Preparation method of fluorine-containing hydrogel and application of fluorine-containing hydrogel in lithium extraction
By preparing fluorinated hydrogels, the problems of low lithium resource extraction efficiency and environmental unfriendliness in existing technologies have been solved, and efficient and selective adsorption and extraction of lithium ions have been achieved.
Patent Information
- Application Number
- CN202511740549.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-25
- Publication Date
- 2026-03-06
- Estimated Expiration
- Not applicable · inactive patent
AI Technical Summary
Existing lithium extraction methods suffer from environmental inefficiency and are particularly problematic in the field of lithium extraction from salt lakes in southern China, where there is a lack of efficient and selective lithium-ion adsorption materials.
A method for preparing fluorinated hydrogels was adopted, which involves acid treatment, silanization modification, N-acetyl-L-cysteine modification, and chitosan oligosaccharide crosslinking of bentonite to form fluorinated hydrogels with specific structures for selective adsorption of lithium ions.
It improves the adsorption performance and selectivity of lithium ions, reduces the adsorption of sodium and potassium ions, and achieves efficient extraction of lithium ions.
Smart Images
Figure CN121609934A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of adsorption materials technology, and in particular to a method for preparing fluorinated hydrogels and their lithium extraction applications. Background Technology
[0002] Lithium, the world's lightest metal, is hailed as the 21st-century green high-energy metal and "white oil" due to its unique physicochemical properties. With the rapid growth in lithium demand, the supply of lithium resources has become increasingly prominent. Many methods exist for lithium extraction, among which adsorption is an environmentally friendly and cost-effective lithium extraction technology.
[0003] Hydrogels, as three-dimensional network materials constructed from hydrophilic polymers through physical or chemical cross-linking, exhibit significant advantages in the field of ion adsorption due to their unique structural designability and interface controllability. The abundant polar groups in their network structure can also form stable organic-inorganic composite interfaces with inorganic materials through multiple hydrogen bonds. In the field of lithium extraction from saltwater in southern China, hydrogel composite adsorbents have become an important research direction due to their environmental friendliness, high adsorption capacity, and recyclability. Summary of the Invention
[0004] Therefore, the present invention provides a method for preparing a fluorinated hydrogel, comprising the following steps: (1) Prepare a hydrochloric acid solution, add bentonite to the hydrochloric acid solution for acid treatment, separate the solid and liquid after acid treatment, wash the solid phase to remove residual acid, and dry to obtain pretreated bentonite; add the pretreated bentonite to ethanol to disperse to form a dispersion, then add γ-(2,3-epoxypropoxy)propyltrimethoxysilane to the dispersion for modification, separate the solid and liquid after modification, wash the solid phase, and dry to obtain modified bentonite; (2) Prepare an N-acetyl-L-cysteine solution in a reaction vessel, add the modified bentonite to the reaction vessel, then seal the reaction vessel and introduce a protective gas to remove the air in the reaction vessel, heat the reaction in a water bath, and after the reaction is completed, separate the solid and liquid, wash the solid phase, dry it, and obtain the modified bentonite. (3) Prepare an aqueous solution of chitosan oligosaccharide. Under stirring, add methanesulfonic acid and sodium hexametaphosphate to the aqueous solution of chitosan oligosaccharide in sequence. After the addition is completed, heat and keep warm. After the heat is kept warm, add excess ether to precipitate. Add the precipitate to deionized water to dissolve. Dialyze to remove unreacted sodium hexametaphosphate. Then concentrate under reduced pressure and freeze dry to obtain pretreated chitosan oligosaccharide. (4) Dissolve the pretreated chitosan oligosaccharide in deionized water to obtain solution I; add the modified bentonite and starch to deionized water and stir evenly to obtain mixture II; then add solution I and mixture II to an aqueous solution of polyvinyl alcohol kept at a temperature above 70°C, stir evenly after the addition is completed, then add 2-fluoroacrylic acid, crosslinking agent and potassium persulfate, stir the reaction after the addition is completed, then separate the solid phase reaction product by solid-liquid separation, soak in deionized water, dry and obtain the fluorinated hydrogel.
[0005] Further, in step (1), the mass percentage of the solute in the hydrochloric acid solution is 5% to 10%; the ratio of bentonite added to the hydrochloric acid solution is bentonite: hydrochloric acid solution = 1g: 20 to 100mL; the temperature of the acid treatment is 60 to 70℃; and the treatment time is 10 to 30min.
[0006] Further, in step (1), the material-to-liquid ratio of the pretreated bentonite to the ethanol to form a dispersion is pretreated bentonite:ethanol = 1g:20-50g. The γ-(2,3-epoxypropoxy)propyltrimethoxysilane is added so that the mass percentage of γ-(2,3-epoxypropoxy)propyltrimethoxysilane in the solution is 5%-8%. The modification temperature of γ-(2,3-epoxypropoxy)propyltrimethoxysilane is 50-60℃, and reflux is carried out during the modification process. The modification time is 3-6h.
[0007] Further, in step (2), the concentration of N-acetyl-L-cysteine in the N-acetyl-L-cysteine solution is 70-80 g / L, and the solvent is a mixture of deionized water and dimethyl sulfoxide; the mass ratio of the added modified bentonite to the volume ratio of the N-acetyl-L-cysteine solution in the reactor is modified bentonite: N-acetyl-L-cysteine solution = 1-1.5 g: 100 mL; the water bath is heated to 80-85°C and kept at that temperature for more than 20 hours.
[0008] Furthermore, the solvent is a mixture of deionized water and dimethyl sulfoxide in a volume ratio of 1:1.
[0009] Furthermore, the protective gas is nitrogen or argon.
[0010] Further, in step (3), chitosan oligosaccharide is dissolved in deionized water kept at 80-85℃ to obtain an aqueous solution of chitosan oligosaccharide, wherein the concentration of chitosan oligosaccharide in the aqueous solution is 7-10g / 100mL; then, under the condition of keeping the water bath at 80-85℃, methanesulfonic acid and sodium hexametaphosphate are added sequentially to the aqueous solution of chitosan oligosaccharide, wherein the mass ratio of the added methanesulfonic acid and sodium hexametaphosphate to the volume ratio of the aqueous solution of chitosan oligosaccharide is methanesulfonic acid: sodium hexametaphosphate: aqueous solution of chitosan oligosaccharide = 2g: 1-5g: 100mL; after the addition is completed, the mixture is kept at 80-85℃ and stirred for more than 1 hour.
[0011] Further, in step (4), the concentration of pretreated chitosan oligosaccharide in solution I is 6-10 g / 100 mL, and the solvent is water; in mixture II, the ratio of modified bentonite and starch to deionized water is modified bentonite: starch: deionized water = 8-10 g: 16-20 g: 500 mL; the aqueous solution of polyvinyl alcohol is obtained by completely dissolving polyvinyl alcohol in deionized water at a constant temperature of 90°C, and the aqueous solution of polyvinyl alcohol contains polyvinyl alcohol. The concentration is 8-10 g / 100 mL; add the solution I and the mixture II to the aqueous solution of polyvinyl alcohol, and then add 2-fluoroacrylic acid, crosslinking agent and potassium persulfate in the following ratio: solution I: mixture II: aqueous solution of polyvinyl alcohol: 2-fluoroacrylic acid: crosslinking agent: potassium persulfate = 20 mL: 50-60 mL: 100 mL: 3-5 g: 0.2-0.3 g: 0.6-0.8 g. After the addition is completed, keep the mixture at 70°C or above and stir for 30-40 min.
[0012] Furthermore, the crosslinking agent is N,N'-methylenebisacrylamide.
[0013] The present invention also discloses the application of the above-mentioned fluorinated hydrogel in the adsorption lithium extraction process, wherein the fluorinated hydrogel is used to selectively adsorb and separate lithium ions in a mixed solution containing lithium ions, sodium ions and potassium ions.
[0014] The beneficial effects of this invention are as follows: the fluorinated hydrogel prepared by the method described in this invention has strong adsorption and extraction performance for lithium ions, while its adsorption for sodium and potassium ions is relatively weak, exhibiting good selectivity for lithium ion adsorption. This makes the fluorinated hydrogel suitable for lithium extraction processes. Modifying the raw material bentonite or pretreating the chitosan oligosaccharide using the method described in this invention can further improve the lithium ion adsorption and selectivity of the fluorinated hydrogel product. This may be because: this invention first acid-treats the bentonite to remove easily soluble impurities or organic matter from the bentonite surface, exposing the main active components of the bentonite and increasing the adsorption sites on the bentonite surface. Simultaneously, acid treatment helps to increase the specific surface area of the bentonite and increase the adsorption pore content. Subsequent modification of the bentonite with a silanizing agent can improve particle dispersibility and introduce active groups on the particle surface, preparing for subsequent modification. Modification with N-acetyl-L-cysteine introduces groups such as -HS and -COOH, which enhances the crosslinking and binding force between bentonite and subsequent pretreated components such as chitosan oligosaccharide and 2-fluoroacrylic acid. Furthermore, the introduced groups, along with the active groups and -F groups introduced into the pretreated chitosan oligosaccharide, can interact with lithium ions, thus achieving lithium ion adsorption. Additionally, the large molecular structure formed by the crosslinking of modified bentonite, pretreated chitosan oligosaccharide, and 2-fluoroacrylic acid selectively adsorbs lithium ions with smaller ionic radii, while physically blocking larger ions such as sodium and potassium ions. The introduced -F groups also preferentially bind to lithium ions based on the Li-F specific interaction, further improving the selective adsorption of lithium ions. Attached Figure Description
[0015] Figure 1 This is a comparison chart showing the adsorption capacity of fluorinated hydrogels for various ions obtained by the methods described in each embodiment and comparative example. Detailed Implementation
[0016] The present invention will be further described below with reference to the embodiments.
[0017] Example 1 A method for preparing a fluorinated hydrogel, comprising the following steps: (1) Prepare a hydrochloric acid solution, wherein the mass percentage of the solute in the hydrochloric acid solution is 5%; add bentonite to the hydrochloric acid solution for acid treatment, wherein the material-to-liquid ratio of bentonite to hydrochloric acid solution is 1g:20mL, the acid treatment temperature is 60℃, and the treatment time is 10min; after acid treatment, separate the solid and liquid phases, wash the solid phase with deionized water to remove residual acid, and dry it at 80℃ for 2h to obtain pretreated bentonite; add the pretreated bentonite to ethanol and disperse it to form a dispersion. The material-to-liquid ratio of the dispersion was pretreated bentonite:ethanol = 1g:20g; then γ-(2,3-epoxypropoxy)propyltrimethoxysilane was added to the dispersion for modification, with the mass percentage of γ-(2,3-epoxypropoxy)propyltrimethoxysilane in the solution being 5%; the modification temperature was 50℃, and reflux was used during the modification process, with a modification time of 6h; after modification, solid and liquid were separated, the solid phase was washed three times with ethanol, and dried at 80℃ for 1h to obtain modified bentonite. (2) An N-acetyl-L-cysteine solution was prepared in a reaction vessel. The concentration of N-acetyl-L-cysteine in the N-acetyl-L-cysteine solution was 70 g / L. The solvent was a mixture of deionized water and dimethyl sulfoxide, with a volume ratio of 1:1. The modified bentonite was added to the reaction vessel. The mass ratio of the modified bentonite added to the volume ratio of the N-acetyl-L-cysteine solution in the reaction vessel was 1 g: 100 mL. The reaction vessel was then sealed and nitrogen gas was introduced to purge the air from the reaction vessel. The vessel was heated to 80°C in a water bath and kept at that temperature for 20 h. The solid and liquid phases were then separated. The solid phase was washed three times with deionized water and dried at 80°C for 2 h to obtain the modified bentonite. (3) Dissolve chitosan oligosaccharide in deionized water kept at 80°C to obtain an aqueous solution of chitosan oligosaccharide, wherein the concentration of chitosan oligosaccharide in the aqueous solution is 7g / 100mL; then, under the conditions of keeping at 80°C in a water bath and stirring, add methanesulfonic acid and sodium hexametaphosphate sequentially to the aqueous solution of chitosan oligosaccharide, wherein the mass ratio of added methanesulfonic acid and sodium hexametaphosphate to the volume ratio of the aqueous solution of chitosan oligosaccharide is methanesulfonic acid: sodium hexametaphosphate: aqueous solution of chitosan oligosaccharide = 2g: 1g: 100mL; after the addition is completed, keep at 80°C for 1h, after the end of the heat preservation, add excess ether to precipitate, then add the precipitate to deionized water to redissolve, dialyze to remove unreacted sodium hexametaphosphate, then concentrate under reduced pressure, freeze dry to obtain pretreated chitosan oligosaccharide; (4) Dissolve the pretreated chitosan oligosaccharide in deionized water to obtain solution I; the concentration of pretreated chitosan oligosaccharide in solution I is 6 g / 100 mL, and the solvent is water; add the modified bentonite and starch to deionized water and stir evenly to obtain mixture II; in mixture II, the ratio of modified bentonite and starch to deionized water is modified bentonite: starch: deionized water = 8 g: 16 g: 500 mL; then add solution I and mixture II to a polyvinyl alcohol aqueous solution kept at 70 °C, stir evenly after the addition is complete, then add 2-fluoroacrylic acid, N,N'-methylenebisacrylamide crosslinking agent and potassium persulfate, the polyvinyl alcohol aqueous solution is obtained by adding polyvinyl alcohol (PVA-1788) to water at 90 °C. The polyvinyl alcohol (PVA) was completely dissolved in deionized water at a constant temperature to obtain the aqueous solution, with a PVA concentration of 8 g / 100 mL. Solution I and Mixture II were added to the PVA aqueous solution, followed by the addition of 2-fluoroacrylic acid, N,N'-methylenebisacrylamide crosslinking agent, and potassium persulfate in a ratio of Solution I: Mixture II: Aqueous solution of PVA: 2-fluoroacrylic acid: Crosslinking agent: Potassium persulfate = 20 mL: 50 mL: 100 mL: 3 g: 0.2 g: 0.6 g. After addition, the mixture was kept at 70 °C and stirred for 30 min. The solid-phase reaction product was then collected through solid-liquid separation, purified by soaking in deionized water for 24 h (water changed every 4 h), dried at 40 °C for 24 h, ground, and passed through a 60-mesh sieve to obtain the fluorinated hydrogel.
[0018] Example 2 A method for preparing a fluorinated hydrogel, comprising the following steps: (1) Prepare a hydrochloric acid solution, wherein the mass percentage of the solute in the hydrochloric acid solution is 5%; add bentonite to the hydrochloric acid solution for acid treatment, wherein the material-to-liquid ratio of bentonite to hydrochloric acid solution is 1g:20mL, the acid treatment temperature is 60℃, and the treatment time is 10min; after acid treatment, separate the solid and liquid phases, wash the solid phase with deionized water to remove residual acid, and dry it at 80℃ for 2h to obtain pretreated bentonite; add the pretreated bentonite to ethanol and disperse it to form a dispersion. The material-to-liquid ratio of the dispersion was 1g of pretreated bentonite to 20g of ethanol. Then, γ-(2,3-epoxypropoxy)propyltrimethoxysilane was added to the dispersion for modification, with the mass percentage of γ-(2,3-epoxypropoxy)propyltrimethoxysilane in the solution being 6%. The modification temperature was 50℃, and reflux was applied during the modification process for 5 hours. After modification, the solid and liquid phases were separated, and the solid phase was washed three times with ethanol and dried at 80℃ for 1 hour to obtain modified bentonite. (2) An N-acetyl-L-cysteine solution was prepared in a reaction vessel. The concentration of N-acetyl-L-cysteine in the N-acetyl-L-cysteine solution was 70 g / L. The solvent was a mixture of deionized water and dimethyl sulfoxide, with a volume ratio of 1:1. The modified bentonite was added to the reaction vessel. The mass ratio of the modified bentonite added to the volume ratio of the N-acetyl-L-cysteine solution in the reaction vessel was 1 g: 100 mL. The reaction vessel was then sealed and nitrogen gas was introduced to purge the air from the reaction vessel. The vessel was heated to 80°C in a water bath and kept at that temperature for 20 h. The solid and liquid phases were then separated. The solid phase was washed three times with deionized water and dried at 80°C for 2 h to obtain the modified bentonite. (3) Dissolve chitosan oligosaccharide in deionized water kept at 80°C to obtain an aqueous solution of chitosan oligosaccharide, wherein the concentration of chitosan oligosaccharide in the aqueous solution is 8g / 100mL; then, under the conditions of keeping at 80°C in a water bath and stirring, add methanesulfonic acid and sodium hexametaphosphate sequentially to the aqueous solution of chitosan oligosaccharide, wherein the mass ratio of added methanesulfonic acid and sodium hexametaphosphate to the volume ratio of the aqueous solution of chitosan oligosaccharide is methanesulfonic acid: sodium hexametaphosphate: aqueous solution of chitosan oligosaccharide = 2g: 3g: 100mL; after the addition is completed, keep at 80°C for 1h, after the heat preservation is completed, add excess ether to precipitate, then add the precipitate to deionized water to redissolve, dialyze to remove unreacted sodium hexametaphosphate, then concentrate under reduced pressure, freeze dry to obtain pretreated chitosan oligosaccharide; (4) Dissolve the pretreated chitosan oligosaccharide in deionized water to obtain solution I; the concentration of pretreated chitosan oligosaccharide in solution I is 8 g / 100 mL, and the solvent is water; add the modified bentonite and starch to deionized water and stir evenly to obtain mixture II; in mixture II, the ratio of modified bentonite to starch to deionized water is modified bentonite: starch: deionized water = 9 g: 18 g: 500 mL; then add solution I and mixture II to a polyvinyl alcohol aqueous solution kept at 70 °C, stir evenly after the addition is completed, and then add 2-fluoroacrylic acid, N,N'-methylenebisacrylamide crosslinking agent and potassium persulfate. The polyvinyl alcohol aqueous solution is obtained by adding polyvinyl alcohol (PVA-1788) to water at 90 °C. The polyvinyl alcohol (PVA) was completely dissolved in deionized water at a constant temperature to obtain a solution with a concentration of 9 g / 100 mL. Solution I and Mixture II were added to the PVA aqueous solution, followed by the addition of 2-fluoroacrylic acid, N,N'-methylenebisacrylamide crosslinking agent, and potassium persulfate in a ratio of Solution I: Mixture II: PVA aqueous solution: 2-fluoroacrylic acid: crosslinking agent: potassium persulfate = 20 mL: 50 mL: 100 mL: 4 g: 0.2 g: 0.7 g. After addition, the mixture was kept at 70 °C and stirred for 30 min. The solid-phase reaction product was then collected through solid-liquid separation, purified by soaking in deionized water for 24 h (water changed every 4 h), dried at 40 °C for 24 h, ground, and passed through a 60-mesh sieve to obtain the fluorinated hydrogel.
[0019] Example 3 A method for preparing a fluorinated hydrogel, comprising the following steps: (1) Prepare a hydrochloric acid solution, wherein the mass percentage of the solute in the hydrochloric acid solution is 5%; add bentonite to the hydrochloric acid solution for acid treatment, wherein the material-to-liquid ratio of bentonite to hydrochloric acid solution is 1g:20mL, the acid treatment temperature is 60℃, and the treatment time is 10min; after acid treatment, separate the solid and liquid phases, wash the solid phase with deionized water to remove residual acid, and dry it at 80℃ for 2h to obtain pretreated bentonite; add the pretreated bentonite to ethanol and disperse it to form a dispersion. The material-to-liquid ratio of the dispersion was pretreated bentonite:ethanol = 1g:20g; then γ-(2,3-epoxypropoxy)propyltrimethoxysilane was added to the dispersion for modification, with the mass percentage of γ-(2,3-epoxypropoxy)propyltrimethoxysilane in the solution being 7%; the modification temperature was 60℃, and reflux was used during the modification process, with a modification time of 4h; after modification, solid and liquid were separated, the solid phase was washed three times with ethanol, and dried at 80℃ for 1h to obtain modified bentonite. (2) An N-acetyl-L-cysteine solution was prepared in a reaction vessel. The concentration of N-acetyl-L-cysteine in the N-acetyl-L-cysteine solution was 80 g / L, and the solvent was a mixture of deionized water and dimethyl sulfoxide with a volume ratio of 1:1. The modified bentonite was added to the reaction vessel. The mass ratio of the modified bentonite added to the volume ratio of the N-acetyl-L-cysteine solution in the reaction vessel was 1.5 g: 100 mL. The reaction vessel was then sealed and nitrogen gas was introduced to purge the air from the reaction vessel. The vessel was heated to 85°C in a water bath and kept at that temperature for 20 h. The solid and liquid phases were then separated. The solid phase was washed three times with deionized water and dried at 80°C for 2 h to obtain the modified bentonite. (3) Dissolve chitosan oligosaccharide in deionized water kept at 80°C to obtain an aqueous solution of chitosan oligosaccharide, wherein the concentration of chitosan oligosaccharide in the aqueous solution is 9 g / 100 mL; then, under the conditions of keeping at 80°C in a water bath and stirring, add methanesulfonic acid and sodium hexametaphosphate sequentially to the aqueous solution of chitosan oligosaccharide, wherein the mass ratio of added methanesulfonic acid and sodium hexametaphosphate to the volume ratio of the aqueous solution of chitosan oligosaccharide is methanesulfonic acid: sodium hexametaphosphate: aqueous solution of chitosan oligosaccharide = 2 g: 3 g: 100 mL; after the addition is completed, keep at 80°C for 1 h, after the heat preservation is completed, add excess ether to precipitate, add the precipitate to deionized water to redissolve, dialyze to remove unreacted sodium hexametaphosphate, then concentrate under reduced pressure, freeze dry to obtain pretreated chitosan oligosaccharide; (4) Dissolve the pretreated chitosan oligosaccharide in deionized water to obtain solution I; the concentration of pretreated chitosan oligosaccharide in solution I is 8 g / 100 mL, and the solvent is water; add the modified bentonite and starch to deionized water and stir evenly to obtain mixture II; in mixture II, the ratio of modified bentonite to starch to deionized water is modified bentonite: starch: deionized water = 9 g: 18 g: 500 mL; then add solution I and mixture II to a polyvinyl alcohol aqueous solution kept at 70 °C, stir evenly after the addition is completed, and then add 2-fluoroacrylic acid, N,N'-methylenebisacrylamide crosslinking agent and potassium persulfate. The polyvinyl alcohol aqueous solution is obtained by adding polyvinyl alcohol (PVA-1788) to water at 90 °C. The polyvinyl alcohol (PVA) was completely dissolved in deionized water at a constant temperature to obtain a solution with a concentration of 9 g / 100 mL. Solution I and Mixture II were added to the PVA aqueous solution, followed by the addition of 2-fluoroacrylic acid, N,N'-methylenebisacrylamide crosslinking agent, and potassium persulfate in a ratio of Solution I: Mixture II: PVA aqueous solution: 2-fluoroacrylic acid: crosslinking agent: potassium persulfate = 20 mL: 60 mL: 100 mL: 4 g: 0.3 g: 0.7 g. After addition, the mixture was kept at 70 °C and stirred for 30 min. The solid-phase reaction product was then collected through solid-liquid separation, purified by soaking in deionized water for 24 h (water changed every 4 h), dried at 40 °C for 24 h, ground, and passed through a 60-mesh sieve to obtain the fluorinated hydrogel.
[0020] Example 4 A method for preparing a fluorinated hydrogel, comprising the following steps: (1) Prepare a hydrochloric acid solution, wherein the mass percentage of the solute in the hydrochloric acid solution is 5%; add bentonite to the hydrochloric acid solution for acid treatment, wherein the material-to-liquid ratio of bentonite to hydrochloric acid solution is 1g:20mL, the acid treatment temperature is 60℃, and the treatment time is 10min; after acid treatment, separate the solid and liquid phases, wash the solid phase with deionized water to remove residual acid, and dry it at 80℃ for 2h to obtain pretreated bentonite; add the pretreated bentonite to ethanol and disperse it to form a dispersion. The material-to-liquid ratio of the dispersion was 1g of pretreated bentonite to 20g of ethanol. Then, γ-(2,3-epoxypropoxy)propyltrimethoxysilane was added to the dispersion for modification, with the mass percentage of γ-(2,3-epoxypropoxy)propyltrimethoxysilane in the solution being 8%. The modification temperature was 60℃, and reflux was applied during the modification process for 3 hours. After modification, the solid and liquid phases were separated, and the solid phase was washed three times with ethanol and dried at 80℃ for 1 hour to obtain modified bentonite. (2) An N-acetyl-L-cysteine solution was prepared in a reaction vessel. The concentration of N-acetyl-L-cysteine in the N-acetyl-L-cysteine solution was 80 g / L, and the solvent was a mixture of deionized water and dimethyl sulfoxide with a volume ratio of 1:1. The modified bentonite was added to the reaction vessel. The mass ratio of the modified bentonite added to the volume ratio of the N-acetyl-L-cysteine solution in the reaction vessel was 1.5 g: 100 mL. The reaction vessel was then sealed and nitrogen gas was introduced to purge the air from the reaction vessel. The vessel was heated to 85°C in a water bath and kept at that temperature for 20 h. The solid and liquid phases were then separated. The solid phase was washed three times with deionized water and dried at 80°C for 2 h to obtain the modified bentonite. (3) Dissolve chitosan oligosaccharide in deionized water kept at 80°C to obtain an aqueous solution of chitosan oligosaccharide, wherein the concentration of chitosan oligosaccharide in the aqueous solution is 10g / 100mL; then, under the conditions of keeping at 80°C in a water bath and stirring, add methanesulfonic acid and sodium hexametaphosphate sequentially to the aqueous solution of chitosan oligosaccharide, wherein the mass ratio of added methanesulfonic acid and sodium hexametaphosphate to the volume ratio of the aqueous solution of chitosan oligosaccharide is methanesulfonic acid: sodium hexametaphosphate: aqueous solution of chitosan oligosaccharide = 2g: 5g: 100mL; after the addition is completed, keep at 80°C for 1h, after the heat preservation is completed, add excess ether to precipitate, then add the precipitate to deionized water to redissolve, dialyze to remove unreacted sodium hexametaphosphate, then concentrate under reduced pressure, freeze dry to obtain pretreated chitosan oligosaccharide; (4) Dissolve the pretreated chitosan oligosaccharide in deionized water to obtain solution I; the concentration of the pretreated chitosan oligosaccharide in solution I is 10g / 100mL, and the solvent is water; add the modified bentonite and starch to deionized water and stir evenly to obtain mixture II; in mixture II, the ratio of modified bentonite and starch to deionized water is modified bentonite: starch: deionized water = 10g: 20g: 500mL; then add solution I and mixture II to a polyvinyl alcohol aqueous solution kept at 70℃, stir evenly after the addition is completed, and then add 2-fluoroacrylic acid, N,N'-methylenebisacrylamide crosslinking agent and potassium persulfate. The polyvinyl alcohol aqueous solution is obtained by adding polyvinyl alcohol (PVA-1788) to water at 90℃. The polyvinyl alcohol (PVA) was completely dissolved in deionized water at a constant temperature to obtain a fluorinated hydrogel with a concentration of 10 g / 100 mL in the aqueous solution. Solution I and Mixture II were added to the aqueous PVA solution, followed by the addition of 2-fluoroacrylic acid, N,N'-methylenebisacrylamide crosslinking agent, and potassium persulfate in a ratio of Solution I: Mixture II: Aqueous PVA: 2-fluoroacrylic acid: Crosslinking agent: Potassium persulfate = 20 mL: 60 mL: 100 mL: 5 g: 0.3 g: 0.8 g. After addition, the mixture was kept at 70 °C and stirred for 30 min. The solid-phase reaction product was then collected through solid-liquid separation, purified by soaking in deionized water for 24 h (water changed every 4 h), dried at 40 °C for 24 h, ground, and passed through a 60-mesh sieve to obtain the fluorinated hydrogel.
[0021] Comparative Example 1 A method for preparing a fluorinated hydrogel as a comparison includes the following steps: (1) Prepare a hydrochloric acid solution, wherein the mass percentage of the solute in the hydrochloric acid solution is 5%; add bentonite to the hydrochloric acid solution for acid treatment, wherein the material-to-liquid ratio of bentonite to hydrochloric acid solution is 1g:20mL, the acid treatment temperature is 60℃, and the treatment time is 10min; after acid treatment, separate the solid and liquid phases, wash the solid phase with deionized water to remove residual acid, and dry it at 80℃ for 2h to obtain pretreated bentonite; add the pretreated bentonite to ethanol and disperse it to form a dispersion. The material-to-liquid ratio of the dispersion was pretreated bentonite:ethanol = 1g:20g; then γ-(2,3-epoxypropoxy)propyltrimethoxysilane was added to the dispersion for modification, with the mass percentage of γ-(2,3-epoxypropoxy)propyltrimethoxysilane in the solution being 7%; the modification temperature was 60℃, and reflux was used during the modification process, with a modification time of 4h; after modification, solid and liquid were separated, the solid phase was washed three times with ethanol, and dried at 80℃ for 1h to obtain modified bentonite. (2) Chitosan oligosaccharide was dissolved in deionized water kept at 80°C to obtain an aqueous solution of chitosan oligosaccharide with a concentration of 9 g / 100 mL. Then, under the conditions of keeping the solution at 80°C and stirring, methanesulfonic acid and sodium hexametaphosphate were added sequentially to the aqueous solution of chitosan oligosaccharide. The ratio of the added mass of methanesulfonic acid and sodium hexametaphosphate to the volume of the aqueous solution of chitosan oligosaccharide was methanesulfonic acid: sodium hexametaphosphate: aqueous solution of chitosan oligosaccharide = 2 g: 3 g: 100 mL. After the addition was completed, the solution was kept at 80°C for 1 h. After the insulation was completed, excess ether was added to precipitate the solution. The precipitate was then re-dissolved in deionized water, dialyzed to remove unreacted sodium hexametaphosphate, concentrated under reduced pressure, and freeze-dried to obtain pretreated chitosan oligosaccharide. (3) Dissolve the pretreated chitosan oligosaccharide in deionized water to obtain solution I; the concentration of the pretreated chitosan oligosaccharide in solution I is 8 g / 100 mL, and the solvent is water; add the modified bentonite and starch to deionized water and stir evenly to obtain mixture II; in mixture II, the ratio of modified bentonite and starch to deionized water is modified bentonite: starch: deionized water = 9 g: 18 g: 500 mL; then add solution I and mixture II to a polyvinyl alcohol aqueous solution kept at 70 °C, stir evenly after the addition is completed, and then add 2-fluoroacrylic acid, N,N'-methylenebisacrylamide crosslinking agent and potassium persulfate. The polyvinyl alcohol aqueous solution is obtained by adding polyvinyl alcohol (PVA-1788) to a 90 °C water bath. The polyvinyl alcohol (PVA) was completely dissolved in warm deionized water to obtain a polyvinyl alcohol aqueous solution with a concentration of 9 g / 100 mL. Solution I and Mixture II were added to the PVA aqueous solution, followed by the addition of 2-fluoroacrylic acid, N,N'-methylenebisacrylamide crosslinking agent, and potassium persulfate in a ratio of Solution I: Mixture II: PVA aqueous solution: 2-fluoroacrylic acid: crosslinking agent: potassium persulfate = 20 mL: 60 mL: 100 mL: 4 g: 0.3 g: 0.7 g. After addition, the mixture was kept at 70 °C and stirred for 30 min. The solid-phase reaction product was then collected through solid-liquid separation, purified by soaking in deionized water for 24 h (water changed every 4 h), dried at 40 °C for 24 h, ground, and passed through a 60-mesh sieve to obtain the fluorinated hydrogel.
[0022] Comparative Example 2 A method for preparing a fluorinated hydrogel as a comparison includes the following steps: (1) Prepare a hydrochloric acid solution, wherein the mass percentage of the solute in the hydrochloric acid solution is 5%; add bentonite to the hydrochloric acid solution for acid treatment, wherein the material-to-liquid ratio of bentonite to hydrochloric acid solution is 1g:20mL, the acid treatment temperature is 60℃, and the treatment time is 10min; after acid treatment, separate the solid and liquid phases, wash the solid phase with deionized water to remove residual acid, and dry it at 80℃ for 2h to obtain pretreated bentonite; add the pretreated bentonite to ethanol and disperse it to form a dispersion. The material-to-liquid ratio of the dispersion was pretreated bentonite:ethanol = 1g:20g; then γ-(2,3-epoxypropoxy)propyltrimethoxysilane was added to the dispersion for modification, with the mass percentage of γ-(2,3-epoxypropoxy)propyltrimethoxysilane in the solution being 7%; the modification temperature was 60℃, and reflux was used during the modification process, with a modification time of 4h; after modification, solid and liquid were separated, the solid phase was washed three times with ethanol, and dried at 80℃ for 1h to obtain modified bentonite. (2) An N-acetyl-L-cysteine solution was prepared in a reaction vessel. The concentration of N-acetyl-L-cysteine in the N-acetyl-L-cysteine solution was 80 g / L, and the solvent was a mixture of deionized water and dimethyl sulfoxide with a volume ratio of 1:1. The modified bentonite was added to the reaction vessel. The mass ratio of the modified bentonite added to the volume ratio of the N-acetyl-L-cysteine solution in the reaction vessel was 1.5 g: 100 mL. The reaction vessel was then sealed and nitrogen gas was introduced to purge the air from the reaction vessel. The vessel was heated to 85°C in a water bath and kept at that temperature for 20 h. The solid and liquid phases were then separated. The solid phase was washed three times with deionized water and dried at 80°C for 2 h to obtain the modified bentonite. (3) Dissolve chitosan oligosaccharide in deionized water to obtain solution I; the concentration of chitosan oligosaccharide in solution I is 8 g / 100 mL, and the solvent is water; add the modified bentonite and starch to deionized water and stir evenly to obtain mixture II; in mixture II, the ratio of modified bentonite and starch to deionized water is modified bentonite: starch: deionized water = 9 g: 18 g: 500 mL; then add solution I and mixture II to a polyvinyl alcohol aqueous solution kept at 70 °C, stir evenly after the addition is complete, then add 2-fluoroacrylic acid, N,N'-methylenebisacrylamide crosslinking agent and potassium persulfate, the polyvinyl alcohol aqueous solution is obtained by adding polyvinyl alcohol (PVA-1788) to a 90 °C water bath for constant temperature. The polyvinyl alcohol (PVA) was completely dissolved in deionized water, and the concentration of PVA in the aqueous solution was 9 g / 100 mL. Solution I and Mixture II were added to the PVA aqueous solution, followed by the addition of 2-fluoroacrylic acid, N,N'-methylenebisacrylamide crosslinking agent, and potassium persulfate in the following ratio: Solution I: Mixture II: Aqueous solution of PVA: 2-fluoroacrylic acid: Crosslinking agent: Potassium persulfate = 20 mL: 60 mL: 100 mL: 4 g: 0.3 g: 0.7 g. After addition, the mixture was kept at 70 °C and stirred for 30 min. The solid-phase reaction product was then collected through solid-liquid separation, purified by soaking in deionized water for 24 h (water changed every 4 h), dried at 40 °C for 24 h, ground, and passed through a 60-mesh sieve to obtain the fluorinated hydrogel.
[0023] Example 5 A lithium-ion test solution was prepared by adding lithium chloride, sodium chloride, and potassium chloride to deionized water. The lithium ion concentration in the test solution was 100 mmol / L, the sodium ion concentration was 2500 mmol / L, and the potassium ion concentration was 100 mmol / L. Fluorinated hydrogels prepared according to the methods described in the above examples and comparative examples were added to the lithium-ion test solution and soaked and stirred at room temperature for 24 hours. The addition ratio was 1 mg of fluorinated hydrogel to 1 mL of lithium-ion test solution. The concentration of each ion in the solution after adsorption was determined using atomic absorption spectrometry to obtain the adsorption capacity of the fluorinated hydrogel for each ion. The results are as follows: Figure 1 As shown.
[0024] Depend on Figure 1It is known that the fluorinated hydrogel prepared by the method described in this invention has strong adsorption and extraction performance for lithium ions, while its adsorption for sodium and potassium ions is relatively weak, exhibiting good selectivity for lithium ion adsorption. This makes the fluorinated hydrogel suitable for lithium extraction processes. Comparative examples 3 and other comparative examples show that modifying the raw material bentonite or pretreating the chitosan oligosaccharide using the method described in this invention can further improve the lithium ion adsorption and selectivity of the fluorinated hydrogel product. This may be because the present invention first acid-treats the bentonite to remove easily soluble impurities or organic matter from the bentonite surface, exposing the main active components and increasing the adsorption sites on the bentonite surface. Simultaneously, acid treatment helps to increase the specific surface area of the bentonite and increase the adsorption pore content. Subsequent modification of the bentonite with a silanizing agent can improve particle dispersibility and introduce active groups on the particle surface, preparing for subsequent modification. Modification with N-acetyl-L-cysteine introduces groups such as -HS and -COOH, which enhances the crosslinking and binding force between bentonite and subsequent pretreated components such as chitosan oligosaccharide and 2-fluoroacrylic acid. Furthermore, the introduced groups, along with the active groups and -F groups introduced into the pretreated chitosan oligosaccharide, can interact with lithium ions, thus achieving lithium ion adsorption. Additionally, the large molecular structure formed by the crosslinking of modified bentonite, pretreated chitosan oligosaccharide, and 2-fluoroacrylic acid selectively adsorbs lithium ions with smaller ionic radii, while physically blocking larger ions such as sodium and potassium ions. The introduced -F groups also preferentially bind to lithium ions based on the Li-F specific interaction, further improving the selective adsorption of lithium ions.
[0025] The technical solutions provided by the present invention have been described in detail above. For those skilled in the art, there will be changes in specific implementation methods and application scope based on the ideas of the embodiments of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.
Claims
1. A process for the preparation of a fluorochemical hydrogel, characterized by the steps of The method comprises the following steps: (1) configuring a hydrochloric acid solution, adding bentonite into the hydrochloric acid solution for acid treatment, performing solid-liquid separation after the acid treatment, washing the solid phase to remove residual acid solution, and drying to obtain pretreated bentonite; dispersing the pretreated bentonite in ethanol to form a dispersion liquid, then adding γ-(2, 3-epoxypropoxy) propyl trimethoxysilane into the dispersion liquid for modification, performing solid-liquid separation after the modification, washing the solid phase, and drying to obtain modified bentonite; (2) configuring an N-acetyl-L-cysteine solution in a reaction kettle, adding the modified bentonite into the reaction kettle, then sealing the reaction kettle and introducing a protective gas to discharge air in the reaction kettle, performing water bath heating reaction, performing solid-liquid separation after the reaction is completed, washing the solid phase, and drying to obtain modified bentonite; (3) configuring a chitosan oligosaccharide aqueous solution, adding methanesulfonic acid and sodium hexametaphosphate into the chitosan oligosaccharide aqueous solution in a stirring state in sequence, heating and keeping warm after the feeding is completed, adding excess diethyl ether for precipitation after the keeping warm is completed, dissolving the precipitate in deionized water, removing unreacted sodium hexametaphosphate by dialysis, reducing and concentrating, and freeze-drying to obtain pretreated chitosan oligosaccharide; (4) dissolving the pretreated chitosan oligosaccharide in deionized water to obtain solution I; adding the modified bentonite and starch into deionized water to obtain mixed liquid II, then adding the solution I and the mixed liquid II into a polyvinyl alcohol aqueous solution kept at a temperature above 70 DEG C, stirring uniformly after the feeding is completed, then adding 2-fluoroacrylic acid, a crosslinking agent and potassium persulfate, stirring and reacting, then collecting the solid phase reaction product by solid-liquid separation, soaking in deionized water, and drying to obtain the fluorine-containing hydrogel.
2. A process for the preparation of a fluorochemical hydrogel according to claim 1, characterized in that, In the step (1), the mass percentage of the solute in the hydrochloric acid solution is 5% to 10%; the ratio of bentonite to the hydrochloric acid solution is 1g:20 to 100mL; the acid treatment temperature is 60 to 70 DEG C; and the treatment time is 10 to 30 minutes.
3. The method of claim 1, wherein the fluorine-containing hydrogel is prepared by the steps of: In the step (1), the ratio of the pretreated bentonite to ethanol for dispersing the pretreated bentonite in ethanol to form a dispersion liquid is 1g:20 to 50g; the mass percentage of γ-(2, 3-epoxypropoxy) propyl trimethoxysilane in the solution is 5% to 8%; the modification temperature of γ-(2, 3-epoxypropoxy) propyl trimethoxysilane is 50 to 60 DEG C; the modification process is condensed and refluxed; and the modification time is 3 to 6 hours.
4. The method of claim 1, wherein the fluorine-containing hydrogel is prepared by the steps of: In the step (2), the concentration of N-acetyl-L-cysteine in the N-acetyl-L-cysteine solution is 70 to 80g / L; the solvent is a mixture of deionized water and dimethyl sulfoxide; the ratio of the mass of the modified bentonite to the volume of the N-acetyl-L-cysteine solution in the reaction kettle is 1 to 1.5g:100mL; and the water bath is heated to 80 to 85 DEG C and kept warm for more than 20 hours.
5. A process for the preparation of a fluorochemical hydrogel according to claim 4, characterized in that, The solvent is a mixture of deionized water and dimethyl sulfoxide in a volume ratio of 1:
1.
6. The method of claim 1, wherein the fluorine-containing hydrogel is prepared by the steps of: The protective gas is nitrogen or argon.
7. The method of claim 1, wherein the fluorohydrogel is prepared by the steps of: In the step (3), chitooligosaccharide is dissolved in deionized water in a water bath at 80-85 ℃ to obtain a chitooligosaccharide aqueous solution, the concentration of chitooligosaccharide in the chitooligosaccharide aqueous solution is 7-10 g / 100 mL; then methanesulfonic acid and sodium hexametaphosphate are sequentially added to the chitooligosaccharide aqueous solution under the condition of water bath at 80-85 ℃, the mass ratio of methanesulfonic acid and sodium hexametaphosphate to the volume of the chitooligosaccharide aqueous solution is methanesulfonic acid:sodium hexametaphosphate:chitooligosaccharide aqueous solution = 2 g:1-5 g:100 mL; after the completion of feeding, 80-85 ℃ is maintained for stirring for more than 1 h.
8. The method of claim 1, wherein the fluorohydrogel is prepared by the steps of: In the step (4), the concentration of pretreated chitooligosaccharide in the solution I is 6-10 g / 100 mL, and the solvent is water; in the mixed solution II, the mass ratio of modified bentonite and starch to deionized water is modified bentonite:starch:deionized water = 8-10 g:16-20 g:500 mL; the polyvinyl alcohol aqueous solution is obtained by completely dissolving polyvinyl alcohol in deionized water in a water bath at 90 ℃, and the concentration of polyvinyl alcohol in the polyvinyl alcohol aqueous solution is 8-10 g / 100 mL; the solution I and the mixed solution II are added to the polyvinyl alcohol aqueous solution, and then 2-fluoroacrylic acid, a crosslinking agent and potassium persulfate are added, the mass ratio is solution I:mixed solution II:polyvinyl alcohol aqueous solution:2-fluoroacrylic acid:crosslinking agent:potassium persulfate = 20 mL:50-60 mL:100 mL:3-5 g:0.2-0.3 g:0.6-0.8 g, and after the completion of feeding, 70 ℃ or higher is maintained for stirring for 30-40 min.
9. The method of claim 1, wherein the fluorohydrogel is prepared by the steps of: The crosslinking agent is N,N'-methylene bisacrylamide.
10. Use of the hydrogel according to any one of claims 1 to 9 in a process for the adsorptive extraction of lithium, characterized in that, The fluorine-containing hydrogel is used for selective adsorption and separation of lithium ions in a mixed solution containing lithium ions, sodium ions and potassium ions.