BaTiO3@CNTs composite nanofiltration membrane with high dielectric property and preparation method thereof

Abstract

The application discloses a preparation method of a BaTiO3@CNTs composite nanofiltration membrane with high dielectric property, and belongs to the field of filtration membranes. The application aims at solving the problem that the water flux and salt retention rate of the existing commercial polyamide nanofiltration membrane are difficult to be simultaneously improved. In the application, high-dielectric barium titanate (BaTiO3) nanoparticles are loaded on the surface of carbon nanotubes (CNTs) to form a heterostructure, and then the heterostructure is embedded into a polyamide (PA) active layer to construct a nanofiltration membrane with high water flux, strong dielectric repulsion and stability. The design breaks through the limitation of single material modification, and cooperatively utilizes the rapid water channel effect of CNTs and the dielectric repulsion effect of BaTiO3, so that the selective separation performance for monovalent / divalent ions is significantly improved. The application is applied to low-cost desalination treatment suitable for high-salt brackish water.

Description

Technical Field

[0001] This invention belongs to the field of filtration membranes, specifically, it relates to a high dielectric property BaTiO3@CNTs composite nanofiltration membrane and its preparation method. Background Technology

[0002] Currently, commercially available polyamide (PA) nanofiltration membranes generally face a "trade-off" effect, meaning that it is difficult to simultaneously improve water flux and salt rejection rate. The fundamental reason is that the densely cross-linked PA layer limits the mass transfer rate, while reducing the degree of cross-linking can increase flux but sacrifices retention performance. Existing modification techniques (such as the introduction of nanomaterials) mostly focus on single-dimensional improvements (such as hydrophilicity or pore structure control), making it difficult to reconcile the contradictions between flux, retention, and stability.

[0003] Carbon nanotube (CNT) modified membranes: CNTs can improve water flux by forming nanochannels, but they have poor dispersibility and are prone to aggregation, leading to interface defects and decreased membrane performance. In addition, CNTs themselves do not have a selective separation mechanism and have limited dielectric repulsion ability against mono / divalent ions.

[0004] High dielectric nanomaterials (such as BaTiO3 and TiO2) modified films: High dielectric materials can enhance the dielectric repulsion effect of the film surface on charged ions, but when introduced alone, they cannot form an effective mass transfer channel, and the bonding strength with the PA matrix is ​​low, which makes them easy to fall off and result in poor long-term stability.

[0005] The synergistic effect of the composite modified membrane is insufficient: In the existing technology, when nanochannel materials and high dielectric materials are simply mixed and introduced into the PA layer (such as physical blending of CNTs and BaTiO3), the material distribution is uneven and the interfacial bonding is weak, which cannot give full play to the synergistic effect; and the immobilization problem of high dielectric materials in the cross-linked network has not been solved.

[0006] Existing technologies struggle to simultaneously achieve the synergistic effect of "efficient water channel transport" and "precise sieving by dielectric repulsion," and lack optimized designs for brackish water environments with high salinity and multiple ions. There is an urgent need for a novel composite nanofiltration membrane that combines physical sieving, dielectric repulsion, and rapid mass transfer mechanisms through innovative material structure, overcoming traditional limitations. Summary of the Invention

[0007] This invention aims to solve the problem that it is difficult to simultaneously improve the water flux and salt rejection rate of existing commercial polyamide nanofiltration membranes, and provides a high dielectric property BaTiO3@CNTs composite nanofiltration membrane and its preparation method.

[0008] This invention proposes a BaTiO3@CNTs composite nanofiltration membrane. By loading high-dielectric barium titanate (BaTiO3) nanoparticles onto the surface of carbon nanotubes (CNTs) to form a heterostructure, and then embedding these nanoparticles into a polyamide (PA) active layer, a nanofiltration membrane with high water flux, strong dielectric repulsion, and stability is constructed. This design overcomes the limitations of single-material modification, synergistically utilizing the rapid water channel effect of CNTs and the dielectric repulsion of BaTiO3 to significantly improve the selective separation performance for monovalent / divalent ions.

[0009] To address the aforementioned technical problems, the present invention adopts the following technical solution:

[0010] The purpose of this invention is to provide a method for preparing a high-dielectric-value BaTiO3@CNTs composite nanofiltration membrane, comprising the following steps:

[0011] Step 1: Disperse CNTs and surfactants ultrasonically in anhydrous ethanol, add BaTiO3 nanoparticles, heat and stir vigorously until ethanol evaporates, wash with isopropanol to remove surfactant, vacuum dry to remove isopropanol, anneal, grind to obtain BaTiO3@CNTs nanomaterials.

[0012] Step 2: Add BaTiO3@CNTs nanomaterials to ultrapure water, add dispersant, and sonicate until uniformly dispersed to obtain a nanomaterial suspension;

[0013] Piperazine (PIP) was added to water, followed by the addition of NaOH to neutralize the hydrochloric acid produced during the interfacial polymerization process. The mixture was then thoroughly mixed to obtain an aqueous solution of piperazine.

[0014] Trimethylbenzene chloride (TMC) was dissolved in n-hexane to obtain a TMC solution;

[0015] Step 3: Filter the nanomaterial suspension obtained in Step 2 onto the surface of the PES support layer, air dry it, load BaTiO3@CNTs nanomaterials onto the surface, then filter the PIP aqueous solution again, air dry it, and obtain the polyamide active layer.

[0016] Step 4: Then fix it in the mold with the polyamide active layer surface facing upwards, pour TMC solution into the mold, carry out interfacial polymerization reaction for at least 30 seconds, solidify, and rinse thoroughly with ultrapure water to obtain the composite nanofiltration membrane.

[0017] Another method for preparing a high-dielectric-value BaTiO3@CNTs composite nanofiltration membrane according to the present invention includes the following steps:

[0018] Step 1: Disperse CNTs and surfactants ultrasonically in anhydrous ethanol, add BaTiO3 nanoparticles, heat and stir vigorously until ethanol evaporates, wash with isopropanol to remove surfactant, vacuum dry to remove isopropanol, anneal, grind to obtain BaTiO3@CNTs nanomaterials.

[0019] Step 2: Add BaTiO3@CNTs nanomaterials to ultrapure water, add dispersant, and sonicate until uniformly dispersed to obtain BaTiO3@CNTs nanomaterial suspension; then add piperazine, followed by NaOH to neutralize the hydrochloric acid generated during interfacial polymerization, mix evenly to obtain piperazine suspension;

[0020] Trimethylbenzene chloride was dissolved in n-hexane to obtain a TMC solution;

[0021] Step 3: Filter the piperazine suspension onto the surface of the PES support layer, air dry, and obtain a PIP layer doped with BaTiO3@CNTs nanomaterials;

[0022] Step 4: Then fix it in the interfacial polymerization mold with the PIP layer surface of the BaTiO3@CNTs nanomaterial facing upwards, pour in TMC solution, carry out interfacial polymerization reaction for at least 30s, solidify, and rinse thoroughly with ultrapure water to obtain the composite nanofiltration membrane.

[0023] Further specifying, in step 1, the CNTs have a diameter of 5nm-20nm and a length of 10μm-30μm.

[0024] Further specifying, in step 1, the average particle size of the BaTiO3 nanoparticles is 100nm-200nm.

[0025] Further specifying, in step 1, the surfactant is hexadecyltrimethylammonium bromide (CTAB).

[0026] Further specifying, in step 1, annealing is performed at 600°C for 2 hours.

[0027] Further specifying, in step 1, the mixture is heated at 60℃-70℃ while being vigorously stirred until the ethanol evaporates.

[0028] Further specifying, in step 2, the dispersant is polyvinylpyrrolidone.

[0029] Further specifying, in step 2, the ratio of CNTs, surfactant and anhydrous ethanol is 0.1g:0.5g:100mL.

[0030] Further specifying, in step 2, the concentration of the nanomaterial suspension is 0.001wt%-0.00005wt%.

[0031] Further specifying, in step 2, the concentration range of the piperazine aqueous solution is 0.5wt%-1wt%.

[0032] Further specifying, in step 2, the concentration of the TMC solution is 0.1 wt.% - 0.4 wt.%.

[0033] Further specifying, in step 4, the product is cured at 60°C for 5 minutes.

[0034] Another object of the present invention is to provide a composite nanofiltration membrane prepared by the above method.

[0035] The BaTiO3@CNTs heterostructure obtained by this method involves loading highly crystalline BaTiO3 nanoparticles (100 nm in diameter) onto the CNT surface at high temperature, forming a "nanowire-particle" composite. This structure combines the axial nanochannels of CNTs with the electric field response characteristics of high-dielectric BaTiO3, thus overcoming the trade-off effect. In this invention, barium titanate and carbon nanotubes on the surface of polyamide do not enhance hydrophilicity, but the carbon nanotubes that penetrate the polyamide act as additional transporters of water molecules, thereby increasing permeability.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] This invention overcomes the "trade-off" effect by using the synergistic effect of the BaTiO3@CNTs heterostructure, with the parallel operation of water channels and dielectric repulsion mechanisms, to increase flux by more than 50% while maintaining a high rejection rate (MgSO4>97%) (compared to traditional PA membranes).

[0038] This invention enables precise ion-selective separation. The high dielectric constant of BaTiO3 (>2000) creates a strong electric field on the membrane surface, achieving selective separation of divalent ions (such as Mg). 2+ The dielectric repulsion of SO42- and CNTs allows monovalent ions (Na+, SO42-) to pass through their nanochannels. + (Cl-) partially permeates, suitable for brackish water softening and resource recycling.

[0039] This invention improves antifouling and stability. The hydrophobicity of CNTs and the negative charge of BaTiO3 synergistically inhibit the adsorption of organic matter, reducing the membrane fouling rate by 40%. The heterostructure is firmly embedded in the PA network through chemical bonding (reaction of CNTs-COOH with PA amide groups), preventing the nanomaterials from falling off.

[0040] This invention offers energy-saving and environmental benefits. Compared to traditional reverse osmosis processes, it reduces operating pressure by 30% and energy consumption by 25%, making it suitable for low-cost desalination of high-salt brackish water.

[0041] To further understand the features and technical content of this invention, please refer to the following detailed description and accompanying drawings. However, the accompanying drawings are for reference and illustration only and are not intended to limit the invention. Attached Figure Description

[0042] Figure 1 This is a SEM image of BaTiO3;

[0043] Figure 2 It is a SEM of CNTs;

[0044] Figure 3 This is a SEM image of the BaTiO3@CNTs nanomaterials prepared in Example 1;

[0045] Figure 4 The Fourier transform infrared spectrum of the BaTiO3@CNTs nanomaterial prepared in Example 1 is shown.

[0046] Figure 5 This is a dielectric constant-frequency diagram of BaTiO3, CNTs, and BaTiO3@CNTs;

[0047] Figure 6 This is a zeta potential diagram of BaTiO3, CNTs, and BaTiO3@CNTs;

[0048] Figure 7 It is a field emission scanning electron microscope for blank films;

[0049] Figure 8 Field emission scanning electron microscopy of the intermediate layer-loaded nanofiltration membrane obtained by the method in Example 2;

[0050] Figure 9 This is a field emission scanning electron microscope image of the composite nanofiltration membrane prepared in Example 1;

[0051] Figure 10 These are the Fourier transform infrared spectra of different membranes;

[0052] Figure 11 Zeta potential of solid surfaces of different films; Detailed Implementation

[0053] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, while not limiting the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0054] Example 1: The method for preparing the high dielectric property BaTiO3@CNTs composite nanofiltration membrane in this example is carried out according to the following steps:

[0055] Step 1: Preparation of nanomaterials

[0056] Using cetyltrimethylammonium bromide (CTAB, 0.2 g) as a surfactant, 0.1 g of CNTs and 0.5 g of CTAB were ultrasonically dispersed in 100 mL of anhydrous ethanol for 60 min to obtain a CNTs suspension. Then, 0.5 g of BaTiO3 (BT) nanoparticles were added to the suspension and dispersed at 70 °C with vigorous stirring until the ethanol evaporated (12 h). The mixture was then washed with isopropanol to remove CTAB and dried under vacuum at 60 °C for 10 h to remove isopropanol. Finally, the mixture was annealed in a tube furnace at 873 K (600 °C) for 2 h and thoroughly ground with agate slurry to obtain a typical CNTs / BT composite material (20% CNTs / BT).

[0057] Step 2: Preparation of the modified nanofiltration membrane. The active layer of the nanofiltration membrane is a polyamide separation film formed by the polymerization reaction of PIP and TMC on the surface of the support layer. The specific steps are as follows:

[0058] First, prepare the PIP solution for the doped nanomaterials: Add 0.002 g of 20 wt% BaTiO3@CNTs nanomaterials to 200 mL of ultrapure water, and sonicate for 60 min until uniformly dispersed to obtain a suspension of BaTiO3@CNTs nanomaterials; add 1 g of PIP to the suspension of BaTiO3@CNTs nanomaterials, and then add 1 g of NaOH to neutralize the hydrochloric acid generated during the interfacial polymerization process. Mix well and set aside to obtain a PIP suspension with a PIP concentration of 0.5 wt% and a nanomaterial concentration of 0.001 wt%.

[0059] Then prepare a 0.1 wt.% TMC solution: Dissolve 0.1 g of TMC in 100 g of n-hexane to obtain a TMC solution.

[0060] Step 3: Fix the PES support layer into the filtration mold, filter 10 ml of PIP suspension onto the membrane surface, and let it air dry.

[0061] Step 4: The membrane is then fixed in an interfacial polymerization mold. 10 ml of a 0.1 wt.% TMC solution is poured into the mold and reacted with the PIP on the support layer surface for 30 seconds to obtain the polyamide active layer. The resulting nanofiltration membrane is transferred to a 60°C oven for curing for 5 minutes for further polymerization. Then, it is thoroughly rinsed with ultrapure water, and finally, the prepared nanofiltration membrane is transferred to ultrapure water and stored at 4°C.

[0062] Testing of the nanofiltration membrane performance in this embodiment:

[0063] ① Test conditions: 2000ppm Na2SO4 solution, pressure 0.4MPa;

[0064] Flux: 91.32±5.2 LMH (57.1% higher than traditional PA membranes);

[0065] Retention rate: Traditional PA membrane 97.36%±0.4% → 97.65%±0.3%;

[0066] ② Test conditions: 2000 mg / L NaCl + MgSO4 mixed solution, pressure 0.4 MPa;

[0067] Flux: 87.3±4.7 LMH (52% higher than traditional PA membranes);

[0068] Retention rates: NaCl 68.2±7.6%, MgSO4 97.5±0.9% (dielectric repulsion-dominated divalent ion retention);

[0069] Example 2: The preparation method of the intermediate layer loading of the high dielectric property BaTiO3@CNTs composite nanofiltration membrane in this embodiment is carried out according to the following steps:

[0070] Step 1: Preparation of nanomaterials (same as Example 1)

[0071] Using cetyltrimethylammonium bromide (CTAB, 0.2 g) as a surfactant, 0.1 g of CNTs and 0.5 g of CTAB were ultrasonically dispersed in 100 mL of anhydrous ethanol for 60 min to obtain a CNTs suspension. Then, 0.5 g of BaTiO3 (BT) nanoparticles were added to the suspension and dispersed at 70 °C with vigorous stirring until the ethanol evaporated (12 h). The mixture was then washed with isopropanol to remove CTAB and dried under vacuum at 60 °C for 10 h to remove isopropanol. Finally, the mixture was annealed in a tube furnace at 873 K (600 °C) for 2 h and thoroughly ground with agate slurry to obtain a typical CNTs / BT composite material (20% CNTs / BT).

[0072] Step 2: Preparation of the modified nanofiltration membrane. First, nanomaterials are loaded onto the surface of the nanofiltration membrane. The active layer of the nanofiltration membrane is a polyamide separation film formed by the polymerization reaction of PIP and TMC on the surface of the support layer. The specific steps are as follows:

[0073] First, prepare a 0.001 wt% aqueous solution of nanomaterials: Add 0.002 g of 20 wt% BaTiO3@CNTs nanomaterials to 200 mL of ultrapure water, and sonicate for 60 min until uniformly dispersed to obtain a suspension of BaTiO3@CNTs nanomaterials. Next, prepare a 0.5 wt% PIP aqueous solution: Add 1 g of PIP to 200 mL of aqueous solution, followed by 1 g of NaOH to neutralize the hydrochloric acid generated during interfacial polymerization. Mix thoroughly and set aside to obtain a 0.5 wt% PIP aqueous solution.

[0074] Then prepare a 0.1 wt.% TMC solution: Dissolve 0.1 g of TMC in 100 g of n-hexane to obtain a TMC solution.

[0075] Step 3: Fix the PES support layer into the vacuum filtration mold, filter 10 ml of 0.001 wt% nanomaterial aqueous solution onto the membrane surface, then filter 10 ml of 0.5 wt% PIP aqueous solution and air dry.

[0076] Step 4: Fix the membrane in an interfacial polymerization mold. Pour 10 ml of a 0.1 wt.% TMC solution into the mold and react it with the PIP on the support layer surface for 30 seconds to obtain the polyamide active layer. Transfer the obtained nanofiltration membrane to a 60°C oven for curing for 5 minutes for further polymerization. Then rinse thoroughly with ultrapure water, and finally transfer the prepared nanofiltration membrane to ultrapure water for storage at 4°C.

[0077] Testing of the nanofiltration membrane performance in this embodiment:

[0078] ① Test conditions: 2000ppm Na2SO4 solution, pressure 0.4MPa;

[0079] Flux: 90.37±7.1 LMH (60.2% higher than conventional PA membranes);

[0080] Retention rate: Traditional PA membrane 97.36% ± 0.4% → 97.93% ± 0.2%;

[0081] ② Test conditions: 2000 mg / L NaCl + MgSO4 mixed solution, pressure 0.4 MPa;

[0082] Flux: 83.3±4.7 LMH (46% higher than traditional PA membranes);

[0083] Retention rates: NaCl 61.2±5.4%, MgSO4 98.3±1.4% (dielectric repulsion-dominated divalent ion retention);

[0084] SEM images of BaTiO3(BT) are as follows: Figure 1 As shown, Figure 1The BT nanoparticles exhibit a certain degree of aggregation. The original surface of the BT nanoparticles is smooth and spherical, with an average diameter of 100 nm. Figure 2 The original carbon nanotubes were randomly stacked. Each carbon nanotube had a length of 10-30 μm and a diameter of 5-20 nm. The prepared CNTs / BT nanocomposite exhibited a grape-like morphology. Figure 3 As a carrier for BT nanoparticles, carbon nanotubes are uniformly dispersed. BT NPs are well distributed and directly coupled to the surface of CNTs, with no significant change in morphology.

[0085] The Fourier transform infrared spectrum of the BaTiO3@CNTs nanomaterials prepared by the method in this embodiment is as follows: Figure 4 As shown in the FTIR image, the CO bond of CNTs is at position 1108 and the Ti-O bond of BT is at position 499. The synthesized nanomaterials have peak values ​​at these two positions, indicating that the nanomaterials were successfully synthesized.

[0086] from Figure 5 As can be seen, the dielectric constants of the three materials are basically in line with expectations. At 40Hz, the dielectric constant of carbon nanotubes is 202.5, the dielectric constant of high-dielectric barium titanate crystal is 4158.1, and the dielectric constant of the synthesized nanomaterial is 1812.8, indicating that the synthesized nanomaterial inherits the high dielectric properties of barium titanate crystal.

[0087] from Figure 6 It can be seen that the isoelectric point of the zeta potential of the synthesized nanomaterial is 3.80.

[0088] from Figure 7 It can be seen that the surface of the blank membrane has a typical nodular structure.

[0089] from Figure 8 It can be seen that the nanofiltration membrane with intermediate layer loading prepared by the method of Example 2 shows that most of the nanomaterials exist in the form of interspersed in polyamide, and a small part can be directly photographed on the outside of the membrane.

[0090] from Figure 9 It can be seen that many complete nanomaterials can be seen on the surface of the polyamide in the nanofiltration membrane prepared in Example 1, indicating that there are more nanomaterials on the membrane surface than in the intermediate layer.

[0091] from Figure 10 It can be seen that the Pristine membrane and the ALC membrane are at 1438 cm⁻¹ -1 1577cm -1 and 1675cm -1 The peak at 1438 cm⁻¹ confirms the successful formation of the polyamide active layer on the support layer. -1The peak at 1577 cm⁻¹ is attributed to the coupling of the OH stretching vibration of the carboxyl group produced by the hydrolysis of acyl chloride. -1 The peak at 1675 cm⁻¹ corresponds to the CN stretching vibration and NH bending of the amide group. -1 The peak value at 505 cm⁻¹ is related to the C=O stretching vibration of the NC=O group. -1 The peak at this point represents the Ti-O bond, demonstrating the successful doping of the nanomaterial.

[0092] from Figure 11 It is known that the PA membrane surface is mainly composed of amino (-NH2, positively charged) and carboxylic acid (-COOH, negatively charged) groups, and its IEP (isopotential potential) is determined by the equilibrium point of these two groups, generally pH = 4–5. The isopotential point of the membrane loaded with the intermediate layer is lower than that of the original membrane, and the isopotential point of the membrane loaded with the active layer is even lower than that of the original membrane. This may be because the nanomaterials in the active layer affect the anions on the membrane surface, and the nanomaterial interface induces the PA to form more carboxylic acid (-COOH) or hydroxyl (-OH) groups. Furthermore, barium titanate has an IEP of approximately pH = 4, directly affecting the membrane surface potential, while carbon nanotubes are more neutral. Most of the nanomaterials in the intermediate layer are located between the nonwoven fabric and the PA layer, with a small portion exposed on the surface in direct contact with the measured liquid. Therefore, its impact on zeta potential performance is less significant than that of the active layer.

[0093] The specific embodiments of the present invention have been described above. It should be noted that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing a high-dielectric-value BaTiO3@CNTs composite nanofiltration membrane, characterized in that, Includes the following steps: Step 1: Disperse carbon nanotubes (CNTs) and surfactants in anhydrous ethanol using ultrasonication, add BaTiO3 nanoparticles, heat and stir vigorously until the ethanol evaporates, wash with isopropanol to remove surfactant, vacuum dry to remove isopropanol, anneal, and grind to obtain BaTiO3@CNTs nanomaterials. The CNTs have a diameter of 5 nm-20 nm and a length of 10 μm-30 μm; the BaTiO3 nanoparticles have an average particle size of 100 nm-200 nm; the surfactant is cetyltrimethylammonium bromide (CTAB). Annealing at 600℃ for 2 hours; Step 2: Add BaTiO3@CNTs nanomaterials to ultrapure water, add dispersant, and sonicate until uniformly dispersed to obtain BaTiO3@CNTs nanomaterial suspension; Piperazine (PIP) was added to water, followed by the addition of NaOH to neutralize the hydrochloric acid produced during the interfacial polymerization process. The mixture was then thoroughly mixed to obtain a piperazine aqueous solution. TMC (trimethylammonium chloride) was dissolved in n-hexane to obtain a TMC solution. Step 3: Filter the BaTiO3@CNTs nanomaterial suspension onto the surface of the PES support layer, air dry it, load the BaTiO3@CNTs nanomaterial onto the surface of the PES support layer, then filter the PIP aqueous solution and air dry it to obtain the PIP layer. Step 4: Then fix it in the interfacial polymerization mold with the PIP layer surface facing upward, pour in the TMC solution, carry out the interfacial polymerization reaction for at least 30 seconds, solidify, and rinse thoroughly with ultrapure water to obtain the composite nanofiltration membrane.

2. A method for preparing a high-dielectric-value BaTiO3@CNTs composite nanofiltration membrane, characterized in that, Includes the following steps: Step 1: Disperse CNTs and surfactants ultrasonically in anhydrous ethanol, add BaTiO3 nanoparticles, heat and stir vigorously until ethanol evaporates, wash with isopropanol to remove surfactant, vacuum dry to remove isopropanol, anneal, grind to obtain BaTiO3@CNTs nanomaterials. The CNTs have a diameter of 5 nm-20 nm and a length of 10 μm-30 μm; the BaTiO3 nanoparticles have an average particle size of 100 nm-200 nm; the surfactant is cetyltrimethylammonium bromide (CTAB). Annealing at 600℃ for 2 hours; Step 2: Add BaTiO3@CNTs nanomaterials to ultrapure water, add dispersant, and sonicate until uniformly dispersed to obtain BaTiO3@CNTs nanomaterial suspension; then add piperazine, followed by NaOH to neutralize the hydrochloric acid generated during interfacial polymerization, mix evenly to obtain piperazine suspension; Trimethylbenzene chloride was dissolved in n-hexane to obtain a TMC solution; Step 3: Filter the piperazine suspension onto the surface of the PES support layer, air dry, and obtain a PIP layer doped with BaTiO3@CNTs nanomaterials; Step 4: Then fix it in the interfacial polymerization mold with the PIP layer surface of the BaTiO3@CNTs nanomaterial facing upwards, pour in TMC solution, carry out interfacial polymerization reaction for at least 30s, solidify, and rinse thoroughly with ultrapure water to obtain the composite nanofiltration membrane.

3. The preparation method according to claim 1 or 2, characterized in that, Heat at 60℃-70℃ while stirring vigorously until the ethanol evaporates.

4. The preparation method according to claim 1 or 2, characterized in that, The dispersant is polyvinylpyrrolidone.

5. The preparation method according to claim 1 or 2, characterized in that, In step 1, the ratio of CNTs, surfactant and anhydrous ethanol is 0.1g:0.5g:100mL.

6. The preparation method according to claim 1 or 2, characterized in that, In step 2, the concentration of BaTiO3@CNTs nanomaterials is 0.001wt%-0.00005wt%; the concentration of piperazine is 0.5wt%-1wt%; and the concentration of TMC solution is 0.1wt.%-0.4wt.%.

7. The preparation method according to claim 1 or 2, characterized in that, Cured at 60℃.

8. A composite nanofiltration membrane prepared by the preparation method according to any one of claims 1-7.

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