A sewage treatment filter membrane and a method for manufacturing the same

Abstract

The application discloses a sewage treatment filtering membrane and a preparation method thereof, and relates to the technical field of membrane materials. In the preparation of the sewage treatment filtering membrane, an amphoteric ion intermediate is reacted with 1,3-propane sulfone lactone to obtain an amphoteric ion monomer; the amphoteric ion monomer and N,N-methylene bisacrylamide are in-situ cross-linked and polymerized in a polyvinylidene fluoride solution to obtain a casting solution; the casting solution is used to prepare a functionalized polyvinylidene fluoride membrane through a non-solvent induced phase separation technology; hydrochloric acid dopamine and polyethylene imine are co-deposited on the surface of the functionalized polyvinylidene fluoride membrane to obtain a porous polyvinylidene fluoride membrane; and copper sulfate pentahydrate is used to catalyze modified indole derivatives to be grafted on the surface of the porous polyvinylidene fluoride membrane, so as to obtain the sewage treatment filtering membrane. The sewage treatment filtering membrane prepared by the application has excellent hydrophilic, anti-pollution and antibacterial properties.

Description

Technical Field

[0001] This invention relates to the field of membrane materials technology, specifically to a wastewater treatment filtration membrane and its preparation method. Background Technology

[0002] Faced with the dual challenges of global water scarcity and increasingly prominent water pollution problems, wastewater treatment and reuse have become a core strategic direction for ensuring water ecological security. Membrane separation technology, due to its advantages of high efficiency, energy saving, and small footprint, is gradually replacing traditional sedimentation and filtration processes, becoming the core technology for modern wastewater treatment and reuse.

[0003] Among various membrane materials, polyvinylidene fluoride (PVDF) has become one of the mainstream materials for preparing microfiltration and ultrafiltration membranes for wastewater treatment due to its excellent chemical stability, resistance to acid and alkali corrosion, thermal stability, and mechanical strength. However, the molecular structure of virgin PVDF membranes is rich in fluorine-carbon bonds, making them inherently hydrophobic. This inherent characteristic requires external pressure to wet the membrane module during startup, severely limiting the operating efficiency and economy of the filter membrane. Furthermore, the hydrophobic surface easily forms intermolecular forces with hydrophobic organic matter such as oils and humic acids in wastewater, leading to rapid adsorption of pollutants. Simultaneously, PVDF membranes lack antibacterial activity, and the hydrophobic surface can cause a large number of microorganisms to attach, multiply, and secrete extracellular polymers, forming a dense biofilm, causing serious irreversible pollution and even leading to membrane failure. It may also cause pathogenic microorganisms in the treated water to exceed standards due to membrane fouling and detachment, resulting in secondary pollution. Therefore, inventing a wastewater treatment filter membrane that simultaneously possesses hydrophilicity, antifouling, and antibacterial properties is of great practical significance for addressing the increasingly complex challenges of water treatment and promoting the wider application of membrane technology. Summary of the Invention

[0004] The purpose of this invention is to provide a wastewater treatment filter membrane and its preparation method to solve the problems existing in the prior art.

[0005] To solve the above-mentioned technical problems, the present invention provides the following solution:

[0006] A wastewater treatment filtration membrane is prepared by reacting an amphoteric intermediate with 1,3-propanesulfonyl lactone to obtain an amphoteric monomer; then, the amphoteric monomer and N,N-methylenebisacrylamide are crosslinked and polymerized in situ in a polyvinylidene fluoride (PVDF) solution to obtain a casting solution; the casting solution is then used to form a functionalized PVDF membrane through a solvent-inducible phase separation technique; dopamine hydrochloride and polyethyleneimine are co-deposited on the surface of the functionalized PVDF membrane to obtain a porous PVDF membrane; finally, an indole derivative modified by copper sulfate pentahydrate is grafted onto the surface of the porous PVDF membrane to obtain the final membrane.

[0007] The zwitterionic intermediate is prepared by reacting 3-chloropropyne with (but-3-en-1-yl)(methyl)amine.

[0008] The modified indole derivative is prepared by grafting 1-azido-2-chloroethane onto 3-ethylindole.

[0009] A method for preparing a wastewater treatment filter membrane, the method comprising the following preparation steps:

[0010] (1) Add the zwitterionic intermediate and 1,3-propanesulfonyl lactone to acetone at a molar ratio of 1:(1~1.1) in 6~8 times the mass of the zwitterionic intermediate and mix them evenly. Stir the reaction at 28~32℃ and 300~500r / min for 4.5~5.5h, let it stand at room temperature for 1.5~2.5h, filter, wash with acetone 2~4 times, and vacuum dry at 35~45℃ for 5~7h to obtain the zwitterionic monomer;

[0011] (2) Pour the casting solution onto a glass plate and coat it evenly with a wet film scraper with a thickness of 180~220μm at a speed of 4~6cm / s. Soak it in deionized water at 38~42℃ with a volume of 20~30 times that of the casting solution for 20~40min. Rinse it with deionized water 3~5 times for 24~28h. Let it air dry at room temperature to obtain a functionalized polyvinylidene fluoride membrane.

[0012] (3) Clean the functionalized polyvinylidene fluoride membrane with ultrasonic cleaning for 8-10 min, press out the air bubbles in the membrane pores with a rubber roller, immerse it completely in the mixed solution, and react with shaking at 100-150 r / min for 20-24 h at room temperature. Soak it in deionized water for 10-14 h and air dry it at room temperature to obtain a porous polyvinylidene fluoride membrane.

[0013] (4) Mix copper sulfate pentahydrate, tris(hydroxymethyl)methylglycine, sodium ascorbate, and mixed solvent in a mass ratio of 1:(3.8~4.2):(4.8~5.2):(1000~1200) until homogeneous. Stir at room temperature for 10~20 min. Add 24~26 times the mass of modified indole derivative of copper sulfate pentahydrate and continue stirring for 10~20 min. Add a porous polyvinylidene fluoride membrane for immersion. Shake at 28~32℃ and 80~120 r / min in the dark for 12~16 h. Wash with deionized water 3~5 times. Immerse the membrane in 0.1 mol / L disodium ethylenediaminetetraacetate aqueous solution and sonicate for 8~12 min. Wash with anhydrous ethanol 3~5 times and air dry at room temperature in the dark to obtain a wastewater treatment filter membrane.

[0014] As an optimization, the preparation process of the zwitterionic intermediate in step (1) is as follows: Weigh 3-chloropropyne and (but-3-en-1-yl)(methyl)amine in a molar ratio of 1:(1.1~1.3), mix (but-3-en-1-yl)(methyl)amine and anhydrous tetrahydrofuran in a mass ratio of 1:(8~10), stir at room temperature for 5~15 min under nitrogen protection, add equimolar amounts of triethylamine to 3-chloropropyne, cool to 0~4℃, continue stirring for 3~5 min, add 3-chloropropyne at a uniform rate over 1~2 h, continue stirring for 50~70 min, raise to room temperature, continue stirring for 6~8 h, filter, remove anhydrous tetrahydrofuran by vacuum distillation, and obtain the zwitterionic intermediate.

[0015] As an optimization, the preparation process of the casting solution in step (2) is as follows: polyvinylidene fluoride, polyethylene glycol, N,N-methylenebisacrylamide, and N-methylpyrrolidone are mixed evenly in a mass ratio of 1:(0.4~0.6):(0.030~0.034):(7.5~7.9). Under nitrogen protection, the mixture is heated to 65~75℃ and stirred at 300~500r / min for 2~3h. Then, zwitterionic monomers of 0.7~0.9 times the mass of polyvinylidene fluoride are added, and the mixture is stirred and reacted for 20~40min. Then, 2,2-azobisisobutyronitrile of 0.0009~0.0011 times the mass of polyvinylidene fluoride are added, and the mixture is stirred and reacted for 8~10h. The mixture is cooled to room temperature and allowed to stand under reduced pressure for 40~60min to obtain the casting solution.

[0016] As an optimization, the polyvinylidene fluoride is of type FR904 and was purchased from Dongguan Yingxiang Plastic Raw Materials Co., Ltd.

[0017] As an optimization, the polyethylene glycol used is PEG-400, purchased from Haian Petrochemical Plant in Jiangsu Province.

[0018] As an optimization, the preparation process of the mixed solution in step (3) is as follows: 10 mmol / L Tris-HCl buffer solution with pH=8.5, dopamine hydrochloride and polyethyleneimine are mixed evenly at a mass ratio of 1:(1.8~2.2):(3.8~4.2), and stirred at room temperature for 20~40 min to obtain the mixed solution.

[0019] As an optimization, the polyethyleneimine used was PEI-25000 Da, purchased from Wuhan Kemic Biomedical Technology Co., Ltd.

[0020] As an optimization, the preparation process of the modified indole derivative in step (4) is as follows: 3-ethylindole, potassium carbonate, and N,N-dimethylformamide are mixed evenly at a mass ratio of 1:(1.35~1.45):(7~9), and stirred at room temperature for 10~20 min. 0.7~0.8 times the mass of 3-ethylindole and 1-azido-2-chloroethane are added at a uniform rate within 30~40 min. The temperature is raised to 75~85℃, and the stirring reaction is continued for 12~16 h. The mixture is poured into ice-cold deionized water at a mass of 6~8 times the mass of N,N-dimethylformamide, filtered, washed 3~5 times with deionized water, and vacuum dried at 40~50℃ for 6~8 h to obtain the modified indole derivative.

[0021] As an optimization, the mixed solvent in step (4) is prepared by uniformly mixing dimethyl sulfoxide and deionized water at a volume ratio of 1:1.

[0022] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0023] In preparing a wastewater treatment filtration membrane, this invention involves reacting 3-chloropropyne and (but-3-en-1-yl)(methyl)amine to obtain an amphoteric intermediate, which is then reacted with 1,3-propanesulfonyl lactone in a ring-opening quaternization reaction to obtain an amphoteric monomer. Using polyethylene glycol as a porogen, the amphoteric monomer and N,N-methylenebisacrylamide are in-situ crosslinked and polymerized in a polyvinylidene fluoride (PVDF) solution to obtain a casting solution. The casting solution is then processed into a functionalized PVDF membrane using a solvent-inducible phase separation technique. Dopamine hydrochloride and polyethyleneimine are co-deposited onto the surface of the functionalized PVDF membrane to obtain a porous PVDF membrane. 1-Azide-2-chloroethane is grafted onto 3-ethylindole to obtain a modified indole derivative. The modified indole derivative is then grafted onto the surface of the porous PVDF membrane using copper sulfate pentahydrate as a catalyst to obtain the wastewater treatment filtration membrane.

[0024] First, an amphoteric intermediate is prepared by reacting 3-chloropropyne with (but-3-en-1-yl)(methyl)amine. This intermediate is then reacted with 1,3-propanesulfonyl lactone via ring-opening quaternization to obtain an amphoteric monomer. Quaternary ammonium salts and sulfonyl groups are introduced onto the surface of a polyvinylidene fluoride (PVDF) membrane. Using polyethylene glycol as a pore-forming agent, the amphoteric monomer and N,N-methylenebisacrylamide are crosslinked and polymerized in situ in a PVDF solution to prepare a casting solution. The casting solution is then used to prepare a functionalized PVDF membrane via a solvent-inducible phase separation technique. The quaternary ammonium cations on the surface of the functionalized PVDF membrane carry a positive charge and can electrostatically adsorb onto the negatively charged phospholipid groups on the bacterial cell membrane surface, inserting into the phospholipid bilayer of the cell membrane. This disrupts the membrane's integrity and permeability, leading to the leakage of intracellular proteins, nucleic acids, and other biomolecules. The sulfonate anions inhibit the activity of bacterial enzymes, ultimately causing bacterial death, thus endowing the wastewater treatment filtration membrane with excellent antibacterial properties. The sulfonate anions and quaternary ammonium cations possess extremely strong hydration energy. The strong ion-dipole interaction can firmly bind a large number of water molecules, forming a dense hydration layer on the membrane surface and inside the pores. This reduces the migration resistance of water molecules on the membrane surface. Simultaneously, during the in-situ crosslinking polymerization process, the introduction of the crosslinking agent N,N-methylenebisacrylamide enables the membrane to form a well-connected porous structure. The extraction effect of the porogen polyethylene glycol further expands the membrane pore size, providing a rapid transport channel for water molecules. This, combined with the hydration layer, achieves a dual effect of high water flux and low attenuation, thus endowing the wastewater treatment filtration membrane with excellent hydrophilicity. Furthermore, the charge balance system formed by sulfonate anions and quaternary ammonium cations can also hinder bacterial attachment and reproduction on the membrane surface through electrostatic repulsion. The dense hydration layer reduces the contact sites between bacteria and the membrane surface, inhibiting the deposition of extracellular polymers secreted by bacteria. This prevents biofilm formation at its source, avoiding the impact of biological pollution on membrane performance, and further improving the antifouling performance of the wastewater treatment filtration membrane.

[0025] Secondly, dopamine hydrochloride and polyethyleneimine are co-deposited on the surface of a functionalized polyvinylidene fluoride (PVDF) membrane to form a porous PVDF membrane. The PDA / PEI co-deposited layer forms an ultra-thin, tough, and highly adhesive biomimetic coating on the membrane surface through strong covalent and non-covalent interactions such as Michael addition, Schiff base reaction, hydrogen bonding, and π-π stacking. This coating firmly locks the zwitterionic groups and indole derivatives introduced through chemical grafting onto the membrane surface, preventing them from falling off or becoming inactive under long-term hydraulic shearing or chemical cleaning, thus endowing the wastewater treatment filtration membrane with long-term interfacial stability. The numerous primary, secondary, and tertiary amine groups on the branched polyethyleneimine molecular chain can undergo protonation reactions to form an ion hydration layer with water molecules. At the same time, they can form electrostatic interactions with sulfonate groups on the membrane surface, making the hydration layer denser. The superposition of the two hydration layers significantly reduces the contact resistance between water molecules and the membrane surface, thereby further improving the hydrophilicity of the wastewater treatment filtration membrane.

[0026] Finally, 1-azido-2-chloroethane was grafted onto 3-ethylindole to prepare a modified indole derivative. The modified indole derivative was then grafted onto the surface of a porous polyvinylidene fluoride membrane using copper sulfate pentahydrate as a catalyst to prepare a wastewater treatment filter membrane. Algae and their secreted extracellular polymers easily form a gel layer on the membrane surface, clogging the membrane pores and being a significant cause of membrane fouling. The planar conjugated heterocyclic structure of the modified indole derivative can bind to chlorophyll a and thylakoid membrane proteins in algal chloroplasts through allelopathic effects, interfering with the electron transport chain of photosynthetic system II, inhibiting the synthesis of ATP and NADPH in the light reaction, and interfering with the energy metabolism pathways of algae through chemical signals. Simultaneously, the indole derivative can block the binding of extracellular polysaccharides secreted by algae to receptors on the surface of algal cells through allelopathic effects, inhibiting the quorum sensing system of algae and preventing algal cell aggregation to form an algal membrane, thus endowing the wastewater treatment filter membrane with excellent antifouling properties. Detailed Implementation

[0027] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0028] Example 1:

[0029] A method for preparing a wastewater treatment filter membrane, the method comprising the following steps:

[0030] (1) Weigh 3-chloropropyne and (but-3-en-1-yl)(methyl)amine in a molar ratio of 1:1.1. Mix (but-3-en-1-yl)(methyl)amine and anhydrous tetrahydrofuran in a mass ratio of 1:8. Stir at room temperature for 5 min under nitrogen protection. Add equimolar amounts of triethylamine to 3-chloropropyne. Cool to 0 °C and continue stirring for 5 min. Add 3-chloropropyne at a uniform rate over 2 h and continue stirring for 70 min. Raise to room temperature and continue stirring for 8 h. Filter and remove anhydrous tetrahydrofuran by vacuum distillation to obtain a zwitterionic intermediate. Add the zwitterionic intermediate and 1,3-propanesulfonyl lactone in a molar ratio of 1:1 to acetone in 6 times the mass of the zwitterionic intermediate and mix well. Stir at 28 °C and 300 r / min for 5.5 h. Let stand at room temperature for 2.5 h. Filter, wash twice with acetone, and dry under vacuum at 35 °C for 7 h to obtain the zwitterionic monomer.

[0031] (2) Polyvinylidene fluoride, polyethylene glycol, N,N-methylenebisacrylamide, and N-methylpyrrolidone were mixed evenly in a mass ratio of 1:0.4:0.030:7.5. Under nitrogen protection, the mixture was heated to 65°C and stirred at 300 r / min for 3 h. 0.7 times the mass of the polyvinylidene fluoride zwitterionic monomer was added and the mixture was stirred for 40 min. 0.0009 times the mass of the polyvinylidene fluoride 2,2-azobisisobutyronitrile was added and the mixture was stirred for 10 h. The mixture was cooled to room temperature and allowed to stand under reduced pressure for 60 min to obtain a casting solution. The casting solution was poured onto a glass plate and coated evenly with a wet film scraper with a thickness of 180 μm at a speed of 4 cm / s. The mixture was soaked in deionized water at 38°C with a volume of 20 times that of the casting solution for 40 min. It was rinsed with deionized water 3 times for 28 h and then air-dried at room temperature to obtain a functionalized polyvinylidene fluoride membrane.

[0032] (3) Mix 10 mmol / L Tris-HCl buffer solution with pH=8.5, dopamine hydrochloride and polyethyleneimine in a mass ratio of 1:1.8:3.8 and stir at room temperature for 40 min to obtain a mixed solution; ultrasonically clean the functionalized polyvinylidene fluoride membrane for 10 min, press out the air bubbles in the membrane pores with a rubber roller, completely immerse it in the mixed solution, shake at 100 r / min for 24 h at room temperature, soak it in deionized water for 14 h, and air dry it at room temperature to obtain a porous polyvinylidene fluoride membrane;

[0033] (4) Mix 3-ethylindole, potassium carbonate, and N,N-dimethylformamide at a mass ratio of 1:1.35:7 until homogeneous. Stir and react at room temperature for 20 min. Add 0.7 times the mass of 3-ethylindole and 1-azido-2-chloroethane at a uniform rate over 40 min. Heat to 75 °C and continue stirring for 16 h. Pour into 6 times the mass of N,N-dimethylformamide in ice-cold deionized water, filter, wash 3 times with deionized water, and vacuum dry at 40 °C for 8 h to obtain the modified indole derivative. Mix dimethyl sulfoxide and deionized water at a volume ratio of 1:1 until homogeneous to obtain a mixed solvent. Add pentahydrate Copper sulfate pentahydrate, tris(hydroxymethyl)methylglycine, sodium ascorbate, and a mixed solvent were mixed evenly at a mass ratio of 1:3.8:4.8:1000 and stirred at room temperature for 20 min. Modified indole derivatives at 24 times their mass of copper sulfate pentahydrate were added, and stirring continued for another 20 min. A porous polyvinylidene fluoride membrane was then added and immersed. The membrane was shaken at 28℃ and 80 r / min in the dark for 16 h. After washing three times with deionized water, the membrane was immersed in a 0.1 mol / L solution of disodium ethylenediaminetetraacetate and sonicated for 12 min. It was then washed three times with anhydrous ethanol and air-dried at room temperature in the dark to obtain a wastewater treatment filter membrane.

[0034] Example 2:

[0035] A method for preparing a wastewater treatment filter membrane, the method comprising the following steps:

[0036] (1) Weigh 3-chloropropyne and (but-3-en-1-yl)(methyl)amine at a molar ratio of 1:1.2. Mix (but-3-en-1-yl)(methyl)amine and anhydrous tetrahydrofuran at a mass ratio of 1:9. Stir at room temperature for 10 min under nitrogen protection. Add equimolar amounts of triethylamine to 3-chloropropyne. Cool to 2°C and continue stirring for 4 min. Add 3-chloropropyne at a uniform rate over 1.5 h and continue stirring for 60 min. Raise to room temperature and continue stirring for 7 h. Filter and remove anhydrous tetrahydrofuran by vacuum distillation to obtain zwitterionic intermediate. Add zwitterionic intermediate and 1,3-propanesulfonyl lactone at a molar ratio of 1:1.05 to acetone at 7 times the mass of zwitterionic intermediate and mix well. Stir at 30°C and 400 r / min for 5 h. Let stand at room temperature for 2 h, filter, wash 3 times with acetone, and vacuum dry at 40°C for 6 h to obtain zwitterionic monomer.

[0037] (2) Polyvinylidene fluoride, polyethylene glycol, N,N-methylenebisacrylamide, and N-methylpyrrolidone were mixed evenly in a mass ratio of 1:0.5:0.032:7.7. Under nitrogen protection, the mixture was heated to 70°C and stirred at 400 r / min for 2.5 h. 0.8 times the mass of the polyvinylidene fluoride zwitterionic monomer was added and the mixture was stirred for 30 min. 0.001 times the mass of the polyvinylidene fluoride 2,2-azobisisobutyronitrile was added and the mixture was stirred for 9 h. The mixture was cooled to room temperature and allowed to stand under reduced pressure for 50 min to obtain the casting solution. The casting solution was poured onto a glass plate and coated evenly with a wet film scraper with a thickness of 200 μm at a speed of 5 cm / s. The mixture was soaked in deionized water at 40°C with a volume of 25 times that of the casting solution for 30 min. It was rinsed with deionized water 4 times for 26 h and then air-dried at room temperature to obtain the functionalized polyvinylidene fluoride membrane.

[0038] (3) Mix 10 mmol / L Tris-HCl buffer solution with pH=8.5, dopamine hydrochloride and polyethyleneimine in a mass ratio of 1:2:4 and stir at room temperature for 30 min to obtain a mixed solution; ultrasonically clean the functionalized polyvinylidene fluoride membrane for 9 min, press out the air bubbles in the membrane pores with a rubber roller, immerse it completely in the mixed solution, shake at 125 r / min for 22 h at room temperature, soak it in deionized water for 12 h, and air dry it at room temperature to obtain a porous polyvinylidene fluoride membrane;

[0039] (4) Mix 3-ethylindole, potassium carbonate, and N,N-dimethylformamide in a mass ratio of 1:1.4:8, stir and react at room temperature for 15 min, add 0.75 times the mass of 3-ethylindole in 1-azido-2-chloroethane at a uniform rate over 35 min, heat to 80 °C, continue stirring and react for 14 h, pour into ice-cold deionized water in a mass ratio of 7 times that of N,N-dimethylformamide, filter, wash 4 times with deionized water, and vacuum dry at 45 °C for 7 h to obtain the modified indole derivative; mix dimethyl sulfoxide and deionized water in a volume ratio of 1:1 to obtain a mixed solvent; Copper sulfate hydrate, tris(hydroxymethyl)methylglycine, sodium ascorbate, and a mixed solvent were mixed evenly at a mass ratio of 1:4:5:1100 and stirred at room temperature for 15 min. Modified indole derivatives at 25 times their mass of copper sulfate pentahydrate were added, and stirring was continued for another 15 min. A porous polyvinylidene fluoride membrane was then added and immersed in the mixture. The mixture was shaken at 30℃ and 100 r / min in the dark for 14 h. After washing four times with deionized water, the membrane was immersed in a 0.1 mol / L solution of disodium ethylenediaminetetraacetate and sonicated for 10 min. It was then washed four times with anhydrous ethanol and air-dried at room temperature in the dark to obtain a wastewater treatment filter membrane.

[0040] Example 3:

[0041] A method for preparing a wastewater treatment filter membrane, the method comprising the following steps:

[0042] (1) Weigh 3-chloropropyne and (but-3-en-1-yl)(methyl)amine in a molar ratio of 1:1.3. Mix (but-3-en-1-yl)(methyl)amine and anhydrous tetrahydrofuran in a mass ratio of 1:10. Stir at room temperature for 5 min under nitrogen protection. Add equimolar amounts of triethylamine to 3-chloropropyne. Cool to 4 °C and continue stirring for 3 min. Add 3-chloropropyne at a uniform rate over 1 h and continue stirring for 50 min. Raise to room temperature and continue stirring for 6 h. Filter and remove anhydrous tetrahydrofuran by vacuum distillation to obtain zwitterionic intermediate. Add zwitterionic intermediate and 1,3-propanesulfonyl lactone in a molar ratio of 1:1.1 to acetone in 8 times the mass of zwitterionic intermediate and mix well. Stir at 32 °C and 500 r / min for 4.5 h. Let stand at room temperature for 1.5 h, filter, wash 4 times with acetone, and dry under vacuum at 45 °C for 5 h to obtain zwitterionic monomer.

[0043] (2) Polyvinylidene fluoride, polyethylene glycol, N,N-methylenebisacrylamide, and N-methylpyrrolidone were mixed evenly in a mass ratio of 1:0.6:0.034:7.9. Under nitrogen protection, the mixture was heated to 75°C and stirred at 500 r / min for 2 h. 0.9 times the mass of the polyvinylidene fluoride zwitterionic monomer was added and the mixture was stirred for another 20 min. 0.0011 times the mass of the polyvinylidene fluoride 2,2-azobisisobutyronitrile was added and the mixture was stirred for another 8 h. The mixture was cooled to room temperature and allowed to stand under reduced pressure for 40 min to obtain a casting solution. The casting solution was poured onto a glass plate and coated evenly with a wet film scraper with a thickness of 220 μm at a speed of 6 cm / s. The mixture was then soaked in deionized water at 42°C with a volume of 30 times that of the casting solution for 20 min. The mixture was rinsed with deionized water 5 times for 24 h and then air-dried at room temperature to obtain a functionalized polyvinylidene fluoride membrane.

[0044] (3) Mix 10 mmol / L Tris-HCl buffer solution with pH=8.5, dopamine hydrochloride and polyethyleneimine at a mass ratio of 1:2.2:4.2 and stir at room temperature for 20 min to obtain a mixed solution; ultrasonically clean the functionalized polyvinylidene fluoride membrane for 8 min, press out the air bubbles in the membrane pores with a rubber roller, immerse it completely in the mixed solution, shake at 150 r / min for 20 h at room temperature, soak it in deionized water for 10 h, and air dry it at room temperature to obtain a porous polyvinylidene fluoride membrane;

[0045] (4) Mix 3-ethylindole, potassium carbonate, and N,N-dimethylformamide at a mass ratio of 1:1.45:9 until homogeneous. Stir and react at room temperature for 100 min. Add 0.8 times the mass of 3-ethylindole and 1-azido-2-chloroethane at a uniform rate over 30 min. Heat to 85 °C and continue stirring for 12 h. Pour into 8 times the mass of N,N-dimethylformamide in ice-cold deionized water. Filter, wash 5 times with deionized water, and dry under vacuum at 50 °C for 6 h to obtain the modified indole derivative. Mix dimethyl sulfoxide and deionized water at a volume ratio of 1:1 until homogeneous to obtain a mixed solvent. Add pentahydrate... Copper sulfate pentahydrate, tris(hydroxymethyl)methylglycine, sodium ascorbate, and a mixed solvent were mixed evenly at a mass ratio of 1:4.2:5.2:1200 and stirred at room temperature for 10 min. Modified indole derivatives at 26 times their mass of copper sulfate pentahydrate were added, and stirring was continued for another 10 min. A porous polyvinylidene fluoride membrane was then added and immersed. The membrane was shaken at 32℃ and 120 r / min in the dark for 12 h. After washing five times with deionized water, the membrane was immersed in a 0.1 mol / L solution of disodium ethylenediaminetetraacetate and sonicated for 8 min. After washing five times with anhydrous ethanol, the membrane was naturally air-dried at room temperature in the dark to obtain a wastewater treatment filter membrane.

[0046] Comparative Example 1:

[0047] The difference between the preparation method of the wastewater treatment filter membrane in Comparative Example 1 and Example 2 is that step (1) is omitted, and step (2) is changed to: polyvinylidene fluoride, polyethylene glycol, N,N-methylenebisacrylamide, and N-methylpyrrolidone are mixed evenly in a mass ratio of 1:0.5:0.032:7.7, heated to 70°C under nitrogen protection, stirred at 400 r / min for 2.5 h, and 1-pentene-4-yne with a mass of 0.8 times that of polyvinylidene fluoride is added. The reaction is continued to be stirred for 30 min. Add 0.001 times the mass of polyvinylidene fluoride (PVDF) to 2,2-azobisisobutyronitrile (2,2-Azobisisobutyronitrile), continue stirring for 9 hours, cool to room temperature, and let stand under reduced pressure for 50 minutes to obtain a casting solution. Pour the casting solution onto a glass plate and coat it evenly with a 200 μm thick wet film scraper at a speed of 5 cm / s. Immerse it in 25 times the volume of deionized water at 40°C for 30 minutes, rinse four times with deionized water for 26 hours, and air dry at room temperature to obtain a functionalized PVDF membrane. The remaining steps are the same as in Example 2.

[0048] Comparative Example 2:

[0049] The difference between the preparation method of the wastewater treatment filter membrane in Comparative Example 2 and Example 2 is that step (3) is omitted, and step (4) is changed to: 3-ethylindole, potassium carbonate, and N,N-dimethylformamide are mixed evenly in a mass ratio of 1:1.4:8, stirred and reacted at room temperature for 15 min, and 0.75 times the mass of 3-ethylindole and 1-azido-2-chloroethane are added at a uniform rate within 35 min, the temperature is raised to 80°C, and the stirring and reaction is continued for 14 h. The mixture is poured into ice-cold deionized water with a mass of 7 times the mass of N,N-dimethylformamide, filtered, washed 4 times with deionized water, and vacuum dried at 45°C for 7 h to obtain the modified indole derivative; dimethyl sulfoxide and deionized water are mixed evenly. A mixed solvent was prepared by mixing water at a volume ratio of 1:1. Copper sulfate pentahydrate, tris(hydroxymethyl)methylglycine, sodium ascorbate, and the mixed solvent were mixed at a mass ratio of 1:4:5:1100 and stirred at room temperature for 15 min. A modified indole derivative, 25 times the mass of copper sulfate pentahydrate, was added, and stirring was continued for another 15 min. A functionalized polyvinylidene fluoride membrane was then added and immersed. The membrane was shaken at 30°C and 100 rpm in the dark for 14 h. After washing four times with deionized water, the membrane was immersed in a 0.1 mol / L solution of disodium ethylenediaminetetraacetate and sonicated for 10 min. After washing four times with anhydrous ethanol, the membrane was air-dried at room temperature in the dark to obtain a wastewater treatment filter membrane. The remaining steps were the same as in Example 2.

[0050] Comparative Example 3:

[0051] The difference between the preparation method of the wastewater treatment filter membrane in Comparative Example 3 and Example 2 is that step (4) is omitted, and step (3) is changed to: mixing 10 mmol / L Tris-HCl buffer solution (pH=8.5), dopamine hydrochloride, and polyethyleneimine at a mass ratio of 1:2:4, stirring at room temperature for 30 min to obtain a mixed solution; ultrasonically cleaning the functionalized polyvinylidene fluoride membrane for 9 min, pressing out air bubbles in the membrane pores with a rubber roller, completely immersing it in the mixed solution, shaking at 125 r / min for 22 h at room temperature, soaking in deionized water for 12 h, and air-drying at room temperature to obtain the wastewater treatment filter membrane. The remaining steps are the same as in Example 2.

[0052] Test Example 1

[0053] Hydrophilicity test

[0054] Test method: The static water contact angle of the wastewater treatment filter membranes in the examples and comparative examples was measured using a contact angle meter. 2 μL of deionized water was dropped onto the sample, and after standing for 15 seconds, the contact angle was measured. The results are shown in Table 1.

[0055] Table 1

[0056] Water contact angle / ° Water contact angle / ° Example 1 23 Comparative Example 1 82 Example 2 21 Comparative Example 2 45 Example 3 22 Comparative Example 3 26

[0057] A comparison of the experimental data from Examples 1-3 and Comparative Examples 1-3 in Table 1 reveals that the wastewater treatment filter membrane prepared by this invention has good hydrophilic properties.

[0058] By comparison, the water contact angles of Examples 1-3 were smaller than those of Comparative Example 1, indicating that the zwitterionic intermediate was prepared by reacting 3-chloropropyne and (but-3-en-1-yl)(methyl)amine, and then reacted with 1,3-propanesulfonyl lactone to undergo ring-opening quaternization to prepare a zwitterionic monomer. Quaternary ammonium salts and sulfonyl groups were introduced onto the surface of the polyvinylidene fluoride (PVDF) membrane. Using polyethylene glycol as a pore-forming agent, the zwitterionic monomer and N,N-methylenebisacrylamide were crosslinked and polymerized in situ in a PVDF solution to prepare a casting solution. The casting solution was then used to prepare a functionalized PVDF membrane via a solvent-inducing phase separation technique. Sulfonate anions and... Quaternary ammonium cations possess extremely strong hydration capabilities, which can tightly bind a large number of water molecules through powerful ion-dipole interactions, forming a dense hydration layer on the membrane surface and within the pores. This reduces the migration resistance of water molecules on the membrane surface. Simultaneously, during the in-situ crosslinking polymerization process, the introduction of the crosslinking agent N,N-methylenebisacrylamide enables the membrane to form a well-connected porous structure, while the extraction effect of the pore-forming agent polyethylene glycol further expands the membrane pore size, providing a rapid transport channel for water molecules. Together with the hydration layer, this achieves the dual effects of high water flux and low attenuation, thus endowing the wastewater treatment filtration membrane with excellent hydrophilicity.

[0059] By comparison, the water contact angles of Examples 1-3 are smaller than those of Comparative Example 2, indicating that co-depositing dopamine hydrochloride and polyethyleneimine on the surface of a functionalized polyvinylidene fluoride membrane produces a porous polyvinylidene fluoride membrane. The numerous primary, secondary, and tertiary amine groups on the branched polyethyleneimine molecular chain can undergo protonation reactions to form an ion hydration layer with water molecules. At the same time, they can form electrostatic interactions with sulfonate groups on the membrane surface, making the hydration layer more compact. The superposition of the two hydration layers significantly reduces the contact resistance between water molecules and the membrane surface, thereby further improving the hydrophilicity of the wastewater treatment filtration membrane.

[0060] Test Example 2

[0061] Antibacterial performance test

[0062] Test method: According to GB / T 37206-2018, the wastewater treatment filter membranes of the examples and comparative examples were cut into circular samples with a diameter of 20 mm and placed in sterile Petri dishes. 0.4 mL of a 5×10⁻⁶ solution was added. 5 A CFU / mL Escherichia coli suspension was added dropwise to the sample surface and incubated for 2 hours in a constant temperature and humidity incubator at 36°C and 92% relative humidity. The sample was then eluted and diluted with phosphate buffer, and the antibacterial rate K was calculated. K = ×100%, where N is the number of colonies after culturing the blank test bacteria, and M is the number of colonies after culturing the sample in contact with the test bacteria. The results are shown in Table 2.

[0063] Table 2

[0064] Antibacterial rate / % Antibacterial rate / % Example 1 98.4 Comparative Example 1 80.6 Example 2 98.9 Comparative Example 2 95.4 Example 3 98.3 Comparative Example 3 92.3

[0065] A comparison of the experimental data from Examples 1-3 and Comparative Examples 1-3 in Table 2 reveals that the wastewater treatment filter membrane prepared by this invention has good antibacterial properties.

[0066] By comparison, the antibacterial rates of Examples 1-3 were greater than those of Comparative Example 1, indicating that the zwitterionic intermediate was prepared by reacting 3-chloropropyne and (but-3-en-1-yl)(methyl)amine, and then reacted with 1,3-propanesulfonyl lactone to undergo ring-opening quaternization to obtain a zwitterionic monomer, which was then introduced into the polyvinylidene fluoride membrane surface as a quaternary ammonium salt and sulfonyl group. Using polyethylene glycol as a porogen, the zwitterionic monomer and N,N-methylenebisacrylamide were crosslinked and polymerized in situ in a polyvinylidene fluoride solution to obtain a casting solution. Then, the solution was further... A functionalized polyvinylidene fluoride (PVDF) membrane is prepared from the casting solution using a non-solvent-induced phase separation technique. The quaternary ammonium cations on the surface of the functionalized PVDF membrane carry a positive charge and can electrostatically adsorb onto the negatively charged phospholipid groups on the surface of bacterial cell membranes. They insert into the phospholipid bilayer of the cell membrane, disrupting the membrane's integrity and permeability, leading to the leakage of intracellular biomacromolecules such as proteins and nucleic acids. Meanwhile, the sulfonate anions can inhibit the activity of enzymes within the bacteria, ultimately causing bacterial death. This process endows the wastewater treatment filtration membrane with excellent antibacterial properties.

[0067] Test Example 3

[0068] Antifouling performance test

[0069] Test method: The wastewater treatment filter membranes of the examples and comparative examples were cut into standard samples with a diameter of 10 mm and placed in a well plate. 2 mL of Microcystis aeruginosa algal solution was added to each well. The samples were placed in an artificial climate chamber and incubated at 25 °C for 72 h. The samples were washed three times with PBS solution, and the adhesion of Microcystis aeruginosa was observed under a 20x fluorescence microscope. The results are shown in Table 3.

[0070] Table 3

[0071] Adhesion on the sample surface Adhesion on the sample surface Example 1 Surface biofilm morphology is sparse Comparative Example 1 A continuous biofilm forms on the surface, but it is not completely covered. Example 2 Surface biofilm morphology is sparse Comparative Example 2 Surface biofilm morphology is sparse Example 3 Surface biofilm morphology is sparse Comparative Example 3 The surface was completely covered by accumulated algae.

[0072] A comparison of the experimental data from Examples 1-3 and Comparative Examples 1-3 in Table 3 shows that the wastewater treatment filter membrane prepared by the present invention has good antifouling performance.

[0073] By comparison, the surface biofilm morphology of Examples 1-3 was sparse, while the surface of Comparative Example 1 formed a continuous biofilm, but it was not completely covered. This indicates that the zwitterionic intermediate was prepared by reacting 3-chloropropyne and (but-3-en-1-yl)(methyl)amine, and then reacted with 1,3-propanesulfonyl lactone to undergo ring-opening quaternization to prepare a zwitterionic monomer. Quaternary ammonium salt and sulfonyl groups were introduced onto the surface of the polyvinylidene fluoride membrane. Polyethylene glycol was used as a porogen, and the zwitterionic monomer and N,N-methylenebisacrylamide were in situ cross-linked in a polyvinylidene fluoride solution. The casting solution is prepared by polymerization; then, a functionalized polyvinylidene fluoride membrane is made from the casting solution by non-solvent-induced phase separation technology. The charge balance system formed by sulfonate anions and quaternary ammonium cations can also inhibit the attachment and reproduction of bacteria on the membrane surface through electrostatic repulsion, and reduce the contact sites between bacteria and the membrane surface through a dense hydration layer, inhibiting the deposition of extracellular polymers secreted by bacteria, thus preventing the formation of biofilm from the source and avoiding the impact of biological pollution on membrane performance, thereby further improving the antifouling performance of wastewater treatment filtration membranes.

[0074] By comparison, the surface biofilm morphology of Examples 1-3 was sparse, while the surface of Comparative Example 3 was completely covered by accumulated algae. This indicates that grafting 1-azido-2-chloroethane onto 3-ethylindole produces a modified indole derivative. Using copper sulfate pentahydrate as a catalyst to graft the modified indole derivative onto the surface of a porous polyvinylidene fluoride membrane, a wastewater treatment filter membrane is prepared. Algae and their secreted extracellular polymers easily form a gel layer on the membrane surface, clogging the membrane pores and being a significant cause of membrane fouling. The planar conjugated heterocyclic structure of the modified indole derivative can bind to chlorophyll a and thylakoid membrane proteins in algal chloroplasts through allelopathic effects, interfering with the electron transport chain of photosynthetic system II, inhibiting the synthesis of ATP and NADPH in the light reaction, and interfering with the energy metabolism pathway of algae through chemical signals. Simultaneously, the indole derivative can block the binding of extracellular polysaccharides secreted by algae to receptors on the surface of algal cells through allelopathic effects, inhibiting the quorum sensing system of algae and preventing algal cell aggregation to form an algal membrane, thereby endowing the wastewater treatment filter membrane with excellent antifouling properties.

[0075] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A wastewater treatment filter membrane, characterized in that, The wastewater treatment filtration membrane is prepared by reacting an amphoteric intermediate with 1,3-propanesulfonyl lactone to obtain an amphoteric monomer; then, the amphoteric monomer and N,N-methylenebisacrylamide are crosslinked and polymerized in situ in a polyvinylidene fluoride solution to obtain a casting solution; the casting solution is then used to form a functionalized polyvinylidene fluoride membrane through a solvent-inducible phase separation technique; dopamine hydrochloride and polyethyleneimine are co-deposited on the surface of the functionalized polyvinylidene fluoride membrane to obtain a porous polyvinylidene fluoride membrane; finally, an indole derivative modified by copper sulfate pentahydrate is grafted onto the surface of the porous polyvinylidene fluoride membrane to obtain the final membrane. The zwitterionic intermediate is prepared by reacting 3-chloropropyne with (but-3-en-1-yl)(methyl)amine. The modified indole derivative is prepared by grafting 1-azido-2-chloroethane onto 3-ethylindole.

2. A method for preparing a wastewater treatment filter membrane, characterized in that, The method for preparing the wastewater treatment filtration membrane includes the following preparation steps: (1) Add the zwitterionic intermediate and 1,3-propanesulfonyl lactone to acetone at a molar ratio of 1:(1~1.1) in 6~8 times the mass of the zwitterionic intermediate and mix them evenly. Stir the reaction at 28~32℃ and 300~500r / min for 4.5~5.5h, let it stand at room temperature for 1.5~2.5h, filter, wash with acetone 2~4 times, and vacuum dry at 35~45℃ for 5~7h to obtain the zwitterionic monomer; (2) Pour the casting solution onto a glass plate and coat it evenly with a wet film scraper with a thickness of 180~220μm at a speed of 4~6cm / s. Soak it in deionized water at 38~42℃ with a volume of 20~30 times that of the casting solution for 20~40min. Rinse it with deionized water 3~5 times for 24~28h. Let it air dry at room temperature to obtain a functionalized polyvinylidene fluoride membrane. (3) Clean the functionalized polyvinylidene fluoride membrane with ultrasonic cleaning for 8-10 min, press out the air bubbles in the membrane pores with a rubber roller, immerse it completely in the mixed solution, and react with shaking at 100-150 r / min for 20-24 h at room temperature. Soak it in deionized water for 10-14 h and air dry it at room temperature to obtain a porous polyvinylidene fluoride membrane. (4) Mix copper sulfate pentahydrate, tris(hydroxymethyl)methylglycine, sodium ascorbate, and mixed solvent in a mass ratio of 1:(3.8~4.2):(4.8~5.2):(1000~1200) until homogeneous. Stir at room temperature for 10~20 min. Add 24~26 times the mass of modified indole derivative of copper sulfate pentahydrate and continue stirring for 10~20 min. Add a porous polyvinylidene fluoride membrane for immersion. Shake at 28~32℃ and 80~120 r / min in the dark for 12~16 h. Wash with deionized water 3~5 times. Immerse the membrane in 0.1 mol / L disodium ethylenediaminetetraacetate aqueous solution and sonicate for 8~12 min. Wash with anhydrous ethanol 3~5 times and air dry at room temperature in the dark to obtain a wastewater treatment filter membrane.

3. The method for preparing a wastewater treatment filter membrane according to claim 2, characterized in that, The preparation process of the zwitterionic intermediate in step (1) is as follows: Weigh 3-chloropropyne and (but-3-en-1-yl)(methyl)amine at a molar ratio of 1:(1.1~1.3), mix (but-3-en-1-yl)(methyl)amine and anhydrous tetrahydrofuran at a mass ratio of 1:(8~10), stir at room temperature for 5~15 min under nitrogen protection, add equimolar amounts of triethylamine to 3-chloropropyne, cool to 0~4℃, continue stirring for 3~5 min, add 3-chloropropyne at a uniform rate over 1~2 h, continue stirring for 50~70 min, raise to room temperature, continue stirring for 6~8 h, filter, remove anhydrous tetrahydrofuran by vacuum distillation, and obtain the zwitterionic intermediate.

4. The method for preparing a wastewater treatment filter membrane according to claim 2, characterized in that, The preparation process of the casting solution in step (2) is as follows: Polyvinylidene fluoride, polyethylene glycol, N,N-methylenebisacrylamide, and N-methylpyrrolidone are mixed evenly in a mass ratio of 1:(0.4~0.6):(0.030~0.034):(7.5~7.9). Under nitrogen protection, the mixture is heated to 65~75℃ and stirred at 300~500r / min for 2~3h. 0.7~0.9 times the mass of polyvinylidene fluoride zwitterionic monomer is added, and the mixture is stirred and reacted for 20~40min. 0.0009~0.0011 times the mass of polyvinylidene fluoride 2,2-azobisisobutyronitrile is added, and the mixture is stirred and reacted for 8~10h. The mixture is cooled to room temperature and allowed to stand under reduced pressure for 40~60min to obtain the casting solution.

5. The method for preparing a wastewater treatment filter membrane according to claim 4, characterized in that, The polyvinylidene fluoride is designated as FR904.

6. The method for preparing a wastewater treatment filter membrane according to claim 4, characterized in that, The polyethylene glycol is of type PEG-400.

7. The method for preparing a wastewater treatment filter membrane according to claim 2, characterized in that, The preparation process of the mixed solution in step (3) is as follows: 10 mmol / L Tris-HCl buffer solution with pH=8.5, dopamine hydrochloride and polyethyleneimine are mixed evenly at a mass ratio of 1:(1.8~2.2):(3.8~4.2) and stirred at room temperature for 20~40 min to obtain the mixed solution.

8. The method for preparing a wastewater treatment filter membrane according to claim 7, characterized in that, The polyethyleneimine in question is designated as PEI-25000 Da.

9. The method for preparing a wastewater treatment filter membrane according to claim 2, characterized in that, The preparation process of the modified indole derivative in step (4) is as follows: 3-ethylindole, potassium carbonate, and N,N-dimethylformamide are mixed evenly at a mass ratio of 1:(1.35~1.45):(7~9), and stirred at room temperature for 10~20 min. 0.7~0.8 times the mass of 3-ethylindole and 1-azido-2-chloroethane are added at a uniform rate over 30~40 min. The temperature is raised to 75~85℃, and the stirring reaction is continued for 12~16 h. The mixture is poured into ice-cold deionized water at a mass of 6~8 times the mass of N,N-dimethylformamide, filtered, washed 3~5 times with deionized water, and vacuum dried at 40~50℃ for 6~8 h to obtain the modified indole derivative.

10. The method for preparing a wastewater treatment filter membrane according to claim 2, characterized in that, The mixed solvent in step (4) is prepared by uniformly mixing dimethyl sulfoxide and deionized water at a volume ratio of 1:1.