A gas permeable membrane electrode, its preparation method and use

Abstract

The application provides a gas-permeable membrane electrode and a preparation method and application thereof, and belongs to the technical field of high-ammonia-nitrogen wastewater treatment and ammonia-nitrogen resource recovery. The gas-permeable membrane electrode comprises a hydrophobic microporous membrane substrate and an anode and a cathode fixed on two sides of the substrate respectively; the material of the hydrophobic microporous membrane substrate is at least one of polytetrafluoroethylene, polyvinylidene fluoride, polypropylene, polyvinyl chloride, polydimethylsiloxane and ceramic; the material of the anode is at least one of platinum, palladium, carbon, iridium oxide, tantalum oxide and titanium oxide; the material of the cathode is at least one of platinum, palladium, carbon, nickel, iron and stainless steel; and the method for fixing the anode and the cathode on two sides of the hydrophobic microporous membrane substrate comprises an electrochemical deposition method and a phase inversion method. The application overcomes the defects of the current membrane absorption method for recovering ammonia-nitrogen in wastewater, such as single membrane separation function, large acid-alkali consumption, electrode acid-alkali production and membrane absorption interface coupling mode, and can in-situ produce acid-alkali to drive membrane absorption for recovering ammonia-nitrogen in wastewater.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high ammonia-nitrogen wastewater treatment and ammonia-nitrogen resource recovery, and in particular to a gas-permeable membrane electrode and a preparation method and application thereof. BACKGROUND

[0002] Ammonia-nitrogen in wastewater is an important inducement of water eutrophication; at the same time, ammonia-nitrogen is a key nitrogen fertilizer raw material and an important carbon-free energy storage and power generation material. Removing ammonia-nitrogen from wastewater and industrial synthetic ammonia-nitrogen both belong to high-energy-consumption and high-carbon-emission processes, which form a vicious cycle over a long period of time. Resource recycling and utilization of wastewater ammonia-nitrogen is undoubtedly the best choice to break this vicious cycle. In recent years, the concept of wastewater ammonia-nitrogen treatment has gradually changed from "removing ammonia-nitrogen" to "recovering ammonia-nitrogen", which can not only recover ammonia-nitrogen resources, but also protect water ecological safety and promote carbon emission reduction.

[0003] Membrane absorption method is concerned due to its high ammonia-nitrogen recovery efficiency, no secondary pollution and low energy consumption. However, the cathode chamber of traditional membrane absorption method needs to consume a large amount of alkali to increase the pH of wastewater to high value to promote the conversion of ammonia-nitrogen into free ammonia, and the anode chamber needs to consume a large amount of acid to keep the low pH of the absorption liquid to absorb ammonia; due to the low concentration and low pH of the direct recovery product, it cannot be directly used as fertilizer, and it needs to be concentrated again and the pH needs to be adjusted to near neutral value by consuming alkali to solve the subsequent utilization problem.

[0004] By coupling the electrochemical system with the membrane absorption unit, the problem of acid and alkali supply in the traditional membrane absorption method is solved by using the electrolysis water reaction, but a large amount of acid and alkali is still needed to adjust the pH of the effluent and the recovery product to near neutral value. However, the existing coupling mode of electrode reaction interface and membrane absorption interface has defects. CN110921796A provides an electrochemical recovery of wastewater nitrogen and phosphorus synchronous hydrogen-oxygen system and method, which uses a cation exchange membrane between the anode chamber and the acid production chamber, and an anion exchange membrane between the acid production chamber and the desalination chamber, so that the acid produced by the anode in the anode chamber is retained in the acid production chamber to realize continuous acid production. However, the acid liquid in the acid production chamber needs to be circulated to the rightmost absorption chamber by a pump for absorbing NH3 transported from the cathode chamber across the membrane, and the desalination chamber plays a role in maintaining ion balance.

[0005] In addition, the current membrane electrode is mostly fixed and assembled in a hot-pressing mode, and its durability needs to be improved. How to utilize the insulating and hydrophobic properties of the hydrophobic microporous membrane to realize the coupling of the anode acid production interface, the cathode alkali production interface and the membrane absorption interface to improve the utilization efficiency of acid and alkali and reduce the energy consumption of acid and alkali liquid transportation is not clear, and the suitable mode and coupling interface synergistic mechanism need to be explored. SUMMARY

[0006] In view of the above problems existing in the prior art, the application provides a gas permeable membrane electrode and a preparation method and application thereof.The application overcomes the defects of the current membrane absorption method for recovering ammonia nitrogen in wastewater, such as single membrane separation function, large acid-base consumption, and electrode acid-base production and membrane absorption interface coupling mode, and can in-situ produce acid-base to drive membrane absorption to recover ammonia nitrogen in wastewater.

[0007] The technical scheme of the application is as follows:

[0008] A gas permeable membrane electrode comprises a hydrophobic microporous membrane substrate, and an anode and a cathode fixed on two sides of the substrate, respectively.

[0009] The material of the hydrophobic microporous membrane substrate is at least one of polytetrafluoroethylene, polyvinylidene fluoride, polypropylene, polyvinyl chloride, polydimethylsiloxane, and ceramic.

[0010] The material of the anode is at least one of platinum, palladium, carbon, iridium oxide, tantalum oxide, and titanium oxide.

[0011] The material of the cathode is at least one of platinum, palladium, carbon, nickel, iron, and stainless steel.

[0012] Preferably, the method for fixing the anode and the cathode on two sides of the hydrophobic microporous membrane substrate comprises an electrochemical deposition method and a phase inversion method.

[0013] Further, the electrochemical deposition method comprises the following steps:

[0014] S1, dispersing carbon nanomaterial in ethanol to obtain a carbon nanomaterial dispersion liquid, and spraying the carbon nanomaterial dispersion liquid to two sides of the hydrophobic microporous membrane substrate;

[0015] S2, preparation of an anode electrodeposition solution: mixing and stirring an anode material with an anode solution and adjusting the pH to 9.0-12.0;

[0016] S3, preparation of a cathode electrodeposition solution: mixing and stirring a cathode material with a cathode solution and adjusting the pH to 1.0-4.0;

[0017] S4, preparation of a hydrophobic microporous membrane substrate-anode: adhering a titanium wire mesh to one side of the hydrophobic microporous membrane substrate after spraying the carbon nanomaterial obtained in step S1, immersing the titanium wire mesh in the anode electrodeposition solution obtained in step S2 as a working electrode, performing anode pre-deposition in a three-electrode electrolytic cell system, taking a glassy carbon electrode as a counter electrode and a saturated calomel electrode as a reference electrode, performing anode electrodeposition, and peeling off the titanium wire mesh from the anode after the anode electrodeposition is completed;

[0018] S5, hydrophobic microporous membrane substrate-cathode preparation: the other side of the hydrophobic microporous membrane substrate loaded with anode obtained in step S4 is attached with a stainless steel wire mesh, and is immersed into the cathode electrodeposition solution obtained in step S3 as a working electrode, with a foamed nickel electrode as a counter electrode and a saturated calomel electrode as a reference electrode, to perform cathode electrodeposition, and after the end, the stainless steel wire mesh is peeled off from the cathode.

[0019] Preferably, the volume ratio of the carbon nanomaterial to ethanol in step S1 is 1:1-2.

[0020] Preferably, the volume ratio of the anode material to the anode solution in step S2 is 1:1-2; the raw materials of the anode solution are deionized water, oxalic acid and hydrogen peroxide; the volume ratio of the deionized water, oxalic acid and hydrogen peroxide is 1:0.5-1.5:0.5-1.5.

[0021] Preferably, the volume ratio of the cathode material to the cathode solution in step S3 is 1:1-2; the raw material of the cathode solution is H3BO3.

[0022] Further, the phase inversion method comprises the following steps:

[0023] M1, hydrophobic microporous membrane substrate-anode preparation: the anode material is dispersed in a dimethyl sulfoxide mixed solution of polyvinylidene fluoride and polyvinylpyrrolidone, then the mixture is uniformly coated on one side of the hydrophobic microporous membrane substrate, exposed in air for a short time to volatilize the solvent, and then the coated substrate is immersed in distilled water to fix the anode material through a phase inversion process.

[0024] M2, hydrophobic microporous membrane substrate-cathode preparation: the cathode material is dispersed in a dimethyl sulfoxide mixed solution of polyvinylidene fluoride and polyvinylpyrrolidone, then the mixture is uniformly coated on the other side of the hydrophobic microporous membrane substrate, exposed in air for a short time to volatilize the solvent, and then the coated substrate is immersed in distilled water to fix the cathode material through a phase inversion process.

[0025] Preferably, the volume ratio of the anode material, polyvinylidene fluoride, polyvinylpyrrolidone and dimethyl sulfoxide in step M1 is 1:1-2:1-2:1-2.

[0026] Preferably, the volume ratio of the cathode material, polyvinylidene fluoride, polyvinylpyrrolidone and dimethyl sulfoxide in step M2 is 1:1-2:1-2:1-2.

[0027] More preferably, the time of the short-time exposure is 5-15 min.

[0028] The application also provides the application of the air-breathing membrane electrode, which is used for high-ammonia-nitrogen sewage treatment and ammonia-nitrogen resource recovery.

[0029] The application further provides the application of the gas permeable membrane electrode, and the gas permeable membrane electrode is used in a stacked electrochemical ammonia-nitrogen recovery system to realize ammonia absorption by the electrochemical membrane.

[0030] The stacked ammonia-nitrogen recovery system comprises a plurality of connected ammonia-nitrogen recovery units, desalination chambers separated by anion exchange membranes are arranged outside the anode chambers, and desalination chambers separated by cation exchange membranes are arranged outside the cathode chambers, the units can be infinitely stacked, desalination chambers are arranged outside the anode chambers and the cathode chambers, respectively, and a plurality of units are amplified or stacked repeatedly according to the processing scale.

[0031] Further, taking a two-unit stacked electrochemical ammonia-nitrogen recovery system as an example, the two-unit electrochemical ammonia-nitrogen recovery system comprises an anode chamber 1, a cathode chamber 2, a first desalination chamber 3, a second desalination chamber 4, a secondary cathode chamber 5, and a secondary anode chamber 6.

[0032] The anode chamber 1 and the cathode chamber 2 are separated by the gas permeable membrane electrode, the anode 8 and the cathode 9 of the gas permeable membrane electrode are located on one side of the anode chamber 1 and the cathode chamber 2, respectively, and the substrate 7 of the gas permeable membrane electrode is located between the anode 8 and the cathode 9.

[0033] The other side of the anode chamber 1 is separated from the first desalination chamber 3 by an anion exchange membrane 10, the other side of the cathode chamber 2 is separated from the second desalination chamber 4 by a cation exchange membrane 11, the other side of the first desalination chamber 3 is separated from the secondary cathode chamber 5 by a cation exchange membrane 11, and the other side of the second desalination chamber 4 is separated from the secondary anode chamber 6 by an anion exchange membrane 10.

[0034] Preferably, the mesh number of the titanium wire mesh in step S4 and the stainless steel wire mesh in step S5 is 60-80 mesh, and most preferably 60 mesh.

[0035] Preferably, the anion exchange membrane 10 is selected from at least one of quaternary amine type, pyridine quaternary amine type, primary amine type, secondary amine type, tertiary amine type, and mixed amine type membrane; and the cation exchange membrane 11 is selected from at least one of sulfonic acid type, phosphoric acid type, phosphonic acid type, carboxylic acid type, phenol type, and phenol sulfonic acid membrane.

[0036] Further, the electrolyte in the anode chamber 1 is an ammonium sulfate solution, the electrolyte in the cathode chamber 2 is high ammonia-nitrogen wastewater, and the electrolyte in the first desalination chamber 3, the second desalination chamber 4, the secondary cathode chamber 5, and the secondary anode chamber 6 is sodium sulfate brine.

[0037] Preferably, a low-concentration ammonium sulfate electrolyte solution is injected into the anode chamber 1.

[0038] Preferably, the high ammonia-nitrogen wastewater injected into the cathode chamber 2 includes but is not limited to high ammonia-nitrogen industrial wastewater, urine, landfill leachate, sludge digestion liquid, organic wastewater digestion liquid, organic waste digestion liquid, and aquaculture biogas liquid.

[0039] Preferably, low-concentration sodium sulfate brine is injected into the first desalination chamber 3 and the second desalination chamber 4, the auxiliary cathode chamber 5, and the auxiliary anode chamber 6.

[0040] The beneficial technical effect of the present application is that:

[0041] 1. The present application is the first to create a gas permeable membrane electrode with an integrated "anode-hydrophobic microporous membrane base-cathode" structure composed of an anode, a hydrophobic microporous membrane base, and a cathode. The present application utilizes the electrolysis of water to form a local strong base and a strong acid on the surface of the anode and cathode, respectively, for the conversion of free ammonia and the transmembrane absorption of ammonia, respectively, to maintain a high ammonia chemical potential difference across the membrane, remove ammonia from wastewater, and recover ammonia resources, while maintaining the pH of the effluent and the recovered product near neutral, thereby achieving energy saving and efficiency improvement in membrane absorption of ammonia.

[0042] 2. The principle of the present application is shown in Figure 1 . The gas permeable membrane electrode realizes electrochemical membrane absorption of ammonia in a stacked electrochemical recovery of wastewater ammonia system. The cathode electro-adsorbs ammonium in wastewater while generating OH - , forming a surface local high-pH layer that promotes the in-situ conversion of ammonium to free ammonia; the anode generates H + , forming a surface local low-pH layer that in-situ absorbs free ammonia that migrates across the hydrophobic microporous membrane to the anode chamber, converts it to ammonium, and fixes it in the anode solution by electro-repulsion, achieving recovery and concentration of wastewater ammonia; the high chemical potential difference across the membrane formed by the two sides of the gas permeable membrane electrode ensures sufficient power for membrane absorption of ammonia and stabilizes the pH of the effluent and the recovered product near neutral. The application of the present application is for high-ammonia wastewater treatment and ammonia resource recovery.

[0043] 3. Compared with CN110921796A, the hydrophobic microporous membrane in the present application serves as a mass transfer channel for NH3, allowing NH3 generated on the surface of the cathode to be immediately transported to the anode side for absorption, thereby minimizing the mass transfer distance of NH3. Based on the traditional electrolysis of water to produce acid and base, the present application utilizes the generated acid and base in-situ without any external force. The cathode produces base to convert wastewater ammonia to free ammonia, and the anode produces acid to absorb free ammonia that migrates across the membrane; while obtaining byproducts hydrogen and oxygen. BRIEF DESCRIPTION OF DRAWINGS

[0044] Figure 1 is a schematic diagram of the structure and principle of the gas permeable membrane electrode of the present application.

[0045] Figure 2 is a schematic diagram of the principle of the present application applied to a stacked electrochemical recovery of wastewater ammonia system.

[0046] Figure 3 is a two-unit stacked electrochemical recovery of wastewater ammonia system.

[0047] In the figure: 1-anode chamber; 2-cathode chamber; 3-first desalination chamber; 4-second desalination chamber; 5-sub-cathode chamber; 6-sub-anode chamber; 7-hydrophobic microporous membrane substrate; 8-anode; 9-cathode; 10-cation exchange membrane; 11-anion exchange membrane; 12-sub-cathode; 13-sub-anode; 14-anode chamber gas collecting pipe; 15-cathode chamber gas collecting pipe; 16-sub-cathode chamber gas collecting pipe; 17-sub-anode chamber gas collecting pipe; 18-gas pocket 1; 19-gas pocket 2; 20-gas pocket 3; 21-gas pocket 4; 22-wire; 23-wire; 24-power supply.

[0048] Figure 4 Ammonia nitrogen recovery rate and removal rate of the membrane electrode prepared by the electrodeposition method when applied in the electrochemical system.

[0049] Figure 5 Ammonia nitrogen flux of the gas permeable membrane electrode prepared by the electrodeposition method when applied.

[0050] Figure 6 Ammonia nitrogen recovery rate and removal rate of the gas permeable membrane electrode prepared by the phase inversion method when applied.

[0051] Figure 7 pH value of the anode liquid and the cathode liquid when the gas permeable membrane electrode prepared by the phase inversion method is applied. DETAILED DESCRIPTION

[0052] The application will be described in detail below with reference to the drawings and examples. Obviously, the described examples are only a part of the examples of the application, rather than all the examples. Based on the examples in the application, all the other examples obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0053] Example 1: preparation of the gas permeable membrane electrode by the electrodeposition method

[0054] In this example, the anode material and the cathode material are fixed on the polytetrafluoroethylene hydrophobic microporous membrane substrate 7 by the electrodeposition method. The selected anode material is iridium oxide, the cathode material is metal nickel, and the hydrophobic microporous membrane substrate (Membrane Solutions Inc., China) is a PTFE membrane with a PP supporting layer, with a pore size of 0.22 μm and a thickness of 150-190 μm.

[0055] The specific steps are as follows:

[0056] (1) Disperse the carbon nanomaterial in ethanol with a volume ratio of 1:1, and ultrasonic treat for 2 h to prepare a carbon nanomaterial dispersion liquid, which is sprayed on both sides of the hydrophobic microporous membrane substrate 7;

[0057] (2) Preparation of anodic electrodeposition solution: 150 mM IrCl4-H2O solution, deionized water, oxalic acid and hydrogen peroxide were added, the volume ratio of IrCl4-H2O solution, deionized water, oxalic acid and hydrogen peroxide was 3:1:1:1, and stirring and mixing were performed for 10 min, and then NaOH was used to adjust the pH to 10.5 to obtain an anodic electrodeposition solution for the anode 8;

[0058] (3) Preparation of cathodic electrodeposition solution: 150 mM NiSO4-7H2O solution, 25 mM NiCl2-6H2O solution and 500 mM H3BO3 solution were prepared, and the three were mixed, the volume ratio of NiSO4-7H2O solution, NiCl2-6H2O solution and H3BO3 solution was 1:1:2, stirring was performed for 10 min, and then H2SO4 was used to adjust the pH to 2.0 to obtain a cathodic electrodeposition solution for the cathode 9;

[0059] (4) Preparation of hydrophobic microporous membrane substrate-anode: one side of the hydrophobic microporous membrane substrate after spraying the carbon nanomaterial obtained in step 1 was attached to a titanium wire mesh (60 mesh) and immersed in the anodic electrodeposition solution as a working electrode, and a three-electrode electrolytic cell system was used for anodic pre-deposition, a glassy carbon electrode was used as a counter electrode, a saturated calomel electrode was used as a reference electrode, a linear voltammetric scan of 0.2-0.4 V was performed on the system, and the scan rate was 50 mV / s; then a constant voltage (0.6-0.9 V) was applied to the system for IrO2 electrodeposition, the electrodeposition time was 6 h, and then the titanium wire mesh was peeled off from the anode to obtain the anode 8;

[0060] (5) Preparation of hydrophobic microporous membrane substrate-cathode: the other side of the hydrophobic microporous membrane substrate loaded with the anode obtained in step (4) was attached to a stainless steel wire mesh (60 mesh), and the stainless steel wire mesh was immersed in the cathodic electrodeposition solution as a cathode, a foamed nickel electrode was used as a counter electrode, a saturated calomel electrode was used as a reference electrode, and a constant current electrodeposition was performed at 20.4 A / m2, the electrodeposition time was 6 h, and then the stainless steel wire mesh was peeled off from the cathode to obtain the cathode 9. The gas permeable membrane electrode was prepared through the above steps. 2

[0061] Example 2: Preparation of a gas permeable membrane electrode by phase inversion method

[0062] In this example, the anode material and the cathode material were fixed on a polytetrafluoroethylene hydrophobic microporous membrane substrate 7 by a phase inversion method, the selected anode material was nano-nickel oxide, the cathode material was nano-nickel, and the hydrophobic microporous membrane substrate (Membrane Solutions Inc., China) was a PTFE membrane with a PP support layer, the pore size was 0.22 μm, and the thickness was 150-190 μm.

[0063] The specific steps are as follows:

[0064] ​(1) The nano nickel oxide is dispersed in a dimethyl sulfoxide mixed solution of polyvinylidene fluoride and polyvinylpyrrolidone, wherein the volume ratio of the nano nickel oxide, polyvinylidene fluoride, polyvinylpyrrolidone and dimethyl sulfoxide is 1:2:1:1; an appropriate amount of the mixture is uniformly coated on one side of the hydrophobic microporous membrane substrate 7, and the solvent is volatilized by exposing the coated substrate in air for 10 minutes; the coated substrate is then put into distilled water to fix the nano nickel oxide through a phase inversion process, thereby forming the anode 8;

[0065] (2) The nano nickel oxide is dispersed in a dimethyl sulfoxide mixed solution of polyvinylidene fluoride and polyvinylpyrrolidone, wherein the volume ratio of the nano nickel oxide, polyvinylidene fluoride, polyvinylpyrrolidone and dimethyl sulfoxide is 1:2:1:1; an appropriate amount of the mixture is uniformly coated on the other side of the hydrophobic microporous membrane substrate 7, and the solvent is volatilized by exposing the coated substrate in air for 10 minutes; the coated substrate is then put into distilled water to fix the nano nickel oxide through a phase inversion process, thereby forming the cathode 9. The gas permeable membrane electrode is prepared through the above steps.

[0066] Example 3: A stacked electrochemical ammonia nitrogen recovery system for wastewater using the gas permeable membrane electrode of the present application

[0067] This example provides a stacked electrochemical ammonia nitrogen recovery system, the schematic diagram of which is shown in Figure 2 The stacked ammonia nitrogen recovery system comprises a plurality of connected ammonia nitrogen recovery units, each of which comprises an anode chamber and a cathode chamber separated by the gas permeable membrane electrode prepared by the present application, a first desalination chamber separated by a cation exchange membrane is arranged outside the anode chamber, and a second desalination chamber separated by an anion exchange membrane is arranged outside the cathode chamber.

[0068] The other side of the first desalination chamber away from the anode chamber (left side in Figure 2 ) is a vice cathode chamber separated by a cation exchange membrane; the other side of the second desalination chamber away from the cathode chamber (right side in Figure 2 ) is a vice anode chamber separated by an anion exchange membrane. The vice cathode chamber and the vice anode chamber are respectively provided with a vice cathode and a vice anode.

[0069] Further, the vice cathode chamber can serve as the cathode chamber of a second recovery unit adjacent to the left side of the present recovery unit, and the vice anode chamber can serve as the cathode chamber of a third recovery unit adjacent to the right side of the present recovery unit, and so on, thereby forming a stack.

[0070] During system operation, the oxygen generated in the anode chamber is collected by the anode chamber gas collecting pipe into a first gas bag, the hydrogen generated in the cathode chamber is collected by the cathode chamber gas collecting pipe into a second gas bag, the hydrogen generated in the vice cathode chamber is collected by the vice cathode chamber gas collecting pipe into a third gas bag, and the oxygen generated in the vice anode chamber is collected by the vice anode chamber gas collecting pipe into a fourth gas bag.

[0071] The system further comprises external circuit including external wires, power supply; the power supply is used for adjusting the current or voltage of the system. The anode is connected with the cathode through wires, and the auxiliary cathode is connected with the auxiliary anode through wires.

[0072] Example 4: Electrochemical recovery of ammonia-nitrogen in wastewater system using the gas permeable membrane electrode of the present application

[0073] In this embodiment, a two-unit stacked electrochemical recovery of ammonia-nitrogen in wastewater system is provided, which has a structure as shown in Figure 3 The system comprises an anode chamber 1, a cathode chamber 2, a first desalination chamber 3, a second desalination chamber 4, an auxiliary cathode chamber 5, and an auxiliary anode chamber 6.

[0074] The anode chamber 1 and the cathode chamber 2 are separated by the gas permeable membrane electrode, the anode 8 and the cathode 9 of the gas permeable membrane electrode are located on one side of the anode chamber 1 and the cathode chamber 2 respectively, and the substrate 7 of the gas permeable membrane electrode is located between the anode 8 and the cathode 9.

[0075] The other side of the anode chamber 1 is separated from the first desalination chamber 3 by the anion exchange membrane 10, the other side of the cathode chamber 2 is separated from the second desalination chamber 4 by the cation exchange membrane 11; the other side of the first desalination chamber 3 is separated from the auxiliary cathode chamber 5 by the cation exchange membrane 11, and the other side of the second desalination chamber 4 is separated from the auxiliary anode chamber 6 by the anion exchange membrane 10.

[0076] The auxiliary cathode chamber 5 and the auxiliary anode chamber 6 are respectively provided with an auxiliary cathode 12 and an auxiliary anode 13.

[0077] The gas bag 1 (18) is connected with the anode chamber 1 by the anode chamber gas collecting pipe 14 for collecting oxygen; the gas bag 2 (19) is connected with the cathode chamber 2 by the cathode chamber gas collecting pipe 15 for collecting hydrogen; the gas bag 3 (20) is connected with the auxiliary cathode chamber 5 by the auxiliary cathode chamber gas collecting pipe 16 for collecting hydrogen; and the gas bag 4 (21) is connected with the auxiliary anode chamber 6 by the auxiliary anode chamber gas collecting pipe 17 for collecting oxygen.

[0078] The external circuit comprises external wires 22, 23, and a power supply 24; the power supply 24 is used for adjusting the current or voltage of the system. The anode 8 is connected with the cathode 9 through the wire 22. The auxiliary cathode 12 is connected with the auxiliary anode 13 through the wire 23.

[0079] The anion exchange membrane 10 is selected from at least one of quaternary amine type, pyridine quaternary amine type, primary amine type, secondary amine type, tertiary amine type, and mixed amine type membrane; and the cation exchange membrane 11 is selected from at least one of sulfonic acid type, phosphoric acid type, phosphonic acid type, carboxylic acid type, phenol type, and phenol sulfonic acid membrane.

[0080] The material of the auxiliary cathode 12 is stainless steel mesh (60 mesh), and the material of the auxiliary anode 13 is iridium titanium mesh electrode (60 mesh).

[0081] The anode chamber 1 is injected with a low-concentration ammonium sulfate electrolyte solution. The high-ammonia-nitrogen wastewater injected into the cathode chamber 2 includes but is not limited to high-ammonia-nitrogen industrial wastewater, urine, landfill leachate, sludge digestion liquid, organic wastewater digestion liquid, organic waste digestion liquid, aquaculture biogas liquid, etc.

[0082] The first desalination chamber 3, the second desalination chamber 4, the auxiliary cathode chamber 5, and the auxiliary anode chamber 6 are injected with a low-concentration sodium sulfate brine.

[0083] II. The operation principle of the electrochemical wastewater ammonia-nitrogen recovery system is as follows:

[0084] Under the action of the power supply 24, a local strong base and a strong acid are formed on the surfaces of the anode and the cathode, respectively, for ammonia conversion and transmembrane absorption, to remove the ammonia-nitrogen in the wastewater and recover the ammonia-nitrogen resource, maintain the pH of the effluent and the recovered product near neutral, and realize the reduction of the consumption and the increase of the efficiency of the membrane absorption of ammonia.

[0085] III. The working mode of the gas-permeable membrane electrode applied to the recovery of wastewater ammonia-nitrogen is as follows:

[0086] First, according to the target product of the ammonia-nitrogen to be recovered, a low-concentration ammonium sulfate electrolyte is injected into the anode chamber 1, ammonia-nitrogen wastewater is injected into the cathode chamber 2, and corresponding high-concentration brine is also injected into the first desalination chamber 3, the second desalination chamber 4, the auxiliary cathode chamber 5, and the auxiliary anode chamber 6;

[0087] Then, the system is started to operate by providing direct current to the system through the power supply 24.

[0088] Finally, after the system is normally operated for a period of time, the power supply is turned off to stop the power supply, the nitrogen recovery product is harvested from the anode chamber 1, pure oxygen is harvested from the gas bag 1 (18) and the gas bag 4 (21), and pure hydrogen is harvested from the gas bag 2 (19) and the gas bag 3 (20). The treatment of high-ammonia-nitrogen wastewater and the recovery of ammonia-nitrogen resource are realized, and the by-products hydrogen and oxygen are obtained at the same time.

[0089] Application Example 1:

[0090] In this application example, the gas-permeable membrane electrode prepared by the electrodeposition method of Example 1 and the electrochemical wastewater ammonia-nitrogen recovery system of Example 4 are used for wastewater ammonia-nitrogen removal.

[0091] Among them, the cation exchange membrane is CMI-7000 (Membranes International Inc., New Jersey, USA), and the anion exchange membrane is AMI-7001 (Membranes International Inc., New Jersey, USA). The material of the auxiliary cathode is a stainless steel mesh (60 mesh), and the material of the auxiliary anode is an iridium-titanium mesh electrode (60 mesh).

[0092] The anode chamber 1 was added with 20 mL of (NH4)2SO4 solution with a concentration of 6 mM; the cathode chamber 2 was added with 20 mL of (NH4)2SO4 solution with a concentration of 400 mM; the first desalination chamber 3 and the second desalination chamber 4 were both added with 20 mL of Na2SO4 solution with a concentration of 500 mM as electrolyte; the auxiliary cathode chamber 5 and the auxiliary anode chamber 6 were both added with 20 mL of Na2SO4 solution with a concentration of 150 mM.

[0093] After the electrolyte was injected into each chamber, the system was operated in a constant current mode of 0.1 A for 4 h. Figure 4 The ammonia nitrogen recovery rate and removal rate of the system are shown in the figure. It can be seen from the figure that after the system was operated for 4 h, the ammonia nitrogen recovery rate was 90.7 ± 0.4%, and the removal rate was 92.4 ± 0.2%, which had little difference.

[0094] Figure 5 The ammonia nitrogen flux change of the membrane electrode is shown. The system maintained a high level of ammonia nitrogen flux during operation. The average ammonia nitrogen flux was 410 ± 40 gN / (m 2 ·d) at 0.5 h, reached a maximum value of 515 ± 68 gN / (m 2 ·d) at 2 h, and decreased to 366 ± 8 gN / (m 2 ·d) at 4 h. The average ammonia nitrogen flux was above 360 gN / (m 2 ·d) during the entire operation process.

[0095] After the system was operated for 4 h, the external power supply was turned off, the nitrogen recovery product was harvested from the anode chamber, oxygen was harvested from the gas bag 1 and the gas bag 4, and hydrogen was harvested from the gas bag 2 and the gas bag 3.

[0096] Application Example 2

[0097] In this application example, the gas permeable membrane electrode prepared by the phase inversion method of Example 2 and the electrochemical recovery of wastewater ammonia nitrogen system of Example 4 were used to remove ammonia nitrogen from wastewater. The materials used for each component were the same as in Application Example 1.

[0098] The anode chamber 1 was added with 20 mL of (NH4)2SO4 solution with a concentration of 6 mM; the cathode chamber 2 was added with 20 mL of (NH4)2SO4 solution with a concentration of 400 mM; the first desalination chamber 3 and the second desalination chamber 4 were both added with 20 mL of Na2SO4 solution with a concentration of 500 mM as electrolyte; the auxiliary cathode chamber 5 and the auxiliary anode chamber 6 were both added with 20 mL of Na2SO4 solution with a concentration of 150 mM.

[0099] After the electrolyte was injected into each chamber, the system was operated in a constant current mode of 0.96 A for 2 h. Figure 6 The ammonia nitrogen recovery rate and removal rate of the system are shown in the figure. It can be seen from the figure that after the system was operated for 2 h, the ammonia nitrogen recovery rate could reach 88.4 ± 4.7%, and the removal rate was 89.5 ± 5.3%, which was basically consistent with the recovery rate.

[0100] Figure 7 The change of bulk pH value of the solution in cathode chamber and anode chamber during the system running is shown. The pH value of cathode chamber is basically below 9.25 in the first 1h of system running, but there is still ammonia nitrogen recovery in this stage, which indicates that NH4 + The main driving force of the conversion of -N to free NH3 is the local high pH value on the cathode surface, and the bulk pH value of the cathode chamber can finally reach about 10. The bulk pH value of the anode chamber is reduced to about 2 at 0.5h and finally to about 1.5.

[0101] The external power is turned off after the system running for 2h, and the nitrogen recovery product is harvested from the anode chamber, the oxygen is harvested from gas bag 1 and gas bag 4, and the hydrogen is harvested from gas bag 2 and gas bag 3.

[0102] Although the embodiments of the present application have been disclosed as above, it is not limited to the use listed in the specification and embodiments, and can be fully applied to various fields suitable for the present application. For those skilled in the art, for ordinary skilled personnel in the art, various changes, modifications, replacements and variations can be made to these embodiments without departing from the principles and spirits of the present application, and therefore the present application is not limited to specific details without departing from the general concept defined by the claims and equivalent ranges.

Claims

1. Use of a gas permeable membrane electrode, characterized in that The air-breathing membrane electrode is used for high-ammonia-nitrogen sewage treatment and ammonia-nitrogen resource recovery, and realizes electrochemical membrane absorption of ammonia in a stacked electrochemical recovery system of sewage ammonia nitrogen; The air-breathing membrane electrode comprises a hydrophobic microporous membrane substrate and an anode and a cathode fixed on two sides of the substrate, respectively; The material of the hydrophobic microporous membrane substrate is at least one of polytetrafluoroethylene, polyvinylidene fluoride, polypropylene, polyvinyl chloride, polydimethylsiloxane and ceramic; The material of the anode is at least one of platinum, palladium, carbon, iridium oxide, tantalum oxide and titanium oxide; The material of the cathode is at least one of platinum, palladium, carbon, nickel, iron and stainless steel; The stacked electrochemical recovery system of sewage ammonia nitrogen comprises a plurality of connected ammonia-nitrogen recovery units, each recovery unit comprising an anode chamber and a cathode chamber separated by an air-breathing membrane electrode, an outside of the anode chamber being provided with a desalination chamber separated by an anion exchange membrane, and an outside of the cathode chamber being provided with a desalination chamber separated by a cation exchange membrane, and the number of units is enlarged or stacked repeatedly according to the processing scale; When the recovery unit is two units, the electrochemical recovery system of sewage ammonia nitrogen comprises an anode chamber (1), a cathode chamber (2), a first desalination chamber (3), a second desalination chamber (4), a secondary cathode chamber (5) and a secondary anode chamber (6); The anode chamber (1) and the cathode chamber (2) are separated by the air-breathing membrane electrode, an anode (8) and a cathode (9) of the air-breathing membrane electrode are located on one side of the anode chamber (1) and the cathode chamber (2), respectively, and a substrate (7) of the air-breathing membrane electrode is located between the anode (8) and the cathode (9); The other side of the anode chamber (1) is separated from the first desalination chamber (3) by an anion exchange membrane (10), the other side of the cathode chamber (2) is separated from the second desalination chamber (4) by a cation exchange membrane (11), the other side of the first desalination chamber (3) is separated from the secondary cathode chamber (5) by the cation exchange membrane (11), and the other side of the second desalination chamber (4) is separated from the secondary anode chamber (6) by the anion exchange membrane (10); Electrolyte in the anode chamber (1) is ammonium sulfate solution, electrolyte in the cathode chamber (2) is high-ammonia-nitrogen sewage, and electrolyte in the first desalination chamber (3), the second desalination chamber (4), the secondary cathode chamber (5) and the secondary anode chamber (6) is sodium sulfate brine; The system further comprises an external circuit, which comprises external leads and a power supply; the power supply is used for adjusting current or voltage of the system; the anode is connected to the cathode through the leads, and the secondary cathode is connected to the secondary anode through the leads.

2. Use according to claim 1, characterized in that, The method for fixing the anode and the cathode on two sides of the hydrophobic microporous membrane substrate comprises electrochemical deposition and phase inversion.

3. Use according to claim 2, characterized in that, The electrochemical deposition method comprises the following steps: S1, dispersing carbon nanomaterial in ethanol to prepare a carbon nanomaterial dispersion liquid, and spraying the carbon nanomaterial dispersion liquid to two sides of the hydrophobic microporous membrane substrate; S2, preparation of anode electrodeposition solution: mixing and stirring anode material and anode solution and adjusting pH to 9.0-12.0; S3, preparation of cathode electrodeposition solution: mixing and stirring cathode material and cathode solution and adjusting pH to 1.0-4.0; S4, hydrophobic microporous membrane base-anode preparation: the side of the hydrophobic microporous membrane base after spraying the carbon nanomaterial obtained in step S1 is pasted with a titanium wire mesh, and the titanium wire mesh is immersed in the anodic electrodeposition solution obtained in step S2 as a working electrode, an anodic pre-deposition is carried out in a three-electrode electrolytic cell system, a glassy carbon electrode is used as a counter electrode, and a saturated calomel electrode is used as a reference electrode, an anodic electrodeposition is carried out, and after the end, the titanium wire mesh is peeled off from the anode; S5, hydrophobic microporous membrane base-cathode preparation: the other side of the hydrophobic microporous membrane base loaded with the anode obtained in step S4 is pasted with a stainless steel wire mesh, and the stainless steel wire mesh is immersed in the cathodic electrodeposition solution obtained in step S3 as a working electrode, a foamed nickel electrode is used as a counter electrode, and a saturated calomel electrode is used as a reference electrode, a cathodic electrodeposition is carried out, and after the end, the stainless steel wire mesh is peeled off from the cathode.

4. Use according to claim 3, characterized in that, The volume ratio of the carbon nanomaterial to ethanol in step S1 is 1:1-2.

5. Use according to claim 3, characterized in that, The volume ratio of the anode material to the anode solution in step S2 is 1:1-2; the raw materials of the anode solution are deionized water, oxalic acid, and hydrogen peroxide; the volume ratio of the deionized water, oxalic acid, and hydrogen peroxide is 1:0.5-1.5:0.5-1.5; The volume ratio of the cathode material to the cathode solution in step S3 is 1:1-2; the raw material of the cathode solution is H3BO3.

6. Use according to claim 2, characterized in that, The phase inversion method comprises the following steps: M1, hydrophobic microporous membrane base-anode preparation: the anode material is dispersed in a dimethyl sulfoxide mixed solution of polyvinylidene fluoride and polyvinylpyrrolidone, then the mixture is uniformly coated on one side of the hydrophobic microporous membrane base, exposed to air for a short time to volatilize the solvent, and then the coated base is immersed in distilled water to fix the anode material through a phase inversion process; M2, hydrophobic microporous membrane base-cathode preparation: the cathode material is dispersed in a dimethyl sulfoxide mixed solution of polyvinylidene fluoride and polyvinylpyrrolidone, then the mixture is uniformly coated on the other side of the hydrophobic microporous membrane base, exposed to air for a short time to volatilize the solvent, and then the coated base is immersed in distilled water to fix the cathode material through a phase inversion process.

7. Use according to claim 6, characterized in that, The volume ratio of the anode material, polyvinylidene fluoride, polyvinylpyrrolidone, and dimethyl sulfoxide in step M1 is 1:1-2:1-2:1-2; The volume ratio of the cathode material, polyvinylidene fluoride, polyvinylpyrrolidone, and dimethyl sulfoxide in step M2 is 1:1-2:1-2:1-2.

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