A mesoporous silica modified hollow filtration membrane and a preparation method thereof

Abstract

The application belongs to the field of membrane separation technology and relates to a preparation method of a hollow filtration membrane based on mesoporous silica modification, which comprises the following steps: dispersing mesoporous silica in an organic solvent, adding a silane coupling agent and performing reaction under stirring, and obtaining aminated mesoporous silica after washing and drying; mixing a polymer matrix, the aminated mesoporous silica, a pore-forming agent and a solvent to form a homogeneous spinning solution; through a dry-wet spinning process, injecting the core liquid into the inner cavity of a spinneret, extruding the spinning solution through the outer cavity to form a nascent fiber; immersing the nascent fiber in a coagulation bath containing water and an organic solvent to perform phase separation and form an asymmetric structure hollow fiber membrane; and cleaning and drying to obtain the hollow filtration membrane. The application introduces aminated mesoporous silica, combines with a gradient coagulation process, constructs a nano channel under a low nano filler loading, cooperatively optimizes the membrane structure, effectively reduces the mass transfer resistance, and ensures stable retention rate while improving the flux.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of membrane separation technology, in particular to a hollow filtration membrane based on mesoporous silica modification and a preparation method thereof. BACKGROUND

[0002] Hollow fiber membranes have a wide application prospect in water treatment, biomedicine and industrial separation due to their high specific surface area, modular integration and low energy consumption characteristics. However, traditional membrane materials face significant challenges in practical applications, especially in high flux demand scenarios such as industrial wastewater reuse or seawater desalination pretreatment. The contradiction between flux and retention rate is particularly prominent. Existing technologies attempt to improve flux by thinning the skin layer or introducing nanomaterials, but ultra-thin skin layers lack mechanical strength under high pressure conditions, leading to a sharp decrease in retention rate. Nanomaterials such as metal organic frameworks or carbon nanotubes can improve performance, but their poor dispersibility requires high loadings, which not only increases costs but also easily causes membrane structural defects. In addition, surface hydrophilic modification techniques such as plasma treatment or polyethylene glycol grafting can temporarily improve antifouling properties, but they easily fail after long-term use or chemical cleaning, even causing membrane pore blockage, further limiting their practical application.

[0003] The complexity of traditional preparation processes also restricts the large-scale production of membrane materials. For example, multi-step interfacial polymerization processes are energy-intensive and have difficulty recovering solvents, while the double-bath coagulation method can increase flux to 120 LMI / bar, but the skin layer thickness exceeds 150 nm, limiting retention rate. Nanofiber membranes prepared by electrospinning technology have high porosity, but their mechanical properties are poor, making it difficult to meet the long-term stability requirements of industrial scenarios. These problems collectively make it difficult for existing membrane materials to balance efficiency and durability under high flux demand.

[0004] In view of the above bottlenecks, there is an urgent need for a new type of membrane material and preparation method that can break through the flux limit while maintaining high retention rate. SUMMARY

[0005] To solve the problems in the background art, the present application proposes a hollow filtration membrane based on mesoporous silica modification and a preparation method thereof. By innovatively introducing amino-functionalized mesoporous silica and combining with gradient coagulation process, a through nano-channel is constructed under low nano-filler loading, which synergistically optimizes the membrane structure, effectively reduces the mass transfer resistance, and thus improves the flux while ensuring stable retention rate. This technical path not only solves the dispersion problem of nanomaterials, but also avoids the cost and energy consumption problems brought by complex processes, providing an efficient and sustainable solution for the field of industrial separation.

[0006] The technical scheme adopted by the present application to solve its technical problems is to provide a preparation method of a hollow filtration membrane based on mesoporous silica modification, comprising the following steps:

[0007] S1, dispersing mesoporous silica in an organic solvent, adding a silane coupling agent to react under stirring, and obtaining aminated mesoporous silica after washing and drying; S2, mixing a polymer matrix, aminated mesoporous silica, a pore-forming agent and a solvent to form a homogeneous spinning solution; S3, through a dry-wet spinning process, injecting the core liquid into the inner cavity of the spinneret, and extruding the spinning solution through the outer cavity to form a nascent fiber; S4, immersing the nascent fiber in a coagulation bath containing water and an organic solvent to perform phase separation, and forming an asymmetric structure hollow fiber membrane; S5, cleaning and gradient drying the asymmetric structure hollow fiber membrane to obtain a hollow filtration membrane.

[0008] Further, in step S1, the organic solvent includes ethanol, isopropanol or acetone; the silane coupling agent is γ-aminopropyl triethoxysilane; the reaction temperature is 60-80℃, and the reaction time is 4-8 hours.

[0009] Further, in step S2, the polymer matrix includes polyether sulfone, polyvinylidene fluoride, polypropylene or polysulfone; the solvent includes N-methyl pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide or dimethyl sulfoxide; the polyether sulfone is PES; the polyvinylidene fluoride is PVDF; the polypropylene is PP; the polysulfone is PSF; the N-methyl pyrrolidone is NMP; the N,N-dimethylacetamide is DMAC; the N,N-dimethylformamide is DMF; the dimethyl sulfoxide is DMSO; the pore-forming agent includes polyvinylpyrrolidone or polyethylene glycol; the organic solvent includes ethanol, isopropanol or acetone. The polyvinylpyrrolidone is PVP; the polyethylene glycol is PEG. The γ-aminopropyl triethoxysilane is KH-550.

[0010] Further, the molecular weight of the polyether sulfone is 50000-60000 Da; the pore size of the mesoporous silica is 3-5 nm, and the specific surface area is greater than 800 m 2 / g.

[0011] Further, in step S3, the inner diameter of the spinneret is 0.7-1.0 mm, and the outer diameter is 1.0-1.5 mm; the core liquid is pure water; the core liquid flow rate is 4-10 mL / min, and the spinning solution extrusion speed is 6-10 mL / min; the air gap is 5-15 cm.

[0012] Further, in step S4, the coagulation bath is composed of water and an organic solvent in a volume ratio of 6:4 to 8:2, the coagulation bath temperature is 20-30℃, the immersion time is 25-35 minutes, and the organic solvent includes ethanol.

[0013] Further, in step S5, the gradient drying includes: a, pre-drying for 1-3 hours in a humidity of 40-60%; b, transferring to a vacuum drying oven for drying; the vacuum drying temperature is 50-70℃, and the drying time is 10-14 hours.

[0014] The application also provides a mesoporous silica modified hollow filtration membrane, comprising a polymer matrix, amino-modified mesoporous silica, a solvent, a pore-forming agent and a silane coupling agent.

[0015] Further, the hollow filtration membrane comprises, by mass percentage,

[0016] the polymer matrix, 15-20%; the amino-modified mesoporous silica, 1-5%; the solvent, 70-80%; the pore-forming agent, 3-8%; and the silane coupling agent, 1-5%.

[0017] the polymer matrix, 15-20%; the amino-modified mesoporous silica, 1-5%; the solvent, 70-80%; the pore-forming agent, 3-8%; and the silane coupling agent, 1-5%.

[0018] The application has the following beneficial effects:

[0019] (1) The hollow filtration membrane prepared by the application has a pure water flux of 150-200 LMH / bar, which is 80%-150% higher than the flux of 80-100 LMH / bar of a traditional polyether sulfone membrane, can meet the high-flow industrial separation demand, effectively improves the processing efficiency and reduces the processing cost.

[0020] (2) The asymmetric structure hollow fiber membrane and the mesoporous SiO2 selective adsorption synergistic effect can greatly improve the flux while maintaining the retention rate of bovine serum albumin and other substances >95%, breaking through the limitation of the traditional membrane "high flux and low retention", and ensuring high filtration speed and good separation effect in the complex industrial separation process, improving the purity and quality of resource recovery.

[0021] (3) The amino-modified mesoporous silica surface is modified by the silane coupling agent, so that the interfacial bonding force of the mesoporous silica and the PES matrix is significantly improved, uniform dispersion is realized under a low loading amount of ≤3wt%, the membrane structure defects caused by the agglomeration of nanoparticles are effectively avoided, the performance stability of the membrane is ensured, and the use amount of the nanomaterial is reduced, thereby reducing the cost.

[0022] (4) The dry-wet spinning process combined with the gradient coagulation bath treatment can accurately control the skin layer thickness and the support layer pore size, form an asymmetric structure hollow fiber membrane, fully and uniformly separate, simplify the preparation process, reduce the energy consumption and solvent recovery difficulty, be conducive to large-scale production, improve the production efficiency, reduce the production cost, and make the technology more competitive in the market. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 SEM image of the hollow filtration membrane prepared in Example 6;

[0024] Figure 2Another SEM image of the hollow filtration membrane prepared for Example 6. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. It can be understood that the specific embodiments described herein are only used to explain the present application, and not to limit the present application. In addition, it should be noted that, for the convenience of description, only the parts related to the present application are shown in the drawings, not all structures.

[0026] Example 1: Preparation of aminated mesoporous silica A.

[0027] 5 g of mesoporous silica was dispersed in 200 ml of ethanol and ultrasonically treated for 30 minutes to ensure uniform dispersion to obtain a dispersion liquid; wherein the pore size of the mesoporous silica was 3-5 nm, and the specific surface area was >800 m² / g. 1.5 mL of γ-aminopropyl triethoxysilane was added to the dispersion liquid, and the reaction was stirred at 70°C for 6 hours to graft amino groups -NH2 onto the surface of SiO2; after the reaction was completed, the solid product was separated by centrifugation at a speed of 5000 rpm for 15 minutes; washed with ethanol for 3 times to remove unreacted coupling agent, and dried in a vacuum drying oven at 60°C for 12 hours to obtain aminated mesoporous silica A.

[0028] Example 2: Preparation of aminated mesoporous silica B.

[0029] 3 g of mesoporous silica was dispersed in 150 mL of ethanol and ultrasonically treated for 40 minutes to obtain a dispersion liquid; wherein the pore size of the mesoporous silica was 3-5 nm, and the specific surface area was >800 m² / g. 1.0 mL of γ-aminopropyl triethoxysilane was added to the dispersion liquid, and the reaction was stirred at 65°C for 8 hours to graft amino groups -NH2 onto the surface of SiO2. After the reaction was completed, the solid product was separated by centrifugation at a speed of 5000 rpm for 15 minutes; washed with ethanol for 3 times to remove residual coupling agent, and then dried in a vacuum drying oven at 60°C for 10 hours to obtain aminated mesoporous silica B.

[0030] Example 3: Preparation of aminated mesoporous silica C.

[0031] 8 g of mesoporous silica was dispersed in 250 mL of ethanol and ultrasonicated for 20 minutes to obtain a dispersion; wherein the mesoporous silica has a pore size of 3-5 nm and a specific surface area > 800 m2 / g. 2.0 mL of γ-aminopropyltriethoxysilane was added to the dispersion and stirred at 75 °C for 4 hours to allow the amino group -NH2 to be grafted onto the surface of SiO2. After the reaction was completed, the solid product was separated by centrifugation at a speed of 5000 rpm for 15 minutes; washed with ethanol for 4 times to remove the residual coupling agent, and finally dried in a vacuum drying oven at 60 °C for 14 hours to obtain the aminated mesoporous silica C.

[0032] Example 4: Preparation of aminated mesoporous silica D.

[0033] 6 g of mesoporous silica was dispersed in 200 mL of isopropanol and ultrasonicated for 35 minutes to obtain a dispersion; wherein the mesoporous silica has a pore size of 3-5 nm and a specific surface area > 800 m2 / g. 1.8 mL of γ-aminopropyltriethoxysilane was added to the dispersion and stirred at 75 °C for 5 hours to allow the amino group -NH2 to be grafted onto the surface of SiO2. After the reaction was completed, the solid product was separated by centrifugation at a speed of 5000 rpm for 15 minutes; washed with acetone for 3 times to remove the residual coupling agent, and finally dried in a vacuum drying oven at 60 °C for 12 hours to obtain the aminated mesoporous silica D.

[0034] Example 5: Preparation of aminated mesoporous silica E.

[0035] 4 g of mesoporous silica was dispersed in 180 mL of acetone and ultrasonicated for 25 minutes to obtain a dispersion; wherein the mesoporous silica has a pore size of 3-5 nm and a specific surface area > 800 m2 / g. 1.2 mL of γ-aminopropyltriethoxysilane was added to the dispersion and stirred at 50 °C for 7 hours to ensure that the amino group -NH2 was grafted. After the reaction was completed, the solid product was separated by centrifugation at a speed of 5000 rpm for 15 minutes; washed with acetone for 3 times to remove the residual coupling agent, and finally dried in a vacuum drying oven at 60 °C for 14 hours to obtain the aminated mesoporous silica E.

[0036] Example 6: Preparation of hollow filtration membrane based on mesoporous silica modification.

[0037] First, the polymer matrix, aminated mesoporous silica, pore-forming agent and solvent were mixed to form a homogeneous spinning solution;

[0038] Spinning solution composition:

[0039] By mass percentage, polyether sulfone, molecular weight 50,000-60,000 Da, 18%; aminated mesoporous silica 3%; polyvinylpyrrolidone, 5%; N-methylpyrrolidone 74%;

[0040] Heat N-methylpyrrolidone to 60°C, add polyvinylpyrrolidone and stir until completely dissolved;

[0041] Slowly add polyethersulfone powder and stir continuously at 60°C for 12 hours to form a transparent homogeneous solution;

[0042] Aminated mesoporous silica was added, and the mixture was ultrasonically treated for 2 hours at a power of 300W in pulse mode to ensure uniform dispersion of the nanofiller.

[0043] After vacuum degassing at 0.1 MPa for 4 hours, a homogeneous spinning solution was obtained.

[0044] Secondly, through a dry-wet spinning process, the core solution is injected into the inner cavity of the spinneret, and the spinning solution is extruded through the outer cavity to form nascent fibers. Equipment parameters: inner diameter of the spinneret 0.8 mm, outer diameter 1.2 mm; core solution (deionized water) flow rate 5 mL / min, spinning solution extrusion speed 8 mL / min; air gap 10 cm; spinning formation: the core solution is injected through the inner cavity of the spinneret, and the spinning solution is extruded from the annular gap, and preliminary phase separation occurs after contact with the core solution; the solvent in the air gap partially evaporates, promoting the densification of the skin layer.

[0045] Then, the nascent fibers are immersed in a coagulation bath containing water and organic solvent for phase separation to form an asymmetric hollow fiber membrane; coagulation bath treatment: the nascent fibers are immersed in a coagulation bath with a water / ethanol volume ratio of 7:3 and a temperature of 25°C for 30 minutes to complete solvent-non-solvent exchange and form an asymmetric structure with a skin thickness of about 80nm and a support layer pore size of 0.2-2μm.

[0046] Finally, the asymmetric hollow fiber membrane was cleaned and gradient dried to obtain the hollow fiber filter membrane. The fiber membrane was cleaned with deionized water for 48 hours to completely remove residual solvent; gradient drying was then performed under the following conditions: a. pre-drying at 50% humidity for 2 hours; b. transferring to a vacuum drying oven and drying at 60°C for 12 hours to obtain the final hollow fiber filter membrane.

[0047] The microstructure of the hollow fiber filtration membrane based on mesoporous silica modification prepared in Example 6 is as follows: Figure 1 and Figure 2 As shown, Figure 1 This is a SEM image of the outer surface of the membrane. Figure 2 The image shows a cross-sectional SEM image of the membrane, revealing a typical asymmetric structure with a dense outer skin layer and uniformly distributed pores in the support layer. This structure helps improve filtration efficiency and maintain good retention performance.

[0048] Examples 6-15: As shown in Table 1; Table 1 shows the composition of the hollow fiber filter membranes in Examples 6-15.

[0049]

[0050] The hollow filtration membranes prepared in Examples 6-15 were subjected to performance tests, as shown in Table 2:

[0051] Table 2 shows the performance test results of the hollow filtration membranes prepared in Examples 6-15.

[0052]

[0053] The mesoporous silica modified hollow filtration membranes prepared in Examples 6-15 have good separation performance, and the pure water flux of the samples prepared in the examples all exceed 150 LMH / bar, among which the sample of Example 10 with polyether sulfone as the matrix and 4% amino-modified mesoporous silica loaded therein reaches 188 LMH / bar; at the same time, the porosity breaks through the high interval of 80.3% to 88.4%, and the high porosity samples such as Examples 6 and 10 can still achieve high efficient interception of 98.7% and 98.9% of bovine serum albumin while maintaining the porosities of 87.2% and 88.4%, respectively.

[0054] The present application breaks the contradiction between flux, interception and porosity in the field of membrane separation by designing the molecular channel of amino-modified mesoporous silica and the gradient coagulation bath process. The mesoporous channel of the present application can reduce the mass transfer resistance and realize the leap of flux; the surface amino group cooperates with the electrostatic repulsion mechanism to ensure high interception rate. The ultra-thin skin layer of the hollow filtration membrane prepared in the present application and the selective adsorption of mesoporous SiO2 synergistically work together to maintain the BSA interception rate of >95% under the flux multiplication, breaking the dilemma of "high flux and low interception" of traditional membranes. The technology provides a revolutionary solution for high-difficulty industrial separation scenarios, and is particularly suitable for seawater desalination pretreatment, heavy metal wastewater reuse and biopharmaceutical separation fields, which can improve the treatment efficiency by more than 50% and reduce the energy consumption by 30%, and promote the industrialization upgrading of water resource sustainable utilization technology.

[0055] The above describes the present application in detail in combination with examples and comparative examples, but the present application is not limited to the above examples, and various changes can be made within the knowledge of those skilled in the art without departing from the spirit of the present application. The contents not described in detail in the present application can adopt the prior art.

Claims

1. A method for producing a hollow filtration membrane based on mesoporous silica modification, characterized by, The method comprises the following steps: S1, dispersing mesoporous silica in an organic solvent by ultrasonic treatment, adding a silane coupling agent and reacting under stirring, and obtaining aminated mesoporous silica after washing and drying; S2, mixing a polymer matrix, aminated mesoporous silica, a pore-forming agent and a solvent to form a homogeneous spinning solution; S3, injecting the core liquid into the inner cavity of the spinneret, and extruding the spinning solution through the outer cavity to form a nascent fiber; S4, immersing the nascent fiber in a coagulation bath containing water and ethanol to perform phase separation, and forming an asymmetric structure hollow fiber membrane; S5, cleaning and gradient drying the asymmetric structure hollow fiber membrane to obtain a hollow filtration membrane; In step S2, the polymer matrix comprises polyether sulfone, polyvinylidene fluoride, polypropylene or polysulfone; The solvent comprises N-methyl pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide or dimethyl sulfoxide; The pore-forming agent comprises polyvinylpyrrolidone or polyethylene glycol; The molecular weight of the polyether sulfone is 50,000-60,000 Da; In step S4, the coagulation bath is composed of water and ethanol in a volume ratio of 6:4 to 8:2, the coagulation bath temperature is 20-30℃, and the immersion time is 25-35 minutes; In step S1, the pore size of the mesoporous silica is 3-5 nm, and the specific surface area is greater than 800 m 2 / g; In step S5, the gradient drying comprises: a, pre-drying for 1-3 hours in a humidity of 40-60%; b, transferring to a vacuum drying oven for drying; the vacuum drying temperature is 50-70℃, and the drying time is 10-14 hours.

2. The method for preparing a hollow filtration membrane based on mesoporous silica modification according to claim 1, wherein: In S1, the organic solvent comprises ethanol, isopropanol or acetone; the silane coupling agent is γ-aminopropyl triethoxysilane; the reaction temperature is 60-80℃, and the reaction time is 4-8 hours.

3. The method for preparing a hollow filtration membrane based on mesoporous silica modification according to claim 1, wherein: In step S3, the inner diameter of the spinneret is 0.7-1.0 mm, the outer diameter is 1.0-1.5 mm; the core liquid flow rate is 4-10 mL / min, the spinning solution extrusion speed is 6-10 mL / min; and the air gap is 5-15 cm. The spinning solution in the preparation method comprises a polymer matrix, aminated mesoporous silica, a solvent and a pore-forming agent.

4. A mesoporous silica-based modified hollow filtration membrane prepared using the method of any one of claims 1 to 3, characterized in that, The spinning solution in the preparation method comprises, by mass percentage:

5. The mesoporous silica modified hollow filtration membrane according to claim 4, wherein, Polymer matrix, 15-20%; Aminated mesoporous silica, 1-5%; Solvent, 70-80%; Pore-forming agent, 3-8%. ​

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