Elastic hydrogel type lithium ion adsorbent and preparation method and use thereof

Abstract

The present application provides a kind of elastic hydrogel type lithium ion adsorbent and its preparation method and purposes, the elastic hydrogel type lithium ion adsorbent, by using hierarchical porous carbon of lithium ion sieve load, make hierarchical pore on it and catechol coupling polylysine interact, cause gelation and obtain elastic gel type material.One aspect, the elastic hydrogel product of hierarchical porous carbon lithium ion sieve load has three-dimensional network structure channel to speed up the infiltration of solution, its elastic characteristic has sufficient mechanical strength and can be more flexible to respond to stress under various environments, on the other hand, the physical entanglement provided by the large-area loading of lithium ion sieve and the pore of hierarchical porous carbon synergistic effect, so that lithium ion sieve can be exposed in three-dimensional hole structure and have the advantage of adsorbing lithium, and the combination is closely supported and has excellent stability.

Description

Technical Field

[0001] This invention belongs to the field of lithium resource extraction technology, and relates to an elastic hydrogel type lithium ion adsorbent, its preparation method and application. Background Technology

[0002] With the widespread application of lithium and its compounds in new energy, medicine, catalysts and optoelectronic ceramics, the consumption of lithium resources is growing rapidly. Traditional lithium extraction methods from ore are energy-intensive, have low output and low economic benefits, and are therefore gradually fading out of industrial applications.

[0003] Lithium-bearing water resources are lithium-containing raw materials distinct from traditional ores. They refer to high-lithium-content salt lake brines or seawater. In China, for example, approximately two-thirds of lithium resources are found in lithium-bearing water resources. Lithium-bearing water resources not only have large exploitable reserves but also low extraction costs, making them more suitable for industrial applications and helping to avoid the impact of the depletion of traditional ores. Various methods exist for extracting lithium from lithium-bearing water resources, with common methods including extraction, membrane methods, precipitation, adsorption, and electrochemical methods.

[0004] Among them, the adsorption method refers to the repeated adsorption and desorption of materials (lithium ion adsorbents) with selective adsorption and deintercalation characteristics. It is not only recyclable and inexpensive, but also reduces the introduction of impurities due to the selective adsorption of lithium ions, thus making it a popular research direction.

[0005] Lithium-ion sieves are lithium-ion adsorbents with high adsorption capacity and high selectivity. Currently, lithium-ion sieve materials mainly include three categories: manganese-based lithium-ion sieves (LMO), titanium-based lithium-ion sieves (LTO), and aluminum-based adsorbents (LiAl-LDHs), as well as phosphate, silicate, and antimonate materials.

[0006] However, regardless of the type of lithium-ion sieve, the synthesized products are mostly in powder form, with poor flowability and permeability. They are difficult to distribute evenly during use, and particle recovery is difficult, easily leading to losses. To achieve industrial applications, it is necessary to consider reshaping the ion sieve powder. Currently used shaping methods, such as granulation, film formation, foaming, spinning, or composite carrier methods, inevitably use binders in bonding granulation and solidification film formation, which come into close contact with the ion sieve, thus blocking the contact sites of the adsorbent. Furthermore, bonded granular adsorbents also suffer from insufficient mechanical strength, and the recyclability of composite adsorbents decreases significantly after long-term use.

[0007] Therefore, there is a need in this field to develop a composite lithium-ion sieve adsorbent that possesses high adsorption capacity, industrial applicability, and high stability for long-term use. Summary of the Invention

[0008] In view of the problems existing in the prior art, the purpose of this invention is to provide an elastic hydrogel-type lithium-ion adsorbent, its preparation method, and its uses. The elastic hydrogel-type lithium-ion adsorbent avoids the problem of using electrically insulating binders for granulation in the prior art, and has high adsorption performance and mechanical strength, as well as excellent recyclability.

[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 an elastic hydrogel-type lithium-ion adsorbent, the method comprising:

[0011] Graded porous carbon, lithium ion sieve raw materials and chelating agent are mixed to prepare a first mixture, and the first mixture undergoes a first reaction to generate a precursor.

[0012] The obtained precursor was calcined to generate a lithium-ion sieve, which was then loaded onto the hierarchical porous carbon to obtain a support.

[0013] The support, catechol-conjugated polylysine, and PBS buffer are mixed to form a third mixture, which is then gelled to obtain an elastic hydrogel lithium-ion adsorbent.

[0014] This invention provides an elastic hydrogel based on a hierarchical porous carbon-supported lithium-ion sieve. First, a lithium-ion sieve is loaded onto hierarchical porous carbon. Then, the elastic gel is manufactured by utilizing the pores on the hierarchical porous carbon and the synergistic effect of catechol-mediated adhesion and interlocking. The catechol-coupled polylysine chains first diffuse freely through the pores of the carbon material in a third mixture, generating physical entanglement and providing mutual support. Then, the coupling effect mediated by catechol causes gelation, resulting in a solid state and a strong entanglement of polymers, thereby realizing the transformation from an ordinary gel to an elastic gel, exhibiting good reversible compressibility. Therefore, on the one hand, the elastic hydrogel product of hierarchical porous carbon-supported lithium-ion sieves not only has a three-dimensional network structure that accelerates solution wetting, but its elastic properties also provide sufficient mechanical strength and allow it to more flexibly cope with stress under various environments. On the other hand, the synergistic effect of the hierarchical porous carbon-supported lithium-ion sieves and the physical entanglement provided by their pores allows the lithium-ion sieves to be exposed in the three-dimensional porous structure, which is beneficial for lithium adsorption and deintercalation. Furthermore, the tightly bound structure provides strong support, allowing for compression operations during delithiation to improve lithium extraction efficiency. It is also less prone to irreversible deformation, resulting in excellent lithium extraction stability. In contrast, products that simply disperse lithium extraction materials into catechol-coupled polylysine hydrogels have similar effects, but the effect is weak and the stability is poor.

[0015] 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.

[0016] As a preferred technical solution of the present invention, the method for preparing the hierarchical porous carbon includes mixing wood raw materials with NaClO2 solution and reacting them, and then sequentially carbonizing and activating the reactants to obtain hierarchical porous carbon.

[0017] This invention removes lignin and cellulose from wood raw materials by mixing and reacting them with NaClO2 solution. Utilizing the natural high specific surface area and hierarchical porous framework of wood, fractional porous carbon is prepared during subsequent carbonization and activation. The pores in the fractional porous carbon are preferably predominantly mesopores (5–30 nm in diameter). Pores that are too small are not conducive to the polylysine chains passing through the pores for coupling reactions. Therefore, preferably, the volume of mesopores in the fractional porous carbon accounts for 80% or more of the total pore volume.

[0018] Preferably, the wood raw material includes wood chips.

[0019] Preferably, the concentration of the NaClO2 solution is 0.4 to 0.6 mol / L, such as 0.4 mol / L, 0.43 mol / L, 0.45 mol / L, 0.48 mol / L, 0.5 mol / L, 0.53 mol / L, 0.55 mol / L, 0.58 mol / L, or 0.6 mol / L, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0020] Preferably, the pH of the mixing reaction is 4 to 5, such as 4, 4.2, 4.4, 4.6 or 4.8, the temperature is 100 to 130°C, such as 100°C, 105°C, 110°C, 115°C, 120°C, 125°C or 130°C, and the time is 3 to 5 hours, such as 3 hours, 3.5 hours, 4 hours, 4.5 hours or 5 hours, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0021] Preferably, the reactants are freeze-dried for 12 to 24 hours before carbonization, for example, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours or 24 hours, but not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0022] Preferably, the carbonization method includes heating to 600–1000°C under a protective atmosphere, such as 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, or 1000°C, and holding at that temperature for 2–3 hours, such as 2 hours, 2.3 hours, 2.5 hours, 2.8 hours, or 3 hours, but is not limited to the listed values; other unlisted values ​​within the above range are also applicable.

[0023] Preferably, the activation method includes heating to 800–1000°C under carbon dioxide and / or water vapor, such as 800°C, 850°C, 900°C, 950°C, or 1000°C, and holding at that temperature for 10–30 minutes, such as 10 minutes, 15 minutes, 20 minutes, 25 minutes, or 30 minutes, but is not limited to the listed values; other unlisted values ​​within the above range are also applicable.

[0024] As a preferred technical solution of the present invention, the mass ratio of the lithium ion sieve raw material to the graded porous carbon is (0.3-0.6):1, for example, 0.3:1, 0.35:1, 0.4:1, 0.45:1, 0.5:1, 0.55:1 or 0.6:1, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0025] As a preferred technical solution of the present invention, the amount of lithium source and titanium source is controlled according to the molar ratio of lithium to titanium of 1:(0.4 to 1.5), such as 1:0.4, 1:0.6, 1:0.8, 1:1, 1:1.2 or 1:1.5, etc., but not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0026] Preferably, the mass percentage concentration of the lithium-ion sieve raw material in the first mixture is 5% to 15%, such as 5%, 7%, 9%, 11%, 13%, or 15%, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0027] Preferably, the lithium-ion sieve raw material includes a lithium source and a titanium source.

[0028] It should be noted that, in the preparation method described in this invention, the preferred method for loading lithium-ion sieves onto hierarchical porous carbon is in-situ loading. This involves using a sol-gel method to form a precursor of the lithium-ion sieve metal salt on porous carbon, followed by calcination to obtain the lithium-ion sieve. This preparation method utilizes the excellent adsorption properties of hierarchical porous carbon, ensuring that the lithium-ion sieves are uniformly distributed on the surface without agglomeration, which is beneficial for maintaining sufficient contact with the liquid phase during lithium extraction. If lithium-poor lithium-ion sieve particles are directly used as raw materials, the mixing method in the solution system cannot achieve complete loading onto the porous carbon, and the loading force and contact conditions are not as superior as those of the in-situ loading method.

[0029] Preferably, the lithium source includes at least one of lithium hydroxide, lithium acetate, lithium chloride, or lithium nitrate. Typical but non-limiting combinations include combinations of lithium hydroxide and lithium acetate, aluminum hydroxide and lithium chloride, lithium hydroxide and lithium nitrate, lithium acetate and lithium chloride, or lithium nitrate and lithium chloride.

[0030] Preferably, the titanium source includes at least one of titanium tetrachloride, isobutyl titanate, tetrabutyl titanate, isopropyl titanate, or titanium acetylacetonate. Typical but non-limiting examples include combinations of titanium tetrachloride and isobutyl titanate, combinations of titanium tetrachloride and tetrabutyl titanate, combinations of titanium tetrachloride and isopropyl titanate, combinations of titanium tetrachloride and titanium acetylacetonate, combinations of isobutyl titanate and tetrabutyl titanate, combinations of isobutyl titanate and isopropyl titanate, or combinations of isobutyl titanate and titanium acetylacetonate.

[0031] As a preferred technical solution of the present invention, the mass ratio of the lithium ion sieve raw material to the chelating agent is 1:(0.7~1.1), such as 1:0.7, 1:0.8, 1:0.9, 1:1 or 1:1.1, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0032] Preferably, the chelating agent includes at least one of oxalic acid, acetic acid, or citric acid.

[0033] This invention uses a chelating agent to enable lithium-ion sieve raw materials, such as metallic titanium sources and lithium sources, to react with the chelating agent to form a gel-like precursor. The lithium-ion sieve is then anchored on hierarchical porous carbon using a sol-gel method, forming a highly dispersed, non-agglomerated ion sieve loaded on the hierarchical porous carbon. This increases the reaction contact area between the lithium-ion sieve and the lithium-containing solution, thereby improving lithium extraction performance.

[0034] As a preferred technical solution of the present invention, the temperature of the first reaction is 50 to 85°C, such as 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C or 85°C, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0035] Preferably, the precursor is dried before calcination, and the drying temperature is 80-130°C, such as 80°C, 90°C, 100°C, 110°C, 120°C or 130°C, but not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0036] Preferably, the calcination is carried out under a protective atmosphere, the heating rate of the calcination is 1 to 10 °C / min, for example, 1 °C / min, 3 °C / min, 5 °C / min, 8 °C / min or 10 °C / min, the holding temperature is 400 to 800 °C, for example, 400 °C, 450 °C, 500 °C, 550 °C, 600 °C, 650 °C, 700 °C, 750 °C or 800 °C, and the holding time is 2 to 18 h, for example, 2 h, 4 h, 6 h, 8 h, 10 h, 12 h, 14 h, 16 h or 18 h, but is not limited to the listed values, other unlisted values ​​within the above range are also applicable.

[0037] As a preferred technical solution of the present invention, the method for preparing the catechol-coupled polylysine includes:

[0038] 3,4-Dihydroxyphenylpropionic acid, N-hydroxysuccinimide, and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride were mixed in a second solvent, and then polylysine and triethylamine were added to form a second mixed solution. The second mixed solution was subjected to a second reaction under a protective atmosphere to obtain a precipitate. The precipitate was filtered, washed, purified by dialysis, and freeze-dried to obtain a catechol-coupled polylysine polymer.

[0039] In this invention, 3,4-dihydroxyphenylpropionic acid is the main reactant, possessing a catechol group; N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride are additives in the coupling process, and triethylamine provides an alkaline environment. The aforementioned raw materials, activated by the carbodiimide and N-hydroxysuccinimide in the hydrochloride molecule, form reactive groups that act as crosslinking agents, allowing the reactant 3,4-dihydroxyphenylpropionic acid to react with the amine on the amino acid under alkaline conditions to form stable chemical bonds.

[0040] Preferably, the second solvent comprises N,N-dimethylformamide and dimethyl sulfoxide in a volume ratio of 1:(2-3), such as 1:2, 1:2.2, 1:2.4, 1:2.6, 1:2.8 or 1:3, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0041] Preferably, the molar ratio of 3,4-dihydroxyphenylpropionic acid, N-hydroxysuccinimide, and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride is (0.6–0.8):1:1, for example, 0.6:1:1, 0.63:1:1, 0.65:1:1, 0.68:1:1, 0.7:1:1, 0.72:1:1, 0.75:1:1, 0.77:1:1, or 0.8:1:1, but is not limited to the listed values; other unlisted values ​​within the above range are also applicable.

[0042] Preferably, the concentration of 3,4-dihydroxyphenylpropionic acid in the second mixture is 0.1 to 0.2 mol / L, such as 0.1 mol / L, 0.12 mol / L, 0.14 mol / L, 0.16 mol / L, 0.18 mol / L, or 0.2 mol / L, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0043] Preferably, the molecular weight of the polylysine is 3.5 to 5 kDa, such as 3.5 kDa, 3.8 kDa, 4 kDa, 4.2 kDa, 4.4 kDa, 4.6 kDa, 4.8 kDa or 5 kDa, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0044] Preferably, the mass ratio of polylysine to 3,4-dihydroxyphenylpropionic acid is 5:(0.9 to 1.3), such as 5:0.9, 5:1, 5:1.1, 5:1.2 or 5:1.3, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0045] Preferably, the triethylamine has a mass percentage concentration of 1% to 3% in the mixture, such as 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.6%, 2.8%, or 3%, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0046] Preferably, the holding temperature of the second reaction is 0 to 5°C, such as 0°C, 1°C, 2°C, 3°C, 4°C or 5°C, and the holding time is 12 to 36 hours, such as 12 hours, 18 hours, 22 hours, 24 hours, 26 hours, 28 hours, 30 hours, 32 hours or 36 hours, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0047] Preferably, the dialysis purification time is 12 to 36 hours, such as 12 hours, 18 hours, 22 hours, 24 hours, 26 hours, 28 hours, 30 hours, 32 hours, or 36 hours, 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 pH of the PBS buffer is 7.2 to 7.4, such as 7.2, 7.25, 7.3, 7.35 or 7.4, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0049] Preferably, the gelation molding method includes rotating in a mold for 10 to 18 hours to form the product, for example, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, or 18 hours, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0050] Preferably, the mass percentage concentration of the support in the third mixture is 3% to 9%, such as 3%, 4%, 5%, 6%, 7%, 8%, or 9%, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0051] Preferably, the mass percentage concentration of the catechol-coupled polylysine in the third mixture is 5% to 20%, such as 5%, 7%, 9%, 11%, 13%, 15%, 17%, 18%, or 20%, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0052] As a preferred technical solution of the present invention, the preparation method further includes delithiation treatment of the support or the elastic hydrogel-type lithium-ion adsorbent.

[0053] In this invention, lithium removal can also be achieved by acid washing after obtaining the elastic hydrogel-type lithium-ion adsorbent. The lithium removal effect is not much different from that of acid washing of the support first. The only difference is that the lithium-ion sieve is already encapsulated in the hydrogel, which leads to a reduction in lithium removal time and efficiency.

[0054] Preferably, the method for delithiation includes acid washing.

[0055] Preferably, the pickling includes stirring in 0.4–0.6 mol / L hydrochloric acid, such as 0.4 mol / L, 0.45 mol / L, 0.5 mol / L, 0.55 mol / L, or 0.6 mol / L, at room temperature for 6–18 hours, such as 6 hours, 8 hours, 10 hours, 12 hours, 14 hours, 16 hours, or 18 hours, but is not limited to the listed values; other unlisted values ​​within the above range are also applicable.

[0056] In a second aspect, the present invention provides an elastic hydrogel-type lithium-ion adsorbent, which is obtained according to the preparation method described in the first aspect.

[0057] Thirdly, the present invention provides an application of the elastic hydrogel-type lithium-ion adsorbent described in the first aspect, the application including lithium extraction from salt lakes.

[0058] Compared with existing technical solutions, the present invention has at least the following beneficial effects:

[0059] The elastic hydrogel-type lithium-ion adsorbent of this invention utilizes hierarchical porous carbon loaded with lithium-ion sieves. The hierarchical pores interact with catechol-coupled polylysine, inducing gelation to obtain an elastic gel material. On one hand, the elastic hydrogel product of hierarchical porous carbon loaded with lithium-ion sieves possesses a three-dimensional network structure that accelerates solution wetting. Its elastic properties provide sufficient mechanical strength and allow for more flexible handling of stress under various environments. On the other hand, the synergistic effect of the large-area lithium-ion sieve loaded on the hierarchical porous carbon and the physical entanglement provided by its pores allows the lithium-ion sieves to be exposed in the three-dimensional porous structure, facilitating lithium adsorption and deintercalation. Furthermore, the tightly bound structure provides strong support and excellent stability. Attached Figure Description

[0060] Figure 1 These are recovery curves of the compression rebound height of the lithium-ion adsorbents obtained in Examples 1, 7, and 8 and Comparative Example 1.

[0061] Figure 2 These are stress-strain curves of the lithium-ion adsorbents obtained in Examples 1, 7, and 8 and Comparative Example 1;

[0062] Figure 3 This is a scanning electron microscope image of the graded porous carbon-supported lithium-ion sieve obtained in Example 1. Detailed Implementation

[0063] The technical solution of the present invention will be further illustrated below through specific embodiments.

[0064] 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.

[0065] Example 1

[0066] This embodiment provides a method for preparing an elastic hydrogel-type lithium-ion adsorbent, the preparation method comprising:

[0067] (1) Preparation of hierarchical porous carbon: Take 150 mL of NaClO2 (0.5 mol / L) solution to adjust its pH to 4.5, add 5 g of sawdust and stir at 110 °C for 4 h, filter and wash, freeze dry for 16 h to obtain lignin-free wood, then place it under nitrogen atmosphere and heat at 750 °C for 2 h, and then place it under carbon dioxide atmosphere and keep at 800 °C for 15 min to form hierarchical porous carbon, in which the pore volume with a pore size of 5-50 nm accounts for 84.9% of the total pore volume;

[0068] (2) Graded porous carbon-supported lithium-ion sieve: Graded porous carbon was dispersed in deionized water and sonicated for 30 min. Lithium acetate and tetrabutyl titanate, the raw materials for lithium-ion sieves, were weighed and added to the dispersion of graded porous carbon at a molar ratio of lithium to titanium of 1:1.25. Acetic acid, a chelating agent, was then added. The mass ratio of chelating agent, lithium-ion sieve raw materials, and graded porous carbon was controlled at 0.4:0.5:1 to form the first mixture. The mixture was stirred and heated to 70°C to carry out the first reaction to form a gel-like precursor. The obtained precursor was dried in an oven at 120°C overnight and calcined at 700°C for 6 h under a nitrogen atmosphere to obtain lithium-rich lithium-ion sieve Li4Ti5O supported by graded porous carbon. 12 The resulting supported material was dispersed in 0.5 mol / L dilute hydrochloric acid and stirred at room temperature for 12 h to remove lithium. The mixture was then filtered, washed, and vacuum dried at 60 °C to obtain a hierarchical porous carbon-supported lithium-poor ion sieve, H4Ti5O. 12 , as a support for the delithiation state;

[0069] (3) Synthesis of catechol-coupled polylysine: 3,4-dihydroxyphenylpropionic acid (DA), N-hydroxysuccinimide (NHS) and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC·HCl) were dissolved in a mixed solution of DMF / DMSO with a volume ratio of 1:2 at a molar ratio of 0.65:1:1. The concentration of DA was controlled at 0.15 mol / L. The mixture was stirred overnight in an ice-water bath. Then, polylysine (EPL) with a molecular weight of 4.5 kDa and triethylamine (TEA) were added to form a second mixture. The mass ratio of EPL to DA was controlled at 5:1. The mass percentage concentration of triethylamine in the second mixture was controlled at 1%. The second reaction was carried out for 2 days under N2 atmosphere. The precipitate was filtered, washed and purified by dialysis for 2 days. The catechol-coupled polylysine was obtained by freeze drying.

[0070] (4) Gel formation: Dissolve catechol-coupled polylysine in PBS buffer and mix well. Then add the delithiated support and stir for 30 min to form a third mixture. Control the mass percentage concentration of catechol-coupled polylysine in the third mixture to be 15% and the mass percentage concentration of the delithiated support in the third mixture to be 7%. Place the third mixture in a mold and slowly rotate for 14 h to form the elastic hydrogel lithium ion adsorbent.

[0071] Example 2

[0072] This embodiment provides a method for preparing an elastic hydrogel-type lithium-ion adsorbent. In step (2), the amount of lithium-ion sieve raw material is reduced, and the mass ratio of lithium-ion sieve raw material to graded porous carbon is adjusted from 0.5:1 to 0.25:1. Except for the above, the other conditions are exactly the same as in Example 1.

[0073] Example 3

[0074] This embodiment provides a method for preparing an elastic hydrogel-type lithium-ion adsorbent. In step (2), the amount of lithium-ion sieve raw material is reduced, and the mass ratio of lithium-ion sieve raw material to graded porous carbon is adjusted from 0.5:1 to 0.35:1. Except for the above, the other conditions are exactly the same as in Example 1.

[0075] Example 4

[0076] This embodiment provides a method for preparing an elastic hydrogel-type lithium-ion adsorbent. In step (2), the amount of lithium-ion sieve raw material is increased, and the mass ratio of lithium-ion sieve raw material to graded porous carbon is adjusted from 0.5:1 to 0.55:1. Except for the above, the other conditions are exactly the same as in Example 1.

[0077] Example 5

[0078] This embodiment provides a method for preparing an elastic hydrogel-type lithium-ion adsorbent. In step (2), the amount of lithium-ion sieve raw material is increased, and the mass ratio of lithium-ion sieve raw material to graded porous carbon is adjusted from 0.5:1 to 0.65:1. Except for the above, the other conditions are exactly the same as in Example 1.

[0079] Example 6

[0080] This embodiment provides a method for preparing an elastic hydrogel-type lithium-ion adsorbent. In step (4) of the preparation method, the mass percentage concentration of the delithiated support in the third mixture is adjusted from 7% to 3%. Except for the above, the other conditions are exactly the same as in Example 1.

[0081] Example 7

[0082] This embodiment provides a method for preparing an elastic hydrogel-type lithium-ion adsorbent. In step (4) of the preparation method, the mass percentage concentration of the delithiated support in the third mixture is adjusted from 7% to 4%. Except for the above, the other conditions are exactly the same as in Example 1.

[0083] Example 8

[0084] This embodiment provides a method for preparing an elastic hydrogel-type lithium-ion adsorbent. In step (4) of the preparation method, the mass percentage concentration of the delithiated support in the third mixture is adjusted from 7% to 9%. Except for the above, the other conditions are exactly the same as in Example 1.

[0085] Example 9

[0086] This embodiment provides a method for preparing an elastic hydrogel-type lithium-ion adsorbent. In step (4) of the preparation method, the mass percentage concentration of the delithiated support in the third mixture is adjusted from 7% to 10%. Except for the above, the other conditions are exactly the same as in Example 1.

[0087] Comparative Example 1

[0088] This comparative example provides a method for preparing an elastic hydrogel-type lithium-ion adsorbent, wherein the preparation method does not use hierarchical porous carbon, and the preparation method includes:

[0089] Lithium acetate and tetrabutyl titanate, the raw materials for lithium-ion sieves, were weighed and added to deionized water at a lithium to titanium molar ratio of 1:1.25. Acetic acid, a chelating agent, was then added, maintaining a chelating agent to lithium-ion sieve raw material mass ratio of 0.8:1 to form a first mixture. The mixture was stirred and heated to 70°C to initiate a first reaction, forming a gel-like precursor. The resulting precursor was dried overnight in a 120°C oven and calcined at 700°C for 6 hours under a nitrogen atmosphere to obtain a fractionated porous carbon-supported lithium-rich lithium-ion sieve, Li₄Ti₅O. 12 The resulting support was dispersed in 0.5 mol / L dilute hydrochloric acid and stirred at room temperature for 12 h to remove lithium. The solution was then filtered, washed, and vacuum dried at 60 °C to obtain lithium-poor ion sieve H4Ti5O. 12 ;

[0090] The method for synthesizing catechol coupled with polylysine is the same as step (3) in Example 1;

[0091] The catechol-coupled polylysine was dissolved in PBS buffer and mixed evenly. Then, lithium-depleted ion sieves were added and stirred for 30 minutes to form a third mixture. The mass percentage concentration of catechol-coupled polylysine in the third mixture was controlled at 15%, and the mass percentage concentration of lithium-depleted ion sieves in the third mixture was controlled at 7%. The third mixture was placed in a mold and slowly rotated for 14 hours to form an elastic hydrogel-type lithium ion adsorbent.

[0092] Comparative Example 2

[0093] This comparative example provides a method for preparing a lithium-ion adsorbent. The preparation method does not use catechol coupled with polylysine to prepare an elastic gel. That is, the preparation method only performs steps (1) and (2) in Example 1, and the delithiated support obtained in step (2) is used for subsequent testing.

[0094] Comparative Example 3

[0095] This comparative example provides a method for preparing an elastic hydrogel-type lithium-ion adsorbent, wherein the preparation method yields hierarchical porous carbon and delithiated lithium-ion sieves, respectively. The preparation method includes:

[0096] Take 150 mL of NaClO2 (0.5 mol / L) solution to adjust its pH to 4.5, add 5 g of sawdust and stir at 110 °C for 4 h, filter and wash, freeze dry for 16 h to obtain lignin-free wood, then place it under nitrogen atmosphere and heat at 750 °C for 2 h, and then place it under carbon dioxide atmosphere and keep at 800 °C for 15 min to form hierarchical porous carbon.

[0097] Lithium acetate and tetrabutyl titanate, the raw materials for lithium-ion sieves, were weighed and added to deionized water at a lithium to titanium molar ratio of 1:1.25. Acetic acid, a chelating agent, was then added, maintaining a chelating agent to lithium-ion sieve raw material mass ratio of 0.8:1 to form a first mixture. The mixture was stirred and heated to 70°C to initiate a first reaction, forming a gel-like precursor. The resulting precursor was dried overnight in a 120°C oven and calcined at 700°C for 6 hours under a nitrogen atmosphere to obtain a fractionated porous carbon-supported lithium-rich lithium-ion sieve, Li₄Ti₅O. 12 The resulting support was dispersed in 0.5 mol / L dilute hydrochloric acid and stirred at room temperature for 12 h to remove lithium. The solution was then filtered, washed, and vacuum dried at 60 °C to obtain lithium-poor ion sieve H4Ti5O. 12 ;

[0098] The method for synthesizing catechol coupled with polylysine is the same as step (3) in Example 1;

[0099] The catechol-coupled polylysine was dissolved in PBS buffer and mixed evenly. Then, lithium-depleted ion sieves and hierarchical porous carbon were added, with the mass ratio of lithium-depleted ion sieves to hierarchical porous carbon controlled at 0.4:1. The mixture was stirred for 30 min to form a third mixture. The mass percentage concentration of catechol-coupled polylysine in the third mixture was controlled at 15%, and the total mass percentage concentration of lithium-depleted ion sieves and hierarchical porous carbon in the third mixture was controlled at 7%. The third mixture was placed in a mold and slowly rotated for 14 h to form an elastic hydrogel-type lithium-ion adsorbent.

[0100] Comparative Example 4

[0101] This comparative example provides a method for preparing a lithium-ion adsorbent. The porous carbon is prepared by not using carbon dioxide to activate the carbonized wood in step (1), but by directly placing the lignin-free wood under a nitrogen atmosphere and heating it at 750°C for 2 hours to obtain a porous carbon material as a support. The pore volume of 5–50 nm accounts for 62.5% of the total pore volume. Except for the above, all other conditions are exactly the same as in Example 1. Material characterization and performance testing:

[0102] 1. Morphological characteristics: Figure 3 This is a scanning electron microscope (SEM) image of the hierarchical porous carbon-supported lithium-ion sieve obtained in Example 1. As can be seen from the image, H4Ti5O... 12 The particles are uniformly distributed on the surface of the hierarchical porous carbon without agglomeration, with a uniform particle size of about 100 nm.

[0103] 2. Compression Test: A cylindrical gel (12mm diameter, 10mm height) was used to compress at a speed of 30mm / min for each strain (0%–80%). The rebound height after compression was then tested. Figure 1 As shown. The samples were prepared into cylindrical gels with a diameter of 20 mm and a height of 10 mm. The compression speed was 5 mm / min, and each group of samples was repeated 5 times. The compressive stress-strain curves are shown below. Figure 2 As shown.

[0104] 3. Adsorption capacity test: Weigh the lithium-ion sieve adsorbent prepared in the above experiment and disperse it in a lithium-containing solution (Li). + The concentration was 100 mg / L, the solid-liquid ratio was 1 g:100 mL, and the solution was placed on a constant temperature shaker (150 r / min) at 25 °C for 14 h for adsorption. The lithium ion content in the solution was measured, and the adsorption amount was calculated using the formula shown below:

[0105]

[0106] Q e (mg / g) represents the equilibrium adsorption capacity, C0 and C e Li +The initial and equilibrium concentrations (in mg / L) are given, V (in L) is the volume of the mixed solution, and m (in g) is the mass of the lithium-ion adsorbent.

[0107] 4. Adsorption capacity retention test: Repeat the adsorption-acid washing step 10 times. The acid washing step involves desorbing the adsorbed lithium ion sieve in a constant temperature shaker at 25℃ (150r / min) with 0.5mol / L HCl for 8 hours. The adsorption capacity obtained after the 10th cycle of adsorption is measured as a percentage of the first adsorption capacity.

[0108] Table 1

[0109]

[0110] From the above results, we can conclude that:

[0111] A comparison of Examples 1 and 2-5 shows that the total mass of the titanium / manganese source and the mass ratio of the hierarchical porous carbon affect the adsorption performance of the product. When the total mass ratio of the titanium / manganese source is too low, the proportion of active material is low, and the adsorption capacity of the product is low. When the total mass ratio of the titanium / manganese source is too high, the loading level of the hierarchical porous carbon is limited, which cannot achieve the purpose of highly uniformly dispersing lithium ions, affecting the contact area of ​​the lithium-containing solution and thus affecting the adsorption performance.

[0112] Comparing Examples 1 and 6-9, the loading amount of the support affects the adsorption performance of the product. When the loading amount is low, there is less porous material, and not enough polymer can pass through the pores to form physical entanglement, resulting in poor mechanical properties. When the loading amount of the support is high, there will be excess porous carbon that cannot form physical entanglement and is just a simple hydrogel composite, resulting in poor compressive stress and deformation stress.

[0113] Comparing Example 1 with Comparative Examples 1-4, Comparative Example 1, lacking hierarchical porous carbon, exhibited the worst compressive stress-strain and deformation resilience when directly composited with the hydrogel using a lithium-ion sieve. In Comparative Example 3, where hierarchical porous carbon and the lithium-ion sieve were composited as two independent materials within the hydrogel, the compressive stress was better than in Comparative Example 1, demonstrating that the presence of hierarchical porous carbon helps improve the mechanical properties of the hydrogel. The lower adsorption capacity is due to the mixed presence of the ion sieve and hydrogel, leading to some adsorption sites being blocked. In Comparative Example 4, when the 5-50 nm pore volume in the hierarchical porous carbon accounted for less than 80% of the total volume, the compressive stress also decreased. This is because when the amount of mesoporous pores in the hierarchical porous carbon material is insufficient, the polylysine chains cannot pass through enough pores to physically entangle, resulting in insufficient support and reduced stress.

[0114] 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.

[0115] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details of 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.

[0116] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable way without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0117] 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 an elastic hydrogel-type lithium-ion adsorbent, characterized in that, The preparation method includes: A first mixture is prepared by mixing hierarchical porous carbon, lithium ion sieve raw materials and chelating agent, and the first mixture is subjected to a first reaction to generate a precursor; the volume of the mesopores in the hierarchical porous carbon accounts for 80% or more of the total pore volume. The obtained precursor was calcined to generate a lithium-ion sieve, which was then loaded onto the hierarchical porous carbon to obtain a support. The support, catechol-conjugated polylysine, and PBS buffer are mixed to form a third mixture, which is then gelled to obtain an elastic hydrogel lithium-ion adsorbent.

2. The preparation method according to claim 1, characterized in that, The method for preparing the hierarchical porous carbon includes mixing wood raw materials with NaClO2 solution and reacting them, and then sequentially carbonizing and activating the reactants to obtain hierarchical porous carbon.

3. The preparation method according to claim 2, characterized in that, The concentration of the NaClO2 solution is 0.4~0.6 mol / L.

4. The preparation method according to claim 2, characterized in that, The pH of the mixed reaction is 4-5, the temperature is 100-130℃, and the time is 3-5h.

5. The preparation method according to claim 2, characterized in that, Before the carbonization process, the reactants are freeze-dried for 12-24 hours.

6. The preparation method according to claim 2, characterized in that, The carbonization method includes heating to 600~1000℃ and holding at that temperature for 2~3 hours under a protective atmosphere.

7. The preparation method according to claim 2, characterized in that, The activation method includes heating to 800~1000℃ under carbon dioxide and / or water vapor and holding for 10~30 minutes.

8. The preparation method according to claim 1, characterized in that, The mass ratio of the lithium-ion sieve raw material to the graded porous carbon is (0.3~0.6):

1.

9. The preparation method according to claim 1, characterized in that, The mass percentage concentration of the lithium ion sieve raw material in the first mixture is 5% to 15%.

10. The preparation method according to claim 1, characterized in that, The raw materials for the lithium-ion sieve include lithium source and titanium source.

11. The preparation method according to claim 10, characterized in that, The amount of lithium source and titanium source used is controlled according to a molar ratio of lithium to titanium of 1:(0.4~1.5).

12. The preparation method according to claim 10, characterized in that, The lithium source includes at least one of lithium hydroxide, lithium acetate, lithium chloride, or lithium nitrate.

13. The preparation method according to claim 10, characterized in that, The titanium source includes at least one of titanium tetrachloride, isobutyl titanate, tetrabutyl titanate, isopropyl titanate, or titanium acetylacetonate.

14. The preparation method according to claim 1, characterized in that, The mass ratio of the lithium-ion sieve raw material to the chelating agent is 1:(0.7~1.1).

15. The preparation method according to claim 1, characterized in that, The chelating agent includes at least one of oxalic acid, acetic acid, or citric acid.

16. The preparation method according to claim 1, characterized in that, The temperature of the first reaction is 50~85℃.

17. The preparation method according to claim 1, characterized in that, The precursor is dried before calcination, and the drying temperature is 80~130℃.

18. The preparation method according to claim 1, characterized in that, The calcination is carried out under a protective atmosphere, with a heating rate of 1~10℃ / min, a holding temperature of 400~800℃, and a holding time of 2~18h.

19. The preparation method according to claim 1, characterized in that, The method for preparing the catechol-coupled polylysine includes: 3,4-Dihydroxyphenylpropionic acid, N-hydroxysuccinimide, and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride were mixed in a second solvent, and then polylysine and triethylamine were added to form a second mixture. The second mixture was subjected to a second reaction under a protective atmosphere to obtain a precipitate. The precipitate was filtered, washed, dialyzed and purified, and then freeze-dried to obtain a catechol-coupled polylysine polymer.

20. The preparation method according to claim 19, characterized in that, The second solvent comprises N,N-dimethylformamide and dimethyl sulfoxide in a volume ratio of 1:(2~3).

21. The preparation method according to claim 19, characterized in that, The molar ratio of 3,4-dihydroxyphenylpropionic acid, N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride is (0.6~0.8):1:

1.

22. The preparation method according to claim 19, characterized in that, The concentration of 3,4-dihydroxyphenylpropionic acid in the second mixture is 0.1~0.2 mol / L.

23. The preparation method according to claim 19, characterized in that, The molecular weight of the polylysine is 3.5~5kDa.

24. The preparation method according to claim 19, characterized in that, The mass ratio of the polylysine to the 3,4-dihydroxyphenylpropionic acid is 5:(0.9~1.3).

25. The preparation method according to claim 19, characterized in that, The triethylamine has a mass percentage concentration of 1% to 3% in the second mixture.

26. The preparation method according to claim 19, characterized in that, The second reaction is kept at a temperature of 0~5℃ for 12~36h.

27. The preparation method according to claim 19, characterized in that, The dialysis purification time is 12-36 hours.

28. The preparation method according to claim 1, characterized in that, The pH of the PBS buffer is 7.2-7.

4.

29. The preparation method according to claim 1, characterized in that, The gelation molding method includes rotating in a mold for 10-18 hours to form the gel.

30. The preparation method according to claim 1, characterized in that, The mass percentage concentration of the support in the third mixture is 3% to 9%.

31. The preparation method according to claim 1, characterized in that, The catechol-coupled polylysine has a mass percentage concentration of 5% to 20% in the third mixture.

32. The preparation method according to claim 1, characterized in that, The preparation method further includes delithiation treatment of the support or the elastic hydrogel-type lithium-ion adsorbent.

33. The preparation method according to claim 32, characterized in that, The delithiation process includes acid washing.

34. The preparation method according to claim 33, characterized in that, The pickling process includes stirring in 0.4-0.6 mol / L hydrochloric acid at room temperature for 6-18 hours.

35. An elastic hydrogel-type lithium-ion adsorbent, characterized in that, The preparation method according to any one of claims 1-34 is obtained.

36. The use of the elastic hydrogel-type lithium-ion adsorbent according to claim 35, characterized in that, The applications include lithium extraction from salt lakes.

Images