Hollow filtering membrane based on mesoporous silica modification and preparation method thereof

Abstract

The invention belongs to the technical field of membrane separation, and relates to a mesoporous silica modification-based hollow filtering membrane preparation method, which comprises: dispersing mesoporous silica in an organic solvent, adding a silane coupling agent, carrying out a reaction under a stirring condition, washing, and drying to obtain aminated mesoporous silica; mixing the polymer matrix, aminated mesoporous silica, a pore forming agent and a solvent to form a homogeneous spinning solution; injecting the core liquid into an inner cavity of a spinning nozzle through a dry-wet spinning process, and extruding the spinning liquid through an outer cavity to form nascent fibers; immersing the nascent fiber in a coagulating bath containing water and an organic solvent for phase separation to form a hollow fiber membrane with an asymmetric structure; and cleaning and drying to obtain the hollow filter membrane. According to the invention, aminated mesoporous silica is introduced, a gradient solidification process is combined, a nano channel is constructed under low nano filler loading capacity, a membrane structure is synergistically optimized, the mass transfer resistance is effectively reduced, and the retention rate is ensured to be stable while the flux is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of membrane separation, and particularly to a hollow filter membrane modified based on mesoporous silica and a preparation method thereof. Background Art

[0002] Hollow fiber membranes have broad application prospects in the fields of 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 scenarios with high-throughput requirements, such as industrial wastewater reuse or seawater desalination pretreatment, the contradiction between flux and rejection rate is particularly prominent. Existing technologies attempt to improve the flux by thinning the skin layer or introducing nanomaterials. However, the ultra-thin skin layer has insufficient mechanical strength under high-pressure conditions, easily leading to a sudden drop in rejection rate; while nanomaterials such as metal-organic frameworks or carbon nanotubes can improve performance, but due to poor dispersibility, high loading amounts are required, which not only increases costs but also easily causes membrane structure defects. In addition, surface hydrophilic modification technologies such as plasma treatment or polyethylene glycol grafting can temporarily improve anti-fouling properties, but are prone to failure after long-term use or chemical cleaning, and even clog membrane pores, further restricting their practical applications.

[0003] The complexity of traditional preparation processes also restricts the large-scale production of membrane materials. For example, the multi-step interfacial polymerization process has high energy consumption and difficult solvent recovery, while the double-bath coagulation method can increase the flux to 120 LMI / bar, but the rejection rate is limited due to the skin layer thickness exceeding 150 nm. The nanofiber membranes prepared by electrospinning technology have high porosity but poor mechanical properties, and it is difficult to meet the long-term stability requirements of industrial scenarios. These problems together lead to the difficulty of existing membrane materials in balancing efficiency and durability under high-throughput requirements.

[0004] In view of the above bottlenecks, there is an urgent need for a new type of membrane material and preparation method that can both break through the flux limitation and maintain a high rejection rate. Summary of the Invention

[0005] To solve the problems in the background art, the present invention proposes a hollow filter membrane modified based on mesoporous silica and a preparation method thereof. By innovatively introducing amino-functionalized mesoporous silica and combining with a gradient coagulation process, through-nano channels are constructed at a low nano-filler loading amount, and the membrane structure is synergistically optimized, effectively reducing the mass transfer resistance, thereby ensuring a stable rejection rate while increasing the flux. This technical path not only solves the problem of nanomaterial dispersion but also avoids the cost and energy consumption problems brought by complex processes, providing an efficient and sustainable solution for the industrial separation field.

[0006] The technical solution adopted by the present invention to solve its technical problems is: to provide a preparation method of a hollow filter membrane modified based on mesoporous silica, including the following steps:

[0007] S1. Disperse mesoporous silica in an organic solvent, add a silane coupling agent and react under stirring conditions, and obtain amino-modified mesoporous silica after washing and drying; S2. Mix the polymer matrix, amino-modified mesoporous silica, pore-forming agent and solvent to form a homogeneous spinning solution; S3. Through the dry-wet spinning process, inject the core liquid into the inner cavity of the spinneret, and extrude the spinning solution through the outer cavity to form nascent fibers; S4. Immerse the nascent fibers in a coagulation bath containing water and organic solvents for phase separation to form an asymmetric hollow fiber membrane; S5. Clean the asymmetric hollow fiber membrane and gradient dry it to obtain a hollow filter membrane.

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

[0009] Furthermore, in step S2, the polymer matrix includes polyethersulfone, polyvinylidene fluoride, polypropylene, or polysulfone; the solvent includes N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, or dimethyl sulfoxide; the polyethersulfone is PES; the polyvinylidene fluoride is PVDF; the polypropylene is PP; the polysulfone is PSF; the N-methylpyrrolidone 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; and the γ-aminopropyltriethoxysilane is KH-550.

[0010] Furthermore, the molecular weight of polyethersulfone is 50,000-60,000 Da; the pore size of mesoporous silica is 3-5 nm, and the specific surface area is greater than 800 m 2 / g.

[0011] Furthermore, 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, the spinning solution extrusion speed is 6-10 mL / min; and the air gap is 5-15 cm.

[0012] Furthermore, 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°C, the immersion time is 25-35 minutes, and the organic solvent includes ethanol.

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

[0014] The present invention also provides a hollow filter membrane modified based on mesoporous silica, which comprises a polymer matrix, aminated mesoporous silica, a solvent, a pore former, and a silane coupling agent.

[0015] Further, by mass percentage, it comprises

[0016] the polymer matrix, 15 - 20%; aminated mesoporous silica, 1 - 5%; the solvent, 70 - 80%;

[0017] the pore former, 3 - 8%; the silane coupling agent, 1 - 5%.

[0018] The beneficial effects of the present invention are as follows:

[0019] (1) Through the synergistic regulation of the nanochannel effect of aminated mesoporous silica and the gradient coagulation bath, the pure water flux of the prepared hollow filter membrane can reach 150 - 200 LMH / bar. Compared with the flux of 80 - 100 LMH / bar of the traditional polyethersulfone membrane, it is increased by 80% - 150%, which can meet the high-flow industrial separation requirements, effectively improve the treatment efficiency, and reduce the treatment cost.

[0020] (2) The synergistic effect of the asymmetric structure hollow fiber membrane and the selective adsorption of mesoporous SiO2 in the present invention not only greatly improves the flux but also maintains the rejection rate of substances such as bovine serum albumin > 95%, breaking through the limitation of the traditional membrane that "high flux must be accompanied by low rejection". In the complex industrial separation process, it can not only ensure a high filtration speed but also ensure a good separation effect, improving the purity and quality of resource recovery.

[0021] (3) The present invention uses a silane coupling agent to carry out amination modification on the surface of mesoporous silica, significantly improving the interfacial binding force with the PES matrix, achieving uniform dispersion at a low loading amount ≤ 3 wt%, effectively avoiding the membrane structure defects caused by nanoparticle aggregation, ensuring the stable performance of the membrane, and reducing the usage amount of nanomaterials and the cost.

[0022] (4) The present invention adopts a dry-wet spinning process combined with gradient coagulation bath treatment, which can accurately control the skin layer thickness and the pore size of the support layer, form an asymmetric structure hollow fiber membrane, with sufficient and uniform phase separation, simplify the preparation process, reduce the energy consumption and the difficulty of solvent recovery, facilitate large-scale production, improve the production efficiency, reduce the production cost, and make this technology more competitive in the market. Description of the Drawings

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

[0024] Figure 2Another SEM image of the hollow filter membrane prepared in Example 6. Detailed implementation

[0025] The technical solutions in the embodiments of the invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the invention. It can be understood that the specific embodiments described herein are only for explaining the present invention, rather than limiting the present invention. Additionally, it should be noted that for ease of description, only the parts related to the present invention are shown in the accompanying drawings, rather than all the structures.

[0026] Example 1: Preparation of amino-functionalized mesoporous silica A.

[0027] Disperse 5 g of mesoporous silica in 200 ml of ethanol and ultrasonically treat for 30 minutes to ensure uniform dispersion to obtain a dispersion; wherein, the pore diameter of the mesoporous silica is 3 - 5 nm and the specific surface area > 800 m² / g. Add 1.5 mL of γ-aminopropyltriethoxysilane to the dispersion and stir and react at 70 °C for 6 hours to graft amino - NH2 onto the SiO2 surface; after the reaction is completed, centrifuge the solid product at a speed of 5000 rpm for 15 minutes; wash with ethanol 3 times to remove the unreacted coupling agent, and dry in a vacuum at 60 °C for 12 hours to obtain amino-functionalized mesoporous silica A.

[0028] Example 2: Preparation of amino-functionalized mesoporous silica B.

[0029] Disperse 3 g of mesoporous silica in 150 mL of ethanol and ultrasonically treat for 40 minutes to obtain a dispersion; wherein, the pore diameter of the mesoporous silica is 3 - 5 nm and the specific surface area > 800 m² / g. Add 1.0 mL of γ-aminopropyltriethoxysilane to the dispersion and stir and react at 65 °C for 8 hours to fully graft amino - NH2 onto the SiO2 surface. After the reaction is completed, centrifuge the solid product at a speed of 5000 rpm for 15 minutes; wash with ethanol 3 times to remove the residual coupling agent, and then dry in a vacuum drying oven at 60 °C for 10 hours to obtain amino-functionalized mesoporous silica B.

[0030] Example 3: Preparation of amino-functionalized mesoporous silica C.

[0031] Disperse 8 g of mesoporous silica in 250 mL of ethanol and ultrasonically treat for 20 minutes to obtain a dispersion; among them, the pore diameter of the mesoporous silica is 3 - 5 nm, and the specific surface area > 800 m² / g. Add 2.0 mL of γ-aminopropyltriethoxysilane to the dispersion and stir and react at 75 °C for 4 hours to fully graft the amino - NH2 onto the SiO2 surface. After the reaction is completed, centrifuge and separate the solid product at a rotation speed of 5000 rpm for 15 minutes; wash with ethanol 4 times to remove the residual coupling agent, and finally dry in a vacuum drying oven at 60 °C for 14 hours to obtain amino-functionalized mesoporous silica C.

[0032] Example 4: Preparation of amino-functionalized mesoporous silica D.

[0033] Disperse 6 g of mesoporous silica in 200 mL of isopropanol and ultrasonically treat for 35 minutes to obtain a dispersion; among them, the pore diameter of the mesoporous silica is 3 - 5 nm, and the specific surface area > 800 m² / g. Add 1.8 mL of γ-aminopropyltriethoxysilane to the dispersion and stir and react at 75 °C for 5 hours to efficiently graft the amino - NH2 onto the SiO2 surface. After the reaction is completed, centrifuge and separate the solid product at a rotation speed of 5000 rpm for 15 minutes; wash with acetone 3 times to remove the residual coupling agent, and finally dry in a vacuum drying oven at 60 °C for 12 hours to obtain amino-functionalized mesoporous silica D.

[0034] Example 5: Preparation of amino-functionalized mesoporous silica E.

[0035] Disperse 4 g of mesoporous silica in 180 mL of acetone and ultrasonically treat for 25 minutes to obtain a dispersion; among them, the pore diameter of the mesoporous silica is 3 - 5 nm, and the specific surface area > 800 m² / g. Add 1.2 mL of γ-aminopropyltriethoxysilane to the dispersion and stir and react at 50 °C for 7 hours to ensure full grafting of the amino - NH2. After the reaction is completed, centrifuge and separate the solid product at a rotation speed of 5000 rpm for 15 minutes; wash with acetone 3 times to remove the residual coupling agent, and finally dry in a vacuum drying oven at 60 °C for 14 hours to obtain amino-functionalized mesoporous silica E.

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

[0037] First, mix the polymer matrix, amino-functionalized mesoporous silica, pore-forming agent, and solvent to form a homogeneous spinning solution;

[0038] Composition of the spinning solution:

[0039] By mass percentage, polyethersulfone with a molecular weight of 50,000 - 60,000 Da, 18%; amino-functionalized 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 continuously stir at 60 °C for 12 hours to form a transparent homogeneous solution;

[0042] Add aminated mesoporous silica and ultrasonically treat for 2 hours at a power of 300 W in pulse mode to ensure uniform dispersion of the nanofiller;

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

[0044] Secondly, through the dry-wet spinning process, inject the core liquid 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 is 0.8 mm, outer diameter is 1.2 mm; flow rate of the core liquid (deionized water) is 5 mL / min, extrusion speed of the spinning solution is 8 mL / min; air gap is 10 cm; spinning and forming: the core liquid is injected through the inner cavity of the spinneret, and the spinning solution is extruded from the annular gap and undergoes preliminary phase separation after contacting the core liquid; part of the solvent volatilizes in the air gap, promoting the densification of the skin layer;

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

[0046] Finally, wash and gradient dry the asymmetric structure hollow fiber membrane to obtain a hollow filtration membrane. Wash the fiber membrane with deionized water for 48 hours to completely remove the residual solvent; perform gradient drying, and the gradient drying conditions are: a. Pre-dry in an environment with a humidity of 50% for 2 hours; b. Transfer to a vacuum drying oven and dry at 60 °C for 12 hours to obtain the final hollow filtration membrane.

[0047] The microstructure of the hollow filtration membrane prepared in Example 6 modified with mesoporous silica is as Figure 1 and Figure 2 shown, Figure 1 is the SEM image of the outer surface of the membrane, Figure 2 is the SEM image of the cross-section of the membrane. It can be seen that the membrane has a typical asymmetric structure, with a dense outer skin layer and uniformly distributed pores in the support layer. This structure helps to improve the filtration efficiency and maintain good retention performance.

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

[0049]

[0050] The performance of the hollow filtration membranes prepared in Examples 6 - 15 was tested, 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 to 15 of the present invention have good separation performance. The pure water fluxes of the samples prepared in the examples all exceed 150 LMH / bar. Among them, Example 10 with polyethersulfone as the matrix and loaded with 4% amino - functionalized mesoporous silica reaches 188 LMH / bar. At the same time, the porosity breaks through the high - level range of 80.3% to 88.4%. High - porosity samples such as Examples 6 and 10 can still achieve high - efficiency interception of 98.7% and 98.9% of bovine serum albumin while maintaining porosities of 87.2% and 88.4%.

[0054] Through the molecular channel design of amino - functionalized mesoporous silica and the gradient coagulation bath process, the present invention solves the long - existing contradiction of flux - interception - porosity in the field of membrane separation. The mesoporous channels of the present invention can reduce the mass transfer resistance and achieve a flux jump; the surface amino groups cooperate with the electrostatic repulsion mechanism to ensure a high interception rate. The synergistic effect of the ultrathin skin layer and mesoporous SiO2 selective adsorption of the hollow filtration membrane prepared by the present invention maintains a BSA interception rate > 95% under the condition of doubled flux, breaking the dilemma of "high flux necessarily means low interception" of traditional membranes. This technology provides a transformative solution for high - difficulty industrial separation scenarios, especially applicable to fields such as seawater desalination pretreatment, heavy metal wastewater reuse, and biopharmaceutical separation, which can increase the treatment efficiency by more than 50% and reduce energy consumption by 30%, promoting the industrial upgrading of water resource sustainable utilization technology.

[0055] The present invention has been described in detail above in combination with examples and comparative examples. However, the present invention is not limited to the above - mentioned examples. Within the scope of knowledge possessed by those of ordinary skill in the art, various changes can be made without departing from the gist of the present invention. The content not described in detail in the present invention can all adopt the existing technology.

Claims

1. A preparation method of a hollow filter membrane based on mesoporous silica modification, characterized in that, It includes the following steps: S1. Disperse mesoporous silica in an organic solvent, add a silane coupling agent, and react under stirring conditions. After washing and drying, amino-functionalized mesoporous silica is obtained; S2. Mix a polymer matrix, amino-functionalized mesoporous silica, a pore-forming agent, and a solvent to form a homogeneous spinning solution; S3. Through a dry-wet spinning process, inject the core liquid into the inner cavity of the spinneret, and extrude the spinning solution through the outer cavity to form a nascent fiber; S4. Immerse the nascent fiber in a coagulation bath containing water and an organic solvent for phase separation to form an asymmetric-structured hollow fiber membrane; S5. Clean and gradient-dry the asymmetric-structured hollow fiber membrane to obtain a hollow filtration membrane.

2. The preparation method of a hollow filtration membrane based on mesoporous silica modification according to claim 1, wherein: In S1, the organic solvent includes ethanol, isopropanol, or acetone; the silane coupling agent is γ-aminopropyltriethoxysilane; the reaction temperature is 60-80 °C, and the reaction time is 4-8 hours.

3. The preparation method of a mesoporous silica-modified hollow filtration membrane according to claim 1, characterized in that, In S2: The polymer matrix includes polyethersulfone, polyvinylidene fluoride, polypropylene, or polysulfone; The solvent includes N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, or dimethyl sulfoxide; The pore-forming agent includes polyvinylpyrrolidone or polyethylene glycol.

4. The preparation method of a mesoporous silica-modified hollow filtration membrane according to claim 3, wherein: The molecular weight of polyethersulfone is 50,000-60,000 Da; The pore diameter of the mesoporous silica is 3 - 5 nm, and the specific surface area is greater than 800 m 2 / g.

5. The preparation method of 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, and the spinning solution extrusion speed is 6-10 mL / min; the air gap is 5-15 cm.

6. The preparation method of a hollow filtration membrane based on mesoporous silica modification according to claim 1, wherein: 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 °C, and the immersion time is 25-35 minutes; the organic solvent includes ethanol.

7. The preparation method of a mesoporous silica-modified hollow filtration membrane according to claim 1, wherein In step S5, the gradient drying includes: a. Pre-dry in an environment with a humidity of 40-60% for 1-3 hours; b. Transfer to a vacuum drying oven for drying; the vacuum drying temperature is 50-70 °C, and the drying time is 10-14 hours.

8. A mesoporous silica-modified hollow filtration membrane prepared by the method according to any one of claims 1-7, characterized in that, It includes a polymer matrix, amino-functionalized mesoporous silica, a solvent, and a pore-forming agent.

9. A hollow filtration membrane modified based on mesoporous silica according to claim 8, characterized in that, By mass percentage, it includes The polymer matrix, 15-20%; amino-functionalized mesoporous silica, 1-5%; The solvent, 70-80%; the pore-forming agent, 3-8%.

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