WO2010024577A2 - Floating-anode microbial fuel cell with thin-layer horizontal flow - Google Patents

Abstract

The present invention relates to a floating-anode microbial fuel cell. More specifically, the present invention relates to a microbial fuel cell having an anaerobic unit, an electrode unit and an outflow unit. In this microbial fuel cell, the electrode unit includes an anode disposed to float horizontally on surface water and a cathode provided horizontally at the bottom of a cathode-reaction tank, and a separating layer for separating the cathode and the anode. The microbial fuel cell is characterised in that the cathode is immersed in, by way of example, a liquid substance containing organic matter and sewage or waste water flowing in a thin fashion horizontally in an anaerobic state, and the anode is formed in such a way that it floats horizontally on the water surface with one of its surfaces in contact with an air layer, while the other surface is in contact with the water layer on the water surface. The microbial fuel cell according to the present invention is advantageous in that it can continuously produce electric power with a high yield from the liquid substance containing organic matter such as sewage or waste water, and it allows the organic matter to be stabilised.

Description

Sleep Floating Anode Microbial Fuel Cell with Thin Horizontal Flow

The present invention is to stabilize the liquid substances containing organic matter, such as sewage, wastewater, etc., and at the same time to obtain a high yield of continuous power therefrom, the anode, water surface immersed in the anaerobic part, wastewater flowing horizontally thin in the anaerobic state It relates to a surface portion positive electrode microbial fuel cell having a horizontal flow of a positive electrode floating in the, the electrode portion consisting of a separation layer of the negative electrode and the positive electrode, and the outlet portion.

A microbial fuel cell is a device that directly converts chemical energy contained in organic matter into electrical energy using microorganisms. In general, a microbial fuel cell has an anaerobic cathode reaction tank carrying a cathode and an anode and anode reactor carrying an electron acceptor or oxidant such as oxygen, an electrolyte and a separation layer between the anode and the cathode, and an external circuit connecting the cathode and the anode. It consists of a load connected to a circuit.

In general, the anode uses carbon materials such as graphite, which have good electrical conductivity and are not oxidized. The anode uses graphite loaded with a catalyst such as platinum or the like to grow microorganisms in graphite felt without catalyst. It has also been reported to use bioanodes that allow microorganisms to act as catalysts. In addition, expensive proton exchange membranes have been used in the separation layer to minimize oxygen diffusion from the anode to the cathode and to selectively transfer only protons from the cathode to the anode.

In microbial fuel cells, liquid materials such as wastewater containing organic matter are usually injected into an anaerobic cathodic reactor, where microorganisms decompose organic matter to produce electrons and protons. At this time, most of the microorganisms in the cathode reaction tank are electrochemically active, and transfer the produced electrons to the cathode. The electrons transferred to the cathode move to the anode through a circuit connected to the cathode, and in this process, electrical energy can be recovered from a load directly connected to an external circuit. On the other hand, protons generated by the decomposition of organic matter by microorganisms move directly to the anode through the electrolyte and separation layer between the anode and the cathode, and react with electron acceptors such as oxygen, iron, and iron cyanide, which are transferred through the circuit at the anode. Water is produced to complete the reaction.

In a microbial fuel cell for wastewater treatment, the injected wastewater becomes an electrolyte. Below is an example of a reaction occurring in a conventional microbial fuel cell using oxygen as an electron acceptor.

Cathode reaction: organic matter -> E (e ^-) + proton (H ⁺⁾ + carbon dioxide (CO ₂₎

Anode reaction: electron (e ^-) + proton (H ⁺⁾ + oxygen (O ₂₎ -> water (H ₂ O)

The performance of microbial fuel cells is typically i) decomposition of organics by microorganisms at the negative electrode and generation of electrons and protons, ii) transfer of electrons generated at the negative electrode, iii) transfer of protons to the positive electrode through the electrolyte and proton exchange membranes. And iv) water production by the reaction of protons, electrons and oxygen at the anode and the shape of the microbial fuel cell that directly affects these factors.

Therefore, researches on the shape design of the microbial fuel cell have been conducted along with the study of the above factors affecting the performance in order to improve the performance of the microbial fuel cell.

In the past, much research has been conducted on the anode reactor using a liquid phase reaction tank carrying an electron acceptor such as oxygen and iron hexacyanide.However, Liu et al. (2004) used microbial fuels by using an air anode that directly exposes the anode to air. It is reported that the performance of the battery can be improved. The use of an air anode allows the anode reactor to be omitted, thereby increasing the power yield per unit volume. Jang et al. (2004) proposed a microbial fuel cell that does not require a proton exchange membrane to facilitate the transfer of protons from the cathode to the anode. In addition, Cheng et al. (2006) control the price between the anode and the anode in a microbial fuel cell that does not use a proton exchange membrane to minimize the oxygen diffused to the cathode and facilitate the transfer of protons from the cathode to the anode to facilitate the It is reported that the efficiency can be improved.

However, the efficiency of the microbial fuel cell has been steadily improved by improving the material of the parts constituting the microbial fuel cell, such as a positive electrode and a negative electrode.

The preferred shape of the microbial fuel cell should not only be able to continuously maintain high performance for a long time in power generation and stabilization of organic matter, but also should be easy to maintain and scale up and easily applicable to large-scale wastewater treatment sites.

The shape design studies of microbial fuel cells have been traditionally conducted by batch experiments centered on dual chamber microbial fuel cells, which consist of a cathode reactor and a cathode reactor. Research on single reactor microbial fuel cells is being actively conducted. This is because a single reactor microbial fuel cell using an air anode is easy to continuously inject and operate wastewater, and has a relatively easy to practical use compared to the above double reactor microbial fuel cell.

Meanwhile, the air cathode single reactor microbial fuel cell, which has been mainly studied, is a tubular or plate-shaped vertical type, in which a cathode is used as a structure filled with electrode material, and a tubular or plate-shaped vertical wall structure exposed to air is used as an anode. Form (Cheng et al. 2006; You et al., 2007). In the above case, since the hydrostatic pressure of the liquid material (electrolyte) such as wastewater in the cathode reaction tank is transmitted to the anode as it is, a leakage phenomenon occurs in which the liquid material leaks into the anode exposed to air. In addition, Kim et al. (2007) report that there is a problem that the efficiency of the anode gradually decreases during long time operation because cations other than protons diffuse into the anode and form crystals by combining with carbonates on the surface of the anode. Therefore, vertical single reactor microbial fuel cells using air anodes have been used to waterproof the anode surface or bond a cation exchange membrane to the anode to prevent leakage (Cheng et al., 2006; Pham et al., 2005). .

However, in the vertical air cathode single reactor microbial fuel cell, the efficiency of the anode due to leakage and crystals formed on the surface of the anode could not be fundamentally solved, and it was difficult to dismantle for long time operation, repair, or cleaning. There were a lot. In addition, another problem of the air anode single reactor microbial fuel cell that has been studied in the past is that it is difficult to control the oxygen diffusion from the anode to the cathode has a limit in improving the power yield.

Accordingly, the present invention is to solve the problems of the prior art as described above, in the present invention, flexible, vertical air to easily apply the results of research on the various influence factors and materials on the performance of the microbial fuel cell It is easy to maintain and improve efficiency by controlling the shortcomings such as leakage phenomenon and crystal formation that occur in air anode of positive electrode microbial fuel cell, and it can maximize the efficiency by controlling oxygen diffused from air cathode to cathode, and easily scale up wastewater It is an object of the present invention to provide a microbial fuel cell capable of producing a high yield of electric power while being able to efficiently and continuously process organic-containing liquid materials in a continuous and semi-continuous manner.

As an example for achieving the above object, the microbial fuel cell of the present invention, the negative electrode is maintained in the anaerobic state, the negative electrode is horizontally immersed in the lower end of the negative electrode reaction tank, the negative electrode is formed on the upper end of the negative electrode A separation layer formed of a water layer so as to be spaced apart from the, and is formed on the upper end of the separation layer and an electrode portion including one side of the electrode comprising an anode forming a floating state in the horizontal direction in contact with the air layer.

Prior to this, terms or words used in the specification and claims should not be construed as having a conventional or dictionary meaning, and the inventors should properly explain the concept of terms in order to best explain their own invention. Based on the principle that can be defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention.

Therefore, the embodiments described in the specification and the configuration shown in the drawings are only the most preferred embodiment of the present invention, and do not represent all of the technical idea of the present invention, these can be replaced at the time of the present application It should be understood that there may be various equivalents and variations.

Hereinafter, the sleep-floating positive electrode microbial fuel cell of the present invention (hereinafter referred to as "microbial fuel cell") will be described in detail with reference to the drawings. The microbial fuel cell 1 of the present invention includes an anaerobic part 10 and an electrode. It consists of a part 20 and the outlet part 30. 1 to 3 is a longitudinal cross-sectional view of the microbial fuel cell of the present invention, the name of each part is as follows.

(10) anaerobic department; (20) electrode portions; 30 outlet; (22) a cathode; (23) a cathode reactor; (21) an anode; (25) microbial anodes; (W) separation layer; (24) separators; (26) Dividers and other weirs, loads, and circuits

The anaerobic part 10 is positioned at the front end of the electrode part 20 and serves to reduce dissolved oxygen and oxides such as sewage, wastewater, and liquid waste flowing into the electrode part 20, and the outlet part 30. Is located at the rear end of the electrode unit 20 is a passage through which the effluent flowing out of the electrode unit 20 is discharged.

That is, liquid substances containing organic substances, such as sewage, wastewater and liquid waste, are introduced into the anaerobic unit 10 to remove dissolved oxygen contained in the inflow wastewater. The anaerobic section 10 aims to reduce the dissolved oxygen contained in the influent wastewater as much as possible. The anaerobic biofilter or air allows the microorganisms to grow on the surface of the media without supplying air after filling the media. A biological method of removing dissolved oxygen contained in the influent wastewater by growing suspended microorganisms without supply is advantageous in terms of cost.

On the other hand, the dissolved oxygen of the influent wastewater may be a chemical method using a reducing agent or a physical degassing method of blowing inert gas such as nitrogen.

In addition, the anaerobic portion 10 may be omitted when the temperature of the liquid substance containing the organic material is 30 degrees Celsius (° C.) or more or the concentration of dissolved oxygen is lower than 2 mg / L. However, in the electrode portion the influent nitrate ion (NO ₃ ^-) when the oxides such as sulfate ion (SO ₄ ^-2), ferric (Fe ⁺³⁾ contained because it may degrade the performance of a microbial fuel cell an anaerobic It is advantageous to remove these substances from the anaerobic section 10 which are operated in the state. The outflow water of the anaerobic part 10 is equally distributed and introduced into the cathode reaction tank 23 through the distributor 26 installed at the inlet of the cathode reaction tank 23 of the electrode part 20.

The electrode unit 20 includes a cathode reaction tank 23 in which a thin plate-shaped cathode 22 is horizontally installed on the bottom of the sealed electrode unit 20 so as not to be exposed to air, and immersed in a liquid material containing an anaerobic organic substance. The cathode 21 and the cathode 22 includes a separation layer (W) to be spaced apart at a predetermined distance on the cathode, the separation layer (W) is such that the protons generated in the cathode 22 is transferred to the anode 21 The electrolyte is usually composed of a water layer. An anode 23 is formed on the upper surface of the separation layer W. The anode 21 is configured to float on the surface in the horizontal direction so that one side thereof is directly exposed to air. The inlet of the cathode reactor 23 includes a distributor 26 for evenly distributing the effluent of the anaerobic portion 10 to the cathode reactor (23).

The outlet 30 has a structure for evenly discharging the effluent passing through the cathode reaction tank 23 of the electrode 20, such as a wear.

The negative electrode 22 of the microbial fuel cell according to the present invention should be a thin film within several centimeters (cm), which should be small in resistance, resistant to oxidation, and capable of providing a large specific surface area. Preferred cathodes 22 have a thickness of 0.01 to 5 millimeters (mm). This is for efficient electron transfer generated by decomposition of organic materials. Preferably, graphite or carbon materials having a large specific surface area, such as graphite felt and porous carbon fibers, may be used. As the material of the cathode 22, graphite or other carbon material carrying a catalyst material such as tungsten may be used to promote electron transfer by microorganisms. Separation layer (W) on the upper side of the cathode 22 is to prevent the short circuit by separating the cathode 22 and the anode 21, and should not interfere with the transfer of protons from the cathode 22 to the anode 21 as much as possible, It should be possible to minimize the diffusion of oxygen from the anode 21 to the cathode 22.

The separation layer (W) is usually composed of a water layer, and may be additionally inserted into the separation plate 24 as necessary. As the separator 24, a nonwoven fabric made of a polymer material such as polypropylene, polyethylene, polyvinyl alcohol, etc. may be used in addition to the expensive cation exchange membrane commonly used. However, when the distance between the cathode 22 and the anode 21 is 1 centimeter (cm) or more, the separation plate 24 in the separation layer W may be omitted.

The anode 21 provided on the water surface above the separation layer W may use a carbon material such as graphite fabric, graphite paper, graphite felt, or RVC at the cathode. At this time, one side of the anode 21 is in contact with the water surface and the other side is installed to float in the horizontal direction to be in direct contact with the air. At this time, it is preferable to carry a catalyst such as platinum on the surface of the anode 21 in contact with the water surface, and the surface directly in contact with a gaseous phase such as air from the air 21 in the air. There may be an air diffusion layer made of Teflon or similar material to control the amount of oxygen supplied to the system.

When using a porous carbon material that does not support platinum as the anode 21 provided on the separation layer (W), it is preferable to keep the anode in a wet state. At this time, the electrode made of a carbon material such as porous graphite is used as the anode on the water layer and the contact surface of the anode is maintained in a wet state, and the microbial membrane layer is attached to the microorganism attached and grown, the reaction of the anode 21 to the microorganism It serves as a microbial anode 25 promoted by, and also has the effect of blocking oxygen diffused from the anode to the cathode. Preferably, the microbial anode 25 made of a porous carbon material and the platinum-supported anode 21 which are kept in a wet state are installed at the same time in order on the separation layer.

On the other hand, the negative electrode reaction tank 23 carrying the negative electrode 22 is preferably to have a rectangular shape longer in the longitudinal direction than the wide direction, the liquid material containing organic matter, such as waste water is a thin layer of the negative electrode reaction tank (23) The nature of the flow during passage has a strong plug flow mode.

The inflow liquid material introduced into the cathode reaction tank 23 is decomposed by the microorganisms attached to the anode 22 while horizontally flowing through the thin layered anode reaction vessel 23 to generate electrons and protons. The electrons move to the anode 21 through a circuit in which a load such as a resistor is connected in series, and the protons move to the upper anode 21 through the separation layer W. In the anode 21, electrons, protons, and oxygen diffused from the air react to form water. Power is then recovered from the load connected to the circuit.

As described above of the present invention, the wastewater that has passed through the anaerobic part 10 for removing dissolved oxygen contained in the inflow wastewater and the distributor 26 for uniformly supplying the inflow wastewater to the electrode portion 20 is a cathode of the thin layer. Passes horizontally through the cathode reaction tank of the electrode portion 20 consisting of the reaction vessel 23 and the cathode 22, and the separation layer (W) and the surface-floating air anode 21, consisting of the outlet portion 30 of the weir structure It provides a method for producing electricity from the chemical energy inherent in organic materials using a microbial fuel cell system characterized in that the stabilization treatment of the liquid containing organic materials.

The organic matter content of the organic matter-containing liquid substance that can be treated by the sleep-rich bipolar microbial fuel cell according to the present invention is not limited, but when the organic matter content is higher than 10,000 mg / L based on the chemical oxygen demand, the power yield is generated due to excessive hydrogen generation. This may decrease. In this case, special operating methods such as effluent recirculation are necessary. The hydraulic residence time of the influent wastewater to the cathode reactor 23 is a function of the organic matter content contained in the influent wastewater, typically 0.1 to 48 hours. If the chemical oxygen demand of the influent wastewater is about 150 mg / L, it is preferably 0.2 to 6.0 hours.

The surface-floating air cathode microbial fuel cell having a thin horizontal flow according to the present invention can be stacked in order to connect a plurality of cells in series and in parallel in order to achieve large power production and water quality of treated water meeting the effluent standard.

As described above, according to the present invention, when the wastewater is treated by using the surface floating anode anode microbial fuel cell system having a horizontal flow of thin layers, it is possible to achieve high organic matter treatment efficiency and high power yield.

In addition, the surface floating bipolar microbial fuel cell system having a thin horizontal flow according to the present invention is capable of continuous or semi-continuous operation without reducing power yield for a long time, and is easy to maintain and maintain without a problem such as leakage during operation. Do.

In addition, the surface-floating positive electrode microbial fuel cell having a thin layer horizontal flow according to the present invention can achieve a high yield of power and the quality of treated water meeting effluent standards by connecting a plurality of stacked and connected in series.

1 to 3 are longitudinal cross-sectional views of the surface-floating anode microbial fuel cell having a horizontal flow of the present invention.

[Name of main parts of drawing]

(10) anaerobic department; (20) electrode portions; 30 outlet; (22) a cathode; (23) a cathode reactor; (21) an anode; (25) microbial anodes; (W) separation layer; (24) separators; 26 dispensers

Hereinafter, the present invention will be described in detail with reference to Examples, but the scope of the present invention is not limited by these Examples.

Example 1

The surface-floating air cathode microbial fuel cell having a thin layer horizontal flow used in the embodiment of the present invention was composed of an anaerobic part, an electrode part, and an outlet part.

The anaerobic section was filled with porous ceramics and operated in the form of a biofiltration phase. The electrode section was a reactor with a width of 14 cm and a length of 47 cm and 0.5 cm, and was used as a cathode by installing a 0.2 cm thick graphite felt plate at the bottom thereof. The prepared graphite cloth was used as an anode. In addition, a polypropylene nonwoven fabric having a thin plate of chitosan and zeolite mixture was installed as a separator between the anode and the cathode. At this time, the anaerobic sludge was planted in the microbial fuel cell, and artificial wastewater prepared using glucose was continuously injected at a hydraulic residence time of 1 hour and operated at room temperature of 20 to 22 degrees Celsius. The COD of the artificial wastewater was about 172 mg / L, with a salinity of 13% and a pH of 7.81.

In the microbial fuel cell according to the present invention, the COD removal rate was about 43.2%, the maximum voltage and current were 0.287V and 49mA, and the power yield per unit surface area of the negative electrode was 213mW / ㎡ ^2, and 42.8W / m ³ per unit volume.

Example 2

In the floating anode microbial fuel cell having a thin layer horizontal flow of the present invention having the same specifications as in Example 1, the membrane was used as a polypropylene nonwoven fabric, and the outer surface of the anode was thinly coated with Teflon to form an air diffusion layer. The same artificial wastewater as in Example 1 was operated under the same conditions. At this time, the COD removal rate was about 42.5%, which was not significantly different from that of Example 1, but the maximum voltage and current were 0.324V and 64.5mA. Compared with Example 1, the yield was higher.

Example 3

In the floating anode microbial fuel cell having a thin layer horizontal flow of the present invention having the same specifications as in Example 1, a polypropylene nonwoven fabric was used as a separator, and a graphite felt having a thickness of about 2 millimeters (mm) was placed on the separator layer. It was installed and kept in a wet state and used as a microbial anode. The platinum coated part of the platinum coated carbon fabric anode was installed on the upper side so as to be in contact with the microbial anode and the other side was in contact with the atmosphere. The prepared microbial fuel cell was operated under the same conditions with the same artificial wastewater as in Example 1. At this time, the COD removal rate was about 45%, which was slightly increased from Examples 1 to 2. The maximum voltage and current were 0.36V and 68mA, and the power yield per unit surface area of the cathode was 372 mW / m 2, and 74.4 W / m 3 per unit volume, which was higher than those in Examples 1 to 2.

[references]

Liu, H. and B.E. Logan, "Electricity generation using an air-cathode single chamber microbial fuel cell in the presence and absence of a proton exchange membrane", Environ. Sci. Technol., 38 (14), 4040-4046 (2004).

Jang, JK, TH Pham, IS Chang, KH Kang, H. Moon, KS Cho and BH Kim, "Construction and operation of a novel mediator- and membrane-less microbial fuel cell", Process Biochem, 39, 1007-1012 ( 2004).

Cheng, S., H. Liu, B.E. Logan, "Increased Power Generation in a Continuous Flow MFC with Advective Flow through the Porous Anode and Reduced Electrode, Spacing", Environ. Sci. Technol. 40, 2426-2432 (2006).

Kim, B.H., I. S. Chang and G. M. Gadd, “Challenges in microbial fuel cell development and operation”, Appl. Microbiol. Biotechnol, 76, 485-494 (2007).

Pham, T. H., J. K. Jang, H. Moon I. S. Chang, B. H. Kim, “Improved performance of a microbial fuel cell using a membrane-electrode assembly”, J. Microbiol. Biotechnol. 15, 438-441 (2005).

You, S., Q. Zhao, J. Zhang, J. Jiang, C. Wan, M. Du, and S. Zhao, “A graphite-granule membrane-less tubular air-cathode microbial fuel cell for power generation under continuously operational conditions (Short Communication) ”, J. Power Sources, 173, 172-177 (2007).

Claims (7)

1. A negative electrode reactor maintained in an anaerobic state, a negative electrode immersed in a horizontal direction at a lower end of the negative electrode reactor, a separation layer formed at an upper end of the negative electrode and separated from the anode by a water layer, and formed at an upper end of the separation layer; One side of the microbial fuel cell comprising an electrode portion comprising an anode in contact with the air layer to form a floating state in the horizontal direction on the water surface.
2. The method according to claim 1,

   Located in the front of the electrode portion includes an anaerobic portion to reduce the dissolved oxygen and oxides of sewage, wastewater and liquid waste flowing into the electrode portion, and an outlet portion located in the rear end of the electrode portion discharged from the electrode portion is discharged Microbial fuel cell characterized in that.
3. The method according to claim 1,

   The anode is a microbial fuel cell, characterized in that the air diffusion layer is formed on the contact surface with the air layer, the catalyst layer is supported on the water layer and the contact surface.
4. The method according to claim 1,

   The microbial fuel cell, characterized in that the porous layer of the microbial anode membrane is attached to the water layer and the contact surface of the positive electrode is kept wet and attached to the microorganism.
5. The method according to claim 1,

   The separation layer is a microbial fuel cell, characterized in that the cation exchange membrane is added between the layer of the positive electrode and the negative electrode
6. The method according to claim 1,

   Inflow water flowing into the electrode unit is characterized in that the microbial fuel cell is characterized in that it is controlled to flow in the horizontal reaction vessel.
7. A method for stabilizing liquid materials containing sewage, waste water and organic materials and producing electricity using the microbial fuel cell according to any one of claims 1 to 6.

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