Nanofiltration membrane and preparation method thereof

Abstract

The invention discloses a nanofiltration membrane and a preparation method thereof. The preparation method comprises the following steps: preparing a porous support layer membrane by a non-solvent induced phase separation method; preparing a titanium dioxide middle layer on the porous supporting layer film to obtain a precursor film; the preparation method comprises the following steps: respectively preparing a water phase solution and an oil phase solution, taking m-xylylenediamine as a water phase monomer in the water phase solution, and taking trimesoyl chloride as an oil phase monomer in the oil phase solution; immersing the precursor membrane into a prepared water phase solution, and ensuring that a water phase monomer is uniformly distributed on the surface of the porous support layer membrane; after the redundant aqueous phase solution on the surface of the infiltrated precursor film is removed, the precursor film soaked with the aqueous phase solution is rapidly soaked into the oil phase solution for interfacial polymerization reaction, and the reaction time is 30-120 s; and removing impurities on the surface of the membrane by using normal hexane liquid, and carrying out thermocuring treatment to obtain the target nanofiltration membrane. The nanofiltration membrane provided by the invention has good desalination performance, membrane flux and durability.

Description

Technical Field

[0001] This invention relates to the field of separation membrane technology, and in particular to a nanofiltration membrane and its preparation method. Background Technology

[0002] With the increasing scarcity of water resources and the aggravation of water pollution problems, the demand for efficient desalination technology is becoming increasingly urgent. Currently, reverse osmosis and nanofiltration are two commonly used desalination technologies. Among them, nanofiltration membranes have broad application prospects in seawater desalination, brackish water treatment, and wastewater reuse due to their selectivity in removing monovalent and divalent ions.

[0003] Traditional nanofiltration membrane preparation methods often employ interfacial polymerization technology. This technology introduces an aqueous phase and an oil phase onto opposite sides of a porous support layer, allowing the two monomers to polymerize at the interface, forming a selective separation layer. However, existing technologies have limited options for the aqueous and oil phase monomers used in nanofiltration membrane preparation, and the polymerization process suffers from difficulties in controlling reaction conditions and unstable membrane performance, resulting in nanofiltration membranes with shortcomings in desalination performance, flux, and durability.

[0004] For example, some existing technologies use aqueous monomers with low reactivity, leading to incomplete polymerization and an uneven selective separation layer structure, which in turn affects the desalination efficiency and stability of the membrane. Furthermore, some oil-phase monomers are prone to phase separation or aggregation during polymerization, further reducing membrane performance.

[0005] Therefore, it is of great significance to develop a new preparation method that can improve the desalination performance and membrane flux of nanofiltration membranes. Summary of the Invention

[0006] The technical problem to be solved by the embodiments of the present invention is to provide a nanofiltration membrane and a method for preparing the same, which can improve the desalination performance and membrane flux of the nanofiltration membrane.

[0007] To address the aforementioned technical problems, this invention provides a method for preparing a nanofiltration membrane. The method includes the following steps: preparing a porous support layer membrane using a solvent-inducible phase separation method; preparing a titanium dioxide interlayer on the porous support layer membrane to obtain a precursor membrane; preparing an aqueous solution and an oil solution, wherein the aqueous solution uses m-phenylenediamine as the aqueous monomer and the oil solution uses trimesoyl pyromellitic acid as the oil monomer; immersing the precursor membrane in the prepared aqueous solution to ensure uniform distribution of the aqueous monomer on the surface of the porous support layer membrane; removing excess aqueous solution from the surface of the immersed precursor membrane; rapidly immersing the precursor membrane in the aqueous solution into the oil solution for interfacial polymerization reaction for 30-120 seconds; after the reaction, removing impurities from the membrane surface using n-hexane liquid; and subjecting the membrane after impurity removal to thermal curing treatment to obtain the target nanofiltration membrane.

[0008] In one feasible implementation, the steps of preparing the porous support layer membrane by the non-solvent-induced phase separation method include the following operations: weighing a certain mass of polymer particles and dissolving them in an organic solvent, stirring at 80℃-85℃ for 10h-15h to completely dissolve the polymer particles, scraping the solution onto a nonwoven fabric to form a film with a thickness of 100-200μm, waiting for the film to completely solidify, obtaining the porous support layer membrane, and storing it in deionized water for later use.

[0009] In one feasible implementation, the polymer is selected from polysulfone and polyethersulfone.

[0010] In one feasible implementation, the organic solvent is selected from one or a mixture of several of N,N-dimethylacetamide, N,N-dimethylformamide, and N-methylpyrrolidone.

[0011] In one feasible implementation, the polymer particles have a mass percentage in the solution ranging from 16% to 18%.

[0012] In one feasible implementation, the steps for preparing the titanium dioxide intermediate layer include the following operations: adding a certain amount of titanium dioxide to an organic solvent to obtain a titanium dioxide dispersion; subjecting the titanium dioxide dispersion to ultrasonic treatment to obtain a uniform milky white suspension; uniformly loading the suspension onto the surface of the porous support layer by vacuum filtration to obtain the precursor film; wherein the mass percentage of titanium dioxide in the titanium dioxide dispersion ranges from 0.01% to 2%.

[0013] In one feasible implementation, the operation of removing excess aqueous solution from the surface of the membrane after impregnation is as follows: the impregnated porous support membrane is removed from the aqueous solution and the residual liquid on the membrane surface is dried with nitrogen or inert gas.

[0014] In one feasible implementation, the mass percentage of intermediate-phenylenediamine in the aqueous solution ranges from 1% to 5%.

[0015] In one feasible implementation, the pH range of the aqueous solution is 8-10.

[0016] In one feasible implementation, the mass percentage of pyromellitic chloroformyl chloride in the oil phase solution ranges from 0.1% to 0.5%. In one feasible implementation, the solvent of the oil phase solution is n-hexane.

[0017] In one feasible implementation, the temperature range of the thermosetting treatment is 60℃~80℃, and the time of the thermosetting treatment is 5min-20min.

[0018] Accordingly, the present invention also provides a nanofiltration membrane, which is prepared by any of the nanofiltration membrane preparation methods described above.

[0019] Implementing this invention has the following beneficial effects: The nanofiltration membrane preparation method provided in this application uses m-phenylenediamine as an aqueous monomer to undergo interfacial polymerization with TMC. By precisely controlling the monomer concentration, reaction time, and reaction conditions, a selective separation layer with excellent desalination performance is formed. This monomer combination provides good reactivity and film-forming properties, ensuring the uniformity and stability of the membrane structure, which is one of the core innovations of this invention. Furthermore, the nanofiltration membrane preparation method provided in this application optimizes the formulation of the oil phase solution, including selecting suitable solvents, TMC concentrations, and catalyst types and amounts. By adjusting these parameters, the rate of the interfacial polymerization reaction and the film-forming quality are effectively controlled, achieving an optimal balance in desalination performance, flux, and durability of the prepared nanofiltration membrane. Further, the nanofiltration membrane preparation method provided in this application also precisely controls the process parameters of the interfacial polymerization reaction, including the wetting time of the aqueous and oil phases, reaction time, drying time, and thermosetting treatment parameters. These parameters have a significant impact on the structure and performance of the nanofiltration membrane. Through systematic experimental research and optimization, the optimal range of process parameters has been determined, enabling the preparation method of this invention to stably produce high-performance nanofiltration membranes.

[0020] The nanofiltration membrane provided in this application comprises a porous support layer membrane and a desalination layer located on the surface of the porous support layer membrane. The porous support layer membrane is prepared by a solvent-inducible phase separation method; the desalination layer is obtained by interfacial polymerization of an aqueous solution with m-phenylenediamine as the aqueous monomer and an oil solution with trimesoyl chloride as the oil monomer. This monomer combination provides good reactivity and film-forming properties, ensuring the uniformity and stability of the membrane structure. Furthermore, by precisely controlling the concentrations of the aqueous and oil monomers, the interfacial polymerization parameters, and the thermosetting conditions, a selective separation layer with excellent desalination performance is formed. Attached Figure Description

[0021] Figure 1 This is a flowchart of the preparation method of nanofiltration membrane according to an embodiment of this application. Detailed Implementation

[0022] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0024] This application provides a method for preparing a nanofiltration membrane. By optimizing the conditions and parameters of the interfacial polymerization reaction between m-phenylenediamine and TMC, the prepared nanofiltration membrane has a more uniform selective separation layer structure, thereby improving the selective permeation capacity for salt ions and enhancing desalination efficiency and pure water flux. Using specific aqueous and oil phase formulations and precise reaction control, the prepared nanofiltration membrane exhibits better stability and durability under different operating conditions (such as pressure, temperature, and water quality), extending the membrane's service life.

[0025] Please refer to Figure 1 The nanofiltration membrane preparation method provided in this application includes the following steps: S110. A porous support layer membrane is prepared by a non-solvent-induced phase separation method.

[0026] In one feasible implementation, the steps of preparing the porous support layer membrane by the non-solvent-induced phase separation method include the following operations: A certain mass of polymer particles is weighed and dissolved in an organic solvent. The mixture is stirred at 80℃-85℃ for 10-15 hours to ensure complete dissolution of the polymer particles. The solution is then scraped onto a nonwoven fabric to form a film with a thickness of 100-200 μm. Once the film has completely solidified, the porous support layer membrane is obtained and stored in deionized water for later use.

[0027] In one feasible implementation, the mass percentage of the polymer particles in the solution ranges from 16% to 18%. Further, the mass percentage of the polymer particles in the solution can be, but is not limited to, any value between 16%, 17%, 18%, or 16%-18%.

[0028] The specific dissolution temperatures can be 80℃, 81℃, 82℃, 83℃, 84℃, or 85℃, and the stirring times can be 10h, 11h, 12h, 13h, 14h, or 15h. The specific thicknesses of the porous support layer membrane can be 100μm, 110μm, 120μm, 130μm, 140μm, 150μm, 160μm, 170μm, 180μm, 190μm, or 200μm.

[0029] In one feasible implementation, the polymer is selected from polysulfone (PSF) and polyethersulfone (PES).

[0030] In one feasible implementation, the organic solvent is selected from one or a mixture of several of N,N-dimethylacetamide, N,N-dimethylformamide (DMF), and N-methylpyrrolidone (NMP).

[0031] S120. A titanium dioxide intermediate layer is prepared on the porous support layer film to obtain a precursor film.

[0032] In this way, a porous hierarchical structure can be constructed through the titanium dioxide intermediate layer. The titanium dioxide layer formed by vacuum filtration deposition promotes the appearance of wrinkled surfaces in the interfacial polymerization layer, thereby increasing the effective membrane area and the overall membrane flux.

[0033] In one feasible implementation, the steps for preparing the titanium dioxide intermediate layer include the following operations: adding a certain amount of titanium dioxide to an organic solvent to obtain a titanium dioxide dispersion; subjecting the titanium dioxide dispersion to ultrasonic treatment to obtain a uniform milky white suspension; and uniformly loading the suspension onto the surface of the porous support layer by vacuum filtration to obtain the precursor film.

[0034] The organic solvent used to disperse titanium dioxide is selected from at least one of N,N-dimethylacetamide, N,N-dimethylformamide, and N-methylpyrrolidone.

[0035] In one feasible implementation, the mass percentage of titanium dioxide in the titanium dioxide dispersion ranges from 0.01% to 2%. Further, the mass percentage of titanium dioxide in the titanium dioxide dispersion can be, but is not limited to, any value between 0.01%, 0.1%, 0.5%, 1%, 1.01%, 1.1%, 1.5%, 2%, or 0.01%-2%.

[0036] Furthermore, the deposition and thickness of titanium dioxide on the surface of the porous support layer are also related to the size of the porous support layer film.

[0037] In one feasible implementation, the titanium dioxide has a particle size of 1 nm to 100 nm. The titanium dioxide is fixed on the surface of the porous support layer by van der Waals forces, hydrogen bonds, and dipole interactions, and is further tightly connected to the porous support layer and the desalination layer through interfacial polymerization.

[0038] S130. Prepare an aqueous solution and an oil solution respectively, wherein the aqueous solution uses m-phenylenediamine as the aqueous monomer and the oil solution uses trimesoyl chloride (TMC) as the oil monomer.

[0039] In one feasible implementation, the mass percentage of m-phenylenediamine in the aqueous solution ranges from 1% to 5%. Further, the mass percentage of m-phenylenediamine can be, but is not limited to, any value between 1%, 2%, 3%, 4%, 5%, or 1%-5%.

[0040] In one feasible implementation, the pH value of the aqueous phase solution is in the range of 8-10. Further, the pH value of the aqueous phase solution may be, but is not limited to, 8, 8.5, 9, 9.5, or 10.

[0041] In one feasible implementation, the mass percentage of pyromellitic chloride in the oil phase solution ranges from 0.1% to 0.5%. Further, the mass percentage of pyromellitic chloride can be, but is not limited to, any value between 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, or 0.1%-0.5%.

[0042] In one feasible implementation, the solvent of the oil phase solution is n-hexane.

[0043] The combination of m-phenylenediamine and trimesoyl chloride provides good reactivity and film-forming properties, ensuring the uniformity and stability of the film structure, which is one of the core innovations of this invention.

[0044] S140. The precursor membrane is first immersed in the prepared aqueous solution to ensure that the aqueous monomers are evenly distributed on the surface of the porous support layer membrane.

[0045] The immersion mentioned here can refer to immersing the precursor membrane in an aqueous solution, pouring the aqueous solution onto the surface of the precursor membrane, spraying it onto the surface of the precursor membrane, or other methods that can uniformly distribute the aqueous solution on the surface of the precursor membrane to facilitate interfacial polymerization.

[0046] S150. After removing excess aqueous solution from the surface of the precursor membrane after wetting, the precursor membrane soaked in aqueous solution is quickly immersed in oil solution to carry out interfacial polymerization reaction for 30s-120s.

[0047] In one feasible implementation, the operation of removing excess aqueous solution from the surface of the wetted membrane is as follows: the wetted precursor membrane is removed from the aqueous solution and the residual liquid on the membrane surface is dried with nitrogen or an inert gas.

[0048] The reaction time can be, but is not limited to, any specific time between 30s, 40s, 50s, 60s, 70s, 80s, 90s, 100s, 110s, 120s or 30s-120s.

[0049] The immersion mentioned here can refer to immersing the precursor membrane in an oil phase solution, pouring the oil phase solution onto the surface of the precursor membrane, spraying it onto the surface of the precursor membrane, or other methods that can uniformly distribute the oil phase solution on the surface of the precursor membrane to facilitate interfacial polymerization.

[0050] S160. After the reaction is complete, remove impurities from the membrane surface with n-hexane liquid.

[0051] The surface is rinsed with n-hexane to remove unreacted monomers and byproducts.

[0052] In one feasible implementation, removing impurities from the membrane surface with liquid hexane can be achieved by rinsing the membrane with hexane to remove unreacted monomers and byproducts. Of course, if the precursor membrane is immersed in an oil phase, it needs to be removed from the oil phase solution.

[0053] S170. The membrane after impurity removal is subjected to thermal curing treatment to obtain the target nanofiltration membrane.

[0054] In one feasible implementation, the temperature range of the thermosetting treatment is 60℃ to 80℃, and the thermosetting treatment time is 5 min to 20 min. Further, the temperature of the thermosetting treatment can be, but is not limited to, 60℃, 70℃, 80℃, or any temperature between 60℃ and 70℃. The time of the thermosetting treatment can be, but is not limited to, 5 min, 10 min, 15 min, 20 min, or any time between 5 min and 20 min. The specific thermosetting treatment time also needs to be set in conjunction with the thermosetting treatment temperature.

[0055] The nanofiltration membrane preparation method provided in this application uses m-phenylenediamine as an aqueous monomer to undergo interfacial polymerization with TMC. This monomer combination provides good reactivity and film-forming properties, ensuring the uniformity and stability of the membrane structure. By precisely controlling the monomer concentration, reaction time, and reaction conditions, a selective separation layer with excellent desalination performance is formed. Furthermore, the nanofiltration membrane preparation method provided in this application effectively controls the rate of the interfacial polymerization reaction and the film quality by optimizing the formulation and steps of the oil phase solution, achieving an optimal balance in desalination performance, flux, and durability of the prepared nanofiltration membrane. Further, the nanofiltration membrane preparation method provided in this application also precisely controls the process parameters of the interfacial polymerization reaction, including the wetting time of the aqueous and oil phases, reaction time, drying time, and thermosetting parameters. These parameters have a significant impact on the structure and performance of the nanofiltration membrane. Through systematic experimental research and optimization, the optimal range of process parameters has been determined, enabling the preparation method of this invention to stably produce high-performance nanofiltration membranes. A titanium dioxide layer is deposited in the intermediate layer through vacuum filtration, which promotes the formation of wrinkled surfaces in the interfacial polymerization layer, thereby increasing the effective membrane area and the overall membrane flux. Under the combined effect of the above-mentioned multiple process conditions, the nanofiltration membrane prepared by the preparation method provided in this application embodiment has good desalination performance, membrane flux, and durability.

[0056] Accordingly, this application also provides a nanofiltration membrane, which is prepared using any of the nanofiltration membrane preparation methods described above.

[0057] Furthermore, the nanofiltration membrane provided in this application comprises a porous support layer membrane, a titanium dioxide interlayer, and a desalination layer located on the surface of the titanium dioxide interlayer. The porous support layer membrane is prepared by a solvent-inducible phase separation method; the titanium dioxide interlayer is deposited on the surface of the porous support layer membrane by vacuum filtration; and the desalination layer is obtained by interfacial polymerization of an aqueous solution with m-phenylenediamine as the aqueous monomer and an oil solution with trimesoyl chloride as the oil monomer. This monomer combination provides good reactivity and film-forming properties, ensuring the uniformity and stability of the membrane structure. Furthermore, by precisely controlling the concentrations of the aqueous and oil monomers, the interfacial polymerization parameters, and the thermosetting conditions, a selective separation layer with excellent desalination performance is formed. The titanium dioxide interlayer further promotes the formation of wrinkled surfaces in the interfacial polymerization layer, thereby increasing the effective membrane area and the overall membrane flux. This results in the nanofiltration membrane provided in this application having excellent desalination performance, membrane flux, and durability.

[0058] Referring to the above implementation details, in order to make the technical solution of this application more specific, clear, and easy to understand, examples of the technical solution of this application are given below. However, it should be noted that the content to be protected by this application is not limited to the following embodiments.

[0059] Example 1 A porous support layer membrane was prepared by a non-solvent-induced phase separation method: 18g of polysulfone particles were weighed and dissolved in 82g of m-phenylenediamine C. The mixture was stirred at 80℃ for 10h until the polysulfone was completely dissolved. A film with a thickness of 140μm was scraped onto a nonwoven fabric. The film was then completely cured to obtain a porous support layer membrane, which was stored in deionized water for later use.

[0060] 200 mg of titanium dioxide was added to 100 ml of N-methylpyrrolidone to obtain a titanium dioxide dispersion. The titanium dioxide dispersion was then sonicated in an ultrasonic instrument for 35 min to obtain a homogeneous milky white suspension. The titanium dioxide was deposited on the surface of a porous support membrane by vacuum filtration to obtain a precursor membrane.

[0061] Dissolve 1.5 g of m-phenylenediamine in 98.5 g of deionized water, sonicate for 30 minutes to prepare an aqueous solution, and adjust the pH of the aqueous solution to 9; dissolve 0.2 g of trimesoyl chloride in 99.8 g of n-hexane, sonicate for 20 minutes to prepare an oil phase solution. The precursor membrane is fixed on the membrane frame, the aqueous solution is poured into the membrane frame and kept for 2 minutes, and the excess aqueous solution is poured off; then the oil solution is poured onto the membrane surface and kept for 1 minute, and the excess oil solution is poured off. The membrane is placed in an oven at 60°C for 10 minutes to obtain the target nanofiltration membrane.

[0062] Example 2 This embodiment is basically the same as Embodiment 1, except that in this embodiment, the aqueous solution is prepared by dissolving 2g of m-phenylenediamine in 98g of deionized water, and the pH value of the aqueous solution is still 9.

[0063] Example 3 This embodiment is basically the same as Embodiment 1, except that in this embodiment, the aqueous phase solution is prepared by dissolving 3g of m-phenylenediamine in 97g of deionized water, and the pH value of the aqueous phase solution is still 9.

[0064] Comparative Example 1 Weigh 18g of polysulfone particles and dissolve them in 82g of DMAC. Stir at 80℃ for 10h until the polysulfone is completely dissolved. Scrape a 140μm thick film composite membrane (TFC) onto a nonwoven fabric. Once the polysulfone is completely cured, store it in deionized water for later use.

[0065] Dissolve 2g of m-phenylenediamine in 98.5g of deionized water and sonicate for 30 minutes; 0.2g of pyromellitic methyl chloride was dissolved in 99.8g of n-hexane and sonicated for 20 minutes; Fix the base membrane onto the membrane frame, pour the aqueous solution containing m-phenylenediamine into the membrane frame, keep it for 2 minutes, and then pour off the excess aqueous phase; then pour the oil phase solution containing trimesoyl chloride onto the membrane surface, keep it for 1 minute, pour off the excess oil phase, and place the composite membrane in an oven at 60°C for 10 minutes.

[0066] Performance testing Flux and retention tests were performed on the nanofiltration membranes prepared in the examples and comparative examples: the test pressure was 4.5 bar, the test solution was an aqueous solution of 30 ppm Congo red dye, the solution temperature was 25°C, and the nanofiltration membrane was run in a cross-flow device for 30 min to measure the flux and retention. The test results are shown in Table 1.

[0067] Table 1. Flux and Rejection Results As shown in the table above, the nanofiltration membranes prepared by the methods provided in this application have better flux and retention rates than the nanofiltration membranes in the comparative examples. Among them, the nanofiltration membrane prepared in Example 2 has the highest flux and retention rate, and the best desalination performance.

[0068] The basic concepts have been described above. Obviously, for those skilled in the art, the detailed disclosure above is merely illustrative and does not constitute a limitation of this specification. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements, and corrections to this specification. Such modifications, improvements, and corrections are suggested in this specification and therefore remain within the spirit and scope of the exemplary embodiments described herein.

[0069] Furthermore, this specification uses specific terms to describe embodiments thereof. For example, "an embodiment," "one embodiment," and / or "some embodiments" refer to a particular feature, structure, or characteristic associated with at least one embodiment of this specification. Therefore, it should be emphasized and noted that references to "an embodiment," "one embodiment," or "an alternative embodiment" in different locations throughout this specification do not necessarily refer to the same embodiment. Moreover, certain features, structures, or characteristics in one or more embodiments of this specification can be appropriately combined.

[0070] Furthermore, unless expressly stated in the claims, the order of processing elements and sequences, the use of numbers and letters, or other names described in this specification are not intended to limit the order of the processes and methods described herein. Although some inventive embodiments that are currently considered useful have been discussed by way of various examples in the foregoing disclosure, it should be understood that such details are for illustrative purposes only, and the appended claims are not limited to the disclosed embodiments. Rather, the claims are intended to cover all modifications and equivalent combinations that conform to the substance and scope of the embodiments described herein.

[0071] Similarly, it should be noted that, in order to simplify the description disclosed herein and thus aid in the understanding of one or more embodiments of the invention, the foregoing description of embodiments in this specification may sometimes combine multiple features into a single embodiment, drawing, or description thereof. However, this method of disclosure does not imply that the subject matter of this specification requires more features than those mentioned in the claims. In fact, the embodiments contain fewer features than all the features of a single embodiment disclosed above.

[0072] In some embodiments, numbers describing the quantity of components and attributes are used. It should be understood that such numbers used in the description of embodiments are modified in some examples with the terms "approximately," "approximately," or "generally." Unless otherwise stated, "approximately," "approximately," or "generally" indicates that the numbers are allowed to vary by ±20%. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximate values, which may be changed depending on the characteristics required by individual embodiments. In some embodiments, numerical parameters should take into account specified significant digits and employ a general method of digit reservation. Although the numerical ranges and parameters used to confirm their breadth of range in some embodiments of this specification are approximate values, in specific embodiments, such values ​​are set as precisely as feasible.

[0073] For each patent, patent application, patent application publication, and other material such as articles, books, specifications, publications, and documents referenced in this specification, the entire contents of which are incorporated herein by reference. This excludes historical application documents that are inconsistent with or conflict with the content of this specification, as well as documents that limit the broadest scope of the claims in this specification (currently or subsequently appended to this specification). It should be noted that in the event of any inconsistency or conflict between the descriptions, definitions, and / or terminology used in the supplementary materials to this specification and the content of this specification, the descriptions, definitions, and / or terminology used in this specification shall prevail.

[0074] Finally, it should be understood that the embodiments described in this specification are merely illustrative of the principles of the embodiments described herein. Other variations may also fall within the scope of this specification. Therefore, alternative configurations of the embodiments described herein are intended to be illustrative rather than limiting, and should be considered consistent with the teachings of this specification. Accordingly, the embodiments described herein are not limited to those explicitly introduced and described herein.

Claims

1. A method for preparing a nanofiltration membrane, characterized in that, The method for preparing the nanofiltration membrane includes the following steps: Porous support membranes were prepared by a solvent-inducible phase separation method. A titanium dioxide intermediate layer is prepared on the porous support layer film to obtain a precursor film; An aqueous phase solution and an oil phase solution are prepared separately, wherein the aqueous phase solution uses m-phenylenediamine as the aqueous phase monomer and the oil phase solution uses pyromellitic trimethylol chloride as the oil phase monomer; The precursor membrane is first immersed in the prepared aqueous solution to ensure that the aqueous monomers are evenly distributed on the surface of the porous support layer membrane. After removing excess aqueous solution from the surface of the precursor membrane after wetting, the precursor membrane containing aqueous solution is quickly immersed in oil solution to carry out interfacial polymerization reaction for 30s-120s. After the reaction is complete, impurities on the membrane surface are removed with n-hexane liquid; The membrane after impurities are removed is subjected to thermal curing to obtain the target nanofiltration membrane.

2. The method for preparing a nanofiltration membrane according to claim 1, characterized in that, The steps for preparing the porous support membrane using the solvent-inducible phase separation method include the following operations: A certain mass of polymer particles is weighed and dissolved in an organic solvent. The mixture is stirred at 80℃-85℃ for 10-15 hours to ensure complete dissolution of the polymer particles. The solution is then scraped onto a nonwoven fabric to form a film with a thickness of 100-200 μm. After the film has completely solidified, the porous support layer membrane is obtained and stored in deionized water for later use.

3. The method for preparing a nanofiltration membrane according to claim 2, characterized in that, The polymer is selected from either polysulfone or polyethersulfone; The organic solvent is selected from one or a mixture of several of N,N-dimethylacetamide, N,N-dimethylformamide and N-methylpyrrolidone; The polymer particles in the solution have a mass percentage range of 16%-18%.

4. The method for preparing a nanofiltration membrane according to claim 1, characterized in that, The steps for preparing the titanium dioxide interlayer include the following operations: A certain amount of titanium dioxide is added to an organic solvent to obtain a titanium dioxide dispersion. The titanium dioxide dispersion was subjected to ultrasonic treatment to obtain a uniform milky white suspension. The precursor membrane is obtained by uniformly loading the porous support layer surface through vacuum filtration. The mass percentage of titanium dioxide in the titanium dioxide dispersion ranges from 0.01% to 2%.

5. The method for preparing a nanofiltration membrane according to claim 1, characterized in that, The procedure for removing excess aqueous solution from the surface of the membrane after impregnation is as follows: remove the impregnated porous support membrane from the aqueous solution and dry the residual liquid on the membrane surface with nitrogen or inert gas.

6. The method for preparing a nanofiltration membrane according to claim 1, characterized in that, The mass percentage of intermediate-phenylenediamine in the aqueous solution ranges from 1% to 5%.

7. The method for preparing a nanofiltration membrane according to claim 1, characterized in that, The pH range of the aqueous solution is 8-10.

8. The method for preparing a nanofiltration membrane according to claim 1, characterized in that, The mass percentage of pyromellitic chloroformyl chloride in the oil phase solution ranges from 0.1% to 0.5%. The solvent for the oil phase solution is n-hexane.

9. The method for preparing a nanofiltration membrane according to claim 1, characterized in that, The temperature range of the thermosetting treatment is 60℃~80℃, and the time of the thermosetting treatment is 5min-20min.

10. A nanofiltration membrane, characterized in that, The nanofiltration membrane was prepared using the preparation method described in any one of claims 1-9.

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