Lithium ion sieve membrane, and preparation method and application thereof

Abstract

The application provides a lithium ion sieve membrane and a preparation method and application thereof, and the preparation method comprises the following steps: (1) mixing a manganese lithium ion sieve adsorbent subjected to carboxyl modification treatment with an organic solvent to obtain a carboxyl modified adsorbent solution, mixing an organic polycation compound, a pore former and an organic solvent to obtain a mixed solution; (2) subjecting a quartz sheet to surface hydroxylation treatment, then soaking the quartz sheet in the mixed solution, blowing dry, then soaking the quartz sheet in the carboxyl modified adsorbent solution to obtain a quartz sheet loaded with a membrane; (3) immersing the quartz sheet loaded with the membrane in a chemical crosslinking agent solution, blowing dry, then performing ultraviolet irradiation treatment, then soaking in lye to obtain the lithium ion sieve membrane. The method can avoid the agglomeration phenomenon of the lithium ion sieve membrane in the membrane forming process, ensure the hydrophilicity and stability of the lithium adsorbent after membrane forming, and reduce the problem of adsorbent adsorption capacity decline caused by the loss of effective components.

Description

Technical Field

[0001] This application relates to the field of lithium extraction technology from salt lakes, such as a lithium-ion screening membrane, its preparation method, and its application. Background Technology

[0002] Lithium and lithium compounds, as an important strategic resource, are widely used in energy, aerospace, alloy materials, ceramics, construction, and chemical industries. In nature, lithium resources are mainly found in liquid resources such as lithium ore, salt lake brine, and seawater. Nearly 80% of my country's liquid lithium resources are distributed in salt lakes in Qinghai and Tibet. However, due to the natural disadvantage of high magnesium-to-lithium ratios in my country's salt lakes, commercially applied lithium ore extraction technologies for salt lake extraction still suffer 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, adsorption has become one of the most promising industrial methods for extracting lithium from salt lake brines in my country. Currently, the main adsorption technology for lithium extraction from salt lakes utilizes ion sieve adsorbents, including manganese-based, aluminum-based, and titanium-based lithium-ion sieve adsorbents. These conventional lithium adsorbents are all in powder form, exhibiting poor flowability and permeability, resulting in high dissolution rates during adsorption and elution, and causing adsorbent loss, which is detrimental to industrial operation.

[0004] CN102211012A discloses a lithium-ion screen membrane and its preparation method, characterized by the following steps: polyvinylidene fluoride is dissolved in N,N-dimethylacetamide to prepare a casting solution, then a lithium manganese oxide precursor is added, and the mixture is heated and stirred; the lithium manganese oxide is fully dispersed in the casting solution by ultrasound, and the mixture is allowed to stand for curing and complete degassing, then a membrane is scraped onto a clean glass plate and immersed in a coagulation bath to gel; finally, the prepared membrane is acid-washed to extract lithium ions from the precursor, thus obtaining the lithium-ion screen membrane.

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

[0006] The above-mentioned methods are prone to agglomeration during film formation, and the lithium adsorbent after film formation has poor hydrophilicity and stability. During recycling, powdering will occur, resulting in the loss of effective components and a decrease in the adsorbent's adsorption capacity. Summary of the Invention

[0007] The following is an overview of the subject matter described in detail herein. This overview is not intended to limit the scope of the claims.

[0008] This application provides a lithium-ion screen membrane, its preparation method, and its application. The method described in this application can avoid the aggregation phenomenon that easily occurs in the lithium-ion screen membrane during the film formation process, ensure the hydrophilicity and stability of the lithium adsorbent after film formation, reduce the occurrence of powdering during recycling, and thus reduce the problem of adsorbent adsorption capacity reduction caused by loss of effective components.

[0009] In a first aspect, this application provides a method for preparing a lithium-ion sieve membrane, the method comprising the following steps:

[0010] (1) After the manganese-based lithium ion sieve adsorbent is modified with carboxyl groups, it is mixed with an organic solvent to obtain a carboxyl-modified adsorbent solution. The organic polycation compound, pore-forming agent and organic solvent are mixed to obtain a mixed solution.

[0011] (2) The quartz sheet is subjected to surface hydroxylation treatment to obtain hydroxylated quartz sheet. The hydroxylated quartz sheet is immersed in the mixed solution prepared in step (1), dried, and then immersed in carboxyl-modified adsorbent solution to obtain quartz sheet with loaded film.

[0012] (3) Immerse the quartz sheet with the loaded membrane obtained in step (2) in a chemical crosslinking agent solution, blow dry and then perform ultraviolet irradiation treatment. After soaking in alkaline solution, the membrane on the quartz sheet falls off to obtain the lithium ion screen membrane.

[0013] In the preparation process of the lithium-ion sieve membrane described in this 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.

[0014] This application describes the preparation of an organic / manganese-based lithium-ion sieve self-assembled, structurally ordered porous membrane by electrostatically cross-linking a negatively charged adsorbent membrane-forming solution (carboxyl-modified adsorbent solution) with a positively charged organic polycationic compound membrane-forming solution (mixed solution). This process effectively improves the aggregation phenomenon of lithium-ion sieve adsorbents during the membrane-forming process and avoids the use of hydrophobic binders such as PVDF during the membrane-forming process. The lithium-ion sieve membrane prepared in this application has good hydrophilic permeability.

[0015] In one embodiment, step (1) carboxyl modification treatment includes mixing an aqueous solution of manganese-based lithium ion sieve adsorbent and an aqueous solution of (3-triethoxysilylpropyl)succinic anhydride, followed by hydrothermal reaction, centrifugation, washing and drying to obtain a carboxyl-modified manganese-based lithium ion sieve adsorbent.

[0016] In one embodiment, the mass ratio of (3-triethoxysilylpropyl)succinic anhydride to 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, etc.

[0017] 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.

[0018] 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.

[0019] In one embodiment, the organic solvent includes anhydrous ethanol and / or anhydrous methanol.

[0020] In one embodiment, the liquid-to-solid ratio of the organic solvent and 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, etc. The mass ratio of (3-triethoxysilylpropyl)succinic anhydride to the manganese-based ion sieve adsorbent described in this application is the same as the mass ratio of the solute in the aqueous solution of (3-triethoxysilylpropyl)succinic anhydride and the aqueous solution of the manganese-based ion sieve adsorbent.

[0021] In one embodiment, the organic polycationic compound in step (1) includes any one or a combination of at least two of polydopamine, polyethyleneimine, or polyallylamine hydrochloride.

[0022] In one embodiment, the porogen includes polyethylene glycol.

[0023] In one embodiment, the organic solvent includes any one or a combination of at least two of methanol, ethanol, or isopropanol.

[0024] 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, etc.

[0025] 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, etc.

[0026] In one embodiment, the surface hydroxylation treatment in step (2) includes placing the quartz sheet in a modifier for modification and then washing it with water to obtain a hydroxylated quartz sheet.

[0027] In this application, quartz sheets are first modified with hydroxyl groups and then immersed in a film-forming solution containing a positively charged organic polycationic compound. The two are bonded by hydrogen bonds, allowing the organic polycationic compound film-forming solution to adhere to the surface of the quartz sheets. The sheets are then immersed in a modified adsorbent solution, where the carboxyl groups on the adsorbent surface further bond with the organic polycations through hydrogen bonds and adhere to the quartz sheets. Subsequently, light irradiation is performed, and the organic polycations in the organic polycations undergo an acylation reaction with the carboxyl groups on the adsorbent surface. This process is repeated, and through covalent cross-linking and layer-by-layer self-assembly, an ordered porous membrane with an organic / manganese-based lithium-ion sieve structure is prepared. This effectively improves the aggregation phenomenon of lithium-ion sieve adsorbents during film formation and avoids the use of hydrophobic binders such as PVDF during film formation. The lithium-ion sieve membrane prepared in this application has good hydrophilic permeability.

[0028] In one embodiment, the modifier comprises concentrated sulfuric acid and hydrogen peroxide.

[0029] 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, etc.

[0030] In one embodiment, the modification time is 30 to 60 minutes, for example: 30 minutes, 35 minutes, 40 minutes, 50 minutes, or 60 minutes.

[0031] 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.

[0032] In one embodiment, the drying gas includes nitrogen.

[0033] 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.

[0034] In one embodiment, the adsorbent is soaked in a carboxyl-modified adsorbent solution and then washed with water and dried with nitrogen.

[0035] In one embodiment, the chemical crosslinking agent solution in step (3) comprises a 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) solution and / or an N-hydroxysuccinimide (NHS) solution.

[0036] 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, etc.

[0037] 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.

[0038] In one embodiment, the apparatus used for the ultraviolet irradiation treatment in step (3) includes a high-pressure mercury lamp.

[0039] In one embodiment, the power of the high-pressure mercury lamp is 350-450W, for example: 350W, 380W, 400W, 420W or 450W.

[0040] 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.

[0041] This application demonstrates that ultraviolet irradiation can induce interlayer and intralayer crosslinks, thereby enhancing the stability of the membrane.

[0042] In one embodiment, the concentration of the alkaline 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, etc.

[0043] In one embodiment, the soaking time in the alkaline solution is 0.5 to 1 hour, for example: 0.5 hours, 0.6 hours, 0.8 hours, 0.9 hours, or 1 hour.

[0044] This application uses alkaline solution immersion to disrupt the interaction between the organic polycationic compound and the quartz substrate, causing the thin film on the quartz sheet to detach. Then, the quartz sheet is placed in water, and the thin film on the surface of the quartz sheet is peeled off to obtain the product.

[0045] Secondly, this application provides a lithium-ion sieve membrane, which is prepared by the method described in the first aspect.

[0046] Thirdly, this application provides an application of the lithium-ion screening membrane as described in the second aspect, wherein the lithium-ion screening membrane is used for lithium extraction from salt lakes.

[0047] Compared with related technologies, this application has the following advantages:

[0048] (1) The method described in this application can avoid the agglomeration phenomenon of lithium ion screen membrane during the film formation process, ensure the hydrophilicity and stability of lithium adsorbent after film formation, reduce the occurrence of powdering during recycling, and thus reduce the problem of adsorbent adsorption capacity reduction caused by loss of effective components.

[0049] (2) The lithium-ion sieve membrane prepared by the method described in this application has an adsorption capacity of more than 10.9 mg / g, a manganese dissolution rate of less than 0.011%, and an adsorption efficiency of more than 94.8% maintained after 10 cycles.

[0050] After reading and understanding the accompanying diagrams and detailed descriptions, the other aspects can be understood. Attached Figure Description

[0051] The accompanying drawings are used to provide a further understanding of the technical solutions in this paper and form part of the specification. They are used together with the embodiments of this application to explain the technical solutions in this paper and do not constitute a limitation on the technical solutions in this paper.

[0052] Figure 1 This is a SEM image of the lithium-ion sieve membrane prepared in Example 1 of this application. Detailed Implementation

[0053] The technical solution of this application will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely to help understand this application and should not be regarded as specific limitations on this application.

[0054] Example 1

[0055] This embodiment provides a lithium-ion sieve membrane, and the preparation method of the lithium-ion sieve membrane is as follows:

[0056] (1) A solution A was obtained by dispersing a manganese-based ion sieve adsorbent in deionized water at a solid-liquid ratio of 1 g: 3 mL. A solution B was obtained by preparing an aqueous solution of (3-triethoxysilylpropyl)succinic anhydride with a concentration of 0.3 g / mL. Solutions A and B were mixed evenly at a volume ratio of 1:1 (the mass ratio of (3-triethoxysilylpropyl)succinic anhydride to manganese-based ion sieve adsorbent was 0.9:1). The mixture was then heated to 120℃ and hydrothermally reacted for 2 h. After the reaction, the product was centrifuged, washed with deionized water, and dried to obtain a lithium ion sieve adsorbent with carboxyl groups on its surface. Anhydrous ethanol was 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 was prepared at a concentration of 0.5 mg / mL. Polyethylene glycol was added as a porogen, and the molar ratio of PAH to polyethylene glycol was 12:1 to obtain a mixed solution.

[0057] (2) The quartz sheet was washed in a concentrated sulfuric acid: hydrogen peroxide solution with a volume ratio of 2.5:1 for 45 min, and then the excess sulfuric acid was washed away with deionized water. After washing, the surface of the quartz sheet was hydroxylated and carried a negative charge, resulting in a hydroxylated quartz sheet. The hydroxylated quartz sheet was soaked in a mixed solution for 15 min, and then washed with deionized water to remove the excess PAH on the quartz sheet. It was then dried with nitrogen. Next, the quartz sheet was immersed in a carboxyl modified adsorbent solution for 15 min, and then washed three times with deionized water. It was then dried with nitrogen. The above process was repeated until a quartz sheet with a loaded film thickness of 500 μm was formed.

[0058] (3) Immerse the quartz sheet with the loaded membrane in a 0.1 mol / L EDC solution for 35 min, then wash it three times in deionized water and dry it with nitrogen gas; then irradiate it with ultraviolet light for 10 min under a 400W high-pressure mercury lamp, and then soak it in a 0.5 mol / L sodium hydroxide solution for 0.7 h to cause the film on the quartz sheet to fall off. Then place the quartz sheet in water and peel off the film on the surface of the quartz sheet to obtain the lithium ion screen membrane.

[0059] SEM image of the prepared lithium-ion sieve is shown below Figure 1 As shown, by Figure 1 It can be seen that the lithium-ion sieve membrane prepared in this application has a porous structure, the membrane surface is relatively flat and uniform, and there is no large particle agglomeration.

[0060] Example 2

[0061] This embodiment provides a lithium-ion sieve membrane, and the preparation method of the lithium-ion sieve membrane is as follows:

[0062] (1) Manganese-based ion sieve adsorbent was dispersed in deionized water at a solid-liquid ratio of 1g:2mL to obtain solution A. A 0.25g / mL aqueous solution of (3-triethoxysilylpropyl)succinic anhydride was prepared to obtain solution B. Solutions A and B were mixed evenly at a volume ratio of 1:1 (the mass ratio of (3-triethoxysilylpropyl)succinic anhydride to manganese-based ion sieve adsorbent was 0.5:1). The mixture was then heated to 100℃ for hydrothermal reaction for 3 hours. After the reaction, the product was centrifuged, washed with deionized water, and dried to obtain a lithium ion sieve adsorbent with carboxyl groups on its surface. Anhydrous ethanol was 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 was prepared at a concentration of 0.01mg / ml. Polyethylene glycol was added as a pore-forming agent, with a molar ratio of PDA to polyethylene glycol of 8:1, to obtain a mixed solution.

[0063] (2) The quartz sheet was washed in a concentrated sulfuric acid: hydrogen peroxide solution with a volume ratio of 2:1 for 60 min, and then the excess sulfuric acid was washed away with deionized water. After washing, the surface of the quartz sheet was hydroxylated and carried a negative charge, resulting in a hydroxylated quartz sheet. The hydroxylated quartz sheet was soaked in a mixed solution for 10 min, and then washed with deionized water to remove the excess PDA on the quartz sheet. It was then dried with nitrogen. Next, the quartz sheet was immersed in a carboxyl modified adsorbent solution for 10 min, and then washed three times with deionized water. It was then dried with nitrogen. The above process was repeated until a quartz sheet with a loaded film thickness of 50 μm was formed.

[0064] (3) Immerse the quartz sheet with the loaded membrane in a 0.12 mol / L NHS solution for 30 min, then wash it three times in deionized water and dry it with nitrogen gas; then irradiate it with ultraviolet light for 5 min under a 400W high-pressure mercury lamp, and then soak it in a 0.1 mol / L sodium hydroxide solution for 1 h to cause the film on the quartz sheet to fall off. Then place the quartz sheet in water and peel off the film on the surface of the quartz sheet to obtain the lithium ion screen membrane.

[0065] Example 3

[0066] This embodiment provides a lithium-ion sieve membrane, and the preparation method of the lithium-ion sieve membrane is as follows:

[0067] (1) A solution A was obtained by dispersing a manganese-based ion sieve adsorbent in deionized water at a solid-liquid ratio of 1 g: 2 mL. A solution B was obtained by preparing an aqueous solution of (3-triethoxysilylpropyl)succinic anhydride with a concentration of 0.6 g / mL. Solutions A and B were mixed evenly at a volume ratio of 1:1 (the mass ratio of (3-triethoxysilylpropyl)succinic anhydride to manganese-based ion sieve adsorbent was 1.2:1). The mixture was then heated to 150℃ and hydrothermally reacted for 1 h. After the reaction, the product was centrifuged, washed with deionized water, and dried to obtain a lithium ion sieve adsorbent with carboxyl groups on its surface. Anhydrous ethanol was added at a solid-liquid ratio of 1:1 to obtain a carboxyl-modified adsorbent solution. A polyethyleneimine (PEI) organic polycationic compound solution was prepared at a concentration of 1 mg / mL using ethanol as a solvent. Polyethylene glycol was added as a porogen, and the molar ratio of PEI to polyethylene glycol was 16:1 to obtain a mixed solution.

[0068] (2) The quartz sheet was washed in a concentrated sulfuric acid: hydrogen peroxide solution with a volume ratio of 3:1 for 30 min, and then the excess sulfuric acid was washed away with deionized water. After washing, the surface of the quartz sheet was hydroxylated and carried a negative charge, resulting in a hydroxylated quartz sheet. The hydroxylated quartz sheet was soaked in a mixed solution for 20 min, and then washed away with deionized water to remove excess PEI. It was then dried with nitrogen. The quartz sheet was then immersed in a carboxyl-modified adsorbent solution for 20 min, and then washed three times with deionized water. It was then dried with nitrogen. The above process was repeated until a quartz sheet with a loaded film of 1000 μm thickness was formed.

[0069] (3) Immerse the quartz sheet with the loaded membrane in a 0.1 mol / L EDC solution for 40 min, then wash it three times in deionized water and dry it with nitrogen gas; then irradiate it with ultraviolet light under a 400W high-pressure mercury lamp for 15 min, and then soak it in a 1 mol / L sodium hydroxide solution for 0.5 h to cause the film on the quartz sheet to fall off. Then place the quartz sheet in water and peel off the film on the surface of the quartz sheet to obtain the lithium ion screen membrane.

[0070] Example 4

[0071] The only difference between this embodiment and Example 1 is that the mass ratio of (3-triethoxysilylpropyl)succinic anhydride to manganese-based ion sieve adsorbent is 0.3:1. All other conditions and parameters are exactly the same as in Example 1.

[0072] Example 5

[0073] The only difference between this embodiment and Example 1 is that the mass ratio of (3-triethoxysilylpropyl)succinic anhydride to manganese-based ion sieve adsorbent is 1.5:1. All other conditions and parameters are exactly the same as in Example 1.

[0074] Example 6

[0075] The only difference between this embodiment and Example 1 is that the concentration of the organic polycationic compound in the mixed solution is 0.005 g / L, while the other conditions and parameters are exactly the same as in Example 1.

[0076] Example 7

[0077] The only difference between this embodiment and Example 1 is that the concentration of the organic polycationic compound in the mixed solution is 2 g / L, while the other conditions and parameters are exactly the same as in Example 1.

[0078] Example 8

[0079] The only difference between this embodiment and Example 1 is that the volume ratio of concentrated sulfuric acid to hydrogen peroxide is 1:1; all other conditions and parameters are exactly the same as in Example 1.

[0080] Example 9

[0081] The only difference between this embodiment and Example 1 is that the volume ratio of concentrated sulfuric acid to hydrogen peroxide is 5:1; all other conditions and parameters are exactly the same as in Example 1.

[0082] Example 10

[0083] The only difference between this embodiment and Example 1 is that the concentration of the chemical crosslinking agent solution is 0.01 mol / L, while the other conditions and parameters are exactly the same as in Example 1.

[0084] Example 11

[0085] The only difference between this embodiment and Example 1 is that the concentration of the chemical crosslinking agent solution is 0.2 mol / L, while the other conditions and parameters are exactly the same as in Example 1.

[0086] Comparative Example 1

[0087] Manganese-based lithium ion sieve powder was mixed with polyvinylidene fluoride (PVDF) powder (an organic film-forming binder) and N,N'-dimethylacetamide (DMAC) (an organic solvent). The mixture was stirred at 60°C for 5 hours to obtain a uniformly mixed casting solution. The solution was poured onto a flatbed film scraper and the film thickness was set to 500 μm. A 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.

[0088] Comparative Example 2

[0089] The only difference between this comparative example and Example 1 is that it is not soaked in the mixed solution; all other conditions and parameters are exactly the same as in Example 1.

[0090] Comparative Example 3

[0091] The only difference between this comparative example and Example 1 is that the adsorbent is not modified with carboxyl groups; all other conditions and parameters are exactly the same as in Example 1.

[0092] Comparative Example 4

[0093] The only difference between this comparative example and Example 1 is that the quartz sheet is not subjected to hydroxyl modification treatment; all other conditions and parameters are exactly the same as in Example 1.

[0094] Performance testing:

[0095] The lithium-ion sieve membranes from the examples and comparative examples were leached with 0.3 mol / L hydrochloric acid to remove lithium ions, yielding a membrane-like lithium-ion sieve adsorbent. The initial Li-ion adsorbent was then circulated using a peristaltic pump at a flow rate of 150 mL / min, employing a test solution circulation method. +A test solution with a concentration of 400 ppm was flowed through the membrane elements of the examples and comparative examples, respectively. After 5 hours, adsorption equilibrium was reached, and the adsorption capacity was tested. The adsorption capacity Q was calculated as follows: Initial Li... + A C0 concentration test solution was used. The 25°C test solution was passed through a membrane element at a controlled flow rate using a peristaltic pump. The supernatant was collected at regular time intervals to test the Li content. + Concentration C t The formula for calculating its adsorption capacity is: Q=(C0-C t V / m, where V: the volume of test liquid passing through the element within a certain time; m: the mass of lithium adsorbent contained in the entire element. The manganese loss rate was obtained by determining the manganese content in the particles before acid leaching and the filtrate after acid leaching using atomic absorption spectrometry. The test results are shown in Table 1.

[0096] Table 1

[0097]

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

[0099] A comparison of Examples 1 and 4-5 shows that the mass ratio of (3-triethoxysilylpropyl)succinic anhydride to manganese-based ion sieve adsorbent affects the performance of the lithium-ion sieve membrane described in this application. Controlling the mass ratio of (3-triethoxysilylpropyl)succinic anhydride to manganese-based ion sieve adsorbent at (0.5–1.2):1 yields a lithium-ion sieve membrane with better performance. If the amount of (3-triethoxysilylpropyl)succinic anhydride added is too high, the specific surface area of ​​the manganese-based adsorbent decreases, reducing the adsorbent's lithium adsorption capacity. If the amount of (3-triethoxysilylpropyl)succinic anhydride added is too low, the carboxyl group content on the ion sieve surface is too low, reducing the uniformity and stability of subsequent film formation and leading to easy membrane degradation.

[0100] A comparison of Examples 1 and 6-7 shows that the concentration of the organic polycationic compound in the mixed solution affects the performance of the lithium-ion sieve membrane described in this application. Controlling the concentration of the organic polycationic compound in the mixed solution to 0.01–1 g / L results in a lithium-ion sieve membrane with better performance. If the concentration of the organic polycationic compound in the mixed solution is too high, the organic polymer membrane layer becomes thicker, reducing the number of lithium adsorption sites and decreasing the lithium adsorption capacity. If the concentration of the organic polycationic compound in the mixed solution is too low, the content of manganese-based ion sieves adsorbed decreases, reducing the lithium adsorption capacity.

[0101] A comparison of Examples 1 and 8-9 shows that the volume ratio of concentrated sulfuric acid to hydrogen peroxide affects the performance of the lithium-ion sieve membrane described in this application. Controlling the volume ratio of concentrated sulfuric acid to hydrogen peroxide to 2-3:1 results in a lithium-ion sieve membrane with better performance. If the amount of concentrated sulfuric acid is too high, the surface roughness of the quartz sheet will be too large, resulting in uneven film formation on its surface and reducing the lithium adsorption capacity. If the amount of concentrated sulfuric acid is too low, there will be too few hydroxyl groups on the quartz surface, leading to insufficient subsequent reactions, unstable ion sieve membrane, and increased dissolution rate.

[0102] A comparison of Examples 1 and 6-7 shows that the concentration of the chemical crosslinking agent solution affects the performance of the lithium-ion screen membrane described in this application. Controlling the concentration of the chemical crosslinking agent solution to 0.05–0.15 mol / L results in a lithium-ion screen membrane with better performance. If the concentration of the chemical crosslinking agent solution is too high, it reduces the number of adsorption active sites in the lithium-ion screen membrane, thus decreasing the lithium adsorption capacity. If the concentration of the chemical crosslinking agent solution is too low, it reduces the stability of the lithium-ion screen membrane and increases the dissolution rate.

[0103] As can be seen from the comparison between Example 1 and Comparative Example 1, the method described in this application can effectively improve the aggregation phenomenon of lithium ion screen adsorbent during the film formation process, and avoid the use of hydrophobic binders such as PVDF during the film formation process. The lithium ion screen membrane prepared in this application has good hydrophilic permeability.

[0104] As can be seen from the comparison between Example 1 and Comparative Examples 2-3, this application prepared an organic / manganese-based lithium ion sieve self-assembled structured ordered porous membrane by covalently cross-linking layer by layer through electrostatic interaction between a modified adsorbent membrane preparation solution containing negative charge and a membrane preparation solution containing positive charge organic polycationic compound.

[0105] As can be seen from the comparison between Example 1 and Comparative Example 4, the present application performs hydroxylation treatment on the quartz sheet, giving it a negative charge on its surface. When immersed in the mixed solution, the quartz sheet and the organic polycationic compound carry opposite charges. Through electrostatic interaction, the organic polycationic compound is adsorbed onto the surface of the quartz sheet. Then, the quartz sheet is immersed in a negatively charged adsorbent solution. Due to the electrostatic interaction, the manganese-based ion sieve adsorbent is adsorbed onto the surface of the quartz sheet, thus cross-linking to form a lithium ion sieve membrane.

[0106] The applicant declares that the above description is only a specific implementation of this application, but the protection scope of this application is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application fall within the protection and disclosure scope of this application.

Claims

1. A method for preparing a lithium-ion sieve membrane, characterized in that, The preparation method includes the following steps: (1) After the manganese-based lithium ion sieve adsorbent is modified with carboxyl groups, it is mixed with an organic solvent to obtain a carboxyl-modified adsorbent solution. The organic polycation compound, pore-forming agent and organic solvent are mixed to obtain a mixed solution. The carboxyl modification treatment includes mixing an aqueous solution of manganese-based lithium ion sieve adsorbent and an aqueous solution of (3-triethoxysilylpropyl)succinic anhydride, followed by hydrothermal reaction, centrifugation, washing and drying to obtain a carboxyl-modified manganese-based lithium ion sieve adsorbent. The organic polycationic compound includes any one or a combination of at least two of polydopamine, polyethyleneimine, or polyallylamine hydrochloride; (2) The quartz sheet is subjected to surface hydroxylation treatment to obtain hydroxylated quartz sheet. The hydroxylated quartz sheet is immersed in the mixed solution prepared in step (1), dried, and then immersed in carboxyl-modified adsorbent solution to obtain quartz sheet with loaded film. (3) Immerse the quartz sheet with the loaded membrane obtained in step (2) into a chemical crosslinking agent solution, blow dry and then perform ultraviolet irradiation treatment. After soaking in alkaline solution, the membrane on the quartz sheet falls off to obtain the lithium ion screen membrane. The chemical crosslinking agent solution includes a 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride solution and / or an N-hydroxysuccinimide solution.

2. The preparation method according to claim 1, characterized in that, The mass ratio of (3-triethoxysilylpropyl)succinic anhydride to manganese-based ion sieve adsorbent is (0.5~1.2):

1.

3. The preparation method according to claim 1, characterized in that, The temperature of the hydrothermal reaction is 100~150℃.

4. The preparation method according to claim 1, characterized in that, The hydrothermal reaction takes 1 to 3 hours.

5. The preparation method according to claim 1, characterized in that, The liquid-to-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 claim 1, characterized in that, The pore-forming agent includes polyethylene glycol.

7. The preparation method according to claim 1, characterized in that, The molar ratio of the organic polycationic compound to the porogen is (8~16):

1.

8. The preparation method according to claim 1, characterized in that, The concentration of the organic polycationic compound in the mixed solution is 0.01~1 g / L.

9. The preparation method according to claim 1, characterized in that, The surface hydroxylation treatment in step (2) includes placing the quartz sheet in a modifier for modification, followed by water washing to obtain hydroxylated quartz sheet.

10. The preparation method according to claim 9, characterized in that, The modifiers include concentrated sulfuric acid and hydrogen peroxide.

11. The preparation method according to claim 10, characterized in that, The volume ratio of concentrated sulfuric acid to hydrogen peroxide is (2~3):

1.

12. The preparation method according to claim 9, characterized in that, The modification time is 30-60 minutes.

13. The preparation method according to claim 1, characterized in that, The soaking time in the mixed solution in step (2) is 10~20 minutes.

14. The preparation method according to claim 1, characterized in that, The drying gas includes nitrogen.

15. The preparation method according to claim 1, characterized in that, The carboxyl-modified adsorbent solution is soaked for 10-20 minutes.

16. The preparation method according to claim 1, characterized in that, After being soaked in the carboxyl-modified adsorbent solution, the adsorbent is washed with water and dried with nitrogen.

17. The preparation method according to claim 1, characterized in that, The concentration of the chemical crosslinking agent solution is 0.05~0.15 mol / L.

18. The preparation method according to claim 1, characterized in that, The immersion time in the chemical crosslinking agent solution is 30-40 minutes.

19. The preparation method according to claim 1, characterized in that, The apparatus used for the ultraviolet irradiation treatment in step (3) includes a high-pressure mercury lamp.

20. The preparation method according to claim 19, characterized in that, The power of the high-pressure mercury lamp is 350~450W.

21. The preparation method according to claim 1, characterized in that, The ultraviolet irradiation treatment time is 5~15 minutes.

22. The preparation method according to claim 1, wherein, The concentration of the alkaline solution in step (3) is 0.1~1 mol / L.

23. The preparation method according to claim 1, characterized in that, The soaking time in the alkaline solution is 0.5 to 1 hour.

24. A lithium-ion sieve membrane, characterized in that, The lithium-ion membrane is prepared by the preparation method according to any one of claims 1-23.

25. An application of the lithium-ion screening membrane as described in claim 24, characterized in that, The lithium-ion screening membrane is used for lithium extraction from salt lakes.

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