Silicon dioxide modified permeable membrane, preparation method thereof and water treatment system

Abstract

The invention discloses a silicon dioxide modified permeable membrane, a preparation method thereof and a water treatment system, and the preparation method comprises the following steps: obtaining a base membrane, preparing a mixed organic solution of which solute is silicon dioxide and bifunctional silane, slowly dropwise adding distilled water into the mixed organic solution, and performing stirring operation to obtain the silicon dioxide modified permeable membrane. A modified polysilsesquioxane polymerized sol is obtained; the modified polysilsesquioxane polymerized sol is prepared to the base membrane through suction filtration, and the silicon dioxide modified permeable membrane is obtained. The preparation method is simple in process, and the prepared silicon dioxide modified permeable membrane is large in flux, capable of treating more water within the same time, stable in structure, resistant to high temperature and chlorine, beneficial to treatment of different conditions, good in adaptability and beneficial to wide application.

Description

Technical Field

[0001] The invention relates to the field of water treatment, and in particular to a silicon dioxide modified permeable membrane and a preparation method thereof and a water treatment system. Background Art

[0002] Reverse Osmosis Membrane (RO membrane) is a semipermeable membrane that allows water molecules to pass through under applied pressure while blocking dissolved salts, organic matter and other impurities. It is the core component of reverse osmosis technology and is widely used in many fields such as seawater desalination, drinking water purification, and industrial wastewater treatment. Polyamide-derived membranes are widely used in the field of reverse osmosis membranes due to their excellent separation properties. However, polyamide-derived membranes generally have low resistance to high temperatures and chlorine, which limits their application. In addition, the flux of reverse osmosis membranes made of other materials is generally small, and the water treatment efficiency is low. Summary of the invention

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

[0004] In order to solve the above technical problems, the present invention provides a method for preparing a silica-modified permeable membrane, which comprises the following steps: obtaining a base membrane; preparing a mixed organic solution whose solute is silica and a bifunctional silane; slowly dropping distilled water into the mixed organic solution and stirring the solution to obtain a modified polysilsesquioxane polymer sol; and preparing the modified polysilsesquioxane polymer sol onto the base membrane by suction filtration to obtain a silica-modified permeable membrane.

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

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

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

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

[0009] In a feasible implementation, 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.

[0010] In a feasible implementation, the stirring operation comprises the following steps:

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

[0012] Then, the mixed organic solution to which the distilled water has been added is diluted with anhydrous ethanol to (0.9-1.1) wt %.

[0013] In a feasible implementation, the mass percentage of the base film to the silica-modified permeable membrane is 30% to 50%.

[0014] Correspondingly, the present invention also provides a silica-modified permeable membrane, which is prepared by any of the above-mentioned methods for preparing a silica-modified permeable membrane.

[0015] In a feasible implementation, the BET surface area of ​​the silica-modified permeable membrane is: 505 g / m 2 The water permeability of the silica modified permeable membrane at a pressure of 1.5 MPa is: 18 L*m -2 h -1 .

[0016] Correspondingly, the present invention also provides a water treatment system, comprising a silica-modified permeable membrane prepared by any of the above-mentioned methods for preparing a silica-modified permeable membrane.

[0017] The implementation of the present invention has the following beneficial effects:

[0018] The preparation method of the above-mentioned silica-modified permeable membrane provided by the present application embodiment is simple in process, and because the bifunctional silane itself is resistant to high temperature, therefore, the obtained silica-modified permeable membrane has good heat resistance, and the preparation method of the silica-modified permeable membrane provided by the present application embodiment, by SiO2 nanoparticles are introduced into the polysilsesquioxane network structure formed by the bifunctional silane by self hydrolysis and polycondensation reaction, SiO2 nanoparticles are introduced to increase the surface area and micropore volume of the polysilsesquioxane network structure by the filling effect, thereby increasing porosity, being conducive to water passing through the film, reducing the water contact angle, thereby improving water permeability. The nanoparticle filler increases the rigidity of the polymer chain by the interaction between the nanoparticles and the polymer, and the nanoparticles can interact with the hydrogen bonds, van der Waals forces, etc. between the organic groups (such as amine groups, silanol groups, etc.) in the bifunctional silane molecules, and limit the movement of the polymer chain. This restriction makes it more difficult for the polymer chain to undergo degradation reaction when heated, because higher energy is needed to overcome the interaction between the nanoparticles and the polymer chain, thereby improving thermal stability and chlorine resistance. The introduction of strong and rigid inorganic SiO2 nanoparticles will stabilize the organic bridged polysilsesquioxane structure by immobilization, which will increase the thermal stability of the membrane. The SiO2-filled polysilsesquioxane polymer is embedded into the base membrane by filtration in the membrane pores, effectively improving the long-term stability of the membrane. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0020] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0022] Please refer to Figure 1 , a method for preparing a silica-modified permeable membrane according to an embodiment of the present application, the preparation method comprising the following steps:

[0023] S10, obtaining a basement membrane.

[0024] In a feasible implementation, the base membrane is selected from a polysulfone base membrane, a polyethersulfone base membrane, a ceramic base membrane, a polyacrylonitrile base membrane, a polyvinylidene fluoride membrane, a polytetrafluoroethylene membrane, a polyimide membrane, a polyvinyl chloride membrane, a polyethylene membrane or a polypropylene membrane. Optionally or preferably, the base membrane is a polysulfone base membrane or a polyethersulfone base membrane. Optionally or preferably, the base membrane is a polysulfone base membrane. Polysulfone has good mechanical properties, including high strength and toughness, which enables it to withstand stretching and other treatments during the manufacturing process, and can also resist certain pressures and physical damage in practical applications. Polysulfone exhibits excellent tolerance to a variety of chemical substances, for example, it is resistant to acids, alkalis and some organic solvents, which is very important for applications that require contact with various water qualities or chemical environments. This material can keep its physical properties unchanged over a wide temperature range, and is suitable for high temperature water treatment or other application scenarios that need to withstand temperature changes. Polysulfone materials are generally considered to be biologically inert and will not react with organisms, so they are very suitable for industries such as medicine and food processing that have strict requirements on sanitary conditions. Polysulfone can be processed into the desired shape and size by injection molding, extrusion and other methods, which is convenient for the production of complex structure products, such as hollow fiber membranes. By adjusting the preparation conditions, the pore size distribution and surface characteristics of the polysulfone membrane can be controlled to meet the needs of specific separation tasks. Certain modification operations can also be performed according to needs to increase the stability of the combination with the modified polysilsesquioxane polymer sol.

[0025] S20, preparing a mixed organic solution containing silicon dioxide and bifunctional silane as solute.

[0026] In step S20, the preparation of a mixed organic solution in which the solute is a silica solution and a bifunctional silane can be: prepare a silica solution and an organic solution of a bifunctional silane respectively, and then mix the two organic solutions. In a feasible implementation, the preparation of a mixed organic solution in which the solute is a silica solution and a bifunctional silane can also be: first calculate the required organic solvent, silica and bifunctional silane according to the concentration of the target mixed organic solution, weigh the required organic solvent, silica and bifunctional silane; then add the weighed silica and bifunctional silane to the organic solvent, wherein the addition method can be to first add one of the silica and bifunctional silane to the organic solvent first, and then add the other; or first mix the silica and bifunctional silane evenly, and then add them together to the organic solvent, which is not limited here.

[0027] In a feasible implementation, the silica can be nano-silica. Due to its extremely small size, nano-silica has a very large specific surface area. In this way, when nano-silica is filled into the polysilsesquioxane network structure through the filling effect, it can not only maintain the stability of the filling structure, but also increase the porosity of the network structure, thereby improving the flux of the silica-modified permeable membrane. At the same time, nano-scale silica is also easier to fill into the polysilsesquioxane network structure to ensure the filling effect and efficiency. In addition, when nano-silica is added to polymers or other materials as a filler, the strength, hardness and wear resistance of the composite material can be significantly improved.

[0028] In a 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). After inspection, the silica-modified permeable membrane prepared by BTESE is smoother than the membrane prepared by BTESPA, and pollutants are not easy to adhere, showing good anti-fouling performance. This is because BTESPA contains amino groups, which will be protonated under acidic conditions, while BTESE does not, so BTESE has better chemical stability. The advantages of using TEOS to prepare polysiloxane nanofiltration membranes are: good chemical stability, resistance to acids, alkalis and solvents; excellent thermal stability, stable structure at high temperatures and extended membrane life; adjustable pore structure to meet different separation requirements; and good film-forming performance. The membrane prepared by BTESE has better structural stability than TEOS at high temperature due to the influence of the bridging groups in its molecular structure.

[0029] In a feasible implementation, the solvent of the mixed organic solution is ethanol. Ethanol is a polar solvent that can dissolve many polar and partially non-polar organic compounds well, which makes it very suitable for preparing solutions of various organic substances. Compared with other organic solvents, such as benzene or chloroform, ethanol is relatively non-toxic and non-flammable, and has a high safety margin. In addition, ethanol is a food-grade solvent and is widely used in the pharmaceutical and cosmetic industries, which means that it is safer for the human body. Ethanol can be produced by fermentation of renewable resources (such as corn, sugarcane, etc.), and is a bio-based solvent that is more environmentally friendly than petroleum-derived organic solvents. Moreover, ethanol is easy to volatilize, does not leave harmful residues, and reduces the impact on the environment. Due to its low boiling point (78.37°C), ethanol can be easily separated from the reaction mixture by distillation and reused, reducing costs and reducing waste emissions. Ethanol can be miscible with water in any proportion, which is very beneficial for reactions that need to be distributed or transferred between aqueous and organic phases. Especially in the process of forming a polysilsesquioxane network structure by hydrolysis and polycondensation of bifunctional silane, the regulating effect of organic solvent 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. At the same time, as a common industrial chemical, ethanol is relatively cheap and has a stable supply chain, which is suitable for large-scale production and application.

[0030] In a feasible implementation, the mass concentration of the bifunctional silane in the mixed organic solution is 2wt% to 8wt%. Optionally or preferably, the mass concentration of the bifunctional silane in the mixed organic solution is 3wt% to 7wt%. Optionally or preferably, the mass concentration of the bifunctional silane in the mixed organic solution is 4wt% to 7wt%. Optionally or preferably, the mass concentration of the bifunctional silane in the mixed organic solution is 4wt%, 5wt%, 6wt% or 7wt%. Optionally or preferably, the mass concentration of the bifunctional silane in the mixed organic solution is 6wt%. 6wt% is an optimal ratio verified by experiments. This concentration helps to control the speed of silane hydrolysis and condensation reaction, so that the reaction is neither too fast nor too slow, thereby obtaining a uniform and stable modified polysilsesquioxane polymer sol. It can ensure sufficient crosslinking density to give the silica modified permeable membrane good mechanical strength, but it will not be excessively crosslinked to cause increased brittleness or pore clogging. The right amount of silane can give the membrane surface the desired roughness, wettability and charge characteristics. The concentration of 6wt% is the result of minimizing the amount of silane while ensuring performance, avoiding unnecessary material waste and reducing production costs. Reasonable control of silane concentration can also reduce unnecessary side reactions, reduce the amount of by-products generated, and simplify subsequent processing steps. After determining the specific silane concentration, the entire preparation process is more standardized, reducing the uncertainty caused by parameter adjustment and improving production efficiency.

[0031] In a feasible implementation, it is characterized in that, in the mixed organic solution, the mass ratio of silicon dioxide to bifunctional silane is (0.02-0.03): 1. Optionally or preferably, in the mixed organic solution, the mass ratio of silicon dioxide to bifunctional silane is (0.021-0.029): 1. Optionally or preferably, in the mixed organic solution, the mass ratio of silicon dioxide to bifunctional silane is (0.021-0.025): 1. Optionally or preferably, in the mixed organic solution, the mass ratio of silica to bifunctional silane is 0.023:1. Such a ratio of 0.023:1 allows the silica filled into the polysilsesquioxane network structure to reach an appropriate ratio and have an optimal filling effect. Under this condition, the silica filling effect can be achieved and the stability of the combination of the polysilsesquioxane network structure and silica can be guaranteed, without increasing the brittleness of the silica-modified permeable membrane, causing mechanical structure or other adverse effects due to excessive addition of silica.

[0032] S30, slowly adding distilled water to the mixed organic solution, and performing stirring operation to obtain a modified polysilsesquioxane polymer sol.

[0033] Step S30, by dropping distilled water into the mixed organic solution and applying stirring operation, a modified polysilsesquioxane polymer sol can be obtained. Specifically, in the presence of water (distilled water), the bifunctional silane in the mixed organic solvent, ethoxy (-OEt) or -Si(OC2H5)3 and other groups are first hydrolyzed to generate silanol (-Si-OH) groups, and the silanol groups generated by hydrolysis are then polycondensed to form silicon oxygen bonds (-Si-O-Si-) to form a polysilsesquioxane network structure. At the same time, the SiO2 nanoparticles in the mixed organic solution are filled in the polysilsesquioxane network structure through the 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 the porosity, facilitating water to pass through the membrane, reducing the water contact angle, and thus improving the water permeability. Nanoparticle fillers increase the rigidity of polymer chains through interactions between nanoparticles and polymers. Nanoparticles can restrict the movement of polymer chains through hydrogen bonding, van der Waals forces, and other interactions with organic groups (such as amines, silanols, etc.) in difunctional silane (BTESPA, BTESE, or TEOS) molecules. This restriction makes it more difficult for the polymer chain to degrade when heated because higher energy is required to overcome the interactions between the nanoparticles and the polymer chains, thereby improving thermal stability. The introduction of strong and rigid inorganic SiO2 nanoparticles will stabilize the organic bridged polysilsesquioxane structure through immobilization, which will increase the thermal stability of the film.

[0034] In a feasible implementation, in the operation of slowly dropping distilled water into the mixed organic solution, the molar ratio of the distilled water to the bifunctional silane is (70-50):1. Optionally or preferably, the molar ratio of the distilled water to the bifunctional silane is (70-55):1. Optionally or preferably, the molar ratio of the distilled water to the bifunctional silane is (70-60):1. Optionally or preferably, the molar ratio of the distilled water to the bifunctional silane is 70:1, 65:1 or 60:1. Slowly dropping distilled water can effectively control the speed of silane hydrolysis and condensation reactions. A higher distilled water ratio (such as 70:1) helps to slow down the reaction rate, making the reaction more uniform and controllable. By gradually adding distilled water, local temperature increases caused by rapid reactions can be prevented, thereby reducing the generation of by-products. Different molar ratios will affect the time it takes for the system to transition from a liquid state to a gel state. Selecting a suitable ratio can help find the best gelation conditions and ensure that a uniform and consistent gel structure is obtained. The proper ratio of distilled water helps to better disperse the silane molecules in the solvent to form a uniform precursor solution, which is critical to the consistency and quality of the silica-modified permeable membrane. Too much silane may cause rapid polymerization and precipitation, while the proper ratio of distilled water can maintain the stability of the solution and prevent the formation of unnecessary precipitates. Different molar ratios will affect the microstructural characteristics of the final material, such as porosity and pore size distribution, and thus affect its permeability, mechanical strength and other properties.

[0035] In a feasible implementation, the stirring operation comprises the following steps:

[0036] The mixed organic solution to which distilled water has been added is stirred at 20°C-25°C for 1.5-2.5 hours, and then diluted with anhydrous ethanol to (0.9-1.1) wt %, or in other words, the modified polysilsesquioxane polymer sol is diluted to (0.9-1.1) wt %.

[0037] In a feasible implementation, the stirring speed is low-speed stirring (200-400rpm). In this way, it is helpful to avoid violent local reaction hot spots, reduce the generation of by-products, ensure that the reaction system is more gentle and controllable, and avoid destroying the modified polysilsesquioxane network structure formed. Then, the mixed organic solution to which distilled water has been added is diluted to (0.9-1.1) wt% with anhydrous ethanol, or it can be said that the modified polysilsesquioxane polymer sol is diluted to (0.9-1.1) wt% concentration as a whole for suction filtration. Because the concentration of the obtained modified polysilsesquioxane polymer sol is too high, it is not conducive to the subsequent suction filtration operation, and it is easy to cause problems such as unevenness or excessive thickness. The mixed organic solution to which distilled water has been added is diluted to (0.9-1.1) wt% with anhydrous ethanol, which is convenient for the operation of the subsequent suction filtration step, and improves the uniformity and reliability of the prepared silica modified permeable membrane.

[0038] S40, preparing the modified polysilsesquioxane polymer sol onto the base membrane by suction filtration to obtain a silica modified permeable membrane.

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

[0040] First, prepare the base membrane to be modified and ensure that its surface is clean and flat to ensure a good filtration effect. Pre-treat the base membrane. The base membrane can be pre-treated (such as plasma treatment, chemical modification, etc.) to enhance the binding force between it and the modified substance.

[0041] The modified polysilsesquioxane polymer sol is prepared. The modified polysilsesquioxane polymer sol can be placed in a refrigerator at 4° C. for storage in order to maintain stable performance.

[0042] Prepare filtration equipment;

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

[0044] Slowly pour an appropriate amount of modified polysilsesquioxane sol onto the base film so that it evenly covers the entire surface;

[0045] Start the vacuum pump and start filtration. At this time, the solvent will be quickly sucked into the suction bottle, while the solid components will gradually settle and embed into the base membrane to form an integrated silica-modified permeable membrane. Control the filtration time and pressure to avoid uneven filtration or damage to the base membrane due to excessive filtration.

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

[0047] Suction filtration can achieve rapid evaporation and uniform distribution of the sol in a short time, thereby embedding the solid part of the modified polysilsesquioxane polymer sol into the base membrane. By adjusting parameters such as sol concentration, filtration time and vacuum degree, the ratio of the solid part of the final modified polysilsesquioxane polymer sol to the base membrane can be accurately controlled to optimize the performance of the permeable membrane; since the negative pressure formed during the filtration process helps the sol to contact the base membrane more closely, this can increase the interaction between the two, thereby improving the adhesion of the coating. Compared with brushing or other manual coating methods, suction filtration can better avoid the generation of defects such as bubbles and streaks, and avoid falling off. Suitable for large-scale production: Once the process parameters are determined, the suction filtration method is easy to automate and mass-produce, and is suitable for the efficient and stable preparation of silica-modified permeable membranes in industrial manufacturing environments.

[0048] In a feasible implementation, the mass percentage of the base membrane to the silica-modified permeable membrane is 30%-50%. Optionally or preferably, the mass percentage of the base membrane to the silica-modified permeable membrane is 30%-40%. Optionally or preferably, the mass percentage of the base membrane to the silica-modified permeable membrane is 30%, 35% or 40%. Optionally or preferably, the mass percentage of the base membrane to the silica-modified permeable membrane is 35%. The initial concentration or initial amount of the modified polysilsesquioxane polymer sol can be adjusted according to the required mass ratio, so that after filtration, a silica-modified permeable membrane that meets the ratio requirements can be obtained. The sol can be uniformly and completely deposited on the base membrane by adjusting the parameters such as the filtration time and the vacuum degree, while avoiding damage to the base membrane or uneven filtration caused by excessive filtration. The mass percentage is 35%, and such a mass ratio can improve the permeation flux, selectivity or mechanical strength, while maintaining the reliability of the basic characteristics of the silica-modified permeable membrane as a permeable membrane.

[0049] The preparation method of the above-mentioned silica-modified permeable membrane provided in the embodiment of the present application is simple in process. Since the bifunctional silane itself is resistant to high temperature, the obtained silica-modified permeable membrane has good heat resistance. The preparation method of the silica-modified permeable membrane provided in the embodiment of the present application introduces SiO2 nanoparticles into the polysilsesquioxane network structure formed by the bifunctional silane through self-hydrolysis and polycondensation reaction. The introduction of SiO2 nanoparticles will increase the surface area and micropore volume of the polysilsesquioxane network structure through the filling effect, thereby increasing the porosity, facilitating water to pass through the membrane, reducing the water contact angle, thereby improving the water permeability, and the prepared silica-modified permeable membrane has a large flux and can process more water in the same time. The nanoparticle filler increases the rigidity of the polymer chain through the interaction between the nanoparticles and the polymer, and the nanoparticles can interact with the hydrogen bonds, van der Waals forces, etc. between the organic groups (such as amine groups, silanol groups, etc.) in the bifunctional silane molecules to limit the movement of the polymer chain. This restriction makes it more difficult for the polymer chain to degrade 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. The introduction of strong and rigid inorganic SiO2 nanoparticles will stabilize the organic bridged polysilsesquioxane structure by immobilization, which will increase the thermal stability of the membrane. The embedded SiO2-filled polysilsesquioxane polymer is embedded in the base membrane by filtration in the membrane pores, effectively improving the long-term stability of the membrane.

[0050] A silica-modified permeable membrane according to an embodiment of the present invention is prepared by any of the above-mentioned methods for preparing a silica-modified permeable membrane.

[0051] The silica-modified permeable membrane of the technical solution of the present invention has excellent comprehensive performance in nanofiltration performance, permeability, chlorine resistance, heat resistance and stability, and is conducive to wide application.

[0052] In a feasible implementation, the BET surface area of ​​the silica-modified permeable membrane is: 505 g / m 2 The water permeability of the silica modified permeable membrane at a pressure of 1.5 MPa is: 18 L*m -2 h -1 Such a silica-modified permeable membrane is prepared by the following method to obtain a polysulfone membrane: prepare a mixed organic solution of silica and bifunctional silane as solute, wherein the solvent is ethanol, the bifunctional silane is BTESE, the mass concentration of BTESE in the mixed organic solution is 6wt%, and the mass ratio of silica to BTESE is 2.3%; slowly add distilled water to the above solution, and the molar ratio of the distilled water to the bifunctional silane is 60:1; stir the mixed organic solution to which the distilled water has been added at 23°C for 2 hours, and then dilute the mixed organic solution to which the distilled water has been added to 1wt% with anhydrous ethanol to obtain a modified polysilsesquioxane polymer sol, which is stored in an environment of 4°C for standby use; prepare the modified polysilsesquioxane polymer sol to the base membrane by suction filtration to obtain a silica-modified permeable membrane, wherein the mass percentage of the polysulfone membrane to the silica-modified permeable membrane is: 35%. The silica modified permeable membrane produced in this way has a large flux, can process more water in the same time, has a stable structure, is resistant to high temperatures and chlorine, is helpful in handling different situations, has good adaptability, and has the best overall performance, which is conducive to wide application.

[0053] A water treatment system in one embodiment includes a silica-modified permeable membrane prepared by any of the above-mentioned methods for preparing a silica-modified permeable membrane.

[0054] The water treatment system of the technical solution of the present invention has excellent comprehensive performance in nanofiltration performance, permeability, chlorine resistance, heat resistance and stability, and is conducive to wide application.

[0055] With reference to the above implementation contents, in order to make the technical solution of the present application more specific, clear and easy to understand, the technical solution of the present application is now exemplified. However, it should be noted that the contents to be protected by the present application are not limited to the following embodiments.

[0056] Embodiment 1:

[0057] Obtaining a polysulfone-based membrane;

[0058] A mixed organic solution containing silicon dioxide and bifunctional silane as solute is prepared, wherein the solvent is ethanol, the bifunctional silane is BTESE, the mass concentration of BTESE in the mixed organic solution is 6wt%, and the mass ratio of silicon dioxide to BTESE is 2.3%;

[0059] Slowly adding distilled water to the 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] Then, the mixed organic solution to which the distilled water has been added is diluted to 1 wt % with anhydrous ethanol to obtain a modified polysilsesquioxane polymer sol, which is stored in an environment of 4° C. for later use;

[0062] The modified polysilsesquioxane polymer sol is prepared to the base membrane by suction filtration to obtain a silica modified permeable membrane,

[0063] The mass percentage of the polysulfone membrane to the silica modified permeable membrane is 35%.

[0064] Example 2

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

[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 the distilled water to the bifunctional silane is 70:1.

[0070] Example 5

[0071] The same as Example 1, except that the mixed organic solution after the distilled water was added was diluted with anhydrous ethanol to 0.9wt%,

[0072] Example 6

[0073] The same as Example 1, except that the mixed organic solution after the distilled water was added was diluted with anhydrous ethanol to 1.1wt%,

[0074] Comparative Example 1

[0075] Distilled water was slowly added dropwise to a 5wt% BTESE ethanol solution until the alkoxysilane / H2O molar ratio was 1 / 60; the reaction mixture was stirred at room temperature for 2 hours to promote polymerization. Then, the reactants were diluted to 1wt% with anhydrous ethanol and stored in a refrigerator at 4°C until membrane preparation. A polysulfone membrane was used as a support membrane. The prepared sol solution was restored to room temperature and poured onto the support membrane surface for 30 seconds. After removing the excess sol solution by decantation, the membrane was dried in air at room temperature for 10 minutes. The 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 use.

[0076] Performance Test:

[0077] 1. Nanofiltration performance test

[0078] At 1.5 MPa pressure, the effective filtration area is 25 cm 2 The cross-flow filtration device was used to evaluate the separation performance and water flux (J, L*m -2 h -1 ) and salt retention rate (R, %), by as well as Where V(L) is the volume of permeate, A(m 2 ) is the effective filtration area, Δt(h) is the filtration time, C p (ppm) and C f (ppm) represent the salt concentration of the permeate and feed solution, respectively.

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

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

[0081] 3. Chlorine resistance

[0082] The permeable membrane samples prepared in the examples and comparative examples were completely immersed in a 1000 ppm sodium hypochlorite (NaClO) aqueous solution 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 2000 ppm NaCl water bath, and the temperature was gradually increased from 25° C. to 100° C., and maintained at each temperature for 180 min. The rejection rate and flux tests were then performed at the selected temperature nodes.

[0085] 5. Stable performance

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

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

[0088]

[0089] According to the above results, the silica-modified permeable membranes provided by embodiments 1 to 6 of the present application are tested and all have good separation performance. Among them, the performance of the silica-modified permeable membrane prepared by embodiment 1 is the best. Since the bifunctional silane itself is resistant to high temperatures, the obtained silica-modified permeable membrane has good heat resistance, and the preparation method of the silica-modified permeable membrane provided by the embodiment of the present application introduces SiO2 nanoparticles into the polysilsesquioxane network structure formed by the bifunctional silane through self-hydrolysis and polycondensation reaction, and the introduction of SiO2 nanoparticles will increase the surface area and micropore volume of the polysilsesquioxane network structure through the filling effect, thereby increasing the porosity, facilitating water to pass through the membrane, reducing the water contact angle, thereby improving the water permeability. The nanoparticle filler increases the rigidity of the polymer chain through the interaction between the nanoparticles and the polymer, and the nanoparticles can interact with the hydrogen bonds, van der Waals forces, etc. between the organic groups (such as amine groups, silanol groups, etc.) in the bifunctional silane (BTESE) molecules to limit the movement of the polymer chain. This restriction makes it more difficult for the polymer chain to degrade when heated, because higher energy is required to overcome the interaction between the nanoparticles and the polymer chain, thereby improving thermal stability. The bond energy of the silicon-oxygen bond is relatively high, which can resist the attack of active chlorine to a certain extent. During the chlorine treatment process, the silicon-oxygen bond network can play a supporting and protective role, slowing down the erosion of the organic part by active chlorine. Although the organic part may be affected to a certain extent, the presence of the silicon-oxygen bond network helps to maintain the overall structure of the membrane, so that the membrane can maintain its separation performance to a certain extent, thus showing good chlorine resistance. The introduction of strong and rigid inorganic SiO2 nanoparticles will stabilize the organic bridged polysilsesquioxane structure by immobilization, which will increase the thermal stability of the membrane. And the embedded SiO2-filled polysilsesquioxane polymer is embedded in the base membrane by suction filtration in the membrane pores, effectively improving the long-term stability of the membrane.

[0090] The basic concepts have been described above. Obviously, for those skilled in the art, the above detailed disclosure is only for example and does not constitute a limitation of this specification. Although not explicitly stated here, 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, so such modifications, improvements and corrections still belong to the spirit and scope of the exemplary embodiments of this specification.

[0091] At the same time, this specification uses specific words to describe the embodiments of this specification. For example, "one embodiment", "an embodiment", and / or "some embodiments" refer to a certain feature, structure or characteristic related to at least one embodiment of this specification. Therefore, it should be emphasized and noted that "one embodiment" or "an embodiment" or "an alternative embodiment" mentioned twice or more in different positions in this specification does not necessarily refer to the same embodiment. In addition, certain features, structures or characteristics in one or more embodiments of this specification can be appropriately combined.

[0092] In addition, unless explicitly stated in the claims, the order of the processing elements and sequences described in this specification, the use of alphanumeric characters, or the use of other names are not intended to limit the order of the processes and methods of this specification. Although the above disclosure discusses some invention embodiments that are currently considered useful through various examples, it should be understood that such details are only for illustrative purposes, and the attached claims are not limited to the disclosed embodiments. On the contrary, the claims are intended to cover all modifications and equivalent combinations that are consistent with the essence and scope of the embodiments of this specification.

[0093] Similarly, it should be noted that in order to simplify the description disclosed in this specification and thus help understand one or more embodiments of the invention, in the above description of the embodiments of this specification, multiple features are sometimes combined into one embodiment, figure or description thereof. However, this disclosure method does not mean that the features required by the subject matter of this specification are more than the features mentioned in the claims. In fact, the features of the embodiments are less than all the features of the single embodiment disclosed above.

[0094] In some embodiments, numbers describing the number of components and attributes are used. It should be understood that such numbers used in the description of the embodiments are modified by the modifiers "about", "approximately" or "substantially" in some examples. Unless otherwise specified, "about", "approximately" or "substantially" indicate 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 change according to the required features of individual embodiments. In some embodiments, the numerical parameters should take into account the specified significant digits and adopt the general method of retaining digits. Although the numerical domains and parameters used to confirm the breadth of their range in some embodiments of this specification are approximate values, in specific embodiments, the setting of such numerical values ​​is as accurate as possible within the feasible range.

[0095] Each patent, patent application, patent application publication, and other materials, such as articles, books, specifications, publications, documents, etc., cited in this specification are hereby incorporated by reference in their entirety. Except for application history documents that are inconsistent with or conflicting with the contents of this specification, documents that limit the broadest scope of the claims of this specification (currently or later attached to this specification) are also excluded. It should be noted that if the descriptions, definitions, and / or use of terms in the materials attached to this specification are inconsistent or conflicting with the contents described in this specification, the descriptions, definitions, and / or use of terms in this specification shall prevail.

[0096] Finally, it should be understood that the embodiments described in this specification are only used to illustrate the principles of the embodiments of this specification. Other variations may also fall within the scope of this specification. Therefore, as an example and not a limitation, alternative configurations of the embodiments of this specification may be considered consistent with the teachings of this specification. Accordingly, the embodiments of this specification are not limited to the embodiments explicitly introduced and described in this specification.

Claims

1. A method for preparing a silicon dioxide modified permeable membrane, characterized in that: The preparation method comprises the following steps: Get the basement membrane, A mixed organic solution containing silicon dioxide and bifunctional silane as solute is prepared. Slowly adding distilled water to the mixed organic solution and stirring the solution to obtain a modified polysilsesquioxane polymer sol; The modified polysilsesquioxane polymer sol is prepared onto the base membrane by suction filtration to obtain a silica-modified permeable membrane.

2. The method for preparing a silicon dioxide modified permeable membrane according to claim 1, wherein: The bifunctional silane is selected from bis[3-(triethoxysilyl)propyl]tetrasulfide, bis[3-(triethoxysilyl)propyl]amine) or tetraethoxysilane.

3. The method for preparing a silicon dioxide modified permeable membrane according to claim 2, wherein: The mass concentration of the bifunctional silane in the mixed organic solution is 2wt% to 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 a silicon dioxide modified permeable membrane according to claim 2, characterized in that: The base membrane is selected from polysulfone base membrane, polyethersulfone base membrane, ceramic base membrane, polyacrylonitrile base membrane, polyvinylidene fluoride membrane, polytetrafluoroethylene membrane, polyimide membrane, polyvinyl chloride membrane, polyethylene membrane or polypropylene membrane.

5. The method for preparing a silicon dioxide modified permeable 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.

6. The method for preparing a silicon dioxide modified permeable membrane according to claim 2, characterized in that: The stirring operation comprises the following steps: Stir the mixed organic solution after adding distilled water at 20℃-25℃ for 1.5-2.5 hours. Then, the mixed organic solution to which the distilled water has been added is diluted with anhydrous ethanol to (0.9-1.1) wt %.

7. The method for preparing a silicon dioxide modified permeable membrane according to claim 2, characterized in that: The mass percentage of the base film to the silicon dioxide modified permeable membrane is 30% to 50%.

8. A silica-modified permeable membrane, characterized in that: The membrane is prepared by the method for preparing a silicon dioxide-modified permeable membrane according to any one of claims 1 to 7.

9. The silicon dioxide modified permeable membrane according to claim 8, characterized in that The BET surface area of ​​the silica modified permeable membrane is: 505 g / m 2 The water permeability of the silica modified permeable membrane at a pressure of 1.5 MPa is: 18 L*m -2 h -1 .

10. A water treatment system, characterized in that: A silica-modified permeable membrane prepared by the method for preparing a silica-modified permeable membrane according to any one of claims 1 to 7.

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