Preparation method of high-lithium-ion-selectivity open-chain crown ether composite membrane

Abstract

The invention relates to the technical field of membrane separation, and discloses a preparation method of a high-lithium-ion-selectivity open-chain crown ether composite membrane. According to the method, a polysulfone (PSF) membrane is used as a base membrane, m-amine monomers are added into a water phase, acyl chloride monomers and o-phenylene dioxodiacetyl chloride (OPDM) monomers are added into an oil phase, the OPDC monomers are introduced into a separation layer through an interfacial polymerization method, and the open-chain crown ether composite membrane with high lithium ion selectivity is prepared. The open-chain crown ether composite membrane prepared by the method shows excellent lithium ion separation performance and stability, and a reference thought is provided for related fields such as preparation of an ion selective membrane, efficient recovery and extraction of liquid-phase lithium resources and the like.

Description

Technical Field

[0001] The present invention belongs to the fields of materials science and membrane separation, and particularly relates to a method for preparing a highly lithium-ion selective open-chain crown ether composite membrane for lithium-ion recovery from liquid solutions, such as membranes and devices for the selective separation of lithium ions from brine. Background Art

[0002] With the continuous growth of global energy demand and the emphasis on environmental sustainability, efficient and clean energy solutions have become particularly crucial. As a core element in energy storage and conversion technologies, the market demand for lithium ions is constantly rising. Currently, the main sources of lithium salts include ore deposits and salt lake resources. Traditional lithium extraction methods usually rely on acid decomposition and chemical leaching of minerals, or enrichment of lithium ions by solar pond evaporation and concentration of brine. However, these processes often have problems such as complex processes, long time consumption, large demand for chemical reagents, or high dependence on climatic conditions.

[0003] In contrast, membrane separation technology has gradually become an ideal choice in the field of lithium extraction due to its advantages such as high selectivity, strong environmental protection, simple operation, and strong scale adaptability. To optimize the lithium extraction process, the present invention proposes the use of an open-chain crown ether composite membrane to replace traditional lithium extraction methods. This technology can more efficiently separate and enrich lithium ions, while reducing the use of chemical reagents, making the whole process more environmentally friendly, and significantly shortening the extraction time, thereby improving the utilization efficiency of lithium resources. Crown ether monomers are organic compounds with macrocyclic or polycyclic, multidentate ligands that can coordinate with cations. The oxygen atoms in crown ethers have unshared electron pairs, which make the inside of the crown ether ring negatively charged. In addition, different crown ethers have cavities of different sizes. The combined effect of the two produces an ion-dipole interaction, which enables crown ethers to bind to metal ions in a host-guest manner and form stable complexes. Among them, the crown ether structure containing four oxygen atoms often forms a good recognition with lithium ions and has excellent lithium-ion selectivity. In addition, the composite membrane prepared by the interfacial polymerization method has good chemical stability and can effectively resist environmental influences such as corrosion and oxidation from seawater. Therefore, combining crown ethers with membrane technology to prepare highly selective lithium-selective composite membranes has good application prospects.

[0004] Defects are likely to occur in the preparation of open-chain crown ether composite membranes, resulting in a decline in their separation performance. Therefore, the present invention obtains a highly selective and dense open-chain crown ether composite membrane by adjusting the monomer ratio and selecting the method of removing the aqueous phase by air spraying.

[0005] Currently, there is an urgent need in this field to develop a lithium-ion selective membrane with high lithium-ion selectivity and capable of stable preparation and scale-up. Summary of the Invention

[0006] The object of the present invention is to overcome the difficulties in lithium extraction in the prior art and provide a method for preparing a highly lithium-ion selective open-chain crown ether composite membrane.

[0007] The technical solution of the present invention is as follows: A method for preparing a highly selective open-chain crown ether composite membrane, and the specific operation is as follows: A. Synthesis of monomers: Dissolve o-phenylenedioxy diacetic acid in thionyl chloride solution in a round-bottom flask, wrap the round-bottom flask with tin foil to form a light-shielded condition, and then place the mixed solution in a nitrogen atmosphere for oil bath heating to form a uniform brown solution; Rotate and evaporate to obtain a crude product, and purify it by sodium bicarbonate chromatography column method, and remove the product solvent by vacuum distillation to obtain o-phenylenedioxy diacetyl chloride (OPDC); B. Preparation of the mixed aqueous phase: At room temperature, add a certain mass fraction of amine monomer, camphorsulfonic acid (CSA) and triethylamine (TEA) to deionized water, and continuously stir to obtain a mixed aqueous phase; C. Preparation of the mixed oil phase: At room temperature, add a certain mass of acyl chloride monomer to a certain mass percentage of o-phenylenedioxy diacetyl chloride and n-hexane, and continuously stir to obtain a mixed oil phase; D. Preparation of the membrane: Cover the mixed aqueous phase solution prepared in step B on the PSF substrate membrane, remove the aqueous phase after staying for a period of time, and wait for the membrane surface to dry and become smooth at room temperature. Cover the mixed oil phase solution prepared in step C on the surface of the above-mentioned membrane to cause an interfacial polymerization reaction, and then remove the excess oil phase solution on the membrane surface; Perform thermal cross-linking and curing treatment in an oven, and rinse the membrane surface with deionized water to obtain a TFC composite membrane, and store it for later use.

[0008] Further, the molar ratio of o-phenylenedioxy diacetic acid to thionyl chloride solution in step A is 0.1-0.2.

[0009] Further, the oil bath temperature for heating and stirring the mixed solution in step A is 50-70 °C, and the time is 2-3 h; the rotation evaporation temperature in step A is 40-50 °C and the rotation speed is 30-100 r / min.

[0010] Further, the amine monomer in step B is one of monomer m-phenylenediamine (MPD), piperazine (PIP), N-methylpiperazine (NMPIP), and polyethyleneimine (PEI); Further, the mass fraction of the amine monomer in step B is 1.0-5.0 wt%, the mass fraction of camphorsulfonic acid is 0.5-3.0 wt%, and the mass fraction of triethylamine is 0.5-7.5 wt%.

[0011] Further, the acyl chloride monomer in step C is one of trimesoyl chloride (TMC) or terephthaloyl chloride (TPC); the mass-volume percentage of the acyl chloride monomer and n-hexane in the oil-phase solution is 0.05-0.45 w / v%, and the mass-volume percentage of o-phenylene dioxy diacetyl chloride and n-hexane is 0.05-0.45 w / v%.

[0012] Further, the method for removing the aqueous phase in step D is air spraying; the air spraying uses an air gun with an air pressure of 0.5-1.0 MPa.

[0013] Further, it is characterized in that the thermal curing treatment temperature in step D is 60-80 °C, and the time is 5-15 min.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: The novel monomer o-phenylene dioxy diacetyl chloride synthesized by the present invention has a unique tetra-oxygen cavity structure and can effectively recognize lithium ions. An open-chain crown ether composite membrane with a dense cross-linked structure is successfully prepared by the interfacial polymerization method. The membrane has excellent lithium-magnesium separation effect and effectively solves the current situation of difficult lithium ion extraction. The present invention demonstrates the broad application prospects of high ion-selective membrane separation. Description of the Drawings

[0015] Figure 1 It is the NMR spectrum of OPDC prepared in Example 3.

[0016] Figure 2 It is the SEM images of the TFC membrane and the TFC-OP-10 membrane in Examples 5 and 7.

[0017] Figure 3 a) It is the FTIR characterization test chart of the OPDC monomer and the prepared composite membrane in Examples 3, 5, 6, 7, and 8; b) It is the XPS total spectrum test chart of the composite membrane in Examples 5, 6, 7, and 8.

[0018] Figure 4 It is the O1s and C1s peak separation spectra and cross-linking degree of the TFC membrane and the TFC-OP-10 membrane in Examples 5 and 7.

[0019] Figure 5 It is the water contact angle and surface energy of the composite membrane in Examples 5, 6, 7, and 8.

[0020] Figure 6 a) It is the schematic diagram of the diffusion membrane module device shown in Example 6; b) It is the schematic diagram of the electrodialysis module device shown in Examples 7 and.

[0021] Figure 7a) is the counter-diffusion ion flux diagram of the TFC membrane and the TFC-OP-10 membrane in Example 5 and Example 7; b) is the lithium-magnesium separation performance of the TFC-OP-10 membrane at different voltages for electrodialysis in Example 7.

[0022] Figure 8 is the diagram of lithium and magnesium ion fluxes and lithium-magnesium separation performance of the TFC-OP-10 membrane, PIP-OP-10 membrane, NMPIP-OP-10 membrane, and PEI-OP-10 membrane under electrodialysis in Example 5 and Example 10. Detailed implementation method Example 1

[0023] This example is used to illustrate the preparation of an acyl chloride monomer with incomplete acyl chlorination.

[0024] Dissolve o-phenylenedioxy diacetic acid and thionyl chloride solution with a mass ratio of 0.1 in a round-bottom flask, wrap the round-bottom flask with tin foil to form a light-shielded condition, and then heat the mixed solution in a 50 °C oil bath under a nitrogen atmosphere for 2 h to form a uniform brown solution; obtain the crude product at 40 °C on a rotary evaporator with a rotary evaporation speed of 30 r / min, and purify it by the sodium bicarbonate chromatography column method. Then, remove the product solvent by vacuum distillation to obtain a monomer with incomplete acyl chlorination reaction. Example 2

[0025] This example is used to illustrate the preparation of an acyl chloride monomer with incomplete acyl chlorination.

[0026] Dissolve o-phenylenedioxy diacetic acid and thionyl chloride solution with a mass ratio of 0.15 in a round-bottom flask, wrap the round-bottom flask with tin foil to form a light-shielded condition, and then heat the mixed solution in a 60 °C oil bath under a nitrogen atmosphere for 2.5 h to form a uniform brown solution; obtain the crude product at 45 °C on a rotary evaporator with a rotary evaporation speed of 70 r / min, and purify it by the sodium bicarbonate chromatography column method. Then, remove the product solvent by vacuum distillation to obtain a monomer with incomplete acyl chlorination reaction. Example 3

[0027] This example is used to illustrate the preparation of a novel o-phenylenedioxy diacetyl chloride.

[0028] Dissolve o-phenylenedioxy diacetic acid and thionyl chloride solution with a mass ratio of 0.2 in a round-bottom flask, wrap the round-bottom flask with tin foil to form a light-shielded condition, and then heat the mixed solution in a 70 °C oil bath under a nitrogen atmosphere for 3 h to form a uniform brown solution; obtain the crude product at 50 °C on a rotary evaporator with a rotary evaporation speed of 100 r / min, and purify it by the sodium bicarbonate chromatography column method. Remove the product solvent by vacuum distillation to obtain o-phenylenedioxy diacetyl chloride (OPDC).

[0029] Figure 1 This is the NMR spectrum of the OPDC prepared in this example. Nuclear magnetic resonance (NMR) testing confirmed the successful preparation of OPDC, and it can be seen that the novel monomer o-phenylenedioxydiacetyl chloride has a unique tetraoxo cavity structure. Example 4

[0030] This example is used to illustrate the preparation of a composite membrane by interfacial polymerization.

[0031] First, prepare the mixed aqueous phase. At room temperature, add MPD monomer with a mass fraction of 1.0 wt%, CSA with a mass fraction of 0.5 wt%, and TEA with a mass fraction of 0.5 wt% to deionized water, and continuously stir to obtain the mixed aqueous phase. Then, prepare the mixed oil phase with a mass-volume percentage of 0.05 w / v% of TPC and n-hexane. Cover the PSF substrate membrane with the mixed aqueous phase solution. After a period of time, use an air gun at 0.5 MPa to remove the aqueous phase, and wait for the membrane surface to dry and become smooth at room temperature. Cover the above membrane surface with the mixed oil phase solution to cause an interfacial polymerization reaction, and then remove the excess oil phase solution on the membrane surface; perform thermal cross-linking and curing treatment in an oven at 60 °C for 5 min, and rinse the membrane surface with deionized water to obtain a TFC composite membrane for electrodialysis testing of lithium-magnesium separation. Example 5

[0032] This example is used to illustrate the preparation of a composite membrane by interfacial polymerization.

[0033] First, prepare the mixed aqueous phase. At room temperature, add MPD monomer with a mass fraction of 1.0 wt%, CSA with a mass fraction of 0.5 wt%, and TEA with a mass fraction of 0.6 wt% to deionized water, and continuously stir to obtain the mixed aqueous phase. Then, prepare the mixed oil phase with a mass-volume percentage of 0.05 w / v% of TMC and n-hexane. Cover the PSF substrate membrane with the mixed aqueous phase solution. After a period of time, use an air gun at 0.5 MPa to remove the aqueous phase, and wait for the membrane surface to dry and become smooth at room temperature. Cover the above membrane surface with the mixed oil phase solution to cause an interfacial polymerization reaction, and then remove the excess oil phase solution on the membrane surface; perform thermal cross-linking and curing treatment in an oven at 60 °C for 5 min, and rinse the membrane surface with deionized water to obtain a TFC composite membrane for electrodialysis testing of lithium-magnesium separation.

[0034] Figure 2 a, 2b are the cross-sectional SEM cross-sectional view and surface morphology diagram of the TFC membrane in this example. It can be seen that the thickness of the selective layer of the membrane is about 90 nm, and a typical ridge-valley structure appears on the membrane surface. Figure 3 b is the XPS survey spectrum of the TFC membrane in this example. Example 6

[0035] This example is used to illustrate the preparation of an open-chain crown ether composite membrane by interfacial polymerization.

[0036] First, prepare the mixed aqueous phase. At room temperature, add MPD monomer with a mass fraction of 2.0 wt%, CSA with a mass fraction of 1.5 wt%, and TEA with a mass fraction of 0.6 wt% to deionized water, and continuously stir to obtain the mixed aqueous phase. Then, prepare the mixed oil phase. The mass-volume percentage of TMC and n-hexane is 0.25 w / v%, and the mass-volume percentage of o-phenylenedioxydiacetyl chloride prepared in Example 3 and n-hexane is 0.05 w / v%. Cover the mixed aqueous phase solution on the PSF substrate membrane. After staying for a period of time, use an air gun at 0.5 MPa to remove the aqueous phase, and wait for the membrane surface to dry and become smooth at room temperature. Cover the mixed oil phase solution on the surface of the above membrane to cause an interfacial polymerization reaction, and then remove the excess oil phase solution on the membrane surface; perform thermal cross-linking and curing treatment in an oven at 60 °C for 5 min, and rinse the membrane surface with deionized water to obtain the TFC-OP-05 membrane. At the same time, under the same ratio and temperature conditions, prepare a TFC without adding o-phenylenedioxydiacetyl chloride as a control group. Use the two membranes for electrodialysis tests for lithium-magnesium separation.

[0037] Figure 3 a is the infrared spectrum of the TFC membrane and the TFC-OP-05 membrane in this example. It can be seen that the TFC-OP-05 membrane generates a C-O-C bond, indicating that the monomer has been successfully polymerized onto the membrane layer. Figure 3 b is the XPS survey spectrum of the TFC membrane and the TFC-OP-05 membrane in this example. Figure 4 a-b are the XPS peak-fitting spectra of O1s and C1s of the TFC membrane in this example. Figure 4 c is the cross-linking degree diagram of the TFC membrane in this example. Figure 5 are the water contact angle and surface energy diagrams of the TFC membrane and the TFC-OP-05 membrane, and the membrane is more hydrophilic. Figure 6 a is the schematic diagram of the counter-diffusion membrane module device used in this example. Figure 7 a is the ion flux diagram of the TFC obtained after the counter-diffusion test in this example. Example 7

[0038] First, prepare the mixed aqueous phase. At room temperature, add MPD monomer with a mass fraction of 5.0 wt%, CSA with a mass fraction of 3.0 wt%, and TEA with a mass fraction of 7.5 wt% to deionized water, and continuously stir to obtain the mixed aqueous phase. Then, prepare the mixed oil phase. The mass-volume percentage of TMC and n-hexane is 0.45 w / v%, and the mass-volume percentage of o-phenylenedioxy diacetyl chloride prepared in Example 3 and n-hexane is 0.10 w / v%. Cover the PSF substrate membrane with the mixed aqueous phase solution. After staying for a period of time, use an air gun at 0.7 MPa to remove the aqueous phase. Wait for the membrane surface to dry and become smooth at room temperature. Cover the above membrane surface with the mixed oil phase solution to cause an interfacial polymerization reaction, and then remove the excess oil phase solution on the membrane surface; perform cross-linking and curing treatment in an oven at 75 °C for 10 min, and rinse the membrane surface with deionized water to obtain the TFC-OP-10 membrane composite membrane for electrodialysis testing of lithium-magnesium separation.

[0039] Figure 2 c and 2d are the cross-sectional SEM cross-sectional diagram and surface morphology diagram of the TFC-OP-10 membrane in this example. It can be seen that the thickness of the selective layer of the membrane is about 40 nm, and the membrane surface is smoother than that of the TFC membrane. Figure 3 a is the infrared spectrum of the TFC-OP-10 membrane in this example. It can be seen that C-O-C bonds are produced, indicating that the monomers are successfully polymerized onto the membrane layer. Figure 3 b is the XPS survey spectrum of the TFC-OP-10 membrane in this example. Figure 4 d - e are the XPS peak-fitting diagrams of O1s and C1s of the TFC-OP-10 membrane in this example. Figure 4 f is the cross-linking degree diagram of the TFC-OP-10 membrane in this example. Compared with TFC, the cross-linking degree decreases. Figure 5 are the water contact angle and surface energy diagrams of the TFC-OP-10 membrane. As the addition of OPDC increases, the membrane surface becomes more hydrophilic and the surface energy is higher. Figure 7 a is the ion flux diagram of the TFC-OP-10 membrane obtained after diffusion testing in this example. Figure 6 b is the schematic diagram of the electrodialysis component device used in this example. Example 8

[0040] First, prepare the mixed aqueous phase. At room temperature, add MPD monomer with a mass fraction of 5.0 wt%, CSA with a mass fraction of 3.0 wt%, and TEA with a mass fraction of 7.5 wt% to deionized water, and continuously stir to obtain the mixed aqueous phase. Then, prepare the mixed oil phase. The mass-volume percentage of TMC and n-hexane is 0.45 w / v%, and the mass-volume percentage of o-phenylenedioxydiacetyl chloride prepared in Example 3 and n-hexane is 0.15 w / v%. Cover the PSF substrate membrane with the mixed aqueous phase solution. After staying for a period of time, use an air gun at 1.0 MPa to remove the aqueous phase. Wait for the membrane surface to dry and become smooth at room temperature. Cover the above membrane surface with the mixed oil phase solution to cause an interfacial polymerization reaction, and then remove the excess oil phase solution on the membrane surface; perform thermal cross-linking and curing treatment in an oven at 75 °C for 10 min, and rinse the membrane surface with deionized water to obtain the TFC-OP-15 composite membrane for electrodialysis testing of lithium-magnesium separation.

[0041] Figure 3 a is the infrared spectrum of the TFC-OP-15 membrane in this example. It can be seen that C-O-C bonds are produced, indicating that the monomers are successfully polymerized onto the membrane layer. Figure 3 b is the XPS survey spectrum of the TFC-OP-15 membrane in this example. Figure 5 It is the water contact angle and surface energy diagram of the TFC-OP-15 membrane. As the addition of OPDC increases, the membrane surface becomes more hydrophilic and has a higher surface energy. Example 9

[0042] First, prepare the mixed aqueous phase. At room temperature, add MPD monomer with a mass fraction of 5.0 wt%, CSA with a mass fraction of 3.0 wt%, and TEA with a mass fraction of 7.5 wt% to deionized water, and continuously stir to obtain the mixed aqueous phase. Then, prepare the mixed oil phase. The mass-volume percentage of TMC and n-hexane is 0.45 w / v%, and the mass-volume percentage of o-phenylenedioxydiacetyl chloride prepared in Example 3 and n-hexane is 0.45 w / v%. Cover the PSF substrate membrane with the mixed aqueous phase solution. After staying for a period of time, use an air gun at 1.0 MPa to remove the aqueous phase. Wait for the membrane surface to dry and become smooth at room temperature. Cover the above membrane surface with the mixed oil phase solution to cause an interfacial polymerization reaction, and then remove the excess oil phase solution on the membrane surface; perform thermal cross-linking and curing treatment in an oven at 75 °C for 10 min, and rinse the membrane surface with deionized water to obtain the TFC-OP-15 composite membrane for electrodialysis testing of lithium-magnesium separation. Example 10

[0043] First, prepare the mixed aqueous phase. At room temperature, add PIP monomer with a mass fraction of 5.0 wt%, CSA with a mass fraction of 3.0 wt%, and TEA with a mass fraction of 7.5 wt% to deionized water, and continuously stir to obtain the mixed aqueous phase. Then, prepare the mixed oil phase. The mass-volume percentage of TMC and n-hexane is 0.45 w / v%, and the mass-volume percentage of o-phenylenedioxydiacetyl chloride prepared in Example 3 and n-hexane is 0.10 w / v%. Cover the mixed aqueous phase solution on the PSF substrate membrane, and after staying for a period of time, use an air gun at 1.0 MPa to remove the aqueous phase. Wait for the membrane surface to dry and become smooth at room temperature. Cover the mixed oil phase solution on the above membrane surface to cause an interfacial polymerization reaction, and then remove the excess oil phase solution on the membrane surface; perform thermal cross-linking and curing treatment in an oven at 80 °C for 10 min, and rinse the membrane surface with deionized water to obtain the PIP-OP-10 composite membrane. At the same time, under the same ratio and temperature conditions, NMPIP and PEI are respectively selected to replace the PIP monomer as the control group. The NMPIP-OP-10 composite membrane and the PEI-OP-10 composite membrane are obtained. The three membranes are used for electrodialysis testing of lithium-magnesium separation.

[0044] Figure 8 This is the comparison chart of Li + , Mg 2+ ion fluxes and separation factors of the PIP-OP-10 composite membrane, NMPIP-OP-10 composite membrane, and PEI-OP-10 composite membrane obtained after electrodialysis testing in this example. Example 11

[0045] This example is used to illustrate the best lithium-magnesium ion selectivity of the open-chain crown ether composite membrane TFC-OP-10 tested by electrodialysis.

[0046] Use the TFC-OP-10 membrane to conduct electrodialysis testing.

[0047] Successively introduce three solutions, namely the feed solution, the lithium-enriched solution, and the electrode solution, into the electrodialysis device. The feed solution is a mixed solution made of 0.1 mol / L LiCl and 0.1 mol / L MgCl2, the lithium-enriched solution is a pure aqueous solution, and the electrode solution is a 0.1 mol / L KCl solution. The voltages applied to the electrodialysis device are 0.5 V, 1.0 V, 1.5 V, 2.0 V, and 2.5 V respectively. The effective area of the membrane during testing is 12.56 cm 2 , and all experiments are carried out at room temperature.

[0048] Over time, lithium will gradually accumulate in the lithium-enriched solution. After 24 h of electrodialysis testing, the lithium ion fluxes of the TFC-OP-10 membrane at voltages of 0.5 V, 1.0 V, 1.5 V, 2.0 V, and 2.5 V can be obtained as 7.9 mmol·m -2 ·h -1 , 16.46 mmol·m -2 ·h -1 , 20.8 mmol·m -2 ·h -1 , 25.6 mmol·m -2 ·h -1 , 28.75 mmol·m -2 ·h -1 . The lithium-magnesium selectivities are 15.3, 26.6, 17.3, 14.2, and 13.9 respectively. It can be concluded that the separation efficiency of lithium and magnesium is the highest when the applied voltage is 1 V.

[0049] Figure 6 Figure b is a schematic diagram of the electrodialysis component device used in this embodiment. Figure 7 Figure b is a graph of the Li + , Mg 2+ ion fluxes and separation factors of the TFC-OP-10 membrane obtained after electrodialysis testing at different voltages in this embodiment.

Claims

1. A method for preparing a high lithium ion selectivity open-chain crown ether composite membrane, characterized in that: The specific steps are as follows: A. Synthesis of monomers: o-phenylenedioxyacetic acid is dissolved in thionyl chloride solution in a round-bottom flask, the round-bottom flask is wrapped with tin foil to form a light-proof condition, and the mixed solution is placed in a nitrogen atmosphere and heated in an oil bath to form a uniform brown solution; a crude product is obtained by rotary evaporation, and a sodium bicarbonate chromatography column method is used for purification, and the product solvent is removed by vacuum distillation to obtain o-phenylenedioxyacetyl chloride (OPDC); Preparation of mixed aqueous phase: A certain mass fraction of amine monomer, camphorsulfonic acid (CSA) and triethylamine (TEA) are added to deionized water at room temperature, and the mixture is stirred continuously to obtain a mixed aqueous phase; C. Preparation of mixed oil phase: adding a certain mass of acyl chloride monomer to a certain mass percentage of o-phenylenedioxy diacetyl chloride and n-hexane at room temperature, and stirring continuously to obtain a mixed oil phase; D. Preparation of membrane: Cover the mixed aqueous solution prepared in step B on the PSF base membrane, remove the aqueous phase after leaving it for a period of time, and wait for the membrane surface to be dry and smooth at room temperature. Cover the mixed oil phase solution prepared in step C on the surface of the above membrane to make it undergo interfacial polymerization reaction, and then remove the excess oil phase solution on the membrane surface; perform thermal crosslinking and curing treatment in an oven, rinse the membrane surface with deionized water to obtain a TFC composite membrane, and store it for later use.

2. The method for preparing a high lithium ion selectivity open-chain crown ether composite membrane according to claim 1, characterized in that: In step A, the molar ratio of o-phenylenedioxyacetic acid to thionyl chloride solution is 0.1-0.

2.

3. The method for preparing a high lithium ion selectivity open-chain crown ether composite membrane according to claim 1, characterized in that: The oil bath temperature for heating and stirring the mixed solution in step A is 50-70°C for 2-3 h; the rotary evaporation temperature in step A is 40-50°C and the rotation speed is 30-100 r / min.

4. The method for preparing a high lithium ion selectivity open-chain crown ether composite membrane according to claim 1, characterized in that: The amine monomer in step B is one of the monomers m-phenylenediamine (MPD), piperazine (PIP), N-methylpiperazine (NMPIP), and polyethyleneimine (PEI).

5. The method for preparing a high lithium ion selectivity open-chain crown ether composite membrane according to claim 1, characterized in that: In step B, the mass fraction of the amine monomer is 1.0-5.0 wt%, the mass fraction of camphorsulfonic acid is 0.5-3.0 wt%, and the mass fraction of triethylamine is 0.5-7.5 wt%.

6. The method for preparing a high lithium ion selectivity open-chain crown ether composite membrane according to claim 1, characterized in that: The acyl chloride monomer in step C is one of trimethylol chloride (TMC) or terephthaloyl chloride (TPC); the mass volume percentage of the acyl chloride monomer to n-hexane in the oil phase solution is 0.05-0.45 w / v%, and the mass volume percentage of o-phenylenedioxy diacetyl chloride to n-hexane is 0.05-0.45 w / v%.

7. The method for preparing a high lithium ion selectivity open-chain crown ether composite membrane according to claim 1, characterized in that: The method for removing the water phase in step D is air spraying; the air spraying uses an air gun with an air pressure of 0.5-1.0 MPa.

8. The method for preparing a high lithium ion selectivity open-chain crown ether composite membrane according to claim 1, characterized in that: The heat curing treatment temperature in step D is 60-80°C and the time is 5-15 minutes.

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