CN116943600A - Lithium ion adsorption membrane and its preparation method and application - Google Patents

Abstract

The invention relates to the field of lithium adsorption, and discloses a lithium ion adsorption membrane and its preparation method and application. The lithium ion adsorption membrane includes a membrane skeleton and a lithium ion screen loaded on the membrane skeleton; wherein the specific surface area of the lithium ion adsorption membrane is 1-7m ² /g. The lithium ion adsorption membrane has high adsorption capacity and adsorption rate, and can significantly improve lithium production efficiency.

Description

Lithium ion adsorption membrane and its preparation method and application

Technical field

The present invention relates to the field of lithium adsorption, and specifically to a lithium ion adsorption membrane and its preparation method and application.

Background technique

With the rapid development of the lithium battery industry, the demand for lithium resources in various industries is continuing to grow, and the importance of lithium production is also increasing. At present, lithium resources are mainly distributed in lithium ores and salt lake brine, but lithium ore resources are constantly decreasing and development costs are increasing. In contrast, lithium water resources in salt lake brine are low-cost and abundant. China is the largest consumer of lithium. Although it has abundant liquid lithium resources, extracting lithium from lithium water resources is a challenging task. Therefore, most upstream lithium source materials still rely on imports. The main methods for extracting lithium from domestic salt lakes include adsorption, precipitation, extraction, electrodialysis, calcination, etc. Among them, the adsorption method has the advantages of simple process, green energy saving, good selectivity, and is superior to other methods in terms of time and cost. ,have a broad vision of application. Due to the common problem of low lithium taste in domestic salt lake brine, the core of lithium extraction by adsorption is to prepare highly selective adsorbents. Highly selective lithium extraction adsorbents mainly include ionic sieve adsorbents and amorphous hydroxides. Adsorbents, both types of adsorbents exist in the form of powder, which are easy to lose in water and difficult to recycle. They require specific molding methods such as granulation, film formation, etc. However, the lithium ion adsorption membrane obtained by the existing molding method still has the problems of low adsorption capacity and low adsorption rate of the adsorbent, which seriously hinders the improvement of lithium production efficiency. Therefore, there is an urgent need to develop a lithium adsorption product with higher adsorption capacity and adsorption rate.

Contents of the invention

The purpose of the present invention is to overcome the above-mentioned problems of the prior art and provide a lithium ion adsorption membrane and its preparation method and application. The lithium ion adsorption membrane has high adsorption capacity and adsorption rate and can significantly improve the production of lithium. efficiency.

In order to achieve the above object, a first aspect of the present invention provides a lithium ion adsorption membrane, which includes a membrane skeleton and a lithium ion screen loaded on the membrane skeleton;

Wherein, the specific surface area of the lithium ion adsorption membrane is 1-7m ² /g.

A second aspect of the present invention provides a method for preparing a lithium ion adsorption film. The method includes: using a film-forming liquid dispersed with lithium ion sieves to form a film, and performing a droplet bath to obtain the lithium ion adsorption film.

A third aspect of the present invention provides a lithium ion adsorption membrane prepared by the above method.

A fourth aspect of the present invention provides the application of the lithium ion adsorption membrane described in the first or third aspect in collecting lithium.

The solution of the present invention evenly disperses the lithium ion sieve on the polymer membrane, avoids the agglomeration of the lithium ion sieve, and also solves the problem that the powder adsorbent is easy to lose and difficult to recycle. In particular, the use of a droplet bath can fully expose the lithium ion sieve dispersed in the casting liquid, which means fully exposing the adsorption sites of the adsorbent, increasing the lithium adsorption capacity, and at the same time increasing the lithium ion adsorption rate. .

In addition, the preparation method provided by the invention is simple, has high production efficiency, and has great industrial application prospects.

Description of the drawings

Figure 1 is a scanning electron microscope (SEM) image of the porous membrane prepared in Example 1;

Figure 2 is a scanning electron microscope image of the porous membrane prepared in Comparative Example 1;

Figure 3 is a scanning electron microscope image of the porous membrane prepared in Comparative Example 2.

Detailed ways

The endpoints of ranges and any values disclosed herein are not limited to the precise range or value, but these ranges or values are to be understood to include values approaching such ranges or values. For numerical ranges, the endpoint values of each range, the endpoint values 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. These values The scope shall be deemed to be specifically disclosed herein.

In a first aspect, the present invention provides a lithium ion adsorption membrane, which is characterized in that the lithium ion adsorption membrane includes a membrane skeleton and a lithium ion screen loaded on the membrane skeleton;

Wherein, the specific surface area of the lithium ion adsorption membrane is 1-7m ² /g.

It can be understood that the lithium ion screen is a lithium adsorbent. Using the lithium ion adsorption membrane provided by the invention, the lithium ion sieve is dispersed on the membrane, which not only solves the problem that the powder lithium ion sieve is easy to lose and difficult to reuse, but also has a larger specific surface area, and the adsorption sites can be fully exposed, and the membrane's The lithium adsorption capacity is larger and the lithium adsorption rate is higher.

According to the present invention, preferably, the specific surface area of the lithium ion adsorption membrane is 3.8-5m ² /g. When the above range is met, the lithium adsorption capacity of the membrane is larger and the lithium adsorption rate is higher.

According to the present invention, preferably, relative to 1 g of lithium ion adsorption membrane, the loading capacity of the lithium ion screen is 0.1-0.6g, more preferably 0.45-0.5g. When the above range is met, the amount of lithium ion screen loaded on the membrane is more appropriate, which can further ensure that the membrane has higher adsorption capacity and adsorption rate.

According to the present invention, preferably, the porosity of the lithium ion adsorption membrane is 60-90%, more preferably 80-83%; when having a porosity in the above range, the presence of pores can further increase the specific surface area of the membrane , allowing lithium ions to more fully contact the membrane, further increasing the adsorption sites, and further improving the adsorption capacity and adsorption rate.

According to the present invention, preferably, the thickness of the lithium ion adsorption film is 100-300 μm, preferably 120-260 μm.

According to the present invention, preferably, micro-protrusion structures are distributed on the lithium ion adsorption film, and the maximum cross-sectional area of the micro-protrusions has a diameter of 1-2 μm. The presence of microprotrusions can further increase the specific surface area of the membrane. The diameter at the maximum cross-sectional area can be observed and measured using a scanning electron microscope.

According to the present invention, preferably, the membrane skeleton thickness of the lithium ion adsorption membrane is 40-240 μm, preferably 60-180 μm. It can be understood that there is a certain difference between the thickness of the membrane skeleton and the thickness of the lithium ion adsorption membrane. The thickness of the membrane skeleton is the sum of the heights of the polymer membrane base and the protruding part of the loaded lithium ion screen. Since the polymer membrane base can also form a film on the support layer, the lithium ion adsorption membrane may also include a support layer, so the lithium ion The thickness of the adsorption film is the sum of the thickness of the membrane skeleton and the thickness of the support layer.

The specific type of the lithium ion screen is not particularly limited and can be a conventional selection in this field. But preferably, the lithium ion screen is at least one of a manganese-based lithium ion screen and a titanium-based ion screen, and more preferably a manganese-based lithium ion screen. The manganese-based ion sieve adsorbent refers to the lithium manganese oxide compound with a spinel structure, and the titanium-based ion sieve adsorbent refers to the layered H ₂ TiO ₃ and spinel structure H ₄ Ti ₅ O ₁₂ .

According to the present invention, preferably, the membrane skeleton is composed of a film-forming polymer, and the film-forming polymer is preferably selected from the group consisting of polyacrylonitrile, polyvinylidene fluoride, polyvinyl alcohol, polyvinyl chloride, polysulfone, and polyethersulfone. , at least one of polyvinyl alcohol, polyimide, cellulose and polycarbonate. The cellulose may be at least one of cellulose acetate, cellulose nitrate, and cellulose triacetate.

According to the present invention, preferably, the weight average molecular weight of the film-forming polymer is 40,000-120,000 g/mol.

According to the present invention, preferably, the lithium ion adsorption membrane further includes a support layer. The support layer can play a supporting role.

Preferably, the porosity of the support layer is 30-40%, and the thickness is 60-80 μm. A support layer that meets the above range can also play a supporting role without affecting the lithium ion adsorption capacity and rate.

Preferably, the support layer is made of at least one material selected from the group consisting of non-woven fabric, woven fabric, polyethylene and polypropylene.

In a second aspect, the present invention provides a method for preparing a lithium ion adsorption film. The method includes: using a film-forming liquid dispersed with lithium ion sieves for film formation, and performing a droplet bath to obtain the lithium ion adsorption film. .

According to the present invention, preferably, the conditions of the droplet bath include: the time is 10-100s, the droplet size is 1-80 μm, and the consumption of droplets is 5-80g/h relative to a ^1m2 film.

The inventor of the present invention found during research that when a casting liquid in which lithium ion sieves are dispersed is used to form a film, the lithium ion sieves on the formed film are dispersed relatively evenly, which can fully avoid the agglomeration of the lithium ion sieves to mask the adsorption sites. point, causing the problem of decreased adsorption capacity and adsorption rate. In addition, subjecting the membrane to a droplet bath can effectively expand the pores on the membrane, fully expose the lithium ion screen wrapped by the film-forming polymer, and avoid clogging of the membrane pore structure by the lithium ion screen, increasing the membrane's durability. The specific surface area ensures that the membrane has high adsorption capacity and adsorption rate. The presence of the lithium ion screen also causes micro-protrusions on the membrane surface, further increasing the specific surface area of the membrane. The droplet bath refers to placing the membrane in an atomized droplet environment. The droplet bath can also form holes on the membrane, further increasing the specific surface area, allowing the membrane and lithium ions to fully contact.

It can be understood that after mixing the lithium ion screen, the film-forming polymer, and the solvent, ultrasound can be performed to make the lithium ion screen more uniformly dispersed in the film casting liquid.

According to the present invention, preferably, the concentration of the film-forming polymer in the film casting liquid is 5-15 mass%, preferably 7-11 mass%.

According to the present invention, preferably, the concentration of the lithium ion sieve in the film casting liquid is 5-15 mass%, preferably 7-11 mass%. When the above range is met, the amount of lithium ion screen loaded on the formed membrane is more appropriate, which can further ensure that the membrane has higher adsorption capacity and adsorption rate.

According to the present invention, preferably, the film-forming polymer is selected from polyacrylonitrile, polyvinylidene fluoride, polyvinyl alcohol, polyvinyl chloride, polysulfone, polyethersulfone, polyvinyl alcohol, polyimide, cellulose and at least one of polycarbonate.

According to the present invention, preferably, the weight average molecular weight of the film-forming polymer is 40,000-120,000 g/mol.

According to the present invention, preferably, the method further includes: forming a film in the presence of a support layer.

Preferably, the porosity of the support layer is 30-40%, and the thickness is 60-80 μm.

Preferably, the support layer is made of at least one material selected from the group consisting of non-woven fabric, woven fabric, polyethylene and polypropylene.

When the support layer as mentioned above is used, the mechanical properties of the membrane can be further ensured.

According to the present invention, preferably, the lithium ion screen is at least one of a manganese-based lithium ion screen and a titanium-based ion screen, and more preferably is a manganese-based lithium ion screen.

According to the present invention, preferably, the particle size of the lithium ion sieve is 1-10 μm, more preferably 2-4 μm.

According to a preferred embodiment of the present invention, the preparation method of the manganese-based lithium ion screen includes: mixing a lithium source and a manganese source, and sequentially grinding, drying, calcining, and pickling to obtain the manganese-based lithium ion screen. .

Preferably, the molar ratio of the lithium source calculated as lithium element and the manganese source calculated as manganese element is 1:1-4, preferably 1:1.25-2.5.

Preferably, the lithium source is selected from at least one of lithium nitrate, lithium carbonate, lithium acetate, lithium chloride and lithium hydroxide.

Preferably, the manganese salt is selected from at least one selected from the group consisting of manganese carbonate, manganese nitrate, manganese dioxide, manganese acetate and manganese oxalate.

Preferably, the grinding method includes: grinding a lithium source, a manganese source, ethanol and ball milling steel balls together. The conditions of the ball milling are such that the particle size of the ground material is 1-10 μm, preferably 2-4 μm. For example, ball milling can be performed at a speed of 100-300 rpm for 1-4 hours. It can be understood that the particle size of the ground material is consistent with the particle size of the lithium ion screen on the finally prepared lithium ion adsorption membrane.

It can be understood that ethanol can better disperse the lithium source and manganese source. Preferably, in terms of mass dosage, (lithium source + manganese source):ethanol is 1:1 to 4, preferably 1:1 to 2.

Ball mill steel balls are the grinding balls needed for grinding. The diameter of the ball milling steel balls may be 2-10 mm, preferably 3-8 mm. In terms of mass and dosage, (lithium source + manganese source): ball-milled steel balls are 1:10-40.

The drying can be oven drying, the temperature can be 40-60°C, and the time can be 6-12 hours.

Under calcination conditions, manganese and lithium can form lithium manganese oxides, such as Li ₄ Mn ₅ O ₁₂ and LiMn ₂ O ₄ . Preferably, the calcination conditions include: performing it in an air atmosphere, with a temperature of 400-700°C and a time of 4-24 hours. After calcination, cooling can be carried out.

Among them, the purpose of pickling is to use hydrogen ions to exchange lithium in the lithium manganese oxide formed after calcination to obtain a manganese-based lithium ion screen. The acid may be at least one of hydrochloric acid, sulfuric acid, nitric acid, ammonium persulfate, etc. The acid concentration may be 0.1-1 mol/L. The pickling time can be 18-36h.

It can be understood that when a manganese-based lithium ion screen is used to adsorb lithium ions, hydrogen ions and lithium ions are exchanged to achieve adsorption. After the adsorption is completed, the lithium ion screen can be regenerated under acidic conditions to regain the ability to adsorb lithium ions.

According to the present invention, preferably, the solvent in the film casting liquid is selected from good solvents for film-forming polymers. The good solvent means that the polymer-solvent interaction parameter χ (Huggins parameter) of the film-forming polymer and the solvent at 25° C. is less than 0.5. Preferably, the solvent is selected from N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, acetone, chloroform, and tributyl phosphate. at least one of them.

The film forming method is not particularly limited and can be a conventional choice in the field. For example, the scraping method can be used.

According to the present invention, preferably, the film formation conditions are such that the thickness of the lithium ion adsorption film is 100-300 μm, preferably 110-250 μm. It can be understood that in specific operations, such as using the scraping method to form a film, the thickness of the scraped film can be set, but the thickness is slightly different from the thickness of the final film. Generally, the thickness of the final film is The thickness should be about 10-40μm lower than the thickness set during film formation.

According to the present invention, in order to further ensure that the lithium ion screen is fully exposed, preferably, the conditions of the droplet bath include: a time of 40-60s, a droplet size of 5-50 μm, and relative to a film of 1 ^m2 , the droplet size is The consumption is 10-40g/h.

According to the present invention, preferably, after the droplet bath, the method further includes: subjecting the materials to non-solvent induced phase separation to remove the solvent introduced into the film casting solution. The non-solvent-induced phase separation means that when forming a film, the casting liquid contains a solvent, and the solvent in the formed film is not removed. At this time, the film is placed in a place where the solvent is more miscible and the film is formed. The solvent of the casting solution is extracted from the poor solvent reagent (also known as non-solvent or extractant) of the membrane polymer to remove the residual solvent on the membrane and solidify the membrane.

Preferably, the phase separation time caused by the non-solvent is 60-300 s.

Preferably, the non-solvent that causes phase separation is selected from at least one of water, ethanol, ethylene glycol, n-butanol, isobutanol and glycerol.

A third aspect of the present invention provides a lithium ion adsorption membrane prepared by the above method.

A fourth aspect of the present invention provides the application of the lithium ion adsorption membrane described in the first or third aspect in collecting lithium.

According to a particularly preferred embodiment of the present invention, a lithium ion adsorption membrane is prepared according to the following method:

(1) Weigh LiNO ₃ and MnCO ₃ at a molar ratio of 1:1.25-2.3, add them to the ball mill tank, and then add ethanol equal to 1.8-2 times the combined mass of the lithium source and manganese source and an amount equal to 1.8-2 times the combined mass of the lithium source and manganese source into the ball mill tank. Use a planetary ball mill to grind 4-5mm ball mill steel balls with 20-30 times the sum of the mass of the lithium source and the manganese source at a speed of 100-180 rpm for 3-4 hours until the particle size of the material is 2-3 μm, and then grind the material at 50-50 After drying at 60°C for 6-7h, put it into a muffle furnace and bake it in an air atmosphere at 400-500°C for 6-7h. After cooling, use 0.5-0.7mol/L HCl to elute for 20-26h to obtain the lithium ion sieve.

(2) Mix polyacrylonitrile, N,N-dimethylformamide, and the lithium ion sieve obtained by the above method to obtain a casting liquid, so that the concentrations of polyacrylonitrile and lithium ion sieve in the casting liquid are both 9- 10% by mass, and ultrasonicize the casting liquid to obtain a uniformly dispersed casting liquid.

After the casting liquid is allowed to stand for defoaming, the film is scraped on a non-woven fabric (thickness 73-78 μm, porosity 35-38%), and the thickness of the scraped film is controlled so that the thickness of the final lithium ion adsorption film is about 170-170 190 μm, and then the film is subjected to a droplet bath. The conditions of the droplet bath include: the time is 40-45s, the droplet size is 5-50 μm, and the consumption of droplets is 20-30g relative to a ^1m2 film. /h.

After the droplet bath is completed, the membrane is immersed in deionized water and stays for 200-240 seconds to perform non-solvent-induced phase separation to obtain a lithium ion adsorption membrane.

The present invention will be described in detail below through examples. In the following examples, the weight average molecular weight of polyacrylonitrile is 78000g/mol, the ultrasonic time for the casting liquid is 60 minutes, the power is 240W, and the frequency is 40kHz.

Example 1

(1) Weigh LiNO ₃ and MnCO ₃ at a molar ratio of 1:1.25, add them to the ball mill tank, and then add ethanol equivalent to twice the combined mass of the lithium source and manganese source and an amount equivalent to the lithium source and manganese source into the ball mill tank. Use a planetary ball mill to grind 4mm ball-milled steel balls with a sum of 20 times the mass for 4 hours at a speed of 100 rpm until the particle size of the material is 2-3 μm. Then dry the material at 50°C for 6 hours, then put it into a muffle furnace and heat it at 400 The lithium ion sieve was obtained by calcining in an air atmosphere at ℃ for 6 hours, cooling and eluting with 0.5 mol/L HCl for 24 hours.

(2) Mix polyacrylonitrile, N,N-dimethylformamide and the lithium ion sieve obtained by the above method to obtain a casting liquid, so that the concentration of polyacrylonitrile and lithium ion sieve in the casting liquid is 9 mass %, and ultrasonicize the casting liquid to obtain a uniformly dispersed casting liquid.

After the casting liquid is allowed to stand for defoaming, the film is scraped on a non-woven fabric (thickness: 75 μm, porosity: 35%). The thickness of the scraped film is controlled so that the thickness of the final lithium ion adsorption film is about 180 μm, and then the film is Droplet bath, the conditions of the droplet bath include: the time is 40s, the droplet size is 5-50 μm, and the consumption of droplets is 30g/h relative to a ^1m2 film.

After the droplet bath is completed, the membrane is immersed in deionized water and stayed for 240 seconds to perform non-solvent-induced phase separation to obtain a lithium ion adsorption membrane.

The obtained lithium ion adsorption film was imaged using a scanning electron microscope (SEM), and the results are shown in Figure 1.

Example 2

(1) Weigh LiOH·H ₂ O and MnO ₂ at a molar ratio of 1:2, add them to the ball mill tank, and then add ethanol equivalent to twice the mass of the lithium source and manganese source into the ball mill tank and equivalent to the lithium source. Use a planetary ball mill to grind 8mm ball-milled steel balls with 40 times the sum of the mass of the manganese source for 2.5 hours at a speed of 200 rpm until the particle size of the material is 3-4 μm. After drying the material at 50°C for 8 hours, put it into a muffle furnace. Calculate in an air atmosphere at 600°C for 8 hours, cool and then elute with 0.1 mol/L HCl for 24 hours to obtain a lithium ion sieve.

(2) Mix polyacrylonitrile, N-methylpyrrolidone and the lithium ion sieve obtained by the above method to obtain a casting liquid, so that the concentrations of polyacrylonitrile and lithium ion sieve in the casting liquid are both 7.8 mass%, and The casting liquid is subjected to ultrasound to obtain a uniformly dispersed casting liquid.

After the casting liquid is allowed to stand for defoaming, the film is scraped on a non-woven fabric (thickness: 80 μm, porosity: 40%). The thickness of the scraped film is controlled so that the thickness of the final lithium ion adsorption film is approximately 140 μm. The film is then Droplet bath, the conditions of the droplet bath include: the time is 60s, the droplet size is 5-50μm, and the consumption of droplets is 40g/h relative to the film of ^1m2 .

After the droplet bath is completed, the membrane is immersed in deionized water and stayed for 300 seconds to perform non-solvent-induced phase separation to obtain a lithium ion adsorption membrane.

Example 3

(1) Weigh Li ₂ CO ₃ and MnCO ₃ at a molar ratio of 1:2.5, add them to the ball mill tank, and then add ethanol equivalent to twice the combined mass of the solid lithium source and manganese source and lithium equivalent to the ball mill tank. Use a planetary ball mill to grind 4mm ball mill steel balls with 20 times the sum of the mass of the manganese source and the manganese source for 1 hour at a speed of 300 rpm until the particle size of the material is 2-3 μm. Then dry the material at 50°C for 8 hours and put it into a muffle furnace. , calcined in an air atmosphere at 400°C for 6h, cooled and eluted with 0.25mol/LH ₂ SO ₄ for 24h to obtain a lithium ion sieve.

(2) Mix polyacrylonitrile, N,N-dimethylacetamide and the lithium ion sieve obtained by the above method to obtain a casting liquid, so that the concentrations of polyacrylonitrile and lithium ion sieve in the casting liquid are both 10.7 mass %, and ultrasonicize the casting liquid to obtain a uniformly dispersed casting liquid.

After the casting liquid is allowed to stand for defoaming, the film is scraped on a non-woven fabric (thickness: 70 μm, porosity: 30%). The thickness of the scraped film is controlled so that the thickness of the final lithium ion adsorption film is approximately 220 μm. The film is then Droplet bath, the conditions of the droplet bath include: the time is 50s, the droplet size is 5-50 μm, and the consumption of droplets is 15g/h relative to a ^1m2 film.

After the droplet bath is completed, the membrane is immersed in deionized water and stays for 60 seconds to perform non-solvent-induced phase separation to obtain a lithium ion adsorption membrane.

Example 4

(1) Weigh LiOAc and Mn(NO ₃ ) ₂ at a molar ratio of 1:2, add them to the ball milling tank, and then add ethanol equivalent to twice the combined mass of the lithium source and manganese source and lithium equivalent to the ball milling tank. Use a planetary ball mill to grind 3mm ball-milled steel balls with 30 times the mass of the manganese source. Mill at a speed of 200 rpm for 2 hours until the particle size is 2-3 μm. Dry the material at 50°C for 6 hours and put it into a muffle furnace. , calcined in an air atmosphere at 700°C for 24h, cooled and eluted with 1mol/L HCl for 24h to obtain a lithium ion sieve.

(2) Mix polyacrylonitrile, dimethyl sulfoxide, and the lithium ion sieve obtained by the above method to obtain a casting liquid, so that the concentrations of polyacrylonitrile and lithium ion sieve in the casting liquid are both 8.9 mass%, and Ultrasonicate the casting liquid to obtain a uniformly dispersed casting liquid.

After the casting liquid is allowed to stand for defoaming, the film is scraped on a non-woven fabric (thickness 60 μm, porosity 30%). Control the thickness of the scraped film so that the thickness of the final lithium ion adsorption film is about 140 μm, and then the film is Droplet bath, the conditions of the droplet bath include: the time is 40s, the droplet size is 5-50 μm, and the consumption of droplets is 30g/h relative to a ^1m2 film.

After the droplet bath is completed, the membrane is immersed in deionized water and stays for 120 seconds to perform non-solvent-induced phase separation to obtain a lithium ion adsorption membrane.

Example 5

A lithium ion adsorption membrane was prepared according to the method of Example 1, except that the lithium ion sieve was a titanium-based ion sieve with a particle size of 3-4 μm.

Example 6

Prepare a lithium ion adsorption membrane according to the method of Example 1. The difference is that the conditions of the droplet bath include: the time is 10s, the droplet size is 1-80 μm, and the consumption of droplets relative to the film of ^1m2 is 5g/h.

Example 7

A lithium ion adsorption film was prepared according to the method of Example 1, except that the thickness of the scraped film was controlled so that the thickness of the final lithium ion adsorption film was about 130 μm, and the concentration of the lithium ion screen in the casting solution was 5 mass%.

Example 8

A lithium ion adsorption film was prepared according to the method of Example 1, except that the thickness of the scraped film was controlled so that the thickness of the final lithium ion adsorption film was about 250 μm, and the concentration of the lithium ion screen in the casting solution was 15 mass%.

Comparative example 1

The membrane was prepared according to the method of Example 1, except that the lithium ion screen was not included in the membrane casting solution. The obtained lithium ion adsorption film was imaged using a scanning electron microscope (SEM), and the results are shown in Figure 2.

Comparative example 2

The membrane was prepared according to the method of Example 1, except that a droplet bath was not performed. The obtained lithium ion adsorption film was imaged using a scanning electron microscope (SEM), and the results are shown in Figure 3.

Test example 1

For the membranes prepared in Examples 1-9 and Comparative Examples 1-2, the specific surface area of the membrane, the loading capacity of the lithium ion screen, the porosity of the membrane, the thickness of the lithium ion adsorption membrane, and the thickness of the membrane skeleton were measured, and the lithium adsorption capacity Q was measured. , the concentration coefficient CF was measured, and whether there were micro-protrusions on the film was observed by scanning electron microscopy (SEM). The test results are shown in Table 1-2.

The specific surface area of the membrane was measured using a TriStarII3020 physical adsorption instrument.

The loading capacity of the lithium ion sieve is measured by using an X-ray microanalyzer (ApolloXT, EDAX, USA) to measure the content of the Mn element in the membrane, and then calculating the loading capacity of the lithium ion sieve in the membrane based on its content percentage.

The porosity of the membrane is measured by using the gravimetric method. First, weigh the dry film mass m _d , then immerse the membrane in water and fully absorb water. Weigh the wet film mass m _w and enter it into the following formula for calculation:

In the formula, ε is the porosity of the membrane, A is the membrane area, l is the membrane thickness, and ρ _w is the density of water.

The thickness of the film was measured by using a millimeter desktop film thickness measuring instrument (Q/ILBN2-2006, Shanghai Precision Instrument Co., Ltd.).

The thickness of the membrane skeleton was measured by peeling off the support layer and then measuring the thickness of the membrane skeleton using a millimeter desktop film thickness measuring instrument (Q/ILBN2-2006, Shanghai Precision Instrument Co., Ltd.).

The adsorption capacity Q is the mass of ions adsorbed from the solution per unit area of the membrane when the adsorption reaches equilibrium at a temperature of 25°C. The calculation formula is:

Among them, the unit of Q is mg/m ² ; C ₀ and C are the ion concentrations in the solution at the beginning and at adsorption saturation, respectively, in mg/L, V is the volume of the adsorption solution, unit: L, and S is film adsorption. Area of agent, unit: m ² . The ion concentration was measured by using an ion chromatograph (ICS-1100, Dionex, USA) to measure the lithium ion concentrations C ₀ and C before and after adsorption. The method for judging that adsorption reaches equilibrium is: when using a lithium ion adsorption membrane to adsorb lithium ions in the liquid to be adsorbed, ion chromatography is also used to measure the changes in the concentration of lithium ions in the liquid to be adsorbed at different times. When the concentration no longer changes, the adsorption reaches Saturation, the time taken at this time is the time required for adsorption saturation, which reflects the speed of adsorption rate.

The concentration coefficient CF represents the degree of lithium enrichment at adsorption equilibrium and is an important indicator of lithium adsorbent. Its calculation formula is:

CF is the concentration coefficient of the lithium adsorption material, the unit is L/m ² , Q _Li is the adsorption capacity of the adsorption material for lithium ions, the unit is mg/m ² , C _Li is the concentration of lithium ions in the solution at adsorption equilibrium, the unit is mg/L.

Table 1

Table 2

In Table 1, "the loading capacity of the lithium ion screen" refers to the loading capacity of the lithium ion screen relative to 1 g of the lithium ion adsorption membrane. It can be seen from the results in Table 1-2 that when used for lithium adsorption, Examples 1-8 using the technical solution of the present invention have higher adsorption capacity and concentration coefficient, and can achieve adsorption equilibrium in a shorter time. , the adsorption rate is faster. As can be seen from Figure 1-3, the lithium ion sieve is successfully loaded onto the membrane skeleton, and the lithium ion sieve is fully exposed, which helps the adsorption sites to contact the lithium ions to be adsorbed, increasing the adsorption capacity and adsorption capacity of the adsorbent. rate. In addition, the preparation method provided by the invention is simple, has high production efficiency, and has great industrial application prospects.

The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the scope of the technical concept of the present invention, many simple modifications can be made to the technical solution of the present invention, including the combination of various technical features in any other suitable manner. These simple modifications and combinations should also be regarded as the disclosed content of the present invention. All belong to the protection scope of the present invention.

Claims (13)

1. The lithium ion adsorption membrane is characterized by comprising a membrane framework and a lithium ion sieve loaded on the membrane framework;

wherein the specific surface area of the lithium ion adsorption film is 1-7m ² /g。

2. The lithium ion-adsorbing membrane as set forth in claim 1, wherein the specific surface area of the lithium ion-adsorbing membrane is 3.8-5m ² /g；

And/or the loading of the lithium ion sieve is 0.1-0.6g, preferably 0.45-0.5g, relative to 1g of the lithium ion adsorption membrane;

and/or the particle size of the lithium ion sieve is 1-10 μm, preferably 2-4 μm;

and/or the porosity of the lithium ion adsorption film is 60-90%, preferably 80-83%;

and/or the thickness of the lithium ion adsorption film is 100-300 mu m, preferably 120-260 mu m;

and/or the lithium ion adsorption film is distributed with a microprotrusion structure, and the diameter of the largest cross section area of the microprotrusions is 1-2 mu m;

and/or the film skeleton thickness of the lithium ion adsorption film is 40-240 μm, preferably 60-180 μm.

3. The lithium ion adsorption membrane according to claim 1 or 2, wherein the lithium ion sieve is selected from at least one of a manganese-based lithium ion sieve, a titanium-based lithium ion sieve, more preferably a manganese-based lithium ion sieve;

and/or the membrane skeleton is composed of a film-forming polymer, preferably at least one selected from the group consisting of polyacrylonitrile, polyvinylidene fluoride, polyvinyl alcohol, polyvinyl chloride, polysulfone, polyethersulfone, polyvinyl alcohol, polyimide, cellulose, and polycarbonate;

and/or the film-forming polymer has a weight average molecular weight of 40000 to 120000g/mol.

4. The lithium ion-adsorbing membrane according to claim 1 or 2, wherein the lithium ion-adsorbing membrane further comprises a support layer;

preferably, the porosity of the supporting layer is 30-40% and the thickness is 60-80 μm;

preferably, the material of the supporting layer is at least one selected from non-woven fabrics, polyethylene and polypropylene.

5. A method for preparing a lithium ion adsorption film, which is characterized by comprising the following steps: using the casting solution dispersed with the lithium ion sieve for film forming, and performing liquid drop bath to obtain the lithium ion adsorption film;

preferably, the conditions of the droplet bath include: the time is 10-100s, the particle size of the liquid drop is 1-80 μm, relative to 1m ² The consumption of droplets is 5-80g/h.

6. The method according to claim 5, wherein the concentration of the film-forming polymer in the casting solution is 5 to 15 mass%, preferably 7 to 11 mass%;

and/or the concentration of the lithium ion sieve in the casting film liquid is 5-15 mass%, preferably 7-11 mass%.

7. The method of claim 6, wherein the film-forming polymer is selected from at least one of polyacrylonitrile, polyvinylidene fluoride, polyvinyl alcohol, polyvinyl chloride, polysulfone, polyethersulfone, polyvinyl alcohol, polyimide, cellulose, and polycarbonate;

and/or the film-forming polymer has a weight average molecular weight of 40000 to 120000g/mol;

and/or, the method further comprises: film formation is carried out in the presence of a support layer;

preferably, the porosity of the supporting layer is 30-40% and the thickness is 60-80 μm;

preferably, the material of the supporting layer is at least one selected from non-woven fabrics, polyethylene and polypropylene.

8. The method according to claim 6 or 7, wherein the lithium ion sieve is selected from at least one of a manganese-based lithium ion sieve, a titanium-based lithium ion sieve, more preferably a manganese-based lithium ion sieve;

and/or the particle size of the lithium ion sieve is 1-10 μm, preferably 2-4 μm.

9. The method according to claim 6 or 7, wherein the solvent in the casting solution is selected from good solvents for film-forming polymers, preferably at least one selected from the group consisting of N, N-dimethylformamide, N-dimethylacetamide, N-methylpyrrolidone, dimethylsulfoxide, acetone, chloroform, tributyl phosphate;

and/or the film forming conditions are such that the thickness of the lithium ion adsorption film is 100 to 300 μm, preferably 110 to 250 μm.

10. The method of claim 5, wherein the conditions of the droplet bath comprise: the time is 40-60s, the particle size of the liquid drop is 5-50 μm, and the particle size is relative to 1m ² The consumption of droplets is 10-40g/h.

11. The method of claim 6, wherein after the droplet bath, the method further comprises: non-solvent induced phase separation is carried out on the materials so as to remove the solvent introduced by the casting solution;

preferably, the time for the non-solvent induced phase separation is 60-300s;

preferably, the non-solvent-induced phase separation non-solvent is selected from at least one of water, ethanol, ethylene glycol, n-butanol, isobutanol and glycerol.

12. A lithium ion-adsorbing membrane prepared by the method of any one of claims 5 to 11.

13. Use of a lithium ion-adsorbing membrane as defined in any one of claims 1 to 4 and claim 12 for lithium collection.