JP2007095471A - Anode for bio-generation, and method and device of power generation utilizing this - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and a device wherein electric energy is efficiently obtained from a water-containing organic material by obtaining a sufficiently low anode potential as a result of keeping an activation overvoltage of the anode low. <P>SOLUTION: This is the power generating device which is equipped with an anaerobic region 4 including a solution or a suspension containing microorganisms capable of growing in anaerobic conditions and an organic material, an electronic mediator, and an anode 1, an aerobic region 5 including molecular oxygen and a cathode 3, a barrier rib 2 to demarcate the anaerobic region 4 and the aerobic region 5, and in which a closed circuit 6 is formed by electrically connecting the anode 1 and the cathode 3 to an electric power utilizing equipment, and an oxidation reaction of the microorganisms in which the organic material in the anaerobic region 4 is used as an electron donor and a reduction reaction in which oxygen in the aerobic region 5 is used as an electron acceptor are utilized. The electron mediator is made coupled with a CNT (carbon nanotube) immobilized on the anode surface or a VGCF (vapor phase growth carbon fiber), and a character that the standard electrode potential (E<SB>O</SB>') range in pH 7 of the anode is -0.13 V to -0.28 V is maintained. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention uses an organic substance such as waste water, waste liquid, human waste, food waste, other organic waste, sludge, or a decomposition product thereof as a substrate, and an anoxic reaction between the substrate and oxygen in the air is anaerobic. The present invention relates to a biopower generation technology that generates power by separating an oxidation reaction by a sex organism and a reduction reaction of oxygen.

  Anaerobic, including methane fermentation, as a method of decomposing waste water, waste liquid, human waste, food waste, other organic waste or sludge (hereinafter referred to as “water-containing organic substance”) and extracting available energy There have been devised methods such as producing methane by fermentation and generating electricity using this, and a biobattery method for taking out electricity directly from the anaerobic respiratory reaction of organisms.

  However, the method of producing methane, ethanol, hydrogen, etc. by anaerobic fermentation methods such as methane fermentation, and generating electricity using these, is a two-stage process of material production by organisms and power generation process using products as fuel. Since steps are required, there is a problem that energy efficiency is poor and the apparatus is complicated.

On the other hand, there is a method in which an electric current is obtained by donating electrons from an electron donor around the anode to an electron acceptor (mainly dissolved oxygen) around the cathode by conducting electrons from the anode and the cathode as a circuit using microorganisms. Have been reported (Patent Documents 1, 2, and 3). In these methods, since the cathode is installed in water, it is highly possible that the diffusion rate of dissolved oxygen in water is the rate-determining factor for the overall reaction. That is, since the reduction reaction of dissolved oxygen in water depends on the diffusion rate of oxygen in water, the maximum amount of current per electrode unit surface area without stirring is ²⁰ μA / cm ² regardless of overvoltage. This is significantly smaller than the value when oxygen in the air is used (about 300 mA / cm ² at an overvoltage of 200 mV), so that it becomes a limiting factor for oxidation of water-containing organic substances and power generation.

  In another example, a method of efficiently extracting electrons by adding an electron mediator (electron transfer medium substance) to a microorganism and maintaining the microorganism in a starved state has been proposed (Patent Document 4). Describes that oxygen or an air electrode can be used as a cathode. However, the document does not include a description and examples of the specific structure of the apparatus when using an air electrode, and does not disclose that a person skilled in the art can implement as a means for solving the problem.

  As a biological battery technology that uses electron mediators, water-containing organic substances or their decomposition products are used as substrates, and the oxidation-reduction reaction between the substrate and oxygen is separated into an oxidation reaction by anaerobic microorganisms and an oxygen reduction reaction. Have been proposed (Patent Document 3 and Non-Patent Documents 1 to 3). However, the standard electrode potential of the electron mediator used in these methods does not overlap with the standard electrode potential of the final electron acceptor of anaerobic microorganisms generally used for biocell reactions, and cannot form an effective potential cascade. There is a problem. For example, the electron mediators proposed so far and their standard electrode potentials are as shown in Table 1 below.

  On the other hand, the standard electrode potentials of sulfur and iron, which are the final electron accepting substances of sulfur-reducing bacteria and iron (III) -reducing bacteria, which are anaerobic microorganisms used in general biological battery reactions, are as shown in Table 2 below. .

  From Table 2, the terminal reductase (sulfur reductase) of the electron transfer system possessed by sulfur-reducing bacteria can reduce substances with a standard electrode potential of -0.28V, while iron (III) -reducing bacteria. It can be seen that the terminal reductase (iron (III) oxide reductase) of the electron transport system has the ability to reduce substances with a standard electrode potential of + 0.20V. These terminal reductases are present in the outer membrane and periplasm of microorganisms and can reduce iron oxide and zero-valent sulfur outside the cells, so that they can be effective catalysts for efficient bioelectric generation. However, as shown in Table 1, the standard electrode potential of the electron mediators that have been proposed so far is lower than the standard electrode potential of iron reduction, so that iron (III) reductase is available. -An effective potential cascade cannot be formed between the electron mediator and the anode. Similarly, since the electron mediators in Tables 1C to G are lower than the standard electrode potential for sulfur reduction, an effective potential cascade cannot be formed between the sulfur reductase-electron mediator-anode. Since the electron mediators in Tables 1A and B are higher than the standard electrode potential for sulfur reduction, they can theoretically be reduced by sulfur reductase, but the potential difference is 0.3 V or more, and biological electron transfer is difficult. There is a high possibility. In addition, in order to increase the power generation efficiency, it is required to generate as large a potential difference as possible with respect to the oxygen reduction reaction of the cathode. However, since the potential of the electron mediator is high, the potential difference of 0.3 V or more is lost, resulting in energy loss. Becomes larger.

  Therefore, in a biological battery system using sulfur-reducing bacteria, a proposal was made to try to improve electron transfer efficiency by adding anthraquinone-2,6-disulfonic acid (AQ-2,6-DS) to the anaerobic region. (Non-patent document 2). The standard electrode potential of AQ-2,6-DS is -0.185 V, which is considered to be a suitable substance for forming an effective potential cascade between sulfur reductase and electron mediator. However, in the proposed system, AQ-2,6-DS is only added in the liquid phase and is not supported on the anode (oxidation electrode). Is only 24% increase in current value. In addition, in the case of continuous power generation, there is a problem that when the substrate solution in the anaerobic region is renewed, the electron mediator is also discharged out of the system together, and the electron mediator must be continuously added. .

  In addition, an attempt to support neutral red on the anode using an amide bond has been proposed (Non-patent Document 3). According to this proposal, when a carboxy group is introduced by oxidation of a graphite electrode and reacted with neutral red in the presence of dicyclohexylcarbodiimide to form an amide bond, the following structural formula:

Among them, it is considered that a carboxy group is bonded to the 9-position secondary amine indicated by an arrow. However, the current peak in neutral voltammetry of neutral red bonded to graphite is observed around -0.42V, which is about 0.1V lower than the standard electrode potential of -0.325V in the free state. This variation makes it more difficult for organisms to use electronic mediators. This is considered to be because the standard electrode potential of neutral red was greatly changed by chemically modifying the 9-position secondary amine.

  That is, in the bioelectric power generation technology using an electron mediator, there is a demand for a technology that forms an effective potential cascade between a terminal reductase of a microorganism, an electron mediator, and an anode, and uses a conductive substrate having a low activation overvoltage.

JP 2000-133327 A JP 2000-133326 A Special Table 2002-520032 US Pat. No. 4,652,501 Japanese Patent Application No. 2005-088158 Roller et al., 1984, Journal of Chemical Technology and Biotechnology 34B: 3-12 Bond et al., 2002, SCIENCE 295: 483-485 Park et al., 2000, Biotechnology Letters 22: 1301-1304

  An object of the present invention is to solve the above-mentioned problems of the prior art and to provide an anode for bioelectric power generation that can efficiently perform bioelectric power generation with a simple device and method, more specifically, anaerobic. It is possible to form an effective potential cascade between the final reductase, the electron mediator, and the anode of the sex organism, and as a result, a sufficiently low anode potential can be obtained to efficiently obtain electric energy from the water-containing organic substance. An anode for bioelectric power generation, a method for producing the same, and a power generation method and apparatus using the same.

  As described above, in order to form an effective potential cascade between the terminal reductase, the electron mediator, and the anode of the microorganism, the potential of the electron mediator must be −0.28 V or higher, which is higher than the standard electrode potential for sulfur reduction. desirable. On the other hand, in the case of aiming at practical power generation, it is considered that the anode potential needs to be as low as possible in order to make the potential difference from the cathode as large as possible.

Based on these findings, the inventors selected an electron mediator using the standard electrode potential of the final electron acceptor of anaerobic microorganisms as an index, and further immobilized it on the anode surface, and if necessary, further added an amino group or a sulfonic acid group. The standard electrode potential of the anode at pH 7 was devised to be as close to -0.28V as possible within the range of -0.13V to -0.28V (Patent Document 5). In the present invention, graphite, porous graphite, gold, platinum, or metal oxide (such as TiO ₂ ) is used as an anode substrate, and an electron mediator is attached to these by amide bond, gold or platinum-sulfur bond or silane coupling. A method for immobilization is disclosed.

  Then, after further research based on the knowledge obtained in the past, by introducing the electron mediator to the conductive base material through the conductive fiber, the above object is more effectively achieved than the conventional invention. It was found that it could be achieved.

The present invention has been made based on the above findings, and according to the present invention, the present invention includes a conductive base material having a conductive fiber protruding from the surface, and an electron mediator is immobilized on the conductive fiber. A bioelectric power generation anode characterized in that a standard electrode potential (E ₀ ′) at pH 7 is in the range of −0.13 V to −0.28 V is provided.

  Further, according to the present invention, a microorganism that can grow in an anaerobic atmosphere, a solution or suspension containing an organic substance, an anaerobic region including the bioelectric power generation anode of the present invention, molecular oxygen, and a cathode. Including an aerobic region, a diaphragm defining the anaerobic region and the aerobic region, and electrically connecting the anode and the cathode to a power utilization device to form a closed circuit, Provided is a power generation apparatus that generates electricity using an oxidation reaction using an organic substance as an electron donor in a sex region and a reduction reaction using oxygen as an electron acceptor in the aerobic region.

  Further, according to the present invention, a microorganism that can grow in an anaerobic atmosphere, a solution or suspension containing an organic substance, an anaerobic region including the bioelectric power generation anode of the present invention, molecular oxygen, and a cathode. Including an aerobic region, a diaphragm defining the anaerobic region and the aerobic region, and electrically connecting the anode and the cathode to a power utilization device to form a closed circuit, There is provided a power generation method for generating electric power by utilizing an oxidation reaction using an organic substance in the sex region as an electron donor and a reduction reaction using oxygen as an electron acceptor in the aerobic region.

Hereinafter, the present invention will be described in more detail.
The bioelectric power generation anode of the present invention comprises a conductive substrate having conductive fibers such as CNT or VGCF protruding from the surface, and an electron mediator fixed to the CNT or VGCF, and a standard electrode potential at pH 7 (E ₀ ′) is in the range of −0.13 V to −0.28 V, preferably in the range of −0.15 V to −0.27 V.

The details will be described below.
The conductive base material that can be used in the present invention is preferably an electrode base material that can be used in a bioelectric power generation apparatus and from which the conductive fiber can protrude from the surface, such as graphite, carbon black, fullerene, Solidified powder materials such as CNT and VGCF, metals such as aluminum, nickel, iron, copper, gold, platinum, stainless steel, nickel-copper alloys such as Monel (Special Metal, registered trademark), iron Preferred examples include alloys such as -silicon alloys, calcium-silicon alloys, aluminum-zinc-silicon alloys, and molybdenum-vanadium alloys. In particular, when a conductive base material containing a carbon six-membered ring such as graphite, carbon black, fullerene, CNT, or VGCF is used, it is strong between CNT or VGCF that is immobilized on the surface by CVD or electrophoresis. It is more preferable because a bond is easily formed. Among the above, carbon black, fullerene, CNT, and VGCF are usually supplied as powders. When used as an electrode base material, do they need to be compacted and then fired or impregnated with petroleum or coal pitch? Or adhesive molding such as polyamine (polyethyleneimine such as Epomin (registered trademark) made by Nippon Shokubai, polyallylamine) or polyamide (polyacrylic acid) diluted with a solvent such as methanol. Alternatively, it can be molded by a method such as impregnation with a Nafion (registered trademark) solution (5% Nafion 117 solution manufactured by DuPont) and consolidation at 170 ° C. while applying a pressure of about 50 kgf / cm ² .

  In addition, as the conductive base material, a base material made of the above-described material and further coated is preferably used. As the coating, electrolytically oxidized (porous) aluminum, porous nickel, porous polysilane film and the like are preferably used. In particular, electrolytic aluminum oxide and porous polysilane film have a pore size of several nanometers to several hundred nanometers, which is compatible with the size of CNT and VGCF, and the pores penetrate from the coated surface to the bottom conductive substrate surface. Therefore, a favorable anode can be formed with low electrical resistance between the CNT or VGCF and the conductive substrate.

  In addition, when a non-conductive substance such as polysilane is used as a coating material, a conductive powder such as carbon black is added to the coating material in advance, so that the porous film thus formed is conductive. And the electrical resistance between the conductive fiber and the conductive substrate can be reduced.

  Examples of the conductive fiber that can be used in the present invention include carbon nanotubes (CNT) and vapor-grown carbon fibers (VGCF) that have a low overvoltage for activating electron transfer with the electron mediator.

  The diameter of CNT or VGCF is preferably about several nanometers to 200 nanometers, and mainly has a single-layer or multilayer six-membered graphite sheet tube structure. Moreover, a cup stack type (for example, a carousel manufactured by Creos Corporation) is also preferable. In the case of single-walled carbon nanotubes, those having a winding angle (chirality) of a graphite sheet with low electrical resistance are more preferable.

  The conductive fiber fixed on the surface of the conductive substrate desirably protrudes at least from the surface of the conductive substrate or coating to a length of 10 nanometers or more, and preferably has a length of 100 nanometers or more. It is desirable that it protrudes.

As described above, the conductive fiber reaches the position protruding from the surface of the anode base material, and the electron mediator is immobilized thereon, thereby having the following favorable effects.
That is, the terminal reductase of a general microorganism is directed to the inside of the cell membrane, the redox substance upstream of the electron transfer system is also contained in the cell membrane, and is isolated from the electrode by the outer membrane. On the other hand, in microorganisms such as Geobacter and Shewanella that can perform final electron transfer (electrode active microorganisms), terminal reductase is located on the outer membrane, and it is thought that electrons are transferred from here to the electrode or electron mediator. . However, even if an electron mediator is immobilized on the electrode surface and the electron mediator has a three-dimensional structure that can be reduced by a terminal reductase, there is still a possibility that an obstacle still remains. All of the above-mentioned electrode active microorganism groups are gram-negative bacteria, but the surface of the outer membrane of the gram-negative bacteria has a lipopolysaccharide having a length of at least about 10 nm and a straight chain of six-membered ring carbons. It is forested, and the thickness of the outer membrane made of phospholipid itself is about 8 nm, and it has been observed that the membrane is considerably uneven. Terminal reductase is thought to exist on the membrane of this phospholipid, and if an electron mediator with a length of less than 1 nm is immobilized on a smooth electrode, the efficiency of physical contact with the terminal reductase is not high. Conceivable. However, if the electron mediator is chemically bonded to the surface of the protruding conductive fiber as described above, the immobilized electron mediator directly binds to the terminal reductase of the microorganism and receives electrons from the electron transfer system. Thus, the electron transmission speed, that is, the power generation speed can be improved.

The preferable occupation ratio of the conductive fibers on the surface of the conductive substrate greatly varies depending on the length of the conductive fibers to be immobilized and the density of the functional groups. As a standard, it is preferable that the amount is 0.1 μmol to 100 μmol / cm ² per projected area of the conductive substrate in terms of the molar amount of the electron mediator to be finally introduced.

  The electron mediator that can be used in the present invention has a standard electrode potential in the range of −0.13 V to −0.28 V, or a standard electrode potential as an anode within the above range after being fixed to the anode, Preferable examples include substances (oxidation-reduction substances) that are stable in the environment in any state of oxidation and reduction, and that can be easily reduced by the organism without inhibiting the respiration of the organism. Preferably, the electron mediator that can be used in the present invention is a redox substance selected from the group consisting of anthraquinone derivatives, naphthoquinone derivatives, benzoquinone derivatives, and isoalloxazine derivatives. Specifically, anthraquinone carboxylic acids (AQC), aminoanthraquinones (AAQ), diaminoanthraquinones (DAAQ), anthraquinone sulfonic acids (AQS), diaminoanthraquinone sulfonic acids (DAAQS), anthraquinone disulfonic acids (AQDS), diaminoanthraquinone Disulfonic acids (DAAQ DS), ethylanthraquinones (EAQ), methylnaphthoquinones (MNQ), methylaminonaphthoquinones (MANQ), bromomethylaminonaphthoquinones (BrMANQ), dimethylnaphthoquinones (DMNQ), dimethylaminonaphthoquinones ( One or more selected from the group consisting of DMANQ), rapacol (LpQ), hydroxy (methylbutenyl) aminonaphthoquinones (ALpQ), naphthoquinonesulfonic acids (NQS), trimethylbenzoquinones (TMABQ), flavin mononucleotides and derivatives thereof More specifically, anthraquinone-2-carboxylic acid (AQC), 1-aminoanthraquinone (AAQ), 1,5-diaminoanthraquinone (DAAQ), anthraquinone-2-sulfonic acid (AQS), 1,5-diaminoanthraquinone-2-sulfonic acid (DAAQS), anthraquinone disulfonic acid (AQDS), 1,5-diaminoanthraquinone disulfonic acid (DAAQ DS), 2-ethylanthraquinone (EAQ), 2-methyl -1,4-naphthoquinone (MNQ), 2-methyl-5-amino-1,4-naphthoquinone (MANQ), 2-bromo-3-methyl-5-amino-1,4-naphthoquinone (BrMANQ), 2, 3-dimethyl-1,4-naphthoquinone (DMNQ), 2,3-dimethyl-5-amino-1,4-naphthoquinone (DMANQ), rapacol (LpQ), 2-hydroxy-3- (3-methyl-2- Butenyl) -5-amino-1,4-naphthoquinone (ALpQ), 1,2-naphthoquinone-4-sulfonic acid (NQS), 2,3,5-trimethylbenzoquinone (TMAB) Q), a substance selected from the group consisting of flavin mononucleotide (FMN) and derivatives thereof can be preferably used. Structural formulas of substances that can be preferably used as an electron mediator in the present invention are shown below.

Next, the manufacturing method of the anode for bioelectric power generation of this invention is demonstrated.
The method for producing an anode for bioelectric power generation according to the present invention includes a pretreatment step of preparing a conductive substrate, and a conductive fiber fixing step of fixing the conductive fiber so that the conductive fiber protrudes from the conductive substrate. And an electron mediator introduction step of immobilizing and introducing the electron mediator to the conductive fiber.

Hereinafter, each step will be described.
<Pretreatment process>
It is preferable that the pretreatment step includes applying an oxidation potential to the aluminum layer present on at least the surface of the substrate to make the surface of the substrate porous (first pretreatment).

Moreover, it is preferable that a pre-processing process includes irradiating an ultraviolet-ray to the polysilane layer which exists in the surface of a base material, and making the base-material surface porous (2nd pre-processing).
By performing such a pretreatment, the porous coating portion forms a channel for holding the conductive fiber, so that there is an advantage that the conductive fiber is not easily dropped from the anode during use.

  In the first pretreatment, for example, an aluminum conductive substrate or a conductive substrate coated with aluminum is used as an anode, and oxidation is performed in a 0.3 mol / L oxalic acid solution at a voltage of 40 V for 1 hour or more. Thus, an irregular porous electrolytic aluminum oxide layer is obtained. Although this may be used as it is, it is more preferable to use one that has undergone the following processing. This aluminum oxide layer is once removed with phosphoric acid or the like, and again subjected to electrolytic oxidation for about 5 minutes in a 0.3 mol / L oxalic acid solution by applying a voltage of 40 to 80 V, so that 100 in a uniform hexagonal lattice arrangement is obtained. This can be done by forming holes with a pitch of ˜200 nm.

  In the second pretreatment, the surface of the conductive substrate is coated with an equal weight mixture of polymethylphenylsilane (molecular weight 130,000) and carbon black having a particle size of 10 nm diluted with toluene to a thickness of about 1 μm. A conductive polysilane gel coating is obtained. By irradiating this with ultraviolet rays and cutting the Si-Si bond, nano-sized holes can be formed as in the case of aluminum.

<Conductive fiber fixing process>
The conductive fiber fixing step can be performed by directly growing on the surface of the conductive substrate by a CVD method or by introducing a separately prepared material into the pores of the porous coating by an electrophoresis method.

As a method using the CVD (chemical vapor deposition) method, for example, iron nanoparticles (particle size 1 to 10 nm for CNT, 10 to 100 nm for VGCF) are attached to the surface of a graphite substrate as a metal catalyst, It can be used as a raw material after heating to remove organic substances to make Fe ₂ O ₃ (can also be purchased from Atomate, USA). Put this in the furnace of the CVD apparatus, and in a reaction time of 5-30 minutes by aerating a gas mixed with ethylene and hydrogen at a ratio of 1:20 together with argon or nitrogen while heating to 700 ° C. Carbon nanotubes (CNT) or vapor grown carbon fibers (VGCF) with a length of μm or longer can be grown. In addition to iron, cobalt or the like may be used as the metal catalyst, and cobalt and molybdenum acetate may be used. Further, acetylene, methane, or ethanol may be used instead of ethylene.

As a method using an electrophoresis method, a conductive substrate made porous by pretreatment is placed in an electrophoresis tank, and conductive fibers previously mixed in isopropanol and dispersed by ultrasonic waves are added. . In this state, the conductive base material is set as a negative pole, and a potential gradient of 2 × 10 ³ V / cm is applied to align the conductive fibers in the solvent and move toward the negative conductive base. Can be electrophoresed. Since the conductive fiber that has reached the surface of the conductive substrate is inserted into the pores of the porous coating and held there, it can be used as an anode. In this case, the electron mediator may be immobilized on the conductive fiber by the method described later after the above electrophoresis / immobilization, or the electrophoresis / immobilization may be performed using the conductive fiber having the electron mediator immobilized beforehand. good.

<Electronic mediator introduction process>
In the present invention, as a method for immobilizing the redox substance, which is an electron mediator, on a polymer, it is preferable to use a method that does not inhibit the redox activity of the electron mediator. Further, it is desirable that the electron mediator immobilized on the polymer is stable in an aqueous environment and has a property and form that does not easily decompose and peel. Specifically, the chemical bonding methods shown in Table 3 below are appropriate.

  Therefore, in the present invention, in order to immobilize the electron mediator on the conductive fiber, it is introduced into the conductive fiber to be used, or it is introduced into the functional group and the electron mediator that have been introduced in advance, or there is a functional that already exists. Depending on the combination with the group, an appropriate chemical modification and bonding method can be selected from the methods shown in Table-3.

  For example, when carbon nanotubes are used as the electrode material and AQC (anthraquinone-2-carboxylic acid) is used as the electron mediator, a bonding method using a carboxy group possessed by AQC can be preferably selected. Specifically, the carbon nanotubes are cleaved by oxidation in a 3: 1 mixture of 98% sulfuric acid / 70% nitric acid or by applying ultrasonic waves in 70% nitric acid to carboxylic acid at the ends, Reaction with thionyl and the like to produce acid chloride. Next, ammonia is reacted with the obtained acid chloride to produce a carboxylic acid amide. Further, the obtained carboxylic acid amide is rearranged to an amino group by a Hofmann rearrangement reaction. When carbon nanotubes thus treated are reacted with AQC in the presence of dicyclohexylcarbodiimide, an amide bond between the carboxy group of AQC and the amino group of graphite is formed, and AQC can be stably immobilized on graphite. .

  The amount of carboxy group introduced can be determined from the consumption of sodium bicarbonate, for example by titration. Carbon nanotubes introduced with carboxy groups in this manner are immersed in dichloromethane, and oxalyl chloride corresponding to about 100 times mole of the introduced carboxy groups and a few drops of dimethylformamide are added and stirred at room temperature for about 4 to 12 hours. The reaction can be carried out while converting the carboxy group into an acid chloride group. Thereafter, the carbon nanotubes are washed with dichloromethane and transferred into a tetrahydrofuran solvent. An amino group can be introduced by adding 1,3-propanediamine to the mixture so as to be about 100-fold mol in the same manner as described above and reacting with stirring at room temperature for about 4 to 12 hours.

Alternatively, it is possible to form an ether bond with an electron mediator having a bromomethyl group using the hydroxy group introduced by the above oxidation method.
Similarly, VGCF is used as the conductive fiber, and AQS, AQ-2,6-DS, AQ-2,7-DS, AQ-1,5-DS, methanyl yellow, methyl orange, etc. as the electron mediator When immobilizing a substance having a sulfonic acid group, an amino group is introduced into the VGCF by the above method, and then a sulfonamide bond is formed by reacting an electron mediator in the presence of dicyclohexylcarbodiimide to form an electron. Mediator can be immobilized on VGCF.

  Alternatively, when immobilizing a substance having a sulfonic acid group as described above, the sulfonic acid group is converted into a sulfonyl chloride group in advance, and then reacted with VGCF in which an amino group is introduced by the electrolytic oxidation method described above. To form a sulfonamide bond.

  Specifically, the sulfonic acid group is reacted with sulfonyl group in an acetonitrile solvent containing an amount of sulfolane equivalent to 1/2 mol and an amount of phosphorus oxychloride equivalent to 4 times mol for 1 hour at 70 ° C. with respect to the electron mediator. Convert to chloride group. This is filtered, washed with ice water, and then dried, whereby the sulfonic acid group of the electron mediator can be converted to a sulfonyl chloride group. This is brought into contact with VGCF into which the amino group has been introduced in a tetrahydrofuran solvent, and reacted for about 12 hours at room temperature while coexisting with an amount of triethylamine corresponding to 5 times the amount of the added sulfonyl chloride, thereby allowing VGCF and the electron mediator to react. And a sulfonamide bond can be formed between them.

  When CNT is used as the conductive fiber and LpQ is used as the electron mediator, the terminal carboxylic acid introduced into the CNT is reduced, a hydroxy group is introduced, and the 4-position carbon of LpQ is bromomethylated. Thereafter, it is more preferable to fix the CNT introduced with a hydroxy group by ether bonding.

  Alternatively, when CNT is used as the conductive fiber and FMN is used as the electron mediator, a hydroxy group is introduced into the CNT, and one of the two methyl groups of FMN is equimolar with N-bromosuccinimide. It can be immobilized with an ether bond by reacting with a brominated product using an alkali.

  The operation of introducing the electron mediator into the conductive fiber may be performed before or after the conductive fiber fixing step. The method of introducing an electron mediator into a conductive fiber before immobilization is often advantageous in terms of operability and yield of chemical reaction. On the other hand, the method of introducing the electron mediator after immobilization introduces the electron mediator only to the exposed surface after immobilization of the conductive fiber, which may be advantageous in terms of maintaining the anode conductivity high. Many. Therefore, when an anode is actually manufactured, both methods should be considered and a method capable of finally obtaining a large current density should be adopted.

  At this time, the electron mediator introduction process may be performed before or after the adhesion / immobilization process. However, when using an electron mediator with multiple amino groups such as 1,5-diaminoanthraquinone, the polymer must be immobilized on a conductive substrate and then contacted with the electron mediator. Since a cross-linking reaction occurs and the polymer is further polymerized and it becomes difficult to apply the polymer to the conductive substrate, it is preferable to perform the adhesion / fixation step first.

Furthermore, according to this invention, the bioelectric power generation apparatus using the above-mentioned bioelectric power generation anode is also provided.
The bioelectric power generation device of the present invention includes an anaerobic region including a microorganism that can grow in an anaerobic atmosphere, a solution or suspension containing an organic substance, and the above-described anode for bioelectric power generation, and molecular oxygen and a cathode. An anaerobic region, a diaphragm defining the anaerobic region and the aerobic region, and electrically connecting the anode and the cathode to a power utilization device to form a closed circuit, and the anaerobic region A bioelectric power generation apparatus that generates electricity using an oxidation reaction of a living body using an organic substance as an electron donor in the region and a reduction reaction using oxygen as an electron acceptor in the aerobic region.

  When the bioelectric power generation anode of the present invention is used in an apparatus for continuously treating a water-containing organic substance over a long period of time, anaerobic microorganisms continuously grow in the water-containing organic substance and on the surface of the anode. If an anode with a fine three-dimensional network structure, thin tube shape, or a laminated plate structure with narrow gaps is used, water-containing organic substances can be decomposed due to blockage of channels, uniflow, dead zone formation, etc. In addition, power generation efficiency may be reduced. For this reason, the form of the anode is a wire mesh, porous, or a primary structure with irregularities or wrinkles on the surface, and a three-dimensional mesh, tube or laminated plate-like space (water-containing organic material flows in). It is desirable that a secondary structure having a flow path) is formed, and that the flow path has an opening of several millimeters to several centimeters depending on the fluidity of the water-containing organic substance to be treated.

  In the present invention, a reduction reaction using oxygen as an electron acceptor proceeds on the cathode side which is an aerobic region. At least a part of the cathode is made of a conductive porous material, mesh or fiber material having a void in the structure, and a water / air contact interface, that is, air (oxygen) and water are adjacent to each other in the void. It is preferable to construct a field, and the efficiency of contact with oxygen in the air and water on the water surface can be increased, and the reduction reaction (electrode reaction) of oxygen in the air can be promoted. For example, by using a conductive porous material with fine pores bound with conductive particles (carbon, inert metal, metal oxide, etc.) with a resin binder as a cathode, capillarity and surface hydrophilization Thus, water can be effectively sucked up to form a water / air contact interface inside the micropores, and oxygen in the air and water can be efficiently contacted to promote the oxygen reduction reaction.

Furthermore, it is preferable to carry a catalyst made of an alloy or compound containing at least one selected from platinum group elements, silver, and transition metal elements on the cathode, and promote the reduction reaction (electrode reaction) of oxygen in the air. Can do. The platinum group element means platinum (Pt), ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), or iridium (Ir), and all are effective as an electrode catalyst. Also, nickel (Ni), bismuth (Bi), silver oxide doped titanium powder, furnace black or colloidal graphite supported silver, iron (Fe), cobalt (Co), phthalocyanine, Those using hemin, perovskite, Mn ₄ N, metalloporphyrin, MnO ₂ , vanadate, or Y ₂ O ₃ —ZrO ₂ composite oxide can also be preferably used as the electrode catalyst.

  In the present invention, the anode and the cathode are electrically connected to a power utilization device or the like, and exchange electrons between them to form a closed circuit. On the other hand, in order to take out the reducing ability of the organic substance as electric energy without waste, the organic substance does not contact the oxidizing agent (reduced substance), that is, oxygen in the air, so that the reducing ability is not consumed. It is preferable to isolate both the organic substance and oxygen in the air so that they do not come into contact with each other. In order to satisfy these conditions at the same time, it is desirable to separate the cathode and a solution or suspension containing microorganisms and organic substances that can grow in an anaerobic atmosphere with a diaphragm, such as a solid polymer diaphragm. By adopting such a structure, the cathode can easily come into contact with oxygen in the air, and can receive hydrogen ions or discharge hydroxide ions through the water present in the diaphragm. it can. Further, it is desirable that the diaphragm should not allow oxygen in the air to permeate as much as possible, and it is desirable to prevent the oxygen from penetrating the anode side, that is, the organic substance and reducing the reducing ability of the organic substance.

  Examples of such a diaphragm include a fluororesin ion exchange membrane (cation exchange membrane) having a sulfonic acid group having hydrophilicity and high cation exchange ability, and a hydroxide ion (anion) having a quaternary ammonium salt. An ion exchange membrane) is preferably used. Further, a fluororesin ion exchange membrane in which only the main chain portion is fluorinated or an aromatic hydrocarbon membrane can be used as a cheaper diaphragm. Examples of such ion exchange membranes include commercial products such as NEPTON CR61AZL-389 manufactured by IONICS, NEOSEPTA CM-1 or CMB manufactured by Tokuyama, Selemion CSV manufactured by Asahi Glass, NEPTON AR103PZL manufactured by IONICS, NEOSEPTA AHA manufactured by Tokuyama, and Selemion ASV manufactured by Asahi Glass. Can be preferably used. The cation exchange membrane can be used to supply hydrogen ions and water necessary for oxygen reduction at the cathode from the anode to the cathode, and the anion exchange membrane is a hydroxylation generated from the reaction between water and oxygen. It can be used to supply physical ions from the cathode to the anode.

  Moreover, an anion exchange membrane can also be used as a diaphragm used for isolating an anaerobic region and an aerobic region. Specifically, a hydroxide ion exchange membrane having an ammonium hydroxide group can be preferably exemplified. As such an anion exchange membrane, for example, commercially available products such as NEPTON AR103PZL-389 manufactured by IONICS, NEOSEPTA ALE manufactured by Tokuyama, and Shelemion ASV manufactured by Asahi Glass can be preferably used. In this case, when an anionic organic substance such as an organic acid present in the anaerobic region passes through the diaphragm and reaches the aerobic region (so-called cross flow phenomenon), oxygen is consumed there and the organic matter is Since it is oxidized wastefully and aerobic organisms grow in the aerobic region and contaminates the cathode, the anion exchange membrane used has a molecular sieving effect and permeates anions having a molecular weight of 60 or more such as acetic acid. It is desirable to have a property that is difficult to do. As an anion exchange membrane having such properties, there is, for example, Astom Neoceptor ALE04-4 A-0006 membrane.

  Furthermore, as a diaphragm that can be used in the present invention, MF (microfilter), UF (ultrafilter) film having no functional group, porous filter media such as ceramic and sintered glass, nylon, polyethylene, and woven fabric made of polypropylene are used. A cloth or the like can be used. These diaphragms having no functional group preferably have a pore diameter of 5 μm or less and do not allow gas permeation under non-pressurized conditions. For example, PE-10 membrane manufactured by Schweiz Seidengazefabrik, NY1-HD membrane manufactured by Flon Industry, etc. Commercial products can be preferably used.

  In the bioelectric power generation device of the present invention, in the anaerobic region, electrons derived from organic substances are finally delivered to the anode via the electron transfer system in the microorganism due to the respiratory reaction of the organism that can grow in an anaerobic atmosphere. The aerobic region is also an air reaction chamber for promoting a reduction reaction using oxygen as an electron acceptor. In the anaerobic region of this bioelectric power generation device, an anode to which an electron mediator having an appropriate potential for transferring electrons between the anaerobic microorganism and the anode is provided is provided. -An effective potential cascade is formed between the electron mediator and the anode. In addition, since the electron mediator is fixed to a conductive fiber such as CNT or VGCF on the anode, polarization during power generation can be suppressed lower than when the electron mediator is fixed to graphite or the like, The power that can be taken out can be increased.

  In addition, since the electron mediator is immobilized on fine protrusions made of conductive fibers, the outer membrane of the microorganism is compared with the case where the electron mediator is immobilized on a relatively smooth surface such as graphite. The contact efficiency with the terminal reductase existing above is improved, and the power generation amount can be increased.

In this bioelectric power generation apparatus, when the diaphragm for defining the anaerobic region (biological reaction chamber) and the aerobic region (air reaction chamber) is a cation exchange membrane, the reduction reaction using hydrogen ions at the cathode Depending on the ion concentration conditions, the overall reaction rate involved in the power generation of the present invention may be limited. That is, since the oxidation reaction at the anode is due to living organisms, extreme acidic conditions may be undesirable because they inhibit the activity of the organism. Further, when the hydrogen ion concentration is low, for example, hydrogen ions are generated on the anode side under the condition of pH 5 or higher, and the hydrogen ions permeate the cation exchange membrane by diffusion and are supplied to the cathode side. Become. At this time, the hydrogen ion concentration on the cathode side is estimated to be about 10 ^-5 mol / L or less. As described above, when the hydrogen ion concentration is low, the rate of the oxygen reduction reaction on the cathode side decreases, and it is also expected that the hydrogen ions on the anode side do not move efficiently to the cathode side. That is, in such a case, there is a possibility that the electric resistance (internal resistance) as the supporting electrolyte forming the battery is increased. On the other hand, the advantage of this reaction system is that water and hydrogen ions are always supplied from the anode side to the cathode side, so that water is sufficiently supplied to the cathode side, and oxygen on the cathode side passes through the membrane. The problem is that a so-called crossflow problem that permeates to the anode side and consumes the reducing ability on the anode side hardly occurs.

  When the cation exchange membrane is used as a diaphragm between the anaerobic region and the aerobic region, water is generated by consuming oxygen in the air in the reaction on the cathode side. For this reason, it is necessary to constantly ventilate and replenish oxygen and prevent the cathode from getting wet excessively except for moisture. However, since the water retention amount on the cathode side varies depending on the humidity and flow rate of the air supplied at this time, it is desirable to appropriately control the drying and humidification. As a method of ventilation by supplying and discharging air, a method of convection replacement naturally in an open system, a method of enclosing the cathode around an outer shell and providing an air chamber, forcibly ventilating with an air blower, Similarly, a method of providing an air chamber, warming the air chamber with heat generated by the oxidation-reduction reaction, generating convection to raise air and water vapor, and ventilating can be considered. It is preferable to adopt a ventilation method according to the conditions.

  On the other hand, when an anion exchange membrane is used as a diaphragm between the anaerobic region and the aerobic region, that is, when a reaction system that generates hydroxide ions from water and oxygen in the aerobic region is adopted, it is preferable. The amount of water retained in the aerobic region is much smaller than that in the anaerobic region. Therefore, if hydroxide ions equivalent to the amount of hydrogen ions generated at the anode are generated at the cathode, the pH on the cathode side, i.e. water The oxide ion concentration can be very high. Since the high concentration of hydroxide ions permeates the anion exchange membrane efficiently, the electric resistance (internal resistance) of the supporting electrolyte can be reduced. On the other hand, in this reaction system, the ion transfer from the cathode side to the anode side is always performed, so that it is difficult to supply water to the cathode side, and the oxygen on the cathode side passes through the membrane along with the ion transfer. There is a problem that the above-described cross flow problem may occur which permeates to the side and consumes the reducing ability on the anode side.

  Further, in the reaction on the cathode side, oxygen and water on the cathode surface are consumed, and hydroxide ions are generated. For this reason, it may be necessary to constantly ventilate and replenish oxygen and replenish moisture to prevent the cathode from drying. In particular, when the ventilation air is dry, when the water supply rate by permeation from the anode side is lower than the water consumption rate by the evaporation and reduction reaction at the cathode, the ventilation air is humidified or water vapor is added. Therefore, it is desirable to supply moisture to the cathode.

  As described above, cation exchange membranes and anion exchange membranes used as a diaphragm between anaerobic and aerobic regions have the effect of greatly changing the reaction system involved in the power generation reaction, and each has advantages and improvements. Therefore, it should be determined according to the structure and application of the device and the nature of the water-containing organic substance.

  Further, in order to increase the transfer efficiency of hydrogen ions or hydroxide ions, the distance between the cathode and the diaphragm is preferably as short as possible, and it is desirable that the two are joined if possible in terms of the device structure. In particular, when a part of the diaphragm enters and joins in the voids inside the porous structure of the cathode electrode, the water formed by the air contained in the porous structure and the water contained in the diaphragm Since the area of the air contact interface increases dramatically, the reaction efficiency for reducing oxygen in the air increases and the power generation performance can be improved.

  Similarly, in order to facilitate the movement of hydrogen ions or hydroxide ions and to reduce the electric resistance of the electrolyte system, it is desirable to shorten the distance between the anode and the diaphragm as much as possible. It is preferable to join. However, in this case, the anode is made of a water-permeable form, for example, a porous material or a net-like material so that the water-containing organic substance comes into contact with the diaphragm and the water therein is absorbed by the diaphragm. Or a form having a water passage hole, for example, a lattice shape or a comb shape. In addition, when it is difficult to arrange the anode and the diaphragm in contact with each other due to the structure of the apparatus, for example, a stirring or circulating water flow is generated to create a water flow that circulates between the anode and the diaphragm. Alternatively, it is desirable to facilitate the movement of hydroxide ions.

  Also, the anode can be impregnated by impregnating the anode with an ion exchange polymer, or by interweaving an anode substrate or conductive fiber and a cation exchange fiber (such as sulfonic acid graft fiber) or mixing as a nonwoven fabric. By collecting the hydrogen ions generated on the side and extending this ion exchange polymer or fiber in some way (for example, through an ion exchange fiber or resin pipe like a salt bridge) and bonding to the cathode, It is also preferable to form a hydrogen ion circuit between the anode and the cathode.

  Moreover, in the bioelectric power generation device of the present invention, it is preferable to increase the surface area of the anode so that electrons of the organic substance can be efficiently transferred to the anode. Further, it is preferable that the anode is in efficient contact with the organic substance, ion exchange is efficiently performed between the anode and the cathode, and at the same time, the anode and the cathode are electrically insulated. Therefore, the form of the reaction vessel defining the biological reaction chamber and the oxygen reaction chamber inside is, for example, a three-layer structure in which the anode is cylindrical, for example, a cylindrical shape, and an organic substance flows through the anode, and the anode and the cathode are sandwiched between them. A structure is preferable. In addition, it should be considered not to form a dead zone in which water-containing organic substances and grown organisms stay. As one method for this purpose, in order to increase the contact efficiency between the organic substance and the anode electrode, it is preferable to provide a stirring device or a circulating water flow generator inside the reaction vessel. Further, when the reaction vessel has an airtight structure, it is desirable to provide some kind of degassing mechanism in order to prevent anaerobic gas from accumulating in the vessel and reducing the effective volume. This anaerobic gas can also be used in a method of flushing the flow path. In addition, a supply mechanism and a discharge mechanism for a solution or suspension containing microorganisms and organic substances that can grow in an anaerobic atmosphere are provided in the anaerobic region, and an oxygen or air supply mechanism and a discharge mechanism are provided in the aerobic region. Is also preferable.

  The bioelectric power generation method of the present invention includes a microorganism that can grow in an anaerobic atmosphere, a solution or suspension containing an organic substance, an anaerobic region that includes the above-described anode for bioelectric power generation, molecular oxygen, and a cathode. An anaerobic region, a diaphragm defining the anaerobic region and the aerobic region, and electrically connecting the anode and the cathode to a power utilization device to form a closed circuit, and the anaerobic region This is a bioelectric power generation method for generating electricity using an oxidation reaction of a microorganism using an organic substance as an electron donor in the region and a reduction reaction using oxygen as an electron acceptor in the aerobic region.

In the present invention, the anode on which the electron mediator is immobilized is brought into contact with a solution or suspension containing a microorganism and an organic substance that can grow in an anaerobic atmosphere, and the microorganism uses the organic substance as an electron donor. The oxidation reaction proceeds. This reaction on the anode side and the oxidation reaction by microorganisms using organic substances as electron donors are biochemically catalyzed by anaerobic microorganisms (passive or absolute anaerobic microorganisms) in water-containing organic substances. Due to the anaerobic respiration of the microorganism, the electrons derived from the organic substance are finally delivered to the anode via the electron transfer system in the microorganism. Therefore, in order to make the power generation reaction according to the present invention proceed efficiently, the electron transfer system is not terminated in the cell membrane of the microorganism, but the electron is easily captured by the anode at the extracellular membrane (outside the cell membrane). It is desirable to use microorganisms (“electrode active microorganisms”) that catalyze the electron transfer. As such microorganisms that catalyze the electron transfer to the anode, sulfur S (0) reducing bacteria, iron (III) oxide reducing bacteria, manganese dioxide MnO ₂ reducing bacteria, dechlorinating bacteria, and the like are preferably used. Such microorganisms include, for example, Desulfuromonas sp., Desulfitobacterium sp., Geobivrio thiophilus sp., Clostridium thiosulfatireducens sp., Acidithiobacillus sp., Thermoterrabacterium ferrireducens sp., Geothrix sp., Geobacter sp., Geoglobus sp., Shewanella putrefaciens. Etc. are particularly preferably used. In particular, sulfur-reducing bacteria have a very low standard electrode potential of sulfur as the final electron acceptor of -0.28 V, so that electrons can be transferred to an electron mediator having a lower potential than iron (III) oxide-reducing bacteria. It is energetically advantageous. As such microorganisms having sulfur reduction activity, for example, Desulfuromonas sp., Desulfitobacterium sp., Geobivrio thiophilus sp., Clostridium thiosulfatireducens sp., Acidithiobacillus sp.

  Since these microorganisms are often not major microorganisms in the water-containing organic material, in carrying out the method of the present invention, these microorganisms are first inoculated on the anode side, and these microorganisms on the anode surface. It is preferable to form a state in which microorganisms are mainly attached. In order for these microorganisms to preferentially grow in the biological reaction chamber, the area of the area where the respiration reaction (electrode respiration) by passing electrons to the anode is more advantageous in energy than acid fermentation or methane fermentation should be increased. Specifically, it is preferable to increase the anode surface area in the anaerobic region (microbe reaction chamber) as much as possible. In addition, after attaching organisms to the anode surface, it is desirable to supply an appropriate medium for the growth of these microorganisms in the anaerobic region (microbe reaction chamber), and further maintaining the anode potential to some extent, It is more desirable to promote the growth of these microorganisms on the anode surface. As a method for culturing these microorganisms (groups) in a pre-culture or in a biological reaction chamber, slurry-like sulfur, iron (III) oxide, manganese dioxide, etc. reported as a medium for these microorganisms (groups) are electronically A medium used as a receptor can be preferably used, for example, the Ancylobacter / Spirosoma medium, Desulfuromonas medium, Fe (III) Lactate Nutrient medium, etc. described in the Handbook of Microbial Media (Atlas et al. 1997, CRC Press) are preferably used. .

  The nature of the organic substance used in the present invention is liquid or suspension, or the solid content is saturated with water so as not to supply molecular oxygen around the anode where microorganisms that can grow in an anaerobic atmosphere grow. It is desirable that Since the oxidation reaction of the organic substance around the anode is mainly catalyzed by a respiratory reaction by microorganisms, the organic substance put into the anode periphery has a small solid particle size and dissolves or disperses well in water. It is desirable to be a low molecular weight substance, and it is desirable to be a substance that is easily degradable to microorganisms. If these conditions are not met by the type of organic material used, physical, chemical or biological pretreatment can be performed to increase the biodegradability of the organic material. Examples of such methods include crushing with a pulverizer, thermal decomposition, ultrasonic treatment, ozone treatment, hypochlorite treatment, hydrogen peroxide treatment, sulfuric acid treatment, biological hydrolysis, acid generation, and low molecular weight. Processing can be considered. The energy required for these pretreatments can be selected in consideration of the balance with the improvement of power generation energy in the main reaction vessel by the pretreatment.

  Further, it is desirable to remove excess microbial cells and extracellular secretions by rinsing the flow passage with water or air over time according to the intended use. At this time, if oxygen is contained in the gas used for air washing, there is a possibility of adversely affecting the anaerobic microorganisms in the reaction vessel which is an anaerobic region (microbe reaction chamber). It is desirable to use the anaerobic gas generated in

Preferred embodiment

  Hereinafter, the power generator according to the present invention will be described more specifically with reference to the accompanying drawings. The following description is to explain some specific embodiments that embody the technical idea of the present invention, and the present invention is not limited to this description.

  FIG. 1 is a specific example of a bioelectric power generation unit according to one embodiment of the present invention. For example, a specific example of the bioelectric power generation device of the present invention shown in FIG. 1 includes an anaerobic region 4 including an anode 1 in which an electron mediator is fixed to a conductive fiber protruding from the electrode substrate surface, a diaphragm (electrolyte membrane) 2) and the aerobic region 5 including the porous cathode 3 is formed by forming a triple cylindrical body. A solution or suspension containing microorganisms and organic substances (also referred to as “substrate”) that can grow under anaerobic conditions is poured into the anaerobic region 4 that is the innermost space form of the cylindrical body. Air containing molecular oxygen is present in the aerobic region 5 which is the outermost space form. The aerobic region 5 is provided with means (not shown) for supplying molecular oxygen. As for the porous cathode arrange | positioned in the aerobic region 5, at least one part of the cathode is formed of the electroconductive porous material which has a space | gap in a structure, a net-like, or fibrous material. The diaphragm 2 that separates the anaerobic region 4 and the aerobic region 5 has a large mass exchange coefficient, for example, a solid polymer electrolyte membrane such as Nafion (registered trademark) manufactured by DuPont, Neoceptor (registered trademark) manufactured by Astom. It consists of

  In the anaerobic region 4, an oxidation reaction of a microorganism using an organic substance as an electron donor proceeds, and in the aerobic region 5, a reduction reaction using oxygen as an electron acceptor proceeds. Thus, a potential difference is generated between the anode 1 and the cathode 3. In this state, the potential difference current flows by electrically connecting the anode 1 and the cathode 3 to the power utilization device by the conductive wire 6, while the ion flows between the anaerobic region 4 and the aerobic region 5 through the electrolyte membrane 2. Moves to form a closed circuit. As the reaction proceeds, hydrogen ions are generated in the anaerobic region 4, and the aqueous solution in the anaerobic region exhibits acidity. On the other hand, hydroxide ions are generated in the aerobic region 5 and the water generated in the aerobic region 5 becomes an alkaline solution.

  You may provide the flow path (not shown) which collect | recovers the alkaline aqueous solutions which generate | occur | produce in the aerobic region 5 suitably, and inject | pours into the anaerobic region 4. FIG. By circulating the alkaline aqueous solution from the aerobic region 5 to the anaerobic region 4 through this flow path, the hydrogen ion concentration in the anaerobic region 4 is extremely increased to inhibit the respiratory activity of the organism, or the introduced basic functional group. It is possible to prevent the neutralization ability of the group from being exceeded.

  The inner diameter of the cylindrical body constituting the power generation unit can be set to several mm to several cm, and in some cases several tens of cm depending on the fluidity of the substrate. The power generation unit as shown in FIG. 1 can be increased in physical strength by being held by a support layer or casing of an appropriate material. In this case, the cylindrical body may be further encapsulated with an outer shell, and a space between the outer shell and the cylindrical body may be used as an air chamber, and means for supplying and discharging air to the air chamber may be formed.

  In the illustrated embodiment, a three-layer structure in which the anode 1, the diaphragm 2 and the cathode 3 are cylindrical is adopted, and the anode 1 and the cathode 3 are arranged via the diaphragm 2. By adopting such a configuration, the surface areas of the anode 1 and the cathode 3 can be increased, and the anode 1 can efficiently contact the substrate and the dead zone where the substrate does not move can be made as small as possible. The anode 1 and the cathode 3 are electrically insulated from each other at the same time, and the electrons of the organic substance (substrate) are efficiently transferred to the anode 1. Further, by contacting with air in a state where a contact interface between air and water is present in the gap of the porous cathode 3, the efficiency of contacting oxygen in the air and water on the water surface can be increased. The oxygen reduction reaction in can be efficiently advanced.

  In the bioelectric power generation device according to the present invention having a three-layered cylindrical body as shown in FIG. 1, an anaerobic region including an anode is disposed on the outside and an aerobic region including a cathode is disposed on the inside depending on the application, and the aerobic region is disposed. A power generation operation can also be performed by arranging means for circulating air in the area and installing the apparatus in the substrate solution. In this case, the cylindrical body may be formed in, for example, a U-shape, and both ends may be protruded from the surface of the substrate solution so that air can flow through the space inside the cylinder. When the aerobic region is configured as an inner cylinder in this way, there is an advantage that no blockage is caused even if the inner diameter of the inner tube of the aerobic region is reduced to about several millimeters or less. Further, in a three-layered cylindrical body, when the inner cylindrical body is an aerobic region including a porous cathode and the outer cylindrical body is an anaerobic region including an anode, the surface area of the outer anode is larger than that of the cathode. This is advantageous because it can be enlarged. Furthermore, in order to increase the surface area of the anode, it is possible to have irregularities and wrinkles on the surface of the anode. On the other hand, the inner diameter on the cathode side is related to the reaction efficiency, but it is sufficient if there is a diameter that allows air to flow easily and there is almost no risk of clogging, so the inner diameter should be reduced to a few millimeters or less. Is possible. In this case, the cylindrical body is further encapsulated with an outer shell, the outer space of the cylindrical body is used as a microbial reaction chamber in which the substrate flows, and the apparatus is configured by arranging means for supplying and discharging the substrate in the biological reaction chamber. be able to.

  Moreover, a bioelectric power generation apparatus can also be configured by arranging a plurality of cylindrical or other forms of biopower generation units as shown in FIG. For example, FIG. 2 shows a form in which a plurality of bioelectric power generation units of FIG. 1 are arranged, and FIG. 4 shows a form in which three plate-like bioelectric power generation units are arranged.

  In the bioelectric power generation apparatus shown in FIG. 2, a plurality of three-layered cylindrical bodies (power generation units) 50 constituted by an anode inner cylinder 1, a diaphragm 2 and a cathode outer cylinder 3 as shown in FIG. Is arranged in the air chamber 7 formed by The substrate is distributed and injected into the inside 4 of the power generation units 50 arranged by the inflow pump 8 through the inflow portion 9. Here, the substrate that has undergone oxidative decomposition exits from the reaction vessel via the outflow part 10 and is then discharged out of the system as the treated substrate 11. A part of the substrate is returned to the inflow portion 9 by the circulation pump 12 again. This circulating flow promotes contact between the anode 1 and the substrate. Biological cells and sludge accumulated in the reaction vessel are discharged by opening the excess sludge discharge port 13 over time. Similarly, from 13, the inside of the reaction vessel can be back-washed or air-washed by injecting water, inert gas, or anaerobic gas. When anaerobic gas is generated in the reaction vessel, it can be discharged from the exhaust port 19. As described above, the anaerobic gas may be stored and used for air washing.

  On the other hand, since oxygen is supplied to the porous cathode 3, the air chamber 7 can be ventilated using the blower 14. However, when forced ventilation is not required according to the application, the apparatus may be configured such that the air chamber 7 is removed and the cathode 3 that is the outer cylinder of each power generation unit 50 is exposed to the outside air. The ventilated air flows through the space 5 between the power generation units in the air chamber 7 and is discharged from the exhaust port 15 after contacting the cathode 3. Moreover, the water produced | generated by the reductive reaction in a cathode is discharged | emitted from the exhaust port 15 as water vapor | steam, or is discharged | emitted from the condensed water drain 16 as condensed water.

  The conducting wire 6 is electrically connected to the inner cylinder 1 of the plurality of power generation units 50 through the connection portion 17 with the anode and to the outer cylinder 3 of the plurality of power generation units 50 through the connection portion 18 with the cathode. At this time, it is necessary that the conductive wire 6 is electrically insulated from the surrounding environment so that an electrical short circuit and a redox reaction on the surface of the conductive wire do not occur.

  2, the cylindrical body 50 of each power generation unit is configured with the cathode as the inner cylinder and the anode as the outer cylinder in the same manner as described above with reference to FIG. It is also possible to supply air to the space so that the substrate contacts the anode outside the cylindrical body of the power generation unit 50.

  As for the cathode, the problem is how to efficiently carry out the oxygen reduction reaction on the electrode. For this purpose, at least a part of the cathode is formed of a conductive porous material, net-like or fibrous material having a void in the structure, and a contact interface between air and water exists in the void of the cathode. It is preferable to increase the efficiency of contact with oxygen in the air and water on the water surface by contacting with air in the state of being allowed to enter.

  FIG. 3 is a sectional view showing an example of a cathode structure that can be employed in the bioelectric power generation apparatus of the present invention. FIG. 3A shows a cross section of the structure of the diaphragm 2 and the cathode 3, and FIG. 3B is a view of FIG. 3A as viewed from the air chamber side 5. Moreover, in FIG. 3, the reaction system in case the diaphragm 2 is a cation exchange membrane is shown. The cathode shown in FIG. 3 has a structure in which a porous matrix 20 supports a catalyst 21 made of an alloy or a compound containing at least one selected from a platinum group element, silver, and a transition metal element (see FIG. 3). 3 (A), it has a network structure when viewed from the air chamber side 5 (FIG. 3 (B). By adopting such a configuration, the cathode is based on water passing through the water surface or the diaphragm. Can be brought into contact with oxygen in the air while being sucked up by the hydrophilic property of the electrode, and by having the air network 22 and the aqueous solution network 23 in the micro structure of the electrode, the area of the air / water contact interface is increased, and the oxygen in the air In addition, the efficiency of contact with water on the water surface can be increased, and the reduction reaction of oxygen in the air can be promoted by the reaction between oxygen and hydrogen ions on the catalyst 21.

  FIG. 3C shows another example of a cathode structure that can be employed in the bioelectric power generation device of the present invention. FIG. 3C also shows a reaction system when the diaphragm 2 is a cation exchange membrane. In the cathode shown in FIG. 3 (C), a part of the diaphragm structure is made porous by applying a solution made of the same material as that of the diaphragm 2 to the bonding surface side of the porous matrix 20 with the diaphragm 2 and drying it. Intruded into the fine pores of the quality matrix 20. By taking such a structure, the utilization rate of ion exchange and a catalyst can be improved, and the reduction reaction of oxygen in the air can be promoted.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, these do not limit this invention at all.
In the following Examples and Comparative Examples, the power generation performance was compared using the laboratory bioelectric power generation apparatus shown in FIG. 4 except that the anode was changed.

  As shown in FIG. 4, the bioelectric power generation apparatus has two cell frames (25, 26) each having a side length of 100 mm and a thickness of 10 mm, and two separators 24 of the same size on both sides of the cell frame. A laminated structure having the separators 24 on both sides was laminated. Inside this laminated structure, an anode 1, a cation exchange membrane (Nafion manufactured by DuPont) as a diaphragm 2, and carbon paper carrying platinum as a cathode 3 are arranged in contact in this order, and the anode 1 and the diaphragm 2 are used using a Nafion solution. The anaerobic region 31 was formed between one frame 24 and the anode 1, and the aerobic region 32 was formed between the other frame 24 and the cathode 3. Three units of this stacked structure were stacked alternately, and the frame 24 between adjacent units was shared to configure an experimental power generator. Substrate solution channels 27-28 were formed in anaerobic regions 31, 31 ', 31 "between three units, and air channels 29-30 were formed in aerobic regions 32, 32', 32". Moreover, although not shown in figure, each anode 1 and each cathode 3 were electrically connected in series with the conducting wire, and the closed circuit was formed through the ammeter and the variable resistor (electric power utilization apparatus). The external resistance of the circuit including the ammeter was 10Ω or less when the variable resistor was 0Ω.

[Example 1, Comparative Example 1]
Comparison of power generation performance when AQDS is immobilized after CNTs are generated by CVD on carbon and when AQDS is immobilized directly on carbon

  After forming CNTs on a conductive substrate (porous carbon) using the CVD method, an anthraquinone-2,6-disulfonic acid (AQ-2,6-DS) is immobilized on the surface as an electron mediator to produce an anode did.

Conductive fiber (CNT) is formed on the carbon paper (EC-20-10-7 manufactured by Electrochem), which is a conductive substrate, using the CVD method described below, and then AQDS, which is an electron mediator, is mixed with diamine. Via immobilization via a sulfonamide bond. At this time, AQDS was immobilized on the conductive fiber at a density of 10 μmol / cm ² per projected area of the conductive substrate. Formation of CNTs on the carbon paper surface by the CVD method and immobilization of the electron mediator AQDS on the CNT surface were performed as follows.

A mixed solution in which cobalt acetate and molybdenum acetate were dissolved in ethanol at a concentration of 1 mmol / L was applied to the surface of carbon paper. After drying, the mixture was heated at 600 ° C. for 1 hour to form metal fine particles and remove organic substances. This was placed in an Atomate Advanced LP CVD system furnace, and heated to 700 ° C. with 100 sccm of ethylene (gas volume cm ³ / min in the standard state) and aerated helium at a rate of 200 sccm. By reacting for 20 minutes, multi-walled carbon nanotubes (MWCNT) were produced.

  This was oxidized in a 3: 1 mixture of 98 wt% sulfuric acid / 70 wt% nitric acid to introduce a carboxy group mainly at the tip of MWCNT. By immersing this in dichloromethane, adding oxalyl chloride corresponding to about 100 times mole of the introduced carboxy group and a few drops of dimethylformamide and reacting at room temperature with stirring for about 4 to 12 hours, the above carboxy group Was converted to an acid chloride group. This was washed with dichloromethane and transferred into a tetrahydrofuran solvent. 1,3-propanediamine was added to the mixture so as to be about 100 times mol as described above, and the amino group was introduced by reacting at room temperature with stirring for about 4 to 12 hours.

  On the other hand, the following operation was performed to make the sulfonic acid group of AQDS an acid chloride group. AQDS is allowed to react at 70 ° C. for 1 hour in an acetonitrile solvent containing an amount of sulfolane equivalent to 1/2 mole of AQDS and an amount of phosphorus oxychloride equivalent to 4 times mole to sulfonyl chloride group of AQDS. It was. This was filtered, washed with ice water, and dried to purify AQDS in which sulfonic acid groups were converted to sulfonyl chloride groups. This is brought into contact with the above-described conductive fiber introduced with an amino group in a tetrahydrofuran solvent, and reacted with MWCNT for 12 hours at room temperature in the presence of triethylamine in an amount corresponding to 5 moles to the added sulfonyl chloride. A sulfonamide bond was formed with the electron mediator.

Using this anode, the discharge was performed by shifting the applied potential from -0.28 V to -0.18 V (hydrogen standard electrode potential) in an aqueous solution of pH 7, so that the standard electrode potential E ₀ ′ of the anode was − It is considered to be between 0.28V and -0.18V.

Comparative Example 1

By directly immobilizing AQDS in accordance with the method of Example 1 without using conductive fibers on carbon paper (Electrochem EC-20-10-7, porous graphite) as a conductive substrate, a control anode ( 1) was formed. At this time, AQDS was immobilized on the conductive substrate at a density of 10 μmol / cm ² per projected area of the conductive substrate. Since this discharge was performed by shifting the applied potential from -0.28 V to -0.13 V (hydrogen standard electrode potential) in an aqueous solution of pH 7 using this control anode (1), the standard of the control anode (1) The electrode potential E ₀ ′ is considered to be between −0.28V and −0.13V.

<Power generation performance>
Using the laboratory bioelectric power generation apparatus shown in FIG. 4, the power generation performance of the bioelectric power generation anodes manufactured in Example 1 and Comparative Example 1 was compared.

  Before the start of operation, 1 mL each of the sulfur-reducing bacteria accumulation culture was added to the anaerobic regions 31, 31 ′, 31 ″ of the bioelectric power generation apparatus. The sulfur-reducing bacteria accumulation culture used was produced by the following method. 100 g of Desulfuromonas medium (Table-4) described in the Handbook of Microbial Media (Atlas et al. 1997, CRC Press) is injected into a 130 mL vial bottle using 0.1 g of soil as the seeding source, and the gas phase is nitrogen gas Add to the replacement, seal, culture with shaking at a temperature of 28 ° C, and repeat the operation 5 times after 5 weeks with 5 mL of the bacterial solution in a freshly prepared vial. The soil that was the seeding source is not particularly limited to Kuroboku soil, and may be loam soil or silt.

As a substrate solution, a substrate solution prepared by mixing 0.01 g / L yeast extract in a 0.1 mol / L aqueous glucose solution as a model of a water-containing organic substance was used.
For 10 days from the start of operation, no liquid is passed to wait for organisms to adhere to the anaerobic zone (biological reaction chamber), and the Desulfuromonas medium described in the Handbook of Microbial Media (Atlas et al. 1997, CRC Press) (Table 4) was filled into the anaerobic zone (biological reaction chamber) to promote the predominance of sulfur-reducing bacteria.

  From the 10th day after the start of operation, the acclimatization operation is performed with the residence time of the substrate solution being 2 days, and from the 20th day after the operation is started, the residence time in the anaerobic region is set to 500 minutes and the normal operation is performed between the anode and the cathode. The current amount and voltage were measured. The supply of air to the aerobic region was performed with a residence time of 0.5 minutes.

  In Example 1 and Comparative Example 1, the variable resistor was adjusted so that the cathode and anode were always electrically connected, including during the acclimatization period, and the maximum amount of power was obtained. The test results are shown in Table-5.

  It can be seen that the average generated current during the measurement period generated 2.3 times higher current amount in Example 1 than in Comparative Example 1. In addition, the average voltage was 1.5 times higher in Example 1 than in Control 1. Therefore, the electric power obtained was 3.45 times greater in Example 1 than in Comparative Example 1.

  From this result, it was confirmed that the anode in which AQDS was immobilized through conductive fibers (CNT) was superior in power generation performance to the anode in which AQDS was directly immobilized.

[Example 2, Comparative Example 2]
When VGCF is formed on electrolytic aluminum oxide by CVD and AQC is then immobilized (Example 2), and when carbon black powder with AQC previously immobilized on electrolytic aluminum oxide is applied (Comparative Example 2) Comparison of power generation performance

  In Example 2, the anode 1 equipped in the bioelectric power generation apparatus was prepared by electrolytic oxidation of a conductive substrate (aluminum), formation of VGCF by CVD, and fixation of an electron mediator anthraquinone-2-carboxylic acid (AQC) by the methods described below. It was made by making. The configuration of the power generation unit and the experimental conditions other than the anode were the same as in Example 1.

Using an aluminum plate with a purity of 99.999% (AL-32-83-0300 manufactured by Rare Metallic) as the conductive base material for the anode 1 and applying a voltage of 40V in 0.3 mol / L oxalic acid solution at 15 ° C A porous electrolytic aluminum oxide layer was obtained by oxidizing for 1 hour. Once this aluminum oxide layer is removed with 1 mol / L phosphoric acid, it is electrolytically oxidized for about 5 minutes in a 0.3 mol / L oxalic acid solution by applying a voltage of 80 V to obtain a uniform hexagonal lattice array. Holes with a pitch of 200 nm were formed. This was immersed in an aqueous 10 μmol / L cobalt acetate solution, and cobalt was deposited inside the aluminum oxide pores by applying a potential gradient of 10 ³ V / cm with the aluminum plate as the negative electrode. In the same manner as in Example 1, this was put into a furnace of an Advanced LP CVD system manufactured by Atomate, and carbon monoxide gas was vented at a rate of 100 sccm while heating at 600 ° C. to reduce cobalt. Thereafter, the temperature was raised to 650 ° C., and the aeration gas was changed to a 1: 9 mixed gas of acetylene / nitrogen and reacted at the same aeration rate for 30 hours to form VGCF having an average diameter of 100 nm.

  The electrode was used as an anode and oxidized in a 70 wt% sulfuric acid solution while applying a potential of +1 V to the hydrogen standard electrode, and a carboxy group was introduced into the VGCF. This was immersed in dichloromethane, and oxalyl chloride corresponding to about 100 times mole of the introduced carboxy group and a few drops of dimethylformamide were added and reacted at room temperature with stirring for about 4 to 12 hours. Was converted to an acid chloride group. This is washed with dichloromethane and transferred into tetrahydrofuran solvent. 1,3-propanediamine was added to the mixture so that it was about 100 times in the same manner as above, and the amino group was introduced by reacting at room temperature with stirring for about 4 to 12 hours.

This was immersed in a 1 g / L dicyclohexylcarbodiimide solution, reacted for 1 hour, then AQC was added to 1 mol / L, and AQC was immobilized by an amide bond.
The standard electrode potential E ₀ ′ of the anode was in the range of −0.21V to −0.16V. The immobilization density of AQC was about 1 μmol / cm ² per projected area of the conductive substrate.

Comparative Example 2

  The control anode (2) used in Comparative Example 2 was obtained by applying carbon black with AQC directly immobilized on the aluminum plate electrolytically oxidized by the method of Example 2. Carbon black was Toka black # 5500 made by Tokai Carbon, suspended in 0.125 mol / L sulfanilic acid aqueous solution to 100 g / L, heated to 70 ° C., stirred for 3 hours, and then cooled to room temperature. Next, nitric acid and sodium nitrite were respectively added to 0.15 mol / L and allowed to react for about 3 hours at a temperature of about 30 ° C. until foaming stopped. This was washed with ethanol to obtain carbon black into which a sulfonic acid group was introduced. Next, this was reacted at 70 ° C. for 1 hour in an acetonitrile solvent containing an amount of sulfolane equivalent to an equimolar amount of sulfonic acid group and an amount of phosphorus oxychloride equivalent to an 8-fold molar amount, and the sulfonic acid group was converted into a sulfonyl chloride group. Converted to. This was filtered, washed with ice water, and dried to purify carbon black in which sulfonic acid groups were converted to sulfonyl chloride groups. This is washed with dichloromethane and transferred into tetrahydrofuran solvent. 1,3-propanediamine was added thereto so as to be about 100 times mol, and the amino group was introduced by reacting with stirring at room temperature for about 4 to 12 hours. This amino group-introduced carbon black was immersed in a 1 g / L dicyclohexylcarbodiimide solution, reacted for 1 hour, then added with AQC to 1 mol / L, and AQC was immobilized by amide bond.

The control black (2) of Comparative Example 2 was prepared by suspending carbon black on which AQC was immobilized by the above operation in a 5% ethanol solution of Epomin (registered trademark) manufactured by Nippon Shokubai, applying to the electrolytic aluminum oxide plate and drying. ). In Comparative Example 2, the electrode coating density by AQC after coating and curing was about 10 μmol / cm ² per projected area of the conductive substrate. The standard electrode potential E ₀ ′ of the control anode (2) was in the range of −0.23V to −0.18V.

<Power generation performance>
Table 6 shows the results of the power generation test performed on the biopower generation device shown in FIG. 4 using the anodes obtained in Example 2 and Comparative Example 2.

  The amount of generated current was 26 times higher in Example 2 than in Comparative Example 2. The generated voltage in Example 2 was 1.53 times higher than that in Comparative Example 2. The reason why the amount of current in Comparative Example 2 was small was that the surface of the conductive substrate was oxidized and the electrical resistance was high, so that only a part of the AQC that entered the hole worked effectively as an electron mediator. It is thought that it was because of. From this result, the anode in which AQC is immobilized on the conductive substrate of aluminum via the conductive fiber (VGCF) is superior in power generation performance than the anode in which AQC is immobilized on carbon black. It was recognized that

  The generated current obtained in Example 2 was 1/2 or less that obtained in Example 1. This is probably because the immobilization density of the electron mediator was low. However, since the conductive fiber (VGCF) produced by the CVD method in Example 2 is held by porous aluminum, it is expected to have excellent durability when used for a long time.

[Example 3, Comparative Example 3]
When a graphite plate is coated with polysilane, made porous with ultraviolet light, immersed in a liquid in which CNTs are dispersed, CNTs are inserted into the polysilane pores by electrophoresis, and AQDS is immobilized (Example 3) Comparison of power generation performance with AQDS fixed directly on graphite plate (Comparative Example 3)

  A porous graphite plate (Tokai Carbon G-50) is used as the conductive substrate, and polysilane (polymethylphenylsilane, molecular weight 130,000) and carbon black (Toka Black # 5500) are each 0.5% in concentration. It was immersed in what was dissolved in. This was taken out and dried to obtain a polysilane-coated conductive substrate.

This was placed under a mercury lamp and irradiated with ultraviolet rays for 10 minutes to obtain porous conductive polysilane. The conductive substrate prepared in this way is placed in an electrophoresis tank filled with isopropanol, and CNT (multilayer of carbon nanotubes manufactured by Wako Pure Chemicals, 20-30 nm) is added so as to be 0.5 g / L. CNT was dispersed by applying sound waves. Thereafter, CNT in the solvent was inserted into the polysilane coating by applying a potential gradient of 2 × 10 ³ V / cm with the conductive substrate as a negative electrode.

  The electrode thus obtained was used as an anode and oxidized in a 70% sulfuric acid solution while applying a potential of +1 V to the hydrogen standard electrode to introduce a carboxy group into the CNT. This was immersed in dichloromethane, and oxalyl chloride corresponding to about 100 times mole of the introduced carboxy group and a few drops of dimethylformamide were added and reacted at room temperature with stirring for about 4 to 12 hours. Was converted to an acid chloride group. This is washed with dichloromethane and transferred into tetrahydrofuran solvent. 1,3-propanediamine was added to the mixture so as to be about 100 times mol as described above, and the amino group was introduced by reacting at room temperature with stirring for about 4 to 12 hours.

  On the other hand, prepared by converting the sulfonic acid group of AQDS into an acid chloride group in the same manner as in Example 1, which was brought into contact with the CNT having the amino group introduced thereinto in a tetrahydrofuran solvent, with respect to the added sulfonyl chloride A sulfonamide bond was formed between graphite and the electron mediator by reacting at room temperature for about 12 hours in the presence of an amount of triethylamine corresponding to 5 moles.

Using this anode, the discharge was performed by shifting the applied potential from -0.28 V to -0.18 V (hydrogen standard electrode potential) in an aqueous solution of pH 7, so that the standard electrode potential E ₀ ′ of the anode was −0.28. It is considered to be between V and -0.18V. The immobilization density of AQDS was about 4 μmol / cm ² per projected area of the conductive substrate.

Comparative Example 3

  In Comparative Example 3, the control anode equipped in the bioelectric power generation apparatus was oxidized in a 70% sulfuric acid solution while directly applying a potential of +1 V to the same porous graphite used in Example 3 to introduce a carboxy group. Thereafter, an amino group was introduced in the same manner as in Example 3, and a control anode (3) was produced by forming a sulfonamide bond with AQDS in which a sulfonic acid group was converted to a sulfonic acid chloride group in advance.

The standard electrode potential E ₀ ′ of the control anode (3) was in the range of −0.21V to −0.16V. The immobilization density of AQDS was about 5 μmol / cm ² per projected area of the conductive substrate.

<Power generation performance>
Table 7 shows the results of a power generation test performed on the biopower generation device shown in FIG. 4 using the anodes obtained in Example 3 and Comparative Example 3.

  The average generated current during the measurement period was 1.85 times higher in Example 3 than in Comparative Example 3. The average generated voltage of Example 3 was 1.5 times higher than that of Comparative Example 3. From this result, the anode in which AQC is immobilized on the graphite conductive substrate via the conductive fiber (VGCF) is superior in power generation performance than the anode in which AQC is immobilized on carbon black. It was recognized that

  The generated current obtained in Example 3 was a little lower value, about 76% of that obtained in Example 1. This is probably because the immobilization density of the electron mediator was low. However, since the immobilized conductive fiber (CNT) produced by electrophoresis in Example 3 is held by porous polysilane, it is expected to have excellent durability when used for a long period of time.

  As described above, bioelectric power generation using the bioelectric power generation anode of the present invention makes it possible to efficiently remove water-containing organic substances such as waste water, waste liquid, human waste, food waste, other organic waste, sludge, or decomposition products thereof. It is possible to obtain more electrical energy than conventional biological batteries. The present invention is expected to be widely used as a power generation method utilizing oxidative decomposition of a water-containing organic substance and a reduction potential.

FIG. 1 is a conceptual diagram showing the configuration of the power generator of the present invention. FIG. 2 is a conceptual diagram illustrating a configuration example of the power generation device of the present invention. FIG. 3 is a conceptual diagram showing an example of the structure of a cathode electrode that can be used in the power generation apparatus of the present invention, FIG. 3A is a cross-sectional view, and FIG. 3B is a plan view seen from the air chamber side of FIG. 3A. FIG. 3C is a cross-sectional view showing another example of the cathode electrode structure. FIG. 4 is a conceptual diagram showing the configuration of the power generator of the present invention used in the examples.

Explanation of symbols

1: Bioelectric power generation anode 2: Diaphragm 3: Cathode 4: Inner cylindrical interior 5: Space around the cylindrical body 6: Conductor 7: Air chamber 8: Inflow pump 9: Inflow section 10: Outflow section 11: Treated organic Substance discharge section 12: Circulation pump 13: Excess sludge discharge port 14: Air blower 15: Exhaust port 16: Condensate drain 17: Connection portion with anode 18: Connection portion with cathode 19: Exhaust port 20: Porous matrix 21: Catalyst 22: Air network 23: Aqueous solution network 24: Separator 25: Cell frame (anaerobic region: anode side)
26: Cell frame (aerobic region: cathode side)
27: Hydrous organic substance inlet 28: Decomposition waste outlet 29: Air inlet 30: Air outlet 31: Anaerobic zone (biological reaction chamber)
32: Aerobic area (air reaction chamber)

Claims (16)

A conductive substrate having a conductive fiber protruding from the surface, the electron fiber being immobilized on the conductive fiber, and a standard electrode potential (E ₀ ′) at pH 7 of −0.13V to −0.28V Bioelectric power generation anode within range. The bioelectric power generation anode according to claim 1, wherein the conductive fiber is a carbon nanotube (CNT) or a vapor growth carbon fiber (VGCF). The bioelectric power generation anode according to claim 1 or 2, wherein the electron mediator is one or more redox substances selected from the group consisting of an anthraquinone derivative, a naphthoquinone derivative, a benzoquinone derivative, and an isoalloxanthin derivative. The electron mediators include anthraquinone carboxylic acids (AQC), aminoanthraquinones (AAQ), diaminoanthraquinones (DAAQ), anthraquinone sulfonic acids (AQS), diaminoanthraquinone sulfonic acids (DAAQS), anthraquinone disulfonic acids (AQDS), diaminoanthraquinones. Disulfonic acids (DAAQ DS), ethylanthraquinones (EAQ), methylnaphthoquinones (MNQ), methylaminonaphthoquinones (MANQ), bromomethylaminonaphthoquinones (BrMANQ), dimethylnaphthoquinones (DMNQ), dimethylaminonaphthoquinones ( DMANQ), rapacol (LpQ), hydroxy (methylbutenyl) aminonaphthoquinones (ALpQ), naphthoquinonesulfonic acids (NQS), trimethylaminobenzoquinones (TMABQ), flavin mononucleotide (FMN) and their derivatives Anode biological power generation according to claim 3 that is one or more redox species selected from the group. The bioelectric power generation anode according to any one of claims 1 to 4, wherein the conductive base material includes a carbon material having conductivity. The bioelectric power generation anode according to claim 5, wherein the conductive substrate includes at least one selected from the group consisting of graphite, carbon black, fullerene, carbon nanotube (CNT), and vapor grown carbon fiber (VGCF). The bioelectric power generation anode according to any one of claims 1 to 6, wherein the conductive substrate further has a porous coating on the surface. The bioelectric power generation anode according to claim 7, wherein the conductive fiber is immobilized on the porous coating on the surface of the conductive base material by electrophoresis. A method for producing an anode for bioelectric power generation according to any one of claims 1 to 8,
A pretreatment step of preparing a conductive substrate;
A conductive fiber fixing step for fixing the conductive fiber so that the conductive fiber protrudes from the conductive substrate;
A method for producing an anode for bioelectric power generation, comprising performing an electron mediator introduction step of immobilizing and introducing an electron mediator to a conductive fiber. The method for producing an anode for bioelectric power generation according to claim 9, wherein the conductive fiber fixing step is performed by a chemical vapor deposition method (CVD method). The method for producing an anode for bioelectric power generation according to claim 9, wherein the conductive fiber fixing step is performed by electrophoresis. The pretreatment step of preparing the conductive substrate includes applying an oxidation potential to at least the aluminum layer present on the surface of the substrate to make the surface of the substrate porous. 2. A method for producing an anode for bioelectric power generation according to item 1. The pretreatment step of preparing the conductive base material includes irradiating the polysilane layer existing on the surface of the base material with ultraviolet rays to make the base material surface porous. The manufacturing method of the anode for bioelectric power generation as described in any one of. The anode for bioelectric power generation according to any one of claims 1 to 7, wherein the conductive fiber is grown by protruding from the surface of the conductive base material by a chemical vapor deposition method (CVD method). Microorganisms that can grow in an anaerobic atmosphere, solutions or suspensions containing organic substances, anaerobic regions including the anode for bioelectric power generation according to any one of claims 1 to 8, molecular oxygen and An aerobic region including a cathode and a diaphragm defining the anaerobic region and the aerobic region, and electrically connecting the anode and the cathode to a power utilization device to form a closed circuit; A power generation apparatus that generates power using an oxidation reaction of a microorganism using an organic substance as an electron donor in the anaerobic region and a reduction reaction using oxygen as an electron acceptor in the aerobic region. Microorganisms that can grow in an anaerobic atmosphere, solutions or suspensions containing organic substances, anaerobic regions including the anode for bioelectric power generation according to any one of claims 1 to 8, molecular oxygen and An aerobic region including a cathode and a diaphragm defining the anaerobic region and the aerobic region, and electrically connecting the anode and the cathode to a power utilization device to form a closed circuit; A power generation method for generating electricity using an oxidation reaction of a microorganism using an organic substance as an electron donor in the anaerobic region and a reduction reaction using oxygen as an electron acceptor in the aerobic region.

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