Lithium-magnesium selective permeable membrane and method for producing the same

Abstract

The application discloses a lithium-magnesium selective permeation membrane and a preparation method thereof, and belongs to the technical field of membrane materials. The preparation method comprises the following steps: dissolving an oil-soluble peroxide initiator, an oil-soluble monomer and an oil-soluble crosslinking agent in an organic solvent to prepare an oil phase, and dissolving a water-soluble initiator and a water-soluble crosslinking agent in water to prepare a water phase; the oil-soluble monomer is one of an unsaturated ester, an unsaturated amide, an unsaturated ether and a polyethylene glycol unsaturated carboxylic acid ester; under the condition of 0-50 DEG C, a polymer support layer is immersed in the water phase for 0.5-30 min, the support layer is taken out, and then the support layer is immersed in the oil phase for 0.5-30 min, and the lithium-magnesium selective permeation membrane is obtained. + / Mg 2+ The selectivity of the lithium-magnesium selective permeation membrane is 5-15, and the lithium-magnesium selective permeation membrane has good effects.

Description

Technical Field

[0001] This invention relates to the field of separation membrane materials technology, specifically to a lithium-magnesium selective permeation membrane and its preparation method. Background Technology

[0002] In recent years, lithium extraction from water resources has become increasingly attractive due to growing demand from the energy industry. As onshore lithium ore mining becomes more difficult, with lower purity and higher extraction costs, the focus of lithium extraction has shifted from ore extraction to brine extraction.

[0003] Lithium extraction methods mainly include four approaches: extraction dialysis, adsorption dialysis, electrochemical dialysis, and membrane dialysis. Among these, extraction technology theoretically offers high economic benefits, but in practice, it is not as straightforward as it seems. Adsorption dialysis is the most promising method in terms of efficiency, product quality, and process cleanliness. However, its disadvantages include the need for longer operation times and difficulties in processing aqueous solutions. In electrochemical dialysis, heterocyclic compounds such as crown ethers are of particular interest due to their selective ion-binding ability. Although 12-crown-4 ethers exhibit high selectivity for lithium, their high cost prevents them from becoming mainstream lithium extraction monomers. Currently, membrane dialysis offers lower energy consumption and preparation costs, demonstrating significant development potential.

[0004] Traditional brine lithium extraction processes typically involve introducing carbonate ions to form lithium carbonate precipitate. However, brine contains not only lithium ions but also a significant amount of divalent magnesium ions. When carbonate ions are added, the magnesium ions precipitate along with the lithium ions, resulting in a high magnesium carbonate content in the product and affecting its purity. Therefore, it is necessary to pre-precipitate the lithium carbonate ions. + and Mg 2+ Separation is performed. Membrane dialysis is a commonly used Li-based method due to its ease of use. + and Mg 2+ The separation methods mostly rely on the positive charge dialysis of Li on the membrane surface. + / Mg 2+ However, the selective dialysis layer of existing nanofiltration membranes is often obtained through interfacial polycondensation of amine and acyl chloride monomers, resulting in a negative charge. Modifying the selective dialysis layer of nanofiltration membranes to possess a positive charge requires economical raw materials and complex reaction conditions. Therefore, it is necessary to find an efficient method for preparing the selective dialysis layer that ensures both economic efficiency and high flux and Li. + / Mg 2+ Selectivity. Summary of the Invention

[0005] To address at least one of the aforementioned problems, this invention provides a lithium-magnesium selective permeation membrane and its preparation method.

[0006] The technical solution of this invention is: a method for preparing a lithium-magnesium selective permeation membrane, characterized by comprising the following steps:

[0007] Take an oil-soluble peroxide initiator, an oil-soluble monomer, and an oil-soluble crosslinking agent, dissolve them in an organic solvent and prepare an oil phase; take a water-soluble initiator and a water-soluble crosslinking agent, dissolve them in water and prepare an aqueous phase.

[0008] Under conditions of 0–50°C, the polymer support layer is immersed in the aqueous phase for 0.5–30 min, the support layer is removed, and then immersed in the oil phase for 0.5–30 min to obtain the product.

[0009] The half-life of both the oil-soluble peroxide initiator and the water-soluble initiator is greater than 50 h under conditions of 0–50 °C. When the oil-soluble peroxide initiator and the water-soluble initiator are mixed, the half-life under conditions of 0–50 °C is no greater than 5 h.

[0010] In this invention, the main reaction process is as follows: Since the water-soluble and oil-soluble initiators have high half-lives when present alone, the aqueous and oil phases do not directly undergo polymerization. After the polymer support layer adsorbs a certain amount of water-soluble initiator and water-soluble crosslinking agent in the aqueous phase, it is then placed in the oil phase. At this time, the water-soluble initiator on the surface of the polymer support layer and the oil-soluble initiator at the interface mix. The water-soluble crosslinking agent on the surface of the polymer support layer, as well as the oil-soluble monomer and oil-soluble crosslinking agent at the interface, begin a free radical polymerization reaction at the interface of the polymer support layer, thereby modifying the polymer support layer.

[0011] While existing technologies also employ free radical polymers to prepare membrane materials, these typically involve spraying a raw material solution (monomer, initiator, crosslinking agent, and solvent) onto the surface of a support layer under conditions conducive to free radical polymerization. The drawback of this technique is that, because the raw material solution is directly sprayed onto the support surface, the final film thickness is usually large and difficult to control, resulting in relatively poor performance. Furthermore, the polymer generated using this method is deposited on the support layer, which has the disadvantage of weak interaction between polymer microparticles and between the polymer and the support layer, leading to lower film strength. Those skilled in the art will recognize that, because this invention utilizes interfacial polymerization, the film thickness is uniform, and the film thickness can be controlled by adjusting the reaction time. Simultaneously, interfacial polymerization allows polymer microparticles to overlap and even crosslink, forming strong interaction forces. The polymer film also has a large contact area with the support layer surface, resulting in strong interaction forces and relatively high film strength.

[0012] One embodiment of the present invention is that the oil-soluble peroxide initiator is at least one selected from cumene hydroperoxide, tert-butyl hydroperoxide, di-tert-butyl peroxide, dicumene hydroperoxide, benzoyl peroxide, diethylhexyl percarbonate, tert-butyl peroxide, and tert-butyl peroxyvalerate; the oil-soluble crosslinking agent is at least one selected from divinylbenzene, polyethylene glycol diacrylate, 1,4-butanediol diacrylate, ethylene glycol dimethacrylate, butylene glycol dimethacrylate, and hexanediol dimethacrylate; and the oil-soluble peroxide initiator, the... The mass ratio of the oil-soluble crosslinking agent to the oil-soluble monomer is 0.1–5:0.1–30:100; the water-soluble initiator is at least one of ascorbic acid, sodium bisulfite, sodium metabisulfite, tetramethylethylenediamine, N,N-diethylaniline, ammonium persulfate, sodium persulfate, and potassium persulfate; the water-soluble crosslinking agent is at least one of N,N-methylenebisacrylamide, polyethylene glycol diacrylate with a molecular weight of 400, and polyethylene glycol dimethacrylate; and the mass ratio of the water-soluble initiator, the water-soluble crosslinking agent, and water is 0.1–5:0–2:100.

[0013] One embodiment of the present invention is that the general structural formula of the oil-soluble monomer is as follows:

[0014]

[0015] In the formula, R1 is a methyl or hydrogen atom;

[0016] R2 is Wherein, R3 is a phenyl or a C1-C12 straight-chain alkyl group; R4 and R5 are independently a phenyl, hydrogen, or a C2-C4 straight-chain alkyl group; R6 is... One of them, n = 2 to 20. Preferably, when R2 is When R2 is a mixture of the first and second monomers in a mass ratio of 1:1, it has a better effect; the first monomer refers to R2 as... The second monomer refers to R2 being... Any one of the monomers in it.

[0017] Furthermore, when R2 is In addition, the oil phase also contains imprinted molecules, which are at least one of n-butyllithium, methyllithium, phenyllithium, and lithium bis(trifluoromethanesulfonylimide), and the molar ratio of the imprinted molecules to the oil-soluble monomer is 0-10:100.

[0018] Furthermore, when containing two or more oil-soluble monomers, the molar ratio of any two oil-soluble monomers is 1:0.1 to 10.

[0019] One embodiment of the present invention is that the organic solvent is one of cyclohexane, ethyl acetate, styrene, butyl acetate, chloromethane, dichloromethane, chloroform, carbon tetrachloride, benzene, toluene, and xylene, and the mass ratio of the organic solvent to the oil-soluble monomer is 0-4:1.

[0020] One embodiment of the present invention includes a water-soluble monomer in the aqueous phase. The water-soluble monomer is acrylic acid and its salts, methacrylic acid and its salts, acrylamide, maleic acid, succinic acid and its salts, vinylpyrrolidone, p-styrenesulfonic acid and its salts, or polyethylene glycol with a double bond at one end. The degree of polymerization of the polyethylene glycol with the double bond at one end is 2-20. The mass ratio of the aqueous monomer to water is 0-30:100. The main function of the water-soluble monomer is to adjust the charge on the surface of the permeate membrane, thereby changing the membrane's rejection rate. For example, when the water-soluble monomer is anionic, it can effectively improve the rejection rate of anions in the water.

[0021] Furthermore, when containing two or more water-soluble monomers, the molar ratio of any two water-soluble monomers is 1:0.1 to 10.

[0022] One embodiment of the present invention is that the polymer support layer is one of polyacrylonitrile, polysulfone, polyethersulfone, polyetherethersulfone ketone, polyarylethersulfone ketone, polyarylethernitrile, polytetrafluoroethylene, and polyvinylidene fluoride, and its surface pore size is 10-100 nm.

[0023] Another object of the present invention is to provide a lithium-magnesium selective permeation membrane prepared by any of the methods described above.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] (1) The lithium-magnesium ion dialysis membrane involved in this invention has a higher magnesium ion rejection rate on its surface active layer. + / Mg 2+ The selectivity ranges from 5 to 15.

[0026] (2) The raw materials for the preparation process of the present invention are readily available, the operation is simple, and all solvents can be recycled and reused, which is environmentally friendly.

[0027] (3) The lithium-magnesium ion dialysis membrane involved in this invention can be applied to nanofiltration, reverse osmosis, forward osmosis and other fields. It has the advantages of high recovery rate, easy cleaning and long service life.

[0028] (4) The lithium magnesium ion dialysis membrane preparation process of the present invention is flexible and versatile. The preparation conditions can be improved according to the needs, thereby adapting to different actual industrial production conditions, which is conducive to industrial production. Detailed Implementation

[0029] The present invention will be further described in detail below with reference to the embodiments, but the implementation of the present invention is not limited thereto.

[0030] Unless otherwise specified, the operating methods used in the following embodiments are all common methods in the art.

[0031] Unless otherwise specified, the raw materials used in the following embodiments are all conventional commercial products.

[0032] In the following examples, the half-life of the initiator in the aqueous phase and the initiator in the oil phase after mixing is less than 5 hours under their respective reaction temperature conditions.

[0033] Example 1

[0034] Take 100g of the oil-soluble monomer shown in the formula below, 5g of cumene hydroperoxide, and 1g of divinylbenzene, and dissolve them in 400g of cyclohexane to prepare the oil phase; take 3.16g of acrylic acid, 2.94g of ascorbic acid, and 2g of N,N-methylenebisacrylamide and dissolve them in 100g of water to prepare the aqueous phase. The half-life of this combination is 3h.

[0035]

[0036] At 26°C, a polyacrylonitrile support layer with a pore size of 50 nm was immersed in an aqueous phase for 16 minutes and then removed. The water on the surface of the support layer was removed, and then it was immersed in an oil phase for 6 minutes and then removed. The oil on the surface was then removed to obtain the final product.

[0037] A 1000 ppm mixed solution of magnesium and lithium at a mass ratio of 20:1 was used as the feed solution, and deionized water was used as the receiving solution. The cross-flow velocity at the membrane surface was 10 cm / s. The final measured magnesium-to-lithium mass ratio of the receiving solution for the lithium-magnesium selective dialysis membrane at room temperature was 1:2.1, and the magnesium-lithium dialysis factor S was... Li,Mg It is 9.74.

[0038] Example 2

[0039] 100g of the oil-soluble monomer shown in the formula below, 1.65g of tert-butyl hydroperoxide, and 4.05g of polyethylene glycol diacrylate with a molecular weight of 400 were dissolved in 189g of ethyl acetate to prepare the oil phase; 9.47g of potassium methacrylate, 1.39g of sodium bisulfite, and 0.1g of N,N-methylenebisacrylamide were dissolved in 100g of water to prepare the aqueous phase. The half-life of this combination is 5 hours.

[0040]

[0041] At 0℃, a polysulfone support layer with a pore size of 40nm is immersed in an aqueous phase for 11 minutes and then removed. The water on the surface of the support layer is removed, and then it is immersed in an oil phase for 12 minutes and then removed. The oil on the surface is then removed to obtain the final product.

[0042] A 1000 ppm mixed solution of magnesium and lithium (mass ratio 20:1) was used as the feed solution, deionized water as the receiving solution, and the cross-flow velocity at the membrane surface was 10 cm / s. The final measured magnesium-to-lithium mass ratio of the receiving solution at room temperature was 1:1.7, and the magnesium-to-lithium dialysis factor S was... Li,Mg It is 11.84.

[0043] Example 3

[0044] 100g of the oil-soluble monomer shown in the formula below, 3.71g of di-tert-butyl hydroperoxide, and 23.89g of 1,4-butanediol diacrylate were dissolved in 21.1g of ethyl acetate to prepare the oil phase; 4.23g of sodium metabisulfite and 0.2g of polyethylene glycol dimethacrylate were dissolved in 100g of water to prepare the aqueous phase. The half-life of this combination is 2 hours.

[0045]

[0046] At 34°C, a polyethersulfone support layer with a pore size of 20 nm is immersed in an aqueous phase for 9 minutes and then removed. The water on the surface of the support layer is removed, and then it is immersed in an oil phase for 2 minutes and then removed. The oil on the surface is then removed to obtain the final product.

[0047] A 1000 ppm mixed solution of magnesium and lithium (mass ratio 20:1) was used as the feed solution, and deionized water was used as the receiving solution. The cross-flow velocity at the membrane surface was 10 cm / s. The final measured magnesium-to-lithium mass ratio of the receiving solution at room temperature was 1:3.3, and the magnesium-to-lithium dialysis factor S was... Li,Mg It is 6.05.

[0048] Example 4

[0049] 50g of the oil-soluble monomer shown in Formula 1, 50g of the oil-soluble monomer shown in Formula 2, 2.16% dicumyl peroxide, 10.16g of ethylene glycol dimethacrylate, and 1.48g of lithium bis(trifluoromethanesulfonyl)imide were dissolved in 42.1g of styrene to prepare the oil phase; 11.05g of vinylpyrrolidone, 2.16g of tetramethylethylenediamine, and 1.3g of N,N-methylenebisacrylamide were dissolved in 100g of water to prepare the aqueous phase. The half-life of this combination is 1 hour.

[0050]

[0051] At 47°C, a 10nm pore size polyether sulfone ketone support layer is immersed in an aqueous phase for 17 minutes and then removed. The water on the surface of the support layer is removed, and then it is immersed in an oil phase for 16 minutes and then removed. The oil on the surface is then removed to obtain the final product.

[0052] A 1000 ppm mixed solution of magnesium and lithium (mass ratio 20:1) was used as the feed solution, and deionized water was used as the receiving solution. The cross-flow velocity at the membrane surface was 10 cm / s. The final measured magnesium-to-lithium mass ratio of the receiving solution for the lithium-magnesium selective dialysis membrane at room temperature was 1:1.4, and the magnesium-lithium dialysis factor S was... Li,Mg It is 13.95.

[0053] Example 5

[0054] Take 50g of the oil-soluble monomer shown in Formula 3 below, and 50g of the oil-soluble monomer shown in Formula 4 below.

[0055] 4.48 g of benzoyl peroxide, 30 g of hexanediol dimethacrylate, and 0.8 g of lithium bis(trifluoromethanesulfonyl)imide were dissolved in 126.3 g of chloromethane to prepare the oil phase; 12.63 g of potassium methacrylate, 2.42 g of N,N-diethylaniline, and 0.9 g of polyethylene glycol diacrylate with a molecular weight of 400 were dissolved in 100 g of water to prepare the aqueous phase. The half-life of this combination is 5 h.

[0056]

[0057] At 3°C, a polyaryletherketone support layer with a pore size of 30 nm is immersed in an aqueous phase for 2 minutes and then removed. The water on the surface of the support layer is removed, and then it is immersed in an oil phase for 8 minutes and then removed. The oil on the surface is then removed to obtain the final product.

[0058] A 1000 ppm mixed solution of magnesium and lithium at a mass ratio of 20:1 was used as the feed solution, and deionized water was used as the receiving solution. The cross-flow velocity at the membrane surface was 10 cm / s. The final measured magnesium-to-lithium mass ratio of the receiving solution at room temperature was 1:1.8, and the magnesium-to-lithium dialysis factor S was... Li,Mg It is 11.32.

[0059] Example 6

[0060] 100g of the oil-soluble monomer shown in the formula below, 1.39g of diethylhexyl peroxide dicarbonate, and 22.37g of polyethylene glycol diacrylate were dissolved in 126.3g of chloromethane to prepare the oil phase; 14.21g of sodium methacrylate, 4.48g of ammonium persulfate, and 0.6g of N,N-methylenebisacrylamide were dissolved in 100g of water to prepare the aqueous phase. The half-life of this combination is 2 hours.

[0061]

[0062] At 42°C, a 20nm PTFE support layer is immersed in an aqueous phase for 14 minutes and then removed. The water on the surface of the support layer is removed, and then it is immersed in an oil phase for 19 minutes and then removed. The oil on the surface is then removed to obtain the final product.

[0063] A 1000 ppm mixed solution of magnesium and lithium (mass ratio 20:1) was used as the feed solution, and deionized water was used as the receiving solution. The cross-flow velocity at the membrane surface was 10 cm / s. The final measured magnesium-to-lithium mass ratio of the receiving solution at room temperature was 1:1.6, and the magnesium-to-lithium dialysis factor S was... Li,Mg It is 12.89.

[0064] Example 7

[0065] 100g of the oil-soluble monomer shown in the formula below, 3.97g of tert-butyl peroxyvalerate, and 16.26g of divinylbenzene were dissolved in 84.2g of chloroform to prepare the oil phase; 7.89g of sodium acrylate, 1.65g of ammonium persulfate, and 1.6g of polyethylene glycol diacrylate with a molecular weight of 400 were dissolved in 100g of deionized water to prepare the aqueous phase. The half-life of this combination is 4 hours.

[0066]

[0067] At 16℃, a polyvinylidene fluoride support layer with a pore size of 40nm is immersed in an aqueous phase for 22 minutes and then removed. The water on the surface of the support layer is removed, and then it is immersed in an oil phase for 20 minutes and then removed. The oil on the surface is then removed to obtain the final product.

[0068] A 1000 ppm mixed solution of magnesium and lithium (mass ratio 20:1) was used as the feed solution, and deionized water was used as the receiving solution. The cross-flow velocity at the membrane surface was 10 cm / s. The final measured magnesium-to-lithium mass ratio of the receiving solution at room temperature was 1:1.6, and the magnesium-to-lithium dialysis factor S was... Li,Mg It is 12.37.

[0069] Example 8

[0070] 100g of the oil-soluble monomer shown in the formula below, 2.68g of dicumyl peroxide, and 5.58g of polyethylene glycol diacrylate were dissolved in 273.7g of carbon tetrachloride to prepare the oil phase; 23.68g of sodium methacrylate, 4.74g of potassium persulfate, and 0.7g of polyethylene glycol diacrylate with a molecular weight of 400 were dissolved in 100g of deionized water to prepare the aqueous phase. The half-life of this combination is 4 hours.

[0071]

[0072] At 13°C, a polyarylether sulfone ketone support layer with a pore size of 30 nm was immersed in an aqueous phase for 8 minutes and then removed. The water on the surface of the support layer was removed, and then it was immersed in an oil phase for 26 minutes and then removed. The oil on the surface was then removed to obtain the final product.

[0073] A 1000 ppm mixed solution of magnesium and lithium at a mass ratio of 20:1 was used as the feed solution, and deionized water was used as the receiving solution. The cross-flow velocity at the membrane surface was 10 cm / s. The final measured magnesium-to-lithium mass ratio of the receiving solution for the lithium-magnesium selective dialysis membrane at room temperature was 1:1.5, and the magnesium-lithium dialysis factor S was... Li,Mg It is 13.42.

[0074] Example 9

[0075] Prepare an oil phase by dissolving 100g of the oil-soluble monomer shown in the formula below, 0.36g of cumene hydroperoxide, and 17.79g of ethylene glycol dimethacrylate; prepare an aqueous phase by dissolving 25.26g of maleic acid, 0.36g of sodium bisulfite, and 0.5g of N,N-methylenebisacrylamide in 100g of deionized water. The half-life of this combination is 4 hours.

[0076]

[0077] At 18°C, a 50nm pore size polyacrylonitrile support layer is immersed in an aqueous phase for 30 seconds, then removed to remove the water from the surface of the support layer. After immersion in an oil phase for 14 minutes, the surface oil is removed to obtain the final product.

[0078] A 1000 ppm mixed solution of magnesium and lithium (mass ratio 20:1) was used as the feed solution, and deionized water was used as the receiving solution. The cross-flow velocity at the membrane surface was 10 cm / s. The final measured magnesium-to-lithium mass ratio of the receiving solution at room temperature was 1:1.9, and the magnesium-to-lithium dialysis factor S was... Li,Mg It is 10.26.

[0079] Example 10

[0080] 100g of the oil-soluble monomer shown in the formula below, 0.62g of benzoyl peroxide, and 8.63g of divinylbenzene were dissolved in 231.6g of toluene to prepare the oil phase; 18.95g of lithium acrylate, 0.87g of tetramethylethylenediamine, and 1.7g of N,N-methylenebisacrylamide were dissolved in 100g of deionized water to prepare the aqueous phase. The half-life of this combination is 1 hour.

[0081]

[0082] At 50°C, a polysulfone support layer with a pore size of 40 nm is immersed in an aqueous phase for 3 minutes and then removed. The water on the surface of the support layer is removed, and then it is immersed in an oil phase for 30 seconds and then removed. The oil on the surface is then removed to obtain the final product.

[0083] A 1000 ppm mixed solution of magnesium and lithium at a mass ratio of 20:1 was used as the feed solution, and deionized water was used as the receiving solution. The cross-flow velocity at the membrane surface was 10 cm / s. The final measured magnesium-to-lithium mass ratio of the receiving solution at room temperature was 1:2.3, and the magnesium-to-lithium dialysis factor S was... Li,MgIt is 8.68.

[0084] Example 11

[0085] 100g of the oil-soluble monomer shown in the formula below, 2.42g of diethylhexyl peroxide dicarbonate, and 26.95g of ethylene glycol dimethacrylate were dissolved in 357.9g of xylene to prepare the oil phase; 4.74g of acrylic acid, 1.91g of N,N-diethylaniline, and 1.5g of polyethylene glycol dimethacrylate were dissolved in 100g of deionized water to prepare the aqueous phase. The half-life of this combination is 2 hours.

[0086]

[0087] At 37°C, a polyarylether sulfone ketone support layer with a pore size of 30 nm is immersed in an aqueous phase for 5 minutes and then removed. The water on the surface of the support layer is removed, and then it is immersed in an oil phase for 28 minutes and then removed. The oil on the surface is then removed to obtain the final product.

[0088] A 1000 ppm mixed solution of magnesium and lithium (mass ratio 20:1) was used as the feed solution, and deionized water was used as the receiving solution. The cross-flow velocity at the membrane surface was 10 cm / s. The final measured magnesium-to-lithium mass ratio of the receiving solution at room temperature was 1:1.9, and the magnesium-to-lithium dialysis factor S was... Li,Mg It is 10.79.

[0089] Example 12

[0090] 100g of the oil-soluble monomer shown in the formula below, 3.45g of tert-butyl peroxide, and 20.84g of divinylbenzene were dissolved in 294.7g of ethyl acetate to prepare the oil phase; 6.32g of sodium p-styrene sulfonate, 2.68g of sodium bisulfite, and 0.4g of polyethylene glycol dimethacrylate were dissolved in 100g of deionized water to prepare the aqueous phase. The half-life of this combination is 4 hours.

[0091]

[0092] At 11°C, a polyacrylonitrile support layer with a pore size of 50 nm was immersed in an aqueous phase for 26 minutes and then removed. The water on the surface of the support layer was removed, and then it was immersed in an oil phase for 11 minutes and then removed. The oil on the surface was then removed to obtain the final product.

[0093] A 1000 ppm mixed solution of magnesium and lithium (mass ratio 20:1) was used as the feed solution, and deionized water was used as the receiving solution. The cross-flow velocity at the membrane surface was 10 cm / s. The final measured magnesium-to-lithium mass ratio of the receiving solution at room temperature was 1:3.6, and the magnesium-to-lithium dialysis factor S was... Li,Mg It is 5.53.

[0094] Example 13

[0095] 100g of the oil-soluble monomer shown in the formula below, 2.42g of diethylhexyl peroxide dicarbonate, and 26.95g of ethylene glycol dimethacrylate were dissolved in 105.3g of cyclohexane to prepare the oil phase; 20.53g of sodium p-styrene sulfonate, 3.97g of potassium persulfate, and 1.4g of N,N-methylenebisacrylamide were dissolved in 100g of deionized water to prepare the aqueous phase. The half-life of this combination is 2 hours.

[0096]

[0097] At 39°C, a polysulfone support layer with a pore size of 40 nm is immersed in an aqueous phase for 12 minutes and then removed. The water on the surface of the support layer is removed, and then it is immersed in an oil phase for 23 minutes and then removed. The oil on the surface is then removed to obtain the final product.

[0098] A 1000 ppm mixed solution of magnesium and lithium (mass ratio 20:1) was used as the feed solution, and deionized water was used as the receiving solution. The cross-flow velocity at the membrane surface was 10 cm / s. The final measured magnesium-to-lithium mass ratio of the receiving solution at room temperature was 1:2.8, and the magnesium-to-lithium dialysis factor S was... Li,Mg It is 7.11.

[0099] Example 14

[0100] 100g of the oil-soluble monomer shown in the formula below, 4.23g of benzoyl peroxide, 7.11g of hexanediol dimethacrylate, and 1.08g of lithium bis(trifluoromethanesulfonyl)imide were dissolved in 105.3g of toluene to prepare the oil phase; 30g of methacrylic acid, 3.19g of N,N-diethylaniline, and 1.1g of N,N-methylenebisacrylamide were dissolved in 100g of deionized water to prepare the aqueous phase. The half-life of this combination is 3 hours.

[0101]

[0102] At 21°C, a polyvinylidene fluoride support layer with a pore size of 40 nm is immersed in an aqueous phase for 6 minutes and then removed. The water on the surface of the support layer is removed, and then it is immersed in an oil phase for 17 minutes and then removed. The oil on the surface is then removed to obtain the final product.

[0103] A 1000 ppm mixed solution of magnesium and lithium (mass ratio 20:1) was used as the feed solution, deionized water as the receiving solution, and the cross-flow velocity at the membrane surface was 10 cm / s. The final measured magnesium-to-lithium mass ratio of the receiving solution at room temperature was 1:4.0, and the magnesium-to-lithium dialysis factor S was... Li,Mg It is 5.

[0104] Example 15

[0105] 100g of the oil-soluble monomer shown in the formula below, 1.13g of cumene hydroperoxide, 28.47g of divinylbenzene, and 1.12g of lithium bis(trifluoromethanesulfonylimide) were dissolved in 105.3g of dichloromethane to prepare the oil phase; 22.11g of sodium methacrylate, 3.71g of sodium bisulfite, and 1.2g of polyethylene glycol diacrylate with a molecular weight of 400 were dissolved in 100g of deionized water to prepare the aqueous phase. The half-life of this combination is 3 hours.

[0106]

[0107] At 24℃, a polyacrylonitrile support layer with a pore size of 50nm is immersed in an aqueous phase for 28 minutes and then removed. The water on the surface of the support layer is removed, and then it is immersed in an oil phase for 9 minutes and then removed. The oil on the surface is then removed to obtain the final product.

[0108] A 1000 ppm mixed solution of magnesium and lithium (mass ratio 20:1) was used as the feed solution, and deionized water was used as the receiving solution. The cross-flow velocity at the membrane surface was 10 cm / s. The final measured magnesium-to-lithium mass ratio of the receiving solution at room temperature was 1:2.5, and the magnesium-to-lithium dialysis factor S was... Li,Mg It is 8.16.

[0109] Example 16

[0110] 100g of the oil-soluble monomer shown in the formula below, 4.74g of tert-butyl peroxyvalerate, and 13.21g of ethylene glycol dimethacrylate were dissolved in 252.6g of styrene to prepare the oil phase; 28.42g of acrylic acid, 1.13g of potassium persulfate, and 0.3g of polyethylene glycol dimethacrylate were dissolved in 100g of deionized water to prepare the aqueous phase. The half-life of this combination is 1 hour.

[0111]

[0112] At 45°C, a 20nm PTFE support layer is immersed in an aqueous phase for 19 minutes and then removed. The water on the surface of the support layer is removed, and then it is immersed in an oil phase for 30 minutes and then removed. The oil on the surface is then removed to obtain the final product.

[0113] A 1000 ppm mixed solution of magnesium and lithium (mass ratio 20:1) was used as the feed solution, and deionized water was used as the receiving solution. The cross-flow velocity at the membrane surface was 10 cm / s. The final measured magnesium-to-lithium mass ratio of the receiving solution at room temperature was 1:2.6, and the magnesium-to-lithium dialysis factor S was... Li,Mg It is 7.63.

[0114] Example 17

[0115] 100g of the oil-soluble monomer shown in the formula below, 3.19g of dicumyl peroxide, and 19.32g of divinylbenzene were dissolved in 315.8g of butyl acetate to prepare the oil phase; 17.37g of maleic acid, 0.1g of ammonium persulfate, and 1.4g of N,N-methylenebisacrylamide were dissolved in 100g of deionized water to prepare the aqueous phase. The half-life of this combination is 2 hours.

[0116]

[0117] At 32°C, a polysulfone support layer with a pore size of 40 nm is immersed in an aqueous phase for 23 minutes and then removed. The water on the surface of the support layer is removed, and then it is immersed in an oil phase for 3 minutes and then removed. The oil on the surface is then removed to obtain the final product.

[0118] A 1000 ppm mixed solution of magnesium and lithium (mass ratio 20:1) was used as the feed solution, and deionized water was used as the receiving solution. The cross-flow velocity at the membrane surface was 10 cm / s. The final measured magnesium-to-lithium mass ratio of the receiving solution at room temperature was 1:1.3, and the magnesium-to-lithium dialysis factor S was... Li,Mg It is 15.

[0119] Example 18

[0120] 100g of the oil-soluble monomer shown in the formula below, 0.1g of tert-dibutyl hydroperoxide, and 25.42g of butylene dimethacrylate were dissolved in 168.4g of carbon tetrachloride to prepare the oil phase; 15.79g of vinylpyrrolidone, 0.62g of N,N-diethylaniline, and 1.9g of polyethylene glycol diacrylate with a molecular weight of 400 were dissolved in 100g of deionized water to prepare the aqueous phase. The half-life of this combination is 4 hours.

[0121]

[0122] At 8°C, a polyacrylonitrile support layer with a pore size of 50 nm is immersed in an aqueous phase for 20 minutes, then removed to remove the water from the surface of the support layer. After immersion in an oil phase for 22 minutes, the surface oil is removed to obtain the final product.

[0123] A 1000 ppm mixed solution of magnesium and lithium (mass ratio 20:1) was used as the feed solution, and deionized water was used as the receiving solution. The cross-flow velocity at the membrane surface was 10 cm / s. The final measured magnesium-to-lithium mass ratio of the receiving solution at room temperature was 1:3.0, and the magnesium-to-lithium dialysis factor S was... Li,Mg It is 6.58.

[0124] Example 19

[0125] 50g of the oil-soluble monomer shown in Formula 5, 50g of the oil-soluble monomer shown in Formula 6, 2.94g of tert-butyl peroxide, 14.74g of polyethylene glycol diacrylate, and 0.84g of lithium bis(trifluoromethanesulfonyl)imide were dissolved in 147.4g of toluene to prepare the oil phase; 26.84g of sodium p-styrene sulfonate, 5g of potassium persulfate, and 1.8g of N,N-methylenebisacrylamide were dissolved in 100g of water to prepare the aqueous phase. The half-life of this combination is 5 hours.

[0126]

[0127] At 5°C, a polytetrafluoroethylene support layer with a pore size of 20 nm is immersed in an aqueous phase for 25 minutes and then removed. The water on the surface of the support layer is removed, and then it is immersed in an oil phase for 5 minutes and then removed. The oil on the surface is then removed to obtain the final product.

[0128] A 1000 ppm mixed solution of magnesium and lithium (mass ratio 20:1) was used as the feed solution, and deionized water was used as the receiving solution. The cross-flow velocity at the membrane surface was 10 cm / s. The final measured magnesium-to-lithium mass ratio of the receiving solution for the lithium-magnesium selective dialysis membrane at room temperature was 1:1.4, and the magnesium-lithium dialysis factor S was... Li,Mg It is 14.47.

[0129] Example 20

[0130] 100g of the oil-soluble monomer shown in the formula below, 0.87g of di-tert-butyl hydroperoxide, and 2.53g of divinylbenzene were dissolved in 63.2g of cyclohexane to prepare the oil phase; 1.58g of acrylic acid, 3.45g of ammonium persulfate, and 0.8g of polyethylene glycol diacrylate with a molecular weight of 400 were dissolved in 100g of deionized water to prepare the aqueous phase. The half-life of this combination is 3 hours.

[0131]

[0132] At 29°C, a 10nm pore size polyether sulfone ketone support layer is immersed in an aqueous phase for 30 minutes, then removed, the water on the surface of the support layer is removed, and then immersed in an oil phase for 25 minutes before being removed and the oil on the surface is removed to obtain the final product.

[0133] A 1000 ppm mixed solution of magnesium and lithium (mass ratio 20:1) was used as the feed solution, and deionized water was used as the receiving solution. The cross-flow velocity at the membrane surface was 10 cm / s. The final measured magnesium-to-lithium mass ratio of the receiving solution at room temperature was 1:2.2, and the magnesium-to-lithium dialysis factor S was... Li,Mg It is 9.21.

[0134] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the embodiments of the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a lithium-magnesium selective permeation membrane, characterized in that, Includes the following steps, Take an oil-soluble peroxide initiator, an oil-soluble monomer, and an oil-soluble crosslinking agent, dissolve them in an organic solvent and prepare an oil phase; take a water-soluble initiator and a water-soluble crosslinking agent, dissolve them in water and prepare an aqueous phase. Under conditions of 0~50℃, the polymer support layer is immersed in the aqueous phase for 0.5~30 min, the support layer is removed, and then immersed in the oil phase for 0.5~30 min to obtain the product. The half-life of both the oil-soluble peroxide initiator and the water-soluble initiator is greater than 50 h under conditions of 0~50℃, and the half-life of the mixture of the oil-soluble peroxide initiator and the water-soluble initiator is not greater than 5 h under conditions of 0~50℃. The general structural formula of the oil-soluble monomer is shown below: In the formula, R1 is a methyl or hydrogen atom; R2 is or or or Wherein, R3 is a phenyl or a C1-C12 straight-chain alkyl group; R4 and R5 are independently a phenyl, hydrogen, or a C2-C4 straight-chain alkyl group; R6 is... or One of them, n=2~20.

2. The method according to claim 1, characterized in that, The oil-soluble peroxide initiator is at least one selected from cumene hydroperoxide, tert-butyl hydroperoxide, di-tert-butyl peroxide, dicumene hydroperoxide, benzoyl peroxide, diethylhexyl percarbonate, tert-butyl peroxide, and tert-butyl peroxyvalerate. The oil-soluble crosslinking agent is at least one selected from divinylbenzene, polyethylene glycol diacrylate, 1,4-butanediol diacrylate, ethylene glycol dimethacrylate, butylene glycol dimethacrylate, and hexanediol dimethacrylate. The mass ratio of monomers is 0.1~5:0.1~30:100; the water-soluble initiator is at least one of ascorbic acid, sodium bisulfite, sodium metabisulfite, tetramethylethylenediamine, N,N-diethylaniline, ammonium persulfate, sodium persulfate, and potassium persulfate; the water-soluble crosslinking agent is at least one of N,N-methylenebisacrylamide, polyethylene glycol diacrylate with a molecular weight of 400, and polyethylene glycol dimethacrylate; and the mass ratio of the water-soluble initiator, water-soluble crosslinking agent, and water is 0.1-5:0-2:100, and the mass of the water-soluble crosslinking agent is not 0.

3. The method according to claim 1, characterized in that, When R2 is At the same time, the oil phase is further added with imprinted molecules, which are at least one of n-butyllithium, methyllithium, phenyllithium, and lithium bis(trifluoromethanesulfonylimide). The molar ratio of the imprinted molecules to the oil-soluble monomer is 0-10:100, and the mass of the imprinted molecules is not 0.

4. The method according to claim 1, characterized in that, The organic solvent is one of cyclohexane, ethyl acetate, styrene, butyl acetate, chloromethane, dichloromethane, chloroform, carbon tetrachloride, benzene, toluene, and xylene. The mass ratio of the organic solvent to the oil-soluble monomer is 0-4:1, and the mass of the organic solvent is not 0.

5. The method according to claim 1, characterized in that, The aqueous phase also includes water-soluble monomers, which are acrylic acid and its salts, methacrylic acid and its salts, acrylamide, maleic acid, succinic acid and its salts, vinylpyrrolidone, p-styrenesulfonic acid and its salts, and polyethylene glycol with a double bond at one end. The degree of polymerization of the polyethylene glycol with a double bond at one end is 2 to 20. The mass ratio of the water-soluble monomer to water is 0 to 30:100, and the mass of the water-soluble monomer is not 0.

6. The method according to claim 1, characterized in that, The polymer support layer is one of polyacrylonitrile, polysulfone, polyethersulfone, polyetherethersulfone ketone, polyarylethersulfone ketone, polyaryletherether nitrile, polytetrafluoroethylene, and polyvinylidene fluoride, and its surface pore size is 10-100 nm.

7. A lithium-magnesium selective permeation membrane, characterized in that, It is prepared by the method described in any one of claims 1 to 6.

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