A modified lithium extraction adsorbent, its preparation method and application

Abstract

The present disclosure provides a modified lithium extraction adsorbent, a preparation method thereof, and an application thereof. The modified lithium extraction adsorbent includes an aluminum-based adsorbent and microcapsules disposed on the surface of the aluminum-based adsorbent. The microcapsules include curing agent microcapsules and binder microcapsules. The microcapsules in the modified lithium extraction adsorbent disclosed in the present disclosure can fill cracks when the lithium extraction adsorbent ruptures due to swelling, reducing the dissolution loss of the adsorbent.

Description

Technical Field

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

[0002] Lithium is the lightest metallic element in the world, and its special properties have increasingly attracted people's attention to it and its compounds. The applications of lithium and its compounds include industries such as medicine, polymers, new materials, and new energy batteries, and it is a strategic resource of great significance in the national economy and national defense construction. In recent years, lithium extraction from salt lakes has become one of the most important ways to obtain lithium resources.

[0003] The methods for lithium extraction from salt lakes can be divided into precipitation methods, extraction methods, membrane methods, adsorption methods, etc. However, the precipitation method has low efficiency, and the equipment of the extraction method is easily corroded by the extractant and the extractant is easily lost. The full membrane method and the adsorption method are emerging technologies in the current salt lake lithium extraction industry, and have the advantages of simple process and little pollution. However, the full membrane method has a high membrane consumption and the membrane is easily polluted, increasing the cost of lithium extraction; the difficulty of the adsorption method lies in the preparation of the lithium adsorbent, but generally speaking, the adsorption method is the most competitive at present.

[0004] The active components of the existing lithium adsorbents such as aluminum-based, manganese-based, and titanium-based are inorganic powders, and direct use has the disadvantages of poor permeability and high dissolution loss. Therefore, it is necessary to granulate the inorganic adsorbent. Common forming methods include granulation, film formation, etc. Among them, granulation is generally divided into two types: physical blending and chemical reaction granulation. Physical blending granulation is a process of uniformly mixing the inorganic adsorbent and an inert binder and then forming. Chemical reaction granulation is a process of uniformly mixing the inorganic adsorbent and an active binder and then reacting and curing.

[0005] CN115155528A discloses a preparation method of a high adsorption capacity granular aluminum salt lithium extraction adsorbent. The method includes: (1) preparing a lithium-inserted aluminum salt precursor slurry, uniformly mixing an aluminum source, a lithium source, and water, and then adding an alkali solution to adjust the PH to obtain a lithium-inserted aluminum salt precursor slurry; (2) integrally granulating the lithium-inserted aluminum salt precursor slurry; (3) after the granulated adsorbent is dried and washed and activated, a granular aluminum salt lithium extraction adsorbent is obtained.

[0006] CN110743516A discloses a granulation technology for an adsorbent suitable for lithium extraction from brine. The granulation method is as follows: 1) mixing a polymer and a latent solvent in a certain proportion; 2) adding a certain amount of stabilizer to the paste in step 1) and kneading evenly to obtain a granulating agent; 3) kneading and mixing a certain amount of lithium adsorbent powder with the granulating agent evenly; 4) after the mixture in step 3) is granulated by a granulator, an adsorbent particle product with a fixed particle shape is obtained.

[0007] Generally, the granulated adsorbent can improve the cycle stability of the adsorbent. However, during the lithium extraction process, the granulated adsorbent will experience a certain volume expansion due to the intercalation and deintercalation of lithium ions, resulting in cracks in the adsorbent and thus leading to the dissolution loss of the adsorbent. Summary of the Invention

[0008] The following is an overview of the subject matter described in detail in this document. This overview is not intended to limit the scope of protection of the claims.

[0009] The purpose of the present disclosure is to provide a modified lithium extraction adsorbent, its preparation method and application. The microcapsules in the modified lithium extraction adsorbent of the present disclosure can fill the cracks and reduce the dissolution loss of the adsorbent when the lithium extraction adsorbent ruptures due to expansion.

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

[0011] In the first aspect, the present disclosure provides a modified lithium extraction adsorbent, which includes an aluminum-based adsorbent and microcapsules disposed on the surface of the aluminum-based adsorbent. The microcapsules include curing agent microcapsules and binder microcapsules.

[0012] The present disclosure disposes microcapsules on the surface of the aluminum-based adsorbent. When the adsorbent particles crack during the cycling process, the microcapsules rupture, and the binder that can be cured in water flows out and reacts with the curing agent to fill the cracks, reduce the dissolution loss of the adsorbent, and improve the cycle performance of the adsorbent.

[0013] In one embodiment, the curing agent microcapsules include an underwater curing agent and a curing composite shell;

[0014] In one embodiment, the curing composite shell includes urea-formaldehyde resin.

[0015] In one embodiment, the underwater curing agent includes any one or at least two combinations of T31 curing agent, JA-IS curing agent, I965 curing agent, 810 curing agent or P117 curing agent;

[0016] In one embodiment, the binder microcapsules include a liquid epoxy resin core and a binder composite shell disposed on the surface of the liquid epoxy resin core;

[0017] In one embodiment, the binder composite shell includes urea-formaldehyde resin.

[0018] In one embodiment, the median particle size D50 of the curing agent microcapsules and the binder microcapsules is independently 100-300 μm, for example: 100 μm, 150 μm, 200 μm, 250 μm or 300 μm, etc.

[0019] In one embodiment, based on the mass of the modified lithium extraction adsorbent being 100%, the mass fraction of the microcapsules is 0.5 - 2%, such as 0.5%, 0.8%, 1%, 1.5% or 2%, etc.

[0020] In one embodiment, the mass ratio of the curing agent microcapsules to the binder microcapsules is (0.3 - 1.5):1, such as 0.3:1, 0.5:1, 1:1, 1.2:1 or 1.5:1, etc.

[0021] In one embodiment, the modified lithium extraction adsorbent further includes a binder.

[0022] In one embodiment, the binder includes polyurethane.

[0023] In a second aspect, the present disclosure provides a method for preparing the modified lithium extraction adsorbent as described in the first aspect, and the preparation method includes the following steps:

[0024] Mix the urea - formaldehyde resin prepolymer solution, the surfactant solution and the binder diluent, heat and stir, then add acid to adjust the pH for reaction to obtain the binder microcapsules;

[0025] Mix the urea - formaldehyde resin prepolymer solution, the surfactant solution and the curing agent diluent, heat and stir, then add acid to adjust the pH for reaction to obtain the curing agent microcapsules;

[0026] Mix the aluminum - based adsorbent, the binder microcapsules, the curing agent microcapsules, the binder and the solvent to obtain a mixed solution, and perform granulation treatment on the mixed solution to obtain the modified lithium extraction adsorbent.

[0027] There is no special requirement for the preparation sequence of the binder microcapsules and the curing agent microcapsules described in the present disclosure. The binder microcapsules can be prepared first for standby, or the curing agent microcapsules can be prepared first for standby, and they can be used when preparing the modified lithium extraction adsorbent.

[0028] In one embodiment, the urea - formaldehyde resin prepolymer solution is prepared by the following method:

[0029] Mix urea and formaldehyde solution to form a mixed solution. After mixing until the urea is completely dissolved, add triethanolamine to adjust the pH of the mixed solution, and perform a water - bath reflux stirring reaction to obtain the urea - formaldehyde resin prepolymer solution.

[0030] In one embodiment, the molar ratio of formaldehyde to urea in the urea and formaldehyde solution is 1:(1.4 - 1.6), such as 1:1.4, 1:1.45, 1:1.5, 1:1.55 or 1:1.6, etc.

[0031] In one embodiment, the pH of the mixed solution is 8 - 9, such as 8, 8.2, 8.5, 8.8 or 9, etc.

[0032] In one embodiment, the temperature of the water bath reflux stirring reaction is 60 to 80 °C, for example: 60 °C, 65 °C, 70 °C, 75 °C or 80 °C, etc.

[0033] In one embodiment, the time of the water bath reflux stirring reaction is 1 to 3 h, for example: 1 h, 1.5 h, 2 h, 2.5 h or 3 h, etc.

[0034] In one embodiment, the mass concentration of the surfactant solution is 0.3 to 0.8%, for example: 0.3%, 0.4%, 0.5%, 0.6% or 0.8%, etc.

[0035] In one embodiment, the surfactant includes any one or a combination of at least two of sodium oleate, sodium stearate, sodium metasilicate or sodium dodecylbenzenesulfonate.

[0036] In one embodiment, the binder diluent is prepared by the following method:

[0037] Mix liquid epoxy resin with a diluent, and after ultrasonic treatment, carry out a water bath heating reaction to obtain the binder diluent.

[0038] In one embodiment, the mass ratio of the liquid epoxy resin to the diluent is 1:(0.1 to 0.2), for example: 1:0.1, 1:0.12, 1:0.15, 1:0.18 or 1:0.2, etc.

[0039] The present disclosure improves the fluidity of the binder in the microcapsule by adding a certain amount of diluent. Excessive addition will reduce the viscosity.

[0040] In one embodiment, the curing agent diluent is prepared by the following method:

[0041] Mix the curing agent, coupling agent and diluent, and after ultrasonic treatment, carry out a water bath heating reaction to obtain the curing agent diluent.

[0042] In one embodiment, the coupling agent includes γ-aminopropyltriethoxysilane (KH-550) and / or γ-glycidoxypropyltrimethoxysilane (KH560).

[0043] In one embodiment, the diluent includes n-butyl glycidyl ether, ethylene glycol monobutyl ether or benzyl glycidyl ether.

[0044] In one embodiment, during the preparation of the binder diluent and the curing agent diluent, the ultrasonic time is independently 30 to 60 min, for example: 30 min, 35 min, 40 min, 50 min or 60 min, etc.

[0045] In one embodiment, during the preparation of the binder diluent and the curing agent diluent, the temperature of the water bath heating reaction is independently 40 to 50 °C, for example: 40 °C, 42 °C, 45 °C, 48 °C or 50 °C, etc.

[0046] In one embodiment, during the preparation of the binder diluent and the curing agent diluent, the time of the water bath heating reaction is independently 0.5 to 1 h, for example: 0.5 h, 0.6 h, 0.8 h, 0.9 h or 1 h, etc.

[0047] In one embodiment, during the preparation of the binder microcapsules and the curing agent capsules, the speed of heating and stirring is independently 500 to 1000 rpm, for example: 500 rpm, 600 rpm, 800 rpm, 900 rpm or 1000 rpm, etc.

[0048] During the preparation of the binder microcapsules and the curing agent capsules, the speed of heating and stirring will affect the coating effect of the capsules themselves (the capsules are core-shell structures). If the rotation speed is too slow, the inner core droplets are large and difficult to be completely wrapped. Agglomeration will occur between the incompletely wrapped particles, further increasing the particles and reducing the proportion of the microcapsule inner core, affecting the repair effect; the degree of reducing the droplet size is limited when the rotation speed continues to increase.

[0049] In one embodiment, during the preparation of the binder microcapsules and the curing agent capsules, the temperature of heating and stirring is independently 40 to 50 °C, for example: 40 °C, 42 °C, 45 °C, 48 °C or 50 °C, etc.

[0050] In one embodiment, during the preparation of the binder microcapsules and the curing agent capsules, the time of heating and stirring is independently 30 to 60 min, for example: 30 min, 35 min, 40 min, 50 min or 60 min, etc.

[0051] In one embodiment, during the preparation of the binder microcapsules and the curing agent capsules, the pH adjusted by adding acid is independently 1.8 to 2.2, for example: 1.8, 1.9, 2, 2.1 or 2.2, etc.

[0052] In one embodiment, during the preparation of the binder microcapsules and the curing agent capsules, the reaction temperature is independently 40 to 60 °C, for example: 40 °C, 45 °C, 50 °C, 55 °C or 60 °C, etc.

[0053] During the preparation of the binder microcapsules and the curing agent capsules, the reaction temperature controls the synthesis rate of urea-formaldehyde resin. If the temperature is too low, the reaction rate is slow and the efficiency is low; if the temperature is too high, the urea-formaldehyde resin is generated too fast and agglomerates before attaching to the surface of the inner core droplets, affecting the formation of the capsule shell and thus affecting the repair effect.

[0054] In one embodiment, during the preparation of the binder microcapsules and the curing agent capsules, the reaction time is independently 2 to 5 h, for example: 2 h, 2.5 h, 3 h, 4 h, or 5 h, etc.

[0055] In one embodiment, the mass ratio of the aluminum-based adsorbent to the binder is 1:(0.2 to 0.8), for example: 1:0.2, 1:0.3, 1:0.5, 1:0.6, or 1:0.8, etc.

[0056] In one embodiment, the solvent includes ethyl acetate.

[0057] In one embodiment, the mass ratio of the solvent to the binder is (2 to 3):1, for example: 2:1, 2.2:1, 2.5:1, 2.8:1, or 3:1, etc.

[0058] In one embodiment, the mass fraction of microcapsules in the mixed solution is 0.5 to 1.5%, for example: 0.5%, 0.8%, 1%, 1.2%, or 1.5%, etc.

[0059] In one embodiment, the granulation treatment includes liquid-phase curing granulation and / or extrusion granulation, and optionally liquid-phase curing granulation.

[0060] In one embodiment, the liquid-phase curing granulation includes: dissolving carboxymethyl cellulose and propylenediamine in saturated brine to form a homogeneous solution, slowly adding the mixed solution to the homogeneous solution, adjusting the stirring rate to 200 to 500 rpm (for example: 200 rpm, 250 rpm, 300 rpm, 400 rpm, or 500 rpm, etc.), obtaining spherical particles with a particle size of 0.5 to 2 mm (for example: 0.5 mm, 0.8 mm, 1 mm, 1.5 mm, or 2 mm, etc.), and filtering and washing after curing at 30 to 60 °C (for example: 30 °C, 35 °C, 40 °C, 50 °C, or 60 °C, etc.) to obtain the modified lithium extraction adsorbent.

[0061] In a third aspect, the present disclosure provides an application of the modified lithium extraction adsorbent as described in the first aspect, and the modified lithium extraction adsorbent is used for extracting lithium from salt lakes.

[0062] Compared with the prior art, the present disclosure has the following beneficial effects:

[0063] (1) The microcapsules in the modified lithium extraction adsorbent of the present disclosure can fill cracks when the lithium extraction adsorbent ruptures due to swelling, reducing the dissolution loss of the adsorbent. The adsorbent does not need to be treated during the lithium extraction process. When the crack > 50 μm, it will cause the microcapsules to rupture and repair the crack, and the repair method is simple.

[0064] (2) The adsorption capacity of the modified lithium extraction adsorbent described in this disclosure can reach more than 8.72 mg / g, and the capacity retention rate can reach more than 98.67% after 100 cycles.

[0065] Other aspects will be apparent after reading and understanding the accompanying drawings and the detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] The accompanying drawings are used to provide a further understanding of the technical solutions in this application, and constitute a part of the specification. Together with the embodiments of this application, they are used to explain the technical solutions in this application and do not constitute a limitation to the technical solutions in this application.

[0067] Figure 1 It is a schematic diagram of the synthesis process of the binder capsule described in an embodiment of this disclosure. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0068] The technical solutions of this disclosure will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand this disclosure and should not be regarded as specific limitations to this disclosure.

[0069] Example 1

[0070] This example provides a modified lithium extraction adsorbent, which is prepared by the following method:

[0071] (1) Mix urea and formaldehyde in a molar ratio of 1:1.5 to prepare a mixed solution with a concentration of 0.1 mol / L. After mixing until the urea is completely dissolved, add triethanolamine dropwise until the pH is 8.5. Place the mixed solution in a water bath at 70 °C and reflux and stir for 1.5 h to obtain a urea-formaldehyde resin prepolymer solution. Prepare a sodium oleate surfactant solution with a mass fraction of 0.5% using pure water. Mix liquid epoxy resin and n-butyl glycidyl ether in a mass ratio of 6:1, ultrasonicate for 40 min, and then place it in a water bath at 50 °C and heat for 1 h until the solution stands without stratification to obtain a uniformly mixed binder diluent. Mix 810 curing agent, KH-550 and n-butyl glycidyl ether, ultrasonicate for 40 min, and then place it in a water bath at 50 °C and heat for 1 h until the solution stands without stratification to obtain a uniformly mixed curing agent diluent;

[0072] (2) Stir the urea-formaldehyde resin prepolymer solution, the surfactant solution and the binder diluent at a speed of 800 rpm at 50 °C for 30 min, then add dilute sulfuric acid dropwise to adjust the reaction pH = 2, control the reaction temperature at 55 °C, react for 3 h, filter, wash and dry to obtain binder microcapsule powder, and the D50 of the binder microcapsule is 180 μm (the schematic diagram of the synthesis process of the binder microcapsule is as Figure 1As shown). The urea-formaldehyde resin prepolymer solution, surfactant solution, and curing agent diluent were stirred at 800 rpm and 50 °C for 30 min. Subsequently, dilute sulfuric acid was added dropwise to adjust the reaction pH to 2, the reaction temperature was controlled at 55 °C, and the reaction was carried out for 3 h. After filtration, washing, and drying, the curing agent microcapsule powder was obtained, and the D50 of the curing agent microcapsule was 180 μm;

[0073] (3) The aluminum-based adsorbent, curing agent microcapsules, binder microcapsules were mixed with polyurethane and ethyl acetate and stirred evenly to form an adsorbent slurry. Among them, the mass ratio of the aluminum-based adsorbent to polyurethane was 1:0.5, the mass ratio of ethyl acetate to polyurethane was 2.5:1, the total mass fraction of the microcapsules in the solid of the adsorbent slurry was 1%, and the mass of the curing agent microcapsules was 80% of that of the binder microcapsules. 5% of carboxymethyl cellulose and propylenediamine were dissolved in saturated brine to form a homogeneous solution. The mass ratio of carboxymethyl cellulose to propylenediamine was 4:1, and the total concentration of carboxymethyl cellulose and propylenediamine in saturated brine was 80 g / L. The adsorbent slurry was slowly added, and the stirring rate was adjusted to 300 rpm to obtain spherical particles with a median particle size of 1.5 mm. After curing at 50 °C for 18 h, filtration and washing were carried out to obtain the modified lithium extraction adsorbent.

[0074] Example 2

[0075] This example provides a modified lithium extraction adsorbent, which is prepared by the following method:

[0076] (1) Urea and formaldehyde were mixed in a molar ratio of 1:1.4 to prepare a mixed solution with a concentration of 0.1 mol / L. After mixing until the urea was completely dissolved, triethanolamine was added dropwise until the pH was 8. The mixed solution was placed in a water bath at 60 °C and refluxed and stirred for 3 h to obtain a urea-formaldehyde resin prepolymer solution. A sodium stearate surfactant solution with a mass fraction of 0.3% was prepared with pure water. Liquid epoxy resin and ethylene glycol monobutyl ether were mixed in a mass ratio of 5:1, ultrasonicated for 60 min, and then placed in a water bath at 40 °C and heated for 1 h until the solution was stationary and did not separate into layers to obtain a uniformly mixed binder diluent. The JA-IS curing agent, KH-560, and ethylene glycol monobutyl ether were mixed, ultrasonicated for 40 min, and then placed in a water bath at 50 °C and heated for 0.8 h until the solution was stationary and did not separate into layers to obtain a uniformly mixed curing agent diluent;

[0077] (2) The urea-formaldehyde resin prepolymer solution, surfactant solution, and binder diluent were stirred at 900 rpm and 50 °C for 30 min. Subsequently, dilute sulfuric acid was added dropwise to adjust the reaction pH to 1.8, the reaction temperature was controlled at 40 °C, and the reaction was carried out for 5 h. After filtration, washing, and drying, the binder microcapsule powder was obtained, and the D50 of the binder microcapsule was 120 μm (the schematic diagram of the synthesis process of the binder microcapsule is as Figure 1As shown). The urea-formaldehyde resin prepolymer solution, surfactant solution, and curing agent diluent were stirred at 500 rpm and 50 °C for 30 min, then dilute sulfuric acid was added dropwise to adjust the reaction pH = 2.2, the reaction temperature was controlled at 60 °C, and the reaction was carried out for 3 h. After filtration, washing, and drying, the curing agent microcapsule powder was obtained, and the D50 of the curing agent microcapsule was 300 μm;

[0078] (3) The aluminum-based adsorbent, curing agent microcapsules, binder microcapsules were mixed with polyurethane and ethyl acetate and stirred evenly to form an adsorbent slurry. Among them, the mass ratio of the aluminum-based adsorbent to polyurethane was 1:0.2, the mass ratio of ethyl acetate to polyurethane was 3:1, and the total mass fraction of the microcapsules in the solid of the adsorbent slurry was 2%. The mass of the curing agent microcapsules was 150% of that of the binder microcapsules. 5% carboxymethyl cellulose and propylenediamine were dissolved in saturated brine to form a homogeneous solution. The mass ratio of carboxymethyl cellulose to propylenediamine was 4:1, and the total concentration of carboxymethyl cellulose and propylenediamine in saturated brine was 80 g / L. The adsorbent slurry was slowly added, and the stirring rate was adjusted to 200 rpm to obtain spherical particles with a median particle size of 2 mm. After curing at 30 °C for 18 h, filtration and washing were carried out to obtain the modified lithium extraction adsorbent.

[0079] Example 3

[0080] This example provides a modified lithium extraction adsorbent, which is prepared by the following method:

[0081] (1) Urea and formaldehyde were mixed in a molar ratio of 1:1.6 to prepare a mixed solution with a concentration of 0.1 mol / L. After mixing until the urea was completely dissolved, triethanolamine was added dropwise until the pH was 9. The mixed solution was refluxed and stirred in a water bath at 80 °C for 1 h to obtain a urea-formaldehyde resin prepolymer solution. A sodium stearate surfactant solution with a mass fraction of 0.3% was prepared using pure water. Liquid epoxy resin and ethylene glycol monobutyl ether were mixed in a mass ratio of 8:1, ultrasonically treated for 30 min, and then placed in a water bath at 50 °C and heated for 0.5 h until the solution was stationary and did not separate into layers to obtain a uniformly mixed binder diluent. T31 curing agent, KH-560, and ethylene glycol monobutyl ether were mixed, ultrasonically treated for 40 min, and then placed in a water bath at 60 °C and heated for 0.8 h until the solution was stationary and did not separate into layers to obtain a uniformly mixed curing agent diluent;

[0082] (2) The urea-formaldehyde resin prepolymer solution, surfactant solution, and binder diluent were stirred at 600 rpm and 40 °C for 30 min, then dilute sulfuric acid was added dropwise to adjust the reaction pH = 2, the reaction temperature was controlled at 40 °C, and the reaction was carried out for 5 h. After filtration, washing, and drying, the binder microcapsule powder was obtained, and the D50 of the binder microcapsule was 220 μm (the schematic diagram of the synthesis process of the binder microcapsule is as Figure 1As shown). The urea-formaldehyde resin prepolymer solution, surfactant solution, and curing agent diluent were stirred at 800 rpm and 50 °C for 30 min. Subsequently, dilute sulfuric acid was added dropwise to adjust the reaction pH to 2.2, the reaction temperature was controlled at 60 °C, and the reaction was carried out for 3 h. After filtration, washing, and drying, the curing agent microcapsule powder was obtained, and the D50 of the curing agent microcapsules was 150 μm;

[0083] (3) The aluminum-based adsorbent, curing agent microcapsules, binder microcapsules, polyurethane, and ethyl acetate were mixed and stirred evenly to form an adsorbent slurry. Among them, the mass ratio of the aluminum-based adsorbent to polyurethane was 1:0.8, the mass ratio of ethyl acetate to polyurethane was 2:1, the total mass fraction of the microcapsules in the solid of the adsorbent slurry was 0.5%, and the mass of the curing agent microcapsules was 30% of that of the binder microcapsules. 5% of carboxymethyl cellulose and propylenediamine were dissolved in saturated brine to form a homogeneous solution. The mass ratio of carboxymethyl cellulose to propylenediamine was 4:1, and the total concentration of carboxymethyl cellulose and propylenediamine in saturated brine was 80 g / L. The adsorbent slurry was slowly added, and the stirring rate was adjusted to 500 rpm to obtain spherical particles with a median particle size of 0.5 mm. After curing at 60 °C for 12 h, filtration and washing were carried out to obtain the modified lithium extraction adsorbent.

[0084] Example 4

[0085] The difference between this example and Example 1 is only that the mass ratio of the curing agent microcapsules to the binder microcapsules is 0.2:1, and other conditions and parameters are exactly the same as those in Example 1.

[0086] Example 5

[0087] The difference between this example and Example 1 is only that the mass ratio of the curing agent microcapsules to the binder microcapsules is 2:1, and other conditions and parameters are exactly the same as those in Example 1.

[0088] Example 6

[0089] The difference between this example and Example 1 is only that the total mass fraction of the microcapsules in the modified lithium extraction adsorbent is 0.3%, and other conditions and parameters are exactly the same as those in Example 1.

[0090] Example 7

[0091] The difference between this example and Example 1 is only that the total mass fraction of the microcapsules in the modified lithium extraction adsorbent is 5%, and other conditions and parameters are exactly the same as those in Example 1.

[0092] Example 8

[0093] The difference between this example and Example 1 is only that during the preparation process of the microcapsules, the stirring speed is 200 rpm, and other conditions and parameters are exactly the same as those in Example 1.

[0094] Example 9

[0095] The difference between this example and Example 1 is only that during the preparation process of the microcapsules, the reaction temperature is 80 °C, and other conditions and parameters are exactly the same as those in Example 1.

[0096] Comparative Example 1

[0097] This comparative example directly uses an aluminum-based adsorbent.

[0098] Comparative Example 2

[0099] The difference between this comparative example and Example 1 is only that the binder microcapsules are not added, and other conditions and parameters are exactly the same as those in Example 1.

[0100] Comparative Example 3

[0101] The difference between this comparative example and Example 1 is only that the curing agent microcapsules are not added, and other conditions and parameters are exactly the same as those in Example 1.

[0102] Performance Test:

[0103] The method for testing the adsorption performance is the static adsorption method. This adsorbent is used for lithium extraction from brine with a Li + concentration of 500 ppm. Take 20 g of deionized water and 2 g of the lithium adsorbent and mix them. Extract lithium at room temperature for 10 h, measure the brine concentration before and after adsorption, and calculate the adsorption capacity according to the following formula.

[0104] The adsorption capacity of the adsorbent is: Q = V(C0 - C) / m;

[0105] Q is the adsorption capacity, mg / g; V is the volume of the adsorption solution, L; m is the mass of the adsorbent, g; C0 and C are the lithium ion concentrations in the brine before and after adsorption, respectively, mg / L.

[0106] The ratio of the adsorption capacity after 100 test cycles to the initial adsorption capacity gives the capacity retention rate after 100 cycles. The test results are shown in Table 1:

[0107] Table 1

[0108] Adsorption capacity mg / g Capacity retention rate after 100 cycles % Example 1 8.78 98.74 Example 2 8.75 98.67 Example 3 8.72 98.70 Example 4 8.69 97.11 Example 5 8.65 96.83 Example 6 8.31 93.75 Example 7 7.85 97.57 Example 8 8.51 93.46 Example 9 8.48 93.26 Comparative Example 1 8.64 97.03 Comparative Example 2 8.53 93.28 Comparative Example 3 8.51 95.47

[0109] As can be seen from Table 1, from Examples 1 - 3, it can be obtained that the adsorption capacity of the modified lithium extraction adsorbent described in the present disclosure can reach more than 8.72 mg / g, and the capacity retention rate after 100 cycles can reach more than 98.67%.

[0110] Comparing Example 1 with Examples 4 - 5, it can be seen that in the modified lithium extraction adsorbent described in the present disclosure, the mass ratio of the curing agent microcapsules to the binder microcapsules affects its performance. When the mass ratio of the curing agent microcapsules to the binder microcapsules is controlled at (0.3 - 1.5):1, the performance of the modified lithium extraction adsorbent is better. If the proportion of the curing agent microcapsules is too high, the overall proportion of the binder will decrease, affecting the repair effect of the adsorbent, thereby affecting the cycle stability of the material. If the proportion of the binder microcapsules is too high, the curing effect of the curing agent will be poor, affecting the cycle stability of the material.

[0111] Comparing Example 1 with Examples 6 - 7, it can be seen that in the modified lithium extraction adsorbent described in the present disclosure, the mass proportion of the microcapsules affects its performance. When the mass fraction of the microcapsules is controlled at 0.5 - 2%, the performance of the modified lithium extraction adsorbent is better. If the proportion of the microcapsules is too high, the adsorption capacity of the adsorbent will be affected. If the proportion of the microcapsules is too low, the adsorbent cannot be repaired well.

[0112] Comparing Example 1 with Example 8, it can be seen that during the preparation process of the microcapsules described in the present disclosure, the stirring speed affects the performance of the prepared modified lithium extraction adsorbent. If the rotation speed is too slow, the core droplets are large and difficult to be completely encapsulated. Agglomeration will occur between the incompletely encapsulated particles, further increasing the particles and reducing the proportion of the microcapsule core, affecting the repair effect.

[0113] Comparing Example 1 with Example 8, it can be seen that during the preparation process of the microcapsules described in the present disclosure, the reaction temperature controls the synthesis rate of urea - formaldehyde resin. If the temperature is too low, the reaction rate is slow and the efficiency is low; if the temperature is too high, the urea - formaldehyde resin is generated too fast and agglomerates before attaching to the surface of the core droplets, affecting the formation of the capsule shell and thus affecting the repair effect.

[0114] Comparing Example 1 with Comparative Example 1, it can be seen that in the present disclosure, microcapsules are provided on the surface of the aluminum - based adsorbent. When the adsorbent particles crack during the circulation process, the microcapsules rupture, and the binder that can be cured in water flows out and reacts with the curing agent to fill the cracks, reducing the dissolution loss of the adsorbent and improving the cycleability of the adsorbent.

[0115] Comparing Example 1 with Comparative Example 2, it can be seen that the binder microcapsules can act with the curing agent microcapsules during the lithium extraction process to fill the cracks in the adsorbent and improve the service life of the adsorbent.

[0116] Comparing Example 1 with Comparative Example 3, it can be seen that the curing agent microcapsules play a role in curing the binder, making the binder existing in the cracks more stable.

Claims

1. A modified lithium extraction adsorbent, comprising an aluminum-based adsorbent and microcapsules disposed on the surface of the aluminum-based adsorbent, wherein the microcapsules include curing agent microcapsules and binder microcapsules.

2. The modified lithium extraction adsorbent according to claim 1, wherein, the curing agent microcapsules include an underwater curing agent and a curing composite shell.

3. The modified lithium extraction adsorbent according to claim 2, wherein, the curing composite shell includes urea-formaldehyde resin.

4. The modified lithium extraction adsorbent according to claim 2, wherein, the underwater curing agent includes any one or a combination of at least two of T31 curing agent, JA-IS curing agent, I965 curing agent, 810 curing agent or P117 curing agent.

5. The modified lithium extraction adsorbent according to claim 1, wherein, the binder microcapsules include a liquid epoxy resin core and a binder composite shell disposed on the surface of the liquid epoxy resin core.

6. The modified lithium extraction adsorbent according to claim 5, wherein, the binder composite shell includes urea-formaldehyde resin.

7. The modified lithium extraction adsorbent according to claim 1, wherein, the median particle size D50 of the curing agent microcapsules and the binder microcapsules is independently 100 - 300 μm.

8. The modified lithium extraction adsorbent according to claim 1, wherein, calculated based on the mass of the modified lithium extraction adsorbent being 100%, the mass fraction of the microcapsules is 0.5 - 2%.

9. The modified lithium extraction adsorbent according to claim 1, wherein, the mass ratio of the curing agent microcapsules to the binder microcapsules is (0.3 - 1.5):

1.

10. The modified lithium extraction adsorbent according to claim 1, wherein, the modified lithium extraction adsorbent further includes a binder.

11. The modified lithium extraction adsorbent according to claim 10, wherein, the binder includes polyurethane.

12. A preparation method of the modified lithium extraction adsorbent according to any one of claims 1 - 11, comprising the following steps: Mix a urea-formaldehyde resin prepolymer solution, a surfactant solution and a binder diluent, heat and stir, then add acid to adjust the pH for reaction to obtain binder microcapsules; Mix a urea-formaldehyde resin prepolymer solution, a surfactant solution and a curing agent diluent, heat and stir, then add acid to adjust the pH for reaction to obtain curing agent microcapsules; Mix the aluminum-based adsorbent, the binder microcapsules, the curing agent microcapsules, the binder and a solvent to obtain a mixed solution, and granulate the mixed solution to obtain the modified lithium extraction adsorbent.

13. The preparation method according to claim 12, wherein, the urea-formaldehyde resin prepolymer solution is prepared by the following method: Mix urea and a formaldehyde solution to form a mixed solution, after mixing until the urea is completely dissolved, add triethanolamine to adjust the pH of the mixed solution, and carry out a water bath reflux stirring reaction to obtain the urea-formaldehyde resin prepolymer solution.

14. The preparation method according to claim 13, wherein, the molar ratio of formaldehyde in the urea and formaldehyde solution is 1:(1.4 - 1.6).

15. The preparation method according to claim 13, wherein, the pH of the mixed solution is 8 - 9.

16. The preparation method according to claim 13, wherein, The temperature of the water bath reflux stirring reaction is 60-80 °C.

17. The preparation method according to claim 13, wherein, the time of the water bath reflux stirring reaction is 1-3 h.

18. The preparation method according to claim 12, wherein, the mass concentration of the surfactant solution is 0.3%-0.8%.

19. The preparation method according to claim 12, wherein, the surfactant includes any one or a combination of at least two of sodium oleate, sodium stearate, sodium metasilicate or sodium dodecylbenzenesulfonate.

20. The preparation method according to claim 12, wherein, the binder diluent is prepared by the following method: Mix liquid epoxy resin with a diluent, perform ultrasonic treatment and then carry out a water bath heating reaction to obtain the binder diluent.

21. The preparation method according to claim 20, wherein, the mass ratio of the liquid epoxy resin to the diluent is 1:(0.1-0.2).

22. The preparation method according to claim 12, wherein, the curing agent diluent is prepared by the following method: Mix a curing agent, a coupling agent and a diluent, perform ultrasonic treatment and then carry out a water bath heating reaction to obtain the curing agent diluent.

23. The preparation method according to claim 22, wherein, the coupling agent includes KH-550 and / or KH560.

24. The preparation method according to claim 22, wherein, the diluent includes n-butyl glycidyl ether, ethylene glycol monobutyl ether or benzyl glycidyl ether.

25. The preparation method according to claim 12, wherein, during the preparation of the binder diluent and the curing agent diluent, the ultrasonic time is independently 30-60 min.

26. The preparation method according to claim 12, wherein, during the preparation of the binder diluent and the curing agent diluent, the temperature of the water bath heating reaction is independently 40-50 °C.

27. The preparation method according to claim 12, wherein, during the preparation of the binder diluent and the curing agent diluent, the time of the water bath heating reaction is independently 0.5-1 h.

28. The preparation method according to claim 12, wherein, during the preparation of the binder microcapsules and the curing agent capsules, the speed of heating and stirring is independently 500-1000 rpm.

29. The preparation method according to claim 12, wherein, during the preparation of the binder microcapsules and the curing agent capsules, the temperature of heating and stirring is independently 40-50 °C.

30. The preparation method according to claim 12, wherein, during the preparation of the binder microcapsules and the curing agent capsules, the time of heating and stirring is independently 30-60 min.

31. The preparation method according to claim 12, wherein, during the preparation of the binder microcapsules and the curing agent capsules, adjusting the pH by adding acid is independently 1.8-2.

2.

32. The preparation method according to claim 12, wherein, during the preparation of the binder microcapsules and the curing agent capsules, the reaction temperature is independently 40-60 °C.

33. The preparation method according to claim 12, wherein, During the preparation processes of the binder microcapsules and the curing agent capsules, the reaction time is independently 2 to 5 h.

34. The preparation method according to claim 12, wherein, the mass ratio of the aluminum-based adsorbent to the binder is 1:(0.2 - 0.8).

35. The preparation method according to claim 12, wherein, the solvent includes ethyl acetate.

36. The preparation method according to claim 12, wherein, the mass ratio of the solvent to the binder is (2 - 3):

1.

37. The preparation method according to claim 12, wherein, the mass fraction of the microcapsules in the mixed solution is 0.5% - 1.5%.

38. The preparation method according to claim 12, wherein, the granulation treatment includes liquid-phase curing granulation and / or extrusion granulation.

39. The preparation method according to claim 38, wherein, the granulation treatment is liquid-phase curing granulation.

40. The preparation method according to claim 39, wherein, the liquid-phase curing granulation includes: dissolving carboxymethyl cellulose and propylenediamine in saturated brine to form a uniform solution, slowly adding the mixed solution to the uniform solution, adjusting the stirring rate to 200 - 500 rpm, obtaining spherical particles with a particle size of 0.5 - 2 mm, and filtering and washing after heat preservation and curing at 30 - 60 °C to obtain the modified lithium extraction adsorbent.

41. Application of the modified lithium extraction adsorbent according to any one of claims 1 - 11 in extracting lithium from salt lakes.

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