A method for preparing a nonwoven fabric-reinforced zwitterion-functionalized polymer composite membrane

Abstract

The application provides a preparation method of a non-woven fabric reinforced zwitterionic functionalized polymer composite membrane. Specifically, first, an amine-terminated tertiary amine compound is grafted onto polystyrene / maleic anhydride (SMA) to prepare a SMA grafted amphiphilic polymer containing a tertiary amine group through an amidation reaction, then the SMA grafted amphiphilic polymer is blended with a high molecular polymer to prepare a casting solution, then the casting solution is scraped on a non-woven fabric as a substrate to prepare a polymer / non-woven fabric composite membrane containing a rich tertiary amine group on the surface by using a non-solvent induced phase inversion method, and finally, a non-woven fabric reinforced zwitterionic functionalized polymer composite membrane containing sulfonic acid anion groups and quaternary ammonium salt cation groups on the surface of the membrane is prepared through in-situ reaction of a sulfolactone with the tertiary amine group.

Description

Technical Field

[0001] This invention belongs to the field of functional polymer membrane separation technology, and specifically relates to a method for preparing a nonwoven-reinforced zwitterionic functionalized polymer / NWF composite membrane. Background Technology

[0002] Industrial development and increased human activity have generated a large amount of oily wastewater, which is not only complex in composition but also poses a serious threat to the ecological environment and water resource security, posing a significant challenge to the scientific and industrial communities. Therefore, the effective recycling and utilization of water and oil resources is of great importance for alleviating the increasingly prominent problems of resource scarcity and environmental pollution, and promoting sustainable economic development.

[0003] Oilfield wastewater typically has high mineralization, containing not only crude oil at a certain concentration but also surfactants, polymers, and other oil displacement agents, forming stable oil-in-water emulsions. Currently, conventional treatment methods include gravity sedimentation, adsorption, and chemical methods. Gravity sedimentation is time-consuming and requires bulky equipment, making it difficult to efficiently treat emulsified oil. Adsorption methods use adsorbents with high regeneration and disposal costs, limiting large-scale application. Chemical methods typically employ reverse demulsifiers (such as positively charged polymeric surfactants) + flocculants (such as polyaluminum chloride and polyferric chloride) to disrupt the oil-water interface film, further achieving oil-water separation. However, suspended solids, emulsified oil, and residual oil displacement polymers (partially hydrolyzed polyacrylamide, HPAM) in oilfield wastewater are negatively charged and easily react with cationic demulsifiers and flocculants to form polymer-containing sludge, causing equipment blockage and secondary pollution, affecting normal oilfield production.

[0004] Membrane separation processes require no chemical reagents and offer advantages such as low energy consumption, high separation efficiency, and simple processes, making them a highly efficient and green separation method widely used in oil-water separation. For example, Chinese invention patent CN109316981B discloses a method for preparing a superhydrophilic polymer membrane with demulsification function, achieving highly efficient oil-water separation. However, because the demulsifier is bonded to the base membrane via ester groups, it cannot be applied to the treatment of alkaline oily wastewater. Furthermore, low permeate flux and poor contamination by the original oil are current bottlenecks in the industrial treatment of oily wastewater using membrane separation technology.

[0005] As is well known, zwitterionic materials refer to materials that simultaneously contain cation and anion groups in a single molecule. Their strong hydrophilicity can be used to construct hydration layers, thereby improving the permeability and antifouling properties of membranes.

[0006] Based on the aforementioned research, this invention combines zwitterionic functionalization with membrane separation technology. First, a terminal tertiary amine compound is grafted onto polystyrene / maleic anhydride (SMA) via a nucleophilic substitution reaction. Then, a polymer membrane containing tertiary amine groups is prepared using a solvent-free phase inversion method. Next, a zwitterionic functionalized polymer membrane is prepared by in-situ reaction between a lactone and the tertiary amine groups. The zwitterionic functionalized membrane forms a stable superhydrophilic layer on its surface through electrostatic interactions and hydrogen bonding, thereby effectively reducing membrane fouling, increasing permeate flux, and maintaining excellent separation performance in complex oil-water environments. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the purpose of this invention is to provide a method for preparing a nonwoven-reinforced zwitterionic functionalized polymer composite membrane.

[0008] The present invention describes a method for preparing a nonwoven fabric-reinforced zwitterionic functionalized polymer composite film, characterized by the following steps: (1) dissolving polystyrene / maleic anhydride in organic solvent A, stirring at 40~90 ºC until dissolved, then slowly adding a terminal amine tertiary amine compound dropwise, stirring at 40~90 ºC for 1~10 h; after the reaction is completed, removing the solvent and excess terminal amine tertiary amine compound by rotary evaporation to obtain an SMA-grafted amphiphilic polymer containing tertiary amine groups; (2) blending the SMA-grafted amphiphilic polymer containing tertiary amine groups with a polymer, dissolving in organic solvent B at 60~90 ºC to prepare a casting solution, degassing and pouring onto the nonwoven fabric, using a spacing of 100~300 mm. A micrometer-sized scraper was used to scrape a liquid film, which was then transferred to a coagulation bath to prepare a polymer / nonwoven composite film with abundant tertiary amine groups on the surface by a non-solvent-induced phase inversion method; (3) The polymer / nonwoven composite film with abundant tertiary amine groups on the surface was immersed in an organic solvent C containing sulfonyl lactone and reacted at 10~70 ºC for 2-12 h. After the reaction was completed, it was washed with deionized water to obtain a nonwoven reinforced zwitterionic functionalized polymer composite film; The molecular weight of the SMA is between 3000 and 180000. The mass content of the acid anhydride is 3-30% between Da and 30%; the terminal amine tertiary amine compound is a class of substances that simultaneously possess primary and tertiary amines, including at least one of N,N-dimethylethylenediamine, 3-dimethylamino-1-propylamine, N,N-dimethyl-1,4-butanediamine, or N,N-dimethyl-1,6-hexanediamine; the polymer is at least one of polyvinylidene fluoride, polyacrylonitrile, polypropylene, polysulfone, polyethersulfone, cellulose acetate, regenerated cellulose, polyvinyl alcohol, polyvinyl alcohol copolymer, and chitosan; the organic solvent A is at least one of tetrahydrofuran, dioxane, ethanol, propanol, butanol, dichloromethane, and chloroform; the organic solvent B is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, or dimethyl sulfoxide; the organic solvent C is diethyl ether, methyl ether, dimethyl sulfoxide ... At least one of alcohol, ethanol, isopropanol, carbon tetrachloride, or acetone; in step (1), the amount of polystyrene / maleic anhydride and the terminal amine tertiary amine compound is controlled such that the molar ratio of the anhydride in polystyrene / maleic anhydride to the terminal amine group in the terminal amine tertiary amine compound is 1:0.5~1.1; in step (2), the mass ratio of the SMA-grafted amphiphilic polymer containing tertiary amine groups to the polymer is 0.1~1:1, and the mass of the polymer is 8~30% of the total mass of the SMA-grafted amphiphilic polymer containing tertiary amine groups and the polymer; in step (3), the sulfonyl lactone is propanesulfonyl lactone or butanesulfonyl lactone, and its mass concentration in organic solvent C is 0.1~10%; the coagulation bath is one or a combination of several of water, ethanol, methanol, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

[0009] This invention also provides a nonwoven-reinforced zwitterionic functionalized polymer composite membrane prepared by the above-described method. The composite membrane has a pure water contact angle of less than 30° and an underwater oil contact angle of greater than 150°.

[0010] Compared with the prior art, the present invention has the following advantages: the non-woven fabric as a substrate enhances the mechanical strength of the membrane, making the membrane applicable to practical scenarios; secondly, after the amphoteric ionization treatment of the membrane surface, the salt resistance and hydrophilicity of the membrane are enhanced, improving the water flux and antifouling properties of the membrane, and it has good prospects for practical application. Detailed Implementation

[0011] The following embodiments are intended to enable those skilled in the art to gain a more comprehensive understanding of the present invention, but do not limit the invention in any way.

[0012] Example 1

[0013] (1) Dissolve 10 g of polystyrene / maleic anhydride (SMA, average molecular weight 120,000, anhydride content 25%) in 30 g of ethanol and stir at 50 °C until dissolved; slowly add N,N-dimethylethylenediamine to the solution and stir for 8 h. After the reaction is complete, remove the solvent and excess N,N-dimethylethylenediamine by rotary evaporation to obtain the SMA-grafted amphiphilic polymer containing tertiary amine groups, abbreviated as DMEDA-g-SMA;

[0014] (2) 2.6 g of DMEDA-g-SMA amphiphilic polymer and 3.2 g of polyethersulfone (PES) were dissolved in 20 g of N,N-dimethylformamide at 70 °C to prepare a casting solution. After degassing, the solution was poured onto a nonwoven fabric and a liquid film was formed using a 250 µm doctor blade. The film was then transferred to ethanol / water and prepared by a non-solvent phase inversion method to obtain a DMEDA-g-SMA / PES / NWF composite membrane.

[0015] (3) The DMEDA-g-SMA / PES / NWF composite membrane was immersed in the ethanol solvent of butyryl lactone and reacted at 50 °C for 10 h. After the reaction was completed, it was washed three times with deionized water to obtain the B4@DMEDA / PES / NWF composite membrane.

[0016] (4) The B4@DMEDA / PES / NWF composite membrane has a pure water contact angle of 28º, an underwater oil (kerosene) contact angle of 156º, and a pure water flux of 1289 L·m at 0.1 MPa. -2 ·h -1 Oilfield wastewater with an oil content of 1000 mg / L was treated with a B4@DMEDA / PES / NWF composite membrane, and the crude oil removal rate in the water reached 98.1%.

[0017] Example 2

[0018] (1) Dissolve 10 g of polystyrene / maleic anhydride (average molecular weight 100,000, anhydride content 18%) in 30 g of tetrahydrofuran and stir at 60 °C until dissolved; slowly add 3-dimethylamino-1-propylamine to the solution and stir for 8 h. After the reaction is complete, remove the solvent and excess 3-dimethylamino-1-propylamine by rotary evaporation to obtain the SMA-grafted amphiphilic polymer containing tertiary amine groups, abbreviated as DMPA-g-SMA;

[0019] (2) 2.6 g of DMPA-g-SMA amphiphilic polymer and 3.2 g of polysulfone (PSF) were dissolved in 20 g of N,N-dimethylacetamide at 70 °C to prepare a casting solution. After degassing, the solution was poured onto a nonwoven fabric and a liquid film was formed using a 200 µm doctor blade. The film was then transferred to water and a DMPA-g-SMA / PSF / NWF composite membrane was prepared by a non-solvent phase inversion method.

[0020] (3) The DMPA-g-SMA / PSF / NWF composite membrane was immersed in methanol solvent of propanesulfonyl lactone and reacted at 60 °C for 10 h. After the reaction was completed, it was washed three times with deionized water to obtain B3@DMPA / PSF / NWF composite membrane.

[0021] (4) The B3@DMPA / PSF / NWF composite membrane has a pure water contact angle of 24º, an underwater oil (kerosene) contact angle of 162º, and a pure water flux of 1344 L·m at 0.1 MPa. -2 ·h -1 Oilfield wastewater with an oil content of 1000 mg / L was treated with a B3@SMA / PSF / NWF composite membrane, and the crude oil removal rate in the water reached 98.3%.

[0022] Example 3

[0023] (1) Dissolve 10 g of polystyrene / maleic anhydride (average molecular weight 100,000, anhydride content 20%) in 30 g of dichloromethane and stir at 60 °C until dissolved; slowly add N,N-dimethyl-1,6-hexanediamine to the solution and stir for 8 h. After the reaction is complete, remove the solvent and excess N,N-dimethyl-1,6-hexanediamine by rotary evaporation to obtain the SMA-grafted amphiphilic polymer containing tertiary amine groups, abbreviated as DMDHA-g-SMA;

[0024] (2) 2.6 g of DMHDA-g-SMA amphiphilic polymer and 3.2 g of polyvinylidene fluoride (PVDF) were dissolved in 20 g of dimethyl sulfoxide at 70 °C to prepare a casting solution. After degassing, the solution was poured onto a nonwoven fabric and a liquid film was formed using a 200 µm doctor blade. The film was then transferred to dimethylacetamide / water and prepared by a non-solvent phase inversion method to obtain a DMHDA-g-SMA / PVDF / NWF composite membrane.

[0025] (3) The DMDHA-g-SMA / PVDF / NWF composite membrane was immersed in methanol solvent of butyryl lactone and reacted at 60 °C for 10 h. After the reaction was completed, it was washed three times with deionized water to obtain B4@DMHDA / PVDF / NWF composite membrane.

[0026] (4) The B4@DMHDA / PVDF / NWF composite membrane has a pure water contact angle of 26º, an underwater oil (kerosene) contact angle of 160º, and a pure water flux of 1312 L·m at 0.1MPa. -2 ·h -1 Oilfield wastewater with an oil content of 1000 mg / L was treated with a B4@DMHDA / PVD / NWF composite membrane, and the crude oil removal rate in the water reached 99.3%.

[0027] Comparative Example 1

[0028] (1) Dissolve 10 g of polystyrene / maleic anhydride (SMA, average molecular weight 120,000, anhydride content 25%) in 30 g of ethanol and stir at 50 °C until dissolved; slowly add N,N-dimethylethylenediamine to the solution and stir for 8 h. After the reaction is complete, remove the solvent and excess N,N-dimethylethylenediamine by rotary evaporation to obtain the SMA-grafted amphiphilic polymer containing tertiary amine groups, abbreviated as DMEDA-g-SMA;

[0029] (2) 2.6 g of DMEDA-g-SMA amphiphilic polymer and 3.2 g of polyethersulfone (PES) were dissolved in 20 g of N,N-dimethylformamide at 70 °C to prepare a casting solution. After degassing, the solution was poured onto a nonwoven fabric and a liquid film was formed using a 250 µm doctor blade. The film was then transferred to ethanol / water and prepared by a non-solvent phase inversion method to obtain a DMEDA-g-SMA / PES / NWF composite membrane.

[0030] (3) The DMEDA-g-SMA / PES / NWF membrane has a pure water contact angle of 35º and an underwater oil (kerosene) contact angle of 142º. The pure water flux at 0.1 MPa is 325 L·m. -2 ·h -1Oilfield wastewater with an oil content of 1000 mg / L was treated with a DMEDA-g-SMA / PES / NWF composite membrane, and the crude oil removal rate in the water was 92.6%.

Claims

1. A method for preparing a nonwoven-reinforced zwitterionic functionalized polymer composite membrane, characterized in that: The method includes the following steps: (1) Dissolve polystyrene / maleic anhydride in organic solvent A and stir at 40~90 ºC until dissolved. Then slowly add the terminal amine tertiary amine compound dropwise and stir at 40~90 ºC for 1~10 h. After the reaction is complete, remove the solvent and excess terminal amine tertiary amine compound by rotary evaporation to obtain SMA grafted amphiphilic polymer containing tertiary amine groups. (2) SMA grafted with amphiphilic polymers containing tertiary amine groups and polymers are blended and dissolved in organic solvent B at 60~90 ºC to prepare a casting solution. After degassing, the solution is poured onto nonwoven fabric and scraped into a liquid film using a doctor blade. Then, it is transferred to a coagulation bath and a polymer / nonwoven fabric composite film with abundant tertiary amine groups on the surface is prepared by a non-solvent phase inversion method. (3) The polymer / nonwoven composite film with abundant tertiary amine groups on its surface is immersed in an organic solvent C containing sulfonyl lactone and reacted at 10~70 ºC for 2-12 h. After the reaction is completed, it is washed with deionized water to obtain a nonwoven reinforced zwitterionic functionalized polymer composite film. The sulfonyl lactone is propanesulfonyl lactone or butanesulfonyl lactone.

2. The method for preparing a nonwoven-reinforced zwitterionic functionalized polymer composite membrane according to claim 1, characterized in that: The molecular weight of the SMA is between 3,000 and 180,000 Da, and the anhydride content is 3% to 30%.

3. The method for preparing a nonwoven-reinforced zwitterionic functionalized polymer composite membrane according to claim 1, characterized in that: The terminal amine tertiary amine compound is a class of substances that simultaneously possess both primary and tertiary amine properties, including at least one of N,N-dimethylethylenediamine, 3-dimethylamino-1-propanediamine, N,N-dimethyl-1,4-butanediamine, or N,N-dimethyl-1,6-hexanediamine.

4. The method for preparing a nonwoven-reinforced zwitterionic functionalized polymer composite membrane according to claim 1, characterized in that: The polymer is at least one of polyvinylidene fluoride, polyacrylonitrile, polypropylene, polysulfone, polyethersulfone, cellulose acetate, regenerated cellulose, polyvinyl alcohol, polyvinyl alcohol copolymer, and chitosan.

5. The method for preparing a nonwoven-reinforced zwitterionic functionalized polymer composite membrane according to claim 1, characterized in that: The organic solvent A is at least one of tetrahydrofuran, dioxane, ethanol, propanol, butanol, dichloromethane, and trichloromethane; The organic solvent B is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, or dimethyl sulfoxide; The organic solvent C is at least one of diethyl ether, methanol, ethanol, isopropanol, carbon tetrachloride, or acetone.

6. The method for preparing a nonwoven-reinforced zwitterionic functionalized polymer composite membrane according to claim 1, characterized in that: In step (1), the amount of polystyrene / maleic anhydride and the terminal amine tertiary amine compound is controlled such that the molar ratio of the anhydride in the polystyrene / maleic anhydride to the terminal amine group in the terminal amine tertiary amine compound is 1:(0.5~1.1).

7. The method for preparing a nonwoven-reinforced zwitterionic functionalized polymer composite membrane according to claim 1, characterized in that: In step (2), the mass ratio of the SMA-grafted amphiphilic polymer containing tertiary amine groups to the polymer is (0.1~1):1, and the mass of the polymer is 8~30% of the total mass of the SMA-grafted amphiphilic polymer containing tertiary amine groups and the polymer.

8. The method for preparing a nonwoven-reinforced zwitterionic functionalized polymer composite membrane according to claim 1, characterized in that: The sulfonyl lactone is soluble in organic solvent C at a mass concentration of 0.1-10%.

9. The method for preparing a nonwoven-reinforced zwitterionic functionalized polymer composite membrane according to claim 1, characterized in that: The coagulation bath is one or a combination of several of the following: water, ethanol, methanol, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

10. The nonwoven reinforced zwitterionic functionalized polymer composite membrane prepared by the preparation method according to any one of claims 1-9, characterized in that: The composite membrane has a pure water contact angle of less than 30° and an underwater oil contact angle of greater than 150°.