Lithium extraction adsorbent as well as preparation method and application thereof

Abstract

The invention belongs to the field of lithium extraction from brine, and provides a lithium extraction adsorbent as well as a preparation method and application thereof. The preparation method of the lithium extraction adsorbent comprises the following steps: carrying out particle forming, drying and activation on granulation slurry containing an adsorbent precursor and an adhesive material liquid; wherein the binder liquid comprises a polymer binder, additives and a solvent, the additives comprise a first additive material, a second additive material and a third additive material, the first additive material is a proton capture material, the second additive material is a negatively charged material, and the third additive material is a phase change microcapsule. The lithium extraction adsorbent disclosed by the invention can keep relatively high stability and relatively long service life at different environment temperatures of adsorption and desorption.

Description

Technical Field

[0001] The present invention belongs to the field of lithium extraction from brine, and specifically provides a lithium extraction adsorbent and a preparation method and application thereof. Background Art

[0002] As the lightest metal element with the lowest standard electrode potential in nature, lithium is known as the "white oil" of the future and is the most ideal battery material. With the development of new energy power and new energy vehicles, the demand for energy storage batteries and automotive batteries has also increased rapidly, and traditional lithium ore extraction can no longer meet market demand. Lithium in nature also exists in large quantities in brine, which is a liquid resource with a high salt content. It can be divided into conventional salt lake brine and unconventional geothermal brine, oilfield brine and salt well brine, and its reserves account for more than 60% of the total lithium resources. How to efficiently extract lithium from brine has become a problem that the industry is committed to solving.

[0003] Brine generally contains Li + 、Na + , K + , Ca 2+ Mg 2+ , B 3+ 、SO4 2- , Cl - 、CO3 2- Plasma, the existing processes for extracting lithium from brine mainly include precipitation, adsorption, extraction, membrane separation, etc. Among them, the core of the adsorption method is to use lithium extraction adsorbents to adsorb brine. The adsorption method is suitable for brine with low lithium concentration and high impurity ion concentration. At present, the main adsorbents for lithium extraction from salt lakes are inorganic adsorbents, which can be divided into two categories: aluminum salt adsorbents and ion sieve adsorbents (manganese adsorbents and titanium adsorbents). The use of these adsorbents involves at least two steps of adsorption and desorption. In actual applications, the process conditions of adsorption and desorption are often very different. For example, in a salt lake lithium extraction process using titanium-based adsorbents, the brine temperature in the salt lake is only 0-5°C and the pH is between 8 and 9. Due to the limitations of on-site natural conditions and costs, it is difficult to change the brine conditions themselves. Therefore, the adsorption is carried out at 0-5°C and pH=8-9. The desorption liquid used in the desorption step is an acid solution with a pH usually less than 0.3. In addition, the required temperature of the desorption process is greater than 30°C, otherwise the adsorbent cannot be completely desorbed. Therefore, the desorption needs to be carried out at >30°C and pH<0.3.

[0004] Therefore, limited by the brine type and environmental factors, the adsorption and desorption processes of lithium extraction adsorbents in actual applications are in environmental conditions with large temperature and pH differences and continuous cyclic changes. The constant changes in the use environment will accelerate the performance degradation of the adsorbent, deteriorate stability, and shorten its service life. Summary of the invention

[0005] The purpose of the present invention is to provide a lithium extraction adsorbent and a preparation method and application thereof. The lithium extraction adsorbent prepared by the present invention can maintain high stability and long service life in different environmental conditions of adsorption and desorption.

[0006] In a first aspect, the present invention provides a method for preparing a lithium-extracting adsorbent, comprising: subjecting a granulation slurry comprising an adsorbent precursor and a binder liquid to particle forming, drying and activating; wherein the binder liquid comprises a polymer binder, an additive and a solvent, the additive comprises a first additive material, a second additive material and a third additive material, the first additive material is a proton capture material, the second additive material is a negatively charged material, and the third additive material is a phase change microcapsule.

[0007] In the preparation method of the present invention, adding phase change microcapsules to the binder liquid can improve the stability of the adsorbent in different temperature environments, and the proton capture material used can react with H in an acidic environment. + Combined to form a stable salt, to avoid the adsorption decline due to acidification, and the added material can also capture protons during the desorption process, to avoid the adsorbent from low H + The environment switches to high H + In the environment, it can slow down the structural damage of the adsorbent caused by excessive hydrogen-lithium replacement; in addition, the use of negatively charged materials can make the adsorbent produce electrostatic repulsion to the anions in the brine, preventing these anions from entering the structure of the adsorbent, and causing cations such as calcium and magnesium to be repelled together (because cations cannot exist alone and must balance the charge with anions), thereby improving the selective adsorption capacity for lithium ions.

[0008] In some embodiments of the present invention, in the binder liquid, the mass content of the polymer binder is 5% to 30%, the mass content of the first additive material is 1% to 20%, the mass content of the second additive material is 0.1% to 10%, the mass content of the third additive material is 2% to 20%, and the mass content of the solvent is 50% to 85%.

[0009] In some embodiments of the present invention, the polymer binder is selected from one or more of polyvinyl butyral, polyacrylonitrile, polysulfone, polyethersulfone, polyarylsulfone, polyvinyl chloride, polyvinylidene fluoride, ethyl cellulose and ethylene-vinyl alcohol copolymer.

[0010] In some embodiments of the present invention, the first additive material is selected from one or more of polyethyleneimine, chitosan, polyamidoamine, polylysine, polydimethyldiallylammonium chloride, polydimethylaminoethyl methacrylate, polymethyl methacrylate-dimethylaminoethyl methacrylate copolymer, polyallylamine and polyaminopropyl biguanide.

[0011] In some embodiments of the present invention, the second additive material is selected from one or more of polyacrylic acid, polymaleic anhydride, sodium polystyrene sulfonate, sulfonated polyetheretherketone, carboxymethyl cellulose, sulfonated polysulfone, polyethylene sulfonic acid, sodium polypropylene sulfonate, polyphosphate, chitosan sulfonate and polyfluorosulfonic acid.

[0012] In some embodiments of the present invention, the phase change microcapsules include a polymer wall material and a core material encapsulated in the polymer wall material; wherein the core material is one or more of paraffin, capric acid, stearic acid, lauric acid, dodecanol, tetradecanol and hexadecanol, and the polymer wall material is one or more of polymethyl methacrylate, polyvinyl chloride, polyvinylidene chloride copolymer, polystyrene and polyvinyl acetate.

[0013] Furthermore, the phase change microcapsules are prepared by suspension polymerization, and include the following steps:

[0014] dissolving a dispersant in an aqueous phase to obtain an aqueous phase;

[0015] The core material, the polymerization monomer, the cross-linking agent and the oil-soluble initiator are uniformly mixed to obtain an oil phase;

[0016] The water phase is heated to 40-90°C, and the oil phase is added dropwise to the water phase under continuous stirring to carry out polymerization reaction. After the addition is completed, stirring and reaction are continued for 2-6 hours to form a suspension containing phase change microcapsules;

[0017] The suspension is centrifuged or filtered, and the obtained crude product is washed and dried to obtain phase change microcapsules.

[0018] In some embodiments of the present invention, the adsorbent precursor is one or more of an aluminum salt adsorbent precursor, a titanium-based ion sieve adsorbent precursor, and a manganese-based ion sieve adsorbent precursor.

[0019] In some embodiments of the present invention, the mass ratio of the adsorbent precursor to the binder liquid is (20-50):100.

[0020] In some embodiments of the present invention, the particle forming method is spray granulation, and the spray granulation process includes: spraying the granulation slurry into an anti-solvent solution to form solid particles, and then removing the anti-solvent solution to obtain adsorbent particles.

[0021] In a second aspect, the present invention provides a lithium extraction adsorbent prepared by the method of the present invention. As described above, the lithium extraction adsorbent prepared by the present invention has the characteristics of strong environmental adaptability, high stability and long service life.

[0022] In a third aspect, the present invention provides the use of the lithium extraction adsorbent described in the second aspect of the present invention in extracting lithium from salt lake brine.

[0023] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0025] Figure 1 A schematic diagram of the preparation process of phase change microcapsules according to one embodiment of the present invention;

[0026] Figure 2 The present invention is a schematic diagram of a process for preparing a lithium extraction adsorbent according to an embodiment of the present invention. DETAILED DESCRIPTION

[0027] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0028] The "range" disclosed in the present invention is defined in the form of a lower limit and / or an upper limit, and a given range is defined by selecting a lower limit and / or an upper limit. The range defined in this way can be inclusive or exclusive of the end value, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form an undefined range, and any lower limit can be combined with other lower limits to form an undefined range, and any upper limit can be combined with any other upper limit to form an undefined range. In addition, each separately disclosed point or single value itself can be combined with any other point or single value as a lower limit or upper limit or with other lower limits or upper limits to form an undefined range.

[0029] In the present invention, the terms "first", "second", and "third" are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. In addition, the meaning of "multiple" is two or more.

[0030] If not otherwise specified, all embodiments and optional embodiments of the present invention may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present invention.

[0031] Limited by the type of brine and environmental factors, the lithium extraction adsorbent is in an environment with extremely different temperature and pH values ​​and constantly changing cycles during the adsorption and desorption process. The constantly changing environmental conditions of the adsorbent require the adsorbent to be resistant to acid, alkali and high temperature, as well as stable for multiple cycles. In order to improve the application effect of the adsorbent, the relevant technologies are proposed respectively: method 1: loading the ion sieve adsorbent on a pH-sensitive responsive polymer gel; method 2: using a thermosensitive polymer to prepare the adsorbent. Regarding method 1, in lithium extraction adsorption, the carboxyl groups provided by the gel will dissociate into carboxylate ions, which have an electrostatic adsorption effect on the surrounding lithium ions. The gel will also swell in the salt lake brine, increasing the contact area between the internal lithium ion sieve and the lithium-containing solution, thereby improving the lithium extraction efficiency. However, when the carboxyl groups dissociate into carboxylate ions, they will be accompanied by protons (H + ) is released, and H + and Li + Exchange, H on ion sieve + Entering the solution, Li in brine + While forming a repulsive effect, it will also reduce the pH of the solution in the vicinity of the adsorbent, which is not conducive to improving the adsorption efficiency. Regarding method 2, after using a thermosensitive polymer to prepare the adsorbent, the pore size of the adsorbent can be adjusted according to the temperature of the adsorption and desorption processes. Under low temperature conditions in the adsorption process, the thermosensitive polymer expands, and the pore size is reduced by extrusion to improve the ion selectivity; while under high temperature conditions in the desorption process, the thermosensitive polymer shrinks, making the pore size larger, increasing the contact between the adsorbent and the desorption liquid, thereby increasing the desorption rate; but in fact, the ion selectivity of inorganic adsorbents comes from the microstructure inside the adsorbent crystals, relying on the nano-level interlayer spacing of the crystals to exclude large ions. The expansion and extrusion of the polymer only reduces the macroscopic pore size, which has no effect on the ion selectivity of the adsorbent. Even if the polymer expands and extrudes to reduce the pore size to the extent of screening ions, it will greatly reduce the contact between the adsorbent and the brine, but reduce the adsorption rate and affect the overall lithium extraction efficiency. It can be seen that the existing lithium extraction adsorbents still have problems such as low adsorption efficiency, low ion selectivity and poor stability, which also leads to the high cost of lithium extraction from salt lakes.

[0032] To this end, the present invention provides a lithium extraction adsorbent and a preparation method thereof, which aims to overcome the influence of the constantly changing environmental conditions on the adsorbent during the adsorption and desorption process of the lithium extraction adsorbent and extend the service life of the adsorbent.

[0033] The preparation method of the lithium extraction adsorbent of the present invention comprises: subjecting a granulation slurry containing an adsorbent precursor and a binder liquid to particle forming, drying and activating, wherein the binder liquid contains a polymer binder, an additive and a solvent.

[0034] The present invention aims to improve the performance of various lithium extraction adsorbents by optimizing the binder liquid component in the lithium extraction adsorbent, so the type of the adsorbent precursor can be selected with reference to the prior art. According to some embodiments, the adsorbent precursor is one or more of an aluminum salt adsorbent precursor, a titanium-based ion sieve adsorbent precursor, and a manganese-based ion sieve adsorbent precursor.

[0035] Preferably, the aluminum salt adsorbent precursor is LiCl·2Al(OH)3·nH2O.

[0036] Preferably, the manganese-based ion sieve adsorbent precursor is LiMn2O4, Li 1.33 Mn 1.67 O4、Li 1.6 Mn 1.6 At least one of O4.

[0037] Preferably, the titanium-based ion sieve adsorbent precursor is Li2TiO3 and / or Li4Ti5O 12 .

[0038] The present invention does not limit the polymer binder, and it can be selected from the existing binders for preparing granular lithium extraction adsorbents. The polymer binder can tightly bind the adsorbent precursor and the additive, provide strong adhesion, and improve the pore distribution and morphology in the granular adsorbent. As some embodiments, the polymer binder can be one or more of polyvinyl butyral (PVB), polyacrylonitrile (PAN), polysulfone (PSU), polyethersulfone (PES), polyarylsulfone (PAS), polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), ethyl cellulose (EC), and ethylene-vinyl alcohol copolymer (EVOH). Further, the specific type of the polymer binder can also be selected according to the application environment of the lithium extraction adsorbent. For example, when the application environment includes high temperature and acidic conditions, PVC can be selected as a binder, and when the application environment includes high temperature and alkaline conditions, PSU can be selected as a binder; in addition, multiple types of binders can also be used in combination, such as combining PVC with a price advantage and a hydrophilic binder (such as PAN, PVB) to improve the insufficient hydrophilicity of PVC used alone.

[0039] In some embodiments, the mass content of the polymer binder in the binder liquid can be 5% to 30%, for example, 5%, 10%, 13%, 14%, 15%, 15.2%, 15.8%, 16%, 17%, 20%, 25%, 30%, etc., preferably 10% to 25%.

[0040] In the present invention, the solvent may generally be an organic solvent. As some examples, the organic solvent may be one or more of N-methylpyrrolidone (NMP), N,N-dimethylacetamide (DMAc), propylene glycol methyl ether acetate (MPA), N,N-dimethylformamide (DMF), ethylene glycol tert-butyl ether (ETB), propylene glycol methyl ether (PM), dimethyl sulfoxide (DMSO), tetrahydrofuran (THF) and isopropyl acetate (IPA).

[0041] In some embodiments, the mass content of the solvent in the binder liquid can be 50% to 85%, for example, 55%, 60%, 62%, 64%, 70%, 71%, 72%, 73.5%, 74%, 75%, 76%, 77%, 80%, 83%, etc., preferably 60% to 80%.

[0042] In the present invention, the additive auxiliary comprises a first additive material, a second additive material and a third additive material.

[0043] In the present invention, the first additive material is a proton capture material, which usually contains basic functional groups, such as amino, amine, oxadiazole, guanidine, etc., which can combine with H+ in an acidic environment to form a stable hydrogen bond or salt form, thereby reducing free H+ and playing a role in adjusting the pH of the solution. As some embodiments, the proton capture material can be selected from one or more of the following materials: polyethyleneimine (PEI), chitosan (CS), polyamidoamine (PAMAM), polylysine (PLL), polydimethyldiallyl ammonium chloride (PDADMAC), polydimethylaminoethyl methacrylate (PDMAEMA), polymethyl methacrylate-dimethylaminoethyl methacrylate copolymer (P(MMA-co-DMAEMA)), polyallylamine (PAA), polyaminopropyl biguanide (PAPG). Preferably, the deacetylation degree of the chitosan is ≥90%.

[0044] During the adsorption process, the acidification of brine often affects the adsorption capacity and yield. The proton capture material is combined with the lithium extraction adsorbent to capture H in the solution. + , so that the pH of the solution remains stable during the adsorption process, avoiding the destruction of the reaction balance caused by acidification, thereby improving the adsorption efficiency. During the desorption process, the material also plays a pH buffering role, capturing protons during desorption to avoid the adsorbent suddenly changing from low concentration H + The environment switches to high H + In a high concentration environment, it can slow down the structural damage of the adsorbent caused by excessive lithium hydrogen replacement.

[0045] In some embodiments, the mass content of the first additive material in the binder liquid is 1% to 20%, such as 1%, 2%, 2.4%, 3%, 5%, 6%, 10%, 15%, 17%, etc. In order to reduce free hydrogen ions while avoiding excessive distribution of the material in the brine and causing excessive cost, preferably, the mass content of the first additive material in the binder liquid is 2% to 10%.

[0046] In the present invention, the second additive material can generally be selected from various anionic polymers. When the anionic groups (such as sulfonic acid groups, carboxyl groups, and phosphate groups) provided by such polymers dissociate in water, protons will be released, making the polymer body negatively charged. The second additive material can realize the negative charge modification of the adsorbent. The negatively charged adsorbent produces an electrostatic repulsion on the anions (such as sulfate, carbonate, silicate, borate, etc.) in the brine, thereby preventing these anions from entering the structure of the adsorbent, and because of the need to balance the charge, cations such as calcium and magnesium are also repelled, which can effectively promote the selective adsorption of lithium ions in the brine. At the same time, the negatively charged adsorbent has good hydrophilicity, which further enhances the efficiency of adsorbing lithium ions.

[0047] In some embodiments, the second additive material is selected from one or more of polyacrylic acid (PAA), polymaleic anhydride (PMAA), sodium polystyrene sulfonate (PSS), sulfonated polyetheretherketone (SPEEK), carboxymethyl cellulose (CMC), sulfonated polysulfone (SPSF), sodium polypropylene sulfonate (PAS), polyphosphate, chitosan sulfonate and polyfluorosulfonic acid. As a preferred example, the second additive material is sulfonated polysulfone, and the sulfonation degree of the sulfonated polysulfone is 20% to 30%.

[0048] In some embodiments, the mass content of the second additive in the binder liquid may be 0.1% to 10%, such as 0.5%, 0.8%, 1%, 1.5%, 2%, 3%, 5%, 8%, etc. Preferably, the mass content of the second additive in the binder liquid is 1% to 7%.

[0049] In the present invention, the third added material is a phase change microcapsule (PCM). This material has the ability to absorb and release latent heat, and can effectively slow down the rate of temperature change when the ambient temperature reaches its phase change point. Specifically, when the ambient temperature of the adsorbent rises, the phase change microcapsules in the binder absorb too much heat to prevent the ambient temperature from rising rapidly; when the ambient temperature of the adsorbent drops, the phase change microcapsules release heat to prevent the temperature from dropping suddenly. In this way, the aging and performance degradation of the adsorbent caused by drastic temperature changes can be effectively delayed, ensuring its stability during the adsorption and desorption stages.

[0050] In the present invention, the phase change microcapsule may include a polymer wall material and a core material encapsulated therein. The core material is encapsulated in the polymer wall material so that its phase change characteristics can be stably controlled, leakage is prevented and durability is improved. The core material can regulate the ambient temperature by absorbing or releasing latent heat. According to some embodiments, the core material is one or more of paraffin (PW), capric acid (CA), stearic acid (SA), lauric acid (LA), dodecanol, tetradecanol and hexadecanol; the polymer wall material is one or more of polymethyl methacrylate (PMMA), polyvinyl chloride, polyvinylidene chloride copolymer, polystyrene, and polyvinyl acetate.

[0051] In some embodiments, in the binder liquid, the mass content of the third additive material can be 2% to 20%, for example, 2%, 3%, 5%, 7%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, etc., preferably 3% to 15%, and more preferably 5% to 10%.

[0052] In the present invention, the phase change microcapsules can be obtained commercially or prepared by methods well known in the art, such as but not limited to emulsion polymerization, suspension polymerization, interfacial polymerization, etc. In some embodiments, the phase change microcapsules are prepared by suspension polymerization, combined with Figure 1 As shown, the following steps are included:

[0053] (1) dissolving a dispersant in an aqueous phase to obtain an aqueous phase; and uniformly mixing a core material, a polymerization monomer, a crosslinking agent, and an oil-soluble initiator to obtain an oil phase;

[0054] (2) heating the water phase to 40 to 90° C. (e.g., 50° C., 55° C., 60° C., 70° C., 80° C., or 85° C.), and dropping the oil phase into the water phase under continuous stirring to carry out a polymerization reaction. After the addition is completed, stirring the reaction is continued for 2 to 6 hours (e.g., 2 hours, 3 hours, 3.5 hours, 4 hours, or 5 hours) to form a suspension containing phase change microcapsules;

[0055] (3) The suspension is centrifuged or filtered, and the resulting crude product is washed and dried to obtain phase change microcapsules.

[0056] It can be understood that the polymerizable monomer refers to a monomer that can form a polymer wall material through a free radical polymerization reaction. For example, when the material of the polymer wall material is PMMA, the polymerizable monomer used is methyl methacrylate (MMA).

[0057] In step (1), the dispersant may be selected from polyvinyl pyrrolidone (PVP) and / or polyvinyl alcohol (PVA). Preferably, the mass ratio of the dispersant to water is 1: (100-500). The dissolution may be carried out under heating and / or high-speed stirring conditions, the heating temperature may be 40-85° C., and the stirring speed may be 1000-3000 rpm.

[0058] As some examples, the crosslinking agent can be selected from one or more of the following multifunctional compounds: pentaerythritol tetraacrylate (PETRA), ethylene glycol dimethacrylate (EGDMA), divinylbenzene (DVB), pentaerythritol triacrylate (PETA), triallyl cyanurate (TAC), bisallyl polyether (DMS-4000). The oil-soluble initiator can be selected from one or more of azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, benzoyl peroxide, and lauroyl peroxide.

[0059] In some embodiments, the mass ratio of the core material, the cross-linking agent and the polymerized monomer can be (0.8-2):(0.1-0.5):1, for example, 0.8:0.3:1, 1.1:0.2:1, 1.2:0.3:1, 1.5:0.3:1, 1.5:0.4:1, etc.; the mass ratio of the oil-soluble initiator to the cross-linking agent can be (5-15):100, for example, 5:100, 10:100, 15:100, etc.

[0060] In some embodiments, the mass amount of the dispersant is 0.5% to 3% of the mass of the core material.

[0061] In step (2), the stirring speed can be 200 to 1000 rpm, preferably 200 to 600 rpm. The polymerization monomer and the cross-linking agent undergo a polymerization reaction under the action of the initiator to form a polymer (i.e., a polymer wall material) to encapsulate the core material to form a phase change microcapsule. Preferably, a pH regulator is added during the reaction to control the pH of the reaction system to 9 to 10. Specific examples of pH regulators include, but are not limited to, sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, hydrochloric acid, acetic acid, citric acid, and phosphoric acid. When the pH regulator is solid, it can be used in the form of an aqueous solution thereof.

[0062] In step (3), washing is to remove impurities such as raw materials that do not participate in the reaction, and the detergent used may be, for example, water and / or ethanol. Drying is to remove moisture in the microcapsules, and the drying method includes, but is not limited to, freeze drying, spray drying, and vacuum drying, and the drying temperature may be 45 to 60°C.

[0063] In some embodiments, in the binder liquid, the total mass content of the additives may be 9% to 20%, for example, 10%, 11%, 11.5%, 12%, 13%, 14%, 15%, 17%, etc.

[0064] In the present invention, the polymer binder can be dissolved in a solvent, and the first additive material, the second additive material and the third additive material are added in sequence and mixed evenly to obtain a binder liquid, and the mixing temperature can be 0 to 75° C., preferably 15 to 60° C. As some specific examples, the mixing temperature when the first additive material is added can be 20 to 40° C., the mixing temperature when the second additive material is added can be 40 to 70° C., and the mixing temperature when the third additive material is added can be 20 to 40° C.

[0065] In some embodiments, the mass ratio of the adsorbent precursor to the binder liquid can be (20-50):100, for example, 22:100, 23:100, 25:100, 30:100, 33:100, 35:100, 40:100, 45:100, etc.

[0066] As some preferred embodiments, the granulation slurry is prepared by mixing the adsorbent precursor with the binder liquid and then mechanically stirring them evenly under vacuum conditions. Vacuum stirring can remove bubbles in the slurry, reduce defect formation, reduce the possibility of large voids and cracks inside the prepared adsorbent, make the particle structure more compact, and help prepare a granular adsorbent with a stable structure and uniform size; reduce the adsorbent rupture loss caused by stress concentration during subsequent use. The vacuum stirring time can be 0.5 to 6 hours, such as 0.5 hours, 1 hour, 1.5 hours, 2 hours, 3 hours or 5 hours, preferably 1 to 3 hours.

[0067] In the present invention, during the particle forming process, droplets can be first formed by spraying or throwing the slurry into an anti-solvent solution. For example, the droplet volume can be adjusted by the injection speed, so that the spherical particle size can be adjusted. When the granulation slurry contacts the anti-solvent solution, phase separation occurs, and it is quickly solidified to form solid particles. The formed particles can be, for example, elliptical, and the particle size range can be 0.3 to 0.8 mm. As some preferred examples, the particle forming method includes jet granulation, and the jet granulation process includes: spraying the granulation slurry into the anti-solvent solution to form solid particles, and then removing the anti-solvent solution to obtain adsorbent particles. Wherein, the granulation slurry can naturally form balls when entering the anti-solvent solution.

[0068] In the present invention, the anti-solvent solution can be an aqueous solution containing 1% to 50% (volume content, such as 1%, 5%, 10%, 15%, 20%, 25%, 30%, etc.) of the anti-solvent. Specific examples of the anti-solvent include, but are not limited to, one or more of methanol, ethanol, propanol, isobutanol, n-butanol, acetone, cyclohexanone, ethyl acetate, n-propyl acetate, isopropyl acetate, butyl acetate, ethylene glycol ethyl ether, and butanone.

[0069] In some embodiments, the drying of the solid particles may include two stages performed sequentially, the first stage: drying the adsorbent particles at 40-60° C. for 15-30 hours to obtain a dried product; the second stage: curing the dried product at 100-180° C. for 1-8 hours. High temperature treatment can promote the volatilization of residual solvents in the particle adsorbent, make the microporous structure more stable, and reduce pore collapse or structural defects. In addition, high temperature treatment can cause the pores or surface structure to shrink, and this shrinkage can also increase the density and strength of the material.

[0070] In the present invention, the activation can be performed in a manner that provides H + The activation solution is activated by + Replace the metal ions in the precursor (such as Li + ) to achieve the adsorption of lithium ions. Specific examples of the activation solution include, but are not limited to, hydrochloric acid, nitric acid, sulfuric acid or sodium persulfate aqueous solution, and the concentration of the activation solution can be 0.1 to 3 mol / L, preferably 0.5 to 2 mol / L.

[0071] In some embodiments, the activation temperature is 45-60°C, for example, 45°C, 50°C, 55°C, 60°C, etc.; the activation time can be 10-24h, for example, 10h, 12h, 15h, 20h, 22h, 24h, etc.

[0072] According to a specific implementation method, Figure 2 As shown, the preparation method of the lithium extraction adsorbent comprises the following steps:

[0073] Add the polymer binder into the organic solvent and stir until dissolved to obtain a transparent homogeneous slurry (slurry 1);

[0074] Add the first additive material to slurry one, and continue to stir evenly to obtain a homogeneous slurry (slurry two);

[0075] Add the second additive material to slurry 2, continue stirring until dissolved, and obtain a homogeneous slurry (slurry 3);

[0076] Adding the third additive material to the slurry three, and stirring until the third additive material is evenly dispersed in the slurry to obtain a binder liquid;

[0077] uniformly dispersing the adsorbent precursor in the binder liquid to obtain a granulation slurry;

[0078] The granulated slurry is sprayed into an anti-solvent solution to coagulate and solidify (naturally form balls), and then the anti-solvent solution is filtered out to obtain adsorbent particles;

[0079] The adsorbent particles are washed, dried and activated to obtain a lithium-extracting adsorbent.

[0080] The present invention also provides a lithium extraction adsorbent prepared by the preparation method of the present invention.

[0081] The preparation method of the present invention improves the adsorption capacity of the adsorbent for lithium ions, especially in the complex environment of brine, and can enable the adsorbent to maintain high lithium selectivity and reduce the adsorption of impurity ions such as calcium and magnesium; enhances the adsorbent's ability to resist organic pollution, improves the system operation stability, and reduces the system maintenance cost; prolongs the service life of the adsorbent and slows down its dissolution and degradation during long-term use.

[0082] To this end, the present invention further provides the use of the lithium extraction adsorbent described in the present invention in extracting lithium from salt lake brine.

[0083] The following are examples of the present invention. The examples described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. The reagents or instruments used without indicating the manufacturer are all conventional products that can be obtained commercially.

[0084] The preparation examples are used to illustrate the preparation methods of the phase change microcapsules used in the following examples and comparative examples.

[0085] Preparation Example 1

[0086] Add 500 g of paraffin wax to a 1 L beaker, heat to melt at 60°C, add 300 g of methyl methacrylate (MMA) and 100 g of pentaerythritol tetraacrylate and disperse evenly, then add 10 g of azobisisobutyronitrile (AIBN) and shake to dissolve, to obtain a uniform oil phase.

[0087] Add 2L of deionized water to a 5L beaker, add 4g of PVA, heat to 80°C, stir and dissolve at 1500rpm to obtain an aqueous phase, slowly drop the oil phase into the aqueous phase, and adjust the stirring speed to 300rpm to carry out a polymerization reaction. The oil phase dropwise addition time is 1h, and stirring is continued for 3h after the dropwise addition is completed. During the reaction process, the pH is controlled to be stable at 9-10 (adjusted with NaOH solution) to form a suspension containing phase change microcapsules; after the reaction is completed, filter while hot, wash three times with anhydrous ethanol, and dry in an oven at 60°C to obtain phase change microcapsules.

[0088] Example 1

[0089] (1) Preparation of adhesive liquid

[0090] Take 200g PVC powder, add it to 1.0L (937g) solvent DMAc, stir (300rpm) at 30°C until completely dissolved, and obtain a transparent homogeneous slurry, then add 30g CS powder (McLean, deacetylation ≥ 95%, the same below) thereto, continue to stir evenly at 30°C, then add 50g SPSF powder (Anhui Monapore Technology Co., Ltd., brand S2000P, the same below), heat to 60°C and stir until completely dissolved to obtain a homogeneous slurry. Continue to stir the slurry and cool it to room temperature, add 100g phase change microcapsules, and stir at low speed (60rpm) at room temperature until the microcapsules are evenly distributed in the slurry to obtain a binder liquid.

[0091] (2) Particle Forming

[0092] 450 g of adsorbent precursor powder Li2TiO3 was added to the binder liquid and stirred evenly with a vacuum machine (vacuum degree: -100 kPa, rotation speed: 60 rpm, stirring for 3 h) to obtain a granulated slurry.

[0093] The granulation slurry was sprayed into an anti-solvent solution (formed by mixing 1 L of ethanol and 5 L of deionized water) by spray granulation to solidify and form particles. The anti-solvent solution was filtered to obtain adsorbent particles.

[0094] (3) Drying and activation

[0095] The adsorbent particles were placed in an oven at 45°C for drying for 24 hours, and then heated to 120°C for curing for 4 hours. The cured adsorbent particles were taken out and placed in hydrochloric acid (HCl concentration was 0.3 mol / L) for activation at 50°C for 12 hours to obtain a lithium-extracting adsorbent, which was recorded as LK-1.

[0096] Comparative Example 1

[0097] (1) Preparation of adhesive liquid

[0098] Take 200g of PVC powder, add it to 1.0L of solvent DMAc, stir at 30°C (300rpm) until it is completely dissolved to obtain a transparent homogeneous slurry, then add 30g of CS powder, continue to stir evenly at 30°C, add 100g of phase change microcapsules, and stir at low speed (60rpm) at room temperature until the microcapsules are evenly distributed in the slurry to obtain a binder liquid.

[0099] (2) Particle Forming

[0100] 450 g of adsorbent precursor powder Li2TiO3 was added to the binder liquid and stirred evenly with a vacuum machine (vacuum degree: -100 kPa, rotation speed: 60 rpm, stirring for 3 h) to obtain a granulated slurry.

[0101] The granulation slurry was sprayed into an anti-solvent solution (formed by mixing 1 L of ethanol and 5 L of deionized water) by spray granulation to solidify and form particles. The anti-solvent solution was filtered to obtain adsorbent particles.

[0102] (3) Drying and activation

[0103] The adsorbent particles were placed in an oven at 45°C for drying for 24 hours, and then heated to 120°C for curing for 4 hours. The cured adsorbent particles were taken out and placed in hydrochloric acid (HCl concentration was 0.3 mol / L) for activation at 50°C for 12 hours to obtain a lithium-extracting adsorbent, which was recorded as LK-D1.

[0104] Comparative Example 2

[0105] (1) Preparation of adhesive liquid

[0106] Take 200g of PVC powder, add it to 1.0L of solvent DMAc, stir at 30°C (300rpm) until it is completely dissolved to obtain a transparent homogeneous slurry; add 100g of phase change microcapsules to the slurry, stir at low speed (60rpm) at room temperature until the microcapsules are evenly distributed in the slurry to obtain a binder liquid.

[0107] (2) Particle Forming

[0108] 450 g of adsorbent precursor powder Li2TiO3 was added to the binder liquid and stirred evenly with a vacuum machine (vacuum degree: -100 kPa, rotation speed: 60 rpm, stirring for 3 h) to obtain a granulated slurry.

[0109] The granulation slurry was sprayed into an anti-solvent solution (formed by mixing 1 L of ethanol and 5 L of deionized water) by spray granulation to solidify and form particles. The anti-solvent solution was filtered to obtain adsorbent particles.

[0110] (3) Drying and activation

[0111] The adsorbent particles were placed in an oven at 45°C for drying for 24 hours, and then heated to 120°C for curing for 4 hours. The cured adsorbent particles were taken out and placed in hydrochloric acid (HCl concentration was 0.3 mol / L) for activation at 50°C for 12 hours to obtain a lithium-extracting adsorbent, which was recorded as LK-D2.

[0112] Comparative Example 3

[0113] (1) Preparation of adhesive liquid

[0114] Take 200g of PVC powder, add it to 1.0L of solvent DMAc, stir at 30°C (300rpm) until completely dissolved to obtain a transparent homogeneous slurry; then add 30g of CS powder, continue to stir evenly at 30°C, add 50g of SPSF powder, heat to 60°C and stir until completely dissolved to obtain a homogeneous slurry, continue to stir the slurry and cool to room temperature to obtain a binder liquid.

[0115] (2) Particle Forming

[0116] 450 g of adsorbent precursor powder Li2TiO3 was added to the binder liquid and stirred evenly with a vacuum machine (vacuum degree: -100 kPa, rotation speed: 60 rpm, stirring for 3 h) to obtain a granulated slurry.

[0117] The granulation slurry was sprayed into an anti-solvent solution (formed by mixing 1 L of ethanol and 5 L of deionized water) by spray granulation to solidify and form particles. The anti-solvent solution was filtered to obtain adsorbent particles.

[0118] (3) Drying and activation

[0119] The adsorbent particles were placed in an oven at 45°C for drying for 24 hours, and then heated to 120°C for curing for 4 hours. The cured adsorbent particles were taken out and placed in hydrochloric acid (HCl concentration was 0.3 mol / L) for activation at 50°C for 12 hours to obtain a lithium-extracting adsorbent, which was recorded as LK-D3.

[0120] Embodiments 2 to 4

[0121] The lithium extraction adsorbent was prepared according to the method of Example 1, except that the formula in the binder solution was adjusted as shown in Table 1, and the prepared lithium extraction adsorbents were recorded as LK-2, LK-3, and LK-4, respectively.

[0122] Table 1

[0123]

[0124] Test Case

[0125] The test examples are used to illustrate the service life and stability of the lithium extraction adsorbents LK-1 to LK-4 prepared in the examples and the lithium extraction adsorbents LK-D1 to LK-D3 prepared in the comparative examples, as well as a commercially available titanium-based lithium adsorbent (a spherical adsorbent made of a polymer binder and a precursor, suitable for pH ≥ 7, hereinafter referred to as "Commodity A").

[0126] Design an adsorbent service life experiment: Use simulated sodium sulfate subtype salt lake brine (brine pH is 9.5, including lithium ion concentration of 200 mg / L, sodium ion concentration of 14000 mg / L, magnesium ion concentration of 1000 mg / L, calcium ion concentration of 200 mg / L, chloride ion concentration of 11600 mg / L, sulfate concentration of 18000 mg / L, carbonate concentration of 1780 mg / L, and bicarbonate concentration of 1380 mg / L) to conduct a long-term single-column continuous adsorption and desorption test, with an adsorbent usage of 10 mL and a brine flow rate of 120 mL / h;

[0127] A complete adsorption-desorption cycle is 6h (the temperature of the adsorption section is 5°C, the adsorption is carried out for 4h, and the brine in the single column is washed out with water for 0.5h, and the water flow rate is 120mL / h; the temperature of the desorption section is 45°C, and the analysis is carried out with hydrochloric acid solution, the pH of the hydrochloric acid solution is 0.1, the flow rate is 180mL / h, and the desorption is repeated 3 times, with 60mL each time; after the acid desorption is completed, the adsorbent is washed with water to neutrality, the flow rate of the water washing acid is 90mL / h, and the time is 0.5h), and continuous monitoring is carried out for 75 days.

[0128] The desorption liquid was taken every day, and the ion concentration was tested by IPC and AA machine to obtain the lithium adsorption capacity, lithium-sodium ratio (Li / Na, representing the selectivity of the adsorbent to monovalent ions), and lithium-magnesium ratio (Li / Mg, representing the selectivity of the adsorbent to divalent ions). The sum of the test results of each round was divided by the number of tests to obtain the average value of each test result. The performance decay rate of the adsorbent was calculated as the percentage of the difference between the average value of the test data of each item in the last 50 times and the average value of the first 50 tests in the average value of the first 50 tests.

[0129] The test results are shown in Table 2.

[0130] Table 2

[0131]

[0132] From Table 2, it can be seen that the average lithium adsorption capacity and its attenuation rate of multiple rounds of adsorption tests of Examples 1 to 4 and Comparative Examples 1 to 3 and Product A show that the LK series adsorbent has no obvious capacity advantage over the commercial titanium-based adsorbent. However, from the perspective of the adsorption capacity attenuation rate, the LK series adsorbent has a relatively small attenuation range in the adsorption capacity of lithium after multiple rounds of continuous adsorption-desorption, especially in terms of ion selectivity; while the ion selectivity of Product A has significantly decayed.

[0133] Furthermore, compared with Comparative Examples 1 to 3, the combination of proton capture material + negatively charged material + phase change microcapsules in Examples 1 to 4 is used as an additive, which can effectively improve the service life of the lithium adsorbent and its stability under two different environmental conditions of adsorption and desorption while maintaining a higher adsorption capacity. Among them, the attenuation amplitudes of the Li adsorption amount and the lithium-sodium ratio are both no more than 6%, and the attenuation amplitude of the lithium-magnesium ratio is below 11%.

[0134] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and specification of the present invention. In particular, as long as there is no structural conflict, the various technical features mentioned in each embodiment can be combined in any way. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A method for preparing a lithium extraction adsorbent, characterized in that: include: The granulation slurry containing the adsorbent precursor and the binder liquid is subjected to particle forming, drying and activation; wherein, The binder liquid comprises a polymer binder, an additive and a solvent, wherein the additive comprises a first additive material, a second additive material and a third additive material, wherein the first additive material is a proton capture material, the second additive material is a negatively charged material, and the third additive material is a phase change microcapsule.

2. The preparation method according to claim 1, characterized in that: In the binder liquid, the mass content of the polymer binder is 5% to 30%, the mass content of the first additive material is 1% to 20%, the mass content of the second additive material is 0.1% to 10%, the mass content of the third additive material is 2% to 20%, and the mass content of the solvent is 50% to 85%; Preferably, in the binder liquid, the mass content of the polymer binder is 10% to 25%, the mass content of the first additive material is 2% to 10%, the mass content of the second additive material is 1% to 7%, the mass content of the third additive material is 3% to 15%, and the mass content of the solvent is 60% to 80%.

3. The preparation method according to claim 1 or 2, characterized in that: The polymer binder is selected from one or more of polyvinyl butyral, polyacrylonitrile, polysulfone, polyether sulfone, polyaryl sulfone, polyvinyl chloride, polyvinylidene fluoride, ethyl cellulose and ethylene-vinyl alcohol copolymer.

4. The preparation method according to any one of claims 1 to 3, characterized in that The first additive material is selected from one or more of polyethyleneimine, chitosan, polyamidoamine, polylysine, polydimethyldiallylammonium chloride, polydimethylaminoethyl methacrylate, polymethyl methacrylate-dimethylaminoethyl methacrylate copolymer, polyallylamine and polyaminopropyl biguanide.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The second additive material is selected from one or more of polyacrylic acid, polymaleic anhydride, sodium polystyrene sulfonate, sulfonated polyetheretherketone, carboxymethyl cellulose, sulfonated polysulfone, sodium polypropylene sulfonate, polyphosphate, chitosan sulfonate and polyfluorosulfonic acid.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The phase-change microcapsule comprises a polymer wall material and a core material encapsulated in the polymer wall material, wherein the core material is one or more of paraffin, capric acid, stearic acid, lauric acid, dodecanol, tetradecanol and hexadecanol, and the polymer wall material is one or more of polymethyl methacrylate, polyvinyl chloride, polyvinylidene chloride copolymer, polystyrene and polyvinyl acetate; Preferably, the phase change microcapsules are prepared by suspension polymerization, and include the following steps: dissolving a dispersant in an aqueous phase to obtain an aqueous phase; The core material, the polymerization monomer, the cross-linking agent and the oil-soluble initiator are uniformly mixed to obtain an oil phase; The water phase is heated to 40-90°C, and the oil phase is added dropwise to the water phase under continuous stirring to carry out polymerization reaction. After the addition is completed, stirring and reaction are continued for 2-6 hours to form a suspension containing phase change microcapsules; The suspension is centrifuged or filtered, and the obtained crude product is washed and dried to obtain phase change microcapsules; Preferably, the mass ratio of the core material, the crosslinking agent and the polymerized monomer is (0.8-2):(0.1-0.5):1, and the mass ratio of the oil-soluble initiator to the crosslinking agent is (5-15):100; Preferably, the mass ratio of the dispersant to water is 1:(100-500); Preferably, the mass amount of the dispersant accounts for 0.5% to 3% of the mass of the core material.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The adsorbent precursor is one or more of an aluminum salt adsorbent precursor, a titanium ion sieve adsorbent precursor, and a manganese ion sieve adsorbent precursor; Preferably, the aluminum salt adsorbent precursor is LiCl·2Al(OH)3·nH2O; Preferably, the manganese-based ion sieve adsorbent precursor is LiMn2O4, Li 1.33 Mn 1.67 O4、Li 1.6 Mn 1.6 One or more of O4; Preferably, the titanium-based ion sieve adsorbent precursor is selected from Li2TiO3 and / or Li4Ti5O 12 ; Preferably, the mass ratio of the adsorbent precursor to the binder liquid is (20-50):100; Preferably, the granulation slurry is prepared by mixing the adsorbent precursor with the binder liquid and then mechanically stirring the mixture under vacuum for 0.5 to 6 hours.

8. The preparation method according to any one of claims 1 to 7, characterized in that: The particle forming method includes spray granulation, and the spray granulation process includes: spraying the granulation slurry into an anti-solvent solution to form solid particles, and then removing the anti-solvent solution to obtain adsorbent particles; Preferably, the anti-solvent solution is a mixture of alcohol and water, and the volume ratio of alcohol to water is (1-5):10; Preferably, the drying comprises two stages carried out sequentially, The first stage: drying the adsorbent particles at 40-60° C. for 15-30 hours to obtain a dry product; The second stage: curing the dried product at 100-180° C. for 1-8 hours; Preferably, the activation is carried out in the presence of an activation solution, the activation temperature is 45 to 60° C., and the activation time is 10 to 24 hours.

9. A lithium extraction adsorbent prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the lithium extraction adsorbent according to claim 9 in extracting lithium from salt lake brine.

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