A multilayer structure nanofiltration membrane

Abstract

The utility model provides a kind of multilayer structure nanofiltration membrane, it is related to nanofiltration membrane technical field, including high-strength support layer, the outer surface wall of high-strength support layer is provided with buffer transition layer, the outer surface wall of buffer transition layer is provided with anti-pollution bottom layer.In the utility model, under the interaction of nanofiltration membrane multilayer structure, the function of nanofiltration membrane can be diversified, efficient and stabilized, wherein high-strength support layer can withstand high pressure, prevent deformation or damage of membrane during operation, protect the structural stability of membrane, buffer transition layer can effectively relieve stress between support layer and other functional layers, make each layer tightly connected, anti-pollution bottom layer can reduce the attachment of pollutants, inhibit microbial growth, prolong the service life of membrane, nanometer channel construction layer can improve the separation precision of membrane, realize efficient interception of target substance, selective separation layer can selectively intercept specific ions and small-molecule organic matter, improve the separation effect of nanofiltration membrane.

Description

Technical Field

[0001] This utility model relates to the field of nanofiltration membrane technology, and in particular to a multilayer nanofiltration membrane. Background Technology

[0002] Nanofiltration membranes are pressure-driven membrane separation materials with pore sizes between 0.5 and 2 nm. They can efficiently retain divalent and multivalent ions and small molecule organic matter with relative molecular masses of 200-1000 by means of sieving effect and charge action, thus achieving precise separation of substances.

[0003] In complex industrial scenarios such as water purification, chemical separation, and food processing, nanofiltration membranes are required to meet the requirements of high rejection rate, high water flux, and good stability simultaneously due to the difficulty of a single structure. Multilayer structures are needed to leverage the advantages of each layer of materials to work synergistically. Multilayer nanofiltration membranes can effectively improve separation efficiency, enhance antifouling ability and chemical stability, thereby improving overall performance and meeting different application needs.

[0004] However, existing multilayer nanofiltration membranes have the following shortcomings:

[0005] In existing technologies, multilayer nanofiltration membranes, due to the use of traditional materials and simple stacking processes, have overly limited functions. When treating complex water quality or high-concentration pollutants, they cannot achieve both high retention rate and high water flux simultaneously. Furthermore, their poor antifouling and stability lead to frequent replacement of membrane modules, increasing treatment costs and maintenance difficulties.

[0006] Therefore, we propose a multilayer nanofiltration membrane to address the problems mentioned above. Utility Model Content

[0007] The purpose of this invention is to provide a multilayer nanofiltration membrane. By scientifically designing the multilayer structure and selecting suitable multilayer materials, it enables efficient separation and screening of substances. By leveraging the unique properties and synergistic effects of each layer of materials, it solves the problems mentioned in the background art.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: a multilayer nanofiltration membrane, comprising a high-strength support layer, a buffer transition layer disposed on the outer wall of the high-strength support layer, and an anti-fouling bottom layer disposed on the outer wall of the buffer transition layer.

[0009] Preferably, the outer wall of the anti-fouling substrate is bonded with a nanochannel building layer.

[0010] Preferably, the outer wall of the nanochannel constructing layer is provided with a selective separation layer.

[0011] Preferably, the outer wall of the selective separation layer is provided with a charge-controlled intermediate layer.

[0012] Preferably, the outer wall of the charge-controlled intermediate layer is provided with an antioxidant protective layer.

[0013] Preferably, the outer wall of the antioxidant protective layer is provided with an anti-pollution surface layer.

[0014] Preferably, the outer wall of the anti-fouling surface layer is provided with a surface modification layer.

[0015] Compared with the prior art, the advantages and positive effects of this utility model are as follows:

[0016] 1. In this utility model, through the interaction of the multi-layer structure of the nanofiltration membrane, the functions of the nanofiltration membrane can be diversified, efficient and stable. The high-strength support layer can withstand high pressure, prevent the membrane from deforming or breaking during operation, and ensure the structural stability of the membrane. The buffer transition layer can effectively relieve the stress between the support layer and other functional layers, so that each layer is tightly connected. The anti-fouling bottom layer can reduce the adhesion of pollutants, inhibit the growth of microorganisms, and extend the service life of the membrane. The nanochannel construction layer can improve the separation accuracy of the membrane and achieve efficient retention of target substances. The selective separation layer can selectively retain specific ions and small molecule organic matter, thereby improving the separation effect of the nanofiltration membrane.

[0017] 2. In this invention, the comprehensive performance of the nanofiltration membrane is further enhanced through the interaction of the multi-layer structure of the nanofiltration membrane. The charge-controlled intermediate layer can optimize the retention performance of different ions and molecules, improve the membrane's adaptability and separation efficiency, the antioxidant protective layer can effectively resist the erosion of oxidants in water, protect the internal functional layers from oxidative damage, and extend the membrane's service life, the antifouling surface layer can significantly reduce the adsorption and adhesion of pollutants on the membrane surface, reduce the degree of membrane fouling, and the surface modification layer can improve the membrane's surface hydrophilicity, antifouling and chemical stability, and enhance the overall performance of the membrane. Attached Figure Description

[0018] Figure 1 This utility model provides a front view of the multilayer nanofiltration membrane structure.

[0019] Figure 2 This utility model provides a front view sectional perspective view of a multilayer nanofiltration membrane.

[0020] Figure 3 This invention provides a front view cross-sectional plan view of a multilayer nanofiltration membrane.

[0021] Legend: 1. High-strength support layer; 2. Buffer transition layer; 3. Anti-fouling bottom layer; 4. Nanochannel construction layer; 5. Selective separation layer; 6. Charge regulation intermediate layer; 7. Antioxidant protective layer; 8. Anti-fouling surface layer; 9. Surface modification layer. Detailed Implementation

[0022] To better understand the above-mentioned objectives, features, and advantages of this utility model, the present utility model will be further described below with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0023] Many specific details are set forth in the following description in order to provide a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the present invention is not limited to the specific embodiments disclosed in the following specification.

[0024] Example 1, as shown in the attached document Figure 1 -Appendix Figure 3 As shown, this utility model provides a technical solution: a multilayer nanofiltration membrane, including a high-strength support layer 1, a buffer transition layer 2 disposed on the outer wall of the high-strength support layer 1, an anti-fouling bottom layer 3 disposed on the outer wall of the buffer transition layer 2, a nanochannel building layer 4 bonded to the outer wall of the anti-fouling bottom layer 3, and a selective separation layer 5 disposed on the outer wall of the nanochannel building layer 4.

[0025] The overall effect achieved in Embodiment 1 is as follows: A high-strength support layer 1 is set at the innermost layer of the nanofiltration membrane. This layer, located at the innermost layer of the nanofiltration membrane, acts as the "skeleton" of the nanofiltration membrane, providing stable physical support for the entire membrane structure. This ensures that the membrane will not rupture or deform under harsh conditions such as high pressure and high flow rate. In practical applications, such as the high-pressure environment of seawater desalination, it can withstand enormous pressure, ensuring the integrity of the membrane and forming the basis for achieving efficient separation. The thickness of the high-strength support layer 1 is 150-200 μm. A buffer transition layer 2 is set on the outer wall of the high-strength support layer 1. The high-strength support layer 1 and the buffer transition layer 2 are connected by a thermosetting process. First, a mixed solution containing polyurethane prepolymer and nano-silica dispersion is homogenized. The polyurethane prepolymer is uniformly coated onto the surface of a high-strength support layer made of polysulfone and carbon fiber reinforced composite material, and then cured at a certain temperature (e.g., 80-100℃) to crosslink the polyurethane prepolymer and form polyurethane. The function of the buffer filter layer 2 is to alleviate the stress difference between the support layer and the subsequent functional layers, making the bonding between the layers tighter and more stable, reducing membrane peeling caused by stress concentration. In operating environments with varying temperatures, it can effectively buffer the stress generated by thermal expansion and contraction, maintaining the stability of the membrane structure. The thickness of the buffer transition layer 2 is 10-15μm. An antifouling underlayer 3 is set on the outer wall of the buffer transition layer 2, and the buffer transition layer 2 and the antifouling underlayer 3 are connected by chemical grafting. Active groups are introduced onto the surface of the buffer transition layer 2. Subsequently, a composite solution containing polyvinyl alcohol with active groups (such as aldehyde groups) and silver nanoparticles is reacted with buffer transition layer 2. The antifouling bottom layer 3 is firmly connected to the buffer transition layer 2 through covalent bonding. The antifouling bottom layer 3 has good hydrophilicity, allowing water molecules to pass through quickly, reducing the adsorption of pollutants on the membrane surface, and inhibiting the growth of microorganisms on the membrane surface, thus preventing biofouling. The thickness of the antifouling bottom layer 3 is 8-12 μm. A nanochannel construction layer 4 is then formed on the outer wall of the antifouling bottom layer 3. The antifouling bottom layer 3 and the nanochannel construction layer 4 are connected using a sol-gel method. The precursor for preparing the nanochannel construction layer 4 (such as tetrabutyl titanate) undergoes hydrolysis and condensation reactions with the active groups (such as hydroxyl groups) on the surface of the antifouling bottom layer 3. Ordered mesoporous titanium dioxide is grown in situ on the surface of the dyeing layer 3, forming a tight connection. The nanochannel construction layer 4 can achieve the sieving effect of molecules of different sizes, improving the separation accuracy of the membrane. When processing mixed solutions containing a variety of molecules of different sizes, it can accurately separate the target substances. The thickness of the nanochannel construction layer 4 is 5-8 μm. By setting a selective separation layer 5 on the outer wall of the nanochannel construction layer 4, the nanochannel construction layer 4 and the selective separation layer 5 are connected by interfacial polymerization. Aqueous monomers (such as m-phenylenediamine) and organic monomers (such as trimesoyl chloride) are introduced into the surface of the nanochannel construction layer 4, respectively. Polymerization reaction occurs at the interface to form a sulfonated polyethersulfone selective separation layer 5, which is tightly connected to the nanochannel construction layer 4.The selective separation layer 5 exhibits highly selective retention capabilities for negatively charged ions and organic matter. When treating wastewater containing heavy metal ions and organic pollutants, it can efficiently retain these harmful substances while allowing water molecules to pass through smoothly, thus achieving water purification. The thickness of the selective separation layer 5 is 0.5-1 μm.

[0026] Example 2, as Figure 2-3 As shown, the outer wall of the selective separation layer 5 is provided with a charge-controlled intermediate layer 6, the outer wall of the charge-controlled intermediate layer 6 is provided with an antioxidant protective layer 7, the outer wall of the antioxidant protective layer 7 is provided with an anti-fouling surface layer 8, and the outer wall of the anti-fouling surface layer 8 is provided with a surface modification layer 9.

[0027] The overall effect achieved in Example 2 is as follows: By setting a charge-controlled intermediate layer 6 on the outer wall of the selective separation layer 5, the selective separation layer 5 and the charge-controlled intermediate layer 6 are connected by a layer-by-layer self-assembly technique. The selective separation layer 5 is sequentially immersed in a positively charged polyelectrolyte solution (such as polydiallyldimethylammonium chloride) and a negatively charged zwitterionic polymer solution, and alternating deposition is achieved through electrostatic interaction to form a stable charge-controlled intermediate layer 6. The charge-controlled intermediate layer 6 can optimize the membrane's retention performance for different ions and molecules in solutions with different pH levels, improve the membrane's adaptability and separation efficiency, and the thickness of the charge-controlled intermediate layer 6 is 0.5-1 μm. An antioxidant protective layer is set on the outer wall of the charge-controlled intermediate layer 6. 7. The charge-controlled intermediate layer 6 and the antioxidant protective layer 7 are connected by hydrogen bonds and π-π stacking interactions. A composite solution of graphene oxide and polydopamine is coated on the surface of the charge-controlled intermediate layer 6. The phenolic hydroxyl groups in polydopamine form hydrogen bonds with the polar groups of the charge-controlled intermediate layer 6. At the same time, the conjugated structure of graphene oxide undergoes π-π stacking interactions with the organic groups in the charge-controlled intermediate layer 6, resulting in a tight adhesion of the antioxidant protective layer 7. The antioxidant protective layer 7 can effectively resist the corrosion of oxidants (such as residual chlorine) in water, protect the internal functional layers from oxidative damage, and extend the service life of the membrane. In drinking water treatment, it can prevent residual chlorine from damaging the membrane and ensure the long-term stable operation of the membrane. The thickness of the antioxidant protective layer 7 is 0.2-0.5 μm. An antifouling surface layer 8 is provided on the outer wall of the antioxidant protective layer 7. The antioxidant protective layer 7 and the antifouling surface layer 8 are bonded together after plasma treatment. First, the surface of the antioxidant protective layer 7 is plasma treated to introduce active free radicals. Then, a fluoropolymer (such as polyvinylidene fluoride-hexafluoropropylene) solution is coated. Under the action of active free radicals, the fluoropolymer and the antioxidant protective layer 7 undergo a cross-linking reaction to form a strong bond. The antioxidant protective layer 7 has extremely low surface energy, which can effectively reduce the adsorption and adhesion of pollutants on the membrane surface. Even when treating wastewater with high concentrations of organic pollutants, it can maintain the cleanliness of the membrane surface, reduce the degree of membrane fouling, and improve the membrane flux recovery rate. The thickness of the antifouling surface layer 8 is 0.3-0.6 μm. A surface modification layer 9 is provided on the outer wall of the antifouling surface layer 8. The antifouling surface layer 8 and the surface modification layer 9 are connected by a silane coupling agent. The silane coupling agent is prepared into a dilute solution and coated on the surface of the antifouling surface layer 8. The organic groups of the silane coupling agent react chemically with the polymer of the antifouling surface layer 8 to form chemical bonds. At the same time, the siloxane groups of the silane coupling agent undergo hydrolysis and condensation to form an organosilicon film on the surface, namely the surface modification layer 9. The surface modification layer 9 can improve the surface properties of the membrane, enhance the membrane's hydrophilicity, antifouling properties, and chemical stability. In addition, this modification film can also enhance the membrane's compatibility with the external environment, reduce the membrane's frictional resistance during use, and improve the overall performance of the membrane. The thickness of the surface modification layer 9 is 20-50 nm.

[0028] The working principle of the entire device is as follows: the order of the outermost to innermost layers of the Teflon heat shrink tubing is as follows: the first layer is the surface modification layer 9, the second layer is the antifouling surface layer 8, the third layer is the anti-oxidation protective layer 7, the fourth layer is the charge regulation intermediate layer 6, the fifth layer is the selective separation layer 5, the sixth layer is the nanochannel construction layer 4, the seventh layer is the antifouling bottom layer 3, the eighth layer is the buffer transition layer 2, and the ninth layer is the high-strength support layer 1. The high-strength support layer 1 is located at the innermost layer of the nanofiltration membrane and is mainly made of polysulfone and carbon fiber reinforced composite material. Polysulfone has good chemical stability and mechanical properties, while carbon fiber significantly enhances the strength and rigidity of the material, providing stable physical support for the entire membrane structure and buffering the transition layer. Layer 2 is a composite material of polyurethane and nano-silica. Polyurethane has good flexibility and cushioning properties, while nano-silica enhances the material's wear resistance and chemical stability. Its function is to alleviate the stress difference between the support layer and subsequent functional layers, making the bonding between layers tighter and more stable, and reducing membrane peeling caused by stress concentration. The antifouling bottom layer 3 is composed of hydrophilic polyvinyl alcohol and antibacterial nano-silver particles. Polyvinyl alcohol has good hydrophilicity, allowing water molecules to pass through quickly and reducing the adsorption of pollutants on the membrane surface; the nano-silver particles can inhibit the growth of microorganisms on the membrane surface and prevent biofouling. The nanochannel construction layer 4 uses ordered mesoporous structures. Titanium dioxide possesses a highly ordered nanoscale pore structure with uniform pore sizes ranging from 1 to 3 nm. These nanochannels serve as the primary transport pathways for water molecules and small solute molecules. Through precise pore size design, it enables the sieving of molecules of different sizes, improving the membrane's separation accuracy. The selective separation layer 5 utilizes sulfonated polyethersulfone material, which contains a large number of sulfonic acid groups. These groups impart a negative charge to the membrane surface. Based on the principle of charge repulsion, this layer exhibits a high selective retention capacity for negatively charged ions and organic matter. The charge-regulating intermediate layer 6 employs a zwitterionic polymer material, such as a carboxylic acid betaine-type polymer. It can dynamically adjust the charge properties and density on the membrane surface according to changes in the solution's pH value. The antioxidant protective layer 7 is composed of graphene oxide and polydopamine. Graphene oxide has excellent chemical stability and barrier properties, while polydopamine can firmly adhere to the membrane surface and provide antioxidant properties. This layer can effectively resist the erosion of oxidants (such as residual chlorine) in water and protect the internal functional layer from oxidative damage. The antifouling surface layer 8 is made of fluoropolymers, such as polyvinylidene fluoride-hexafluoropropylene, which has extremely low surface energy and can effectively reduce the adsorption and adhesion of pollutants on the membrane surface. The surface modification layer 9 is treated with a silane coupling agent, which can form an extremely thin organic silicon film on the membrane surface, further improving the surface properties of the membrane and enhancing its hydrophilicity, antifouling properties and chemical stability.

[0029] The above description is merely a preferred embodiment of the present utility model and is not intended to limit the present utility model in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments for application in other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present utility model without departing from the technical solution of the present utility model shall still fall within the protection scope of the technical solution of the present utility model.

Claims

1. A multilayer nanofiltration membrane, characterized in that: It includes a high-strength support layer (1) and an anti-pollution surface layer (8). The outer wall of the high-strength support layer (1) is provided with a buffer transition layer (2), and the outer wall of the buffer transition layer (2) is provided with an anti-pollution bottom layer (3). The outer wall of the anti-pollution bottom layer (3) is bonded with a nanochannel building layer (4). The outer wall of the nanochannel construction layer (4) is provided with a selective separation layer (5); The selective separation layer (5) has a charge-controlled intermediate layer (6) disposed on its outer wall. The outer wall of the anti-pollution surface layer (8) is provided with a surface modification layer (9).

2. The multilayer nanofiltration membrane according to claim 1, characterized in that: An antioxidant protective layer (7) is provided on the outer wall of the charge-controlled intermediate layer (6).

3. The multilayer nanofiltration membrane according to claim 2, characterized in that: The outer wall of the antioxidant protective layer (7) is provided with an anti-pollution surface layer (8).

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