A modified hydrogel adsorbent and its preparation method and application

Abstract

The present disclosure provides a modified hydrogel adsorbent and a preparation method and application thereof, the preparation method comprising the following steps: (1) mixing a first polymer solution with an acid solution to obtain solution A, mixing a second polymer, a crosslinking agent and a solvent to obtain solution B, mixing solution A and solution B to obtain a mixed solution, adding a lithium ion sieve to obtain a pre-polymer solution, and after reaction, freezing treatment is performed to obtain a hydrogel adsorbent; (2) mixing a linear polymer monomer and an initiator to obtain a modified precursor solution, mixing the hydrogel adsorbent and the modified precursor solution, and performing light irradiation reaction to obtain the modified hydrogel adsorbent. The present disclosure wraps the adsorbent / ion sieve into the hydrogel to prepare a hydrogel adsorbent with good mechanical stability, the impurity ion level in the adsorbent is constant, the method for extracting lithium by concentrating brine through light irradiation can be realized, lithium is extracted while concentrating, a by-product salt is obtained, and no additional concentration step is required.

Description

TECHNICAL FIELD

[0001] The present disclosure belongs to the technical field of lithium extraction from salt lakes, and relates to a modified hydrogel adsorbent and a preparation method and application thereof. BACKGROUND

[0002] Lithium is the lightest metal element in the world, has strong electrochemical properties, and is often used in the battery industry. Today, new energy electric vehicles and hybrid vehicles are gradually replacing traditional fossil fuel vehicles, leading to an increasing demand for lithium ion batteries, and the price of lithium is rising. The development of the new energy vehicle industry must have enough lithium resources as a foundation.

[0003] The methods for extracting lithium from salt lake brine mainly include extraction, nanofiltration, adsorption, and ion exchange. The extraction method is mature but causes serious pollution, and is not suitable for salt lake brine in the Qinghai-Tibet region from the perspective of environmental protection. The adsorption method has high ion selectivity and is simple and environmentally friendly, and therefore has gradually attracted attention.

[0004] CN116121557A discloses a method for extracting lithium from sodium sulfate or sodium carbonate type salt lakes using an aluminum-based adsorbent. The specific process is as follows: S1, dilution of brine; S2, removal of sulfate and carbonate by nanofiltration; S3, treatment with anion resin; S4, deep removal of calcium and magnesium by resin; S5, concentration of brine: high-pressure reverse osmosis is used to concentrate the brine treated in step S4; S6, adsorption of lithium: the concentrated water produced by high-pressure reverse osmosis is pumped into an aluminum-based adsorption column for lithium adsorption, and the lithium desorption solution obtained by desorption of the lithium-loaded aluminum-based adsorption column is used to prepare lithium carbonate or lithium hydroxide products.

[0005] CN116395719A discloses a method for concentrating and removing impurities from lithium extraction liquid from salt lakes by adsorption, which belongs to the technical field of lithium extraction from salt lakes. The method includes: pretreating the salt lake brine after lithium extraction by adsorption by nanofiltration to remove most of the calcium ions and magnesium ions in the brine; the wastewater after nanofiltration pretreatment enters a divalent ion separation electrodialysis system to intercept calcium ions, magnesium ions and boron ions, to concentrate lithium ions in the brine and obtain concentrated water products and dilute water products; the concentrated water products enter an MVR evaporator to further increase the concentration of lithium ions in the concentrated water products; then sodium carbonate is introduced for lithium precipitation, and sodium chloride filtrate and lithium carbonate products are obtained after centrifugal separation.

[0006] The above-mentioned scheme usually concentrates the brine before lithium extraction in order to improve the adsorption efficiency of the adsorbent, which is complicated. SUMMARY

[0007] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0008] The purpose of the present disclosure is to provide a modified hydrogel adsorbent and its preparation method and application, the present disclosure wraps the adsorbent / ionic sieve into the hydrogel to prepare a hydrogel adsorbent with good mechanical stability, the impurity ion level in the adsorbent is constant and does not increase with the evaporation of brine, the lithium extraction method using light concentration of brine can be realized, lithium is extracted while concentrating, and a byproduct salt is obtained without an additional concentration step.

[0009] To achieve this purpose, the present disclosure adopts the following technical solutions:

[0010] In a first aspect, the present disclosure provides a preparation method of a modified hydrogel adsorbent, the preparation method comprising the following steps:

[0011] (1) mixing a first polymer solution with an acid solution to obtain solution A, mixing a second polymer, a crosslinking agent and a solvent to obtain solution B, mixing solution A and solution B to obtain a mixed solution, adding a lithium ion sieve to obtain a modified hydrogel adsorbent pre-polymer solution, and after reaction, freezing treatment to obtain a hydrogel adsorbent;

[0012] (2) mixing a linear polymer monomer and an initiator to obtain a modified precursor solution, mixing the hydrogel adsorbent and the modified precursor solution, and performing light reaction to obtain the modified hydrogel adsorbent.

[0013] The solvent of the acid solution in the present disclosure is water.

[0014] The present disclosure prepares a modified hydrogel adsorbent by linear polymer modification under light conditions, which can make it have better mechanical stability and be beneficial to improve the service life of the adsorbent as a whole. The method of the present disclosure can directly wrap the adsorbent / ionic sieve into the hydrogel, and the process is simple and does not need to be granulated again.

[0015] In one embodiment, the first polymer in step (1) includes any one or a combination of at least two of polypyrrole, chitosan or sodium alginate.

[0016] In one embodiment, the concentration of the first polymer solution is 10-50 g / L, for example: 10 g / L, 20 g / L, 30 g / L, 40 g / L or 50 g / L, etc.

[0017] In one embodiment, the acid solution includes hydrochloric acid.

[0018] In one embodiment, the concentration of the acid solution is 1-2 mol / L, for example: 1 mol / L, 1.2 mol / L, 1.5 mol / L, 1.8 mol / L or 2 mol / L, etc.

[0019] In one embodiment, the volume ratio of the first polymer solution to the acid solution is 1:(2~3), for example, 1:2, 1:2.2, 1:2.5, 1:2.8, or 1:3, etc.

[0020] In one embodiment, the second polymer of step (1) comprises any one or a combination of at least two of polyvinyl alcohol, polyethylene glycol, or polyvinyl acetate.

[0021] In one embodiment, the cross-linking agent comprises any one or a combination of at least two of glutaraldehyde, glyoxal, or N,N-methylenebisacrylamide.

[0022] In one embodiment, the mass of the cross-linking agent is 0.1%~2% of the mass of the second polymer, for example, 0.1%, 0.5%, 1%, 1.5%, or 2%, etc.

[0023] In one embodiment, the solvent comprises deionized water.

[0024] In one embodiment, the temperature of the solvent is 85~95℃, for example, 85℃, 88℃, 90℃, 92℃, or 95℃, etc.

[0025] In one embodiment, the mass-to-volume ratio of the second polymer and the solvent is 50~150 g / L, for example, 50 g / L, 80 g / L, 100 g / L, 120 g / L, or 150 g / L, etc.

[0026] In one embodiment, the mass ratio of the first polymer to the second polymer in the mixed solution of step (1) is 1:(10~20), for example, 1:10, 1:12, 1:15, 1:18, or 1:20, etc.

[0027] In one embodiment, the lithium ion sieve comprises a manganese-based lithium ion sieve and / or an aluminum-based lithium ion sieve.

[0028] In one embodiment, the mass of the lithium ion sieve is 10%~15% of the total mass of the first polymer and the second polymer, for example, 10%, 11%, 12%, 14%, or 15%, etc.

[0029] In one embodiment, the ultrasonic treatment is performed after the lithium ion sieve is added.

[0030] In one embodiment, the ultrasonic treatment is performed for 30~60 min, for example, 30 min, 35 min, 40 min, 50 min, or 60 min, etc.

[0031] In one embodiment, the reaction is performed for 2~5 h, for example, 2 h, 2.5 h, 3 h, 4 h, or 5 h, etc.

[0032] In one embodiment, the freezing treatment in step (1) comprises pre-freezing and freeze-drying.

[0033] In one embodiment, the pre-freezing temperature is -20~-40℃, for example, -20℃, -25℃, -30℃, -35℃ or -40℃, etc.

[0034] In one embodiment, the pre-freezing time is 12~48h, for example, 12 h, 18 h, 24 h, 36 h or 48 h, etc.

[0035] In one embodiment, the freeze-drying time is 12~48h, for example, 12 h, 18 h, 24 h, 36 h or 48 h, etc.

[0036] In one embodiment, the linear polymer monomer in step (2) comprises any one or a combination of at least two of acrylamide, acrylic acid, sodium acrylate, 2-acrylamido-2-methylpropanesulfonic acid or sodium 2-acrylamido-2-methylpropanesulfonate.

[0037] In one embodiment, the initiator comprises any one or a combination of at least two of 2-oxoglutaric acid, potassium persulfate, ammonium persulfate, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone or 2-hydroxy-2-methylpropiophenone.

[0038] In one embodiment, the mass of the initiator is 0.5%~1.5% of the mass of the linear polymer monomer, for example, 0.5%, 0.8%, 1%, 1.2% or 1.5%, etc.

[0039] In one embodiment, the concentration of the linear polymer monomer in the modified precursor solution is 0.2~1 mol / L, for example, 0.2 mol / L, 0.5 mol / L, 0.6 mol / L, 0.8 mol / L or 1 mol / L, etc.

[0040] In one embodiment, the wavelength of the light irradiation in step (2) is 355~375nm, for example, 355 nm, 360nm, 365 nm, 370 nm or 375 nm, etc.

[0041] In one embodiment, the light intensity of the light irradiation is 3~5 mW / cm 2 , for example, 3 mW / cm 2 , 3.5 mW / cm 2 , 4 mW / cm 2 , 4.5 mW / cm 2 or 5 mW / cm2 wait.

[0042] In one embodiment, the photoreaction time is 2 to 3 hours, for example: 2 hours, 2.2 hours, 2.5 hours, 2.8 hours, or 3 hours.

[0043] In a second aspect, this disclosure provides a modified hydrogel adsorbent, which is prepared by the method described in the first aspect.

[0044] The modified hydrogel adsorbent prepared by the method described in this disclosure has a constant level of impurity ions that does not increase with the evaporation of brine. Therefore, during the lithium extraction process, it can ensure that the lithium ion concentration increases without increasing the impurity ion concentration.

[0045] Thirdly, this disclosure provides a lithium extraction method, which includes the following steps:

[0046] The modified hydrogel adsorbent as described in the first aspect is immersed in brine until swelling equilibrium is reached, and then the brine is stirred.

[0047] The modified hydrogel adsorbent, which was fully adsorbed, was obtained by exposure to light, along with saturated brine and pure water collected by water vapor.

[0048] The fully adsorbed modified hydrogel adsorbent was leached to obtain a lithium-rich solution, and the saturated brine was evaporated to obtain industrial salt byproducts.

[0049] The modified hydrogel adsorbent disclosed herein utilizes light irradiation to concentrate brine during lithium extraction, thereby increasing the lithium concentration in the hydrogel and improving the adsorbent's adsorption efficiency. The aluminum-based lithium ion sieve and manganese-based lithium ion sieve in the modified hydrogel adsorbent possess good thermal conductivity. The adsorbent not only selectively extracts lithium but also promotes water evaporation. The lithium extraction method described herein achieves simultaneous concentration and extraction of lithium, yielding a byproduct salt, eliminating the need for additional concentration steps. The reaction process is simple and offers multiple benefits.

[0050] In one embodiment, the agitation method includes any one or a combination of at least two of external pipe circulation, magnetic stirring, or ultrasonic oscillation.

[0051] In one embodiment, the intensity of the illumination is 0.5~2kW / m². 2 For example: 0.5 kW / m 2 0.8kW / m 2 1kW / m 2 1.5kW / m 2 or 2kW / m 2 wait.

[0052] In one embodiment, the exposure time is 15-30 h, for example, 15 h, 18 h, 20 h, 25 h, or 30 h, etc.

[0053] In one embodiment, the leaching treatment method comprises water leaching and / or acid leaching.

[0054] Compared with the prior art, the present disclosure has the following beneficial effects:

[0055] (1) The present disclosure modifies the hydrogel adsorbent by linear polymerization under light irradiation, directly wraps the adsorbent / ion sieve into the hydrogel, which can improve the mechanical stability of the adsorbent and prolong its service life. The modified hydrogel adsorbent has a constant level of impurity ions, which will not increase with the evaporation of the brine, so it can ensure the increase of lithium ion concentration without increasing the concentration of impurity ions during the lithium extraction process.

[0056] (2) The highly swollen network formed after the swelling of the hydrogel adsorbent has poor mechanical properties, and the brine shock caused by stirring or ultrasonic during the lithium extraction process will cause the structure to break. The present disclosure modifies the hydrogel adsorbent by linear polymerization, which can improve its mechanical stability and help to improve the overall service life of the adsorbent.

[0057] (3) The modified hydrogel adsorbent of the present disclosure is used in the method for extracting lithium from salt lake of the present disclosure, and the adsorption capacity can reach more than 8.84 mg / g, and the capacity retention rate can reach more than 86.54% after 100 cycles. Among them, the leaching method selected for the modified hydrogel adsorbent with complete adsorption during the lithium extraction process from salt lake will affect its effect. The use of acid leaching will greatly improve the adsorption capacity, but the cycle performance will decrease. Here, you can choose according to the actual situation.

[0058] Other aspects can be apparent after reading and understanding the accompanying drawings and detailed description. BRIEF DESCRIPTION OF DRAWINGS

[0059] The accompanying drawings are used to provide a further understanding of the technical solutions of the present disclosure, and constitute a part of the specification, and together with the embodiments of the present application, are used to explain the technical solutions of the present disclosure, and do not constitute a limitation on the technical solutions of the present disclosure.

[0060] Figure 1 is the SEM image of the modified hydrogel adsorbent prepared in Example 1 of the present disclosure.

[0061] Figure 2 is the infrared spectrum of the modified hydrogel adsorbent prepared in Example 1 of the present disclosure.

[0062] Figure 3 is a schematic diagram of the method for extracting lithium from salt lake according to Example 1 of the present disclosure.

[0063] Figure 4 This is a graph showing the concentration changes of various ions in the hydrogel during the lithium extraction process described in Application Example 1 of this disclosure. Detailed Implementation

[0064] The technical solutions of this disclosure will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of this disclosure and should not be construed as specific limitations thereof.

[0065] Example 1

[0066] This embodiment provides a modified hydrogel adsorbent, and the preparation method of the modified hydrogel adsorbent is as follows:

[0067] (1) A solution A was obtained by mixing a 20 g / L polypyrrole dispersion with 1.2 mol / L hydrochloric acid. The volume ratio of the polypyrrole dispersion to the hydrochloric acid solution was 1:2. A solution B was obtained by dissolving polyvinyl alcohol and glutaraldehyde in deionized water at 90°C. The mass of glutaraldehyde was 0.5% of the mass of polyvinyl alcohol, and the mass-volume ratio of polyvinyl alcohol to deionized water was 100 g / L. A solution A and solution B were mixed. The mass ratio of polypyrrole to polyvinyl alcohol in the mixture was 1:15. An aluminum-based lithium ion sieve was added to the mixed solution. The mass of the lithium ion sieve was 12% of the sum of the masses of polypyrrole and polyvinyl alcohol. After sonication for 30 min, a prepolymer of the hydrogel adsorbent was obtained. After reacting for 3 h, the prepolymer was formed and then pre-frozen in a refrigerator at -20°C for 24 h. The sample was freeze-dried for 24 h using a freeze dryer until it was completely dehydrated to obtain the hydrogel adsorbent.

[0068] (2) Prepare a mixed solution of sodium 2-acrylamide-2-methylpropanesulfonate and 2-oxoglutaric acid (modified precursor solution, the concentration of sodium 2-acrylamide-2-methylpropanesulfonate is 0.5 mol / L, and the mass ratio of sodium 2-acrylamide-2-methylpropanesulfonate to 2-oxoglutaric acid is 100:1). Immerse the hydrogel adsorbent in the modified precursor solution for 15 h, and use ultraviolet light initiation with a wavelength of 365 nm and a light intensity of 4 mW / cm. 2 The hydrogel was irradiated for 2.5 hours to induce linear polymerization, thus obtaining the modified hydrogel adsorbent.

[0069] The SEM image of the modified hydrogel adsorbent is shown below. Figure 1 As shown, by Figure 1 It can be seen that the hydrogel adsorbent has an ordered structure and a network structure.

[0070] The infrared spectrum of the modified hydrogel adsorbent is as follows: Figure 2 As shown, by Figure 2It can be seen that the characteristic peaks of polypyrrole, 2-acrylamide-2-methylpropanesulfonic acid sodium linear polymer and polyvinyl alcohol appear in the hydrogel adsorbent, which proves the successful synthesis of the modified hydrogel adsorbent.

[0071] Example 2

[0072] The present example provides a modified hydrogel adsorbent, and a preparation method of the modified hydrogel adsorbent is as follows:

[0073] (1) A solution A is obtained by mixing a chitosan dispersion solution with a concentration of 25 g / L and 1.5 mol / L hydrochloric acid, and the volume ratio of the chitosan dispersion solution to the hydrochloric acid solution is 1:3. A solution B is obtained by dissolving polyethylene glycol and glyoxal in deionized water at 85°C. The mass of glyoxal is 1% of the mass of polyethylene glycol, and the mass / volume ratio of polyethylene glycol to deionized water is 50 g / L. Solution A and solution B are mixed, and the mass ratio of chitosan to polyethylene glycol in the mixed solution is 1:10. Manganese lithium ion sieve is added to the mixed solution, and the mass of the lithium ion sieve is 10% of the sum of the masses of chitosan and polyethylene glycol. After ultrasonic treatment for 50 min, a hydrogel adsorbent pre-polymer solution is obtained, and the pre-polymer solution is shaped after 2 h of reaction, and then pre-frozen in a refrigerator at -30°C for 15 h. The sample is freeze-dried using a freeze dryer for 36 h until completely dehydrated to obtain a hydrogel adsorbent;

[0074] (2) An acrylamide and 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone mixed solution (modified precursor solution, the concentration of acrylamide is 0.5 mol / L, and the mass ratio of acrylamide to 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone is 100:0.5) is configured, and the hydrogel adsorbent is soaked in the modified precursor solution for 20 h, and linear polymerization is induced using ultraviolet light with a wavelength of 365 nm and an intensity of 3 mW / cm 2 for 3 h to make the hydrogel adsorbent occur linear polymerization to obtain the modified hydrogel adsorbent.

[0075] Example 3

[0076] The present example provides a modified hydrogel adsorbent, and a preparation method of the modified hydrogel adsorbent is as follows:

[0077] (1) A solution A is obtained by mixing a 20 g / L sodium alginate dispersion liquid with 2 mol / L hydrochloric acid, the volume ratio of the sodium alginate dispersion liquid to the hydrochloric acid solution being 1:2. A solution B is obtained by dissolving polyvinyl acetate and N,N-methylene bisacrylamide in deionized water at 95°C, wherein the mass of N,N-methylene bisacrylamide is 2% of the mass of polyvinyl acetate, and the mass / volume ratio of polyvinyl acetate to deionized water is 150 g / L. Solution A and solution B are mixed, and the mass ratio of sodium alginate to polyvinyl acetate in the mixed solution is 1:20. A manganese lithium ion sieve is added to the mixed solution, and the mass of the lithium ion sieve is 15% of the sum of the masses of sodium alginate and polyvinyl acetate. After ultrasonic treatment for 60 min, a hydrogel adsorbent pre-polymer solution is obtained, and the pre-polymer solution is shaped after 5 h of reaction, followed by pre-freezing in a refrigerator at -40°C for 48 h. The sample is freeze-dried using a freeze dryer for 12 h until completely dehydrated to obtain a hydrogel adsorbent;

[0078] (2) A mixed solution of 2-acrylamide-2-methylpropanesulfonic acid and ammonium persulfate (modified precursor solution, the concentration of 2-acrylamide-2-methylpropanesulfonic acid being 1 mol / L, and the mass ratio of 2-acrylamide-2-methylpropanesulfonic acid to ammonium persulfate being 100:1.5) is configured, the hydrogel adsorbent is soaked in the modified precursor solution for 24 h, ultraviolet light is used for initiation, the wavelength of the ultraviolet light is 365 nm, the light intensity is 5 mW / cm 2 , the soaked hydrogel is irradiated for 2 h to cause linear polymerization, and the modified hydrogel adsorbent is obtained.

[0079] Example 4

[0080] The difference between this example and Example 1 is that the mass ratio of the first polymer to the second polymer (polyvinyl alcohol) in the mixed solution is 1:5, and the other conditions and parameters are completely the same as those in Example 1.

[0081] Example 5

[0082] The difference between this example and Example 1 is that the mass ratio of the first polymer to the second polymer (polyvinyl alcohol) in the mixed solution is 1:30, and the other conditions and parameters are completely the same as those in Example 1.

[0083] Example 6

[0084] The difference between this example and Example 1 is that the concentration of the linear polymer monomer (sodium 2-acrylamide-2-methylpropanesulfonate) in the modified precursor solution is 0.1 mol / L, and the other conditions and parameters are completely the same as those in Example 1.

[0085] Example 7

[0086] The embodiment differs from example 1 only in that the concentration of the linear polymer monomer (2-acrylamido-2-methylpropanesulfonic acid sodium salt) in the modified precursor solution is 1.5 mol / L, and other conditions and parameters are exactly the same as in example 1.

[0087] Example 8

[0088] The embodiment differs from example 1 only in that the light intensity of the light irradiation reaction is 2 mW / cm 2 , and other conditions and parameters are exactly the same as in example 1.

[0089] Example 9

[0090] The embodiment differs from example 1 only in that the light intensity of the light irradiation reaction is 6 mW / cm 2 , and other conditions and parameters are exactly the same as in example 1.

[0091] Comparative example 1

[0092] The comparative example differs from example 1 only in that step (2) is not performed, and other conditions and parameters are exactly the same as in example 1.

[0093] Application example 1

[0094] The application example provides a method for extracting lithium from a salt lake, and a schematic diagram of the method is shown in Figure 3 The method for extracting lithium from a salt lake comprises the following steps:

[0095] (A) After the modified hydrogel adsorbent prepared in example 1 is soaked in brine to reach swelling equilibrium, the brine is stirred by magnetic stirring;

[0096] (B) Under constant sunlight (1 kW / m 2 ) for 20 h to obtain a saturated brine, a completely adsorbed adsorbent, and pure water collected by water vapor;

[0097] (C) The completely adsorbed modified hydrogel adsorbent is treated by water immersion to obtain a lithium-rich solution, and the saturated brine is treated by evaporation to obtain an industrial salt byproduct.

[0098] During the lithium extraction process, the concentration change curve of each ion in the hydrogel is shown in Figure 4 It can be seen from Figure 4 that the impurity ion level in the modified hydrogel adsorbent prepared by the present disclosure is constant and does not increase with the evaporation of the brine, so that the lithium ion concentration can be increased without increasing the impurity ion concentration during the lithium extraction process.

[0099] Application example 2

[0100] The application example provides a salt lake lithium extraction method, and the salt lake lithium extraction method comprises the following steps:

[0101] (A) After the modified hydrogel adsorbent prepared in Example 2 is soaked in brine to reach a swelling equilibrium, the brine is stirred by an external pipeline;

[0102] (B) The brine is continuously exposed to constant sunlight (0.5 kW / m 2 ) for 30 hours to obtain saturated brine, pure water collected by water vapor, and an adsorbent completely adsorbed;

[0103] (C) The modified hydrogel adsorbent completely adsorbed is soaked in 1 mol / L hydrochloric acid for 2 hours to perform lithium desorption, to obtain a lithium-rich solution, and the saturated brine is subjected to evaporation treatment to obtain an industrial salt byproduct.

[0104] Application Example 3

[0105] The application example provides a salt lake lithium extraction method, and the salt lake lithium extraction method comprises the following steps:

[0106] (A) After the modified hydrogel adsorbent prepared in Example 3 is soaked in brine to reach a swelling equilibrium, the brine is stirred by ultrasonic oscillation;

[0107] (B) The brine is continuously exposed to constant sunlight (2 kW / m 2 ) for 15 hours to obtain saturated brine, pure water collected by water vapor, and an adsorbent completely adsorbed;

[0108] (C) The modified hydrogel adsorbent completely adsorbed is soaked in 1 mol / L hydrochloric acid for 2 hours to perform lithium desorption, to obtain a lithium-rich solution, and the saturated brine is subjected to evaporation treatment to obtain an industrial salt byproduct.

[0109] Application Example 4

[0110] The application example is different from the application example 1 only in that the modified hydrogel adsorbent prepared in Example 4 is used, and other conditions and parameters are completely same as the application example 1.

[0111] Application Example 5

[0112] The application example is different from the application example 1 only in that the modified hydrogel adsorbent prepared in Example 5 is used, and other conditions and parameters are completely same as the application example 1.

[0113] Application Example 6

[0114] The application example is different from the application example 1 only in that the modified hydrogel adsorbent prepared in Example 6 is used, and other conditions and parameters are completely same as the application example 1.

[0115] Application Example 7

[0116] The application example differs from application example 1 only in that the modified hydrogel adsorbent prepared in Example 7 is used, and other conditions and parameters are exactly the same as in application example 1.

[0117] Application Example 8

[0118] The application example differs from application example 1 only in that the modified hydrogel adsorbent prepared in Example 8 is used, and other conditions and parameters are exactly the same as in application example 1.

[0119] Application Example 9

[0120] The application example differs from application example 1 only in that the modified hydrogel adsorbent prepared in Example 9 is used, and other conditions and parameters are exactly the same as in application example 1.

[0121] Comparative Application Example 1

[0122] The comparative application example differs from application example 1 only in that the hydrogel adsorbent prepared in Comparative Example 1 is used, and other conditions and parameters are exactly the same as in application example 1.

[0123] Performance test:

[0124] The Li content in the lithium-rich solution prepared in the application examples and the comparative application examples was tested by ICP. + The adsorption capacity was calculated by the following formula:

[0125] Q = (Co - Ce) x V1 / m

[0126] Q: adsorption capacity mg / g, Co: brine concentration before adsorption mg / L, Ce: brine concentration after adsorption mg / L, V1: brine volume before lithium extraction L, V2: brine volume after lithium extraction L, m: lithium ion sieve mass g.

[0127] The ratio of the adsorption capacity after 100 cycles to the initial adsorption capacity was obtained to obtain the capacity retention rate after 100 cycles. The test results are shown in Table 1:

[0128] Table 1

[0129] Adsorption capacity (mg / g) Capacity retention rate (%) after 100 cycles Application Example 1 8.84 98.54 Application Example 2 26.54 86.67 Application Example 3 26.33 86.54 Application Example 4 8.35 96.47 Application Example 5 8.21 95.83 Application Example 6 8.59 97.15 Application Example 7 8.17 98.04 Application Example 8 8.72 96.55 Application Example 9 8.74 98.39 Comparative Application Example 1 8.12 92.15

[0130] As can be seen from Table 1, from application examples 1-3, it can be seen that the modified hydrogel adsorbent described in the present disclosure is used in the method for extracting lithium from salt lakes described in the present disclosure, and the adsorption capacity can reach 8.84 mg / g or more, and the capacity retention rate after 100 cycles can reach 86.54% or more. In the process of extracting lithium from salt lakes, the leaching method selected for the completely adsorbed modified hydrogel adsorbent will affect its effect, and the use of acid leaching will greatly improve the adsorption capacity, but the cycle performance will decrease. Here, the actual situation can be selected.

[0131] From the comparison of application example 1 and application examples 4-5, it can be seen that in the preparation process of the modified hydrogel adsorbent, the mass ratio of the first polymer and the second polymer in the mixed solution will affect the properties of the modified hydrogel adsorbent, and then affect the lithium extraction performance. If the mass ratio of the first polymer and the second polymer in the mixed solution is controlled to be 1:10-20, the performance of the modified hydrogel adsorbent prepared is better. If the amount of the second polymer is too small or too large, it will affect the crosslinking effect of the polymer, which is not conducive to the adsorbent / ion sieve.

[0132] From the comparison of application example 1 and application examples 6-7, it can be seen that in the preparation process of the modified hydrogel adsorbent, the concentration of the linear polymer monomer in the modified precursor solution will affect the properties of the modified hydrogel adsorbent, and then affect the lithium extraction performance. If the concentration of the linear polymer monomer in the modified precursor solution is controlled to be 0.2-1 mol / L, the performance of the modified hydrogel adsorbent prepared is better. If the concentration of the linear polymer monomer in the modified precursor solution is too low, the service life of the modified hydrogel adsorbent prepared will be reduced. If the concentration of the linear polymer monomer in the modified precursor solution is too high, the proportion of the lithium ion sieve will be reduced, and the lithium extraction capacity of the modified hydrogel adsorbent will be reduced.

[0133] From the comparison of application example 1 and application examples 8-9, it can be seen that in the preparation process of the modified hydrogel adsorbent, the light intensity of the light reaction will affect the properties of the modified hydrogel adsorbent, and then affect the lithium extraction performance. If the light intensity of the light reaction is controlled to be 3-5 mW / cm 2 , the performance of the modified hydrogel adsorbent prepared is better. If the light intensity of the light reaction is too small, the photoinitiator does not have enough energy to convert all into active species to initiate monomer polymerization, resulting in a slow polymerization rate of the monomer in the system, and finally resulting in a low content of linear polymers in the modified hydrogel adsorbent. If the light intensity of the light reaction is too large, it cannot speed up the reaction, but only causes waste of energy.

[0134] From the comparison of application example 1 and comparative application example 1, it can be seen that the modified hydrogel adsorbent prepared by modifying the linear polymer under light conditions can have better cycle stability, and can improve the adsorption capacity and the service life of the adsorbent as a whole.

Claims

1. A method for preparing a modified hydrogel adsorbent, comprising the following steps: (1) mixing a first polymer solution with an acid solution to obtain solution A, mixing a second polymer, a crosslinking agent and a solvent to obtain solution B, mixing solution A and solution B to obtain a mixed solution, adding lithium ion sieves to obtain a modified hydrogel adsorbent pre-polymer solution, and after reaction, performing freeze treatment to obtain a hydrogel adsorbent; (2) mixing a linear polymer monomer and an initiator to obtain a modified precursor solution, mixing the hydrogel adsorbent and the modified precursor solution, and performing a photo-irradiation reaction to obtain the modified hydrogel adsorbent; in step (1), the first polymer comprises any one or a combination of at least two of polypyrrole, chitosan or sodium alginate, and the second polymer comprises any one or a combination of at least two of polyvinyl alcohol, polyethylene glycol or polyvinyl acetate; in step (2), the linear polymer monomer comprises any one or a combination of at least two of acrylamide, acrylic acid, sodium acrylate, 2-acrylamido-2-methylpropanesulfonic acid or sodium 2-acrylamido-2-methylpropanesulfonate, and the initiator comprises any one or a combination of at least two of 2-oxoglutaric acid, potassium persulfate, ammonium persulfate, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone or 2-hydroxy-2-methylpropiophenone.

2. The production method according to claim 1, wherein The concentration of the first polymer solution is 10-50 g / L.

3. The production method according to claim 1, wherein The acid solution comprises hydrochloric acid.

4. The production method according to claim 1, wherein The concentration of the acid solution is 1-2 mol / L.

5. The production method according to claim 1, wherein The volume ratio of the first polymer solution to the acid solution is 1:(2-3).

6. The production method according to claim 1, wherein The crosslinking agent comprises any one or a combination of at least two of glutaraldehyde, glyoxal or N,N-methylene bisacrylamide.

7. The production method according to claim 1, wherein The mass of the crosslinking agent is 0.1%-2% of the mass of the second polymer.

8. The production method according to claim 1, wherein The solvent comprises deionized water.

9. The production method as claimed in claim 1, wherein, The temperature of the solvent is 85-95℃.

10. The production method as claimed in claim 1, wherein, The mass-volume ratio of the second polymer and the solvent is 50-150 g / L.

11. The production method as claimed in claim 1, wherein, In step (1), the mass ratio of the first polymer to the second polymer in the mixed solution is 1:(10-20).

12. The production method as claimed in claim 1, wherein, The lithium ion sieves comprise manganese-based lithium ion sieves and / or aluminum-based lithium ion sieves.

13. The production method according to claim 1, wherein The mass of the lithium ion sieves is 10%-15% of the total mass of the first polymer and the second polymer.

14. The production method according to claim 1, wherein After adding the lithium ion sieves, ultrasonic treatment is performed.

15. The production method according to claim 14, wherein The ultrasonic treatment time is 30-60 min.

16. The production method as claimed in claim 1, wherein, The reaction time is 2-5 h.

17. The production method as claimed in claim 1, wherein, In step (1), the freeze treatment comprises pre-freezing and freeze-drying.

18. The production method according to claim 17, wherein The pre-freezing temperature is -20--40℃.

19. The production method according to claim 17, wherein The pre-freezing time is 12-48 h.

20. The production method according to claim 17, wherein The freeze-drying time is 12-48 h.

21. The production method as claimed in claim 1, wherein, The mass of the initiator is 0.5%-1.5% of the mass of the linear polymer monomer.

22. The production method as claimed in claim 1, wherein, The concentration of the linear polymer monomer in the modified precursor solution is 0.2-1 mol / L.

23. The production method as claimed in claim 1, wherein, In step (2), the wavelength of the photo-irradiation reaction is 355-375 nm.

24. The production method as claimed in claim 1, wherein, The light intensity of the light irradiation reaction is 3-5 mW / cm 2 .

25. The production method as claimed in claim 1, wherein, The photo-irradiation reaction time is 2-3 h. 26.A modified hydrogel adsorbent prepared by the method of any one of claims 1-25. 27.A method for extracting lithium, comprising the following steps: After the modified hydrogel adsorbent as claimed in claim 26 is immersed in the brine to reach a swelling equilibrium, the brine is agitated; The modified hydrogel adsorbent after complete adsorption, the saturated brine and the pure water collected by water vapor are exposed to light; The modified hydrogel adsorbent after complete adsorption is subjected to leaching treatment to obtain a lithium-rich solution, and the saturated brine is subjected to evaporation treatment to obtain an industrial salt byproduct.

28. The method for lithium extraction as claimed in claim 27 wherein, The method of agitation comprises any one or a combination of at least two of external pipe circulation, magnetic stirring or ultrasonic oscillation.

29. The method for lithium extraction as claimed in claim 27 wherein, The intensity of the light is 0.5-2 kW / m 2 .

30. The method for lithium extraction as claimed in claim 27 wherein, The exposure time is 15-30 h.

31. The method for lithium extraction as claimed in claim 27 wherein, The method of leaching treatment comprises water leaching and / or acid leaching.

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