An electro-dialysis-membrane contactor coupling system with anode reaction path reconstruction

Abstract

The application provides an electro-dialysis-membrane contactor coupled system with anode reaction path reconstruction. By reconstructing the anode reaction in the electro-dialysis process from the high-energy consumption oxygen evolution reaction to the low-potential hydrogen oxidation reaction (HOR), combining the in-situ utilization of the hydrogen (H2) produced by the cathode hydrogen evolution reaction and the acid absorption technology of the membrane contactor, a four-chamber structure electro-dialysis unit is constructed. The application utilizes the thermodynamic advantage of the HOR reaction to reduce the overall energy consumption, and the NH4 + The high-value-added target ammonium salt is converted by the membrane contactor, so that the closed-loop cooperation of ammonia nitrogen directional recovery and wastewater denitrification is realized.

Description

Technical Field

[0001] This application relates to the fields of wastewater treatment technology and resource recycling, and in particular to an electrodialysis-membrane contactor coupling system with anodic reaction path reconstruction. Background Technology

[0002] Anaerobic digestion is currently one of the mainstream technologies for treating organic solid waste. The rapid development of anaerobic engineering will inevitably generate a large amount of digestion byproducts, and anaerobic digestate is one of the main components of these byproducts. Its high concentration of ammonia nitrogen becomes a "sink" of reactive nitrogen. If discharged into a wastewater treatment plant, it will significantly increase the treatment load and ultimately trigger cross-media pollution such as aquatic organism toxicity and eutrophication. Therefore, the efficient recovery of ammonia nitrogen from anaerobic digestate is a feasible path to simultaneously solve pollution and resource problems.

[0003] Ammonia nitrogen is mainly in the form of polar NH4. + NH4 exists in the form of anaerobic digestion liquid. Currently, the resource recovery of anaerobic digestion liquid is still in the exploratory stage, with methods such as stripping, chemical precipitation, and ion adsorption being used. However, these processes are limited by high chemical energy consumption, complex regeneration, and high risk of secondary pollution. Because NH4 exists in the form of anaerobic digestion liquid, its resource recovery is still in the exploratory stage. + As a weak electrolyte, the design of new separation and recovery methods based on its charge characteristics and dynamic dissociation properties is key to achieving low-consumption and high-efficiency recovery of ammonia nitrogen from anaerobic digestion liquid. Summary of the Invention

[0004] In view of the above-mentioned prior art, and to solve at least one of the above-mentioned technical problems, this application proposes an electrodialysis-membrane contactor coupling system with anodic reaction path reconstruction, which can significantly reduce the energy consumption level of the electrodialysis process, generate high-value-added target ammonium salt products, and realize closed-loop synergy of ammonia nitrogen directional recovery and wastewater denitrification.

[0005] According to this application, an electrodialysis-membrane contactor coupling system with anodic reaction path reconfiguration is proposed, including an electrodialysis device and a membrane contactor;

[0006] The electrodialysis device includes an anode chamber, a dilute chamber, a concentrated chamber, and a cathode chamber, which are separated by a membrane electrode assembly, a cation exchange membrane, and an anion exchange membrane; the cathode of the cathode chamber and the membrane electrode assembly are respectively connected to the negative and positive terminals of an external power source.

[0007] In the cathode chamber, the first electrolyte undergoes a hydrogen evolution reaction to produce H2 and OH. - Ions, and simultaneously transport H2 to the anode chamber while OH - Ions enter the concentration chamber; in the anode chamber, H2 undergoes a hydroxide reaction to produce H+. + Ions migrate into the dilute chamber, while NH4 in the solution to be treated in the dilute chamber... + Ions migrate to the concentration chamber and react with OH-- The ions are converted into NH3·H2O;

[0008] The membrane contactor includes an acid absorption chamber through which an acid solution is circulated, for receiving NH3·H2O generated in the concentration chamber and generating the target ammonium salt.

[0009] In some embodiments, the membrane electrode assembly includes a cation exchange membrane with a catalyst layer disposed on the side of the catalyst layer away from the cation exchange membrane, and a conductive support layer disposed on the side of the cation exchange membrane facing the cathode chamber; the conductive support layer is connected to the positive terminal of an external power source.

[0010] In some embodiments, the conductive support layer is made of a titanium-based conductive material.

[0011] In some embodiments, the cathode comprises a Pt / Ti electrode with a Pt metal coating disposed on the surface of a Ti mesh electrode.

[0012] In some embodiments, the cathode further includes a conductive sheet, which is a titanium-based conductive sheet and is connected to the Pt / Ti electrode to enhance current transmission.

[0013] In some embodiments, the H2 generated in the cathode chamber is transported to the anode chamber by an external carrier gas to maintain gas phase transport efficiency; the external carrier gas is an inert gas.

[0014] In some embodiments, an acid solution with a concentration of 0.1M is circulated into the anode chamber; an acid solution containing NH4 is circulated into the dilute chamber. + The solution to be treated contains ions; a salt solution is circulated through the concentration chamber; and an alkaline solution with a concentration of 0.1M is circulated through the cathode chamber.

[0015] In some embodiments, the membrane contactor further includes a contact chamber, and a breathable and hydrophobic membrane separates the membrane contactor into a contact chamber and an acid absorption chamber; the contact chamber is connected to the concentration chamber for receiving NH3·H2O; an acid solution is circulated into the acid absorption chamber, and gaseous ammonia in the contact chamber enters the acid absorption chamber and reacts with the acid solution to generate a target ammonium salt.

[0016] In some embodiments, the breathable and hydrophobic membrane is a hydrophobic polytetrafluoroethylene (PTFE) membrane, an aqueous PTFE membrane, having a PP support layer and a porosity ≥80%, used for the specific separation of NH3.

[0017] In some embodiments, the acid solution introduced into the acid absorption chamber is 0.1M H2SO4, HCl or HNO3; the target ammonium salt includes ammonium sulfate, ammonium chloride or ammonium nitrate.

[0018] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0019] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0020] Figure 1 This is a schematic diagram of the structure of an electrodialysis-membrane contactor coupling system provided in an embodiment of this application;

[0021] Figure 2 A schematic diagram of the model structure of an electrodialysis-membrane contactor coupling system provided in another embodiment of this application;

[0022] Figure 3 This is a schematic diagram of the structure of a membrane electrode assembly provided in an embodiment of this application;

[0023] Figure 4 A flowchart of an embodiment of the ammonia nitrogen resource recovery method provided in this application;

[0024] In the diagram, 1 is the anode chamber; 2 is the dilute chamber; 3 is the concentrated chamber; 4 is the cathode chamber; 5 is the contact chamber; 6 is the acid absorption chamber; 7 is the membrane electrode assembly; 71 is the gas diffusion layer; 72 is the catalyst layer; 73 is the cation exchange membrane; 74 is the conductive support layer; 8 is the cation exchange diaphragm; 9 is the anion exchange membrane; 10 is the cathode; 11 is the gas-permeable and hydrophobic membrane; 12 is the power supply; 13 is the membrane contactor; and 14 is the pump. Detailed Implementation

[0025] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are merely a part of the embodiments of the present application, not all of them, and are not intended to limit the scope of the disclosure of the present application. Furthermore, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion regarding the concepts disclosed in the present application. All other embodiments obtained by those skilled in the art based on the embodiments of the present application without creative effort should fall within the scope of protection of the present application.

[0026] The accompanying drawings show structural schematic diagrams according to embodiments disclosed in this application. These drawings are not drawn to scale, and some details have been enlarged and may have been omitted for clarity. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0027] This application represents an improvement on the following related technologies: Anaerobic digestion is currently one of the mainstream technologies for treating organic solid waste. The rapid development of anaerobic engineering will inevitably generate a large amount of digestion products, and anaerobic digestate is one of the main components of these products. Its high concentration of ammonia nitrogen becomes a "sink" of reactive nitrogen. Discharging it into a wastewater treatment plant would significantly increase the treatment load, ultimately triggering cross-media pollution such as aquatic organism toxicity and eutrophication. Therefore, the efficient recovery of ammonia nitrogen from anaerobic digestate is a feasible path to simultaneously solve pollution and resource problems. Ammonia nitrogen is mainly in the form of polar NH4+. + NH4 exists in the form of anaerobic digestion liquid. Currently, the resource recovery of anaerobic digestion liquid is still in the exploratory stage, with methods such as stripping, chemical precipitation, and ion adsorption being used. However, these processes are limited by high chemical energy consumption, complex regeneration, and high risk of secondary pollution. Because NH4 exists in the form of anaerobic digestion liquid, its resource recovery is still in the exploratory stage. + As a weak electrolyte, the design of new separation and recovery methods based on its charge characteristics and dynamic dissociation properties is key to achieving low-consumption and high-efficiency recovery of ammonia nitrogen from anaerobic digestion liquid.

[0028] The related technology discloses an electrochemical system and method for recovering ammonia nitrogen and rare earth ions from low-concentration rare earth wastewater. The system includes an electrolytic cell, a membrane reactor, and a wastewater tank. The electrolytic cell is separated into a cathode chamber and an anode chamber by a bipolar membrane on both sides. One or more treatment units are provided between the cathode chamber and the anode chamber. The treatment unit includes an ammonium sulfate chamber, a wastewater chamber, a rare earth ion chamber, and an ammonia water chamber arranged in sequence. An anion exchange membrane is provided between the ammonium sulfate chamber and the wastewater chamber, a cation exchange membrane is provided between the wastewater chamber and the rare earth ion chamber, and a divalent cation exchange membrane is provided between the rare earth ion chamber and the ammonia water chamber. The membrane reactor has a first chamber and a second chamber. The first chamber is connected to the ammonium sulfate chamber of the electrolytic cell and is used to output the ammonium sulfate-containing solution to the ammonium sulfate chamber. The second chamber is connected to the ammonia water chamber of the electrolytic cell through a second pipeline. The wastewater tank is connected to the wastewater chamber through a third pipeline. The related technologies disclose an ammonia nitrogen wastewater treatment device and method capable of generating target ammonium salts, including a bipolar membrane electrodialysis device and a membrane contactor. The bipolar membrane electrodialysis device includes at least one treatment unit and an anode chamber and a cathode chamber separated from the treatment unit. The treatment unit includes a front bipolar membrane, a front cation exchange membrane, a middle bipolar membrane, an anion exchange membrane, a rear cation exchange membrane, and a rear bipolar membrane arranged sequentially from the anode chamber to the cathode chamber. The spaces generated between the corresponding membranes respectively form a feed chamber, an ammonia production chamber, an acid production chamber, a desalination chamber, and an alkali production chamber. The membrane contactor includes a breathable and hydrophobic membrane that divides its inner cavity into a first chamber and a second chamber. The first chamber and the second chamber are respectively connected to the ammonia production chamber and the acid production chamber through pipes.

[0029] The above-mentioned technologies are essentially electrodialysis methods. By constructing a non-equilibrium electric field to drive the migration of charged ions, and based on the enrichment of ammonia nitrogen, the concentrated water can be used in a membrane contact reactor to initiate NH4+ ionization through local pH oscillation. + / NH3 dynamic dissociation fixes NH3, generating high value-added products and simultaneously realizing the resource utilization of ammonia nitrogen. However, the above scheme still has the following problems: (1) The electrode undergoes water electrolysis reaction, in which the oxygen evolution reaction at the anode has a high overpotential, resulting in a large energy loss in the system; (2) The coexisting cations NH4 in the solution + / Na + / K + There is competitive migration, which reduces NH4. + The selectivity of the recycled products leads to increased energy consumption and reduced purity and economic value of the recycled products; (3) The H2 generated by the hydrogen evolution reaction at the cathode in the traditional electrodialysis method is a clean energy source with high energy density, but its resource utilization potential has been ignored and has not been rationally utilized.

[0030] This application proposes an electrodialysis-membrane contactor coupling system with reconstructed anodic reaction pathway. By reconstructing the anodic reaction during electrodialysis from a high-energy-consuming oxygen evolution reaction to a low-potential hydrogen oxidation reaction (HOR), and combining this with in-situ utilization of H2, the product of the cathode hydrogen evolution reaction, and acid absorption technology via the membrane contactor, a four-chamber electrodialysis unit is constructed. This application utilizes the thermodynamic advantages of the HOR reaction to reduce overall energy consumption, and the concentrated NH4 in the concentrate chamber... + The ammonia nitrogen is converted into high-value-added target ammonium salt via a membrane contactor, achieving a closed-loop synergy between targeted ammonia nitrogen recovery and wastewater denitrification. The system described in this application is suitable for the resource-based treatment of high-ammonia nitrogen wastewater such as anaerobic digester broth. It features low energy consumption, high efficiency, and no secondary pollution, making it highly valuable for application and promotion.

[0031] The following is a reference to the appendix. Figure 1 The embodiments described herein are illustrated. Specifically, according to the first aspect of this application, an electrodialysis-membrane contactor 13 coupling system is provided, including an electrodialysis device and a membrane contactor 13; wherein the electrodialysis device includes an anode chamber 1, a dilute chamber 2, a concentrated chamber 3, and a cathode chamber 4, which are separated by a membrane electrode assembly 7, a cation exchange membrane 8, and an anion exchange membrane 9 arranged at intervals; the cathode chamber 4 is connected to the negative terminal of an external power supply 12 through a cathode 10, and the anode chamber 1 is connected to the positive terminal of the external power supply 12 through the membrane electrode assembly 7; in the cathode chamber 4, a first electrolyte undergoes a hydrogen evolution reaction to produce H2 and OH. - Ions, and simultaneously transport H2 to anode chamber 1 while OH- - Ions enter concentration chamber 3; in anode chamber 1, H2 undergoes a hydroxide reaction to produce H+. + Ions migrate into dilute chamber 2, while NH4+ in the solution to be treated in dilute chamber 2... + Ions migrate to concentration chamber 3 and react with OH- - The ions are converted into NH3·H2O;

[0032] The membrane contactor 13 includes a contact chamber 5 and an acid absorption chamber 6 separated by a breathable and hydrophobic membrane 11; the contact chamber 5 is connected to the concentration chamber 3 for receiving NH3·H2O; an acid solution is circulated into the acid absorption chamber 6, and gaseous ammonia in the contact chamber 5 enters the acid absorption chamber 6 to generate the target ammonium salt with the acid solution.

[0033] In this embodiment, the electrodialysis device includes an anode chamber 1, a dilute chamber 2, a concentrate chamber 3, and a cathode chamber 4 arranged sequentially and adjacently. The anode chamber 1 and the dilute chamber 2 are separated by a membrane electrode assembly 7; the dilute chamber 2 and the concentrate chamber 3 are separated by a cation exchange membrane 8; and the concentrate chamber 3 and the cathode chamber 4 are separated by an anion exchange membrane 9. In other words, as... Figure 1 and Figure 2As shown, the anode chamber 1 is connected to the positive terminal of the external power supply 12 via the membrane electrode assembly 7, and the cathode chamber 4 is connected to the negative terminal of the external power supply 12 via the cathode 10. The external power supply 12 provides a DC electric field, enabling electrolysis in the electrodialysis device. A second electrolyte, such as a 0.1M acid solution (which can be sulfuric acid), is circulated through the anode chamber 1. The dilute chamber 2 is circulated with an electrolyte containing NH4+. + The solution to be treated with ions; a third electrolyte is circulated in the concentration chamber 3, such as a 0.1M salt solution, which can be Na2SO4; a first electrolyte is circulated in the cathode chamber 4, which can be a 0.1M alkaline solution, which can be NaOH.

[0034] Each of the anode chamber 1, dilute chamber 2, concentrate chamber 3, and cathode chamber 4 is equipped with a corresponding self-circulating loop. A pump 14 is installed in each self-circulating loop to allow the circulating electrolyte and the corresponding solution to be treated to be introduced into the loop. When cathode chamber 4 is connected to the negative terminal of an external power supply 12 via cathode 10, and anode chamber 1 is connected to the positive terminal of the external power supply 12 via membrane electrode assembly 7, and the external power supply 12 provides a DC electric field, the corresponding electrolytes and solutions for anode chamber 1, dilute chamber 2, concentrate chamber 3, and cathode chamber 4 are introduced into these loops. In cathode chamber 4, the first electrolyte undergoes a hydrogen evolution reaction (HER) to produce H2 and OH-. - Ions, OH - Driven by the concentration gradient, ions can migrate through the anion exchange membrane 9 (AEM) between the cathode chamber 4 and the concentration chamber 3 to the concentration chamber 3; while the H2 generated in the cathode chamber 4 is transported to the anode chamber 1. For example, in some embodiments, the H2 generated in the cathode chamber 4 is transported to the anode chamber 1 by an external carrier gas to maintain the gas phase transport efficiency; the external carrier gas is an inert gas.

[0035] In the anode chamber 1, protons released from H2 on the surface of the membrane electrode assembly 7 undergo a hydrogenation reaction (HOR) to generate H2. + Ions, H + Ions migrate directionally to dilute chamber 2 via membrane electrode assembly 7, and simultaneously, under the drive of an electric field, NH4+ in the solution to be treated in dilute chamber 2... + NH4+ migrates across cation exchange membrane 8 to concentration chamber 3; NH4+ migrates in concentration chamber 3. + With OH - A neutralization reaction occurs to produce NH3·H2O. This process achieves NH4+ through the synergistic effect of membrane separation and electrochemical regulation. +The application achieves efficient retention and form transformation. Therefore, it utilizes the thermodynamic advantages of the hydroxide reaction to reduce overall energy consumption. Compared to related technologies that switch the anode reaction path from the oxygen evolution reaction to the hydroxide reaction in this application, the thermodynamic potential decreases from 1.23V to near 0V, reducing the thermodynamic equilibrium potential between the two electrodes, strengthening the local electric field, and eliminating the inherent thermodynamic barrier of the oxygen evolution reaction. Simultaneously, this application utilizes the H2 generated by the hydrogen evolution reaction in its cathode chamber 4, leveraging its high energy density, to transport it to the anode chamber 1 to drive the hydroxide reaction, converting the unutilized H2 byproducts in related technologies into a recyclable energy carrier, further improving the system's energy efficiency.

[0036] Therefore, the system of this application can significantly reduce system energy consumption and improve energy utilization efficiency. By reconstructing the reaction path in anode chamber 1 from the high-overpotential oxygen evolution reaction (theoretical potential 1.23V) to the low-potential hydrogen oxidation reaction (theoretical potential close to 0V), the thermodynamic equilibrium potential is greatly reduced, effectively eliminating the inherent thermodynamic barrier of the oxygen evolution reaction and reducing anode overpotential loss. At the same time, the H2 generated by the hydrogen evolution reaction in cathode chamber 4 is transported in situ to anode chamber 1 as a reactant, converting the unused H2 byproduct in the traditional process into a recyclable energy carrier, realizing closed-loop energy utilization within the system. This dual optimization reduces overall energy consumption and breaks through the high-energy-consumption bottleneck of traditional electrodialysis technology.

[0037] In addition, this system eliminates the risk of secondary pollution and achieves closed-loop collaborative treatment. The recycling of H2 within the system avoids the safety hazards of flammable gas emissions.

[0038] In this embodiment, the membrane contactor 13 includes a contact chamber 5 and an acid absorption chamber 6 separated by a breathable and hydrophobic membrane 11. The contact chamber 5 is located on the self-circulating loop corresponding to the concentration chamber 3 and is used to receive NH3·H2O generated in the concentration chamber 3. Simultaneously, the acid absorption chamber 6 is provided with a self-circulating loop for circulating an acid solution into the acid absorption chamber 6. Gaseous ammonia in the contact chamber 5 enters the acid absorption chamber 6 and reacts with the acid solution to generate the target ammonium salt. In other words, in this application, the contact chamber 5 is connected to the concentration chamber 3 to receive NH3·H2O from the concentration chamber 3. The NH3·H2O solution flows through the breathable and hydrophobic membrane 11, and under the transmembrane pressure difference, gaseous NH3 molecules selectively permeate into the acid absorption chamber 6. An acid solution is circulated within the acid absorption chamber 6, and NH3 undergoes a gas-liquid mass transfer reaction with the acid solution to generate the target ammonium salt.

[0039] Therefore, this application can change the type of target ammonium salt generated according to needs, and customize the type of acid solution introduced into the acid absorption chamber 6 as needed to achieve targeted recovery of ammonia nitrogen; for example, the acid solution introduced into the acid absorption chamber 6 is 0.1M H2SO4, HCl or HNO3; the target ammonium salt includes ammonium sulfate, ammonium chloride or ammonium nitrate, to achieve high-quality and high-purity recovery of ammonia nitrogen, which can meet personalized customization needs and has high application value.

[0040] Furthermore, this invention features a separate membrane contactor unit 13, which separates ammonia nitrogen in the form of NH3 through a breathable and hydrophobic membrane 11, avoiding interference from other competing cations. The type of acid absorbent in the membrane contactor 13 can be customized as needed, thereby altering the type of ammonium salt generated. This achieves targeted resource recovery, high-quality, and high-purity ammonia nitrogen recovery, breaking through the limitations of traditional processes with a single product. It can meet personalized customization needs and has high application value. This design allows for flexible adjustment of the chemical form of the recovered product according to market demand, enhancing the economic value and adaptability of the resource recovery process. Simultaneously, the complete conversion of NH3 in the acid absorption chamber 6 effectively prevents the escape of gaseous ammonia, achieving a closed-loop synergy between wastewater denitrification and resource recovery, with no chemical additive residues, completely avoiding the secondary pollution risks of traditional processes.

[0041] In some embodiments, the membrane electrode assembly 7 includes a cation exchange membrane 73 with a catalyst layer 72 disposed on the side facing the anode chamber 1, a gas diffusion layer 71 disposed on the side of the catalyst layer 72 away from the cation exchange membrane 73, and a conductive support layer 74 disposed on the side of the cation exchange membrane 73 facing the cathode chamber 4; the conductive support layer 74 is connected to the positive electrode of an external power source 12.

[0042] Taking an electrodialysis device comprising an anode chamber 1, a dilute chamber 2, a concentrate chamber 3, and a cathode chamber 4 arranged sequentially from left to right as an example, the membrane electrode assembly 7 is as follows: Figure 3 The diagram shows a cation exchange membrane 73, with an anode chamber 1 on the left and a dilute chamber 2 on the right. A catalyst layer 72 is disposed on the left side of the cation exchange membrane 73, which is obtained by spraying a Pt / C catalyst onto the surface of the cation exchange membrane 73. A gas diffusion layer 71 (GDL) is then integrated on one side of the catalyst layer 72, facing the anode chamber 1. A conductive support layer 74 is disposed on the right side of the cation exchange membrane 73. The conductive support layer 74 is used to connect to the positive terminal of an external power supply 12. In some embodiments, the conductive support layer 74 is made of a titanium-based conductive material.

[0043] Compared to related technologies that switch the oxygen evolution reaction at the anode to a hydrogenation reaction, this application establishes a directional chemical potential gradient (Donnan effect) at the membrane interface of the catalyst layer 72 in the membrane electrode assembly 7 through the hydrogenation reaction in the anode chamber 1. This novel reaction pathway reduces the anode overpotential and strengthens the local electric field. The directional chemical potential gradient at the membrane interface, achieved through the Donnan effect, provides additional NH4+ compared to field-driven migration. + Mass transfer driving force, weakening Na + K + The migration interference of competing cations significantly enhances NH4+. +First, the migration selectivity is improved, alleviating competitive ion migration. Second, the anodic reaction pathway reconstruction process replaces the oxygen evolution reaction of the four-electron oxidation process with the proton-coupled two-electron hydrogenation reaction, reducing the reaction ΔG and avoiding overpotential loss, thus eliminating the inherent thermodynamic barrier of the oxygen evolution reaction. Third, the anodic reaction pathway reconstruction utilizes the H2 generated by the hydrogen evolution reaction at the cathode, taking advantage of its high energy density, to transport it to the anode to drive the hydrogenation reaction, converting the unused H2 byproduct in the traditional electrodialysis process into a recyclable energy carrier, further reducing system energy consumption.

[0044] In some embodiments, the cathode 10 includes a Pt / Ti electrode with a Pt metal coating disposed on the surface of a Ti mesh electrode.

[0045] The cathode 10 includes a Pt / Ti electrode with a Pt metal coating on the surface of a Ti mesh electrode. In some embodiments, the cathode 10 also includes a conductive sheet, which is a titanium-based conductive sheet with a thickness of 0.5 mm and is connected to the Pt / Ti electrode to enhance current transmission. The fabrication process of the cathode 10 and the method of connecting it to the negative terminal of the external power supply 12 can be found in relevant technologies and will not be described in detail here.

[0046] In some embodiments, the breathable and hydrophobic membrane 11 is a hydrophobic polytetrafluoroethylene membrane having a PP support layer and a porosity ≥80%, used for the specific separation of NH3.

[0047] In this embodiment, the breathable and hydrophobic membrane 11, a hydrophobic polytetrafluoroethylene membrane with a PP support layer and a porosity ≥80%, further ensures the efficient and specific separation of NH3 due to its high permeability and hydrophobicity, preventing other cations from entering the acid absorption chamber 6. This results in a high purity of the recovered ammonium salt, meeting the demands of high-value-added products. Enhanced selective migration of ammonia nitrogen and improved purity of the recovered product result in a higher ammonia nitrogen recovery flux compared to traditional electrodialysis technology.

[0048] In summary, this application utilizes the coupling design of the membrane contactor 13 in a four-chamber electrodialysis device to control the pH gradient (OH in the concentration chamber 3) - With NH4 + The combination of NH3·H2O significantly enhances the mass transfer rate of NH3, optimizes the system structure in related technologies, and improves mass transfer and reaction efficiency.

[0049] The system in any of the above embodiments can be used for ammonia nitrogen resource recovery, such as... Figure 4 This includes the following steps:

[0050] S1: Contains NH4 + The solution to be treated with ions is introduced into the dilute chamber 2, and the corresponding electrolytes are introduced into the concentrated chamber 3, the anode chamber 1, and the cathode chamber 4; at the same time, the external power supply 12 provides a DC electric field.

[0051] S2: H2 and OH produced by hydrogen evolution from the first electrolyte - Ions, H2, are transported to anode chamber 1 while OH- ions are simultaneously transported. - Ions enter concentration chamber 3; in anode chamber 1, H2 undergoes a hydroxide reaction on membrane electrode assembly 7 to produce H2. + Ions, H + Ions migrate into dilute chamber 2; NH4+ in dilute chamber 2 + Ions migrate to concentration chamber 3 under the drive of an electric field and react with OH groups. - The ions are converted into NH3·H2O;

[0052] S3: Contact chamber 5 receives NH3·H2O generated in concentration chamber 3, while acid solution is circulated into acid absorption chamber 6. Gaseous ammonia in contact chamber 5 enters acid absorption chamber 6 and reacts with acid solution to form target ammonium salt.

[0053] In S1, NH4 is circulated into the dilute chamber 2. + The solution to be treated contains ions. Simultaneously, a second electrolyte, such as a 0.1M acid solution (e.g., sulfuric acid), is circulated through the anode chamber 1; a third electrolyte, such as a 0.1M salt solution (e.g., Na₂SO₄), is circulated through the concentration chamber 3; and a first electrolyte, which can be a 0.1M alkaline solution (e.g., NaOH), is circulated through the cathode chamber 4. The anode chamber 1 is connected to the positive terminal of an external power supply 12 via the membrane electrode assembly 7, and the cathode chamber 4 is connected to the negative terminal of the external power supply 12 via the cathode 10. The current density provided by the external power supply 12 is 10–100 mA / m². 2 It generates a DC electric field.

[0054] In S2, within cathode chamber 4, a 0.1M NaOH solution acts as the electrolyte, undergoing the hydrogen evolution reaction (HER) to produce H2, along with the generation of OH-. - Ions migrate through the anion exchange membrane 9 (AEM) to the concentration chamber 3 driven by a concentration gradient; H2 is transported to the anode chamber 1 via an external carrier gas, such as an inert gas, nitrogen, or helium; in the anode chamber 1, H2 undergoes a hydrogenation reaction (HOR) on the surface of the catalyst layer 72 of the membrane electrode assembly 7, HOR: H2 → 2H + +2e - The protons released by H2 produce H + Ions. H + Ions migrate directionally through the cation exchange membrane into dilute chamber 2. Simultaneously, driven by an electric field, NH4+ in the solution to be treated... + NH4+ migrates across cation exchange membrane 8 to concentration chamber 3; in concentration chamber 3, the migrating NH4+... + With OH - A neutralization reaction occurs to produce NH3·H2O. This process achieves NH4+ through the synergistic effect of membrane separation and electrochemical regulation.+ Efficient interception and morphological transformation.

[0055] In S3, the electrolyte self-circulation loop of the concentration chamber 3 allows NH3·H2O in the concentration chamber 3 to enter the contact chamber 5 through the flow channel. In some embodiments, the NH3·H2O received in the contact chamber 5 flows through the gas-permeable hydrophobic membrane 11. Under the transmembrane pressure difference, NH3 gas molecules selectively permeate into the acid absorption chamber 6, thereby enhancing the mass transfer rate of NH3.

[0056] An acid solution is introduced into the acid absorption chamber 6. The acid solution introduced into the acid absorption chamber 6 is 0.1M H2SO4, HCl or HNO3. In this embodiment, 1M H2SO4 solution is introduced into the acid absorption chamber 6 as an example for circulation. NH3 diffuses into the acid absorption chamber 6 through the gas-permeable hydrophobic membrane 11. The acid solution in the NH3·H2O solution undergoes a gas-liquid mass transfer reaction to generate ammonium sulfate, thus realizing the resource recovery of ammonia nitrogen.

[0057] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0058] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0059] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. An electrodialysis-membrane contactor coupling system with anodic reaction path reconstruction, characterized in that, Includes electrodialysis units and membrane contactors; The electrodialysis device includes an anode chamber, a dilute chamber, a concentrated chamber, and a cathode chamber, which are separated by a membrane electrode assembly, a cation exchange membrane, and an anion exchange membrane; the cathode of the cathode chamber and the membrane electrode assembly are respectively connected to the negative and positive terminals of an external power source. In the cathode chamber, the first electrolyte undergoes a hydrogen evolution reaction to produce H2 and OH. - Ions, and simultaneously transport H2 to the anode chamber while OH - Ions enter the concentration chamber; in the anode chamber, H2 undergoes a hydroxide reaction to produce H+. + Ions migrate into the dilute chamber, while NH4 in the solution to be treated in the dilute chamber... + Ions migrate to the concentration chamber and react with OH- - The ions are converted into NH3·H2O; The membrane contactor includes an acid absorption chamber through which an acid solution is circulated, for receiving NH3·H2O generated in the concentration chamber and generating the target ammonium salt.

2. The system according to claim 1, characterized in that, The membrane electrode assembly includes a cation exchange membrane with a catalyst layer disposed on the side facing the anode chamber, a gas diffusion layer disposed on the side of the catalyst layer away from the cation exchange membrane, and a conductive support layer disposed on the side of the cation exchange membrane facing the cathode chamber; the conductive support layer is connected to the positive terminal of an external power source.

3. The system according to claim 2, characterized in that, The conductive support layer is made of titanium-based conductive material.

4. The system according to claim 1, characterized in that, The cathode includes a Pt / Ti electrode with a Pt metal coating on the surface of a Ti mesh electrode.

5. The system according to claim 4, characterized in that, The cathode also includes a conductive sheet, which is a titanium-based conductive sheet and is connected to the Pt / Ti electrode to enhance current transmission.

6. The system according to any one of claims 1-5, characterized in that, The H2 generated in the cathode chamber is transported to the anode chamber by an external carrier gas to maintain the gas phase transport efficiency; the external carrier gas is an inert gas.

7. The system according to claim 6, characterized in that, A 0.1M acid solution is circulated through the anode chamber; an acid solution containing NH4+ is circulated through the dilute chamber. + The solution to be treated contains ions; a salt solution is circulated through the concentration chamber; and an alkaline solution with a concentration of 0.1M is circulated through the cathode chamber.

8. The system according to claim 6, characterized in that, The membrane contactor also includes a contact chamber, and a breathable and hydrophobic membrane separates the membrane contactor into a contact chamber and an acid absorption chamber; the contact chamber is connected to the concentration chamber for receiving NH3·H2O; an acid solution is circulated into the acid absorption chamber, and gaseous ammonia in the contact chamber enters the acid absorption chamber and reacts with the acid solution to generate the target ammonium salt.

9. The system according to claim 8, wherein the breathable and hydrophobic membrane is a hydrophobic polytetrafluoroethylene membrane or an aqueous polytetrafluoroethylene membrane, having a PP support layer and a porosity ≥80%, for the specific separation of NH3.

10. The system according to claim 6, characterized in that, The acid solution introduced into the acid absorption chamber is 0.1M H2SO4, HCl or HNO3; the target ammonium salt includes ammonium sulfate, ammonium chloride or ammonium nitrate.

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