A double-cathode coupled organic wastewater treatment method using a single-atom Cu / NC catalyst

Abstract

The application discloses a double-cathode coupling organic wastewater treatment method using a single-atom Cu / NC catalyst, and steps include: after wastewater enters a regulating pool, entering a biological carbon adsorption pool and then entering an electrolytic cell for electrolysis; the electrolytic cell comprises a first cathode, a first anode, a second cathode and a second anode; the first cathode is a crack gas diffusion electrode, comprising graphite felt and a single-atom Cu / NC doped carbon black-PTFE catalyst coated on the graphite felt; the second cathode comprises graphite felt and a FeOCl catalyst coated on the graphite felt; after water out of the electrolytic cell is precipitated in a coagulation sedimentation tank, the water is discharged. The application first adsorbs part of organic pollutants in wastewater through a biological carbon adsorption pool, improves the biodegradability of the wastewater and reduces the chroma of the wastewater; then, the double-cathode GDE in-situ electro-Fenton device is used to target degradation of organic matters in the wastewater, without the need of cooperating with other auxiliary devices, the product is green and environmentally friendly and has no secondary pollution, and the high-efficiency degradation effect can be achieved.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a dual-cathode coupled organic wastewater treatment method using a single-atom Cu / NC catalyst. Background Technology

[0002] Electrocatalytic H2O2 production technology is a highly efficient, low-energy, and environmentally friendly treatment solution for removing organic matter from wastewater. In-situ electrochemical production of H2O2 relies on an effective oxygen supply. In in-situ H2O2 electrochemical systems, due to the difference in electron transfer between the anode (four-electron OER process) and the cathode (two-electron ORR process), the oxygen consumed by the cathode to produce H2O2 is twice that of conventional methods. Therefore, existing electrocatalytic H2O2 production devices generally require additional oxygen supply, such as the three-dimensional carbon aeration electrode for high-efficiency hydrogen peroxide production disclosed in patent CN110408955A. While injecting oxygen into the water is feasible, this process requires additional oxygen supply equipment installation and energy consumption. Furthermore, in the two-electron ORR process, high-current-induced rapid electrowetting disrupts the initial gas capture channels of the electrode, leading to O2 starvation at the electroactive interface, thus reducing the efficiency of the electrochemical in-situ H2O2 production reaction.

[0003] How can in-situ electrochemically generated H2O2 be applied in industrial water treatment? This involves advanced electrochemical oxidation (AO) processes. Technologies based on Fenton reaction chemistry, such as electro-Fenton (EF), have proven to be the most robust. The EF reaction involves the generation of strongly oxidizing hydroxyl radicals (OH), which are then converted into hydrogen peroxide (H2O2) through the cathode and externally added Fe. 2+ Fenton reaction between catalysts. However, conventional homogeneous EF methods have drawbacks such as a narrow working pH window (2.8–3.5) and the formation of iron sludge. Summary of the Invention

[0004] This invention aims to overcome the aforementioned problems in the prior art by providing a dual-cathode coupled organic wastewater treatment method utilizing a single-atom Cu / NC catalyst. First, the wastewater undergoes a biochar adsorption tank to adsorb some organic pollutants, improving its biodegradability and reducing its color. Then, a dual-cathode GDE in-situ electro-Fenton device is used. The first cathode is loaded with a single-atom catalyst, which efficiently generates hydrogen peroxide, while the second cathode is loaded with FeOCl, which can... 2+ Oxidized to Fe 3+ To achieve Fe 2+ The device is recyclable, and the first and second anodes can generate O2 without the need for external O2 supply. It can target and degrade organic matter in wastewater, achieving efficient degradation of organic matter in wastewater while promoting the resource utilization and harmlessness of the products.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A method for treating organic wastewater using a dual-cathode coupled single-atom Cu / NC catalyst, comprising the following steps: (1) Wastewater enters the equalization tank to balance water quality and quantity; (2) The effluent from the equalization tank enters the biochar adsorption tank for biochar adsorption; (3) The effluent from the biochar adsorption tank enters the electrolytic cell for electrolysis. The electrolytic cell includes a first cathode, a first anode, a second cathode, and a second anode arranged in an alternating manner; The first cathode is a crack gas diffusion electrode, comprising a graphite felt and a single-atom Cu / NC doped carbon black-PTFE catalyst coated on the graphite felt. The second cathode includes a graphite felt and a FeOCl catalyst coated on the graphite felt; The first and second anodes are made of foamed nickel or foamed copper; (4) The effluent from the electrolytic cell is discharged after sedimentation in the coagulation sedimentation tank.

[0006] This invention first adsorbs some organic pollutants in wastewater through a biochar adsorption tank, improving the wastewater's biodegradability and reducing its color. Then, a dual-cathode GDE in-situ electro-Fenton device targets and degrades the organic matter in the wastewater, effectively removing it. No other auxiliary devices are required, and the product is green, environmentally friendly, and produces no secondary pollution, achieving highly efficient degradation.

[0007] The biochar adsorbent in the biochar adsorption tank of this invention is made from agricultural waste, sludge and other renewable resources, which can reduce disposal costs; and the biochar stably seals carbon elements, which can reduce CO2 emissions; no chemical agents are added in the biochar adsorption tank, and the waste biochar can be safely disposed of or recycled without secondary pollution.

[0008] The main reaction formulas for the wastewater degradation process in the electrolytic cell of this invention are as follows: Near the first cathode: ; Near the first anode: ; Near the second anode: ; ; Near the second cathode: ; ; .

[0009] This invention produces oxygen via a first anode (MMO) and then utilizes a cracked gas diffusion electrode as the first cathode to produce H2O2. The O2 generated by the anodic oxygen evolution reaction (OER) during electrochemical in-situ H2O2 production supplies oxygen to the first cathode, achieving in-situ self-sufficient oxygen production of hydrogen peroxide. This process eliminates the need for additional oxygen supply, reducing workload and energy consumption. Furthermore, this invention employs a cracked gas diffusion electrode to overcome the electrowetting effect during long-term electrolysis under harsh industrial conditions. Even under severe electrolysis conditions, due to the weakening of the local electric field and liquid permeation capillary force caused by spatial discontinuities, these micron-sized film defects counterintuitively maintain strong superhydrophobicity, allowing O2 to diffuse freely and rapidly within these channels. This invention incorporates a single-atom Cu / NC catalyst doped into the first cathode. The doping of the single-atom Cu / NC catalyst allows for precise control of the electronic structure of the active sites: the single atom forms a coordination structure with the carbon substrate, optimizing the adsorption strength of •OOH through the interaction of the metal d orbitals with O2 molecules, bringing it closer to the ideal value of 2e-ORR (~4.2 eV); secondly, the single-atom Cu / NC catalyst can suppress the four-electron pathway: by reducing the tendency for O2 / O bond breaking (e.g., avoiding continuous active sites of metal clusters or particles), the generation of H2O is reduced; furthermore, the metal atoms in the single-atom catalyst are dispersed in an isolated form on the carbon substrate surface, exposing 100% atomic utilization, which significantly increases the density of effective active sites; the high conductivity of the carbon substrate (promoting electron transport) combined with the high catalytic activity of the single-atom sites accelerates the adsorption, activation, and reduction processes of O2; the synergistic effect of the porous structure of the carbon-based electrode (e.g., carbon nanotubes, graphene) and the single-atom sites also enhances the diffusion and interfacial reaction efficiency of O2. Therefore, by doping a single-atom Cu / NC catalyst in the first cathode, the present invention can increase the rate of hydrogen peroxide production and further increase the rate of pollutant degradation. Compared with a catalyst without Cu / NC doping, the hourly hydrogen peroxide production can be more than doubled.

[0010] The second cathode of this invention uses FeOCl as a catalyst. Ferric chloride (FeOCl) is a two-dimensional layered metal chloride oxide with high electron mobility and electron delocalization properties. It can not only efficiently activate and produce ·OH, but also... 3+ Electroreduction to produce Fe 2+ It also has a high pH adaptability.

[0011] Therefore, the electrolyzer of this invention constructs a self-oxygenated in-situ hydrogen peroxide-FeOCl dual-cathode system. The dual-cathode system of this invention utilizes electro-Fenton to efficiently treat wastewater without the need for auxiliary devices such as oxygen supply devices. The product is green and environmentally friendly and has no secondary pollution, and can achieve efficient degradation of poultry and livestock wastewater.

[0012] Preferably, in step (2), the biochar in the biochar adsorption tank is 3 to 7% of the mass of the wastewater.

[0013] Preferably, in step (3), the mass ratio of carbon black to single-atom Cu / NC catalyst in the first cathode is 25~75:1; and the mass ratio of carbon black to PTFE is 5:2~4.

[0014] Preferably, the method for preparing the first cathode in step (3) is as follows: A) Dissolve thiourea in deionized water to obtain a thiourea solution; B) Add soluble copper salt to thiourea solution, stir the reaction, and then dry, calcine, and grind the product to obtain a single-atom Cu / NC catalyst; C) Soak the graphite felt in a PTFE suspension and then remove and dry it; D) Mix carbon black and anhydrous ethanol evenly, then add PTFE suspension and single-atom Cu / NC catalyst dropwise, and stir vigorously until a wet paste is formed to obtain the coating material; E) The obtained coating material is applied to the surface of the dried graphite felt obtained in step C), and then calcined to obtain the first cathode.

[0015] Preferably, the molar ratio of copper ions to thiourea added in step B) is 0.04 to 0.06.

[0016] As a preferred method, the preparation method of the second cathode in step (3) is as follows: ferric chloride is dissolved in anhydrous ethanol to obtain ferric chloride solution; graphite felt is immersed in ferric chloride solution and then dried and calcined once; the electrode after the first calcination is cleaned with anhydrous ethanol and deionized water and then immersed in PTFE suspension, and then calcined a second time to obtain the second cathode.

[0017] Preferably, the primary calcination temperature is 210~230℃, and the secondary calcination temperature is 170~190℃.

[0018] Preferably, the loading of single-atom Cu / NC doped carbon black-PTFE catalyst in the first cathode is 25~35 mg / cm³. 2 The loading of FeOCl catalyst in the second cathode is 5~40 mg / cm³. 2 .

[0019] Preferably, in the electrolytic cell of step (3), an ion exchange membrane is provided between the first anode and the second cathode. This allows the H2O2 generated at the first cathode to flow naturally to the other side.

[0020] Preferably, in the electrolytic cell of step (3), the area ratio of the first anode and the first cathode, and the area ratio of the second anode and the second cathode are all 0.1 to 1:1.

[0021] Therefore, the present invention has the following beneficial effects: (1) The first anode used in the device is loaded with a single-atom catalyst, which can efficiently produce hydrogen peroxide. The second cathode is loaded with FeOCl, which can make Fe 2+ Oxidized to Fe 3+ To achieve Fe 2+ The device is recyclable, and the first and second anodes can generate O2 without the need for external O2 supply. It can target and degrade organic matter in wastewater, achieving efficient degradation of organic matter in wastewater while promoting the resource utilization and harmlessness of the products. (2) It has high efficiency in removing organic matter, with an organic matter removal rate of over 90% in wastewater, achieving efficient degradation of organic matter in wastewater; and saving the cost of iron and oxygen. (3) The effluent quality after treatment by the present invention meets the discharge standards and does not require further secondary treatment, which further reduces the treatment cost. Attached Figure Description

[0022] Figure 1 This is a graph showing the changes in COD concentration in the electrolytic cells of the embodiments and comparative examples of the present invention.

[0023] Figure 2 This is a graph showing the changes in total nitrogen concentration in the electrolytic cells of the embodiments and comparative examples of the present invention.

[0024] Figure 3 This is a graph showing the changes in total phosphorus concentration in the electrolytic cells of the embodiments and comparative examples of the present invention. Detailed Implementation

[0025] The present invention will now be further described with reference to the accompanying drawings and specific embodiments.

[0026] In this invention, unless otherwise specified, all equipment and raw materials are available from the market or commonly used in the industry. Unless otherwise specified, the methods in the following embodiments are conventional methods in the art.

[0027] General Implementation Examples: A method for treating organic wastewater using a dual-cathode coupled single-atom Cu / NC catalyst, comprising the following steps: (1) Wastewater enters the equalization tank to balance water quality and quantity; (2) The effluent from the equalization tank enters the biochar adsorption tank for biochar adsorption; (3) The effluent from the biochar adsorption tank enters the electrolytic cell for electrolysis. The electrolytic cell includes a first cathode, a first anode, a second cathode, and a second anode arranged in an alternating manner; The first cathode is a crack gas diffusion electrode, comprising a graphite felt and a single-atom Cu / NC doped carbon black-PTFE catalyst coated on the graphite felt. The second cathode includes a graphite felt and a FeOCl catalyst coated on the graphite felt; The first and second anodes are made of foamed nickel or foamed copper; (4) The effluent from the electrolytic cell is discharged after sedimentation in the coagulation sedimentation tank.

[0028] In one specific implementation, the hydraulic retention time of the regulating tank in step (1) is 25~35 min.

[0029] In one specific implementation, the biochar in the biochar adsorption tank of step (2) has a mass of 3 to 7% of the wastewater mass.

[0030] In one specific implementation, the hydraulic retention time of the biochar adsorption tank in step (2) is 1~3h.

[0031] In one specific implementation, in step (3), the mass ratio of carbon black to single-atom Cu / NC catalyst in the first cathode is 25~75:1; the mass ratio of carbon black to PTFE is 5:2~4.

[0032] As one specific implementation method, the preparation method of the first cathode in step (3) is as follows: A) Dissolve thiourea in deionized water to obtain a thiourea solution; B) Add soluble copper salt to thiourea solution, stir the reaction, and then dry, calcine, and grind the product to obtain a single-atom Cu / NC catalyst; C) Soak the graphite felt in a PTFE suspension and then remove and dry it; D) Mix carbon black and anhydrous ethanol evenly, then add PTFE suspension and single-atom Cu / NC catalyst dropwise, and stir vigorously until a wet paste is formed to obtain the coating material; E) The obtained coating material is applied to the surface of the dried graphite felt obtained in step C), and then calcined to obtain the first cathode.

[0033] In one specific implementation, the mass-to-volume ratio of thiourea and water in step A) is 10g:20~40mL.

[0034] In one specific implementation, the molar ratio of copper ions to thiourea added in step B) is 0.04 to 0.06.

[0035] In one specific implementation, the stirring reaction time in step B) is 2-4 hours; the drying temperature is 60-80℃ and the drying time is 2-4 hours.

[0036] In one specific implementation, in step B), the calcination temperature is 600~700℃, the calcination time is 3~5h, the calcination atmosphere is air, and the heating rate during calcination is 1~10℃ / min.

[0037] In one specific implementation, the solid content of the PTFE suspension in step C) is 5~10wt%, and the soaking time is 25~35min.

[0038] In one specific implementation, the stirring temperature in step D) is 65~75℃.

[0039] In one specific implementation, the calcination temperature in step E) is 330~370℃ and the calcination time is 150~200min.

[0040] As a specific implementation method, the preparation method of the second cathode in step (3) is as follows: ferric chloride is dissolved in anhydrous ethanol to obtain ferric chloride solution; graphite felt is immersed in ferric chloride solution and then dried and calcined once; the electrode after the first calcination is cleaned with anhydrous ethanol and deionized water and then immersed in PTFE suspension, and then calcined a second time to obtain the second cathode.

[0041] In one specific implementation, the primary calcination temperature is 210~230℃ and the calcination time is 1~2h; the secondary calcination temperature is 170~190℃ and the calcination time is 1~2h.

[0042] In one specific implementation, the concentration of the ferric chloride solution is 0.025~0.035 g / mL; the immersion time of the graphite felt in the ferric chloride solution is 1~2 h.

[0043] In one specific implementation, the solid content of the PTFE suspension is 5-10 wt%, and the immersion time of the electrode in the PTFE suspension is 25-35 min.

[0044] In one specific embodiment, the loading of single-atom Cu / NC doped carbon black-PTFE catalyst in the first cathode is 25~35 mg / cm³. 2 The loading of FeOCl catalyst in the second cathode is 5~40 mg / cm³. 2 .

[0045] In one specific implementation, in the electrolytic cell of step (3), an ion exchange membrane is provided between the first anode and the second cathode.

[0046] In one specific implementation, in the electrolytic cell of step (3), the area ratio of the first anode and the first cathode, and the area ratio of the second anode and the second cathode are all 0.1 to 1:1.

[0047] In one specific implementation, the first anode and the second anode are connected to the positive terminal of an external power supply, and the first cathode and the second cathode are connected to the negative terminal of an external power supply; the effective voltage of the external power supply is 0~30V, and the effective current is 0~20A.

[0048] In one specific implementation, the hydraulic residence time of the electrolytic cell in step (3) is 2~4h.

[0049] As a specific implementation method, in step (4), a coagulant is added to the coagulation sedimentation tank to carry out the coagulation reaction, and the amount of coagulant added is 10~30mg / L.

[0050] In one specific implementation, the hydraulic retention time of the coagulation sedimentation tank in step (4) is 1~3h.

[0051] Example 1: A method for treating organic wastewater using a dual-cathode coupled single-atom Cu / NC catalyst, comprising the following steps: (1) Take 8L of poultry and livestock wastewater (pH value is 13, initial COD concentration is 2900mg / L) and store it in the water storage tank. Then, it enters the regulating tank through the first water inlet pump to balance the water quality and quantity. (2) The effluent from the equalization tank enters the biochar adsorption tank for biochar adsorption; the mass of biochar in the biochar adsorption tank is 5% of the mass of wastewater, and the hydraulic retention time of the biochar adsorption tank is 2 hours. (3) The effluent from the biochar adsorption tank enters the electrolytic cell for electrolysis; the hydraulic retention time of the electrolytic cell is 3 hours. The electrolytic cell includes a first cathode, a first anode, a second cathode, and a second anode arranged in an alternating manner; the first cathode and the second anode are separated by a polymer ion exchange membrane; the first anode and the second anode are connected to the positive terminal of an external power supply, and the first cathode and the second cathode are connected to the negative terminal of an external power supply. The first cathode is a crack gas diffusion electrode, comprising a graphite felt and a single-atom Cu / NC-doped carbon black-PTFE catalyst coated on the graphite felt; the preparation method is as follows: A) Dissolve 10g of thiourea in 30mL of deionized water and then sonicate to form a clear and transparent thiourea solution. B) Slowly add 0.918g CuCl2·2H2O to the thiourea solution, stir magnetically for 3h, collect the white crystals by centrifugation, and dry in an oven at 70℃ for 3h; C) The white crystals were heated to 650°C in air at a rate of 5°C / min and held at that temperature for 4 hours. The calcined product was then manually ground into powder to obtain a single-atom Cu-NC catalyst. D) The graphite felt (GF) was ultrasonically cleaned in acetone and deionized water to remove impurities. Then the cleaned GF was soaked in a PTFE suspension (5wt% solid content) for 30 minutes. Finally, the GF was removed and dried at room temperature. E) Mix 2.56g of carbon black with 40mL of anhydrous ethanol evenly, sonicate, then add 1.78g of PTFE suspension (70% solid content) and 0.05g of single-atom metal catalyst Cu-NC dropwise, and stir vigorously at 70℃ until a wet paste is formed to obtain the coating material; F) The obtained coating material is coated onto one side of the GF obtained in step D), and calcined at 350°C for 180 min to obtain a single-atom Cu / NC doped carbon black-PTFE catalyst with a loading of 31.26 mg / cm³. 2 The first cathode; The second cathode comprises a graphite felt and a FeOCl catalyst coated on the graphite felt; the preparation method is as follows: First, 0.27 g of FeCl3·6H2O was dissolved in 10 mL of anhydrous ethanol and sonicated for 10 minutes to form a homogeneous ferric chloride solution. Then, GF was immersed in the ferric chloride solution for 1 hour, removed, dried, and transferred to a sealed crucible for calcination at 220 °C for 1 hour. After cooling to room temperature, the electrode was repeatedly washed with anhydrous ethanol and deionized water and dried in a vacuum drying oven at 50 °C for 12 hours. Finally, the electrode was immersed in a PTFE suspension (5 wt% solids) for 30 minutes, followed by calcination at 180 °C for 1 hour, resulting in a final FeOCl catalyst loading of 32.05 mg / cm³. 2 The second cathode; The first and second anodes are made of nickel foam; The area of ​​both the first and second anodes is 1 cm². 2 The first and second cathodes are circles with a diameter of 1.5 cm; The current density during operation of the electrolytic cell is 5 mA / cm². 2 ; (4) The effluent from the electrolytic cell enters the coagulation sedimentation tank through the fourth inlet pump. After coagulation and sedimentation, the effluent is discharged with the addition of coagulant PAC. The dosage of coagulant is 20 mg / L, and the hydraulic retention time of the coagulation sedimentation tank is 2 hours.

[0052] Example 2: A method for treating organic wastewater using a dual-cathode coupled single-atom Cu / NC catalyst, comprising the following steps: (1) Take 8L of poultry and livestock wastewater (pH value is 13, initial COD concentration is 2900mg / L) and store it in the water storage tank. Then, it enters the regulating tank through the first water inlet pump to balance the water quality and quantity. (2) The effluent from the equalization tank enters the biochar adsorption tank for biochar adsorption; the mass of biochar in the biochar adsorption tank is 5% of the mass of wastewater, and the hydraulic retention time of the biochar adsorption tank is 2 hours. (3) The effluent from the biochar adsorption tank enters the electrolytic cell for electrolysis; the hydraulic retention time of the electrolytic cell is 3 hours. The electrolytic cell includes a first cathode, a first anode, a second cathode, and a second anode arranged in an alternating manner; the first cathode and the second anode are separated by a polymer ion exchange membrane; the first anode and the second anode are connected to the positive terminal of an external power supply, and the first cathode and the second cathode are connected to the negative terminal of an external power supply. The first cathode is a crack gas diffusion electrode, comprising a graphite felt and a single-atom Cu / NC doped carbon black-PTFE catalyst coated on the graphite felt; the preparation method is the same as in Example 1; The second cathode comprises a graphite felt and a FeOCl catalyst coated on the graphite felt; the preparation method is the same as in Example 1; The first and second anodes are made of nickel foam; The area of ​​both the first and second anodes is 1 cm². 2 The first and second cathodes are circles with a diameter of 1.5 cm; The current density during electrolytic cell operation is 10 mA / cm². 2 ; (4) The effluent from the electrolytic cell enters the coagulation sedimentation tank through the fourth inlet pump. After coagulation and sedimentation, the effluent is discharged with the addition of coagulant PAC. The dosage of coagulant is 25 mg / L, and the hydraulic retention time of the coagulation sedimentation tank is 2 hours.

[0053] Example 3: A method for treating organic wastewater using a dual-cathode coupled single-atom Cu / NC catalyst, comprising the following steps: (1) Take 8L of poultry and livestock wastewater (pH value is 13, initial COD concentration is 2900mg / L) and store it in the water storage tank. Then, it enters the regulating tank through the first water inlet pump to balance the water quality and quantity. (2) The effluent from the equalization tank enters the biochar adsorption tank for biochar adsorption; the mass of biochar in the biochar adsorption tank is 5% of the mass of wastewater, and the hydraulic retention time of the biochar adsorption tank is 2 hours. (3) The effluent from the biochar adsorption tank enters the electrolytic cell for electrolysis; the hydraulic retention time of the electrolytic cell is 3 hours. The electrolytic cell includes a first cathode, a first anode, a second cathode, and a second anode arranged in an alternating manner; the first cathode and the second anode are separated by a polymer ion exchange membrane; the first anode and the second anode are connected to the positive terminal of an external power supply, and the first cathode and the second cathode are connected to the negative terminal of an external power supply. The first cathode is a crack gas diffusion electrode, comprising a graphite felt and a single-atom Cu / NC doped carbon black-PTFE catalyst coated on the graphite felt; the preparation method is the same as in Example 1; The second cathode comprises a graphite felt and a FeOCl catalyst coated on the graphite felt; the preparation method is the same as in Example 1; The first and second anodes are made of nickel foam; The area of ​​both the first and second anodes is 1 cm². 2 The first and second cathodes are circles with a diameter of 1.5 cm; The current density during electrolytic cell operation is 15 mA / cm². 2 ; (4) The effluent from the electrolytic cell enters the coagulation sedimentation tank through the fourth inlet pump. After coagulation and sedimentation, the effluent is discharged with the addition of coagulant PAC. The dosage of coagulant is 15 mg / L, and the hydraulic retention time of the coagulation sedimentation tank is 3 hours.

[0054] Example 4: A method for treating organic wastewater using a dual-cathode coupled single-atom Cu / NC catalyst, comprising the following steps: (1) Take 8L of poultry and livestock wastewater (pH value is 13, initial COD concentration is 2900mg / L) and store it in the water storage tank. Then, it enters the regulating tank through the first water inlet pump to balance the water quality and quantity. (2) The effluent from the equalization tank enters the biochar adsorption tank for biochar adsorption; the mass of biochar in the biochar adsorption tank is 5% of the mass of wastewater, and the hydraulic retention time of the biochar adsorption tank is 2 hours. (3) The effluent from the biochar adsorption tank enters the electrolytic cell for electrolysis; the hydraulic retention time of the electrolytic cell is 3 hours. The electrolytic cell includes a first cathode, a first anode, a second cathode, and a second anode arranged in an alternating manner; the first cathode and the second anode are separated by a polymer ion exchange membrane; the first anode and the second anode are connected to the positive terminal of an external power supply, and the first cathode and the second cathode are connected to the negative terminal of an external power supply. The first cathode is a crack gas diffusion electrode, comprising a graphite felt and a single-atom Cu / NC doped carbon black-PTFE catalyst coated on the graphite felt; the preparation method is the same as in Example 1; The second cathode comprises a graphite felt and a FeOCl catalyst coated on the graphite felt; the preparation method is the same as in Example 1; The first and second anodes are made of nickel foam; The area of ​​both the first and second anodes is 1 cm². 2 The first and second cathodes are circles with a diameter of 1.5 cm; The current density during electrolytic cell operation is 20 mA / cm². 2 ; (4) The effluent from the electrolytic cell enters the coagulation sedimentation tank through the fourth inlet pump. After coagulation and sedimentation, the effluent is discharged with the addition of coagulant PAC. The dosage of coagulant is 25 mg / L, and the hydraulic retention time of the coagulation sedimentation tank is 2 hours.

[0055] Comparative Example 1 (Undoped single-atom Cu / NC): The difference between Comparative Example 1 and Example 1 is that the first cathode is a crack gas diffusion electrode, comprising a graphite felt and a carbon black-PTFE catalyst coated on the graphite felt; the preparation method is as follows: A) The graphite felt (GF) was ultrasonically cleaned in acetone and deionized water to remove impurities. Then the cleaned GF was soaked in a PTFE suspension (5wt% solid content) for 30 minutes. Finally, the GF was removed and dried at room temperature. B) Mix 2.56g of carbon black with 40mL of anhydrous ethanol evenly, sonicate, then add 1.78g of PTFE suspension (70wt% solid content), and stir vigorously at 70℃ until a wet paste is formed to obtain the coating material; C) The obtained coating material is coated onto one side of the GF obtained in step A), and calcined at 350°C for 180 min to obtain a carbon black-PTFE catalyst with a loading of 31.26 mg / cm³. 2 The first cathode; Everything else is the same as in Example 1.

[0056] Every half hour, samples of the solution in the electrolytic cell of the above embodiments and comparative examples were taken to determine the COD concentration. The test results are as follows: Figures 1-3 As shown in Table 1.

[0057] Table 1: Results of livestock wastewater treatment.

[0058] Example 1 91.67 70.1 92.5 Example 2 92.78 73.3 95.7 Example 3 93.88 75.2 97.3 Example 4 94.99 77.5 97.8 Comparative Example 1 80.63 63.0 81.1 From Table 1 and Figure 1 The results show that the method of the present invention used in Examples 1-4 has high efficiency in removing organic matter, with an organic matter removal rate of over 90% in wastewater, achieving efficient degradation of organic matter in livestock and poultry wastewater. In contrast, the first cathode in Comparative Example 1 uses a carbon black-PTFE catalyst without single-atom Cu / NC doping, resulting in a lower hydrogen peroxide production compared to the electrodes doped with single-atom Cu / NC in the examples, leading to a significant decrease in pollutant degradation performance compared to the examples.

[0059] This invention first adsorbs some organic pollutants in wastewater through a biochar adsorption tank, improving the wastewater's biodegradability and reducing its color. Then, a dual-cathode GDE in-situ electro-Fenton device targets and degrades the organic matter in the wastewater, effectively removing it. No other auxiliary devices are required, and the product is green, environmentally friendly, and free of secondary pollution, achieving highly efficient degradation. The biochar adsorbent in the biochar adsorption tank is made from recycled resources such as agricultural waste and sludge, reducing disposal costs. Furthermore, the biochar stably sequesters carbon, reducing CO2 emissions. No chemical reagents are added to the biochar adsorption tank, and waste biochar can be safely disposed of or recycled without secondary pollution. The electrolytic cell of this invention constructs a self-oxygenated in-situ hydrogen peroxide-FeOCl dual-cathode system. This dual-cathode system utilizes electro-Fenton to efficiently treat wastewater, eliminating the need for oxygen supply devices or other auxiliary devices. The product is green, environmentally friendly, and free of secondary pollution, achieving highly efficient degradation of livestock wastewater.

[0060] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for treating organic wastewater using a dual-cathode coupled single-atom Cu / NC catalyst, characterized in that the steps include... include: (1) Wastewater enters the equalization tank to balance water quality and quantity; (2) The effluent from the equalization tank enters the biochar adsorption tank for biochar adsorption; (3) The effluent from the biochar adsorption tank enters the electrolytic cell for electrolysis. The electrolytic cell includes a first cathode, a first anode, a second cathode, and a second anode arranged in an alternating manner; The first cathode is a crack gas diffusion electrode, comprising a graphite felt and a single-atom Cu / NC-doped carbon black-PTFE catalyst coated thereon; the preparation method is as follows: A) Dissolve thiourea in deionized water to obtain a thiourea solution; B) Add soluble copper salt to thiourea solution, stir the reaction, and then dry, calcine, and grind the product to obtain a single-atom Cu / NC catalyst; C) Soak the graphite felt in a PTFE suspension and then remove and dry it; D) Mix carbon black and anhydrous ethanol evenly, then add PTFE suspension and single-atom Cu / NC catalyst dropwise, and stir vigorously until a wet paste is formed to obtain the coating material; E) Apply the coating material to the surface of the graphite felt after drying in step C), and calcine to obtain the final product; The second cathode includes a graphite felt and a FeOCl catalyst coated on the graphite felt; The first and second anodes are made of foamed nickel or foamed copper; (4) The effluent from the electrolytic cell is discharged after sedimentation in the coagulation sedimentation tank.

2. The method for treating organic wastewater using a dual-cathode coupled single-atom Cu / NC catalyst according to claim 1, characterized in that, In step (2), the biochar adsorption tank contains biochar at a mass of 3-7% of the wastewater mass.

3. The method for treating organic wastewater using a dual-cathode coupled single-atom Cu / NC catalyst according to claim 1, characterized in that, In step (3), the mass ratio of carbon black to single-atom Cu / NC catalyst in the first cathode is 25~75:1; the mass ratio of carbon black to PTFE is 5:2~4.

4. The method for treating organic wastewater using a dual-cathode coupled single-atom Cu / NC catalyst according to claim 1, characterized in that, The molar ratio of copper ions to thiourea added in step B) is 0.04~0.

06.

5. The method for treating organic wastewater using a dual-cathode coupled single-atom Cu / NC catalyst according to claim 1, characterized in that, The preparation method of the second cathode in step (3) is as follows: ferric chloride is dissolved in anhydrous ethanol to obtain ferric chloride solution; graphite felt is immersed in ferric chloride solution and then dried and calcined once; the electrode after the first calcination is cleaned with anhydrous ethanol and deionized water and then immersed in PTFE suspension, and then calcined a second time to obtain the second cathode.

6. The method for treating organic wastewater using a dual-cathode coupled single-atom Cu / NC catalyst according to claim 5, characterized in that, The primary calcination temperature is 210~230℃, and the secondary calcination temperature is 170~190℃.

7. The method for treating organic wastewater using a dual-cathode coupled single-atom Cu / NC catalyst according to claim 1, characterized in that, The loading of single-atom Cu / NC doped carbon black-PTFE catalyst in the first cathode is 25~35 mg / cm³. 2 The loading of FeOCl catalyst in the second cathode is 5~40 mg / cm³. 2 .

8. The method for treating organic wastewater using a dual-cathode coupled single-atom Cu / NC catalyst according to claim 1, characterized in that, In the electrolytic cell of step (3), an ion exchange membrane is provided between the first anode and the second cathode.

9. The method for treating organic wastewater using a dual-cathode coupled single-atom Cu / NC catalyst according to claim 1, characterized in that, In the electrolytic cell of step (3), the area ratio of the first anode and the first cathode, and the area ratio of the second anode and the second cathode are all 0.1~1:1.

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