Application of microbial electrochemical coupling anaerobic reaction to enhance biological methane synthesis in carbon neutralization

Abstract

The application discloses application of microbial electrochemical coupling anaerobic reaction reinforced biological methane synthesis in carbon neutralization. A microbial electrolysis cell is composed of an anode chamber, a cathode chamber and a proton exchange membrane, the anode chamber and the cathode chamber are connected through the proton exchange membrane, a mixed solution of sewage, ionic liquid and a solution of first methanogenic microorganisms is used as a substrate in the anode chamber, a mixed solution of culture medium, ionic liquid and a solution of second methanogenic microorganisms is used as a substrate in the cathode chamber, under the action of an external power source, the sewage in the anode chamber is degraded to generate electrons and H + , H + CO2 in the cathode chamber is converted into methane under the action of microorganisms; the first ionic liquid or the second ionic liquid is an amino acid anion type ionic liquid. The microbial electrolysis cell is convenient to operate and maintain and has a small floor area.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of biofuel cell technology, in particular to the application of microbial electrochemical coupling anaerobic reaction to strengthen biological methane synthesis in carbon neutralization. BACKGROUND

[0002] Environmental safety is the focus of global attention at present, and greenhouse effect is one of the problems to be solved urgently. CO2, as a main greenhouse gas, can also be regarded as a valuable C-containing resource. Around the recovery and utilization of CO2, the establishment of an efficient artificial carbon cycle, the transformation of energy development mode, and the acceleration of renewable energy alternative technology development will help to solve the environmental and energy problems at the same time, so as to realize green and sustainable development in the new era. Microbial electrolysis cell (MEC) is a new bioelectrocatalysis technology, which can reduce CO2 to produce high value-added chemicals such as acetic acid and methane under normal temperature and pressure. Among them, CO2 bioelectromethanation is considered as an ideal artificial carbon neutralization method because of the high calorific value of methane and the mature and widespread application technology. However, the cathode of this technology is widely used, but the anode is not well utilized, resulting in waste of energy. At the same time, there are still many problems to be solved in this technology, such as low methane yield, long start-up time due to slow biofilm formation, and unclear interface electron transfer molecular mechanism. Ionic liquids have a wide application in carbon capture, but they are mostly used in traditional fuel cells and have not been combined with microorganisms. SUMMARY

[0003] In order to overcome the above-mentioned problems existing in the prior art, the present application provides the application of microbial electrochemical coupling anaerobic reaction to strengthen biological methane synthesis in carbon neutralization, which designs a methanogenic microbial electrolysis cell capable of utilizing the anode and the cathode at the same time, and adds ionic liquid of affinity microorganism to improve the methanogenic rate.

[0004] The present application provides a microbial electrolysis cell, which is composed of an anode chamber, a cathode chamber and an exchange membrane. The anode chamber and the cathode chamber are connected by a proton exchange membrane. A mixed solution of sewage, a first ionic liquid and a first methanogenic microbial solution is used as a substrate in the anode chamber. A mixed solution of culture medium, a second ionic liquid and a second methanogenic microbial solution is used as a substrate in the cathode chamber. Under the action of an external power source, electrons and H + , H + CO2 in the cathode chamber is converted to methane under the action of microorganisms. The first ionic liquid or the second ionic liquid is an amino acid anion type ionic liquid. The exchange membrane in the present application is a proton exchange membrane or an ion exchange membrane.

[0005] Preferably, the amino acid anion ionic liquid is tetraethylammonium glycine, the structural diagram of which is shown as Figure 1 Preferably, the concentration of the first ionic liquid in the substrate of the anode chamber is 8-12 mmol / L, and the concentration of the second ionic liquid in the substrate of the cathode chamber is 8-12 mmol / L. Further preferably, the concentration of the first ionic liquid in the substrate of the anode chamber is 10 mmol / L, and the concentration of the second ionic liquid in the substrate of the cathode chamber is 10 mmol / L.

[0006] Preferably, the volume ratio of the wastewater and the first methanogenic microorganism solution in the substrate of the anode chamber is 8-12:1, and the volume ratio of the culture medium and the second methanogenic microorganism solution in the substrate of the cathode chamber is 8-12:1. The methanogenic microorganism in the cathode chamber and the anode chamber is hydrogenophilic methanogen, which refers to methanogen capable of using H2 and / or CO2 as nutrition, and the hydrogenophilic methanogen is domesticated and incubated by the microbial electrolysis cell system provided in the application.

[0007] The culture medium comprises organic nitrogen source yeast extract and peptone, and the COD carbon concentration is removed, preferably with C / N maintained at 10 or more, the pH value of the culture medium solution is 8.0±0.2, and 100 mM of dipeptide is used as a buffer salt in the culture medium solution; the culture medium solution needs to be pre-sterilized by oxygen removal before being placed in the cathode chamber. In the application, the process of oxygen removal sterilization is preferably that the culture medium solution is aerated for 30 min under high-purity nitrogen, and then sterilized at 121℃ for 20 min by using a high-pressure steam sterilization pot.

[0008] Preferably, the first methanogenic microorganism solution or the second methanogenic microorganism solution is obtained by domesticating the wastewater combined with the electrolysis cell, and is specifically obtained by the following steps: the anode chamber and the cathode chamber are connected by an exchange membrane, a mixed solution of wastewater, culture medium, a third ionic liquid and first anaerobic sludge is used as the substrate in the anode chamber, carbon dioxide is used as the only carbon source in the cathode chamber, a fourth ionic liquid and second anaerobic sludge are used as the substrate, and the microorganism is domesticated under the action of an external power source until a stable efficiency is reached, to obtain a hydrogenophilic methanogenic microorganism solution.

[0009] Further preferably, the volume fraction of the first anaerobic sludge in the substrate of the anode chamber is 8%-12%, and the voltage of the external power source is -0.6 V. Still further preferably, the volume fraction of the first anaerobic sludge in the substrate of the anode chamber is 10%.

[0010] Further preferably, the third ionic liquid or the fourth ionic liquid is an amino acid anion type ionic liquid, the concentration of the third ionic liquid in the substrate of the anode chamber is 8-12 mmol / L, and the concentration of the fourth ionic liquid in the substrate of the cathode chamber is 8-12 mmol / L. Still further preferably, the concentration of the third ionic liquid in the substrate of the anode chamber is 10 mmol / L, and the concentration of the fourth ionic liquid in the substrate of the cathode chamber is 10 mmol / L.

[0011] Preferably, the voltage of the external power source is -0.6 V.

[0012] Preferably, the anode is carbon cloth, and the cathode is carbon brush.

[0013] Preferably, the domestic sewage is wastewater with COD to be degraded, i.e., the concentration of COD in the domestic sewage is more than 1000 mg / L.

[0014] The application also protects the application of the microbial electrochemical coupling anaerobic reaction reinforced biological methane synthesis in carbon neutralization, in which carbon cloth is used as the anode, carbon brush is used as the cathode, the cathode and the anode are connected through an exchange membrane, the anode uses sewage, a first methanogenic microorganism solution and a solution containing a first ionic liquid as the substrate; the cathode uses a culture medium, a second methanogenic microorganism solution and a solution containing a second ionic liquid as the substrate, CO2 is the only carbon source of the cathode, under the action of an external power source, the anode degrades the sewage to generate electrons and H + , H + The CO2 is converted into methane by the cathode microorganism under the action of the cathode microorganism.

[0015] Compared with the prior art, the application has the following advantages:

[0016] 1. The application fully utilizes the anode chamber and the cathode chamber of the double-chamber electrolytic cell, and does not cause energy waste compared with the traditional double-chamber microbial electrolytic cell.

[0017] 2. The application effectively improves the methane production and the COD degradation rate of the microbial electrolytic cell system by adding ionic liquids.

[0018] 3. The microbial electrolytic cell proposed in the application is easy to operate and maintain, and has a small footprint. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The structural formula of the ionic liquid in Example 1 is shown in the figure.

[0020] Figure 2 The structural schematic diagram of the microbial electrolytic cell proposed in the application is shown in the figure.

[0021] Reference signs: 1, microbial electrolysis cell; 2, carbon cloth; 3, proton exchange membrane; 4, electrochemical workstation; 5, gas outlet rubber tube; 6, gas chromatograph; 7, carbon brush; 8, methanogenic microbial solution; 9, feeding port; 10, gas inlet. DETAILED DESCRIPTION

[0022] The following examples are further illustrations of the present application and are not intended to limit the present application.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present application. Unless otherwise specified, the experimental materials and reagents used herein are commercially available products commonly used in the art. The exchange membrane proposed in the present application is a proton exchange membrane or an ion exchange membrane. In the following examples, the exchange membrane is preferably a proton exchange membrane.

[0024] As shown in Figure 2 , the microbial electrolysis cell 1 is composed of an anode chamber, a cathode chamber and a proton exchange membrane 3. The anode chamber and the cathode chamber are connected by the proton exchange membrane 3. The mixed solution of sewage, the first ionic liquid and the methanogenic microbial solution 8 is used as the substrate (i.e. the anode electrolyte) in the anode chamber. The anode is placed in the substrate of the anode chamber. The mixed solution of culture medium, the second ionic liquid and the methanogenic microbial solution 8 is used as the substrate (i.e. the cathode electrolyte) in the cathode chamber. The cathode is placed in the substrate of the cathode chamber. The anode and the cathode are connected by the electrochemical workstation 4. The sewage, the first ionic liquid and the methanogenic microbial solution enter the anode chamber through the feeding port 9. The culture medium, the second ionic liquid and the methanogenic microbial solution enter the cathode chamber through the feeding port of the cathode chamber. Under the action of an external power source, electrons and H + , H + enter the cathode chamber through the proton exchange membrane. CO2 is introduced into the cathode chamber through the gas inlet 10. Under the action of microorganisms in the cathode chamber, CO2 is converted into methane. Methane is discharged through the gas outlet rubber tube 5 and detected by the gas chromatograph 6.

[0025] In the following examples, the volume ratio of sewage to methanogenic microbial solution in the substrate of the anode chamber is preferably 8-12:1. The volume ratio of culture medium to the second methanogenic microbial solution in the substrate of the cathode chamber is preferably 8-12:1. Further preferably, the volume ratio of sewage to methanogenic microbial solution in the substrate of the anode chamber is 10:1. The volume ratio of culture medium to the second methanogenic microbial solution in the substrate of the cathode chamber is 10:1.

[0026] In the following examples, the first ionic liquid or the second ionic liquid is preferably an amino acid anion type ionic liquid.

[0027] In the following examples, carbon cloth 2 is preferably used as the anode and carbon brush 7 is preferably used as the cathode.

[0028] In the following examples, the culture medium includes organic nitrogen sources of yeast extract and peptone, and the COD carbon concentration is removed, preferably with a C / N ratio of 10 or more, and the pH value of the culture medium solution is 8.0±0.2, and in the culture medium solution, a final concentration of 100 mM of diglycolide is used as a buffer salt; and the culture medium solution needs to be sterilized by oxygen removal before being placed in the cathode chamber. In the present application, the process of oxygen removal sterilization is preferably that the culture medium solution is aerated for 30 min under high-purity nitrogen, and then sterilized at 121°C for 20 min by using a high-pressure steam sterilization pot.

[0029] In the present application, the methanogenic microorganism is a hydrogenophilic methanogen, which is domesticated by the sewage treatment environment and the electrolytic cell proposed in the present application. The first methanogenic microorganism solution or the second methanogenic microorganism solution is obtained by domesticating sewage and an electrolytic cell, and is obtained by the following steps: the anode chamber and the cathode chamber are connected by an exchange film, a mixed solution of sewage, culture medium, third ionic liquid, and first anaerobic sludge is used as the substrate in the anode chamber, carbon dioxide is used as the only carbon source in the cathode chamber, fourth ionic liquid and second anaerobic sludge are used as the substrate, and under the action of an external power source, the microorganism is domesticated at room temperature until the stable efficiency is reached, and a hydrogenophilic methanogenic microorganism solution is obtained. The culture medium in the anode chamber substrate includes organic nitrogen sources of yeast extract and peptone, and the COD carbon concentration in the sewage is removed, so that the C / N ratio is maintained at 10 or more, and the addition amount of the sewage and the culture medium is not specifically limited, as long as the carbon-nitrogen ratio is maintained. The above-mentioned anaerobic sludge is collected in a sewage pool to be treated. The culture medium includes organic nitrogen sources of yeast extract and peptone, and the COD carbon concentration is removed, preferably with a C / N ratio of 10 or more, and the pH value of the culture medium solution is 8.0±0.2, and in the culture medium solution, a final concentration of 100 mM of diglycolide is used as a buffer salt; and the culture medium solution needs to be sterilized by oxygen removal before being placed in the cathode chamber. In the present application, the process of oxygen removal sterilization is preferably that the culture medium solution is aerated for 30 min under high-purity nitrogen, and then sterilized at 121°C for 20 min by using a high-pressure steam sterilization pot.

[0030] In the following examples, the volume fraction of the first anaerobic sludge in the substrate of the anode chamber is 8%-12%, and the voltage of the external power source is -0.6 V. Further preferably, the volume fraction of the first anaerobic sludge in the substrate of the anode chamber is 10%.

[0031] Preferably, in the following examples, the third ionic liquid or the fourth ionic liquid is an amino acid anion type ionic liquid, the concentration of the third ionic liquid in the substrate of the anode chamber is 8-12 mmol / L, and the concentration of the fourth ionic liquid in the substrate of the cathode chamber is 8-12 mmol / L. Further preferably, the concentration of the third ionic liquid in the substrate of the anode chamber is 10 mmol / L, and the concentration of the fourth ionic liquid in the substrate of the cathode chamber is 10 mmol / L.

[0032] Preferably, the hydrogenophilic methanogen is inoculated into the electrolyte in the cathode chamber in advance in the present application. The process of inoculating the hydrogenophilic methanogen into the electrolyte in the cathode chamber in advance is not particularly limited in the present application, and any process known to those skilled in the art can be used.

[0033] Example 1

[0034] The methanogenic microbial solution is obtained by domesticating the methanogenic microbial solution in the sewage combined electrolysis cell. Specifically, the methanogenic microbial solution is obtained by the following steps: connecting the anode chamber and the cathode chamber by a proton exchange membrane, using a mixture solution of sewage, culture medium, 10 mmol / L tetraethylammonium glycine and anaerobic sludge as the substrate in the anode chamber, using carbon dioxide as the only carbon source, 10 mmol / L tetraethylammonium glycine and anaerobic sludge as the substrate in the cathode chamber, domesticating the microorganism at room temperature under the action of an external power source until the stable efficiency is reached, and obtaining the hydrogenophilic methanogenic microbial solution. The culture medium in the anode chamber includes organic nitrogen source yeast extract and peptone, and the COD carbon concentration in the sewage is removed to maintain the C / N ratio above 10. The pH value of the culture medium solution is 8.0±0.2. In the culture medium solution, 100 mM dipeptide is used as the buffer salt. The culture medium solution needs to be pre-sterilized by oxygen removal before being placed in the cathode chamber. The process of oxygen removal sterilization is as follows: after the culture medium solution is aerated for 30 min under high-purity nitrogen, high-pressure steam sterilization pot is used for sterilization at 121°C for 20 min. In the anode chamber, the volume fraction of anaerobic sludge in the substrate of the anode chamber is 10%, and the voltage of the external power source is -0.6 V.

[0035] As shown in Figures 1-2 , the anode chamber uses the sewage with a COD concentration of 1200 mg / L, the above-prepared methanogenic microbial solution and 10 mmol / L tetraethylammonium glycine as the electron transfer enhancer, and the volume ratio of the sewage to the methanogenic microbial solution in the substrate is 10:1; the cathode chamber uses the culture medium, the above-prepared methanogenic microbial solution and 10 mmol / L tetraethylammonium glycine as the substrate, and the volume ratio of the culture medium to the methanogenic microbial solution in the substrate is 10:1, wherein CO2 is the only carbon source in the cathode. Under the action of an external power source of -0.6 V, the inhaled CO2 is converted into methane.

[0036] Comparative Example 1

[0037] The same as example 1, except that only the methanogenic microorganism solution and the wastewater were added, and the ionic liquid (tetraethylammonium glycine) was not added.

[0038] Comparative example 2:

[0039] The same as example 1, except that the methanogenic microorganism solution was not added, and only the ionic liquid (tetraethylammonium glycine) was added, at a concentration of 10 mmol / L.

[0040] The experimental data of example 1 and comparative examples 1-2 are shown in Table 1 below.

[0041] Table 1 CH4 production and COD degradation rate of different groups

[0042]

[0043] Example 2:

[0044] The same as example 1, except that the volume ratio of wastewater to methanogenic microorganism solution in the substrate of the anode chamber was 8:1, the volume ratio of culture medium to methanogenic microorganism solution in the substrate of the cathode chamber was 8:1, and the concentration of the ionic liquid in the anode chamber and the cathode chamber was 8 mmol / L.

[0045] Example 3:

[0046] The same as example 1, except that the volume ratio of wastewater to methanogenic microorganism solution in the substrate of the anode chamber was 12:1, the volume ratio of culture medium to methanogenic microorganism solution in the substrate of the cathode chamber was 12:1, and the concentration of the ionic liquid in the anode chamber and the cathode chamber was 12 mmol / L.

[0047] The above description of the examples is only to help understand the technical solutions of the present application and its core idea. It should be noted that for those skilled in the art, without departing from the principles of the present application, the present application can be improved and modified in several ways, and these improvements and modifications also fall within the scope of protection of the claims of the present application.

Claims

1. A method for enhancing biomethane synthesis through microbial electrochemical coupling of anaerobic reactions, characterized in that, It consists of an anode chamber, a cathode chamber, and an exchange membrane. The anode and cathode chambers are connected by the exchange membrane. The anode chamber uses a mixed solution of wastewater, a first ionic liquid, and a first methanogenic microorganism solution as the substrate, while the cathode chamber uses a mixed solution of culture medium, a second ionic liquid, and a second methanogenic microorganism solution as the substrate. Under the action of an external power source, the wastewater in the anode chamber is degraded to produce electrons and H₂. + H + CO2 enters the cathode chamber through the proton exchange membrane and is converted into methane by microorganisms in the cathode chamber; the first or second ionic liquid is an amino acid anionic ionic liquid.

2. The method according to claim 1, characterized in that, The amino acid anionic ionic liquid is tetraethylammonium glycine. The concentration of the first ionic liquid in the substrate of the anode chamber is 8-12 mmol / L, and the concentration of the second ionic liquid in the substrate of the cathode chamber is 8-12 mmol / L.

3. The method according to claim 1 or 2, characterized in that, The volume ratio of wastewater to the first methanogenic microorganism solution in the substrate of the anode chamber is 8-12:1; the volume ratio of culture medium to the second methanogenic microorganism solution in the substrate of the cathode chamber is 8-12:

1.

4. The method according to claim 1, characterized in that, The first or second methanogenic microbial solution is obtained through the following steps: the anode chamber and the cathode chamber are connected by an exchange membrane. In the anode chamber, a mixed solution of sewage, culture medium, third ionic liquid, and first anaerobic sludge is used as the substrate. In the cathode chamber, carbon dioxide is used as the sole carbon source, and a fourth ionic liquid and second anaerobic sludge are used as the substrate. The microorganisms are domesticated under the action of an external power source until a stable efficiency is reached, thus obtaining a hydrogenophilic methanogenic microbial solution. The third or fourth ionic liquid is an amino acid anionic ionic liquid.

5. The method according to claim 4, characterized in that, The first anaerobic sludge accounts for 8%-12% of the volume fraction of the substrate in the anode chamber, and the voltage of the external power supply is -0.6 V.

6. The method according to claim 4, characterized in that, The concentration of the third ionic liquid in the substrate of the anode chamber is 8-12 mmol / L, and the concentration of the fourth ionic liquid in the substrate of the cathode chamber is 8-12 mmol / L.

7. The method according to claim 1 or 2, characterized in that, The voltage of the external power supply is -0.6 V.

8. The method according to claim 1 or 2, characterized in that, The anode is carbon cloth, and the cathode is a carbon brush.

9. The method according to claim 1 or 2, characterized in that, Domestic sewage is wastewater that requires COD degradation.

10. Application of microbial electrochemical coupling anaerobic reaction to enhance biomethane synthesis in carbon neutralization, characterized in that, Using carbon cloth as the anode and carbon brush as the cathode, the anode and cathode are connected by an exchange membrane. The anode uses wastewater, a solution of the first methanogenic microorganism, and a solution containing the first ionic liquid as substrates; the cathode uses culture medium, a solution of the second methanogenic microorganism, and a solution containing the second ionic liquid as substrates. CO2 is the sole carbon source for the cathode. Under the action of an external power source, the anode degrades wastewater to produce electrons and H2. + H + The CO2 passes through the exchange membrane to the cathode, where it is converted into methane by microorganisms. The first or second ionic liquid is an amino acid anionic ionic liquid.

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