establishments that discharge nitrate-containing wastewater. Biological reduction treatment technology has been almost established as a treatment method for this nitrate nitrogen-containing wastewater, but denitrifying bacteria used in this treatment technology are easily affected by pH and water temperature, and the reaction rate is slow and numerous. There is a disadvantage that sludge is also generated.

  In contrast, physicochemical reduction treatment techniques such as anion exchange method, cation exchange method, and electrodialysis method have the advantage that the treatment speed is significantly faster than biological reduction treatment. However, in this method, there is a problem in that a waste liquid containing high-concentration nitrate ions is generated and further processing is required.

In recent years, Patent Document 1 and Non-Patent Document 1 disclose a method for treating nitrate nitrogen-containing wastewater using electrolytic reduction.
This method is a method in which the nitrate nitrogen-containing wastewater is subjected to electrolytic treatment in an electrolytic cell having a diaphragm such as an ion exchange membrane. In the cathode side, using a cathode made of a copper-based alloy exhibiting high catalytic ability to reduction reaction of nitrate nitrogen compounds, NO ₃ ^- by reducing NO ₂ ^- was produced and then, the NO ₂ ^- further Reduce to produce ammonia. On the anode side, a dimensional stability electrode in which platinum, iridium dioxide, etc. are coated on a Ti substrate is used. Chlorine is produced on the electrode, and ammonia produced on the cathode side is reacted with the chlorine to produce nitrogen. By denitrifying the wastewater. In this way, it is possible to perform advanced wastewater treatment by sterilizing and decomposing germs and organic substances contained in the wastewater with the generated chlorine.

Here, with respect to the reduction electrode used in the above-described treatment method, it is generally said that the copper-based alloy exhibits a high catalytic ability for the reduction of the nitrate nitrogen compound. The fact that when an aqueous solution containing nitrate nitrogen is electrolytically reduced by the diaphragmless method, the conversion product is mainly nitrite nitrogen and the catalytic ability to convert nitrite nitrogen to ammonia nitrogen is not high. Was recognized.
In addition, the copper alloy electrode is easily corroded by the potential difference between the negative electrode and the positive electrode and the corrosive substance contained in the treatment liquid, and there is also an electrode poisoning problem that loses its catalytic ability, so it is even more durable There is a demand for a negative electrode having the property.

  Chlorine produced at the anode is used to denitrify ammonia and decompose and disinfect organic substances and bacteria in the wastewater, enabling more advanced wastewater treatment while efficiently producing excess chlorine. Therefore, since it is necessary to add a halogen raw material such as sodium chloride, the processing apparatus becomes complicated, and a simpler method is required from an economical viewpoint. In addition, there is a problem that organic substances such as humic substances may react with excess chlorine to produce carcinogenic trihalomethane, and therefore, it is necessary to develop a treatment method that can avoid the electrolytic treatment method accompanied by chlorine generation. ing.

For the above problems, it is expected to use active oxygen as an alternative to chlorine.
Patent Document 2 discloses a method for generating active oxygen by an electrochemical method using an electrode for electrolysis in which a conductive material surface is coated with a conductive composition composed of powder of a conductive material, a binder, and polyaniline. It is disclosed. However, there are many unclear points about the reduction catalytic ability by electrolytic treatment of nitrate-containing water by using the conductive polymer-coated electrode.

  Furthermore, since polyaniline has an electrochemically very precious potential, when it contacts a metal having a base potential, a local battery is formed and the metal dissolves. A method using carbon as a conductive material is also conceivable, but when used as a cathode, there is a problem in terms of electrode life that stress is generated inside the electrode due to hydrogen intercalation and the electrode collapses in a short time. .

JP 2003-88870 A Japanese Patent Laid-Open No. 10-316403 Hiroki Naoki, Jun Hirose, Naoki Kitayama, Electrochemistry, 2003, Vol. 71, No. 1, p. 24-28

  The object of the present invention is to comprehensively solve the above-mentioned problems, and the first problem is to quickly reduce nitrate nitrogen compounds contained in the water to be treated to ammonia nitrogen compounds. Another object of the present invention is to provide a poisoning-resistant electrolysis electrode that can be used stably without being corroded even in the presence of a corrosive substance contained in the liquid to be treated. In addition, the second problem is that an electrode for electrolysis that can easily treat sterilization / decomposition of germs and organic substances in the liquid to be treated without using excessive chlorine, and treatment of waste liquid containing nitrate compounds using the same. Is to provide a method.

In light of the above problems, the present inventors have conducted extensive studies,
As a result of reducing the water to be treated using an electrode for electrolysis formed by forming a conductive polymer layer on the surface of a metal or carbon core material, nitrate nitrogen compounds can be quickly reduced, and the same electrode From this, it was found that active oxygen can be generated with high efficiency, and the present invention has been completed.
That is, this invention is shown to the following (1)-(5).

  (1) An electrode for electrolysis wherein a conductive polymer layer is formed on the surface of a metal or carbon core substrate having a center line average roughness of 1.5 to 15 μm.

  (2) The electrode for electrolysis according to (1), wherein the conductive polymer layer is at least one selected from the group consisting of a polypyrrole derivative, a polythiophene derivative, and a polyaniline derivative.

  (3) The electrode for electrolysis according to (1) or (2) above, wherein the electric conductivity of the conductive polymer layer is 1 S / cm to 100 S / cm.

  (4) The electrode for electrolysis according to any one of (1) to (3), wherein the use is an electrolytic reduction reaction of a nitrogen compound contained in the water to be treated.

(5) A treatment method for electrochemical reduction by electrolyzing a nitrogen compound contained in the water to be treated,
Using the electrode for electrolysis according to any one of the above (1) to (4), a nitrate nitrogen compound contained in the water to be treated is reduced to ammonia nitrogen, and further various bacteria contained in the water to be treated; A method for treating a nitrogen compound-containing aqueous solution, wherein organic matter is sterilized and decomposed by active oxygen generated from the electrode for electrolysis.

  According to the present invention, a conductive polymer layer is provided on a metal or carbon core substrate and used as an electrolysis cathode electrode for nitrate nitrogen reduction function and active oxygen generation by an electrochemical method. The highly functional polymer functions highly as an electrode catalyst for nitrate nitrogen reduction reaction and active oxygen generation, and high water treatment is possible with one electrode.

  That is, a metal or carbon having a center line average roughness of 1.5 μm or more is used as a core substrate, and the surface of the core substrate is preferably 1 S / cm which is an electrode active material by an electrolytic polymerization method or a chemical polymerization method. By using an electrode formed with a conductive polymer having the above conductivity, it has good adhesion even in electrolysis with gas generation, and nitrate nitrogen reduction reaction and active oxygen generation on one electrode surface It becomes possible to act simultaneously as a catalyst for.

  Furthermore, since the electrode coated with the conductive polymer layer has significantly improved corrosion resistance, it becomes an electrode for electrolysis excellent in poisoning resistance.

  In the electrode for electrolysis of the present invention, the core substrate used is a metal or carbon, and when used as a cathode, carbon or iron, nickel, cobalt, titanium, zirconium, niobium, tantalum, from the viewpoint of corrosion resistance to the use environment. It is preferably at least one metal substrate selected from the group consisting of aluminum, copper, zinc, tin, platinum, ruthenium, iridium, and alloys based on them.

  By increasing the substantial surface area of the core material substrate, the characteristics of the conductive polymer layer, which is an electrode active material, can be fully extracted, and after the surface is cleaned, the core material and the conductive polymer layer are activated. In order to improve the adhesion, it is preferable to use a surface of which the surface is roughened by blasting, etching or the like in advance.

  As the surface roughness, the center line average roughness of the substrate surface is preferably 1.5 μm or more or 15.0 μm or less. This is because if the average roughness of the center line on the surface of the substrate is less than 1.5 μm or more than 15.0 μm, the effect of increasing the adhesion and the surface area decreases, and it becomes difficult to form an electrode active material more uniformly. It is. In particular, from the viewpoint of adhesion and ease of roughening by chemical and physical methods, the degree of roughening is more preferably 2.5 μm or more and 10 μm or less, and most preferably the degree of roughening is 3.5 μm or more and 10 μm or less. The method for roughening the surface of the core material substrate is not particularly limited, and a conventionally known method can be used, such as a blasting method using alumina particles or the like, a wet etching method using hydrofluoric acid, etc. A method suitable for the core material substrate can be selected.

  Next, a conductive polymer film that is an electrode active material is coated on the roughened core material substrate.

The type of the conductive polymer that can be used in the present invention is not particularly limited, but at least one selected from the group consisting of a polypyrrole derivative, a polythiophene derivative, and a polyaniline derivative in terms of conductivity, stability, and reduction catalyst performance. Is preferred. Among these, polypyrrole derivatives and polythiophene derivatives that are excellent in heat resistance and oxidation resistance are more preferable because they are used in an atmosphere such as heat generation due to electrode resistance and a nitrate substance that is an oxidizing substance contained in an aqueous solution.
Specific examples of the polypyrrole derivative include polypyrrole, and specific examples of the polythiophene derivative include poly-3,4-ethylenedioxythiophene.

Examples of the method for coating the conductive polymer include an electrolytic polymerization method and a chemical polymerization method.
As a method for forming a conductive polymer film by electrolytic polymerization, for example, when a polypyrrole film is formed, pyrrole as a monomer, sodium naphthalenesulfonate functioning as a supporting electrolyte, tetraethylammonium tetrafluoroborate, etc. A polypyrrole film can be formed on the substrate by dissolution in a solvent such as pure water and electrolytic oxidation polymerization using a stainless steel substrate as a cathode and a roughened core substrate as an anode. The electrode active material layer by the electrolytic polymerization method is dense and highly regular, and has a long polymer chain and can be entangled with the dopant molecule well, so that a film that is difficult to be dedoped and excellent in mechanical strength can be obtained. Features are suitable for the formation of polypyrrole, polyaniline and their derivatives.
In the chemical polymerization method, a conductive polymer film having high corrosion resistance can be formed by bringing a monomer of a desired conductive polymer into contact with an oxidizing agent solution on a roughened core material substrate. it can.
For example, when a poly-3,4-ethylenedioxythiophene film is formed, 3,4-ethylenedioxythiophene as a monomer and p-toluene as an oxidant are formed on a roughened core substrate. A poly-3,4-ethylenedioxythiophene coating can be obtained by contacting a butanol solution containing iron (III) sulfonate. The chemical polymerization method is suitable for forming a polythiophene derivative, because fine particles are densely packed, can further increase the substantial surface area, and can dramatically bring out the characteristics of the electrode material.

Further, a conductive polymer such as polyaniline powder is dissolved in a special solvent such as N-pyrrolidone to prepare a coating solution, and the coating solution is applied to the surface of the conductive material and then dried at a high temperature of 100 ° C. or higher. Although the solution method can also be used, the soluble conductive polymer is limited, the conductivity of the electrode active material is low in molecular structure, and the solvent has a large environmental load. Furthermore, since high internal stress is generated due to shrinkage caused by solvent removal during drying and shrinkage generated during cooling, it may be difficult to maintain adhesion to the substrate during electrolysis accompanied by gas generation.
Therefore, in order to achieve the effect of the present invention better, the chemical polymerization method and the electrolytic polymerization method are suitable.

  This electrode functions as a cathode electrode in an aqueous solution, but involves a hydrogen generation reaction in addition to the reduction reaction of nitrate nitrogen and the reaction of generating active oxygen. The hydrogen generates a force to peel the conductive polymer film, which is an electrode active material, from the core material substrate. Therefore, there is a coating method by an electropolymerization method that can easily increase the mechanical strength and easily obtain good adhesion. Among them, a polypyrrole film having high nitrate nitrogen reducing ability and active oxygen generating ability is more preferred.

  In order to function as an electrode for electrolysis, the conductive polymer is required to have high conductivity. If it is less than 1 S / cm, the electrolysis voltage becomes abnormally high and the conductive polymer as the electrode active material is destroyed. Therefore, a π-conjugated conductive polymer having a conductivity of about 1 to 100 S / cm is used. Although preferable, from a viewpoint of electrolytic reduction ability, More preferably, it is 5-100 S / cm, More preferably, it is 10-100 S / cm. In addition, polypyrrole, polythiophene, and derivatives thereof formed by the above-described method are highly doped with a dopant firmly fixed to a polymer chain and having a conductivity of about 1 to 100 S / cm and a high conductivity electrode active material. It can be formed easily.

  In addition, the core material substrate is subjected to bending processing such as press processing, cutting processing, etching processing, etc., and then conducting a conductive polymer forming step, so that even a complex-shaped electrode is conductive. The effect of the conductive polymer film can be reliably obtained without damaging the conductive polymer film. For example, regarding the formation of a conductive polymer film, if electrolytic polymerization is performed using the processed core material substrate as an electrode as described above, the conductive polymer film can be uniformly formed even if the substrate surface is uneven by processing. It becomes possible to form, and stable performance can be obtained.

  The thickness of the conductive polymer layer to be formed is suitably 0.01 μm to 100 μm, but from the viewpoints of economy and mechanical strength, 0.05 μm to 50 μm is more preferable, and 0.5 μm to 35 μm is most preferable. .

  Next, a method for electrolytic reduction of the nitrogen compound contained in the water to be treated according to the present invention will be described. Specifically, in the electrolytic cell, the electrode for electrolysis of the present invention is set as a cathode, and an electrode made of platinum foil or the like is set as an anode, and an aqueous solution containing a nitrate nitrogen source is subjected to diaphragmless electrolysis so that nitrate nitrogen is obtained. Can be reduced to nitrite nitrogen and even ammonia nitrogen.

  Hereinafter, the present invention will be described in more detail with reference to examples. In addition, this invention is not limited at all by this Example.

Example 1
A Ti substrate (JIS type 2) was used as the metal substrate. The Ti substrate is a rolled material having a size of 50 × 50 mm and a thickness of 0.5 mm. The substrate was finished with a satin finish by shot blasting using a zircon shot to obtain a surface with a center line average roughness of 11.5 μm. Next, after degreasing treatment with an acetone solvent, the substrate was immersed in 3N hydrochloric acid for 30 seconds to perform acid aqueous solution cleaning, and then washed with water to complete the Ti substrate surface treatment step.

Next, a conductive polymer film that is an electrode active material is formed by electrolytic polymerization on the Ti substrate that has undergone the surface treatment process. A Ti substrate subjected to surface treatment using an electrolytic solution containing pure water as a solvent, pyrrole 0.5 mol / L as a monomer, and tetraethylammonium-p-toluenesulfonic acid 0.25 mol / L as a supporting electrolyte is an anode. SUS304 was used as the cathode, the electropolymerization time was 1 hour, and the current density was 1 mA / cm ² , and electropolymerization was performed to form a 25 μm-thick polypyrrole film to prepare a cathode electrode for electrolysis.
The electrical conductivity of the conductive polymer film was measured and found to be 53 S / cm.

(Example 2)
A SUS316 substrate was used as the metal substrate. The SUS316 substrate is a rolled material having a size of 50 × 50 mm and a thickness of 0.5 mm. The substrate was satin-finished by shot blasting using zircon shot to obtain a surface with a center line average roughness of 9.5 μm. Next, after degreasing treatment with an acetone solvent, the substrate was immersed in 3N hydrochloric acid for 30 seconds, washed with an aqueous acid solution, washed with water, and the SUS316 substrate surface treatment step was completed.

Next, a conductive polymer film as an electrode active material is formed by chemical polymerization. On the surface of the SUS316 substrate after finishing the surface treatment process, an ethanol solution containing pyrrole as a monomer and tetraethylammonium polyvinylsulfonate (average molecular weight 100,000) as a dopant agent is applied by spraying, and then an oxidizer solution. This series of steps of spraying a butanol solution in which iron (III) polyvinyl sulfonate was dissolved and drying at 40 ° C. for 5 minutes was repeated to form a polypyrrole film having a thickness of 21 μm, and a cathode electrode for electrolysis was produced.
The electrical conductivity of the conductive polymer film was measured and found to be 16 S / cm.

(Example 3)
A high purity graphite substrate was used as the carbon substrate. The high purity graphite substrate is a plate material having a size of 50 × 50 mm and a thickness of 5 mm. The substrate was finished with a satin finish by blasting using glass beads to obtain a surface with a centerline average roughness of 10.7 μm. Next, after degreasing treatment with an acetone solvent, the substrate was immersed in 1N hydrofluoric acid for 1 minute, washed with an acid aqueous solution, washed with water, and the carbon substrate surface treatment step was completed.

Next, a conductive polymer film, which is an electrode active material, is formed on the high-purity graphite substrate after the surface treatment process by an electrolytic polymerization method. The solvent is propylene carbonate, the monomer is ethylenedioxythiophene 0.2 mol / L, and the supporting electrolyte is tetraethylammonium-6- [3,6-bis (diethylamino) xanthenium-9-yl] benzene-1,3-disulfone Using an electrolytic solution containing 0.1 mol / L of acid, surface-treated high-purity graphite substrate is used as an anode, SUS304 is used as a cathode, electrode electropolymerization time is 1 hour, and current density is 1 mA / cm ^2. A polyethylene dioxythiophene film having a thickness of 13 μm was formed to produce a cathode electrode for electrolysis.
The electrical conductivity of the conductive polymer film was measured and found to be 22 S / cm.

Example 4
A phosphorous deoxidized copper substrate was used as the metal substrate. The phosphorous deoxidized copper substrate is a rolled material having a size of 50 × 50 mm and a thickness of 0.5 mm. The base was finished by blasting using alumina particles to obtain a surface with a centerline average roughness of 9.9 μm. Next, after degreasing treatment with an acetone solvent, the substrate was immersed in 1N hydrochloric acid for 1 minute to wash with an aqueous acid solution, and washed with water to finish the phosphorous deoxidized copper substrate surface treatment step.

Next, a conductive polymer film as an electrode active material is formed by chemical polymerization. On the surface of the phosphorous deoxidized copper substrate after the surface treatment step, an ethanol solution containing ethylenedioxythiophene as a monomer and tetraethylammonium-p-toluenesulfonic acid as a dopant agent is applied by spray, and then an oxidant solution. This series of steps of spraying a butanol solution in which iron (III) p-toluenesulfonate is dissolved and drying at 40 ° C. for 5 minutes is repeated to form a polyethylene dioxythiophene film having a thickness of 9 μm. A cathode electrode was prepared.
The electrical conductivity of the conductive polymer film was measured and found to be 32 S / cm.

(Example 5)
A high purity graphite substrate was used as the carbon substrate. The high purity graphite substrate is a plate material having a size of 50 × 50 mm and a thickness of 5 mm. The substrate was finished with a satin finish by blasting using glass beads to obtain a surface with a center line average roughness of 8.9 μm. Next, after degreasing treatment with an acetone solvent, it was immersed in 1N hydrofluoric acid for 1 minute, washed with an aqueous acid solution, washed with water, and the high purity graphite substrate surface treatment step was completed.

Next, a conductive polymer film as an electrode active material is formed by chemical polymerization. The high-purity graphite substrate after the surface treatment step was immersed in a solution containing 0.1M aniline as a monomer and 0.2M dodecylbenzenesulfonic acid as a dopant agent (adjusted to pH 1 with sulfuric acid) for 1 minute. The aqueous aniline solution was applied to the surface by pulling up at a pulling rate of 10 mm / min. Subsequently, this series of steps of spraying a 2.5 M aqueous solution of ammonium persulfate by spraying and drying at 40 ° C. for 15 minutes was repeated to form a polyaniline film having a thickness of 11 μm, thereby preparing a cathode electrode for electrolysis.
The electrical conductivity of the conductive polymer film was measured and found to be 1.8 S / cm.

(Comparative Example 1)
A cathode electrode for electrolysis made of Ti was produced in the same manner as in Example 1 except that the conductive polymer film as the electrode active material was not formed.

(Comparative Example 2)
In Example 2, a SUS316 electrolysis cathode electrode was produced in the same manner except that the conductive polymer film as the electrode active material was not formed.

(Comparative Example 3)
A high-purity graphite electrolysis cathode electrode was produced in the same manner as in Example 3 except that the conductive polymer film as the electrode active material was not formed.

(Comparative Example 4)
A cathode electrode for electrolysis made of phosphorus-deoxidized copper base was prepared in the same manner as in Example 4 except that the conductive polymer film as the electrode active material was not formed.

1: Evaluation as an electrode for reducing nitrate nitrogen A solution containing nitrate nitrogen was made to act as an electrode for electrolysis on the cathode electrode for electrolysis according to the present invention and the electrode prepared in the comparative example. Comparison was made by electrolytic reduction. The electrode for electrolysis produced in the examples and comparative examples was used as a cathode, a platinum plate as an anode, ultrapure water as a solvent, potassium nitrate as a supporting electrolyte, and an electrolyte prepared to 100 mM as a substrate concentration, and 0.5 A / dm ² This was carried out by constant current non-electrolytic membrane electrolysis. During the reaction, the reduction performance was compared by quantitatively analyzing nitrite nitrogen and ammonia nitrogen generated by reduction of nitrate nitrogen by ion chromatography (IC method). FIG. 1 shows the change over time in the nitrate nitrogen concentration when using the electrodes prepared in Examples 1 to 5, FIG. 2 shows the change over time in the nitrite nitrogen concentration, and FIG. 3 shows the change over time in the ammonia nitrogen concentration. Indicated. Further, FIG. 4 shows the change over time in the nitrate nitrogen concentration when using the electrodes prepared in Comparative Examples 1 to 4, FIG. 5 shows the change over time in the nitrite nitrogen concentration, and FIG. 5 shows the change over time in the ammonia nitrogen concentration. This is shown in FIG.

2: Evaluation as an electrode for hydrogen peroxide generation Further, in the previous experimental conditions, in order to measure the generated active oxygen as hydrogen peroxide, a high performance liquid chromatography method (HPLC method) equipped with an electrochemical detector was used. The results of quantitative analysis and comparison of the production performance are shown in FIG. 7 (when using the electrodes prepared in Examples 1 to 5) and FIG. 8 (when using the electrodes prepared in Comparative Examples 1 to 4).

  According to the results of FIG. 1, in electrolysis using the cathode electrode for electrolysis according to the present invention, nitrate nitrogen greatly decreased to 40 mM or less in all electrodes after 10 hours of electrolysis, and very high reducing ability. It was found that On the other hand, according to FIG. 4 which is a result of using the electrode produced in the comparative example, it was shown that in the comparative example 4, the nitrate nitrogen was greatly reduced and the nitrate nitrogen reducing ability was obtained. It was confirmed that the electrode of 2 was 60 mM or more, and the electrode of Comparative Examples 1 and 3 was 95% or more, which was not suitable as an electrode for treating nitrate nitrogen.

  According to the result of FIG. 2, in the electrolysis using the cathode electrode for electrolysis according to the present invention, nitrate nitrogen is reduced at the initial stage of electrolysis, and nitrite nitrogen is gradually generated, so that the concentration is temporarily high. However, the nitrite nitrogen also starts to reduce and gradually decreases. After 10 hours of electrolysis, in all the electrodes, the nitrite nitrogen concentration was suppressed to 50 mM or less, and it was confirmed that the performance of reducing nitrite nitrogen was excellent. On the other hand, according to FIG. 5, which is the result of using the electrode prepared in the comparative example, the nitrite nitrogen concentration was increased with the electrolysis time even in the electrode manufactured in Comparative Example 4 in which nitrate nitrogen was highly reduced. The reduction performance of nitrite nitrogen was confirmed to be low because it increased more than the example and the decreasing tendency seen thereafter was small.

  According to the results of FIG. 3, in electrolysis using the cathode electrode for electrolysis according to the present invention, nitrite nitrogen is reduced with the electrolysis time to produce ammonia nitrogen, and in particular, polypyrrole which is an electrode active material It has been confirmed that polyethylene dioxythiophene formed by electrolytic polymerization is excellent. On the other hand, according to FIG. 6 which is the result of using the electrode produced in the comparative example, it was confirmed that the ammonia-nitrogen production reaction hardly occurred, so that the ability to reduce nitrite nitrogen was inferior.

  According to the results of FIG. 7, in the electrolysis using the cathode electrode for electrolysis according to the present invention, the generation of hydrogen peroxide was observed, and in the case where the electrode active material was made of polypyrrole or polyethylenedioxythiophene, 5 ppm or more. It was confirmed to be excellent. On the other hand, according to FIG. 8, which is the result of using the electrode produced in the comparative example, since the production of hydrogen peroxide cannot be confirmed with the electrode produced in the comparative example, excess by electrolytic reduction using metal or carbon is not possible. Production of hydrogen oxide proved difficult.

  The cathode electrode for electrolysis according to the present invention is mainly used for an electrode for generating active oxygen effective for electrochemical reduction of nitrate nitrogen, sterilization / sterilization, or decomposition of organic substances. It can also be suitably used as a reaction electrode.

In nitrate ion reduction experiment, it is the figure which showed the change of the nitrate ion concentration with the electrolysis time at the time of using the cathode electrode for electrolysis produced in Examples 1-5. In nitrate ion reduction experiment, it is the figure which showed the change of nitrite ion with the electrolysis time at the time of using the cathode electrode for electrolysis produced in Examples 1-5. In nitrate ion reduction experiment, it is the figure which showed the change of the ammonium ion concentration with electrolysis time at the time of using the cathode electrode for electrolysis produced in Examples 1-5. In nitrate ion reduction experiment, it is the figure which showed the change of the nitrate ion concentration with the electrolysis time at the time of using the cathode electrode for electrolysis produced in Comparative Examples 1-4. In nitrate ion reduction experiment, it is the figure which showed the change of the nitrite ion concentration with the electrolysis time at the time of using the cathode electrode for electrolysis produced in Comparative Examples 1-4. In nitrate ion reduction experiment, it is the figure which showed the change of the nitrite ion density | concentration accompanying the electrolysis time at the time of using the cathode electrode for electrolysis produced in Comparative Examples 1-4. In a nitrate ion reduction experiment, it is the figure which showed the change of the hydrogen peroxide concentration with electrolysis time at the time of using the cathode electrode for electrolysis produced in Examples 1-5. In a nitrate ion reduction experiment, it is the figure which showed the change of the hydrogen peroxide concentration with electrolysis time at the time of using the cathode electrode for electrolysis produced in Comparative Examples 1-4.

Claims (5)

  An electrode for electrolysis, wherein a conductive polymer layer is formed on the surface of a metal or carbon core substrate having a center line average roughness of 1.5 μm to 15 μm.   The electrode for electrolysis according to claim 1, wherein the conductive polymer layer is at least one selected from the group consisting of a polypyrrole derivative, a polythiophene derivative, and a polyaniline derivative.   The electrode for electrolysis according to claim 1 or 2, wherein the electric conductivity of the conductive polymer layer is 1 S / cm to 100 S / cm.   The electrode for electrolysis according to any one of claims 1 to 3, wherein the use is an electrolytic reduction reaction of a nitrogen compound contained in the water to be treated. A treatment method for electrochemical reduction of a nitrogen compound contained in water to be treated by electrolysis,
Using the electrode for electrolysis according to any one of claims 1 to 4, the nitrate nitrogen compound contained in the water to be treated is reduced to ammonia nitrogen, and the germs and organic matter contained in the water to be treated are further reduced. A method for treating an aqueous solution containing a nitrogen compound, which comprises sterilizing and decomposing by active oxygen generated from the electrode for electrolysis.

Images