Pmip / f127 / ta porous membrane and preparation method thereof

Abstract

The application discloses a PMIA / F127 / TA porous membrane and a preparation method thereof. The membrane is prepared by using PMIA polymer as a film-forming main matrix, Pluronic F127 as an additive, and placing the membrane in a TA coagulation bath by adopting the NIPS method. The surface of the membrane presents a uniform, smooth and porous structure, and the cross section of the membrane has a typical asymmetric structure, including a compact epidermis layer on the upper surface, a transition sublayer with finger-like pores and a supporting bottom layer containing a large number of cell cavity structures. With the increase of the Pluronic F127 additive amount, the finger-like sublayer of the membrane gradually changes into a network pore structure composed of connected large pores. Due to the introduction of TA, the segregation phenomenon on the surface of the membrane is improved, the roughness of the film formation is increased, the hydrophilicity is improved, the average pore diameter presents a moderate downward trend, and the porosity presents an upward trend. Therefore, the porous membrane with an ideal pore structure and excellent permeability is prepared.

Description

TECHNICAL FIELD

[0001] The present application relates to a porous membrane, in particular to a PMIA / F127 / TA porous membrane and a preparation method thereof, and belongs to the technical field of novel high-permeability porous membranes. BACKGROUND

[0002] Porous membranes have been widely used in water treatment technology fields such as wastewater reuse, drinking water purification and seawater desalination. Membrane filtration is a high-efficiency, environmentally friendly separation process with very simple operation, and is therefore often used in water purification treatment with high-end requirements. High-efficiency filtration operation in the industrial field requires membrane materials with high flux, effective solute rejection and excellent antifouling performance to meet more economical and efficient water treatment needs. The pore structure and surface properties of the membrane material largely determine the above-mentioned characteristics. Studies have shown that increasing the surface hydrophilicity of the membrane material can improve its wettability and antifouling performance, and increasing the porosity of the membrane with molecular sieving properties can effectively improve the permeability of water. Generally, the porosity of the membrane determines its permeability, and the pore size determines its selectivity, so high permeability and selectivity require high porosity and appropriate pore size distribution. In the development of membranes, phase separation of polymer solutions can control the pore size and shape to meet different application requirements.

[0003] A large number of researches have been put into the prior art to explore several methods that can control the porosity of the membrane. Initially, researchers found that by increasing the solvent and non-solvent affinity, reducing the polymer mass content and increasing the phase separation temperature, the surface porosity and pore size of the membrane can be increased. The adjustment of the surface porosity parameters of the membrane usually uses pore-forming agents and additives in the casting solution. With the progress of research, it has been found that pore-forming agents, such as hydrophilic polymers and amphiphilic block polymers, have different effects on the surface porosity and pore size. Specifically, compared with hydrophilic polymers, amphiphilic block polymers produce higher surface porosity and larger pore size.

[0004] Poly-m-phenylene isophthalamide (PMIA) is a polymer with remarkable characteristics. Compared with traditional membrane materials such as polysulfone (PSF) and polyether sulfone (PES), PMIA exhibits excellent performance due to its unique structure (connected by alternating benzene rings and amide groups in the backbone chain, polar amide groups form a hydrogen bond network to enhance intermolecular forces, and a conjugated system can be formed between benzene rings and amide groups), including excellent mechanical strength, good physical and chemical stability and hydrophilicity, and is widely used in many fields, including but not limited to space suits, flame retardants and films. This material has great application potential and is expected to become the preferred material for membrane manufacturing. In order to further optimize the performance of PMIA membranes, the most common strategy to increase the surface porosity is to increase the exchange rate of the solvent and the non-solvent, but this will lead to an increase in the pore size of the membrane surface.

[0005] Therefore, it is necessary to further study the preparation method of the PMIA polymer membrane with high permeability and high open porosity, so as to obtain the porous membrane with ideal pores and performance, and further promote the application. SUMMARY

[0006] In order to solve the problems in the prior art, the purpose of the present application is to provide a PMIA / F127 / TA porous membrane and a preparation method thereof.

[0007] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0008] The present application first discloses a PMIA / F127 / TA porous membrane, which is prepared by using PMIA polymer as the main matrix for film preparation, Pluronic F127 as an additive, and placing the membrane in a TA coagulation bath, and using the NIPS method.

[0009] Preferably, the cross-section of the porous membrane has a characteristic asymmetric structure, including a tight epidermis layer on the upper surface, a transition sub-layer with finger-like pores, and a support bottom layer containing a large number of cell cavity pores.

[0010] The present application also discloses a preparation method of the PMIA / F127 / TA porous membrane as described above, which comprises the following steps:

[0011] S1, dry the PMIA in an oven, mix lithium chloride and DMAc as a compound solvent system, stir and dissolve at 25 DEG C to form a uniform solution;

[0012] S2, add a certain amount of Pluronic F127 to the solution and continuously stir until the Pluronic F127 is completely dissolved to form a uniform solution;

[0013] S3, add dry PMIA fibers to the mixture solution and place it in an oven at 60-100 DEG C, continuously stir the polymer solution to accelerate dissolution and ensure uniformity;

[0014] S4, cool the polymer solution at 25 DEG C, coat it on a glass plate with a non-woven fabric support substrate, and control the thickness to be 100-180 microns;

[0015] S5, in order to make the film surface get the best porosity, the glass plate coated with nascent polymer film is quickly immersed in TA coagulation bath at 25℃, after 10-60 minutes, the TA solution is carefully removed from the glass plate;

[0016] S6, the film surface is washed with deionized water, and then immersed in NaOH solution (pH=12) for 6-12 hours to effectively dissolve TA on the film.

[0017] S7, the target product PMIA / F127 / TA porous film is prepared and stored in deionized water for standby.

[0018] It should be noted that the solvent used for the dissolution of PMIA polymer here is a complex solvent of DMAc and lithium chloride, because the polarity of DMAc alone is not enough to dissolve PMIA polymer. After adding lithium chloride in DMAc solvent, a solid complex of interaction between Li + and DMAc is formed, which can effectively dissolve PMIA by constructing amine groups through the coordination bond between Li + and PMIA carbonyl group, and the hydrogen bond between Cl - and DMAc.

[0019] Preferably, in the foregoing complex solvent, the mass percentage of lithium chloride is 4%.

[0020] More preferably, in the foregoing step S1, the PMIA fiber is dried in an oven at 90℃ for at least 3 hours.

[0021] More preferably, in the foregoing step S2, the mass percentage of Pluronic F127 in the solution is 0-2.5%.

[0022] More preferably, in the foregoing step S5, the mass percentage of TA in the coagulation bath is 1.0-3.0%.

[0023] The present application has the advantages of:

[0024] (1) The present application adopts the method of combining NIPS and surface forced segregation process to prepare porous film, successfully segregates more Pluronic F127 into the surface pore structure and internal pore structure of PMIA film, and the film presents a typical asymmetric porous structure. With the increase of the amount of Pluronic F127, the finger-like sublayer of the film gradually changes into a network pore structure composed of connected large pores. Due to the surface forced segregation effect of TA, the roughness of the film increases, the hydrophilicity improves, the average pore size shows a moderate downward trend, and the porosity shows an upward trend, thereby increasing the permeability of the film.

[0025] (2) Tannic acid (TA) as coagulation bath additive, which is rich in phenolic hydroxyl groups and can interact with materials through hydrogen bonds, can modify the surface and internal pore structure of polymer membranes. After treatment with 2.0 wt.% TA coagulation bath, the membrane flux reached 1000 L·m -2 ·h -1 Therefore, the present application provides strong theoretical support and guidance for the formulation, design and manufacturing process of PMIA polymer membranes, and can produce porous membranes with ideal pore structure and excellent performance. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 Preparation principle of PMIA / F127 / TA membrane of the present application;

[0027] Figure 2 FTIR of PMIA / F127 / TA membrane of the present application;

[0028] Figure 3 SEM structure of the surface of PMIA / F127 / TA membrane of the present application;

[0029] Figure 4 SEM structure of the cross section of PMIA / F127 / TA membrane of the present application;

[0030] Figure 5 AFM of PMIA / F127 / TA membrane of the present application;

[0031] Figure 6 Water contact angle measurement results of PMIA / F127 / TA membrane of the present application;

[0032] Figure 7 Nanometer CT pore structure and porosity data of PMIA / F127 / TA membrane of the present application;

[0033] Figure 8 Different profile nanometer CT structure of PMIA / F127 / TA membrane of the present application;

[0034] Figure 9 Cross-sectional nanometer CT structure of PMIA / F127 / TA membrane of the present application;

[0035] Figure 10 Pore size distribution of PMIA / F127 / TA membrane of the present application;

[0036] Figure 11 Overall porosity test results of PMIA / F127 / TA membrane of the present application;

[0037] Figure 12Figure 1 shows the pure water flux test results of the PMIA / F127 / TA membrane of the present application, wherein (a) is the membrane flux change at different Pluronic F127 addition contents using deionized water and TA as the coagulation bath, respectively; (b) is the membrane flux change using different TA concentrations as the coagulation bath; (c) is the membrane flux change at different Pluronic F127 addition contents using TA as the coagulation bath. DETAILED DESCRIPTION

[0038] The present application will be described in detail below with reference to the accompanying drawings and specific examples.

[0039] In the present application, the raw materials used are commercially available unless otherwise specified, and the preferred commercially available routes are shown in Table 1 below:

[0040]

[0041] Table 1 Preferred commercially available routes of each raw material

[0042] Figure 1 The flowchart shown is the preparation process of the PMIA / F127 / TA membrane of the present application by NIPS method, and the specific preparation steps are as follows:

[0043] First, dry the PMIA fibers in an oven at 90°C for at least 3 hours. Mix lithium chloride and DMAc accurately and stir to dissolve at 25°C to form a uniform solution.

[0044] Then, add a certain amount of Pluronic F127 to the solution and continue stirring until the Pluronic F127 is completely dissolved.

[0045] Next, add the dried PMIA fibers to the mixture solution and place it in an oven at 90°C. It should be noted that the solvent used to dissolve the PMIA polymer here is a mixture of DMAc and lithium chloride, because DMAc alone is not polar enough to dissolve the PMIA polymer. After adding lithium chloride to the DMAc solvent, an interactive complex is formed between Li + and DMAc, which effectively dissolves the PMIA by utilizing the carbonyl coordination bond between Li + and PMIA, and the hydrogen bond between Cl - and DMAc.

[0046] Continue to stir the polymer solution to accelerate dissolution and ensure uniformity. Then cool the polymer solution at room temperature at 25°C, coat it on a glass plate with a non-woven fabric support substrate, and the thickness is about 150 μm.

[0047] Next, to achieve the best segregation of F127 on the film surface, the glass plates coated with the liquid film were quickly immersed in a TA coagulation bath at 25 °C with TA concentrations of 1.0, 1.5, 2.0, and 3.0 wt.%, respectively. After 10 minutes of immersion, the TA solution was carefully removed from the glass plates. Then, the film surface was washed with deionized water and immersed in a NaOH solution (pH = 12) for 8 hours to effectively dissolve the TA on the film. Finally, the finished film was immersed in deionized water for testing and characterization.

[0048] The preparation steps of Examples 1-8 are basically the same as above, the main difference is the raw materials and the amount of each example (see Table 2 for details).

[0049]

[0050]

[0051] Table 2 Film codes of Examples 1-8 and their corresponding component ratios

[0052] Structural characterization and performance analysis

[0053] (1) Surface chemical structure of the film - FTIR infrared detection

[0054] The surface functional groups of the PMIA / F127 / TA film were analyzed by infrared spectrometer FTIR (Bruker, VERTEX 80V, Germany). Each sample was completely dried before being attached to the infrared test platform for testing. The scanning spectrum ranged from 500 to 4000 cm -1 .

[0055] The surface chemical properties of the film were characterized and analyzed by FTIR, and the results are shown in Figure 2 . The film showed a wide absorption band near 3283 cm -1 , indicating the stretching vibration of the N-H bond in the PMIA structure. The absorption vibration near 1535 cm -1 was attributed to the stretching vibration of the C-N bond, which was another prominent peak in the PMIA structure. The peaks observed in the range of 1564-1078 cm -1 were related to the distortion vibration of the carbon-hydrogen (C-H) bond in PMIA. The absorption intensity of these peaks remained consistent regardless of the concentration of Pluronic F127. This finding indicates that the PMIA / F127 / TA film prepared retains the beneficial chemical structure of PMIA material, enabling it to exhibit the ideal physical and chemical properties of PMIA polymer when used as a film.

[0056] 2884 cm -1The nearby peaks are due to the stretching vibration of C-H groups in Pluronic F127. With the increase of Pluronic F127 content in the membrane, the absorption band intensity at 2884 cm -1 slightly increased. In addition, M1-M5 membranes appeared a distinct peak at 1078 cm -1 , indicating the stretching vibration of C-O functional groups of Pluronic F127. It can be seen that increasing the amount of Pluronic F127 in the casting solution can enhance the absorption band of C-O stretching vibration.

[0057] The above test results show that Pluronic F127 has completely entered the PMIA matrix.

[0058] (2) Microstructure of the membrane - SEM characterization

[0059] In order to carefully evaluate the influence of Pluronic F127 on the development of membrane structure, scanning electron microscopy was used to characterize the morphology and structure of the membrane. Figure 3 The surface microstructure of the prepared membranes is shown, and all the prepared membranes show uniform, smooth and porous surfaces. When the concentration of Pluronic F127 in the casting solution increases, the number and permeability of the surface macropores also increase, and the change of the pore size will be verified by subsequent pore size distribution analysis.

[0060] According to the characterization results, it can be seen that Pluronic F127 can be used as a pore inducer and modifier to effectively improve the average pore size and surface porosity of the membrane. This is mainly because the hydrophilic PEO segment on the Pluronic F127 chain can be segregated into the coagulation bath, thereby helping to form a large number of pores and improve the overall porosity. In addition, the SEM graph shows that there are fibrous particles on the M4 membrane. With the increase of concentration, the incompatibility between Pluronic F127 and PMIA leads to the observed fibrous behavior. Simply put, due to the presence of Pluronic F127 in the casting solution, the membrane structure will undergo minor changes, therefore, the addition of amphiphilic Pluronic F127 may disturb the interaction between the solvent, inorganic salt and polymer, thereby leading to the formation of the above fibrous material.

[0061] Figure 4The cross-sectional morphology of the PMIA / F127 / TA membranes. From the cross-sectional morphology, it can be seen that the membranes have a typical asymmetric structure, including a compact skin layer on the top surface, a transition sublayer with finger-like pores, and a supporting bottom layer containing a large number of cellular pore. One of the main reasons for the formation of this special structure is that during the NIPS process, due to the strong attraction between the non-solvent and the solvent, leading to instantaneous phase separation, a porous cross-sectional structure with multiple pores is formed. In addition, with the increase of Pluronic F127 content, the cross-section of the membrane gradually changes from finger-like sublayer to macropore, becoming irregular and curved, and the connectivity of the macropore is enhanced, which is because the rate of phase separation caused by the self-assembly of amphiphilic block copolymer is increased, increasing the rate of gel bath immersion into the polymer body, leading to the formation of porous structure, in addition to the introduction of TA solution as a forced segregant, further enhancing the segregation of hydrophilic amphiphilic polymer Pluronic F127 on the surface and internal pore structure of the membrane, further promoting the increase of membrane porosity, thereby improving the permeability of the membrane, which will be verified by subsequent permeation flux test.

[0062] The connectivity between the porous structures of the membranes of the present application is enhanced, thanks to the segregation effect of Pluronic F127 and the forced segregation effect brought by the introduction of TA, and the development of the pore structure effectively improves the permeability of the membrane. With the increase of Pluronic F127 concentration, the thickness of the membrane gradually increases, which is mainly due to the addition of amphiphilic block copolymer which greatly improves the viscosity of the cast polymer solution, thereby increasing the thickness of the membrane. The specific membrane thickness measured is shown in Table 3.

[0063] Serial number Pluronic F127 content (wt. %) Film thickness (μm) Example 1 0 164.4±5.59 Example 2 1 176.6±5.27 Example 3 1.5 179.4±7.33 Example 4 2 181.0±4.30 Example 5 2.5 186.2±0.84

[0064] Table 3 Thickness of PMIA / F127 / TA membranes

[0065] (3) Surface morphology and properties of the membrane

[0066] The topography of the membrane surface was characterized and evaluated by atomic force microscopy AFM ((Dimension FastScan, Bruker, Germany). As shown in Figure 5 The three-dimensional atomic force microscope images of the membrane surface are shown, and the corresponding roughness values of the membrane surface are listed in Table 4 below.

[0067] Film number R a (nm) R max (nm) R q (nm) M1 11.77±0.12 125.67±19.73 15.03±0.47 M2 13.70±0.36 130.33±9.61 17.47±0.65 M3 16.10±0.60 141.67±11.72 20.03±0.85 M4 17.97±2.66 181.00±56.72 22.93±2.48 M5 21.03±3.12 169.00±8.50 26.20±3.24

[0068] Table 4 Surface roughness values of PMIA / F127 / TA membranes

[0069] The results showed that, with TA as a forced surface segregation coagulation bath additive, the surface roughness of the film increased with increasing Pluronic F127 concentration, from 11.77 ± 0.12 nm to 21.03 ± 3.12 nm. This observation is consistent with... Figure 3 The scanning electron microscope results shown are consistent. After analysis, we believe that the increase in roughness can be attributed to the following factors: (1) When Pluronic F127 is used as a pore-forming modifier, it may greatly increase the size and porosity of the membrane, thereby increasing its roughness; (2) Pluronic F127 undergoes surface segregation during the NIPS process. Due to the low interfacial energy between water molecules and hydrophilic bulk PEO, hydrophilic PEO segments migrate to the overlap between the membrane surface and the inner pore wall, thereby increasing the surface roughness of the membrane; (3) When TA is used as a coagulation bath, it further promotes the segregation of Pluronic F127, especially in the subsequent NaOH post-treatment process, which further enhances the surface pore structure of the membrane; In addition, the increase of Pluronic F127 in the casting solution may also lead to an increase in membrane roughness, which may be due to the formation of fibrous structures, such as Figure 3 The SEM surface image is shown in the image.

[0070] The hydrophilicity of the membrane surface is crucial to its antifouling ability; therefore, the water contact method was further employed to investigate changes in membrane hydrophilicity. Figure 6 As shown, the water contact angle of the M1 membrane is 70.0±1.06°, exhibiting a certain degree of hydrophilicity. This is mainly due to the amino groups contained in the PMIA polymer itself and the hydrogen bonding forces between the PMIA polymer molecular chains, which provide a certain degree of hydrophilicity to the PMIA matrix. However, when the content of Pluronic F127 increases to 2.5 wt.%, the water contact angle decreases from 70.0±1.06° to 60.9±1.56°, and the membrane surface shows a more hydrophilic trend. This may be because during the NIPS diffusion process, the introduction of TA as a coagulation bath, and the segregation of more hydrophilic segments of Pluronic F127 to the membrane surface, thereby increasing the membrane's hydrophilicity.

[0071] The above analysis results indicate that the addition of Pluronic F127 copolymer, in conjunction with TA as a coagulation bath and the NaOH post-treatment process, can significantly improve the hydrophilicity of the membrane material.

[0072] (4) Nano-CT structure of PMIA / F127 / TA film

[0073] Nano-CT is a technique that creates high-resolution three-dimensional (3D) images of materials at the nanoscale, providing detailed views of objects millions of times smaller than millimeters. It is used to assess the structural features of membrane surfaces and their interiors with extremely high precision.

[0074] Figure 7 Nanometer CT pore structure diagram and porosity data of PMIA / F127 / TA membrane, Figure 8 Different profile nanometer CT structure diagram of PMIA / F127 / TA membrane, Figure 9 Cross-section nanometer CT structure diagram of PMIA / F127 / TA membrane, which clearly shows that the porosity of the surface of the M4 membrane (2% of Pluronic F127) increases from 82.00% to 85.71% compared with the M1 membrane (without Pluronic F127), which is due to the presence of Pluronic F127 as a pore generator, and due to the TA as a coagulation bath additive, together with NaOH post-processing, the development trend of the pore structure is improved.

[0075] The study also shows that the concentration of TA in the coagulation bath also has an important influence on the porosity of the membrane, among 1wt.% (M6), 2wt.% (M4) and 3wt.% (M8), the porosity of the membrane increases from 84.89% to 85.71% and finally significantly increases to 90.09%, which shows that the introduction of TA, together with NaOH post-processing, can effectively improve the segregation rate of Pluronic F127 in the phase inversion process through forced segregation, and the TA etched by NaOH post-processing also contributes a lot to the improvement of the porosity of the membrane.

[0076] The pore structure distribution characteristics of the membrane are crucial to the separation efficiency of the membrane. Figure 10 The pore size distribution of the PMIA / F127 / TA membrane is shown, when the amount of Pluronic F127 increases, the average size of the membrane pores shows a trend of first increasing and then decreasing, overall, without adding and adding at a high concentration, the pore size of the membrane decreases from 0.25±0.02 μm to 0.22±0.03 μm, showing a moderate downward trend. It can be seen that the PMIA / F127 / TA membrane constructed by the preparation method of the present application has a consistent pore structure, which helps to improve the selectivity and permeability of the membrane.

[0077] Further, the overall porosity data of the membrane is tested by using the "dry and wet weight method", and the test results are as follows Figure 11As shown, the porosity of the membranes increased from 59.84 ± 4.23% to 62.44 ± 1.13% with the increase of Pluronic F127. Pluronic F127 can be used as a surface segregant to improve the affinity between the membrane surface and water molecules through the surface segregation process. During the entire NIPS process, the membrane matrix has the ability to attract more water molecules, resulting in the expansion of the membrane pores. This expansion leads to an increase in the size and permeability of the membrane pores. At the same time, the introduction of TA as a component of the coagulation bath improves the segregation efficiency, and the subsequent etching treatment with NaOH further improves the pore structure. In addition, due to the self-assembly of the block copolymer, micelles are formed in the casting solution, which affects the affinity between the solvent and the block copolymer, resulting in the formation of more pore structures during the separation process. In summary, the addition of Pluronic F127, the use of TA as a component of the coagulation bath, and the subsequent etching treatment all bring synergistic gain effects to the development of the membrane porous structure.

[0078] (6) Filtration performance of PMIA / F127 / TA membranes

[0079] The separation and permeability of the membrane are key performance of the membrane, therefore, the present application measured the change of pure water flux of various PMIA / F127 / TA membranes under different Pluronic F127 additive contents, different coagulation bath types, and different coagulation bath compositions, and the results are shown in Figure 12 (a) is the change of membrane flux under different Pluronic F127 additive contents using deionized water and TA as coagulation bath, respectively; (b) is the change of membrane flux using different TA concentrations as coagulation bath; (c) is the change of membrane flux under different Pluronic F127 additive contents using TA as coagulation bath.

[0080] From Figure 12 (a) can be seen, with the increase of Pluronic F127 content, the membrane flux using water and TA as coagulation bath is gradually increased, but the membrane permeation flux using TA as coagulation bath is higher, which shows that the introduction of TA effectively promotes the formation and development of membrane pore structure, thereby improving the permeability of the membrane. Figure 12(b) The influence of different TA concentrations in the coagulation bath on the membrane flux was investigated. As shown in the figure, the permeation performance of the membrane was significantly improved as the TA concentration increased from 1% to 2%, which was mainly due to the introduction of TA, which improved the surface segregation degree of F127 in the membrane, promoted the phase separation rate, and increased the number of membrane openings. When 3% TA was introduced into the coagulation bath, it was found that the flux of the membrane decreased compared to the 2% concentration, which was mainly due to the introduction of too much TA, which increased the viscosity of the coagulation bath, to some extent, limited the phase separation rate, and thus affected the membrane formation rate and the growth and development speed of the pores, resulting in a decrease in flux. However, the membrane flux generated by 3% TA was still higher than that of 1.5% TA concentration.

[0081] When the weight percentage of Pluronic F127 increased to 2.0%, the pure water flux of the PMIA / F127 / TA membrane increased from 586.20±38.63L·m -2 ·h -1 to 1073.70±77.85L·m -2 ·h -1 , which was mainly due to the change in pore structure having a significant impact on the membrane water flux, and the addition of high concentration of Pluronic F127 would lead to an increase in membrane porosity and pore size. Therefore, the resistance of water molecules flowing through the membrane pores decreased, allowing a large number of water molecules to enter the membrane, i.e. the water permeability of the membrane was improved. In addition, the addition of Pluronic F127 in the membrane also enhanced the hydrophilicity of the membrane, and at the same time, the PEO segment could attract more water molecules and retain them in the membrane matrix, greatly improving the permeability of the membrane.

[0082] In the present application, the permeability enhancement achieved by using Pluronic F127 additive, TA promotes the occurrence rate of phase separation by forced segregation, and improves the opening number and pore structure of the membrane surface and internal structure, which can promote the segregation phenomenon of Pluronic F127, thereby improving the phase inversion rate of the membrane formation process, promoting the improvement of membrane porosity, and improving the hydrophilic property of the membrane. The above beneficial effects further improve the membrane flux. The preparation method of the present application is expected to save a lot of energy in membrane application and greatly reduce the input cost and application cost of the membrane.

[0083] In summary, the porous membrane is prepared by the method of combining NIPS and surface forced segregation process, Pluronic F127 is successfully segregated to the surface pore structure and internal pore structure of PMIA membrane, and the membrane presents a typical asymmetric porous structure. In the case of TA as coagulation bath additive, with the increase of the addition amount of Pluronic F127, the finger-like sublayer of the membrane gradually changes into a network pore structure composed of connected large pores, due to the forced segregation effect of TA, the roughness of the membrane increases, the hydrophilicity improves, the pore structure develops, the average pore size increases first and then decreases with the increase of the addition amount of Pluronic F127, and in the case of no addition and high concentration addition, it presents a moderate downward trend, the porosity presents an upward trend, and then the permeability of the membrane increases.

[0084] Further, after being treated in a 2.0wt.% TA bath, the membrane flux is as high as 1073.70±77.85 L·m -2 ·h -1 The present application provides strong theoretical support and guidance for the formula, design and manufacturing process of PMIA polymer membrane, and can produce porous membranes with ideal pore structure and performance.

[0085] The basic principles, main features and advantages of the present application are shown and described above. Those skilled in the art should understand that the above examples do not limit the present application in any form, and any technical solutions obtained by equivalent replacement or equivalent transformation fall within the protection scope of the present application.

Claims

1. A method for preparing a PMIA / F127 / TA porous membrane, characterized by, The PMIA polymer is used as a film-forming main matrix, Pluronic F127 is used as an additive, and the film is placed in a TA coagulation bath, and a NIPS method is used to prepare the film, and the surface of the film presents a uniform, smooth and porous structure; the cross section of the porous film has a typical asymmetric structure, including a tight epidermis layer on the surface, a transition sublayer with finger-shaped pores, and a supporting bottom layer containing a large number of cell cavities, including the following steps: S1, dry the PMIA in an oven, mix lithium chloride and DMAc as a compound solvent system, the addition amount of LiCl is 4%, and the solution is stirred and dissolved at 25 DEG C to form a uniform solution; S2, a certain amount of Pluronic F127 is added to the solution, and stirring is continuously carried out until the Pluronic F127 is completely dissolved to form a uniform mixture solution; S3, dry PMIA fibers are added to the mixture solution, and the polymer solution is formed by continuously stirring in an oven at 60-100 DEG C, so as to accelerate the dissolution and ensure uniformity; S4, the polymer solution is cooled at 25 DEG C, coated on a glass plate with a non-woven fabric support substrate, and the thickness is controlled to be 100-180 μm; S5, the glass plate coated with the nascent polymer film is quickly immersed into the coagulation bath containing TA at 25 DEG C, and after soaking for 10-60 minutes, the TA solution is carefully removed from the glass plate; S6, the film surface is washed with deionized water, and then immersed in a NaOH solution for 6-12 hours to effectively dissolve the TA on the film. S7, the target product PMIA / F127 / TA porous membrane is prepared, and stored in deionized water for standby, and the permeation flux of the porous membrane is up to 1073.70±77.85 L·m -2 ·h -1 .

2. The method of claim 1, wherein the PMIA / F127 / TA porous membrane is prepared by the steps of: In the step S1, the PMIA fibers are dried in an oven at 90 DEG C for at least 3 hours.

3. The method of claim 1, wherein the PMIA / F127 / TA porous membrane is prepared by the steps of: In the step S1, the mass percentage of lithium chloride in the compound solvent of lithium chloride and DMAc is 4%.

4. The method of claim 1, wherein the PMIA / F127 / TA porous membrane is prepared by the steps of: In the step S2, the mass percentage of Pluronic F127 in the solution is 0-2.5%.

5. The method of claim 1, wherein the PMIA / F127 / TA porous membrane is prepared by the steps of: In the step S5, the mass percentage of TA in the coagulation bath is 1.0-3.0 %.

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