Adsorptive material for extracting lithium, preparation method and application

Abstract

This invention relates to an adsorbent material for lithium extraction, its preparation method, and its application, belonging to the field of new material preparation technology. The preparation method is as follows: (1) a polymer, a photothermal conversion substance, and a lithium adsorbent are added to water. The polymer is a hydrophilic polymer that can form a hydrogel, and a prepolymer solution is obtained. The prepolymer solution is cross-linked and pore-forming to obtain a hydrogel. A metallophenol network with photothermal effect is used to modify a sponge, and then the modified sponge is hydrophobically modified to obtain a hydrophobic sponge. (2) The hydrogel and the hydrophobic sponge are arranged alternately from left to right, and then bound and fixed with a hydrophilic material. The hydrogel is then placed on top of the alternately arranged hydrogel and the hydrophobic sponge to obtain the adsorbent material for lithium extraction. The adsorbent material in this invention has excellent lithium adsorption performance and salt resistance, and has the characteristics of simple process and low cost, making it suitable for large-scale lithium extraction in salt lake water or seawater.

Description

Technical Field

[0001] This invention belongs to the field of new material preparation technology, and more specifically, relates to an adsorbent material for lithium extraction, its preparation method and application. Background Technology

[0002] Lithium, as an energy metal element, holds a crucial strategic position in energy storage materials and clean energy. As one of the core resources for global carbon neutrality, lithium's largest current application is in the power batteries of new energy vehicles. Additionally, lithium has wide applications in aerospace and industry. Statistics show that by 2030, the world will face a 50% lithium resource shortage. How to further develop lithium resources has become a matter of close concern for industry and research. Global lithium reserves are relatively abundant, and their distribution is diverse and widespread. Besides lithium mines, seawater and salt lake brines also contain approximately 60% of lithium resources. In recent years, due to the increasing depletion of solid lithium resources and the advantages of low cost and simple processing methods for lithium extraction from salt lake water, lithium extraction from salt lake brines will become the mainstay of future lithium resource development.

[0003] my country's salt lakes are rich in lithium reserves, accounting for over 83% of the country's total lithium resources. However, compared to salt lakes abroad, my country's salt lake brines have a high magnesium-to-lithium ratio, making the mature salt field concentration and precipitation method unsuitable. Therefore, it is necessary to explore lithium extraction methods from salt lakes that are unique to my country and have a high magnesium-to-lithium ratio. Various methods have been tried to extract lithium from salt lake water, such as chemical precipitation, ion exchange, evaporation concentration, membrane separation, and adsorption. Adsorption is an effective and promising method for selectively extracting lithium resources from salt lake brines with a high magnesium-to-lithium ratio, offering advantages such as simple operation and environmental cleanliness. During the adsorption process, Li... + Li is captured by highly selective adsorbents and desorbed by certain solvents, thereby removing Li + Separation from other coexisting ions. Adsorbents are mainly divided into two categories: inorganic adsorbents and organic adsorbents. Organic adsorbents, due to their high production costs and significant environmental pollution, cannot be used in large-scale industrial production. Therefore, in the last two decades, scholars both domestically and internationally have focused on inorganic adsorbents. Inorganic adsorbents include many types, such as aluminum salt adsorbents, natural minerals and carbon materials, and lithium-ion sieves. These adsorbents have advantages such as high selectivity, stable properties, and simple preparation. Lithium-ion sieves are adsorbents with lithium memory and can be used to extract lithium ions from salt lakes or seawater. The target lithium ion is introduced into an inorganic compound to form a precursor, and then lithium ions are extracted from the precursor using an eluent without changing the crystal structure of the precursor, thus obtaining a lithium-ion sieve adsorbent. The vacancies formed can accommodate radii less than or equal to Li... +Lithium ions are the smallest metal ions, allowing for selective adsorption of lithium. Lithium-ion sieves are considered the most promising lithium-ion adsorption materials due to their low cost, high selectivity, and environmental friendliness. However, the difficulty in recovering nano-lithium-ion sieve powder and the inability to utilize fixed-bed adsorption limit their industrial applications. Furthermore, the hydrophobic and dense structure of lithium-ion sieves restricts adsorption to the surface, rendering internal adsorption sites ineffective, resulting in low adsorption efficiency and slow adsorption rates. Traditional lithium-ion sieve adsorption materials are often processed into large-scale bulk materials or granulated, limiting their adsorption rate and capacity at room temperature. This necessitates additional energy-intensive methods such as mixing and mechanical stirring to achieve lithium-ion enrichment and adsorption. Summary of the Invention

[0004] This invention solves the technical problems of low adsorption efficiency and slow adsorption rate of lithium extraction materials in the prior art. By arranging the photothermal conversion material and the lithium adsorbent in alternating polymer hydrogels and hydrophobic sponges, the present invention prepares an adsorbent material with excellent lithium adsorption performance, overcoming the technical problem of limited lithium extraction rate of existing lithium extraction materials.

[0005] According to a first aspect of the present invention, a method for preparing an adsorbent material for lithium extraction is provided, comprising the following steps: (1) Add a polymer, a photothermal conversion substance and a lithium adsorbent to water, wherein the polymer is a hydrophilic polymer that can form a hydrogel, to obtain a prepolymer solution; after crosslinking and pore formation, the prepolymer solution is used to obtain a hydrogel; the sponge is modified with a metal phenol network with photothermal effect, and then hydrophobically modified to obtain a hydrophobic sponge; wherein the metal phenol network is a network structure formed by the complexation of metal ions and phenolic substances; (2) The hydrogel and hydrophobic sponge obtained in step (1) are arranged alternately in the horizontal direction, then bound with a hydrophilic material, and then the hydrogel obtained in step (1) is placed on the top surface of the alternately arranged hydrogel and hydrophobic sponge to obtain the adsorbent material for lithium extraction.

[0006] Preferably, the alternating hydrogels and hydrophobic sponges are positioned on both sides in the horizontal direction as hydrogels.

[0007] Preferably, the hydrophilic polymer capable of forming a hydrogel is polyvinyl alcohol, sodium alginate, polyacrylamide, polyacrylic acid, or gelatin.

[0008] Preferably, the photothermal conversion material is a carbon material, a photothermal polymer material, or a metal oxide; Preferably, the carbon material is carbon black, graphene, carbon nanotubes, or MXene; the photothermal polymer material is polypyrrole; and the metal oxide is manganese oxide or molybdenum oxide.

[0009] Preferably, the lithium adsorbent is any one of titanium-based lithium ion sieves, manganese-based lithium ion sieves, aluminum-based lithium ion sieves, or doped lithium ion sieves.

[0010] Preferably, the metal ion is Fe. 3+ Al 3+ Cu 2+ Ti 4+ or Ag + The phenolic substances mentioned are tannic acid, gallocatechin, gallic acid esters, or dopamine.

[0011] Preferably, the hydrophobic modification specifically involves immersing the sponge in a hydrophobic modification solution; The hydrophobic modification liquid is octadecyltrimethoxysilane, hexadecyltrimethoxysilane, polydimethylsiloxane, or dodecafluoroheptyl methacrylate.

[0012] According to another aspect of the present invention, an adsorbent material prepared by any one of the methods is provided.

[0013] According to another aspect of the present invention, the adsorbent material is provided for use in lithium extraction from salt lake water or seawater.

[0014] Preferably, the pH of the salt lake water or seawater is alkaline, and the lithium ion concentration in the salt lake water or seawater is 50-300 ppm; Preferably, the pH of the salt lake water or seawater is 8.7-12.6.

[0015] In summary, compared with the prior art, the above-described technical solutions conceived by this invention mainly possess the following technical advantages: (1) This invention provides a method for preparing a lithium-extracting adsorbent material. By alternating the arrangement of a polymer hydrogel and a hydrophobic sponge containing a photothermal conversion material and a lithium adsorbent, the lithium-extracting hydrogel components and the corresponding preparation method are improved. Photothermal conversion material and lithium adsorbent are added to the hydrogel material. Considering that when used in actual application scenarios such as seawater or salt lake water, the evaporator will precipitate salt crystals, causing blockage of water and ion transport channels and evaporator failure, the sponge is modified with a metal phenol network and hydrophobic modification, and the evaporator structure is further designed to achieve salt resistance. The three-dimensional evaporator obtained by this invention overcomes the inherent problems of limited lithium extraction rate and high energy consumption in traditional salt lake lithium extraction methods. Its hydrophilic and three-dimensional porous hydrogel can promote the migration of lithium ions into the material interior, increasing the utilization efficiency of adsorption sites. By utilizing solar energy, an inexhaustible energy source, and combining the advantages of interfacial photothermal, the surface temperature of the three-dimensional evaporator is successfully increased, thereby accelerating the lithium adsorption kinetics and increasing the maximum adsorption capacity. At the same time, during the water evaporation process, the water transport from bottom to top within the hydrogel drives the active diffusion of lithium ions to the adsorbent, achieving active adsorption, thus effectively making up for the shortcomings of the prior art.

[0016] (2) The present invention is an adsorbent material that is made by introducing photothermal material and lithium adsorbent into a hydrogel network; in addition, a metal phenol network and a hydrophobic modifier are introduced to modify the sponge, and the hydrogel and hydrophobic sponge are assembled into a three-dimensional evaporator, which has excellent adsorption performance of lithium in salt lake water or seawater.

[0017] (3) The adsorption material (three-dimensional evaporator) in this invention has excellent lithium adsorption performance, especially in the case of high lithium concentration in salt lake water or seawater, and its alternating hydrophilic and hydrophobic structure design can achieve salt resistance and directional salt crystallization, which can form a joint production chain with seawater desalination, salt field sodium chloride extraction, etc., and improve economic advantages. Attached Figure Description

[0018] Figure 1 SEM image of the lithium-extracting hydrogel prepared in Example 1.

[0019] Figure 2 SEM image of the hydrophobic sponge prepared in Example 1.

[0020] Figure 3 This is a physical image of the three-dimensional evaporator prepared in Example 1.

[0021] Figure 4 XPS comparison images of the hydrogel in the three-dimensional evaporator prepared in Example 1 before and after lithium adsorption.

[0022] Figure 5 A comparison of the saturated adsorption capacity of the three-dimensional evaporator prepared in Example 2 in lithium solutions of different pH values.

[0023] Figure 6 A comparison of the saturated adsorption capacity of the three-dimensional evaporator prepared in Example 3 in lithium solutions of different concentrations.

[0024] Figure 7 The temperature comparison graph of the three-dimensional evaporator prepared in Example 4 under sunlight and dark conditions.

[0025] Figure 8 Evaporation rate of the three-dimensional evaporator prepared in Example 5 when treating 20 wt.% brine. The insets are photographs showing salt precipitation at different treatment times.

[0026] Figure 9 This is a comparison of the lithium extraction performance of the hydrogel portion in the three-dimensional evaporator prepared in Comparative Example 1 with and without the addition of carbon black.

[0027] Figure 10 The evaporation rate of the three-dimensional evaporator prepared for Comparative Example 2 when processing 20 wt.% brine. The inset shows photographs of salt crystals precipitated from the evaporator at different processing times. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0029] This invention discloses an adsorbent material for lithium extraction from salt lake water and its preparation method, comprising the following steps: (1) Add a hydrophilic polymer that can form a hydrogel, a photothermal conversion material, and a lithium adsorbent to deionized water to obtain a polymer aqueous solution; the hydrophilic polymer that can form a hydrogel is any one or any combination of polyvinyl alcohol (PVA), sodium alginate, polyacrylamide (PAM), polyacrylic acid, and gelatin; the photothermal conversion material can be any one of carbon black, graphene, carbon nanotubes, MXene, polypyrrole, and metal oxides (manganese oxide, molybdenum oxide); the lithium adsorbent can be any one of titanium-based lithium ion sieves, manganese-based lithium ion sieves, aluminum-based ion sieves, and doped lithium ion sieves; The prepared prepolymer solution is cross-linked and pore-forming to obtain a hydrogel; pore-forming can be achieved by any method such as gas foaming, freeze-thaw method, or phase separation. The sponge was modified using a metallophenol network with photothermal effect, and then the resulting sponge was immersed in a hydrophobic modification solution to obtain a hydrophobic sponge. (2) A three-dimensional evaporator is formed by alternately stacking the hydrogel obtained in step (1) and the superhydrophobic sponge obtained in step (1), and then binding them with hydrophilic materials (such as hydrophilic cotton thread). Then, a hydrogel is placed vertically on the bound alternating hydrophilic and hydrophobic material structure as a top cover and assembled.

[0030] In some embodiments, in step (1), the mass ratio of the hydrophilic polymer that can form a hydrogel to the deionized water is (5-25):100.

[0031] In some embodiments, in step (1), the photothermal conversion material is any one of carbon black, graphene, carbon nanotubes, MXene, polypyrrole, metal oxides (manganese oxide, molybdenum oxide), etc.; the mass ratio of the photothermal conversion material to the polymer aqueous solution is (1-10):100; the crosslinking agent is any one of glutaraldehyde, boric acid, epichlorohydrin, soluble calcium salt, etc.; the mass ratio of the crosslinking agent to the polymer aqueous solution is (1-5):100; and the crosslinking time is 2-24 hours.

[0032] In some embodiments, in step (1), the lithium adsorbent is any one of titanium-based lithium ion sieve HTO, manganese-based lithium ion sieve HMO, aluminum-based lithium ion sieve HAlO, and doped lithium ion sieve; the mass ratio of the lithium adsorbent to the polymer aqueous solution is (0.5-10):100.

[0033] In some embodiments, the pore-forming method in step (1) can be any one of gas foaming, freeze-thaw method, salting out, or phase separation.

[0034] In some embodiments, in step (1), the sponge can be any one of rubber sponge, polyurethane sponge, or polyether sponge; the metallophenol network is Fe 3+ Al 3+ Cu 2+ Ti 4+ and Ag + A network structure formed by complexing with any one of the metals and phenols, including tannic acid, gallocatechin, gallic acid ester, and dopamine; the hydrophobic modifying agent is any one of octadecyltrimethoxysilane, hexadecyltrimethoxysilane, polydimethylsiloxane, and dodecafluoroheptyl methacrylate, or the sponge is hydrophobically modified by spraying Fe3O4 nanoparticles or nano-TiO2.

[0035] In some embodiments, the hydrophobic modification time is 13-24 h.

[0036] In some embodiments, in step (1), the three-dimensional evaporator may be composed of alternating layers of hydrogel and hydrophobic sponge, each with two, three, four or five layers.

[0037] The three-dimensional evaporator prepared by this invention is used to achieve efficient lithium extraction from salt lake water under sunlight.

[0038] The following are specific embodiments. It should be noted that: 1) The lithium solutions of different concentrations used for lithium adsorption in the following examples were all obtained by diluting a 200 ppm lithium standard solution. Preparation method of 200 ppm lithium standard stock solution: Accurately weigh 122.14 mg of lithium chloride into a 100 mL reagent bottle, stir until completely dissolved, and obtain a lithium standard stock solution with a concentration of 200 ppm, which is ready for use.

[0039] 2) Adsorption capacity determination method: After mixing 100 μL of the test solution and 2900 μL of HNO3 solution with a concentration of 0.1 mol / L evenly, the adsorption capacity is measured by an inductively coupled plasma spectrometer and the adsorption capacity of the adsorbent is calculated according to formula (1).

[0040] (1) In formula (1), Q Adsorption capacity (mg / g); C 0 represents the initial concentration of the lithium solution (mg / L). C The concentration of lithium in the solution after adsorption (mg / L); V The volume of the lithium solution is in L. m The mass (g) of lithium adsorbent in the three-dimensional evaporator.

[0041] Example 1 An adsorbent material for lithium extraction from salt lake water and its preparation method thereof, comprising the following steps: (1) Preparation of hydrogels Weigh 3g of polyvinyl alcohol, 45mg of H2TiO3, and 45mg of carbon black into 27mL of water, add 80μL of glutaraldehyde and 1mL of hydrochloric acid (1.2 mol / L) as crosslinking agents, mix evenly by ultrasonication, and let stand for 18 hours to obtain hydrogel.

[0042] (2) Pore formation of hydrogels Add 15 g of sodium bicarbonate to 85 g of deionized water and stir until homogeneous to obtain a solution. Immerse the resulting hydrogel in a 15 wt.% sodium carbonate solution and stir at 90°C for 3 hours to create pores, then wash with deionized water.

[0043] (3) Preparation of hydrophobic sponges 0.05 g of tannic acid was added to 25 mL of buffer solution (Tris-HCl, pH=8.5), and 5 mL of ethanol containing 0.05 mL of (3-aminopropyl)triethoxysilane was added to the above TA solution. The rubber sponge was placed in the above solution at room temperature for 24 hours, washed with distilled water and ethanol respectively, and then the sample was placed in a 2 mg / mL Fe2(SO4)3 solution for 2 hours to obtain a photothermal sponge. Subsequently, the photothermal sponge was soaked in a solution containing 0.1 g of octadecyltrimethoxysilane, 20 mL of ethanol, and 2 mL of deionized water for 24 hours, and then the sponge was thoroughly washed with ethanol to obtain a hydrophobic sponge.

[0044] (4) Assembly of three-dimensional evaporator Two hydrophobic sponges obtained in step (3) and three hydrogels obtained in step (2) are stacked horizontally alternately and wrapped and fixed with two hydrophilic cotton threads. Then, a piece of hydrogel is placed vertically on the alternating structure of hydrophilic and hydrophobic materials to complete the assembly of the three-dimensional evaporator, and a three-dimensional evaporator for lithium extraction from salt lake water can be obtained.

[0045] Figure 1 SEM images of the prepared hydrogel, such as Figure 1 As shown, the prepared sample has a three-dimensional network structure. The carbon black and lithium-ion sieve nanoparticles attached to the inner wall of the hydrogel network structure prove the successful synthesis of lithium extraction hydrogel. Figure 2 The image shows a SEM image of the prepared superhydrophobic sponge. Figure 3 The image shows the physical model of the prepared three-dimensional evaporator. The prepared three-dimensional evaporator was placed in a lithium solution and irradiated with a xenon lamp for a certain period of time. The hydrogel was then recovered for X-ray photoelectron spectroscopy analysis. Figure 4 The X-ray photoelectron spectra of the prepared lithium-extracting hydrogel before and after lithium adsorption are compared. As can be seen from the figure, the hydrogel has a characteristic Li 1s peak at 56.01 eV after lithium adsorption, indicating that lithium was successfully adsorbed on the sample.

[0046] Example 2 An adsorbent material for lithium extraction from salt lake water and its preparation method thereof, comprising the following steps: (1) Preparation of hydrogels Weigh 3g of polyacrylamide, 45mg of HMn2O4, and 50mg of carbon nanotubes into 27mL of water, add 1mL of N,N-methylenebisacrylamide as a crosslinking agent, irradiate under a 500W UV lamp for 20min, and let stand for 14 hours to obtain a hydrogel.

[0047] (2) Pore formation of hydrogels Add 25 g of sodium citrate to 75 g of deionized water and stir until homogeneous to obtain a solution. Immerse the resulting hydrogel in a 25 wt.% sodium citrate solution for 12 hours to create pores, and then wash with deionized water.

[0048] (3) Preparation of hydrophobic sponges 0.05 g of tannic acid was added to 25 mL of buffer solution (Tris-HCl, pH=8.5), followed by 150 mg of Fe3O4 nanoparticles. The mixture was sonicated for 30 minutes to ensure homogeneity. Dopamine hydrochloride solution (150 mg) was then dissolved in the homogeneous solution. A polyurethane sponge was then immersed in the homogeneous solution and vigorously stirred magnetically at 25 °C for 12 hours. After rinsing with deionized water, the sponge was dried in an oven at 60 °C for 6 hours. Finally, the sponge was immersed in 50 mL of 3 mg / mL solution. -1 A hydrophobic sponge was obtained by placing a solution of heptadecafluorodecyltrimethoxysilane in an ethanol solution at 40°C for 12 hours and then washing it with ethanol.

[0049] (4) Assembly of three-dimensional evaporator Two hydrophobic sponges obtained in step (3) and three hydrogels obtained in step (2) are stacked horizontally alternately and wrapped and fixed with two hydrophilic cotton threads. Then, a piece of hydrogel is placed vertically on the alternating structure of hydrophilic and hydrophobic materials to complete the assembly of the three-dimensional evaporator, and a three-dimensional evaporator for lithium extraction from salt lake water can be obtained.

[0050] This embodiment explores the adsorption performance of a three-dimensional evaporator prepared under pH conditions (8.7-12.6) for lithium. Lithium adsorption test method: A certain amount of 200 ppm LiCl standard solution was taken, and the pH of the lithium solution was adjusted to 8.7, 10, 11, 12, and 12.6 with NaOH / HCl. Then, under simulated sunlight, the prepared three-dimensional evaporator was suspended on the solution through PS foam, and water was transported using water-conducting paper. The solutions before and after adsorption were filtered through a micron-level aqueous phase filter head before and after 10 hours of light exposure. The concentration of lithium in the filtered solution was measured, and the adsorption amount was calculated using formula (1). Figure 5 The figure shows a comparison of the saturated adsorption capacity of the prepared three-dimensional evaporator in lithium solutions at different pH values. It can be seen from the figure that the sample exhibits the best adsorption at a lithium solution pH of 12.0, with an adsorption capacity reaching 93.89 mg·g⁻¹. -1 .

[0051] Example 3 An adsorbent material for lithium extraction from salt lake water and its preparation method thereof, comprising the following steps: (1) Preparation of hydrogels Weigh 3g sodium alginate, 45mg HAl2(OH)7·2H2O, and 50mg carbon black into 27 mL of water. Place the mixture in a -20°C refrigerator for 1 hour, then soak it in 50 mL of 1wt.% calcium chloride solution. After 12 hours, wash with deionized water to obtain a hydrogel.

[0052] (2) Pore formation of hydrogels 25 g of sodium sulfate was added to 75 g of deionized water and stirred until a solution was obtained. The resulting hydrogel was then immersed in a 25 wt.% sodium sulfate solution for 12 hours to create pores, and then washed with deionized water.

[0053] (3) Preparation of hydrophobic sponges 0.05 g of tannic acid was added to 25 mL of buffer solution (Tris-HCl, pH=8.5), and 5 mL of ethanol containing 0.05 mL of (3-aminopropyl)triethoxysilane was added to the above TA solution. The rubber sponge was placed in the above solution at room temperature for 24 hours, washed with distilled water and ethanol respectively, and then the sample was placed in a 2 mg / mL Fe2(SO4)3 solution for 2 hours to obtain a photothermal sponge. Subsequently, the photothermal sponge was soaked in a solution containing 0.1 g of octadecyltrimethoxysilane, 20 mL of ethanol, and 2 mL of deionized water for 24 hours, and then thoroughly washed with ethanol to obtain a hydrophobic sponge.

[0054] (4) Assembly of three-dimensional evaporator Two hydrophobic sponges obtained in step (3) and three hydrogels obtained in step (2) are stacked horizontally alternately and wrapped and fixed with two hydrophilic cotton threads. Then, a piece of hydrogel is placed vertically on the alternating structure of hydrophilic and hydrophobic materials to complete the assembly of the three-dimensional evaporator, and a three-dimensional evaporator for lithium extraction from salt lake water can be obtained.

[0055] This embodiment explores the adsorption performance of lithium by a three-dimensional evaporator prepared under different concentrations of lithium solution (50-250 ppm). Lithium adsorption test method: A certain amount of 200 ppm LiCl standard solution was taken and diluted with deionized water to 50, 100, and 150 ppm respectively, and a new 250 ppm LiCl standard solution was prepared. The pH of the solution was adjusted to 12 with NaOH solution. Then, under simulated sunlight, the prepared three-dimensional evaporator was suspended on the solution through PS foam and water was transported using water-conducting paper. After 10 hours of illumination, the adsorbed solution was filtered through a micron-level aqueous phase filter head. The concentration of lithium in the filtered solution was measured, and the adsorption amount was calculated using formula (1). Figure 6 The figure shows a comparison of the saturated adsorption capacity of the prepared three-dimensional evaporator in lithium solutions of different concentrations. It can be seen from the figure that the sample exhibits the best adsorption at a lithium solution concentration of 250 ppm, with an adsorption capacity reaching 86.53 mg·g⁻¹.-1 .

[0056] Example 4 An adsorbent material for lithium extraction from salt lake water and its preparation method thereof, comprising the following steps: (1) Preparation of hydrogels Weigh 3g PVA, 50 mg HAlTiO4, and 40 mg carbon black into 27 mL of water, add 100 μL boric acid as a crosslinking agent, mix evenly by ultrasonication, and let stand for 16 hours to obtain a porous hydrogel.

[0057] (2) Pore formation of hydrogels The hydrogel obtained in step (1) was frozen in a -20 °C refrigerator for 12 hours and then left at room temperature for 12 hours. This process was repeated three times to obtain a porous hydrogel.

[0058] (3) Preparation of hydrophobic sponges 0.05 g of tannic acid was added to 25 ml of buffer solution (Tris-HCl, pH=8.5), and 5 ml of ethanol containing 0.05 ml of (3-aminopropyl)triethoxysilane was added to the above TA solution. The rubber sponge was placed in the above solution at room temperature for 24 hours, washed with distilled water and ethanol respectively, and then the sample was placed in a 2 mg / mL Fe2(SO4)3 solution for 2 hours to obtain a photothermal sponge. Subsequently, the photothermal sponge was soaked in a solution containing 0.1 g of hexadecyltrimethoxysilane, 20 ml of ethanol, and 2 ml of deionized water for 24 hours, and then the sponge was thoroughly washed with ethanol to obtain a hydrophobic sponge.

[0059] (4) Assembly of three-dimensional evaporator Two hydrophobic sponges obtained in step (3) and three hydrogels obtained in step (2) are stacked horizontally alternately and wrapped and fixed with two hydrophilic cotton threads. Then, a piece of hydrogel is placed vertically on the alternating structure of hydrophilic and hydrophobic materials to complete the assembly of the three-dimensional evaporator, and a three-dimensional evaporator for lithium extraction from salt lake water can be obtained.

[0060] Figure 7 The high solar energy absorption capacity of the three-dimensional evaporator results in a significant temperature increase under one sun.

[0061] Example 5 An adsorbent material for lithium extraction from salt lake water and its preparation method thereof, comprising the following steps: (1) Preparation of hydrogels Weigh out 3g of polyvinyl alcohol and 50mg of H4TiO. 12 45 mg of carbon black was added to 27 mL of water, along with 80 μL of glutaraldehyde and 1 mL of hydrochloric acid (1.2 mol / L) as a crosslinking agent. The mixture was ultrasonically mixed and allowed to stand for 16 hours to obtain a hydrogel.

[0062] (2) Pore formation of hydrogels Add 15g of sodium bicarbonate to 85g of deionized water and stir until homogeneous to obtain a solution. Immerse the resulting hydrogel in a 15wt.% sodium carbonate solution and stir at 90°C for 3 hours to create pores, then wash with deionized water.

[0063] (3) Preparation of hydrophobic sponges 0.05 g of tannic acid was added to 25 mL of buffer solution (Tris-HCl, pH=8.5), and 5 mL of ethanol containing 0.05 mL of (3-aminopropyl)triethoxysilane was added to the above TA solution. The rubber sponge was placed in the above solution at room temperature for 24 hours, washed with distilled water and ethanol respectively, and then the sample was placed in a 2 mg / mL Fe2(SO4)3 solution for 2 hours to obtain a photothermal sponge. Subsequently, the photothermal sponge was soaked in a solution containing 0.1 g of hexadecyltrimethoxysilane, 20 mL of ethanol, and 2 mL of deionized water for 24 hours, and then thoroughly washed with ethanol to obtain a hydrophobic sponge.

[0064] (4) Assembly of three-dimensional evaporator Two hydrophobic sponges obtained in step (3) and three hydrogels obtained in step (2) are stacked horizontally alternately and wrapped and fixed with two hydrophilic cotton threads. Then, a piece of hydrogel is placed vertically on the alternating structure of hydrophilic and hydrophobic materials to complete the assembly of the three-dimensional evaporator, and a three-dimensional evaporator for lithium extraction from salt lake water can be obtained.

[0065] Figure 8 The evaporation rate of the prepared three-dimensional evaporator when treating a 20 wt.% NaCl solution was determined. Under solar irradiation, the water evaporation rate of the 20 wt% NaCl solution reached approximately 2.9 kg m³. -2 h -1 Salts gradually and selectively crystallize on the side line of the superhydrophobic sponge, rather than on the top surface or inside the evaporator.

[0066] Comparative Example 1 In Example 1, step (1) is modified so that carbon black is not added; otherwise, the steps remain the same as in Example 1. Figure 9 In the sample obtained without adding carbon black, there is no photothermal conversion capability and the lithium adsorption performance is reduced.

[0067] Comparative Example 2 In step (3) of Example 5, cetyltrimethoxysilane was not added; otherwise, it remained the same as in Example 2. The final sample had no salt resistance.

[0068] This comparative example investigated the effect of introducing a hydrophobic sponge into the structure on its salt resistance. Example 5 used the same light irradiation method as Comparative Example 2. In Example 5, the salt gradually and selectively crystallized along the side line in contact with the superhydrophobic sponge, rather than on the top surface or inside the evaporator. This directional crystallization of the salt provided sufficient space on the side surface of the evaporator for water vapor to escape, thus maintaining a high and stable water evaporation rate over a long period. Conversely, Figure 10 In Comparative Example 2, the three-dimensional evaporator, composed only of hydrophilic hydrogel and superhydrophilic sponge, was completely covered by salt crystals, resulting in a severe decrease in water evaporation rate. Figure 10 This visually demonstrates that a single hydrophilic three-dimensional structure does not exhibit significant salt resistance.

[0069] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing an adsorbent material for lithium extraction, characterized in that, Includes the following steps: (1) Add a polymer, a photothermal conversion substance and a lithium adsorbent to water, wherein the polymer is a hydrophilic polymer that can form a hydrogel, to obtain a prepolymer solution; after crosslinking and pore formation, the prepolymer solution is used to obtain a hydrogel; the sponge is modified with a metal phenol network with photothermal effect, and then hydrophobically modified to obtain a hydrophobic sponge; wherein the metal phenol network is a network structure formed by the complexation of metal ions and phenolic substances; (2) The hydrogel and hydrophobic sponge obtained in step (1) are arranged alternately in the horizontal direction, then bound with a hydrophilic material, and then the hydrogel obtained in step (1) is placed on the top surface of the alternately arranged hydrogel and hydrophobic sponge to obtain the adsorbent material for lithium extraction.

2. The method for preparing the adsorbent material for lithium extraction as described in claim 1, characterized in that, The alternating hydrogels and hydrophobic sponges are located on both sides in the horizontal direction of the hydrogel.

3. The method for preparing the adsorbent material for lithium extraction as described in claim 1, characterized in that, The hydrophilic polymer that can form a hydrogel is polyvinyl alcohol, sodium alginate, polyacrylamide, polyacrylic acid, or gelatin.

4. The method for preparing the adsorbent material for lithium extraction as described in claim 1, characterized in that, The photothermal conversion material is a carbon material, a photothermal polymer material, or a metal oxide.

5. The method for preparing the adsorbent material for lithium extraction as described in claim 4, characterized in that, The carbon material is carbon black, graphene, or carbon nanotubes; the photothermal polymer material is polypyrrole; and the metal oxide is manganese oxide or molybdenum oxide.

6. The method for preparing the adsorbent material for lithium extraction as described in claim 1, characterized in that, The lithium adsorbent is any one of titanium-based lithium ion sieves, manganese-based lithium ion sieves, or aluminum-based ion sieves.

7. The method for preparing the adsorbent material for lithium extraction as described in claim 1, characterized in that, The metal ion is Fe. 3+ Al 3+ Cu 2+ Ti 4+ or Ag + The phenolic substances mentioned are tannic acid, gallocatechin, gallic acid esters, or dopamine.

8. The method for preparing the adsorbent material for lithium extraction as described in claim 1, characterized in that, The hydrophobic modification specifically involves immersing the sponge in a hydrophobic modification solution; The hydrophobic modification liquid is octadecyltrimethoxysilane, hexadecyltrimethoxysilane, polydimethylsiloxane, or dodecafluoroheptyl methacrylate.

9. The adsorbent material prepared by any one of claims 1-8.

10. The adsorbent material as described in claim 9 is used for lithium extraction from salt lake water or seawater.

11. The application as described in claim 10, characterized in that, The pH of the salt lake water or seawater is alkaline, and the lithium ion concentration in the salt lake water or seawater is 50-300 ppm.

12. The application as described in claim 11, characterized in that, The pH of the salt lake water or seawater is 8.7-12.6.

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