Anti-pollution nanofiltration membrane as well as preparation method and application thereof

Abstract

The invention relates to an anti-pollution nanofiltration membrane and a preparation method and application thereof, the preparation method comprises the following steps: (1) mixing and dissolving a membrane forming material and an organic solvent to obtain a membrane casting solution; sequentially carrying out membrane preparation and phase inversion on the membrane casting solution on a substrate material to obtain a bottom membrane; (2) carrying out interfacial polymerization on the base membrane obtained in the step (1) by adopting a reaction water phase and a reaction oil phase to obtain a nanofiltration membrane; a modifier is added into the reaction water phase, and the modifier comprises polyethylene oxide. The nanofiltration membrane provided by the invention has the advantages of high pure water flux, good surface hydrophilicity, strong anti-fouling performance and the like, can stably operate for a long time, and is simple in preparation method and beneficial to industrial application.

Description

Technical Field

[0001] The invention relates to the field of water treatment membrane materials, and in particular to an anti-pollution nanofiltration membrane and a preparation method and application thereof. Background Art

[0002] Due to the shortage of total freshwater resources and the continuous increase in industrial water consumption, the proportion of water costs in the total cost of industrial production has continued to increase, limiting the development of high-water-consuming industrial manufacturing. Therefore, how to save water and recycle water resources is an important research direction at present.

[0003] Membrane water treatment technology is an efficient and environmentally friendly water treatment technology that has been widely studied and applied in my country in recent years. This technology uses special membrane materials to separate harmful substances in water through physical or chemical methods to achieve the purpose of purifying water. Membrane water treatment technology has the advantages of simple operation, high efficiency, small footprint, and good water quality. It can effectively solve the problems of water shortage and water environment pollution in my country.

[0004] The research on membrane water treatment technology mainly focuses on the research and development of membrane materials, the optimization of membrane processes, and the control of membrane pollution. With the continuous advancement of materials science and membrane process technology, new membrane materials and membrane processes continue to emerge, such as nanofiltration, reverse osmosis, and ultrafiltration. These new membrane materials and membrane processes have higher filtration efficiency, better anti-pollution performance, and longer service life, providing strong support for the development of membrane water treatment technology. On a theoretical level, membrane water treatment technology is based on the principle of molecular sieves, and separates harmful substances from water through the selective separation of membranes. In this process, factors such as the properties of membrane materials, the design of membrane processes, and operating conditions will affect the treatment effect. Therefore, for different application scenarios and water treatment needs, it is necessary to select suitable membrane materials and membrane processes, and optimize operating conditions to achieve efficient and stable water treatment effects.

[0005] Nanofiltration membrane is one of the key technologies in membrane water treatment technology. Due to its excellent selective separation ability, it has broad application prospects in the fields of seawater desalination pretreatment and zero discharge of industrial wastewater. Traditional nanofiltration membrane is similar to reverse osmosis membrane, which is mainly composed of polyester non-woven fabric support layer, polysulfone / polyethersulfone base layer and polyamide separation layer. Unlike reverse osmosis membrane, the separation layer structure of nanofiltration membrane is mainly semi-aromatic polyamide, which is mainly polymerized by piperazine (PIP) and acyl chloride through interfacial polymerization technology. Therefore, its separation layer has a relatively low cross-linking degree, and the separation ability is significantly affected by the surface charge, which has a significant selective separation ability. However, traditional nanofiltration membranes often face the disadvantages of low flux and poor antifouling, which makes the operating cost of membrane systems in industrial applications high, seriously hindering the wider application of nanofiltration membranes.

[0006] Therefore, providing a nanofiltration membrane with good flux and anti-fouling performance is a technical problem that needs to be solved in the current field. Summary of the invention

[0007] In view of the shortcomings of the prior art, the purpose of the present invention is to provide an anti-pollution nanofiltration membrane and a preparation method and use thereof. Compared with the prior art, the nanofiltration membrane provided by the present invention has the advantages of high pure water flux, good surface hydrophilicity and strong anti-fouling performance, can operate stably for a long time, and the preparation method is simple, which is conducive to industrial application.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a method for preparing an anti-fouling nanofiltration membrane, the preparation method comprising the following steps:

[0010] (1) mixing a film-forming material and an organic solvent and dissolving them to obtain a casting solution; sequentially performing film formation and phase conversion on the casting solution on a base material to obtain a base film;

[0011] (2) using a reaction water phase and a reaction oil phase to perform interfacial polymerization on the base membrane obtained in step (1) to obtain a nanofiltration membrane;

[0012] A modifier is added into the reaction water phase, and the modifier comprises polyethylene oxide.

[0013] In the preparation method provided by the present invention, a separation layer is prepared on a base membrane by interfacial polymerization, and polyethylene oxide (PEO) is introduced into the reaction water phase of the interfacial polymerization, which can cause the interfacial polymerization process to be in a thermodynamically unstable state, resulting in the formation of a large number of regular Turing structures on the membrane surface. The presence of the structure can significantly improve the surface roughness of the membrane, thereby increasing the effective area of ​​the membrane, and thus improving the flux; and polyethylene oxide itself is non-toxic and does not participate in the reaction, and has little effect on the density of the polyamide layer. Its longer polymer chain segments will be embedded in the membrane surface by the polymerization reaction, thereby enhancing the hydrophilicity of the membrane, which is beneficial to the improvement of the flux and anti-fouling properties.

[0014] Preferably, the film-forming material in step (1) comprises any one of polysulfone, polyethersulfone or polyvinyl chloride, or a combination of at least two thereof.

[0015] In the present invention, the weight average molecular weight of the polysulfone is generally 60000-80000Da, for example, it can be 60000Da, 65000Da, 70000Da, 75000Da or 80000Da, but it is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable; the weight average molecular weight of the polyethersulfone is 50000-200000Da, for example, it can be 50000Da, 100000Da, 150000Da or 200000Da, but it is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable; the molecular weight of the polyvinyl chloride is 50000-110000Da, for example, it can be 50000Da, 60000Da, 80000Da, 100000Da or 110000Da, but it is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable.

[0016] Preferably, the mass percentage of the film-forming material in the casting solution is 15-20%, for example, 15%, 16%, 17%, 18%, 19% or 20%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0017] Preferably, the organic solvent in step (1) comprises any one of N N dimethylformamide, N N dimethylacetamide or dimethyl sulfoxide, or a combination of at least two thereof.

[0018] Preferably, the dissolution temperature in step (1) is 60-80°C, for example, it can be 60°C, 62°C, 64°C, 66°C, 68°C, 70°C, 72°C, 74°C, 76°C, 78°C or 80°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0019] Preferably, the dissolution time is 6-8 h, for example, 6 h, 6.5 h, 7 h, 7.5 h or 8 h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0020] Preferably, stirring is performed during the dissolving process.

[0021] Preferably, after the dissolution, the mixture is kept warm and allowed to stand for degassing.

[0022] Preferably, the film-forming process in step (1) comprises: using the casting solution to perform film-forming by doctor blade coating on the surface of the base material.

[0023] Preferably, the phase inversion process comprises: immersing the film-formed base material into a coagulation bath to obtain a base film.

[0024] Preferably, the base material comprises a nonwoven fabric.

[0025] In the present invention, the nonwoven fabric may be, for example, a polyester nonwoven fabric.

[0026] Preferably, the coagulation bath comprises water.

[0027] Preferably, NN dimethylformamide is also added to the coagulation bath.

[0028] Preferably, the mass percentage of N-N dimethylformamide in the coagulation bath is ≤5%, for example, it can be 5%, 4.5%, 4%, 3.5%, 3%, 2.5%, 2%, 1.5% or 1%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0029] Preferably, the reaction aqueous phase in step (2) comprises water-soluble monomers, polyethylene oxide and water.

[0030] Preferably, the water-soluble monomer comprises piperazine.

[0031] Preferably, the mass percentage of the water-soluble monomer in the reaction aqueous phase is 0.5-2%, for example, it can be 0.5%, 0.6%, 0.8%, 1%, 1.2%, 1.4%, 1.6%, 1.8% or 2%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0032] Preferably, the mass percentage of polyethylene oxide in the reaction aqueous phase is 0.1-2%, for example, it can be 0.1%, 0.2%, 0.4%, 0.6%, 0.8%, 1%, 1.2%, 1.4%, 1.6%, 1.8% or 2%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0033] In the present invention, by preferably controlling the mass percentage of polyethylene oxide in the reaction water phase, the viscosity of the reaction water phase can be effectively controlled, thereby regulating the diffusion rate of PIP during the interfacial polymerization process.

[0034] Preferably, the reaction oil phase in step (2) comprises oil-soluble monomers and an organic solvent.

[0035] Preferably, the oil-soluble monomer comprises trimesoyl chloride and / or terephthaloyl chloride.

[0036] Preferably, the organic solvent in step (2) comprises any one of n-hexane, n-heptane, isoalkane E or isoalkane G, or a combination of at least two of them.

[0037] Preferably, the mass percentage of the oil-soluble monomer in the reaction oil phase is 0.01-0.15%, for example, it can be 0.01%, 0.02%, 0.04%, 0.06%, 0.08%, 0.1%, 0.12%, 0.14% or 0.15%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0038] Preferably, the process of interfacial polymerization in step (2) comprises: contacting one side of the base membrane containing the film-forming material with a reaction water phase for 30-120 s, for example, 30 s, 40 s, 50 s, 60 s, 70 s, 80 s, 90 s, 100 s, 110 s or 120 s, but not limited to the listed values, and other values ​​not listed in the numerical range are also applicable, and then removing excess reaction water phase; then contacting the side that has been in contact with the reaction water phase with a reaction oil phase for 30-120 s, for example, 30 s, 40 s, 50 s, 60 s, 70 s, 80 s, 90 s, 100 s, 110 s or 120 s, but not limited to the listed values, and other values ​​not listed in the numerical range are also applicable, and then removing excess reaction oil phase, and finally performing heat treatment to obtain a nanofiltration membrane.

[0039] Preferably, the temperature of the heat treatment is 40-60°C, for example, it can be 40°C, 42°C, 44°C, 46°C, 48°C, 50°C, 52°C, 54°C, 56°C, 58°C or 60°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0040] In the present invention, the heat treatment time generally needs to be selected according to the type of organic solvent used.

[0041] As a preferred technical solution of the first aspect of the present invention, the preparation method comprises the following steps:

[0042] (1) mixing a film-forming material and an organic solvent and stirring and dissolving them at a temperature of 60-80° C. for 6-8 hours, wherein the film-forming material comprises any one of polysulfone, polyethersulfone or polyvinyl chloride or a combination of at least two thereof, and the organic solvent comprises any one of N—N dimethylformamide, N—N dimethylacetamide or dimethyl sulfoxide or a combination of at least two thereof, and then keeping the mixture warm and standing to degas, thereby obtaining a casting solution, wherein the mass percentage of the film-forming material in the casting solution is 15-20%; applying the casting solution on the surface of a non-woven fabric by a doctor blade to form a film, and then immersing the non-woven fabric in a coagulation bath to obtain a base film;

[0043] (2) using a reaction water phase and a reaction oil phase to carry out interfacial polymerization on the base film obtained in step (1), wherein the reaction water phase comprises piperazine, polyethylene oxide and water, the mass percentage of piperazine in the reaction water phase is 0.5-2%, the mass percentage of polyethylene oxide is 0.1-2%, the reaction oil phase comprises an oil-soluble monomer and an organic solvent, the oil-soluble monomer comprises trimesoyl chloride and / or terephthaloyl chloride, and the organic solvent comprises n-hexane, n-heptane, isoparaffin E or isoparaffin Any one or a combination of at least two of the hydrocarbons G, the mass percentage of the oil-soluble monomer in the reaction oil phase is 0.01-0.15%, and the process of interfacial polymerization includes: contacting the side of the base membrane containing the film-forming material with the reaction water phase for 30-120s, and then removing the excess reaction water phase; then contacting the side that has contacted the reaction water phase with the reaction oil phase for 30-120s, and then removing the excess reaction oil phase, and finally performing heat treatment at a temperature of 40-60°C to obtain a nanofiltration membrane.

[0044] In a second aspect, the present invention provides an anti-pollution nanofiltration membrane, which is obtained by the preparation method of the anti-pollution nanofiltration membrane described in the first aspect of the present invention.

[0045] The surface of the polyamide separation layer in the anti-fouling nanofiltration membrane provided by the present invention has a large number of regular Turing structures, has a high surface roughness and strong hydrophilicity, can improve its flux and anti-fouling properties, and has a stable surface structure and can operate stably for a long time.

[0046] In a third aspect, the present invention provides a use of the anti-pollution nanofiltration membrane as described in the second aspect of the present invention, wherein the anti-pollution nanofiltration membrane is used in the field of water treatment.

[0047] The anti-pollution nanofiltration membrane provided by the present invention is used in the field of water treatment, can give full play to its flux and hydrophilicity advantages, has good anti-pollution properties, and has broad application prospects.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] (1) In the preparation method provided by the present invention, by introducing polyethylene oxide into the reaction water phase used for interfacial polymerization, on the one hand, the interfacial polymerization process can be made thermodynamically unstable, thereby forming a large number of regular Turing structures on the membrane surface, which can greatly improve the surface roughness of the membrane, increase the effective area of ​​the membrane, and thus improve the flux; on the other hand, polyethylene oxide itself is non-toxic and does not participate in the reaction, and has little effect on the density of the polyamide separation layer, and its longer polymer chain segments will be embedded in the membrane surface by the polymerization reaction, thereby enhancing its hydrophilicity and further improving its flux and anti-fouling properties.

[0050] (2) In the preparation method provided by the present invention, the polyethylene oxide modifier used is green, environmentally friendly, low-priced, and is conducive to industrial application.

[0051] (3) The anti-pollution nanofiltration membrane provided by the present invention has the advantages of good hydrophilicity, strong anti-fouling property, stable surface structure, etc., can operate stably for a long time, and has broad application prospects in the field of water treatment.

[0052] (4) Specifically, taking the membrane separation performance test of Na2SO4 as an example, under optimal conditions, the Na2SO4 flux of the nanofiltration membrane provided by the present invention can reach 61.9L / (m 2 ·h·MPa), the Na2SO4 retention rate is above 92.64%. Taking the anti-fouling performance test of bovine serum albumin as an example, the flux decline rate is below 9.30%, and the flux recovery rate is above 88.33%. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 is a comparison diagram of Fourier infrared spectra of Example 7 of the present invention and Comparative Example 1;

[0054] Figure 2 is a SEM image of the surface of the nanofiltration membrane provided in Example 7 of the present invention;

[0055] Figure 3 This is a SEM image of the nanofiltration membrane surface provided in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0056] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0057] Example 1

[0058] This embodiment provides a method for preparing an anti-pollution nanofiltration membrane, the preparation method comprising the following steps:

[0059] (1) mixing polysulfone (molecular weight of 60000-70000Da, manufactured by Solvay, USA) and N-N-dimethylformamide and stirring and dissolving them at a temperature of 60°C for 7 hours, then keeping the mixture at a temperature of 15°C and standing to degas, to obtain a casting solution, wherein the mass percentage of polysulfone in the casting solution is 18%; applying the casting solution on the surface of a polyester non-woven fabric by a doctor blade to form a film, and then immersing the film in a coagulation bath, wherein the coagulation bath comprises water and N-N-dimethylformamide, wherein the mass percentage of N-N-dimethylformamide in the coagulation bath is 4%, to obtain a base film;

[0060] (2) using piperazine, polyethylene oxide (molecular weight of 50,000 Da, manufactured by BASF, Germany) and water as a reaction water phase, wherein the mass percentage of piperazine is 2%, the mass percentage of polyethylene oxide is 0.1%, and using trimesoyl chloride and n-hexane as a reaction oil phase, wherein the mass percentage of trimesoyl chloride is 0.15%, and using the reaction water phase and the reaction oil phase to perform interfacial polymerization on the base membrane obtained in step (1), wherein the interfacial polymerization process comprises: using a polytetrafluoroethylene frame and a metal clamp to clamp the base membrane, pouring the water phase into the frame so that the side of the base membrane containing polysulfone is in contact with the reaction water phase for 120 seconds, then pouring out the excess water phase, and using a rubber roller to remove the excess water phase on the surface; then pouring the reaction oil phase into the frame so that the side that has been in contact with the reaction water phase is in contact with the reaction oil phase for 60 seconds, then pouring out the excess reaction oil phase, and finally transferring the membrane into an oven at a temperature of 50° C. for heat treatment for 5 minutes to obtain a nanofiltration membrane.

[0061] Example 2

[0062] This embodiment provides a method for preparing an anti-pollution nanofiltration membrane, the preparation method comprising the following steps:

[0063] (1) mixing polysulfone (molecular weight of 60000-70000Da, manufactured by Solvay, USA) and N-N-dimethylformamide and stirring and dissolving them at a temperature of 60°C for 6 hours, then keeping the mixture at a temperature of 100°C and standing to degas, to obtain a casting solution, wherein the mass percentage of polysulfone in the casting solution is 20%; applying the casting solution on the surface of a polyester non-woven fabric by a doctor blade to form a film, and then immersing the film in a coagulation bath, wherein the coagulation bath comprises water and N-N-dimethylformamide, wherein the mass percentage of N-N-dimethylformamide in the coagulation bath is 3%, to obtain a base film;

[0064] (2) using piperazine, polyethylene oxide (molecular weight of 50,000 Da, manufactured by BASF, Germany) and water as a reaction water phase, wherein the mass percentage of piperazine is 0.5%, the mass percentage of polyethylene oxide is 1%, and using trimesoyl chloride and n-heptane as a reaction oil phase, wherein the mass percentage of trimesoyl chloride is 0.07%, and using the reaction water phase and the reaction oil phase to perform interfacial polymerization on the base membrane obtained in step (1), the interfacial polymerization process comprising: using a polytetrafluoroethylene frame and a metal clamp to clamp the base membrane, pouring the water phase into the frame so that the side of the base membrane containing polyethersulfone is in contact with the reaction water phase for 60 seconds, then pouring out the excess water phase, and using a rubber roller to remove the excess water phase on the surface; then pouring the reaction oil phase into the frame so that the side that has been in contact with the reaction water phase is in contact with the reaction oil phase for 120 seconds, then pouring out the excess reaction oil phase, and finally transferring the membrane into an oven at a temperature of 60° C. for heat treatment for 4 minutes to obtain a nanofiltration membrane.

[0065] Example 3

[0066] This embodiment provides a method for preparing an anti-pollution nanofiltration membrane, the preparation method comprising the following steps:

[0067] (1) mixing polysulfone (molecular weight of 60000-70000Da, manufactured by Solvay, USA) and N-N-dimethylacetamide and stirring and dissolving them at a temperature of 60°C for 8 hours, then keeping the mixture at a temperature of 15°C for degassing to obtain a casting solution, wherein the mass percentage of polysulfone in the casting solution is 15%; applying the casting solution on the surface of a polyester non-woven fabric by a doctor blade to form a film, and then immersing the film in a coagulation bath, wherein the coagulation bath comprises water and N-N-dimethylformamide, wherein the mass percentage of N-N-dimethylformamide in the coagulation bath is 2%, to obtain a base film;

[0068] (2) Using piperazine, polyethylene oxide (molecular weight of 50,000 Da, manufactured by BASF, Germany) and water as the reaction water phase, wherein the mass percentage of piperazine is 1.2%, the mass percentage of polyethylene oxide is 2%, and using trimesoyl chloride and isoalkane E as the reaction oil phase, wherein the mass percentage of trimesoyl chloride is 0.02%, and using the reaction water phase and the reaction oil phase to perform interfacial polymerization on the base membrane obtained in step (1), the interfacial polymerization process comprising: using a polytetrafluoroethylene frame and a metal clamp to clamp the base membrane, pouring the water phase into the frame so that the side of the base membrane containing polysulfone is in contact with the reaction water phase for 30 seconds, then pouring out the excess water phase, and using a rubber roller to remove the excess water phase on the surface; then pouring the reaction oil phase into the frame so that the side that has been in contact with the reaction water phase is in contact with the reaction oil phase for 30 seconds, then pouring out the excess reaction oil phase, and finally transferring the membrane into an oven at a temperature of 40° C. for heat treatment for 6 minutes to obtain a nanofiltration membrane.

[0069] Example 4

[0070] This embodiment provides a method for preparing an anti-pollution nanofiltration membrane. The difference between the preparation method and embodiment 1 is that the mass percentage of polyethylene oxide in the reaction water phase is 0.3%.

[0071] Example 5

[0072] This embodiment provides a method for preparing an anti-pollution nanofiltration membrane. The difference between the preparation method and embodiment 1 is that the mass percentage of polyethylene oxide in the reaction water phase is 0.5%.

[0073] Example 6

[0074] This embodiment provides a method for preparing an anti-pollution nanofiltration membrane. The difference between the preparation method and Example 1 is that the mass percentage of polyethylene oxide in the reaction water phase is 0.7%.

[0075] Example 7

[0076] This embodiment provides a method for preparing an anti-pollution nanofiltration membrane. The difference between the preparation method and Example 1 is that the mass percentage of polyethylene oxide in the reaction water phase is 1%.

[0077] Example 8

[0078] This embodiment provides a method for preparing an anti-pollution nanofiltration membrane. The difference between the preparation method and Example 7 is that the mass percentage of polyethylene oxide in the reaction water phase is 3%.

[0079] Comparative Example 1

[0080] This comparative example provides a method for preparing an anti-fouling nanofiltration membrane, which is different from Example 7 only in that polyethylene oxide is not added to the reaction aqueous phase.

[0081] Performance Test:

[0082] (1) Membrane separation performance test: 2 g / L sodium sulfate solution was used as the feed solution, and the separation performance of the prepared nanofiltration membrane was tested using a laboratory self-assembled nanofiltration membrane separation performance test device. The conductivity of the feed solution and the produced water was measured using a conductivity meter, and the salt retention rate of the membrane was calculated. The data of Examples 1-8 are shown in Table 1, and the data of Comparative Example 1 is shown in Table 2.

[0083] (2) Membrane anti-fouling performance test: A 1 g / L bovine serum albumin solution was prepared as the feed solution, and the membrane's anti-fouling performance against bovine serum albumin and the performance recovery after flushing were tested, expressed as flux decrease rate and flux recovery rate. The data of Examples 1-8 are shown in Table 1, and the data of Comparative Example 1 is shown in Table 2.

[0084] Table 1

[0085]

[0086]

[0087] From the data in Table 1, we can see that:

[0088] (1) The data of Examples 1-7 show that the nanofiltration membrane provided by the present invention has good separation performance and anti-pollution performance. Taking the membrane separation performance test of Na2SO4 as an example, under optimal conditions, the Na2SO4 flux of the nanofiltration membrane provided by the present invention can reach 61.9 L / (m 2 ·h·MPa), the Na2SO4 retention rate is above 92.64%. Taking the anti-fouling performance test of bovine serum albumin as an example, the flux decline rate is below 9.30%, and the flux recovery rate is above 88.33%.

[0089] (2) The data of Examples 1 and 4-7 show that the salt flux of the membrane gradually increases and tends to be stable as the concentration of polyethylene oxide in the reaction water phase increases. When the PEO concentration is 1%, the flux and retention rate are both good, and the overall performance is optimal.

[0090] (3) By comparing Example 1 and Example 8, it can be seen that when PEO is excessive, the viscosity of the reaction water phase is too high, which makes it difficult to remove the excess water phase on the surface, resulting in uneven distribution of the surface water phase, defects in the formed polyamide layer, and reduced salt retention rate. In addition, since the defective parts are more susceptible to fouling, the anti-fouling property is not ideal. Therefore, the addition of PEO should not be excessive.

[0091] Table 2

[0092]

[0093]

[0094] Taking the comparison between Example 7 and Comparative Example 1 as an example, it can be seen from the data in Table 2 that in Example 7, by adding polyethylene oxide to the reaction aqueous phase, when the Na2SO4 retention rate is similar, the Na2SO4 flux in Example 1 is more than 3 times that of Comparative Example 1, indicating that the anti-fouling nanofiltration membrane provided by the present invention has excellent membrane separation performance; at the same time, under the same operating conditions, the anti-fouling performance in Example 7 is significantly better than that in Comparative Example 1, which shows that the anti-fouling nanofiltration membrane provided by the present invention also has excellent anti-fouling performance.

[0095] Based on the above data, the comparison of the Fourier transform infrared spectra of the nanofiltration membrane in Example 7 and Comparative Example 1 is shown in the figure below. Figure 1 As shown, from Figure 1 It can be seen that the addition of polyethylene oxide does not cause additional peaks or prominent peak intensity changes in the infrared of the membrane surface, which proves that polyethylene oxide does not participate in the interfacial polymerization and only plays a role in regulating the reaction rate during the entire interfacial polymerization process; the SEM images of the nanofiltration membranes obtained in Example 7 and Comparative Example 1 are shown respectively. Figure 2 and Figure 3 As shown, it can be seen that in Example 7, a regular Turing structure can be formed by adding polyethylene oxide. The appearance of the regular Turing structure is generally considered to be caused by the large difference in the diffusion rate of the two-phase monomers participating in the reaction at the interface. The SEM image proves that the addition of polyethylene oxide causes a large change in the diffusion rate of the water-soluble monomer piperazine, which further confirms that the preparation method provided by the present invention can improve the separation performance and anti-fouling performance of the nanofiltration membrane by adding polyethylene oxide to the reaction water phase.

[0096] In summary, the nanofiltration membrane provided by the present invention has the advantages of high pure water flux, good surface hydrophilicity and strong anti-fouling performance, can operate stably for a long time, and has a simple preparation method, which is conducive to industrial application.

[0097] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing an anti-pollution nanofiltration membrane, characterized in that: The preparation method comprises the following steps: (1) mixing a film-forming material and an organic solvent and dissolving them to obtain a casting solution; sequentially performing film formation and phase conversion on the casting solution on a base material to obtain a base film; (2) using a reaction water phase and a reaction oil phase to perform interfacial polymerization on the base membrane obtained in step (1) to obtain a nanofiltration membrane; A modifier is added into the reaction water phase, and the modifier comprises polyethylene oxide.

2. The preparation method according to claim 1, characterized in that: The film-forming material in step (1) comprises any one of polysulfone, polyethersulfone or polyvinyl chloride or a combination of at least two thereof; Preferably, the mass percentage of the film-forming material in the casting solution is 15-20%; Preferably, the organic solvent in step (1) comprises any one of N N dimethylformamide, N N dimethylacetamide or dimethyl sulfoxide, or a combination of at least two thereof.

3. The preparation method according to claim 1 or 2, characterized in that: The dissolving temperature in step (1) is 60-80°C; Preferably, the dissolution time is 6-8h; Preferably, stirring is performed during the dissolving process; Preferably, after the dissolution, the mixture is kept warm and allowed to stand for degassing.

4. The preparation method according to any one of claims 1 to 3, characterized in that The film-making process in step (1) comprises: using the film-making liquid to apply a doctor blade to the surface of the substrate material to form a film; Preferably, the phase inversion process comprises: immersing the film-formed base material into a coagulation bath to obtain a base film; Preferably, the base material comprises a nonwoven fabric; Preferably, the coagulation bath comprises water; Preferably, NN dimethylformamide is also added to the coagulation bath; Preferably, the mass percentage of N-N-dimethylformamide in the coagulation bath is ≤5%.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The reaction aqueous phase in step (2) comprises water-soluble monomers, polyethylene oxide and water; Preferably, the water-soluble monomer comprises piperazine; Preferably, the mass percentage of the water-soluble monomer in the reaction water phase is 0.5-2%; Preferably, the mass percentage of polyethylene oxide in the reaction water phase is 0.1-2%.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The reaction oil phase in step (2) comprises an oil-soluble monomer and an organic solvent; Preferably, the oil-soluble monomer comprises trimesoyl chloride and / or terephthaloyl chloride; Preferably, the organic solvent in step (2) comprises any one of n-hexane, n-heptane, isoalkane E or isoalkane G, or a combination of at least two thereof; Preferably, the mass percentage of the oil-soluble monomer in the reaction oil phase is 0.01-0.15%.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The interfacial polymerization process in step (2) comprises: contacting the side of the base membrane containing the membrane-forming material with a reaction water phase for 30-120 seconds, and then removing the excess reaction water phase; then contacting the side that has been in contact with the reaction water phase with a reaction oil phase for 30-120 seconds, and then removing the excess reaction oil phase, and finally performing heat treatment to obtain a nanofiltration membrane; Preferably, the heat treatment temperature is 40-60°C.

8. The preparation method according to any one of claims 1 to 7, characterized in that: The preparation method comprises the following steps: (1) mixing a film-forming material and an organic solvent and stirring and dissolving them at a temperature of 60-80° C. for 6-8 hours, wherein the film-forming material comprises any one of polysulfone, polyethersulfone or polyvinyl chloride or a combination of at least two thereof, and the organic solvent comprises any one of N—N dimethylformamide, N—N dimethylacetamide or dimethyl sulfoxide or a combination of at least two thereof, and then keeping the mixture warm and standing to degas, thereby obtaining a casting solution, wherein the mass percentage of the film-forming material in the casting solution is 15-20%; applying the casting solution on the surface of a non-woven fabric by a doctor blade to form a film, and then immersing the non-woven fabric in a coagulation bath to obtain a base film; (2) using a reaction water phase and a reaction oil phase to carry out interfacial polymerization on the base film obtained in step (1), wherein the reaction water phase comprises piperazine, polyethylene oxide and water, the mass percentage of piperazine in the reaction water phase is 0.5-2%, the mass percentage of polyethylene oxide is 0.1-2%, the reaction oil phase comprises an oil-soluble monomer and an organic solvent, the oil-soluble monomer comprises trimesoyl chloride and / or terephthaloyl chloride, and the organic solvent comprises n-hexane, n-heptane, isoparaffin E or isoparaffin Any one or a combination of at least two of the hydrocarbons G, the mass percentage of the oil-soluble monomer in the reaction oil phase is 0.01-0.15%, and the process of interfacial polymerization includes: contacting the side of the base membrane containing the film-forming material with the reaction water phase for 30-120s, and then removing the excess reaction water phase; then contacting the side that has contacted the reaction water phase with the reaction oil phase for 30-120s, and then removing the excess reaction oil phase, and finally performing heat treatment at a temperature of 40-60°C to obtain a nanofiltration membrane.

9. An anti-pollution nanofiltration membrane, characterized in that: The anti-pollution nanofiltration membrane is obtained by the preparation method of the anti-pollution nanofiltration membrane according to any one of claims 1 to 8.

10. A use of the anti-pollution nanofiltration membrane as claimed in claim 9, characterized in that: The anti-pollution nanofiltration membrane is used in the field of water treatment.

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