Reverse osmosis membrane as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of membrane modification, and particularly relates to a reverse osmosis membrane and a preparation method thereof. The preparation method comprises the following steps: firstly, carrying out hydration reaction on dispersion liquid containing carboxylated single-walled carbon nanotubes and a phospholipid layer to form phospholipid vesicle dispersion liquid in which the carbon nanotubes are vertically embedded; then taking an ultrafiltration membrane as a base membrane, breaking the phospholipid vesicles through suction filtration, forming a phospholipid bilayer structure on the surface of the base membrane, and vertically arranging the carbon nanotubes between the phospholipid bilayers to construct a phospholipid-carbon nanotube composite intermediate layer; and finally, forming a cross-linked polyamide layer on the surface of the composite intermediate layer through an interfacial polymerization reaction, and vertically fixing the carbon nanotubes in the membrane structure to complete the preparation of the reverse osmosis membrane. According to the method, the carbon nano tube is really used as a water channel, and the water molecule permeation rate of the reverse osmosis membrane is remarkably improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of membrane modification, and particularly relates to a reverse osmosis membrane and a preparation method and application thereof. BACKGROUND

[0002] At present, fresh water resources are scarce, and coastal areas rely on seawater desalination technology. In seawater desalination, reverse osmosis technology occupies a dominant position due to low energy consumption and high efficiency. However, the traditional reverse osmosis membrane is still restricted by two core bottlenecks, specifically, it is difficult to balance water flux and anti-pollution; the cost of treating concentrated brine is high, and the energy consumption accounts for 30% to 40% of the total energy consumption.

[0003] Carbon nanotubes, namely CNTs, are regarded as a key material for breaking through the performance limit of reverse osmosis membranes due to their unique one-dimensional tubular structure, super-hydrophobic inner wall and super-high water transmission rate. How to efficiently integrate CNTs into the membrane has become the core research topic. At present, most researches focus on indirect modification strategies, mainly including physical doping and surface modification. Physical doping is to embed CNTs into the polyamide selective layer, and to use the rigid skeleton of CNTs to construct interfacial gaps in the polymer network, so as to increase the porosity of the membrane to improve the water flux. Surface modification is to improve the compatibility of CNTs and the polymer matrix by hydroxyl and carboxyl functionalization, and to reduce the membrane pollution rate. However, in the above methods, CNTs are arranged in disorder, and CNTs cannot truly realize the role of water channels, and the improvement of the water molecule transmission rate of the reverse osmosis membrane is limited. SUMMARY

[0004] In order to solve the above technical problems, the application provides a reverse osmosis membrane and a preparation method and application thereof. By providing a suitable carrier, CNTs are vertically arranged in the reverse osmosis membrane structure, CNTs are directly used as water channels, and then the water molecule transmission rate of the reverse osmosis membrane is improved.

[0005] To achieve the above purpose, the technical scheme adopted by the application is: A preparation method of a reverse osmosis membrane, comprising the following steps: The phospholipid solution is dried to form a phospholipid layer, and a dispersion liquid containing carboxylated single-walled carbon nanotubes is added, and through a hydration reaction, the carboxylated single-walled carbon nanotubes are vertically embedded in the phospholipid layer and form phospholipid vesicles, to obtain a phospholipid vesicle dispersion liquid; an ultrafiltration membrane is used as a base film, and the phospholipid vesicle dispersion liquid is subjected to suction filtration, the phospholipid vesicles are broken and self-assembled into a phospholipid bilayer structure on the surface of the base film, and at the same time, the carbon nanotubes are vertically and directionally arranged between the phospholipid bilayers, to obtain a base film loaded with a phospholipid-carbon nanotube composite intermediate layer; the base film loaded with the phospholipid-carbon nanotube composite intermediate layer is immersed in a solution containing m-phenylenediamine, triformylchloride and a surfactant, and through an interfacial polymerization reaction, a cross-linked polyamide layer is formed on the surface of the phospholipid-carbon nanotube composite intermediate layer, and the carbon nanotubes are fixed in the membrane structure, to obtain a reverse osmosis membrane.

[0006] The present application realizes the vertical directional arrangement of the carbon nanotubes in the reverse osmosis membrane structure by introducing the phospholipid bilayer membrane as a biomimetic carrier, so that the carbon nanotubes directly act as water channels, thereby significantly improving the water molecule permeation rate of the reverse osmosis membrane. The method breaks through the limitation of traditional carbon nanotubes as a modifier, realizes the direct functionalization of the carbon nanotubes as water channels, and effectively improves the water flux of the membrane.

[0007] Further, the particle size of the carboxylated single-walled carbon nanotubes is 10nm-16nm. The above particle size can realize the matching of the size of the carbon nanotubes and the thickness of the phospholipid bilayer, and a particle size that is too large cannot be spontaneously vertically embedded in the phospholipid bilayer, and a particle size that is too small is easy to penetrate the phospholipid bilayer.

[0008] Further, in the preparation process of the phospholipid vesicle dispersion liquid, the dosage ratio of the phospholipid to the carboxylated single-walled carbon nanotubes is 5-10:1. The mass ratio of the phospholipid to the CNTs needs to be controlled in a proper range. When the CNTs content is too high, agglomeration is easy to occur, causing the CNTs to be unable to vertically embed in the phospholipid bilayer to act as water channels, and when the CNTs content is too low, the number of the CNTs embedded to act as water channels is small, which will cause the water molecule transmission path to be reduced, resulting in a low water flux.

[0009] Further, the concentration of the phospholipid vesicle dispersion liquid is 0.1mg / L-1.0mg / mL. When the concentration of the phospholipid vesicle dispersion liquid is too high, the carbon nanotubes are easy to agglomerate and cannot act as water channels, and when the concentration is too low, there are not enough carbon nanotubes embedded in the phospholipid bilayer, and the water molecule permeation rate of the reverse osmosis membrane is difficult to be effectively improved.

[0010] Further, the specific operation of the hydration reaction is: after ultrasonic treatment for 20min-45min, vortex treatment is performed for 10min-30min.

[0011] Further, the concentration of the carbon nanotube phospholipid vesicle dispersion liquid is 0.1mg / mL-1.0mg / mL.

[0012] Further, the time of the interfacial polymerization reaction is 10s-30s. The interfacial polymerization reaction time needs to be performed within a certain time. If the interfacial polymerization reaction time is too short, the cross-linked structure is not fully constructed, which can cause defects in the interfacial polymerization layer, and ions can still cross the membrane, resulting in a low retention rate. If the reaction time is too long, the cross-linking degree of the polymerization membrane is large, the interfacial polymerization layer is dense, the water molecule transmembrane resistance is large, and the permeability is poor.

[0013] Further, the phospholipid is 1,2-dioleoyl-sn-glycero-3-phosphocholine or 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine.

[0014] Further, the ultrafiltration membrane is one of polyether sulfone membrane, polystyrene membrane and polyvinylidene fluoride membrane.

[0015] Further, the concentration of the phospholipid solution is 0.1mg / mL-1mg / mL, the dispersion liquid containing carboxylated single-walled carbon nanotubes is prepared by mixing PBS buffer and carboxylated single-walled carbon nanotube water dispersion liquid, the concentration of the carboxylated single-walled carbon nanotube water dispersion liquid is 0.1mg / mL-0.5mg / mL, and the volume ratio of the phospholipid solution to the carboxylated single-walled carbon nanotube water dispersion liquid is 15:4-6. If the concentration of the phospholipid solution is too high, the number of spreading layers is too large, and the water molecule transmembrane resistance is increased. If the concentration of the carboxylated single-walled carbon nanotube water dispersion liquid is too large, the carbon nanotubes are aggregated, and the difficulty of embedding the carbon nanotubes into the phospholipid vesicle is increased. If the volume ratio of the phospholipid solution to the carboxylated single-walled carbon nanotube water dispersion liquid is too large, there is not enough CNTs embedded into the phospholipid vesicle, and if the volume ratio is too small, the CNTs are easily aggregated, and the vesicle is unstable. Therefore, the concentration of the phospholipid solution, the concentration of the carboxylated single-walled carbon nanotube water dispersion liquid and the volume ratio of the phospholipid solution to the carboxylated single-walled carbon nanotube water dispersion liquid are crucial for improving the performance of the product.

[0016] Further, the base membrane with the phospholipid-carbon nanotube composite intermediate layer is first immersed in an aqueous solution containing 1wt%-2wt% of m-phenylenediamine and 0.1wt%-0.3wt% of sodium dodecyl sulfate, and then immersed in a n-hexane solution containing 0.1wt%-0.3wt% of trimesoyl chloride after being dried.

[0017] Further, after the hydration reaction is completed, the method further comprises freezing and thawing and extrusion treatment to obtain a phospholipid vesicle dispersion liquid.

[0018] The reverse osmosis membrane prepared by the preparation method.

[0019] The application of the reverse osmosis membrane in seawater desalination treatment.

[0020] Compared with the prior art, the application has the following beneficial effects: The application first carries out hydration reaction of the dispersion liquid containing carboxylated single-walled carbon nanotubes and phospholipid layer, and then embeds the carboxylated single-walled carbon nanotubes in the phospholipid layer vertically and forms phospholipid vesicles to obtain a phospholipid vesicle dispersion liquid; subsequently, the phospholipid vesicles are broken by suction filtration and the phospholipid bilayer structure is formed on the surface of the base membrane with the carbon nanotubes arranged vertically between the phospholipid bilayers by using the ultrafiltration membrane as the base membrane, so as to construct a phospholipid-carbon nanotube composite intermediate layer; finally, a cross-linked polyamide layer is formed on the surface of the composite intermediate layer by interfacial polymerization, so as to fix the carbon nanotubes in the membrane structure and complete the preparation of the reverse osmosis membrane. The application utilizes the amphiphilic property and self-assembly characteristics of the phospholipid molecules, first prepares the phospholipid vesicles with the vertically embedded CNTs by the hydration reaction, and then arranges the CNTs in the phospholipid bilayer of the vesicles in a radial direction. Subsequently, the vesicles are broken and spread on the surface of the ultrafiltration base membrane in the suction filtration process, so as to form a continuous phospholipid bilayer, which synchronously and fixedly arranges the previously vertically embedded CNTs in the phospholipid carrier, and thus constructs the regular and vertical carbon nanotube water channel in the membrane. This biomimetic design changes the CNTs from the traditional modifier role to the direct functional water channel, and the superhydrophobic inner wall of the CNTs provides a low-resistance and high-speed transmission path for the water molecules, which fundamentally overcomes the limitation of the disordered CNTs on the water flux due to the tortuous path and the interface resistance, and thus significantly improves the water molecule transmission rate of the reverse osmosis membrane.

[0021] The application discloses a preparation method of a carbon nanotube directly used as a water channel high-performance reverse osmosis membrane. The carbon nanotubes are laid on the surface of a base membrane by a suction filtration method, and the carbon nanotubes are arranged vertically on the surface of the membrane. Subsequently, m-phenylenediamine and trimesoyl chloride are selected as reaction agents, and an interfacial polymerization reaction is adopted to generate a polyamide layer on the ultrafiltration membrane, and the carbon nanotubes are fixed in the polyamide layer to form a water channel. The application aims to make the carbon nanotubes really used as a water channel, and improve the water molecule transmission rate of the reverse osmosis membrane. Under the optimal conditions, the CNTs directly used as the water channel can contribute to 74.3% of the improvement of the water molecule transmission rate.

[0022] The application innovatively introduces a phospholipid bilayer membrane as a biomimetic carrier of the CNTs, and realizes multiple effects. Biocompatibility and self-assembly ability: the phospholipid bilayer membrane is formed by self-assembly of amphiphilic phospholipid molecules, the hydrophobic tail chain of which can be combined with the outer wall of the CNTs through Van der Waals force, and the hydrophilic head part is in contact with the water phase, so that the CNTs are arranged in a directional manner and uniformly dispersed. Selective permeation regulation: the fluidity of the phospholipid bilayer membrane can dynamically regulate the channel density of the CNTs, and the ion rejection rate is enhanced through electrostatic action, such as the negative phospholipid head part repelling Cl⁻. The experimental results show that the Cl⁻ rejection rate is improved to 99.6%. Anti-pollution and mechanical strength: the cell-like membrane structure of the phospholipid bilayer membrane can inhibit the adsorption of proteins and microorganisms, and the high strength of the CNTs compensates for the mechanical weakness of the phospholipid bilayer membrane, prolongs the service life of the membrane, and the simulation experiment shows that the pressure difference resistance is up to 60 bar.

[0023] In summary, the present application breaks through the traditional positioning of carbon nanotubes as a modifier in reverse osmosis membranes, creating a new paradigm for integrated design of biomimetic channels-carriers, and providing a core solution for the research and development of the next generation of high-efficiency, low-consumption seawater desalination membranes. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0025] Figure 1 Freeze electron microscope image of carbon nanotube phospholipid vesicle prepared for Example 1.

[0026] Figure 2 Surface scanning electron microscope image of reverse osmosis membrane prepared for Example 1, wherein a is the scanning electron microscope image of the reverse osmosis membrane obtained in Comparative Example 1, and b is the scanning electron microscope image of the reverse osmosis membrane obtained in Example 1.

[0027] Figure 3 Water permeability and rejection rate test results of the reverse osmosis membranes prepared in Example 1, Comparative Example 1 and Comparative Example 2. DETAILED DESCRIPTION

[0028] The specific embodiments of the present application will be described in detail below, but it should be understood that the protection scope of the present application is not limited by the specific embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application. The experimental methods described in the embodiments of the present application are all conventional methods, and the materials, reagents, etc. used in the following embodiments are commercially available unless otherwise specified. Carboxylated single-walled carbon nanotubes, inner diameter 1 nm-2 nm, length 1 μm-3 μm, purity >95%, purchased from Jiangsu XF Nanotechnology Co., Ltd.; polyether sulfone membrane, UE050, 250 μm, purchased from Beijing Membrane Technology Co., Ltd.; polystyrene membrane, US050, 250 μm, purchased from Beijing Membrane Technology Co., Ltd.; polyvinylidene fluoride membrane, UF100, 250 μm, purchased from Beijing Membrane Technology Co., Ltd.

[0029] Example 1 A preparation method of a reverse osmosis membrane, comprising the following steps: 1. Preparation of carbon nanotube phospholipid vesicle dispersion: a. Take 15 mL of 1,2-dioleoyl-sn-glycero-3-phosphocholine chloroform solution, i.e. phospholipid solution, with a concentration of 1 mg / mL, and place it in a round-bottom flask; remove the solvent under vacuum at 40 °C for 12 h to form a dry phospholipid layer at the bottom of the flask. This step aims to remove the organic solvent chloroform to ensure that the subsequent embedding of CNTs is not affected by chloroform.

[0030] b. Continue to add 12 mL of PBS buffer and 3 mL of broken carboxylated single-walled carbon nanotube water dispersion with a concentration of 0.5 mg / mL to the above flask. The broken treatment is broken by a 300 W ultrasonic crusher for 24 h, and then treated by a 100 W ultrasonic crusher for 45 min, so that the formed dry phospholipid layer is peeled off from the wall of the flask, and the phospholipid molecules spontaneously form vesicles. Then use a vortex oscillator to oscillate at 2000 rpm for 30 min to further promote the formation of vesicles, and complete the hydration process. This step aims to form CNTs vertically embedded phospholipid vesicles. With the center of the vesicle as the base point, the carbon nanotubes are radially and vertically embedded in the phospholipid bilayer of the vesicle. The original carboxylated single-walled carbon nanotubes need to be broken to a length of 10 nm to 16 nm in the subsequent breaking step to realize the matching of their size and the thickness of the phospholipid bilayer. If the particle size is too large, it cannot be spontaneously vertically embedded in the phospholipid bilayer, and if it is too small, it can easily penetrate the phospholipid bilayer.

[0031] c. After the hydration of the mixed solution is completed, it is respectively quickly frozen in liquid nitrogen and thawed in a water bath, and the freezing and thawing is repeated for 8 times to further fix and shape the phospholipid vesicles; then use a micro-extruder to extrude 21 times through a polycarbonate membrane with a pore size of about 200 nm to ensure the formation of a single-layer liposome, and obtain a carbon nanotube phospholipid vesicle dispersion with a final concentration of 1.0 mg / mL, i.e. a carbon nanotube vertically embedded phospholipid vesicle dispersion, and the mass ratio of phospholipid to CNTs in the carbon nanotube phospholipid vesicle dispersion is 10:1. This step aims to form CNTs vertically embedded phospholipid vesicles with more uniform particle size. After extruding 21 times through a 200 nm polycarbonate membrane, large vesicles will spontaneously adjust to small vesicles through compression.

[0032] 2. Preparation of phospholipid-carbon nanotube composite intermediate layer The carbon nanotube water channel intermediate layer is prepared by suction filtration. 50 mL of 1.0 mg / mL carbon nanotube phospholipid vesicle dispersion is added to a suction filtration device with a diameter of 9 cm, and a vacuum pump is used to suck the solution through the polycarbonate membrane with a pore size of about 200 nm at a speed of 64 cm 2The polyether sulfone (PES) ultrafiltration membrane is used as the filtration membrane. After the first filtration is completed, the second filtration is performed again. The filtration membrane is used as the base membrane, and a phospholipid-carbon nanotube composite intermediate layer is formed on the surface of the base membrane after drying. The phospholipid vesicles prepared in step 1 have embedded vertically arranged CNTs. During the suction filtration process, the vesicles are broken, and the phospholipid bilayer membrane originally constituting the vesicles spreads on the surface of the base membrane to form a continuous phospholipid bilayer membrane. The CNTs embedded in the phospholipid bilayer membrane are vertically arranged on the surface of the base membrane. The phospholipid bilayer membrane acts as a carrier.

[0033] 3. Preparation of the interfacial polymerization layer The base membrane loaded with the phospholipid-carbon nanotube composite intermediate layer obtained in step 2 is first immersed in 50 mL of an aqueous solution containing 2 wt% of m-phenylenediamine and 0.1 wt% of sodium dodecyl sulfate for 2 min, and then dried. Subsequently, the base membrane is immersed in 50 mL of a n-hexane solution containing 0.15 wt% of trimesoyl chloride for 30 s. Through the interfacial polymerization reaction, the preparation of the interfacial polymerization layer is completed. Finally, the reverse osmosis membrane is obtained by heat treatment at 60°C for 10 min. Subsequently, the reverse osmosis membrane is stored in deionized water for standby use. The formation of the interfacial polymerization layer in this step further fixes the CNTs embedded in the phospholipid bilayer membrane. At this time, the CNTs are in a state of being vertically embedded in the interfacial polymerization layer.

[0034] The reverse osmosis membrane obtained in this example has a water flux of 51.6 L / (m 2 ·h) and a NaCl rejection rate of 99.18% at 1.6 MPa. This is due to the fact that the phospholipid-carbon nanotube composite intermediate layer optimizes the structure of the interfacial polymerization layer, making the interfacial polymerization layer thinner and reducing the resistance of water molecules to cross the membrane. At the same time, the vertically arranged CNTs act as water channels, increasing the transmission rate of water molecules.

[0035] Example 2 A method for preparing a reverse osmosis membrane, which is prepared according to the method described in Example 1, with the difference that the amount of PBS buffer used in step 1 is 11 mL, and the amount of carboxylated single-walled carbon nanotube aqueous dispersion used is 4 mL, i.e., the mass ratio of phospholipid to CNTs in the carbon nanotube phospholipid vesicle dispersion is 7.5:1.

[0036] The reverse osmosis membrane obtained in this example has a water flux of 45.1 L / (m 2The water flux of the reverse osmosis membrane obtained in this example was 44.7 L / (m2·h) and the NaCl rejection rate was 99.08% under 1.6 MPa. This was due to the phospholipid-carbon nanotube composite intermediate layer optimizing the structure of the interfacial polymerization layer, making the interfacial polymerization layer thinner and reducing the transmembrane resistance of water molecules. The vertically arranged CNTs served as water channels. At the same time, it was found that the water flux of this example was slightly smaller than that of Example 1, and the rejection rate decreased slightly. Therefore, the mass ratio of phospholipid to CNTs needs to be controlled within a suitable range. When the content of CNTs is too high, agglomeration is easy to occur, which causes CNTs to be unable to vertically embed in the phospholipid bilayer membrane to serve as water channels. When the content of CNTs is too low, the number of CNTs embedded to serve as water channels is small, which will cause the path of water molecule transmission to be reduced, resulting in a lower water flux.

[0037] Example 3 A method for preparing a reverse osmosis membrane, prepared according to the method described in Example 1, with the difference that the amount of PBS buffer used in step 1 is 9 mL and the amount of carboxylated single-walled carbon nanotube aqueous dispersion used is 6 mL, i.e. the mass ratio of phospholipid to CNTs in the carbon nanotube phospholipid vesicle dispersion is 5:1.

[0038] The reverse osmosis membrane obtained in this example had a water flux of 44.7 L / (m2·h) and a NaCl rejection rate of 99.0% under 1.6 MPa. 2 The reverse osmosis membrane obtained in this example had a water flux of 44.7 L / (m2·h) and a NaCl rejection rate of 99.0% under 1.6 MPa.

[0039] Example 4 A method for preparing a reverse osmosis membrane, prepared according to the method described in Example 1, with the difference that the amount of PBS used in step 1 is 147 mL, i.e. the concentration of the carbon nanotube phospholipid vesicle dispersion is 0.1 mg / L, and the mass ratio of phospholipid to CNTs in the carbon nanotube phospholipid vesicle dispersion is 10:1.

[0040] The reverse osmosis membrane obtained in this example had a water flux of 44.7 L / (m2·h) and a NaCl rejection rate of 99.0% under 1.6 MPa. 2 The reverse osmosis membrane obtained in this example had a water flux of 44.7 L / (m2·h) and a NaCl rejection rate of 99.0% under 1.6 MPa.

[0041] Example 5 A method for preparing a reverse osmosis membrane, prepared according to the method described in Example 1, with the difference that the amount of PBS used is 27 mL, the concentration of the carbon nanotube phospholipid vesicle dispersion is 0.5 mg / L, and the mass ratio of phospholipid to CNTs in the phospholipid solution is 10:1.

[0042] The reverse osmosis membrane obtained in this example had a water flux of 44.7 L / (m2·h) and a NaCl rejection rate of 99.0% under 1.6 MPa. 2 The reverse osmosis membrane obtained in this example had a water flux of 44.7 L / (m2·h) and a NaCl rejection rate of 99.0% under 1.6 MPa.

[0043] Example 6 A method for preparing a reverse osmosis membrane, prepared according to the method described in Example 1, with the difference that in step 3, the time of immersion in the solution of trimesoyl chloride in n-hexane is 10 s.

[0044] The reverse osmosis membrane obtained in this example has a water flux of 42.1 L / (m 2 ・h) and a NaCl rejection rate of 97.5% at 1.6 MPa.

[0045] Example 7 A method for preparing a reverse osmosis membrane, prepared according to the method described in Example 1, with the difference that in step 3, the time of immersion in the solution of trimesoyl chloride in n-hexane is 20 s.

[0046] The reverse osmosis membrane obtained in this example has a water flux of 40.3 L / (m 2 ・h) and a NaCl rejection rate of 98.3% at 1.6 MPa.

[0047] Example 8 A method for preparing a reverse osmosis membrane, prepared according to the method described in Example 1, with the difference that in step 2, the ultrafiltration membrane used is a polyvinylidene fluoride membrane.

[0048] The reverse osmosis membrane obtained in this example has a water flux of 47.5 L / (m 2 ・h) and a NaCl rejection rate of 88.7% at 1.6 MPa.

[0049] Example 9 A method for preparing a reverse osmosis membrane, prepared according to the method described in Example 1, with the difference that in step 1 b, the ultrasonic treatment is performed for 20 min, followed by the use of a vortex shaker for 20 min.

[0050] The reverse osmosis membrane obtained in this example has a water flux of 41.7 L / (m 2 ・h) and a NaCl rejection rate of 99.0% at 1.6 MPa.

[0051] Example 10 A method for preparing a reverse osmosis membrane, prepared according to the method described in Example 1, with the difference that in step 1 b, the ultrasonic treatment is performed for 35 min, followed by the use of a vortex shaker for 10 min.

[0052] The reverse osmosis membrane obtained in this example has a water flux of 42.3 L / (m 2 ・h) and a NaCl rejection rate of 99.0% at 1.6 MPa.

[0053] Example 11 A method for preparing a reverse osmosis membrane, prepared according to the method described in Example 1, except that in step 1, the phospholipid used is 1,2-dioleoyl-sn-glycerol-3-phosphoethanolamine.

[0054] The reverse osmosis membrane obtained in this embodiment has a water flux of 48.5 L / (m²) at 1.6 MPa. 2 •h), the NaCl retention rate was 99.1%.

[0055] Example 12 A method for preparing a reverse osmosis membrane, prepared according to the method described in Example 1, except that in step 2, the ultrafiltration membrane used is a polystyrene membrane.

[0056] The reverse osmosis membrane obtained in this embodiment has a water flux of 43.6 L / (m²) at 1.6 MPa. 2 •h), the NaCl retention rate was 98.6%.

[0057] Comparative Example 1 A method for preparing a reverse osmosis membrane includes the following steps: 64cm 2 The polyethersulfone (PES) ultrafiltration membrane was first immersed in 50 mL of an aqueous solution containing 2 wt% m-phenylenediamine and 0.1 wt% sodium dodecyl sulfate for 2 min, and then air-dried. Next, it was immersed in 50 mL of a hexane solution containing 0.15 wt% trimesoyl chloride for 30 s to complete the preparation of the interfacial polymer layer through an interfacial polymerization reaction. Finally, it was heat-treated at 60 °C for 10 min to obtain the reverse osmosis membrane. It was then stored in deionized water for later use.

[0058] This comparative example aims to prepare a reverse osmosis membrane without a phospholipid-carbon nanotube composite interlayer. The composite reverse osmosis membrane obtained in this comparative example exhibits a water flux of 23.1 L / (m²) at 1.6 MPa. 2 •h), NaCl rejection rate was 99.04%. The water flux was much lower than that of the reverse osmosis membrane in the example. This is because traditional interfacial polymer membranes have a high degree of cross-linking and a dense interfacial polymer layer, resulting in high resistance to water molecules crossing the membrane, low diffusion rate, poor permeability, low water molecule transmembrane rate, and poor water flux.

[0059] Comparative Example 2 A method for preparing a reverse osmosis membrane includes the following steps: 1. Preparation of phospholipid vesicles: a. Take 15 mL of 1 mg / mL 1,2-dioleoyl-sn-glycerol-3-phosphocholine chloroform solution and place it in a round-bottom flask; remove the solvent by vacuum drying at 40°C for 12 h, and a dry phospholipid layer will form at the bottom of the flask.

[0060] b. Continue to add 15 mL PBS buffer to the flask, and ultrasonic treatment for 45 min to make the dry phospholipid layer from the bottle wall and make the phospholipid molecules spontaneously form vesicles, and then use a vortex oscillator to oscillate for 30 min to further complete the formation of the vesicles, and complete the hydration process.

[0061] c. The mixed solution after completing the hydration process is respectively subjected to liquid nitrogen quick freezing, water bath thawing, and repeated freezing and thawing for 8 times to further fix the phospholipid vesicles; a micro-extruder is used to extrude the sample through a polycarbonate membrane with a pore size of about 200 nm for 21 times to ensure the formation of single-layer liposomes, and a phospholipid solution with a final concentration of 1.0 mg / mL is obtained.

[0062] 2. Preparation of phospholipid intermediate layer 50 mL of 0.1 mg / mL phospholipid solution is added to the suction filtration device, and the diameter of the suction filtration device is 9 cm. The phospholipid solution is filtered at a speed of 64 cm 2 The polyether sulfone ultrafiltration membrane is the filtration membrane. After the first filtration is completed, the extract is subjected to a second filtration again, and the phospholipid intermediate layer is formed on the surface of the base membrane after drying.

[0063] 3. Preparation of interfacial polymerization layer The product obtained in step 2 is first immersed in 50 mL of an aqueous solution containing 2 wt% of m-phenylenediamine and 0.1 wt% of sodium dodecyl sulfate for 2 min, and then dried. Then it is immersed in 50 mL of a n-hexane solution containing 0.15 wt% of trimesoyl chloride for 30 s, and the preparation of the interfacial polymerization layer is completed through the interfacial polymerization reaction. Finally, it is heat treated at 60°C for 10 min to obtain a reverse osmosis membrane. Then it is stored in deionized water for standby.

[0064] The composite reverse osmosis membrane obtained in the present comparative example has a water flux of 35.5 L / (m 2 ·h) and a NaCl rejection rate of 99.18% at 1.6 MPa. The water flux is less than that of the reverse osmosis membrane in the example but higher than that of the unmodified reverse osmosis membrane in Comparative Example 1. This is because the phospholipid intermediate layer optimizes the structure of the interfacial polymerization layer, making the interfacial polymerization layer thinner and reducing the transmembrane resistance of water molecules, thereby improving the water flux. However, the interfacial polymerization layer of the reverse osmosis membrane containing only the phospholipid intermediate layer is still relatively dense and lacks water molecule channels, so the permeability is poorer than that of the reverse osmosis membrane in the example.

[0065] Comparative Example 3 A method for preparing a reverse osmosis membrane, which is prepared according to the method described in Comparative Example 2, except that the amount of phospholipid solution in step 2 is 100 mL, i.e. the amount of phospholipid is 10 mg.

[0066] The reverse osmosis membrane obtained in the present comparative example has a water flux of 27.9 L / (m 2The water flux was less than that of the reverse osmosis membrane in Comparative Example 2, but was still higher than that of the unmodified reverse osmosis membrane in Comparative Example 1. In this comparative example, the amount of phospholipid used was 10 mg, and the phospholipid bilayer was prone to forming multiple layers when forming the intermediate layer. Compared with Examples 1-3 and Comparative Example 2, the intermediate layer in this comparative example became thick and dense, resulting in a lower water flux than that in Comparative Example 2. However, due to the optimization of the interface polymerization layer structure by the phospholipid intermediate layer, the interface polymerization layer became thinner, reducing the transmembrane resistance of water molecules, so the water flux was still improved compared with Comparative Example 1.

[0067] Application Example 1 The application of the reverse osmosis membrane in seawater desalination specifically includes the following steps: The water flux and salt rejection rate of the reverse osmosis membrane with an area of 24 cm 2 at 25°C were tested. First, the membrane was pre-compressed at a pressure of 1.8 MPa for 0.5 h to achieve a stable water permeability, and then the operating pressure was adjusted to 1.6 MPa for testing. The separation performance of the reverse osmosis membrane was determined using a typical salt solution of 2000 ppm NaCl. The water flux and salt rejection rate can be calculated by the following formula:

[0068] ; ; In the formula, J v is the water flux, L / (m 2 ·h); ΔV is the solution permeation amount, L; S is the membrane area, m 2 ; ΔT is the sampling time interval, h; R is the rejection rate, %; C p is the permeate solute concentration; C f is the feed solute concentration.

[0069] To prove that carbon nanotubes have been successfully embedded in liposomes, the carbon nanotube phospholipid vesicle dispersion prepared in Example 1 was freeze-dried and characterized using a Japanese JEM 1400plus type cryo-transmission electron microscope, an American Gatan CP3 type low-temperature sampling system. The experiment needs to be carried out in a liquid nitrogen environment to ensure that the sample is continuously in an ultra-low temperature state. Image acquisition uses a Zeiss Libra 120 type transmission electron microscope with an operating voltage of 200 kV, and uses zero-loss filtering technology with an energy slit width of 20 eV. The cryo-TEM image of the carbon nanotube phospholipid vesicle prepared in Example 1 is shown in Figure 1 . Figure 1 In the image, carbon nanotubes can be clearly seen vertically embedded in the phospholipid vesicle.

[0070] In order to observe the surface morphology of the reverse osmosis membrane and the structure of the interfacial polymerization layer, a S-4800 scanning electron microscope of Japan Hitachi Company was used for characterization. Before observation, the sample was treated with gold spraying for 50 seconds to enhance its conductivity. The scanning electron microscope image of the reverse osmosis membrane prepared in Example 1 is shown in Figure 2 . Figure 2 In the figure, a is the scanning electron microscope image of the reverse osmosis membrane obtained in Comparative Example 1, and b is the scanning electron microscope image of the reverse osmosis membrane obtained in Example 1. It can be found that after the construction of the intermediate layer containing the carbon nanotube phospholipid bilayer membrane, the leaf-shaped structure of the interfacial polymerization layer is reduced, and the surface becomes flat, which is due to the mediation of the intermediate layer to the interfacial polymerization reaction, resulting in the improvement of the structure of the interfacial polymerization layer.

[0071] NaCl solution as the feed liquid, according to the method of Application Example 1, the water permeability and retention rate of the reverse osmosis membranes prepared in Example 1, Comparative Example 1 and Comparative Example 2 were evaluated. The results are shown in Figure 3 . Figure 3 In the figure, the water flux of the reverse osmosis membrane of Example 1 is 51.6 L / (m 2 ·h), in Comparative Example 2, the water flux of the reverse osmosis membrane is 35.5 L / (m 2 ·h), and in Comparative Example 1, the water flux of the reverse osmosis membrane is 23.1 L / (m 2 ·h). It can be found that after the construction of the pure phospholipid intermediate layer, the water flux is increased from 23.1 L / m 2 to 35.5 L / (m 2 ·h), and the water flux is increased by 54.3%. After the construction of the phospholipid intermediate layer containing vertically arranged CNTs, the water flux is further increased from 35.5 L / m 2 to 51.6 L / (m 2 ·h), and the water flux is further increased by 74.3%, which is contributed by CNTs. That is to say, CNTs directly contribute to the increase of 74.3% of the water flux as water channels, indicating that carbon nanotubes directly as water channels have important significance in improving the permeability of reverse osmosis membranes.

[0072] Although the preferred embodiments of the present application have been described, those skilled in the art can make further changes and modifications to these embodiments once they know the inventive concept of the present application, and these changes and modifications all fall within the scope of the present application.

[0073] Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application. If these modifications and variations of the present application fall within the scope of the equivalent technology of the present application, the present application also intends to include these modifications and variations.

Claims

1. A method for producing a reverse osmosis membrane, characterized by, The method comprises the following steps: drying the phospholipid solution to form a phospholipid layer, adding a dispersion liquid containing carboxylated single-walled carbon nanotubes, vertically embedding the carboxylated single-walled carbon nanotubes into the phospholipid layer through a hydration reaction, and forming a phospholipid vesicle to obtain a phospholipid vesicle dispersion liquid; using an ultrafiltration membrane as a base membrane, performing suction filtration on the phospholipid vesicle dispersion liquid, rupturing the phospholipid vesicle and self-assembling a phospholipid bilayer structure on the surface of the base membrane, and vertically orienting and arranging the carbon nanotubes between the phospholipid bilayers to obtain a base membrane loaded with a phospholipid-carbon nanotube composite intermediate layer; immersing the base membrane loaded with the phospholipid-carbon nanotube composite intermediate layer in a solution containing m-phenylenediamine, trimesoyl chloride and a surfactant, forming a cross-linked polyamide layer on the surface of the phospholipid-carbon nanotube composite intermediate layer through an interfacial polymerization reaction, and fixing the carbon nanotubes in the membrane structure to obtain a reverse osmosis membrane.

2. The method for producing a reverse osmosis membrane according to claim 1, characterized by, The particle size of the carboxylated single-walled carbon nanotubes is 10nm-16nm.

3. The method of producing a reverse osmosis membrane according to claim 1, characterized by, In the preparation process of the phospholipid vesicle dispersion liquid, the ratio of the amount of phospholipid to the amount of carboxylated single-walled carbon nanotubes is 5-10:

1.

4. The method of producing a reverse osmosis membrane according to claim 1, characterized by, The concentration of the phospholipid vesicle dispersion liquid is 0.1mg / L-1.0mg / mL.

5. The method of producing a reverse osmosis membrane according to claim 1, wherein The specific operation of the hydration reaction is: after ultrasonic treatment for 20min-45min, vortex treatment is performed for 10min-30min.

6. The method of producing a reverse osmosis membrane according to claim 1, wherein The time of the interfacial polymerization reaction is 10s-30s.

7. The method of producing a reverse osmosis membrane according to claim 1, wherein The phospholipid in the phospholipid solution is 1,2-dioleoyl-sn-glycero-3-phosphocholine or 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine.

8. The method of producing a reverse osmosis membrane according to claim 1, wherein The ultrafiltration membrane is one of a polyethersulfone membrane, a polystyrene membrane and a polyvinylidene fluoride membrane.

9. A reverse osmosis membrane, characterized by, The reverse osmosis membrane is prepared by the preparation method of any one of claims 1-8.

10. Use of a reverse osmosis membrane in a seawater desalination process, characterized in that, The reverse osmosis membrane is the reverse osmosis membrane of claim 9.

Images