Preparation method and application of nanoparticle blending modified forward osmosis membrane

Abstract

The invention belongs to the technical field of forward osmosis separation membranes, and particularly relates to a preparation method and application of a nanoparticle blending modified forward osmosis membrane. The preparation method comprises the following steps: initiating phase separation through exchange of a solvent and a non-solvent by adopting a phase inversion method to form a polyethersulfone membrane with a porous net structure as a base membrane of the forward osmosis membrane, and preparing a compact polyimide active layer on the base membrane by utilizing an interfacial polymerization reaction of m-phenylenediamine and triformyl chloride, the nanoparticle blending modified forward osmosis membrane is prepared by modifying the base membrane and the active layer, and the membrane has excellent pure water flux and oil retention rate, can realize efficient and stable oil-water separation, has excellent anti-pollution performance and long-term stability, and is good in morphology, simple and feasible in preparation method, low in cost and suitable for industrial production. The method can be used for batch production, has a wide application prospect in the field of membrane treatment oil-water separation, and can be applied to the technical fields of environmental governance, new energy and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of forward osmosis separation membranes, and specifically relates to a preparation method and application of a nanoparticle blended modified forward osmosis membrane. Background Art

[0002] Conventional separation methods, such as precipitation, adsorption, and centrifugation, have been used to treat oily wastewater. Although these technologies can effectively purify wastewater containing suspended oil, they are unable to treat emulsified oil stabilized by surfactants. Membrane separation technology has become an emerging solution due to its excellent separation efficiency, low energy demand, simple operation, and environmental sustainability. However, conventional membrane technologies such as ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO) require pressure to drive the separation process. This not only increases energy consumption, but also exacerbates the membrane fouling problem, resulting in low water recovery efficiency and frequent membrane cleaning. Compared with other pressure-driven membrane processes, the forward osmosis process does not require external pressure. It uses the osmotic pressure difference on both sides of the forward osmosis membrane as the driving force. This process consumes less energy, thus providing another option for sustainable oily water recovery. However, due to the ubiquity of oil contamination, FO technology is still plagued by membrane fouling in the treatment of oily wastewater. In addition to organic contamination caused by oil, the problem of concentration polarization and the low mechanical strength of the membrane itself is particularly significant in the treatment of such high-viscosity and high-mineralization emulsions.

[0003] Therefore, it is necessary to develop a nanoparticle blended modified forward osmosis membrane that not only has strong anti-pollution performance and high mechanical strength, but also can achieve long-term and efficient oil-water separation. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing a nanoparticle blended modified forward osmosis membrane and its application. The prepared forward osmosis membrane not only has excellent pure water flux and oil retention rate, can achieve efficient and stable oil-water separation, but also performs well in anti-pollution performance and long-term stability. It has broad application prospects in the field of membrane treatment oil-water separation.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The method for preparing the nanoparticle blended modified forward osmosis membrane comprises the following steps:

[0007] S1. Add polyethersulfone, polyvinylpyrrolidone, modified zinc oxide and polyether into N-methylpyrrolidone, heat to 65-75°C and stir for 5-7h to obtain a uniform and transparent solution, and then stand at room temperature for 12h or more to obtain a casting solution;

[0008] S2. Pour the casting solution onto a smooth glass plate, scrape it with a metal rod into a solution film with a thickness of 100-200 μm, and immediately immerse the glass plate in deionized water. Let it stand until the film falls off automatically, then take it out and rinse it with deionized water for 5-8 times to obtain a base film.

[0009] S3, adding the nanoparticles into the m-phenylenediamine aqueous solution and subjecting it to ultrasonic stirring to obtain a nanoparticle dispersion;

[0010] S4. Completely immerse the base film in the nanoparticle dispersion for 8-15 minutes, then take it out and let it stand for 1-2 minutes, then absorb the excess water on the surface, drip a mixed solution of benzyl chloride and n-hexane on the surface, heat treat it at 110-120°C for 2-5 minutes to form an interfacial polymerization layer, rinse the surface water stains with n-hexane, cure it in an air circulation oven at 55-65°C for 8-15 minutes, cool it to room temperature, wash it with deionized water 3-5 times, and dry it.

[0011] Preferably, the apparent density of the polyethersulfone is 0.2-0.3 g / cm 3 , viscosity number is 100-110cm 3 / g, and a molecular weight of 90000-110000 g / mol; further preferably, the apparent density of the polyethersulfone is 0.25 g / cm 3 , viscosity number is 105cm 3 / g, and the molecular weight is 92000g / mol.

[0012] In some preferred embodiments, the polyethersulfone is purchased from BASF, Germany. E7020P.

[0013] Preferably, the K value of the polyvinyl pyrrolidone is 27-32.4, and the viscosity average molecular weight is 45000-58000.

[0014] In some preferred embodiments, the polyvinyl pyrrolidone is purchased from Boai New Open Source Medical Technology Group Co., Ltd. PVP-K30.

[0015] Preferably, the average molecular weight of the polyether is 10500-12500, the cloud point of the polyether aqueous solution with a polyether mass fraction of 1% is ≥100°C, and the unsaturation is 0.03-0.1 mmol / g.

[0016] In some preferred embodiments, the polyether is purchased from Nanjing Dulai Biotechnology Co., Ltd., and is block polyether F-127.

[0017] Preferably, the mass ratio of the polyethersulfone, polyether and modified zinc oxide is (40-50):(4-8):1; more preferably, it is 45:6:1.

[0018] The specific polyethersulfone is used to prepare the base membrane (support layer) of the forward osmosis membrane. It has excellent chemical stability and heat resistance, and good dimensional stability. It can be used to prepare the support layer of the forward osmosis membrane. However, it is hydrophobic. During the oil-water separation process, the polymers in the oil droplets and wastewater are easily adsorbed on the surface of the membrane, causing the membrane to be blocked, resulting in a decrease in the water flux and separation efficiency of the membrane, while affecting the cycle stability and life. The use of zinc oxide and specific polyethers to modify polyethersulfone can improve the hydrophilicity of the polyethersulfone membrane while improving its anti-pollution performance. This may be because there is a synergistic effect between the two, forming a "double-layer protection" mechanism on the surface of the polyethersulfone membrane. On the one hand, the specific polyether has amphiphilicity, the hydrophobic end can enhance its anchoring effect on the polyethersulfone membrane body, and the hydrophilic end has a certain hydrophilic modification effect, thereby reducing the initial attachment of pollutants. On the other hand, the addition of zinc oxide not only enhances this hydrophilic effect, but also continuously removes a small amount of pollutants that may be formed through its photocatalytic activity. The two work together to greatly improve the anti-pollution ability of the membrane. At the same time, zinc oxide, as an inorganic filler, plays a reinforcing role in the membrane, improving the tensile strength and tear strength of the membrane, and the addition of polyether also improves the toughness of the membrane, making it less likely to break when facing external forces, extending the service life of the membrane and maintaining a high water flux and separation efficiency. However, zinc oxide has poor chemical stability, low visible light utilization efficiency, and is easy to agglomerate, which affects its co-modification effect with polyether on polyethersulfone, and thus affects the performance of the forward osmosis membrane.

[0019] The preparation method of the modified zinc oxide comprises the following steps:

[0020] A1. Graphene oxide and zinc acetate are mixed with ethanol respectively, and ultrasonically stirred for 1-2 hours to obtain graphene oxide / ethanol solution and zinc acetate / ethanol solution respectively;

[0021] A2. Graphene oxide / ethanol solution and zinc acetate / ethanol solution are mixed to obtain a mixed solution, the pH of the mixed solution is adjusted to 8-10, and the mixed solution is subjected to hydrothermal reaction at 175-185° C. for 10-15 h, cooled to room temperature, filtered, washed with deionized water until neutral, vacuum dried, ground, and passed through a 1000-2000 mesh sieve to obtain.

[0022] Preferably, the graphene oxide includes single-layer graphene oxide and multi-layer graphene oxide.

[0023] Preferably, the mass ratio of the single-layer graphene oxide to the multi-layer graphene oxide is (1-3):1; further preferably, it is 2:1.

[0024] Preferably, the single-layer graphene oxide has a sheet diameter of 0.5-5 μm and a thickness of 0.8-1.2 nm.

[0025] In some preferred embodiments, the single-layer graphene oxide is purchased from Jiangsu Xianfeng Nanomaterial Technology Co., Ltd.

[0026] Preferably, the multilayer graphene oxide has a sheet diameter of 10-300 nm, a layer number of ≤5, and a specific surface area of ​​480-520 m 2 / g.

[0027] In some preferred embodiments, the multilayer graphene oxide is purchased from Beijing Graphene Research Institute Co., Ltd.

[0028] Preferably, the mass fraction of graphene oxide in the graphene oxide / ethanol solution is 5%-10%.

[0029] Preferably, the mass fraction of zinc acetate in the zinc acetate / ethanol solution is 10%-20%.

[0030] Preferably, the mass ratio of graphene oxide to zinc acetate in the mixed solution is 1:(15-25); further preferably, it is 1:20.

[0031] The use of specific graphene oxide to modify zinc oxide can not only improve the dispersibility and stability of zinc oxide, but also reduce the resistance of water flux and improve the oil-water separation performance of the forward osmosis membrane. This may be due to the synergistic effect of the two. The presence of graphene oxide sheets provides growth sites for zinc oxide, avoiding the agglomeration of nano zinc oxide, and the growth of nano zinc oxide on graphene oxide sheets also reduces the interaction between graphene oxide sheets to a certain extent, thereby reducing its agglomeration, thereby achieving excellent modification effects. The hydroxyl, carboxyl and other functional groups on the surface of graphene oxide and the hydrogen bonding between zinc oxide and water molecules can jointly improve the hydrophilicity of the membrane surface, thereby improving the oil-water separation effect of the forward osmosis membrane. At the same time, the compounding of single-layer graphene oxide and multi-layer graphene oxide with different sheet diameters not only effectively prevents the agglomeration of zinc oxide particles, but also significantly improves the dispersibility and stability of zinc oxide in the modified system. This synergistic effect further optimizes the structure of the membrane, forms a multi-level network structure, provides more transmission channels for water molecules, and enhances the mechanical properties of the membrane, making it more durable and stable. Although the modification of graphene oxide has improved the dispersibility and stability of zinc oxide to a certain extent, the addition of excessive inorganic particles during the preparation of the base membrane may still cause agglomeration, causing the base membrane to become too brittle, affecting its flexibility and mechanical strength, and thus affecting its oil-water separation effect. At the same time, the performance improvement of the forward osmosis membrane by modified zinc oxide and polyether is also limited. Therefore, it is necessary to further treat the polyamide active layer to further improve the oil-water separation effect of the forward osmosis membrane.

[0032] Preferably, the added amount of polyvinyl pyrrolidone is 20%-25% of the mass of polyether sulfone.

[0033] Preferably, the added amount of N-methylpyrrolidone is 4-4.5 times the mass of polyethersulfone.

[0034] Preferably, the nanoparticles include one or more of nano-calcium carbonate and nano-titanium dioxide.

[0035] Preferably, the mass ratio of the nano-calcium carbonate to the nano-titanium dioxide is (1-2):1; further preferably, it is 3:2.

[0036] Preferably, the nano calcium carbonate is a hydrophilic nano calcium carbonate with a particle size of 180-220 nm and a specific surface area of ​​25-35 m 2 / g, moisture (mass fraction) ≤1%.

[0037] In some preferred embodiments, the nano calcium carbonate is purchased from Hangzhou Jikang New Materials Co., Ltd., SS-CAC50.

[0038] The use of nano-titanium dioxide and nano-calcium carbonate to modify the polyimide active layer can not only improve the pure water flux and oil retention rate, and achieve good oil-water separation effects, but also have excellent anti-pollution performance and long-term stability. Nano-titanium dioxide has attracted much attention in oil-water separation materials due to its excellent hydrophilic and oleophobic properties, but pure nano-titanium dioxide is difficult to use alone due to the fragility of its particle structure and easy accumulation. By interfacial polymerization, the two components of nano-calcium carbonate and nano-titanium dioxide are blended and doped into the polyimide active layer, which can further optimize the comprehensive performance of the oil-water separation membrane and provide a new solution for practical applications in complex environments. There is a synergistic effect between nano-titanium dioxide and nano-calcium carbonate. The hydroxyl groups on the surface of nano-titanium dioxide enhance the hydrophilicity of the membrane surface by forming hydrogen bonds with water molecules. The formation of hydrogen bonds promotes the penetration of water molecules, improves the stability of the membrane, and at the same time improves the repellency of oil and promotes the emulsification and rupture of the oil-water emulsion. When the oil droplets come into contact with the pre-wetted water surface, the membrane surface has an upward force on the water and an upward repulsive force on the oil droplets, which will only allow the water to pass through and form a water layer to repel the oil. At the same time, the polarity of titanium dioxide enhances the repulsive ability of hydrophobic oil droplets, making the oil droplets easier to slide off. The accumulation of nano-calcium carbonate on the membrane surface leads to a decrease in the average pore size and an increase in the capillary effect, and further inhibits the oil droplets from entering the membrane pores through the electrostatic repulsion of the carbonate group. With the increase in the surface capillary force and the improvement of the surface wettability, water molecules are more likely to pass through the membrane, and further reduce the embedding and attachment of oil droplets. This property can reduce the operating cost of the membrane, extend the service life of the membrane, and make it suitable for continuous operation requirements in actual oil-water separation. By controlling its ratio, the prepared forward osmosis membrane can show excellent pure water flux and oil retention rate, and also excel in anti-fouling performance and long-term stability. At the same time, nano-titanium dioxide enhances the hydrophilicity and oil pollution resistance of the membrane, while nano-calcium carbonate optimizes the pore structure and provides mechanical support, enhancing the structural stability of the membrane, avoiding the problems of excessive membrane roughness and accumulation of particles and oil pollutants caused by high concentrations of nano-titanium dioxide, improving the separation efficiency of the material, and reducing the frequency of cleaning and maintenance. The synergistic effect of the two achieves an effective balance between hydrophilicity, oleophobicity and mechanical stability. This design significantly improves the water flux and oil retention performance of the membrane, while effectively reducing the reverse solute flux. Especially when dealing with high-concentration, high-viscosity oil-water emulsions, the modified membrane exhibits excellent anti-pollution ability and chemical stability, making the prepared membrane have a wide range of applicability, excellent chemical compatibility, the ability to handle complex emulsification systems and good stability, and is suitable for oil-water separation needs in multiple fields. In addition, the problem of particle agglomeration and excessive membrane roughness is avoided through precise particle doping ratios, forming a uniform microporous structure.

[0039] The preparation method of nano titanium dioxide comprises the following steps:

[0040] B1. Tetrabutyl titanate is dissolved in anhydrous ethanol to obtain a tetrabutyl titanate / ethanol solution, and a nitrogen source and a carbon source are dissolved in water to obtain a doping solution;

[0041] B2. Drop the doping solution into the tetrabutyl titanate ethanol solution, stir at a speed of 800-1200r / min for 1-3h, adjust the system pH to 2-3, continue stirring at a speed of 800-1200r / min for 1-3h, age at room temperature for 20-25h, dry at 60-80°C for 20-25h, calcine in a nitrogen atmosphere at 500-700°C for 2-3h, grind and pass through a 1000-2000 mesh sieve to obtain.

[0042] Preferably, the mass ratio of tetrabutyl titanate to anhydrous ethanol is 1:(8-10); further preferably, it is 1:9.

[0043] Preferably, in the doping solution, the total mass percentage of the nitrogen source and the carbon source is 1%-2%.

[0044] Preferably, the nitrogen source comprises urea.

[0045] Preferably, the carbon source includes one or more of glucose, fructose and melamine; further preferably, it is glucose.

[0046] Preferably, in step B2, the mass ratio of tetrabutyl titanate, nitrogen source and carbon source is (20-25):1:(2-4); further preferably, it is 22:1:3.

[0047] In order to further improve the water flux and separation efficiency of the forward osmosis membrane, nitrogen and carbon elements are selected to dope and modify nano-titanium dioxide. This may be because, on the one hand, nitrogen atoms can replace oxygen atoms or exist in the form of interstitial atoms, thereby changing the surface chemical properties of titanium dioxide, enhancing its interaction with water molecules, and increasing hydrophilicity. On the other hand, the incorporation of carbon elements can extend the absorption wavelength of titanium dioxide to the visible light region and change the surface structure, making nano-titanium dioxide a super-hydrophilic surface. The co-doping of the two elements improves the water flux and separation efficiency of the forward osmosis membrane.

[0048] Preferably, the mass percentage of m-phenylenediamine in the m-phenylenediamine aqueous solution is 1.5%-2.5%.

[0049] Preferably, the added amount of the m-phenylenediamine aqueous solution is 950-1050 times the mass of the nanoparticles.

[0050] In step S3, the specific conditions for ultrasonic stirring treatment are: first ultrasonic treatment at 28-32° C. for 0.5-1.5 h, then stirring at room temperature for 20-40 min, and repeating 4-6 times until all nanoparticles are completely dispersed.

[0051] Preferably, in the mixed solution of trimesoyl chloride and n-hexane, the mass percentage of trimesoyl chloride is 0.1%-0.2%.

[0052] The method for preparing the nanoparticle blended modified forward osmosis membrane prepares the nanoparticle blended modified forward osmosis membrane.

[0053] The nanoparticle blended modified forward osmosis membrane is used in the technical fields of environmental management, new energy and the like.

[0054] Compared with the prior art, the advantages and beneficial effects of the present invention are:

[0055] 1. The present invention provides a preparation method and application of a nanoparticle blended modified forward osmosis membrane. First, a phase inversion method is used to induce phase separation through the exchange of solvent and non-solvent to form a polyethersulfone membrane with a porous network structure as the base membrane of the forward osmosis membrane. Then, a dense polyimide active layer is prepared on the base membrane by the interfacial polymerization reaction of m-phenylenediamine and triformyl chloride. The forward osmosis membrane is prepared by modifying the base membrane and the active layer. It not only has excellent pure water flux and oil retention rate, but also can achieve efficient and stable oil-water separation. It also performs well in anti-pollution performance and long-term stability. After 10 oil-water separation cycle tests, the membrane can still maintain efficient separation ability, proving its application potential in the treatment of complex oil-water emulsions. The forward osmosis membrane prepared by the present invention has excellent performance and good morphology, and the preparation method is simple and easy, low cost, and can be mass-produced. It has broad application prospects in the field of membrane treatment oil-water separation.

[0056] 2. The present invention uses zinc oxide and a specific polyether to modify polyethersulfone, which can improve the hydrophilicity of the polyethersulfone membrane and improve its anti-pollution performance.

[0057] 3. The present invention uses specific graphene oxide to modify zinc oxide, which can not only improve the dispersibility and stability of zinc oxide, but also reduce the resistance of water flux and improve the oil-water separation performance of the forward osmosis membrane.

[0058] 4. The present invention uses nano-titanium dioxide and nano-calcium carbonate to modify the polyimide active layer, which can not only improve the pure water flux and oil retention rate, but also has a good oil-water separation effect, and has excellent anti-pollution performance and long-term stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art.

[0060] Figure 1 This is a SEM surface image of the nanoparticle blended modified forward osmosis membrane described in Example 1 of the present invention.

[0061] Figure 2 This is a SEM cross-sectional view of the nanoparticle blended modified forward osmosis membrane described in Example 1 of the present invention.

[0062] Figure 3 This is an AFM three-dimensional image of the nanoparticle blended modified forward osmosis membrane described in Example 1 of the present invention.

[0063] Figure 4 This is an AFM two-dimensional image of the nanoparticle blended modified forward osmosis membrane described in Example 1 of the present invention.

[0064] Figure 5 Optical microscope images of the raw material liquid and the drawn liquid before and after the separation of n-hexadecane oil-water emulsion by the nanoparticle blended modified forward osmosis membrane described in Example 1 of the present invention.

[0065] Figure 6 The water flux and retention rate of the nanoparticle blended modified forward osmosis membrane described in Example 1 of the present invention in different oils.

[0066] Figure 7 The flux and retention rate of the nanoparticle blended modified forward osmosis membrane for separating n-hexadecane oil-water emulsion for 120 min as described in Example 1 of the present invention.

[0067] Figure 8 The flux and retention rate of the nanoparticle blended modified forward osmosis membrane for separating n-hexadecane oil-water emulsion for 10 cycles as described in Example 1 of the present invention. DETAILED DESCRIPTION

[0068] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0069] The raw materials used in the present invention are all commercially available, specifically:

[0070] The apparent density of polyethersulfone is 0.25g / cm 3 , viscosity number is 105cm 3 / g, molecular weight 92000g / mol, purchased from BASF, Germany, E-7020P.

[0071] Polyvinyl pyrrolidone has a K value of 27-32.4 and a viscosity-average molecular weight of 45,000-58,000 and was purchased from Boai New Open Source Medical Technology Group Co., Ltd. PVP-K30.

[0072] The single-layer graphene oxide has a sheet diameter of 0.5-5 μm and a thickness of 0.8-1.2 nm and was purchased from Jiangsu Xianfeng Nanomaterial Technology Co., Ltd.

[0073] The sheet diameter of multilayer graphene oxide is 10-300nm, the number of layers is ≤5, and the specific surface area is 480-520m 2 / g, purchased from Beijing Graphene Research Institute Co., Ltd.

[0074] The average molecular weight of the polyether is 10500-12500, the turbidity point of the polyether aqueous solution with a polyether mass fraction of 1% is ≥100°C, and the unsaturation is 0.03-0.1 mmol / g. It is purchased from Nanjing Dulai Biotechnology Co., Ltd., and is block polyether F-127.

[0075] Nano calcium carbonate is a hydrophilic nano calcium carbonate with a particle size of 180-220nm and a specific surface area of ​​25-35m 2 / g, moisture (mass fraction) ≤ 1%, purchased from Hangzhou Jikang New Materials Co., Ltd., SS-CAC50.

[0076] Example 1

[0077] This embodiment provides a method for preparing a nanoparticle blended modified forward osmosis membrane, the steps are:

[0078] S1. Add 18 g polyethersulfone, 4 g polyvinylpyrrolidone, 0.4 g modified zinc oxide and 2.4 g polyether to 75.56 g N-methylpyrrolidone, heat to 70°C and stir for 6 h to obtain a uniform and transparent solution, and then stand at room temperature for 12 h.

[0079] S2, pour the casting solution onto a smooth glass plate, scrape it into a 150 μm thick solution film with a metal rod, and immediately immerse the glass plate in deionized water, let it stand, and take it out after the film falls off automatically, and rinse it with deionized water for 7 times to obtain the base film;

[0080] S3, adding 0.1 g of nanoparticles into 100 g of m-phenylenediamine aqueous solution and subjecting to ultrasonic stirring to obtain a nanoparticle dispersion;

[0081] S4. Completely immerse the base film in the nanoparticle dispersion for 10 minutes, then take it out and let it stand for 1.5 minutes, then absorb the excess water on the surface, drop 5mL of a mixed solution of benzyl chloride and n-hexane on the surface, heat treat it at 105°C for 3 minutes to form an interfacial polymerization layer, rinse the surface water stains with n-hexane, cure it in an air circulation oven at 60°C for 10 minutes, cool it to room temperature, wash it with deionized water 4 times, and dry it.

[0082] The preparation method of the modified zinc oxide comprises the following steps:

[0083] A1. Graphene oxide and zinc acetate are mixed with ethanol respectively, and ultrasonically stirred for 1.5 to obtain a graphene oxide / ethanol solution and a zinc acetate / ethanol solution respectively;

[0084] A2. Graphene oxide / ethanol solution and zinc acetate / ethanol solution are mixed to obtain a mixed solution, the pH of the mixed solution is adjusted to 9, and the mixed solution is subjected to hydrothermal reaction at 180° C. for 12 h, cooled to room temperature, filtered, washed with deionized water until neutral, vacuum dried, ground, and passed through a 1500-mesh sieve to obtain the product.

[0085] The graphene oxide is single-layer graphene oxide and multi-layer graphene oxide, and the mass ratio is 2:1.

[0086] The mass fraction of graphene oxide in the graphene oxide / ethanol solution is 8%.

[0087] The mass fraction of zinc acetate in the zinc acetate / ethanol solution is 15%.

[0088] The mass ratio of graphene oxide to zinc acetate in the mixed solution is 1:20.

[0089] The nanoparticles are nano calcium carbonate and nano titanium dioxide, with a mass ratio of 3:2.

[0090] The preparation method of the nano titanium dioxide comprises the following steps:

[0091] B1. Tetrabutyl titanate is dissolved in anhydrous ethanol to obtain a tetrabutyl titanate / ethanol solution, and urea and glucose are dissolved in water to obtain a doping solution;

[0092] B2. Drop the doping solution into the tetrabutyl titanate ethanol solution, stir at 1000 r / min for 2 hours, adjust the system pH to 2, continue stirring at 1000 r / min for 2 hours, age at room temperature for 24 hours, dry at 70°C for 24 hours, calcine at 600°C in a nitrogen atmosphere for 2.5 hours, grind and pass through a 1500 mesh sieve to obtain.

[0093] The mass ratio of tetrabutyl titanate to anhydrous ethanol is 1:9.

[0094] In the doping solution, the total mass percentage of the nitrogen source and the carbon source is 1.5%.

[0095] In the step B2, the mass ratio of tetrabutyl titanate, the nitrogen source and the carbon source is 22:1:3.

[0096] The mass percentage of m-phenylenediamine in the m-phenylenediamine aqueous solution is 2%.

[0097] In step S3, the specific conditions for the ultrasonic stirring treatment are: firstly ultrasonic treatment at 30° C. for 1 hour, then stirring at room temperature for 30 minutes, and repeating 5 times until all the nanoparticles are completely dispersed.

[0098] In the mixed solution of trimesoyl chloride and n-hexane, the mass percentage of trimesoyl chloride is 0.15%.

[0099] Example 2

[0100] The difference between this embodiment and embodiment 1 is that the nanoparticles are nano-calcium carbonate and nano-titanium dioxide, and the mass ratio is 1:1.

[0101] Comparative Example 1

[0102] The difference between this comparative example and Example 1 is as follows: S1, 18g polyethersulfone, 4g polyvinylpyrrolidone, 0.4g modified zinc oxide, and 2.4g polyether are added to 77.96g N-methylpyrrolidone, the temperature is raised to 70 and stirred for 6h to obtain a uniform and transparent solution, and then the solution is allowed to stand at room temperature for 12h;

[0103] S2, pour the casting solution onto a smooth glass plate, scrape it into a 150 μm thick solution film with a metal rod, and immediately immerse the glass plate in deionized water, let it stand, and take it out after the film falls off automatically, and rinse it with deionized water for 7 times to obtain the base film;

[0104] S3, preparing an aqueous solution of m-phenylenediamine;

[0105] S4. Completely immerse the base film in the aqueous solution of m-phenylenediamine for 10 minutes, then take it out and let it stand for 1.5 minutes, then absorb the excess water on the surface, drop 5mL of a mixed solution of benzyl chloride and n-hexane on the surface, heat treat it at 105°C for 3 minutes to form an interfacial polymerization layer, rinse the surface water stains with n-hexane, cure it in an air circulation oven at 60°C for 10 minutes, cool it to room temperature, wash it with deionized water 4 times, and dry it.

[0106] Comparative Example 2

[0107] The difference between this comparative example and Example 1 is that the nanoparticles are nano calcium carbonate and nano titanium dioxide, and the mass ratio is 4:1.

[0108] Comparative Example 3

[0109] The difference between this comparative example and Example 1 is that the nanoparticles are nano calcium carbonate and nano titanium dioxide, and the mass ratio is 2:3.

[0110] Comparative Example 4

[0111] The difference between this comparative example and Example 1 is that the nanoparticles are nano calcium carbonate and nano titanium dioxide, and the mass ratio is 1:4.

[0112] Comparative Example 5

[0113] The difference between this comparative example and Example 1 is as follows: S1, 18 g of polyethersulfone, 4 g of polyvinylpyrrolidone, and 2.4 g of polyether are added to 77.96 g of N-methylpyrrolidone, the temperature is raised to 70°C and stirred for 6 h to obtain a uniform and transparent solution, and then the solution is allowed to stand at room temperature for 12 h;

[0114] S2, pour the casting solution onto a smooth glass plate, scrape it into a 150 μm thick solution film with a metal rod, and immediately immerse the glass plate in deionized water, let it stand, and take it out after the film falls off automatically, and rinse it with deionized water for 7 times to obtain the base film;

[0115] S3, adding 0.1 g of nanoparticles into an aqueous solution of m-phenylenediamine and subjecting it to ultrasonic stirring to obtain a nanoparticle dispersion;

[0116] S4. Completely immerse the base film in the nanoparticle dispersion for 10 minutes, then take it out and let it stand for 1.5 minutes, then absorb the excess water on the surface, drop 5mL of a mixed solution of benzyl chloride and n-hexane on the surface, heat treat it at 105°C for 3 minutes to form an interfacial polymerization layer, rinse the surface water stains with n-hexane, cure it in an air circulation oven at 60°C for 10 minutes, cool it to room temperature, wash it with deionized water 4 times, and dry it.

[0117] Comparative Example 6

[0118] The difference between this comparative example and Example 1 is as follows: S1, 18g polyethersulfone, 4g polyvinylpyrrolidone, 0.4g zinc oxide, and 2.4g polyether are added to 77.96g N-methylpyrrolidone, the temperature is raised to 70 and stirred for 6h to obtain a uniform and transparent solution, and then the solution is allowed to stand at room temperature for 12h;

[0119] S2, pour the casting solution onto a smooth glass plate, scrape it into a 150 μm thick solution film with a metal rod, and immediately immerse the glass plate in deionized water, let it stand, and take it out after the film falls off automatically, and rinse it with deionized water for 7 times to obtain the base film;

[0120] S3, adding 0.1 g of nanoparticles into an aqueous solution of m-phenylenediamine and subjecting it to ultrasonic stirring to obtain a nanoparticle dispersion;

[0121] S4. Completely immerse the base film in the nanoparticle dispersion for 10 minutes, then take it out and let it stand for 1.5 minutes, then absorb the excess water on the surface, drop 5mL of a mixed solution of benzyl chloride and n-hexane on the surface, heat treat it at 105°C for 3 minutes to form an interfacial polymerization layer, rinse the surface water stains with n-hexane, cure it in an air circulation oven at 60°C for 10 minutes, cool it to room temperature, wash it with deionized water 4 times, and dry it.

[0122] Comparative Example 7

[0123] The difference between this comparative example and Example 1 is that the graphene oxide is a single-layer graphene oxide.

[0124] Comparative Example 8

[0125] The difference between this comparative example and Example 1 is that the preparation method of the nano titanium dioxide comprises the following steps: dissolving tetrabutyl titanate in anhydrous ethanol to obtain a tetrabutyl titanate / ethanol solution, stirring at a speed of 1000 r / min for 2 hours, adjusting the pH of the system to 2, continuing to stir at a speed of 1000 r / min for 2 hours, aging at room temperature for 24 hours, drying at 70°C for 24 hours, calcining in a nitrogen atmosphere at 600°C for 2.5 hours, grinding and passing through a 1500 mesh sieve to obtain.

[0126] Performance Testing

[0127] 1. Surface morphology test: The SEM surface image, SEM cross-sectional image and AFM image of the forward osmosis membrane prepared in Test Example 1 are shown in Table 1. Figure 1 to Figure 4 .

[0128] from Figure 1 to Figure 4 It can be seen that Figure 1 The surface pores are evenly distributed, the pores are regular in shape and moderate in diameter, and the surface is smooth overall without losing the porous structure. The ratio of TiO2 nanoparticles and CaCO2 nanoparticles on the membrane achieves uniform dispersion between particles, which not only improves the hydrophilicity and oleophobicity, but also avoids particle agglomeration and pore collapse. Figure 2 The pore distribution of the PA active layer in the cross section is uniform, the pore walls are regular and well connected, and the pores present a relatively clear microporous structure. Figure 3 , 4 This is an atomic force microscope characterization image. The characterization shows that the introduction of fillers changes the dynamics of interfacial polymerization, resulting in relatively uniform and slightly significant particle protrusions on the membrane surface. This moderate degree of roughness helps to balance the hydrophilicity and oleophobicity and anti-fouling properties of the membrane to achieve better water treatment effects.

[0129] 2. Water treatment performance and separation performance test: A 2 mol / L NaCl aqueous solution was selected as the draw liquid, and the water flux (unit: L·m-2·h-1), reverse solute flux (unit: L·m-2·h-1), and Js / Jw (unit: g·L-1) of the forward osmosis membranes obtained in Examples 1-2 and Comparative Examples 1-8 were tested. The results are shown in Table 1.

[0130] Table 1 Measurement results

[0131] Water flux Reverse solute flux Js / Jw Example 1 30.44 3.68 0.12 Example 2 29.53 3.77 0.13 Comparative Example 1 17.00 8.00 0.47 Comparative Example 2 20.44 4.30 0.21 Comparative Example 3 26.48 4.79 0.18 Comparative Example 4 25.06 5.30 0.21 Comparative Example 5 21.62 4.35 0.20 Comparative Example 6 24.45 4.03 0.17 Comparative Example 7 28.51 3.94 0.15 Comparative Example 8 27.86 3.98 0.16

[0132] According to statistics, the nanoparticle blended modified forward osmosis membrane prepared by Examples 1-2 of the present invention has high water flux, low reverse solute flux and Js / Jw, indicating that the prepared forward osmosis membrane has excellent water treatment performance and oil-water separation ability. Comparative Example 1 does not introduce nano calcium carbonate and nano titanium dioxide, the mass ratios of nano calcium carbonate and nano titanium dioxide in Comparative Examples 2-4 are all high or low, Comparative Example 5 does not add modified zinc oxide, Comparative Example 6 does not modify zinc oxide, Comparative Example 7 does not add multilayer graphene oxide, Comparative Example 8 does not dope and modify nano titanium dioxide, and the prepared forward osmosis membrane has low water flux, high reverse solute flux and Js / Jw, indicating that its water treatment performance and oil-water separation ability are poor.

[0133] 3. Hexadecane oil-water emulsion separation test: The forward osmosis membrane prepared in Example 1 was used to carry out a separation test on the hexadecane oil-water emulsion. Optical microscope images of the raw material liquid and the drawn liquid before and after separation were taken. Figure 5 .

[0134] from Figure 5 It can be seen that the n-hexadecane oil-water emulsion before separation is light-colored and contains a large number of oil droplets; after separation, the raw liquid turns milky white, the water is effectively separated, the oil droplets are trapped, and the oil droplet concentration increases significantly. The drawn liquid remains transparent before and after separation, and the optical microscope image shows that no oil droplets have penetrated.

[0135] 4. Applicability test: In order to verify the wide applicability of the forward osmosis membrane prepared in Example 1, low-viscosity petroleum ether and n-hexane, high-polarity toluene, and high-viscosity n-hexadecane were selected for separation tests, and their water flux and retention rate were tested. The results are shown in Figure 6 .

[0136] from Figure 6 It can be seen that the forward osmosis membrane prepared in Example 1 always maintains a high separation efficiency, a stable water flux of 25-28 L·m-2·h-1, and a retention rate of more than 99%, whether facing low-viscosity petroleum ether and n-hexane, or high-polarity toluene and high-viscosity n-hexadecane. This shows that the forward osmosis membrane prepared in Example 1 has a wide range of applicability, excellent chemical compatibility, the ability to handle complex emulsified systems, and good stability, and is suitable for oil-water separation needs in multiple fields.

[0137] 5. Anti-pollution and durability test: In order to verify the anti-pollution and durability of the forward osmosis membrane prepared in Example 1, n-hexadecane was selected to carry out a 120-minute oil-water separation performance test and a 10-cycle test on the membrane. The results are shown in Table 1. Figure 7 and Figure 8 .

[0138] from Figure 7It can be seen that the forward osmosis membrane prepared in Example 1 exhibited excellent anti-pollution performance during the 120-minute oil-water separation performance test, and its water flux only decreased from 26.3 L·m-2·h-1 to 20.3 L·m-2·h-1, while the separation efficiency remained above 99%. Figure 8 It can be seen that after 10 cycles, the retention rate still remains above 99%, and although the flux is slightly reduced, it is still 20L·m-2·h-1. This stability and anti-fouling ability can be explained by the capillary effect and Laplace theory. The surface hydroxyl groups of nano-titanium dioxide on the membrane improve the stability of the membrane by forming hydrogen bonds with water molecules, while promoting the emulsification and rupture of the oil-water emulsion. When the oil droplets come into contact with the pre-wetted water surface, the membrane surface has an upward force on the water and an upward repulsive force on the oil droplets, which only allows water to pass through and form a water layer to repel the oil. At the same time, the polarity of nano-titanium dioxide enhances the repulsive ability of hydrophobic oil droplets, making the oil droplets easier to slide off. The accumulation of nano-calcium carbonate on the membrane surface leads to a decrease in the average pore size and an increase in the capillary effect. With the increase in surface capillary force and the improvement of surface wettability, water molecules are more likely to pass through the membrane, and the embedding and attachment of oil droplets are further reduced. This property can reduce the operating cost of the membrane, extend the service life of the membrane, and make it suitable for continuous operation requirements in actual oil-water separation.

[0139] Therefore, the nanoparticle blended modified forward osmosis membrane prepared by the method described in this application not only has excellent pure water flux and oil retention rate, can achieve efficient and stable oil-water separation, but also performs well in anti-pollution performance and long-term stability. After 10 oil-water separation cycle tests, the membrane can still maintain efficient separation ability, proving its application potential in the treatment of complex oil-water emulsions. At the same time, the membrane surface morphology is good, the preparation method is simple and easy, the cost is low, and it can be mass-produced, which has broad application prospects in the field of membrane treatment oil-water separation.

[0140] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a nanoparticle blended modified forward osmosis membrane, characterized in that: The following steps are involved: S1. Add polyethersulfone, polyvinylpyrrolidone, modified zinc oxide and polyether into N-methylpyrrolidone, heat to 65-75°C and stir for 5-7h to obtain a uniform and transparent solution, and then stand at room temperature for 12h or more to obtain a casting solution; S2. Pour the casting solution onto a smooth glass plate, scrape it with a metal rod into a solution film with a thickness of 100-200 μm, and immediately immerse the glass plate in deionized water. Let it stand until the film falls off automatically, then take it out and rinse it with deionized water for 5-8 times to obtain a base film. S3, adding the nanoparticles into the m-phenylenediamine aqueous solution and subjecting it to ultrasonic stirring to obtain a nanoparticle dispersion; S4. Completely immerse the base film in the nanoparticle dispersion for 8-15 minutes, then take it out and let it stand for 1-2 minutes, then absorb the excess water on the surface, drip a mixed solution of benzyl chloride and n-hexane on the surface, heat treat it at 110-120°C for 2-5 minutes to form an interfacial polymerization layer, rinse the surface water stains with n-hexane, cure it in an air circulation oven at 55-65°C for 8-15 minutes, cool it to room temperature, wash it with deionized water 3-5 times, and dry it.

2. The method for preparing the nanoparticle blended modified forward osmosis membrane according to claim 1, characterized in that: The apparent density of the polyethersulfone is 0.2-0.3 g / cm 3 , viscosity number is 100-110cm 3 / g, and the molecular weight is 90000-110000g / mol.

3. The method for preparing the nanoparticle blended modified forward osmosis membrane according to claim 1, characterized in that, The K value of the polyvinyl pyrrolidone is 27-32.4, and the viscosity average molecular weight is 45000-58000.

4. The method for preparing the nanoparticle blended modified forward osmosis membrane according to claim 1, characterized in that: The preparation method of the modified zinc oxide comprises the following steps: A1. Graphene oxide and zinc acetate are mixed with ethanol respectively, and ultrasonically stirred for 1-2 hours to obtain graphene oxide / ethanol solution and zinc acetate / ethanol solution respectively; A2. Graphene oxide / ethanol solution and zinc acetate / ethanol solution are mixed to obtain a mixed solution, the pH of the mixed solution is adjusted to 8-10, and the mixed solution is subjected to hydrothermal reaction at 175-185° C. for 10-15 h, cooled to room temperature, filtered, washed with deionized water until neutral, vacuum dried, ground, and passed through a 1000-2000 mesh sieve to obtain.

5. The method for preparing the nanoparticle blended modified forward osmosis membrane according to claim 4, characterized in that: The graphene oxide includes single-layer graphene oxide and multi-layer graphene oxide.

6. The method for preparing the nanoparticle blended modified forward osmosis membrane according to claim 5, characterized in that: The single-layer graphene oxide has a sheet diameter of 0.5-5 μm and a thickness of 0.8-1.2 nm; the multi-layer graphene oxide has a sheet diameter of 10-300 nm, a layer number of ≤5, and a specific surface area of ​​480-520 m 2 / g.

7. The method for preparing the nanoparticle blended modified forward osmosis membrane according to claim 1, characterized in that: The nanoparticles include one or more of nano calcium carbonate and nano titanium dioxide.

8. The method for preparing the nanoparticle blended modified forward osmosis membrane according to claim 7, characterized in that: The mass ratio of the nano calcium carbonate to the nano titanium dioxide is (1-2):

1.

9. A nanoparticle blended modified forward osmosis membrane prepared according to the method for preparing a nanoparticle blended modified forward osmosis membrane according to any one of claims 1 to 8.

10. An application of the nanoparticle blended modified forward osmosis membrane according to claim 9 in the technical fields of environmental management and new energy.

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