A high-swelling lithium ion sieve composite hydrogel, a preparation method thereof and application thereof in seawater lithium extraction

Abstract

This invention belongs to the field of polymer material preparation technology. To address the problems of existing lithium-ion sieves being powdery, difficult to recycle, and having low adsorption rates, this invention provides a highly swellable lithium-ion sieve composite hydrogel, its preparation method, and its application in seawater lithium extraction. Manganese carbonate and lithium carbonate are mixed and heat-treated in high-temperature air to obtain lithium manganese oxide. A solution A is obtained by mixing polyvinyl alcohol solution, acrylamide, methylenebisacrylamide, and lithium manganese oxide. An ammonium persulfate solution is then prepared and added to solution A to react and obtain a precursor-encapsulated LMO composite hydrogel, LMO@PPH. This hydrogel is then immersed in hydrochloric acid solution and rinsed with deionized water to obtain the lithium-ion sieve composite hydrogel, HMO@PPH. At room temperature, 40% HMO@PPH exhibits an adsorption content of 25.01 mg / g in an initial concentration of 25 ppm LiCl solution, demonstrating high selectivity. Even after five adsorption-desorption cycles, it still retains high adsorption capacity.

Description

A highly swellable lithium-ion sieve composite hydrogel, its preparation method, and its application in seawater lithium extraction. Technical Field

[0001] This invention belongs to the field of polymer material preparation technology, specifically relating to a highly swellable lithium-ion sieve composite hydrogel, its preparation method, and its application in seawater lithium extraction. For the complex natural solution system of seawater, a method using Li-based lithium sieves is proposed. 1.33 Mn 1.67 O4 as Li + Imprinting sites were selected, and highly swellable porous lithium-ion sieve composite hydrogels HMO@PPH were prepared using different substrate materials and simple synthesis methods. Background Technology

[0002] In recent years, lithium has been widely used in ceramics, glass, rechargeable lithium batteries, nuclear fusion fuels, and energy storage materials. However, with increasing demand, meeting the supply of lithium resources has become a significant challenge. According to relevant research, lithium resources mainly originate from ores, salt lakes, and seawater. Seawater contains a particularly large amount of lithium. + High content, but low concentration; at the same time, seawater also contains a large amount of coexisting alkali metal ions (Na+). + K + Ca 2+ Mg 2+ This gives us a way to extract Li + This has brought enormous difficulties. HMO-based lithium-ion sieves, with their excellent lithium selectivity and high lithium adsorption capacity, have become one of the most popular lithium adsorbents. Although HMOs have significant advantages in lithium... + It exhibits excellent selectivity, but there are some problems that limit its practical application when extracting lithium using physical methods, such as: ① significant Mn loss during acid leaching; ② easy loss of powder during adsorption; ③ long adsorption time, etc. Summary of the Invention

[0003] To address the problems of existing lithium-ion sieves being powdery, difficult to recycle, and having low adsorption rates, this invention provides a highly swellable lithium-ion sieve composite hydrogel, its preparation method, and its application in seawater lithium extraction.

[0004] This invention is achieved by the following technical solution: a method for preparing a highly swellable lithium-ion sieve composite hydrogel, comprising: mixing manganese carbonate (MnCO3) and lithium carbonate (Li2CO3) in a molar ratio and then heat-treating them in high-temperature air to obtain the precursor lithium manganese oxide (LMO); preparing a polyvinyl alcohol (PVA) solution, and then mixing the PVA solution, acrylamide (AM), methylenebisacrylamide (MBA), and different amounts of LMO to obtain solution A; preparing an ammonium persulfate (APS) solution, and adding it to solution A to react and obtain the precursor, which is the LMO-encapsulated composite hydrogel LMO@PPH; immersing the prepared LMO-encapsulated composite hydrogel LMO@PPH in a hydrochloric acid (HCl) solution, and then rinsing it with deionized water to obtain the lithium-ion sieve composite hydrogel HMO@PPH.

[0005] The specific method includes the following steps:

[0006] (1) Preparation of lithium manganese oxide (LMO): Manganese carbonate (MnCO3) and lithium carbonate (Li2CO3) were mixed according to a Li / Mn molar ratio of 1.33:1.67 and heat-treated in air at 500°C for 4 h to obtain lithium manganese oxide (LMO).

[0007] (2) Preparation of HMO nanoparticles: The lithium manganese oxide (LMO) obtained in step (1) was acid-washed with 0.5M HCl solution for 24h, washed with deionized water until the pH was neutral, and then the material was dried at 60℃ to prepare HMO nanoparticles.

[0008] (3) Preparation of LMO@PPH composite hydrogel encapsulating LMO: Polyvinyl alcohol PVA was dissolved in deionized water, swollen at 60℃ for 1h, and then dissolved at 90℃ for 1h to obtain a polyvinyl alcohol PVA solution with a mass concentration of 5%.

[0009] Add 0.5-1g of acrylamide AM, 0.015-0.030g of methylenebisacrylamide MBA and 0.5-1mL of deionized water to the obtained polyvinyl alcohol PVA solution (1.5-3g). Stir at room temperature for 1h, then add LMO obtained in step (1). The amount of LMO added is 40% of the mass of LMO / hydrogel. Stir at room temperature for 1h until the bubbles disappear to obtain solution A.

[0010] Solution B is prepared by dissolving 30-150 mg of ammonium persulfate (APS) in 0.5-2.5 mL of deionized water.

[0011] Add 0.5 ml of solution B to solution A with stirring, and stir at room temperature for 10-20 min to fully dissolve it in solution A; react at 50℃ for 6-8 h, and then soak it in deionized water for 36-48 h to obtain the composite hydrogel LMO@PPH encapsulated with LMO;

[0012] (3) Preparation of lithium ion sieve composite hydrogel HMO@PPH: The prepared LMO-encapsulated composite hydrogel LMO@PPH was soaked in 0.5M HCl solution for 36-48h, and then rinsed with deionized water to obtain lithium ion sieve composite hydrogel HMO@PPH.

[0013] This invention provides a highly swellable lithium-ion sieve composite hydrogel HMO@PPH prepared by the method described above.

[0014] This invention also provides the application of the lithium-ion sieve composite hydrogel HMO@PPH in seawater lithium extraction, specifically, the method being: preparing hydrogels of the same concentration containing different ions (Li... + Na + Ca 2+ K + Mg 2+ The coexisting ion solution was subjected to oscillation adsorption in a constant temperature shaker at 25℃ and a rotation speed of 150 rpm. The lithium ion concentration in the solution at different times was determined by inductively coupled plasma optical emission spectrometry (ICP-OES).

[0015] This invention yields a highly swollen, regenerable lithium-ion sieve composite hydrogel, and investigates the adsorption of Li from LiCl solution and solutions with different coexisting ions. + The results showed that the addition of LMO increased the swelling capacity of the hydrogel, thereby regulating the pore structure. This exposed the vast majority of Li through abundant pores and extremely high swelling properties. + At room temperature, the adsorption content of 40% lithium ion sieve composite hydrogel HMO@PPH can reach up to 27.88 mg / g in an initial concentration of 25 ppm LiCl solution. In addition, lithium ion sieve composite hydrogel HMO@PPH has high selectivity and still has high adsorption capacity after 5 adsorption-desorption cycles. Attached Figure Description

[0016] Figure 1 shows the SEM images of the three-dimensional porous composite hydrogel LMO@PPH with 40% LMO encapsulation and the composite hydrogel HMO@PPH with 40% lithium ion sieve.

[0017] Figure 2 shows the EDS images of the composite hydrogel LMO@PPH with 40% LMO encapsulation and the composite hydrogel HMO@PPH with 40% lithium ion sieve.

[0018] Figure 3 shows a photograph of the 40% lithium ion sieve composite hydrogel HMO@PPH.

[0019] Figure 4 shows the curves of lithium ion adsorption capacity of HMO particles and HMO@PPH composite hydrogels with different lithium ion sieve contents as a function of concentration.

[0020] Figure 5 shows the cycling performance of the 40% lithium ion sieve composite hydrogel HMO@PPH;

[0021] Figure 6 shows the selectivity of the 40% lithium ion sieve composite hydrogel HMO@PPH. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains, and all materials publicly cited herein and cited by them are incorporated herein by reference.

[0024] Equivalent technologies of the specific embodiments described herein that are readily apparent to those skilled in the art through routine experimentation are included in this application.

[0025] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the instruments and equipment used in the following examples are all standard laboratory instruments and equipment; unless otherwise specified, the experimental materials used in the following examples were all purchased from regular biochemical reagent stores.

[0026] Example 1: This embodiment describes a method for preparing an HMO@PPH composite material for lithium extraction from seawater. Manganese carbonate (MnCO3) and lithium carbonate (Li2CO3) are mixed in a specific molar ratio and then heat-treated in high-temperature air to obtain lithium manganese oxide (LMO). A polyvinyl alcohol (PVA) solution is prepared, and then PVA, acrylamide (AM), methylenebisacrylamide (MBA), and a certain amount of LMO are mixed. After the bubbles disappear, solution A is obtained. Next, an ammonium persulfate (APS) solution is prepared and added to solution A, and the reaction is carried out under specific conditions. The prepared LMO-encapsulated composite hydrogel LMO@PPH is immersed in an HCl solution and then rinsed with deionized water to obtain a lithium-ion sieve composite hydrogel HMO@PPH.

[0027] The specific steps are as follows:

[0028] (1) Li 1.33 Mn 1.67Preparation of O4: A mixture of manganese carbonate (MnCO3) and lithium carbonate (Li2CO3) was heat-treated in air at 500°C for 4 hours under the condition that the Li / Mn molar ratio was 1.33:1.67 to prepare lithium manganese oxide (LMO) powder.

[0029] (2) Preparation of HMO nanoparticles: The lithium manganese oxide (LMO) obtained in step (1) was acid-washed with 0.5M HCl solution for 24h, washed with deionized water until the pH was neutral, and then the material was dried at 60℃ to prepare HMO nanoparticles.

[0030] (3) Preparation of LMO@PPH composite hydrogel encapsulated with LMO: First, prepare a 5% polyvinyl alcohol (PVA) solution (PVA is dissolved in deionized water, swells at 60℃ for 1h, and then dissolves at 90℃ for 1h); take 1.5-3g of 5wt% polyvinyl alcohol PVA solution, add 0.5-1g of acrylamide (AM), 0.015-0.030g of methylenebisacrylamide (MBA) and 0.5-1mL of deionized water, stir at room temperature for 1h, then add LMO powder, the mass ratio of LMO powder to LMO-encapsulated composite hydrogel is 0.4:1.0. Stir at room temperature for 1h until the bubbles disappear, to obtain solution A;

[0031] Then, 30-150 mg of ammonium persulfate (APS) was dissolved in 0.5-2.5 mL of deionized water, referred to as solution B. Then, 0.5 mL of solution B was added to solution A with stirring, and the mixture was stirred at room temperature for 10-20 min to ensure complete dissolution in solution A. The reaction was carried out at 50 °C for 6-8 h. The prepared LMO-encapsulated composite hydrogel LMO@PPH was then immersed in deionized water for 36-48 h to obtain the LMO-encapsulated composite hydrogel LMO@PPH.

[0032] (4) Preparation of lithium ion sieve composite hydrogel HMO@PPH: The prepared LMO-encapsulated composite hydrogel LMO@PPH was soaked in 0.5M HCl solution for 36-48h, and then rinsed with deionized water to obtain lithium ion sieve composite hydrogel HMO@PPH.

[0033] The 40% lithium ion sieve composite hydrogel HMO@PPH exhibits excellent adsorption capacity in lithium chloride solution. At room temperature and an initial concentration of 25 ppm, the adsorption capacity of the 40% lithium ion sieve composite hydrogel HMO@PPH is 27.88 mg / g, which exceeds the adsorption capacity of HMO particles (20.07 mg / g).

[0034] Example 2: In this example, the mass ratio of LMO powder to the composite hydrogel encapsulating LMO is 0.07:0.67, and other parameters are the same as in Example 1. In this example, the adsorption capacity of the lithium ion sieve composite hydrogel HMO@PPH reaches 27.49 mg / g.

[0035] Example 3: In this example, the mass ratio of LMO powder to the composite hydrogel encapsulating LMO is 0.15:0.75, and other parameters are the same as in Example 1. In this example, the adsorption capacity of the lithium ion sieve composite hydrogel HMO@PPH reaches 26.38 mg / g.

[0036] Example 4: In this example, the mass ratio of LMO powder to the composite hydrogel encapsulating LMO is 0.26:0.86, and other parameters are the same as in Example 1. In this example, the adsorption capacity of the lithium ion sieve composite hydrogel HMO@PPH reaches 25.84 mg / g.

[0037] Example 5: In this example, the mass ratio of LMO powder to the composite hydrogel encapsulating LMO is 0.60:1.20, and other parameters are the same as in Example 1. In this example, the adsorption capacity of the lithium ion sieve composite hydrogel HMO@PPH reaches 24.85 mg / g.

[0038] The resulting composite materials were tested. Figure 1 shows the SEM images of the 40% LMO-encapsulated composite hydrogel LMO@PPH and the 40% lithium ion sieve composite hydrogel HMO@PPH. The results indicate that the addition of LMO followed by acid washing makes the pores of the material more uniform and the swelling effect of the material before acid washing more obvious, which is beneficial to Li + Uniform exposure of adsorption sites, which is beneficial to Li ＋ De-embedding;

[0039] Figure 2 shows the energy dispersive spectroscopy (EDS) mapping of the composite hydrogel LMO@PPH with 40% LMO encapsulation and the composite hydrogel HMO@PPH with 40% lithium ion sieve. The EDS mapping revealed the presence of elements such as Mn, N and O, which confirms that LMO and HMO are uniformly dispersed in the hydrogel.

[0040] Figure 3 shows a photograph of the composite hydrogel LMO@PPH with 40% LMO encapsulation, which demonstrates that the material has good swelling properties in water.

[0041] Figure 4 shows the lithium-ion adsorption capacity of HMO@PPH, a lithium-ion sieve composite hydrogel obtained by acid washing of HMO particles, pure hydrogel, and composite hydrogels with different LMO contents, as a function of concentration. As can be seen from the figure, the adsorption capacity gradually increases with the addition of LMO. Moreover, the adsorption capacity of 40% lithium-ion sieve composite hydrogel HMO@PPH is much greater than that of HMO particles (at an initial concentration of 25 ppm at room temperature, the adsorption capacity of HMO particles is 20.07 mg / g, while that of 40% lithium-ion sieve composite hydrogel HMO@PPH is 27.88 mg / g). Therefore, this composite material solves both the problem of adsorption capacity and the problem of powder being difficult to recycle.

[0042] Figure 5 shows the cycling performance of the 40% lithium-ion sieve composite hydrogel HMO@PPH. It can be seen that Li... + The adsorption retention is relatively high. The lithium ion adsorption capacity increases slowly from the first cycle to the fourth cycle, and only decreases in the fifth cycle. Therefore, the 40% lithium ion sieve composite hydrogel HMO@PPH has excellent cycle stability.

[0043] Figure 6 shows the selectivity of 40% lithium-ion sieve composite hydrogel HMO@PPH for different coexisting ions. As shown in Figure 6, the lithium ion extraction capacity of 40% lithium-ion sieve composite hydrogel HMO@PPH in solutions of different coexisting ions at the same concentration is 4.136 mmol g. -1 It is far higher than that of other metal ions.

[0044] Therefore, the results show that the 40% lithium-ion sieve composite hydrogel HMO@PPH can be subjected to Li ionization in different coexisting ion solutions. + It has great potential for application in the selective separation of Li. Various Li-Mn-O ion sieves have significant potential for Li... + The adsorption performance of the adsorption products is compared in Table 1.

[0045] Table 1: Ion sieves of various Li-Mn-O systems for Li + Adsorption performance comparison

[0046]

[0047] The table above provides a statistical comparison of gels and membranes in the same field. The results show that the composite hydrogel prepared by this invention has the highest adsorption capacity, demonstrating the advanced nature of the hydrogel prepared by this invention.

[0048] References:

[0049] [1] Meng, Z.; Wang, M.; Cao, X.; Wang, T.; Wang, Y.; Xu, Y.; Liu, W.;Chen, L.; Huang, Y.; Liu, X., Highly flexible interconnected Li + ion-sieveporous hydrogels with self-regulating nanonetwork structure for marinelithium recovery. Chem. Eng. J. 2022, 445, 136780.

[0050] [2] H.-J. Hong, I.-S. Park, T. Ryu, J. Ryu, B.-G. Kim, K.-S. Chung,Granulation of Li1.33Mn1.67O4 (LMO) through the use of cross-linked chitosanfor the effective recovery of Li+ from seawater, Chemical Engineering Journal234 (2013) 16-22.

[0051] [3] L. Tian, Y. Yang, G. Chen, A. Tiraferri, B. Liu, EfficientLithium Extraction from Shale Gas Wastewater Using Sodium Alginate / H1.33Mn1.67O4 Composite Granular Adsorbents, ACS ES&T Engineering 3(11)(2023) 1676-1685.

[0052] [4] M. Wang, T. Zhang, Z. Meng, C. Wang, W. Dong, J. Liu, S. Yang, X. Hou, X. Cheng, W. Liu, C. Xing, X. Liu, J. Zhou, Self-intercepting interference of hydrogen-bond induced flexible hybrid film to facilitate lithium extraction, Chemical Engineering Journal 458 (2023).

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a highly swellable lithium-ion sieve composite hydrogel, characterized in that: Manganese carbonate (MnCO3) and lithium carbonate (Li2CO3) were mixed in a molar ratio and then heat-treated in high-temperature air to obtain the precursor lithium manganese oxide (LMO). The lithium manganese oxide (LMO) is a Li... 1.33 Mn 1.67 O4; Prepare a polyvinyl alcohol (PVA) solution, then mix the PVA solution, acrylamide (AM), methylenebisacrylamide (MBA), and LMO of different amounts to obtain solution A; Next, prepare an ammonium persulfate (APS) solution, add it to solution A to react and obtain the precursor, which is the LMO-encapsulated composite hydrogel LMO@PPH; Immerse the prepared LMO-encapsulated composite hydrogel LMO@PPH in hydrochloric acid (HCl) solution, and then rinse with deionized water to obtain the lithium ion sieve composite hydrogel HMO@PPH.

2. The method for preparing a highly swelling lithium-ion sieve composite hydrogel according to claim 1, characterized in that: The specific method includes the following steps: (1) Preparation of precursor lithium manganese oxide (LMO): Manganese carbonate (MnCO3) and lithium carbonate (Li2CO3) are mixed according to the Li / Mn molar ratio of 1.33:1.67 and heat-treated in air at 500°C for 4 hours to obtain lithium manganese oxide (LMO); (2) Preparation of HMO nanoparticles: The lithium manganese oxide (LMO) obtained in step (1) is acid-washed with 0.5M HCl solution for 24 hours, washed with deionized water until the pH is neutral, and then the material is dried at 60°C to obtain HMO nanoparticles; (3) Preparation of composite hydrogel LMO@PPH encapsulating LMO: Polyvinyl alcohol (PVA) is dissolved in deionized water, swollen at 60°C for 1 hour, and then dissolved at 90°C for 1 hour to obtain a polyvinyl alcohol (PVA) solution with a mass concentration of 5%; Add 0.5-1g of acrylamide AM, 0.015-0.030g of methylenebisacrylamide MBA, and 0.5-1mL of deionized water to the obtained polyvinyl alcohol (PVA) solution (1.5-3g). Stir at room temperature for 1h, then add lithium manganese oxide (LMO) obtained in step (1), with the amount of LMO added being 40% of the mass of LMO / hydrogel. Stir at room temperature for 1h until the bubbles disappear to obtain solution A; dissolve 30-150mg of ammonium persulfate (APS) in 0.5-2.5 mL of water. In deionized water, 0.5 ml of solution B is added to solution A with stirring. Stir for 10-20 min at room temperature to fully dissolve it in solution A. The reaction is carried out at 50℃ for 6-8 h. Then, it is soaked in deionized water for 36-48 h to swell and obtain LMO-encapsulated composite hydrogel LMO@PPH. (3) Preparation of lithium ion sieve composite hydrogel HMO@PPH: The prepared LMO-encapsulated composite hydrogel LMO@PPH is soaked in 0.5 M hydrochloric acid HCl solution for 36-48 h and then rinsed with deionized water to obtain lithium ion sieve composite hydrogel HMO@PPH.

3. The highly swellable lithium-ion sieve composite hydrogel HMO@PPH prepared by the method described in claim 1 or 2.

4. The application of the lithium-ion sieve composite hydrogel HMO@PPH as described in claim 3 in lithium extraction from seawater, characterized in that: The specific method is as follows: Prepare a solution containing Li at the same concentration. + Na + Ca 2+ K + Mg 2+ The coexisting ion solution was subjected to adsorption by shaking in a constant temperature shaker at 25℃ and a rotation speed of 150 rpm. The lithium ion concentration in the solution at different times was determined by inductively coupled plasma optical emission spectrometry (ICP-OES).

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