A lithium adsorbent and a method for preparing the same

Abstract

This invention provides a lithium adsorbent and its preparation method. The lithium adsorbent comprises: a binder framework and a lithium-ion sieve precursor located on at least a portion of the surface of the binder framework. The binder framework has a mesh-like interconnected pore structure, and the sphericity of the lithium adsorbent after grinding is not less than 95%. The lithium adsorbent provided by this invention, due to the mesh-like interconnected pore structure of its binder framework, avoids the formation of a dense skin layer on the surface of the lithium adsorbent and effectively increases the contact area between the lithium-containing liquid and the lithium-ion sieve, thereby significantly improving the adsorption and desorption efficiency of lithium.

Description

Technical Field

[0001] The invention relates to the field of lithium adsorption and extraction, and in particular to a lithium adsorbent and its preparation method. Background Technology

[0002] Lithium metal is widely used in rechargeable batteries, glass, ceramics, alloys, lubricants, medicines and other fields. In recent years, with the continuous growth of market demand for lithium, terrestrial lithium resources are far from meeting the demand, and the extraction of lithium from liquid lithium resources has become a hot topic of interest.

[0003] There are various methods for extracting lithium from liquid lithium resources, among which adsorption is a highly efficient, environmentally friendly, and low-cost method. Lithium adsorbent materials are the most crucial component in this method. Lithium-ion sieve materials possess numerous advantages, including structural stability, good acid resistance, stable adsorption performance, and the ability to be recycled multiple times, making them a hot research topic for scientists. However, most lithium-ion sieve materials are in powder form, with poor flowability and permeability, hindering industrial operation and commercial application. Therefore, many researchers have conducted granulation studies on powdered lithium-ion sieves to prepare granular lithium adsorbents.

[0004] Wet granulation is a commonly used process in the existing lithium adsorbent preparation technology. In order to make the prepared lithium adsorbent have high strength, lithium ion sieve powder, polymer binder and solvent are generally blended and granulated. However, in this process, a dense skin layer is formed on the surface of the lithium adsorbent or the lithium ion sieve powder is buried, which reduces the ion transport rate and affects the lithium adsorption and desorption rate. Summary of the Invention

[0005] This invention provides a lithium adsorbent. Because the binder skeleton of the lithium adsorbent has a mesh-like interconnected pore structure, it can increase the proportion of lithium ion sieves without affecting the strength of the lithium adsorbent, effectively increase the contact area between the lithium-containing liquid and the lithium ion sieves, and avoid the formation of a dense skin layer on the surface of the lithium adsorbent, thereby increasing the adsorption and desorption efficiency of lithium.

[0006] The present invention also provides a method for preparing the above-mentioned lithium adsorbent, which is capable of preparing the above-mentioned lithium adsorbent and has a simple process.

[0007] In a first aspect, the present invention provides a lithium adsorbent, comprising: a binder skeleton and a lithium ion sieve located on at least a portion of the surface of the binder skeleton, the binder skeleton having a mesh-like interconnected channel structure, and the sphericity of the lithium adsorbent after grinding being not less than 95%.

[0008] Furthermore, the mesh-like interconnected channel structure includes a first hole and a second hole, wherein the diameter of the first hole is 500-1500 nm and the diameter of the second hole is 100-500 nm.

[0009] Preferably, the average pore diameter of the first pore is greater than 1000 nm, and the average pore diameter of the second pore is less than 500 nm.

[0010] Furthermore, the total pore volume of the lithium adsorbent is 10-30 mL / g, and the specific surface area is 35-50 m² / g. 2 / g.

[0011] Furthermore, the sphericity of the lithium adsorbent after grinding is 95%-99.5%.

[0012] Furthermore, the lithium-ion sieve is a titanium-based lithium-ion sieve.

[0013] And / or, the average particle size of the lithium ion sieve is 2-10 μm.

[0014] Furthermore, the lithium-ion sieve accounts for 50-65% of the mass of the lithium adsorbent.

[0015] In a second aspect, the present invention provides a method for preparing a lithium adsorbent as described in the first aspect, comprising the following steps:

[0016] A mixture containing lithium-ion sieves, polyvinylidene fluoride, and solvent is subjected to a one-time molding process to obtain a solid material;

[0017] The solid material is contacted with an alkaline solution containing glycerol and subjected to a secondary molding process to obtain the lithium adsorbent.

[0018] Furthermore, the molecular weight of the polyvinylidene fluoride is 600,000 to 1,000,000, preferably 750,000 to 850,000;

[0019] And / or, the mass ratio of the polyvinylidene fluoride, solvent and lithium ion sieve is 1:1-20:6-12, preferably 1:10-20:9-10.

[0020] Furthermore, the alkali in the alkaline solution includes at least one of methylamine, dimethylamine, ethylamine, diethylamine, sodium hydroxide, and potassium hydroxide;

[0021] And / or, the alkali concentration in the alkaline solution is 0.05 to 0.5 mol / L.

[0022] Furthermore, the volume concentration of glycerol in the alkaline solution is 5% to 20%.

[0023] Furthermore, the mixture is prepared through the following process:

[0024] Polyvinylidene fluoride is dissolved in a solvent by stirring to form a solution; lithium ion sieve inorganic powder is mixed with the solution to obtain the mixture.

[0025] The lithium adsorbent provided by this invention includes a binder skeleton with a network of interconnected pores and a lithium ion sieve precursor. This allows for an increase in the proportion of lithium ion sieves without affecting the strength of the lithium adsorbent, effectively increasing the contact area between the lithium-containing liquid and the lithium ion sieve, and preventing the formation of a dense skin layer on the surface of the lithium adsorbent, thereby increasing the adsorption and desorption efficiency of lithium. Attached Figure Description

[0026] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0027] Figure 1 This is a schematic diagram illustrating the mechanism by which base attack on polyvinylidene fluoride forms a gel with alternating single and double bonds, according to a specific embodiment of the present invention.

[0028] Figure 2 This is a SEM image of the lithium adsorbent of Example 1 of the present invention.

[0029] Figure 3 This is a SEM image of the lithium adsorbent of Comparative Example 1 of the present invention. Detailed Implementation

[0030] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below. The specific embodiments listed below are merely descriptions of the principles and features of the present invention, and the examples are only for explaining the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] In this application, the term "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0032] In this application, the terms "first" and "second" are used for descriptive purposes only, to distinguish objects, such as substances, from one another, and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. For example, without departing from the scope of the embodiments of this application, "first XX" may also be referred to as "second XX," and similarly, "second XX" may also be referred to as "first XX." Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of that feature.

[0033] In this application, references to "an embodiment," "an example," or "an example" mean that a specific feature, structure, or characteristic described in connection with that embodiment, example, or example is included in at least one embodiment of the invention. Therefore, the phrases "an embodiment," "an example," "an example," "an example," or "an example" appearing in various places throughout the specification do not necessarily refer to the same embodiment or example. Furthermore, specific features, structures, or characteristics can be combined in one or more embodiments or examples in any suitable combination and / or sub-combination.

[0034] Traditional lithium adsorbents are granulated from a mixture of polymer binders and lithium-ion sieves. However, due to the dense texture of the polymer binders, a dense skin layer can form on the surface of the lithium adsorbent, or the lithium-ion sieve powder can be embedded, resulting in a low lithium adsorption-desorption rate. To solve this problem, the present invention provides the following technical solution:

[0035] In a first aspect, the present invention provides a lithium adsorbent, comprising: a binder skeleton and a lithium ion sieve located on at least a portion of the surface of the binder skeleton, the binder skeleton having a mesh-like interconnected channel structure, and the sphericity of the lithium adsorbent after grinding being not less than 95%.

[0036] In this invention, the binder skeleton with a network of interconnected pores provides the lithium adsorbent with a larger specific surface area and more active sites, significantly improving the adsorption rate. The network of interconnected pores also gives the binder skeleton good mechanical strength and stability, enabling it to maintain structural integrity during use and regeneration, thus ensuring the adsorbent's service life.

[0037] It should be noted that the lithium-ion sieve is located on at least a portion of the surface of the binder skeleton, which mainly includes the outer surface of the binder skeleton (outside the mesh-connected channel structure).

[0038] In one specific embodiment, the mesh-like interconnected channel structure includes a first hole and a second hole, wherein the diameter of the first hole is 500-1500 nm and the diameter of the second hole is 100-500 nm.

[0039] As described above, the mesh-like interconnected pore structure includes first and second pores of different sizes. The two pore structures can synergistically optimize the adsorption performance of the adsorbent. The first pore provides a flow channel for the fluid, allowing the fluid to enter the interior of the adsorbent more quickly and increasing the flow rate. The second pore increases the pore volume of the adsorbent, increases the effective contact area between the fluid and the lithium ion sieve, and improves the mass transfer efficiency.

[0040] The testing method for the first and second pores is as follows: using scanning electron microscopy (SEM): under scanning electron microscopy (SEM), observe the pore size of the lithium adsorbent. The pore size is 500-1500nm, which is the first pore size, and the pore size is 100-500nm, which is the second pore size.

[0041] In a preferred embodiment, the average pore diameter of the first pore is greater than 1000 nm, and the average pore diameter of the second pore is less than 500 nm.

[0042] In one specific embodiment, the total pore volume of the lithium adsorbent is 10-30 mL / g, and the specific surface area is 35-45 m². 2 / g.

[0043] The embodiments described above result in a larger total pore volume and specific surface area of ​​the lithium adsorbent, higher mass transfer efficiency, and more active sites, which helps to further improve the adsorption efficiency and rate of lithium.

[0044] In one specific embodiment, the sphericity of the lithium adsorbent after grinding is 95%-99.9%. Lithium adsorbents within this strength range are not easily worn or crushed during use, especially under high pressure or high flow rate operating conditions. They can maintain their structure and function and are not easily damaged, thus ensuring process stability.

[0045] The excessive proportion of lithium-ion sieves in traditional lithium adsorbents may affect the mechanical strength and stability of the lithium adsorbent, especially in the absence of sufficient supporting materials or binders. This may lead to the loss of inorganic powder during the use of the adsorbent. However, the lithium adsorbent of the present invention, due to the inclusion of a binder skeleton with a mesh-like interconnected pore structure, can increase the proportion of lithium-ion sieves without affecting the strength of the lithium adsorbent.

[0046] In one specific embodiment, the lithium-ion sieve accounts for 50-65% of the mass of the lithium adsorbent. This content of lithium-ion sieve provides the lithium adsorbent with more active sites for lithium-ion adsorption, thereby improving its adsorption capacity for lithium.

[0047] For example, the lithium ion sieve accounts for any value or a range of any two of 50%, 52%, 55%, 58%, 60%, 62%, 65% of the mass of the lithium adsorbent.

[0048] In one specific embodiment, the average particle size of the lithium-ion sieve is 2-10 μm.

[0049] The shape of the lithium adsorbent described above is not particularly limited in this invention. In some embodiments, the lithium adsorbent is at least one of spherical, elongated, cylindrical, or irregular shapes. For example, the lithium adsorbent is a spherical particle with a diameter ranging from 0.5 to 2 mm.

[0050] In one specific embodiment, the lithium-ion sieve is a titanium-based lithium-ion sieve. The main component of the titanium-based lithium-ion sieve is Li₂TiO₃.

[0051] Titanium-based lithium-ion sieves (Li2TiO3) can be purchased commercially or prepared using existing processes, such as by the following method: Li2CO3 and TiO2 are thoroughly mixed in a 2:1 ratio and then calcined at 750°C for 24 hours to obtain titanium-based lithium-ion sieves.

[0052] In a second aspect, the present invention provides a method for preparing a lithium adsorbent as described in the first aspect, comprising the following steps:

[0053] A solid material is obtained by one-time molding of a mixture containing lithium ion sieves, polyvinylidene fluoride, and solvent.

[0054] The solid material is contacted with an alkaline solution containing glycerol and subjected to a secondary molding process to obtain the lithium adsorbent.

[0055] In the above preparation method, after the mixture is formed in one step, it is immersed in an alkaline solution for solidification and shaping. As the solvent in the mixture is gradually replaced by water, the PVDF gradually solidifies from a dissolved state, forming a supporting framework for the lithium adsorbent. When the PVDF comes into contact with the alkali, as... Figure 1 As shown, polyvinylidene fluoride (PVDF) undergoes a bimolecular elimination reaction under the attack of bases, generating double bonds. Since these double bonds are unstable, they break and crosslink with adjacent molecules, resulting in gelation and forming a framework with a network of interconnected channels. However, gelation causes shrinkage during PVDF curing, leading to separation of PVDF from lithium-ion sieve particles and disrupting the PVDF's bonding effect. Therefore, simply introducing alkali during curing easily damages the strength of the lithium adsorbent. To obtain a lithium adsorbent that balances adsorption efficiency and strength, the curing and conditioning process must not only introduce alkali to induce gelation but also prevent rapid shrinkage of the binder, which could lead to weak bonding of inorganic particles. To address this, this invention introduces glycerol (glycerol) into the water. Because glycerol has a higher viscosity and lower polarity than water, its solvent exchange rate is slower, preventing the collapse of the crosslinked network structure of PVDF during solvent exchange. This results in a lithium adsorbent with a sphericity of at least 95% after grinding.

[0056] The specific process of the above-mentioned one-time molding process is not limited in this invention. In some embodiments, the one-time molding process adopts an extrusion molding process, more specifically, extrusion into strips.

[0057] To further ensure the uniform dispersion of polyvinylidene fluoride, the solvent is one or more of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC), and N-methylpyrrolidone (NMP), preferably N,N-dimethylacetamide; the alkaline solution is an aqueous solution of an alkali.

[0058] The present invention does not specifically limit the manner in which the solid material comes into contact with the alkaline solution. In some embodiments, the solid material is immersed in the alkaline solution for soaking treatment to ensure full contact between the two.

[0059] The concentration of the alkaline solution is not specifically limited in this invention. In order to further enable the solid material to react fully with the alkaline solution, in some embodiments, the concentration of the alkaline solution is in the range of 0.05-0.5 mol / L, preferably 0.2 mol / L.

[0060] The temperature of the alkaline solution is not limited in this invention. In order to further enable the solid material to react fully with the alkaline solution, in some embodiments, the temperature of the alkaline solution is 30-80°C, preferably 60°C.

[0061] In one specific embodiment, the polyvinylidene fluoride (PVDF) has a molecular weight of 600,000 to 1,000,000 Daltons. This molecular weight of PVDF can further improve the mechanical strength of the lithium adsorbent. For example, the PVDF is PVDF powder with molecular weights of 600,000, 800,000, and 1,000,000.

[0062] In some embodiments, the molecular weight of the polyvinylidene fluoride is 750,000 to 850,000.

[0063] In one specific embodiment, the mass ratio of the polyvinylidene fluoride, solvent, and lithium ion sieve is 1:1-20:6-12, preferably 1:10-20:9-10.

[0064] The embodiments described above, by controlling the mass ratio of polyvinylidene fluoride, solvent, and lithium ion sieve, can further ensure product strength while improving lithium adsorption.

[0065] In one specific embodiment, the alkali in the alkaline solution includes at least one of methylamine, dimethylamine, ethylamine, diethylamine, sodium hydroxide, and potassium hydroxide.

[0066] In one specific embodiment, the alkali concentration in the alkaline solution is in the range of 0.05-0.5 mol / L.

[0067] The concentration of glycerol added to the alkaline solution is not specifically limited in this invention. In order to effectively suppress the shrinkage of the binder in the alkaline solution, in some embodiments, the volume concentration of glycerol in the alkaline solution is 5%-20%.

[0068] In one specific embodiment, the mixture is prepared by the following process:

[0069] Polyvinylidene fluoride is dissolved in a solvent by stirring to form a solution; lithium ion sieve inorganic powder is mixed with the solution to obtain the mixture.

[0070] The present invention does not specifically limit the melting temperature. In order to further ensure the uniformity of polyvinylidene fluoride dispersion, in some embodiments, the stirring temperature is 40-90°C, preferably 70°C.

[0071] The stirring speed is not specifically limited in this invention. In order to further ensure the uniformity of polyvinylidene fluoride dispersion, in some embodiments, the stirring speed is 100-1000 rpm, preferably 500 rpm.

[0072] In some embodiments, the above mixing is carried out in a high-speed mixer, the mixing speed of which is 5-30 rpm, preferably 20 rpm.

[0073] To further understand the present invention, the technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0074] The following test methods for the first pore, the second pore, and the average of the two are as follows: Scanning electron microscopy (SEM) is used for testing: Under a scanning electron microscope (SEM), the pore size of the lithium adsorbent is observed. The pore size is 500-1500 nm, and the pore size is 100-500 nm. Then, the pore size of at least 50 first pores in a random area is measured. The average pore size of the first pores in this area is calculated as the sum of the pore sizes of all pores / the total number of pores. This process is repeated 5 times, and the average value is taken as the average pore size of the first pore. The average pore size of the second pore is determined by referring to the average pore size test method.

[0075] The following test method for determining the sphericity after grinding involves the following steps: Measure 50 mL of lithium adsorbent sample using a 100 mL graduated cylinder. Transfer the entire sample to a grinding drum using 150 mL of water. Add 8 ceramic balls and tighten the drum lid. Fix the drum to a ball mill, set the rotation speed to 125 rpm, and grind for 30 minutes. Remove the drum and transfer all the water and lithium adsorbent sample to a 0.5 mm aperture sieve. Place a matching tray under the sieve to collect the water and broken lithium adsorbent sample that have passed through the sieve. Dry the water in an oven at 105℃. After drying, vibrate the sieve to transfer the broken lithium adsorbent sample to the tray. Place the particles that pass through the sieve and those that pass through the sieve into weighing bottles and weigh them on an analytical balance. Record the masses of the particles that pass through the sieve and the broken particles that pass through the sieve as m1 and m2, respectively. The sphericity of the lithium adsorbent sample after grinding is calculated as m1 / (m1+m2)×100%.

[0076] Unless otherwise specified, all reagents involved in the embodiments of this invention are commercially available products and can be purchased through commercial channels.

[0077] The preparation method of titanium-based lithium-ion sieve (Li2TiO3) is as follows: Li2CO3 and TiO2 are thoroughly mixed in a 2:1 ratio and then calcined at 750℃ for 24 hours to obtain the titanium-based lithium-ion sieve. Other raw material specifications or sources are shown in Table 1.

[0078] Table 1:

[0079]

[0080]

[0081] Example 1

[0082] This example provides a lithium adsorbent, comprising a binder framework and a titanium-based lithium-ion sieve. The binder framework has a mesh-like interconnected channel structure. See [link to documentation]. Figure 2 The mesh-like interconnected pore structure includes a first pore and a second pore. The average pore diameter of the first pore is 1223 nm, and the average pore diameter of the second pore is 318 nm. The total pore volume of the lithium adsorbent is 21 mL / g, and the specific surface area is 42 m². 2 / g, the sphericity after grinding is 98.3%; titanium-based lithium ion sieves (average particle size of 5μm) account for 58% of the lithium adsorbent mass.

[0083] The preparation method includes the following steps: 1 kg of PVDF powder with a molecular weight of 800,000 is dissolved in 10 kg of dimethylacetamide (DMAC) solvent at a solid-liquid ratio of 1:10, the dissolution temperature is 70℃, and the stirring speed is 200 rpm to form a uniform and stable PVDF solution; 9 kg of titanium-based lithium ion sieve powder is added to the PVDF solution and stirred at 20 rpm in a high-speed mixer to obtain a uniform mixture; the mixture is extruded into strips through an extruder at an extrusion temperature of 70℃; the extruded strips are cut into granules and soaked in an aqueous solution at 60℃, with a methylamine concentration of 0.2 mol / L and a glycerol volume concentration of 15% for 1 hour for phase separation, and lithium adsorbent particles with a median particle size of 1.0 mm are obtained.

[0084] Example 2

[0085] This example provides a lithium adsorbent, comprising a binder framework and a titanium-based lithium-ion sieve. The binder framework has a mesh-like interconnected pore structure, including a first pore and a second pore. The average pore size of the first pore is 887 nm, and the average pore size of the second pore is 295 nm. The total pore volume of the lithium adsorbent is 12 mL / g, and the specific surface area is 35 m². 2 / g, with a sphericity of 99.9% after grinding; titanium-based lithium ion sieves (average particle size of 7μm) account for 50% of the lithium adsorbent mass.

[0086] The preparation method includes the following steps: 10 kg of PVDF powder with a molecular weight of 600,000 is dissolved in 10 kg of DMAC solvent at a solid-liquid ratio of 1:1, the dissolution temperature is 40℃, and the stirring speed is 1000 rpm to form a uniform and stable solution; 60 kg of titanium-based lithium ion sieve powder is added to the PVDF solution and stirred at 30 rpm in a high-speed mixer to obtain a uniform mixture; the mixture is extruded into strips through an extruder at an extrusion temperature of 40℃; the extruded strips are cut into granules and soaked in an aqueous solution at 30℃, with a methylamine concentration of 0.05 mol / L and a glycerol volume concentration of 5% for 1 hour for phase separation, and lithium adsorbent particles with a median particle size of 0.5 mm are obtained.

[0087] Example 3

[0088] This example provides a lithium adsorbent, comprising a binder framework and a titanium-based lithium-ion sieve. The binder framework has a mesh-like interconnected pore structure, including a first pore and a second pore. The average pore size of the first pore is 1154 nm, and the average pore size of the second pore is 298 nm. The total pore volume of the lithium adsorbent is 29 mL / g, and the specific surface area is 45 m². 2 / g, the sphericity after grinding is 95.2%; titanium-based lithium ion sieves (average particle size of 3um) account for 65% of the lithium adsorbent mass.

[0089] The preparation method includes the following steps: 1 kg of PVDF powder with a molecular weight of 1 million is dissolved in 20 kg of DMAC solvent at a solid-liquid ratio of 1:20, the dissolution temperature is 90℃, and the stirring speed is 100 rpm to form a uniform and stable solution; 12 kg of titanium-based lithium ion sieve powder is added to the PVDF solution and stirred at 5 rpm in a high-speed mixer to obtain a uniform mixture; the mixture is extruded into strips through an extruder at an extrusion temperature of 70℃; the extruded strips are cut into granules and soaked in an aqueous solution at 80℃, with a methylamine concentration of 0.5 mol / L and a glycerol volume concentration of 20% for 1 hour for phase separation, and lithium adsorbent particles with a median particle size of 2 mm are obtained.

[0090] Example 4

[0091] This example provides a lithium adsorbent, comprising a binder framework and a titanium-based lithium-ion sieve. The binder framework has a mesh-like interconnected pore structure, including a first pore and a second pore. The average pore size of the first pore is 1255 nm, and the average pore size of the second pore is 388 nm. The total pore volume of the lithium adsorbent is 32 mL / g, and the specific surface area is 48 m². 2 / g, the sphericity after grinding is 99.3%; titanium-based lithium ion sieves (average particle size of 8um) account for 58% of the lithium adsorbent mass.

[0092] The preparation method includes the following steps: 1 kg of PVDF powder with a molecular weight of 800,000 is dissolved in 10 kg of DMAC solvent at a solid-liquid ratio of 1:10, the dissolution temperature is 70℃, and the stirring speed is 200 rpm to form a uniform and stable solution; 9 kg of titanium-based lithium ion sieve powder is added to the PVDF solution, and the mixture is stirred at 20 rpm in a high-speed mixer to obtain a uniform mixture; the mixture is extruded into strips through an extruder at an extrusion temperature of 70℃; the extruded strips are cut into granules, and the granules are soaked in an aqueous solution at 60℃ with a sodium hydroxide concentration of 0.2 mol / L and a glycerol volume concentration of 10% for 1 hour for phase separation, and lithium adsorbent particles with a median particle size of 1.0 mm are obtained.

[0093] Example 5

[0094] This example provides a lithium adsorbent, comprising a binder framework and a titanium-based lithium-ion sieve. The binder framework has a mesh-like interconnected pore structure, including a first pore and a second pore. The average pore size of the first pore is 1268 nm, and the average pore size of the second pore is 412 nm. The total pore volume of the lithium adsorbent is 30 mL / g, and the specific surface area is 40 m². 2 / g, the sphericity after grinding is 98.5%; titanium-based lithium ion sieves (average particle size of 5um) account for 59% of the lithium adsorbent mass.

[0095] The preparation method includes the following steps: 1 kg of PVDF powder with a molecular weight of 800,000 is dissolved in 10 kg of DMAC solvent at a solid-liquid ratio of 1:10, the dissolution temperature is 70℃, and the stirring speed is 200 rpm to form a uniform and stable solution; 9 kg of titanium-based lithium ion sieve powder is added to the PVDF solution, and the mixture is stirred at 20 rpm in a high-speed mixer to obtain a uniform mixture; the mixture is extruded into strips through an extruder at an extrusion temperature of 70℃; the extruded strips are cut into granules, and the granules are soaked in an aqueous solution at 60℃ with an ethylamine concentration of 0.2 mol / L and a glycerol volume concentration of 10% for 1 hour for phase separation, and lithium adsorbent particles with a median particle size of 1.0 mm are obtained.

[0096] Example 6

[0097] This example provides a lithium adsorbent, comprising a binder framework and a titanium-based lithium-ion sieve. The binder framework has a mesh-like interconnected pore structure, including a first pore and a second pore. The average pore size of the first pore is 1263 nm, and the average pore size of the second pore is 292 nm. The total pore volume of the lithium adsorbent is 23 mL / g, and the specific surface area is 39 m². 2 / g, the sphericity after grinding is 98.9%; titanium-based lithium ion sieves (average particle size of 5um) account for 58% of the lithium adsorbent mass.

[0098] The preparation method includes the following steps: 1 kg of PVDF powder with a molecular weight of 800,000 is dissolved in 10 kg of DMF solvent at a solid-liquid ratio of 1:10, the dissolution temperature is 70℃, and the stirring speed is 200 rpm to form a uniform and stable solution; 9 kg of titanium-based lithium ion sieve powder is added to the PVDF solution and stirred at 20 rpm in a high-speed mixer to obtain a uniform mixture; the mixture is extruded into strips through an extruder at an extrusion temperature of 70℃; the extruded strips are cut into granules and soaked in an aqueous solution at 60℃, with a methylamine concentration of 0.2 mol / L and a glycerol volume concentration of 10% for 1 hour for phase separation, and lithium adsorbent particles with a median particle size of 1.0 mm are obtained.

[0099] Comparative Example 1

[0100] This example provides a binder framework and a lithium-ion sieve precursor. See [link to documentation]. Figure 3 The binder skeleton consists of only a small number of pores with a diameter in the range of 1000-3500 nm, and these pores are not interconnected to form a network. The average pore diameter is 1618 nm. The total pore volume of the lithium adsorbent is 15 mL / g, and the specific surface area is 33 m². 2 / g, the sphericity after grinding is 97.5%; titanium-based lithium ion sieves (average particle size of 5um) account for 56% of the lithium adsorbent mass.

[0101] The preparation method includes the following steps: 1 kg of PVDF powder with a molecular weight of 800,000 is dissolved in 10 kg of DMAC solvent at a solid-liquid ratio of 1:10, the dissolution temperature is 70℃, and the stirring speed is 200 rpm to form a uniform and stable solution; 9 kg of titanium-based lithium ion sieve powder is added to the PVDF solution, and the mixture is stirred at 20 rpm in a high-speed mixer to obtain a uniform mixture; the mixture is extruded into strips through an extruder at an extrusion temperature of 70℃; the extruded strips are cut into granules, and the granules are soaked in an aqueous solution at 60℃ without the addition of alkali for 1 hour for phase separation, and lithium adsorbent particles with a median particle size of 1.0 mm are obtained.

[0102] Comparative Example 2

[0103] This example provides a binder framework and a lithium-ion sieve precursor. The mesh-like interconnected channel structure includes a first pore and a second pore. The average pore size of the first pore is 1823 nm, and the average pore size of the second pore is 354 nm. The total pore volume of the lithium adsorbent is 20 mL / g, and the specific surface area is 30 m². 2 / g, the sphericity after grinding is 71.5%; titanium-based lithium ion sieves (average particle size of 5um) account for 55% of the lithium adsorbent mass.

[0104] The preparation method includes the following steps: 1 kg of PVDF powder with a molecular weight of 800,000 is dissolved in 10 kg of DMAC solvent at a solid-liquid ratio of 1:10, the dissolution temperature is 70℃, and the stirring speed is 200 rpm to form a uniform and stable solution; 9 kg of titanium-based lithium ion sieve powder is added to the PVDF solution, and the mixture is stirred at 20 rpm in a high-speed mixer to obtain a uniform mixture; the mixture is extruded into strips through an extruder at an extrusion temperature of 70℃; the extruded strips are cut into granules, and the granules are soaked in an aqueous solution at 60℃ with a methylamine concentration of 0.2 mol / L and without the addition of glycerol for 1 hour for phase separation, and lithium adsorbent particles with a median particle size of 1.0 mm are obtained.

[0105] Test case

[0106] The adsorption performance of the lithium adsorbents in the test examples and comparative examples was investigated. The adsorbed brine used in the following tests was Zabuye raw brine, and its main components are shown in Table 2 below. The test results are shown in Table 3.

[0107] Test method:

[0108] Adsorption capacity: Add 100g of lithium adsorbent to the adsorption column, pump 10BV of pure water at a flow rate of 2BV / h for delithiation, and then pump Zabuye raw brine with a lithium concentration of C0 (ppm) at a flow rate of 2BV / h. Stop feeding when the effluent concentration is higher than 150ppm. The feed rate is L1 and the tail liquid concentration is C1. Then the adsorption capacity (mg / g) = (C0-C1)×L1 / 100g.

[0109] Desorption amount: The adsorbed lithium adsorbent was eluted with 0.1M hydrochloric acid, and the Li concentration C2 (g / L) in the desorption solution was detected. The volume of the desorption solution was L2. Therefore, the desorption amount (mg / g) = C2 × L2 / 100g.

[0110] Table 2: Main components of Zabuye raw brine

[0111]

[0112] Table 3: Evaluation Results

[0113]

[0114] As shown in Table 3, the Zabuye raw brine of the present invention has a high adsorption and desorption capacity in the brine. However, in Comparative Example 1, since no alkali was added to the aqueous phase, the adsorbent lacks a network of interconnected pores, resulting in a significant decrease in adsorption and desorption capacity. In Comparative Example 2, since no glycerol was added to the aqueous phase, the binder shrinks when it solidifies in the alkaline solution, reducing its bonding performance to inorganic particles and causing a significant decrease in the strength of the lithium adsorbent. Although the initial lithium adsorption and desorption capacity are high, it is easily worn or crushed during use, especially under high pressure or high flow rate operating conditions. The structure of the lithium adsorbent is easily damaged, thus affecting the adsorption life and reducing the stability of the process.

[0115] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A lithium adsorbent, characterized in that, include: The binder skeleton and a lithium-ion sieve located on at least a portion of the surface of the binder skeleton, the binder skeleton having a mesh-like interconnected channel structure, and the sphericity of the lithium adsorbent after grinding being not less than 95%.

2. The lithium adsorbent according to claim 1, characterized in that, The mesh-like interconnected channel structure includes a first hole and a second hole, wherein the diameter of the first hole is 500-1500 nm and the diameter of the second hole is 100-500 nm. Preferably, the average pore diameter of the first pore is greater than 1000 nm, and the average pore diameter of the second pore is less than 500 nm.

3. The lithium adsorbent according to claim 1 or 2, characterized in that, The total pore volume of the lithium adsorbent is 10-30 mL / g, and the specific surface area is 35-50 m². 2 / g.

4. The lithium adsorbent according to claim 1 or 2, characterized in that, The sphericity of the lithium adsorbent after grinding is 95%-99.5%.

5. The lithium adsorbent according to claim 1 or 2, characterized in that, The lithium-ion screen is a titanium-based lithium-ion screen.

6. The lithium adsorbent according to claim 1 or 2, characterized in that, The lithium-ion sieve accounts for 50-65% of the mass of the lithium adsorbent; And / or, the average particle size of the lithium ion sieve is 2-10 μm.

7. A method for preparing a lithium adsorbent as described in any one of claims 1-6, characterized in that, Includes the following steps: A mixture containing lithium-ion sieves, polyvinylidene fluoride, and solvent is subjected to a one-time molding process to obtain a solid material; The solid material is contacted with an alkaline solution containing glycerol and subjected to a secondary molding process to obtain the lithium adsorbent.

8. The preparation method according to claim 7, characterized in that, The polyvinylidene fluoride has a molecular weight of 600,000 to 1,000,000, preferably 750,000 to 850,000. And / or, the mass ratio of the polyvinylidene fluoride, solvent and lithium ion sieve is 1:1-20:6-12, preferably 1:10-20:9-10.

9. The preparation method according to claim 7, characterized in that, The alkali in the alkaline solution includes at least one of methylamine, dimethylamine, ethylamine, diethylamine, sodium hydroxide, and potassium hydroxide. And / or, the alkali concentration in the alkaline solution is 0.05–0.5 mol / L; And / or, the volume concentration of glycerol in the alkaline solution is 5% to 20%.

10. The preparation method according to claim 7, characterized in that, The mixture is prepared by the following process: Polyvinylidene fluoride is dissolved in a solvent by stirring to form a solution; lithium ion sieve inorganic powder is mixed with the solution to obtain the mixture.

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