Conjugated microporous acid-resistant nanofiltration membrane as well as preparation method and application thereof

Abstract

The invention discloses a conjugated microporous acid-resistant nanofiltration membrane as well as a preparation method and application thereof, and relates to the technical field of membrane preparation. The conjugated microporous acid-resistant nanofiltration membrane comprises a base membrane and a functional separation layer compounded on the surface of the base membrane, and the polymer forming the functional separation layer is formed by a polymerization reaction of a monomer A containing an acetyl aromatic ring and a monomer B containing acetyl tertiary amine. According to the invention, tertiary amine groups are introduced into the conjugated microporous structure, and the chemical stability of the conjugated microporous structure and the surface positively charged property under an acidic condition are fully combined, so that efficient interception and excellent acid-resistant stability of heavy metal ions are realized. The prepared composite membrane has excellent heavy metal removal capacity and high-efficiency acid permeation capacity in a strong acid environment, and has good potential in the aspects of acid wastewater treatment and resource recycling.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of membrane preparation, and particularly relates to a conjugated microporous acid-resistant nanofiltration membrane and a preparation method and application thereof. BACKGROUND

[0002] With the development of the electronic information era, the demand for circuit boards increases year by year. The electroplating wastewater produced in the production of circuit boards contains high concentrations of acid and various recyclable heavy metal resources such as copper, nickel, chromium, and zinc. Direct discharge will corrode the pipeline, damage the ecological environment, and harm human health. Therefore, the treatment and resource recycling of electroplating wastewater are of great significance.

[0003] The traditional chemical precipitation method for treating electroplating wastewater produces a large amount of sludge and consumes a large amount of chemical agents. More importantly, the disposal cost of heavy metal-containing sludge is extremely high. Nanofiltration membrane separation technology, as a low-energy and green sustainable development separation technology, has significant advantages in wastewater treatment and resource recycling. However, existing water treatment nanofiltration membranes cannot withstand strong acidic environments. The amide bonds in the separation layer are easily attacked by nucleophilic hydrogen ions and hydrolyzed to break, resulting in a sharp decline in separation performance. Acid-resistant nanofiltration membranes are a type of membrane material specifically designed to work in strong acid environments. These membranes can effectively separate metal ions and inorganic salts from strong acidic wastewater. Currently, acid-resistant nanofiltration membrane materials are in the development stage, and the main materials include polysulfonamide, triazine ring, sulfonated polymer, and polyelectrolyte. However, the existing acid-resistant nanofiltration membranes in the prior art have weak stability and poor separation ability for heavy metal ions and acid, making it difficult to achieve simultaneous recovery of acid and heavy metal ions.

[0004] Conjugated microporous polymer materials have good chemical stability due to their C-C rigid backbone and conjugated microporous structure. However, conjugated microporous polymers usually do not have surface charges, and the separation effect for positively charged heavy metal ions is poor. How to prepare conjugated microporous polymer membranes with charges is of great significance for acid wastewater treatment and resource recycling.

[0005] Chinese Patent CN119926191A proposes a conjugated microporous organic solvent-resistant nanofiltration composite membrane and its preparation method and application. The nanofiltration composite membrane includes a base membrane and a separation layer composite in the pores and / or surface of the base membrane. The polymer forming the separation layer includes a repeating structural unit containing an aromatic ring, wherein part of the aromatic rings of the repeating structural units are connected with halogen substituents. The nanofiltration composite membrane has excellent acid and alkali resistance, excellent non-polar solvent permeability, and good chemical stability. However, the rejection performance of the nanofiltration composite membrane for heavy metal cations needs to be improved. SUMMARY

[0006] The present application aims to overcome the defects of poor metal ion interception and poor acid resistance of the prior art acid-resistant nanofiltration membrane, and provides a conjugated microporous acid-resistant nanofiltration membrane which has strong heavy metal removal capacity and good stability and has a wide application prospect in ion separation of an acid aqueous solution system.

[0007] Another object of the present application is to provide a preparation method of the conjugated microporous acid-resistant nanofiltration membrane.

[0008] Another object of the present application is to provide an application of the conjugated microporous acid-resistant nanofiltration membrane in heavy metal ion separation.

[0009] The above objects of the present application are achieved by the following technical solutions. The present application protects a conjugated microporous acid-resistant nanofiltration membrane, which comprises a base film and a functional separation layer which is compounded on the surface of the base film; and the polymer forming the functional separation layer is obtained by polymerization reaction of a monomer A containing an acetyl aromatic ring and a monomer B containing an acetyl tertiary amine.

[0010] In some embodiments, the structure of the monomer A is shown in formula (I), Formula (I), wherein R1, R2, R3, R4, R5, R6 are each independently selected from any one of H, C1-C6 substituted or unsubstituted alkyl, C6-C12 substituted or unsubstituted aryl, amine group, acetyl group, halogen substituent, and at least two of R1, R2, R3, R4, R5 and R6 contain acetyl groups.

[0011] In some embodiments, the monomer A is selected from at least one of 1,3,5-triacetylbenzene, 1,4-diacetylbenzene and 1,3-diacetylbenzene.

[0012] In some embodiments, the structure of the monomer B is shown in formula (II), Formula (II), wherein R7 is a tertiary amine type substituted or unsubstituted nitrogen heterocycle or a C3-C12 substituted or unsubstituted alkyl containing a tertiary amine.

[0013] The tertiary amine type nitrogen heterocycle is a 3-6 membered nitrogen-containing heterocycle; specifically, the nitrogen-containing heterocycle includes but is not limited to any one of imidazole, pyridine, piperazine, piperidine and aziridine structure. Optionally, the substituent of the tertiary amine type substituted nitrogen heterocycle can be at least one of C1-C4 alkyl, C1-C4 alkyl imino, amine group and aldehyde group. In some embodiments, the monomer B is selected from at least one of 4-acetyl imidazole, methyl-3-pyridyl ketone, tetraacetyl ethylenediamine, 1-acetyl-N-methyl piperidine amine hydrochloride, N-ethyl acetamide, N,N-diethyl acetamide, N-ethyl-N-methyl acetamide, N,N-formyl acetamide, N-acetyl vinyl imine, 4-acetyl piperazine-1-formaldehyde, 4-acetyl-1-piperazine ethylamine, 4-acetyl-1,1-dimethyl piperazinium iodide and N,N-bis-isopropyl-acetamide. Preferably, the monomer B is 4-acetyl imidazole, methyl-3-pyridyl ketone or tetraacetyl ethylenediamine. The above reaction monomer can construct a tertiary amine substituent connected with an aromatic ring, has suitable steric hindrance, and has good Donnan exclusion effect, so that the nanofiltration membrane has strong charge exclusion effect on heavy metal cations under acidic conditions, thereby realizing ion separation.

[0014] The heavy metal cation of the present application includes but is not limited to copper ion, magnesium ion, lead ion, cadmium ion, zinc ion, nickel ion or chromium ion.

[0015] In some embodiments, the molar ratio of the monomer A to the monomer B is 1:(0.5-2).

[0016] Optionally, the molar ratio of the monomer A to the monomer B can be any one of 1:0.5, 1:1, 1:1.5 or 1:2 or any range between any two of them.

[0017] The base film of the present application is a porous nanofiltration membrane, and the pore size is 0.3-0.6 μm; preferably 0.4-0.5 μm.

[0018] The base film of the present application is not particularly limited, and any conventional base film that can be used for acid-resistant nanofiltration membranes can be applied to the present application; optionally, the material of the base film is selected from at least one of polytetrafluoroethylene, polypropylene, polyvinylidene fluoride, polyamide, polyether ether ketone and polybenzimidazole.

[0019] The present application protects a preparation method of a conjugated microporous acid-resistant nanofiltration membrane, which comprises the following steps: S1, under the condition of a superacid catalyst, pre-polymerizing monomer A and monomer B to obtain a pre-polymerization solution; S2, immersing the base film in the pre-polymerization solution, taking out and performing a deep polymerization reaction to obtain the conjugated microporous acid-resistant nanofiltration membrane.

[0020] In some embodiments, the pre-polymerization reaction temperature in step S1 is 40-90℃, and the reaction time is 5-24 h.

[0021] In some embodiments, the super acid catalyst in step S1 is at least one selected from trifluoromethanesulfonic acid, carborane acid, fluorosulfonic acid, fluorantimonic acid, chlorosulfonic acid, magic acid, methanesulfonic acid, and p-toluenesulfonic acid.

[0022] In some embodiments, the organic solvent used in the reaction system in step S1 is at least one selected from tetrahydrofuran, 1,4-dioxane, toluene, and m-xylene, or a mixed solvent thereof.

[0023] In some embodiments, the temperature of the deep polymerization reaction in step S2 is 50-120℃, and the reaction time is 0.5-24 h.

[0024] In some embodiments, the immersion time of the base film in the pre-polymerization solution in step S2 is 30 s-8 min, and the immersion temperature is 40-90℃.

[0025] Preferably, before the base film is immersed in the pre-polymerization solution, the pre-polymerization solution is subjected to a dilution treatment; specifically, a diluent is added to the pre-polymerization solution, the volume ratio of the pre-polymerization solution to the diluent is adjusted to 1:(0.1-1), and the mixture is stirred uniformly while the temperature is controlled at 40-90℃.

[0026] Preferably, after the deep polymerization reaction, the conjugated microporous acid-resistant nanofiltration membrane is subjected to a washing and drying treatment; optionally, the washing agent is at least one selected from water, methanol, and tetrahydrofuran.

[0027] More preferably, after washing, the conjugated microporous acid-resistant nanofiltration membrane is contacted with a pore-retaining agent, and then subjected to the drying treatment; the pore-retaining agent is at least one selected from glycerol, polyethylene glycol, camphor sulfonic acid, triethylamine, and sodium dodecyl sulfate.

[0028] The application protects the use of a conjugated microporous acid-resistant nanofiltration membrane in the separation of heavy metal ions.

[0029] Compared with the prior art, the application has the following beneficial effects: The conjugated microporous acid-resistant nanofiltration membrane of the application contains a polymer monomer structural unit with an aromatic ring, which can form a conjugated microporous structure coupled by C-C, and a tertiary amine substituent is connected to the aromatic ring in part of the structural units with the aromatic ring. The tertiary amine substituent is strongly positively charged after protonation in an acidic environment, and based on the Donnan exclusion effect, the nanofiltration membrane has strong repulsion to heavy metal cations, thereby realizing ion separation. Meanwhile, the conjugated microporous structure provides a channel for the permeation of hydrogen ions, realizing the recovery of waste acid.

[0030] The present application introduces tertiary amine groups into the conjugated microporous structure, fully combines the chemical stability of the conjugated microporous structure and the surface positive charge under acidic conditions, realizes efficient interception of heavy metal ions and excellent stability under acidic conditions. The prepared composite membrane has excellent heavy metal removal capacity and high efficiency acid permeability in a strong acidic (pH = 0 ~ 2) environment, and has good potential in acid wastewater treatment and resource recycling. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is a physical map of the conjugated microporous acid-resistant nanofiltration membrane in Example 1 of the present application; Figure 2 is a Fourier transform infrared spectrum (FTIR) of the conjugated microporous acid-resistant nanofiltration membrane in Example 1, Example 2 and Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0032] The present application will be further described below in conjunction with specific embodiments, but the embodiments do not limit the present application in any form. Example 1

[0033] A preparation method of a conjugated microporous acid-resistant nanofiltration membrane, comprising the following steps: 1) 3 mmol of 1,3,5-triacetylbenzene and 3 mmol of 4-acetylimidazole are placed in a 25 ml round-bottom flask, 10 ml of tetrahydrofuran is added at room temperature, and then the temperature is raised to 70°C for stirring; after the monomers are fully dissolved, 1 ml of trifluoromethanesulfonic acid is quickly added, and the reaction is carried out for 12 h to obtain a prepolymerization solution; 2) 5 ml of tetrahydrofuran diluent is added to the prepolymerization solution, and stirred uniformly at 70°C; 3) The prepolymerization solution is poured into a petri dish, immersed in a polytetrafluoroethylene base film (pore size is 0.45 μm) for 30 s, and the immersion temperature is controlled at 70°C; 4) After the base film is taken out, it is placed in a 70°C oven for further polymerization for 12 h to obtain a composite membrane precursor; 5) The composite membrane precursor is sequentially immersed in water, methanol and tetrahydrofuran for washing, then immersed in glycerol and dried to obtain a composite nanofiltration membrane, which is denoted as P1.

[0034] The physical map is shown in Figure 1 The surface chemical structure is characterized by FTIR, and the results are shown in Figure 2 . Example 2

[0035] A preparation method of a conjugated microporous acid-resistant nanofiltration membrane, comprising the following steps: 1) 3 mmol of 1,3,5-triacetylbenzene, 1 mmol of 4-acetyl imidazole were placed in a 25 ml round-bottom flask, 20 ml of tetrahydrofuran was added at room temperature, and then the temperature was raised to 90°C for stirring; after the monomers were fully dissolved, 1 ml of trifluoromethanesulfonic acid was quickly added, and the reaction was carried out for 5 h to obtain a prepolymerization solution; 2) 2 ml of tetrahydrofuran diluent was added to the prepolymerization solution, and stirring was carried out uniformly at 90°C; 3) The prepolymerization solution was poured into a culture dish, and a polytetrafluoroethylene base film (pore size 0.45 μm) was immersed for 2 min, with the immersion temperature controlled at 90°C; 4) After the base film was taken out, it was placed in a 90°C oven for further polymerization for 0.5 h to obtain a composite membrane precursor; 5) The composite membrane precursor was sequentially immersed in water, methanol and tetrahydrofuran for washing, and then immersed in glycerol and dried to obtain a composite nanofiltration membrane, which was recorded as P2. The surface chemical structure was characterized by FTIR, and the results are shown in Figure 2 . Example 3

[0036] A preparation method of a conjugated microporous acid-resistant nanofiltration membrane, comprising the following steps: 1) 3 mmol of 1,3,5-triacetylbenzene, 0.6 mmol of methyl-3-pyridyl ketone were placed in a 25 mL round-bottom flask, 5 ml of 1,4-dioxane was added at room temperature, and then the temperature was raised to 40°C for stirring; after the monomers were fully dissolved, 5 ml of trifluoromethanesulfonic acid was quickly added, and the reaction was carried out for 24 h to obtain a prepolymerization solution; 2) 8 ml of 1,4-dioxane diluent was added to the prepolymerization solution, and stirring was carried out uniformly at 40°C; 3) The prepolymerization solution was poured into a culture dish, and a polytetrafluoroethylene base film (pore size 0.45 μm) was immersed for 8 min, with the immersion temperature controlled at 40°C; 4) After the base film was taken out, it was placed in a 50°C oven for further polymerization for 24 h to obtain a composite membrane precursor; 5) The composite membrane precursor was sequentially immersed in water, methanol and tetrahydrofuran for washing, and then immersed in glycerol and dried to obtain a composite nanofiltration membrane, which was recorded as P3. Example 4

[0037] A preparation method of a conjugated microporous acid-resistant nanofiltration membrane, comprising the following steps: 1) 3 mmol of 1,3,5-triacetylbenzene, 3 mmol of tetraacetyl ethylenediamine were placed in a 25 ml round-bottom flask, 10 ml of 1,4-dioxane was added at room temperature, and then the temperature was raised to 70°C for stirring; after the monomers were fully dissolved, 1 ml of trifluoromethanesulfonic acid was quickly added, and the reaction was carried out for 12 h to obtain a prepolymerization solution; 2) 5 ml of 1,4-dioxane diluent was added to the prepolymerization solution, and stirred uniformly at 70°C; 3) The prepolymerization solution was poured into a culture dish, and immersed in a polytetrafluoroethylene base film (pore size of 0.45 μm) for 30 s, with the immersion temperature controlled at 70°C; 4) After the base film was taken out, it was placed in a 70°C oven for further polymerization for 12 h to obtain a composite membrane precursor; 5) The composite membrane precursor was sequentially immersed in water, methanol and tetrahydrofuran for washing, and then immersed in glycerol and dried to obtain a composite nanofiltration membrane, which was recorded as P4.

[0038] A method for preparing a nanofiltration membrane, comprising the following steps: 1) 3 mmol of 1,3,5-triacetylbenzene was placed in a 25 ml round-bottom flask, 10 mL of tetrahydrofuran was added at room temperature, and then the temperature was raised to 70°C for stirring; after the monomer was fully dissolved, 1 ml of trifluoromethanesulfonic acid was quickly added, and the reaction was carried out for 12 h to obtain a prepolymerization solution.

[0039] 2) 10 ml of tetrahydrofuran diluent was added to the prepolymerization solution, and stirred uniformly at 70°C; 3) The prepolymerization solution was poured into a culture dish, and quickly immersed in a polytetrafluoroethylene base film (pore size of 0.45 μm) for 30 s, and then taken out and placed in a 70°C oven for further polymerization for 12 h.

[0040] 4) The composite membrane was sequentially immersed in water, methanol and tetrahydrofuran for washing, and then immersed in glycerol and dried to obtain a composite membrane, which was recorded as DP1. The surface chemical structure was characterized by FTIR, and the results are shown in Figure 2 .

[0041] The following performance tests were carried out on the examples and comparative examples.

[0042] 1, FTIR characterization Examples 1, 2 and Comparative Example 1 were characterized by Fourier Transform Infrared Spectroscopy (FTIR), and the spectrum is shown in Figure 2 .

[0043] The results show that, compared with Comparative Example 1, the materials of Examples 1 and 2 have a stretching vibration absorption peak of imidazole ring at 1030 cm -1 , which proves that the tertiary amine group in imidazole is successfully introduced into the conjugated microporous structure.

[0044] 2, Surface zeta potential characterization of the separation membrane The surface zeta potential of the membrane was measured by a zeta potential analyzer (SurPASS 3, Anton Paar Co., Austria) at 0.001 mol L -1Charge characteristics in potassium chloride electrolyte solution. The charge characteristics of the membranes were measured in 0.05 mol L -1 Hydrochloric acid and sodium hydroxide were used to adjust the pH value, and the gap height was fixed at 100 μm. Before testing, the samples were cleaned with isopropanol to remove impurities and excess monomers on the surface of the membranes. The results are shown in Table 1.

[0045]

[0046] As can be seen from the data in Table 1, the surface of the conjugated microporous acid-resistant nanofiltration membrane prepared in the examples has strong positive charge properties under the conditions of pH = 7 and pH = 2, which is mainly due to the protonation of the tertiary amine groups introduced in the conjugated microporous polymer, resulting in positive charges on the surface of the membrane. The surface of the membrane of Comparative Example 1 exhibits a negative potential under the condition of pH = 7, indicating that it does not have cationic groups, and the surface positive charge under acidic conditions is much lower than that of the examples.

[0047] 3. Performance evaluation of separation membranes 3.1 Static evaluation method The acid resistance stability of the membranes was evaluated by immersing the composite membranes in a 20 wt% sulfuric acid solution at room temperature for 30 days. After taking out the membrane pieces, they were cleaned with pure water, and the water flux and heavy metal removal performance of the membranes were tested using a cross-flow running device.

[0048] Water flux test of separation membranes: water flux is the volume of solution (V, L) that passes through a unit membrane area (A, m 2 ) under a unit pressure (P, bar) in a unit time (t, h) under certain operating pressure conditions; the separation membrane is placed in a cross-flow filtration device and operated under a certain pressure, and the water flow rate per unit time is recorded; finally, the water flux is calculated according to the following formula: P = V / (A·t·ΔP); Retention performance test of separation membranes: retention rate is the ability of a membrane to prevent a component in a feed solution from passing through or to retain a certain component; the retention rate is tested by measuring the ratio of the difference in solute concentration (C P ) between the feed solution and the permeate solution during the membrane filtration process to the solute concentration (C F ) of the feed solution, and the calculation formula is as follows: R = (1 - C P / C F ) x 100%; The feed solution was a magnesium sulfate solution containing 2000 mg / L of magnesium sulfate (pH: ~6.5). The cross-flow test device was used at room temperature, the cross-flow flow rate was 60 L / h, and the test was conducted at a pressure of 10 bar for 5 h. The concentration of magnesium sulfate was determined using a conductivity meter (FE38-Standard, Mettler Toledo). The results of the static evaluation are shown in Table 2.

[0049]

[0050] As shown in Table 2, the composite membrane exhibits excellent acid resistance under long-term immersion in high-concentration sulfuric acid, with a magnesium sulfate rejection rate exceeding 90%. Compared to Comparative Example 1, the surface charge of the composite nanofiltration membrane prepared in this embodiment plays a significant role, demonstrating a high rejection capacity for divalent ions, and its water flux is significantly higher than that of the comparative example. This indicates that the introduction of charge into the conjugated microporous composite membrane has a strong electrostatic repulsion effect, which is beneficial to improving separation performance.

[0051] 3.2 Dynamic Evaluation Method The feed solution was a copper sulfate solution containing 2000 mg / L, with a sulfuric acid content of 20 wt%. An acid-resistant cross-flow testing device was used at room temperature, with a cross-flow rate of 60 L / h and a pressure of 10 bar for 10 h. The concentration of copper sulfate was determined by inductively coupled plasma mass spectrometry (ICP-MS).

[0052] The acid rejection rate (%) was calculated based on pH changes. The pH of the feed solution and permeate was converted into hydrogen ion concentration, and then the rejection rate formula was used for calculation. The dynamic evaluation results are shown in Table 3.

[0053]

[0054] Referring to Table 3, the composite nanofiltration membrane prepared in the embodiments of the present invention has excellent acid resistance and stability. Under dynamic strong acid conditions, it still maintains excellent removal rate of divalent heavy metal ions, and the removal rate of copper sulfate can reach up to 98.5%. Moreover, the acid permeability is very good, which can realize the simultaneous separation of acid and metal ions. It has good application prospects in the treatment and resource recycling of acidic electroplating wastewater, battery recycling, and rare earth wastewater.

[0055] The above embodiments of the present invention are merely examples for clearly illustrating the present invention and are not intended to limit the implementation of the present invention. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively describe all possible implementations here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A conjugated microporous acid-resistant nanofiltration membrane, characterized in that, The functional separation layer is formed by polymerization of monomer A containing acetyl aromatic ring and monomer B containing acetyl tertiary amine.

2. The conjugated microporous acid-resistant nanofiltration membrane according to claim 1, wherein, The structure of the monomer A is shown in formula (I), Formula (I), wherein R1, R2, R3, R4, R5, R6 are each independently selected from any one of H, C1-C6 substituted or unsubstituted alkyl, C6-C12 substituted or unsubstituted aryl, amine group, acetyl group, halogen substituent, and at least two of R1, R2, R3, R4, R5 and R6 contain acetyl group.

3. The conjugated microporous acid-resistant nanofiltration membrane according to claim 1 or 2, wherein, The monomer A is selected from at least one of 1,3,5-triacetylbenzene, 1,4-diacetylbenzene and 1,3-diacetylbenzene.

4. The conjugated microporous acid-resistant nanofiltration membrane according to claim 1, wherein, The structure of the monomer B is shown in formula (II), Formula (II), wherein R7 is tertiary amine type substituted or unsubstituted nitrogen heterocycle or C3-C12 substituted or unsubstituted alkyl containing tertiary amine.

5. The conjugated microporous acid-resistant nanofiltration membrane according to claim 1 or 4, wherein, The monomer B is selected from at least one of 4-acetylimidazole, methyl-3-pyridyl ketone, tetraacetyl ethylenediamine, 1-acetyl-N-methylpiperidinamine hydrochloride, N-ethylacetamide, N,N-diethylacetamide, N-ethyl-N-methylacetamide, N,N-methylformamide, N-acetylvinylimine, 4-acetylpiperazine-1-carboxaldehyde, 4-acetyl-1-piperazine ethylamine, 4-acetyl-1,1-dimethylpiperazinium iodide and N,N-bis-isopropyl-acetamide.

6. The conjugated microporous acid-resistant nanofiltration membrane according to claim 1, wherein, The molar ratio of the monomer A to the monomer B is 1: (0.5-2).

7. A method for preparing the conjugated microporous acid-resistant nanofiltration membrane according to any one of claims 1-6, characterized in that, The method comprises the following steps: S1, under the condition of super acid catalyst, pre-polymerization of monomer A and monomer B to obtain a pre-polymerization solution; S2, immersing the base film in the pre-polymerization solution, taking out and performing deep polymerization to obtain the conjugated microporous acid-resistant nanofiltration membrane.

8. The method of claim 7, wherein the conjugated microporous acid-resistant nanofiltration membrane is prepared by the method comprising: In step S1, the pre-polymerization temperature is 40-90℃, and the reaction time is 5-24 h; and / or, In step S2, the deep polymerization temperature is 50-120℃, and the reaction time is 0.5-24 h.

9. The method for preparing the conjugate microporous acid-resistant nanofiltration membrane according to claim 7, characterized in that, In step S1, the super acid catalyst is selected from at least one of trifluoromethanesulfonic acid, carborane acid, fluorosulfonic acid, fluorine antimony acid, chlorosulfonic acid, magic acid, methanesulfonic acid and p-toluenesulfonic acid.

10. Use of the conjugated microporous acid-resistant nanofiltration membrane according to any one of claims 1-6 in heavy metal ion separation.

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