JP2005230707A - Electrochemical reaction method and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrochemical reaction method and apparatus capable of effectively producing an objective substance at low costs by reducing waste of power supply due to overvoltage. <P>SOLUTION: The electrochemical reaction apparatus 10 is equipped with an anode member 13 and a cathode member 14 oppositely disposed in a solution inside an electrolytic cell 15, and an electric signal generater for applying electric signals superimposed with positive pulse high voltage component and direct voltage component between these electrodes. In the apparatus, the solution in the vicinity of the electrode interface is subjected to the electrochemical reaction by the application of the electric signals. In the electrochemical reaction apparatus 10, the anode member 13 has a structure of supporting catalysts on a substrate formed with conductive materials. The catalysts are oxidized on the surface of the anode member 13 by the application of the electric signals to be a highly oxidized state, which are metals or metal oxides capable of oxidizing organic matters in the solution. The catalysts may preferably be Ru, Fe, Os, Mn, Mo, Co, Ir, Ni, or W, or an oxide of one of them or a mixture of their oxides. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electrochemical reaction method and an apparatus for applying a predetermined electrical signal between electrodes immersed in an aqueous solution to subject the aqueous solution to an electrochemical treatment, and particularly to an organic substance, a nitrogen compound, or a difficulty contained in the aqueous solution. The present invention relates to an electrochemical reaction method capable of decomposing and removing decomposable substances and the like and the apparatus.

  Conventionally, as a method of removing organic substances and the like from an aqueous solution in a wastewater treatment facility or the like, there is a method of decomposing and removing using a catalyst and an oxidizing agent as disclosed in, for example, Japanese Patent Publication No. 51-48387 (Patent Document 1). In this method, sodium hypochlorite is used as an oxidizing agent, and these substances are removed by passing an aqueous solution through a packed bed of a nickel peroxide-based catalyst or a cobalt peroxide-based catalyst. It has difficulty in decomposing difficult-to-decompose organic substances, and it is necessary to use an excess amount of sodium hypochlorite with respect to the stoichiometric amount in order to completely decompose organic substances to a low concentration. It was.

  Moreover, there exists Unexamined-Japanese-Patent No. 2003-251357 (patent document 2) etc. as a processing method which combined electrolysis and a catalyst layer. This method is a method in which an oxidizable substance-containing water is electrolyzed in the presence of chloride ions, and a step of contacting the metal oxide catalyst in the presence of free residual chlorine. Since the layers are arranged separately, there is a problem that radical active species with a short lifetime other than hypochlorous acid generated in the electrolytic cell cannot be used efficiently in the catalyst layer. Furthermore, in electrolysis, diamond electrodes are used. Therefore, there was a problem of high cost and peeling.

  Furthermore, a method for decomposing and removing organic substances using an electrochemical reaction is disclosed in Japanese Patent Application Laid-Open No. 2001-286866 (Patent Document 3). Such a method is a method in which an active species such as titanium oxide, cobalt oxide, tin oxide, iridium oxide, nickel oxide, and iron oxide is supported on the anode and electrolyzed in a direct current or pulse manner. However, when electrolysis is performed with direct current in this way, there are problems such as separation of the catalyst species supported on the surface of the anode and low generation efficiency of oxidation active species. Further, in the pulse electrolysis, a reverse current flows when the voltage application is stopped, and the applied voltage is reversed, so that the active species generated when the voltage is applied is diffused and is not consumed and is wasted.

Japanese Patent Publication No. 51-48387 JP 2003-251357 A JP 2001-286866 A

  Thus, in removing organic substances, nitrogen compounds, or hardly decomposable substances contained in the aqueous solution, only the oxidative decomposition treatment with an oxidizing agent or catalyst such as sodium hypochlorite is due to excessive use of the oxidizing agent. Since the increase in processing cost becomes a problem, processing using an electrochemical reaction is regarded as an effective method. In particular, radical active species having strong oxidizing power such as oxidized radicals and hydroxy radicals generated by electrochemical reaction of aqueous solutions can easily oxidize and decompose hardly decomposable substances such as dioxins and PCBs, Further, since an oxidizing agent such as hypochlorous acid or hydrogen peroxide that decomposes these oxidizable substances can be generated, a significant improvement in the decomposition reaction efficiency can be achieved.

However, as described above, since radically active species have low stability and short life, the conventional treatment method cannot efficiently control the decomposition reaction. Further, when the applied voltage is set high in order to improve the reaction efficiency, most of the input electric power escapes to thermal energy as an overvoltage, which is difficult to establish economically.
Accordingly, the present invention provides an electrochemical reaction method and apparatus capable of reducing the waste of supplied power due to overvoltage and generating a target substance more efficiently and inexpensively in view of the above-mentioned problems of the prior art. The purpose is to do.

  First, the concept of a general electrochemical reaction will be described. As shown in FIG. 7, in general, an electrochemical reaction is composed of an electron transfer process involving a reaction at the interface between an electrode member and an aqueous solution, and a material transport process in which the reactant is transported from the aqueous solution side to the electrode member. Has been. Next, as shown in FIG. 8, in the case of the anode, when a positive voltage is applied from the power source, negative ions present in the aqueous solution gather in the vicinity of the anode, and the positively charged thin layer in the anode and the negative ions in the aqueous solution are collected. As a result, an electric double layer is formed in which the negatively charged thin layers face each other, and the electric field in the aqueous solution is neutralized. When the value of the applied positive voltage is a small value of about several [V], an electric field is hardly applied inside the aqueous solution due to the electric double layer formed in the vicinity of the electrode surface.

  If the voltage is continuously applied as it is, electron transfer occurs on the electrode surface due to an electrochemical reaction, and the concentration of the reaction precursor material decreases, resulting in a charge imbalance (electron transfer process). In order to compensate for the charge imbalance, a new reaction precursor is supplied from the aqueous solution (mass transport process). In this case, if the electrode voltage is set to a value slightly higher than the voltage necessary for the electrochemical reaction, the electrochemical reaction can be caused, and the input power can be contributed to the electrochemical reaction. However, when the electrode voltage (overvoltage) is small, the electric field strength applied to the aqueous solution is small, and the driving force in the mass transport process for supplying a new reaction precursor is small, so that the reaction does not proceed moderately.

  On the other hand, in order to forcibly drive ions, which are reaction precursors in an aqueous solution, by an external electric field, it is necessary to apply a high voltage higher than the electric field canceled by the electric double layer. However, in this case, the applied voltage higher than the number of voltages [V] required for the electrochemical reaction (for example, 1.2 [V] in water splitting) becomes an overvoltage and consumed as Joule heat. Therefore, the input power energy is wasted.

  In view of this, the present inventors disclosed in Japanese Patent Application Laid-Open No. 2003-211165 and Japanese Patent Application No. 2003-16456 previously filed between an anode member and a cathode member installed in an electrolytic treatment tank for storing an aqueous solution to be treated. In addition, an electrical signal in which a positive pulse high voltage component and a DC positive voltage component are superimposed is applied, and an electrical signal is applied to the interface between the anode member, the cathode member, and the aqueous solution by applying the electrical signal of the positive pulse high voltage component. It has been proposed that a double layer is formed and an aqueous solution in the vicinity of the anode member interface and in the vicinity of the cathode member interface is caused to undergo an electrochemical reaction by applying an electric signal of the DC positive voltage component.

  According to this configuration, the anion of the aqueous solution in the electrolytic treatment tank is attracted to the surface of the anode member during the time width in which the voltage corresponding to the pulse width of the positive pulse high voltage component is applied between the anode member and the cathode member. An electric double layer is formed at the interface with the aqueous solution, and immediately after that, by applying a positive DC voltage capable of causing an electrochemical reaction at the interface between the attracted anion and the anode member, the attracted anion is An electrochemical reaction can be performed. Accordingly, it is possible to reduce the waste of supplied power due to overvoltage and to generate a desired substance more efficiently.

Furthermore, in the present invention, as a method for developing Japanese Patent Application Laid-Open No. 2003-211165 and Japanese Patent Application No. 2003-16456, and performing such electrochemical reaction more efficiently,
1st invention applies the electrical signal which superimposed the positive pulse high voltage component and the direct-current voltage component between the anode member and cathode member which were opposingly arranged in the aqueous solution in an electrolytic treatment tank, and this electrical signal In the method of causing an electrochemical reaction of an aqueous solution near the electrode interface by applying
The anode member has a structure in which a catalyst made of metal or metal oxide is supported on a substrate formed of a conductive material, and an electric signal is applied to the anode member to The electrochemical reaction method is characterized in that the catalyst is brought into a highly oxidized state and an organic substance in the aqueous solution is oxidized by the catalyst in the highly oxidized state.
In addition, as an apparatus for suitably carrying out such a method, an anode member and a cathode member which are disposed opposite to each other in an aqueous solution in an electrolytic treatment tank, and an electric pulse in which a positive pulse high voltage component and a DC voltage component are superimposed between these electrodes. In an electrochemical reaction device comprising an electrical signal generator for applying a signal, and electrochemically reacting an aqueous solution in the vicinity of an electrode interface by applying the electrical signal,
The anode member has a structure in which a catalyst is supported on a substrate formed of a conductive material, and the catalyst is oxidized on the surface of the anode member by application of the electric signal to be in a highly oxidized state. Then, an electrochemical reaction device is proposed, which is a metal or metal oxide capable of oxidizing an organic substance in an aqueous solution.
At this time, it is preferable that the catalyst is any one of Ti, Sn, Pb, and oxides thereof, or a mixture thereof.

As described above, the present invention uses a metal or metal oxide that can be in a state of different valences as a catalyst, thereby causing reactions as shown in the following reaction formulas (1) to (4).
MO _x + H ₂ O → MO _x (.OH) + H ⁺ + e ⁻ (1)
MO _x (.OH) → MO _{x + 1} + H ⁺ + e ⁻ (2)
MO _{x + 1} → MO _x + 1 / 2O ₂ (3)
MO _{x + 1} + R → MO _x + RO (4)
That is, a low-oxygen state metal produces a highly oxidized metal via a chemisorbed .OH radical (hydroxy radical). An organic substance (described as R in the above formula (4)) is oxidized by the highly oxidized metal. Since this reaction occurs at the MO _x / MO _{x + 1} redox potential, the high oxidation state is O ₂ / H ₂ O redox potential (1.23 V vs RHE) and H ₂ O / H ₂ O ₂ redox potential (1.77 V).
vs RHE) is desirable.

As another invention, in the second invention, an electrical signal in which a positive pulse high voltage component and a DC voltage component are superimposed is applied between an anode member and a cathode member which are disposed to face each other in an aqueous solution in an electrolytic treatment tank. In the method of electrochemically reacting the aqueous solution near the electrode interface by applying the electric signal,
The anode member has a structure in which a catalyst made of a metal or a metal oxide is supported on a substrate formed of a conductive material, has a high oxygen overvoltage, and applies an electric signal to the anode member. An electrochemical reaction method is proposed which oxidizes organic substances in an aqueous solution by promoting the formation reaction of radical active species including hydroxy radicals on the surface of a member.
Further, an anode member and a cathode member that are disposed opposite to each other in the aqueous solution in the electrolytic treatment tank, and an electrical signal generator that applies an electrical signal in which a positive pulse high voltage component and a DC voltage component are superimposed between these electrodes, In an electrochemical reaction device for electrochemically reacting an aqueous solution in the vicinity of an electrode interface by applying the electrical signal,
The anode member has a structure in which a catalyst is supported on a substrate formed of a conductive material, and the catalyst has a high oxygen overvoltage and promotes a generation reaction of radical active species including hydroxy radicals. It is a metal oxide.
More preferably, the catalyst may be any one of Ti, Sn, Pb, and oxides thereof, or a mixture thereof.

In this way, the anode member has a structure in which a metal or metal oxide that has a high oxygen overpotential and promotes a reaction of generating radical active species including a hydroxy radical is supported, whereby the following reaction formulas (5), (6 The organic substance can be decomposed to CO ₂ by the reaction mechanism shown in FIG.
MO _x + H ₂ O → MO _x (.OH) + H ⁺ + e ⁻ (5)
MO _x (.OH) + R → MO _x + mCO ₂ + H ⁺ + e ⁻ (6)
That is, OH radicals physically adsorbed on the surface of the metal or metal oxide are generated, and the OH radicals oxidize and decompose organic substances. This reaction is a reaction using H ₂ O ₂ as an intermediate, and occurs at an H ₂ O / H ₂ O ₂ redox potential (1.77 V vs RHE).

Further, the third invention applies an electrical signal in which a positive pulse high voltage component and a direct current voltage component are superimposed between an anode member and a cathode member which are disposed opposite to each other in an aqueous solution in an electrolytic treatment tank, In the method of causing an electrochemical reaction of an aqueous solution near the electrode interface by applying an electric signal,
The anode member has a structure in which a catalyst made of metal or metal oxide is supported on a substrate formed of a conductive material, and an electric signal is applied to the anode member to We propose an electrochemical reaction method characterized in that oxygen dissociation is promoted to oxidize organic substances in an aqueous solution.
Furthermore, an anode member and a cathode member that are arranged opposite to each other in the aqueous solution in the electrolytic treatment tank, and an electrical signal generator that applies an electrical signal in which a positive pulse high voltage component and a DC voltage component are superimposed between these electrodes, In an electrochemical reaction device for electrochemically reacting an aqueous solution in the vicinity of an electrode interface by applying the electrical signal,
The anode has a structure in which a catalyst is supported on a substrate formed of a conductive material, and the catalyst is a metal or a metal oxide that promotes oxygen dissociation.
At this time, it is preferable that the catalyst is any one of Pt, Pd, and oxides thereof, or a mixture thereof. According to this invention, the decomposition efficiency of organic matter can be improved by promoting oxygen dissociation.

As described above, by adopting the configurations of the first to third inventions, it is possible to reduce the waste of supplied power due to overvoltage and to generate a desired substance more efficiently, and to support the anode member. Oxidized substances such as organic substances can be decomposed and removed with high efficiency by the action of the catalyst.
In these inventions, when the oxidizable substance is a component that can be decomposed relatively easily, the organic substance can be decomposed by using the first invention, but dioxins, PCBs, acetic acid and the like are hardly decomposed. In the case where the organic organic substance is contained, it is difficult to completely decompose in the first invention. Therefore, a mixture of a metal or metal oxide belonging to the second invention is mixed to generate a strong oxidizing power / OH radical. This makes it possible to decompose with high efficiency.・ OH radicals cause a hydrogen abstraction reaction, which can cause an auto-oxidation reaction of organic matter. Moreover, by applying the third invention to these inventions to promote oxygen dissociation, the decomposition efficiency is further improved.
As described above, it is desirable to combine the above-mentioned inventions depending on the properties of the target aqueous solution, but it is desirable that at least one of the catalysts shown in these inventions is included.

In the first to third inventions,
The anode substrate is any one of titanium, a titanium alloy, a carbon material such as activated carbon, or a conductive ceramic, whereby an electrode having high corrosion resistance and a long life can be provided.
In addition, a dielectric layer containing at least one of silica compound, alumina, and titania is interposed between the anode substrate and the catalyst, thereby increasing the capacitance of the electrode, It is possible to generate radically active species with efficiency.
Furthermore, a sacrificial electrode having a structure substantially similar to that of the anode member is disposed between the anode member and the cathode member. According to this invention, since the area of an anode becomes large, a reaction field can be expanded.
Also, a carrier carrying a catalyst is disposed between the anode member and the cathode member on a substrate formed of at least one of titania, silica, alumina, a compound material thereof, or a carbon material. It is characterized by. According to this, the oxidation active species can be generated in the entire reaction field, and the reaction efficiency can be improved.

Still further, there is provided a means for adjusting the chloride ion concentration of the aqueous solution to be about 1000 mg / L or more. Thereby, hypochlorous acid having strong oxidizing power is formed in the aqueous solution, the concentration of the active species in the aqueous solution is increased, and the substance to be oxidized can be decomposed with high efficiency.
In order to promote the oxidative decomposition reaction, it is preferable to provide means for supplying at least one oxidizing agent of air, ozone, hydrogen peroxide, hypochlorous acid to the aqueous solution, Thereby, the oxidation active species density | concentration in aqueous solution can be raised, and the decomposition reaction of a to-be-oxidized substance can be accelerated | stimulated.

Furthermore, when the oxidation reaction of the substance to be oxidized proceeds during the electrochemical reaction, H ⁺ is released to lower the pH, which may inhibit the oxidation reaction. In that case, there are provided means for measuring the pH value in the aqueous solution and means for adding a pH adjuster based on the measured pH value to maintain the pH value of the aqueous solution within a weakly acidic to alkaline range. It is preferable.
The electrochemical reaction method and apparatus according to the present invention includes organic matter-containing human waste, livestock manure, methane fermentation liquid, domestic wastewater, factory wastewater, landfill leachate, food factory wastewater, textile factory wastewater, laundry wastewater, etc. It can be installed in a wastewater treatment facility to remove organic substances, persistent substances, nitrogen, etc. contained in the wastewater.

  As described above, according to the present invention, it is possible to more efficiently generate a desired substance by reducing waste of supplied power due to an overvoltage, and organic substances and the like by the action of a catalyst supported on an anode member. It is possible to decompose and remove oxidizable substances with high efficiency.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Not too much.
1 to 5 are schematic configuration diagrams of an electrochemical reaction apparatus according to the present invention, and FIG. 6 is a table showing a removal rate of an oxidizable substance when the electrochemical reaction apparatus according to the present embodiment is used.
The electrochemical reaction apparatus shown in FIG. 1 is applied to Examples 1 to 8 and Example 11, the electrochemical reaction apparatus shown in FIG. 2 is applied to Example 9, and the electrochemical reaction apparatus shown in FIG. The electrochemical reaction apparatus shown in FIG. 4 applied to Example 10 is applied to Examples 12 and 13, and the electrochemical reaction apparatus shown in FIG. 5 is applied to Example 14.

  First, the structure of the electrochemical reaction apparatus 10 according to the first embodiment will be described with reference to FIG. The electrochemical reaction apparatus 10 shown in FIG. 1 includes a function generator 11 that generates an electric signal waveform, a power amplifier 12 that amplifies the electric signal to a predetermined current condition, an electrolytic treatment tank 15 that stores a target liquid, The anode 13 and the cathode 14 disposed opposite to each other in the electrolytic treatment tank 15 are the main components. As the target liquid, wastewater discharged from various factories, seawater, or an aqueous solution to which chloride ions such as salt are added can be used. The function generator 11 generates an electric signal in which a positive pulse high voltage component and a DC voltage component are superimposed.

In the present embodiment, an electric signal on which a pulse component generated by an electric signal generator composed of the function generator 11 and the power amplifier 12 is superimposed is applied between the anode 13 and the cathode 14, thereby The liquid is electrochemically reacted to decompose and remove organic substances, nitrogen compounds and hardly decomposable substances contained in the treatment liquid.
Here, the action of the electrochemical reaction by the electrochemical reaction device 10 will be described.
First, when an electric signal of a positive pulse high voltage component is applied by the electric signal generator, ions move in the aqueous solution in the electrolytic treatment tank 10 to form an electric double layer. During the formation of this electric double tank, since the electric shield inside the aqueous solution is insufficient, an electric field is sufficiently applied to the inside of the aqueous solution farther from the surfaces of the electrodes 13 and 14, and the mass transfer of ions as a reaction precursor is performed. Be promoted. Therefore, by applying an electric signal of a positive pulse high voltage component, an electric field is generated inside the aqueous solution to efficiently attract ions serving as reaction precursors to the electrode surface, and the power supplied as a positive pulse high voltage is: It can be accumulated on the electrode surface side as a charge corresponding to the electrostatic capacity of the electric double layer.

  The ions as reaction precursors collected on the electrode surface by the electrical signal of the positive pulse high voltage component are diffused in the aqueous solution after the positive pulse high voltage component is applied and reduced before the following. It is preferable to apply a positive pulse high voltage. The time until the electric double layer is formed depends on the voltage value and pulse width of the positive pulse high voltage component. Therefore, if the voltage value is determined, the time required until the electric double layer is formed and the electric charging is completed is sufficient as the pulse width. Although it is not preferable because it is wasted in terms of energy, the pulse width may be made longer than the time until the electric double layer is formed at a high voltage.

  The voltage value of the positive pulse high voltage component is preferably 10 V or more. Since the ion mobility increases as the voltage value increases, the time for forming the electric double layer can be shortened, and ions constituting the electric double layer can be made high in concentration. However, at a high voltage value, those that cannot contribute to the electrochemical reaction after application are wasted and diffused to the aqueous solution side. Therefore, the voltage value, pulse width, and pulse interval are set according to the properties of the treatment solution so that ions as a reaction precursor attracted by the electrical signal of the positive pulse high voltage component are consumed as much as possible when a DC voltage is applied. It is desirable to do.

  On the other hand, the electrical signal of the DC positive voltage component is such that after application of the electrical signal of the positive pulse high voltage component, ions attracted by the electrical signal of the positive pulse high voltage component diffuse into the aqueous solution by concentration diffusion, and This prevents the charge of the electrode forming the multilayer from being released and contributes to the electrochemical reaction. That is, in terms of circuit, by applying a DC voltage component that blocks a reverse current flowing to the power source side connecting the anode member and the cathode member after application of an electric signal of a positive pulse high voltage component, the electrode plate Thus, the electric charge accumulated in the water does not flow as a reverse current to the power source side, and can contribute to the electrochemical reaction on the aqueous solution side.

In the electrochemical reaction apparatus 10 in the present embodiment, an electric signal having a positive pulse high voltage component only for the time during which the electric double layer is formed is applied to concentrate ions serving as reaction precursors in the vicinity of the electrode surface. After applying the electric signal of the high voltage component, an electric signal of a DC voltage component equal to or higher than the electrochemical potential suitable for the target reaction generation is applied to the electrode. Therefore, the electric charge stored on the electrode surface side as an electric double layer when an electric signal of a positive pulse high voltage component is applied can be held on the electrode surface side and contribute to the electrochemical reaction.
When applying an electric signal of this DC voltage component, the reverse current due to the charge accumulated on the electrode when applying an electric signal of a positive pulse high voltage component is suppressed, and there is almost no current supply from the power source during this time, and the power is very efficient. Can contribute to the electrochemical reaction. The power supplied from the power source is voltage × current. In the case of only the DC positive voltage component, the current from the power source can be adjusted to a value close to zero, so that there is almost no power supply during this period.

Therefore, in the control of the electrochemical reaction apparatus of this embodiment, it is only necessary to supply electric power with an electric signal of a positive pulse high voltage component, so that an electrochemical reaction can be performed efficiently with low power consumption. Become.
Since the formation of the electric double layer after the voltage is applied to the electrodes 13 and 14 occurs with the movement of ions in the aqueous solution, the time until the electric double layer is formed depends on the pH of the target aqueous solution. Depending on conductivity, ion species, and concentration, it has been confirmed by experiments that the time is from microseconds to several tens of milliseconds. Moreover, since the electric shield by the electric double layer is insufficient within this time, an electric field is applied to the inside of the aqueous solution, and the mass transfer of the reaction precursor can be promoted.
Therefore, if a pulse high voltage of microseconds to several tens of milliseconds, which is a time width until the electric double layer is formed, is applied, an electric field is generated inside the aqueous solution and ions serving as reaction precursors are efficiently applied to the electrode surface. In addition, charges corresponding to the electrostatic capacity of the electric double layer can be accumulated in the electrodes 13 and 14.

  The DC positive voltage component is applied between the two positive pulse high voltage components, and the reaction precursor collected near the interface between the electrodes 13 and 14 and the aqueous solution diffuses into the aqueous solution from the vicinity of the interface. And a voltage necessary for electrochemical reaction. Further, the superposition of the positive pulse high voltage component and the DC positive voltage component is generated by superimposing the function waveforms of the respective components or by alternately outputting the respective components. Also good. Furthermore, it is preferable that the voltage of the anode 13 or the voltage of the sacrificial electrode 20 described later has at least an electrochemical potential suitable for the intended reaction generation due to the DC positive voltage component.

Therefore, by applying an electric signal in which a positive pulse high voltage component and a DC positive voltage component are superimposed, a problem that has occurred when only an electric signal of a positive pulse high voltage component is applied, for example, pulling by an electric signal. The diffused ions diffuse into the aqueous solution due to concentration diffusion, and the charge of the electrode forming the electric double layer is released, resulting in a decrease in reaction efficiency and between the anode member and the cathode member after application. It is possible to solve the problem that the reverse current that flows on the power source side connecting the active species reduces the active species generated by the oxidation reaction and wastes the active species.
In addition, even when only the DC positive voltage component is used, the electric field strength applied to the aqueous solution is small, and the driving force in the mass transport process for supplying a new reaction precursor is small. Thus, since the concentration of the new reaction precursor becomes low and a competitive reaction occurs, the problem that the current efficiency of active species generation decreases can be solved.

Further, as a characteristic feature of the present embodiment, the anode 13 has a structure in which a catalyst is supported on a substrate formed of a conductive material, and the catalyst is placed on the surface of the anode member. Oxidized by application of a signal to become a highly oxidized state, an organic substance in an aqueous solution is made a metal or metal oxide that can be oxidized. At this time, it is preferable to use Ru, Fe, Os, Mn, Mo, Co, Ir, Ni, W, or any of these oxides or a mixture thereof as the catalyst.
Thereby, reactions as shown in the following reaction formulas (1) to (4) occur.
MO _x + H ₂ O → MO _x (.OH) + H ⁺ + e ⁻ (1)
MO _x (.OH) → MO _{x + 1} + H ⁺ + e ⁻ (2)
MO _{x + 1} → MO _x + 1 / 2O ₂ (3)
MO _{x + 1} + R → MO _x + RO (4)
That is, a low-oxygen state metal produces a highly oxidized metal via a chemisorbed .OH radical (hydroxy radical). An organic substance (described as R in the above formula (4)) is oxidized by the highly oxidized metal. Since this reaction occurs at the MO _x / MO _{x + 1} redox potential, the high oxidation state is O ₂ / H ₂ O redox potential (1.23 V vs RHE) and H ₂ O / H ₂ O ₂ redox potential (1.77 V).
vs RHE) is desirable.

Further, as the catalyst, a metal or a metal oxide that has a high oxygen overvoltage and promotes a reaction of generating a radical active species including a hydroxy radical may be used, preferably Ti, Sn, Pb, or these oxides. Among these, any one kind or a mixture thereof is mentioned.
Thus, the following reaction formula (5), it is possible to break down organic matter to CO ₂ by reaction mechanism shown in (6).
MO _x + H ₂ O → MO _x (.OH) + H ⁺ + e ⁻ (5)
MO _x (.OH) + R → MO _x + mCO ₂ + H ⁺ + e ⁻ (6)
That is, OH radicals physically adsorbed on the surface of the metal or metal oxide are generated, and the OH radicals oxidize and decompose organic substances. This reaction is a reaction using H ₂ O ₂ as an intermediate, and occurs at an H ₂ O / H ₂ O ₂ redox potential (1.77 V vs RHE).

Furthermore, a metal or a metal oxide that promotes oxygen dissociation can be used as the catalyst, and Pt, Pd, or any of these oxides or a mixture thereof can be preferably used. Thereby, the decomposition efficiency of organic substance can be improved by promoting oxygen dissociation.
A combination of these catalysts may also be used.

In Example 1, a test was performed in which an anode 13 on which a plurality of catalysts selected from the above catalysts were supported in combination was subjected to an electrochemical treatment on a target liquid containing an oxidizable substance. RuO ₂ , IrO ₂ , TiO ₂ , and Pt are used as the catalyst, and an anode 13 having the catalyst supported on a titanium substrate surface and a cathode 14 made of titanium or a titanium alloy are provided in the electrolytic treatment tank 15 as electrodes. Installed at an interval of 30 mm. Furthermore, the treatment volume of the electrolytic treatment tank is 0.5L. The target liquid was human waste.
In this test, after injecting the target liquid into the electrolytic treatment tank 15, an electric signal is transmitted from the function generator 11 so as to satisfy the following electrolysis conditions, and then amplified by the power amplifier 12 to a predetermined current condition. , 14 was applied to start the test. The electrolysis conditions were as follows: peak current: 150 mA / cm ² , base current: 1 μA / cm ² , frequency: 100 kHz, pulse width: 1 μsec, and electrolysis time of 60 minutes.

The test results are shown in FIG. According to this, the COD concentration decreased from 1980 mg / l to 842 mg / l, and the COD removal rate was 57%. The NH ₄ -N concentration also decreased from 2200 mg / l to 492 mg / l, and the NH ₄ -N removal rate was 78%. In this way, RuO ₂ , IrO ₂ , TiO ₂ , and Pt catalyst components are supported on the anode, so that the decomposition of organic matter is promoted, and the electric field is efficiently used by the electric field that superimposes the DC component and the pulse component. It was possible to decompose organic substances with high efficiency.

  Hereinafter, in Examples 2 to 8, an example in which the configuration is substantially the same as that of the electrochemical reaction apparatus 10 of Example 1 and only the configuration of the catalyst component or the electrode structure of Example 1 is changed will be described. . Therefore, the description of the same configuration as in the first embodiment is omitted.

In Example 2, a member in which V ₂ O ₅ , IrO ₂ , TiO ₂ , and Pt are supported on the surface of a titanium substrate as the anode 13 in the electrolytic treatment tank 15, titanium or a titanium alloy as the cathode 14, and an electrode interval of 30 mm. Was installed as. Further, the treatment volume of the electrolytic treatment tank 15 was set to 0.5 L, and a test was performed in which the target liquid was subjected to electrochemical treatment as the urine.
In this test, after injecting the target liquid into the electrolytic treatment tank 15, an electric signal is transmitted from the function generator 11 so as to satisfy the following electrolysis conditions, and then amplified by the power amplifier 12 to a predetermined current condition. , 14 to start the test. The electrolysis was carried out at a peak current of 150 mA / cm ² , a base current of 1 μA / cm ² , a frequency of 100 kHz, a pulse width of 1 μsec, and an electrolysis time of 60 minutes.

The test results are shown in FIG. According to this, the COD concentration decreased from 1980 mg / l to 654 mg / l, and the COD removal rate was 67%. The NH ₄ -N concentration also decreased from 2200 mg / l to 360 mg / l, and the NH ₄ -N removal rate was 84%. Thus, by supporting the catalyst component of V, Ir, Ti, and Pt on the anode 13, the decomposition of the organic substance is promoted, and the electric field is efficiently utilized by the electric field in which the direct current component and the pulse component are superimposed. Could be decomposed with high efficiency.

In Example 3, a member having NiO, Co ₂ O ₄ , TiO ₂ , and Pt supported on the surface of a titanium substrate as the anode 13 in the electrolytic treatment tank 15, titanium as the cathode 14, and an electrode interval of 30 mm were installed. Further, a test was conducted in which the treatment volume of the electrolytic treatment tank was 0.5 L, and the target liquid was subjected to electrochemical treatment as urine.
In such a test, after injecting the target liquid into the electrolytic treatment tank 15, an electric signal is transmitted from the function generator 11 so as to satisfy the following electrolysis conditions, and then amplified to a predetermined current condition by the power amplifier 12. To start the test. The electrolysis was carried out at a peak current of 150 mA / cm ² , a base current of 1 μA / cm ² , a frequency of 100 kHz, a pulse width of 1 μsec, and an electrolysis time of 60 minutes.

The test results are shown in FIG. According to this, the COD concentration decreased from 1980 mg / l to 990 mg / l, and the COD removal rate was 50%. The NH ₄ -N concentration also decreased from 2200 mg / l to 858 mg / l, and the NH4-N removal rate was 61%. In this way, by supporting the catalyst components of Ni, Co, Ti, and Pt on the anode, the decomposition of the organic matter is promoted, and the electric field is efficiently utilized by the electric field in which the direct current component and the pulse component are superimposed. The decomposition could be performed with high efficiency.

In Example 4, a member in which MnO ₂ , NiO, TiO ₂ and Pt were supported on the surface of a titanium substrate as an anode, titanium as a cathode 14, and an electrode interval of 30 mm were installed in an electrolytic treatment tank 15. Further, a test was conducted in which the treatment volume of the electrolytic treatment tank was 0.5 L, and the target liquid was subjected to electrochemical treatment as urine.
In such a test, after injecting the target liquid into the electrolytic treatment tank 15, an electric signal is transmitted from the function generator 11 so as to satisfy the following electrolysis conditions, and then amplified to a predetermined current condition by the power amplifier 12. To start the test. The electrolysis was carried out at a peak current of 150 mA / cm ² , a base current of 1 μA / cm ² , a frequency of 100 kHz, a pulse width of 1 μsec, and an electrolysis time of 60 minutes.

The test results are shown in FIG. According to this, the COD concentration decreased from 1980 mg / l to 1024 mg / l, and the COD removal rate was 48%. In addition, the NH ₄ —N concentration also decreased from 2200 mg / l to 648 mg / l, and the NH ₄ —N removal rate was 71%. Thus, by supporting the catalyst components of Mn, Ni, Ti, and Pt on the anode 13, the decomposition of the organic matter is promoted, and the electric field is efficiently utilized by the electric field in which the direct current component and the pulse component are superimposed. Could be decomposed with high efficiency.

In Example 5, a member having RuO ₂ , IrO ₂ , PbO ₂ , and Pt supported on the surface of a titanium substrate as an anode, titanium as a cathode, and an electrode interval of 30 mm were installed in the electrolytic treatment tank 14. Further, a test was conducted in which the treatment volume of the electrolytic treatment tank was 0.5 L, and the target liquid was subjected to electrochemical treatment as urine.
In such a test, after injecting the target liquid into the electrolytic treatment tank 15, an electric signal is transmitted from the function generator 11 so as to satisfy the following electrolysis conditions, and then amplified to a predetermined current condition by the power amplifier 12. To start the test. The electrolysis was carried out at a peak current of 150 mA / cm ² , a base current of 1 μA / cm ² , a frequency of 100 kHz, a pulse width of 1 μsec, and an electrolysis time of 60 minutes.

The test results are shown in FIG. According to this, the COD concentration decreased from 1980 mg / l to 974 mg / l, and the COD removal rate was 51%. The NH ₄ -N concentration also decreased from 2200 mg / l to 576 mg / l, and the NH ₄ -N removal rate was 74%. As described above, by supporting the catalyst components of Ru, Ir, Pb, and Pt on the anode 13, the decomposition of the organic matter is promoted, and the electric field is efficiently utilized by the electric field in which the direct current component and the pulse component are superimposed. Could be decomposed with high efficiency.

In this Example 6, a member having V ₂ O ₅ , RuO ₂ , SnO ₂ , and Pt supported on the surface of a titanium substrate as the anode 13, titanium as the cathode 14, and an electrode spacing of 20 mm were installed in the electrolytic treatment tank 15. . Further, a test was conducted in which the treatment volume of the electrolytic treatment tank was 0.5 L, and the target liquid was subjected to electrochemical treatment as urine.
In such a test, after injecting the target liquid into the electrolytic treatment tank 15, an electric signal is transmitted from the function generator 11 so as to satisfy the following electrolysis conditions, and then amplified to a predetermined current condition by the power amplifier 12. To start the test. The electrolysis was carried out at a peak current of 150 mA / cm ² , a base current of 1 μA / cm ² , a frequency of 100 kHz, a pulse width of 1 μsec, and an electrolysis time of 60 minutes.

The test results are shown in FIG. According to this, the COD concentration decreased from 1980 mg / l to 796 mg / l, and the COD removal rate was 60%. Further, the NH ₄ -N concentration was also reduced from 2200 mg / l to 429 mg / l, and the NH ₄ -N removal rate was 81%. Thus, by supporting the catalyst components of V, Ru, Sn, and Pt on the anode 13, the decomposition of the organic matter is promoted, and the electric field is efficiently utilized by the electric field in which the direct current component and the pulse component are superimposed. Could be decomposed with high efficiency.

In this Example 7, in the electrolytic treatment tank 15, a member carrying V ₂ O ₅ , IrO ₂ , TiO ₂ , WO ₃ , Pt on the titanium substrate surface as the anode 13, titanium as the cathode 14, and electrode spacing of 20 mm Was installed as. Further, a test was conducted in which the treatment volume of the electrolytic treatment tank was 0.5 L, and the target liquid was subjected to electrochemical treatment as urine.
In such a test, after injecting the target liquid into the electrolytic treatment tank 15, an electric signal is transmitted from the function generator 11 so as to satisfy the following electrolysis conditions, and then amplified to a predetermined current condition by the power amplifier 12. To start the test. The electrolysis was carried out at a peak current of 150 mA / cm ² , a base current of 1 μA / cm ² , a frequency of 100 kHz, a pulse width of 1 μsec, and an electrolysis time of 60 minutes.

The test results are shown in FIG. According to this, the COD concentration decreased from 1980 mg / l to 694 mg / l, and the COD removal rate was 65%. Further, the NH ₄ -N concentration was also reduced from 2200 mg / l to 393 mg / l, and the NH ₄ -N removal rate was 82%. As described above, by supporting the catalyst components of V, Ir, Ti, W, and Pt on the anode 13, the decomposition of the organic matter is promoted, and the electric field is efficiently used by the electric field in which the DC component and the pulse component are superimposed. It was possible to decompose organic substances with high efficiency.

  As in Example 1, Example 8 has the structure of the electrochemical reaction device 10 shown in FIG. 1 and includes the base material formed of the conductive material of the anode 13 and the catalyst layer. A dielectric layer (not shown) made of a mixture of at least one of silica compound, alumina, and titania is interposed therebetween. In this way, by adopting a configuration in which the dielectric layer is interposed, the charge supplied by the pulse component can be retained, and the function of the catalytically active species supported on the anode surface can be efficiently exhibited. Further, according to such a structure, it is possible to increase the capacitance, so that radical active species can be generated with high efficiency, and the amount of reaction can be increased. The thickness of the dielectric layer is desirably 1 to 10 μm. If it is too thin, the above effect cannot be expected, and if it is too thick, the overvoltage increases and is consumed as thermal energy, making it difficult to achieve economically.

As an example in the present embodiment, a member in which a dielectric layer made of a silica compound is provided on the surface of a titanium substrate as an anode 13 in an electrolytic treatment tank 15 and V ₂ O ₅ , IrO ₂ , TiO ₂ , Pt is supported thereon. In addition, a test was conducted in which titanium was set as the cathode 14, the electrode interval was set to 30 mm, the treatment volume of the electrolytic treatment tank was 0.5 L, and the target liquid was subjected to electrochemical treatment as the urine.
In such a test, after injecting the target liquid into the electrolytic treatment tank 15, an electric signal is transmitted from the function generator 11 so as to satisfy the following electrolysis conditions, and then amplified to a predetermined current condition by the power amplifier 12. To start the test. The electrolysis was conducted under the conditions of peak current: 170 mA / cm ² , base current: 1 μA / cm ² , frequency: 100 kHz, pulse width: 1 μsec, and electrolysis time of 60 minutes.

The test results are shown in FIG. According to this, the COD concentration decreased from 1980 mg / l to 261 mg / l, and the COD removal rate was 87%. Further, the NH ₄ -N concentration was also reduced from 2200 mg / l to 256 mg / l, and the NH ₄ -N removal rate was 88%. Thus, by providing the dielectric layer in the electrode, the capacitance of the electrode is increased, the processing efficiency is improved, and the processing time can be shortened.

An electrochemical reaction apparatus 10 according to Example 9 is shown in FIG. Since the ninth embodiment has the same configuration as that of the first embodiment shown in FIG. 1, the description of the same components is omitted.
The electrochemical reaction apparatus 10 has a configuration in which at least one or more sacrificial electrodes 20 having a structure substantially similar to that of the anode 13 are disposed between the anode 13 and the cathode 14 which are disposed to face each other in the aqueous solution in the electrolytic treatment tank 15. It is said. This is because, by arranging an electrode having the same structure as that of the anode 13 between the anode 13 and the cathode 14, the area of the anode is increased, so that the reaction field can be expanded. Here, since the side facing the anode side functions as a cathode, the catalyst layer can be supported only on the side functioning as the anode. Thereby, the amount of catalyst can be reduced and the cost of electrode production can be reduced.

As an example in the present embodiment, an electrolytic treatment tank 15 is provided with a member carrying V ₂ O ₅ , IrO ₂ , TiO ₂ , Pt on the surface of a titanium substrate as an anode 13, titanium as a cathode 14, and an electrode interval of 30 mm. Then, four sacrificial electrodes 20 having the same structure as the anode were arranged between the anode 13 and the cathode 14. Further, a test was conducted in which the treatment volume of the electrolytic treatment tank was 0.5 L, and the target liquid was subjected to electrochemical treatment as urine.
In such a test, after injecting the target liquid into the electrolytic treatment tank 15, an electric signal is transmitted from the function generator 11 so as to satisfy the following electrolysis conditions, and then amplified to a predetermined current condition by the power amplifier 12. To start the test. The electrolysis was carried out at a peak current of 150 mA / cm ² , a base current of 1 μA / cm ² , a frequency of 100 kHz, a pulse width of 1 μsec, and an electrolysis time of 60 minutes.

The test results are shown in FIG. According to this, the COD concentration decreased from 1980 mg / l to 450 mg / l, and the COD removal rate was 77%. Further, the NH ₄ —N concentration was also reduced from 2200 mg / l to 504 mg / l, and the NH ₄ —N removal rate was 77%. By disposing a metal carrying a catalyst similar to the anode between the anode and the cathode, the active surface became large and the reaction was promoted.

An electrochemical reaction apparatus 10 according to Example 10 is shown in FIG. Since the tenth embodiment has substantially the same configuration as that of the first embodiment shown in FIG. 1, the description of the same components is omitted.
Such an electrochemical reaction device 10 includes one or more of titania, silica, alumina, a compound material thereof, and a carbon material between an anode 13 and a cathode 14 that are disposed to face each other in an aqueous solution in an electrolytic treatment tank 15. A carrier 21 carrying a catalyst is disposed on the substrate formed in step (b). The substrate is preferably one of a titania compound, a silica compound, alumina, activated carbon, glassy carbon, carbon fiber, and carbon black. The catalyst is preferably Ru, Fe, Os, Mn, Mo, Co, Ir, Ni, W, Ti, Sn, Pb, Pt, Pd or an oxide thereof. Further, a treatment water tank 23 is provided in the electrolytic treatment tank 15, and the treatment liquid drawn out from the electrolytic treatment tank 15 and stored in the treatment water tank 23 is returned to the treatment tank 14 by the circulation pump 22 and circulated. .
Thus, by arranging the carrier 21 between the anode 13 and the cathode 14, oxidation active species can be generated in the entire reaction field, and the reaction efficiency is improved.

As an example in the present embodiment, an electrolytic treatment tank 15 is provided with a member carrying V ₂ O ₅ , IrO ₂ , TiO ₂ , Pt on the surface of a titanium substrate as an anode 13, titanium as a cathode 14, and an electrode interval of 30 mm. did. In this embodiment, a carrier 21 carrying a catalyst is disposed between the electrodes 13 and 14. The support 21 is impregnated with methanol butanol in which ruthenium chloride (III), iridium chloride (III), and platinum chloride (VI) acid are dissolved in a molar ratio = 1: 1: 6 to TiO ₂ particles having a particle diameter of 3 mm. After drying in the range of 25 to 100 ° C., it was manufactured by sintering at 500 ° C. in the atmosphere.

Further, a test was conducted in which the treatment volume of the electrolytic treatment tank was 0.5 L, and the target liquid was subjected to electrochemical treatment as urine.
In such a test, after injecting the target liquid into the electrolytic treatment tank 15, an electrical signal is transmitted from the function generator 11 so that the following electrolysis conditions are satisfied, and then the power amplifier 12 amplifies to a predetermined current condition and interelectrodes. At the same time, the test was started by circulating water in the electrolytic treatment tank 15 and the treated water tank 23 with a circulation pump. The electrolysis was carried out at a peak current of 150 mA / cm ² , a base current of 1 μA / cm ² , a frequency of 100 kHz, a pulse width of 1 μsec, and an electrolysis time of 60 minutes.

The test results are shown in FIG. According to this, the COD concentration decreased from 1980 mg / l to 363 mg / l, and the COD removal rate was 82%. Further, the NH ₄ -N concentration was also reduced from 2200 mg / l to 288 mg / l, and the NH ₄ -N removal rate was 87%. As described above, the catalyst on the carrier 21 arranged between the electrodes 13 and 14 improves the contact efficiency between the oxidizable substance and the catalyst and can generate the oxidation active species in the entire reaction field. The rate could be improved.

An electrochemical reaction apparatus 10 according to Example 11 is shown in FIG. Since the present Example 11 has a structure substantially the same as the said Example 1 of FIG. 1, description is abbreviate | omitted about the same component.
Such an electrochemical reaction device 10 is configured so that the chloride ion concentration in the electrolytic treatment tank 15 is 1,000 mg / l or more.
In general, when electrolysis is performed using a material having a high oxygen overvoltage in a system in which chloride ions are not present as the anode 13, hydrogen peroxide, ozone is expressed at the anode 13 according to the following reaction formulas (7), (8), and (9). Oxidation active species such as hydroxy radicals are generated.
_{2H 2 O ⇔ H 2 O 2} + 2H + + 2e - E 0 = 1.763V ... (7)
O ₂ + H ₂ O⇔O ₃ + 2H ⁺ + 2e ⁻
E ⁰ = 2.08V (8)
H ₂ O⇔ · OH + H ⁺ + e ⁻ E ⁰ = 1.763 V (9)

At this time, hydrogen peroxide and ozone are stable, and easily decomposable oxidizable substances can be decomposed, but difficult to decompose substances are difficult to decompose. On the other hand, although the hydroxy radical has a very strong oxidizing power, it has a short lifetime, so it is consumed before reacting with the target substance to be oxidized, and the reaction field cannot be expanded.
Therefore, the presence of chloride ions causes equilibrium reactions of the following reaction formulas (10) and (11).
OH + Cl ⁻ ⇔ HOCl ⁻ ⇔ OH ⁻ + Cl · (10)
Cl · + Cl ⁻ ⇔ Cl ₂ · ⁻ (11)

In the vicinity of the anode 13, since it is in a strongly acidic state, the equation (10) exists in the state of Cl. If so, the equilibrium shifts to the left and returns to OH, and a very strong oxidizing power can be recovered. The (11) also in the formula, the anode 13 near the relatively stable Cl ₂ · undergo reaction of (10) ^- is present in the form of, by diffusion into the bulk, decreases the concentration of Cl · Therefore, the balance is shifted to the left.
In addition, after chloride ions are converted into chlorine molecules by the electrode reaction, hypochlorous acid having strong oxidizing power is formed in the solution.
2Cl ⁻ ＣｌCl ₂ + 2e ⁻ E ⁰ = 1.396 V (12)
Cl ₂ + H ₂ O⇔HOCl + H ⁺ + Cl ⁻ (13)
Accordingly, the concentration of the active species in the treatment liquid is increased, and the oxidizable substance can also form radicals by the auto-oxidation reaction. Therefore, the radical chain reaction is promoted, and the oxidizable substance can be decomposed with high efficiency.

As an example in the present embodiment, an electrolytic treatment tank 15 is provided with a member carrying V ₂ O ₅ , IrO ₂ , TiO ₂ , Pt on the surface of a titanium substrate as an anode 13, titanium as a cathode 14, and an electrode interval of 30 mm. did. The amount of treated water in the electrolytic treatment tank 15 is 0.5L. This time, the chloride ion concentration in the human urine was 1800 mg / l, so the solution was added with NaCl so as to be 5000 mg / l.
In such a test, after injecting the target liquid into the electrolytic treatment tank 15, an electrical signal is transmitted from the function generator 11 so that the following electrolysis conditions are satisfied, and then the power amplifier 12 amplifies to a predetermined current condition and interelectrodes. At the same time, the test was started by circulating water in the electrolytic treatment tank 15 and the treated water tank 23 with a circulation pump. The electrolysis was carried out at a peak current of 150 mA / cm ² , a base current of 1 μA / cm ² , a frequency of 100 kHz, a pulse width of 1 μsec, and an electrolysis time of 60 minutes.

The test results are shown in FIG. According to this, the COD concentration decreased from 1980 mg / l to 674 mg / l, and the COD removal rate was 66%. In addition, the NH ₄ -N concentration was reduced from 2200 mg / l to 357 mg / l, and the NH ₄ -N removal rate was 84%. In this way, by increasing the concentration of chloride ions, the concentration of active species in the electrolytic treatment tank 15 is increased, and the oxidizable substance can also form radicals by auto-oxidation, thereby promoting the radical chain reaction. An oxidizable substance can be decomposed with high efficiency.

An electrochemical reaction apparatus 10 according to Example 12 is shown in FIG. Since the present Example 12 has a structure substantially the same as the said Example 1 of FIG. 1, description is abbreviate | omitted about the same component.
The electrochemical reaction apparatus 10 includes an oxidant tank 24 that stores one or more kinds of oxidants among air, ozone, hydrogen peroxide, and hypochlorous acid in the electrolytic treatment tank 15, and the electrolytic treatment tank 15. It is set as the structure provided with the diffuser tube 25 installed in the bottom part. In the electrochemical reaction, the oxidant in the oxidant tank 24 is appropriately supplied from the air diffuser 25.
In this way, by supplying an oxidizing agent such as ozone, hydrogen peroxide, and hypochlorous acid, the concentration of the active species in the treatment liquid can be increased, and the decomposition reaction of the oxidizable substance can be promoted. it can. Further, when the concentration of an oxidizable substance is high, dissolved oxygen is consumed by an auto-oxidation reaction, resulting in an oxygen-deficient state, thereby inhibiting the reaction. Therefore, the auto-oxidation reaction can be promoted by supplying air and oxygen from the outside through the air diffuser 25 or the like.

As an example in the present embodiment, an electrolytic treatment tank 15 is provided with a member carrying V ₂ O ₅ , IrO ₂ , TiO ₂ , Pt on the surface of a titanium substrate as an anode 13, titanium as a cathode 14, and an electrode interval of 30 mm. did. The amount of treated water in the electrolytic treatment tank is 0.5L. The target solution was a solution (TOC: 9980 mg / l) in which sucrose was added to an aqueous NaCl solution adjusted to a conductivity of 2.0 S / m.
In such a test, after injecting the target liquid into the electrolytic treatment tank 15, an electrical signal is transmitted from the function generator 11 so that the following electrolysis conditions are satisfied, and then the power amplifier 12 amplifies to a predetermined current condition and interelectrodes. To start the test. The electrolysis was conducted at a peak current of 200 mA / cm ² , a base current of 1 μA / cm ² , a frequency of 10 kHz, a pulse width of 10 μsec, and an electrolysis time of 6 hours. Further, in this example, a comparison was made between the case where air was supplied from the air diffuser 24 at a flow rate of 1 L / min and the case where air was not supplied [Comparative Example 1].

  The test results are shown in FIG. According to this, when air was not supplied, the TOC concentration in the treated water was 6420 mg / l and the TOC removal rate was 36%, but when air was supplied, the TOC concentration in the treated water was 5520 mg / l. The TOC removal rate was 45%. Thus, compared to the case where no air was supplied, the auto-oxidation reaction was promoted by supplying air, and the TOC removal rate was improved from 36% to 45%. Compared to the case where no air was supplied, the supply of air promoted the auto-oxidation reaction and improved the TOC removal rate from 36% to 45%.

The present embodiment 13 has a configuration substantially similar to that of the embodiment 12 shown in FIG. 4, and shows a case where the configuration of the catalyst supported on the anode 13 is changed and the oxidizing agent is changed to ozone.
The electrochemical reaction device 15 of this example uses a member carrying RuO ₂ , IrO ₂ , TiO ₂ , and Pt on the surface of a titanium substrate as the anode 13, titanium as the cathode 14, an electrode interval of 20 mm, and a lower part of the electrolysis Has an aeration tube 25 and an oxidant tank 24 storing ozone. The treatment volume was 0.5 L, and the target solution was a solution (TOC: 9980 mg / l) obtained by adding sucrose to an aqueous NaCl solution adjusted to a conductivity of 2.0 S / m.
In such a test, after injecting the target liquid into the electrolytic treatment tank 15, an electrical signal is transmitted from the function generator 11 so that the following electrolysis conditions are satisfied, and then the power amplifier 12 amplifies to a predetermined current condition and interelectrodes. To start the test. The electrolysis was conducted at a peak current of 200 mA / cm ² , a base current of 1 μA / cm ² , a frequency of 10 kHz, a pulse width of 10 μsec, and an electrolysis time of 6 hours. In this example, ozonized air having an ozone concentration of 10 g / Nm ³ was supplied from the air diffuser 25 at a flow rate of 1 L / min.

  The test results are shown in FIG. According to this, when ozonized air was not supplied, the TOC concentration in the treated water was 5520 mg / l and the TOC removal rate was 45%. The concentration was 1440 mg / l and the TOC removal rate was 86%. Thus, by supplying ozonized air, generation of radical active species is promoted by ozone, and after the reaction, oxygen is generated and contributes to an increase in the dissolved oxygen concentration, so that the reaction rate is improved.

The electrochemical reaction apparatus 10 according to Example 14 is shown in FIG. Since the present Example 14 has a structure substantially the same as the said Example 1 of FIG. 1, description is abbreviate | omitted about the same component.
The electrochemical reaction apparatus 10 includes an oxidant tank 24 that stores air in the electrolytic treatment tank 15, and an air diffuser 25 installed at the bottom of the electrolytic treatment tank 15. Further, a pH detector 27 for measuring the pH value in the electrolytic treatment tank 15, a storage tank 28 for storing a pH adjusting agent such as sodium hydroxide, and the storage tank 28 based on the measured value of the pH detector 27. A pump 29 for adding a predetermined amount of a pH adjuster into the treatment tank 15 is provided.

In this embodiment, during the electrochemical reaction, the oxidant in the oxidant tank 24 is appropriately supplied from the diffuser tube 25, and the pH value measured by the pH detector 27 is maintained between weakly acidic and alkaline. As described above, a pH adjusting agent is appropriately added from the storage tank 28.
Generally, in this experimental system, when the oxidation reaction of the oxidizable substance proceeds, H + is released and the pH is lowered. Therefore, in this embodiment, a pH adjusting agent such as sodium hydroxide or magnesium hydroxide is added to weaken the pH. The acidity to alkalinity was maintained. Thereby, organic substance is oxidized in the redox reaction by the metal oxide on the electrode surface, for example.

As an example in the present embodiment, in the electrolytic treatment tank 15, a member having V ₂ O ₅ , IrO ₂ , TiO ₂ , and Pt supported on the titanium substrate surface as the anode 13, titanium as the cathode 14, and an electrode interval of 20 mm. did. Further, an air diffuser 25 was disposed at the lower part of the reaction tank. The treatment volume of the electrolytic treatment tank 15 was 0.5 L, and the target solution was a solution (TOC: 9980 mg / l) obtained by adding sucrose to an aqueous NaCl solution adjusted to 2.0 S / m.
In such a test, after injecting the target liquid into the electrolytic treatment tank 15, an electrical signal is transmitted from the function generator 11 so that the following electrolysis conditions are satisfied, and then the power amplifier 12 amplifies to a predetermined current condition and interelectrodes. To start the test. The electrolysis was conducted at a peak current of 200 mA / cm ² , a base current of 1 μA / cm ² , a frequency of 10 kHz, a pulse width of 10 μsec, and an electrolysis time of 6 hours. In this example, air was supplied from the air diffuser at a flow rate of 1 L / min, pH was continuously measured, and sodium hydroxide was added to adjust the pH value of the treatment liquid to around 7.

  The test results are shown in FIG. According to this, in the test result in Example 12 where pH adjustment was not performed, the TOC concentration in the treated water was a reduction effect up to 5520 mg / l, but the pH was adjusted to 7.0 as in this example. In some cases, the TOC concentration in the treated water was reduced to 3660 mg / l. Thus, by adjusting the pH and maintaining the pH value in the electrolytic treatment tank 15 from weakly acidic to alkaline without being in a strongly acidic state, it becomes easier to generate hydroxy radicals having stronger oxidizing power than chlorine radicals, The decomposition reaction can proceed with high efficiency.

  The electrochemical reaction apparatus according to the present invention is used for wastewater treatment facilities such as human waste containing organic matter, livestock manure, methane fermentation liquid, domestic wastewater, factory wastewater, landfill leachate, food factory wastewater, textile factory wastewater, laundry wastewater, etc. It can be installed to remove organic substances, persistent substances, nitrogen, etc. contained in wastewater.

The schematic block diagram of the electrochemical reaction apparatus which concerns on embodiment of this invention is shown. The schematic block diagram of the electrochemical reaction apparatus which concerns on another embodiment of FIG. 1 is shown. The schematic block diagram of the electrochemical reaction apparatus which concerns on another embodiment of FIG. 1 is shown. The schematic block diagram of the electrochemical reaction apparatus which concerns on another embodiment of FIG. 1 is shown. The schematic block diagram of the electrochemical reaction apparatus which concerns on another embodiment of FIG. 1 is shown. It is a table | surface which shows the removal rate of the to-be-oxidized substance when the electrochemical reaction apparatus which concerns on this embodiment is used. It is a figure explaining the concept of a general electrochemical reaction. It is a figure explaining the concept of a general electrochemical reaction.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Electrochemical reaction apparatus 11 Function generator 12 Power amplifier 13 Anode 14 Cathode 15 Electrolytic processing tank 20 Sacrificial electrode 21 Carrier 24 Oxidant tank 25 Aeration pipe 27 pH detector 28 Storage tank

Claims (22)

An electric signal in which a positive pulse high voltage component and a DC voltage component are superimposed is applied between an anode member and a cathode member that are arranged opposite to each other in an aqueous solution in an electrolytic treatment tank, and the vicinity of the electrode interface is obtained by applying the electric signal. In a method of electrochemically reacting an aqueous solution of
The anode member has a structure in which a catalyst made of metal or metal oxide is supported on a substrate formed of a conductive material, and an electric signal is applied to the anode member to The electrochemical reaction method is characterized in that the catalyst is brought into a highly oxidized state and an organic substance in the aqueous solution is oxidized by the catalyst in the highly oxidized state. An electric signal in which a positive pulse high voltage component and a DC voltage component are superimposed is applied between an anode member and a cathode member that are arranged opposite to each other in an aqueous solution in an electrolytic treatment tank, and the vicinity of the electrode interface is obtained by applying the electric signal. In a method of electrochemically reacting an aqueous solution of
The anode member has a structure in which a catalyst made of a metal or a metal oxide is supported on a substrate formed of a conductive material, has a high oxygen overvoltage, and applies an electric signal to the anode member. An electrochemical reaction method characterized by oxidizing an organic substance in an aqueous solution by promoting a generation reaction of radical active species including a hydroxy radical on a surface of a member. An electric signal in which a positive pulse high voltage component and a DC voltage component are superimposed is applied between an anode member and a cathode member that are arranged opposite to each other in an aqueous solution in an electrolytic treatment tank, and the vicinity of the electrode interface is obtained by applying the electric signal. In a method of electrochemically reacting an aqueous solution of
The anode member has a structure in which a catalyst made of metal or metal oxide is supported on a substrate formed of a conductive material, and an electric signal is applied to the anode member to An electrochemical reaction method characterized in that oxygen dissociation is promoted to oxidize organic substances in an aqueous solution.   The electrochemical reaction according to any one of claims 1 to 3, wherein a dielectric layer containing at least one of silica compound, alumina, and titania is interposed between the anode substrate and the catalyst. Method.   4. The electrochemical reaction method according to claim 1, wherein a sacrificial electrode having a structure substantially the same as that of the anode member is disposed between the anode member and the cathode member.   Between the anode member and the cathode member, a carrier carrying a catalyst is disposed on a substrate formed of at least one of titania, silica, alumina, a compound material thereof, or a carbon material. The electrochemical reaction method according to any one of claims 1 to 3.   The electrochemical reaction method according to any one of claims 1 to 3, wherein the chloride ion concentration of the aqueous solution is adjusted to be about 1000 mg / L or more.   4. The electrochemical reaction method according to claim 1, wherein at least one oxidizing agent selected from the group consisting of air, ozone, hydrogen peroxide, and hypochlorous acid is supplied to the aqueous solution.   The pH value in the aqueous solution is measured, and a pH adjuster is added based on the measured pH value to maintain the pH value of the aqueous solution within a weakly acidic to alkaline range. The electrochemical reaction method according to any one of the above. An anode member and a cathode member disposed opposite to each other in an aqueous solution in the electrolytic treatment tank, and an electric signal generator that applies an electric signal in which a positive pulse high voltage component and a DC voltage component are superimposed between the electrodes. In an electrochemical reaction device that causes an electrochemical reaction of an aqueous solution near the electrode interface by application of the electrical signal,
The anode member has a structure in which a catalyst is supported on a substrate formed of a conductive material, and the catalyst is oxidized on the surface of the anode member by application of the electric signal to be in a highly oxidized state. An electrochemical reaction device characterized in that it is a metal or metal oxide capable of oxidizing an organic substance in an aqueous solution.   11. The electricity according to claim 10, wherein the catalyst is any one of Ru, Fe, Os, Mn, Mo, Co, Ir, Ni, W, or an oxide thereof, or a mixture thereof. Chemical reactor. An anode member and a cathode member disposed opposite to each other in an aqueous solution in the electrolytic treatment tank, and an electric signal generator that applies an electric signal in which a positive pulse high voltage component and a DC voltage component are superimposed between the electrodes. In an electrochemical reaction device that causes an electrochemical reaction of an aqueous solution near the electrode interface by application of the electrical signal,
The anode member has a structure in which a catalyst is supported on a substrate formed of a conductive material, and the catalyst has a high oxygen overvoltage and promotes a generation reaction of radical active species including hydroxy radicals. An electrochemical reaction device characterized by being a metal oxide.   The electrochemical reaction device according to claim 12, wherein the catalyst is any one of Ti, Sn, Pb, and oxides thereof, or a mixture thereof. An anode member and a cathode member disposed opposite to each other in an aqueous solution in the electrolytic treatment tank, and an electric signal generator that applies an electric signal in which a positive pulse high voltage component and a DC voltage component are superimposed between the electrodes. In an electrochemical reaction device that causes an electrochemical reaction of an aqueous solution near the electrode interface by application of the electrical signal,
The electrochemical reaction characterized in that the anode member has a structure in which a catalyst is supported on a substrate formed of a conductive material, and the catalyst is a metal or a metal oxide that promotes oxygen dissociation. apparatus.   The electrochemical reaction device according to claim 14, wherein the catalyst is any one of Pt, Pd, or an oxide thereof or a mixture thereof.   15. The electrochemical reaction device according to claim 10, wherein the anode substrate is any one of titanium, a titanium alloy, a carbon material such as activated carbon, or a conductive ceramic.   15. The electricity according to claim 10, 12 or 14, wherein a dielectric layer containing at least one of silica compound, alumina and titania is interposed between the anode substrate and the catalyst. Chemical reactor.   The electrochemical reaction device according to any one of claims 10 to 17, wherein a sacrificial electrode having a structure substantially the same as that of the anode member is disposed between the anode member and the cathode member.   Between the anode member and the cathode member, a carrier carrying a catalyst is disposed on a substrate formed of at least one of titania, silica, alumina, a compound material thereof, or a carbon material. The electrochemical reaction device according to any one of claims 10 to 17.   The electrochemical reaction device according to any one of claims 10, 12, and 14, further comprising means for adjusting the chloride ion concentration of the aqueous solution to be about 1000 mg / L or more.   The means for supplying at least one or more oxidizing agents of air, ozone, hydrogen peroxide, and hypochlorous acid to the aqueous solution is provided. Electrochemical reaction device.   A means for measuring the pH value in the aqueous solution and a means for adding a pH adjuster based on the measured pH value to maintain the pH value of the aqueous solution within a weakly acidic to alkaline range are provided. The electrochemical reaction device according to any one of claims 10, 12, and 14.

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