Lithium adsorption material, preparation method therefor and use thereof

Abstract

The present invention relates to the field of adsorption materials. Disclosed are a lithium adsorption material, a preparation method therefor and a use thereof. The lithium adsorption material comprises a core and a shell covering the surface of the core; pores are formed in the shell of the lithium adsorption material, and the average diameter of the pores measured by a SEM electron microscope is 0.01-2.5 μm; the core of the lithium adsorption material comprises finger-like pores, and in the cross section of the lithium adsorption material, the maximum average length of the finger-like pores measured by the SEM electron microscope is 1-7 μm, and the minimum average length is 0.05-2.5 μm; and the thickness of the shell of the lithium adsorption material measured by the SEM electron microscope is 1-550 μm. The lithium adsorption material with the specific structure has a special structure having small pores in the outer shell and large pores in the inner core, the mass transfer rate of water and salt can be increased, and when the lithium adsorption material is used for extracting lithium in a liquid environment, the adsorption capacity for lithium can be significantly improved.

Description

Lithium adsorption material and preparation method and application thereof

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of Chinese patent application 202310769636.1 filed on June 27, 2023, the contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to the field of adsorption materials, and in particular to a lithium ion adsorption material and a preparation method and application thereof. Background Art

[0004] With the rapid development of the lithium battery industry, demand for lithium resources continues to grow across various industries, and the importance of lithium production is also increasing. Currently, lithium resources are mainly distributed in lithium ore and salt lake brine. However, lithium ore resources are dwindling and development costs are increasing. In contrast, lithium water resources in salt lake brine are low-cost and abundant. my country has abundant liquid lithium resources, but extracting lithium from these resources is a challenging task.

[0005] Currently, the main methods for extracting lithium from salt lakes include adsorption, precipitation, extraction, electrodialysis, and calcination. The adsorption method, with its advantages of simplicity, environmental friendliness, energy efficiency, and good selectivity, is superior to other methods in terms of both time and cost, and thus has broad application prospects. Since salt lake brine often has a low lithium grade, the key to extracting lithium using the adsorption method is the preparation of highly selective adsorbents. Highly selective lithium adsorbents primarily include ion sieve adsorbents and amorphous hydroxide adsorbents. However, since these adsorbents are in powder form after synthesis, they cannot be directly applied to conventional equipment such as fixed beds for adsorption-desorption lithium extraction. At present, lithium adsorbents are also granulated to obtain granular lithium adsorbent materials. Common granulation methods are: (1) using inorganic binders such as alumina, silica gel, etc. for granulation. The granular adsorbent prepared by this method is simple, but has poor stability and often needs to be used together with a polymer granulation method; (2) using natural polymer materials such as chitosan, sodium alginate, etc. for granulation, but the long-term performance stability of the product prepared by this method is poor; (3) using organic polymer materials such as PU, PAM, PVC as binders for granulation, but the prepared granular adsorbent has poor hydrophilicity and is prone to embedding of powdered adsorbents, which greatly reduces the adsorption capacity and has poor long-term cycle performance.

[0006] Based on the above background, there is an urgent need to solve the problems of poor hydrophilicity of PVC-based granulation products, adsorbent embedding and long-term cycle performance degradation.

[0007] Summary of the Invention

[0008] The purpose of the present invention is to overcome the problems in the prior art of granulated products with polyvinyl chloride as the skeleton, such as poor hydrophilicity, poor wrapping stability of lithium ion sieve, easy agglomeration of lithium ion sieve, and clogging and rupture of adsorbent pores due to salt crystallization during recycling. A lithium adsorption material and its preparation method and application are provided. The lithium adsorption material comprises a core with a specific pore structure and surface pores with a specific average diameter coated on the surface of the core, and the shell has a specific thickness. The lithium adsorption material with the above-mentioned specific structure presents a special structure with small outer shell pores and large inner core pores, which can increase the mass transfer rate of water and salt. When it is used to extract lithium in a liquid environment, it can significantly improve the adsorption capacity of lithium.

[0009] In order to achieve the above object, the present invention provides a lithium adsorption material in a first aspect, wherein the lithium adsorption material comprises a core and a shell layer coated on the surface of the core;

[0010] There are pores on the shell layer of the lithium adsorption material, and the average diameter of the pores measured by SEM electron microscopy is 0.01-2.5 μm;

[0011] The core of the lithium adsorption material contains finger-shaped pores, and the longest average length of the finger-shaped pores measured by SEM electron microscopy on the cross section of the lithium adsorption material is 1-7 μm; the shortest average length is 0.05-2.5 μm;

[0012] The shortest average length of the finger-like pores in the core is greater than the average diameter of the pores in the shell;

[0013] The thickness of the shell of the lithium adsorption material measured by SEM electron microscopy is 1-550 μm.

[0014] A second aspect of the present invention provides a method for preparing a lithium adsorption material, the method comprising the following steps:

[0015] (1) mixing polyvinyl chloride, polyacrylic acid, lithium ion sieve and oil phase solvent to obtain a mixed solution;

[0016] (2) Under the conditions of temperature of 20-60° C. and humidity of 40-80%, the mixed solution is added dropwise to an aqueous solvent to obtain a lithium adsorption material.

[0017] The third aspect of the present invention provides a lithium adsorption material prepared by the above method.

[0018] A fourth aspect of the present invention provides an application of a lithium adsorption material in lithium extraction.

[0019] Through the above technical solution, the lithium adsorption material provided by the present invention and its preparation method and application achieve the following beneficial effects:

[0020] The lithium adsorption material provided by the present invention comprises a core having a specific pore structure and pores with a specific average diameter coated on the surface of the core, and the shell has a specific thickness. The lithium adsorption material with the above-mentioned specific structure presents a special structure with small pores in the outer shell and large pores in the inner core, which can increase the mass transfer rate of water. When it is used for lithium extraction in a liquid environment, it can significantly improve the adsorption capacity of lithium.

[0021] Furthermore, the lithium adsorption material includes a skeleton and a hydroxyl-modified lithium ion sieve dispersed in the skeleton, and the skeleton includes polyvinyl chloride (PVC) and polyacrylic acid, and the lithium ion sieve is connected to the skeleton via hydroxyl groups. The hydroxyl groups in the lithium ion sieve have good compatibility with the polar groups (-COOH) on the polyacrylic acid molecular chain and the polyvinyl chloride, enabling the lithium ion sieve to be evenly dispersed in the skeleton comprising polyvinyl chloride and polyacrylic acid, reducing the embedding phenomenon of the adsorbent (lithium ion sieve). At the same time, the carboxyl groups (-COOH) on the polyacrylic acid molecular chain can promote lithium ion transfer, thereby significantly improving the adsorption rate of the lithium adsorption material.

[0022] Furthermore, polyacrylic acid can inhibit the formation of salt crystals, especially the formation of salt crystals under high salt conditions, thereby reducing the phenomenon of pore blockage of the lithium adsorption material due to the formation of inorganic salt crystals in the internal pores of the lithium adsorption material during the cyclic adsorption and desorption process. The desorption efficiency of lithium ions is improved, and the phenomenon of polyvinyl chloride rupture caused by the exchange of water flow and salt during long-term use is avoided, thereby extending the recycling period of the lithium adsorption material.

[0023] Furthermore, polyacrylic acid has excellent hydrophilicity and mechanical strength, and can significantly improve the mechanical properties and swelling properties of the skeleton containing polyacrylic acid in a salt solution.

[0024] In the method for preparing a lithium adsorption material provided in the present invention, a mixed solution containing polyvinyl chloride, polyacrylic acid, and a lithium ion sieve is dropwise added to an aqueous solvent under specific temperature and humidity conditions. The resulting lithium adsorption material comprises a core having a specific pore structure and a surface pore structure with a specific average diameter coated on the surface of the core, and the shell has a specific thickness. The lithium adsorption material having the above-mentioned specific structure exhibits a special structure with small pores in the outer shell and large pores in the inner core, which can increase the mass transfer rate of water and salt. When used for lithium extraction in a liquid environment, it can significantly improve the adsorption capacity of lithium. In addition, polyacrylic acid has excellent hydrophilicity and mechanical strength, which can significantly improve the mechanical properties of the skeleton containing polyacrylic acid and its swelling properties in salt solutions. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG1 is a SEM electron microscope photograph of the surface of the lithium adsorption material prepared in Example 1;

[0026] FIG2 is a SEM electron microscope photograph of a cross section of the lithium adsorption material obtained in Example 1;

[0027] FIG3 is a SEM electron microscope image of a cross section of the lithium adsorption material obtained in Example 1;

[0028] FIG4 is a SEM electron microscope image of a cross section of the lithium adsorption material of Comparative Example 1;

[0029] FIG5 is a SEM electron microscope image of a cross section of the lithium adsorption material of Comparative Example 2;

[0030] FIG6 is a SEM electron microscope image of a cross section of the lithium adsorption material of Example 1 after being used 30 times in an adsorption column;

[0031] FIG7 is a SEM electron microscope image of the cross section of the lithium adsorption material adsorption column of Comparative Example 1 after being used 30 times.

[0032] FIG8 is a photograph of the lithium adsorption material prepared in Example 1. DETAILED DESCRIPTION

[0033] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0034] A first aspect of the present invention provides a lithium adsorption material, comprising a core and a shell layer coated on the surface of the core;

[0035] There are pores on the shell layer of the lithium adsorption material, and the average diameter of the pores measured by SEM electron microscopy is 0.01-2.5 μm;

[0036] The core of the lithium adsorption material contains finger-shaped pores, and the longest average length of the finger-shaped pores measured by SEM electron microscopy on the cross section of the lithium adsorption material is 1-7 μm; the shortest average length is 0.05-2.5 μm;

[0037] The shortest average length of the finger-like pores in the core is greater than the average diameter of the pores in the shell;

[0038] The thickness of the shell of the lithium adsorption material measured by SEM electron microscopy is 1-550 μm.

[0039] In the present invention, the lithium adsorption material comprises a core having a specific pore structure and pores with a specific average diameter coated on the surface of the core, and the shell has a specific thickness. The lithium adsorption material with the above-mentioned specific structure presents a special structure with small pores in the outer shell and large pores in the inner core, which can increase the mass transfer rate of water. When used for lithium extraction in a liquid environment, it can significantly improve the adsorption capacity of lithium without leaking the powdered lithium ion sieve.

[0040] In the present invention, the lithium adsorbent material was sectioned at intervals of 0.5 mm along the equatorial direction parallel to the particles of the lithium adsorbent material and perpendicular to the equatorial direction of the particles of the lithium adsorbent material to observe the core structure of lithium ion adsorption in different cross-sections. Through observation, it can be found that in different cross-sections, the core of the lithium adsorbent material contains finger-like pores, and the longest average length of the finger-like pores measured by SEM electron microscopy in each cross-section is 1-7 μm; the shortest average length is 0.05-2.5 μm. Based on this, the inventors of this application reasonably expect that the core of the lithium adsorbent material contains finger-like pores throughout, and that the finger-like pores are three-dimensional and have the specific structure described in the present invention.

[0041] In the present invention, when the longest average length and the shortest average length of the finger-like pores in the core of the lithium adsorption material are tested using an SEM electron microscope, 10 observation points are randomly selected for SEM testing, each observation area is not less than 500×500 μm, and the average value is calculated.

[0042] In the present invention, when using an SEM electron microscope to measure the average diameter of the pores in the shell layer of the lithium adsorption material, 10 observation points are randomly selected for SEM testing, with each observation area being no less than 500×500 μm. The average value is calculated, and the long side diameter and short side diameter of all pores in the observation area are statistically analyzed. The average pore diameter is the average of the statistical long side diameters and short side diameters. The long side is the longest dimension of the pore, that is, the distance between the two points on the pore profile that are farthest apart; the short side is the length between the intersection points of a line perpendicular to the long side and intersecting the pore profile with the longest distance.

[0043] In the present invention, the average diameter of the pores in the shell of the lithium adsorption material measured by SEM electron microscopy is 0.01-2.5 μm, for example, 0.01 μm, 0.02 μm, 0.04 μm, 0.06 μm, 0.08 μm, 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, 0.3 μm, 0.35 μm, 0.4 μm, 0.45 μm, 0.5 μm, 0.55 μm, 0. .6μm, 0.65μm, 0.7μm, 0.75μm, 0.8μm, 0.85μm, 0.9μm, 1μm, 1.1μm, 1.2μm, 1.3μm, 1.4μm, 1.5μm, 1.6μm, 1.7μm, 1.8μm, 1.9μm, 2μm, 2.1μm, 2.2μm, 2.3μm, 2.4μm, 2.5μm, and ranges consisting of any two values.

[0044] In the present invention, the longest average length of the pores of the cross section of the lithium adsorption material measured by SEM electron microscopy is 1-7 μm, for example, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, and a range consisting of any two values; the shortest average length is 0.5-1.5 μm, for example, 0.05 μm, 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, 0.3 μm, 0. 35μm, 0.4μm, 0.45μm, 0.5μm, 0.55μm, 0.6μm, 0.65μm, 0.7μm, 0.75μm, 0.8μm, 0.85μm, 0.9μm, 0.95μm, 1μm, 1.1μm, 1.2μm, 1.3μm, 1.4μm, 1.5μm, 1.6μm, 1.7μm, 1.8μm, 1.9μm, 2μm, 2.1μm, 2.2μm, 2.3μm, 2.4μm, 2.5μm, and ranges consisting of any two values.

[0045] In the present invention, the thickness of the shell of the lithium adsorption material measured by SEM electron microscopy is 1-550 μm, for example, it can be 1 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm, 200 μm, 210 μm, 220 μm, 230 μm, 240 μm, 250 μm, 260 μm, 270 μm, 280 μm, 290 μm, 300 μm, 310 μm, 320 μm, 330 μm, 340 μm, 350 μm, 360 μm, 370 μm, 380 μm, 390 μm, 400 μm, 410 μm, 420 μm, 430 μm, 440 μm, 450 μm, 460 μm, 470 μm, 480 μm, 490 μm, 500 μm, 510 μm, 520 μm, 530 μm, 540 μm, 550 μm, 560 μm, 570 μm, 580 μm, 590 μm, 600 μm, 610 μm, 620 μm, 630 μm, 640 μm, 650 μm, 660 μm, 670 μm, 680 μm 60μm, 270μm, 280μm, 290μm, 300μm, 310μm, 320μm, 330μm, 340μm, 350μm, 360μm, 370μm, 380μm, 390μm, 400μm, 410μm, 420μm, 430μm, 440μm, 450μm, 460μm, 470μm, 480μm, 490μm, 500μm, 510μm, 520μm, 530μm, 540μm, 550μm, and ranges consisting of any two values.

[0046] Furthermore, the average diameter of the pores in the shell of the lithium adsorption material measured by SEM electron microscopy is 0.1-0.5 μm;

[0047] The longest average length of the pores of the cross section of the lithium adsorption material measured by SEM electron microscopy is 2-5 μm; the shortest average length is 0.5-1.5 μm;

[0048] The thickness of the shell of the lithium adsorption material measured by SEM electron microscopy is 30-500 μm.

[0049] According to the present invention, the porosity of the lithium adsorption material is 60-80%.

[0050] In the present invention, when the porosity of the lithium adsorption material is controlled to meet the above range, the lithium adsorption material has a faster water mass transfer rate.

[0051] In the present invention, the porosity of the lithium adsorption material is 60-80%, for example, it can be 60%, 62%, 65%, 67%, 70%, 72%, 75%, 77%, 80%, or a range consisting of any two values.

[0052] Furthermore, the porosity of the lithium adsorption material is 65-75%.

[0053] According to the present invention, the lithium adsorption material is spherical and / or quasi-spherical.

[0054] In the present invention, the term "spherical or quasi-spherical" refers to lithium adsorbent material particles having an aspect ratio substantially within the range of 1-2. "Substantially" means that at least 90% of the lithium adsorbent material particles have an aspect ratio within the range of 1-2. The aspect ratio is the ratio of the longest dimension of the particle (the distance between the two most distant points on the particle's outline, i.e., the longitudinal axis) to the length of the longest straight line between the intersections of a plane perpendicular to the longitudinal axis and the particle's outline (the transverse axis). Preferably, at least 95% of the lithium adsorbent material has an aspect ratio of 1-2.

[0055] According to the present invention, the average particle size of the lithium adsorption material is 2-5 mm, for example, it can be 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, or a range consisting of any two values.

[0056] In the present invention, for spherical particles, the average particle size is the arithmetic average of the vertical axis and horizontal axis of the lithium adsorption material particles obtained by SEM electron microscopy. Specifically, the average particle size of the lithium adsorption material = (vertical axis + horizontal axis) / 2.

[0057] Furthermore, the average particle size of the lithium adsorption material is 3-4 mm.

[0058] According to the present invention, the specific surface area of ​​the lithium adsorption material is 10-100m 2 / g.

[0059] In the present invention, when the specific surface area of ​​the lithium adsorption material satisfies the above range, the lithium adsorption material can have a faster water mass transfer rate.

[0060] In the present invention, the specific surface area of ​​the lithium adsorption material is 10-100m 2 / g, for example, 10m 2 / g,15m 2 / g,20m 2 / g,25m 2 / g,30m 2 / g,35m 2 / g,40m 2 / g,45m 2 / g,50m 2 / g,55m 2 / g,60m 2 / g,65m 2 / g,70m 2 / g,75m 2 / g,80m 2 / g,85m 2 / g,90m 2 / g,95m 2 / g,100m2 / g, and any range of two values.

[0061] Furthermore, the specific surface area of ​​the lithium adsorption material is 35-65m 2 / g.

[0062] According to the present invention, the ratio of the sum of the surface areas S1 of the pores on the shell to the sum of the maximum cross-sectional areas S2 of the finger-shaped pores in the core is 0.5-0.9:1.

[0063] In the present invention, in the lithium adsorption material, when the surface area S1 of the pores on the shell layer and the sum S2 of the maximum cross-sectional area of ​​the finger-shaped pores in the core body meet the above range, the lithium adsorption material has a faster water mass transfer rate inside the shell and the lithium ion sieve in the lithium adsorption material will not fall off under the pressure of the flushing water, thereby ensuring that the lithium adsorption material maintains a high adsorption capacity while the lithium adsorption material is not damaged or broken.

[0064] In the present invention, the total surface area of ​​the pores in the shell layer is measured using a SEM electron microscope (SEM) on the lithium adsorption material. Ten observation points are randomly selected for SEM testing, each with an area of ​​no less than 500 × 500 μm. The total surface area of ​​the shell layer and the total surface area of ​​all pores in the shell layer within the observation range are calculated. The histogram and magic wand tools in Photoshop can be used to obtain the number of pixels representing the dark areas of the membrane pores. This percentage is then calculated relative to the total number of pixels in the SEM image to represent the total surface area of ​​the shell layer (S1).

[0065] The sum of the maximum cross-sectional areas of the finger-like pores in the core was analyzed by using Image J on the cross-sectional SEM image of the obtained lithium adsorption material, and the sum of the maximum cross-sectional areas of the finger-like pores S2 was measured and calculated.

[0066] In the present invention, the ratio of the sum of the surface areas S1 of the holes on the shell layer to the sum of the maximum cross-sectional areas S2 of the finger-like holes in the core body is 0.5-0.9:1, for example, it can be 0.5:1,, 0.52:1, 0.54:1, 0.56:1, 0.58:1, 0.6:1, 0.62:1, 0.64:1, 0.66:1, 0.68:1, 0.7:1, 0.72:1, 0.74:1, 0.76:1, 0.78:1, 0.8:1, 0.82:1, 0.84:1, 0.86:1, 0.88:1, 0.9:1, and the range between any two values.

[0067] Furthermore, the ratio of the sum of the surface areas S1 of the pores on the shell layer to the sum of the maximum cross-sectional areas S2 of the finger-shaped pores in the core body is 0.6-0.8:1.

[0068] According to the present invention, the lithium adsorption material includes a skeleton and lithium ion sieves dispersed in the skeleton;

[0069] The skeleton comprises polyvinyl chloride and polyacrylic acid.

[0070] Furthermore, the lithium ion sieve is a hydroxyl-modified lithium ion sieve, and the lithium ion sieve is connected to the skeleton via hydroxyl groups.

[0071] In the present invention, the lithium adsorption material includes a skeleton and a hydroxyl-modified lithium ion sieve dispersed in the skeleton, and the skeleton includes polyvinyl chloride (PVC) and polyacrylic acid, and the lithium ion sieve is connected to the skeleton via hydroxyl groups. The hydroxyl groups in the lithium ion sieve have good compatibility with the polar groups (-COOH) on the polyacrylic acid molecular chain and the polyvinyl chloride, enabling the lithium ion sieve to be evenly dispersed in the skeleton comprising polyvinyl chloride and polyacrylic acid, reducing the embedding phenomenon of the lithium ion sieve. At the same time, the carboxyl groups (-COOH) on the polyacrylic acid molecular chain can promote lithium ion transfer, thereby significantly improving the adsorption and desorption rate of the lithium adsorption material.

[0072] In the present invention, the compound providing hydroxyl groups in the hydroxyl-modified lithium ion sieve forms a coating layer on the surface of the lithium ion sieve.

[0073] Furthermore, polyacrylic acid can inhibit the formation of salt crystals, especially the formation of salt crystals under high salt conditions, thereby reducing the phenomenon of pore blockage of the lithium adsorption material due to the formation of inorganic salt crystals in the internal pores of the lithium adsorption material during the cyclic adsorption and desorption process, and avoids the phenomenon of polyvinyl chloride rupture caused by the exchange of water flow and salt during long-term use, thereby extending the cycle service life of the lithium adsorption material.

[0074] Furthermore, polyacrylic acid has excellent hydrophilicity and mechanical strength, and can significantly improve the mechanical properties and swelling properties of the skeleton containing polyacrylic acid in a salt solution.

[0075] According to the present invention, based on the total weight of the lithium adsorption material, the content of the polyvinyl chloride is 16-67 wt %; the content of the polyacrylic acid is 0.06-9 wt %; and the content of the lithium ion sieve is 45-85 wt %.

[0076] In the present invention, the total content of polyvinyl chloride, polyacrylic acid and lithium ion sieve in the lithium adsorption material is 100 wt%.

[0077] In the present invention, based on the total weight of the lithium adsorption material, the content of the polyvinyl chloride is 16-67wt%, for example, it can be 16wt%, 18wt%, 20wt%, 22wt%, 24wt%, 26wt%, 28wt%, 30wt%, 32wt%, 34wt%, 36wt%, 38wt%, 40wt%, 42wt%, 44wt%, 46wt%, 48wt%, 50wt%, 52wt%, 54wt%, 56wt%, 58wt%, 60wt%, 62wt%, 64wt%, 66wt%, 67wt%, and a range consisting of any two values; the content of the polyacrylic acid is 0.06-9wt%, for example, it can be 0 .06wt%, 0.08wt%, 0.1wt%, 0.15wt%, 0.2wt%, 0.25wt%, 0.3wt%, 0.35wt%, 0.4wt%, 0.45wt%, 0.5wt%, 0.55wt%, 0.6wt%, 0.65wt%, 0.7wt%, 0.75wt%, 0.8wt%, 0.85wt%, 0.9wt%, and a range consisting of any two values; the content of the lithium ion sieve is 45-85wt%, for example, it can be 45wt%, 50wt%, 55wt%, 60wt%, 65wt%, 70wt%, 75wt%, 80wt%, 85wt%, and a range consisting of any two values.

[0078] In the present invention, when the contents of polyvinyl chloride, polyacrylic acid and lithium ion sieve in the lithium adsorption material meet the above ranges, the lithium adsorption material can have high adsorption capacity, fast mass transfer rate, high mechanical properties, excellent anti-swelling properties, and can inhibit salt crystallization.

[0079] Furthermore, based on the total weight of the lithium adsorption material, the content of the polyvinyl chloride is 16-54 wt %; the content of the polyacrylic acid is 0.9-9 wt %; and the content of the lithium ion sieve is 45-80 wt %.

[0080] According to the present invention, the thickness of the coating layer formed by the compound providing hydroxyl groups in the hydroxyl-modified lithium ion sieve is 1-5 nm.

[0081] In the present invention, when the thickness of the coating layer formed by the compound providing hydroxyl groups in the hydroxyl-modified lithium ion sieve is controlled to meet the above range, it is possible to ensure excellent compatibility between the lithium ion sieve and the polymer, and the hydroxyl-modified lithium ion sieve thus obtained can be uniformly dispersed in the polymer skeleton, and the loading amount of the hydroxyl-modified lithium ion sieve in the polymer skeleton is increased, and the lithium ion sieve in the lithium adsorption material thus obtained has a high specific surface area, thereby improving the adsorption capacity of the lithium adsorption material.

[0082] In the present invention, the thickness of the coating layer formed by the compound providing hydroxyl groups in the hydroxyl-modified lithium ion sieve is 1-5 nm, for example, it can be 1 nm, 1.5 nm, 2 nm, 2.5 nm, 3 nm, 3.5 nm, 4 nm, 4.5 nm, 5 nm, and a range consisting of any two values.

[0083] Furthermore, the thickness of the coating layer formed by the compound providing hydroxyl groups in the hydroxyl-modified lithium ion sieve is 3-5 nm.

[0084] In the present invention, the thickness of the coating layer formed by the compound providing hydroxyl groups in the hydroxyl-modified lithium ion sieve is measured by SEM electron microscope observation.

[0085] According to the present invention, the hydroxyl-modified lithium ion sieve is a polyphenol-modified lithium ion sieve.

[0086] In the present invention, when the hydroxyl-modified lithium ion sieve is a polyphenol-modified lithium ion sieve, while improving the compatibility between the lithium ion sieve and the polymer, so that the lithium ion sieve has better dispersion in the polymer skeleton, the modification conditions are milder, and the lithium adsorption material can have a high adsorption capacity.

[0087] According to the present invention, the polyphenol is selected from at least one of tannic acid, tea polyphenols, apple polyphenols, grape polyphenols, eriodictyol, naringenin, epicatechin, luteolin, naringenin, kaempferol, myricetin and genistein, preferably at least one of tannic acid, tea polyphenols and apple polyphenols.

[0088] According to the present invention, the lithium ion sieve is selected from titanium-based lithium ion sieves and / or manganese-based ion sieves.

[0089] According to the present invention, the lithium ions are selected from LiMn2O4, Li 1.6 Mn 1.6 O4、Li 1.33 Mn 1.67 O4、Li4Mn5O 12 、LiMnO2、Li2TiO3、Li 1.33 Ti 1.66 O4 and Li4Ti5O 12 At least one of .

[0090] According to the present invention, the water content of the hydroxyl-modified lithium ion sieve is less than or equal to 0.5 wt %.

[0091] In the present invention, when the moisture content of the hydroxyl-modified lithium ion sieve is controlled to meet the above range, phase separation between the polymer and the hydroxyl-modified lithium ion sieve due to the presence of water can be avoided, thereby causing the dispersion of the hydroxyl-modified lithium ion sieve in the skeleton to deteriorate.

[0092] In the present invention, the moisture content of the hydroxyl-modified lithium ion sieve refers to the free water content in the hydroxyl-modified lithium ion sieve.

[0093] In the present invention, the moisture content of the hydroxyl-modified lithium ion sieve is less than or equal to 0.5wt%, for example, it can be 0.5wt%, 0.45wt%, 0.4wt%, 0.35wt%, 0.3wt%, 0.25wt%, 0.2wt%, 0.15wt%, 0.1wt%, and a range consisting of any two values.

[0094] Furthermore, the water content of the hydroxyl-modified lithium ion sieve is 0.1-0.3 wt %.

[0095] According to the present invention, the average particle diameter of the lithium ion sieve in the cross section of the lithium adsorption material measured by SEM electron microscopy is less than or equal to 2.5 μm.

[0096] In the present invention, when the average particle diameter of the lithium ion sieve in the cross section of the lithium adsorption material meets the above range, the effective adsorption performance of the lithium ion sieve is maximized, so that the adsorption capacity of the lithium adsorption material is large and the desorption efficiency of lithium ions is high.

[0097] In the present invention, the average particle diameter of the lithium ion sieve in the lithium adsorption material refers to the average diameter of a single lithium ion sieve or the average diameter of an aggregate formed by multiple lithium ion sieve particles. However, as long as the average particle diameter of a single lithium ion sieve particle and an aggregate formed by multiple lithium ion sieve particles in the cross section of the lithium adsorption material meets the above range, it indicates that the lithium ion sieve is uniformly distributed in the lithium adsorption material.

[0098] In the present invention, the average particle diameter of the lithium ion sieve in the lithium adsorption material is measured by SEM electron microscopy. Ten observation points are randomly selected for scanning electron microscopy testing, and the size of each observation area is not less than 500×500 μm. When the lithium ion sieve is completely free of agglomeration, the average particle diameter is the average particle diameter of a single lithium ion sieve. When the lithium ion sieve is partially agglomerated, the average particle diameter is the maximum particle diameter of the aggregate.

[0099] In the present invention, the average particle diameter of the lithium ion sieve in the cross section of the lithium adsorption material measured by SEM electron microscopy is less than or equal to 2.5 μm, for example, it can be 2.5 μm, 2 μm, 1.5 μm, 1 μm, 0.5 μm, 0.4 μm, 0.3 μm, 0.2 μm, 0.1 μm, and a range consisting of any two values.

[0100] Furthermore, the average particle diameter of the lithium ion sieve in the cross section of the lithium adsorption material measured by SEM electron microscopy is less than or equal to 1.5 μm, preferably 0.1-1.5 μm.

[0101] According to the present invention, based on the total surface area of ​​the shell layer of the lithium adsorption material, the sum S1 of the surfaces of the pores present in the shell layer is 30-90%.

[0102] In the present invention, when the sum S1 of the surfaces of the pores existing on the shell layer covering the surface of the core in the lithium adsorption material meets the above range, the lithium adsorption material has a fast water adsorption mass transfer rate, a fast adsorption rate, a high desorption efficiency, and a small decrease in recycling performance.

[0103] In the present invention, the total area of ​​the pores present in the shell layer refers to the sum of the surface areas of all the pores present in the shell layer.

[0104] In the present invention, the sum of the total surface area of ​​the shell layer of the lithium adsorption material and the surface area of ​​the pores in the shell layer (S1) is measured using a scanning electron microscope (SEM). Specifically, the lithium adsorption material is tested using a SEM electron microscope. Ten observation points are randomly selected for SEM testing, each observation area being no less than 500 × 500 μm. The sum of the surface area of ​​the shell layer and the sum of the areas of all pores in the shell layer within the observation range are calculated. The number of pixels representing the dark areas of the membrane pores can be obtained using the histogram and magic wand tools in Photoshop. The ratio of this number to the total number of pixels in the SEM image is then calculated to obtain the percentage of the sum of the surface area of ​​the pores in the shell layer (S1) to the total surface area of ​​the shell layer.

[0105] In the present invention, based on the total surface area of ​​the shell of the lithium adsorption material, the sum of the surface areas S1 of the pores present in the shell is 30-90%, for example, it can be 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, and a range consisting of any two values.

[0106] Furthermore, based on the total surface area of ​​the shell layer of the lithium adsorption material, the sum of the surface areas S1 of the pores present in the shell layer is 50-90%.

[0107] A second aspect of the present invention provides a method for preparing a lithium adsorption material, characterized in that the method comprises the following steps:

[0108] (1) mixing polyvinyl chloride, polyacrylic acid, lithium ion sieve and oil phase solvent to obtain a mixed solution;

[0109] (2) Under the conditions of temperature of 20-60° C. and humidity of 40-80%, the mixed solution is added dropwise to an aqueous solvent to obtain a lithium adsorption material.

[0110] In the present invention, the lithium adsorption material is prepared using the above-mentioned method. Specifically, under specific temperature and humidity conditions, a mixture containing polyvinyl chloride, polyacrylic acid, and lithium ion sieve is dropwise added to an aqueous solvent to produce the lithium adsorption material described in the first aspect of the present invention. Specifically, under the specific temperature and humidity conditions, a difference in the rates of internal and surface phase transformation is achieved, resulting in a structure with small surface pores and large internal pores. This allows the lithium adsorption material to have a relatively fast water mass transfer rate within the shell while preventing the lithium ion sieve powder from leaking out under the pressure of the flushing water. The resulting lithium adsorption material has a high adsorption capacity and a long service life.

[0111] According to the present invention, the lithium ion sieve is selected from titanium-based lithium ion sieves and / or manganese-based ion sieves.

[0112] According to the present invention, the lithium ion is selected from LiMn2O4, Li 1.6 Mn 1.6 O4、Li 1.33 Mn 1.67 O4、Li4Mn5O 12 、LiMnO2、 Li2TiO3、Li 1.33 Ti 1.66 O4 and Li4Ti5O 12 At least one of .

[0113] In the present invention, the average particle size of the lithium ion sieve is 0.1-1 μm, for example, it can be 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, and a range consisting of any two values.

[0114] According to the present invention, in step (1), the weight average molecular weight of the polyvinyl chloride is 50,000-110,000 g / mol, for example, it can be 50,000 g / mol, 55,000 g / mol, 60,000 g / mol, 65,000 g / mol, 70,000 g / mol, 75,000 g / mol, 80,000 g / mol, 85,000 g / mol, 90,000 g / mol, 95,000 g / mol, 100,000 g / mol, 105,000 g / mol, 110,000 g / mol, and a range consisting of any two values.

[0115] Furthermore, the weight average molecular weight of the polyvinyl chloride is 70,000-90,000 g / mol.

[0116] In the present invention, there is no particular limitation on the type of oil phase solvent, and conventional oil phase solvents in the art can be used, such as at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone and dimethyl sulfoxide.

[0117] According to the present invention, the weight average molecular weight of the polyacrylic acid is 100,000-1.3 million g / mol.

[0118] In the present invention, the selection of the polyacrylic acid having a specific weight-average molecular weight can improve the mechanical strength of the interpenetrating network structure formed between the polyacrylic acid and the polyvinyl chloride molecular chains, and simultaneously inhibit salt crystallization, promote lithium ion transfer and resist swelling, thereby significantly improving the mechanical properties, lithium adsorption capacity and anti-swelling properties of the prepared lithium adsorption material.

[0119] In the present invention, the weight average molecular weight of the polyacrylic acid is 100,000-1,300,000 g / mol, for example, 100,000 g / mol, 150,000 g / mol, 200,000 g / mol, 250,000 g / mol, 300,000 g / mol, 350,000 g / mol, 400,000 g / mol, 450,000 g / mol, 500,000 g / mol, 550,000 g / mol, 600,000 g / mol, 650,000 g / mol, 700,000 g / mol, 750,000 g / mol, 800,000 g / mol, 850,000 g / mol, 900,000 g / mol, 950,000 g / mol, 1,000,000 g / mol, 1,100,000 g / mol, 1,200,000 g / mol, 1,300,000 g / mol, and a range consisting of any two values.

[0120] Furthermore, the weight average molecular weight of the polyacrylic acid is 1-1.3 million g / mol.

[0121] According to the present invention, in step (1), the amounts of the polyvinyl chloride, the polyacrylic acid and the lithium ion sieve are such that, based on the total weight of the lithium adsorption material, the content of the polyvinyl chloride is 16-67 wt%; the content of the polyacrylic acid is 0.06-9 wt%; and the content of the lithium ion sieve is 45-85 wt%.

[0122] In the present invention, when the amounts of polyvinyl chloride, polyacrylic acid and lithium ion sieve are controlled to meet the above ranges, the interpenetrating network structure formed between the polyacrylic acid and polyvinyl chloride molecular chains can have improved mechanical strength, and at the same time has the effects of inhibiting salt crystallization, promoting lithium ion transfer and resisting swelling, ultimately resulting in significantly improved mechanical properties, lithium adsorption capacity and anti-swelling properties of the prepared lithium adsorption material.

[0123] Furthermore, in step (1), the amounts of the polyvinyl chloride, the polyacrylic acid and the lithium ion sieve are such that, based on the total weight of the lithium adsorption material, the content of the polyvinyl chloride is 16-54 wt%; the content of the polyacrylic acid is 0.9-9 wt%; and the content of the lithium ion sieve is 45-80 wt%.

[0124] In the present invention, there is no particular limitation on the mixing conditions of step (1), as long as the polyvinyl chloride, polyacrylic acid, lithium ion sieve and oil phase solvent can be fully mixed to obtain a mixed solution, for example, the mixing is carried out at 20-70° C. under stirring conditions.

[0125] In a specific embodiment of the present invention, in step (1), in order to ensure that the materials in the mixed liquid are fully mixed and uniform, preferably, during the mixing process, a step-by-step feeding method is adopted. Specifically, after polyvinyl chloride, polyacrylic acid and oil phase solvent are mixed, lithium ion sieve is added to the above mixed product to obtain the mixed liquid.

[0126] In the present invention, in step (2), the temperature is 20-60°C, for example, it can be 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, and a range consisting of any two values; the humidity is 40-80%, for example, it can be 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, and a range consisting of any two values.

[0127] Furthermore, in step (2), the mixed solution is added dropwise to the aqueous solvent at a temperature of 35-60° C. and a humidity of 60-80%.

[0128] According to the present invention, the aqueous phase solvent is selected from at least one of water, ethanol and acetic acid, preferably water.

[0129] According to the present invention, in order to further improve the dispersibility of the lithium ion sieve in the polymer network structure formed by polyvinyl chloride and polyacrylic acid, preferably, the lithium ions are hydroxyl-modified lithium ion sieve.

[0130] According to the present invention, the lithium ion sieve is modified by using an aqueous solution containing a hydroxyl compound, and the hydroxyl-modified lithium ion sieve is obtained after solid-liquid separation and drying.

[0131] According to the present invention, the hydroxyl-containing compound is a polyphenol; preferably selected from at least one of tannic acid, tea polyphenols, apple polyphenols, grape polyphenols, eriodictyol, naringenin, epicatechin, luteolin, naringenin, kaempferol, myricetin and genistein, preferably at least one of tannic acid, tea polyphenols and apple polyphenols.

[0132] According to the present invention, the concentration of the aqueous solution containing hydroxyl compounds is 0.05 mg / L-1 mg / L, for example, it can be 0.05 mg / L, 0.15 mg / L, 0.2 mg / L, 0.25 mg / L, 0.3 mg / L, 0.35 mg / L, 0.4 mg / L, 0.45 mg / L, 0.5 mg / L, 0.55 mg / L, 0.6 mg / L, 0.65 mg / L, 0.7 mg / L, 0.75 mg / L, 0.8 mg / L, 0.85 mg / L, 0.9 mg / L, 0.95 mg / L, 1 mg / L, and a range consisting of any two values.

[0133] In the present invention, when the concentration of the aqueous solution containing the hydroxyl compound is controlled to meet the above range, it can ensure that the hydroxyl groups form a coating layer with a suitable thickness on the surface of the lithium ion sieve, ensuring that the hydroxyl-modified lithium ion sieve can have good dispersion in the polymer skeleton.

[0134] According to the present invention, the mass ratio of the lithium ion sieve to the hydroxyl-containing compound is 1:0.01-0.3.

[0135] In the present invention, when the mass ratio of the lithium ion sieve to the hydroxyl-containing compound is controlled to meet the above range, it can ensure that the lithium ion sieve and the hydroxyl-containing compound fully react, and the hydroxyl-containing compound can form a uniform coating layer on the surface of the lithium ion sieve, thereby significantly improving the dispersibility of the obtained hydroxyl-modified lithium ion sieve.

[0136] In the present invention, the mass ratio of the lithium ion sieve to the hydroxyl-containing compound is 1:0.01-0.3, for example, it can be 1:0.01, 1:0.05, 1:0.1, 1:0.15, 1:0.2, 1:0.25, 1:0.3, and a range consisting of any two values.

[0137] Furthermore, the mass ratio of the lithium ion sieve to the hydroxyl-containing compound is 1:0.05-0.08.

[0138] According to the present invention, the modification conditions include: a reaction time of 30 min-4 h, for example, 30 min, 40 min, 50 min, 60 min, 1.1 h, 1.2 h, 1.3 h, 1.4 h, 1.5 h, 1.6 h, 1.7 h, 1.8 h, 1.9 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, and a range consisting of any two values; a reaction temperature of 25-40 ° C, for example, 25 ° C, 26 ° C, 27 ° C, 28 ° C, 29 ° C, 30 ° C, 31 ° C, 32 ° C, 33 ° C, 34 ° C, 35 ° C, 36 ° C, 37 ° C, 38 ° C, 39 ° C, 40 ° C, and a range consisting of any two values.

[0139] In the present invention, the modification reaction is carried out under the above conditions, which can ensure that the lithium ion sieve and the hydroxyl-containing compound fully react, and the hydroxyl-containing compound can form a uniform coating layer on the surface of the lithium ion sieve, thereby significantly improving the dispersibility of the prepared hydroxyl-modified lithium ion sieve.

[0140] In the present invention, there is no particular limitation on the methods and conditions for solid-liquid separation and drying. Conventional solid-liquid separation methods in the art, such as centrifugal separation, and conventional drying methods and conditions can be used, as long as the moisture content of the hydroxyl-modified lithium ion sieve after drying meets the requirements of the present invention.

[0141] According to the present invention, the method further comprises the step of washing the lithium adsorption material with an acidic solution.

[0142] In the present invention, the lithium adsorption material is a lithium adsorption material precursor, and the lithium adsorption material is washed with an acidic solution to make the Li + and H + Exchange to activate the precursor and obtain H-type lithium ion sieve, such as Li 1.33 Mn 1.67 O4 to H 1.33 Mn 1.67 O4, the obtained H-type lithium ion sieve has a specific adsorption effect on lithium ions.

[0143] Furthermore, under the action of a peristaltic pump, an acidic solution is used to circulate and wash the lithium adsorption material.

[0144] Furthermore, the acidic solution is selected from at least one of hydrochloric acid, phosphoric acid and sulfuric acid.

[0145] Furthermore, H + Ion meter, the concentration of the acidic solution is 0.1-1 mol / L, for example, it can be 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, and a range consisting of any two values.

[0146] Further, the flow rate of the peristaltic pump is 1-25BV / h, for example, it can be 1BV / h, 5BV / h, 10BV / h, 15BV / h, 20BV / h, 25BV / h, and a range consisting of any two values, and the cycle time is 1-48h, for example, it can be 1h, 2h, 4h, 6h, 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h, 24h, 26h, 28h, 30h, 32h, 34h, 36h, 38h, 40h, 42h, 44h, 46h, 48h, and a range consisting of any two values.

[0147] In the present invention, when the conditions for circulating washing or the concentration of the acidic solution are controlled to meet the above range, ion exchange can be achieved without destroying the structure of the lithium ion sieve, ensuring that the washed lithium adsorption material has high mechanical strength, high adsorption capacity for lithium and excellent anti-swelling performance.

[0148] In a specific embodiment of the present invention, the concentration of the acidic solution is 0.1-0.5 mol / L; the flow rate of the peristaltic pump is 2-10 BV / h, and the circulation time is 4-24 h.

[0149] The third aspect of the present invention provides a lithium adsorption material prepared by the above method.

[0150] A fourth aspect of the present invention provides an application of the lithium adsorption material in lithium extraction, preferably in a liquid environment.

[0151] In the present invention, unless otherwise specified, the average diameter, average particle size, etc. refer to the volume average diameter and volume average particle size of the particles.

[0152] The present invention will be described in detail below by way of examples.

[0153] The morphology of the granulated products was characterized by scanning electron microscopy (SEM, S-4800, Japan).

[0154] The shell thickness and the average diameter of the pores in the shell were measured by scanning electron microscopy.

[0155] The sum of the surface areas of the pores on the shell layer S1 and the sum of the maximum cross-sectional areas of the finger-like pores in the core S2 were analyzed by Image J to measure the sum of the surface areas of the pores and the sum of the maximum cross-sectional areas of the finger-like pores in the core.

[0156] The longest average length and the shortest average length of the finger-like pores contained in the core of the lithium adsorption material are measured using a scanning electron microscope and calculated.

[0157] In the present invention, the average particle diameter of the lithium ion sieve in the lithium adsorption material is measured by SEM electron microscopy. When the lithium ion sieve is completely free of agglomeration, the average particle diameter is the average particle diameter of a single lithium ion sieve. When the lithium ion sieve is partially agglomerated, the average particle diameter is the average particle diameter of the largest aggregate.

[0158] The sum of the surface areas of the shell layer of the lithium adsorption material and the sum of the surface areas of the pores in the shell layer are measured using a scanning electron microscope (SEM). Specifically, when testing the density of pores in the shell layer of the lithium adsorption material using a SEM electron microscope, 10 observation points are randomly selected for SEM testing, with each observation area being no less than 500 × 500 μm. The sum of the surface areas of the shell layer and the sum of the surface areas of all pores in the shell layer within the observation range are calculated. The histogram and magic wand tools in Photoshop can be used to obtain the number of pixels representing the dark areas of the membrane pores. This percentage is then calculated relative to the total number of pixels in the SEM image to represent the percentage of the sum of the surface areas of the pores in the shell layer (S1) to the total surface area of ​​the shell layer.

[0159] The average particle size of the lithium adsorbent material and the hydroxyl-modified ion sieve was measured by scanning electron microscopy.

[0160] The porosity was measured using a mercury intrusion instrument AutoPore IV 9500 (Micromeritics Instruments, USA). The specific test method was to press mercury into the pores of the lithium adsorption material at a pressure of 0.1 to 60 kPa, and the porosity was obtained based on the mercury change curve data.

[0161] The specific surface area is determined by the BET method. The specific method is to measure the adsorption-desorption isotherm of the lithium adsorption material to N2 at 77K and obtain the BET specific surface area by fitting.

[0162] The contents of polyvinyl chloride, polyacrylic acid and hydroxyl-modified lithium ion sieve in the lithium adsorption material are obtained by measuring the element contents using X-ray photoelectron spectroscopy (XPS), wherein the content of PVC in the lithium adsorption material is calculated from the Cl element content, and the content of hydroxyl-modified lithium ion sieve is calculated from the content of metal Mn or Ti. The content of polyacrylic acid = the weight of the lithium adsorption material particles - the content of polyvinyl chloride - the content of hydroxyl-modified lithium ion sieve.

[0163] The thickness of the coating layer formed by polyphenols in the polyphenol-modified lithium ion sieve was measured using a transmission electron microscope.

[0164] The moisture content of the hydroxyl-modified lithium ion sieve was measured using a moisture meter.

[0165] Adsorption and desorption cycle: The obtained lithium adsorption material particles (4 g) were loaded into a glass column and acid-washed (using H +, 0.5mol / L hydrochloric acid was washed at a rate of 2BV / h for 24h), and a mixture of lithium chloride and magnesium chloride (lithium ion content 100mg / L, magnesium ion concentration 20000mg / L, ammonia water was used to adjust the pH of the mixture to 9.5, V=400mL) was pumped in at a flow rate of 2BV / h with a peristaltic pump for dynamic adsorption-desorption cycle adsorption for 24h. Then 0.5M hydrochloric acid (200mL) was pumped in at a flow rate of 2BV / h with a peristaltic pump for 24h to desorb the lithium ions in the particles. Then washing with deionized water until neutral is one cycle. During one of the adsorption processes, the change of adsorption capacity over time was monitored and the saturated adsorption capacity Q was calculated. The calculation formula is as follows:

[0166] Where Q is the saturated adsorption capacity (mg / g), reflecting the amount adsorbed at equilibrium; C0 and C are the initial and saturated lithium ion concentrations in the solution (mg / L), respectively; V is the volume of the adsorption solution (L); and m is the mass of the granular adsorbent (g). Ion concentrations were determined using ion chromatography (ICS-1100, DIONEX, America).

[0167] Lithium ion desorption efficiency D Li+ :D Li+ (%) = (c1*V2) / m*100%, where c1 is the concentration of lithium in the desorption solution, mg / L; V2 is the volume of the desorption solution, L; and m is the mass of the adsorbed lithium ions, g.

[0168] The adsorption capacity decrease rate after 30 cycles of operation is calculated according to the following formula:

[0169] The adsorption capacity decrease rate after 30 cycles of operation is % = (Q1-Q30) / Q1*100%, where Q1 is the first adsorption capacity and Q30 is the 30th adsorption capacity.

[0170] Water mass transfer rate: the time it takes for a unit mass of dry lithium adsorbent material (mass m0) to reach a completely water-absorbed state (m, where the mass no longer increases) when the unit mass of dry lithium adsorbent material (mass m0) is immersed in water, in units of min / g.

[0171] Mechanical properties: After 30 cycles of adsorption and desorption (adsorption under the condition of adjusting the pH of the mixed solution to 9.5 with ammonia water, and desorption with 0.5M hydrochloric acid), SEM observation showed that there were no cracks on the surface of the lithium adsorption material.

[0172] Anti-swelling performance: A unit mass of lithium adsorption material was immersed in a high salt solution (lithium ion content 100 mg / L, magnesium ion concentration 20,000 mg / L) for 48 h, and the anti-swelling performance of the lithium adsorption material was characterized by the volume change rate, where volume change rate (%) = (volume after swelling - volume before swelling) / volume before swelling × 100%.

[0173] In the following examples and comparative examples, all reagents were purchased from J&K Technology Co., Ltd.

[0174] Example 1

[0175] (1) Take powder Li 1.33 Mn 1.67 O4 (average particle size 0.5 μm) was mixed with a tannic acid aqueous solution (wherein the concentration of tannic acid was 0.1 mg / L) so that the mass ratio of the lithium ion sieve and the polyphenol substance was 1:0.05, stirred at 30°C for 2 hours, and then centrifuged. The solid phase material was dried, ground and sieved to obtain a hydroxyl-modified (polyphenol-modified) lithium ion sieve with a moisture content of 0.3wt% and a coating layer formed by hydroxyl groups on the surface of the lithium ion sieve with a thickness of 5nm.

[0176] (2) Weigh 10 g of polyvinyl chloride (weight average molecular weight 62,000 g / mol) powder, 2 g of polyacrylic acid (weight average molecular weight 350,000 g / mol) and 88 g of DMF, place them in a beaker and stir, heat to 60°C, dissolve them, cool to 30°C, add 40 g of hydroxyl-modified (polyphenol-modified) lithium ion sieve, stir and mix them at 30°C to obtain a mixed solution.

[0177] (3) The mixed solution was added dropwise to water at a temperature of 30°C and a humidity of 56% to obtain lithium adsorption material particles A1. The moisture content of the hydroxyl-modified lithium ion sieve and the thickness of the coating layer formed by the hydroxyl groups on the surface of the lithium ion sieve are shown in Table 1.

[0178] The microscopic morphology parameters of the lithium adsorption material particles are shown in Table 2, and the contents of polyvinyl chloride, polyacrylic acid and hydroxyl-modified lithium ion sieve in the lithium adsorption material particles are shown in Table 2.

[0179] Example 2

[0180] (1) Take powder Li 1.33 Mn 1.67 O4 (average particle size 0.5 μm) was mixed with a tannic acid aqueous solution (wherein the concentration of tannic acid was 0.05 mg / L) so that the mass ratio of the lithium ion sieve material and the polyphenol substance was 1:0.05, stirred at 30°C for 1 hour, and then centrifuged. The solid phase material was dried, ground and sieved to obtain a hydroxyl-modified (polyphenol-modified) lithium ion sieve with a moisture content of 0.3wt% and a coating layer formed by hydroxyl groups on the surface of the lithium ion sieve with a thickness of 3nm.

[0181] (2) Weigh 8 g of polyvinyl chloride (weight average molecular weight 62,000 g / mol) powder, 0.2 g of polyacrylic acid (weight average molecular weight 350,000 g / mol) and 91.8 g of DMF into a beaker and stir. Heat to 60°C, dissolve, and cool to 30°C. Then, add 10 g of hydroxyl-modified (polyphenol-modified) lithium ion sieve and stir at 30°C to obtain a mixed solution.

[0182] (3) The second mixed solution was added dropwise to water at a temperature of 55° C. and a humidity of 75% to obtain lithium adsorption material particles A2. The moisture content of the hydroxyl-modified lithium ion sieve and the thickness of the coating layer formed by the hydroxyl groups on the surface of the lithium ion sieve are shown in Table 1.

[0183] The microscopic morphology parameters of the lithium adsorption material particles are shown in Table 2, and the contents of polyvinyl chloride, polyacrylic acid and hydroxyl-modified lithium ion sieve in the lithium adsorption material particles are shown in Table 2.

[0184] Example 3

[0185] (1) Take powder Li 1.33 Mn 1.67 O4 (average particle size 0.5 μm) was mixed with a tannic acid aqueous solution (wherein the concentration of tannic acid was 0.1 mg / L) so that the mass ratio of the lithium ion sieve material and the polyphenol substance was 1:0.01, stirred at 30°C for 1 hour, and then centrifuged. The solid phase material was dried, ground and sieved to obtain a hydroxyl-modified (polyphenol-modified) lithium ion sieve with a moisture content of 0.3wt% and a coating layer formed by hydroxyl groups on the surface of the lithium ion sieve with a thickness of 3.2nm.

[0186] (2) Weigh 12 g of polyvinyl chloride (weight average molecular weight 62,000 g / mol) powder, 3 g of polyacrylic acid (weight average molecular weight 350,000 g / mol) and 85 g of DMF, place them in a beaker and stir, heat to 60°C, dissolve them, cool to 30°C, add 20 g of hydroxyl-modified (polyphenol-modified) lithium ion sieve, stir and mix them at 30°C to obtain a mixed solution.

[0187] (3) The mixed solution was added dropwise to water at a temperature of 40°C and a humidity of 42% to obtain lithium adsorption material particles A3. The moisture content of the hydroxyl-modified lithium ion sieve and the thickness of the coating layer formed by the hydroxyl groups on the surface of the lithium ion sieve are shown in Table 1.

[0188] The microscopic morphology parameters of the lithium adsorption material particles are shown in Table 2, and the contents of polyvinyl chloride, polyacrylic acid and hydroxyl-modified lithium ion sieve in the lithium adsorption material particles are shown in Table 2.

[0189] Example 4

[0190] (1) Take powder Li 1.33 Mn 1.67O4 (average particle size 0.5 μm) was mixed with a tannic acid aqueous solution (wherein the concentration of tannic acid was 0.01 mg / L) so that the mass ratio of the lithium ion sieve material and the polyphenol substance was 1:0.01, stirred at 30°C for 1 hour, and then centrifuged. The solid phase material was dried, ground and sieved to obtain a hydroxyl-modified (polyphenol-modified) lithium ion sieve with a moisture content of 0.3 wt% and a coating layer formed by hydroxyl groups on the surface of the lithium ion sieve with a thickness of 2 nm.

[0191] (2) Weigh 6 g of polyvinyl chloride (weight average molecular weight 62,000 g / mol) powder, 0.1 g of polyacrylic acid (weight average molecular weight 350,000 g / mol) and 93.9 g of DMF, place them in a beaker and stir, heat to 60°C, dissolve them and cool to 30°C, then add 5 g of hydroxyl-modified (polyphenol-modified) lithium ion sieve, stir and mix them at 30°C to obtain a mixed solution.

[0192] (4) The mixed solution was added dropwise to water at a temperature of 30°C and a humidity of 52% to obtain lithium adsorption material particles A4. The moisture content of the hydroxyl-modified lithium ion sieve and the thickness of the coating layer formed by the hydroxyl groups on the surface of the lithium ion sieve are shown in Table 1.

[0193] The microscopic morphology parameters of the lithium adsorption material particles are shown in Table 2, and the contents of polyvinyl chloride, polyacrylic acid and hydroxyl-modified lithium ion sieve in the lithium adsorption material particles are shown in Table 2.

[0194] Example 5

[0195] (1) Same as Example 1.

[0196] (2) Weigh 10 g of polyvinyl chloride (weight average molecular weight 62,000 g / mol) powder, 0.1 g of polyacrylic acid (weight average molecular weight 350,000 g / mol) and 93.9 g of DMF, place them in a beaker and stir, heat to 60°C, dissolve them, cool to 30°C, add 5 g of hydroxyl-modified (polyphenol-modified) lithium ion sieve, and stir and mix them at 30°C to obtain a mixed solution.

[0197] (3) The lithium adsorption material particles A5 were obtained in the same manner as in Example 1. The moisture content of the hydroxyl-modified lithium ion sieve and the thickness of the coating layer formed by the hydroxyl groups on the surface of the lithium ion sieve are shown in Table 1.

[0198] The microscopic morphology parameters of the lithium adsorption material particles are shown in Table 2, and the contents of polyvinyl chloride, polyacrylic acid and hydroxyl-modified lithium ion sieve in the lithium adsorption material particles are shown in Table 2.

[0199] Example 6

[0200] (1) Take powder Li 1.33 Mn 1.67O4 (average particle size 0.5 μm) was mixed with a tannic acid aqueous solution (wherein the concentration of tannic acid was 0.1 mg / L) so that the mass ratio of the lithium ion sieve material and the polyphenol substance was 1:0.3, stirred at 30°C for 2 hours, and then centrifuged. The solid phase material was dried, ground and sieved to obtain a hydroxyl-modified (polyphenol-modified) lithium ion sieve with a moisture content of 0.3wt% and a coating layer formed by hydroxyl groups on the surface of the lithium ion sieve with a thickness of 2nm.

[0201] (2) Weigh 10 g of polyvinyl chloride (weight average molecular weight 62,000 g / mol) powder, 0.1 g of polyacrylic acid (weight average molecular weight 350,000 g / mol) and 93.9 g of DMF, place them in a beaker and stir, heat to 60°C, dissolve them, cool to 30°C, add 50 g of hydroxyl-modified (polyphenol-modified) lithium ion sieve, and stir and mix them at 30°C to obtain a mixed solution.

[0202] (3) The mixed solution was added dropwise to water at a temperature of 30°C and a humidity of 56% to obtain lithium adsorption material particles A6. The moisture content of the hydroxyl-modified lithium ion sieve and the thickness of the coating layer formed by the hydroxyl groups on the surface of the lithium ion sieve are shown in Table 1.

[0203] The microscopic morphology parameters of the lithium adsorption material particles are shown in Table 2, and the contents of polyvinyl chloride, polyacrylic acid and hydroxyl-modified lithium ion sieve in the lithium adsorption material particles are shown in Table 2.

[0204] Example 7

[0205] As in Example 1, in step (1), tannic acid was replaced with polyethylene glycol (molecular weight 1000 g / mol) to obtain a hydroxyl-modified (alcoholic hydroxyl-modified) lithium ion sieve having a moisture content of 0.3 wt % and a 3 nm thick coating layer formed by the hydroxyl groups on the surface of the lithium ion sieve. Lithium adsorbent material A7 was obtained. The moisture content and thickness of the coating layer formed by the hydroxyl groups on the surface of the lithium ion sieve are shown in Table 1.

[0206] The microscopic morphology parameters of the lithium adsorption material particles are shown in Table 2, and the contents of polyvinyl chloride, polyacrylic acid and hydroxyl-modified lithium ion sieve in the lithium adsorption material particles are shown in Table 2.

[0207] Example 8

[0208] The same method as in Example 1 was used, except that the weight-average molecular weight of polyvinyl chloride was 78,000 g / mol and the weight-average molecular weight of polyacrylic acid was 1.3 million g / mol to produce lithium adsorption material A8. The moisture content of the hydroxyl-modified lithium ion sieve and the thickness of the coating layer formed by the hydroxyl groups on the surface of the lithium ion sieve are shown in Table 1.

[0209] The microscopic morphology parameters of the lithium adsorption material particles are shown in Table 2, and the contents of polyvinyl chloride, polyacrylic acid and hydroxyl-modified lithium ion sieve in the lithium adsorption material particles are shown in Table 2.

[0210] Example 9

[0211] The same method as in Example 1 was used without modification in step (1) and the lithium ion sieve was used directly to prepare lithium adsorption material A9. The water content of the lithium ion sieve is shown in Table 1.

[0212] The microscopic morphology parameters of the lithium adsorption material particles are shown in Table 2, and the contents of polyvinyl chloride, polyacrylic acid and hydroxyl-modified lithium ion sieve in the lithium adsorption material particles are shown in Table 2.

[0213] Example 10

[0214] As in Example 1, in step (1), tannic acid was replaced with tea polyphenols. A hydroxyl-modified (phenolic hydroxyl-modified) lithium ion sieve was obtained, having a moisture content of 0.3 wt %, and a hydroxyl coating layer on the surface of the lithium ion sieve having a thickness of 3 nm. Lithium adsorption material A10 was obtained. The moisture content and thickness of the hydroxyl coating layer on the surface of the lithium ion sieve are shown in Table 1.

[0215] The microscopic morphology parameters of the lithium adsorption material particles are shown in Table 2, and the contents of polyvinyl chloride, polyacrylic acid and hydroxyl-modified lithium ion sieve in the lithium adsorption material particles are shown in Table 2.

[0216] Example 11

[0217] As in Example 1, in step (1), the lithium ion sieve was replaced with Li2TiO3 (average particle size 1 μm), resulting in a hydroxyl-modified lithium ion sieve having a moisture content of 0.3 wt %. The thickness of the hydroxyl coating layer formed on the lithium ion sieve was 4.9 nm. Lithium adsorption material A11 was obtained. The moisture content of the hydroxyl-modified lithium ion sieve and the thickness of the hydroxyl coating layer formed on the surface of the lithium ion sieve are shown in Table 1.

[0218] The microscopic morphology parameters of the lithium adsorption material particles are shown in Table 2, and the contents of polyvinyl chloride, polyacrylic acid and hydroxyl-modified lithium ion sieve in the lithium adsorption material particles are shown in Table 2.

[0219] Comparative Example 1

[0220] The same method as in Example 1 was used, but without adding polyacrylic acid, to obtain lithium adsorption material D1.

[0221] Comparative Example 2

[0222] Same as in Example 1, in step (4), the temperature is 20° C. and the humidity is 10%, thereby obtaining lithium adsorption material D2.

[0223] Comparative Example 3

[0224] The same method as in Example 1 was used, except that the modification operation in step (1) was not performed. In step (4), the temperature was 20° C. and the humidity was 10%. Thus, a lithium adsorption material D3 was obtained.

[0225] Comparative Example 4

[0226] The same method as in Example 1 was used, but without the modification operation in step (1), and polyacrylic acid was replaced with polyacrylonitrile (weight average molecular weight of 80,000 g / mol) to obtain lithium adsorption material D4.

[0227] Comparative Example 5

[0228] Granulation was performed by extrusion. 525g PVC (weight average molecular weight 62,000 g / mol) and 175g thermoplastic acrylic resin (weight average molecular weight 120,000 g / mol) were melted at 170°C. 250g Li 1.33 Mn 1.67 O4 (average particle size 0.5 μm) powder was stirred evenly, extruded, cooled and formed to obtain lithium adsorption material D5.

[0229] Table 1

[0230] Table 2

[0231] Note: S1 is the sum of the surface areas of the pores on the shell; S2 is the sum of the maximum cross-sectional areas of the finger-shaped pores in the core.

[0232] Table 2 (continued)

[0233] 1 It refers to the sum of the surface areas of the pores on the shell layer S1 / total surface area of ​​the shell layer × 100%.

[0234] Table 2 (continued)

[0235] * refers to the content of unmodified lithium ion sieve; ** refers to the content of polyacrylonitrile.

[0236] As can be seen from Table 2, the lithium adsorption materials provided by Examples 1-11 of the present invention have a core with a specific pore structure and pores with a specific average diameter coated on the surface of the core, and the shell has a specific thickness. The lithium adsorption material having the above-mentioned specific structure presents a special structure with small pores in the outer shell and large pores in the inner core, which can increase the mass transfer rate of water. When used for lithium extraction in a liquid environment, it can significantly improve the adsorption capacity of lithium.

[0237] Combined with Table 1, it can be seen that the lithium ion sieve is modified by using a hydroxyl-containing compound to obtain a hydroxyl-modified lithium ion sieve. When the hydroxyl-modified lithium ion sieve is used to prepare a lithium adsorption material, the lithium ion sieve in the prepared lithium adsorption material has better dispersibility and pore size distribution due to the increased compatibility, thereby improving the adsorption capacity, water mass transfer rate and other properties of the lithium adsorption material when extracting lithium in a liquid environment.

[0238] Figure 1 is a surface SEM image of the lithium adsorbent material of Example 1, and Figure 2 is a cross-sectional SEM image of the lithium adsorbent material of Example 1. It can be seen that the pores on the surface of the particles of Example 1 are uniform, approximately 0.5 μm in diameter. The cross-section is characterized by finger-like pores, with the longest average length being 2.5 μm and the shortest average length being 1 μm. Figure 3 is a cross-sectional SEM image of the lithium adsorbent material of Example 1, showing that the shell thickness of the particles of Example 1 is approximately 35.5 μm.

[0239] Although the lithium adsorption materials prepared in Comparative Examples 1-3 are also spherical and have an average particle size of 2-5 mm, the lithium adsorption materials prepared in Comparative Examples 1-3 do not have the specific pore structure defined in the present invention, and the shell pores and cross-sectional pores of the lithium adsorption materials are dense and few, resulting in a significant decrease in the porosity and BET of the lithium adsorption materials.

[0240] Figure 4 is an SEM electron microscope image of the cross section of the lithium adsorption material of Comparative Example 1, and Figure 5 is an SEM electron microscope image of the cross section of the lithium adsorption material of Comparative Example 2. It can be seen from Figures 4 and 5 that the adsorption material powders prepared in Comparative Examples 1-2 are agglomerated in large quantities in the polymer skeleton, and in Table 2, the average particle diameter of the lithium ion sieve in the cross section of the lithium adsorption materials prepared in Comparative Examples 1 and 2 is significantly increased.

[0241] The adsorption performance of the lithium adsorption materials obtained in the examples and comparative examples was tested, and the results are shown in Table 3.

[0242] Table 3

[0243] It can be seen from the results in Table 3 that compared with Comparative Examples 1-3, the lithium adsorption materials in Examples 1-11 of the present invention have a faster water mass transfer rate and a correspondingly larger adsorption capacity. In addition, after being immersed in a high salt solution (lithium ion content 100 mg / L, magnesium ion concentration 20000 mg / L) for 48 hours, the volume change (volume expansion rate) is within 1%, indicating that the lithium adsorption material provided by the present invention has high swelling resistance.

[0244] The lithium adsorption material of Example 1-11 was adsorbed at pH = 9.5 and desorbed with 0.5M HCl. After 30 cycles, the solution became clear, indicating that the lithium ion sieve did not fall off the skeleton of the lithium adsorption material, and the adsorption capacity did not decrease significantly after 30 cycles.

[0245] Furthermore, as shown in FIG6 , by observing the SEM electron microscope image of the cross section of the lithium adsorption material of Example 1 after 30 cycles of use in the adsorption column (pH = 9.5 adsorption, 0.5 M HCl desorption), it can be found that the lithium ion sieve powder in the lithium adsorption material is evenly dispersed, and the internal pores of the lithium adsorption material are free of salt crystals and cracks, indicating that the lithium adsorption material has excellent mechanical properties.

[0246] However, after 30 cycles of adsorption and desorption (pH = 9.5 for adsorption, 0.5M HCl for desorption) of the lithium adsorption materials of Comparative Examples 1 and 3, the solutions turned dark brown, lithium ion sieve powder leaked out of the solutions, and the adsorption and desorption performances decreased significantly.

[0247] Furthermore, as shown in FIG7 , by observing the SEM electron microscope image of the cross section of the lithium adsorption material of Comparative Example 1 after 30 cycles of use in the adsorption column (pH = 9.5 adsorption, 0.5 M HCl desorption), it can be found that salt crystals and cracks exist in the pores of the lithium adsorption material.

[0248] FIG8 is a photograph of the lithium ion adsorption material prepared in Example 1 of the present invention. As can be seen from FIG8 , the lithium ion adsorption material of the present invention is spherical or quasi-spherical.

[0249] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A lithium adsorption material, characterized in that: The lithium adsorption material comprises a core body and a shell layer coated on the surface of the core body; There are pores on the shell layer of the lithium adsorption material, and the average diameter of the pores measured by SEM electron microscopy is 0.01-2.5 μm; The core of the lithium adsorption material contains finger-shaped pores, and the longest average length of the finger-shaped pores measured by SEM electron microscopy on the cross section of the lithium adsorption material is 1-7 μm, and the shortest average length is 0.05-2.5 μm; The shortest average length of the finger-like holes in the core is greater than the average diameter of the holes in the shell; The thickness of the shell layer of the lithium adsorption material measured by SEM electron microscope is 1-550 μm.

2. The lithium adsorption material according to claim 1, wherein The average diameter of the pores in the shell of the lithium adsorption material measured by SEM electron microscopy is 0.1-0.5 μm; The longest average length of the pores of the cross section of the lithium adsorption material measured by SEM electron microscopy is 2-5 μm; the shortest average length is 0.5-1.5 μm; The thickness of the shell layer of the lithium adsorption material measured by SEM electron microscopy is 30-500 μm.

3. The lithium adsorption material according to claim 1 or 2, wherein The porosity of the lithium adsorption material is 60-80%, preferably 65-75%; Preferably, the lithium adsorption material is spherical and / or quasi-spherical; Preferably, the average particle size of the lithium adsorption material is 2-5 mm, preferably 3-4 mm; Preferably, the specific surface area of ​​the lithium adsorption material is 10-100m 2 / g, preferably 35-65m 2 / g.

4. The lithium adsorption material according to any one of claims 1 to 3, wherein The ratio of the sum of the surface areas S1 of the holes on the shell layer to the sum of the maximum cross-sectional areas S2 of the finger-shaped holes in the core body is 0.5-0.9:1, preferably 0.6-0.8:

1.

5. The lithium adsorption material according to any one of claims 1 to 4, wherein The lithium adsorption material includes a skeleton and a lithium ion sieve dispersed in the skeleton; The skeleton comprises polyvinyl chloride and polyacrylic acid; Preferably, the lithium ion sieve is a hydroxyl-modified lithium ion sieve, and the lithium ion sieve is connected to the framework via hydroxyl groups.

6. The lithium adsorption material according to claim 5, wherein Based on the total weight of the lithium adsorption material, the content of the polyvinyl chloride is 16-67wt%; the content of the polyacrylic acid is 0.06-9wt%; and the content of the lithium ion sieve is 45-85wt%; Preferably, based on the total weight of the lithium adsorption material, the content of the polyvinyl chloride is 16-54wt%; the content of the polyacrylic acid is 0.9-9wt%; and the content of the lithium ion sieve is 45-80wt%.

7. The lithium adsorption material according to claim 5 or 6, wherein The thickness of the coating layer formed by the compound providing hydroxyl groups in the hydroxyl-modified lithium ion sieve is 1-5 nm, preferably 3-5 nm; Preferably, the hydroxyl-modified lithium ion sieve is a polyphenol-modified lithium ion sieve; Preferably, the polyphenol is selected from at least one of tannic acid, tea polyphenol, apple polyphenol, grape polyphenol, eriodictyol, naringenin, epicatechin, luteolin, naringenin, kaempferol, myricetin and genistein; Preferably, the lithium ion sieve is selected from titanium-based lithium ion sieves and / or manganese-based ion sieves; Preferably, the lithium ion is selected from LiMn2O4, Li 1.6 Mn 1.6 O4、Li 1.33 Mn 1.67 O4、Li4Mn5O 12 、LiMnO2、Li2TiO3、Li 1.33 Ti 1.66 O4 and Li4Ti5O 12 At least one of; Preferably, the water content of the hydroxyl-modified lithium ion sieve is less than or equal to 0.5wt%, preferably 0.1-0.3wt%.

8. The lithium adsorption material according to any one of claims 5 to 7, wherein: The average particle diameter of the lithium ion sieve in the cross section of the lithium adsorption material measured by SEM electron microscope is less than or equal to 2.5 μm, preferably less than or equal to 1.5 μm.

9. The lithium adsorption material according to any one of claims 1 to 8, wherein Based on the total surface area of ​​the shell layer of the lithium adsorption material, the total area of ​​the pores on the shell layer is 30-90%, preferably 50-90%.

10. A method for preparing the lithium adsorption material according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: (1) mixing polyvinyl chloride, polyacrylic acid, lithium ion sieve and oil phase solvent to obtain a mixed solution; (2) Under the conditions of temperature of 20-60° C. and humidity of 40-80%, the mixed solution is added dropwise to an aqueous solvent to obtain a lithium adsorption material.

11. The method according to claim 10, wherein: In step (1), the lithium ions are screened from titanium-based lithium ion sieves and / or manganese-based ion sieves; Preferably, the lithium ion is selected from LiMn2O4, Li 1.6 Mn 1.6 O4、Li 1.33 Mn 1.67 O4、Li4Mn5O 12 、LiMnO2、Li2TiO3、Li 1.33 Ti 1.66 O4 and Li4Ti5O 12 At least one of; Preferably, the weight average molecular weight of the polyvinyl chloride is 50,000-110,000 g / mol; Preferably, the weight average molecular weight of the polyacrylic acid is 100,000-1.3 million g / mol; Preferably, the oil phase solvent is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone and dimethyl sulfoxide; Preferably, the amounts of the polyvinyl chloride, the polyacrylic acid and the hydroxyl-modified lithium ion sieve are such that, based on the total weight of the lithium adsorbent material, the content of the polyvinyl chloride is 16-67wt%; the content of the polyacrylic acid is 0.06-9wt%; and the content of the lithium ion sieve is 45-85wt%; Preferably, based on the total weight of the lithium adsorption material, the content of the polyvinyl chloride is 16-54wt%; the content of the polyacrylic acid is 0.9-9wt%; and the content of the lithium ion sieve is 45-80wt%.

12. The method according to claim 10 or 11, wherein: In step (2), the mixed solution is added dropwise to the aqueous phase solvent at a temperature of 35-60° C. and a humidity of 60-80%; Preferably, the aqueous phase solvent is selected from at least one of water, ethanol and acetic acid, preferably water.

13. The method according to any one of claims 10 to 12, wherein: The lithium ion sieve is a hydroxyl-modified lithium ion sieve; Preferably, the lithium ion sieve is modified by using an aqueous solution containing a hydroxyl compound, and the hydroxyl-modified lithium ion sieve is obtained after solid-liquid separation and drying; Preferably, the hydroxyl-containing compound is a polyphenol; preferably at least one selected from tannic acid, tea polyphenols, apple polyphenols, grape polyphenols, eriodictyol, naringenin, epicatechin, luteolin, naringenin, kaempferol, myricetin and genistein; Preferably, the concentration of the aqueous solution containing the hydroxyl compound is 0.05 mg / L-0.1 mg / L; Preferably, the mass ratio of the lithium ion sieve to the hydroxyl-containing compound is 1:0.01-0.3; Preferably, the modification conditions include: reaction time of 30 min-4 h, reaction temperature of 25-40°C.

14. The method according to any one of claims 10 to 13, wherein: The method further comprises: a step of washing the lithium adsorption material with an acidic solution; Preferably, the lithium adsorption material is circulated and washed with an acidic solution under the action of a peristaltic pump; Preferably, the acidic solution is selected from at least one of hydrochloric acid, phosphoric acid and sulfuric acid; Preferably, H + Ion meter, the concentration of the acidic solution is 0.1-1 mol / L; Preferably, the flow rate of the peristaltic pump is 1-25 BV / h, and the cycle time is 1-48 h.

15. A lithium adsorption material obtained by the method according to any one of claims 10 to 14.

16. Use of the lithium adsorption material according to any one of claims 1 to 9 and 15 in lithium extraction, preferably in lithium extraction in a liquid environment.

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