High-flux anti-pollution PVDF (Polyvinylidene Fluoride) ultrafiltration membrane separation layer and preparation method thereof
By synergistically modifying PVDF ultrafiltration membranes with amphiphilic zwitterionic copolymers, polyvinyl alcohol, and hydrophilic nanoparticles, an ultrahydrophilic surface is constructed, which solves the problem of insufficient antifouling performance of PVDF ultrafiltration membranes and achieves high-flux and long-life membrane separation effects.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-30
- Publication Date
- 2026-03-27
AI Technical Summary
The existing PVDF ultrafiltration membrane separation layer has insufficient antifouling performance, resulting in shortened membrane life, increased operation and maintenance costs, and difficulty in resisting the adsorption of complex pollutants such as proteins and colloids.
A high-flux, antifouling PVDF ultrafiltration membrane separation layer was constructed by using a synergistic modification system of amphiphilic zwitterionic copolymer, polyvinyl alcohol and hydrophilic nanoparticles, supplemented by PVP porogen and NMP solvent. By forming multi-level micro-nano protrusions and superhydrophilic surfaces, the contact area and adsorption amount of pollutants were reduced.
It achieves a pollutant adsorption reduction of over 95%, a flux recovery rate of 99.5%, a pure water flux increase of 50%, and a membrane lifespan extended to 2-3 years, meeting the requirements of high-pressure filtration.
Smart Images
Figure CN121731968A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application relates to the technical field of membrane separation materials, in particular to a high-flux anti-pollution PVDF ultrafiltration membrane separation layer and a preparation method thereof. BACKGROUND
[0002] Polyvinylidene fluoride (PVDF) occupies a dominant position in the field of ultrafiltration membrane base materials due to its excellent chemical stability and high mechanical strength. However, the existing PVDF ultrafiltration membrane separation layer has the problem of insufficient anti-pollution performance. The anti-pollution performance is a key factor determining the service life of the PVDF ultrafiltration membrane. In the prior art, the improvement of the anti-pollution performance of the membrane mainly adopts a single hydrophilic modification method, for example, only polyvinyl alcohol is used for modification treatment. This method can only improve the flux recovery rate of the membrane to 90-95%, and it is difficult to resist the adsorption of complex pollutants such as proteins and colloids. The service life of the membrane is shortened to less than one year, which leads to performance degradation of the membrane due to the attachment of pollutants in the long-term use process, and greatly increases the operation and maintenance cost of industrial application. SUMMARY
[0003] The application aims to at least partially overcome the above technical problems and / or other potential problems in the prior art: taking PVDF as the separation layer base material, constructing a ternary synergistic modification system of "amphiphilic zwitterionic copolymer-polyvinyl alcohol-nano hydrophilic particles", and providing a high-flux anti-pollution PVDF ultrafiltration membrane separation layer and a preparation method thereof.
[0004] The technical solution of the application is as follows: a high-flux anti-pollution PVDF ultrafiltration membrane separation layer, prepared from the following raw materials in mass percentage: PVDF 12-15%; amphiphilic zwitterionic copolymer 2-5%; polyvinyl alcohol 0.5-1.5%; nano hydrophilic particles 0.8-1.5%; PVP 3-6%; and the balance being NMP.
[0005] As an optimization, the amphiphilic zwitterionic copolymer is one or both of poly(2-acrylamide-2-methyl-1-propanesulfonic acid-co-acrylonitrile) (PAMPSA-co-PAN) and poly(2-acrylamide-2-methyl-1-propanesulfonic acid-co-poly methyl methacrylate) (PAMPSA-co-PMMA) with a molecular weight of 30000-150000.
[0006] As an optimization, the nano hydrophilic particles are nano silicon dioxide with a particle size of 20-80 nm or are compounded nano hydrophilic particles composed of nano silicon dioxide with a particle size of 20-30 nm and nano titanium dioxide with a particle size of 60-80 nm in a mass ratio of (1-2):1.
[0007] As optimization, the nanosilica is aminated nanosilica.
[0008] The NMP is N-methyl pyrrolidone; and the PVP is polyvinyl pyrrolidone.
[0009] The application also provides a preparation method of a high-flux anti-pollution PVDF ultrafiltration membrane separation layer, comprising the following steps: 1) The raw materials are weighed according to the ratio, NMP is heated to 55-80℃, then PVDF, amphiphilic zwitterionic copolymer and nanohydrophilic particles are added in sequence and stirred to disperse uniformly; polyvinyl alcohol and PVP are added and continue to stir for 2.0-4.0h until uniform and transparent to obtain a casting solution; 2) The casting solution is vacuum degassed, then sprayed on the surface of the support substrate to form a film to obtain a PVDF ultrafiltration membrane separation layer.
[0010] As optimization, the support substrate is PET non-woven fabric.
[0011] As optimization, the nanohydrophilic particles are treated with a silane coupling agent, and the specific steps are as follows: 1) Pretreatment: the nanohydrophilic particles are pickled, dried and surface impurities are removed to activate the hydroxyl groups; 2) Grafting reaction: the nanohydrophilic particles are dispersed in a solvent, a silane coupling agent is added, and refluxing reaction is carried out at 50-80℃ for 4-24h, then centrifugation, washing to remove unreacted coupling agent, and vacuum drying.
[0012] The specific steps of aminated nanosilica are as follows: 1) Pretreatment: the nanohydrophilic particles are pickled, dried and surface impurities are removed to activate the hydroxyl groups; 2) Grafting reaction: the nanosilica is dispersed in a solvent such as anhydrous ethanol or toluene, an amino silane coupling agent is added, and refluxing reaction is carried out at 50-80℃ for 4-24h, then centrifugation, washing to remove unreacted coupling agent, and vacuum drying to obtain an aminated product.
[0013] As optimization, in step 2), the film thickness is 20-80μm.
[0014] The beneficial effects of the present application are: the present application takes PVDF as a separation layer substrate, constructs a ternary synergistic modification system of "amphiphilic zwitterionic copolymer-polyvinyl alcohol-nano hydrophilic particles", and composites the amphiphilic zwitterionic copolymer (charged repulsion), polyvinyl alcohol (hydrophilic film layer) and nano hydrophilic particles (micro-nano rough structure), especially uses the small particle size of the compounded nano hydrophilic particles to fill the gap of the large particle size particles to form a multi-stage micro-nano protrusion, constructs a super-hydrophilic surface with a contact angle ≤45° through the Cassie-Baxter effect, the water forms a continuous water film on the surface, the actual contact area of the pollutants is reduced by more than 40%, the adsorption amount of the pollutants is reduced by more than 95%, and the flux recovery rate reaches ≥99.5%; supplemented by the PVP pore-forming agent and the NMP solvent, the performance index can be improved in a leap: the pure water flux is >750Lmh / bar (as high as 880-950Lmh / bar), which is 50% higher than that of the traditional membrane; the membrane life is extended to 2-3 years; the burst pressure is ≥1.0MPa, meeting the high-pressure filtration demand. BRIEF DESCRIPTION OF DRAWINGS
[0015] Figure 1 The cross-section electron microscope graph of the ultrafiltration membrane separation layer prepared for Example 3.
[0016] Figure 2 The surface electron microscope graph of the ultrafiltration membrane separation layer prepared for Example 3.
[0017] Figure 3 The pore size distribution of the ultrafiltration membrane separation layer prepared for Example 3. DETAILED DESCRIPTION
[0018] The embodiments of the present application will be described in detail below with reference to the examples, but those skilled in the art will understand that the following examples are only for illustration of the present application and should not be regarded as limiting the scope of the present application. If the specific conditions are not specified in the examples, the conventional conditions or the conditions recommended by the manufacturer are used. If the reagents or instruments used are not specified by the manufacturer, they are all conventional products that can be purchased on the market.
[0019] Example 1
[0020] The high-flux anti-pollution PVDF ultrafiltration membrane separation layer is prepared according to the following steps: 1) The following raw materials are weighed: PVDF 13g; poly(2-acrylamide-2-methyl-1-propanesulfonic acid-co-acrylonitrile) (PAMPSA-co-PAN) with a molecular weight of 30000-150000 3g; polyvinyl alcohol 1g; amino-functionalized nanosilica with a particle size of 20-80nm 1g; PVP 5g; and the balance is NMP to make the total weight of the components 100g.
[0021] First, heat NMP to 65-80°C, then add PVDF, PAMPSA-co-PAN, and amino- nanosilica in sequence, stir with a blender (500-1000 r / min) for 4.0-5.0 h until evenly dispersed; then add polyvinyl alcohol and PVP, continue stirring for 2.0-4.0 h until uniformly transparent to obtain a casting solution (viscosity 800-2500 mPa s, 25°C); 2) The casting solution is continuously degassed by a three-stage vacuum degassing device (first stage - 0.07~0.08 MPa, 15 min; second stage - 0.08~0.09 MPa, 10 min; third stage - 0.09~0.1 MPa, 5 min), with a bubble removal rate of ≥99.5% and no visible bubbles; 3) After spraying the casting solution on the surface of the PET non-woven fabric support substrate through a 45-55°C nozzle, pass through a gradient coagulation bath: first stage 25-35°C deionized water, 3-8 min, second stage 15-25°C deionized water, 2-5 min; third stage room temperature deionized water, 1-4 min; 4) Low-pressure cyclone water washing (0.05-0.1 MPa, water flow rotation speed 500-800 r / min, 1-2 h, water washing water quality conductivity ≤5 μS / cm) to obtain a PVDF ultrafiltration membrane separation layer with a film thickness of 40 μm.
[0022] This example provides a separation skeleton by PVDF, introduces negative sulfonic acid groups and positive amine groups to repel charged pollutants by PAMPSA-co-PAN, forms a hydrophilic protective film by polyvinyl alcohol, constructs a super-hydrophilic effect to reduce contact by amino-nanosilica, and regulates 30-40 nm through channels to achieve a sponge hole composite structure by PVP. The separation layer has a porosity of ≥80% (scanning electron microscope detection), a three-dimensional connectivity rate of sponge-like holes of ≥95%, a surface micro-nano roughness structure roughness Ra of 0.25-0.35 μm (atomic force microscope detection), a surface contact angle of ≤37° (contact angle meter detection, deionized water, 25°C), a surface water film continuity under Cassie-Baxter effect of ≥98%, a residual solvent content of <50 ppm (GC-MS method detection, according to GB / T 23990-2009), an anti-back pressure capacity of ≥0.1 MPa (back pressure test bench detection, no rupture and no membrane layer falling off for 30 min), and a flux decay rate of ≤3% under pressure compaction performance (0.5 MPa cyclic compaction 100 times).
[0023] Example 2
[0024] Prepare a high-flux anti-pollution PVDF ultrafiltration membrane separation layer according to the following steps: 1) The following raw materials are weighed: PVDF 14 g; poly(2-acrylamide-2-methyl-1-propanesulfonic acid-co-poly-methyl methacrylate) (PAMPSA-co-PMMA) with a molecular weight of 30000-150000 3 g; polyvinyl alcohol 0.8 g; aminated nanosilica with a particle size of 20-80 nm 0.8 g; PVP 4 g; the balance is NMP to make the total weight of the components 100 g.
[0025] First, heat the NMP to 55-75°C, then add the PVDF, PAMPSA-co-PMMA, and aminated nanosilica in order, and stir with a blender (500-1000 r / min) for 4.0-5.0 h until uniformly dispersed; then add the polyvinyl alcohol and PVP, and continue stirring for 2.0-4.0 h until uniformly transparent to obtain a casting solution (viscosity 800-2500 mPa s, 25°C); 2) The casting solution is continuously degassed by a three-stage vacuum degassing device (first stage - 0.07~-0.08 MPa, 15 min; second stage - 0.08~-0.09 MPa, 10 min; third stage - 0.09~-0.1 MPa, 5 min), with a bubble removal rate ≥99.5% and no visible bubbles; 3) After spraying the casting solution on the surface of the PET non-woven support substrate through a 45-55°C nozzle, it is passed through a gradient coagulation bath: first stage 25-35°C deionized water, 3-8 min, second stage 15-25°C deionized water, 2-5 min; third stage room temperature deionized water, 1-4 min; 4) Low-pressure cyclone water washing (0.05-0.1 MPa, water flow rotation speed 500-800 r / min, 1-2 h, water washing water quality conductivity ≤5 μS / cm) to obtain a PVDF ultrafiltration membrane separation layer with a film thickness of 80 μm.
[0026] Example 3
[0027] A high-flux anti-pollution PVDF ultrafiltration membrane separation layer is prepared according to the following steps: 1) The following raw materials are weighed: PVDF 12 g; poly(2-acrylamido-2-methyl-1-propanesulfonic acid-co-acrylonitrile) (PAMPSA-co-PAN) with a molecular weight of 30000-150000 2 g; poly(2-acrylamido-2-methyl-1-propanesulfonic acid-co-poly(methyl methacrylate)) (PAMPSA-co-PMMA) with a molecular weight of 30000-150000 3 g; polyvinyl alcohol 1.5 g; compounded nano-hydrophilic particles 1.2 g (consisting of 0.6 g of nano-silicon dioxide with a particle size of 20 nm and 0.6 g of nano-titanium dioxide with a particle size of 60 nm); PVP 6 g; and the balance is NMP to make the total weight of the components 100 g.
[0028] First, heat the NMP to 55-75℃, then add PVDF, PAMPSA-co-PAN, PAMPSA-co-PMMA, and compounded nano-hydrophilic particles in sequence, and stir with a blender (500-1000 r / min) for 4.0-5.0 h until uniformly dispersed; then add polyvinyl alcohol and PVP, and continue stirring for 2.0-4.0 h until uniformly transparent to obtain a casting solution (viscosity 800-2500 mPa s, 25℃); 2) The casting solution is continuously degassed by a three-stage vacuum degassing device (first stage - 0.07~-0.08MPa, 15min; second stage - 0.08~-0.09MPa, 10min; third stage - 0.09~-0.1MPa, 5min), with a bubble removal rate ≥99.5%, and no visible bubbles; 3) After spraying the casting solution on the surface of the PET non-woven fabric support substrate by a 45-55℃ nozzle, it is subjected to a gradient coagulation bath: first stage 25-35℃ deionized water, 3-8min, second stage 15-25℃ deionized water, 2-5min; third stage room temperature deionized water, 1-4min; 4) Low-pressure cyclone water washing (0.05-0.1MPa, water flow rotation speed 500-800 r / min, 1-2h, water washing water quality conductivity ≤5μS / cm) to obtain a PVDF ultrafiltration membrane separation layer with a film thickness of 20μm, the cross-sectional electron microscope image of the ultrafiltration membrane separation layer prepared in this example is shown in Figure 1 , the electron microscope image of the separation layer surface is shown in Figure 2 , and the separation layer pore size distribution detection result is shown in Figure 3 .
[0029] The above is only a characteristic implementation example of the present application, and does not constitute any limitation on the protection scope of the present application. Any technical solution formed by equivalent exchange or equivalent replacement falls within the scope of protection of the present application.
Claims
1. A high-flux, fouling-resistant PVDF ultrafiltration membrane separation layer, characterized in that, The raw materials for its preparation, by mass percentage, include the following components: PVDF 12-15%; amphiphilic zwitterionic copolymer 2-5%; polyvinyl alcohol 0.5-1.5%; nano-hydrophilic particles 0.8-1.5%; PVP 3-6%; and the balance is NMP.
2. The high-flux, anti-fouling PVDF ultrafiltration membrane separation layer according to claim 1, characterized in that, The amphiphilic zwitterionic copolymer is one or both of poly(2-acrylamide-2-methyl-1-propanesulfonic acid-co-acrylonitrile) (PAMPSA-co-PAN) and poly(2-acrylamide-2-methyl-1-propanesulfonic acid-co-polymethyl methacrylate) (PAMPSA-co-PMMA) with a molecular weight of 30,000-150,000.
3. The high-flux, anti-fouling PVDF ultrafiltration membrane separation layer according to claim 2, characterized in that, The hydrophilic nanoparticles are either nano-silica with a particle size of 20-80 nm or composite hydrophilic nanoparticles made by mixing nano-silica with a particle size of 20-30 nm and nano-titanium dioxide with a particle size of 60-80 nm in a mass ratio of (1-2):
1.
4. The high-flux, anti-fouling PVDF ultrafiltration membrane separation layer according to claim 3, characterized in that, The nano-silica is aminated nano-silica.
5. The high-flux, anti-fouling PVDF ultrafiltration membrane separation layer according to claim 1, characterized in that, The NMP is N-methylpyrrolidone; the PVP is polyvinylpyrrolidone.
6. A method for preparing the high-flux, anti-fouling PVDF ultrafiltration membrane separation layer according to claim 1, characterized in that, Includes the following steps: 1) Weigh each raw material according to the formula. First, heat NMP to 55-80℃, then add PVDF, amphiphilic zwitterionic copolymer and nano-hydrophilic particles in sequence and stir to disperse evenly; then add polyvinyl alcohol and PVP, and continue stirring for 2.0-4.0h until uniform and transparent to obtain casting solution; 2) After vacuum degassing, the casting solution is sprayed onto the surface of the supporting substrate to form a film, thus obtaining a PVDF ultrafiltration membrane separation layer.
7. The method for preparing the high-flux, anti-fouling PVDF ultrafiltration membrane separation layer according to claim 6, characterized in that, The film thickness is 20-80 μm.
8. The method for preparing the high-flux, anti-fouling PVDF ultrafiltration membrane separation layer according to claim 7, characterized in that, The supporting substrate is PET nonwoven fabric.
9. The method for preparing the high-flux, anti-fouling PVDF ultrafiltration membrane separation layer according to claim 7, characterized in that, The hydrophilic nanoparticles are treated with a silane coupling agent, and the specific steps are as follows: 1) Pretreatment: The nano-hydrophilic particles are acid-washed, dried, and have surface impurities removed; 2) Grafting reaction: Disperse the hydrophilic nanoparticles in a solvent, add silane coupling agent, reflux at 50-80℃ for 4-24 hours, centrifuge, wash to remove unreacted coupling agent, and vacuum dry.
10. The method for preparing the high-flux, anti-fouling PVDF ultrafiltration membrane separation layer according to claim 9, characterized in that, The specific steps for film formation are as follows: First, the film is subjected to a gradient coagulation bath: Level 1: 25-35℃ deionized water, 3-8 min; Level 2: 15-25℃ deionized water, 2-5 min; Level 3: room temperature deionized water, 1-4 min; then washed and dried.