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

Abstract

The application discloses an interface in-situ assembled gel and nanoparticle composite polyether sulfone membrane and preparation and application, and belongs to the field of nanometer material and membrane separation technology. The application in-situ constructs a gel and nanoparticle composite structure on the membrane surface and in the pore channel through a phase separation strategy for the first time, a main gel layer is formed by cross-linking of polyphenol and zirconium oxychloride, and nanoparticles are formed by complexing of polyethylene imine and free sites of the 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 mixing hydrophilic gel and nanospheres.

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 reduce 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;

[0004] 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;

[0005] Patent CN114984784A discloses a kind of hydrophilic surface modified methyl methacrylate diethylaminoethyl methacrylate (PDEAEMA) titanium dioxide nanotube added into polysulfone casting solution, and a hydrophilic hybrid polysulfone membrane is prepared; but the particles are easy to agglomerate and migrate, and it is difficult to form a uniform and firm nanoscale functional layer at the membrane-pore interface.

[0006] Therefore, it is urgent to develop a method that can realize the in-situ assembly and stable anchoring of hydrophilic nanostructures on the membrane surface and in the pore under the dynamic change environment of the interface 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

[0007] [TECHNICAL PROBLEM]

[0008] Constructing a hydrophilic layer by post-processing steps all have problems such as complex process and poor stability of the modified layer;

[0009] Adding nanoparticles to construct a hydrophilic layer, but the particles are easy to agglomerate and migrate, and it is difficult to form a uniform and firm nanoscale functional layer at the membrane-pore interface.

[0010] [Technical scheme]

[0011] 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 surface and in the channel of the membrane in-situ by 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 the post-processing method of surface modification, the method of the application has the advantages of process integration and stable coating; compared with the mixed matrix membrane constructed by zeolite and carbon nanotube, the application avoids agglomeration and polymer embedding, and can form a coating layer on the surface of the polymer, which is constructed by mixing hydrophilic gel and nanospheres.

[0012] The 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:

[0013] (1) heating a polyether sulfone solution to 155-165℃, 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;

[0014] (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;

[0015] (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;

[0016] (4) casting the casting solution into a membrane, and drying to obtain an interface in-situ assembled gel and nanoparticle composite polyether sulfone membrane.

[0017] 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.

[0018] In an embodiment of the application, the heating to 155-165℃ in step (1) is to make the solution present in a clear and transparent state.

[0019] In an embodiment of the application, the polyethyleneimine in step (1) is linear or branched, and the molecular weight is less than 100000.

[0020] In an embodiment of the present 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.

[0021] In an embodiment of the present application, the polyphenol in step (2) is one or more of tannic acid, phenolic acid, flavonoids, lignan, stilbene and the like.

[0022] In an 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.

[0023] In an 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).

[0024] In an embodiment of the present application, the time for ultrasonic dispersion in step (2) is 30-60 min.

[0025] In an embodiment of the present application, the stirring speed in step (3) is 100-200 rpm.

[0026] In an 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.

[0027] In an 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.

[0028] In an embodiment of the present application, the time for standing and degassing in step (3) is 12-24 h.

[0029] In an embodiment of the present application, the film casting in step (4) is performed by pouring the casting solution into a mold, uniformly coating the casting solution using a doctor blade, and then placing the mold in a coagulation bath for coagulation; wherein the doctor blade is 200-300 μm, the coating 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.

[0030] In an embodiment of the present application, after the film formation in step (4), the film is stored in deionized water to remove residual solvent.

[0031] In one embodiment of the present application, the drying in step (4) is natural air drying.

[0032] A 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.

[0033] A 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.

[0034] A 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:

[0035] (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;

[0036] (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;

[0037] (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;

[0038] (4) casting the casting solution into a membrane, and drying to obtain the interface in-situ assembled gel and nanoparticle composite polyether sulfone membrane.

[0039] A fifth object of the present application is to provide a method for adsorbing and separating metal ions, which uses the interface in-situ assembled gel and nanoparticle composite polyether sulfone membrane of the present application.

[0040] In one 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.

[0041] In one embodiment of the present application, the method for adsorbing and separating metal ions comprises the following steps:

[0042] The interface in-situ assembled gel and nanoparticle composite polyether sulfone membrane is placed in a filter, and 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 adsorb metal ions. After the adsorption 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.

[0043] A sixth object of the present application is to provide a method for adsorbing and recovering metal ions, which employs the interfacially-assembled gel and nanoparticle composite polyethersulfone membrane described in the present application.

[0044] In one embodiment of the present application, the metal ions are heavy metals, specifically including one or more of Cu 2+ , Pb 2+ , Fe 3+ .

[0045] In one embodiment of the present application, the recovery is carried out in an acid solution.

[0046] In one embodiment of the present application, the method for adsorbing and recovering metal ions comprises the following steps:

[0047] The interfacially-assembled gel and nanoparticle composite polyethersulfone 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 interfacially-assembled gel and nanoparticle composite polyethersulfone membrane is soaked in an acid solution to recover the metal ions, after the recovery of the metal ions is completed, the interfacially-assembled gel and nanoparticle composite polyethersulfone membrane is taken out, washed with deionized water, and then used next time.

[0048] [Advantages]

[0049] (1) Principle of the present application:

[0050] In the process of phase separation, the non-solvent and the solvent exchange dramatically, while smaller chains or smaller groups tend to move to the interface faster. The polyphenol substance, which is classified by molecular weight as a small molecule, has a high hydrophilic property 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.

[0051] However, the complexation between the polyphenol and the water-soluble macromolecule provides a feasible solution for anchoring on the surface of the polymer. The Michael addition reaction between the polyethyleneimine and the polyphenol forms nanoparticles, and the covalent interaction between them can fix 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 pre-formed by deep cross-linking between the polyphenol and zirconium oxychloride, and then the gel is added into the casting solution.

[0052] According to the above principle, a gel and nanoparticle composite structure is constructed in situ on the membrane surface and in the pore channel by a phase separation strategy, the main gel layer is formed by cross-linking of polyphenol and zirconium oxychloride, and the nanoparticle is formed by complexing of polyethyleneimine and the free site of polyphenol, which provides nucleation sites for the in-situ construction of the gel layer on the surface.

[0053] (2) The coating structure composed of polyphenol metal gel and polyphenol polyethyleneimine nanoparticles is constructed in situ on the surface and inside the pore channel of the original polyether sulfone membrane, which has high hydrophilicity and metal ion capturing capacity. Compared with the prior art, the advantages of the present application are:

[0054] The present application combines the gelation reaction of polyphenol and zirconium oxychloride, and the Michael addition reaction of polyphenol and polyethyleneimine, and modifies the nanoparticle and gelation composite structure on the membrane surface and inside the pore channel, which realizes the super-hydrophilic modification of the membrane surface and the membrane inside the pore channel, and helps to improve the membrane permeation flux and anti-pollution performance;

[0055] The stable anchoring of polyphenol gel and nanoparticles on the membrane surface and inside realizes the chemical customization of the metal ion capturing layer on the membrane surface and inside the pore channel, which can be used for high capacity and high flux metal ion adsorption and separation;

[0056] Prepared by one-step phase inversion method, it can be carried out by using conventional equipment and method without any post-treatment step, and is easy to realize industrialization.

[0057] (3) The key problem of the present application is how to form a mixed structure of polyphenol gel and nanoparticles on the interface of the polymer surface and inside the pore channel. In the phase separation process, polyethyleneimine plays a key role in anchoring the polyphenol gel on the interface, and the free site of polyphenol simultaneously forms nanoparticles with polyethyleneimine. Therefore, the appropriate molar ratio between polyethyleneimine and polyphenol is needed to realize the growth on the interface of the whole pore channel. BRIEF DESCRIPTION OF DRAWINGS

[0058] Figure 1 Figure 1 is the scanning electron microscope image of the membrane in Example 1; wherein A is the surface image, B is the cross-sectional image, and C is the detailed enlarged image of the internal pore channel of the membrane.

[0059] Figure 2 Figure 2 is the scanning electron microscope image of the membrane in Example 2; wherein A is the surface image, B is the cross-sectional image, and C is the detailed enlarged image of the internal pore channel of the membrane.

[0060] Figure 3 Figure 3 is the scanning electron microscope image of the membrane in Example 3; wherein A is the surface image, B is the cross-sectional image, and C is the detailed enlarged image of the internal pore channel of the membrane.

[0061] Figure 4Scanning electron microscope image of the film 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 film.

[0062] Figure 5 Scanning electron microscope image of the film 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 film.

[0063] Figure 6 Contact angle measurement instrument image of the film in Example 1.

[0064] Figure 7 Contact angle measurement instrument image of the film in Example 2.

[0065] Figure 8 Contact angle measurement instrument image of the film in Example 3.

[0066] Figure 9 Contact angle measurement instrument image of the film in Example 4.

[0067] Figure 10 Contact angle measurement instrument image of the film in Comparative Example 1.

[0068] Figure 11 Image of the water contact angle of the film in Example 3 over time; wherein (a) is 0 s; (b) is 0.1 s; (c) is 0.3 s; and (d) is 0.5 s.

[0069] 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 pores of the film.

[0070] 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 pores of the film.

[0071] 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 pores of the film. DETAILED DESCRIPTION

[0072] 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.

[0073] Test method:

[0074] 1. Test method for hydrophilicity of the film:

[0075] Hydrophilicity is tested by a contact angle measurement instrument (OCA). The smaller the contact angle, the higher the degree of hydrophilization.

[0076] 2. Test method of permeation flux of membrane:

[0077] The permeation flux is expressed by pure water flux J. The water volume through unit membrane area in a certain time is measured by dead-end filtration. Flux (J): water volume through unit membrane area (A) in unit time (t).

[0078] The specific calculation formula is as follows:

[0079]

[0080] 3. Test method of anti-pollution performance:

[0081] 1000 mg / L humic acid (HA) is used as a pollutant, and the anti-pollution performance is tested by dead-end filtration. The test steps are as follows:

[0082] (1) The membrane is fixed in a customized filter, and the initial water flux J0 of the test membrane is tested;

[0083] (2) The feed liquid is replaced with humic acid, and the membrane is passed through for 60 minutes, followed by cleaning with deionized water;

[0084] (3) Repeat step (2) 10 times, and test the pure water flux J after 10 pollution-cleaning cycles 10

[0085] The anti-pollution performance is characterized by flux recovery rate (FRR) and single flux decay rate (FDR);

[0086] The formula is as follows:

[0087]

[0088] Wherein, J w1 and J w2 respectively represent the pure water flux of single pollution experiment.

[0089]

[0090] Wherein, J1 and J s respectively represent the pure water flux before the first experiment and the pure water flux after the s-th experiment.

[0091] 4. The test of the adsorption performance of the membrane to metal ions is carried out in the following way

[0092] Removal efficiency experiment:

[0093] All metal solutions (Cu 2+ , Pb 2+ , Fe 3+ , K + , Ca 2+Na + Mg 2+ The concentration of each of the above-mentioned ions (e.g., Ca2+, Na+, Mg2+, etc.) is 100 ppb, the solution volume is 1 L, and the pH is adjusted to 5. The water is circulated in the filter for 24 h.

[0094] The pH of the solution is adjusted to 5 using standard HCl and NaOH solutions, and the adsorption is shaken on a shaker for 24 hours. 1 mL of water sample is taken before and after the start of the adsorption, and the concentration is determined by ICP-MS, and the adsorption capacity and removal rate before and after the adsorption are calculated.

[0095] The adsorption capacity (qe) of the membrane is calculated using the following formula:

[0096] qe = V(C0 - Ce) / m

[0097] In the formula, V is the solution volume, C0 is the initial concentration, Ce is the final concentration, and m is the mass of the membrane.

[0098] The raw materials used in the examples are as follows:

[0099] Polyethyleneimine: CAS: 9002-98-6, linear type; purchased from Macklin Company; molecular weight is 70,000, purity is greater than 99%, 50% wt in H2O;

[0100] Polyphenol (tannic acid): purchased from Shanghai Aldrich Company; CAS: 1401-55-4, purity is ACS grade;

[0101] Zirconium oxychloride: zirconium oxychloride octahydrate, CAS: 13520-92-8, purity is greater than 98%, purchased from Shanghai Aldrich Company;

[0102] N,N-dimethylformamide: CAS: 68-12-2, purity is AR, ≥99.5%, purchased from Shanghai Aldrich Company;

[0103] The other raw materials used in the examples and comparative examples are conventional raw materials, which can be purchased on the market.

[0104] The reaction temperature not specifically indicated in the examples and comparative examples is room temperature (20-30°C).

[0105] Example 1

[0106] A method for preparing an interface in-situ assembled gel and nanoparticle composite polyether sulfone membrane, comprising the following steps:

[0107] (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 heated in a water bath at 160°C and stirred at 120 rpm until a clear and transparent solution is formed; 0.1 g of polyethyleneimine is gradually added and stirred until completely dissolved to obtain a casting solution precursor solution;

[0108] (2) 8 g of tannic acid was dissolved in 25 mL of N,N-dimethylformamide to obtain a tannic acid solution;

[0109] 2.5 g of zirconium oxychloride was dissolved in 25 mL of N,N-dimethylformamide to obtain a zirconium hydroxide solution;

[0110] 2 mL of the tannic acid solution and 1 mL of the zirconium oxychloride solution were mixed and shaken in a vortex shaker until a dark yellow gelled material was formed, which was dispersed by ultrasonic generator for 45 min to obtain a gel precursor solution;

[0111] (3) 3 mL of the gel precursor solution was added dropwise into 20 mL of the casting solution precursor solution by a pipette under stirring at 120 rpm, and the amount of each addition was 250 microliters, and the interval between each dropwise addition was about 1 minute to ensure that the casting solution was clear and no aggregation occurred during the whole process. The casting solution was deaerated for 24 h to obtain a casting solution;

[0112] (4) The casting solution was poured into a glass substrate and coated as a continuous and uniform liquid film by a 250 μm doctor blade 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 to remove residual solvents. Natural air drying was performed to obtain a polyethersulfone membrane with in-situ assembled gel and nanoparticles.

[0113] Example 2

[0114] The amount of polyethyleneimine in step (1) of Example 1 was adjusted to 0.25 g, and the other conditions were the same as those in Example 1 to obtain a polyethersulfone membrane.

[0115] Example 3

[0116] The amount of polyethyleneimine in step (1) of Example 1 was adjusted to 0.4 g, and the other conditions were the same as those in Example 1 to obtain a polyethersulfone membrane.

[0117] Example 4

[0118] The amount of polyethyleneimine in step (1) of Example 1 was adjusted to 0.55 g, and the other conditions were the same as those in Example 1 to obtain a polyethersulfone membrane.

[0119] Comparative Example 1

[0120] A method for preparing a polyethersulfone membrane, comprising the following steps:

[0121] (1) Put 3 g of polyether sulfone powder and 20 ml of N,N-dimethylformamide into a three-necked flask, heat in a water bath at 160 °C and 120 rpm for 3 h with continuous stirring, mix uniformly until the solution forms a clear and transparent shape, stand for 24 h of degassing, to obtain a casting solution;

[0122] (2) Pour the casting solution into a glass substrate, use a 250 μm doctor blade, and coat it as a continuous and uniform liquid film at 60 °C and 70% humidity. Immerse the glass substrate with the liquid film into a coagulation bath composed of N,N-dimethylformamide and deionized water (volume ratio 70:30), coagulate at 25 °C for 15 min until the liquid film is completely solidified, then transfer the liquid film to deionized water for storage; air dry to obtain a polyether sulfone membrane.

[0123] Test the performance of the obtained polyether sulfone membrane, and the test results are as follows:

[0124] Figure 1 The 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 pore of the membrane. From Figure 1 It can be seen that: the surface of the membrane grows very rough wrinkle microspheres, these microspheres are due to the very violent exchange between the liquid film and the non-solvent, which leads to the migration of the polyphenol metal gel to the non-solvent, but it lacks binding sites between the polymer membrane and self-aggregation. Although gel microspheres are formed on the surface, in the narrow internal pore, due to the limited space of solvent-nonsolvent exchange and the lack of nucleation sites, polyphenol agglomeration occurs in some areas, but the entire pore is not modified.

[0125] Figure 2 The 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 pore of the membrane. From Figure 2 It can be seen that: the surface of the membrane has no wrinkle microspheres, and the relatively smooth surface has a convex nanotube structure in some areas. The internal pore electron microscope clearly observes that the entire pore is modified by a composite structure of gel layer and nanoscale ball mixed modification, and the entire pore is modified without any agglomeration phenomenon.

[0126] Figure 3 The 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 pore of the membrane. From Figure 3 It can be seen that: the surface porosity of the membrane 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 membrane shows a macroscopic and uniform sponge-like hole, and in the magnified image, it can be observed that the entire pore is modified by a composite structure of gel and nanoparticles.

[0127] Figure 4The scanning electron microscope images of the film in Example 4; wherein, A is the surface image, B is the cross-sectional image, and C is the detailed magnified image of the internal pore channel of the film. From Figure 4 It can be seen that: the excess polyethyleneimine is added. The polyphenol gel is basically combined with the polyethyleneimine to form nanoparticles. The surface pores are smaller, and the internal nanoparticles appear agglomeration phenomenon, and the modification of the whole pore channel cannot be realized

[0128] Figure 5 The scanning electron microscope images of the film in Comparative Example 1; wherein, A is the surface image, B is the cross-sectional image, and C is the detailed magnified image of the internal pore channel of the film. From Figure 5 It can be seen that: the surface and cross-section of the film are not modified.

[0129] Figure 11 The image of the water contact angle change with time of the film in Example 3. From Figure 11 It can be seen that: the water contact angle reaches 0 degree within 0.5 seconds, showing extremely low water resistance and excellent water penetration characteristics.

[0130] Table 1 is the film performance test results, as follows:

[0131] Table 1 Film performance test

[0132]

[0133] Table 2 is the metal adsorption performance test, as follows:

[0134] Table 2 Metal adsorption performance test

[0135]

[0136] Comparative Example 2

[0137] Omit the tannic acid in Example 3, and keep the rest the same as Example 3, to obtain a polyether sulfone film.

[0138] It is found that a large amount of zirconium oxychloride is precipitated during the phase separation process, and the gel and nanoparticle composite layer cannot be formed at the interface, the film quality is poor, and the next performance test is no longer needed.

[0139] Comparative Example 3

[0140] Adjust the step (3) in Example 3 to be directly added once (add 250 microliters each time, and the interval between each drop is about 1 minute), and keep the rest the same as Example 3, to obtain a polyether sulfone film.

[0141] The results show that the casting solution has obvious agglomeration phenomenon, the agglomerated particles are about microns, which leads to uneven coating of the liquid film and failure to form a film. This proves that the step of adding a small amount of multiple times in batches is extremely important, which promotes the gradual and uniform combination between long-chain polyethyleneimine and small-molecule polyphenol, and avoids the uneven combination of some parts with polyphenol leading to particle nucleation agglomeration.

[0142] Comparative Example 4

[0143] Zirconium oxychloride in Example 3 is omitted, and the rest is consistent with Example 3, to obtain a polyether sulfone membrane.

[0144] The membrane electron microscope image is shown in Figure 12 .

[0145] The results show that: there is no gel layer on the surface and inside of the membrane, only some nanometer particles grow in the membrane matrix on the surface, and part of the nanometer particle agglomeration appears in the membrane channel, and the composite structure of the whole channel gel and nanometer particles is not achieved. This is due to the lack of metal crosslinking sites, and the gel structure cannot be formed; the permeation flux is 292.36 L / (m 2 ·h), and the flux recovery ratio (FRR) is 60%.

[0146] Comparative Example 5

[0147] Polyethyleneimine in Example 3 is omitted, and the rest is consistent with Example 3, to obtain a polyether sulfone membrane.

[0148] The membrane electron microscope image is shown in Figure 13 .

[0149] The results show that: a large number of particle agglomerations appear on the surface and inside of the membrane, and the polyphenol-zirconium oxychloride gel cannot be well combined with the membrane matrix. This is due to the lack of chain entanglement and binding sites between small-molecule polyphenol and high-molecular polyether sulfone, so that the small-molecule polyphenol gel will be precipitated in large quantities during phase separation, and the ones that cannot be precipitated will accumulate or block the channel, and the 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), and the flux recovery ratio is 78%, and the polyphenol precipitates during the test, indicating that the stability of the membrane is poor.

[0150] Comparative Example 6

[0151] Adjust the zirconium oxychloride in Example 3 to tetravalent metal titanium, and the specific steps are as follows:

[0152] (1) 3 g of polyether sulfone powder and 20 ml of N,N-dimethylformamide were added into a three-necked flask, and stirred constantly at 160 °C and 120 rpm in a water bath, mixed uniformly until a clear and transparent solution was formed; 0.1 g of polyethyleneimine was gradually added and stirred until completely dissolved, to obtain a casting solution precursor solution;

[0153] (2) 8 g of tannic acid was dissolved in 25 mL of N,N-dimethylformamide to obtain a tannic acid solution;

[0154] 1 ml of di (2-hydroxypropionic acid) dihydroxide diammonium titanium (mass fraction 50%, aqueous solution) was added to the tannic acid solution, and mixed in a vortex oscillator until a dark red gel-like material was formed, and dispersed in an ultrasonic generator for 45 min to obtain a gel precursor solution;

[0155] (3) 3 mL of the gel precursor solution was added dropwise into 20 mL of the casting solution precursor solution in a pipette under 120 rpm stirring, and the amount of each addition was 250 microliters, with an interval of about 1 minute, to ensure that the whole process of the casting solution was clear and no aggregation, and was left to stand and degas for 24 h to obtain an orange casting solution;

[0156] (4) The casting solution was poured into a glass substrate, and a 250 μm doctor blade was used for continuous and uniform liquid film coating at 60 °C and 70% humidity, and 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 at 25 °C for 15 min until the liquid film was completely solidified, and then the liquid film was transferred to deionized water for storage. Natural air drying was performed to obtain a polyether sulfone membrane with in-situ assembled gel and nanoparticles.

[0157] The membrane electron microscope image is shown in Figure 14 .

[0158] It was found that particles and gel-like mixed structures appeared on the membrane surface and inside, and compared with zirconium metal, the in-situ grown coating was thicker on the surface and thinner inside the membrane channel. This may be due to the higher diffusion coefficient of titanium in the non-solvent (water) than zirconium, which leads to faster migration to the interface during phase separation. This structure can promote the improvement of hydrophilicity and permeation flux, but the anti-pollution property in the long-term use process is far inferior to the structure formed by zirconium oxychloride in Example 3. The permeation flux was 409.72 L / (m 2 ·h), and the flux recovery rate was 71%.

[0159] Example 5

[0160] A method for adsorbing and separating metal ions, comprising the following steps:

[0161] 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 and magnesium ion were prepared respectively, the concentration was 100 ppb, the solution volume was 1 L, and the pH was adjusted to 5. The water was circulated in the filter for 24 h.

[0162] 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. 1 mL 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 the adsorption were calculated.

[0163] The test results are as follows:

[0164] 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 0.1 ppb, and the concentrations of other metals after adsorption are below 30 ppb 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 recovery of precious metals.

[0165] Table 3 Test results of metal adsorption effect (ppb)

[0166]

[0167] Although the present application has been disclosed with reference to the preferred embodiments, 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, and therefore the protection scope of the present application should be defined by the claims.

Claims

1. A method for preparing an interfacial in-situ assembled gel and nanoparticle composite polyethersulfone membrane, characterized in that, Comprising the following steps: (1) heating the polyether sulfone solution to 155-165℃, adding polyethyleneimine, mixing uniformly to obtain a casting solution precursor solution; wherein the mass ratio of polyethyleneimine and polyether sulfone is 0.25-0.4:3; (2) mixing the polyphenol solution and the zirconium oxychloride solution, oscillating mixing in a vortex oscillator until a dark yellow gel-like substance is generated, ultrasonic bombardment dispersion to obtain a gel precursor solution; (3) under stirring, adding the gel precursor solution dropwise into the casting solution precursor solution, standing and degassing to obtain a casting solution; (4) casting the casting solution into a film, drying to obtain a polyether sulfone membrane with in-situ assembled gel and nanoparticles at the interface.

2. The method of claim 1, wherein, The solvent of the polyether sulfone solution in step (1) comprises one or more of N,N-dimethylformamide, N,N'-dimethylacetamide, N-methylpyrrolidone, with a concentration of 10-20% g / 100mL.

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

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

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

20.

6. The polyether sulfone membrane with in-situ assembled gel and nanoparticles at the interface prepared by the method of any one of claims 1-5.

7. The application of the polyether sulfone membrane with in-situ assembled gel and nanoparticles at the interface of claim 6 in the field of water treatment.

8. A method for recovering metal ions by adsorptive separation, characterized by, The polyether sulfone membrane with in-situ assembled gel and nanoparticles at the interface of claim 6 is used.

Images