A hydrophilic anti-pollution MXene / PVDF composite membrane, a preparation method and application thereof

Abstract

The application provides a hydrophilic anti-pollution MXene / PVDF composite membrane and a preparation method and application thereof, and relates to the technical field of separation membrane manufacturing.The preparation method of the hydrophilic anti-pollution MXene / PVDF composite membrane provided by the application comprises the following steps: mixing PVDF powder, a pore former and an organic solvent to obtain a PVDF casting solution; mixing the PVDF casting solution and a few-layer MXene nanosheet dispersion solution to obtain a MXene / PVDF casting solution; coating the MXene / PVDF casting solution onto a non-woven fabric, and sequentially performing coagulation bath and drying to obtain the hydrophilic anti-pollution MXene / PVDF composite membrane.The hydrophilic anti-pollution MXene / PVDF composite membrane provided by the application enhances hydrophilicity and improves BSA rejection rate, exhibits high anti-pollution property, excellent reusability and chemical stability, and has a simple process and is suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention relates to the field of separation membrane manufacturing technology, specifically to a hydrophilic antifouling MXene / PVDF composite membrane, its preparation method, and its application. Background Technology

[0002] Polyvinylidene fluoride (PVDF) membranes are semi-crystalline polymers with excellent thermal stability, chemical resistance, and high mechanical properties. They are soluble in aprotic polar solvents, resistant to chemical corrosion at room temperature, and exhibit resistance to fading, UV radiation, and impact in harsh environments, making them widely used in the preparation of ultrafiltration and microfiltration membranes. However, due to the low surface energy of PVDF, it exhibits hydrophobic properties, allowing pollutant molecules to gradually adsorb onto the membrane surface and dominate the membrane boundary layer. This makes polymer separation membranes prone to membrane fouling during use, leading to increased membrane resistance and decreased membrane flux. Consequently, this results in reduced membrane separation efficiency, increased operating and maintenance costs, and a continuously decreasing membrane lifespan. Blending and modifying membranes is the simplest and most effective method to improve membrane performance, allowing the membrane to possess the combined advantages of blended materials. Therefore, hydrophilic materials can be used to prepare membranes. Blending hydrophilic and hydrophobic polymers yields polymers with hydrolyzable groups, which hydrolyze the membrane surface, making it hydrophilic and reducing mass transfer resistance during membrane separation. This improves the separation performance and resistance to pollutant accumulation of the polymer membrane. Meanwhile, blending inorganic materials with polymers has multiple advantages, such as simple operation, readily available materials, low cost, obvious effects, and the ability to maintain the hydrophilicity of membranes for a long time. It is also one of the hot methods for modifying membrane materials.

[0003] Transition metal carbonitrides (MXenes) have the general formula M n+1 X n T x(n = 1, 2, or 3), where M is a transition metal and X is nitrogen or carbon. This material possesses physicochemical properties such as high specific surface area, high electronic conductivity, hydrophilicity, and tunable surface functional groups, and has been widely used in fields involving multiple energy conversions, such as lithium batteries, catalysis, and solar energy development and utilization. Termination groups on the MXene surface, such as -O, -OH, and -F, can interact with the PVDF matrix at the interface, thereby significantly improving the performance of the PVDF film. When treated in HF solution or other acidic solutions containing fluoride ions, the morphology of MXene is an accordion-like stack of closely packed layers. The morphology of MXene is altered by the additional intercalation of various ions and molecules in its interlayer space, leading to an increase in the distance between individual two-dimensional sheets, thereby promoting further peeling of the two-dimensional MXene sheets. Due to the weakening of the interaction forces between individual sheets, the accordion-shaped stack expands and spontaneously delaminates. Compared to multilayer MXene nanosheets, few-layer MXene nanosheets generate more hydroxyl radicals, which can be attributed to their higher content of available active TiO2 sites, providing more redox reaction sites and enhancing their significant adsorption capacity at the -OH surface ends. Furthermore, the two-dimensional sheet structure of MXene and its sharp edges directly contact the bacterial surface, leading to cell membrane disruption and inducing a complete loss of bacterial and microbial function, thus improving the antibacterial effect of the composite material. Currently, the main methods for preparing MXene / PVDF composite membranes include blending and vacuum filtration. Vacuum filtration cannot accurately control the membrane thickness through solution quantity and mass difference. When the MXene layer is too thick, the interfacial structure between MXene and PVDF may be unstable, and the surface active layer may easily peel off, negatively impacting the quality of the composite membrane. This limitation restricts this method to the experimental stage, resulting in low production efficiency and making it difficult to use for large-scale industrial production. Summary of the Invention

[0004] The purpose of this invention is to provide a hydrophilic antifouling MXene / PVDF composite membrane, its preparation method, and its application. Compared with the unmodified pure PVDF membrane, the hydrophilic antifouling MXene / PVDF composite membrane prepared by this invention has significantly improved hydrophilicity and membrane flux, has a high rejection rate for large molecular proteins (taking bovine serum albumin BSA as an example), and has improved membrane flux recovery rate. It can be widely used in the field of water treatment.

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

[0006] This invention provides a method for preparing a hydrophilic antifouling MXene / PVDF composite membrane, comprising the following steps:

[0007] PVDF powder, pore-forming agent and organic solvent are mixed to obtain PVDF casting solution;

[0008] The PVDF casting solution and the few-layer MXene nanosheet dispersion were mixed to obtain an MXene / PVDF casting solution;

[0009] The MXene / PVDF casting solution was coated onto a nonwoven fabric, and then subjected to a coagulation bath and drying to obtain a hydrophilic antifouling MXene / PVDF composite membrane.

[0010] Preferably, the mass ratio of the PVDF powder, pore-forming agent, and organic solvent is 1:1 to 5:6 to 10.

[0011] Preferably, the pore-forming agent includes at least one of polyvinylpyrrolidone and polyethylene glycol;

[0012] The organic solvent includes at least one of dimethyl sulfoxide and N,N-dimethylacetamide.

[0013] Preferably, the method for preparing the few-layer MXene nanosheet dispersion includes:

[0014] The MAX phase raw material was mixed with an acidic solution and etched to obtain multilayer MXene nanosheets;

[0015] The multilayer MXene nanosheets are mixed with an intercalating agent and intercalated to obtain few-layer MXene nanosheets.

[0016] The few-layer MXene nanosheets were dispersed in an organic solvent to obtain a few-layer MXene nanosheet dispersion.

[0017] Preferably, the acidic solution comprises fluoride and hydrochloric acid; the ratio of fluoride to hydrochloric acid is 1g:20-50mL; and the concentration of hydrochloric acid is 5-10mol / L.

[0018] Preferably, the etching temperature is 30–50°C.

[0019] Preferably, the intercalating agent comprises one or more of dimethyl sulfoxide, ethanol, tetrabutylammonium hydroxide, and tetramethylammonium hydroxide.

[0020] Preferably, the concentration of few-layer MXene nanosheets in the few-layer MXene nanosheet dispersion in the MXene / PVDF casting solution is 0.5–10 mg / mL.

[0021] The present invention provides a hydrophilic antifouling MXene / PVDF composite membrane prepared by the preparation method described above, comprising a nonwoven fabric and a PVDF membrane attached to the surface of the nonwoven fabric; MXene nanosheets are uniformly distributed in the PVDF membrane.

[0022] This invention provides the application of the hydrophilic antifouling MXene / PVDF composite membrane described above in the field of water treatment.

[0023] This invention provides a method for preparing a hydrophilic antifouling MXene / PVDF composite membrane. The invention modifies the PVDF membrane through blending, utilizing few-layer MXene nanosheets containing a large number of -OH groups to improve the hydrophilicity and antifouling properties of the composite membrane, thereby enhancing its filtration and separation efficiency. After blending modification, the flux of the hydrophilic antifouling MXene / PVDF composite membrane increased by 87.6%, the BSA rejection rate reached 97.28%, and the flux recovery rate reached 80.78%.

[0024] Furthermore, the present invention obtains multilayer MXene nanosheets containing a large number of -OH groups by treating the multilayer MXene nanosheets obtained by etching and stripping with an intercalating agent to obtain few-layer MXene nanosheets. The hydrophilic antifouling MXene / PVDF composite membrane provided by the present invention enhances hydrophilicity, improves BSA rejection rate, and exhibits high antifouling properties, excellent reusability and chemical stability. The process is relatively simple, which can greatly improve production efficiency, reduce production costs, and is suitable for large-scale industrial production. Attached Figure Description

[0025] Figure 1 SEM images of the multilayer MXene nanosheets prepared for the example;

[0026] Figure 2 TEM images of few-layer MXene nanosheets prepared for the example;

[0027] Figure 3 EDS spectra of few-layer MXene nanosheets prepared for the example;

[0028] Figure 4 The contact angle of the hydrophilic antifouling MXene / PVDF composite membrane prepared for the example;

[0029] Figure 5 The pure water flux of the hydrophilic antifouling MXene / PVDF composite membrane prepared for the example;

[0030] Figure 6 BSA rejection rate of the hydrophilic antifouling MXene / PVDF composite membrane prepared for the example;

[0031] Figure 7 Antifouling analysis of the hydrophilic antifouling MXene / PVDF composite membrane prepared for the example. Detailed Implementation

[0032] This invention provides a method for preparing a hydrophilic antifouling MXene / PVDF composite membrane, comprising the following steps:

[0033] PVDF powder, pore-forming agent and organic solvent are mixed to obtain PVDF casting solution;

[0034] The PVDF casting solution and the few-layer MXene nanosheet dispersion were mixed to obtain an MXene / PVDF casting solution;

[0035] The MXene / PVDF casting solution was coated onto a nonwoven fabric, and then subjected to a coagulation bath and drying to obtain a hydrophilic antifouling MXene / PVDF composite membrane.

[0036] This invention involves mixing PVDF powder, a pore-forming agent, and an organic solvent to obtain a PVDF casting solution. In this invention, the preferred mass ratio of the PVDF powder, pore-forming agent, and organic solvent is 1:1 to 5:6 to 10, more preferably 1:1:6. In this invention, the preferred particle size of the PVDF powder is 100 to 200 μm, more preferably 120 to 180 μm.

[0037] In this invention, the porogen preferably includes at least one of polyvinylpyrrolidone (PVP) and polyethylene glycol (PEG); when the porogen contains PVP and PEG, the volume ratio of PVP to PEG is preferably 1:1. In this invention, the molecular weight range of the polyvinylpyrrolidone is preferably 44,000 to 54,000, more preferably 40,000. The molecular weight range of the polyethylene glycol is preferably 200 to 800, more preferably 400.

[0038] In this invention, the organic solvent preferably includes at least one of dimethyl sulfoxide (DMSO) and N,N-dimethylacetamide (DMAc); when the organic solvent contains DMSO and DMAc, the volume ratio of DMSO and DMAc is preferably 1:1.

[0039] In this invention, the mixing of PVDF powder, pore-forming agent, and organic solvent preferably comprises adding PVDF powder to a mixed solution of pore-forming agent and organic solvent. In this invention, the mixing is preferably carried out under heating and stirring conditions; the heating and stirring temperature is preferably 60–80°C, more preferably 70–80°C; the heating and stirring time is preferably 12–24 hours, more preferably 18–24 hours. In this invention, the heating and stirring is preferably done with a glass rod. Compared with mechanical stirring, manual glass rod stirring allows for a more complete reaction of the organic solvent and avoids the problem of PVDF powder agglomeration.

[0040] After obtaining the PVDF casting solution, the present invention mixes the PVDF casting solution with a few-layer MXene nanosheet dispersion to obtain an MXene / PVDF casting solution. In the present invention, the concentration of few-layer MXene nanosheets in the few-layer MXene nanosheet dispersion in the MXene / PVDF casting solution is preferably 0.5–10 mg / mL, more preferably 5–7.5 mg / mL. In the present invention, the mixing is preferably carried out under heating and stirring conditions; the heating and stirring temperature is preferably 60–80°C, more preferably 70–80°C; and the heating and stirring time is preferably 12–24 h, more preferably 18–24 h.

[0041] In this invention, the method for preparing the few-layer MXene nanosheet dispersion preferably includes:

[0042] The MAX phase raw material was mixed with an acidic solution and etched to obtain multilayer MXene nanosheets;

[0043] The multilayer MXene nanosheets are mixed with an intercalating agent and intercalated to obtain few-layer MXene nanosheets.

[0044] The few-layer MXene nanosheets were dispersed in an organic solvent to obtain a few-layer MXene nanosheet dispersion.

[0045] In this invention, a MAX phase raw material is preferably mixed with an acidic solution and etched to obtain multilayer MXene nanosheets. In this invention, the MAX phase raw material preferably comprises Ti3AlC2. In this invention, the particle size of the MAX phase raw material is preferably 20–50 μm, more preferably 25–38 μm.

[0046] In this invention, the acidic solution preferably comprises a fluoride and hydrochloric acid. The fluoride preferably comprises a fluoride salt, more preferably one or more of lithium fluoride, cobalt fluoride, and sodium fluoride. The concentration of the hydrochloric acid is preferably 5–10 mol / L, more preferably 5–9 mol / L. The ratio of fluoride to hydrochloric acid is preferably 1 g: 20–50 mL, more preferably 1 g: 30–40 mL. The etching temperature is preferably 30–50 °C, more preferably 40–45 °C. The etching is preferably performed under magnetic stirring; the stirring speed is preferably 20–50 rpm, more preferably 30–45 rpm; and the stirring time is preferably 24–72 h, more preferably 36–48 h.

[0047] Preferably, after etching, the resulting etched system is acid-washed, centrifuged, and the supernatant is removed. The system is then repeatedly washed with water until the pH of the reaction solution is neutral, followed by vacuum drying to obtain multilayer MXene nanosheets. In this invention, the acid washing reagent is preferably an aqueous hydrochloric acid solution; the volume ratio of hydrochloric acid to water in the aqueous hydrochloric acid solution is preferably 1:1 to 5, more preferably 1:1 to 3; the concentration of the hydrochloric acid is preferably 12 mol / L. In this invention, the centrifugation speed is preferably 3000 to 15000 rpm, more preferably 8000 to 10000 rpm; the centrifugation time is preferably 5 to 10 min, more preferably 6 to 8 min. In this invention, the vacuum drying temperature is preferably 60 to 100℃, more preferably 80 to 90℃; the vacuum drying time is preferably 12 to 24 h, more preferably 18 to 24 h. In this invention, the thickness of the multilayer MXene nanosheets is preferably 1.5 to 5 μm.

[0048] After obtaining multilayer MXene nanosheets, the present invention preferably mixes the multilayer MXene nanosheets with an intercalating agent and performs intercalation to obtain few-layer MXene nanosheets. In the present invention, the intercalating agent preferably includes one or more of DMSO, ethanol, tetrabutylammonium hydroxide, and tetramethylammonium hydroxide. In the present invention, the mass ratio of the multilayer MXene nanosheets to the intercalating agent is preferably 1:15-30, more preferably 1:20-25. In the present invention, the intercalation preferably includes: magnetically stirring the mixed dispersion of multilayer MXene nanosheets and the intercalating agent, centrifuging the dispersion with deionized water, adding the precipitate to deionized water for dispersion, ultrasonicating, and then centrifuging at low speed, collecting the supernatant and vacuum drying to obtain few-layer MXene nanosheets. In this invention, the magnetic stirring time is preferably 24–72 h, more preferably 36–48 h; the centrifugation speed is preferably 5000–10000 rpm, more preferably 6000–10000 rpm; the centrifugation dispersion time is preferably 5–20 min, more preferably 10–15 min; the ultrasonication time for adding deionized water is preferably 5–10 min, more preferably 6–8 min; the low-speed centrifugation speed is preferably 2000–3000 rpm, more preferably 2200–2500 rpm; the vacuum drying temperature is preferably 60–100℃, more preferably 80–90℃; and the vacuum drying time is preferably 12–24 h, more preferably 18–24 h.

[0049] This invention utilizes the layering effect of intercalating agents to prepare few-layer MXene nanosheets, thereby improving the hydrophilicity of the composite membrane. This results in a membrane with advantages such as antifouling properties and high membrane separation efficiency, making it suitable for large-scale industrial production and showing great promise for wastewater treatment.

[0050] In this invention, the thickness of the few-layer MXene nanosheets is preferably 1.3 to 9 nm.

[0051] After obtaining few-layer MXene nanosheets, the present invention preferably disperses the few-layer MXene nanosheets in an organic solvent to obtain a few-layer MXene nanosheet dispersion. In the present invention, the organic solvent preferably includes DMSO, DMF, or NMP. In the present invention, the mass ratio of the few-layer MXene nanosheets to the organic solvent is preferably 1:10–500, more preferably 1:20–400, and even more preferably 1:40–80.

[0052] After obtaining the MXene / PVDF casting solution, this invention coats the MXene / PVDF casting solution onto a nonwoven fabric, and then sequentially performs a coagulation bath and drying to obtain a hydrophilic antifouling MXene / PVDF composite membrane. This invention prepares the hydrophilic antifouling MXene / PVDF composite membrane using a non-solvent-induced phase separation (NIPS) method, where membrane preparation and modification are completed simultaneously, resulting in low energy consumption, short membrane preparation time, and high membrane flux.

[0053] In this invention, the MXene / PVDF casting solution preferably further includes a degassing treatment before coating. In this invention, the degassing treatment is preferably performed by static degassing; the degassing treatment is preferably carried out in a vacuum drying oven. In this invention, the temperature of the vacuum degassing is preferably 60–80°C, more preferably 70–80°C. In this invention, the time of the degassing treatment is preferably 1–3 hours, more preferably 2 hours.

[0054] In this invention, the nonwoven fabric is preferably a polyester nonwoven fabric, more preferably a polyethylene nonwoven fabric or a polypropylene nonwoven fabric. In this invention, the polyester nonwoven fabric has hydrophilicity, a finer fiber diameter, a larger specific surface area, and a higher porosity.

[0055] In this invention, the coating is preferably applied by coating; the equipment used for coating is preferably a film scraper. In this invention, the coating thickness is preferably set to 200-300 μm, more preferably 250-280 μm; the settling time after coating is preferably 10-30 s, more preferably 20-30 s.

[0056] In this invention, the coagulation bath is preferably a deionized water coagulation bath. In this invention, the soaking time in the coagulation bath is preferably 12–24 hours, more preferably 18–24 hours. In this invention, the temperature of the coagulation bath is preferably 20–30°C, more preferably 25°C.

[0057] In this invention, the drying temperature is preferably 40-80°C, more preferably 45-70°C; the drying time is preferably 5-12 hours, more preferably 8-10 hours.

[0058] This invention provides a hydrophilic antifouling MXene / PVDF composite membrane prepared by the preparation method described above, comprising a nonwoven fabric and a PVDF membrane attached to the surface of the nonwoven fabric; MXene nanosheets are uniformly distributed in the PVDF membrane. In this invention, MXene nanosheets are uniformly distributed on the surface and inside the hydrophilic antifouling MXene / PVDF composite membrane.

[0059] The present invention provides the application of the hydrophilic antifouling MXene / PVDF composite membrane described above in the field of water treatment, preferably as a separation membrane.

[0060] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0061] Example

[0062] (1) Add 3g of LiF raw material and 90mL of concentrated hydrochloric acid (mass concentration of 9mol / L) to a polytetrafluoroethylene etching cup and stir magnetically to obtain a mixture; then weigh 3g of 400-mesh Ti3AlC2 and slowly add it to the mixture in multiple batches, heat it to 40℃ under a magnetic stirrer, stir at 45rpm, and etch for 48h;

[0063] (2) After the reaction is complete, prepare a hydrochloric acid aqueous solution with a volume ratio of 1:1 of water and hydrochloric acid (concentration of 12 mol / L). Wash the reactants with acid and centrifuge several times until the hydrochloric acid aqueous solution is used up. The centrifuge speed is 10000 rpm and centrifuge for 8 minutes each time. Discard the supernatant liquid after acid washing, add distilled water, shake well and centrifuge. Discard the supernatant liquid and repeat the water washing until the water washing liquid is neutral.

[0064] (3) The obtained powder was vacuum dried at 80°C for 24 h to obtain multilayer MXene nanosheets;

[0065] (4) Weigh 1g of the multilayer MXene nanosheets and add them to 25mL of DMSO solution. Mix them evenly and stir on a magnetic stirrer at room temperature for 48h. Centrifuge the resulting solution at 10000rpm for 10min to obtain a precipitate. Add the precipitate to deionized water and sonicate for 8min. Then centrifuge at 2500rpm. Repeat the water washing-centrifugation steps several times. Collect the supernatant and vacuum dry it at 80℃ for 24h to obtain few-layer MXene nanosheets.

[0066] (5) Place 60 mL of DMSO and 60 mL of DMAc organic solvent in a wide-mouth bottle and mix them evenly with a glass rod. Add 20 mL of PEG porogen (molecular weight of 400 Da) and mix. Then slowly add 20 g of PVDF powder (particle size of 120 μm) in multiple batches and place it in an electric heating drying oven at 80 °C. Stir with a glass rod for 12 h to obtain PVDF casting solution.

[0067] (6) Weigh 0g, 0.1g, 0.5g, 1g, 1.5g, and 2g of the few-layer MXene nanosheets prepared in step (4) and add them to 40mL of DMSO organic solvent. Mix them evenly by ultrasonication to obtain a few-layer MXene nanosheet dispersion, which is numbered as M1 (corresponding to 0g of few-layer MXene nanosheets), M2 (corresponding to 0.1g of few-layer MXene nanosheets), M3 (corresponding to 0.5g of few-layer MXene nanosheets), M4 (corresponding to 1g of few-layer MXene nanosheets), M5 (corresponding to 1.5g of few-layer MXene nanosheets), and M6 (corresponding to 2g of few-layer MXene nanosheets);

[0068] (7) Weigh 1.5g of the few-layer MXene nanosheets prepared in step (4) and label them as BLK; add BLK, M1-M6 to the PVDF casting solution prepared in step (5) respectively, place them in an electric heating drying oven at 80°C and stir with a glass rod for 12h to obtain MXene / PVDF casting solution, which are sequentially labeled as MPBLK (corresponding to BLK), MP1 (corresponding to M1), MP2 (corresponding to M2), MP3 (corresponding to M3), MP4 (corresponding to M4), MP5 (corresponding to M5), and MP6 (corresponding to M6);

[0069] (8) The MXene / PVDF casting solution (MPBLK, MP1-MP6) was placed in a vacuum drying oven at 80°C for 2 hours to remove bubbles. The thickness of the doctor blade of the film-coating machine was adjusted to 250 μm. The film was then coated onto a nonwoven fabric and evaporated for 30 seconds. The film was then placed in a deionized water coagulation bath and soaked for 24 hours. Finally, the film was dried in a drying oven at 45°C for 8 hours to obtain a hydrophilic antifouling MXene / PVDF composite film, which was sequentially numbered as M0 (corresponding to MPBLK), MD1 (corresponding to MP1), MD2 (corresponding to MP2), MD3 (corresponding to MP3), MD4 (corresponding to MP4), MD5 (corresponding to MP5), and MD6 (corresponding to MP6).

[0070] Structural characterization

[0071] According to the preparation method of the above embodiments, the nonwoven fabric in the embodiments was changed to a glass plate to prepare a hydrophilic antifouling MXene / PVDF composite membrane for structural characterization.

[0072] SEM images of the multilayer MXene nanosheets prepared in the examples are shown below. Figure 1 As shown, the prepared multilayer MXene nanosheets resemble an accordion, with densely packed particles in the two-dimensional layer, which confirms the successful removal of the Al layer from the Ti3AlC2 structure.

[0073] TEM images of the few-layer MXene nanosheets prepared in the examples are shown below. Figure 2 As shown in the figure, the prepared few-layer MXene nanosheets exhibit a monolayer structure, indicating that DMSO facilitates the layering of multilayer MXene.

[0074] EDS images of the few-layer MXene nanosheets prepared in the examples are shown below. Figure 3 As shown, the prepared few-layer MXene nanosheets contain C, O, Ti, and F elements, but not Al elements, indicating that the etching was successful.

[0075] Test Example 1

[0076] The hydrophilic antifouling MXene / PVDF composite membrane prepared in the examples was placed in an MSC-300 ultrafiltration cup to test its pure water flux and antifouling performance. The membrane to be tested (the hydrophilic antifouling MXene / PVDF composite membrane prepared in the examples) was placed in the ultrafiltration cup, and pure water was introduced from the upper solution inlet. After ensuring the ultrafiltration cup was airtight, the gas cylinder and valve were opened, allowing water molecules to pass through the membrane pores under gas pressure. The filtered water flowed out from the lower outlet, and the membrane was pre-pressurized at 0.1 MPa for half an hour. The pure water flux (Jw1) was measured first, followed by the flux of a 1 g / L BSA solution (Jp) to simulate protein contamination. After cleaning the contaminated membrane, the pure water flux of the cleaned membrane was measured again (Jw2).

[0077] BSA standard solutions of 0.1 g / L, 0.3 g / L, 0.5 g / L, 0.7 g / L, 0.9 g / L, and 1.0 g / L were prepared for use. The BSA solutions of different concentrations were tested at 280 nm using a TU-1950 UV-Vis spectrophotometer. Based on the absorbance, a BSA standard curve was obtained, y = 0.5801x, where x is the concentration of the BSA solution in g / L and y is the absorbance.

[0078] The formula for calculating the pure water flux (Jw1) is shown in Equation 1:

[0079] In Equation 1, Jw1 represents the pure water flux, with units of L·m -2 ·h -1 V1 represents the volume of pure water, in liters (L); A1 represents the effective area of ​​the membrane under test, in square meters (m²). 2 T1 represents the filtration time, in hours (h).

[0080] The formula for calculating the BSA solution flux (Jp) is shown in Equation 2:

[0081] In Equation 2, Jp represents the BSA solution flux, with units of L·m -2 ·h -1 V P The volume of the BSA solution is expressed in liters (L); A P This represents the effective area of ​​the membrane under test, in meters (m²). 2 ;T P This indicates the filtration time, in hours (h).

[0082] The formula for calculating the pure water flux (Jw2) of the cleaning membrane is shown in Equation 3:

[0083] In Equation 3, Jw2 represents the pure water flux of the cleaning membrane, in L·m -2 ·h -1 V2 represents the volume of pure water, in liters (L); A2 represents the effective area of ​​the cleaning membrane, in square meters (m²). 2 T2 represents the filtration time, in hours (h).

[0084] The formula for calculating the BSA rejection rate (R) is shown in Equation 4:

[0085] In Equation 4, R represents the BSA rejection rate, in percentage (%); C f This indicates the initial concentration of the BSA solution, in g / L; C p This indicates the concentration of the filtered solution calculated using the BSA standard curve, expressed in g / L.

[0086] The formula for calculating flux recovery rate (FRR) is shown in Equation 5:

[0087]

[0088] The formula for calculating the total pollution rate (Rt) is shown in Equation 6:

[0089]

[0090] The formula for calculating the reversible contamination rate (Rr) is shown in Equation 7:

[0091]

[0092] The formula for calculating the irreversible contamination rate (Rir) is shown in Equation 8:

[0093]

[0094] Test Example 2

[0095] Five hydrophilic antifouling MXene / PVDF composite membranes prepared in the examples were cut into 2.5cm × 7cm pieces. After soaking in distilled water for 24 hours, they were dried in a 45℃ oven for 12 hours. The membranes were then adhered to glass slides with double-sided tape, and the contact angles of the membrane surfaces were measured using a contact angle meter. Pure water was used as the liquid medium for measuring the membrane contact angles under constant room temperature and humidity conditions. The droplet volume was set to 4μL, and measurements were taken at five different points for each sample, with the average value calculated.

[0096] Figure 4 The contact angle of the hydrophilic antifouling MXene / PVDF composite membrane prepared for the example; Figure 5 The pure water flux of the hydrophilic antifouling MXene / PVDF composite membrane prepared for the example; Figure 6 BSA rejection rate of the hydrophilic antifouling MXene / PVDF composite membrane prepared for the example; Figure 7 Antifouling performance analysis of the hydrophilic antifouling MXene / PVDF composite membrane prepared for this example. Combined with... Figures 4-7 The results show that the contact angle of the pure PVDF membrane MD1 is 87.5°, and the pure water flux is 15.6 L / (m²). 2 For 1 g / L BSA, the rejection rate was 99.15%, and the flux recovery rate (FRR) after physical cleaning was 60.90%. The water flux of the hydrophilic antifouling MXene / PVDF composite membrane was significantly improved compared to the pure PVDF membrane, and the MXene / PVDF membrane exhibited good flux recovery. The contact angles of the modified membranes MD2-MD6 were 75.4°, 72.4°, 64.6°, 58.6°, and 65.5°, respectively, and the pure water flux was 36.2 L / (m²). 2 ·h), 63.7L / (m 2 ·h), 105.1L / (m 2 ·h), 126.4L / (m 2 ·h), 80.6L / (m 2 The BSA rejection rates were 98.52%, 98.33%, 97.94%, 97.28%, and 97.15%, respectively, and the flux recovery rates of the membranes after physical cleaning were 64.92%, 68.60%, 77.83%, 80.78%, and 73.45%, respectively.

[0097] M0, serving as a control group, was prepared by adding MXene and PVDF powder together to an organic solvent, resulting in a composite membrane with a contact angle of 73.18° and a pure water flux of 58.4 L / (m²). 2 The hydrophilicity of the modified membrane was improved compared to the unmodified membrane, but the membrane flux was lower than that of MD5. This is because the nanoparticles agglomerated when MXene powder was directly added to the casting solution, resulting in a less significant improvement in membrane flux.

[0098] The presence of -OH groups in MXene gives the prepared MXene / PVDF hybrid matrix membrane high hydrophilicity, effectively improving the membrane's antifouling performance.

[0099] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a hydrophilic antifouling MXene / PVDF composite membrane, comprising the following steps: Polyvinylidene fluoride powder, pore-forming agent and organic solvent are mixed to obtain PVDF casting solution; The PVDF casting solution and the few-layer MXene nanosheet dispersion were mixed to obtain an MXene / PVDF casting solution; The MXene / PVDF casting solution was coated onto a nonwoven fabric, and then subjected to a coagulation bath and drying in sequence to obtain a hydrophilic, antifouling MXene / PVDF composite membrane. The mass ratio of the polyvinylidene fluoride powder, the pore-forming agent, and the organic solvent is 1:1~5:6~10; The preparation method of the few-layer MXene nanosheet dispersion includes: The MAX phase raw material was mixed with an acidic solution and etched to obtain multilayer MXene nanosheets; The multilayer MXene nanosheets are mixed with an intercalating agent and intercalated to obtain few-layer MXene nanosheets. The few-layer MXene nanosheets were dispersed in an organic solvent to obtain a few-layer MXene nanosheet dispersion. The thickness of the few-layer MXene nanosheets is 1.3~9 nm; The concentration of few-layer MXene nanosheets in the few-layer MXene nanosheet dispersion in the MXene / PVDF casting solution is 0.5~10 mg / mL.

2. The preparation method according to claim 1, characterized in that, The pore-forming agent includes at least one of polyvinylpyrrolidone and polyethylene glycol; The organic solvent includes at least one of dimethyl sulfoxide and N,N-dimethylacetamide.

3. The preparation method according to claim 1, characterized in that, The acidic solution comprises fluoride and hydrochloric acid; the ratio of fluoride to hydrochloric acid is 1g:20~50mL; and the concentration of hydrochloric acid is 5~10mol / L.

4. The preparation method according to claim 1 or 3, characterized in that, The etching temperature is 30~50℃.

5. The preparation method according to claim 1, characterized in that, The intercalating agent includes one or more of dimethyl sulfoxide, ethanol, tetrabutylammonium hydroxide, and tetramethylammonium hydroxide.

6. The hydrophilic antifouling MXene / PVDF composite membrane prepared by the preparation method according to any one of claims 1 to 5 comprises a nonwoven fabric and a PVDF membrane attached to the surface of the nonwoven fabric; wherein MXene nanosheets are uniformly distributed in the PVDF membrane.

7. The application of the hydrophilic antifouling MXene / PVDF composite membrane according to claim 6 in the field of water treatment.

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