WO2019107303A1

WO2019107303A1 - Purification device and purification electrode

Info

Publication number: WO2019107303A1
Application number: PCT/JP2018/043342
Authority: WO
Inventors: 雄也鈴木; 直毅吉川; 周次中西; 恒太木村; 三島　俊一
Original assignee: パナソニック株式会社; 国立大学法人大阪大学; メタウォーター株式会社
Priority date: 2017-11-30
Filing date: 2018-11-26
Publication date: 2019-06-06
Also published as: JPWO2019107303A1; JP7010303B2

Abstract

Provided is a purification device (100) having a purification structure (10) which includes an electric conductor (1) and induces a redox reaction, and a treatment tank (20) for holding thereinside the purification structure and water (30) to be purified by the purification structure. A part of the purification structure is in contact with a gas phase (40), and the other part of the purification structure is in contact with the water to be treated. The purification structure is installed inside the treatment tank so that the length (L1) in the vertical direction (Y) is longer than the length (L2) in the width direction (Z) perpendicular to the vertical direction (Y). The purification electrode consists only of a conductor, a redox catalyst carried on the conductor, and a binder.

Description

Purification device and purification electrode

The present invention relates to a purification device and a purification electrode.

Heretofore, various water treatment methods have been provided to remove organic substances and the like contained in waste water. Specifically, water treatment methods such as an activated sludge method utilizing aerobic respiration of microorganisms and an anaerobic treatment method utilizing anaerobic respiration of microorganisms are provided.

In the activated sludge method, mud (activated sludge) containing microorganisms and wastewater are mixed in a biological reaction tank, and air necessary for the microorganisms to oxidize and decompose organic matter in the wastewater is sent to the biological reaction tank and agitated. And the wastewater is being purified. However, the activated sludge method requires a great deal of power for aeration of the biological reaction tank. In addition, as a result of the oxygen respiration by the microorganism and active metabolism, a large amount of industrial waste material (the death of the microorganism) is generated.

On the other hand, since the aeration is unnecessary in the anaerobic treatment method, the required power can be significantly reduced as compared with the activated sludge method. In addition, since the free energy acquired by microorganisms is small, the amount of sludge generated is reduced. As a wastewater treatment apparatus using such an anaerobic treatment method, a microbial fuel cell described in Patent Document 1 is disclosed. This microbial fuel cell is provided with a negative electrode which is immersed in an organic substrate to carry an anaerobic microorganism, and a closed type hollow cassette having an outer shell formed at least in part by an ion permeable diaphragm and an inlet / outlet. There is. Furthermore, the microbial fuel cell comprises a positive electrode which is enclosed with the electrolyte in a hollow cassette or is attached to the inside of the diaphragm of the cassette and inserted into the organic substrate. Then, it is also disclosed that oxygen is supplied into the cassette via the inlet / outlet and electricity is taken out via a circuit that electrically connects the negative electrode and the positive electrode. Such a microbial fuel cell can shorten the number of days required for wastewater treatment as compared with other anaerobic treatment methods, and is a technology capable of efficiently removing organic matter.

Patent No. 5164511 gazette

However, a wastewater treatment apparatus using a microbial fuel cell such as that disclosed in Patent Document 1 has a complicated electrode structure, which increases the manufacturing cost and the maintenance cost, so a simple treatment apparatus is required.

The present invention has been made in view of the problems of the prior art. And the object of the present invention is to provide a purification device which has a simple structure and can efficiently purify waste water, and a purification electrode using the purification device.

In order to solve the above-mentioned subject, the purification device concerning the first mode of the present invention has a conductor, and is purified by the purification structure which makes an oxygen reduction reaction occur, and the purification structure concerned and the purification structure. And a treatment tank for holding the water to be treated inside. A part of the purification structure is in contact with the gas phase, and the other part of the purification structure is in contact with the water to be treated. And a purification | cleaning structure is installed inside a processing tank so that the length of the perpendicular direction may become longer than the length of the width direction perpendicular | vertical to the perpendicular direction.

The purification electrode according to the second aspect of the present invention is a purification electrode used in the above-described purification device, and comprises only a conductor, an oxygen reduction catalyst supported on the conductor, and a binder.

A purification electrode according to a third aspect of the present invention comprises a purification structure having a conductor and causing an oxygen reduction reaction, a part of the purification structure being in contact with the gas phase, and the purification structure The other part is in contact with the water to be treated, and the purification structure is a purification electrode used in a purification device installed so that the length in the vertical direction is longer than the length in the width direction perpendicular to the vertical direction . The purification electrode comprises only a conductor, an oxygen reduction catalyst supported on the conductor, and a binder.

FIG. 1 is a perspective view showing an example of the purification device according to the present embodiment. FIG. 2 is a cross-sectional view taken along the line AA in FIG. FIG. 3 is a cross-sectional view taken along the line BB in FIG. FIG. 4 is a cross-sectional view for explaining the mechanism for purifying the water to be treated by the purification structure. FIG. 5 is a cross-sectional view for explaining a mechanism for purifying the water to be treated by the purification structure. FIG. 6 is a graph showing an average value of total organic carbon concentration in organic wastewater when using the purification structures of Examples 1-1 and 1-2 and Examples 2-1 and 2-2. is there. FIG. 7 shows the results of measurement of the ratio of Geobacter to total fungi (Ratio of Geobacter) in the microorganisms attached to the purified structures of Examples 1-1 and 1-2 and Examples 2-1 and 2-2. FIG.

Hereinafter, the purification device and the purification electrode according to the present embodiment will be described in detail. The dimensional ratios in the drawings are exaggerated for the convenience of description, and may differ from the actual ratios.

[Purification device]
As shown in FIGS. 1 to 3, the purification device 100 according to the present embodiment includes the purification structure 10 that causes an oxygen reduction reaction, and the treated water 30 to be purified by the purification structure 10 and the purification structure 10. And a processing tank 20 for holding the inside. And the purification structure 10 is installed in the inside of the processing tank 20 so that the upper part 10a may contact with the gaseous phase 40, and the lower part 10b may contact with the to-be-processed water 30.

(Purification structure)
In the present embodiment, the purification structure 10 includes the conductor 1. As shown in FIG. 1 to FIG. 3, the conductor 1 is made of a conductive material, and is formed of a flat plate member having a substantially rectangular parallelepiped shape.

Purification structure 10 has a site where an oxygen reduction reaction that reduces oxygen in gas phase 40 occurs, and a site where an organic matter oxidation reaction that oxidizes organic matter in treated water 30 to generate hydrogen ions and electrons occurs. doing. Specifically, in the purification structure 10, the site at which the oxygen reduction reaction occurs is the upper portion 10a in contact with the gas phase 40, and the site at which the organic oxidation reaction occurs is the lower section in contact with the water 30 to be treated. 10b.

The conductor 1 constituting the purification structure 10 preferably has an internal space for hydrogen ions (H ⁺ ) to move between the upper portion 10a in which the oxygen reduction reaction occurs and the lower portion 10b in which the organic substance oxidation reaction occurs. . The presence of the continuous space inside the conductor 1 enables the hydrogen ions generated in the lower portion 10b to move to the upper portion 10a through the inner space, as described later.

The configuration of the conductor 1 is not particularly limited as long as it has an internal space for hydrogen ions to move and is electrically connected from the lower portion 10b to the upper portion 10a. The conductor 1 may extend continuously from the lower portion 10 b toward the upper portion 10 a. Alternatively, the conductor 1 may be composed of a plurality of electrically connected conductive portions. Furthermore, a part of the material constituting the conductor 1 may extend continuously from the lower portion 10b toward the upper portion 10a, or may extend across the inner space. That is, part of the material constituting the conductor 1 may extend continuously in the longitudinal direction of the conductor 1 (vertical direction Y in FIGS. 1 to 3), and the direction perpendicular to the longitudinal direction (FIG. 1) To 3 may extend in the X direction and / or the Z direction).

The material of the conductor 1 is not particularly limited as long as the conductivity can be ensured, but for example, at least one selected from the group consisting of a conductive metal, a carbon material, and a conductive polymer material can be used. As the conductive metal, for example, at least one selected from the group consisting of aluminum, copper, stainless steel, nickel and titanium can be used. As the carbon material, for example, at least one selected from the group consisting of carbon paper, carbon felt, carbon cloth and graphite foil can be used. As the conductive polymer material, at least one selected from the group consisting of polyacetylene, polythiophene, polyaniline, poly (p-phenylenevinylene), polypyrrole and poly (p-phenylene sulfide) can be used.

As described above, the conductor 1 preferably has a continuous space from the lower portion 10b to the upper portion 10a because it is preferable to have an internal space for hydrogen ions to move between the upper portion 10a and the lower portion 10b. Is preferred. In order to secure such an internal space, the conductor 1 is preferably provided with a porous conductive sheet. The conductor 1 is more preferably made of a porous conductive sheet. Such a porous conductive sheet has a large number of pores inside, so that hydrogen ions can easily move.

The conductor 1 preferably includes at least one of a woven conductive sheet and a non-woven conductive sheet. Since the woven conductive sheet and the non-woven conductive sheet have a large number of pores, the movement of hydrogen ions can be facilitated. The conductor 1 may be a metal plate having a plurality of through holes from the lower portion 10 b to the upper portion 10 a.

The conductor 1 more preferably comprises a non-woven conductive sheet, and particularly preferably comprises a non-woven conductive sheet. The non-woven fabric can easily change its thickness and porosity, so as described later, an anaerobic microorganism is attached to the lower portion 10b of the conductor 1, and an oxygen reduction catalyst or an aerobic microorganism is easily supported on the upper portion 10a. It becomes possible. The pore diameter of the space in the conductor 1 is not particularly limited as long as hydrogen ions can move from the lower portion 10 b to the upper portion 10 a.

From the above viewpoint, the conductive material constituting the conductor 1 is particularly preferably at least one selected from the group consisting of graphite foil, carbon paper, carbon cloth, carbon felt and stainless steel (SUS).

As shown in FIGS. 1 to 3, it is preferable that the length L1 in the vertical direction Y in the purification structure 10 be longer than the length L2 in the width direction Z perpendicular to the vertical direction Y. Further, it is particularly preferable that the purification structure 10 be plate-like. As a result, the distance between the lower portion 10 b of the purification structure 10 and the water surface 30 a of the water 30 to be treated is increased, and the periphery of the lower portion 10 b becomes anaerobic. Therefore, an anaerobic microorganism adheres to the lower part 10b of the purification structure 10, and it becomes possible to oxidize an organic matter efficiently. Further, in the purification structure 10, a potential difference is generated between the site (upper part 10a) where the oxygen reduction reaction occurs and the site (lower part 10b) where the organic substance oxidation reaction occurs, and the electrons from the lower part 10b to the upper part 10a through the conductor 1 Can be conducted efficiently.

The length L1 in the vertical direction Y in the purification structure 10 is preferably longer than the length L2 in the width direction Z. The length L1 in the vertical direction Y in the purification structure 10 is preferably twice or more, more preferably five times or more, and eight times or more the length L2 in the width direction Z. It is more preferable, and 10 times or more is particularly preferable. Although the upper limit of the length L1 of the vertical direction Y in the purification structure 10 is not particularly limited, for example, the upper limit of the length L2 of the width direction Z is preferably 50 times or less.

As described above, the shape of the purification structure 10 is more preferably plate-like. However, the shape of the purification structure 10 is not limited to such an aspect, and if it is possible to make the length L1 in the vertical direction Y longer than the length L2 in the width direction Z, it is rod-like or string-like It is also good. When the shape of the purification structure is plate-like, rod-like or string-like, the distance between the lower portion 10 b of the purification structure 10 and the water surface 30 a of the water 30 to be treated becomes large. Sexual microorganisms can be attached. Moreover, in the purification structure 10, a potential difference is generated between the upper portion 10a in which the oxygen reduction reaction occurs and the lower portion 10b in which the organic substance oxidation reaction occurs, and it becomes possible to control the metabolism of the microorganism. When the shape of the purification structure 10 is rod-like or string-like, the length L2 in the width direction Z perpendicular to the vertical direction Y refers to the maximum linear distance between two points on the outer periphery of the purification structure 10.

As shown in FIG. 4, it is preferable that the oxygen reduction catalyst 2 be supported on a portion (upper portion 10 a) where the oxygen reduction reaction occurs in the purification structure 10. By supporting the oxygen reduction catalyst 2, the oxygen reduction reaction by oxygen, hydrogen ions and electrons can be efficiently advanced in the upper portion 10a. The oxygen reduction catalyst 2 may be carried on the surface of the conductor 1 or may be carried inside the conductor 1.

The oxygen reduction catalyst 2 that can be supported on the conductor 1 is not particularly limited, but preferably contains platinum. The oxygen reduction catalyst 2 may also include carbon particles doped with at least one nonmetal atom and a metal atom. There are no particular limitations on the atoms doped into the carbon particles. The nonmetal atom is preferably at least one selected from the group consisting of, for example, a nitrogen atom, a boron atom, a sulfur atom and a phosphorus atom. The metal atom is preferably, for example, at least one of an iron atom and a copper atom.

The oxygen reduction catalyst 2 may be bound to the conductor 1 using a binder. That is, the oxygen reduction catalyst 2 may be supported on the surface of the conductor 1 and inside the pores using a binder. Thereby, the oxygen reduction catalyst 2 can be prevented from being detached from the conductor 1 and the oxygen reduction characteristics can be prevented from being degraded. As the binder, it is preferable to use at least one selected from the group consisting of polytetrafluoroethylene, polyvinylidene fluoride (PVDF), and ethylene-propylene-diene copolymer (EPDM), for example. Moreover, it is also preferable to use NAFION (trademark) as a binder.

It is preferable that it is an anaerobic microorganism which decomposes | disassembles the organic substance in the to-be-processed water 30, and produces | generates a hydrogen ion and an electron as microorganisms adhering to the site | part (lower part 10b) which organic substance oxidation reaction generate | occur | produces. The anaerobic microorganism 3 does not require oxygen for growth, and does not require air for oxidatively decomposing the organic matter in the water 30 to be treated. Therefore, the power required to feed the air can be significantly reduced. In addition, since the free energy obtained by microorganisms is small, it is possible to reduce the amount of sludge generated.

The anaerobic microorganism attached to the lower portion 10b of the purification structure 10 is preferably, for example, an electroproducing bacterium having an extracellular electron transfer mechanism. Specifically, examples of anaerobic microorganisms include, for example, bacteria belonging to the genus Geobacter, bacteria belonging to the genus Shewanella, bacteria belonging to the genus Aeromonas, bacteria belonging to the genus Geothrix, and bacteria belonging to the genus Saccharomyces.

Anaerobic microorganisms may be attached to the lower portion 10 b by superimposing and fixing a biofilm including an anaerobic microorganism on the lower portion 10 b of the purification structure 10. Biofilm generally refers to a three-dimensional structure including a microbial population and an extracellular polymeric substance (EPS) produced by the microbial population. However, the anaerobic microorganism may be attached to the lower part 10b without depending on the biofilm. Also, the anaerobic microorganism may be attached not only to the surface of the lower portion 10 b but also to the inside.

The microorganism attached to the site (upper portion 10a) where the oxygen reduction reaction occurs in the purification structure 10 is preferably an aerobic microorganism that reacts oxygen in the gas phase 40 with hydrogen ions and electrons to generate water. . Examples of such aerobic microorganisms 4 include Sphingobacterium bacteria, Acinetobacterium bacteria, and Acinetobacter bacteria.

The purification structure 10 may be made of only the conductor 1. As described later, when both the anaerobic microorganism 3 and the aerobic microorganism 4 are present in the water 30 to be treated, the anaerobic microorganism 3 adheres to the upper portion 10a and the aerobic microorganism 4 adheres to the lower portion 10b. As a result, local cell reactions occur and it becomes possible to oxidatively decompose the organic matter. Further, as described later, the purification structure 10 may constitute a purification electrode together with the oxygen reduction catalyst 2 and the binder. Also by using such a purification electrode, a local cell reaction occurs, and the organic matter can be oxidized and decomposed.

(Treatment tank)
The purification apparatus 100 includes a substantially rectangular processing tank 20 that holds therein the water to be treated 30 containing an organic substance. The front wall 23 of the processing tank 20 is provided with an inlet 21 for supplying the water 30 to the processing tank 20. Further, the rear wall 24 of the treatment tank 20 is provided with an outlet 22 for discharging the treated water 30 after treatment from the treatment tank 20.

The treated water 30 is continuously supplied to the inside of the treatment tank 20 through the inlet 21. Further, as shown in FIG. 1 and FIG. 2, the purification structure 10 is disposed inside the treatment tank 20 so as to be immersed in the water 30 to be treated. Therefore, the water to be treated 30 supplied from the inlet 21 of the treatment tank 20 flows while being in contact with the purification structure 10 and then discharged from the outlet 22.

The treated water 30 to be treated by the purification device 100 can be, for example, a liquid containing an organic substance composed of at least one of an organic substance and a nitrogen-containing compound (nitrogen-containing compound). The water 30 to be treated may be an electrolyte.

Next, the operation of the purification device 100 of the present embodiment will be described. In the purification device 100, the purification structure 10 is installed inside the treatment tank 20 holding the treated water 30. Under the present circumstances, as shown in FIG. 2, the purification structure 10 is installed in the inside of the processing tank 20 so that the main surface 1a of the conductor 1 may become substantially parallel to the perpendicular direction Y. As shown in FIG.

When the purification structure 10 is installed inside the treatment tank 20, as shown in FIGS. 4 and 5, a part of the upper portion 10a of the purification structure 10 contacts the gas phase 40 and the water surface 30a of the water 30 to be treated. doing. Furthermore, a portion of the upper portion 10 a of the purification structure 10 is also in contact with the water 30 to be treated. In addition, since the to-be-processed water 30 which contacts the upper part 10a is located in the vicinity of the gaseous phase 40, it is in the state which the oxygen concentration to melt | dissolve is high.

The lower portion 10 b of the purification structure 10 is immersed in the water 30 to be treated. Since the length L1 in the vertical direction Y in the purification structure 10 is longer than the length L2 in the width direction Z, the lower portion 10b is separated from the water surface 30a, and the dissolved oxygen concentration is low.

And as above-mentioned, since the to-be-processed water 30 which contacts the upper part 10a of the purification structure 10 has a high oxygen concentration to be dissolved, when the to-be-processed water 30 contains the aerobic microorganisms 4, The aerobic microorganism 4 adheres to 10a. Here, for example, when the conductor 1 is a porous body, the water to be treated 30 rises by capillary action, and the water to be treated 30 can be held up to the upper end of the conductor 1. Therefore, the aerobic microorganism 4 can be attached to the entire upper portion of the purification structure 10.

Further, the lower portion 10b of the purification structure 10 is separated from the water surface 30a, and the surrounding area has a low concentration of oxygen, so the anaerobic microorganism 3 adheres to the lower portion 10b.

In the purification device 100 having such a configuration, in the lower portion 10b of the purification structure 10, the oxidation reaction of the organic substance contained in the treated water 30 proceeds by the metabolism of the anaerobic microorganism 3, and hydrogen ions (H ⁺ ) and electrons ( e ^-) is generated. The hydrogen ions generated by the oxidation reaction move to the upper portion 10 a of the purification structure 10 through the internal space of the purification structure 10. Further, electrons generated by the oxidation reaction move to the upper portion 10 a of the purification structure 10 through the conductor 1.

Then, in the upper portion 10a of the purification structure 10, electrons and hydrogen ions transferred from the lower portion 10b react with oxygen molecules by the action of the oxygen reduction catalyst and / or the aerobic microorganism to generate water. Thus, the oxidation reaction of the organic matter proceeds in the lower portion 10b of the purification structure 10, and the reduction reaction of oxygen proceeds in the upper portion 10a, so that a local battery circuit is formed as the entire purification device.

Specifically, for example, when the water 30 to be treated contains glucose as an organic substance, the local cell reaction (half cell reaction) occurring in the upper portion 10a and the lower portion 10b is represented by the following equation.
Lower part 10 b (anode): C ₆ H ₁₂ O ₆ +6 H ₂ O → ₆ CO ₂ + 24 H ⁺ + 24 e ⁻
Upper 10a _{^{(cathode): 6O 2 + 24H + +}} 24e - → 12H 2 O

As described above, the catalytic action of the anaerobic microorganism 3 in the lower portion 10 b can decompose the organic matter in the water to be treated 30 and purify the water to be treated 30.

Here, the purification structure 10 is a portion (upper portion 10a) where an oxygen reduction reaction that reduces oxygen in the gas phase 40 occurs, and an organic matter oxidation that oxidizes the organic matter in the water 30 to generate hydrogen ions and electrons. Preferably, a potential difference is generated between the site where the reaction takes place (lower part 10b). As a result, it is preferable that electrons are conducted from the site where the organic substance oxidation reaction occurs through the conductor 1 to the site where the oxygen reduction reaction occurs.

Specifically, since the length L1 in the vertical direction Y in the purification structure 10 is longer than the length L2 in the width direction Z, the upper portion 10a and the lower portion 10b are separated. And since the conductor 1 which exists between the upper part 10a and the lower part 10b has high electrical resistivity, an electrical potential difference arises between the upper part 10a and the lower part 10b. That is, since the electrical resistivity of the conductor 1 between the upper portion 10a and the lower portion 10b is relatively high, the upper portion 10a and the lower portion 10b can be controlled to an appropriate potential. It becomes possible to secure a potential difference. Then, since the potential difference is maintained, and the metabolism of the microorganism is controlled, electrons are efficiently conducted from the lower portion 10b to the upper portion 10a through the conductor 1, and the decomposition efficiency of the organic matter in the water 30 to be treated is further enhanced. It is possible to enhance. Furthermore, in the purification structure 10, there is no need to provide wiring such as an external circuit for securing a potential difference and a boosting system, and the upper portion 10a and the lower portion 10b are short-circuited.

In the purification structure 10, in the method of generating a potential difference between the upper portion 10a and the lower portion 10b, the length L1 in the vertical direction Y is made larger than the length L2 in the width direction Z, and between the upper portion 10a and the lower portion 10b. There is a way to increase the distance of There is also a method of increasing the electrical resistivity of the conductor 1 itself in the purification structure 10. The preferable potential difference between the upper portion 10a and the lower portion 10b can be determined by the theoretical potential of the oxygen reduction reaction generated in the upper portion 10a serving as the cathode, the theoretical potential of the organic substance oxidation reaction occurring in the lower portion 10b serving as the cathode, and overvoltage. .

Thus, the purification device 100 of the present embodiment includes the purification structure 10 having the conductor 1 and causing an oxygen reduction reaction, and the treated water 30 to be purified by the purification structure 10 and the purification structure 10. And a processing tank 20 for holding the inside thereof. Then, a part of the purification structure 10 contacts the gas phase 40, and the other part of the purification structure 10 contacts the water 30 to be treated. The purification structure 10 is installed inside the processing tank 20 so that the length L1 in the vertical direction Y is longer than the length L2 in the width direction Z perpendicular to the vertical direction Y. Then, the anaerobic microorganism 3 adheres to a portion (lower portion 10b) where the organic substance oxidation reaction occurs in which the organic substance in the treated water 30 is oxidized to generate hydrogen ions and electrons in the purification structure 10 preferable.

The purification device 100 can efficiently oxidize and decompose the organic matter contained in the water to be treated 30 through the electron transfer reaction. Specifically, the organic matter contained in the water to be treated 30 is decomposed and removed by the metabolism of the anaerobic microorganism 3, that is, the growth of the anaerobic microorganism 3. And since this oxidative decomposition treatment is carried out under anaerobic conditions, the conversion efficiency from organic matter to new cells of microorganisms can be suppressed to a lower level than when carried out under aerobic conditions. For this reason, it is possible to reduce the growth of microorganisms, that is, the amount of generated sludge, as compared with the case of using the activated sludge method. Moreover, although the odorous methane gas is produced | generated by a normal anaerobic process, in the oxidation decomposition process in this embodiment, since a metabolic product is carbon dioxide gas, generation | occurrence | production of methane gas can be suppressed. Furthermore, since the purification device 100 is configured by the purification structure 10 having the conductor 1 and the treatment tank 20, the structure is simple, and the manufacturing cost and the maintenance cost can be suppressed.

In addition, since the purification structure 10 is installed in the treatment tank 20 so that the length L1 in the vertical direction Y becomes long, the lower portion 10b is separated from the water surface 30a, and the surrounding oxygen concentration decreases. Therefore, since many anaerobic microorganisms 3 adhere to lower part 10b, it becomes possible to oxidize and decompose the organic substance in to-be-processed water 30 efficiently.

In the purification structure 10, an oxygen reduction reaction that reduces oxygen in the gas phase 40 (upper part 10a) and an organic matter oxidation reaction that oxidizes the organic matter in the water 30 to generate hydrogen ions and electrons occur Preferably, a potential difference is generated between the site (lower part 10b). Thus, electrons can be efficiently conducted from the site where the organic substance oxidation reaction occurs through the conductor 1 to the site where the oxygen reduction reaction occurs. As a result, the metabolism of the anaerobic microorganism 3 accompanied by electron conduction is also promoted. In addition, the anaerobic microorganism 3 migrates and adheres to the lower portion 10b where the metabolism of the anaerobic microorganism 3 is promoted. Therefore, in the lower portion 10b, it is possible to further increase the decomposition efficiency of the organic matter in the water 30 to be treated.

It is preferable that the aerobic microorganism 4 adheres to the part (upper part 10a) which the oxygen reduction reaction which reduce | restores the oxygen in the gaseous phase 40 in the purification | cleaning structure 10 produces. In addition, it is preferable that the oxygen reduction catalyst 2 be supported on a part (upper part 10 a) in the purification structure 10 where the oxygen reduction reaction for reducing the oxygen in the gas phase 40 occurs. Thereby, electrons and hydrogen ions transferred from the lower portion 10 b of the purification structure 10 easily react with oxygen molecules by the action of the oxygen reduction catalyst 2 and / or the aerobic microorganism 4. Therefore, the metabolism of the anaerobic microorganism 3 is promoted, and the oxidative decomposition of the organic matter can be performed more efficiently.

As described above, when the lower portion 10b of the purification structure 10 is separated from the water surface 30a, the anaerobic microorganism 3 easily adheres to the lower portion 10b. Therefore, as shown in FIGS. 1 to 3, the purification structure 10 is preferably disposed inside the processing tank 20 so that the main surface 1 a of the conductor 1 is substantially parallel to the vertical direction Y.

In the purification device 100 shown in FIGS. 1 to 3, one purification structure 10 is installed inside one treatment tank 20. However, the present embodiment is not limited to such an aspect, and a plurality of purification structures 10 may be installed inside the treatment tank 20. By installing the plurality of purification structures 10 inside one treatment tank 20, it becomes possible to more efficiently purify the organic matter in the water 30 to be treated.

In the lower portion 10b of the purification structure 10, for example, an electron transfer mediator molecule may be modified. Alternatively, the treated water 30 in the treatment tank 20 may contain an electron transfer mediator molecule. Thereby, electron transfer from the anaerobic microorganism 3 to the lower portion 10b can be promoted, and more efficient liquid processing can be realized.

Specifically, in the metabolic mechanism by the anaerobic microorganism 3, electrons are exchanged in cells or with the final electron acceptor. When a mediator molecule is introduced into the water 30 to be treated, the mediator molecule acts as a final electron acceptor for metabolism and delivers the received electron to the lower part 10b. As a result, it is possible to increase the rate of oxidative decomposition of the organic matter in the lower portion 10b. The same effect can be obtained even if the mediator molecule is supported on the surface of the lower portion 10b. Such electron transfer mediator molecules are not particularly limited. As the electron transfer mediator molecule, for example, at least one selected from the group consisting of neutral red, anthraquinone-2,6-disulfonic acid (AQDS), thionine, potassium ferricyanide, and methyl viologen can be used.

[Purification electrode]
Next, the purification electrode according to the present embodiment will be described. In addition, the same code | symbol is attached | subjected to the same structure as the above-mentioned purification apparatus, and the overlapping description is abbreviate | omitted.

The purification electrode of the present embodiment is used in a purification device, and comprises only the conductor 1, the oxygen reduction catalyst 2 supported on the conductor 1, and the binder. That is, the purification electrode includes the conductor 1 as the purification structure 10, the oxygen reduction catalyst 2 supported on the portion (upper portion 10a) where the oxygen reduction reaction of the conductor 1 occurs, and the oxygen reduction catalyst 2 as the conductor 1 It consists only of the binder to bind. By immersing such a purification electrode in the water 30 to be treated, as shown in FIG. 4, in the upper portion 10 a, an oxygen reduction reaction that reduces oxygen in the gas phase 40 occurs by the action of the oxygen reduction catalyst 2. In the lower portion 10b, the action of the anaerobic microorganism 3 causes an organic matter oxidation reaction that oxidizes the organic matter in the water to be treated 30 to generate hydrogen ions and electrons. Furthermore, by arranging the potential difference between the upper portion 10a and the lower portion 10b of the purification structure 10, electrons are efficiently conducted from the lower portion 10b to the upper portion 10a through the conductor 1. As a result, since the metabolism of the anaerobic microorganism 3 accompanied by electron conduction is also promoted, it is possible to further enhance the decomposition efficiency of the organic matter in the water 30 to be treated.

The application of the purification electrode is not limited to the purification device 100 including the treatment tank 20. That is, the purification electrode can efficiently oxidize and decompose the organic matter contained in the water to be treated 30 through the electron transfer reaction only by immersing in the water to be treated in which the anaerobic microorganism is present. Therefore, the purification electrode of the present embodiment can be applied to a purification device that does not use the treatment tank 20.

Therefore, the purification electrode includes the conductor 1 and is provided with the purification structure 10 causing the oxygen reduction reaction, a part of the purification structure 10 is in contact with the gas phase, and the other part of the purification structure 10 is It is preferable to use for the purification apparatus which contacts the to-be-processed water 30. FIG. In such a purification device, the purification structure 10 is installed such that the length L1 in the vertical direction Y is longer than the length L1 in the width direction Z perpendicular to the vertical direction Y. The purification electrode preferably comprises only the conductor 1, the oxygen reduction catalyst 2 supported on the conductor 1, and the binder. By using such a purification electrode, it is possible to purify the water to be treated with a simple system while suppressing the generation of biogas. In addition, it is not necessary to apply power necessary for operation from the outside to the purification electrode, and the operation can be performed only by inserting the purification electrode into the water to be treated. It becomes possible.

Hereinafter, the present embodiment will be described in more detail by way of examples, but the present embodiment is not limited to these examples.

Example 1
In Example 1, a purification structure having an oxygen reduction catalyst supported on a conductor was produced. Specifically, first, eight square columnar carbon felts 5 mm long, 5 mm wide, and 100 mm long were prepared as a conductor.

Next, a catalyst slurry was prepared by dispersing 80 mg of a carbon-based catalyst composed of carbon black supporting iron and nitrogen in a mixed solution of 0.76 mL of a 5% by mass Nafion solution and 2.8 mL of ethanol. Then, 50 μL each of the obtained catalyst slurry was dropped on four faces of the upper 20 mm portion of each carbon felt to dry it. As a result, eight purification structures having a carbon-based catalyst supported on the top of the carbon felt were obtained. In addition, in this example, eight purification structures were made into one set, and two sets in total were produced.

Example 2
Eight square columnar carbon felts 5 mm long, 5 mm wide and 100 mm long used in Example 1 were prepared. And the said carbon felt was used as a purification structure as it was. In addition, also in this example, eight purification structures were regarded as one set, and two sets in total were prepared.

[Evaluation]
The purification structures obtained in Example 1 and Example 2 were immersed in the organic wastewater as the water to be treated, and the purification rate of the water to be treated after operating for 28 days was measured.

Specifically, first, a vial having a volume of 100 mL was prepared as a container. Then, one set of purification structures was installed in the vertical direction inside the vial, and organic wastewater was further injected. At this time, the injection amount of the organic wastewater was adjusted so that 80 mm from the bottom of the purification structure was immersed in the organic wastewater. Specifically, by putting eight purification structures and 48 mL of organic wastewater into the inside of one vial, 80 mm from the bottom was immersed in the organic wastewater. In addition, as organic wastewater, a liquid with a total organic carbon (TOC) of 272 mg / L was used.

In addition, the organic wastewater of the vial contained the seed for the microbial fuel cell. Then, after putting the purification structure, the organic wastewater and the inoculum into a vial and sealing the container, two sets of purification devices (batch systems) of Example 1 and Example 2 were produced. In addition, in the purification apparatus of each example, it adjusted so that oxygen could be continuously supplied inside from an apparatus exterior.

The resulting purifiers of Examples 1-1 and 1-2 and the purifiers of Examples 2-1 and 2-2 were each operated for 28 days. At this time, TOC of the organic wastewater was measured twice a week. In addition, the purification structure and the organic wastewater were transferred to a new vial for each TOC measurement, and 60 mL of new organic wastewater was further injected. In addition, after operating the purifier of each example for 28 days, TOC in organic wastewater was measured.

The average value of the TOC measurement results of a total of nine times twice a week and one time after operation for 28 days is shown in FIG. As shown in FIG. 6, in both of the purification structures of Example 1 and Example 2, the TOC is half or less compared to that before the treatment, and it can be seen that the organic wastewater is purified. Furthermore, when Examples 1-1 and 1-2 carrying an oxygen reduction catalyst and Examples 2-1 and 2-2 not carrying an oxygen reduction catalyst are compared, One can see that the TOC is falling. Therefore, it is understood that the oxygen reduction reaction can be promoted and the water to be treated can be purified more efficiently by supporting the oxygen reduction catalyst on the purification structure.

Thus, the purification structure of Example 1 carrying an oxygen reduction catalyst can oxidize organic matter more efficiently than the purification structure of Example 2 carrying no oxygen reduction catalyst. However, even if the purification structure which does not support the oxygen reduction catalyst has a TOC of half or less compared to that before the treatment, it can be seen that the purification structure consisting only of the conductor can also exhibit high purification performance.

Furthermore, the ratio of Geobacter to total fungi (Ratio of Geobacter) was determined from the purified structures of Examples 1-1 and 1-2 and Examples 2-1 and 2-2 after 28 days of operation. Specifically, first, DNA was extracted from the microorganisms attached to the lower part of the purification structures of Examples 1-1 and 1-2 and Examples 2-1 and 2-2. Next, using extracted DNA, the DNA concentration of all fungi and Geobacter bacteria was quantified by quantitative PCR. And the ratio of Geobacter bacteria to all fungi was calculated from Formula 1.

The calibration curve used for measuring the DNA concentration of all fungi was obtained from quantitative PCR using DNA extracted from E. coli and the following primers. Also, the parenthesis indicates the base sequence.
B1055F (5'-ATG GYT GTC GTC AGCT-3 ')
B1392R (5'-ACG GGC GGT GTG TAC-3 ')
Moreover, the calibration curve used for measurement of the DNA concentration of Geobacter bacteria was obtained from quantitative PCR using DNA extracted from geobacter sulfurreducens and the following primers. In parentheses, the base sequence is shown.
Geo494F (5'-AGG AAG CAC CGG CTAACT CC-3 ')
Geo 825 R (5'-TAC CCG CRA CAC CTA GT-3 ')

The ratio of Geobacter to total fungi in the purified structures of Examples 1-1 and 1-2 and Examples 2-1 and 2-2 calculated as described above is shown in FIG. As shown in FIG. 7, the purification structures of Examples 1-1 and 1-2 using the oxygen reduction catalyst are compared with the purification structures of Examples 2-1 and 2-2 not using the oxygen reduction catalyst. Thus, it can be seen that the proportion of Geobacter bacteria is high. That is, it is understood that the purification structures of Examples 1-1 and 1-2 have a higher percentage of the current generating bacteria attached. From this, by supporting the oxygen reduction catalyst, the oxygen reduction reaction proceeds in the upper part of the purification structure, and the electrons from the lower part to the upper part are easily moved accordingly, thereby promoting the growth of the anaerobic microorganism. I understand that.

As mentioned above, although this embodiment was described, this embodiment is not limited to these, A various deformation | transformation is possible within the range of the summary of this embodiment. In addition, the purification device and the purification electrode according to the present embodiment can be widely applied to the treatment of a liquid containing an organic substance, for example, wastewater generated from factories of various industries or organic wastewater such as sewage sludge. Furthermore, the purification device and the purification electrode can be used to improve the environment of the water area.

The entire contents of Japanese Patent Application No. 2017-230016 (filing date: November 30, 2017) are incorporated herein by reference.

According to the present disclosure, it is possible to obtain a purification device having a simple structure and capable of efficiently purifying waste water, and a purification electrode using the purification device.

1,1A Conductor 10a upper part (site where oxygen reduction reaction occurs)
10b Lower part (site where organic substance oxidation reaction occurs)
2 Oxygen reduction catalyst 3 Anaerobic microorganism 4 Aerobic microorganism 10, 10A Purification structure 20 Treatment tank 30 Water to be treated 40 Gas phase 100 Purification device

Claims

A purification structure having a conductor and causing an oxygen reduction reaction;
A treatment tank for internally holding the purification structure and the water to be treated which is purified by the purification structure;
Equipped with
A part of the purification structure is in contact with the gas phase, and the other part of the purification structure is in contact with the water to be treated,
The purification apparatus is installed inside the processing tank such that the length in the vertical direction is longer than the length in the width direction perpendicular to the vertical direction.
The purification structure is between a site where an oxygen reduction reaction that reduces oxygen in the gas phase takes place and a site where an organic matter oxidation reaction that produces hydrogen ions and electrons by oxidizing organic substances in the water to be treated occurs. The purification device according to claim 1, wherein a potential difference is generated, and the electrons are conducted from the site where the organic substance oxidation reaction occurs to the site where the oxygen reduction reaction occurs through the conductor.
The purification device according to claim 1 or 2, wherein an aerobic microorganism is attached to a portion of the purification structure in which an oxygen reduction reaction for reducing oxygen in the gas phase occurs.
The purification apparatus according to any one of claims 1 to 3, wherein an oxygen reduction catalyst is supported at a site where an oxygen reduction reaction for reducing oxygen in the gas phase occurs in the purification structure.
The anaerobic microbe adheres to the site | part which the organic substance oxidation reaction which oxidizes the organic substance in the said to-be-processed water in the said purification structure, and produces | generates a hydrogen ion and an electron occurs. The purification device as described in a paragraph.
The purification device according to any one of claims 1 to 5, wherein a shape of the purification structure is a plate shape, a rod shape, or a string shape.
The purification apparatus according to any one of claims 1 to 6, wherein a plurality of the purification structures are installed inside the treatment tank.
It is a purification electrode used for the purification apparatus as described in any one of Claims 1 thru | or 7, Comprising:
A purification electrode comprising only the conductor, an oxygen reduction catalyst supported on the conductor, and a binder.
A purification structure having a conductor and causing an oxygen reduction reaction, wherein a part of the purification structure is in contact with a gas phase, and the other part of the purification structure is in contact with the water to be treated, The purification structure is a purification electrode used for a purification device installed so that the length in the vertical direction is longer than the length in the width direction perpendicular to the vertical direction,
A purification electrode comprising only the conductor, an oxygen reduction catalyst supported on the conductor, and a binder.