Lithium adsorbents, methods of making and using the same

Abstract

The application provides a lithium adsorbent and a preparation method and application thereof. The lithium adsorbent comprises a magnetic core and a porous shell layer coated on the surface of the magnetic core, and the porous shell layer comprises LiX*2Al(OH)3*nH2O, wherein X is an inorganic acid radical ion; the average sphericity of the lithium adsorbent is greater than or equal to 0.7. The lithium adsorbent has the advantages of high adsorption capacity and good stability, can efficiently extract lithium ions from a lithium-containing solution with low lithium concentration, and can be quickly separated from the solution by an external magnetic field, thereby being favorable for reducing the cost of lithium extraction by adsorption.

Description

Technical Field

[0001] This application relates to the field of lithium extraction technology, specifically to a lithium adsorbent, its preparation method, and its application. Background Technology

[0002] Lithium has important applications in electronics, metallurgy, chemical industry, and medicine. In nature, lithium is mainly found in lithium ores, salt lake brines, geothermal brines, and seawater. For liquid lithium resources (salt lake brines, geothermal brines, and seawater), the adsorbent method can be used to extract lithium. Aluminum-based lithium adsorbents extract lithium through the adsorption of lithium into lithium ore. + The memory effect and steric hindrance effect on larger metal ions enable selective adsorption of lithium, offering advantages in terms of economy and environmental friendliness. However, existing aluminum-based lithium adsorbents suffer from low adsorption capacity and poor cycle stability, hindering their industrial application. Therefore, it is necessary to provide a novel lithium adsorbent to improve the efficiency of lithium extraction by adsorption, reduce adsorbent loss, and achieve highly efficient lithium extraction. Summary of the Invention

[0003] In view of this, this application provides a lithium adsorbent with the advantages of high adsorption capacity and good stability, which can efficiently extract lithium ions from lithium-containing solutions with low lithium concentration. Furthermore, the adsorbent can be rapidly separated from the solution by an external magnetic field, which helps to reduce the cost of lithium extraction by adsorption.

[0004] The first aspect of this application provides a lithium adsorbent, comprising a magnetic core and a porous shell coating the surface of the magnetic core, wherein the porous shell comprises LiX·2Al(OH)3·nH2O, wherein X is an inorganic acid radical ion; and the average sphericity of the lithium adsorbent is greater than or equal to 0.7.

[0005] The lithium adsorbent of this application uses a magnetic material as its core, enabling the lithium adsorbent to be separated from lithium-containing solutions via magnetic separation, significantly reducing the cost of lithium extraction. The magnetic core is coated with a porous shell of LiCl·2Al(OH)3·nH2O. The porous shell structure facilitates the full adsorption of lithium ions in the solution, increasing the adsorption capacity of the adsorbent. Moreover, this lithium adsorbent has a high sphericity, which helps reduce wear during use and allows the adsorbent to better encapsulate the magnetic core, preventing its exposure and reducing the risk of separation between the magnetic core and the active components of the adsorbent, as well as the loss of magnetism from the magnetic core. This improves the cycle stability of the lithium adsorbent. Applying this lithium adsorbent to lithium extraction processes helps reduce production costs and achieve efficient lithium extraction, showing promising application prospects.

[0006] Optionally, the porosity of the lithium adsorbent is 10% to 35%.

[0007] Optionally, the average pore size of the porous shell structure is 1 nm to 10 nm.

[0008] Optionally, the specific surface area of ​​the lithium adsorbent is greater than or equal to 150 m². 2 / g.

[0009] Optionally, the magnetic core comprises one or more of elemental iron, elemental cobalt, elemental nickel, iron(II,III) oxide, or ferrates.

[0010] Optionally, the average particle size of the magnetic core is 50 nm to 50 μm.

[0011] Optionally, the mass ratio of the magnetic core to the aluminum hydroxide in the porous shell is 1:(0.5-20).

[0012] Optionally, the porous shell further includes an adhesive.

[0013] Optionally, the adhesive includes one or more of polyethylene, epoxy resin, phenolic resin, polycarbonate, polyvinyl acetal, polystyrene, polyvinylidene fluoride, or polyacrylate.

[0014] Optionally, the adhesive has a mass percentage content of 10% to 70% in the porous shell.

[0015] Optionally, the particle size ratio of the magnetic core to the lithium adsorbent is 1:(5-100).

[0016] Optionally, the average particle size of the lithium adsorbent is 2 μm to 2 mm.

[0017] Optionally, the average particle size of the lithium adsorbent is 2 μm to 800 μm.

[0018] Optionally, the average particle size of the lithium adsorbent is 10 μm to 100 μm.

[0019] Optionally, the lithium adsorbent has an adsorption capacity greater than or equal to 6 mg / g.

[0020] Optionally, the saturation magnetization of the lithium adsorbent is greater than or equal to 5 emu / g.

[0021] Secondly, this application provides a method for preparing a lithium adsorbent, comprising: depositing Al(OH)3 on the surface of a magnetic core to obtain a first precursor, mixing and reacting the first precursor with a lithium compound to obtain a second precursor, and preparing the second precursor into a suspension and then spray drying it to obtain a lithium adsorbent.

[0022] Optionally, the lithium compound includes one or more of lithium salts or lithium hydroxide.

[0023] Optionally, the solid content of the suspension is 0.1% to 75%.

[0024] Optionally, the solid content of the suspension is less than or equal to 30%.

[0025] Optionally, the solid content of the suspension is 1% to 30%.

[0026] Optionally, the solid content of the suspension is 10% to 20%.

[0027] Optionally, the spray drying temperature is 105℃~350℃.

[0028] Optionally, the spray drying temperature is 130℃~250℃.

[0029] Optionally, the fan speed of the spray dryer is 20% to 80%, and the needle-passing time of the spray dryer is 15s to 60s.

[0030] Optionally, the deposition of Al(OH)3 on the surface of the magnetic core includes: adding the magnetic core to an aluminum salt or aluminate solution to obtain a magnetic core suspension, and adding an alkaline compound to the magnetic core suspension to form an Al(OH)3 colloid coating the surface of the magnetic core; the alkaline compound includes one or more of ammonia, sodium hydroxide, potassium hydroxide, sodium bicarbonate, and potassium bicarbonate.

[0031] Optionally, the step of preparing the second precursor into a suspension and then spray-drying it to obtain the lithium adsorbent includes:

[0032] The second precursor is made into a suspension, and the third precursor is obtained by spray drying. The third precursor is mixed with water at a volume ratio of 1:(5-100), and then dried to obtain a lithium adsorbent.

[0033] Optionally, the mixing temperature is 30℃~50℃; the mixing speed is 100rpm / min~500rpm / min; and the mixing time is 2h~6h.

[0034] Thirdly, this application provides a method for extracting lithium, comprising: immersing a lithium adsorbent as described in the first aspect or a lithium adsorbent prepared by the preparation method described in the second aspect into a lithium-containing solution, wherein at least a portion of the lithium ions in the lithium-containing solution are adsorbed by the lithium adsorbent; and separating the lithium adsorbent from the mixed system to achieve lithium extraction. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the structure of a lithium adsorbent provided in one embodiment of this application;

[0036] Figure 2A flowchart illustrating the preparation process of a lithium adsorbent provided in an embodiment of this application;

[0037] Figure 3 A flowchart illustrating the preparation process of a lithium adsorbent provided in an embodiment of this application;

[0038] Figure 4 A schematic diagram illustrating particle sphericity according to an embodiment of this application;

[0039] Figure 5 This is a morphological characterization diagram of the lithium adsorbent in Example 1;

[0040] Figure 6 This is a morphological characterization diagram of the lithium adsorbent in Example 1;

[0041] Figure 7 This is an elemental distribution diagram of the lithium adsorbent in Example 1;

[0042] Figure 8 The image shows the morphology of the lithium adsorbent in Comparative Example 1.

[0043] Figure 9 This is an elemental distribution diagram of the lithium adsorbent in Comparative Example 1. Detailed Implementation

[0044] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0045] This application provides a lithium adsorbent that not only has a high adsorption capacity for lithium and good cycle stability, but also low loss during long-term use. Furthermore, the lithium adsorbent has low manufacturing cost, environmentally friendly preparation method, and simple process, and has good application prospects.

[0046] Please see Figure 1 , Figure 1This is a schematic diagram of the structure of a lithium adsorbent provided in one embodiment of this application. The lithium adsorbent includes a magnetic core 10 and a porous shell 20 covering the surface of the magnetic core 10. The porous shell can protect the magnetic core and inhibit oxidation that leads to a decrease in magnetism. Furthermore, the pore structure in the porous shell can significantly increase the specific surface area of ​​the magnetic core, thereby improving the adsorption capacity of the lithium adsorbent for lithium ions. In this application, the chemical structural formula of the lithium adsorbent can be represented as: magnetic core@LiX·2Al(OH)3·nH2O, where X is an inorganic acid radical ion, including one or more of chloride, sulfate, nitrate, or carbonate ions. The type of X is related to the aluminum source used in the preparation process. For example, if Al(OH)3 is prepared using aluminum chloride (AlCl3) as a raw material, then X is Cl... - If we use the aluminum salt lithium sulfate (Al2(SO4)3), then X corresponds to SO4. 2- .

[0047] In this embodiment, the sphericity of the lithium adsorbent is greater than or equal to 0.7. Specifically, the sphericity of the lithium adsorbent can be, but is not limited to, 0.7, 0.75, 0.8, 0.85, 0.9, or 0.95. The lithium adsorbent of this application has a high sphericity, which reduces wear during use and extends its service life. Furthermore, the spherical structure of the adsorbent has a higher volumetric capacity compared to easily stacked blocky adsorbents, thus improving the adsorption capacity.

[0048] In some embodiments of this application, the average pore size of the lithium adsorbent is 1 nm to 10 nm. The average pore size refers to the average pore size of the surface channel structure of the lithium adsorbent, i.e., the average pore size of the channels on the outer surface of the porous shell. This average pore size can be measured by the BET surface area adsorption method. Specifically, the average pore size of the lithium adsorbent can be, but is not limited to, 1 nm, 3 nm, 5 nm, 8 nm, or 10 nm. At this pore size, the lithium-containing solution can easily and fully penetrate the pore structure of the lithium adsorbent, which is beneficial to improving the adsorption capacity and adsorption rate of the adsorbent. In some embodiments of this application, the porosity of the lithium adsorbent is 10% to 35%. Specifically, the porosity of the lithium adsorbent can be, but is not limited to, 10%, 15%, 20%, 25%, 30%, or 35%. Controlling the porosity of the lithium adsorbent within the above range ensures that the lithium adsorbent has a high adsorption capacity, and the porous shell can fully cover the magnetic core, achieving effective protection of the magnetic core.

[0049] In some embodiments of this application, the specific surface area of ​​the lithium adsorbent is greater than or equal to 150 m². 2 / g, the specific surface area of ​​the lithium adsorbent can be, but is not limited to, 150m². 2 / g, 160m 2 / g、170m 2 / g、180m 2 / g、190m 2 / g、200m 2 / g、230m 2 / g etc. The lithium adsorbent of this application has a high specific surface area, which is beneficial to the full contact between the lithium adsorbent and the solution, thereby improving the adsorption / desorption efficiency of lithium ions.

[0050] In some embodiments of this application, the magnetic core comprises one or more of elemental iron, elemental cobalt, elemental nickel, iron(II,III) oxide, or ferrates, and the average particle size of the magnetic core is 50 nm to 50 μm. These substances possess good magnetic properties. When the size of the magnetic core is controlled within the range of 50 nm to 50 μm, the lithium adsorbent can exhibit high saturation magnetization, which is beneficial for the rapid separation of the lithium adsorbent from the solution using a magnetic field. Furthermore, the specific surface area of ​​the magnetic core is relatively moderate, which is conducive to the uniform coating of the porous shell onto the surface of the magnetic core.

[0051] In some embodiments of this application, the mass ratio of the magnetic core to the aluminum hydroxide in the porous shell is 1:(0.5-20). Specifically, but not limited to, the mass ratio of the magnetic core to the aluminum hydroxide in the porous shell can be 1:0.5, 1:1, 1:2, 1:5, 1:10, 1:15, or 1:20. Controlling the mass ratio of the magnetic core to the aluminum hydroxide in the porous shell ensures that the lithium adsorbent possesses both high magnetism and adsorption capacity. In some embodiments, the mass ratio of the magnetic core to the aluminum hydroxide in the porous shell is 1:(2-10). In some embodiments of this application, the particle size ratio of the magnetic core to the lithium adsorbent is 1:(5-100). Specifically, but not limited to, the particle size ratio of the magnetic core to the lithium adsorbent can be 1:5, 1:8, 1:10, 1:15, 1:20, 1:30, 1:50, 1:80, or 1:100. When the particle size ratio of the magnetic core to the lithium adsorbent is controlled at 1:(5~100), the porous shell can fully coat the magnetic core. On the one hand, this is beneficial to improving the structural stability of lithium adsorption and inhibiting the shedding of the magnetic core. On the other hand, it can inhibit the oxidation of the magnetic core and ensure that the magnetic core still has high magnetism under long-term use.

[0052] In some embodiments of this application, the porous shell further includes a binder. The binder not only enhances the structural stability of lithium adsorption but also adjusts the size and morphology of the lithium adsorbent, promoting the formation of a spherical adsorbent structure. Larger particle sizes of the adsorbent help reduce the osmotic pressure of the separation column and accelerate the solid-liquid separation rate. In some embodiments, the binder includes a hydrophilic polymer. The hydrophilic polymer can enhance the hydrophilicity of the adsorbent surface, which helps reduce the non-specific adsorption of organic matter in the solution during lithium extraction, inhibits the clogging of the adsorbent channels, and extends the adsorbent's lifespan. In some embodiments of this application, the binder includes one or more of polyethylene, epoxy resin, phenolic resin, polycarbonate, polyvinyl acetal, polystyrene, polyvinylidene fluoride, or polyacrylate. In some embodiments of this application, the mass percentage of the binder is 10% to 70%, and the specific mass percentage of the binder can be, but is not limited to, 10%, 20%, 30%, 50%, or 70%. When the binder content is controlled within the above range, the lithium adsorbent can possess both high adsorption capacity and cycle stability. In some embodiments, the lithium adsorbent containing the binder has a particle size of 800 μm to 2 mm.

[0053] In some embodiments of this application, the average particle size of the lithium adsorbent is 2 μm to 2 mm. Specifically, but not limited to, the average particle size of the lithium adsorbent can be 2 μm, 5 μm, 10 μm, 30 μm, 50 μm, 100 μm, 300 μm, 500 μm, 800 μm, 1 mm, 1.5 mm, or 2 mm. Lithium adsorbents within this particle size range are less prone to loss during application, require moderate osmotic pressure for the separation column, and exhibit high adsorption efficiency. In some embodiments, the average particle size of the lithium adsorbent is 2 μm to 800 μm. In some embodiments of this application, the saturation magnetization of the lithium adsorbent is greater than or equal to 5 emu / g, and specifically, but not limited to, 5 emu / g, 8 emu / g, 10 emu / g, 12 emu / g, 15 emu / g, 18 emu / g, or 20 emu / g. In some embodiments of this application, the adsorption capacity of the lithium adsorbent is greater than or equal to 6 mg / g. The specific adsorption capacity of the lithium adsorbent may be, but is not limited to, 6 mg / g, 8 mg / g, 10 mg / g, 12 mg / g or 15 mg / g.

[0054] The lithium adsorbent provided in this application has a high adsorption capacity and good structural stability, making it less prone to breakage. The adsorbent has a low consumption rate, which helps to accelerate the lithium extraction process and reduce production costs when applied to it, thus showing good application prospects.

[0055] This application also provides a method for preparing the above-mentioned lithium adsorbent; please refer to [link / reference needed]. Figure 2 , Figure 2This is a flowchart illustrating the preparation process of a lithium adsorbent according to an embodiment of this application. The method for preparing the lithium adsorbent includes:

[0056] Step 100: Deposit Al(OH)3 on the surface of the magnetic core to obtain the first precursor;

[0057] Step 200: The first precursor is mixed with a lithium compound and reacted to obtain the second precursor;

[0058] Step 300: The second precursor is made into a suspension and then spray-dried to obtain a lithium adsorbent.

[0059] In step 100 of this application, the magnetic core includes one or more of elemental iron, elemental cobalt, elemental nickel, iron(II,III) oxide, or ferrates. The average particle size of the magnetic core is 50 nm to 50 μm. Magnetic cores with particle sizes above this range are well dispersed and do not easily agglomerate. Furthermore, the magnetic core has a high specific surface area and can carry a large amount of Al(OH)3. In some embodiments of this application, depositing Al(OH)3 on the surface of the magnetic core includes: adding the magnetic core to an aluminum source solution to obtain a magnetic core suspension, and then adding an alkaline compound to the magnetic core suspension to form an Al(OH)3 colloid. The Al(OH)3 colloid coats the surface of the magnetic core to form a coating layer. The aluminum source solution includes an aqueous solution of aluminum salt or aluminate. The aluminum salt includes one or more of aluminum sulfate, aluminum chloride, and aluminum nitrate. The aluminate includes sodium aluminate. The alkaline compound includes one or more of ammonia, sodium hydroxide, potassium hydroxide, sodium bicarbonate, and potassium bicarbonate.

[0060] In some embodiments, step 100 includes:

[0061] (1) Preparation of aluminum source solution: Dissolve aluminum source in water. The concentration range of aluminum source solution is 0.1 mol / L to 1 mol / L, and the dissolution temperature is 20℃ to 80℃.

[0062] (2) Preparation of alkaline solution: Dissolve the alkaline compound in water. The concentration range of the alkaline solution is 0.1 mol / L to 3 mol / L, and the dissolution temperature is 20℃ to 80℃.

[0063] (3) Preparation of magnetic core @Al(OH)3 colloid: The magnetic core is added to the aluminum source solution and stirred for 5 min to 30 min to ensure that the magnetic core is fully dispersed; an alkaline solution is added dropwise to the aluminum source solution containing the magnetic core during stirring at a stirring rate of 500 rpm / min to 1300 rpm / min, and the reaction time is 0.5 h to 4 h. As the alkaline solution is added, the reaction solution gradually becomes a colloidal state. The magnetic core is uniformly dispersed and coated during the formation of aluminum hydroxide colloid, forming a magnetic core @Al(OH)3 colloidal suspension. In some embodiments of this application, the particle size ratio of the magnetic core to the magnetic core @Al(OH)3 is 1:(3 to 50).

[0064] In some embodiments of this application, the alkaline compound includes one or more of sodium hydroxide, potassium hydroxide, sodium bicarbonate, and potassium bicarbonate. The alkaline compound reacts with the aluminum source to form corresponding salts. For example, sodium hydroxide reacts with aluminum chloride to produce sodium chloride, and potassium hydroxide reacts with aluminum nitrate to produce potassium nitrate. The resulting salts have good water solubility. Therefore, in the preparation of the adsorbent, the reaction products of the alkaline compound and the aluminum source can be used as pore-forming agents. By washing the adsorbent with water, the pore structure of the adsorbent can be enriched, giving the adsorbent a larger pore volume and specific surface area, thereby improving the adsorption capacity of the adsorbent.

[0065] In step 200 of this application, a first precursor is mixed with a lithium compound to obtain a second precursor. The lithium compound includes one or more lithium salts or lithium hydroxide. When the reactant is lithium hydroxide, a magnetic core @LiOH·2Al(OH)3·nH2O is prepared. A certain amount of acid HX (X is an inorganic acid radical ion) is then added to convert LiOH into the lithium salt LiX, resulting in the second precursor magnetic core @LiX·2Al(OH)3·nH2O. In step 200, lithium hydroxide or lithium salts can enter the aluminum hydroxide lattice. Before the adsorbent is used, it is washed out, leaving a lithium salt entry / exit channel within the aluminum hydroxide lattice. Placing it in a lithium-containing solution allows for lithium extraction. In some embodiments of this application, the reaction of the first precursor with lithium salt or lithium hydroxide includes: dispersing the first precursor (magnetic core@Al(OH)3 colloid) in water, adding lithium salt or lithium hydroxide to the first precursor dispersion at a Li:Al molar ratio of 1:(0.5-2), reacting at a temperature of 20°C to 90°C, stirring at a rate of 300 rpm / min to 500 rpm / min, and mixing for 1 h to 4 h. The lithium salt includes one or more of lithium chloride, lithium sulfate, lithium nitrate, and lithium acetate. In some embodiments, the molar ratio of lithium salt or lithium hydroxide to aluminum hydroxide is (0.8-2):1, and the reaction temperature is 60°C to 80°C. In some embodiments, the first precursor is reacted with lithium salt or lithium hydroxide and then aged for 8 h to 24 h. Aging the mixture facilitates a complete reaction of the reactants, allowing the lithium compounds to fully enter the aluminum hydroxide lattice, thereby better forming a LiX·2Al(OH)3·nH2O layer on the surface of the magnetic core.

[0066] In step 300 of this application, the second precursor is made into a suspension and then spray-dried to obtain a lithium adsorbent. The spray-drying method ensures good structural stability of the adsorbent. Specifically, when the second precursor is in the suspension, the LiX·2Al(OH)3·nH2O colloid uniformly coats the surface of the magnetic core. The suspension is sprayed into a mist and instantly dried at high temperature to obtain a powder. The LiX·2Al(OH)3·nH2O colloid dries instantly, and the magnetic core in the adsorbent remains uniformly coated, preserving its magnetic properties. This effectively maintains the core-shell structure of the adsorbent, greatly improving its structural stability, inhibiting the separation of the magnetic core and shell during use, and enhancing the cycle stability of the adsorbent.

[0067] In some embodiments of this application, the preparation of the second precursor suspension may involve: filtering the aged reaction liquid obtained in step 200 and dispersing it in a certain amount of water, with the solid content of the resulting suspension ranging from 0.1% to 75%. Specifically, the solid content of the suspension may be, but is not limited to, 0.1%, 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 50%, 60%, or 70%. In some embodiments of this application, the solid content of the suspension is 1% to 30%. In some embodiments, the solid content of the suspension is 10% to 20%. When the solid content of the suspension is too low, the preparation process is energy-intensive and time-consuming; when the solid content of the suspension is too high, the particle size distribution of the obtained material is uneven, the structure is affected, and the sphericity is poor.

[0068] In some embodiments of this application, the spray drying temperature is 105℃ to 350℃. The specific spray drying temperature can be, but is not limited to, 105℃, 110℃, 120℃, 130℃, 150℃, 180℃, 200℃, 230℃, 250℃, 270℃, 300℃, or 350℃. In some embodiments, the spray drying temperature is 130℃ to 250℃. At this temperature, the particles in the suspension can be fully dried and have good particle dispersion. More importantly, the colloidal state of Al(OH)3 can be well maintained during the drying process, ensuring that the Al(OH)3 in the adsorbent can fully coat the magnetic core. In some embodiments of this application, the second precursor suspension is fed into the spray dryer via a peristaltic pump (adjusting the pump speed to 10% to 70%). The spray drying temperature is 130℃ to 250℃, the fan speed is 20% to 80%, and the needle passage time is 15s to 60s, resulting in dried powder in the sample receiving chamber.

[0069] In some embodiments of this application, the suspension is spray-dried to obtain a third precursor. The third precursor is then mixed with water at a volume ratio of 1:(5-100), and dried to obtain a lithium adsorbent. The volume ratio of the third precursor to water can be, but is not limited to, 1:5, 1:20, 1:50, 1:80, or 1:100. During the mixing process, lithium in the third precursor is eluted, generating lithium vacancies, thus enabling the product to adsorb lithium. In addition, when the alkaline compound used includes one or more of sodium hydroxide, potassium hydroxide, sodium bicarbonate, and potassium bicarbonate, the resulting salt product (pore-forming agent) also dissolves in water, giving the adsorbent a multi-layered pore structure, thereby increasing the specific surface area of ​​the adsorbent. Stirring and mixing can fully dissolve lithium ions and pore-forming agents in the precursor. In some embodiments, the stirring rate is 100 rpm / min to 500 rpm / min, the stirring temperature is 30°C to 50°C, and the stirring time is 2 h to 6 h. The stirring rate can be, but is not limited to, 100 rpm / min, 200 rpm / min, 300 rpm / min, or 500 rpm / min. In some embodiments of this application, after pre-desorption of the third precursor, it is filtered, and the filtrate is dried at 50°C to 100°C for 1 h to 3 h to obtain the lithium adsorbent.

[0070] Please see Figure 3 , Figure 3 This is a flowchart illustrating the preparation process of a lithium adsorbent according to an embodiment of this application. The application describes the preparation of a magnetic colloidal aluminum-based adsorbent using a colloid synthesis method. During the generation of aluminum hydroxide colloid, the magnetic core is uniformly dispersed in the Al(OH)3 colloidal medium. The Al(OH)3 colloid uniformly coats the magnetic core. A certain amount of lithium salt solution is then added to react with the aluminum hydroxide colloid, resulting in a colloidal core-shell structured magnetic core @LiX·2Al(OH)3·nH2O suspension. This suspension is then spray-dried to obtain the magnetic core @LiX·2Al(OH)3·nH2O magnetic adsorbent. The adsorbent prepared by this method exhibits uniform coating of the magnetic core, preserving its characteristics and maintaining the core-shell structure effectively. This significantly improves the structural stability of the adsorbent and inhibits the separation of the magnetic core from the adsorbent during use.

[0071] This application also provides a method for extracting lithium, comprising: immersing a lithium adsorbent in a lithium-containing solution, and then separating the lithium adsorbent from the mixed system to achieve lithium extraction. The lithium-containing solution can be brine or seawater. In this application, because the lithium adsorbent possesses a certain degree of magnetism, an external magnetic field can be used to separate the lithium adsorbent from the mixed system, i.e., magnetic separation is used to efficiently separate the adsorbent from the brine or seawater. This method helps reduce production costs, and the lithium adsorbent exhibits good cycle performance, low solubility after long-term use, and still retains high adsorption activity, resulting in a long service life.

[0072] The technical solution of this application will be further described below with reference to several embodiments.

[0073] Example 1

[0074] A method for preparing a lithium adsorbent, comprising:

[0075] Weigh 10.08 g of NaHCO3 and 9.6572 g of AlCl3·6H2O and dissolve them in 200 mL of deionized water. Then, add 1.248 g of Fe3O4 magnetic nuclei with an average particle size of 100 nm to the AlCl3·6H2O solution and stir vigorously for 30 minutes. Add the NaHCO3 solution dropwise to the above AlCl3·6H2O solution containing Fe3O4. React in a water bath at 80 °C at 600 rpm / min for 4 hours to generate a gel-like substance. Add the gel-like substance to 200 mL of a solution containing 1.208 g of LiCl·H2O and react at 25 °C at 600 rpm / min for 2 hours. Then, age for 12 hours. After filtration, wash several times with deionized water and add 100 mL of deionized water to obtain a suspension with a solid content of 15%. The adsorbent precursor was obtained by spray drying at 180℃. The adsorbent precursor was then mixed with water at a volume ratio of 1:5 at 40℃ for 2 hours at a stirring rate of 500 rpm / min. After filtration, the filtrate was dried at 80℃ for 2 hours to obtain a core-shell structured Fe3O4@LiCl·2Al(OH)3·nH2O magnetic aluminum-based lithium adsorbent.

[0076] Example 2

[0077] The difference between Example 2 and Example 1 is that the temperature during spray drying of the suspension is 300°C, and the adsorbent precursor obtained after spray drying is stirred, washed and dried using the same method as in Example 1 to obtain a core-shell structured Fe3O4@LiCl·2Al(OH)3·nH2O magnetic aluminum-based lithium adsorbent.

[0078] Example 3

[0079] The difference between Example 3 and Example 1 is that the temperature during spray drying of the suspension is 110°C, and the adsorbent precursor obtained after spray drying is stirred, washed and dried using the same method as in Example 1 to obtain a core-shell structured Fe3O4@LiCl·2Al(OH)3·nH2O magnetic aluminum-based lithium adsorbent.

[0080] Example 4

[0081] The difference between Example 4 and Example 1 is that the gelatinous substance was reacted with a lithium salt solution and aged for 12 hours, washed several times with deionized water, and then 20 mL of deionized water was added to obtain a suspension with a solid content of 60%. The suspension was spray-dried and post-treated in the same way as in Example 1 to obtain a core-shell structured Fe3O4@LiCl·2Al(OH)3·nH2O magnetic aluminum-based lithium adsorbent.

[0082] Example 5

[0083] A method for preparing a lithium adsorbent, comprising:

[0084] Prepare 100 mL of AlCl3·6H2O solution with a molar concentration of 0.2 mol / L. Add 1.248 g of Fe3O4 magnetic cores with an average particle size of 50 μm. Stir at 25 °C for 30 minutes. Add 12% ammonia solution to adjust the pH of the solution to 6-7, at which point colloids are formed. React in a water bath at 80 °C at 600 rpm / min for 4 hours. Weigh 1.208 g of LiCl·H2O and dissolve it in 120 mL of deionized water. Add the obtained Fe3O4@Al(OH)3 to the solution and react at 600 rpm / min at room temperature for 2 hours. Aging for 12 hours, wash several times with deionized water, and then add 100 mL of deionized water to obtain a suspension with a solid content of 15%. The adsorbent precursor was obtained by spray drying at 180℃. The adsorbent precursor was then mixed with water at a volume ratio of 1:5 at 40℃ for 2 hours at a stirring rate of 500 rpm / min. After filtration, the filtrate was dried at 80℃ for 2 hours to obtain a core-shell structured Fe3O4@LiCl·2Al(OH)3·nH2O magnetic aluminum-based lithium adsorbent.

[0085] To highlight the beneficial effects of this application, the following comparative examples are provided.

[0086] Comparative Example 1

[0087] The difference between Comparative Example 1 and Example 1 is that after reacting the gelatinous substance with the lithium salt solution and aging it for 12 hours, it was washed several times with deionized water and the magnetic adsorbent was obtained by centrifugation (7000 rpm / min, centrifugation time set to 5 minutes). The magnetic adsorbent and water were added to deionized water at a volume ratio of 1:5 for pretreatment. The mixing temperature was 40°C, the mixing time was 2 hours, and the stirring rate was 500 rpm / min. After filtration, the filtrate was dried in an oven at 80°C for 2 hours to obtain Fe3O4@LiCl·2Al(OH)3·nH2O magnetic aluminum-based lithium adsorbent.

[0088] Effect Example

[0089] To strongly support the beneficial effects of the technical solutions in the embodiments of this application, the following tests are provided:

[0090] 1) The morphology of the lithium adsorbents prepared in Examples 1-5 and Comparative Example 1 was characterized using scanning electron microscopy and energy dispersive spectroscopy. Specifically, the particle size and sphericity of the adsorbents were directly obtained from the scale bars of the images. Sphericity was obtained by the ratio of the width to the length of the particles, which can be considered as ellipsoidal. Please refer to [link to relevant documentation]. Figure 4 , Figure 4 This is a schematic diagram of particle sphericity provided in an embodiment of this application. The particle width refers to the particle's dimension along its minor axis (the direction with the smallest particle diameter), and the particle length refers to the particle's dimension along its major axis (the direction with the largest particle diameter). The sphericity of the adsorbent is the average ratio of the width to the length of each adsorbent particle. Please refer to... Figure 5 , Figure 5 This is a morphological characterization diagram of the lithium adsorbent in Example 1, from... Figure 5 It can be seen that the average particle size of the lithium adsorbent is approximately 5.78 μm, and the average sphericity is 0.88. Based on the average particle size of the magnetic core material being 100 nm, the calculated shell thickness in the adsorbent is 2.84 μm. Please refer to [link / reference]. Figure 6 and Figure 7 , Figure 6 This is a morphological characterization diagram of the lithium adsorbent in Example 1. Figure 7 This is the elemental distribution diagram of the lithium adsorbent in Example 1, from... Figure 6 and Figure 7 It can be seen that the surface of the lithium adsorbent is uniformly coated with Al(OH)3. (See also...) Figure 8 and Figure 9 , Figure 8 This is a morphological characterization diagram of the lithium adsorbent in Comparative Example 1. Figure 9 The elemental distribution diagram of the lithium adsorbent in Comparative Example 1 is shown below. Figure 8 and Figure 9It can be seen that the lithium adsorbent in Comparative Example 1 has a sheet-like structure, and some magnetic cores are exposed on the surface of the lithium adsorbent. The lithium adsorbent with this structure has poor stability, and the magnetic cores are prone to separating from the adsorbent during long-term use, causing the adsorbent to lose its magnetism. The structural parameters of the adsorbents in Examples 2-5 and Comparative Example 1 were measured using the same method and are summarized in Table 1.

[0091] Table 1. Structural parameters of the adsorbents in each embodiment and comparative example.

[0092]

[0093] Depend on Figure 5 As can be seen from Table 1, the adsorbents prepared by spray drying in the embodiments of this application have high sphericity and good uniformity. In Example 3, the spray drying temperature was low, resulting in poor drying effect and shell deformation, leading to low sphericity. In Example 4, the high solid content of the suspension resulted in poor drying effect and low sphericity of the obtained adsorbent. The lithium adsorbent in Comparative Example 1, because the filtrate after the reaction was dried in an oven, had even worse particle uniformity than the adsorbent obtained by spray drying in the embodiments of this application, with smaller sphericity and larger particle size.

[0094] 2) The specific surface area, pore volume and pore size of the lithium adsorbent in each example and comparative example were tested using the gas adsorption method (BET method). The test standard was ISO-9277 / GB / T19587-2017. The test results are shown in Table 2.

[0095] Table 2. Structural parameters of the adsorbents in each embodiment and comparative example.

[0096] experimental group <![CDATA[Specific surface area (m 2 / g)]]> Total pore volume (ml / g) Average pore diameter (nm) Example 1 193.8315 0.2132 6.2185 Example 2 184.3256 0.2013 5.9432 Example 3 196.7237 0.2145 6.7393 Example 4 136.7865 0.1323 3.8941 Example 5 142.7926 0.1489 3.9778 Comparative Example 1 120.9935 0.1187 3.7908

[0097] As shown in Table 2, the lithium adsorbent prepared by spray drying in this application embodiment has a higher specific surface area, pore volume, and pore size ratio than the adsorbent obtained by centrifugal sedimentation in Comparative Example 1. For each embodiment, Example 1 uses NaHCO3 as the raw material for adsorbent preparation, and Example 5 uses ammonia as the raw material. The lithium adsorbent obtained in Example 1 has a higher specific surface area, pore volume, and pore size ratio than the adsorbent in Example 5. This is because the NaCl generated from NaHCO3 and AlCl3 in Example 1 acts as a pore-forming agent. During the water washing process after spray drying, the NaCl in the adsorbent dissolves, creating pores and increasing the specific surface area. This structure also makes it easier to increase the contact area with the brine and improve the adsorption capacity. In Example 4, the suspension has a high solid content, resulting in poor dispersion and drying during spray drying. The magnetic adsorbent material does not spherize well and tends to agglomerate, leading to a smaller specific surface area and pore size.

[0098] 3) The adsorption performance of the lithium adsorbents in each embodiment and comparative example was tested. The test conditions were as follows: a certain amount of lithium-containing brine was taken for adsorption and desorption testing, and the Li in the brine was... + The mass concentration is 0.0209%, Mg 2+ The mass concentration was 8.2860%. 2.00 g of adsorbent was weighed and adsorbed with brine at a ratio of 1:50 at room temperature. The stirring rate was 500 rpm, and the adsorption time was 90 min. After adsorption, the adsorbent and solution were separated by magnetic separation to obtain the adsorbed liquid. Deionized water was added to the adsorbent at a ratio of 1:50 for desorption. The reaction temperature was controlled at 40℃, the stirring speed at 500 rpm, and the desorption time at 120 min. The desorbed filtrate was obtained by magnetic separation. Twenty cycles were continuously tested, and the adsorbent was dried and weighed after 20 cycles. The content of each ion in the adsorbed liquid and desorbed filtrate was measured by ICP to calculate the adsorption capacity and desorption capacity. The mass of the adsorbent after 20 cycles was also measured. The experimental results are shown in Tables 3 and 4.

[0099] Table 3. Adsorption performance of lithium adsorbents in each embodiment and comparative example.

[0100]

[0101] Table 4. Adsorption performance of lithium adsorbents in each example and comparative example.

[0102]

[0103] As can be seen from Tables 3 and 4, the lithium adsorbent obtained by spray drying in this embodiment has a higher adsorption capacity and faster lithium ion desorption efficiency compared to the adsorbent obtained by centrifugal sedimentation in Comparative Example 1. Furthermore, the lithium adsorbent retains its adsorption activity better after cycling, and its loss is less. This indicates that spray drying can effectively protect the core-shell structure of the adsorbent, thereby reducing its loss during use. In Example 2, the spray drying temperature was higher, and in Example 5, the solid content of the suspension was higher. During the spray drying process, the shell layer underwent some deformation, resulting in reduced uniformity of the coating layer and poorer adsorption capacity and stability compared to Example 1. In Example 3, the spray drying temperature was lower, the material had excessive moisture content, and the particles were not thoroughly dried, resulting in slightly lower sphericity of the adsorbent and poorer adsorption capacity and stability compared to Example 1.

[0104] 4) The saturation magnetization of the lithium adsorbent after 20 cycles was tested using a VSM (vibrating sample magnetometer). The experimental results of each example and comparative example are shown in Table 5.

[0105] Table 5. Specific saturation magnetization of lithium adsorbents after 20 adsorption cycles in each embodiment and comparative example.

[0106] experimental group Specific saturation magnetization (emu / g) Example 1 15.0 Example 2 14.7 Example 3 12.8 Example 4 13.2 Example 5 14.1 Comparative Example 1 12.5

[0107] As can be seen from Table 5, after the lithium adsorbents of each embodiment and the comparative example were cycled 20 times under the same conditions, the lithium adsorbent in the embodiments of this application had a higher specific saturation magnetization than the adsorbent in the comparative example. Since the magnetic cores of each embodiment and the comparative example were prepared using the same structure, it can be shown that the lithium adsorbent prepared by the method of this application has good stability and less loss of magnetic cores after multiple cycles.

[0108] The above description represents the preferred embodiments of this application, but should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this application, and these improvements and modifications are also considered to be within the scope of protection of this application.

Claims

1. A lithium adsorbent, characterized in that, The adsorbent comprises a magnetic core and a porous shell coating the surface of the magnetic core, wherein the porous shell comprises LiX·2Al(OH)3·nH2O, and X is an inorganic acid radical ion; the lithium adsorbent has an average sphericity greater than or equal to 0.7 and a specific surface area greater than or equal to 150 m². 2 / g, with an average pore size of 5nm-10nm; the ratio of the particle size of the magnetic core to that of the lithium adsorbent is 1:(50~100).

2. The lithium adsorbent as described in claim 1, characterized in that, The porosity of the lithium adsorbent is 10%~35%.

3. The lithium adsorbent as described in claim 1 or 2, characterized in that, The porous shell also includes an adhesive.

4. The lithium adsorbent as described in claim 1 or 2, characterized in that, The average particle size of the lithium adsorbent is 2 µm to 2 mm.

5. The lithium adsorbent as described in claim 1 or 2, characterized in that, The lithium adsorbent has an adsorption capacity greater than or equal to 6 mg / g; the lithium adsorbent has a specific saturation magnetization greater than or equal to 5 emu / g.

6. A method for preparing the lithium adsorbent as described in claim 1, characterized in that, include: A first precursor is obtained by depositing Al(OH)3 on the surface of a magnetic core. The first precursor is then mixed with a lithium compound to obtain a second precursor. The second precursor is then made into a suspension and spray-dried to obtain a lithium adsorbent.

7. The preparation method according to claim 6, characterized in that, The solid content of the suspension is less than or equal to 30%.

8. The preparation method according to claim 6 or 7, characterized in that, The spray drying temperature is 130℃~250℃.

9. The preparation method according to claim 6 or 7, characterized in that, The deposition of Al(OH)3 on the surface of the magnetic core includes: adding the magnetic core to an aluminum salt or aluminate solution to obtain a magnetic core suspension, and adding an alkaline compound to the magnetic core suspension to form an Al(OH)3 colloid coating the surface of the magnetic core; the alkaline compound includes one or more of ammonia, sodium hydroxide, potassium hydroxide, sodium bicarbonate and potassium bicarbonate.

10. The preparation method according to claim 6 or 7, characterized in that, The process of preparing the second precursor into a suspension and then spray-drying it to obtain the lithium adsorbent includes: The second precursor is made into a suspension, and the third precursor is obtained by spray drying. The third precursor is mixed with water at a volume ratio of 1: (5~100), and then dried to obtain a lithium adsorbent.

11. A method for extracting lithium, characterized in that, include: The lithium adsorbent prepared by the lithium adsorbent preparation method according to any one of claims 1-5 or any one of claims 6-10 is immersed in a lithium-containing solution, wherein at least a portion of the lithium ions in the lithium-containing solution are adsorbed by the lithium adsorbent; the lithium adsorbent is then separated from the mixed system to achieve lithium extraction.

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