Preparation Method of Adsorbent for Lithium Extraction from Salt Lake Brine

Abstract

The present invention provides a method for preparing an adsorbent for extracting lithium from salt lake brine, belonging to the technical field of adsorbents for extracting lithium from salt lakes. By introducing hydrophilic silica materials and utilizing their characteristics of high porosity, high specific surface area and hydrophilicity, the composite material has good wettability, can wet a large number of pores in a short time, shorten the mass transfer time of lithium ions, and improve the adsorption efficiency of lithium ions; pseudo-boehmite powder is selected as the binder, and due to its strong adhesiveness, the powder is more strongly wrapped, and there will be no powder loss during use. At the same time, it has good wear resistance and pressure resistance, increasing the service life of the adsorbent.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium adsorbents for extracting lithium from salt lakes, and specifically relates to a method for preparing an adsorbent for extracting lithium from salt lake brine. Background Art

[0002] Lithium, as a strategic resource, is widely used in fields such as lithium-ion batteries, catalysts, fusion fuels, rubber synthesis, and pharmaceuticals. It is reported that lithium in salt lake brines accounts for 66% of the total lithium resources, and the development of lithium extraction technology from salt lakes is extremely urgent. Currently, lithium extraction technologies include evaporation crystallization method, precipitation method, solvent extraction method, membrane separation method, adsorption method, etc. Among them, the adsorption method has been proven to be an effective method for extracting lithium from salt lake brines due to its high selectivity, low production cost, and environmental friendliness. However, commonly used lithium adsorbents usually exist in powder form, which leads to various disadvantages in industrial applications, such as: being prone to caking during the adsorption process, inconvenient recovery, poor fluidity, high energy consumption, large losses, which limit its further development. Molding is currently the most effective means to solve the application of powder adsorbents, and common molding methods include film formation, droplet granulation, etc.

[0003] The film formation method often uses polyvinylidene fluoride, polysulfone, polyethersulfone, etc. as film-forming agents. After dissolution, the ion sieve powder is added thereto, and after mixing evenly, it is formed into a film by spinning or casting. This method uses a large amount of organic solvents in the production and preparation process, which has an adverse impact on human health and brings great pressure to environmental protection. In addition, the formed adsorbent has many large cavities and large pores on the surface, resulting in unstable loading of the adsorbent. During long-term use, the powder loss is relatively serious, seriously affecting the operation stability, and the adsorption capacity also gradually decreases with the powder loss. Moreover, most of the membrane materials are hydrophobic materials and do not have permanent hydrophilicity, which affects the adsorption rate.

[0004] Droplet granulation is one of the common forms in current commercial products. This method has a short production process and simple technology, but droplet granulation has high requirements for the powder particle size and dispersion degree. During the preparation process, the phenomenon of pore blockage often occurs due to powder agglomeration, and it is difficult to achieve continuous production. In addition, this method has high requirements for droplet granulation equipment and it is difficult to prepare adsorbents with smaller sizes, resulting in a long mass transfer path of the adsorbent, seriously affecting its mass transfer efficiency. At the same time, the adsorbent prepared by this method has a lower bulk density, which limits the lithium recovery rate during application.

[0005] In summary, the currently commonly used methods for forming lithium adsorption agents from salt lakes are the film-forming method and the droplet granulation method. The film-forming method often uses polyvinylidene fluoride, polysulfone, polyethersulfone, etc. as film-forming agents. This method of forming will use a large amount of organic solvents during the production process, which has an adverse impact on human health and brings great pressure to environmental protection. In addition, there are many large cavities in the formed adsorbent and large pores on the surface, resulting in unstable loading of the adsorbent. During long-term use, the powder loss is relatively serious, seriously affecting the stability of operation, and the adsorption capacity also gradually decreases with the powder loss. Moreover, most of the membrane materials are hydrophobic materials and cannot have permanent hydrophilicity, affecting the adsorption rate. The droplet granulation method has high requirements for the particle size and dispersion degree of the powder. During the preparation process, the pores are often blocked due to powder agglomeration, and it is difficult to achieve continuous production. In addition, this method has high requirements for droplet granulation equipment and it is difficult to prepare adsorbents with smaller sizes, resulting in a long mass transfer path of the adsorbent and seriously affecting its mass transfer efficiency. At the same time, the adsorbents prepared by this method have a low bulk density, which limits the lithium recovery rate during application. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for preparing an adsorbent for extracting lithium from salt lake brine to solve at least one of the technical problems existing in the above background technology.

[0007] To achieve the above purpose, the present invention adopts the following technical solutions:

[0008] A method for preparing an adsorbent for extracting lithium from salt lake brine, comprising:

[0009] Weigh a certain amount of a macroporous agent, hydrophilic silica, lithium ion sieve and pseudo-boehmite powder and place them in a rolling ball device, and mix them evenly at a certain rotation speed;

[0010] Prepare a nitric acid solution with a certain concentration. While the rolling ball device is rotating, spray the nitric acid solution to control the rolling ball diameter between 200 μm and 400 μm, and obtain seed particles after screening;

[0011] Weigh a certain amount of ammonium bicarbonate, hydrophilic silica, lithium ion sieve and pseudo-boehmite powder and place them in a rolling ball machine, mix them evenly, place the obtained seed particles in the rolling ball machine for rolling, and control the diameter of the spherical adsorbent between 600 μm and 1000 μm;

[0012] After rolling, place it in an oven for low-temperature treatment, and then calcine it at high temperature in a muffle furnace;

[0013] After calcination, a gradient pore structure LIS-SiO 2 composite adsorbent material is obtained.

[0014] Optionally, the mass ratio of the polymer pore former, hydrophilic silica, lithium ion sieve, and pseudoboehmite is controlled between 0.1 - 0.3:0.05 - 0.2:1:0.1 - 0.5.

[0015] Optionally, the nitric acid concentration is controlled between 4% - 8%.

[0016] Optionally, the mass ratio of ammonium bicarbonate, hydrophilic silica, lithium ion sieve, and pseudoboehmite powder is controlled between 0.1 - 0.3:0.05 - 0.2:1:0.1 - 0.5.

[0017] Optionally, the low-temperature treatment temperature in the oven is controlled between 50 - 80 °C.

[0018] Optionally, high-temperature calcination is carried out in a muffle furnace, and the temperature is controlled between 400 - 600 °C.

[0019] Optionally, the polymer pore former is one of polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyvinyl chloride (PVC), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polysulfone (PSF), polystyrene (PS), or polyvinyl butyral (PES).

[0020] Advantages of the present invention:

[0021] (1) By introducing hydrophilic silica materials, using their high porosity, high specific surface area, and hydrophilic characteristics, the composite material has good wettability, can wet a large number of pores in a short time, shorten the mass transfer time of lithium ions, and improve the adsorption efficiency of lithium ions.

[0022] (2) The present invention selects pseudoboehmite powder as the binder. Due to its strong adhesiveness, the powder can be better wrapped, and there will be no powder loss during use. At the same time, it has good wear and pressure resistance, increasing the service life of the adsorbent.

[0023] (3) The present invention selects ammonium bicarbonate with a low decomposition temperature as the microporous pore former and a polymer material with a decomposition temperature between 200 - 300 °C as the mesoporous pore former. During the heat treatment process, a rich pore structure is formed, increasing the specific surface area, improving the powder utilization rate, and the adsorption rate.

[0024] (4) Using a two-step rolling ball process, the adsorbent and the polymer material are mixed and rolled into particles with a particle size of 200 - 400 μm as seeds, and then the outer layer is rolled with a mixture of the adsorbent and ammonium bicarbonate. During the heat treatment process, the outer layer of ammonium bicarbonate decomposes first to form a microporous structure, and when the temperature continues to rise, the internal polymer material further decomposes to form a mesoporous structure, enabling the adsorbent to form a gradient pore structure. While ensuring that the pores are rich and connected, it has high mechanical strength.

[0025] (5) By adopting the rolling ball process, the proportion of adsorbent powder can be effectively adjusted, and a composite material with a high proportion of adsorbent powder can be prepared, which can effectively increase the powder dosage and bulk density, making the proportion of active ingredients in a unit volume higher, having a higher adsorption capacity, and improving the lithium extraction efficiency and production capacity.

[0026] (6) Without using organic solvents, the production is more environmentally friendly and the process is simple, which is convenient for industrial scale-up.

[0027] The advantages of the additional aspects of the present invention will be more clearly given in the following description part, or understood through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0029] Figure 1 Flow chart for preparing the gradient pore structure LIS-SiO 2 composite adsorbent.

[0030] Figure 2 For the LIS-SiO 2 electron microscopy image of the internal pore structure of the composite adsorbent described in the embodiments of the present invention.

[0031] Figure 3 Schematic diagram of the change curve of the adsorption capacity of the adsorbent with different granulation methods with the adsorption time described in the embodiments of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions from beginning to end. The embodiments described through the drawings are exemplary and are only used to explain the present invention, and cannot be construed as a limitation of the present invention.

[0033] Those skilled in the art of the present technology can understand that unless otherwise defined, all terms (including technical terms and scientific terms) used here have the same meaning as the general understanding of those of ordinary skill in the art in the field to which the present invention belongs.

[0034] It should also be understood that terms such as those defined in a general dictionary should be understood to have a meaning consistent with the meaning in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless defined as here.

[0035] Those skilled in the art can understand that, unless specifically stated otherwise, the singular forms "a", "an", "the" and "said" used herein may also include the plural forms. It should be further understood that the term "comprising" used in the specification of the present invention means the presence of the described features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements and / or their groups.

[0036] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. Moreover, the specific features, structures, materials or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0037] For the convenience of understanding the present invention, the present invention will be further explained below with specific examples in conjunction with the accompanying drawings, and the specific examples do not constitute a limitation to the embodiments of the present invention.

[0038] Those skilled in the art should understand that the drawings are only schematic diagrams of the embodiments, and the components in the drawings are not necessarily essential for implementing the present invention.

[0039] The present invention provides a preparation method of an adsorbent composite material that can quickly adsorb lithium ions, and at the same time has high adsorption capacity and high operation stability. Aiming at the problems of low powder utilization rate, slow adsorption rate, low adsorption capacity and short life due to powder loss during the operation process caused by the forming process of the adsorbent for extracting lithium from salt lakes, it solves the environmental protection problems brought by the need to use a large amount of organic solvents in the film-forming method, and at the same time solves the problems of powder loss and short life caused by large surface pores and loose wrapping. At the same time, it solves the problems of high production difficulty, low adsorption capacity and poor mass transfer efficiency in the droplet method. This composite material is an advanced material with broad prospects in the field of extracting lithium from salt lakes.

[0040] Example 1

[0041] Weigh 500 g of titanium-based lithium ion sieve, 50 g of PVC powder, 25 g of hydrophilic silica, and 100 g of pseudo-boehmite powder, place them in a rolling ball device and roll, control the rotation speed at 50 r / min, and the rolling time at 40 min to obtain spherical samples with a particle size of 300 μm. After screening, seeds are obtained. Place the seeds in a mixed powder of 500 g of titanium-based lithium ion sieve, 50 g of ammonium bicarbonate, 25 g of hydrophilic silica, and 100 g of pseudo-boehmite powder, control the rotation speed at 35 r / min, and the rolling time at 50 min to obtain spherical materials with a particle size of 800 μm. Place the obtained spherical materials in an oven at 70 °C for 3 h and then place them in a muffle furnace, set the temperature at 500 °C, and calcine for 2 h to obtain LIS-SiO with a gradient pore structure 2 Composite adsorbent. Figure 2 It is the SEM image of the composite adsorbent and its internal pore structure.

[0042] Example 2

[0043] Compare the adsorption rates and adsorption capacities of adsorbents with different granulation forms on the market. The comparison results are as Figure 3 shown. It can be seen from the figure that the adsorption rate of the gradient pore LIS-SiO 2 composite adsorbent is much higher than that of hollow fiber and drop granule adsorbents. The saturated adsorption capacity is 26 mg / g, which has the characteristics of high adsorption capacity and fast adsorption rate, and has broad application prospects in the field of lithium extraction.

[0044] Example 3

[0045] Weigh 500 g of titanium-based lithium ion sieve, 100 g of PES powder, 50 g of hydrophilic silica, and 80 g of pseudo-boehmite powder, place them in a rolling ball device and roll, control the rotation speed at 45 r / min, and the rolling time at 45 min to obtain spherical samples with a particle size of 200 μm. After screening, seeds are obtained. Place the seeds in a mixed powder of 500 g of titanium-based lithium ion sieve, 100 g of ammonium bicarbonate, 50 g of hydrophilic silica, and 50 g of pseudo-boehmite powder, control the rotation speed at 40 r / min, and the rolling time at 50 min to obtain spherical materials with a particle size of 900 μm. Place the obtained spherical materials in an oven at 80 °C for 3 h and then place them in a muffle furnace, set the temperature at 550 °C, and calcine for 2 h to obtain LIS-SiO with a gradient pore structure 2 composite adsorbent. Test its adsorption capacity, selectivity, abrasion resistance, pressure resistance strength, bulk density and other parameters. The test results are shown in Table 1. This adsorbent has good mechanical strength and adsorption performance and has broad application prospects.

[0046] Table 1 Basic performance parameters of the gradient pore structure LIS-SiO 2 composite adsorbent

[0047]

[0048] In summary, the preparation method of the adsorbent for extracting lithium from salt lake brine described in the embodiments of the present invention adopts a rolling ball forming process, with lithium ion sieve as the main component. The lithium ion sieve is a titanium-based adsorbent or a manganese-based adsorbent powder, which is used for the adsorption and enrichment of lithium ions in salt lake brine. Using hydrophilic silica as an additive, taking full advantage of its high porosity, high specific surface area and hydrophilicity characteristics, when using this material in salt lake brine, it can achieve the effect of quickly infiltrating the internal pores, increasing the collision probability between lithium ions and adsorption sites, effectively improving the adsorption rate of lithium ions. At the same time, using pseudo-boehmite powder as a binder and nitric acid as a peptizing agent, which has strong viscosity, can greatly improve the strength of the adsorbent, increase its resistance to mechanical wear and pressure resistance, and extend its service life. Through further heat treatment, a rich pore structure is formed, the pore volume is increased, and the mass transfer effect is enhanced. Finally, ammonium bicarbonate with a low decomposition temperature and a polymer material with a decomposition temperature between 200-300 °C are selected as pore-forming agents, which are gradually decomposed and form pores during the heat treatment process, forming a gradient pore structure. On the basis of the penetration of ion transport pores, a relatively high strength is maintained. At the same time, the rolling ball process is adopted to ensure a relatively high proportion of the adsorbent in the material, and the packing density is increased significantly, so that the effective component proportion of the adsorbent in the unit volume is high, increasing the lithium extraction production capacity and extending the service life of the material.

[0049] By introducing hydrophilic silica material, taking advantage of its high porosity, high specific surface area and hydrophilicity characteristics, the composite material has good wettability, can wet a large number of pores in a short time, shorten the mass transfer time of lithium ions, and improve the adsorption efficiency of lithium ions; selecting pseudo-boehmite powder as a binder, using its strong viscosity, making the wrapping of the powder stronger, and there will be no powder loss during use. At the same time, it has good wear and pressure resistance, increasing the service life of the adsorbent. Selecting ammonium bicarbonate with a low decomposition temperature as the micropore-forming agent and a polymer material with a decomposition temperature between 200-300 °C as the mesopore-forming agent, during the heat treatment process, a rich pore structure is formed, the specific surface area is increased, and the powder utilization rate and adsorption rate are increased. Adopting a two-step rolling ball process, the adsorbent and the polymer material are mixed and rolled into particles with a particle size of 200-400 μm as seeds, and then the outer layer is rolled with a mixture of the adsorbent and ammonium bicarbonate. During the heat treatment process, the outer layer ammonium bicarbonate decomposes first to form a microporous structure, and then continues to heat up, and the internal polymer material further decomposes to form a mesoporous structure, so that the adsorbent forms a gradient pore structure, ensuring that the pores are rich and connected while having relatively high mechanical strength. The rolling ball process can effectively adjust the proportion of the adsorbent powder, prepare a composite material with a high proportion of the adsorbent powder, effectively improve the powder dosage and packing density, make the proportion of the effective component in the unit volume higher, and have a higher adsorption capacity. It improves the lithium extraction efficiency and production capacity. Without using organic solvents, the production is more environmentally friendly and the process is simple, which is convenient for industrial scale-up.

[0050] Although the specific implementation manners of the present invention have been described above in conjunction with the accompanying drawings, they do not limit the protection scope of the present invention. Those skilled in the art should understand that, based on the technical solutions disclosed in the present invention, various modifications or deformations that can be made by those skilled in the art without creative efforts should be covered within the protection scope of the present invention.

Claims

1. A method for preparing an adsorbent for extracting lithium from salt lake brine, characterized in that: include: Weigh a certain amount of polymer porogen, hydrophilic silica, lithium ion sieve and pseudo-boehmite powder and place them in a rolling ball device, and mix them evenly at a certain speed; A nitric acid solution of a certain concentration is prepared, and the nitric acid solution is sprayed while the rolling ball device rotates, and the particle size of the rolling balls is controlled to be between 200 μm and 400 μm, and seed particles are obtained after screening; Weigh a certain amount of ammonium bicarbonate, hydrophilic silica, lithium ion sieve and pseudo-boehmite powder and place them in a ball rolling machine, mix them evenly, and roll the obtained seed particles in the ball rolling machine to control the particle size of the spherical adsorbent to be between 600 μm and 1000 μm; After rolling, it is placed in an oven for low-temperature treatment, and then calcined in a muffle furnace at high temperature; After calcination, a LIS-SiO2 composite adsorption material with a gradient pore structure is obtained.

2. The method for preparing an adsorbent for extracting lithium from salt lake brine according to claim 1, characterized in that: The mass ratio of polymer porogen, hydrophilic silica, lithium ion sieve and pseudo-boehmite is controlled between 0.1-0.3:0.05-0.2:1:0.1-0.

5.

3. The method for preparing an adsorbent for extracting lithium from salt lake brine according to claim 1, characterized in that: The nitric acid concentration is controlled at 4%-8%.

4. The method for preparing an adsorbent for extracting lithium from salt lake brine according to claim 1, characterized in that: The mass ratio of ammonium bicarbonate, hydrophilic silica, lithium ion sieve and pseudo-boehmite powder is controlled between 0.1-0.3:0.05-0.2:1:0.1-0.

5.

5. The method for preparing an adsorbent for extracting lithium from salt lake brine according to claim 1, characterized in that: The low temperature treatment temperature in the oven is controlled at 50-80°C.

6. The method for preparing an adsorbent for extracting lithium from salt lake brine according to claim 5, characterized in that: High temperature calcination is carried out in a muffle furnace, and the temperature is controlled between 400-600℃.

7. The method for preparing an adsorbent for extracting lithium from salt lake brine according to claim 1, characterized in that: The polymer porogen is one of polyvinyl alcohol, polyvinyl pyrrolidone, polyvinyl chloride, polyacrylonitrile, polyvinylidene fluoride, polysulfone, polystyrene or polyvinyl butyral.

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