Lithium-ion sieve membrane, and preparation method therefor and use thereof

Abstract

A lithium-ion sieve membrane, and a preparation method therefor and a use thereof. The preparation method comprises the following steps: (1) performing carboxyl modification treatment on a manganese-based lithium-ion sieve adsorbent, then mixing same with an organic solvent to obtain a carboxyl modified adsorbent solution, and mixing an organic polycationic compound, a pore-foaming agent, and the organic solvent to obtain a mixed solution; (2) performing surface hydroxylation treatment on a quartz plate, then soaking same in the mixed solution, blow-drying, and then soaking the quartz plate in the carboxyl modified adsorbent solution to obtain a membrane-loaded quartz plate; and (3) soaking the membrane-loaded quartz plate in a chemical cross-linking agent solution, blow-drying, performing ultraviolet irradiation treatment, and then soaking the membrane-loaded quartz plate in alkali liquor to obtain a lithium-ion sieve membrane. The method can avoid the occurrence of agglomeration during the formation of the lithium-ion sieve membrane, and ensures the hydrophilicity and stability of the lithium adsorbent after membrane formation, thereby reducing the problem of reduction of the adsorption capacity of the adsorbent caused by loss of effective components.

Description

A lithium ion sieve membrane and its preparation method and application Technical Field

[0001] The present application relates to the technical field of lithium extraction from salt lakes, for example, a lithium ion sieve membrane and its preparation method and application. Background Art

[0002] Lithium and lithium compounds, as a key strategic resource, are widely used in industries such as energy, aerospace, alloy materials, ceramics, construction, and the chemical industry. Naturally, lithium resources primarily exist in liquid forms such as lithium ore, salt lake brine, and seawater. Nearly 80% of my country's liquid lithium resources are located in salt lakes in Qinghai and Tibet. However, due to the high magnesium-to-lithium ratio inherent in my country's salt lakes, commercial lithium ore extraction technology applied to salt lakes still suffers from low lithium content and purity. Therefore, research on lithium extraction from salt lake brine is of great strategic significance for the development and utilization of lithium resources.

[0003] Due to its simple process, environmental friendliness, and low cost, the adsorption method has become one of the most promising methods for extracting lithium from salt lake brine in my country. Currently, adsorption technology for lithium extraction from salt lakes primarily uses ion sieve adsorbents, including manganese-based lithium ion sieve adsorbents, aluminum-based lithium ion sieve adsorbents, and titanium-based lithium ion sieve adsorbents. These conventional lithium adsorbents are all in powder form, with poor fluidity and permeability. They also have high dissolution rates during adsorption and elution, resulting in adsorbent loss and hindering industrial operations.

[0004] CN102211012A discloses a lithium ion sieve membrane and a preparation method thereof, characterized in that it is prepared by the following steps: dissolving polyvinylidene fluoride in N,N-dimethylacetamide to prepare a casting solution, then adding a lithium manganese oxide precursor, mixing and heating and stirring; fully dispersing the lithium manganese oxide in the casting solution by ultrasound, standing and aging to completely degas, scraping it onto a clean glass plate to form a film, and immersing it in a coagulation bath to gel; finally, acid-washing the prepared membrane to extract lithium ions from the precursor to obtain a lithium ion sieve membrane.

[0005] CN107261864A discloses a method for preparing a lithium ion sieve membrane and its application in separating lithium ions in salt lakes. The method comprises blending polyvinylidene fluoride powder with a prepared lithium ion sieve and preparing the lithium ion sieve membrane by phase inversion technology.

[0006] The above scheme is prone to agglomeration during the film formation process, and the hydrophilicity and stability of the lithium adsorbent after film formation are poor. Powdering will occur during the recycling process, resulting in the loss of effective ingredients and a decrease in the adsorption capacity of the adsorbent.

[0007] Summary of the Invention

[0008] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0009] The present application provides a lithium ion sieve membrane, a preparation method and application thereof. The method described in the present application can avoid the agglomeration of the lithium ion sieve membrane during the film formation process, ensure the hydrophilicity and stability of the lithium adsorbent after film formation, reduce the occurrence of powder shedding during the recycling process, and thus reduce the problem of decreased adsorption capacity of the adsorbent due to the loss of effective ingredients.

[0010] In a first aspect, the present application provides a method for preparing a lithium ion sieve membrane, the preparation method comprising the following steps:

[0011] (1) performing carboxyl modification on a manganese-based lithium ion sieve adsorbent and mixing the mixture with an organic solvent to obtain a carboxyl-modified adsorbent solution, and mixing an organic polycationic compound, a porogen, and the organic solvent to obtain a mixed solution;

[0012] (2) performing surface hydroxylation treatment on the quartz sheet to obtain a hydroxylated quartz sheet, soaking the hydroxylated quartz sheet in the mixed solution prepared in step (1), drying the sheet and then soaking the sheet in a carboxyl-modified adsorbent solution to obtain a membrane-loaded quartz sheet;

[0013] (3) Immersing the quartz sheet loaded with the membrane obtained in step (2) in a chemical crosslinking agent solution, drying it, and then subjecting it to ultraviolet irradiation treatment. After soaking it in an alkaline solution, the membrane on the quartz sheet falls off, thereby obtaining the lithium ion sieve membrane.

[0014] During the preparation of the lithium ion sieve membrane described in the present application, the number of film layers can be controlled by repeating the operation steps of step (2), thereby controlling the film thickness and improving the stability of the membrane.

[0015] The present application obtains a negatively charged adsorbent membrane-forming liquid (carboxyl-modified adsorbent solution) and a positively charged organic polycationic compound membrane-forming liquid (mixed solution) through electrostatic action for covalent cross-linking layer-by-layer self-assembly to prepare an organic / manganese-based lithium ion sieve self-assembled structurally ordered porous membrane, which can effectively improve the agglomeration phenomenon of the lithium ion sieve adsorbent during the film formation process and avoid the use of hydrophobic binders such as PVDF during the film formation process. The lithium ion sieve membrane prepared in the present application has good hydrophilic permeability.

[0016] In one embodiment, the carboxyl modification treatment in step (1) comprises mixing an aqueous solution of a manganese-based lithium ion sieve adsorbent and an aqueous solution of (3-triethoxysilylpropyl)succinic anhydride, and after hydrothermal reaction, centrifuging, washing, and drying to obtain a carboxyl-modified manganese-based lithium ion sieve adsorbent.

[0017] In one embodiment, the mass ratio of (3-triethoxysilylpropyl)succinic anhydride to the manganese-based ion sieve adsorbent is (0.5-1.2):1, for example, 0.5:1, 0.6:1, 0.9:1, 1:1, 1.1:1 or 1.2:1.

[0018] In one embodiment, the temperature of the hydrothermal reaction is 100-150°C, for example, 100°C, 110°C, 120°C, 140°C or 150°C.

[0019] In one embodiment, the hydrothermal reaction time is 1 to 3 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours or 3 hours.

[0020] In one embodiment, the organic solvent includes anhydrous ethanol and / or anhydrous methanol.

[0021] In one embodiment, the liquid-to-solid ratio of the organic solvent to the carboxyl-modified manganese-based lithium ion sieve adsorbent is (0.8-1.2):1, for example, 0.8:1, 0.9:1, 1:1, 1.1:1, or 1.2:1. The mass ratio of the (3-triethoxysilylpropyl)succinic anhydride to the manganese-based ion sieve adsorbent described in this application is the mass ratio of the solutes in the (3-triethoxysilylpropyl)succinic anhydride aqueous solution to the manganese-based ion sieve adsorbent aqueous solution.

[0022] In one embodiment, the organic polycationic compound in step (1) comprises any one of polydopamine, polyethyleneimine or polyallylamine hydrochloride, or a combination of at least two thereof.

[0023] In one embodiment, the porogen comprises polyethylene glycol.

[0024] In one embodiment, the organic solvent includes any one of methanol, ethanol or isopropanol, or a combination of at least two of them.

[0025] In one embodiment, the molar ratio of the organic polycationic compound to the porogen is (8-16):1, for example, 8:1, 10:1, 12:1, 14:1 or 16:1.

[0026] In one embodiment, the concentration of the organic polycationic compound in the mixed solution is 0.01 to 1 g / L, for example, 0.01 g / L, 0.05 g / L, 0.1 g / L, 0.6 g / L or 1 g / L.

[0027] In one embodiment, the surface hydroxylation treatment in step (2) comprises placing the quartz sheet in a modifier for modification, and washing the quartz sheet with water to obtain a hydroxylated quartz sheet.

[0028] In the present application, the quartz plate is pre-modified with hydroxyl groups and then immersed in a membrane-forming liquid of a positively charged organic polycationic compound. The two are hydrogen-bonded so that the organic polycationic compound membrane-forming liquid adheres to the surface of the quartz plate. The quartz plate is then immersed in the modified adsorbent solution, and the carboxyl groups on the surface of the adsorbent further hydrogen-bond with the organic polycations and adhere to the surface of the quartz plate. Subsequently, the organic polycations in the organic polycations undergo an acylation reaction with the carboxyl groups on the surface of the adsorbent. The above process is repeated, and through covalent cross-linking layer-by-layer self-assembly, an organic / manganese-based lithium ion sieve self-assembled structurally ordered porous membrane is prepared, which can effectively improve the agglomeration phenomenon of the lithium ion sieve adsorbent during the film formation process and avoid the use of hydrophobic binders such as PVDF during the film formation process. The lithium ion sieve membrane prepared in the present application has good hydrophilic permeability.

[0029] In one embodiment, the modifier includes concentrated sulfuric acid and hydrogen peroxide.

[0030] In one embodiment, the volume ratio of concentrated sulfuric acid to hydrogen peroxide is (2-3):1, for example, 2:1, 2.2:1, 2.5:1, 2.8:1 or 3:1.

[0031] In one embodiment, the modification time is 30 to 60 minutes, for example, 30 minutes, 35 minutes, 40 minutes, 50 minutes or 60 minutes.

[0032] In one embodiment, the soaking time in the mixed solution in step (2) is 10 to 20 minutes, for example, 10 minutes, 12 minutes, 15 minutes, 18 minutes or 20 minutes.

[0033] In one embodiment, the drying gas comprises nitrogen.

[0034] In one embodiment, the soaking time in the carboxyl-modified adsorbent solution is 10 to 20 minutes, for example, 10 minutes, 12 minutes, 15 minutes, 18 minutes or 20 minutes.

[0035] In one embodiment, the sample is immersed in the carboxyl modified adsorbent solution and then washed with water and dried with nitrogen.

[0036] In one embodiment, the chemical crosslinking agent solution in step (3) includes 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) solution and / or N-hydroxysuccinimide (NHS) solution.

[0037] In one embodiment, the concentration of the chemical crosslinking agent solution is 0.05 to 0.15 mol / L, for example, 0.05 mol / L, 0.08 mol / L, 0.1 mol / L, 0.12 mol / L or 0.15 mol / L.

[0038] In one embodiment, the immersion time in the chemical crosslinking agent solution is 30 to 40 minutes, for example, 30 minutes, 32 minutes, 35 minutes, 38 minutes or 40 minutes.

[0039] In one embodiment, the device used for the ultraviolet irradiation treatment in step (3) includes a high-pressure mercury lamp.

[0040] In one embodiment, the power of the high-pressure mercury lamp is 350-450W, for example, 350W, 380W, 400W, 420W or 450W.

[0041] In one embodiment, the ultraviolet irradiation treatment time is 5 to 15 minutes, for example, 5 minutes, 8 minutes, 10 minutes, 12 minutes or 15 minutes.

[0042] The present application can induce interlayer and intralayer crosslinking through ultraviolet irradiation, thereby enhancing the stability of the film.

[0043] In one embodiment, the concentration of the alkali solution in step (3) is 0.1 to 1 mol / L, for example, 0.1 mol / L, 0.2 mol / L, 0.5 mol / L, 0.8 mol / L or 1 mol / L.

[0044] In one embodiment, the soaking time in the alkali solution is 0.5 to 1 hour, for example, 0.5 hours, 0.6 hours, 0.8 hours, 0.9 hours or 1 hour.

[0045] The present application uses alkaline solution soaking to destroy the interaction between the organic polycationic compound and the quartz substrate, causing the film on the quartz substrate to fall off, and then the quartz substrate is placed in water to peel off the film on the surface of the quartz substrate to obtain the product.

[0046] In a second aspect, the present application provides a lithium ion sieve membrane, which is prepared by the method described in the first aspect.

[0047] In a third aspect, the present application provides an application of the lithium ion sieve membrane as described in the second aspect, wherein the lithium ion sieve membrane is used for extracting lithium from salt lakes.

[0048] Compared with the related art, this application has the following beneficial effects:

[0049] (1) The method described in the present application can avoid the agglomeration of lithium ion sieve membranes during the film formation process, ensure the hydrophilicity and stability of the lithium adsorbent after film formation, reduce the occurrence of powder shedding during recycling, and thus reduce the problem of decreased adsorption capacity of the adsorbent caused by the loss of effective ingredients.

[0050] (2) The adsorption capacity of the lithium ion sieve membrane prepared by the method described in the present application can reach more than 10.9 mg / g, the manganese dissolution rate can reach less than 0.011%, and the adsorption efficiency maintained after 10 cycles can reach more than 94.8%.

[0051] Still other aspects will become apparent upon reading and understanding the accompanying drawings and detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] The accompanying drawings are used to provide a further understanding of the technical solution of this article and constitute a part of the specification. Together with the embodiments of this application, they are used to explain the technical solution of this article and do not constitute a limitation on the technical solution of this article.

[0053] FIG1 is a SEM image of the lithium ion sieve membrane prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0054] The technical solution of the present application is further described below through specific implementation methods. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as specific limitations of the present application.

[0055] Example 1

[0056] This embodiment provides a lithium ion sieve membrane, and the preparation method of the lithium ion sieve membrane is as follows:

[0057] (1) A manganese ion sieve adsorbent is dispersed in deionized water at a solid-liquid ratio of 1 g:3 mL to obtain solution A, and a (3-triethoxysilylpropyl) succinic anhydride aqueous solution with a concentration of 0.3 g / mL is prepared to obtain solution B. Solution A and solution B are mixed evenly at a volume ratio of 1:1 (the mass ratio of (3-triethoxysilylpropyl) succinic anhydride to manganese ion sieve adsorbent is 0.9:1), and then heated to 120°C for hydrothermal reaction for 2 hours. After the reaction, the product is centrifuged and washed with deionized water and dried to obtain a lithium ion sieve adsorbent with carboxyl groups on the surface. Anhydrous ethanol is added at a solid-liquid ratio of 1:1 to obtain a carboxyl-modified adsorbent solution. Using ethanol as a solvent, a polyallylamine hydrochloride (PAH) organic polycationic compound solution is prepared at a concentration of 0.5 mg / mL, and polyethylene glycol is added as a porogen. The molar ratio of PAH to polyethylene glycol is 12:1 to obtain a mixed solution.

[0058] (2) The quartz plate was placed in a concentrated sulfuric acid: hydrogen peroxide solution with a volume ratio of 2.5:1 and washed for 45 minutes, and then the excess sulfuric acid was washed away with deionized water. After washing, the surface of the quartz plate was hydroxylated and negatively charged, thereby obtaining a hydroxylated quartz plate. The hydroxylated quartz plate was soaked in the mixed solution for 15 minutes, and then washed in deionized water to remove the excess PAH on the quartz plate, and then dried with nitrogen. The quartz plate was then immersed in a carboxyl modified adsorbent solution and soaked for 15 minutes, and then washed three times in deionized water and dried with nitrogen. The above process was repeated until a quartz plate with a loaded membrane thickness of 500 μm was formed.

[0059] (3) Immerse the quartz sheet carrying the membrane in a 0.1 mol / L EDC solution for 35 minutes, then rinse it three times in deionized water and blow it dry with nitrogen; then irradiate it with ultraviolet light for 10 minutes under a 400 W high-pressure mercury lamp, and then soak it in a 0.5 mol / L sodium hydroxide solution for 0.7 hours to cause the thin film on the quartz sheet to fall off. Then, place the quartz sheet in water and peel off the thin film on the surface of the quartz sheet to obtain the lithium ion sieve membrane.

[0060] The SEM image of the prepared lithium ion sieve is shown in FIG1 . As can be seen from FIG1 , the lithium ion sieve membrane prepared in the present application has a porous structure, the membrane surface is relatively flat and uniform, and there is no large particle agglomeration.

[0061] Example 2

[0062] This embodiment provides a lithium ion sieve membrane, and the preparation method of the lithium ion sieve membrane is as follows:

[0063] (1) A manganese ion sieve adsorbent is dispersed in deionized water at a solid-liquid ratio of 1 g:2 mL to obtain solution A, and a (3-triethoxysilylpropyl) succinic anhydride aqueous solution with a concentration of 0.25 g / mL is prepared to obtain solution B. Solution A and solution B are mixed evenly at a volume ratio of 1:1 (the mass ratio of (3-triethoxysilylpropyl) succinic anhydride to manganese ion sieve adsorbent is 0.5:1), and then heated to 100°C for hydrothermal reaction for 3 hours. After the reaction, the product is centrifuged and washed with deionized water and dried to obtain a lithium ion sieve adsorbent with carboxyl groups on the surface. Anhydrous ethanol is added at a solid-liquid ratio of 1:1 to obtain a carboxyl-modified adsorbent solution. Using ethanol as a solvent, a polydopamine (PDA) organic polycationic compound solution is prepared at a concentration of 0.01 mg / ml, and polyethylene glycol is added as a porogen. The molar ratio of PDA to polyethylene glycol is 8:1 to obtain a mixed solution.

[0064] (2) The quartz sheet was placed in a concentrated sulfuric acid: hydrogen peroxide solution with a volume ratio of 2:1 and washed for 60 minutes, and then the excess sulfuric acid was washed away with deionized water. After washing, the surface of the quartz sheet was hydroxylated and negatively charged to obtain a hydroxylated quartz sheet. The hydroxylated quartz sheet was soaked in the mixed solution for 10 minutes, and then washed in deionized water to remove the excess PDA on the quartz sheet, and dried with nitrogen. The quartz sheet was then immersed in a carboxyl modified adsorbent solution and soaked for 10 minutes, and then washed three times in deionized water and dried with nitrogen. The above process was repeated until a quartz sheet with a loaded membrane thickness of 50 μm was formed.

[0065] (3) Immerse the quartz sheet carrying the membrane in a 0.12 mol / L NHS solution for 30 minutes, then rinse it three times in deionized water and blow it dry with nitrogen; then irradiate it with ultraviolet light for 5 minutes under a 400 W high-pressure mercury lamp, and then soak it in a 0.1 mol / L sodium hydroxide solution for 1 hour to cause the thin film on the quartz sheet to fall off. Then, place the quartz sheet in water and peel off the thin film on the surface of the quartz sheet to obtain the lithium ion sieve membrane.

[0066] Example 3

[0067] This embodiment provides a lithium ion sieve membrane, and the preparation method of the lithium ion sieve membrane is as follows:

[0068] (1) A manganese ion sieve adsorbent is dispersed in deionized water at a solid-liquid ratio of 1 g:2 mL to obtain solution A, and a (3-triethoxysilylpropyl) succinic anhydride aqueous solution with a concentration of 0.6 g / mL is prepared to obtain solution B. Solution A and solution B are mixed evenly at a volume ratio of 1:1 (the mass ratio of (3-triethoxysilylpropyl) succinic anhydride to manganese ion sieve adsorbent is 1.2:1), and then heated to 150°C for hydrothermal reaction for 1 hour. After the reaction, the product is centrifuged and washed with deionized water and dried to obtain a lithium ion sieve adsorbent with carboxyl groups on the surface. Anhydrous ethanol is added at a solid-liquid ratio of 1:1 to obtain a carboxyl-modified adsorbent solution. Using ethanol as a solvent, a polyethyleneimine (PEI) organic polycationic compound solution is prepared at a concentration of 1 mg / mL, and polyethylene glycol is added as a porogen. The molar ratio of PEI to polyethylene glycol is 16:1 to obtain a mixed solution.

[0069] (2) The quartz sheet was placed in a concentrated sulfuric acid: hydrogen peroxide solution with a volume ratio of 3:1 and washed for 30 minutes, and then the excess sulfuric acid was washed away with deionized water. After washing, the surface of the quartz sheet was hydroxylated and negatively charged to obtain a hydroxylated quartz sheet. The hydroxylated quartz sheet was soaked in the mixed solution for 20 minutes, and then washed in deionized water to remove the excess PEI on the quartz sheet, and dried with nitrogen. The quartz sheet was then immersed in a carboxyl modified adsorbent solution and soaked for 20 minutes, and then washed three times in deionized water and dried with nitrogen. The above process was repeated until a quartz sheet with a loaded membrane thickness of 1000 μm was formed.

[0070] (3) Immerse the quartz plate carrying the membrane in a 0.1 mol / L EDC solution for 40 minutes, then rinse it three times in deionized water and blow it dry with nitrogen; then irradiate it with ultraviolet light for 15 minutes under a 400 W high-pressure mercury lamp, and then soak it in a 1 mol / L sodium hydroxide solution for 0.5 hours to cause the thin film on the quartz plate to fall off. Then, place the quartz plate in water and peel off the thin film on the surface of the quartz plate to obtain the lithium ion sieve membrane.

[0071] Example 4

[0072] The only difference between this embodiment and embodiment 1 is that the mass ratio of (3-triethoxysilylpropyl)succinic anhydride to the manganese-based ion sieve adsorbent is 0.3:1, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0073] Example 5

[0074] The only difference between this embodiment and embodiment 1 is that the mass ratio of (3-triethoxysilylpropyl)succinic anhydride to the manganese-based ion sieve adsorbent is 1.5:1, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0075] Example 6

[0076] The only difference between this embodiment and embodiment 1 is that the concentration of the organic polycationic compound in the mixed solution is 0.005 g / L, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0077] Example 7

[0078] The only difference between this embodiment and embodiment 1 is that the concentration of the organic polycationic compound in the mixed solution is 2 g / L, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0079] Example 8

[0080] The only difference between this embodiment and embodiment 1 is that the volume ratio of concentrated sulfuric acid to hydrogen peroxide is 1:1, and other conditions and parameters are exactly the same as those in embodiment 1.

[0081] Example 9

[0082] The only difference between this embodiment and embodiment 1 is that the volume ratio of concentrated sulfuric acid to hydrogen peroxide is 5:1, and other conditions and parameters are exactly the same as those in embodiment 1.

[0083] Example 10

[0084] The only difference between this embodiment and embodiment 1 is that the concentration of the chemical cross-linking agent solution is 0.01 mol / L, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0085] Example 11

[0086] The only difference between this embodiment and embodiment 1 is that the concentration of the chemical cross-linking agent solution is 0.2 mol / L, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0087] Comparative Example 1

[0088] Manganese-based lithium ion sieve powder was mixed with organic film-forming binder polyvinylidene fluoride (PVDF) powder and organic solvent N,N'-dimethylacetamide (DMAC), and stirred at 60°C for 5 hours to obtain a uniformly mixed casting solution. The solution was poured onto a flat-plate scraping machine with a scraping thickness of 500 μm. The lithium ion sieve membrane was formed using phase inversion technology. The ratio of lithium manganese ion sieve powder, PVDF powder, and DMAC solution was 2 g: 1 g: 10 mL.

[0089] Comparative Example 2

[0090] The only difference between this comparative example and Example 1 is that the samples were not immersed in the mixed solution, and the other conditions and parameters were exactly the same as those in Example 1.

[0091] Comparative Example 3

[0092] The only difference between this comparative example and Example 1 is that the adsorbent is not carboxyl-modified, and the other conditions and parameters are exactly the same as those in Example 1.

[0093] Comparative Example 4

[0094] The only difference between this comparative example and Example 1 is that the quartz plate is not subjected to hydroxyl modification treatment, and the other conditions and parameters are exactly the same as those in Example 1.

[0095] Performance testing:

[0096] The lithium ion sieve membranes in the examples and comparative examples were leached with 0.3 mol / L hydrochloric acid to remove lithium ions, and a membrane-like lithium ion sieve adsorbent was obtained. The initial Li +The test solution with a concentration of 400ppm was passed through the membrane elements of the embodiment and the comparative example respectively, and the adsorption capacity was measured after reaching adsorption equilibrium after 5 hours. + The concentration is C0 test solution, and the test solution at 25℃ is passed through the membrane element at a certain flow rate using a peristaltic pump. The supernatant is taken at a certain time interval to test Li + Concentration C t The adsorption capacity calculation formula is: Q = (C0-C t )V / m, where V is the volume of the test solution passing through the component within a certain period of time; m is the mass of the lithium adsorbent contained in the entire component. The manganese content in the pellets before acid leaching and in the filtrate after acid leaching was measured using an atomic absorption spectrometer to obtain the manganese dissolution rate. The test results are shown in Table 1:

[0097] Table 1

[0098] As can be seen from Table 1, from Examples 1-3, the adsorption capacity of the lithium ion sieve membrane prepared by the method described in the present application can reach more than 10.9 mg / g, the manganese dissolution rate can reach less than 0.011%, and the adsorption efficiency maintained after 10 cycles can reach more than 94.8%.

[0099] By comparing Example 1 and Examples 4-5, it can be seen that in the preparation process of the lithium ion sieve membrane described in the present application, the mass ratio of (3-triethoxysilylpropyl)succinic anhydride and the manganese-based ion sieve adsorbent will affect its performance. The mass ratio of (3-triethoxysilylpropyl)succinic anhydride and the manganese-based ion sieve adsorbent is controlled at (0.5-1.2):1, and the lithium ion sieve membrane with better performance is obtained. If the addition amount of (3-triethoxysilylpropyl)succinic anhydride is too high, the specific surface area of ​​the manganese-based adsorbent is reduced, and the capacity of the adsorbent to adsorb lithium is reduced. If the addition amount of (3-triethoxysilylpropyl)succinic anhydride is too low, the carboxyl content on the surface of the ion sieve is too low, which reduces the uniformity and stability of subsequent film formation and causes the membrane to be easily dissolved.

[0100] By comparing Example 1 with Examples 6-7, it can be seen that during the preparation process of the lithium ion sieve membrane described in the present application, the concentration of the organic polycationic compound in the mixed solution will affect its performance. When the concentration of the organic polycationic compound in the mixed solution is controlled at 0.01 to 1 g / L, the lithium ion sieve membrane with better performance is obtained. If the concentration of the organic polycationic compound in the mixed solution is too high, the organic polymer film layer will be thicker, the adsorption sites of lithium will be reduced, and the lithium adsorption capacity will be reduced. If the concentration of the organic polycationic compound in the mixed solution is too low, the content of the adsorbed manganese ion sieve is reduced, thereby reducing the adsorption capacity of lithium.

[0101] By comparing Example 1 with Examples 8-9, it can be seen that in the preparation process of the lithium ion sieve membrane described in this application, the volume ratio of concentrated sulfuric acid and hydrogen peroxide will affect its performance. When the volume ratio of concentrated sulfuric acid and hydrogen peroxide is controlled at 2 to 3:1, the lithium ion sieve membrane with better performance is obtained. If the amount of concentrated sulfuric acid is too high, the surface roughness of the quartz sheet will be too large, the film formation on its surface will be uneven, and the adsorption capacity of lithium will be reduced. If the amount of concentrated sulfuric acid is too low, the hydroxyl groups on the quartz surface will be too few, resulting in insufficient subsequent reaction, the prepared ion sieve membrane will be unstable, and the dissolution rate will increase.

[0102] By comparing Example 1 with Examples 6-7, it can be seen that during the preparation process of the lithium ion sieve membrane described in this application, the concentration of the chemical crosslinker solution will affect its performance. When the concentration of the chemical crosslinker solution is controlled at 0.05-0.15 mol / L, the lithium ion sieve membrane with better performance is obtained. If the concentration of the chemical crosslinker solution is too high, the adsorption active sites in the lithium ion sieve membrane will be reduced, and the adsorption capacity of lithium will be reduced. If the concentration of the chemical crosslinker solution is too low, the stability of the lithium ion sieve membrane will be reduced and the dissolution rate will be increased.

[0103] By comparing Example 1 and Comparative Example 1, it can be seen that the method described in the present application can effectively improve the agglomeration phenomenon of the lithium ion sieve adsorbent during the film formation process, and avoid the use of hydrophobic binders such as PVDF during the film formation process. The lithium ion sieve membrane prepared in the present application has good hydrophilic permeability.

[0104] By comparing Example 1 with Comparative Examples 2-3, it can be seen that the present application obtains a negatively charged adsorbent membrane-forming liquid and a positively charged organic polycationic compound membrane-forming liquid through electrostatic action, and covalently cross-links the membrane layer by layer to self-assemble, thereby preparing a structurally ordered porous membrane of an organic / manganese-based lithium ion sieve self-assembled.

[0105] A comparison of Example 1 and Comparative Example 4 demonstrates that the present invention applies a hydroxylation treatment to the quartz wafer, imparting a negative surface charge. When immersed in a mixed solution, the quartz wafer and the organic polycationic compound have opposite charges. Electrostatic interactions allow the organic polycationic compound to adsorb to the quartz wafer's surface. Subsequently, the quartz wafer is immersed in a negatively charged adsorbent solution. Electrostatic interactions allow the manganese-based ion-sieving adsorbent to adsorb to the quartz wafer's surface, allowing cross-linking to form a lithium ion-sieving membrane.

[0106] The applicant declares that the above is only a specific implementation method of the present application, but the protection scope of the present application is not limited thereto. Technical personnel in the relevant technical field should understand that any changes or substitutions that can be easily thought of by technical personnel in the relevant technical field within the technical scope disclosed in this application fall within the protection scope and disclosure scope of this application.

Claims

1. A method for preparing a lithium ion sieve membrane, which comprises the following steps: (1) After carboxyl modification treatment of a manganese-based lithium ion sieve adsorbent, it is mixed with an organic solvent to obtain a carboxyl-modified adsorbent solution. An organic polycationic compound, a pore-forming agent and an organic solvent are mixed to obtain a mixed solution; (2) The quartz wafer is subjected to surface hydroxylation treatment to obtain a hydroxylated quartz wafer. The hydroxylated quartz wafer is immersed in the mixed solution prepared in step (1), dried and then immersed in the carboxyl-modified adsorbent solution to obtain a quartz wafer with a loaded membrane; (3) The quartz wafer with the loaded membrane prepared in step (2) is immersed in a chemical crosslinking agent solution, dried and then subjected to ultraviolet irradiation treatment. After immersion in an alkaline solution, the membrane on the quartz wafer falls off to obtain the lithium ion sieve membrane.

2. The preparation method according to claim 1, wherein, The carboxyl modification treatment in step (1) includes mixing an aqueous solution of a manganese-based lithium ion sieve adsorbent and an aqueous solution of (3-triethoxysilylpropyl) succinic anhydride. After hydrothermal reaction, it is subjected to centrifugation, washing and drying treatment to obtain a carboxyl-modified manganese-based lithium ion sieve adsorbent.

3. The preparation method according to claim 2, wherein The mass ratio of the (3-triethoxysilylpropyl) succinic anhydride to the manganese-based ion sieve adsorbent is (0.5-1.2):

1.

4. The preparation method according to claim 2 or 3, wherein, The temperature of the hydrothermal reaction is 100-150 °C; Optionally, the time of the hydrothermal reaction is 1-3 h.

5. The preparation method according to any one of claims 2-4, wherein, The organic solvent includes anhydrous ethanol and / or anhydrous methanol; Optionally, the liquid-solid ratio of the organic solvent and the carboxyl-modified manganese-based lithium ion sieve adsorbent is (0.8-1.2):

1.

6. The preparation method according to any one of claims 1-5, wherein, The organic polycationic compound in step (1) includes any one or a combination of at least two of polydopamine, polyethyleneimine or polyallylamine hydrochloride.

7. The preparation method according to any one of claims 1-6, wherein, The pore-forming agent includes polyethylene glycol; Optionally, the organic solvent includes any one or a combination of at least two of methanol, ethanol or isopropanol.

8. The preparation method according to any one of claims 1-7, wherein, The molar ratio of the organic polycationic compound to the pore-forming agent is (8-16):1; Optionally, the concentration of the organic polycationic compound in the mixed solution is 0.01-1 g / L.

9. The preparation method according to any one of claims 1 to 8, wherein, The surface hydroxylation treatment in step (2) includes modifying the quartz wafer with a modifier and then washing it with water to obtain a hydroxylated quartz wafer; Optionally, the modifier includes concentrated sulfuric acid and hydrogen peroxide; Optionally, the volume ratio of the concentrated sulfuric acid to the hydrogen peroxide is (2-3):1; Optionally, the time of the modification is 30-60 min.

10. The preparation method according to any one of claims 1-9, wherein, The immersion time in the mixed solution in step (2) is 10-20 min; Optionally, the gas for drying includes nitrogen; Optionally, the immersion time in the carboxyl-modified adsorbent solution is 10-20 min; Optionally, after immersion in the carboxyl-modified adsorbent solution, it is washed with water and dried with nitrogen.

11. The preparation method according to any one of claims 1-10, wherein, The chemical crosslinking agent solution in step (3) includes 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride solution and / or N-hydroxysuccinimide solution; Optionally, the concentration of the chemical crosslinking agent solution is 0.05-0.15 mol / L; Optionally, the immersion time in the chemical crosslinking agent solution is 30-40 min.

12. The preparation method according to any one of claims 1-11, wherein, The device used for the ultraviolet irradiation treatment in step (3) includes a high-pressure mercury lamp; Optionally, the power of the high-pressure mercury lamp is 350-450 W; Optionally, the time of the ultraviolet irradiation treatment is 5-15 min.

13. The preparation method according to any one of claims 1-12, wherein, The concentration of the alkali solution in step (3) is 0.1-1 mol / L; Optionally, the immersion time in the alkali solution is 0.5-1 h.

14. A lithium ion sieve membrane, wherein, The lithium ion sieve membrane is prepared by the method according to any one of claims 1-13.

15. An application of the lithium ion sieve membrane as described in claim 14, wherein, The lithium ion sieve membrane is used for extracting lithium from salt lakes.

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