Composite biological membrane anode of microbial fuel cell as well as preparation method and application of composite biological membrane anode

Abstract

The invention discloses a composite biological membrane anode of a microbial fuel cell as well as a preparation method and application of the composite biological membrane anode. The method comprises the following steps: (1) preparing an MLG / MWCNT dispersion liquid; (2) preparation of a PANI-rMLG / MWCNT precursor; (3) preparation of a composite biofilm anode: adding a PANI-rMLG / MWCNT precursor into water to obtain a uniform precursor suspension, mixing the flora culture solution and the precursor suspension, co-culturing, centrifuging, and dispersing the precipitate in a PBS buffer solution to obtain a precursor suspension; and carbonizing a substrate material carbon cloth at 500-600 DEG C under an anaerobic condition, and then soaking the carbonized carbon cloth in the precursor suspension to obtain the PANI-rMLG / MWCNT-coated biofilm anode. The composite biological membrane anode disclosed by the invention can be used for remarkably improving the electricity generation performance and the environmental suitability of an MFC (Microbial Fuel Cell).

Description

Technical Field

[0001] The present invention belongs to the technical field of microbial fuel cells, and particularly relates to a composite biofilm anode of a microbial fuel cell, a preparation method thereof, and an application thereof. Background Art

[0002] The wastewater in the seawater aquaculture area is characterized by high salinity, with the peak value of COD (chemical oxygen demand) reaching 12,000 mg / L, the ammonia nitrogen concentration being 80 - 220 mg / L, and the antibiotic residues such as sulfamethoxazole and enrofloxacin reaching 85 - 310 μg / L and 62 - 180 μg / L respectively. When using traditional processes such as the activated sludge method, the aeration energy consumption soars to 6.2 kWh / m³ in a high-salt environment, the cost per ton of water for ozone oxidation exceeds 18 yuan, and excessive bromate is generated. There are problems such as high energy consumption and secondary pollution in the treatment process.

[0003] Although microbial fuel cells (MFCs) can simultaneously degrade pollutants and generate electricity, their anode materials face significant bottlenecks in application: (1) Conventional carbon-based materials (such as carbon felt) have poor conductivity, poor biocompatibility, and low electron transfer efficiency, resulting in insufficient power generation density; (2) In a high-salt environment, the biofilm is prone to shedding, and the activity of electroactive bacteria is inhibited; (3) Antibiotic residues further weaken the microbial metabolism ability. These defects are further amplified in the scenario of aquaculture wastewater, highlighting the necessity of developing new, efficient, and non-secondary-pollution technologies.

[0004] At present, regarding the research in this aspect, for example, Chinese Patent CN117303445A discloses a novel FeS2 / MoS2 heterostructure and its application as an anode material for a microbial fuel cell to treat wastewater. The novel FeS2 / MoS2 heterostructure is loaded onto carbon cloth, etc., to obtain an anode for a microbial fuel cell to treat medium and high-concentration organic wastewater. Under the condition that the influent COD is 3000 mg / L, the removal rate reaches 97.41%. When the influent COD is 12000 mg / L, the removal rate reaches 83.41%. Chinese Patent CN118039928A discloses the preparation of a biomass-derived hybrid hydrogel electrode and its application as an anode for a microbial fuel cell. Using carbon cloth as the substrate material, a hybrid hydrogel (PPy-CMC-MXene / CC) is prepared by doping a small amount of MXene, carboxymethyl cellulose, and polypyrrole as the anode of the MFC. While outputting voltage and power density, the removal rate of COD reaches 89.2%. Chinese Patent CN106920972B discloses a preparation method of a novel composite anode based on sludge-derived nitrogen-doped biochar and porous volcanic rock and a microbial fuel cell. The prepared novel nitrogen-doped porous biochar anode effectively increases the loading amount of electricity-producing bacteria and improves the conversion rate of biomass energy in wastewater. However, most of the existing research is designed for urban wastewater and does not consider the high-salt and high-antibiotic characteristics of aquaculture wastewater. During actual application, it may reduce the biological activity of electricity-producing and degrading bacteria, resulting in poor treatment effect of MFC on production and breeding wastewater. Therefore, there is an urgent need to develop a composite biofilm anode material suitable for aquaculture wastewater, and through the cross-scale coordination of material microstructure regulation and functional flora directional domestication, achieve efficient pollutant removal and stable energy recovery.

[0005] It should be noted that the information disclosed in the above background art section is only used to enhance the understanding of the background of the present disclosure, and thus may include information that does not constitute the prior art known to those of ordinary skill in the art. Summary of the Invention

[0006] The object of the present invention is to provide a composite biofilm anode for a microbial fuel cell, its preparation method and application, which solve the problem that the existing anode of a microbial fuel cell has a poor treatment effect on production and breeding wastewater, and can reduce the COD in the wastewater in sewage. The composite biofilm anode of the present invention can significantly improve the power generation performance and environmental adaptability of the MFC.

[0007] To achieve the above object, the present invention provides a preparation method of a composite biofilm anode for a microbial fuel cell, and the method comprises the following steps: (1) Preparation of MLG / MWCNT dispersion Multilayer graphene, carboxylated multi-walled carbon nanotubes, and sodium dodecyl sulfate were added to a mixed solution of water and ethanol to obtain a uniformly mixed dispersion, denoted as the MLG / MWCNT dispersion; (2) Preparation of PANI-rMLG / MWCNT precursor Polyaniline was added to a mixed solution of water and ethanol, and stirred at 0 - 5 °C to dissolve it uniformly. Then, the MLG / MWCNT dispersion prepared in step (1) was added, and an FeCl3 solution was dropped while stirring to obtain a polyaniline-reduced multilayer graphene / multi-walled carbon nanotube precursor, denoted as the PANI-rMLG / MWCNT precursor; (3) Preparation of composite biofilm anode The PANI-rMLG / MWCNT precursor was added to water to obtain a uniform precursor suspension. The bacterial culture solution was mixed with the precursor suspension, co-cultured, centrifuged, and the precipitate was dispersed in PBS buffer to obtain a precursor suspension; wherein, the bacterial culture solution was obtained by mixing Bacillus toyonensis BCT-7112, Bacillus albus MCCC1A02146, and Alcanivorax pacificus W11-5T according to an equal inoculation amount and co-culturing; The substrate material carbon cloth was carbonized under anaerobic conditions at 500 - 600 °C, and then the carbonized carbon cloth was immersed in the precursor suspension to obtain the PANI-rMLG / MWCNT@biofilm anode.

[0008] Preferably, in step (1), an intermittently ultrasonic oscillation was adopted to obtain a uniformly mixed dispersion.

[0009] Preferably, the power of the intermittently ultrasonic oscillation was set to 300 W, ultrasonicated for 30 min, and intermittently statically placed for 10 min.

[0010] Preferably, in step (1), the mass ratio of the multilayer graphene to the carboxylated multi-walled carbon nanotubes was 1:1; and / or, in step (2), the volume ratio of the polyaniline to the mass of FeCl3 and multilayer graphene was 0.3 mL:2.4 g:15 mg; and / or, in step (2), the concentration of the FeCl3 solution was 0.4 g / mL; and / or, in steps (1) and (2), in the mixed solution of water and ethanol, water and ethanol were mixed in equal volumes.

[0011] Preferably, in step (2), when dropping the FeCl3 solution, the dropping rate was 0.2 mL / min; and / or, in step (2), when dropping the FeCl3 solution, stirring was carried out for 24 h; and / or, in step (2), after the stirring ended, centrifugation, washing, and drying treatments were carried out.

[0012] More preferably, in step (2), the conditions for centrifugation are centrifugation at 8000 rpm; the washing is carried out by rinsing with water and ethanol; the drying is carried out in a vacuum environment at 60 °C.

[0013] Preferably, in step (2), the temperature for vacuum drying is 60 °C.

[0014] Preferably, in step (3), for the co-culture, the oscillation frequency of the culture environment is 150 rpm and the temperature is 30 °C; or / and, in step (3), after the co-culture ends, the mixture is centrifuged at 6000 rpm for 5 min; or / and, in step (3), for the microbial community culture solution, the total inoculation amount of each bacterium is 5%; or / and, in step (3), the preparation method of the microbial community culture solution includes: inoculating the colonies of each bacterium into NB medium, culturing in a constant temperature shaking incubator at 30 °C and 120 rpm, and after the strain culture solution shows a slightly turbid state, transferring the strain culture solution to MSM medium containing aquaculture wastewater and continuing to culture in a constant temperature shaking incubator at 30 °C and 180 rpm. After the culture ends, a microbial community culture solution is obtained.

[0015] More preferably, in step (3), for the microbial community culture solution, each bacterium is inoculated in NB medium and cultured in a constant temperature shaking incubator. After the strain culture solution shows a slightly turbid state, the strain culture solution is transferred to MSM medium containing aquaculture wastewater and continues to be cultured in a constant temperature shaking incubator. After the culture ends, a bacterial culture solution is obtained for the preparation of the composite biofilm anode of the microbial fuel cell.

[0016] Preferably, in step (3), the temperature for carbonization is 550 °C and the time is 2 h; or / and, in step (3), the carbon cloth after carbonization treatment is immersed in the precursor suspension for 48 h.

[0017] The second object of the present invention is to provide the composite biofilm anode of the microbial fuel cell obtained by the preparation method described above.

[0018] The third object of the present invention is to provide the application of the composite biofilm anode of the microbial fuel cell in a microbial fuel cell.

[0019] The composite biofilm anode of the microbial fuel cell of the present invention, its preparation method and application solve the problem that the existing anodes of microbial fuel cells have poor treatment effects on aquaculture wastewater, and have the following advantages: In the present invention, a three-dimensional conductive framework is constructed by PANI and MLG / MWCNT, which has a high porosity, significantly reduces the anodic charge transfer resistance, shortens the electron transfer path between the microbial community and the electrode, and increases the loading amount of electricity-producing bacteria (i.e., the composite bacteria in the present invention). The composite biofilm anode prepared by multi-scale structure design and biological interface optimization has an obvious promoting effect on the electron transfer efficiency, biofilm stability and pollutant degradation efficiency, and significantly improves the electricity generation performance and environmental adaptability of MFC. Description of the Drawings

[0020] Figure 1 It is the preparation flow chart of the composite biofilm anode of the microbial fuel cell of the present invention.

[0021] Figure 2 It is the SEM micrograph of different anode materials of the present invention; among them, (A) PANI-rMLG / MWCNT@biofilm anode; (B) MLG / MWCNT anode; (C) PANI-rMLG / MWCNT anode.

[0022] Figure 3 It is the measurement result of the contact angle size of different anode materials of the present invention; (a) MLG / MWCNT anode; (b) PANI-rMLG / MWCNT anode.

[0023] Figure 4 It is the polarization curve graph of different anode materials of the present invention.

[0024] Figure 5 It is the power density graph of MFC with different anodes of the present invention.

[0025] Figure 6 It is the removal rate of COD in aquaculture wastewater by MFC with different anodes of the present invention. Detailed Embodiments

[0026] Next, the technical solutions in the embodiments of the present invention will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0027] It should be noted that: for those not specified in the embodiments, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. For the instruments not specified in the manufacturer, they are all conventional products that can be purchased through the market. For the raw materials and reagents not specified in the manufacturer, they are all commercially available products or can be prepared by known methods.

[0028] In the present invention, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are only for the sake of simplicity and convenience. Accordingly, the description of a numerical range or percentage range should be regarded as having covered and specifically disclosed all possible sub-ranges and individual numerical values within the range (including integers and fractions).

[0029] The features mentioned in the present invention can be combined arbitrarily, as long as there is no contradiction in the combination of these features. All possible combinations should be considered as being within the scope described in this specification. Each feature disclosed in the specification can be replaced by an alternative feature that can achieve the same, equivalent, or similar purpose. Therefore, unless otherwise specified, the disclosed features are only general examples of equivalent or similar features.

[0030] The present invention provides a microbial fuel cell composite biofilm anode, its preparation method, and application. Refer to Figure 1 , in the present invention, the PANI-rMLG / MWCNT precursor and the culture solution of the constructed microbial community are co-cultured, and the carbon cloth is used as the substrate material. After carbonization, the carbon cloth is impregnated in the culture solution to obtain the PANI-rMLG / MWCNT@biofilm anode.

[0031] Before constructing the microbial community in the present invention, the COD degradation performance of selected multiple strains is measured. The tested strains are respectively: Bacillus toyonensis BCT-7112, Bacillus albus MCCC1A02146, Alcanivorax pacificus W11-5T and Oceanbacillus manasiensis YD3-56. The specific experimental process is as follows: 10 mL of the bacterial suspension (the single-bacterial suspension of the selected multiple strains or the bacterial suspension of their combination, and each bacterium is combined according to an equal inoculation amount) and the MSM medium (90 mL) containing 5% (v / v) of aquaculture wastewater are added to a flask, and cultured with shaking at 120 rpm at 30 °C for 10 days. The medium without inoculated microbial community is used as the blank control. Finally, the presented data are averages to reduce experimental errors. After 10 days, an appropriate amount of the culture solution is taken to measure the COD content. The calculation formula for the COD removal rate is as follows:

[0032] COD removal rate (%) = (COD （初） -COD （终） ) / COD （初） × 100% In the above formula, COD （初） represents the COD content in the MSM containing 5% (v / v) of aquaculture wastewater at the initial time; COD （终） represents the COD content after culturing the bacterial suspension with the MSM containing 5% (v / v) of aquaculture wastewater.

[0033] The results showed that for single strains, among them Bacillus toyonensis the degradation rate of the single strain of BCT-7112 was 52.37%, Bacillus albus the degradation rate of the single strain of MCCC1A02146 was 56.25%; Alcanivorax pacificus the degradation rate of the single strain of W11-5T was 57.39%; Oceanbacillus manasiensis the degradation rate of the single strain of YD3-56 was 52.17%. For the combination of two strains, among them Bacillus toyonensis the degradation rate of the combined flora of BCT-7112 and Bacillus albus MCCC1A02146 was 68.12%; Bacillus toyonensis the degradation rate of the combined flora of BCT-7112 and Alcanivorax pacificus W11-5T was 71.27%; Bacillus toyonensis the degradation rate of the combined flora of BCT-7112 and Oceanbacillus manasiensis YD3-56 was 75.81%; Bacillus albus the degradation rate of the combined flora of MCCC1A02146 and Alcanivorax pacificus W11-5T was 77.13%; Bacillus albus the degradation rate of the combined flora of MCCC1A02146 and Oceanbacillus manasiensis YD3-56 was 70.92%; Alcanivorax pacificus the degradation rate of the combined flora of W11-5T and Oceanbacillus manasiensis YD3-56 was 73.50%. For the combination of three strains, among them Bacillus toyonensis the degradation rate of BCT-7112, Bacillus albus MCCC1A02146 and Alcanivorax pacificus W11-5T was 90.86%; Bacillus toyonensis the degradation rate of BCT-7112, Bacillus albus MCCC1A02146 and Oceanbacillus manasiensis YD3-56 of the combined flora was 84.73%; Bacillus toyonensis the degradation rate of BCT-7112, Alcanivorax pacificus W11-5T and Oceanbacillus manasiensis YD3-56 of the combined flora was 87.47%; Bacillus albus the degradation rate of MCCC1A02146, Alcanivorax pacificus W11-5T and Oceanbacillus manasiensis YD3-56 of the combined flora was 88.15%. For the combination of four strains, Bacillus toyonensis the degradation rate of the combined flora of BCT-7112, Bacillus albus MCCC1A02146, Alcanivorax pacificus W11-5T and Oceanbacillus manasiensis YD3-56 was 85.21%.

[0034] Therefore, the bacterial flora adopted in the present invention is Bacillus toyonensis BCT-7112, Bacillus albus MCCC1A02146 and Alcanivorax pacificus W11-5T, which has better degradation performance for COD.

[0035] The following provides a detailed description of a microbial fuel cell composite biofilm anode and its preparation method and application provided by the present invention through examples, comparative examples and experimental examples.

[0036] Example 1 A microbial fuel cell composite biofilm anode (PANI-rMLG / MWCNT@biofilm anode), the preparation method of which includes: (1) Preparation of MLG / MWCNT dispersion Take 15 mg of MLG (multi-layer graphene, purchased from Chenghuang Technology (Hainan) Co., Ltd., which has good dispersibility in water), 15 mg of carboxylated MWCNT| (multi-walled carbon nanotubes, purchased from Tianjin Kemiou Chemical Reagent Co., Ltd.), and a final concentration of 0.1 wt% SDS (sodium dodecyl sulfate, the concentration of SDS in the finally prepared mixed solution is 0.1 wt%) and add them to 30 mL of a mixed solution of deionized water and absolute ethanol with a volume ratio of 1:1. Intermittent ultrasonic oscillation is carried out for 2 h to obtain a uniformly mixed dispersion, denoted as MLG / MWCNT dispersion, for standby; among them, the power of intermittent ultrasonic oscillation is set to 300 W, ultrasonic for 30 min, stand still for 10 min, and cycle 3 times; (2) Preparation of PANI-rMLG / MWCNT precursor Take 0.3 mL of PANI (polyaniline, purchased from Shanghai Yika Biotechnology Co., Ltd.) and add it to 30 mL of a mixed solution of deionized water and absolute ethanol with a volume ratio of 1:1. Stir it evenly at 0-5°C in an ice bath for 1 h, then add the MLG / MWCNT dispersion prepared in step (1), and add 6 mL of 0.4 g / mL FeCl3 solution dropwise at a dropping rate of 0.2 mL / min in a dropwise manner, and stir magnetically for 24 h. Centrifuge at 8000 rpm for 30 min to collect the precipitate, and wash the precipitate with deionized water and absolute ethanol to obtain a powder. Finally, dry the powder in a vacuum environment at 60°C for 24 h to obtain a polyaniline-reduced multi-layer graphene / multi-walled carbon nanotube precursor, denoted as PANI-rMLG / MWCNT precursor.

[0037] (3) Preparation of composite biofilm anode Take 20 mg of the PANI-rMLG / MWCNT precursor and add it to 10 mL of deionized water, then ultrasonically treat it for 2 h to obtain a uniform 10 mL suspension. Mix 5% (total inoculum amount during the cultivation of each bacterium) of the bacterial culture solution with the 10 mL suspension by magnetic stirring, and co-culture for 48 h. The oscillation frequency of the culture environment is 150 rpm, and the temperature is 30 °C to form a complex of bacterial biofilm and PANI-rMLG / MWCNT. Centrifuge the mixed solution at 6000 rpm for 5 min, discard the supernatant, gently rinse the precipitate with PBS, and finally redisperse the precipitate in PBS to obtain a precursor suspension for subsequent immersion of the carbon cloth. Among them, the bacterial culture solution is obtained by Bacillus toyonensis BCT-7112 (purchased from Ningbo Mingzhou Biotechnology Co., Ltd.), Bacillus albus MCCC1A02146 (purchased from Beijing NaiXi Biochemical Technology Co., Ltd.) and Alcanivorax pacificus W11-5T (purchased from Taizé (Guangzhou) Biotechnology Co., Ltd.) are mixed and cultured according to equal inoculum amounts, and all the strains used can be directly purchased.

[0038] The specific preparation process of the bacterial culture solution is as follows: First, use an inoculation loop to pick a certain amount of colonies of each bacterium growing on a TSA (Tryptone Soy Agar) plate and place them in an NB (Nutrient Broth) medium, and culture overnight in a constant temperature shaking incubator (30 °C, 120 rpm). After the bacterial culture solution shows a slightly turbid state, it indicates that the bacteria begin to exhibit exponential growth. At this time, use a pipette to transfer 5 aliquots (about 5 mL) of the bacterial culture solution to 100 mL of MSM medium containing 1% (v / v) of aquaculture wastewater (large particulate matter and easily sedimentable substances in the wastewater need to be removed by filtration, centrifugation, and precipitation), and continue to culture in a constant temperature shaking incubator (30 °C, 180 rpm) for 8 h. After the culture is completed, the bacterial culture solution is obtained for the preparation of the composite biofilm anode.

[0039] Place a square (1×2 cm) substrate material, carbon cloth (CC), in a muffle furnace, set the temperature to 450 °C, and carbonize it for 2 h under anaerobic conditions. Then immerse the carbonized CC in the above-mentioned precursor suspension for 48 h to allow the biofilm complex to be fully adsorbed onto the surface of the carbon cloth fibers. Take out the loaded CC, gently rinse the unbound particles with deionized water, and dry it in a vacuum at 60 °C for 24 h to obtain the PANI-rMLG / MWCNT@biofilm anode.

[0040] Comparative Example 1 An MLG / MWCNT anode, the preparation method of which includes: (1)Preparation of MLG / MWCNT dispersion Same as the preparation of MLG / MWCNT dispersion in Example 1; (2)Preparation of MLG / MWCNT anode Place the square (1×2 cm) substrate material carbon cloth (CC) in a muffle furnace, set the temperature to 450 °C, and carbonize it under anaerobic conditions for 2 h. Take 10 mL of the MLG / MWCNT dispersion and mix it with the carbonized CC, ultrasonically treat it for 1 h, let it stand for 24 h, remove the supernatant, and then dry the solid powder in a vacuum environment at 60 °C for 24 h to obtain the MLG / MWCNT anode.

[0041] Comparative Example 2 A PANI-rMLG / MWCNT anode, the preparation method of which includes: (1)Preparation of MLG / MWCNT dispersion Same as the preparation of MLG / MWCNT dispersion in Example 1; (2)Preparation of PANI-rMLG / MWCNT precursor Same as the preparation of PANI-rMLG / MWCNT precursor in Example 1; (3)Preparation of PANI-rMLG / MWCNT anode Take 20 mg of the PANI-rMLG / MWCNT precursor and add it to 10 mL of deionized water, then ultrasonically treat it for 2 h to obtain a uniform suspension. Place the square (1×2 cm) substrate material carbon cloth (CC) in a muffle furnace, set the temperature to 450 °C, and carbonize it under anaerobic conditions for 2 h. Then immerse the carbonized CC in the ultrasonically treated suspension for 48 h, let it stand for 24 h, remove the supernatant, and then dry the powder in a vacuum environment at 60 °C for 24 h to obtain the PANI-rMLG / MWCNT anode.

[0042] Experimental Example 1 Material Structure Characterization For the anodes prepared in the above examples and comparative examples, structural characterization was carried out by scanning electron microscopy. The experimental process is as follows: The prepared MLG / MWCNT anode and PANI-rMLG / MWCNT anode were respectively run in a dual-chamber MFC for a period of time (24 h). During the operation, these two anodes would combine with the bacteria in the anode chamber of the MFC and then be taken out for SEM characterization. For the PANI-rMLG / MWCNT@biofilm anode, it was also run in the MFC for a period of time (24 h), but no bacteria were added to the MFC.

[0043] The double-chamber MFC used has an anode chamber and a cathode chamber with a volume of 50 mL each, an electrode spacing of 4 cm, and the two electrode chambers are separated by a proton exchange membrane (Nafion 117). In the cathode chamber, a mixed solution of potassium ferricyanide (0.02 g / mL) and PBS (0.01 M) is used as the electrolyte, and in the anode chamber, an MSM medium containing 5% (v / v) aquaculture wastewater is used as the electrolyte. For the MLG / MWCNT anode and the PANI-rMLG / MWCNT anode, 10 mL of the bacterial cell suspension is added to the MFC anode chamber. The bacterial cell suspension is the same as the bacteria used to prepare the composite electrode, that is Bacillus toyonensis BCT-7112, Bacillus albus MCCC1A02146 and Alcanivorax pacificus W11-5T are mixed according to equal inoculation amounts.

[0044] The anode after running in the MFC for a period of time is taken out, placed on the sample stage for gold spraying pretreatment, and then the sample is scanned at a working voltage of 15 kV. The scanning electron microscope used is Sigma 300, and it is observed and photographed at different magnifications.

[0045] As Figure 2 shown in (A) of, the SEM image of the PANI-rMLG / MWCNT@biofilm anode prepared in Example 1 of the present invention is shown. A blocky interconnected porous network structure composite biofilm can be observed on the PANI-rMLG / MWCNT@biofilm anode. This phenomenon indicates that there is good biocompatibility between the bacteria and PANI-rMLG / MWCNT@biofilm, and the bacteria can attach and multiply on its surface in large numbers.

[0046] As Figure 2 shown in (B) of, the SEM image of the MLG / MWCNT anode prepared in Comparative Example 1 of the present invention is shown. An irregular, porous and intertwined structure can be observed. In addition, the insertion of MWCNT alleviates the poor condition of MLG accumulation and aggregation. At the same time, the tight adsorption of MLG and MWCNT also prevents the problem that MWCNT is easily entangled and bundled in the aqueous phase. The open macroporous structure of MLG / MWCNT can provide enough habitats for electrogenic microorganisms to metabolize and reproduce, greatly increasing the active site area. However, only sparse electrogenic microorganisms are observed in the figure, which may be related to the poor biocompatibility between the bacteria and MLG / MWCNT, resulting in a large number of strains not being able to attach to the electrode surface but remaining free in the electrolyte.

[0047] As Figure 2As shown in (C) of the present invention, the SEM image of the PANI-rMLG / MWCNT anode prepared in Comparative Example 2 of the present invention is shown. The bacteria are cross-linked with PANI-rMLG / MWCNT and adsorbed on the surface of the CC. The adsorption amount and cell density of the strains have been greatly improved. The reason for this phenomenon is related to the addition of PANI. However, the cell density of the biofilm growing naturally on the PANI-rMLG / MWCNT anode is still relatively low, and there is a large lack of electrochemically active sites, which is difficult to meet the requirements for constructing a high-output power MFC.

[0048] Experimental Example 2 Contact Angle Measurement For the anodes prepared in the above-mentioned examples and comparative examples, the contact angles of the materials were measured with a contact angle measuring instrument.

[0049] The results are as Figure 3 shown. It can be seen that the contact angle of the MLG / MWCNT anode material prepared in Comparative Example 1 is 39.139°, and the contact angle of the PANI-rMLG / MWCNT anode material prepared in Comparative Example 2 is 29.128°. The doping of PANI can effectively change the surface wettability of the material, greatly improve the hydrophilicity of the electrode material surface, and thus be conducive to the formation of electroactive biofilms.

[0050] Experimental Example 3 Electrochemical Performance Test For the anodes prepared in the above-mentioned examples and comparative examples, the electrochemical performance tests were carried out with an electrochemical workstation as follows: The electrode to be tested was used as the working electrode, the platinum electrode was used as the auxiliary electrode, and the saturated calomel electrode was used as the reference electrode for testing. The polarization curve was tested by the constant resistance discharge method. The adjustable external resistance varied between 9000 Ω and 60 Ω. When the MFC started and stabilized for 1 h, the real-time voltage value was recorded with a data acquisition card. The polarization curve graph of the MFC was obtained by plotting the curve between the discharge voltage and the current density. The power density curve graph showing the curve relationship between the discharge voltage and the power density of the MFC was plotted.

[0051] Current density ( I , mA / m 2 ) The calculation formula is: (1); Power density ( P , mW / m 2 ) The calculation formula is: (2); In the above formulas (1) and (2), A is the anode area (cm 2 ); U is the discharge voltage of the MFC (load voltage, V); R is the adjustable external resistance (Ω).

[0052] As Figure 4 shown, the polarization curve diagrams of different anode materials are presented. It can be seen that when the prepared PANI-rMLG / MWCNT@biofilm anode material is used as the anode of the MFC, its performance is the best, and the maximum output current density is 11,650 mA / m 2 , which is 2.54 times and 1.02 times higher than that of the MLG / MWCNT anode and the PANI-rMLG / MWCNT anode, respectively.

[0053] As Figure 5 shown, the power density diagrams of MFCs with different anodes are presented. The maximum power density is 3,732.61 mW / m 2 , which is 563.6% and 30.5% higher than that of the MLG / MWCNT anode and the PANI-rMLG / MWCNT anode, respectively. The specific indicators are shown in Table 1.

[0054] Experimental Example 4 Experiment on COD Removal from Aquaculture Wastewater 10 mL of the microbial cell suspension (the microbial community suspension in Example 1 of the present invention) and the MSM medium (40 mL) containing 5% (v / v) aquaculture wastewater were added to the anode chamber of the MFC. The above-prepared MLG / MWCNT anode and PANI-rMLG / MWCNT anode were respectively operated in the MFC for 10 days. In addition, the above-prepared PANI-rMLG / MWCNT@biofilm anode material was used as the anode of the MFC, and the anode chamber of the MFC only contained the MSM medium with 5% (v / v) aquaculture wastewater, and it was operated for 10 days under the same conditions.

[0055] After 10 days, an appropriate amount of the culture solution was taken from the three MFC anode chambers with different anodes configured, and the COD content was measured, and the COD removal rate was calculated according to the aforementioned COD removal rate calculation formula.

[0056] For each group, three parallel experiments were set up, and the salt concentrations of each group were 0 mM, 200 mM, 400 mM, and 600 mM, and the medium without inoculated microbial communities was used as the blank control. Finally, the presented data are the averages to reduce experimental errors.

[0057] As Figure 6 shown, the COD removal rates of MFCs with different anodes for aquaculture wastewater are presented. As the salt concentration increases (from 0 to 600 mM), the COD removal rates of MFCs with each anode change little with the salt concentration, but there are significant differences among MFCs with different anodes. The MFC constructed with the PANI-rMLG / MWCNT@biofilm anode of the present invention has the best COD removal rate for the wastewater, which can reach 93%.

[0058] Table 1 Performance indicators of different anode materials

[0059] Note: " / " indicates that the contact angle of this material has not been measured.

[0060] Although the content of the present invention has been introduced in detail through the above preferred embodiments, it should be recognized that the above description should not be considered as a limitation of the present invention. After those skilled in the art have read the above content, various modifications and substitutions to the present invention will be obvious. Therefore, the protection scope of the present invention should be defined by the appended claims.

Claims

1. A preparation method of a composite biofilm anode for a microbial fuel cell, characterized in that, The method comprises the following steps: (1) Preparation of MLG / MWCNT dispersion Multilayer graphene, carboxylated multi-walled carbon nanotubes, and sodium dodecyl sulfate are added to a mixed solution of water and ethanol to obtain a uniformly mixed dispersion, denoted as the MLG / MWCNT dispersion; (2) Preparation of PANI-rMLG / MWCNT precursor Polyaniline is added to a mixed solution of water and ethanol, and stirred at 0 - 5 °C to dissolve it uniformly. Then, the MLG / MWCNT dispersion prepared in step (1) is added, and an FeCl3 solution is dropped while stirring to obtain a polyaniline-reduced multilayer graphene / multi-walled carbon nanotube precursor, denoted as the PANI-rMLG / MWCNT precursor; (3) Preparation of composite biofilm anode Add the PANI-rMLG / MWCNT precursor to water to obtain a uniform precursor suspension. Mix the bacterial culture solution with the precursor suspension, co-culture, centrifuge, and disperse the precipitate in PBS buffer to obtain a precursor suspension. Among them, the bacterial culture solution is obtained by mixing and culturing Bacillus toyonensis BCT-7112, Bacillus albus MCCC1A02146, and Alcanivorax pacificus W11-5T according to equal inoculation amounts. The substrate material, carbon cloth, is carbonized under anaerobic conditions at 500 - 600 °C, and then the carbonized carbon cloth is immersed in the precursor suspension to obtain the PANI-rMLG / MWCNT@biofilm anode.

2. The preparation method according to claim 1, wherein, In step (1), intermittent ultrasonic oscillation is adopted to obtain a uniformly mixed dispersion.

3. The preparation method according to claim 2, wherein The power of the intermittent ultrasonic oscillation is set to 300 W, ultrasonic treatment is carried out for 30 min, and intermittent static standing is for 10 min.

4. The preparation method according to claim 1, wherein In step (1), the mass ratio of the multilayer graphene to the carboxylated multi-walled carbon nanotubes is 1:1; Or / and, in step (2), the volume ratio of the polyaniline to the mass of FeCl3 and multilayer graphene is 0.3 mL:2.4 g:15 mg; Or / and, in step (2), the concentration of the FeCl3 solution is 0.4 g / mL; Or / and, in steps (1) and (2), for the mixed solution of water and ethanol, water and ethanol are mixed in equal volumes.

5. The preparation method according to claim 4, characterized in that, In step (2), when dropping the FeCl3 solution, the dropping rate is 0.2 mL / min; Or / and, in step (2), when dropping the FeCl3 solution, stirring is carried out for 24 h; Or / and, in step (2), after the stirring ends, centrifugation, washing, and drying treatments are carried out.

6. The preparation method according to claim 5, wherein In step (2), the conditions for centrifugation are 8000 rpm; the washing is carried out by rinsing with water and ethanol; the drying is carried out in a vacuum environment at 60 °C.

7. The preparation method according to claim 1, characterized in that, In step (3), for the co-culture, the oscillation frequency of the culture environment is 150 rpm, and the temperature is 30 °C; Or / and, in step (3), after the co-culture ends, the mixed solution is centrifuged at 6000 rpm for 5 min; Or / and, in step (3), for the bacterial culture solution, the total inoculation amount of each bacterium is 5%; Or / and, in step (3), the preparation method of the bacterial culture solution includes: Inoculate the colonies of each bacterium into NB medium, and culture them in a constant temperature incubator shaker at 30 °C and 120 rpm. After the strain culture solution shows a slightly turbid state, transfer the strain culture solution to MSM medium containing aquaculture wastewater, and continue to culture it in a constant temperature incubator shaker at 30 °C and 180 rpm. After the culture is completed, a bacterial community culture solution is obtained.

8. The preparation method according to claim 1, wherein In step (3), the temperature of carbonization is 550 °C and the time is 2 h; Or / and, in step (3), immerse the carbon cloth after carbonization treatment in the precursor suspension for 48 h.

9. The microbial fuel cell composite biofilm anode obtained by the preparation method according to any one of claims 1 to 8.

10. The application of the microbial fuel cell composite biofilm anode according to claim 9 in a microbial fuel cell.

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