Anti-fouling pvdf ultrafiltration membrane and preparation method thereof
By modifying PVDF ultrafiltration membranes through supercritical carbon dioxide swelling and oxygen-enriched microwave plasma treatment, combined with modified chitosan, the problem of PVDF ultrafiltration membranes being easily fouled was solved, achieving high throughput and high anti-fouling effect.
Patent Information
- Application Number
- CN202611483493.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-09-22
- Publication Date
- 2026-11-03
AI Technical Summary
Existing PVDF ultrafiltration membranes are susceptible to fouling during water treatment, leading to flux reduction, increased transmembrane pressure difference, increased cleaning frequency, and shortened service life.
Modified polyvinylidene fluoride was prepared by supercritical carbon dioxide swelling treatment, and chitosan with a deacetylation degree of 70%-80% was treated by oxygen-enriched microwave plasma treatment. The modified chitosan was then mixed with polyvinylpyrrolidone and N,N-dimethylacetamide to form a casting solution, which was then cast into a film.
It improves the antifouling performance and flux of PVDF ultrafiltration membranes, achieving a balance between high antifouling and high flux, reducing the adsorption of pollutants on the membrane surface, and extending the membrane's service life.
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Figure CN123024445A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of ultrafiltration membrane technology, and in particular to an antifouling PVDF ultrafiltration membrane and its preparation method. Background Technology
[0002] Polyvinylidene fluoride (PVDF) is widely used in ultrafiltration separation processes in municipal water supply, industrial wastewater reuse, membrane bioreactors, and pharmaceutical and food industries due to its excellent mechanical strength, chemical corrosion resistance, thermal stability, and good film-forming properties. During ultrafiltration, PVDF membranes can retain colloids, suspended solids, proteins, and some large organic molecules. However, due to its low surface energy and strong intrinsic hydrophobicity, it has poor wettability when in contact with aqueous systems. Proteins, natural organic matter, oils, and colloidal particles easily adsorb and deposit on the membrane surface and enter the membrane pores, forming reversible and irreversible fouling. This leads to flux decline, increased transmembrane pressure, increased cleaning frequency, and shortened service life.
[0003] Therefore, the antifouling performance and flux of existing PVDF ultrafiltration membranes need to be further improved.
[0004] It should be noted that the foregoing statements are only used to provide background information related to the present invention and do not necessarily constitute prior art. Summary of the Invention
[0005] To address the above problems, this invention provides an anti-fouling PVDF ultrafiltration membrane and its preparation method.
[0006] In a first aspect, the present invention provides a method for preparing an antifouling PVDF ultrafiltration membrane, comprising the following steps: Modified polyvinylidene fluoride was obtained by supercritical carbon dioxide swelling treatment of polyvinylidene fluoride. Chitosan with a degree of deacetylation of 70%~80% was subjected to oxygen-enriched microwave plasma treatment to obtain modified chitosan. The modified polyvinylidene fluoride and polyvinylpyrrolidone were added to N,N-dimethylacetamide for a first stirring and mixing to obtain a casting solution; The modified chitosan is added to the casting solution and stirred for a second time. After standing and degassing, the mixture is cast to obtain the PVDF ultrafiltration membrane.
[0007] Furthermore, the working conditions for the supercritical carbon dioxide swelling treatment include: a temperature of 50℃-60℃, a pressure of 8MPa-15MPa, and a time of 8min-15min.
[0008] Furthermore, the working conditions for the supercritical carbon dioxide swelling treatment include: a temperature of 58°C, a pressure of 12 MPa, and a time of 10 min.
[0009] Furthermore, the operating conditions for the oxygen-rich microwave plasma treatment include: microwave power of 340W-500W and glow discharge treatment of 60s-120s.
[0010] Furthermore, the operating conditions for the oxygen-rich microwave plasma treatment include: microwave power of 450W and glow discharge treatment for 85s.
[0011] Further, the mass ratio of the modified polyvinylidene fluoride, the polyvinylpyrrolidone and the N,N-dimethylacetamide is (15-20):(1-1.5):(75-85).
[0012] Furthermore, the modified chitosan is added in an amount of 0.5%-1.5% of the total mass of the casting solution, by mass percentage.
[0013] Furthermore, the working conditions parameters for the first stirring and mixing include: temperature of 60℃-70℃, stirring speed of 200rpm-300rpm, and time of 6h-10h.
[0014] Furthermore, the working conditions parameters for the second stirring and mixing include: temperature of 55℃-65℃, stirring speed of 400rpm-500rpm, and time of 4h-7h.
[0015] Secondly, the present invention provides an antifouling PVDF ultrafiltration membrane, which is prepared by the method for preparing an antifouling PVDF ultrafiltration membrane described in the first aspect.
[0016] The technical solutions provided in the embodiments of the present invention have at least the following advantages compared with the prior art: This invention provides an antifouling PVDF ultrafiltration membrane and its preparation method. Compared with the prior art, this invention employs a supercritical carbon dioxide process to swell and modify polyvinylidene fluoride (PVDF) and introduces chitosan with a suitable degree of deacetylation after treatment with oxygen-enriched microwave plasma. This results in a PVDF ultrafiltration membrane that combines high antifouling properties with high flux, overcoming the shortcomings of existing technologies. Specifically: 1) Supercritical carbon dioxide swelling treatment of polyvinylidene fluoride Polyvinylidene fluoride (PVDF) itself has strong crystallinity and low surface energy, making it prone to hydrophobicity after film formation. During water treatment, organic matter, colloidal and proteinaceous pollutants easily adsorb onto the membrane surface or enter the membrane pores, causing flux attenuation. Supercritical carbon dioxide swelling treatment utilizes the low viscosity, low surface tension, and good permeability of supercritical CO2 to the amorphous regions of the polymer, allowing CO2 to enter the interstices of the PVDF molecular chains, weakening the tight packing between chains and producing reversible swelling. This process can improve the porosity of the substrate without damaging the main chain, which is beneficial for improving subsequent N,N... The solubility and dispersibility of dimethylacetamide provide a more uniform matrix for the exchange of non-solvent and solvent and the formation of pore structures during the phase transition in casting. Supercritical treatment can also be combined with pressure and temperature to control the local relaxation degree of PVDF, so that crystallization and separation do not become extreme during subsequent film formation, thereby reducing the mass transfer resistance caused by simply high crystallinity.
[0017] 2) Modified chitosan Chitosan with a deacetylation degree of 70%-80% is selected because this range retains an appropriate amount of hydrophilic groups such as amino and hydroxyl groups while maintaining suitable molecular chain flexibility and film-forming properties. Too low a deacetylation degree results in insufficient positive charge and reactivity, limiting its contribution to electrostatic repulsion and hydrophilic modification of pollutants; too high a deacetylation degree increases molecular chain rigidity, reduces dispersion stability in water and polar organic systems, and easily leads to agglomeration during blending, affecting membrane pore uniformity. Oxygen-enriched microwave plasma treatment of chitosan involves generating active particles, free radicals, and UV / electromagnetic interactions under microwave excitation. These particles act on the chitosan surface and molecular chains, introducing oxygen-containing polar groups such as hydroxyl, carbonyl, and carboxyl groups, while simultaneously generating active sites. Chitosan treated in this way exhibits enhanced hydrophilicity and improved compatibility with PVDF / PVP casting systems, enabling more uniform distribution on the membrane body and surface during phase transformation, forming a continuous hydrophilic modification or anti-adsorption layer.
[0018] Therefore, based on the existing technology, the present invention uses a combination of specific modified polyvinylidene fluoride and specific modified chitosan, and the two work synergistically to achieve a balance between high flux and high antifouling, thus obtaining a PVDF ultrafiltration membrane that has both high antifouling and high flux. Attached Figure Description
[0019] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.
[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0021] Figure 1 This is a schematic flowchart illustrating the preparation method of the antifouling PVDF ultrafiltration membrane provided in an embodiment of the present invention. Detailed Implementation
[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0023] Unless otherwise specified, all raw materials, reagents, instruments, and equipment used in this invention can be purchased commercially or prepared using existing methods. For example, in the antifouling PVDF ultrafiltration membrane and its preparation method provided in the embodiments of this invention, unless otherwise specified or limited, the raw materials used can be commercially available products; at the same time, unless otherwise specified or limited, the process steps and parameters involved can be carried out according to the preparation process disclosed in the prior art or using existing equipment and conventional operating methods.
[0024] In a first aspect, the present invention provides a method for preparing an antifouling PVDF ultrafiltration membrane, such as... Figure 1 As shown, it includes the following steps: Modified polyvinylidene fluoride was obtained by supercritical carbon dioxide swelling treatment of polyvinylidene fluoride. Chitosan with a degree of deacetylation of 70%~80% was subjected to oxygen-enriched microwave plasma treatment to obtain modified chitosan. The modified polyvinylidene fluoride and polyvinylpyrrolidone were added to N,N-dimethylacetamide for a first stirring and mixing to obtain a casting solution; The modified chitosan is added to the casting solution and stirred for a second time. After standing and degassing, the mixture is cast to obtain the PVDF ultrafiltration membrane.
[0025] In some specific embodiments, the operating conditions for the supercritical carbon dioxide swelling treatment include: a temperature of 50℃-60℃, a pressure of 8MPa-15MPa, and a time of 8min-15min. These parameters can appropriately open the inter-chain voids of PVDF, improving its wetting and dissolution rate in DMAc and reducing the initial stirring time; simultaneously, they avoid excessive swelling that could lead to particle size aggregation or uneven subsequent casting thickness. After this treatment, when blended with PVP and modified chitosan, the casting solution viscosity is more stable, the solvent / non-solvent dual diffusion during phase inversion is more uniform, the ratio of finger pores to sponge pores in the resulting membrane is more reasonable, and the pure water flux is increased without a significant decrease in the rejection rate.
[0026] As an example, the temperature of the supercritical carbon dioxide swelling treatment can be 50°C, 53°C, 55°C, 58°C, 60°C, or any of the aforementioned values.
[0027] As an example, the pressure of the supercritical carbon dioxide swelling treatment can be 8 MPa, 9 MPa, 10 MPa, 13 MPa, 15 MPa, or any of the aforementioned values.
[0028] As an example, the time for the supercritical carbon dioxide swelling treatment can be 8 min, 10 min, 13 min, 15 min, or any of the aforementioned values.
[0029] As an example, the present invention involves subjecting polyvinylidene fluoride to supercritical carbon dioxide swelling treatment to obtain modified polyvinylidene fluoride. In actual operation, the process may include the following steps: placing polyvinylidene fluoride in a closed device, removing air and introducing CO2, adjusting the system temperature and pressure to preset values and maintaining this supercritical state for supercritical carbon dioxide swelling treatment, depressurizing, and drying to obtain the modified polyvinylidene fluoride.
[0030] In some specific embodiments, the operating conditions for the supercritical carbon dioxide swelling treatment include: a temperature of 58°C, a pressure of 12 MPa, and a time of 10 min. These parameters can further improve the overall performance of the PVDF ultrafiltration membrane.
[0031] In some specific embodiments, the operating conditions for the oxygen-enriched microwave plasma treatment include: microwave power of 340W-500W and glow discharge treatment for 60s-120s. Modified chitosan treated within this range is more easily dispersed at the nanoscale in the DMAc casting solution through a second stirring process; its amino retention ratio is matched with the ratio of plasma-containing oxygen groups, providing both electrostatic repulsion against negatively charged contaminants and forming a stable interface with PVP and PVDF through numerous hydrogen bonding sites. Compared to untreated chitosan, this reduces agglomeration, lowers the membrane defect rate, and improves the long-term filtration flux recovery rate.
[0032] As an example, the microwave power of the oxygen-rich microwave plasma treatment can be 340W, 370W, 440W, 480W, 500W or any of the aforementioned values, and the glow discharge treatment time can be 60s, 75s, 90s, 100s, 120s or any of the aforementioned values. As an example, in this invention, chitosan with a degree of deacetylation of 70%~80% is subjected to oxygen-enriched microwave plasma treatment to obtain modified chitosan. In actual operation, the process may include the following steps: placing the chitosan in a microwave plasma treatment instrument, introducing oxygen and argon in a volume ratio of 4:1 as the working medium, performing glow discharge treatment for 60s~120s under microwave power of 340W-500W and gas flow rate of 80~95 mL / min, and then continuing to introduce oxygen for 5min-10min to obtain the modified chitosan.
[0033] As an example, commercially available chitosan can be used directly in this invention, such as chitosan 1: brand or product model C915936, with a degree of deacetylation of 70%; chitosan 2: brand or product model C915934, with a degree of deacetylation of 80%, etc.
[0034] In some specific embodiments, the operating conditions for the oxygen-enriched microwave plasma treatment include: a microwave power of 450W and a glow discharge treatment time of 85s. These parameters can further improve the overall performance of the PVDF ultrafiltration membrane.
[0035] In some specific embodiments, the mass ratio of the modified polyvinylidene fluoride, the polyvinylpyrrolidone, and the N,N-dimethylacetamide is (15-20):(1-1.5):(75-85), for example, 15:1:77, 18:1:77, 20:1:77, 20:1.3:80, etc. Within this range, the amount of PVP is sufficient to improve hydrophilicity and pore formation, but not excessive to avoid excessively high pure water flux and decreased retention rate, and also to prevent long-term antifouling instability due to easy elution of PVP; the DMAc ratio ensures sufficient dissolution of the modified PVDF, and the combination with the supercritical swelling substrate can reduce gel particles. The overall casting solution has a balanced stability, flowability, and pore formation, and the obtained ultrafiltration membrane has both high flux and good macromolecular retention.
[0036] As an example, take 17g of modified PVDF, 1.2g of PVPK30, and 78g of DMAc, and first stir to obtain a casting solution; then add 0.5%-1.5% of modified chitosan based on the total casting solution. This formula can produce an ultrafiltration membrane with a viscosity suitable for scraping and uniform pore size after phase inversion.
[0037] In some specific embodiments, the modified chitosan is added at a mass percentage of 0.5%-1.5% of the total mass of the casting solution, for example, 0.5%, 0.8%, 1.0%, 1.2%, 1.5%, or any range between the aforementioned values. At this dosage, the modified chitosan can be uniformly embedded in the membrane and enriched on the membrane surface, forming a hydrophilic synergy with PVP: PVP mainly functions as a pore-forming agent and initial wetting agent, while chitosan mainly functions as a long-term anti-adsorption agent, a weakly positively charged repulsive agent, and an oxygen-containing cluster that retains water. For water containing proteins, colloids, and natural organic matter, the fouling layer on the membrane surface is looser and easier to recover from backwashing; simultaneously, because the chitosan has undergone plasma treatment, its dispersibility is good, and no significant aggregation defects will occur due to the increased dosage.
[0038] In some specific embodiments, the operating conditions for the first stirring and mixing include: a temperature of 60℃-70℃, a stirring speed of 200rpm-300rpm, and a time of 6h-10h. This results in a uniformly stirred system.
[0039] As an example, the working conditions for the first stirring and mixing include: a temperature of 65°C, a stirring speed of 260 rpm, and a time of 8 hours.
[0040] In some specific embodiments, the operating conditions for the second stirring and mixing include: a temperature of 55℃-65℃, a stirring speed of 400rpm-500rpm, and a time of 4h-7h. This results in a uniformly stirred system.
[0041] As an example, the operating conditions for the second stirring and mixing include: a temperature of 60°C, a stirring speed of 450 rpm, and a time of 6 hours.
[0042] Secondly, the present invention provides an antifouling PVDF ultrafiltration membrane, which is prepared by the method for preparing an antifouling PVDF ultrafiltration membrane described in the first aspect.
[0043] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless otherwise specified, are generally performed according to national standards. If no corresponding national standard exists, then generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer are followed.
[0044] Example 1 This example provides an antifouling PVDF ultrafiltration membrane and its preparation method, including the following steps: Polyvinylidene fluoride was placed in a closed device, air was removed and CO2 was introduced. The system temperature and pressure were adjusted to the preset values - temperature 58℃ and pressure 12 MPa. The system was then subjected to supercritical carbon dioxide swelling treatment for 10 minutes under this supercritical state. The pressure was released and the system was dried to obtain modified polyvinylidene fluoride. Chitosan with a degree of deacetylation of 70% was placed in a microwave plasma processor and oxygen and argon in a volume ratio of 4:1 were introduced as working medium. Glow discharge treatment was performed for 85s under microwave power of 450W and gas flow rate of 90 mL / min. Then oxygen was introduced for another 10min to obtain modified chitosan. The modified polyvinylidene fluoride and polyvinylpyrrolidone (PVP-K30) were added to N,N-dimethylacetamide for a first stirring and mixing process. The mass ratio of the modified polyvinylidene fluoride, the polyvinylpyrrolidone, and the N,N-dimethylacetamide was 17:1.2:81.8. The working conditions for the first stirring and mixing included: a temperature of 65°C, a stirring speed of 240 rpm, and a time of 8 hours, to obtain the casting solution. The modified chitosan (by mass percentage, the amount of modified chitosan added accounts for 1% of the total mass of the casting solution) is added to the casting solution for a second stirring and mixing. The working conditions for the second stirring and mixing include: temperature of 60°C, stirring speed of 450 rpm, and time of 5 h. After standing and degassing, the cooled casting solution containing modified chitosan is poured onto the glass plate (scraper plate) of the film scraper for film scraping. Then, the glass plate is immersed in a pure water coagulation bath for 48 h to remove the residual N,N-dimethylacetamide solvent in the membrane pores. After removal, it is naturally air-dried for 24 h to obtain the PVDF ultrafiltration membrane.
[0045] Example 2 This example provides an antifouling PVDF ultrafiltration membrane and its preparation method, including the following steps: Polyvinylidene fluoride was placed in a closed device, air was removed and CO2 was introduced. The system temperature and pressure were adjusted to preset values - temperature 50℃ and pressure 8 MPa. The system was then subjected to supercritical carbon dioxide swelling treatment for 15 minutes under this supercritical state. The pressure was released and the system was dried to obtain modified polyvinylidene fluoride. Chitosan with a degree of deacetylation of 80% was placed in a microwave plasma processor, and oxygen and argon in a volume ratio of 4:1 were introduced as working media. Glow discharge treatment was performed for 120s under the conditions of microwave power of 340W and gas flow rate of 90 mL / min. Then oxygen was introduced for another 10min to obtain modified chitosan. The modified polyvinylidene fluoride and polyvinylpyrrolidone (PVP-K30) were added to N,N-dimethylacetamide for a first stirring and mixing process. The mass ratio of the modified polyvinylidene fluoride, the polyvinylpyrrolidone, and the N,N-dimethylacetamide was 15:1:84. The working conditions for the first stirring and mixing process included: a temperature of 65°C, a stirring speed of 240 rpm, and a time of 8 hours, to obtain the casting solution. The modified chitosan (by mass percentage, the amount of modified chitosan added accounts for 1% of the total mass of the casting solution) is added to the casting solution for a second stirring and mixing. The working conditions for the second stirring and mixing include: temperature of 60°C, stirring speed of 450 rpm, and time of 5 h. After standing and degassing, the cooled casting solution containing modified chitosan is poured onto the glass plate (scraper plate) of the film scraper for film scraping. Then, the glass plate is immersed in a pure water coagulation bath for 48 h to remove the residual N,N-dimethylacetamide solvent in the membrane pores. After removal, it is naturally air-dried for 24 h to obtain the PVDF ultrafiltration membrane.
[0046] Example 3 This example provides an antifouling PVDF ultrafiltration membrane and its preparation method, including the following steps: Polyvinylidene fluoride was placed in a closed device, air was removed and CO2 was introduced. The system temperature and pressure were adjusted to the preset values - temperature 60℃ and pressure 15 MPa. The system was then subjected to supercritical carbon dioxide swelling treatment for 8 minutes under this supercritical state. The pressure was released and the system was dried to obtain modified polyvinylidene fluoride. Chitosan with a degree of deacetylation of 70% was placed in a microwave plasma processor, and oxygen and argon in a volume ratio of 4:1 were introduced as working media. Glow discharge treatment was performed for 100s under the conditions of microwave power of 480W and gas flow rate of 90 mL / min. Then oxygen was introduced for another 10min to obtain modified chitosan. The modified polyvinylidene fluoride and polyvinylpyrrolidone (PVP-K30) were added to N,N-dimethylacetamide for a first stirring and mixing process. The mass ratio of the modified polyvinylidene fluoride, the polyvinylpyrrolidone, and the N,N-dimethylacetamide was 20:1:79. The working conditions for the first stirring and mixing process included: a temperature of 65°C, a stirring speed of 240 rpm, and a time of 8 hours, to obtain the casting solution. The modified chitosan (by mass percentage, the amount of modified chitosan added accounts for 1% of the total mass of the casting solution) is added to the casting solution for a second stirring and mixing. The working conditions for the second stirring and mixing include: temperature of 60°C, stirring speed of 450 rpm, and time of 5 h. After standing and degassing, the cooled casting solution containing modified chitosan is poured onto the glass plate (scraper plate) of the film scraper for film scraping. Then, the glass plate is immersed in a pure water coagulation bath for 48 h to remove the residual N,N-dimethylacetamide solvent in the membrane pores. After removal, it is naturally air-dried for 24 h to obtain the PVDF ultrafiltration membrane.
[0047] Comparative Example 1 The only difference between this example and Example 1 is that: (1) Polyvinylidene fluoride was not subjected to supercritical carbon dioxide swelling treatment.
[0048] (2) Chitosan was not subjected to oxygen-enriched microwave plasma treatment.
[0049] Comparative Example 2 The only difference between this example and Example 1 is that: (1) Polyvinylidene fluoride was not subjected to supercritical carbon dioxide swelling treatment.
[0050] Comparative Example 3 The only difference between this example and Example 1 is that: (1) Chitosan was not subjected to oxygen-enriched microwave plasma treatment.
[0051] Comparative Example 4 The only difference between this example and Example 1 is that: (1) The degree of deacetylation of chitosan is 90%.
[0052] Test Example 1 In this example, the flux attenuation performance of the PVDF ultrafiltration membranes obtained in Examples 1-3 and Comparative Examples 1-3 above was tested.
[0053] Test method: Continuous operation for 200 hours. Test conditions: 0.1 MPa, 25℃, 200 mg / L bovine serum albumin solution. Based on the initial flux (J0) and the flux after 200 hours (J200), the flux decay rate was calculated according to the following formula: .
[0054] The test results are shown in Table 1.
[0055] Table 1 Based on the above, this test example further tested the pure water flux of the PVDF ultrafiltration membranes obtained in Examples 1-3. Ultrapure water at 25°C was introduced under a pressure of 0.1 MPa, and after stabilization for 30 minutes, the permeate was collected, and the flux was calculated using the following formula: Where V: permeate volume (L), A: membrane area (m2), and t: time (h).
[0056] The test results are shown in Table 2.
[0057] Table 2 Test Example 2 Based on the above test example 1, this example further tests the antifouling performance of the PVDF ultrafiltration membranes obtained in Examples 1-3.
[0058] The testing method is as follows: A UV-Vis-IR spectrophotometer was used for testing. Measurement was performed under external pressure at 0.1 MPa, using bovine serum albumin (BSA) with a molecular weight of 80,000 and a concentration of 1 g / L as the test sample. The residual amount of BSA on the membrane was measured, and the ultrafiltration membrane rejection rate (RO) was determined using the following formula: Where Cp is the concentration of bovine serum albumin in the influent and Cf is the concentration of bovine serum albumin in the purified water.
[0059] The test results are shown in Table 3.
[0060] Table 3 As shown in Tables 1, 2 and 3, compared with the prior art, the present invention uses a supercritical carbon dioxide process to swell and modify polyvinylidene fluoride, and introduces chitosan with suitable deacetylation degree after being treated with oxygen-enriched microwave plasma, thereby obtaining a PVDF ultrafiltration membrane with both high antifouling and high flux, which makes up for the shortcomings of the prior art.
[0061] Various embodiments of the present invention may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible subranges and single numerical values within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the range referred to.
[0062] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.
Claims
1. A method for preparing an antifouling PVDF ultrafiltration membrane, characterized in that, Includes the following steps: Modified polyvinylidene fluoride was obtained by supercritical carbon dioxide swelling treatment of polyvinylidene fluoride. Chitosan with a degree of deacetylation of 70%~80% was subjected to oxygen-enriched microwave plasma treatment to obtain modified chitosan. The modified polyvinylidene fluoride and polyvinylpyrrolidone were added to N,N-dimethylacetamide for a first stirring and mixing to obtain a casting solution; The modified chitosan is added to the casting solution and stirred for a second time. After standing and degassing, the mixture is cast to obtain the PVDF ultrafiltration membrane.
2. The method for preparing the antifouling PVDF ultrafiltration membrane according to claim 1, characterized in that, The working conditions for the supercritical carbon dioxide swelling treatment include: temperature of 50℃-60℃, pressure of 8MPa-15MPa, and time of 8min-15min.
3. The method for preparing the antifouling PVDF ultrafiltration membrane according to claim 1, characterized in that, The working conditions for the supercritical carbon dioxide swelling treatment include: a temperature of 58°C, a pressure of 12 MPa, and a time of 10 min.
4. The method for preparing the antifouling PVDF ultrafiltration membrane according to claim 1, characterized in that, The operating conditions for the oxygen-rich microwave plasma treatment include: microwave power of 340W-500W and glow discharge treatment of 60s-120s.
5. The method for preparing the antifouling PVDF ultrafiltration membrane according to claim 1, characterized in that, The operating conditions for the oxygen-enriched microwave plasma treatment include: microwave power of 450W and glow discharge treatment for 85s.
6. The method for preparing the antifouling PVDF ultrafiltration membrane according to any one of claims 1-5, characterized in that, The mass ratio of the modified polyvinylidene fluoride, the polyvinylpyrrolidone, and the N,N-dimethylacetamide is (15-20):(1-1.5):(75-85).
7. The method for preparing the antifouling PVDF ultrafiltration membrane according to any one of claims 1-5, characterized in that, The modified chitosan is added in an amount of 0.5%-1.5% of the total mass of the casting solution, by mass percentage.
8. The method for preparing the antifouling PVDF ultrafiltration membrane according to any one of claims 1-5, characterized in that, The working conditions for the first stirring and mixing include: temperature of 60℃-70℃, stirring speed of 200rpm-300rpm, and time of 6h-10h.
9. The method for preparing the antifouling PVDF ultrafiltration membrane according to any one of claims 1-5, characterized in that, The working conditions for the second stirring and mixing include: temperature of 55℃-65℃, stirring speed of 400rpm-500rpm, and time of 4h-7h.
10. A fouling-resistant PVDF ultrafiltration membrane, characterized in that, The antifouling PVDF ultrafiltration membrane was prepared using the method described in any one of claims 1-9.