Nanofiltration membrane and preparation method thereof

Abstract

The present invention relates to the field of water treatment technology, and in particular to a nanofiltration membrane and a preparation method thereof. The preparation method comprises: A) applying an aqueous phase solution on a base membrane, and after the surface is dried, applying an oil phase solution, performing an interfacial polymerization reaction, and then performing a heat treatment to obtain a membrane material; B) spraying a specific post-treatment solution on the side of the membrane material coated with the oil phase solution, and drying the surface; C) coating a PVA solution on the side of the membrane material obtained in step B) coated with the post-treatment solution, and drying to obtain a nanofiltration membrane. Pluronic F-127 can be used to surface-coat nano-ZnO particles to form modified nano-metal particles, thereby improving the problem that nano-ZnO particles are easy to agglomerate and difficult to combine. On the one hand, polyethylene glycol diglycidyl ether can be well connected to the surface of the polyamide layer, and on the other hand, it can be well connected to the nano-ZnO particles wrapped with Pluronic F-127, thereby achieving improved membrane performance and antibacterial properties.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, and in particular to a nanofiltration membrane and a preparation method thereof. Background Art

[0002] Water shortage has become a global problem.

[0003] Nanofiltration membrane, also known as low-pressure reverse osmosis membrane, is an emerging field of membrane separation technology. Its separation performance is between reverse osmosis and ultrafiltration. It is used to separate substances with relatively small molecular weight, such as inorganic salts, glucose, sucrose and other small molecular organic substances from solvents, allowing some inorganic salts and certain solvents to pass through the membrane, thereby achieving the separation effect.

[0004] Nanofiltration membranes typically consist of a nonwoven fabric layer, a porous support layer, and a separation layer. The porous support layer is typically formed on the surface of the nonwoven fabric layer using a phase inversion process using polysulfone / DMF. The separation layer is formed on the porous support layer using interfacial polymerization of polyamine monomers and polyacyl chloride monomers at the water-oil interface.

[0005] Since nanofiltration membranes are widely used in domestic and municipal water, the membranes themselves are prone to breeding bacteria, which limits their long-term effective use.

[0006] Currently, the antibacterial properties of nanofiltration membranes are mostly adjusted by adding antibacterial substances to the water-oil phase formula or by directly affecting the polyamide layer of the base membrane to improve the antibacterial properties. However, these methods all have certain drawbacks:

[0007] 1) Adding it to the water-oil phase formula or base film often has a negative impact on performance and increases production uncertainty;

[0008] 2) Direct coating on the surface of the polyamide layer often fails to effectively combine and cannot achieve the corresponding effect. Summary of the Invention

[0009] In view of this, the technical problem to be solved by the present invention is to provide a nanofiltration membrane and a preparation method thereof. The nanofiltration membrane provided by the present invention can obtain better membrane performance while obtaining better antibacterial performance.

[0010] The present invention provides a method for preparing a nanofiltration membrane, comprising the following steps:

[0011] A) coating an aqueous solution on a base film, and after the surface is dried, coating an oil phase solution, performing an interfacial polymerization reaction, and then heat treating to obtain a membrane material;

[0012] B) coating the post-treatment solution on the side of the membrane material coated with the oil phase solution and allowing the surface to dry;

[0013] The post-treatment solution includes polyethylene glycol diglycidyl ether, Pluronic F127, nano ZnO particles and water;

[0014] C) coating one side of the membrane material obtained in step B) with the post-treatment solution by flow coating with a PVA solution, and drying the membrane to obtain a nanofiltration membrane.

[0015] Preferably, in step B), in the post-treatment solution, the mass content of polyethylene glycol diglycidyl ether is 0.1% to 0.5%, the mass content of Pluronic F127 is 0.1% to 0.5%, and the mass content of nano ZnO particles is 0.1% to 0.5%.

[0016] Preferably, in step B), the flow coating time is 0.5 to 1.5 minutes.

[0017] Preferably, in step A), the base film comprises a non-woven fabric and a polymer layer composited on the non-woven fabric;

[0018] The material of the polymer layer includes at least one of polysulfone, polyethersulfone and polyvinylidene fluoride;

[0019] The thickness of the polymer layer is 30 to 50 μm; the thickness of the non-woven fabric is 90 to 100 μm.

[0020] Preferably, in step A), the aqueous phase solution comprises a polyamine monomer and an aqueous phase additive;

[0021] The polyamine monomer includes at least one of piperazine, m-phenylenediamine and polyvinylamine;

[0022] The aqueous phase additives include dextrorotatory camphorsulfonic acid, sodium hydroxide and sodium lauryl sulfate;

[0023] In the aqueous phase solution, the mass content of the polyamine monomer is 0.5% to 1.5%, the mass content of dextrorotatory camphorsulfonic acid is 1.5% to 3.0%, the mass content of sodium hydroxide is 0.3% to 0.6%, and the mass content of sodium lauryl sulfate is 0.01% to 0.1%.

[0024] Preferably, in step A), the oil phase solution comprises an acyl chloride monomer and an organic solvent;

[0025] The acyl chloride monomer includes at least one of trimesoyl chloride and adipoyl chloride;

[0026] The organic solvent comprises at least one of n-hexane, Isopar G and Isopar L;

[0027] In the oil phase solution, the mass content of the acyl chloride monomer is 0.2% to 0.5%.

[0028] Preferably, in step A), the coating amount of the aqueous solution is 20 to 40 g / m 2 ;

[0029] The coating amount of the oil phase solution is 10 to 30 g / m 2 .

[0030] Preferably, in step A), the temperature of the interfacial polymerization reaction is 50-70°C;

[0031] The heat treatment temperature is 60-100° C. and the time is 2-3 minutes.

[0032] Preferably, in step C), the mass concentration of the PVA solution is 3% to 6%;

[0033] The coating has a thickness of 0.01 to 0.2 μm.

[0034] The present invention also provides a nanofiltration membrane prepared by the preparation method described above.

[0035] The present invention provides a method for preparing a nanofiltration membrane, comprising the following steps: A) coating a base membrane with an aqueous solution, allowing the surface to dry, then coating the base membrane with an oily solution, performing an interfacial polymerization reaction, and then heat treating the base membrane to obtain a membrane material; B) spray-coating a post-treatment solution onto the side of the membrane material coated with the oily solution, allowing the surface to dry; the post-treatment solution comprises polyethylene glycol diglycidyl ether, Pluronic F127, nano-ZnO particles, and water; and C) coating the side of the membrane material obtained in step B) coated with the post-treatment solution with a PVA solution, drying the solution, to obtain a nanofiltration membrane. In the present invention, Pluronic F-127 can coat the nano-ZnO particles to form modified nano-metal particles, thereby resolving the problem of the nano-ZnO particles being easily agglomerated and difficult to bond. The polyethylene glycol diglycidyl ether can effectively bond with the surface of the polyamide layer and with the nano-ZnO particles coated with Pluronic F-127, thereby improving the membrane's performance and antibacterial properties. DETAILED DESCRIPTION

[0036] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all 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.

[0037] The present invention provides a method for preparing a nanofiltration membrane, comprising the following steps:

[0038] A) coating an aqueous solution on a base film, and after the surface is dried, coating an oil phase solution, performing an interfacial polymerization reaction, and then heat treating to obtain a membrane material;

[0039] B) coating the post-treatment solution on the side of the membrane material coated with the oil phase solution and allowing the surface to dry;

[0040] The post-treatment solution includes polyethylene glycol diglycidyl ether, Pluronic F127, nano ZnO particles and water;

[0041] C) coating one side of the membrane material obtained in step B) with the post-treatment solution by flow coating with a PVA solution, and drying the membrane to obtain a nanofiltration membrane.

[0042] Regarding step A):

[0043] A water phase solution is coated on the base film, and after the surface is dried, an oil phase solution is coated, and an interfacial polymerization reaction is carried out, followed by heat treatment to obtain a membrane material.

[0044] In certain embodiments of the present invention, the base film comprises a non-woven fabric and a polymer layer composited onto the non-woven fabric. The polymer layer is made of at least one of polysulfone, polyethersulfone, and polyvinylidene fluoride. The polymer layer has a thickness of 30 to 50 μm, such as 40 μm. The non-woven fabric has a thickness of 90 to 100 μm, such as 95 μm.

[0045] The present invention has no particular limitation on the preparation method of the base film, and the base film can be formed on the surface of the non-woven fabric layer by using polysulfone and DMF through a phase inversion method.

[0046] In certain embodiments of the present invention, the aqueous solution includes a polyamine monomer and an aqueous phase additive. The polyamine monomer is selected from at least one of piperazine, m-phenylenediamine, and polyvinylamine, preferably piperazine. The mass content of the polyamine monomer in the aqueous solution is 0.5% to 1.5%, such as 0.8%. The aqueous phase additive includes dextrorotatory camphorsulfonic acid, sodium hydroxide, and sodium lauryl sulfate. In the aqueous solution, the mass content of dextrorotatory camphorsulfonic acid is 1.5% to 3.0%, such as 2.4%; the mass content of sodium hydroxide is 0.3% to 0.6%, such as 0.48%; and the mass content of sodium lauryl sulfate is 0.01% to 0.1%, such as 0.02%.

[0047] In certain embodiments of the present invention, coating the aqueous solution on the base film includes: coating the aqueous solution on the front side of the base film. The coating amount of the aqueous solution is 20 to 40 g / m 2 , such as 30g / m 2 .

[0048] In certain embodiments of the present invention, the surface drying method may be vacuum water absorption and / or heating by a heating roller.

[0049] In certain embodiments of the present invention, the oil phase solution comprises an acyl chloride monomer and an organic solvent. The acyl chloride monomer is selected from at least one of trimesoyl chloride and adipoyl chloride, preferably trimesoyl chloride. The mass content of the acyl chloride monomer in the oil phase solution is 0.2% to 0.5%, such as 0.31%. The organic solvent is selected from at least one of n-hexane, Isopar G, and Isopar L, such as Isopar G.

[0050] In certain embodiments of the present invention, the coating amount of the oil phase solution is 10 to 30 g / m 2 , such as 15g / m 2 The oil phase solution is applied on the side of the base film where the water phase solution is applied.

[0051] In certain embodiments of the present invention, the temperature of the interfacial polymerization reaction is 50-70°C, such as 65°C.

[0052] The heat treatment is to further the cross-linking reaction. In certain embodiments of the present invention, the heat treatment is performed in an HC oven at a temperature of 60 to 100° C., such as 70° C., and for a time of 2 to 3 minutes, such as 3 minutes.

[0053] Regarding step B):

[0054] Spraying the post-treatment solution on the side of the membrane material coated with the oil phase solution and letting the surface dry;

[0055] The post-treatment solution includes polyethylene glycol diglycidyl ether, Pluronic F127, nano ZnO particles and water.

[0056] In certain embodiments of the present invention, in the post-treatment solution, the mass content of polyethylene glycol diglycidyl ether is 0.1% to 0.5%, such as 0.1% to 0.2%, specifically 0.1%, 0.15%, and 0.18%; the mass content of Pluronic F127 is 0.1% to 0.5%, such as 0.1%, 0.15%, and 0.2%; and the mass content of nano-ZnO particles is 0.1% to 0.5%, such as 0.2%, 0.3%, 0.4%, and 0.5%.

[0057] The particle size of the nano ZnO particles is 10-30 nm.

[0058] In certain embodiments of the present invention, the flow coating time is 0.5 to 1.5 minutes, such as 1 minute.

[0059] In certain embodiments of the present invention, the surface drying method may be vacuum water absorption or heating by a heating roller.

[0060] Regarding step C):

[0061] The PVA solution is coated on one side of the membrane material obtained in step B) after flow-coating the post-treatment solution, and then dried to obtain a nanofiltration membrane.

[0062] In certain embodiments of the present invention, the mass concentration of the PVA solution is 3% to 6%, such as 4%. The purpose of coating the PVA solution is to form a protective layer on the surface of the membrane material to protect the functional layer from human damage.

[0063] In certain embodiments of the present invention, the coating has a thickness of 0.01 to 0.2 μm, such as 0.05 μm.

[0064] The present invention also provides a nanofiltration membrane prepared by the preparation method described above.

[0065] The present invention further effectively cross-links the residual amino groups to improve the performance of the membrane, and the polyethylene glycol diglycidyl ether (cross-linking agent) can also be combined with the inorganic nanomaterial to improve the antibacterial property of the membrane.

[0066] In the present invention, Pluronic F-127 can be used to coat the surface of nano ZnO particles to form modified nano metal particles, thereby improving the problem that the nano ZnO particles are prone to agglomeration and difficult to combine.

[0067] The polyethylene glycol diglycidyl ether can be well connected with the surface of the polyamide layer (specifically the polypiperazineamide layer) on the one hand, and can be well connected with the nano ZnO particles wrapped by Pluronic F-127 on the other hand, thereby improving the performance and antibacterial properties of the membrane.

[0068] The Pluronic F127 has a long hydrophobic block and a low CMC value. Its unique structure not only improves the dispersion stability of the nano-ZnO particles in water, but also allows for connection with polyethylene glycol diglycidyl ether. This connection with polyethylene glycol diglycidyl ether allows for indirect attachment to the membrane surface, thereby enhancing the membrane's antibacterial properties without damaging the membrane structure.

[0069] The present invention has no particular limitation on the sources of the raw materials used above, and they can be generally commercially available.

[0070] In order to further illustrate the present invention, a nanofiltration membrane and a preparation method thereof provided by the present invention are described in detail below in conjunction with examples, but they should not be construed as limiting the scope of protection of the present invention.

[0071] The reagents used in the following examples and comparative examples are all commercially available.

[0072] Example 1

[0073] 1) The base film includes a non-woven fabric (the thickness of the non-woven fabric is 95 μm) and a polysulfone layer composited on the non-woven fabric (the thickness of the polysulfone layer is 40 μm);

[0074] The aqueous phase solution comprises a polyamine monomer (piperazine), dextrorotatory camphorsulfonic acid, sodium hydroxide and sodium lauryl sulfate; in the aqueous phase solution, the mass content of the polyamine monomer is 0.8%, the mass content of dextrorotatory camphorsulfonic acid is 2.4%, the mass content of sodium hydroxide is 0.48%, and the mass content of sodium lauryl sulfate is 0.02%.

[0075] The oil phase solution is trimesoyl chloride and an organic solvent, Isopar G; the mass content of the acyl chloride compound in the oil phase solution is 0.31%;

[0076] Apply 30g / m2 on the front side of the base film 2 The aqueous solution is dried by vacuum absorption and heating with a heating roller, and then the oil phase solution (15g / m 2 ), interfacial polymerization reaction was carried out at 65°C, and then heat treated at 70°C for 3 minutes to obtain a membrane material.

[0077] 2) coating the post-treatment solution on the side of the membrane material coated with the oil phase solution for 1 minute, and drying the surface by vacuum absorption and heating with a heating roller;

[0078] The post-treatment solution comprises polyethylene glycol diglycidyl ether, Pluronic F127, nano-ZnO particles, and water. The post-treatment solution contains 0.1% polyethylene glycol diglycidyl ether, 0.1% Pluronic F127, and 0.2% nano-ZnO particles, as shown in Table 1. The nano-ZnO particles have a particle size of 10 to 30 nm.

[0079] 3) The membrane material obtained in step 2) was coated with a PVA solution (with a concentration of 4% and a coating thickness of 0.05 μm) on one side of the treatment solution after flow coating, and then dried to obtain a nanofiltration membrane.

[0080] Example 2

[0081] The difference from Example 1 is:

[0082] In step 2), the post-treatment solution comprises polyethylene glycol diglycidyl ether, Pluronic F127, nano-ZnO particles, and water. The post-treatment solution comprises 0.15% polyethylene glycol diglycidyl ether, 0.15% Pluronic F127, and 0.3% nano-ZnO particles, as shown in Table 1. The nano-ZnO particles have a particle size of 10 to 30 nm.

[0083] The remaining steps and parameters were the same as those in Example 1 to obtain a nanofiltration membrane.

[0084] Example 3

[0085] The difference from Example 1 is:

[0086] In step 2), the post-treatment solution comprises polyethylene glycol diglycidyl ether, Pluronic F127, nano-ZnO particles, and water. The post-treatment solution comprises 0.15% polyethylene glycol diglycidyl ether, 0.15% Pluronic F127, and 0.4% nano-ZnO particles, as shown in Table 1. The nano-ZnO particles have a particle size of 10 to 30 nm.

[0087] The remaining steps and parameters were the same as those in Example 1 to obtain a nanofiltration membrane.

[0088] Example 4

[0089] The difference from Example 1 is:

[0090] In step 2), the post-treatment solution comprises polyethylene glycol diglycidyl ether, Pluronic F127, nano-ZnO particles, and water. The post-treatment solution comprises 0.18% polyethylene glycol diglycidyl ether, 0.2% Pluronic F127, and 0.5% nano-ZnO particles, as shown in Table 1. The nano-ZnO particles have a particle size of 10 to 30 nm.

[0091] The remaining steps and parameters were the same as those in Example 1 to obtain a nanofiltration membrane.

[0092] Comparative Example 1

[0093] The difference from Example 1 is:

[0094] In step 2), the post-treatment solution is polyethylene glycol diglycidyl ether and water; the mass content of polyethylene glycol diglycidyl ether in the post-treatment solution is 0.15%, as shown in Table 1. The particle size of the nano ZnO particles is 10 to 30 nm.

[0095] The remaining steps and parameters were the same as those in Example 1 to obtain a nanofiltration membrane.

[0096] Comparative Example 2

[0097] The difference from Example 1 is:

[0098] In step 2), the post-treatment solution comprises Pluronic F127, nano-ZnO particles, and water; the mass content of Pluronic F127 in the post-treatment solution is 0.15%, and the mass content of nano-ZnO particles is 0.3%, as shown in Table 1. The particle size of the nano-ZnO particles is 10 to 30 nm.

[0099] The remaining steps and parameters were the same as those in Example 1 to obtain a nanofiltration membrane.

[0100] Comparative Example 3

[0101] The difference from Example 1 is:

[0102] Without step 2);

[0103] Step 3) is:

[0104] A PVA solution (with a concentration of 4% and a coating thickness of 0.05 μm) was coated on one side of the membrane material obtained in step 1), and then dried to obtain a nanofiltration membrane.

[0105] Comparative Example 4

[0106] The difference from Example 1 is:

[0107] The polyethylene glycol diglycidyl ether in the post-treatment solution of Example 1 was replaced with aza-12-crown-4.

[0108] The remaining steps and parameters were the same as those in Example 1 to obtain a nanofiltration membrane.

[0109] Comparative Example 5

[0110] The difference from Example 1 is:

[0111] The polyethylene glycol diglycidyl ether in the post-treatment solution of Example 1 was replaced with 2-hydroxymethyl-18-crown-6.

[0112] The remaining steps and parameters were the same as those in Example 1 to obtain a nanofiltration membrane.

[0113] The performance of the resulting nanofiltration membrane was tested, and the results are shown in Table 1. Membrane testing: 2240 μm / cm MgSO₄ aqueous solution was tested at a pressure of 0.48 MPa, with the test solution temperature at 25 ± 0.5°C. Antibacterial testing: Escherichia coli was tested according to the AATCC 100-2019 standard.

[0114] Table 1 Content of each component in the post-treatment solution and performance of the nanofiltration membrane

[0115]

[0116]

[0117] As can be seen from Table 1, the solution in the embodiment of the present invention has a significant effect on improving the antibacterial rate, and the membrane desalination rate is also improved to a certain extent.

[0118] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a nanofiltration membrane, comprising the following steps: A) applying an aqueous solution on a base film, and after the surface is dried, applying an oily solution, performing an interfacial polymerization reaction, and then heat treating to obtain a membrane material; B) coating the post-treatment solution on the side of the membrane material coated with the oil phase solution and allowing the surface to dry; The post-treatment solution includes polyethylene glycol diglycidyl ether, Pluronic F127, nano ZnO particles and water; C) coating one side of the membrane material obtained in step B) with the post-treatment solution by flow coating with a PVA solution, and drying the membrane to obtain a nanofiltration membrane.

2. The preparation method according to claim 1, characterized in that In step B), in the post-treatment solution, the mass content of polyethylene glycol diglycidyl ether is 0.1% to 0.5%, the mass content of Pluronic F127 is 0.1% to 0.5%, and the mass content of nano ZnO particles is 0.1% to 0.5%.

3. The preparation method according to claim 1, characterized in that In step B), the flow coating time is 0.5 to 1.5 minutes.

4. The preparation method according to claim 1, characterized in that In step A), the base film comprises a non-woven fabric and a polymer layer composited on the non-woven fabric; The material of the polymer layer includes at least one of polysulfone, polyethersulfone and polyvinylidene fluoride; The thickness of the polymer layer is 30 to 50 μm; the thickness of the non-woven fabric is 90 to 100 μm.

5. The preparation method according to claim 1, characterized in that In step A), the aqueous phase solution includes a polyamine monomer and an aqueous phase additive; The polyamine monomer includes at least one of piperazine, m-phenylenediamine and polyvinylamine; The aqueous phase additives include dextrorotatory camphorsulfonic acid, sodium hydroxide and sodium lauryl sulfate; In the aqueous phase solution, the mass content of the polyamine monomer is 0.5% to 1.5%, the mass content of dextrorotatory camphorsulfonic acid is 1.5% to 3.0%, the mass content of sodium hydroxide is 0.3% to 0.6%, and the mass content of sodium lauryl sulfate is 0.01% to 0.1%.

6. The preparation method according to claim 1, characterized in that In step A), the oil phase solution comprises an acyl chloride monomer and an organic solvent; The acyl chloride monomer includes at least one of trimesoyl chloride and adipoyl chloride; The organic solvent comprises at least one of n-hexane, Isopar G and Isopar L; In the oil phase solution, the mass content of the acyl chloride monomer is 0.2% to 0.5%.

7. The preparation method according to claim 1, characterized in that In step A), the coating amount of the aqueous solution is 20 to 40 g / m 2 ; The coating amount of the oil phase solution is 10 to 30 g / m 2 .

8. The preparation method according to claim 1, characterized in that In step A), the temperature of the interfacial polymerization reaction is 50-70° C.; The heat treatment temperature is 60-100° C. and the time is 2-3 minutes.

9. The preparation method according to claim 1, characterized in that In step C), the mass concentration of the PVA solution is 3% to 6%; The coating has a thickness of 0.01 to 0.2 μm.

10. A nanofiltration membrane prepared by the method according to any one of claims 1 to 9.

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