An anti-pollution hydrophilic PVDF / Ac-Dex-PEG composite membrane, a preparation method thereof and application thereof

Abstract

The application discloses an anti-pollution hydrophilic PVDF / Ac-Dex-PEG composite membrane and a preparation method and application thereof, and belongs to the technical field of water treatment. The preparation method of the anti-pollution hydrophilic PVDF / Ac-Dex-PEG composite membrane comprises the following steps: (1) dextran amination (Dex-NH2), (2) amino dextran acetylation (Ac-Dex-NH2), (3) synthesis of polyethylene glycol-dextran anhydride (Ac-Dex-PEG), and (4) preparation of the PVDF / Ac-Dex-PEG composite membrane. The preparation method connects 1,2-ethylenediamine to the surface of dextran, and reacts with 2-methoxy propylene to synthesize an amino dextran anhydride acetylation product. The amino dextran anhydride acetylation product is grafted with polyethylene glycol to prepare an amphiphilic polymer polyethylene glycol-dextran anhydride (Ac-Dex-PEG). Under the action of the polyethylene glycol-dextran anhydride, a hydrophilic layer can be formed on the surface of the PVDF / Ac-Dex-PEG composite membrane. Moreover, the Dex-PEG hydrophilic segment can effectively prevent the contact of proteins with the hydrophilic layer formed by the PVDF / Ac-Dex-PEG composite membrane, so that the effect of resisting protein pollution is achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of water treatment, and particularly relates to an anti-pollution hydrophilic PVDF / Ac-Dex-PEG composite membrane and a preparation method and application thereof. BACKGROUND

[0002] Polyvinylidene fluoride (PVDF) is a high-performance polymer material, which is widely used as a membrane separation material in the field of water treatment due to its unique molecular structure and chemical stability. Studies have shown that PVDF material not only exhibits excellent corrosion resistance in the field of water treatment, but also can withstand harsh environments such as strong acid and strong alkali; at the same time, PVDF also has outstanding mechanical strength, which ensures the structural stability of the membrane assembly during long-term operation. However, due to the strong electronegativity of fluorine atoms in the molecular chain, PVDF membranes often exhibit obvious hydrophobic characteristics. This hydrophobic characteristic, although helpful for some scene applications, can easily cause serious membrane pollution problems in sewage application systems containing biological macromolecules such as proteins, polysaccharides or microorganisms. This generally specifically manifests as: 1) the hydrophobic surface promotes the adsorption and deposition of organic pollutants on the membrane surface; 2) microorganisms are more likely to adhere and grow on the hydrophobic surface, eventually leading to significant attenuation of water flux and significant increase of operating pressure. These phenomena not only seriously affect the separation efficiency of PVDF membranes, but also shorten the service life of the membranes and increase the operating cost. Therefore, developing effective surface modification technology to improve the anti-pollution performance of PVDF membranes has become a key scientific problem that needs to be solved in the current membrane separation field. SUMMARY

[0003] The purpose of the present application is to provide an anti-pollution hydrophilic PVDF / Ac-Dex-PEG composite membrane and a preparation method and application thereof, which can construct a hydrophilic structure on the surface of the PVDF / Ac-Dex-PEG composite membrane to achieve the purpose of hydrophilic anti-pollution.

[0004] To achieve the above-mentioned purpose, the present application provides a preparation method of an anti-pollution hydrophilic PVDF / Ac-Dex-PEG composite membrane, which comprises the following steps:

[0005] (1) Aminoization of dextran (Dex-NH2): dextran and ethylenediamine are dissolved in dimethyl sulfoxide (DMSO) to form a reaction solution, sodium cyanoborohydride is added to the reaction solution, stirring, cooling to room temperature, precipitation, purification, and then aminoized dextran (Dex-NH2) is obtained;

[0006] (2) Amino dextran acetylation (Ac-Dex-NH2): Dex-NH2 synthesized in step (1) is added to anhydrous DMSO under nitrogen protection, and stirred at room temperature for 10-60 min, pyridine p-toluenesulfonic acid and 2-methoxy propylene are added to the solution, sealed and stirred, followed by quenching, precipitation, centrifugal separation, washing, to obtain amino dextran acetylation (Ac-Dex-NH2);

[0007] (3) Synthesis of polyethylene glycol-dextran acetylation (Ac-Dex-PEG): Ac-Dex-NH2 synthesized in step (2), carboxylated polyethylene glycol (PEG-COOH) and 1,1'-carbonyl diimidazole (CDI) are dispersed in anhydrous DMSO, stirred, dialyzed, freeze-dried, to obtain white polyethylene glycol-dextran acetylation (Ac-Dex-PEG) powder;

[0008] (4) Preparation of PVDF / Ac-Dex-PEG composite membrane: Ac-Dex-PEG polymer synthesized in step (3), pore-forming agent and PVDF powder are dispersed in organic solvent in turn, stirred, deaerated, cooled to room temperature, then the casting solution is scraped on a glass plate with a doctor blade, the glass plate with the casting solution is slowly put into deionized water, and the PVDF / Ac-Dex-PEG composite membrane is obtained after 12-24 hours of sufficient phase inversion.

[0009] Further, in step (1), the concentration of dextran is 0.1-1 g / mL, the mass ratio of dextran to ethylenediamine is (1-100):1, the mass ratio of dextran to sodium cyanoborohydride is (10-1000):1, the stirring temperature is 50-100℃, the stirring time is 2-10 days, the precipitant is methanol, the purification solvent is water and methanol, and the purification times is 3-5 times.

[0010] Further, in step (2), the concentration of Dex-NH2 is 0.025-1 g / mL, the mass ratio of Dex-NH2 to pyridine p-toluenesulfonic acid is (10-500):1, the mass ratio of Dex-NH2 to 2-methoxy propylene is (0.05-5):1, the sealed stirring time is 1-5 hours, and the precipitant is deionized water.

[0011] Further, in step (3), the mass ratio of Ac-Dex-NH2 to PEG-COOH is (0.1-10):1, the mass ratio of Ac-Dex-NH2 to CDI is (5-250):1, the stirring temperature is 50-100℃, the stirring time is 6-24 hours, the dialysis bag is MW=2-10K, and the dialysis time is 1-5 days.

[0012] Further, in the step (4), the concentration of Ac-Dex-PEG is 0.01-0.05 g / mL, the mass ratio of Ac-Dex-PEG to the pore-forming agent is (0.1-5):1, the mass ratio of Ac-Dex-PEG to PVDF is (0.05-0.5):1, the stirring temperature is 50-95 DEG C, the stirring time is 6-18 hours, the defoaming temperature is 25-75 DEG C, and the defoaming time is 5-10 hours.

[0013] Further, in the step (4), the pore-forming agent is one of polyvinylpyrrolidone (PVP) and polyethylene glycol (PEG), and the organic solvent is one of dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide and dimethylformamide.

[0014] The application further provides an anti-pollution hydrophilic PVDF / Ac-Dex-PEG composite membrane, which is prepared by the method for preparing the anti-pollution hydrophilic PVDF / Ac-Dex-PEG composite membrane.

[0015] Further, the contact angle of the PVDF / Ac-Dex-PEG composite membrane is 45 DEG, the protein adsorption amount is 13 mg / m 2 , and the water flux is 200 L / m 2 ·h.

[0016] The application further provides that the anti-pollution hydrophilic PVDF / Ac-Dex-PEG composite membrane is mainly applied in the field of water treatment.

[0017] The application connects amino groups to the surface of dextran (Dex) to prepare amino-dextran (Dex-NH2), and then prepares amino-dextran anhydride (Ac-Dex-NH2) through an acetylation reaction; then, polyethylene glycol is chemically connected to Ac-Dex-NH2 through an amidation reaction to prepare polyethylene glycol-dextran anhydride (Ac-Dex-PEG) hydrophilic additive; finally, the Ac-Dex-PEG is added to a PVDF casting solution to prepare a hydrophilic anti-pollution PVDF / Ac-Dex-PEG composite membrane.

[0018] Compared with the prior art, the application has the following beneficial effects:

[0019] (1) The amphiphilic polyethylene glycol-dextran anhydride not only has good biocompatibility and biosafety, but also can improve the stability in the membrane through the anchoring of the hydrophobic dextran anhydride segment and the PVDF matrix material.

[0020] (2) The polyethylene glycol-dextran anhydride hydrophilic segment has significant hydrophilic effect, and can form a hydrophilic layer on the surface of the PVDF / Ac-Dex-PEG composite membrane, which makes the PVDF / Ac-Dex-PEG composite membrane have good anti-protein contamination performance.

[0021] (3) The polyethylene glycol-dextran anhydride promotes the construction of the water channel of the PVDF / Ac-Dex-PEG composite membrane, and can improve the water consumption of the PVDF / Ac-Dex-PEG composite membrane.

[0022] (4) The preparation method is stable and has high repeatability, the PVDF / Ac-Dex-PEG composite membrane prepared has good biological safety and low water contact angle, so that the hydrophilic modification of the PVDF membrane is realized, and a new idea for the hydrophilic anti-pollution of the PVDF membrane is provided. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is the infrared spectrum of PEG-COOH, Dex and Ac-Dex-PEG of the application;

[0024] Figure 2 is the water contact angle of PVDF, PVDF / PEG and PVDF / Ac-Dex-PEG composite membranes of the application;

[0025] Figure 3 is the BSA adsorption amount diagram of PVDF, PVDF / PEG and PVDF / Ac-Dex-PEG composite membranes of the application;

[0026] Figure 4 is the water flux diagram of PVDF, PVDF / PEG and PVDF / Ac-Dex-PEG composite membranes of the application;

[0027] Figure 5 is a preparation schematic diagram of the amphiphilic polymer Ac-Dex-PEG composite membrane of the application;

[0028] Figure 6 is a preparation step flow chart of an anti-pollution hydrophilic PVDF / Ac-Dex-PEG composite membrane according to one embodiment of the application. DETAILED DESCRIPTION

[0029] In order for those skilled in the art to better understand the technical solutions in the specification, the technical solutions in the specification will be clearly and completely described below in combination with the drawings in the specification. Obviously, the described embodiments are only part of the embodiments of the specification, not all. Based on the embodiments in the specification, all other embodiments obtained by those of ordinary skill in the art without creative labor should be within the scope of protection of the specification.

[0030] Embodiment 1:

[0031] (1) Aminization of dextran (Dex-NH2): First, 5 g of dextran and 0.5 g of ethylenediamine were dissolved in 50 mL of dimethyl sulfoxide (DMSO), and 0.02 g of sodium cyanoborohydride was added to the reaction solution. After the mixed solution was stirred at 60°C for 7 days, the reaction was terminated by cooling the reaction solution to room temperature, and the reaction product was precipitated with methanol. Finally, the product was purified with water and methanol three times to obtain aminated dextran (Dex-NH2).

[0032] (2) Acetylation of aminated dextran (Ac-Dex-NH2): Under nitrogen protection, 1 g of synthesized Dex-NH2 was added to 10 mL of anhydrous DMSO and stirred at room temperature for 30 min. Then, 0.015 g of pyridine p-toluenesulfonic acid and 2 g of 2-methoxyacrylate were added to the solution, and the stirring was continued under a sealed condition for 3 hours. After the reaction was completed, the reaction was quenched with 1 mL of triethanolamine, and the acetylated aminated dextran anhydride was precipitated with 100 mL of deionized water. Finally, the product was separated by centrifugation, and the obtained precipitate was further washed with deionized water to obtain aminated dextran anhydride (Ac-Dex-NH2).

[0033] (3) Synthesis of polyethylene glycol-dextran anhydride (Ac-Dex-PEG): 1 g of Ac-Dex-NH2, 1 g of carboxylated polyethylene glycol (PEG-COOH), and 0.04 g of 1,1'-carbonyldiimidazole (CDI) were dispersed in 50 mL of anhydrous DMSO and stirred at 80°C for 12 hours. After the reaction was completed, the reaction solution was dialyzed in a dialysis bag (MW=8K) in deionized water for 3 days. Finally, the obtained solution was freeze-dried at -50°C to obtain white polyethylene glycol-dextran anhydride (Ac-Dex-PEG) powder; the infrared test results showed that: Figure 1 ): PEG-COOH (PEG) appeared a characteristic absorption peak of C=O in COOH at 1740 cm -1 -1. When PEG-COOH was connected to the hydroxyl group of dextran, the characteristic absorption peak at 1740 cm -1 -1 of Ac-Dex-PEG (Dex-PEG) became smaller, but still existed. At the same time, the characteristic absorption peak of PEG-COOH (PEG) at 1110 cm -1A new CO absorption peak appeared at 827 cm⁻¹, indicating the formation of an ester bond. Furthermore, the infrared absorption spectrum of Ac-Dex-PEG not only showed the characteristic OH absorption peak of Dex, but also a peak at 827 cm⁻¹. -1 948cm -1 1242cm -1 The presence of characteristic absorption peaks of PEG further confirms the successful preparation of Ac-Dex-PEG.

[0034] (4) Preparation of PVDF / Ac-Dex-PEG composite membrane: 5g Ac-Dex-PEG polymer, 8g pore-forming agent and 16g PVDF powder were sequentially dispersed in 76mL of solvent and stirred at 75℃ for 10 hours. Then, the mixture was allowed to stand at 25℃ for 10 hours to achieve degassing. Next, the reaction solution was cooled to room temperature, and casting solution was coated onto a glass plate using a 100μm thick doctor blade. Then, the glass plate with the casting solution was slowly immersed in deionized water. Finally, after 24 hours of complete phase inversion, the PVDF / Ac-Dex-PEG composite membrane was obtained.

[0035] By comparing the water contact angles of pure PVDF membranes and PVDF / Ac-Dex-PEG composite membranes, it can be observed that the contact angle of the PVDF / Ac-Dex-PEG composite membrane is 45°, which is 50% lower than the contact angle of the pure PVDF membrane (90°). Figure 2 This indicates that Ac-Dex-PEG significantly improves the surface hydrophilicity of the PVDF / Ac-Dex-PEG composite membrane. Furthermore, to further investigate whether Ac-Dex-PEG can improve the antifouling ability of the PVDF / Ac-Dex-PEG composite membrane, BSA protein adsorption tests were performed on both the PVDF and PVDF / Ac-Dex-PEG composite membranes. The results showed that the protein adsorption capacity of the PVDF / Ac-Dex-PEG composite membrane was only 13 mg / m³. 2 Compared to the protein adsorption capacity of pure PVDF membrane (67 mg / m³), 2 ) decreased by 80% Figure 3 This indicates that the addition of Ac-Dex-PEG significantly improved the antifouling ability of the PVDF / Ac-Dex-PEG composite membrane. Simultaneously, the hydrophilic segments of Ac-Dex-PEG may provide hydrophilic channels for the PVDF / Ac-Dex-PEG composite membrane. Water flux testing showed that the prepared PVDF / Ac-Dex-PEG composite membrane had a water flux of 200 L / m³. 2 ·h, compared to the water flux of a pure PVDF membrane (60 L / m³) 2 •h) increased by 70% ( Figure 4 ).

[0036] The application is not limited to the details of the foregoing exemplary embodiments. The embodiments are exemplary and not limiting, the scope of the application being defined by the claims appended hereto rather than the description preceding them, so no limitation of the claims by any referenced figure should be inferred.

[0037] The above description is merely exemplary of one or more embodiments of the present description and is not intended to limit the present description. Since various changes and modifications can be made to the one or more embodiments of the present description, it should be understood that the present description is not limited to the details of the foregoing description but can be practiced with the exact details of the one or more embodiments. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present description should be included in the scope of the claims.

Claims

1. A method for preparing an antifouling hydrophilic PVDF / Ac-Dex-PEG composite membrane, characterized in that, Includes the following steps: (1) Dextran amination (Dex-NH2): Dextran and ethylenediamine were dissolved in dimethyl sulfoxide (DMSO) to form a reaction solution. Sodium cyanoborohydride was added to the reaction solution, stirred, cooled to room temperature, precipitated, and purified to obtain amination dextran (Dex-NH2). (2) Acetylation of aminodextran (Ac-Dex-NH2): Under nitrogen protection, Dex-NH2 synthesized in step (1) was added to anhydrous DMSO and stirred at room temperature for 10-60 min. Pyridine p-toluenesulfonate and 2-methoxypropylene were added to the solution, sealed and stirred, and then quenched, precipitated, centrifuged and washed to obtain aminodextran anhydride (Ac-Dex-NH2). (3) Synthesis of polyethylene glycol-dextran anhydride (Ac-Dex-PEG): The Ac-Dex-NH2 synthesized in step (2), carboxylated polyethylene glycol (PEG-COOH) and 1,1'-carbonyl diimidazole (CDI) were dispersed in anhydrous DMSO, stirred, dialyzed and freeze-dried to obtain white polyethylene glycol-dextran anhydride (Ac-Dex-PEG) powder; (4) Preparation of PVDF / Ac-Dex-PEG composite membrane: The Ac-Dex-PEG polymer synthesized in step (3), the pore-forming agent and PVDF powder are dispersed in an organic solvent in sequence, stirred, allowed to stand to degas, and cooled to room temperature. Then, the casting solution is coated on a glass plate with a scraper. The glass plate with the casting solution is slowly placed into deionized water. After 12 to 24 hours of complete phase inversion, the PVDF / Ac-Dex-PEG composite membrane is obtained.

2. The method for preparing the antifouling hydrophilic PVDF / Ac-Dex-PEG composite membrane according to claim 1, characterized in that, In step (1), the concentration of dextran is 0.01-1 g / mL, the mass ratio of dextran to ethylenediamine is (1-100):1, the mass ratio of dextran to sodium cyanoborohydride is (10-1000):1, the stirring temperature is 50-100℃, the stirring time is 2-10 days, the precipitant is methanol, the purification solvent is water and methanol, and the purification is performed 3-5 times.

3. The method for preparing the antifouling hydrophilic PVDF / Ac-Dex-PEG composite membrane according to claim 1, characterized in that, In step (2), the concentration of Dex-NH2 is 0.025-1 g / mL, the mass ratio of Dex-NH2 to p-toluenesulfonic acid pyridine is (10-500):1, the mass ratio of Dex-NH2 to 2-methoxypropylene is (0.05-5):1, the sealing and stirring time is 1-5 hours, and the precipitant is deionized water.

4. The method for preparing the antifouling hydrophilic PVDF / Ac-Dex-PEG composite membrane according to claim 1, characterized in that, In step (3), the mass ratio of Ac-Dex-NH2 to PEG-COOH is (0.1-10):1, the mass ratio of Ac-Dex-NH2 to CDI is (5-250):1, the stirring temperature is 50-100℃, the stirring time is 6-24 hours, the dialysis bag has a MW of 2-10K, and the dialysis time is 1-5 days.

5. The method for preparing the antifouling hydrophilic PVDF / Ac-Dex-PEG composite membrane according to claim 1, characterized in that, In step (4), the concentration of Ac-Dex-PEG is 0.01-0.05 g / mL, the mass ratio of Ac-Dex-PEG to porogen is (0.1-5):1, the mass ratio of Ac-Dex-PEG to PVDF is (0.05-0.5):1, the stirring temperature is 50-95℃, the stirring time is 6-18 hours, the degassing temperature is 25-75℃, and the degassing time is 5-10 hours.

6. The method for preparing the antifouling hydrophilic PVDF / Ac-Dex-PEG composite membrane according to claim 1, characterized in that, In step (4), the pore-forming agent is one of polyvinylpyrrolidone (PVP) and polyethylene glycol (PEG), and the organic solvent is one of dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, and dimethylformamide.

7. A pollution-resistant hydrophilic PVDF / Ac-Dex-PEG composite membrane, characterized in that, The antifouling hydrophilic PVDFF / Ac-Dex-PEG composite membrane is prepared by the method described in any one of claims 1-6.

8. The antifouling hydrophilic PVDF / Ac-Dex-PEG composite membrane according to claim 7, characterized in that, The PVDF / Ac-Dex-PEG composite membrane has a contact angle of 45° and a protein adsorption capacity of 13 mg / m³. 2 The water flux is 200 L / m 2 ·h.

9. The antifouling hydrophilic PVDF / Ac-Dex-PEG composite membrane as described in claim 7 is applied in the field of water treatment.

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