A simultaneous denitrification method and device based on electrodeposition spinel permeable electrode

Abstract

The application discloses a kind of based on electrodeposition spinel through electrode synchronous denitrification method and device, and synchronous denitrification method includes: with porous conductive material as substrate, through electrodeposition and heat treatment preparation load spinel type oxide through electrode;Reactor is constructed and electrode is installed perpendicular to fluid flow direction;Make the wastewater containing ammonium and nitrate under pressure driving through electrode aperture, utilize hole microturbulence mass transfer strengthening, and under the action of electric field, ion is induced in interface coupling generation nitrogen;Through cyclic treatment until water quality reaches standard.The application constructs through flow reaction environment, eliminates concentration polarization, and can realize the synchronous removal of ammonia nitrogen and nitrate in single system without additional carbon source, with the advantages of low cost, mass transfer fast, high current efficiency and no secondary pollution.

Description

Technical Field

[0001] This invention relates to the field of electrochemical wastewater treatment technology, specifically to a method and apparatus for simultaneous denitrification based on an electrodeposited spinel permeable electrode. Background Technology

[0002] With the rapid development of industry and agriculture and the acceleration of urbanization, nitrogen pollution in water bodies is becoming increasingly serious. Excessive nitrates in water bodies (… ) and ammonium salts ( Discharge of nitrogen oxides not only leads to severe eutrophication of water bodies and disrupts the aquatic ecological balance, but also poses a potential threat to human health. Currently, urban sewage treatment and industrial wastewater treatment mainly rely on traditional biological nitrogen removal processes (such as nitrification-denitrification). However, biological methods face many insurmountable bottlenecks in engineering practice: First, the denitrification process heavily relies on organic carbon sources. For wastewater with a widely existing low carbon-to-nitrogen ratio (C / N), it is often necessary to add external carbon sources such as methanol and sodium acetate, resulting in high treatment costs and the generation of greenhouse gases; second, the nitrification process requires continuous aeration, resulting in huge energy consumption; third, the biological community is sensitive to temperature, pH, and toxic substances, and the system has poor resistance to shock loads, making it difficult to adapt to the treatment needs of high-concentration or complex industrial wastewater. Therefore, developing a physicochemical nitrogen removal technology that does not rely on external carbon sources, has a rapid reaction, and is highly controllable is particularly urgent.

[0003] Electrochemical water treatment technology is considered a powerful alternative to biological denitrification due to its advantages such as compact equipment, no sludge increase, and ease of automation. Existing research on electrochemical denitrification mainly focuses on the conversion of single ions: for nitrate reduction, commonly used copper and iron-based cathodes often over-reduce it to ammonium ions (…). This only achieves the transfer of pollutant forms, not removal; for ammonium oxidation, it usually relies on the active chlorine or hydroxyl radicals generated at the anode, which can easily re-oxidize it to nitrate or generate toxic chloramine byproducts. How can this be achieved in a single system? and Simultaneous removal and directional conversion to nitrogen ( This is currently a research hotspot in the field.

[0004] From a thermodynamic perspective, the reaction is: 5NH4 + +3NO3 − →4N2+9H2O+2H + It exhibits a significant spontaneous tendency. However, in real aquatic environments, due to the strong solvation effect and spatial isolation effect of water molecules, positively charged... and Negatively charged molecules are discretely distributed in solution, making it difficult for them to effectively contact each other and transfer electrons, resulting in an extremely high kinetic energy barrier for the reaction.

[0005] Current electrochemical reactors mostly employ plate electrode configurations, where the reaction is limited by the liquid-solid mass transfer process at the electrode surface. When treating low-concentration or high-flow-rate wastewater, a concentration polarization layer easily forms on the electrode surface, leading to low current efficiency. Furthermore, existing electrode materials lack the ability to address the challenges posed by concentration polarization. and The active sites for synergistic adsorption and catalysis cannot construct a reaction environment with close ion proximity at the microscopic interface, making it difficult to trigger the aforementioned coupled reactions. Although some studies have attempted to enhance mass transfer using flow-through electrodes, most studies only focus on the removal of single pollutants and lack dedicated catalytic materials designed for simultaneous denitrification reactions (such as spinel oxides with specific crystal faces), making it difficult to achieve efficient and low-consumption "short-range" denitrification.

[0006] Chinese patent application CN116253435A discloses a wastewater treatment system and process. This system directly transforms the water tanks in a traditional wastewater treatment system into simultaneous denitrification reactors without reaction walls, connecting them sequentially. Combined with a secondary sedimentation tank and sludge distribution well, it achieves sludge return, avoiding the high costs and increased land area required for traditional system demolition and reconstruction. Furthermore, it effectively improves denitrification efficiency through simultaneous nitrification and denitrification. However, this process requires precise control of the reaction environment, relying on dissolved oxygen meters and online oxidation-reduction potential analyzers in each reactor. It necessitates dynamic adjustment of aeration and denitrification devices based on real-time environmental parameters to maintain optimal denitrification efficiency of the catalytic packing, increasing the complexity of system operation and control.

[0007] Chinese patent application CN103936106A discloses an electrochemical simultaneous nitrogen and phosphorus removal device and a method for treating urban wastewater. This device combines a shape-stabilized electrode, an iron, aluminum, magnesium, and copper-modified stainless steel electrode within an electrolytic cell. It utilizes metal ions generated by electrochemical induction to perform electrocoagulation, electrooxidation, and reduction reactions, enabling the simultaneous and efficient removal of chemical oxygen demand (COD), ammonia nitrogen, and total phosphorus from wastewater. However, this system integrates five electrodes of different materials, and involves the continuous consumption of sacrificial anodes such as iron, aluminum, and magnesium. This results in inconsistent electrode maintenance and replacement cycles, making it difficult to precisely control the release ratio of each metal ion during long-term operation. Furthermore, frequent reversal of electrode polarity is required to alleviate electrode passivation, increasing the complexity of operation and management.

[0008] Chinese patent application CN109336328A discloses a bioelectrochemical simultaneous nitrogen and phosphorus removal device and method. This device connects a primary anoxic tank and an aerobic tank in series, with a built-in metal electrode pair in a secondary anoxic tank. Phosphorus is removed by the reaction of metal ions generated by anodic electrolysis with phosphate ions, while hydrogen generated at the cathode is used as an electron donor for hydrogen autotrophic denitrification. This invention combines phosphorus and nitrogen removal systems, effectively solving the dependence of traditional processes on organic carbon sources and chemical flocculants, achieving simultaneous and efficient nitrogen and phosphorus removal while reducing land area. However, this process involves continuous electrolytic consumption of metal electrodes (such as aluminum electrodes), leading to electrode wear and replacement maintenance issues. Furthermore, to prevent electrode passivation, strict control of current density and voltage is required, along with periodic electrode reversal and aeration cleaning devices, increasing the complexity of system operation and control and equipment maintenance requirements. Summary of the Invention

[0009] In order to overcome the technical defects of low liquid-solid mass transfer efficiency and severe concentration polarization in the prior art, the present invention provides a synchronous denitrification method and apparatus based on electrodeposited spinel through-hole electrode.

[0010] To solve the above problems, the present invention is implemented according to the following technical solution:

[0011] The first aspect of this invention provides a simultaneous denitrification method based on an electrodeposited spinel through-hole electrode, comprising the following steps:

[0012] Step (1): Using a porous conductive material as a substrate, prepare an electrolyte containing metal salt, and use an electrodeposition process to deposit a spinel-type oxide catalytic active layer on the porous conductive material substrate, followed by heat treatment to obtain a permeable electrode.

[0013] Step (II): Construct a reactor including an electrolytic cell, an inlet and outlet liquid system, a collection device, and a DC power supply. Install the permeable electrode as the anode and cathode perpendicular to the fluid flow direction within the electrolytic cell; [The reactor will then contain...] and The wastewater to be treated is transported to the reactor;

[0014] Step (3): Turn on the DC power supply and the liquid inlet system, allowing the wastewater to flow through the internal pores of the permeable electrode under pressure; utilize the micro-turbulence within the pores of the permeable electrode to enhance mass transfer, and induce [the flow] under the influence of the electric field and spinel oxide. and Nitrogen gas is generated through coupling at the electrode interface;

[0015] Step (4): The wastewater flowing through the permeable electrode is transported to the collection device and then returned to the inlet of the reactor through the fluid transport device to form an electrolyte circulation treatment system until the nitrogen concentration in the wastewater reaches the preset standard.

[0016] In conjunction with the first aspect, the present invention provides a first specific embodiment of the first aspect, in step (a):

[0017] The general chemical formula of the spinel-type oxide is AB2O4;

[0018] The element at the B site is Co, and the element at the A site is selected from Cu, Fe, Mn, Ni, and Zn.

[0019] In conjunction with the first aspect, the present invention provides a second specific embodiment of the first aspect, wherein in step (i), the method for preparing the electrolyte is as follows:

[0020] A mixed solution was prepared using A-site metal nitrate, cobalt nitrate, and potassium chloride as raw materials;

[0021] The molar ratio of metal nitrate, cobalt nitrate, and potassium chloride at site A is 1:2:1.

[0022] In conjunction with the first aspect, the present invention provides a third specific embodiment of the first aspect, wherein in step (a), the specific conditions of the electrodeposition process are as follows:

[0023] A three-electrode system was used, with Ag / AgCl as the reference electrode, and the deposition potential was controlled from -0.9V to -1.1V, with a deposition time of 10 to 40 minutes.

[0024] In conjunction with the first aspect, the present invention provides a fourth specific embodiment of the first aspect, wherein in step (a), the specific conditions for heat treatment are as follows:

[0025] The electrode after electrodeposition is placed in an air atmosphere and kept at a temperature of 250°C to 500°C for 1 to 3 hours to form a stable spinel crystal phase.

[0026] In conjunction with the first aspect, the present invention provides a fifth specific embodiment of the first aspect, in step (iii):

[0027] By controlling the current density, NH4 + The oxidation rate of NO3 - The reduction rate is matched to suppress the accumulation of the byproduct nitrite.

[0028] The second aspect of the present invention provides a synchronous denitrification reaction device for implementing the method. The synchronous denitrification method based on electrodeposited spinel permeable electrode as described in any one of the first aspects of the present invention includes: an electrolytic cell, a liquid inlet system, a liquid outlet system, a collection device, a DC power supply, and an electrode assembly installed in the electrolytic cell.

[0029] The electrode assembly includes an anode and a cathode. The anode and cathode adopt a permeable porous structure arranged perpendicular to the fluid flow direction, so that the wastewater to be treated flows through the internal pores of the electrode under pressure.

[0030] In conjunction with the second aspect, the present invention provides a first specific embodiment of the second aspect, wherein the substrate material of the permeable porous structure is selected from one of foamed titanium, graphite plate, graphite felt, and stainless steel plate; the pore size range of the substrate material of the permeable porous structure is 50-150μm.

[0031] In conjunction with the second aspect, the present invention provides a second specific embodiment of the second aspect, wherein the spinel-type oxide on the surface of the electrode assembly is specifically one of CuCo2O4, FeCo2O4, MnCo2O4, NiCo2O4, and ZnCo2O4.

[0032] In conjunction with the second aspect, the present invention provides a third specific embodiment of the second aspect, wherein the reactor is a permeable configuration for treating NH4-containing reactors. + and NO3 - Wastewater.

[0033] Compared with the prior art, the beneficial effects of the present invention are:

[0034] This invention discloses a simultaneous denitrification method based on an electrodeposited spinel permeable electrode. In step (I), the invention uses spinel-type oxide as the catalytic active layer, which reduces material costs compared to traditional precious metal electrodes. Simultaneously, the unique mixed valence states of the spinel structure provide abundant active sites, exhibiting excellent transport capacity and catalytic performance. Through in-situ growth via electrodeposition followed by heat treatment, a strong chemical bond is formed between the catalytic active layer and the porous conductive substrate, making it difficult to peel off. This preparation method maintains the electrode's relative stability under long-term water flow scouring and electrochemical reactions, extending the electrode's lifespan. In step (II), the permeable electrode is installed perpendicular to the fluid flow direction, structurally changing the tangential flow mode of traditional plate electrodes and creating a through-flow reaction environment. This configuration forces wastewater to pass through the electrode pores, solving the problem of insufficient contact between reactants and the electrode surface in traditional reactors. This system introduces substances containing... and NO3 -The wastewater is designed to utilize a spontaneous coupling reaction between the two, eliminating the need for external carbon sources like methanol as required by biological denitrification, and avoiding the reliance on large amounts of chloride ions as in traditional electro-oxidation. This reduces operating costs and avoids secondary pollution. In step (III), the micro-turbulence effect generated by the pressure-driven wastewater flow through the pores compresses the thickness of the liquid-solid diffusion layer on the electrode surface. This eliminates the concentration polarization phenomenon common in traditional electrochemical reactors, allowing pollutants to quickly reach the electrode surface and participate in the reaction, thus improving current efficiency and reaction rate. Under the bifunctional catalysis of the electric field and spinel oxide, NH4+ is induced... + Oxidation and NO3 - Reduction occurs at the electrode's micro-interface, where a directional coupling reaction directly generates nitrogen gas. This process opens up a short-pathway for nitrogen removal, avoiding ineffective cycling of nitrogen between ammonia and nitrate, and solving the problem of simultaneously removing two nitrogen pollutants in a single system, a challenge in existing technologies. In step (iv), considering the short residence time of the permeable electrode, a circulating treatment system is constructed to increase the effective contact time between wastewater and the electrode. Multiple cycles gradually degrade pollutants, ensuring that the final effluent nitrogen concentration consistently meets standards. The circulating flow operation mode, combined with efficient catalytic reaction, helps to promptly bring reaction intermediates, such as highly toxic nitrite, back to the electrode surface for further conversion, inhibiting the accumulation of byproducts and improving process safety and environmental friendliness.

[0035] This invention discloses a simultaneous denitrification reactor. The device employs vertically arranged permeable electrodes, allowing wastewater to pass through the micropores of the electrodes under pressure. This flow pattern generates micro-turbulence within the pores, eliminating the concentration polarization layer on the electrode surface and enabling reactants to rapidly contact the catalytic sites, thereby improving the reaction rate and current efficiency. The porous structure serves as a substrate, providing a large specific surface area for the electrochemical reaction. The device features a collection and circulation system, allowing for a closed-loop treatment mode. This enables the device to treat not only low-concentration wastewater but also, through multiple cycles, efficiently treat high-concentration, recalcitrant nitrogen-containing wastewater, ensuring stable effluent compliance with standards. Attached Figure Description

[0036] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings, wherein:

[0037] Figure 1 This is a schematic diagram of the electrochemical denitrification reaction device of the present invention;

[0038] Figure 2 This is a microstructure and elemental distribution diagram of the catalytic active layer on the surface of the permeable electrode prepared according to an embodiment of the present invention;

[0039] Figure 3 This is a schematic diagram of the process flow of a synchronous denitrification method based on an electrodeposited spinel through-hole electrode according to the present invention.

[0040] In the diagram: 1-Electrolytic cell, 2-DC power supply, 3-Peristaltic pump, 4-Collection device. Detailed Implementation

[0041] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0042] Example 1

[0043] like Figures 1-3 As shown, the first aspect of the present invention provides a method for simultaneous denitrification based on an electrodeposited spinel through-hole electrode, comprising the following steps:

[0044] Step (1) Electrode preparation steps: Using a porous conductive material as a substrate, an electrolyte containing metal salt is prepared, and a permeable electrode is obtained by electrodeposition on a spinel-type oxide catalytic active layer on a porous conductive material substrate and heat treatment.

[0045] Step (II) System Construction Steps: Construct a reactor including an electrolytic cell, inlet and outlet liquid systems, a collection device, and a DC power supply. Install permeable electrodes as anode and cathode perpendicular to the fluid flow direction within the electrolytic cell; simultaneously containing NH4 + and NO3 - The wastewater to be treated is transported to the reactor;

[0046] Step (III) Simultaneous Denitrification: Turn on the DC power supply and the inlet system, allowing the wastewater to flow through the internal pores of the permeable electrode under pressure; utilize the micro-turbulence within the permeable electrode pores to enhance mass transfer, and under the influence of the electric field and spinel oxides, induce NH4+. + and NO3 - Nitrogen gas is generated through coupling at the electrode interface;

[0047] Step (iv) Recycling treatment step: The wastewater flowing through the permeable electrode is transported to the collection device and then returned to the inlet of the reactor through the fluid transport device to form an electrolyte recycling treatment system until the nitrogen concentration in the wastewater reaches the preset standard.

[0048] In this embodiment, the specific steps are as follows:

[0049] Step (I) Electrode Preparation: A porous conductive material substrate of 50-150 μm pore size was selected. The titanium foam substrate was cleaned and pretreated. An electrolyte was prepared by dissolving copper nitrate (Cu(NO3)2), cobalt nitrate (Co(NO3)2), and potassium chloride (KCl) in deionized water, with a molar ratio of copper, cobalt, and potassium ions of 1:2:1. A three-electrode system was constructed, using the titanium foam substrate as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode. Electrodeposition Process: The working electrode was immersed in the electrolyte, connected to an electrochemical workstation, and the deposition potential was set to -1.0 V for 20 minutes. A precursor layer was deposited on the surface of the titanium foam substrate. Post-treatment: The deposited electrode was removed, rinsed with deionized water to remove residual electrolyte, and dried. Heat Treatment: The dried electrode was placed in a muffle furnace under air atmosphere, heated to 300 °C at a rate of 5 °C / min, and held for 2 hours. After natural cooling, a permeable electrode with a CuCo2O4 spinel-type oxide catalytic active layer was obtained.

[0050] To verify the microstructure and crystal structure of the electrode obtained by the above preparation process, the fabricated permeable electrode was characterized, and the results are as follows: Figure 2 As shown:

[0051] The figure shows the microstructure characterization results of the CuCo2O4 permeable electrode prepared in the examples.

[0052] (a) and (b) are scanning electron microscope images at different magnifications. It can be seen that the catalytic active layer exhibits a uniform nanoneedle / nanofacial array structure on the substrate surface. This open structure is beneficial for increasing the specific surface area and exposing more active sites.

[0053] (e) is a transmission electron microscope image that further clarifies the morphology of a single nanoneedle / nanofamber.

[0054] (f) is a high-resolution transmission electron microscope image and a selected area electron diffraction inset. The clearly visible lattice fringe spacing (0.245 nm) corresponds to the (311) crystal plane of spinel CuCo2O4, confirming the high crystallinity of the material.

[0055] Images (c), (d), (g), and (h) are energy-dispersive X-ray spectroscopy (EDS) elemental surface scan images. (c) corresponds to cobalt (Co), (d) to copper (Cu), (g) to oxygen (O), and (h) is a mixed elemental diagram. The results show that Cu, Co, and O are uniformly distributed in the nanostructure, further confirming the successful synthesis of the CuCo₂O₄ compound.

[0056] Step (II) System Construction: Construct the reactor, which includes an electrolytic cell made of plexiglass, an inlet pipe, an outlet pipe, a peristaltic pump (fluid delivery device), a collection tank, and a DC regulated power supply. Electrode Installation: Select two permeable electrodes prepared in Step (I) as the anode and cathode, respectively. Place the anode and cathode parallel to each other in the electrolytic cell, with the electrode plates perpendicular to the fluid flow direction. Place sealing gaskets between the electrode edges and the inner wall of the electrolytic cell. Set the electrode spacing to 10 mm. Wastewater Introduction: Prepare simulated wastewater containing 1 mol / L ammonium chloride (providing NH4+). + ) and 1 mol / L sodium nitrate (providing NO3) - The simulated wastewater was then injected into the collection tank.

[0057] Step (III) Synchronous Denitrification: Turn on the DC power supply, connect the anode and cathode, and set the constant current to 204mA (or a specific current density set according to the electrode area). Turn on the peristaltic pump to pump the wastewater from the collection tank into the electrolytic cell through the inlet pipe. Driven by the pressure provided by the peristaltic pump, the wastewater flows through the internal pores of the anode and cathode. Under energized conditions, NH4... + and NO3 - A reaction occurs at the solid-liquid interface of the permeable electrode, generating nitrogen gas.

[0058] Step (IV) Circulation Treatment: The wastewater flowing through the permeable electrode exits the electrolyzer through the outlet pipe and enters the collection tank. The wastewater in the collection tank is then drawn back in by the peristaltic pump and transported to the inlet of the electrolyzer. This circulation process is maintained for 180 minutes. After the reaction is complete, the power supply and peristaltic pump are turned off, and the treated wastewater is discharged. The remaining total nitrogen concentration in the wastewater is measured.

[0059] In conjunction with the first aspect, the present invention provides a first specific embodiment of the first aspect, in step (a):

[0060] The general chemical formula for spinel-type oxides is AB₂O₄;

[0061] The element at the B site is Co, and the element at the A site is selected from Cu, Fe, Mn, Ni, and Zn.

[0062] Based on the preparation process in step (I), this embodiment prepares five sets of permeable electrodes with the general chemical formula AB2O4 by changing the type of metal salt at the A site in the electrolyte, where B is Co and A is Cu, Fe, Mn, Ni and Zn respectively.

[0063] 1. Preparation of CuCo2O4 electrode

[0064] Prepare the electrolyte: the solutes are copper nitrate Cu(NO3)2, cobalt nitrate Co(NO3)2, and potassium chloride KCl, and the solvent is deionized water. The molar ratio of copper ions to cobalt ions in the solution is 1:2.

[0065] Preparation process: Using titanium foam as the working electrode, deposition was performed at -1.0V for 20 minutes. After cleaning and drying, it was heat-treated at 300℃ for 2 hours to obtain a permeable electrode with a CuCo2O4 active layer.

[0066] 2. Preparation of FeCo2O4 electrode

[0067] Prepare the electrolyte: the solutes are ferric nitrate (Fe(NO3)3), cobalt nitrate, and potassium chloride. The molar ratio of ferric ions to cobalt ions in the solution is 1:2.

[0068] Preparation process: Same as above. A permeable electrode loaded with an FeCo2O4 active layer was obtained.

[0069] 3. Preparation of MnCo2O4 electrode

[0070] Prepare the electrolyte: the solutes are manganese nitrate (Mn(NO3)2), cobalt nitrate, and potassium chloride. The molar ratio of manganese ions to cobalt ions in the solution is 1:2.

[0071] Preparation process: Same as above. A permeable electrode loaded with a MnCo2O4 active layer was obtained.

[0072] 4. Preparation of NiCo2O4 Electrode

[0073] Prepare the electrolyte: The solutes are nickel nitrate (Ni(NO3)2), cobalt nitrate, and potassium chloride. The molar ratio of nickel ions to cobalt ions in the solution is 1:2.

[0074] Preparation process: Same as above. A permeable electrode loaded with a NiCo2O4 active layer was obtained.

[0075] 5. Preparation of ZnCo2O4 electrode

[0076] Prepare the electrolyte: the solutes are zinc nitrate (Zn(NO3)2), cobalt nitrate, and potassium chloride. The molar ratio of zinc ions to cobalt ions in the solution is 1:2.

[0077] Preparation process: Same as above. A permeable electrode loaded with a ZnCo2O4 active layer was obtained.

[0078] In conjunction with the first aspect, the present invention provides a second specific embodiment of the first aspect, wherein in step (i), the method for preparing the electrolyte is as follows:

[0079] A mixed solution was prepared using A-site metal nitrate, cobalt nitrate, and potassium chloride as raw materials;

[0080] The molar ratio of metal nitrate, cobalt nitrate, and potassium chloride at site A is 1:2:1.

[0081] In step (I), the preparation process of the electrolyte is described in detail.

[0082] Taking the electrolyte used to prepare the CuCo2O4 electrode as an example:

[0083] Raw material weighing:

[0084] Weigh out 0.01 mol of copper nitrate trihydrate Cu(NO3)2·3H2O as the A-site metal nitrate.

[0085] Weigh out 0.02 mol of cobalt nitrate hexahydrate Co(NO3)2·6H2O.

[0086] Weigh out 0.01 mol of potassium chloride (KCl).

[0087] In the above raw materials, the molar ratio of copper ions, cobalt ions and potassium ions is 1:2:1.

[0088] Dissolving and mixing:

[0089] Measure 100 mL of deionized water into a beaker.

[0090] Add the weighed copper nitrate, cobalt nitrate, and potassium chloride to the beaker in sequence.

[0091] Stir with a glass rod (or a magnetic stirrer) until the solid is completely dissolved.

[0092] Prepare Cu 2+ Co 2+ and K + A mixed salt solution is used as the electrolyte in the electrodeposition process.

[0093] It should be noted that if other A-site metal elements are selected, such as Fe, Mn, Ni, and Zn, simply replace the copper nitrate mentioned above with equimolar amounts of iron nitrate, manganese nitrate, nickel nitrate, or zinc nitrate, while keeping the other steps and parameters unchanged.

[0094] In conjunction with the first aspect, the present invention provides a third specific embodiment of the first aspect, wherein in step (a), the specific conditions of the electrodeposition process are as follows:

[0095] A three-electrode system was used, with Ag / AgCl as the reference electrode, and the deposition potential was controlled from -0.9V to -1.1V, with a deposition time of 10 to 40 minutes.

[0096] In this embodiment, specifically in the electrodeposition step (I), a three-electrode system is used, with Ag / AgCl as the reference electrode, a platinum sheet as the counter electrode, and titanium foam as the working electrode. Three sets of permeable electrodes are prepared by setting different deposition potentials and deposition times. The specific details are as follows:

[0097] 1. The first group of experiments used a low potential and short time. The deposition potential of the electrochemical workstation was set to -0.9V, and the deposition time was set to 10 minutes. The program was started for constant potential deposition. After the reaction was completed, the foamed titanium electrode was removed, the surface was rinsed with deionized water, dried, and heat-treated at 300℃ to obtain the permeable electrode sample A.

[0098] 2. In the second group of experiments, the deposition potential of the electrochemical workstation was set to -1.0V and the deposition time to 20 minutes. The program was started for constant potential deposition. After the reaction was completed, the foamed titanium electrode was removed, the surface was rinsed with deionized water, dried, and heat-treated at 300℃ to obtain the permeable electrode sample B.

[0099] 3. For the third group of experiments, a high-potential, long-duration deposition process was performed. The deposition potential of the electrochemical workstation was set to -1.1V, and the deposition time was set to 40 minutes. The program was started for constant-potential deposition. After the reaction was completed, the foamed titanium electrode was removed, the surface was rinsed with deionized water, dried, and heat-treated at 300℃ to obtain the permeable electrode sample C.

[0100] In conjunction with the first aspect, the present invention provides a fourth specific embodiment of the first aspect, wherein in step (a), the specific conditions for heat treatment are as follows:

[0101] The electrode after electrodeposition is placed in an air atmosphere and kept at a temperature of 250°C to 500°C for 1 to 3 hours to form a stable spinel crystal phase.

[0102] In the heat treatment step (I), the foamed titanium electrode precursors, after electrodeposition, cleaning, and drying, are divided into three groups and placed in muffle furnaces with an air atmosphere, where they are treated at different temperatures and holding times. The specific details are as follows:

[0103] 1. The first group of experiments involved low-temperature short-time treatment. The heating temperature of the muffle furnace was set to 250℃, and the holding time was set to 1 hour. The temperature was increased to the set temperature at a heating rate of 5℃ / min and held for 1 hour. After heating, the sample was allowed to cool naturally to room temperature. A permeable electrode sample D with a heat treatment temperature of 250℃ was obtained.

[0104] 2. In the second group of experiments, a medium-temperature treatment was performed. The heating temperature of the muffle furnace was set to 350℃, and the holding time was set to 2 hours. The temperature was increased at a rate of 5℃ / min to the set temperature and held for 2 hours. After heating, the sample was allowed to cool naturally to room temperature. A permeable electrode sample E with a heat treatment temperature of 350℃ was obtained.

[0105] 3. The third group of experiments involved high-temperature long-term treatment. The heating temperature of the muffle furnace was set to 500℃, and the holding time was set to 3 hours. The temperature was increased to the set temperature at a heating rate of 5℃ / min and held for 3 hours. After heating, the sample was allowed to cool naturally to room temperature. A permeable electrode sample F with a heat treatment temperature of 500℃ was obtained.

[0106] As shown in Table 1 below, in this embodiment, in order to investigate the influence of different preparation process conditions on the performance of the permeable electrode, the key process parameters of samples A to F are summarized respectively. Among them, samples A, B, and C focus on the changes in electrodeposition conditions, with the heat treatment condition fixed at 300℃ / 2h; samples D, E, and F focus on the changes in heat treatment conditions, with the electrodeposition condition fixed at -1.0V / 20min.

[0107]

[0108] As shown in Table 2 below, in order to verify the actual denitrification effect of the electrodes prepared under the different process conditions described above, a simultaneous denitrification reaction device with the same steps as described above was constructed. Samples A to F were installed in the electrolytic cell as anode and cathode, respectively.

[0109] The test conditions are as follows:

[0110] Simulated wastewater: containing 1 mol / L NH4∙H2O and 1 mol / L HNO3.

[0111] Operating parameters: current intensity 204mA, flow rate 50mL / min, circulation treatment time 180 minutes.

[0112] Detection indicators: Measure the concentrations of ammonia nitrogen and nitrate before and after the reaction, and calculate the removal rate.

[0113]

[0114] As shown in Table 2, the electrodeposition process and heat treatment process have a significant impact on the final performance of the electrode.

[0115] Sample B (-1.0V / 20min) showed a higher removal rate than samples A and C. This indicates that suitable deposition potential and time can ensure uniform coverage of the active material on the substrate surface while avoiding pore blockage caused by excessive deposition. Sample E (350℃ / 2h) showed a higher removal rate than samples D and F. This indicates that heat treatment at around 350℃ is more conducive to the formation of a stable spinel-type oxide crystal phase; too low a temperature leads to incomplete crystal phase transformation, while too high a temperature causes sintering and agglomeration of catalyst particles, both of which reduce catalytic activity. In summary, the process range described in this invention can prepare an effective denitrification electrode, wherein the electrode prepared within the preferred range exhibits higher reactivity.

[0116] In conjunction with the first aspect, the present invention provides a fifth specific embodiment of the first aspect, in step (iii):

[0117] By controlling the current density, NH4 + The oxidation rate of NO3 - The reduction rate is matched to suppress the accumulation of the byproduct nitrite.

[0118] As shown in Table 3 below, in step (iii), the CuCo2O4 permeable electrode (sample E) prepared in Example 2 was selected as the working electrode. Keeping the influent flow rate (50 mL / min) and initial concentration (1 mol / L) constant, the output current was adjusted using a DC power supply, and three different current densities were set to investigate their effects on the reaction rate and the accumulation of the intermediate product nitrite.

[0119] 1. Experimental group setup

[0120] Low current density group: The current density is set to 10mA / cm².

[0121] Medium current density group: The current density is set to 20mA / cm².

[0122] High current density group: The current density is set to 30mA / cm².

[0123] 2. Testing Process

[0124] Start the peristaltic pump and DC power supply, and run the system for 180 minutes.

[0125] Samples are taken every 30 minutes.

[0126] Determination of NH4 in water samples using ultraviolet spectrophotometry + NO3 - and NO2 - Nitrite concentration.

[0127] Calculate NH4 +The oxidation reaction rate constant and NO3 - The rate constant of the reduction reaction.

[0128]

[0129] According to the data in Table 3, in the low current density group (10 mA / cm²), the cathode reduction rate was greater than the anodic oxidation rate, with a ratio of 0.67, indicating a mismatch in reaction rates. The test results showed a high nitrite concentration of 45.2 mg / L, suggesting that some nitrate ions, after being reduced to nitrite, were not promptly oxidized or further converted. In the medium current density group (20 mA / cm²), the anodic oxidation rate and cathode reduction rate were basically the same, with a ratio of 0.96, close to 1:1. The lowest nitrite concentration was 2.1 mg / L. This indicates that at this current density, NH₄⁺... + The oxidation process and NO3 - The reduction process reaches kinetic equilibrium, with intermediate products being rapidly consumed, inhibiting nitrite accumulation. In the high current density group (30 mA / cm²), the anodic oxidation rate is significantly greater than the cathodic reduction rate, with a ratio of 1.31. Although the overall reaction rate increases, the nitrite concentration rebounds to 18.6 mg / L, and energy consumption increases. By controlling the current density to 20 mA / cm², NH₄⁺ can be reduced to a lower nitrite concentration. + The oxidation rate of NO3 - The reduction rate is matched to keep the accumulation of the byproduct nitrite at a minimum.

[0130] Example 2

[0131] The second aspect of this invention provides a simultaneous denitrification reaction apparatus for implementing this method, and a simultaneous denitrification method based on an electrodeposited spinel through-hole electrode according to any one of the first aspects of this invention, such as... Figure 1 As shown, it includes: an electrolytic cell 1, a liquid inlet system, a liquid outlet system, a collection device 4, a DC power supply 2, and an electrode assembly installed in the electrolytic cell 1;

[0132] The electrode assembly includes an anode and a cathode, which adopt a permeable porous structure arranged perpendicular to the fluid flow direction, so that the wastewater to be treated flows through the internal pores of the electrode under pressure.

[0133] This embodiment provides a simultaneous denitrification reaction apparatus for implementing the method described in the first aspect of the present invention. Figure 1 As shown, the device mainly consists of an electrolytic cell 1, an inlet system, an outlet system, a collection device 4, a DC power supply 2, and an electrode assembly.

[0134] Electrolytic cell 1 is a hollow cavity structure made of plexiglass. One end of electrolytic cell 1 has a liquid inlet, and the other end has a liquid outlet. Fluid channels are formed inside electrolytic cell 1.

[0135] The electrode assembly is installed within the fluid channel of electrolytic cell 1. The electrode assembly includes an anode and a cathode. Both the anode and cathode are flat, permeable porous structures with a substrate material of titanium foam, graphite felt, or stainless steel mesh. The anode and cathode are arranged in parallel intervals, with the electrode plates perpendicular to the fluid flow direction within the fluid channel. Rubber sealing gaskets are provided between the edges of the anode and cathode and the inner wall of electrolytic cell 1. These gaskets fill the gap between the electrode and the cell wall, forcing fluid to flow only through the internal pores of the electrode body. The distance between the anode and cathode is fixed at 5 mm to 20 mm.

[0136] The liquid inlet system includes a peristaltic pump 3 (fluid transport device) and an inlet pipeline. The inlet of the peristaltic pump 3 is connected to the collection device 4 via a pipeline, and the outlet of the peristaltic pump 3 is connected to the inlet of the electrolytic cell 1 via the inlet pipeline. The liquid outlet system includes an outlet pipeline. The outlet of the electrolytic cell 1 is connected to the collection device 4 via the outlet pipeline.

[0137] The collection device 4 is an open or sealed container used to hold the nitrogen-containing wastewater to be treated. The collection device 4 is connected to the inlet system and the outlet system through pipelines to form a fluid circulation loop.

[0138] The positive output terminal of DC power supply 2 is connected to the anode in electrolytic cell 1 via a wire, and the negative output terminal is connected to the cathode in electrolytic cell 1 via a wire.

[0139] During operation, the wastewater to be treated is placed in the collection device 4. The peristaltic pump 3 is turned on, and the wastewater enters the electrolytic cell 1 through the inlet. Driven by pressure, the wastewater flows sequentially through the vertically arranged internal pores of the anode and cathode. After passing through the electrodes, the wastewater flows out through the outlet and returns to the collection device 4 via the outlet pipe. The DC power supply 2 is turned on, applying voltage between the anode and cathode, causing an electrochemical reaction to occur as the wastewater passes through the electrode pores.

[0140] In conjunction with the second aspect, the present invention provides a first specific embodiment of the second aspect, wherein the substrate material of the permeable porous structure is selected from one of foamed titanium, graphite plate, graphite felt, and stainless steel plate; the pore size range of the substrate material of the permeable porous structure is 50-150μm.

[0141] In this embodiment, the substrate materials of the anode and cathode of the electrode assembly adopt one of the following four specific configurations according to different corrosion resistance requirements and conductivity properties:

[0142] The electrode substrate is a titanium foam plate with a purity of TA1. The titanium foam plate has a three-dimensional mesh-like porous structure with a pore size of 50 μm and a plate thickness of 2 mm. After the edges of the titanium foam plate are compacted, it is installed in the slot of electrolytic cell 1.

[0143] The graphite felt substrate is made of polyacrylonitrile-based graphite felt as the electrode substrate. The graphite felt is woven from carbon fibers and has a porous fiber structure. The pore size is set at 100 μm. The felt thickness is 5 mm. Due to the soft texture of the graphite felt, it is clamped and fixed by titanium mesh during installation to maintain a flat plate shape perpendicular to the fluid.

[0144] The porous stainless steel plate substrate uses 316L type porous stainless steel plate (sintered mesh plate) as the electrode substrate. This stainless steel plate is made of multiple layers of stainless steel wire mesh sintered together. The pore size is set at 150μm. The plate thickness is 1mm. The substrate is mainly used to treat nitrogen-containing wastewater with a pH value of neutral or alkaline.

[0145] High-strength porous graphite plates are selected as the electrode substrate. The graphite plates are prepared using a sintering process with a pore-forming agent, forming interconnected pores inside. The pore size is set at 80 μm. The plate thickness is 3 mm. The substrate surface is polished to remove surface closed pores and expose the internal interconnected channels.

[0146] In conjunction with the second aspect, the present invention provides a second specific embodiment of the second aspect, wherein the spinel-type oxide on the surface of the electrode assembly is specifically one of CuCo2O4, FeCo2O4, MnCo2O4, NiCo2O4, and ZnCo2O4.

[0147] In the reaction apparatus of this embodiment, the catalytic active layer covering the surfaces of the anode and cathode substrates is a spinel-type oxide.

[0148] The specific chemical composition of spinel-type oxides is selected from one of the following five compounds:

[0149] Copper cobalt oxide CuCo2O4, iron cobalt oxide FeCo2O4, manganese cobalt oxide MnCo2O4, nickel cobalt oxide NiCo2O4, and zinc cobalt oxide ZnCo2O4.

[0150] It should be noted that the oxides mentioned above correspond to electrodes prepared by different A-site metal elements mentioned in Example 1.

[0151] In conjunction with the second aspect, the present invention provides a third specific embodiment of the second aspect, wherein the reactor is a permeable configuration for treating NH4-containing reactors. + and NO3 - Wastewater.

[0152] It should be noted that the through-type configuration refers to an electrode assembly where the anode and cathode plates are positioned perpendicular to the fluid flow direction, and the electrode edges are sealed to the reactor inner wall, with no bypass channels. The wastewater to be treated, driven by external pressure such as a pump, passes through the micron-sized pore channels inside the electrode substrate. During this process, microscopic convection occurs within the pores, renewing the diffusion layer at the electrode solid-liquid interface, allowing the reactants to contact the catalytically active layer loaded within the pores. This configuration utilizes the internal three-dimensional space of the porous electrode as the reaction site, unlike the plate configuration where the fluid flows parallel to the electrode surface.

[0153] In this configuration, the electrode assembly is vertically mounted on the cross-section of the fluid channel, and the electrode edges are sealed to the inner wall of the reactor without any bypass gaps. The fluid flow path within the fluid channel passes through the internal micropores of the electrode body.

[0154] This reactor is used to treat wastewater containing specific nitrogen pollutants.

[0155] Specifically, the wastewater also contains ammonium ions (NH4+). + and nitrate ions NO3 - .

[0156] During operation, nitrogen-containing wastewater enters through the inlet, is forced to flow through the pores inside the electrode under pressure, and is discharged from the outlet after electrochemical reaction.

[0157] In summary, this invention provides a method and apparatus for simultaneous nitrogen removal based on an electrodeposited spinel permeable electrode. Through electrodeposition and thermal treatment, a structurally stable spinel-type oxide catalytic active layer is grown in situ on a porous conductive substrate. Combined with a permeable reactor configuration perpendicular to the fluid direction, the microturbulence effect within the micropores significantly enhances the liquid-solid mass transfer process. Experimental data show that, under optimized preparation processes and operating parameters, this system can achieve simultaneous nitrogen removal of NH4+. + Oxidation rate and NO3 - By matching the reduction rate, the accumulation of the byproduct nitrite is suppressed, enabling clean and efficient treatment of high-concentration nitrogen-containing wastewater.

[0158] The working principle of the simultaneous denitrification method and apparatus based on an electrodeposited spinel permeable electrode described in this invention is as follows: Under the action of a DC electric field and fluid pressure, nitrogen-containing wastewater is forced to pass through the micropores of the electrode loaded with a spinel catalyst layer. On the one hand, the fluid forms strong microturbulence within the micron-sized channels, compressing the diffusion layer thickness on the electrode surface, eliminating concentration polarization, and enabling pollutants to be rapidly transported to the catalytically active sites; on the other hand, the spinel oxide lowers the activation energy of the reaction, and the anodic induction of NH4+... + An oxidation reaction occurs, and the cathode induces NO3. -A reduction reaction occurs. Due to the confined microscopic reaction environment provided by the porous structure, the oxidation intermediate and the reduction intermediate collide at a high frequency at the electrode interface and undergo a disproportionation coupling reaction, generating nitrogen gas which is then released. This achieves the simultaneous removal of ammonia nitrogen and nitrate within a single reaction system.

[0159] Other structures of the synchronous denitrification device described in this invention are available in the prior art.

[0160] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Therefore, any modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for simultaneous denitrification based on an electrodeposited spinel through-hole electrode, characterized in that, Includes the following steps: Step (1): Using a porous conductive material as a substrate, prepare an electrolyte containing metal salt, and use an electrodeposition process to deposit a spinel-type oxide catalytic active layer on the porous conductive material substrate, followed by heat treatment to obtain a permeable electrode. Step (II): Construct a reactor including an electrolytic cell, an inlet and outlet liquid system, a collection device, and a DC power supply. Install the permeable electrode as the anode and cathode perpendicular to the fluid flow direction within the electrolytic cell; [The reactor will then contain...] and The wastewater to be treated is transported to the reactor; Step (3): Turn on the DC power supply and the liquid inlet system, so that the wastewater to be treated flows through the internal pores of the permeable electrode under pressure. Mass transfer is enhanced by microturbulence within the pores of a permeable electrode, and under the influence of an electric field and spinel-type oxide, it induces… and Nitrogen gas is generated through coupling at the electrode interface; Step (4): The wastewater flowing through the permeable electrode is transported to the collection device and then returned to the inlet of the reactor through the fluid transport device to form an electrolyte circulation treatment system until the nitrogen concentration in the wastewater reaches the preset standard.

2. The simultaneous denitrification method based on an electrodeposited spinel through-hole electrode according to claim 1, characterized in that, In step (one): The general chemical formula of the spinel-type oxide is: ; The element at the B site is Co, and the element at the A site is selected from Cu, Fe, Mn, Ni, and Zn.

3. The simultaneous denitrification method based on an electrodeposited spinel through-hole electrode according to claim 2, characterized in that, In step (i), the electrolyte is prepared as follows: A mixed solution was prepared using A-site metal nitrate, cobalt nitrate, and potassium chloride as raw materials; The molar ratio of metal nitrate, cobalt nitrate, and potassium chloride at site A is 1:2:

1.

4. The simultaneous denitrification method based on an electrodeposited spinel through-hole electrode according to claim 3, characterized in that, In step (i), the specific conditions for the electrodeposition process are as follows: A three-electrode system was used, with Ag / AgCl as the reference electrode, and the deposition potential was controlled from -0.9V to -1.1V, with a deposition time of 10 to 40 minutes.

5. The simultaneous denitrification method based on an electrodeposited spinel through-hole electrode according to claim 1, characterized in that, In step (i), the specific conditions for heat treatment are as follows: The electrode after electrodeposition is placed in an air atmosphere and kept at a temperature of 250°C to 500°C for 1 to 3 hours to form a stable spinel crystal phase.

6. The simultaneous denitrification method based on an electrodeposited spinel through-hole electrode according to claim 1, characterized in that, In step (iii): By controlling the current density, NH4 + The oxidation rate of NO3 - The reduction rate is matched to suppress the accumulation of the byproduct nitrite.

7. A simultaneous denitrification reaction apparatus for implementing the simultaneous denitrification method based on an electrodeposited spinel through-electrode as described in any one of claims 1-6, characterized in that, include: Electrolytic cell, liquid inlet system, liquid outlet system, collection device, DC power supply, and electrode assembly installed in the electrolytic cell; The electrode assembly includes an anode and a cathode, which adopt a permeable porous structure arranged perpendicular to the fluid flow direction, so that the wastewater to be treated flows through the internal pores of the electrode under pressure.

8. The simultaneous denitrification reaction apparatus according to claim 7, characterized in that: The substrate material of the permeable porous structure is selected from one of foamed titanium, graphite plate, graphite felt, and stainless steel plate; the pore size range of the substrate material of the permeable porous structure is 50-150μm.

9. A simultaneous denitrification reaction apparatus according to claim 7, characterized in that: The spinel-type oxide on the surface of the electrode assembly is specifically one of CuCo2O4, FeCo2O4, MnCo2O4, NiCo2O4, and ZnCo2O4.

10. A simultaneous denitrification reaction apparatus according to claim 7, characterized in that: The reactor is a permeable configuration used to treat NH4+-containing reactors. + and NO3 - Wastewater.

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