C3N5 modified composite catalytic electrode, coupled microbial fuel cell system constructed by C3N5 modified composite catalytic electrode and wastewater treatment method

Abstract

The invention provides a C3N5 modified composite catalytic electrode, a coupled microbial fuel cell system constructed by the C3N5 modified composite catalytic electrode and a wastewater treatment method. Inlet water of the system is high-concentration new energy wastewater with COD (Chemical Oxygen Demand) of about 20000 mg / L, and the wastewater flows into the reactor from a water inlet at the bottom of the reactor through a peristaltic pump, passes through a microbial anode chamber, a gravel filling layer and an upper cathode chamber and then flows out. A carbon rod is used as a conducting medium of an anode, and wastewater overflows out of a cathode area for effluent collection. The highest COD removal rate reaches 83%, the highest treatment capacity reaches 6kg COD / (m < 3 >. D), and available electric energy is synchronously generated. According to the method, the capacity of converting wastewater pollutants and generating electricity of microorganisms is utilized, the photoelectric response and catalytic capacity of the nano-catalyst are combined, energy-saving and efficient treatment of the pollutants in the industrial wastewater is achieved, meanwhile, secondary pollution is avoided, and the method is a low-carbon and environment-friendly refractory wastewater treatment method with large technical and economic advantages.

Description

Technical Field

[0001] This invention belongs to the field of industrial wastewater treatment and energy utilization technology, and relates to the preparation of a high-efficiency CeO2-Fe-WO3 / CN-AC catalyst, as well as a photoelectrocatalytic synergistic treatment system for high-concentration industrial wastewater using a composite electrode coupled with a microbial fuel cell, achieving significant treatment effects. It achieves production capacity while treating industrial wastewater, and the system has low operating costs, providing important reference value for the further development of low-carbon and high-efficiency wastewater treatment technologies. Background Technology

[0002] High-concentration organic industrial wastewater refers to industrial wastewater with organic matter content such as COD and BOD ≥10000 mg / L. It is often characterized by high concentration, complex composition, and poor biodegradability, and is commonly found in industries such as chemical, pharmaceutical, and papermaking. Due to the high concentration and strong toxicity of pollutants, this type of wastewater has become a challenge in the field of water treatment.

[0003] Microbial fuel cells (MFCs) are a resource-based water treatment technology. Their bio-electrogenous anodes utilize widely existing electrogenic microorganisms and synergistic bacterial communities to directly or indirectly treat wastewater pollutants, converting the chemical energy of organic matter in the wastewater into directly usable electrical energy. The electrogenic microorganisms at the anode are diverse and highly adaptable, and after domestication, they are widely used to treat various types of wastewater. Currently, there are challenges such as low power generation efficiency, and improving the quality and efficiency of treated effluent requires strengthening in-situ utilization of bio-electrogenation and achieving the driving force of the endogenous electric field for electrocatalysis. The MFC-PEC system is a coupled reactor of microbial fuel cells and photocatalysis. It superimposes the two driving forces of "microbial power generation" and "photogenerated carrier catalysis," achieving temporal and spatial synergy of "oxidation-reduction," specifically designed to treat high-concentration, highly toxic, or recalcitrant industrial wastewater / gas.

[0004] Graphite-phase nitrogen-rich carbon nitride (g-C3N5) is a nitrogen-rich n-type inorganic semiconductor with high electron-rich potentials in the visible light range, exhibiting a wide photoresponse range and a narrow band gap (approximately 2.0 eV). However, it presents a significant challenge to photocatalytic performance: photogenerated electrons and holes readily recombine during photocatalysis, resulting in low separation efficiency. Research indicates that combining g-C3N5 with CeO2 to construct a heterojunction with a long electron-hole transport distance enables spatial separation of electrons and holes. By utilizing the oxidation capacity of valence band holes and the reduction capacity of conduction band electrons, this spatial separation of electrons and holes can be achieved, thereby enhancing both the oxidation and reduction half-reactions.

[0005] Based on existing research, this invention constructs a photoelectrocatalytic fuel cell system, which combines the synthesized materials with the fuel cell to remove high-concentration industrial wastewater, improving treatment efficiency, increasing production capacity and reducing operating costs. At the same time, it generates no secondary pollution, making it a low-carbon, green method for treating recalcitrant wastewater with significant technical and economic advantages. Summary of the Invention

[0006] This invention prepares a novel, high-efficiency, and low-cost metal heterojunction catalyst and successfully applies it to a photoelectrocatalytic coupled microbial power generation system (PEC-MFC) for energy-efficient and high-performance treatment of industrial wastewater. By modifying the anode microbial portion of the microbial fuel cell, the ability of the microorganisms to convert wastewater pollutants and generate electricity is improved. Combined with the photoelectric response and catalytic capabilities of the cathode nanocatalyst, further efficient treatment of industrial wastewater is achieved, increasing the system's power generation capacity, saving treatment costs and energy consumption. This solves the problems of traditional industrial wastewater treatment processes, such as the need for large amounts of chemical reagents, long operating procedures, high equipment costs, large footprints, and high energy consumption.

[0007] This invention is achieved through the following technical solution:

[0008] A C3N5 modified composite catalytic electrode, wherein the C3N5 modified composite catalytic electrode is a multi-element single-atom catalytic cathode CeO2-Fe-WO3 / CN-AC, and its preparation method is as follows:

[0009] CeO2-Fe-WO3 / CN-AC was synthesized via thermal polymerization. Granular activated carbon was thoroughly dispersed in deionized water with ferric nitrate, cerium nitrate, nano-tungsten trioxide, and 3-amino-1,2,4-triazole. The resulting mixture was dried in an oven to obtain a dried precursor, which was then calcined in a muffle furnace to obtain granular activated carbon supported on a single-atom catalyst.

[0010] Wherein: the amount of ferric nitrate used is 0.5%-1% of the mass of 3-amino-1,2,4-triazole; the amount of cerium nitrate used is 0.5%-1% of the mass of 3-amino-1,2,4-triazole; the amount of nano-tungsten trioxide powder used is 0.5%-1% of the mass of 3-amino-1,2,4-triazole; and the ratio of the mass of granular activated carbon to the mass of 3-amino-1,2,4-triazole is 10:1 to 30:1.

[0011] Furthermore, the stirring and dispersing is carried out by stirring with a magnetic rotor stirrer at 1000-1200 rpm for 3-5 hours;

[0012] Furthermore, the drying temperature is 75~85 ℃ and the drying time is 12~16 h;

[0013] Furthermore, the calcination temperature in the muffle furnace is 500℃-550℃;

[0014] Furthermore, the calcination time in the muffle furnace is 2-4 hours;

[0015] Furthermore, the heating rate of the muffle furnace calcination is set to 3-5℃ / min;

[0016] A microbial fuel cell system constructed using a C3N5 modified composite catalytic electrode specifically includes:

[0017] The microbial fuel cell system includes an upper cathode chamber and a lower anode chamber. The anode chamber and cathode chamber need to be transparent, and the spacer between them is filled with a gravel layer. The spacer can isolate dissolved oxygen in the cathode chamber to create an anaerobic environment for the anode chamber.

[0018] The anode chamber is filled with two materials: one half is filled with activated carbon particles loaded with domesticated microorganisms; the other half is filled with C3N5 modified composite catalytic electrode material; an aeration head is installed at the bottom of the anode chamber, and the interface of the aeration head is connected to the water inlet pipe.

[0019] The cathode chamber is filled with C3N5 modified composite catalytic electrode material and equipped with an aeration head and a water outlet.

[0020] Inert conductive materials are inserted into the cathode chamber and anode chamber respectively. After the inert conductive materials extend out, they are connected to a variable resistor through an external wire to form a closed circuit.

[0021] Furthermore, except for the contact areas, the inert conductive material is wrapped with waterproof tape on other parts.

[0022] Furthermore, the filling rate of activated carbon particles in the anode chamber is 85% to 95%.

[0023] Furthermore, the inert conductive material is a carbon rod, and the cathode material is the aforementioned multi-element single-atom catalytic cathode CeO2-Fe-WO3 / CN-AC.

[0024] Furthermore, the ratio of the anode chamber to the cathode chamber can be adjusted according to the actual wastewater treatment situation.

[0025] Furthermore, the industrial wastewater treated by the photoelectrocatalytic coupled microbial fuel cell is new energy wastewater, and the retention time is set to 8~12h.

[0026] The wastewater is introduced into the system through a buffer aeration head, which homogenizes the influent and reduces the impact of the influent on the system.

[0027] Except for the portion in contact with the bio-anode and the portion connected to the wire, the conductive material of the anode is treated to be waterproof and anti-electric, thereby improving the electron transmission efficiency. For example, waterproof tape is used to wrap and cover the conductive material.

[0028] The beneficial effects of this invention are:

[0029] (1) A multi-metal-doped single-atom catalytic material was prepared, with the metal components uniformly dispersed and anchored, exhibiting high catalytic ability;

[0030] (2) Under the premise of meeting energy conservation and production capacity, the reactor construction mode was improved, which achieved good results and provided ideas for the technical coupling treatment of high-concentration industrial wastewater.

[0031] (3) Design a single-atom catalytic material coupled with a bioelectrochemical system for actual wastewater treatment. This system is low-cost, low-energy, high-degradation-efficiency, and has green and low-carbon characteristics.

[0032] (4) Simultaneously modifying the anode and cathode of the coupling system improves the system's efficiency. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of a photoelectrocatalytic coupled microbial fuel cell system (PEC-MFC).

[0034] Figure 2 These are graphs showing the COD index data of the influent and effluent from three sets of MFC coupled reactors.

[0035] Figure 3 This is a graph showing the COD index data of the effluent from the reflux treatment of three sets of MFC coupled reactors.

[0036] Figure 4 These are UV full-spectrum scans of the influent and effluent from three MFC coupled reactors. Detailed Implementation

[0037] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the following description is exemplary and intended to illustrate the technical solutions of the present invention, rather than to limit the present invention.

[0038] 1. Cathode material preparation

[0039] 1.1 Preparation of activated carbon catalytic cathodes supported on single-atom catalysts:

[0040] Example 1: In this embodiment, the cathode single-atom catalyst is prepared according to the following steps:

[0041] (1) Add 10 g of 3-amino-1,2,4-triazole, 0.05 g of ferric nitrate (Fe), 0.1 g of cerium nitrate (Ce), 0.05 g of nano tungsten trioxide powder (WO3), 400 ml of deionized water and 100 g of activated carbon (AC) carrier material with a diameter of 1.2-1.5 mm to the container.

[0042] (2) Place a stir bar in a 1000ml beaker, place it on a magnetic stirrer, and stir at 1000 rpm for 5 hours to ensure that the components are fully mixed and dispersed.

[0043] (3) Place the mixture obtained in step (2) in an oven and dry it at 80 °C for 16 h to obtain the dried precursor.

[0044] (4) Transfer the dried precursor to a high-temperature resistant container (such as a crucible) and place it in a high-temperature furnace (such as a muffle furnace). Increase the temperature to 500 °C at a heating rate of 5 °C / min and maintain the temperature at this temperature for 2 hours. After calcination, allow it to cool naturally to room temperature to obtain the supported single-atom catalyst.

[0045] Example 2

[0046] (1) Add 10 g of 3-amino-1,2,4-triazole, 0.075 g of ferric nitrate (Fe), 0.05 g of cerium nitrate (Ce), 0.075 g of nano tungsten trioxide powder (WO3), 400 ml of deionized water, and 100 g of activated carbon (AC) as a carrier material with a diameter of 1.2-1.5 mm to the container.

[0047] (2) Place a stir bar in a 1000ml beaker, place it on a magnetic stirrer, and stir at 1100rpm for 4 hours to ensure that the components are fully mixed and dispersed.

[0048] (3) Place the mixture obtained in step (2) in an oven and dry it at 85°C for 12 h to obtain the dried precursor.

[0049] (4) Transfer the dried precursor to a high-temperature resistant container (such as a crucible) and place it in a high-temperature furnace (such as a muffle furnace). Increase the temperature to 525°C at a heating rate of 4°C / min and maintain the temperature at this temperature for 4 hours. After calcination, allow it to cool naturally to room temperature to obtain the supported single-atom catalyst.

[0050] Example 3

[0051] (1) Add 10 g of 3-amino-1,2,4-triazole, 0.1 g of ferric nitrate (Fe), 0.075 g of cerium nitrate (Ce), 0.1 g of nano tungsten trioxide powder (WO3), 400 ml of deionized water and 100 g of activated carbon (AC) carrier material with a diameter of 1.2-1.5 mm to the container.

[0052] (2) Place a stir bar in a 1000ml beaker, place it on a magnetic stirrer, and stir at 1200 rpm for 3 hours to ensure that the components are fully mixed and dispersed.

[0053] (3) Place the mixture obtained in step (2) in an oven and dry it at 75 °C for 16 h to obtain the dried precursor.

[0054] (4) Transfer the dried precursor to a high-temperature resistant container (such as a crucible) and place it in a high-temperature furnace (such as a muffle furnace). Increase the temperature to 550 °C at a heating rate of 3 °C / min and maintain the calcination at this temperature for 3 h. After calcination, allow it to cool naturally to room temperature to obtain the supported single-atom catalyst.

[0055] 1.2 Preparation of microbially loaded granular activated carbon anodes:

[0056] (1) Take a sufficient amount of granular activated carbon with a diameter of 1.2-1.5 mm and ultrasonically wash it with water until no carbon powder falls off. Then soak the washed activated carbon in 75% industrial alcohol for 10 hours to remove surface organic matter. After soaking, drain it. Rinse off the residual alcohol with deionized water and finally dry it overnight at 70°C.

[0057] (2) Place the granular activated carbon in an incubator inoculated with Shewanella electrogenic bacteria, and control the temperature at 25℃. Add an appropriate amount of culture medium (culture medium formula: 1L deionized water, 8g sucrose, 0.05g CaCl2, 1.045g NH4Cl, 0.22g MgSO4, 0.29g K2HPO4) to the incubator, using the granular activated carbon as a carrier for microbial growth. Once the microbial growth is stable, take a portion of the microorganisms into another container and pour in the new energy wastewater to be treated, using the wastewater to acclimate the microbial activity. The acclimatization period is 14-20 days.

[0058] 2. Equipment Setup

[0059] according to Figure 1To construct the system, a cylindrical glass container was used, with an opening at the bottom. An aerator of appropriate size was sealed at the opening, and the interface of the aerator was connected to the inlet pipe. The activated carbon anode prepared above was then filled into the bottom of the reactor. The middle layer was a sandbag sewn from cotton cloth. The top and bottom of the sandbag were cut with scissors to allow the carbon rod to be inserted. The carbon rod was then wrapped with waterproof tape except for the part in contact with the anode. The carbon rod was long enough to connect to the cathode at the bottom, passing through the sandbag and protruding from the top of the container. The activated carbon catalytic cathode with a single-atom catalyst prepared in Example 1 was then placed in a mesh bag of appropriate size and placed at the top of the reactor as the cathode. The carbon rod was inserted into the cathode chamber, and the outside was connected with an external wire and a resistor (1Ω) to form a closed loop. A peristaltic pump was connected to the inlet at the bottom of the reactor and to the wastewater sample to be treated. The flow rate was controlled by adjusting the peristaltic pump to ensure that the inlet and outlet water retention time was 12 hours. An outlet was set at the top of the reactor, and the water would automatically flow out when the liquid level controlled by the retention time was reached, serving as the effluent. This reaction system serves as reactor 2.

[0060] Similarly, reactors 1 and 3 were constructed, with the difference being that the anode of reactor 1 was half activated carbon loaded with domesticated microorganisms and half activated carbon loaded with single-atom catalyst prepared in Example 1, and the cathode was activated carbon loaded with single-atom catalyst prepared in Example 1; the anode of reactor 3 was activated carbon loaded with domesticated microorganisms, and the cathode was washed and dried granular activated carbon.

[0061] Application examples

[0062] Three reactors were operated simultaneously for 5 days, with effluent samples taken every 24 hours. The current and voltage of the closed loop were measured using a multimeter. After 5 days of continuous sampling, the COD values ​​of all water samples and the treated raw water were tested. The COD index was determined using the national standard rapid digestion spectrophotometric method. The influent and effluent COD values ​​of the three reactors are as follows: Figure 2 As shown. After 5 days of continuous influent and effluent treatment with a retention time of 12 hours, with the influent COD value being 22252 mg / L, the effluent COD value of reactor 1 reached 6980 mg / L, achieving a removal rate of 68.63%, and a treatment capacity of 6 kg COD / (m³). 3 •d); The COD value of the effluent from reactor 2 reached 8087 mg / L, with a removal rate of 63.65%, and a treatment capacity of 5.56 kg COD / (m³). 3 •d); The COD value of the effluent from reactor 3 reached 8210 mg / L, with a removal rate of 63.10%, and a treatment capacity of 5.52 kg COD / (m³). 3 (d). Calculations show that the maximum power of reactor 1 reaches 133.33 μW, the maximum power of reactor 2 reaches 259.89 μW, and the maximum power of reactor 3 reaches 3.71 μW.

[0063] After the first cycle of operation, the effluent from the three reactors was refluxed, with samples taken every 12 hours for a total of 60 hours of continuous reflux. After all sampling was completed, the COD value of all samples was measured. The results are as follows: Figure 3 As shown in the figure, the lowest effluent COD value of reactor 1 reached 3618 mg / L, with a removal rate of 83.74%; the lowest effluent COD value of reactor 2 reached 4435 mg / L, with a removal rate of 80.06%; and the effluent COD value of reactor 3 reached 7168 mg / L, with a removal rate of 67.78%. Calculations show that the maximum power of reactor 1 reached 86.82 μW, reactor 2 reached 176.19 μW, and reactor 3 reached 4.74 μW. The removal rate of reactor 3 remained basically unchanged at 60%-70%, indicating the adsorption effect of the anode biological agents and the cathode activated carbon. Compared to reactor 3, the removal rate of reactor 1 increased by 15.96%, and the removal rate of reactor 2 increased by 12.28%, verifying the modification effect of the cathode catalyst and the modification effect of changing the anode from pure biological to biological + catalyst, i.e., the simultaneous modification effect of the anode and cathode of this coupled system.

[0064] Ultraviolet full-spectrum scanning was performed on the reflux effluent from three types of reactors to examine changes in the organic matter content of the effluent, such as... Figure 4 According to the full spectrum analysis, the absorption peaks of the three reactors decreased sequentially, proving that the original pollutants in the wastewater were effectively degraded, and reactor 1 with modified anode and cathode showed the best degradation effect.

[0065] This invention provides a photoelectrocatalytic-microbial fuel cell coupling system and its application. By coupling electrocatalytic oxidation technology with microbial fuel cell technology, it effectively utilizes the synergistic effect of light energy, electrical energy, and biological energy to achieve efficient treatment of high-concentration industrial wastewater. Even with an influent COD concentration of 22252 mg / L, it achieves a maximum COD removal rate of 83% and a maximum treatment capacity of 6 kg COD / (m³). 3 ·d), and simultaneously generate usable electrical energy. The specific reactor structure design and simultaneous modification of its anode and cathode, and the cathode catalyst (single-atom catalyst) are the key to achieving low carbon and high efficiency in this scheme.

Claims

1. A C3N5 modified composite catalytic electrode, characterized in that, The C3N5 modified composite catalytic electrode is a multi-element single-atom catalytic cathode CeO2-Fe-WO3 / CN-AC, and its preparation method is as follows: CeO2-Fe-WO3 / CN-AC was synthesized by thermal polymerization. Granular activated carbon was then thoroughly dispersed in deionized water with ferric nitrate, cerium nitrate, nano-tungsten trioxide, and 3-amino-1,2,4-triazole. The resulting mixture was dried in an oven to obtain a dried precursor, which was then calcined in a muffle furnace to obtain granular activated carbon supported on a single-atom catalyst.

2. The C3N5 modified composite catalytic electrode according to claim 1, characterized in that, The amount of ferric nitrate used is 0.5%-1% of the mass of 3-amino-1,2,4-triazole; the amount of cerium nitrate used is 0.5%-1% of the mass of 3-amino-1,2,4-triazole; the amount of nano-tungsten trioxide powder used is 0.5%-1% of the mass of 3-amino-1,2,4-triazole; and the ratio of the mass of granular activated carbon to the mass of 3-amino-1,2,4-triazole is 10:1 to 30:

1.

3. The C3N5 modified composite catalytic electrode according to claim 1, characterized in that, The stirring and dispersing process involves stirring at 1000-1200 rpm for 3-5 hours using a magnetic rotor stirrer; the drying temperature is 75-85 ℃ and the drying time is 12-16 hours.

4. The C3N5 modified composite catalytic electrode according to claim 1, characterized in that, The calcination temperature in the muffle furnace is 500℃-550℃; the calcination time in the muffle furnace is 2-4h; and the heating rate in the muffle furnace is set to 3-5℃ / min.

5. A microbial fuel cell system constructed using a C3N5 modified composite catalytic electrode as described in any one of claims 1-4, characterized in that, Specifically, it includes: The microbial fuel cell system includes an upper cathode chamber and a lower anode chamber. The anode chamber and cathode chamber need to be transparent, and the spacer between them is filled with a gravel layer. The spacer can isolate dissolved oxygen in the cathode chamber to create an anaerobic environment for the anode chamber. The anode chamber is filled with two parts of material: one half is filled with activated carbon particles loaded with domesticated microorganisms; the other half is filled with C3N5 modified composite catalytic electrode material; an aeration head is installed at the bottom of the anode chamber, and the interface of the aeration head is connected to the water inlet pipe. The cathode chamber is filled with C3N5 modified composite catalytic electrode material and equipped with an aeration head and a water outlet. Inert conductive materials are inserted into the cathode chamber and anode chamber respectively. After the inert conductive materials extend out, they are connected to a variable resistor through an external wire to form a closed circuit.

6. The microbial fuel cell system according to claim 5, characterized in that, Except for the contact areas, all other parts of the inert conductive material are wrapped with waterproof tape.

7. The microbial fuel cell system according to claim 5, characterized in that, The filling rate of activated carbon particles in the anode chamber is 85% to 95%.

8. The microbial fuel cell system according to claim 5, characterized in that, The inert conductive material is a carbon rod, and the cathode material is the aforementioned multi-element single-atom catalytic cathode CeO2-Fe-WO3 / CN-AC.

9. The microbial fuel cell system according to claim 5, characterized in that, The ratio of the anode chamber to the cathode chamber can be adjusted according to the actual wastewater treatment situation.

10. The microbial fuel cell system according to claim 5, characterized in that, The industrial wastewater treated by the photoelectrocatalytic coupled microbial fuel cell is new energy wastewater, and the retention time is set to 8~12h.

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