Device for coupling flowing capacitive deionization with electrochemical denitrification

Abstract

The utility model provides a device for coupling flowing capacitive deionization with electrochemical denitrification, and belongs to the technical field of water treatment. When the device provided by the utility model is used for treating the wastewater, the FCDI process is carried out by taking the flowing electrode as a cathode and the carbon-based fixed electrode as an anode, and the wastewater in the reaction cavity is contacted with the cation exchange membrane and the anion exchange membrane; ammonia nitrogen and hardness ions in the wastewater are adsorbed by an electrode material filled in an S-shaped flow channel of an electrode cavity through a cation exchange membrane, so that the effects of removing the ammonia nitrogen and controlling deposition and blockage of the hardness ions in the wastewater in the denitrification process are achieved; meanwhile, interference of competitive anions is removed through a carbon-based material, so that nitrate ions in the wastewater are enriched at the anode; after the FCDI process is completed, the flowing electrode is used as an anode, the fixed electrode is used as a cathode, the NO3RR process is carried out, and in the process, enriched nitrate ions are reduced into N2, so that harmless conversion of nitrate and nitrogen can be efficiently realized.

Description

Technical Field

[0001] The utility model relates to the technical field of water treatment, in particular to a device and method for coupling flow-through capacitive deionization with electrochemical denitrification. Background Art

[0002] The accumulation of nitrate nitrogen in industrialized recirculating aquaculture systems (RAS) is one of the important environmental problems, and it is particularly important to achieve the harmless conversion of nitrate nitrogen. At present, the main treatment methods for the harmless conversion of nitrate nitrogen include: ion exchange, reverse osmosis, biological denitrification, catalytic hydrogenation, and electrochemical reduction, etc. The electrochemical reduction of nitrate nitrogen technology (NO3RR) has the advantages of high removal efficiency, mild operating conditions, controllable selectivity of target products, and environmental friendliness, and thus has gradually become a research hotspot. However, the influence of interfering ions, the electrostatic repulsion on the electrode surface, and the poor selectivity of electrocatalysts severely restrict the efficient removal of nitrate nitrogen by the electrochemical reduction of nitrate nitrogen technology and its application in RAS.

[0003] The flow-through capacitive deionization (FCDI) technology is a new electro-adsorption water treatment technology. The basic principle of the FCDI technology is to apply an external voltage or current at both ends of the cathode and anode to form an electrostatic field between the electrodes. Charged ions or particles move towards the electrode chamber with the opposite electric charge due to the electrostatic force in the electrostatic field and are finally adsorbed on the surface of the current collector plate or electrode particles to form an electric double layer and be stored therein. However, when this method is applied in RAS, it cannot achieve the harmless conversion of nitrate nitrogen.

[0004] Therefore, the existing methods for the harmless conversion of nitrate nitrogen have unsatisfactory ammonia nitrogen removal effects, and there is no reported device for achieving the efficient harmless conversion of nitrate nitrogen by coupling NO3RR with FCDI. Summary of the Utility Model

[0005] The purpose of the utility model is to provide a device for coupling flow-through capacitive deionization with electrochemical denitrification. The device for coupling flow-through capacitive deionization with electrochemical denitrification provided by the utility model can efficiently achieve the harmless conversion of nitrate nitrogen.

[0006] In order to achieve the above-mentioned utility model purpose, the utility model provides the following technical solutions:

[0007] The utility model provides a flow electrode, a cation exchange membrane, a reaction cavity, an anion exchange membrane, and a carbon-based fixed electrode that are sequentially in contact;

[0008] A serpentine flow channel is engraved on the side surface of the electrode cavity of the flow electrode that is in contact with the cation exchange membrane; a liquid inlet and a liquid outlet are provided on the electrode cavity, and the liquid inlet and the liquid outlet are respectively arranged at both ends of the serpentine flow channel;

[0009] The reaction cavity is a silica gel plate with a serpentine hollow; the serpentine hollow coincides with the projection of the serpentine flow channel in the electrode cavity on the cation exchange membrane; the space formed by the serpentine hollow, the cation exchange membrane and the anion exchange membrane is the reaction chamber; the reaction cavity is provided with a water inlet and a water outlet; the water inlet is arranged at one end of the serpentine hollow corresponding to the liquid inlet; the water outlet is arranged at one end of the serpentine hollow corresponding to the liquid outlet; the reaction chamber includes through holes with nuts.

[0010] Preferably, the liquid inlet and the liquid outlet are connected to an external regeneration pool.

[0011] Preferably, the length of the electrode cavity is 80 - 200 mm, the width of the electrode cavity is 50 - 120 mm, and the thickness of the electrode cavity is 5 - 15 mm.

[0012] Preferably, the length of the electrode cavity is 120 mm, the width of the electrode cavity is 80 mm, and the thickness of the electrode cavity is 8 mm.

[0013] Preferably, the depth of the serpentine flow channel is 1 - 3 mm.

[0014] Preferably, the width of the serpentine flow channel is 1 - 3 mm.

[0015] Preferably, the number of columns of the serpentine flow channel is 15 - 35 columns.

[0016] Preferably, the depth of the serpentine flow channel is 2 mm, the width of the serpentine flow channel is 2 mm, and the number of columns of the serpentine flow channel is 18 columns.

[0017] Preferably, the number of through holes with nuts is more than two.

[0018] Preferably, the number of through holes with nuts is two.

[0019] The present utility model provides a device for flow-through capacitive deionization coupled with electrochemical denitrification, which includes a flow electrode, a cation exchange membrane, a reaction cavity, an anion exchange membrane, and a carbon-based fixed electrode that are sequentially in contact; a serpentine flow channel is engraved on the side surface of the electrode cavity of the flow electrode that contacts the cation exchange membrane; a liquid inlet and a liquid outlet are provided on the electrode cavity, and the liquid inlet and the liquid outlet are respectively arranged at both ends of the serpentine flow channel; the reaction cavity is a silica gel plate with serpentine hollowing; the serpentine hollowing coincides with the projection of the serpentine flow channel in the electrode cavity on the cation exchange membrane; the space formed by the serpentine hollowing, the cation exchange membrane, and the anion exchange membrane is the reaction chamber; a water inlet and a water outlet are provided on the reaction cavity; the water inlet is arranged at one end of the serpentine hollowing corresponding to the liquid inlet; the water outlet is arranged at one end of the serpentine hollowing corresponding to the liquid outlet; the reaction chamber includes through holes with nuts. When the device provided by the present utility model treats wastewater, first, the flow electrode is used as the cathode and the carbon-based fixed electrode is used as the anode to carry out the FCDI process. During this process, the wastewater in the reaction cavity contacts the cation exchange membrane and the anion exchange membrane, so that ammonia nitrogen and hardness ions (such as Ca 2+ 、Mg 2+ etc.) in the wastewater are adsorbed by the electrode material filled in the serpentine flow channel of the electrode cavity through the cation exchange membrane, achieving the effect of removing ammonia nitrogen and hardness interfering ions in the wastewater; at the same time, anions (such as NO 3- etc.) in the wastewater are enriched to the anode; after the FCDI process is completed, by switching the positive and negative poles of the power supply, the flow electrode is used as the anode and the fixed electrode is used as the cathode to carry out the NO3RR process. During this process, the enriched anions are reduced to N2, and thus the harmless conversion of nitrate nitrogen can be efficiently realized. The results of the examples show that when the flow-through capacitive deionization coupled with electrochemical denitrification device provided by the present utility model operates for 50 minutes, at different initial concentrations, the removal rate of NO 3- can be maintained above 93%, and the N2 selectivity is maintained above 96%, and the harmless conversion of nitrate nitrogen can be efficiently realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is an exploded schematic view of the device for flow-through capacitive deionization coupled with electrochemical denitrification of the present utility model. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] The present utility model provides a device for flow-through capacitive deionization coupled with electrochemical denitrification, which includes a flow electrode, a cation exchange membrane, a reaction cavity, an anion exchange membrane, and a carbon-based fixed electrode that are sequentially in contact;

[0022] On the side of the electrode cavity of the flow electrode that contacts the cation exchange membrane, a serpentine flow channel is engraved; an inlet and an outlet are provided on the electrode cavity, and the inlet and the outlet are respectively arranged at both ends of the serpentine flow channel;

[0023] The reaction cavity is a conductive plate with serpentine hollowing; the serpentine hollowing coincides with the projection of the serpentine flow channel in the electrode cavity on the cation exchange membrane; the space formed by the serpentine hollowing, the cation exchange membrane and the anion exchange membrane is the reaction chamber; an inlet and an outlet are provided on the reaction cavity; the inlet is arranged at one end of the serpentine hollowing corresponding to the inlet; the outlet is arranged at one end of the serpentine hollowing corresponding to the outlet; the reaction chamber includes through holes with nuts.

[0024] As Figure 1 shown, in the present invention, the device for flow-capacitive deionization coupled electrochemical denitrification includes a flow electrode, a cation exchange membrane, a reaction cavity, an anion exchange membrane and a carbon-based fixed electrode which are sequentially arranged in contact.

[0025] In the present invention, the device for flow-capacitive deionization coupled electrochemical denitrification includes a flow electrode.

[0026] In the present invention, a serpentine flow channel is engraved on the side of the electrode cavity of the flow electrode that contacts the cation exchange membrane. The present invention uses the serpentine flow channel as the flow channel of the liquid-phase electrode material, which can enable the liquid-phase electrode material to contact the cation exchange membrane and adsorb the hardness interfering ions in the wastewater.

[0027] In the present invention, the length of the electrode cavity is preferably 80 - 200 mm, more preferably 120 mm; the width of the electrode cavity is preferably 50 - 120 mm, more preferably 80 mm; the thickness of the electrode cavity is preferably 5 - 15 mm, more preferably 8 mm. The present invention selects the size of the electrode cavity according to the amount of wastewater and the mechanical bearing capacity of the reaction device. When the size of the electrode cavity is within the above range, it is more conducive to increasing the treatment amount of wastewater.

[0028] The present invention has no special limitation on the material of the electrode cavity, and conventional electrode cavities can be used. In the present invention, the material of the electrode cavity is preferably graphite.

[0029] In the present utility model, the depth of the serpentine flow channel is preferably 1 - 3 mm, more preferably 2 mm; the width of the serpentine flow channel is preferably 1 - 3 mm, more preferably 2 mm; the number of columns of the serpentine flow channel is preferably 15 - 35 columns, more preferably 18 columns. By controlling the parameters of the serpentine flow channel within the above ranges, the present utility model can enable the cation exchange membrane to have an appropriate contact area with the electrode cavity, which is more conducive to increasing the wastewater treatment capacity. In one embodiment of the present utility model, the contact area between the cation exchange membrane and the serpentine flow channel of the electrode cavity is preferably 25 cm 2 .

[0030] In the present utility model, a liquid inlet and a liquid outlet are provided on the electrode cavity, and the liquid inlet and the liquid outlet are respectively arranged at both ends of the serpentine flow channel. In one embodiment of the present utility model, the liquid inlet and the liquid outlet are connected to an external regeneration tank. By connecting both ends of the serpentine flow channel to an external regeneration tank, the present utility model can regenerate the liquid-phase electrode material that adsorbs hardness ions and improve the service life of the electrode.

[0031] The present utility model has no special limitation on the material of the liquid-phase electrode material, and any conventional liquid-phase electrode material for a flow electrode can be used. In one embodiment of the present utility model, the liquid-phase electrode material is preferably an activated carbon suspension, which is obtained by dispersing activated carbon in a 0.1 mol / L NaCl solution, and the mass of the activated carbon accounts for 5% of the mass of the NaCl solution.

[0032] In the present utility model, the device for flow-through capacitive deionization coupled with electrochemical denitrification includes a cation exchange membrane that contacts one side of the electrode cavity engraved with a serpentine flow channel.

[0033] The present utility model has no special limitation on the material of the cation exchange membrane, and any conventional commercially available cation exchange membrane can be used. In one embodiment of the present utility model, the source of the cation exchange membrane is preferably Corning Water. The present utility model uses a flow electrode to remove ammonia nitrogen and hardness ions from wastewater.

[0034] In the present utility model, the device for flow-through capacitive deionization coupled with electrochemical denitrification includes a reaction cavity that contacts the cation exchange membrane.

[0035] In the present utility model, the reaction cavity is a silica gel plate with serpentine hollowing.

[0036] The present utility model has no special limitation on the source of the silica gel plate, and any conventional silica gel plate can be used.

[0037] In the present utility model, the serpentine hollowing coincides with the projection of the serpentine flow channel in the electrode cavity on the cation exchange membrane. The present utility model uses the space formed by the serpentine hollowing, the cation exchange membrane, and the anion exchange membrane as the reaction chamber for the wastewater to be treated.

[0038] In the present utility model, the reaction chamber is provided with a water inlet and a water outlet; the water inlet is arranged at one end of the serpentine hollowing corresponding to the liquid inlet; the water outlet is arranged at one end of the serpentine hollowing corresponding to the liquid outlet. In the present utility model, the wastewater to be treated enters the reaction chamber through the water inlet, and the treated wastewater flows out through the water outlet, enabling the wastewater to be circulated through the reaction chamber for treatment.

[0039] In the present utility model, the reaction chamber includes through holes with nuts. In the present utility model, the number of the through holes with nuts is preferably more than two, and more preferably two. In the present utility model, by providing through holes with nuts on the reaction chamber, the function of the nuts can control the opening and closing of the through holes. After the nuts are opened, the through holes are opened, which is more conducive to the discharge of the generated N2.

[0040] In the present utility model, the wastewater in the wastewater tank enters the reaction chamber through the water inlet, undergoes flow-through capacitive deionization reaction in the reaction chamber, then flows out of the reaction chamber through the water outlet, and enters the wastewater tank, achieving the deposition blockage removal effect of hardness ions in the wastewater during the denitrification process through the circulation process.

[0041] In the present utility model, the device for flow-through capacitive deionization coupled with electrochemical denitrification includes an anion exchange membrane in contact with the reaction chamber.

[0042] The present utility model has no special limitation on the material of the anion exchange membrane, and a conventional commercially available anion exchange membrane can be used. In an embodiment of the present utility model, the source of the anion exchange membrane is preferably Corning Water. The present utility model uses the anion exchange membrane to enrich anions in the wastewater.

[0043] In the present utility model, the device for flow-through capacitive deionization coupled with electrochemical denitrification includes a carbon-based fixed electrode in contact with the anion exchange membrane.

[0044] In the present utility model, the carbon-based fixed electrode is preferably a carbon-based fixed electrode formed by coating a carbon-based composite material powder on a current collector or a self-supporting carbon-based composite material.

[0045] In the present utility model, the carbon-based composite material is preferably activated carbon.

[0046] In the present utility model, the current collector is preferably a graphite plate.

[0047] When the device provided by the present utility model treats wastewater, first, a flow electrode is used as the cathode and a carbon-based fixed electrode is used as the anode to carry out the FCDI process. During this process, the wastewater in the reaction chamber contacts the cation exchange membrane and the anion exchange membrane, so that the hardness ions (such as Ca 2+ 、Mg 2+ etc.) in the wastewater are selectively adsorbed by the electrode material filled in the serpentine flow channel of the electrode chamber through the cation exchange membrane, achieving the effect of removing the hardness interfering ions in the wastewater; at the same time, the anions (such as NO 3- etc.) in the wastewater are enriched to the anion exchange membrane; after the FCDI process is completed, by switching the positive and negative poles of the power supply, the flow electrode is used as the anode and the fixed electrode is used as the cathode to carry out the NO3RR process. During this process, the enriched anions are reduced to N2, and thus the harmless conversion of nitrate nitrogen can be efficiently realized.

[0048] Next, the technical solutions in the present utility model will be clearly and completely described in conjunction with the embodiments in the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all the embodiments. Based on the embodiments in the present utility model, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the protection scope of the present utility model.

[0049] Example 1

[0050] As Figure 1 shown, the device for flow-through capacitive deionization coupled with electrochemical denitrification in this embodiment includes a flow electrode, a cation exchange membrane, a reaction chamber, an anion exchange membrane, and a carbon-based fixed electrode that are sequentially in contact;

[0051] A serpentine flow channel is engraved on the side of the electrode chamber of the flow electrode that contacts the cation exchange membrane; an inlet and an outlet are provided on the electrode chamber, and the inlet and the outlet are respectively arranged at both ends of the serpentine flow channel;

[0052] The reaction chamber is a silica gel plate with serpentine hollowing; the serpentine hollowing coincides with the projection of the serpentine flow channel in the electrode chamber on the cation exchange membrane; the space formed by the serpentine hollowing, the cation exchange membrane, and the anion exchange membrane is the reaction chamber; an inlet and an outlet are provided on the reaction chamber; the inlet is arranged at one end of the serpentine hollowing corresponding to the inlet; the outlet is arranged at one end of the serpentine hollowing corresponding to the outlet; the reaction chamber includes through holes with nuts.

[0053] Example 2

[0054] The device for flow-through capacitive deionization coupled with electrochemical denitrification in this embodiment includes a flow electrode, a cation exchange membrane, a reaction chamber, an anion exchange membrane, and a carbon-based fixed electrode that are sequentially in contact; the self-supporting activated carbon of the carbon-based fixed electrode;

[0055] Both the cation exchange membrane and the anion exchange membrane are from Corning Water.

[0056] On the side of the electrode cavity of the flow electrode that contacts the cation exchange membrane, a serpentine flow channel is engraved; the length of the flow electrode is 120 mm; the width of the flow electrode is 80 mm; the thickness of the flow electrode is a graphite plate of 8 mm; the depth of the serpentine flow channel is 2 mm; the width of the serpentine flow channel is 2 mm; the number of columns of the serpentine flow channel is 18 columns; the serpentine flow channel serves as the flow channel for the liquid-phase electrode material, and the liquid-phase electrode material is an activated carbon suspension, which is obtained by dispersing activated carbon in a 0.1 mol / L NaCl solution, and the mass of the activated carbon accounts for 5% of the mass of the NaCl solution;

[0057] The electrode cavity is provided with a liquid inlet and a liquid outlet, and the liquid inlet and the liquid outlet are respectively arranged at both ends of the serpentine flow channel; the liquid inlet and the liquid outlet are connected to an external regeneration pool;

[0058] The reaction chamber is a silica gel plate with serpentine hollowing; the serpentine hollowing coincides with the projection of the serpentine flow channel in the electrode cavity on the cation exchange membrane; the reaction chamber is provided with a water inlet and a water outlet; the water inlet is arranged at one end of the serpentine hollowing corresponding to the liquid inlet; the water outlet is arranged at one end of the serpentine hollowing corresponding to the liquid outlet; the water inlet and the water outlet are connected to an external circulation pool; there are two through holes with nuts on the reaction chamber.

[0059] The method for denitrification using the above device for flow-through capacitive deionization coupled with electrochemical denitrification is as follows:

[0060] Prepare 100 mL of simulated seawater aquaculture circulating water in advance as the wastewater to be treated for standby, with an initial Cl- concentration of 19000 mg / L -1 , and regulate the initial concentration of NO3 - (10 mg / L -1 , 20 mg / L -1 , 50 mg / L -1 , 100 mg / L -1 , and 200 mg / L -1 ).

[0061] The liquid-phase electrode material is introduced into the serpentine flow channel of the electrode cavity through the liquid inlet at a flow rate of 5 mL / min by a peristaltic pump to form a flowing electrode; wherein, the liquid-phase electrode material is an activated carbon suspension obtained by dispersing activated carbon in a 0.1 mol / L NaCl solution, and the mass of the activated carbon accounts for 5% of the mass of the NaCl solution.

[0062] The flowing electrode is connected to the negative electrode of an external power supply, and the fixed electrode is connected to the positive electrode of the external power supply. The voltage is 1.2 V to obtain an FCDI system.

[0063] The NO3 - with an initial concentration of 10 mg / L -1 of the wastewater to be treated is introduced into the reaction cavity through the water inlet at a flow rate of 12 mL / min and flows out through the water outlet. The FCDI process is cycled for 20 min. After the cation content in the treated wastewater reaches the standard (concentration < 7 mg / L), the introduction of the wastewater to be treated is stopped, and the remaining wastewater in the reaction chamber is retained.

[0064] The positive and negative electrodes of the external power supply are switched so that the flowing electrode is connected to the positive electrode of the external power supply and the fixed electrode is connected to the negative electrode of the external power supply to obtain a NO3RR system.

[0065] The through-hole of the reaction chamber is opened. The remaining wastewater is in the NO3RR system, and the current density is controlled at 30 mA / cm -2 , and it runs for 30 min to carry out an electrochemical reduction reaction until no more gas is generated.

[0066] Example 3

[0067] The difference from Example 2 is that the NO3 - has an initial concentration of 20 mg / L -1 , and the remaining steps are the same as those in Example 2.

[0068] Example 4

[0069] The difference from Example 2 is that the NO3 - has an initial concentration of 50 mg / L -1 , and the remaining steps are the same as those in Example 2.

[0070] Example 5

[0071] The difference from Example 2 is that the NO3 - has an initial concentration of 100 mg / L -1 , and the remaining steps are the same as those in Example 2.

[0072] Example 6

[0073] The difference from Example 2 is that the NO3 - has an initial concentration of 200 mg / L-1 , and the remaining steps are the same as those in Example 2.

[0074] The purified water obtained in Examples 2 to 6 was respectively measured for NO by ultraviolet-visible absorption spectrometry 3- and NO 2- concentrations. The ammonia nitrogen and total nitrogen (TN) concentrations were measured by Nessler's reagent and alkaline potassium persulfate digestion-ultraviolet spectrophotometry respectively, and the yield of N2 was calculated therefrom. The removal rate of NO 3- and the selectivity of N2 are shown in Table 1:

[0075] Table 1 Removal rate of NO 3- and selectivity results of N2 for the methods of Examples 2 to 6

[0076] <![CDATA[Removal rate of NO3 - > <![CDATA[Selectivity of N2]]> Example 2 95.2％ 97.7％ Example 3 96.3％ 98.3％ Example 4 97.7％ 99.2％ Example 5 95.5％ 97.5％ Example 6 93.7％ 96.9％

[0077] As can be seen from Table 1, after treating the wastewater with the device provided by the present utility model, the removal rate of NO3 - can be maintained above 93%, and the selectivity of N2 is maintained above 96%. This is because the device provided by the present utility model utilizes FCDI to adsorb hardness ions (Ca 2+ , Mg 2+ , etc.), solves the problem of electrode blockage in the electrochemical reduction process, and at the same time utilizes the anode to adsorb NO 3- , and the enriched NO 3- can improve the efficiency of electrochemical reduction of nitrate nitrogen.

[0078] The above are only the preferred embodiments of the present utility model. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present utility model, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present utility model.

Claims

1. A device for flow-through capacitive deionization coupled with electrochemical denitrification, comprising a flow electrode, a cation exchange membrane, a reaction cavity, an anion exchange membrane and a carbon-based fixed electrode which are arranged in contact in sequence; On the side of the electrode cavity of the flow electrode in contact with the cation exchange membrane, a serpentine flow channel is engraved; an inlet and an outlet are provided on the electrode cavity, and the inlet and the outlet are respectively arranged at both ends of the serpentine flow channel; The reaction cavity is a silica gel plate with serpentine hollowing; the serpentine hollowing coincides with the projection of the serpentine flow channel in the electrode cavity on the cation exchange membrane; the space formed by the serpentine hollowing, the cation exchange membrane and the anion exchange membrane is the reaction chamber; an inlet and an outlet are provided on the reaction cavity; the inlet is arranged at one end of the serpentine hollowing corresponding to the inlet; the outlet is arranged at one end of the serpentine hollowing corresponding to the outlet; the reaction chamber includes through holes with nuts; 2. The device for flow-through capacitive deionization coupled electrochemical denitrification according to claim 1, wherein The inlet and the outlet are connected to an external regeneration pool.

3. The device for flow-through capacitive deionization coupled electrochemical denitrification according to claim 1, characterized in that, The length of the electrode cavity is 80 - 200 mm, the width of the electrode cavity is 50 - 120 mm, and the thickness of the electrode cavity is 5 - 15 mm.

4. The device for flow-through capacitive deionization coupled with electrochemical denitrification according to claim 3, wherein, The length of the electrode cavity is 120 mm, the width of the electrode cavity is 80 mm, and the thickness of the electrode cavity is 8 mm.

5. The device for flow-through capacitive deionization coupled electrochemical denitrification according to claim 1, wherein The depth of the serpentine flow channel is 1 - 3 mm.

6. The device for flow-through capacitive deionization coupled electrochemical denitrification according to claim 1 or 5, characterized in that, The width of the serpentine flow channel is 1 - 3 mm.

7. The device for flow-through capacitive deionization coupled with electrochemical denitrification according to claim 1 or 5, characterized in that, The number of columns of the serpentine flow channel is 15 - 35 columns.

8. The device for flow-through capacitive deionization coupled electrochemical denitrification according to claim 1, wherein The depth of the serpentine flow channel is 2 mm, the width of the serpentine flow channel is 2 mm, and the number of columns of the serpentine flow channel is 18 columns.

9. The device for flow-through capacitive deionization coupled with electrochemical denitrification according to claim 1, characterized in that, The number of through holes with nuts is more than two.

10. The device for flow-through capacitive deionization coupled electrochemical denitrification according to claim 9, wherein, The number of through holes with nuts is two.

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