Lithium adsorbent and preparation method therefor

Abstract

The present disclosure provides a lithium adsorbent and a preparation method therefor. On the basis of the special morphology and size design of the tubular lithium adsorbent, the lithium adsorbent has good adsorption capacity, desorption capacity, adsorption rate and desorption rate as well as excellent magnesium-lithium separation efficiency, and also has good structural strength; thus, the lithium adsorbent has long service life and low pulverization rate.

Description

Lithium adsorbent and preparation method thereof

[0001] This disclosure claims priority to Chinese patent application number 202311777154.7, filed with the Patent Office of China on December 21, 2023, entitled “Lithium Adsorbent and Preparation Method Thereof,” the entire contents of which are incorporated herein by reference. Technical Field

[0002] The present disclosure relates to the technical field of lithium adsorbents, and in particular to lithium adsorbents and preparation methods thereof. Background Art

[0003] Lithium has a strong ability to gain and lose electrons and is one of the important raw materials for battery materials. With the development of the new energy industry, the global demand for lithium has increased dramatically. Lithium exists in two main forms in nature: one is in the form of lithium ore, and the other is in the form of lithium ions in brine such as salt lake brine. my country has large reserves of lithium resources in salt lakes, but the problem of excessively high magnesium-lithium ratios is common, so large-scale development and application have not been achieved. In recent years, the process of extracting lithium from salt lake brines with high magnesium-lithium ratios by adsorption has been widely favored, but the technical difficulty of the above process lies in the development of lithium adsorbents with excellent performance. The lithium adsorbent particles commonly used in industry currently generally have high strength, but limited adsorption / desorption effects, or have acceptable adsorption and desorption amounts, but low strength, high pulverization rate, and short service life.

[0004] Summary of the Invention

[0005] In view of this, the embodiments of the present disclosure provide a lithium adsorbent and a preparation method thereof. Based on the special morphology and size design of the lithium adsorbent, it has good adsorption capacity and desorption amount, adsorption rate and desorption rate, and better magnesium-lithium screening rate, while also having good structural strength, thereby having a long service life and a low pulverization rate.

[0006] In a first aspect of an embodiment of the present disclosure, a lithium adsorbent is provided, which is tubular and includes a skeleton structure and one or more through-holes along its length; the inner diameter of the pores is 0.1 mm to 0.7 mm, and the wall thickness of the lithium adsorbent is 0.2 mm to 1 mm; the skeleton structure of the lithium adsorbent includes a polymer matrix and adsorbent particles dispersed in the polymer matrix.

[0007] In the above-mentioned lithium adsorbent, the adsorbent particles are dispersed in a polymer matrix, which can reduce the risk of adsorbent particle pulverization and shedding, thereby improving the service life of the lithium adsorbent to a certain extent. The lithium adsorbent also has a suitable pore inner diameter, which not only allows brine to infiltrate and fill its pores, allowing it to fully interact with the adsorbent particles, but also significantly improves the adsorption efficiency and magnesium-lithium screening rate of the lithium adsorbent. In addition, the appropriate wall thickness can also enhance the structural strength of the lithium adsorbent, further reducing the pulverization rate, thereby improving the cycle performance and service life of lithium adsorption. Therefore, the above-mentioned lithium adsorbent can take into account high lithium ion adsorption / desorption efficiency, good magnesium-lithium screening rate, and long cycle life.

[0008] A second aspect of an embodiment of the present disclosure provides a method for preparing a lithium adsorbent, comprising: mixing the polymer matrix, the adsorbent particles, and a solvent to obtain a first material; placing the first material and the second material in a accommodating cavity of a spinning device, and spinning them according to a preset size using a coaxial spinning process, so that the first material and the second material serving as a core liquid are coaxially extruded to obtain initial fibers; wherein the second material includes a substance that cannot be solidified during the spinning process; and solidifying and cutting the initial fibers to obtain the lithium adsorbent.

[0009] The preparation method has simple steps, strong process reliability, high process flexibility, high production efficiency, and is suitable for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG1A is a schematic structural diagram of a cross section of a lithium adsorbent provided in one embodiment of the present disclosure.

[0011] FIG. 1B is a schematic structural diagram of a longitudinal section of the lithium adsorbent in FIG. 1A .

[0012] FIG2 is a schematic structural diagram of a cross section of a lithium adsorbent provided in another embodiment of the present disclosure.

[0013] (a), (b), and (c) in FIG3 are scanning electron microscope (SEM) photos of the outer surface of the lithium adsorbent of Example 3 at different magnifications.

[0014] (a), (b), and (c) in FIG4 are scanning electron microscope (SEM) images of the cross section of the lithium adsorbent of Example 3 at different magnifications.

[0015] (a) and (b) in FIG5 are scanning electron microscope (SEM) images of the surface of the lithium adsorbent facing the pores in Example 3 at different magnifications.

[0016] FIG6 is a SEM photograph of a cross section of the lithium adsorbent of Example 5.

[0017] FIG7 shows the pulverization test results of the lithium adsorbent of Example 3 in water.

[0018] FIG8 is a pulverization test result of the lithium adsorbent of Comparative Example 1 in water.

[0019] FIG9 is a pulverization test result of the lithium adsorbent of Comparative Example 2 in water.

[0020] Explanation of the accompanying figures: 100 - lithium adsorbent; 10 - skeleton structure; 11 - polymer matrix; 12 - adsorbent particles; 20 - pores DETAILED DESCRIPTION

[0021] In order to simultaneously improve the adsorption / desorption effect and service life of the lithium adsorbent, an embodiment of the present disclosure provides a lithium adsorbent. Specifically, referring to Figures 1A-2, the lithium adsorbent 100 provided in the embodiment of the present disclosure is tubular, comprising a skeleton structure 10 and one or more through-holes 20 along its length. The inner diameter (d1) of the pore 20 is 0.1mm-0.7mm, and the wall thickness (d2) of the lithium adsorbent is 0.2mm-1mm. The skeleton structure 10 comprises a polymer matrix 11 and adsorbent particles 12 dispersed in the polymer matrix 11. It should be noted that Figures 1A-2 are exemplary structural diagrams, and the distribution position, number, and size of the adsorbent particles in the figures are not limited to the examples in the figures. Among them, the cross section is a cross section obtained by cutting the lithium adsorbent 100 with a plane perpendicular to the length direction of the lithium adsorbent 100; the longitudinal section is a cross section obtained by cutting the lithium adsorbent 100 with a plane parallel to the length direction of the lithium adsorbent 100 and through a pore 20 of the lithium adsorbent 100.

[0022] In the lithium adsorbent 100, adsorbent particles 12 capable of adsorption / desorption are dispersed within the polymer matrix 11, reducing the risk of pulverization of the adsorbent particles 12 and, to a certain extent, improving its service life. When the lithium adsorbent 100 is mixed with brine, the brine can infiltrate the outer surface of the lithium adsorbent 100 (i.e., the surface of the skeleton 10 facing away from the pores 20). Due to the suitable inner diameter, the brine is induced to infiltrate and fill the pores 20, promoting brine adsorption through the pore 20 surfaces. When the brine is further stirred, the brine can diffuse from the inner and outer surfaces and end faces of the lithium adsorbent 100 into the interior of the lithium adsorbent 100, thereby smoothly infiltrating the lithium adsorbent 100 from the inner surface (the pore walls of the pores 20). Similarly, during the elution and desorption processes, the eluent and desorbent (e.g., water) can also infiltrate the lithium adsorbent 100 from both the inner and outer surfaces. This significantly improves the adsorption capacity and rate of the lithium adsorbent 100 during the adsorption process, the desorption capacity and rate during the desorption process, and the elution efficiency of impurity ions (such as magnesium ions), making it easier to obtain a desorption solution with a low magnesium-lithium ratio and a high lithium content. Furthermore, a suitable wall thickness and inner diameter can significantly enhance the adsorption efficiency of the lithium adsorbent 100 while increasing its strength and further reducing its pulverization rate, thereby significantly improving the cycle performance and service life of the lithium adsorbent 100.

[0023] For example, the inner diameter of the pores 20 may be, but is not limited to, 0.10 mm, 0.15 mm, 0.20 mm, 0.25 mm, 0.30 mm, 0.35 mm, 0.40 mm, 0.45 mm, 0.50 mm, 0.55 mm, 0.60 mm, 0.65 mm, or 0.70 mm. Considering that brine generally has a certain viscosity, if the inner diameter of the pores 20 is too small (<0.1 mm), it is difficult for the brine to completely infiltrate the inner wall of the pores 20, and it is not possible to smoothly infiltrate the entire pore of the lithium adsorbent 100, so that the surface of the pores 20 cannot be exposed to the brine in a short time, which seriously affects the adsorption capacity and rate. On the other hand, if the inner diameter of the pores 20 is too large (>0.7 mm), it will affect the strength of the lithium adsorbent 100, shorten its service life, and reduce the packing density of the lithium adsorbent 100, affecting the adsorption effect of lithium in the brine.

[0024] In the embodiments of the present disclosure, the inner diameter (d1) of the pore 20 refers to the average value of the maximum transverse dimension of the pore 20 along a cross-section of the lithium adsorbent 100. The cross-section is the cross-section of the lithium adsorbent 100 cut perpendicular to its length. For a lithium adsorbent 100 containing only one pore 20, the data from three cross-sections at both ends and the middle are averaged to obtain the inner diameter of the tubular lithium adsorbent pore 20. For a lithium adsorbent 100 containing multiple pores 20, the dimensions of each pore 20 at the three locations are measured and the inner diameter of each pore 20 is calculated. The inner diameter of each pore 20 must be within the range of 0.1 mm to 0.7 mm. The inner diameters of multiple pores 20 can be the same or different. In the embodiments of the present disclosure, the inner diameter of the pore 20 can be measured using an optical microscope or a scanning electron microscope (SEM). The cross-section of the lithium adsorbent 100 can be prepared using a brittle fracture method.

[0025] In some embodiments of the present disclosure, the skeleton structure 10 is a porous structure. Thus, the lithium adsorbent has a multidimensional pore structure, which can increase the specific surface area of ​​the lithium adsorbent 100, allowing brine to better penetrate the skeleton structure 10 and fully contact the adsorbent particles 12 dispersed in the polymer matrix 11, thereby fully utilizing the adsorption and desorption capabilities of the lithium adsorbent 100. Specifically, the porous structure within the skeleton structure 10 is primarily formed by stacking the adsorbent particles 12, and the polymer matrix 11 for adhering / fixing the adsorbent particles is located between the adsorbent particles 12. This allows the specific surface area of ​​the skeleton structure 10 to be controlled within a suitable range. Furthermore, the total pore volume and specific surface area of ​​the lithium adsorbent 100 can be controlled within a suitable range.

[0026] When the skeleton structure 10 is a porous structure, in some embodiments of the present disclosure, the BET specific surface area of ​​the lithium adsorbent 100 is ≥17 m 2 / g; for example, 17m 2 / g-22m 2 / g. In the embodiment of the present disclosure, a gas adsorption desorption instrument is used to test the BET specific surface area of ​​the lithium adsorbent 100. For example, the BET specific surface area of ​​the lithium adsorbent 100 can be, but is not limited to, 17m 2 / g, 17.5m 2 / g、18m 2 / g, 18.5m 2 / g、19m 2 / g, 19.5m 2 / g, 20m 2 / g, 20.5m 2 / g, 21m 2 / g, 21.5m2 / g, 22.0m 2 It can be understood that the adsorbent particles 12 themselves have a porous structure, so the above BET surface area includes the pores 20, the porous structure of the skeleton structure 10 and the porous structure of the adsorbent particles 12.

[0027] In some specific embodiments, the pores on the surface of the skeleton structure 10 facing the pores 20 and on the surface facing away from the pores 20 have a pore diameter of 10 nm to 200 nm. In some embodiments of the present disclosure, during the preparation of the lithium adsorbent 100, the matrix and adsorbent particles are dispersed in a solvent. In this case, the pores on the surface of the skeleton structure 10 are primarily formed by the solvent precipitating from the skeleton structure during the preparation of the lithium adsorbent 100. This facilitates the penetration of brine and desorbent, while ensuring good mechanical properties of the skeleton structure 10 and further reducing the pulverization rate of the adsorbent particles 12. This improves the mechanical properties and cyclic stability of the lithium adsorbent 100, extending its service life while ensuring the adsorption efficiency of the lithium adsorbent 100 and, to a certain extent, improving the magnesium-lithium selectivity of the lithium adsorbent 100. For example, the pore diameters of the pores may be, but are not limited to, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, etc. In the disclosed embodiment, SEM may be used to characterize the pore diameters of the pores on the surface of the skeleton structure 10 facing the pore channel 20 and on the surface facing away from the pore channel 20.

[0028] In the disclosed embodiment, the wall thickness of the lithium adsorbent 100 can be measured simultaneously with the inner diameter of the pore 20. Specifically, the wall thickness of the lithium adsorbent 100 is determined by measuring the wall thickness at three locations (ends and the middle) on a cross section of the lithium adsorbent 100 having only one pore 20, and then taking the average value. In particular, for the lithium adsorbent 100 containing multiple channels 20, the minimum distance from each channel to the outer surface of the skeleton structure (the surface away from the channel) is measured and recorded as a, and the minimum spacing between two adjacent channels is recorded as b. The minimum value of a and b is taken as the wall thickness of the lithium adsorbent 100 on the cross section. The wall thickness of the lithium adsorbent 100 corresponding to each channel is within the range of 0.2mm-1mm; similarly, for the lithium adsorbent containing multiple channels 20, it is also necessary to measure the wall thickness corresponding to different channels 20 on the cross section of the lithium adsorbent 100 at three different positions (two ends and the middle position). For each channel 20, the average value of the three corresponding wall thicknesses is taken as the wall thickness corresponding to the channel 20.

[0029] For example, the wall thickness of the lithium adsorbent 100 (d2) can be, but is not limited to, 0.20 mm, 0.25 mm, 0.30 mm, 0.35 mm, 0.40 mm, 0.45 mm, 0.50 mm, 0.55 mm, 0.60 mm, 0.65 mm, 0.70 mm, 0.75 mm, 0.80 mm, 0.85 mm, 0.90 mm, 0.95 mm, 1.00 mm, etc. A smaller wall thickness of the lithium adsorbent 100 may facilitate the diffusion of brine, eluent, and desorbent within the lithium adsorbent 100. However, if the thickness of the lithium adsorbent 100 is too small (<0.2 mm), its strength and service life may be seriously affected. If the thickness of the lithium adsorbent 100 is too large (>1 mm), the adsorption / desorption rate of the lithium adsorbent 100 is reduced, the adsorption / desorption amount is reduced, and the residual impurity ions (e.g., magnesium ions) in the desorbent are increased.

[0030] In the embodiment of the present disclosure, the number of pores 20 in the lithium adsorbent 100 may be one or more, such as 2, 3, 4, 5, 6, etc. In the embodiment of the present disclosure, when the lithium adsorbent 100 has multiple pores 20 extending therethrough, their relative positions are not restricted, and the parameters corresponding to each pore 20 may conform to the parameter limitations of the embodiment of the present disclosure. For example, it can be understood that the distribution of multiple channels 20 on the end surface of the lithium adsorbent 100 is described below: when there are three channels, the holes of the three channels 20 on the end surface of the lithium adsorbent 100 can be arranged in a triangular arrangement or a simple horizontal arrangement; when there are four channels, the holes of the four channels 20 on the end surface of the lithium adsorbent 100 can be arranged in a rectangular arrangement, a diamond arrangement, or a horizontal arrangement. The horizontal arrangement can be a single row or multiple rows; it can also be arranged in other ways around a hole; when there are five channels, the holes of the five channels 20 on the end surface of the lithium adsorbent 100 can be arranged in a pentagonal arrangement, or in other ways around a hole, or even in a horizontal arrangement. The horizontal arrangement can be a single row or multiple rows. Those skilled in the art can make analogies based on the above examples and make choices based on actual production conditions.

[0031] In some embodiments of the present disclosure, the ratio of the inner diameter to the wall thickness of the pores 20 is 1:(0.3-2). This allows the lithium adsorbent 100 to better balance strength and adsorption performance, where adsorption performance includes adsorption capacity, adsorption rate, and magnesium-lithium selectivity. For example, the ratio of the inner diameter to the wall thickness of the pores 20 can be, but is not limited to, 1:03, 1:05, 1:0.6, 1:0.8, 1:1.0, 1:1.2, 1:1.5, 1:1.6, 1:1.8, 1:2.0, etc.

[0032] In some embodiments of the present disclosure, referring to FIG. 1B , the length L of the lithium adsorbent 100 is between 0.5 mm and 3 mm. Controlling the length of the lithium adsorbent 100 within this range can provide the lithium adsorbent 100 with a larger specific surface area, facilitate complete infiltration of brine with a certain viscosity into and filling the pores 20 of the lithium adsorbent 100, thereby allowing the lithium adsorbent 100 to fully volatilize its adsorption capacity. Furthermore, this helps increase the packing density of the lithium adsorbent 100, thereby improving lithium extraction efficiency. For example, the length of the lithium adsorbent 100 can be, but is not limited to, 0.5 mm, 0.75 mm, 1.0 mm, 1.25 mm, 1.5 mm, 1.75 mm, 2.0 mm, 2.25 mm, 2.5 mm, 2.75 mm, 3.0 mm, etc.

[0033] In some embodiments of the present disclosure, the polymer matrix 11 includes, but is not limited to, at least one of polyvinylidene fluoride, polyvinyl butyral, polyethersulfone, polysulfone, polyacrylonitrile, polyvinyl chloride, and polyethylene. In some specific embodiments, the above materials have certain mechanical properties, which are conducive to ensuring the high strength of the lithium adsorbent 100; in addition, the above materials have good solubility in organic materials and good spinnability, which are conducive to improving the production efficiency of the lithium adsorbent 100. In some specific embodiments, in order to increase the interaction between the polymer matrix 11 and the adsorbent particles 12 and further improve the structural stability of the lithium adsorbent 100, the above polymers can also be modified, specifically including but not limited to copolymerization modification. For example, a vinylidene fluoride monomer can be copolymerized with a small amount of an acrylic ester monomer to obtain a vinylidene fluoride-acrylic ester copolymer. Of course, other copolymer monomers can also be selected. Similarly, those skilled in the art can select the copolymerization modification of other polymers according to actual needs, which will not be described in detail here.

[0034] In some embodiments of the present disclosure, the adsorbent particles 12 include but are not limited to at least one of aluminum-based adsorbent particles, titanium-based adsorbent particles, and manganese-based adsorbent particles. For example, the material of the aluminum-based adsorbent particles is but is not limited to LiX·2Al(OH)3·nH2O (X is an inorganic acid radical ion, n>0). The material of the titanium-based adsorbent particles is but is not limited to H2TiO3 ion sieve, H4Ti5O 12 Ion sieve, etc. The material of manganese-based adsorbent particles 12 includes but is not limited to LiMnO4, LiMn2O4, Li 1.6 Mn 1.6 O4、Li 1.33 Mn 1.67 O4, etc.

[0035] In some embodiments of the present disclosure, the D50 particle size of the adsorbent particles 12 is between 0.01 μm and 10 μm. By controlling the D50 particle size of the adsorbent particles 12 within the above range, the adsorbent particles 12 themselves have a more suitable specific surface area, which is more conducive to the adsorption / desorption of lithium ions and improves the adsorption efficiency. In addition, the adsorbent particles 12 can also serve as a reinforcing phase to ensure the strength of the lithium adsorbent 100 and are evenly dispersed in the skeleton structure 10, thereby improving the uniformity of the lithium adsorbent 100. For example, the D50 particle size of the adsorbent particles 12 can be, but is not limited to, 0.01 μm, 0.02 μm, 0.05 μm, 0.1 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, etc. In the embodiments of the present disclosure, the D50 particle size of the adsorbed particles may be measured using SEM.

[0036] In some embodiments of the present disclosure, the surface of the pores 20 is modified with hydrophilic particles. That is, the inner surface of the lithium adsorbent 100 is modified with hydrophilic particles. This significantly improves the hydrophilicity of the inner surface (pore wall) of the lithium adsorbent 100, making it easier for brine to contact and infiltrate the inner surface of the lithium adsorbent 100, thereby promoting the adsorption of brine on the inner surface of the lithium adsorbent 100 and thereby improving the adsorption efficiency of the lithium adsorbent 100. In the embodiments of the present disclosure, the material of the hydrophilic particles can be any hydrophilic material known in the art. In some specific embodiments, the material of the hydrophilic particles is the same as that of the adsorbent particles 12. For example, the hydrophilic particles can be selected from at least one of aluminum-based adsorbents, titanium-based adsorbents, and manganese-based adsorbents, but are not limited thereto. In this case, the hydrophilic particles themselves also have a certain adsorption capacity, which is more conducive to the infiltration of brine and the adsorption of lithium ions.

[0037] In some embodiments of the present disclosure, the D50 particle size of the hydrophilic particles is 0.01 μm-1 μm. Controlling the D50 particle size of the hydrophilic particles within the above range not only facilitates their better adhesion to the pore walls, reducing the risk of the hydrophilic particles being washed away during repeated brine immersion and cleaning fluid flushing, but also prevents them from occupying excessive space in the pores 20, further facilitating the flow of brine within the pores 20, thereby improving the overall performance of the lithium adsorbent 100. For example, the D50 of the hydrophilic particles can be, but is not limited to, 0.01 μm, 0.05 μm, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, etc. In the embodiments of the present disclosure, the D50 particle size of the adsorbent particles 12 in the lithium adsorbent 100 was measured using SEM.

[0038] Considering that in some embodiments, the skeleton structure 10 of the lithium adsorbent 100 is prepared by first mixing the adsorbent particles 12 with an organic solution of the polymer matrix 11, in order to improve the moldability of the skeleton structure 10 and increase the total pore volume of the pores 20 in the lithium adsorbent 100, in some embodiments of the present disclosure, the ratio of the sum of the mass of the adsorbent particles 12 to the mass of the polymer matrix 11 is controlled to be 100:(9-16). In some specific embodiments, the ratio of the sum of the mass of the adsorbent particles 12 to the mass of the polymer matrix 11 is 100:(12-15). This can improve the hydrophilicity of the skeleton structure 10 of the lithium adsorbent 100 to a certain extent, and can also form a suitable pore structure in the skeleton structure 10. The porosity of the skeleton structure 10 (or the total pore volume of the lithium adsorbent 100) is controlled within a suitable range, ensuring high strength and good cyclic stability of the lithium adsorbent 100. It also facilitates the formation of a multidimensional pore structure, further improving the adsorption-desorption efficiency of the lithium adsorbent 100. For example, the ratio of the sum of the mass of the adsorbent particles 12 to the mass of the polymer matrix 11 may be, but is not limited to, 100:9, 11:1, 10.5:1, 10:1, 9.5:1, 9:1, 8.5:1, 8:1, 7.5:1, 7:1, 6.5:1, 6.4:1, 6.3:1, 6.28:1, 6.25:1, etc. In the embodiment of the present disclosure, the mass ratio of the adsorbent particles 12 to the polymer matrix 11 in the lithium adsorbent 100 may be determined by thermogravimetry.

[0039] In some embodiments of the present disclosure, the compressive strength of the lithium adsorbent 100 is ≥5 N; for example, 5 N to 6.5 N. A compressive strength of ≥5 N makes the lithium adsorbent 100 less susceptible to deformation, breakage, or loss of adsorbent particles 12 when loaded into an adsorption column during use, resulting in excellent structural stability and a longer cycle life.

[0040] The present disclosure also provides a method for preparing a lithium adsorbent, which can be used to prepare the aforementioned lithium adsorbent 100 and includes the following steps.

[0041] S01. Mixing a polymer matrix, adsorbent particles, and a solvent to obtain a first material.

[0042] S02. Place the first material and the second material in a containing cavity, and use a coaxial spinning process to spin according to a preset size, so that the first material and the second material as the core liquid are coaxially extruded to obtain initial fibers; wherein the second material includes a substance that cannot be solidified during the spinning process; the above-mentioned non-solidified substance includes but is not limited to water; the initial fibers are solidified and cut to obtain a lithium adsorbent.

[0043] In the embodiment of the present disclosure, coaxial spinning refers to the extrusion of different materials from the same nozzle at the same time. It can be understood that when preparing a lithium adsorbent containing only one channel, for example: the front view of the nozzle includes a first flow channel and a second flow channel that are concentrically or eccentrically arranged, the second material is extruded from the second flow channel as a core liquid, and the first material is extruded from the space formed by the second flow channel and the first flow channel to obtain an initial fiber. The first material solidifies during the subsequent coagulation process to form a skeleton structure; the second material as the core liquid cannot be solidified, and the space occupied by the second material in the initial fiber is converted into a channel in the lithium adsorbent. When preparing a lithium adsorbent containing multiple channels, the number of second flow channels in the nozzle is adjusted, and the relative positions of the first flow channel and the multiple second flow channels are adjusted according to the number of channels and the preset size of the lithium adsorbent. At this time, the first flow channel and each second flow channel can be eccentrically arranged.

[0044] In the embodiment of the present disclosure, the size of the lithium adsorbent can be adjusted by adjusting parameters such as the outlet size of the first flow channel and the second flow channel.

[0045] The preparation method has simple steps, strong process reliability, high process flexibility, high production efficiency, and is suitable for large-scale industrial production.

[0046] In the above preparation method, the solvent is used to dissolve the polymer matrix, and the polymer matrix is ​​dissolved in the solvent to form a polymer glue with a certain viscosity. The adsorbent particles are dispersed in the above polymer solution, or in other words, the polymer glue with a certain viscosity is dispersed between the adsorbent particles and acts to bind the adsorbent particles. In this way, in the lithium adsorbent obtained, the adsorbent particles are more evenly dispersed in the skeleton structure. In some specific embodiments, the polymer matrix is ​​first mixed with the solvent to obtain a polymer glue, and then the adsorbent particles are mixed with the above polymer glue to obtain the first material. In this way, the risk of uneven dispersion or even agglomeration of the adsorbent particles can be greatly reduced, and the occurrence of nozzle blockage and the like can be avoided. The uniformity of the lithium adsorbent skeleton structure is further improved, the strength of the lithium adsorbent is increased, and the adsorption efficiency and capacity are improved. The pulverization rate of the lithium adsorbent can also be further reduced. The polymer glue and the adsorbent particles can be mixed by external stirring, and the stirring rate can be 100rpm-800rpm. In some specific embodiments, the polymer matrix and the solvent are mixed at room temperature to 80° C., preferably at 40° C.-80° C.; similarly, the polymer glue and the adsorbent particles can also be mixed within the above temperature range.

[0047] The polymer glue has a certain viscosity. During the mixing process of the adsorbent particles and the polymer glue, stirring is often required, which may cause bubbles to be present in the mixture of the two. In order to remove the bubbles and avoid the formation of a large number of uncontrollable pores in the final lithium adsorbent, in some embodiments of the present disclosure, in step S01, before spinning, the first material is also subjected to a degassing treatment. In some specific embodiments, the degassing treatment includes: placing the first material in a closed container and performing a vacuum treatment at a pressure of 26-200 kPa for a vacuuming time of 10 minutes to 30 minutes.

[0048] It is understood that in order to dissolve the polymer matrix, the solvent used in S01 is an organic solvent. In some specific embodiments, the solvent includes, but is not limited to, at least one of N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, tetrahydrofuran, methyl ethyl acetone, dimethyl sulfoxide, tetrachloromethane, chloroform, dichloromethane, ethyl acetate, and ethanol. Those skilled in the art can select the solvent based on the specific material of the polymer matrix.

[0049] In some embodiments of the present disclosure, the mass proportion of the polymer matrix in the polymer glue is 5%-13%. In some specific embodiments, the mass proportion of the polymer matrix in the polymer glue is 6%-10%. In this way, the viscosity of the polymer glue is more appropriate, which is conducive to the dispersion of the adsorbent particles therein and is also conducive to improving the spinnability of the first material finally obtained. In the embodiments of the present disclosure, regulating the polymer matrix in the polymer glue can regulate the size of the lithium adsorbent. Exemplarily, the mass proportion of the polymer matrix in the polymer glue can be, but is not limited to, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, and 13%.

[0050] In some embodiments of the present disclosure, the adsorbent particles include, but are not limited to, at least one of aluminum-based adsorbent particles, titanium-based adsorbent particles, and manganese-based adsorbent particles. For details, please refer to the description of lithium adsorbents above and will not be repeated here. In some embodiments of the present disclosure, the adsorbent particles 12 have a D50 particle size of 0.01 μm to 10 μm. In this case, the particle size of the adsorbent particles can be measured using a laser particle size analyzer.

[0051] In some embodiments of the present disclosure, the second material contains hydrophilic particles. In some specific embodiments, the second material is a suspension containing hydrophilic particles. In this way, during the preparation of the lithium adsorbent, the hydrophilic particles can be modified on the inner surface (pore wall) of the lithium adsorbent without adding any additional processes, thereby improving the adsorption efficiency of the lithium adsorbent. In some specific embodiments, the material selection of the hydrophilic particles is the same as the material selection of the adsorbent particles. Please refer to the relevant content of the lithium adsorbent section in the previous text, which will not be repeated here. In some specific embodiments, the D50 particle size of the hydrophilic particles is 0.01μm-1μm. At this time, a laser particle size analyzer can be used to test the particle size of the hydrophilic particles.

[0052] In some embodiments of the present disclosure, when the second material contains hydrophilic particles, the hydrophilic particles can be stirred with a solvent and mixed to obtain the second material. The solvent includes but is not limited to water. In some specific embodiments, the mass proportion of the hydrophilic particles in the second material is 0.1%-5%. In this way, the fluidity of the second material is better, and its fluidity is highly matched with the first material, which is conducive to the flexible regulation of the size of the pores in the lithium adsorbent. Exemplarily, the mass proportion of the hydrophilic particles in the second material can be, but is not limited to, 0.1%, 0.2%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc.

[0053] Considering that in some cases, there is a difference in viscosity between the first material and the second material, in order to better prepare the lithium adsorbent and make the pore structure of the skeleton structure more suitable, in some embodiments of the present disclosure, during the spinning process of step S02, the extrusion flow rate ratio of the first material to the second material is 1:(1-5). For example, the extrusion flow rate ratio of the first material to the second material can be, but is not limited to, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, etc.

[0054] To improve the spinnability of the first material, the temperature of the first material can be within a range of room temperature to 80°C. In some specific embodiments, it is preferably 40°C to 60°C. This provides a suitable viscosity for the first material, making it easier to control the size of the lithium adsorbent. Furthermore, the nozzle temperature during the spinning process is also within a range of room temperature to 80°C, more preferably 40°C to 60°C.

[0055] In the embodiments of the present disclosure, the specific spinning process can be any spinning process known in the fields of wet spinning, dry-jet wet spinning, etc., which is suitable for preparing a lithium adsorbent having the size of the embodiments of the present disclosure.

[0056] In some embodiments of the present disclosure, the lithium adsorbent is prepared by wet spinning, wherein the nozzle is immersed in a coagulation bath, and the initial fibers are extruded directly in the coagulation bath, and the formation of the initial fibers and the coagulation process occur almost simultaneously.

[0057] In some cases, solvent dissolves from the initial fibers during solidification, and this excess solvent can be channeled into pores on the surface of the final lithium adsorbent's backbone structure, both away from and toward the pores. In some embodiments, the resulting pores have a diameter of 10 nm to 200 nm. Therefore, controlling the polymer matrix to a mass fraction of 5% to 10% in the polymer glue solution also facilitates the formation of the desired pore structure within the backbone structure.

[0058] In some embodiments of the present disclosure, when wet spinning is employed, the components of the coagulation bath include, but are not limited to, water, or a mixture of water and a solvent. The range of choice of the aforementioned solvent may be the same as the range of choice of the solvent used in step S01, and the solvent components used in the coagulation bath may be the same as or different from those used in step S01.

[0059] In some embodiments of the present disclosure, the temperature of the coagulation bath is controlled to be within the range of room temperature to 80° C., preferably within the range of room temperature to 40° C. This facilitates the formation of the lithium adsorbent and the formation of a relatively ideal pore structure in the skeleton structure.

[0060] Of course, in the embodiment of the present disclosure, a dry-jet wet spinning process can also be used, that is, the first material and the second material are ejected in the air (air bath) to obtain initial fibers, and then the initial fibers enter the coagulation bath. In some embodiments of the present disclosure, the nozzle is set in the direction of the ground, so that gravity can be used to draft the first material, which is beneficial to the formation of the initial fibers. In some specific embodiments, the height of the air bath is 5cm-30cm, so that it is beneficial to obtain a lithium adsorbent of the target structure. For example, the height of the air bath can be, but is not limited to, 5cm, 10cm, 15cm, 20cm, 25cm, 30cm, etc.

[0061] It can be understood that the solid material obtained after the coagulation treatment is in the form of long fibers, and for the application of the lithium adsorbent, it needs to be cut. In the embodiment of the present disclosure, in order to remove the residual solvent in the above-mentioned solid material, step S02 also includes washing before cutting. Furthermore, the solid material obtained after the coagulation treatment can be washed and cut in sequence. Furthermore, the cut material can also be dried to obtain a lithium adsorbent. In some specific embodiments, the solid material obtained after the coagulation treatment is washed with water; the mass ratio of water to solid material is (2-10):1, but is not limited thereto.

[0062] The technical solution of the present disclosure is further illustrated below with multiple embodiments.

[0063] Example 1

[0064] (1) Dissolving a polymer matrix (specifically polyvinylidene fluoride) in a solvent (specifically N-methylpyrrolidone) at 80° C. to obtain a polymer glue; the mass proportion of the polymer matrix in the polymer glue is 8.8%; mixing the aforementioned polymer glue and aluminum-based adsorbent particles (specifically LiCl·2Al(OH)3·nH2O) having a D50 particle size of 3.5 μm at a mass ratio of 1.7:1, stirring at 40° C., and after sufficient mixing, performing a vacuum treatment for 30 minutes to obtain a first material.

[0065] (2) The first material and the second material as the core liquid are squeezed out from the nozzle to perform dry-jet wet spinning, with the nozzle being arranged toward the ground; wherein the second material is water.

[0066] The extrusion flow rate ratio of the second material to the first material is 2:1, the height of the air bath is 20 cm, and initial fibers are obtained. The initial fibers are placed in a 40°C coagulation bath (specifically water) for coagulation treatment to obtain a solid material; then washed with water (the mass ratio of water to solid material is 10:1), and cut to obtain a lithium adsorbent with an inner diameter of 0.6 mm, a wall thickness of 0.4 mm, and a length of 1.5 mm. The mass ratio of the adsorbent particles in the lithium adsorbent to the polymer matrix is ​​20:3; the pore diameters of the pores on the surfaces of the skeleton structure of the lithium adsorbent facing and away from the pores are in the range of 10 nm to 200 nm.

[0067] Example 2

[0068] The difference from Example 1 is that in step (1), the mass ratio of the polymer matrix to the polymer glue is 6.0%, and in the first material, the mass ratio of the polymer glue to the adsorbent particles is 2.5:1; wherein, in step (2), the extrusion flow rate ratio of the second material to the first material is 5:1. A lithium adsorbent having an inner diameter of 0.6 mm, a wall thickness of 0.7 mm, and a length of 1.5 mm is obtained, and the mass ratio of the adsorbent particles to the polymer matrix in the lithium adsorbent is 20:3.

[0069] Example 3

[0070] The only difference from Example 1 is that the second material is a suspension containing hydrophilic particles (specifically, an aluminum-based adsorbent with a D50 particle size of 0.2 μm). The dispersion medium is water, and the hydrophilic particles account for 2% by weight of the suspension. The resulting lithium adsorbent has an inner diameter of 0.6 mm, a wall thickness of 0.4 mm, and a length of 1.5 mm. The mass ratio of adsorbent particles to polymer matrix in the lithium adsorbent is 20:3.

[0071] Example 4

[0072] The difference from Example 3 is that the mass proportion of the hydrophilic particles in the second material is 6%.

[0073] Example 5

[0074] The difference from Example 3 is that the nozzle shape is modified to include three second flow channels for extruding the second material. The resulting lithium adsorbent includes a skeleton structure and three channels extending along its length. The resulting lithium adsorbent has three channels with inner diameters of 0.56 / 0.54 / 0.54 mm, corresponding to wall thicknesses of 0.23 / 0.20 / 0.20 mm, and a length of 1.5 mm.

[0075] Example 6

[0076] The difference from Example 3 is that the outer diameter of the inner hole of the spinning head is changed to 0.8 mm, so that the inner diameter of the pores of the lithium adsorbent is 0.7 mm.

[0077] Example 7

[0078] The difference from Example 3 is that the mass proportion of the polymer matrix in the polymer glue is reduced to 7.1%, so that the mass ratio of the adsorbent particles to the polymer matrix is ​​25:3.

[0079] Example 8

[0080] The difference from Example 3 is that the mass proportion of the polymer matrix in the polymer glue is reduced to 5.3%, so that the mass ratio of the adsorbent particles to the polymer matrix is ​​100:9.

[0081] Example 9

[0082] The difference from Example 3 is that the mass proportion of the polymer matrix in the polymer glue is increased to 14.7%, so that the mass ratio of the adsorbent particles to the polymer matrix is ​​4:1.

[0083] Example 10

[0084] The difference from Example 3 is that the outer diameter of the inner hole of the spinning head is changed to 0.15 mm, so that the inner diameter of the pores of the lithium adsorbent is 0.1 mm.

[0085] Example 11

[0086] The difference from Example 3 is that the outer diameter of the inner hole of the spinning head is changed to 0.4 mm, so that the inner diameter of the pores of the lithium adsorbent is 0.3 mm.

[0087] Example 12

[0088] The difference from Example 3 is that the inner diameter of the outer hole of the spinning head is changed to 1.2 mm, so that the wall thickness of the lithium adsorbent is 0.2 mm.

[0089] Example 13

[0090] The difference from Example 3 is that the inner diameter of the outer hole of the spinning head is changed to 3.0 mm, so that the wall thickness of the lithium adsorbent is 1.0 mm.

[0091] Example 14

[0092] The difference from Example 3 is that the D50 particle size of the adsorbent particles is 1.5 μm.

[0093] Example 15

[0094] The difference from Example 3 is that the cutting parameters are changed so that the length of the lithium adsorbent is 4.3 mm.

[0095] Example 16

[0096] The difference from Example 3 is that the cutting parameters are changed so that the length of the lithium adsorbent is 0.3 mm.

[0097] Example 17

[0098] The difference from Example 3 is that the mass proportion of the polymer matrix in the polymer glue is 4%, and the pore diameter of the pores on the surface of the skeleton structure of the finally obtained lithium adsorbent facing away from and toward the pore channel is greater than 200 nm.

[0099] In order to highlight the beneficial effects of the embodiments of the present disclosure, the following comparative examples are provided.

[0100] Comparative Example 1

[0101] A tubular lithium adsorbent, which differs from Example 1 in that its inner diameter is 0.05 mm, its wall thickness is 0.15 mm, and the mass ratio of the adsorbent particles to the polymer matrix is ​​37:16.

[0102] Comparative Example 2

[0103] A tubular lithium adsorbent, which differs from Example 1 in that its inner diameter is 0.8 mm, its wall thickness is 1.5 mm, and the mass ratio of the adsorbent particles to the polymer matrix is ​​25:4.

[0104] Parameter characterization of lithium adsorbents

[0105] (1) Morphological characterization: The lithium adsorbents of each embodiment and comparative example were fractured to expose their cross sections. The surface morphology and cross-sectional morphology of the lithium adsorbents of each embodiment and comparative example were observed under SEM. SEM photographs of the inner / outer surfaces and cross sections of Example 3 are shown in Figures 3 to 5 , and an SEM photograph of the cross section of Example 5 is shown in Figure 6 . The inner diameter (if any) and wall thickness (if any) of the pores of the lithium adsorbents of each embodiment and comparative example were measured under SEM. Three lithium adsorbent samples were taken for each embodiment and comparative example for testing, and the average value was taken. For the results, please refer to the relevant description of the embodiments and comparative examples above.

[0106] (2) Specific surface area test: Referring to the test in GB / T 19587-2017, three lithium adsorbent samples were taken for each embodiment and comparative example for testing, and the average value was taken. The results are summarized in Table 1.

[0107] (3) Compressive Strength: The compressive strength of the lithium adsorbent was measured using a compressive strength tester. The method is as follows: a single lithium adsorbent was placed in the center of the lower probe platform. The upper probe automatically dropped down for testing after the upper probe stopped and the adsorbent deformation rate was 5%. The reading displayed on the screen is the compressive strength of the lithium adsorbent. 50 sets of data were measured, outliers were removed, and the average value was calculated. The results are summarized in Table 1.

[0108] Table 1

[0109] Brine adsorption performance test

[0110] Take lithium-containing brine with high magnesium-lithium ratio for testing, the Li + The concentration is 326ppm, Mg 2+ The concentration is 92910ppm, and the mass ratio of magnesium to lithium in the brine is 285:1. 10g of the lithium adsorbent of each embodiment and comparative example was weighed respectively, and adsorption was carried out at a solid-liquid ratio of 1:50 at room temperature. The brine was stirred at a stirring rate of 300rpm and an adsorption time of 90min. After adsorption, the lithium adsorbent was filtered and rinsed at the same time, and the amount of rinsing water was 200mL. After rinsing, pure water was used for desorption at a solid-liquid ratio of 1:50, the stirring rate was 500rpm, the temperature was 40°C, and the desorption time was 60min. The concentration of each ion in the solution was tested by inductively coupled plasma atomic emission spectrometer (ICP-OES), and the measured adsorption capacity (adsorption capacity = (Li + Concentration-Li in adsorption tail liquid + The working adsorption capacity of the adsorbent is (concentration)*brine volume / adsorbent mass). The results are summarized in Table 2.

[0111] Table 2

[0112] Stability test of lithium adsorbents in water: 1 g of lithium adsorbent from each example and comparative example was stirred in 50 mL of water at 40°C for 2 h (at a stirring rate of 800 rpm). The mixture was then allowed to stand and its morphology was observed. The test results for Example 3, Comparative Example 1, and Comparative Example 2 are summarized in Figures 7-9. The lithium adsorbent in Figure 7 (Example 3) sank in water, and the solution was clear, indicating that the lithium adsorbent was wetted in water and had a low pulverization rate. The lithium adsorbent particles in Figure 8 (Comparative Example 1) floated on the water surface, indicating that the adsorbent had small internal pores and strong hydrophobicity, and did not wet in water. In contrast, the solution in Figure 9 (Comparative Example 2) was very turbid, reflecting a high pulverization rate. As can be seen from Figures 7-9, the hydrophilicity and stability of the lithium adsorbent in water in Example 3 were significantly better than those in Comparative Examples 1 and 2. In other words, the hydrophilicity was significantly better than that in Comparative Example 1, and the pulverization rate was significantly lower than that in Comparative Example 2.

[0113] Combining the parameters in Tables 1 and 2, it can be found that the adsorption effect of the lithium adsorbent provided by the embodiments of the present disclosure is better than that of the comparative lithium adsorbent after 50 cycles, and the comprehensive adsorption effect of the lithium adsorbent of each embodiment is better. Comparing the data of Examples 1 and 3, it can be found that when hydrophilic particles are attached to the surface of the pores of the lithium adsorbent, it is more conducive to improving the adsorption effect of the lithium adsorbent. Further, comparing the data between Example 3 and Examples 6-8, it can be found that when the mass ratio of the adsorbent particles to the polymer matrix is ​​within the range suggested by the present disclosure (Examples 3, 6, and 7), the comprehensive performance of the lithium adsorbent is better; when the above values ​​are within the range further suggested by the present disclosure (Example 3), the adsorption capacity, desorption amount, magnesium-lithium selectivity, and cycle performance and strength of the lithium adsorbent are all better. Comparing Examples 3, 15, and 16, it can be found that when the length of the lithium adsorbent is within the range suggested by the present disclosure, the various performances of the lithium adsorbent are more balanced, and the cycle performance is better.

[0114] The above is an exemplary embodiment of the present disclosure. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made thereto without departing from the principles of the present disclosure. These improvements and modifications are also considered to be within the scope of protection of the present disclosure.

Claims

1. A lithium adsorbent (100), characterized in that: The lithium adsorbent is tubular, comprising a skeleton structure (10) and one or more pores (20) extending through the skeleton structure along its length; the inner diameter of the pores (20) is 0.1 mm to 0.7 mm, and the wall thickness of the lithium adsorbent (100) is 0.2 mm to 1 mm; the skeleton structure (10) comprises a polymer matrix (11) and adsorbent particles (12) dispersed in the polymer matrix (11).

2. The lithium adsorbent (100) according to claim 1, characterized in that: The ratio of the inner diameter of the channel (20) to the wall thickness is 1:(0.3-2).

3. The lithium adsorbent (100) according to claim 1 or 2, characterized in that: The length of the lithium adsorbent (100) is 0.5 mm to 3 mm.

4. The lithium adsorbent (100) according to any one of claims 1 to 3, characterized in that: The surface of the pore (20) is modified with hydrophilic particles; the D50 particle size of the hydrophilic particles is 0.01 μm-1 μm.

5. The lithium adsorbent (100) according to claim 4, characterized in that: The hydrophilic particles are made of the same material as the adsorbent particles (12).

6. The lithium adsorbent (100) according to any one of claims 1 to 5, characterized in that: The adsorbent particles (12) are selected from at least one of aluminum-based adsorbent particles, titanium-based adsorbent particles and manganese-based adsorbent particles; the D50 particle size of the adsorbent particles (12) is 0.01 μm-10 μm.

7. According to any one of claims 1 to 6, the skeleton structure (10) is a porous structure; the pore diameters of the pores on the surface of the skeleton structure (10) facing the pore channel (20) and away from the pore channel (20) are 10 nm to 200 nm.

8. The lithium adsorbent (100) according to any one of claims 1 to 7, characterized in that: The polymer matrix (11) includes at least one of polyvinylidene fluoride, polyvinyl butyral, polyether sulfone, polysulfone, polyacrylonitrile, polyvinyl chloride and polyethylene.

9. The lithium adsorbent (100) according to any one of claims 1 to 8, characterized in that: In the lithium adsorbent (100), the ratio of the sum of the mass of the adsorbent particles (12) to the mass of the polymer matrix (11) is 100:(9-16).

10. The lithium adsorbent (100) according to any one of claims 1 to 9, characterized in that: The BET specific surface area of ​​the lithium adsorbent (100) is ≥17 m 2 / g.

11. The lithium adsorbent (100) according to any one of claims 1 to 10, characterized in that: The compressive strength of the lithium adsorbent (100) is ≥5N.

12. A method for preparing the lithium adsorbent (100) according to any one of claims 1 to 11, characterized in that: include: Mixing the polymer matrix (11), the adsorbent particles (12) and a solvent to obtain a first material; The first material and the second material are placed in a containing cavity, and a coaxial spinning process is used to spin the first material and the second material as a core liquid coaxially to obtain initial fibers; as well as The initial fibers are coagulated and cut to obtain the lithium adsorbent (100).

13. The method for preparing the lithium adsorbent (100) according to claim 12, characterized in that: The second material contains hydrophilic particles.

14. The method for preparing the lithium adsorbent (100) according to claim 12, characterized in that: The mass of the polymer matrix (11) is 5% to 13% of the sum of the mass of the polymer matrix (11) and the solvent.

15. The method for preparing the lithium adsorbent (100) according to any one of claims 12 to 14, characterized in that: During the spinning process, the extrusion flow rate ratio of the first material to the second material is 1:(1-5).

16. The method for preparing the lithium adsorbent (100) according to any one of claims 12 to 15, characterized in that: The coagulation treatment includes passing the initial fiber through a coagulation liquid; the temperature of the coagulation liquid is from room temperature to 80°C.

17. The method for preparing a lithium adsorbent (100) according to any one of claims 12 to 16, characterized in that: The second material includes a substance that cannot be solidified during the spinning process; the non-solidified substance includes water.

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