Preparation method of non-woven fabric reinforced zwitterionic functionalized polymer composite membrane

Abstract

The invention provides a preparation method of a non-woven fabric reinforced zwitterionic functionalized polymer composite membrane. Specifically, firstly, an amine-terminated tertiary amine compound is grafted to polystyrene / maleic anhydride (SMA), an SMA grafted amphiphilic polymer containing a tertiary amine group is prepared through an amidation reaction, then the SMA grafted amphiphilic polymer and a high-molecular polymer are blended to prepare a membrane casting solution, then a non-woven fabric serves as a substrate, the membrane casting solution is scraped on the non-woven fabric, and the membrane is prepared. The preparation method comprises the following steps: preparing a polymer / non-woven fabric composite membrane with rich tertiary amine groups on the surface by adopting a non-solvent-induced phase inversion method, and finally, carrying out in-situ reaction on sultone and the tertiary amine groups to prepare the non-woven fabric reinforced zwitterionic functionalized polymer composite membrane with the membrane surface containing sulfonic acid anion groups and quaternary ammonium salt cation groups at the same time.

Description

Technical Field

[0001] The invention belongs to the technical field of functional polymer membrane separation, and in particular relates to a method for preparing a non-woven fabric reinforced zwitterionic functionalized polymer / NWF composite membrane. Background Art

[0002] Industrial development and intensified human activities have generated large quantities of oily wastewater. This wastewater is not only complex in composition but also poses a serious threat to the ecological environment and water resource security, presenting a significant challenge for both the scientific and industrial communities. Therefore, the effective recycling and utilization of water and oil resources is crucial for alleviating the increasingly prominent challenges of resource shortages and environmental pollution, and for promoting sustainable economic development.

[0003] Oilfield wastewater is typically highly mineralized. Besides a certain concentration of crude oil, it also contains oil-displacing agents such as surfactants and polymers, which form a stable oil-in-water emulsion. Currently, conventional treatment methods include gravity sedimentation, adsorption, and chemical methods. Gravity sedimentation, however, requires long settling times and bulky equipment, making it difficult to efficiently treat the emulsified oil. The high regeneration and disposal costs of the adsorbents used in adsorption methods hinder large-scale application. Chemical methods typically employ a reverse demulsifier (such as a positively charged polymer surfactant) combined with a flocculant (such as polyaluminum chloride or polyferric chloride) to disrupt the oil-water interface and further achieve oil-water separation. However, the suspended matter, emulsified oil, and residual oil-displacing polymer (partially hydrolyzed polyacrylamide, HPAM) in produced wastewater are all negatively charged, which can easily form polymer-containing sludge upon reaction with cationic demulsifiers and flocculants. This can cause equipment blockage and secondary pollution, impacting normal oilfield production.

[0004] The membrane separation process does not require the addition of chemical agents and has the advantages of low energy consumption, high separation efficiency, and simple process. It has become an efficient and green separation method and is widely used in the field of oil-water separation. For example, Chinese invention patent CN109316981B discloses a method for preparing a super-hydrophilic polymer membrane with demulsification function, which achieves efficient oil-water separation. However, due to the ester bond between the demulsifier and the base membrane, it cannot be applied to alkaline oil production wastewater treatment. In addition, low permeation flux and poor anti-oil contamination resistance are bottlenecks of current membrane separation technology in the industrial treatment of oily wastewater.

[0005] As we all know, zwitterionic materials refer to materials that have both cationic and anionic groups in one molecule. Their strong hydrophilicity can be used to construct a hydration layer to improve the permeability and anti-fouling properties of the membrane.

[0006] Building on the above research, the present invention combines zwitterion functionalization with membrane separation technology. First, an amino-terminated tertiary amine compound is grafted onto polystyrene / maleic anhydride (SMA) via a nucleophilic substitution reaction. A polymer membrane containing tertiary amine groups is then prepared using a non-solvent-induced phase inversion method. A lactone is then reacted with the tertiary amine groups in situ to prepare the zwitterion-functionalized polymer membrane. The zwitterion-functionalized membrane forms a stable super-hydrophilic layer on its surface through electrostatic interactions and hydrogen bonding, effectively reducing membrane fouling, improving permeation flux, and maintaining excellent separation performance in complex oil-water environments. Summary of the Invention

[0007] In view of the shortcomings of the prior art, the present invention aims to provide a method for preparing a non-woven fabric reinforced zwitterionic functionalized polymer composite membrane.

[0008] The preparation method of a non-woven fabric reinforced zwitterionic functionalized polymer composite membrane described in the present invention is characterized in that the method comprises the following steps: (1) dissolving polystyrene / maleic anhydride in an organic solvent A, stirring at 40-90°C until dissolved, then slowly adding a terminal amine tertiary amine compound dropwise thereto, and stirring and reacting at 40-90°C for 1-10 hours; after the reaction is completed, removing the solvent and excess terminal amine compound by rotary evaporation to obtain an SMA grafted amphiphilic polymer containing a tertiary amine group; (2) blending the SMA grafted amphiphilic polymer containing a tertiary amine group and a high molecular polymer, dissolving them in an organic solvent B at 60-90°C, and preparing a casting solution, which is poured onto a non-woven fabric after degassing, and the mixture is heated to 100°C. The liquid film is scraped with a scraper of 0 to 300 μm, and then transferred to a coagulation bath to prepare a polymer / non-woven fabric composite membrane with rich tertiary amine groups on the surface through a non-solvent induced phase inversion method; (3) the prepared polymer / non-woven fabric composite membrane with rich tertiary amine groups on the surface is immersed in an organic solvent C containing sultone, reacted at 10 to 70 ° C for 2 to 12 hours, and washed with deionized water after the reaction to obtain a non-woven fabric reinforced zwitterionic functionalized polymer composite membrane; the molecular weight of the SMA is between 3000 and 180000 Da, and the anhydride content is 3 to 30%; the terminal amino tertiary amine compound is a class of substances with both primary and tertiary amines, including N, N-dimethylethylenediamine, 3-dimethylamino-1 -propylamine, N,N-dimethyl-1,4-butanediamine or N,N-dimethyl-1,6-hexanediamine; the high molecular polymer is at least one of polyvinylidene fluoride, polyacrylonitrile, polypropylene, polysulfone, polyethersulfone, cellulose acetate, regenerated cellulose, polyvinyl alcohol, polyethylene vinyl alcohol, 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 at least one of ether, methanol, ethanol, isopropanol, carbon tetrachloride or acetone ; The amounts of polystyrene / maleic anhydride and the terminal amine tertiary amine compound in the step (1) are controlled so that the molar ratio of the anhydride in the polystyrene / maleic anhydride to the terminal amine in the terminal tertiary amine compound is 1:0.5-1.1; the mass ratio of the SMA grafted amphiphilic polymer of the tertiary amine group to the high molecular weight polymer in the step (2) is 0.1-1:1, and the mass of the high molecular weight polymer is 8-30% of the total mass; the sultone in the step (3) is propane sultone or butane sultone, and its mass concentration dissolved in the organic solvent C is 0.1-10%; the coagulation bath is one or more of water, ethanol, methanol, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

[0009] The present invention also provides a non-woven fabric reinforced zwitterion functionalized polymer composite membrane prepared by the above preparation 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:

[0011] The non-woven fabric as the base enhances the mechanical strength of the membrane, making the membrane applicable to practical scenarios; secondly, after the zwitterion treatment of the membrane surface, the salt resistance and hydrophilicity of the membrane are enhanced, which improves the water flux and anti-pollution properties of the membrane, and has good practical application prospects. DETAILED DESCRIPTION

[0012] The following examples may enable those skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0013] Example 1

[0014] (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 dropwise 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 an SMA-grafted amphiphilic polymer containing tertiary amine groups, referred to as DMEDA-g-SMA.

[0015] (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 non-woven fabric and a 250 μm doctor blade was used to form a liquid film. The liquid film was then transferred to ethanol / water and a non-solvent-induced phase inversion method was used to prepare a DMEDA-g-SMA / PES / NWF composite membrane.

[0016] (3) The DMEDA-g-SMA / PES / NWF composite membrane was immersed in an ethanol solvent of butane sultone and reacted at 50 °C for 10 h. After the reaction, it was washed with deionized water three times to obtain the B4@DMEDA / PES / NWF composite membrane;

[0017] (4) The pure water contact angle of the B4@DMEDA / PES / NWF composite membrane is 28°, the underwater oil (kerosene) contact angle is 156°, and the pure water flux is 1289 L·m at 0.1 MPa. -2 ·h -1 After the oil wastewater with an oil content of 1000 mg / L was treated with the B4@DMEDA / PES / NWF composite membrane, the removal rate of crude oil in the water reached 98.1%.

[0018] Example 2

[0019] (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 dropwise 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 an SMA-grafted amphiphilic polymer containing tertiary amine groups, referred to as DMPA-g-SMA.

[0020] (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 non-woven fabric and a 200 μm doctor blade was used to form a liquid film. The liquid film was then transferred to water and prepared by a non-solvent-induced phase inversion method to obtain a DMPA-g-SMA / PSF / NWF composite membrane.

[0021] (3) The DMPA-g-SMA / PSF / NWF composite membrane was immersed in a methanol solvent of propane sultone and reacted at 60 °C for 10 h. After the reaction, it was washed three times with deionized water to obtain the B3@DMPA / PSF / NWF composite membrane.

[0022] (4) The pure water contact angle of the B3@DMPA / PSF / NWF composite membrane is 24°, the underwater oil (kerosene) contact angle is 162°, and the pure water flux at 0.1 MPa is 1344 L·m -2 ·h -1 After the oil-producing wastewater with an oil content of 1000 mg / L was treated with the B3@SMA / PSF / NWF composite membrane, the removal rate of crude oil in the water reached 98.3%.

[0023] Example 3

[0024] (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 dropwise 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 an SMA-grafted amphiphilic polymer containing tertiary amine groups, referred to as DMHDA-g-SMA.

[0025] (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 non-woven fabric and a 200 μm scraper was used to form a liquid film. The liquid film was then transferred to dimethylacetamide / water and a non-solvent-induced phase inversion method was used to prepare a DMHDA-g-SMA / PVDF / NWF composite membrane.

[0026] (3) The DMHDA-g-SMA / PVDF / NWF composite membrane was immersed in a methanol solvent of butane sultone and reacted at 60 °C for 10 h. After the reaction, it was washed three times with deionized water to obtain the B4@DMHDA / PVDF / NWF composite membrane.

[0027] (4) The pure water contact angle of the B4@DMHDA / PVDF / NWF composite membrane is 26°, the underwater oil (kerosene) contact angle is 160°, and the pure water flux at 0.1 MPa is 1312 L·m -2 ·h -1 After the oil-producing wastewater with an oil content of 1000 mg / L was treated with the B4@DMHDA / PVD / NWF composite membrane, the removal rate of crude oil in the water reached 99.3%.

[0028] Comparative Example 1

[0029] (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 dropwise 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 an SMA-grafted amphiphilic polymer containing tertiary amine groups, referred to as DMEDA-g-SMA.

[0030] (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 non-woven fabric and a 250 μm doctor blade was used to form a liquid film. The liquid film was then transferred to ethanol / water and a non-solvent-induced phase inversion method was used to prepare a DMEDA-g-SMA / PES / NWF composite membrane.

[0031] (3) The pure water contact angle of the DMEDA-g-SMA / PES / NWF membrane is 35°, the underwater oil (kerosene) contact angle is 142°, and the pure water flux at 0.1 MPa is 325 L·m -2 ·h -1 After the oil-producing wastewater with an oil content of 1000 mg / L was treated with the DMEDA-g-SMA / PES / NWF composite membrane, the removal rate of crude oil in the water was 92.6%.

Claims

1. A method for preparing a non-woven fabric reinforced zwitterion functionalized polymer composite membrane, characterized in that: The method comprises the following steps: (1) Dissolve polystyrene / maleic anhydride in organic solvent A, stir at 40-90°C until dissolved, then slowly add the terminal amine tertiary amine compound dropwise thereto, and stir and react at 40-90°C for 1-10 hours; after the reaction is completed, remove the solvent and excess terminal amine compound by rotary evaporation to obtain an SMA grafted amphiphilic polymer containing a tertiary amine group; (2) The SMA grafted amphiphilic polymer containing tertiary amine groups and the high molecular weight polymer are blended and dissolved in an organic solvent B at 60-90°C to prepare a casting solution, which is poured onto a non-woven fabric after degassing and scraped into a liquid film using a scraper. The liquid film is then transferred to a coagulation bath and a polymer / non-woven fabric composite membrane with rich tertiary amine groups on the surface is prepared by a non-solvent-induced phase inversion method; (3) The prepared polymer / non-woven fabric composite membrane with rich tertiary amine groups on the surface is immersed in an organic solvent C containing sultone, reacted at 10-70°C for 2-12 hours, and washed with deionized water after the reaction to obtain a non-woven fabric reinforced zwitterionic functionalized polymer composite membrane.

2. The method for preparing a non-woven fabric reinforced zwitterion functionalized polymer composite membrane according to claim 1, wherein: The molecular weight of the SMA is between 3000 and 180000 Da, and the anhydride content is 3 to 30%.

3. The method for preparing a non-woven fabric reinforced zwitterion functionalized polymer composite membrane according to claim 1, wherein: The terminal amino group tertiary amine compound is a substance having both 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.

4. The method for preparing a non-woven fabric reinforced zwitterion functionalized polymer composite membrane according to claim 1, wherein: The high molecular polymer is at least one of polyvinylidene fluoride, polyacrylonitrile, polypropylene, polysulfone, polyethersulfone, cellulose acetate, regenerated cellulose, polyvinyl alcohol, polyethylene vinyl alcohol, and chitosan.

5. The method for preparing a non-woven fabric reinforced zwitterion functionalized polymer composite membrane according to claim 1, wherein: 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 at least one of ether, methanol, ethanol, isopropanol, carbon tetrachloride or acetone.

6. The method for preparing a non-woven fabric reinforced zwitterion functionalized polymer composite membrane according to claim 1, wherein: In the step (1), the amounts of polystyrene / maleic anhydride and the amine-terminated tertiary amine compound are controlled so that the molar ratio of the anhydride in the polystyrene / maleic anhydride to the terminal amine group in the amine-terminated tertiary amine compound is 1:0.5-1.

1.

7. The method for preparing a non-woven fabric reinforced zwitterion functionalized polymer composite membrane according to claim 1, characterized in that: In the step (2), the mass ratio of the SMA grafted amphiphilic polymer with tertiary amine groups to the high molecular weight polymer is 0.1 to 1:1, and the mass of the high molecular weight polymer is 8 to 30% of the total mass.

8. The method for preparing a non-woven fabric reinforced zwitterion functionalized polymer composite membrane according to claim 1, characterized in that: In step (3), the sultone is propane sultone or butane sultone, and the mass concentration of the sultone dissolved in the organic solvent C is 0.1 to 10%.

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

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