Method for enhancing electricity generation of microbial fuel cell by interface modification of free magnetic-rich carbon three-dimensional anode and bacteria

Abstract

The application provides a method for enhancing electricity generation of a microbial fuel cell by modifying the interface between a free magnetic carbon three-dimensional biological anode and bacteria, and the method adopts a solvothermal method to prepare a hydrophilic magnetic nano Fe3O4@ formed porous carbon composite material which has strong electromagnetic performance, a large specific surface area and high biocompatibility, can be used as a three-dimensional biological anode in a microbial fuel cell (MFC), is beneficial to the adhesion of microorganisms and maximizes the colonization space of the microorganisms, can promote the extracellular electron transfer efficiency of bacteria and enhance interspecies electron transfer between bacteria and archaea as an excellent electron medium, improves the conversion rate of a biological anode and the output of electrons, and enhances electricity generation of the MFC.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of microbial fuel cell, in particular to a method for enhancing electricity production of microbial fuel cell by modifying the interface between free magnetic-rich carbon three-dimensional bio-anode and bacteria. BACKGROUND

[0002] Microbial fuel cell (MFC) is a typical bioelectrochemical system that harvests electricity from organic substrates using energy metabolism of electroactive bacteria. It has attracted extensive attention due to its potential for simultaneous clean energy production and organic waste treatment. Despite the great progress in recent years, the limited extracellular electron transfer efficiency of microorganisms limits the practical application of MFC.

[0003] It is feasible to regulate the extracellular electron transfer of microorganisms by using electron transfer mediators. It can shorten the complex electron transfer process in anaerobic process, improve the degradation rate of digestion substrate and electron output, and strengthen the connection between bacteria, thereby increasing the conductivity of anaerobic system and enhancing the extracellular electron transfer process of microorganisms. Nano Fe3O4 has good quantum size effect, strong electromagnetic performance, large specific surface area, small size distribution, low toxicity, high biocompatibility and strong adsorption capacity, and can be used as an ideal medium for electron transfer in anaerobic process. However, the Fe3O4 nanoparticles obtained by traditional coprecipitation method have poor crystallinity, which reduces the conductivity and magnetization intensity, and is prone to aggregation. The thermal decomposition of organometallic and coordination compounds in non-polar solutions has been successfully used to synthesize monodisperse magnetic nanocrystals with high crystallinity and small size at the nanoscale. However, the magnetic nanocrystals synthesized by these methods are usually hydrophobic and have low magnetization intensity.

[0004] Due to its non-biological toxicity, high specific surface area and numerous pores available for modification, and low price, biochar is often used in anaerobic digestion, which can promote direct electron transfer. The high specific surface area and porous structure of biochar can significantly improve the mass transfer efficiency, especially the formed porous biochar material, which can provide a three-dimensional spatial network structure for the adhesion and growth of microorganisms. In addition, loading Fe3O4 nanoparticles on the formed porous biochar can effectively solve the problem of aggregation and loss of nano Fe3O4 particles. However, biochar is usually calcined under high-temperature anaerobic conditions, and is generally hydrophobic. The higher the calcination temperature, the stronger the hydrophobicity. Loading hydrophobic magnetic Fe3O4 nanocrystals on biochar with the same hydrophobic property is not conducive to the adhesion of microorganisms, which hinders the development of biofilm and the extracellular electron transfer of electroactive bacteria. SUMMARY

[0005] In view of this, the present application provides a method for enhancing electricity production of microbial fuel cell by modifying the interface between free magnetic-rich carbon three-dimensional bio-anode and bacteria, which solves the above problems.

[0006] The technical scheme of the present application is implemented as follows:

[0007] A method for enhancing electricity generation of a microbial fuel cell by modifying the interface between a free magnetic-rich carbon three-dimensional biological anode and bacteria, the preparation method of the free magnetic-rich carbon three-dimensional biological anode comprising the following steps:

[0008] (1) Biomass is pulverized to obtain biomass powder, and the biomass powder is mixed with phenol and a catalyst to perform a liquefaction reaction, thereby obtaining a biomass liquefaction product;

[0009] (2) The biomass liquefaction product is reacted with formaldehyde to obtain a resinification reaction product, and the resinification reaction product is subjected to a hydrothermal reaction to obtain a hydrothermal reaction product;

[0010] (3) The hydrothermal reaction product is mixed with zinc chloride and then placed in a mold, and the obtained product is subjected to demolding, carbonization, acid pickling and water washing to obtain a shaped porous carbon;

[0011] (4) An iron source, trisodium citrate and ethylene glycol are mixed, the shaped porous carbon is added and stirred, and then sodium acetate is added and mixed to obtain a mixture, and the mixture is subjected to a solvothermal reaction to obtain a free magnetic-rich carbon three-dimensional biological anode.

[0012] Further, in step (1), the mass ratio of the biomass powder to the phenol is 1:1-6; and the catalyst is one or more of sulfuric acid, phosphoric acid and p-toluenesulfonic acid, and the mass ratio of the catalyst to the biomass powder is 0.1-0.6:1.

[0013] Further, in step (1), the temperature of the liquefaction reaction is 120-170°C, and the reaction time is 0.5-5h.

[0014] Further, in step (2), the mass ratio of the formaldehyde to the biomass liquefaction product is 0.8-3:1, the temperature of the resinification reaction is 50-100°C, the resinification reaction time is 30-120min, the temperature of the hydrothermal reaction is 100-160°C, and the hydrothermal reaction time is 6-24h.

[0015] Further, in step (3), the mass ratio of the biomass powder to the zinc chloride is 1:1.6-4.8, the shape of the mold is one of a spherical shape, a cylindrical shape and a cubic shape, the carbonization is performed at 400-1000°C for 30-180min in a nitrogen atmosphere, the acid pickling uses one of hydrochloric acid and sulfuric acid, and the concentration of the acid pickling is 0.1-2mol / L.

[0016] Further, in step (4), the iron source is one or both of ferric chloride and ferric nitrate, the concentration of the iron source is 0.05-0.35 mol / L, the concentration of trisodium citrate is 8-80 mmol / L, the concentration of the shaped porous carbon is 20-120 g / L, the concentration of sodium acetate is 0.2-1.5 mol / L, the solvent thermal reaction temperature is 200-220 DEG C, and the reaction time is 4-15 h.

[0017] Further, the bacteria are electrically active bacteria Shewanella onesidensis MR-1.

[0018] Further, the OD 600 of the Shewanella in the anode liquid is 0.9-1.1.

[0019] Further, the MFC reactor is built and started: a double-chamber reactor is used, the anode chamber and the cathode chamber are separated by Nafion 117 proton exchange membrane, the anode material is a carbon brush, and the cathode material is a graphite rod.

[0020] Further, the free magnetic carbon three-dimensional biological anode is added to the anode chamber, electrically active bacteria Shewanella onesidensis MR-1 are selected as the inoculated bacteria, MR-1 suspension is dispersed in the anode liquid to inoculate the MFC reactor, and nitrogen is bubbled for 15 min to form an anaerobic environment. The composition of the anode liquid is: 50 mmol / L phosphate buffer (formula: 10.36 g / L Na2HPO4·12H2O, 3.32 g / L NaH2PO4·2H2O, 0.31 g / L NH4Cl and 0.13 g / L KCl), 1 mL / L trace element solution, carbon source and electron donor are added. The cathode liquid is a mixed solution of potassium ferricyanide (50 mmol / L) and potassium chloride (50 mmol / L). The cathode and the anode are connected through a 1kΩ external resistance, and a Gao Shi Li universal meter is used to collect output voltage data, one point is collected every 10 min. The environmental temperature of the MFC reactor is 30 DEG C.

[0021] Further, the application of a free magnetic carbon three-dimensional biological anode and bacterial interface modification in degrading p-xylene.

[0022] Further, the MFC reactor anode liquid also contains Klebsiella HN02 with OD 600 of 0.9-1.1.

[0023] Compared with the prior art, the application has the beneficial effects that:

[0024] (1) The application adopts a solvothermal method to prepare hydrophilic magnetic nano Fe3O4@ shaped porous carbon composite materials with strong electromagnetic performance, large specific surface area and high biocompatibility, which can be used as a three-dimensional biological anode in MFC, is conducive to the adhesion of microorganisms and maximizes their colonization space, and as an excellent electronic medium, can promote the efficiency of bacterial extracellular electron transfer, enhance interspecies electron transfer between bacteria and archaea, improve the biological anode conversion rate and electron output, thereby improving the overall performance of MFC and promoting the practical application process of MFC.

[0025] (2) The application can synthesize magnetite particles with high hydrophilicity by using sodium acetate as an alkali source, biocompatible trisodium citrate as an electrostatic stabilizer, ethylene glycol as a solvent and a reducing agent, and performing a solvothermal reaction at high temperature. 3+ The three carboxyl groups in trisodium citrate have strong coordination affinity, and in the solvothermal reaction process, the citric acid groups can be anchored on the surface of the magnetite nanocrystals, enhancing the dispersibility of the magnetite particles and inhibiting the growth of the crystal grains, thereby obtaining small-size and uniformly-sized highly hydrophilic magnetic Fe3O4 nanoparticles. Thus, in the reaction process, the magnetic nanoparticles grow inside and on the surface of the porous carbon material rich in pore structure, improving the hydrophobicity of the carbon spheres and providing more electron transfer sites to improve the overall conductivity of the porous carbon, thereby accelerating the extracellular electron transfer and interspecies electron transfer processes of microorganisms. In addition, the magnetic nano Fe3O4@ shaped porous carbon can be used as a three-dimensional biological anode to provide a larger surface area for microbial growth in each volume of reactor, thereby improving the biological anode conversion rate. Secondly, the charges can be stored in the pores of the shaped porous carbon in the form of a double electric layer, which can significantly improve the performance of the three-dimensional biological anode and enhance the diversity, stability and bioelectricity of the microbial community.

[0026] The MR-1+HNO2+Fe3O4@ shaped porous carbon sphere system in the application can improve the removal effect of p-xylene. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 Example 1 Synergistic MFC power generation schematic diagram

[0028] Figure 2 MR-1 system, MR-1+ shaped porous carbon sphere system, MR-1+Fe3O4@ shaped porous carbon sphere system MFC output voltage comparison chart

[0029] Figure 3 Fe3O4@ shaped porous carbon sphere actual object diagram

[0030] Figure 4 Comparative Example 2 power generation comparison chart

[0031] Figure 5Comparison chart of electricity generation performance of Example 2 and Comparative Example 3

[0032] Figure 6 Comparison chart of p-xylene degradation effect of Example 2 and Comparative Example 3 DETAILED DESCRIPTION

[0033] In order to better understand the technical content of the present application, the following specific examples are provided to further illustrate the present application.

[0034] The experimental methods used in the embodiments of the present application are conventional methods unless otherwise specified.

[0035] The materials, reagents, etc. used in the embodiments of the present application can be obtained from commercial channels unless otherwise specified.

[0036] The electrically active bacteria Shewanella oneidensis MR-1 used in the embodiments of the present application can be purchased from the Microbial Culture Collection Center.

[0037] Example 1

[0038] (1) Preparation of shaped porous carbon spheres: 5 g of eucalyptus wood powder, 15 g of phenol and 0.49 mL of sulfuric acid were sequentially placed in a three-necked flask for liquefaction reaction at 150°C for 2 h. After the liquefaction product was cooled to room temperature, it was washed with methanol, vacuum filtered to obtain a methanol-liquefaction product, and then the methanol was removed by distillation under reduced pressure to obtain the liquefaction product. The liquefaction product was uniformly mixed with 0.72 g of NaOH and 30 mL of deionized water, 17 mL of 37% formaldehyde solution was added dropwise at 70°C, stirred for 30 min, then 30 mL of anhydrous ethanol and 10 mL of deionized water were added, and stirring was continued for 2 h. Finally, 140 mL of deionized water was added for dilution, and the mixture was transferred to a polytetrafluoroethylene-lined stainless steel reactor, which was hydrothermally reacted at 130°C for 24 h. After washing and centrifuging with anhydrous ethanol and deionized water, a hydrothermal product was obtained. The hydrothermal product was uniformly mixed with 12 g of ZnCl2 and filled into a spherical mold, dried, and then placed in a tube furnace, which was heated to 600°C at a heating rate of 5°C / min and maintained for 90 min. The obtained carbon spheres were washed with 1 mol / L HCl solution and then with deionized water until neutral, and dried to obtain shaped porous carbon spheres.

[0039] (2) Preparation of magnetic carbon spheres: 2.16 g of FeCl3·6H2O and 0.4 g of trisodium citrate were dissolved in 40 mL of ethylene glycol, 2.4 g of sodium acetate was added, and the mixture was stirred for 30 min, then the shaped porous carbon spheres were added and stirred for another 30 min, and then the mixture was transferred to a polytetrafluoroethylene-lined reactor, which was reacted at 200°C for 12 h. After the reaction was completed, the product was washed with anhydrous ethanol and water, and dried to obtain Fe3O4@shaped porous carbon spheres.

[0040] (3) The construction and start-up of MFC reactor: A double-chambered organic glass reactor was used, with an effective volume of 100 mL for both the anode and cathode chambers, which were separated by a Nafion 117 proton exchange membrane. The anode material was a carbon brush (3 cm in diameter and 3 cm in length), and the cathode material was a graphite rod (6 mm in diameter and 10 cm in length).

[0041] (4) Fe3O4@shaped porous carbon spheres (20 g / L) were added to the anode chamber, and the electroactive bacteria Shewanella onesidensis MR-1 was selected as the inoculated bacteria. The MR-1 suspension was dispersed in 90 mL of anolyte to an OD 600 of 1.0, and then inoculated into the MFC reactor. Nitrogen was bubbled for 15 min to form an anaerobic environment. The composition of the anolyte was 50 mmol / L phosphate buffer (formula: 10.36 g / L Na2HPO4·12H2O, 3.32 g / L NaH2PO4·2H2O, 0.31 g / L NH4Cl, and 0.13 g / L KCl), 1 mL / L trace element solution, 18 mmol / L sodium lactate as a carbon source and electron donor. The catholyte was a mixture of 90 mL of potassium ferricyanide (50 mmol / L) and potassium chloride (50 mmol / L). The cathode and anode were connected by a 1 kΩ external resistor, and a multimeter was used to collect output voltage data, with one point collected every 10 min. The environmental temperature of the MFC reactor was 30°C.

[0042] Comparative Example 1

[0043] On the basis of Example 1, two different systems of MFC reactors were constructed, including the MR-1 system and the MR-1+shaped porous carbon sphere system.

[0044] MR-1 system: The electroactive bacteria Shewanella onesidensis MR-1 was selected as the inoculated bacteria, and the MR-1 suspension was dispersed in 90 mL of anolyte to an OD 600The pH value was 1.0, and then inoculated into the MFC reactor, nitrogen was bubbled for 15 min to form an anaerobic environment. The composition of the anolyte: 50 mmol / L phosphate buffer (formula: 10.36 g / L Na2HPO4·12H2O, 3.32 g / L NaH2PO4·2H2O, 0.31 g / L NH4Cl and 0.13 g / L KCl), 1 mL / L trace element solution, 18 mmol / L sodium lactate as carbon source and electron donor. The catholyte was a mixture of 90 mL potassium ferricyanide (50 mmol / L) and potassium chloride (50 mmol / L). The cathode and anode were connected by a 1 kΩ external resistance, and the output voltage data were collected by a multimeter, with one point collected every 10 min. The ambient temperature of the MFC reactor was 30°C.

[0045] MR-1+ shaped porous carbon ball system: (1) Preparation of shaped porous carbon balls: 5 g of eucalyptus powder, 15 g of phenol and 0.49 mL of sulfuric acid were sequentially placed in a three-necked flask for liquefaction reaction at 150°C for 2 h. After the liquefaction product was cooled to room temperature, it was washed with methanol, vacuum filtered to obtain a methanol-liquefaction product, and then the methanol was removed by distillation under reduced pressure to obtain the liquefaction product. The liquefaction product was uniformly mixed with 0.72 g of NaOH and 30 mL of deionized water, 17 mL of 37% formaldehyde solution was added dropwise at 70°C, stirred for 30 min, then 30 mL of anhydrous ethanol and 10 mL of deionized water were added, and stirring was continued for 2 h. Finally, 140 mL of deionized water was added for dilution, and the mixture was transferred into a polytetrafluoroethylene-lined stainless steel reactor, which was hydrothermally reacted at 130°C for 24 h. After washing and centrifuging with anhydrous ethanol and deionized water, a hydrothermal product was obtained. The hydrothermal product was uniformly stirred with 12 g of ZnCl2 and filled into a spherical mold, dried, and then placed in a tube furnace, with a heating rate of 5°C / min to 600°C, and kept for 90 min. The obtained carbon balls were washed with 1 mol / L HCl solution and then with deionized water until neutral, and dried to obtain shaped porous carbon balls.

[0046] Shaped porous carbon balls (20 g / L) were added to the anode chamber, and the electroactive bacteria Shewanella oneidensis MR-1 was selected as the inoculated bacteria. The MR-1 suspension was dispersed in 90 mL of anolyte to OD 600The initial pH value of the anolyte was 1.0, and then inoculated into the MFC reactor, and nitrogen was bubbled for 15 min to form an anaerobic environment. The composition of the anolyte: 50 mmol / L phosphate buffer (formula: 10.36 g / L Na2HPO4·12H2O, 3.32 g / L NaH2PO4·2H2O, 0.31 g / L NH4Cl and 0.13 g / L KCl), 1 mL / L trace element solution, 18 mmol / L sodium lactate as carbon source and electron donor. The catholyte was a mixture of 90 mL potassium ferricyanide (50 mmol / L) and potassium chloride (50 mmol / L). The cathode and anode were connected by a 1 kΩ external resistance, and a Giehling multimeter was used to collect output voltage data, with one point collected every 10 min. The environmental temperature of the MFC reactor was 30°C.

[0047] Test Example 1

[0048] The power generation performance of Test Example 1 and Comparative Example 1 was tested.

[0049] Reference Figure 1 Fe3O4@ shaped porous carbon balls of Example 1 were used as a three-dimensional biological anode and a magnetic electron medium. The space for bacterial colonization was optimized, the porous structure had good adsorption effect on organic substrates, could improve the conversion rate of the biological anode, store electric charge, enhance the extracellular electron transfer of bacteria and interspecies electron transfer, and improve the power generation performance of the MFC.

[0050] Reference Figure 2 The power generation of MFC reactors in three different systems, i.e. a simple MR-1 system, an MR-1 + shaped porous carbon ball system, and an MR-1 + Fe3O4@ shaped porous carbon ball system, was compared. The maximum output voltage of the simple MR-1 system was 354 mV. After adding the porous carbon balls (MR-1 + porous carbon ball system), the maximum output voltage increased to 400 mV, indicating that the porous carbon balls as electron mediators accelerated the extracellular electron transfer of electroactive bacteria. After adding the magnetized porous carbon balls to the system (MR-1 + Fe3O4@ porous carbon ball system), the maximum output voltage increased to 452 mV, which was attributed to the synergistic effect of the magnetic electron medium and the porous carbon balls. As a three-dimensional biological anode, the porous structure of Fe3O4@ shaped porous carbon balls was beneficial for the adhesion, growth and reproduction of microorganisms, and could enrich organic substrates and improve the conversion rate of the biological anode. In addition, as a magnetic electron medium, it could be closely combined with the outer surface of bacteria to accelerate the extracellular electron transfer of bacteria.

[0051] Comparative Example 2

[0052] The particle size of Fe3O4@ shaped porous carbon balls was adjusted to 2 mm and 8 mm based on Example 1.

[0053] Test Example 2

[0054] The particle size of the Fe3O4@shaped porous carbon balls prepared in Comparative Example 2 was detected by referring to the output voltage detection method in Example 1.

[0055] Referring to Figure 3 The particle size of the Fe3O4@shaped porous carbon balls prepared in Example 1 was about 5 mm.

[0056] Referring to Figure 4 The effects of Fe3O4@shaped porous carbon balls with different particle sizes on MFC electricity generation were compared. The maximum output voltage of Fe3O4@shaped porous carbon balls with a particle size of 2 mm was 381 mV, and the maximum output voltage of Fe3O4@shaped porous carbon balls with a particle size of 8 mm was 399 mV, both of which were smaller than the maximum output voltage (452 mV) of Fe3O4@shaped porous carbon balls with a particle size of 5 mm. This indicates that Fe3O4@shaped porous carbon balls with too large or too small particle sizes are not conducive to MFC electricity generation.

[0057] Example 2

[0058] Fe3O4@shaped porous carbon balls synthesized in Example 1 were used to mediate the synergistic degradation of p-xylene by Shewanella oneidensis MR-1 and Klebsiella HN02 and MFC electricity generation.

[0059] Klebsiella HN02 was deposited in the Guangdong Microbial Culture Collection Center, named Klebsiella sp. HN02, with the accession number GDMCC No: 62011, and the deposit date was November 4, 2021.

[0060] (1) Construction and start-up of MFC reactor: a double-chamber glass reactor was used, with an effective volume of 350 mL in the anode and cathode chambers, separated by a Nafion 117 proton exchange membrane. The anode material was a carbon brush (diameter 3 cm, length 5 cm), and the cathode material was a graphite rod (diameter 6 mm, length 15 cm).

[0061] Fe3O4@shaped porous carbon balls synthesized in Example 1 were used, and 5 g / L of Fe3O4@shaped porous carbon balls were added to the anode chamber. The enriched Klebsiella HN02 was washed and centrifuged, and dispersed in 250 mL of anode liquid to an OD 600The value of R was 1.0, and the same amount of Shewanella onesidensis MR-1 was added, and then inoculated into the MFC reactor, and nitrogen was bubbled for 15 min to form an anaerobic environment. 10 μL of p-xylene liquid was added as the sole carbon source and electron donor on day 0 and day 2, respectively. A magnetic stirrer was started, and the magnetic speed was set to 350 rpm to promote the mass transfer process of hydrophobic p-xylene. The composition of the anode liquid: 50 mmol / L phosphate buffer (composition: 10.36 g / L Na2HPO4·12H2O, 3.32 g / L NaH2PO4·2H2O, 0.31 g / L NH4Cl and 0.13 g / L KCl), 1 mL / L trace element solution. The cathode liquid was a mixture of 250 mL potassium ferricyanide (50 mmol / L) and potassium chloride (50 mmol / L). The cathode and anode were connected by a 1 kΩ external resistor, and a multimeter was used to collect output voltage data, with one point collected every 10 min. The environmental temperature of the MFC reactor was 30°C. The p-xylene concentration was detected by a gas chromatograph (Agilent 7890B, USA), with the column oven temperature set to 60°C, the injection port temperature set to 200°C, and the detector temperature set to 200°C.

[0062] Comparative Example 3

[0063] On the basis of Example 2, MFC reactors of two different systems, MR-1 system and MR-1+Fe3O4@shaped porous carbon ball system, were constructed.

[0064] MR-1 system: The electroactive bacteria Shewanella onesidensis MR-1 was selected as the inoculated bacteria, and the MR-1 suspension was dispersed in 250 mL of anode liquid to OD 600The MFC reactor was inoculated with a pH of 1.0 and then bubbling nitrogen for 15 minutes to create an oxygen-free environment. On days 0 and 2, 10 μL of p-xylene was added as the sole carbon source and electron donor. Stirring was initiated to promote mass transfer of the hydrophobic p-xylene. A magnetic stirrer was activated and set to 350 rpm to facilitate mass transfer of the hydrophobic p-xylene. The anolyte consisted of 50 mmol / L phosphate buffer (formula: 10.36 g / L Na2HPO4·12H2O, 3.32 g / L NaH2PO4·2H2O, 0.31 g / L NH4Cl, and 0.13 g / L KCl) and 1 mL / L trace element solution. The catholyte was a mixture of 250 mL of potassium ferricyanide (50 mmol / L) and potassium chloride (50 mmol / L). The cathode and anode were connected via a 1 kΩ external resistor, and a Keithley multimeter was used to collect output voltage data every 10 minutes. The MFC reactor was operated at an ambient temperature of 30°C. Para-xylene concentration was measured using a gas chromatograph (Agilent 7890B, USA) with column oven temperature set at 60°C, inlet temperature at 200°C, and detector temperature at 200°C.

[0065] MR-1+Fe3O4@formed porous carbon ball system: Fe3O4@formed porous carbon balls synthesized in Example 1 were used, 5 g / L of Fe3O4@formed porous carbon balls were added to the anode chamber, and the electroactive bacteria Shewanella onesidensis MR-1 was selected as the inoculum. The MR-1 suspension was dispersed in 250 mL of the anode solution until the OD 600 The MFC reactor was inoculated with a pH of 1.0 and then bubbling nitrogen for 15 minutes to create an oxygen-free environment. On days 0 and 2, 10 μL of p-xylene was added as the sole carbon source and electron donor. Stirring was initiated to promote mass transfer of the hydrophobic p-xylene. A magnetic stirrer was activated and the magnetic speed was set to 350 rpm to promote mass transfer of the hydrophobic p-xylene. The anolyte consisted of 50 mmol / L phosphate buffer (formula: 10.36 g / L Na2HPO4·12H2O, 3.32 g / L NaH2PO4·2H2O, 0.31 g / L NH4Cl, and 0.13 g / L KCl) and 1 mL / L trace element solution. The catholyte was a mixture of 250 mL of potassium ferricyanide (50 mmol / L) and potassium chloride (50 mmol / L). The cathode and anode were connected via a 1 kΩ external resistor, and a Keithley multimeter was used to collect output voltage data every 10 minutes. The MFC reactor was operated at an ambient temperature of 30°C. Para-xylene concentration was measured using a gas chromatograph (Agilent 7890B, USA) with column oven temperature set at 60°C, inlet temperature at 200°C, and detector temperature at 200°C.

[0066] Test Example 3

[0067] The electricity generation performance of Test Example 2 and Comparative Example 3 was tested.

[0068] Referring to Figures 5-6 The electricity generation of MFC reactors of three different systems, i.e. the MR-1 system, the MR-1+Fe3O4@shaped porous carbon ball system and the MR-1+HN02+Fe3O4@shaped porous carbon ball system, was compared. The initial voltage of the MR-1+Fe3O4@shaped porous carbon ball system (128 mV) and the MR-1+HN02+Fe3O4@shaped porous carbon ball system (130 mV) was higher than that of the MR-1 system (47 mV), which was attributed to the rapid electron transfer between the bacteria and the electrode interface caused by the presence of Fe3O4@shaped porous carbon balls. In addition, the maximum output voltage of the MR-1 system was 154 mV, the maximum output voltage of the MR-1+Fe3O4@shaped porous carbon ball system was 165 mV, and the maximum output voltage of the MR-1+HN02+Fe3O4@shaped porous carbon ball system was 254 mV, which was the highest among the three systems. Through monitoring the concentration of p-xylene, it was found that the p-xylene removal rate of the system with Fe3O4@shaped porous carbon balls was higher than that of the MR-1 system. On the one hand, the porous structure of the Fe3O4@shaped porous carbon ball as a three-dimensional bio-anode was beneficial to the adhesion, growth and reproduction of microorganisms, and could enrich organic substrates and improve the bio-anode conversion rate. On the other hand, the Fe3O4@shaped porous carbon ball as a magnetic electron mediator could be closely combined with the outer surface of the bacteria, promote the extracellular electron transfer, accelerate the electron transfer between the organic substrates and the bacteria and between the bacteria and the electrode, and also could act as a "bridge" between the bacteria, enhance the interspecific electron transfer between the Shewanella and the Klebsiella, and thus improve the overall performance of the MFC.

[0069] The above only describes preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a free magnetic carbon-rich three-dimensional bioanode, characterized in that: The following steps are involved: (1) crushing the biomass to obtain biomass powder, mixing the biomass powder with phenol and a catalyst to carry out a liquefaction reaction to obtain a biomass liquefaction product; (2) reacting the biomass liquefaction product with formaldehyde to obtain a resin reaction product, and subjecting the resin reaction product to a hydrothermal reaction to obtain a hydrothermal reaction product; (3) mixing the hydrothermal reaction product and zinc chloride and placing the mixture in a mold, demolding, carbonizing, pickling, and washing with water to obtain porous shaped carbon; (4) An iron source, trisodium citrate, and ethylene glycol are mixed, added to the shaped porous carbon and stirred, and then sodium acetate is added and mixed to prepare a mixed material. The mixed material is subjected to a solvent thermal reaction to prepare a free magnetic carbon-rich three-dimensional bioanode, which is used to assemble a bacterial interface modified enhanced microbial fuel cell.

2. The method for preparing a free magnetic carbon-rich three-dimensional bioanode according to claim 1, wherein: In step (1), the mass ratio of biomass powder to phenol is 1:1-6; the catalyst is one or more of sulfuric acid, phosphoric acid, and p-toluenesulfonic acid, and the mass ratio of the catalyst to biomass powder is 0.1-0.6:

1.

3. The method for preparing a free magnetic carbon-rich three-dimensional bioanode according to claim 1, wherein: In step (1), the temperature of the liquefaction reaction is 120-170° C., and the reaction time is 0.5-5 h.

4. The method for preparing a free magnetic carbon-rich three-dimensional bioanode according to claim 1, wherein: In step (2), the mass ratio of the formaldehyde to the biomass liquefaction product is 0.8-3:1, the temperature of the resinification reaction is 50-100°C, the resinification reaction time is 30-120 minutes, the temperature of the hydrothermal reaction is 100-160°C, and the hydrothermal reaction time is 6-24 hours.

5. The method for preparing a free magnetic carbon-rich three-dimensional bioanode according to claim 1, wherein: In step (3), the mass ratio of biomass powder to zinc chloride is 1:1.6-4.8, the shape of the mold is one of spherical, cylindrical, and cubic, the carbonization is carried out at 400-1000°C for 30-180 minutes under a nitrogen atmosphere, and the pickling is carried out using one of hydrochloric acid and sulfuric acid, and the concentration of the pickling is 0.1-2 mol / L.

6. The method for preparing a free magnetic carbon-rich three-dimensional bioanode according to claim 1, wherein: In step (4), the iron source is one or both of ferric chloride and ferric nitrate, the iron source concentration is 0.05-0.35 mol / L, the trisodium citrate concentration is 8-80 mmol / L, the formed porous carbon concentration is 20-120 g / L, the sodium acetate concentration is 0.2-1.5 mol / L, the solvent thermal reaction temperature is 200-220°C, and the reaction time is 4-15 h.

7. The method for preparing a free magnetic carbon-rich three-dimensional bioanode according to claim 1, wherein: The bacteria is the electroactive bacteria Shewanella Shewanella onesidensis MR-1.

8. The method for preparing a free magnetic carbon-rich three-dimensional bioanode according to claim 7, wherein: The OD of the Shewanella anolyte 600 It is 0.9-1.

1.

9. Use of the free magnetic carbon-rich three-dimensional bioanode prepared by the preparation method of the free magnetic carbon-rich three-dimensional bioanode according to any one of claims 1 to 8 in the degradation of p-xylene.

10. The use according to claim 9, characterized in that The MFC reactor anode liquid also contains OD 600 The Klebsiella HN02 is 0.9-1.1.

Images