JP2009231231A - Microbial power generation method, and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance efficiency of microbial power generation in a microbial power generation device retaining an oxidation reduction catalyst in a positive electrode chamber solution. <P>SOLUTION: By arranging two plate-like anion exchange membranes 31, 31 parallel in a bath 30, a negative electrode chamber 32 is formed between the anion exchange membranes 31, 31, and two positive electrode chambers 33, 33 are formed by being separated with the negative electrode chamber 32 and each of the anion exchange membranes 31. Oxygen-containing gas is supplied to an air diffusion pipe 51 of the positive electrode chamber 33 to aerate a positive electrode solution, a negative electrode solution L is supplied to the negative electrode chamber, and preferably, the negative electrode solution is circulated. The positive electrode solution is kept in pH 9-12 and contains manganese ions. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a power generation method and apparatus using a metabolic reaction of microorganisms. In particular, the present invention relates to a microbial power generation method and apparatus for taking out the reducing power obtained when an organic substance is oxidatively decomposed into microorganisms as electric energy.

  In recent years, the need for a power generation method in consideration of the global environment has increased, and technological development of microbial power generation has been promoted. Microbial power generation is a method of generating electricity by taking out electrical energy obtained when microorganisms assimilate organic matter.

  In general, in microbial power generation, microorganisms, organic substances assimilated by microorganisms, and electron transfer media (electron mediators) coexist in a negative electrode chamber in which a negative electrode is arranged. The electron mediator enters the microorganism, receives the electrons generated by the microorganisms oxidizing the organic matter, and passes them to the negative electrode. The negative electrode is electrically connected to the positive electrode via an external resistance (load), and the electrons transferred to the negative electrode move to the positive electrode via the external resistance (load) and are transferred to the electron acceptor in contact with the positive electrode. A current flows between the positive electrode and the negative electrode due to such movement of electrons.

  In microbial power generation, the electron mediator takes out electrons directly from the microbial body, so the theoretical energy conversion efficiency is high. However, actual energy conversion efficiency is low, and improvement in power generation efficiency is required. Therefore, in order to increase power generation efficiency, various studies and developments have been made on electrode materials and structures, types of electron mediators, selection of microbial species, and the like (for example, Patent Documents 1 to 3).

  In Patent Document 1, the positive electrode chamber and the negative electrode chamber are separated by an alkali ion conductor made of a solid electrolyte, the positive electrode chamber and the negative electrode chamber are set to pH 7 with a phosphate buffer (buffer), and air is blown into the positive electrode chamber to generate power. It is described to do. In paragraph 0010 of Patent Document 1, it is described that potassium ferricyanide is present as a redox reagent in the positive electrode solution.

Patent Document 2 describes that a positive electrode and a negative electrode are installed so as to be in contact with an electrolyte membrane such as an ion exchange membrane that partitions the positive electrode chamber and the negative electrode chamber, the positive electrode chamber is an empty chamber, and air is circulated. ing. In paragraphs 0012 to 0013 of Patent Document 2, it is described that MnO ₂ is supported on the positive electrode as a catalyst for promoting electrode reaction.

  Patent Document 3 describes that a positive electrode chamber and a negative electrode chamber are partitioned by a proton exchange membrane, iron ions are contained in the positive electrode solution, and the positive electrode solution is aerated with an oxygen-containing gas.

In the publication, Fe ²⁺ is oxidized to Fe ³⁺ by microorganisms, and this Fe ³⁺ is subjected to a reduction electrode reaction Fe ³⁺ + e ⁻ → Fe ²⁺ on the surface of the positive electrode.
JP 2000-133326 A Japanese Patent Application Laid-Open No. 2004-342412 Special Table 2007-505442

  Potassium ferricyanide as a redox reagent to be present in the positive electrode solution is expensive and increases the power generation cost.

  In the case where iron ions are used as in Patent Document 3, it is considered that the positive electrode solution is made to be strongly acidic at pH 1-2, particularly 1.8 in order to prevent the precipitation of iron hydroxide (Patent Documents 0044 and 0047). Paragraph), members such as containers and pipes having corrosion resistance to such strongly acidic solutions are expensive.

  In addition, when the microbial power generation apparatus in which the positive electrode chamber and the negative electrode chamber were partitioned with a cation exchange membrane and manganese ions were contained in the positive electrode solution and the manganese ions were microbially oxidized was tested, the power generation amount was small. This is presumably because the proton moving speed from the negative electrode chamber side to the positive electrode chamber side is small.

  The present invention solves the above-mentioned conventional problems, and in a microbial power generation apparatus in which a positive electrode solution is held on a positive electrode, a microbial power generation method and apparatus that can increase the efficiency of microbial power generation without increasing costs. The purpose is to provide.

  The microbial power generation method of the present invention (Claim 1) has a negative electrode, a negative electrode chamber holding a liquid containing microorganisms and an electron donor, and is separated from the negative electrode chamber via an ion exchange membrane. In a microbial power generation method for generating power by supplying an oxygen-containing gas to the positive electrode solution of a microbial power generation apparatus having a positive electrode chamber holding a positive electrode solution, the ion exchange membrane is an anion exchange membrane, Manganese ions are present in the positive electrode solution, and the pH of the positive electrode solution is 9 or more.

  The microbial power generation method according to claim 2 is characterized in that, in claim 1, the pH of the positive electrode solution is 11 or more.

The microbial power generation method according to claim 3 is characterized in that, in claim 1 or 2, the manganese ion concentration of the positive electrode solution is 1,000 to 50,000 mg / L in terms of MnO ₂ .

  The microbial power generation device of the present invention (Claim 4) has a negative electrode, and is separated from a negative electrode chamber holding a liquid containing microorganisms and an electron donor, and the negative electrode chamber via an ion exchange membrane. And a positive electrode chamber that holds the positive electrode solution, and an oxygen supply unit that supplies oxygen to the positive electrode solution, wherein the ion exchange membrane is an anion exchange membrane, and the positive electrode solution is manganese In addition to containing ions, the pH is 9 or more.

  According to a fifth aspect of the present invention, there is provided a microorganism power generation apparatus according to the fourth aspect, characterized in that an aeration tube is provided as the oxygen supply means so as to aerate the positive electrode chamber.

  The microorganism power generation apparatus according to claim 6 is characterized in that in claim 4, the oxygen supply means is provided with an aeration chamber that receives and aerates the positive electrode solution in the positive electrode chamber and returns the aerated positive electrode solution to the positive electrode chamber. It is what.

  In the present invention, the positive electrode chamber and the negative electrode chamber are partitioned by an anion exchange membrane, the positive electrode solution is adjusted to pH 9 or more, manganese ions are present in the positive electrode solution, and oxygen is supplied to the positive electrode solution by aeration or the like. Is.

  In the present invention, the proton moving speed from the negative electrode chamber side to the positive electrode chamber side is high, and the power generation efficiency of microbial power generation is high. Further, when an oxygen-containing gas is supplied to the positive electrode solution having a pH of 9 or more, the oxygen gas and manganese ions react directly. That is, even if oxygen gas does not become dissolved oxygen, it reacts with manganese ions. Therefore, the reaction efficiency of oxygen is high, and manganese ions can be sufficiently oxidized with a small supply amount of oxygen-containing gas.

  In addition, according to the present invention, since the positive electrode solution is made alkaline, the cost of members constituting the apparatus is lower than that in the case of making it strongly acidic.

  Hereinafter, the present invention will be described in more detail.

  FIG. 1 is a schematic cross-sectional view showing a schematic configuration of a microbial power generation apparatus according to an embodiment of the present invention.

  The tank body 1 is partitioned into a positive electrode chamber 3 and a negative electrode chamber 4 by an anion exchange membrane 2. In the positive electrode chamber 3, a positive electrode 5 made of a conductive porous material is disposed so as to be in close contact with the anion exchange membrane 2. The space between the positive electrode 5 and the wall surface of the tank body 1 is filled with the positive electrode solution. A diffuser tube 7 is provided in the lower part of the positive electrode chamber 3 so as to aerate the positive electrode solution. Oxygen-containing gas such as air is introduced into the diffuser tube 7 and aeration exhaust gas flows out from the gas outlet 8 at the upper part of the positive electrode chamber. In addition, since the positive electrode solution evaporates or decreases due to aeration, the replenishment positive electrode solution is appropriately supplied from the replenishing port 16 having the valve 15.

  The pH of this positive electrode solution is 9 or more, preferably 9 to 12, particularly preferably 10.5 to 12, especially 11 to 12. Manganese ions are dissolved in this positive electrode solution. A preferable range of the manganese ion concentration will be described in detail later.

A negative electrode 6 made of a conductive porous material is disposed in the negative electrode chamber 4. The negative electrode 6 is in close contact with the anion exchange membrane 2, and protons (H ⁺ ) can be transferred from the negative electrode 6 to the anion exchange membrane 2.

  Microorganisms are supported on the negative electrode 6 made of this porous material. The negative electrode solution 4 is introduced into the negative electrode chamber 4 from the inlet 4a, and the waste liquid is discharged from the outlet 4b. The inside of the negative electrode chamber 4 is anaerobic.

  The negative electrode solution L in the negative electrode chamber 4 is circulated through a circulation outlet 9, a circulation pipe 10, a circulation pump 11 and a circulation return port 12. The circulation pipe 10 is provided with a pH meter 14 for measuring the pH of the liquid flowing out from the negative electrode chamber 4 and connected with an alkali addition pipe 13 such as a sodium hydroxide aqueous solution.

When the pH in the negative electrode chamber 4 is set to 7 to 9 and the positive electrode chamber 3 is set to pH 9 or more, OH ⁻ present in a large amount in the positive electrode chamber 3 permeates the anion exchange membrane and moves into the negative electrode chamber 4. Then, air is supplied to the air diffuser tube 7 to aerate the positive electrode solution in the positive electrode chamber 3, and the negative electrode solution L is circulated by operating the pump 11 as necessary. The organic substance reacts with OH ⁻ , and the formation reaction of CO ₂ , H ₂ O and e ⁻ proceeds. For example, when the organic substance is acetic acid,
CH ₃ COOH + 8OH ⁻ → 2CO ₂ + 6H ₂ O + 8e ⁻
The reaction proceeds. The electrons e ⁻ flow to the positive electrode 5 through the negative electrode 6, the terminal 22, the external resistor 21, and the terminal 20.

On the other hand, in the positive electrode chamber 3, the manganese ion (II) oxidation reaction of Mn ²⁺ + 2O ₂ + 2H ₂ O → MnO ₂ + 4OH ⁻ or Mn ²⁺ + 1 / 2O ₂ + H ₂ O → Mn ⁴⁺ + 2OH ⁻ in water and the positive electrode 5 _MnO 2 ₊ 2H 2 O ₊ 8e on ^- → ^Mn 2+ + 4OH ^- or ^Mn 4+ + 2e ^- → ^{Mn 2+} that proceed the reduction reaction and is concurrently manganese ion (IV), when viewed in the entire positive electrode chamber 3
O ₂ + 2H ₂ O + 4e ⁻ → 4OH ⁻
The electron consumption reaction and the OH ⁻ production reaction proceed. The generated OH ⁻ permeates the anion exchange membrane and moves to the negative electrode chamber 4. Due to such a reaction, an electromotive force is generated between the positive electrode 5 and the negative electrode 6, and a current flows to the external resistor 21 through the terminals 20 and 22.

In the negative electrode chamber 4, the pH tends to decrease due to the generation of CO ₂ by the decomposition reaction of water by microorganisms. Therefore, alkali is added to the negative electrode solution L so that the detected pH of the pH meter 14 is preferably 7-9. This alkali may be added directly to the negative electrode chamber 6, but by adding to the circulating water, the entire area in the negative electrode chamber 6 can be maintained at pH 7 to 9 without partial bias. In addition, when the pH of the negative electrode chamber 4 is out of the range of 7 to 9, the biological reaction in the negative electrode chamber 4 is remarkably suppressed, and the power generation efficiency decreases.

  FIG. 2 is a schematic cross-sectional view of a microbial power generation apparatus according to another embodiment of the present invention.

  Two plate-like anion exchange membranes 31 are arranged in parallel to each other in a substantially rectangular parallelepiped tank 30 to form a negative electrode chamber 32 between the anion exchange membranes 31, 31. Two positive electrode chambers 33, 33 are formed with the anion exchange membrane 31 being spaced from each other.

A negative electrode 34 made of a porous material is disposed in the negative electrode chamber 32 so as to be in close contact with each anion exchange membrane 31. The negative electrode 34 is lightly pressed against the anion exchange membrane (for example, at a pressure of 0.1 kg / cm ² or less).

In the positive electrode chamber 33, a positive electrode 35 made of a porous material is disposed in contact with the anion exchange membrane 31. The positive electrode 35 is pressed against a spacer 36 made of rubber or the like and is lightly pressed (for example, with a pressure of 0.1 kg / cm ² or less) and is in close contact with the anion exchange membrane 31. In order to improve the adhesion between the positive electrode 35 and the anion exchange membrane 31, they may be welded or partially bonded with an adhesive.

  The positive electrode 35 and the negative electrode 34 are connected to an external resistor 38 via terminals 37 and 39.

  The space between the positive electrode 35 and the side wall of the tank body 30 is filled with the positive electrode solution. A diffuser tube 51 is installed in the lower part of each positive electrode chamber 33 so that the positive electrode solution can be aerated. Aeration exhaust gas flows out from the gas outlet 52 at the top of the positive electrode chamber 33. In addition, although illustration is abbreviate | omitted, the replenishing port is provided so that the positive electrode solution may be replenished with respect to each positive electrode chamber 33. FIG. The positive electrode solution pH is 9 or more, preferably 9 to 12, particularly preferably 10.5 to 12, especially 11 to 12. Manganese ions are dissolved in the positive electrode solution.

  The negative electrode solution 32 is introduced into the negative electrode chamber 32 from the inlet 32a, and the waste liquid flows out from the outlet 32b. The inside of the negative electrode chamber 32 is anaerobic.

  The negative electrode solution in the negative electrode chamber 32 is circulated through the circulation outlet 41, the circulation pipe 42, the circulation pump 43 and the circulation return port 44. The circulation pipe 42 is provided with a pH meter 47 and an alkali addition pipe 45 is connected thereto. The pH of the negative electrode solution flowing out from the negative electrode chamber 32 is detected by a pH meter 47, and an alkali such as an aqueous sodium hydroxide solution is added so that this pH is preferably 7-9.

  Also in the microbial power generation apparatus of FIG. 2, the oxygen-containing gas is supplied to the air diffuser 51 to aerate the positive electrode solution in the positive electrode chamber 33, and the negative electrode solution is circulated through the negative electrode chamber 32, preferably circulating the negative electrode solution. As a result, a potential difference is generated between the positive electrode 35 and the negative electrode 34, and a current flows through the external resistor 38.

  In FIGS. 1 and 2, the diffuser tube is arranged in the positive electrode chambers 3 and 33 and the positive electrode solution is aerated in the positive electrode chambers 3 and 33. However, the positive electrode solution in the positive electrode chamber is introduced into another aeration chamber. May be aerated.

  FIG. 3 shows an embodiment in which the aeration chamber 63 is provided separately from the positive electrode chamber in the microbial power generation apparatus of FIG.

  In the embodiment shown in FIG. 3, the positive electrode solution in the positive electrode chamber 33 is introduced from the outlet 61 into the aeration chamber 63 through the pipe 62 and the pump 66, and aerated by the aeration tube 63a. Aeration exhaust gas flows out from the exhaust gas outlet 63b of the aeration chamber. The aerated positive electrode solution returns to the positive electrode chamber 33 via the pipe 64 and the return port 65.

  Although the aeration exhaust gas outlet 52 is not provided in the positive electrode chamber 33, a gas vent portion may be provided. Of course, no aeration tube is provided in the positive electrode chamber 33.

  This positive electrode solution also has a pH of 9 or more, preferably 9 to 12, particularly preferably 10.5 to 12, especially 11 to 12, and manganese ions are dissolved therein.

  Other configurations of the microbial power generation apparatus of FIG. 3 are the same as those of FIG. 2, and the same reference numerals denote the same parts.

  Also in the microbial power generation apparatus of FIG. 3, the positive electrode solution in the positive electrode chamber 33 is circulated through the aeration chamber 63 and aerated in the aeration chamber 63, and the negative electrode solution is circulated in the negative electrode chamber 32, preferably By circulating the negative electrode solution, a potential difference is generated between the positive electrode 35 and the negative electrode 34, and a current flows through the external resistor 38.

  Next, in addition to the microorganisms, negative electrode solution, positive electrode solution, and the like of this microbial power generation device, suitable materials for the anion exchange membrane, the negative electrode, and the positive electrode will be described.

  Microorganisms that produce electrical energy by being contained in the negative electrode solution L are not particularly limited as long as they have a function as an electron donor. For example, Saccharomyces, Hansenula, Candida, Micrococcus, Staphylococcus, Streptococcus, Leuconostoa, Lactobacillus, Corynebacterium, Arthrobacter, Bacillus, Clostridium, Neisseria, Escherichia, Enterobacter, Serratia, Aigenes Examples include bacteria, filamentous fungi, and yeasts belonging to the genera Gluconobacter, Pseudomonas, Xanthomonas, Vibrio, Comamonas, and Proteus (Proteus vulgaris). As a sludge containing such microorganisms, activated sludge obtained from biological treatment tanks that treat organic matter-containing water such as sewage, microorganisms contained in effluent from the first sedimentation basin of sewage, anaerobic digested sludge, etc. The microorganism can be held in the negative electrode by supplying to the chamber. In order to increase the power generation efficiency, the amount of microorganisms retained in the negative electrode chamber is preferably high, and for example, the microorganism concentration is preferably 1 to 50 g / L.

  As the negative electrode solution L, a solution that holds microorganisms or cells and has a composition necessary for power generation is used. For example, in the case of generating electricity in the respiratory system, the negative side solution includes energy required for respiratory system metabolism such as bouillon medium, M9 medium, L medium, Malt Extract, MY medium, and nitrifying bacteria selection medium. A medium having a composition such as a source and nutrients can be used. The negative electrode solution L contains an organic substance. The organic substance is not particularly limited as long as it can be decomposed by microorganisms. For example, water-soluble organic substances, organic fine particles dispersed in water, and the like are used. The negative electrode solution may be an organic waste liquid such as sewage or food factory effluent, or a dispersion of organic waste such as garbage. The organic substance concentration in the negative electrode solution L is preferably a high concentration of about 100 to 10000 mg / L in order to increase the power generation efficiency.

  The negative electrode solution L may contain an electron mediator in order to make it easier to extract electrons from microorganisms or cells. Examples of the electron mediator include compounds having a thionin skeleton such as thionine, dimethyldisulfonated thionine, new methylene blue, toluidine blue-O, and 2-hydroxy-1,4-naphthoquinone such as 2-hydroxy-1,4-naphthoquinone. Examples include compounds having a skeleton, brilliant cresyl blue, galocyanine, resorufin, alizarin brilliant blue, phenothiazinone, phenazine esosulphate, safranin-O, dichlorophenolindophenol, ferrocene, benzoquinone, phthalocyanine, or benzyl viologen and their derivatives. be able to.

  Furthermore, if materials that increase the power generation function of microorganisms, such as antioxidants such as vitamin C, or materials that increase the function of only specific electron transfer systems or substance transfer systems in microorganisms, are dissolved, power can be more efficiently generated. Is preferable.

  The negative electrode solution L may contain a phosphate buffer as necessary.

  The temperature of the negative electrode solution is preferably about 10 to 70 ° C.

As the positive electrode solution, a solution containing manganese ions is used. Specifically, it is preferable to dissolve a soluble manganese salt composed of at least one of manganese sulfate, manganese chloride and the like. Manganese ions are preferably present at a concentration of 100 to 100,000 mg / L, more preferably 1,000 to 50,000 mg / L, and even more preferably 10,000 to 50,000 mg / L in terms of MnO ₂ . It is preferable. If the amount of manganese ions present is too small, the electron accepting reaction between the positive electrode 35 and the manganese ions and the oxidation regeneration reaction of the reduced manganese ions are slowed.

  Manganese ions may be added to the positive electrode chamber in addition to the presence of manganese ions at the start of the operation of the microbial power generation apparatus, and additional manganese salt aqueous solution may be added after the operation is started.

  When manganese dioxide powder is used instead of dissolving soluble manganese salt, the reaction rate tends to be slower than when soluble manganese salt is used. The reason for this is not clear, but it is presumed that the powdered manganese dioxide has a small surface area. In the present invention, since manganese ions are present in the positive electrode solution, the reaction between oxygen supplied by aeration and manganese ions proceeds rapidly, and the power generation efficiency is improved.

As described above, the divalent manganese ion Mn ²⁺ in the positive electrode solution is oxidized to be tetravalent by aeration of the oxygen-containing gas, and then is reduced on the positive electrode to return to Mn ²⁺ . The reaction of consuming electrons and the production of OH ⁻ proceed with O ₂ + 2H ₂ O + 4e ⁻ → 4OH ⁻ using oxygen. This OH ⁻ permeates the anion exchange membrane and moves to the negative electrode.

  Divalent manganese can be directly oxidized to tetravalent (oxygen oxidation) by aeration of a positive electrode solution containing divalent manganese ions under alkaline conditions. In the case of this oxygen oxidation, since the reaction rate is higher when the pH is increased, it is preferable to increase the pH of the positive electrode solution from the viewpoint of the reaction rate. For example, the pH is preferably 10.5 or more, particularly 11 or more. However, if the pH exceeds 12, alkali metals such as Na and K may move from the positive electrode chamber to the negative electrode chamber, leading to a decrease in power generation efficiency. Also, a large amount of alkaline agent is required to maintain the positive electrode solution at a high pH. Therefore, it is preferable to perform aeration by setting the pH of the positive electrode solution to 9 to 12, particularly 10.5 to 12, particularly 11 to 12.

  In addition, since the oxidation reaction rate of divalent manganese is increased under such a high pH condition, a sufficient power generation amount can be obtained even if the volume of the positive electrode chamber is reduced.

  When the pH of the positive electrode solution is relatively close to 9 (for example, about 8.5 to 9.5), manganese-oxidizing bacteria can grow in the positive electrode solution. At least a part of the ions may be oxidized by biological oxidation using manganese oxidizing bacteria. When performing biooxidation, manganese-oxidizing bacteria are added to the aeration chamber. Manganese-oxidizing bacteria are always present in activated sludge retained in a biological treatment tank or the like for treating sewage, outflow water from the first sedimentation basin, river water, and the like. Therefore, a small amount of these manganese-oxidizing bacterial sources may be inoculated into the positive electrode chamber or the aeration chamber where aeration is performed at the start of operation of the microbial power generation apparatus. When manganese ions are oxidized by manganese-oxidizing bacteria, the positive electrode solution preferably contains a nitrogen component (for example, ammonium chloride) and a phosphorus component (for example, phosphate), which are essential nutrient salts of microorganisms. The method of biological reaction in the aeration chamber is not limited, and any of a fixed bed, a floating method, and a fluidized bed may be used. The microorganism concentration in the aeration chamber is preferably a high concentration in the range of about 100 to 1,000 mg / L, and adopting a fixed bed and fluidized bed system is preferable because the microorganism concentration per unit volume can be increased.

  In the case of oxygen oxidation and biological oxidation, the amount of aeration may be such that DO is detected (for example, 0.5 mg / L or less) when the dissolved oxygen (DO) concentration of the positive electrode solution is measured.

  When the positive electrode solution is aerated in an aeration chamber different from the positive electrode chamber, the volume of the aeration chamber may be equal to or less than the volume of the positive electrode chamber. Specifically, when oxygen oxidation is performed, the volume of the aeration chamber may be approximately the same as the positive electrode chamber volume to about 1/100. When performing biological oxidation, it is desirable that the volume of the aeration chamber be larger than that when performing oxygen oxidation. Specifically, the volume of the aeration chamber may be approximately the same as the positive electrode chamber volume to about 1/20.

  The positive electrode solution may contain a chelating agent. By blending the chelating agent, tetravalent manganese is present in a dissolved state, so that an effect of increasing the reaction rate can be obtained.

  Any chelating agent can be used without limitation as long as it forms a chelate compound with manganese ions. Specifically, ethylenediaminetetraacetic acid (EDTA), 1,2-dihydroxyanthraquinone-3-yl-methylamino-N, N′-diacetic acid, 5,5′-dibromopyrogallolsulfophthalein, 1- (1- Hydroxy-2-naphthylazo) -6-nitro-2-naphthol-4-sulfonic acid sodium salt, cyclo-tris- [7- (1-azo-8-hydroxynaphthalene-3,6-disulfonic acid)] 6 sodium salt 4-Methylumbelliferone-8-methyleneiminodiacetic acid, 3-sulfo-2,6-dichloro-3 ′, 3 ″ -dimethyl-4′-fuxone-5 ′, 5 ″ -dicarboxylic acid trisodium salt Salt, 3,3′-bis [N, N-di (carboxymethyl) aminomethyl] thymol sulfonephthalein, sodium salt, 7- (1-naphthylazo) -8-hydroxyquinoline-5-sulfonic acid sodium salt 4- (2-pi Jiruazo) resorcinol, pyrocatechol sulfone phthalein, 3,3'-bis [N, N-di (carboxymethyl) aminomethyl] - ortho - cresol sulfonic phthalein, etc. disodium salt. The chelating agent is preferably a stable one that is not easily biodegradable.

  The addition amount of the chelating agent is not particularly limited, but it is desirable that the addition amount is such that there is an amount for chelating all the manganese ions present in the positive electrode solution. Although depending on the chelating agent to be added, the addition amount is preferably about 100 mg / L to 100,000 mg / L. When manganese is oxidized and regenerated by biological oxidation, if the concentration of the chelating agent is too high, the biological reaction is inhibited. Therefore, it is preferably 50,000 mg / L or less, particularly preferably 10,000 mg / L or less.

  Air is suitable as the oxygen-containing gas for aeration of the positive electrode solution. The exhaust gas from the positive electrode chamber may be deoxygenated as necessary, and then vented to the negative electrode chamber to be used for purging dissolved oxygen from the negative electrode solution L.

  The anion exchange membrane is preferably strong and thin with a thickness of 30 to 300 μm, particularly about 30 to 200 μm. As the anion exchange membrane, an anion exchange membrane made by Astom, an anion type electrolyte membrane made by Tokuyama, and the like are suitable, but not limited thereto.

  As described above, in the present invention, by using an anion exchange membrane as an ion exchange membrane that separates the positive electrode chamber and the negative electrode chamber, the transfer rate of protons from the negative electrode chamber to the positive electrode chamber is increased as compared with the case of using a cation exchange membrane. , Power generation efficiency is improved.

  The negative electrode is preferably a porous body having a large surface area and a large number of voids and water permeability so that a large number of microorganisms can be retained. Specific examples include a conductive material sheet having a roughened surface and a porous conductor (for example, graphite felt, expanded titanium, expanded stainless steel, etc.) in which the conductive material is made into a felt-like porous sheet. . When such a porous negative electrode is brought into close contact with the anion exchange membrane, electrons generated by the microbial reaction can be transferred to the negative electrode without using an electron mediator, and the electron mediator can be dispensed with.

  The negative electrode is preferably made of a fibrous body such as felt. When the negative electrode has a thickness larger than the thickness of the negative electrode chamber, the negative electrode is compressed and inserted into the negative electrode chamber, and comes into close contact with the anion exchange membrane by its own restoring elasticity.

  A plurality of sheet-like conductors may be laminated to form a negative electrode. In this case, the same kind of conductor sheets may be laminated, or different kinds of conductor sheets (for example, a graphite sheet having a rough surface and a graphite felt) may be laminated.

  The negative electrode preferably has a total thickness of 3 mm to 50 mm, particularly about 5 to 40 mm. When a negative electrode is constituted by a laminated sheet, it is preferable to orient the laminated surface in a direction connecting the liquid inlet and outlet so that the liquid flows along a mating surface (laminated surface) between the sheets.

  The positive electrode is made of a felt-like or porous conductive material such as graphite felt, foamed stainless steel, or foamed titanium. In the case of a porous material, the void diameter is preferably about 0.01 to 1 mm. As the positive electrode, it is preferable to use a material obtained by molding these conductive materials into a shape (for example, a plate shape) that is easily adhered to the anion exchange membrane. The thickness of the positive electrode is preferably 2 to 50 mm. When biological oxidation is performed in the presence of manganese-oxidizing bacteria in the positive electrode chamber, it is preferable that the positive electrode has a thickness of about 2 to 50 mm because the amount of microorganisms retained can be increased.

  In the present invention, the negative electrode chamber may be divided into a plurality of compartments, and the pH of the liquid in the negative electrode compartment may be adjusted after suppressing the pH drop in each compartment by connecting the compartments in series. If the negative electrode chamber is divided, the amount of organic matter decomposition in each of the compartments is reduced, and as a result, the amount of carbon dioxide gas produced is also reduced, so that the pH drop in each compartment can be reduced. What is necessary is just to add an alkali to the liquid which flows through a negative electrode chamber, when flowing from the former compartment to the latter compartment. If it does in this way, the pH of the liquid in which the pH has decreased in the front compartment can be raised and flowed into the rear compartment, and the pH of the liquid in the negative compartment can be easily adjusted to the above range.

  Hereinafter, examples and comparative examples will be described.

[Example 1]
A microbial power generation apparatus shown in FIG. 2 was prepared. The overall volume of the tank body 30 of this power generator is 700 mL, the volume of the negative electrode chamber 32 is 350 mL, and the volume of each positive electrode chamber 33 is 175 mL. Each positive electrode chamber 33 is provided with an air outlet at the top and an air diffuser 51 at the bottom.

  As anion exchange membrane 31, an anion exchange membrane (thickness 220 μm) manufactured by Astom Co., Ltd. was used.

  As the negative electrode 34, two graphite felts (manufactured by Toyo Carbon Co., Ltd.) having a thickness of 250 mm × 70 mm and a thickness of 10 mm were bonded together with a conductive adhesive. The adhesive is applied partially (about 10% of the entire surface) to the surface of the graphite felt (avoids so-called “solid coating”), and the fine irregularities on the surfaces of the graphite felt facing each other are filled with the adhesive. I tried to avoid it. Both surfaces of each graphite felt are rough. The laminate of two carbon felts has the same thickness as the negative electrode chamber 32, fills the entire negative electrode chamber 32, and contacts the anion exchange membrane 31.

  Accordingly, the microbial power generation apparatus is configured such that all the liquid supplied to the negative electrode chamber 32 passes through the porous negative electrode 34 and passes through the negative electrode chamber 32 without passing through the negative electrode 34 (short path). ) Is substantially eliminated. In the negative electrode chamber 32, activated sludge collected from a biological treatment tank of a sewage treatment plant was added and cultured as an inoculum, and microorganisms were attached to the surface of each graphite felt constituting the negative electrode. The microorganism concentration in the negative electrode chamber 32 was about 2200 mg / L.

  Each of the positive electrodes 35 was composed of one piece of graphite felt having a thickness of 5 mm. A honeycomb spacer 36 having a thickness of 5 mm was disposed, and the positive electrode 35 was brought into contact with the anion exchange membrane 31.

  In the positive electrode chamber 33, manganese sulfate having a concentration of 50,000 mg / L was added, and the pH was adjusted to 11 with NaOH.

  The positive electrode solution was aerated by aeration of air through the diffusing tube 51 at 0.5 L / min. A negative electrode solution containing acetic acid at a concentration of 1,000 mg / L, a phosphate buffer at a concentration of 50 mM, and 300 mg / L of ammonium chloride was supplied to the negative electrode chamber 32 at an inflow rate of 70 mL / min. The waste liquid was discharged.

  The circulation flow rate of the circulation pipe 42 was 10 mL / min. 1N sodium hydroxide was added to the circulating liquid so that the pH detected by the pH meter 47 was about 8.2. The external resistance was 5Ω.

When the operation was started under the above conditions, a voltage of 380 mV was obtained. The current at this time was 76 mA, and the generated power per unit volume of the negative electrode was 82.5 W / m ³ . As a result of continuing the operation under the same conditions, almost the same output was stably obtained for one month.

[Comparative Example 1]
In Example 1, microbial power generation was performed under the same conditions as in Example 1 except that a cation exchange membrane (manufactured by Astom Co., Ltd., thickness 210 μm) was used instead of the anion exchange membrane.

The generated voltage was 285 mV, and the current was 57 mA. At this time, the resistance of the circuit was 5Ω. Therefore, the amount of power generation per unit volume of the negative electrode was 46.4 W / m ³ .

  From the above Examples and Comparative Examples, it was confirmed that large electric power can be obtained by separating the positive electrode chamber and the negative electrode chamber by an anion exchange membrane.

It is a cross-sectional schematic diagram of the microbial power generation device which concerns on one Embodiment of this invention. It is a cross-sectional schematic diagram of the microbial power generation device which concerns on one Embodiment of this invention. It is a cross-sectional schematic diagram of the microbial power generation device which concerns on one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,30 Tank 2,31 Anion exchange membrane 3,33 Positive electrode chamber 4,32 Negative electrode chamber 5,35 Positive electrode 6,34 Negative electrode 7,51,63a Air diffuser 63 Aeration chamber

Claims (6)

A negative electrode chamber having a negative electrode and holding a liquid containing microorganisms and an electron donor;
Electric power is generated by supplying an oxygen-containing gas to the positive electrode solution of a microbial power generation device that is separated from the negative electrode chamber via an ion exchange membrane and has a positive electrode and a positive electrode chamber that holds the positive electrode solution. In the microbial power generation method,
The ion exchange membrane is an anion exchange membrane;
A microbial power generation method, wherein manganese ions are present in the cathode solution, and the pH of the cathode solution is 9 or more.   The microbial power generation method according to claim 1, wherein the pH of the positive electrode solution is 11 or more. According to claim 1 or 2, microbial power generation method characterized by manganese ion concentration of the cathode solution is 1,000~50,000mg / L in terms of MnO _2. A negative electrode chamber having a negative electrode and holding a liquid containing microorganisms and an electron donor;
A positive electrode chamber separated from the negative electrode chamber via an ion exchange membrane, having a positive electrode and holding a positive electrode solution;
Oxygen supply means for supplying oxygen to the cathode solution;
In a microbial power generation apparatus comprising:
The ion exchange membrane is an anion exchange membrane;
A microbial power generation apparatus, wherein the positive electrode solution contains manganese ions and has a pH of 9 or more.   5. The microbial power generation apparatus according to claim 4, wherein a diffuser tube is provided as the oxygen supply means so as to aerate the positive electrode chamber.   5. The microbial power generation apparatus according to claim 4, wherein an aeration chamber is provided as the oxygen supply means that receives and aerates the positive electrode solution in the positive electrode chamber and returns the aerated positive electrode solution to the positive electrode chamber.

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