Recyclable carbon nanotube composite membrane and application thereof in organic matters in industrial wastewater

Abstract

The invention relates to the technical field of industrial wastewater treatment, and discloses a recoverable carbon nanotube composite membrane and an application thereof in industrial wastewater organic matters, the carbon nanotube composite membrane comprises the following components by weight: a modified host polymer matrix; functionalizing the carbon nano tube; a multifunctional sacrificial layer polymer; p-toluenesulfonic acid; the modified main body polymer matrix is a secondary amino functionalized polyethersulfone matrix, the functionalized carbon nanotube is an aldehyde group functionalized carbon nanotube, the multifunctional sacrificial layer polymer is a copolymer containing a primary amino group, an epoxy group and a spiropyrane functional group, and the solvent is N, N-dimethylformamide, N, N-dimethylformamide, N, N-dimethylformamide, N, N-dimethylformamide, N, N-dimethylformamide, N, N-dimethylformamide, N, N-dimethylformamide, N, N-dimethylformamide, N, N-dimethylformamide and N, N-dimethylformamide. The solvent is a mixed solvent of N, N-dimethylformamide and N-methyl pyrrolidone, and the volume ratio of the N, N-dimethylformamide to the N-methyl pyrrolidone is (1-3): 1. By constructing a dual chemical bonding network, stable fixation of functional components and acid response recovery of a main matrix are realized.

Description

Technical Field

[0001] This invention relates to the field of industrial wastewater treatment technology, specifically to recyclable carbon nanotube composite membranes and their application in organic matter in industrial wastewater. Background Technology

[0002] Industrial wastewater contains highly toxic and persistent pollutants such as organic dyes and phenols, posing a threat to the environment and ecosystem. Membrane separation and adsorption technologies are effective methods for treating this type of wastewater. Carbon nanotubes, due to their high specific surface area and adsorption capacity, have attracted attention in the development of composite adsorption membranes.

[0003] Existing carbon nanotube composite membrane preparation technologies typically employ physical blending or surface deposition methods. Physical blending involves using carbon nanotubes (or surface-modified carbon nanotubes) as fillers, dissolving them in a solvent with a host polymer such as polyethersulfone or polyvinylidene fluoride, and preparing the blend membrane through a solvent-free phase inversion process. Surface deposition involves fixing functionalized carbon nanotube layers onto an existing porous base membrane through coating, layer-by-layer self-assembly, or chemical grafting.

[0004] While existing technologies utilize the adsorption properties of carbon nanotubes to some extent, several shortcomings remain. For physically blended membranes, the bonding between carbon nanotubes and the host polymer relies primarily on van der Waals forces or hydrogen bonds. These non-covalent forces are relatively weak, leading to the easy detachment and leaching of carbon nanotubes from the membrane matrix during long-term water rinsing or backwashing, resulting in functional failure and secondary pollution. For surface-deposited or grafted membranes, the preparation process is relatively complex, and the bonding force between the functional layer and the substrate may still fail under harsh application conditions. Furthermore, regardless of the preparation method, carbon nanotubes tend to aggregate in the polymer matrix, reducing the exposure of effective adsorption sites. Simultaneously, traditional host polymers (such as PES) and carbon nanotubes are often hydrophobic, causing the membrane surface to easily adsorb organic matter, leading to irreversible pollution and reduced throughput and lifespan. More critically, existing composite membranes are mostly permanent chemical cross-linked or physically entangled structures. Once the adsorption sites are saturated, it is difficult to achieve material disintegration and the recovery of high-value components (such as the host matrix). Waste membranes are typically disposed of by incineration or landfill, which does not meet the requirements for material recycling and imposes an environmental burden. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a recyclable carbon nanotube composite membrane and its application in organic matter in industrial wastewater, solving the problems of easy loss of functional components, irreversible pollution, and difficulty in recycling and reusing the main matrix after adsorption saturation in existing carbon nanotube composite membranes.

[0006] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a casting composition for preparing a recyclable carbon nanotube composite membrane, the carbon nanotube composite membrane comprising the following components in parts by weight: Modified main polymer matrix: 100 parts; Functionalized carbon nanotubes: 0.5-5 parts; Multifunctional sacrificial layer polymer: 10-30 parts; p-Toluenesulfonic acid: 0.005-0.02 parts; Solvent: 400-800 parts.

[0007] By employing the above technical solution, a dual chemically bonded network is constructed in situ during the preparation process of this composition. The mechanism is as follows: Stable anchor formation: The multifunctional sacrificial layer polymer (containing epoxy groups) in the composition reacts with the modified host polymer matrix (containing secondary amine groups) in a solvent to form stable CN covalent bonds through an epoxy-amine ring-opening reaction. This structure anchors the sacrificial layer polymer to the host matrix, solving the problem of dissolution and loss of functional components in subsequent applications.

[0008] Dynamic network crosslinking: Under the acid catalysis of p-toluenesulfonic acid, functionalized carbon nanotubes (containing aldehyde groups) and multifunctional sacrificial layer polymers (containing primary amine groups) undergo Schiff base condensation to form reversible dynamic imine bonds (C=N). This reaction crosslinks the carbon nanotubes and sacrificial layer polymers to construct a three-dimensional functional network.

[0009] Functional integration: The formed three-dimensional network (carbon nanotubes and amine groups) provides a high density of adsorption sites for capturing organic pollutants; the hydrophilic segments and spiropyran units in the sacrificial layer polymer endow the material with anti-pollution and pollutant sensing functions, respectively.

[0010] Acid-responsive recovery mechanism: Imine bonds (C=N) can undergo hydrolytic breakage under acidic conditions (e.g., pH 3.0), leading to the disintegration of the functional network; while the CN anchor points formed in step 1) remain stable under acidic conditions. This chemical difference allows the functional components (carbon nanotubes, sacrificial layer polymers) to be separated from the insoluble host matrix, and the host matrix (e.g., polyethersulfone) can be recovered and regenerated through physical filtration.

[0011] Preferably, the modified host polymer matrix is ​​a secondary amine-functionalized polyethersulfone matrix.

[0012] Preferably, the functionalized carbon nanotubes are aldehyde-functionalized carbon nanotubes.

[0013] Preferably, the multifunctional sacrificial layer polymer is a copolymer containing primary amine groups, epoxy groups and spiropyran functional groups.

[0014] Preferably, the solvent is a mixed solvent of N,N-dimethylformamide and N-methylpyrrolidone, and the volume ratio of N,N-dimethylformamide to N-methylpyrrolidone is 1:1 to 3:1.

[0015] Secondly, the present invention provides a method for preparing a recyclable carbon nanotube composite membrane, comprising the following steps: S1. The modified main polymer matrix, functionalized carbon nanotubes, multifunctional sacrificial layer polymer and p-toluenesulfonic acid are dissolved in a solvent and stirred to form a casting solution. S2. Let the casting solution stand for 1-2 hours, and then degas it for 1-3 hours under a vacuum of -0.08 to -0.09 MPa. S3. The degassed casting solution is scraped into a film, exposed to air, and then immersed in a coagulation bath to undergo phase transformation to obtain a molded film. S4. The molded film is soaked, heat-treated and dried.

[0016] By employing the above technical solution, in step S1, prior to phase inversion and membrane formation, the epoxy-amine ring-opening reaction (stabilizing anchor points) and aldehyde-amine condensation reaction (dynamic network) in the system are catalyzed by p-toluenesulfonic acid, ensuring the uniform chemical bonding of functional components in the matrix. The degassing treatment in step S2 guarantees the uniformity of the membrane structure. The phase inversion process in step S3 is used to construct a porous structure. The heat treatment (60-90℃) in step S4 helps to further crosslink and solidify unreacted functional groups, improves the stability of the imine bond network, and optimizes the final performance of the membrane.

[0017] Preferably, step S1 specifically includes the following steps: The modified main polymer matrix is ​​added to the solvent and stirred at 40-60°C for 12-24 hours until dissolved; After cooling to room temperature, the functionalized carbon nanotubes and the multifunctional sacrificial layer polymer are added sequentially, and stirring is continued for 2-4 hours. Finally, add the p-toluenesulfonic acid and stir the mixture at 25-40°C for 6-12 hours.

[0018] Preferably, step S3 specifically includes the following steps: In an environment with a relative humidity of 50-70%, the casting solution is coated onto a polyester nonwoven fabric or glass plate to form a film, with the coating thickness controlled at 200-400μm. After being exposed to air for 10-30 seconds, immerse it in a coagulation bath at a temperature of 20-30°C for 10-30 minutes. The coagulation bath is a mixed solution of deionized water and ethanol, and the volume ratio of deionized water to ethanol is 1:1 to 3:1.

[0019] Preferably, step S4 specifically includes the following steps: The molded membrane was soaked in deionized water for 24 hours, with the water changed every 4-8 hours during the process. After cleaning, place the wet film in an oven at 60-90℃ for 2-6 hours for heat treatment, and finally dry it in a ventilated environment at 20-30℃ for 12-24 hours.

[0020] Thirdly, the present invention provides an application of the recyclable carbon nanotube composite membrane prepared as described above in the organic matter of industrial wastewater.

[0021] By adopting the above technical solution, the composite membrane removes organic pollutants by utilizing the high-density adsorption sites (carbon nanotubes and amine groups) of its functional network. At the same time, its hydrophilic surface has anti-pollution properties. After adsorption saturation, the main matrix can be recycled and regenerated through acid treatment, which solves the application limitations of traditional adsorption materials.

[0022] This invention provides a recyclable carbon nanotube composite membrane and its application in the treatment of organic matter in industrial wastewater. It offers the following advantages: 1. This invention constructs a dual chemical bonding network in situ using an epoxy-amine ring-opening reaction and a Schiff base condensation reaction in a casting solution. The stable CN covalent bonds formed by the epoxy-amine reaction anchor the functional layer to the host matrix, while the dynamic imine bonds (C=N) formed by the Schiff base reaction crosslink and fix the functionalized carbon nanotubes, solving the problem of easy loss of functional components during application and ensuring the structural stability of the composite membrane.

[0023] 2. This invention utilizes the chemical difference between the imine bond (C=N) network, which hydrolyzes and breaks under acidic conditions, and the CN anchor points, which remain stable. This design allows the composite membrane to selectively disintegrate its functional network through acid treatment after adsorption saturation, while the insoluble main polymer matrix can be recovered through physical filtration, thus realizing the recycling of the substrate material and reducing material waste costs and environmental pollution.

[0024] 3. This invention uses an in-situ reaction in step S1 to uniformly composite functionalized carbon nanotubes with high specific surface area and multifunctional sacrificial polymers with hydrophilic segments; the resulting membrane material has both high density of adsorption sites (from carbon nanotubes and amine groups) and antifouling properties, thus improving its adsorption efficiency and operational stability when treating organic wastewater. Attached Figure Description

[0025] Figure 1 This is a schematic diagram showing the water storage flux results of each embodiment 1-5 and comparative examples 1-8 of the present invention; Figure 2 This is a schematic diagram showing the BSA rejection rate results of each of the embodiments 1-5 and comparative examples 1-8 of the present invention; Figure 3 This is a schematic diagram showing the flux attenuation rate results of various embodiments 1-5 and comparative examples 1-8 of the present invention; Figure 4 This is a schematic diagram showing the flux recovery rate results of various embodiments 1-5 and comparative examples 1-8 of the present invention. Detailed Implementation

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Please see the appendix Figure 1 -Appendix Figure 4 The present invention provides recyclable carbon nanotube composite membranes and their application in organic matter in industrial wastewater, including...

[0028] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0029] Multi-walled carbon nanotubes are carbonaceous materials prepared by chemical vapor deposition with a purity better than 95%, an outer diameter ranging from 5 to 20 nm, and a length ranging from 1 to 50 μm.

[0030] Polyethersulfone (PES), CAS No.: 25667-42-9, has a chemical structure consisting of ether bonds and sulfone groups connecting aromatic rings. The weight-average molecular weight of the polyethersulfone used in this invention ranges from 50,000 to 150,000 g / mol.

[0031] Spiropyran derivatives are organic photochromic compounds containing a spiropyran structure and polymerizable functional groups. Their specific chemical structures and preparation methods are detailed in the preparation examples section of this invention.

[0032] Diethylenetriamine (DETA), CAS No.: 111-40-0, is used as a reagent to introduce secondary amine groups onto a polymer matrix.

[0033] 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC·HCl), CAS No.: 25952-53-8, is used as an activator of the carboxyl group.

[0034] N-hydroxysuccinimide (NHS), CAS No.: 6066-82-6, is used as an auxiliary agent for carboxyl activation reactions.

[0035] N-tert-Butoxycarbonylethylenediamine, CAS No.: 57260-73-8, is an amination reagent protected on one side by a tert-butoxycarbonyl group.

[0036] Glutaraldehyde, CAS No.: 111-30-8, is used as a crosslinking agent to introduce aldehyde groups.

[0037] Acrylamide (AM), CAS No.: 79-06-1, is used as the main monomer for synthesizing multifunctional sacrificial layer polymers.

[0038] Epoxy methacrylate (GMA), CAS No.: 106-91-2, is a monomer containing both epoxy groups and polymerizable methacrylate groups.

[0039] p-Toluenesulfonic acid (PTSA), CAS No.: 6192-52-5 (monohydrate), is used as a catalyst for dynamic covalent bond formation.

[0040] Example 1: This embodiment provides a recyclable carbon nanotube composite membrane comprising the following components in parts by weight: modified host polymer matrix (prepared using Preparation Example 3.3): 100 parts; functionalized carbon nanotubes (prepared using Preparation Example 1.3): 5 parts; multifunctional sacrificial layer polymer (prepared using Preparation Example 2.3): 30 parts; p-toluenesulfonic acid: 0.02 parts; N,N-dimethylformamide / N-methylpyrrolidone mixed solvent (volume ratio 1:1): 800 parts.

[0041] This embodiment also provides a method for preparing a recyclable carbon nanotube composite membrane, including the following steps: S1. Preparation of casting solution: 100 parts of modified main polymer matrix were added to 800 parts of N,N-dimethylformamide / N-methylpyrrolidone mixed solvent and stirred at 60°C for 24 hours until completely dissolved; after cooling to room temperature, 5 parts of functionalized carbon nanotubes and 30 parts of multifunctional sacrificial layer polymer were added in sequence and stirred for another 4 hours; finally, 0.02 parts of p-toluenesulfonic acid were added and stirred at 40°C for 12 hours to form a uniform casting solution. S2, Degassing treatment: The casting solution obtained in step S1 was allowed to stand for 2 hours, and then degassed for 3 hours under a vacuum of -0.09MPa. S3. Phase inversion film formation: In an environment with a relative humidity of 70%, the degassed casting solution is coated onto a clean polyester nonwoven fabric using a doctor blade to form a film with a coating thickness of 400 μm. After being exposed to air for 30 seconds, it is immersed in a deionized water / ethanol (volume ratio 1:1) coagulation bath at a temperature of 30°C for 30 minutes. S4. Post-treatment: Remove the molded film from the coagulation bath and soak it in deionized water for 24 hours, changing the water every 4 hours during this period; place the cleaned wet film in a 90℃ oven for 6 hours for heat treatment, and finally let it air dry in a 30℃ ventilated environment for 24 hours to obtain the finished product.

[0042] Example 2: This embodiment provides a recyclable carbon nanotube composite membrane comprising the following components in parts by weight: modified host polymer matrix (prepared using Preparation Example 3.2): 100 parts; functionalized carbon nanotubes (prepared using Preparation Example 1.2): 2.5 parts; multifunctional sacrificial layer polymer (prepared using Preparation Example 2.2): 20 parts; p-toluenesulfonic acid: 0.01 parts; N,N-dimethylformamide / N-methylpyrrolidone mixed solvent (volume ratio 2:1): 600 parts.

[0043] This embodiment also provides a method for preparing a recyclable carbon nanotube composite membrane, including the following steps: S1. Preparation of casting solution: 100 parts of modified main polymer matrix were added to 600 parts of N,N-dimethylformamide / N-methylpyrrolidone mixed solvent and stirred at 50°C for 18 hours until completely dissolved; after cooling to room temperature, 2.5 parts of functionalized carbon nanotubes and 20 parts of multifunctional sacrificial layer polymer were added sequentially and stirred for 3 hours; finally, 0.01 parts of p-toluenesulfonic acid were added and stirred at 32°C for 9 hours to form a uniform casting solution; S2, Degassing treatment: The casting solution obtained in step S1 was allowed to stand for 1.5 hours, and then degassed for 2 hours under a vacuum of -0.085MPa. S3, Phase transformation to film formation: In an environment with a relative humidity of 60%, the degassed casting solution is coated onto a clean glass plate using a scraper to form a film with a coating thickness of 300 μm; after being exposed to air for 20 seconds, it is immersed in a deionized water coagulation bath at a temperature of 25°C for 20 minutes. S4. Post-treatment: Remove the molded film from the coagulation bath and soak it in deionized water for 24 hours, changing the water every 6 hours during this period; place the cleaned wet film in a 75℃ oven for 4 hours for heat treatment, and finally let it air dry in a 25℃ ventilated environment for 24 hours to obtain the finished product.

[0044] Example 3: This embodiment provides a recyclable carbon nanotube composite membrane comprising the following components in parts by weight: modified host polymer matrix (prepared using Preparation Example 3.1): 100 parts; functionalized carbon nanotubes (prepared using Preparation Example 1.1): 0.5 parts; multifunctional sacrificial layer polymer (prepared using Preparation Example 2.1): 10 parts; p-toluenesulfonic acid: 0.005 parts; N,N-dimethylformamide / N-methylpyrrolidone mixed solvent (volume ratio 3:1): 400 parts.

[0045] This embodiment also provides a method for preparing a recyclable carbon nanotube composite membrane, including the following steps: S1. Preparation of casting solution: 100 parts of modified main polymer matrix were added to 400 parts of N,N-dimethylformamide / N-methylpyrrolidone mixed solvent and stirred at 40°C for 12 hours until completely dissolved; after cooling to room temperature, 0.5 parts of functionalized carbon nanotubes and 10 parts of multifunctional sacrificial layer polymer were added sequentially and stirred for 2 hours; finally, 0.005 parts of p-toluenesulfonic acid were added and stirred at 25°C for 6 hours to form a uniform casting solution; S2, Degassing treatment: The casting solution obtained in step S1 is allowed to stand for 1 hour, and then degassed under a vacuum of -0.08MPa for 1 hour. S3. Phase transformation film formation: In an environment with a relative humidity of 50%, the degassed casting solution is coated onto a clean glass plate using a scraper to form a film with a coating thickness of 200 μm. After being exposed to air for 10 seconds, it is immersed in a deionized water / ethanol (volume ratio 3:1) coagulation bath at a temperature of 20°C for 10 minutes. S4. Post-treatment: Remove the molded film from the coagulation bath and soak it in deionized water for 24 hours, changing the water every 8 hours during this period; place the cleaned wet film in a 60℃ oven for 2 hours for heat treatment, and finally let it air dry in a 20℃ ventilated environment for 12 hours to obtain the finished product.

[0046] Example 4: This embodiment provides a recyclable carbon nanotube composite membrane comprising the following components in parts by weight: modified host polymer matrix (prepared using Preparation Example 3.2): 100 parts; functionalized carbon nanotubes (prepared using Preparation Example 1.3): 3 parts; multifunctional sacrificial layer polymer (prepared using Preparation Example 2.1): 15 parts; p-toluenesulfonic acid: 0.015 parts; N-methylpyrrolidone: 500 parts.

[0047] This embodiment also provides a method for preparing a recyclable carbon nanotube composite membrane, including the following steps: S1. Preparation of casting solution: 100 parts of modified main polymer matrix were added to 500 parts of N-methylpyrrolidone and stirred at 55°C for 20 hours until completely dissolved; after cooling to room temperature, 3 parts of functionalized carbon nanotubes and 15 parts of multifunctional sacrificial layer polymer were added in sequence and stirred for another 3 hours; finally, 0.015 parts of p-toluenesulfonic acid were added and stirred at 35°C for 10 hours to form a uniform casting solution. S2, Degassing treatment: The casting solution obtained in step S1 is allowed to stand for 1.5 hours, and then degassed under a vacuum of -0.08MPa for 2.5 hours. S3, Phase transformation to film formation: In an environment with a relative humidity of 55%, the degassed casting solution is coated onto a clean glass plate using a scraper to form a film with a coating thickness controlled at 250 μm; after being exposed to air for 15 seconds, it is immersed in a deionized water coagulation bath at a temperature of 25°C for 15 minutes. S4. Post-treatment: Remove the molded film from the coagulation bath and soak it in deionized water for 24 hours, changing the water every 6 hours during this period; place the cleaned wet film in an 80℃ oven for heat treatment for 3 hours, and finally let it air dry in a 25℃ ventilated environment for 24 hours to obtain the finished product.

[0048] Example 5: This embodiment provides a recyclable carbon nanotube composite membrane comprising the following components in parts by weight: modified host polymer matrix (prepared using Preparation Example 3.1): 100 parts; functionalized carbon nanotubes (prepared using Preparation Example 1.1): 1 part; multifunctional sacrificial layer polymer (prepared using Preparation Example 2.3): 25 parts; acetic acid: 0.01 parts; N,N-dimethylformamide: 700 parts.

[0049] This embodiment also provides a method for preparing a recyclable carbon nanotube composite membrane, including the following steps: S1. Preparation of casting solution: 100 parts of modified main polymer matrix were added to 700 parts of N,N-dimethylformamide and stirred at 45°C for 15 hours until completely dissolved; after cooling to room temperature, 1 part of functionalized carbon nanotubes and 25 parts of multifunctional sacrificial layer polymer were added in sequence, and stirring was continued for 2.5 hours; finally, 0.01 parts of acetic acid were added and stirred at 28°C for 8 hours to form a uniform casting solution. S2, Degassing treatment: The casting solution obtained in step S1 was allowed to stand for 2 hours, and then degassed for 1.5 hours under a vacuum of -0.09MPa. S3, Phase transformation film formation: In an environment with a relative humidity of 65%, the degassed casting solution is coated onto a clean polyester nonwoven fabric using a doctor blade to form a film with a coating thickness of 350μm; after being exposed to air for 25 seconds, it is immersed in a deionized water coagulation bath at a temperature of 20℃ for 25 minutes. S4. Post-treatment: Remove the molded film from the coagulation bath and soak it in deionized water for 24 hours, changing the water every 4 hours during this period; place the cleaned wet film in a 70℃ oven for heat treatment for 5 hours, and finally let it air dry in a 20℃ ventilated environment for 24 hours to obtain the finished product.

[0050] Comparative Example 1: Compared with Example 2, the difference is that no functionalized carbon nanotubes and multifunctional sacrificial layer polymers are added. Only unmodified polyethersulfone (PES, weight average molecular weight of about 80,000 g / mol) is used as the main polymer matrix. The casting solution formulation is 100 parts of polyethersulfone and 600 parts of N,N-dimethylformamide / N-methylpyrrolidone mixed solvent (volume ratio 2:1). All other aspects are the same.

[0051] Comparative Example 2: Compared to Example 2, the difference is that unmodified polyethersulfone (PES, weight average molecular weight of about 80,000 g / mol) was used as the main polymer matrix, and no multifunctional sacrificial layer polymer was added; otherwise, they are the same.

[0052] Comparative Example 3: Compared to Example 2, the difference is that spiropyran acrylate monomers are not introduced during the synthesis of the multifunctional sacrificial layer polymer (i.e., a sacrificial layer polymer containing only primary amine and epoxy groups is used), while all other aspects are the same.

[0053] Comparative Example 4: Compared with Example 2, the difference is that unfunctionalized original multi-walled carbon nanotubes (purity greater than 95%, outer diameter range 5-20 nm, length range 1-50 μm) are used instead of functionalized carbon nanotubes, and no multifunctional sacrificial layer polymer is added; otherwise, they are the same.

[0054] Comparative Example 5: The difference from Example 2 is that p-toluenesulfonic acid catalyst is not added; otherwise, they are the same.

[0055] Comparative Example 6: Compared to Example 2, the difference is that the multifunctional sacrificial layer polymer in the casting solution is replaced with a polyacrylamide homopolymer (weight average molecular weight of about 50,000 g / mol) without primary amine and epoxy groups, while the rest are the same.

[0056] Comparative Example 7: Compared with Example 2, the difference is that the functionalized carbon nanotubes (Preparation Example 1.2) in the casting solution are replaced by an equal amount of carboxylated but not modified with primary amino and aldehyde carbon nanotubes (MWCNTs-COOH), otherwise the same.

[0057] Comparative Example 8: Compared with Example 2, the difference is that the heat treatment step in preparation step S4 is removed, that is, after the membrane is washed with deionized water, it is directly air-dried in a ventilated environment at 25°C for 24 hours, and the rest are the same.

[0058] Test Example 1: Experimental steps: The composite films prepared in Examples 1-5 and Comparative Examples 1-8 were selected and cut into square samples with a size of 20mm × 20mm. All samples were dried in a vacuum oven at 40℃ for 24 hours before testing to eliminate the interference of residual solvent and moisture on infrared spectroscopy testing.

[0059] Initial state test: The dried membrane sample was immersed in a phosphate buffer solution (0.1M) at pH 8.0 and treated in a constant temperature shaker at 25°C for 2 hours to ensure that the imine bonds in the membrane were fully formed. The sample was then removed, and residual salts were quickly rinsed off with deionized water. The surface moisture was immediately blotted dry with filter paper and then placed in a vacuum desiccator to dry at room temperature for 4 hours. The infrared spectrum of the sample was acquired using a Fourier transform infrared spectrometer (FTIR) in total reflectance mode (ATR) and recorded at 1655 cm⁻¹. -1 The absorbance value of the characteristic peak is denoted as . .

[0060] Acid-treated dissociation test: After the test, the same membrane sample was immersed in a hydrochloric acid aqueous solution with a pH of 3.0 and magnetically stirred at 40°C for 1 hour to initiate acid-catalyzed hydrolysis of imine bonds. After treatment, the sample was removed, rinsed with plenty of deionized water until the washing solution was neutral, dried under the same conditions as above, and infrared spectra were collected and recorded at 1655 cm⁻¹. -1 The absorbance value of the characteristic peak is denoted as . .

[0061] Alkali treatment regeneration test: After the test, the membrane sample was re-immersed in a phosphate buffer solution with a pH of 8.0 and treated at 25°C for 2 hours for in-situ regeneration. After removal, it was rinsed and dried, and infrared spectra were collected and recorded at 1655 cm⁻¹. -1 The absorbance value of the characteristic peak is denoted as . .

[0062] The regeneration recovery rate of dynamic covalent bonds is calculated using the following formula: .

[0063] The test results are shown in Table 1.

[0064] Table 1: Infrared spectral data of reversible dynamic covalent bonds in composite films Sample number <![CDATA[Initial absorbance (1655 cm -1 )]]> <![CDATA[Absorbance after acid treatment (1655 cm -1 ).]]> <![CDATA[Absorbance after regeneration (1655 cm -1 ).]]> Recovery rate (%) Example 1 0.942 0.115 0.897 95.2 Example 2 0.785 0.094 0.731 93.1 Example 3 0.456 0.062 0.421 92.3 Example 4 0.812 0.103 0.758 93.3 Example 5 0.764 0.088 0.715 93.6 Comparative Example 1 0.015 0.013 0.019 126.7 Comparative Example 2 0.021 0.018 0.017 80.9 Comparative Example 3 0.112 0.072 0.083 74.1 Comparative Example 4 0.018 0.016 0.015 83.3 Comparative Example 5 0.148 0.051 0.061 41.2 Comparative Example 6 0.035 0.032 0.041 117.1 Comparative Example 7 0.028 0.025 0.024 85.7 Comparative Example 8 0.022 0.021 0.029 131.8 From Table 1, we can obtain: Examples 1-5 at 1655cm -1 All of them showed obvious characteristic absorption peaks ( >0.45), this peak corresponds to the stretching vibration of the carbon-nitrogen double bond (C=N), indicating that the aldehyde group on the surface of the functionalized carbon nanotube successfully underwent a Schiff base reaction with the primary amine group on the polymer chain of the multifunctional sacrificial layer, forming an effective imine bond crosslinking network.

[0065] In an acidic environment at pH 3.0, the intensity of the C=N characteristic peak in the sample samples decreased significantly (e.g., from 0.942 to 0.115 in Example 1), demonstrating that the acidic conditions effectively induced the hydrolytic breakage of the imine bonds, causing the crosslinked network to disintegrate. Subsequently, in an acidic environment at pH 8.0, the intensity of this characteristic peak recovered significantly, with the recovery rate for Examples 1-5 remaining above 92%. This data indicates that the aldehyde and amine components in the system did not experience significant loss after acidic dissociation but remained stably anchored in the membrane matrix, possessing the ability to react again to form covalent bonds. This anchoring ensures the spatial confinement of the dynamic reaction sites (aldehyde and primary amine groups), preventing their diffusion and loss in the dissociated state.

[0066] The comparative results further support the above mechanism. The initial absorbance of Comparative Examples 1, 2, 4, 6, 7, and 8... All values ​​were below 0.04, which is within the instrument's detection baseline (noise) level, confirming that imine bonds failed to form in these samples. The calculated recovery rates (e.g., 80.9%, 126.7%) fluctuated wildly and irregularly, which is typical of random fluctuations in baseline noise and has no significance regarding chemical reversibility.

[0067] Initial of Comparative Example 5 (0.148) is significantly lower than that of the example (e.g., 0.785), and the recovery rate is only 41.2%, indicating that the formation efficiency of imine bonds is low and the reversibility is poor in the absence of a catalyst. The initial value of Comparative Example 3... The value of (0.112) was also significantly low, with a recovery rate of only 74.1%, indicating that this component has a synergistic effect on the effective formation of dynamic networks.

[0068] Test Example 2: Experimental steps: The composite membranes prepared in Examples 1-5 and Comparative Examples 1-8 were selected and cut into 20mm × 20mm samples. The samples were dried in an 80℃ vacuum oven for 24 hours until constant weight was achieved. The samples were then precisely weighed using an analytical balance, and the initial dry weight was recorded. .

[0069] The dried sample pieces were immersed in sealed screw-top bottles containing 40 mL of N,N-dimethylformamide (DMF). The bottles were then placed in a 50°C constant-temperature shaking water bath and shaken continuously at 100 rpm for 48 hours to simulate long-term stability under strong solvent conditions.

[0070] After shaking, the membrane sample was removed and rinsed with a small amount of fresh DMF to remove residual solvent. The sample was then placed in an 80°C vacuum oven for 24 hours to dry to constant weight. The final dry weight was measured using an analytical balance. .

[0071] The formula for calculating the membrane dissolution rate is: Dissolution rate (%) = .

[0072] The test results are shown in Table 2.

[0073] Table 2: Data on the solubility loss of the composite membrane in DMF Sample number Initial dry weight (g) Final dry weight (g) Dissolution rate (%) Example 1 0.4522 0.4484 0.84 Example 2 0.4315 0.4276 0.90 Example 3 0.4603 0.4568 0.76 Example 4 0.4489 0.4452 0.82 Example 5 0.4531 0.4488 0.95 Comparative Example 1 0.4158 0.4141 0.41 Comparative Example 2 0.4381 0.3838 12.40 Comparative Example 3 0.4505 0.4289 4.80 Comparative Example 4 0.4426 0.3751 15.25 Comparative Example 5 0.4372 0.4151 5.06 Comparative Example 6 0.4297 0.3928 8.59 Comparative Example 7 0.4401 0.3994 9.25 Comparative Example 8 0.4334 0.4292 0.97 From Table 2, we can obtain: After immersion in DMF for 48 hours, the membrane samples of Examples 1-5 showed a solubility loss rate of less than 1.0% (e.g., 0.90% in Example 2). This result indicates that the functional components (carbon nanotubes and sacrificial polymer layer) are immobilized in the membrane structure and do not undergo significant detachment in strong solvents.

[0074] During the casting solution preparation stage, an irreversible epoxy-amine ring-opening reaction occurred between the modified host polymer matrix (PES-secondary amine group) and the multifunctional sacrificial layer polymer (containing epoxy groups). This reaction formed stable CN covalent bonds between the two, constituting a stable covalent anchor point. This anchor point binds the sacrificial layer polymer chain segments to the PES matrix, while the functionalized carbon nanotubes are also indirectly fixed through dynamic cross-linking with the sacrificial layer polymer, thereby ensuring the structural stability of the entire functional system.

[0075] Comparative Example 4 supported the above analysis, exhibiting the highest solubility loss rate (15.25%), indicating that the physically adsorbed components could not maintain stability in DMF. Comparative Examples 2, 6, and 7 (using unanchored functional components) also showed high solubility loss rates (8.59%–12.40%), confirming the necessity of stable anchors to prevent functional layer loss.

[0076] Comparative Examples 1 and 8 showed low solubility loss rates. The data for Comparative Example 1 (0.41%) represents the stability of the PES matrix itself in the solvent. The data for Comparative Example 8 (0.97%) is close to that of the Examples, indicating that the formation of stable anchor points mainly occurs in the solution stage and is not affected by subsequent heat treatment steps. The solubility loss rates of Comparative Examples 3 and 5 (4.80%-5.06%) were higher than those of the Examples, indicating that the spiropyran components or catalysts have a synergistic effect on the integrity of the overall functional network structure, and the lack of these components would lead to the loss of some unanchored or insufficiently cross-linked components.

[0077] Test Example 3: Experimental steps: The composite films prepared in Examples 1-5 and Comparative Examples 1-8 were selected and cut into 20mm × 20mm samples. Before testing, the samples were dried in a vacuum oven at 40℃ for 4 hours, and their initial appearance color was recorded.

[0078] Immerse all dried samples in petri dishes containing 50 mL of 200 mg / L phenol aqueous solution, and let stand at 25 °C in the dark for 6 hours. Observe and record the color change on the membrane surface.

[0079] Remove the membrane sample that has changed color and rinse it quickly with deionized water. Then immerse it in an acetic acid solution with a pH of 4.0 and stir for 10 minutes. After removing it, rinse it with deionized water and observe whether the color of the membrane sample has returned to its initial state.

[0080] The test results are shown in Table 3. In the table, (+), (++), and (+++) indicate the visually observable increase in blue depth.

[0081] Table 3: Test of Visual Pollution Indication Function of Composite Membrane Sample number Initial appearance In a 200 mg / L phenol solution (6 h) After rinsing with pH 4.0 acetic acid solution Example 1 Light gray Dark blue (+++) Light gray Example 2 Light gray Blue (++) Light gray Example 3 Light gray Blue-gray (+) Light gray Example 4 Light gray Blue (++) Light gray Example 5 Light gray Dark blue (+++) Light gray Comparative Example 1 White White (No change) Comparative Example 2 Light gray Blue (++) Light gray Comparative Example 3 Light gray Light gray (No change) Comparative Example 4 Light gray Light gray (No change) Comparative Example 5 Light gray Blue (++) Light gray Comparative Example 6 White White (No change) Comparative Example 7 Light gray Blue (++) Light gray Comparative Example 8 Light gray Blue (++) Light gray From Table 3, we can obtain: The membrane samples in Examples 1-5 all underwent an appearance change from light gray to blue / dark blue after contact with phenol solution, and this process was reversible after rinsing with acidic solution (pH 4.0), with the membrane returning to its initial light gray color.

[0082] Spiropyrans undergo isomerization under specific chemical conditions (such as coordination or polar induction of phenol molecules) to transform into a colored open-ring anthocyanin form, which macroscopically manifests as a color change.

[0083] The data from Comparative Example 3 are crucial. No spiropyran acrylate monomer was added during the preparation of the multifunctional sacrificial layer polymer in Comparative Example 3, and its membrane sample showed no color change in phenol solution. This result, compared with Examples 1-5, confirms that the spiropyran component is a necessary structure for achieving this indicator function.

[0084] Comparative Examples 1, 4, and 6 all lacked a spiropyran structure and therefore did not display a color response.

[0085] Comparative Examples 2, 5, 7, and 8 contain spiropyran components and therefore also exhibit color responses. This indicates that although these comparative examples are deficient in other aspects (such as anchoring stability or dynamic bond efficiency), their basic photochemical / chemical responsiveness is preserved as long as the spiropyran unit is successfully introduced.

[0086] Test Example 4: Experimental steps: Composite membranes from Examples 1-5 and Comparative Examples 1-8 were selected, cut into circular samples, and installed in a dead-end filtration device (effective filtration area 10.0 cm²). 2 First, the membrane was pre-compacted for 30 minutes at a pressure of 0.15 MPa. Then, the operating pressure was reduced to 0.1 MPa, and the purified water flux after stabilization was tested and recorded using deionized water. ).

[0087] Replace the feed solution with a 100 mg / L bovine serum albumin (BSA) solution, stabilize the filter at 0.1 MPa for 15 minutes, and collect the permeate. Measure the absorbance of the feed solution and permeate at 280 nm using a UV-Vis spectrophotometer, and calculate the BSA rejection rate.

[0088] To evaluate antifouling performance, the feed solution was replaced with simulated wastewater containing 1 g / L LBSA and 200 mg / L humic acid. Continuous filtration was performed at 0.1 MPa pressure for 3 hours, and the flux in the third hour was recorded. ).

[0089] After filtration, the filter tank was drained, and the membrane surface was rinsed with deionized water for 5 minutes. After rinsing, the pure water flux was tested again using deionized water at 0.1 MPa. ).

[0090] according to , and Calculate flux decay rate and flux recovery rate .

[0091] The test results are shown in Table 4.

[0092] Table 4: Test data on separation performance and antifouling performance of composite membranes Sample number <![CDATA[Pure water flux (L / (m 2 ·h))]]> BSA Retention Rate (%) Flux Decay Rate (FDR) (%) Flux recovery rate (FRR) (%) Example 1 412 99.1 31.5 92.4 Example 2 451 99.3 28.1 94.1 Example 3 478 98.9 33.6 91.5 Example 4 436 99.2 29.8 93.2 Example 5 422 99.4 27.5 94.8 Comparative Example 1 613 95.4 66.2 44.1 Comparative Example 2 491 98.5 55.9 51.3 Comparative Example 3 447 99.0 39.1 84.5 Comparative Example 4 384 97.1 61.0 53.8 Comparative Example 5 463 98.8 42.5 79.2 Comparative Example 6 531 91.2 51.7 60.1 Comparative Example 7 476 98.6 58.3 50.5 Comparative Example 8 459 98.7 48.8 65.4 From Table 4, we can obtain: The composite membranes in Examples 1-5 all achieved high BSA rejection rates (>98.9%) and high flux recovery rates (FRR>91.5%), demonstrating a balance between separation performance and antifouling performance.

[0093] Through the synergistic effect of stable covalent anchors (epoxide-amine) and dynamic covalent bonds (imine bonds), a three-dimensional functional network integrating multifunctional sacrificial layer polymers and functionalized carbon nanotubes was constructed on the membrane surface and within the pores. This network structure endows the membrane surface with high hydrophilicity (derived from the hydrophilic segments of the sacrificial layer polymers) and charge repulsion effect (derived from the functional groups of carbon nanotubes and sacrificial layer polymers), effectively hindering the irreversible adsorption of hydrophobic organic pollutants such as BSA and humic acid.

[0094] The flux decline rates in Examples 1-5 remained at a low level (27.5%-33.6%), and the flux recovery rates all exceeded 90%. This indicates that the contaminants mainly adhere to the membrane surface in a reversible manner and can be removed by simple hydraulic rinsing.

[0095] Comparative Example 1 exhibited a high FDR (66.2%) and a low FRR (44.1%), which is a result of severe irreversible fouling on a typical hydrophobic membrane surface. The FRRs of Comparative Examples 4 and 7 were both below 54%, indicating that functional components not chemically bonded and fixed by this scheme cannot form an effective antifouling interface, and may even exacerbate pore blockage due to aggregation.

[0096] The FRR of Comparative Examples 2 and 5 (51.3% and 79.2%, respectively) were significantly lower than those of the Example, confirming the importance of stable anchor points and efficient dynamic bond crosslinking for constructing a robust antifouling layer. The FRR of Comparative Example 8 (65.4%) was also low, indicating that the heat treatment step in S4 plays a role in optimizing the final surface structure and antifouling stability of the film.

[0097] Test Example 5: Experimental steps: The composite membranes prepared in Examples 1-5 and Comparative Examples 1-8 were selected, cut into small pieces, and vacuum dried. Approximately 50.0 mg (m) of the dried membrane sample was accurately weighed and placed in 50 mL Erlenmeyer flasks.

[0098] Add 40.0 mL (V) of a 100 mg / L solution to each conical flask. An aqueous solution of methyl orange (MO) was prepared. The conical flask was sealed and placed in a constant temperature shaker at 25°C and 150 rpm for 24 hours to ensure adsorption equilibrium was reached.

[0099] After shaking, the supernatant was collected and filtered through a 0.22 μm syringe filter. The absorbance of the filtrate was measured using a UV-Vis spectrophotometer at the maximum absorption wavelength of methyl orange (464 nm), and its equilibrium concentration was calculated using a standard curve. ).

[0100] Calculate the equilibrium adsorption capacity of the membrane ( (The unit is mg / g). The calculation formula is: .

[0101] The test results are shown in Table 5.

[0102] Table 5: Static adsorption performance of the composite membrane for methyl orange Sample number Equilibrium adsorption capacity (mg / g) Example 1 158.2 Example 2 161.4 Example 3 153.7 Example 4 159.1 Example 5 163.5 Comparative Example 1 3.1 Comparative Example 2 45.3 Comparative Example 3 155.9 Comparative Example 4 31.7 Comparative Example 5 68.4 Comparative Example 6 10.2 Comparative Example 7 41.5 Comparative Example 8 157.8 From Table 5, we can obtain: Examples 1-5 all exhibited high equilibrium adsorption capacities (>150 mg / g) for methyl orange. Comparative Example 1 (pure PES) The lowest value (3.1 mg / g) can be considered the baseline due to the lack of effective adsorption sites.

[0103] The adsorption performance of this scheme originates from the three-dimensional functional network formed by the cross-linking of functionalized carbon nanotubes (aldehyde groups) and multifunctional sacrificial layer polymers (primary amine groups) through imine bonds (C=N). This network provides a high-density π-π conjugated system of amine groups, imine bonds, and carbon nanotubes as adsorption sites, which work synergistically to capture organic dye molecules such as methyl orange.

[0104] Comparative Example 4 (physical blend of CNTs, 31.7 mg / g) and Comparative Example 7 (MWCNTs-COOH, 41.5 mg / g) The values ​​are significantly lower than those in the examples. This comparison shows that the adsorption capacity of non-functionalized CNTs, or CNTs that rely solely on carboxyl functional groups, is far less than that of the cross-linked network structure constructed by the Schiff base reaction in this scheme.

[0105] Comparative Example 2 (unmodified PES) and Comparative Example 5 (no catalyst) The values ​​(45.3 mg / g and 68.4 mg / g, respectively) were also at a low level. Analysis of the data from Test Example 2 (dissolution rate) and Test Example 1 (C=N formation rate) showed that if the sacrificial layer polymer was not stably anchored (Comparative Example 2), the functional network would become structurally unstable or be lost in solution; if the imine bond network was not effectively formed (Comparative Example 5), the effective adsorption site density would be insufficient. Neither approach could achieve high adsorption capacity.

[0106] Comparative Example 3 (without spiropyran) and Comparative Example 8 (without heat treatment) The values ​​(155.9 mg / g and 157.8 mg / g) are close to those in the examples. This result indicates that the spiropyran component and the heat treatment step have no significant effect on the chemical structure and number of static adsorption sites.

[0107] Test Example 6: Experimental steps: Select membrane samples from Examples 1-5 and Comparative Examples 1-8 that were saturated with adsorption in Test Example 5, cut and weigh approximately 0.5 g of the sample (recorded as...). ).

[0108] The membrane samples were immersed in 50 mL of hydrochloric acid solution with a pH of 3.0 and stirred at 50 °C and 100 rpm for 2 hours. The structural changes of each membrane sample were observed and recorded.

[0109] For samples that underwent structural disintegration (Examples 1-5), filtration was performed using a Buchner funnel to collect the insoluble solid residue (i.e., the modified host polymer matrix). Samples that retained their structural integrity (Comparative Examples 1-8) were recorded as unseparable.

[0110] The collected solid residue was repeatedly washed with deionized water until the filtrate was neutral, and then dried in a vacuum oven at 80°C to constant weight. The mass of the recovered main polymer matrix was weighed and recorded as follows: The recovery rate of the main matrix is ​​calculated based on the theoretical mass fraction of the main polymer in the original formulation.

[0111] Take the recovered main polymer matrix ( According to the material ratio of the original embodiment (e.g., Example 2), newly prepared functionalized carbon nanotubes, multifunctional sacrificial layer polymers and catalysts are added, dissolved in solvent, and the regenerated membrane is prepared according to the original preparation method (S1-S4).

[0112] Following the method in Test Example 5, the equilibrium adsorption capacity of the regenerated membrane for methyl orange was tested. ), and compared with the initial adsorption amount in Test Example 5 ( By comparison, the adsorption performance recovery rate (%) was calculated. .

[0113] The test results are shown in Table 6. "—" indicates that the separation, recovery and regeneration steps could not be performed because the sample was not disassembled.

[0114] Table 6: Composite Membrane Recycling and Regeneration Performance Tests Sample number Structural changes after acid treatment Main matrix recovery rate (%) Adsorption capacity of regenerated membrane (mg / g) Adsorption performance recovery rate (%) Example 1 Structural disintegration 98.1 147.3 93.1 Example 2 Structural disintegration 97.4 154.1 95.5 Example 3 Structural disintegration 98.6 142.6 92.8 Example 4 Structural disintegration 96.9 149.7 94.1 Example 5 Structural disintegration 97.7 150.7 92.2 Comparative Example 1 Structure retention — — — Comparative Example 2 Structure retention — — — Comparative Example 3 Structure retention — — — Comparative Example 4 Structure retention — — — Comparative Example 5 Structure retention — — — Comparative Example 6 Structure retention — — — Comparative Example 7 Structure retention — — — Comparative Example 8 Structure retention — — — From Table 6, we can obtain: The membrane samples in Examples 1-5 all underwent structural disintegration in an acidic solution at pH 3.0, while all comparative sample samples maintained structural integrity.

[0115] The mechanism of this phenomenon is that in the dual network structure constructed by this scheme, the dynamic imine bond (C=N) undergoes hydrolysis under acidic conditions, leading to the disintegration of the functional network composed of functionalized carbon nanotubes and sacrificial layer polymers.

[0116] Meanwhile, the stable CN covalent anchors formed between the modified host polymer matrix (PES-secondary amine group) and the sacrificial layer polymer (epoxy group) remain stable under acidic conditions. This matrix is ​​insoluble in aqueous solution, and therefore, after the functional network disintegrates, it can still exist in solid form and be recovered through physical filtration (vacuum filtration).

[0117] The recovery rate of the main matrix in Examples 1-5 all exceeded 96%, indicating that the main polymer material was lost in the recycling process.

[0118] The samples in Comparative Examples 1-8, lacking such an acid-responsive dynamic imine bond network or having anchoring structures not designed for this scheme, could not achieve selective disintegration under acidic conditions, and therefore could not be recovered from the host matrix through this route.

[0119] Data on regeneration performance is crucial. The regenerated membranes prepared using the recycled matrix all achieved a methyl orange adsorption performance recovery rate of over 92%. This data indicates that the recycled main polymer matrix was not significantly damaged in terms of chemical functionality and can be repeatedly used as a substrate material to prepare functional composite membranes, verifying the feasibility of the closed-loop recycling of the material system in this scheme.

[0120] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A recyclable carbon nanotube composite membrane, characterized in that, The carbon nanotube composite film comprises the following components in parts by weight: Modified main polymer matrix: 100 parts; Functionalized carbon nanotubes: 0.5-5 parts; Multifunctional sacrificial layer polymer: 10-30 parts; p-Toluenesulfonic acid: 0.005-0.02 parts; Solvent: 400-800 parts.

2. The recyclable carbon nanotube composite membrane according to claim 1, characterized in that, The modified host polymer matrix is ​​a secondary amine-functionalized polyethersulfone matrix.

3. The recyclable carbon nanotube composite membrane according to claim 1, characterized in that, The functionalized carbon nanotubes are aldehyde-functionalized carbon nanotubes.

4. The recyclable carbon nanotube composite membrane according to claim 1, characterized in that, The multifunctional sacrificial layer polymer is a copolymer containing primary amine groups, epoxy groups, and spiropyran functional groups.

5. The recyclable carbon nanotube composite membrane according to claim 1, characterized in that, The solvent is a mixture of N,N-dimethylformamide and N-methylpyrrolidone, and the volume ratio of N,N-dimethylformamide to N-methylpyrrolidone is 1-3:

1.

6. A method for preparing a recyclable carbon nanotube composite membrane, characterized in that, The method for preparing the recyclable carbon nanotube composite membrane according to any one of claims 1-5 comprises the following steps: S1. The modified main polymer matrix, functionalized carbon nanotubes, multifunctional sacrificial layer polymer and p-toluenesulfonic acid are dissolved in a solvent and stirred to form a casting solution. S2. Let the casting solution stand for 1-2 hours, and then degas it for 1-3 hours under a vacuum of -0.08 to -0.09 MPa. S3. The degassed casting solution is scraped into a film, exposed to air, and then immersed in a coagulation bath to undergo phase transformation to obtain a molded film. S4. The molded film is soaked, heat-treated and dried.

7. The method for preparing the recyclable carbon nanotube composite membrane according to claim 6, characterized in that, S1 specifically includes the following steps: The modified main polymer matrix is ​​added to the solvent and stirred at 40-60°C for 12-24 hours until dissolved; After cooling to room temperature, the functionalized carbon nanotubes and the multifunctional sacrificial layer polymer are added sequentially, and stirring is continued for 2-4 hours. Finally, add the p-toluenesulfonic acid and stir the mixture at 25-40°C for 6-12 hours.

8. The method for preparing the recyclable carbon nanotube composite membrane according to claim 6, characterized in that, S3 specifically includes the following steps: In an environment with a relative humidity of 50-70%, the casting solution is coated onto a polyester nonwoven fabric or glass plate to form a film, with the coating thickness controlled at 200-400μm. After being exposed to air for 10-30 seconds, immerse it in a coagulation bath at a temperature of 20-30°C for 10-30 minutes. The coagulation bath is a mixed solution of deionized water and ethanol, and the volume ratio of deionized water to ethanol is 1-3:

1.

9. The method for preparing the recyclable carbon nanotube composite membrane according to claim 6, characterized in that, S4 specifically includes the following steps: The molded membrane was soaked in deionized water for 24 hours, with the water changed every 4-8 hours during the process. After cleaning, place the wet film in an oven at 60-90℃ for 2-6 hours for heat treatment, and finally dry it in a ventilated environment at 20-30℃ for 12-24 hours.

10. The application of a recyclable carbon nanotube composite membrane as described in any one of claims 1-5 in the treatment of organic matter in industrial wastewater.

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