A microbial fuel cell with photo / electro-thermal catalytic evaporation desalination electrode for treating salt-containing wastewater and application

Abstract

The application provides a microbial fuel cell with a photo / electrothermal catalytic evaporation desalination electrode for treating salt-containing wastewater and an application, and belongs to the technical field of environmental pollution control and energy utilization. A PVDF / CFC membrane loaded with a catalyst Fe@MoS2 and activated carbon are used as double cathodes of the system, microorganisms and a carbon rod are used as an anode of the system, an external resistance is arranged between the two, and wires are connected to form a loop, which can generate electric energy while treating pollutants. A xenon lamp is used to irradiate the evaporation catalytic membrane, so that the evaporation body can perform photo-thermal conversion, and water is changed into steam while heat is generated, so that desalination and water purification of high-salt wastewater are realized. In addition, the evaporation catalytic membrane can generate a photocatalytic effect under irradiation, realizes self-cleaning of the membrane, and can be recycled. The system adopts two kinds of water feeding modes, i.e., a circulating batch mode and a continuous feeding mode, so that the effects of the biological anode and the catalytic cathode are fully utilized to realize wastewater treatment and power generation.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment and energy recovery technology, and relates to a highly efficient Fe@MoS2 catalytic evaporation electrode membrane coupled with activated carbon as the cathode in a microbial fuel cell system, which shows significant effectiveness in treating industrial saline wastewater. This evaporation membrane electrode, used as the cathode, has good conductivity, good light absorption, and good pollutant treatment effect. Furthermore, through evaporation, condensation, and reflux, water and some pollutants can be separated. The total organic carbon and total nitrogen content of the distilled water are significantly lower than those of the microbial fuel cell effluent. Moreover, electricity can be generated simultaneously while treating pollutants. The system has low operating costs, and the effluent and distilled water quality are good, demonstrating certain engineering advantages. Background Technology

[0002] High-salt industrial wastewater is characterized by its high salt content, difficulty in treatment, high organic matter content, and high TOC content, which has a significant impact on the environment. It is one of the most difficult types of industrial wastewater to treat, and conventional water treatment methods are insufficient to simultaneously degrade pollutants and desalinate the water.

[0003] Microbial fuel cells (BMFCs) are a technology that combines wastewater treatment with electricity generation. Electrogenerating microorganisms act as the anode, oxidizing organic pollutants and simultaneously generating electrons. These electrons then transfer from the anode to the cathode, forming an electric current. This method offers advantages such as simple operation, low operating costs, effective pollutant treatment, environmental friendliness, and no secondary pollution, making it a promising candidate for application. However, the generally high cost of cathode materials limits the application of BMFCs, and their relatively low electricity generation capacity necessitates further improvements.

[0004] Single-atom catalysts, due to their high atomic utilization, large specific surface area, and excellent catalytic effect, have been widely used in catalytic treatment. The principle of photocatalysis is that when sunlight shines on a photocatalyst, and the energy of the sunlight exceeds the band gap energy of the photocatalyst, electron / hole pairs are generated to degrade organic pollutants in water. Coupled photocatalysis with single-atom catalysts, solar energy can be used as an energy source, and solar energy has the advantages of being pollution-free, cost-free, and widely available, making it a clean energy source. However, photocatalytic single-atom catalysts suffer from the drawback of easy recombination of electron / hole pairs, and how to promote their separation is a research hotspot. Coupled photocatalytic single-atom catalysts with microbial fuel cells, the voltage generated by the cell structure promotes the separation of electron-hole pairs in the single-atom catalyst, thereby improving the efficiency of pollutant treatment.

[0005] Photothermal evaporation is an emerging technology for desalinating wastewater containing saline pollutants. It utilizes sunlight to irradiate the surface of an evaporator, raising the surface temperature through photothermal conversion, thereby evaporating and desalinating the water to obtain purified water. It is easy to operate, has simple equipment, low cost, and can operate without external energy, making it a promising method for wastewater treatment.

[0006] This invention utilizes a Fe@MoS2 evaporative catalytic membrane and activated carbon as a cathode coupled with a microbial fuel cell for treating high-salinity wastewater. This dual-cathode system significantly improves the potential of the microbial fuel cell, and the Fe@MoS2 evaporative catalytic membrane cathode achieves desalination and purification, producing higher quality and purer freshwater, representing an excellent water treatment desalination method. The system employs an internal circulation or continuous influent / outfluent mode. Water enters from the bottom of the MFC (Microbial Fuel Cell) and exits from the top, flowing into a storage tank. Current and voltage are generated every 12 hours, and water and evaporative condensate are discharged every 24 hours, resulting in desalinated water with a lower TOC concentration. Summary of the Invention

[0007] The purpose of this invention is to provide a microbial fuel cell system with a photo / electrothermal catalytic evaporation desalination electrode for treating saline wastewater, achieving both desalination and water purification.

[0008] The technical solution of this invention:

[0009] A microbial fuel cell with a photo / electrothermal catalytic evaporation desalination electrode for treating saline wastewater is disclosed. The microbial fuel cell has a two-part structure: a lower anode chamber and an upper cathode chamber. A bottom opening serves as an inlet 1, and a top opening serves as an outlet 4. An outer storage tank 2 is installed, and water stored in the microbial fuel cell overflows from the upper outlet 4. The anode chamber is filled with activated carbon particles loaded with electrogenic bacteria, while the cathode chamber is filled in parallel with unloaded activated carbon particles and an evaporator. A sand chamber separates the anode and cathode chambers. Two carbon rods connect the activated carbon particles in the anode and cathode chambers, respectively, with a resistor between the two rods. A xenon lamp is installed above the evaporator, and a glass cover is installed above the microbial fuel cell. A water-cooled bag is installed on the outside of the glass cover to condense the evaporated water on the glass cover. A water collection tank is installed at the lower edge of the glass cover to collect the condensed distillate.

[0010] Furthermore, the evaporator is a Fe@MoS2 evaporation catalytic membrane.

[0011] Preparation of Fe@MoS2 evaporation catalytic membrane:

[0012] (1) Preparation of PVDF / CFC catalytic evaporation electrode membrane through two steps: coating and phase inversion: The carbon fiber cloth CFC substrate was cleaned, and then PVDF and DMF were mixed and stirred to form a semi-transparent colloidal casting solution. After ultrasonic degassing of the colloidal casting solution, it was quickly poured onto the CFC substrate, uniformly coated, and immediately placed in deionized water for phase inversion. After the phase inversion process was completed, the PVDF / CFC membrane was removed and allowed to air dry naturally.

[0013] (2) The prepared PVDF / CFC membrane was cut to the required size, and a seed solution was prepared by mixing Na2MoO4·2H2O and CH4N2S in deionized water. The cut PVDF / CFC membrane was immersed in the seed solution. The mixed solution of Fe2(SO4)3, Na2MoO4·2H2O and CH4N2S was stirred evenly. The PVDF / CFC membrane coated with the seed solution and the mixed solution were transferred to a hydrothermal reactor for hydrothermal reaction. After the reaction, the hydrothermal reactor was naturally cooled to room temperature, and the Fe@MoS2 / PVDF / CFC was taken out, rinsed with ethanol and deionized water respectively, and finally dried in an oven to obtain the Fe@MoS2 evaporative catalytic membrane.

[0014] Furthermore, in step (1), the mass ratio of PVDF and DMF is 1:1 to 1:30.

[0015] Furthermore, in step (2), the concentrations of Na2MoO4·2H2O and CH4N2S in the seed solution are 0.001 mol / L to 0.1 mol / L for Na2MoO4·2H2O and 0.002 mol / L to 0.2 mol / L for CH4N2S.

[0016] Furthermore, in step (2), the concentrations of Fe2(SO4)3, Na2MoO4·2H2O and CH4N2S in the mixed solution are 0.002mol / L to 0.2mol / L for Fe2(SO4)3, 0.008mol / L to 0.8mol / L for Na2MoO4·2H2O, and 0.02mol / L to 2mol / L for CH4N2S.

[0017] Furthermore, in step (2), the hydrothermal reaction temperature is 100-200℃ and the hydrothermal reaction time is 5-24h.

[0018] Furthermore, in step (2), the PVDF / CFC membrane coating the seed solution is 4×3~9cm. 2 The volume of the mixed solution is 30-100 ml.

[0019] Furthermore, a heat-insulating material (preferably a foam board) is placed between the Fe@MoS2 evaporation catalytic membrane and the water, and a water-absorbing material (preferably cotton thread) passes through the heat-insulating material, with its two ends in contact with the Fe@MoS2 evaporation catalytic membrane and the water, respectively, so as to absorb the water onto the Fe@MoS2 evaporation catalytic membrane for evaporation.

[0020] An application of a microbial fuel cell with a photo / electrothermal catalytic evaporation desalination electrode for treating saline wastewater involves diluting high-salt wastewater to a concentration that allows microorganisms to survive, using an internal circulation batch or continuous water inlet / outlet method, controlling the water inlet rate, measuring the current and voltage of an external resistor at intervals, and measuring the TOC concentration in the microbial fuel cell, water storage tank 2, and distillate at intervals.

[0021] The internal circulation batch water inlet and outlet method is as follows: a fixed amount of water is injected into the water storage tank 2, and water is continuously supplied from the water storage tank 2 to the microbial fuel cell. The water outlet of the microbial fuel cell flows into the water storage tank 2.

[0022] The continuous water inlet and outlet method is as follows: water is continuously supplied from the outside into the microbial fuel cell, and the water outlet of the microbial fuel cell flows into the water storage tank 2.

[0023] The advantage of this invention is that by combining a microbial fuel cell with an Fe@MoS2 evaporative catalytic membrane, the power generation and pollutant treatment of the microbial fuel cell can be carried out simultaneously, achieving the dual functions of purifying wastewater and desalination. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the coupling device.

[0025] Figure 2 The evaporation rate of the Fe@MoS2 evaporation catalytic membrane under different conditions is represented by the x-axis as time in minutes and the y-axis as mass change in grams.

[0026] Figure 3 The graph shows the treatment of high-salt wastewater by a Fe@MoS2 evaporation catalyst membrane and activated carbon coupled with a microbial fuel cell system under a batch-feed system with internal circulation. The horizontal axis represents time in days, and the vertical axis represents the degradation rate (%).

[0027] Figure 4 The graph shows the treatment of high-salt wastewater by a Fe@MoS2 evaporation catalytic membrane and activated carbon coupled as a cathode in a microbial fuel cell system under continuous water inflow and outflow conditions. The horizontal axis represents time in days, and the vertical axis represents the degradation rate (%).

[0028] Figure 5The graph shows the power generation of a microbial fuel cell system with Fe@MoS2 evaporation catalyst membrane and activated carbon as cathodes under a batch-feed system with internal circulation. The horizontal axis represents time in hours, and the vertical axis represents millivolts (mV) or milliamperes (mA).

[0029] Figure 6 The graph shows the power generation of a microbial fuel cell system with Fe@MoS2 evaporation catalyst membrane and activated carbon as cathodes under a batch-feed system with internal circulation. The horizontal axis represents time in hours, and the vertical axis represents millivolts (mV) or milliamperes (mA).

[0030] In the diagram: 1. Inlet; 2. Water storage tank; 3. Activated carbon A; 4. Outlet; 5. Wire A; 6. Carbon rod A; 7. Resistor; 8. Wire B; 9. Carbon rod B; 10. Evaporator; 11. Cotton thread; 12. Sand; 13. Activated carbon B. Detailed Implementation

[0031] The specific embodiments of the present invention will be described in detail below with reference to the technical solutions and accompanying drawings.

[0032] Example 1:

[0033] 1.1 Preparation of Fe@MoS2 catalytic evaporation membrane electrode

[0034] PVDF / CFC evaporative catalytic membranes were prepared in two steps: coating and phase inversion. First, the carbon fiber cloth (CFC) substrate was ultrasonically cleaned sequentially with ethanol and water. Then, 1g of PVDF powder and 9g of DMF were mixed in a beaker. The beaker was covered with plastic wrap to prevent DMF evaporation and placed on a magnetic stirrer. The mixture was stirred until a semi-transparent, gel-like casting solution was formed. The stir bar was removed using a magnet, and the casting solution was ultrasonically injected to prevent air bubbles from damaging the membrane. After degassing, the casting solution was quickly poured onto the CFC substrate and uniformly coated from top to bottom using a coating blade (500μm thickness). The membrane was immediately placed in a deionized water bath for phase inversion. After the phase inversion process was complete, the PVDF / CFC membrane was removed and allowed to air dry naturally.

[0035] Preparation of Fe@MoS2 evaporative catalytic membrane: Three 4cm × 3cm membranes were cut from the PVDF / CFC membrane prepared in the previous step. A seed solution was prepared by mixing 0.169g Na2MoO4·2H2O and 0.106g CH4N2S in 70ml deionized water. The cut PVDF / CFC membranes were immersed in the seed solution. A mixture of 0.56g Fe2(SO4)3, 1.355g Na2MoO4·2H2O, 1.064g CH4N2S, and 70ml water was stirred until homogeneous. The seed-coated PVDF / CFC membranes and the mixed solution were transferred to a hydrothermal reactor. The hydrothermal reaction was carried out at 200℃ for 20h. After the reactor cooled naturally to room temperature, the Fe@MoS2 / PVDF / CFC membranes were removed, rinsed three times with ethanol and deionized water, and dried in an oven at 80℃.

[0036] 1.2: Construction of a microbial fuel cell system with a photo / electrothermal catalytic evaporation desalination electrode for treating saline wastewater.

[0037] A microbial fuel cell system with a photo / electrothermal catalytic evaporation desalination electrode for treating saline wastewater is disclosed. The microbial fuel cell has a two-tiered structure: a lower anode chamber and an upper cathode chamber. A bottom opening serves as the inlet 1, and a top opening serves as the outlet 4. An external water storage tank 2 is installed, from which water is pumped into the MFC. The water stored in the MFC overflows from the upper outlet 4, forming an internal circulation batch treatment system. The influent rate is 30 mL / h. 300 mL of activated carbon particles containing Sheva electrogenic bacteria (Sheva electrogenic bacteria are mixed bacteria cultivated and domesticated from bottom sediment in the Yellow Sea waters near Xinghai Square, Dalian; the electrogenic potential of the bacteria is greater than 0.06 V when measured using a 232-type reference electrode) is placed into the reactor as the anode. 20 g of activated carbon and a Fe@MoS2 evaporation catalytic membrane are connected in parallel as dual cathodes. A sand chamber separates the anode and cathode chambers. Electrons are drawn from the carbon rod and connected to the cathode via a 1000-ohm resistor. The reactor is equipped with a xenon lamp that illuminates the catalytic evaporation electrode membrane. A glass cover surrounds the device, and water-cooled bags on either side of the cover condense the evaporated water, which then flows into a container below for collection. See the detailed diagram for reference. Figure 1 .

[0038] Example 2. Evaporation rate of the electrode membrane for evaporative desalination.

[0039] Place a 3.5 wt% NaCl solution into a beaker, and block the mouth of the beaker with a perforated foam board. Use a cotton thread to guide the salt solution into the beaker through the perforation. Place a layer of filter paper above the cotton thread, and place the Fe@MoS2 evaporation catalyst membrane on top. Place the assembled evaporation device on a balance, turn on the xenon lamp to irradiate the evaporator, and record the mass change of the balance every 5 minutes. Figure 2The results show the change in the mass of evaporated water from different materials under different conditions over time. In the absence of light, the evaporation rate of the Fe@MoS2-loaded film is faster than that of the unloaded film, possibly because Fe@MoS2 is highly hydrophilic. Under light, the evaporation rate of the Fe@MoS2-loaded material is slightly higher than that of the unloaded film. However, since the amount of Fe@MoS2-loaded material is relatively small, its effect is not significant.

[0040] Example 3. The system circulates water inlet, measures electricity generation, and performs water treatment.

[0041] According to Example 1.2, an internal circulation batch influent system was adopted to treat wastewater. The current and voltage were measured every 12 hours, and the TOC concentration of the effluent and distilled water was measured every 24 hours. Figure 3 The changes in TOC concentration in the distillate of the circulating batch-feed water system are shown. As time increases, the TOC concentration in the distillate gradually decreases, indicating that the reaction system is very effective in treating pollutants. Figure 5 The changes in current and voltage of the circulating batch water intake system are shown. As time increases, the current and voltage first increase and then decrease. The increase indicates that the microorganisms are acclimatizing and growing, while the decrease may be due to the activated carbon cathode being contaminated, which reduces its conductivity and causes the current and voltage to decrease continuously.

[0042] Example 4. The system continuously feeds in and out water, measures the electricity generated, and performs water treatment.

[0043] According to Example 1.2, a continuous influent system was adopted to treat wastewater. The current and voltage were measured every 12 hours, and the TOC concentration of the effluent and distilled water was measured every 24 hours. Figure 3 The changes in TOC concentration in the distillate of the circulating batch-feed water system are shown. As time increases, the TOC concentration in the distillate gradually decreases, indicating that the reaction system is very effective in treating pollutants. Figure 5 The data shows the changes in current and voltage in a continuous feed system. As time increases, the current and voltage first increase and then decrease. The increase indicates that the microorganisms are acclimating and growing. The decrease may be due to the contamination of the activated carbon cathode, which reduces its conductivity, leading to a continuous decrease in current and voltage. However, at 84 hours, the current and voltage suddenly increase. This is because the feed water contains flocculent matter, which obstructs the flow of water and prevents the microorganisms at the anode from flowing out of the reactor, resulting in vigorous growth. This leads to a subsequent increase in voltage. Afterward, the voltage shows a decreasing trend because the activated carbon at the cathode is contaminated, reducing its conductivity and causing a gradual decrease in voltage and current.

Claims

1. A microbial fuel cell with a photo / electrothermal catalytic evaporation desalination electrode for treating saline wastewater, characterized in that, The microbial fuel cell has a two-tiered structure, with the lower part being the anode chamber and the upper part being the cathode chamber. A bottom opening serves as the water inlet, and a top opening serves as the water outlet. An outer storage tank is installed, and water stored in the microbial fuel cell overflows from the upper outlet. The anode chamber is filled with activated carbon particles loaded with electrogenic bacteria, while the cathode chamber is filled in parallel with unloaded activated carbon particles and an evaporator. A sand chamber separates the anode and cathode chambers. Two carbon rods connect the activated carbon particles in the anode and cathode chambers, respectively, with a resistor between the two rods. A xenon lamp is installed above the evaporator, and a glass cover is installed above the microbial fuel cell. A water-cooling bag is installed on the outside of the glass cover to condense the evaporated water on the glass cover. A water collection tank is installed at the lower edge of the glass cover to collect the condensed distillate. The evaporator is a Fe@MoS2 evaporative catalytic membrane, and the preparation process of the Fe@MoS2 evaporative catalytic membrane is as follows: (1) PVDF / CFC catalytic evaporation electrode membrane was prepared by two steps: coating and phase inversion. The carbon fiber cloth CFC substrate was cleaned, and then PVDF and DMF were mixed and stirred to form a semi-transparent gel casting solution. After ultrasonic degassing of the gel casting solution, it was quickly poured onto the CFC substrate, coated evenly, and then immediately placed in deionized water for phase inversion. After the phase inversion process was completed, the PVDF / CFC membrane was taken out and placed in the air to air dry naturally. (2) Cut the prepared PVDF / CFC membrane to the required size, mix Na2MoO4·2H2O and CH4N2S in deionized water to prepare a seed solution; immerse the cut PVDF / CFC membrane in the seed solution; stir the mixed solution of Fe2(SO4)3, Na2MoO4·2H2O and CH4N2S evenly; transfer the PVDF / CFC membrane coated with the seed solution and the mixed solution to a hydrothermal reactor for hydrothermal reaction; after the reaction, cool the hydrothermal reactor to room temperature naturally, take out Fe@MoS2 / PVDF / CFC, rinse with ethanol and deionized water respectively, and finally dry in an oven to obtain Fe@MoS2 evaporation catalytic membrane.

2. A microbial fuel cell with a photo / electrothermal catalytic evaporation desalination electrode for treating saline wastewater according to claim 1, characterized in that, In step (1), the mass ratio of PVDF and DMF is 1:1 to 1:

30.

3. A microbial fuel cell with a photo / electrothermal catalytic evaporation desalination electrode for treating saline wastewater according to claim 1, characterized in that, In step (2), the concentrations of Na2MoO4·2H2O and CH4N2S in the seed solution are respectively Na2MoO4·2H2O ... . 2H₂O is 0.001 mol / L~0.1 mol / L, CH₄N₂S is 0.002 mol / L~0.2 mol / L; Fe₂(SO₄)₃, Na₂MoO₄ . The concentrations of 2H₂O and CH₄N₂S in the mixed solution are 0.002 mol / L to 0.2 mol / L for Fe₂(SO₄)₃ and 0.002 mol / L for Na₂MoO₄. . The concentrations of 2H₂O are 0.008 mol / L to 0.8 mol / L, and those of CH₄N₂S are 0.02 mol / L to 2 mol / L.

4. A microbial fuel cell with a photo / electrothermal catalytic evaporation desalination electrode for treating saline wastewater according to claim 1, characterized in that, In step (2), the hydrothermal reaction temperature is 100~200℃ and the hydrothermal reaction time is 5-24h.

5. A microbial fuel cell with a photo / electrothermal catalytic evaporation desalination electrode for treating saline wastewater according to claim 1, characterized in that, In step (2), the PVDF / CFC membrane coated with the seed solution is 4×3~9cm. 2 The volume of the mixed solution is 30-100 ml.

6. A microbial fuel cell with a photo / electrothermal catalytic evaporation desalination electrode for treating saline wastewater according to any one of claims 1-5, characterized in that, A heat-insulating material is placed between the Fe@MoS2 evaporation catalytic membrane and water. The water-absorbing material passes through the heat-insulating material, and its two ends are in contact with the Fe@MoS2 evaporation catalytic membrane and water, respectively, so as to absorb water onto the Fe@MoS2 evaporation catalytic membrane for evaporation.

7. The application of a microbial fuel cell with a photo / electrothermal catalytic evaporation desalination electrode as described in any one of claims 1-6 for treating saline wastewater, characterized in that, High-salt wastewater is diluted to a concentration that allows microorganisms to survive. The influent rate is controlled by using an internal circulation batch or continuous influent / outfluent method. The current and voltage of the external resistor are measured at intervals, and the TOC concentration in the microbial fuel cell, reservoir, and distillate are measured at intervals.

8. The application according to claim 7, characterized in that, The internal circulation batch water inlet and outlet method is as follows: a fixed amount of water is injected into the water storage tank, and water is continuously supplied from the water storage tank to the microbial fuel cell. The water outlet of the microbial fuel cell flows back into the water storage tank.

9. The application according to claim 7, characterized in that, The continuous water inlet and outlet method is as follows: water is continuously supplied from the outside into the microbial fuel cell, and the water outlet of the microbial fuel cell flows into the water storage tank.

Images