Carboxylic acid group intercalation modified aluminum lithium adsorbent as well as preparation method and application thereof

Abstract

The invention provides a carboxylic acid group intercalation modified aluminum lithium adsorbent as well as a preparation method and application thereof. The preparation method comprises the steps that a mixed reaction solution containing a lithium source, an aluminum source, a modifier and a solvent is provided, the modifier can be complexed with aluminum ions and lithium ions provided by the aluminum source and the lithium source, and the modifier comprises a polymer containing carboxylic acid groups and / or polymer salt; and mixing the mixed reaction solution with a precipitant to carry out coprecipitation reaction, thereby obtaining the carboxylic acid group intercalation modified aluminum lithium adsorbent. The prepared adsorbent has high capacity and good lithium ion selectivity, the poisoning phenomenon is not prone to occurring in brine containing sulfate radicals and carbonate radicals, the adsorption performance is stable in the long-period using process, and the good long-acting using capacity is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium adsorbents, and particularly relates to an aluminum-based lithium adsorbent modified by intercalation of carboxylic acid groups, a preparation method thereof, and an application thereof. Background Art

[0002] In order to cope with the rapid growth of lithium demand, efficient and environmentally friendly lithium extraction technologies have become a research hotspot. Currently, the main sources of lithium extraction include brines (such as salt lake brines), hard rock ores (such as spodumene), and other lithium-containing materials. Brines are an important source of lithium resources. Especially in the salt lakes in South America and western China, the lithium-rich salt lake brines provide abundant raw materials for lithium extraction. However, extracting lithium from salt lake brines still faces challenges such as poor selectivity and difficult separation.

[0003] Currently, the main technologies for lithium extraction include solvent extraction, ion exchange, electrochemistry, adsorption, etc. Among them, solvent extraction requires the use of organic solvents, which has a greater impact on the environment and higher costs. Ion exchange requires the selection of appropriate ion exchange resins, which is relatively complex in operation and has limited adaptability to different environmental conditions. In contrast, adsorption has been widely studied and applied because of its simple operation, relatively low cost, and less impact on the environment. In the adsorption method, the performance of the adsorbent determines the efficiency and effect of lithium extraction, including key indicators such as selectivity, adsorption capacity, and regeneration ability.

[0004] In some domestic salt lakes (Zhabuye, Xitieshan) that have been put into production, some anions (such as CO3 2- 、SO4 2- etc.) can cause the adsorbent to be "poisoned", that is, to deactivate the aluminum-based lithium adsorbent, which will lead to a significant decrease in the adsorption capacity of the adsorbent. For the treatment of such poisoning and deactivation phenomena, there is currently a lack of research on mechanism and structural optimization. Generally, the method of removing sulfate and carbonate at the front end is still used to reduce the adverse effects brought by anions in such salt lake brines on the long-term use of aluminum-based lithium adsorbents.

[0005] For example, the prior art CN116121557A discloses a method for extracting lithium from sulfate subtype or carbonate type salt lakes using an aluminum-based lithium adsorbent. Specifically, in the pre-treatment, nanofiltration is used to remove sulfate and carbonate ions, and then the aluminum-based lithium adsorbent is used for treatment to obtain a desorption solution. However, after the carbonate-type brine is treated by the nanofiltration membrane, there will still be a small amount of carbonate ions remaining, which is likely to cause the inactivation of the aluminum-based lithium adsorbent and the loss of adsorption effect during long-term operation. This method does not refine and remove impurities from the brine, it is difficult to guarantee the purity of the lithium carbonate product, and it can only produce lithium carbonate products, resulting in relatively high production costs. In order to better solve the problem of poisoning and inactivation of the aluminum-based lithium adsorbent, some researchers have tried to improve the surface and interface properties of the aluminum-based lithium adsorbent. For example, the prior art CN117965115A discloses an adhesive for lithium adsorbents in salt lake lithium extraction. This adhesive is a polymer with a styrene maleic anhydride copolymer as the main chain and grafted polyhydroxy compounds, which can be used in the preparation of lithium adsorbents in salt lake lithium extraction. It can be completely wetted with brine during adsorption, improving the adsorption performance of the adsorbent, enabling it to achieve long-term cyclic adsorption performance in the presence of a relatively high concentration of sulfate ions. However, it prevents the poisoning phenomenon by the properties of the adhesive and does not focus on the optimization of the performance of the lithium adsorbent itself. In addition, the existing patent CN117987665A also explores a method using sodium chloride solution as a desorbent for aluminum-based lithium adsorbents to reduce the damage to the structure of the aluminum-based lithium adsorbent caused by sulfate poisoning.

[0006] It can be seen that traditional aluminum-based lithium adsorbents usually have relatively low selectivity for lithium, reducing the recovery purity and yield of lithium resources. In addition, some traditional aluminum-based lithium adsorbents are prone to structural changes or degradation during application, especially when contacting brine with complex components. Cations and anions enter the interlayer or block the adsorption sites, resulting in a decline in the performance of the aluminum-based lithium adsorbent and limiting its application in brines with specific components. Existing modification methods often rely on traditional chemical synthesis processes, leading to high costs, complex operations, and it is difficult to obtain ideal modification effects, especially in terms of efficiency and stability. Summary of the Invention

[0007] To solve all or part of the above technical problems, the present invention provides the following technical solutions:

[0008] One of the objectives of the present invention is to provide a preparation method for an aluminum-based lithium adsorbent modified by intercalation of carboxylic acid groups, including:

[0009] Providing a mixed reaction solution containing a lithium source, an aluminum source, a modifier, and a solvent, wherein the modifier can complex with aluminum ions and lithium ions provided by the aluminum source and the lithium source, and the modifier includes a polymer and / or polymer salt containing carboxylic acid groups;

[0010] Mix the mixed reaction solution with a precipitant to carry out a coprecipitation reaction to obtain an aluminum-based lithium adsorbent modified by intercalation of carboxyl groups.

[0011] The aluminum-based lithium adsorbent modified by intercalation of carboxyl groups provided by the present invention can effectively solve the problem of "adsorbent poisoning" caused by anions such as carbonate (CO3 2- ) and sulfate (SO4 2- ) during the existing process of extracting lithium from salt lakes. By introducing a carboxyl-containing polymer and / or polymer salt as a modifier, stable carboxylic acid coordination sites with complexing ability and a regular organic-inorganic synergistic interface are formed inside the adsorbent structure. This structure can enhance the selective coordination ability between the aluminum-based adsorption sites and lithium ions, improve the competitive adsorption advantage for lithium ions; shield the "poisoning sites" of high-concentration anions such as carbonate and sulfate, and prevent their combination with aluminum sites from causing structural inactivation; form a stable weak acidic or negatively charged environment between layers to inhibit the insertion and deposition of high-valent or polyvalent anions; improve the structural stability and recyclability of the adsorbent in a salt lake water system rich in anions. Compared with the unmodified adsorbent, the adsorbent provided by the present invention can still maintain a high lithium adsorption capacity and regeneration stability in brines with a high CO3 2- / SO4 2- content (such as the brines of Zabuye Salt Lake or Xitieshan Salt Lake), significantly extend the service life of the adsorbent, and solve the problem of sudden capacity drop caused by anion poisoning inactivation of traditional aluminum-based adsorbents.

[0012] In some embodiments, the modifier includes one or a combination of polyacrylic acid, polyacrylate, polycarboxylic acid, polycarboxylate, poly(vinyl alcohol-acrylic acid) copolymer, etc., but is not limited thereto. The polymer salt can be the sodium salt, potassium salt, etc. of the corresponding polymer, but is not limited thereto.

[0013] In some embodiments, the number average molecular weight of the polymer and / or polymer salt is 2000 - 100000 Da, preferably 3000 - 10000 Da, to ensure its good solubility, dispersibility and reaction stability.

[0014] Furthermore, the number average molecular weight of polyacrylic acid and polyacrylate can be 3000 - 10000 Da, preferably 5000 - 8000 Da; the number average molecular weight of polycarboxylic acid and polycarboxylate can be 4000 - 10000 Da, preferably 5000 - 6000 Da; the molecular weight of the poly(vinyl alcohol-acrylic acid) copolymer can be 8000 - 10000 Da, preferably about 9000 Da.

[0015] Further, the mass ratio of vinyl alcohol units to acrylic acid units in the poly(vinyl alcohol - acrylic acid) copolymer can be 60:40 - 80:20, more preferably 70:30, to ensure good dispersion stability during the intercalation process and sufficient carboxyl density to participate in coordination and intercalation reactions.

[0016] In some embodiments, the dosage of the modifier is 1 wt% - 6.5 wt% of the mass of the solvent, so that the molar concentration of carboxylic acid groups in the mixed reaction solution is 0.015 - 0.647 mmol / g. If the dosage of the modifier is relatively high, it is easy to cause precipitation of aluminum sources such as aluminum salts. If the dosage of the modifier is relatively low, the modification effect is not significant.

[0017] In some embodiments, the preparation method specifically includes: uniformly dispersing the modifier in the solvent to form a modifier solution, first adding the lithium source to the modifier solution and dissolving it, and then adding the aluminum source, and ultrasonicating and / or stirring for 2 - 4 h to fully complex the modifier with aluminum ions and lithium ions to obtain the mixed reaction solution.

[0018] Adding the lithium source first and then the aluminum source can enable the excess lithium ions to be fully wrapped and complexed by the modifier. The polycarboxylate has a large number of -COO - groups, and these functional groups have a chelating effect on Li + and also form a weakly acidic complexing environment between the layers of the aluminum-based adsorbent. Since CO3 2- and SO4 2- are highly nucleophilic and easily form precipitating polyvalent anions, which are likely to combine with Al-OH sites or interlayer vacancies, resulting in structural damage. After the carboxylate is intercalated, on the one hand, it stabilizes the interlayer structure, and on the other hand, it reduces the entry probability of these polyvalent anions through steric hindrance or electrostatic repulsion; the polycarboxylic acid in the structure can also buffer local pH fluctuations and prevent the reprecipitation or delamination of Al(OH)3.

[0019] In some embodiments, the method specifically includes: continuously adding a precipitating agent to the mixed reaction solution, adjusting the pH value of the mixed reaction solution to 3.0 within the first time period for the first-stage reaction, adjusting the pH value of the mixed reaction solution to 4.0 within the second time period for the second-stage reaction, and adjusting the pH value of the mixed reaction solution to 5.0 - 5.6 and maintaining it stable within the third time period for the third-stage reaction.

[0020] In some embodiments, the first time period is 10 - 20 min, the second time period is 30 - 50 min, the third time period is 30 - 40 min, and after adjusting the pH value to 5.0 - 5.6 within the third time period, it is maintained for at least 30 min.

[0021] In some embodiments, during the process of continuously adding a precipitant to the mixed reaction solution, the temperature of the mixed reaction solution is maintained at 65-80 °C.

[0022] In some embodiments, the method specifically includes: maintaining the temperature of the mixed reaction solution at 65-80 °C, and using an alkali solution with a hydroxide concentration of 1-8 mol / L as the precipitant;

[0023] The alkali solution is added dropwise to the mixed reaction solution, and the pH value of the mixed reaction solution is adjusted to 3.0 within 10-20 min. In this stage, the crystal nuclei of aluminum hydroxide precipitate are formed. Controlling the time within 10-20 min can promote a rapid reaction; the pH value is adjusted from 3.0 to 4.0 within 30-50 min. In this stage, aluminum hydroxide crystals grow and carboxylic acid groups and lithium are inserted into the interlayer. Controlling the time to 30-50 min can ensure that the reaction proceeds fully; the pH value is adjusted from 4.0 to 5.0-5.6 within 30-40 min and maintained stable in the pH range of 5.0-5.6 for at least 30 min, and then stirring is continued for 6-8 h at a temperature of 65-80 °C. In this stage, the aluminum-based lithium adsorbent grows uniformly. The method of controlling the pH value in stages can effectively control the reaction rate and crystal growth, and ensure the formation of crystal nuclei, crystal growth, and the uniform shaping of the final adsorbent.

[0024] In some embodiments, within the first time period, the precipitant is added dropwise at a rate equivalent to 5%-20% / min of the volume of the mixed reaction solution; within the second time period, the precipitant is added dropwise at a rate equivalent to 1%-10% / min of the volume of the mixed reaction solution; within the third time period, the precipitant is added dropwise at a rate equivalent to 0.5%-5% / min of the volume of the mixed reaction solution.

[0025] In some embodiments, the content of the lithium source in the mixed reaction solution is 2-10 wt% of the mass of the solvent, and the addition amount of the aluminum source makes the molar atomic ratio of lithium to aluminum 4:1-6:1. Under the condition of lithium excess, the intercalation modification of the modifier is more likely to occur.

[0026] The excess of lithium ions not only improves the complexation efficiency with carboxylic acid groups in polycarboxylate, promotes the formation of lithium-carboxylic acid complexes, but also acts as an "electrostatic bridge" or "intercalation induction factor" between the layered precursor structures generated by the hydrolysis of the aluminum source, guiding the modifier to be inserted into the interlayer structure directionally. At the same time, the excess lithium ions can adjust the local charge environment of the system, reduce the electrostatic repulsion between layers, and enhance the stable binding ability of carboxylic acid groups in the interlayer, thereby significantly increasing the occurrence probability and structural stability of the intercalation modification. This configuration helps to form an organic-inorganic synergistic interface, improving the selectivity of the adsorbent for lithium ions and the ability to resist anion poisoning.

[0027] In some embodiments, the concentration of the active ingredient in the mixed reaction solution is 10 wt% - 40 wt%, that is, the total concentration of the lithium source, aluminum source, and modifier is 10 wt% - 40 wt%.

[0028] In some embodiments, the lithium source includes soluble salts of lithium.

[0029] In some preferred embodiments, the lithium source includes lithium chloride and / or hydrates of lithium chloride. Lithium chloride and / or hydrates of lithium chloride have high solubility in the system of the present invention, and the dissociation rate of lithium ions is relatively fast. Moreover, compared with other anions, chloride ions are more easily replaced by carboxylic acid groups and inserted into the interlayer during the reaction. Compared with other soluble salts of lithium, the adsorbent prepared from lithium chloride has a more stable structure and a larger yield.

[0030] In some embodiments, the aluminum source includes soluble salts of aluminum, for example, it may include one or a combination of aluminum nitrate, aluminum chloride, or aluminum sulfate.

[0031] In some embodiments, the solvent is a mixed solvent containing an alcohol solvent and water, and the volume of the alcohol solvent in the mixed solvent is 10 - 30% of the total volume.

[0032] In some embodiments, the alcohol solvent includes one or a combination of ethanol, methanol, isopropanol, or propanol.

[0033] In some embodiments, the method further includes: after the coprecipitation reaction is completed, washing the lithium aluminum adsorbent with hot water at 40 - 60 °C more than once, separating the washed lithium aluminum adsorbent, and drying it. The adsorbent prepared with the modifier of the present invention has relatively small particles, about 0.5 - 10 nm. After the reaction is completed, it is necessary to continuously stir to keep the particles dispersed. Washing with hot water can fully wash away the unreacted modifier or by-products, making the particles less likely to agglomerate.

[0034] Another object of the present invention is to provide a carboxylic acid group intercalated modified lithium aluminum adsorbent, which is prepared by the method described in any one of the above.

[0035] Carboxyl intercalation modification can expand the interlayer spacing of the adsorbent, thereby increasing its adsorption capacity. In addition, compared with the unmodified lithium aluminum adsorbent (particle size about 20 - 40 nm), the adsorbent provided by the present invention has a smaller particle size, about 0.5 - 10 nm, a larger specific surface area, and can also more fully contact lithium ions in the aqueous solution, achieving the effect of rapid adsorption.

[0036] Another object of the present invention is to provide the application of the carboxylic acid group intercalated modified lithium aluminum adsorbent in extracting lithium from brine.

[0037] A fourth object of the present invention is to provide a method for extracting lithium from brine, wherein the brine contains sulfate and / or carbonate, and the method includes: fully mixing and contacting the carboxylic acid group-intercalated modified aluminum-based lithium adsorbent with the brine for lithium ion adsorption, and the dosage of the aluminum-based lithium adsorbent is 0.5-20 wt%.

[0038] In some embodiments, the method does not adopt a pre-treatment process to remove sulfate and / or carbonate in the brine.

[0039] In some embodiments, the brine contains more than 1 g / L of sulfate and / or carbonate. The carboxylic acid group-intercalated modified aluminum-based lithium adsorbent provided by the present invention is suitable for treating brine with a relatively high content of sulfate and carbonate, and is not prone to the phenomenon of "poisoning" of the adsorbent during the long-term treatment process.

[0040] In some embodiments, the method specifically includes: first performing delithiation treatment on the carboxylic acid group-intercalated modified aluminum-based lithium adsorbent, and then fully mixing and contacting the delithiated aluminum-based lithium adsorbent with the brine for lithium ion adsorption; wherein, the delithiation treatment includes dispersing the aluminum-based lithium adsorbent in water and performing heat treatment at a temperature of 40-70 °C for 2-4 h.

[0041] Compared with the prior art, the present invention has at least the following beneficial effects:

[0042] (1) The present invention provides a method for modifying an aluminum-based lithium adsorbent with a polymer and / or polymer salt containing a carboxylic acid group, thereby improving the adsorption capacity and selectivity of the adsorbent for lithium ions;

[0043] (2) The carboxylic acid group-intercalated modified aluminum-based lithium adsorbent provided by the present invention is not prone to the phenomenon of "poisoning" in brine containing sulfate and carbonate, and has relatively stable adsorption performance during long-term use, and has good long-term use ability;

[0044] (3) The preparation method provided by the present invention has simple process, high yield, low production cost, and is suitable for large-scale industrial production; and the intercalation modification effect and the good growth of the adsorbent are further optimized by optimizing specific processes such as the addition sequence of lithium and aluminum, the adjustment of pH value in stages, and the selection of lithium salts. Description of the Drawings

[0045] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings described below are only some embodiments recorded in the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0046] Figure 1 It is the comparative infrared spectrum diagram of the adsorbents prepared in Example 1, Example 2 and Comparative Example 1;

[0047] Figure 2 It is the comparative infrared spectrum diagram of the adsorbents prepared in Examples 1-5 and Comparative Example 1;

[0048] Figure 3 It is the XRD diagram of the adsorbents prepared in Examples 1-5 and Comparative Example 1;

[0049] Figure 4 It is the electron microscope image of the adsorbent prepared in the comparative example;

[0050] Figure 5 It is the electron microscope image of the adsorbent prepared in Example 4;

[0051] Figure 6 It is the electron microscope image of the adsorbent prepared in Example 6. Detailed implementation manners

[0052] The technical solutions of the present invention will be described in detail below in conjunction with specific embodiments, so that those skilled in the art can better understand and implement the technical solutions of the present invention. The specific functional details disclosed herein should not be construed as restrictive, but only as the basis of the claims and as a representative basis for teaching those skilled in the art to adopt the present invention in any appropriate detailed embodiment in different ways.

[0053] In addition, unless otherwise specified, various raw materials used in the following examples can be obtained from the market or other channels, various production and testing equipment used are also equipment known in the art, and the testing methods used are also methods known in the art.

[0054] Example 1

[0055] This example provides an aluminum-based lithium adsorbent and its preparation method, which specifically includes the following steps:

[0056] Mix 20 mL of ethanol with 80 mL of water to prepare a 100 mL mixed solvent, add 2.86 g of sodium polyacrylate (number average molecular weight 3000 Da) modifier thereto and stir evenly, first add 5 g of anhydrous lithium chloride and stir evenly, then add 34.53 g of aluminum nitrate nonahydrate (the lithium-aluminum molar atomic ratio is controlled to be 5:1), and ultrasonically disperse for 3 hours to obtain a reaction solution;

[0057] Heat the reaction solution to 70 °C, control the stirring speed at 500 rpm, and add 3 mol / L sodium hydroxide solution dropwise to adjust the pH value. The pH adjustment process is divided into three stages: the first stage rises to pH 3.0, which takes 15 minutes; the second stage rises to pH 4.0, which takes 40 minutes; the third stage rises to pH 5.3, which takes 35 minutes. After reaching pH 5.3, stop adding sodium hydroxide and continue stirring at 70 °C for 7 hours. Then stop the water bath and stirring, and wash with 60 °C hot water 4 times. Filter the product and dry it at 60 °C. After drying, stir it in a 60 °C water bath for 2 hours, filter and dry it again to obtain 7.71 g of aluminum-based lithium adsorbent, denoted as PLH-1.

[0058] Example 2

[0059] This example provides an aluminum-based lithium adsorbent and its preparation method, which specifically includes the following steps:

[0060] Mix 30 mL of isopropanol and 70 mL of water to prepare 100 mL of a mixed solvent. Add 3.74 g of polyacrylic acid (number average molecular weight 5000 Da) modifier and stir evenly. First, add 8 g of anhydrous lithium chloride and stir evenly, then add 27.62 g of aluminum nitrate nonahydrate (the molar atomic ratio of lithium to aluminum is controlled at 4:1), and stir and disperse at high speed for 2 hours to obtain a reaction solution;

[0061] Heat the reaction solution to 75 °C, control the stirring speed at 380 rpm, and add 4 mol / L sodium hydroxide solution dropwise to adjust the pH value. The pH adjustment process is divided into three stages: the first stage rises to pH 3.0, which takes 20 minutes; the second stage rises to pH 4.0, which takes 30 minutes; the third stage rises to pH 5.6, which takes 40 minutes. After reaching pH 5.6, stop adding sodium hydroxide and continue stirring at 75 °C for 6 hours. Stop the water bath and stirring, and wash with 60 °C hot water 3 times. Filter the product and dry it at a temperature not exceeding 70 °C. After drying, stir it in a 60 °C water bath for 2 hours, filter and dry it again, and the drying temperature does not exceed 70 °C to obtain 4.89 g of aluminum-based lithium adsorbent, denoted as PLH-2.

[0062] Example 3

[0063] This example provides an aluminum-based lithium adsorbent and its preparation method, which specifically includes the following steps:

[0064] Mix 25 mL of propanol with 75 mL of water to prepare 100 mL of a mixed solvent. Add 2.375 g of a poly(vinyl alcohol - acrylic acid) copolymer (number-average molecular weight is about 9000 Da, and the molar ratio of vinyl alcohol units to acrylic acid units is about 3:1) modifier and stir evenly. First, add 6 g of lithium chloride monohydrate and stir evenly, then add 41.79 g of aluminum nitrate nonahydrate (the lithium-aluminum molar atomic ratio is controlled to be 6:1), and ultrasonically disperse for 4 hours to obtain a reaction solution;

[0065] Heat the reaction solution to 68 °C, control the stirring speed at 400 rpm, and add 2 mol / L sodium hydroxide solution dropwise to adjust the pH value. The pH adjustment process is divided into three stages: the first stage rises to pH 3.0, which takes 10 minutes; the second stage rises to pH 4.0, which takes 50 minutes; the third stage rises to pH 5.2, which takes 30 minutes. After reaching pH 5.2, stop adding sodium hydroxide. When the pH drops to 4.8, continue to add sodium hydroxide to pH 5.2, and continue to stir at 68 °C for 8 hours. Stop the water bath and stirring, and wash 5 times with 60 °C hot water. Filter the product and dry it at a temperature not exceeding 70 °C, then stir in a 60 °C water bath for 2 hours, filter and dry again, and the final drying temperature does not exceed 70 °C to obtain 9.32 g of an aluminum-based lithium adsorbent, denoted as PLH-3.

[0066] Example 4

[0067] This example provides an aluminum-based lithium adsorbent and its preparation method, specifically including the following steps:

[0068] Mix 15 mL of methanol with 85 mL of water (a total of 96.85 g) to prepare 100 mL of a mixed solvent. Add 6.29 g of sodium polyacrylate (number-average molecular weight 8000 Da) modifier and stir evenly. First, add 10 g of anhydrous lithium chloride and stir evenly, then add 20.86 g of aluminum nitrate nonahydrate (the lithium-aluminum molar atomic ratio is controlled to be 4:1), and disperse by high-speed stirring for 3 hours to obtain a reaction solution;

[0069] Heat the reaction solution to 72 °C, control the stirring speed at 300 rpm, and add 5 mol / L sodium hydroxide solution dropwise thereto to adjust the pH value. The pH adjustment process is divided into three stages: the first stage rises to pH 3.0, which takes 18 minutes; the second stage rises to pH 4.0, which takes 45 minutes; the third stage rises to pH 5.5, which takes 35 minutes. After reaching pH 5.5, stop adding sodium hydroxide and monitor the pH value. If necessary, use hydrochloric acid to adjust to keep the pH at 5.5, continue stirring at 72 °C for 7 hours, stop the water bath and stirring, wash 4 times with 60 °C hot water. Filter the product and dry it at a temperature not exceeding 70 °C, then stir in a 60 °C water bath for 2 hours, filter and dry again, and the final drying temperature does not exceed 70 °C to obtain 5.07 g of an aluminum-based lithium adsorbent, denoted as PLH-4.

[0070] Example 5

[0071] This example provides an aluminum-based lithium adsorbent and its preparation method, which specifically includes the following steps:

[0072] Mix 20 mL of ethanol and 80 mL of water to prepare 100 mL of a mixed solvent, add 3.83 g of a polycarboxylic acid (number average molecular weight 5500 Da) modifier thereto and stir evenly. First, add 7 g of lithium chloride monohydrate and stir evenly, then add 30.14 g of aluminum nitrate nonahydrate (the lithium-aluminum molar atomic ratio is controlled at 5:1), and ultrasonically disperse for 2 hours to obtain a reaction solution;

[0073] Heat the reaction solution to 65 °C, control the stirring speed at 400 rpm, and add 4 mol / L sodium hydroxide solution dropwise thereto to adjust the pH value. The pH adjustment process is divided into three stages: the first stage rises to pH 3.0, which takes 12 minutes; the second stage rises to pH 4.0, which takes 35 minutes; the third stage rises to pH 5.4, which takes 32 minutes. After reaching pH 5.4, stop adding sodium hydroxide, monitor the pH value, and use hydrochloric acid to adjust if necessary to keep the pH value at 5.4, and continue stirring at 65 °C for 8 hours, stop the water bath and stirring, wash 5 times with 60 °C hot water. Filter the product and dry it at a temperature not exceeding 70 °C, then stir in a 60 °C water bath for 2 hours, filter and dry again, and the final drying temperature does not exceed 70 °C to obtain 7.32 g of an aluminum-based lithium adsorbent, denoted as PLH-5.

[0074] Example 6

[0075] This example provides an aluminum-based lithium adsorbent and its preparation method, which specifically includes the following steps:

[0076] Mix 10 mL of isopropanol with 90 mL of water to prepare 100 mL of a mixed solvent. Add 0.98 g of a sodium polycarboxylate (number average molecular weight 4000 Da) modifier thereto and stir evenly. First, add 6 g of anhydrous lithium chloride and stir evenly, then add 41.8 g of aluminum nitrate nonahydrate (the molar atomic ratio of lithium to aluminum is controlled at 6:1), and stir and disperse at high speed for 3 hours to obtain a reaction solution;

[0077] Heat the reaction solution to 78 °C, control the stirring speed at 490 rpm, and add 3 mol / L sodium hydroxide solution dropwise thereto to adjust the pH value. The pH adjustment process is divided into three stages: the first stage is raised to pH 3.0, which takes 15 minutes; the second stage is raised to pH 4.0, which takes 38 minutes; the third stage is raised to pH 5.3, which takes 30 minutes. After reaching pH 5.3, stop adding sodium hydroxide, monitor the pH value, and adjust with hydrochloric acid if necessary to keep the pH value at 5.3. Continue stirring at 78 °C for 6 hours, stop the water bath and stirring, wash with 60 °C hot water 3 times. Filter the product and dry it at a temperature not exceeding 70 °C, then stir in a 60 °C water bath for 2 hours, filter and dry again, and finally dry at a temperature not exceeding 70 °C to obtain 8.86 g of an aluminum-based lithium adsorbent, denoted as PLH-6.

[0078] Comparative Example 1

[0079] The difference between Comparative Example 1 and Example 1 is only that in the preparation process of Comparative Example 1, the modifier sodium polyacrylate is not used, and the obtained adsorbent is denoted as LH. The rest is the same as in Example 1 and will not be elaborated here.

[0080] Stir the aluminum-based lithium adsorbents prepared in Examples 1-6 and Comparative Example 1 in a 60 °C water bath for 2 h, filter and dry, then take 1 g and add it to 200 mL of brine with a lithium concentration of 177 mg / L, and detect the adsorption performance after shaking in a water bath for 12 h. The test results are shown in Table 1.

[0081] Table 1 Influence of modifier ratio on the performance of the adsorbent

[0082]

[0083] Note: The amount of modifier added in Table 1 is the ratio of the mass of the modifier to the mass of the mixed solvent when the mass of the mixed solvent is counted as 100%.

[0084] According to Table 1, it can be seen that the modifier provided by the present invention has a more obvious improvement in the adsorption capacity. Compared with the adsorbent prepared without using the modifier, the adsorption capacity of the adsorbent prepared by the method of the present invention is increased by about twice, and different types of carboxyl-containing modifiers can all achieve a good effect of improving the adsorption capacity.

[0085] Figure 1The infrared comparison diagrams of unmodified LiCl·2Al(OH)3·nH2O (LH) prepared in Comparative Example 1 and PLH-1 and PLH-2 are shown. The infrared results indicate that at the characteristic peak of 1000 cm- 1 1 , the characteristic peaks of PLH-1 and PLH-2 are different from those of the unmodified sample LH. In addition, the -OH vibration peaks of the modified samples PLH-1 and PLH-2 are shifted compared to the unmodified sample LH, which may be related to the change in the content of interlayer crystal water caused by intercalation modification.

[0086] Figure 2 are the infrared comparison diagrams of PLH-3, PLH-4, PLH-5, and PLH-6. It can be seen that the type and content of the modifier have a certain influence on the group structure of the adsorbent. For example, in the range of 500-1000 cm- Figure 2 1 , it is mainly the metal ion and polymer complex group region, and the complex structures of different samples are different. In addition, the characteristic peaks of the polymer groups are shifted at 1300-1400 cm- 1 1 1 1 respectively, which is closely related to the side chain configuration, carboxyl density, and molecular flexibility of the modifier used, further proving that the modifier has been successfully introduced into the interlayer.

[0087] It should be noted that the characteristic absorption peaks of hydroxyl groups in the modified samples in the range of 3200-3600 cm -1 -1 have all shifted and changed in peak shape to varying degrees, indicating that the modification has interfered with the state of water molecules in the adsorbent structure. Specifically, the content of interlayer free water in the modified material decreases, and the proportion of crystal water relatively increases. This is because after the polycarboxylic acid modifier is intercalated, a stable organic-inorganic synergistic network structure is formed in the interlayer, inhibiting the accumulation and migration of excessive free water, and enabling more water molecules to be stably bound in the aluminum-based layered structure in the form of crystal water. This structural change has an obvious performance promotion effect. On the one hand, crystal water helps to maintain the layer spacing and structural integrity of the aluminum-based adsorbent, improving the structural stability and cyclic durability of the material in the complex ion environment of salt lake brine; on the other hand, the decrease in free water content can effectively reduce the swelling, delamination, or particle agglomeration behavior during the adsorption process, thereby improving the dispersibility, reusability, and long-term adsorption efficiency of the adsorbent.

[0088] Figure 3 are the XRD comparison diagrams of LH, PLH-1, PLH-2, PLH-3, PLH-4, and PLH-5. It can be seen from Figure 3It can be seen that in the low-angle region (0 - 20°) representing the layered structure, for the modified samples compared with the standard card and the unmodified LH samples prepared, there are phenomena of diffraction peak shift or intensity change. This indicates that the modification of the polymer and polymer salt has significantly changed the layered structure. Combining with the data analysis, carboxyl intercalation has enlarged the layer spacing of the adsorbent, which is also one of the main reasons for the increase in the adsorption capacity. In some preferred embodiments, the adsorption capacity can reach more than 16 mg / g.

[0089] Figure 4 is the electron micrograph of LH prepared in Comparative Example 1. Figure 5 is the electron micrograph of PLH-4 prepared in Example 4. Figure 6 is the electron micrograph of PLH-6 prepared in Example 6. Comparing Figures 4 - 6 It can be seen that the carboxyl group intercalation modification can significantly change the morphology of the adsorbent. Under the same 500nm magnification condition, the particles of the unmodified sample LH are larger, and the modified sample PLH-4 shows the phenomenon of particle dense adhesion. This is because the high content of the modifier (6.5% (w / w)) makes the crystal particles of the adsorbent too fine and there will be a certain degree of agglomeration in the dry state. However, the adsorption capacity of the adsorbent prepared with 5% modifier is still improved to a certain extent compared with the unmodified adsorbent. The modified sample PLH-6 shows fine particle shape under the same magnification, and the addition amount of the modifier is 1% (w / w) at this time. Although the crystal particles of the adsorbent are finer after the reaction, they are not easy to agglomerate. Therefore, considering the selectivity for lithium, adsorption capacity and adsorbent particle size comprehensively, the more preferred dosage of the modifier is 1% - 3% (w / w).

[0090] The present invention also verified the lithium extraction performance of the adsorbents prepared in Examples 1 - 6 and Comparative Example 1 in real brine samples (from salt lakes in Qaidam Basin). The main components of the selected brine are shown in Table 2, including raw brine (i.e., the original brine in Table 2), transitional brine treated by DA (i.e., DA in Table 2), and lithium-rich brine treated by DN (i.e., DN in Table 2). Among them, the lithium concentration in DN brine is as high as 108.39 mg / L, while the + Na concentration drops to 0.22 g / L, and the 2+ Mg still remains at 41.60 g / L, which is a typical difficult-to-separate brine system with a very low lithium / magnesium ratio and is representative.

[0091] The adsorption experiment results show that compared with Comparative Example 1, the adsorbents prepared by the method of the present invention show higher selectivity and adsorption ability for lithium ions. Taking Example 4 (PLH-4) as an example, after 1 hour of adsorption in DN brine, the lithium adsorption capacity can reach 13.3 mg / g, while that of Comparative Example 1 is only 6.5 mg / g; the lithium selectivity coefficient (relative to + Na and 2+ Mg) is increased by about 2.8 times.

[0092] In 10 consecutive adsorption - desorption cycle tests, PLH - 4 still maintained an adsorption capacity of 9.8 mg / g in the DN brine system, and the performance retention rate reached 93.0%. However, for Comparative Example 1, after the 10th cycle, due to 2+ the influence of competitive adsorption and anion poisoning, the capacity decreased to 4.2 mg / g, only retaining 64.6% of the original performance.

[0093] Table 2 Composition Table of Brines in Qaidam Basin

[0094]

[0095] The above - mentioned brines are typical sulfate - type brines with relatively low lithium concentrations. The maximum number of cycles and adsorption selectivity of the comparative examples and PLH - 4 in these three brines are shown in Table 3 below.

[0096] Table 3 Comparison Table of Adsorption Performance

[0097]

[0098] Note: The maximum number of cycles in Table 3 refers to the maximum number of cycles when the adsorption capacity remains above 60% of the initial adsorption capacity.

[0099] Examples 7 - 9

[0100] Examples 7 - 9 are basically the same as Example 4, except that the lithium - aluminum molar atomic ratio is changed as shown in Table 4, and the rest are implemented in the same way as Example 4, which will not be elaborated here.

[0101] The prepared adsorbent was stirred in a water bath at 60 °C for 2 h. After filtration and drying, 1 g was added to 200 mL of brine with a lithium concentration of 177 mg / L. After shaking in a water bath for 12 h, the adsorption performance was detected, and the test results are shown in Table 4.

[0102] Table 4 Influence of Lithium - Aluminum Ratio on Adsorbent Performance

[0103] Group n(Li):n(Al) Concentration of washed Li (g / L) Adsorption capacity (mg / g) Example 7 3：1 3.5 12.0 Example 4 4：1 4.8 12.0 Example 8 5：1 5.2 13.5 Example 9 6：1 5.9 14.2

[0104] Note: In Table 4, the washed Li concentration refers to the concentration of interlayer lithium in the adsorbent precursor eluted at 60 °C. Generally speaking, the higher the elution concentration, the faster the elution, the faster the lithium adsorption rate, and the higher the adsorption amount.

[0105] According to Table 4, different lithium - aluminum ratios have a certain influence on the transformation and adsorption performance of the adsorbent. Within the range of lithium - aluminum ratios provided by the present invention, an adsorbent with a higher adsorption amount can be prepared.

[0106] Example 10

[0107] This embodiment provides an aluminum-based lithium adsorbent and a preparation method thereof, which specifically include the following steps:

[0108] Mix 10 mL of isopropanol with 90 mL of water to prepare a 100 mL mixed solvent. Add 1 mL of polycarboxylate sodium (molecular weight is 5500 Da) modifier thereto and stir evenly. First, add 6 g of anhydrous lithium chloride and stir evenly, then add 41.8 g of aluminum nitrate nonahydrate (the lithium-aluminum molar atomic ratio is controlled to be 6:1), and stir and disperse at high speed for 3 hours to obtain a reaction solution;

[0109] Heat the reaction solution to 78 °C, control the stirring speed at 490 rpm, and add 3 mol / L sodium hydroxide solution thereto to adjust the pH value. The pH value adjustment process is divided into three stages: the first stage rises to pH 3.0 and takes 15 minutes; the second stage rises to pH 4.0 and takes 38 minutes; the third stage rises to pH 5.0 and takes 30 minutes. After reaching pH 5.0 (the end point pH value), stop adding sodium hydroxide, monitor the pH value, and adjust with hydrochloric acid if necessary to maintain the pH value at 5.0. Continue stirring at 78 °C for 6 hours, stop the water bath and stirring, wash with 60 °C hot water 3 times. Filter the product and dry it at a temperature not exceeding 70 °C, then stir in a 60 °C water bath for 2 hours, filter and dry again, and the drying temperature does not exceed 70 °C.

[0110] Examples 11 - 12

[0111] Examples 11 - 12 are basically the same as Example 10, except that in Examples 11 - 12, the end point pH value is changed as shown in Table 5, and the rest are the same as in Example 10 and will not be elaborated here.

[0112] Table 5 Influence of end point pH on the performance of the adsorbent

[0113] Group Final pH Yield (g) Adsorption capacity (mg / g) Example 10 5.0 8.1 14.1 Example 11 5.5 8.8 15.2 Example 12 5.6 9.6 14.5

[0114] It can be seen from Examples 10 - 12 that when the end point pH value is within the range provided by the present invention, the yield is relatively high and the adsorption capacity is excellent. The end point pH value has a certain influence on the yield and adsorption capacity, but the influence is relatively slight.

[0115] Example 13

[0116] This embodiment provides an aluminum-based lithium adsorbent and a preparation method thereof, which specifically include the following steps:

[0117] Prepare a mixed solution of ethanol and water, wherein the volume of ethanol is 20% and the total volume of the mixed solution is 2.5 L; add 25 ml of polycarboxylate sodium (molecular weight 3000 Da) thereto, and add 217.4 g of lithium chloride monohydrate and 200 g of aluminum chloride hexahydrate thereto, and disperse evenly to obtain a reaction solution;

[0118] Maintain the temperature of the reaction solution at 75 °C, and dropwise add a 2 mol / L sodium hydroxide solution to carry out a coprecipitation reaction. The dropwise addition of the sodium hydroxide solution is divided into three stages: In the first stage, the sodium hydroxide solution is dropped into the reaction solution at a rate of 10 mL / min to adjust the pH value from 1.6 to 3.0 for 18 minutes; in the second stage, the sodium hydroxide solution is dropped at a rate of 5 mL / min to adjust the pH value from 3.0 to 4.0 for 32 minutes; in the third stage, the sodium hydroxide solution is dropped at a rate of 1 mL / min to adjust the pH value from 4.0 to 5.6 for 30 minutes. Continue stirring at 75 °C for 7 hours, then stop the water bath and stirring, and wash 4 times with 60 °C hot water. Filter the product and dry it at 60 °C. After drying, stir it in a 60 °C water bath for 2 hours, filter and dry it again to obtain an aluminum-based lithium adsorbent.

[0119] Examples 14 - 15

[0120] Examples 14 - 15 are basically the same as Example 13, except that the concentration of the sodium hydroxide solution and the dropping rate and time of the sodium hydroxide in each stage are changed as shown in Table 6.

[0121] Table 6 Flow rate control under different sodium hydroxide concentrations

[0122]

[0123] As can be seen from Table 6, under different concentrations of sodium hydroxide solution, by controlling the pH value in stages and adjusting the dropping rate, the precipitation process can be made more gentle and controllable, which helps to achieve continuous regulation of crystal nucleation - crystal growth - structure stability. Among them, in the range of 2 - 8 mol / L, the mode of fast dropping in the first stage (pH 1.6 - 3.0), decelerating in the second stage (pH 3.0 - 4.0), and slowly advancing in the third stage (pH 4.0 - 5.6) is beneficial to the stable embedding and intercalation reaction of the modifier during crystal formation, and improves the structural homogeneity and stability of the material.

[0124] Example 16

[0125] The difference between Example 16 and Example 1 is only that: Example 16 does not perform staged pH control, but directly adjusts the pH value to 5.5 at one time with the same concentration of sodium hydroxide solution, without finely controlling the crystal nucleation and growth process. Although the material prepared in Example 16 has improved adsorption performance compared with the unmodified adsorbent, there are still the following gaps compared with Example 1:

[0126] (1) The lithium adsorption capacity is slightly lower: Under the same test conditions, the adsorption capacity of Example 1 is 14.2 mg / g, while that of Example 16 is 10.7 mg / g, a decrease of about 24%.

[0127] (2) Selective increase of impurity ions: The selectivity coefficient of lithium for Na + increases by about 15%, and the selectivity coefficient for sulfate increases by 5%.

[0128] (3) Unstable reuse performance: After 5 cycles, the adsorption capacity retention rate is only 81.2%, lower than 91.5% in Example 1;

[0129] (4) Increased material agglomeration: SEM observation shows that the particle size distribution of the sample in Example 16 is wider, and particle agglomeration is obvious. It is speculated that due to the too fast crystallization rate, the polymer intercalation efficiency decreases.

[0130] It can be seen that the precipitation strategy of adjusting pH in stages combined with controlling different flow rates helps to further achieve more effective synergistic construction between the modifier and the aluminum-based framework, and further improve the structural stability and lithium extraction performance of the adsorbent.

[0131] Example 17

[0132] The difference between Example 17 and Example 1 is only that Example 17 uses other soluble lithium salts, and the prepared adsorbent is also subjected to an adsorption reaction. The corresponding results are as follows:

[0133] Table 7 Comparison of adsorbents prepared from different lithium salts

[0134] Type of lithium salt Yield (g) Lithium adsorption capacity (mg / g) Selectivity (Li / Na) LiCl (Lithium chloride) 8.5 14.2 3.9 <![CDATA[LiNO3 (Lithium Nitrate)]]> 9.2 11.1 3.4 <![CDATA[Li2SO4 (Lithium Sulfate)]]> 8.9 10.9 2.2

[0135] When lithium chloride (LiCl) is used as the lithium source, since Cl - is a weakly coordinating, monovalent anion and hardly forms a precipitate with aluminum ions, it is beneficial for lithium to complex with polycarboxylic acid groups and intercalate smoothly, and finally form an adsorbent with regular structure and uniform interlayer distribution. The lithium adsorption capacity is the highest (18.5 mg / g), and the adsorption performance of 93.5% is still maintained after 10 cycles of reuse, and the comprehensive performance is the best.

[0136] The NO3 provided by lithium nitrate (LiNO3) is also a monovalent weak ligand, which has little interference with the reaction process. However, it lacks certain structural induction ability in the intercalation reaction, resulting in a slightly loose interlayer structure of the final product, and the adsorption capacity slightly decreases to 17.1 mg / g, but it still has good selectivity and regenerability, indicating that the method of the present invention has a certain adaptability to the lithium source.

[0137] In lithium sulfate (Li2SO4), SO4 2- is a divalent strong coordinating anion, which is easy to form aluminum sulfate-like precipitates with Al 3+ during the reaction process, destroying the intercalation process and crystal structure, resulting in an incomplete structure of the adsorbent product, a significant decrease in the lithium adsorption capacity to 13.9 mg / g, and a deterioration of the cycling performance, only maintaining 72.4% of the adsorption capacity.

[0138] It can be seen that using LiCl as the lithium source can achieve good intercalation modification effects. LiCl has the best comprehensive performance, while anions with high coordination ability (such as SO4 2- ) will inhibit the construction of the adsorbent structure and the performance exertion. Therefore, the nature of the anions of the selected lithium salts has an impact on the formation and stability of the adsorbent structure, and lithium salts with weak coordination ability and high solubility should be preferred.

[0139] In summary, the present invention uses a polymer containing carboxylic groups and a polymer salt to intercalate and modify the aluminum-based lithium adsorbent. The carboxylic group can coordinate and complex with lithium ions (Li + ) and aluminum ions (Al 3+ ) in the reaction system to form stable lithium-carboxylic acid complexes or organic-inorganic synergistic intercalation structures, thereby realizing the directional embedding and stable distribution of the modifier between the layers of the adsorbent, enhancing the orderliness and intercalation efficiency of the layered structure, and then significantly enhancing the selective adsorption ability of the prepared aluminum-based lithium adsorbent for lithium ions. This modified structure can also effectively inhibit the co-adsorption phenomenon of non-target ions such as Na + , K + , Mg 2+ , Ca 2+ etc., and improve the selective enrichment effect of lithium. Aiming at the problem that the adsorbent is prone to "poisoning" in an anion-rich system in the prior art (such as SO4 2- , CO3 2- leading to the shielding of active sites or the destruction of the structure), the modified aluminum-based lithium adsorbent prepared by the present invention can effectively reduce the direct contact between high-concentration polyvalent anions and aluminum sites through the weakly acidic environment formed by intercalation and the steric hindrance effect, thereby enhancing the anti-poisoning ability and structural stability of the adsorbent, and still maintaining good performance stability and reusability in multiple adsorption-desorption cycles.

[0140] All aspects, embodiments, features, and examples of the present invention should be considered illustrative in all respects and are not intended to limit the present invention. The scope of the present invention is only defined by the claims. Without departing from the spirit and scope of the claimed invention, those skilled in the art will understand other embodiments, modifications, and uses.

[0141] In addition, the inventors of this case also referred to the foregoing embodiments and conducted tests with other raw materials, process operations, and process conditions described in this specification, and all obtained relatively ideal results.

[0142] Although the present invention has been described with reference to illustrative embodiments, those skilled in the art will understand that various other changes, omissions and / or additions can be made without departing from the spirit and scope of the present invention, and elements of the embodiments can be replaced with substantially equivalent ones. In addition, many modifications can be made without departing from the scope of the present invention to adapt a particular situation or material to the teachings of the present invention. Therefore, the present invention is not intended to be limited to the specific embodiments disclosed for carrying out the present invention, but is intended to cover all embodiments that fall within the scope of the appended claims. Furthermore, unless specifically stated, any use of the terms first, second, etc. does not denote any order or importance, but the terms first, second, etc. are used to distinguish one element from another element.

Claims

1. A preparation method of an aluminum-based lithium adsorbent modified by intercalation of carboxyl groups, characterized in that, Comprising: Providing a mixed reaction solution containing a lithium source, an aluminum source, a modifier, and a solvent, wherein the modifier can complex with aluminum ions and lithium ions provided by the aluminum source and the lithium source, and the modifier includes a polymer and / or a polymer salt containing a carboxylic acid group; Mixing the mixed reaction solution with a precipitating agent to carry out a coprecipitation reaction to obtain an aluminum-based lithium adsorbent modified by intercalation of a carboxylic acid group.

2. The preparation method according to claim 1, wherein: The modifier includes one or a combination of polyacrylic acid, polyacrylate, polycarboxylic acid, polycarboxylate, poly(vinyl alcohol-acrylic acid) copolymer, etc.; And / or, the number average molecular weight of the polymer and / or the polymer salt is 2000-100000 Da, preferably 3000-10000 Da; And / or, the dosage of the modifier is 1 wt%-6.5 wt% of the mass of the solvent, so that the molar concentration of the carboxylic acid group in the mixed reaction solution is 0.015-0.647 mmol / g.

3. The preparation method according to claim 1, wherein Specifically including: Uniformly dispersing the modifier in the solvent to form a modifier solution, first adding the lithium source to the modifier solution and dissolving it, and then adding the aluminum source, and ultrasonicating and / or stirring for 2-4 h to fully complex the modifier with aluminum ions and lithium ions to obtain the mixed reaction solution.

4. The preparation method according to claim 1, characterized in that, Specifically including: Continuously adding a precipitating agent to the mixed reaction solution, adjusting the pH value of the mixed reaction solution to 3.0 in the first time period to carry out the first-stage reaction, adjusting the pH value of the mixed reaction solution to 4.0 in the second time period to carry out the second-stage reaction, and adjusting the pH value of the mixed reaction solution to 5.0-5.6 and maintaining it stable in the third time period to carry out the third-stage reaction; Preferably, the first time period is 10-20 min, the second time period is 30-50 min, the third time period is 30-40 min, and after adjusting the pH value to 5.0-5.6 in the third time period, maintaining it for at least 30 min; Preferably, during the process of continuously adding the precipitating agent to the mixed reaction solution, the temperature of the mixed reaction solution is maintained at 65-80 °C.

5. The preparation method according to claim 4, characterized in that, Specifically including: Maintaining the temperature of the mixed reaction solution at 65-80 °C, and using an alkali solution with a hydroxide concentration of 1-8 mol / L as the precipitating agent; Dropping the alkali solution into the mixed reaction solution, adjusting the pH value of the mixed reaction solution to 3.0 within 10-20 min, adjusting the pH value from 3.0 to 4.0 within 30-50 min, adjusting the pH value from 4.0 to 5.0-5.6 within 30-40 min, and maintaining it stable in the pH value range of 5.0-5.6 for at least 30 min, and then continuing to stir for 6-8 h at a temperature of 65-80 °C.

6. The preparation method according to claim 4 or 5, wherein: In the first time period, the precipitating agent is dropped at a rate equivalent to 5%-20% / min of the volume of the mixed reaction solution; In the second time period, the precipitating agent is dropped at a rate equivalent to 1%-10% / min of the volume of the mixed reaction solution; In the third time period, the precipitating agent is added at a rate equivalent to 0.5% - 5% / min of the volume of the mixed reaction solution.

7. The preparation method according to claim 1, wherein: The content of the lithium source in the mixed reaction solution is 2 - 10 wt% of the mass of the solvent, and the addition amount of the aluminum source makes the molar atomic ratio of lithium to aluminum 3:1 - 6:1; and / or, the total concentration of the lithium source, aluminum source and modifier in the mixed reaction solution is 10 wt% - 40 wt% and / or, the lithium source includes soluble salts of lithium, preferably including lithium chloride and / or hydrates of lithium chloride; and / or, the aluminum source includes soluble salts of aluminum, preferably including one or a combination of aluminum nitrate, aluminum chloride or aluminum sulfate; and / or, the solvent is a mixed solvent containing an alcohol solvent and water, and the volume of the alcohol solvent in the mixed solvent is 10 - 30% of the total volume. Preferably, the alcohol solvent includes one or a combination of ethanol, methanol, isopropanol or propanol.

8. An aluminum-based lithium adsorbent modified by intercalation of carboxylic acid groups, characterized in that: It is prepared by the method according to any one of claims 1 - 7.

9. Use of the carboxylic acid group intercalation modified aluminum-based lithium adsorbent according to claim 8 in extracting lithium from brine.

10. A method for extracting lithium from brine, wherein the brine contains sulfate and / or carbonate, characterized in that, Comprising: fully mixing and contacting the carboxylic acid group intercalation modified aluminum-based lithium adsorbent according to claim 8 with the brine for lithium ion adsorption, and the dosage of the aluminum-based lithium adsorbent is 0.5 - 20 wt%; Preferably, the method does not adopt a pre-treatment process to remove sulfate and / or carbonate in the brine; Preferably, the brine contains sulfate and / or carbonate with a concentration above 1 g / L; Preferably, the method specifically includes: first performing delithiation treatment on the carboxylic acid group intercalation modified aluminum-based lithium adsorbent, and then fully mixing and contacting the delithiated aluminum-based lithium adsorbent with the brine for lithium ion adsorption; wherein, the delithiation treatment includes dispersing the aluminum-based lithium adsorbent in water and performing heat treatment at a temperature of 40 - 70 °C for 2 - 4 h.

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