Membrane-based electro-catalysis nanofluid reactor for purifying sewage containing nitrate nitrogen, purification system, purification method and application of membrane-based electro-catalysis nanofluid reactor

Abstract

The invention belongs to the technical field of sewage treatment, and particularly relates to a membrane-based electro-catalysis nanofluid reactor for purifying sewage containing nitrate nitrogen, a purification system, a purification method and application of the membrane-based electro-catalysis nanofluid reactor. The membrane-based electro-catalysis nano-fluid reactor comprises a reference electrode, a conductive nano-pore membrane and a counter electrode which form a three-electrode system, the conductive nanopore membrane is a place where sewage containing nitrate nitrogen is subjected to electrocatalytic reduction. According to the invention, the conductive nano-pore membrane is used as a main place for electrocatalytic reduction of sewage containing nitrate nitrogen, nitrate ions collide with active catalytic sites in pores of the conductive nano-pore membrane and are degraded into harmless product nitrogen under the action of an electric field, so that short hydraulic retention time is realized, and the sewage treatment efficiency is improved. The removal efficiency of nitrate ions in the sewage is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage treatment, and in particular relates to a membrane-based electrocatalytic nanofluid reactor for purifying sewage containing nitrate nitrogen, a purification system, a purification method and applications thereof. Background Art

[0002] Due to its advantages such as high efficiency and no pollution, electrochemical reduction has attracted great attention in the field of nitrate nitrogen removal. In recent years, the research work on electrochemical reduction has been aimed at developing highly active electrodes and efficient reactors. However, electrochemical reduction for nitrate nitrogen removal still faces the problem of obtaining high activity and selectivity in the electrochemical reduction process.

[0003] The catalytic activity and selectivity of the electrode are improved by selecting and optimizing the catalytic components. Commonly used catalysts include metal oxides and metals (monometallic or bimetallic). Metal oxide catalysts exhibit strong catalytic reduction activity. Su et al. reported the electrochemical reduction of nitrate using Co3O4 or Fe3O4 loaded on a titanium cathode, in which the nitrate removal rate and total nitrogen (TN) removal rate reached 99% and 65%, respectively [Su, L., Li, K., Zhang, H., Fan, M., Ying, D., Sun, T., Wang, Y., Jia, J., 2017. Electrochemical nitrate reduction by using a novel Co3O4 / Ti cathode. Water Res. 120, 1–11]. Kim et al. used a TiO2 / Ti cathode and obtained a nitrate removal rate of 97.8% with a removal rate of 0.0391 mg L -1 min -1[Kim, DE, Pak, D., 2019. Ti plate with TiO2 nanotube arrays as a novel cathode for nitrate reduction. Chemosphere 228, 611–618]. Some studies on single metals such as Rh, Pt, Cu, Al, Ni, Fe, Ti and Sn also achieved high electrocatalytic activity. However, noble metals such as Pt perform poorly in neutral media [Duca, M., Weeks, JR, Fedor, JG, Weiner, JH, Vincent, KA, 2015. Combining noble metals and enzymes for relay cascade electrocatalysis of nitrate reduction to ammonia at neutral pH. Chem ElectroChem 2 (8), 1086–1089], while non-noble metals such as Cu will undergo passivation or metal dissolution during the catalytic process [Hasnat, MA, Ben Aoun, S., Rahman, MM, Asiri, AM, Mohamed, N., 2015. Lean Cuimmobilized Pt and Pd films / H+ conducting membrane assemblies: relative electrocatalytic nitrate reduction activities. J. Ind. Eng. Chem. 28, 131–137]. Bimetallic catalysts exhibit higher catalytic activity than single metal catalysts in nitrate electrocatalytic reactions. In bimetallic systems, catalytic metals (such as Cu, Sn, Ag, In, and Ni) can provide NO3 - and NO2 - catalytic sites, while noble metals (such as Pd, Pt and Rh) further convert NO2 - Reduction to N2 and NH4 +[Chen, M., Wang, H., Zhao, Y., Luo, W., Li, L., Bian, Z., Wang, L., Jiang, W., Yang, J., 2018. Achieving high-performance nitrate electrocatalysis with PdCunanoparticles confined in nitrogen-doped carbon coralline. Nanoscale 10(40), 19023–19030]. According to the study of bimetallic catalytic performance, the Cu-Pd catalytic system has high catalytic activity. Fan et al. used Cu-Pd alloy to carry out nitrate electroreduction experiments, and the nitrate conversion rate reached 28.7% and the nitrogen selectivity was 74% [Fan, J., Xu, H., Lv, M., Wang, J., Teng, W., Ran, X., Gou, X., Wang, X., Sun, Y., Yang, J., 2017. Mesoporous carbon confined palladium–copper alloy composites for highperformance nitrogen selective nitrate reduction electrocatalysis. New J. Chem. 41(6), 2349–2357]. Zhang et al. obtained better results (nitrogen selectivity of 80.37% and conversion of 100%) using Pd-Cu / γAl2O3 catalyst [Zhang, ZQ, Xu, YP, Shi, WX, Wang, W., Zhang, RJ, Bao, X., Zhang, B., Li, L., Cui, FY, 2016. Electrochemical-catalytic reduction of nitrate over Pd–Cu / γAl2O3 catalyst in cathode chamber: enhanced removal efficiency and N2 selectivity. Chem. Eng. J. 290, 201–208].Su et al. showed that Cu-Pd catalyst supported on stainless steel can achieve 100% nitrate conversion and 43% nitrogen selectivity [Su, JF, Ruzybayev, I., Shah, I., Huang, CP, 2016. The electrochemical reduction of nitrate over micro-architectured metal electrodes with stainless steel scaffold. Appl. Catal. B Environ. 180, 199–209]. Although bimetallic catalysts have shown high activity or selectivity in nitrate removal, it remains challenging to have both high activity and high selectivity.

[0004] In addition to the influence of electrode activity, the type of reactor also has an important influence on the electrocatalytic reduction process. Electrochemical reactors include flow-through and flow-through types. Flow-through reactors are based on dense electrodes, and the water flow direction is parallel to the electrode surface. However, the efficiency of reactors using dense electrodes is not ideal because of their limited specific surface area and few electrocatalytic active sites. In order to overcome this shortcoming, porous electrodes such as carbon cloth, carbon fiber and granular activated carbon reactors were introduced to increase the surface area of ​​their electrodes. Chen et al. reported that Cu-Pd catalyst was loaded in nitrogen-doped porous carbon for electrocatalytic reduction to remove nitrate nitrogen from water, with a single-pass removal rate of nitrate nitrogen (95%) and nitrogen selectivity (80%) [Chen, M., Wang, H., Zhao, Y., Luo, W., Li, L., Bian, Z., Wang, L., Jiang, W., Yang, J., 2018. Achieving high-performance nitrate electrocatalysis with PdCu nanoparticles confined in nitrogen-doped carbon coralline. Nanoscale 10(40), 19023–19030]. However, the efficiency of this reactor is affected by diffusion within the pores. In addition, Geyan et al. also designed an electrocatalytic membrane reactor for nitrate removal, with Cu-Pd catalyst loaded on Magneli phase TiO2, showing low energy consumption (0.12 kWhmol -1 , for 100mMNO3 -), 67% nitrate conversion, the main products are N2 and N2O, with selectivities of 56% and 43%, respectively [Gayen, P., Spataro, J., Avasarala, S., Ali, AM, Cerrato, JM, Chaplin, BP, 2018. Electrocatalytic reduction of nitrate using magnetic phase TiO2 reactive electrochemical membranes doped with Pd-based catalysts. Environ. Sci. Technol. 52(16), 9370–9379]. Nitrate reduction is a complex reaction process that produces a variety of intermediates or other final products, including NO2, NO2 - , NO, N2O, NH2OH, NH2NH2, H2N2O3, HNO (or its dimer H2N2O2), H2NO, NH2NO2, NH3 and NH4 + The high selectivity of nitrogen depends on direct reduction or indirect reduction such as adding a reducing agent (such as Cl - ). Direct reduction mainly involves electron transfer and hydrogen reduction processes, where nitrate is adsorbed on the electrode surface and then reduced to nitrite (rate-determining step). Then, nitrite is reduced to NO, a step that determines the formation of the final product (NH4 + or N2). In addition, metal catalysts like Fe or Cu lose electrons and promote the reduction of nitrates. In addition, nitrates can also promote the electroreduction process through adsorbed hydrogen (H(ads)). The presence of H(ads) favors the formation of NH bonds, thereby forming NH4 + Hydrogen can assist in reducing nitrates to nitrogen because hydrogen breaks the NO bond to form nitrogen. However, in conventional reactors, this method cannot completely reduce nitrates to nitrogen, has limited selectivity, generally not exceeding 60%, and requires the addition of an oxidant. In the electrochemical process, NO3 - Converted to NH4 at the cathode + The reaction of Cl - The ions can be oxidized at the anode to form Cl2. Then, Cl2 reacts chemically with water to form ClO - , which can effectively convert NH4 + Oxidation to N2. However, the addition of NaCl produces Cl2, which can cause secondary pollution. Therefore, a new method that does not require additives but still achieves high nitrate conversion and high nitrogen selectivity is essential. Summary of the invention

[0005] Problem to be solved by the present invention: When removing nitrate nitrogen from water, the existing sewage treatment method has the problem that the electrochemical reduction process cannot simultaneously obtain a high nitrate conversion rate and a high nitrogen selectivity.

[0006] In order to solve the problems existing in the prior art, the present invention provides a membrane-based electrocatalytic nanofluid reactor, a purification system, a purification method and applications thereof for purifying wastewater containing nitrate nitrogen.

[0007] Specifically, the present invention provides the following technical solutions:

[0008] The present invention provides a membrane-based electrocatalytic nanofluid reactor for purifying sewage containing nitrate nitrogen. The membrane-based electrocatalytic nanofluid reactor comprises:

[0009] An external power source for providing an electric field;

[0010] A reference electrode, the reference electrode, the conductive nanoporous membrane and the counter electrode form a three-electrode system;

[0011] The conductive nanoporous membrane is connected to the external power source and is used as a cathode. The conductive nanoporous membrane is the place where the wastewater containing nitrate nitrogen undergoes electrocatalytic reduction, wherein the wastewater containing nitrate nitrogen undergoes an electrocatalytic reduction chemical reaction in the pores of the conductive nanoporous membrane;

[0012] The counter electrode is disposed on the upstream side or the downstream side of the conductive nanoporous membrane and connected to an external power source to serve as an anode;

[0013] The chemical reaction equations of electrocatalytic reduction are shown in (1)-(5):

[0014] 2NO3 - (ads)+5H2→N2+2OH - +4H2O(2)

[0015] NO3 - (ads)+H2→NO2 - +H2O(3)

[0016] 2NO2 - (ads)+2H + +3H2→N2+H2O(4)

[0017] 2NO3 - +8H2→2NH4 + +4OH - +2H2O(5).

[0018] Preferably, the membrane-based electrocatalytic nanofluid reactor further comprises: epoxy glue, which covers one end of the conductive nanoporous membrane to seal the membrane tube of the conductive nanoporous membrane, preferably, the epoxy glue is PKM12C-1 epoxy glue;

[0019] The cation exchange membrane is used to separate the anode and the cathode to prevent the reduction product after electrocatalytic reduction from being oxidized. Preferably, the reduction product is anion and / or gas, and more preferably, the reduction product is NO2 - and / or nitrogen; preferably, the cation exchange membrane is a Nafion 117 cation exchange membrane.

[0020] Preferably, the conductive nanoporous membrane is a porous conductive membrane.

[0021] Preferably, the porous conductive membrane is a surface-modified porous conductive membrane and / or a porous conductive membrane with catalytically active components loaded in the pores;

[0022] More preferably, the surface-modified porous conductive membrane is a surface-modified porous conductive membrane filled with activated carbon;

[0023] More preferably, the porous conductive membrane having catalytically active components loaded in the pores is a porous conductive membrane having catalytically active components loaded in the pores and filled with activated carbon;

[0024] Most preferably, the catalytically active component is a bimetallic palladium-copper catalyst, or a diatomic palladium-copper catalyst.

[0025] Preferably, the porous conductive film is one or more of a porous metal film, a porous carbon film, a porous carbide film, a porous metal oxide film, a porous polymer film and a porous conductive composite film;

[0026] Preferably, the porous metal membrane is a titanium membrane;

[0027] Preferably, the porous carbon membrane is one of a tubular carbon membrane and a flat carbon membrane, and more preferably, the porous carbon membrane is a tubular carbon membrane.

[0028] Preferably, the average pore size of the tubular carbon membrane is 4 to 660 nm; preferably, the average pore size of the tubular carbon membrane is 4 to 430 nm, and more preferably, the average pore size of the tubular carbon membrane is 4 to 8.3 nm.

[0029] Preferably, the loading amount of the bimetallic palladium-copper catalyst is 0.01-1 wt % based on the weight of the tubular carbon membrane.

[0030] Preferably, the loading amount of the diatomic palladium-copper catalyst is 0.001-0.1 wt % based on the weight of the tubular carbon membrane.

[0031] Preferably, the reference electrode is a mercuric oxide electrode in an alkaline electrolyte, or a saturated calomel electrode in a neutral or acidic electrolyte; preferably, the alkaline electrolyte is: 0.05-1M sodium hydroxide solution, preferably, the neutral electrolyte is 0.05-1M sodium sulfate solution.

[0032] Preferably, the conductive nanoporous membrane is electrically connected to an external power source to serve as a cathode.

[0033] Preferably, the operating voltage of the external power supply is -10 to -2 V vs SCE, preferably -4 to -2 V vs SCE, and more preferably -4 to -3 V vs SCE.

[0034] Preferably, the counter electrode is arranged on the upstream side or the downstream side close to the conductive nanoporous membrane according to the direction in which the wastewater containing nitrate nitrogen passes through the conductive nanoporous membrane.

[0035] Preferably, the counter electrode is one or more of a metal, an intermetallic compound, a carbide, a carbon electrode and a conductive nanoporous membrane; preferably, the counter electrode is one or more of a platinum electrode, stainless steel, a graphite plate and a carbon electrode; more preferably, the counter electrode is a platinum electrode.

[0036] Preferably, the nitrate nitrogen concentration in the nitrate nitrogen-containing wastewater is 1-1000 mM, preferably, the concentration is 40-70 mM.

[0037] Beneficial effects of the present invention:

[0038] (1) The membrane-based electrocatalytic nanofluid reactor for purifying wastewater containing nitrate nitrogen provided by the present invention couples the confinement effect of the pores of the conductive nanoporous membrane and the electric field effect of the electrocatalytic process. Specifically, the conductive nanoporous membrane is used as the main place for electrocatalytic reduction of wastewater containing nitrate nitrogen. When the wastewater containing nitrate nitrogen flows through the pores of the conductive nanoporous membrane, the nitrate ions in the wastewater collide with the active catalytic sites in the pores of the conductive nanoporous membrane. Under the action of the electric field, the nitrate ions are degraded into harmless nitrogen gas, thereby achieving a shorter hydraulic retention time and improving the removal efficiency of nitrate ions in wastewater.

[0039] (2) The present invention provides a membrane-based electrocatalytic nanofluid reactor for purifying wastewater containing nitrate nitrogen. The conductive nanoporous membrane in the membrane-based electrocatalytic nanofluid reactor is a tubular carbon membrane with an average pore size of 4 to 660 nm. When the wastewater containing nitrate nitrogen flows through the pores of the conductive nanoporous membrane, the contact opportunity between the pollutants and the active catalytic sites in the pores of the conductive nanoporous membrane is increased, thereby improving the "electrode area / number of pollutants" ratio and improving the efficiency of the single-pass electrocatalytic reduction reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 Schematic diagram of the principle of the membrane-based electrocatalytic nanofluid reactor provided for Examples 1-14; wherein, 1-external power supply, 2-reference electrode, 3-conductive nanoporous membrane, 4-epoxy glue, 5-counter electrode, 6-cation exchange membrane.

[0041] Figure 2 A purification system for removing nitrate nitrogen from water provided in Examples 1-14, wherein: 1-external power supply, 2-reference electrode, 3-conductive nanoporous membrane, 4-epoxy glue, 5-counter electrode, 6-cation exchange membrane, 7-mechanical stirring device; 8-cathode tank; 9-anode tank; 10-pressure sensor; 11-peristaltic pump; 12-purification tank.

[0042] Figure 3 Schematic diagram of nitrate ions being degraded into nitrogen after colliding with the pore wall in a single pore of a tubular carbon membrane loaded with catalytically active components.

[0043] Figure 4 Figure 1. Tubular carbon membrane for supporting catalytically active components is filled with activated carbon in the membrane tube.

[0044] Figure 5 The sewage treatment reactor for removing nitrate nitrogen from water of comparative example 1, wherein: 1 is an external power supply, 2 is a reference electrode, 3 is a conductive nanoporous membrane, 5 is a counter electrode, 13 is a magneton, 14 is a magnetic stirrer, and 15 is a reaction tank. DETAILED DESCRIPTION

[0045] In order to better understand the above technical solution, the technical solution of the present invention is clearly and completely explained in conjunction with the specific implementation method below. It should be noted that the content in the specific implementation method is only a specific implementation and explanation of the technical solution of the present invention, and should not be understood as limiting the scope of protection of the present invention.

[0046] It should be noted that the conductive nanoporous membrane, the counter electrode and the reference electrode are respectively connected to the external power supply to form a current loop with the wastewater containing nitrate nitrogen, and then the electric field is generated by the external power supply to cause an electrocatalytic reduction process. The conductive nanoporous membrane is used as the cathode, the counter electrode is used as the anode, and a cation exchange membrane is used to separate the anode and the cathode, allowing only cations to pass through to prevent the generated reduction products from being oxidized again.

[0047] When removing nitrate nitrogen from water, the existing sewage treatment method has the problem that the electrochemical reduction process cannot simultaneously obtain a high nitrate conversion rate and a high nitrogen selectivity.

[0048] In order to solve the problems existing in the prior art, the present invention provides a membrane-based electrocatalytic nanofluid reactor, a purification system, a purification method and applications thereof for purifying wastewater containing nitrate nitrogen.

[0049] Specifically, the present invention provides the following technical solutions:

[0050] 1.1. A membrane-based electrocatalytic nanofluid reactor for purifying wastewater containing nitrate nitrogen, characterized in that the membrane-based electrocatalytic nanofluid reactor comprises:

[0051] An external power source for providing an electric field;

[0052] A reference electrode, the reference electrode, the conductive nanoporous membrane and the counter electrode form a three-electrode system;

[0053] The conductive nanoporous membrane is connected to the external power source and is used as a cathode. The conductive nanoporous membrane is the place where the wastewater containing nitrate nitrogen undergoes electrocatalytic reduction, wherein the wastewater containing nitrate nitrogen undergoes an electrocatalytic reduction chemical reaction in the pores of the conductive nanoporous membrane;

[0054] The counter electrode is disposed on the upstream side or the downstream side of the conductive nanoporous membrane and connected to an external power source to serve as an anode;

[0055] The chemical reaction equations of electrocatalytic reduction are shown in (1)-(5):

[0056] 2NO3 - (ads)+5H2→N2+2OH - +4H2O(2)

[0057] NO3 - (ads)+H2→NO2 - +H2O(3)

[0058] 2NO2 - (ads)+2H + +3H2→N2+H2O(4)

[0059] 2NO3 - +8H2→2NH4 + +4OH - +2H2O(5).

[0060] 1.2. The membrane-based electrocatalytic fluid reactor according to technical solution 1.1 is characterized in that the membrane-based electrocatalytic nanofluid reactor further comprises:

[0061] Epoxy glue, which covers one end of the conductive nanoporous membrane and is used to seal the membrane tube of the conductive nanoporous membrane. Preferably, the epoxy glue is PKM12C-1 epoxy glue;

[0062] The cation exchange membrane is used to separate the anode and the cathode to prevent the reduction product after electrocatalytic reduction from being oxidized. Preferably, the reduction product is anion and / or gas, and more preferably, the reduction product is NO2 - and / or nitrogen; preferably, the cation exchange membrane is a Nafion 117 cation exchange membrane.

[0063] 1.3. The membrane-based electrocatalytic fluid reactor according to technical solution 1.1, characterized in that the conductive nanoporous membrane is a porous conductive membrane;

[0064] Preferably, the porous conductive membrane is a surface-modified porous conductive membrane and / or a porous conductive membrane with catalytically active components loaded in the pores;

[0065] More preferably, the surface-modified porous conductive membrane is a surface-modified porous conductive membrane filled with activated carbon;

[0066] More preferably, the porous conductive membrane having catalytically active components loaded in the pores is a porous conductive membrane having catalytically active components loaded in the pores and filled with activated carbon;

[0067] Most preferably, the catalytically active component is a bimetallic palladium-copper catalyst, or a diatomic palladium-copper catalyst.

[0068] 1.4. The membrane-based electrocatalytic nanofluid reactor according to technical solution 1.3 is characterized in that the porous conductive membrane is one or more of a porous metal membrane, a porous carbon membrane, a porous carbide membrane, a porous metal oxide membrane, a porous polymer membrane and a porous conductive composite membrane;

[0069] Preferably, the porous metal membrane is a titanium membrane;

[0070] Preferably, the porous carbon membrane is one of a tubular carbon membrane and a flat carbon membrane, and more preferably, the porous carbon membrane is a tubular carbon membrane.

[0071] 1.5. The membrane-based electrocatalytic nanofluid reactor according to technical solution 1.4 is characterized in that the average pore size of the tubular carbon membrane is 4 to 660 nm; preferably, the average pore size of the tubular carbon membrane is 4 to 430 nm, and more preferably, the average pore size of the tubular carbon membrane is 4 to 8.3 nm.

[0072] 1.6. The membrane-based electrocatalytic nanofluid reactor according to technical solution 1.5 is characterized in that the loading amount of the bimetallic palladium-copper catalyst is 0.01-1wt% based on the weight of the tubular carbon membrane.

[0073] 1.7. The membrane-based electrocatalytic nanofluid reactor according to technical solution 1.5 is characterized in that the loading amount of the diatomic palladium-copper catalyst is 0.001-0.1wt% based on the weight of the tubular carbon membrane

[0074] 1.8. A membrane-based electrocatalytic nanofluid reactor according to any one of technical solutions 1.1-1.7, characterized in that a mercuric oxide electrode is used as the reference electrode under an alkaline electrolyte, or a saturated calomel electrode is used as the reference electrode under a neutral or acidic electrolyte; preferably, the alkaline electrolyte is: 0.05~1M sodium hydroxide solution, preferably, the neutral electrolyte is 0.05~1M sodium sulfate solution.

[0075] 1.9. The membrane-based electrocatalytic nanofluid reactor according to any one of technical solutions 1.1-1.8 is characterized in that the conductive nanoporous membrane is electrically connected to an external power source to serve as a cathode.

[0076] 1.10. The membrane-based electrocatalytic fluid reactor according to any one of technical solutions 1.1 to 1.9 is characterized in that the operating voltage of the external power supply is -10 to -2 V vs SCE, preferably -4 to -2 V vs SCE, and more preferably -4 to -3 V vs SCE.

[0077] 1.11. The membrane-based electrocatalytic fluid reactor according to any one of technical solutions 1.1-1.10 is characterized in that a counter electrode is arranged on the upstream side or downstream side close to the conductive nanoporous membrane according to the direction in which the wastewater containing nitrate nitrogen passes through the conductive nanoporous membrane.

[0078] 1.12. A membrane-based electrocatalytic nanofluid reactor according to any one of technical solutions 1.1-1.11, characterized in that the counter electrode is one or more of a metal, an intermetallic compound, a carbide, a carbon electrode and a conductive nanoporous membrane; preferably, the counter electrode is one or more of a platinum electrode, stainless steel, a graphite plate and a carbon electrode; more preferably, the counter electrode is a platinum electrode.

[0079] 1.13. The membrane-based electrocatalytic nanofluid reactor according to any one of technical solutions 1.1-1.12 is characterized in that the nitrate nitrogen concentration in the nitrate nitrogen-containing wastewater is 1 to 1000 mM, preferably, the concentration is 40-70 mM.

[0080] 1.14. The membrane-based electrocatalytic nanofluid reactor according to any one of technical solutions 1.1 to 1.13, characterized in that the connection method is electrical connection;

[0081] 1.15. The membrane-based electrocatalytic nanofluid reactor according to any one of technical solutions 1.1 to 1.14, characterized in that the membrane-based electrocatalytic nanofluid reactor comprises:

[0082] A reference electrode, the reference electrode, the conductive nanoporous membrane and the counter electrode form a three-electrode system, wherein the reference electrode is a mercuric oxide electrode under alkaline electrolyte and a saturated calomel electrode under neutral or acidic electrolyte; preferably, the neutral electrolyte is a 0.05-1M sodium sulfate solution;

[0083] The conductive nanoporous membrane is connected to the external power source and is used as a cathode. The conductive nanoporous membrane is a place where the sewage containing nitrate nitrogen undergoes electrocatalytic reduction, wherein the sewage containing nitrate nitrogen undergoes an electrocatalytic reduction chemical reaction in the pores of the conductive nanoporous membrane, wherein the conductive nanoporous membrane adopts a tubular carbon membrane with an average pore size of 4-660nm; preferably, the conductive nanoporous membrane adopts a tubular carbon membrane with an average pore size of 4-8.3nm;

[0084] A counter electrode, which is disposed on the upstream side or the downstream side of the conductive nanoporous membrane and connected to an external power source to serve as an anode, wherein the counter electrode is a platinum sheet electrode;

[0085] Epoxy glue, which covers one end of the conductive nanoporous membrane to seal the membrane tube of the conductive nanoporous membrane. Preferably, the epoxy glue is PKM12C-1 epoxy glue;

[0086] The cation exchange membrane is used to separate the anode and the cathode to prevent the reduction product after electrocatalytic reduction from being oxidized. Preferably, the reduction product is anion and / or gas, and more preferably, the reduction product is NO2 - and / or nitrogen; preferably, the cation exchange membrane is a Nafion 117 cation exchange membrane.

[0087] 1.16. The membrane-based electrocatalytic nanofluid reactor according to any one of technical solutions 1.1 to 1.15 is characterized in that the membrane-based electrocatalytic nanofluid reactor comprises: a reference electrode, a conductive nanoporous membrane, and a counter electrode forming a three-electrode system, wherein the reference electrode is a mercuric oxide electrode under an alkaline electrolyte, or a saturated calomel electrode under a neutral or acidic electrolyte; preferably, the alkaline electrolyte is a 0.05-1M sodium hydroxide solution, and preferably, the neutral electrolyte is a 0.05-1M sodium sulfate solution;

[0088] The conductive nanoporous membrane is connected to the external power source and is used as a cathode. The conductive nanoporous membrane is a place where the sewage containing nitrate nitrogen undergoes electrocatalytic reduction, wherein the sewage containing nitrate nitrogen undergoes an electrocatalytic reduction chemical reaction in the pores of the conductive nanoporous membrane, wherein the conductive nanoporous membrane adopts a tubular carbon membrane with an average pore size of 4-8.3nm and loaded with 0.01-1wt% bimetallic palladium copper catalyst;

[0089] A counter electrode, which is disposed on the upstream side or the downstream side of the conductive nanoporous membrane and connected to an external power source to serve as an anode, wherein the counter electrode is a platinum sheet electrode;

[0090] Epoxy glue, which covers one end of the conductive nanoporous membrane to seal the membrane tube of the conductive nanoporous membrane. Preferably, the epoxy glue is PKM12C-1 epoxy glue;

[0091] The cation exchange membrane is used to separate the anode and the cathode to prevent the reduction product after electrocatalytic reduction from being oxidized. Preferably, the reduction product is anion and / or gas, and more preferably, the reduction product is NO2 - and / or nitrogen; preferably, the cation exchange membrane is a Nafion 117 cation exchange membrane.

[0092] 1.17. The membrane-based electrocatalytic nanofluid reactor according to any one of technical solutions 1.1 to 1.16, characterized in that the membrane-based electrocatalytic nanofluid reactor comprises:

[0093] An external power supply for providing an electric field, wherein the working voltage of the external power supply is -10 to -2 V vs SCE; preferably, the working voltage of the external power supply is -10 to -3 V vs SCE; more preferably, the working voltage of the external power supply is -10 to -4 V vs SCE;

[0094] A reference electrode, the reference electrode, the conductive nanoporous membrane and the counter electrode form a three-electrode system, wherein the reference electrode is a mercuric oxide electrode in an alkaline electrolyte, or a saturated calomel electrode in a neutral or acidic electrolyte; preferably, the neutral electrolyte is a 0.05-1M sodium sulfate solution;

[0095] The conductive nanoporous membrane is connected to the external power supply and is used as a cathode. The conductive nanoporous membrane is a place where the sewage containing nitrate nitrogen undergoes electrocatalytic reduction, wherein the sewage containing nitrate nitrogen undergoes an electrocatalytic reduction chemical reaction in the pores of the conductive nanoporous membrane, wherein the conductive nanoporous membrane adopts a tubular carbon membrane loaded with 0.001-0.1wt% diatomic palladium copper catalyst and an average pore size of 4-660nm; preferably, the conductive nanoporous membrane adopts a tubular carbon membrane loaded with 0.001-0.1wt% diatomic palladium copper catalyst and an average pore size of 4-430nm; more preferably, the conductive nanoporous membrane adopts a tubular carbon membrane loaded with 0.001-0.1wt% diatomic palladium copper catalyst and an average pore size of 4-8.3nm;

[0096] A counter electrode, which is disposed on the upstream side or the downstream side of the conductive nanoporous membrane and connected to an external power source to serve as an anode, wherein the counter electrode is a platinum sheet electrode;

[0097] Epoxy glue, which covers the conductive nanoporous membrane and is used to seal the membrane tube of the conductive nanoporous membrane. Preferably, the epoxy glue is PKM12C-1 epoxy glue;

[0098] The cation exchange membrane is used to separate the anode and the cathode to prevent the reduction product after electrocatalytic reduction from being oxidized. Preferably, the reduction product is anion and / or gas, and more preferably, the reduction product is NO2 - and / or nitrogen; preferably, the cation exchange membrane is a Nafion 117 cation exchange membrane.

[0099] 1.18. The membrane-based electrocatalytic nanofluid reactor according to any one of technical solutions 1.1-1.17, characterized in that:

[0100] An external power supply is used to provide an electric field, wherein the working voltage of the external power supply is -4 to -2V vs SCE;

[0101] A reference electrode, the reference electrode, the conductive nanoporous membrane and the counter electrode form a three-electrode system, wherein the reference electrode is a mercuric oxide electrode in an alkaline electrolyte, or a saturated calomel electrode in a neutral or acidic electrolyte; preferably, the alkaline electrolyte is a 0.05-1M sodium hydroxide solution;

[0102] The conductive nanoporous membrane is connected to the external power source and is used as a cathode. The conductive nanoporous membrane is a place where the sewage containing nitrate nitrogen undergoes electrocatalytic reduction, wherein the sewage containing nitrate nitrogen undergoes an electrocatalytic reduction chemical reaction in the pores of the conductive nanoporous membrane, wherein the conductive nanoporous membrane adopts a tubular carbon membrane with an average pore size of 4-8.3nm, which is loaded with 0.01-1wt% bimetallic palladium copper catalyst and filled with activated carbon inside the membrane tube;

[0103] A counter electrode, which is disposed on the upstream side or the downstream side of the conductive nanoporous membrane and connected to an external power source to serve as an anode, wherein the counter electrode is a platinum sheet electrode;

[0104] Epoxy glue, which covers the conductive nanoporous membrane and is used to seal the membrane tube of the conductive nanoporous membrane. Preferably, the epoxy glue is PKM12C-1 epoxy glue;

[0105] The cation exchange membrane is used to separate the anode and the cathode to prevent the reduction product after electrocatalytic reduction from being oxidized. Preferably, the reduction product is anion and / or gas, and more preferably, the reduction product is NO2 - and / or nitrogen; preferably, the cation exchange membrane is a Nafion 117 cation exchange membrane.

[0106] 1.19. A purification system for purifying wastewater containing nitrate nitrogen, characterized in that the purification system comprises: a membrane-based electrocatalytic nanofluid reactor as described in any one of technical solutions 1.1 to 1.18, and a pressure difference driving device for driving the membrane-based electrocatalytic nanofluid reactor to operate,

[0107] The pressure difference driving device is connected to the conductive nanoporous membrane in the membrane-based electrocatalytic nanofluid reactor through a polytetrafluoroethylene tube to provide a transmembrane pressure difference in the pores of the conductive nanoporous membrane. Through the transmembrane pressure difference, the wastewater containing nitrate nitrogen enters the pores of the conductive nanoporous membrane from the surface of the conductive nanoporous membrane.

[0108] Wherein, the membrane-based electrocatalytic nanofluid reactor comprises:

[0109] An external power source for providing an electric field;

[0110] A reference electrode, the reference electrode, the conductive nanoporous membrane and the counter electrode form a three-electrode system;

[0111] The conductive nanoporous membrane is connected to the external power source and is used as a cathode. The conductive nanoporous membrane is the place where the wastewater containing nitrate nitrogen undergoes electrocatalytic reduction, wherein the wastewater containing nitrate nitrogen undergoes an electrocatalytic reduction chemical reaction in the pores of the conductive nanoporous membrane;

[0112] The counter electrode is disposed on the upstream side or the downstream side of the conductive nanoporous membrane and connected to an external power source to serve as an anode;

[0113] The chemical reaction equations of electrocatalytic reduction are shown in (1)-(5):

[0114]

[0115] 2NO3 - (ads)+5H2→N2+2OH - +4H2O(2)

[0116] NO3 - (ads)+H2→NO2 - +H2O(3)

[0117] 2NO2 - (ads)+2H + +3H2→N2+H2O(4)

[0118] 2NO3 - +8H2→2NH4 + +4OH - +2H2O(5).

[0119] 1.20. The purification system according to technical solution 1.19 is characterized in that it also includes: a mechanical stirring device, characterized in that the mechanical stirring device is placed in the cathode tank to enhance mass transfer; and / or the cathode tank is used as a storage tank for wastewater containing nitrate nitrogen;

[0120] and / or an anode cell, used as a reservoir for the electrolyte solution;

[0121] and / or a pressure sensor connected to the polytetrafluoroethylene tube to record the pressure inside the pores of the conductive nanoporous membrane; and / or a purification tank used as a storage tank to collect purified sewage;

[0122] Wherein, the conductive nanoporous membrane and the counter electrode in the membrane-based electrocatalytic nanofluid reactor are placed in an area to be purified consisting of a cathode pool and an anode pool; preferably, the conductive nanoporous membrane and the counter electrode in the membrane-based electrocatalytic nanofluid reactor are placed in an area to be purified consisting of a cathode pool and an anode pool separated by a cation exchange membrane, wherein the conductive nanoporous membrane is placed in the cathode pool and the counter electrode is placed in the anode pool.

[0123] 1.21. The purification system according to technical solution 1.19 or 1.20 is characterized in that the purification system comprises: the conductive nanoporous membrane in the membrane-based electrocatalytic nanofluid reactor described in any one of technical solutions 1.1-1.18 is placed in the cathode pool.

[0124] 1.22. A purification system according to any one of technical solutions 1.19-1.21, characterized in that the wastewater containing nitrate nitrogen includes: an electrolyte solution and nitrate nitrogen wastewater.

[0125] 1.23. A purification system according to any one of technical solutions 1.19-1.22, characterized in that the concentration of the electrolyte solution is 0.05 to 1M.

[0126] 1.24. The purification system according to any one of technical solutions 1.19-1.23 is characterized in that the electrolyte solution is one or more of sodium sulfate solution, sodium chloride solution, ammonium sulfate solution, ferric nitrate solution, barium sulfate solution, sodium hydroxide solution, potassium hydroxide solution, barium hydroxide solution and calcium hydroxide solution; preferably, the electrolyte solution is one or more of sodium sulfate solution and sodium hydroxide solution.

[0127] 1.25. A purification system according to any one of technical solutions 1.19-1.24, characterized in that the concentration of nitrate nitrogen in the nitrate nitrogen-containing wastewater is 1 to 1000 mM, preferably, the concentration is 60-70 mM.

[0128] 1.26. A purification system according to any one of technical solutions 1.19-1.25, characterized in that the pressure difference driving device is one or more of a water pump, a vacuum pump and a peristaltic pump;

[0129] And / or the transmembrane pressure difference is greater than 0 and less than or equal to 0.1 MPa.

[0130] 1.27. A method for purifying wastewater containing nitrate nitrogen, characterized in that it comprises the following steps:

[0131] Through the membrane-based electrocatalytic nanofluid reactor described in any one of technical solutions 1.1-1.18, or the purification system described in any one of technical solutions 19-26, the nitrate nitrogen-containing wastewater is passed through a conductive nanoporous membrane for electrocatalytic reduction to remove nitrate nitrogen from the mixed solution and generate a harmless product, nitrogen gas, to obtain purified water, thereby completing the purification treatment of the nitrate nitrogen-containing wastewater.

[0132] 1.28. The purification method according to technical solution 1.27 is characterized in that it includes the following steps: connecting the conductive nanoporous membrane, the counter electrode and the reference electrode to an external power supply; and using a pressure difference driving device to provide negative pressure to the conductive nanoporous membrane to form a transmembrane pressure difference; under the drive of the transmembrane pressure difference, the nitrate nitrogen-containing wastewater flows through the conductive nanoporous membrane for electrocatalytic reduction to remove nitrate nitrogen in the mixed solution and generate a harmless product nitrogen gas to obtain purified water, thereby completing the purification treatment of the nitrate nitrogen-containing wastewater.

[0133] 1.29. The purification method according to technical solution 1.27 or 1.28, characterized in that the method comprises the following steps:

[0134] (1) placing a conductive nanoporous membrane in a cathode tank, and placing a counter electrode in an anode tank, so that the counter electrode, the conductive nanoporous membrane, the wastewater containing nitrate nitrogen, and an external power source form a current loop;

[0135] (2) turning on an external power source to generate an electric field, thereby causing the wastewater containing nitrate nitrogen to undergo electrocatalytic reduction on the conductive nanoporous membrane;

[0136] (3) using a pressure difference driving device as a driver to provide negative pressure to the purification area in the conductive nanoporous membrane, thereby forming a transmembrane pressure difference, and detecting the transmembrane pressure difference through a pressure sensor;

[0137] (4) Driven by the transmembrane pressure difference, the wastewater containing nitrate nitrogen in the cathode pool flows into the conductive nanoporous membrane 3, so that the wastewater containing nitrate nitrogen undergoes electrocatalytic reduction in the pores of the conductive nanoporous membrane to obtain purified water, and then the purified water flows to the purification pool, thus completing the purification treatment of the wastewater containing nitrate nitrogen.

[0138] 1.30. The purification method according to any one of technical solutions 1.27-1.29 is characterized in that the stirring speed is 100-300r / min.

[0139] 1.31. A sewage treatment device, characterized in that it contains a membrane-based electrocatalytic nanofluid reactor as described in any one of technical solutions 1.1-1.18.

[0140] .32. Application of the membrane-based electrocatalytic nanofluid reactor described in any one of Technical Solutions 1.1-1.18 in sewage treatment.

[0141] 1.33. The sewage treatment device described in Technical Solution 1.31 or the application described in Technical Solution 1.32 is characterized in that the sewage contains nitrate nitrogen.

[0142] In some specific embodiments of the present invention, a membrane-based electrocatalytic nanofluid reactor for purifying wastewater containing nitrate nitrogen is provided. The membrane-based electrocatalytic nanofluid reactor, such as Figure 3 As shown, Figure 3 The schematic diagram is a diagram of nitrate ions being degraded into nitrogen after colliding with the pore wall in a single pore of a tubular carbon membrane loaded with catalytic active components. The membrane-based electrocatalytic nanofluid reactor specifically includes:

[0143] A reference electrode, the reference electrode, the conductive nanoporous membrane and the counter electrode form a three-electrode system; wherein the reference electrode is a saturated calomel electrode or a mercuric oxide electrode;

[0144] The conductive nanoporous membrane is connected to the external power source and is used as a cathode. The conductive nanoporous membrane is the place where the wastewater containing nitrate nitrogen undergoes electrocatalytic reduction, wherein the wastewater containing nitrate nitrogen undergoes an electrocatalytic reduction chemical reaction in the pores of the conductive nanoporous membrane.

[0145] Wherein, the conductive nanoporous membrane adopts a tubular carbon membrane with catalytically active components loaded through the pores. Preferably, the conductive nanoporous membrane adopts a tubular carbon membrane with an average pore size of 4-660nm loaded with 0.01-1wt% bimetallic palladium copper catalyst and a tubular carbon membrane with an average pore size of 4-660nm, and a tubular carbon membrane with an average pore size of 4-660nm loaded with 0.001-0.1wt% diatomic palladium copper catalyst; More preferably, the conductive nanoporous membrane adopts a tubular carbon membrane with an average pore size of 4-8.3nm loaded with 0.01-1wt% bimetallic palladium copper catalyst and a tubular carbon membrane with an average pore size of 4-430nm; Most preferably, the conductive nanoporous membrane adopts a tubular carbon membrane with an average pore size of 4-8.3nm loaded with 0.001-0.1wt% diatomic palladium copper catalyst;

[0146] A counter electrode, which is disposed on the upstream side or the downstream side of the conductive nanoporous membrane and connected to an external power source to serve as an anode, wherein the counter electrode is a platinum sheet electrode;

[0147] Epoxy glue, which covers one end of the conductive nanoporous membrane to seal the membrane tube of the conductive nanoporous membrane. Preferably, the epoxy glue is PKM12C-1 epoxy glue;

[0148] The cation exchange membrane is used to separate the anode and the cathode to prevent the reduction product after electrocatalytic reduction from being oxidized. Preferably, the reduction product is anion and / or gas, and more preferably, the reduction product is NO2 - and / or nitrogen; preferably, the cation exchange membrane is a cation exchange membrane of model Nafion 117,

[0149] It should be noted that the present invention provides a membrane-based electrocatalytic nanofluid reactor for purifying wastewater containing nitrate nitrogen. The membrane-based electrocatalytic nanofluid reactor can be a system with catalytically active components loaded, that is, the above-mentioned conductive nanoporous membrane adopts a tubular carbon membrane with catalytically active components loaded through the pores; it can also be a system without catalytically active components loaded, that is, the above-mentioned conductive nanoporous membrane adopts a tubular carbon membrane. The process of nitrate ions in wastewater containing nitrate nitrogen being degraded is as follows Figure 3 As shown, Figure 3 A schematic diagram of nitrate ions being degraded into nitrogen after colliding with the pore wall in a single pore of a tubular carbon membrane loaded with catalytically active components;

[0150] The reaction principle is that nitrate ions in wastewater containing nitrate nitrogen are electrocatalytically reduced in the pores of the conductive nanoporous membrane to remove nitrate nitrogen from the wastewater containing nitrate nitrogen and generate harmless product nitrogen gas to obtain purified water.

[0151] The chemical reaction equations of electrocatalytic reduction are shown in (1)-(5):

[0152]

[0153] 2NO3 - (ads)+5H2→N2+2OH - +4H2O(2)

[0154] NO3 - (ads)+H2→NO2 - +H2O(3)

[0155] 2NO2 - (ads)+2H + +3H2→N2+H2O(4)

[0156] 2NO3 - +8H2→2NH4 + +4OH - +2H2O(5).

[0157] In some specific embodiments of the present invention, a membrane-based electrocatalytic nanofluid reactor for purifying wastewater containing nitrate nitrogen is provided. The membrane-based electrocatalytic nanofluid reactor, such as Figure 4 As shown, Figure 4 The activated carbon diagram is filled in the membrane tube of the tubular carbon membrane for supporting catalytic active components. The membrane-based electrocatalytic nanofluid reactor comprises:

[0158] An external power supply is used to provide an electric field, wherein the working voltage of the external power supply is -10 to -2 V vs SCE;

[0159] A reference electrode, the reference electrode, the conductive nanoporous membrane and the counter electrode form a three-electrode system, wherein the reference electrode is a mercuric oxide electrode or a saturated calomel electrode;

[0160] The conductive nanoporous membrane is connected to the external power source and is used as a cathode. The conductive nanoporous membrane is the place where the wastewater containing nitrate nitrogen undergoes electrocatalytic reduction, wherein the wastewater containing nitrate nitrogen undergoes an electrocatalytic reduction chemical reaction in the pores of the conductive nanoporous membrane.

[0161] The conductive nanoporous membrane adopts a porous conductive membrane with catalytically active components loaded in the pores and filled with activated carbon. Preferably, the conductive nanoporous membrane adopts a tubular carbon membrane with an average pore size of 4-660nm, which is loaded with 0.01-1wt% bimetallic palladium copper catalyst and filled with activated carbon inside the membrane tube. More preferably, the conductive nanoporous membrane adopts a tubular carbon membrane with an average pore size of 4-8.3nm, which is loaded with 0.01-1wt% bimetallic palladium copper catalyst.

[0162] A counter electrode, which is disposed on the upstream side or the downstream side of the conductive nanoporous membrane and connected to an external power source to serve as an anode, wherein the counter electrode is a platinum sheet electrode;

[0163] Epoxy glue, which covers the conductive nanoporous membrane and is used to seal the membrane tube of the conductive nanoporous membrane. Preferably, the epoxy glue is PKM12C-1 epoxy glue;

[0164] The cation exchange membrane is used to separate the anode and the cathode to prevent the reduction product after electrocatalytic reduction from being oxidized. Preferably, the reduction product is anion and / or gas, and more preferably, the reduction product is NO2 - and / or nitrogen; preferably, the cation exchange membrane is a Nafion 117 cation exchange membrane.

[0165] It should be noted that, in a specific implementation, the external power supply can be arbitrary and is not limited to the model and source of the external power supply provided by the present invention, as long as it plays the same role as the external power supply provided by the present invention.

[0166] In a specific embodiment, the reference electrode can be any, not limited to the model and source of the reference electrode provided by the present invention, as long as it plays the same role as the reference electrode provided by the present invention.

[0167] In a specific embodiment, the epoxy adhesive can be any, not limited to the model and source of the epoxy adhesive provided by the present invention, as long as it plays the same role as the epoxy adhesive provided by the present invention.

[0168] In a specific embodiment, the counter electrode can be any, not limited to the model and source of the counter electrode provided by the present invention, as long as it plays the same role as the counter electrode provided by the present invention.

[0169] In a specific embodiment, the cation exchange membrane can be any, not limited to the model and source of the cation exchange membrane provided by the present invention, as long as it plays the same role as the cation exchange membrane provided by the present invention.

[0170] In some specific embodiments of the present invention, a purification system for purifying wastewater containing nitrate nitrogen is provided, the purification system comprising: a membrane-based electrocatalytic nanofluid reactor, and a pressure difference driving device for driving the membrane-based electrocatalytic nanofluid reactor to operate.

[0171] and / or a mechanical stirring device placed in the cathode cell to enhance mass transfer;

[0172] and / or cathode tanks used as storage tanks for wastewater containing nitrate nitrogen;

[0173] and / or an anode cell, used as a reservoir for the electrolyte solution;

[0174] and / or a pressure sensor connected to the polytetrafluoroethylene tube to record the intrapore pressure of the conductive nanoporous membrane;

[0175] and / or purification tanks, which serve as storage tanks for collecting purified sewage;

[0176] The pressure difference driving device is connected to the conductive nanoporous membrane in the membrane-based electrocatalytic nanofluid reactor through a polytetrafluoroethylene tube to provide a transmembrane pressure difference in the pores of the conductive nanoporous membrane. Through the transmembrane pressure difference, the wastewater containing nitrate nitrogen enters the pores of the conductive nanoporous membrane from the surface of the conductive nanoporous membrane.

[0177] Wherein, the membrane-based electrocatalytic nanofluid reactor comprises:

[0178] An external power source for providing an electric field;

[0179] A reference electrode, the reference electrode, the conductive nanoporous membrane and the counter electrode form a three-electrode system;

[0180] The conductive nanoporous membrane is connected to the external power source and is used as a cathode. The conductive nanoporous membrane is the place where the wastewater containing nitrate nitrogen undergoes electrocatalytic reduction, wherein the wastewater containing nitrate nitrogen undergoes an electrocatalytic reduction chemical reaction in the pores of the conductive nanoporous membrane;

[0181] The counter electrode is arranged at the upstream side or the downstream side of the conductive nanoporous membrane and connected to an external power source to serve as an anode.

[0182] It should be noted that, in a specific embodiment, the mechanical stirring device can be any and is not limited to the model and source of the mechanical stirring device provided by the present invention, as long as it plays the same role as the mechanical stirring device provided by the present invention.

[0183] In a specific embodiment, the cathode pool can be any type and is not limited to the type and source of the cathode pool provided by the present invention, as long as it plays the same role as the cathode pool provided by the present invention.

[0184] In a specific embodiment, the anode pool can be any type and is not limited to the model and source of the anode pool provided by the present invention, as long as it plays the same role as the anode pool provided by the present invention.

[0185] In a specific implementation, the pressure sensor can be any type and is not limited to the model and source of the pressure sensor provided by the present invention, as long as it plays the same role as the pressure sensor provided by the present invention.

[0186] In a specific implementation, the pressure difference driving device can be any, not limited to the model and source of the pressure difference driving device provided by the present invention, as long as it plays the same role as the pressure difference driving device provided by the present invention.

[0187] In a specific embodiment, the purification pool can be any, not limited to the purification pool and source provided by the present invention, as long as it plays the same role as the purification pool provided by the present invention.

[0188] In order to better understand the technical solution of the present invention, the technical solution of the present invention is described in detail below in conjunction with specific embodiments.

[0189] Unless otherwise specified, the various reagents / instruments used in the examples and comparative examples of the present invention are conventional commercially available products. The sources of the experimental reagents / instruments used in the present invention are shown in the following table:

[0190] Table 1 Experimental materials / instrument information

[0191]

[0192]

[0193] 1. A method for preparing a tubular carbon membrane with an average pore size of 430-660nm, as follows: methyl cellulose, phenolic resin containing 2-3wt% hexamethylenetetramine and water are mixed into a dough. A tubular carbon membrane blank is obtained by vacuum extrusion equipment, and a tubular carbon membrane support is obtained after drying at room temperature and solidifying and carbonizing, that is, a tubular carbon membrane with an average pore size of 430-660nm is obtained, wherein the curing agent is preferably hexamethylenetetramine, and preferably, the weight mixing ratio of methyl cellulose: phenolic resin containing 2-3wt% hexamethylenetetramine: water is 1:20:10.

[0194] The preparation methods of the tubular carbon membrane with an average pore size of 430 nm and the tubular carbon membrane with an average pore size of 660 nm involved in the embodiments and comparative examples are specifically as follows:

[0195] (1) Tubular carbon membrane with an average pore size of 430 nm: methyl cellulose, phenolic resin containing 2 wt% hexamethylenetetramine and water are mixed into a dough-like state according to the weight ratio of methyl cellulose: phenolic resin containing 2 wt% hexamethylenetetramine: water = 1:20:10. The tubular carbon membrane blank is obtained by vacuum extrusion equipment, and the tubular carbon membrane support is obtained after drying at room temperature, curing and carbonization, i.e., the tubular carbon membrane with an average pore size of 430 nm.

[0196] (2) Tubular carbon membrane with an average pore size of 660 nm: methyl cellulose, phenolic resin containing 3 wt% hexamethylenetetramine and water are mixed into a dough-like state according to the weight ratio of methyl cellulose: phenolic resin containing 3 wt% hexamethylenetetramine: water = 1:20:10. The tubular carbon membrane blank is obtained by vacuum extrusion equipment, and the tubular carbon membrane support is obtained after drying at room temperature and solidification and carbonization, i.e., the tubular carbon membrane with an average pore size of 660 nm.

[0197] 2. A method for preparing a tubular carbon membrane with an average pore size of 4-8.3 nm. The specific content of the preparation method has been recorded in the Chinese patent with patent number CN102107123B.

[0198] The preparation methods of the tubular carbon membrane with an average pore size of 4 nm and the tubular carbon membrane with an average pore size of 8.3 nm involved in the embodiments and comparative examples are specifically as follows:

[0199] (1) Tubular carbon membrane with an average pore size of 4 nm: Resorcinol (R) and formaldehyde (F) are prepared into an aqueous solution with a total concentration of 20% (the mass sum of resorcinol and formaldehyde divided by the total volume of the solution) according to the ratio of R:F (molar ratio) = 1:2. The aqueous solution contains hexadecyltrimethylammonium bromide, the content of which is 1 / 500 of the molar number of resorcinol. The prepared solution is sealed in a ground-mouth bottle and placed in an oven for reaction for 10 hours. A carbon membrane separation layer is coated on the carbon membrane support by an immersion and pulling method. The membrane is dried in a formaldehyde atmosphere for 48 hours and then dried at room temperature for 48 hours. After curing and carbonization, an asymmetric carbon membrane, i.e., a 4 nm tubular carbon membrane, is obtained.

[0200] (2) Tubular carbon membrane with an average pore size of 8.3 nm: Resorcinol (R) and formaldehyde (F) are prepared into an aqueous solution with a total concentration of 20% (the mass sum of resorcinol and formaldehyde divided by the total volume of the solution) according to the ratio of R:F (molar ratio) = 1:2. The aqueous solution contains hexadecyltrimethylammonium bromide, and the content is 1 / 500 of the molar number of resorcinol. The prepared solution is sealed in a ground-mouth bottle and placed in an oven for reaction for 19 hours. A carbon membrane separation layer is coated on the carbon membrane support by an immersion and pulling method. The membrane is dried in a formaldehyde atmosphere for 48 hours and then dried at room temperature for 48 hours. After curing and carbonization, an asymmetric carbon membrane, i.e., an 8.3 nm tubular carbon membrane, is obtained.

[0201] 3. A method for preparing a tubular carbon membrane loaded with 0.01-1wt% bimetallic palladium copper catalyst and having an average pore size of 8.3-660nm, as follows: a tubular carbon membrane with an average pore size of 8.3-660nm is used as a cathode, a platinum sheet is used as an anode, a saturated calomel electrode is used as a reference electrode, and an electrolyte is a mixture of 0.5-5mM palladium nitrate, 0.5-5mM copper nitrate and 0.5-0.5M ammonium chloride. The deposition is completed at a constant potential of -0.8-1.0V for 5-30min, and a tubular carbon membrane loaded with 0.01-1wt% bimetallic palladium copper catalyst and having an average pore size of 8.3-660nm is obtained after 4-8 depositions;

[0202] Among them, the preparation methods of the tubular carbon membrane loaded with 0.1wt% bimetallic palladium copper catalyst and having an average pore size of 8.3nm and the tubular carbon membrane loaded with 0.1wt% bimetallic palladium copper catalyst and having an average pore size of 660nm involved in the embodiments and comparative examples are specifically as follows:

[0203] (1) A tubular carbon membrane loaded with 0.1 wt% bimetallic palladium copper catalyst and having an average pore size of 8.3 nm: prepared by constant potential electrodeposition, specifically: an 8.3 nm tubular carbon membrane is used as the cathode, a platinum sheet is used as the anode, a saturated calomel electrode is used as the reference electrode, and the electrolyte is 5 mM palladium nitrate + 5 mM copper nitrate + 0.5 M ammonium chloride. One deposition is completed at a constant potential of -0.8 V for 20 min. After 4 depositions, a tubular carbon membrane loaded with 0.1 wt% bimetallic palladium copper catalyst and having an average pore size of 8.3 nm is obtained.

[0204] (2) A tubular carbon membrane loaded with 0.1 wt% bimetallic palladium-copper catalyst and having an average pore size of 660 nm: prepared by constant potential electrodeposition, specifically: a 660 nm tubular carbon membrane was used as the cathode, a platinum sheet was used as the anode, a saturated calomel electrode was used as the reference electrode, and the electrolyte was 5 mM palladium nitrate + 5 mM copper nitrate + 0.5 M ammonium chloride. One deposition was completed at a constant potential of -0.8 V for 20 min. After 4 depositions, a tubular carbon membrane loaded with 0.1 wt% bimetallic palladium-copper catalyst and having an average pore size of 660 nm was obtained.

[0205] 4. A method for preparing a tubular carbon membrane loaded with 0.001-0.1wt% diatomic palladium copper catalyst and an average pore size of 4-660nm, as follows: a tubular carbon membrane with an average pore size of 4-660nm is used as a cathode, a platinum sheet is used as an anode, a pulsed electric field is applied to the electrode surface, and the electrolyte flows into the pores of the tubular carbon membrane. The processing conditions are set as follows: transmembrane pressure difference 50-100kPa, water temperature 20-25℃, working voltage -0.8-1.0V vs.SCE, power-on interval 0.01-1s, the time of one deposition unit is 0.4-200s, and the interval time between two deposition units is 0.1-500s. Wherein, the electrolyte is a mixture of 0.5-5mM palladium nitrate, 0.5-5mM copper nitrate and 0.5-0.5M ammonium chloride.

[0206] Among them, the tubular carbon membrane loaded with 0.1wt% diatomic palladium copper catalyst and an average pore size of 660nm, the tubular carbon membrane loaded with 0.1wt% diatomic palladium copper catalyst and an average pore size of 430nm, the tubular carbon membrane loaded with 0.1wt% diatomic palladium copper catalyst and an average pore size of 8.3nm, and the preparation method of the tubular carbon membrane loaded with 0.1wt% diatomic palladium copper catalyst and an average pore size of 4nm involved in the embodiments and comparative examples are specifically as follows:

[0207] (1) Tubular carbon membrane loaded with 0.1wt% diatomic palladium copper catalyst and average pore size of 660nm: prepared by flow pulse electrodeposition, specifically: 660nm tubular carbon membrane as cathode, platinum sheet as anode, pulse electric field applied on the electrode surface, so that the electrolyte flows into the pores of the tubular carbon membrane. Set the processing conditions: transmembrane pressure difference 50kPa, water temperature 25℃, working voltage -0.8Vvs.SCE, power-on interval 0.05s, one deposition time 33.6s, 4 depositions as one deposition unit, and the interval between deposition units is 400s. Among them, the electrolyte is 5mM palladium nitrate + 5mM copper nitrate + 0.5M ammonium chloride.

[0208] (2) Tubular carbon membrane loaded with 0.1wt% diatomic palladium copper catalyst and average pore size of 430nm: prepared by flow pulse electrodeposition, specifically: 430nm tubular carbon membrane as cathode, platinum sheet as anode, pulse electric field applied on the electrode surface, so that the electrolyte flows into the pores of the tubular carbon membrane. Set the processing conditions: transmembrane pressure difference 50kPa, water temperature 25℃, working voltage -0.8Vvs.SCE, power-on interval 0.05s, one deposition time 33.6s, 4 depositions as one deposition unit, and the interval between deposition units is 400s. Among them, the electrolyte is 5mM palladium nitrate + 5mM copper nitrate + 0.5M ammonium chloride.

[0209] (3) Tubular carbon membrane loaded with 0.1wt% diatomic palladium copper catalyst and average pore size of 8.3nm: prepared by flow pulse electrodeposition, specifically: using 8.3nm tubular carbon membrane as cathode, platinum sheet as anode, applying pulse electric field on the electrode surface, so that electrolyte flows into the pores of tubular carbon membrane. Set processing conditions: transmembrane pressure difference 50kPa, water temperature 25℃, working voltage -0.8Vvs.SCE, power-on interval 0.05s, one deposition time 33.6s, 4 depositions as one deposition unit, deposition unit interval 400s. Wherein, the electrolyte is 5mM palladium nitrate + 5mM copper nitrate + 0.5M ammonium chloride.

[0210] (4) Tubular carbon membrane loaded with 0.1wt% diatomic palladium copper catalyst and average pore size of 4nm: prepared by flow pulse electrodeposition, specifically: using 4nm tubular carbon membrane as cathode, platinum sheet as anode, applying pulse electric field on the electrode surface, so that electrolyte flows into the pores of tubular carbon membrane. Set processing conditions: transmembrane pressure difference 50kPa, water temperature 25℃, working voltage -0.8Vvs.SCE, power-on interval 0.05s, one deposition time 33.6s, 4 depositions as one deposition unit, deposition unit interval 400s. Wherein, the electrolyte is 5mM palladium nitrate + 5mM copper nitrate + 0.5M ammonium chloride.

[0211] 5. A method for preparing a tubular carbon membrane loaded with 0.01-1wt% bimetallic palladium-copper catalyst and an average pore size of 8.3-660nm and filling the inside of the membrane tube with activated carbon, as specifically described as follows: the membrane tube of the tubular carbon membrane loaded with 0.01-1wt% bimetallic palladium-copper catalyst and an average pore size of 8.3-660nm is filled with activated carbon.

[0212] Among them, the preparation methods of the tubular carbon membrane loaded with 0.1wt% bimetallic palladium copper catalyst, an average pore size of 660nm and filled with activated carbon inside the membrane tube, and the tubular carbon membrane loaded with 0.1wt% bimetallic palladium copper catalyst, an average pore size of 8.3nm and filled with activated carbon inside the membrane tube involved in the embodiments and comparative examples are specifically as follows:

[0213] (1) A tubular carbon membrane loaded with 0.1 wt% bimetallic palladium copper catalyst and an average pore size of 660 nm and filled with activated carbon inside the membrane tube: The membrane tube of the tubular carbon membrane loaded with 0.1 wt% bimetallic palladium copper catalyst and an average pore size of 600 nm is filled with activated carbon.

[0214] (2) A tubular carbon membrane loaded with 0.1 wt% bimetallic palladium-copper catalyst and having an average pore size of 8.3 nm and filled with activated carbon inside the membrane tube: The membrane tube of the tubular carbon membrane loaded with 0.1 wt% bimetallic palladium-copper catalyst and having an average pore size of 8.3 nm is filled with activated carbon.

[0215] Example 1

[0216] (I) Embodiment 1 of the present invention provides a membrane-based electrocatalytic nanofluid reactor for purifying wastewater containing nitrate nitrogen, and the specific structural schematic diagram is shown in FIG. Figure 1 As shown, the membrane-based electrocatalytic nanofluid reactor comprises: an external power source 1, a reference electrode 2, a conductive nanoporous membrane 3, an epoxy glue 4, a counter electrode 5 and a cation exchange membrane 6, wherein:

[0217] An external power source 1, whose operating voltage is -4V vs SCE, is used to provide an electric field.

[0218] The reference electrode 2 is a saturated calomel electrode, and is electrically connected to the conductive nanoporous membrane 3 to form a three-electrode system with the conductive nanoporous membrane 3 and the counter electrode 5 .

[0219] A conductive nanoporous membrane 3, which is electrically connected to the external power source 1 and is used as a cathode. The conductive nanoporous membrane 3 is a tubular carbon membrane with an average pore size of 8.3 nm;

[0220] The counter electrode 5 is a 2cm*2cm platinum sheet electrode, which is electrically connected to the external power supply 1 and serves as an anode.

[0221] The epoxy glue 4 covers the purified area of ​​the conductive nanoporous membrane 3 to seal the membrane tube of the conductive nanoporous membrane 3 .

[0222] The cation exchange membrane 6 is located at the anode cell port to separate the positive and negative electrodes and prevent the NO2 - and nitrogen are oxidized.

[0223] (ii) Based on the membrane-based electrocatalytic nanofluid reactor, Example 1 of the present invention provides a purification system for purifying wastewater containing nitrate nitrogen, and its specific structural schematic diagram is shown in FIG. Figure 2 As shown, the purification system for purifying wastewater containing nitrate nitrogen comprises: the membrane-based electrocatalytic nanofluid reactor, a mechanical stirring device 7, a cathode pool 8, an anode pool 9, a pressure sensor 10, a peristaltic pump 11 and a purification pool 12;

[0224] The stirring device 7 is placed in the cathode cell 8 to increase the speed and efficiency of the wastewater containing nitrate nitrogen entering the area to be purified of the conductive nanoporous membrane 3 .

[0225] The cathode pool 8 is used as a storage pool for nitrate nitrogen-containing wastewater, wherein the volume of the nitrate nitrogen-containing wastewater is 13L, the temperature of the nitrate nitrogen-containing wastewater is 25°C, and the nitrate nitrogen-containing wastewater includes: an electrolyte solution: a 0.5M sodium sulfate solution, and transparent nitrate nitrogen wastewater with a concentration of 50mM and a pH value of 6.5.

[0226] The anode cell 9 is used as a storage cell for the electrolyte solution, wherein the volume of the electrolyte solution is 150 mL and the electrolyte solution is a 0.5 M sodium sulfate solution.

[0227] The pressure sensor 10 is connected to a polytetrafluoro tube with an outer diameter of 3 mm, and is used to record the pressure in the pores of the conductive nanoporous membrane in the membrane-based electrocatalytic nanofluid reactor.

[0228] The peristaltic pump 11 is connected to the conductive nanoporous membrane in the membrane-based electrocatalytic nanofluid reactor through a polytetrafluoroethylene tube with an outer diameter of 3 mm to provide a transmembrane pressure difference in the pores of the conductive nanoporous membrane. The transmembrane pressure difference allows the wastewater containing nitrate nitrogen to enter the pores of the conductive nanoporous membrane from the surface of the conductive nanoporous membrane.

[0229] The purification tank 12 is connected to one end of a polytetrafluoro tube with an outer diameter of 3 mm and serves as a purified water storage tank for storing purified water output from the polytetrafluoro tube.

[0230] (III) Based on the purification system for purifying sewage containing nitrate nitrogen, Embodiment 1 of the present invention provides a purification method for purifying sewage containing nitrate nitrogen, the method comprising the following steps:

[0231] (1) The conductive nanoporous membrane 3 in the membrane-based electrocatalytic nanofluid reactor is placed in the cathode tank 8, and the counter electrode 5 in the membrane-based electrocatalytic nanofluid reactor is placed in the anode tank 9, and the wastewater containing nitrate nitrogen passes through the conductive nanoporous membrane 3 in the direction (such as Figure 1 A counter electrode 5 is arranged on the upstream or downstream side close to the conductive nanoporous membrane 3, so that the counter electrode 5, the conductive nanoporous membrane 3, the wastewater containing nitrate nitrogen, and the external power supply 1 form a current loop.

[0232] (2) Turn on the external power supply 1 to generate an electric field, and use the stirring device 7 to stir at a speed of 200 r / min.

[0233] (3) The peristaltic pump 11 is used as a driver to provide negative pressure to the conductive nanoporous membrane 3 to form a transmembrane pressure difference, and the transmembrane pressure difference is detected by the pressure sensor 10 to be 0.05 MPa.

[0234] (4) Driven by the transmembrane pressure difference, the wastewater containing nitrate nitrogen in the cathode pool 8 flows into the conductive nanoporous membrane 3, so that the wastewater containing nitrate nitrogen undergoes electrocatalytic reduction in the pores of the conductive nanoporous membrane 3 to obtain purified water, and then the purified water flows to the purification pool 12, thus completing the purification treatment of the wastewater containing nitrate nitrogen.

[0235] The specific principle of electrocatalytic reduction is: nitrate ions in wastewater containing nitrate nitrogen are electrocatalytically reduced in the pores of the conductive nanoporous membrane 3 to remove nitrate nitrogen from wastewater containing nitrate nitrogen and generate harmless nitrogen gas to obtain purified water. The specific chemical reaction equation of electrocatalytic reduction is as follows:

[0236]

[0237] 2NO3 - (ads)+5H2→N2+2OH - +4H2O(2)

[0238] NO3 - (ads)+H2→NO2 - +H2O(3)

[0239] 2NO2 - (ads)+2H + +3H2→N2+H2O(4)

[0240] 2NO3 - +8H2→2NH4 + +4OH - +2H2O(5)

[0241] (5) The permeation flux of the conductive nanoporous membrane 3 is calculated using formula 1, the one-way removal rate of nitrate nitrogen in the purified water is calculated using formula 2, the nitrogen selectivity in the purified water is calculated using formula 3, and the hydraulic retention time is calculated using formula 4.

[0242]

[0243] Where Q is the permeation flux (L h -1 m -2 bar -1 ), V is the volume passing through the membrane in time (L), t is the reaction time (h), and S is the membrane area (m 2 ), Δp is expressed as the transmembrane pressure difference (bar).

[0244]

[0245] Wherein, τ represents the one-way removal rate of nitrate nitrogen (%); C0 represents the concentration of nitrate in the mixed solution at the initial time; C t Expressed as the concentration of nitrate in the mixed solution at the end time.

[0246]

[0247] Among them, S iIt is expressed as nitrogen selectivity (%); C0 is the concentration of nitrate in the mixed solution at the initial time; C t Expressed as the concentration of nitrate in the mixed solution at the end time.

[0248]

[0249] Among them, T r Expressed as hydraulic retention time (s), V m Expressed as the volume of the membrane (cm 3 ), ε is expressed as porosity (%).

[0250] The results showed that the permeate flux was 30 L h -1 m -2 bar -1 , the single-pass removal efficiency of nitrate nitrogen was 55%, the nitrogen selectivity was 47%, and the hydraulic retention time was 502s.

[0251] Example 2

[0252] Embodiment 2 of the present invention provides a membrane-based electrocatalytic nanofluid reactor for purifying wastewater containing nitrate nitrogen, which is different from Embodiment 1 in that: the conductive nanoporous membrane 3 adopts a tubular carbon membrane with an average pore size of 4 nm.

[0253] Based on the membrane-based electrocatalytic nanofluid reactor, a purification system for purifying wastewater containing nitrate nitrogen provided in Example 2 of the present invention is the same as that in Example 1.

[0254] Based on the purification system for purifying wastewater containing nitrate nitrogen, a purification method for purifying wastewater containing nitrate nitrogen provided in Example 2 of the present invention is the same as that in Example 1.

[0255] The results showed that the permeate flux was 15 L h -1 m -2 bar -1 , the nitrate nitrogen single-pass removal rate is 100%, the nitrogen selectivity is 60%, and the hydraulic retention time is 800s.

[0256] Example 3

[0257] Embodiment 3 of the present invention provides a membrane-based electrocatalytic nanofluid reactor for purifying wastewater containing nitrate nitrogen, which is different from Embodiment 1 in that: the conductive nanoporous membrane 3 adopts a tubular carbon membrane with an average pore size of 660 nm.

[0258] Based on the membrane-based electrocatalytic nanofluid reactor, a purification system for purifying wastewater containing nitrate nitrogen provided in Example 3 of the present invention is the same as that in Example 1.

[0259] Based on the purification system for purifying wastewater containing nitrate nitrogen, a purification method for purifying wastewater containing nitrate nitrogen provided in Example 3 of the present invention is the same as that in Example 1.

[0260] The results showed that the permeate flux was 50 L h -1 m -2 bar -1 , the single-pass removal efficiency of nitrate nitrogen was 36%, the nitrogen selectivity was 39%, and the hydraulic retention time was 86.35s.

[0261] Example 4

[0262] Example 4 of the present invention provides a membrane-based electrocatalytic nanofluid reactor for purifying wastewater containing nitrate nitrogen, which is different from Example 1 in that: the conductive nanoporous membrane 3 uses a tubular carbon membrane with an average pore size of 8.3nm to load 0.1wt% bimetallic palladium copper catalyst.

[0263] Based on the membrane-based electrocatalytic nanofluid reactor, Example 4 of the present invention provides a purification system for purifying wastewater containing nitrate nitrogen, which is the same as Example 1.

[0264] Based on the purification system for purifying wastewater containing nitrate nitrogen, a purification method for purifying wastewater containing nitrate nitrogen provided in Example 4 of the present invention is the same as that in Example 1.

[0265] The results showed that the permeate flux was 25 L h -1 m -2 bar -1 , the nitrate nitrogen single-pass removal efficiency is 97%, the nitrogen selectivity is 36%, and the hydraulic retention time is 283s.

[0266] Example 5

[0267] A membrane-based electrocatalytic nanofluid reactor for purifying wastewater containing nitrate nitrogen provided in Example 5 of the present invention is different from Example 1 in that: a conductive nanoporous membrane 3 is a tubular carbon membrane with an average pore size of 8.3 nm loaded with 0.1 wt% bimetallic palladium copper catalyst; a reference electrode 2 is a mercuric oxide electrode.

[0268] Based on the membrane-based electrocatalytic nanofluid reactor, Example 5 of the present invention provides a purification system for purifying wastewater containing nitrate nitrogen, which is different from Example 1 in that the electrolyte solution is a 0.5M sodium hydroxide solution.

[0269] Based on the purification system for purifying wastewater containing nitrate nitrogen, a purification method for purifying wastewater containing nitrate nitrogen provided in Example 5 of the present invention is the same as that in Example 1.

[0270] The results showed that the permeate flux was 35 L h -1 m -2 bar -1 The single-pass removal efficiency of nitrate nitrogen is 91%, the nitrogen selectivity is 96%, and the hydraulic retention time is 156s.

[0271] Example 6

[0272] Example 6 of the present invention provides a membrane-based electrocatalytic nanofluid reactor for purifying wastewater containing nitrate nitrogen, which is different from Example 1 in that: the conductive nanoporous membrane 3 uses a tubular carbon membrane with an average pore size of 8.3nm to load 0.1wt% diatomic palladium copper catalyst.

[0273] Based on the membrane-based electrocatalytic nanofluid reactor, a purification system for purifying wastewater containing nitrate nitrogen provided in Example 6 of the present invention is the same as that in Example 1.

[0274] Based on the purification system for purifying wastewater containing nitrate nitrogen, a purification method for purifying wastewater containing nitrate nitrogen provided in Example 6 of the present invention is the same as that in Example 1.

[0275] The results showed that the permeate flux was 13 L h -1 m -2 bar -1 , the single-pass removal rate of nitrate nitrogen is 100%, the nitrogen selectivity is 100%, and the hydraulic retention time is 276s.

[0276] Example 7

[0277] Example 7 of the present invention provides a membrane-based electrocatalytic nanofluid reactor for purifying wastewater containing nitrate nitrogen, which is different from Example 1 in that: a conductive nanoporous membrane 3 adopts a tubular carbon membrane with an average pore size of 8.3nm and loads 0.1wt% diatomic palladium copper catalyst, and the operating voltage of the external power supply 1 is -2V vs SCE.

[0278] Based on the membrane-based electrocatalytic nanofluid reactor, Example 7 of the present invention provides a purification system for purifying wastewater containing nitrate nitrogen, which is the same as Example 1.

[0279] Based on the purification system for purifying wastewater containing nitrate nitrogen, Example 7 of the present invention provides a purification method for purifying wastewater containing nitrate nitrogen, which is the same as Example 1.

[0280] The results showed that the permeate flux was 10 L h -1 m -2 bar -1 , the single-pass removal efficiency of nitrate nitrogen is 60%, the nitrogen selectivity is 40%, and the hydraulic retention time is 342s.

[0281] Example 8

[0282] Example 8 of the present invention provides a membrane-based electrocatalytic nanofluid reactor for purifying wastewater containing nitrate nitrogen, which is different from Example 1 in that: a conductive nanoporous membrane 3 uses a tubular carbon membrane with an average pore size of 8.3 nm loaded with 0.1 wt% diatomic palladium copper catalyst as the cathode, and the operating voltage of the external power supply 1 is -10 V vs SCE.

[0283] Based on the membrane-based electrocatalytic nanofluid reactor, Example 8 of the present invention provides a purification system for purifying wastewater containing nitrate nitrogen, which is the same as Example 1.

[0284] Based on the purification system for purifying wastewater containing nitrate nitrogen, Example 8 of the present invention provides a purification method for purifying wastewater containing nitrate nitrogen, which is the same as Example 1.

[0285] The results showed that the permeate flux was 15 L h -1 m -2 bar -1 , the single-pass removal rate of nitrate nitrogen is 100%, the nitrogen selectivity is 70%, and the hydraulic retention time is 158s.

[0286] Example 9

[0287] Embodiment 9 of the present invention provides a membrane-based electrocatalytic nanofluid reactor for purifying wastewater containing nitrate nitrogen, which is different from Embodiment 1 in that: the conductive nanoporous membrane 3 uses a tubular carbon membrane with an average pore size of 8.3 nm to load 0.1 wt% of a bimetallic palladium copper catalyst, and the inside of the membrane tube is filled with activated carbon. The reference electrode 2 uses a mercuric oxide electrode.

[0288] Based on the membrane-based electrocatalytic nanofluid reactor, a purification system for purifying wastewater containing nitrate nitrogen is provided in Example 9 of the present invention, which is different from Example 1 in that: the electrolyte solution is a 0.5M sodium hydroxide solution

[0289] Based on the purification system for purifying wastewater containing nitrate nitrogen, a purification method for purifying wastewater containing nitrate nitrogen provided in Example 9 of the present invention is the same as that in Example 1.

[0290] The results showed that the permeate flux was 7.2 L h -1 m -2 bar -1 , the nitrate nitrogen single-pass removal rate is 100%, the nitrogen selectivity is 94.25%, and the hydraulic retention time is 417.6S.

[0291] Example 10

[0292] Embodiment 10 of the present invention provides a membrane-based electrocatalytic nanofluid reactor for purifying wastewater containing nitrate nitrogen, which is different from Embodiment 1 in that: a conductive nanoporous membrane 3 adopts a tubular carbon membrane with an average pore size of 8.3 nm loaded with 0.1 wt% diatomic palladium copper catalyst as the cathode, and the operating voltage of the external power supply 1 is -3 V vs SCE.

[0293] Based on the membrane-based electrocatalytic nanofluid reactor, Example 10 of the present invention provides a purification system for purifying wastewater containing nitrate nitrogen, which is the same as Example 1.

[0294] Based on the purification system for purifying wastewater containing nitrate nitrogen, Example 10 of the present invention provides a purification method for purifying wastewater containing nitrate nitrogen, which is the same as Example 1.

[0295] The results showed that the permeate flux was 11 L h -1 m -2 bar -1 , the single-pass removal efficiency of nitrate nitrogen is 70%, the nitrogen selectivity is 60%, and the hydraulic retention time is 305s.

[0296] Embodiment 11

[0297] Example 11 of the present invention provides a membrane-based electrocatalytic nanofluid reactor for purifying wastewater containing nitrate nitrogen, which is different from Example 1 in that: a conductive nanoporous membrane 3 uses a tubular carbon membrane with an average pore size of 4nm and loaded with 0.1wt% diatomic palladium copper catalyst as the cathode.

[0298] Based on the membrane-based electrocatalytic nanofluid reactor, Example 11 of the present invention provides a purification system for purifying wastewater containing nitrate nitrogen, which is the same as Example 1.

[0299] Based on the purification system for purifying wastewater containing nitrate nitrogen, Example 11 of the present invention provides a purification method for purifying wastewater containing nitrate nitrogen, which is the same as Example 1.

[0300] The results showed that the permeate flux was 6 L h -1 m -2 bar -1 , the single-pass removal rate of nitrate nitrogen is 100%, the nitrogen selectivity is 91%, and the hydraulic retention time is 651s.

[0301] Example 12

[0302] Example 12 of the present invention provides a membrane-based electrocatalytic nanofluid reactor for purifying wastewater containing nitrate nitrogen, which is different from Example 1 in that: a conductive nanoporous membrane 3 uses a tubular carbon membrane with an average pore size of 430 nm loaded with 0.1 wt% diatomic palladium copper catalyst as the cathode.

[0303] Based on the membrane-based electrocatalytic nanofluid reactor, Example 12 of the present invention provides a purification system for purifying wastewater containing nitrate nitrogen, which is the same as Example 1.

[0304] Based on the purification system for purifying wastewater containing nitrate nitrogen, Example 12 of the present invention provides a purification method for purifying wastewater containing nitrate nitrogen, which is the same as Example 1.

[0305] The results showed that the permeate flux was 35 L h -1 m -2 bar -1 The single-pass removal rate of nitrate nitrogen is 43%, the nitrogen selectivity is 48%, and the hydraulic retention time is 0.001s.

[0306] Example 13

[0307] Example 13 of the present invention provides a membrane-based electrocatalytic nanofluid reactor for purifying wastewater containing nitrate nitrogen, which is different from Example 1 in that: a conductive nanoporous membrane 3 uses a tubular carbon membrane with an average pore size of 660 nm loaded with 0.1 wt% diatomic palladium copper catalyst as the cathode.

[0308] Based on the membrane-based electrocatalytic nanofluid reactor, Example 13 of the present invention provides a purification system for purifying wastewater containing nitrate nitrogen, which is the same as Example 1.

[0309] Based on the purification system for purifying wastewater containing nitrate nitrogen, Example 13 of the present invention provides a purification method for purifying wastewater containing nitrate nitrogen, which is the same as Example 1.

[0310] The results showed that the permeate flux was 55 L h -1 m -2 bar -1 The single-pass removal rate of nitrate nitrogen is 46%, the nitrogen selectivity is 59%, and the hydraulic retention time is 0.0004s.

[0311] Embodiment 14

[0312] Example 14 of the present invention provides a membrane-based electrocatalytic nanofluid reactor for purifying wastewater containing nitrate nitrogen, which is different from Example 1 in that: a conductive nanoporous membrane 3 uses a tubular carbon membrane with an average pore size of 8.3 nm loaded with 0.1 wt% diatomic palladium copper catalyst as the cathode.

[0313] Based on the membrane-based electrocatalytic nanofluid reactor, Example 14 of the present invention provides a purification system for purifying wastewater containing nitrate nitrogen, which is different from Example 1 in that the concentration of nitrate nitrogen in the wastewater is 1 mM.

[0314] Based on the purification system for purifying wastewater containing nitrate nitrogen, Example 14 of the present invention provides a purification method for purifying wastewater containing nitrate nitrogen, which is the same as Example 1.

[0315] The results showed that the permeate flux was 25 L h -1 m -2 bar -1 , the single-pass removal rate of nitrate nitrogen is 100%, the nitrogen selectivity is 65%, and the hydraulic retention time is 283s.

[0316] Embodiment 15

[0317] Example 15 of the present invention provides a membrane-based electrocatalytic nanofluid reactor for purifying wastewater containing nitrate nitrogen, which is different from Example 1 in that: a conductive nanoporous membrane 3 uses a tubular carbon membrane with an average pore size of 8.3 nm loaded with 0.1 wt% diatomic palladium copper catalyst as the cathode.

[0318] Based on the membrane-based electrocatalytic nanofluid reactor, Example 15 of the present invention provides a purification system for purifying wastewater containing nitrate nitrogen, which is different from Example 1 in that the concentration of nitrate nitrogen wastewater is 1000 mM.

[0319] Based on the purification system for purifying wastewater containing nitrate nitrogen, Example 15 of the present invention provides a purification method for purifying wastewater containing nitrate nitrogen, which is the same as Example 1.

[0320] The results showed that the permeate flux was 25 L h -1 m -2 bar -1 , the single-pass removal efficiency of nitrate nitrogen is 85%, the nitrogen selectivity is 10%, and the hydraulic retention time is 283s.

[0321] Comparative Example 1

[0322] (i) The flow-through reactor provided in Comparative Example 1 is different from that in Example 1 in that: the conductive nanoporous membrane 3 uses a tubular carbon membrane with an average pore size of 8.3 nm to load 0.1 wt% of a bimetallic palladium-copper catalyst, and no cation exchange membrane 6 is provided.

[0323] (ii) Based on the flow-through reactor, the purification system for removing nitrate nitrogen from water provided in Comparative Example 1 has a specific structure as follows Figure 5 As shown, it includes: a flow-through reactor, a reaction tank 15 , a magnet 13 and a magnetic stirrer 14 .

[0324] The reaction tank 15 is used as a storage tank for nitrate nitrogen-containing wastewater, wherein the volume of the nitrate nitrogen-containing wastewater is 100 mL, the temperature of the nitrate nitrogen-containing wastewater is 25° C., and the nitrate nitrogen-containing wastewater includes: an electrolyte solution: 0.5 M sodium sulfate solution and 0.05 M sodium nitrate solution, and transparent nitrate nitrogen wastewater with a concentration of 50 mM and a pH value of 6.5.

[0325] The magneton 13 is placed in the cathode pool 8 to cooperate with the magnetic stirrer 14 to stir at a speed of 200 r / min to increase the speed and efficiency of the nitrate nitrogen-containing wastewater entering the area to be purified of the conductive nanoporous membrane 3.

[0326] The results showed that the single-pass removal efficiency of nitrate nitrogen was 40%, the nitrogen selectivity was 20%, and the hydraulic retention time was 10h.

[0327] Comparative Example 2

[0328] Comparative Example 2 provides a flow-through reactor, which is different from Comparative Example 1 in that: the conductive nanoporous membrane 3 uses a tubular carbon membrane with an average pore size of 4 nm loaded with 0.1 wt% diatomic palladium copper catalyst as the cathode.

[0329] Based on the flow-through reactor, Comparative Example 2 provides a purification system for purifying wastewater containing nitrate nitrogen, which is the same as Comparative Example 1.

[0330] The results showed that the single-pass removal efficiency of nitrate nitrogen was 50%, the nitrogen selectivity was 25%, and the hydraulic retention time was 10h.

[0331] Comparative Example 3

[0332] Comparative Example 3 provides a flow-through reactor, which is different from Comparative Example 1 in that: the conductive nanoporous membrane 3 uses a tubular carbon membrane with an average pore size of 660 nm loaded with 0.1 wt% diatomic palladium copper catalyst as the cathode.

[0333] Based on the flow-through reactor, Comparative Example 3 provides a purification system for purifying wastewater containing nitrate nitrogen, which is the same as Comparative Example 1.

[0334] The results showed that the single-pass removal efficiency of nitrate nitrogen was 35%, the nitrogen selectivity was 10%, and the hydraulic retention time was 10h.

[0335] Comparative Example 4

[0336] Comparative Example 4 provides a flow-through reactor, which is different from Comparative Example 1 in that: the conductive nanoporous membrane 3 uses a tubular carbon membrane with an average pore size of 8.3 nm loaded with 0.1 wt% bimetallic palladium copper catalyst as the cathode, and activated carbon is filled inside the membrane tube.

[0337] Based on the flow-through reactor, Comparative Example 4 provides a purification system for purifying wastewater containing nitrate nitrogen, which is the same as Comparative Example 1.

[0338] The results showed that the single-pass removal efficiency of nitrate nitrogen was 60%, the nitrogen selectivity was 45%, and the hydraulic retention time was 10h.

[0339] Comparative Example 5

[0340] Comparative Example 5 provides a flow-through reactor, which is different from Comparative Example 1 in that: the conductive nanoporous membrane 3 uses a tubular carbon membrane with an average pore size of 660nm loaded with 0.1wt% bimetallic palladium copper catalyst as the cathode, and activated carbon is filled inside the membrane tube.

[0341] Based on the flow-through reactor, Comparative Example 5 provides a purification system for purifying wastewater containing nitrate nitrogen, which is the same as Comparative Example 1.

[0342] The results showed that the single-pass removal efficiency of nitrate nitrogen was 55%, the nitrogen selectivity was 40%, and the hydraulic retention time was 10h.

[0343] Comparative Example 6

[0344] Comparative Example 6 provides a flow-through reactor, which is different from Comparative Example 1 in that: the conductive nanoporous membrane 3 uses a tubular carbon membrane with an average pore size of 8.3nm loaded with 0.1wt% diatomic palladium copper catalyst as the cathode, and the working voltage of the external power supply 1 is -10V vs SCE.

[0345] Based on the flow-through reactor, Comparative Example 6 provides a purification system for purifying wastewater containing nitrate nitrogen, which is the same as Comparative Example 1.

[0346] The results showed that the single-pass removal efficiency of nitrate nitrogen was 70%, the nitrogen selectivity was 3%, and the hydraulic retention time was 10h.

[0347] In summary, from the comparison of the results of the single-pass removal rate of nitrate nitrogen and the nitrogen selectivity of Examples 1 to 15 and Comparative Examples 1 to 6, it can be seen that the sewage treatment method for removing nitrate nitrogen in water provided by the present invention, by coupling the confinement effect in the membrane pores and the electric field effect of the electrocatalytic process, causes nitrate ions to collide with the active catalytic sites on the pore walls in the membrane pores, and are catalytically degraded into harmless product nitrogen under the action of the electric field, with a short hydraulic retention time, and efficient removal of nitrate ions in sewage, which significantly improves the efficiency of the reactor and significantly improves the degree of harmlessness of the product.

Claims

1. A membrane-based electrocatalytic nanofluid reactor for purifying wastewater containing nitrate nitrogen, characterized in that: The membrane-based electrocatalytic nanofluid reactor comprises: An external power source for providing an electric field; A reference electrode, the reference electrode, the conductive nanoporous membrane and the counter electrode form a three-electrode system; The conductive nanoporous membrane is connected to the external power source and is used as a cathode. The conductive nanoporous membrane is the place where the wastewater containing nitrate nitrogen undergoes electrocatalytic reduction, wherein the wastewater containing nitrate nitrogen undergoes an electrocatalytic reduction chemical reaction in the pores of the conductive nanoporous membrane; The counter electrode is disposed on the upstream side or the downstream side of the conductive nanoporous membrane and connected to an external power source to serve as an anode; The chemical reaction equations of electrocatalytic reduction are shown in (1)-(5): 2NO3 - (ads)+5H2→N2+2OH - +4H2O(2) NO3 - (ads)+H2→NO2 - +H2O(3) <h2 style=";text-align:left;direction:ltr">2NO2<h2 style=";text-align:left;direction:ltr"> - <h2 style=";text-align:left;direction:ltr"> (ads)+2H<h2 style=";text-align:left;direction:ltr"> + <h2 style=";text-align:left;direction:ltr"> +3H2→N2+H2O(4) <h2 style=";text-align:left;direction:ltr">2NO3<h2 style=";text-align:left;direction:ltr"> - <h2 style=";text-align:left;direction:ltr"> +8H2→2NH4<h2 style=";text-align:left;direction:ltr"> + <h2 style=";text-align:left;direction:ltr"> +4OH<h2 style=";text-align:left;direction:ltr"> - <h2 style=";text-align:left;direction:ltr"> +2H2O(5)。 2. The membrane-based electrocatalytic fluid reactor according to claim 1, characterized in that: The membrane-based electrocatalytic nanofluid reactor further comprises: epoxy glue, which covers one end of the conductive nanoporous membrane to seal the membrane tube of the conductive nanoporous membrane. Preferably, the epoxy glue is PKM12C-1 epoxy glue; The cation exchange membrane is used to separate the anode and the cathode to prevent the reduction product after electrocatalytic reduction from being oxidized. Preferably, the reduction product is anion and / or gas, and more preferably, the reduction product is NO2 - and / or nitrogen; Preferably, the cation exchange membrane is a Nafion 117 cation exchange membrane.

3. The membrane-based electrocatalytic fluid reactor according to claim 1, characterized in that: The conductive nanoporous membrane is a porous conductive membrane; Preferably, the porous conductive membrane is a surface-modified porous conductive membrane and / or a porous conductive membrane with catalytically active components loaded in the pores; More preferably, the surface-modified porous conductive membrane is a surface-modified porous conductive membrane filled with activated carbon; More preferably, the porous conductive membrane having catalytically active components loaded in the pores is a porous conductive membrane having catalytically active components loaded in the pores and filled with activated carbon; Most preferably, the catalytically active component is a bimetallic palladium-copper catalyst, or a diatomic palladium-copper catalyst.

4. The membrane-based electrocatalytic nanofluid reactor according to claim 3, characterized in that: The porous conductive film is one or more of a porous metal film, a porous carbon film, a porous carbide film, a porous metal oxide film, a porous polymer film and a porous conductive composite film; Preferably, the porous metal membrane is a titanium membrane; Preferably, the porous carbon membrane is one of a tubular carbon membrane and a flat carbon membrane, and more preferably, the porous carbon membrane is a tubular carbon membrane.

5. The membrane-based electrocatalytic nanofluid reactor according to claim 4, characterized in that: The average pore size of the tubular carbon membrane is 4 to 660 nm; preferably, the average pore size of the tubular carbon membrane is 4 to 430 nm, and more preferably, the average pore size of the tubular carbon membrane is 4 to 8.3 nm.

6. The membrane-based electrocatalytic nanofluid reactor according to claim 5, characterized in that: The loading amount of the bimetallic palladium-copper catalyst is 0.01-1 wt % based on the weight of the tubular carbon membrane.

7. The membrane-based electrocatalytic nanofluid reactor according to claim 5, characterized in that: The loading amount of the diatomic palladium-copper catalyst is 0.001-0.1 wt % based on the weight of the tubular carbon membrane.

8. The membrane-based electrocatalytic nanofluid reactor according to any one of claims 1 to 7, characterized in that: The reference electrode is a mercuric oxide electrode in an alkaline electrolyte, or a saturated calomel electrode in a neutral or acidic electrolyte; preferably, the alkaline electrolyte is 0.05-1M sodium hydroxide solution, and preferably, the neutral electrolyte is 0.05-1M sodium sulfate solution.

9. The membrane-based electrocatalytic nanofluid reactor according to any one of claims 1 to 8, characterized in that: The conductive nanoporous membrane is electrically connected to an external power source to serve as a cathode.

10. The membrane-based electrocatalytic nanofluid reactor according to any one of claims 1 to 9, characterized in that: The operating voltage of the external power supply is -10 to -2 V vs SCE, preferably -4 to -2 V vs SCE, and more preferably -4 to -3 V vs SCE.

11. The membrane-based electrocatalytic fluid reactor according to any one of claims 1 to 10 is characterized in that: According to the direction in which the wastewater containing nitrate nitrogen passes through the conductive nanoporous membrane, a counter electrode is arranged near the upstream side or the downstream side of the conductive nanoporous membrane.

12. The membrane-based electrocatalytic nanofluid reactor according to any one of claims 1 to 11, characterized in that: The counter electrode is one or more of a metal, an intermetallic compound, a carbide, a carbon electrode and a conductive nanoporous membrane; preferably, the counter electrode is one or more of a platinum electrode, stainless steel, a graphite plate and a carbon electrode; more preferably, the counter electrode is a platinum electrode.

13. The membrane-based electrocatalytic nanofluid reactor according to any one of claims 1 to 12, characterized in that: The nitrate nitrogen concentration in the nitrate nitrogen-containing wastewater is 1-1000 mM, preferably, the concentration is 40-70 mM.

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