Preparation method and application of nanoparticle blending modified forward osmosis membrane

Abstract

The application belongs to the technical field of forward osmosis separation membrane, and particularly relates to a preparation method of a nanoparticle blending modified forward osmosis membrane and application thereof. The application first adopts a phase inversion method to form a porous network structure polyether sulfone membrane as a base membrane of the forward osmosis membrane through exchange of a solvent and a non-solvent to initiate phase separation, and then utilizes an interfacial polymerization reaction of m-phenylenediamine and triformyl chloride to prepare a dense polyimide active layer on the base membrane. The nanoparticle blending modified forward osmosis membrane is prepared through modification of the base membrane and the active layer. The membrane not only has excellent pure water flux and oil retention rate, can realize efficient and stable oil-water separation, and is excellent in anti-fouling performance and long-term stability, but also has a good morphology, the preparation method is simple and easy to implement, the cost is low, and the membrane can be mass-produced. The nanoparticle blending modified forward osmosis membrane has a wide application prospect in the field of membrane treatment oil-water separation, and can be applied to technical fields such as environmental governance and new energy.

Description

Technical Field

[0001] This invention belongs to the field of forward osmosis separation membrane technology, specifically relating to a method for preparing a nanoparticle blended modified forward osmosis membrane and its application. Background Technology

[0002] Traditional separation methods, such as sedimentation, adsorption, and centrifugation, have been used to treat oily wastewater. While these technologies are effective at purifying wastewater containing suspended oil, they cannot handle surfactant-stabilized emulsions. Membrane separation technology has emerged as an emerging solution due to its superior separation efficiency, low energy requirements, ease of operation, and environmental sustainability. However, traditional 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 membrane fouling, leading to low water recovery efficiency and frequent membrane cleaning. Compared to other pressure-driven membrane processes, forward osmosis does not require external pressure. It utilizes the osmotic pressure difference across the forward osmotic membrane as the driving force, consuming less energy and thus providing an alternative for sustainable oily water recovery. However, due to the prevalence of oil contamination, forward osmosis technology remains plagued by membrane fouling in oily wastewater treatment. In addition to organic fouling caused by oil, concentration polarization and the low mechanical strength of the membrane itself are particularly problematic in treating such viscous, highly mineralized emulsions.

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

[0004] The purpose of this 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 rejection rate, enabling efficient and stable oil-water separation, but also exhibits excellent antifouling performance and long-term stability, and has broad application prospects in the field of membrane treatment oil-water separation.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] The preparation method of the nanoparticle blend-modified forward osmosis membrane includes the following steps:

[0007] S1. Add polyethersulfone, polyvinylpyrrolidone, modified zinc oxide, and polyether to N-methylpyrrolidone, heat to 65-75℃ and stir for 5-7 hours to obtain a uniform and transparent solution, and then let it stand at room temperature for 12 hours or more to obtain the casting solution.

[0008] S2. Pour the casting solution onto a smooth glass plate and scrape it into a solution film 100-200μm thick with a metal rod. Immediately immerse the glass plate and the film in deionized water and let it stand. After the film automatically detaches, remove it and rinse it with deionized water 5-8 times to obtain the base film.

[0009] S3. Add the nanoparticles to an aqueous solution of m-phenylenediamine and stir ultrasonically to obtain a nanoparticle dispersion.

[0010] S4. After completely immersing the base film in the nanoparticle dispersion for 8-15 minutes, remove it and let it stand for 1-2 minutes. Then, absorb the excess water on the surface and drop a mixed solution of benzotrimethylammonium chloride and n-hexane onto the surface. Heat-treat at 110-120℃ for 2-5 minutes to form an interfacial polymerization layer. Rinse the surface with n-hexane to remove water stains. Cure in an air-circulating oven at 55-65℃ for 8-15 minutes. After cooling to room temperature, wash with deionized water 3-5 times and dry to obtain the final product.

[0011] Preferably, the apparent density of the polyethersulfone is 0.2-0.3 g / cm³. 3 The adhesion count is 100-110cm. 3 / g, with a molecular weight of 90,000-110,000 g / mol; more preferably, the apparent density of the polyethersulfone is 0.25 g / cm³. 3 The viscosity is 105cm. 3 / g, with a molecular weight of 92000g / mol.

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

[0013] Preferably, the polyvinylpyrrolidone has a K value of 27-32.4 and a viscosity-average molecular weight of 45,000-58,000.

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

[0015] Preferably, the polyether has an average molecular weight of 10,500-12,500, the turbidity point of the 1% polyether aqueous solution is ≥100℃, and the degree of 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 polyethersulfone, polyether, and modified zinc oxide is (40-50):(4-8):1; more preferably, it is 45:6:1.

[0018] Specific polyethersulfones (PES) are used to prepare the base membrane (support layer) of forward osmosis membranes. PES exhibits excellent chemical stability, heat resistance, and dimensional stability, making it suitable for use as a support layer in forward osmosis membranes. However, its hydrophobic nature means that during oil-water separation, polymers from oil droplets and wastewater easily adsorb onto the membrane surface, causing membrane blockage. This leads to a decrease in water flux and separation efficiency, while also affecting cycle stability and lifespan. Modifying PES with zinc oxide and specific polyethers can improve the hydrophilicity of the PES membrane while simultaneously enhancing its antifouling properties. This is likely due to a synergistic effect between the two, forming a "double-layer protection" mechanism on the PES membrane surface. On the one hand, certain polyethers are amphiphilic; the hydrophobic end enhances their anchoring effect on the polyethersulfone membrane, while the hydrophilic end provides hydrophilic modification, thus reducing the initial adhesion of contaminants. On the other hand, the addition of zinc oxide not only enhances this hydrophilic effect but also continuously removes any small amounts of contaminants that may form through its photocatalytic activity. The combined effect of these two factors significantly improves the membrane's antifouling ability. Simultaneously, zinc oxide, as an inorganic filler, acts as a reinforcing agent in the membrane, increasing its tensile and tear strength. The addition of polyether also improves the membrane's toughness, making it less prone to breakage under external forces, extending its service life, and maintaining high water flux and separation efficiency. However, zinc oxide has poor chemical stability, low visible light utilization efficiency, and is prone to aggregation, affecting its co-modification effect with polyether on polyethersulfone, and consequently impacting the performance of the forward osmosis membrane.

[0019] The method for preparing the modified zinc oxide includes the following steps:

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

[0021] A2. Mix graphene oxide / ethanol solution and zinc acetate / ethanol solution to obtain a mixed solution. Adjust the pH of the mixed solution to 8-10. After hydrothermal reaction at 175-185℃ for 10-15 hours, cool to room temperature, filter and wash with deionized water until neutral. After vacuum drying, grind and pass through a 1000-2000 mesh sieve to obtain the final product.

[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; more 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 monolayer graphene oxide is purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd.

[0026] Preferably, the multilayer graphene oxide has a sheet diameter of 10-300 nm, a number of layers ≤ 5, and a specific surface area of ​​480-520 m². 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 zinc acetate / ethanol solution contains 10%-20% zinc acetate by mass.

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

[0031] Modifying zinc oxide with specific graphene oxide not only improves its dispersibility and stability but also reduces water flux resistance, enhancing the oil-water separation performance of forward osmosis membranes. This is likely due to a synergistic effect: the presence of graphene oxide sheets provides growth sites for zinc oxide, preventing the aggregation of nano-zinc oxide; conversely, the growth of nano-zinc oxide on graphene oxide sheets reduces the interlayer interactions, mitigating aggregation and achieving excellent modification results. The hydroxyl and carboxyl functional groups on the graphene oxide surface, along with the hydrogen bonds between zinc oxide and water molecules, collectively increase the hydrophilicity of the membrane surface, further improving the oil-water separation efficiency of forward osmosis membranes. Furthermore, the combination of single-layer and multi-layer graphene oxide with different sheet sizes effectively prevents zinc oxide particle aggregation and significantly improves its dispersibility and stability in the modified system. This synergistic effect further optimizes the membrane structure, forming a multi-layered network structure that provides more transport channels for water molecules, while also enhancing the membrane's mechanical properties, making it more durable and stable. Although the modification of graphene oxide improves the dispersibility and stability of zinc oxide to some extent, the addition of excessive inorganic particles during the preparation of the base membrane may still lead to agglomeration, making the base membrane too brittle and affecting its flexibility and mechanical strength, thus affecting its oil-water separation effect. At the same time, the performance improvement of modified zinc oxide and polyether on forward osmosis membrane is also limited. Therefore, further treatment of the polyamide active layer is needed to further improve the oil-water separation effect of the forward osmosis membrane.

[0032] Preferably, the amount of polyvinylpyrrolidone added is 20%-25% of the mass of polyethersulfone.

[0033] Preferably, the amount of N-methylpyrrolidone added 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; more preferably, it is 3:2.

[0036] Preferably, the nano-calcium carbonate is hydrophilic nano-calcium carbonate with a particle size of 180-220 nm and a specific surface area of ​​25-35 m². 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] Modifying the polyimide active layer with nano-titanium dioxide and nano-calcium carbonate not only improves pure water flux and oil rejection rate, resulting in excellent oil-water separation, but also exhibits superior anti-fouling properties and long-term stability. Nano-titanium dioxide has attracted considerable attention in oil-water separation materials due to its excellent hydrophilic and oleophobic properties; however, pure nano-titanium dioxide is difficult to use alone due to its fragile particle structure and tendency to accumulate. By interfacial polymerization, a two-component blend of nano-calcium carbonate and nano-titanium dioxide is incorporated into the polyimide active layer, further optimizing the overall performance of the oil-water separation membrane and providing a new solution for practical applications in complex environments. Nano-titanium dioxide and nano-calcium carbonate exhibit a synergistic effect. The hydroxyl groups on the surface of nano-titanium dioxide form hydrogen bonds with water molecules, enhancing the hydrophilicity of the membrane surface. These hydrogen bonds promote water molecule penetration, improving membrane stability and simultaneously increasing oil repellency, thus promoting the emulsification and breakdown of oil-water emulsions. When oil droplets come into contact with a pre-wetted water surface, the membrane surface exerts an upward force on the water and an upward repulsive force on the oil droplets. This allows water to pass through and form a water layer that repels the oil. Simultaneously, the polarity of titanium dioxide enhances the repulsion of hydrophobic oil droplets, making them easier to slide off. The accumulation of nano-calcium carbonate on the membrane surface leads to a reduction in average pore size and an increase in capillary effect. Furthermore, the electrostatic repulsion of carbonate groups further inhibits oil droplet entry into the membrane channels. With the increase in surface capillary force and improved surface wettability, water molecules can more easily pass through the membrane, further reducing oil droplet embedding and adhesion. This property reduces membrane operating costs, extends membrane lifespan, and makes it suitable for continuous operation in practical oil-water separation. By controlling its proportions, the prepared forward osmosis membrane can exhibit excellent pure water flux and oil rejection rate, while also demonstrating superior antifouling performance and long-term stability. Meanwhile, nano-titanium dioxide enhances the membrane's hydrophilicity and oil-fouling resistance, while nano-calcium carbonate optimizes the pore structure and provides mechanical support, enhancing the membrane's structural stability. This avoids the problems of excessive membrane roughness and particle and oil contaminant accumulation caused by high-concentration nano-titanium dioxide, improving the material's separation efficiency 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 membrane's water flux and oil rejection performance, while effectively reducing reverse solute flux. Especially when processing high-concentration, high-viscosity oil-water emulsions, the modified membrane exhibits excellent antifouling ability and chemical stability, making the prepared membrane widely applicable, with excellent chemical compatibility, the ability to handle complex emulsion systems, and good stability, suitable for oil-water separation needs in multiple fields. Furthermore, the precise particle doping ratio avoids the problems of particle agglomeration and excessive membrane roughness, forming a uniform microporous structure.

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

[0040] B1. Tetrabutyl titanate is dissolved in anhydrous ethanol to obtain a tetrabutyl titanate / ethanol solution. Nitrogen source and carbon source are dissolved in water to obtain a doped solution.

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

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

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

[0044] Preferably, the nitrogen source includes urea.

[0045] Preferably, the carbon source includes one or more of glucose, fructose, and melamine; more 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); more preferably, it is 22:1:3.

[0047] To further improve the water flux and separation efficiency of forward osmosis membranes, nitrogen and carbon elements were selected for doping modification of nano-titanium dioxide. This is likely because, on the one hand, nitrogen atoms can replace oxygen atoms or exist as interstitial atoms, thereby altering the surface chemistry of titanium dioxide, enhancing its interaction with water molecules, and increasing its hydrophilicity. On the other hand, the incorporation of carbon can extend the absorption wavelength of titanium dioxide into the visible light range and change its surface structure, making nano-titanium dioxide a superhydrophilic surface. The co-doping of these two elements improves both the water flux and separation efficiency of the forward osmosis membrane.

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

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

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

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

[0052] The nanoparticle blended modified forward osmosis membrane prepared by the method described above is a nanoparticle blended modified forward osmosis membrane.

[0053] Applications of the nanoparticle blended modified forward osmosis membrane in environmental governance, new energy and other technical fields.

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

[0055] 1. This invention provides a method for preparing a nanoparticle-modified forward osmosis membrane and its application. First, a phase inversion method is used to initiate phase separation through solvent and non-solvent exchange, forming a polyethersulfone membrane with a porous network structure as the base membrane for the forward osmosis membrane. Then, a dense polyimide active layer is prepared on the base membrane using an interfacial polymerization reaction of m-phenylenediamine and triformyl chloride. Through modification of the base membrane and the active layer, a forward osmosis membrane is obtained. This membrane not only exhibits excellent pure water flux and oil rejection rate, enabling efficient and stable oil-water separation, but also demonstrates excellent antifouling performance and long-term stability. After 10 oil-water separation cycle tests, the membrane still maintains high separation efficiency, proving its application potential in the treatment of complex oil-water emulsions. The forward osmosis membrane prepared by this invention has excellent performance and good morphology. The preparation method is simple, easy to implement, and low in cost, allowing for mass production and showing broad application prospects in the field of membrane treatment and oil-water separation.

[0056] 2. In this invention, zinc oxide and a specific polyether are used to modify polyethersulfone, which can improve the hydrophilicity of polyethersulfone membranes while improving their antifouling properties.

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

[0058] 4. This invention uses nano-titanium dioxide and nano-calcium carbonate to modify the polyimide active layer, which not only improves the pure water flux and oil rejection rate, resulting in good oil-water separation, but also has excellent anti-fouling properties and long-term stability. Attached Figure Description

[0059] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0060] Figure 1 This is a SEM 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 blend-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 blend-modified forward osmosis membrane described in Example 1 of the present invention.

[0064] Figure 5 The images shown are optical microscope images of the feed liquid and the draw liquid before and after separation of n-hexadecane oil-water emulsion using a nanoparticle blend-modified forward osmosis membrane as described in Example 1 of this invention.

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

[0066] Figure 7 The flux and rejection rate of the nanoparticle blended modified forward osmosis membrane used in Example 1 of this invention for separating n-hexadecane oil-water emulsion for 120 min are given.

[0067] Figure 8 The flux and rejection rate of the nanoparticle blended modified forward osmosis membrane for separating n-hexadecane oil-water emulsion were measured after 10 cycles, as described in Example 1 of this invention. Detailed Implementation

[0068] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0069] All raw materials used in this invention are commercially available, specifically:

[0070] The apparent density of polyethersulfone is 0.25 g / cm³. 3 The viscosity is 105cm. 3 / g, molecular weight 92000 g / mol, purchased from BASF, Germany. E 7020P.

[0071] Polyvinylpyrrolidone (PVP) with a K value of 27-32.4 and a viscosity-average molecular weight of 45,000-58,000 was purchased from Boai Xinkaiyuan Medical Technology Group Co., Ltd. PVP-K30.

[0072] The single-layer graphene oxide sheets have a diameter of 0.5-5 μm and a thickness of 0.8-1.2 nm and were purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd.

[0073] Multilayer graphene oxide has a sheet diameter of 10-300 nm, a number of layers ≤ 5, and a specific surface area of ​​480-520 m². 2 / g, purchased from Beijing Graphene Research Institute Co., Ltd.

[0074] The polyether has an average molecular weight of 10,500-12,500, a turbidity point of ≥100℃ for a 1% polyether aqueous solution, and an unsaturation of 0.03-0.1 mmol / g. It was purchased from Nanjing Dulai Biotechnology Co., Ltd. as block polyether F-127.

[0075] 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 m². 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 forward osmosis membrane modified with nanoparticle blending, the steps of which are as follows:

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

[0079] S2. Pour the casting solution onto a smooth glass plate and scrape it into a 150μm thick solution film with a metal rod. Immediately immerse the glass plate and the film in deionized water, let it stand, and remove it after the film automatically detaches. Rinse it 7 times with deionized water to obtain the base film.

[0080] S3. Add 0.1g of nanoparticles to 100g of m-phenylenediamine aqueous solution and stir ultrasonically to obtain a nanoparticle dispersion.

[0081] S4. After completely immersing the base film in the nanoparticle dispersion for 10 minutes, remove it and let it stand for 1.5 minutes. Then, absorb the excess water on the surface and drop 5 mL of a mixed solution of benzotrimethylammonium chloride and n-hexane onto the surface. Heat-treat at 105°C for 3 minutes to form an interfacial polymerization layer. Rinse the surface with n-hexane to remove water stains. Cure in an air-circulating oven at 60°C for 10 minutes. After cooling to room temperature, wash with deionized water 4 times and dry to obtain the final product.

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

[0083] A1. Graphene oxide and zinc acetate were mixed with ethanol respectively and ultrasonically stirred for 1.5 minutes to obtain graphene oxide / ethanol solution and zinc acetate / ethanol solution respectively.

[0084] A2. After mixing graphene oxide / ethanol solution and zinc acetate / ethanol solution, the pH of the mixture is adjusted to 9. After hydrothermal reaction at 180℃ for 12 hours, it is cooled to room temperature, filtered, washed with deionized water until neutral, vacuum dried, ground and passed through a 1500-mesh sieve to obtain the final product.

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

[0086] The graphene oxide / ethanol solution contains 8% graphene oxide by mass.

[0087] The zinc acetate / ethanol solution contains 15% zinc acetate by mass.

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

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

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

[0091] B1. Tetrabutyl titanate is dissolved in anhydrous ethanol to obtain a tetrabutyl titanate / ethanol solution. Urea and glucose are dissolved in water to obtain a doped solution.

[0092] B2. Add the doped solution dropwise into the tetrabutyl titanate ethanol solution, stir at 1000 r / min for 2 h, adjust the pH of the system to 2, continue stirring at 1000 r / min for 2 h, age at room temperature for 24 h, dry at 70℃ for 24 h, calcine at 600℃ in a nitrogen atmosphere for 2.5 h, grind and pass through a 1500 mesh sieve to obtain the final product.

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

[0094] The total mass percentage of nitrogen and carbon sources in the doped solution is 1.5%.

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

[0096] The aqueous solution of m-phenylenediamine has a m-phenylenediamine mass percentage of 2%.

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

[0098] In the mixed solution of benzotricarboxylic acid chloride and n-hexane, the mass percentage of benzotricarboxylic acid 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 in a mass ratio of 1:1.

[0101] Comparative Example 1

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

[0103] S2. Pour the casting solution onto a smooth glass plate and scrape it into a 150μm thick solution film with a metal rod. Immediately immerse the glass plate and the film in deionized water, let it stand, and remove it after the film automatically detaches. Rinse it 7 times with deionized water to obtain the base film.

[0104] S3. Prepare an aqueous solution of m-phenylenediamine;

[0105] S4. After completely immersing the base film in an aqueous solution of m-phenylenediamine for 10 minutes, remove it and let it stand for 1.5 minutes. Then, absorb the excess water on the surface and drop 5 mL of a mixed solution of benzotrimethylammonium chloride and n-hexane onto the surface. After heat treatment at 105°C for 3 minutes to form an interfacial polymerization layer, rinse the surface water stains with n-hexane and cure it in an air-circulating oven at 60°C for 10 minutes. After cooling to room temperature, wash it 4 times with deionized water and dry it to obtain the final product.

[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 in a mass ratio of 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 in a mass ratio of 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 in a mass ratio of 1:4.

[0112] Comparative Example 5

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

[0114] S2. Pour the casting solution onto a smooth glass plate and scrape it into a 150μm thick solution film with a metal rod. Immediately immerse the glass plate and the film in deionized water, let it stand, and remove it after the film automatically detaches. Rinse it 7 times with deionized water to obtain the base film.

[0115] S3. Add 0.1g of nanoparticles to an aqueous solution of m-phenylenediamine and stir ultrasonically to obtain a nanoparticle dispersion.

[0116] S4. After completely immersing the base film in the nanoparticle dispersion for 10 minutes, remove it and let it stand for 1.5 minutes. Then, absorb the excess water on the surface and drop 5 mL of a mixed solution of benzotrimethylammonium chloride and n-hexane onto the surface. Heat-treat at 105°C for 3 minutes to form an interfacial polymerization layer. Rinse the surface with n-hexane to remove water stains. Cure in an air-circulating oven at 60°C for 10 minutes. After cooling to room temperature, wash with deionized water 4 times and dry to obtain the final product.

[0117] Comparative Example 6

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

[0119] S2. Pour the casting solution onto a smooth glass plate and scrape it into a 150μm thick solution film with a metal rod. Immediately immerse the glass plate and the film in deionized water, let it stand, and remove it after the film automatically detaches. Rinse it 7 times with deionized water to obtain the base film.

[0120] S3. Add 0.1g of nanoparticles to an aqueous solution of m-phenylenediamine and stir ultrasonically to obtain a nanoparticle dispersion.

[0121] S4. After completely immersing the base film in the nanoparticle dispersion for 10 minutes, remove it and let it stand for 1.5 minutes. Then, absorb the excess water on the surface and drop 5 mL of a mixed solution of benzotrimethylammonium chloride and n-hexane onto the surface. Heat-treat at 105°C for 3 minutes to form an interfacial polymerization layer. Rinse the surface with n-hexane to remove water stains. Cure in an air-circulating oven at 60°C for 10 minutes. After cooling to room temperature, wash with deionized water 4 times and dry to obtain the final product.

[0122] Comparative Example 7

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

[0124] Comparative Example 8

[0125] The difference between this comparative example and Example 1 is as follows: the preparation method of the nano titanium dioxide is as follows: tetrabutyl titanate is dissolved in anhydrous ethanol to obtain a tetrabutyl titanate / ethanol solution. After stirring at 1000 r / min for 2 h, the pH of the system is adjusted to 2, and stirring is continued at 1000 r / min for 2 h. After aging at room temperature for 24 h, it is dried at 70 °C for 24 h, calcined in a nitrogen atmosphere at 600 °C for 2.5 h, ground and passed through a 1500 mesh sieve to obtain the final product.

[0126] Performance testing

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

[0128] from Figures 1-4 It can be seen that, Figure 1 The surface has a uniform pore distribution, regular pore shape and moderate pore size, and the surface is smooth overall but retains a porous structure. The ratio of TiO2 nanoparticles to CaCO2 nanoparticles on the membrane achieves uniform dispersion among the particles, which not only improves hydrophilicity and oleophobicity but also avoids particle aggregation and pore collapse. Figure 2 The pores in the PA active layer of the cross section are uniformly distributed, with regular pore walls and good connectivity, and the channels exhibit a relatively clear microporous structure. Figure 3 , 4 The image is an atomic force microscopy (AFM) characterization image. The characterization shows that the introduction of the filler altered the dynamics of interfacial polymerization, resulting in relatively uniform and slightly prominent particle protrusions on the membrane surface. This moderate roughness helps to balance the membrane's hydrophilicity, oleophobicity, and antifouling properties, thereby achieving better water treatment results.

[0129] 2. Water treatment performance and separation performance test: The NaCl aqueous solution with a concentration of 2 mol / L was used as the draw solution. 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 membranes prepared in Examples 1-2 of this invention have high water flux and low reverse solute flux and Js / Jw, indicating that the prepared forward osmosis membranes have excellent water treatment performance and oil-water separation ability. Comparative Example 1 did 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 were either too high or too low; Comparative Example 5 did not add modified zinc oxide; Comparative Example 6 did not modify zinc oxide; Comparative Example 7 did not add multilayer graphene oxide; and Comparative Example 8 did not dope or modify nano-titanium dioxide. The prepared forward osmosis membranes had low water flux and high reverse solute flux and Js / Jw, indicating poor water treatment performance and oil-water separation ability.

[0133] 3. Separation test of n-hexadecane oil-water emulsion: The forward osmosis membrane prepared in Example 1 was used to separate the n-hexadecane oil-water emulsion. Optical micrographs of the feed solution and the draw solution before and after separation were taken, see [reference]. Figure 5 .

[0134] from Figure 5 As can be seen, the n-hexadecane oil-water emulsion before separation was light-colored and contained a large number of oil droplets; after separation, the feed liquid turned milky white, the water was effectively separated, the oil droplets were retained, and the oil droplet concentration increased significantly. The extract remained transparent before and after separation, and optical microscope images showed no oil droplet infiltration.

[0135] 4. Suitability Test: To verify the versatility of the forward osmosis membrane prepared in Example 1, separation tests were conducted using low-viscosity petroleum ether and n-hexane, highly polar toluene, and high-viscosity n-hexadecane, respectively. The water flux and rejection rate were tested, and the results are shown in [Figure Number]. Figure 6 .

[0136] from Figure 6 As can be seen, the forward osmosis membrane prepared in Example 1 maintains a high separation efficiency regardless of whether it is used with low-viscosity petroleum ether and n-hexane, or with highly polar toluene and high-viscosity n-hexadecane. The water flux is stable at 25-28 L·m⁻²·h⁻¹, and the rejection rate exceeds 99%. This indicates that the forward osmosis membrane prepared in Example 1 has wide applicability, excellent chemical compatibility, the ability to handle complex emulsion systems, and good stability, making it suitable for oil-water separation needs in multiple fields.

[0137] 5. Antifouling and Durability Tests: To verify the antifouling and durability of the forward osmosis membrane prepared in Example 1, n-hexadecane was used to conduct a 120-minute oil-water separation performance test and a 10-cycle test on the membrane. The results are shown below. Figure 7 and Figure 8 .

[0138] from Figure 7It can be seen that the forward osmosis membrane prepared in Example 1 exhibited excellent antifouling performance during the 120-minute oil-water separation performance test. Its water flux decreased only 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 As can be seen, after 10 cycles, the rejection rate remained above 99%, and although the flux decreased slightly, it still reached 20 L·m⁻²·h⁻¹. This stability and antifouling ability can be explained by the capillary effect and Laplace's theory. The surface hydroxyl groups of nano-titanium dioxide on the membrane enhance the membrane's stability by forming hydrogen bonds with water molecules, while simultaneously promoting the emulsion breakdown of oil-water emulsions. When oil droplets come into contact with a pre-wetted water surface, the membrane surface exerts an upward force on the water and an upward repulsive force on the oil droplets, allowing water to pass through and forming a water layer to repel oil. Simultaneously, the polarity of nano-titanium dioxide enhances the repulsion of hydrophobic oil droplets, making them easier to slide off. The accumulation of nano-calcium carbonate on the membrane surface leads to a reduction in average pore size and an increase in capillary effect. With the increase in surface capillary force and improved surface wettability, water molecules can more easily pass through the membrane, further reducing oil droplet embedding and adhesion. This property can reduce membrane operating costs, extend membrane life, and make it suitable for continuous operation requirements in practical 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 rejection rate, enabling efficient and stable oil-water separation, but also exhibits excellent antifouling performance and long-term stability. After 10 oil-water separation cycle tests, the membrane still maintains high separation efficiency, demonstrating its application potential in the treatment of complex oil-water emulsions. At the same time, the membrane has good surface morphology, the preparation method is simple and easy to implement, the cost is low, and it can be mass-produced, showing broad application prospects in the field of membrane treatment and oil-water separation.

[0140] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a forward osmosis membrane modified with nanoparticle blending, characterized in that, Includes the following steps: S1. Add polyethersulfone, polyvinylpyrrolidone, modified zinc oxide, and polyether to N-methylpyrrolidone, heat to 65-75℃ and stir for 5-7 hours to obtain a uniform and transparent solution, and then let it stand at room temperature for 12 hours or more to obtain the casting solution. S2. Pour the casting solution onto a smooth glass plate and scrape it into a solution film 100-200µm thick with a metal rod. Immediately immerse the glass plate and the film in deionized water and let it stand. After the film automatically detaches, remove it and rinse it with deionized water 5-8 times to obtain the base film. S3. Add the nanoparticles to an aqueous solution of m-phenylenediamine and stir ultrasonically to obtain a nanoparticle dispersion. S4. After completely immersing the base film in the nanoparticle dispersion for 8-15 minutes, remove it and let it stand for 1-2 minutes. Then, absorb the excess water on the surface and drop a mixed solution of benzotrimethylammonium chloride and n-hexane onto the surface. Heat-treat at 110-120℃ for 2-5 minutes to form an interfacial polymerization layer. Rinse the surface with n-hexane to remove water stains. Cure in an air-circulating oven at 55-65℃ for 8-15 minutes. After cooling to room temperature, wash with deionized water 3-5 times and dry to obtain the final product. Methods for preparing modified zinc oxide include: A1. Graphene oxide and zinc acetate were mixed with ethanol and ultrasonically stirred for 1-2 hours to obtain graphene oxide / ethanol solution and zinc acetate / ethanol solution, respectively. A2. Mix graphene oxide / ethanol solution and zinc acetate / ethanol solution to obtain a mixture. Adjust the pH of the mixture to 8-10. After hydrothermal reaction at 175-185℃ for 10-15 hours, cool to room temperature, filter, wash with deionized water until neutral, vacuum dry, grind and pass through a 1000-2000 mesh sieve to obtain the final product. Graphene oxide includes monolayer graphene oxide and multilayer graphene oxide. Monolayer graphene oxide has a sheet diameter of 0.5-5 μm and a thickness of 0.8-1.2 nm; multilayer graphene oxide has a sheet diameter of 10-300 nm, ≤5 layers, and a specific surface area of ​​480-520 m². 2 / g; The nanoparticles include nano-calcium carbonate and nano-titanium dioxide in a mass ratio of (1-2):

1.

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 / cm³. 3 The adhesion count is 100-110cm. 3 / g, with a molecular weight of 90,000-110,000 g / mol.

3. The method for preparing the nanoparticle blended modified forward osmosis membrane according to claim 1, characterized in that, The polyvinylpyrrolidone has a K value of 27-32.4 and a viscosity-average molecular weight of 45,000-58,000.

4. A nanoparticle blended modified forward osmosis membrane prepared by a method according to any one of claims 1 to 3.

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