CN115364701B - Preparation method of in-situ synthesized nano-silver PVDF antibacterial ultrafiltration membrane - Google Patents
Preparation method of in-situ synthesized nano-silver PVDF antibacterial ultrafiltration membrane Download PDFInfo
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- CN115364701B CN115364701B CN202211006511.5A CN202211006511A CN115364701B CN 115364701 B CN115364701 B CN 115364701B CN 202211006511 A CN202211006511 A CN 202211006511A CN 115364701 B CN115364701 B CN 115364701B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
- B01D71/06—Organic material
- B01D71/30—Polyalkenyl halides
- B01D71/32—Polyalkenyl halides containing fluorine atoms
- B01D71/34—Polyvinylidene fluoride
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/02—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor characterised by their properties
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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Abstract
The invention discloses a preparation method of an in-situ synthesized nano-silver PVDF antibacterial ultrafiltration membrane, which comprises the following steps: s1, preparing a nano silver mixed solution: uniformly dissolving polyvinylpyrrolidone, silver nitrate and sodium citrate in N, N-dimethylacetamide, and stirring to obtain a nano silver mixed solution; s2, preparing nano silver casting film liquid: standing and cooling the nano silver mixed solution, cooling, adding PVDF powder, stirring, and defoaming to obtain nano silver casting solution; s3, pouring and film forming: after the nano silver casting film liquid is scraped by a scraper, the glass plate is put into a pure water coagulation bath, and is soaked at room temperature by a non-solvent induced phase separation method, so that the nano silver antibacterial ultrafiltration film is obtained. According to the preparation method of the in-situ synthesized nano-silver PVDF antibacterial ultrafiltration membrane, the hydrophilic performance and the antibacterial performance are synchronously improved on the basis of ensuring the high interception and high permeability of the ultrafiltration membrane, and the problems that the nano-silver particles are unevenly distributed, easy to agglomerate, unstable to fix, easy to fall off and the like caused by directly doping the nano-silver particles are effectively solved.
Description
Technical Field
The invention relates to the technical field of ultrafiltration membrane material preparation, in particular to a preparation method of an in-situ synthesized nano-silver PVDF antibacterial ultrafiltration membrane.
Background
The ultrafiltration is a membrane separation process in which the pressure difference at two sides of the membrane is used as the driving force, the ultrafiltration membrane is used as a filtering medium, and factors such as the pore diameter and material characteristics of the membrane are utilized to enable solvents and small molecular solutes to permeate the ultrafiltration membrane, and macromolecular substances such as bacteria, colloid, protein and the like are intercepted by the membrane. The ultrafiltration membrane is the core of the ultrafiltration separation process, and the properties of the ultrafiltration membrane material influence the structure and the performance of the ultrafiltration membrane and are important to the ultrafiltration effect. Biological pollution of the ultrafiltration membrane can cause deterioration of membrane performance, restricts long-term operation of an ultrafiltration system, and is a long-term difficult problem of the ultrafiltration membrane process.
Nano silver is widely applied to the preparation process of ultrafiltration membranes because of its good sterilization capability. At present, the method for fixing nano silver is divided into two types of surface modification and blending modification. The surface modified silver ions are only embedded on the surface of the ultrafiltration membrane, and long-acting and lasting sterilization cannot be realized. The blending modified ultrafiltration membrane has the defects of serious aggregation phenomenon of nano silver particles, unstable fixation and easy falling of nano silver, no obvious improvement of the hydrophilicity of the surface of the membrane and the like, so that the anti-biological pollution performance of the finally prepared nano silver antibacterial ultrafiltration membrane is reduced.
Disclosure of Invention
The invention aims to provide a preparation method of an in-situ synthesized nano-silver PVDF antibacterial ultrafiltration membrane, which solves the problems of uneven distribution, easy agglomeration, unstable fixation, easy falling-off and the like of nano-silver particles in the nano-silver antibacterial ultrafiltration membrane in the background art.
In order to achieve the aim, the invention provides a preparation method of an in-situ synthesized nano-silver PVDF antibacterial ultrafiltration membrane, which comprises the following steps:
s1, uniformly dissolving polyvinylpyrrolidone, silver nitrate and sodium citrate in N, N-dimethylacetamide, and stirring at 80-120 ℃ for 20-50 min to obtain a nano silver mixed solution;
s2, preparing nano silver casting film liquid: standing and cooling the nano silver mixed solution obtained in the step S1, adding PVDF powder after the temperature of the solution is reduced to room temperature, stirring for 8-12 h at 50-70 ℃, and standing and defoaming for 12-15 h in a constant temperature cabinet at 25-30 ℃ to obtain nano silver casting solution;
s3, pouring and film forming: scraping the defoamed nano silver casting film liquid on a clean glass plate by using a scraper, rapidly putting the glass plate into a pure water coagulation bath, and soaking for 24 hours at room temperature by using a non-solvent induced phase separation method to obtain the nano silver antibacterial ultrafiltration film.
Preferably, in the step S1, the molecular weight of the polyvinylpyrrolidone is 8000-58000, and the mass fraction is controlled to be 1-5wt%; the mass ratio of the silver nitrate to the sodium citrate is 0.5:1-1:8.
Preferably, in step S1, the order of adding the reactants to N, N-dimethylacetamide is polyvinylpyrrolidone, silver nitrate, and sodium citrate in this order.
Preferably, in the steps S1 and S2, the mass ratio of the silver nitrate to the PVDF is 0.001:1-0.05:1, and the mass fraction of the PVDF is 15-19 wt%.
Preferably, in the step S2, the standing time of the nano silver solution is 20-40 min.
Preferably, in step S1, oil bath magnetic stirring is used in the stirring; in the step S2, water bath magnetic stirring is adopted for stirring.
Preferably, in the step S3, the thickness of the scraper is 50-250 μm, and the scraping speed of the scraper is 0.2-0.8 m/S.
Preferably, in the step S3, the space conversion time before the casting solution is scraped on the glass plate and then put into the pure water coagulation bath is 5-15S; the water temperature of the pure water coagulation bath was 25.+ -. 1 ℃ and water was changed 3 times in 24 hours at room temperature.
Preferably, during the preparation process, the room temperature is 25+/-2 ℃ and the humidity is 50+/-5% RH.
Therefore, the preparation method of the in-situ synthesized nano-silver PVDF antibacterial ultrafiltration membrane utilizes in-situ synthesis of nano-silver in a membrane casting solution, so that nano-silver particles are fixedly wound and uniformly distributed in a polymer matrix, nano-silver particles are uniformly distributed on the surface and in the membrane pores of the membrane and are not easy to fall off, and the advantages of the nano-silver particles are utilized to the greatest extent in the membrane. Greatly improves the permeability, retention, hydrophilicity and stability of the ultrafiltration membrane, realizes the improvement of the antibacterial capacity of the ultrafiltration membrane, and effectively relieves the organic pollution and biological pollution of the ultrafiltration membrane.
The technical scheme of the invention is further described in detail through the drawings and the embodiments.
Drawings
FIG. 1 is a flow chart of a preparation method of an in-situ synthesized nano-silver PVDF antibacterial ultrafiltration membrane;
FIG. 2 shows the absorbance test results of casting solutions with different nano silver contents in the preparation method of the in-situ synthesized nano silver PVDF antibacterial ultrafiltration membrane;
FIG. 3 shows pure water flux tests of antibacterial ultrafiltration membranes with different nano-silver contents in the preparation method of the in-situ synthesized nano-silver PVDF antibacterial ultrafiltration membrane;
FIG. 4 shows water contact angle tests of antibacterial ultrafiltration membranes with different nano-silver contents in the preparation method of the in-situ synthesized nano-silver PVDF antibacterial ultrafiltration membrane;
FIG. 5 shows the retention rate test of the antibacterial ultrafiltration membranes BSA with different nano silver contents in the preparation method of the in-situ synthesized nano silver PVDF antibacterial ultrafiltration membrane;
FIG. 6 shows the antibacterial rate test of antibacterial ultrafiltration membranes with different nano-silver contents by using a living cell counting method in the preparation method of the in-situ synthesized nano-silver PVDF antibacterial ultrafiltration membrane;
FIG. 7 shows the antibacterial ratio test of antibacterial ultrafiltration membranes with different nano-silver contents by using the antibacterial circle size in the preparation method of the in-situ synthesized nano-silver PVDF antibacterial ultrafiltration membrane.
Detailed Description
The technical scheme of the invention is further described below through the attached drawings and the embodiments.
Unless defined otherwise, technical or scientific terms used herein should be given the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs.
Examples
The preparation process of in-situ synthesized nanometer silver PVDF antiseptic ultrafilter film includes the following steps:
s1, preparing a nano silver mixed solution: sequentially and uniformly dissolving polyvinylpyrrolidone, silver nitrate and sodium citrate in N, N-dimethylacetamide, and magnetically stirring in an oil bath at 100 ℃ for 35min to obtain a nano silver mixed solution. The molecular weight of polyvinylpyrrolidone was 58000 and the mass fraction was 2wt%. The mass ratio of the silver nitrate to the sodium citrate is 1:2.
S2, preparing nano silver casting film liquid: and (3) standing and cooling the nano silver mixed solution obtained in the step (S1) for 30min. After the temperature was reduced to room temperature, PVDF powder was added, with a PVDF mass fraction of 16wt%. After magnetically stirring for 10 hours in a water bath at 60 ℃, placing the mixture in a constant temperature box at 30 ℃ for standing and defoaming for 13 hours to obtain nano silver casting film liquid.
Wherein, the room temperature is 25 ℃, the humidity is 50% RH, and the in-situ synthesized nano-silver PVDF antibacterial ultrafiltration membrane casting solution is prepared according to the mass ratio of silver nitrate to PVDF of 0:1, 0.005:1, 0.01:1 and 0.02:1 respectively.
Test
(I) effect test of in-situ synthesis of nano silver: the film casting solution prepared according to different mass ratios of silver nitrate and PVDF is diluted ten times by N, N-dimethylacetamide solvent, and the absorbance is measured respectively. Wherein, the absorption peak between 400 and 500nm is nano silver absorption peak, and the test result is shown in figure 2.
And (II) scraping the casting solution on a clean glass plate by using a scraper with the thickness of 150 mu m on the basis of the defoamed nano silver casting solution obtained in the step S2, and controlling the scraping speed to be 0.5m/S. After the scraping was completed, space transformation was performed for 10s. And then the glass plate is quickly placed into a pure water coagulating bath, the water temperature of the pure water coagulating bath is 25 ℃, the non-solvent induced phase separation method is utilized to soak for 24 hours at room temperature, and water is changed for 3 times during the soaking period, so that the nano-silver antibacterial ultrafiltration membrane is obtained.
The ultrafiltration membranes with different nano silver contents are subjected to pure water flux test, water contact angle (hydrophilicity) test, BSA interception performance test and antibacterial experiment:
(1) And (3) testing pure water flux of an ultrafiltration membrane: the model of the membrane tank adopts CF016P, sterlitech, USA, the test temperature is 25+/-0.5 ℃, the cross flow mode is adopted in the test process, pure water is set as a measurement solution, and the flow rate is 0.24 m.s -1 . Firstly, cutting an ultrafiltration membrane into an effective area of 11.65cm 2 Then the membrane is fixed in the membrane tank with the front face facing downwards. After pre-pressing for 30min under 0.1MPa, adjusting the operating pressure to 0.05MPa to measure the pure water flux of the ultrafiltration membrane, continuously measuring for 15min, and taking an average value.
(2) Water contact angle (hydrophilicity) test: the contact angle meter was used with model JYSP-360, jinhengxin, china, test temperature was 23.0℃and test humidity was 50% RH, with thermometer and hygrometer accuracy divided into 0.1% and 1%. The experiment sets the pure water liquid volume to 2 mu L, and after the pure water liquid drop contacts the film surface for 5s by adopting the hanging drop method, the contact angle measurement value and the stable morphology of the liquid drop are recorded. In the measuring process, at least five different positions of each sample membrane are measured, and the average value and the error range are calculated to obtain a final result.
(3) BSA retention performance test: 500 mg.L is adopted -1 A BSA solution having a molecular weight of 66kDa was prepared at 0.05MPa and the feed temperature was maintained at 25.+ -. 0.5 ℃. The absorbance of the raw material liquid and the permeate liquid was measured at 280nm by an ultraviolet-visible spectrophotometer and converted into the concentration of protein by a standard curve.
The results of the ultrafiltration membrane pure water flux test, the water contact angle (hydrophilicity) test, and the BSA retention performance test are shown in table 1:
TABLE 1 Ultrafiltration Membrane Performance test results
(4) Antibacterial experiments are carried out on the nano silver antibacterial PVDF ultrafiltration membrane with different nano silver contents by using escherichia coli and staphylococcus aureus, and the test results are shown in fig. 6 and 7.
The bacterial inhibition rate of the ultrafiltration membrane is tested by a living cell counting method: membrane bacteria were first washed by ultrasound for 30min and uv irradiation for 30min, then rinsed with PBS buffer solution and transferred into 24-well plates. Taking the concentration to be 10 5 And (3) diluting 20 mu L of CFU/ml bacterial liquid, inoculating the bacterial liquid into an LB culture medium, and immersing the surface of an ultrafiltration membrane by the bacterial liquid. After 2h incubation at 37℃the bacterial solution was added to 1980. Mu.L buffer. 60 mu L of the mixed bacterial liquid is evenly placed on an agar plate, and is continuously cultured for 12 hours at 37 ℃ for counting.
Antibacterial ratio of ultrafiltration membrane is tested to antibacterial circle size: using cultured 10 5 The CFU/ml bacterial liquid is taken, and 0.1ml bacterial liquid is evenly coated on LB culture medium. Cutting ultrafiltration membrane to be tested into 1cm diameter disc, sterilizing, covering the culture medium with the cut sterilized ultrafiltration membrane with its front face downward, and discharging ultrafiltration membrane and bacteria as much as possibleBubbles between the solutions were used to ensure sufficient contact between the membrane surface and the bacterial solution, and the dishes were placed face down in a 37℃incubator for 24h. Three groups were tested for each parallel and averaged.
Therefore, the preparation method of the in-situ synthesized nano-silver PVDF antibacterial ultrafiltration membrane with the structure utilizes in-situ synthesis of nano-silver in membrane casting liquid, so that nano-silver particles are fixedly wound and uniformly distributed in a polymer matrix, nano-silver particles are uniformly distributed on the surface of the membrane and in the membrane pores and are not easy to fall off, and the advantages of the nano-silver particles are utilized to the greatest extent in the membrane. Greatly improves the permeability, retention, hydrophilicity and stability of the ultrafiltration membrane, realizes the improvement of the antibacterial capacity of the ultrafiltration membrane, and effectively relieves the organic pollution and biological pollution of the ultrafiltration membrane.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention and not for limiting it, and although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that: the technical scheme of the invention can be modified or replaced by the same, and the modified technical scheme cannot deviate from the spirit and scope of the technical scheme of the invention.
Claims (6)
1. A preparation method of an in-situ synthesized nano-silver PVDF antibacterial ultrafiltration membrane is characterized by comprising the following steps of: the method comprises the following steps:
s1, preparing a nano silver mixed solution: uniformly dissolving polyvinylpyrrolidone, silver nitrate and sodium citrate in N, N-dimethylacetamide, and stirring at 80-120 ℃ for 20-50 min to obtain a nano silver mixed solution;
s2, preparing nano silver casting film liquid: standing and cooling the nano silver mixed solution obtained in the step S1, adding PVDF powder after the temperature of the solution is reduced to room temperature, stirring for 8-12 h at 50-70 ℃, and standing and defoaming for 12-15 h in a constant temperature cabinet at 25-30 ℃ to obtain nano silver casting solution;
s3, pouring and film forming: scraping the defoamed nano silver casting film liquid on a clean glass plate by using a scraper, rapidly putting the glass plate into a pure water coagulation bath, and soaking for 24 hours at room temperature by using a non-solvent induced phase separation method to obtain a nano silver antibacterial ultrafiltration film;
in the step S1, the molecular weight of polyvinylpyrrolidone is 8000-58000, and the mass fraction is controlled to be 1-5wt%; the mass ratio of the silver nitrate to the sodium citrate is 0.5:1-1:8;
in the step S1, oil bath magnetic stirring is used in stirring; in the step S2, water bath magnetic stirring is adopted for stirring;
in the steps S1 and S2, the mass ratio of the silver nitrate to the PVDF is 0.001:1-0.05:1, and the mass fraction of the PVDF is 15-19 wt%.
2. The method for preparing the in-situ synthesized nano-silver PVDF antibacterial ultrafiltration membrane, which is characterized in that: in step S1, the reactants are added to N, N-dimethylacetamide in the order of polyvinylpyrrolidone, silver nitrate and sodium citrate.
3. The method for preparing the in-situ synthesized nano-silver PVDF antibacterial ultrafiltration membrane, which is characterized in that: in the step S2, the standing time of the nano silver solution is 20-40 min.
4. The method for preparing the in-situ synthesized nano-silver PVDF antibacterial ultrafiltration membrane, which is characterized in that: in the step S3, the thickness of the scraper is 50-250 mu m, and the scraping speed of the scraper is 0.2-0.8 m/S.
5. The method for preparing the in-situ synthesized nano-silver PVDF antibacterial ultrafiltration membrane, which is characterized in that: in the step S3, the space conversion time before the casting film liquid is scraped on the glass plate and then put into the pure water coagulation bath is 5-30S; the water temperature of the pure water coagulation bath was 25±1 ℃, and water was changed 3 times within 24 hours of soaking.
6. The method for preparing the in-situ synthesized nano-silver PVDF antibacterial ultrafiltration membrane, which is characterized in that: in the preparation process, the room temperature is 25+/-2 ℃, and the humidity is 50+/-5% RH.
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