Lithium adsorbent precursor and processing method thereof

Abstract

The invention belongs to the field of inorganic adsorbent materials, and discloses a lithium adsorbent precursor and a processing method thereof.The processing method of the lithium adsorbent precursor comprises the steps that the pH of a mixed solution of water-soluble lithium salt and water-soluble aluminum salt is adjusted in a segmented mode, and the pH change rate of the first stage, the pH change rate of the second stage and the pH change rate of the third stage are accurately controlled; and carrying out combined crushing process treatment on the filtered precursor, including coarse crushing, intermediate crushing and fine crushing to a certain particle size range, so as to obtain the lithium adsorbent precursor LiCl. 3Al (OH) 3. NH2O powder. By adjusting the processing process of the lithium adsorbent precursor, the highest adsorption capacity of the lithium adsorbent can reach 6.93 mg / g without modifying the precursor, the solution loss rate of the adsorbent after 5 times of circulation can still be kept below 0.035%, the lowest solution loss rate is 0.002%, and a new thought is provided for processing and preparation of the adsorbent precursor.

Description

Technical Field

[0001] This application belongs to the field of inorganic adsorbent materials, and particularly relates to a lithium adsorbent precursor and a processing method thereof. Background Art

[0002] Oxides and hydroxides with layered structures have attracted great attention from scientific researchers due to their unique properties and advantages. The aluminum-based lithium adsorbent is prepared by aluminum salt precipitation. Its essence is that LiCl is inserted into Al(OH)3 to form Li-Al layered hydroxide (Li / Al-LDH), and the expression is usually: LiCl·mAl(OH)3·nH2O or [LiAl2(OH)6]Cl·nH2O, where n is the number of crystal water molecules contained. The adsorption mechanism of Li / Al-LDH stems from the precipitation reaction of Li+ and Al(OH)3. In this reaction, Li+ is inserted into the amorphous Al(OH)3 layer and enters the Al-O octahedral holes. Under the combined influence of hydration and ionic radius differences, a memory effect and a steric hindrance effect are formed, and this adsorbent has a high selective adsorption ability for Li+. It is worth mentioning that the Li / Al-LDH adsorbent only requires an aqueous solution during the lithium desorption process and does not require an acid-base solution, so its application is very extensive.

[0003] However, the problems of the aluminum-based lithium adsorbent are that its adsorption capacity is relatively low compared with other types of lithium adsorbents, and at the same time, the dissolution loss is large and the recyclability is poor. These problems all need to be studied and improved urgently. There are many studies focusing on the improvement of the adsorbent precursor. Related technologies include doping europium elements in the aluminum-based lithium adsorbent precursor. The prepared europium-containing aluminum-based lithium adsorbent precursor has a high internal specific surface area, a large adsorption capacity and a fast adsorption rate, but a new doping element europium is introduced. There are also related technologies that use metal-organic framework mofs materials as precursors to prepare aluminum-based lithium adsorbents, which have a highly porous structure and a high specific surface area, and the adsorption capacity can reach 6.8 mg / g.

[0004] Therefore, there is an urgent need to provide a processing method for the precursor that has a simple process flow, does not require modification of the precursor, and the adsorption performance of the prepared adsorbent can still maintain a high level. Summary of the Invention

[0005] Based on the above, one technical problem to be solved by this application is to provide a processing method for a lithium adsorbent precursor. Starting from the preparation process of the lithium adsorbent precursor, the pH value of the system is adjusted step by step, and the crushing process is adjusted. A multi-stage crushing process of coarse crushing, medium crushing and fine crushing is adopted, and a precursor with a specific particle size range can be obtained without modifying the precursor, and the adsorption performance of the prepared adsorbent is maintained at a high level.

[0006] The technical solution adopted by this application is:

[0007] On the one hand, a processing method of a lithium adsorbent precursor is provided, including the following steps:

[0008] S1. Prepare a mixed solution of a water-soluble lithium salt and a water-soluble aluminum salt, and adjust the pH in stages. The pH adjustment in stages includes dropping an alkali solution to a pH of 10 - 11 in the first stage and then stopping dropping, reacting for 0.2 - 0.5 h, and dropping an acid solution to a pH of 6 - 7 at an average pH change rate of 0.1 - 0.5 / min in the second stage to prepare the lithium adsorbent precursor;

[0009] S2. Filter out the lithium adsorbent precursor and use a combined comminution process to obtain a powder of the lithium adsorbent precursor. The combined comminution process includes first performing coarse crushing to a particle size of 500 μm ≤ D50 ≤ 1000 μm, then performing medium crushing to a particle size of 100 μm ≤ D50 ≤ 500 μm, and finally performing fine crushing to a particle size of D50 = 10 - 50 μm.

[0010] In some embodiments, in step S1, the water-soluble lithium salt is at least one of lithium acetate, lithium nitrate, lithium chloride, and lithium hydroxide.

[0011] In some embodiments, in step S1, the water-soluble aluminum salt is aluminum chloride and / or aluminum sulfate.

[0012] In some embodiments, in step S1, the alkali solution includes at least one of sodium hydroxide, potassium hydroxide, and lithium hydroxide.

[0013] In some embodiments, in step S1, the acid solution includes at least one of hydrogen chloride, sulfuric acid, phosphoric acid, and nitric acid.

[0014] In some embodiments, in step S1, the lithium adsorbent precursor is LiCl·3Al(OH)3·nH2O, where n satisfies 8 ≤ n ≤ 10.

[0015] In some embodiments, the device for coarse crushing generally uses a conventional comminution device in the art, such as a jaw crusher. The medium crushing generally uses a ball mill. Preferably, a wet ball milling process is used. The fine crushing generally can use a ball mill or a jet mill.

[0016] In this application, for example, during the coarse crushing process, fine powder may be generated, resulting in a too small D50 and unable to meet the requirements. At this time, screening or classification means can be used to achieve the particle size range in the coarse crushing stage. For example, the material is first passed through a 1000 μm sieve to remove particles larger than 1000 μm, and then through a 500 μm sieve to remove particles smaller than 500 μm. The particles remaining on the 500 μm sieve are the target products. Medium crushing and fine crushing can also be combined with screening or classification processes.

[0017] In some embodiments, in step S2, the time for coarse crushing is 10 - 30 min, the time for medium crushing is 15 - 30 min, and the time for fine crushing is 5 - 20 min.

[0018] In some embodiments, in step S2, a common filter can generally be used as the filtering device.

[0019] In some embodiments, in step S2, before adopting the combined crushing process, it may further include the step of washing the filtered precursor and then naturally drying it.

[0020] On the other hand, the present application also provides a lithium adsorbent precursor prepared by the above processing method.

[0021] Compared with the prior art, the present application has the following advantages:

[0022] By adopting a segmented regulation system for the pH value, the present application helps to control the crystal growth and morphology. According to the characteristics of the precursor itself, it guides the crystal to grow and optimize along a specific direction, which is beneficial to obtaining a product with better crystallinity and more uniform particle size distribution. And in the second stage, by controlling the pH change rate, it is beneficial to avoid agglomeration or non-uniformity caused by rapid pH changes, and at the same time, it can inhibit the risk of dissolution loss caused by the relatively unstable structure that may exist on the surface of the particles. Cooperating with gradually crushing the particles to a suitable particle size range can increase the reactive active sites of the adsorbent and more stably expose them to the external environment, increasing the contact opportunity with lithium ions. At the same time, it can also reduce energy consumption. The whole process of gradual crushing only takes 30 - 80 min, avoiding the high energy consumption problem caused by one-time crushing, and is especially suitable for large-scale production.

[0023] Finally, the present application can achieve the highest adsorption capacity of up to 6.93 mg / g for the lithium adsorbent without modifying the precursor, and the dissolution loss rate of the adsorbent after 5 cycles can still be maintained below 0.035%, with the lowest being 0.002%, providing a new idea for the processing and preparation of the adsorbent precursor. Specific Embodiments

[0024] To make the above objects, features, and advantages of the present application more obvious and understandable, the following specific embodiments are used to elaborate the specific implementation manners of the present application in detail. The following embodiments are exemplary and are only used to explain the present embodiment, and should not be construed as a limitation to the present embodiment.

[0025] In the description of this embodiment, "several" means one or more, "multiple" means two or more, and understandings such as "greater than", "less than", "exceeding", etc. do not include the present number, and understandings such as "above", "below", "within", etc. include the present number. If the first and second are described only for the purpose of distinguishing technical features, they cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features or implicitly indicating the sequence relationship of the indicated technical features.

[0026] In the description of this embodiment, it should be noted that all ranges disclosed in this application will be understood to cover any and all sub-ranges subsumed therein. For example, the stated range "3% to 20%" should be considered to include any and all of the following sub-ranges: starting with a minimum value of 3% or greater and ending with a maximum value of 20% or less, such as 4% to 19%, or 4.5% to 15%, or 12% to 13%. At the same time, all ranges disclosed in this application are also considered to include the endpoints of the stated range, unless otherwise clearly stated. For example, a range "between 4 and 6" or "4 to 6" or "4 - 6" should generally be considered to include the endpoints 4 and 6.

[0027] In related technologies, in order to improve the performance of adsorbents, generally, the focus is mainly on the improvement of adsorbent precursors, and at this time, new impurity elements usually need to be introduced. To solve the above problems, this embodiment provides a processing method for a lithium adsorbent precursor, including the following steps:

[0028] S1. Prepare a mixed solution of a water-soluble lithium salt and a water-soluble aluminum salt, and adjust the pH in stages. The stagewise pH adjustment includes dropping an alkali solution to a pH of 10 - 11 in the first stage and then stopping dropping, reacting for 0.2 - 0.5 h, and in the second stage, dropping an acid solution to a pH of 6 - 7 at an average pH change rate of 0.1 - 0.5 / min to prepare the lithium adsorbent precursor.

[0029] Preferably, in the second stage, the acid solution is dropped to a pH of 6.5 - 7 at an average pH change rate of 0.2 - 0.4 / min.

[0030] During the preparation of the precursor, the reasons for first adjusting the pH of the system to alkaline and then to slightly neutral are considered as follows: First, under alkaline conditions, some metal ions may form hydroxide precipitates, and these precipitates can serve as crystal nuclei in subsequent reactions to promote the growth and development of the lithium adsorbent precursor crystals. When adjusted to slightly neutral, the structure formed under alkaline conditions is finely tuned to further optimize the crystal structure of the precursor, making it more conducive to the adsorption of lithium ions. Second, under alkaline conditions, smaller particles or primary particles with specific morphologies may be generated, and then these particles further grow and aggregate under slightly neutral conditions to form a precursor with a suitable particle size and ideal morphology, which is beneficial to improving the specific surface area and adsorption performance of the adsorbent.

[0031] In some embodiments, the water-soluble lithium salt and the water-soluble aluminum salt are generally conventional in the art. For example, the water-soluble lithium salt can be at least one of lithium acetate, lithium nitrate, lithium chloride, and lithium hydroxide.

[0032] In some embodiments, the water-soluble aluminum salt can be aluminum chloride and / or aluminum sulfate.

[0033] In some embodiments, the alkali solution and the acid solution are generally conventional in the art. For example, the alkali solution can be at least one of sodium hydroxide, potassium hydroxide, and lithium hydroxide.

[0034] In some embodiments, the acid solution can be at least one of hydrogen chloride, sulfuric acid, phosphoric acid, and nitric acid.

[0035] In the present application, the lithium adsorbent precursor obtained through the processing technology is generally LiCl·3Al(OH)3·nH2O, where n satisfies 8≤n≤10.

[0036] S2. Filter out the lithium adsorbent precursor, and use a combined crushing process to obtain a lithium adsorbent precursor powder. The combined crushing process includes first performing coarse crushing to a particle size of 500μm≤D50≤1000μm, then performing medium crushing to a particle size of 100μm≤D50≤500μm, and finally performing fine crushing to a particle size of D50 = 10 - 50μm.

[0037] Among them, preferably, the coarse crushing is to a particle size of 600μm≤D50≤800μm, and more preferably 600μm≤D50≤700μm.

[0038] Among them, preferably, the medium crushing is to a particle size of 200μm≤D50≤400μm, and more preferably 200μm≤D50≤300μm.

[0039] Among them, preferably, the fine crushing is to a particle size of D50 of 15 - 25μm.

[0040] In some embodiments, a common filter can generally be used as the device for filtering out.

[0041] In some embodiments, the device for coarse crushing usually adopts a conventional crushing device in the art, such as a jaw crusher. The medium crushing generally adopts a ball mill. Preferably, a wet ball milling process is used. The fine crushing generally can adopt a ball mill or a jet mill. The operations of coarse crushing, medium crushing, and fine crushing to a suitable particle size range generally adopt conventional operating means in the art.

[0042] In this application, for example, fine powder may be produced during the coarse crushing process, resulting in a smaller D50 that cannot meet the requirements. In this case, screening or grading methods can be used to achieve the particle size range of the coarse crushing stage, such as first passing the material through a 1000μm sieve to remove particles larger than 1000μm, and then passing the material through a 500μm sieve to remove particles smaller than 500μm. The particles remaining on the 500μm sieve are the target products. Intermediate and fine crushing can also be combined with screening or grading processes.

[0043] In some embodiments, before the combined pulverization process is used, a step of washing the filtered precursor and then drying it naturally may be included.

[0044] In some embodiments, the time for the coarse crushing is 10-30 min, the time for the medium crushing is 15-30 min, and the time for the fine crushing is 5-20 min.

[0045] Preferably, the coarse crushing time is 10-18 min.

[0046] Preferably, the medium crushing time is 15-20 minutes.

[0047] Preferably, the crushing time is 5-6 minutes.

[0048] In the present application, in combination with the characteristics of the lithium adsorbent precursor itself, coarse crushing, medium crushing and airflow powder treatment are carried out in stages, and a crushing process for appropriate particle segments is set. This step-by-step crushing process can make the fine particles after airflow crushing have a larger specific surface area and more active sites, while also reducing energy consumption. The entire process only takes 30-80 minutes, avoiding the high energy consumption problem caused by one-time crushing.

[0049] On the other hand, the present application also provides a lithium adsorbent precursor prepared by the above preparation method.

[0050] The present application is further explained below in conjunction with embodiments.

[0051] All raw materials, reagents, etc. used without specifying the manufacturer are conventional products that can be purchased from the market.

[0052] Example 1

[0053] Example 1 of the present application provides a method for preparing an aluminum-based lithium adsorbent, comprising the following steps:

[0054] Preparation of precursor: In a reaction flask, 5 L of aluminum chloride solution with a concentration of 26.67 g / L and 2.8 L of lithium hydroxide solution with a concentration of 0.85 g / L were respectively prepared and mixed. The atomic ratio of Al to Li was Al:Li = 1:1. Then, the pH of the mixed solution was adjusted in stages while inserting an online pH meter for real-time monitoring. In the first stage, sodium hydroxide with a concentration of 5 M was added dropwise to the mixed solution system until the pH reached 11, and then the addition was stopped and the reaction was carried out for 0.2 h. In the second stage, hydrochloric acid with a concentration of 2 M was added dropwise to the mixed solution system at an average pH change rate of 0.4 / min until the pH reached 6.5.

[0055] Subsequently, the precipitate was filtered out with a filter, washed and then naturally dried. The combined comminution process was adopted. First, the precursor was coarsely crushed to a particle size D50 in the range of 600 μm - 800 μm by a jaw crusher, and the crushing time was 15 min. Then, it was ball-milled to a particle size D50 in the range of 200 μm - 400 μm, and the crushing time was 20 min. Finally, it was jet-milled to a particle size D50 of 25 μm, and the crushing time was 8 min to obtain the lithium adsorbent precursor LiCl·3Al(OH)3·nH2O powder.

[0056] Preparation of aluminum-based lithium adsorbent: 800 g of the precursor, 80 g of a mixed solution of polyvinyl chloride, tetrahydrofuran and dichloromethane were put into a closed stirrer and stirred until it became a paste. The slurry was put into an extruder, and then the obtained strip-shaped substance was cut into particles with a length of 1 mm and dried to obtain the aluminum-based lithium adsorbent.

[0057] Example 2

[0058] Example 2 of this application provides a method for preparing an aluminum-based lithium adsorbent, which is different from Example 1 in the preparation steps of the precursor.

[0059] Preparation of precursor: In a reaction flask, 5 L of aluminum chloride solution with a concentration of 26.67 g / L and 2.8 L of lithium hydroxide solution with a concentration of 0.85 g / L were respectively prepared and mixed. The atomic ratio of Al to Li was Al:Li = 1:1. Then, the pH of the mixed solution was adjusted in stages while inserting an online pH meter for real-time monitoring. In the first stage, sodium hydroxide with a concentration of 5 M was added dropwise to the mixed solution system until the pH reached 11, and then the addition was stopped and the reaction was carried out for 0.4 h. In the second stage, hydrochloric acid with a concentration of 2 M was added dropwise to the mixed solution system at an average pH change rate of 0.2 / min until the pH reached 7.

[0060] Subsequently, the precipitate was filtered out with a filter, washed and then air-dried naturally. The combined crushing process was adopted. First, the precursor was coarsely crushed by a jaw crusher to a particle size D50 in the range of 600 μm - 700 μm, and the crushing time was 18 min. Then, it was crushed by a ball mill to a particle size D50 in the range of 200 μm - 300 μm, and the crushing time was 20 min. Finally, it was subjected to jet milling to a particle size D50 of 20 μm, and the crushing time was 6 min to obtain the lithium adsorbent precursor LiCl·3Al(OH)3·nH2O powder.

[0061] Example 3

[0062] Example 3 of this application provides a preparation method of an aluminum-based lithium adsorbent, which is different from Example 1 in the preparation steps of the precursor.

[0063] Preparation of the precursor: In a reaction flask, 5 L of an aluminum chloride solution with a concentration of 26.67 g / L and 2.8 L of a lithium hydroxide solution with a concentration of 0.85 g / L were respectively prepared and mixed. The atomic ratio of Al to Li was 1:1. Then, the pH of the mixed solution was adjusted in stages, and an online pH meter was inserted for real-time monitoring. In the first stage, sodium hydroxide with a concentration of 5 M was added dropwise to the mixed solution system until the pH reached 11, and then the addition was stopped. The reaction was carried out for 0.4 h. In the second stage, hydrochloric acid with a concentration of 2 M was added dropwise to the mixed solution system at an average pH change rate of 0.3 / min until the pH reached 6.3.

[0064] Subsequently, the precipitate was filtered out with a filter, washed and then air-dried naturally. The combined crushing process was adopted. First, the precursor was coarsely crushed by a jaw crusher to a particle size D50 in the range of 800 μm - 1000 μm, and the crushing time was 10 min. Then, it was crushed by a ball mill to a particle size D50 in the range of 300 μm - 500 μm, and the crushing time was 20 min. Finally, it was subjected to jet milling to a particle size D50 of 50 μm, and the crushing time was 6 min to obtain the lithium adsorbent precursor LiCl·3Al(OH)3·nH2O powder.

[0065] Example 4

[0066] Example 4 of this application provides a preparation method of an aluminum-based lithium adsorbent, which is different from Example 1 in the preparation steps of the precursor.

[0067] Preparation of the precursor: Prepare 5 L of aluminum chloride solution with a concentration of 26.67 g / L and 2.8 L of lithium hydroxide solution with a concentration of 0.85 g / L in a reaction flask and mix them. The atomic ratio of Al to Li is 1:1. Then, adjust the pH of the mixed solution in stages while inserting an on-line pH meter for real-time monitoring. In the first stage, add 5 M sodium hydroxide to the mixed solution system dropwise until the pH reaches 10, then stop adding and react for 0.2 h. In the second stage, add 2 M hydrochloric acid to the mixed solution system dropwise at an average pH change rate of 0.2 / min until the pH reaches 6.

[0068] Subsequently, filter out the precipitate with a filter, wash it, and air-dry it naturally. Adopt a combined comminution process. First, use a jaw crusher to coarsely crush the precursor to a particle size D50 in the range of 500 μm - 600 μm, and the comminution time is 20 min. Then, use a ball mill to crush it to a particle size D50 in the range of 100 μm - 200 μm, and the comminution time is 20 min. Finally, perform jet milling to a particle size D50 of 15 μm, and the comminution time is 10 min to obtain the lithium adsorbent precursor LiCl·3Al(OH)3·nH2O powder.

[0069] Example 5

[0070] Example 5 of this application provides a preparation method of an aluminum-based lithium adsorbent. The difference from Example 1 is only that the pH is adjusted to 6 in the second stage.

[0071] Example 6

[0072] Example 6 of this application provides a preparation method of an aluminum-based lithium adsorbent. The difference from Example 1 is only the combined comminution process. First, use a jaw crusher to coarsely crush the precursor to a particle size D50 in the range of 600 μm - 700 μm, and the comminution time is 18 min. Then, use a ball mill to crush it to a particle size D50 in the range of 200 μm - 300 μm, and the comminution time is 20 min. Finally, perform jet milling to a particle size D50 of 15 μm, and the comminution time is 6 min to obtain the lithium adsorbent precursor LiCl·3Al(OH)3·nH2O powder.

[0073] Example 7

[0074] Example 7 of this application provides a preparation method of an aluminum-based lithium adsorbent. The difference from Example 1 is only that the average pH change rate in the second stage is 0.1 / min.

[0075] Example 8

[0076] Example 8 of this application provides a preparation method of an aluminum-based lithium adsorbent. The difference from Example 1 is only that in the first stage, 5 M sodium hydroxide is added dropwise to the mixed solution system until the pH reaches 11, then stop adding and react for 0.5 h.

[0077] Comparative Example 1

[0078] Compared with Example 4, the difference is only that in the first stage, sodium hydroxide with a concentration of 5 M is added dropwise to the mixed solution system until the pH reaches 12.

[0079] Comparative Example 2

[0080] Compared with Example 4, the difference is only that the step of adjusting the pH in stages is not carried out, and sodium hydroxide is directly added dropwise until the pH reaches 6.

[0081] Comparative Example 3

[0082] Compared with Example 4, the difference is only that the pH adjustment reaction is carried out for 1.0 h in the first stage.

[0083] Comparative Example 4

[0084] Compared with Example 4, the difference is only that the average pH change rate in the second stage is 1.2 / min.

[0085] Comparative Example 5

[0086] Compared with Example 4, the difference is only that one-step air jet milling is directly carried out until the particle size D50 is 15 μm, and the milling time is 4.5 h.

[0087] Comparative Example 6

[0088] Compared with Example 4, the difference is only that only two-step milling is carried out, that is, ball milling is used to mill to a particle size D50 in the range of 100 μm - 200 μm, the milling time is 45 min, and then air jet milling is carried out until the particle size D50 is 15 μm, and the milling time is 2 h.

[0089] Comparative Example 7

[0090] Compared with Example 4, the difference is only that only two-step milling is carried out, that is, the precursor is milled to a particle size D50 in the range of 300 μm - 450 μm using a jaw crusher, the milling time is 30 min, and then air jet milling is carried out until the particle size D50 is 15 μm, and the milling time is 3 h.

[0091] Comparative Example 8

[0092] Compared with Example 2, the difference is that the preparation method of the precursor refers to the prior art CN106673023B and includes the following steps:

[0093] Preparation of the precursor: In a reaction flask, 5 L of an aluminum chloride solution with a concentration of 26.67 g / L and 2.8 L of a lithium hydroxide solution with a concentration of 0.85 g / L are respectively prepared and mixed. The atomic ratio of Al to Li is Al:Li = 1:1. Then, a NaOH solution is added until the pH reaches 7.

[0094] At room temperature, the mixture after the above reaction is stirred for 30 minutes, and then the precipitate is filtered out with a filter, washed and air-dried naturally to obtain the active ingredient substance of LiCl·3Al(OH)3·nH2O (8≤n≤10); subsequently, the active substance with hydrate is crushed into particles and sieved with a 60-mesh sieve to obtain powdery particles of 20 μm.

[0095] Effect examples

[0096] Adsorption capacity detection

[0097] Put 3 kg of lithium-enriched material into a reaction tube with a diameter of 10 cm, and the salt lake brine passes through the tower at a speed of 8 cubic decimeters per hour. After 4 hours of treatment, the lithium-enriched material in adsorption steady state is obtained. Subsequently, the lithium-enriched material in adsorption steady state is desorbed with distilled water, and the lithium is collected by removing impurities through a filter membrane and the weight is calculated, and this weight is the adsorption capacity (mg / g).

[0098] Dissolution loss rate detection

[0099] Repeat the above adsorption capacity experiment 5 times, finally measure the weight of the lithium-enriched material, and divide it by the initial 3 kg to obtain the dissolution loss rate.

[0100] Table 1 shows the condition settings of each example and comparative example.

[0101] Table 1

[0102]

[0103]

[0104] Table 2 shows the adsorption performance and dissolution loss rate results of the aluminum-based lithium adsorbents prepared in different examples and comparative examples.

[0105] Table 2

[0106] Number Li adsorption capacity / (mg / g) Dissolution loss rate after 5 cycles / % Example 1 5.76 0.018 Example 2 6.93 0.002 Example 3 5.32 0.023 Example 4 5.01 0.035 Example 5 5.54 0.021 Example 6 6.32 0.010 Example 7 5.97 0.014 Example 8 6.06 0.012 Comparative Example 1 4.04 0.162 Comparative Example 2 3.34 0.327 Comparative Example 3 4.73 0.102 Comparative Example 4 3.91 0.178 Comparative Example 5 3.83 0.189 Comparative Example 6 3.42 0.283 Comparative Example 7 3.65 0.311 Comparative Example 8 3.20 0.536

[0107] Combined with the data in Table 2, by comparing Example 4 with Comparative Examples 1-2, it can be seen that first adjusting the pH of the system to alkaline and then gradually adjusting it to 6-7 helps to control crystal growth and morphology, thereby obtaining a product with better crystallinity and more uniform particle size distribution, which is beneficial to improving the quality and performance of the product; and under different pH conditions, the existence forms and chemical activities of aluminum salts and lithium salts are different. By adjusting to near-neutrality with alkali first and then acid, the ion concentration and chemical equilibrium in the system can be in a relatively stable state, which is beneficial to subsequent possible other reaction or treatment operations and avoids problems such as reaction runaway and product decomposition caused by too high or too low pH. In addition, the pH value in the first stage should not be too high, which will cause a sharp decline in the adsorption performance of the prepared adsorbent product. This is because in this environment, excessive OH- in the solution will compete with lithium ions for adsorption sites, resulting in a decrease in the adsorption amount of lithium ions. Therefore, the pH value should be strictly controlled within an appropriate range in the first stage to ensure that the performance of the adsorbent reaches the best.

[0108] By comparing Example 4 with Comparative Example 5, it can be seen that by performing coarse crushing, medium crushing and air flow crushing in stages, larger pieces of the lithium adsorbent precursor can be quickly broken into smaller particles first, accelerating the efficiency of subsequent medium crushing and fine crushing; then medium crushing can further increase the specific surface area of the lithium adsorbent precursor; finally, breaking the lithium adsorbent precursor into smaller particles can provide more active adsorption sites. Such a step-by-step crushing process can make the fine particles after air flow crushing have a larger specific surface area and more active sites, which is crucial for improving the adsorption performance and adsorption capacity of the lithium adsorbent, especially in application scenarios with higher requirements for adsorption efficiency, and the effect is more obvious.

[0109] By comparing Example 4 with Comparative Examples 5-7, it can be clearly found that staged crushing is beneficial to energy conservation, reduces the crushing time, from 4.5 h required for one-step crushing to 20 microns to 50 min for staged crushing, and the cost is also greatly reduced, avoiding the high energy consumption problem caused by one-time crushing, and is especially suitable for large-scale production.

[0110] By comparing Example 4 with Comparative Examples 3 and 4, it is found in this application that if the time of maintaining the alkaline environment and the rate of adjusting to the end-point pH are controlled during the staged pH adjustment process, the formation of a high-quality precursor can be more effectively achieved, thereby preparing an adsorbent product with stronger adsorption performance and lower dissolution loss rate.

[0111] By comparing Example 4 and Comparative Example 8, it can be seen that the technical solution of the present application is to first optimize the crystal structure by adjusting the pH in segments, making the internal structure of the adsorbent more conducive to the diffusion and fixation of lithium ions; then crush the particles to a suitable particle size through a segmented crushing process to ensure that the active sites are fully exposed and the overall structure is reasonable. The two work together to improve the lithium ion adsorption capacity of the adsorbent in multiple aspects, making the adsorption performance reach the best state, and at the same time ensuring a low dissolution loss rate of the adsorbent product.

[0112] The above is a further detailed description of the present application, and it should not be regarded as a limitation to the specific implementation of the present application. For those of ordinary skill in the technical field to which the present application belongs, any simple deduction or replacement without departing from the concept of the present application falls within the protection scope of the present application.

Claims

1. A processing method for a lithium adsorbent precursor, characterized in that, It includes the following steps: S1. Prepare a mixed solution of a water-soluble lithium salt and a water-soluble aluminum salt, and adjust the pH in stages. The pH adjustment in stages includes stopping the addition of an alkali solution after dropping it to a pH of 10 - 11 in the first stage and reacting for 0.2 - 0.5 h, and dropping an acid solution at an average pH change rate of 0.1 - 0.5 / min to a pH of 6 - 7 in the second stage to prepare a lithium adsorbent precursor; S2. Filter out the lithium adsorbent precursor, and use a combined crushing process to obtain a lithium adsorbent precursor powder. The combined crushing process includes first performing coarse crushing to a particle size of 500 μm ≤ D50 ≤ 1000 μm, then performing medium crushing to a particle size of 100 μm ≤ D50 ≤ 500 μm, and finally performing fine crushing to a particle size of D50 = 10 - 50 μm.

2. The processing method according to claim 1, wherein In step S1, the water-soluble lithium salt is at least one of lithium acetate, lithium nitrate, lithium chloride, and lithium hydroxide.

3. The processing method according to claim 1, characterized in that, In step S1, the water-soluble aluminum salt is aluminum chloride and / or aluminum sulfate.

4. The processing method according to claim 1, characterized in that, In step S1, the alkali solution includes at least one of sodium hydroxide, potassium hydroxide, and lithium hydroxide.

5. The processing method according to claim 1, wherein In step S1, the acid solution includes at least one of hydrogen chloride, sulfuric acid, phosphoric acid, and nitric acid.

6. The processing method according to claim 1, wherein, In step S1, the lithium adsorbent precursor is LiCl·3Al(OH)3·nH2O, where n satisfies 8 ≤ n ≤ 10.

7. The processing method according to claim 1, characterized in that, In step S2, the time for coarse crushing is 10 - 30 min, the time for medium crushing is 15 - 30 min, and the time for fine crushing is 5 - 20 min.

8. A lithium adsorbent precursor prepared by the processing method according to any one of claims 1 - 7.

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