Ultra-high water permeable nanofiltration membrane based on hydrophilic-hydrophobic alternating nanochannel and preparation method thereof

Abstract

The application discloses a kind of based on hydrophilic-hydrophobic alternating nanochannel strengthening ultra-high water permeability nanofiltration membrane and preparation method thereof, belong to membrane separation technical field.The specific preparation method of the nanofiltration membrane is as follows: by vacuum filtration, simultaneously having hydrophilic and hydrophobic region's lignocellulose nanofiber is loaded to porous support layer, water phase and oil phase monomer are contacted with the middle layer of lignocellulose nanofiber with hydrophilic-hydrophobic alternating structure respectively, interface polymerization reaction is initiated, and finally obtained nanofiltration membrane has ultra-high water permeability and can effectively remove a variety of trace organic pollutants, lignocellulose nanofiber middle layer not only can be based on hydrophilic-hydrophobic alternating site control interface polymerization process, also can be through hydrophilic site-hydrophobic site synergistic effect to speed up water in middle layer transmission.The problem of low water permeability of traditional nanofiltration membrane is solved, and a promising method is provided for realizing the energy saving and cost reduction of nanofiltration membrane water treatment process.

Description

Technical Field

[0001] This invention relates to the field of membrane separation technology, specifically to an ultra-high water permeability nanofiltration membrane enhanced by alternating hydrophilic and hydrophobic nanochannels and its preparation method. Background Technology

[0002] Trace organic pollutants (such as endocrine disruptors, drugs, and antibiotics) are highly toxic and widely present in wastewater. Although they often exist at trace concentrations (ng / L-μg / L), they still pose a significant threat to human health. Therefore, effectively removing these trace organic pollutants is crucial for ensuring water safety. Nanofiltration membrane separation is an emerging technology for advanced wastewater treatment and resource recovery, characterized by ease of operation, low energy consumption, and environmental friendliness. Currently, nanofiltration membranes are widely used for the removal of trace organic pollutants; however, the limited water permeability of traditional nanofiltration membranes leads to high system energy consumption, restricting their application in wastewater treatment and resource recovery.

[0003] Introducing an interlayer between the nanofiltration membrane base and the polyamide retention layer can optimize the water transport path of the nanofiltration membrane, shorten the water transport distance, and thus improve the overall water permeability of the membrane. Furthermore, the abundant active sites on the interlayer can also regulate the interfacial polymerization process, thereby affecting the properties of the polyamide retention layer. However, water must also pass through the interlayer when permeating the nanofiltration membrane, so the presence of the interlayer may also provide additional resistance to water transport. Water permeation through the interlayer mainly involves the following two steps: (1) water adsorption onto the surface of the interlayer; (2) water permeation through the interlayer. For hydrophilic interlayers, the strong interaction between water and nanomaterials facilitates water adsorption onto the interlayer surface but inhibits water permeation; for hydrophobic interlayers, the weak interaction between water and nanomaterials inhibits water adsorption onto the interlayer surface, but the hydrophobic structure allows water molecules already adsorbed on the interlayer to slide and quickly pass through the interlayer. How to regulate the interlayer to enable rapid water adsorption and permeation is a problem urgently needing to be solved in this field.

[0004] To address the aforementioned issues, this invention proposes an ultra-high water permeability nanofiltration membrane based on alternating hydrophilic and hydrophobic nanochannels. Through the construction of an intermediate layer with alternating hydrophilic and hydrophobic structures, water molecules can be adsorbed onto the surface of the intermediate layer through the hydrophilic regions and permeate through the intermediate layer from the hydrophobic regions. This simultaneously enhances the adsorption and permeation rates of water in the intermediate layer, thereby significantly reducing the resistance of the intermediate layer and resulting in an ultra-high water permeability nanofiltration membrane. The ultra-high water permeability nanofiltration membrane prepared by this method saves system energy consumption without sacrificing pollutant selectivity, simultaneously ensuring the removal efficiency of trace organic pollutants, and has excellent application prospects in wastewater treatment and resource recovery. Summary of the Invention

[0005] To achieve the above objectives, this invention provides an ultra-high water permeability nanofiltration membrane enhanced by alternating hydrophilic and hydrophobic nanochannels and its preparation method. This invention utilizes lignocellulose nanofibers to construct an intermediate layer with an alternating hydrophilic and hydrophobic structure, optimizing the water transport path and reducing water transport resistance. The abundant active sites on the hydrophilic and hydrophobic regions of the lignocellulose nanofiber intermediate layer regulate the interfacial polymerization process. The nanofiltration membrane prepared by this invention exhibits ultra-high water permeability and a high rejection rate for various trace organic pollutants, solving the bottleneck problem of low permeability in existing nanofiltration membranes used for removing trace organic pollutants.

[0006] This invention first provides the following technical solution: a method for preparing an ultra-high water permeability nanofiltration membrane based on alternating hydrophilic and hydrophobic nanochannels, comprising the following steps:

[0007] a) Lignocellulose nanofibers with both hydrophilic and hydrophobic regions are added to water to prepare an aqueous dispersion of lignocellulose nanofibers;

[0008] b) Place the porous support layer in a vacuum filtration device and add an aqueous dispersion of lignocellulose nanofibers to load the lignocellulose nanofibers on the surface of the porous support layer to prepare a lignocellulose nanofiber intermediate layer with alternating hydrophilic and hydrophobic structures.

[0009] c) The intermediate layer of lignocellulose nanofibers with alternating hydrophilic and hydrophobic structures is brought into full contact with and reacted with aqueous and oil-phase monomers, respectively;

[0010] d) Rinse the prepared membrane with n-hexane and store it.

[0011] In step a), the lignin content in the lignocellulose nanofibers is 0.5–80 wt%.

[0012] Further, in step a), the lignin content in the lignocellulose nanofibers is 0.5–5 wt%.

[0013] Further, in step a), the content of lignocellulose nanofibers in the aqueous dispersion of lignocellulose nanofibers is 0-25 wt%, wherein the endpoint 0 is not taken.

[0014] Furthermore, in step b), the porous support layer is an ultrafiltration membrane or microfiltration membrane made of polysulfone, polyethersulfone, polyimide, polyvinylidene fluoride, or polyacrylonitrile, with a pore size of 0.01 to 5 μm.

[0015] Furthermore, the loading content of the lignocellulose nanofibers on the porous support layer in step b) is 5 × 10⁻⁶. -4 ~1×10 -2 mg / cm 2 .

[0016] Further, the aqueous monomer in step c) is one or more of piperazine, m-phenylenediamine, diethylenetriamine, polyethyleneimine, polyethyleneamine, polyvinyl alcohol, polyvinyl glycol diglycidyl ether, bisphenol A, and polyethylene glycol.

[0017] Further, in step c), the oil phase monomer is one or more of isophthaloyl chloride, 1,3,5-pyromellitic trichlorochloro, 3,3′,5,5′-biphenyltetracarboxylic chloride, and biphenylhexacarboxylic chloride, and the solvent is n-hexane.

[0018] Further, in step c), the concentration ratio of the aqueous phase monomer to the oil phase monomer is 0.05–5, wherein the concentration of the aqueous phase monomer is 0.01–5 wt%.

[0019] Furthermore, the reaction time of the aqueous phase and oil phase monomers in step c) is 5s-120min.

[0020] Secondly, the present invention also provides a nanofiltration membrane prepared by the above preparation method, which has lignocellulose nanofibers as the intermediate layer.

[0021] Furthermore, the present invention also provides a wastewater treatment method, wherein the method uses the above-mentioned nanofiltration membrane with lignocellulose nanofibers as the intermediate layer for wastewater treatment.

[0022] The present invention also provides a wastewater treatment device, the device comprising the above-mentioned nanofiltration membrane with lignocellulose nanofibers as the intermediate layer.

[0023] Finally, this invention provides the application of the above-mentioned nanofiltration membrane with lignocellulose nanofibers as the intermediate layer in the field of water treatment.

[0024] The beneficial effects of this invention are as follows:

[0025] 1. This invention uses lignocellulose nanofibers as the intermediate layer of a nanofiltration membrane, optimizes the water transport path, reduces water transport resistance, overcomes the inherent funnel effect of traditional nanofiltration membranes, and improves the water permeability of the nanofiltration membrane.

[0026] 2. This invention uses lignocellulose nanofibers as the intermediate layer of a nanofiltration membrane. By utilizing the alternating hydrophilic and hydrophobic nanochannels on the intermediate layer, water molecules can be adsorbed onto the surface of the intermediate layer through the hydrophilic region and rapidly slide through the intermediate layer from the hydrophobic region. This simultaneously increases the adsorption and permeation rates of water in the intermediate layer, thereby significantly reducing the resistance of the intermediate layer and enabling the prepared nanofiltration membrane to have ultra-high water permeability.

[0027] 3. This invention uses lignocellulose nanofibers as the intermediate layer of a nanofiltration membrane. By utilizing the abundant active sites on the intermediate layer, the interfacial polymerization process is regulated, resulting in a nanofiltration membrane with ultra-high water permeability. This reduces system energy consumption without sacrificing pollutant selectivity, thus ensuring the removal effect of trace organic pollutants.

[0028] 4. The nanofiltration membrane provided by this invention has the advantages of simple preparation method, low cost, strong stability, high permeability and good retention effect. It solves the problem of low water permeability of existing nanofiltration membranes used to remove trace organic matter, and provides a promising method for realizing low-pressure operation and energy saving of nanofiltration membranes. Attached Figure Description

[0029] The invention will now be described in more detail with reference to embodiments and the accompanying drawings.

[0030] Figure 1 This is a comparison chart of the water permeability and Na2SO4 retention performance of the nanofiltration membranes prepared in Example 1, Comparative Example 1, and Comparative Example 2, where the bar chart represents water permeability.

[0031] Figure 2 This is a comparison diagram of the water permeability of nanofiltration membranes prepared in Examples 1-3 and Comparative Example 3.

[0032] Figure 3 This is a comparison chart showing the retention rates of nine trace organic pollutants by the nanofiltration membranes prepared in Example 1 and Comparative Example 3. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] The lignocellulose nanofibers used in the embodiments and comparative examples of this invention were all purchased from ScienceK.

[0035] Example 1

[0036] Preparation of nanofiltration membrane using lignocellulose nanofibers (lignin content 2 wt%) as the intermediate layer:

[0037] 1) A commercially available polyethersulfone (PES) microfiltration membrane with a pore size of 0.22 μm was used as a porous support layer.

[0038] 2) Disperse 13.0g of lignocellulose nanofibers (LCNF) into 200mL of deionized water and stir thoroughly to prepare a dispersion of lignocellulose nanofibers.

[0039] 3) A dispersion of 0.5 mL of lignocellulose nanofibers (LCNF) was deposited on the surface of a PES membrane (40 mm in diameter) by vacuum filtration. The resulting membrane was named PES-LCNF0.5 membrane.

[0040] 4) Place the PES-LCNF0.5 membrane in a custom polytetrafluoroethylene membrane frame, gently add 5 mL of 0.05 wt% piperazine aqueous solution to the surface of the PES-LCNF0.5 membrane and let it stand for 5 min.

[0041] 5) Then pour out the piperazine aqueous solution in the membrane frame and make sure there are no obvious water marks on the surface of the PES-LCNF0.5 membrane.

[0042] 6) Pour a 0.04 wt% hexane solution of 1,3,5-pyromellitic chloride into the surface of a piperazine-saturated PES-LCNF0.5 membrane and react for 1 min.

[0043] 7) After the reaction is complete, discard the hexane solution of 1,3,5-trimethylammonium chloride in the membrane frame, rinse twice with hexane solution, and place in an oven at 60°C for 2 min to obtain the NF-LCNF0.5 membrane.

[0044] Comparative Example 1

[0045] Preparation of nanofiltration membrane with cellulose (0 wt% lignin content) as the intermediate layer:

[0046] 1) A commercially available polyethersulfone (PES) microfiltration membrane with a pore size of 0.22 μm was used as a porous support layer.

[0047] 2) Disperse cellulose (CNF, hydrophilic mesolayer) of the same mass as the lignocellulose nanofibers into 200 mL of deionized water and stir thoroughly to prepare a cellulose dispersion.

[0048] 3) A dispersion of 0.5 mL of cellulose (CNF) was deposited on the surface of a PES membrane (40 mm in diameter) by vacuum filtration. The resulting membrane was named PES-CNF0.5 membrane.

[0049] 4) Place the PES-CNF0.5 membrane in a custom polytetrafluoroethylene membrane frame, gently add 5 mL of 0.05 wt% piperazine aqueous solution to the surface of the PES-CNF0.5 membrane and let it stand for 5 min.

[0050] 5) Then pour out the piperazine aqueous solution in the membrane frame and make sure there are no obvious water marks on the surface of the PES-CNF0.5 membrane.

[0051] 6) Pour a 0.04 wt% hexane solution of 1,3,5-pyromellitic chloride into the surface of a piperazine-saturated PES-CNF0.5 membrane and react for 1 min.

[0052] 7) After the reaction is complete, discard the hexane solution of 1,3,5-trimethylammonium chloride in the membrane frame, rinse twice with hexane solution, and place in an oven at 60°C for 2 min to obtain the NF-CNF0.5 membrane.

[0053] Comparative Example 2

[0054] Preparation of nanofiltration membrane with lignin (100 wt% lignin content) as the intermediate layer:

[0055] 1) A commercially available polyethersulfone (PES) microfiltration membrane with a pore size of 0.22 μm was used as a porous support layer.

[0056] 2) Disperse lignin (hydrophobic mesolayer) of the same mass as the lignocellulose nanofibers into 200 mL of deionized water and stir thoroughly to prepare a lignin dispersion.

[0057] 3) A dispersion of 0.5 mL of lignin was deposited on the surface of a PES membrane (40 mm in diameter) by vacuum filtration. The resulting membrane was named PES-Lignin0.5 membrane.

[0058] 4) Place the PES-Lignin 0.5 membrane in a custom polytetrafluoroethylene membrane frame, gently add 5 mL of 0.05 wt% piperazine aqueous solution to the surface of the PES-Lignin 0.5 membrane and let it stand for 5 min.

[0059] 5) Then pour out the piperazine aqueous solution in the membrane frame and make sure there are no obvious water marks on the surface of the PES-Lignin 0.5 membrane.

[0060] 6) Pour a 0.04 wt% hexane solution of 1,3,5-pyromellitic chloride into the surface of a piperazine-saturated PES-Lignin 0.5 membrane and react for 1 min.

[0061] 7) After the reaction is complete, discard the hexane solution of 1,3,5-trimethylammonium chloride in the membrane frame, rinse twice with hexane solution, and place in an oven at 60°C for 2 min to obtain the NF-Lignin0.5 membrane.

[0062] Example 2

[0063] By varying the deposition amount of lignocellulose nanofibers (lignin content 2 wt%) on a PES membrane, a nanofiltration membrane containing an intermediate layer was prepared.

[0064] 1) A commercially available polyethersulfone (PES) microfiltration membrane with a pore size of 0.22 μm was used as a porous support layer.

[0065] 2) 13.0 g of lignocellulose nanofibers (LCNF) were dispersed in 200 mL of deionized water and stirred thoroughly to prepare a dispersion of lignocellulose nanofibers.

[0066] 3) A dispersion of 0.25 mL of lignocellulose nanofibers (LCNF) was deposited on the surface of a PES membrane (40 mm in diameter) by vacuum filtration. The resulting membrane was named PES-LCNF0.25 membrane.

[0067] 4) Place the PES-LCNF0.25 membrane in a custom polytetrafluoroethylene membrane frame, gently add 5 mL of 0.05 wt% piperazine aqueous solution to the surface of the PES-LCNF0.25 membrane and let it stand for 5 min.

[0068] 5) Then pour out the piperazine aqueous solution in the membrane frame and make sure there are no obvious water marks on the surface of the PES-LCNF0.25 membrane.

[0069] 6) Pour a 0.04 wt% hexane solution of 1,3,5-pyromellitic chloride into the surface of a piperazine-saturated PES-LCNF0.25 membrane and react for 1 min.

[0070] 7) After the reaction is complete, discard the hexane solution of 1,3,5-trimethylammonium chloride in the membrane frame, rinse twice with hexane solution, and place in an oven at 60°C for 2 min to obtain the NF-LCNF0.25 membrane.

[0071] Example 3

[0072] By varying the deposition amount of lignocellulose nanofibers (lignin content 2 wt%) on a PES membrane, a nanofiltration membrane containing an intermediate layer was prepared.

[0073] 1) A commercially available polyethersulfone (PES) microfiltration membrane with a pore size of 0.22 μm was used as a porous support layer.

[0074] 2) 13.0 g of lignocellulose nanofibers (LCNF) were dispersed in 200 mL of deionized water and stirred thoroughly to prepare a dispersion of lignocellulose nanofibers.

[0075] 3) A dispersion of 1.0 mL of lignocellulose nanofibers (LCNF) was deposited on the surface of a PES membrane (40 mm in diameter) by vacuum filtration. The resulting membrane was named PES-LCNF1.0 membrane.

[0076] 4) Place the PES-LCNF0.5 membrane in a custom polytetrafluoroethylene membrane frame, gently add 5 mL of 0.05 wt% piperazine aqueous solution to the surface of the PES-LCNF1.0 membrane and let it stand for 5 min.

[0077] 5) Then pour out the piperazine aqueous solution in the membrane frame and make sure there are no obvious water marks on the surface of the PES-LCNF1.0 membrane.

[0078] 6) Pour a 0.04 wt% hexane solution of 1,3,5-pyromellitic chloride into the surface of a piperazine-saturated PES-LCNF1.0 membrane and react for 1 min.

[0079] 7) After the reaction is complete, pour off the hexane solution of 1,3,5-trimethylammonium chloride in the membrane frame, rinse twice with hexane solution, and place in an oven at 60°C for 2 min to obtain the NF-LCNF1.0 membrane.

[0080] Comparative Example 3

[0081] The method for preparing the control nanofiltration membrane in this comparative example is carried out according to the following steps:

[0082] 1) A commercially available polyethersulfone (PES) microfiltration membrane with a pore size of 0.22 μm was used as a porous support layer.

[0083] 2) Place the PES membrane in a custom polytetrafluoroethylene membrane frame, gently add 5 mL of 0.05 wt% piperazine aqueous solution to the surface of the PES membrane and let it stand for 5 min to obtain PES-LCNF0.

[0084] 5) Then pour out the piperazine aqueous solution in the membrane frame and make sure there are no obvious water marks on the surface of the PES-LCNF0 membrane.

[0085] 6) Pour a 0.04 wt% hexane solution of 1,3,5-pyromellitic chloride into the surface of a piperazine-saturated PES-LCNF0 membrane and react for 1 min.

[0086] 7) After the reaction is complete, discard the hexane solution of 1,3,5-trimethylammonium chloride in the membrane frame, rinse twice with hexane solution, and place in an oven at 60°C for 2 min to obtain the NF-LCNF0 membrane.

[0087] To verify the selectivity of the nanofiltration membranes prepared in the examples and comparative examples, the present invention provides experimental examples 1-2.

[0088] Experimental Example 1

[0089] The nanofiltration membranes prepared in Examples 1-3 and Comparative Examples 1-3 were tested for their pure water permeability. Furthermore, the nanofiltration membranes prepared in Example 1, Comparative Example 1, and Comparative Example 2 were tested for their Na₂SO₄ retention performance. A laboratory-scale cross-flow apparatus (with an effective membrane cell area of ​​6.3 cm²) was used. 2 The membrane was pre-compressed at an operating pressure of 6 bar until the membrane flux stabilized. The water temperature was 25.0 ± 0.5℃, the crossflow velocity was 20 cm / s, and the Na₂SO₄ concentration was 10 mM. The test results are shown in [reference needed]. Figure 1 and Figure 2 .

[0090] from Figure 1 It can be seen that the nanofiltration membrane prepared in Example 1 has the highest water permeability and Na2SO4 rejection rate, while the nanofiltration membranes prepared in Comparative Examples 1 and 2 have poor performance. This indicates that materials with only hydrophilic or only hydrophobic properties are not as suitable as materials with alternating hydrophilic and hydrophobic properties for the middle layer of nanofiltration membranes.

[0091] from Figure 2 It can be seen that the nanofiltration membrane prepared in Example 1 has the highest water permeability, at 52.4 L·m. -2 ·h -1 The concentration of lignocellulose nanofibers at this level is higher than that reported in current literature, indicating that the lignocellulose nanofibers are optimal as an intermediate layer.

[0092] Experiment Example 2

[0093] The nanofiltration membranes prepared in Example 1 and Comparative Example 3 were tested for their ability to retain trace organic pollutants. The concentrations of all nine trace organic pollutants were 200 μg / L, and the test conditions were the same as in Example 1. The concentrations of trace organic matter in the influent and effluent were determined using liquid chromatography-mass spectrometry (LC-MS). The test results are shown in [Figure 1]. Figure 3 .

[0094] from Figure 3 It can be seen that the nanofiltration membranes prepared in Example 1 and Comparative Example 3 have high rejection rates for all nine trace organic pollutants, and the rejection rate of Example 1 is slightly higher than that of Comparative Example 3. This indicates that the alternating hydrophilic and hydrophobic intermediate layer can improve the water permeability of the nanofiltration membrane without sacrificing the removal rate of trace organic pollutants.

[0095] Example 4

[0096] Preparation of nanofiltration membranes containing an intermediate layer using lignocellulose nanofibers (lignin content of 1 wt%) as an intermediate layer, with the remaining steps and parameters the same as in Example 1.

[0097] Performance tests were conducted according to Experiments 1 and 2. The results showed that the water permeability of the nanofiltration membrane prepared in Example 4 was 46.9 L·m⁻¹. -2 ·h -1 • bar, with good water permeability. And it does not compromise the removal rate of trace organic pollutants.

[0098] Example 5

[0099] Preparation of nanofiltration membranes containing an intermediate layer using lignocellulose nanofibers (lignin content of 5 wt%) as an intermediate layer, with the remaining steps and parameters the same as in Example 1.

[0100] Performance tests were conducted according to Experiments 1 and 2. The results showed that the water permeability of the nanofiltration membrane prepared in Example 5 was 49.2 L·m⁻². -2 ·h -1 • bar, with good water permeability. And it does not compromise the removal rate of trace organic pollutants.

[0101] Comparative Example 4

[0102] Preparation of nanofiltration membranes containing an intermediate layer using lignocellulose nanofibers (lignin content of 80 wt%) as an intermediate layer, with the remaining steps and parameters the same as in Example 1.

[0103] Performance tests were conducted according to Experiments 1 and 2. The results showed that the water permeability of the nanofiltration membrane prepared in Comparative Example 4 was 43.7 L·m⁻². -2 ·h -1 •bar, its water permeability is worse than that of this invention.

[0104] It is understood that the above detailed description of the present invention is for illustrative purposes only and is not intended to limit the technical solutions described in the embodiments of the present invention. Those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention to achieve the same technical effects; as long as the usage requirements are met, they are all within the protection scope of the present invention.

Claims

1. A method for preparing a water-permeable nanofiltration membrane enhanced by alternating hydrophilic and hydrophobic nanochannels, characterized in that, Includes the following steps: a) Lignocellulose nanofibers with both hydrophilic and hydrophobic regions are added to water to prepare an aqueous dispersion of lignocellulose nanofibers; b) Place the porous support layer into a vacuum filtration device, add an aqueous dispersion of lignocellulose nanofibers, so that the lignocellulose nanofibers are loaded on the surface of the porous support layer to prepare a lignocellulose nanofiber intermediate layer with alternating hydrophilic and hydrophobic structures. c) The lignocellulose nanofiber interlayer with alternating hydrophilic and hydrophobic structures is brought into full contact and reacted with aqueous and oil-phase monomers, respectively; d) Rinse the prepared membrane with n-hexane and store it. In step a), the lignin content in the lignocellulose nanofibers is 0.5~80 wt%.

2. The preparation method according to claim 1, characterized in that, In step a), the lignin content in the lignocellulose nanofibers is 0.5~5 wt%.

3. The preparation method according to claim 1, characterized in that, The content of lignocellulose nanofibers in the aqueous dispersion of lignocellulose nanofibers is 0~25 wt%, wherein the endpoint 0 is not taken.

4. The preparation method according to claim 1, characterized in that, In step b), the porous support layer is an ultrafiltration or microfiltration membrane made of polysulfone, polyethersulfone, polyimide, polyvinylidene fluoride, or polyacrylonitrile, with a pore size of 0.01~5 µm.

5. The preparation method according to claim 1, characterized in that, The loading content of the lignocellulose nanofibers on the porous support layer in step b) is 5 × 10⁻⁶. -4 ~1×10 -2 mg / cm 2 .

6. The preparation method according to any one of claims 1 to 5, characterized in that, The aqueous monomer in step c) is one or more of piperazine, m-phenylenediamine, diethylenetriamine, polyethyleneimine, polyethyleneamine, polyvinyl alcohol, polyvinyl glycol diglycidyl ether, bisphenol A, and polyethylene glycol.

7. The preparation method according to any one of claims 1 to 5, characterized in that, The oil phase monomer in step c) is one or more of isophthaloyl chloride, 1,3,5-pyromellitic tricarboxylate chloride, 3,3′,5,5′-biphenyltetracarboxylate chloride, and biphenylhexacarboxylate chloride, and the solvent is n-hexane.

8. A nanofiltration membrane with lignocellulose nanofibers as the intermediate layer is prepared by the preparation method according to any one of claims 1 to 7.

9. A wastewater treatment method, characterized in that, The method uses the nanofiltration membrane with lignocellulose nanofibers as the intermediate layer as described in claim 8 for wastewater treatment.

10. A wastewater treatment device, characterized in that, The device includes the nanofiltration membrane of claim 8, which has lignocellulose nanofibers as the intermediate layer.

11. The application of the nanofiltration membrane with lignocellulose nanofibers as the intermediate layer as described in claim 8 in the field of water treatment.

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