SDS micelle mediated swelling enhanced adsorption lithium ion sieve HMO coated PPSH hydrogel as well as preparation method and application of SDS micelle mediated swelling enhanced adsorption lithium ion sieve HMO coated PPSH hydrogel

Abstract

The invention belongs to the technical field of preparation of high polymer materials, and provides a lithium ion sieve HMO (at) PPSH hydrogel with SDS micelle mediated swelling enhanced adsorption, and a preparation method and application of the lithium ion sieve HMO (at) PPSH hydrogel. The preparation method comprises the following steps: mixing MnCO3 and Li2CO3 according to a molar ratio of Li / Mn of 1.33: 1.67, and carrying out heat treatment in air at 500 DEG C for 4 hours to obtain a precursor LMO; the preparation method comprises the following steps: preparing a PVA solution and an SDS solution, mixing the PVA solution, the SDS solution, AM, MBA and LMO, and obtaining a solution A after bubbles disappear; adding an ammonium persulfate solution into the solution A, and reacting at 60 DEG C for 6-8 hours to obtain LMO-coated PPSH; and soaking the LMO-coated PPSH in an HCl solution, and washing with deionized water to obtain the HMO-coated PPSH composite material. And the adsorption content of 30% HMO coated PPSH is up to 52.79 mg / g. And the extraction efficiency of Li < + > in natural seawater is up to 98.12%, and the adsorbent still has high adsorption capacity under 10 times of adsorption-desorption circulation.

Description

Technical Field

[0001] This invention belongs to the field of polymer material preparation technology, specifically relating to an SDS micelle-mediated swelling-enhanced adsorption lithium-ion sieve HMO@PPSH hydrogel, its preparation method, and applications. More specifically, it is a sodium dodecyl sulfate micelle-mediated swelling-enhanced adsorption lithium-ion sieve hydrogel. This invention addresses the complex natural solution system of seawater, proposing a method using Li... 1.33 Mn 1.67 O4 as Li + By selecting different substrate materials, porous HMO@PPSH composite materials with high swelling capacity and enhanced lithium-ion adsorption were prepared using a simple synthesis method to identify imprinted sites. 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 pose significant challenges to Li... + It exhibits excellent selectivity, but there are some problems that restrict its practical application when extracting lithium by physical methods, such as: (1) more Mn is lost during acid leaching; (2) powder is easily lost during adsorption; (3) adsorption time is long; (4) powder agglomeration and burying of adsorption sites lead to capacity reduction. Summary of the Invention

[0003] To address the problems of existing lithium-ion sieves, such as powdery form, difficulty in recycling, and decreased adsorption capacity due to powder agglomeration and adsorption site embedding, this invention provides an SDS micelle-mediated swelling-enhanced adsorption lithium-ion sieve HMO@PPSH hydrogel, its preparation method, and applications. The hydrogel is coated with HMO@PPSH using sodium dodecyl sulfate (SDS) anionic surfactant micelles. 1.33 Mn 1.67 The O4 composite material (HMO@PPSH) with surfactant modification enhances the sustained swelling capacity of the lithium-ion sieve hydrogel during adsorption, thereby promoting H 1.33 Mn 1.67 The exposure of O4 active sites ultimately enhances its adsorption performance for lithium ions.

[0004] This invention is achieved by the following technical solution: a method for preparing lithium-ion sieve HMO@PPSH hydrogel with SDS micelle-mediated swelling and enhanced adsorption, wherein MnCO3 and Li2CO3 are mixed according to a Li / Mn molar ratio of 1.33:1.67 and heat-treated in air at 500°C for 4 hours to obtain the precursor lithium manganese oxide (LMO); polyvinyl alcohol (PVA) solution, sodium dodecyl sulfate (SDS), acrylamide (AM), methylenebisacrylamide (MBA), and LMO are mixed, and solution A is obtained after the bubbles disappear; ammonium persulfate (APS) solution is added to solution A and reacted at 60°C for 6-8 hours to obtain LMO@PPSH; finally, the prepared LMO@PPSH is immersed in 0.5 M HCl solution and rinsed with deionized water to obtain the HMO@PPSH composite material.

[0005] Specifically, the steps include the following: (1) Li 1.33 Mn 1.67 Preparation of O4: MnCO3 and Li2CO3 were mixed according to the molar ratio of Li / Mn of 1.33:1.67, and the mixture was heat-treated in air at 500℃ for 4h to obtain the precursor lithium manganese oxide (LMO). (2) Preparation of LMO@PPSH composite material: First, prepare a 5% polyvinyl alcohol (PVA) solution (PVA is dissolved in deionized water, swells at 60 ℃ for 1 h, and then dissolves at 90 ℃ for 1 h). Take 1.2-3.5 g of 5wt% PVA solution, add 0.0577-0.1154 g SDS and 0.25-0.5 mL of water, stir in a 50 ℃ water bath until no bubbles are present, then add 0.5 g of AM, 0.015-0.030 g of MBA and 0.5-1 mL of deionized water at room temperature, stir at room temperature for 1 h, and then add LMO obtained in step (1) according to the mass ratio of LMO / LMO composite hydrogel of 10%, 20%, 30%, 40%, and 50%, stir at room temperature for 1 h until the bubbles disappear, and obtain solution A; 30-150 mg of APS is dissolved in 0.5-2.5 mL of deionized water to form solution B; solution B is added to solution A while stirring, and stirred at room temperature for 1-2 min to ensure it is fully dissolved in solution A; the reaction is carried out at 60℃ for 6-8 h to obtain LMO@PPSH composite material; (3) Preparation of HMO@PPSH composite material: The LMO@PPSH obtained in step (3) was soaked in 0.5 M HCl solution for 24 h and rinsed with deionized water to obtain HMO@PPSH composite material.

[0006] Furthermore, in step (2), the mass ratio of LMO / LMO composite hydrogel is 30%; in step (3), the mass percentage of HMO to HMO@PPSH in the prepared HMO@PPSH is 30%.

[0007] The present invention also provides a lithium-ion sieve HMO@PPSH hydrogel with SDS micelle-mediated swelling enhanced adsorption obtained by the method described above.

[0008] The present invention also provides the application of the HMO@PPSH hydrogel in lithium extraction from seawater.

[0009] The specific method is as follows: the HMO@PPSH hydrogel is immersed in seawater at a constant temperature of 25°C and adsorbed by stirring at a speed of 150 rpm. The lithium ion concentration in the solution at different times is determined by inductively coupled plasma atomic emission spectrometry (ICP-MS).

[0010] This invention yields a highly swollen, regenerable SDS micelle-doped HMO@PPSH composite material, and investigates the adsorption of Li from LiCl solutions with different lithium ion concentrations and natural seawater. + The results showed that the addition of SDS micelles further increased the swelling capacity of the LMO hydrogel, resulting in a swelling degree of up to 878.24% after immersion in pure water for 48 hours. This high swelling capacity promoted pore size increase, exposing nearly 100% of the Li through abundant, uniform macropores and ultra-high swelling. + The adsorption sites show that the adsorption content of 30% HMO@PPSH (30% represents a 30% mass percentage of HMO to HMO@PPSH) can reach as high as 52.79 mg / g HMO. Furthermore, the HMO@PPSH composite material exhibits high selectivity in Li₂ from natural seawater. + The extraction efficiency is as high as 98.12%, Na + K + Mg 2+ Ca 2+ The extraction efficiencies were only 0.115%, 2.137%, 1.533%, and 2.551%. Meanwhile, it maintained 80% of its adsorption capacity even after 10 adsorption-desorption cycles. Attached Figure Description

[0011] Figure 1 SEM images of 30% LMO@PPSH and 30% HMO@PPSH composites with three-dimensional porous structures; Figure 2 EDS plots of 30% LMO@PPSH and 30% HMO@PPSH composites; Figure 3Physical photos and SEM images of the adsorption, swelling and desorption performance of 30% HMO@PPSH composite material; Figure 4 Physical photos and SEM images of the adsorption, swelling and desorption performance of 30% HMO@PPH composite material; Figure 5 The graphs show the changes in lithium ion adsorption capacity as a function of concentration for the 30% HMO@PPH and 30% HMO@PPH composite materials. Figure 6 The adsorption kinetics of 30% HMO@PPH and 30% HMO@PPH composite materials; Figure 7 Cyclic performance of 30% HMO@PPSH composites; Figure 8 Swelling kinetics curves of 30% LMO@PPSH composite and 30% LMO@PPH composite in natural seawater; Figure 9 Natural seawater selectivity for 30% HMO@PPSH composite materials. Detailed Implementation

[0012] 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.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] Example 1: A method for preparing a lithium-ion sieve HMO@PPSH hydrogel with SDS micelle-mediated swelling and enhanced adsorption. MnCO3 and Li2CO3 were mixed at a Li / Mn molar ratio of 1.33:1.67 and heat-treated in air at 500°C for 4 hours to obtain the precursor lithium manganese oxide (LMO). Polyvinyl alcohol (PVA) solution, sodium dodecyl sulfate (SDS), acrylamide (AM), methylenebisacrylamide (MBA), and LMO were mixed, and solution A was obtained after the bubbles disappeared. Ammonium persulfate (APS) solution was added to solution A and reacted at 60°C for 6-8 hours to obtain LMO@PPSH. Finally, the prepared LMO@PPSH was immersed in HCl solution and rinsed with deionized water to obtain the HMO@PPSH composite material. In this embodiment, precursor powder (LMO) is composited with a porous hydrogel material. The specific steps are as follows: 1. Li 1.33 Mn 1.67 Preparation of O4: A mixture of MnCO3 and Li2CO3 was heat-treated in air at 500℃ for 4 h under the condition of Li / Mn molar ratio of 1.33:1.67 to prepare precursor lithium manganese oxide (LMO) powder.

[0017] 2. Preparation of LMO@PPSH composite material: First, prepare a 5% polyvinyl alcohol (PVA) solution (PVA dissolved in deionized water, swollen at 60℃ for 1 h, and then dissolved at 90℃ for 1 h). Take 1.2-3.5 g of 5wt% PVA solution, add 0.0577-0.1154 g of sodium dodecyl sulfate (SDS) and 0.25-0.5 mL of water, stir in a 50℃ water bath until no bubbles are present, then add 0.5 g of acrylamide (AM), 0.015-0.030 g of methylenebisacrylamide (MBA) and 0.5-1 mL of deionized water at room temperature, stir at room temperature for 1 h, and add LMO according to the mass ratio of LMO / LMO composite hydrogel of 10%, 20%, 30%, 40%, and 50%, stir at room temperature for 1 h until the bubbles disappear, and obtain solution A. The mass ratios of the LMO powder to the LMO-free matrix hydrogel are 0.0708:0.6372, 0.1593:0.6372, 0.2730:0.6372, 0.4248:0.6372, and 0.6372:0.6372, respectively.

[0018] Then, 30-150 mg of ammonium persulfate (APS) was dissolved in 0.5-2.5 mL of deionized water, referred to as solution B. Solution B was then added to solution A with stirring, and the mixture was stirred at room temperature for 1-2 minutes to ensure complete dissolution in solution A. The reaction was carried out at 60 °C for 6-8 hours to obtain LMO@PPSH composite materials containing different percentages of LMO (10%, 20%, 30%, 40%, 50%).

[0019] 3. Preparation of HMO@PPSH composite material: The prepared LMO@PPSH hydrogels with different LMO addition amounts were soaked in 0.5M HCl solution for 24h, and then rinsed with deionized water to obtain HMO@PPSH hydrogels with different HMO addition amounts (10%, 20%, 30%, 40%, 50%).

[0020] 4. Preparation of LMO@PPH composite material: LMO@PPH is prepared using the same method as LMO@PPSH, except that SDS solution is not added during the preparation process.

[0021] 5. Preparation of HMO@PPH composite material: HMO@PPH was prepared using the same method as HMO@PPSH.

[0022] Table 1 shows the performance comparison of HMO@PPSH and HMO@PPH in LiCl solution with pH=10 and an initial lithium ion concentration of 25ppm after 24 hours when LMO addition amounts are 10%, 20%, 30%, 40%, and 50%.

[0023] Table 1. Lithium-ion extraction capacity of HMO@PPSH and HMO@PPH under different HMO contents The results in Table 1 show that, under different loading levels, the lithium-ion adsorption capacity of HMO@PPSH is consistently and significantly higher than that of HMO@PPH.

[0024] The resulting HMO@PPSH and HMO@PPH composites with an HMO content of 30% (30%HMO@PPSH and 30%HMO@PPH) were characterized and tested.

[0025] Figure 1 SEM images of the 30% LMO@PPSH and 30% HMO@PPSH composites with three-dimensional porous structures are shown. The results indicate that 30% LMO@PPSH possesses a rich three-dimensional porous structure, while the pores of 30% HMO@PPSH remain uniform after acid washing, which is beneficial to Li + Uniform exposure of adsorption sites, which is beneficial to Li ＋ De-embedding.

[0026] Figure 2 The image shows the energy dispersive spectroscopy (EDS) mapping of the 30% LMO@PPSH and HMO@PPSH composite material. The EDS mapping revealed the presence of elements such as S, Mn, N, and O, which confirms that SDS, LMO, and HMO are uniformly dispersed in the hydrogel.

[0027] Figure 3 SEM images and photographs of the 30% HMO@PPSH composite material after lithium ion adsorption, post-adsorption swelling, and post-adsorption desorption are presented. The SEM images and photographs show that the material retains a uniform porous structure without significant particle aggregation after adsorption, and its volume expands by nearly two times after adsorption. This indicates that during adsorption, 30% HMO@PPSH can overcome HMO aggregation through swelling, gradually exposing active sites and thus improving adsorption capacity. Furthermore, both the macroscopic and microscopic structures of 30% HMO@PPSH can recover to their initial state during adsorption and desorption, which is beneficial for reuse.

[0028] Figure 4 SEM images and photographs of a 30% HMO@PPH composite material after lithium ion adsorption, post-adsorption swelling, and post-adsorption desorption. Figure 3 In comparison, this indicates that the pore structure of 30% HMO@PPH is not sufficiently rich and three-dimensional, and the material exhibits severe particle aggregation after adsorption. This severe structural inhomogeneity hinders the exposure of HMO active sites during adsorption. Furthermore, although 30% HMO@PPH also recovers to its initial state during adsorption swelling and desorption, it requires further swelling to overcome aggregation after adsorption, which is detrimental to the efficient operation of the adsorbent. Additionally, through comparison... Figure 3 and Figure 4 The images of 30% HMO@PPSH and 30% HMO@PPH show that 30% HMO@PPSH exhibits stronger swelling properties during adsorption than 30% HMO@PPH, confirming the role of SDS micelles in enhancing swelling adsorption.

[0029] Figure 5The effect of lithium ion concentration variation on the adsorption capacity of 30% HMO@PPSH and 30% HMO@PPH composites in a LiCl solution at pH 10 was demonstrated. It can be seen that the adsorption capacity gradually increases with increasing lithium ion concentration, and the adsorption capacity of 30% HMO@PPSH is significantly higher than that of 30% HMO@PPH (at room temperature and an initial concentration of 150 ppm, the adsorption capacity of HMO is 30.04 mg / g, while that of 30% HMO@PPSH is 52.79 mg / g). Furthermore, the high adsorption capacity of 30% HMO@PPSH is close to the theoretical adsorption capacity (approximately 59 mg / g HMO). Therefore, this composite material solves both the adsorption capacity problem and the difficulty in recovering the powder.

[0030] Figure 6 The kinetic fitting curves (0–48 h) of lithium-ion adsorption in LiCl solution at pH 10 and a lithium-ion concentration of 25 ppm for 30% HMO@PPSH and 30% HMO@PPH composite materials are presented. Kinetic studies show that both materials follow a pseudo-second-order kinetic model, and 30% HMO@PPSH exhibits a higher adsorption capacity than 30% HMO@PPH at all time points. More importantly, the adsorption rate constant of 30% HMO@PPSH (K2 = 4.17) is higher than that of 30% HMO@PPH (K2 = 3.52), indicating that 30% HMO@PPSH has faster lithium-ion adsorption kinetics.

[0031] Figure 7 To assess the cycling performance of the 30% HMO@PPSH composite material, cyclic experiments were conducted with adsorption in a 25 ppm LiCl solution at pH 10, followed by desorption in 0.5 M hydrochloric acid. The results showed that the 30% HMO@PPSH exhibited high lithium-ion adsorption capacity in all cycles, and after 10 cycles, its capacity retained approximately 80% of its initial value, demonstrating the excellent cycling stability of the 30% HMO@PPSH composite material.

[0032] Figure 8 The figure shows the kinetic curves of swelling of 30% LMO@PPSH composite material and 30% LMO@PPH composite material in natural seawater for 120 hours. The swelling capacity of 30% LMO@PPSH is always higher than that of 30% LMO@PPH. After 120 hours, the swelling rate of 30% LMO@PPSH is as high as 296.68%, indicating that the strengthening effect of SDS on the swelling of hydrogel is still effective in real environment.

[0033] Figure 9The lithium-ion extraction efficiency of the 30% HMO@PPSH composite material in Bohai Sea water at a liquid-to-solid ratio of 1.6 L / g is shown in the figure. The lithium-ion extraction efficiency of the 30% HMO@PPSH composite material in seawater is 98.12%, significantly higher than that of other ions (Na+). + K + Mg 2+ Ca 2+ The extraction efficiencies were only 0.115%, 2.137%, 1.533%, and 2.551%, while maintaining extremely high separation factors for Na⁺, K⁺, Mg²⁺, and Ca²⁺, at 42602, 3026.4, 4244.4, and 2525.2, respectively. Therefore, the results indicate that the 30% HMO@PPSH composite material is suitable for the extraction of Li⁺ in natural seawater. + It has great potential for application in selective extraction.

[0034] Mechanism of surfactant-enhanced lithium-ion adsorption: The composite hydrogel of this invention enhances lithium-ion adsorption through surfactant micelles. 1.33 Mn 1.67 The hydrogel was modified with O4 to obtain the product. This modification strategy significantly enhanced the hydrogel's sustained swelling capacity and structural deformability during lithium-ion adsorption. Based on this, the present invention achieves a triple synergistic enhancement mechanism: First, the enhanced hydrophilicity and porosity establish a larger water diffusion and swelling pressure gradient, driving strong entropic elastic deformation; second, this strong swelling effect effectively inhibits the aggregation of active particles during adsorption, ensuring H+ ion adsorption. 1.33 Mn 1.67 The high dispersion of O4 and the full exposure of active sites, combined with the optimized hydrophilic network structure, simultaneously accelerate the transport kinetics of lithium ions within the gel. These mechanisms work together to synergistically enhance the material's adsorption capacity and rate for lithium ions.

[0035] 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; and these 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 an SDS micelle-mediated swelling-enhanced adsorption lithium-ion sieve HMO@PPSH hydrogel, characterized in that: MnCO3 and Li2CO3 were mixed at a Li / Mn molar ratio of 1.33:1.67 and heat-treated in air at 500°C for 4 hours to obtain the precursor lithium manganese oxide (LMO). Polyvinyl alcohol (PVA) solution, sodium dodecyl sulfate (SDS) solution, acrylamide (AM), methylenebisacrylamide (MBA), and LMO were mixed, and solution A was obtained after the bubbles disappeared. Ammonium persulfate (APS) solution was added to solution A and reacted at 60°C for 6-8 hours to obtain LMO@PPSH. Finally, the prepared LMO@PPSH was immersed in HCl solution and rinsed with deionized water to obtain the HMO@PPSH composite material.

2. The preparation method according to claim 1, characterized in that: Specifically, the steps include the following: (1) Li 1.33 Mn 1.67 Preparation of O4: MnCO3 and Li2CO3 were mixed according to the molar ratio of Li / Mn of 1.33:1.67, and the mixture was heat-treated in air at 500℃ for 4h to obtain the precursor lithium manganese oxide (LMO). (2) Preparation of LMO@PPSH composite material: First, prepare a 5% PVA solution. Dissolve PVA in deionized water and swell at 60℃ for 1h, then dissolve at 90℃ for 1h. Take 1.2-3.5g of 5wt% PVA, add 0.0577-0.1154g of SDS and 0.25-0.5mL of water, stir in a 50℃ water bath until no bubbles are present, then add 0.5g of AM, 0.015-0.030g of MBA and 0.5-1mL of deionized water at room temperature, stir at room temperature for 1h, then add LMO obtained in step (1) according to the mass ratio of LMO / LMO composite hydrogel of 10%, 20%, 30%, 40% and 50%, stir at room temperature for 1h until bubbles disappear, and obtain solution A. 30-150 mg of APS is dissolved in 0.5-2.5 mL of deionized water to form solution B; solution B is added to solution A while stirring, and stirred at room temperature for 1-2 min to ensure it is fully dissolved in solution A; the reaction is carried out at 60℃ for 6-8 h to obtain LMO@PPSH composite material; (3) Preparation of HMO@PPSH composite material: The LMO@PPSH obtained in step (3) was soaked in 0.5M HCl solution for 24h and rinsed with deionized water to obtain HMO@PPSH composite material.

3. The preparation method according to claim 2, characterized in that: In step (2), the mass ratio of LMO / LMO composite hydrogel is 30%; in step (3), the mass percentage of HMO to HMO@PPSH in the prepared HMO@PPSH is 30%.

4. The SDS micelle-mediated swelling-enhanced adsorption lithium-ion sieve HMO@PPSH hydrogel obtained by any of the methods described in claims 1-3.

5. The application of the HMO@PPSH hydrogel according to claim 4 in lithium extraction from seawater.

6. The application according to claim 5, characterized in that: The specific method is as follows: the HMO@PPSH hydrogel is immersed in seawater at a constant temperature of 25°C and adsorbed by stirring at a speed of 150 rpm. The lithium ion concentration in the solution at different times is determined by inductively coupled plasma atomic emission spectrometry (ICP-MS).

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