JP6358352B1 - Microbial power generation apparatus and microbial power generation method - Google Patents

Abstract

Provided is a microbial power generation apparatus in which an air permeability of an ion-permeable non-conductive membrane is appropriate and a stable high power generation amount can be obtained. A negative electrode chamber (4) having a negative electrode (6) and holding a liquid containing microorganisms and an electron donor is separated from the negative electrode chamber (4) via an ion-permeable nonconductive film (2). A microbial power generation apparatus including a positive electrode chamber 3 having an air cathode in contact with a permeable nonconductive film 2, wherein the ion permeable nonconductive film 2 has a Gurley value of 1,000 sec / 100 mL or more. A microbial power generation apparatus characterized by [Selection] Figure 1

Description

  The present invention relates to a power generation device that utilizes a metabolic reaction of a microorganism. In particular, the present invention relates to a microbial power generation apparatus that extracts, as electric energy, a reducing power obtained when an organic substance is oxidatively decomposed into microorganisms.

  As a power generation device using microorganisms, Patent Document 1 discloses that a porous body is installed as a positive electrode plate so as to be in contact with an electrolyte membrane partitioning a positive electrode chamber and a negative electrode chamber, and air is circulated through the positive electrode chamber. It describes what makes air and liquid contact in the voids of the body. In the following, a positive electrode that circulates an oxygen-containing gas such as air in the positive electrode chamber and uses oxygen as an electron acceptor may be referred to as an “air cathode”.

  A microbial power generation apparatus using an air cathode has the advantage that no catholyte is required, and only an oxygen-containing gas needs to be circulated in the positive electrode chamber, and there is no need for aeration into the catholyte.

  Patent Document 2 discloses a microbial power generation apparatus that uses paper, woven fabric, non-woven fabric, honeycomb formed body, or lattice-shaped formed body made of a non-conductive material as an ion permeable film that separates a positive electrode chamber and a negative electrode chamber. Have been described. Such an ion permeable membrane is less expensive than an ion exchange membrane.

Japanese Patent Application Laid-Open No. 2004-342412 JP 2009-231229 A

  A microbial power generation device using an air cathode creates and operates a device that uses several types of paper, woven fabric, non-woven fabric, etc., in an ion-permeable membrane that separates the positive electrode chamber and the negative electrode chamber. Some things were not available. As a result of investigation, it was found that the air permeability of the ion permeable membrane has an influence on the power generation performance. A membrane having a high ion permeability is preferable for obtaining a high power generation amount, but a membrane having a high ion permeability generally tends to transmit air. In a membrane that has high ion permeability and easily allows air to permeate, the amount of air (oxygen) that permeates from the cathode to the anode increases, and organic matter decomposition occurs due to an aerobic reaction at the anode, thereby reducing power generation efficiency. In other words, power generation microorganisms can oxidize organic matter under anaerobic conditions, but if oxygen is present, they cannot grow and other aerobic microorganisms propagate, leading to a decrease in power generation efficiency. There is a concern that will occur and adhere. Here, when the bactericide is used, the aerobic microorganisms are removed, but the power generation microorganisms are also affected. Further, the diaphragm and the electrode catalyst are deteriorated and the performance is lowered, so that it is not desirable to use the bactericide.

  An object of the present invention is to provide a microbial power generation apparatus in which the air permeability of an ion-permeable non-conductive film is appropriate and a high power generation amount can be stably obtained.

  The microbial power generation device of the present invention has a negative electrode and holds a negative electrode chamber holding a liquid containing microorganisms and an electron donor, and is separated from the negative electrode chamber via an ion-permeable non-conductive film. In the microorganism power generation apparatus including a positive electrode chamber having an air cathode in contact with the permeable nonconductive film, the ion permeable nonconductive film is a hydrophilic nonconductive film having a Gurley value of 1,000 sec / 100 mL or more. It is characterized by.

  In one aspect of the present invention, the ion-permeable non-conductive film is paper, woven fabric, or non-woven fabric made of a non-conductive substance.

  Microbial power generation devices with low Gurley values, that is, with ion-permeable non-conductive membranes that allow air to easily permeate, have a large amount of air (oxygen) permeating from the cathode to the anode, and organic matter decomposition by an aerobic reaction occurs at the anode. It happens and power generation efficiency decreases. On the other hand, in a microbial power generation apparatus having an ion-permeable non-conductive film that has a high Gurley value, that is, it is difficult for air to permeate, an aerobic reaction hardly occurs at the anode, and the power generation reaction efficiency can be improved.

  In the microbial power generation device of the present invention, an ion permeable membrane having a Gurley value of 1,000 sec / 100 mL or more is used, and the power generation efficiency is high.

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

  Hereinafter, an embodiment of the microbial power generation apparatus of the present invention will be described in detail with reference to FIG. FIG. 1 is a schematic cross-sectional view showing a schematic configuration of a microbial power generation apparatus of the present invention.

  In this microbial power generation device, the inside of the tank body 1 is partitioned into a positive electrode chamber 3 and a negative electrode chamber 4 by an ion-permeable non-conductive film 2. A positive electrode 5 is disposed in the positive electrode chamber 3 so as to be in contact with the ion-permeable nonconductive film 2.

A negative electrode 6 made of a conductive porous material is disposed in the negative electrode chamber 4. The negative electrode 6 has a microbial film of about 1 to 2 layers on the ion-permeable non-conductive film 2 having a Gurley value of 1,000 sec / 100 mL or more, preferably 1,000 to 6,000 sec / 100 mL. If the ion-permeable non-conductive membrane 2 is a cation exchange membrane, protons (H ⁺ ) can be transferred from the negative electrode 6 to the ion-permeable non-conductive membrane 2.

  The inside of the positive electrode chamber 3 is an empty chamber, oxygen-containing gas (air in the present embodiment) is introduced from the gas inlet 7, and the exhaust gas flows out from the gas outlet 8 through the discharge pipe 25.

  Microorganisms are supported on the negative electrode 6 made of a 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 an aqueous sodium hydroxide solution, so that the pH of the negative electrode solution L is 7 An alkali is added as needed so that it may become ~ 9.

  The condensed water generated in the positive electrode chamber 3 is drained from a condensed water outlet not shown.

  Due to the electromotive force generated between the positive electrode 5 and the negative electrode 6, a current flows through the external resistor 21 via the terminals 20 and 22.

In the negative electrode chamber 4, the aerobic biological treatment exhaust gas containing oxygen, carbon dioxide gas, and water vapor is passed through the positive electrode chamber 3, and the negative electrode solution L is circulated by operating the pump 11 as necessary.
(Organic) + H ₂ O → CO ₂ + H ⁺ + e ⁻
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.

Proton H ⁺ generated by the above reaction moves to the positive electrode 5 through the ion-permeable non-conductive membrane 2. In the positive electrode 5,
O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O
The reaction proceeds.

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.

  As the ion permeable non-conductive film 2 having a Gurley value of 1,000 sec / 100 mL or more, paper, woven fabric, or non-woven fabric is preferably used. The Gurley value is measured according to JIS P8117: 2009. The Gurley value indicates the difficulty of air passage in the thickness direction of the film, and is widely used as a test method for representing the air permeability of paper and the like. It is represented by the time (sec) required for permeation of a constant volume (100 mL) of air when a certain pressure is applied. A smaller value means that it is easier to pass through, and a larger value means that it is more difficult to pass. That is, a smaller value means better communication in the thickness direction of the film, and a larger value means poor communication in the thickness direction of the film. Communication is the degree of connection of holes in the thickness direction.

  An ion-permeable membrane that has a low Gurley value, that is, air can easily pass therethrough, has a large amount of air (oxygen) permeating from the cathode to the anode, and organic matter decomposition occurs due to an aerobic reaction at the anode, resulting in reduced power generation efficiency. . On the other hand, an ion-permeable membrane having a high Gurley value, that is, an air-permeable membrane that hardly permeates air, hardly causes an aerobic reaction at the anode, and can improve power generation reaction efficiency.

  The ion-permeable membrane is in contact with a liquid containing microorganisms and an electron donor held in the negative electrode chamber, and is hydrophilic (easy to wet with water, water droplets) in order to efficiently transmit ions in the liquid to the air cathode. It is desirable to have For example, paper, woven fabric, or non-woven fabric made of a material having a water contact angle of 90 ° or less, such as polyolefin, glass, or silica, or a film (paper, woven fabric, or non-woven fabric) surface-treated with the above material is preferable.

  Specific examples of non-conductive materials constituting paper, woven fabric, and non-woven fabric include polyethylene, polypropylene, polycarbonate, polyethersulfone (PES), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), Polyvinyl alcohol (PVA), cellulose, cellulose acetate and the like are suitable. In order to facilitate the permeation of protons, the ion-permeable non-conductive membrane is preferably as thin as 10 μm to 1000 μm, particularly about 25 to 100 μm.

  Next, in addition to the microorganisms and the negative electrode solution of the microbial power generation apparatus, suitable materials for 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 Gluconobacter, Pseudomonas, Xanthomonas, Vibrio, Comamonas and Proteus (Proteus
and vulgaris) bacteria, filamentous fungi, yeasts and the like. 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, when generating electricity in the respiratory system, the negative electrode side solution is bouillon medium, M9 medium, L medium, Malt.
A medium having a composition such as an energy source and nutrients necessary for carrying out respiratory metabolism such as Extract, MY medium, and nitrifying bacteria selection medium can be used. In addition, organic waste such as sewage, organic industrial wastewater, and garbage can be used.

  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 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 organic wastewater such as sewage and food factory effluent. 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 gas to be circulated in the positive electrode chamber is preferably air, but is not limited to this as long as it contains oxygen.

  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 contact with an ion-permeable non-conductive membrane directly or through a microbial layer, electrons generated by a microbial reaction can pass to the negative electrode without using an electron mediator. The electronic mediator can be dispensed with.

  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 40 mm, particularly about 5 to 20 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 preferably has a conductive substrate and an oxygen reduction catalyst supported on the conductive substrate.

  As the conductive base material, any material may be used as long as it has high electrical conductivity, high corrosion resistance, sufficient electrical conductivity and corrosion resistance even when the thickness is small, and further has mechanical strength as the conductive base material. However, graphite paper, graphite felt, graphite cloth, stainless mesh, titanium mesh, etc. can be used. Of these, graphite paper, graphite felt, graphite cloth, etc., particularly in terms of durability and ease of processing. A graphite-based substrate such as graphite is preferable, and graphite paper is particularly preferable. These graphite base materials may be those made hydrophobic by a fluororesin such as polytetrafluoroethylene (PTFE).

  The thickness of the conductive base material of the positive electrode is about 20 to 3000 μm because oxygen permeation is poor when it is too thick, and when it is too thin, the required properties such as strength required for the base material cannot be satisfied. Is preferred.

As the oxygen reduction catalyst, in addition to noble metals such as platinum, metal oxides such as manganese dioxide are preferred because they are inexpensive and have good catalytic activity, and the supported amount is 0.01 to 2.0 mg / it is preferable that the cm ^2.

  Hereinafter, examples and comparative examples will be described.

  In the following examples and comparative examples, microbial power generation devices having the following structures were used, and different ion permeable membranes were used.

<Structure of microbial power generation device>
A negative electrode was formed by stacking and filling two 1 cm thick graphite felts into a 7 cm × 25 cm × 2 cm (thickness) negative electrode chamber. A positive electrode chamber was formed on the negative electrode through an ion-permeable non-conductive film. The positive electrode chamber has a size of 7 cm × 25 cm × 0.5 cm (thickness), and is made of Pt catalyst (Pt-supported carbon black, Pt made by Tanaka Kikinzoku Co., Ltd.) on carbon paper (manufactured by Toray Industries, Inc.) having a thickness of 160 μm that has been subjected to water repellent treatment with PTFE. A solution in which a content of 50% by weight) is dispersed in a 5% by weight Nafion (registered trademark) solution (manufactured by DuPont) is applied so that the adhesion amount is 0.4 mg / cm ² and dried at 50 ° C. The obtained product was used as a positive electrode and adhered to the film. A stainless steel wire was bonded to the negative electrode graphite felt and the positive electrode carbon paper with a conductive paste to form an electrical lead wire and connected with a resistance of 2Ω.

  Through the negative electrode chamber, the pH was maintained at 7.5, and a negative electrode solution containing 1,000 mg / L of acetic acid, phosphoric acid and ammonia was passed. This negative electrode solution was previously heated to 35 ° C. in a separate water tank, and then passed through the negative electrode chamber at 10 mL / min, whereby the temperature of the negative electrode chamber was heated to 35 ° C. Prior to passing the negative electrode solution, the effluent of another microbial power generation device was passed as an inoculum. Room temperature air was vented to the positive electrode chamber at a flow rate of 0.5 L / min.

  As an ion-permeable non-conductive film, the Gurley value is 80 sec / 100 mL (Comparative Example 1), 600 sec / 100 mL (Comparative Example 2), 1200 sec / 100 mL (Example 1), or 4500 sec / 100 mL (Example 2) as follows. 4 series using polyolefin (polypropylene) non-woven fabric (thickness 30 to 40 μm) was operated for 1 month each. The results were as follows.

[Comparative Example 1] (Gurley value 80 sec / 100 mL)
No increase in power generation was observed immediately after the start of the flow of the negative electrode solution, and the power generation per 1 m ^{3 of the} negative electrode chamber was 0.2 to 0.5 W (0.2 to 0.5 W / m ³ ) for one month. It changed in.

[Comparative Example 2] (Gurley value 600 sec / 100 mL)
Although the amount of power generation increased from the start of the flow of the negative electrode solution, it reached a peak when it reached 30 W / m ³ after 5 days, and remained at around 10 W / m ³ after 10 days.

[Example 1] (Gurley value 1,200 sec / 100 mL)
Power generation from liquid passing the start of the anode solution is raised, after reaching a 200 W / ^{m 3} after 5 days, for about 2 weeks, remained 170~210W / ^{m 3,} a 1 month later be 150 W / ^{m 3} Was maintained.

[Example 2] (Gurley value 4,500 sec / 100 mL)
Power generation from liquid passing the start of the anode solution is raised, after reaching a 180 W / ^{m 3} after 7 days, were stable and remained until after one month 160~180W / ^{m 3.}

  From the above, it was confirmed that a high power generation amount was stably maintained over a long period of time by using a nonwoven fabric having a Gurley value of 1,000 sec / 100 mL or more.

DESCRIPTION OF SYMBOLS 1 Tank 2 Ion permeable nonelectroconductive film | membrane 3 Positive electrode chamber 4 Negative electrode chamber 5 Positive electrode 6 Negative electrode

Claims (2)

A negative electrode chamber having a negative electrode and holding a liquid containing a microorganism and an electron donor is separated from the negative electrode chamber via an ion-permeable non-conductive film, and is in contact with the ion-permeable non-conductive film in a microorganism power generator and a positive electrode chamber having an air cathode, wherein the ion-permeable non-conductive membrane Gurley value 1,000 sec / 100 mL or more hydrophilic non-conductive film der is, the ion-permeable non-conductive The microorganism power generation apparatus , wherein the membrane is paper, woven fabric, or nonwoven fabric made of a non-conductive substance . A microbial power generation method using the microbial power generation apparatus according to claim 1, wherein oxygen permeation from a positive electrode chamber to a negative electrode chamber is suppressed by the ion-permeable non-conductive film having a Gurley value of 1,000 sec / 100 mL or more. Microbial power generation method.

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