A high-temperature resistant nanofiltration membrane based on rigid amine monomers, its preparation method and application

Abstract

The present invention discloses a high-temperature resistant nanofiltration membrane based on a rigid amine monomer, its preparation method and application, belonging to the technical field of water treatment materials. The preparation method of the high-temperature resistant nanofiltration membrane includes: after an interfacial polymerization reaction occurs between a solution containing a rigid amine monomer and an oil-phase solution containing a polyvalent acyl chloride monomer on a porous support membrane, curing and crosslinking are carried out to prepare the high-temperature resistant nanofiltration membrane based on the rigid amine monomer; the rigid amine monomer is selected from 3,3'-dihydroxybenzidine, 3,3'-dimethylbenzidine, 3,3'-diaminobenzidine, 2,2'-benzidine disulfonic acid, etc. The introduction of the rigid amine monomer combined with the improvement of the process can effectively improve the temperature resistance of the polyamide separation layer. The method steps of the present invention are simple and efficient, and the prepared nanofiltration membrane has a high density and can be used to intercept the high-valence anion salts in high-temperature saline feed liquid, and has good application prospects in the treatment of high-temperature saline feed liquid.

Description

Technical Field

[0001] The present invention belongs to the technical field of water treatment materials, and particularly relates to a high-temperature resistant nanofiltration membrane based on a rigid amine monomer, a preparation method thereof, and an application thereof. Background Art

[0002] In many actual scenarios in industries such as chemical fiber and medicine, it is often necessary to separate high-temperature feed liquids. Membrane separation technology has the advantages of high efficiency, simple operation, strong adaptability, low energy consumption, etc., and is one of the highly favored efficient separation methods in the above industries. Currently, when facing the problem of high-temperature feed liquid treatment, since the separation performance of most separation membranes will significantly decay when the operating temperature is higher than 60°C, in the prior art, the high-temperature feed liquid is usually cooled to room temperature for separation, and then raised to the required temperature for subsequent reactions. In order to reduce energy consumption in the production process and improve production efficiency, it is necessary to improve the high-temperature resistance of the separation membrane.

[0003] Methods for improving the high-temperature resistance of separation membranes include: introducing high-temperature resistant additives, selecting high-temperature stable raw materials, or optimizing the preparation process, etc. For example, the Chinese patent document with the publication number CN109289549A discloses a high-temperature resistant and organic solvent resistant high-performance separation membrane and a preparation method thereof. The invention uses a high-temperature resistant epoxy resin as the main raw material, and is combined with graphite powder, ceramic powder, and a heat stabilizer, so as to ensure the high-temperature resistance of the separation membrane, and also adds a corrosion inhibitor to avoid being corroded during actual use and ensure its service life. The Chinese patent document with the publication number CN105617887A discloses a high-temperature resistant nanofiltration membrane and a preparation method thereof. The invention dissolves each component of the nanofiltration membrane material (high polymer polypropylene, polyethersulfone, graphene, silica fiber) in a solvent, and at the same time adds an additive and a pore-forming agent, stirs evenly to form a casting solution, performs vacuum defoaming, sprays it on a mold, and obtains the high-temperature resistant nanofiltration membrane after drying and forming. However, in the above inventions, the raw materials used and the film-making process are relatively complex.

[0004] Although introducing nanomaterials can effectively improve the temperature resistance of the separation membrane, this process has high requirements for the process and needs to consider the compatibility between the nanomaterials and the organic polymerization monomers; for example, the Chinese patent document with the publication number CN116899419A discloses a high-temperature resistant nanofiltration membrane based on a nanomaterial intermediate layer, a preparation method thereof, and an application thereof. The invention introduces a nanomaterial intermediate layer modified with an amino silane coupling agent between the polyamide separation layer and the porous substrate membrane. The prepared high-temperature resistant nanofiltration membrane has excellent nanofiltration performance and high-temperature resistance, and can maintain the stability of the structure and performance at a higher working temperature.

[0005] Although the introduction of nanomaterials can prepare nanofiltration membranes with certain temperature resistance, the method of using nanomaterials as the intermediate layer does not essentially change the chemical structure of the polyamide separation layer. There are still challenges in directly improving the temperature resistance of the separation layer through monomer design. Summary of the Invention

[0006] The present invention provides a method for preparing a high-temperature resistant nanofiltration membrane based on rigid amine monomers. The introduction of rigid amine monomers combined with process improvement can effectively improve the temperature resistance of the polyamide separation layer. The method of the present invention is simple and efficient, and the prepared nanofiltration membrane has a high density and can be used to intercept high-valent anion salts in high-temperature saline feed solutions.

[0007] The specific technical solution adopted is as follows:

[0008] A method for preparing a high-temperature resistant nanofiltration membrane based on rigid amine monomers, comprising: after an interfacial polymerization reaction occurs between a solution containing rigid amine monomers and an oil-phase solution containing polyacyl chloride monomers on a porous support membrane, curing and crosslinking to prepare the high-temperature resistant nanofiltration membrane based on rigid amine monomers; in the solution containing rigid amine monomers, the solvent uses a mixed solvent of water and an organic solvent;

[0009] The rigid amine monomers are selected from at least one of 3,3'-dihydroxybenzidine, 3,3'-dimethylbenzidine, 3,3'-diaminobenzidine, 2,2'-benzidine disulfonic acid, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl disulfide, 4,4'-diaminostilbene-2,2'-disulfonic acid, 4,4'-diaminodiphenyl ether-2,2'-disulfonic acid, 1,3,5-tris(4-aminophenyl)benzene, and tetrakis(4-aminophenyl)methane.

[0010] The present invention uses rigid amine monomers to replace traditional aliphatic aqueous-phase monomers (such as piperazine, etc.), introduces a more stable polybenzene ring structure into the interfacial polymerization system, increases the rigidity of the polyamide crosslinking network, is beneficial to improving its temperature resistance, and by adjusting the mixing ratio of water and the organic solvent, to a certain extent, promotes the diffusion of rigid amine monomers and acyl chloride monomers, which is beneficial to the interfacial polymerization reaction, thereby generating a polyamide separation layer with a dense and defect-free structure.

[0011] Specifically, in the solution containing rigid amine monomers, the concentration of the rigid amine monomers is 0.1 - 20 g / L, and further preferably 0.1 - 10 g / L.

[0012] In the mixed solvent, the mass ratio of water to the organic solvent is 1 - 6:1; the organic solvent is at least one of N,N'-dimethylacetamide, N,N'-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, and tetrahydrofuran.

[0013] The polyacid chloride monomers described above are trimesoyl chloride, isophthaloyl chloride or terephthaloyl chloride; the polyacid chloride monomers with benzene rings and rigid amine monomers are used as an interfacial polymerization system. In the polymer molecular chain, there are not only a large number of rigid benzene ring structures, which are stable in structure, but also there are many reactive groups in the acid chloride monomers and amine monomers, and the reaction activity is high, which is beneficial to the formation of polyamide.

[0014] In the oil phase solution containing polyacid chloride monomers, the solvent is selected from at least one of n-hexane, cyclohexane, n-heptane, isoparaffin, toluene, and ethyl acetate.

[0015] Specifically, in the oil phase solution containing polyacid chloride monomers, the concentration of the polyacid chloride monomer is 0.1-20 g / L, and more preferably 0.1-5 g / L.

[0016] The porous support membrane described above includes but is not limited to polyethersulfone ultrafiltration membrane, polysulfone ultrafiltration membrane, polybenzimidazole ultrafiltration membrane, polyimide ultrafiltration membrane, polyetheretherketone ultrafiltration membrane, polyacrylonitrile ultrafiltration membrane or poly(m-phenylene isophthalamide) ultrafiltration membrane.

[0017] Preferably, the porous support membrane is completely immersed in the solution containing rigid amine monomers, taken out after standing for 0.2-30 min, the excess liquid on the membrane surface is removed, and then the treated porous support membrane is completely immersed in the oil phase solution containing polyacid chloride monomers, taken out after standing for 0.2-30 min, the excess liquid on the membrane surface is removed, and then cured and crosslinked at 50-100 °C for 3-60 min to obtain the high-temperature resistant nanofiltration membrane based on rigid amine monomers.

[0018] The present invention also provides a high-temperature resistant nanofiltration membrane based on rigid amine monomers prepared by the preparation method of the high-temperature resistant nanofiltration membrane based on rigid amine monomers described above.

[0019] The present invention also provides the application of the high-temperature resistant nanofiltration membrane based on rigid amine monomers in the field of water treatment.

[0020] The present invention also provides a method for selectively separating high-valent anion salts in a high-temperature saline feed liquid, using the high-temperature resistant nanofiltration membrane based on rigid amine monomers to filter the high-temperature saline feed liquid.

[0021] Preferably, the temperature of the high-temperature saline feed liquid is ≥40 °C, more preferably 40-85 °C, and the high-valent anion salts include divalent anion salts.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] (1) The method of the present invention introduces rigid amine monomers into the interfacial polymerization system to prepare a high-temperature resistant nanofiltration membrane, with simple raw materials, low equipment requirements, mild reaction conditions, and simple experimental process.

[0024] (2) By introducing rigid amine monomers into the interfacial polymerization system, the present invention increases the proportion of aromatic components in the polyamide separation layer, effectively improving the rigidity of the polymer chains. By adjusting the mixing ratio of water and organic solvents, the diffusion of rigid amine monomers and acyl chloride monomers is promoted to a certain extent, which is conducive to the interfacial polymerization reaction. The prepared nanofiltration membrane separation layer has a dense and defect-free structure and is structurally stable at high temperatures, showing good temperature resistance.

[0025] (3) The high-temperature resistant nanofiltration membrane prepared by the method of the present invention has excellent nanofiltration performance and long-term stability. The sodium sulfate rejection rate is greater than 97% after operating at 85 °C for 120 days. Description of the Drawings

[0026] Figure 1 It is the surface SEM image of the polyimide ultrafiltration membrane.

[0027] Figure 2 It is the surface SEM image of the high-temperature resistant nanofiltration membrane based on rigid amine monomers in Example 8.

[0028] Figure 3 It is the surface SEM image of the thin film composite separation membrane in Comparative Example 1. Detailed Embodiments

[0029] The present invention will be further clarified below in conjunction with the embodiments and the drawings. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0030] Example 1

[0031] (1) Dissolve 3,3'-diaminobenzidine in a mixed solvent to obtain a solution containing rigid amine monomers; the mixed solvent is prepared from water and N,N'-dimethylacetamide at a mass ratio of 1:1, and the concentration of 3,3'-diaminobenzidine in the solution containing rigid amine monomers is 1 g / L; dissolve trimesoyl chloride in n-hexane to obtain an oil-phase solution containing polyacyl chloride monomers with a trimesoyl chloride concentration of 1.5 g / L;

[0032] (2) Immerse the polyimide ultrafiltration membrane completely in the solution containing rigid amine monomers, take it out after standing for 5 minutes, remove the excess liquid on the membrane surface, then immerse the treated porous support membrane completely in the oil-phase solution containing polyacyl chloride monomers, take it out after standing for 1 minute, remove the excess liquid on the membrane surface, and cure and crosslink at 60 °C for 5 minutes to obtain the high-temperature resistant nanofiltration membrane based on rigid amine monomers.

[0033] Example 2

[0034] In the process of preparing the high-temperature resistant nanofiltration membrane based on rigid amine monomers in this example, the difference from Example 1 is only that in the solution containing rigid amine monomers, the concentration of 3,3'-diaminobenzidine is 0.5 g / L.

[0035] Example 3

[0036] In the process of preparing the high-temperature resistant nanofiltration membrane based on rigid amine monomers in this example, the difference from Example 1 is only that in the solution containing rigid amine monomers, the concentration of 3,3'-diaminobenzidine is 5 g / L.

[0037] Example 4

[0038] In the process of preparing the high-temperature resistant nanofiltration membrane based on rigid amine monomers in this example, the difference from Example 1 is only that in the solution containing rigid amine monomers, the concentration of 3,3'-diaminobenzidine is 10 g / L.

[0039] Example 5

[0040] In the process of preparing the high-temperature resistant nanofiltration membrane based on rigid amine monomers in this example, the difference from Example 1 is only that the rigid amine monomer is 3,3'-dihydroxybenzidine.

[0041] Example 6

[0042] In the process of preparing the high-temperature resistant nanofiltration membrane based on rigid amine monomers in this example, the difference from Example 1 is only that the rigid amine monomer is 3,3'-dimethylbenzidine.

[0043] Example 7

[0044] In the process of preparing the high-temperature resistant nanofiltration membrane based on rigid amine monomers in this example, the difference from Example 1 is only that the rigid amine monomer is 2,2'-benzidine disulfonic acid.

[0045] Example 8

[0046] In the process of preparing the high-temperature resistant nanofiltration membrane based on rigid amine monomers in this example, the difference from Example 1 is only that the mixed solvent is prepared from water and N,N'-dimethylacetamide at a mass ratio of 2:1.

[0047] Example 9

[0048] In the process of preparing the high-temperature resistant nanofiltration membrane based on rigid amine monomers in this example, the difference from Example 1 is only that the mixed solvent is prepared from water and N,N'-dimethylacetamide at a mass ratio of 4:1.

[0049] Example 10

[0050] In the process of preparing the high-temperature resistant nanofiltration membrane based on rigid amine monomers in this example, the difference from Example 1 is only that the mixed solvent is prepared from water and N,N'-dimethylacetamide at a mass ratio of 6:1.

[0051] Example 11

[0052] In the process of preparing the high-temperature resistant nanofiltration membrane based on rigid amine monomers in this example, the difference from Example 8 is only that in the oil-phase solution containing polyvalent acyl chloride monomers, the concentration of trimesoyl chloride is 1 g / L.

[0053] Example 12

[0054] In the process of preparing the high-temperature resistant nanofiltration membrane based on rigid amine monomers in this example, the difference from Example 8 is only that in the oil-phase solution containing polyvalent acyl chloride monomers, the concentration of trimesoyl chloride is 3 g / L.

[0055] Example 13

[0056] In the process of preparing the high-temperature resistant nanofiltration membrane based on rigid amine monomers in this example, the difference from Example 8 is only that in the oil-phase solution containing polyvalent acyl chloride monomers, the concentration of trimesoyl chloride is 5 g / L.

[0057] Example 14

[0058] In the process of preparing the high-temperature resistant nanofiltration membrane based on rigid amine monomers in this example, the difference from Example 8 is only that the porous support membrane used is a polybenzimidazole ultrafiltration membrane.

[0059] Example 15

[0060] In the process of preparing the high-temperature resistant nanofiltration membrane based on rigid amine monomers in this example, the difference from Example 8 is only that the porous support membrane used is a polyether ether ketone ultrafiltration membrane.

[0061] Example 16

[0062] In the process of preparing the high-temperature resistant nanofiltration membrane based on rigid amine monomers in this example, the difference from Example 8 is only that the porous support membrane used is a polyacrylonitrile ultrafiltration membrane.

[0063] Example 17

[0064] In the process of preparing the high-temperature resistant nanofiltration membrane based on rigid amine monomers in this example, the difference from Example 8 is only that the conditions for curing and crosslinking are 60 °C for 10 min.

[0065] Example 18

[0066] In the process of preparing the high-temperature resistant nanofiltration membrane based on rigid amine monomers in this example, the only difference from Example 8 is that the curing and crosslinking conditions are 80 °C for 10 min.

[0067] Example 19

[0068] In the process of preparing the high-temperature resistant nanofiltration membrane based on rigid amine monomers in this example, the only difference from Example 8 is that the curing and crosslinking conditions are 100 °C for 10 min.

[0069] Example 20

[0070] In the process of preparing the high-temperature resistant nanofiltration membrane based on rigid amine monomers in this example, the only difference from Example 8 is that the porous support membrane after being treated with rigid amine monomers is completely immersed in the oil-phase solution containing polyvalent acyl chloride monomers, and taken out after standing for 5 min.

[0071] Example 21

[0072] In the process of preparing the high-temperature resistant nanofiltration membrane based on rigid amine monomers in this example, the only difference from Example 8 is that the porous support membrane after being treated with rigid amine monomers is completely immersed in the oil-phase solution containing polyvalent acyl chloride monomers, and taken out after standing for 10 min.

[0073] Comparative Example 1

[0074] (1) Dissolve piperazine in water to obtain an aqueous solution with a concentration of 1 g / L; dissolve trimesoyl chloride in n-hexane to obtain an oil-phase solution containing polyvalent acyl chloride monomers with a trimesoyl chloride concentration of 1.5 g / L;

[0075] (2) Completely immerse the polyimide ultrafiltration membrane in the aqueous solution, take it out after standing for 5 min, remove the excess liquid on the membrane surface, then completely immerse the treated porous support membrane in the oil-phase solution containing polyvalent acyl chloride monomers, take it out after standing for 1 min, remove the excess liquid on the membrane surface, and cure and crosslink at 60 °C for 5 min to obtain a thin-film composite separation membrane.

[0076] Sample Analysis

[0077] (1) Morphology Characterization

[0078] The surface morphologies of the polyimide ultrafiltration membrane, the high-temperature resistant nanofiltration membrane based on rigid amine monomers in Example 8, and the thin-film composite separation membrane in Comparative Example 1 were characterized by scanning electron microscopy, as shown respectively in Figures 1-3 shown, Figure 1 It can be seen that there are pores about dozens of nanometers dispersed on the surface of the polyimide ultrafiltration membrane; Figure 2 and Figure 3 It can be seen that a dense separation layer is formed on the membrane surface, and there are some convex structures on the surface at the same time.

[0079] (2) Separation performance of nanofiltration membrane

[0080] The rejection rate and permeation flux of the separation membrane are measured by a cross-flow nanofiltration performance test device.

[0081] The permeation flux F (unit: L m -1 h -1 bar -1 ) reflects the permeability of the separation membrane and is defined as: where V represents the volume of the solution passing through the nanofiltration membrane during the operation time, with the unit of L; A represents the effective test membrane area, with the unit of m 2 ; T represents the test time, with the unit of h; p represents the test pressure, with the unit of bar.

[0082] The rejection rate R (unit: %) reflects the separation ability of the separation membrane and is defined as: where C f and C p represent the concentrations of salt ions in the feed liquid and the filtrate, respectively.

[0083] Since in Examples 1-21 and Comparative Example 1, a rigid amine monomer or piperazine was used as the amine monomer for interfacial polymerization, the surface of the prepared nanofiltration membrane has a negative charge due to the hydrolysis of acyl chloride into carboxyl groups, and can preferentially achieve the rejection of inorganic salts with high-valent anions such as sodium sulfate and magnesium sulfate. The nanofiltration membranes prepared in Examples 1-21 and Comparative Example 1 were respectively subjected to a high-temperature resistance performance test to measure their water flux and sodium sulfate rejection rate at different temperatures, and the results are shown in Table 1.

[0084] Table 1 Test results of water flux and sodium sulfate rejection rate of the nanofiltration membranes in Examples 1-21 and Comparative Example 1 at different temperatures

[0085]

[0086] As can be seen from Table 1, compared with Comparative Example 1, the high-temperature resistant nanofiltration membrane based on rigid amine monomers prepared by the method in Examples 1-21 not only has a higher rejection rate at 25 °C, but also has excellent high-temperature resistance performance. Even at a high temperature of 85 °C, the rejection rate of sodium sulfate remains above 98%. At the same time, due to the increase in the temperature of the feed liquid, the solution viscosity decreases, and the movement of water molecules gradually accelerates, which is beneficial to the transmembrane transport of water molecules. Therefore, the water flux increases significantly. Since the rigid amine monomer has a stronger rigid structure than the aliphatic piperazine monomer, the structure of the cross-linked network is more stable at high temperatures, so a relatively high rejection rate can still be maintained.

[0087] Table 2 Test results of water flux and magnesium sulfate rejection rate of the nanofiltration membranes in Example 8 and Comparative Example 1 at different temperatures

[0088]

[0089] As can be seen from Table 2, for the composite nanofiltration membrane without rigid amine monomers, during the heating process, the movement ability of polymer segments increases, the cross-linked network expands, resulting in an increase in membrane pore size. Therefore, the rejection rate of magnesium sulfate decreases significantly.

[0090] As can be seen from Tables 1-2, the high-temperature resistant nanofiltration membrane based on rigid amine monomers prepared by the method of the present invention has good universality for various substrates and various rigid amine systems. The prepared composite nanofiltration membranes all have excellent temperature resistance and can be used for the treatment of aqueous solutions in high-temperature processes.

[0091] (3) Continuous heating and cooling cycle performance of the nanofiltration membrane

[0092] The high-temperature resistant nanofiltration membrane based on rigid amine monomers prepared in Example 8 was subjected to heating and cooling cycle experiments to test its water flux and sodium sulfate rejection rate at different temperatures. The results are shown in Table 3.

[0093] Table 3 Water flux and sodium sulfate rejection rate of the nanofiltration membrane in Example 8 at different temperatures

[0094]

[0095] As can be seen from Table 3, during the heating process of the high-temperature resistant nanofiltration membrane based on rigid amine monomers, the water flux gradually increases. This is because the increase in temperature leads to a decrease in the viscosity of the feed liquid and an acceleration of the thermal movement of water molecules. After the temperature decreases, the viscosity of the feed liquid increases and the movement of water molecules slows down, and the flux returns to the initial value. It should be noted that during the continuous heating and cooling cycle process, the rejection of sodium sulfate by the nanofiltration membrane hardly changes. Thus, it can be seen that this composite nanofiltration membrane has excellent high-temperature resistance.

[0096] (4) High-temperature long-term stability of the nanofiltration membrane

[0097] The high-temperature resistant nanofiltration membrane based on rigid amine monomers prepared in Example 8 was subjected to a high-temperature long-term stability experiment at 85 °C to test the changes in its water flux and sodium sulfate rejection rate with time during high-temperature operation. The results are shown in Table 4.

[0098] Table 4 Water flux and sodium sulfate rejection rate of the nanofiltration membrane in Example 8 during long-term operation at 85 °C

[0099]

[0100] As can be seen from Table 4, the high-temperature resistant nanofiltration membrane based on rigid amine monomers prepared in Example 8 can still maintain a rejection rate of over 97% for sodium sulfate after continuous operation at 85°C for 120 days, with a decay rate < 5%, and has a high water flux, demonstrating that the high-temperature resistant nanofiltration membrane based on rigid amine monomers has excellent long-term high-temperature stability and has good application prospects in the field of water treatment, especially in the treatment of high-temperature saline feed solutions.

[0101] The above-described embodiments have detailed the technical solutions of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, supplements, or substitutions in a similar manner made within the scope of the principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a high temperature resistant nanofiltration membrane based on rigid amine monomers, characterized in that: include: The solution containing rigid amine monomers and the oil phase solution containing polyacyl chloride monomers undergo interfacial polymerization reaction on the porous support membrane, and then solidify and cross-link to prepare the high temperature resistant nanofiltration membrane based on rigid amine monomers; The solvent in the solution containing the rigid amine monomer is a mixed solvent of water and an organic solvent; The rigid amine monomer is selected from at least one of 3,3'-dihydroxybenzidine, 3,3'-dimethylbenzidine, 3,3'-diaminobenzidine and 2,2'-benzidine disulfonic acid; The porous support membrane is a polyethersulfone ultrafiltration membrane, a polysulfone ultrafiltration membrane, a polybenzimidazole ultrafiltration membrane, a polyimide ultrafiltration membrane, a polyetheretherketone ultrafiltration membrane or a polyisophthalamide ultrafiltration membrane; The polyacyl chloride monomer is trimesoyl chloride, isophthaloyl chloride or terephthaloyl chloride; In the mixed solvent, the mass ratio of water to the organic solvent is 1 to 6:1; the organic solvent is at least one of N,N'-dimethylacetamide, N,N'-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone and tetrahydrofuran.

2. The method for preparing a high temperature resistant nanofiltration membrane based on rigid amine monomers according to claim 1, characterized in that: In the solution containing the rigid amine monomer, the concentration of the rigid amine monomer is 0.1 to 20 g / L.

3. The method for preparing a high temperature resistant nanofiltration membrane based on rigid amine monomers according to claim 1, characterized in that: In the oil phase solution containing the polyacyl chloride monomer, the concentration of the polyacyl chloride monomer is 0.1 to 20 g / L.

4. The method for preparing a high temperature resistant nanofiltration membrane based on rigid amine monomers according to claim 1, characterized in that: The porous support membrane is completely immersed in a solution containing rigid amine monomers, and taken out after standing for 0.2 to 30 minutes to remove excess liquid on the membrane surface. The treated porous support membrane is then completely immersed in an oil phase solution containing polyacyl chloride monomers, and taken out after standing for 0.2 to 30 minutes to remove excess liquid on the membrane surface. The membrane is cured and cross-linked at 50 to 100° C. for 3 to 60 minutes to obtain the high temperature resistant nanofiltration membrane based on rigid amine monomers.

5. A high temperature resistant nanofiltration membrane based on rigid amine monomers obtained according to the method for preparing a high temperature resistant nanofiltration membrane based on rigid amine monomers according to any one of claims 1 to 4.

6. Application of the high temperature resistant nanofiltration membrane based on rigid amine monomers according to claim 5 in the field of water treatment.

7. A method for selectively separating high-valent anion salts from a high-temperature saline solution, characterized in that: The high temperature resistant nanofiltration membrane based on rigid amine monomers as claimed in claim 5 is used to filter high temperature salt-containing liquid.

8. The method for selectively separating high-valent anion salts from high-temperature saline solution according to claim 7, characterized in that: The temperature of the high-temperature salt-containing liquid is ≥40°C, and the high-valent anion salt includes a divalent anion salt.

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