Acid and alkali resistant high-strength ultrafiltration membrane and preparation method thereof

Abstract

The invention discloses an acid- and alkali-resistant high-strength ultrafiltration membrane and a preparation method thereof. The method specifically comprises the following steps: placing polyvinylidene fluoride, composite graphene, N,N-dimethylacetamide and an auxiliary additive in a reactor, heating to 75-85°C, stirring for 0.5-1h, and standing to remove bubbles to obtain a casting solution. The invention comprises the following steps: preparing the casting solution from the olefin-modified composite graphene, polyvinylidene fluoride and the auxiliary additive, preparing the casting solution into an ultrafiltration base membrane by a phase inversion method, modifying a carboxyl structure on the ultrafiltration base membrane by an olefin free radical polymerization reaction, activating the carboxyl structure in a composite buffer, and further undergoing an amidation reaction with a modified polysiloxane with an end-amino group to obtain an ultrafiltration membrane. The ultrafiltration membrane not only effectively improves the acid- and alkali resistance of the ultrafiltration membrane, but also improves its mechanical properties.

Description

Technical Field

[0001] The present invention relates to the technical field of filter membrane processing, and in particular to an acid- and alkali-resistant high-strength ultrafiltration membrane and a preparation method thereof. Background Art

[0002] In recent years, with the continuous growth of the economy, steel production has increased significantly. This change has directly led to the vigorous development of the coke oven business. As a core link in the steel manufacturing process, during the coking process, the heat recovery steps of quenching coke, coke oven gas purification and coal derivative recovery will produce coking wastewater. The complexity and potential toxicity of these wastewaters mainly come from the presence of difficult-to-biodegrade components such as polycyclic aromatic hydrocarbons, phenolic compounds, heterocyclic compounds, thiocyanates, ammonia and cyanide.

[0003] In the field of wastewater treatment, traditional methods cover a variety of technologies such as redox and biochemical. However, in actual application scenarios, these methods are often limited by high initial investment costs, process energy consumption and the complexity of the operating procedures. Compared with traditional treatment processes, membrane separation technology has the advantages of high efficiency, low energy consumption and high degree of automation in water treatment. It has attracted much attention from researchers in recent years. The ultrafiltration membrane can not only effectively separate and purify substances, but also realize the concentration of solutions and show excellent performance in the post-treatment of wastewater. However, for the separation and treatment of wastewater containing organic compounds, the acid and alkali resistance and mechanical strength of the ultrafiltration membrane need to be improved.

[0004] When preparing ultrafiltration membranes for treating organic wastewater, polyvinylidene fluoride can be selected as the base material. The polyvinylidene fluoride molecular chain is composed of fluorine atoms and carbon chains. The strong electronegativity and high stability of fluorine atoms give polyvinylidene fluoride higher mechanical strength and rigidity. The strong CF bond formed between its fluorine atoms and carbon atoms has high chemical stability. However, due to the presence of fluorine atoms, the hydrophilicity of the membrane is poor, which further affects its flux and anti-pollution properties. The addition of oxidatively modified inorganic materials can introduce a large number of oxygen-containing functional groups to improve the hydrophilicity of the ultrafiltration membrane. The inorganic material itself has excellent mechanical properties, which can further improve the strength of the ultrafiltration membrane. However, the inorganic material is easy to agglomerate during use, and the polyvinylidene fluoride membrane itself has good mechanical strength. However, during long-term use, especially under high pressure or extreme environments, the membrane material may reduce its mechanical properties due to aging.

[0005] In view of the technical defects in this aspect, a solution is now proposed. Summary of the Invention

[0006] The object of the present invention is to provide an acid- and alkali-resistant high-strength ultrafiltration membrane and a preparation method thereof, so as to solve the technical problem in the prior art that the acid- and alkali-resistant performance and mechanical properties of the ultrafiltration membrane need to be further improved.

[0007] The purpose of the present invention can be achieved by the following technical solution: A method for preparing an acid- and alkali-resistant high-strength ultrafiltration membrane comprises the following steps:

[0008] S1. Place polyvinylidene fluoride, composite graphene, N,N-dimethylacetamide and auxiliary additives in a reaction kettle, heat to 75-85° C., stir for 0.5-1 hour, and allow to stand to remove bubbles to obtain a casting solution;

[0009] S2. Cast the casting solution on a glass plate, scrape it flat with a scraper, let it stand for 1-2 minutes, immerse it in deionized water, soak it for 20-24 hours, and post-treat it to obtain an ultrafiltration base membrane;

[0010] S3, immersing the ultrafiltration base membrane in methacrylic acid solution, blowing nitrogen for 25-35 minutes, adding ammonium sulfite and ammonium persulfate, heating to 55-65°C, keeping the temperature and shaking for 4-6 hours, and post-treating to obtain an ultrafiltration membrane precursor;

[0011] The preparation reaction principle of ultrafiltration membrane precursor is:

[0012] During the reaction, under high temperature conditions, persulfate reacts with bisulfite to produce sulfate radicals and sulfite radicals, which trigger free radical polymerization of methacrylic acid monomers and olefins on the surface of the ultrafiltration base membrane to obtain an ultrafiltration membrane precursor.

[0013] S4. Place the ultrafiltration membrane precursor in a composite buffer solution, immerse for 1-1.5 hours, transfer to a modification solution, heat to 25-35°C, keep warm and shake for 4-6 hours, and post-treat to obtain an ultrafiltration membrane.

[0014] The preparation reaction principle of ultrafiltration membrane is:

[0015] During the reaction, the imine group of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and the hydroxyl group of N-hydroxysuccinimide can react with the carboxyl groups on the surface of the ultrafiltration membrane precursor to generate a highly active intermediate that can react with amino groups. 2-(N-morpholino)ethanesulfonic acid acts as a buffer to maintain the stability of the intermediate. The carboxyl groups on the surface of the ultrafiltration membrane precursor are activated and further undergo an amide reaction with the amino groups in the modification liquid to form a chemical bond, thereby obtaining an ultrafiltration membrane with a surface-modified polysiloxane.

[0016] Furthermore, in step S1, the amount ratio of the polyvinylidene fluoride, composite graphene, N,N-dimethylacetamide and auxiliary additives is 20-25g:2-4g:300-350mL:5-8g, the auxiliary additives are composed of a porogen, a plasticizer and an antibacterial agent in a mass ratio of 2:0.5:0.5, the porogen is one or both of polyethylene glycol and polyvinyl pyrrolidone, the plasticizer is one or both of dibutyl phthalate and polyvinyl alcohol, and the antibacterial agent is one or both of nanosilver and titanium dioxide; in step S2, the post-treatment step includes: after the immersion is completed, the membrane is washed 1-2 times with deionized water, transferred to a drying oven at a temperature of 30-40°C, and dried to constant weight to obtain an ultrafiltration base membrane.

[0017] Furthermore, in step S3, the methacrylic acid solution is composed of methacrylic acid and pure water in a dosage ratio of 3-5g:100mL, and the dosage ratio of the methacrylic acid solution, ammonium sulfite and ammonium persulfate is 300-500mL:1-2g:1-2g. The post-treatment step comprises: after the reaction is completed, washing the membrane with deionized water 1-2 times, transferring it to a drying oven at a temperature of 30-40°C, and drying it to a constant weight to obtain an ultrafiltration membrane precursor; in step S4, the composite buffer is 1-ethyl-3-(3-dimethoxy-1-[1-(1-[1-(1-dimethylamino)propene]-1-ol]-1-ol]-1-ol The invention discloses a method for preparing an ultrafiltration membrane by mixing a mixture of 2-(methylaminopropyl)carbodiimide, N-hydroxysuccinimide, 2-(N-morpholino)ethanesulfonic acid and deionized water in a dosage ratio of 7-8 g:4-5 g:1.5-2 g:100 mL. The post-treatment step comprises: after the reaction is completed, washing the membrane with deionized water 1-2 times, transferring the membrane to a drying oven at a temperature of 30-40° C., and drying the membrane to a constant weight to obtain an ultrafiltration membrane. The bath ratio of the ultrafiltration membrane precursor and the composite buffer solution is 1:30-35, and the bath ratio of the ultrafiltration membrane precursor and the modifying liquid is 1:32-35.

[0018] Furthermore, the modified liquid is obtained by the following preparation method:

[0019] A1. Aminopropylmethyldiethoxysilane, octamethylcyclotetrasiloxane, and xylene are placed in a reactor protected by a nitrogen atmosphere, heated to 110-120° C., formic acid solution is added, and the mixture is kept warm for 2-4 hours. Tetramethyldivinyldisiloxane is added, and the mixture is kept warm for 3-4 hours. Post-treatment is performed to obtain a modified polysiloxane precursor.

[0020] The preparation reaction formula of modified polysiloxane precursor is:

[0021]

[0022] The preparation principle of modified polysiloxane precursor is:

[0023] During the reaction, under the catalysis of formic acid, the methoxysilane groups in the aminopropylmethyldiethoxysilane and octamethylcyclotetrasiloxane molecules undergo hydrolysis to generate silanols, which then condense with each other to prepare a long polysiloxane chain modified with an amino group. During the reaction, tetramethyldivinyldisiloxane is used as a chain-terminating end group to form an unsaturated olefin double bond modification on the polysiloxane chain segment.

[0024] A2. Place a modified polysiloxane precursor, sodium styrene sulfonate, and N,N-dimethylformamide in a reaction kettle, heat to 70-80° C., stir for 5-10 minutes, add ammonium persulfate, keep the temperature for reaction for 2-4 hours, and post-treat to obtain a modified polysiloxane;

[0025] Preparation reaction principle of modified polysiloxane:

[0026] During the reaction, a modified polysiloxane precursor and sodium styrene sulfonate undergo a free radical polymerization reaction under the initiation of ammonium persulfate to obtain a modified polysiloxane modified with sulfonate.

[0027] A3. Place the modified polysiloxane and deionized water in a reaction kettle, mix them evenly, add phosphate buffer solution into the reaction kettle, and adjust the pH to 8.5±0.5 to obtain a modified solution.

[0028] Furthermore, in step A1, the ratio of aminopropylmethyldiethoxysilane, octamethylcyclotetrasiloxane, xylene, formic acid solution and tetramethyldivinyldisiloxane is 10-15g:18-20g:250-300mL:5-10mL:2-5g, the concentration of the formic acid solution is 15-20wt%, and the post-treatment step comprises: after the reaction is completed, the reaction temperature is cooled to room temperature, saturated salt water is added to the reaction solution, the phases are allowed to stand, the organic phase is washed with pure water 1-2 times, and the organic phase is transferred to a rotary evaporator at a temperature of 110-120°C, and low-boiling substances are evaporated under reduced pressure to obtain a modified polysiloxane precursor;

[0029] Furthermore, in step A2, the amount ratio of the modified polysiloxane precursor, sodium styrene sulfonate, N,N-dimethylformamide and ammonium persulfate is 10-12g:15-20g:220-250mL:1-1.5g, and the post-treatment step includes: after the reaction is completed, heating to 120-130°C, and distilling under reduced pressure until no liquid is recovered to obtain modified polysiloxane; in step A3, the amount ratio of the modified polysiloxane and deionized water is 10-15g:80-100mL.

[0030] Furthermore, the composite graphene is prepared by the following steps:

[0031] B1. Place acidified graphene oxide, zinc nitrate hexahydrate, and methanol in a reactor, stir for 10-15 minutes, add 2-methylimidazole, stir for 3-4 hours, and post-treat to obtain a composite graphene precursor;

[0032] The preparation reaction principle of composite graphene precursor is:

[0033] During the reaction, zinc nitrate hexahydrate dissociates in methanol to generate Zn2 + The oxygen-containing functional groups on the surface of acidified graphene oxide, hydroxyl and carboxyl groups serve as metal loading sites, and Zn2 is adsorbed by electrostatic interaction. + , Zn2 + It acts as a metal node and coordinates with 2-methylimidazole to form a Zn-N coordination bond, thereby constituting a composite graphene precursor.

[0034] B2. Place the composite graphene precursor, γ-methacryloxypropyltrimethoxysilane, deionized water and ethanol in a reactor, heat to 45-55° C., keep the temperature for reaction for 4-5 hours, and post-treat to obtain composite graphene.

[0035] The preparation reaction principle of composite graphene is:

[0036] During the reaction, the silicon-oxygen bond of γ-methacryloxypropyltrimethoxysilane is hydrolyzed and broken into Si-OH under the action of deionized water. Si-OH further undergoes condensation reaction with the hydroxyl groups on the surface of the composite stone precursor to obtain composite graphene modified with a silane coupling agent.

[0037] Furthermore, in step B1, the amount ratio of the acidified graphene oxide, zinc nitrate hexahydrate, methanol and 2-methylimidazole is 2-4g:20-25g:700-750mL:32-34g, and the post-treatment step includes: after the reaction is completed, filtering, washing the filter cake with deionized water and methanol 1-2 times, transferring it to a drying oven at a temperature of 40-50°C, and drying it to constant weight to obtain a composite graphene precursor; in step B2, the amount ratio of the composite graphene precursor, γ-methacryloxypropyltrimethoxysilane, deionized water and ethanol is 5-10g:1.5-2g:5-10mL:200-300mL, and the post-treatment step includes: after the reaction is completed, filtering, washing the filter cake with deionized water and ethanol 1-2 times, transferring it to a drying oven at a temperature of 40-50°C, and drying it to constant weight to obtain a composite graphene.

[0038] Furthermore, the acidified graphene oxide is prepared by the following method:

[0039] C1. Graphite powder and concentrated sulfuric acid are placed in a reactor, mixed evenly, ammonium persulfate and phosphorus pentoxide are added, the temperature is raised to 75-85°C, the reaction is kept at this temperature for 2-5 minutes, and post-processed to obtain acidified graphene;

[0040] The preparation reaction principle of acidified graphene is:

[0041] During the reaction, concentrated sulfuric acid provides an acidic environment, and concentrated sulfuric acid molecules are inserted between graphite layers, increasing the interlayer spacing of graphite powder and weakening the van der Waals force between graphite layers. Ammonium persulfate decomposes under acidic conditions, releasing sulfate radicals, which have strong oxidizing properties and directly attack the graphite carbon skeleton to generate oxygen-containing functional groups such as carboxyl and hydroxyl groups. Phosphorus pentoxide acts as an auxiliary oxidant to supplement reactive oxygen species and improve oxidation efficiency.

[0042] C2. Place the acidified graphene and concentrated sulfuric acid in a reactor, cool to 0-3°C in an ice bath, add potassium permanganate, stir for 15-25 minutes, add hydrogen peroxide solution, and post-treat to obtain acidified graphene oxide.

[0043] The preparation reaction principle of acidified graphene oxide is:

[0044] During the reaction, the low temperature environment suppresses the violent exothermic reaction between potassium permanganate and concentrated sulfuric acid, preventing local overheating from causing excessive damage to the graphite structure or uncontrolled decomposition of the oxidant. Potassium permanganate decomposes in concentrated sulfuric acid to produce manganese ions and sulfate ions, which attack the graphite carbon layer to form oxygen-containing functional groups such as hydroxyl, carboxyl and epoxy groups, achieving deep oxidation of the graphite. After the addition of hydrogen peroxide, its reducing properties reduce the unreacted potassium permanganate and high-valent manganese oxides to divalent manganese ions, terminating the oxidation process and avoiding excessive functionalization that leads to carbon skeleton breakage.

[0045] Furthermore, in step C1, the amount ratio of the graphite powder, concentrated sulfuric acid, ammonium persulfate and phosphorus pentoxide is 5-8g:250-300mL:4-6g:6-7g, and the post-treatment step includes: after the reaction is completed, filtering with suction, transferring the filter cake to a drying oven at a temperature of 40-50°C, and drying to constant weight to obtain acidified graphene; in step C2, the concentration of the hydrogen peroxide solution is 30-35wt%, and the amount ratio of the acidified graphene, concentrated sulfuric acid, potassium permanganate and hydrogen peroxide solution is 4-6g:200-250mL:8-10g:20-30mL. After the reaction is completed, filtering with suction, washing the filter cake with deionized water and ethanol 1-2 times, transferring it to a freeze dryer at a temperature of -40°C, and freeze-drying it to constant weight to obtain acidified graphene oxide.

[0046] The present invention also provides an acid- and alkali-resistant high-strength ultrafiltration membrane, which is obtained by adopting a preparation method of the acid- and alkali-resistant high-strength ultrafiltration membrane.

[0047] The present invention has the following beneficial effects:

[0048] 1. An acid- and alkali-resistant high-strength ultrafiltration membrane prepared by the present invention comprises the following steps: firstly preparing deeply oxidized acidified graphene oxide, combining the acidified graphene oxide with an organic metal skeleton by an in-situ deposition method to obtain a composite graphene precursor, and then modifying the composite graphene with a silane coupling agent; heating and refluxing aminopropylmethyldiethoxysilane to obtain an amino-terminated modified polysiloxane with a hyperbranched structure, and preparing the modified polysiloxane with a phosphate buffer to obtain a modified solution; preparing the olefin-modified composite graphene, polyvinylidene fluoride and auxiliary additives into a casting solution, and then using a phase inversion method to prepare the casting solution into an ultrafiltration base membrane; modifying the carboxyl structure on the ultrafiltration base membrane by an olefin free radical polymerization reaction, the carboxyl structure being activated in the composite buffer and further amidating with the amino-terminated modified polysiloxane. reaction to obtain an ultrafiltration membrane; first, deeply oxidized acidified graphene oxide is prepared, and its oxygen-containing functional groups are combined with an organic metal framework to obtain a composite graphene precursor, the hydrophobic imidazole ring structure of the composite graphene precursor can form a local barrier in an acidic and alkaline environment, reduce the direct contact between the oxygen-containing functional groups at the edge of the acidified graphene oxide sheet and the acid and alkali, inhibit the oxidative degradation of the acidified graphene oxide, and improve the acid and alkali resistance of the ultrafiltration membrane, while the rigid tetrahedral coordination structure of the composite graphene precursor is uniformly dispersed between the sheets of the acidified graphene oxide as a nanofiller, and the mechanical properties of the ultrafiltration membrane are improved by physically hindering the slip of the acidified graphene oxide sheets, and the composite graphene precursor is modified by adding an olefin-containing silane coupling agent, which can increase the reaction sites of the ultrafiltration base membrane and improve the mechanical properties of the ultrafiltration membrane.

[0049] 2. The present invention is to hydrolyze and condense aminopropylmethyldiethoxysilane and octamethylcyclotetrasiloxane to obtain a long polysiloxane chain modified with an amino group, and use tetramethyldivinyldisiloxane as a chain-terminating end group to form an unsaturated olefin double bond modification on the polysiloxane chain segment to obtain a modified polysiloxane precursor. Further, through a free radical initiation reaction, sodium styrenesulfonate containing a sulfonic acid group is chemically modified on the modified polysiloxane precursor to obtain a hydrophilic modified polysiloxane, thereby improving the dispersibility of the ultrafiltration membrane in water and the flux of the membrane. Then, through an amidation reaction, the modified The modified polysiloxane is chemically bonded to the surface of the ultrafiltration base membrane to form a mesh-like polysiloxane layer. The main chain of the polysiloxane is a Si-O-Si structure. The Si-O bond has high bond energy and can maintain stability in acidic and alkaline environments, protecting the ultrafiltration base membrane from chemical erosion. The molecular structure of the modified polysiloxane is highly branched and rigid, so that it forms a strong chemical cross-linking structure on the membrane surface, which can enhance the mechanical strength and anti-aging properties of the ultrafiltration membrane. The amino group of the modified polysiloxane side chain is a hydrophilic group, which can form a strong hydration with water molecules through hydrogen bonds and van der Waals forces, reducing the attachment of hydrophobic pollutants to the membrane surface.

[0050] 3. In the process of preparing ultrafiltration membrane of the present invention, polyvinylidene fluoride is selected as the base material, and is prepared into a casting liquid together with composite graphene, N,N-dimethylacetamide and auxiliary additives. The casting liquid is prepared into an ultrafiltration base membrane by a phase inversion method. The hydrophilic functional groups in the composite graphene give the casting liquid good hydrophilicity. In the phase separation process, the casting liquid interacts with water molecules through hydrogen bonds. This interaction promotes the exchange between the solvent and water, thereby accelerating the growth of the polymer-poor phase nucleus, resulting in a significant increase in the porosity of the ultrafiltration membrane, further improving the flux of the ultrafiltration membrane, and modifying the carboxyl structure on the ultrafiltration base membrane through olefin free radical polymerization. The carboxyl structure is activated in the composite buffer solution, and further undergoes an amidation reaction with the modified polysiloxane with terminal amino groups to obtain an ultrafiltration membrane. The carboxyl structure is activated by the composite buffer solution, which increases the reaction activity of the amidation and further improves the mechanical properties and acid and alkali resistance of the ultrafiltration membrane. DETAILED DESCRIPTION

[0051] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0052] The phosphate buffer used in the present invention was purchased from Chengdu Beilanmijin Biotechnology Co., Ltd., model FL10210, pH 7.4;

[0053] Example 1

[0054] This embodiment provides a method for preparing an acid- and alkali-resistant high-strength ultrafiltration membrane, comprising the following steps:

[0055] S1. Preparation of composite graphene

[0056] Weigh: 50g of graphite powder and 2500mL of concentrated sulfuric acid are placed in a reactor and mixed evenly. 40g of ammonium persulfate and 60g of phosphorus pentoxide are added. The temperature is raised to 75°C and kept for reaction for 2 minutes. After the reaction is complete, filter the filter cake and transfer it to a drying oven at 40°C and dry it to constant weight to obtain acidified graphene.

[0057] Weigh: 40 g of acidified graphene and 2000 mL of concentrated sulfuric acid were placed in a reactor, ice-bathed to 0°C, 80 g of potassium permanganate was added, stirred for 15 min, and 200 mL of 30 wt% hydrogen peroxide solution was added. After the reaction was completed, the filter cake was filtered and washed once with deionized water and ethanol, transferred to a freeze dryer at a temperature of -40°C, and freeze-dried to constant weight to obtain acidified graphene oxide;

[0058] Weigh: 20 g of acidified graphene oxide, 200 g of zinc nitrate hexahydrate, and 7000 mL of methanol, place them in a reactor, stir for 10 min, add 320 g of 2-methylimidazole, and stir for 3 h. After the reaction is complete, filter, wash the filter cake once with deionized water and methanol, transfer it to a drying oven at 40°C, and dry it to constant weight to obtain a composite graphene precursor;

[0059] Weigh: 50 g of composite graphene precursor, 15 g of γ-methacryloxypropyltrimethoxysilane, 50 mL of deionized water and 2000 mL of ethanol, place them in a reactor, heat to 45 ° C, and keep warm for 4 hours. After the reaction is completed, filter, wash the filter cake with deionized water and ethanol once, transfer it to a drying oven at a temperature of 40 ° C, and dry it to constant weight to obtain composite graphene.

[0060] S2. Preparation of modified liquid

[0061] Weigh: 100 g of aminopropylmethyldiethoxysilane, 180 g of octamethylcyclotetrasiloxane, and 2500 mL of xylene, place them in a reactor protected by a nitrogen atmosphere, heat to 110 ° C, add 50 mL of 15 wt% formic acid solution, and keep the reaction for 2 h. Add 20 g of tetramethyldivinyldisiloxane and keep the reaction for 3 h. After the reaction is completed, wait for the reaction to cool to room temperature, add saturated salt water to the reaction solution, let it stand for phase separation, wash the organic phase with pure water once, transfer it to a rotary evaporator at a temperature of 110 ° C, and evaporate under reduced pressure to remove low-boiling substances to obtain a modified polysiloxane precursor;

[0062] Weigh: 100 g of modified polysiloxane precursor, 150 g of sodium styrene sulfonate, and 2200 mL of N,N-dimethylformamide, place them in a reactor, heat to 70°C, stir for 5 minutes, add 10 g of ammonium persulfate, and keep the temperature for reaction for 2 hours. After the reaction is completed, heat to 120°C and distill under reduced pressure until no liquid is recovered to obtain modified polysiloxane;

[0063] Weigh: 100 g of modified polysiloxane and 800 mL of deionized water are placed in a reactor and mixed evenly. Phosphate buffer is added to the reactor and the pH is adjusted to 8.1 to obtain a modified solution.

[0064] S3. Preparation of ultrafiltration membrane

[0065] Polyvinyl pyrrolidone, dibutyl phthalate and titanium dioxide are uniformly mixed in a mass ratio of 2:0.5:0.5 to obtain an auxiliary additive, which is set aside;

[0066] Weigh 200 g of polyvinylidene fluoride, 20 g of composite graphene, 3000 mL of N,N-dimethylacetamide, and 50 g of auxiliary additives into a reactor, heat to 75° C., stir for 0.5 h, and allow to stand to remove bubbles to obtain a casting solution;

[0067] The casting solution was cast on a glass plate, scraped flat with a scraper, allowed to stand for 1 minute, and immersed in deionized water for 20 hours. After the soaking was completed, the membrane was washed once with deionized water, transferred to a drying oven at a temperature of 30°C, and dried to constant weight to obtain an ultrafiltration base membrane;

[0068] Weigh: 30 g of methacrylic acid and 1000 mL of pure water and mix them evenly to obtain a methacrylic acid solution for later use;

[0069] Weigh: The ultrafiltration base membrane was immersed in 3000 mL of methacrylic acid solution, nitrogen was blown for 25 minutes, 10 g of ammonium sulfite and 10 g of ammonium persulfate were added, the temperature was raised to 55°C, and the temperature was kept and shaken for 4 hours. After the reaction was completed, the membrane was washed once with deionized water, transferred to a drying oven at a temperature of 30°C, and dried to constant weight to obtain an ultrafiltration membrane precursor;

[0070] Weigh 70 g of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, 40 g of N-hydroxysuccinimide, 15 g of 2-(N-morpholino)ethanesulfonic acid, and 1000 mL of deionized water, mix well to obtain a composite buffer solution for later use.

[0071] Weigh: The ultrafiltration membrane precursor is placed in a composite buffer solution with a bath ratio of 1:30, immersed for 1 hour, transferred to the modification liquid with a bath ratio of 1:32, heated to 25°C, kept warm and shaken for 4 hours. After the reaction is completed, the membrane is washed twice with deionized water, transferred to a drying oven at a temperature of 30°C, and dried to constant weight to obtain an ultrafiltration membrane.

[0072] Example 2

[0073] This embodiment provides a method for preparing an acid- and alkali-resistant high-strength ultrafiltration membrane, comprising the following steps:

[0074] S1. Preparation of composite graphene

[0075] Weigh: 65 g of graphite powder and 2700 mL of concentrated sulfuric acid are placed in a reactor and mixed evenly. 50 g of ammonium persulfate and 65 g of phosphorus pentoxide are added. The temperature is raised to 80°C and kept for reaction for 3 minutes. After the reaction is complete, filter the filter cake and transfer it to a drying oven at 45°C and dry it to constant weight to obtain acidified graphene.

[0076] Weigh: 50 g of acidified graphene and 2250 mL of concentrated sulfuric acid are placed in a reactor, ice-bathed to 2°C, 90 g of potassium permanganate is added, stirred for 20 min, and 250 mL of 32 wt% hydrogen peroxide solution is added. After the reaction is completed, filter and wash the filter cake twice with deionized water and ethanol, transfer to a freeze dryer at -40°C, and freeze-dry to constant weight to obtain acidified graphene oxide;

[0077] Weigh: 30 g of acidified graphene oxide, 225 g of zinc nitrate hexahydrate, and 7250 mL of methanol are placed in a reactor and stirred for 13 min. 330 g of 2-methylimidazole is added and stirred for 3.5 h. After the reaction is completed, filter and wash the filter cake twice with deionized water and methanol, transfer it to a drying oven at 45 ° C, and dry it to constant weight to obtain a composite graphene precursor;

[0078] Weigh: 75 g of composite graphene precursor, 17 g of γ-methacryloxypropyltrimethoxysilane, 70 mL of deionized water and 2500 mL of ethanol, place them in a reactor, heat to 50 ° C, and keep warm for 4.5 hours. After the reaction is completed, filter, wash the filter cake twice with deionized water and ethanol, transfer it to a drying oven at a temperature of 45 ° C, and dry it to constant weight to obtain composite graphene.

[0079] S2. Preparation of modified liquid

[0080] Weigh: 120 g of aminopropylmethyldiethoxysilane, 190 g of octamethylcyclotetrasiloxane, and 2700 mL of xylene, place them in a reactor protected by a nitrogen atmosphere, heat to 115 ° C, add 70 mL of 17 wt% formic acid solution, and keep the temperature for 3 h. Add 20 g of tetramethyldivinyldisiloxane and keep the temperature for 3.5 h. After the reaction is completed, heat to 125 ° C and distill under reduced pressure until no liquid is produced to obtain a modified polysiloxane precursor;

[0081] Weigh: 110 g of modified polysiloxane precursor, 170 g of sodium styrene sulfonate, and 2400 mL of N,N-dimethylformamide into a reactor, heat to 75°C, stir for 7 minutes, add 12 g of ammonium persulfate, and keep warm for 3 hours. After the reaction is completed, wait for the reaction to cool to room temperature, add ethyl acetate and pure water to the reaction solution, let it stand for phase separation, wash the organic phase with pure water twice, transfer it to a rotary evaporator at a temperature of 110°C, and evaporate low-boiling substances under reduced pressure to obtain modified polysiloxane;

[0082] Weigh: 120 g of modified polysiloxane and 900 mL of deionized water are placed in a reactor and mixed evenly. Phosphate buffer is added to the reactor and the pH is adjusted to 8.3 to obtain a modified solution.

[0083] S3. Preparation of ultrafiltration membrane

[0084] Polyvinyl pyrrolidone, dibutyl phthalate and titanium dioxide are uniformly mixed in a mass ratio of 2:0.5:0.5 to obtain an auxiliary additive, which is set aside;

[0085] Weigh 225 g of polyvinylidene fluoride, 30 g of composite graphene, 3250 mL of N,N-dimethylacetamide, and 70 g of auxiliary additives into a reactor, heat to 80° C., stir for 1 h, and allow to stand to remove bubbles to obtain a casting solution;

[0086] The casting solution was cast on a glass plate, scraped flat with a scraper, allowed to stand for 2 minutes, and immersed in deionized water for 22 hours. After the soaking was completed, the membrane was washed twice with deionized water, transferred to a drying oven at a temperature of 35°C, and dried to constant weight to obtain an ultrafiltration base membrane;

[0087] Weigh: 40 g of methacrylic acid and 100 mL of pure water and mix them evenly to obtain a methacrylic acid solution for later use;

[0088] Weigh: The ultrafiltration base membrane was immersed in 4000 mL of methacrylic acid solution, nitrogen was blown for 30 minutes, 15 g of ammonium sulfite and 15 g of ammonium persulfate were added, the temperature was raised to 60°C, and the temperature was kept and shaken for 5 hours. After the reaction was completed, the membrane was washed twice with deionized water, transferred to a drying oven at a temperature of 35°C, and dried to constant weight to obtain an ultrafiltration membrane precursor;

[0089] Weigh 75 g of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, 45 g of N-hydroxysuccinimide, 17 g of 2-(N-morpholino)ethanesulfonic acid, and 1000 mL of deionized water, mix well to obtain a composite buffer solution, and set aside.

[0090] Weigh: The ultrafiltration membrane precursor is placed in a composite buffer solution with a bath ratio of 1:32, immersed for 1.5 hours, transferred to the modification liquid with a bath ratio of 1:33, heated to 30°C, kept warm and shaken for 4.5 hours. After the reaction is completed, the membrane is washed 1-2 times with deionized water, transferred to a drying oven at a temperature of 35°C, and dried to constant weight to obtain an ultrafiltration membrane.

[0091] Example 3

[0092] This embodiment provides a method for preparing an acid- and alkali-resistant high-strength ultrafiltration membrane, comprising the following steps:

[0093] S1. Preparation of composite graphene

[0094] Weigh: 80g of graphite powder and 3000mL of concentrated sulfuric acid are placed in a reactor and mixed evenly. 60g of ammonium persulfate and 70g of phosphorus pentoxide are added. The temperature is raised to 85°C and kept for reaction for 5min. After the reaction is complete, filter the mixture and transfer the filter cake to a drying oven at 50°C and dry it to constant weight to obtain acidified graphene.

[0095] Weigh: 60 g of acidified graphene and 2500 mL of concentrated sulfuric acid were placed in a reactor, ice-bathed to 3°C, 100 g of potassium permanganate was added, stirred for 25 min, and 300 mL of 35 wt% hydrogen peroxide solution was added. After the reaction was completed, the filter cake was filtered and washed twice with deionized water and ethanol, transferred to a freeze dryer at a temperature of -40°C, and freeze-dried to constant weight to obtain acidified graphene oxide;

[0096] Weigh: 40 g of acidified graphene oxide, 250 g of zinc nitrate hexahydrate, and 7500 mL of methanol are placed in a reactor and stirred for 15 min. 340 g of 2-methylimidazole is added and stirred for 4 h. After the reaction is completed, filter and wash the filter cake twice with deionized water and methanol, transfer to a drying oven at 50°C, and dry to constant weight to obtain a composite graphene precursor;

[0097] Weigh: 100 g of composite graphene precursor, 20 g of γ-methacryloxypropyltrimethoxysilane, 100 mL of deionized water and 3000 mL of ethanol, place them in a reactor, heat to 55 ° C, and keep warm for 5 hours. After the reaction is completed, filter, wash the filter cake twice with deionized water and ethanol, transfer it to a drying oven at a temperature of 50 ° C, and dry it to constant weight to obtain composite graphene.

[0098] S2. Preparation of modified liquid

[0099] Weigh: 150 g of aminopropylmethyldiethoxysilane, 200 g of octamethylcyclotetrasiloxane, and 3000 mL of xylene are placed in a reactor protected by a nitrogen atmosphere, heated to 120° C., 100 mL of a 20 wt% formic acid solution is added, and the reaction is kept warm for 4 h. 50 g of tetramethyldivinyldisiloxane is added and the reaction is kept warm for 4 h. After the reaction is completed, the reaction mixture is cooled to room temperature, saturated brine is added to the reaction solution, and the phases are allowed to stand. The organic phase is washed twice with pure water, transferred to a rotary evaporator at 120° C., and low-boiling substances are evaporated under reduced pressure to obtain a modified polysiloxane precursor;

[0100] Weigh: 120 g of modified polysiloxane precursor, 200 g of sodium styrene sulfonate, and 2500 mL of N,N-dimethylformamide into a reactor, heat to 80°C, stir for 10 min, add 15 g of ammonium persulfate, and keep warm for 4 h. After the reaction is completed, heat to 130°C and distill under reduced pressure until no liquid is recovered to obtain modified polysiloxane;

[0101] Weigh: 150 g of modified polysiloxane and 1000 mL of deionized water are placed in a reactor, mixed evenly, and phosphate buffer is added to the reactor, and the pH is adjusted to 8.5 to obtain a modified solution.

[0102] S3. Preparation of ultrafiltration membrane

[0103] Polyvinyl pyrrolidone, dibutyl phthalate and titanium dioxide are uniformly mixed in a mass ratio of 2:0.5:0.5 to obtain an auxiliary additive, which is set aside;

[0104] Weigh 250 g of polyvinylidene fluoride, 40 g of composite graphene, 3500 mL of N,N-dimethylacetamide, and 80 g of auxiliary additives into a reactor, heat to 85° C., stir for 1 h, and allow to stand to remove bubbles to obtain a casting solution;

[0105] The casting solution was cast on a glass plate, scraped flat with a scraper, allowed to stand for 2 minutes, and immersed in deionized water for 24 hours. After the soaking was completed, the membrane was washed twice with deionized water, transferred to a drying oven at a temperature of 40°C, and dried to constant weight to obtain an ultrafiltration base membrane;

[0106] Weigh: 50 g of methacrylic acid and 1000 mL of pure water and mix them evenly to obtain a methacrylic acid solution for later use;

[0107] Weigh: The ultrafiltration base membrane was immersed in 5000 mL of methacrylic acid solution, nitrogen was blown for 35 minutes, 20 g of ammonium sulfite and 20 g of ammonium persulfate were added, the temperature was raised to 65°C, and the temperature was kept and shaken for 6 hours. After the reaction was completed, the membrane was washed twice with deionized water, transferred to a drying oven at a temperature of 40°C, and dried to constant weight to obtain an ultrafiltration membrane precursor;

[0108] Weigh 80 g of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, 50 g of N-hydroxysuccinimide, 20 g of 2-(N-morpholino)ethanesulfonic acid, and 1000 mL of deionized water, mix well to obtain a composite buffer solution, and set aside.

[0109] Weigh: The ultrafiltration membrane precursor is placed in a composite buffer solution with a bath ratio of 1:35, immersed for 1.5 hours, transferred to the modification liquid with a bath ratio of 1:35, heated to 35°C, kept warm and shaken for 6 hours. After the reaction is completed, the membrane is washed 1-2 times with deionized water, transferred to a drying oven at a temperature of 40°C, and dried to constant weight to obtain an ultrafiltration membrane.

[0110] Comparative Example 1

[0111] The difference between this comparative example and Example 2 is that in step S3, the composite graphene used is replaced by an equal amount of the acidified graphene oxide in step S1.

[0112] Comparative Example 2

[0113] The difference between this comparative example and Example 2 is that in step S3, no modifying liquid is used during the preparation of the ultrafiltration membrane used.

[0114] Comparative Example 3

[0115] The difference between this comparative example and Example 2 is that in step S3, an ultrafiltration base membrane is used as an ultrafiltration membrane precursor.

[0116] Performance testing:

[0117] The pure water flux of the ultrafiltration membranes prepared in Examples 1-3 and Comparative Examples 1-3 at a pressure of 0.01 MPa was tested with reference to the standard HY / T 053-2001 "Microporous Filtration Membrane";

[0118] The acid and alkali resistance of the ultrafiltration membranes prepared in Examples 1-3 and Comparative Examples 1-3 were tested with reference to the standard HG / T 3984-2007 "Chemical Corrosion Resistant Modified Polypropylene Storage Tanks";

[0119] The porosity of the ultrafiltration membranes prepared in Examples 1-3 and Comparative Examples 1-3 was tested with reference to HY / T 065-2002 "Polyvinylidene fluoride microporous membrane";

[0120] The tensile strength and elongation at break of the ultrafiltration membranes prepared in Examples 1-3 and Comparative Examples 1-3 were tested in accordance with the standard HY / T 213-2016 “Determination of tensile strength at break of hollow fiber ultrafiltration / microfiltration membranes”.

[0121] The water contact angles of the ultrafiltration membranes prepared in Examples 1-3 and Comparative Examples 1-3 were tested according to the standard HY / T 266-2018 "Contact Angle Method for Testing the Hydrophilicity of the Surface of Externally Pressurized Hollow Fiber Ultrafiltration Membranes". The specific data are shown in Table 1.

[0122] The ultrafiltration membranes prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to heat aging tests with reference to the standard GB / T 37382-2019 “Determination of high temperature and high humidity aging properties of optically functional thin films for liquid crystal display backlight modules”. The tensile strength and elongation at break of the materials were determined with reference to the standard HY / T 213-2016 “Determination of tensile strength at break of hollow fiber ultrafiltration / microfiltration membranes”. The specific data are shown in Table 2.

[0123] Table 1 - Performance test data of each sample

[0124]

[0125]

[0126] Table 2 - Performance test data of each sample after thermal aging

[0127]

[0128] Data Analysis:

[0129] Comparing and analyzing the data in Table 1 above, the acid- and alkali-resistant high-strength ultrafiltration membrane prepared by the present invention is resistant to corrosion by saturated calcium hydroxide solution and 10wt% nitric acid solution, and its pure water flux is 80.87L·m -2 h, tensile strength of 6.31 MPa, elongation at break of 36.83%, water contact angle of 22°, and porosity of 78.93%; after thermal aging, the tensile strength was 6.02 MPa and the elongation at break was 36.21%;

[0130] By comparing the data of Example 2 and Comparative Example 1, it can be found that the ultrafiltration membrane of Comparative Example 1 is not resistant to corrosion by saturated calcium hydroxide solution and 10wt% nitric acid solution, and its tensile strength and elongation at break are significantly reduced, indicating that the present invention first prepares deeply oxidized acidified graphene oxide, and combines its oxygen-containing functional groups with an organic metal framework to obtain a composite graphene precursor. The hydrophobic imidazole ring structure of the composite graphene precursor can form a local barrier in an acidic and alkaline environment, reduce the direct contact between the oxygen-containing functional groups at the edge of the acidified graphene oxide sheet and the acid and alkali, inhibit the oxidative degradation of the acidified graphene oxide, and improve the acid and alkali resistance of the ultrafiltration membrane. At the same time, the rigid tetrahedral coordination structure of the composite graphene precursor is uniformly dispersed between the sheets of the acidified graphene oxide as a nanofiller, and the mechanical properties of the ultrafiltration membrane are improved by physically hindering the slip of the acidified graphene oxide sheets. At the same time, the addition of an olefin-containing silane coupling agent to modify the composite graphene precursor can increase the reaction sites of the ultrafiltration base membrane and improve the mechanical properties of the ultrafiltration membrane.

[0131] By comparing the data of Example 2 and Comparative Example 2, it can be found that the ultrafiltration membrane of Comparative Example 2 is not resistant to corrosion by saturated calcium hydroxide solution and 10wt% nitric acid solution, and the water contact angle and pure water flux are significantly reduced, and the tensile strength and elongation at break after heat aging are reduced, indicating that the present invention hydrolyzes and condenses aminopropylmethyldiethoxysilane and octamethylcyclotetrasiloxane to obtain a long polysiloxane chain modified with an amino group, uses tetramethyldivinyldisiloxane as a chain-terminating end group, forms an unsaturated olefin double bond modification on the polysiloxane chain segment, and obtains a modified polysiloxane precursor. Further, through a free radical initiation reaction, sodium styrenesulfonate containing a sulfonic acid group is chemically modified on the modified polysiloxane precursor to obtain a hydrophilic The modified polysiloxane improves the dispersibility of the ultrafiltration membrane in water and the flux of the membrane. Then, through the amidation reaction, the modified polysiloxane is chemically bonded to the surface of the ultrafiltration base membrane to form a mesh-like polysiloxane layer. The main chain of the polysiloxane is a Si-O-Si structure. The Si-O bond has high bond energy and can maintain stability in acidic and alkaline environments, protecting the ultrafiltration base membrane from chemical erosion. The molecular structure of the modified polysiloxane is highly branched and rigid, so that it forms a strong chemical cross-linking structure on the membrane surface, which can enhance the mechanical strength and anti-aging properties of the ultrafiltration membrane. The amino group of the modified polysiloxane side chain is a hydrophilic group, which can form a strong hydration with water molecules through hydrogen bonds and van der Waals forces, reducing the adhesion of hydrophobic pollutants to the membrane surface.

[0132] By comparing the data of Example 2 and Comparative Example 3, it can be found that the ultrafiltration membrane of Comparative Example 3 is still resistant to corrosion by saturated calcium hydroxide solution and 10wt% nitric acid solution, and the tensile strength and elongation at break are significantly reduced, and the tensile strength and elongation at break after heat aging are reduced, indicating that the present invention modifies the carboxyl structure on the ultrafiltration base membrane through olefin free radical polymerization reaction, and the carboxyl structure is activated in the composite buffer, and further undergoes amidation reaction with the modified polysiloxane with terminal amino group to obtain the ultrafiltration membrane. The carboxyl structure is activated by the composite buffer, which increases the reaction activity of amidation and further improves the mechanical properties and acid and alkali resistance of the ultrafiltration membrane. The carboxyl group is not modified on the ultrafiltration base membrane through free radical polymerization reaction, which reduces the grafting rate of the modified polysiloxane on the ultrafiltration membrane, further reducing its mechanical properties and anti-aging performance.

[0133] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to specific embodiments. Obviously, many modifications and variations are possible based on the contents of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing an acid- and alkali-resistant high-strength ultrafiltration membrane, characterized in that: The following steps are involved: S1. Place polyvinylidene fluoride, composite graphene, N,N-dimethylacetamide and auxiliary additives in a reaction kettle, heat to 75-85° C., stir for 0.5-1 hour, and allow to stand to remove bubbles to obtain a casting solution; S2. Cast the casting solution on a glass plate, scrape it flat with a scraper, let it stand for 1-2 minutes, immerse it in deionized water, soak it for 20-24 hours, and post-treat it to obtain an ultrafiltration base membrane; S3, immersing the ultrafiltration base membrane in methacrylic acid solution, blowing nitrogen for 25-35 minutes, adding ammonium sulfite and ammonium persulfate, heating to 55-65°C, keeping the temperature and shaking for 4-6 hours, and post-treating to obtain an ultrafiltration membrane precursor; S4, placing the ultrafiltration membrane precursor in a composite buffer solution, immersing for 1-1.5 hours, transferring to a modification solution, heating to 25-35°C, keeping the temperature and shaking for 4-6 hours, and post-treating to obtain an ultrafiltration membrane; In step S1, the amount ratio of the polyvinylidene fluoride, composite graphene, N,N-dimethylacetamide and auxiliary additives is 20-25g:2-4g:300-350mL:5-8g; in step S3, the methacrylic acid solution is composed of methacrylic acid and pure water in a ratio of 3-5g:100mL, and the amount ratio of the methacrylic acid solution, ammonium sulfite and ammonium persulfate is 300-500mL:1-2g: 1-2g; in step S4, the composite buffer is composed of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, N-hydroxysuccinimide, 2-(N-morpholino)ethanesulfonic acid and deionized water in a dosage ratio of 7-8g:4-5g:1.5-2g:100mL, the bath ratio of the ultrafiltration membrane precursor and the composite buffer is 1:30-35, and the bath ratio of the ultrafiltration membrane precursor and the modifying liquid is 1:32-35; The modified liquid is obtained by the following preparation method: A1. Aminopropylmethyldiethoxysilane, octamethylcyclotetrasiloxane, and xylene are placed in a reactor protected by a nitrogen atmosphere, heated to 110-120° C., formic acid solution is added, and the mixture is kept warm for 2-4 hours. Tetramethyldivinyldisiloxane is added, and the mixture is kept warm for 3-4 hours. Post-treatment is performed to obtain a modified polysiloxane precursor. A2. Place a modified polysiloxane precursor, sodium styrene sulfonate, and N,N-dimethylformamide in a reaction kettle, heat to 70-80° C., stir for 5-10 minutes, add ammonium persulfate, keep the temperature for reaction for 2-4 hours, and post-treat to obtain a modified polysiloxane; A3. Place the modified polysiloxane and deionized water in a reaction kettle, mix well, add phosphate buffer solution into the reaction kettle, and adjust the pH to 8.5±0.5 to obtain a modified solution; In step A1, the amount ratio of aminopropylmethyldiethoxysilane, octamethylcyclotetrasiloxane, xylene, formic acid solution and tetramethyldivinyldisiloxane is 10-15g:18-20g:250-300mL:5-10mL:2-5g, and the concentration of the formic acid solution is 15-20wt%; in step A2, the amount ratio of the modified polysiloxane precursor, sodium styrenesulfonate, N,N-dimethylformamide and ammonium persulfate is 10-12g:15-20g:220-250mL:1-1.5g; in step A3, the amount ratio of the modified polysiloxane and deionized water is 10-15g:80-100mL; The composite graphene is prepared by the following steps: B1. Place acidified graphene oxide, zinc nitrate hexahydrate, and methanol in a reactor, stir for 10-15 minutes, add 2-methylimidazole, stir for 3-4 hours, and post-treat to obtain a composite graphene precursor; B2. Place the composite graphene precursor, γ-methacryloxypropyltrimethoxysilane, deionized water and ethanol in a reactor, heat to 45-55° C., keep the temperature for reaction for 4-5 hours, and post-treat to obtain composite graphene.

2. The method for preparing an acid- and alkali-resistant high-strength ultrafiltration membrane according to claim 1, characterized in that: In step B1, the amount ratio of the acidified graphene oxide, zinc nitrate hexahydrate, methanol and 2-methylimidazole is 2-4g:20-25g:700-750mL:32-34g; in step B2, the amount ratio of the composite graphene precursor, γ-methacryloxypropyltrimethoxysilane, deionized water and ethanol is 5-10g:1.5-2g:5-10mL:200-300mL.

3. The method for preparing an acid- and alkali-resistant high-strength ultrafiltration membrane according to claim 1, characterized in that: Acidized graphene oxide was prepared by the following method: C1. Graphite powder and concentrated sulfuric acid are placed in a reactor, mixed evenly, ammonium persulfate and phosphorus pentoxide are added, the temperature is raised to 75-85°C, the reaction is kept at this temperature for 2-5 minutes, and post-processed to obtain acidified graphene; C2. Place the acidified graphene and concentrated sulfuric acid in a reactor, cool to 0-3°C in an ice bath, add potassium permanganate, stir for 15-25 minutes, add hydrogen peroxide solution, and post-treat to obtain acidified graphene oxide.

4. The method for preparing an acid- and alkali-resistant high-strength ultrafiltration membrane according to claim 3, characterized in that: In step C1, the ratio of the graphite powder, concentrated sulfuric acid, ammonium persulfate and phosphorus pentoxide is 5-8 g:250-300 mL:4-6 g:6-7 g; in step C2, the concentration of the hydrogen peroxide solution is 30-35 wt%, and the ratio of the acidified graphene, concentrated sulfuric acid, potassium permanganate and hydrogen peroxide solution is 4-6 g:200-250 mL:8-10 g:20-30 mL.

5. An acid and alkali resistant high strength ultrafiltration membrane, characterized in that: The acid- and alkali-resistant high-strength ultrafiltration membrane adopts the preparation method of the acid- and alkali-resistant high-strength ultrafiltration membrane according to any one of claims 1 to 4.

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