Protein pollution resistant polyacrylonitrile hydrolysis modified ultrafiltration membrane and preparation method thereof

Abstract

The invention discloses a protein pollution resistant polyacrylonitrile hydrolysis modified ultrafiltration membrane, which is prepared by mixing hydrolyzed polyacrylonitrile (H-PAN) and graphene oxide (GO), and the content of the GO is 0.005-0.04 wt% of the weight of a membrane casting solution. The preparation method has the advantages that the hydrolyzed polyacrylonitrile is used as a base membrane material, and the two-dimensional nano material graphene oxide rich in carboxyl and hydroxyl is introduced and has a synergistic effect with the base membrane material to improve the anti-pollution performance of the ultrafiltration membrane. The core of the invention is that hydrolyzed polyacrylonitrile H-PAN and graphene oxide GO are ingeniously combined to form a novel H-PAN / GO mixed matrix ultrafiltration membrane.

Description

Technical Field

[0001] The invention relates to the technical field of ultrafiltration membranes, in particular to a polyacrylonitrile hydrolysis-modified ultrafiltration membrane resistant to protein pollution and a preparation method thereof. Background Art

[0002] With the increasing shortage of global water resources and the intensification of environmental pollution, efficient and economical water treatment technology has become particularly important. As an efficient separation technology, ultrafiltration membrane technology has been widely used in water treatment, biopharmaceuticals, food processing and other fields. Ultrafiltration membrane (UF) is a type of membrane separation technology with a large effective pore size, and its pore size is usually in the range of 2-50nm. This size range makes ultrafiltration membrane very suitable for intercepting macromolecular substances such as proteins, viruses, bacteria and larger molecular organic pollutants. Polyacrylonitrile, as a synthetic polymer material with good thermal stability and mechanical strength, has been widely used in the preparation of ultrafiltration membranes. However, the anti-pollution performance of polyacrylonitrile ultrafiltration membranes still needs to be improved, especially in the filtration process of biological macromolecules such as protein separation, the membrane fouling problem is particularly prominent.

[0003] Polyacrylonitrile ultrafiltration membranes are widely used due to their good thermal stability and mechanical strength, but when processing biomacromolecule solutions, serious membrane fouling is prone to occur, resulting in decreased membrane flux and reduced separation performance. This membrane fouling phenomenon is particularly obvious during use, and the anti-fouling performance is insufficient, requiring frequent cleaning or replacement, which not only increases operating costs, but also creates an additional burden on the environment.

[0004] At present, in order to improve the anti-pollution performance of ultrafiltration membranes, the methods used mainly include surface modification and material innovation. Among them, surface modification technologies such as surface coating and chemical grafting improve the anti-pollution ability of the membrane by changing the chemical composition and physical structure of the membrane surface. Representative ones include: Chinese patent CN201610271953.0 discloses a modified ultrafiltration membrane and a preparation method thereof. The preparation method of the modified ultrafiltration membrane of the invention includes: preparing a polyvinylidene fluoride ultrafiltration membrane, and then immersing the polyvinylidene fluoride ultrafiltration membrane in a nanofiber boehmite solution to obtain a modified ultrafiltration membrane. Through the above-mentioned method, a modified PVDF ultrafiltration membrane with strong hydrophilicity, high membrane flux and strong anti-pollution ability can be obtained. The ultrafiltration membrane prepared by this method connects γ-AlOOH and PVDF ultrafiltration membrane base membrane through the action of biological glue. The γ-AlOOH surface modified PVDF ultrafiltration membrane has a high cost. This patent uses hydrolyzed polyacrylonitrile as the base membrane material. The membrane material is cheap and easy, and the membrane preparation process is simple to operate, and the membrane can be formed in one step. In addition, by introducing GO, the anti-fouling performance of the membrane is significantly improved, the cleaning frequency and maintenance cost of the membrane are reduced, and the two-dimensional nanomaterial graphene oxide rich in carboxyl and hydroxyl groups is introduced to synergize with the base membrane material to improve the anti-fouling performance of the ultrafiltration membrane. Chinese patent CN202410535222.7 prepared a triblock copolymer with an ABA structure, in which segment A is polyamide and segment B is a polysulfone segment. After the block copolymer is configured into a casting liquid, a porous ultrafiltration membrane is prepared by a phase inversion method. The preparation process of the block copolymer is complicated and the material cost is high. The polyacrylonitrile hydrolysis modified ultrafiltration membrane and the preparation method thereof that are resistant to protein pollution proposed by the present invention have a low cost for membrane preparation, and at the same time, because the ultrafiltration membrane has high anti-fouling performance, the operating cost is reduced. This patent aims to obtain a high-performance ultrafiltration membrane by selecting specific membrane materials and preparation techniques, and significantly improve the anti-fouling performance of the membrane. Summary of the invention

[0005] In order to solve the problem that ultrafiltration membranes are easily contaminated during operation, the present invention prepares a polyacrylonitrile hydrolysis modified ultrafiltration membrane that is resistant to protein contamination. First, polyacrylonitrile is hydrolyzed in an alkaline solution to prepare hydrolyzed polyacrylonitrile (H-PAN), which is then used to prepare a casting solution, and GO is introduced into the casting solution to improve the anti-pollution performance of the H-PAN ultrafiltration membrane. GO is a two-dimensional nanomaterial composed of a single-layer graphene layer and oxygen-containing functional groups, with a high specific surface area, excellent mechanical strength and chemical stability. The introduction of GO can effectively improve the separation performance of the H-PAN ultrafiltration membrane, and can also improve the membrane's anti-protein contamination performance.

[0006] A polyacrylonitrile hydrolysis modified ultrafiltration membrane resistant to protein pollution is prepared by mixing hydrolyzed polyacrylonitrile (H-PAN) and graphene oxide (GO), wherein the content of GO is 0.005-0.04wt% of the weight of the casting solution.

[0007] A method for preparing a polyacrylonitrile hydrolysis-modified ultrafiltration membrane resistant to protein pollution comprises the following steps:

[0008] a. dissolving H-PAN in DMF to obtain a polymer solution;

[0009] b. ultrasonically dispersing GO in DMF to form a GO dispersion;

[0010] c. Mix the H-PAN solution with the GO dispersion and form a transparent and uniform polymer solution containing GO through mechanical stirring. The solution is degassed and aged to obtain a casting solution; the above steps a, b, and c are the preparation process of the casting solution.

[0011] d. After the casting solution was centrifuged and degassed in a high-speed centrifuge, the primary membrane was obtained by scraping the membrane and then an ultrafiltration membrane was prepared in deionized water by a non-solvent induced phase inversion method;

[0012] e. Take the ultrafiltration membrane out of the coagulation bath and place it in 50°C hot water to fully wash away the residual organic solvent.

[0013] Furthermore, the support is a sheet-like two-dimensional porous material, preferably a polyester non-woven fabric.

[0014] Furthermore, the preparation method is characterized in that the time of ultrasonic dispersion of GO is at least 0.5 hours to ensure that GO is evenly dispersed in the casting solution.

[0015] Furthermore, in order to prevent the gas in the casting liquid from affecting the ultrafiltration membrane, the casting liquid in step d needs to be poured onto the surface of the support after removing the bubbles, and the film needs to be scraped to ensure the uniformity of the ultrafiltration membrane.

[0016] Furthermore, the non-solvent induced phase inversion method in step d includes scraping the film on the support - phase inversion in the coagulation bath - immersing the film in water - finished film.

[0017] Furthermore, in the non-solvent induced phase inversion method in step d, the film is scraped with a scraper, and the blade gap of the scraper is 150 μm.

[0018] Furthermore, the scraping environment temperature is room temperature 30±5°C, and the coagulation bath temperature is 30±2°C.

[0019] The present invention adds GO to the solvent DMF for ultrasonic treatment to ensure the uniform dispersion of GO in the casting solution. Adding GO to the casting solution can increase the porosity of the ultrafiltration membrane, thereby increasing the flux of the ultrafiltration membrane. In terms of performance evaluation, this study used bovine serum albumin as a model substance to measure the pure water flux, retention rate and anti-pollution performance of the prepared ultrafiltration membrane. The experimental results show that compared with the original H-PAN membrane, after adding GO, the prepared ultrafiltration membrane shows better anti-pollution performance while maintaining a higher protein retention rate.

[0020] Advantages of the present invention: using hydrolyzed polyacrylonitrile as the base membrane material, introducing two-dimensional nanomaterial graphene oxide rich in carboxyl and hydroxyl groups, and synergizing with the base membrane material to improve the anti-pollution performance of the ultrafiltration membrane. The core of the present invention is to cleverly combine hydrolyzed polyacrylonitrile H-PAN with graphene oxide GO to form a new type of H-PAN / GO mixed matrix ultrafiltration membrane. As a two-dimensional flaky material, graphene oxide tends to be horizontally distributed on the membrane surface and in the membrane body material during the preparation of the primary membrane due to the shearing effect of the scraper moving forward, forming a unique membrane structure. This structure not only enhances the mechanical strength of the membrane, but also significantly improves the anti-pollution performance of the membrane.

[0021] In addition, the surface of the ultrafiltration membrane exhibits a water contact angle of about 40 degrees, which indicates its excellent hydrophilicity. The hydrogen bonding between the surface of the ultrafiltration membrane and water molecules promotes a stable hydration layer, effectively preventing direct contact between protein molecules and the membrane surface, thereby further improving the membrane's anti-fouling ability.

[0022] What is even more striking is that after introducing GO rich in carboxyl and hydroxyl groups into the base membrane material, the surface of the H-PAN / GO mixed matrix ultrafiltration membrane has a negative charge. This characteristic increases the electrostatic repulsion between the ultrafiltration membrane and negatively charged pollutants, further enhances the anti-pollution ability of the ultrafiltration membrane, and ensures its stability in long-term operation.

[0023] The ultrafiltration membrane of the present invention is not only innovative in its preparation method, but also has achieved significant improvements in performance, especially in resistance to protein pollution. It is expected to play an important role in water treatment, biopharmaceuticals, food processing and other fields, and contribute to the sustainable utilization of global water resources and environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for describing the embodiments are briefly introduced below.

[0025] Figure 1 This is a scanning electron microscope photograph of the cross-sectional structure of the ultrafiltration membrane of the present invention;

[0026] Figure 2 This is a dynamic anti-protein pollution experiment of the ultrafiltration membrane of the present invention;

[0027] Figure 3 It is the anti-pollution index of the ultrafiltration membrane of the present invention. DETAILED DESCRIPTION

[0028] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments:

[0029] In order to further understand the present invention, the preparation method and application of the ultrafiltration membrane provided by the present invention are described in detail below in conjunction with the embodiments. The protection scope of the present invention is not limited by the following embodiments.

[0030] The embodiment of the present invention discloses a method for preparing an ultrafiltration membrane, comprising the following steps:

[0031] a. dissolving H-PAN in DMF to obtain a polymer solution;

[0032] b. ultrasonically dispersing GO in DMF to form a GO dispersion;

[0033] c. Mixing the H-PAN solution with the GO dispersion and forming a transparent and uniform casting solution containing GO by mechanical stirring;

[0034] d. After the casting solution was centrifuged and degassed in a high-speed centrifuge, the primary membrane was obtained by scraping the membrane and then an ultrafiltration membrane was prepared in deionized water by a non-solvent induced phase inversion method;

[0035] According to the present invention, for the preparation of ultrafiltration membrane, hydrolyzed polyacrylonitrile (H-PAN) is first selected as the base membrane material, graphene oxide (GO) is introduced into the base membrane material to prepare a polymer solution, the solution is used as a casting solution, and it is dissolved in deionized water as a coagulation bath, and the ultrafiltration membrane is prepared by a non-solvent induced phase inversion method. More specifically:

[0036] The base film material H-PAN is fully dissolved in DMF, and GO is ultrasonically dispersed in DMF; then the two are mixed in a certain proportion to obtain an H-PAN / GO mixed solution; the mixed solution is stirred and fully mixed to obtain a transparent and uniform polymer solution containing GO; then the polymer solution is centrifuged at high speed to remove bubbles, thereby obtaining a polymer casting solution. In the embodiment, the solid content of the polymer solution is 15wt%.

[0037] After obtaining the polymer solution, in order to avoid the gas in the polymer solution affecting the ultrafiltration membrane, the present invention removes the bubbles from the polymer solution and then pours it onto the surface of the support, and performs film scraping to ensure the uniformity of the ultrafiltration membrane. The film scraping can be performed according to the technical means familiar to those skilled in the art, and there is no special limitation in this application; for example, the film scraping is performed by a scraper in this application, and the blade gap of the scraper is 150 μm. The preferred film scraping environment temperature of this application is room temperature 30±5°C, and the coagulation bath temperature is 30±2°C; after scraping, the primary membrane is obtained, and the primary membrane is immediately immersed in the coagulation bath solution for phase inversion, that is, the ultrafiltration membrane is obtained. The placement time in the above coagulation bath solution is 20 to 30 minutes. The coagulation bath aqueous solution is preferably deionized water. In order to remove the organic solvent in the membrane obtained after the phase inversion in the coagulation bath, this application preferably takes the membrane out of the coagulation bath and puts it into 50°C hot water to fully wash away the residual organic solvent. The preparation process of the ultrafiltration membrane specifically includes: polymer solution (preparation of casting solution) - scraping membrane on support - phase conversion in coagulation bath - immersion of membrane in water - finished membrane. The support described in the present application is a support well known to those skilled in the art, but for ultrafiltration membrane, polyester non-woven fabric is preferably used in the present application embodiment.

[0038] In order to further understand the present invention, the preparation method and application of the ultrafiltration membrane provided by the present invention are described in detail below in conjunction with the embodiments. The protection scope of the present invention is not limited by the following embodiments.

[0039] Example 1

[0040] H-PAN is used as the base film material, dissolved in N,N-dimethylformamide (DMF), and GO is ultrasonically dispersed in DMF, the two are mixed in a certain proportion and mechanically stirred to obtain a uniform and transparent polymer solution, and the polymer solution is centrifuged and matured to obtain a casting solution. In this embodiment, the GO content is 0.005wt%, and the solid content of the polymer is 15wt%; the casting solution is poured on a non-woven fabric at an ambient temperature of 30±5℃, and the film is scraped with a scraper with a knife gap of 150μm; after the solvent evaporates for 5s, the primary film is immediately placed in a coagulation bath aqueous solution for 20min; the film is taken out of the coagulation bath and placed in 50℃ hot water to fully wash away the residual organic solvent. Figure 1 (b) is a cross-sectional structural picture of the ultrafiltration membrane prepared in this example.

[0041] Testing of ultrafiltration membrane performance: Cut the membrane into a circular shape and install it in an area with an effective test area of ​​3.14 cm 2 The test temperature is 25℃ and the operating test pressure is 0.1MPa. The membrane needs to be pre-pressed at the above pressure for 2h before the formal test. The performance of pure water flux and protein retention rate is mainly examined.

[0042] Protein solution flux: The permeation flux (Flux, F) of the protein solution through the membrane can be measured by calculating the volume of water that passes through the effective area of ​​the ultrafiltration membrane per unit time. Its unit is L·m -2 ·h -1 , the formula is as follows:

[0043]

[0044] Where V is the volume of water passing through the effective area of ​​the membrane per unit time, A is the effective area of ​​the membrane, and t is time.

[0045] Protein retention rate: Under the operating pressure of 0.1MPa, the concentration of bovine serum albumin is 1000mg·L -1 The protein retention of the ultrafiltration membrane was tested and the rejection rate (Rejection, R) was calculated by the following formula:

[0046]

[0047] Among them C p and C f are the protein concentrations in the permeate and the mother liquor, respectively. The retention rate value is the average value of three sets of parallel experiments.

[0048] The anti-fouling performance of the ultrafiltration membrane is determined by the dynamic filtration experiment of the membrane on proteins. The test process is as follows: prepare 10mmol L -1 , pH = 7.4 phosphate buffer solution, and then add bovine serum albumin to dissolve to obtain 1000 mg·L -1 The pure water flux of the membrane is denoted as J w,1 , calculated by formula (1); the membrane filtered the protein solution at 0.1 MPa for 1 h, and its permeation flux was recorded as J p ; Then wash with deionized water for 0.5h, and measure the pure water flux of the membrane after washing, which is recorded as J w,2 Repeat this process, measure the pure water flux of the membrane and the permeation flux of the protein solution, and then calculate the dynamic anti-fouling index of the membrane. The flux recovery rate (FRR) and the total fouling index (R t ) are calculated by formula (3) and (4) respectively. The value is measured every 10 minutes, the flux is measured 6 times in one hour, and the average value of the 6 fluxes is taken to calculate the FRR and anti-pollution index. t The reversible pollution index (R r ) and irreversible pollution index (R ir ) are determined by formulas (5) and (6) respectively. The results are shown in Table 1.

[0049]

[0050] Example 2

[0051] An ultrafiltration membrane was prepared according to the method of Example 1, except that the GO content in the casting solution was 0.01 wt%. Figure 1 (c) is a cross-sectional structural picture of the ultrafiltration membrane prepared in this example. The water flux recovery rate FRR and anti-pollution index of the ultrafiltration membrane were measured, and the results are shown in Table 1.

[0052] Example 3

[0053] An ultrafiltration membrane was prepared according to the method of Example 1, except that the GO content in the casting solution was 0.015 wt%. Figure 1 (d) is a cross-sectional structural picture of the ultrafiltration membrane prepared in this example. The water flux recovery rate FRR and anti-pollution index of the ultrafiltration membrane were measured, and the results are shown in Table 1.

[0054] Example 4

[0055] An ultrafiltration membrane was prepared according to the method of Example 1, except that the GO content in the casting solution was 0.02 wt%. Figure 1 (e) is a cross-sectional structural picture of the ultrafiltration membrane prepared in this example. The water flux recovery rate FRR and anti-pollution index of the ultrafiltration membrane were measured, and the results are shown in Table 1.

[0056] Example 5

[0057] An ultrafiltration membrane was prepared according to the method of Example 1, except that the GO content in the casting solution was 0.03 wt%. Figure 1 (f) is a cross-sectional structural picture of the ultrafiltration membrane prepared in this example. The water flux recovery rate FRR and anti-pollution index of the ultrafiltration membrane were measured, and the results are shown in Table 1.

[0058] Example 6

[0059] An ultrafiltration membrane was prepared according to the method of Example 1, except that the GO content in the casting solution was 0.04 wt%. Figure 1 (g) is a cross-sectional structural picture of the ultrafiltration membrane prepared in this example. The water flux recovery rate FRR and anti-pollution index of the ultrafiltration membrane were measured, and the results are shown in Table 1.

[0060] Comparative Example 1

[0061] An ultrafiltration membrane was prepared according to the method of Example 1, except that the casting solution did not contain GO. Figure 1 (a) is a cross-sectional structural picture of the ultrafiltration membrane prepared in this example. The water flux recovery rate FRR and anti-pollution index of the ultrafiltration membrane were measured, and the results are shown in Table 1: Performance comparison data table of ultrafiltration membranes of this application.

[0062] The anti-fouling index of the ultrafiltration membrane is shown in Table 1. S1 to S6 represent Examples 1 to 6, and D1 represents Comparative Example 1.

[0063] Table 1 Anti-pollution index of ultrafiltration membrane

[0064]

[0065] Dynamic anti-protein fouling experiment of ultrafiltration membrane Figure 2 As shown, the water flux recovery rate FRR of the ultrafiltration membrane and the total pollution index R t , reversible pollution index R r and irreversible pollution index R ir like Figure 3 shown.

[0066] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one 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 present invention. Therefore, the present invention will not be limited to the embodiments shown in the text, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A polyacrylonitrile hydrolysis-modified ultrafiltration membrane resistant to protein contamination, It is characterized in that The ultrafiltration membrane is prepared by mixing hydrolyzed polyacrylonitrile H-PAN and graphene oxide GO, and the content of the graphene oxide GO is 0.005-0.04wt% of the weight of the casting solution.

2. The polyacrylonitrile hydrolysis-modified ultrafiltration membrane resistant to protein pollution according to claim 1, It is characterized in that The pore size of the ultrafiltration membrane is in the range of 2-10 nm.

3. A method for preparing a polyacrylonitrile hydrolysis-modified ultrafiltration membrane resistant to protein contamination, It is characterized in that The following steps are involved: a. dissolving H-PAN in DMF to obtain a polymer solution; b. ultrasonically dispersing GO in DMF to form a GO dispersion; c. Mix the H-PAN solution with the GO dispersion and form a transparent and uniform polymer solution containing GO through mechanical stirring. The solution is degassed and aged to obtain a casting solution; d. After the casting solution was centrifuged and degassed in a high-speed centrifuge, the primary membrane was obtained by scraping the membrane and then an ultrafiltration membrane was prepared in deionized water by a non-solvent induced phase inversion method; e. Take the ultrafiltration membrane out of the coagulation bath and place it in 50°C hot water to fully wash away the residual organic solvent.

4. The method for preparing a polyacrylonitrile hydrolysis-modified ultrafiltration membrane resistant to protein pollution according to claim 3, It is characterized in that The support is polyester non-woven fabric.

5. The method for preparing a polyacrylonitrile hydrolysis-modified ultrafiltration membrane resistant to protein pollution according to claim 3, It is characterized in that In step b, the time for ultrasonic dispersion of GO is at least 0.5 hours.

6. The method for preparing a polyacrylonitrile hydrolysis-modified ultrafiltration membrane resistant to protein pollution according to claim 3, It is characterized in that The non-solvent induced phase inversion method in step d comprises scraping the film on the support - phase inversion in the coagulation bath - immersing the film in water - finished film.

7. The method for preparing a polyacrylonitrile hydrolysis-modified ultrafiltration membrane resistant to protein pollution according to claim 6, It is characterized in that In the non-solvent induced phase inversion method in step d, the film is scraped with a scraper, and the blade gap of the scraper is 150 μm.

8. The method for preparing a polyacrylonitrile hydrolysis-modified ultrafiltration membrane resistant to protein pollution according to claim 6, It is characterized in that The scraping environment temperature is room temperature 30±5℃, and the coagulation bath temperature is 30±2℃.

Images