Fenton technology coupled microbial fuel cell, preparation method and application

Abstract

The invention provides a Fenton technology coupled microbial fuel cell, a preparation method and application, and relates to the field of environment, materials and energy, the specific technical scheme is as follows: the Fenton technology coupled microbial fuel cell comprises an anode, a cathode and a catholyte, and is characterized in that the anode is a biological anode, the cathode is an air cathode, and the air cathode is an air cathode; the air cathode comprises an oxygen reduction electrocatalyst and a cathode substrate I, the oxygen reduction electrocatalyst is attached to the cathode substrate I, and the catholyte is common industrial and domestic wastewater. The electro-Fenton technology is introduced into the air cathode of the microbial fuel cell, the cathode fully utilizes electrons generated by metabolism of a biological anode to carry out an oxygen reduction process in the presence of air, so that hydrogen peroxide is generated in situ and is activated into active species such as hydroxyl free radicals through a Fenton catalyst, and the hydrogen peroxide is converted into hydrogen peroxide. Therefore, the purpose of degrading complex pollutants with low energy consumption is achieved.

Description

Technical Field

[0001] The invention belongs to the fields of environment, materials and energy, and in particular relates to a Fenton technology coupled microbial fuel cell, a preparation method and an application thereof. Background Art

[0002] Microbial fuel cells (MFCs) are bioelectrochemical systems that use electrochemically active microorganisms to oxidize organic substrates in wastewater and generate electricity at the same time. Due to the environmental and sustainable advantages of MFC, it has gradually attracted attention in the field of wastewater treatment, but its low treatment efficiency for wastewater limits its practical application. The electro-fenton (EF) process has been proven to be a promising technology due to its high efficiency in pollutant degradation and the advantages of in-situ synthesis of hydrogen peroxide (H2O2). It provides an excellent solution to the high cost of H2O2 in terms of transportation, storage and use risks, and effectively alleviates the problem of large amounts of iron sludge produced during the reaction of traditional Fenton oxidation technology. Generally, the EF process generates H2O2 in situ through electrons in the cathode oxygen reduction reaction, which can then be activated by Fenton or Fenton-like catalysts to generate ·OH, thereby effectively degrading pollutants. In this process, the synthesis of H2O2 still requires the consumption of additional energy to provide electrons for the reaction. MFC-Fenton has attracted attention due to its self-driven degradation of pollutants, power generation and good environmental compatibility. In the MFC-Fenton system, organic matter is oxidized to produce electrons and protons through the metabolic process of anode microorganisms. The metabolic process of anode microorganisms has no harmful byproducts, and it efficiently utilizes low-cost carbon sources, thereby improving overall productivity. After the electrons and protons reach the cathode chamber through the external circuit and the proton exchange membrane respectively, they jointly undergo the reduction process of the electron acceptor. O2 generates H2O2 through a double electron path at the cathode, and after activation, active species are generated, thereby achieving the purpose of low energy consumption and rapid degradation of pollutants. Summary of the invention

[0003] The purpose of this application is to solve the problem of low degradation efficiency of organic pollutants under low energy consumption, and to provide a Fenton technology coupled microbial fuel cell, preparation method and application. The present invention introduces an oxygen reduction electrocatalyst into the microbial fuel cell, and uses the oxygen reduction electrocatalyst and the electrode substrate loaded thereon as an air cathode to receive electrons generated from the anode of the microbial fuel cell to synthesize H2O2 in situ, and generates active species after activation by metal ions, thereby accelerating the degradation of organic pollutants and improving the degradation efficiency of the microbial fuel cell.

[0004] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0005] A Fenton technology coupled microbial fuel cell comprises an anode, a cathode and a cathode liquid, wherein the anode is a biological anode, the cathode is an air cathode, the air cathode comprises an oxygen reduction electrocatalyst and a cathode substrate I, the oxygen reduction electrocatalyst is attached to the cathode substrate I, and the cathode liquid is industrial, domestic and environmental wastewater.

[0006] Furthermore, the bioanode includes microorganisms and an anode substrate II, wherein the microorganisms are mainly electrogenic bacteria and are attached to the anode substrate II.

[0007] Furthermore, the anode substrate II is a two-dimensional carbon material or a three-dimensional carbon material. Preferably, the two-dimensional carbon material includes carbon cloth or carbon paper, and the three-dimensional carbon material is carbon felt.

[0008] Furthermore, the cathode substrate I is a two-dimensional carbon material or a three-dimensional carbon material. Preferably, the two-dimensional carbon material includes a catalyst-free commercial air electrode, and the three-dimensional carbon material is carbon felt.

[0009] Furthermore, the air cathode also includes oxygen in the air.

[0010] Furthermore, the pollutants in the cathode liquid are one or a combination of several pollutants selected from phenols, antibiotics, pesticides, dyes and organic solvents in battery wastewater.

[0011] Furthermore, the antibiotics are one or a combination of several pollutants selected from tetracycline, amoxicillin, ciprofloxacin, and ofloxacin; the pesticides are one or a combination of several pollutants selected from sulfonylurea, amide, and triazine; the dyes are one or a combination of several pollutants selected from azo dyes, sulfur dyes, anthraquinone dyes, and aromatic methane dyes; and the organic solvents in the battery wastewater are one or a combination of several pollutants selected from dimethyl carbonate, ethylene carbonate, and N-methylpyrrolidone.

[0012] Furthermore, the specific preparation process of the oxygen reduction electrocatalyst is to pickle the commercial carbon black BP2000 with 9M nitric acid or sulfuric acid at 90°C for 9 hours, then take 100mg of the acid-activated carbon black and add it to a solution of 44ml water and 72mg of the metal compound and stir overnight to fully adsorb cobalt ions on the surface of the carbon black, then wash and dry, grind it with urea at a mass ratio of 1:10, and calcine it in an Ar atmosphere at 700-900°C for 1-3 hours. The final sample is named CB@Co-NC, wherein the metal compound is a Co, Fe, Mn, Cu-based metal compound with Fenton or Fenton-like properties.

[0013] A method for preparing the above-mentioned Fenton technology coupled microbial fuel cell comprises the following steps:

[0014] Step 1: Ultrasonically mix 10 mg of oxygen reduction electrocatalyst and 1 mL of binder, coat them on cathode substrate I, and dry them to obtain an air cathode; the total amount of the binder is 1 mL, consisting of 30 μL of component A and 970 μL of component B, component A is a 5% Nafion solution, and component B is a combination of one or more of ethanol, isopropanol, polytetrafluoroethylene aqueous dispersion, and polydimethylsiloxane.

[0015] Step 2: Assemble and start the microorganisms and anode substrate II to form a bioanode;

[0016] Step 3: Construct a Fenton technology-coupled microbial fuel cell.

[0017] An application of the above-mentioned Fenton technology coupled microbial fuel cell includes the following steps: when the microorganisms form a biofilm at the anode of the Fenton technology coupled microbial fuel cell, they begin to provide electrons for the oxygen reduction electrocatalyst at the cathode, generate hydrogen peroxide in situ at the cathode, produce the Fenton effect under the activation of metal ions, add pollutants, and start the degradation process.

[0018] The beneficial effects of the present invention compared to the prior art are:

[0019] (1) In terms of the preparation of oxygen reduction electrocatalysts, the preparation process of carbon black-supported metal carbonitride (CB@Co-NC) is compared with that of traditional metal carbonitride (Co-NC). The modified electrocatalyst has a higher degree of metal dispersion, greatly reduces the clustering of metal particles, and provides a larger surface area, thereby providing more electrochemical reaction sites for the electrochemical reaction, greatly improving the oxygen reduction ability of the catalyst, thereby increasing the hydrogen peroxide yield.

[0020] (2) The significant advantage of the present invention is that the bioanode of the Fenton technology coupled microbial fuel cell can generate a considerable amount of electrons through microbial metabolism and transmit them to the cathode through an external circuit to participate in the oxygen reduction process. In the cathode chamber, in the presence of oxygen and metal carbon nitrogen catalyst, a certain amount of hydrogen peroxide can be produced through a 2-electron oxygen reduction process. The metal acts as an active center for activating hydrogen peroxide, generating active species such as hydroxyl radicals, thereby achieving the purpose of degrading pollutants in the cathode chamber.

[0021] (3) The hydrogen peroxide yield of the modified CB@Co-NC is significantly higher than that of Co-NC, and the electron transfer number of CB@Co-NC is closer to 2 electrons, which means that the modified material can produce more hydrogen peroxide and thus has better degradation performance.

[0022] (4) The electron transfer impedance of the modified CB@Co-NC is significantly smaller than that of Co-NC, which greatly improves the conductivity during the oxygen reduction process and is conducive to the reaction.

[0023] In summary, the present invention loads an oxygen reduction electrocatalyst on a cathode substrate to prepare an air cathode and introduces microorganisms into an anode to obtain a bioanode, and operates a microbial fuel cell under the condition that the cathode contacts the air. The hydrogen peroxide yield of the modified CB@Co-NC at a potential of 0.2V is 58.1%, which is much higher than the 27.3% of the Co-NC catalyst under the same conditions. And in terms of the number of electron transfers, the performance of the CB@Co-NC catalyst (2.9) is better than that of Co-NC (3.5). The electron transfer impedance of CB@Co-NC is 55.74Ω, which is much smaller than the electron transfer impedance of Co-NC (84.35Ω). The present invention uses the Fenton technology coupling method to divide the microbial fuel cell into two parts, one of which is that the modified oxygen reduction electrocatalyst exhibits a better in-situ hydrogen peroxide yield in the electrochemical process, and the other is that the more dispersed metal sites provide more abundant reaction sites for the electrochemical reaction and the activation of hydrogen peroxide. The significant advantage of the present invention is that the electrode manufacturing steps of the Fenton technology coupled microbial fuel cell are simple, the materials are easy to synthesize, and the electrons generated by the anode can be used to synthesize hydrogen peroxide in situ at the cathode to degrade pollutants. While reasonably utilizing energy, it makes up for the shortcomings of traditional microbial fuel cells in degradation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Transmission electron microscopy image of CB@Co-NC;

[0025] Figure 2 Transmission electron microscopy image of Co-NC;

[0026] Figure 3 The comparison chart of hydrogen peroxide yield of CB@Co-NC and Co-NC;

[0027] Figure 4 The comparison diagram of the electron transfer number of CB@Co-NC and Co-NC;

[0028] Figure 5 CV curves of CB@Co-NC at different scan rates;

[0029] Figure 6 CV curves of Co-NC at different scan rates;

[0030] Figure 7 Comparison of electrochemical active areas of CB@Co-NC and Co-NC;

[0031] Figure 8 The comparison diagram of Tafel slope between CB@Co-NC and Co-NC;

[0032] Fig. 9 This is a comparison diagram of the electron transfer impedance of CB@Co-NC and Co-NC;

[0033] Fig.10 CB@Co-NC and Co-NC were used as air cathode catalyst materials at 10 mg L -1 Comparison of degradation curves under tetracycline concentration conditions;

[0034] Fig.11 CB@Co-NC and Co-NC were used as air cathode catalyst materials at 30 mg L -1 Comparison of degradation curves under tetracycline concentration conditions;

[0035] Fig.12 CB@Co-NC and Co-NC were used as air cathode catalyst materials at 50 mg L -1 Comparison of degradation curves under tetracycline concentration conditions. DETAILED DESCRIPTION

[0036] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention should be included in the protection scope of the present invention.

[0037] Example 1

[0038] A method for preparing a Fenton technology coupled microbial fuel cell, the method comprises the following specific steps:

[0039] Step 1: Use isopropyl alcohol, deionized water and anhydrous ethanol to ultrasonically clean the normal commercial air cathode to remove dirt and impurities on the surface;

[0040] Step 2: 100 mg of carbon black was acid-washed and mixed with 44 ml of water and 72 mg of cobalt nitrate hexahydrate solution and stirred overnight. After drying, it was evenly ground with urea at a mass ratio of 1:10 and calcined at 900 ° C for 1 hour to obtain CB@Co-NC powder; the CB@Co-NC powder was tested by transmission electron microscopy. The obtained CB@Co-NC( Figure 1 ) is much smaller than the particle size range of Co-NC before modification ( Figure 2 ) particles, and the distribution of Co particles is more uniform without obvious clusters;

[0041] Step 3: 10 mg of the CB@Co-NC powder was weighed, mixed with 30 μl of Nafion and 970 μl of ethanol, and ultrasonicated for 1 hour to form an ink-like dispersion, which was then drop-coated on a commercial air cathode, which was fixed with a fixing member. After the air cathode was dried, an air cathode (CB@Co-NC) was obtained.

[0042] Step 4: The air cathode (CB@Co-NC) and the bioanode with introduced microorganisms together constitute a Fenton technology coupled microbial fuel cell. The electrochemical performance of the prepared electrode is tested using an electrochemical workstation.

[0043] The prepared air cathode was used to assemble a double-chamber (100mL / chamber) microbial fuel cell to examine the cathode performance, and the performance of the modified CB@Co-NC air cathode and the unmodified Co-NC air cathode was compared. It was found that the hydrogen peroxide yield of the modified air cathode reached 58.1%, which was much higher than the 27.3% of the Co-NC catalyst under the same conditions ( Figure 3 ). The electron transfer number is an important indicator to measure the ability to synthesize hydrogen peroxide during the oxygen reduction process. The ability of CB@Co-NC catalyst (2.9) to synthesize hydrogen peroxide is significantly better than that of Co-NC (3.5) ( Figure 4 In addition, the CV curves at different scan rates were tested in the same potential range ( Figure 5 and 6 ) to determine the electrochemical active area and site. CB@Co-NC catalyst (10.75mF cm -2 ) is much higher than Co-NC (1.93 mF cm -2 )( Figure 7 ). This indicates that the introduction of modified carbon black increases the conductivity and makes the metal particles more evenly dispersed, thereby providing more reaction sites and improving the synthesis and activation of hydrogen peroxide. In addition, by drawing the Tafel curve to evaluate the activity of the catalyst, it can be clearly seen that the CB@Co-NC catalyst (132.77mv dec -1 ) than Co-NC (135.21mv dec -1 ) has a lower Tafel slope. This indicates that it has a faster electrochemical kinetic process ( Figure 8 ). In addition, the electron transfer impedance of CB@Co-NC is 55.74Ω, which is much smaller than that of Co-NC (84.35Ω). This shows that the introduction of modified carbon black greatly improves the conductivity of the catalyst ( Fig. 9 ).

[0044] Furthermore, in step 2, the mass ratio of the carbon black to the urea is 1:10.

[0045] Furthermore, in step 3, the fixing member is a metal wire or an electrode clip, preferably an alligator clip. Other metal wires or electrode clips that are stable in the cathode electrolyte or dissolve in small amounts without significant effects on the electrode material may also be selected to fix the cathode.

[0046] Example 2

[0047] An application of Fenton technology coupled to a microbial fuel cell includes the following steps: when microorganisms form a biofilm on the anode of the microbial fuel cell, it indicates that electrons can be provided to the cathode to carry out the oxygen reduction process, tetracycline is added to the cathode chamber, the voltage change is determined by a data acquisition device, a certain amount of cathode liquid is taken at different time points, impurities are filtered using a 0.22 μm filter membrane, and the antibiotic absorbance is determined by an ultraviolet spectrophotometer to determine the antibiotic concentration. It was found that the degradation rate of the microbial fuel cell prepared at the CB@Co-NC modified air cathode (98.4%) was significantly higher than that of the Co-NC microbial fuel cell (80.3%), such as Figures 10-12 shown.

[0048] Furthermore, the added tetracycline antibiotics can also be other pollutants, such as phenols; antibiotics: tetracycline, amoxicillin, ciprofloxacin, ofloxacin, etc.; pesticides: sulfonylurea, amide, triazine; dyes: azo dyes, sulfur dyes, anthraquinone dyes, aromatic methane dyes, etc.; organic solvents: dimethyl carbonate, ethylene carbonate, N-methylpyrrolidone, etc.

[0049] The Fenton technology coupled microbial fuel cell described in the present invention is compared in terms of hydrogen peroxide yield, electron transfer number, electrochemical performance and pollutant degradation efficiency under different air cathode conditions to reflect the superiority of Fenton technology coupling.

[0050] Example 3

[0051] An application of a photocatalytic closely coupled microbial fuel cell comprises the following steps:

[0052] Step 1: The commercial carbon black BP2000 was acid-washed with 9M nitric acid at 90°C for 9 hours, and then 100 mg of the acid-washed activated carbon black was added to a solution of 44 ml water and 72 mg of cobalt nitrate hexahydrate and stirred overnight to fully adsorb cobalt ions on the surface of the carbon black. After that, it was washed and dried, and fully ground with urea in a mass ratio of 1:10, and calcined in an Ar atmosphere at 900°C for 1 hour. The final sample was named CB@Co-NC.

[0053] Step 2: Weigh 10 mg of CB@Co-NC into a centrifuge tube, add 30 μL of 5% Nafion and 970 μL of ethanol, mix, and ultrasonicate for about an hour until the liquid forms a viscous ink-like state. Use a pipette to drop it on the cleaned commercial air cathode substrate. After drying, the cathode part can be obtained. Use carbon felt as the anode substrate, introduce microorganisms to obtain a bioanode, and assemble the air cathode and the bioanode into a microbial fuel cell. The prepared microbial fuel cell is suitable for inoculating pure bacteria or mixed strains, and is not limited by the battery configuration.

[0054] Step 3: Use JEM-2100 transmission electron microscope (TEM) to observe the morphology and pore structure of nanoparticles. Use AMETEK Solartron's SI1287 electrochemical workstation and SI1260 impedance meter to measure the AC impedance of the electrode; and use Keithley 2700 data acquisition device to collect and record the battery voltage.

[0055] Step 4: Add tetracycline in the third cycle of the microbial fuel cell, and use the hydroxyl radicals produced by Fenton to quickly degrade the antibiotics. Pay attention to the changes in voltage and the concentration of antibiotics during illumination. Antibiotics are added in the third cycle of the microbial fuel cell because the microorganisms have formed a thick biofilm in the third cycle, which can provide a stable voltage and stable electrons to participate in the oxygen reduction process of the cathode, thereby producing a certain concentration of hydrogen peroxide for the degradation of pollutants, avoiding the inconvenience of adding additional hydrogen peroxide. The absorbance of the antibiotic is determined by a UV spectrophotometer, and its concentration change is determined by the standard curve of absorbance and concentration measured before the experiment.

[0056] Example 4

[0057] Referring to Example 3, in this example, 72 mg of cobalt nitrate hexahydrate powder and 720 mg of urea were weighed and fully ground and mixed, and then calcined in an Ar atmosphere at 900°C for 1 hour. The final sample was named Co-NC. 10 mg of Co-NC was weighed in a centrifuge tube, and 30 μL of 5% Nafion and 970 μL of ethanol were added respectively, mixed, and ultrasonicated for about one hour until the liquid formed a viscous ink-like state, and then applied to the cleaned commercial air cathode substrate with a pipette gun, and after drying, the cathode part was obtained, which was used as a comparative sample.

Claims

1. A Fenton technology coupled microbial fuel cell, comprising an anode, a cathode and a cathode liquid, characterized in that: The anode is a biological anode, the cathode is an air cathode, the air cathode comprises an oxygen reduction electrocatalyst and a cathode substrate I, the oxygen reduction electrocatalyst is attached to the cathode substrate I, and the cathode liquid is industrial, domestic and environmental wastewater.

2. A Fenton technology coupled microbial fuel cell according to claim 1, characterized in that: The biological anode comprises microorganisms and an anode substrate II. The microorganisms are mainly electrogenic bacteria and are attached to the anode substrate II.

3. A Fenton technology coupled microbial fuel cell according to claim 2, characterized in that: The anode substrate II is a two-dimensional carbon material or a three-dimensional carbon material.

4. A Fenton technology coupled microbial fuel cell according to claim 1, characterized in that: The cathode substrate I is a two-dimensional carbon material or a three-dimensional carbon material.

5. A Fenton technology coupled microbial fuel cell according to claim 1, characterized in that: The air cathode also includes oxygen.

6. A Fenton technology coupled microbial fuel cell according to claim 1, characterized in that: The pollutants in the cathode liquid are one or a combination of several pollutants selected from phenols, antibiotics, pesticides, dyes, and organic solvents in battery waste water.

7. A Fenton technology coupled microbial fuel cell according to claim 6, characterized in that: The antibiotics are one or a combination of several pollutants selected from tetracycline, amoxicillin, ciprofloxacin, and ofloxacin; the pesticides are one or a combination of several pollutants selected from sulfonylurea, amide, and triazine; the dyes are one or a combination of several pollutants selected from azo dyes, sulfur dyes, anthraquinone dyes, and aromatic methane dyes; the organic solvents in the battery wastewater are one or a combination of several pollutants selected from dimethyl carbonate, ethylene carbonate, and N-methylpyrrolidone.

8. A Fenton technology coupled microbial fuel cell according to any one of claims 1 to 7, characterized in that: The specific preparation process of the oxygen reduction electrocatalyst is to acid wash the commercial carbon black BP2000 with 9M nitric acid or sulfuric acid at 90°C for 9 hours, then take 100mg of the acid-washed activated carbon black and add it to a solution of 44ml water and 72mg of a metal compound and stir overnight to fully adsorb cobalt ions on the surface of the carbon black, then wash and dry, and grind it with urea at a mass ratio of 1:10, and calcine it in an Ar atmosphere at 700-900°C for 1-3 hours, wherein the metal compound is a Co, Fe, Mn, Cu-based metal compound with Fenton or Fenton-like properties.

9. A method for preparing a Fenton technology coupled microbial fuel cell according to any one of claims 1 to 8, characterized in that: The following steps are involved: Step 1: 10 mg of oxygen reduction electrocatalyst and 1 mL of binder are ultrasonically mixed and coated on cathode substrate Ⅰ, and dried to obtain an air cathode; Step 2: Assemble and start the microorganisms and anode substrate II to form a bioanode; Step 3: Construct a Fenton technology-coupled microbial fuel cell.

10. An application of a Fenton technology coupled microbial fuel cell according to any one of claims 1 to 8, characterized in that: The following steps are involved: When microorganisms form a biofilm at the anode of the Fenton technology-coupled microbial fuel cell, they begin to provide electrons to the oxygen reduction electrocatalyst at the cathode, generate hydrogen peroxide in situ at the cathode, produce the Fenton effect under the activation of metal ions, add pollutants, and start the degradation process.

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