Modified hydrogel adsorbent, and preparation method therefor and use thereof

Abstract

The present disclosure provides a modified hydrogel adsorbent, and a preparation method therefor and a use thereof. The preparation method comprises the following steps: (1) mixing a first polymer solution with an acid solution to obtain a solution A, mixing a second polymer, a cross-linking agent and a solvent to obtain a solution B, mixing the solution A with the solution B to obtain a mixed solution, adding a lithium ion sieve to obtain a prepolymer solution, and carrying out freezing treatment after a reaction to obtain the hydrogel adsorbent; and (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 carrying out an illumination reaction to obtain the modified hydrogel adsorbent. According to the present disclosure, the adsorbent / ion sieve is entrapped in a hydrogel to prepare the hydrogel adsorbent having good mechanical stability; the impurity ion level in the adsorbent retains constant, thereby enabling a lithium extraction method for concentrating brine by illumination; and the method allows for simultaneous concentration and lithium extraction to obtain by-product salts, without the need for additional concentration steps.

Description

A modified hydrogel adsorbent and its preparation method and application Technical Field

[0001] The present invention 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 Art

[0002] Lithium, the world's lightest metal, possesses strong electrochemical properties and is commonly used in the battery industry. As new energy electric and hybrid vehicles gradually replace traditional fossil fuel vehicles, demand for lithium-ion batteries is steadily increasing, and lithium prices are consequently rising. The development of the new energy vehicle industry requires sufficient lithium resources as a foundation.

[0003] The main methods for extracting lithium from salt lake brine include extraction, nanofiltration, adsorption, and ion exchange. Extraction is a mature method, but it is highly polluting and, from an environmental perspective, unsuitable for the salt lake brine of the Qinghai-Tibet region. Adsorption, however, is gaining increasing attention due to its technical advantages, including high ion selectivity, simplicity, and environmental friendliness.

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

[0005] CN116395719A discloses a method for concentrating and removing impurities from lithium-extracted salt lake solution using an adsorption method, belonging to the technical field of salt lake lithium extraction. The method comprises subjecting salt lake brine, after lithium extraction through adsorption, to nanofiltration pretreatment to remove most of the calcium and magnesium ions in the brine. The wastewater after nanofiltration pretreatment enters a monovalent and divalent separation electrodialysis system to intercept calcium, magnesium, and boron ions, thereby concentrating the lithium ions in the brine and producing a concentrated water product and a fresh water product. The concentrated water product enters an MVR evaporator to further increase the lithium ion concentration in the concentrated water product. Sodium carbonate is then introduced to cause lithium precipitation, and after centrifugation, a sodium chloride filtrate and a lithium carbonate product are obtained.

[0006] In order to improve the adsorption efficiency of the adsorbent, the above scheme usually concentrates the brine before lithium extraction, which is a cumbersome process.

[0007] Summary of the Invention

[0008] 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.

[0009] The purpose of the present disclosure is to provide a modified hydrogel adsorbent, a preparation method and application thereof. The present disclosure wraps an adsorbent / ion sieve into a hydrogel to produce a hydrogel adsorbent with good mechanical stability. The level of impurity ions in the adsorbent is constant and does not increase with the evaporation of brine. A lithium extraction method using light-concentrated brine can be implemented, where lithium is extracted while concentrating to obtain by-product salt without the need for an additional concentration step.

[0010] To achieve this purpose, the present disclosure adopts the following technical solutions:

[0011] In a first aspect, the present disclosure provides a method for preparing a modified hydrogel adsorbent, the method comprising the following steps:

[0012] (1) mixing a first polymer solution with an acid solution to obtain solution A, mixing a second polymer, a cross-linking 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 prepolymer solution, and freezing the mixture after the reaction to obtain a hydrogel adsorbent;

[0013] (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 subjecting the mixture to a light irradiation reaction to obtain the modified hydrogel adsorbent.

[0014] This modified hydrogel adsorbent, produced by modifying a linear polymer under light conditions, possesses improved mechanical stability, thereby increasing the overall lifespan of the adsorbent. The method described in this disclosure allows the adsorbent / ion sieve to be directly incorporated into the hydrogel, simplifying the process and eliminating the need for granulation.

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

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

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

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

[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.

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

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

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

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

[0024] In one embodiment, the temperature of the solvent is 85-95°C, for example, 85°C, 88°C, 90°C, 92°C or 95°C.

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

[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.

[0027] In one embodiment, the lithium ion sieve includes 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% to 15% of the total mass of the first polymer and the second polymer, for example, 10%, 11%, 12%, 14% or 15%.

[0029] In one embodiment, the adding of the lithium ion sieve is followed by ultrasonic treatment.

[0030] In one embodiment, the ultrasonic treatment time is 30 to 60 minutes, for example, 30 minutes, 35 minutes, 40 minutes, 50 minutes or 60 minutes;

[0031] In one embodiment, the reaction time is 2 to 5 hours, for example, 2 hours, 2.5 hours, 3 hours, 4 hours or 5 hours.

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

[0033] In one embodiment, the pre-freezing temperature is -20 to -40°C, for example, -20°C, -25°C, -30°C, -35°C or -40°C.

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

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

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

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

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

[0039] In one embodiment, the concentration of the linear polymer monomer in the modified precursor solution is 0.2 to 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.

[0040] In one embodiment, the wavelength of the illumination reaction in step (2) is 355-375 nm, for example, 355 nm, 360 nm, 365 nm, 370 nm or 375 nm.

[0041] In one embodiment, the light intensity of the light reaction is 3 to 5 mW / cm 2 , for example: 3mW / cm 2 、3.5mW / cm 2 , 4mW / cm 2 , 4.5mW / cm 2 or 5mW / cm 2 wait.

[0042] In one embodiment, the light irradiation reaction 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, the present 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 disclosed herein has a constant level of impurity ions that does not increase with the evaporation of brine. Therefore, during the lithium extraction process, the increase in lithium ion concentration can be ensured without increasing the concentration of impurity ions.

[0045] In a third aspect, the present disclosure provides a method for extracting lithium, comprising the following steps:

[0046] soaking the modified hydrogel adsorbent according to the first aspect in brine until swelling equilibrium is reached, and stirring the brine;

[0047] The modified hydrogel adsorbent with complete adsorption, saturated brine and pure water obtained by water vapor collection were obtained by exposure to light.

[0048] The modified hydrogel adsorbent that has been completely adsorbed 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 by-product.

[0049] The modified hydrogel adsorbent disclosed herein can concentrate brine using light during lithium extraction, increasing the lithium concentration in the hydrogel and improving the adsorption efficiency of the adsorbent. The aluminum-based lithium ion sieve and manganese-based ion sieve in the modified hydrogel adsorbent have good thermal conductivity. The adsorbent can not only selectively extract lithium but also promote water evaporation. The lithium extraction method disclosed herein can achieve simultaneous lithium extraction and concentration, producing a byproduct salt without the need for an additional concentration step. The reaction process is simple, achieving multiple goals at once.

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

[0051] In one embodiment, the intensity of the light is 0.5 to 2 kW / m 2 , for example: 0.5kW / 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 to 30 hours, for example, 15 hours, 18 hours, 20 hours, 25 hours or 30 hours.

[0053] In one embodiment, the leaching treatment method includes 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 a hydrogel adsorbent with a linear polymer by light irradiation, directly encapsulating the adsorbent / ion sieve within the hydrogel, thereby improving the mechanical stability of the adsorbent and extending its service life. The resulting modified hydrogel adsorbent maintains a constant level of impurity ions that does not increase with brine evaporation. Therefore, during the lithium extraction process, the lithium ion concentration is maintained while the impurity ion concentration is minimized.

[0056] (2) The highly swollen network formed after the hydrogel adsorbent swells has poor mechanical properties. The brine vibration caused by stirring or ultrasound during the lithium extraction process will cause its structure to break. The present disclosure modifies the hydrogel adsorbent through linear polymers, which can make it have better mechanical stability and help to improve the overall service life of the adsorbent.

[0057] (3) The modified hydrogel adsorbent disclosed in the present invention is used in the method for extracting lithium from salt lakes disclosed in the present invention, 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. In the process of extracting lithium from salt lakes, the leaching method selected for the modified hydrogel adsorbent that has been fully adsorbed will affect its effect. The adsorption capacity will be greatly improved by using acid leaching, but the cycle performance will decrease. Here, the selection can be made according to the actual situation.

[0058] Still other aspects will become apparent upon reading and understanding the accompanying drawings and detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] The accompanying drawings are used to provide a further understanding of the technical solution of this article and constitute a part of the specification. Together with the embodiments of this application, they are used to explain the technical solution of this article and do not constitute a limitation on the technical solution of this article.

[0060] FIG1 is a SEM image of the modified hydrogel adsorbent prepared in Example 1 of the present disclosure.

[0061] FIG2 is an infrared spectrum of the modified hydrogel adsorbent prepared in Example 1 of the present disclosure.

[0062] FIG3 is a schematic diagram of the method for extracting lithium from a salt lake as described in Application Example 1 of the present disclosure.

[0063] FIG4 is a graph showing the concentration changes of various ions in the hydrogel during the lithium extraction process described in Application Example 1 of the present disclosure. DETAILED DESCRIPTION

[0064] The technical solution of the present disclosure is further described below through specific implementation methods. Those skilled in the art should understand that the embodiments are only used to help understand the present disclosure and should not be regarded as specific limitations of the present disclosure.

[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 polypyrrole dispersion with a concentration of 20 g / L was mixed with 1.2 mol / L hydrochloric acid to obtain solution A, and the volume ratio of the polypyrrole dispersion added to the hydrochloric acid solution was 1:2. Polyvinyl alcohol and glutaraldehyde were dissolved in deionized water at 90°C to obtain solution B. Among them, 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. Solution A was mixed with solution B, and the mass ratio of polypyrrole and polyvinyl alcohol in the mixed solution was 1:15. Aluminum-based lithium ion sieve was added to the mixed solution, and the mass of the lithium ion sieve was 12% of the sum of the mass of polypyrrole and polyvinyl alcohol. After ultrasonication for 30 minutes, a hydrogel adsorbent prepolymer solution was obtained. After reaction for 3 hours, the prepolymer solution was formed and then pre-frozen in a refrigerator at -20°C for 24 hours. The sample was freeze-dried using a freeze dryer for 24 hours until completely dehydrated to obtain a hydrogel adsorbent;

[0068] (2) A mixed solution of sodium 2-acrylamide-2-methylpropanesulfonate and 2-oxoglutaric acid was prepared (a modified precursor solution, wherein the concentration of sodium 2-acrylamide-2-methylpropanesulfonate was 0.5 mol / L and the mass ratio of sodium 2-acrylamide-2-methylpropanesulfonate to 2-oxoglutaric acid was 100:1). The hydrogel adsorbent was immersed in the modified precursor solution for 15 h and initiated by ultraviolet light with a wavelength of 365 nm and a light intensity of 4 mW / cm 2 The soaked hydrogel was irradiated for 2.5 hours to cause linear polymerization to obtain the modified hydrogel adsorbent.

[0069] The SEM image of the modified hydrogel adsorbent is shown in FIG1 . As can be seen from FIG1 , the hydrogel adsorbent has an orderly structure and a network structure.

[0070] The infrared spectrum of the modified hydrogel adsorbent is shown in FIG2 . As can be seen from FIG2 , characteristic peaks of polypyrrole, linear polymer of sodium 2-acrylamide-2-methylpropanesulfonate, and polyvinyl alcohol appear in the hydrogel adsorbent, proving the successful synthesis of the modified hydrogel adsorbent.

[0071] Example 2

[0072] This embodiment provides a modified hydrogel adsorbent, and the preparation method of the modified hydrogel adsorbent is as follows:

[0073] (1) A chitosan dispersion with a concentration of 25 g / L was mixed with 1.5 mol / L hydrochloric acid to obtain solution A, and the volume ratio of the chitosan dispersion added to the hydrochloric acid solution was 1:3. Polyethylene glycol and glyoxal were dissolved in deionized water at 85°C to obtain solution B. Among them, the mass of glyoxal was 1% of the mass of polyethylene glycol, and the mass volume ratio of polyethylene glycol to deionized water was 50 g / L. Solution A was mixed with solution B, and the mass ratio of chitosan and polyethylene glycol in the mixed solution was 1:10. Manganese-based lithium ion sieve was added to the mixed solution, and the mass of the lithium ion sieve was 10% of the sum of the masses of chitosan and polyethylene glycol. After ultrasonication for 50 minutes, a hydrogel adsorbent prepolymer solution was obtained. After reacting for 2 hours, the prepolymer solution was formed and then pre-frozen in a refrigerator at -30°C for 15 hours. The sample was freeze-dried using a freeze dryer for 36 hours until completely dehydrated to obtain a hydrogel adsorbent;

[0074] (2) A mixed solution of acrylamide and 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone was prepared (a modified precursor solution, wherein the concentration of acrylamide was 0.5 mol / L and the mass ratio of acrylamide to 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone was 100:0.5). The hydrogel adsorbent was immersed in the modified precursor solution for 20 h and initiated by ultraviolet light with a wavelength of 365 nm and a light intensity of 3 mW / cm 2 The soaked hydrogel is irradiated for 3 hours to cause linear polymerization to obtain the modified hydrogel adsorbent.

[0075] Example 3

[0076] This embodiment provides a modified hydrogel adsorbent, and the preparation method of the modified hydrogel adsorbent is as follows:

[0077] (1) A 20 g / L sodium alginate dispersion was mixed with 2 mol / L hydrochloric acid to obtain solution A. The volume ratio of the sodium alginate dispersion to the hydrochloric acid solution was 1:2. Polyvinyl acetate and N,N-methylenebisacrylamide were dissolved in 95°C deionized water to obtain solution B. The mass of N,N-methylenebisacrylamide was 2% of the mass of polyvinyl acetate, and the mass-volume ratio of polyvinyl acetate to deionized water was 150 g / L. Solution A was mixed with solution B. The mass ratio of sodium alginate to polyvinyl acetate in the mixed solution was 1:20. Manganese-based lithium ion sieve was added to the mixed solution. The mass of the lithium ion sieve was 15% of the sum of the mass of sodium alginate and polyvinyl acetate. After ultrasonication for 60 minutes, a hydrogel adsorbent prepolymer solution was obtained. After reacting for 5 hours, the prepolymer solution was formed and then pre-frozen in a refrigerator at -40°C for 48 hours. The sample was 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 was prepared (a modified precursor solution, wherein the concentration of 2-acrylamide-2-methylpropanesulfonic acid was 1 mol / L and the mass ratio of 2-acrylamide-2-methylpropanesulfonic acid to ammonium persulfate was 100:1.5). The hydrogel adsorbent was immersed in the modified precursor solution for 24 h and initiated by ultraviolet light with a wavelength of 365 nm and a light intensity of 5 mW / cm 2 The soaked hydrogel is irradiated for 2 hours to cause linear polymerization to occur, thereby obtaining the modified hydrogel adsorbent.

[0079] Example 4

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

[0081] Example 5

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

[0083] Example 6

[0084] The only difference between this embodiment and embodiment 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 exactly the same as those in embodiment 1.

[0085] Example 7

[0086] The only difference between this embodiment and embodiment 1 is that the concentration of the linear polymer monomer (sodium 2-acrylamide-2-methylpropanesulfonate) in the modified precursor solution is 1.5 mol / L, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0087] Example 8

[0088] The only difference between this embodiment and embodiment 1 is that the light intensity of the illumination reaction is 2mW / cm 2 , other conditions and parameters are exactly the same as those in Example 1.

[0089] Example 9

[0090] The only difference between this embodiment and embodiment 1 is that the light intensity of the illumination reaction is 6mW / cm 2 , other conditions and parameters are exactly the same as those in Example 1.

[0091] Comparative Example 1

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

[0093] Application Example 1

[0094] This application example provides a method for extracting lithium from a salt lake. The schematic diagram of the method is shown in FIG3 . The method comprises the following steps:

[0095] (A) soaking the modified hydrogel adsorbent prepared in Example 1 in brine until swelling equilibrium is reached, and then stirring the brine by magnetic stirring;

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

[0097] (C) The modified hydrogel adsorbent that has been completely adsorbed is subjected to water immersion treatment to obtain a lithium-rich solution, and the saturated brine is evaporated to obtain an industrial salt by-product.

[0098] During the lithium extraction process, the concentration change curve of each ion in the hydrogel is shown in Figure 4. As can be seen from Figure 4, the level of impurity ions in the modified hydrogel adsorbent prepared by the present invention is constant and does not increase with the evaporation of brine. Therefore, during the lithium extraction process, it is possible to ensure an increase in the lithium ion concentration without increasing the impurity ion concentration.

[0099] Application Example 2

[0100] This application example provides a method for extracting lithium from a salt lake, which includes the following steps:

[0101] (A) soaking the modified hydrogel adsorbent prepared in Example 2 in brine until swelling equilibrium is reached, and then circulating and stirring the brine through an external pipe;

[0102] (B) Under constant sunlight (0.5kW / m 2 ) Continuous exposure for 30 h yields a fully adsorbed adsorbent, saturated brine, and pure water collected by water vapor;

[0103] (C) The modified hydrogel adsorbent that has been completely adsorbed is immersed in 1 mol / L hydrochloric acid for 2 h to delithiate to obtain a lithium-rich solution, and the saturated brine is evaporated to obtain an industrial salt by-product.

[0104] Application Example 3

[0105] This application example provides a method for extracting lithium from a salt lake, which includes the following steps:

[0106] (A) soaking the modified hydrogel adsorbent prepared in Example 3 in brine until swelling equilibrium is reached, and then stirring the brine by ultrasonic vibration;

[0107] (B) Under constant sunlight (2kW / m 2 ) Continuous exposure for 15 h yields a fully adsorbed adsorbent, saturated brine, and pure water collected by water vapor;

[0108] (C) The modified hydrogel adsorbent that has been completely adsorbed is immersed in 1 mol / L hydrochloric acid for 2 h to delithiate to obtain a lithium-rich solution, and the saturated brine is evaporated to obtain an industrial salt by-product.

[0109] Application Example 4

[0110] The only difference between this application example and application example 1 is that the modified hydrogel adsorbent prepared in Example 4 is used, and the other conditions and parameters are exactly the same as those in application example 1.

[0111] Application Example 5

[0112] The only difference between this application example and application example 1 is that the modified hydrogel adsorbent prepared in Example 5 is used, and the other conditions and parameters are exactly the same as those in application example 1.

[0113] Application Example 6

[0114] The only difference between this application example and application example 1 is that the modified hydrogel adsorbent prepared in Example 6 is used, and the other conditions and parameters are exactly the same as those in application example 1.

[0115] Application Example 7

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

[0117] Application Example 8

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

[0119] Application Example 9

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

[0121] Comparative Application Example 1

[0122] The only difference between this comparative application example and application example 1 is that the hydrogel adsorbent prepared in comparative example 1 is used, and the other conditions and parameters are exactly the same as those in application example 1.

[0123] Performance testing:

[0124] Li in lithium-rich solution prepared by ICP test application example and comparative application example + Content. The adsorption capacity is calculated by the following formula:

[0125] Q: adsorption capacity mg / g, Co: brine concentration before adsorption mg / L, Ce: brine concentration after adsorption mg / L, V1: volume of dissolved brine before lithium extraction L, V2: volume of brine after lithium extraction L, m: mass of lithium ion sieve g.

[0126] The ratio of the adsorption capacity after 100 cycles to the initial adsorption capacity is the capacity retention rate after 100 cycles. The test results are shown in Table 1:

[0127] Table 1

[0128] As can be seen from Table 1, from Application Examples 1-3, the modified hydrogel adsorbent disclosed in the present invention is used in the method for extracting lithium from salt lakes disclosed in the present invention, and the adsorption capacity can reach more than 8.84 mg / g, and the capacity retention rate after 100 cycles can reach more than 86.54%. In the process of extracting lithium from salt lakes, the leaching method selected for the fully adsorbed modified hydrogel adsorbent will affect its effect. The adsorption capacity will be greatly improved by using acid leaching, but the cycle performance will decrease. Here, the selection can be made according to the actual situation.

[0129] By comparing Application Example 1 with Application Examples 4-5, it can be seen that in the preparation process of the modified hydrogel adsorbent described in the present disclosure, the mass ratio of the first polymer to the second polymer in the mixed solution will affect the properties of the modified hydrogel adsorbent, and thus affect the lithium extraction performance. When the mass ratio of the first polymer to the second polymer in the mixed solution is controlled at 1:10 to 20, the performance of the modified hydrogel adsorbent is better. If the amount of the second polymer added is too small or too large, it will affect the effect of polymer cross-linking, which is not conducive to the wrapped adsorbent / ion sieve.

[0130] By comparing Application Example 1 and Application Examples 6-7, it can be seen that in the preparation process of the modified hydrogel adsorbent described in the present disclosure, the concentration of the linear polymer monomer in the modified precursor solution will affect the properties of the modified hydrogel adsorbent, and thus affect the lithium extraction performance. By controlling the concentration of the linear polymer monomer in the modified precursor solution at 0.2-1 mol / L, the performance of the modified hydrogel adsorbent 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 is reduced. If the concentration of the linear polymer monomer in the modified precursor solution is too high, the proportion of lithium ion sieve will be reduced, and the lithium extraction capacity of the modified hydrogel adsorbent will be reduced.

[0131] From the comparison between Application Example 1 and Application Examples 8-9, it can be seen that during the preparation process of the modified hydrogel adsorbent disclosed in the present invention, the light intensity of the illumination reaction will affect the properties of the modified hydrogel adsorbent, and thus affect the lithium extraction performance. The light intensity of the illumination reaction is controlled at 3-5 mW / cm 2 The modified hydrogel adsorbent has better performance. If the light intensity of the light reaction is too low, the photoinitiator does not have enough energy to fully convert into active species to initiate monomer polymerization, resulting in a slow polymerization rate of the monomers in the system and ultimately a low content of linear polymers in the modified hydrogel adsorbent. If the light intensity of the light reaction is too high, it will not speed up the reaction and will only result in energy waste.

[0132] From the comparison between 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 cyclic stability, thereby increasing the adsorption capacity and the overall service life of the adsorbent.

Claims

1. A preparation method of a modified hydrogel adsorbent, comprising the following steps: (1) Mix a first polymer solution and an acid solution to obtain solution A, mix a second polymer, a crosslinking agent and a solvent to obtain solution B, mix solution A and solution B to obtain a mixed solution, add a lithium ion sieve to obtain a prepolymer solution of the modified hydrogel adsorbent, and after reaction, perform a freezing treatment to obtain the hydrogel adsorbent; (2) Mix a linear polymer monomer and an initiator to obtain a pre-modification precursor solution, mix the hydrogel adsorbent and the pre-modification precursor solution, and perform a light reaction to obtain the modified hydrogel adsorbent.

2. The preparation method according to claim 1, wherein, The first polymer in step (1) includes any one or a combination of at least two of polypyrrole, chitosan or sodium alginate.

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

4. The preparation method according to any one of claims 1-3, wherein, The acid solution includes hydrochloric acid.

5. The preparation method according to any one of claims 1-4, wherein, The concentration of the acid solution is 1 - 2 mol / L.

6. The preparation method according to any one of claims 1-5, wherein, The volume ratio of the first polymer solution to the acid solution is 1:(2 - 3).

7. The preparation method according to any one of claims 1-6, wherein, The second polymer in step (1) includes any one or a combination of at least two of polyvinyl alcohol, polyethylene glycol or polyvinyl acetate.

8. The preparation method according to any one of claims 1 to 7, wherein, The crosslinking agent includes any one or a combination of at least two of glutaraldehyde, glyoxal or N,N'-methylenebisacrylamide.

9. The preparation method according to any one of claims 1-8, wherein, The mass of the crosslinking agent is 0.1% - 2% of the mass of the second polymer.

10. The preparation method according to any one of claims 1-9, wherein, The solvent includes deionized water; Optionally, the temperature of the solvent is 85 - 95 °C.

11. The preparation method according to claims 1-10, wherein, The mass-volume ratio of the second polymer to the solvent is 50 - 150 g / L.

12. The preparation method according to any one of claims 1-11, wherein, In the mixed solution in step (1), the mass ratio of the first polymer to the second polymer is 1:(10 - 20); Optionally, the lithium ion sieve includes a manganese-based lithium ion sieve and / or an aluminum-based lithium ion sieve; Optionally, the mass of the lithium ion sieve is 10% - 15% of the total mass of the first polymer and the second polymer; Optionally, ultrasonic treatment is performed after adding the lithium ion sieve; Optionally, the time of the ultrasonic treatment is 30 - 60 min; Optionally, the reaction time is 2 - 5 h.

13. The preparation method according to any one of claims 1 to 12, wherein, The freezing treatment in step (1) includes pre-freezing and freeze-drying; Optionally, the temperature of the pre-freezing is -20 - -40 °C; Optionally, the time of the pre-freezing is 12 - 48 h; Optionally, the time of the freeze-drying is 12 - 48 h.

14. The preparation method according to any one of claims 1-13, wherein, The linear polymer monomer in step (2) includes 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; Optionally, the initiator includes 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; Optionally, the mass of the initiator is 0.5% - 1.5% of the mass of the linear polymer monomer; Optionally, the concentration of the linear polymer monomer in the pre-modification precursor solution is 0.2 - 1 mol / L.

15. The preparation method according to any one of claims 1-14, wherein, The wavelength of the light reaction in step (2) is 355 - 375 nm; Optionally, the light intensity of the photoreaction is 3 to 5 mW / cm 2 ; Optionally, the time of the light reaction is 2 - 3 h.

16. A modified hydrogel adsorbent prepared by the method according to any one of claims 1-15.

17. A method for extracting lithium, comprising the following steps: Soaking the modified hydrogel adsorbent according to claim 16 in brine until swelling equilibrium is reached, and then agitating the brine; Exposing under light to obtain a modified hydrogel adsorbent with complete adsorption, saturated brine, and pure water collected through water vapor; Performing leaching treatment on the modified hydrogel adsorbent with complete adsorption to obtain a lithium-rich solution, and performing evaporation treatment on the saturated brine to obtain an industrial salt by-product.

18. The lithium extraction method according to claim 17, wherein, The method of agitation includes any one or a combination of at least two of external pipeline circulation, magnetic stirring, or ultrasonic oscillation; Optionally, the intensity of the light is 0.5 to 2 kW / m 2 ; Optionally, the exposure time is 15-30 h; Optionally, the method of leaching treatment includes water leaching and / or acid leaching.

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