JP2019160454A - Electrode for bioelectrochemical system, bioelectrochemical system, and method for manufacturing electrode for bioelectrochemical system - Google Patents

Abstract

To provide a bioelectrochemical system excellent in processing speed of the entire device as compared with conventional bioelectrochemical systems, and an electrode used therein.SOLUTION: A bioelectrochemical system includes: a container; a liquid received in the container and containing an organic substance and an electron donating microorganism; an anode arranged to be in contact with the liquid; and a cathode arranged to be in contact with the liquid or to be adjacent to the liquid with a cation permeable diaphragm sandwiched therebetween. The anode includes an integrally molded conductive structure with a three-dimensional lattice shape, the conductive structure including lattices having a lattice spacing of 2.5 mm or more and 3.5 mm or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electrode for a bioelectrochemical system, a bioelectrochemical system, and a method for producing an electrode for a bioelectrochemical system.

  For livestock farmers, the treatment of wastewater from barns is a heavy burden because it requires a great deal of cost and labor. In addition, in order to prevent environmental impacts, the development of new wastewater treatment technology that responds to the recycling of livestock biomass and stricter wastewater treatment standards is required. The development of new technologies that enable the appropriate treatment of organic wastewater and the recovery of resources from organic wastewater is required not only in the field of livestock production but also in a wide range of fields such as food processing, brewing, and sewage treatment in urban areas. Yes.

  In recent years, a new technology called a bioelectrochemical system (BES) has attracted attention. The bioelectrochemical system is a general term for an apparatus (bioreactor) that uses a living organism as a catalyst for promoting a reaction on an electrode. Examples of bioelectrochemical systems include Microbial Fuel Cell (MFC), Microbial Electrolysis Cell (MEC), and devices that produce or decompose microbial electrochemical or enzymatic electrochemical materials. Is included. In microbial fuel cells and microbial electrolysis cells, microorganisms have a role of decomposing organic substances by oxidation-reduction reaction under anaerobic conditions and passing electrons generated at that time to an anode (negative electrode).

  A microbial fuel cell is a bioreactor that generates power (energy recovery) by collecting excess reducing power (electrons) generated by microorganisms decomposing (oxidizing) organic matter under anaerobic conditions at the anode (negative electrode). . In the microbial fuel cell, hydrogen ions generated by the decomposition of organic matter move to the cathode (positive electrode) side. On the other hand, the electrons generated by the decomposition of the organic matter are collected at the anode and move to the cathode via an external circuit. On the cathode surface, hydrogen ions and electrons that have moved from the anode side react with oxygen to generate water.

  A microbial electrolysis cell is a bioreactor that recovers excess reducing power (electrons) generated by microorganisms decomposing (oxidizing) organic substances under anaerobic conditions as hydrogen at a cathode (positive electrode). In the microbial electrolysis cell, hydrogen ions generated by the decomposition of organic substances move to the cathode (positive electrode) side. On the other hand, the electrons generated by the decomposition of the organic matter are recovered at the anode by applying a voltage between the anode (negative electrode) and the cathode (positive electrode), and move to the cathode via an external circuit. On the cathode surface, hydrogen ions and electrons react to generate hydrogen gas. By recovering this hydrogen, energy can be recovered. Since the amount of energy obtained as hydrogen is larger than the amount of energy input as voltage application, the entire microbial electrolysis cell has recovered energy from waste water. Thus, the microbial electrolysis cell needs to apply a voltage between the anode and the cathode by a voltage application unit (power source, potentiostat, etc.) connected to the anode and the cathode.

  Bioelectrochemical systems such as microbial fuel cells and microbial electrolysis cells can treat various types of organic wastewater. Since the organic matter in the wastewater is decomposed by this treatment, the bioelectrochemical system also has a function of purifying the wastewater (removing the organic matter). Thus, the bioelectrochemical system is expected as a new technology in the future because it can simultaneously purify wastewater and recover energy from wastewater.

  In a bioelectrochemical system, it is very important to speed up the reaction of passing electrons generated by decomposition of organic substances to the anode, and the speed of this reaction greatly affects the processing speed of the entire apparatus. As the anode, a carbon electrode such as graphite, carbon cloth, carbon felt, or carbon brush is usually used (for example, see Non-Patent Document 1 and Non-Patent Document 2).

  In addition, a method of manufacturing a porous anode by a three-dimensional modeling method such as a powder bed fusion bonding method has been studied (for example, see Non-Patent Documents 3 to 5).

K. P. Nevin, et al., "Power output and columbic efficiencies from biofilms of Geobacter sulfurreducens comparable to mixed community microbial fuel cells", Environmental Microbiology, Vol. 10, pp. 2505-2514. Douglas Call, and Bruce E. Logan, "Hydrogen Production in a Single Chamber Microbial Electrolysis Cell Lacking a Membrane", Environ. Sci. Technol., Vol. 42, pp. 3401-3406. Flaviana Calignano, et al., "Additive Manufacturing of a Microbial Fuel Cell-A detailed study", Sci. Rep., Vol. 5, 13737. Yu Zhou, et al., "A novel anode fabricated by three-dimensional printing for use in urine-powered microbial fuel cell", Biochemical Engineering Journal, Vol. 124 (2017), pp. 36-43. Bin Bian, et al., "3D printed porous carbon anode for enhanced power generation in microbial fuel cell", Nano Energy, Vol. 44 (2018), pp. 174-180.

  The conventional bioelectrochemical system has a problem that the reaction rate on the electrode is slow. For practical use, it is necessary to improve the reaction rate on the electrode. In general, the overall processing rate of a device in a bioelectrochemical system (related to output in microbial fuel cells and microbial electrolysis cells) depends on the charge transfer efficiency from the microorganism to the anode. As described above, in the conventional microbial electrochemical system, the carbon electrode was used as the anode. However, there is room for further improvement in the anode from the viewpoint of improving the processing speed of the entire apparatus.

  On the other hand, according to a three-dimensional modeling method such as a powder bed fusion bonding method as described in Non-Patent Document 3 to Non-Patent Document 5, an anode having an arbitrary porous shape can be manufactured. As a result, if an anode having a shape that facilitates introduction of organic substances and electron-donating microorganisms as fuel into the interior is produced and used, a biofilm formed by electron-donating microorganisms can be sufficiently formed inside the anode, and bioelectrochemistry It is expected that the processing speed of the system can be further improved. However, according to the study by the present inventors, even when an anode as described in Non-Patent Document 3 to Non-Patent Document 5 is used, a biofilm by electron donating microorganisms is sufficiently formed to the inside of the anode. I couldn't do it.

  The present invention has been made in view of the above points, and is an electrode that can be used in a bioelectrochemical system manufactured by a three-dimensional modeling method, and sufficiently fills an anode with organic matter and electron-donating microorganisms that serve as fuel. To provide an electrode capable of further improving the processing speed of the bioelectrochemical system and increasing the current production amount, a bioelectrochemical system using the electrode, and a method of manufacturing the electrode With the goal.

  The present inventors have found that the above-mentioned problems can be solved by using a conductive shaped object shaped in a three-dimensional lattice shape for the anode, and have further studied and completed the present invention.

That is, the present invention relates to the following electrodes for bioelectrochemical systems, bioelectrochemical systems, and methods for producing bioelectrochemical system electrodes.
[1] An electrode used as an anode in a bioelectrochemical system, including an integrally formed three-dimensional grid-shaped conductive molding including a grid having a grid interval of 2.5 mm to 3.5 mm Electrodes for bioelectrochemical systems.
[2] The specific surface area is the ratio of surface area to volume is not more than 469mm ² / cm ³ or more 1542mm ² / cm ^3, bioelectrochemical systems electrode according to [1].
[3] The electrode for a bioelectrochemical system according to [1] or [2], wherein the solid occupancy is 6.1% or more and 19.3% or less.
[4] The electrode for a bioelectrochemical system according to any one of [1] to [3], wherein the lattice is a lattice in which a wire diameter of a frame constituting the lattice is 0.5 mm or less.
[5] The conductive shaped article is formed by continuously forming a single-shaped lattice having a lattice interval of 2.5 mm or more and 3.5 mm or less from the outermost surface to the inside. [1] to [4] An electrode for a bioelectrochemical system according to any one of the above.
[6] The conductive shaped article is formed by combining a plurality of types of lattices having different lattice intervals so that the lattice intervals become smaller continuously or discontinuously as moving from the outside to the inside. The electrode for a bioelectrochemical system according to any one of [1] to [4], wherein at least a part of the plurality of types of lattices is a lattice having a lattice interval of 2.5 mm to 3.5 mm.
[7] The bioelectrochemical system electrode according to any one of [1] to [6], wherein the conductive shaped article has an insertion hole into which the medium introduction device can be inserted from the outermost surface to the inside.
[8] The electrode for a bioelectrochemical system according to any one of [1] to [7], wherein the conductive shaped article has a rotation driving unit that rotates the conductive shaped article.
[9] The bioelectrochemical system electrode according to any one of [1] to [8], wherein the conductive shaped article is a shaped article made of a metal or a metal oxide.
[10] The electrode for a bioelectrochemical system according to [9], wherein a surface of the conductive shaped article is oxidized.
[11] A container, a liquid containing organic matter and electron-donating microorganisms contained in the container, an anode arranged to contact the liquid, and a liquid that is in contact with the liquid or cation-permeable. And a cathode disposed adjacent to the liquid with a diaphragm interposed therebetween, wherein the anode is the electrode for a bioelectrochemical system according to any one of [1] to [10] system.
[12] The bioelectrochemical system according to [11], wherein the bioelectrochemical system is a microbial fuel cell.
[13] The apparatus further includes a voltage applying unit that applies a voltage between the anode and the cathode so that electrons flow from the anode to the cathode, and the bioelectrochemical system is a microbial electrolysis cell. The bioelectrochemical system according to 11].
[14] Conducting a powder melting step including supplying a powder material containing fine particles of a conductive substance and irradiating the supplied powder material with a laser or an electron beam a plurality of times to obtain the three-dimensional lattice-shaped conductive shaped article The manufacturing method of the electrode for bioelectrochemical systems in any one of [1]-[10] which has the process to shape | mold integrally.
[15] After the step of shaping the conductive shaped article, the conductive shaped article is brought into contact with fire in the air or in the presence of oxygen, or heat-treated at 200 ° C. or higher. The manufacturing method of the electrode for bioelectrochemical systems as described in [14] which has the process of heating.

  ADVANTAGE OF THE INVENTION According to this invention, it is an electrode used for the bioelectrochemical system manufactured by the three-dimensional modeling method, Comprising: The electrode which can improve the process speed of a bioelectrochemical system more and can raise an electric current production amount more is provided. can do. Thereby, according to this invention, the microbial fuel cell and microbial electrolysis cell which are excellent in an output compared with the conventional bioelectrochemical system can be provided.

FIG. 1 is a schematic diagram showing a configuration of a microbial electrolysis cell according to Embodiment 1. FIG. FIG. 2 is a perspective view showing a configuration of a conductive shaped article that the microbial electrolysis cell according to Embodiment 1 has as an anode. 3A is a projection view of the conductive shaped article shown in FIG. 2, FIG. 3B is an enlarged view of a region indicated by a dotted line in FIG. 3A, and FIGS. 3C, 3D, and 3E are planes shown in FIG. It is a schematic diagram which shows the shape of a grating | lattice. FIG. 4 is a schematic diagram showing a configuration of a microbial fuel cell according to Embodiment 2. FIG. 5 is a schematic diagram showing a configuration of a microbial fuel cell according to a modification of the second embodiment. FIG. 6 is a schematic diagram showing the shape of the lattice of the conductive shaped article having the octahedral lattice shape produced in Example 1. FIG. 7A and 7B are graphs showing the current production amount for each anode in the example.

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

[Embodiment 1]
In Embodiment 1, a microbial electrolysis cell will be described as an example of the bioelectrochemical system according to the present invention.

(Configuration of microbial electrolysis cell)
FIG. 1 is a schematic cross-sectional view showing a configuration of a microbial electrolysis cell 100 according to Embodiment 1. As shown in FIG. As shown in FIG. 1, a microbial electrolysis cell 100 includes a container 110, a liquid 120, an anode (negative electrode, working electrode) 130, a cathode (positive electrode, counter electrode) 140, a reference electrode 150, a potentiostat 160, a hydrogen recovery unit 170, and A hydrogen storage unit 180 is included. The anode 130, the cathode 140, and the reference electrode 150 are electrically connected to the potentiostat 160. The liquid 120 includes an organic substance and an electron donating microorganism 122.

  The container 110 constitutes the main body of the microbial electrolysis cell 100 and accommodates the liquid 120. The material, shape, and size of the container 110 are not particularly limited, and can be set as appropriate according to the application.

The liquid 120 is accommodated in the container 110 and contains an organic substance serving as a fuel and an electron donating microorganism 122. Usually, the liquid 120 is an aqueous solution containing one or more electrolytes. The type of electrolyte is not particularly limited as long as it is a substance that can be ionized in water. Examples of the electrolyte include NaH ₂ PO ₄ / Na ₂ HPO ₄ , KH ₂ PO ₄ / K ₂ HPO ₄ , NaCO ₃ / NaHCO ₃ , NaCl, KCl, NH ₄ Cl and the like. Further, the liquid 120 may further contain an electron-transmitting intermediary material such as an electron mediator or conductive fine particles as necessary.

  Among the electron donating microorganisms 122 in the liquid 120, at least some of the electron donating microorganisms 122 are supported on the anode 130. That is, the anode 130 also functions as a carrier that holds the electron-donating microorganism 122 at a high density. There may be one kind of electron-donating microorganism 122, or two or more kinds. When organic wastewater or sludge is used as fuel, electron-donating microorganisms that inhabit them can be used as they are without adding electron-donating microorganisms from the outside. For example, Pseudomonas, Geobacter, etc. inhabit every part of the natural environment such as soil, fresh water, seawater, etc., so if organic wastewater or sludge is used as fuel, they can be used without being added from the outside.

  The kind of the organic substance serving as the fuel is not particularly limited as long as the electron donating microorganism 122 can be metabolized. Organic materials used as fuel include not only useful resources such as alcohol, monosaccharides, polysaccharides, and proteins, but also unused resources (organic waste) such as agricultural and industrial waste, organic waste liquid, human waste, sludge, and food residues. Can be used. An organic substance serving as a fuel is added as necessary to maintain and propagate the electron-donating microorganism 122 and to continuously operate the microbial electrolysis cell 100.

  The anode 130 is disposed so as to contact the liquid 120. In the present embodiment, the anode 130 is immersed in the liquid 120.

  One feature of the microbial electrolysis cell 100 according to the present embodiment is that the anode 130 (electrode for a bioelectrochemical system) includes a three-dimensional grid-shaped conductive shaped article formed integrally. In the anode 130 having the above characteristics, the inventors of the present invention remarkably improve the current production amount in the microbial electrolysis cell by using a conductive shaped article including a lattice having a lattice interval of 2.5 mm or more and 3.5 mm or less. (See Examples). The principle of improving the current production amount is unknown, but it is considered that the three-dimensional grid-shaped conductive shaped article has sufficient water permeability and specific surface area.

  That is, by using a three-dimensional grid-shaped conductive shaped article having a lattice spacing of 2.5 mm or more as the anode 130, the organic matter serving as the fuel and the electron-donating microorganism 122 sufficiently flow into the anode 130 having water permeability. As a result, the electron donating microorganism 122 can adhere to the surface of the conductive shaped object inside the anode 130 and the current can be generated more efficiently, so that the electron transfer from the electron donating microorganism 122 to the anode 130 (conductive shaped object). Is assumed to be easier. In addition, by forming a three-dimensional grid-shaped conductive shaped object having a lattice spacing of 2.5 mm or more as the anode 130, by-products such as carbon dioxide and protons generated as by-products of current production are washed away from the inside of the anode. It is also considered that the product inhibition that current production decreases due to the accumulation of is suppressed.

  In particular, when an organic substance having a complicated structure such as saccharides and proteins is used as the organic substance serving as a fuel, the thickness of the biofilm may be 1 mm to several mm. In such a case, if the lattice spacing of the anode is small, the lattice gap is immediately closed, the water permeability is lowered, and current production inside the anode is hindered. On the other hand, if the lattice spacing of the lattice contained in the conductive shaped object is 2.5 mm or more, the opening of the anode is difficult to close even when the organic material having the above complex structure is used, and sufficient current production is possible even inside the anode. Is possible.

  Since carbon felt, stainless steel felt, stainless steel mesh, and the like usually have a smaller lattice spacing, when used as an anode, the biofilm formed on the surface causes the organic matter serving as fuel and the electron-donating microorganism 122 to Intrusion into the anode tends to be hindered. On the other hand, since the conductive shaped article having the lattice spacing has a sufficiently large opening, the organic matter and the electron-donating microorganism 122 serving as the fuel remain after the biofilm is first formed on the surface of the anode. It is easy to enter the inside of the anode, and the current productivity in the whole anode can be improved.

  On the other hand, as a result of the specific surface area inside the anode 130 becoming sufficiently large by using the anode 130 as a three-dimensional lattice-shaped conductive shaped object having a lattice spacing of 3.5 mm or less, the conductive material is introduced into the anode 130. It is inferred that the amount of electron transfer from the electron donating microorganism 122 to the anode 130 (conducting shaped object) could be increased by the fact that the electron donating microorganism 122 was able to form a sufficiently large biofilm (principle) Is not limited to this).

  Note that having water permeability means that when water is supplied to the anode, most of the supplied water from the side opposite to the side where the water is supplied at a sufficient speed (for example, within a few seconds). (For example, 80% or more) is discharged.

  Further, the lattice spacing means a distance having a minimum value among the distances between the centers of adjacent lattices.

  At the same time, from the viewpoint of increasing the current production amount, it is preferable that the three-dimensional grid-shaped conductive shaped article has a grid interval with such a width that it can pass through a sphere having a radius of 0.6 mm to 1.5 mm. The larger the radius of the sphere that can be passed, the higher the water permeability and the current production. On the other hand, if the radius of the sphere that can pass is too large, the specific surface area decreases, and it becomes difficult to increase the amount of biofilm that can be attached.

From the viewpoint of enhancing the current production at the same time, the three-dimensional lattice-shaped conductive shaped object preferably has a specific surface area is the ratio of surface area to volume is 469mm ² / cm ³ or more 1542mm ² / cm ³ or less, 469Mm More preferably, it is ² / cm ³ or more and 1200 mm ² / cm ³ or less. The larger the specific surface area, the more biofilm can be attached and the current production can be increased. On the other hand, when the specific surface area is too large, it becomes difficult to realize the lattice spacing.

  Similarly, from the viewpoint of simultaneously increasing current production, the solid lattice-shaped conductive shaped article may have a solid occupancy that is the volume of the solid portion with respect to the volume of 6.1% or more and 19.3% or less. Preferably, it is 6.1% or more and 15.0% or less. The greater the solid occupancy, the more biofilm can be deposited and the current production can be increased. On the other hand, if the solid occupancy is too large, it becomes difficult to realize the lattice spacing.

  From the viewpoint of increasing the specific surface area and the solid occupancy rate while setting the lattice spacing to 2.5 mm or more and 3.5 mm or less, the wire diameter (thickness) of the frame constituting the lattice is preferably 0.5 mm or less, More preferably, it is 0.3 mm or less. Although the minimum value of the said wire diameter is not specifically limited as long as the intensity | strength when using an electroconductive structure as an anode is enough, For example, it can be 0.01 mm or more.

  The lattice spacing, the radius of the sphere that can pass through, the specific surface area, and the solid occupancy can be calculated from the shape of the conductive shaped object and the observation results using a microscope or the like using known analysis software.

  Note that the lattice spacing is assumed to be a virtual three-dimensional shape composed of only a straight line having no thickness and an intersection where the plurality of straight lines intersect each other. Means the interval between the intersections. In the conductive structure, the radius, specific surface area, and solid occupancy of the sphere that can be passed can be adjusted by the wire diameter of the frame constituting each lattice.

  The three-dimensional lattice-shaped conductive shaped article may have a shape in which lattices of the same shape are formed periodically and continuously, or may be a shape formed by combining lattices of different shapes. For example, in the three-dimensional grid-shaped conductive shaped article, a single-shaped grid having the grid interval of 2.5 mm or more and 3.5 mm or less may be continuously formed from the outermost surface to the inside.

In addition, from the viewpoint of increasing the specific surface area while ensuring that the organic matter and the electron-donating microorganisms 122 as fuel enter the anode, the three-dimensional lattice-shaped conductive shaped article has a continuous lattice interval as it moves from the outside to the inside. A plurality of types of lattices having different lattice intervals may be combined to be smaller or smaller continuously. When the three-dimensional lattice-shaped conductive shaped object has a shape obtained by combining the differently shaped lattices, at least one of the different lattices has a lattice including a lattice having a lattice interval of 2.5 mm or more and 3.5 mm or less. In addition, if it is integrally molded, the amount of current produced can be increased by attaching a larger amount of biofilm to the inside while increasing the water permeability to the inside near the surface. In this case, the three-dimensional lattice-shaped conductive shaped object preferably has a specific surface area is the ratio of surface area to volume is not more than 469mm ² / cm ³ or more ^{1542mm 2 / cm 3, 469mm 2} / cm 3 or more 1200 mm ² More preferably, it is not more than / cm ³ . In this case, the solid lattice-shaped conductive shaped object preferably has a solid occupancy ratio that is the volume of the solid portion with respect to the volume of 6.1% or more and 19.3% or less, and is 6.1% or more and 15 or less. More preferably, it is 0.0% or less. For example, the lattice spacing of the lattice with the largest lattice spacing disposed on the outermost surface is 6.0 mm, and the lattice spacing of the lattice with the smallest lattice spacing disposed on the innermost side is 1.5 mm. It is preferable to discontinuously change the distance because the specific surface area can be about 1100 mm ² / cm ³ and the solid occupancy can be about 14%.

  From the viewpoint of increasing the ease of control of the degree of improvement in current production and the ease of modeling, the conductive shaped object has a shape in which the lattices of the same shape are formed periodically and continuously. When it has, it is preferable to have the shape where the space of the same shape formed by combining the some linear frame which consists of an electroconductive material is arrange | positioned continuously. For example, the conductive shaped object includes a plurality of triangles including isosceles triangles and equilateral triangles, trapezoids, parallelograms, rectangles including rectangles and squares, and hexagonal lattices including regular hexagons. It can be made into the shape where a plane lattice crossed. Among these, from the viewpoint of increasing the hydraulic diameter required by (4 × void area / wetting edge length) to further increase water permeability, a quadrangle and a hexagon are preferable, and a hexagon is more preferable. The angle at which the planar lattices intersect may be constant or indefinite, and the angle formed by the planes on which the planar lattices are formed can be arbitrarily set within a range of 15 ° to 90 °, for example.

  Examples of the conductive material include metals and metal oxides. Conductive materials include tungsten, tungsten oxide, copper, silver, platinum, gold, zinc, niobium, iron, cobalt, titanium, molybdenum, molybdenum oxide, tin, tin oxide, nickel, and oxide from the viewpoint of further increasing current production. Nickel and alloys containing these or oxides thereof can be used. Examples of alloys containing iron include stainless steel and alloys containing 35.0 to 50.0% by weight of Ni and 50.0 to 65.0% of Fe. In addition, even if carbon is integrally molded in a three-dimensional lattice shape, it does not become a conductive shaped article.

  The porous shaped shaped object having the shape as described above can be produced by a three-dimensional shaping method such as a powder bed fusion bonding method. In the powder bed fusion bonding method, a powder material containing fine particles of a conductive substance is thinly arranged in a sheet shape with a uniform thickness, and a predetermined region of the arranged powder material is irradiated with a laser or an electron beam and included in the powder material. The conductive material to be melted. By conducting the arrangement of the powder material and the melting of the conductive substance a plurality of times in the height direction, it is possible to form a porous shaped conductive shaped article having each shape as described above.

  The conductive shaped article produced in this way may be oxidized. The method of oxidation treatment is not particularly limited. For example, the conductive shaped article may be heated by bringing it into contact with fire in the air or in the presence of oxygen, or the conductive shaped article is heated at 200 ° C. or higher, preferably 500 ° C. or higher and 700 ° C. or lower in an electric furnace. May be. The heating temperature and heating time of the conductive shaped article can be appropriately set according to the material and shape of the conductive shaped article to be used, the supply rate of oxygen, and the like. The maximum heat treatment temperature during the oxidation treatment by heating is preferably about 400 to 3500 ° C, and more preferably 550 to 1600 ° C. Further, when the conductive shaped article is an alloy mainly containing iron, the maximum heat treatment temperature is preferably 550 ° C. or higher and 650 ° C. or lower. At this time, the highest ultimate temperature and heat treatment temperature of the conductive shaped article may be temperatures exceeding the melting point of the material of the conductive shaped article unless the conductive shaped article is completely melted and deformed. The heating time is, for example, 1 second to 30 minutes, although it depends on the heating equipment used. Specifically, the surface of the conductive shaped object is sufficiently discolored, and a part or the entire surface of the conductive shaped object is patchy, and the electric resistance is 0.01 Ω / cm to several hundreds Ω / cm or higher. It is preferable to heat until. In addition, when performing oxidation treatment by heating with a gas that generates a combustion temperature higher than the melting point of the material of the conductive shaped object, before the shape is deformed, in order to prevent the conductive shaped object from being completely melted It is preferable to stop the heating.

  Thus, the composition in the surface vicinity changes by oxidizing an electroconductive molded object. Typically, by energy dispersive X-ray spectroscopy (EDS / EDX), exposure is performed by cutting the concentration of each element on the surface of the conductive shaped article after the oxidation treatment and the conductive shaped article after the oxidation treatment. By comparing the concentration of each element in a portion (inside) that is 5 μm or more away from the surface in the cross section that has been made, it can be confirmed whether or not the conductive shaped article has been subjected to a predetermined oxidation treatment.

  In the present embodiment, as shown in FIG. 2 which is a perspective view, the anode 130 includes a plurality of planar lattices formed in a square lattice shape integrally formed from stainless steel by a powder bed fusion bonding method. The conductive shaped object has an octahedral lattice shape in which the angles formed by the planes intersect with each other to be 60 °. FIG. 3A is a plan view of the conductive shaped article shown in FIG. 2, and FIG. 3B is an enlarged view of a region 130a indicated by a dotted line in FIG. 3A. As shown in FIG. 3B, the conductive shaped object according to the present embodiment has a plurality of planar lattices 132a, 132b and 132c arranged at different angles, and the angle between the planes is 60 °. It is a shape that intersects. As shown in FIGS. 3C, 3D, and 3E, each of the planar lattices 132a, 132b, and 132c has a shape in which squares are continuously arranged in the planar direction.

  The cathode 140 is disposed so as to contact the liquid 120. In the present embodiment, the cathode 140 is immersed in the liquid 120. The material of the cathode 140 is not particularly limited as long as it has conductivity and is chemically stable. Further, the shape of the cathode 140 is not particularly limited, and can be appropriately selected according to the ease of recovery of hydrogen gas. Examples of the material of the cathode 140 include carbon, metal, metal oxide, and the like. Examples of the cathode 140 include carbon cloth, carbon felt, stainless steel mesh, stainless felt, platinum mesh, and the like. Further, a hydrogen ion reduction catalyst such as platinum may be supported on these surfaces.

  The reference electrode 150 is disposed so as to contact the liquid 120. In the present embodiment, the reference electrode 150 is immersed in the liquid 120. The type of the reference electrode 150 is not particularly limited and can be appropriately selected. Examples of the reference electrode 150 include a silver-silver chloride electrode, a standard hydrogen electrode, a calomel electrode, and the like.

  The potentiostat 160 is electrically connected to the anode 130, the cathode 140, and the reference electrode 150, and the electrode potential of the anode (working electrode) 130 is −0.4V (vs. Ag / AgCl) (Ag / AgCl: silver). -Silver chloride electrode) or more, preferably -0.2 to 2.0 V (vs. Ag / AgCl). The reference electrode 150 is used as a reference for controlling the electrode potential, and the electrode potential of the anode (working electrode) 130 is kept constant by passing electrons through the cathode (counter electrode) 140. As a result, the potentiostat 160 applies a voltage between the anode (working electrode) 130 and the cathode (counter electrode) 140, and electrons generated by the decomposition of the organic matter are transferred from the anode (working electrode) 130 to the potentiostat 160. And finally flows to the cathode 140, and hydrogen gas 172 is generated on the surface of the cathode 140. Thus, the electrode potential of the anode (working electrode) 130 is always lower than the electrode potential of the cathode 140 by a predetermined potential difference.

  The hydrogen recovery unit 170 recovers the hydrogen gas 172 generated on the surface of the cathode 140. The configuration of the hydrogen recovery unit 170 is not particularly limited as long as the above object can be achieved. In the present embodiment, the hydrogen recovery unit 170 is a funnel-shaped member disposed on the cathode 140 in the liquid 120. The hydrogen recovery unit 170 sends the recovered hydrogen gas to the hydrogen storage unit 180.

  The hydrogen storage unit 180 stores the hydrogen gas recovered by the hydrogen recovery unit 170. The configuration of the hydrogen storage unit 180 is not particularly limited as long as the above object can be achieved. Examples of the hydrogen storage unit 180 include a gas holder.

(Operation of microbial electrolysis cell)
Next, the operation of the microbial electrolysis cell 100 according to the present embodiment will be described.

  The potentiostat 160 causes the anode 130 and the cathode 140 to use the reference electrode 150 as a reference so that the electrode potential of the anode (working electrode) 130 always becomes a predetermined value (for example, 0.2 V (vs. Ag / AgCl)). When the microorganism electrolysis cell 100 is operated by applying a voltage between the two, an organic substance (for example, acetic acid) is decomposed into carbon dioxide by the electron donating microorganism 122 in the container 110, and hydrogen ions and electrons are generated. The Hydrogen ions generated by the decomposition of the organic matter move to the surface of the cathode 140. On the other hand, the electrons generated by the decomposition of the organic matter are collected by the anode 130 and move to the cathode 140 via an external circuit. In such a situation, hydrogen gas 172 is generated on the surface of the cathode 140 by the reaction between hydrogen ions and electrons. Therefore, by supplying an organic substance into the container 110, the above cycle can be maintained and the hydrogen gas 172 can be continuously generated.

  At this time, the liquid 120 in the container 110 may be agitated with a magnetic stirrer or the like in order to promote the introduction of the organic substance serving as fuel and the electron donating microorganism 122 into the anode 130.

(effect)
As described above, the microbial electrolysis cell 100 according to the present embodiment includes an anode including an integrally formed three-dimensional grid-shaped conductive molding including a grid having a grid interval of 2.5 mm to 3.5 mm. Since 130 is used, it is superior to the conventional microbial electrolysis cell in terms of output (current production amount) (see Examples). For example, when an organic waste liquid is used as a fuel, the microbial electrolysis cell 100 according to the present embodiment can not only recover hydrogen gas from the organic waste liquid but also perform a purification process of the organic waste liquid.

  In the present embodiment, the microbial electrolysis cell 100 having the potentiostat 160 as a voltage application unit for applying a voltage between the anode 130 and the cathode 140 has been described. However, instead of the potentiostat 160 as a voltage application unit, a power source is used. May be arranged. In this case, the power source is electrically connected to the anode 130 and the cathode 140, and applies a voltage between the anode 130 and the cathode 140 so that electrons flow from the anode 130 to the cathode 140. The reference electrode 150 is not necessary.

  In the present embodiment, a gas containing oxygen may be sent into the liquid 120 by an aeration apparatus (not shown). Aeration may be performed continuously, or may be performed intermittently because the aerobic state and the anaerobic state are repeated in the liquid 120. Even if aeration is performed continuously, the biofilm formed by attaching electron-donating microorganisms 122 and the like to the inside of the anode 130 is in an anaerobic state, so that output from the microbial electrolysis cell 100 is possible.

(Modification of anode 130)
The three-dimensional grid-shaped conductive shaped object constituting the anode 130 may have an insertion hole through which a medium introduction device such as a tube and a pipette can be inserted from the outermost surface to the inside. The insertion hole can be used to introduce an organic substance serving as a fuel and the electron donating microorganism 122 into the anode 130 by inserting a medium introduction device. The size of the insertion hole is not particularly limited, but may be about 5 mm in diameter.

  Alternatively, the three-dimensional grid-shaped conductive modeling object constituting the anode 130 may have a rotation drive unit that rotates the anode 130 by rotating the conductive modeling object. By rotating the anode 130, it is possible to promote the introduction of the organic matter serving as the fuel and the electron donating microorganism 122 into the anode 130. The rotation drive unit is, for example, a drive member such as a motor, which is disposed at a position not in contact with the conductive shaped object, among rod-shaped members disposed so as to extend from the outer extending part of the conductive shaped object. And so on. The drive member can rotate and move the anode 130 by applying a driving force to the rod-shaped member in a direction shifted from the center of the anode 130 to the conductive shaped article. The rotation speed of the anode 130 at this time can be set to, for example, 6 rpm or more and 60 rpm or less.

[Embodiment 2]
In the second embodiment, a microbial fuel cell will be described as an example of the bioelectrochemical system according to the present invention.

(Configuration of microbial fuel cell)
FIG. 4 is a schematic diagram showing the configuration of the microbial fuel cell 200 according to Embodiment 2. As shown in FIG. As shown in FIG. 4, the microbial fuel cell 200 includes a container 210, a liquid 220, an anode (negative electrode) 230, and a membrane electrode assembly 240. The liquid 220 includes organic matter and electron donating microorganisms 222. The membrane electrode assembly 240 includes a diaphragm 242 and a cathode (positive electrode) 244. In addition, the anode 230 and the cathode 244 are electrically connected by a conductive wire constituting an external circuit.

  The container 210 constitutes the main body of the microbial fuel cell 200 and contains the liquid 220. The material, shape, and size of the container 210 are not particularly limited, and can be set as appropriate according to the application. In the microbial fuel cell 200 according to the present embodiment, the membrane electrode assembly 240 including the diaphragm 242 and the cathode 244 constitutes a part of the wall surface of the container 210.

  The liquid 220 is contained in the container 210 and includes an organic substance serving as a fuel and an electron donating microorganism 222. The liquid 220 is the same as the liquid 120 of the microbial electrolysis cell 100 according to Embodiment 1.

  The anode 230 is arranged so that at least a part thereof is in contact with the liquid 220. The anode 230 is the same as the anode 130 of the microbial electric field cell 100 according to Embodiment 1. In the present embodiment, the anode 230 is immersed in the container 210. For example, the anode 230 may be fixed to the liquid 220 or may be arranged to constitute a part of the inner wall of the container 210.

  The membrane electrode assembly 240 includes a diaphragm 242 having cation permeability and a cathode 244 having gas permeability. The diaphragm 242 and the cathode 244 are integrated to form a membrane electrode assembly 240. The membrane electrode assembly 240 is disposed such that the diaphragm 242 contacts the liquid 220 and the cathode 244 contacts the outside air. In the present embodiment, membrane electrode assembly 240 is arranged to constitute a part of the inner wall of container 210.

  The diaphragm 242 is a film that can selectively permeate cations, and is disposed between the liquid 220 and the cathode 244. The type of the diaphragm 242 is not particularly limited as long as it can selectively permeate cations. Examples of the diaphragm 242 include a proton exchange membrane. The proton exchange membrane is a membrane made of a proton conductive ion exchange polymer electrolyte. Examples of the material of the proton exchange membrane include perfluorosulfonic acid-based fluorine ion exchange resins and organic / inorganic composite compounds. Perfluorosulfonic acid-based fluorine ion exchange resins include, for example, a copolymer containing a polymer unit based on perfluorovinyl ether having a sulfo group and / or a carboxyl group and a polymer unit based on tetrafluoroethylene. Including. Nafion (registered trademark) is known as such a fluorine ion exchange resin. The organic / inorganic composite compound is a substance composed of a compound in which a hydrocarbon polymer (for example, polyvinyl alcohol) and an inorganic compound (for example, tungstic acid) are combined. Membranes made of these materials are commercially available.

  The cathode (air cathode) 244 is disposed so as to be adjacent to the liquid 220 with the diaphragm 242 interposed therebetween. The material and shape of the cathode 244 are not particularly limited as long as both gas permeability and conductivity can be achieved. Examples of the material of the cathode 244 include carbon and metal. Examples of the cathode 244 include carbon paper, carbon cloth, carbon mesh, graphite particles, activated graphite particles, carbon felt, reticulated vitrified carbon, stainless steel mesh, and the like. Further, an oxygen reduction catalyst such as platinum or activated carbon may be supported on these surfaces.

(Operation of microbial fuel cell)
Next, the operation of the microbial fuel cell 200 according to the present embodiment will be described.

  As shown in FIG. 4, when the microbial fuel cell 200 according to the present embodiment is operated, hydrogen ions are generated when an organic substance (for example, acetic acid) is decomposed into carbon dioxide by the electron donating microorganism 222 in the container 210. And electrons are generated. Hydrogen ions generated by the decomposition of the organic matter pass through the diaphragm 242 and move to the surface of the cathode 244. On the other hand, the electrons generated by the decomposition of the organic matter are collected by the anode 230 and move to the cathode 244 via an external circuit. Further, since the cathode 244 has air permeability, oxygen is also present on the surface of the cathode 244. Under such circumstances, water is generated on the surface of the cathode 244 by the reaction of hydrogen ions and electrons with oxygen. Therefore, by supplying the organic substance into the container 210, the above cycle can be maintained and power can be continuously supplied to the external circuit.

  Also in the present embodiment, as in the modification of the first embodiment, in order to promote the introduction of the organic matter serving as the fuel and the electron donating microorganism 222 into the anode 230, the liquid in the container 210 may be replaced with a magnetic stirrer or the like. 220 may be stirred.

(effect)
As described above, the microbial fuel cell 200 according to the present embodiment includes an anode including an integrally formed three-dimensional grid-shaped conductive molding including a grid having a grid interval of 2.5 mm to 3.5 mm. Since 230 is used, it is superior to the conventional microbial fuel cell in terms of output (power density per unit area of the anode) (see Examples). For example, when an organic waste liquid is used as a fuel, the microbial fuel cell 200 according to the present embodiment can not only recover electrical energy from the organic waste liquid but also perform a purification process of the organic waste liquid.

  In the present embodiment, the microbial fuel cell 200 having the diaphragm 242 has been described. However, the diaphragm 242 is not an essential component. That is, as shown in FIG. 5, the cathode 244 may be in direct contact with the liquid 220. However, considering the long-term sustainability of the battery and the energy recovery efficiency, it is preferable that the diaphragm 242 is present.

  In the present embodiment, an air cathode type (single tank type) microbial fuel cell has been described. However, the bioelectrochemical system according to the present invention may be a two tank type microbial fuel cell. In this case, the container 210 is divided into an anode tank and a cathode tank by the diaphragm 242. The anode 230 is immersed in a liquid containing the organic matter and the electron donating microorganisms 222 housed in the anode tank, and the cathode 244 is immersed in the liquid housed in the cathode tank.

  Also in the present embodiment, a gas containing oxygen may be fed into the liquid 220 by an aeration apparatus (not shown). Aeration may be performed continuously, or may be performed intermittently because the aerobic state and the anaerobic state are repeated in the liquid 220. Even if continuous aeration is performed, the inside of the biofilm formed by adhering the electron donating microorganisms 222 and the like to the inside of the anode 230 is in an anaerobic state, so that the output from the microbial fuel cell 200 is possible.

  Also in the present embodiment, as in the modification of the first embodiment, the three-dimensional grid-shaped conductive shaped object constituting the anode 230 is provided with a medium introduction device such as a tube and a pipette from the outermost surface to the inside. You may have an insertion hole which can be inserted. The insertion hole can be used to insert a medium introduction device and introduce organic matter and electron donating microorganisms 222 as fuel into the anode 230. The size of the insertion hole is not particularly limited, but may be about 5 mm in diameter.

  Also in the present embodiment, as in the modification of the first embodiment, the three-dimensional lattice-shaped conductive shaped object constituting the anode 230 rotates the anode 230 by rotating the conductive shaped object. You may have a rotation drive part. By rotating the anode 230, it is possible to promote the introduction of the organic matter serving as the fuel and the electron donating microorganism 222 into the anode 230. The rotation drive unit is, for example, a drive member such as a motor, which is disposed at a position not in contact with the conductive shaped object, among rod-shaped members disposed so as to extend from the outer extending part of the conductive shaped object. And so on. The driving member can rotate and move the anode 230 by applying a driving force to the rod-shaped member in a direction shifted from the center of the anode 230 to the conductive shaped object. At this time, the rotation speed of the anode 230 can be set to, for example, 6 rpm or more and 60 rpm or less.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail with reference to an Example, this invention is not limited by these Examples.

[Example 1]
1. Production of Anode Four types of anodes were produced using a modeling apparatus by a powder bed fusion bonding method. These anodes have a shape in which a plurality of planar lattices formed in a square lattice shape with a frame having a wire diameter of 0.5 mm intersect so that the angles between the planes are all 60 °. It is a conductive shaped article having an octahedral lattice shape. In each case, stainless steel powder is used as a material, and the supply of the powder and the sintering of the stainless steel by laser irradiation to the supplied powder are repeated to form a three-dimensional lattice shape formed by forming stainless steel into a regular shape. A conductive model was modeled. The sizes of the conductive shaped objects are all 30 mm × 30 mm × 25 mm. Four types of conductive shaped objects were modeled by setting the intervals between the lattice points constituting the planar lattice (lattice interval) to 1.5 mm, 3.0 mm, 4.5 mm, and 6.0 mm.

  The four types of modeled conductive shaped articles were heat-treated at a heat treatment temperature of 600 ° C. and subjected to an oxidation treatment. As for the electroconductive molded object after an oxidation process, the surface and the inside are all black and it was confirmed that the iron oxide was formed. After the oxidation treatment, conductive moldings having intervals between lattice points of 1.5 mm, 3.0 mm, 4.5 mm, and 6.0 mm were respectively converted into an anode (O-1.5) and an anode (O-3. 0), anode (O-4.5) and anode (O-6.0). The anode (O-1.5), the anode (O-3.0), the anode (O-4.5) and the anode (O-6.0) are all supplied from two directions orthogonal to each other. However, both passed through the anode to the opposite side.

  Each of the anodes is formed with a continuous grid having the shape shown in FIG. 6A. In FIG. 6A, the length indicated by “P” is the lattice spacing (for example, 3.0 mm for the anode (O-3.0)). 6B is a diagram of the lattice having the shape shown in FIG. 6A when viewed in the Y direction in the drawing. The length of the diagonal D is (P-2 × (L / √2) when the diameter of the lattice frame is L (0.5 mm for the anode (O-3.0)). )) (Anode (O-3.0) is approximately 2.3 mm). Therefore, a sphere that can pass through this lattice is a sphere that can pass through a square plane frame with a side of (D / √2) (about 1.6 mm if anode (O-3.0)), and its radius is In the case of the anode (O-3.0), it is about 0.8 mm.

  Four other types of anodes were prepared using a modeling apparatus using a powder bed fusion bonding method. These anodes are regular hexahedral lattices in which a plurality of planar lattices formed in a square lattice shape with a frame having a wire diameter of 0.5 mm intersect so that the angles between the planes are all 90 °. It is a conductive shaped article having a shape. In each case, stainless steel powder is used as a material, and the supply of the powder and the sintering of the stainless steel by laser irradiation to the supplied powder are repeated to form a three-dimensional lattice shape formed by forming stainless steel into a regular shape. A conductive model was modeled. The sizes of the conductive shaped objects are all 30 mm × 30 mm × 25 mm. Four types of conductive shaped objects were formed by setting intervals between lattice points constituting the planar lattice to 1.5 mm, 3.0 mm, 4.5 mm, and 6.0 mm.

  The four types of modeled conductive shaped articles were heat-treated at a heat treatment temperature of 600 ° C. and subjected to an oxidation treatment. As for the electroconductive molded object after an oxidation process, the surface and the inside are all black and it was confirmed that the iron oxide was formed. After the oxidation treatment, conductive shaped objects having intervals between lattice points (lattice intervals) of 1.5 mm, 3.0 mm, 4.5 mm, and 6.0 mm were respectively converted into anode (H-1.5) and anode ( H-3.0), anode (H-4.5) and anode (H-6.0). The anode (H-1.5), the anode (H-3.0), the anode (H-4.5), and the anode (H-6.0) are all supplied from two directions orthogonal to each other. However, both passed through the anode to the opposite side.

  Each of the anodes has a cubic lattice formed continuously. The inside of this lattice has a length of one side of (P−2 × (L / 2) (L / 2) when the diameter of the lattice frame is L (0.5 mm for the anode (H-3.0)). It is a square which is an anode (about 2.5 mm for O-3.0). Therefore, the radius of the sphere that can pass through this lattice is about 1.3 mm for the anode (H-3.0).

  An anode having a size of 30 mm × 30 mm × 25 mm was produced by closely adhering and overlapping carbon felts having a thickness of 5 mm. This anode was designated as an anode (CF).

2. Production of Microbial Electrolysis Cell A cubic container made of acrylic resin having a capacity of 125 mL (inner dimensions: 5 cm × 5 cm × 5 cm) was prepared. Artificial drainage was prepared by mixing a medium having the composition shown in the following table and activated sludge as a source of electron-donating microorganisms at a ratio of 5: 1. 125 mL of the obtained artificial waste water was introduced into the container. The bacteria group contained in the activated sludge was inoculated into artificial wastewater in the container as an inoculum.

  Any of the anodes (working electrode, negative electrode) produced above, a platinum electrode as a cathode (counter electrode, positive electrode), and a silver-silver chloride electrode as a reference electrode were immersed in the artificial waste water in the container. These electrodes are all connected to a potentiostat.

3. Evaluation of Microbial Electrolysis Cell While stirring the artificial waste water at 30 ° C., voltage was applied to the anode and cathode so that the electrode potential of the anode was −0.2 V with respect to the potential of the silver-silver chloride electrode (reference electrode). The produced microbial electrolysis cell was operated. The medium was changed every 3 or 4 days. Each time the medium was changed for the first time, the cathode and reference electrode were washed. In addition, the value of current production stabilized in about 10 days from the start of culture. Two weeks after the start of the culture, the current flowing between the anode and the cathode was measured.

Table 2 shows the maximum sphere radius, specific surface area (surface area / volume), solid occupancy, and current production per cm ^{3 of} electrode for each anode.

Anode (O-1.5), anode (O-3.0), anode (O-4.5) and anode (O-6.0), which are conductive shaped objects having an octahedral lattice shape, are used. FIG. 7A shows the relationship between the lattice spacing and the current production amount. The anode (H-1.5), anode (H-3.0), anode (H-4.5) and anode (H-6.0), which are conductive shaped objects having a hexahedral lattice shape, were used. FIG. 7B shows the relationship between the lattice spacing and the current production amount. In FIGS. 7A and 7B, the current production amount (0.66 mA per 1 cm ^{3 of} electrode) when the anode (CF) is used is shown by a solid line. As apparent from FIGS. 7A and 7B, the current production increases remarkably in the vicinity of the grid spacing of 3.0 mm, and particularly when the grid spacing is 2.5 mm or more and 3.5 mm or less. Was shown to be higher.

  In addition, when each anode was observed with an optical microscope after the experiment, a large amount of bacteria (electron-donating microorganisms) adhered to the outer surface of the anode 1.5 and anode CF, and a thick biofilm was formed. However, almost no bacteria adhered to the inside of the electrode. In these electrodes, the surface of the electrode is clogged due to biofilm formation, and the substrate and bacteria cannot enter the inside of the electrode, and it is considered that the current production was low. On the other hand, in the anode 3.0, the anode 4.5, and the anode 6.0, the bacteria adhered to the electrode surface outside and inside the electrode. The gap between anode 3.0, anode 4.5, and anode 6.0 is considered to be sized to allow the substrate and bacteria to enter the interior of the electrode.

  The surface areas of the electrodes of the anode 4.5 and the anode 6.0 are smaller than that of the anode 3.0. Therefore, it is considered that the anode 4.5 and the anode 6.0 did not form a sufficient amount of biofilm, and the anode 3.0 could produce a smaller amount of current.

[Example 2]
In Example 1, the lattice shape of the octahedron is reduced so that the lattice spacing becomes discontinuously smaller from 6.0 mm → 4.5 mm → 3.0 mm → 1.5 mm as it moves from the outermost surface to the inside. A conductive shaped article formed by combining a plurality of types of lattices was formed. When this was heat-treated and subjected to an oxidation treatment, it was confirmed that the surface of the conductive shaped article after the oxidation treatment was blackened and iron oxide was formed. The conductive shaped article after the oxidation treatment was used as an anode (O-I).

When a test was performed in the same manner as in Example 1 except that the anode (O-I) was used as the anode, the current production amount was 1.24 mA / cm ³ per 1 cm ³ of the electrode.

  In Example 1, a plurality of hexahedral lattice shapes are formed so that the lattice spacing is discontinuously decreased from 6.0 mm to 4.5 mm → 3.0 mm → 1.5 mm as it moves from the outside to the inside. A conductive shaped article formed by combining seed lattices was formed. When this was heat-treated and subjected to an oxidation treatment, it was confirmed that the surface of the conductive shaped article after the oxidation treatment was blackened and iron oxide was formed. The conductive shaped article after the oxidation treatment was used as an anode (HI).

When a test was performed in the same manner as in Example 1 except that the anode (HI) was used as the anode, the current production amount was 1.29 mA / cm ³ per 1 cm ³ of the electrode.

  From these results, it is assumed that a conductive structure formed by combining a plurality of types of lattices having different lattice shapes so as to discontinuously decrease the lattice interval as it moves from the outside to the inside is used as an anode. It can be seen that the production amount further increases.

[Example 3]
An insertion hole having a diameter of 5.0 mm was formed from the upper part to the central part of the anode (O-3.0) and the anode (H-3.0) in Example 1. When a tube was inserted into the insertion hole and the medium was introduced into the electrode from the tube and then tested in the same manner as in Example 1, the current production increased by about 10%.

[Example 4]
A stainless steel rod having a diameter of 1 mm and a length of 8 cm was attached to the side surfaces of the anode (O-3.0) and the anode (H-3.0) in Example 1. A test was performed in the same manner as in Example 1 while attaching a motor to a position of the rod extending from the outer extension of the anode and not contacting the anode, and rotating the anode so that the rotation speed was 6 rpm to 60 rpm. As a result, the current production increased by about 10%.

  From these results, when an integrally formed three-dimensional grid-shaped conductive shaped article including a grid having a grid interval of 2.5 mm or more and 3.5 mm or less is used for the anode, the current production amount (treatment) in the microbial electrolysis cell Speed) was confirmed to increase. In addition, the reason why the current production increased was that it was assumed that many electron-donating microorganisms adhered to the surface outside and inside the electrode, so the current production in other bioelectrochemical systems such as microbial fuel cells. It is presumed that the (processing speed) can be similarly increased.

  The electrode for a bioelectrochemical system according to the present invention includes an electrode for a biochemical oxygen demand (BOD) real-time biosensor using a power generation bacterium, an anode such as a microbial electrolysis cell and a microbial fuel cell, and a microorganism ( It is also useful as an electrode used in electrochemical decomposition and synthesis methods.

  The bioelectrochemical system according to the present invention is useful in, for example, wastewater treatment in livestock barns, wastewater treatment in food processing factories, etc., purification treatment of combined treatment septic tanks in rural villages, and sewage treatment in urban areas.

100 Microbial electrolysis cell 110, 210 Container 120, 220 Liquid 122, 222 Electron donating microorganism 130, 230 Anode 130a Region 132a, 132b, 132c Planar lattice 140, 244 Cathode 150 Reference electrode 160 Potentiostat 170 Hydrogen recovery part 172 Hydrogen gas 180 Hydrogen Storage unit 200 Microbial fuel cell 240 Membrane electrode assembly 242 Membrane

Claims (15)

An electrode used as an anode in a bioelectrochemical system,
Including a three-dimensional lattice-shaped conductive shaped article integrally formed, including a lattice having a lattice interval of 2.5 mm or more and 3.5 mm or less,
Electrode for bioelectrochemical systems. The specific surface area is the ratio of surface area to volume is not more than 469mm ² / cm ³ or more 1542mm ² / cm ^3, bioelectrochemical systems electrode according to claim 1.   The electrode for a bioelectrochemical system according to claim 1 or 2, wherein the solid occupancy is 6.1% or more and 19.3% or less.   The electrode for a bioelectrochemical system according to any one of claims 1 to 3, wherein the lattice is a lattice in which a diameter of a frame constituting the lattice is 0.5 mm or less.   The conductive modeled object according to any one of claims 1 to 4, wherein a single-shaped lattice having a lattice interval of 2.5 mm or more and 3.5 mm or less is continuously formed from the outermost surface to the inside. The electrode for bioelectrochemical systems described in 1. The conductive shaped article is formed by combining a plurality of types of lattices having different lattice intervals so that the lattice intervals become smaller continuously or discontinuously as it moves from outside to inside,
At least one of the plurality of types of lattices is a lattice having a lattice interval of 2.5 mm to 3.5 mm.
The electrode for a bioelectrochemical system according to any one of claims 1 to 4.   The electrode for a bioelectrochemical system according to any one of claims 1 to 6, wherein the conductive shaped article has an insertion hole into which a medium introduction device can be inserted from the outermost surface to the inside.   The electrode for a bioelectrochemical system according to any one of claims 1 to 7, wherein the conductive shaped article has a rotation drive unit that rotates the conductive shaped article.   The electrode for a bioelectrochemical system according to claim 1, wherein the conductive shaped article is a shaped article made of a metal or a metal oxide.   The electrode for a bioelectrochemical system according to claim 9, wherein a surface of the conductive shaped article is oxidized. A container,
A liquid containing organic matter and electron-donating microorganisms contained in the container;
An anode disposed in contact with the liquid;
A cathode disposed in contact with the liquid or adjacent to the liquid across a cation permeable membrane;
The anode is an electrode for a bioelectrochemical system according to any one of claims 1 to 10.
Bioelectrochemical system.   12. The bioelectrochemical system according to claim 11, wherein the bioelectrochemical system is a microbial fuel cell. A voltage application unit that applies a voltage between the anode and the cathode so that electrons flow from the anode to the cathode;
The bioelectrochemical system is a microbial electrolysis cell;
The bioelectrochemical system according to claim 11. Conducting a powder melting step including supplying a powder material containing fine particles of a conductive substance and irradiating the supplied powder material with a laser or an electron beam a plurality of times to integrally form the three-dimensional lattice-shaped conductive shaped object Having a process of shaping,
The manufacturing method of the electrode for bioelectrochemical systems of any one of Claims 1-10.   After the step of modeling the conductive modeling object, the conductive modeling object is heated by bringing the modeled conductive modeling object into contact with fire in the air or in the presence of oxygen, or by heat treatment at 200 ° C. or higher. The manufacturing method of the electrode for bioelectrochemical systems of Claim 14 which has a process.