Silica-modified permeable membrane, method for preparing the same, and water treatment system

Abstract

The application discloses a silica modified permeable membrane, a preparation method thereof and a water treatment system. The preparation method comprises the following steps: obtaining a base film, preparing a mixed organic solution with silica and a bifunctional silane as solutes, slowly adding distilled water into the mixed organic solution, and stirring to obtain a modified polysilsesquioxane polymeric sol; and preparing the modified polysilsesquioxane polymeric sol to the base film through suction filtration to obtain the silica modified permeable membrane. The preparation method is simple in process, the prepared silica modified permeable membrane has a large flux, can treat more water in the same time, is stable in structure, has high-temperature resistance and chlorine resistance, is helpful to treat different conditions, has good adaptability, and is favorable for wide application.

Description

Technical Field

[0001] This invention relates to the field of water treatment, and in particular to a silica-modified permeable membrane, its preparation method, and a water treatment system. Background Technology

[0002] Reverse osmosis (RO) membranes are semi-permeable membranes that allow water molecules to pass through while blocking dissolved salts, organic matter, and other impurities under applied pressure. They are the core component of reverse osmosis technology and are widely used in seawater desalination, drinking water purification, industrial wastewater treatment, and many other fields. Polyamide-derived membranes are widely used in RO membrane applications due to their excellent separation performance. However, polyamide-derived membranes typically have low resistance to high temperatures and chlorine, which limits their application. Furthermore, RO membranes made from other materials generally have low flux and low water treatment efficiency. Summary of the Invention

[0003] The technical problem to be solved by the embodiments of the present invention is to provide a silica-modified permeation membrane, its preparation method and water treatment system, which can improve water treatment flux and heat resistance.

[0004] To address the aforementioned technical problems, this invention provides a method for preparing a silica-modified permeation membrane. The method includes the following steps: obtaining a base membrane; preparing a mixed organic solution containing silica and a bifunctional silane as the solute; slowly adding distilled water dropwise to the mixed organic solution while stirring to obtain a modified polysilsesquioxane polymer sol; and applying the modified polysilsesquioxane polymer sol to the base membrane via filtration to obtain the silica-modified permeation membrane.

[0005] In one feasible implementation, the bifunctional silane is selected from bis[3-(triethoxysilyl)propyl]tetrasulfide, bis[3-(triethoxysilyl)propyl]amine, or tetraethoxysilane.

[0006] In one feasible implementation, the mass concentration of the bifunctional silane in the mixed organic solution is 2 wt% to 8 wt%.

[0007] In the mixed organic solution, the mass ratio of silicon dioxide to bifunctional silane is (0.02-0.03):1.

[0008] In one feasible implementation, the base film is selected from polysulfone-based film, polyethersulfone-based film, ceramic-based film, polyacrylonitrile-based film, polyvinylidene fluoride film, polytetrafluoroethylene film, polyimide film, polyvinyl chloride film, polyethylene film, or polypropylene film.

[0009] In one feasible implementation, during the slow dropwise addition of distilled water to the mixed organic solution, the molar ratio of the distilled water to the bifunctional silane is (70-50):1.

[0010] In one feasible implementation, the stirring operation includes the following steps:

[0011] After adding distilled water, stir the mixed organic solution at 20℃-25℃ for 1.5-2.5 hours.

[0012] The mixed organic solution after the addition of distilled water was then diluted with anhydrous ethanol to (0.9-1.1) wt%.

[0013] In one feasible implementation, the base membrane accounts for 30% to 50% of the mass of the silica-modified permeation membrane.

[0014] Accordingly, the present invention also provides a silica-modified permeation membrane, which is prepared by any of the silica-modified permeation membrane preparation methods described above.

[0015] In one feasible implementation, the BET surface area of ​​the silica-modified permeation membrane is 505 g / m². 2 The silica-modified permeable membrane has a water permeability of 18 L / m³ under a pressure of 1.5 MPa. -2 h -1 .

[0016] Accordingly, the present invention also provides a water treatment system, including a silica-modified permeation membrane prepared by the method described in any one of the above claims.

[0017] Implementing this invention has the following beneficial effects:

[0018] The preparation method of the silica-modified permeable membrane provided in this application embodiment is simple. Since the bifunctional silane itself is heat-resistant, the resulting silica-modified permeable membrane exhibits good heat resistance. Furthermore, the preparation method of the silica-modified permeable membrane provided in this application embodiment introduces SiO2 nanoparticles into the polysilsesquioxane network structure formed by the self-hydrolysis and condensation reaction of the bifunctional silane. The introduction of SiO2 nanoparticles increases the surface area and micropore volume of the polysilsesquioxane network structure through a filling effect, thereby increasing porosity, facilitating water passage through the membrane, reducing the water contact angle, and thus improving permeability. The nanoparticle filler increases the rigidity of the polymer chain through the interaction between the nanoparticles and the polymer. The nanoparticles can restrict the movement of the polymer chain through hydrogen bonds and van der Waals forces with the organic groups (such as amino groups and silanol groups) in the bifunctional silane molecule. This restriction makes it more difficult for the polymer chain to undergo degradation reactions when heated, as higher energy is required to overcome the interaction between the nanoparticles and the polymer chain, thereby improving thermal stability and chlorine resistance. Introducing robust and rigid inorganic SiO2 nanoparticles will stabilize the organically bridged polysilsesquioxane structure through immobilization, thereby increasing the thermal stability of the membrane. Furthermore, embedding the SiO2-filled polysilsesquioxane polymer into the base membrane through vacuum filtration within the membrane pores effectively improves the long-term stability of the membrane. Attached Figure Description

[0019] Figure 1 This is a flowchart of a method for preparing a silica-modified permeable membrane according to an embodiment of the present invention. Detailed Implementation

[0020] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0022] Please refer to Figure 1 The present application discloses a method for preparing a silica-modified permeable membrane, the method comprising the following steps:

[0023] S10. Obtain the base film.

[0024] In one feasible implementation, the base membrane is selected from polysulfone-based membranes, polyethersulfone-based membranes, ceramic-based membranes, polyacrylonitrile-based membranes, polyvinylidene fluoride membranes, polytetrafluoroethylene membranes, polyimide membranes, polyvinyl chloride membranes, polyethylene membranes, or polypropylene membranes. Optionally or preferably, the base membrane is a polysulfone-based membrane or a polyethersulfone-based membrane. Optionally or preferably, the base membrane is a polysulfone-based membrane. Polysulfone has good mechanical properties, including high strength and toughness, which allows it to withstand stretching and other treatments during manufacturing and resist certain pressures and physical damage in practical applications. Polysulfone exhibits excellent resistance to a variety of chemicals, such as acids, alkalis, and some organic solvents, which is important for applications that need to be exposed to various water qualities or chemical environments. This material can maintain its physical properties over a wide temperature range, making it suitable for high-temperature water treatment or other applications that require exposure to temperature changes. Polysulfone materials are generally considered bioinert and do not react with living organisms, making them ideal for industries with strict hygiene requirements, such as pharmaceuticals and food processing. Polysulfone can be processed into desired shapes and sizes through various methods such as injection molding and extrusion, facilitating the production of products with complex structures, such as hollow fiber membranes. By adjusting the preparation conditions, the pore size distribution and surface properties of polysulfone membranes can be controlled to meet the needs of specific separation tasks. Furthermore, certain modification operations can be performed as needed to increase the stability of the bond with modified polysilsesquioxane polymer sols.

[0025] S20. Prepare a mixed organic solution with silica and difunctional silane as the solute.

[0026] In step S20, preparing a mixed organic solution containing a silica solution and a bifunctional silane can be achieved by: preparing separate organic solutions of silica and bifunctional silane, and then mixing the two organic solutions. In a feasible implementation, preparing the mixed organic solution containing a silica solution and a bifunctional silane can also involve: first calculating the required organic solvent, silica, and bifunctional silane based on the concentration of the target mixed organic solution, and weighing the required organic solvent, silica, and bifunctional silane; then adding the weighed silica and bifunctional silane to the organic solvent. The method of addition can be either to add one of the silica and bifunctional silane to the organic solvent first, followed by the other; or to mix the silica and bifunctional silane thoroughly before adding them together to the organic solvent. No limitation is made here.

[0027] In one feasible implementation, silica can be nano-silica. Due to its extremely small size, nano-silica possesses a very large specific surface area. Thus, when nano-silica is incorporated into a polysilsesquioxane network structure through a filling effect, it can maintain the stability of the filling structure while increasing the porosity of the network structure, thereby improving the flux of the silica-modified permeation membrane. Simultaneously, nano-sized silica is also easier to fill into polysilsesquioxane network structures, ensuring the filling effect and efficiency. Furthermore, when nano-silica is added as a filler to polymers or other materials, it can significantly improve the strength, hardness, and wear resistance of the composite material.

[0028] In one feasible implementation, the bifunctional silane is selected from bis[3-(triethoxysilyl)propyl]tetrasulfide (BTESE), bis[3-(triethoxysilyl)propyl]amine (BTESPA), or tetraethoxysilane (TEOS). Optionally or preferably, the bifunctional silane is selected from bis[3-(triethoxysilyl)propyl]tetrasulfide (BTESE) or tetraethoxysilane (TEOS). Testing has shown that silica-modified permeation membranes prepared with BTESE are smoother than those prepared with BTESPA, exhibiting better antifouling properties due to less contaminant adhesion. This is because BTESPA contains amino groups, which undergo protonation under acidic conditions, while BTESE does not, resulting in better chemical stability. The advantages of using TEOS to prepare polysiloxane nanofiltration membranes include: good chemical stability, resistance to acids, alkalis, and solvents; excellent thermal stability, stable structure at high temperatures, and extended membrane life; tunable pore structure to adapt to different separation requirements; and excellent membrane formation performance. Due to the influence of bridging groups in its molecular structure, the membrane prepared by BTESE exhibits superior structural stability at high temperatures compared to TEOS.

[0029] In one feasible implementation, the solvent for the mixed organic solution is ethanol. Ethanol is a polar solvent that dissolves many polar and some nonpolar organic compounds well, making it ideal for preparing solutions of various organic substances. Compared to other organic solvents, such as benzene or chloroform, ethanol is relatively non-toxic and non-flammable, offering a high safety margin. Furthermore, ethanol is a food-grade solvent widely used in the pharmaceutical and cosmetic industries, meaning it is relatively safe for human use. Ethanol can be produced through fermentation from renewable resources (such as corn and sugarcane), making it a bio-based solvent and more environmentally friendly than petroleum-derived organic solvents. Moreover, ethanol is volatile, leaving no harmful residues and reducing environmental impact. Due to its low boiling point (78.37°C), ethanol can be easily separated from the reaction mixture and reused by methods such as distillation, reducing costs and waste emissions. Ethanol is miscible with water in any proportion, which is highly advantageous for reactions requiring partitioning or transfer between aqueous and organic phases. Especially in the process of forming polysilsesquioxane network structures from bifunctional silanes through self-hydrolysis and condensation reactions, the moderating effect of organic solvents and water is required. Ethanol can selectively dissolve reactants without dissolving impurities that may cause side reactions, or its presence can inhibit undesirable side reactions. Furthermore, as a common industrial chemical, ethanol is relatively inexpensive and has a stable supply chain, making it suitable for large-scale production and application.

[0030] In one feasible implementation, the mass concentration of the bifunctional silane in the mixed organic solution is 2 wt% to 8 wt%. Optionally or preferably, the mass concentration of the bifunctional silane in the mixed organic solution is 3 wt% to 7 wt%. Optionally or preferably, the mass concentration of the bifunctional silane in the mixed organic solution is 4 wt% to 7 wt%. Optionally or preferably, the mass concentration of the bifunctional silane in the mixed organic solution is 4 wt%, 5 wt%, 6 wt%, or 7 wt%. Optionally or preferably, the mass concentration of the bifunctional silane in the mixed organic solution is 6 wt%. 6 wt% is an experimentally verified optimal ratio. This concentration helps control the rate of silane hydrolysis and condensation reactions, ensuring that the reaction is neither too fast nor too slow, thereby obtaining a uniform and stable modified polysilsesquioxane polymer sol. This ensures sufficient crosslinking density to impart good mechanical strength to the silica-modified permeation membrane without excessive crosslinking leading to increased brittleness or pore blockage. An appropriate amount of silane can give the membrane surface the desired roughness, wettability, and charge properties. A 6wt% concentration represents the minimum amount of silane used while ensuring performance, avoiding unnecessary material waste and reducing production costs. Properly controlling the silane concentration can also reduce unnecessary side reactions, decrease the amount of byproducts, and simplify subsequent processing steps. Determining the specific silane concentration makes the entire preparation process more standardized, reducing uncertainties caused by parameter adjustments and improving production efficiency.

[0031] In one feasible implementation, the mass ratio of silicon dioxide to difunctional silane in the mixed organic solution is (0.02–0.03):1. Optionally or preferably, the mass ratio of silicon dioxide to difunctional silane in the mixed organic solution is (0.021–0.029):1. Optionally or preferably, the mass ratio of silicon dioxide to difunctional silane in the mixed organic solution is (0.021–0.025):1. Optionally or preferably, the mass ratio of silica to bifunctional silane in the mixed organic solution is 0.023:1. This ratio of 0.023:1 ensures that the silica filled into the polysilsesquioxane network structure reaches an appropriate proportion, achieving optimal filling effect. Under this condition, the silica filling effect can be guaranteed, the stability of the bond between the polysilsesquioxane network structure and silica can be ensured, and excessive addition of silica will not lead to increased brittleness, mechanical structure, or other adverse effects on the silica-modified permeable membrane.

[0032] S30. Distilled water is slowly added dropwise to the mixed organic solution, and stirring is performed to obtain modified polysilsesquioxane polymer sol.

[0033] In step S30, a modified polysilsesquioxane polymer sol is obtained by adding distilled water dropwise to the mixed organic solution and applying a stirring operation. Specifically, in the presence of water (distilled water), the bifunctional silane in the mixed organic solvent undergoes hydrolysis of ethoxy (-OEt) or -Si(OC2H5)3 groups to generate silanol (-Si-OH) groups. The silanol groups generated by hydrolysis then condense to form siloxane bonds (-Si-O-Si-), forming a polysilsesquioxane network structure. Simultaneously, SiO2 nanoparticles in the mixed organic solution fill the polysilsesquioxane network structure through a filling effect, forming a modified polysilsesquioxane structure. The introduction of SiO2 nanoparticles increases the surface area and micropore volume of the polysilsesquioxane network, thereby increasing porosity, facilitating water passage through the membrane, reducing the water contact angle, and thus improving water permeability. Nanoparticle fillers increase the rigidity of polymer chains through interactions between nanoparticles and polymers. Nanoparticles can restrict polymer chain movement through hydrogen bonds and van der Waals forces with organic groups (such as amines and silanols) in bifunctional silane (BTESPA, BTESE, or TEOS) molecules. This restriction makes the polymer chains more susceptible to degradation under heat, as higher energy is required to overcome the interactions between the nanoparticles and the polymer chains, thus improving thermal stability. Introducing robust and rigid inorganic SiO2 nanoparticles will stabilize the organically bridged polysilsesquioxane structure through immobilization, further increasing the thermal stability of the film.

[0034] In one feasible implementation, during the slow dropwise addition of distilled water to the mixed organic solution, the molar ratio of distilled water to the bifunctional silane is (70-50):1. Optionally or preferably, the molar ratio of distilled water to the bifunctional silane is (70-55):1. Optionally or preferably, the molar ratio of distilled water to the bifunctional silane is (70-60):1. Optionally or preferably, the molar ratio of distilled water to the bifunctional silane is 70:1, 65:1, or 60:1. Slowly adding distilled water can effectively control the rate of silane hydrolysis and condensation reactions. A higher distilled water ratio (e.g., 70:1) helps to slow down the reaction rate, making the reaction more uniform and controllable. By gradually adding distilled water, localized temperature increases caused by rapid reactions can be prevented, thereby reducing the formation of byproducts. Different molar ratios affect the time required for the system to transition from a liquid to a gel state. Choosing an appropriate ratio can help find the optimal gelation conditions to ensure a uniform gel structure. An appropriate proportion of distilled water helps to better disperse silane molecules in the solvent, forming a homogeneous precursor solution, which is crucial for the consistency and quality of silica-modified permeable membranes. Excessive silane can lead to rapid polymerization and precipitation, while an appropriate proportion of distilled water can maintain solution stability and prevent unnecessary precipitate formation. Different molar ratios affect the microstructural characteristics of the final material, such as porosity and pore size distribution, thereby influencing its permeability, mechanical strength, and other properties.

[0035] In one feasible implementation, the stirring operation includes the following steps:

[0036] The mixed organic solution after adding distilled water was stirred at 20℃-25℃ for 1.5-2.5 hours, and then diluted with anhydrous ethanol to (0.9-1.1)wt%. Alternatively, the modified polysilsesquioxane polymer sol was diluted to (0.9-1.1)wt%.

[0037] In one feasible implementation, the stirring speed is low (200-400 rpm). This helps avoid violent local reaction hotspots, reduces the formation of byproducts, ensures a more mild and controllable reaction system, and avoids damaging the formed modified polysilsesquioxane network structure. The mixed organic solution after the addition of distilled water is then diluted to (0.9-1.1) wt% with anhydrous ethanol; in other words, the modified polysilsesquioxane polymer sol is diluted to a concentration of (0.9-1.1) wt% for filtration. Because an excessively high concentration of the prepared modified polysilsesquioxane polymer sol is not conducive to subsequent filtration operations and can easily cause problems such as unevenness or excessive thickness, diluting the mixed organic solution after the addition of distilled water with anhydrous ethanol to (0.9-1.1) wt% facilitates the subsequent filtration steps and improves the uniformity and reliability of the prepared silica-modified permeation membrane.

[0038] S40. The modified polysilsesquioxane polymer sol is prepared onto the base membrane by vacuum filtration to obtain a silica-modified permeation membrane.

[0039] In step S40, the filtration operation may include the following operations:

[0040] First, prepare the base membrane to be modified, ensuring its surface is clean and flat to guarantee good filtration performance. Pre-treatment of the base membrane (such as plasma treatment or chemical modification) can enhance its adhesion to the modifying material.

[0041] Prepare a modified polysilsesquioxane polymer sol. When ready for use, the modified polysilsesquioxane polymer sol can be refrigerated at 4°C to maintain stable performance.

[0042] Prepare the filtration equipment;

[0043] Filtration process: Carefully place the base membrane on the filter paper, ensuring it is flat and not curled;

[0044] Slowly pour an appropriate amount of modified polysilsesquioxane sol onto the base film to evenly cover the entire surface;

[0045] Start the vacuum pump to begin filtration; at this time, the solvent will be rapidly drawn into the filtration flask, while the solid components will gradually deposit and embed into the base membrane to form an integrated silica-modified permeation membrane. Control the filtration time and pressure to avoid uneven filtration or damage to the base membrane caused by excessive speed.

[0046] Post-processing: After filtration, the silica-modified permeation membrane is removed. Depending on the situation, post-processing steps such as drying and curing may be required to stabilize the structure.

[0047] Vacuum filtration enables rapid evaporation and uniform distribution of the sol within a short time, embedding the solid portion of the modified polysilsesquioxane polymer sol into the base membrane. By adjusting parameters such as sol concentration, filtration time, and vacuum level, the ratio of the final solid portion of the modified polysilsesquioxane polymer sol to the base membrane can be precisely controlled, optimizing membrane performance. The negative pressure generated during filtration helps the sol to contact the base membrane more closely, increasing the interaction force between them and thus improving coating adhesion. Compared to brushing or other manual coating methods, vacuum filtration better avoids defects such as bubbles and streaks, preventing peeling. Suitable for large-scale production: Once the process parameters are determined, vacuum filtration is easily automated and scaled up for production, making it suitable for the efficient and stable preparation of silica-modified permeable membranes in industrial manufacturing environments.

[0048] In one feasible implementation, the base membrane accounts for 30%-50% of the mass percentage of the silica-modified permeation membrane. Optionally or preferably, the base membrane accounts for 30%-40% of the mass percentage of the silica-modified permeation membrane. Optionally or preferably, the base membrane accounts for 30%, 35%, or 40% of the mass percentage of the silica-modified permeation membrane. Optionally or preferably, the base membrane accounts for 35% of the mass percentage of the silica-modified permeation membrane. The initial concentration or amount of the modified polysilsesquioxane polymer sol can be adjusted according to the required mass ratio so that a silica-modified permeation membrane meeting the required proportion can be obtained after filtration. By adjusting parameters such as filtration time and vacuum degree, it can be ensured that the sol is uniformly and completely deposited on the base membrane, while avoiding over-filtration that could damage the base membrane or cause uneven filtration. A mass percentage of 35% can improve permeation flux, selectivity, or mechanical strength, while maintaining the reliability of the basic properties of the silica-modified permeation membrane as a permeation membrane.

[0049] The preparation method of the silica-modified permeable membrane provided in this application embodiment is simple. Since the bifunctional silane itself is heat-resistant, the resulting silica-modified permeable membrane exhibits good heat resistance. Furthermore, the preparation method of the silica-modified permeable membrane provided in this application embodiment introduces SiO2 nanoparticles into the polysilsesquioxane network structure formed by the self-hydrolysis and condensation reaction of the bifunctional silane. The introduction of SiO2 nanoparticles increases the surface area and micropore volume of the polysilsesquioxane network structure through a filling effect, thereby increasing porosity, facilitating water passage through the membrane, reducing the water contact angle, and thus improving permeability. The prepared silica-modified permeable membrane has a high flux and can treat more water in the same amount of time. The nanoparticle filler increases the rigidity of the polymer chain through the interaction between the nanoparticles and the polymer. The nanoparticles can restrict the movement of the polymer chain through hydrogen bonds and van der Waals forces with the organic groups (such as amino groups and silanol groups) in the bifunctional silane molecule. This limitation makes it more difficult for the polymer chains to degrade when heated, as higher energy is required to overcome the interaction between the nanoparticles and the polymer chains, thus improving thermal stability and chlorine resistance. Introducing robust and rigid inorganic SiO2 nanoparticles will stabilize the organically bridged polysilsesquioxane structure through immobilization, which will increase the membrane's thermal stability. Furthermore, embedding the SiO2-filled polysilsesquioxane polymer into the base membrane through vacuum filtration within the membrane pores effectively improves the membrane's long-term stability.

[0050] The silica-modified permeation membrane of one embodiment is prepared by any of the above-described methods for preparing silica-modified permeation membranes.

[0051] The silica-modified permeation membrane of this invention has superior comprehensive performance in terms of nanofiltration performance, permeability, chlorine resistance, heat resistance and stability, which is conducive to its widespread application.

[0052] In one feasible implementation, the BET surface area of ​​the silica-modified permeation membrane is 505 g / m². 2 The silica-modified permeable membrane has a water permeability of 18 L / m³ under a pressure of 1.5 MPa. -2 h -1 Such a silica-modified permeation membrane is prepared by the following method to obtain a polysulfone membrane: A mixed organic solution of silica and a bifunctional silane is prepared, wherein the solvent is ethanol, the bifunctional silane is BTESE, the mass concentration of BTESE in the mixed organic solution is 6 wt%, and the mass ratio of silica to BTESE is 2.3%; distilled water is slowly added dropwise to the above solution, the molar ratio of distilled water to the bifunctional silane is 60:1; the mixed organic solution after the addition of distilled water is stirred at 23°C for 2 hours, and then diluted to 1 wt% with anhydrous ethanol to obtain a modified polysilsesquioxane polymer sol, which is stored at 4°C for later use; the modified polysilsesquioxane polymer sol is filtered to prepare the base membrane to obtain a silica-modified permeation membrane, wherein the polysulfone membrane accounts for 35% of the mass percentage of the silica-modified permeation membrane. The silica-modified permeation membrane prepared in this way has a high flux, can process more water in the same amount of time, has a stable structure, and is resistant to high temperature and chlorine, which helps to handle different situations. It has good adaptability, optimal overall performance, and is conducive to wide application.

[0053] One embodiment of the water treatment system includes a silica-modified permeation membrane prepared by any of the above-described methods.

[0054] The water treatment system of this invention has superior overall performance in terms of nanofiltration performance, flow rate, chlorine resistance, heat resistance, and stability, which is conducive to its widespread application.

[0055] Referring to the above implementation details, in order to make the technical solution of this application more specific, clear, and easy to understand, examples of the technical solution of this application are given below. However, it should be noted that the content to be protected by this application is not limited to the following embodiments.

[0056] Example 1:

[0057] Obtain polysulfone-based films;

[0058] A mixed organic solution containing silica and a difunctional silane was prepared, wherein the solvent was ethanol, the difunctional silane was BTESE, the mass concentration of BTESE in the mixed organic solution was 6 wt%, and the mass ratio of silica to BTESE was 2.3%.

[0059] Distilled water is slowly added dropwise to the above solution, wherein the molar ratio of the distilled water to the bifunctional silane is 60:1;

[0060] The mixed organic solution after adding distilled water was stirred at 23°C for 2 hours.

[0061] The mixed organic solution after adding distilled water was then diluted to 1 wt% with anhydrous ethanol to obtain the modified polysilsesquioxane polymer sol, which was stored at 4°C for later use.

[0062] The modified polysilsesquioxane polymer sol was prepared onto the base membrane by vacuum filtration to obtain a silica-modified permeation membrane.

[0063] The polysulfone membrane accounts for 35% of the mass of the silica-modified permeation membrane.

[0064] Example 2

[0065] It is basically the same as Example 1, except that the base film is a polyethersulfone base film.

[0066] Example 3

[0067] It is basically the same as Example 1, except that the molar ratio of the distilled water to the bifunctional silane is 50:1.

[0068] Example 4

[0069] The molar ratio of distilled water to the bifunctional silane is 70:1.

[0070] Example 5

[0071] The process is essentially the same as in Example 1, except that the mixed organic solution after the addition of distilled water is diluted to 0.9 wt% with anhydrous ethanol.

[0072] Example 6

[0073] The process is essentially the same as in Example 1, except that the mixed organic solution after the addition of distilled water is diluted to 1.1 wt% with anhydrous ethanol.

[0074] Comparative Example 1

[0075] Distilled water was slowly added dropwise to a 5 wt% BTESE ethanol solution until the alkoxysilane / H₂O molar ratio reached 1 / 60. The reaction mixture was stirred at room temperature for 2 hours to promote polymerization. The reactants were then diluted to 1 wt% with anhydrous ethanol and stored at 4°C until membrane preparation. A polysulfone membrane was used as the supporting membrane. The prepared sol solution was brought to room temperature and poured onto the supporting membrane surface for 30 seconds. After removing excess sol solution by decantation, the membrane was air-dried at room temperature for 10 minutes. This coating process was repeated twice, and the resulting composite membrane was calcined at 150°C for 10 minutes to promote further gelation. After calcination, the composite membrane was cooled to room temperature and washed with distilled water for later use.

[0076] Performance testing:

[0077] 1. Nanofiltration performance testing

[0078] Under a pressure of 1.5 MPa, using an effective filtration area of ​​25 cm² 2 Evaluation of the separation performance and water flux (J, L*m) of the cross-flow filtration device for NF membranes -2 h -1 ) and salt rejection rate (R, %), by as well as Where V(L) is the volume of permeate, and A(m) is the volume of permeate. 2 ) is the effective filtration area, Δt(h) is the filtration time, and C is the effective filtration area. p (ppm) and C f (ppm) represents the salt concentration of the permeate and the feed solution, respectively.

[0079] 2. Detection of BET surface area (specific surface area) and micropore volume

[0080] Nitrogen adsorption / desorption isotherm measurements were performed using a BELSORP-MAX II 034VP-MZ (MicrotracBEL) instrument. The BET area and pore volume were determined by combining the actual BET theoretical model and the pore structure analysis model.

[0081] 3. Chlorine resistance

[0082] The permeation membrane samples prepared in the examples and comparative examples were completely immersed in a 1000 ppm sodium hypochlorite (NaClO) aqueous solution and soaked at room temperature for 10 hours.

[0083] 4. Heat resistance

[0084] The membrane devices prepared in the examples and comparative examples were placed in a 2000ppm NaCl water bath, and the temperature was gradually increased from 25°C to 100°C. The temperature was maintained for 180 minutes at each temperature, and then the rejection rate and flux were tested at the selected temperature nodes.

[0085] 5. Stability performance

[0086] The membranes prepared in the examples and comparative examples were assembled into nanofiltration devices and used for 10 months to compare water permeability and salt rejection rate.

[0087] The experimental results are shown in the table below:

[0088]

[0089] Based on the above results, the silica-modified permeation membranes provided in Examples 1 to 6 of this application all exhibit good separation performance after testing. Among them, the silica-modified permeation membrane prepared in Example 1 has the best performance. Since bifunctional silanes are inherently heat-resistant, the prepared silica-modified permeation membranes have good heat resistance. The preparation method of the silica-modified permeation membranes provided in this application introduces SiO2 nanoparticles into the polysilsesquioxane network structure formed by the self-hydrolysis and condensation reaction of bifunctional silanes. The introduction of SiO2 nanoparticles increases the surface area and micropore volume of the polysilsesquioxane network structure through a filling effect, thereby increasing porosity, facilitating water passage through the membrane, reducing the water contact angle, and thus improving permeability. The nanoparticle filler increases the rigidity of the polymer chain through the interaction between the nanoparticles and the polymer. The nanoparticles can restrict the movement of the polymer chain through hydrogen bonds and van der Waals forces with the organic groups (such as amino groups and silanol groups) in the bifunctional silane (BTESE) molecule. This limitation makes it more difficult for polymer chains to undergo degradation reactions when heated, as higher energy is required to overcome the interaction between nanoparticles and polymer chains, thus improving thermal stability. The relatively high bond energy of the silicon-oxygen bond provides some resistance to the attack of active chlorine. During chlorine treatment, the silicon-oxygen bond network acts as a support and protector, slowing down the erosion of the organic components by active chlorine. Although the organic components may be affected to some extent, the presence of the silicon-oxygen bond network helps maintain the overall structure of the membrane, allowing it to retain its separation performance to a certain extent, thus exhibiting good chlorine resistance. Introducing robust and rigid inorganic SiO2 nanoparticles will stabilize the organically bridged polysilsesquioxane structure through immobilization, which will increase the thermal stability of the membrane. Furthermore, embedding the SiO2-filled polysilsesquioxane polymer into the base membrane through vacuum filtration within the membrane pores effectively improves the long-term stability of the membrane.

[0090] The basic concepts have been described above. Obviously, for those skilled in the art, the detailed disclosure above is merely illustrative and does not constitute a limitation of this specification. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements, and corrections to this specification. Such modifications, improvements, and corrections are suggested in this specification and therefore remain within the spirit and scope of the exemplary embodiments described herein.

[0091] Furthermore, this specification uses specific terms to describe embodiments thereof. For example, "an embodiment," "one embodiment," and / or "some embodiments" refer to a particular feature, structure, or characteristic associated with at least one embodiment of this specification. Therefore, it should be emphasized and noted that references to "an embodiment," "one embodiment," or "an alternative embodiment" in different locations throughout this specification do not necessarily refer to the same embodiment. Moreover, certain features, structures, or characteristics in one or more embodiments of this specification can be appropriately combined.

[0092] Furthermore, unless expressly stated in the claims, the order of processing elements and sequences, the use of numbers and letters, or other names described in this specification are not intended to limit the order of the processes and methods described herein. Although some inventive embodiments that are currently considered useful have been discussed by way of various examples in the foregoing disclosure, it should be understood that such details are for illustrative purposes only, and the appended claims are not limited to the disclosed embodiments. Rather, the claims are intended to cover all modifications and equivalent combinations that conform to the substance and scope of the embodiments described herein.

[0093] Similarly, it should be noted that, in order to simplify the description disclosed herein and thus aid in the understanding of one or more embodiments of the invention, the foregoing description of embodiments in this specification may sometimes combine multiple features into a single embodiment, drawing, or description thereof. However, this method of disclosure does not imply that the subject matter of this specification requires more features than those mentioned in the claims. In fact, the embodiments contain fewer features than all the features of a single embodiment disclosed above.

[0094] In some embodiments, numbers describing the quantity of components and attributes are used. It should be understood that such numbers used in the description of embodiments are modified in some examples with the terms "approximately," "approximately," or "generally." Unless otherwise stated, "approximately," "approximately," or "generally" indicates that the numbers are allowed to vary by ±20%. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximate values, which may be changed depending on the characteristics required by individual embodiments. In some embodiments, numerical parameters should take into account specified significant digits and employ a general method of digit reservation. Although the numerical ranges and parameters used to confirm their breadth of range in some embodiments of this specification are approximate values, in specific embodiments, such values ​​are set as precisely as feasible.

[0095] For each patent, patent application, patent application publication, and other material, such as articles, books, specifications, publications, and documents, referenced in this specification, the entire contents of which are incorporated herein by reference. This excludes historical application documents that are inconsistent with or conflict with the content of this specification, as well as documents that limit the broadest scope of the claims in this specification (currently or subsequently appended to this specification). It should be noted that in the event of any inconsistency or conflict between the descriptions, definitions, and / or terminology used in the supplementary materials to this specification and the content of this specification, the descriptions, definitions, and / or terminology used in this specification shall prevail.

[0096] Finally, it should be understood that the embodiments described in this specification are merely illustrative of the principles of the embodiments described herein. Other variations may also fall within the scope of this specification. Therefore, alternative configurations of the embodiments described herein are intended to be illustrative rather than limiting, and should be considered consistent with the teachings of this specification. Accordingly, the embodiments described herein are not limited to those explicitly introduced and described herein.

Claims

1. A method for preparing a silica-modified permeable membrane, characterized in that, The preparation method includes the following steps: Obtain the base film. A mixed organic solution containing nano-silica and difunctional silane as solutes was prepared. Distilled water was slowly added dropwise to the mixed organic solution while stirring to obtain a modified polysilsesquioxane polymer sol. The modified polysilsesquioxane polymer sol was prepared onto the base membrane by vacuum filtration to obtain a silica-modified permeation membrane; The base membrane is selected from polysulfone-based membranes or polyethersulfone-based membranes; The base membrane accounts for 30% to 50% of the mass of the silica-modified permeable membrane.

2. The method for preparing the silica-modified permeation membrane according to claim 1, characterized in that, The bifunctional silane is selected from bis[3-(triethoxysilyl)propyl]tetrasulfide, bis[3-(triethoxysilyl)propyl]amine, or tetraethoxysilane.

3. The method for preparing the silica-modified permeation membrane according to claim 2, characterized in that, The mass concentration of the bifunctional silane in the mixed organic solution is 2wt%~8wt%; In the mixed organic solution, the mass ratio of silicon dioxide to bifunctional silane is (0.02~0.03):

1.

4. The method for preparing the silica-modified permeation membrane according to claim 2, characterized in that, In the operation of slowly adding distilled water to the mixed organic solution, the molar ratio of the distilled water to the bifunctional silane is (70-50):

1.

5. The method for preparing the silica-modified permeation membrane according to claim 2, characterized in that, The stirring operation includes the following steps: After adding distilled water, stir the mixed organic solution at 20℃-25℃ for 1.5-2.5 hours. The mixed organic solution after the addition of distilled water was then diluted with anhydrous ethanol to (0.9-1.1) wt%.

6. A silica-modified permeation membrane, characterized in that, The silica-modified permeation membrane was prepared using any one of the preparation methods described in claims 1 to 5.

7. The silica-modified permeation membrane according to claim 6, characterized in that, The BET surface area of ​​the silica-modified permeable membrane is 505 g / m². 2 The silica-modified permeable membrane has a water permeability of 18 L / m³ under a pressure of 1.5 MPa. - 2 h -1 .

8. A water treatment system, characterized in that, The silica-modified permeation membrane includes the silica-modified permeation membrane prepared by the method described in any one of claims 1 to 5.

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