Method for improving organic wastewater degradation efficiency of microbial fuel cell
By using conductive carbon felt and an applied voltage in a single-chamber microbial fuel cell, the structure is simplified and an oxygen gradient is formed, which solves the problem of poor performance of microbial fuel cells and achieves efficient degradation of organic wastewater.
Patent Information
- Application Number
- CN202411777450.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-05
- Publication Date
- 2026-01-20
AI Technical Summary
Existing microbial fuel cells have complex structures, separate anodes and cathodes, and require external resistors. The reaction conditions are difficult to control, resulting in poor battery performance. Oxygen inhibits anode microorganisms and reduces coulombic efficiency.
A single-chamber microbial fuel cell is used, with conductive carbon felt fixed in the reactor. Enrichment is achieved by applying an external voltage to create different dissolved oxygen gradients. Combined with DC voltage, an electrode environment is created at the top and bottom of the carbon felt, enabling the directional aggregation and stable reaction of microorganisms.
Aerobic, facultative, and anaerobic processes were achieved in one reactor, which improved the degradation efficiency of organic wastewater, with a COD degradation rate of 92.39%.
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Figure CN121361886A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of wastewater treatment, in particular to a method for improving the efficiency of microbial fuel cells in degrading organic wastewater. BACKGROUND
[0002] Microbial fuel cells (MFCs) are a kind of electrical energy device that uses microorganisms as anode catalyst to directly convert chemical energy in organic matter into electrical energy. It is a new and efficient way of utilizing biomass energy. It can generate electricity by decomposing biomass with bacteria, and has the advantages of no pollution, high energy conversion efficiency, and wide range of use. Therefore, MFCs have gradually become one of the research hotspots in today's society.
[0003] The common MFCs at present are double-chamber structures, which mainly consist of an anode, a cathode and a proton exchange membrane separating the anode and the cathode. In the anode chamber, the catalytic oxidation of organic matter by bacteria produces protons, electrons and metabolic products directly. The oxidation process produces electrons that are transmitted to the electrode surface through a carrier. The H + + produced by the anode diffuses through the proton exchange membrane to the cathode, while the electrons produced by the anode flow through an external circuit to reach the cathode of the battery. When the electrons flow through the external resistance, electrical energy is output. The electrons combine with the electron acceptor in the cathode chamber under the catalytic action of the cathode, and a reduction reaction occurs.
[0004] In recent years, microbial fuel cells have been tried to be used to treat biodegradable organic wastewater, to produce electricity while degrading the wastewater. However, so far, due to the complex structure of MFCs, in order to realize different reaction processes, the anode and cathode are generally in different reactors, and an ion exchange membrane is arranged between the anode and the cathode, an external resistance is needed between the electrodes, and different wastewaters need to be supplied to the anode and cathode chambers, which is complex in structure, and in addition, different reaction conditions need to be provided in different reaction chambers, for example, the anode is mostly anaerobic reaction, and the cathode needs aerobic reaction, which requires different dissolved oxygen conditions. These complex structures and reaction conditions result in the performance of MFCs being far lower than the ideal state. There are single-chamber microbial fuel cells in the prior art, which eliminate the cathode chamber, and the substances are oxidized by microorganisms at the single-chamber anode, the electrons are transferred from the anode to the external circuit to reach the cathode, and the protons are transferred through the proton exchange membrane to reach the cathode. The cathode is exposed to air, and oxygen serves as a direct electron acceptor. However, this single-chamber MFC still separates the anode and the cathode, and still needs an external resistance. In addition, due to the small distance between the cathode and the anode in the single-chamber structure, oxygen is easily transferred to the anode, which inhibits the production of electricity by microorganisms, and the reaction conditions of the anode and the cathode are difficult to control, which reduces the performance of the battery. In addition, since oxygen oxidizes the substances that should be oxidized by microorganisms, material loss occurs, which reduces the coulombic efficiency of the battery and the performance of the battery. Electrochemical methods have been reported to enhance anaerobic digestion, but continuous power supply and complex electrodes installed in the reactor limit the effectiveness and practical application. SUMMARY
[0005] Based on the above problems, the purpose of the present application is to provide a method for improving the degradation efficiency of organic wastewater by microbial fuel cells, which simplifies the structure of the microbial fuel cell system, and at the same time, through the enrichment treatment of the conductive carbon felt by an external voltage, an electrode is formed, and under the long-term action of the direct current external voltage, the microbial fuel cell is promoted to degrade the wastewater efficiently.
[0006] The purpose of the present application is achieved by the following technical solutions: A method for improving the degradation efficiency of organic wastewater by microbial fuel cells, characterized in that the microbial fuel cell is a single-chamber microbial fuel cell, a strip-shaped conductive carbon felt is fixed in a reactor, and an enrichment treatment is first performed, and after the completion of the electrode biological enrichment, water is introduced for degradation, the water flows into the reactor from the top and flows out from the bottom, the upper part of the reactor is connected to the positive electrode (+) of a direct current power supply, and the lower part of the reactor is connected to the negative electrode (-) of the direct current power supply, and the voltage of the direct current power supply is 0.2-0.8 V.
[0007] Further, the water inflow rate of the reactor is 5-12 mL / min, the dissolved oxygen content of the wastewater is about 2-4 mg / L, and the hydraulic retention time (HRT) is 2-5 h.
[0008] Further, the length of the conductive carbon felt is 15 cm, and the effective length is 12-13 cm.
[0009] Further, the enrichment treatment is that the inoculated sludge is poured into the reactor, the top of the reactor is opened, and the voltage of 0.2-0.6 V is applied for 5-7 days, after the enrichment is completed, the reactor is rested for 2 h, the sludge is discharged from the bottom, and then the reactor is sealed.
[0010] It has been proved in the prior art that the output power of single-chamber MFCs is different when different substances are used as fuel, that is, the type of fuel will affect the energy output of MFCs.
[0011] Most specifically, a method for improving the wastewater degradation efficiency of a microbial fuel cell, characterized by comprising the following steps: (1) conductive carbon felt pretreatment The conductive carbon felt with a length of 15 cm is ultrasonically treated in a acetone solution for 30 min, then the conductive carbon felt is pickled in a HCl solution with a mass concentration of 10% for 5 min, then washed with deionized water until neutral, and dried; (2) enrichment preparation of electrode The pretreated conductive carbon felt is fixed in the reactor, the inoculated sludge is poured into the reactor, and the voltage of 0.2-0.6 V is applied for 5-7 days. (3) degradation treatment of wastewater After the enrichment is completed, the reactor is rested for 2 h, the sludge is discharged from the bottom, the reactor is resealed, the upper part of the reactor is connected to the positive electrode (+) of a direct current power supply, and the lower part of the reactor is connected to the negative electrode (-) of the direct current power supply, the voltage of the direct current power supply is 0.2-0.8 V, the wastewater is pumped into the solution for degradation treatment, the wastewater inflow rate is 5-12 mL / min, the wastewater dissolved oxygen content is 2-4 mg / L, and the hydraulic retention time (HRT) is 2-5 h.
[0012] The present application has the following technical effects: The present application forms a gradient change of the dissolved oxygen concentration by applying a voltage, realizes different dissolved oxygen gradients in one reactor, realizes the aerobic, facultative and anaerobic processes, fixes the conductive carbon felt in the reactor, connects the upper and lower ends of the carbon felt to the direct current voltage, forms different electrode environments on the upper and lower ends of the carbon felt by using the external voltage, further combines the dissolved oxygen to further form stable anode and cathode processes, realizes the directional aggregation of the electricity-producing microorganisms and the electricity-consuming microorganisms in the reactor under the action of the dissolved oxygen and the voltage, and finally realizes the deep treatment of the organic wastewater, and the COD degradation rate of the treated organic wastewater reaches 92.39%. BRIEF DESCRIPTION OF DRAWINGS
[0013] Figure 1 : The schematic diagram of the structure principle of the reactor used in the present application.
[0014] Figure 2 SEM image of the conductive carbon felt after enrichment treatment in the present application.
[0015] Figure 3 COD removal rate curve and voltage change curve in three stages of testing in the present application.
[0016] Figure 4 COD removal rate curve and voltage change curve of short-term voltage on wastewater degradation in the present application. DETAILED DESCRIPTION
[0017] The present application will be described in detail below by examples, it is necessary to point out here that the following examples are only used to further illustrate the present application, and cannot be understood as limiting the scope of protection of the present application, the skilled in the art can make some non-essential improvements and adjustments to the present application according to the above content of the present application.
[0018] Example 1 A method for improving the efficiency of microbial fuel cell in degrading wastewater, comprising the following steps: (1) Pretreatment of conductive carbon felt The conductive carbon felt with a length of 15 cm is treated by ultrasonic in acetone solution for 30 min, then the conductive carbon felt is pickled in HCl solution with a mass concentration of 10% for 5 min, then washed with deionized water until neutral, and dried; (2) Enrichment preparation of electrode The pretreated conductive carbon felt is fixed in the reactor, the reactor is filled with inoculated sludge, an external voltage of 0.2 V is applied, and the treatment is carried out for 7 days; (3) Degradation of wastewater After enrichment, the reactor is placed for 2 h, the sludge is discharged from the bottom, the reactor is resealed, the upper part of the reactor is connected to the positive electrode (+) of the direct current power supply, and the lower part is connected to the negative electrode (-) of the direct current power supply, the voltage of the direct current power supply is 0.2 V, the wastewater is pumped into the solution for degradation treatment, the wastewater inflow rate is 12 mL / min, the wastewater dissolved oxygen content is 3 mg / L, and the hydraulic retention time (HRT) is 5 h.
[0019] The single-chamber reactor structure in the present application is shown in Figure 1 .
[0020] The microorganism adhesion on the anode and cathode of the reactor was observed by scanning electron microscope (SEM). The conductive carbon felt was immersed in 2.5% (mass percent) glutaraldehyde solution at 4℃ for 10-12 h, then washed with 0.1M PBS solution, and then immersed in 25%, 50%, 70%, 90% and 100% ethanol solution for 15 min, respectively. Finally, the conductive carbon felt was freeze-dried.
[0021] The SEM image of the conductive carbon felt after enrichment treatment is shown in Figure 2 . After inoculation of microorganism, obvious enrichment of microorganism was observed on the two electrode ends of the conductive carbon felt under the action of voltage. The surface of the carbon felt fiber was relatively rough, while the microorganism loading in the middle of the carbon felt was relatively less. The carbon felt part without microorganism loading was smooth. It was indicated that the steady DC voltage accelerated the rapid and selective enrichment of microorganism on the carbon felt.
[0022] In the process of organic wastewater treatment, the effect of short-term voltage and long-term voltage on wastewater treatment was monitored, and the changes of COD in organic wastewater and voltage were observed. For the effect of long-term voltage, three stages were monitored. The first stage was stable from the 5th day, and the second stage was entered after 3 days of stabilization, and the third stage was entered after 5 days of the second stage.
[0023] The results are shown in Figure 3 (a). It was indicated that the DC voltage promoted the activity of microorganism on the surface of conductive carbon felt. Under the action of 0.2V DC voltage, the average COD of effluent in the second stage was 14.42 mg / L, and the COD removal rate was 85.58%. After removing the voltage in the third stage, the average COD of effluent increased to 55.90 mg / L, and the COD removal rate was 45.10%, which decreased by about 40 percentage points.
[0024] The voltage change of the reactor is shown in Figure 3 (b). It can be seen that the voltage of the reactor was stabilized at 0.2V during the loading of DC voltage, and the voltage of the reactor decreased to 0V after removing the voltage. It was indicated that the 0.2V external DC voltage promoted the activity of microorganism in the reactor, thereby promoting the removal of COD. After removing the voltage, the COD value of the effluent of the reactor increased, which indicated that the activity of microorganism in the reactor decreased after removing the voltage. After the voltage was zero, the activity of microorganism on the surface of the conductive carbon felt decreased, and the conductivity of the conductive carbon felt decreased, which led to the increase of the internal resistance R of the whole reactor, the decrease of the electron movement speed, and the disordered movement of the electrons.
[0025] For the effect of short-term voltage, 0.2V DC voltage was maintained for 6 h after the effluent quality of the reactor was stable, and then the voltage was removed. The results are shown inFigure 4 (a) as shown, under the action of voltage, the average COD of effluent is 25.37 mg / L, after the voltage is removed, the COD of effluent increases obviously to 45.29 mg / L, the removal rate decreases from 74.63% to 54.71%, which shows that the voltage has obvious effect on microbial activity, in addition, the voltage can also promote the directional movement of electrons in the reactor, and reduce the internal resistance of the reactor. The voltage change is as shown in Figure 4 (b) as shown, before and after the action of external voltage, the voltage of the reactor changes, which is probably due to the stimulation effect of external voltage on microorganisms, after the effect disappears, the microbial activity of the microbial load of the conductive carbon felt decreases, at the same time, the removal of the applied voltage causes the disorder of the electron flow in the conductive carbon felt, and increases the internal resistance of the reactor, and the electrons of the anode and cathode cannot form effective transmission.
[0026] Comparative Example 1 The wastewater treatment is carried out in the manner of Example 1, the initial COD of the wastewater is 210.6 mg / L, compared with Example 1, the enrichment treatment is carried out by using different applied voltages, after the long-term action of the applied voltage, the detection results of the effluent water quality after stabilization are shown in Table 1.
[0027] Table 1:
[0028] From the above table, it can be seen that the conductive carbon felt obtained by enrichment treatment under the action of different applied voltages is used as the anode and cathode of the microbial fuel cell for wastewater degradation treatment, and the COD and degradation efficiency obtained are obviously different, among which the conductive carbon felt obtained by enrichment treatment under 0.2-0.6 V is used as the electrode of the microbial fuel cell, the degradation efficiency of wastewater is obviously improved, and the COD degradation rate reaches the highest at 0.6 V, while the COD removal rate of the conductive carbon felt enriched under the action of 0.8 V applied voltage decreases obviously. In addition, when treating actual organic wastewater, the treatment effect is obviously better than that of simulated wastewater, which can be due to the more complex microenvironment in the actual organic wastewater, which affects the attachment of microorganisms on the electrode surface and the movement of electrons.
[0029] Comparative Example 2 The wastewater with an initial COD of 210.6 mg / L is treated according to the treatment method of Example 1, by changing the long-term action of the applied direct current voltage, after the effluent water quality is stabilized, the wastewater degradation effect is detected, and the results are shown in Table 2.
[0030] Table 2:
[0031] It can be seen that the organic wastewater treatment results are obviously different under the action of different degradation applied voltages. When the voltage is 0.2-0.8 V, the COD degradation rate gradually increases with the increase of the voltage, and when the voltage is higher than 0.8 V, the COD degradation rate obviously decreases.
[0032] Example 2 A method for improving the wastewater degradation efficiency of a microbial fuel cell, comprising the following steps: (1) Pretreatment of conductive carbon felt The conductive carbon felt with a length of 15 cm is ultrasonically treated in an acetone solution for 30 min, then the conductive carbon felt is acid washed in a 10% HCl solution for 5 min, and then washed with deionized water until neutral, and dried; (2) Enrichment and preparation of electrode The pretreated conductive carbon felt is fixed in a reactor, inoculated sludge is poured into the reactor, an applied voltage of 0.4 V is applied, and the treatment is performed for 5 days; (3) Degradation of wastewater After the enrichment, the reactor is left for 2 h, the sludge is discharged from the bottom, the reactor is resealed, the upper part of the reactor is connected to the positive electrode (+) of a direct current power supply, the lower part of the reactor is connected to the negative electrode (-) of the direct current power supply, the voltage of the direct current power supply is 0.8 V, wastewater is pumped into the solution for degradation treatment, the wastewater inflow rate is 5 mL / min, the wastewater dissolved oxygen content is 2 mg / L, and the hydraulic retention time (HRT) is 2 h.
[0033] The initial COD of the wastewater treated in this example is 192.8 mg / L, the effluent COD after stable treatment is 14.67 mg / L, and the COD degradation rate reaches 92.39%.
[0034] Example 3 A method for improving the wastewater degradation efficiency of a microbial fuel cell, comprising the following steps: (1) Pretreatment of conductive carbon felt The conductive carbon felt with a length of 15 cm is ultrasonically treated in an acetone solution for 30 min, then the conductive carbon felt is acid washed in a 10% HCl solution for 5 min, and then washed with deionized water until neutral, and dried; (2) Enrichment and preparation of electrode The pretreated conductive carbon felt is fixed in a reactor, inoculated sludge is poured into the reactor, an applied voltage of 0.6 V is applied, and the treatment is performed for 6 days; (3) Degradation of wastewater After the enrichment, the reactor was left for 2 h, the sludge was discharged from the bottom, the reactor was resealed, the upper part of the reactor was connected to the positive electrode (+) of the direct current power supply, the lower part was connected to the negative electrode (-) of the direct current power supply, the voltage of the direct current power supply was 0.6 V, wastewater was pumped into the solution for degradation treatment, the wastewater inflow rate was 10 mL / min, the dissolved oxygen content of the wastewater was 4 mg / L, and the hydraulic retention time (HRT) was 4 h.
[0035] The initial COD of the wastewater treated in the example was 192.8 mg / L, the effluent COD after treatment was stabilized at 15.79 mg / L, and the COD degradation rate reached 91.81%.
Claims
1. A method for improving the efficiency of microbial fuel cell in degrading organic wastewater, characterized in that: The microbial fuel cell is a single-chamber microbial fuel cell, which is fixed with strip-shaped conductive carbon felt in a reactor, and mainly enriched to form electrode dominant microorganisms, and then water is fed to degrade. The reactor has water flowing from top to bottom. The upper part of the reactor is connected to the positive electrode of a direct current power supply, and the lower part is connected to the negative electrode of the direct current power supply. The voltage of the direct current power supply is 0.2-0.8 V.
2. The method for improving the efficiency of microbial fuel cell in degrading organic wastewater according to claim 1, characterized in that: The water feeding rate of the reactor is 5-12 mL / min, the dissolved oxygen content of the wastewater is about 2-4 mg / L, and the hydraulic retention time (HRT) is 2-5 h.
3. The method for improving the efficiency of microbial fuel cell in degrading organic wastewater according to claim 1 or 2, characterized in that: The enrichment treatment is to fill the reactor with inoculated sludge, open the top of the reactor, and treat for 5-7 days by an external voltage of 0.2-0.6 V. After the enrichment is completed, the reactor is static for 2 h, the sludge is discharged from the bottom, and then the reactor is sealed.
4. A method for improving the efficiency of wastewater degradation by microbial fuel cells, characterized in that, The method comprises the following steps: (1) Pretreatment of conductive carbon felt The length of the conductive carbon felt is 15 cm, which is treated in acetone solution for 30 min, then the conductive carbon felt is acid washed in 10% HCl solution for 5 min, then washed with deionized water until neutral, and dried; (2) Enrichment preparation of electrode The pretreated conductive carbon felt is fixed in the reactor, and the reactor is filled with inoculated sludge. The external voltage is 0.2-0.6 V, and the treatment is performed for 5-7 days; (3) Degrading wastewater After the enrichment is completed, the reactor is static for 2 h, the sludge is discharged from the bottom, the reactor is resealed, the upper part of the reactor is connected to the positive electrode of a direct current power supply, the lower part is connected to the negative electrode of the direct current power supply, the voltage of the direct current power supply is 0.2-0.8 V, the wastewater is pumped into the solution for degradation treatment, the wastewater feeding rate is 5-12 mL / min, the dissolved oxygen content of the wastewater is 2-4 mg / L, and the hydraulic retention time (HRT) is 2-5 h.