A boron nitride nanosheet-doped polyamide composite nanofiltration membrane and a preparation method thereof

Abstract

The application provides a boron nitride nanosheet-doped polyamide composite nanofiltration membrane and a preparation method. The method uniformly disperses boron nitride nanosheets in deionized water, and then uniformly mixes the boron nitride nanosheets with a piperazine aqueous solution. The mass ratio of the boron nitride nanosheets to the piperazine is (5.01-20.04):(60-200), and a mixed solution is obtained. The mixed solution is vacuum filtered on a polyether sulfone ultrafiltration membrane, and the polyether sulfone ultrafiltration membrane is left with a mixture of uniformly dispersed boron nitride nanosheets and piperazine. A triformylchloride solution is poured on the mixture of the boron nitride nanosheets and the piperazine. The mass ratio of the boron nitride nanosheets to the triformylchloride is (5.01-20.04):100. The triformylchloride and the piperazine are interfacially polymerized on the surface of the polyether sulfone ultrafiltration membrane. The solvent of the triformylchloride solution is then poured off. After drying, a boron nitride nanosheet-doped polyamide composite nanofiltration membrane is obtained, and the permeation flux and the antifouling property of the polyamide nanofiltration membrane are improved.

Description

TECHNICAL FIELD

[0001] The application relates to composite nanofiltration membrane preparation, in particular to a boron nitride nanosheet doped polyamide composite nanofiltration membrane and a preparation method. BACKGROUND

[0002] Water resource shortage is one of the most challenging problems at present, in order to effectively get rid of the current situation of water resource shortage, people begin to use various technologies to desalinate seawater, reuse domestic sewage and industrial wastewater. Membrane separation technology is an important way to solve water pollution problem. Polyamide (PA) nanofiltration membrane has low operating pressure, high water flux and low energy consumption, has high rejection rate for divalent ions which are easy to form scale, and can reject multivalent ions and neutral small molecules while allowing monovalent ions to pass through, so as to realize selective separation of target substances. Therefore, it is widely used in the field of seawater desalination.

[0003] Up to now, there are still problems in the separation performance of PA nanofiltration membrane, such as still low permeation flux, and there is a trade-off effect between permeability and selectivity of the membrane, that is, the rejection rate decreases when the flux increases, and the flux decreases when the rejection rate increases, and it is still a great challenge to improve the permeability and selectivity of the nanofiltration membrane. Introducing nanomaterials into PA nanofiltration membrane is an effective method to improve its separation performance. In recent years, two-dimensional materials have attracted the attention of technology workers due to their excellent physical and chemical properties, and have been gradually used in the field of water treatment. The interlayer channel formed by the parallel arrangement of two-dimensional nanosheets can make water molecules pass through but reject salt ions, thereby improving the permeability and selectivity of the nanofiltration membrane.

[0004] At present, two-dimensional materials used for PA nanofiltration membrane include graphene oxide (GO), transition metal carbon / nitride (MXene) and graphite carbon nitride. However, GO membrane is easy to swell in aqueous solution, and after absorbing water, the interlayer spacing of the membrane will become larger, which greatly limits its screening performance. MXene membrane is easy to degrade in aqueous solution, mild oxidant and high temperature, which leads to the disintegration of the sheet structure and limits its application in the field of water treatment. SUMMARY

[0005] In view of the problems in the prior art, the application provides a boron nitride nanosheet doped polyamide composite nanofiltration membrane and a preparation method, which improves the permeation flux and antifouling property of the polyamide nanofiltration membrane.

[0006] The application is realized by the following technical scheme:

[0007] A preparation method of a boron nitride nanosheet doped polyamide composite nanofiltration membrane, comprising the following steps:

[0008] S1, uniformly dispersing boron nitride nanosheets in deionized water, then mixing with piperazine aqueous solution, the mass ratio of boron nitride nanosheets and piperazine being (5.01-20.04):(60-200), to obtain a mixed solution;

[0009] S2, vacuum filtration of the mixed solution on a polyether sulfone ultrafiltration membrane, leaving a mixture of uniformly dispersed boron nitride nanosheets and piperazine on the polyether sulfone ultrafiltration membrane;

[0010] S3, pouring a solution of trimesoyl chloride on the mixture of boron nitride nanosheets and piperazine, the mass ratio of boron nitride nanosheets to trimesoyl chloride being (5.01-20.04):100, interfacial polymerization of trimesoyl chloride and piperazine on the surface of the polyether sulfone ultrafiltration membrane, then pouring off the solvent of the trimesoyl chloride solution, and drying to obtain a boron nitride nanosheet-doped polyamide composite nanofiltration membrane.

[0011] Preferably, S1 uniformly disperses boron nitride nanosheets in deionized water to obtain a boron nitride nanosheet / water suspension with a concentration of 1-4 mg / mL, then uniformly mixes the boron nitride nanosheet / water suspension with a piperazine aqueous solution.

[0012] Further, the boron nitride nanosheet / water suspension of S1 is obtained by the following process:

[0013] Hexagonal boron nitride, boric acid and ball milling beads are ball milled at a speed of 500-600 rpm for 7-8 h, the obtained powder is washed with deionized water for 1-3 times, deionized water is added, and finally ultrasonic treatment is performed for 5-10 min to obtain the boron nitride nanosheet / water suspension.

[0014] Further, S1 adds the boron nitride nanosheet / water suspension to the piperazine aqueous solution to uniformly mix to obtain a mixed solution.

[0015] Preferably, the concentration of the piperazine aqueous solution of S1 is 0.2-2 mg / mL.

[0016] Preferably, S2 performs vacuum filtration of the mixed solution at a pressure of -0.2 to -0.1 MPa, leaving a mixture of uniformly dispersed boron nitride nanosheets and piperazine on the polyether sulfone ultrafiltration membrane.

[0017] Preferably, the solvent of the trimesoyl chloride solution in S3 is n-hexane.

[0018] Preferably, the concentration of the trimesoyl chloride solution in S3 is 0.2-2 mg / mL.

[0019] Preferably, the drying of S3 is performed at 50-60°C for 10-20 min.

[0020] A boron nitride nanosheet-doped polyamide composite nanofiltration membrane obtained by the preparation method of boron nitride nanosheet-doped polyamide composite nanofiltration membrane according to any one of the above methods.

[0021] Compared with the prior art, the present invention has the following beneficial technical effects:

[0022] This invention discloses a method for preparing a boron nitride nanosheet-doped polyamide composite nanofiltration membrane. Boron nitride nanosheets (BNNS), as an emerging two-dimensional material, possess high chemical stability, high oxidation resistance, and chemical corrosion resistance, and can be used to enhance the separation performance of nanofiltration membranes. Using a polyethersulfone (PES) ultrafiltration membrane as a substrate, BNNS is introduced into a piperazine (PIP) aqueous solution. Through interfacial polymerization with trimesoyl chloride (TMC) on the surface of the PES ultrafiltration membrane, the PA separation layer structure is controlled by introducing BNNS into the polyamide nanofiltration membrane, thereby improving the permeate flux of the PA nanofiltration membrane. BNNS / PA exhibits high hydrophilicity, forming a hydration layer on the nanofiltration membrane surface. Combined with the high chemical stability of BNNS, this enhances the antifouling properties of the polyamide nanofiltration membrane. This invention prepares a boron nitride nanosheet-doped polyamide composite nanofiltration membrane via interfacial polymerization, improving the thickness, hydrophilicity, and surface roughness of the polyamide nanofiltration membrane, thus enhancing its separation performance.

[0023] Furthermore, boric acid was used to assist in ball milling of hexagonal boron nitride, and the boron nitride was stripped by ball milling combined with ultrasonication and then introduced into PIP aqueous solution, which is convenient, easy to operate and low in cost. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the PIP and TMC interfacial polymerization reaction of the present invention.

[0025] Figure 2 The rejection rate and permeation flux of Na2SO4 by the PA prepared in Comparative Example 1 and the BNNS / PA nanofiltration membrane prepared in Example 1 of this invention are shown.

[0026] Figure 3a This is a planar SEM image of the PA prepared in Comparative Example 1 of this invention at 5 μm.

[0027] Figure 3b The image shows a planar SEM image of the BNNS / PA composite nanofiltration membrane prepared in Example 1 of this invention at a depth of 5 μm.

[0028] Figure 3c This is a cross-sectional SEM image of the PA prepared in Comparative Example 1 of the present invention at 5 μm.

[0029] Figure 3d The image shows a cross-sectional SEM image of the BNNS / PA composite nanofiltration membrane prepared in Example 1 of this invention at 5 μm.

[0030] Figure 4 Water contact angle images of PA prepared for Invention Comparative Example 1 and BNNS / PA nanofiltration membrane prepared for Example 1.

[0031] Figure 5 Surface roughness images of PA prepared for Invention Comparative Example 1 and BNNS / PA nanofiltration membrane prepared for Example 1.

[0032] Figure 6 Antifouling images of PA prepared for Invention Comparative Example 1 and BNNS / PA nanofiltration membrane prepared for Example 1. DETAILED DESCRIPTION

[0033] The application will be further described in conjunction with specific examples, which are intended to explain but not limit the application.

[0034] The application is a preparation method of boronic acid ball-milled boron nitride nanosheet doped polyamide composite nanofiltration membrane, and the specific steps are as follows:

[0035] Step 1: Take 1-3 g of hexagonal boron nitride (h-BN), 1-3 g of boric acid and 100-200 g of ball milling beads, and ball mill at 500-600 rpm for 7-8 h. The obtained powder is washed with deionized water for 1-3 times, and its concentration is diluted to 1 mg / mL-4 mg / mL with deionized water, and then ultrasonic for 5-10 min to obtain a uniformly dispersed BNNS (boron nitride nanosheet) / water suspension for standby.

[0036] Step 2: Weigh 60-200 mg of piperazine (PIP), and dissolve it in 100-300 mL of deionized water to obtain a PIP aqueous solution with a concentration of 0.2 mg / mL-2 mg / mL.

[0037] Step 3: Take the BNNS / water suspension prepared in step 1, and add it to the PIP aqueous solution obtained in step 2 and mix uniformly, and the mass ratio of boron nitride nanosheet to piperazine is (5.01-20.04):(60-200), to obtain a BNNS / PIP mixed solution.

[0038] Step 4: Weigh 60-200 mg of trimesoyl chloride (TMC), and dissolve it in 100-300 mL of n-hexane to obtain a TMC n-hexane solution with a concentration of 0.2 mg / mL-2 mg / mL, and the mass ratio of BNNS to TMC in step 3 is (5.01-20.04):100.

[0039] Step 5, put polyether sulfone ultrafiltration membrane into the filter flask, pour the BNNS / PIP mixed solution prepared in step 3 into the polyether sulfone ultrafiltration membrane as a base, and perform filtration under a pressure of -0.2 to -0.1 MPa, with deionized water being filtered into the filter flask, leaving a uniform dispersion of the BNNS and PIP mixture on the polyether sulfone ultrafiltration membrane, pour the TMC n-hexane solution prepared in step 4 onto the uniform dispersion of the BNNS and PIP mixture, and perform interfacial polymerization of the TMC on the surface of the PIP, leaving n-hexane on the PA composite nanofiltration membrane, which can be poured out, and after drying at 50 to 60°C for 10 to 20 min, the BNNS-doped PA composite nanofiltration membrane is finally obtained.

[0040] Example 1

[0041] The present application is a preparation method of a boronic acid ball-milled boron nitride nanosheet-doped polyamide composite nanofiltration membrane, and the specific steps are as follows:

[0042] (1) Take 2 g of boric acid and 2 g of h-BN and 200 g of ball milling beads, place these materials in a ball mill jar, and mill at 500 rpm for 7 h, then wash the obtained powder with deionized water twice, dilute it to 3 mg / mL with deionized water, and then use a cell crusher to ultrasonic for 5 min to obtain a uniform dispersion of the BNNS / water dispersion.

[0043] (2) Weigh 100 mg of PIP and dissolve it in 100 mL of deionized water to obtain a PIP aqueous solution with a concentration of 1 mg / mL.

[0044] (3) Take 1.67 mL of the BNNS / water suspension prepared in (1) and add it to the PIP aqueous solution obtained in (2) to obtain a BNNS / PIP mixed solution, wherein the BNNS accounts for 0.005% of the mass of the mixed solution.

[0045] (4) Weigh 100 mg of TMC and dissolve it in 100 mL of n-hexane to obtain a TMC n-hexane solution with a concentration of 1 mg / mL.

[0046] (5) Put polyether sulfone ultrafiltration membrane into the filter flask, pour the BNNS / PIP mixed solution prepared in step 3 into the polyether sulfone ultrafiltration membrane as a base, and perform filtration under a pressure of -0.2 MPa, with deionized water being filtered into the filter flask, leaving a uniform dispersion of the BNNS and PIP mixture on the polyether sulfone ultrafiltration membrane, pour the TMC n-hexane solution prepared in step 4 onto the uniform dispersion of the BNNS and PIP mixture, and perform interfacial polymerization of the TMC on the surface of the PIP, leaving n-hexane on the PA composite nanofiltration membrane, which can be poured out, and after drying at 60°C for 15 min, the BNNS-doped PA composite nanofiltration membrane is finally obtained.

[0047] Example 2

[0048] The preparation method of the boronic acid ball-milled boron nitride nanosheet doped polyamide composite nanofiltration membrane of the application is as follows:

[0049] (1) Take 2g of boric acid and 2g of h-BN and 200g of ball milling beads, place these materials in a ball mill jar and ball mill at 500rpm for 7h, wash the obtained powder with deionized water for 2 times, then dilute it to 3mg / mL with deionized water, and obtain a uniformly dispersed BNNS / water dispersion after ultrasonic treatment for 5min with a cell crusher.

[0050] (2) Weigh 100mg of PIP and dissolve it in 100mL of deionized water to obtain a PIP aqueous solution with a concentration of 1mg / mL.

[0051] (3) Take 3.34mL of the BNNS / water suspension prepared in (1) and add it to the PIP aqueous solution obtained in (2) to obtain a BNNS / PIP mixed solution, wherein the BNNS accounts for 0.01% of the mass of the mixed solution.

[0052] (4) Weigh 100mg of TMC and dissolve it in 100mL of n-hexane to obtain a TMC n-hexane solution with a concentration of 1mg / mL.

[0053] (5) Put a polyether sulfone ultrafiltration membrane into a suction filter bottle, take the BNNS / PIP mixed solution prepared in step 3 and pour it into the polyether sulfone ultrafiltration membrane, perform suction filtration under a pressure of-0.15MPa, and deionized water is suctioned into the suction filter bottle, leaving a uniformly dispersed BNNS and PIP mixture on the polyether sulfone ultrafiltration membrane, pour the TMC n-hexane solution prepared in step 4 onto the uniformly dispersed BNNS and PIP mixture, and perform interfacial polymerization of TMC on the surface of PIP, leaving n-hexane on the PA composite nanofiltration membrane, which can be poured out, and after drying at 60℃ for 15min, the BNNS doped PA composite nanofiltration membrane is finally obtained.

[0054] Example 3

[0055] The preparation method of the boronic acid ball-milled boron nitride nanosheet doped polyamide composite nanofiltration membrane of the application is as follows:

[0056] (1) Take 2g of boric acid and 2g of h-BN and 200g of ball milling beads, place these materials in a ball mill jar and ball mill at 500rpm for 7h, wash the obtained powder with deionized water for 2 times, then dilute it to 3mg / mL with deionized water, and obtain a uniformly dispersed BNNS / water dispersion after ultrasonic treatment for 5min with a cell crusher.

[0057] (2) Take 100 mg of PIP and dissolve it in 100 mL of deionized water to obtain a PIP aqueous solution with a concentration of 1 mg / mL.

[0058] (3) Take 5.01 mL of the BNNS / water suspension prepared in (1) and add it to the PIP aqueous solution obtained in (2) to obtain a BNNS / PIP mixed solution, wherein the BNNS accounts for 0.015% of the mass of the mixed solution.

[0059] (4) Take 100 mg of TMC and dissolve it in 100 mL of n-hexane to obtain a TMC n-hexane solution with a concentration of 1 mg / mL.

[0060] (5) Place a polyether sulfone ultrafiltration membrane in a suction filter bottle, use the polyether sulfone ultrafiltration membrane as a base, pour the BNNS / PIP mixed solution prepared in step 3 into the polyether sulfone ultrafiltration membrane, perform suction filtration under a pressure of -0.1 MPa, and deionized water is suctioned into the suction filter bottle. The polyether sulfone ultrafiltration membrane has a uniformly dispersed BNNS and PIP mixture on it. Pour the TMC n-hexane solution prepared in step 4 onto the uniformly dispersed BNNS and PIP mixture, and the TMC performs interfacial polymerization on the surface of the PIP. The PA composite nanofiltration membrane retains n-hexane, which can be poured out. After drying at 60°C for 15 min, a BNNS-doped PA composite nanofiltration membrane is finally obtained.

[0061] Example 4

[0062] The present application is a preparation method of a boronic acid ball-milled boron nitride nanosheet-doped polyamide composite nanofiltration membrane, and the specific steps are as follows:

[0063] (1) Take 2 g of boric acid, 2 g of h-BN, and 200 g of ball milling beads, place these materials in a ball mill jar, and ball mill at 500 rpm for 7 h. Wash the obtained powder with deionized water twice, then dilute it to 3 mg / mL with deionized water, and use a cell crusher to ultrasonic for 5 min to obtain a uniformly dispersed BNNS / water dispersion.

[0064] (2) Take 100 mg of PIP and dissolve it in 100 mL of deionized water to obtain a PIP aqueous solution with a concentration of 1 mg / mL.

[0065] (3) Take 6.68 mL of the BNNS / water suspension prepared in (1) and add it to the PIP aqueous solution obtained in (2) to obtain a BNNS / PIP mixed solution, wherein the BNNS accounts for 0.02% of the mass of the mixed solution.

[0066] (4) Take 100 mg of TMC and dissolve it in 100 mL of n-hexane to obtain a TMC n-hexane solution with a concentration of 1 mg / mL.

[0067] (5) Put polyether sulfone ultrafiltration membrane into the filter flask, pour the BNNS / PIP mixed solution prepared in step 3 into the polyether sulfone ultrafiltration membrane, and perform filtration under a pressure of-0.18 MPa, with deionized water being filtered into the filter flask, and the polyether sulfone ultrafiltration membrane being left with a uniformly dispersed BNNS and PIP mixture, pour the TMC n-hexane solution prepared in step 4 onto the uniformly dispersed BNNS and PIP mixture, perform interfacial polymerization of TMC on the surface of PIP, and leave n-hexane on the PA composite nanofiltration membrane, which can be poured out, and after drying at 60°C for 15 min, the BNNS-doped PA composite nanofiltration membrane is finally obtained.

[0068] Figure 1 The figure is a schematic diagram of the polymerization reaction of PIP and TMC. Interfacial polymerization is a process in which two kinds of monomers or oligomers with certain reaction functions are respectively dissolved in two kinds of mutually incompatible solutions, when the two solutions are contacted, a thin polymer film is generated by condensation polymerization at the interface of the two phases. In the present application, piperazine (PIP) is used as the water-phase polymerization monomer, and trimesoyl chloride (TMC) is used as the oil-phase polymerization monomer, and a polyamide nanofiltration membrane is prepared on a polyether sulfone base film by interfacial polymerization.

[0069] Figure 2 The rejection rate and permeation flux of Na2SO4 of the prepared polyamide nanofiltration membrane (i.e., without the description of BNNS in steps 1 and 3 of Example 1, which is Comparative Example 1) and the boron nitride nanosheet / polyamide composite nanofiltration membrane were determined. The separation performance of the prepared polyamide nanofiltration membrane and the boron nitride nanosheet / polyamide composite nanofiltration membrane was evaluated by using a cross-flow filtration device. The filtration area (A, unit: m -2 ) of the nanofiltration membrane was 1.5 cm -2 , the test pressure (P, unit: bar) was 4 bar, and the feed liquid was a 1000 ppm Na2SO4 solution. Every 20 mL (V, unit: mL) of filtrate was collected, the corresponding time (t, unit: h) was recorded, and the conductivity of the feed liquid (C F ) and the filtrate (C P ) was tested by using a conductivity meter. The calculation formula of the permeation flux (P) is shown in formula (1):

[0070] P = V / (A x t x P) (1)

[0071] The calculation formula of the rejection rate (R) is shown in formula (2):

[0072] R = (1-C P / C F ) (2)

[0073] Figure 2It can be seen that the permeation flux of the polyamide nanofiltration membrane is 11.52 LMH / bar, and the rejection rate of Na2SO4 is 95.65%; the permeation flux of the boron nitride nanosheet / polyamide composite nanofiltration membrane can reach 15.90 LMH / bar, and the rejection rate of Na2SO4 is 94.08%, and the addition of boron nitride nanosheet improves the permeation flux of the nanofiltration membrane while maintaining high rejection rate.

[0074] Figure 3a PA is a planar SEM image at 5 μm, Figure 3b BNNS / PA composite nanofiltration membrane is a planar SEM image at 5 μm, Figure 3c PA is a cross-sectional SEM image at 5 μm, Figure 3d BNNS / PA composite nanofiltration membrane is a cross-sectional SEM image at 5 μm. Comparison Figure 3a and Figure 3b , and Figure 3c and Figure 3d It can be seen that the addition of BNNS causes the polyamide layer to appear Turing structure, increasing the wrinkle structure of the polyamide layer. The wrinkle structure first increases the surface roughness, improves the hydrophilicity, and thus improves the water permeation flux, and secondly increases the effective contact area with water molecules, thus improving the water permeation flux of the nanofiltration membrane. In addition, Figure 3c The thickness of PA in is about equal to 154 nm, Figure 3d The thickness of the BNNS / PA composite nanofiltration membrane in is about equal to 113 nm, and the thickness of the BNNS / PA composite nanofiltration membrane is reduced, and the transport path of water molecules is shortened, so the water permeation flux is improved.

[0075] Figure 4 The surface roughness of PA and BNNS / PA composite nanofiltration membranes is shown in Table 1, it can be seen that after adding BNNS, the surface roughness of the nanofiltration membrane is improved, which is consistent with the conclusion of the planar SEM image of the membrane in Figure 3b .

[0076] Figure 5 The water contact angle of PA and BNNS / PA composite nanofiltration membranes is shown in Table 1, it can be seen that after adding BNNS, due to the increase of roughness, the water contact angle of the BNNS / PA composite nanofiltration membrane surface is reduced, the hydrophilicity is improved, which is beneficial to improve the permeation flux.

[0077] Figure 6 The antifouling property of PA and BNNS / PA composite nanofiltration membranes is shown in Table 1. Bovine serum albumin (BSA) was used as a contaminant to test the antifouling performance of PA and BNNS / PA composite nanofiltration membranes. First, the initial permeation flux (J0, unit: L·m -2 h -1 bar -1), then the feed solution was replaced by 1000 ppm BSA solution, and the permeate flux (J, unit: L·m -2 h -1 bar -1 ), then the PA and BNNS / PA composite nanofiltration membranes were rinsed with a large amount of deionized water to remove the residual pollutants on the membrane surface, and finally tested the permeate flux (J, unit: L·m -2 h - 1 bar -1 ), the calculation formula of the permeate flux is shown in formula (1). The calculation formula of the flux recovery rate (FRR) is shown in formula (3):

[0078] FRR = (J / J0) x 100% (3)

[0079] It can be seen that, due to the high hydrophilicity of BNNS / PA, a hydration layer can be formed on the surface of the nanofiltration membrane, thereby improving the antifouling property of the nanofiltration membrane.

Claims

1. A method for preparing a boron nitride nanosheet-doped polyamide composite nanofiltration membrane, characterized in that, Includes the following steps: S1, according to the mass ratio of (1~3):(1~3):(100~200), hexagonal boron nitride, boric acid and ball milling beads are ball milled at a rate of 500~600 rpm for 7~8 h. The obtained powder is washed with deionized water 1~3 times, then deionized water is added again, and finally ultrasonicated for 5~10 min to obtain a boron nitride nanosheet / water suspension with a concentration of 1~4 mg / mL. Then, the boron nitride nanosheet / water suspension is added to piperazine aqueous solution and mixed evenly. The concentration of piperazine aqueous solution is 0.2~2 mg / mL, and the mass ratio of boron nitride nanosheets to piperazine is (5.01~20.04):(60~200) to obtain a mixed solution. S2, the mixture is vacuum filtered on a polyethersulfone ultrafiltration membrane at a pressure of -0.2~-0.1MPa, leaving a uniformly dispersed mixture of boron nitride nanosheets and piperazine on the polyethersulfone ultrafiltration membrane; S3, a 0.2~2 mg / mL solution of trimellityl chloride is poured onto a mixture of boron nitride nanosheets and piperazine. The solvent of the trimellityl chloride solution is n-hexane. The mass ratio of boron nitride nanosheets to trimellityl chloride is (5.01~20.04):

100. Triellityl chloride and piperazine undergo interfacial polymerization on the surface of the polyethersulfone ultrafiltration membrane. Then, the n-hexane is discarded, and the membrane is dried at 50~60℃ for 10~20 min to obtain a boron nitride nanosheet-doped polyamide composite nanofiltration membrane.

2. A boron nitride nanosheet-doped polyamide composite nanofiltration membrane obtained by the preparation method of the boron nitride nanosheet-doped polyamide composite nanofiltration membrane according to claim 1.

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