CN116099387B - A kind of anti-pollution type ultrafiltration membrane and preparation method thereof - Google Patents
A kind of anti-pollution type ultrafiltration membrane and preparation method thereof Download PDFInfo
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Abstract
The invention provides an anti-pollution ultrafiltration membrane and a preparation method thereof, wherein the ultrafiltration membrane is modified by adopting a nano material with a visible light photocatalysis function, so that the modified ultrafiltration membrane not only has self-cleaning performance under visible light, but also has obviously improved hydrophilic performance on the surface of the membrane, thereby improving the anti-pollution performance and the application range of the ultrafiltration membrane. The modification method is simple and feasible to operate and easy to industrialize and amplify.
Description
Technical Field
The invention relates to the technical field of membranes, in particular to an anti-pollution ultrafiltration membrane and a preparation method thereof.
Background
With the rapid development of society, environmental pollution problems are becoming more and more interesting. Particularly, the discharge of industrial wastewater has become a key bottleneck restricting the sustainable development of society. The membrane technology plays an important role in environmental management as a unique advantage of low energy consumption and no need of other chemical reagents, and is particularly favored in the aspects of material separation and water treatment.
At present, the separation membrane material has the main problems of low flux, limited application range, easy pollution and the like. The flux of the traditional high molecular membrane is not high, the flux is easily reduced due to concentration polarization when wastewater is treated, the surface and the membrane holes of the membrane are easily polluted when wastewater containing small molecular organic matters is treated, the separation performance of the membrane is directly influenced, and the water treatment cost is increased. In order to reduce membrane pollution, researchers blend ultraviolet light catalysts (such as TiO 2) with PVDF to prepare photocatalytic mixed matrix membranes, however, the mixed matrix membranes have better anti-pollution performance only under ultraviolet light irradiation. As is known, the ultraviolet light only accounts for 4% of the solar spectrum, and the high energy consumption and the high cost become the limits for the practical application and popularization of the ultraviolet light photocatalyst mixed matrix film. Therefore, development of a nontoxic, environment-friendly, cheap, easily available and stable-chemical visible light photocatalyst is needed to replace an ultraviolet light photocatalyst to efficiently modify a separation membrane, and development of an anti-pollution ultrafiltration membrane with long-term stability is needed.
Disclosure of Invention
In order to overcome the defects and shortcomings of the photocatalytic separation membrane, the visible light photocatalyst is adopted to replace the ultraviolet light photocatalyst to carry out high-efficiency modification on the surface of the separation membrane, so that the prepared modified separation membrane has good anti-pollution performance under the irradiation of visible light, and the preparation method of the ultrafiltration membrane with the advantages of self-cleaning capability of visible light catalysis, excellent hydrophilic performance and strong anti-pollution performance is provided.
In one aspect, the invention provides an anti-pollution ultrafiltration membrane which is formed by compounding an ultrafiltration base membrane and a modified layer, wherein the ultrafiltration base membrane is selected from polyacrylonitrile or polyvinylidene fluoride, or a combination thereof; the modified layer is an amino acid functionalized graphene quantum dot with a visible light photocatalysis function.
In another aspect, the invention provides a method for preparing an anti-pollution ultrafiltration membrane, comprising the steps of:
step S1, preparing ultrafiltration base membrane casting solution;
step S2, preparing a base film containing a non-woven fabric base material;
Step S3, carrying out alkali treatment on the base film containing the non-woven fabric base material prepared in the step S2, and introducing double bonds;
and S4, chemically modifying the film surface of the base film, and introducing amino acid functionalized graphene quantum dots with visible light photocatalysis function.
In some embodiments, step S1 of preparing the ultrafiltration membrane is to add N-methylpyrrolidone to polyvinylidene fluoride and polyvinylpyrrolidone and stir at room temperature and constant temperature; and then standing and defoaming at room temperature to obtain uniform and stable casting film liquid.
In some embodiments, step 2) uniformly coating the casting solution prepared in step 1) on a non-woven fabric substrate, then entering a pure water gel bath, wherein the gel bath temperature is 30 ℃, the solvent exchange in the film is ensured to be complete in a coagulating bath, and the ambient temperature in the film coating process is 25 ℃ and the ambient humidity is 50%; the dry process is 10cm; the film scraping speed is 2m/min to obtain the base film containing the non-woven fabric base material.
In some embodiments, the alkali treatment in step S2 is to soak the base film containing the nonwoven fabric substrate obtained in step S2 in an alcohol solution of alkali metal hydroxide with a mass concentration of 0.1-5%.
In some embodiments, step S4 is obtained by immersing the film after the alkali treatment of step S3 in an aqueous dispersion of amino acid functionalized graphene quantum dots, grafting the amino acid functionalized graphene quantum dots to the film surface; the concentration of the amino acid functionalized graphene quantum dots is 0.1-3%, and the aqueous dispersion liquid also contains an activator which is EDC/NHS.
In some embodiments, the preparation method of the amino acid functionalized graphene quantum dot uses citric acid as a carbon source and amino acid as a functionalized source, and the preparation method is prepared by a 'bottom-up' hydrothermal method in one step, and comprises the following steps:
step 1, mixing citric acid and amino acid according to the mass ratio of 0.5-2:1, adding a proper amount of pure water, and then carrying out ultrasonic treatment to uniformly dissolve the pure water;
step 2, stirring and heating the solution at constant temperature, slowly raising the temperature from room temperature to 200-300 ℃ within 10-30 minutes, changing the color of the solution from colorless to dark color after 2-3 hours of reaction, and stopping heating;
step 3, adjusting the pH value of the solution to be neutral by using 0.1-1 mol/L NaOH aqueous solution and HCl aqueous solution;
Step 4, cooling the solution to room temperature, filtering the solution by using a filter membrane, and concentrating and desalting the solution by using a nanofiltration membrane with the molecular weight cutoff of 500-2000 Da;
and step5, drying the nanofiltration concentrated solution to obtain the amino acid functionalized graphene quantum dots, and preserving the amino acid functionalized graphene quantum dots for later use.
Use of an anti-fouling membrane in a filtration process of a solution containing organic matter.
In the use, the method further comprises: after filtration, the surface of the modified film was irradiated with visible light.
In some embodiments, the ultrafiltration base membrane is selected from Polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), and the like.
In some embodiments, the modification layer is an amino acid functionalized graphene quantum dot with a visible light photocatalytic function.
The invention has the advantages that:
(1) According to the invention, the amino acid functionalized graphene quantum dots with the visible light photocatalysis function are fixed on the surface of the high polymer ultrafiltration membrane through chemical bonds, so that the firmness, stability and safety of the visible light photocatalyst on the surface of the ultrafiltration membrane are improved, the problem that the photocatalyst is continuously lost when the photocatalyst is embedded or embedded into the high polymer separation membrane matrix by utilizing the physical effect by the traditional physical blending method is solved, and the modified separation membrane with the visible light photocatalysis performance, good stability and remarkably improved hydrophilic performance is prepared.
(2) The visible light photocatalyst-amino acid functionalized graphene quantum dot prepared by the method has the advantages of low raw material cost, easiness in preparation, good biocompatibility, low toxicity and the like, and has excellent hydrophilic performance and abundant reactive sites, so that the visible light photocatalyst-amino acid functionalized graphene quantum dot is more easily grafted to the surface of an ultrafiltration membrane in a chemical reaction mode.
Drawings
FIG. 1 is a fluorescence microscope image of PVDF blank film prepared in comparative example 1 at different excitation wavelengths.
Fig. 2 is a fluorescence microscope image of the amino acid functionalized graphene quantum dot modified PVDF separation membrane prepared in example 1 at different excitation wavelengths.
Fig. 3 is a graph comparing dynamic anti-contamination performance of lysozyme with the PVDF blank film prepared in comparative example 1 and the amino acid functionalized graphene quantum dot modified PVDF separation film prepared in example 1.
Fig. 4 is a graph comparing dynamic anti-pollution performance of the PVDF blank film prepared in comparative example 1 and the amino acid functionalized graphene quantum dot modified PVDF separation film prepared in example 1 to bovine serum albumin.
Detailed Description
In order to better understand the technical solution of the present invention, some non-limiting examples are further disclosed below to further describe the present invention in detail.
The reagents used in the present invention are all commercially available or can be prepared by the methods described herein.
Example 1:
(1) Preparation of amino acid functionalized graphene quantum dots
The preparation method comprises the following steps of:
step 1), citric acid and amino acid are mixed according to the following formula 1:1, adding a proper amount of pure water, and then carrying out ultrasonic treatment to uniformly dissolve the pure water;
Step 2), stirring and heating the solution at constant temperature, slowly raising the temperature from room temperature to 250 ℃ within 20 minutes, and stopping heating after the solution reacts for 2 hours, wherein the color of the solution is changed from colorless to dark;
step 3), adjusting the pH value of the solution to be neutral by using 1mol/L NaOH aqueous solution and HCl aqueous solution;
Step 4), cooling the solution to room temperature, filtering with a 0.22 mu m filter membrane, and concentrating and desalting the solution with a nanofiltration membrane with a molecular weight cut-off of 1000 Da;
And 5) freeze-drying the nanofiltration concentrated solution to obtain the amino acid functionalized graphene quantum dots, and storing the amino acid functionalized graphene quantum dots for later use.
(2) Preparation of anti-pollution ultrafiltration membrane
The anti-pollution ultrafiltration membrane is prepared by the following steps:
step 1) preparing a polyvinylidene fluoride ultrafiltration base film with the pore diameter of 50 nm: 340g of polyvinylidene fluoride and 200g of polyvinylpyrrolidone are added into 1236g N-methylpyrrolidone, and the mixture is stirred for 24 hours at a constant temperature of 25 ℃; and then standing and defoaming for 12 hours at the temperature of 25 ℃ to obtain uniform and stable casting film liquid for standby.
Step 2) uniformly coating the casting solution prepared in the step 1) on a non-woven fabric substrate through a flat-plate film scraping machine, and then entering a pure water gel bath, wherein the gel bath temperature is 30 ℃, and the complete solvent exchange in the film is ensured in a coagulation bath. The ambient temperature in the film coating process is 25 ℃ and the ambient humidity is 50%; the dry process is 10cm; the film scraping speed was 2m/min to obtain a base film containing a nonwoven fabric substrate, and the thickness was 0.23mm.
Step 3) soaking the base film containing the non-woven fabric base material obtained in the step 2) in a 1% NaOH-ethanol solution for 1min, and carrying out alkali treatment on the base film;
step 4) dispersing 2g of amino acid functionalized graphene quantum dots in an EDC/NHS reaction system (0.05 mol/LEDC and 0.05mol/L NHS are dissolved in 100ml of MES buffer solution with the concentration of 10 mmol/L), and activating carboxyl groups for 1h. And finally, pouring the reacted solution into a die provided with an alkali treatment ultrafiltration base film, and reacting for 24 hours to prepare the modified separation film containing the amino acid functionalized graphene quantum dots.
Example 2:
(1) Preparation of amino acid functionalized graphene quantum dots
The preparation method comprises the following steps of:
Step 1), citric acid and amino acid according to 0.5:1, adding a proper amount of pure water, and then carrying out ultrasonic treatment to uniformly dissolve the pure water;
Step 2), stirring and heating the solution at constant temperature, slowly raising the temperature from room temperature to 200 ℃ within 10 minutes, and stopping heating after reacting for 2.5 hours until the color of the solution is changed from colorless to dark;
step 3), adjusting the pH value of the solution to be neutral by using 0.1mol/L NaOH aqueous solution and HCl aqueous solution;
step 4), cooling the solution to room temperature, filtering with a 0.22 mu m filter membrane, and concentrating and desalting the solution with a nanofiltration membrane with a molecular weight cut-off of 500 Da;
And 5) spray drying the nanofiltration concentrated solution to obtain the amino acid functionalized graphene quantum dots, and preserving the amino acid functionalized graphene quantum dots for later use.
(2) Preparation of anti-pollution ultrafiltration membrane
The anti-pollution ultrafiltration membrane is prepared by the following steps:
Step 1) preparing a polyvinylidene fluoride ultrafiltration base membrane with the aperture of 100 nm; 150g of polyvinylidene fluoride and 100g of polyvinylpyrrolidone are added into 660g N-methylpyrrolidone, and the mixture is stirred for 24 hours at a constant temperature of 25 ℃; and then standing and defoaming for 12 hours at the temperature of 25 ℃ to obtain uniform and stable casting film liquid for standby.
Step 2) uniformly coating the casting solution prepared in the step 1) on a non-woven fabric substrate through a flat-plate film scraping machine, and then entering a pure water gel bath, wherein the gel bath temperature is 40 ℃, and the complete solvent exchange in the film is ensured in a coagulation bath. The ambient temperature in the film coating process is 25 ℃ and the ambient humidity is 50%; the dry process is 10cm; the film scraping speed is 3m/min; the film thickness of the nonwoven fabric-containing substrate was 0.23mm.
Step 3) soaking the polyvinylidene fluoride ultrafiltration base membrane obtained in the step 2) in 0.5% NaOH-ethanol solution for 1min, and carrying out alkali treatment on the base membrane;
Step 4) 3g of amino acid functionalized graphene quantum dots are dispersed in an EDC/NHS reaction system (0.1 mol/LEDC and 0.1mol/L NHS are dissolved in 100ml of MES buffer solution with the concentration of 10 mmol/L), and carboxyl groups are activated for 2h. And finally, pouring the reacted solution into a die provided with an alkali treatment ultrafiltration base film, and reacting for 12 hours to prepare the modified separation film containing the amino acid functionalized graphene quantum dots.
Example 3:
(1) Preparation of amino acid functionalized graphene quantum dots
The preparation method comprises the following steps of:
Step 1), citric acid and amino acid are mixed according to the following formula 2:1, adding a proper amount of pure water, and then carrying out ultrasonic treatment to uniformly dissolve the pure water;
Step 2), stirring and heating the solution at constant temperature, slowly raising the temperature from room temperature to 300 ℃ within 30 minutes, and stopping heating after the solution reacts for 3 hours, wherein the color of the solution is changed from colorless to dark;
Step 3), adjusting the pH value of the solution to be neutral by using 0.5mol/L NaOH aqueous solution and HCl aqueous solution;
Step 4), cooling the solution to room temperature, filtering with a 0.22 mu m filter membrane, and concentrating and desalting the solution with a nanofiltration membrane with a molecular weight cut-off of 2000 Da;
And 5) freeze-drying the nanofiltration concentrated solution to obtain the amino acid functionalized graphene quantum dots, and storing the amino acid functionalized graphene quantum dots for later use.
(2) Preparation of anti-pollution ultrafiltration membrane
The anti-pollution ultrafiltration membrane is prepared by the following steps:
Step 1) preparing a polyvinylidene fluoride ultrafiltration base membrane with the pore diameter of 30 nm; 170g of polyvinylidene fluoride and 60g of polyvinylpyrrolidone are added into 500g N-methylpyrrolidone, and the mixture is stirred for 24 hours at a constant temperature of 25 ℃; and then standing and defoaming for 12 hours at the temperature of 25 ℃ to obtain uniform and stable casting film liquid for standby.
Step 2) uniformly coating the casting solution prepared in the step 1) on a non-woven fabric substrate through a flat-plate film scraping machine, and then entering a pure water gel bath, wherein the gel bath temperature is 20 ℃, and the complete solvent exchange in the film is ensured in a coagulation bath. The ambient temperature in the film coating process is 25 ℃ and the ambient humidity is 50%; the dry process is 15cm; the film scraping speed is 3m/min; the film thickness of the nonwoven fabric-containing substrate was 0.23mm.
Step 3) soaking the polyvinylidene fluoride ultrafiltration base membrane obtained in the step 2) in 2% NaOH-ethanol solution for 1min, and carrying out alkali treatment on the base membrane;
Step 4) dispersing 1g of amino acid functionalized graphene quantum dots in an EDC/NHS reaction system (0.05 mol/LEDC and 0.05mol/L NHS are dissolved in 100ml of MES buffer solution with the concentration of 10 mmol/L), and activating carboxyl groups for 2h. And finally, pouring the reacted solution into a die provided with an alkali treatment ultrafiltration base film, and reacting for 16 hours to prepare the modified separation film containing the amino acid functionalized graphene quantum dots.
Example 4:
(1) Preparation of amino acid functionalized graphene quantum dots
The preparation method comprises the following steps of:
Step 1), citric acid and amino acid according to 1.5:1, adding a proper amount of pure water, and then carrying out ultrasonic treatment to uniformly dissolve the pure water;
Step 2), stirring and heating the solution at constant temperature, slowly raising the temperature from room temperature to 250 ℃ within 25 minutes, and stopping heating after the solution reacts for 2.5 hours and the color of the solution changes from colorless to dark;
Step 3), adjusting the pH value of the solution to be neutral by using 0.75mol/L NaOH aqueous solution and HCl aqueous solution;
step 4), cooling the solution to room temperature, filtering with a 0.22 mu m filter membrane, and concentrating and desalting the solution with a nanofiltration membrane with a molecular weight cut-off of 800 Da;
And 5) freeze-drying the nanofiltration concentrated solution to obtain the amino acid functionalized graphene quantum dots, and storing the amino acid functionalized graphene quantum dots for later use.
(2) Preparation of anti-pollution ultrafiltration membrane
The anti-pollution ultrafiltration membrane is prepared by the following steps:
step 1) preparing a polyacrylonitrile ultrafiltration base membrane with the pore diameter of 50 nm; 50g of polyacrylonitrile and 30g of polyvinylpyrrolidone are added into 300g N-methylpyrrolidone, and the mixture is stirred for 24 hours at a constant temperature of 25 ℃; and then standing and defoaming for 12 hours at the temperature of 25 ℃ to obtain uniform and stable casting film liquid for standby.
Step 2) uniformly coating the casting solution prepared in the step 1) on a non-woven fabric substrate through a flat-plate film scraping machine, and then entering a pure water gel bath, wherein the gel bath temperature is 35 ℃, and the complete solvent exchange in the film is ensured in a coagulation bath. The ambient temperature in the film coating process is 25 ℃ and the ambient humidity is 60%; the dry process is 15cm; the film scraping speed is 1m/min; the film thickness of the nonwoven fabric-containing substrate was 0.22mm.
Step 3) soaking the polyacrylonitrile ultrafiltration base membrane obtained in the step 2) in a 1% NaOH-ethanol solution for 2min, and carrying out alkali treatment on the base membrane;
Step 4) dispersing 1g of amino acid functionalized graphene quantum dots in an EDC/NHS reaction system (0.1 mol/LEDC and 0.1mol/L NHS are dissolved in 100ml of MES buffer solution with the concentration of20 mmol/L), and activating carboxyl groups for 1h. And finally, pouring the reacted solution into a die provided with an alkali treatment ultrafiltration base film, and reacting for 16 hours to prepare the modified separation film containing the amino acid functionalized graphene quantum dots.
Example 5:
(1) Preparation of amino acid functionalized graphene quantum dots
The preparation method comprises the following steps of:
Step 1), citric acid and amino acid according to 0.6:1, adding a proper amount of pure water, and then carrying out ultrasonic treatment to uniformly dissolve the pure water;
step 2), stirring and heating the solution at constant temperature, slowly raising the temperature from room temperature to 220 ℃ within 15 minutes, and stopping heating after the solution reacts for 2.3 hours and the color of the solution changes from colorless to dark;
step 3), adjusting the pH value of the solution to be neutral by using 0.6mol/L NaOH aqueous solution and HCl aqueous solution;
step 4), cooling the solution to room temperature, filtering with a 0.22 mu m filter membrane, and concentrating and desalting the solution with a nanofiltration membrane with a molecular weight cut-off of 500 Da;
And 5) spray drying the nanofiltration concentrated solution to obtain the amino acid functionalized graphene quantum dots, and preserving the amino acid functionalized graphene quantum dots for later use.
(2) Preparation of anti-pollution ultrafiltration membrane
The anti-pollution ultrafiltration membrane is prepared by the following steps:
Step 1) preparing a polyacrylonitrile ultrafiltration base membrane with the aperture of 100 nm; adding 30g of polyacrylonitrile and 30g of polyvinylpyrrolidone into 200g N-methylpyrrolidone, and stirring at constant temperature for 24 hours at 25 ℃; and then standing and defoaming for 12 hours at the temperature of 25 ℃ to obtain uniform and stable casting film liquid for standby.
Step 2) uniformly coating the casting solution prepared in the step 1) on a non-woven fabric substrate through a flat-plate film scraping machine, and then entering a pure water gel bath, wherein the gel bath temperature is 20 ℃, and the complete solvent exchange in the film is ensured in a coagulation bath. The ambient temperature in the film coating process is 25 ℃ and the ambient humidity is 50%; the dry process is 20cm; the film scraping speed is 2m/min; the film thickness of the nonwoven fabric-containing substrate was 0.23mm.
Step 3) soaking the polyacrylonitrile ultrafiltration base membrane obtained in the step 2) in 0.5% NaOH-ethanol solution for 1min, and performing alkali treatment on the base membrane;
Step 4) 3g of amino acid functionalized graphene quantum dots are dispersed in an EDC/NHS reaction system (0.15 mol/LEDC and 0.15mol/L NHS are dissolved in 100ml of MES buffer solution with the concentration of 10 mmol/L), and carboxyl groups are activated for 2h. And finally, pouring the reacted solution into a die provided with an alkali treatment ultrafiltration base film, and reacting for 24 hours to prepare the modified separation film containing the amino acid functionalized graphene quantum dots.
Comparative example 1:
(1) Preparation of amino acid functionalized graphene quantum dots
The preparation method comprises the following steps of:
Step 1), mixing citric acid and amino acid according to the mass ratio of 1:1, adding a proper amount of pure water, and then carrying out ultrasonic treatment to uniformly dissolve the pure water;
Step 2), stirring and heating the solution at constant temperature, slowly raising the temperature from room temperature to 250 ℃ within 20 minutes, and stopping heating after the solution reacts for 2 hours, wherein the color of the solution is changed from colorless to dark;
step 3), adjusting the pH value of the solution to be neutral by using 1mol/L NaOH aqueous solution and HCl aqueous solution;
Step 4), cooling the solution to room temperature, filtering with a 0.22 mu m filter membrane, and concentrating and desalting the solution with a nanofiltration membrane with a molecular weight cut-off of 1000 Da;
And 5) freeze-drying the nanofiltration concentrated solution to obtain the amino acid functionalized graphene quantum dots, and storing the amino acid functionalized graphene quantum dots for later use.
(2) Preparation of anti-pollution ultrafiltration membrane
A PVDF blank control membrane separation membrane was prepared as follows:
Step 1) preparing a polyvinylidene fluoride ultrafiltration base membrane with the pore diameter of 50 nm; 340g of polyvinylidene fluoride and 200g of polyvinylpyrrolidone are added into 1236g N-methylpyrrolidone, and the mixture is stirred for 24 hours at a constant temperature of 25 ℃; and then standing and defoaming for 12 hours at the temperature of 25 ℃ to obtain uniform and stable casting film liquid for standby.
Step 2) uniformly coating the casting solution prepared in the step 1) on a non-woven fabric substrate through a flat-plate film scraping machine, and then entering a pure water gel bath, wherein the gel bath temperature is 30 ℃, and the complete solvent exchange in the film is ensured in a coagulation bath. The ambient temperature in the film coating process is 25 ℃ and the ambient humidity is 50%; the dry process is 10cm; the film scraping speed is 2m/min; the film thickness of the nonwoven fabric-containing substrate was 0.23mm.
Test example:
(1) And (5) testing dynamic anti-pollution performance. After the membrane is put into a membrane separation device, pure water and a pollutant solution (lysozyme and bovine serum albumin) are used as feed liquid for circulation, and the five stages are used as one stage in 60 minutes, and the test is carried out according to the sequence of water-pollution-water-pollutant-water (the pollutant needs to be cleaned before the water flux is tested). Water flux detection conditions: the instantaneous membrane flux was tested at 25 ℃ and 0.2MPa at 6 minute intervals, and all data was converted to normalized flux after the test was completed. The normalized flux (Nomalized flux) is equal to the instantaneous membrane flux divided by the initial membrane flux.
(2) Determination of the Water flux recovery of the photocatalytic Membrane
PBS buffer solution containing 0.5g/L bovine serum albumin is prepared, the prepared membrane is filtered for 60 minutes under the conditions of the operating temperature of 25 ℃ and the operating pressure of 0.2MPa, then the membrane is irradiated for 30 minutes under a 75-watt LED white light lamp, and the change condition of water flux before and after photocatalysis is compared, and the membrane is characterized by the water flux recovery rate which is = (water flux after photocatalysis irradiation/initial water flux) multiplied by 100%.
(3) Determination of the hydrophilic Properties of the Membrane surface
The water contact angle of the film surface was measured by a water contact angle measuring instrument by a profile image analysis method. The film was dried and cut into 1.5cm x 1.5cm squares, and the film was attached to the slide surface with the front side facing upward for testing, the water drop volume was 2 μl, the contact angle was tested after 30s contact with the film surface, and the average value was taken 5 times for each sample.
The results of the main property tests of the films obtained in examples 1 to 5 and comparative example 1 are shown in Table 1:
TABLE 1
Claims (8)
1. The preparation method of the anti-pollution ultrafiltration membrane is characterized by comprising the following steps of:
step S1, preparing ultrafiltration base membrane casting solution;
step S2, preparing a base film containing a non-woven fabric base material;
Step S3, carrying out alkali treatment on the base film containing the non-woven fabric base material prepared in the step S2, and introducing double bonds;
S4, chemically modifying the film surface of the base film, and introducing amino acid functionalized graphene quantum dots with visible light photocatalysis function;
The alkali treatment in the step S3 is to soak the base film containing the non-woven fabric base material obtained in the step S2 in an alcohol solution of alkali metal hydroxide with the mass concentration of 0.1-5%;
And step S4, immersing the membrane subjected to the alkali treatment in the step S3 in an aqueous dispersion liquid of amino acid functionalized graphene quantum dots, so that the amino acid functionalized graphene quantum dots are grafted on the surface of the membrane, wherein the aqueous dispersion liquid contains an activator, and the activator is EDC/NHS.
2. The method for preparing an anti-pollution ultrafiltration membrane according to claim 1, wherein the step S1 is to add N-methyl pyrrolidone into polyvinylidene fluoride and polyvinylpyrrolidone, and stir at room temperature and constant temperature; and then standing and defoaming at room temperature to obtain uniform and stable casting film liquid.
3. The method for preparing an anti-pollution ultrafiltration membrane according to claim 1, wherein in the step S2, the casting solution prepared in the step S1 is uniformly coated on a non-woven fabric substrate, then the non-woven fabric substrate enters a pure water gel bath, the gel bath temperature is 30 ℃, the solvent exchange in the membrane is ensured to be complete in a coagulation bath, and the ambient temperature in the coating process is 25 ℃ and the ambient humidity is 50%; the dry process is 10cm; the film scraping speed is 2m/min to obtain the base film containing the non-woven fabric base material.
4. The method for preparing the anti-pollution ultrafiltration membrane according to claim 1, wherein the concentration of the amino acid functionalized graphene quantum dots is 0.1-3%.
5. The preparation method of the anti-pollution ultrafiltration membrane according to claim 1, wherein the preparation method of the amino acid functionalized graphene quantum dot comprises the steps of taking citric acid as a carbon source and amino acid as a functionalized source, and preparing the amino acid functionalized graphene quantum dot by a 'bottom-up' hydrothermal method in one step, and comprises the following steps:
Step 1, mixing citric acid and amino acid according to the mass ratio of 0.5-2:1, adding a proper amount of pure water, and then carrying out ultrasonic treatment to uniformly dissolve the pure water;
Step 2, stirring and heating the solution obtained in the step 1 at constant temperature, slowly raising the temperature from room temperature to 200-300 ℃ within 10-30 minutes, changing the color of the solution from colorless to dark color after reacting for 2-3 hours, and stopping heating;
step 3, adjusting the pH value of the solution obtained in the step 2 to be neutral by using 0.1-1 mol/L NaOH aqueous solution and HCl aqueous solution; step 4, cooling the solution obtained in the step 3 to room temperature, filtering the solution by using a filter membrane, and concentrating and desalting the solution by using a nanofiltration membrane with the molecular weight cutoff of 500-2000 Da;
and step5, drying the nanofiltration concentrated solution to obtain the amino acid functionalized graphene quantum dots, and preserving the amino acid functionalized graphene quantum dots for later use.
6. An anti-pollution ultrafiltration membrane prepared by the preparation method of any one of claims 1 to 5, which is characterized in that the anti-pollution ultrafiltration membrane is formed by compounding an ultrafiltration base membrane and a modified layer, wherein the ultrafiltration base membrane is selected from polyacrylonitrile or polyvinylidene fluoride, or a combination thereof; the modified layer is an amino acid functionalized graphene quantum dot with a visible light photocatalysis function.
7. Use of an anti-fouling ultrafiltration membrane according to claim 6 in a filtration process of an organic-containing solution.
8. The use according to claim 7, further comprising, in said use: after filtration, the surface of the modified film was irradiated with visible light.
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