A gel-state lithium ion adsorbent and a preparation method and a delithiation method thereof

Abstract

The present application belongs to the technical field of lithium resource extraction. The present application provides a gel-state lithium ion adsorbent and a preparation method and a delithiation method thereof. The preparation method comprises mixing lithium ion sieve material, alginate, galloyl glucose compound and calcium chloride to gel, and then drying to obtain dry gel, thereby obtaining the gel-state lithium ion adsorbent. The preparation method uses alginate and galloyl glucose compound to mix and crosslink, thereby improving the crosslinking strength and the compression resistance of the gel, and making the pore size distribution of the gel more uniform and dense, which is beneficial to improving the lithium extraction capacity. The obtained dry gel has a larger particle size than the powder, and has better hydrophilicity, which can increase the flowability during lithium extraction and reduce the loss, thereby improving the cycle efficiency.

Description

Technical Field

[0001] This invention belongs to the field of lithium resource extraction technology, and relates to a gel-state lithium ion adsorbent and its preparation and delithiation methods. Background Technology

[0002] With the rapid and large-scale development of lithium-ion energy storage, the demand for lithium resources is increasing. Lithium extraction technology refers to the technology of extracting lithium from various lithium-containing raw materials. Liquid lithium resources are a new type of lithium-containing raw material, which refers to brine or seawater with high lithium content. Brine-type lithium resources account for about 90% of the world's proven lithium resources, and their abundant reserves help to avoid the impact of the depletion of traditional mineral raw materials.

[0003] However, liquid lithium resources are generally characterized by low lithium-ion concentration, high magnesium-to-lithium ratio (in salt lake brines), complex composition, and numerous associated elements. Coupled with the lack of mature separation and extraction technologies, liquid lithium resources cannot yet be industrially developed and utilized on a large scale. To separate and extract lithium ions from liquid lithium ore, researchers have successively developed various lithium extraction methods, such as calcination impregnation, solar evaporation, co-precipitation, solvent extraction, and adsorption. These methods all have certain technical limitations. Adsorption, however, is a more ideal lithium extraction technology, better suited for the separation and enrichment of lithium ions in large-volume liquids, and features low energy consumption, environmental friendliness, high lithium selectivity, and ease of operation.

[0004] One of the keys to achieving adsorption methods lies in the selection and use of high-performance lithium-ion sieves (or lithium-ion adsorbents). A lithium-ion sieve is a material that can selectively identify and adsorb lithium ions. Based on the mechanism of ion exchange, it has the ability to re-introduce the target lithium ions after they have been extracted (or in a lithium-depleted or delithiated state) and react to form a composite material (in a lithium-rich state).

[0005] Currently, lithium-ion sieve materials mainly fall into three categories: manganese-based lithium-ion sieves, titanium-based lithium-ion sieves, and aluminum-based adsorbents. However, regardless of the type, existing lithium-ion sieve materials are all produced in powder or particle form. Directly applying these powdered materials to lithium extraction presents numerous problems, such as poor flowability, poor water wettability, low cycle efficiency, easy loss, and large pressure drop, leading to high energy consumption in column operations. These issues are all detrimental to industrial applications.

[0006] To address this, existing technologies involve reshaping lithium-ion sieve powder through granulation, film formation, foaming, and electrospinning, typically using hydrophobic polymers such as PVC and PVDF as binders. However, these binders result in poor water wettability of the lithium-ion sieve. Therefore, existing technologies often incorporate hydrophilic polymers such as agar, chitosan, polyacrylonitrile, or polyacrylamide as hydrophilic modifiers to mix with the binder. However, these hydrophilic substances can leach into the water during lithium-ion sieve use, affecting its stability. Alternatively, some reports have described using hydrophilic polymers as binders with the addition of crosslinking agents for chemical crosslinking and curing. Furthermore, there are reports of using hydrophilic polymers to block-modify PVDF and PVC. However, both of these methods are complex and costly, hindering large-scale industrial production.

[0007] Therefore, new technical solutions are still needed to address the problems encountered when using powdered lithium-ion sieves, which is of great significance for promoting the development of liquid lithium ore extraction technology. Summary of the Invention

[0008] In view of the problems existing in the prior art, the purpose of this invention is to provide a gel-state lithium-ion adsorbent and its preparation method and delithiation method. The preparation method includes mixing lithium-ion sieve material, alginate, galloyl glucose compound, and calcium chloride, gelling the mixture, and then drying it to generate a dry gel, thereby obtaining the gel-state lithium-ion adsorbent. The preparation method uses alginate and galloyl glucose compound for mixed crosslinking, which improves the crosslinking strength and the compressibility of the gel, and also makes the pore size distribution in the gel more uniform and dense, which is beneficial to improving the lithium extraction capacity. The resulting dry gel has a larger particle size than powder and better hydrophilicity, which can increase the flowability during lithium extraction and reduce losses, thereby improving the cycle efficiency.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a method for preparing a gel-state lithium-ion adsorbent, the method comprising:

[0011] A mixture of lithium-ion sieve material, alginate, galloyl glucose compound and calcium chloride is gelled to obtain a wet gel.

[0012] The obtained wet gel is dried to form a dry gel, thus obtaining a gel-state lithium ion adsorbent.

[0013] The preparation method of the present invention involves reacting alginate and galloyl glucose compound with Ca in calcium chloride. 2+Cross-linking is performed to generate a hydrogel, which loads lithium-ion sieve material. After drying, a dry gel is obtained as the gel-state lithium-ion adsorbent, which can be directly used for lithium extraction. The hydrogel provided by the preparation method of the present invention has good hydrophilicity, which is conducive to the diffusion of lithium ions. Furthermore, by adding galloyl glucose compound for mixed cross-linking, the polyphenol structure contained therein has a higher cross-linking strength with calcium ions, which effectively improves the compressibility of the hydrogel and makes the pore size distribution of the hydrogel more uniform and dense, which is beneficial to improving the lithium extraction capacity. The resulting dry gel has a larger particle size than powder and has better hydrophilicity, which can be well adapted to column-type lithium extraction operation, effectively increasing the flowability during lithium extraction and reducing losses, thereby improving the cycle efficiency.

[0014] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following technical solutions.

[0015] As a preferred technical solution of the present invention, the preparation method includes:

[0016] An aqueous solution of alginate and galloyl glucose compound was prepared, and lithium ion sieve material was added and ultrasonically dispersed to obtain suspension A.

[0017] Prepare an aqueous solution of calcium chloride to obtain solution B;

[0018] Suspension A is added dropwise to solution B, and the mixture is stirred to gelatinize and form gel spheres. After washing with water, the gel is obtained as the wet gel.

[0019] As a preferred technical solution of the present invention, the preparation method further includes controlling the dropping speed and dropping amount of suspension A to generate gel spheres with a radius of 1 to 5 mm, such as 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm or 5 mm, but not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0020] This invention achieves granulation by forming gel spheres. Compared to powder, particles with a certain macroscopic size can avoid losses during lithium extraction applications. Therefore, the particle size of the gel spheres cannot be too small, while excessively large gel spheres are prone to breakage, affecting their use.

[0021] As a preferred technical solution of the present invention, the mass concentration of alginate in the suspension A is 2% to 4%, such as 2%, 2.2%, 2.4%, 2.6%, 2.8%, 3%, 3.2%, 3.4%, 3.6%, 3.8%, or 4%, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0022] Preferably, the mass concentration of calcium chloride in solution B is 1% to 3%, such as 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.6%, 2.8%, or 3%, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0023] As a preferred embodiment of the present invention, the lithium-ion sieve material includes delithiated manganese oxide and / or titanium oxide.

[0024] Preferably, the manganese oxide comprises at least one of MnO2·0.5H2O, λ-MnO2, or MnO2·0.3H2O. Typical but non-limiting combinations include combinations of MnO2·0.5H2O and λ-MnO2, combinations of MnO2·0.5H2O and MnO2·0.3H2O, or combinations of λ-MnO2 and MnO2·0.3H2O, etc.; the titanium oxide comprises H2TiO3 and / or H4Ti5O. 12 .

[0025] Preferably, the alginate includes at least one of sodium alginate, potassium alginate, lithium alginate, or ammonium alginate. Typical but non-limiting combinations include combinations of sodium alginate and potassium alginate, combinations of sodium alginate and lithium alginate, combinations of potassium alginate and ammonium alginate, or combinations of potassium alginate and lithium alginate.

[0026] Preferably, the galloyl glucose compound comprises at least one of 1,6-di-O-B-D-galloyl glucose, 1,3,6-trigalloyl glucose, 1,3,4,6-tetragalloyl glucose, and 1,2,3,4,6-O-pentagalloyl glucose, for example, typical but non-limiting combinations include combinations of 1,6-di-O-B-D-galloyl glucose and 1,3,6-trigalloyl glucose, 1,6-di-O-B-D-galloyl glucose and 1,3,4,6-O-pentagalloyl glucose. Combinations of 1,6-tetragalloglucose, 1,6-di-O-β-D-galloglucose with 1,2,3,4,6-O-pentagalloglucose, 1,3,6-trigalloglucose with 1,3,4,6-tetragalloglucose, 1,3,6-trigalloglucose with 1,2,3,4,6-O-pentagalloglucose, or 1,3,4,6-tetragalloglucose with 1,2,3,4,6-O-pentagalloglucose, etc.

[0027] Preferably, the amounts of alginate, galloyl glucose compound, and lithium-ion sieve material are controlled according to a mass ratio of (8-9):(1-2):1, for example, 8:1:1, 8.3:1:1, 8.5:1:1, 8.8:1:1, 9:1:1, 8:1.3:1, 8.3:1.3:1, 8.5:1.3:1, 8.8:1.3:1, 9:1.3:1, 8:1.5:1, 8.3:1 The range of values ​​is 0.5:1, 8.5:1.5:1, 8.8:1.5:1, 9:1.5:1, 8:1.8:1, 8.3:1.8:1, 8.5:1.8:1, 8.8:1.8:1, 9:1.8:1, 8:2:1, 8.3:2:1, 8.5:2:1, 8.8:2:1, or 9:2:1, etc., but is not limited to the listed values. Other unlisted values ​​within the above range also apply.

[0028] As a preferred embodiment of the present invention, the drying method includes freeze drying.

[0029] Preferably, the freeze-drying process includes performing a first freeze-drying, then immersing the product in a solvent for swelling, performing a second freeze-drying after the swelling has reached equilibrium, and then sequentially performing the swelling and a third freeze-drying to obtain the dry gel.

[0030] The present invention preferably obtains the dry gel product through a specific freeze-drying process. This specific freeze-drying process can make the hydrogel pore size distribution more uniform and dense, further improving the lithium extraction speed and lithium extraction capacity.

[0031] Preferably, the first freeze-drying process includes pre-freezing at a first temperature for 12-24 hours, such as 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours, or 24 hours, and then drying at a second temperature with reduced vacuum for 36-60 hours, such as 36 hours, 38 hours, 40 hours, 42 hours, 44 hours, 46 hours, 48 ​​hours, 50 hours, 52 hours, 54 hours, 56 hours, 58 hours, or 60 hours, but is not limited to the listed values; other unlisted values ​​within the above range are also applicable.

[0032] Preferably, the second and third freeze-drying processes each include pre-freezing at a first temperature for 6 to 12 hours, such as 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, or 12 hours, and then drying at a second temperature with reduced vacuum for 12 to 24 hours, such as 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours, or 24 hours, but are not limited to the listed values; other unlisted values ​​within the above range are also applicable.

[0033] Preferably, the first temperature is -20 to -30°C, such as -20°C, -22°C, -24°C, -26°C, -28°C, or -30°C, and the second temperature is -60 to -80°C, such as -60°C, -62°C, -64°C, -66°C, -68°C, -70°C, -72°C, -74°C, -76°C, -78°C, or -80°C, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0034] Preferably, the vacuum range for reducing the vacuum degree is 10 to 30 Pa, such as 10 Pa, 12 Pa, 14 Pa, 16 Pa, 18 Pa, 20 Pa, 22 Pa, 24 Pa, 26 Pa, 28 Pa or 30 Pa, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0035] Preferably, the solvent includes at least one of methanol, ethanol, dimethyl sulfoxide, or tert-butanol. Typical but non-limiting combinations include combinations of methanol and ethanol, methanol and dimethyl sulfoxide, methanol and tert-butanol, ethanol and dimethyl sulfoxide, ethanol and tert-butanol, or dimethyl sulfoxide and tert-butanol.

[0036] Preferably, during swelling in the solvent, the solid-liquid ratio (S / L) is controlled to be 1g:(80-120)mL to control the amount of the gel-state lithium-ion adsorbent and the solvent, for example, 1g:80mL, 1g:85mL, 1g:90mL, 1g:95mL, 1g:100mL, 1g:105mL, 1g:110mL, 1g:115mL or 1g:120mL, etc., but not limited to the values ​​listed above. Other unlisted values ​​within the above range are also applicable.

[0037] In a second aspect, the present invention provides a gel-state lithium-ion adsorbent, which is obtained using the preparation method described in the first aspect.

[0038] When the dry gel obtained by this invention is immersed in liquid lithium ore resources or lithium-containing solutions to adsorb lithium (extract lithium), it swells due to water absorption and forms a hydrogel state.

[0039] Thirdly, the present invention provides a method for delithiation of a gel-state lithium-ion adsorbent, the method comprising:

[0040] The gel-state lithium-ion adsorbent described in the second aspect, after lithium adsorption, is subjected to acid treatment to obtain Li-containing... + Solution and lithium ion sieve powder;

[0041] Li-containing + Lithium was extracted from the solution to obtain Li. + Concentrated liquid and waste liquid C;

[0042] The waste liquid C is neutralized to obtain calcium precipitate and waste liquid D.

[0043] Waste liquid D was subjected to organic solvent extraction (DCM) to separate inorganic salts and organic matter, wherein the organic matter contained alginate and galloyl glucose.

[0044] The preparation method of this invention yields a gel-state lithium-ion adsorbent that belongs to a physical cross-linking system. During the acid washing and delithiation process of the hydrogel, it will dissociate and release lithium-ion sieve powder material, which is beneficial to the full delithiation of the material and thus avoids the decrease in lithium extraction capacity due to insufficient delithiation. The delithiation method provided by this invention can recycle and reuse lithium-ion sieve material, alginate, galloyl glucose compound, and calcium precipitate, and then re-prepare the gel-state lithium-ion adsorbent to achieve regeneration and recycling.

[0045] As a preferred embodiment of the present invention, the delithiation method includes immersing the gel-state lithium-ion adsorbent after lithium adsorption into a hydrochloric acid solution, ultrasonically degassing it, then shaking it in a shaking box at room temperature to fully disintegrate the gel carrier and fully release the lithium ions, followed by centrifugation to obtain a Li-containing... + Solution and lithium ion sieve powder.

[0046] Preferably, the concentration of the hydrochloric acid is 0.2 to 0.8 mol / L, such as 0.2 mol / L, 0.25 mol / L, 0.3 mol / L, 0.35 mol / L, 0.4 mol / L, 0.45 mol / L, 0.5 mol / L, 0.55 mol / L, 0.6 mol / L, 0.65 mol / L, 0.7 mol / L, 0.75 mol / L, or 0.8 mol / L, but is not limited to the listed values; other unlisted values ​​within the above range are also applicable.

[0047] Preferably, the amount of gel-state lithium-ion adsorbent and hydrochloric acid is controlled according to a solid-liquid ratio (S / L) of 1g:(80-120)mL, such as 1g:80mL, 1g:85mL, 1g:90mL, 1g:95mL, 1g:100mL, 1g:105mL, 1g:110mL, 1g:115mL, or 1g:120mL, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0048] As a preferred technical solution of the present invention, the lithium extraction method includes membrane separation and / or electrochemical methods;

[0049] Preferably, the neutralization reaction uses sodium bicarbonate to obtain calcium carbonate precipitate, and the obtained calcium carbonate precipitate is used to prepare calcium chloride solution.

[0050] Compared with existing technical solutions, the present invention has at least the following beneficial effects:

[0051] The preparation method of this invention uses alginate and galloyl glucose compounds for mixed crosslinking, which improves the crosslinking strength and compressibility of the gel, and makes the pore size distribution in the gel more uniform and dense, which is beneficial to improving lithium extraction capacity. The resulting dry gel has a larger particle size than powder and better water wettability, which can increase the flowability during lithium extraction and reduce losses, thereby improving cycle efficiency. The preparation method is simple and low-cost, and suitable for large-scale industrial production.

[0052] The gel-state lithium-ion adsorbent obtained by this invention belongs to a physical cross-linking system. During the acid washing and delithiation process of the hydrogel, it will dissociate and release lithium-ion sieve powder material, which is conducive to the full delithiation of the material and thus avoids the decrease in lithium extraction capacity due to insufficient delithiation.

[0053] The delithiation method described in this invention can simultaneously delithilate the gel-state lithium-ion adsorbent and recycle lithium-ion sieve materials, alginate, galloyl glucose compounds, and calcium precipitates, thereby enabling the regeneration and recycling of the gel-state lithium-ion adsorbent and further reducing costs. Attached Figure Description

[0054] Figure 1(a) is a cross-sectional SEM image of the lithium-ion adsorbent obtained in Example 3;

[0055] Figure 1(b) is a cross-sectional SEM image of the lithium-ion adsorbent obtained in Comparative Example 1;

[0056] Figure 1(c) is a cross-sectional SEM image of the lithium-ion adsorbent obtained in Example 7;

[0057] Figure 2 These are the stress-strain curves of the lithium-ion adsorbents obtained in Examples 2-4, Example 7, and Comparative Example 1;

[0058] Figure 3 This is a schematic flowchart of the delithiation method of the gel-state lithium-ion adsorbent in Example 8. Detailed Implementation

[0059] The technical solution of the present invention will be further illustrated below through specific embodiments.

[0060] Those skilled in the art will understand that the embodiments described are merely illustrative of the invention and should not be construed as limiting the invention.

[0061] Example 1

[0062] This embodiment provides a method for preparing a gel-state lithium-ion adsorbent, the preparation method comprising:

[0063] (1) Sodium alginate was used as the alginate and 1,6-di-O-B-D-galloglucoside was used as the galloyl glucose compound. An aqueous solution of the two was prepared, and the mass concentration of the alginate was controlled to be 3%. Then, lithium ion sieve material λ-MnO2 was added. The λ-MnO2 was obtained by eluting LiMn2O4 in 0.3M HCl solution. The mass ratio of the alginate, the galloyl glucose compound and the lithium ion sieve material was controlled to be 8.5:1.5:1. After ultrasonic dispersion, suspension A was obtained.

[0064] (2) Prepare a 2% calcium chloride aqueous solution to obtain solution B;

[0065] (3) Add suspension A vertically to solution B using a peristaltic pump, control the dropping rate and amount of suspension A, generate gel spheres with a radius of 2-4 mm, continue to stir slowly for 12 hours, remove the gel spheres, rinse them with water 5 times, and use them as wet gels.

[0066] (4) The wet gel was freeze-dried for the first time. It was pre-frozen at -20℃ for 24h, and then dried at -70℃ with a vacuum of 30Pa for 48h to obtain the first dry gel. The first dry gel was immersed in the solvent with tert-butanol as the solvent to swell. The solid-liquid ratio S / L was controlled at 1g:100mL. After swelling equilibrium, it was taken out and freeze-dried for the second time. It was pre-frozen at -20℃ for 12h, and then dried at -70℃ with a vacuum of 20Pa for 24h to obtain the second dry gel. The second dry gel was immersed in the solvent again to swell. The solid-liquid ratio S / L was controlled at 1g:100mL. After swelling equilibrium, it was taken out and freeze-dried for the third time. It was pre-frozen at -30℃ for 12h, and then dried at -60℃ with a vacuum of 10Pa for 12h to obtain a usable dry gel, i.e., a gel-state lithium ion adsorbent.

[0067] Example 2

[0068] This embodiment provides a method for preparing a gel-state lithium-ion adsorbent. The method replaces the 1,6-di-O-B-D-galloglucoside compound with 1,2,3,4,6-O-pentagalloglucoside, and adjusts the mass ratio of the alginate, the galloglucoside compound, and the lithium-ion sieve material from 8.5:1.5:1 to 9:1:1. Except for the above, the other conditions are exactly the same as in Example 1.

[0069] Example 3

[0070] This embodiment provides a method for preparing a gel-state lithium-ion adsorbent. The preparation method adjusts the mass ratio of alginate, galloyl glucose compound and lithium-ion sieve material from 9:1:1 to 8.5:1.5:1. Except for the above, the other conditions are exactly the same as in Example 2.

[0071] Example 4

[0072] This embodiment provides a method for preparing a gel-state lithium-ion adsorbent. The preparation method adjusts the mass ratio of alginate, galloyl glucose compound and lithium-ion sieve material from 9:1:1 to 8:2:1. Except for the above, the other conditions are exactly the same as in Example 2.

[0073] Example 5

[0074] This embodiment provides a method for preparing a gel-state lithium-ion adsorbent, the preparation method comprising:

[0075] (1) Sodium alginate was used as the alginate and 1,3,6-trigalloglucoside was used as the galloyl glucose compound. An aqueous solution of the two was prepared, and the mass concentration of the alginate was controlled to be 2%. Then, lithium ion sieve material λ-MnO2 was added. The λ-MnO2 was obtained by eluting LiMn2O4 in 0.3M HCl solution. The mass ratio of the alginate, the galloyl glucose compound and the lithium ion sieve material was controlled to be 8.5:1.5:1. After ultrasonic dispersion, suspension A was obtained.

[0076] (2) Prepare a 2% calcium chloride aqueous solution to obtain solution B;

[0077] (3) Add suspension A vertically to solution B using a peristaltic pump, control the dropping rate and amount of suspension A, generate gel spheres with a radius of 2-4 mm, continue to stir slowly for 12 hours, remove the gel spheres, rinse them with water 5 times, and use them as wet gels.

[0078] (4) The wet gel was freeze-dried for the first time. It was pre-frozen at -20℃ for 24h, and then dried at -70℃ with a vacuum of 30Pa for 48h to obtain the first dry gel. Using DMSO as a solvent, the first dry gel was immersed in the solvent for swelling, with a solid-liquid ratio of S / L = 1g:100mL. After swelling equilibrium, it was taken out and freeze-dried for the second time. It was pre-frozen at -30℃ for 12h, and then dried at -80℃ with a vacuum of 30Pa for 12h to obtain the second dry gel. The second dry gel was immersed in the solvent again for swelling, with a solid-liquid ratio of S / L = 1g:100mL. After swelling equilibrium, it was taken out and freeze-dried for the third time. It was pre-frozen at -30℃ for 12h, and then dried at -80℃ with a vacuum of 20Pa for 12h to obtain a usable dry gel, i.e., a gel-state lithium ion adsorbent.

[0079] Example 6

[0080] This embodiment provides a method for preparing a gel-state lithium-ion adsorbent, the preparation method comprising:

[0081] (1) Sodium alginate was used as the alginate and 1,2,3,4,6-O-pentagalactiae was used as the galloyl glucose compound. An aqueous solution of the two was prepared and the mass concentration of the alginate was controlled to be 2%. Then, lithium ion sieve material λ-MnO2 was added. The λ-MnO2 was obtained by eluting LiMn2O4 in 0.3M HCl solution. The mass ratio of the alginate, the galloyl glucose compound and the lithium ion sieve material was controlled to be 8.5:1.5:1. After ultrasonic dispersion, suspension A was obtained.

[0082] (2) Prepare a 3% calcium chloride aqueous solution to obtain solution B;

[0083] (3) Add suspension A vertically to solution B using a peristaltic pump, control the dropping rate and amount of suspension A, generate gel spheres with a radius of 2-4 mm, continue to stir slowly for 12 hours, remove the gel spheres, rinse them with water 5 times, and use them as wet gels.

[0084] (4) The wet gel was freeze-dried for the first time. It was pre-frozen at -20℃ for 24h, and then dried at -70℃ with a vacuum of 30Pa for 48h to obtain the first dry gel. The first dry gel was immersed in methanol as a solvent to swell. The solid-liquid ratio S / L was controlled at 1g:100mL. After swelling equilibrium, it was taken out and freeze-dried for the second time. It was pre-frozen at -30℃ for 12h, and then dried at -80℃ with a vacuum of 30Pa for 12h to obtain the second dry gel. The second dry gel was immersed in the solvent again to swell. The solid-liquid ratio S / L was controlled at 1g:100mL. After swelling equilibrium, it was taken out and freeze-dried for the third time. It was pre-frozen at -30℃ for 12h, and then dried at -80℃ with a vacuum of 30Pa for 24h to obtain a usable dry gel, i.e., a gel-state lithium ion adsorbent.

[0085] Example 7

[0086] This embodiment provides a method for preparing a gel-state lithium-ion adsorbent. In step (4), the preparation method only performs a first freeze-drying, without swelling, a second freeze-drying, or a third freeze-drying. The first dry gel is used as the gel-state lithium-ion adsorbent. Apart from this, the other conditions are exactly the same as in Example 3.

[0087] Comparative Example 1

[0088] This comparative example provides a method for preparing a gel-state lithium-ion adsorbent. The preparation method does not use galloyl glucose compound, that is, it replaces 1,2,3,4,6-O-pentagalloyl glucose with an equal mass of sodium alginate. Apart from this, the other conditions are exactly the same as in Example 3.

[0089] Comparative Example 2

[0090] This comparative example provides a method for preparing a lithium-ion adsorbent, wherein the preparation method uses a binder for granulation, and the preparation method includes:

[0091] According to the feeding mass ratio of 30:12:85, λ-MnO2, polyvinyl chloride adhesive PVC and N-methylpyrrolidone were mixed and dispersed to obtain a first solution. Then, the first solution was dripped into water with an injection agent to form particles. The particle diameter was controlled to be 2-4 mm. The obtained particles were washed with deionized water and dried at 80°C for 12 h to obtain the formed lithium ion adsorbent material particles.

[0092] Characterization and testing:

[0093] (1) The lithium-ion adsorbents prepared in the examples and comparative examples were tested for lithium-ion sieve loading capacity as follows: A mass of m1 = 1 ± 0.2 g of lithium-ion adsorbent was weighed and placed in the treatment solution and shaken. The treatment solution used in Examples 1-7 and Comparative Example 1 was 50 mL of 0.5 M HCl solution, and the treatment solution used in Comparative Example 2 was 100 mL of N-methylpyrrolidone. This allowed the adsorbent to decompose and release the lithium-ion sieve. The adsorbent was centrifuged, the lithium-ion sieve was washed with water several times, and dried at 60 °C to constant weight. The obtained mass m2 was weighed, and the loading capacity was calculated as m2 / m1 × 100%. The results are recorded in Table 1.

[0094] (2) The microstructure of the lithium-ion adsorbent was observed using a JEOL JSM-6490LV scanning electron microscope. Figures 1(a), 1(b) and 1(c) are SEM images of the cross-sections of the lithium-ion adsorbents obtained in Example 3, Comparative Example 1 and Example 7, respectively. It can be seen from the figures that, compared with Comparative Example 1, Example 3 added galloyl glucose compound, resulting in a more uniform and dense gel with a more complete pore structure. Compared with Example 7, after solvent replacement and multiple freeze-drying, the pore size of the gel in Example 3 was smaller and more uniform.

[0095] (3) Lithium-ion sieve adsorption capacity and desorption rate test:

[0096] I. Adsorption Capacity Test: A certain mass of lithium-ion adsorbent was immersed in a lithium-containing solution (lithium concentration 0.05 mol / L), with a solid-liquid ratio of S / L = 1 g: 1000 mL. The solution was shaken at 100 rpm in a constant-temperature shaking chamber at 25°C for 24 hours to ensure adsorption equilibrium was reached. The Li content in the solution was determined using ICP-OES. + The content of . Adsorption capacity Q e The formula for calculating (mg / g) is as follows:

[0097]

[0098] In the formula, C0 (mg / L) represents Li + The initial concentration of C; e (mg / L) is the concentration of lithium ions when adsorption equilibrium is reached; V(L) is the volume of the solution; m(g) is the mass of the lithium ion sieve, which is determined by the dry mass of the lithium ion adsorbent × the loading.

[0099] II. Desorption Rate Test: The lithium-ion adsorbent after lithium adsorption was immersed in hydrochloric acid solution (0.5 mol / L), and the solid-liquid ratio was controlled at S / L = 1 g: 100 mL. After ultrasonic degassing, it was shaken in a shaker at room temperature to fully disintegrate the gel carrier and release lithium ions. The supernatant was collected with a pipette, and the concentration of metal cations in the solution was measured using ICP-OES. The released lithium-ion sieve material was collected by centrifugation, dried to constant weight, and weighed. The lithium desorption rate (DE) was then calculated using the following formula. Li ):

[0100]

[0101] In the formula, c Li (mg / L) represents the Li in the eluent. + The concentration of ; V1(L) is the volume of the eluent; m Li (mg) represents the mass of lithium in the adsorbent, calculated as the dry mass of the lithium-ion adsorbent material × loading × Q. e To be confirmed.

[0102] The results are recorded in Table 1.

[0103] (3) The specific surface area and pore size distribution of the gel-state lithium-ion adsorbent were analyzed using an ASAP2020M specific surface area and microporous adsorption analyzer. The results are recorded in Table 1.

[0104] (4) The compressibility of the gel-state lithium-ion adsorbent was tested using an INSTRON 3344 electronic universal testing machine. The compression deformation was set to 80%, the compression rate to 5 mm / min, and the sample size to be a cylinder with a diameter of 20 mm and a height of 10 mm. The compressive stress-strain curves of the lithium-ion adsorbents obtained in Examples 2-4, Example 7, and Comparative Example 1 are shown in [reference needed]. Figure 2 The maximum fracture strain value in the figure and the maximum fracture strain values ​​of other examples are listed in Table 1.

[0105] Table 1

[0106]

[0107]

[0108] As can be seen from Table 1:

[0109] The degree of substitution and amount of galloyl glucose compounds significantly affect the pore structure and mechanical properties of the adsorbent material. Specifically: the higher the degree of substitution of hydroxyl groups in the galloyl glucose compound, the better the compressibility, the larger the specific surface area, and the smaller the average pore size. The higher the proportion of galloyl glucose compounds, the higher the compressibility initially, followed by a decrease. The material exhibits optimal compressibility when the ratio of sodium alginate to galloyl glucose compounds is 8.5:1.5. Galloyl glucose compounds also regulate the density of gel crosslinking; compared to sodium alginate, its crosslinking density with Ca... 2+ The system has more cross-linking active sites. Therefore, when the content of galloyl glucose compound is low, the degree of cross-linking of the system is low and the mechanical properties are poor. When the content of galloyl glucose compound is high, the degree of cross-linking of the system is high, the material becomes more brittle, resulting in a smaller fracture strain value but a larger fracture stress. In addition, the higher the proportion of galloyl glucose compound, the smaller the specific surface area and pore size of the material. This is because the higher the content of galloyl glucose compound, the higher the degree of cross-linking of the material, the smaller the unit mass volume, the smaller the specific surface area, and the smaller the average pore size.

[0110] Freeze-drying has a significant impact on the pore structure and mechanical properties of gel-state lithium-ion adsorbents. As can be seen from the comparison between Examples 3 and 7, secondary freeze-drying with different solvents can further optimize the pore structure of the material, resulting in a material with a more uniform pore size distribution, thereby avoiding poor mechanical properties caused by local stress overload.

[0111] Example 8

[0112] This embodiment provides a method for delithiation of a gel-state lithium-ion adsorbent, such as... Figure 3 As shown, the delithiation method includes:

[0113] The gel-state lithium ion adsorbent of Example 3 after lithium adsorption was immersed in hydrochloric acid solution (0.5 mol / L), and the solid-liquid ratio was controlled at S / L = 1 g: 100 mL. After ultrasonic degassing, it was shaken in a shaker at room temperature to fully disintegrate the gel carrier and fully release the lithium ions. After centrifugation, the supernatant and lithium ion sieve powder were obtained.

[0114] The separated lithium-ion sieve powder was washed three times with water and then dried at 60°C to constant weight to obtain the recovered lithium-ion sieve powder.

[0115] The washing water was mixed with the supernatant after centrifugation to obtain a Li-containing solution (Li + A Li-containing solution (with a concentration of 0.5–0.7 g / L) is pumped into a membrane separation device, which contains an ultrafiltration membrane (membrane flux 600 L / (m²)). 2 ·h), membrane area 0.25m 2(with a pore size of 0.1 nm), ultrafiltration permeate and waste liquid C were obtained;

[0116] The ultrafiltration permeate was mixed with a 0.6M hydrochloric acid solution and pumped through a filter into the RO reverse osmosis unit (membrane flux 58L / (m²)). 2 •h), retention rate 99%, membrane area 2.5m² 2 The membrane concentrate is produced and pumped to the electrodialysis membrane unit to produce electrodialysis concentrate. The retained permeate is then mixed with waste liquid C.

[0117] Sodium carbonate solution and electrodialysis concentrate are fed into a lithium precipitation reactor. After a full reaction, lithium carbonate solution is obtained. The lithium carbonate filter cake is obtained by plate and frame filtration. The filter cake is mixed with high-temperature pure water in a slurry tank and washed to obtain wet lithium carbonate. After drying, lithium carbonate with a purity ≥99% is obtained.

[0118] The mixed waste liquid C was fed into a calcium precipitation reactor. Sodium bicarbonate was added while stirring at 100 rpm to adjust the pH of the solution to 7-7.5. After stirring for 3 hours, the solution was allowed to stand for 12 hours. The calcium carbonate filter cake and waste liquid D were obtained by plate and frame filtration. The calcium carbonate filter cake was mixed with low-temperature pure water in a slurry tank and washed to obtain wet calcium carbonate. The wet calcium carbonate was then dried to obtain recovered calcium carbonate with a purity ≥98%.

[0119] Waste liquid D was concentrated to half its original volume and subjected to four-stage continuous countercurrent extraction with dichloromethane at a volume ratio of 3:1 in an extraction clarification tank to obtain an organic phase containing organic matter. The organic phase was dried to obtain a mixture of alginate and galloyl glucose compounds with a recovery rate of 70%–80%. The two compounds can be further separated by mass spectrometry at a mass ratio of 6–6.2.

[0120] The recovered calcium carbonate is reacted with hydrochloric acid to prepare calcium chloride solution, and the resulting lithium ion sieve powder, alginate and galloyl glucose compound are recycled into the preparation method described in this invention to re-prepare the gel-state lithium ion adsorbent.

[0121] As can be seen from the above, the preparation method of this invention uses alginate and galloyl glucose compound for mixed crosslinking, which improves the crosslinking strength and the compressibility of the gel, and makes the pore size distribution in the gel more uniform and dense, which is beneficial to improving the lithium extraction capacity. The resulting dry gel has a larger particle size than the powder and has better water wettability, which can increase the flowability during lithium extraction and reduce losses, thereby improving the recycling efficiency. The preparation method is simple and low-cost, and suitable for large-scale industrial production. Furthermore, through the delithiation method of this invention, while realizing the delithiation of the gel-state lithium-ion adsorbent, the lithium-ion sieve material, alginate, galloyl glucose compound, and calcium precipitate can be recycled and reused, thereby re-preparing the gel-state lithium-ion adsorbent for regeneration and recycling, which is beneficial to further reduce costs.

[0122] This invention illustrates the detailed process equipment and process flow through the above embodiments. However, this invention is not limited to the detailed process equipment and process flow described above, meaning that this invention does not necessarily depend on the detailed process equipment and process flow to be implemented. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of raw materials for the product of this invention, addition of auxiliary components, and selection of specific methods, all fall within the protection scope and disclosure scope of this invention.

[0123] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0124] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0125] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for preparing a gel-state lithium-ion adsorbent, characterized in that, The preparation method includes: A mixture of lithium-ion sieve material, alginate, galloyl glucose compound and calcium chloride is gelled to obtain a wet gel. The obtained wet gel is dried to generate a dry gel, thus obtaining a gel-state lithium ion adsorbent; The galloyl glucose compound includes at least one of 1,6-di-O-B-D-galloyl glucose, 1,3,6-trigalloyl glucose, 1,3,4,6-tetragalloyl glucose, and 1,2,3,4,6-O-pentagalloyl glucose. The amount of alginate, galloyl glucose compound and lithium ion sieve material should be controlled according to a mass ratio of (8~9):(1~2):1; The drying method includes freeze drying; The freeze-drying process includes first performing a first freeze-drying, then immersing the product in a solvent for swelling, and after the swelling reaches equilibrium, performing a second freeze-drying, followed by the swelling and a third freeze-drying in sequence to obtain the dry gel. The solvent includes at least one of methanol, ethanol, dimethyl sulfoxide, or tert-butanol.

2. The preparation method according to claim 1, characterized in that, The preparation method includes: An aqueous solution of alginate and galloyl glucose compound was prepared, and lithium ion sieve material was added and ultrasonically dispersed to obtain suspension A. Prepare an aqueous solution of calcium chloride to obtain solution B; Suspension A is added dropwise to solution B, and the mixture is stirred to gelatinize and form gel spheres. After washing with water, the gel is obtained as the wet gel.

3. The preparation method according to claim 2, characterized in that, The preparation method further includes controlling the dropping speed and amount of suspension A to generate gel spheres with a radius of 1-5 mm.

4. The preparation method according to claim 2, characterized in that, The mass concentration of alginate in suspension A is 2% to 4%.

5. The preparation method according to claim 2, characterized in that, In solution B, the mass concentration of calcium chloride is 1% to 3%.

6. The preparation method according to claim 1, characterized in that, The lithium-ion sieve material includes delithiated manganese oxide and / or titanium oxide.

7. The preparation method according to claim 6, characterized in that, The manganese oxide includes at least one selected from MnO2·0.5H2O, λ-MnO2, or MnO2·0.3H2O; the titanium oxide includes H2TiO3 and / or H4Ti5O. 12 .

8. The preparation method according to claim 1, characterized in that, The alginate includes at least one of sodium alginate, potassium alginate, lithium alginate, or ammonium alginate.

9. The preparation method according to claim 1, characterized in that, The first freeze-drying process includes pre-freezing at -20~-30℃ for 12~24h, and then drying at -60~-80℃ with a vacuum degree controlled at 10~30Pa for 36~60h.

10. The preparation method according to claim 1, characterized in that, The second and third freeze-drying processes both include pre-freezing at -20~-30℃ for 6~12 hours, and then drying at -60~-80℃ with a vacuum degree controlled at 10~30Pa for 12~24 hours.

11. A gel-state lithium-ion adsorbent, characterized in that, It is obtained using the preparation method according to any one of claims 1-10.

12. A method for delithiation of a gel-state lithium-ion adsorbent, characterized in that, The delithiation method includes: The gel-state lithium-ion adsorbent of claim 11, after lithium adsorption, is subjected to acid treatment to obtain Li-containing... + Solution and lithium ion sieve powder; Li-containing + Lithium was extracted from the solution to obtain Li. + Concentrated liquid and waste liquid C; The waste liquid C is neutralized to obtain calcium precipitate and waste liquid D. Waste liquid D was extracted with an organic solvent to separate inorganic salts and organic matter, wherein the organic matter contained alginate and galloyl glucose.

13. The delithiation method according to claim 12, characterized in that, The lithium removal method includes immersing the lithium-adsorbed gel-state lithium-ion adsorbent in a hydrochloric acid solution, ultrasonically degassing it, then shaking it in a shaking chamber at room temperature and centrifuging it to obtain a lithium-containing product. + Solution and lithium ion sieve powder.

14. The delithiation method according to claim 13, characterized in that, The concentration of the hydrochloric acid is 0.2~0.8 mol / L.

15. The delithiation method according to claim 13, characterized in that, The amount of the gel-state lithium-ion adsorbent and hydrochloric acid is controlled according to a solid-liquid ratio of 1g:(80~120)mL.

16. The delithiation method according to claim 12, characterized in that, The lithium extraction methods include membrane separation and / or electrochemical methods.

17. The delithiation method according to claim 12, characterized in that, The neutralization reaction uses sodium bicarbonate to obtain calcium carbonate precipitate, which is then used to prepare calcium chloride solution.

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