Manganese-based ion sieve composite hydrogel and preparation method thereof

Abstract

The application belongs to the technical field of ion sieve adsorption, and particularly relates to a manganese-based ion sieve composite hydrogel and a preparation method thereof. 1.6 Mn 1.6 O4 precursor, and further processing obtains H 1.6 Mn 1.6 O4 ion sieve. The H 1.6 Mn 1.6 O4 ion sieve is mixed with a photo-thermal agent and a surfactant to obtain an HMO suspension; the HMO suspension is mixed with a gelatin aqueous solution, acrylamide and a pore-forming agent to obtain a hydrogel premix; the hydrogel premix is subjected to low-temperature initiation and high-temperature curing, and then is soaked in deionized water to obtain the manganese-based ion sieve composite hydrogel. The composite hydrogel prepared by the application has strong lithium ion adsorption force and can effectively complete the function of lithium extraction from salt lake brine.

Description

Technical Field

[0001] This invention belongs to the field of ion sieve adsorption technology, specifically relating to a manganese-based ion sieve composite hydrogel and its preparation method. Background Technology

[0002] With the development of new energy technologies, new energy storage technology centered on lithium-ion batteries has become a key engine. Approximately 70% of the world's lithium resources are found in salt lake brines, offering greater potential for reserves and lower costs compared to lithium extraction from ore. However, with the depletion of high-quality, low-magnesium-to-lithium ratio resources, the dominant high-magnesium-to-lithium ratio brines make traditional precipitation methods unsuitable due to severe interference from magnesium ions.

[0003] Among numerous lithium extraction technologies, lithium-ion sieves based on spinel-type manganese oxides are considered one of the optimal technical routes for lithium extraction from high magnesium-to-lithium ratio brines due to their unique lattice hole "memory effect," which enables precise capture of lithium ions from complex competing ion systems. Their specific recognition capability stems from the high match between the hole size left after acid treatment and lithium ions, effectively rejecting larger sodium and potassium ions and magnesium ions with huge hydration radii. Although manganese-based ion sieve materials exhibit extremely high selectivity, traditional inorganic ion sieves are typically synthesized as micron or nanometer-sized powders. This powder form presents serious hydrodynamic and process defects in practical industrial applications. In fixed-bed adsorption columns, fine powders cause extremely high fluid resistance, leading to a surge in energy consumption and even interruption of liquid flow; the powder is easily lost with the fluid during elution and regeneration, resulting not only in the loss of expensive active components but also potential pollution of downstream products and the environment; nanoparticles are prone to agglomeration under repeated acid-base cycling, leading to a decrease in specific surface area and even lattice collapse. To overcome the aforementioned challenges in powder engineering, immobilizing inorganic ion sieves within porous polymer matrices has become a current technological trend. Among these, hydrogels, with their unique three-dimensional hydrophilic network structure, have emerged as ideal carriers for loading ion sieves.

[0004] To address the issue of poor cycle stability of existing manganese-based ion sieves in lithium ion separation applications, a manganese-based ion sieve composite hydrogel and its preparation method are proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a manganese-based ion-sieve composite hydrogel and its preparation method. This invention first synthesizes Li... 1.6 Mn 1.6 O4 precursor, further processed to obtain H 1.6 Mn 1.6 O4 ion sieve. H+ 1.6 Mn 1.6O4 ion sieves are actively mixed with photothermal agents and surfactants to obtain HMO suspensions; the HMO suspensions are then mixed with gelatin aqueous solution, acrylamide and pore-forming agents to obtain hydrogel premixes; the hydrogel premixes are subjected to low-temperature initiation and high-temperature curing, and then soaked in deionized water to obtain manganese-based ion sieve composite hydrogels.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for preparing a manganese-based ion sieve composite hydrogel includes the following steps:

[0008] Unless otherwise specified, the parts in this invention refer to parts by mass.

[0009] 20 parts of manganese trioxide were dispersed in 500 parts of 2M LiOH aqueous solution and reacted in a hydrothermal reactor at 180-200℃ for 72 hours. The solid product was collected, washed, and dried, and then calcined at 950℃ for 12 hours under an oxygen atmosphere to obtain Li. 1.6 Mn 1.6 O4 precursor (hereinafter referred to as LMO).

[0010] The LMO precursor was immersed in a 1M HCl aqueous solution for 48 hours, then washed until neutral and dried to obtain H. 1.6 Mn 1.6 O4 (HMO) ion sieve.

[0011] Five parts of HMO ion sieve were dispersed in 10 parts of deionized water, and two parts of carbon black aqueous dispersion and 0.05 parts of sodium dodecyl sulfate were added. The mixture was treated under an ice-water bath at an ultrasonic frequency of 40 kHz for 60 min to obtain an HMO suspension. The solid content of the carbon black aqueous dispersion was 0.5 wt%, and its main functional component was carbon black. The carbon black aqueous dispersion acts as a photothermal agent.

[0012] Monomer mixing stage: 20 parts gelatin were dissolved in 190 parts deionized water at 80℃, stirred for 150-180 min, cooled to 45℃, and 10 parts HMO suspension were added, followed by stirring for 60 min. Then, 25 parts acrylamide, 2 parts polyethylene glycol, and 0.5 parts sodium bicarbonate were added to the mixture, and stirring continued for 10 min, followed by the addition of 0.3 parts N,N'-methylenebisacrylamide. The pH of the mixture was adjusted to 6.8-7.5, and nitrogen gas was purged. After stirring at 45℃ for 100-120 min, a hydrogel premix was obtained. Polyethylene glycol and sodium bicarbonate act as pore-forming agents.

[0013] The average molecular weight of polyethylene glycol is 4000.

[0014] Low-temperature initiation stage: Maintaining an operating temperature of 45°C, add 2 parts of ammonium persulfate aqueous solution to the hydrogel premix, stir for 2 minutes, then add 5 parts of glutaraldehyde aqueous solution, stir for 1 minute, and maintain the temperature for 4 hours. High-temperature curing stage: Raise the temperature to 70°C and maintain the temperature for 20 hours to obtain the hydrogel precursor. The mass concentration of the ammonium persulfate aqueous solution is 20 wt%, and the mass concentration of the glutaraldehyde aqueous solution is 25 wt%.

[0015] The hydrogel precursor was soaked in deionized water at a temperature of 4-10℃ for 48 hours, with the water changed every 8 hours. After completion, a manganese-based ion sieve composite hydrogel was obtained, hereinafter referred to as HMO / Gel@AM.

[0016] A manganese-based ion sieve composite hydrogel, comprising: H 1.6 Mn 1.6 O4 ion sieve and hydrogel matrix.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] Before combining HMO with the hydrogel, HMO and a photothermal agent are first mixed in an active manner to obtain an HMO suspension. This pre-coating strategy effectively improves the dispersibility of HMO, while the uniformly dispersed photothermal agent and HMO achieve effective contact between the heat source and adsorption sites in the subsequent hydrogel product. Driven by solar energy, heat is transferred to the HMO sites more efficiently, accelerating the ion desorption process.

[0019] During the hydrogel curing process, a temperature control strategy of low-temperature initiation and high-temperature curing was employed. In the low-temperature initiation stage, a relatively low processing temperature was used, at which point the decomposition rate of the APS initiator was moderate, controlling the free radical polymerization rate of acrylamide and forming a uniform main framework, avoiding microstructural inhomogeneity caused by rapid polymerization. In the high-temperature curing stage, the temperature was increased to promote the cross-linking of glutaraldehyde and gelatin and the overall densification of the gel network. This strategy avoided bubble defects and uneven polymer chain length distribution caused by excessively rapid APS decomposition at high temperatures, significantly improving the mechanical toughness and light transmittance uniformity of the composite hydrogel.

[0020] In the monomer mixing stage, polyethylene glycol and sodium bicarbonate are introduced as pore-forming agents. After the reaction, they are dissolved by water washing, leaving interconnected microporous channels. During the lithium-ion extraction process of the composite hydrogel product, this structure can effectively construct vertically connected water transport channels, greatly improving the efficiency of water molecule transport to the surface, thereby enhancing the evaporation rate and ion adsorption mass transfer rate.

[0021] During the cross-linking stage, the pH is controlled to be neutral before adding glutaraldehyde to facilitate the rapid formation of a gel structure and prevent HMO particles from settling due to gravity before gel formation. This control method ensures that the system gels at the moment when HMO dispersion is most uniform. Combined with a dual cross-linking system with a specific ratio of MBA and glutaraldehyde, this guarantees good dispersibility of HMO and the crystal structure during the composite process, effectively balancing the mechanical strength and adsorption capacity of the hydrogel and improving the efficiency of lithium ion extraction from the composite hydrogel product.

[0022] By controlling the synthesis conditions of HMO, an LMO precursor was first prepared, and after calcination, a quasi-spherical aggregate morphology of HMO ion sieve was obtained through a protonation process. The combination of this ion sieve structure with the hydrogel composite structure yielded a highly ordered porous network structure. This network structure, acting as a nucleation site, effectively optimized the microstructure of the hydrogel, forming more regular and uniform porous channels, and effectively improving the mass transfer efficiency of the composite hydrogel product. Attached Figure Description

[0023] Figure 1 This is a scanning electron microscope (SEM) image of the manganese-based ion sieve composite hydrogel in this invention.

[0024] Figure 2 This is a SEM image of the manganese-based ion sieve in this invention.

[0025] Figure 3 This is a SEM image of the hydrogel matrix that does not contain manganese-based ion sieves in this invention. Detailed Implementation

[0026] The technical solution of the present invention will be clearly and completely described below through some embodiments and experimental examples. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] Reference Figure 1 The process flow diagram shown illustrates that this invention provides a manganese-based ion sieve composite hydrogel and its preparation method. The technical solution is as follows: Example

[0028] 20 parts of manganese trioxide were dispersed in 500 parts of 2M LiOH aqueous solution and reacted in a hydrothermal reactor at 180°C for 72 hours. The solid product was collected, washed, and dried, and then calcined at 950°C for 12 hours under an oxygen atmosphere to obtain Li. 1.6 Mn 1.6 O4 precursor (hereinafter referred to as LMO).

[0029] The LMO precursor was immersed in a 1M HCl aqueous solution for 48 hours, then washed until neutral and dried to obtain the HMO ion sieve.

[0030] Five parts of HMO ion sieve were dispersed in 10 parts of deionized water, and two parts of carbon black aqueous dispersion and 0.05 parts of sodium dodecyl sulfate were added. The mixture was treated in an ice-water bath at an ultrasonic frequency of 40 kHz for 60 min to obtain an HMO suspension. The solid content of the carbon black aqueous dispersion was 0.5 wt%, and its main functional component was carbon black.

[0031] Monomer mixing stage: 20 parts gelatin were dissolved in 190 parts deionized water at 80℃, stirred for 150 min, cooled to 45℃, and 10 parts HMO suspension were added, followed by stirring for 60 min. Subsequently, 25 parts acrylamide, 2 parts polyethylene glycol, and 0.5 parts sodium bicarbonate were added to the mixture, and stirring was continued for 10 min, followed by the addition of 0.3 parts N,N'-methylenebisacrylamide (MBA). The pH of the mixture was adjusted to 6.8-7.5, and nitrogen gas was purged. After stirring at 45℃ for 100 min, the hydrogel premix was obtained.

[0032] The average molecular weight of polyethylene glycol is 4000.

[0033] Low-temperature initiation stage: Maintaining an operating temperature of 45°C, add 2 parts of ammonium persulfate aqueous solution to the hydrogel premix, stir for 2 minutes, then add 5 parts of glutaraldehyde aqueous solution, stir for 1 minute, and keep warm for 4 hours. High-temperature curing stage: Raise the temperature to 70°C and keep warm for 20 hours to obtain the hydrogel precursor.

[0034] The hydrogel precursor was soaked in deionized water at 4°C for 48 hours, with the water changed every 8 hours, to obtain HMO / Gel@AM.

[0035] Examples 2-15 differ from Example 1 in operating parameters, but the other process steps and the range of raw material selection are the same.

[0036] The specific changes in operating parameters are summarized in Table 1.

[0037] Table 1. Changes in operating parameters in Examples 1-15

[0038] The heating reaction temperature of manganese trioxide (°C) Mixing time (min) during monomer mixing stage Nitrogen-protected stirring time (min) Deionized water soaking temperature (°C) Example 1 180 150 100 4 Example 2 200 180 120 10 Example 3 192 165 112 6 Example 4 185 172 105 9 Example 5 198 155 118 5 Example 6 183 178 108 8 Example 7 195 162 115 4 Example 8 188 175 102 10 Example 9 191 158 119 7 Example 10 182 168 110 5 Example 11 196 153 106 9 Example 12 189 176 114 6 Example 13 199 160 103 8 Example 14 184 170 117 5 Example 15 193 166 109 7

[0039] Comparative Example 1

[0040] Unlike Example 1, no HMO suspension was prepared. Instead, solid HMO ion sieve powder and an equal amount of carbon black aqueous dispersion were directly added to the gelatin aqueous solution, while all other process parameters remained the same.

[0041] Comparative Example 2

[0042] Unlike Example 1, carbon black aqueous dispersion was not added as a photothermal agent, but all other process parameters remained the same.

[0043] Comparative Example 3

[0044] Unlike Example 4, the temperature of the low-temperature initiation stage was adjusted to 70°C, while all other process parameters remained the same.

[0045] Comparative Example 4

[0046] Unlike Example 4, the heat preservation time during the high-temperature curing stage was adjusted to 8 hours, while other process parameters remained the same.

[0047] Comparative Example 5

[0048] Unlike Example 7, polyethylene glycol and sodium bicarbonate were not added, but all other process parameters remained the same.

[0049] Comparative Example 6

[0050] Unlike Example 7, only polyethylene glycol was added, without sodium bicarbonate, while all other process parameters remained the same.

[0051] Comparative Example 7

[0052] Unlike Example 10, no pH adjustment was performed before nitrogen protection was introduced during the monomer mixing stage; all other process parameters remained the same.

[0053] Comparative Example 8

[0054] Unlike Example 10, no ammonium persulfate aqueous solution was added during the low-temperature initiation stage, while all other process parameters remained the same.

[0055] Comparative Example 9

[0056] Unlike Example 13, no HMO suspension was added, and a simple hydrogel matrix was prepared, while all other process parameters remained the same.

[0057] Comparative Example 10

[0058] Unlike Example 13, manganese dioxide powder with an average particle size of 50-100 nm was used instead of HMO ion sieve, while other process parameters remained the same.

[0059] Experimental Example 1

[0060] The lithium-ion adsorption rates of the composite hydrogel products prepared in Examples 1-3 and Comparative Examples 1-2 were tested, and the relevant results are summarized in Table 2.

[0061] The test used simulated brine from a salt lake with a Li ion concentration of 50 mg / L, and impurity solutes of 0.2 M NaCl and 0.2 M MgCl2. Hydrogel products were cut into 1 cm thick samples with 10 cm sides, laid flat on the surface of the simulated brine, and tested at 1 kW / m². 2 The lithium ion adsorption capacity (mg / g) was recorded at 60 min and 240 min after processing at a power density of [value missing].

[0062] Table 2. Lithium-ion adsorption rates of the composite hydrogel products prepared in Examples 1-3 and Comparative Examples 1-2

[0063] Lithium ion adsorption capacity (mg / g) over 60 minutes Lithium ion adsorption capacity (mg / g) over 240 min Example 1 25.8 44.5 Example 2 27.2 45.1 Example 3 26.4 44.9 Comparative Example 1 17.7 31.9 Comparative Example 2 10.2 22.4

[0064] As shown in Table 2, Examples 1 to 3 showed significantly higher lithium ion adsorption capacities at 60 min and 240 min than Comparative Example 1 and Comparative Example 2, indicating that the manganese-based ion sieve composite hydrogel prepared in this invention has significant advantages in improving lithium ion adsorption rate and adsorption capacity.

[0065] Comparative Example 1 did not employ a pre-prepared HMO suspension process; instead, it directly mixed solid powders, lacking the surfactant-assisted ultrasonic dispersion process. This resulted in poor dispersion of HMO particles in the hydrogel matrix, and the photothermal agent failed to tightly coat the adsorption site surface, reducing photothermal transfer efficiency and causing a decrease in both adsorption rate and final adsorption capacity. Comparative Example 2 did not add carbon black aqueous dispersion as a photothermal agent, lacking a photothermal conversion medium. The system could not utilize solar energy to generate local thermal effects to drive ion movement, resulting in the slowest adsorption rate and the lowest adsorption capacity. This demonstrates the necessity of introducing a photothermal agent and constructing a photothermal-assisted system.

[0066] In summary, this invention employs a pre-coating strategy of preparing a suspension by actively mixing HMO and a photothermal agent. The use of surfactants and ultrasonic treatment achieves uniform dispersion of HMO particles and ensures effective contact between the photothermal agent and adsorption sites, resulting in a significant synergistic effect. Excellent dispersibility exposes more active sites, while the tight coating structure allows for more efficient heat transfer to the HMO sites under solar energy, significantly accelerating ion mass transfer and desorption. The specific pre-coating process, combined with the introduction of the photothermal agent, synergistically optimizes the thermodynamic environment during adsorption, maximizing the utilization of photothermal energy and significantly improving the adsorption rate and saturation adsorption capacity of the composite hydrogel for lithium ions. This ensures efficient adsorption while simultaneously improving the extraction efficiency of lithium resources.

[0067] Experiment Example 2

[0068] The mechanical tensile properties of the composite hydrogel products prepared in Examples 4-6 and Comparative Examples 3-4 were tested, and the relevant results are summarized in Table 3.

[0069] The hydrogel product was cut into dumbbell-shaped specimens with a gauge length of 25 mm and a width of 4 mm according to GB / T 528 standard. The tensile strength at break (kPa) was tested.

[0070] Table 3 Mechanical tensile properties of the composite hydrogel products prepared in Examples 4-6 and Comparative Examples 3-4

[0071] Tensile strength at break (kPa) Example 4 605 Example 5 603 Example 6 598 Comparative Example 3 318 Comparative Example 4 462

[0072] As shown in Table 3, the tensile strength at break of Examples 4 to 6 was significantly higher than that of Comparative Example 3 and Comparative Example 4, indicating that the composite hydrogel prepared in Example 4 has a significant advantage in improving the mechanical strength and structural stability of the material.

[0073] Comparative Example 3 adjusted the temperature of the low-temperature initiation stage to 70 degrees Celsius, which caused the ammonium persulfate initiator to decompose too quickly, triggering a rapid polymerization reaction of acrylamide, resulting in uneven microstructure and bubble defects, leading to a significant decrease in tensile strength at break. Comparative Example 4 shortened the holding time of the high-temperature curing stage to 8 hours, which resulted in incomplete cross-linking reaction between glutaraldehyde and gelatin, and the gel network failed to achieve sufficient overall densification. Its mechanical properties were significantly different from those of the examples, which also proved the necessity of the long-term high-temperature curing process.

[0074] In summary, this invention employs a segmented temperature control strategy combining low-temperature initiation and high-temperature curing, which produces a significant synergistic effect: the low-temperature environment moderately controls the decomposition of the initiator and the rate of free radical polymerization, forming a uniform polymer backbone and avoiding structural defects caused by rapid polymerization; the high-temperature environment promotes the deep reaction between the crosslinking agent and the matrix, as well as the densification of the network. Specific segmented temperature adjustments and matching reaction times synergistically optimize the entire process of hydrogel polymerization from microscopic to macroscopic formation, maximizing the uniformity and density of the network structure, significantly improving the mechanical toughness and tensile strength of the composite hydrogel product, and greatly enhancing the mechanical stability of the material while ensuring uniform light transmission.

[0075] Experimental Example 3

[0076] The water evaporation rate and saturated water content of the composite hydrogel products prepared in Examples 7-9 and Comparative Examples 5-6 were tested. The relevant results are summarized in Table 4.

[0077] The test method for water evaporation rate is the same as in Experiment Example 1. Record the amount of water evaporated after 240 minutes and calculate the corresponding average evaporation rate (kg / (m²)). 2•h)). Saturated water content is the amount of water absorbed (g / g) after the hydrogel has been freeze-dried to constant weight and swollen in deionized water for 48 hours.

[0078] Table 4. Water evaporation rate and saturated water content of the composite hydrogel products prepared in Examples 7-9 and Comparative Examples 5-6

[0079] <![CDATA[Average evaporation rate (kg / (m 2 ·h))]]> Saturated water content (g / g) Example 7 1.9 25.8 Example 8 2.1 24.7 Example 9 2.1 25.2 Comparative Example 5 1.0 9.5 Comparative Example 6 1.4 14.9

[0080] As shown in Table 4, the average evaporation rate and saturated water content of Examples 7 to 9 were significantly higher than those of Comparative Example 5 and Comparative Example 6, indicating that the composite hydrogel prepared in Example 7 has significant advantages in improving water transport efficiency and enhancing evaporation performance.

[0081] Comparative Example 5 did not add polyethylene glycol and sodium bicarbonate during the monomer mixing stage, thus lacking a key pore-forming component. This resulted in the formation of a dense network structure inside the hydrogel, significantly reducing its saturated water content and subsequent water evaporation rate. Comparative Example 6 only added polyethylene glycol without adding sodium bicarbonate, thus lacking the synergistic effect of the composite pore-forming agent. This led to insufficient connectivity of the internal channels, resulting in a significant difference in water evaporation rate compared to Example 7, which also proves the rationality of the dual pore-forming agent formulation.

[0082] In summary, this invention introduces polyethylene glycol and sodium bicarbonate as composite pore-forming agents, and utilizes the water washing and dissolution process to leave interconnected microporous channels. These two agents produce a significant synergistic effect: polyethylene glycol forms the basic pores through a site-occupying effect, while sodium bicarbonate assists in constructing vertically interconnected water transport channels. This specific combination of pore-forming agents, combined with the dissolution process, synergistically optimizes the water transport path within the hydrogel, maximizing the efficiency of water molecule transport to the surface. This significantly improves the water evaporation rate and saturated water content of the composite hydrogel product, ensuring the water supply required for evaporation while providing efficient channels for ion adsorption and mass transfer processes.

[0083] Experiment Example 4

[0084] The cycling stability of the composite hydrogel products prepared in Examples 10-12 and Comparative Examples 7-8 was tested, and the relevant results are summarized in Table 5.

[0085] The lithium-ion adsorption capacity of the hydrogel product was measured using the same experimental method as in Example 1. The difference was that after 4 hours of adsorption, the sample was rinsed with 0.5M HCl solution for 2 hours, followed by immersion in deionized water three times for 30 minutes each time, completing this cycle. The lithium-ion adsorption capacity of the hydrogel sample was recorded after 20 cycles and 240 minutes, and its retention rate (%) relative to the initial lithium-ion adsorption capacity was calculated.

[0086] Table 5 Cyclic stability of the composite hydrogel products prepared in Examples 10-12 and Comparative Examples 7-8

[0087] Lithium-ion adsorption retention rate (%) Example 10 89.2 Example 11 88.3 Example 12 89.0 Comparative Example 7 79.4 Comparative Example 8 45.1

[0088] As shown in Table 5, the lithium ion adsorption retention rates of Examples 10 to 12 were significantly higher than those of Comparative Examples 7 and 8, indicating that the composite hydrogel prepared in Example 10 has significant advantages in improving the material's cycle stability and acid cleaning resistance.

[0089] Comparative Example 7 did not perform pH adjustment during the monomer mixing stage, missing the key condition of promoting rapid molding under neutral conditions. This resulted in a slowdown in the crosslinking reaction rate and gravity sedimentation of HMO particles before gel formation, significantly reducing its cycle retention rate. Comparative Example 8 did not add ammonium persulfate aqueous solution during the low-temperature initiation stage, missing the key initiator for constructing the polyacrylamide backbone in the dual crosslinking network. As a result, the gel system relied only on a single crosslinking network for support and could not resist the erosion of the acidic eluent. Its adsorption retention rate was the worst, which also proves the necessity of constructing a dual crosslinking system.

[0090] In summary, this invention controls the pH to be neutral during the crosslinking stage and utilizes MBA and glutaraldehyde to construct a dual crosslinking system. These two elements produce a significant synergistic effect: the neutral environment ensures rapid gelation of the system at the point of most uniform HMO dispersion, effectively preventing particle sedimentation; the dual crosslinking system combines the advantages of different polymer networks, guaranteeing good dispersion of HMO and crystal structure stability during the composite process. Specific pH control combined with the dual crosslinking network design synergistically optimizes the molding quality and structural tolerance of the composite hydrogel, maximizing the balance between mechanical strength and adsorption capacity. This significantly improves the cycle stability and lithium-ion extraction efficiency of the composite hydrogel product, ensuring long-term material durability while maintaining high-efficiency resource recovery capabilities.

[0091] Experimental Example 5

[0092] The hydrophilicity and lithium ion adsorption efficiency of the hydrogel products prepared in Examples 13-15 and Comparative Examples 9-10 were tested, and the relevant results are summarized in Table 6.

[0093] The lithium-ion adsorption efficiency test method is the same as in Experiment Example 1, and the hydrophilicity test method is the water contact angle method.

[0094] Table 6. Lithium-ion adsorption efficiency and hydrophilicity of the hydrogel products prepared in Examples 13-15 and Comparative Examples 9-10

[0095] Lithium ion adsorption capacity (mg / g) over 240 min Water contact angle (°) Example 13 45.2 36.3 Example 14 45.6 36.1 Example 15 44.9 36.7 Comparative Example 9 3.5 55.9 Comparative Example 10 14.8 45.2

[0096] As shown in Table 6, the lithium-ion adsorption capacity and water contact angle of Examples 13 to 15 at 240 min were significantly better than those of Comparative Examples 9 and 10, indicating that the composite hydrogel prepared in Example 13 has significant advantages in improving the hydrophilicity of the material and enhancing the lithium-ion adsorption efficiency. Meanwhile, referring to... Figure 2 The HMO ion sieve prepared in the examples consists of quasi-spherical aggregates, which are significantly different in morphology from conventional manganese dioxide nanoparticles.

[0097] Comparative Example 9 did not add HMO suspension during preparation, lacking key adsorption active components and microstructure modifiers. This resulted in the hydrogel matrix failing to form a highly ordered porous network and lacking chemisorption sites for lithium ions, leading to a significant decrease in adsorption capacity and surface wettability. Comparative Example 10 used nano-manganese dioxide powder instead of HMO ion sieves, lacking the crystal structure and quasi-spherical morphology unique to the LMO precursor method. This prevented the inorganic filler from serving as effective nucleation sites to optimize the microchannels of the hydrogel, and it lacked a specific memory effect for lithium ions. Compared to Example 13, its adsorption efficiency and hydrophilicity showed a significant difference, further demonstrating the necessity of a specific precursor synthesis process. (Reference) Figure 1 The microstructure of the composite hydrogel shown is illustrated. The HMO / Gel@AM composite hydrogel prepared in this invention possesses a highly ordered and interconnected 3D porous network structure. (Reference) Figure 3 In contrast, the pure Gel@hydrogel matrix without HMO particles exhibited relatively large and irregular pores. The results indicate that the introduction of HMO particles, acting as nucleation sites, synergistically optimized the microstructure of the hydrogel, forming more regular and uniform porous channels, which is beneficial for mass transfer processes in subsequent applications.

[0098] In summary, this invention prepares an LMO precursor by controlling the synthesis conditions and then protonates it to obtain a quasi-spherical aggregate morphology of HMO ion sieves. This structure is then composited with a hydrogel, resulting in a significant synergistic effect: the ion sieve with its specific morphology effectively optimizes the microstructure of the hydrogel, promoting the formation of more regular and uniform porous channels, while the highly ordered network structure further exposes the active sites of the ion sieve. The specific synthesis process combined with the composite structure design synergistically optimizes the microstructure and mass transfer pathway of the material, maximizing surface hydrophilicity and internal mass transfer efficiency. This significantly improves the hydrophilicity and lithium-ion adsorption efficiency of the composite hydrogel product, ensuring rapid solution penetration while achieving precise and efficient capture of target ions.

[0099] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a manganese-based ion-sieve composite hydrogel, characterized by: The preparation method is as follows: Mn203dispersed in aqueous lithium hydroxide solution, the solid product was collected after hydrothermal reaction, and LiMn204precursor was obtained after calcination under oxygen atmosphere. 1.6 Mn 1.6 O4precursor; The Li 1.6 Mn 1.6 O4 precursor is soaked with an aqueous hydrogen chloride solution and then washed to obtain H 1.6 Mn 1.6 O4 ion sieve; The H 1.6 Mn 1.6 O4 ion sieve is actively mixed with a photothermal agent and a surfactant to obtain an HMO suspension; The specific process of the active mixing is as follows: The H... 1.6 Mn 1.6 O4 ion sieves are dispersed in deionized water, and the photothermal agent and the surfactant are added. After ultrasonic treatment in an ice-water bath, the HMO suspension is obtained. The photothermal agent is specifically a carbon black aqueous dispersion. The surfactant is specifically sodium dodecyl sulfate. The HMO suspension was mixed with gelatin aqueous solution, acrylamide and porogen, and the pH of the mixture was adjusted to 6.8-7.5 to obtain a hydrogel premix. The pore-forming agent includes polyethylene glycol and sodium bicarbonate; The hydrogel premix was subjected to low-temperature initiation and high-temperature aging, and then soaked in deionized water to obtain the manganese-based ion sieve composite hydrogel. The low-temperature initiation process specifically involves: maintaining an operating temperature of 45°C, adding an ammonium persulfate aqueous solution to the hydrogel premix, stirring, adding a glutaraldehyde aqueous solution, stirring, and then keeping warm. The high-temperature curing process specifically involves: keeping the hydrogel premix that has undergone the low-temperature initiation process at 70°C for 20 hours to obtain the hydrogel precursor.

2. The method according to claim 1, wherein the method is characterized by: The Li 1.6 Mn 1.6 The process of soaking the O4 precursor in an aqueous hydrogen chloride solution specifically involves: [The process is described in the original text, which is incomplete and likely refers to a separate step]. 1.6 Mn 1.6 The O4 precursor was immersed in a 1M aqueous solution of hydrogen chloride for 48 hours, then washed until neutral and dried.

3. The method according to claim 1, wherein the method is characterized by: After the high-temperature curing process, the hydrogel precursor is immersed in deionized water at a temperature of 4-10°C for 48 hours, with an 8-hour water change interval.

4. A manganese-based ion-sieve composite hydrogel comprising: H 1.6 Mn 1.6 O4 ion sieves and hydrogel matrices; further characterized in that the manganese-based ion sieve composite hydrogels are prepared by the method of any one of claims 1-3.

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