Composite hydrogel, preparation method thereof and application of composite hydrogel in salt lake lithium extraction
By combining composite hydrogels with solar evaporators, lithium ions were efficiently extracted from salt lake brine using osmotic pressure and ion separation membranes. This method solves the problems of high energy consumption and low selectivity in traditional methods and provides a clean and efficient way to extract lithium resources.
Patent Information
- Application Number
- CN202511636471.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2024-12-05
- Filing Date
- 2025-11-10
- Publication Date
- 2026-01-23
AI Technical Summary
Existing technologies for lithium extraction from salt lakes are energy-intensive, costly, and difficult to achieve efficient separation of lithium and magnesium ions. Traditional nanofiltration membranes have low ion molecular selectivity and cannot meet practical needs.
A composite hydrogel, including a photothermal hydrogel and an outer surface ion separation membrane, is used. A solar evaporator is used to absorb water and lithium ions from salt lake brine through osmotic pressure, and the ion separation membrane is used to achieve selective separation of lithium and magnesium. The photothermal material converts sunlight into heat energy to drive water evaporation.
This method enables stable lithium enrichment in high-concentration salt solutions, providing a clean and efficient way to extract lithium resources from salt lakes, reducing energy consumption and improving the selective separation efficiency of lithium and magnesium.
Smart Images
Figure CN121372218A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application belongs to the technical field of ion separation, and particularly relates to a composite hydrogel, a preparation method thereof and application of the composite hydrogel in lithium extraction from salt lakes. BACKGROUND
[0002] In recent years, with the rapid development of new energy vehicles, electronic devices and high-power energy storage technologies, the application of lithium in new energy materials has attracted high attention, and the demand for lithium ions has also increased year by year. China has proven lithium reserves of about 1 million tons, and more than 80% of lithium resources exist in salt lake brine. Due to the existence of a large number of competitive ions (such as Mg 2+ ) in the salt lake brine in China, the difficulty of lithium extraction from salt lakes is greatly increased. Traditional lithium-magnesium separation methods such as calcination, adsorption and extraction require the consumption of huge amounts of energy and chemical reagents, and the cost of lithium extraction is high. The nanofiltration membrane separation technology based on pressure driving can realize the selective separation of ions according to the size and valence of ions, and thus has great application prospects in the field of lithium extraction from salt lakes. However, the ion molecule selectivity of the current commercial nanofiltration membrane is low, which cannot meet the demand of actual lithium-magnesium separation. In addition, the existing nanofiltration separation process needs to go through three processes of "dilution-separation-concentration", which not only has high energy consumption but also consumes a large amount of fresh water.
[0003] Therefore, it is urgent to develop high-performance lithium-magnesium separation materials and efficient and low-energy-consumption lithium resource extraction technologies. SUMMARY
[0004] To solve the above technical problems, the present application provides a composite hydrogel, a preparation method thereof and application of the composite hydrogel in lithium extraction from salt lakes. In nature, some salt-tolerant plants have evolved the ability to survive in saline-alkali environment, such as Agrostis stolonifera, Artemisia scoparia, Salicornia europaea and the like, which have the unique ability to grow in saline-alkali environment. This is mainly because the cell membranes of their roots contain rich soluble carbohydrates, and the osmotic pressure is high, so the root cells can absorb water from the saline-alkali soil. In addition, they can also use ion channel proteins on the cell membrane to selectively absorb the ions and nutrients needed for their growth. Under the transpiration of plants, water and ions, nutrients are transported to other parts of the plant. Inspired by the selective ion absorption and transport process of the root cells of salt-tolerant plants, the structure of the composite hydrogel of the present application includes a photo-thermal hydrogel and an ion separation membrane grown on the outer surface. By utilizing the synergistic effect of the ion separation membrane and the solar evaporator, lithium chloride can be directly extracted from salt lake brine.
[0005] The first object of the present application is to provide a preparation method of a composite hydrogel, comprising the following steps: S1, reacting a hydrogel precursor, a photo-thermal material, a crosslinking agent and an initiator in water to obtain a photo-thermal hydrogel; the hydrogel precursor is selected from one or more of polyvinyl alcohol, acrylamide and sodium acrylate; S2, sequentially immersing the photo-thermal hydrogel in the organic amine compound solution and the trimesoyl chloride solution to form an ion separation film on the surface of the photo-thermal hydrogel through polymerization, thereby obtaining the composite hydrogel.
[0006] In one embodiment of the present application, in S1, the photo-thermal material is selected from one or more of activated carbon, molybdenum disulfide, carbon black and polypyrrole, and the photo-thermal material can convert sunlight into heat energy.
[0007] In one embodiment of the present application, in S1, the crosslinking agent is selected from glutaraldehyde and / or N,N-methylene bisacrylamide.
[0008] In one embodiment of the present application, in S1, the initiator is selected from one or more of hydrochloric acid, benzoyl peroxide, azobisisobutyronitrile and ammonium persulfate.
[0009] In one embodiment of the present application, in S1, the concentration of the hydrogel precursor is 0.5wt%-20wt%, and the concentration of the photo-thermal material is 0.1wt%-10wt%.
[0010] In one embodiment of the present application, in S1, the reaction temperature is 60℃-70℃, and the reaction time is 1h-4h.
[0011] In one embodiment of the present application, in S2, the organic amine compound is selected from one or more of piperazine, p-phenylenediamine and polyethyleneimine, and the concentration of the organic amine compound solution is 0.5mg / mL-20mg / mL.
[0012] In one embodiment of the present application, in S2, the concentration of the trimesoyl chloride solution is 0.2mg / mL-30mg / mL.
[0013] In one embodiment of the present application, in S2, the partial immersion refers to that the bottom and the side of the photo-thermal hydrogel are in sufficient contact with the solution, while the top of the photo-thermal hydrogel is kept above the surface of the solution to avoid being soaked by the solution. The partial immersion allows the photo-thermal hydrogel to have one open side, which facilitates the overflow of water vapor.
[0014] The second object of the present application is to provide a composite hydrogel prepared by the method.
[0015] The third object of the present application is to provide an application of the composite hydrogel in lithium extraction from salt lakes.
[0016] The technical solution of the present application has the following advantages compared with the prior art: (1) The composite hydrogel described in this invention differs from the traditional pressure-driven nanofiltration separation mechanism. The lithium extraction mechanism of the composite hydrogel includes three main steps: First, the strong affinity between water molecules and the hydrophilic groups of the photothermal hydrogel polymer network generates a high osmotic pressure inside the photothermal hydrogel, which drives the photothermal hydrogel to absorb water and ions from the solution; second, under the action of the ion separation membrane outside the photothermal hydrogel, magnesium ions are retained, but lithium ions can pass through rapidly; third, lithium ions gradually accumulate in the photothermal hydrogel, and when a certain concentration is reached, the hydrogel can be soaked in clean water to release the accumulated lithium. This solar evaporator based on the ion separation membrane can maintain stable lithium accumulation even when processing high-concentration salt solutions.
[0017] (2) The composite hydrogel described in this invention utilizes the strong osmotic pressure generated by the photothermal hydrogel to absorb water and ions from the brine of a salt lake. Because the surface of the photothermal hydrogel is covered with a monovalent / divalent ion separation membrane, monovalent ions are carried through the membrane and into the interior of the photothermal hydrogel during water absorption; while divalent ions are retained by the membrane, thus achieving the separation of monovalent and divalent ions. Under sunlight, the photothermal material in the photothermal hydrogel converts light into heat to evaporate the absorbed water, thereby continuously absorbing water and lithium ions from the salt lake.
[0018] (3) The composite hydrogel described in this invention has ion selectivity and can achieve ion separation under solar energy drive, thereby realizing a cleaner and more efficient method for extracting lithium resources from salt lakes. It provides an effective way to obtain high-purity lithium directly from salt lake brine using sustainable energy. Attached Figure Description
[0019] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein: Figure 1 This is a diagram illustrating the lithium extraction mechanism of the composite hydrogel of the present invention. Detailed Implementation
[0020] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. It should be understood that the specific embodiments are only used to explain the present invention, but the embodiments are not intended to limit the present invention.
[0021] In this invention, unless otherwise stated, the 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.
[0022] In the present application, the term "and / or" used in the present application includes any and all combinations of one or more of the associated listed items, unless otherwise specified.
[0023] In the present application, unless otherwise specified, the experimental methods used in the embodiments of the present application are conventional methods, and the materials, reagents, etc. used are commercially available, unless otherwise specified. Example 1
[0024] The composite hydrogel and the preparation method thereof of the present embodiment specifically include the following steps: S1, preparation of the photothermal hydrogel: 1 g of polyvinyl alcohol, 0.1 g of carbon black and 10 mL of deionized water were added into a beaker, heated and stirred at 90℃ for 6 h, and then placed at room temperature for 2 h; then 1 mL of glutaraldehyde solution with a concentration of 10% was added, and after stirring and mixing uniformly, it was poured into a cylindrical mold with a diameter of 3 cm, and placed in a 70℃ oven for 2 h to form a photothermal hydrogel through chemical crosslinking; finally, the photothermal hydrogel was soaked in deionized water for 4 h to remove impurities and swell to equilibrium, and stored for later use.
[0025] S2, preparation of the ion separation membrane: first, prepare a piperazine aqueous solution with a concentration of 5 mg / mL and a trimesoyl chloride n-hexane solution with a concentration of 2 mg / mL; then partially immerse the photothermal hydrogel in the piperazine aqueous solution, with the bottom and side surfaces of the photothermal hydrogel in contact with the solution for 100 s; then partially immerse the photothermal hydrogel in the trimesoyl chloride n-hexane solution, with the bottom and side surfaces of the photothermal hydrogel in contact with the solution for 100 s; then wash with the n-hexane solution to remove unreacted trimesoyl chloride, to obtain a composite hydrogel, which is stored in water for subsequent use.
[0026] The temperature of the solar-driven lithium extraction experiment was 25.0±0.5℃, and the relative humidity was 40±5%. LiCl and MgCl2 mixed solution was added into a container. The indoor test used a solar simulator with an illumination intensity of 1 kW / m 2 The composite hydrogel was floated on the surface of a mixed solution of MgCl2 and LiCl with a total concentration of 40 mg / mL (the mass ratio of MgCl2 to LiCl was 20:1). The place where the composite hydrogel contacted with the solution was covered with an ion separation membrane; the top of the composite hydrogel irradiated by sunlight was not covered with an ion separation membrane. After irradiation by sunlight on the surface of the mixed solution for 4 h, the composite hydrogel was immersed in a certain amount of pure water for 6 h, and the content of lithium ions and magnesium ions in the composite hydrogel was tested by inductively coupled plasma emission spectrometry.
[0027] After testing, the water evaporation rate of the composite hydrogel was 2.98 kg m -2 h -1, the rate of lithium ion permeating into the composite hydrogel through the ion separation membrane is 4.98 g m -2 h -1 , and the lithium-magnesium selectivity is 16.2. Example 2
[0028] The composite hydrogel and the preparation method thereof of the present example specifically include the following steps: S1, preparation of the photothermal hydrogel: 2 g of acrylamide and 10 mL of water are added into a container and stirred until uniform; then 0.08 g of N,N-methylenebisacrylamide, 0.6 g of ammonium persulfate and 200 μL of polypyrrole solution are sequentially added and stirred until uniform; the photothermal hydrogel is formed by chemical crosslinking in a 60°C oven for 60 min; finally, the photothermal hydrogel is soaked in deionized water for 4 h to remove impurities and swell to equilibrium, and is stored for later use.
[0029] S2, preparation of the ion separation membrane: first, a polyethyleneimine aqueous solution (PEI molecular weight is 1000) with a concentration of 4 mg / mL and a trimesoyl trichloride n-hexane solution with a concentration of 3 mg / mL are prepared; then the photothermal hydrogel is partially immersed in the polyethyleneimine aqueous solution, and the bottom and side surfaces of the photothermal hydrogel are in contact with the solution for 100 s; then the photothermal hydrogel is partially immersed in the trimesoyl trichloride n-hexane solution, and the bottom and side surfaces of the photothermal hydrogel are in contact with the solution for 100 s; subsequently, the unreacted trimesoyl trichloride is removed by washing with the n-hexane solution to obtain the composite hydrogel, which is stored in water for subsequent use.
[0030] The temperature of the solar-driven lithium extraction experiment is 25.0±0.5°C, and the relative humidity is 40±5%. A LiCl and MgCl2 mixed solution is added into a container. A solar simulator is used for indoor test, and the light intensity is 1 kW / m 2 . The composite hydrogel is floated on the surface of a mixed solution of MgCl2 and LiCl with a total concentration of 40 mg / mL (the mass ratio of MgCl2 to LiCl is 20:1). The place where the composite hydrogel contacts with the solution is covered with an ion separation membrane; the top of the composite hydrogel irradiated by sunlight is not covered with an ion separation membrane. After being irradiated by sunlight on the surface of the mixed solution for 4 h, the composite hydrogel is immersed in a certain amount of pure water for 6 h, and the contents of lithium ions and magnesium ions in the composite hydrogel are tested by inductively coupled plasma emission spectrometry.
[0031] Test results show that the water evaporation rate of the composite hydrogel is 2.56 kg m -2 h -1 , the rate of lithium ion permeating into the composite hydrogel through the ion separation membrane is 3.01 g m -2 h -1 , and the lithium-magnesium selectivity is 10.1. Example 3
[0032] The composite hydrogel of the embodiment and the preparation method thereof specifically include the following steps: S1, preparation of the photothermal hydrogel: 2 g of sodium acrylate, 0.2 g of N,N-methylenebisacrylamide, 0.2 g of ammonium persulfate and 0.2 g of molybdenum disulfide are added to 10 mL of deionized water and stirred uniformly; the photothermal hydrogel is formed by chemical crosslinking in a 70℃ oven for 4 h; finally, the photothermal hydrogel is soaked in deionized water for 4 h to remove impurities and swell to equilibrium, and is stored for later use.
[0033] S2, preparation of the ion separation membrane: first, a p-phenylenediamine aqueous solution with a concentration of 30 mg / mL and a trimesoyl chloride n-hexane solution with a concentration of 2 mg / mL are prepared; then, the photothermal hydrogel is partially immersed in the p-phenylenediamine aqueous solution, with the bottom and side surfaces of the photothermal hydrogel in contact with the solution for 100 s; subsequently, the photothermal hydrogel is partially immersed in the trimesoyl chloride n-hexane solution, with the bottom and side surfaces of the photothermal hydrogel in contact with the solution for 100 s; then, the photothermal hydrogel is washed with the n-hexane solution to remove unreacted trimesoyl chloride, to obtain the composite hydrogel, which is stored in water for later use.
[0034] The temperature of the solar-driven lithium extraction experiment is 25.0±0.5℃, and the relative humidity is 40±5%. A mixed solution of LiCl and MgCl2 is added to the container. The indoor test uses a solar simulator, and the light intensity is 1 kW / m 2 . The composite hydrogel is floated on the surface of a mixed solution of MgCl2 and LiCl with a total concentration of 40 mg / mL (the mass ratio of MgCl2 to LiCl is 20:1). The place where the composite hydrogel contacts the solution is covered with an ion separation membrane; the top of the composite hydrogel irradiated by sunlight is not covered with an ion separation membrane. After irradiation by sunlight on the surface of the mixed solution for 4 h, the composite hydrogel is immersed in a certain amount of pure water for 6 h, and the content of lithium ions and magnesium ions in the composite hydrogel is tested by inductively coupled plasma emission spectroscopy.
[0035] After testing, the water evaporation rate of the composite hydrogel is 2.61 kg m -2 h -1 , the rate of lithium ions penetrating the ion separation membrane into the composite hydrogel is 2.98 g m -2 h -1 , and the lithium-magnesium selectivity is 9.8. Comparative Example 1
[0036] The basic procedure is the same as that of Example 1, except that the ion separation membrane is not prepared on the surface of the photothermal hydrogel, and specifically includes the following steps: In a beaker, 1 g of polyvinyl alcohol, 0.1 g of carbon black and 10 mL of deionized water were added, heated and stirred at 90°C for 6 h, and left at room temperature for 2 h; then 1 mL of 10% glutaraldehyde solution was added, stirred and mixed uniformly, and then poured into a cylindrical mold with a diameter of 3 cm, and placed in a 70°C oven for 2 h to form a photo-thermal hydrogel by chemical crosslinking; finally, the photo-thermal hydrogel was soaked in deionized water for 4 h to remove impurities and swell to equilibrium, and stored for later use.
[0037] The temperature of the solar-driven lithium extraction experiment was 25.0±0.5°C, and the relative humidity was 40±5%. A mixed solution of LiCl and MgCl2 was added to the container. The indoor test used a solar simulator with an illumination intensity of 1 kW / m 2 The composite hydrogel was floated on the surface of a mixed solution of MgCl2 and LiCl with a total concentration of 40 mg / mL (the mass ratio of MgCl2 to LiCl was 20:1). The composite hydrogel was covered with an ion separation membrane where it was in contact with the solution; the top of the composite hydrogel exposed to sunlight was not covered with an ion separation membrane. After 4 h of sunlight irradiation on the surface of the mixed solution, the composite hydrogel was immersed in a certain amount of pure water for 6 h, and the contents of lithium ions and magnesium ions in the composite hydrogel were tested by inductively coupled plasma emission spectroscopy.
[0038] The test showed that the water evaporation rate of the composite hydrogel was 3.80 kg m -2 h -1 The rate of lithium ions penetrating the ion separation membrane into the composite hydrogel was 8.20 g m -2 h -1 The lithium-magnesium selectivity was 1.05, and the separation of lithium ions and magnesium ions was not achieved. Comparative Example 2
[0039] The basic procedure was the same as in Example 1, except that no photo-thermal material was added, which included the following steps: S1, Preparation of photo-thermal hydrogel: In a beaker, 1 g of polyvinyl alcohol and 10 mL of deionized water were added, heated and stirred at 90°C for 6 h, and left at room temperature for 2 h; then 1 mL of 10% glutaraldehyde solution was added, stirred and mixed uniformly, and then poured into a cylindrical mold with a diameter of 3 cm, and placed in a 70°C oven for 2 h to form a photo-thermal hydrogel by chemical crosslinking; finally, the photo-thermal hydrogel was soaked in deionized water for 4 h to remove impurities and swell to equilibrium, and stored for later use.
[0040] S2, Preparation of ion separation membrane: first, prepare a piperazine aqueous solution with a concentration of 5 mg / mL and a trimesoyl chloride n-hexane solution with a concentration of 2 mg / mL; then immerse the photo-thermal hydrogel part in the piperazine aqueous solution, and the bottom and side surfaces of the photo-thermal hydrogel are in contact with the solution for 100 s; then immerse the photo-thermal hydrogel part in the trimesoyl chloride n-hexane solution, and the bottom and side surfaces of the photo-thermal hydrogel are in contact with the solution for 100 s; then wash with a n-hexane solution to remove unreacted trimesoyl chloride, to obtain a composite hydrogel, which is stored in water for subsequent use.
[0041] The temperature of the solar-driven lithium extraction experiment was 25.0±0.5℃, and the relative humidity was 40±5%. A mixed solution of LiCl and MgCl2 was added to the container. The indoor test used a solar simulator, and the light intensity was 1 kW / m 2 . The composite hydrogel was floated on the surface of a mixed solution of MgCl2 and LiCl with a total concentration of 40 mg / mL (the mass ratio of MgCl2 to LiCl was 20:1). The place where the composite hydrogel contacted with the solution was covered with an ion separation membrane; the top of the composite hydrogel irradiated by sunlight was not covered with an ion separation membrane. After irradiation by sunlight on the surface of the mixed solution for 4 h, the composite hydrogel was immersed in a certain amount of pure water for 6 h, and the contents of lithium ions and magnesium ions in the composite hydrogel were tested by inductively coupled plasma emission spectrometry.
[0042] It was tested that the water evaporation rate of the composite hydrogel was 0.18 kg m -2 h -1 , the rate of lithium ions penetrating into the composite hydrogel through the ion separation membrane was 0.05 g m -2 h -1 , and the lithium-magnesium selectivity was 15.2. Comparative Example 3
[0043] The basic procedure was the same as in Example 2, except that no ion separation membrane was prepared on the surface of the photo-thermal hydrogel, which specifically included the following steps: In a container, 2 g of acrylamide and 10 mL of water were stirred until uniform; then 0.08 g of N,N-methylenebisacrylamide, 0.6 g of ammonium persulfate, and 200 μL of polypyrrole solution were added in sequence, and stirred uniformly; the photo-thermal hydrogel was formed by chemical crosslinking in a 60℃ oven for 60 min; finally, the photo-thermal hydrogel was immersed in deionized water for 4 h to remove impurities and swell to equilibrium, and stored for later use.
[0044] The temperature of the solar-driven lithium extraction experiment was 25.0±0.5℃, and the relative humidity was 40±5%. A mixed solution of LiCl and MgCl2 was added to the container. The indoor test used a solar simulator, and the light intensity was 1 kW / m 2The composite hydrogel was floated on the surface of a mixed solution of MgCl2and LiCl with a total concentration of 40 mg / mL (the mass ratio of MgCl2to LiCl was 20:1). The composite hydrogel was covered with an ion separation film where it contacted the solution; the top of the composite hydrogel exposed to sunlight was not covered with an ion separation film. After 4 h of sunlight irradiation on the surface of the mixed solution, the composite hydrogel was immersed in a certain amount of pure water for 6 h, and the contents of lithium ions and magnesium ions in the composite hydrogel were tested by inductively coupled plasma emission spectroscopy.
[0045] The water evaporation rate of the composite hydrogel was 3.20 kg m -2 h -1 The rate of lithium ions penetrating the ion separation film into the composite hydrogel was 6.24 g m -2 h -1 The lithium-magnesium selectivity was 1.08, and the separation of lithium ions and magnesium ions was not achieved. Comparative Example 4
[0046] The procedure was basically the same as in Example 3, except that an ion separation film was not prepared on the surface of the photothermal hydrogel, and specifically comprising the following steps: 2 g of sodium acrylate, 0.2 g of N,N-methylenebisacrylamide, 0.2 g of ammonium persulfate, and 0.2 g of molybdenum disulfide were added to 10 mL of deionized water and stirred uniformly; the photothermal hydrogel was formed by chemical crosslinking in a 70°C oven for 4 h; finally, the photothermal hydrogel was immersed in deionized water for 4 h to remove impurities and swell to equilibrium, and was stored for later use.
[0047] The temperature for the solar-driven lithium extraction experiment was 25.0±0.5°C, and the relative humidity was 40±5%. The LiCl and MgCl2mixed solution was added to a container. A solar simulator was used for indoor testing, and the light intensity was 1 kW / m 2 The composite hydrogel was floated on the surface of a mixed solution of MgCl2and LiCl with a total concentration of 40 mg / mL (the mass ratio of MgCl2to LiCl was 20:1). The composite hydrogel was covered with an ion separation film where it contacted the solution; the top of the composite hydrogel exposed to sunlight was not covered with an ion separation film. After 4 h of sunlight irradiation on the surface of the mixed solution, the composite hydrogel was immersed in a certain amount of pure water for 6 h, and the contents of lithium ions and magnesium ions in the composite hydrogel were tested by inductively coupled plasma emission spectroscopy.
[0048] The water evaporation rate of the composite hydrogel was 3.50 kg m -2 h -1 The rate of lithium ions penetrating the ion separation film into the composite hydrogel was 6.54 g m -2 h -1, the lithium-magnesium selectivity is 1.0, and the separation of lithium ions and magnesium ions is not achieved.
[0049] From the results of Examples 1-3 and Comparative Examples 1-4, it can be seen that, because the surface of the photothermal hydrogel is covered with a monovalent / divalent ion separation membrane formed by interfacial polymerization of an organic amine compound and trimesoyl chloride, lithium ions will be driven to penetrate the ion separation membrane and enter the interior of the photothermal hydrogel during the water absorption process of the photothermal hydrogel; while magnesium ions are intercepted by the ion separation membrane, thereby achieving efficient separation of lithium ions and magnesium ions.
[0050] From the results of Example 1 and Comparative Example 2, it can be seen that, under sunlight irradiation, the photothermal material in the photothermal hydrogel will convert light into heat to evaporate the absorbed water, and then the photothermal hydrogel will continuously absorb water and lithium ions from the salt lake. If there is no photothermal material, the water evaporation rate of the hydrogel is very low, and the transmembrane transport rate of lithium ions is also reduced, and only ion diffusion cannot achieve rapid ion separation. Therefore, the photothermal material increases the water transport rate, and at the same time accelerates the transmembrane transport rate of lithium ions. Figure 1 ).
[0051] Obviously, the above examples are merely examples for the purpose of clarity, and are not limiting of the embodiments. For those of ordinary skill in the art, other different forms of changes or variations can be made on the basis of the above description. Here, it is not necessary and impossible to exhaust all the embodiments. The obvious changes or variations derived therefrom are still within the protection scope of the present application.
Claims
1. A method for preparing a composite hydrogel, characterized in that, Includes the following steps: S1. A hydrogel precursor, a photothermal material, a crosslinking agent, and an initiator are reacted in water to obtain a photothermal hydrogel; the hydrogel precursor is selected from one or more of polyvinyl alcohol, acrylamide, and sodium acrylate. S2. The photothermal hydrogel described in S1 is sequentially partially immersed in an organic amine compound solution and a trimesoyl chloride solution. After polymerization, an ion separation membrane is formed on the surface of the photothermal hydrogel to obtain the composite hydrogel.
2. The method for preparing the composite hydrogel according to claim 1, characterized in that, In S1, the photothermal material is selected from one or more of activated carbon, molybdenum disulfide, carbon black, and polypyrrole.
3. The method for preparing the composite hydrogel according to claim 1, characterized in that, In S1, the crosslinking agent is selected from glutaraldehyde and / or N,N-methylenebisacrylamide.
4. The method for preparing the composite hydrogel according to claim 1, characterized in that, In S1, the initiator is selected from one or more of hydrochloric acid, benzoyl peroxide, azobisisobutyronitrile, and ammonium persulfate.
5. The method for preparing the composite hydrogel according to claim 1, characterized in that, In S1, the concentration of the hydrogel precursor is 0.5wt%-20wt%; the concentration of the photothermal material is 0.1wt%-10wt%.
6. The method for preparing the composite hydrogel according to claim 1, characterized in that, In S1, the reaction temperature is 60℃-70℃ and the time is 1h-4h.
7. The method for preparing the composite hydrogel according to claim 1, characterized in that, In S2, the organic amine compound is selected from one or more of piperazine, p-phenylenediamine, and polyethyleneimine; the concentration of the organic amine compound solution is 0.5 mg / mL to 20 mg / mL.
8. The method for preparing the composite hydrogel according to claim 1, characterized in that, In S2, the concentration of the pyromellitic acid chloride solution is 0.2 mg / mL to 30 mg / mL.
9. A composite hydrogel prepared by the method according to any one of claims 1-8.
10. The application of the composite hydrogel as described in claim 9 in lithium extraction from salt lakes.