Chemically resistant polyphenylene sulfone nanofiltration membranes and methods for their preparation

Abstract

The application relates to the technical field of nanofiltration membranes, and discloses a chemical-resistant polyphenylene sulfone nanofiltration membrane and a preparation method thereof. A silicon-containing compound with good chemical stability is introduced into a functional layer of the nanofiltration membrane, so that the preparation process of the nanofiltration membrane is simple, energy consumption is low, and industrialized continuous production can be realized. Graphene is rich in oxygen-containing functional groups, which is beneficial to enhancing the hydrophilic capacity of the membrane; meanwhile, graphene itself has high mechanical strength, which is beneficial to enhancing the mechanical properties of the membrane. Concentrated sulfuric acid is used to sulfonate polyphenylene sulfone, so as to introduce sulfonic acid groups on the molecular chain of the polyphenylene sulfone, electrostatic interaction is generated between the sulfonic acid groups and the amino groups of the aminated graphene, an internal crosslinking network is established between the polyphenylene sulfone main chains, the stability of the nanofiltration membrane in a solvent and the chemical resistance of the membrane are improved, meanwhile, the separation performance, the anti-pollution performance and the mechanical properties of the nanofiltration membrane are greatly improved, and the application of the nanofiltration membrane in the fields of petroleum chemical industry and the like is widened.

Description

Technical Field

[0001] This invention relates to the field of nanofiltration membrane technology, specifically to a chemically resistant polyphenylene sulfone nanofiltration membrane and its preparation method. Background Technology

[0002] Nanofiltration membranes, also known as "loose" reverse osmosis membranes, have nanoscale pore sizes and high rejection rates for divalent and multivalent ions and small organic molecules. They are widely used in the separation and recycling of industrial wastewater, petrochemicals, fine chemicals, food and pharmaceutical processing, and other fields. In industries such as petrochemicals, many processes involve organic solvent systems. Compared with traditional separation methods, nanofiltration membrane operation not only achieves separation efficiently but also brings significant economic and environmental benefits. However, nanofiltration membranes generally have poor chemical stability in solvents and are prone to swelling, which can lead to partial dissolution and a decline in membrane performance, thus limiting the large-scale application of nanofiltration technology. In order to maintain membrane stability and long-term high efficiency in organic solvents, the research and development of chemically resistant nanofiltration membranes is of great significance for broadening the application of nanofiltration processes.

[0003] Since the chemical stability of the membrane material directly determines its solvent resistance, selecting high-performance membrane materials is crucial for preparing high-performance solvent-resistant nanofiltration membranes. Currently used membrane raw materials, such as polyvinylidene fluoride (PVDF) and polyamides, are linear polymers with large inter-chain spacing, resulting in poor desalination efficiency. Although cross-linking can form a three-dimensional structure, the hydrophilicity of the material significantly impacts membrane flux and antifouling performance. Cross-linking of the functional groups of hydrophilic cross-linking monomers consumes these functional groups, reducing the membrane's hydrophilicity, flux, and antifouling performance. Due to the inherent properties of nanofiltration materials, traditional nanofiltration membranes degrade in extreme chemical environments, especially in highly polar solvents. While existing technologies modify nanofiltration by adding inorganic particles to the casting solution, uneven particle dispersion and significant differences in the materials of the separation and support layers lead to different swelling degrees in organic solvents. This instability of the nanofiltration membrane greatly limits its application.

[0004] This invention improves the solvent resistance and mechanical properties of nanofiltration membranes by introducing chemically stable organosilicon into the biphenyl molecular chain, polymerizing it with diphenyl sulfone to form thermally stable polyphenylene sulfone, and then electrostatically interacting the introduced sulfonic acid groups with the amino groups of aminated graphene to form a cross-linked network system. Summary of the Invention

[0005] The technical problem solved by this invention is:

[0006] To address the shortcomings of existing technologies, this invention provides a chemically resistant polyphenylene sulfone nanofiltration membrane and its preparation method, thereby improving the chemical resistance and mechanical properties of the nanofiltration membrane.

[0007] The technical solution is as follows:

[0008] A method for preparing a chemical-resistant polyphenylene sulfone nanofiltration membrane, comprising the following steps: under a nitrogen atmosphere, sulfonated organosilicon polyphenylene sulfone and N,N-dimethylformamide are added to a reaction flask and stirred and dispersed. Then, aminated graphene is added to carry out a crosslinking reaction. Butanone and lithium chloride are then added and stirred at 40-55°C for 15-30 min to form a uniform and transparent casting solution. After standing to remove bubbles, the prepared casting solution is uniformly coated onto a dry and clean glass plate with a scraper. After coating, the glass plate is quickly immersed in a deionized water coagulation bath for 5-10 min to solidify and form a film, thereby obtaining a chemical-resistant polyphenylene sulfone nanofiltration membrane.

[0009] Furthermore, the ratio of the substances is as follows: sulfonated organosilicon polyphenyl sulfone: aminated graphene: N,N-dimethylformamide: butanone: lithium chloride: = 1g: 0.2-0.5g: 25-40mL: 0.8-1.2g: 0.09-0.15g.

[0010] Furthermore, the crosslinking reaction is carried out at a temperature of 50-90°C for 16-24 hours.

[0011] Further, the preparation method of the sulfonated organosilicon polyphenylene sulfone is carried out according to the following steps:

[0012] S1. Add 5,5'-dienyl-[1,1'-biphenyl]-2,2'-diol and tetrahydrofuran to a reaction flask equipped with a reflux device. After heating and stirring to dissolve, add an isopropanol solution of chloroplatinic acid. After nitrogen purging, add bis(trimethylsiloxymethylsilane), stir the reaction, concentrate after the reaction is complete, add methanol, precipitate, filter, wash with deionized water, and dry to obtain the organosilicon biphenyl hydroquinone intermediate. The preparation process is as follows:

[0013]

[0014] S2. Under a nitrogen atmosphere, sulfolane solvent is added to a reaction flask equipped with a condenser and a water separator. The temperature is raised to 75-85℃, and organosilicon biphenyl sulfone intermediate and 4,4'-dichlorodiphenyl sulfone are added. The mixture is stirred until fully dissolved, then potassium carbonate and toluene are added. When no water flows out of the water separator, the mixture is heated to carry out a polycondensation reaction. The temperature is then lowered to 110-130℃, and the mixture is poured into deionized water to precipitate the precipitate. After filtration and drying, organosilicon polyphenylene sulfone is obtained. The preparation process is as follows:

[0015]

[0016] S3. Add organosilicon polyphenylene sulfone and 1,2-dichloroethane to a reaction flask equipped with a dropping funnel. After stirring and dissolving, add concentrated sulfuric acid dropwise. React at 40-50℃ for 45-70 min, then concentrate, wash with deionized water until neutral, and dry to obtain sulfonated organosilicon polyphenylene sulfone.

[0017] Further, the ratio of each substance in step S1 is as follows: 5,5'-dienyl-[1,1'-biphenyl]-2,2'-diol: chloroplatinic acid: bis(trimethylsiloxymethylsilane): tetrahydrofuran = 1 mmol: 0.02-0.04 mmol: 2.05-2.3 mmol: 3-6 mL.

[0018] Furthermore, in step S1, the reaction temperature is 55-70℃ and the reaction time is 5-10h.

[0019] Furthermore, the ratio of each substance in step S2 is as follows: organosilicon biphenyl intermediate: 4,4'-dichlorodiphenyl sulfone: potassium carbonate = 0.9-1.1 mmol: 1 mmol: 0.02-0.05 mmol.

[0020] Furthermore, in step S2, the polycondensation reaction temperature is 200-220℃, and the polycondensation reaction time is 3-6h.

[0021] Furthermore, the ratio of each substance in step S3 is as follows: organosilicon polyphenyl sulfone: concentrated sulfuric acid: 1,2-dichloroethane = 1g: 0.4-0.8mL: 10-15mL.

[0022] Compared with the prior art, the technical effects of the present invention are reflected in:

[0023] This invention first involves a hydrosilylation reaction of 5,5'-dienyl-[1,1'-biphenyl]-2,2'-diol with bis(trimethylsiloxymethylsilane) under the catalysis of chloroplatinic acid to obtain an organosilicon biphenylol intermediate. This intermediate is then polymerized with 4,4'-dichlorodiphenyl sulfone to obtain organosilicon polyphenyl sulfone. Subsequently, a sulfonation reaction is carried out under the action of concentrated sulfuric acid to obtain sulfonated organosilicon polyphenyl sulfone. The sulfonic acid groups of the sulfonated polyphenyl sulfone interact electrostatically with the amino groups on the surface of the aminated graphene to achieve a crosslinking reaction between the polyphenyl sulfone and the aminated graphene. Then, butanone and lithium chloride are added to form a casting solution. After curing the film using an immersion precipitation phase inversion method, a chemically resistant polyphenyl sulfone nanofiltration membrane is obtained.

[0024] By introducing chemically stable silicon-containing compounds into the functional layers of nanofiltration membranes, the preparation process of silicon-containing solvent-resistant nanofiltration membranes becomes simple, energy-efficient, and capable of continuous industrial production. Graphene, rich in oxygen-containing functional groups, enhances the membrane's hydrophilicity, while its high mechanical strength further enhances the membrane's mechanical properties. Sulfonation of polyphenylene sulfone with concentrated sulfuric acid introduces sulfonic acid groups into its molecular chain, which crosslink with the amino groups of aminated graphene. Through electrostatic interactions, an internal crosslinked network structure is established between the polysulfone backbone. This crosslinked network structure significantly improves the membrane's stability in solvents and its solvent resistance, further enhancing the separation performance, antifouling performance, and chemical resistance of the nanofiltration membrane.

[0025] The formation of the cross-linked network structure gradually increases the viscosity of the casting solution system. When immersed in the gel bath and cured into a film, a dense surface layer is formed, which hinders the exchange between solvent and non-solvent, delays phase separation, and results in a thick and dense membrane layer. The higher the cross-linking density, the denser the membrane surface, enabling the nanofiltration membrane to have good separation effects on both polar aprotic solvents and protic solvents. The amino groups of amination graphene and the sulfonic acid of sulfonated polyphenylene sulfone undergo electrostatic interaction, realizing the cross-linking reaction between polyphenylene sulfone and amination graphene, improving their compatibility and effectively enhancing the interfacial bonding strength. Under tensile stress, the good compatibility and cross-linked network system can effectively buffer the external force, and the introduction of unique organosilicon structural units into the molecular chain of polyphenylene sulfone improves the tensile properties of the composite material, broadening its application range in fields involving organic systems such as petrochemicals. Detailed Implementation

[0026] The following detailed description, in conjunction with specific embodiments, further clarifies the invention. However, the scope and content of this patent are not limited to the following embodiments. Any variations or implementations that do not depart from the scope and content of this invention should be included within the technical scope of this invention.

[0027] Amine graphene: thickness 0.6-1.2nm, sheet diameter 0.5-5μm, amino content 4wt%.

[0028] Example 1

[0029] S1. Add 1 mmol of 5,5'-dienyl-[1,1'-biphenyl]-2,2'-diol and 5 mL of tetrahydrofuran to a reaction flask equipped with a reflux device. After heating and stirring to dissolve, add 0.03 mmol of isopropanol solution of chloroplatinic acid. After purging with nitrogen, add 2.2 mmol of bis(trimethylsiloxymethylsilane). React at 65 °C for 8 h, concentrate, add methanol, precipitate, filter, wash with deionized water, and dry to obtain organosilicon biphenyl intermediate.

[0030] S2. Under a nitrogen atmosphere, 45 mL of sulfolane solvent was added to a reaction flask equipped with a condenser and a water separator. The temperature was raised to 80 °C, and 1.05 mmol of organosilicon biphenyl sulfone intermediate and 1 mmol of 4,4'-dichlorodiphenyl sulfone were added. The mixture was stirred until fully dissolved, and 0.04 mmol of potassium carbonate and 12 mL of toluene were added. When no water flowed out of the water separator, the mixture was polycondensed at 210 °C for 5 h. Then the temperature was lowered to 120 °C, and the mixture was poured into deionized water. The precipitate was precipitated, filtered, and dried to obtain organosilicon polyphenylene sulfone.

[0031] S3. Add 10g of organosilicon polyphenylene sulfone and 120mL of 1,2-dichloroethane to a reaction flask equipped with a dropping funnel. After stirring and dissolving, add 6mL of concentrated sulfuric acid. React at 45℃ for 60min, concentrate, wash with deionized water until neutral, and dry to obtain sulfonated organosilicon polyphenylene sulfone.

[0032] S4. Under a nitrogen atmosphere, add 10g of sulfonated organosilicon polyphenylsulfone and 300mL of N,N-dimethylformamide to the reaction flask. After stirring and dispersing, add 2g of aminated graphene and carry out a crosslinking reaction at 85℃ for 20h. Then add 9g of butanone and 1.1g of lithium chloride and stir at 50℃ for 25min to form a uniform and transparent casting solution. Let it stand to remove bubbles, and then use a scraper to evenly coat the prepared casting solution onto a dry and clean glass plate. After coating, quickly immerse the glass plate in a deionized water coagulation bath for 8min to solidify and form a film, thus obtaining a chemical-resistant polyphenylsulfone nanofiltration membrane.

[0033] Example 2

[0034] S1. Add 2 mmol of 5,5'-dienyl-[1,1'-biphenyl]-2,2'-diol and 10 mL of tetrahydrofuran to a reaction flask equipped with a reflux device. After heating and stirring to dissolve, add 0.08 mmol of isopropanol solution of chloroplatinic acid. After purging with nitrogen, add 4.6 mmol of bis(trimethylsiloxymethylsilane). React at 55 °C for 5 h, concentrate, add methanol, precipitate, filter, wash with deionized water, and dry to obtain organosilicon biphenyl intermediate.

[0035] S2. Under a nitrogen atmosphere, 50 mL of sulfolane solvent was added to a reaction flask equipped with a condenser and a water separator. The temperature was raised to 85 °C, and 1.1 mmol of organosilicon biphenyl sulfone intermediate and 1 mmol of 4,4'-dichlorodiphenyl sulfone were added. The mixture was stirred until fully dissolved, and 0.05 mmol of potassium carbonate and 15 mL of toluene were added. When no water flowed out of the water separator, the mixture was polycondensed at 220 °C for 3 h. Then the temperature was lowered to 110 °C, and the mixture was poured into deionized water. The precipitate was precipitated, filtered, and dried to obtain organosilicon polyphenylene sulfone.

[0036] S3. Add 5g of organosilicon polyphenylene sulfone and 60mL of 1,2-dichloroethane to a reaction flask equipped with a dropping funnel. After stirring and dissolving, add 2.5mL of concentrated sulfuric acid. React at 50℃ for 45min, concentrate, wash with deionized water until neutral, and dry to obtain sulfonated organosilicon polyphenylene sulfone.

[0037] S4. Under a nitrogen atmosphere, add 10g of sulfonated organosilicon polyphenylsulfone and 400mL of N,N-dimethylformamide to the reaction flask. After stirring and dispersing, add 3g of aminated graphene and carry out a crosslinking reaction at 90℃ for 24h. Then add 10g of butanone and 0.9g of lithium chloride and stir at 55℃ for 15min to form a uniform and transparent casting solution. Allow it to stand to remove bubbles, and then use a scraper to evenly coat the prepared casting solution onto a dry and clean glass plate. After coating, quickly immerse the glass plate in a deionized water coagulation bath for 10min to solidify and form a film, thus obtaining a chemical-resistant polyphenylsulfone nanofiltration membrane.

[0038] Example 3

[0039] S1. Add 5 mmol of 5,5'-dienyl-[1,1'-biphenyl]-2,2'-diol and 25 mL of tetrahydrofuran to a reaction flask equipped with a reflux device. After heating and stirring to dissolve, add 0.1 mmol of isopropanol solution of chloroplatinic acid. After purging with nitrogen, add 10.3 mmol of bis(trimethylsiloxymethylsilane). React at 70 °C for 10 h, concentrate, add methanol, precipitate, filter, wash with deionized water, and dry to obtain organosilicon biphenyl intermediate.

[0040] S2. Under a nitrogen atmosphere, 50 mL of sulfolane solvent was added to a reaction flask equipped with a condenser and a water separator. The temperature was raised to 85 °C, and 1 mmol of organosilicon biphenyl sulfone intermediate and 1 mmol of 4,4'-dichlorodiphenyl sulfone were added. The mixture was stirred until fully dissolved, and 0.05 mmol of potassium carbonate and 12 mL of toluene were added. When no water flowed out of the water separator, the mixture was polycondensed at 200 °C for 6 h. Then the temperature was lowered to 125 °C, and the mixture was poured into deionized water. The precipitate was precipitated, filtered, and dried to obtain organosilicon polyphenylene sulfone.

[0041] S3. Add 3g of organosilicon polyphenylene sulfone and 30mL of 1,2-dichloroethane to a reaction flask equipped with a dropping funnel. After stirring and dissolving, add 1.2mL of concentrated sulfuric acid. React at 40℃ for 70min, concentrate, wash with deionized water until neutral, and dry to obtain sulfonated organosilicon polyphenylene sulfone.

[0042] S4. Under a nitrogen atmosphere, add 10g of sulfonated organosilicon polyphenylsulfone and 350mL of N,N-dimethylformamide to the reaction flask. After stirring and dispersing, add 4g of aminated graphene and carry out a crosslinking reaction at 75℃ for 24h. Then add 12g of butanone and 1g of lithium chloride and stir at 55℃ for 20min to form a uniform and transparent casting solution. Let it stand to remove bubbles, and then use a scraper to evenly coat the prepared casting solution onto a dry and clean glass plate. After coating, quickly immerse the glass plate in a deionized water coagulation bath for 5min to solidify and form a film, thus obtaining a chemical-resistant polyphenylsulfone nanofiltration membrane.

[0043] Example 4

[0044] S1. Add 10 mmol of 5,5'-dienyl-[1,1'-biphenyl]-2,2'-diol and 50 mL of tetrahydrofuran to a reaction flask equipped with a reflux device. After heating and stirring to dissolve, add 0.3 mmol of isopropanol solution of chloroplatinic acid. After purging with nitrogen, add 21 mmol of bis(trimethylsiloxymethylsilane). React at 65 °C for 9 h, concentrate, add methanol, precipitate, filter, wash with deionized water, and dry to obtain organosilicon biphenyl intermediate.

[0045] S2. Under a nitrogen atmosphere, 35 mL of sulfolane solvent was added to a reaction flask equipped with a condenser and a water separator. The temperature was raised to 80 °C, and 0.9 mmol of organosilicon biphenyl phenol intermediate and 1 mmol of 4,4'-dichlorodiphenyl sulfone were added. The mixture was stirred until fully dissolved, and 0.25 mmol of potassium carbonate and 13 mL of toluene were added. When no water flowed out of the water separator, the mixture was polycondensed at 215 °C for 5 h. Then the temperature was lowered to 130 °C, and the mixture was poured into deionized water. The precipitate was precipitated, filtered, and dried to obtain organosilicon polyphenylene sulfone.

[0046] S3. Add 10g of organosilicon polyphenylene sulfone and 140mL of 1,2-dichloroethane to a reaction flask equipped with a dropping funnel. After stirring and dissolving, add 6mL of concentrated sulfuric acid. React at 50℃ for 55min, concentrate, wash with deionized water until neutral, and dry to obtain sulfonated organosilicon polyphenylene sulfone.

[0047] S4. Under a nitrogen atmosphere, add 10g of sulfonated organosilicon polyphenylsulfone and 250mL of N,N-dimethylformamide to the reaction flask. After stirring and dispersing, add 5g of aminated graphene and carry out a crosslinking reaction at 60℃ for 18h. Then add 11g of butanone and 1.3g of lithium chloride and stir at 50℃ for 25min to form a uniform and transparent casting solution. Allow it to stand to remove bubbles, and then use a scraper to evenly coat the prepared casting solution onto a dry and clean glass plate. After coating, quickly immerse the glass plate in a deionized water coagulation bath for 8min to solidify and form a film, thus obtaining a chemical-resistant polyphenylsulfone nanofiltration membrane.

[0048] Comparative Example 1

[0049] S1. Under a nitrogen atmosphere, 45 mL of sulfolane solvent was added to a reaction flask equipped with a condenser and a water separator. The temperature was raised to 80 °C, and 0.9 mmol of biphenyl hydroquinone and 1 mmol of 4,4'-dichlorodiphenyl sulfone were added. The mixture was stirred until fully dissolved, and 0.04 mmol of potassium carbonate and 12 mL of toluene were added. When no water flowed out of the water separator, the mixture was polycondensed at 210 °C for 5 h. Then the temperature was lowered to 120 °C, and the mixture was poured into deionized water. The precipitate was precipitated, filtered, and dried to obtain polyphenylene sulfone.

[0050] S2. Under a nitrogen atmosphere, add 10g of polyphenylene sulfone and 300mL of N,N-dimethylformamide to the reaction flask. After stirring and dispersing, add 9g of butanone and 1.1g of lithium chloride. Stir at 50℃ for 25min to form a uniform and transparent casting solution. Let it stand to remove bubbles. Use a scraper to evenly coat the prepared casting solution onto a dry and clean glass plate. After coating, quickly immerse the glass plate in a deionized water coagulation bath for 8min to solidify and form a film, thus obtaining a polyphenylene sulfone nanofiltration membrane.

[0051] Comparative Example 2

[0052] Under a nitrogen atmosphere, 10g of sulfonated organosilicon polyphenylsulfone (prepared in Example 1) and 300mL of N,N-dimethylformamide were added to a reaction flask. After stirring and dispersing, 9g of butanone and 1.1g of lithium chloride were added. The mixture was stirred at 50°C for 25 minutes to form a uniform and transparent casting solution. After standing to remove bubbles, the prepared casting solution was evenly coated onto a dry and clean glass plate with a scraper. After coating, the glass plate was quickly immersed in a deionized water coagulation bath for 8 minutes to solidify and form a film, thus obtaining a polyphenylsulfone nanofiltration membrane.

[0053] Comparative Example 3

[0054] Under a nitrogen atmosphere, 10g of organosilicon polyphenyl sulfone (prepared in Example 1) and 300mL of N,N-dimethylformamide were added to a reaction flask. After stirring and dispersing, 2g of aminated graphene was added, and a crosslinking reaction was carried out at 85°C for 20h. Then, 9g of butanone and 1.1g of lithium chloride were added, and the mixture was stirred at 50°C for 25min to form a uniform and transparent casting solution. After standing to remove bubbles, the prepared casting solution was evenly coated onto a dry and clean glass plate with a scraper. After coating, the glass plate was quickly immersed in a deionized water coagulation bath for 8min to solidify and form a film, thus obtaining a polyphenyl sulfone nanofiltration membrane.

[0055] Comparative Example 4

[0056] S1. Add 10g of polyphenylene sulfone (prepared from Comparative Example 1) and 120mL of 1,2-dichloroethane to a reaction flask equipped with a dropping funnel. After stirring and dissolving, add 6mL of concentrated sulfuric acid. React at 45℃ for 60min, concentrate, wash with deionized water until neutral, and dry to obtain sulfonated polyphenylene sulfone.

[0057] S2. Under a nitrogen atmosphere, add 10g of sulfonated polyphenylene sulfone and 300mL of N,N-dimethylformamide to the reaction flask. After stirring and dispersing, add 2g of aminated graphene and carry out a crosslinking reaction at 85℃ for 20h. Then add 9g of butanone and 1.1g of lithium chloride and stir at 50℃ for 25min to form a uniform and transparent casting solution. Allow it to stand to remove bubbles. Use a scraper to evenly coat the prepared casting solution onto a dry and clean glass plate. After coating, quickly immerse the glass plate in a deionized water coagulation bath for 8min to solidify and form a film, thus obtaining a polyphenylene sulfone nanofiltration membrane.

[0058] Solvent resistance test: The solvent resistance of the membrane is expressed as the mass retention rate. The nanofiltration membrane to be tested is placed in a vacuum drying oven and dried thoroughly. Then, a 2cm×2cm membrane piece is cut and weighed as m0. It is then immersed in different solvents at 25℃ for 7 days each. After removal, the solvent is thoroughly washed away with deionized water, and the membrane is thoroughly dried and weighed as m1. The mass retention rate is calculated as (m1 / m0)×100%. The higher the mass retention rate, the worse the solubility and the better the solvent resistance.

[0059] Table 1. Quality retention rates of Examples 1-4 and Comparative Examples 1-4

[0060]

[0061] As shown in the test results in the table above, Examples 1-4 exhibited good mass retention rates in different solvents. The mass retention rates in N-methylpyrrolidone were above 96%, in dimethyl sulfoxide above 97%, and in tetrahydrofuran and chloroform above 99%, with the highest reaching 100%. This indicates that the prepared nanofiltration membranes did not undergo significant dissolution in different solvents, demonstrating good solvent resistance. This is because, on the one hand, organosilicon has stable chemical bonds and low surface energy, exhibiting solvent resistance characteristics; on the other hand, the sulfonic acid of sulfonated polyphenylene sulfone interacts electrostatically with the amino group of aminated graphene to form a cross-linked network system. When solidified into a film, this forms a dense surface layer, hindering the exchange between solvent and non-solvent, delaying phase separation, and greatly improving the stability of the membrane in solvents, thus enhancing the solvent resistance of the nanofiltration membrane and consequently its chemical resistance.

[0062] Comparative Example 1 is a common polyphenylene sulfone nanofiltration membrane, which is completely soluble in several solvents and has the worst solvent resistance; Comparative Example 2 is a sulfonated silicone polyphenylene sulfone nanofiltration membrane, and Comparative Example 3 is a silicone polyphenylene sulfone nanofiltration membrane. Neither of them has formed an electrostatic cross-linked structure with graphene, and their solvent resistance is average; Comparative Example 4 is a common polyphenylene sulfone nanofiltration membrane cross-linked with aminated graphene, but it does not contain a solvent-resistant silicone structure, and its solvent resistance is not as good as the examples.

[0063] Tensile property test: The tensile properties of the composite material were tested using an electronic tensile testing machine. Before the test, the nanofiltration membrane was cut into dumbbell-shaped specimens of 50mm×5mm×2mm. The tensile test speed was 10mm / min and the test temperature was 25℃.

[0064] Table 2 Tensile strength test

[0065]

[0066] As shown in the test data in the table above, the tensile strength of the nanofiltration membranes in Examples 1-4 reached a maximum of 216.4 MPa, which is significantly improved compared to the ordinary polyphenylene sulfone nanofiltration membrane in Comparative Example 1. This is because the amino group of the amination graphene and the sulfonic acid of the sulfonated polyphenylene sulfone undergo electrostatic interaction, realizing the cross-linking reaction between polyphenylene sulfone and amination graphene, improving their compatibility and effectively improving the interfacial bonding strength between them. Under tensile stress, the good compatibility and cross-linked network system can effectively buffer the external force, and the introduction of unique organosilicon structural units into the molecular chain of polyphenylene sulfone improves the tensile properties of the composite material. Comparative Example 2 is a sulfonated organosilicon polyphenylene sulfone nanofiltration membrane, and Comparative Example 3 is an organosilicon polyphenylene sulfone nanofiltration membrane. Neither of them has generated an electrostatic cross-linked structure, but both contain organosilicon, and their tensile strength is higher than that of Comparative Example 1. Comparative Example 4 is an ordinary polyphenylene sulfone nanofiltration membrane cross-linked with amination graphene, but without organosilicon. Its tensile strength is stronger than that of Comparative Examples 2 and 3, but not as strong as that of Example 1.

[0067] The above description is only a preferred embodiment of the present invention. For those skilled in the art, there will be changes in the specific implementation and application scope based on the ideas of the present invention. The content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for preparing a chemically resistant polyphenylene sulfone nanofiltration membrane, characterized in that, The preparation method is carried out according to the following steps: under a nitrogen atmosphere, sulfonated organosilicon polyphenyl sulfone and N,N-dimethylformamide are added to a reaction flask and stirred and dispersed. Then, amine graphene is added to carry out a cross-linking reaction. Then, butanone and lithium chloride are added and stirred at 40-55℃ for 15-30 min to form a uniform and transparent casting solution. After standing to remove bubbles, the prepared casting solution is evenly coated onto a dry and clean glass plate with a scraper. After the coating is completed, the glass plate is quickly immersed in a deionized water coagulation bath for 5-10 min to solidify and form a film, thereby obtaining a chemical-resistant polyphenyl sulfone nanofiltration membrane. The preparation method of the sulfonated organosilicon polyphenylene sulfone is carried out according to the following steps: S1. Add 5,5'-dienyl-[1,1'-biphenyl]-2,2'-diol and tetrahydrofuran to a reaction flask equipped with a reflux device. After heating and stirring to dissolve, add an isopropanol solution of chloroplatinic acid. After nitrogen purging, add bis(trimethylsiloxymethylsilane) and stir to react. After the reaction is complete, concentrate the solution, add methanol to precipitate the precipitate, filter, wash with deionized water, and dry to obtain the organosilicon biphenyl intermediate. S2. Under a nitrogen atmosphere, add sulfolane solvent to a reaction flask equipped with a condenser and a water separator, heat to 75-85℃, add organosilicon biphenyl phenol intermediate and 4,4'-dichlorodiphenyl sulfone, stir until fully dissolved, add potassium carbonate and toluene, and when no water flows out of the water separator, heat to carry out polycondensation reaction, then cool to 110-130℃, pour into deionized water, precipitate out, filter, and dry to obtain organosilicon polyphenylene sulfone; S3. Add organosilicon polyphenylene sulfone and 1,2-dichloroethane to a reaction flask equipped with a dropping funnel. After stirring and dissolving, add concentrated sulfuric acid dropwise. React at 40-50℃ for 45-70 min, concentrate, wash with deionized water until neutral, and dry to obtain sulfonated organosilicon polyphenylene sulfone. The ratio of each substance in step S1 is as follows: 5,5'-dienyl-[1,1'-biphenyl]-2,2'-diol: chloroplatinic acid: bis(trimethylsiloxymethylsilane): tetrahydrofuran = 1 mmol: 0.02-0.04 mmol: 2.05-2.3 mmol: 3-6 mL; The ratio of each substance in step S2 is as follows: organosilicon biphenyl phenol intermediate: 4,4'-dichlorodiphenyl sulfone: potassium carbonate = 0.9-1.1 mmol: 1 mmol: 0.02-0.05 mmol; The ratio of each substance in step S3 is as follows: organosilicon polyphenyl sulfone: concentrated sulfuric acid: 1,2-dichloroethane = 1g: 0.4-0.8mL: 10-15mL.

2. The method for preparing the chemically resistant polyphenylene sulfone nanofiltration membrane according to claim 1, characterized in that, The proportions of the substances are as follows: sulfonated organosilicon polyphenyl sulfone: aminated graphene: N,N-dimethylformamide: butanone: lithium chloride: = 1g: 0.2-0.5g: 25-40mL: 0.8-1.2g: 0.09-0.15g.

3. The method for preparing the chemically resistant polyphenylene sulfone nanofiltration membrane according to claim 1, characterized in that, The crosslinking reaction is carried out at a temperature of 50-90℃ for 16-24 hours.

4. The method for preparing the chemically resistant polyphenylene sulfone nanofiltration membrane according to claim 1, characterized in that, In step S1, the reaction temperature is 55-70℃ and the reaction time is 5-10h.

5. The method for preparing the chemically resistant polyphenylene sulfone nanofiltration membrane according to claim 1, characterized in that, In step S2, the polycondensation reaction temperature is 200-220℃ and the polycondensation reaction time is 3-6h.

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