Modified nanofiltration membrane with antifouling coating and method for preparing the same

Abstract

The application discloses a modified nanofiltration membrane with an antifouling coating and a preparation method thereof, and belongs to the field of water treatment nanofiltration membranes. The modified nanofiltration membrane with the antifouling coating is prepared by adopting poly-sulfobetaine methacrylate coupling bovine serum albumin to construct the antifouling coating on the surface of the nanofiltration membrane. The reduced bovine serum albumin is used as an anchoring layer, has good viscosity and can be stably anchored on the surface of the nanofiltration membrane. The poly-sulfobetaine methacrylate is used as a functional layer and can improve the hydrophilicity of the nanofiltration membrane, thereby enhancing the antifouling capacity of the nanofiltration membrane. The antifouling coating constructed by the application has good antifouling capacity, high viscosity, is not easy to fall off and can be repeatedly cleaned and used.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of nanofiltration membranes for water treatment, and particularly relates to a modified nanofiltration membrane with an antifouling coating and a preparation method thereof. BACKGROUND

[0002] With the development of industry and the improvement of people's living standards, the amount of domestic water and industrial wastewater discharge continues to grow, and the demand for water treatment effect and efficiency is increasingly high. Nanofiltration membranes are widely used in the fields of drinking water purification and industrial wastewater treatment due to their high rejection capability for divalent ions and organic matter and low energy consumption characteristics. However, organic matter (such as humic acid and protein) in water, colloidal particles and microorganisms are easily adsorbed on the membrane surface to form a pollution layer, resulting in a decrease in membrane permeability and separation efficiency, and frequent chemical cleaning, which shortens the service life of the membrane and increases the operating cost. Therefore, some nanofiltration membranes for water treatment have appeared on the market, such as the modified nanofiltration membranes disclosed in Patent Nos. CN117509827A and CN118304759A. However, the modified nanofiltration membranes are chemically reacted with the nanofiltration membranes themselves, which changes the properties of the membranes and reduces the surface modification rate. Moreover, the reaction is limited by the material of the nanofiltration membranes, which lacks universality. SUMMARY

[0003] The technical problem to be solved by the present application is to overcome the shortcomings of the prior art and provide a modified nanofiltration membrane with an antifouling coating that can overcome the above problems or at least partially solve the above problems.

[0004] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0005] The modified nanofiltration membrane with an antifouling coating is prepared by anchoring an antifouling coating on the surface of a nanofiltration membrane. The antifouling coating is constructed by poly-sulfobetaine methacrylate coupled bovine serum albumin (BSA@pSBMA). The poly-sulfobetaine methacrylate coupled bovine serum albumin is prepared from reduced bovine serum albumin (re-BSA), which is prepared from bovine serum albumin (BSA). In the antifouling coating anchored on the surface of the nanofiltration membrane, the reduced bovine serum albumin serves as an anchor layer and is anchored on the surface of the nanofiltration membrane. The poly-sulfobetaine methacrylate coupled with the reduced bovine serum albumin can improve the hydrophilicity of the nanofiltration membrane and enhance the antifouling ability of the nanofiltration membrane.

[0006] Further, the antifouling coating is prepared by immersing the nanofiltration membrane in a mixed solution of poly-sulfobetaine methacrylate coupled bovine serum albumin, tris-hydroxymethyl aminomethane hydrochloride and ethylenediaminetetraacetic acid, and then drying.

[0007] Further, the poly-sulfobetaine methacrylate conjugated bovine serum albumin is generated by thiol-ene click chemistry reaction between reduced bovine serum albumin and sulfobetaine methacrylate.

[0008] Further, the reduced bovine serum albumin is generated by reacting bovine serum albumin with sodium borohydride (chemical formula: NaBH4) solution.

[0009] Further, a method for preparing a modified nanofiltration membrane with an antifouling coating, comprising:

[0010] Step one: mixing and stirring 7-9 mg / mL bovine serum albumin solution with 80-120 mM sodium borohydride solution to obtain reduced bovine serum albumin;

[0011] Step two: using ultraviolet crosslinking agent to initiate thiol-ene click chemistry reaction between reduced bovine serum albumin and 350-450 mM sulfobetaine methacrylate, irradiating under 25-35 W purple light for 25-35 min, and then stirring at room temperature to generate poly-sulfobetaine methacrylate conjugated bovine serum albumin;

[0012] Step three: adding 40-60 mM tris-hydroxymethyl aminomethane hydrochloride and 0.5-2 mM ethylenediaminetetraacetic acid to the synthesized poly-sulfobetaine methacrylate conjugated bovine serum albumin solution, and adjusting the pH of the mixed solution with hydrochloric acid;

[0013] Step four: placing the nanofiltration membrane into the mixed solution in step three, immersing for 1-2 h, taking out, immersing in deionized water for 0.5-2 min, and then placing the nanofiltration membrane in an oven at 55-65°C for drying for 11-13 h to obtain the modified nanofiltration membrane with an antifouling coating.

[0014] Preferably, the stirring time in step one is 25-35 min.

[0015] Preferably, the stirring time in step two is 29-31 h.

[0016] Preferably, the pH of the adjusted mixed solution in step three is 4-6.

[0017] Further, the antifouling coating can also be formed by amphoteric grafting coupling of any one of the amphoteric monomers [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl) ammonium hydroxide, 3-methacryloyl sulfopropyl potassium salt, N-acryloyl-L-glutamic acid, and carboxybetaine methacrylate with reduced bovine serum albumin.

[0018] Furthermore, the nanofiltration membrane in the modified nanofiltration membrane with the antifouling coating can be replaced with a microfiltration membrane or an ultrafiltration membrane.

[0019] By adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art:

[0020] 1. This invention improves the hydrophilicity of the nanofiltration membrane surface by constructing an antifouling coating on the membrane surface, thereby enhancing the membrane surface's antifouling ability; at the same time, the modification process is simple, mature, and easy to promote.

[0021] 2. The present invention utilizes the anchoring effect of bovine serum albumin to construct an antifouling coating with a high density of zwitterionic polymers on the surface, good adhesion, and resistance to peeling. The antifouling ability is long-lasting and will not be affected by the reduction in water flow after cleaning.

[0022] 3. The present invention constructs an antifouling coating on the surface of a nanofiltration membrane without changing the chemical properties of the nanofiltration membrane itself, and has high modification efficiency; it is also not limited by the properties of the nanofiltration membrane itself, has good versatility, and can be applied to a variety of membrane surfaces. Attached Figure Description

[0023] Figure 1 The images show physical examples of a modified nanofiltration membrane with an antifouling coating proposed in this invention, specifically Example 1, and a comparative example corresponding to Example 1.

[0024] Figure 2 The images show magnified micrographs of the membrane surfaces of Example 1 (left) and the comparative example (right) corresponding to Example 1, which are modified nanofiltration membranes with antifouling coatings proposed in this invention.

[0025] Figure 3 Fluorescence images of pollutant distribution before (left), after (middle), and after (right) cleaning, corresponding to Example 1, for a modified nanofiltration membrane with an antifouling coating proposed in this invention.

[0026] Figure 4 Fluorescence images of pollutant distribution before (left), after (middle), and after (right) contamination in Example 1 of a modified nanofiltration membrane with an antifouling coating proposed in this invention;

[0027] Figure 5 The graph shows the changes in total fluorescence intensity before, after, and after cleaning of Example 1 of the modified nanofiltration membrane with an antifouling coating proposed in this invention, and the corresponding comparative example.

[0028] Figure 6 The graph shows the normalized flux variation of pure water in an organic-inorganic mixed pollution environment for Example 1 of the modified nanofiltration membrane with antifouling coating proposed in this invention and the corresponding comparative example.

[0029] Figure 7 The graph shows the normalized flux variation of pure water in an inorganic pollution environment for Example 1 of the modified nanofiltration membrane with antifouling coating proposed in this invention and the corresponding comparative example in Example 1.

[0030] Figure 8 The graph shows the normalized flux variation of pure water for Example 1 of the modified nanofiltration membrane with antifouling coating proposed in this invention and the corresponding comparative examples of polysaccharide solution (left) and protein solution (right).

[0031] Figure 9 The graph shows the changes in pure water flux before (left) and after (right) cleaning of Example 1 of the modified nanofiltration membrane with antifouling coating proposed in this invention, and a comparative example corresponding to Example 1. Detailed Implementation

[0032] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0033] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0034] Example 1:

[0035] A method for preparing a modified nanofiltration membrane with an antifouling coating, comprising:

[0036] Step 1: Mix and stir an 8 mg / mL bovine serum albumin solution with a 100 mM sodium borohydride solution to obtain reduced bovine serum albumin;

[0037] Step 2: Use a UV crosslinking agent to initiate a thiol-olefin click chemical reaction between reduced bovine serum albumin and 400mM sulfobetaine methacrylate. After irradiation under a 30W UV lamp for 30 minutes, stir at room temperature to generate polysulfobetaine methacrylate coupled with bovine serum albumin.

[0038] Step 3: Add 50 mM tris(hydroxymethyl)aminomethane hydrochloride and 1 mM ethylenediaminetetraacetic acid to the synthesized polysulfobetaine methacrylate coupled bovine serum albumin solution, and adjust the pH of the mixed solution with hydrochloric acid.

[0039] Step 4: Immerse the nanofiltration membrane in the mixed solution from Step 3 for 1.5 hours, then remove it, soak it in deionized water for 1 minute, and finally dry the nanofiltration membrane in an oven at 60°C for 12 hours to obtain the sample.

[0040] Example 2:

[0041] A method for preparing a modified nanofiltration membrane with an antifouling coating, comprising:

[0042] Step 1: Mix and stir a 7 mg / mL bovine serum albumin solution with an 80 mM sodium borohydride solution to obtain reduced bovine serum albumin;

[0043] Step 2: Use a UV crosslinking agent to initiate a thiol-olefin click chemical reaction between reduced bovine serum albumin and 350mM sulfobetaine methacrylate. After irradiation under a 25W UV lamp for 25 minutes, stir at room temperature to generate polysulfobetaine methacrylate coupled with bovine serum albumin.

[0044] Step 3: Add 40 mM tris(hydroxymethyl)aminomethane hydrochloride and 0.5 mM ethylenediaminetetraacetic acid to the synthesized polysulfobetaine methacrylate coupled bovine serum albumin solution, and adjust the pH of the mixed solution with hydrochloric acid;

[0045] Step 4: Immerse the nanofiltration membrane in the mixed solution from Step 3 for 1 hour, then remove it, soak it in deionized water for 0.5 minutes, and finally dry the nanofiltration membrane in an oven at 55°C for 11 hours to obtain the sample.

[0046] Example 3:

[0047] A method for preparing a modified nanofiltration membrane with an antifouling coating, comprising:

[0048] Step 1: Mix and stir a 9 mg / mL bovine serum albumin solution with a 120 mM sodium borohydride solution to obtain reduced bovine serum albumin;

[0049] Step 2: Use a UV crosslinking agent to initiate a thiol-olefin click chemical reaction between reduced bovine serum albumin and 450mM sulfobetaine methacrylate. After irradiation under a 35W UV lamp for 35 minutes, stir at room temperature to generate polysulfobetaine methacrylate coupled with bovine serum albumin.

[0050] Step 3: Add 60 mM tris(hydroxymethyl)aminomethane hydrochloride and 2 mM ethylenediaminetetraacetic acid to the synthesized polysulfobetaine methacrylate coupled bovine serum albumin solution, and adjust the pH of the mixed solution with hydrochloric acid.

[0051] Step 4: Immerse the nanofiltration membrane in the mixed solution from Step 3 for 2 hours, then remove it, soak it in deionized water for 2 minutes, and then dry the nanofiltration membrane in an oven at 65°C for 13 hours to obtain the sample.

[0052] Comparative examples corresponding to Example 1:

[0053] The comparative example corresponding to Example 1 is an unmodified GC-NF3001 polyamide nanofiltration membrane produced by Guochu Technology.

[0054] The following performance tests were conducted on the membrane products prepared in Example 1 and the comparative examples corresponding to Example 1:

[0055] I. Pollutant Fluorescence Measurement

[0056] The samples prepared in Example 1 and the corresponding comparative examples were subjected to pollutant fluorescence measurement before, after, and after cleaning.

[0057] II. Determination of Normalized Flux in Polluted Environments

[0058] Under a test pressure of 0.5 MPa, samples were permeated with organic-inorganic mixed contaminants, inorganic contaminants, sodium alginate solution, and protein solution, respectively. The time t for pure water to permeate the sample and the volume V of pure water passing through the membrane during the time t were recorded. Let A be the effective area for pure water to permeate the sample, and J0 be the initial flux of the sample. The pure water flux of the membrane was calculated using J = V / A / t, and then calculated using Φ... n =J / J0 calculates the normalized flux of the membrane for pure water.

[0059] III. Measurement of water flux before and after cleaning

[0060] The water flux of the sample was measured under a test pressure of 0.5 MPa. After the measurement was completed, the sample was cleaned and then the pure water flux of the cleaned sample was measured.

[0061] For the measurements I, II, and III, the comparative example corresponding to Example 1 is an unmodified nanofiltration membrane, which is a GC-NF3001 polyamide nanofiltration membrane produced by Guochu Technology; Example 1 is a modified nanofiltration membrane with an antifouling coating as described in this invention.

[0062] Figure 3 The images show the fluorescence distribution of contaminants before (left), after (middle), and after (right) cleaning, corresponding to Example 1. Figure 4 The images show the fluorescence distribution of pollutants before (left), after (middle), and after (right) contamination in Example 1. By comparison, it can be seen that in the comparison of the area of ​​the fluorescent region after contamination and after cleaning, Example 1 is smaller than the corresponding comparative example of Example 1.

[0063] Figure 5 This is a graph showing the changes in total fluorescence intensity before, after, and after cleaning of Example 1 and its corresponding comparative examples. The vertical axis represents total fluorescence intensity, and the horizontal axis represents different measurement groups, namely the comparative example group and the Example 1 group, respectively. Figure 5 It can be seen that the total fluorescence intensity of the comparative example corresponding to Example 1 and before contamination in Example 1 is close to 0. The relationship between the total fluorescence intensity after contamination and after cleaning is: Example 1 < Comparative example corresponding to Example 1;

[0064] Figure 6 This is a graph showing the normalized flux variation of pure water in Example 1 and the corresponding comparative example under an organic-inorganic mixed pollution environment. The vertical axis represents the normalized flux of pure water, and the horizontal axis represents the time it takes for pure water to permeate the sample. Figure 6 It can be seen that in organic-inorganic mixed pollution, the normalized flux relationship of pure water is: Example 1 > Comparative example corresponding to Example 1;

[0065] Figure 7 This is a graph showing the normalized flux variation of pure water in Example 1 and the corresponding comparative example under an inorganic pollution environment. The vertical axis represents the normalized flux of pure water, and the horizontal axis represents the time it takes for pure water to permeate the sample. Figure 7 It can be seen that, in inorganic pollution, the normalized flux relationship of pure water is: Example 1 > Comparative example corresponding to Example 1;

[0066] Figure 8 This is a graph showing the normalized flux variation of pure water for Example 1 and the corresponding comparative examples, polysaccharide solution (left) and protein solution (right). The vertical axis represents the normalized flux of pure water, and the horizontal axis represents the time it takes for pure water to permeate the sample. Figure 8 It can be seen that the normalized flux relationship of pure water for sodium alginate solution and protein solution is: Example 1 > Comparative example corresponding to Example 1;

[0067] Figure 9 This is a graph showing the changes in pure water flux before (left) and after (right) cleaning for Example 1 and its corresponding comparative example. The vertical axis represents the normalized pure water flux, and the horizontal axis represents the different measurement groups, namely the comparative example group and the Example 1 group, respectively. Figure 9 It can be seen that the water flux after cleaning in Example 1 is almost equal to that before cleaning, while the pure water flux after cleaning in the comparative example corresponding to Example 1 is less than that before cleaning.

[0068] According to the test results of Example 1, compared with the comparative example corresponding to Example 1, the present invention can enhance the hydrophilicity and antifouling ability of the nanofiltration membrane by constructing an antifouling coating on the surface of the nanofiltration membrane; at the same time, the constructed antifouling coating has high adhesion, is not easy to fall off during cleaning, and has good stability.

[0069] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A modified nanofiltration membrane with an antifouling coating, prepared by anchoring an antifouling coating onto the surface of a nanofiltration membrane, characterized in that, The antifouling coating can be formed by amphoteric graft coupling of any one of the following: [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfonylpropyl)ammonium hydroxide, potassium sulfonyl propyl 3-methacrylate, N-acryloyl-L-glutamic acid, and carboxybetaine methacrylate with reduced bovine serum albumin.

2. The modified nanofiltration membrane with an antifouling coating according to claim 1, characterized in that, The antifouling coating is constructed by coupling polysulfobetaine methacrylate with bovine serum albumin (BSAL). The BSAL is prepared from reduced BSAL. In the antifouling coating anchored to the nanofiltration membrane surface, the reduced BSAL serves as an anchoring layer. The BSAL coupled with the reduced BSAL improves the hydrophilicity of the nanofiltration membrane and enhances its antifouling ability.

3. A modified nanofiltration membrane with an antifouling coating according to claim 2, characterized in that, The antifouling coating is prepared by immersing a nanofiltration membrane in a mixed solution of polysulfobetaine methacrylate coupled with bovine serum albumin, tris(hydroxymethyl)aminomethane hydrochloride, and ethylenediaminetetraacetic acid, and then drying it.

4. A modified nanofiltration membrane with an antifouling coating according to claim 3, characterized in that, The polysulfobetaine methacrylate coupled with bovine serum albumin is generated by a thiol-ene click chemical reaction between reduced bovine serum albumin and sulfobetaine methacrylate.

5. A modified nanofiltration membrane with an antifouling coating according to claim 4, characterized in that, The reduced bovine serum albumin is generated by reacting bovine serum albumin with sodium borohydride solution.

6. A modified nanofiltration membrane with an antifouling coating according to claim 5, comprising the following preparation method: Step 1: Mix and stir a 7-9 mg / mL bovine serum albumin solution with an 80-120 mM sodium borohydride solution to obtain reduced bovine serum albumin; Step 2: Use a UV crosslinking agent to initiate a thiol-olefin click chemical reaction between reduced bovine serum albumin and 350-450mM sulfobetaine methacrylate. After irradiation under a 25-35W UV lamp for 25-35 minutes, stir at room temperature to generate polysulfobetaine methacrylate-coupled bovine serum albumin. Step 3: Add 40-60 mM tris(hydroxymethyl)aminomethane hydrochloride and 0.5-2 mM ethylenediaminetetraacetic acid to the synthesized polysulfobetaine methacrylate coupled bovine serum albumin solution, and adjust the pH of the mixed solution with hydrochloric acid. Step 4: Immerse the nanofiltration membrane in the mixed solution from Step 3 for 1-2 hours, then remove it and soak it in deionized water for 0.5-2 minutes. Finally, place the nanofiltration membrane in an oven at 55-65°C and dry it for 11-13 hours to obtain the modified nanofiltration membrane with an antifouling coating.

7. A modified nanofiltration membrane with an antifouling coating according to claim 6, characterized in that, The stirring time in step one is 25-35 minutes.

8. A modified nanofiltration membrane with an antifouling coating according to claim 7, characterized in that, The stirring time in step two is 29-31 hours.

9. A modified nanofiltration membrane with an antifouling coating according to claim 8, characterized in that, In step three, hydrochloric acid is used to adjust the pH of the mixed solution, and the pH of the adjusted mixed solution is 4-6.

10. A modified nanofiltration membrane with an antifouling coating according to claim 1, characterized in that, The nanofiltration membrane in the modified nanofiltration membrane with the antifouling coating can be replaced with a microfiltration membrane or an ultrafiltration membrane.

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