Interface in-situ assembled gel and nanoparticle composite polyether sulfone membrane as well as preparation and application thereof

Abstract

The invention discloses an interface in-situ assembled gel and nanoparticle composite polyether sulfone membrane as well as preparation and application thereof, and belongs to the technical field of nano material and membrane separation. According to the invention, a gel and nanoparticle composite structure is constructed in situ on the surface of the membrane and in pores through a phase separation strategy for the first time, a gel layer of a main body is formed by crosslinking polyphenol and zirconium oxychloride, and nanoparticles are formed by complexing unoccupied sites of polyethyleneimine and polyphenol; a nucleation site is provided for in-situ construction of the gel layer on the surface. Compared with a surface modification post-treatment method, the method disclosed by the invention has the advantages of process integration, coating stability and the like; compared with a mixed matrix membrane constructed by zeolite and carbon nanotubes, agglomeration and polymer embedding are avoided, and a coating constructed by mixing hydrophilic gel and nanospheres can be formed on the surface of the polymer.

Description

TECHNICAL FIELD

[0001] The application relates to an interface in-situ assembled gel and nanoparticle composite polyether sulfone membrane and preparation and application, and belongs to the technical field of nanomaterials and membrane separation. BACKGROUND

[0002] Hydrophilic separation membranes can greatly weaken the water molecule transmission resistance and effectively inhibit the adhesion of hydrophobic pollutants (such as oils, proteins and colloids) on the membrane surface, thereby having high permeation flux and excellent anti-pollution properties. However, the current dominant market polymer separation membranes are mainly prepared by phase separation method. Although this method is mature and efficient, the surface of the obtained membrane often presents inherent hydrophobicity or insufficient hydrophilicity. In order to endow the membrane with ideal hydrophilicity and anti-pollution ability, additional post-processing steps of coating or grafting must be carried out.

[0003] For example, patent CN101966433A discloses uniformly depositing a polyvinyl alcohol or polyvinylpyrrolidone aqueous solution on the surface of an ultrafiltration membrane, and forming a hydrophilic ultrafiltration membrane by crosslinking with glutaraldehyde or ammonium persulfate; Patent CN104998562A discloses a method of grafting hydrophilic polyacrylic acid and metal titanium ions onto the surface of polytetrafluoroethylene by plasma grafting, and the contact angle is reduced to 35° to 99.5°. These methods for constructing a hydrophilic interface by post-processing steps all have problems such as complex process and poor stability of the modified layer, which significantly restricts the large-scale preparation and application potential of high-performance hydrophilic membranes; Patent CN114984784A discloses adding surface-modified hydrophilic methyl acrylate diethylaminoethyl methacrylate (PDEAEMA) titanium dioxide nanotubes into a polysulfone casting solution to prepare a hydrophilic hybrid polysulfone membrane; however, the particles are prone to aggregation and migration, and it is difficult to form a uniform and firm nanoscale functional layer at the membrane-pore interface.

[0004] Therefore, it is urgent to develop a method capable of in-situ assembling and stably anchoring hydrophilic nanostructures on the membrane surface and in the pores in the dynamic interface change environment induced by the phase separation process, so as to efficiently obtain an advanced separation membrane with high permeability, strong anti-pollution property and long-term stability in one step. SUMMARY

[0005] [TECHNICAL PROBLEM] Constructing a hydrophilic layer by post-processing steps all have problems such as complex process and poor stability of the modified layer; Adding nanoparticles to construct a hydrophilic layer, but the nanoparticles are prone to aggregation and migration, and it is difficult to form a uniform and firm nanoscale functional layer at the membrane-pore interface.

[0006] [TECHNICAL SCHEME] To solve the above problems, the application provides an interface in-situ assembled gel and nanoparticle composite polyether sulfone membrane and preparation and application. Specifically, the application first constructs a gel and nanoparticle composite structure on the membrane surface and in the pore channel in-situ through a phase separation strategy. The main gel layer is formed by cross-linking of polyphenol and zirconium oxychloride, and the nanoparticles are formed by complexing of polyethyleneimine and the free sites of polyphenol, which provides nucleation sites for the in-situ construction of the gel layer on the surface. Compared with a post-processing method of surface modification, the method has the advantages of process integration and stable coating; compared with a mixed matrix membrane constructed by zeolite and carbon nanotube, the application avoids agglomeration and polymer embedding, and can form a coating layer on the polymer surface which is constructed by hydrophilic gel and nanospheres.

[0007] A first object of the application is to provide a method for preparing an interface in-situ assembled gel and nanoparticle composite polyether sulfone membrane, comprising the following steps: (1) heating a polyether sulfone solution to 155-165°C, adding polyethyleneimine, and uniformly mixing to obtain a casting solution precursor solution; wherein the mass ratio of polyethyleneimine to polyether sulfone is 0.25-0.4:3; (2) mixing a polyphenol solution and a zirconium oxychloride solution, oscillating and mixing in a vortex oscillator until a dark yellow gel-like substance is formed, and dispersing by ultrasonic bombardment to obtain a gel precursor solution; (3) under stirring, adding the gel precursor solution drop by drop into the casting solution precursor solution, and standing and degassing to obtain a casting solution; (4) casting the casting solution into a membrane, and drying to obtain an interface in-situ assembled gel and nanoparticle composite polyether sulfone membrane.

[0008] In an embodiment of the application, the solvent of the polyether sulfone solution in step (1) comprises one or more of N,N-dimethylformamide, N,N'-dimethylacetamide and N-methylpyrrolidone, and the concentration is 10-20% g / 100 mL.

[0009] In an embodiment of the application, the heating to 155-165°C in step (1) is to make the solution present in a clear and transparent state.

[0010] In an embodiment of the application, the polyethyleneimine in step (1) is linear or branched, and the molecular weight is less than 100000.

[0011] In an embodiment of the application, the solvent of the polyphenol solution in step (2) is one or more of N,N-dimethylformamide, N,N'-dimethylacetamide and N-methylpyrrolidone, and the concentration is 30-40% g / 100 mL.

[0012] In one embodiment of the present application, the polyphenol in step (2) is one or more of tannic acid, phenolic acid, flavonoids, lignan, stilbenes and the like.

[0013] In one embodiment of the present application, the solvent of the zirconium oxychloride solution in step (2) is one or more of N,N-dimethylformamide, N,N'-dimethylacetamide and N-methylpyrrolidone, and the concentration is 5-10% g / 100 mL.

[0014] In one embodiment of the present application, the volume ratio of the polyphenol solution and the zirconium oxychloride solution in step (2) is 2: (0.5-1).

[0015] In one embodiment of the present application, the time for ultrasonic dispersion in step (2) is 30-60 min.

[0016] In one embodiment of the present application, the stirring speed in step (3) is 100-200 rpm.

[0017] In one embodiment of the present application, the volume ratio of the gel precursor solution and the casting solution precursor solution in step (3) is 3-5:20.

[0018] In one embodiment of the present application, the dropwise addition in step (3) is performed using a pipette to add 200-300 μL of the polyphenol gel solution each time, and mechanical stirring is performed at a speed of 120 rpm for 50-70 s between each dropwise addition to fully mix the casting solution.

[0019] In one embodiment of the present application, the time for standing and degassing in step (3) is 12-24 h.

[0020] In one embodiment of the present application, the film formation by flow casting in step (4) is performed by pouring the casting solution into a mold, and then uniformly spreading the solution by scraping, and then placing the mold in a coagulation bath for coagulation; wherein the doctor blade is 200-300 μm, the scraping temperature is 50-70 °C, and the humidity is 50-80%; the coagulation bath is a mixed solution of organic solvent and water at a volume ratio of 7:3, the organic solvent is one or more of N,N-dimethylformamide, N,N'-dimethylacetamide and N-methylpyrrolidone; and the coagulation is performed at 20-30 °C for 5-20 min.

[0021] In one embodiment of the present application, after the film formation in step (4), the film is stored in deionized water to remove residual solvent.

[0022] In one embodiment of the present application, the drying in step (4) is natural air drying.

[0023] The second object of the present application is the interface in-situ assembled gel and nanoparticle composite polyether sulfone membrane prepared by the method of the present application.

[0024] The third object of the present application is the application of the interface in-situ assembled gel and nanoparticle composite polyether sulfone membrane of the present application in water treatment.

[0025] The fourth object of the present application is to provide a method for improving the permeability, anti-fouling property and long-term stability of polyether sulfone membrane, comprising the following steps: (1) heating the polyether sulfone solution to 155-165℃, gradually adding polyethyleneimine, and mixing uniformly to obtain a casting solution precursor solution; wherein the mass ratio of polyethyleneimine to polyether sulfone is 0.25-0.4:3; (2) mixing the polyphenol solution and the zirconium oxychloride solution, oscillating and mixing in a vortex oscillator until a dark yellow gel-like substance is formed, and dispersing by ultrasonic bombardment to obtain a gel precursor solution; (3) under stirring, adding the gel precursor solution drop by drop into the casting solution precursor solution, and standing and degassing to obtain a casting solution; (4) casting the casting solution into a membrane, and drying to obtain the interface in-situ assembled gel and nanoparticle composite polyether sulfone membrane.

[0026] The fifth object of the present application is to provide a method for adsorbing and separating metal ions, which adopts the interface in-situ assembled gel and nanoparticle composite polyether sulfone membrane of the present application.

[0027] In an embodiment of the present application, the metal ions are heavy metals, specifically including one or more of copper ions, vanadium ions, lead ions, indium ions, zirconium ions, titanium ions, platinum ions, mercury ions, cadmium ions, iron ions and lanthanum ions.

[0028] In an embodiment of the present application, the method for adsorbing and separating metal ions comprises the following steps: placing the interface in-situ assembled gel and nanoparticle composite polyether sulfone membrane in a filter, pushing the liquid to be treated through the membrane by a peristaltic pump, after the treatment is completed, immersing the interface in-situ assembled gel and nanoparticle composite polyether sulfone membrane in an acid solution to adsorb metal ions, after the adsorption of metal ions is completed, taking out the interface in-situ assembled gel and nanoparticle composite polyether sulfone membrane, and washing with deionized water before the next use.

[0029] The sixth object of the present application is to provide a method for adsorbing and recovering metal ions, which adopts the interface in-situ assembled gel and nanoparticle composite polyether sulfone membrane of the present application.

[0030] In an embodiment of the present application, the metal ions are heavy metals, specifically including Cu 2+ , Pb2+ Fe 3+ one or more of the group consisting of Fe

[0031] In one embodiment of the present application, the recovery is carried out in an acid solution.

[0032] In one embodiment of the present application, the method for adsorbing and recovering metal ions comprises the following steps: The interface in-situ assembled gel and nanoparticle composite polyether sulfone membrane is placed in a filter, the liquid to be treated is pushed through the membrane by a peristaltic pump, after the treatment is completed, the interface in-situ assembled gel and nanoparticle composite polyether sulfone membrane is soaked in an acid solution to recover metal ions, after the recovery of metal ions is completed, the interface in-situ assembled gel and nanoparticle composite polyether sulfone membrane is taken out, washed with deionized water, and then used next time.

[0033] [Advantages] (1) Principle of the present application: In the process of phase separation, the non-solvent and the solvent exchange sharply, and smaller chains or smaller groups tend to move to the interface faster. The polyphenol substance is classified as a small molecule according to the molecular weight, and has high hydrophilicity and metal chelating ability, and tends to migrate to the surface of the polymer and the solvent in the process of phase separation, and will not be embedded in the polymer. However, the surface of the polymer lacks nucleation sites, and the polyphenol is easy to precipitate without being attached to the surface of the high molecular polymer.

[0034] However, the complexation between the polyphenol and the water-soluble macromolecule provides a feasible scheme for anchoring on the surface of the polymer. The Michael addition reaction occurs between the polyethyleneimine and the polyphenol to form nanoparticles, and the covalent interaction between the nanoparticles can realize the fixation of the polyphenol to the interface without precipitating into the non-solvent. By adding the macromolecular polyethyleneimine into the casting solution, a state of physical blending of the high molecular polymer and the macromolecular polyethyleneimine is formed. In order to form a gel-like hydrated layer on the interface, a polyphenol-metal gel is formed in advance by deep crosslinking between the polyphenol and the zirconium oxychloride, and then the gel is added into the casting solution.

[0035] According to the above principle, a gel and nanoparticle composite structure is constructed in-situ on the surface and in the pores of the membrane by the phase separation strategy. The main gel layer is formed by the crosslinking of the polyphenol and the zirconium oxychloride, and the nanoparticles are formed by the complexation of the polyethyleneimine and the free sites of the polyphenol, which provides nucleation sites for the in-situ construction of the gel layer on the surface.

[0036] (2) The present application constructs a coating structure composed of a polyphenol-metal gel and a polyphenol-polyethyleneimine nanoparticle composite on the surface of the original polyether sulfone membrane and in the pores, which has high hydrophilicity and metal ion capturing ability. Compared with the prior art, the advantages of the present application are: The gelation reaction of polyphenol and zirconium oxychloride, and the Michael addition reaction of polyphenol and polyethyleneimine are combined, nanoparticles and gelation composite structures are modified on the surface and internal pores of the membrane, the surface and internal pores of the membrane are simultaneously super-hydrophilic modified, and the membrane permeation flux and anti-pollution performance are improved; The stable anchoring of polyphenol gel and nanoparticles on the surface and internal pores of the membrane realizes the chemical customization of the metal ion capture layer on the surface and internal pores of the membrane, and can be used for high-capacity and high-flux metal ion adsorption and separation. Prepared by one-step phase inversion method, can be carried out by using conventional equipment and method, without any post-treatment step, easy to realize industrialization.

[0037] (3) The key problem of the application is how to form a mixed structure of polyphenol gel and nanoparticles on the interface of the surface and internal pores of the polymer. In the phase separation process, polyethyleneimine plays a key role in anchoring the polyphenol gel on the interface, and the free sites of polyphenol simultaneously form nanoparticles with polyethyleneimine. Therefore, the appropriate molar ratio between polyethyleneimine and polyphenol is needed to realize the growth on the interface of the whole pores. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 It is a scanning electron microscope image of the membrane in Example 1; wherein A is a surface image, B is a cross-sectional image, and C is a detailed magnified image of the internal pores of the membrane.

[0039] Figure 2 It is a scanning electron microscope image of the membrane in Example 2; wherein A is a surface image, B is a cross-sectional image, and C is a detailed magnified image of the internal pores of the membrane.

[0040] Figure 3 It is a scanning electron microscope image of the membrane in Example 3; wherein A is a surface image, B is a cross-sectional image, and C is a detailed magnified image of the internal pores of the membrane.

[0041] Figure 4 It is a scanning electron microscope image of the membrane in Example 4; wherein A is a surface image, B is a cross-sectional image, and C is a detailed magnified image of the internal pores of the membrane.

[0042] Figure 5 It is a scanning electron microscope image of the membrane in Comparative Example 1; wherein A is a surface image, B is a cross-sectional image, and C is a detailed magnified image of the internal pores of the membrane.

[0043] Figure 6 It is a contact angle measuring instrument image of the membrane in Example 1.

[0044] Figure 7 It is a contact angle measuring instrument image of the membrane in Example 2.

[0045] Figure 8Contact angle goniometer image of the film in Example 3.

[0046] Figure 9 Contact angle goniometer image of the film in Example 4.

[0047] Figure 10 Contact angle goniometer image of the film in Comparative Example 1.

[0048] Figure 11 Image of the water contact angle of the film in Example 3 changing with time; wherein (a) is 0s; (b) is 0.1s; (c) is 0.3s; (d) is 0.5s.

[0049] Figure 12 Scanning electron microscope image of the film in Comparative Example 4; wherein A is a surface image, B is a cross-sectional image, and C is a detailed magnified image of the internal pore of the film.

[0050] Figure 13 Scanning electron microscope image of the film in Comparative Example 5; wherein A is a surface image, B is a cross-sectional image, and C is a detailed magnified image of the internal pore of the film.

[0051] Figure 14 Scanning electron microscope image of the film in Comparative Example 6; wherein A is a surface image, B is a cross-sectional image, and C is a detailed magnified image of the internal pore of the film. DETAILED DESCRIPTION

[0052] The following describes preferred embodiments of the present application, and it should be understood that the embodiments are for better explaining the present application and are not intended to limit the present application.

[0053] Test method: 1. Test method for hydrophilicity of the film: Hydrophilicity is tested by a contact angle goniometer (OCA). The smaller the contact angle, the higher the degree of hydrophilization.

[0054] 2. Test method for permeation flux of the film: Permeation flux is represented by pure water flux J. The water volume passing through a unit membrane area in a certain time is measured by dead-end filtration. Flux (J): water volume per unit membrane area (A) per unit time (t).

[0055] The specific calculation formula is as follows:

[0056] 3. Test method for anti-pollution performance: 1000mg / L humic acid (HA) is used as a pollutant to test the anti-pollution performance by dead-end filtration. The test steps are as follows: (1) The film is fixed in a customized filter, and the initial water flux J0 of the film is tested; (2) Change the feed solution to humic acid, pass through the membrane for 60 minutes, then clean with deionized water by passing through the membrane; (3) Repeat step (2) for 10 times, test the pure water flux J after 10 times of pollution-cleaning cycle 10 The anti-pollution performance is characterized by flux recovery rate (FRR) and single flux decay rate (FDR); The formula is as follows:

[0057] Wherein, J w1 and J w2 respectively represent the pure water flux of single pollution experiment.

[0058]

[0059] Wherein, J1and J s respectively represent the pure water flux before the first experiment and the pure water flux after the s-th experiment.

[0060] 4. The membrane adsorption performance test for metal ions is carried out in the following manner Removal efficiency experiment: The concentration of all metal solutions (Cu 2+ , Pb 2+ , Fe 3+ , K + , Ca 2+ , Na + , Mg 2+ , etc.) is 100 ppb, the solution volume is 1 L, and the pH is adjusted to 5. Circulating water is carried out in the filter for 24 h.

[0061] The solution pH is adjusted to 5 with standard HCl and NaOH solution, and the adsorption is shaken on a shaker for 24 hours. 1 mL of water sample is taken out before and after the start of adsorption, and the concentration is measured by ICP-MS, and then the adsorption amount and removal rate before and after adsorption are calculated.

[0062] The adsorption amount (qe) of the membrane is calculated by the following formula: qe = V(C0 - Ce) / m In the formula, V is the solution volume, C0is the initial concentration, Ceis the final concentration, and m is the mass of the membrane.

[0063] Raw materials used in the examples: Polyethyleneimine: CAS: 9002-98-6, linear type; purchased from the Macron company; molecular weight is 70000, purity is greater than 99%, 50%wt in H2O; Polyphenol (Tannic acid): purchased from Shanghai Aladdin Bio-Chem Technology Co., Ltd.; CAS: 1401-55-4, purity of ACS grade; Zirconium oxychloride: Zirconium oxychloride octahydrate, CAS: 13520-92-8, purity of more than 98%, purchased from Shanghai Aladdin Bio-Chem Technology Co., Ltd.; N,N-dimethylformamide: CAS: 68-12-2, purity of AR, ≥99.5%, purchased from Shanghai Aladdin Bio-Chem Technology Co., Ltd.; Other raw materials used in the examples and comparative examples are all conventional raw materials, which can be purchased on the market.

[0064] The reaction temperature not specifically indicated in the examples and comparative examples refers to normal temperature (20-30℃) reaction.

[0065] Example 1 A method for preparing an interface in-situ assembled gel and nanoparticle composite polyether sulfone membrane, comprising the following steps: (1) 3g of polyether sulfone powder and 20ml of N,N-dimethylformamide were added into a three-necked flask, and the mixture was heated in a water bath at 160℃ with continuous stirring at 120rpm until a clear and transparent solution was formed. Then 0.1g of polyethyleneimine was gradually added and continuously stirred until completely dissolved, to obtain a casting solution precursor solution; (2) 8g of tannic acid was dissolved in 25mL of N,N-dimethylformamide to obtain a tannic acid solution; 2.5g of zirconium oxychloride was dissolved in 25mL of N,N-dimethylformamide to obtain a zirconium hydroxide solution; 2mL of the tannic acid solution and 1mL of the zirconium oxychloride solution were mixed and oscillated in a vortex oscillator until a dark yellow gel-like substance was formed, which was dispersed in an ultrasonic generator for 45min to obtain a gel precursor solution; (3) Under the condition of 120rpm stirring, 3mL of the gel precursor solution was added into 20mL of the casting solution precursor solution by a pipette, and the amount of each addition was 250 microliters, with an interval of about 1 minute between each addition, to ensure that the whole process of the casting solution was clear without aggregation. The casting solution was deaerated for 24h to obtain a casting solution; (4) The casting solution was poured into a glass substrate, and a 250μm doctor blade was used for continuous and uniform coating of a liquid film at 60℃ and 70% humidity. The glass substrate loaded with the liquid film was immersed in a coagulation bath composed of N,N-dimethylformamide and deionized water (volume ratio of 70:30) for coagulation at 25℃ for 15min until the liquid film was completely solidified. Then the liquid film was transferred to deionized water for storage to remove residual solvents. Natural air drying was performed to obtain an interface in-situ assembled gel and nanoparticle composite polyether sulfone membrane.

[0066] Example 2 The amount of polyethyleneimine in step (1) of Example 1 is adjusted to 0.25 g, and the rest is consistent with Example 1 to obtain a polyether sulfone membrane.

[0067] Example 3 The amount of polyethyleneimine in step (1) of Example 1 is adjusted to 0.4 g, and the rest is consistent with Example 1 to obtain a polyether sulfone membrane.

[0068] Example 4 The amount of polyethyleneimine in step (1) of Example 1 is adjusted to 0.55 g, and the rest is consistent with Example 1 to obtain a polyether sulfone membrane.

[0069] Comparative Example 1 A method for preparing a polyether sulfone membrane, comprising the following steps: (1) 3 g of polyether sulfone powder and 20 ml of N,N-dimethylformamide are added to a three-necked flask, and the mixture is stirred at 160°C and 120 rpm in a water bath for 3 h, and then the solution is degassed for 24 h to obtain a casting solution; (2) The casting solution is poured into a glass substrate, and a 250 μm doctor blade is used to coat a continuous and uniform liquid film at 60°C and 70% humidity. The glass substrate with the liquid film is immersed in a coagulation bath composed of N,N-dimethylformamide and deionized water (volume ratio 70:30) at 25°C for 15 min to completely solidify the liquid film, and then the liquid film is transferred to deionized water for storage; natural air drying to obtain a polyether sulfone membrane.

[0070] The obtained polyether sulfone membrane is tested for performance, and the test results are as follows: Figure 1 The scanning electron microscope image of the membrane in Example 1 is shown in Figure 1; wherein A is a surface image, B is a cross-sectional image, and C is a detailed magnified image of the internal pore of the membrane. From Figure 1 It can be seen that very rough wrinkle microspheres grow on the surface of the membrane, which are caused by the rapid migration of polyphenol metal gel to the non-solvent due to the very violent exchange between the liquid film and the non-solvent, but lack of binding sites between the polymer membrane and the gel microspheres. Although gel microspheres are formed on the surface, in the narrow internal pores, due to the limited space for solvent-non-solvent exchange and the lack of nucleation sites, polyphenol agglomeration occurs in some areas, but the entire pore is not modified.

[0071] Figure 2 The scanning electron microscope image of the membrane in Example 2 is shown in Figure 2; wherein A is a surface image, B is a cross-sectional image, and C is a detailed magnified image of the internal pore of the membrane. From Figure 2It can be seen that the surface of the film is not wrinkled microspheres, and the smooth surface part has protruding nanotube structure. The internal pore electron microscope image clearly observes that the whole pore is modified by the composite structure of gel layer and nanoscale ball mixed modification, and the whole pore is modified and no agglomeration phenomenon occurs.

[0072] Figure 3 The scanning electron microscope image of the film in Example 3 is shown in Figure 2. Wherein, A is the surface image, B is the cross-sectional image, and C is the detail magnification of the internal pore of the film. From Figure 3 It can be seen that the surface porosity of the film is significantly increased, and the equivalent pore size is about 1-10 nm, which is due to the accelerated exchange between the solvent and the non-solvent caused by the polyphenol gel. The cross-section of the film shows a macroscopic and uniform sponge-like pore, and in the magnified image, it can be observed that the whole pore is modified by the composite structure of gel and nanoparticles.

[0073] Figure 4 The scanning electron microscope image of the film in Example 4 is shown in Figure 3. Wherein, A is the surface image, B is the cross-sectional image, and C is the detail magnification of the internal pore of the film. From Figure 4 It can be seen that an excess of polyethyleneimine is added. The polyphenol gel is basically combined with polyethyleneimine to form nanoparticles. The surface pore is smaller, and the internal nanoparticles appear agglomeration phenomenon, which cannot realize the modification of the whole pore Figure 5 The scanning electron microscope image of the film in Comparative Example 1 is shown in Figure 4. Wherein, A is the surface image, B is the cross-sectional image, and C is the detail magnification of the internal pore of the film. From Figure 5 It can be seen that the surface and cross-section of the film are not modified.

[0074] Figure 11 The image of the water contact angle of the film in Example 3 with time is shown in Figure 5. From Figure 11 It can be seen that the water contact angle reaches 0 degree within 0.5 seconds, which shows extremely low water resistance and excellent water penetration characteristics.

[0075] Table 1 is the test results of the film performance, which is as follows: Table 1 Film performance test

[0076] Table 2 is the metal adsorption performance test, which is as follows: Table 2 Metal adsorption performance test

[0077] Comparative Example 2 Omit the tannic acid in Example 3, and keep the rest the same as Example 3 to obtain a polyether sulfone film.

[0078] The results show that a large amount of zirconium oxychloride is precipitated during phase separation, which cannot form a gel and a nanoparticle composite layer at the interface, and the film forming quality is poor, so there is no need to perform the next step of performance test.

[0079] Comparative Example 3 In Comparative Example 3, the step of dropwise addition in Example 3 Step (3) is changed to direct one-time addition, and other conditions are the same as those in Example 3, to obtain a polyether sulfone membrane.

[0080] The results show that obvious agglomeration occurs in the casting solution, and the agglomerated particles are about microns, which leads to uneven liquid film and cannot form a film. This proves that the step of adding small amounts of multiple batches is extremely important, which promotes the gradual and uniform combination between long-chain polyethyleneimine and small-molecule polyphenol, and avoids the agglomeration of particles caused by the uneven combination of some parts with polyphenol.

[0081] Comparative Example 4 In Comparative Example 4, zirconium oxychloride in Example 3 is omitted, and other conditions are the same as those in Example 3, to obtain a polyether sulfone membrane.

[0082] The membrane electron microscope image is shown in Figure 12 .

[0083] The results show that: there is no gel layer on the surface and inside of the membrane, only some nanoparticle-like substances grow on the surface of the membrane matrix, and part of the nanoparticles agglomerate in the inside of the membrane channel, and the full-channel gel and nanoparticle composite structure is not achieved. This is because the lack of metal crosslinking sites, the gel structure cannot be formed; the permeation flux is 292.36 L / (m 2 ·h), and the flux recovery ratio (FRR) is 60%.

[0084] Comparative Example 5 In Comparative Example 5, polyethyleneimine in Example 3 is omitted, and other conditions are the same as those in Example 3, to obtain a polyether sulfone membrane.

[0085] The membrane electron microscope image is shown in Figure 13 .

[0086] The results show that: a large amount of particle agglomeration occurs on the surface and inside of the membrane, and the polyphenol-zirconium oxychloride gel cannot be well combined with the membrane matrix. This is because there is a lack of chain entanglement and binding sites between small-molecule polyphenol and high-molecular polyether sulfone, so that a large amount of small-molecule polyphenol gel is precipitated in the non-solvent during phase separation, and the small-molecule polyphenol that cannot be precipitated is accumulated or blocked in the channel, and a gel layer cannot be formed on the interface. This fully proves the dual role of polyethyleneimine: 1. Forming chain entanglement with polyether sulfone substrate; 2. Providing binding sites for small-molecule polyphenol. The permeation flux is 331.52 L / (m 2• h), the flux recovery rate was 78%, and the polyphenol was precipitated during the test, which meant that the stability of the membrane was poor.

[0087] Comparative Example 6 The zirconium oxychloride in Example 3 was replaced by the tetravalent metal titanium, and the specific steps were as follows: (1) 3 g of polyether sulfone powder and 20 ml of N,N-dimethylformamide were added to a three-necked flask, and the mixture was heated in a water bath at 160°C and stirred at 120 rpm until a clear and transparent solution was formed. Then, 0.1 g of polyethyleneimine was gradually added and continuously stirred until completely dissolved to obtain a casting solution precursor solution; (2) 8 g of tannic acid was dissolved in 25 mL of N,N-dimethylformamide to obtain a tannic acid solution; 1 ml of di (2-hydroxypropionic acid) dihydroxylammonium titanium (50% by mass, aqueous solution) was added to the tannic acid solution, and the mixture was oscillated in a vortex oscillator until a dark red gel-like material was formed. The gel precursor solution was dispersed in an ultrasonic generator for 45 min to obtain a gel precursor solution; (3) Under the condition of stirring at 120 rpm, 3 mL of the gel precursor solution was added dropwise into 20 mL of the casting solution precursor solution by a pipette, and the amount of each addition was 250 microliters. The interval between each drop was about 1 minute to ensure that the casting solution was clear and no agglomeration occurred during the whole process. The solution was deaerated for 24 h to obtain an orange casting solution; (4) The casting solution was poured into a glass substrate, and a 250 μm doctor blade was used for continuous and uniform coating at 60°C and 70% humidity. The glass substrate loaded with the liquid film was immersed in a coagulation bath composed of N,N-dimethylformamide and deionized water (volume ratio 70:30) to coagulate for 15 min at 25°C until the liquid film was completely solidified. Then, the liquid film was transferred to deionized water for storage. After natural air drying, an interface in-situ assembled gel and nanoparticle composite polyether sulfone membrane was obtained.

[0088] The membrane electron microscope image is shown in Figure 14 .

[0089] It was found that particles and gel-like mixed structures appeared on the surface and inside of the membrane. Compared with the metal zirconium, the in-situ grown coating was thicker on the surface and thinner inside the membrane channel. This may be due to the fact that the diffusion coefficient of titanium in the non-solvent (water) is higher than that of zirconium, which leads to faster migration to the interface during the phase separation process. This structure can promote the improvement of hydrophilicity and permeation flux, but the anti-pollution property during long-term use is far inferior to the structure formed by zirconium oxychloride in Example 3. The permeation flux was 409.72 L / (m 2 • h), the flux recovery rate was 78%, and the polyphenol was precipitated during the test, which meant that the stability of the membrane was poor.

[0090] Example 5 A method for adsorbing and separating metal ions, comprising the following steps: The chloride salt solutions of copper ion, lead ion, indium ion, cadmium ion, titanium ion, zinc ion, lanthanum ion, platinum ion, mercury ion, ytterbium ion, iron ion, nickel ion, dysprosium ion, erbium ion, vanadium ion, thulium ion, zirconium ion, potassium ion, calcium ion, sodium ion, magnesium ion were prepared respectively, the concentration was 100ppb, the solution volume was 1L, and the pH was adjusted to 5. The water was circulated in the filter for 24h.

[0091] The pH of the solution was adjusted to 5 by using standard HCl and NaOH solutions, and the interface in-situ assembled gel and nanoparticle composite polyether sulfone membrane of Example 1 was placed in the solution, and then shaken on a shaker for 24 hours. 1mL of water sample was taken at the beginning and the end of the adsorption, and the concentration was determined by ICP-MS, and then the adsorption capacity and removal rate before and after adsorption were calculated.

[0092] The test results are as follows: Table 3 is the test results of metal adsorption effect (ppb). As can be seen from Table 3, the concentrations of copper ion, vanadium ion, lead ion, indium ion, zirconium ion and titanium ion after adsorption are less than 0.1ppb, and the concentrations of other metals after adsorption are below 30ppb except potassium ion, calcium ion, sodium ion and magnesium ion. It shows that the interface in-situ assembled gel and nanoparticle composite polyether sulfone membrane has high adsorption efficiency for various heavy metals, and has application potential in heavy metal prevention and noble metal recovery.

[0093] Table 3 Test results of metal adsorption effect (ppb)

[0094] Although the present application has been disclosed with reference to the preferred embodiments as above, it is not intended to limit the present application, and any person skilled in the art can make various modifications and modifications without departing from the spirit and scope of the present application, therefore the protection scope of the present application should be defined by the claims.

Claims

1. A method for preparing a polyethersulfone film composed of an interfacial in-situ assembled gel and nanoparticles, characterized in that, Includes the following steps: (1) Heat the polyethersulfone solution to 155-165℃, add polyethyleneimine, mix well to obtain the casting solution precursor solution; wherein the mass ratio of polyethyleneimine to polyethersulfone is 0.25-0.4:3; (2) Mix the polyphenol solution and zirconium oxychloride solution, and mix them in a vortex mixer until a deep yellow gel-like substance is generated. Disperse the mixture by ultrasonic bombardment to obtain a gel precursor solution. (3) Under stirring, the gel precursor solution is added dropwise to the casting solution precursor solution, and the mixture is allowed to stand to degas, thus obtaining the casting solution. (4) Cast the casting solution into a film, dry it, and obtain a polyethersulfone film composed of in-situ assembled gel and nanoparticles at the interface.

2. The method according to claim 1, characterized in that, The solvent of the polyethersulfone solution in step (1) includes one or more of N,N-dimethylformamide, N,N'-dimethylacetamide, and N-methylpyrrolidone, with a concentration of 10-20% and a percentage of g / 100mL.

3. The method according to claim 1, characterized in that, In step (2), the solvent for the polyphenol solution is one or more of N,N-dimethylformamide, N,N'-dimethylacetamide, and N-methylpyrrolidone, with a concentration of 30-40% and a percentage of g / 100mL.

4. The method according to claim 1, characterized in that, In step (2), the solvent for the zirconium oxychloride solution is one or more of N,N-dimethylformamide, N,N'-dimethylacetamide, and N-methylpyrrolidone, with a concentration of 5-10% and a percentage of g / 100mL.

5. The method according to claim 1, characterized in that, In step (2), the volume ratio of polyphenol solution to zirconium oxychloride solution is 2:(0.5-1); in step (3), the volume ratio of gel precursor solution to casting solution precursor solution is 3-5:

20.

6. The polyethersulfone membrane composed of interfacial in-situ assembled gel and nanoparticles prepared by the method according to any one of claims 1-5.

7. The application of the polyethersulfone membrane composed of in-situ assembled gel and nanoparticles as described in claim 6 in the field of water treatment.

8. A method for improving the permeability, antifouling properties, and long-term stability of polyethersulfone membranes, characterized in that, Includes the following steps: (1) Heat the polyethersulfone solution to 155-165℃, add polyethyleneimine, mix well to obtain the casting solution precursor solution; wherein the mass ratio of polyethyleneimine to polyethersulfone is 0.25-0.4:3; (2) Mix the polyphenol solution and zirconium oxychloride solution, and mix them in a vortex mixer until a deep yellow gel-like substance is generated. Disperse the mixture by ultrasonic bombardment to obtain a gel precursor solution. (3) Under stirring, the gel precursor solution is added dropwise to the casting solution precursor solution, and the mixture is allowed to stand to degas, thus obtaining the casting solution. (4) Cast the casting solution into a film, dry it, and obtain a polyethersulfone film composed of in-situ assembled gel and nanoparticles at the interface.

9. A method for adsorbing and separating metal ions, characterized in that, The polyethersulfone membrane, which is a composite of interface in-situ assembled gel and nanoparticles as described in claim 6, was used.

10. A method for adsorbing and recovering metal ions, characterized in that, The polyethersulfone membrane, which is a composite of interface in-situ assembled gel and nanoparticles as described in claim 6, was used.

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