Method for efficiently producing methane by utilizing iron-carbon composite material and microbial electrochemical coupling anaerobic digestion system

Abstract

The invention provides a method for efficiently producing methane by utilizing an iron-carbon composite material and a microbial electrochemical coupling anaerobic digestion system, and belongs to the technical field of microbial electrochemical environment-friendly treatment processes. The Fe-C material is successfully loaded on the anaerobic granular sludge through a special treatment mode by constructing the Fe-C material, so that the Fe-C material forms a micro-electrolysis system in a reaction system, the contact area of microorganisms and electrodes is enlarged, efficient electron transfer among the microorganisms is enhanced, and the methane production performance and the system stability of a microbial electrochemical system (MEC) are improved. Compared with a traditional MEC-AD system, the system provided by the invention can greatly improve the accumulated methane yield and the direct interspecific electron transfer (DIET) methane yield.

Description

Technical Field

[0001] The invention belongs to the technical field of microbial electrochemical environmental protection treatment process, and specifically relates to a method for efficiently producing methane by utilizing an iron-carbon composite material and a microbial electrochemically coupled anaerobic digestion system. Background Art

[0002] The overexploitation and utilization of fossil energy has led to increasingly prominent problems of energy shortage, environmental pollution and climate warming. Microbial electrochemical technology has been widely reported to be used to alleviate energy crises and solve environmental problems. Through the catalytic action of microorganisms, pollutant degradation, waste energy utilization and CO2 reduction can be achieved simultaneously in microbial electrolysis cells. 2 However, due to the limitations of electrode materials, extracellular electron transfer rate and metabolic pathways of methanogenic microorganisms, and Coulomb efficiency, microbial electrochemical methanogenesis is still in the laboratory scale research stage and is difficult to be applied on a large scale in actual production.

[0003] A variety of conductive materials (iron-based, carbon-based) have been shown to act as electron conduits to promote electron transfer between microorganisms. 2+ / Fe 3+ The redox cycle and electrical conductivity of conductive materials mediate the direct interspecies electron transfer (DIET) process between microorganisms, thereby enriching the electron transfer pathway, enhancing the electron utilization efficiency, and improving the methanogenesis performance of the microbial electrochemical system (MEC). However, due to the poor microbial adhesion, easy aggregation, and uneven distribution of conductive materials, the contact area with microorganisms is greatly affected, and there is a serious loss problem of conductive materials. It is difficult to maintain high efficiency in the microbial electrochemical anaerobic digestion coupling system (MEC-AD) during long-term operation, thus affecting the methane production and quality.

[0004] Chinese patent document CN 106207230 B provides an anaerobic cathode photoelectric microbial fuel cell and a method for synchronously generating electricity and methane, which improves the CH4 produced to a certain extent. 4 The yield and quality of the nano-TiO 2 The price of powder is relatively high, and its methane production still needs to be further improved.

[0005] As a conductive material, iron-carbon composite materials have the advantages of easy availability of raw materials and low cost compared to other materials. However, when used in microbial electrochemical systems, iron-carbon composite materials have poor adhesion to microorganisms, small contact area, and easy loss, which seriously affects their methane production efficiency, thus limiting their application in anaerobic digestion systems.

[0006] Therefore, how to develop a method to use iron-carbon composite materials in microbial electrochemical anaerobic digestion coupling systems and significantly increase their methane production to solve the defect that they cannot be used in anaerobic digestion systems has become a technical problem that needs to be solved urgently. Summary of the invention

[0007] The present invention is to solve the above technical problems, thereby providing a method for efficiently producing methane by using an iron-carbon composite material and an electrochemically coupled anaerobic digestion system with microorganisms. The technical purpose of the present invention is to provide a method for using an iron-carbon composite material in an anaerobic digestion system to solve the problems of poor adhesion between the micro-electrolysis system formed by the microorganisms, easy agglomeration and loss, small contact area, and low efficiency of methane production.

[0008] In order to achieve the above technical objectives, the technical solution adopted by the present invention is as follows:

[0009] The present invention provides a method for efficiently producing methane by using an anaerobic digestion system coupled with an iron-carbon composite material and microbial electrochemical coupling, comprising the following steps:

[0010] (1) Preparation of Fe@C materials by ball milling or sol-gel method;

[0011] (2) treating anaerobic granular sludge with a biofilm dissociator, wherein the biofilm dissociator is a mixture of bis(3-aminopropyl)amine and D-tyrosine in a molar ratio of 1:1, the concentration of the mixture is 0.5 to 8 mM, the dissociation reaction time is 1 to 8 h, the extracellular polymers are separated, and then the Fe@C material is loaded into the anaerobic granular sludge to obtain a Fe@C-anaerobic granular sludge complex;

[0012] (3) constructing a microbial electrochemical coupled anaerobic digestion system, using graphite felt or carbon felt as anode and cathode electrodes, using the Fe@C-anaerobic granular sludge complex obtained in step (2) as a microbial inoculum, and separating the anode chamber and the cathode chamber by a proton exchange membrane;

[0013] (4) Organic matter and sodium bicarbonate were used as anode and cathode substrates, respectively, and phosphate buffer and trace elements were added to achieve methanogenesis from anode organic matter oxidation and CO2 production from cathode in a microbial electrochemical coupled anaerobic digestion system. 2 Reductive methanogenesis.

[0014] The iron-carbon material forms a micro-electrolysis system in the reaction system, expands the contact area between the microorganisms and the electrode, strengthens the efficient electron transfer between the microorganisms, and improves the methane production performance and system stability of the microbial electrochemical system (MEC).

[0015] The present invention constructs Fe@C material and successfully loads it into anaerobic granular sludge through a special treatment method, so that the iron-carbon material forms a micro-electrolysis system in the reaction system, solves the problem that its particles are easy to agglomerate and lose, and have poor adhesion to microorganisms, expands the contact area between microorganisms and electrodes, strengthens the efficient electron transfer between microorganisms, and improves the methanogenic performance and system stability of the microbial electrochemical system (MEC). The experimental results of the present invention show that compared with the MEC-AD system inoculated with ordinary anaerobic granular sludge, the MEC-AD system inoculated with anaerobic granular sludge loaded with Fe@CB conductive material can increase the cumulative methane production and direct interspecies electron transfer (DIET) of the maximum methane production by 40.46% and 55.96%, respectively.

[0016] Furthermore, the method for preparing Fe@C material by ball milling in step (1) is: 2 O 3 ) was mixed with glucose in a molar ratio of 1:3.5, and then the mixture and zirconium oxide grinding balls were added into a ball mill in a weight ratio of 1:10, and ball milling was performed at 500 rpm for 8 hours. The rotation direction was changed every 0.5 hour during the ball milling process, and the mixture was stopped for 10 minutes every hour. After the ball milling, the mixture was calcined in a nitrogen atmosphere at 700°C for 4 hours, and then cooled to 500°C and calcined for 2 hours to obtain Fe@C material.

[0017] Furthermore, the method for preparing Fe@C material by sol-gel method in step (1) is: 3 ) 3 9H 2 O, glucose and citric acid monohydrate were added to deionized water in sequence, and the molar ratio of the raw materials was controlled to be Fe: citric acid: glucose: deionized water = 1:1:3.5:55. After stirring at room temperature for 30 minutes, the resulting solution was heated and stirred at 80°C until a viscous gel was formed, and the sample was dried at 105°C for 24 hours. The resultant was calcined at 700°C in a nitrogen atmosphere for 4 hours, and then cooled to 500°C and calcined for 2 hours to obtain Fe@C material.

[0018] Furthermore, in step (2), the concentration of anaerobic granular sludge is controlled to be 10-20 gVS / L, the concentration of Fe@C material is controlled to be 40-100 mmol / L, the weight ratio of Fe to biomass is controlled to be 1:14, and the loading time is 12-24 h.

[0019] Furthermore, in step (2), the biological activity of the anaerobic granular sludge is maintained by supplementing an inorganic salt culture solution and a carbon source; wherein the formula of the inorganic salt culture solution is: NH 4 HCO 3 460 mg / L, KH2 PO 4 70 mg / L, NaHCO 3 1000 mg / L, CaCl 2 7.5mg / L and trace element solution 1mL / L; the composition of the trace element solution is: NiSO 4 6H 2 O 500mg / L, MnCl 2 ·4H 2 O 500mg / L, FeSO 4 7H 2 O 500mg / L, ZnSO 4 7H 2 O 100mg / L, H 3 BO 3 100 mg / L, Na 2 MoO 4 ·2H 2 O 50mg / L, COCl 2 6H 2 O 50mg / L, CuSO 4 ·5H 2 O 5mg / L.

[0020] Furthermore, the carbon source is one or more of glucose, sucrose and sodium acetate, with a concentration of 2000-3500 mg / L.

[0021] Furthermore, the reaction process of step (2) is maintained under anaerobic conditions, and the reaction system is placed in a constant temperature shaker at 100-150 rpm in the dark and the reaction temperature is 30-45°C.

[0022] Furthermore, the inoculation amount of the Fe@C-anaerobic granular sludge in step (3) is 15-30 gVS / L.

[0023] Furthermore, in step (4), the organic matter used as the anode substrate includes one or more of acetic acid, glucose, protein, municipal sludge, and kitchen waste; the concentration of the organic matter is 1000 to 6000 mg / L; and the concentration of the cathode substrate sodium bicarbonate is 500 to 1500 mg / L.

[0024] Furthermore, in step (4), the applied voltage of the microbial electrochemical coupled anaerobic digestion system is controlled to be 0.8-1.0 V, the culture temperature is 35-40° C., the culture cycle is 3 hydraulic retention times, and the single hydraulic retention time is 2-4 days.

[0025] The beneficial effects of the present invention are as follows:

[0026] (1) The method provided by the present invention can couple the iron-carbon composite material in the MEC-AD system, and form a micro-electrolysis system by itself through Fe acting as the anode and C acting as the cathode. After being loaded into the anaerobic granular sludge, it can effectively increase the contact area between the microorganisms and the electrode, promote the direct interspecies electron transfer (DIET) of the microorganisms, optimize the environmental factors and microbial communities, and improve the efficiency of anaerobic digestion.

[0027] (2) The biofilm dissociation agent used in the present invention can moderately dissociate the extracellular polymers (EPS) of anaerobic granular sludge, increase the porosity of the three-dimensional structure of anaerobic granular sludge, facilitate the Fe@C conductive material to better enter the anaerobic granular sludge, fully contact with microorganisms, promote the DIET effect between symbiotic microorganisms, and effectively improve the anaerobic digestion and methane production performance of organic matter in the MEC-AD system.

[0028] (3) The method proposed in the present invention for loading Fe@C conductive material onto anaerobic granular sludge and applying it in the MEC-AD system is simple to operate, environmentally friendly, and can effectively improve the efficiency and stability of the MEC-AD system during long-term operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is the scanning electron microscope image of Fe@CB conductive material prepared by ball milling;

[0030] Figure 2 This is a scanning electron microscope image of Fe@CS conductive material prepared by sol-gel method;

[0031] Figure 3 This is a graph of methane production in a MEC-AD reactor after inoculation with anaerobic granular sludge loaded with Fe@CB conductive material in Example 2;

[0032] Figure 4 This is a graph of methane production in the MEC-AD reactor after inoculation with anaerobic granular sludge loaded with Fe@CS conductive material in Example 5. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is described in detail below in conjunction with the embodiments. It is necessary to point out that the following embodiments are only used to explain and illustrate the present invention and are not used to limit the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above invention content still belong to the protection scope of the present invention.

[0034] Example 1

[0035] 10g Fe 2 O 3The powder mixed with 35g glucose and zirconium oxide grinding balls (8mm in diameter) were added to an agate jar at a weight ratio of 1:10 and placed in a ball mill. The ball mill was milled at 500rpm for 8 hours, and the rotation direction was changed every 0.5 hours and stopped for 10 minutes every 1 hour. After mechanical treatment, the powder was calcined at 700℃ in a nitrogen atmosphere for 4 hours, and then reduced to 500℃ for calcination for 2 hours to obtain Fe@C nano-additive (abbreviated as Fe@CB).

[0036] Take anaerobic granular sludge, prepare phosphate buffer solution for cleaning, and place it in a 500mL blue cap bottle to make the sludge concentration 6g VS / L, the effective volume 300mL, add 2000mg / L glucose as carbon source, add 3mM bis(3-aminopropyl)amine and D-tyrosine coupling biofilm dissociation agent, and adjust the system pH to 7. After nitrogen blowing for 5min, seal it and culture it in a constant temperature shaker at 35℃ and 150rpm in the dark for 12h. Among them, the molar ratio of bis(3-aminopropyl)amine and D-tyrosine is 1:1 (concentration ratio). After precipitation, pour out the supernatant, add 500mg / L freshly prepared nano-Fe@CB conductive material suspension, and control the Fe / biomass ratio to 1:14. The inorganic salt culture medium was supplemented, 2000 mg / L glucose was used as the carbon source, nitrogen was blown for 5 minutes and then sealed, and cultured in a constant temperature shaker at 35°C and 150 rpm for 24 hours in the dark to obtain anaerobic granular sludge with negative Fe@CB conductive material.

[0037] The Fe@CB anaerobic granular sludge complex was washed three times and added to the anode chamber and cathode chamber of the MEC-AD reactor. After acclimatization and cultivation with PBS-prepared culture solution (acetic acid: ethanol = 1:2), the anaerobic digestion test of glucose solution simulating organic wastewater was carried out. The concentration of anaerobic granular sludge in the MEC-AD reactor was 20gVS / L, and the concentration of glucose was 2000mg / L. In order to ensure that other nutrient elements such as N and P in the influent meet the basic needs of anaerobic microbial growth, the system C, N, and P concentration ratio was adjusted to C: N: P = 200: 5: 1. The reactor was purged with nitrogen for 5 minutes and then sealed at 35°C for anaerobic digestion. The gas produced during anaerobic digestion was collected with a gas collection bag, and the methane content was measured.

[0038] Comparative Example 1

[0039] The method of Example 1 was followed, except that Fe@C material was not added, and ordinary anaerobic granular sludge was inoculated to construct a MEC-AD system for methane production.

[0040] The test results show that compared with the method of comparative example 1, the cumulative methane production and direct interspecies electron transfer (DIET) methane production of the MEC-AD system inoculated with anaerobic granular sludge loaded with Fe@CB conductive material (the method of example 1) increased by 40.46% and 55.96%, respectively.

[0041] Example 2

[0042] 10g Fe 2 O 3 The powder mixed with 35g glucose and zirconium oxide grinding balls (8mm in diameter) were added to an agate jar at a weight ratio of 1:10 and placed in a ball mill. The powder was milled at 500rpm for 8 hours, the rotation direction was changed every 0.5 hours, and it was stopped for 10 minutes every hour. After mechanical treatment, the powder was calcined at 700℃ in a nitrogen atmosphere for 4 hours, and then reduced to 500℃ for calcination for 2 hours to obtain Fe@C nano-additive, which is referred to as Fe@CB in the following content.

[0043] Take anaerobic granular sludge, prepare phosphate buffer solution for cleaning, and place it in a 500mL blue cap bottle to make the sludge concentration 6g VS / L, the effective volume 300mL, add 2000mg / L glucose as carbon source, add 3mM bis(3-aminopropyl)amine and D-tyrosine coupling biofilm dissociation agent, and adjust the system pH to 7. After nitrogen blowing for 5min, seal it and culture it in a constant temperature shaker at 35℃ and 150rpm in the dark for 12h. Among them, the molar ratio of bis(3-aminopropyl)amine and D-tyrosine is 1:1 (concentration ratio). After precipitation, pour out the supernatant, add 1000mg / L freshly prepared nano-Fe@CB conductive material suspension, and control the Fe / biomass ratio to 1:14. The inorganic salt culture medium was supplemented, 2000 mg / L glucose was used as the carbon source, nitrogen was blown for 5 minutes and then sealed, and cultured in a constant temperature shaker at 35°C and 150 rpm for 24 hours in the dark to obtain anaerobic granular sludge with negative Fe@CB conductive material.

[0044] The Fe@CB anaerobic granular sludge complex was washed three times and added to the anode chamber and cathode chamber of the MEC-AD reactor. After acclimatization and cultivation with PBS-prepared culture solution (acetic acid: ethanol = 1:2), the anaerobic digestion test of glucose solution simulating organic wastewater was carried out. The concentration of anaerobic granular sludge in the MEC-AD reactor was 20gVS / L, and the concentration of glucose was 2000mg / L. In order to ensure that other nutrient elements such as N and P in the influent meet the basic needs of anaerobic microbial growth, the system C, N, and P concentration ratio was adjusted to C: N: P = 200: 5: 1. The reactor was purged with nitrogen for 5 minutes and then sealed at 35°C for anaerobic digestion. The gas produced during anaerobic digestion was collected with a gas collection bag, and the methane content was measured.

[0045] Comparative Example 2

[0046] Referring to the method of Example 2, instead of using a biofilm dissociation agent to treat the anaerobic granular sludge, the Fe@C material was directly mixed with the anaerobic granular sludge to construct MEC-AD.

[0047] The test results show that compared with the method of Comparative Example 2, the cumulative methane production and direct interspecies electron transfer (DIET) methane production of the MEC-AD system of Fe@CB conductive material and anaerobic granular sludge treated with a biofilm dissociator (the method of Example 2) increased by 27.87% and 41.28%, respectively.

[0048] Example 3

[0049] 10g Fe 2 O 3 The powder mixed with 35g glucose and zirconium oxide grinding balls (8mm in diameter) were added to an agate jar at a weight ratio of 1:10 and placed in a ball mill. The powder was milled at 500rpm for 8 hours, the rotation direction was changed every 0.5 hours, and it was stopped for 10 minutes every hour. After mechanical treatment, the powder was calcined at 700℃ in a nitrogen atmosphere for 4 hours, and then reduced to 500℃ for calcination for 2 hours to obtain Fe@C nano-additive, which is referred to as Fe@CB in the following content.

[0050] Take anaerobic granular sludge, prepare phosphate buffer solution for cleaning, and place it in a 500mL blue cap bottle to make the sludge concentration 6g VS / L, the effective volume 300mL, add 2000mg / L glucose as carbon source, add 3mM bis(3-aminopropyl)amine and D-tyrosine coupling biofilm dissociation agent, and adjust the system pH to 7. After nitrogen blowing for 5min, seal it and culture it in a constant temperature shaker at 35℃ and 150rpm in the dark for 12h. Among them, the molar ratio of bis(3-aminopropyl)amine and D-tyrosine is 1:1 (concentration ratio). After precipitation, pour out the supernatant, add 1500mg / L freshly prepared nano-Fe@CB conductive material suspension, and control the Fe / biomass ratio to 1:14. The inorganic salt culture medium was supplemented, 2000 mg / L glucose was used as the carbon source, nitrogen was blown for 5 minutes and then sealed, and cultured in a constant temperature shaker at 35°C and 150 rpm for 24 hours in the dark to obtain anaerobic granular sludge with negative Fe@CB conductive material.

[0051] The Fe@CB anaerobic granular sludge complex was washed three times and added to the anode chamber and cathode chamber of the MEC-AD reactor. After acclimatization and cultivation with PBS-prepared culture solution (acetic acid: ethanol = 1:2), the anaerobic digestion test of glucose solution simulating organic wastewater was carried out. The concentration of anaerobic granular sludge in the MEC-AD reactor was 20gVS / L, and the concentration of glucose was 2000mg / L. In order to ensure that other nutrient elements such as N and P in the influent meet the basic needs of anaerobic microbial growth, the system C, N, and P concentration ratio was adjusted to C: N: P = 200: 5: 1. The reactor was purged with nitrogen for 5 minutes and then sealed at 35°C for anaerobic digestion. The gas produced during anaerobic digestion was collected with a gas collection bag, and the methane content was measured.

[0052] Comparative Example 3

[0053] The method of Example 3 was followed, except that bis(3-aminopropyl)amine was used as the biofilm dissociation agent, and the other steps were the same.

[0054] The test results show that compared with the method of Comparative Example 3, the cumulative methane production and direct interspecies electron transfer (DIET) methane production of the MEC-AD system of Example 3 increased by 14.94% and 20.73%, respectively.

[0055] Example 4

[0056] 10g Fe(NO 3 ) 3 9H 2 O, 10 g citric acid monohydrate and 35 g glucose were added sequentially into 550 g deionized water (the molar ratio of Fe: citric acid: glucose was 1:1:3.5; the molar ratio of iron to deionized water was 1:55), and after stirring at room temperature for 30 min, the resulting solution was heated at 80 °C with continuous stirring until a viscous gel was formed and the sample was dried at 105 °C for 24 h, calcined at 700 °C in a nitrogen atmosphere for 4 h, and then cooled to 500 °C and calcined for 2 h to obtain the Fe@C nano-adjuvant, referred to as Fe@CS in the following content.

[0057] Take anaerobic granular sludge, prepare phosphate buffer solution for cleaning, and place it in a 500mL blue cap bottle to make the sludge concentration 6g VS / L, the effective volume 300mL, add 2000mg / L glucose as carbon source, add 3mM bis(3-aminopropyl)amine and D-tyrosine coupling biofilm dissociation agent, and adjust the system pH to 7. After nitrogen blowing for 5min, seal it and culture it in a constant temperature shaker at 35℃ and 150rpm in the dark for 12h. Among them, the molar ratio of bis(3-aminopropyl)amine and D-tyrosine is 1:1 (concentration ratio). After precipitation, pour out the supernatant, add 500mg / L freshly prepared nano-Fe@CS conductive material suspension, and control the Fe / biomass ratio to 1:14. The inorganic salt culture medium was supplemented, 2000 mg / L glucose was used as the carbon source, nitrogen was blown for 5 minutes and then sealed, and cultured in a constant temperature shaker at 35°C and 150 rpm for 24 hours in the dark to obtain anaerobic granular sludge with negative Fe@CS conductive material.

[0058] The Fe@CS anaerobic granular sludge complex was washed three times and added to the anode chamber and cathode chamber of the MEC-AD reactor. After acclimatization and cultivation with PBS-prepared culture solution (acetic acid: ethanol = 1:2), the anaerobic digestion test of glucose solution simulating organic wastewater was carried out. The concentration of anaerobic granular sludge in the MEC-AD reactor was 20gVS / L, and the concentration of glucose was 2000mg / L. In order to ensure that other nutrient elements such as N and P in the influent meet the basic needs of anaerobic microbial growth, the system C, N, and P concentration ratio was adjusted to C: N: P = 200: 5: 1. The reactor was purged with nitrogen for 5 minutes and then sealed at 35°C for anaerobic digestion. The gas produced during anaerobic digestion was collected with a gas collection bag, and the methane content was measured.

[0059] Comparative Example 4

[0060] The method of Example 4 was followed, except that D-tyrosine was used as the biofilm dissociation agent, and the other steps were the same.

[0061] The test results show that compared with Comparative Example 4, the cumulative methane production and DIET methane production of the MEC-AD system of Example 4 increased by 12.23% and 26.01%, respectively.

[0062] Example 5

[0063] 10g Fe(NO 3 ) 3 9H 2 O, 10 g citric acid monohydrate and 35 g glucose were added sequentially into 550 g deionized water (the molar ratio of Fe: citric acid: glucose was 1:1:3.5; the molar ratio of iron to deionized water was 1:55), and after stirring at room temperature for 30 min, the resulting solution was heated at 80 °C with continuous stirring until a viscous gel was formed and the sample was dried at 105 °C for 24 h, calcined at 700 °C in a nitrogen atmosphere for 4 h, and then cooled to 500 °C and calcined for 2 h to obtain the Fe@C nano-adjuvant, referred to as Fe@CS in the following content.

[0064] Take anaerobic granular sludge, prepare phosphate buffer solution for cleaning, and place it in a 500mL blue cap bottle to make the sludge concentration 6g VS / L, the effective volume 300mL, add 2000mg / L glucose as carbon source, add 3mM bis(3-aminopropyl)amine and D-tyrosine coupling biofilm dissociation agent, and adjust the system pH to 7. After nitrogen blowing for 5min, seal it and culture it in a constant temperature shaker at 35℃ and 150rpm in the dark for 12h. Among them, the molar ratio of bis(3-aminopropyl)amine and D-tyrosine is 1:1 (concentration ratio). After precipitation, pour out the supernatant, add 1000mg / L freshly prepared nano-Fe@CS conductive material suspension, and control the Fe / biomass ratio to 1:14. The inorganic salt culture medium was supplemented, 2000 mg / L glucose was used as the carbon source, nitrogen was blown for 5 minutes and then sealed, and cultured in a constant temperature shaker at 35°C and 150 rpm for 24 hours in the dark to obtain anaerobic granular sludge with negative Fe@CS conductive material.

[0065] The Fe@CS anaerobic granular sludge complex was washed three times and added to the anode chamber and cathode chamber of the MEC-AD reactor. After acclimatization and cultivation with PBS-prepared culture solution (acetic acid: ethanol = 1:2), the anaerobic digestion test of glucose solution simulating organic wastewater was carried out. The concentration of anaerobic granular sludge in the MEC-AD reactor was 20gVS / L, and the concentration of glucose was 2000mg / L. In order to ensure that other nutrient elements such as N and P in the influent meet the basic needs of anaerobic microbial growth, the system C, N, and P concentration ratio was adjusted to C: N: P = 200: 5: 1. The reactor was purged with nitrogen for 5 minutes and then sealed at 35°C for anaerobic digestion. The gas produced during anaerobic digestion was collected with a gas collection bag, and the methane content was measured.

[0066] Comparative Example 5

[0067] According to the method of Example 5, bis(3-aminopropyl)amine and D-tyrosine were used as biofilm dissociation agents in a molar ratio of 1:2, and other steps were the same.

[0068] The test results show that compared with Comparative Example 5, the cumulative methane production and DIET methane production of the MEC-AD system of Example 5 increased by 22.69% and 35.96%, respectively.

Claims

1. A method for efficiently producing methane by using an anaerobic digestion system coupled with an iron-carbon composite material and microbial electrochemical coupling, characterized in that: The following steps are involved: (1) Preparation of Fe@C materials by ball milling or sol-gel method; (2) treating anaerobic granular sludge with a biofilm dissociator, wherein the biofilm dissociator is a mixture of bis(3-aminopropyl)amine and D-tyrosine in a molar ratio of 1:1, the concentration of the mixture is 0.5 to 8 mM, the dissociation reaction time is 1 to 8 h, the extracellular polymers are separated, and then the Fe@C material is loaded into the anaerobic granular sludge to obtain a Fe@C-anaerobic granular sludge complex; (3) constructing a microbial electrochemical coupled anaerobic digestion system, using graphite felt or carbon felt as anode and cathode electrodes, using the Fe@C-anaerobic granular sludge complex obtained in step (2) as a microbial inoculum, and separating the anode chamber and the cathode chamber by a proton exchange membrane; (4) Organic matter and sodium bicarbonate were used as anode and cathode substrates, respectively. Phosphate buffer and trace elements were added to the microbial electrochemical coupled anaerobic digestion system to achieve anode organic matter oxidation to produce methane and cathode CO2 reduction to produce methane.

2. The method according to claim 1, characterized in that The method for preparing Fe@C material by ball milling described in step (1) is: Fe2O3 and glucose are mixed in a molar ratio of 1:3.5, and then the mixture and zirconium oxide grinding balls are added to a ball mill in a weight ratio of 1:10, and ball milling is performed at 500 rpm for 8 hours. During the ball milling process, the rotation direction is changed every 0.5 hour, and the mixture is stopped for 10 minutes every 1 hour. After the ball milling is completed, the mixture is calcined in a nitrogen atmosphere at 700°C for 4 hours, and then cooled to 500°C and calcined for 2 hours to obtain Fe@C material.

3. The preparation method according to claim 1, characterized in that: The method for preparing Fe@C material by the sol-gel method described in step (1) is: Fe(NO3)3·9H2O, glucose and citric acid monohydrate are added to deionized water in sequence, and the molar ratio of the raw materials is controlled to be Fe: citric acid: glucose: deionized water = 1:1:3.5:

55. After stirring at room temperature for 30 minutes, the resulting solution is heated and stirred at 80°C until a viscous gel is formed, and the sample is dried at 105°C for 24 hours. The resulting product is calcined at 700°C in a nitrogen atmosphere for 4 hours, then cooled to 500°C and calcined for 2 hours to obtain Fe@C material.

4. The preparation method according to claim 1, characterized in that: In step (2), the concentration of anaerobic granular sludge is controlled to be 10-20 gVS / L, the concentration of Fe@C material is controlled to be 40-100 mmol / L, the weight ratio of Fe to biomass is controlled to be 1:14, and the loading time is 12-24 h.

5. The preparation method according to claim 1, characterized in that: In step (2), the biological activity of the anaerobic granular sludge is maintained by supplementing an inorganic salt culture solution and a carbon source; wherein the formula of the inorganic salt culture solution is: 460 mg / L NH4HCO3, 70 mg / L KH2PO4, 1000 mg / L NaHCO3, 7.5 mg / L CaCl2 and 1 mL / L trace element solution; the components of the trace element solution are: 500 mg / L NiSO4·6H2O, 500 mg / L MnCl2·4H2O, 500 mg / L FeSO4·7H2O, 100 mg / L ZnSO4·7H2O, 100 mg / L H3BO3, 50 mg / L Na2MoO4·2H2O, 50 mg / L COCl2·6H2O and 5 mg / L CuSO4·5H2O.

6. The preparation method according to claim 5, characterized in that: The carbon source is one or more of glucose, sucrose and sodium acetate, and the concentration is 2000-3500 mg / L.

7. The preparation method according to claim 1, characterized in that: The reaction process of step (2) is maintained under anaerobic conditions, and the reaction system is placed in a constant temperature shaker at 100-150 rpm and shaken in the dark, and the reaction temperature is 30-45°C.

8. The preparation method according to claim 1, characterized in that: The inoculation amount of the Fe@C-anaerobic granular sludge in step (3) is 15-30 gVS / L.

9. The preparation method according to claim 1, characterized in that: In step (4), the organic matter used as the anode substrate includes one or more of acetic acid, glucose, protein, municipal sludge, and kitchen waste; the concentration of the organic matter is 1000 to 6000 mg / L; and the concentration of the cathode substrate sodium bicarbonate is 500 to 1500 mg / L.

10. The preparation method according to claim 1, characterized in that: In step (4), the applied voltage of the microbial electrochemical coupled anaerobic digestion system is controlled to be 0.8-1.0 V, the culture temperature is 35-40° C., the culture cycle is 3 hydraulic retention times, and the single hydraulic retention time is 2-4 days.

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