Nanofiltration membrane prepared by ultraviolet curing and preparation method thereof

Abstract

The invention discloses a nanofiltration membrane prepared by ultraviolet light curing and a preparation method thereof, the nanofiltration membrane comprises a supporting layer and a photocuring compact surface layer, the photocuring compact surface layer is prepared by coating the surface of the supporting layer with a membrane casting solution, curing by ultraviolet light and then carrying out modification treatment; and a membrane casting solution of the photocuring compact surface layer comprises an active monomer and a photoinitiator. Aiming at the problems of low membrane preparation efficiency, poor membrane forming property and the like in the background technology, the invention provides the nanofiltration membrane prepared by ultraviolet curing and the preparation method thereof, the nanofiltration membrane is formed by ultraviolet curing and crosslinking by taking an acrylic acid derivative as an active monomer, and the prepared nanofiltration membrane is high in separation efficiency, large in flux and excellent in oxidation resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of nanofiltration membranes, and in particular to a nanofiltration membrane prepared by ultraviolet light curing and a preparation method thereof. Background Art

[0002] Nanofiltration membranes can intercept nanoscale (0.001 micron) substances. The operating range of nanofiltration membranes is between ultrafiltration and reverse osmosis. The molecular weight of organic matter they intercept is approximately 200-800 MW, and their ability to intercept dissolved salts is between 20% and 98%. The removal rate of soluble monovalent ions is lower than that of high-valent ions. Nanofiltration is generally used to remove organic matter and pigments from surface water, hardness and radium from groundwater, and partially remove dissolved salts. It is also used for the extraction and concentration of useful substances in food and pharmaceutical production. The current development trend of nanofiltration membranes is to develop high-performance nanofiltration membranes that are heat-resistant, acid-resistant, alkali-resistant, and oxidative-resistant, with high water flux, high retention rate, and pollution resistance.

[0003] Currently, nanofiltration membranes are typically prepared using phase inversion, coating-crosslinking, layer-by-layer self-assembly, and interfacial polymerization methods. For example, the technical solutions described in Chinese patents CN114682105A, CN114618320A, CN114471157A, and CN1071100A typically generate large amounts of wastewater during the preparation process. The post-processing process is complex, and byproducts are difficult to remove from the polymer. However, using photocuring to prepare nanofiltration membranes offers high production efficiency, shortened production time, and eliminates the generation of significant wastewater during the production process.

[0004] Currently, most commercial nanofiltration membranes are produced through interfacial polymerization. The primary material for the active separation layer is aromatic polyphthalamide. While these nanofiltration membranes exhibit excellent separation performance, they are complex to manufacture, difficult to control product quality, and result in high equipment investment and production costs. Consequently, the development of new technologies for nanofiltration membrane production has garnered widespread attention from researchers in the membrane separation and water treatment fields.

[0005] The widespread application of membrane technology in the biological and medical fields in recent years has placed higher demands on membrane materials. In addition to high selectivity and permeation flux, they also need to have strong resistance to fouling substances such as proteins and colloids. Numerous studies have shown that while hydrophilicity can be improved through hydrophilization of polymers, the poor film-forming properties of hydrophilic polymers make it difficult to find suitable precipitants. Even if a membrane is formed, such a membrane will significantly swell in aqueous solution, resulting in mechanical strength that does not meet the required performance requirements.

[0006] In response to the above problems, there is an urgent need for innovative design based on the original nanofiltration membrane preparation. Summary of the Invention

[0007] In response to the problems of low film-making efficiency and poor film-forming properties raised in the background technology, one of the purposes of the present invention is to provide a nanofiltration membrane prepared by ultraviolet light curing and a preparation method thereof. Acrylic acid derivatives are used as active monomers and are cross-linked by ultraviolet light curing to form a film. The prepared nanofiltration membrane has high separation efficiency, large flux, and excellent antioxidant properties.

[0008] The first object of the present invention is to provide a nanofiltration membrane prepared by ultraviolet curing, comprising: The supporting layer and the light-cured dense surface layer are prepared by applying a casting liquid to the surface of the supporting layer, curing it with ultraviolet light, and then performing a modification treatment; The casting solution for the photocurable dense surface layer includes reactive monomers and photoinitiators.

[0009] Furthermore, the molecular weight cut-off of the photocured dense surface layer is 100Da~1000Da.

[0010] Furthermore, the support layer is an ultrafiltration membrane or a microfiltration membrane.

[0011] Furthermore, the active monomer in the casting solution is selected from any one of acrylic acid, hydroxyethyl methacrylate, methyl methacrylate, methacrylic acid, acrylic resin, polyimide, polybenzimidazolone, ethylene glycol dimethacrylate, triethylene glycol acrylate, acrylamide, N-isopropylacrylamide, N-methylacrylic acid, vinylamide, vinylbenzene, vinyl methacrylate, and vinyl methacrylate, or a combination of at least two thereof.

[0012] Furthermore, the modifier used in the modification treatment is selected from any one of propylene oxide, caprolactam, and sodium styrene sulfonate, or a combination of at least two of them.

[0013] Furthermore, the photoinitiator in the casting solution is selected from any one of dimethyl sulfoxide, diisopropyl dithiocarbonamide, benzoyl acetone, triacetyltriethyloxysilane, vinyl mercaptan, and 2,4,6-trimethylphenyl peroxide, or a combination of at least two thereof.

[0014] The second object of the present invention is to provide a method for preparing a nanofiltration membrane prepared by an ultraviolet curing method, wherein the method comprises the following steps: S1: preparing a casting solution, mixing the active monomer and the photoinitiator in a certain proportion, and vacuum degassing for a period of time to obtain a casting solution; S2: coating the casting solution, pouring the casting solution obtained in step S1 onto the surface of the support layer, evenly coating the surface of the support layer, and curing it under ultraviolet light for a period of time, then rinsing it with deionized water and drying it to obtain the initial nanofiltration membrane; S3: Modification treatment: Place the initial nanofiltration membrane at the bottom of the reactor, pour the prepared modifier solution into the reactor, and place the reactor under an ultraviolet lamp for secondary photocuring and cross-linking to obtain the finished nanofiltration membrane.

[0015] Furthermore, the total concentration of active monomers in the casting solution is 95% to 99%; And / or, the concentration of the photoinitiator in the casting solution is 1% to 5%, preferably 3%; Furthermore, the concentration of the modifier is 0% to 7%, preferably 5%. Furthermore, the UV curing time in step S2 is 1 min to 20 min; And / or, the time of the secondary photocuring cross-linking in step S3 is 1 min to 40 min.

[0016] Compared with the prior art, the present invention has the following advantages and beneficial effects: (1) The photocurable dense surface layer of the present invention uses acrylic acid derivatives as active monomers and free radical materials as photoinitiators to form a film through ultraviolet light curing and crosslinking. Then, an acid-type or carboxylic acid-type styrene monomer is used as a modifier, and after secondary ultraviolet light curing and crosslinking, a finished nanofiltration membrane is obtained. The polymer of the membrane material has a high molecular weight and a certain degree of crosslinking, so that the finished nanofiltration membrane has sufficient strength and tolerance to the separated liquid, and can be widely used to remove impurities, small molecules and multivalent salts in various complex water bodies.

[0017] (2) The photocuring method used in the present invention can rapidly cure monomers, oligomers, or polymer matrices under light induction, and is characterized by high efficiency, wide adaptability, economy, energy saving, and environmental protection. Nanofiltration membranes produced by the photocuring method are easier to industrialize than nanofiltration membranes produced by other methods.

[0018] (3) The UV curing film-forming method developed in the present invention has a simple process, is easy to operate, easy to control, and easy to scale up industrially. By changing the concentration of prepolymer, active monomer or modifier, the structure and filtration performance of the prepared nanofiltration membrane can be regulated, providing a reference direction for the development of membrane materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 SEM surface images and cross-sectional images of nanofiltration membranes prepared by the UV curing method of Examples 1-3 of the present invention and Comparative Example 1; Figure 2 The pure water flux and Na2SO4 rejection rate of the photocurable nanofiltration membranes prepared with different SSS contents in Examples 1-3 of the present invention and Comparative Example 1 are shown; Figure 3The figure shows the retention rates of the photocurable nanofiltration membranes prepared in Examples 1-3 of the present invention and Comparative Example 1 for polyethylene glycol (PEG) with different molecular weights; Figure 4 It shows the rejection rate of the composite nanofiltration membrane prepared in Example 2 of the present invention for different dyes; Figure 5 The figure shows the effect of the immersion time of the composite nanofiltration membrane prepared in Example 2 of the present invention in a sodium hypochlorite solution on the nanofiltration performance. DETAILED DESCRIPTION

[0020] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention. Example

[0021] See also Figure 1-5 The nanofiltration membrane of this embodiment, produced using UV curing, comprises a support layer and a photocurable dense surface layer. The photocurable dense surface layer is produced by applying a casting solution to the surface of the support layer, curing it with UV light, and then subjecting it to a modification treatment. The casting solution for the photocurable dense surface layer comprises an active monomer and a photoinitiator. The photocuring method employed in this invention enables rapid light-induced curing of monomer, oligomer, or polymer matrices, resulting in high efficiency, wide adaptability, economy, energy conservation, and environmental friendliness.

[0022] The active monomer in the casting solution in this embodiment is selected from any one of acrylic acid, hydroxyethyl methacrylate, methyl methacrylate, methacrylic acid, acrylic resin, polyimide, polybenzimidazolone, ethylene glycol dimethacrylate, triethylene glycol acrylate, acrylamide, N-isopropylacrylamide, N-methylacrylic acid, vinylamide, vinylbenzene, vinyl methacrylate, and vinyl methacrylate, or a combination of at least two thereof.

[0023] Furthermore, in this embodiment, the photoinitiator in the casting solution is selected from any one or a combination of at least two of dimethyl sulfoxide, diisopropyldithiocarbonamide, benzoyl acetone, triacetyltriethyloxysilane, vinyl mercaptan, and 2,4,6-trimethylphenyl peroxide. The modifier used in the modification treatment is selected from any one or a combination of at least two of propylene oxide, caprolactam, and sodium styrene sulfonate.

[0024] The dense, photocured surface layer, which uses acrylic acid derivatives as active monomers and free radical materials as photoinitiators, is cross-linked through UV curing to form a membrane. Acidic or carboxylic acid-type styrene monomers are then used as modifiers, followed by secondary UV curing and cross-linking to produce the finished nanofiltration membrane. The polymer of the membrane material has a high molecular weight and a certain degree of cross-linking, giving the finished nanofiltration membrane sufficient strength and tolerance to the liquid being separated, making it widely applicable for the removal of impurities, small molecules, and multivalent salts from various complex water bodies.

[0025] Preferably, the molecular weight cut-off of the photocured dense surface layer in this embodiment is 100Da to 1000Da. The support layer is an ultrafiltration membrane or a microfiltration membrane.

[0026] The method for preparing a nanofiltration membrane prepared by a UV curing method of this embodiment includes the following steps: S1: Prepare a casting solution, mix the active monomers and photoinitiator in a certain proportion, and vacuum degas for a period of time to obtain a casting solution. Furthermore, in this embodiment, the total concentration of the active monomers in the casting solution is 95% to 99%, and the concentration of the photoinitiator in the casting solution is 1% to 5%. Specifically, in this embodiment, 5.1 g of acrylic acid, 4.6 g of hydroxyethyl methacrylate, and 0.3 g of photoinitiator TPO are added to a beaker in sequence. To uniformly disperse the solutes in the solution, the beaker is placed in an ultrasonic disperser and ultrasonically dispersed for 0.5 h. After dispersion, the solution is magnetically stirred, stirred evenly, and vacuum degassing is performed to obtain a casting solution, wherein the concentration of the photoinitiator TPO is 3%, and the concentrations of the active monomers acrylic acid and hydroxyethyl methacrylate in the casting solution are 97%.

[0027] S2: Apply the casting solution obtained in step S1 onto the surface of the support layer, evenly coating it. Use a scraper to scrape the surface of the support layer to form a film of a certain thickness, with a thickness of 2 μm. Place the scraped film solution under ultraviolet light to cure for 1 minute, then rinse with deionized water and dry in an oven to obtain the initial nanofiltration membrane.

[0028] S3: Modification treatment, placing the initial nanofiltration membrane at the bottom of the reactor, pouring the configured modifier solution into the reactor, and placing the reactor under an ultraviolet lamp for secondary photocuring and cross-linking to obtain a finished nanofiltration membrane, wherein the concentration of the modifier is 0% to 7%. Specifically, in this embodiment, a sodium styrene sulfonate solution with a concentration of 5% is configured as the modifier solution. Furthermore, in this embodiment, the time for secondary photocuring and cross-linking is 30 minutes. The wavelength of the ultraviolet lamp is 365 nm, and the distance between the ultraviolet lamp and the reactor is controlled to be 7 cm; the oven temperature is set to 40°C to 60°C.

[0029] According to conventional membrane performance evaluation methods, at a pressure of 0.4 MPa, the prepared nanofiltration membrane had a retention rate of 98.84% for methyl orange (molecular weight 327) solution and a pure water flux of 55.64 L / m 2 ·h, and the rejection rate of 1000 ppm Na2SO4 solution was 92.31%.

[0030] Figure 1 The following are SEM surface images and cross-sectional images of the nanofiltration membranes prepared in Examples 1-3 of the present invention and Comparative Example 1. In Comparative Example 1, the sodium styrene sulfonate (SSS) content was 0%, and the resulting nanofiltration membrane was labeled as a HEMA-PES composite membrane. In Examples 1-3, the nanofiltration membranes prepared using different sodium styrene sulfonate (SSS) contents were labeled as SSS@HEMA-PES composite membranes.

[0031] like Figure 1 As shown, Figure 1 The upper row of pictures are surface SEM images of the composite films in Comparative Example 1 and Examples 1-3. Figure 1 The lower row of images shows cross-sectional SEM images of the composite membranes. Comparison reveals that the HEMA-PES composite membranes prepared in Comparative Example 1 and Examples 1-3 exhibit similarly smooth, dense, wrinkle-free surfaces and lack significant defects, compared to the surface SEM images of the SSS@HEMA-PES composite membranes. The cross-sectional images reveal that the dense layer thickness of the HEMA-PES composite membrane prepared in Comparative Example 1 and the SSS@HEMA-PES composite membranes prepared in Examples 1-3 is only approximately 1 μm, and is uniform.

[0032] Figure 2 The flux of pure water and the retention rate of Na2SO4 of the light-cured nanofiltration membrane prepared in Comparative Example 1 and Examples 1-3 of the present invention are shown. Figure 2 The curve showing the separation performance of the composite membrane changes with the concentration of sodium styrene sulfonate (SSS). Figure 2 It can be seen that when the content of the modifier sodium styrene sulfonate (SSS) increases from 0% to 7%, the pure water flux increases from 72.33L / m 2 ·h dropped to 51.73L / m 2h (test pressure 0.4 MPa); the retention rate of Na₂SO₄ increased from 75.8% to 93.07%; and the retention rate of NaCl increased from 16.8% to 34.03%. This is because as the content of the modifier sodium styrene sulfonate (SSS) continues to increase, the number of active free radicals generated by the active monomers participating in the reaction increases. As a result, the degree of cross-linking between the active monomers and the composite membrane also increases, making the membrane denser. As a result, the flux from the perspective of size screening decreases, while the retention rate for inorganic salts increases. When the concentration of the modifier sodium styrene sulfonate (SSS) continues to increase from 5% to 7%, the changes in the permeation flux and the retention rate are basically stable. This is because the active sites that can be cross-linked on the surface of the composite membrane are limited. When the concentration of the modifier sodium styrene sulfonate (SSS) continues to increase, the active monomer will not only cross-link with the HEMA-PES composite membrane, but will also undergo self-cross-linking. Therefore, when the concentration of sodium styrene sulfonate (SSS) continues to increase from 5%, the cross-linking degree of the composite membrane will still increase slightly, so the flux of the composite membrane will decrease, and the retention rate for inorganic salts will increase. Therefore, from the perspective of economy and practicality, it is most appropriate to use 5% sodium styrene sulfonate (SSS) as a modifier for secondary UV curing and cross-linking. The permeation flux of the prepared nanofiltration membrane is 53.44 L / m 2 ·h, the rejection rate for Na2SO4 is 92.31%; the rejection rate for NaCl is 33.24%.

[0033] Figure 3 The retention rates of the photocurable nanofiltration membranes prepared in Examples 1-3 and Comparative Example 1 for polyethylene glycol (PEG) of different molecular weights were shown. Retention experiments were conducted on neutral solute PEG of different molecular weights, and the corresponding retention rates were obtained by TOC test. The molecular weight cut-off (MWCO) of the composite nanofiltration membranes was then calculated when the retention rate of the SSS@HEMA-PES composite membrane and the HEMA-PES composite membrane was 90%. Figure 3 As shown in the figure, the molecular weight cutoff (MWCO) of the SSS@HEMA-PES composite nanofiltration membrane is 260, and the molecular weight cutoff (MWCO) of the HEMA-PES composite membrane is 379. The molecular weight cutoff (MWCO) of the SSS@HEMA-PES composite membrane is significantly smaller than that of the HEMA-PES composite membrane. This is because the introduction of the active monomer sodium styrene sulfonate (SSS) as a modifier increases the cross-linking degree of the solidified layer, making the pore size of the composite membrane smaller. This proves that sodium styrene sulfonate (SSS) monomer cross-linking is an effective modification of the composite membrane. Example

[0034] This embodiment provides a method for preparing a nanofiltration membrane using a UV curing method. The basic steps for preparing the nanofiltration membrane are consistent with those of Example 1, except that in this embodiment, 5.1 g of acrylic acid, 4.6 g of hydroxyethyl methacrylate, and 0.3 g of a photoinitiator, TPO, are added to a beaker in this order. Ultrasonic dispersion is performed in an ultrasonic disperser for 0.5 h to uniformly disperse the solutes in the solution. After dispersion, the solution is magnetically stirred and, after uniform stirring, placed in a vacuum deaerator for degassing. After degassing, the solution is evenly poured on the PES base membrane and scraped into a film of a certain thickness (2 μm) with a scraper. The scraped casting liquid is placed under an ultraviolet lamp for curing. After curing for 1 min, it is rinsed with deionized water and then placed in an oven for drying. After drying, the initial nanofiltration membrane is obtained; the initial nanofiltration membrane is placed at the bottom of the reactor and fixed, and a prepared 3% sodium styrene sulfonate solution is poured into the reactor, and the reactor is placed under an ultraviolet lamp for secondary photocuring and cross-linking. After cross-linking for 30 min, the membrane is taken out, cleaned with pure water, and placed in an oven for drying to obtain the finished nanofiltration membrane of this embodiment.

[0035] According to the conventional membrane performance evaluation method, under a pressure of 0.4 MPa, the retention rate of the prepared nanofiltration membrane for methyl orange (molecular weight 327) solution was 90.54%, and the pure water flux was 78.26 L / m 2 h, and the rejection rate of 1000 ppm Na2SO4 solution was 58.33%.

[0036] Figure 4 The retention rate of the composite nanofiltration membrane prepared in Example 2 of the present invention for different dyes. The separation performance test of different types of dyes was carried out, and the test results are as follows: Figure 4As shown, the retention rates of RB and X-3B were 99.13% and 98.11%, respectively. RB and X-3B are non-ionic dyes, with RB having a molecular weight of approximately 973 and X-3B approximately 615. RB also has a larger Stokes radius. Size sieving plays a primary role in the separation of these two dyes, and the transport process conforms to a pore model, resulting in a higher retention rate for RB. MO (methyl orange) and MB are ionic dyes. MO, an anionic dye, has a retention rate of 98.84%, while MB, a cationic dye, has a retention rate of 62.25%. For ionic dyes, electrostatic repulsion and size sieving play the primary roles in separation. Separation experimental results are consistent with zeta potential measurements, indicating that the prepared composite nanofiltration membrane has a negative surface charge, thus exhibiting electrostatic repulsion towards negatively charged substances. Specifically, it is because the negative charge on the surface of the nanofiltration membrane has the same charge as the anionic dye MO. The long-range electrostatic repulsion caused by the Donnan effect makes the solute have a high retention rate on the dye. At the same time, due to the effect of steric hindrance, the solute has a larger steric hindrance and retention rate in the micropores on the membrane surface, so that the retention rate of MO is much higher than that of MB.

[0037] Figure 5 The effect of the immersion time of the composite nanofiltration membrane prepared in Example 2 of the present invention in sodium hypochlorite solution on the nanofiltration performance. Figure 5 It can be seen that the nanofiltration separation effect of the nanofiltration membrane for 1000 mg / L Na2SO4 solution after immersion for 3 days is not much different from that before immersion. The red line in the figure represents the permeation flux, which is basically stable at 53.44 L / m 2 The blue line in the figure represents the Na₂SO₄ retention rate, which remains essentially stable at 92.31%. Furthermore, the contact angle of the membrane surface remains essentially unchanged after immersion. This is because the hydroxyl groups in the reactive monomer hydroxyethyl methacrylate (HEMA) in the light-curing system polymerize with the acyloxy groups in the reactive monomer sodium styrene sulfonate (SSS) used as a modifier, resulting in strong stability in the sodium hypochlorite solution. Example

[0038] This embodiment provides a method for preparing a nanofiltration membrane using a UV curing method. The basic steps for preparing the nanofiltration membrane are the same as those in Example 1, except that in this embodiment, 5.1 g of acrylic acid, 4.6 g of hydroxyethyl methacrylate, and 0.3 g of photoinitiator TPO are added to a beaker in this order. To uniformly disperse the solutes in the solution, the beaker is placed in an ultrasonic disperser for ultrasonic dispersion for 0.5 h. After dispersion, the solution is magnetically stirred and, after uniform stirring, placed in a vacuum deaerator for degassing. After degassing, the solution is evenly poured on the PES base membrane and scraped into a film of a certain thickness (2 μm) with a scraper. The scraped casting liquid is placed under an ultraviolet lamp for curing. After curing for 1 min, it is rinsed with deionized water and then placed in an oven for drying. After drying, the initial nanofiltration membrane is obtained; the initial nanofiltration membrane is placed at the bottom of the reactor and fixed, and a prepared sodium styrene sulfonate solution with a concentration of 7% is poured into the reactor, and the reactor is placed under an ultraviolet lamp for secondary photocuring and cross-linking. After cross-linking for 30 min, the membrane is taken out, cleaned with pure water, and placed in an oven for drying to obtain the finished nanofiltration membrane of this embodiment.

[0039] According to the conventional membrane performance evaluation method, under a pressure of 0.4 MPa, the retention rate of the prepared nanofiltration membrane for methyl orange (molecular weight 327) solution was 86.32%, and the pure water flux was 37.14 L / m 2 h, and the rejection rate of 1000 ppm Na2SO4 solution was 94.53%.

[0040] In this comparative example, a method for preparing a nanofiltration membrane using a UV curing method is described. 5.1 g of acrylic acid, 4.6 g of hydroxyethyl methacrylate, and 0.3 g of a photoinitiator, TPO, are added to a beaker in this order. To uniformly disperse the solutes in the solution, the solution is placed in an ultrasonic disperser for ultrasonic dispersion for 0.5 h. After dispersion, the solution is magnetically stirred, stirred evenly, and then placed in a vacuum deaerator for degassing. After degassing, the solution is evenly poured onto a PES base film and scraped with a spatula to form a film of a certain thickness (2 μm). The scraped casting solution is then placed under a UV lamp for curing. After curing for 1 minute, it is rinsed with deionized water and then dried in an oven to obtain a nanofiltration membrane.

[0041] According to the conventional membrane performance evaluation method, under a pressure of 0.4 MPa, the retention rate of the prepared nanofiltration membrane for methyl orange (molecular weight 327) solution was 83.35%, and the pure water flux was 72.33 L / m 2 h, and the rejection rate for 1000 ppm Na2SO4 solution was 75.8%. Example

[0042] The method for preparing a nanofiltration membrane prepared by a UV curing method in this embodiment is consistent with the basic operating steps of Example 1. The difference is that in this embodiment, 4.8 g of acrylic acid, 4.5 g of hydroxyethyl methacrylate, and 0.7 g of photoinitiator TPO are added to a beaker in this order. To uniformly disperse the solute in the solution, the beaker is placed in an ultrasonic disperser for ultrasonic dispersion for 0.5 h. After dispersion, the solution is magnetically stirred and, after uniform stirring, placed in a vacuum deaerator for degassing. After degassing, the solution was evenly poured on the PES base membrane and scraped into a film of a certain thickness (3 μm) with a scraper. The scraped casting liquid was placed under an ultraviolet lamp for curing. After curing for 2 minutes, it was rinsed with deionized water and then placed in an oven for drying. After drying, the initial nanofiltration membrane was obtained; the initial nanofiltration membrane was placed at the bottom of the reactor and fixed, and the prepared 7% propylene oxide solution was poured into the reactor, and the reactor was placed under an ultraviolet lamp for secondary photocuring and cross-linking. After cross-linking for 2 minutes, the membrane was taken out, washed with pure water, and placed in an oven for drying to obtain the finished nanofiltration membrane of this embodiment.

[0043] According to the conventional membrane performance evaluation method, under a pressure of 0.4 MPa, the retention rate of the prepared nanofiltration membrane for methyl orange (molecular weight 327) solution was 83.35%, and the pure water flux was 33.37 L / m 2 ·h, and the rejection rate of 1000 ppm Na2SO4 solution was 93.08%. Example

[0044] The method for preparing a nanofiltration membrane prepared by a UV curing method in this embodiment is consistent with the basic operating steps of Example 1. The difference is that in this embodiment, 4.8 g of acrylic acid, 4.5 g of hydroxyethyl methacrylate, and 0.7 g of photoinitiator TPO are added to a beaker in this order. To uniformly disperse the solute in the solution, the beaker is placed in an ultrasonic disperser for ultrasonic dispersion for 0.5 h. After dispersion, the solution is magnetically stirred and, after uniform stirring, placed in a vacuum deaerator for degassing. After degassing, the solution was evenly poured on the PES base membrane and scraped into a film of a certain thickness (3 μm) with a scraper. The scraped casting liquid was placed under an ultraviolet lamp for curing. After curing for 2 minutes, it was rinsed with deionized water and then placed in an oven for drying. After drying, the initial nanofiltration membrane was obtained; the initial nanofiltration membrane was placed at the bottom of the reactor and fixed, and the prepared 5% propylene oxide solution was poured into the reactor, and the reactor was placed under an ultraviolet lamp for secondary photocuring and cross-linking. After cross-linking for 2 minutes, the membrane was taken out, cleaned with pure water, and placed in an oven for drying to obtain the finished nanofiltration membrane of this embodiment.

[0045] According to conventional membrane performance evaluation methods, at a pressure of 0.4 MPa, the prepared nanofiltration membrane had a retention rate of 87.38% for methyl orange (molecular weight 327) solution and a pure water flux of 35.66 L / m 2 ·h, and the rejection rate of 1000 ppm Na2SO4 solution was 95.13%. Example

[0046] The method for preparing a nanofiltration membrane prepared by a UV curing method in this embodiment is consistent with the basic operating steps of Example 1. The difference is that in this embodiment, 4.8 g of acrylic acid, 4.5 g of hydroxyethyl methacrylate, and 0.7 g of photoinitiator TPO are added to a beaker in this order. To uniformly disperse the solute in the solution, the beaker is placed in an ultrasonic disperser for ultrasonic dispersion for 0.5 h. After dispersion, the solution is magnetically stirred and, after uniform stirring, placed in a vacuum deaerator for degassing. After degassing, the solution was evenly poured on the PES base membrane and scraped into a film of a certain thickness (3 μm) with a scraper. The scraped casting liquid was placed under an ultraviolet lamp for curing. After curing for 2 minutes, it was rinsed with deionized water and then placed in an oven for drying. After drying, the initial nanofiltration membrane was obtained; the initial nanofiltration membrane was placed at the bottom of the reactor and fixed, and the prepared 3% propylene oxide solution was poured into the reactor, and the reactor was placed under an ultraviolet lamp for secondary photocuring and cross-linking. After cross-linking for 2 minutes, the membrane was taken out, cleaned with pure water, and placed in an oven for drying to obtain the finished nanofiltration membrane of this embodiment.

[0047] According to the conventional membrane performance evaluation method, under a pressure of 0.4 MPa, the retention rate of the prepared nanofiltration membrane for methyl orange (molecular weight 327) solution was 85.03%, and the pure water flux was 34.55 L / m 2 ·h, and the rejection rate of 1000 ppm Na2SO4 solution was 92.86%.

[0048] Any content not described in detail in this specification is prior art known to those skilled in the art. In the description of the present invention, unless otherwise specified, "plurality" means two or more. Terms such as "upper," "lower," "left," "right," "inner," "outer," "front," "rear," "head," and "tail" indicate positions or relationships based on those shown in the accompanying drawings and are intended solely for ease of description and simplification. They do not indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation and are therefore not to be construed as limiting the present invention. Furthermore, terms such as "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. In the description of the present invention, unless otherwise specified or limited, the terms "connected" and "connected" are to be understood broadly, meaning, for example, fixedly connected, detachably connected, or integrally connected; mechanically connected, electrically connected; directly connected, or indirectly connected through an intermediary. Those skilled in the art will understand the specific meanings of these terms in the present invention on a case-by-case basis.

[0049] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A nanofiltration membrane prepared by ultraviolet curing, characterized in that: include: A support layer and a light-cured dense surface layer, wherein the light-cured dense surface layer is prepared by applying a casting solution to the surface of the support layer, curing it with ultraviolet light, and then performing a modification treatment; The casting solution of the photocurable dense surface layer includes active monomers and photoinitiators.

2. The nanofiltration membrane prepared by the ultraviolet curing method according to claim 1, characterized in that: The molecular weight cut-off of the photocured dense surface layer is 100Da~1000Da.

3. The nanofiltration membrane prepared by the ultraviolet curing method according to claim 1, characterized in that: The supporting layer is an ultrafiltration membrane or a microfiltration membrane.

4. The nanofiltration membrane prepared by the ultraviolet curing method according to claim 1, characterized in that: The active monomer in the casting solution is selected from any one of acrylic acid, hydroxyethyl methacrylate, methyl methacrylate, methacrylic acid, acrylic resin, polyimide, polybenzimidazolone, ethylene glycol dimethacrylate, triethylene glycol acrylate, acrylamide, N-isopropylacrylamide, N-methylacrylic acid, vinylamide, vinylbenzene, vinyl methacrylate, and vinyl methacrylate, or a combination of at least two thereof.

5. The nanofiltration membrane prepared by the ultraviolet curing method according to claim 1, characterized in that: The modifier used in the modification treatment is selected from any one of propylene oxide, caprolactam, and sodium styrene sulfonate, or a combination of at least two of them.

6. A nanofiltration membrane prepared by the UV curing method according to any one of claims 1 to 5, characterized in that: The photoinitiator in the casting solution is selected from any one of dimethyl sulfoxide, diisopropyl dithiocarbonamide, benzoyl acetone, triacetyltriethyloxysilane, vinyl mercaptan, and 2,4,6-trimethylphenyl peroxide, or a combination of at least two thereof.

7. A method for preparing a nanofiltration membrane prepared by an ultraviolet curing method, wherein the nanofiltration membrane according to any one of claims 1 to 6 is prepared, characterized in that: The following steps are included: S1: preparing a casting solution, mixing the active monomer and the photoinitiator in a certain proportion, and vacuum degassing for a period of time to obtain a casting solution; S2: coating the casting solution, pouring the casting solution obtained in step S1 onto the surface of the support layer, evenly coating the surface of the support layer, and curing it under ultraviolet light for a period of time, then rinsing it with deionized water and drying it to obtain the initial nanofiltration membrane; S3: Modification treatment: Place the initial nanofiltration membrane at the bottom of the reactor, pour the prepared modifier solution into the reactor, and place the reactor under an ultraviolet lamp for secondary photocuring and cross-linking to obtain a modified nanofiltration membrane.

8. The method for preparing a nanofiltration membrane prepared by an ultraviolet curing method according to claim 7, characterized in that: The total concentration of active monomers in the casting solution is 95% to 99%; And / or, the concentration of the photoinitiator in the casting solution is 1% to 5%.

9. The method for preparing a nanofiltration membrane prepared by an ultraviolet curing method according to claim 7, characterized in that: The concentration of the modifier in step S3 is 0% to 7%.

10. The method for preparing a nanofiltration membrane prepared by an ultraviolet curing method according to claim 7, characterized in that: The UV curing time in step S2 is 1 min to 20 min; And / or, the time for the secondary photocuring cross-linking in step S3 is 1 min to 40 min.

Images