Composite nanofiltration membrane based on gas molecule regulation and control interfacial polymerization as well as preparation method and application of composite nanofiltration membrane

Abstract

The invention provides a composite nanofiltration membrane based on gas molecule regulation and control interfacial polymerization as well as a preparation method and application of the composite nanofiltration membrane. Different gases are introduced into a water-phase solution to regulate and control the interfacial polymerization process and prepare the nanofiltration membrane, and due to introduction of the gases, on one hand, some gases can chemically react with water-phase monomers to generate new monomers with ionic groups, and the ionic new monomers can further serve as additives to regulate and control the interfacial polymerization process; on the other hand, the gases can effectively regulate and control the pH environment of the aqueous phase solution, so that the interfacial polymerization reaction is influenced. On the basis of the characteristics, the interface polymerization process can be regulated and controlled from multiple aspects, customization of the structure and surface characteristics of the nanofiltration membrane is facilitated, the performance of the nanofiltration membrane is further improved, and meanwhile a new thought is provided for recycling of gas.

Description

Technical Field

[0001] This invention belongs to the field of separation membrane technology, specifically relating to a composite nanofiltration membrane based on gas molecule-controlled interfacial polymerization, its preparation method, and its application. Background Technology

[0002] With the increasing scarcity of water resources, membrane separation technologies, represented by nanofiltration, are receiving widespread attention due to their energy-saving, environmentally friendly, and high separation efficiency. Currently, nanofiltration technology is widely used in wastewater treatment, food, and pharmaceutical fields. Nanofiltration membranes, as a key component of nanofiltration technology, are typically prepared using interfacial polymerization. Interfacial polymerization is the most mainstream method for preparing composite nanofiltration membranes. It involves the condensation reaction of aqueous monomers (usually amines) and oil monomers (usually acyl chlorides) on the surface of a porous support layer to form a dense polyamide separation layer.

[0003] However, traditional interfacial polymerization processes are characterized by rapid reaction rates and the generation of heat and acid, leading to low water flux and poor selectivity in currently prepared nanofiltration membranes. Therefore, it is generally believed that effectively controlling the interfacial polymerization process through certain technical means is key to further improving the performance of nanofiltration membranes.

[0004] According to literature reports, methods for controlling interfacial polymerization mainly focus on three aspects: optimization and modification of aqueous monomers, construction of intermediate layers, and aqueous additives. Optimization and modification of aqueous monomers requires complex chemical synthesis, which is not conducive to widespread application. Constructing intermediate layers on the substrate membrane surface is also overly complex and results in poor membrane performance reproducibility. Therefore, the aqueous additive method has attracted widespread attention due to its simplicity and wide variety of additives. Currently, these additives mainly include inorganic salts such as sodium chloride and sodium bicarbonate, which are used to regulate the surface tension of the aqueous solution to influence the interfacial polymerization process. There are also reports of using nanomaterials such as carbon nanotubes, silicon nanospheres, and graphene as aqueous additives, utilizing their size effect to limit the diffusion of aqueous monomers and thus control the interfacial polymerization process. In addition, various organic molecules, due to their rich variety and good solubility, have also been reported as aqueous additives. From the perspective of practical operation and the effect of interfacial polymerization control, although the additive method is a relatively ideal technical means, the current additive costs are generally high, which is not conducive to large-scale industrial application.

[0005] Furthermore, the treatment and resource utilization of industrial waste gases (such as CO2, HCl, and NH3) has always been an important issue in the field of environmental protection. If these gas molecules can be innovatively applied to the material preparation process, not only can waste be turned into treasure, but new ideas can also be provided for membrane preparation technology.

[0006] Therefore, developing a simple, low-cost, environmentally friendly, and highly effective interfacial polymerization control method is of great practical significance for improving nanofiltration membrane performance, reducing production costs, and promoting the industrial application of nanofiltration technology. Summary of the Invention

[0007] To address the limitations of existing methods for regulating interfacial polymerization and the high cost of additives, this invention proposes a composite nanofiltration membrane based on gas molecule-regulated interfacial polymerization, along with its preparation method and applications. Different gases are used as novel, low-cost, and multifunctional additives to regulate interfacial polymerization. The chemical reaction between gas molecules and aqueous monomers, along with the control of the pH environment of the aqueous solution, achieves this regulation, enhancing nanofiltration membrane performance. This results in the preparation of a composite nanofiltration membrane with high flux, high selectivity, and excellent surface properties, while also providing a new pathway for gas emission reduction and reuse.

[0008] This invention defines a method for preparing a composite nanofiltration membrane based on gas molecule-controlled interfacial polymerization. Specifically, a gas is passed into an aqueous solution containing amines and thoroughly mixed and dissolved to obtain an aqueous phase solution. A porous substrate membrane is added to the above aqueous phase solution for room temperature impregnation. Then, the porous substrate membrane after aqueous phase impregnation is added to an oil phase solution containing aromatic acyl chloride monomers to carry out an interfacial polymerization process. By utilizing the chemical reaction between gas molecules and aqueous phase monomers and the influence of the pH environment of the aqueous phase solution, the interfacial polymerization process can be controlled to construct a high-performance composite nanofiltration membrane.

[0009] Furthermore, the present invention also specifies a method for preparing a composite nanofiltration membrane based on gas molecule-controlled interfacial polymerization, specifically including the following steps: 1) The gas is passed into an aqueous solution containing amine monomers and fully dissolved and mixed to obtain an aqueous solution; 2) Immerse the porous base membrane in the aqueous solution obtained in step 1) at room temperature for immersion reaction. After the reaction is completed, remove the porous base membrane and drain the excess solution from the surface. 3) The porous substrate membrane after aqueous phase treatment in step 2) is immersed in an oil phase containing aromatic acyl chloride monomer to carry out interfacial polymerization reaction. After the reaction is completed, it is heat-treated and soaked and cleaned to obtain a composite nanofiltration membrane.

[0010] The introduction of the gas serves to dually regulate the interfacial polymerization process: firstly, the gas reacts chemically with amine monomers to generate new ionic monomers, which can then act as additives to further regulate the interfacial polymerization process; secondly, the gas adjusts the pH of the aqueous solution, a key parameter affecting the nucleophilicity of amine monomers and the rate of interfacial polymerization. For example, introducing carbon dioxide gas into the aqueous piperazine solution causes a chemical reaction between carbon dioxide and piperazine to generate a new monomer containing a carboxylic acid group (PIP-COOH). Because this new monomer contains both carboxylic acid and amino groups, the carboxylic acid groups interact with the remaining aqueous monomers through hydrogen bonds, electrostatic interactions, and other mechanisms, thus controlling the diffusion rate of the aqueous monomers and regulating the interfacial polymerization process. Furthermore, its amino groups can react with oil-phase monomers, allowing them to penetrate the polyamide network and further enhance the negative charge and hydrophilicity of the nanofiltration membrane surface. In addition, since interfacial polymerization is a condensation reaction that generates acid, introducing ammonia gas into the aqueous monomer solution can raise the pH of the aqueous solution and neutralize the acid produced by the interfacial polymerization reaction, thereby promoting the interfacial polymerization reaction.

[0011] Furthermore, the present invention also specifies that the porous substrate membrane is a commercially available ultrafiltration membrane, preferably polysulfone, polyethersulfone, or polyvinylidene fluoride.

[0012] Furthermore, the present invention specifies that the gas is at least one of carbon dioxide, hydrogen chloride, ammonia, etc., and the flow rate of the gas introduced into the aqueous solution of the amine monomer is 20~100 L / h, and the introduction time is 10~60 min. The introduction of the gas can not only react chemically with the amine monomer to form new monomers, but also effectively regulate the pH environment of the aqueous solution, which helps to control the interfacial polymerization process and realize the reuse of the gas.

[0013] Furthermore, the present invention further specifies that the amine monomer is one or more of piperazine, polyethyleneimine, ethylenediamine, and p-phenylenediamine, and the mass concentration of the amine monomer in the aqueous solution is 0.3~20 wt%.

[0014] Furthermore, the present invention also limits the immersion time in the aqueous solution at room temperature to 5-30 min.

[0015] Furthermore, the present invention further specifies that the aromatic acyl chloride in the oil phase is one or more of pyromellitic trimethylolpropionate chloride, phthaloyl chloride, isophthaloyl chloride, terephthaloyl chloride or pyromellitic tetramethylolpropionate chloride, and the mass concentration of the acyl chloride monomer in the oil phase solution is 0.1~2.0 wt%.

[0016] Finally, the present invention also specifies that the immersion time in the oil phase solution at room temperature is 1 to 20 minutes.

[0017] The present invention also proposes a composite nanofiltration membrane based on gas molecule-controlled interfacial polymerization prepared by the above preparation method; The present invention also proposes the application of the above-mentioned composite nanofiltration membrane in the fields of liquid separation, wastewater treatment or desalination.

[0018] By employing the techniques defined above, the beneficial effects of the present invention compared to the prior art are as follows: (1) For the first time, gas was used as an active additive for interfacial polymerization control. The cost of gas (especially CO2) is much lower than that of traditional additives and it is widely available, which greatly reduces the preparation cost of high-performance nanofiltration membranes.

[0019] (2) This invention effectively regulates interfacial polymerization by selecting gas molecules. On the one hand, gas molecules can react chemically with aqueous monomers to form new monomers, which can then act as additives, thereby controlling the diffusion rate of aqueous monomers. On the other hand, the introduction of gas can effectively regulate the pH environment of the aqueous solution, thus affecting the interfacial polymerization reaction. Combining these two aspects, the interfacial polymerization process can be controlled from multiple angles, achieving precise customization of membrane structure and surface properties, thereby improving membrane separation performance.

[0020] (3) In addition, the selected gases are mostly waste gases that are harmful to the environment, which also provides a new idea for the reduction and reuse of waste gases. This method has great industrialization potential. Attached Figure Description

[0021] Figure 1 A comparison chart of pH values ​​of aqueous solutions with and without gas-passing aqueous additives; Figure 2 This is a schematic diagram comparing the pH values ​​of the aqueous solution with and without CO2 during the preparation process of Example 1 and Comparative Example 1. Figure 3 This is a comparison chart of the surface water contact angle test results of the composite nanofiltration membranes obtained in Comparative Example 1 and Example 1;

[0022] Figure 4 This is a comparison chart of the surface Zeta potential test results of the composite nanofiltration membranes obtained in Comparative Example 1 and Example 1. Detailed Implementation

[0023] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, so that the features of the present invention can be easily understood by researchers in the art, thereby providing a more detailed definition of the scope of protection of the present invention.

[0024] Example 1

[0025] This embodiment provides a method for preparing nanofiltration membranes using gas-based interfacial polymerization control, specifically including the following steps: Carbon dioxide was introduced into an aqueous solution of piperazine with a mass concentration of 0.3 wt% at a flow rate of 20 L / h. After continuous stirring for 10 min, an aqueous solution was obtained. The wet-washed polysulfone substrate membrane was then immersed in the aqueous solution for 5 min. After removal, it was dried and ready for use. A cyclohexane oil phase solution of pyromellitic trimethylol chloride (100 g) with a concentration of 0.1 wt% was prepared. The dried polysulfone substrate membrane was immersed in the oil phase solution and subjected to interfacial polymerization for 1 min. After removal, it was placed in a 60 ℃ oven for 10 min and then rinsed with deionized water to obtain a composite nanofiltration membrane.

[0026] Example 2

[0027] This embodiment provides a method for controlling interfacial polymerization and preparing nanofiltration membranes using gas, which is prepared according to the following steps: The carbon dioxide flux in Example 1 above was changed to 1.0 L / h, while the other steps remained unchanged.

[0028] Example 3

[0029] This embodiment provides a method for controlling interfacial polymerization and preparing nanofiltration membranes using gas, which is prepared according to the following steps: The carbon dioxide flux in Example 1 above was changed to 50 L / h, while the other steps remained unchanged.

[0030] Example 4

[0031] This embodiment provides a method for controlling interfacial polymerization and preparing nanofiltration membranes using gas, which is prepared according to the following steps: The carbon dioxide flux in Example 1 above was changed to 60 L / h, while the other steps remained unchanged.

[0032] Example 5

[0033] This embodiment provides a method for controlling interfacial polymerization and preparing nanofiltration membranes using gas, which is prepared according to the following steps: The carbon dioxide flux in Example 1 above was changed to 100 L / h, while the other steps remained unchanged.

[0034] Example 6

[0035] This embodiment provides a method for controlling interfacial polymerization and preparing nanofiltration membranes using gas, which is prepared according to the following steps: Replace carbon dioxide in Example 1 with ammonia, while keeping the other steps unchanged.

[0036] Example 7

[0037] This embodiment provides a method for controlling interfacial polymerization and preparing nanofiltration membranes using gas, which is prepared according to the following steps: Replace carbon dioxide in Example 1 with hydrogen chloride, while keeping the other steps unchanged.

[0038] Examples 8-10: The gas introduction time in Example 1 was replaced with 1 min, 30 min and 60 min respectively, while other steps remained unchanged, to obtain the composite nanofiltration membranes of Examples 8-10.

[0039] Examples 11-13: The amine monomer piperazine in Example 1 was replaced with polyethyleneimine, ethylenediamine, and p-phenylenediamine, respectively, while other steps remained unchanged, to obtain the composite nanofiltration membranes of Examples 11-13.

[0040] In Examples 14-16, the concentration of piperazine monomer in Example 1 was replaced with 0.01 wt%, 10 wt%, and 20 wt%, respectively, while other steps remained unchanged, to obtain the composite nanofiltration membranes of Examples 14-16.

[0041] Examples 17-19: The aqueous phase soaking time of 5 min in Example 1 was replaced with 1 min, 20 min, and 30 min respectively, while other steps remained unchanged, to obtain the composite nanofiltration membranes of Examples 17-19.

[0042] Examples 20-22: The oil phase acyl chloride monomer pyromellitic chloride in Example 1 was replaced with phthaloyl chloride, isophthaloyl chloride, and terephthaloyl chloride, respectively, while other steps remained unchanged, to obtain the composite nanofiltration membranes of Examples 20-22.

[0043] In Examples 23-25, the concentration of acyl chloride monomer in Example 1 was replaced with 0.01 wt%, 1.5 wt%, and 2.0 wt%, respectively, while other steps remained unchanged, to obtain the composite nanofiltration membranes of Examples 23-25.

[0044] Examples 26-28: The oil phase soaking time of 1 min in Example 1 was replaced with 5.0 min, 20 min, and 60 min respectively, while other steps remained unchanged, to obtain the composite nanofiltration membranes of Examples 26-28.

[0045] Examples 29-30: The polysulfone substrate membrane in Example 1 was replaced with polyethersulfone and polyvinylidene fluoride, respectively, while other steps remained unchanged, to obtain the composite nanofiltration membranes of Examples 29-30.

[0046] Comparative Example 1 This comparative example provides a method for preparing a nanofiltration membrane without additives, which is prepared according to the following steps: Piperazine was dissolved in water at a concentration of 0.3 wt%, and sonicated for 10 min to ensure complete dissolution. The wet-state, cleaned polysulfone substrate membrane was immersed in the aqueous solution for 5 min, then removed and dried. A 0.1 wt% cyclohexane oil phase solution of trimesoyl chloride was prepared; the polysulfone substrate membrane was immersed in the oil phase solution for 1 min, then removed. The composite membrane was heat-treated in a 60 °C oven for 10 min. After rinsing several times with deionized water, the composite nanofiltration membrane was obtained.

[0047] Figure 1 This demonstrates that the pH of an aqueous solution can be controlled by introducing different gas molecules, thereby affecting the interfacial polymerization reaction. For example, carbon dioxide can lower the pH of the aqueous solution, while ammonia can raise it.

[0048] Figure 2 This indicates that the pH of the aqueous solution decreases after carbon dioxide is introduced, which to some extent affects the intensity of the interfacial polymerization reaction and regulates the performance of the nanofiltration membrane in Example 1.

[0049] Figure 3 This indicates that the introduction of carbon dioxide generates a new ionic monomer containing carboxyl groups. This monomer can participate in the reaction with the oil phase and intercalate into the polyamide network, thereby increasing the number of carboxyl groups on the membrane surface and resulting in improved hydrophilicity of the nanofiltration membrane surface in Example 1. Figure 4 Improvement of surface negative charge.

[0050] Experimental Example 1 The nanofiltration membranes of Examples 1-5 and Comparative Example 2 were tested for water flux and sodium sulfate rejection, with an operating pressure of 0.6 MPa and a sodium sulfate concentration of 1 g / L. The flux and salt rejection results are shown in Table 1.

[0051] Table 1. Nanofiltration membrane flux and salt rejection results for Examples 1-5 and Comparative Example 1

[0052] Table 1 shows that introducing CO2 gas significantly increases water flux. When the CO2 flux is 20 L / h, the membrane performance is optimized, with a high water flux (approximately 150% higher than the control) while maintaining a high rejection rate for 1 g / L sodium sulfate aqueous solution, and the desalination rate remains at a high level (97.8%). Too low a flux (1 L / h) has limited control effect; too high a flux (≥50 L / h) may lead to excessive acidification of the aqueous phase or an overly vigorous reaction. Although this further increases the flux, it damages the compactness of the polyamide layer, resulting in a significant decrease in rejection rate.

[0053] Experimental Example 2 The nanofiltration membranes from Examples 1 and 6-7 were tested for water flux and sodium sulfate rejection, with an operating pressure of 0.6 MPa and a sodium sulfate concentration of 1 g / L. The flux and salt rejection results are shown in Table 2.

[0054] Table 2. Nanofiltration membrane flux and salt rejection results for Examples 1 and 6-7

[0055] Table 2 shows that the control effect varies significantly depending on the chemical properties of different gases. When carbon dioxide is introduced, the membrane performance is optimized, with a high water flux while maintaining a high rejection rate for 1 g / L sodium sulfate aqueous solution. Under alkaline conditions, NH3 may promote amine monomer diffusion or alter the reaction pathway, but its boosting effect is not as good as CO2. Excessively acidic HCl may lead to excessive protonation of amine monomers or excessive hydrolysis of acyl chlorides, negatively impacting the rejection rate.

[0056] Experimental Example 3 The nanofiltration membranes from Examples 1 and 8-10 were tested for water flux and sodium sulfate rejection, with an operating pressure of 0.6 MPa and a sodium sulfate concentration of 1 g / L. The flux and salt rejection results are shown in Table 3.

[0057] Table 3. Nanofiltration membrane flux and salt rejection results for Examples 1, 8-10

[0058] Table 3 shows that sufficient gas introduction time is required to ensure complete gas dissolution and interaction. When the gas introduction time is 10 min, the membrane performance is optimized, with high water flux while maintaining a high retention rate for 1 g / L sodium sulfate aqueous solution. Too short a time results in insufficient interaction, while too long a time may lead to over-regulation and a decrease in retention rate.

[0059] Test Example 4 The nanofiltration membranes of Examples 1 and 11-13 were tested for water flux and sodium sulfate rejection, with an operating pressure of 0.6 MPa and a sodium sulfate concentration of 1 g / L. The flux and salt rejection results are shown in Table 4.

[0060] Table 4. Nanofiltration membrane flux and salt rejection results for Examples 1, 11-13

[0061] As shown in Table 4, when the aqueous phase amine monomer is piperazine, the membrane performance is optimized, with a high water flux, while maintaining a high rejection performance for 1 g / L sodium sulfate aqueous solution.

[0062] Experimental Example 5 The nanofiltration membranes of Examples 1, 14-16 were tested for water flux and sodium sulfate rejection, with an operating pressure of 0.6 MPa and a sodium sulfate concentration of 1 g / L. The flux and salt rejection results are shown in Table 5.

[0063] Table 5. Nanofiltration membrane flux and salt rejection results for Examples 1, 14-16

[0064] Table 5 shows that the membrane performance is optimized when the amine monomer concentration is 0.3 wt%, resulting in high water flux while maintaining high retention performance for 1 g / L sodium sulfate aqueous solution. Too low a concentration leads to insufficient cross-linking and a sharp drop in retention rate, while too high a concentration results in an excessively thick and dense membrane layer, reducing flux.

[0065] Experimental Example 6 The nanofiltration membranes of Examples 1 and 17-19 were tested for water flux and sodium sulfate rejection, with an operating pressure of 0.6 MPa and a sodium sulfate concentration of 1 g / L. The flux and salt rejection results are shown in Table 6.

[0066] Table 6. Nanofiltration membrane flux and salt rejection results for Examples 1, 17-19

[0067] As shown in Table 6, the membrane performance is optimized when the aqueous phase soaking time is 5.0 min, with a high water flux and a high rejection rate for 1 g / L sodium sulfate aqueous solution.

[0068] Experimental Example 7 The nanofiltration membranes of Examples 1 and 20-22 were tested for water flux and sodium sulfate rejection, with an operating pressure of 0.6 MPa and a sodium sulfate concentration of 1 g / L. The flux and salt rejection results are shown in Table 7.

[0069] Table 7. Nanofiltration membrane flux and salt rejection results for Examples 1, 20-22

[0070] As shown in Table 7, when the oil phase monomer is pyromellitic chloride, the membrane performance is optimized, with a high water flux, while maintaining a high rejection performance for 1 g / L sodium sulfate aqueous solution.

[0071] Experimental Example 8 The nanofiltration membranes of Examples 1 and 23-25 ​​were tested for water flux and sodium sulfate rejection, with an operating pressure of 0.6 MPa and a sodium sulfate concentration of 1 g / L. The flux and salt rejection results are shown in Table 8.

[0072] Table 8. Nanofiltration membrane flux and salt rejection results for Examples 1, 20-22

[0073] As shown in Table 8, the membrane performance is optimized when the oil phase monomer concentration is 0.1 wt%, with a high water flux and a high rejection rate for 1 g / L sodium sulfate aqueous solution.

[0074] Experimental Example 9 The nanofiltration membranes of Examples 1 and 26-28 were tested for water flux and sodium sulfate rejection, with an operating pressure of 0.6 MPa and a sodium sulfate concentration of 1 g / L. The flux and salt rejection results are shown in Table 9.

[0075] Table 9. Nanofiltration membrane flux and salt rejection results for Examples 1, 26-28

[0076] As shown in Table 9, the membrane performance is optimized when the oil phase reaction time is 1.0 min, with a high water flux and a high rejection rate for 1 g / L sodium sulfate aqueous solution.

[0077] Experimental Example 10 The nanofiltration membranes of Examples 1 and 29-30 were tested for water flux and sodium sulfate rejection, with an operating pressure of 0.6 MPa and a sodium sulfate concentration of 1 g / L. The flux and salt rejection results are shown in Table 10.

[0078] Table 10. Nanofiltration membrane flux and salt rejection results for Examples 29-30

[0079] As shown in Table 10, when the base membrane is polysulfone, the membrane performance is optimized, with a high water flux, while maintaining a high rejection performance for 1 g / L sodium sulfate aqueous solution.

[0080] Experimental Example 11 The nanofiltration membrane of Comparative Example 1 was tested for water flux and sodium sulfate rejection, with an operating pressure of 0.6 MPa and a sodium sulfate concentration of 1 g / L. Its flux and salt rejection are shown in Table 10.

[0081] Table 11 Nanofiltration membrane flux and salt rejection results for the comparative example and Example 1

[0082] Table 11 shows that the water flux of the nanofiltration membrane obtained without gas treatment of the aqueous solution is much lower than that of the nanofiltration membrane prepared with gas treatment of the aqueous solution, while the salt rejection of the two types of nanofiltration membranes is comparable. This indicates that introducing gas can achieve interfacial polymerization regulation, greatly improving the performance of the nanofiltration membrane.

[0083] In summary, this invention, by introducing a specific gas into the interfacial polymerization aqueous phase and utilizing its dual effects of chemical reaction and pH adjustment, effectively controls the structure of the polyamide separation layer, successfully preparing a composite nanofiltration membrane with both ultra-high water flux and high selectivity. This method is simple, economical, and environmentally friendly, and has broad prospects for industrial application.

[0084] The embodiments described above are some, but not all, embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for preparing a composite nanofiltration membrane based on gas molecule-controlled interfacial polymerization, characterized in that, Includes the following steps: 1) The gas is passed into an aqueous solution containing amine monomers and fully dissolved and mixed to obtain an aqueous solution; 2) Immerse the porous base membrane in the aqueous solution obtained in step 1) at room temperature for immersion reaction. After the reaction is completed, remove the porous base membrane and drain the excess solution from the surface. 3) The porous substrate membrane after aqueous phase treatment in step 2) is immersed in an oil phase containing aromatic acyl chloride monomer to carry out interfacial polymerization reaction. After the reaction is completed, it is heat-treated and soaked and cleaned to obtain a composite nanofiltration membrane.

2. The method for preparing a composite nanofiltration membrane based on gas molecule-controlled interfacial polymerization as described in claim 1, characterized in that, The porous base membrane is one of polysulfone, polyethersulfone, or polyvinylidene fluoride.

3. The method for preparing a composite nanofiltration membrane based on gas molecule-controlled interfacial polymerization as described in claim 1, characterized in that, The gas is at least one of carbon dioxide, hydrogen chloride, and ammonia. The flow rate of the gas into the aqueous solution of the amine monomer is 20-100 L / h, and the introduction time is 10-60 min.

4. The method for preparing a composite nanofiltration membrane based on gas molecule-controlled interfacial polymerization as described in claim 1, characterized in that, The amine monomer is one or more of piperazine, polyethyleneimine, ethylenediamine, and p-phenylenediamine, and the mass concentration of the amine monomer in the aqueous solution is 0.3~20 wt%.

5. The method for preparing a composite nanofiltration membrane based on gas molecule-controlled interfacial polymerization as described in claim 1, characterized in that, The immersion time in the aqueous solution at room temperature is 5~30 min.

6. The method for preparing a composite nanofiltration membrane based on gas molecule-controlled interfacial polymerization as described in claim 1, characterized in that, The aromatic acyl chloride is one or more of pyromellitic acyl chloride, phthaloyl chloride, isophthaloyl chloride, terephthaloyl chloride or pyromellitic tetrachloroyl chloride, and the mass concentration of the acyl chloride monomer in the oil phase solution is 0.1~2.0 wt%.

7. The method for preparing a composite nanofiltration membrane based on gas molecule-controlled interfacial polymerization as described in claim 1, characterized in that, The immersion time in the oil phase solution at room temperature is 1~20 min.

8. A composite nanofiltration membrane based on gas molecule-controlled interfacial polymerization, characterized in that, It is prepared by the method described in any one of claims 1-7.

9. The application of the composite nanofiltration membrane based on gas molecule-controlled interfacial polymerization as described in claim 8 in the fields of liquid separation, wastewater treatment or desalination.

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