Composite nanofiltration membrane containing gelatin-zirconium phosphate nanoparticle interlayer and method of preparation

Abstract

The application relates to a composite nanofiltration membrane containing a gelatin-zirconium phosphate nanoparticle intermediate layer and a preparation method, and the preparation method comprises the following steps: 1, a porous support membrane is fully washed with an ethanol aqueous solution, and residual water on the surface of the porous support membrane is removed; 2, a gelatin modification solution is coated on the surface of the porous support membrane to obtain a modified porous support membrane containing a gelatin intermediate layer; 3, a solution containing zirconium ions is coated on the surface of the porous support membrane containing the gelatin intermediate layer; 4, a phosphoric acid solution is coated on the surface of the modified porous support membrane coated with the zirconium ion solution, and zirconium phosphate nanoparticles are in-situ grown on the modified porous support membrane; 5, an aqueous solution containing one or more multifunctional group-containing organic amines is coated on the surface of the porous support membrane containing the gelatin-zirconium phosphate nanoparticle intermediate layer; 6, one or more multifunctional group-containing organic acid chlorides are further coated to perform an interfacial polymerization reaction; and 7, a composite nanofiltration membrane containing a gelatin-zirconium phosphate nanoparticle intermediate layer is obtained after heat treatment.

Description

Technical Field

[0001] This invention belongs to the field of water treatment membrane technology, and specifically relates to a composite nanofiltration membrane containing a gelatin-zirconium phosphate nanoparticle interlayer and its preparation method. Background Technology

[0002] The emergence of transmembrane composite (TFC) membranes has brought about a qualitative leap in the performance of separation membranes, especially in the separation performance and pressure resistance of membrane materials. In recent years, to further improve the separation performance of TFC nanofiltration (NF) membranes, researchers have further optimized the TFC membrane structure. By constructing an "intermediate layer" between the ultrafiltration porous support membrane and the polyamide (PA) separation layer, the traditional "three-layer" composite membrane structure has been transformed into a "four-layer" composite membrane structure, thereby optimizing the separation performance of the TFCNF membrane.

[0003] The hydrophilic nature of the polymer interlayer can enhance the interaction between the base membrane and the aqueous monomers, optimizing the interfacial polymerization process and thus improving the separation performance of the composite membrane. Furthermore, the flexibility of the polymer interlayer often ensures good compatibility with the PA separation layer, reducing the risk of defects in the separation layer. In addition, the polymer interlayer can repair defects on the base membrane surface, regulate the distribution and diffusion of aqueous monomers, thereby influencing the interfacial polymerization process and forming a smooth PA separation layer. However, the flexible polymer interlayer has poor mechanical properties and contributes less to improving the pressure resistance of the TFC membrane.

[0004] In comparison, rigid nanoparticles (molecular sieves, metal oxides, metal-organic frameworks, carbon nanotubes, graphene oxide, etc.) possess stronger mechanical properties, making them more suitable for the preparation of pressure-resistant composite membranes. Furthermore, under high pressure, the "membrane compaction" effect of TFC membranes mainly occurs at the interface between the separation layer and the porous support layer, causing significant deformation of the skin portion of the porous support layer, thus affecting the separation performance of the TFC membrane. Therefore, improving the mechanical properties of the skin portion of the porous support layer can enhance the pressure resistance of the TFC membrane. Simultaneously, constructing a rigid nanoparticle intermediate protective layer on the ultrafiltration porous support layer is also expected to improve the pressure resistance of the TFC membrane to some extent. However, the rigid nanoparticle intermediate layer is often hampered by nanoparticle aggregation, which may introduce unnecessary defects into the separation layer, reducing the retention rate.

[0005] Non-environmentally friendly nanoparticles used in TFC membrane preparation may cause leaching problems during use, potentially harming the environment and human health. Zirconium phosphate (ZrP) is a biocompatible nanomaterial often used in combination with polymer matrix materials to enhance the mechanical properties of the matrix. Furthermore, the solvent required for ZrP preparation can be a pure aqueous system, avoiding the use of organic solvents, making it an environmentally friendly preparation method. However, ZrP nanomaterials synthesized via hydrothermal synthesis generally have a layered stacked structure, often requiring chemical or physical methods for exfoliation and dispersion to achieve a monodisperse state during use. Related research indicates that in-situ synthesis is an effective means to address the aggregation problem of nanomaterials during preparation. Without considering the crystallinity state, ZrP can be grown in situ on the membrane surface. Therefore, applying a polymer-rigid nanoparticle interlayer prepared by in-situ growth to the preparation of nanofiltration membranes can not only optimize the separation performance of nanofiltration membranes but also significantly improve their compaction resistance and fouling resistance.

[0006] Chinese patent CN202210286734.5 discloses a nanofiltration membrane based on a reactive support layer, its preparation method, and its application. Its purpose is to provide a method for preparing a nanofiltration membrane based on a reactive support layer that is simple in process, requires low equipment, and produces a nanofiltration membrane with high water permeation flux, good ion selectivity, and strong retention capacity for divalent anions. The technical solution is as follows: The preparation method of the nanofiltration membrane based on a reactive support layer includes the following steps: (1) performing an amino grafting reaction on a porous support membrane to prepare a reactive support membrane; (2) preparing the nanofiltration membrane based on the reactive support layer by interfacial polymerization of an aqueous solution and an oil phase solution containing polyacrylamide chloride monomers on the reactive support membrane. Its drawback is that the amino grafting is a flexible organic saturated amine molecular chain. Although the separation performance of the composite nanofiltration membrane can be improved by improving the interfacial polymerization kinetics, it cannot improve the compaction resistance and fouling resistance of the nanofiltration membrane.

[0007] Chinese Patent 201410168497.8 discloses a composite nanofiltration membrane containing composite nanoparticles and its preparation method. Its purpose is to provide a method that, by adding attapulgite-nano silica composite nanoparticles to an organic phase and then performing interfacial polymerization, uniformly disperses the nanoparticles in the functional layer, resulting in a composite nanofiltration membrane with superior overall performance. The technical solution is as follows: The preparation method of the composite nanofiltration membrane containing composite nanoparticles includes the following steps: (1) contacting a porous support base membrane with an aqueous solution containing two or more reactive amino compounds; (2) removing excess aqueous solution from the surface of the porous support base membrane after aqueous wetting; (3) contacting the porous support base membrane treated in step (2) with an acyl chloride compound containing two or more acyl chloride groups and an organic phase solution of purified and organically modified attapulgite and nano silica; (4) obtaining the composite nanofiltration membrane containing composite nanoparticles after heat treatment and water washing. Its shortcomings are: (1) Although the patent emphasizes that the dispersibility of organically modified attapulgite and nano silica has been improved, it still cannot solve the problem of nanoparticle aggregation in organic phase solution, which may cause unnecessary defects in the separation layer and reduce the retention rate; (2) It cannot solve the compatibility problem between nanoparticles and PA layer. When operating under high pressure, non-selective defects may be generated at the contact between nanoparticles and PA layer, affecting the long-term operating stability of nanofiltration membrane and shortening the service life of nanofiltration membrane.

[0008] Chinese Patent 201810424974.0 discloses a porous support layer, its preparation method, and its application. Its purpose is to provide a porous support layer with superior performance and, based on this, to construct a new high-performance forward osmosis composite membrane. The preparation method of the porous support layer in this technical solution includes the following steps: (1) preparing a casting solution containing hydrotalcite-like nanoparticles and a polymer, wherein the polymer is selected from one or more of polysulfone, polyethersulfone, polyphenylene sulfone, polyvinylidene fluoride, and polybenzimidazole; the mass of the hydrotalcite-like nanoparticles is 1-15% of the polymer mass; (2) after molding the casting solution prepared in step (1), immersing it in an acid solution for 6-24 hours, and then thoroughly rinsing it with deionized water. Its shortcomings are: (1) although adding hydrotalcite-like nanoparticles to the polymer can increase the porosity of the porous support layer, thereby improving the water flux of the composite membrane and enhancing the anti-salt flux of the composite membrane. However, the increased porosity will lead to a decrease in the compaction resistance of the porous support layer. Under high pressure and long-term operation, the water flux of the composite membrane will decrease relatively quickly. (2) This method of adding hydrotalcite-like nanoparticles to the polymer to optimize the porous support layer requires the addition of a large amount of nanoparticles, with an addition amount of 1-15%. Moreover, these nanoparticles will leach out or dissolve after being rinsed with acid solution, which is not conducive to improving the compaction resistance of the composite membrane separation layer.

[0009] Separation and Purification Technology, 2021, 264, 118391, reported the construction of a hydrophilic homogeneous gelatin interlayer with a thickness exceeding 100 nm on a polysulfone substrate, and the preparation of a high-performance composite nanofiltration membrane via interfacial polymerization. This interlayer not only influences the diffusion rate of amine monomers in the interfacial process, forming a thin separation layer, but also provides additional channels for water diffusion, thereby significantly improving the permeability of the nanofiltration membrane. Its drawback is that the gelatin interlayer is a flexible polymer interlayer. Although the separation performance of the composite nanofiltration membrane can be enhanced by repairing substrate defects and controlling interfacial polymerization, the mechanical properties of this interlayer are poor, contributing little to improving the compaction resistance of the composite nanofiltration membrane. Summary of the Invention

[0010] The purpose of this invention is to provide a gelatin-zirconium phosphate nanoparticle interlayer for the preparation of composite nanofiltration membranes, addressing the problems of easy compaction and poor fouling resistance in existing nanofiltration membranes. By using a flexible organic polymer-rigid nanoparticle interlayer, the separation performance of the nanofiltration membrane can be enhanced by repairing substrate defects and regulating interfacial polymerization. Furthermore, the compaction resistance and fouling resistance of the nanofiltration membrane can be improved by introducing rigid nanoparticles into the substrate and separation layer. This effectively regulates the interfacial polymerization process, controls the structure of the separation layer, and enhances the mechanical properties of the substrate membrane, thereby improving the compaction resistance and fouling resistance of the composite nanofiltration membrane containing the gelatin-zirconium phosphate nanoparticle interlayer. Another objective of this invention is to provide a method for preparing a composite nanofiltration membrane with excellent pressure resistance and fouling resistance by utilizing in-situ growth technology to grow ZrP nanoparticles in situ on the surface of a gelatin (GT) modified porous support membrane, resulting in a gelatin-zirconium phosphate nanoparticle interlayer.

[0011] The technical solution of the present invention is a method for preparing a composite nanofiltration membrane containing a gelatin-zirconium phosphate nanoparticle interlayer, which is characterized by including the following steps:

[0012] (1) Wash the porous support membrane thoroughly with an ethanol-water solution to remove any residual water on the surface of the porous support membrane;

[0013] (2) The gelatin modification solution is coated on the surface of the porous support membrane to obtain a modified porous support membrane containing a gelatin interlayer;

[0014] (3) Coating the surface of a porous support membrane containing a gelatin interlayer with a solution containing zirconium ions;

[0015] (4) A phosphoric acid solution is coated on the surface of a modified porous support membrane coated with zirconium ion solution, and zirconium phosphate nanoparticles are grown in situ on the modified porous support membrane.

[0016] (5) Coating the surface of a porous support membrane containing a gelatin-zirconium phosphate nanoparticle interlayer with an aqueous solution of one or more organic amines containing multifunctional groups;

[0017] (6) Then coat with one or more organic acyl chloride solutions containing multifunctional groups for interfacial polymerization reaction;

[0018] (7) After heat treatment, a composite nanofiltration membrane containing a gelatin-zirconium phosphate nanoparticle interlayer is obtained.

[0019] Preferably, the gelatin includes one or a mixture of several types of edible gelatin, pharmaceutical gelatin, photographic gelatin, and industrial gelatin, with a concentration of 0.01 to 30 wt%.

[0020] 3. The method for preparing a composite nanofiltration membrane containing a gelatin-zirconium phosphate nanoparticle interlayer according to claim 1, characterized in that the zirconium phosphate nanoparticles in step (4) are composed of zirconium ions (Zr... 4+ ) and phosphate ions (PO4) 3- The zirconium phosphate nanoparticles were prepared by in-situ growth on the surface of a porous support membrane; the growth time of the zirconium phosphate nanoparticles was 2–180 min.

[0021] The zirconium ions are taken from one or a mixture of zirconium salts of zirconium dichloride (ZrOCl2), zirconium chloride (ZrCl4), zirconium nitrate [Zr(NO3)4] and zirconium sulfate [Zr(SO4)2], and the concentration of the zirconium salt solution is 0.1-5 wt%.

[0022] The phosphate ions are derived from phosphoric acid (H3PO4), and the concentration of the phosphoric acid solution is 0.1–30 wt%.

[0023] Preferably, the interfacial polymerization reaction time is 5–300 s, the heat treatment temperature is 30–80 ℃, and the heat treatment time is 1–60 min.

[0024] Another technical solution of the present invention is the composite nanofiltration membrane containing a gelatin-zirconium phosphate nanoparticle intermediate layer, which is characterized in that it is prepared according to any of the above preparation methods.

[0025] Another technical solution of the present invention is the composite nanofiltration membrane containing a gelatin-zirconium phosphate nanoparticle interlayer: Its unique feature is that a gelatin-modified layer is coated onto a porous support membrane, followed by sequential coating with a zirconium ion-containing solution and a phosphoric acid solution, thereby growing a zirconium phosphate nanoparticle layer in situ on the gelatin-modified porous support membrane; then, a multifunctional organic amine aqueous solution and a multifunctional organic acyl chloride solution are sequentially applied to the surface of the zirconium phosphate nanoparticle layer, forming a polyamide composite nanofiltration membrane containing a gelatin-zirconium phosphate nanoparticle interlayer through an interfacial polymerization reaction. Compared with the prior art, the beneficial effects of the present invention are:

[0026] (1) The gelatin / zirconium phosphate nanoparticle interlayer of the present invention can repair defects on the polymer porous support membrane to a certain extent, control the distribution and diffusion of aqueous monomers, and further regulate the rate and extent of interfacial polymerization reaction, thereby obtaining a denser, thinner and smoother separation layer, thereby improving the separation performance and fouling resistance of the composite nanofiltration membrane.

[0027] (2) The zirconium phosphate nanoparticles encapsulated in the polyamide separation layer and the nanoparticles grown in the polymer porous support membrane of the present invention can enhance the mechanical properties of the composite nanofiltration membrane, thereby enhancing the anti-compaction performance and long-term operational stability of the composite nanofiltration membrane.

[0028] (3) The preparation method of the present invention is simple to operate and low in cost. It can effectively improve the fouling resistance, compaction resistance and long-term operation stability of composite nanofiltration membranes in a short time and has broad application prospects.

[0029] (4) Through the gelatin-zirconium phosphate nanoparticle intermediate layer, the present invention can not only improve the separation performance of nanofiltration membrane, but also effectively improve the compaction resistance and fouling resistance of nanofiltration membrane. Attached Figure Description

[0030] Figure 1-1 This is a surface SEM image of the base film in Embodiment 2 of the present invention;

[0031] Figure 1-2 This is a surface SEM image of the composite nanofiltration membrane in Example 2 of this invention;

[0032] Figure 2-1 This is a surface SEM image of the base film in Comparative Example 1 of the present invention;

[0033] Figure 2-2 This is a surface SEM image of the composite nanofiltration membrane in Comparative Example 1 of the present invention;

[0034] Figure 3-1 This is a surface SEM image of the base film in Comparative Example 2 of the present invention;

[0035] Figure 3-2 This is a surface SEM image of the composite nanofiltration membrane in Comparative Example 2 of the present invention. Detailed Implementation

[0036] The present invention will be further described in detail below with reference to embodiments and accompanying drawings:

[0037] In the following examples, after pre-pressurization for 3 hours at 1.0 MPa, 25°C, and 7 LPM, the removal rate and permeate flux of the prepared nanofiltration membrane for a 2000 mg / L Na2SO4 solution were tested. The permeate flux of the nanofiltration membrane is expressed in liters per square meter per hour (LMH).

[0038] Example 1

[0039] The preparation method of a composite nanofiltration membrane with excellent pressure resistance and fouling resistance, containing a gelatin-zirconium phosphate nanoparticle interlayer, is as follows:

[0040] (1) Wash the polysulfone ultrafiltration membrane with a 30 wt% aqueous ethanol solution;

[0041] (2) Coat the surface of the polysulfone ultrafiltration membrane in step (1) with a gelatin intermediate layer modification solution with a concentration of 0.1 w% and let it stand for 15 min; then wash it thoroughly with deionized water and store it in deionized water for later use.

[0042] (3) Wash the polysulfone ultrafiltration membrane from step (2) thoroughly with deionized water and dry it with an air knife; under normal pressure, temperature of 25°C and relative humidity of 40%, coat the surface of the polysulfone porous support membrane containing the gelatin interlayer with a 0.25wt% zirconium oxychloride aqueous solution, let it stand for 15 minutes, pour it out and dry it with an air knife.

[0043] (4) A phosphoric acid aqueous solution with a mass concentration of 8.5 wt% was uniformly coated on the surface of the modified membrane obtained in step (3), and allowed to stand for 120 min to allow the zirconium phosphate nanoparticles to grow in situ. The phosphoric acid solution was then discarded, and the membrane was washed with deionized water to obtain a polysulfone ultrafiltration membrane modified with a gelatin-zirconia phosphate nanoparticle intermediate layer.

[0044] (5) Wash the modified polysulfone ultrafiltration membrane from step (4) thoroughly with deionized water, remove the water from the membrane surface with an air knife, and coat the polysulfone membrane surface containing the intermediate layer with a 1 wt% piperazine solution under normal pressure, temperature of 25°C and relative humidity of 40%. Let it stand for 2 minutes, pour it out, and remove the excess piperazine solution with an air knife.

[0045] (6) A hexane solution of 1,3,5-benzenetricarboxyl chloride with a mass concentration of 0.1 wt% was uniformly coated on the surface of the polysulfone membrane containing the intermediate layer obtained in step (5) to initiate an interfacial polymerization reaction. After the reaction was carried out for 30 seconds, the membrane surface was rinsed with hexane.

[0046] (7) The obtained composite membrane was placed in a 60℃ oven for 2 minutes for heat treatment. The reaction was completed, and the composite nanofiltration membrane was obtained.

[0047] The separation performance of the prepared nanofiltration membrane was tested: the flux of the nanofiltration membrane prepared by polysulfone ultrafiltration membrane was 131 LMH, and the rejection rate of Na2SO4 was 98.8%; under a pressure of 3.6 MPa, after a compaction test for 9 hours, the flux loss of the nanofiltration membrane was 19.2%; in the contamination test of bovine serum albumin solution with a concentration of 500 ppm, the flux recovery rate was 93.4%.

[0048] Example 2

[0049] The preparation method of a composite nanofiltration membrane with excellent pressure resistance and fouling resistance, containing a gelatin-zirconium phosphate nanoparticle interlayer, is as follows:

[0050] (1) Wash the polysulfone ultrafiltration membrane with a 30 wt% aqueous ethanol solution;

[0051] (2) Coat the surface of the polysulfone ultrafiltration membrane in step (1) with a gelatin intermediate layer modification solution with a concentration of 0.1 w% and let it stand for 15 min; then wash it thoroughly with deionized water and store it in deionized water for later use.

[0052] (3) Wash the polysulfone ultrafiltration membrane from step (2) thoroughly with deionized water and dry it with an air knife; under normal pressure, temperature of 25°C and relative humidity of 40%, coat the surface of the polysulfone porous support membrane containing the gelatin interlayer with a 0.50wt% zirconium oxychloride aqueous solution, let it stand for 15 minutes, pour it out and dry it with an air knife.

[0053] (4) A phosphoric acid aqueous solution with a mass concentration of 8.5 wt% was uniformly coated onto the surface of the modified membrane obtained in step (3). The membrane was allowed to stand for 120 min to allow the zirconium phosphate nanoparticles to grow in situ. The phosphoric acid solution was then discarded, and the membrane was washed with deionized water to obtain a polysulfone ultrafiltration membrane modified with a gelatin-zirconia phosphate nanoparticle interlayer (see [link to relevant documentation]). Figure 1-1 );

[0054] (5) Wash the modified polysulfone ultrafiltration membrane from step (4) thoroughly with deionized water, remove the water from the membrane surface with an air knife, and coat the polysulfone membrane surface containing the intermediate layer with a 1 wt% piperazine solution under normal pressure, temperature of 25°C and relative humidity of 40%. Let it stand for 2 minutes, pour it out, and remove the excess piperazine solution with an air knife.

[0055] (6) A hexane solution of 1,3,5-benzenetricarboxyl chloride with a mass concentration of 0.1 wt% was uniformly coated on the surface of the polysulfone membrane containing the intermediate layer obtained in step (5) to initiate an interfacial polymerization reaction. After the reaction was carried out for 30 seconds, the membrane surface was rinsed with hexane.

[0056] (7) The obtained composite membrane was heat-treated in a 60℃ oven for 2 minutes. After the reaction was completed, the composite nanofiltration membrane was obtained (see [reference]). Figure 1-2 );

[0057] The separation performance of the prepared nanofiltration membrane was tested: the flux of the nanofiltration membrane prepared by polysulfone ultrafiltration membrane was 149 LMH, and the rejection rate of Na2SO4 was 98.7%; under a pressure of 3.6 MPa, after a compaction test for 9 hours, the flux loss of the nanofiltration membrane was 15.7%; in the contamination test of bovine serum albumin solution with a concentration of 500 ppm, the flux recovery rate was 93.8%.

[0058] Example 3

[0059] The preparation method of a composite nanofiltration membrane with excellent pressure resistance and fouling resistance, containing a gelatin-zirconium phosphate nanoparticle interlayer, is as follows:

[0060] (1) Wash the polysulfone ultrafiltration membrane with a 30 wt% aqueous ethanol solution;

[0061] (2) Coat the surface of the polysulfone ultrafiltration membrane in step (1) with a gelatin intermediate layer modification solution with a concentration of 0.1 w% and let it stand for 15 min; then wash it thoroughly with deionized water and store it in deionized water for later use.

[0062] (3) Wash the polysulfone ultrafiltration membrane from step (2) thoroughly with deionized water and dry it with an air knife; under normal pressure, temperature of 25°C and relative humidity of 40%, coat the surface of the polysulfone porous support membrane containing the gelatin interlayer with a 1.00wt% zirconium oxychloride aqueous solution, let it stand for 15 minutes, pour it out and dry it with an air knife.

[0063] (4) A phosphoric acid aqueous solution with a mass concentration of 8.5 wt% was uniformly coated on the surface of the modified membrane obtained in step (3), and allowed to stand for 120 min to allow the zirconium phosphate nanoparticles to grow in situ. The phosphoric acid solution was then discarded, and the membrane was washed with deionized water to obtain a polysulfone ultrafiltration membrane modified with a gelatin-zirconia phosphate nanoparticle intermediate layer.

[0064] (5) Wash the modified polysulfone ultrafiltration membrane from step (4) thoroughly with deionized water, remove the water from the membrane surface with an air knife, and coat the polysulfone membrane surface containing the intermediate layer with a 1 wt% piperazine solution under normal pressure, temperature of 25°C and relative humidity of 40%. Let it stand for 2 minutes, pour it out, and remove the excess piperazine solution with an air knife.

[0065] (6) A hexane solution of 1,3,5-benzenetricarboxyl chloride with a mass concentration of 0.1 wt% was uniformly coated on the surface of the polysulfone membrane containing the intermediate layer obtained in step (5) to initiate an interfacial polymerization reaction. After the reaction was carried out for 30 seconds, the membrane surface was rinsed with hexane.

[0066] (7) The obtained composite membrane was placed in a 60℃ oven for 2 minutes for heat treatment. The reaction was completed, and the composite nanofiltration membrane was obtained.

[0067] The separation performance of the prepared nanofiltration membrane was tested: the flux of the nanofiltration membrane prepared by polysulfone ultrafiltration membrane was 186 LMH, and the rejection rate of Na2SO4 was 95.3%; under a pressure of 3.6 MPa, after a compaction test for 9 hours, the flux loss of the nanofiltration membrane was 12.3%; in the contamination test of bovine serum albumin solution with a concentration of 500 ppm, the flux recovery rate was 89.5%.

[0068] Comparative Example 1

[0069] The preparation method of nanofiltration membrane without intermediate layer is as follows:

[0070] (1) Use polysulfone ultrafiltration membrane (see Figure 2-1 Wash with a 30wt% aqueous ethanol solution;

[0071] (2) Wash the polysulfone ultrafiltration membrane from step (1) thoroughly with deionized water and remove the water from the membrane surface with an air knife; under normal pressure, temperature of 25°C and relative humidity of 40%, coat the polysulfone membrane surface containing the intermediate layer with a piperazine solution with a mass concentration of 1 wt%, let it stand for 2 minutes, pour it out, and remove the excess piperazine solution from the membrane surface with an air knife.

[0072] (3) A hexane solution of 1,3,5-benzenetricarboxyl chloride with a mass concentration of 0.1 wt% was uniformly coated on the surface of the polysulfone membrane containing the intermediate layer obtained in step (2) to initiate the interfacial polymerization reaction. After the reaction was carried out for 30 seconds, the membrane surface was rinsed with hexane.

[0073] (4) Place the obtained composite membrane in a 60℃ oven for 2 minutes to complete the reaction, and obtain the composite nanofiltration membrane (see [reference]). Figure 2-2 );

[0074] The performance of the prepared nanofiltration membrane was tested: the flux of the nanofiltration membrane prepared by polysulfone ultrafiltration membrane was 71 LMH, and the rejection rate of Na2SO4 was 98.1%; under a pressure of 3.6 MPa, after a compaction test for 9 hours, the flux loss of the nanofiltration membrane was 34.4%; in the contamination test of bovine serum albumin solution with a concentration of 500 ppm, the flux recovery rate was 87.2%.

[0075] Comparative Example 2

[0076] The preparation method of the composite nanofiltration membrane containing a gelatin interlayer is as follows:

[0077] (2) Wash the polysulfone ultrafiltration membrane with a 30 wt% aqueous ethanol solution.

[0078] (2) A 0.1 w% gelatin interlayer modification solution was coated onto the surface of the polysulfone ultrafiltration membrane from step (1), allowed to stand for 15 min, and then thoroughly washed with deionized water to obtain a gelatin interlayer modified polysulfone ultrafiltration membrane (see [link to article]). Figure 3-1 );

[0079] (3) Wash the modified polysulfone ultrafiltration membrane from step (2) thoroughly with deionized water and remove the water from the membrane surface with an air knife; under normal pressure, temperature of 25°C and relative humidity of 40%, coat the polysulfone membrane surface containing the intermediate layer with a piperazine solution with a mass concentration of 1 wt%, let it stand for 2 minutes, pour it out, and remove the excess piperazine solution with an air knife.

[0080] (4) A hexane solution of 1,3,5-benzenetricarboxyl chloride with a mass concentration of 0.1 wt% was uniformly coated on the surface of the polysulfone membrane containing the intermediate layer obtained in step (3) to initiate the interfacial polymerization reaction. After the reaction was carried out for 30 seconds, the membrane surface was rinsed with hexane.

[0081] (5) The obtained composite membrane was heat-treated in a 60℃ oven for 2 minutes. After the reaction was completed, the composite nanofiltration membrane was obtained (see [reference]). Figure 3-2 );

[0082] The performance of the prepared nanofiltration membrane was tested: the flux of the nanofiltration membrane prepared by polysulfone ultrafiltration membrane was 121 LMH, and the rejection rate of Na2SO4 was 99.1%; under a pressure of 3.6 MPa, after a compaction test for 9 hours, the flux loss of the nanofiltration membrane was 30.1%; in the contamination test of bovine serum albumin solution with a concentration of 500 ppm, the flux recovery rate was 94.5%.

[0083] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be covered by the claims of the present invention.

Claims

1. A method for preparing a composite nanofiltration membrane containing a gelatin-zirconium phosphate nanoparticle interlayer, characterized in that, Includes the following steps: (1) Wash the porous support membrane thoroughly with an ethanol-water solution to remove any residual water on the surface of the porous support membrane; (2) The gelatin modification solution is coated on the surface of the porous support membrane to obtain a modified porous support membrane containing a gelatin interlayer; (3) Coating the surface of a porous support membrane containing a gelatin interlayer with a solution containing zirconium ions; (4) A phosphoric acid solution is coated on the surface of a modified porous support membrane coated with zirconium ion solution, and zirconium phosphate nanoparticles are grown in situ on the modified porous support membrane. (5) Coating the surface of a porous support membrane containing a gelatin-zirconium phosphate nanoparticle interlayer with an aqueous solution of one or more organic amines containing multifunctional groups; (6) Then coat with one or more organic acyl chloride solutions containing multifunctional groups for interfacial polymerization reaction; (7) After heat treatment, a composite nanofiltration membrane containing a gelatin-zirconium phosphate nanoparticle interlayer is obtained.

2. The method for preparing a composite nanofiltration membrane containing a gelatin-zirconium phosphate nanoparticle interlayer according to claim 1, characterized in that, The gelatin includes one or a mixture of several types of edible gelatin, pharmaceutical gelatin, photographic gelatin, and industrial gelatin, with a concentration of 0.01 to 30 wt%.

3. The method for preparing a composite nanofiltration membrane containing a gelatin-zirconium phosphate nanoparticle interlayer according to claim 1, characterized in that, The zirconium phosphate nanoparticles described in step (4) are composed of zirconium ions (Zr). 4+ ) and phosphate ions (PO4) 3- The zirconium phosphate nanoparticles were prepared by in-situ growth on the surface of a porous support membrane; the growth time of the zirconium phosphate nanoparticles was 2–180 min. The zirconium ions are taken from one or a mixture of zirconium salts of zirconium dichloride (ZrOCl2), zirconium chloride (ZrCl4), zirconium nitrate [Zr(NO3)4] and zirconium sulfate [Zr(SO4)2], and the concentration of the zirconium salt solution is 0.1-5 wt%. The phosphate ions are derived from phosphoric acid (H3PO4), and the concentration of the phosphoric acid solution is 0.1–30 wt%.

4. The method for preparing a composite nanofiltration membrane containing a gelatin-zirconium phosphate nanoparticle interlayer according to claim 1, characterized in that, The interfacial polymerization reaction time is 5–300 s, the heat treatment temperature is 30–80 ℃, and the heat treatment time is 1–60 min.

5. A composite nanofiltration membrane containing a gelatin-zirconium phosphate nanoparticle interlayer, characterized in that, Prepared by the preparation method according to any one of claims 1 to 4.

6. A composite nanofiltration membrane containing a gelatin-zirconium phosphate nanoparticle interlayer: characterized in that, A gelatin-modified layer is coated onto a porous support membrane, followed by a zirconium ion solution and a phosphoric acid solution, thereby growing a zirconium phosphate nanoparticle layer in situ on the gelatin-modified porous support membrane. Then, a multifunctional organic amine aqueous solution and a multifunctional organic acyl chloride solution are successively coated onto the surface of the zirconium phosphate nanoparticle layer, and a polyamide composite nanofiltration membrane containing a gelatin-zirconia phosphate nanoparticle intermediate layer is formed through an interfacial polymerization reaction.

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