Solar-powered electrocatalytic AOR coupled with biological denitrification total nitrogen removal device and method

Abstract

This invention proposes a solar-powered electrocatalytic AOR coupled with biological denitrification for complete nitrogen removal, comprising a solar power unit, an ammonia electrolyzer, and a biological denitrification unit. In the ammonia electrolyzer, the anode and cathode are connected to the positive and negative terminals of the solar power unit, respectively. The anode includes a conductive substrate and a heteroatom-doped nickel-based metal catalyst loaded on it. Solar power reduces energy consumption, and the battery allows for continuous operation even at night, extending the unit's lifespan. The solar-powered electrocatalytic AOR coupled with biological denitrification provided by this invention has a reasonable design, uses a low-cost conductive substrate as the catalytic electrode, has a simple preparation method, is easy to scale up, is highly efficient, and produces green and pollution-free products. It achieves a nitrogen removal efficiency of over 98%. Electrocatalytic ammonia oxidation combined with multiple electrode sets accelerates the ammonia oxidation process, saving significant time and costs and enhancing ammonia nitrogen treatment capabilities.

Description

Technical Field

[0001] This invention relates to the fields of electrochemical and biological denitrification technology, and in particular to a solar-powered electrocatalytic AOR coupled with biological denitrification complete denitrification device and method. Background Technology

[0002] With the rapid development of industry and agriculture, the discharge of wastewater containing ammonia nitrogen and nitrate nitrogen has gradually increased, seriously impacting the receiving aquatic environment and the integrity of aquatic organisms, such as eutrophication and aquatic ecological imbalance. Excessive ammonia nitrogen discharged into slow-flowing water bodies such as lakes, rivers, and reservoirs leads to the proliferation of algae, which excessively consumes dissolved oxygen, causing water quality deterioration and resulting in the death of aerobic aquatic organisms such as fish and shrimp due to oxygen deficiency. The sediments from these dead organisms then release ammonia nitrogen back into the water, creating a vicious cycle that severely affects the ecological balance. Currently, biological nitrification / denitrification is the most widely used nitrogen removal technology. The process mainly involves: ammonia nitrogen being oxidized to hydroxylamine by ammonia monooxygenase, then oxidized to nitric oxide and nitrite by hydroxylamine dehydrogenase and nitrite reductase, and finally oxidized to nitrate nitrogen by nitrite oxidoreductase. Subsequently, under the combined action of various denitrifying enzymes such as nitrate reductase, nitrite reductase, nitric oxide reductase, and nitric oxide reductase, nitrate nitrogen is reduced to N2 through cellular respiration of denitrifying bacteria. However, many drawbacks of biological nitrification have long been a concern, such as the need for continuous aeration, large footprint, slow growth of autotrophic nitrifying bacteria, and the need for strict control of temperature, C / N ratio, and pH.

[0003] Traditional denitrification technologies, such as breakpoint chlorination, are suitable for treating low-concentration ammonia nitrogen wastewater, but they consume large amounts of liquid chlorine and easily generate toxic chlorinated byproducts, causing secondary pollution. Chemical precipitation and ion exchange methods have poor treatment effects and small treatment capacities; the former's efficiency is highly dependent on the reaction pH. Air stripping has high infrastructure costs, requires long reaction times, and calcium carbonate scale forms in the stripping tower packing, affecting efficiency, and is only suitable for high-concentration ammonia nitrogen treatment. Direct electrocatalytic oxidation technology can directly oxidize ammonia molecules on the anode to generate nitrogen gas and nitrogen oxides. This process is simple to operate, reacts rapidly, has high tolerance to ammonia nitrogen concentrations, is environmentally friendly, and is easy to combine with other processes, making it considered a green ammonia nitrogen treatment technology. For example, Chinese patent document CN115007169A discloses "A catalyst for electrochemical oxidation of ammonia, its preparation method, and its application," which demonstrates good electrocatalytic oxidation activity of ammonia using a platinum-nickel hydroxide material supported by foamed nickel prepared by a hydrothermal method. However, many electrocatalytic ammonia oxidation studies are currently limited to small-scale devices and small-scale catalytic electrodes, and their research methods are not easily scaled up and have not been applied to actual wastewater. In addition, traditional electrocatalytic ammonia oxidation (AOR) is mainly powered by the national grid, which consumes a lot of energy and is not economical. Summary of the Invention

[0004] This invention addresses the shortcomings of existing traditional biological denitrification technologies and the high energy consumption of electrocatalytic ammonia oxidation (AOR). It provides a solar-powered electrocatalytic AOR coupled with biological denitrification for complete nitrogen removal. The ammonia electrolyzer utilizes electrodes loaded with heteroatom-doped nickel-based metal catalysts as the anode. Solar energy provides green kinetic energy to drive electrocatalytic ammonia oxidation, rapidly oxidizing ammonia into nitrogen gas and nitrogen oxides instead of biological nitrification, while coupling with biological denitrification. The final product is green and pollution-free. The catalytic electrode preparation method is simple, and the device is easily scaled up, achieving complete nitrogen removal from wastewater containing both ammonia and nitrate nitrogen.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] This invention proposes a solar-powered electrocatalytic AOR coupled biological denitrification complete nitrogen removal device, comprising an ammonia electrolyzer, an equalization tank, and a biological denitrification unit connected sequentially via a liquid delivery pipeline. The ammonia electrolyzer is powered by a solar energy source. The ammonia electrolyzer contains several sets of electrodes, including an anode and a cathode. The anode is a heteroatom-doped nickel-based metal catalytic electrode, comprising a conductive substrate and a heteroatom-doped nickel-based metal catalyst supported on the conductive substrate. The solar energy source powers the ammonia electrolyzer, where an ammonia oxidation reaction occurs, electrocatalytically oxidizing and degrading ammonia nitrogen to produce nitrogen gas and nitrogen oxides. The biological denitrification unit is a closed system to ensure an anaerobic environment. The biological denitrification unit denitrifies the wastewater from the electrocatalytic ammonia oxidation in the ammonia electrolyzer, efficiently removing nitrogen from the wastewater.

[0007] Wastewater containing ammonia nitrogen enters the ammonia electrolyzer and undergoes an ammonia oxidation reaction. Ammonia nitrogen loses electrons at the anode and is oxidized into nitrogen gas and nitrogen oxides. The specific reactions are shown in formulas (1)-(3):

[0008] 2NH3 + 6OH - →N2 + 6H2O + 6e - (1)

[0009]

[0010] The wastewater after ammonia electro-oxidation enters the biological denitrification unit to undergo denitrification reaction to generate nitrogen gas. The specific reaction is shown in formulas (4)-(5):

[0011]

[0012] The solar-powered electrocatalytic AOR coupled biological denitrification total nitrogen removal device provided by this invention has a reasonable design, simple catalytic electrode preparation, and easy device scale-up. It is highly efficient, and the products are green and pollution-free. It shows good denitrification effect on actual ammonia nitrogen wastewater, achieving a nitrogen removal efficiency of over 98%. Solar power reduces energy consumption and saves costs. Electrocatalytic ammonia oxidation combined with multiple electrode sets significantly accelerates the ammonia oxidation rate, saving considerable time and enhancing ammonia nitrogen treatment capacity.

[0013] Preferably, the electrode spacing between the cathode and anode electrodes in the ammonia electrolyzer is 0.5 cm to 2 cm.

[0014] Preferably, the solar power supply device includes a solar panel, on which a voltage regulator, a battery, and a battery switch are fixed side by side.

[0015] Preferably, the cathode in the ammonia electrolyzer is one of the following: titanium sheet electrode, nickel foam electrode, copper plate electrode, stainless steel electrode, or Pt electrode.

[0016] Another aspect of this invention proposes a method for complete nitrogen removal from wastewater using a solar-powered electrocatalytic AOR coupled with a biological denitrification system, comprising the following steps:

[0017] (A) Wastewater enters the ammonia electrolyzer, which is powered by a solar energy device to carry out electrocatalytic ammonia oxidation reaction; (B) The effluent from the ammonia electrolyzer enters the equalization tank, where the pH of the wastewater is adjusted to neutral.

[0018] (C) The effluent from the equalization tank enters the biological denitrification device to carry out the biological denitrification reaction and achieve complete denitrification of the wastewater.

[0019] As a preferred embodiment, the method for preparing the heteroatom-doped nickel-based metal catalytic electrode in the ammonia electrolyzer is as follows:

[0020] S1. Place the conductive substrate in a solution of dilute hydrochloric acid and anhydrous ethanol to remove oxides and impurities from the surface of the conductive substrate, then wash it repeatedly with deionized water and dry it at room temperature.

[0021] S2, nickel salt, metal salt M1, metal salt M2, urea and thiourea are dissolved in deionized water and mixed evenly to obtain an electrolyte;

[0022] S3. Place the dried conductive substrate from S1 into the electrolyte obtained in S2, and electrodeposit to obtain a heteroatom-doped nickel-based metal precatalytic electrode.

[0023] S4. The heteroatom-doped nickel-based metal precatalytic electrode obtained in S4 is electrochemically tuned and reconstructed to obtain a heteroatom-doped nickel-based metal catalytic electrode.

[0024] The number of active sites on the surface of the heteroatom-doped nickel-based metal catalytic electrode prepared by this invention is significantly increased, which is more conducive to the contact between the electrode and more reactants. In addition, the active material on the catalyst surface is uniform in size and densely distributed, exposing more contact surface, which is more conducive to the contact between reactants and the electrode and electron transport, thereby improving the efficiency of ammonia oxidation.

[0025] Preferably, the nickel salt is one of nickel chloride, nickel sulfate, nickel nitrate, and nickel acetate; the metal salt M1 is one of copper chloride, copper sulfate, copper iodide, copper acetate, copper acetate, and copper carbonate; and the metal salt M2 is one of ferric sulfate, ferric chloride, and ferric nitrate.

[0026] Preferably, the molar ratio of metal ions in nickel salt, metal salt M1 and metal salt M2 is 0.8-1.2:0.8-1.2:0.5-1.

[0027] Preferably, the electrodeposition time in S3 is 120s to 240s.

[0028] Preferably, the hydraulic retention time in the ammonia electrolyzer is 20–30 h; the hydraulic retention time in the biological denitrification unit is 20–30 h.

[0029] Therefore, the present invention has the following beneficial effects:

[0030] (1) The anode used in the device is loaded with a heteroatom-doped nickel-based metal catalyst, which accelerates the ammonia oxidation rate and improves the ammonia electro-oxidation activity; the device can treat nitrogen-containing wastewater with a total nitrogen concentration of at least 350 mg / L and achieve a denitrification effect of more than 98%.

[0031] (2) The device can reduce energy consumption and save costs by using solar energy; the ammonia oxidation rate can be greatly accelerated by electrocatalytic ammonia oxidation and multiple sets of electrodes in series, saving a lot of time and enhancing the ammonia nitrogen treatment capacity.

[0032] (3) The device is reasonably designed and easy to scale up. It is highly efficient and produces green and pollution-free products with good denitrification effect. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the structure of the solar-powered electrocatalytic AOR coupled biological denitrification complete nitrogen removal device of the present invention.

[0034] In the diagram: 1-liquid level, 2-anode, 3-cathode, 4-ammonia electrolysis cell, 5-battery, 6-voltage stabilizer, 7-power switch, 8-solar circuit board, 9-inlet valve, 10-regulating tank, 11-rear inlet valve, 12-biological denitrification device, 13-positive electrode, 14-negative electrode.

[0035] Figure 2It is the Ni1Cu1Fe loaded on the anode in Embodiment 1 of the present invention. 0.5 SEM image of -S / Ti heteroatoms doped nickel-based metal catalyst.

[0036] Figure 3 These are cyclic voltammetry (CV) test results of the heteroatom-doped nickel-based metal catalysts prepared in Example 1, Comparative Examples 1 and 2 of this invention.

[0037] Figure 4 This invention uses Ni1Cu1Fe prepared in Example 1. 0.5 The effect of the -S / Ti catalytic electrode on the removal of total nitrogen from ammonia nitrogen wastewater in rare earth mines in southern Jiangxi Province is shown in the figure.

[0038] Figure 5 This is a comparison chart of the total nitrogen concentration of ammonia nitrogen wastewater from the Gannan rare earth mine before and after treatment by this device, as shown in Example 1 of the present invention.

[0039] Figure 6 It is Ni1Cu1Fe in Embodiment 1 of the present invention 0.5 Comparison of ammonia nitrogen removal between the S / Ti catalytic electrode and the commercial Ti electrode in Comparative Example 3 and the commercial DSA electrode in Comparative Example 4. Detailed Implementation

[0040] The present invention will now be further described with reference to the accompanying drawings and specific embodiments.

[0041] The main structure of this invention, in its specific embodiments, includes a solar power supply device, an ammonia electrolyzer, an equalization tank, and a biological denitrification device. For example... Figure 1 As shown, the solar energy collected by the solar circuit board 8 charges the battery 5 through the voltage regulator 6. The battery is equipped with a power switch 7. The anode 2 and cathode 3 in the ammonia electrolysis cell 4 are connected to the positive terminal 13 and negative terminal 14 of the battery through wires. After turning on the battery power switch 7, the electrocatalytic ammonia oxidation reaction begins, and the anode 2 begins to degrade ammonia nitrogen. Multiple sets of electrodes can be set in the ammonia electrolysis cell 4 to treat ammonia nitrogen wastewater simultaneously. The liquid level 1 of the wastewater in the ammonia electrolysis cell 4 is above the anode 2 and cathode 3. After ammonia electrooxidation treatment, the wastewater flows into the regulating tank 10 through the inlet valve 9. After the pH of the wastewater is adjusted to neutral, it flows into the biological denitrification device 12 through the outlet valve 11. The biological denitrification device 12 is filled with domesticated denitrifying bacteria for biological denitrification. The biological denitrification device 12 is a closed device to ensure an anaerobic environment. The biological denitrification device 12 performs a denitrification reaction on the wastewater after electrocatalytic ammonia oxidation in the ammonia electrolysis cell 4, efficiently removing nitrogen from the wastewater.

[0042] In one specific embodiment of the present invention, the electrode spacing between the anode and cathode electrodes in the ammonia electrolyzer is 0.5cm to 2cm.

[0043] In one specific embodiment of the present invention, the solar power supply device includes a solar power panel, on which a voltage regulator, a storage battery, and a storage battery switch are fixed side by side.

[0044] In one specific embodiment of the present invention, the electrodes in the ammonia electrolyzer may be one or more sets of electrodes.

[0045] A specific embodiment of the present invention provides a method for complete nitrogen removal from wastewater using a solar-powered electrocatalytic AOR coupled with a biological denitrification system. The specific steps are as follows:

[0046] (A) Wastewater enters the ammonia electrolyzer, which is powered by a solar energy device to carry out electrocatalytic ammonia oxidation reaction; (B) The effluent from the ammonia electrolyzer enters the equalization tank, where the pH of the wastewater is adjusted to neutral.

[0047] (C) The effluent from the equalization tank enters the biological denitrification device to carry out the biological denitrification reaction and achieve complete denitrification of the wastewater.

[0048] In a specific embodiment of the present invention, the method for preparing the heteroatom-doped nickel-based metal catalytic electrode in the ammonia electrolyzer is as follows: S1, the conductive substrate is placed in a solution of dilute hydrochloric acid and anhydrous ethanol to remove oxides and impurities on the surface of the conductive substrate, and then repeatedly washed with deionized water and dried at room temperature.

[0049] S2, nickel salt, metal salt M1, metal salt M2, urea and thiourea are dissolved in deionized water and mixed evenly to obtain an electrolyte;

[0050] S3. Place the dried conductive substrate from S1 into the electrolyte obtained in S2, and electrodeposit to obtain a heteroatom-doped nickel-based metal precatalytic electrode.

[0051] S4. The heteroatom-doped nickel-based metal precatalytic electrode obtained in S4 is electrochemically tuned and reconstructed to obtain a heteroatom-doped nickel-based metal catalytic electrode.

[0052] In a specific embodiment of the present invention, the nickel salt may be one of nickel chloride, nickel sulfate, nickel nitrate, and nickel acetate; the metal salt M1 may be one of copper chloride, copper sulfate, copper iodide, copper acetate, and copper carbonate; and the metal salt M2 may be one of ferric sulfate, ferric chloride, and ferric nitrate.

[0053] In one specific embodiment of the present invention, the molar ratio of metal ions of nickel salt, metal salt M1 and metal salt M2 is 0.8-1.2:0.8-1.2:0.5-1.

[0054] In one specific embodiment of the present invention, the hydraulic retention time in the ammonia electrolyzer is 20-30 hours; the hydraulic retention time in the biological denitrification device is 20-30 hours.

[0055] Example 1

[0056] A solar-powered electrocatalytic AOR coupled biological denitrification complete nitrogen removal device: The anode and cathode of an ammonia electrolyzer are connected to the positive and negative electrodes of a solar-powered device via wires, respectively. One side of the ammonia electrolyzer is connected to an equalization tank via a liquid delivery pipeline, and the other end of the equalization tank is connected to a biological denitrification device via a liquid delivery pipeline, thus obtaining a solar-powered electrocatalytic AOR coupled biological denitrification complete nitrogen removal device. Ni1Cu1Fe is selected in the ammonia electrolyzer. 0.5 -S / Ti catalytic electrode is used as the anode, and titanium sheet electrode is used as the cathode.

[0057] A total nitrogen removal process for ammonia nitrogen wastewater is achieved using a solar-powered electrocatalytic AOR coupled with biological denitrification. The method is as follows:

[0058] Step (A): 300 mL of ammonia nitrogen wastewater from the Gannan rare earth mine (pH = 13, initial total nitrogen approximately 350 mL / L) was added to the ammonia electrolysis cell. The solar power supply device provided a total voltage of 2.0 V to the ammonia electrolysis cell for ammonia electro-oxidation, which completely removed the ammonia nitrogen from the wastewater. The hydraulic retention time in the ammonia electrolysis cell was 24 h, and the removal rates of ammonia nitrogen and total nitrogen were 99.2% and 61.1%, respectively.

[0059] Step (B): The wastewater that has been treated to meet the standards in the ammonia electrolysis cell is introduced into the equalization tank through the infusion pipeline, and the pH of the wastewater is adjusted to about 7, with a hydraulic retention time of about 10 minutes.

[0060] Step (C): The wastewater conditioned in the equalization tank is fed into the biological denitrification unit through the infusion pipeline. After a hydraulic retention time of 24 hours, the total nitrogen removal rate is approximately 98.7%.

[0061] Heteroatomic doped nickel-based metal catalytic electrode (Ni1Cu1Fe) in ammonia electrolyzer 0.5 The preparation method of the -S / Ti catalytic electrode includes the following steps:

[0062] S1. Electrode pretreatment: Place the 5*10*0.1cm titanium sheet electrode in 3mol / L HCl solution and anhydrous ethanol solution and sonicate for 30min to remove oxides and impurities on the surface of the electrode sheet. After sonication, wash the electrode sheet repeatedly with deionized water and dry it at room temperature.

[0063] S2, Ni1Cu1Fe 0.5Preparation of the -S / Ti precatalytic electrode: In an electrolyte composed of 0.1 mol / L thiourea, 0.1 mol / L urea, 0.01 mol / L Ni(NO3)2·6H2O, 0.01 mol / L Cu(NO3)2·3H2O, and 0.0025 mol / L Fe2(SO4)3, a Ti sheet electrode, an Hg / HgO electrode, and a Pt wire were used as the working electrode, reference electrode, and counter electrode in a three-electrode system, respectively. Electrodeposition was performed at a constant potential of -1.3 V vs. Hg / HgO for 180 s on an electrochemical workstation to obtain Ni1Cu1Fe. 0.5 The initial product of the -S / Ti precatalytic electrode was dried at 60℃ in a constant temperature drying oven to obtain Ni1Cu1Fe. 0.5 -S / Ti precatalytic electrode finished product;

[0064] S3, Ni1Cu1Fe 0.5 Preparation of -S / Ti catalytic electrode: Ni1Cu1Fe 0.5 The -S / Ti precatalytic electrode was used as the working electrode, with the reference and counter electrodes remaining unchanged. The electrolyte was a 0.5 mol / L NaOH solution. Cyclic voltammetry was used in the potential range of 0–0.7 V at a scan rate of 50 mV / s. -1 Electrochemically tuned surface reconstruction was performed for 20 consecutive cycles to obtain highly efficient Ni1Cu1Fe 0.5 -S / Ti catalytic electrode.

[0065] Example 2

[0066] A solar-powered electrocatalytic AOR coupled biological denitrification complete nitrogen removal device: The anode and cathode of an ammonia electrolyzer are connected to the positive and negative electrodes of a solar-powered device via wires, respectively. One side of the ammonia electrolyzer is connected to an equalization tank via a liquid delivery pipeline, and the other end of the equalization tank is connected to a biological denitrification device via a liquid delivery pipeline, thus obtaining a solar-powered electrocatalytic AOR coupled biological denitrification complete nitrogen removal device. Ni1Cu1Fe is selected in the ammonia electrolyzer. 0.5 -S / Ti was used as the anode, and nickel foam electrode was used as the cathode.

[0067] A solar-powered electrocatalytic AOR coupled with biological denitrification is used to completely remove nitrogen from ammonia nitrogen wastewater. The method is as follows: Step (A): 300 mL of ammonia nitrogen wastewater from the Gannan rare earth mine (pH=13, initial total nitrogen is about 350 mL / L) is added to the ammonia electrolysis cell. The solar-powered device provides a total voltage of 2.0 V to the ammonia electrolysis cell for ammonia electro-oxidation, which removes all ammonia nitrogen from the wastewater. The hydraulic retention time in the ammonia electrolysis cell is 24 h.

[0068] Step (B): The wastewater that has been treated to meet the standards in the ammonia electrolysis cell is introduced into the equalization tank through the infusion pipeline, and the pH of the wastewater is adjusted to about 7, with a hydraulic retention time of about 10 minutes.

[0069] Step (C): The wastewater conditioned in the equalization tank is fed into the biological denitrification device through the infusion pipeline. After a hydraulic retention time of 24 hours, the total nitrogen removal rate is measured.

[0070] Anode heteroatom-doped nickel-based metal catalytic electrode (Ni1Cu1Fe) in ammonia electrolyzer 0.5 The preparation method of the -S / Ti catalytic electrode is as follows:

[0071] S1. Electrode pretreatment: Place the 5*10*0.1cm titanium sheet electrode in 3mol / L HCl solution and anhydrous ethanol solution and sonicate for 30min to remove oxides and impurities on the surface of the electrode sheet. After sonication, wash the electrode sheet repeatedly with deionized water and dry it at room temperature.

[0072] S2, Ni1Cu1Fe 0.5 Preparation of the -S / Ti precatalytic electrode: In an electrolyte composed of 0.1 mol / L thiourea, 0.08 mol / L urea, 0.01 mol / L Ni(NO3)2·6H2O, 0.01 mol / L Cu(NO3)2·3H2O, and 0.0025 mol / L Fe2(SO4)3, a Ti sheet electrode, an Hg / HgO electrode, and a Pt wire were used as the working electrode, reference electrode, and counter electrode in a three-electrode system, respectively. Electrodeposition was performed at a constant potential of -1.3 V vs. Hg / HgO for 240 s on an electrochemical workstation to obtain Ni1Cu1Fe. 0.5 The initial product of the -S / Ti precatalytic electrode was dried at 60℃ in a constant temperature drying oven to obtain Ni1Cu1Fe. 0.5 -S / Ti precatalytic electrode finished product;

[0073] S3, Ni1Cu1Fe 0.5 Preparation of -S / Ti catalytic electrode: Ni1Cu1Fe 0.5 The -S / Ti precatalytic electrode was used as the working electrode, with the reference and counter electrodes remaining unchanged. The electrolyte was a 0.5 mol / L NaOH solution. Cyclic voltammetry was used in the potential range of 0–0.7 V at a scan rate of 50 mV / s. -1 Electrochemically tuned surface reconstruction was performed for 20 consecutive cycles to obtain highly efficient Ni1Cu1Fe 0.5 -S / Ti catalytic electrode.

[0074] Example 3

[0075] A solar-powered electrocatalytic AOR coupled biological denitrification complete nitrogen removal device: The anode and cathode of an ammonia electrolyzer are connected to the positive and negative electrodes of a solar-powered device via wires, respectively. One side of the ammonia electrolyzer is connected to an equalization tank via a liquid delivery pipeline, and the other end of the equalization tank is connected to a biological denitrification device via a liquid delivery pipeline, thus obtaining a solar-powered electrocatalytic AOR coupled biological denitrification complete nitrogen removal device. Ni1Cu1Fe is selected in the ammonia electrolyzer. 0.5 -S / Ti was used as the anode, and a stainless steel electrode was used as the cathode.

[0076] A solar-powered electrocatalytic AOR coupled with biological denitrification is used to completely remove nitrogen from ammonia nitrogen wastewater. The method is as follows: Step (A): 300 mL of ammonia nitrogen wastewater from the Gannan rare earth mine (pH=13, initial total nitrogen is about 350 mL / L) is added to the ammonia electrolysis cell. The solar-powered device provides a total voltage of 2.0 V to the ammonia electrolysis cell for ammonia electro-oxidation, which removes all ammonia nitrogen from the wastewater. The hydraulic retention time in the ammonia electrolysis cell is 24 h.

[0077] Step (B): The wastewater that has been treated to meet the standards in the ammonia electrolysis cell is introduced into the equalization tank through the infusion pipeline, and the pH of the wastewater is adjusted to about 7, with a hydraulic retention time of about 10 minutes.

[0078] Step (C): The wastewater conditioned in the equalization tank is fed into the biological denitrification device through the infusion pipeline. After a hydraulic retention time of 24 hours, the total nitrogen removal rate is measured.

[0079] Heteroatomic doped nickel-based metal catalytic electrode (Ni1Cu1Fe) in ammonia electrolyzer 0.5 The preparation method of the -S / Ti catalytic electrode is as follows:

[0080] S1. Electrode pretreatment: Place the 5*10*0.1cm titanium sheet electrode in 3mol / L HCl solution and anhydrous ethanol solution and sonicate for 30min to remove oxides and impurities on the surface of the electrode sheet. After sonication, wash the electrode sheet repeatedly with deionized water and dry it at room temperature.

[0081] S2, Ni1Cu1Fe 0.5 Preparation of the -S / Ti precatalytic electrode: In an electrolyte composed of 0.1 mol / L thiourea, 0.12 mol / L urea, 0.01 mol / L Ni(NO3)2·6H2O, 0.01 mol / L Cu(NO3)2·3H2O, and 0.0025 mol / L Fe2(SO4)3, a Ti sheet electrode, an Hg / HgO electrode, and a Pt wire were used as the working electrode, reference electrode, and counter electrode in a three-electrode system, respectively. Electrodeposition was performed at a constant potential of -1.3 V vs. Hg / HgO for 120 s on an electrochemical workstation to obtain Ni1Cu1Fe. 0.5The initial product of the -S / Ti precatalytic electrode was dried at 60℃ in a constant temperature drying oven to obtain Ni1Cu1Fe. 0.5 -S / Ti precatalytic electrode finished product;

[0082] S3, Ni1Cu1Fe 0.5 Preparation of -S / Ti catalytic electrode: Ni1Cu1Fe 0.5 The -S / Ti precatalytic electrode was used as the working electrode, with the reference and counter electrodes remaining unchanged. The electrolyte was a 0.5 mol / L NaOH solution. Cyclic voltammetry was used in the potential range of 0–0.7 V at a scan rate of 50 mV / s. -1 Electrochemically tuned surface reconstruction was performed for 20 consecutive cycles to obtain highly efficient Ni1Cu1Fe 0.5 -S / Ti catalytic electrode.

[0083] Comparative Example 1 (Ni1Cu1Fe) 0.5 / Ti electrode)

[0084] A solar-powered electrocatalytic AOR coupled biological denitrification complete nitrogen removal device: The anode and cathode of an ammonia electrolyzer are connected to the positive and negative electrodes of a solar-powered device via wires, respectively. One side of the ammonia electrolyzer is connected to an equalization tank via a liquid delivery pipeline, and the other end of the equalization tank is connected to a biological denitrification device via a liquid delivery pipeline, thus obtaining a solar-powered electrocatalytic AOR coupled biological denitrification complete nitrogen removal device. Ni1Cu1Fe is selected in the ammonia electrolyzer. 0.5 Ti is used as the anode, and the titanium electrode is used as the cathode.

[0085] A solar-powered electrocatalytic AOR coupled with biological denitrification is used to completely remove nitrogen from ammonia nitrogen wastewater. The method is as follows: Step (A): 300 mL of ammonia nitrogen wastewater from the Gannan rare earth mine (pH=13, initial total nitrogen is about 350 mL / L) is added to the ammonia electrolysis cell. The solar-powered device provides a total voltage of 2.0 V to the ammonia electrolysis cell for ammonia electro-oxidation, which removes all ammonia nitrogen from the wastewater. The hydraulic retention time in the ammonia electrolysis cell is 24 h.

[0086] Step (B): The wastewater that has been treated to meet the standards in the ammonia electrolysis cell is introduced into the equalization tank through the infusion pipeline, and the pH of the wastewater is adjusted to about 7, with a hydraulic retention time of about 10 minutes.

[0087] Step (C): The wastewater conditioned in the equalization tank is fed into the biological denitrification device through the infusion pipeline. After a hydraulic retention time of 24 hours, the total nitrogen removal rate is measured.

[0088] Heteroatomic doped nickel-based metal catalytic electrode (Ni1Cu1Fe) in ammonia electrolyzer 0.5The preparation method of the / Ti electrode is as follows: S1, electrode pretreatment: 5*10*0.1cm titanium sheet electrode is placed in 3mol / L HCl solution and anhydrous ethanol solution and ultrasonically treated for 30min to remove oxides and impurities on the surface of the electrode sheet. After ultrasonic treatment, the electrode sheet is repeatedly washed with deionized water and then dried at room temperature.

[0089] S2, Ni1Cu1Fe 0.5 Preparation of the / Ti precatalytic electrode: In an electrolyte composed of 0.1 mol / L urea, 0.01 mol / L Ni(NO3)2·6H2O, 0.01 mol / L Cu(NO3)2·3H2O, and 0.0025 mol / L Fe2(SO4)3, a Ti sheet electrode, an Hg / HgO electrode, and a Pt wire were used as the working electrode, reference electrode, and counter electrode in a three-electrode system, respectively. Electrodeposition was performed at a constant potential of -1.3 V vs. Hg / HgO for 180 s on an electrochemical workstation to obtain Ni1Cu1Fe. 0.5 The initial product of the / Ti pre-catalyzed electrode was dried at 60℃ in a constant temperature drying oven to obtain Ni1Cu1Fe. 0.5 / Ti pre-catalyzed electrode finished product;

[0090] S3, Ni1Cu1Fe 0.5 Preparation of / Ti catalytic electrode: Ni1Cu1Fe 0.5 The Ti pre-catalyzed electrode was used as the working electrode, with the reference and counter electrodes remaining unchanged. The electrolyte was a 0.5 mol / L NaOH solution. Cyclic voltammetry was used in the potential range of 0–0.7 V at a scan rate of 50 mV / s. -1 Electrochemically tuned surface reconstruction was performed for 20 consecutive cycles to obtain highly efficient Ni1Cu1Fe 0.5 / Ti catalytic electrode.

[0091] Comparative Example 2 (Ni1Cu1 / Ti electrode)

[0092] A solar-powered electrocatalytic AOR coupled biological denitrification complete nitrogen removal device: The anode and cathode of an ammonia electrolyzer are connected to the positive and negative electrodes of a solar-powered device via wires, respectively. One side of the ammonia electrolyzer is connected to an equalization tank via a liquid delivery pipeline, and the other end of the equalization tank is connected to the biological denitrification device via a liquid delivery pipeline, thus obtaining a solar-powered electrocatalytic AOR coupled biological denitrification complete nitrogen removal device. In the ammonia electrolyzer, a Ni1Cu1 / Ti electrode is selected as the anode, and a titanium electrode is selected as the cathode.

[0093] A solar-powered electrocatalytic AOR coupled with biological denitrification is used to completely remove nitrogen from ammonia nitrogen wastewater. The method is as follows: Step (A): 300 mL of ammonia nitrogen wastewater from the Gannan rare earth mine (pH=13, initial total nitrogen is about 350 mL / L) is added to the ammonia electrolysis cell. The solar-powered device provides a total voltage of 2.0 V to the ammonia electrolysis cell for ammonia electro-oxidation, which removes all ammonia nitrogen from the wastewater. The hydraulic retention time in the ammonia electrolysis cell is 24 h.

[0094] Step (B): The wastewater that has been treated to meet the standards in the ammonia electrolysis cell is introduced into the equalization tank through the infusion pipeline, and the pH of the wastewater is adjusted to about 7, with a hydraulic retention time of about 10 minutes.

[0095] Step (C): The wastewater conditioned in the equalization tank is fed into the biological denitrification device through the infusion pipeline. After a hydraulic retention time of 24 hours, the total nitrogen removal rate is measured.

[0096] The preparation method of heteroatom-doped nickel-based metal catalytic electrode (Ni1Cu1 / Ti electrode) in an ammonia electrolyzer includes the following steps:

[0097] S1. Electrode pretreatment: Place the 5*10*0.1cm titanium sheet electrode in 3mol / L HCl solution and anhydrous ethanol solution and sonicate for 30min to remove oxides and impurities on the surface of the electrode sheet. After sonication, wash the electrode sheet repeatedly with deionized water and dry it at room temperature.

[0098] Preparation of S2 and Ni1Cu1 / Ti precatalytic electrodes: In an electrolyte composed of 0.1 mol / L urea, 0.01 mol / L Ni(NO3)2·6H2O and 0.01 mol / L Cu(NO3)2·3H2O, Ti sheet electrode, Hg / HgO electrode and Pt wire were used as the working electrode, reference electrode and counter electrode in the three-electrode system, respectively. Electrodeposition was performed at a constant potential of -1.3V vs. Hg / HgO for 180s on an electrochemical workstation to obtain the initial product of Ni1Cu1 / Ti precatalytic electrode. The product was then dried at 60℃ in a constant temperature drying oven to obtain the finished Ni1Cu1 / Ti precatalytic electrode.

[0099] Preparation of S3, Ni1Cu1 / Ti catalytic electrode: Ni1Cu1Fe 0.5 The Ti pre-catalyzed electrode was used as the working electrode, with the reference and counter electrodes remaining unchanged. The electrolyte was a 0.5 mol / L NaOH solution. Cyclic voltammetry was used in the potential range of 0–0.7 V at a scan rate of 50 mV / s. -1 By continuously cycling for 20 cycles to perform electrochemical tuning and surface reconstruction, a highly efficient Ni1Cu1 / Ti catalytic electrode was obtained.

[0100] Comparative Example 3

[0101] The preparation method of the solar-powered electrocatalytic AOR coupled biological denitrification complete nitrogen removal device is the same as in Example 1, except that the materials of the cathode and anode in Example 1 are replaced. The solar-powered electrocatalytic AOR coupled biological denitrification complete nitrogen removal device, using a commercially available Ti electrode as the anode and a titanium electrode as the cathode, performs complete nitrogen removal from ammonia nitrogen wastewater. The method is as follows:

[0102] Step (A): 300 mL of ammonia nitrogen wastewater from rare earth mines in southern Jiangxi (pH=13, initial total nitrogen about 350 mL / L) was added to the ammonia electrolysis cell. The solar power supply device provided a total voltage of 2.0 V to the ammonia electrolysis cell for ammonia electro-oxidation, which removed all the ammonia nitrogen in the wastewater. The hydraulic retention time in the ammonia electrolysis cell was 24 h.

[0103] Step (B): The wastewater that has been treated to meet the standards in the ammonia electrolysis cell is introduced into the equalization tank through the infusion pipeline, and the pH of the wastewater is adjusted to about 7, with a hydraulic retention time of about 10 minutes.

[0104] Step (C): The wastewater conditioned in the equalization tank is fed into the biological denitrification device through the infusion pipeline. After a hydraulic retention time of 24 hours, the total nitrogen removal rate is measured.

[0105] Comparative Example 4

[0106] The preparation method of the solar-powered electrocatalytic AOR coupled biological denitrification complete nitrogen removal device is the same as in Example 1, except that the materials of the cathode and anode in Example 1 are replaced. The solar-powered electrocatalytic AOR coupled biological denitrification complete nitrogen removal device, using a commercially available DSA electrode as the anode and a titanium electrode as the cathode, performs complete nitrogen removal from ammonia nitrogen wastewater. The method is as follows:

[0107] Step (A): 300 mL of ammonia nitrogen wastewater from rare earth mines in southern Jiangxi (pH=13, initial total nitrogen about 350 mL / L) was added to the ammonia electrolysis cell. The solar power supply device provided a total voltage of 2.0 V to the ammonia electrolysis cell for ammonia electro-oxidation, which removed all the ammonia nitrogen in the wastewater. The hydraulic retention time in the ammonia electrolysis cell was 24 h.

[0108] Step (B): The wastewater that has been treated to meet the standards in the ammonia electrolysis cell is introduced into the equalization tank through the infusion pipeline, and the pH of the wastewater is adjusted to about 7, with a hydraulic retention time of about 10 minutes.

[0109] Step (C): The wastewater conditioned in the equalization tank is fed into the biological denitrification device through the infusion pipeline. After a hydraulic retention time of 24 hours, the total nitrogen removal rate is measured.

[0110] The Ni1Cu1Fe prepared in Example 1 0.5 -S / Ti electrodes were used for scanning electron microscopy testing, such as Figure 2 As shown. Ni1Cu1Fe 0.5The -S / Ti electrode surface forms a unique nanospherical layered structure, significantly increasing the number of surface active sites. This facilitates greater contact between the electrode and reactants, improving the efficiency of electrocatalytic ammonia oxidation of AOR. (Ni1Cu1Fe) 0.5 The uniform size and dense distribution of active materials on the surface of the -S / Ti electrode indicate that more contact surface is exposed, which is more conducive to the contact and electron transport between the reactants and the electrode, thereby improving the ammonia electro-oxidation activity.

[0111] The electrochemical performance of the anode catalytic electrode prepared in the above examples was investigated using a three-electrode system on a CHI 604E electrochemical workstation. The prepared catalytic anode was used as the working electrode, the platinum wire as the counter electrode, and Hg / HgO as the reference electrode.

[0112] Figure 3 The CV test results show that Ni1Cu1Fe 0.5 -S / Ti electrodes are respectively more efficient than binary alloy electrodes (Ni1Cu1 / Ti, 9.16 mA·cm⁻¹) -2 ) and ternary non-sulfur-doped electrode (Ni1Cu1Fe 0.5 / Ti, 19.76 mA·cm -2 ) exhibits higher current density (Ni1Cu1Fe) 0.5 -S / Ti, 54.48 mA·cm -2 This indicates that Ni1Cu1Fe 0.5 -S / Ti electrodes exhibit highly efficient AOR catalytic performance. Ni1Cu1Fe 0.5 The significant improvement in AOR performance of the -S / Ti electrode is attributed to the synergistic effect of Ni-Cu-Fe metals and the exposure of more catalyst active sites.

[0113] like Figure 4 As shown, the Ni1Cu1Fe prepared in Example 1 was used. 0.5 -S / Ti catalytic electrodes were used to perform electrocatalytic ammonia oxidation on ammonia nitrogen wastewater from rare earth mines in southern Jiangxi. After electrocatalytic ammonia oxidation, the ammonia nitrogen removal rate reached 99.8%, the total nitrogen removal rate reached 61.1%, and the nitrate nitrogen removal rate reached 48.1%. After biological denitrification, the total nitrogen removal rate reached 98.7%, almost achieving complete nitrogen removal.

[0114] like Figure 5 As shown, the concentrations of ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen in the wastewater before and after treatment by this device are from... Figure 5 It is clear that the concentrations of all three substances were significantly reduced after being treated by this device.

[0115] like Figure 6 As shown, Ni1Cu1Fe from Example 1 is used. 0.5The -S / Ti electrode, along with the commercial Ti electrode in Comparative Example 3 and the commercial DSA electrode in Comparative Example 4, were used as control denitrification experiments for ammonia electro-oxidation. Within the same 20-hour electrolysis time, the ammonia nitrogen removal rates of the Ti sheet electrode and the DSA electrode were only 42.4% and 66.8%, respectively, while the Ni1Cu1Fe electrode achieved significantly higher removal rates. 0.5 The ammonia nitrogen removal rate of the -S / Ti electrode reached 92.2%, with a difference of 49.8% and 25.4% between the two. This shows that Ni1Cu1Fe 0.5 The -S / Ti electrode significantly improves the ammonia nitrogen removal rate through the synergistic effect of ternary metal alloy and heteroatom doping, resulting in the removal of more ammonia nitrogen after modification.

[0116] The working principle of this invention is as follows: Solar energy powers the ammonia electrolysis process. The anode in the ammonia electrolysis cell converts ammonia nitrogen in wastewater into nitrogen gas and nitrogen oxides. After passing through an equalization tank, the mixture enters a biological denitrification device, where nitrogen oxides in the wastewater are biologically denitrified into environmentally friendly nitrogen gas. Solar power reduces energy consumption and costs, and the rechargeable battery allows for continuous operation even at night, extending the lifespan of this invention. Multiple electrode sets accelerate the conversion of ammonia nitrogen into nitrogen gas and nitrogen oxides, and after biological denitrification, efficient denitrification of nitrogen-containing wastewater is achieved.

Claims

1. A solar-powered electrocatalytic AOR coupled with biological denitrification for complete nitrogen removal, characterized in that, It includes an ammonia electrolyzer, an equalization tank, and a biological denitrification unit, which are connected in sequence via infusion pipelines; the ammonia electrolyzer is powered by a solar energy supply device; The ammonia electrolyzer is equipped with several sets of electrodes, including an anode and a cathode. The anode is a heteroatom-doped nickel-based metal catalytic electrode, comprising a conductive substrate and a heteroatom-doped nickel-based metal catalyst supported on the conductive substrate. The heteroatom-doped nickel-based metal catalytic electrode is made of Ni1Cu1Fe 0.5 -S / Ti pre-catalytic electrode, which is made by electrochemical tuning surface reconstruction through cyclic voltammetry, Ni1Cu1Fe 0.5 -S / Ti pre-catalytic electrode is made of an electrolyte composed of 0.1 mol / L thiourea, 0.1 mol / L urea, 0.01 mol / L nickel nitrate hexahydrate, 0.01 mol / L copper nitrate trihydrate and 0.0025 mol / L ferric sulfate, and is made by electrodeposition at a constant potential of-1.3 V vs. Hg / HgO for 180 s on an electrochemical workstation with a titanium sheet electrode, a Hg / HgO electrode and a platinum wire as the working electrode, the reference electrode and the counter electrode respectively, and the surface of the heteroatom-doped nickel-based metal catalytic electrode is a nanospherical layered structure.

2. The solar-powered electrocatalytic AOR coupled biological denitrification total nitrogen removal device according to claim 1, characterized in that, The electrode spacing between the cathode and anode electrodes in the ammonia electrolysis cell is 0.5cm to 2cm.

3. A solar-powered electrocatalytic AOR coupled biological denitrification total nitrogen removal device according to claim 1 or 2, characterized in that, The cathode of the ammonia electrolyzer is one of the following: titanium sheet electrode, nickel foam electrode, copper plate electrode, stainless steel electrode, or Pt electrode.

4. The solar-powered electrocatalytic AOR coupled biological denitrification total nitrogen removal device according to claim 1, characterized in that, The solar power supply device includes a solar panel, on which a voltage regulator, a battery, and a battery switch are installed.

5. A method for complete nitrogen removal from wastewater using a solar-powered electrocatalytic AOR coupled biological denitrification complete nitrogen removal device as described in any one of claims 1 to 4, characterized in that, Includes the following steps: (A) Wastewater enters the ammonia electrolyzer, which is powered by a solar energy supply device to carry out the electrocatalytic ammonia oxidation reaction; (B) The effluent from the ammonia electrolysis cell enters the equalization tank, where the pH of the wastewater is adjusted to neutral. (C) The effluent from the equalization tank enters the biological denitrification device to carry out the biological denitrification reaction and achieve complete denitrification of the wastewater.

6. The wastewater denitrification method according to claim 5, characterized in that, ammonia The method for preparing heteroatom-doped nickel-based metal catalytic electrodes in electrolytic cells is as follows: S1. Place the conductive substrate in a solution of dilute hydrochloric acid and anhydrous ethanol to remove oxides and impurities from the surface of the conductive substrate, then wash it repeatedly with deionized water and dry it at room temperature. S2, nickel salt, metal salt M1, metal salt M2, urea and thiourea are dissolved in deionized water and mixed evenly to obtain the electrolyte; S3. Place the dried conductive substrate from S1 into the electrolyte obtained in S2, and electrodeposit to obtain a heteroatom-doped nickel-based metal precatalytic electrode. S4. The heteroatom-doped nickel-based metal precatalytic electrode obtained in S4 is electrochemically tuned and reconstructed to obtain a heteroatom-doped nickel-based metal catalytic electrode.

7. The wastewater denitrification method according to claim 6, characterized in that, Nickel salts are one of nickel chloride, nickel sulfate, nickel nitrate, and nickel acetate; Metal salt M1 is one of copper chloride, copper sulfate, copper iodide, copper acetate, copper acetate, and copper carbonate; Metal salt M2 is one of ferric sulfate, ferric chloride, and ferric nitrate.

8. The wastewater denitrification method according to claim 6, characterized in that, The molar ratio of metal ions in nickel salt, metal salt M1 and metal salt M2 is 0.8~1.2:0.8~1.2:0.5~1.

9. The wastewater denitrification method according to claim 6, characterized in that, The electrodeposition time in S3 is 120~240s.

10. The wastewater denitrification method according to claim 5, characterized in that, The hydraulic retention time in the ammonia electrolyzer is 20-30 hours. The hydraulic retention time in a biological denitrification unit is 20-30 hours.

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