A hydrophilic modified hollow fiber ultrafiltration membrane and its preparation method
By introducing graphene quantum dots as a hydrophilic modifier into hollow fiber ultrafiltration membranes, the problem of poor hydrophilicity of polyvinylidene fluoride ultrafiltration membranes was solved, improving water permeation flux and antifouling performance, and achieving efficient separation effect.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHANDONG JINYU MEMBRANE TECH DEV CO LTD
- Filing Date
- 2024-03-14
- Publication Date
- 2026-08-04
AI Technical Summary
Existing polyvinylidene fluoride ultrafiltration membranes have poor hydrophilicity and easily adsorb pollutants, leading to reduced water permeate flux and severe membrane fouling.
Graphene quantum dots were used as hydrophilic modifiers to prepare amine-based graphene quantum dots by reacting them with polyamine compounds. These amine quantum dots were then mixed with polyvinylidene fluoride (PVDF) as hydrophilic modifiers to prepare a casting solution, which was then coated onto an inner braided tube to prepare a hollow fiber ultrafiltration membrane.
The hydrophilicity and mechanical stability of the hollow fiber ultrafiltration membrane were improved, and the water permeation flux and antifouling ability were enhanced. The water permeation flux was >400.0 L/(m2 h bar), and the bovine serum albumin rejection rate was >90.0%.
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Figure CN117942774B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of water treatment membrane technology in chemical new materials, specifically to a hydrophilic modified hollow fiber ultrafiltration membrane and its preparation method. Background Technology
[0002] Ultrafiltration membranes are separation membranes with sieving capabilities. Generally, the pore size of ultrafiltration membranes is considered to be between 2-50 nanometers. During ultrafiltration separation, substances smaller than the membrane pore size can pass through the ultrafiltration membrane, while substances larger than the pore size are retained. Therefore, ultrafiltration membranes can achieve the sieving and separation of substances of different particle sizes. Ultrafiltration membranes are widely used in water treatment and material separation and concentration. Combined ultrafiltration and reverse osmosis processes are used for the deep purification of surface water to produce industrial pure water; ultrafiltration membrane concentration and separation processes are used for the pre-concentration of natural products and materials in microbial fermentation broths; and ultrafiltration membranes in membrane bioreactors (MBRs) for wastewater treatment can prevent membrane pore clogging, resist membrane fouling, and maintain longer-term stable operation.
[0003] The main forms of ultrafiltration membranes are flat sheet membranes and hollow fiber membranes. Hollow fiber ultrafiltration membrane modules have a higher packing density and are widely used in water treatment and material separation and concentration processes. To improve the strength of hollow fiber ultrafiltration membranes, a braided inner lining is generally used as the support. A casting solution is coated onto the inner lining support, and the ultrafiltration membrane is prepared through a phase inversion method. Hollow fiber ultrafiltration membranes reinforced with braided inner linings have strong tensile strength, solving the problem of fiber breakage in hollow fiber membranes. The main polymer materials for ultrafiltration membranes include polyacrylonitrile, polyvinylidene fluoride (PVDF), polysulfone, and polyethersulfone. PVDF is the most commonly used material due to its better chemical stability and ability to withstand frequent chemical cleaning. However, PVDF ultrafiltration membranes have poor hydrophilicity, easily adsorbing pollutants and resulting in severe membrane fouling. Furthermore, PVDF membranes are prone to compaction, leading to a gradual decrease in water permeate flux. Introducing nanomaterials into the ultrafiltration membrane matrix can improve the water flux and antifouling properties of the ultrafiltration membrane. Therefore, the present invention provides a hydrophilic modified hollow fiber ultrafiltration membrane and its preparation method. Summary of the Invention
[0004] The purpose of this invention is to provide a hydrophilic modified hollow fiber ultrafiltration membrane and its preparation method. The ultrafiltration membrane prepared by this method has good hydrophilicity, good mechanical stability, high water permeation flux, and strong anti-fouling ability.
[0005] To achieve the above objectives, the present invention provides a method for preparing a hydrophilic modified hollow fiber ultrafiltration membrane, comprising the following steps:
[0006] (1) Preparation of graphene quantum dots: Graphene quantum dots were prepared by citric acid pyrolysis;
[0007] (2) Preparation of amino-based graphene quantum dots: Prepare an aqueous solution of graphene quantum dots and add a multi-amino compound to prepare solid amino-based graphene quantum dots;
[0008] (3) Preparation of casting solution: Using amino-based graphene quantum dots as hydrophilic modifiers, polyvinylidene fluoride as the main membrane material, and dimethylacetamide as solvent, the casting solution is prepared by mixing and stirring.
[0009] (4) Preparation of hydrophilic modified hollow fiber ultrafiltration membrane: Using the inner braided tube as the support, the hydrophilic modified hollow fiber ultrafiltration membrane is prepared by spinning coating and phase inversion methods.
[0010] Preferably, in step (1), the pyrolysis temperature is 200℃ and the pyrolysis time is 2h.
[0011] Preferably, in step (2), the polyamine compound is one of diethylenetriamine, triethylenetetramine, or tetraethylenepentamine.
[0012] Preferably, the specific operation of step (2) is as follows: prepare a graphene quantum dot aqueous solution with a mass fraction of 10-20%, add a polyamine compound with a mass fraction of 1-5%, and obtain a mixed aqueous solution. Heat and reflux at 100°C for 5-10 hours, and obtain amino-based graphene quantum dot solids after evaporation to remove water.
[0013] Preferably, in the mixed aqueous solution, the mass ratio of the polyamine compound to the graphene quantum dots is 1:5.
[0014] Preferably, in step (3), the mass fraction of amino-based graphene quantum dots in the casting solution is 0.1-3.0%, and the mass fraction of polyvinylidene fluoride is 16-20%.
[0015] Preferably, the specific operation in step (4) is as follows: using the inner braided tube as a support, after coating the casting solution through the spinning head, the hollow fiber ultrafiltration membrane is prepared by phase inversion in a hydrogel bath; the organic solvent is removed by washing with water, and then soaked in a glycerol aqueous solution to keep it moist, and then dried to obtain a hydrophilic modified hollow fiber ultrafiltration membrane.
[0016] Preferably, the glycerol aqueous solution has a mass fraction of 20-30%.
[0017] Therefore, the present invention provides a hydrophilic modified hollow fiber ultrafiltration membrane and its preparation method, which has the following beneficial effects:
[0018] (1) Graphene quantum dots are zero-dimensional nano-carbon materials with good compatibility with polymers. Graphene quantum dots have abundant carboxyl and epoxy groups, which can react with polyamine compounds to synthesize amine-based graphene quantum dots. In the casting solution, through the interaction between amine groups and fluorine atoms, graphene quantum dots can be stably distributed on the surface and inside of the polyvinylidene fluoride ultrafiltration membrane.
[0019] (2) The graphene quantum dots distributed on the surface improve the hydrophilicity of the hollow fiber ultrafiltration membrane; the graphene quantum dots distributed inside improve the mechanical stability of the hollow fiber ultrafiltration membrane, prevent compaction and compaction during the ultrafiltration membrane separation process, and improve the stability of the ultrafiltration membrane separation process.
[0020] (3) The hydrophilic modified hollow fiber ultrafiltration membrane prepared by this invention has high water permeation flux and strong anti-fouling ability. The water permeation flux of the hydrophilic modified hollow fiber ultrafiltration membrane is >400.0 L / (m²). 2 h bar), bovine serum albumin retention rate >90.0%.
[0021] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description
[0022] Figure 1 This is an electron microscope image of the surface of the hydrophilic modified hollow fiber ultrafiltration membrane prepared in Example 1 of the present invention;
[0023] Figure 2 This is a cross-sectional electron microscope image of the hydrophilic modified hollow fiber ultrafiltration membrane prepared in Example 1 of the present invention. Detailed Implementation
[0024] This invention provides a method for preparing a hydrophilic modified hollow fiber ultrafiltration membrane, comprising the following steps:
[0025] (1) Preparation of graphene quantum dots: Graphene quantum dots were obtained by pyrolysis of citric acid in an oven at 200 degrees for 2 hours.
[0026] (2) Preparation of amino-based graphene quantum dots: Prepare an aqueous solution of graphene quantum dots with a mass fraction of 10-20%, and add a polyamine compound with a mass fraction of 1-5% to obtain a mixed aqueous solution. Heat the solution under reflux at 100°C for 5-10 hours, and then evaporate the water to obtain solid amino-based graphene quantum dots.
[0027] (3) Preparation of casting solution: using amino-based graphene quantum dots as hydrophilic modifiers, polyvinylidene fluoride as the main membrane material, and dimethylacetamide as solvent, the casting solution is prepared by mixing and stirring.
[0028] (4) Preparation of hydrophilic modified hollow fiber ultrafiltration membrane: Using the inner braided tube as the support, the membrane casting solution is coated through the spinning head and then the membrane is prepared by phase inversion in a hydrogel bath. The organic solvent is removed by washing with water, and then the membrane is soaked in glycerol aqueous solution to keep it moist and then dried to obtain the hydrophilic modified hollow fiber ultrafiltration membrane.
[0029] In this invention, the polyamine compound in step (2) is one of diethylenetriamine, triethylenetetramine, or tetraethylenepentamine, preferably triethylenetetramine.
[0030] In this invention, in the mixed aqueous solution of step (2), the mass ratio of polyamine compound to graphene quantum dots is 1:5; preferably, the mass fraction of graphene quantum dots is 15% and the mass fraction of polyamine compound is 3%.
[0031] In this invention, in step (3), the mass fraction of amine-based graphene quantum dots in the casting solution is 0.1-3.0%, and the mass fraction of polyvinylidene fluoride is 16-20%; wherein, the mass fraction of graphene quantum dots is preferably 1% or 2%; and the mass fraction of polyvinylidene fluoride is preferably 18%.
[0032] In this invention, the mass fraction of the glycerol aqueous solution in step (4) is 20-30%.
[0033] The water permeation flux, protein rejection rate, and antifouling performance of the hydrophilic modified hollow fiber ultrafiltration membrane prepared in this invention were tested using a hollow fiber membrane module encapsulated with epoxy resin.
[0034] 1. Calculate the water permeation flux of the hollow fiber ultrafiltration membrane using formula (1):
[0035]
[0036] In equation (1): J is the water flux, L / (m³). 2 h bar); V is the permeate volume, L; A is the membrane surface area, m². 2 Δt is the running time, in hours; P is the operating pressure, in bars.
[0037] 2. Using bovine serum albumin aqueous solution as the raw material, the protein concentration was measured using a UV spectrophotometer. The rejection rate of the ultrafiltration membrane was calculated using formula (2):
[0038]
[0039] In formula (2): R is the bovine serum albumin retention rate, %; C p The protein concentration of the filtrate is in mg / L; C f The concentration of protein in the raw material solution is mg / L.
[0040] 3. Using a 1.0 g / L yeast aqueous solution as the raw material, the antifouling performance of the hollow fiber ultrafiltration membrane was tested. The ultrafiltration membrane was operated at 0.5 bar pressure for 5 hours, and the permeation flux was measured. The flux decay rate of the ultrafiltration membrane was calculated according to formula (3):
[0041]
[0042] In equation (3): FDR is the flux decay rate; J0 is the initial flux of the hollow fiber ultrafiltration membrane, J t This represents the flux after the ultrafiltration membrane has been running for 5 hours. The lower the flux decay rate, the better the antifouling performance of the ultrafiltration membrane.
[0043] The following detailed description of embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.
[0044] Example 1
[0045] This embodiment provides a hydrophilic modified hollow fiber ultrafiltration membrane and its preparation method, the specific steps of which are as follows:
[0046] (1) Citric acid was pyrolyzed in a 200°C oven for 2 hours to obtain graphene quantum dots.
[0047] (2) Prepare a 20% (w / w) aqueous solution of graphene quantum dots, add 5% (w / w) of triethylenetetramine to obtain a mixed aqueous solution, and heat it under reflux at 100°C for 5 hours. Then evaporate the aqueous solution to prepare amino-based graphene quantum dot solids.
[0048] (3) Prepare a dimethylacetamide solution with a mass fraction of 1% for amino-based graphene quantum dots and a mass fraction of 18% for polyvinylidene fluoride. Stir evenly and let stand at 60°C for 5 hours to remove bubbles, and obtain the casting solution.
[0049] (4) Using the inner braided tube as the support, the hollow fiber ultrafiltration membrane is prepared by coating the casting solution through the spinning head and then in the hydrogel bath phase inversion method; the organic solvent is removed by washing with water, and then soaked in 30% glycerol aqueous solution to keep moist and dried to obtain the hydrophilic modified hollow fiber ultrafiltration membrane.
[0050] Depend on Figure 1 and Figure 2 It can be seen that a hydrophilic modified hollow fiber ultrafiltration membrane was prepared by this method.
[0051] The water flux of the hydrophilic modified hollow fiber ultrafiltration membrane prepared in this embodiment was measured to be 480.6 L / (m²) using the above performance testing methods. 2The retention rate of bovine serum albumin was 92.0%, and the flux attenuation rate of yeast ultrafiltration membrane separation was 35.5%.
[0052] Example 2
[0053] The only difference between this embodiment and Example 1 is that diethylenetriamine is used to prepare amino-based graphene quantum dot solids. All other aspects are the same as in Example 1 and will not be repeated here.
[0054] The water flux of the hydrophilic modified hollow fiber ultrafiltration membrane prepared in this embodiment was measured to be 420.2 L / (m²) using the above performance testing methods. 2 The retention rate of bovine serum albumin was 91.1%, and the flux attenuation rate of yeast ultrafiltration membrane separation was 37.4%.
[0055] Example 3
[0056] The only difference between this embodiment and Example 1 is that tetraethylenepentamine is used to prepare amino-based graphene quantum dot solids. All other aspects are the same as in Example 1 and will not be repeated here.
[0057] The water flux of the hydrophilic modified hollow fiber ultrafiltration membrane prepared in this embodiment was measured to be 450.3 L / (m²) using the above performance testing methods. 2 The retention rate of bovine serum albumin was 94.1%, and the flux decay rate of the yeast ultrafiltration membrane separation process was 32.6%.
[0058] Example 4
[0059] The only difference between this embodiment and Example 1 is that a 15% graphene quantum dot aqueous solution is prepared, and 4% triethylenetetramine is added to prepare amino-based graphene quantum dot solids. All other aspects are the same as in Example 1 and will not be repeated here.
[0060] The water flux of the hydrophilic modified hollow fiber ultrafiltration membrane prepared in this embodiment was measured to be 490.2 L / (m²) using the above performance testing methods. 2 The retention rate of bovine serum albumin was 90.1%, and the flux attenuation rate of yeast ultrafiltration membrane separation was 38.8%.
[0061] Example 5
[0062] The only difference between this embodiment and Example 1 is that a 10% graphene quantum dot aqueous solution is prepared, and 3% triethylenetetramine is added to prepare amino-based graphene quantum dot solids. All other aspects are the same as in Example 1 and will not be repeated here.
[0063] The water flux of the hydrophilic modified hollow fiber ultrafiltration membrane prepared in this embodiment was measured to be 432.2 L / (m²) using the above performance testing methods. 2 The retention rate of bovine serum albumin was 94.3%, and the flux attenuation rate of yeast ultrafiltration membrane separation was 34.6%.
[0064] Example 6
[0065] The only difference between this embodiment and Example 1 is that the casting solution is a dimethylacetamide solution with a mass fraction of 1% amino-based graphene quantum dots and a mass fraction of 17% polyvinylidene fluoride. All other aspects are the same as in Example 1 and will not be repeated here.
[0066] The water flux of the hydrophilic modified hollow fiber ultrafiltration membrane prepared in this embodiment was measured to be 542.7 L / (m²) using the above performance testing methods. 2 The retention rate of bovine serum albumin was 91.3%, and the flux attenuation rate of yeast ultrafiltration membrane separation was 29.6%.
[0067] Example 7
[0068] The only difference between this embodiment and Example 1 is that the casting solution is a dimethylacetamide solution with a mass fraction of 1% amino-based graphene quantum dots and a mass fraction of 20% polyvinylidene fluoride. All other aspects are the same as in Example 1 and will not be repeated here.
[0069] The water flux of the hydrophilic modified hollow fiber ultrafiltration membrane prepared in this embodiment was measured to be 332.7 L / (m²) using the above performance testing methods. 2 The retention rate of bovine serum albumin was 94.3%, and the flux attenuation rate of yeast ultrafiltration membrane separation was 32.6%.
[0070] Example 8
[0071] The only difference between this embodiment and Example 1 is that the mass fraction of aminated quantum dots in the casting solution is 2%. All other aspects are the same as in Example 1 and will not be repeated here.
[0072] The water flux of the hydrophilic modified hollow fiber ultrafiltration membrane prepared in this embodiment was measured to be 554.2 L / (m²) using the above performance testing methods. 2 The retention rate of bovine serum albumin was 91.7%, and the flux attenuation rate of yeast ultrafiltration membrane separation was 32.6%.
[0073] Example 9
[0074] The only difference between this embodiment and Example 1 is that the mass fraction of amylated quantum dots in the casting solution is 3%. All other aspects are the same as in Example 1 and will not be repeated here.
[0075] The water flux of the hydrophilic modified hollow fiber ultrafiltration membrane prepared in this embodiment was measured to be 510.3 L / (m²) using the above performance testing methods. 2 The retention rate of bovine serum albumin was 91.4%, and the flux attenuation rate of yeast ultrafiltration membrane separation was 35.4%.
[0076] Comparative Example 1
[0077] A dimethylacetamide solution containing 1% graphene quantum dots and 18% polyvinylidene fluoride was prepared. The solution was stirred thoroughly and allowed to stand at 60°C for 5 hours to remove bubbles, yielding a casting solution. A hollow fiber ultrafiltration membrane was prepared using a polyester-lined braided tube as a support, employing spinning, coating, and phase inversion methods. The membrane was washed with water to remove organic solvents, soaked in a 30% glycerol aqueous solution, and then dried to obtain a lined reinforced hollow fiber ultrafiltration membrane.
[0078] The water flux of the hollow fiber ultrafiltration membrane prepared in this comparative example was measured to be 161.3 L / (m²) using the above performance testing methods. 2 The retention rate of bovine serum albumin was 78.0%, and the flux attenuation rate of yeast ultrafiltration membrane separation was 53.5%.
[0079] Comparing Example 1 and Comparative Example 1, the amino-based graphene quantum dots of the present invention, as a hydrophilic modifier, significantly outperform graphene quantum dot modifiers in enhancing the water flux and reducing membrane fouling of hollow fiber ultrafiltration membranes. Through the interaction between the amino groups and fluorine atoms, graphene quantum dots can be stably distributed inside and on the surface of the polyvinylidene fluoride (PVDF) ultrafiltration membrane. The amino-based graphene quantum dots on the surface of the ultrafiltration membrane exhibit good hydrophilicity and antifouling properties, thereby improving the water permeation flux and antifouling performance of the PVDF ultrafiltration membrane. The graphene quantum dots used in Comparative Example 1 are merely pore-forming agents and cannot function as hydrophilic modifiers. Therefore, the ultrafiltration membrane in the comparative example has low water flux and poor antifouling performance.
[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.
Claims
1. A method for preparing a hydrophilic modified hollow fiber ultrafiltration membrane, characterized in that, Includes the following steps: (1) Preparation of graphene quantum dots: Graphene quantum dots were prepared by citric acid pyrolysis; (2) Preparation of amino-based graphene quantum dots: Prepare an aqueous solution of graphene quantum dots and add a multi-amino compound to prepare solid amino-based graphene quantum dots; (3) Preparation of casting solution: using amino-based graphene quantum dots as hydrophilic modifiers, polyvinylidene fluoride as the main membrane material, and dimethylacetamide as solvent, the casting solution is prepared by mixing and stirring. (4) Preparation of hydrophilic modified hollow fiber ultrafiltration membrane: Using the inner braided tube as the support, the hydrophilic modified hollow fiber ultrafiltration membrane is prepared by spinning coating and phase inversion methods.
2. The method for preparing a hydrophilic modified hollow fiber ultrafiltration membrane according to claim 1, characterized in that: In step (1), the pyrolysis temperature is 200℃ and the pyrolysis time is 2h.
3. The method for preparing a hydrophilic modified hollow fiber ultrafiltration membrane according to claim 1, characterized in that: In step (2), the polyamine compound is one of diethylenetriamine, triethylenetetramine, or tetraethylenepentamine.
4. The method for preparing a hydrophilic modified hollow fiber ultrafiltration membrane according to claim 1, characterized in that, The specific operation of step (2) is as follows: prepare a graphene quantum dot aqueous solution with a mass fraction of 10-20%, add a polyamine compound with a mass fraction of 1-5%, and obtain a mixed aqueous solution. Heat and reflux at 100°C for 5-10 hours, and obtain amino-based graphene quantum dot solids after evaporation to remove water.
5. The method for preparing a hydrophilic modified hollow fiber ultrafiltration membrane according to claim 4, characterized in that: In the mixed aqueous solution, the mass ratio of the polyamine compound to the graphene quantum dots is 1:
5.
6. The method for preparing a hydrophilic modified hollow fiber ultrafiltration membrane according to claim 1, characterized in that: In step (3), the mass fraction of amino-based graphene quantum dots in the casting solution is 0.1-3.0%, and the mass fraction of polyvinylidene fluoride is 16-20%.
7. The method for preparing a hydrophilic modified hollow fiber ultrafiltration membrane according to claim 1, characterized in that, The specific operation in step (4) is as follows: using the inner braided tube as the support, after coating the casting liquid through the spinning head, the hollow fiber ultrafiltration membrane is prepared by phase transformation in the hydrogel bath; the organic solvent is removed by washing with water, and then soaked in glycerol aqueous solution to keep moist, and dried to obtain the hydrophilic modified hollow fiber ultrafiltration membrane.
8. The method for preparing a hydrophilic modified hollow fiber ultrafiltration membrane according to claim 7, characterized in that: The mass fraction of the glycerol aqueous solution is 20-30%.