Zwitterionic crosslinked ultrafiltration membrane with high antibacterial performance and preparation method thereof

Abstract

The application provides a zwitterionic crosslinked ultrafiltration membrane with high antibacterial performance and a preparation method thereof, and belongs to the field of membrane separation technology.The zwitterionic crosslinked polymer ultrafiltration membrane with high antibacterial performance is prepared by using sodium p-aminobenzenesulfonate as an additive and a modifier, controlling the electrophilic substitution and crosslinking reaction between the sodium p-aminobenzenesulfonate and chloromethyl in a chloroalkyl functionalized polymer to control the crosslinking degree, and adopting a one-pot non-solvent induced phase inversion method.The application controls the thermodynamics of a casting solution through a chemical reaction, and then controls the polymer film forming kinetics, realizes the control of the morphology, microporous structure and performance of the polymer ultrafiltration membrane, endows the zwitterionic crosslinked ultrafiltration membrane with permanent hydrophilicity and antibacterial performance, and provides a new idea for preparing a polymer porous functional membrane.

Description

Technical Field

[0001] This invention belongs to the field of membrane separation technology, and in particular relates to an amphoteric crosslinked ultrafiltration membrane with high antibacterial properties and its preparation method. Background Technology

[0002] With the increasing severity of global water resource problems, water recycling and reuse have become crucial. Membrane separation technology is widely used in water purification due to its simple operation, good environmental compatibility, and wide applicability. Ultrafiltration membranes (pore size 2-100nm) can more accurately separate large organic molecules and particles in water, thereby achieving water purification and reuse. Membrane fouling remains a challenge to be addressed in pressure-driven membrane processes. This is because fouling reduces membrane permeate flux, selectivity, separation capacity, and membrane lifespan.

[0003] Zwitterionic modified membranes have attracted widespread attention from scientists due to their advantages of high hydrophilicity, good durability, and good environmental stability. Zwitterionic ultrafiltration membranes are generally classified into copolymer membranes, polymer blend membranes, and polymer crosslinked membranes. Among them, polymer crosslinked membranes introduce zwitterionic crosslinking agents into the polymer, which increases the membrane's separation performance and antifouling properties, while also improving the stability of the separation membrane. Although zwitterionic modified polymer membranes have the above advantages, existing preparation methods are cumbersome and expensive, limiting their industrial application. Summary of the Invention

[0004] This invention provides a zwitterionic crosslinked ultrafiltration membrane with high-efficiency antibacterial properties and its preparation method. The method regulates the thermodynamics of the casting solution through chemical reaction, thereby regulating the polymer film-forming kinetics, achieving control over the morphology, microporous structure and properties of the polymer ultrafiltration membrane, endowing the zwitterionic crosslinked ultrafiltration membrane with permanent hydrophilicity and antibacterial properties, and providing a new approach for the preparation of polymer porous functional membranes.

[0005] To achieve the above objectives, the present invention provides an amphoteric crosslinked polymer ultrafiltration membrane with high antibacterial properties, which is prepared by a one-pot, solvent-controlled phase inversion method using sodium p-aminobenzenesulfonate as an additive and modifier, by controlling the degree of crosslinking through electrophilic substitution and crosslinking reactions between sodium p-aminobenzenesulfonate and chloromethyl groups in chloroalkyl functionalized polymers.

[0006] In the above scheme, the amino groups in sodium aminobenzenesulfonate (ABS) can undergo electrophilic substitution reactions with chloroalkyl functionalized polymers rich in chloromethyl groups, such as polychloromethylated polysulfone (CMPSf), chloromethylated polyethersulfone (CMPES), and chloromethylated polyimide (CMPI). By introducing sulfonate groups into the membrane material, the hydrophilicity and antibacterial properties of the membrane material can be improved. Simultaneously, sodium aminobenzenesulfonate also undergoes crosslinking reactions with chloroalkyl functionalized polymers such as CMPSf, CMPES, and CMPI to generate tertiary amine groups, thus preparing a crosslinked ultrafiltration membrane rich in tertiary amines to form a zwitterionic structure. Structural adjustments to the ABS crosslinked zwitterionic ultrafiltration membrane further improve the hydrophilicity and antibacterial properties of the membrane material. Using this crosslinked polymer solution as the casting solution, a one-pot, solvent-controlled phase inversion method is employed to regulate the membrane structure and prepare a zwitterionic crosslinked ultrafiltration membrane. More specifically, the crosslinked structure can play a role in delaying phase separation during membrane formation, inhibiting macropore formation, forming a polymer membrane with a continuous pore structure, reducing mass transfer resistance, and improving the selectivity of the separation membrane.

[0007] Preferably, the chloroalkyl functionalized polymer is selected from any one of polychloromethylated polysulfone (CMPSf), chloromethylated polyethersulfone (CMPES), and chloromethylated polyimide (CMPI).

[0008] Preferably, the degree of chloromethyl substitution of the chloroalkyl functionalized polymer is 20% to 60%. It is understood that if the substitution is too high, the crosslinking reaction will be violent and difficult to control, while if the substitution is too low, the number of zwitterionic groups generated by crosslinking will be low, resulting in poor antibacterial effect.

[0009] Preferably, the degree of crosslinking between the chloroalkyl functionalized polymer and sodium p-aminobenzenesulfonate is 30% to 80%. It is understood that too low a degree of crosslinking will not generate a sufficient amount of zwitterionic groups, while too high a degree of crosslinking will cause the casting solution to gel and fail to form a film.

[0010] Preferably, the molar ratio of chloromethyl to sodium p-aminobenzenesulfonate in the added chloroalkyl functionalized polymer is 1:(2-8). It is understood that an excess of sodium p-aminobenzenesulfonate can promote the cross-linking reaction.

[0011] Preferably, the obtained zwitterionic crosslinked polymer ultrafiltration membrane has a completely sponge-like structure, without a distinct dense skin layer, finger-like pores, or large cavity structure; its pure water permeability is 300 L / m³. -2 h -1 bar -1 ~1000Lm -2 h -1 bar -1 The antibacterial rate against Escherichia coli is 81.7%–97%.

[0012] This invention provides a method for preparing a zwitterionic crosslinked polymer ultrafiltration membrane according to any of the above technical solutions, comprising the following steps:

[0013] The chloroalkyl functionalized polymer was dissolved in an appropriate amount of organic solvent, and sodium p-aminobenzenesulfonate was used as an additive and modifier. The degree of crosslinking was controlled by regulating the electrophilic substitution and crosslinking reaction between sodium p-aminobenzenesulfonate and chloromethyl groups in the chloroalkyl functionalized polymer. That is, the reaction was terminated when the reaction system reached a certain viscosity to prevent gelation. The reaction system at this point was used as the casting solution, and the film was prepared by a one-pot non-solvent controlled phase inversion method and post-treatment with dilute hydrochloric acid.

[0014] Preferably, the organic solvent is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide.

[0015] Preferably, the electrophilic substitution and crosslinking reactions are carried out at temperatures ranging from 40°C to 60°C, with reaction times ranging from 12 h to 24 h, and the viscosity of the reaction system controlled within the range of 2000 mPa·s to 5000 mPa·s. It is understood that when the reaction temperature exceeds 60°C, the reaction rate becomes too fast, making it difficult to control the reaction process; conversely, when the reaction temperature is below 40°C, the reaction rate becomes too slow, failing to achieve the desired reaction degree. Furthermore, by controlling the viscosity of the reaction system, it can be directly used as a casting solution for membrane preparation, avoiding gelation, solving the problem of insolubility and infusibility after crosslinking of the grafted polymer, and eliminating the need for separation and purification of the grafted polymer.

[0016] As a preferred method, the film-forming conditions for the one-pot non-solvent controlled phase inversion method are as follows: the casting solution is a cross-linking reaction system, the coagulation bath is selected from at least one of water, ethanol, DMF, DMAc and NMP, the coagulation bath temperature is 20℃~60℃, and the concentration of HCl is 0.1~2M mol.

[0017] Compared with the prior art, the advantages and positive effects of the present invention are as follows:

[0018] 1. This invention proposes a reaction-controlled phase inversion method. Its core idea lies in regulating the thermodynamics of the casting solution through chemical reactions, thereby controlling the polymer film-forming kinetics. Specifically, through delayed phase separation of the polymer, the morphology, micropore structure, and properties of the polymer ultrafiltration membrane are controlled, endowing the membrane with permanent hydrophilicity and antibacterial properties. This reaction-controlled phase inversion method differs from the traditional NIPS method by regulating the thermodynamics of the polymer casting solution, including viscosity, through chemical reactions.

[0019] 2. This invention uses sodium p-aminobenzenesulfonate as an additive and reactant to control the degree of crosslinking through nucleophilic substitution and crosslinking reactions with chloroalkyl functionalized polymers, employing a one-pot, solvent-free controlled phase inversion method to prepare polymer-based ultrafiltration membranes. This method operates under mild and environmentally friendly conditions, eliminates the need for crosslinked polymer separation and purification, and solves the problems of insolubility, infusibility, and inability to form membranes with crosslinked polymers. It provides a new approach for using crosslinked polymers to prepare porous polymer functional membranes.

[0020] 3. The method of this invention can prepare polymer supermembranes at relatively low polymer solid content (10%–20%), and the membrane structure is easy to control, allowing for the preparation of membranes with different microstructures depending on the degree of reaction. Compared with pure CMPSf, CMPES, or CMPI membranes, the introduction of sodium p-aminobenzenesulfonate leads to the introduction of hydrophilic zwitterionic groups through cross-linking reactions between molecular chains, which can permanently improve the hydrophilicity and antibacterial properties of the membrane. Attached Figure Description

[0021] Figure 1 Schematic diagram of the preparation of a zwitterionic ultrafiltration membrane of polymer (CMPSf) / sodium p-aminobenzenesulfonate crosslinked with a reaction-controlled phase inversion method;

[0022] Figure 2 The XPS spectrum of the zwitterionic polymer ultrafiltration membrane of CMPSf obtained by crosslinking CMPSf and ABS in Example 1 is shown. ABS crosslinked CMPSf is a polymer that did not undergo gelation reaction under low reaction conditions.

[0023] Figure 3 The infrared spectrum of the CMPSf zwitterionic polymer ultrafiltration membrane obtained by crosslinking CMPSf and ABS in Example 1 is shown.

[0024] Figure 4 The images show cross-sectional scanning electron microscope (SEM) images of the ABS cross-linked CMPsf zwitterionic polymer ultrafiltration membranes prepared in Examples 1-4 with cross-linking degrees of 30.5%, 38.6%, 48.6%, and 59.8%, respectively. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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.

[0026] Example 1

[0027] An ABS crosslinked CMPsf zwitterionic polymer ultrafiltration membrane was prepared by a reaction-controlled phase inversion method, as shown in the schematic diagram below. Figure 1As shown, the specific steps are as follows: 5g of CMPSf (chloromethyl substitution degree 20%) was added to 45g of DMAc (solid content 5 / (5+45)=10%) and stirred at room temperature for 8h to completely dissolve it. Subsequently, 2.5g of ABS was added to the above casting solution system CMPSf / ABS (10wt.%). The chloromethyl group in CMPSf and the amino group in ABS underwent an electrophilic substitution crosslinking reaction under heating conditions. The reaction was carried out at 45℃ for 20h, and the degree of crosslinking was 30.5%. The solution was degassed in a vacuum oven (50℃), and the homogeneous reaction solution was coated onto a glass plate with a thickness of 300μm using an automatic membrane coater. Subsequently, the membrane was removed and placed in a 0.3Mmol hydrochloric acid solution for 3h, and then immersed in a hydrogel bath at room temperature (25±1.5℃) to finally obtain an ABS crosslinked CMPSf zwitterionic polymer ultrafiltration membrane. The XPS spectrum and infrared spectrum of this zwitterionic crosslinked membrane are shown below. Figure 2-3 As shown, the cross-sectional scanning electron microscope image of the zwitterionic cross-linked membrane is as follows. Figure 4 As shown in the first row of figures, the surface openings are evenly distributed, and the cross-section has a completely sponge-like structure.

[0028] The ABS cross-linked CMPsf zwitterionic polymer ultrafiltration membrane obtained under the above conditions has a completely sponge-like structure in cross-section, with a porosity of 85.6%, a surface pore size of 10.05 nm, and a pure water permeability of 324.1 L / m³. 2 h bar -1 The antibacterial rate against Escherichia coli was 81.7%.

[0029] Example 2

[0030] An ABS-crosslinked CMPES zwitterionic polymer ultrafiltration membrane was prepared by a reaction-controlled phase inversion method, as follows: 6 g of CMPES (chloromethyl substitution degree 30%) was added to 44 g of DMAc and stirred at 50 °C for 8 h until completely dissolved. Subsequently, 2.5 g of ABS was added to the above casting solution system of CMPES / ABS (12 wt.%). The chloromethyl group in CMPES and the amino group in ABS underwent an electrophilic substitution crosslinking reaction under heating conditions. The reaction was carried out at 50 °C for 20 h, and the degree of crosslinking was 38.6%. The solution was degassed in a vacuum oven (50 °C), and the homogeneous reaction solution was coated onto a glass plate with a thickness of 300 μm using an automated membrane coater. Subsequently, the membrane was removed and placed in a 0.4 Mmol hydrochloric acid solution for 3 h, and then immersed in a condensation bath at room temperature (25 ± 1.5 °C) to finally obtain the ABS-crosslinked CMPES zwitterionic polymer ultrafiltration membrane. The cross-sectional scanning electron microscope image of the zwitterionic crosslinked membrane is shown below. Figure 4 As shown in the second row of the image.

[0031] The CMPES-based ultrafiltration membrane obtained under the above conditions has a completely sponge-like cross-section, a porosity of 77.7%, a surface pore size of 6.06 nm, and a pure water permeability of 535.8 L / m³. 2 h bar -1 The antibacterial rate against Escherichia coli was 87.40%.

[0032] Example 3

[0033] A CMPSf / ABS crosslinked zwitterionic polymer ultrafiltration membrane was prepared by a reaction-controlled phase inversion method, as follows: 8 g of CMPSf (chloromethyl substitution degree 40%) was added to 43 g of DMAc and stirred at 50 °C for 8 h until completely dissolved. Subsequently, 3.5 g of ABS was added to the above casting solution system of CMPSf / ABS (16 wt.%). The chloromethyl group in CMPSf and the amino group in ABS underwent an electrophilic substitution crosslinking reaction under heating conditions. The reaction was carried out at 50 °C for 20 h, and the degree of crosslinking was 48.6%. The solution was degassed in a vacuum oven (50 °C), and the homogeneous reaction solution was coated onto a glass plate with a thickness of 300 μm using an automated membrane coater. Subsequently, the membrane was removed and placed in a 0.5 mmol hydrochloric acid solution for 2 h, and then immersed in a condensation bath at room temperature (25 ± 1.5 °C) to obtain the CMPSf / ABS crosslinked zwitterionic polymer ultrafiltration membrane. The cross-sectional scanning electron microscope image of this zwitterionic crosslinked membrane is shown below. Figure 4 As shown in the third row of the image.

[0034] The CMPSf-based ultrafiltration membrane obtained under the above conditions has a completely sponge-like cross-section, a porosity of 87.7%, a surface pore size of 6.48 nm, and a pure water permeability of 420.8 L / m³. 2 h bar -1 The antibacterial rate against Escherichia coli was 85.4%.

[0035] Example 4

[0036] A CMPI / ABS crosslinked zwitterionic polymer ultrafiltration membrane was prepared by a reaction-controlled phase inversion method, as follows: 9 g of CMPI (chloromethyl substitution degree 50%) was added to 41 g of DMAc and stirred at 50 °C for 8 h until completely dissolved. Subsequently, 4.5 g of ABS was added to the above casting solution system containing CMPI (18 wt.%). The chloromethyl group in CMPI and the amino group in ABS underwent an electrophilic substitution crosslinking reaction under heating conditions. The reaction was carried out at 60 °C for 18 h, achieving a crosslinking degree of 59.8%. The solution was degassed in a vacuum oven (50 °C), and the homogeneous reaction solution was coated onto a glass plate with a thickness of 250 μm using an automated membrane coater. The membrane was then removed and placed in a 1 Mmol hydrochloric acid solution for 3 h, followed by immersion in a condensation bath at room temperature (25 ± 1.5 °C) to obtain the CMPI / ABS crosslinked zwitterionic polymer ultrafiltration membrane.

[0037] The CMPI-based ultrafiltration membrane obtained under the above conditions has a completely sponge-like cross-section, a porosity of 68.4%, a surface pore size of 6.84 nm, and a pure water permeability of 501.2 L / m³. 2 h bar -1 The antibacterial rate against Escherichia coli was 92.26%.

[0038] Example 5

[0039] A CMPSf / ABS crosslinked zwitterionic polymer ultrafiltration membrane was prepared by a reaction-controlled phase inversion method, as follows: 10 g of CMPSf (chloromethyl substitution degree of 60%) was added to 40 g of DMAc and stirred at 50 °C for 8 h until completely dissolved. Subsequently, 5.5 g of ABS was added to the above casting solution system CMPSf / ABS (20 wt.%). The chloromethyl group in CMPSf and the amino group in ABS underwent an electrophilic substitution crosslinking reaction under heating conditions. The reaction was carried out at 40 °C for 36 h, achieving a crosslinking degree of 70.6%. The solution was degassed in a vacuum oven (50 °C), and the homogeneous reaction solution was coated onto a glass plate using an automated membrane coater with a thickness of 300 μm through a doctor blade. Subsequently, the membrane was removed and placed in a 0.5 mmol hydrochloric acid solution for 3 h, followed by immersion in a hydrogel bath at room temperature (25 ± 1.5 °C) to finally obtain the CMPSf / ABS crosslinked zwitterionic polymer ultrafiltration membrane.

[0040] The CMPSf-based ultrafiltration membrane obtained under the above conditions has a completely sponge-like cross-section, a porosity of 82.6%, a surface pore size of 6.56 nm, and a pure water permeability of 405.6 L / m³. 2 h bar -1 The antibacterial rate against Escherichia coli was 96.43%.

[0041] Comparative Example 1

[0042] CMPSf polymer ultrafiltration membranes were prepared by a reaction-controlled phase inversion method, as follows: 6 g of CMPSf (chloromethyl substitution degree of 30%) was added to 44 g of DMAc and stirred at 50 °C for 8 h until completely dissolved. The solution was degassed in a vacuum oven (50 °C), and the homogeneous reaction solution was coated onto a glass plate with a thickness of 300 μm using an automated membrane coater. Subsequently, the membrane was immersed in a condensation bath at room temperature (25 ± 1.5 °C) to obtain the CMPSf polymer ultrafiltration membrane. A cross-sectional scanning electron microscope image of this zwitterionic crosslinked membrane is shown below. Figure 4 As shown in the fourth row of figures, it displays a relatively large surface aperture, and the cross-section has an asymmetric finger-like pore structure.

[0043] The CMPSf-based ultrafiltration membrane obtained under the above conditions has an asymmetric finger-like pore structure, a porosity of 64.4%, a surface pore size of 12.26 nm, and a pure water permeability of 47.5 L / m³. 2 h bar -1 The antibacterial rate against Escherichia coli was 13.24%.

[0044] Comparative Example 2

[0045] A CMPSf / ABS crosslinked zwitterionic polymer ultrafiltration membrane was prepared by a reaction-controlled phase inversion method, as follows: 10 g of CMPSf (chloromethyl substitution degree of 10%) was added to 40 g of DMAc and stirred at 50 °C for 8 h until completely dissolved. Subsequently, 5.5 g of ABS was added to the above casting solution system CMPSf / ABS (20 wt.%). The chloromethyl group in CMPSf and the amino group in ABS underwent an electrophilic substitution crosslinking reaction under heating conditions. The reaction was carried out at 40 °C for 36 h, with a crosslinking degree of 11.2%. The solution was degassed in a vacuum oven (50 °C), and the homogeneous reaction solution was coated onto a glass plate using an automated membrane coater with a thickness of 300 μm through a doctor blade. Subsequently, the membrane was removed and placed in a 0.5 mmol hydrochloric acid solution for 3 h, and then immersed in a condensation bath at room temperature (25 ± 1.5 °C) to finally obtain the CMPSf / ABS crosslinked zwitterionic polymer ultrafiltration membrane. The cross-sectional scanning electron microscope image of the zwitterionic crosslinked membrane is shown below. Figure 4 As shown in the fifth row of figures, it displays a relatively large surface aperture, and the cross-section has an asymmetric finger-like pore structure.

[0046] The CMPSf-based ultrafiltration membrane obtained under the above conditions has an asymmetric finger-like pore structure, a porosity of 73.4%, a surface pore size of 16.26 nm, and a pure water permeability of 97.5 L / m³. 2 h bar -1 The antibacterial rate against Escherichia coli was 29.74%.

[0047] Comparative Example 3

[0048] 9 g of CMPI (70% chloromethyl substitution) was added to 41 g of DMAc and stirred at 50 °C for 8 h until completely dissolved. Subsequently, 4.5 g of ABS was added to the above casting solution system containing CMPI (18 wt.%). The chloromethyl group in CMPI and the amino group in ABS underwent an electrophilic substitution crosslinking reaction under heating conditions. The reaction was carried out at 45 °C for 3 h, with a crosslinking degree of 21.8%. Subsequently, the crosslinking degree increased rapidly within 30 min, reaching a gel state, at which point film formation was impossible.

Claims

1. A method for preparing a zwitterionic crosslinked polymer ultrafiltration membrane with high-efficiency antibacterial properties, characterized in that, Includes the following steps: The chloroalkyl functionalized polymer was dissolved in an appropriate amount of organic solvent. Sodium p-aminobenzenesulfonate was used as an additive and modifier. The degree of crosslinking was controlled by adjusting the electrophilic substitution and crosslinking reaction between sodium p-aminobenzenesulfonate and the chloromethyl group in the chloroalkyl functionalized polymer. The reaction temperature of the electrophilic substitution and crosslinking reaction was 40℃~60℃, the reaction time was 12h~24h, and the viscosity of the reaction system was controlled in the range of 2000mPa·s~5000mPa·s. The reaction system at this time was used as the casting solution. After the film was formed, the film was taken out and placed in a 0.1~2Mmol hydrochloric acid solution for 2-3h. Then the film was immersed in a water condensation bath at room temperature. The chloroalkyl functionalized polymer is selected from any one of polychloromethylated polysulfone, chloromethylated polyethersulfone, and chloromethylated polyimide; The degree of chloromethyl substitution of the chloroalkyl functionalized polymer is 20% to 60%.

2. The preparation method according to claim 1, characterized in that, The organic solvent is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide.

3. The zwitterionic crosslinked polymer ultrafiltration membrane prepared by the preparation method according to claim 1 or 2, characterized in that, The degree of crosslinking between the chloroalkyl functionalized polymer and sodium p-aminobenzenesulfonate is 30% to 80%.

4. The zwitterionic crosslinked polymer ultrafiltration membrane according to claim 3, characterized in that, The molar ratio of chloromethyl to sodium p-aminobenzenesulfonate in the added chloroalkyl functionalized polymer is 1:(2~8).

5. The zwitterionic crosslinked polymer ultrafiltration membrane according to claim 3 or 4, characterized in that, The resulting zwitterionic crosslinked polymer ultrafiltration membrane has a completely sponge-like structure, without a distinct dense skin, finger-like pores, or large cavity structure.

6. The zwitterionic crosslinked polymer ultrafiltration membrane according to claim 5, characterized in that, The pure water permeability of the obtained zwitterionic crosslinked polymer ultrafiltration membrane is 300 L / m³. -2 h -1 bar -1 ~1000 L m -2 h -1 bar -1 The antibacterial rate of Escherichia coli is 81.7%~97%.

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