Defect-free nanofiltration membrane containing tp pa-cof interlayer

Abstract

The application relates to a preparation method of a nanofiltration membrane containing a covalent organic framework (COF) interlayer, wherein the nanofiltration membrane (NF) comprises a base film, an interlayer and a separation surface layer. The interlayer is formed in situ by polyphenol and diamine under the action of an oxidant, and the separation surface layer is formed by interface polymerization of water-phase active monomers and polyacyl chloride. The application introduces an imine-based covalent organic framework (TpPa-COF) film interlayer, and a surface layer of polyamide is prepared through interface polymerization, so that the hydrophilicity of the membrane and the removal capacity of the membrane to divalent cations are improved. The application aims to solve the trade-off problem between low flux and high separation effect of the NF membrane in the separation of monovalent and divalent cations, ensure ideal water flux while maintaining high separation effect, and solve the defect problem of the separation layer of the traditional NF membrane. The two-dimensional TpPa-COF material can effectively control the pore size distribution and hydrophilicity of the base surface, and improve the separation performance of the composite membrane. The preparation method is simple, and the obtained nanofiltration membrane has wide application prospects.

Description

TECHNICAL FIELD

[0001] The application relates to a method for in-situ intergrowth preparation of a COFs interlayer nanofiltration membrane, and belongs to the technical field of membrane preparation. BACKGROUND

[0002] High-salinity wastewater treatment is a global problem. More than 300 million cubic meters of high-salinity wastewater is generated in China every year, resulting in more than 10 million tons of high-salinity hazardous waste, most of which has not been properly treated, causing great pressure on the ecological environment. Although high-salinity wastewater regeneration treatment can remove most harmful substances, a small amount of impurities such as Mg 2+ , Na + and other monovalent and divalent cations remain. In the chlor-alkali industry, these impurities need to be treated to ensure the normal operation of the electrolysis process and obtain refined salt water that meets the requirements. By separating monovalent and divalent ions, the required resources can be extracted from high-salinity wastewater.

[0003] In the past few decades, heavy metal ions have been removed by traditional methods such as chemical precipitation, ion flotation, ion exchange, coagulation / flocculation, adsorption, and electrochemistry. However, these low-cost methods have problems such as incomplete heavy metal removal, high energy consumption, and the generation of toxic sludge.

[0004] Existing solutions: methods for separating monovalent and divalent ions using COFs. For example, CN202410632726.0 discloses a preparation method of COF@Dopamine composite membrane and ion separation application, but the preparation process of COF nanosheets is complicated and time-consuming, and the flux decreases greatly, the research and development cost is high, and it cannot be applied industrially. Two-dimensional TpPa-COF material is an imine-based covalent organic framework with large specific surface area, high porosity, easy functionalization, and strong designability. When introduced into the membrane, it can effectively control the pore size distribution and hydrophilicity of the membrane surface, and improve the separation performance of the composite membrane. However, the introduction of COFs into the membrane for separating monovalent and divalent cations also has the problem of insufficient adhesion between the COF layer and the substrate, which leads to a decrease in the mechanical strength and durability of the membrane. The in-situ intergrowth method can avoid the gap defects between the separation layer and the substrate, and form a strong COF composite membrane with strict interface compatibility, in order to solve the above problems. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a preparation method of a COFs interlayer nanofiltration membrane for separating monovalent and divalent ions, which improves the trade-off effect of the existing process.

[0006] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows: a preparation method of a TpPa-COF interlayer nanofiltration membrane, the specific steps of which are as follows:

[0007] (1) Preparation of TpPa-COF film

[0008] A 2 mol / L sodium hydroxide solution is prepared, the base film is immersed in the prepared sodium hydroxide solution, and is placed in a constant temperature water bath at 60°C for 2 h. The film is washed with pure water for 3 times, and then is immersed in pure water for 24 h for standby. The substances involved in the preparation process of the TpPa-COF film are composed of the following mass percentages: 0.5-2.5% of diamine organic matter, a certain amount of 1,3,5-triformylphloroglucinol, 0.05-0.2% of oxidizing agent, and the remaining amount of ultrapure water and organic solvent. A certain amount of oxidizing agent powder is slowly added to the diamine aqueous solution, and then is ultrasonically dissolved for 0.1-1 h. After complete dissolution, solution 1 is obtained. A certain concentration of 1,3,5-triformylphloroglucinol organic solution is prepared, and is ultrasonically dispersed until completely dissolved, to obtain solution 2. The two solutions are poured into a beaker according to a certain proportion, stirred for 5-30 s, and the pretreated base film is horizontally immersed therein, and is grown in situ for 0.5-24 h, to introduce the TpPa-COF film on the commodity.

[0009] (2) Preparation of aqueous phase and oil phase monomer solution

[0010] The substances involved in the preparation process of the aqueous phase monomer mixed solution are composed of the following mass percentages: 0.5-1.5% of surfactant, 0.5-2.5% of diamine compound, and the remaining amount of ultrapure water. A diamine aqueous solution of a certain concentration is prepared, and is magnetically stirred for 5-10 min. After complete dissolution, the surfactant is added dropwise. The mixed solution is magnetically stirred for 10-15 min, to obtain the aqueous phase monomer mixed solution.

[0011] The substances involved in the preparation process of the oil phase monomer solution are composed of the following mass percentages: 0.15-0.3% of 1,3,5-benzene triformyl chloride, and the remaining amount of n-hexane. The 1,3,5-benzene triformyl chloride is dissolved in n-hexane to prepare an oil phase solution, and is ultrasonically dispersed for 5-10 min, to obtain the oil phase solution.

[0012] (3) Preparation of nanofiltration membrane containing TpPa-COF interlayer

[0013] The water phase solution prepared in (2) is stirred uniformly and then is left to stand for 5 min, the film prepared in (1) is taken out from pure water, and the excess water is wiped off using an industrial wiping paper; 15-25 mL of the water phase solution is poured on the surface of the base film, and after being kept for 1-3 min, the excess water phase solution is wiped off using an industrial wiping paper, then 15-25 mL of the oil phase solution is poured to cause an interfacial polymerization reaction, after being reacted for 1-2 min, the excess oil phase solution is poured out, after being washed twice with n-hexane, the prepared nanofiltration membrane is put into an oven and is heated for 5-20 min, after being dried, the membrane is taken out and is soaked in ultrapure water, and the membrane is stored for use.

[0014] Preferably, the solvent of 1,3,5-triformylphloroglucinol in step (1) is one of ethanol, diethyl ether and methanol.

[0015] Preferably, the oxidant in step (1) is one of dopamine hydrochloride, tannic acid and gallic acid.

[0016] Preferably, the commercial film in step (1) is one of polyacrylonitrile, polyvinylidene fluoride, polyethersulfone and polysulfone.

[0017] Preferably, the surfactant in step (2) is one of trimethylamine, triethylamine and dodecyl dimethyl benzyl ammonium bromide.

[0018] Preferably, the diamine compound in step (2) is one of p-phenylenediamine, m-phenylenediamine and o-phenylenediamine.

[0019] The application proposes a thought of preparing a TpPa-COF thin film interlayer by interfacial polymerization and in-situ growth respectively, and preparing a surface polyamide layer by interfacial polymerization, so as to improve the hydrophilicity of the membrane and the removal capacity of divalent cations; aims to break the trade-off effect of high separation effect and low flux of NF membrane applied to the treatment of monovalent / divalent cations, ensure ideal water flux under as high separation effect as possible, and solve the defects of the separation layer of the traditional NF membrane, easy pollution and low recycling difficulty. The two-dimensional COFs material can effectively control the pore size distribution and hydrophobicity of the substrate surface, and improve the separation performance of the composite membrane.

[0020] Beneficial effects:

[0021] The TpPa-COF has the advantages of large specific surface area, high porosity, easy functionalization and strong designability. When it is added into the NF membrane as an interlayer, the hydrophilicity of the NF membrane can be adjusted, and the membrane flux can be increased. The pores and charges of the material can enhance the screening and electrostatic repulsion, which helps to break the trade-off effect of selectivity and flux to a certain extent.

[0022] Dopamine hydrochloride or phenols with catechol groups can be oxidized to quinones during polymerization. Through oxidation, cyclization and rearrangement, a metastable intermediate (5,6-dihydroxyindole) is formed, which can produce semiquinone radicals that react with oxidized quinones. These radicals are easily reoxidized, simultaneously forming ROS (O 2- ) and orthoquinones. This step can produce defect-free and dense COF films under mild environmental conditions. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 Surface scanning electron micrograph of the nanofiltration membrane of Example 1

[0024] Figure 2 Surface scanning electron micrograph of the nanofiltration membrane of Example 5

[0025] Figure 3 Surface scanning electron micrograph of the nanofiltration membrane of Example 7 DETAILED DESCRIPTION

[0026] The application will be further described in the following detailed description with reference to the drawings. However, those skilled in the art will appreciate that the following examples are intended to be illustrative only and are not intended to limit the scope of the present application.

[0027] The zwitterionic nanofiltration membrane prepared by the present application can be used to separate cations in mono / divalent state, so the rejection rate of divalent cations, the permeation rate of monovalent cations, and the water flux are three important parameters for evaluating the nanofiltration membrane.

[0028] The test conditions for water flux, rejection rate of divalent cations, and permeation rate of monovalent cations are as follows: dead-end filtration device, inorganic salt selected from MgCl2 and LiCl commonly found in salt lake brine, total cation concentration of 1000 mg / L, mass ratio of Mg 2+ to Li + is 20:1, test temperature is 25°C, pH=7, and test pressure is 0.6 MPa.

[0029] The rejection rate of divalent cations (magnesium ions) is defined as:

[0030] wherein R1 represents the rejection rate of magnesium ions, C p1 and C f1 are the concentrations of magnesium ions in the permeate and the raw material solution, respectively.

[0031] The rejection rate of monovalent cations (lithium ions) is defined as:

[0032] wherein R2 represents the rejection rate of lithium ions, C p2 and C f2 are the concentrations of lithium ions in the permeate and the raw material solution, respectively.

[0033] Water flux is defined as the volume of water that passes through the effective area of the membrane per unit of time under a unit of pressure.

[0034] Example 1:

[0035] (1) Prepare a 2 mol / L sodium hydroxide solution, immerse the commercial membrane in the prepared sodium hydroxide solution, and place it in a constant temperature water bath at 60°C for 2 hours. Take out the membrane and wash it with pure water for 3 times, then immerse it in pure water for 24 hours for standby. At room temperature, weigh 2 g of p-phenylenediamine and dissolve it in 50 mL of ultrapure water. After complete dissolution, weigh 0.2 g of dopamine hydrochloride and add it to the solution. Ultrasonic dispersion for 10 min to obtain solution 1. Weigh 50 mg of 1,3,5-triformylphloroglucinol and add it to 50 mL of ethanol. Ultrasonic until the solution is clear to obtain solution 2. Pour the two solutions into a beaker and stir for 10 s. Put the pretreated base membrane into it and grow in situ for 12 h. Then wash the reacted membrane with deionized water for three times. After washing, put it into a 120°C oven for drying for 2 h. After drying, put it into deionized water for storage.

[0036] (2) Weigh 0.5 g of p-phenylenediamine and dissolve it in 50 mL of ultrapure water. Stir magnetically for 10 min. Add 0.5 mL of triethylamine and stir the mixed solution magnetically for 10 min to obtain the aqueous monomer mixed solution.

[0037] Dissolve 1,3,5-benzene triformyl chloride in n-hexane to prepare a 50 mL oil phase solution with a concentration of 0.25 %w / v. Ultrasonic dispersion until the solution is clear.

[0038] (3) After stirring the aqueous solution prepared in (2) uniformly, stand for 5 min for standby. Take out the membrane prepared in (1) from pure water and use industrial wiping paper to wipe off the excess water. Pour 25 mL of aqueous solution on the surface of the base membrane, keep for 90 s, then use industrial wiping paper to wipe off the excess aqueous solution. Then pour 25 mL of oil phase solution to occur interfacial polymerization reaction. After 2 min, pour out the excess oil phase solution. After washing twice with n-hexane, put the prepared nanofiltration membrane into the oven and heat for 20 min. After drying, take it out and immerse it in ultrapure water. Store the membrane for use.

[0039] Test the performance of the nanofiltration membrane prepared in Example 1. The water flux of the nanofiltration membrane is 49.8 L·m -2 ·h -1 ·bar -1 , Li + retention rate is 38.3%, Mg 2+ retention rate is 95.1%.

[0040] Example 2:

[0041] (1) Prepare 2 mol / L sodium hydroxide solution, immerse the commercial membrane in the prepared sodium hydroxide solution, and place it in a constant temperature water bath at 60°C for 2 h. Take out the membrane and wash it with pure water for 3 times, and then soak it in pure water for 24 h for standby. Under room temperature conditions, weigh 2 g of p-phenylenediamine and dissolve it in 50 mL of ultrapure water. After complete dissolution, weigh 0.2 g of dopamine hydrochloride and add it, ultrasonic dispersion for 10 min to obtain solution 1. Weigh 50 mg of 1,3,5-triformylphloroglucinol and add it to 50 mL of methanol, ultrasonic until the solution is clear, to obtain solution 2. Pour the two solutions into a beaker, stir for 10 s, and then put the pretreated base membrane into it, and grow in situ for 12 h. Then wash the reacted membrane with deionized water for 3 times, and then put it into a 120°C oven for drying for 2 h. After drying, put it into deionized water for standby.

[0042] (2) Weigh 0.5 g of o-phenylenediamine and dissolve it in 50 mL of ultrapure water, and magnetically stir for 10 min. Add 0.5 mL of triethylamine, and magnetically stir the mixed solution for 10 min to obtain the aqueous monomer mixed solution.

[0043] Dissolve 1,3,5-benzene triformyl chloride in n-hexane to prepare a 50 mL oil phase solution with a concentration of 0.25 %w / v, and ultrasonic dispersion until the solution is clear.

[0044] (3) After the aqueous solution prepared in (2) is stirred uniformly, stand for 5 min for standby. Take out the membrane prepared in (1) from pure water, and use industrial wiping paper to wipe off the excess water. Pour 25 mL of aqueous solution on the surface of the base membrane, and keep for 90 s. Then use industrial wiping paper to wipe off the excess aqueous solution, and then pour 25 mL of oil phase solution to occur interfacial polymerization. After 2 min of reaction, pour out the excess oil phase solution, wash it twice with n-hexane, and then put the prepared nanofiltration membrane into an oven for heating for 20 min. After drying, take it out and soak it in ultrapure water for storage and use.

[0045] The performance of the nanofiltration membrane prepared in Example 2 was tested. The water flux of the nanofiltration membrane was 39.8 L·m -2 ·h -1 ·bar -1 , the Li + retention rate was 40.3%, and the Mg 2+ retention rate was 98.1%.

[0046] Example 3:

[0047] (1) Prepare 2 mol / L sodium hydroxide solution, immerse the commercial membrane in the prepared sodium hydroxide solution, and place it in a constant temperature water bath at 60°C for 2 h. Take out the membrane and wash it with pure water for 3 times, and then soak it in pure water for 24 h for standby. At room temperature, weigh 1.5 g of p-phenylenediamine and dissolve it in 50 mL of ultrapure water. After complete dissolution, weigh 0.15 g of dopamine hydrochloride and add it to the solution. Ultrasonic dispersion for 10 min to obtain solution 1. Weigh 50 mg of 1,3,5-triformylphloroglucinol and add it to 50 mL of ethanol. Ultrasonic until the solution is clear to obtain solution 2. Pour the two solutions into a beaker, stir for 10 s, and then place the pretreated base membrane into the solution for in-situ growth for 12 h. Then wash the reacted membrane with deionized water for 3 times, and then place it in a 120°C oven for drying for 2 h. After drying, store it in deionized water for standby.

[0048] (2) Weigh 1 g of p-phenylenediamine and dissolve it in 50 mL of ultrapure water. Stir magnetically for 10 min. Add 0.5 mL of triethylamine and stir the mixture magnetically for 10 min to obtain the aqueous monomer mixture solution.

[0049] Dissolve 1,3,5-benzene triformyl chloride in n-hexane to prepare a 50 mL oil phase solution with a concentration of 0.25 %w / v. Ultrasonic dispersion until the solution is clear.

[0050] (3) After stirring the aqueous solution prepared in (2) uniformly, stand for 5 min for standby. Take out the membrane prepared in (1) from pure water and wipe off the excess water with industrial wiping paper. Pour 25 mL of aqueous solution on the surface of the base membrane, and then wipe off the excess aqueous solution with industrial wiping paper. Then pour 25 mL of oil phase solution to occur interfacial polymerization reaction. After 2 min of reaction, pour out the excess oil phase solution. After washing twice with n-hexane, place the prepared nanofiltration membrane in an oven for heating for 20 min. After drying, take it out and soak it in ultrapure water for storage and use.

[0051] The performance of the nanofiltration membrane prepared in Example 3 was tested. The water flux of the nanofiltration membrane was 42.4 L·m -2 ·h -1 ·bar -1 , the Li + rejection rate was 33.3%, and the Mg 2+ rejection rate was 96.1%.

[0052] Example 4:

[0053] (1) Prepare 2 mol / L sodium hydroxide solution, immerse the commercial membrane in the prepared sodium hydroxide solution, and place it in a constant temperature water bath at 60°C for 2 h. Take out the membrane and wash it with pure water for 3 times, and then soak it in pure water for 24 h for standby. At room temperature, weigh 1.5 g of p-phenylenediamine and dissolve it in 50 mL of ultrapure water. After complete dissolution, weigh 0.15 g of gallic acid and add it to the solution. Ultrasonic dispersion for 10 min to obtain solution 1. Weigh 50 mg of 1,3,5-triformylphloroglucinol and add it to 50 mL of ethanol. Ultrasonic until the solution is clear to obtain solution 2. Pour the two solutions into a beaker, stir for 10 s, and then place the pretreated base membrane into the solution for in-situ growth for 12 h. Then wash the reacted membrane with deionized water for 3 times. After washing, place it in a 120°C oven for drying for 2 h. After drying, place it in deionized water for standby.

[0054] (2) Weigh 1 g of m-phenylenediamine and dissolve it in 50 mL of ultrapure water. Stir magnetically for 10 min. Add 0.5 mL of triethylamine and stir the mixed solution magnetically for 10 min to obtain the aqueous monomer mixed solution.

[0055] Dissolve 1,3,5-benzene triformyl chloride in n-hexane to prepare a 50 mL oil phase solution with a concentration of 0.25 %w / v. Ultrasonic dispersion until the solution is clear.

[0056] (3) After stirring the aqueous solution prepared in (2) uniformly, stand for 5 min for standby. Take out the membrane prepared in (1) from pure water and use industrial wiping paper to wipe off the excess water. Pour 25 mL of aqueous solution on the surface of the base membrane, keep for 90 s, then use industrial wiping paper to wipe off the excess aqueous solution, and then pour 25 mL of oil phase solution to occur interfacial polymerization. After 2 min of reaction, pour out the excess oil phase solution. After washing twice with n-hexane, place the prepared nanofiltration membrane in an oven for heating for 20 min. After drying, take it out and soak it in ultrapure water. Store the membrane for use.

[0057] Test the performance of the nanofiltration membrane prepared in Example 4. The water flux of the nanofiltration membrane is 40.4 L·m -2 ·h -1 ·bar -1 , the Li + rejection rate is 29.3%, and the Mg 2+ rejection rate is 96.2%.

[0058] Example 5:

[0059] (1) Prepare 2 mol / L sodium hydroxide solution, immerse the commercial membrane in the prepared sodium hydroxide solution, and place it in a constant temperature water bath at 60°C for 2 h. Take out the membrane and wash it with pure water for 3 times, and then soak it in pure water for 24 h for standby. Under room temperature conditions, weigh 2 g of p-phenylenediamine and dissolve it in 50 mL of ultrapure water. After complete dissolution, weigh 0.2 g of dopamine hydrochloride and add it, ultrasonic dispersion for 10 min to obtain solution 1. Weigh 50 mg of 1,3,5-triformylphloroglucinol and add it to 50 mL of ethanol, ultrasonic until the solution is clear, to obtain solution 2. Pour the two solutions into a beaker, stir for 10 s, and then put the pretreated base membrane into it, and grow in situ for 24 h. Then wash the reacted membrane with deionized water for 3 times, and then put it into a 120°C oven for drying for 2 h. After drying, put it into deionized water for standby.

[0060] (2) Weigh 0.5 g of p-phenylenediamine and dissolve it in 50 mL of ultrapure water, and magnetically stir for 10 min. Add 0.5 mL of triethylamine, and magnetically stir the mixed solution for 10 min to obtain the aqueous monomer mixed solution.

[0061] Dissolve 1,3,5-benzene triformyl chloride in n-hexane to prepare a 50 mL oil phase solution with a concentration of 0.25 %w / v, and ultrasonic dispersion until the solution is clear

[0062] (3) After the aqueous solution prepared in (2) is stirred uniformly, stand for 5 min for standby. Take out the membrane prepared in (1) from pure water, and use industrial wiping paper to wipe off the excess water. Pour 25 mL of aqueous solution on the surface of the base membrane, and keep for 90 s. Then use industrial wiping paper to wipe off the excess aqueous solution, and then pour 25 mL of oil phase solution to occur interfacial polymerization. After 2 min of reaction, pour out the excess oil phase solution, wash it twice with n-hexane, and then put the prepared nanofiltration membrane into an oven for heating for 20 min. After drying, take it out and soak it in ultrapure water for storage and use.

[0063] The performance of the nanofiltration membrane prepared in Example 5 was tested. The water flux of the nanofiltration membrane was 40.8 L·m -2 ·h -1 ·bar -1 , the Li + retention rate was 29.5%, and the Mg 2+ retention rate was 98.5%.

[0064] Example 6:

[0065] (1) Prepare 2 mol / L sodium hydroxide solution, immerse the commercial membrane in the prepared sodium hydroxide solution, and place it in a constant temperature water bath at 60°C for 2 h. Take out the membrane and wash it with pure water for 3 times, and then soak it in pure water for 24 h for standby. Under room temperature conditions, weigh 2 g of p-phenylenediamine and dissolve it in 50 mL of ultrapure water. After complete dissolution, weigh 0.2 g of tannic acid and add it to the solution. Ultrasonic dispersion for 10 min to obtain solution 1. Weigh 50 mg of 1,3,5-triformylphloroglucinol and add it to 50 mL of diethyl ether. Ultrasonic until the solution is clear to obtain solution 2. Pour the two solutions into a beaker, stir for 10 s, and then place the pretreated base membrane into the solution for in-situ growth for 24 h. Then wash the reacted membrane with deionized water for 3 times. After washing, place it in a 120°C oven for drying for 2 h. After drying, place it in deionized water for storage.

[0066] (2) Weigh 0.5 g of p-phenylenediamine and dissolve it in 50 mL of ultrapure water. Stir magnetically for 10 min. Add 0.5 mL of trimethylamine and stir the mixed solution magnetically for 10 min to obtain the aqueous monomer mixture solution.

[0067] Dissolve 1,3,5-benzene triformyl chloride in n-hexane to prepare a 50 mL oil phase solution with a concentration of 0.25 %w / v. Ultrasonic dispersion until the solution is clear.

[0068] (3) After stirring the aqueous solution prepared in (2) uniformly, stand for 5 min for standby. Take out the membrane prepared in (1) from pure water and use industrial wiping paper to wipe off the excess water. Pour 25 mL of aqueous solution on the surface of the base membrane, keep for 90 s, then use industrial wiping paper to wipe off the excess aqueous solution, and then pour 25 mL of oil phase solution to occur interfacial polymerization. After 2 min of reaction, pour out the excess oil phase solution. After washing twice with n-hexane, place the prepared nanofiltration membrane in an oven for heating for 20 min. After drying, take it out and soak it in ultrapure water. Store the membrane for use.

[0069] Test the performance of the nanofiltration membrane prepared in Example 6. The water flux of the nanofiltration membrane is 49.8 L·m -2 ·h -1 ·bar -1 , the Li + retention rate is 38.5%, and the Mg 2+ retention rate is 97.5%.

[0070] Example 7:

[0071] (1) Prepare 2 mol / L sodium hydroxide solution, immerse the commercial membrane in the prepared sodium hydroxide solution, and place it in a constant temperature water bath at 60°C for 2 h. Take out the membrane and wash it with pure water for 3 times, and then soak it in pure water for 24 h for standby. At room temperature, weigh 1.5 g of p-phenylenediamine and dissolve it in 50 mL of ultrapure water. After complete dissolution, weigh 0.15 g of dopamine hydrochloride and add it, ultrasonic dispersion for 10 min to obtain solution 1. Weigh 50 mg of 1,3,5-triformylphloroglucinol and add it to 50 mL of ethanol, ultrasonic until the solution is clear, to obtain solution 2. Pour the two solutions into a beaker, stir for 10 s, and then put the pretreated base membrane into it, and grow in situ for 24 h. Then wash the reacted membrane with deionized water for 3 times, and then put it into a 120°C oven for drying for 2 h. After drying, put it into deionized water for standby.

[0072] (2) Weigh 1 g of p-phenylenediamine and dissolve it in 50 mL of ultrapure water, and magnetically stir for 10 min. Add 0.5 mL of triethylamine, and magnetically stir the mixed solution for 10 min to obtain the aqueous monomer mixed solution.

[0073] Dissolve 1,3,5-benzene triformyl chloride in n-hexane to prepare a 50 mL oil phase solution with a concentration of 0.25 %w / v, and ultrasonic dispersion until the solution is clear.

[0074] (3) After the aqueous solution prepared in (2) is stirred uniformly, stand for 5 min for standby. Take out the membrane prepared in (1) from pure water, and use industrial wiping paper to wipe off the excess water. Pour 25 mL of aqueous solution on the surface of the base membrane, and keep for 90 s. Then use industrial wiping paper to wipe off the excess aqueous solution, and then pour 25 mL of oil phase solution to occur interfacial polymerization. After 2 min of reaction, pour out the excess oil phase solution, wash it twice with n-hexane, and then put the prepared nanofiltration membrane into an oven for heating for 20 min. After drying, take it out and soak it in ultrapure water for storage and use.

[0075] The performance of the nanofiltration membrane prepared in Example 7 was tested. The water flux of the nanofiltration membrane was 50.8 L·m -2 ·h -1 ·bar -1 , the Li + retention rate was 32.6%, and the Mg 2+ retention rate was 96.7%.

[0076] Example 8:

[0077] (1) Prepare 2 mol / L sodium hydroxide solution, immerse the commercial membrane in the prepared sodium hydroxide solution, and place it in a constant temperature water bath at 60°C for 2 h. Take out the membrane and wash it with pure water for 3 times, and then soak it in pure water for 24 h for standby. Under room temperature conditions, weigh 2 g of p-phenylenediamine and dissolve it in 50 mL of ultrapure water. After complete dissolution, weigh 0.2 g of dopamine hydrochloride and add it, ultrasonic dispersion for 10 min to obtain solution 1. Weigh 50 mg of 1,3,5-triformylphloroglucinol and add it to 50 mL of ethanol, ultrasonic until the solution is clear, to obtain solution 2. Pour the two solutions into a beaker, stir for 10 s, and then put the pretreated base membrane into it, and grow in situ for 2 h. Then wash the reacted membrane with deionized water for 3 times, and then put it into a 120°C oven for drying for 2 h. After drying, put it into deionized water for standby.

[0078] (2) Weigh 0.5 g of p-phenylenediamine and dissolve it in 50 mL of ultrapure water, and magnetically stir for 10 min. Add 0.5 mL of triethylamine, and magnetically stir the mixed solution for 10 min to obtain the aqueous monomer mixed solution.

[0079] Dissolve 1,3,5-benzene triformyl chloride in n-hexane to prepare a 50 mL oil phase solution with a concentration of 0.25 %w / v, and ultrasonic dispersion until the solution is clear.

[0080] (3) After the aqueous solution prepared in (2) is stirred uniformly, stand for 5 min for standby. Take out the membrane prepared in (1) from pure water, and use industrial wiping paper to wipe off the excess water. Pour 25 mL of aqueous solution on the surface of the base membrane, and keep for 90 s. Then use industrial wiping paper to wipe off the excess aqueous solution, and then pour 25 mL of oil phase solution to occur interfacial polymerization. After 2 min of reaction, pour out the excess oil phase solution, wash it twice with n-hexane, and then put the prepared nanofiltration membrane into an oven for heating for 20 min. After drying, take it out and soak it in ultrapure water for storage and use.

[0081] The performance of the nanofiltration membrane prepared in Example 8 was tested. The water flux of the nanofiltration membrane was 56.8 L·m -2 ·h -1 ·bar -1 , the Li + retention rate was 36.6%, and the Mg 2+ retention rate was 96.3%.

[0082] Example 9:

[0083] (1) Prepare 2 mol / L sodium hydroxide solution, immerse the commercial membrane in the prepared sodium hydroxide solution, and place it in a constant temperature water bath at 60°C for 2 h. Take out the membrane and wash it with pure water for 3 times, and then soak it in pure water for 24 h for standby. Under room temperature conditions, weigh 2 g of p-phenylenediamine and dissolve it in 50 mL of ultrapure water. After complete dissolution, weigh 0.2 g of dopamine hydrochloride and add it, ultrasonic dispersion for 10 min to obtain solution 1. Weigh 50 mg of 1,3,5-triformylphloroglucinol and add it to 50 mL of methanol, ultrasonic until the solution is clear, to obtain solution 2. Pour the two solutions into a beaker, stir for 10 s, and then put the pretreated base membrane into it, and grow in situ for 2 h. Then wash the reacted membrane with deionized water for 3 times, and then put it into a 120°C oven for drying for 2 h. After drying, put it into deionized water for standby.

[0084] (2) Weigh 0.5 g of m-phenylenediamine and dissolve it in 50 mL of ultrapure water, and magnetically stir for 10 min. Add 0.5 mL of triethylamine, and magnetically stir the mixed solution for 10 min to obtain the aqueous monomer mixed solution.

[0085] Dissolve 1,3,5-benzene triformyl chloride in n-hexane to prepare a 50 mL oil phase solution with a concentration of 0.25 %w / v, and ultrasonic dispersion until the solution is clear.

[0086] (3) After the aqueous solution prepared in (2) is stirred uniformly, stand for 5 min for standby. Take out the membrane prepared in (1) from pure water, and use industrial wiping paper to wipe off the excess water. Pour 25 mL of aqueous solution on the surface of the base membrane, and keep for 90 s. Then use industrial wiping paper to wipe off the excess aqueous solution, and then pour 25 mL of oil phase solution to occur interfacial polymerization. After 2 min of reaction, pour out the excess oil phase solution, wash it twice with n-hexane, and then put the prepared nanofiltration membrane into an oven for heating for 20 min. After drying, take it out and soak it in ultrapure water for storage and use.

[0087] The performance of the nanofiltration membrane prepared in Example 9 was tested. The water flux of the nanofiltration membrane was 42.8 L·m -2 ·h -1 ·bar -1 , the Li + retention rate was 34.5%, and the Mg 2+ retention rate was 97.3%.

[0088] Example 10:

[0089] (1) Prepare 2 mol / L sodium hydroxide solution, immerse the commercial membrane in the prepared sodium hydroxide solution, and place it in a constant temperature water bath at 60°C for 2 h. Take out the membrane and wash it with pure water for 3 times, and then soak it in pure water for 24 h for standby. At room temperature, weigh 1.5 g of p-phenylenediamine and dissolve it in 50 mL of ultrapure water. After complete dissolution, weigh 0.15 g of dopamine hydrochloride and add it, ultrasonic dispersion for 10 min to obtain solution 1. Weigh 50 mg of 1,3,5-triformylphloroglucinol and add it to 50 mL of ethanol, ultrasonic until the solution is clear, to obtain solution 2. Pour the two solutions into a beaker, stir for 10 s, and then put the pretreated base membrane into it, and grow in situ for 2 h. Then wash the reacted membrane with deionized water for 3 times, and then put it into a 120°C oven for drying for 2 h. After drying, put it into deionized water for standby.

[0090] (2) Weigh 1 g of p-phenylenediamine and dissolve it in 50 mL of ultrapure water, and magnetically stir for 10 min. Add 0.5 mL of triethylamine, and magnetically stir the mixed solution for 10 min to obtain the aqueous monomer mixed solution.

[0091] Dissolve 1,3,5-benzene triformyl chloride in n-hexane to prepare a 50 mL oil phase solution with a concentration of 0.25 %w / v, and ultrasonic dispersion until the solution is clear.

[0092] (3) After the aqueous solution prepared in (2) is stirred uniformly, stand for 5 min for standby. Take out the membrane prepared in (1) from pure water, and use industrial wiping paper to wipe off the excess water. Pour 25 mL of aqueous solution on the surface of the base membrane, and keep for 90 s. Then use industrial wiping paper to wipe off the excess aqueous solution, and then pour 25 mL of oil phase solution to occur interfacial polymerization. After 2 min of reaction, pour out the excess oil phase solution, wash it twice with n-hexane, and then put the prepared nanofiltration membrane into an oven for heating for 20 min. After drying, take it out and soak it in ultrapure water for storage and use.

[0093] The performance of the nanofiltration membrane prepared in Example 10 was tested. The water flux of the nanofiltration membrane was 48.8 L·m -2 ·h -1 ·bar -1 , the Li + retention rate was 30.6%, and the Mg 2+ retention rate was 98.3%.

[0094] Example 11:

[0095] (1) Prepare 2 mol / L sodium hydroxide solution, immerse the commercial membrane in the prepared sodium hydroxide solution, and place it in a constant temperature water bath at 60°C for 2 h. Take out the membrane and wash it with pure water for 3 times, and then soak it in pure water for 24 h for standby. At room temperature, weigh 0.5 g of p-phenylenediamine and dissolve it in 50 mL of ultrapure water. After complete dissolution, weigh 0.05 g of dopamine hydrochloride and add it, ultrasonic dispersion for 10 min to obtain solution 1. Weigh 50 mg of 1,3,5-triformylphloroglucinol and add it to 50 mL of ethanol, ultrasonic until the solution is clear, to obtain solution 2. Pour the two solutions into a beaker, stir for 10 s, and then put the pretreated base membrane into it, and grow in situ for 12 h. Then wash the reacted membrane with deionized water for 3 times, and then put it into a 120°C oven for drying for 2 h. After drying, put it into deionized water for standby.

[0096] (2) Weigh 1 g of p-phenylenediamine and dissolve it in 50 mL of ultrapure water, and magnetically stir for 10 min. Add 0.5 mL of triethylamine, and magnetically stir the mixed solution for 10 min to obtain the aqueous monomer mixed solution.

[0097] Dissolve 1,3,5-benzene triformyl chloride in n-hexane to prepare a 50 mL oil phase solution with a concentration of 0.25 %w / v, and ultrasonic dispersion until the solution is clear.

[0098] (3) After the aqueous solution prepared in (2) is stirred uniformly, stand for 5 min for standby. Take out the membrane prepared in (1) from pure water, and use industrial wiping paper to wipe off the excess water. Pour 25 mL of aqueous solution on the surface of the base membrane, and keep for 90 s. Then use industrial wiping paper to wipe off the excess aqueous solution, and then pour 25 mL of oil phase solution to occur interfacial polymerization. After 2 min of reaction, pour out the excess oil phase solution, wash it twice with n-hexane, and then put the prepared nanofiltration membrane into an oven for heating for 20 min. After drying, take it out and soak it in ultrapure water for storage and use.

[0099] The performance of the nanofiltration membrane prepared in Example 11 was tested. The water flux of the nanofiltration membrane was 45.8 L·m -2 ·h -1 ·bar -1 , the Li + retention rate was 33.2%, and the Mg 2+ retention rate was 98.7%.

[0100] Example 12:

[0101] (1) Prepare a 2 mol / L sodium hydroxide solution, immerse the commercial membrane in the prepared sodium hydroxide solution, and place it in a constant temperature water bath at 60°C for 2 h. Take out the membrane and wash it with pure water for 3 times, and then soak it in pure water for 24 h for standby. At room temperature, weigh 0.5 g of p-phenylenediamine and dissolve it in 50 mL of ultrapure water. After complete dissolution, weigh 0.05 g of dopamine hydrochloride and add it, ultrasonic dispersion for 10 min to obtain solution 1. Weigh 50 mg of 1,3,5-triformylphloroglucinol and add it to 50 mL of ethanol, ultrasonic until the solution is clear, to obtain solution 1. Pour the two solutions into a beaker, stir for 10 s, and then put the pretreated base membrane into it, and grow in situ for 12 h. Then wash the reacted membrane with deionized water for 3 times, and then put it into a 120°C oven for drying for 2 h. After drying, put it into deionized water for standby.

[0102] (2) Weigh 0.7 g of p-phenylenediamine and dissolve it in 50 mL of ultrapure water, and magnetically stir for 10 min. Add 0.5 mL of triethylamine, and magnetically stir the mixed solution for 10 min to obtain the aqueous monomer mixed solution.

[0103] Dissolve 1,3,5-benzene triformyl chloride in n-hexane to prepare a 50 mL oil phase solution with a concentration of 0.25 %w / v, and ultrasonic dispersion until the solution is clear.

[0104] (3) After the aqueous solution prepared in (2) is stirred uniformly, it is placed for standby for 5 min. Take out the membrane prepared in (1) from pure water, and use industrial wiping paper to wipe off the excess water. Pour 25 mL of aqueous solution on the surface of the base membrane, and keep for 90 s. Then use industrial wiping paper to wipe off the excess aqueous solution, and then pour 25 mL of oil phase solution to occur interfacial polymerization. After 2 min of reaction, pour out the excess oil phase solution, wash it twice with n-hexane, and then put the prepared nanofiltration membrane into an oven for heating for 20 min. After drying, take it out and soak it in ultrapure water for storage and use.

[0105] The nanofiltration membrane prepared in Example 12 was tested for performance. The water flux of the nanofiltration membrane was 40.8 L·m -2 ·h -1 ·bar -1 , the Li + retention rate was 35.2%, and the Mg 2+ retention rate was 97.7%.

Claims

1. A preparation method of a TpPa-COF interlayer nanofiltration membrane, comprising the following specific steps: (1) Preparation of TpPa-COF film A 2 mol / L sodium hydroxide solution is prepared, the base film is immersed in the prepared sodium hydroxide solution, and is kept in a constant temperature water bath at 60°C for 2 h. The film is washed with pure water for 3 times, and then is immersed in pure water for 24 h for standby. The substances involved in the preparation process of the TpPa-COF film are composed of the following mass percentages: 0.5-2.5% of a diamine organic substance, a certain amount of 1,3,5-triformylphloroglucinol, 0.05-0.2% of an oxidizing agent, and the remaining amount of ultrapure water and an organic solvent. A certain amount of oxidizing agent powder is slowly added to the diamine aqueous solution, and then is ultrasonically dissolved for 0.1-1 h. After complete dissolution, solution 1 is obtained. A certain concentration of 1,3,5-triformylphloroglucinol organic solution is prepared, and is ultrasonically dispersed until completely dissolved, to obtain solution 2. The two solutions are poured into a beaker according to a certain proportion, are stirred for 5-30 s, and the pretreated base film is horizontally immersed therein, In-situ growth for 0.5-24 h to introduce TpPa-COF film on the commodity; (2) Preparation of water phase and oil phase monomer solution The substances involved in the preparation process of the water phase monomer mixed solution are composed of the following mass percentages: 0.5-1.5% of surfactant, 0.5-2.5% of diamine compound, and the remaining amount of ultrapure water; a diamine aqueous solution with a certain concentration is prepared, and magnetic stirring is performed for 5-10 min; after complete dissolution, the surfactant is added dropwise; the mixed solution is magnetically stirred for 10-15 min to obtain the water phase monomer mixed solution; The substances involved in the preparation process of the oil phase monomer solution are composed of the following mass percentages: 0.15-0.3% of 1,3,5-benzene tricarbonyl chloride, and the remaining amount of n-hexane; 1,3,5-benzene tricarbonyl chloride is dissolved in n-hexane to prepare an oil phase solution, and ultrasonic dispersion is performed for 5-10 min to obtain the oil phase solution; (3) Preparation of TpPa-COF interlayer nanofiltration membrane The water phase solution prepared in (2) is stirred uniformly and then placed for 5 min for standby, the film piece prepared in (1) is taken out from pure water, and the excess water is wiped off using industrial wiping paper; 15-25 mL of water phase solution is poured on the surface of the base film, which is kept for 1-3 min, and then the excess water phase solution is wiped off using industrial wiping paper, and then 15-25 mL of oil phase solution is poured to occur interfacial polymerization reaction, the excess oil phase solution is poured out after reaction for 1-2 min, the prepared nanofiltration membrane is placed in an oven and heated for 5-20 min, and then taken out and soaked in ultrapure water for storage and use.

2. The method of claim 1, wherein In step (1), the solvent of 1,3,5-triformylphloroglucinol is one of ethanol, diethyl ether, and methanol.

3. The method of claim 1, wherein In step (1), the oxide is one of hydrochloric acid dopamine, tannic acid, and gallic acid.

4. The method of claim 1, wherein In step (1), the base film is one of polyacrylonitrile, polyvinylidene fluoride, polyether sulfone, and polysulfone.

5. The method of claim 1, wherein In step (2), the surfactant is one of trimethylamine, triethylamine, and dodecyl dimethyl benzyl ammonium bromide.

6. The method of claim 1, wherein In step (2), the diamine compound is one of p-phenylenediamine, m-phenylenediamine, and o-phenylenediamine.

7. The TpPa-COF interlayer nanofiltration membrane prepared by the method according to any one of claims 1-5, characterized in that, The pure water flux of the nanofiltration membrane is greater than or equal to 40 L·m -2 ·h -1 ·bar -1 In the separation test of monovalent lithium ions and divalent magnesium ions, the retention rate of monovalent lithium ions is less than or equal to 40%, the retention rate of divalent magnesium ions is greater than or equal to 95%, the membrane flux recovery rate is greater than or equal to 95%, and the anti-biological pollution effect is obvious.

Images