A composite nanofiltration membrane based on rigid torsion phenolamine monomer, its preparation method and application

Abstract

This invention discloses a composite nanofiltration membrane based on a rigid-torsional phenolamine monomer, relating to the field of separation membrane technology. The membrane includes a base membrane and a functional separation layer on the surface of the base membrane. The functional separation layer is formed by crosslinking an aqueous monomer and an organic monomer. The aqueous monomer is a rigid-torsional phenolamine monomer, and the organic monomer is a polyacrylamide chloride. This invention prepares the composite nanofiltration membrane using interfacial polymerization, a method with advantages such as simple process, mild reaction conditions, and short film formation time. The rigid-torsional phenolamine monomer possesses unique molecular structural characteristics; its rigid framework structure can form a polymer network with high microporosity, while the torsible nature of the molecule helps to construct an ordered pore structure. Simultaneously, the larger molecular size and ionization morphology of this monomer effectively reduce the diffusion rate into the organic phase, which is beneficial for forming an ultrathin and structurally regular separation layer.

Description

Technical Field

[0001] This invention relates to the field of separation membrane technology, specifically to a composite nanofiltration membrane based on rigid torsion phenolamine monomer, its preparation method, and its application. Background Technology

[0002] Currently, organic solvents are widely used in industries such as petrochemicals, pharmaceuticals, and food processing, inevitably involving issues such as the separation, purification, concentration, and solvent recovery of small molecules in organic solvent systems. However, traditional separation techniques, such as distillation, rectification, and extraction, often suffer from problems such as large footprint, high energy consumption, complex operation, and potential damage to heat-sensitive substances. These problems not only increase production costs but also impose additional burdens on the environment.

[0003] In recent years, with the growing acceptance of green chemistry and sustainable development concepts, efficient, energy-saving, and environmentally friendly separation technologies have become a research hotspot. Membrane separation technology, due to its unique advantages such as ease of operation, low energy consumption, no phase change, and environmental friendliness, has gradually become an important research direction in the field of organic solvent separation. Organic solvent nanofiltration (OSN), also known as solvent-resistant nanofiltration (SRNF), can effectively separate molecules with molecular weights between 200 and 1000 Da from organic solvents, providing a promising alternative for the separation and concentration of organic systems in industrial sectors.

[0004] The core of OSN technology is the OSN membrane. Currently, OSN membranes are mainly divided into two categories: one is the integral asymmetric membrane (ISA membrane), and the other is the thin-layer composite membrane (TFC membrane). Among them, ISA membranes are generally produced by phase inversion method, which has the characteristics of easy processing and industrial production. However, due to its thick and dense top skin layer, the permeation resistance is relatively large, which limits its further application. On the other hand, TFC membranes are generally synthesized in situ on top of a porous support layer or coated with a thin and dense separation layer. They have the characteristics of large-scale production, ultra-thin separation layer, and independent adjustment of separation layer and support layer. The high-performance TFC OSN membrane has become the academic frontier and research hotspot in related fields.

[0005] Membrane structure determines membrane performance, and optimizing the structure of the separation layer is of great significance for improving the separation performance of TFC OSN membranes. In recent years, as reported by Livingston et al. (Nature Material, 15(2016):760-767.), using the bisphenol molecule 9,9-bis(4-hydroxyphenyl)fluorene (BHPF) with a Cardo overhang structure as an aqueous phase IP monomer significantly increased the free volume of polyarylate nanomembranes, resulting in a methanol permeation an order of magnitude higher than that of composite membranes prepared from planar monomers. Recently, Pang et al. (Journal of Membrane Science, 666(2023)121179.) selected DMF as an aqueous phase co-solvent to dissolve the insoluble diamine molecule 9,9-bis(4-aminophenyl)fluorine (BAF) for interfacial polymerization, preparing a membrane with high microporosity. This membrane had a methanol permeation of 23.88 LMH / bar, but a relatively large MWCO value (≈600 Da). Similarly, Zhu et al. (Journal of Membrane Science, 15(2016):760-767.) Science, 704(2024)122879 et al. used a multi-cycle molecular layer deposition (MLD) strategy to prepare microporous membranes with excellent solvent permeability and solute selectivity using BAF monomers. However, some problems still exist, especially the limited free volume of the selective layer formed by traditional monomers, which is relatively thick and dense, resulting in low or moderate solvent permeability.

[0006] Therefore, providing a composite nanofiltration membrane with excellent permeation selectivity and stability is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] The present invention aims to provide a composite nanofiltration membrane based on rigid torsion phenolamine monomers to overcome the shortcomings of insufficient stability and low upper limit of permeation selectivity in existing organic solvent nanofiltration membranes.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A composite nanofiltration membrane based on rigid torsion phenolamine monomer includes a base membrane and a functional separation layer on the surface of the base membrane;

[0010] The functional separation layer is formed by cross-linking aqueous phase monomers and organic phase monomers;

[0011] The structural formula of the aqueous phase monomer is as follows:

[0012]

[0013] The organic phase monomer is a polyacyl chloride.

[0014] This invention uses polyacrylonitrile or polyimide ultrafiltration membranes as the base membrane. The membrane is first soaked in an aqueous solution containing a rigid torsion phenolamine monomer, then soaked in an organic solution containing polyacrylamide chlorides for interfacial polymerization, and finally subjected to thermal crosslinking post-treatment to obtain a composite nanofiltration membrane. This invention relates to a method for preparing a high-performance composite nanofiltration membrane, characterized by the introduction of large-size rigid torsion phenolamine monomers, which significantly improves the permeation selectivity of the resulting membrane material compared to polyester membranes with similar torsion skeleton structures. Simultaneously, it exhibits high stability in tests with various polar solvents, thus possessing high economic value in industrial processes involving molecular separation and solution concentration in organic solvent systems, particularly in the field of drug separation.

[0015] Preferably, the base membrane is a polyacrylonitrile or polyimide ultrafiltration membrane.

[0016] Preferably, the polyacrylamide chloride is at least one selected from pyromellitic chloride, isophthaloyl chloride, and terephthaloyl chloride.

[0017] Preferably, the crosslinking conditions are a reaction at 50-80°C for 2-10 minutes.

[0018] Preferably, the mass ratio of the aqueous monomer to the polyacrylamide chloride is 0.1-2:0.02-0.5.

[0019] The preparation method of the composite nanofiltration membrane based on rigid torsion phenolamine monomer described above includes the following steps:

[0020] The base membrane was sequentially immersed in an aqueous solution of the monomer and an organic solution of polyacrylamide chloride, and then heated to crosslink, thus obtaining a composite nanofiltration membrane based on a rigid torsion phenolamine monomer.

[0021] Preferably, all soakings are performed at room temperature.

[0022] Preferably, the concentration of the aqueous solution is 0.1-2 wt%, the pH of the aqueous solution is 9.0-13.0, and the soaking time in the aqueous solution is 1-2 min.

[0023] Preferably, the aqueous solution further includes an alkaline auxiliary agent, which is at least one selected from sodium hydroxide, potassium hydroxide, and triethylamine.

[0024] The concentration of the alkali auxiliary agent in the aqueous solution is 0.2-5 wt%.

[0025] Preferably, the concentration of the organic solution is 0.02-0.5 wt%, the soaking time in the organic solution is 15 s-10 min, and the solvent of the organic solution is at least one of n-hexane, isoalkanes, and toluene.

[0026] Preferably, the base membrane undergoes the following pretreatment steps: immersing the base membrane in deionized water for 4 hours, changing the water every hour to fully remove the pore-retaining agent from the membrane surface.

[0027] Applications of composite nanofiltration membranes as described above or composite nanofiltration membranes prepared by the methods described above in the separation and purification of organic solvent systems.

[0028] The composite nanofiltration membrane prepared by this invention has a high permeation flux (>17 LMH / bar) to organic solvents such as acetone and methanol, and can effectively retain dye molecules such as methyl orange, tetracycline, acid blue, orange yellow G, rhodamine B, acid red 27, and brilliant blue R. It can be fully applied to chemical processes such as the separation and concentration of active drugs and the recovery of homogeneous catalysts in organic solvent systems.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] This invention prepares composite nanofiltration membranes using interfacial polymerization, a method that offers advantages such as simple process, mild reaction conditions, and short film formation time. Specifically, the rigid-torsional phenolamine monomer possesses unique molecular structural characteristics; its rigid framework structure can form a polymer network with high microporosity, while the torsible nature of the molecule helps construct an ordered pore structure. Simultaneously, the monomer's large molecular size and ionization morphology effectively reduce the diffusion rate into the organic phase, facilitating the formation of an ultrathin and structurally regular separation layer.

[0031] Furthermore, based on the stable three-dimensional network structure formed by the rigid torsion phenolamine monomer and polyacrylamide chloride through a "4+3" crosslinking mode, the resulting membrane material exhibits excellent thermal stability and solvent resistance. Therefore, the composite nanofiltration membrane prepared in this invention maintains a high rejection rate for small molecule dyes while significantly improving its organic solvent flux compared to traditional polyamide membranes. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings in this description are merely embodiments of the present invention.

[0033] Figure 1 This is a surface electron microscope image of the polyacrylonitrile-based film of Example 1 of the present invention;

[0034] Figure 2 This is an electron microscope image of the surface of the composite nanofiltration membrane prepared in Example 1 of the present invention;

[0035] Figure 3 This is an electron microscope image of the surface of the composite nanofiltration membrane prepared in Example 5 of the present invention;

[0036] Figure 4This is a graph showing the separation performance of the composite nanofiltration membrane prepared in Example 1 of this invention for various dyes;

[0037] Figure 5 This is a graph showing the permeation performance of the composite nanofiltration membrane prepared in Example 1 of this invention to various solvents;

[0038] Figure 6 This is a graph showing the separation performance of the composite nanofiltration membrane prepared in Example 6 of this invention for various dyes. Detailed Implementation

[0039] Embodiments of the present invention are described below, examples of which are shown in the accompanying drawings. The embodiments described with reference to the drawings are exemplary and intended to explain the present invention, but are not to be construed as limiting the present invention.

[0040] Example 1

[0041] This invention provides a method for preparing a composite nanofiltration membrane based on a rigid torsion phenolic amine monomer, comprising the following steps:

[0042] (1) Soak the polyacrylonitrile ultrafiltration membrane in pure water for 4 hours, changing the water every hour to fully remove the pore-retaining agent (glycerol, polyethylene glycol, etc.) on the membrane surface, and set it aside for later use;

[0043] (2) Take out the polyacrylonitrile ultrafiltration membrane from step (1), wipe the water droplets remaining on the surface of the ultrafiltration membrane with lint-free paper, and immerse it in an aqueous solution of monomer (I) 9,9'-bis(3-amino4-hydroxyphenyl)fluorene with a concentration of 1.0 wt%, triethylamine with a concentration of 4.0 wt%, and sodium hydroxide with a concentration of 2 eq for 2 min at 25°C. Take out the ultrafiltration membrane and remove the water droplets remaining on the membrane surface with a rubber roller for later use.

[0044] (3) At 25°C, the polyacrylonitrile ultrafiltration membrane treated in step (2) was immersed in a hexane solution with a pyromellitic chloride concentration of 0.1 wt% and reacted for 5 min.

[0045] (4) The filter membrane after the reaction in step (3) is placed in an oven at 60°C and heated for 5 minutes to obtain a composite nanofiltration membrane based on rigid torsion phenolamine monomer, wherein, Figure 1 This is an electron microscope image of the surface of a polyacrylonitrile-based film. Figure 2 The surface electron microscope image of the composite nanofiltration membrane shows that a continuous, smooth, and defect-free polyesteramide active layer was formed on the polyacrylonitrile ultrafiltration membrane substrate.

[0046] The prepared composite nanofiltration membrane was used to separate 4-nitroaniline, Sudan Orange G (SOG), methyl orange (MO), orange yellow G (OG), rhodamine B (RDB), acid red 27 (AR27), and brilliant blue R (BBR). The experimental results are as follows: Figure 4As shown in the figure, the retention capacity gradually increases with the increase of the dye molecular weight; the molecular weight cutoff of the above organic solvent nanofiltration membrane is about 298 Da.

[0047] The prepared composite nanofiltration membrane was used to filter methanol, tetrahydrofuran, ethanol, isopropanol, toluene, water, and n-hexane sequentially, and its flux performance was tested. The conclusions are attached. Figure 5 As shown in the figure, the measured permeation flux of the composite nanofiltration membrane for methanol is 18.0 LMH / bar, and the permeation flux for acetone is 21.5 LMH / bar.

[0048] Example 2

[0049] This invention provides a method for preparing a composite nanofiltration membrane based on a rigid torsion phenolic amine monomer, comprising the following steps:

[0050] (1) Soak the polyacrylonitrile ultrafiltration membrane in pure water for 4 hours, changing the water every hour to fully remove the pore-retaining agent (glycerol, polyethylene glycol, etc.) on the membrane surface, and set it aside for later use;

[0051] (2) Take out the polyacrylonitrile ultrafiltration membrane from step (1), wipe the water droplets remaining on the surface of the ultrafiltration membrane with lint-free paper, and immerse it in an aqueous solution of monomer (I) 9,9'-bis(3-amino4-hydroxyphenyl)fluorene with a concentration of 1.0 wt%, triethylamine with a concentration of 4.0 wt%, and sodium hydroxide with a concentration of 2 eq for 2 min at 25°C. Take out the ultrafiltration membrane and remove the water droplets remaining on the membrane surface with a rubber roller for later use.

[0052] (3) At 25°C, the polyacrylonitrile ultrafiltration membrane treated in step (2) was immersed in a hexane solution with a pyromellitic chloride concentration of 0.1 wt% and reacted for 1 min.

[0053] (4) Place the filter membrane after the reaction in step (3) in an oven at 60°C and heat for 2 min to obtain a composite nanofiltration membrane based on rigid torsion phenolamine monomer;

[0054] The separation performance test of the prepared composite nanofiltration membrane showed that the methanol flux was 17.9 LMH / bar and the rejection rate of methyl orange (MW 327 Da) was 87.8%.

[0055] Example 3

[0056] This invention provides a method for preparing a composite nanofiltration membrane based on a rigid torsion phenolic amine monomer, comprising the following steps:

[0057] (1) Soak the polyacrylonitrile ultrafiltration membrane in pure water for 4 hours, changing the water every hour to fully remove the pore-retaining agent (glycerol, polyethylene glycol, etc.) on the membrane surface, and set it aside for later use;

[0058] (2) Take out the polyacrylonitrile ultrafiltration membrane from step (1), wipe the water droplets remaining on the surface of the ultrafiltration membrane with lint-free paper, and soak it in an aqueous solution of monomer (II) 5,5'-diamino-3,3,3',3'-tetramethyl-2,2',3,3'-tetrahydro-1,1'-spirodi[indene]-6,6'-diol at 25°C for 2 min. Take out the ultrafiltration membrane and remove the water droplets remaining on the membrane surface with a rubber roller for later use.

[0059] (3) At 25°C, the polyacrylonitrile ultrafiltration membrane treated in step (2) was immersed in a hexane solution with a pyromellitic chloride concentration of 0.1 wt% and reacted for 5 min.

[0060] (4) Place the filter membrane after the reaction in step (3) in an oven at 60°C and heat for 5 minutes to obtain a composite nanofiltration membrane based on rigid torsion phenolamine monomer.

[0061] The separation performance test of the prepared composite nanofiltration membrane showed that the methanol flux was 22.5 LMH / bar and the rejection rate of methyl orange (MW 327 Da) was 87.9%.

[0062] Example 4

[0063] This invention provides a method for preparing a composite nanofiltration membrane based on a rigid torsion phenolic amine monomer, comprising the following steps:

[0064] (1) Soak the polyacrylonitrile ultrafiltration membrane in pure water for 4 hours, changing the water every hour to fully remove the pore-retaining agent (glycerol, polyethylene glycol, etc.) on the membrane surface, and set it aside for later use;

[0065] (2) Take out the polyacrylonitrile ultrafiltration membrane from step (1), wipe the water droplets remaining on the surface of the ultrafiltration membrane with lint-free paper, and soak it in an aqueous solution of monomer (II) 5,5'-diamino-3,3,3',3'-tetramethyl-2,2',3,3'-tetrahydro-1,1'-spirodi[indene]-6,6'-diol at 25°C for 2 min. Take out the ultrafiltration membrane and remove the water droplets remaining on the membrane surface with a rubber roller for later use.

[0066] (3) At 25°C, the polyacrylonitrile ultrafiltration membrane treated in step (2) was immersed in a hexane solution with a pyromellitic chloride concentration of 0.2 wt% and reacted for 5 min.

[0067] (4) Place the filter membrane after the reaction in step (3) in an oven at 60°C and heat for 5 minutes to obtain a composite nanofiltration membrane based on rigid torsion phenolamine monomer.

[0068] The separation performance test of the prepared composite nanofiltration membrane showed that the methanol flux was 18.3 LMH / bar and the rejection rate of methyl orange (MW 327 Da) was 96.2%.

[0069] Example 5

[0070] This invention provides a method for preparing a composite nanofiltration membrane based on a rigid torsion phenolic amine monomer, comprising the following steps:

[0071] (1) Soak the polyacrylonitrile ultrafiltration membrane in pure water for 4 hours, changing the water every hour to fully remove the pore-retaining agent (glycerol, polyethylene glycol, etc.) on the membrane surface, and set it aside for later use;

[0072] (2) Take out the polyacrylonitrile ultrafiltration membrane from step (1), wipe the water droplets remaining on the surface of the ultrafiltration membrane with lint-free paper, and soak it in an aqueous solution of monomer (III) 5,7'-diamino-3,3,3',3'-tetramethyl-2,2',3,3'-tetrahydro-1,1'-spirodi[indene]-6,6'-diol at 25°C for 2 min. Take out the ultrafiltration membrane and remove the water droplets remaining on the membrane surface with a rubber roller for later use.

[0073] (3) At 25°C, the polyacrylonitrile ultrafiltration membrane treated in step (2) was immersed in a hexane solution with a pyromellitic chloride concentration of 0.2 wt% and reacted for 5 min.

[0074] (4) The filter membrane after the reaction in step (3) is placed in an oven at 60°C and heated for 5 minutes to obtain a composite nanofiltration membrane based on rigid torsion phenolamine monomer; wherein, Figure 3 The image shows an electron microscope image of the composite nanofiltration membrane prepared in this embodiment. As can be seen from the image, a continuous and defect-free polyesteramide active layer was formed on the polyacrylonitrile ultrafiltration membrane substrate. This layer has a Turing stripe-like surface structure, which significantly increases the effective filtration area of ​​the membrane and thus improves the membrane permeation flux.

[0075] The separation performance test of the prepared composite nanofiltration membrane showed that the methanol flux was 19.8 LMH / bar and the rejection rate of methyl orange (MW 327 Da) was 94.9%.

[0076] Example 6

[0077] This invention provides a method for preparing a composite nanofiltration membrane based on a rigid torsion phenolic amine monomer, comprising the following steps:

[0078] (1) Soak the polyacrylonitrile ultrafiltration membrane in pure water for 4 hours, changing the water every hour to fully remove the pore-retaining agent (glycerol, polyethylene glycol, etc.) on the membrane surface, and set it aside for later use;

[0079] (2) Take out the polyacrylonitrile ultrafiltration membrane from step (1), wipe the water droplets remaining on the surface of the ultrafiltration membrane with lint-free paper, and soak it in an aqueous solution of monomer (IV) 7,7'-diamino-3,3,3',3'-tetramethyl-2,2',3,3'-tetrahydro-1,1'-spirodi[indene]-6,6'-diol at 25°C for 2 min. Take out the ultrafiltration membrane and remove the water droplets remaining on the membrane surface with a rubber roller for later use.

[0080] (3) At 25°C, the polyacrylonitrile ultrafiltration membrane treated in step (2) was immersed in a hexane solution with a pyromellitic chloride concentration of 0.2 wt% and reacted for 5 min.

[0081] (4) Place the filter membrane after the reaction in step (3) in an oven at 60°C and heat for 5 minutes to obtain a composite nanofiltration membrane based on rigid torsion phenolamine monomer.

[0082] The separation performance test of the prepared composite nanofiltration membrane showed that the methanol flux was 17.8 LMH / bar and the rejection rate of methyl orange (MW 327 Da) was 96.2%.

[0083] The prepared composite nanofiltration membrane was used to separate 4-nitroaniline, Sudan Orange G (SOG), methyl orange (MO), orange yellow G (OG), rhodamine B (RDB), acid red 27 (AR27), and brilliant blue R (BBR). The experimental results are as follows: Figure 6 As shown in the figure, the retention capacity gradually increases with the increase of the dye molecular weight; the molecular weight cutoff of the above organic solvent nanofiltration membrane is about 253 Da.

[0084] Example 7

[0085] This invention provides a method for preparing a composite nanofiltration membrane based on a rigid torsion phenolic amine monomer, comprising the following steps:

[0086] (1) Soak the polyacrylonitrile ultrafiltration membrane in pure water for 4 hours, changing the water every hour to fully remove the pore-retaining agent (glycerol, polyethylene glycol, etc.) on the membrane surface, and set it aside for later use;

[0087] (2) Take out the polyacrylonitrile ultrafiltration membrane from step (1), wipe the water droplets remaining on the surface of the ultrafiltration membrane with lint-free paper, and immerse it in an aqueous solution of monomer (I) 9,9'-bis(3-amino4-hydroxyphenyl)fluorene with a concentration of 1.0 wt%, triethylamine with a concentration of 4.0 wt%, and sodium hydroxide with a concentration of 2 eq for 2 min at 25°C. Take out the ultrafiltration membrane and remove the water droplets remaining on the membrane surface with a rubber roller for later use.

[0088] (3) At 25°C, the polyacrylonitrile ultrafiltration membrane treated in step (2) was immersed in a hexane solution with a terephthaloyl chloride concentration of 0.2 wt% and reacted for 5 min.

[0089] (4) Place the filter membrane after the reaction in step (3) in an oven at 60°C and heat for 5 minutes to obtain a composite nanofiltration membrane based on rigid torsion phenolamine monomer.

[0090] The separation performance test of the prepared composite nanofiltration membrane showed that the methanol flux was 21.5 LMH / bar, the rejection rate for Orange G (OG) was 94.3%, and the rejection rate for Brilliant Blue R (BBR) was 99.2%.

[0091] Example 8

[0092] This invention provides a method for preparing a composite nanofiltration membrane based on a rigid torsion phenolic amine monomer, comprising the following steps:

[0093] (1) Soak the polyacrylonitrile ultrafiltration membrane in pure water for 4 hours, changing the water every hour to fully remove the pore-retaining agent (glycerol, polyethylene glycol, etc.) on the membrane surface, and set it aside for later use;

[0094] (2) Take out the polyacrylonitrile ultrafiltration membrane from step (1), wipe the water droplets remaining on the surface of the ultrafiltration membrane with a lint-free paper, and immerse it in an aqueous solution containing monomers (II), (III) and (IV) at 25°C for 2 minutes. Take out the ultrafiltration membrane and remove the water droplets remaining on the membrane surface with a rubber roller for later use.

[0095] (3) At 25°C, the polyacrylonitrile ultrafiltration membrane treated in step (2) was immersed in a hexane solution with an isophthaloyl chloride concentration of 0.2wt% and reacted for 5 min.

[0096] (4) Place the filter membrane after the reaction in step (3) in an oven at 60°C and heat for 5 minutes to obtain a composite nanofiltration membrane based on rigid torsion phenolamine monomer.

[0097] The separation performance test of the prepared composite nanofiltration membrane showed that the methanol flux was 24.5 LMH / bar, the rejection rate of Orange G (OG) was 93.8%, and the rejection rate of Acid Red 27 (AR27) was 95.9%.

[0098] Example 9

[0099] This invention provides a method for preparing a composite nanofiltration membrane based on a rigid torsion phenolic amine monomer, comprising the following steps:

[0100] (1) Soak the polyacrylonitrile ultrafiltration membrane in pure water for 4 hours, changing the water every hour to fully remove the pore-retaining agent (glycerol, polyethylene glycol, etc.) on the membrane surface, and set it aside for later use;

[0101] (2) Take out the polyacrylonitrile ultrafiltration membrane from step (1), wipe the water droplets remaining on the surface of the ultrafiltration membrane with a lint-free paper, and immerse it in a mixed solution of monomers (II), (III) and (IV) at 25°C for 2 min in an aqueous solution with a concentration of 1.0 wt% and a sodium hydroxide concentration of 4 eq. Take out the ultrafiltration membrane and remove the water droplets remaining on the membrane surface with a rubber roller for later use.

[0102] (3) At 25°C, the polyacrylonitrile ultrafiltration membrane treated in step (2) was immersed in a hexane solution with a terephthaloyl chloride concentration of 0.2 wt% and reacted for 5 min.

[0103] (4) Place the filter membrane after the reaction in step (3) in an oven at 60°C and heat for 5 minutes to obtain a composite nanofiltration membrane based on rigid torsion phenolamine monomer.

[0104] The separation performance test of the prepared composite nanofiltration membrane showed that the methanol flux was 25.8 LMH / bar, the rejection rate for Orange G (OG) was 96.9%, the rejection rate for Acid Red 27 (AR27) was 94.2%, and the rejection rate for Brilliant Blue R (BBR) was 98.5%.

[0105] Comparative Example 1

[0106] A method for preparing a composite nanofiltration membrane is provided, comprising the following steps:

[0107] (1) Soak the polyacrylonitrile ultrafiltration membrane in pure water for 4 hours, changing the water every hour to fully remove the pore-retaining agent (glycerol, polyethylene glycol, etc.) on the membrane surface, and set it aside for later use;

[0108] (2) Take out the polyacrylonitrile ultrafiltration membrane from step (1), wipe the water droplets remaining on the surface of the ultrafiltration membrane with a lint-free paper, and immerse it in an aqueous solution at 25°C with a concentration of 1.0 wt% of bisphenol molecule 9,9-bis(4-hydroxyphenyl)fluorene (BHPF), a concentration of 4.0 wt% of triethylamine, and a concentration of 2 eq of sodium hydroxide for 2 min. Take out the ultrafiltration membrane and remove the water droplets remaining on the membrane surface with a rubber roller for later use.

[0109] (3) At 25°C, the polyacrylonitrile ultrafiltration membrane treated in step (2) was immersed in a hexane solution with a pyromellitic chloride concentration of 0.1 wt% and reacted for 5 min.

[0110] (4) Place the filter membrane after the reaction in step (3) in an oven at 60°C and heat for 5 minutes to obtain a composite nanofiltration membrane based on rigid torsion phenolamine monomer.

[0111] The separation performance test of the prepared composite nanofiltration membrane showed that the methanol flux was 10.3 LMH / bar and the rejection rate of methyl orange (MW 327 Da) was 56.9%.

[0112] Comparing Example 1 with Comparative Example 1, it can be seen that under the same conditions, when monomer (I) is used instead of the bisphenol molecule 9,9-bis(4-hydroxyphenyl)fluorene to prepare the composite nanofiltration membrane, its methanol flux is increased by nearly 2 times, while its retention of organic molecules is significantly improved. The retention rate of methyl orange (MW 327Da) increased from 56.9% to 91.2%. This fully demonstrates the great performance advantage of the applied monomer (I) based on the rigid torsion fluorene group structure of phenolic amine molecules as interfacial polymerization monomer molecules for membrane preparation.

[0113] Comparative Example 2

[0114] A method for preparing a composite nanofiltration membrane is provided, comprising the following steps:

[0115] (1) Soak the polyacrylonitrile ultrafiltration membrane in pure water for 4 hours, changing the water every hour to fully remove the pore-retaining agent (glycerol, polyethylene glycol, etc.) on the membrane surface, and set it aside for later use;

[0116] (2) Take out the polyacrylonitrile ultrafiltration membrane from step (1), wipe the water droplets remaining on the surface of the ultrafiltration membrane with lint-free paper, and immerse it in an aqueous solution of 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethylspirodiindane (TTSBI) with a spirocyclic structure of bisphenol molecules at 25°C for 2 min. Take out the ultrafiltration membrane and remove the water droplets remaining on the membrane surface with a rubber roller for later use.

[0117] (3) At 25°C, the polyacrylonitrile ultrafiltration membrane treated in step (2) was immersed in a hexane solution with a pyromellitic chloride concentration of 0.1 wt% and reacted for 5 min.

[0118] (4) Place the filter membrane after the reaction in step (3) in an oven at 60°C and heat for 5 minutes to obtain a composite nanofiltration membrane based on rigid torsion phenolamine monomer.

[0119] The separation performance test of the prepared composite nanofiltration membrane showed that the methanol flux was 6.3 LMH / bar and the rejection rate of methyl orange (MW 327 Da) was 92.9%.

[0120] Comparing Example 6 with Comparative Example 2, it can be seen that under the same conditions, when monomer (II) is used to replace the bisphenol molecule TTSBI to prepare the composite nanofiltration membrane, its methanol flux is increased by nearly 3 times, while its retention of organic molecules is significantly improved. The retention rate of methyl orange (MW327 Da) increases from 92.9% to 96.2%, which fully demonstrates the great performance advantages of the monomer based on the rigid torsion spirodiinden structure as an interfacial polymerization monomer molecule for membrane preparation.

[0121] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A composite nanofiltration membrane based on rigid torsion phenolamine monomer, characterized in that, Includes a base film and a functional separation layer on the surface of the base film; The functional separation layer is formed by cross-linking aqueous phase monomers and organic phase monomers; The structural formula of the aqueous phase monomer is as follows: ； The organic phase monomer is a polyacyl chloride; The method for preparing a composite nanofiltration membrane based on a rigid torsion phenolamine monomer includes the following steps: The base membrane is sequentially immersed in an aqueous solution of an aqueous monomer and an organic solution of a polyacrylamide chloride, and then heated to crosslink, thereby obtaining a composite nanofiltration membrane based on a rigid torsion phenolamine monomer. The aqueous solution also includes an alkaline additive.

2. The composite nanofiltration membrane based on rigid torsion phenolamine monomer according to claim 1, characterized in that, The base membrane is a polyacrylonitrile or polyimide ultrafiltration membrane.

3. The composite nanofiltration membrane based on rigid torsion phenolamine monomer according to claim 1, characterized in that, The polyacrylic chloride is at least one of pyromellitic chloride, isophthaloyl chloride, and terephthaloyl chloride.

4. The composite nanofiltration membrane based on rigid torsion phenolamine monomer according to claim 1, characterized in that, The crosslinking conditions are a reaction at 50-80°C for 2-10 minutes.

5. The composite nanofiltration membrane based on rigid torsion phenolamine monomer according to claim 1, characterized in that, The mass ratio of the aqueous monomer to the polyacrylamide chloride is 0.1-2:0.02-0.

50.

6. The composite nanofiltration membrane based on rigid torsion phenolamine monomer according to claim 1, characterized in that, The concentration of the aqueous monomer in the aqueous solution is 0.1-2 wt%, the pH of the aqueous solution is 9.0-13.0, and the soaking time in the aqueous solution is 1-2 min.

7. The composite nanofiltration membrane based on rigid torsion phenolamine monomer according to claim 1, characterized in that, The alkaline additive is at least one of sodium hydroxide, potassium hydroxide, and triethylamine; The concentration of the alkali auxiliary agent in the aqueous solution is 0.2-5 wt%.

8. The composite nanofiltration membrane based on rigid torsion phenolamine monomer according to claim 1, characterized in that, The concentration of polyacrylamide chloride in the organic solution is 0.02-0.5 wt%, the soaking time in the organic solution is 15 s-10 min, and the solvent of the organic solution is at least one of n-hexane, isoalkanes, and toluene.

9. The application of the composite nanofiltration membrane as described in any one of claims 1-8 in the separation and purification of organic solvent systems.

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