Preparation method and application of highly selective lithium ion imprinted channel polyelectrolyte composite membrane

Abstract

A preparation method and application of a highly selective lithium ion imprinted channel polyelectrolyte composite membrane, which relates to a preparation method of a polyelectrolyte composite membrane. The purpose of the present invention is to solve the problem that the ion imprinted membrane prepared by the existing method has a low adsorption capacity and a cumbersome preparation process, which restricts its further development. Method: 1. Preparation of PAN hydrolysis membrane, polymer solution and polyanion solution; 2. Preparation of cross-linked polyethyleneimine dithiocarbamate; 3. Self-assembly of multilayer composite membrane; 4. Preparation of highly selective lithium ion imprinted channel polyelectrolyte composite membrane. A highly selective lithium ion imprinted channel polyelectrolyte composite membrane is used to extract lithium from lithium ion leachate. The present invention utilizes the synergistic effect of the screening effect of the ion imprinted channel and the electrostatic repulsion effect of the polyelectrolyte layer to improve the selective permeability of the composite membrane to the target ions. The preparation process of the present invention is simple, low-cost, and convenient for industrial production.

Description

Technical Field

[0001] The invention relates to a method for preparing a polyelectrolyte composite membrane. Background Art

[0002] Lithium batteries, with their excellent safety performance and lack of memory effect, show great application prospects in the energy supply sector. With the continuous expansion of the electric vehicle market, the demand for lithium-ion batteries (LIBs) continues to increase. Waste lithium-ion batteries contain a large amount of rare metals, such as Li, Co, Ni, and Mn, which are valuable secondary resources. Leaching lithium with organic acids is considered an effective and feasible method for recycling waste lithium.

[0003] Ion-imprinted polymers (IITs) are polymer materials that exhibit specific recognition for target ions. Combining IITs with membrane separation techniques to create ion-imprinted membranes offers the dual advantages of specific recognition and excellent flux, making them ideal materials for lithium-ion separation. Ion sieves are inorganic oxides that possess the ability to "screen" and "remember" target ions. Combining IITs with membrane separation techniques to create ion-sieving membranes combines the advantages of both ion sieves and membrane separation materials, enabling efficient and selective lithium extraction. These two categories of lithium-ion selective separation membrane materials effectively address the drawbacks of traditional adsorption-based materials, such as difficulty in recycling and poor selectivity, while also offering advantages such as continuous operation, excellent stability, and multiple recycling capabilities. However, these materials also have certain drawbacks. Although ion-imprinted membranes prepared using IITs exhibit high selectivity and affinity for template ions, their low adsorption capacity and cumbersome preparation process have hindered their further development. Furthermore, lithium-ion sieve membranes suffer from issues such as ion sieve shedding and loss, making them unsuitable for large-scale industrial production. Summary of the Invention

[0004] The purpose of the present invention is to solve the problem that the ion imprinted membrane prepared by the existing method has low adsorption capacity and cumbersome preparation process, which restricts its further development, and to provide a preparation method and application of a highly selective lithium ion imprinted channel polyelectrolyte composite membrane.

[0005] The present invention combines ion imprinting technology and membrane separation technology to develop a lithium ion imprinting channel polyelectrolyte composite membrane. + 、Co 2+ 、Mn 2+ 、Ni 2+ As a model system, the hydration radius is selected between Li + Pb between interfering ions 2+ Ions were used as templates to construct a polyelectrolyte layer through layer-by-layer self-assembly (LbL) method, and the polyelectrolyte layer was modified using ion imprinting technology to form a target Li +The selective screening ion imprinted channel improves the selectivity of the composite membrane to the target ions by introducing the ion imprinted channel. The present invention can be applied to extract lithium from lithium ion leachate.

[0006] A method for preparing a highly selective lithium ion imprinted channel polyelectrolyte composite membrane is specifically completed by the following steps:

[0007] 1. Preparation of PAN hydrolysis membrane, polymer solution and polyanion solution:

[0008] ①. Use polyacrylonitrile ultrafiltration membrane as base membrane, immerse it in NaOH solution, heat it to 60℃~65℃, and hydrolyze it in NaOH solution at 60℃~65℃ to obtain PAN hydrolyzed membrane;

[0009] ②, dissolve polyethyleneimine and Pb(Cl)2 in 0.5mol / L NaCl solution to obtain a mixed solution. 2 + Polymerize with polyethyleneimine to form a polymer solution;

[0010] ③ Dissolve polyacrylic acid in 0.5 mol / L NaCl to obtain a polyanion solution;

[0011] 2. Add the polymer solution and anhydrous ethanol to an oil bath at 60°C to 65°C, stir evenly, then add epichlorohydrin, and continue stirring at 60°C to 65°C for 2h to 3h, adding sodium cyanoborohydride in portions during the stirring reaction; after the stirring reaction is completed, lower the reaction temperature to room temperature, and then add carbon disulfide to obtain a reaction product; ultrasonically treat the reaction product, filter it, wash it, and dry it to obtain a cross-linked polyethyleneimine dithiocarbamate;

[0012] 3. Self-assembled multilayer composite film:

[0013] ① Pour the polyanion solution onto the PAN hydrolysis membrane and allow it to settle for a while. Then pour out the polyanion solution on the PAN hydrolysis membrane and wash away the free polyelectrolyte on the membrane surface with deionized water. Finally, blow dry with nitrogen to obtain a layer of PAA.

[0014] ② Pour the cross-linked polyethyleneimine dithiocarbamate anhydrous ethanol solution onto the PAN hydrolysis membrane and allow it to settle for a while. Then pour out the solution on the PAN hydrolysis membrane and wash off the free polyelectrolyte on the membrane surface with deionized water. Finally, blow dry with nitrogen to obtain a layer of PEI-CS2.

[0015] ③, cycle steps ① to ② 0 to 2 times or cycle steps ① to ② 0 to 2 times and then cycle step ② 1 time to obtain a polyelectrolyte self-assembled multilayer composite membrane with the desired number of layers;

[0016] Fourth, first, the polyelectrolyte self-assembled multilayer composite film with the required number of layers is dried in air at room temperature for 5 minutes to 10 minutes, and then the composite film is immersed in a 2% to 5% mass fraction of epichlorohydrin solution for cross-linking; after the reaction is terminated, it is cooled to room temperature and allowed to stand for degassing, and then the composite film is immersed in 0.1 molL -1 Wash repeatedly with ethylenediaminetetraacetic acid disodium salt solution until no Pb is detected in the washing solution. 2+ Finally, the composite membrane is air-dried at room temperature to obtain a highly selective lithium ion imprinted channel polyelectrolyte composite membrane.

[0017] The main principles of the present invention:

[0018] The present invention modifies the ultrafiltration membrane by layer-by-layer self-assembly method (LbL) and ion imprinting technology; first, lead ions (Pb 2+ ) as template ions and introduced into cross-linked polyethyleneimine dithiocarbamate (PEI-CS2); PEI-CS2 as a functional monomer, the amine groups contained in its molecular structure have a strong chelating ability for lead ions; PEI-CS2 and polyacrylic acid (PSS) are alternately assembled on the surface of polyacrylonitrile (PAN) membrane to form a polyelectrolyte layer; secondly, epichlorohydrin (ECH) is added for cross-linking to improve the stability of the polyelectrolyte layer; finally, ethylenediaminetetraacetic acid disodium salt (EDTA-2Na) is added to elute the template ions, and ion imprinted channels of specific sizes are formed in the polyelectrolyte layer, which are closely related to Pb 2+ The size-matched channels facilitate the screening of lithium ions while intercepting other interfering ions; the screening effect of the ion-imprinted channels and the electrostatic repulsion effect of the polyelectrolyte layer improve the Li-ion ion separation of the composite membrane. + By analyzing the mechanism of ion imprinting technology to improve separation performance, it is believed that this method provides a new way to extract lithium from lithium ion acid leaching solution.

[0019] Beneficial effects of the present invention:

[0020] First, the present invention can selectively screen target ions by constructing ion imprinting channels to improve the selectivity of target ions, while retaining other interfering ions to facilitate the subsequent separation of interfering ions;

[0021] Second, the present invention utilizes the synergistic effect of the screening effect of the ion-imprinted channel and the electrostatic repulsion effect of the polyelectrolyte layer to improve the selective permeability of the composite membrane to the target ions;

[0022] 3. The present invention targets the complex environment of the acid leaching solution of waste lithium batteries. The PEI complex (PEI-CS2) exhibits stronger stability in the acidic environment, and the composite membrane has good durability.

[0023] Fourth, the polymerization process of traditional ion imprinting technology is relatively long. Traditional acid elution takes between 9 and 12 hours. Compared with traditional ion imprinting technology, the present invention does not require subsequent adsorption and desorption, and can operate continuously, greatly improving the operating efficiency.

[0024] Fifth, the traditional ion imprinting technology has a complicated preparation process and low adsorption capacity, which restricts its further development. The present invention has a simple preparation process, low cost, and is easy to industrialize. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is the surface morphology of PAN ultrafiltration membrane;

[0026] Figure 2 This is the surface morphology of the highly selective lithium ion imprinted channel polyelectrolyte composite membrane prepared in Example 3. DETAILED DESCRIPTION

[0027] Specific embodiment 1: In this embodiment, a method for preparing a highly selective lithium ion imprinted channel polyelectrolyte composite membrane is completed by the following steps:

[0028] 1. Preparation of PAN hydrolysis membrane, polymer solution and polyanion solution:

[0029] ①. Use polyacrylonitrile ultrafiltration membrane as base membrane, immerse it in NaOH solution, heat it to 60℃~65℃, and hydrolyze it in NaOH solution at 60℃~65℃ to obtain PAN hydrolyzed membrane;

[0030] ②, dissolve polyethyleneimine and Pb(Cl)2 in 0.5mol / L NaCl solution to obtain a mixed solution. 2 + Polymerize with polyethyleneimine to form a polymer solution;

[0031] ③ Dissolve polyacrylic acid in 0.5 mol / L NaCl to obtain a polyanion solution;

[0032] 2. Add the polymer solution and anhydrous ethanol to an oil bath at 60°C to 65°C, stir evenly, then add epichlorohydrin, and continue stirring at 60°C to 65°C for 2h to 3h, adding sodium cyanoborohydride in portions during the stirring reaction; after the stirring reaction is completed, lower the reaction temperature to room temperature, and then add carbon disulfide to obtain a reaction product; ultrasonically treat the reaction product, filter it, wash it, and dry it to obtain a cross-linked polyethyleneimine dithiocarbamate;

[0033] 3. Self-assembled multilayer composite film:

[0034] ① Pour the polyanion solution onto the PAN hydrolysis membrane and allow it to settle for a while. Then pour out the polyanion solution on the PAN hydrolysis membrane and wash away the free polyelectrolyte on the membrane surface with deionized water. Finally, blow dry with nitrogen to obtain a layer of PAA.

[0035] ② Pour the cross-linked polyethyleneimine dithiocarbamate anhydrous ethanol solution onto the PAN hydrolysis membrane and allow it to settle for a while. Then pour out the solution on the PAN hydrolysis membrane and wash off the free polyelectrolyte on the membrane surface with deionized water. Finally, blow dry with nitrogen to obtain a layer of PEI-CS2.

[0036] ③, cycle steps ① to ② 0 to 2 times or cycle steps ① to ② 0 to 2 times and then cycle step ② 1 time to obtain a polyelectrolyte self-assembled multilayer composite membrane with the desired number of layers;

[0037] Fourth, first, the polyelectrolyte self-assembled multilayer composite film with the required number of layers is dried in air at room temperature for 5 minutes to 10 minutes, and then the composite film is immersed in a 2% to 5% mass fraction of epichlorohydrin solution for cross-linking; after the reaction is terminated, it is cooled to room temperature and allowed to stand for degassing, and then the composite film is immersed in 0.1 molL -1 Wash repeatedly with ethylenediaminetetraacetic acid disodium salt solution until no Pb is detected in the washing solution. 2+ Finally, the composite membrane is air-dried at room temperature to obtain a highly selective lithium ion imprinted channel polyelectrolyte composite membrane.

[0038] This embodiment combines ion imprinting technology with membrane separation technology to prepare an ion imprinted channel polyelectrolyte composite membrane with high selectivity. This process is simple to prepare, has good stability under acidic conditions, is suitable for large-scale production, and helps promote the industrialization of ion imprinted membranes.

[0039] Specific embodiment 2: This embodiment differs from specific embodiment 1 in that the concentration of the NaOH solution in step 1 (1) is 2 mol / L; the hydrolysis time is 30 to 40 minutes; and the molecular weight of the polyacrylonitrile ultrafiltration membrane in step 1 (1) is 50,000 Da. Other steps are the same as those in specific embodiment 1.

[0040] Specific embodiment three: The difference between this embodiment and specific embodiment one or two is that: the concentration of polyethyleneimine in the mixed solution described in step 1 ② is 3g / L; the molecular weight cut-off Mw of polyethyleneimine described in step 1 ② is 70000g / mol; the Pb in the mixed solution described in step 1 ② is 0. 2+ The molar ratio of the polyethylenimine to the polyethylenimine is (8-20): 1. The other steps are the same as those in the first or second embodiment.

[0041] Specific embodiment 4: This embodiment differs from specific embodiments 1 to 3 in that the concentration of polyacrylic acid in the polyanion solution in step 1 (3) is 3 g / L. The other steps are the same as those in specific embodiments 1 to 3.

[0042] Specific embodiment 5: This embodiment differs from specific embodiments 1 to 4 in that the volume ratio of the polymer solution to anhydrous ethanol in step 2 is 1.5 g:(15 mL to 20 mL); the volume ratio of the epichlorohydrin to anhydrous ethanol in step 2 is (0.23 g to 0.27 g):(15 mL to 20 mL); the volume ratio of the sodium cyanoborohydride to anhydrous ethanol in step 2 is (0.23 g to 0.27 g):(15 mL to 20 mL); and the volume ratio of the carbon disulfide to anhydrous ethanol in step 2 is 0.5 g:(15 mL to 20 mL). The other steps are the same as specific embodiments 1 to 4.

[0043] Specific Embodiment 6: This embodiment differs from Specific Embodiments 1 to 5 in that, in step 2, the reaction product is sonicated for 30 to 35 minutes, then transferred to a Buchner funnel for filtration, washed two to three times with 95% ethanol, and finally dried in an oven at 60°C for 22 to 24 hours to obtain a cross-linked polyethyleneiminodithiocarbamate. The other steps are the same as Specific Embodiments 1 to 5.

[0044] Specific embodiment seven: The difference between this embodiment and specific embodiments one to six is ​​that the volume ratio of the polyanion solution described in step three ① to the surface area of ​​the PAN hydrolysis membrane is (25mL to 30mL): (16cm 2 ~25cm 2 The deposition time in step 3① is 15 to 20 minutes. The other steps are the same as those in the first to sixth embodiments.

[0045] Specific embodiment eight: The difference between this embodiment and specific embodiments one to seven is that the volume ratio of the cross-linked polyethyleneimine dithiocarbamate anhydrous ethanol solution described in step three ② to the surface area of ​​the PAN hydrolyzed membrane is (25mL~30mL): (16cm 2 ~25cm 2 ); the deposition time in step 3 (2) is 15 to 20 minutes; the cross-linked polyethyleneimino dithiocarbamate anhydrous ethanol solution in step 3 (2) is cross-linked polyethyleneimino dithiocarbamate dissolved in anhydrous ethanol at a mass fraction of 50% to 55%. The other steps are the same as those in specific embodiments 1 to 7.

[0046] Specific embodiment 9: This embodiment differs from specific embodiments 1 to 8 in that the crosslinking time in step 4 is 30 to 40 minutes; the static degassing time in step 4 is 15 to 20 minutes; and the shaking washing time in step 4 is 15 to 20 minutes. The other steps are the same as specific embodiments 1 to 8.

[0047] Specific embodiment ten: This embodiment is a highly selective lithium ion imprinted channel polyelectrolyte composite membrane used to extract lithium from lithium ion leachate.

[0048] The following examples are used to verify the beneficial effects of the present invention:

[0049] Example 1: A method for preparing a highly selective lithium ion imprinted channel polyelectrolyte composite membrane is specifically completed by the following steps:

[0050] 1. Preparation of PAN hydrolysis membrane, polymer solution and polyanion solution:

[0051] ①, using a polyacrylonitrile ultrafiltration membrane (PAN ultrafiltration membrane) with a molecular weight cutoff of 50,000 Da as the base membrane, immersing it in a 2 mol / L NaOH solution, then heating it to 60°C and hydrolyzing it in the 60°C NaOH solution for 30 min to obtain a PAN hydrolyzed membrane;

[0052] ②, dissolve polyethyleneimine (PEI) with a weight average molecular weight Mw of 70000 g / mol and Pb(Cl)2 in 0.5 mol / L NaCl solution to obtain a mixed solution. 2+ Polymerize with polyethyleneimine to form a polymer solution;

[0053] The concentration of polyethyleneimine in the mixed solution described in step 1② is 3g / L;

[0054] Pb in the mixed solution described in step 1② 2+ The molar ratio with polyethyleneimine is 16:1;

[0055] ③ Dissolve polyacrylic acid (PAA) with a weight average molecular weight of 5000 g / mol in 0.5 mol / L NaCl solution to obtain a polyanion solution;

[0056] The concentration of polyacrylic acid in the polyanion solution described in step 1 (3) is 3 g / L;

[0057] 2. Add the polymer solution and anhydrous ethanol to an oil bath at 60°C, stir evenly, then add epichlorohydrin (ECH), continue stirring at 60°C for 2.5 hours, add sodium cyanoborohydride (NaBH3CN) three times during the stirring reaction, add 0.05g~0.075g each time; after the stirring reaction is completed, the reaction temperature is lowered to room temperature, and carbon disulfide (CS2) is added to obtain a reaction product; the reaction product is ultrasonicated for 30 minutes, then transferred to a Buchner funnel for filtration, washed three times with 95% ethanol by mass, and finally dried in an oven at 60°C for 23 hours to obtain cross-linked polyethyleneimine dithiocarbamate (PEI-CS2);

[0058] The volume ratio of the polymer solution to anhydrous ethanol in step 2 is 1.5 g:20 mL;

[0059] The mass ratio of epichlorohydrin described in step 2 to anhydrous ethanol is 0.25g:20mL;

[0060] The mass ratio of sodium cyanoborohydride to anhydrous ethanol described in step 2 is 0.25g:20mL;

[0061] The mass ratio of carbon disulfide to anhydrous ethanol described in step 2 is 0.5g:20mL;

[0062] 3. Self-assembled multilayer composite film:

[0063] ①. Pour the polyanion solution onto the PAN ultrafiltration membrane and let it settle for 20 minutes. Pour the polyanion solution on the PAN hydrolysis membrane, then use deionized water to wash off the free polyelectrolyte on the membrane surface, and finally blow dry with nitrogen to obtain a layer of PAA.

[0064] The ratio of the volume of the polyanion solution described in step 3① to the surface area of ​​the PAN hydrolysis membrane is 30mL:20cm 2 ;

[0065] ② Pour the cross-linked polyethyleneimine dithiocarbamate anhydrous ethanol solution onto the PAN hydrolysis membrane and let it settle for 20 minutes. Pour out the solution on the PAN hydrolysis membrane and then use deionized water to wash away the free polyelectrolyte on the membrane surface. Finally, blow dry with nitrogen to obtain a layer of PEI-CS2.

[0066] The volume ratio of the cross-linked polyethyleneimine dithiocarbamate anhydrous ethanol solution described in step 3② to the surface area of ​​the PAN hydrolyzed membrane is 30mL:20cm 2 ;

[0067] The cross-linked polyethyleneimine dithiocarbamate anhydrous ethanol solution described in step 3② is cross-linked polyethyleneimine dithiocarbamate dissolved in anhydrous ethanol, with a mass fraction of 50%;

[0068] ③. Repeat steps ① to ② 0 times to obtain a polyelectrolyte self-assembled multilayer composite membrane with the required number of layers; (the composite membrane consists of one layer of PEI-CS2 and one layer of PAA, with the outermost layer of the membrane being PEI-CS2);

[0069] Fourth, first, the polyelectrolyte self-assembled multilayer composite film with the required number of layers was dried in air at room temperature for 10 minutes, and then the composite film was immersed in a 3% mass fraction of epichlorohydrin solution for cross-linking; after the reaction was terminated, it was cooled to room temperature and allowed to stand for degassing, and then the composite film was immersed in 0.1 molL -1 Wash repeatedly with ethylenediaminetetraacetic acid disodium salt solution until no Pb is detected in the washing solution. 2+ Finally, the composite membrane is air-dried at room temperature to obtain a highly selective lithium ion imprinted channel polyelectrolyte composite membrane;

[0070] The cross-linking time in step 4 is 35 min;

[0071] The degassing time in step 4 is 20 minutes;

[0072] The duration of each shaking wash in step 4 is 20 minutes.

[0073] Example 2: This example differs from Example 1 in that steps 1 through 2 are repeated 0 times, followed by 2 once, to obtain a polyelectrolyte self-assembled multilayer composite membrane having the desired number of layers (the composite membrane consists of two layers of PEI-CS2 and one layer of PAA, with the outermost layer being PEI-CS2). All other steps and parameters are the same as in Example 1.

[0074] Example 3: This example differs from Example 1 in that steps 1 through 2 in three were repeated once, followed by step 2 in three again, to obtain a polyelectrolyte self-assembled multilayer composite membrane having the desired number of layers (the composite membrane consisted of three layers of PEI-CS2 and two layers of PAA, with the outermost layer being PEI-CS2). All other steps and parameters were the same as in Example 1.

[0075] Example 4: This example differs from Example 1 in that steps 1 through 2 in three were repeated twice, followed by step 2 in three once, to obtain a polyelectrolyte self-assembled multilayer composite membrane having the desired number of layers (the composite membrane consisted of four layers of PEI-CS2 and three layers of PAA, with the outermost layer being PEI-CS2). All other steps and parameters were the same as in Example 1.

[0076] Table 1 shows the effect of the number of polyelectrolyte layers prepared in Examples 1 to 4 on the selectivity.

[0077] Table 1

[0078]

[0079] From Table 1, we can see that as the number of bilayers increases from 1.5 bilayers (Example 2) to 3.5 bilayers (Example 4), the pure water flux increases from 10.02 L·m -2 h -1 Down to 8.34 L·m -2 h -1 This is because as the thickness of the modified layer increases, the permeation resistance gradually increases. The selectivity coefficient of 2.5 bilayer Pb-IILM is 4.24. When the number of bilayers exceeds 2.5 bilayers, some ion channels may be covered by the excess polyelectrolyte layer. This is not conducive to the Li + In addition, the 2.5-bilayer Pb-IILM exhibits good acid stability.

[0080] Figure 1 This is the surface morphology of PAN ultrafiltration membrane;

[0081] Figure 2 This is the surface morphology of the highly selective lithium ion imprinted channel polyelectrolyte composite membrane prepared in Example 3.

[0082] from Figure 1 and Figure 2 It can be seen that a relatively rough surface with uniformly dispersed micro-protrusions can be observed on the PAN ultrafiltration membrane. As the polyelectrolyte layer is assembled, the surface of the membrane becomes flat and smooth.

[0083] Example 5: The difference between this example and Example 3 is that the Pb 2+ The molar ratio of the polyimide to the polyethyleneimine was 20: 1. The other steps and parameters were the same as those in Example 1.

[0084] Example 6: The difference between this example and Example 3 is that the Pb in the mixed solution described in step 1② 2+ The molar ratio of the polyimide to the polyethyleneimine was 12: 1. The other steps and parameters were the same as those in Example 1.

[0085] Example 7: The difference between this example and Example 3 is that the Pb in the mixed solution described in step 1② 2+ The molar ratio of the polyethylenimine to the polyethylenimine was 8: 1. The other steps and parameters were the same as those in Example 1.

[0086] In Example 3 and Examples 5 to 7, Pb was changed. 2+ The molar ratio of PEI and the effect of the number of polyelectrolyte layers on the selectivity are listed in Table 2;

[0087] Table 2

[0088] Molar ratio (Pb / P) Unit price selectivity Example 5 3.37 Example 3 4.24 Example 6 3.79 Example 7 3.51

[0089] From Table 2, we can see that Pb 2+ The molar ratio of Pb to PEI affects the formation of the complex and the multilayer self-assembly process. PEI macromolecules bind metal ions to amine groups, so the Pb / P ratio is used to describe the number of ion-imprinted template ions. Pb-IILM (2.5 bilayers, Pb / P = 1 / 16) has good monovalent cation selectivity (selectivity coefficient 4.24) and water flux (8.51 L·m -2 h -1 ).

[0090] The above describes the specific embodiments of the present invention in detail, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in this field without departing from the scope of the present invention.

Claims

1. A method for preparing a highly selective lithium ion imprinted channel polyelectrolyte composite membrane, characterized in that The preparation method is specifically completed according to the following steps:

1. Preparation of PAN hydrolysis membrane, polymer solution and polyanion solution: ①. Use polyacrylonitrile ultrafiltration membrane as base membrane, immerse it in NaOH solution, heat it to 60℃~65℃, and hydrolyze it in NaOH solution at 60℃~65℃ to obtain PAN hydrolyzed membrane; ②, dissolve polyethyleneimine and Pb(Cl)2 in 0.5mol / L NaCl solution to obtain a mixed solution. 2+ Polymerize with polyethyleneimine to form a polymer solution; ③ Dissolve polyacrylic acid in 0.5 mol / L NaCl to obtain a polyanion solution; 2. Add the polymer solution and anhydrous ethanol to an oil bath at 60°C to 65°C, stir evenly, then add epichlorohydrin, and continue stirring at 60°C to 65°C for 2h to 3h, adding sodium cyanoborohydride in portions during the stirring reaction; after the stirring reaction is completed, lower the reaction temperature to room temperature, and then add carbon disulfide to obtain a reaction product; ultrasonically treat the reaction product, filter it, wash it, and dry it to obtain a cross-linked polyethyleneimine dithiocarbamate; 3. Self-assembled multilayer composite film: ① Pour the polyanion solution onto the PAN hydrolysis membrane and allow it to settle for a while. Then pour out the polyanion solution on the PAN hydrolysis membrane and wash away the free polyelectrolyte on the membrane surface with deionized water. Finally, blow dry with nitrogen to obtain a layer of PAA. ② Pour the cross-linked polyethyleneimine dithiocarbamate anhydrous ethanol solution onto the PAN hydrolysis membrane and allow it to settle for a while. Then pour out the solution on the PAN hydrolysis membrane and wash off the free polyelectrolyte on the membrane surface with deionized water. Finally, blow dry with nitrogen to obtain a layer of PEI-CS2. ③, cycle steps ① to ② 0 to 2 times or cycle steps ① to ② 0 to 2 times and then cycle step ② 1 time to obtain a polyelectrolyte self-assembled multilayer composite membrane with the desired number of layers; Fourth, first, the polyelectrolyte self-assembled multilayer composite film with the required number of layers is dried in air at room temperature for 5 minutes to 10 minutes, and then the composite film is immersed in a 2% to 5% mass fraction of epichlorohydrin solution for cross-linking; after the reaction is terminated, it is cooled to room temperature and allowed to stand for degassing, and then the composite film is immersed in 0.1 molL -1 Wash repeatedly with ethylenediaminetetraacetic acid disodium salt solution until no Pb is detected in the washing solution. 2+ Finally, the composite membrane is air-dried at room temperature to obtain a highly selective lithium ion imprinted channel polyelectrolyte composite membrane.

2. The method for preparing a highly selective lithium ion imprinted channel polyelectrolyte composite membrane according to claim 1, characterized in that The concentration of the NaOH solution in step 1① is 2 mol / L; the hydrolysis time is 30 min to 40 min; the molecular weight of the polyacrylonitrile ultrafiltration membrane in step 1① is 50,000 Da.

3. The method for preparing a highly selective lithium ion imprinted channel polyelectrolyte composite membrane according to claim 1, characterized in that The concentration of polyethyleneimine in the mixed solution in step 1 ② is 3 g / L; the molecular weight cut-off Mw of polyethyleneimine in step 1 ② is 70000 g / mol; the Pb in the mixed solution in step 1 ② is 100 g / mol; 2+ The molar ratio of polyethyleneimine is (8-20):

1.

4. The method for preparing a highly selective lithium ion imprinted channel polyelectrolyte composite membrane according to claim 1, characterized in that The concentration of polyacrylic acid in the polyanion solution described in step 1 (3) is 3 g / L.

5. The method for preparing a highly selective lithium ion imprinted channel polyelectrolyte composite membrane according to claim 1, characterized in that The volume ratio of the polymer solution described in step 2 to anhydrous ethanol is 1.5 g: (15 mL to 20 mL); the volume ratio of the epichlorohydrin described in step 2 to anhydrous ethanol is (0.23 g to 0.27 g): (15 mL to 20 mL); the volume ratio of the sodium cyanoborohydride described in step 2 to anhydrous ethanol is (0.23 g to 0.27 g): (15 mL to 20 mL); the volume ratio of the carbon disulfide described in step 2 to anhydrous ethanol is 0.5 g: (15 mL to 20 mL).

6. The method for preparing a highly selective lithium ion imprinted channel polyelectrolyte composite membrane according to claim 1, characterized in that In step 2, the reaction product is ultrasonically treated for 30 to 35 minutes, then transferred to a Buchner funnel for filtration, washed 2 to 3 times with 95% ethanol by mass, and finally dried in an oven at 60° C. for 22 to 24 hours to obtain cross-linked polyethyleneimine dithiocarbamate.

7. The method for preparing a highly selective lithium ion imprinted channel polyelectrolyte composite membrane according to claim 1, characterized in that The volume ratio of the polyanion solution described in step 3① to the surface area of ​​the PAN hydrolysis membrane is (25mL~30mL): (16cm 2 ~25cm 2 ); the deposition time described in step 3① is 15min to 20min.

8. The method for preparing a highly selective lithium ion imprinted channel polyelectrolyte composite membrane according to claim 1, characterized in that The volume ratio of the cross-linked polyethyleneimine dithiocarbamate anhydrous ethanol solution described in step 3② to the surface area of ​​the PAN hydrolyzed membrane is (25mL~30mL): (16cm 2 ~25cm 2 ); the deposition time in step three ② is 15 min to 20 min; the cross-linked polyethylene imine dithiocarbamate anhydrous ethanol solution in step three ② is cross-linked polyethylene imine dithiocarbamate dissolved in anhydrous ethanol, with a mass fraction of 50% to 55%.

9. The method for preparing a highly selective lithium ion imprinted channel polyelectrolyte composite membrane according to claim 1, characterized in that The cross-linking time in step 4 is 30 min to 40 min; the standing degassing time in step 4 is 15 min to 20 min; and the shaking washing time in step 4 is 15 min to 20 min.

10. Use of a highly selective lithium ion imprinted channel polyelectrolyte composite membrane prepared by the preparation method according to claim 1, characterized in that A highly selective lithium ion imprinted channel polyelectrolyte composite membrane is used to extract lithium from lithium ion leachate.

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