A high-throughput, anti-pollution polyvinylidene fluoride hybrid ultrafiltration membrane, preparation method and application

Abstract

The invention discloses a high-flux anti-pollution polyvinylidene fluoride hybrid ultrafiltration membrane, a preparation method and application thereof. The preparation method comprises the following steps: using potassium hydroxide and ethanol as raw materials to prepare an alkaline solution, adding polyvinylidene fluoride, a first catalyst and the alkaline solution into a reaction container, stirring evenly to form a mixed solution for reaction, and then washing and drying to obtain alkali-treated defluorinated polyvinylidene fluoride; dissolving ethylenediamine in distilled water, adding graphene, a coagulant and a coupling agent, stirring evenly to form a mixed solution, heating in a water bath, and then washing and drying to obtain aminated graphene oxide; a chemical grafting method comprises the following steps: adding defluorinated polyvinylidene fluoride, aminated graphene oxide particles and a second catalyst into a methanol solvent for reaction, and then washing and drying; adding alkali-treated polyvinylidene fluoride aminated graphene oxide powder, polyethylene glycol, methyl pyrrolidone and polyoxyethylene sorbitan monooleate into a three-necked flask, heating in a water bath to obtain a membrane casting solution; and performing degassing treatment to obtain the ultrafiltration membrane.

Description

Technical Field

[0001] The present invention relates to the field of ultrafiltration membrane preparation, in particular to a high-flux anti-pollution polyvinylidene fluoride hybrid ultrafiltration membrane, a preparation method and applications thereof. Background Art

[0002] Membrane separation technology primarily utilizes the selective permeability of membranes to selectively permeate, separate, and purify different components in a liquid, thereby achieving concentration. Compared to traditional separation technologies, membrane separation offers lower energy consumption, no secondary pollution, simpler procedures, and higher separation efficiency. Consequently, membrane separation technology has been widely used in wastewater treatment, gas processing, food, medicine, petrochemicals, and other fields. Existing membrane separation technologies are categorized into microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO) electrodialysis.

[0003] Composite membrane materials are composed of multiple membrane materials, overcoming the inherent shortcomings of single membrane materials and improving the hydrophilicity, filtration performance, and anti-fouling capabilities of separation membranes. Common composite membranes include organic-inorganic hybrid composite membranes, inorganic composite membranes, and organic composite membranes. Cu2S, GO, Mg-Al nanoparticles, and carbon nanotubes are often added to organic-inorganic hybrid composite membranes to improve the performance of inorganic-organic composite membranes. However, the addition of Cu2S, GO, Mg-Al nanoparticles, and carbon nanotubes can easily cause membrane fouling, which reduces the pure water flux of the membrane and shortens its service life. Summary of the Invention

[0004] In order to improve the anti-pollution performance of an ultrafiltration membrane, the present invention provides a method for preparing a high-flux anti-pollution polyvinylidene fluoride hybrid ultrafiltration membrane.

[0005] The first object of the present invention is to provide a high-throughput anti-pollution polyvinylidene fluoride hybrid ultrafiltration membrane and a preparation method thereof, using the following technical solutions:

[0006] A method for preparing a high-throughput, anti-pollution polyvinylidene fluoride hybrid ultrafiltration membrane comprises the following steps:

[0007] The preparation method of polyvinylidene fluoride by alkali treatment comprises: using potassium hydroxide and ethanol as raw materials to prepare an alkali solution, adding polyvinylidene fluoride, a first catalyst and the alkali solution into a reaction vessel, stirring uniformly to form a mixed solution, stirring and reacting at 50°C-100°C for 0.3h-1h, vacuum filtering, washing the obtained powder, and then drying it in a vacuum drying oven at a temperature of 40°C-100°C for 5h-11h to obtain alkali-treated defluorinated polyvinylidene fluoride; wherein the weight ratio of potassium hydroxide to ethanol is 1:(1-15); and the weight ratio of the first catalyst to the alkali solution to polyvinylidene fluoride is 1:1:(10-20).

[0008] The preparation method of aminated graphene oxide comprises: dissolving 1g of ethylenediamine in 10-100g of distilled water, adding graphene, a coagulant, and a coupling agent into a reactor, and stirring to form a mixed solution; then adjusting the pH of the reaction system to 4-6 with 0.01mol / L-1mol / L HCl, heating the reaction system in a water bath at 15-45°C, and magnetically stirring the mixture for 8-24 hours, followed by vacuum filtration, washing, and drying to obtain aminated graphene oxide nanoparticles; wherein the reaction molar ratio of graphene oxide, ethylenediamine, coagulant, and coupling agent is: (1-10):(1-10):(1-10):1;

[0009] The preparation method of chemical grafting of aminated graphene oxide and polyvinylidene fluoride is as follows:

[0010] S1: Addition reaction: 1 g of the defluorinated polyvinylidene fluoride obtained in step (1), 0.01-10 g of the aminated graphene oxide particles obtained in step (2), and the second catalyst are added to a methanol solvent in a ratio of 1450 mg of the second catalyst: polyvinylidene fluoride: methanol: 20 mL, and then reacted at a temperature within the range of 25-32° C. for 18 h, and then vacuum filtered, washed, and dried;

[0011] S2: Casting solution: 1 g of the alkali-treated polyvinylidene fluoride aminated graphene oxide powder obtained in S1, 0.7-0.9 g of polyethylene glycol with a molecular weight of 10,000, 3-7 g of methyl pyrrolidone, and 0.2-0.45 g of polyoxyethylene sorbitan monooleate were added to a three-necked flask, and heated in a water bath at 50-70°C with mechanical stirring for 6-12 h to obtain a casting solution;

[0012] S3: degassing treatment; scraping the degassing membrane obtained in step S2 and solidifying it to obtain a high-flux anti-pollution polyvinylidene fluoride hybrid ultrafiltration membrane.

[0013] By adopting the above technical solution, the present application effectively removes the highly hydrophobic fluorine element and increases the hydrophilicity of the ultrafiltration membrane by alkaline treatment of polyvinylidene fluoride; and by grafting aminated graphene oxide onto the defluorinated polyvinylidene fluoride, the polyvinylidene fluoride membrane is modified to improve the pure water flux of the ultrafiltration membrane. At the same time, the chemical grafting method also effectively improves the anti-pollution performance of the ultrafiltration membrane, avoiding the phenomenon of reduced membrane flux due to membrane contamination during the post-treatment process.

[0014] In step (2), the coagulant and the coupling agent jointly activate the carboxyl groups in the graphene, and then ethylenediamine connects the amino groups to the activated carboxyl groups, and then reacts with the carbon-carbon double bonds generated after the defluorination treatment in step (1) to reduce the probability of membrane contamination. The addition of aminated graphene oxide not only increases the phase exchange rate, but also promotes the formation of a macroporous structure of the composite membrane, thereby increasing the pores of the composite membrane, thereby improving the water flux and permeability of the composite membrane. However, when the amount of aminated graphene oxide added is too large, the viscosity of the casting solution will increase, resulting in delayed phase separation during the film formation process, and since the membrane easily forms a compact structure, the membrane flux is reduced. Moreover, if too much aminated graphene oxide is added, the pore size of the composite membrane will be too large, which will reduce the retention rate.

[0015] In addition, the hydrophilicity of graphene is improved after amination oxidation, which reduces the water permeability resistance of the ultrafiltration membrane.

[0016] Preferably, the first catalyst in step (1) is tetrabutylammonium bromide, benzyltriethylammonium chloride, tetrabutylammonium chloride, tetrabutylammonium hydrogen sulfate, trioctylmethylammonium chloride, dodecyltrimethylammonium chloride, or tetradecyltrimethylammonium chloride.

[0017] Preferably, in step (2), the coagulant is 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride; and the coupling agent is N-hydroxysuccinimide.

[0018] Preferably, the second catalyst in step S1 is prepared by the following method: 32 g of KF·2H2O is dissolved in 100 ml of water, the potassium fluoride solution is poured into a flask, and 30 g of basic alumina with a mesh size of 100-200 mesh is added. The mixture is heated in a water bath at 65-75° C. with magnetic stirring for 1 hour, the water is removed by vacuum filtration, and the mixture is dried in a vacuum oven at 80-130° C. for 4-10 hours to obtain a white powder.

[0019] By adopting the above technical solution, the second catalyst obtained by the above preparation method has a short reaction time and high reaction efficiency.

[0020] Preferably, the mixed solution in step (1) is reacted under magnetic stirring at 300-500 r / min for 0.3-1 h.

[0021] Preferably, the mechanical stirring in step S2 is carried out at 300-900 r / min for 6-12 h.

[0022] By adopting the above technical solution, when the casting liquid is stirred at this stirring speed, it is beneficial to discharge the bubbles in the casting liquid, making the casting liquid more uniform, and at the same time making the subsequent film more uniform, avoiding the occurrence of voids in the later stage.

[0023] Preferably, in step S3, the casting solution is allowed to stand for degassing at normal pressure and a temperature of 15-70° C. for 8-20 hours.

[0024] The second object of the present invention is to provide an ultrafiltration membrane obtained by the preparation method of the above-mentioned high-flux anti-pollution polyvinylidene fluoride hybrid ultrafiltration membrane.

[0025] The third object of the present invention is to provide a high-throughput anti-pollution polyvinylidene fluoride hybrid ultrafiltration membrane for use in wastewater.

[0026] In summary, the present invention has the following beneficial effects:

[0027] 1. This application utilizes aminated graphene oxide nanomaterials to in situ modify defluorinated polyvinylidene fluoride. Compared with surface modification and physical blending membrane preparation methods, the preparation method of this application can simultaneously improve the membrane's anti-fouling performance and membrane flux, avoiding the membrane fouling and low membrane flux recovery rate caused by the post-treatment process;

[0028] 2. This application uses aminated graphene oxide nanomaterials as modifiers. Compared with the use of inorganic nanomaterial modifiers, this method can significantly improve the distribution of the nanomaterial modifier within the membrane, thereby inhibiting the agglomeration and poor compatibility of the nanomaterial modifier during the membrane preparation process and avoiding the formation of structural defects within the membrane;

[0029] 3. The preparation method of the present application is simple to operate, does not require secondary modification of the obtained ultrafiltration membrane, and is easy to carry out large-scale industrial production on existing ultrafiltration membrane production equipment. At the same time, the raw materials of the present application are selected from cheap and easily available chemicals, which are low-cost and easier to expand production. DETAILED DESCRIPTION

[0030] The present invention is further described in detail below with reference to the examples.

[0031] In the present application, the carboxyl groups in graphene oxide first undergo a condensation reaction with a coagulant, then further undergo protonation, then undergo an esterification reaction with a coupling agent, and then undergo a deprotonation reaction with a coagulant again to achieve the purpose of activating the carboxyl groups. Finally, an aminolysis reaction occurs with ethylenediamine, so that ethylenediamine is connected to the carboxyl groups to form an amide bond, and then an addition reaction is carried out with the defluorinated polyvinylidene fluoride obtained by alkali treatment.

[0032] Preparation Example 1

[0033] A method for preparing a second catalyst comprises the following steps:

[0034] Dissolve 20g of KF·2H2O in 50mL of water, pour the potassium fluoride solution into a flask, and then add 20g of basic alumina with a mesh size of 100-200 mesh. Heat in a water bath at 65°C with magnetic stirring for 1 hour. Remove water by vacuum filtration and dry in a vacuum oven at 80°C for 4 hours to obtain a white powder.

[0035] Preparation Example 2

[0036] A method for preparing a second catalyst comprises the following steps:

[0037] Dissolve 30 g of KF·2H2O in 100 mL of water, pour the potassium fluoride solution into a flask, and then add 30 g of basic alumina with a mesh size of 100-200 mesh. Heat in a water bath at 65°C with magnetic stirring for 1 hour. Remove water by vacuum filtration and dry in a vacuum oven at 80°C for 4 hours to obtain a white powder.

[0038] Preparation Example 3

[0039] A method for preparing a second catalyst comprises the following steps:

[0040] Dissolve 40g of KF·2H2O in 150mL of water, pour the potassium fluoride solution into a flask, and then add 40g of basic alumina with a mesh size of 100-200 mesh. Heat in a water bath at 65°C with magnetic stirring for 1 hour. Remove water by vacuum filtration and dry in a vacuum oven at 80°C for 4 hours to obtain a white powder.

[0041] Preparation Example 4

[0042] A method for preparing a second catalyst comprises the following steps:

[0043] Dissolve 50g of KF·2H2O in 200mL of water, pour the potassium fluoride solution into a flask, and then add 50g of basic alumina with a mesh size of 100-200 mesh. Heat in a water bath at 65°C with magnetic stirring for 1 hour. Remove water by vacuum filtration and dry in a vacuum oven at 80°C for 4 hours to obtain a white powder.

[0044] Preparation Example 5

[0045] A method for preparing a second catalyst comprises the following steps:

[0046] Dissolve 40g of KF·2H2O in 150mL of water, pour the potassium fluoride solution into a flask, and then add 40g of basic alumina with a mesh size of 100-200 mesh. Heat in a water bath at 75°C with magnetic stirring for 1 hour. Remove water by vacuum filtration and dry in a vacuum oven at 130°C for 10 hours to obtain a white powder.

[0047] Example 1

[0048] A method for preparing a high-throughput, anti-pollution polyvinylidene fluoride hybrid ultrafiltration membrane comprises the following steps:

[0049] Preparation method of polyvinylidene fluoride treated with alkali: 10 g of polyvinylidene fluoride, 1 g of tetrabutylammonium bromide and 200 mL of a 2 mol / L potassium hydroxide ethanol solution are added to a reaction vessel, stirred evenly to form a mixed solution, stirred and reacted at a temperature of 50°C and a stirring speed of 300 r / min for 0.3 h, and then vacuum filtered to obtain a powder portion, washed, and then dried in a vacuum drying oven at a temperature of 40°C for 5 h to obtain alkali-treated defluorinated polyvinylidene fluoride;

[0050] The preparation method of aminated graphene oxide is as follows: 60 g of ethylenediamine is dissolved in 3 L of distilled water, and then 12 g of graphene, 155 g of a coagulant 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, and 15 g of a coupling agent N-hydroxysuccinimide are added to a reactor, and stirred to form a mixed solution. Subsequently, the pH of the reaction system is adjusted to 4 with HCl acid, and the mixture is heated in a water bath at 15° C. and magnetically stirred for 8 hours. After vacuum filtration, washing, and drying, aminated graphene oxide nanoparticles are obtained.

[0051] The preparation method of chemical grafting of aminated graphene oxide and polyvinylidene fluoride is as follows:

[0052] S1: Addition reaction: 1 g of the defluorinated polyvinylidene fluoride obtained in step (1), 0.01 g of the aminated graphene oxide particles obtained in step (2), and 1.4 g of the second catalyst obtained in Preparation Example 1 were added to 20 mL of methanol solvent, and then reacted at a temperature of 25° C. for 15 h, and then vacuum filtered, washed, and dried to obtain aminated graphene oxide;

[0053] S2: Casting solution: 1 g of the alkali-treated polyvinylidene fluoride aminated graphene oxide powder obtained in S1 was added to 3 g of methyl pyrrolidone and dispersed evenly. Then, 0.7 g of polyethylene glycol with a molecular weight of 10,000 and 0.2 g of polyoxyethylene sorbitan monooleate were added. The mixture was heated in a water bath at a temperature of 50°C and a stirring speed of 300 r / min and mechanically stirred for 6 h to obtain a casting solution.

[0054] S3: Degassing treatment; the casting liquid obtained in step S2 is allowed to stand for degassing at normal pressure and a temperature of 15°C for 8 hours, and then the degassed casting liquid is poured onto a glass plate, and the casting liquid is scraped into a continuous and uniform flat liquid film by a scraper, wherein the distance between the scraper and the glass plate is 100 μm, and then the flat liquid film is immersed in deionized water at a temperature of 15°C for solidification, and then the solidified membrane is soaked in deionized water to remove residual methylpyrrolidone, and finally stored in deionized water to obtain a high-flux and anti-pollution polyvinylidene fluoride hybrid ultrafiltration membrane.

[0055] Example 2

[0056] A method for preparing a high-flux anti-fouling polyvinylidene fluoride hybrid ultrafiltration membrane, which differs from Example 1 in that the polyvinylidene fluoride alkali treatment comprises the following steps:

[0057] Preparation method of polyvinylidene fluoride treated with alkali: 15 g of polyvinylidene fluoride, 1 g of benzyltriethylammonium chloride and 300 mL of 24 mol / L potassium hydroxide ethanol solution are added to a reaction vessel, stirred evenly to form a mixed solution, and stirred for 0.3 h at a temperature of 50° C. and a stirring speed of 300 r / min. After vacuum filtration, the powder is partially washed and then dried in a vacuum drying oven at a temperature of 40° C. for 5 h to obtain alkali-treated defluorinated polyvinylidene fluoride; the remaining steps are the same as in Example 1.

[0058] Example 3

[0059] A method for preparing a high-flux anti-fouling polyvinylidene fluoride hybrid ultrafiltration membrane, which differs from Example 1 in that the polyvinylidene fluoride alkali treatment comprises the following steps:

[0060] Preparation method of polyvinylidene fluoride treated with alkali: 20 g of polyvinylidene fluoride, 1 g of tetrabutylammonium chloride and 400 mL of 6 mol / L potassium hydroxide ethanol solution were added to a reaction vessel, stirred evenly to form a mixed solution, and stirred for 0.3 h at a temperature of 50°C and a stirring speed of 300 r / min. After vacuum filtration, the powder was partially washed and then dried in a vacuum drying oven at a temperature of 40°C for 5 h to obtain alkali-treated defluorinated polyvinylidene fluoride; the remaining steps were the same as in Example 1.

[0061] Example 4

[0062] A method for preparing a high-flux anti-fouling polyvinylidene fluoride hybrid ultrafiltration membrane, which differs from Example 2 in that the polyvinylidene fluoride alkali treatment comprises the following steps:

[0063] Preparation method of polyvinylidene fluoride by alkali treatment: 15 g of polyvinylidene fluoride, 1 g of tetrabutylammonium hydrogen sulfate and 300 mL of 4 mol / L potassium hydroxide ethanol solution are added to a reaction vessel, stirred evenly to form a mixed solution, and stirred at a temperature of 100° C. and a stirring speed of 500 r / min for 1 hour. After that, vacuum filtration is performed to obtain a powder portion, which is washed and then dried in a vacuum drying oven at a temperature of 100° C. for 11 hours to obtain alkali-treated defluorinated polyvinylidene fluoride; the remaining steps are the same as in Example 2.

[0064] Example 5

[0065] A method for preparing a high-throughput anti-pollution polyvinylidene fluoride hybrid ultrafiltration membrane is different from Example 2 in that the method for preparing aminated graphene oxide comprises the following steps:

[0066] The preparation method of aminated graphene oxide is as follows: 100 g of ethylenediamine is dissolved in 4 L of distilled water, 30 g of graphene, 300 g of a coagulant 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, and 15 g of a coupling agent N-hydroxysuccinimide are added to a reactor, and the mixture is stirred to form a mixed solution. Subsequently, the pH of the reaction system is adjusted to 4 with HCl acid, and the mixture is heated in a water bath at 15° C. and magnetically stirred for 8 hours. The mixture is then vacuum filtered, washed, and dried to obtain aminated graphene oxide nanoparticles.

[0067] The remaining steps are the same as those in Example 2.

[0068] Example 6

[0069] A method for preparing a high-throughput anti-pollution polyvinylidene fluoride hybrid ultrafiltration membrane is different from Example 2 in that the method for preparing aminated graphene oxide comprises the following steps:

[0070] The preparation method of aminated graphene oxide is as follows: 200 g of ethylenediamine is dissolved in 5 L of distilled water, 60 g of graphene, 700 g of a coagulant 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, and 15 g of a coupling agent N-hydroxysuccinimide are added to a reactor, and the mixture is stirred to form a mixed solution. Subsequently, the pH of the reaction system is adjusted to 4 with HCl acid, and the mixture is heated in a water bath at 15° C. and magnetically stirred for 8 hours. The mixture is then vacuum filtered, washed, and dried to obtain aminated graphene oxide nanoparticles.

[0071] The remaining steps are the same as those in Example 2.

[0072] Example 7

[0073] A method for preparing a high-throughput anti-pollution polyvinylidene fluoride hybrid ultrafiltration membrane is different from Example 2 in that the method for preparing aminated graphene oxide comprises the following steps:

[0074] The preparation method of aminated graphene oxide is as follows: 300 g of ethylenediamine is dissolved in 6 L of distilled water, 80 g of graphene, 1000 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride as a coagulant, and 15 g of N-hydroxysuccinimide as a coupling agent are added to a reactor, and the mixture is stirred to form a mixed solution. Subsequently, the pH of the reaction system is adjusted to 4 with HCl acid, the mixture is heated in a water bath at 15° C., and magnetically stirred for 8 h, followed by vacuum filtration, washing, and drying to obtain aminated graphene oxide nanoparticles. The remaining steps are the same as those in Example 2.

[0075] Example 8

[0076] A method for preparing a high-throughput anti-pollution polyvinylidene fluoride hybrid ultrafiltration membrane is different from Example 2 in that the method for preparing aminated graphene oxide comprises the following steps:

[0077] The preparation method of aminated graphene oxide is as follows: 400 g of ethylenediamine is dissolved in 6 L of distilled water, 100 g of graphene, 1300 g of a coagulant 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, and 15 g of a coupling agent N-hydroxysuccinimide are added to a reactor, and the mixture is stirred to form a mixed solution. Subsequently, the pH of the reaction system is adjusted to 4 with HCl acid, and the mixture is heated in a water bath at 15° C. and magnetically stirred for 8 h. The mixture is then vacuum filtered, washed, and dried to obtain aminated graphene oxide nanoparticles. The remaining steps are the same as those in Example 2.

[0078] Example 9

[0079] A method for preparing a high-throughput anti-pollution polyvinylidene fluoride hybrid ultrafiltration membrane is different from Example 2 in that the method for preparing aminated graphene oxide comprises the following steps:

[0080] The preparation method of aminated graphene oxide is as follows: 600 g of ethylenediamine is dissolved in 7.5 L of distilled water, 120 g of graphene, 1550 g of a coagulant 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, and 15 g of a coupling agent N-hydroxysuccinimide are added to a reactor, and the mixture is stirred uniformly to form a mixed solution. Subsequently, the pH of the reaction system is adjusted to 4 with HCl acid, the mixture is heated in a water bath at 15° C., and magnetically stirred for 8 h, followed by vacuum filtration, washing, and drying to obtain aminated graphene oxide nanoparticles; the remaining steps are the same as those in Example 2.

[0081] Example 10

[0082] A method for preparing a high-throughput anti-pollution polyvinylidene fluoride hybrid ultrafiltration membrane, which differs from Example 7 in that the method for preparing aminated graphene oxide comprises the following steps:

[0083] The preparation method of aminated graphene oxide is as follows: 300 g of ethylenediamine is dissolved in 6 L of distilled water, 80 g of graphene, 1000 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride as a coagulant, and 15 g of N-hydroxysuccinimide as a coupling agent are added to a reactor, and the mixture is stirred to form a mixed solution. Subsequently, the pH of the reaction system is adjusted to 6 with HCl acid, and the mixture is heated in a water bath at 45° C. and magnetically stirred for 24 h. The mixture is then vacuum filtered, washed, and dried to obtain aminated graphene oxide nanoparticles. The remaining steps are the same as those in Example 6.

[0084] Example 11

[0085] A method for preparing a high-flux anti-fouling polyvinylidene fluoride hybrid ultrafiltration membrane, which differs from Example 7 in that the preparation method of chemically grafting aminated graphene oxide and polyvinylidene fluoride comprises the following steps:

[0086] S1: Addition reaction: 1 g of the defluorinated polyvinylidene fluoride obtained in step (1), 1.2 g of the aminated graphene oxide particles obtained in step (2), and 1.5 g of the second catalyst obtained in Preparation Example 2 were added to 20 mL of methanol solvent, and then reacted at a temperature of 25° C. for 15 h, and then vacuum filtered, washed, and dried to obtain aminated graphene oxide;

[0087] S2: Casting solution: 1 g of the alkali-treated polyvinylidene fluoride aminated graphene oxide powder obtained in S1 was added to 4 g of methyl pyrrolidone and dispersed evenly. Then, 0.7 g of polyethylene glycol with a molecular weight of 10,000 and 0.24 g of polyoxyethylene sorbitan monooleate were added. The mixture was heated in a water bath at a temperature of 50°C and a stirring speed of 300 r / min and mechanically stirred for 6 h to obtain a casting solution.

[0088] S3: Degassing treatment; the casting liquid obtained in step S2 is allowed to stand for degassing at normal pressure and a temperature of 15°C for 8 hours, and then the degassed casting liquid is poured onto a glass plate, and the casting liquid is scraped into a continuous and uniform flat liquid film by a scraper, wherein the distance between the scraper and the glass plate is 100 μm, and then the flat liquid film is immersed in deionized water at a temperature of 15°C for solidification, and then the solidified membrane is soaked in deionized water to remove residual methylpyrrolidone, and finally stored in deionized water to obtain a high-flux and anti-pollution polyvinylidene fluoride hybrid ultrafiltration membrane.

[0089] Example 12

[0090] A method for preparing a high-flux anti-fouling polyvinylidene fluoride hybrid ultrafiltration membrane, which differs from Example 7 in that the preparation method of chemically grafting aminated graphene oxide and polyvinylidene fluoride comprises the following steps:

[0091] S1: Addition reaction: 1 g of the defluorinated polyvinylidene fluoride obtained in step (1), 3.5 g of the aminated graphene oxide particles obtained in step (2), and 1.4 g of the second catalyst obtained in Preparation Example 3 were added to 20 mL of methanol solvent, and then reacted at a temperature of 30° C. for 15 h, and then vacuum filtered, washed, and dried to obtain aminated graphene oxide;

[0092] S2: Casting solution: 1 g of the alkali-treated polyvinylidene fluoride aminated graphene oxide powder obtained in S1 was added to 4 g of methyl pyrrolidone and dispersed evenly. Then, 0.7 g of polyethylene glycol with a molecular weight of 10,000 and 0.32 g of polyoxyethylene sorbitan monooleate were added. The mixture was heated in a water bath at 60°C and stirred at 500 r / min for 6 h to obtain a casting solution.

[0093] S3: Degassing treatment; the casting liquid obtained in step S2 is allowed to stand for degassing at normal pressure and a temperature of 15°C for 12 hours, and then the degassed casting liquid is poured onto a glass plate, and the casting liquid is scraped into a continuous and uniform flat liquid film by a scraper, wherein the distance between the scraper and the glass plate is 100 μm, and then the flat liquid film is immersed in deionized water at a temperature of 15°C for solidification, and then the solidified membrane is soaked in deionized water to remove residual methylpyrrolidone, and finally stored in deionized water to obtain a high-flux and anti-pollution polyvinylidene fluoride hybrid ultrafiltration membrane.

[0094] Example 13

[0095] A method for preparing a high-flux anti-fouling polyvinylidene fluoride hybrid ultrafiltration membrane, which differs from Example 7 in that the preparation method of chemically grafting aminated graphene oxide and polyvinylidene fluoride comprises the following steps:

[0096] S1: Addition reaction: 1 g of the defluorinated polyvinylidene fluoride obtained in step (1), 7.4 g of the aminated graphene oxide particles obtained in step (2), and 1.4 g of the second catalyst obtained in Preparation Example 4 were added to 20 mL of methanol solvent, and then reacted at a temperature of 32° C. for 18 h, and then vacuum filtered, washed, and dried to obtain aminated graphene oxide;

[0097] S2: Casting solution: 1 g of the alkali-treated polyvinylidene fluoride aminated graphene oxide powder obtained in S1 was added to 7 g of methyl pyrrolidone and dispersed evenly. Then, 0.8 g of polyethylene glycol with a molecular weight of 10,000 and 0.38 g of polyoxyethylene sorbitan monooleate were added. The mixture was heated in a water bath at 60°C and stirred at 700 r / min for 10 h to obtain a casting solution.

[0098] S3: Degassing treatment; the casting liquid obtained in step S2 is allowed to stand for degassing at normal pressure and a temperature of 45°C for 15 hours, and then the degassed casting liquid is poured onto a glass plate, and the casting liquid is scraped into a continuous and uniform flat liquid film by a scraper, wherein the distance between the scraper and the glass plate is 100 μm, and then the flat liquid film is immersed in deionized water at a temperature of 15°C for solidification, and then the solidified membrane is soaked in deionized water to remove residual methylpyrrolidone, and finally stored in deionized water to obtain a high-flux and anti-pollution polyvinylidene fluoride hybrid ultrafiltration membrane.

[0099] Example 14

[0100] A method for preparing a high-flux anti-fouling polyvinylidene fluoride hybrid ultrafiltration membrane, which differs from Example 7 in that the preparation method of chemically grafting aminated graphene oxide and polyvinylidene fluoride comprises the following steps:

[0101] S1: Addition reaction: 1 g of the defluorinated polyvinylidene fluoride obtained in step (1), 10 g of the aminated graphene oxide particles obtained in step (2), and 1.4 g of the second catalyst obtained in Preparation Example 5 were added to 20 mL of methanol solvent, and then reacted at a temperature of 32° C. for 20 h, and then vacuum filtered, washed, and dried to obtain aminated graphene oxide;

[0102] S2: Casting solution: 1 g of the alkali-treated polyvinylidene fluoride aminated graphene oxide powder obtained in S1 was added to 7 g of methyl pyrrolidone and dispersed evenly. Then, 0.9 g of polyethylene glycol with a molecular weight of 10,000 and 0.45 g of polyoxyethylene sorbitan monooleate were added. The mixture was heated in a water bath at a temperature of 70°C and a stirring speed of 900 r / min and mechanically stirred for 12 h to obtain a casting solution.

[0103] S3: Degassing treatment; the casting liquid obtained in step S2 is allowed to stand for degassing at normal pressure and a temperature of 70°C for 20 hours, and then the degassed casting liquid is poured onto a glass plate, and the casting liquid is scraped into a continuous and uniform flat liquid film by a scraper, wherein the distance between the scraper and the glass plate is 100 μm, and then the flat liquid film is immersed in deionized water at a temperature of 15°C for solidification, and then the solidified membrane is soaked in deionized water to remove residual methylpyrrolidone, and finally stored in deionized water to obtain a high-flux and anti-pollution polyvinylidene fluoride hybrid ultrafiltration membrane.

[0104] Comparative Example 1

[0105] Preparation method of polyvinylidene fluoride-based membrane: 14wt% of polyvinylidene fluoride, 11wt% of polyethylene glycol with a molecular weight of 10,000, 70wt% of methyl pyrrolidone, and 5% of polyoxyethylene sorbitan monooleate are added to a three-necked flask, heated in a water bath at 60°C and stirred for 6 hours to obtain a casting solution, the casting solution is allowed to stand and degas for 12 hours, and mechanically scraped, and the casting solution is coated on a clean glass plate. Subsequently, the glass is immersed in deionized water at 28°C for 48 hours to obtain an ultrafiltration membrane.

[0106] Comparative Example 2

[0107] Preparation of physical blend membrane: 2wt% of graphene powder was added to 68wt% of methyl pyrrolidone, and then 14wt% of polyvinylidene fluoride, 5wt% of polyoxyethylene sorbitan monooleate, and 11wt% of polyethylene glycol with a molecular weight of 10,000 were added and shaken for 30 minutes using a CNC ultrasonic cleaner to obtain a casting liquid. The film was then scraped and the casting liquid was coated onto a clean glass plate. Subsequently, the glass was immersed in deionized water at 28°C for 48 hours to obtain an ultrafiltration membrane.

[0108] Comparative Example 3

[0109] The difference from Example 13 is that 14 wt% of defluorinated polyvinylidene fluoride obtained by alkali treatment, 11 wt% of polyethylene glycol with a molecular weight of 10,000, 70 wt% of methyl pyrrolidone, and 5 wt% of polyoxyethylene dehydrated sorbitan monooleate are added to a three-necked flask, heated in a water bath at 60°C and stirred for 6 hours to obtain a casting solution, the casting solution is allowed to stand and degas for 12 hours, and mechanically scraped, and the casting solution is coated on a clean glass plate. Subsequently, the glass is immersed in deionized water at 28°C for 48 hours to obtain an ultrafiltration membrane.

[0110] Performance testing

[0111] (1) The ultrafiltration membranes obtained in Examples 1-14 and Comparative Examples 1-3 were tested for pure water flux, retention of bovine serum albumin, contact angle, tensile strength, fracture stress, and membrane flux recovery rate. The testing methods are as follows, and the test results are shown in Table 1.

[0112] Pure water flux test method: Pure water flux is an important parameter to characterize membrane permeability. The pure water flux of ultrafiltration membrane was measured by dead-end filtration. First, the membrane to be tested was cut to an appropriate size (effective membrane area of ​​43 cm 2 ), slowly rinse the excised membrane with deionized water and place it on an ultrafiltration cup. After adding deionized water to the ultrafiltration cup, pressurize it to 0.1 MPa with nitrogen. Prepress at 0.1 MPa for 30 minutes to obtain a stable pure water flux. The water volume is then recorded at constant intervals. The pure water flux J is calculated using the following formula:

[0113]

[0114] Where M is the volume of the effluent (L), A is the effective area of ​​the membrane (m 2 ), Δt is the penetration time (h).

[0115] Bovine serum albumin retention rate test method: Cut the ultrafiltration membrane into appropriate size and place it on the ultrafiltration cup for dead-end filtration. Pre-pressurize with pure water at 0.1 MPa for 30 minutes. Then, evaluate the retention performance of the ultrafiltration membrane using a 1000 ppm BSA solution. Use a UV spectrophotometer to measure the absorbance of the stock solution and filtrate at a wavelength of 280 nm, and calculate the retention rate according to the formula:

[0116]

[0117] Among them C p and C f is the concentration of the component in the filtrate and the original solution.

[0118] Contact Angle Measurement Method: To investigate the hydrophilicity of each membrane, static water contact angles were measured using a fully automated contact angle meter (DSA30SKRUSS). All membranes were oven-dried before testing, cut into appropriate shapes, and affixed to glass slides. Water contact angle measurements were performed at room temperature, with five replicates performed for each membrane sample, and the average value was calculated.

[0119] Tensile Strength Test Method: Tensile strength (Rm) is the maximum nominal tensile stress a specimen can withstand before breaking. Tensile strength refers to the maximum stress a material can withstand before breaking. Unit: MPa.

[0120] Fracture stress test method: Fix the two ends of the PVDF flat membrane on the clamp of the tensile testing machine, stretch the membrane at a certain rate until the membrane is broken, and the fracture stress is expressed by σ, the standard unit is N / m, and it is usually expressed in N / mm. The calculation formula is: σ=P / A

[0121] Where: σ--fracture stress or volume specific strength, Pa; P--fracture strength, N; A--cross-sectional area, m 2 .

[0122] The flux recovery rate (FRR) was tested to evaluate the anti-fouling ability of the ultrafiltration membrane. The ultrafiltration membrane was cleaned with deionized water and then placed on the ultrafiltration cup. The membrane was cut and fixed on the ultrafiltration cup and pre-pressed with deionized water for 30 minutes. After the flux stabilized, the pure water flow rate was recorded for 10 minutes (JP1). The 1000ppm BSA solution was replaced and filtered for 30 minutes. The flux of the BSA solution was recorded for 10 minutes. The test membrane was removed, rinsed with deionized water, and then immersed in a 1000ppm sodium hypochlorite solution. After 4 hours, the membrane was cleaned and the pure water flow rate was continued to be measured for 10 minutes (JP2). The experimental pressure was 0.1MPa. The FRR was calculated using the following formula:

[0123]

[0124] Table 1 Ultrafiltration membrane performance test results

[0125]

[0126] As can be seen from Table 1, the pure water flux, bovine serum albumin retention rate, contact angle, tensile strength and breaking stress of the ultrafiltration membranes obtained in Examples 1-14 of the present application are better than those of the polyvinylidene fluoride-based membrane obtained in Comparative Example 1 and the blended membrane obtained in Comparative Example 1. It can be seen that the preparation method of the present application can effectively improve the flux of the ultrafiltration membrane.

[0127] The membrane flux recovery rate reflects the anti-pollution ability of the ultrafiltration membrane. The higher the membrane flux recovery rate, the higher the anti-pollution ability. The hydrophilicity of the ultrafiltration membrane obtained in the present application is better than the hydrophilicity of the ultrafiltration membrane in the comparative documents 1-3, so the membrane flux recovery rate of the ultrafiltration membrane obtained in the present application is also better than the membrane flux recovery rate in the comparative example. In addition, the ultrafiltration membrane of the present application forms a hydration layer on the outside of the membrane that is not easily destroyed, which can prevent the contact between the membrane surface and the pollution source, thereby improving the anti-pollution ability of the ultrafiltration membrane obtained in the present application. In addition, the addition of graphene can increase the electronegativity of the membrane surface, thereby increasing the electrostatic repulsion between the membrane surface and the pollution source, thereby improving the anti-pollution performance of the ultrafiltration membrane.

[0128] (2) The ultrafiltration membranes obtained in Examples 2, 7, and 13 of the present application and Comparative Examples 1-3 were used to test the removal of COD and humic acid from wastewater. The test method was as follows: the ultrafiltration membrane was cut into appropriate sizes and placed on an ultrafiltration cup for dead-end filtration. The membrane was pre-pressed with COD raw water or humic acid solution at a pressure of 0.1 MPa for 30 minutes, and the retention performance of the ultrafiltration membrane was evaluated using the COD raw water solution or humic acid solution. The absorbance of the raw solution and the filtrate was measured using an ultraviolet spectrophotometer, and the COD or humic acid solution retention rate was calculated according to the formula:

[0129] R(%)=(1-C p / C f )×100%

[0130] Among them C p and C f The test results are shown in Table 2.

[0131] Table 2 Ultrafiltration membrane removal test table for COD and humic acid

[0132]

[0133] As can be seen from Table 2, the removal rates of COD and humic acid by the ultrafiltration membranes obtained in the present application are better than those of the ultrafiltration membranes of Comparative Examples 1-3, indicating that the ultrafiltration membranes obtained in the present application have good hydrophilic properties and retention rates.

[0134] The embodiments of this specific implementation method are all preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, any equivalent changes made based on the structure, shape, and principle of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a high-throughput anti-pollution polyvinylidene fluoride hybrid ultrafiltration membrane, characterized in that: The steps include: (1) Preparation method of polyvinylidene fluoride by alkali treatment: polyvinylidene fluoride, a first catalyst and 200-400 mL of 2-6 mol / L potassium hydroxide ethanol solution are added to a reaction container, stirred evenly to form a mixed solution, stirred and reacted at 50°C-100°C for 0.3h-1h, vacuum filtered, the powder obtained is partially washed, and then dried in a vacuum drying oven at a temperature of 40°C-100°C for 5h-11h to obtain alkali-treated defluorinated polyvinylidene fluoride; the first catalyst is one of tetrabutylammonium bromide, benzyltriethylammonium chloride, tetrabutylammonium chloride, and tetrabutylammonium hydrogen sulfate; the weight ratio of the first catalyst to polyvinylidene fluoride is 1:(10-20); (2) The preparation method of aminated graphene oxide is as follows: dissolving ethylenediamine in 3-7.5 L of distilled water, adding graphene, a coagulant, and a coupling agent to a reactor, and stirring to form a mixed solution. Subsequently, the pH of the reaction system is adjusted to 4-6 with an acid, and the mixture is heated in a water bath at 15°C-45°C and magnetically stirred for 8h-24h, and then vacuum filtered, washed, and dried to obtain aminated graphene oxide nanoparticles; The weight ratio of graphene, ethylenediamine, coagulant and coupling agent is (12-120): (60-600): (155-1550): 15; (3) The preparation method of chemical grafting of aminated graphene oxide and polyvinylidene fluoride is: S1: Addition reaction: 1 g of the defluorinated polyvinylidene fluoride obtained in step (1), 0.01-10 g of the aminated graphene oxide particles obtained in step (2), and 1.4-1.5 g of the second catalyst are added to 20 mL of methanol solvent, and then reacted at a temperature within the range of 25-32° C. for 15-20 h, and then vacuum filtered, washed, and dried to obtain alkali-treated polyvinylidene fluoride aminated graphene oxide powder; the second catalyst is basic alumina-supported potassium fluoride powder; S2: Casting solution: 1 g of the alkali-treated polyvinylidene fluoride aminated graphene oxide powder obtained in S1 was added to 3-7 g of methyl pyrrolidone and dispersed evenly. Then, 0.7-0.9 g of polyethylene glycol with a molecular weight of 10,000 and 0.2-0.45 g of polyoxyethylene sorbitan monooleate were added. The mixture was heated in a water bath at 50-70°C with mechanical stirring for 6-12 h to obtain a casting solution. S3: degassing treatment; scraping the degassing membrane obtained in step S2 and solidifying it to obtain a high-flux anti-pollution polyvinylidene fluoride hybrid ultrafiltration membrane.

2. The method for preparing a high-throughput anti-pollution polyvinylidene fluoride hybrid ultrafiltration membrane according to claim 1, characterized in that: In the step (2), the coagulant is 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride; and the coupling agent is N-hydroxysuccinimide.

3. The method for preparing a high-throughput anti-pollution polyvinylidene fluoride hybrid ultrafiltration membrane according to claim 1, characterized in that: The second catalyst in step S1 is prepared by the following method: dissolving 20-50 g of KF·2H2O in 50-200 mL of water, pouring the potassium fluoride solution into a flask, adding 20-50 g of 100-200 mesh basic alumina, heating in a water bath at 65-75° C. with magnetic stirring for 1 hour, removing water by vacuum filtration, and drying in a vacuum oven at 80-130° C. for 4-10 hours to obtain a white powder.

4. The method for preparing a high-throughput anti-pollution polyvinylidene fluoride hybrid ultrafiltration membrane according to claim 1, characterized in that: The mixed solution of step (1) is reacted under magnetic stirring at 300-500 r / min for 0.3-1 h.

5. The method for preparing a high-throughput anti-pollution polyvinylidene fluoride hybrid ultrafiltration membrane according to claim 1, characterized in that: The mechanical stirring in step S2 is carried out at 300-900 r / min for 6-12 hours.

6. The method for preparing a high-throughput anti-pollution polyvinylidene fluoride hybrid ultrafiltration membrane according to claim 1, characterized in that: In the step S3, the casting solution is allowed to stand for degassing at a temperature of 15-70° C. under normal pressure for 8-20 hours.

7. An ultrafiltration membrane obtained by the method for preparing a high-flux anti-fouling polyvinylidene fluoride hybrid ultrafiltration membrane according to any one of claims 1 to 6.

8. Use of the high-flux anti-pollution polyvinylidene fluoride hybrid ultrafiltration membrane according to claim 7 in wastewater.

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