Double-layer lithium-ion sieve fiber material, and preparation method therefor and use thereof

Abstract

The present disclosure relates to the technical field of lithium resources. Disclosed are a double-layer lithium-ion sieve fiber material, and a preparation method therefor and the use thereof. The double-layer lithium-ion sieve fiber material comprises a core layer and a coating layer. The core layer comprises a flexible carrier and a manganese ion sieve dispersed in the flexible carrier, wherein the flexible carrier is made of a soft polyvinyl chloride and a hydrophilic polyether sulfone, and a plurality of first holes are constructed in the flexible carrier. The coating layer comprises a rigid carrier and a titanium ion sieve dispersed in the rigid carrier, wherein the rigid carrier is made of polyparaphenylene terephthamide and polyhexamethylene adipamide, and a plurality of second holes are constructed in the flexible carrier. The double-layer lithium-ion sieve fiber material provided in the present disclosure is rigid outside and soft inside, has good water pressure resistance and fracture resistance; in addition, the manganese ion sieve has a low solution loss, and excellent cycle performance and lithium-ion adsorption performance, and can be widely used for extraction of lithium from brine.

Description

A double-layer lithium ion sieve fiber material and its preparation method and application Technical Field

[0001] The present disclosure relates to the field of lithium resource technology, and in particular to a double-layer lithium ion sieve fiber material, a preparation method thereof, and applications thereof. Background Art

[0002] In the field of lithium extraction from salt lakes, adsorption methods offer excellent selectivity, even for brines with high magnesium-to-lithium ratios. Ion sieves are a common and important adsorbent for lithium extraction from salt lakes. However, ion sieves are typically powdered raw materials, resulting in poor fluidity and difficulty in recycling. This is typically addressed through granulation or film casting. The granulated ion sieve is then used to fill columns, making recycling easier. However, the adsorption performance of ion sieves after granulation and film casting is generally lower than that of powdered ion sieves.

[0003] At present, innovative research on extracting lithium from salt lakes using adsorption methods is emerging in an endless stream. It is of great significance to develop an adsorption material with strong adsorption capacity, small ion sieve dissolution loss and good cycle performance.

[0004] In view of this, the present disclosure is proposed.

[0005] Summary of the Invention

[0006] The purpose of the present disclosure is to provide a double-layer lithium ion sieve fiber material and a preparation method and application thereof.

[0007] The present disclosure is achieved as follows:

[0008] In a first aspect, the present disclosure provides a double-layer lithium ion sieve fiber material, which comprises a core layer and a coating layer from the inside to the outside;

[0009] The core layer includes a flexible carrier and a manganese ion sieve dispersed in the flexible carrier, the flexible carrier is composed of soft polyvinyl chloride and hydrophilic polyethersulfone, and a plurality of first holes are constructed on the flexible carrier;

[0010] The coating layer includes a rigid carrier and a titanium ion sieve dispersed in the rigid carrier. The rigid carrier is composed of poly(p-phenylene terephthalamide) and poly(hexamethylene adipamide). A plurality of second holes are constructed on the flexible carrier.

[0011] In an optional embodiment, the thickness ratio of the core layer to the cladding layer is 1:(1-3).

[0012] In an optional embodiment, the specific surface area of ​​the core layer is 5m 2 / g-12m 2 / g.

[0013] In an optional embodiment, the specific surface area of ​​the coating layer is 5m 2 / g-12m 2 / g.

[0014] In an optional embodiment, the mass ratio of the manganese ion sieve, the soft polyvinyl chloride and the hydrophilic polyethersulfone is (25-40): (70-100): (25-50).

[0015] In an optional embodiment, the mass ratio of the titanium ion sieve, the poly(p-phenylene terephthalamide) and the poly(hexamethylene adipamide) is (25-40):(45-80):(25-50).

[0016] In an optional embodiment, the density of the soft polyvinyl chloride is 1.2 g / cm 3 -1.3g / cm 3 , the yield strength is 15MPa~25MPa.

[0017] In an optional embodiment, the double-layer lithium ion sieve fiber material is a fiber membrane or a fiber wire.

[0018] In an optional embodiment, the diameter of the fiber line is 0.5 μm-100 μm.

[0019] In a second aspect, the present disclosure provides a method for preparing a double-layer lithium ion sieve fiber material, comprising:

[0020] The manganese ion sieve, soft polyvinyl chloride, hydrophilic polyethersulfone, core layer solvent and sodium bicarbonate are mixed to form a core layer spinning solution;

[0021] The titanium ion sieve, poly (p-phenylene terephthalamide), poly (hexamethylene adipamide), a coating layer solvent and sodium carbonate are mixed to form a coating layer spinning solution;

[0022] Spinning the core layer spinning solution and the cladding layer spinning solution to form a double-layer fiber intermediate product in which the cladding layer covers the core layer;

[0023] The double-layer fiber intermediate product is subjected to acid leaching to form pores, and then dried to obtain the double-layer lithium ion sieve fiber material.

[0024] In an optional embodiment, the mass ratio of the manganese ion sieve, the soft polyvinyl chloride, the hydrophilic polyethersulfone, the core layer solvent and the sodium bicarbonate is (25-40): (70-100): (25-50): (135-235): (15-30).

[0025] In an optional embodiment, the core layer solvent includes at least one of dimethylformamide and N-methylpyrrolidone.

[0026] In an optional embodiment, the core layer solvent comprises dimethylformamide and N-methylpyrrolidone in a mass ratio of (75-135): (60-100).

[0027] In an optional embodiment, the mass ratio of the titanium ion sieve, the poly(p-phenylene terephthalamide), the poly(hexamethylene adipamide), the coating layer solvent and the sodium carbonate is (25-40):(45-80):(25-50):(140-250):(15-30).

[0028] In an optional embodiment, the coating layer solvent includes at least one of methanesulfonic acid and m-cresol.

[0029] In an optional embodiment, the coating layer solvent comprises methanesulfonic acid and m-cresol in a mass ratio of (90-150):(50-100).

[0030] In an optional embodiment, the spinning includes dry spinning, wet spinning or electrospinning.

[0031] In an optional embodiment, the spinning is coaxial electrospinning.

[0032] In an optional embodiment, the spinning environment temperature of the coaxial electrospinning is 15° C.-25° C., the ambient humidity is less than 30%, and the spinning voltage is 15 kV-25 kV.

[0033] In an optional embodiment, during the coaxial electrospinning, the propulsion flow rate of the core layer spinning solution is 0.18 mL / h-0.25 mL / h, and the propulsion flow rate of the cladding layer spinning solution is 0.10 mL / h-0.15 mL / h.

[0034] In an optional embodiment, the acid used for pickling is hydrochloric acid.

[0035] In an optional embodiment, the acid leaching time is 0.5h-1.5h.

[0036] In an optional embodiment, the preparation method of the core layer spinning solution includes: mixing the core layer solvent with the soft polyvinyl chloride and hydrophilic polyethersulfone, heating to 70°C-85°C, stirring for 5h-7h, cooling to room temperature, then adding the sodium bicarbonate, stirring evenly, and then adding the manganese ion sieve, stirring evenly to obtain the core layer spinning solution.

[0037] In an optional embodiment, the coating layer solvent includes methanesulfonic acid and m-cresol, and the method for preparing the coating layer spinning solution includes: first mixing the methanesulfonic acid and the poly(p-phenylene terephthalamide), heating them to 70°C-85°C, and stirring them for 5h-6h to obtain a poly(p-phenylene terephthalamide) solution; then mixing the m-cresol with the poly(hexamethylene adipamide), heating them to 70°C-85°C, and stirring them for 5h-6h to obtain a poly(hexamethylene adipamide) solution; mixing the poly(p-phenylene terephthalamide) solution and the poly(hexamethylene adipamide) solution, stirring them evenly, cooling them to room temperature, and then adding the sodium carbonate, stirring them evenly, and then adding the titanium ion sieve, stirring them evenly, to obtain the coating layer spinning solution.

[0038] In a third aspect, the present disclosure provides the use of a double-layer lithium ion sieve fiber material as described in any of the aforementioned embodiments or a double-layer lithium ion sieve fiber material prepared by the preparation method of the double-layer lithium ion sieve fiber material as described in any of the aforementioned embodiments as an adsorbent in lithium extraction from salt lake brine.

[0039] In an optional embodiment, the salt lake brine includes at least one of original brine and aged brine.

[0040] The present disclosure has the following beneficial effects:

[0041] The double-layer lithium ion sieve fiber material provided by the present disclosure optimizes the formula of the core layer material and the coating layer material, and obtains a fiber material that is rigid on the outside and soft on the inside. The coating layer fiber has good rigidity, high strength, is not easy to break, plays a good supporting role, can well resist water pressure, and better maintain the structural integrity of the fiber material; the core layer fiber has good flexibility, which can further reduce the probability of the material breaking during use. The core layer material does not directly contact the brine during use, and the present disclosure improves the inward penetration and infiltration of the brine by using hydrophilic polyethersulfone to modify the core layer material, thereby improving the adsorption performance of lithium ions. The double-layer lithium ion sieve fiber material provided by the present disclosure places the manganese ion sieve, which is more easily dissolved, in the core layer of the fiber material, and the coating layer fiber material forms a protective layer for the manganese ion sieve, reducing the direct contact between the acid and the manganese ion sieve, inhibiting the corrosion of the acid on the manganese ion sieve, thereby reducing the dissolution of the manganese ion sieve and ensuring the circulation performance of the fiber material.

[0042] The preparation method of the double-layer lithium ion sieve fiber material provided by the present disclosure is prepared by a spinning process technology. The fiber material obtained by spinning has a high porosity and a large specific surface area. Then, pores are formed by an acid leaching pore-forming process. Since the present disclosure adopts sodium carbonate as the coating layer fiber pore-forming agent and sodium bicarbonate as the core layer fiber pore-forming agent, the fiber can form more pores. At the same time, the bubbles generated when the core layer fiber is pore-formed are discharged from the inside to the outside, further promoting the formation of pores. During the acid leaching process, the precipitation of carbon dioxide further increases the porosity of the fiber material, so that the lithium ion sieve exposes more adsorption sites, thereby increasing the adsorption capacity of lithium ions. The prepared double-layer lithium ion sieve fiber material can be widely used in brine for lithium extraction. DETAILED DESCRIPTION

[0043] To make the purpose, technical solutions, and advantages of the embodiments of the present disclosure more clear, the technical solutions in the embodiments of the present disclosure are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer were followed. Reagents or instruments used where the manufacturer is not specified are conventional products that can be purchased commercially.

[0044] The present disclosure provides a double-layer lithium ion sieve fiber material, which includes a core layer and a cladding layer, wherein the thickness ratio of the core layer to the cladding layer is 1:(1-3).

[0045] The core layer includes a flexible carrier and a manganese ion sieve dispersed in the flexible carrier. The flexible carrier is composed of soft polyvinyl chloride and hydrophilic polyethersulfone. A plurality of first holes are constructed on the flexible carrier. The specific surface area of ​​the core layer is 5m 2 / g-12m 2 The coating layer includes a rigid carrier and a titanium ion sieve dispersed in the rigid carrier. The rigid carrier is composed of poly(p-phenylene terephthalamide) and poly(hexamethylene adipamide). A plurality of second holes are constructed on the flexible carrier. The specific surface area of ​​the coating layer is 5m 2 / g-12m 2 / g.

[0046] Specifically, the raw materials of the core layer include the following components in parts by weight: 25-40 parts of manganese ion sieve, 70-100 parts of soft polyvinyl chloride, 25-50 parts of hydrophilic polyethersulfone, 135-235 parts of core layer solvent and 15-30 parts of sodium bicarbonate; the raw materials of the coating layer include the following components in parts by weight: 25-40 parts of titanium ion sieve, 45-80 parts of poly(p-phenylene terephthalamide), 25-50 parts of poly(hexamethylene adipamide), 140-250 parts of coating layer solvent and 15-30 parts of sodium carbonate.

[0047] Manganese-based ion sieves have a high affinity for lithium ions and exhibit excellent adsorption properties. However, during the adsorption and desorption process, particularly during the desorption phase, manganese dissolution is significant, potentially causing water pollution. Titanium-based ion sieves, on the other hand, exhibit less dissolution and are generally the least polluting type of ion sieve.

[0048] In the present disclosure, the manganese ion sieve is arranged in the core layer and the titanium ion sieve is arranged in the coating layer. Since the dissolution loss rate of the titanium ion sieve is small, it can fully contact with the brine to adsorb lithium ions, and the fiber strength of the coating layer is large and not easy to break, and can well resist water pressure, and better maintain the structural integrity of the fiber material; the manganese ion sieve is placed in the core layer, and the fiber material of the coating layer can form protection for the manganese ion sieve of the core layer, reducing the direct contact of the manganese ion sieve with the acid during desorption, inhibiting the corrosion effect of the acid on the manganese ion sieve, and reducing the dissolution loss of the manganese ion sieve. At the same time, the hydrophilicity of the core layer material is large, which can increase the inward permeability of the brine, improve the wettability of the core layer material, and increase the adsorption amount of lithium ions.

[0049] In the fiber material of the coating layer, the molecular chain of poly(p-phenylene terephthalamide) exhibits rigidity, good strength, high tensile strength, and toughness; while poly(hexamethylene adipamide) has high mechanical strength, high rigidity, and high tensile strength. The present invention utilizes poly(p-phenylene terephthalamide) and poly(hexamethylene adipamide) as the skeleton materials for the fiber coating layer. The resulting coating layer material has high mechanical strength, providing support for the material, while also providing the material with suitable flexibility, making it less prone to breakage and highly resistant to water pressure, thereby better maintaining the structural integrity of the fiber material and increasing its service life.

[0050] In the core fiber material, the density of soft polyvinyl chloride is 1.2g / cm 3 -1.3g / cm 3 The yield strength is 15MPa-25MPa. It has excellent softness and high elongation at break, making the material rigid on the outside and soft on the inside, not easy to break but with good strength. At the same time, the core material is modified by adding hydrophilic polyethersulfone to improve the hydrophilicity of the core fiber material, improving the permeability and wettability of the core fiber material, and ensuring the lithium ion adsorption effect of the core material.

[0051] Sodium carbonate is a pore-forming agent for the coating fiber material, and sodium bicarbonate is a pore-forming agent for the core fiber material. After the fiber material is spun, the fiber material is placed in an acid solution for immersion. Sodium carbonate and sodium bicarbonate will react chemically with the acid solution to produce carbon dioxide. The precipitation of carbon dioxide will cause the material to form many pores, thereby increasing the porosity of the fiber material. The core fiber material is coated with the coating fiber material. During acid immersion, the acid first contacts the coating fiber material and reacts with the sodium carbonate on it to produce carbon dioxide. After passing through the coating fiber material, the acid enters the core fiber material and reacts with the sodium bicarbonate on the core fiber to produce carbon dioxide. The reaction of sodium bicarbonate with acid is more intense than that of sodium carbonate with acid. The core fiber ensures that the core fiber material produces more bubbles through a more intense reaction. The bubbles produced in the core layer precipitate from the inside to the outside, further promoting the coating material to produce more pores. In the present disclosure, the use of sodium carbonate and sodium bicarbonate to react with acid to form pores can significantly increase the specific surface area of ​​the core layer and the coating layer, thereby having a more excellent adsorption effect.

[0052] Furthermore, the core layer comprises the following components in parts by weight: 28-38 parts of manganese ion sieve, 80-90 parts of soft polyvinyl chloride, 30-45 parts of hydrophilic polyethersulfone, 155-210 parts of core layer solvent and 20-28 parts of sodium bicarbonate; the coating layer comprises the following components in parts by weight: 28-38 parts of titanium ion sieve, 50-75 parts of poly(p-phenylene terephthalamide), 30-45 parts of poly(hexamethylene adipamide), 160-220 parts of coating layer solvent and 18-28 parts of sodium carbonate.

[0053] In certain embodiments, the weight parts of manganese ion sieve can be, for example, 28 parts, 30 parts, 32 parts, 35 parts, 36 parts or 38 parts, or any range between two of them; the weight parts of soft polyvinyl chloride can be, for example, 80 parts, 82 parts, 85 parts, 87 parts, 88 parts, 90 parts, or any range between two of them; the weight parts of hydrophilic polyether sulfone can be, for example, 30 parts, 32 parts, 35 parts, 38 parts, 40 parts or 45 parts, or any range between two of them; the weight parts of core layer solvent can be, for example, 155 parts, 165 parts, 175 parts, 185 parts, 195 parts, 200 parts, 205 parts or 210 parts, or any range between two of them; the weight parts of sodium bicarbonate can be, for example, 20 parts, 22 parts, 25 parts, 26 parts, 27 parts or 28 parts, or any range between two of them; the weight parts of titanium ion sieve can be, for example, 28 parts, 30 parts, 32 parts, 35 parts, 36 parts or 38 parts, or any range between two of them; the weight parts of poly(p-phenylene terephthalamide) can be, for example, 50 parts, 55 parts, 60 parts, 65 parts, 70 parts, 75 parts, or any range between two of them; the weight parts of poly(hexamethylene adipamide) can be, for example, 30 parts, 34 parts, 38 parts, 42 parts or 45 parts, or any range between two of them; the weight parts of coating layer solvent can be, for example, 160 parts to 220 parts, or any range between two of them; the weight parts of sodium carbonate can be, for example, 18 parts to 28 parts, or any range between two of them.

[0054] In the present disclosure, the core layer solvent only needs to be able to dissolve the components of the core layer. Similarly, the coating layer solvent only needs to be able to dissolve the components of the coating layer. There is no specific limitation on its selection. In certain typical but non-limiting embodiments of the present disclosure, the core layer solvent includes at least one of dimethylformamide and N-methylpyrrolidone. The core layer solvent includes dimethylformamide and N-methylpyrrolidone in a mass ratio of (75-135): (60-100). The core layer solvent includes dimethylformamide and N-methylpyrrolidone in a mass ratio of (85-120): (70-90). The coating layer solvent includes at least one of methanesulfonic acid and meta-cresol. The coating layer solvent includes methanesulfonic acid and meta-cresol in a mass ratio of (90-150): (50-100). The coating layer solvent includes methanesulfonic acid and meta-cresol in a mass ratio of (100-130): (60-90).

[0055] The double-layer lithium ion sieve fiber material is a fiber membrane or a fiber line. When the double-layer lithium ion sieve fiber material is a fiber line, its diameter is 0.5 μm to 100 μm, for example, nanometer level (500 to 1000 nm) or micrometer level (1 to 100 μm).

[0056] The present invention provides a preparation method of a double-layer lithium ion sieve fiber material, which comprises: preparing the components of the core layer and the coating layer of the double-layer lithium ion sieve fiber material into a core layer spinning solution and a coating layer spinning solution, placing the core layer spinning solution in a core layer storage tank and the coating layer spinning solution respectively, and spinning them to form a double-layer fiber intermediate product; acid-leaching the double-layer fiber intermediate product to form pores, and then drying it to obtain the double-layer lithium ion sieve fiber material.

[0057] Specifically, the following steps are included:

[0058] S1. Prepare the core layer spinning solution.

[0059] The core layer solvent is mixed with soft polyvinyl chloride and hydrophilic polyethersulfone, heated to 70-85°C, stirred for 5-7 hours, cooled to room temperature, and then sodium bicarbonate is added and stirred evenly, and then manganese ion sieve is added and stirred evenly to obtain the core layer spinning solution.

[0060] In the present disclosure, by first mixing soft polyvinyl chloride and hydrophilic polyethersulfone with a core layer solvent and then adding sodium bicarbonate and manganese ion sieve to mix them thoroughly, they can be evenly dispersed in the solution, and the mixing effect between the various components is more uniform.

[0061] S2. Prepare the coating layer spinning solution.

[0062] The coating layer solvent includes methanesulfonic acid and meta-cresol. The coating layer spinning solution is prepared by: first, mixing methanesulfonic acid and poly(p-phenylene terephthalamide), heating to 70°C-85°C, and stirring for 5-6 hours to obtain a poly(p-phenylene terephthalamide) solution. Then, mixing meta-cresol with poly(hexamethylene adipamide), heating to 70°C-85°C, and stirring for 5-6 hours to obtain a poly(hexamethylene adipamide) solution. Then, mixing the poly(p-phenylene terephthalamide) solution and the poly(hexamethylene adipamide) solution, stirring uniformly, cooling to room temperature, adding sodium carbonate, stirring uniformly, and then adding a titanium ion sieve and stirring uniformly to obtain a coating layer spinning solution.

[0063] In the present disclosure, poly(p-phenylene terephthalamide) and poly(hexamethylene adipamide) are prepared into solutions using solvents respectively, which makes it easier to mix the two. Then, sodium carbonate and titanium ion sieve are added to achieve uniform dispersion in the solution, and the mixing effect between the various components is more uniform.

[0064] S3. Spinning.

[0065] The present disclosure utilizes spinning technology to prepare the double-layer material, and the spinning methods include but are not limited to dry spinning, wet spinning or electrospinning.

[0066] This disclosure provides a typical but non-limiting example in which coaxial electrospinning is used for spinning. Specifically, the spinning environment temperature for coaxial electrospinning is 15°C-25°C, the ambient humidity is less than 30%, and the spinning voltage is 15kV-25kV. During coaxial electrospinning, the propulsion flow rate of the core layer spinning solution is 0.18mL / h-0.25mL / h, and the propulsion flow rate of the cladding layer spinning solution is 0.28mL / h-0.3mL / h.

[0067] The spinning environment temperature can be, for example, any one of 15°C, 18°C, 20°C, 22°C, or 25°C, or a range between any two thereof. The spinning voltage can be, for example, any one of 15kV, 18kV, 20kV, 22kV, or 25kV, or a range between any two thereof. During coaxial electrospinning, the propulsion flow rate of the core layer spinning solution can be, for example, any one of 0.18mL / h, 0.20mL / h, 0.22mL / h, 0.24mL / h, or 0.25mL / h, or a range between any two thereof. The propulsion flow rate of the coating layer spinning solution can be any one of 0.28mL / h, 0.29mL / h, or 0.3mL / h, or a range between any two thereof.

[0068] It should be understood that when other spinning methods are selected, the specific process parameters can be adjusted according to actual conditions.

[0069] S4. Acid leaching.

[0070] The double-layer fiber intermediate product is immersed in an acid solution, wherein the acid used for the acid immersion is hydrochloric acid, and the acid immersion time is 0.5h-1.5h.

[0071] In the present disclosure, acid solution is used to react with the porogen (sodium carbonate) of the coating layer and the porogen (sodium bicarbonate) of the core layer to generate carbon dioxide. The precipitation of carbon dioxide will form many pores in the material, thereby increasing the porosity of the fiber material.

[0072] S5. Drying.

[0073] The double-layer fiber material after acid leaching is dried to obtain the double-layer fiber material. There are various drying methods disclosed in the present invention, such as ventilation drying, oven drying, etc., as long as the double-layer fiber material can be dried.

[0074] The double-layer lithium ion sieve fiber material prepared by the above method can be widely used as an adsorbent in lithium extraction from salt lake brine. The salt lake brine includes at least one of original brine and aged brine.

[0075] The features and performance of the present disclosure are further described in detail below with reference to the embodiments.

[0076] Example 1

[0077] This embodiment provides a double-layer lithium ion sieve fiber material, including a core layer and a coating layer, the core layer including the following components in parts by weight: 25 parts of manganese ion sieve, 70 parts of soft polyvinyl chloride, 25 parts of hydrophilic polyethersulfone, 75 parts of dimethylformamide, 60 parts of N-methylpyrrolidone, and 15 parts of sodium bicarbonate; the coating layer includes the following components in parts by weight: 25 parts of titanium ion sieve, 45 parts of poly(p-phenylene terephthalamide), 25 parts of poly(hexamethylene adipamide), 90 parts of methanesulfonic acid, 50 parts of meta-cresol, and 15 parts of sodium carbonate.

[0078] The preparation method comprises the following steps:

[0079] (1) Preparation of core layer spinning solution: Mix the formulated amounts of dimethylformamide and N-methylpyrrolidone, then add the formulated amounts of soft polyvinyl chloride and hydrophilic polyethersulfone, heat to 80°C, stir for 6 hours, cool to room temperature, then add the formulated amount of sodium bicarbonate, stir evenly, then add the formulated amount of manganese ion sieve, stir evenly to obtain the core layer spinning solution.

[0080] (2) Preparation of coating layer spinning solution: take a formulated amount of methanesulfonic acid, add a formulated amount of poly(p-phenylene terephthalamide), heat to 80°C, and stir for 5.5 hours to obtain a poly(p-phenylene terephthalamide) solution; then take a formulated amount of m-cresol, add a formulated amount of poly(hexamethylene adipamide), heat to 80°C, and stir for 5.5 hours to obtain a poly(hexamethylene adipamide) solution; mix the poly(p-phenylene terephthalamide) solution and the poly(hexamethylene adipamide) solution, stir evenly, cool to room temperature, then add a formulated amount of sodium carbonate, stir evenly, and then add a formulated amount of titanium ion sieve, stir evenly, to obtain a coating layer spinning solution.

[0081] (3) Coaxial electrospinning: the core layer spinning solution is placed in a core layer spinning solution storage tank, the cladding layer spinning solution is placed in a cladding layer spinning solution storage tank, the core layer spinning solution storage tank is connected to the inner tube of the nozzle, the cladding layer spinning solution storage tank is connected to the outer tube of the nozzle, the coaxial electrospinning equipment is started, the core layer spinning solution and the cladding layer spinning solution are ejected from the nozzle at the same time, and a double-layer fiber material is formed on the receiving equipment, and the material is in a film shape; during the coaxial electrospinning process, the ambient temperature is set to 20±5℃, the ambient humidity is less than 30%, the spinning voltage is 20kV, the cladding layer melt spinning solution propulsion flow rate is 0.29mL / h, and the core layer spinning solution propulsion flow rate is 0.12mL / h.

[0082] (4) Acid leaching: The obtained double-layer fiber material is placed in a hydrochloric acid solution and soaked for 1 hour.

[0083] (5) Drying: Drying the double-layer fiber material after acid immersion.

[0084] Example 2

[0085] This embodiment is basically the same as embodiment 1, the only difference being the formula of the double-layer lithium ion sieve fiber material, which is as follows:

[0086] A double-layer lithium ion sieve fiber material includes a core layer and a coating layer. The core layer includes the following components in parts by weight: 40 parts of manganese ion sieve, 100 parts of soft polyvinyl chloride, 50 parts of hydrophilic polyethersulfone, 135 parts of dimethylformamide, 100 parts of N-methylpyrrolidone, and 30 parts of sodium bicarbonate; the coating layer includes the following components in parts by weight: 40 parts of titanium ion sieve, 80 parts of poly(p-phenylene terephthalamide), 50 parts of poly(hexamethylene adipamide), 150 parts of methanesulfonic acid, 100 parts of meta-cresol, and 30 parts of sodium carbonate.

[0087] Example 3

[0088] This embodiment is basically the same as embodiment 1, the only difference being the formula of the double-layer lithium ion sieve fiber material, which is as follows:

[0089] A double-layer lithium ion sieve fiber material comprises a core layer and a coating layer. The core layer comprises the following components in parts by weight: 28 parts of manganese ion sieve, 80 parts of soft polyvinyl chloride, 30 parts of hydrophilic polyethersulfone, 85 parts of dimethylformamide, 70 parts of N-methylpyrrolidone, and 20 parts of sodium bicarbonate; the coating layer comprises the following components in parts by weight: 28 parts of titanium ion sieve, 50 parts of poly(p-phenylene terephthalamide), 30 parts of poly(hexamethylene adipamide), 100 parts of methanesulfonic acid, 60 parts of meta-cresol, and 18 parts of sodium carbonate.

[0090] Example 4

[0091] This embodiment is basically the same as embodiment 1, the only difference being the formula of the double-layer lithium ion sieve fiber material, which is as follows:

[0092] A double-layer lithium ion sieve fiber material comprises a core layer and a coating layer. The core layer comprises the following components in parts by weight: 38 parts of manganese ion sieve, 90 parts of soft polyvinyl chloride, 45 parts of hydrophilic polyethersulfone, 120 parts of dimethylformamide, 90 parts of N-methylpyrrolidone, and 28 parts of sodium bicarbonate; the coating layer comprises the following components in parts by weight: 38 parts of titanium ion sieve, 75 parts of poly(p-phenylene terephthalamide), 45 parts of poly(hexamethylene adipamide), 130 parts of methanesulfonic acid, 90 parts of meta-cresol, and 28 parts of sodium carbonate.

[0093] Example 5

[0094] This embodiment is basically the same as embodiment 1, the only difference being the formula of the double-layer lithium ion sieve fiber material, which is as follows:

[0095] A double-layer lithium ion sieve fiber material comprises a core layer and a coating layer. The core layer comprises the following components in parts by weight: 30 parts of manganese ion sieve, 85 parts of soft polyvinyl chloride, 35 parts of hydrophilic polyethersulfone, 110 parts of dimethylformamide, 80 parts of N-methylpyrrolidone, and 27 parts of sodium bicarbonate; the coating layer comprises the following components in parts by weight: 30 parts of titanium ion sieve, 65 parts of poly(p-phenylene terephthalamide), 35 parts of poly(hexamethylene adipamide), 120 parts of methanesulfonic acid, 80 parts of meta-cresol, and 25 parts of sodium carbonate.

[0096] Example 6

[0097] This embodiment is basically the same as embodiment 1, except that the preparation method is different, as follows:

[0098] (1) Preparation of core layer spinning solution: Mix the formulated amounts of dimethylformamide and N-methylpyrrolidone, then add the formulated amounts of soft polyvinyl chloride and hydrophilic polyethersulfone, heat to 70°C, stir for 7 hours, cool to room temperature, then add the formulated amount of sodium bicarbonate, stir evenly, then add the formulated amount of manganese ion sieve, stir evenly to obtain the core layer spinning solution.

[0099] (2) Preparation of coating layer spinning solution: take a formulated amount of methanesulfonic acid, add a formulated amount of poly(p-phenylene terephthalamide), heat to 70°C, and stir for 6 hours to obtain a poly(p-phenylene terephthalamide) solution; then take a formulated amount of m-cresol, add a formulated amount of poly(hexamethylene adipamide), heat to 70°C, and stir for 6 hours to obtain a poly(hexamethylene adipamide) solution; mix the poly(p-phenylene terephthalamide) solution and the poly(hexamethylene adipamide) solution, stir evenly, cool to room temperature, then add a formulated amount of sodium carbonate, stir evenly, and then add a formulated amount of titanium ion sieve, stir evenly, to obtain a coating layer spinning solution.

[0100] (3) Coaxial electrospinning: the core layer spinning solution is placed in a core layer spinning solution storage tank, the cladding layer spinning solution is placed in a cladding layer spinning solution storage tank, the core layer spinning solution storage tank is connected to the inner tube of the nozzle, the cladding layer spinning solution storage tank is connected to the outer tube of the nozzle, the coaxial electrospinning equipment is started, the core layer spinning solution and the cladding layer spinning solution are ejected from the nozzle at the same time, and a double-layer fiber material is formed on the receiving equipment, and the material is in a film shape; during the coaxial electrospinning process, the ambient temperature is set to 20±5℃, the ambient humidity is less than 30%, the spinning voltage is 15kV, the cladding layer melt spinning solution propulsion flow rate is 0.28mL / h, and the core layer spinning solution propulsion flow rate is 0.18mL / h.

[0101] (4) Acid leaching: The obtained double-layer fiber material is placed in a hydrochloric acid solution and soaked for 1 hour.

[0102] (5) Drying: Drying the double-layer fiber material after acid immersion.

[0103] Comparative Example 1

[0104] Comparative Example 1 differs from Example 1 in that the core layer spinning solution and the cladding layer spinning solution of Example 1 are blended to form a blended solution, which is produced using a conventional electrospinning process, rather than coaxial electrospinning. During the electrospinning process, the ambient temperature was set at 20±5°C, the ambient humidity was less than 30%, the spinning voltage was 20 kV, and the spinning solution propulsion flow rate was 0.25 mL / h.

[0105] The acid leaching and drying processes after electrospinning are the same as those in Example 1.

[0106] Comparative Example 2

[0107] The difference between Comparative Example 2 and Example 1 is that the manganese ion sieve of the core layer fiber is replaced by a titanium ion sieve, and the titanium ion sieve of the cladding layer fiber is replaced by a manganese ion sieve.

[0108] Comparative Example 3

[0109] The difference between Comparative Example 3 and Example 1 is that the core layer spinning solution of Example 1 is used as the coating layer spinning solution, and the coating layer spinning solution is used as the core layer spinning solution, but the ion sieve of the core layer spinning solution is still a manganese ion sieve, and the ion sieve of the coating layer spinning solution is still a titanium ion sieve. The details are as follows:

[0110] A double-layer lithium ion sieve fiber material comprises a core layer and a coating layer, wherein the core layer comprises the following components in parts by weight: 25 parts of manganese ion sieve, 45 parts of poly(p-phenylene terephthalamide), 25 parts of poly(hexamethylene adipamide), 90 parts of methanesulfonic acid, 50 parts of meta-cresol, and 15 parts of sodium carbonate; and the coating layer comprises the following components in parts by weight: 25 parts of titanium ion sieve, 70 parts of soft polyvinyl chloride, 25 parts of hydrophilic polyethersulfone, 75 parts of dimethylformamide, 60 parts of N-methylpyrrolidone, and 15 parts of sodium bicarbonate.

[0111] The fiber material obtained in Comparative Example 3 is soft on the outside and hard on the inside, and the coating layer is more hydrophilic.

[0112] Comparative Example 4

[0113] Comparative Example 4 differs from Example 1 in that: in the core layer material, the amount of soft polyvinyl chloride is adjusted to 95 parts, and the hydrophilic polyethersulfone is omitted. In the cladding layer material, the amount of poly(p-phenylene terephthalamide) is adjusted to 70 parts, and poly(hexamethylene adipamide) is omitted. The amount of methanesulfonic acid is adjusted to 140 parts, and m-cresol is omitted.

[0114] Comparative Example 5

[0115] Comparative Example 5 differs from Example 1 in that: in the core layer material, the amount of hydrophilic polyethersulfone is adjusted to 95 parts, and the soft polyvinyl chloride is omitted. In the cladding layer material, the amount of polyhexamethylene adipamide is adjusted to 70 parts, and poly(p-phenylene terephthalamide) is omitted. The amount of m-cresol is adjusted to 140 parts, and methanesulfonic acid is omitted.

[0116] Comparative Example 6

[0117] The difference between Comparative Example 6 and Example 1 is that in the core layer material, the pore-forming agent is adjusted to sodium carbonate, which is the same as the pore-forming agent of the coating layer material.

[0118] Experimental Example 1: Adsorption capacity detection

[0119] 100 g of the fiber material obtained in Examples 1-6 and Comparative Examples 1-6 were taken respectively to carry out lithium ion adsorption experiments, and 100 g of the fiber material was placed in the experimental brine to extract lithium from the brine. After soaking for 5 hours, the fiber material after adsorbing lithium ions was soaked in 0.4 mol / L hydrochloric acid solution for desorption. After desorption was completed, the fiber material was subjected to the next round of adsorption experiment, and each group of materials repeated 3 rounds of adsorption experiments. The lithium content in the water was determined by inductively coupled plasma atomic emission spectrometry (ICP-OES). The composition of the experimental brine is shown in Table 1 below. The adsorption capacity of the ion sieve fiber material for lithium ions was calculated, and the results are shown in Table 2 below.

[0120] Table 1. Composition of brine used in the experiment

[0121] Table 2. Adsorption capacity result record

[0122] From the records in Table 2, it can be seen that the double-layer lithium ion sieve fiber materials of Examples 1-6 have a large adsorption capacity for lithium ions and good cycle performance, which shows that the dissolution loss of the ion sieve in the material is small during the adsorption and desorption process.

[0123] The fiber material obtained in Comparative Example 1 is not a double-layer material. The manganese ion sieve is not protected by the coating layer of fibers, and the hydrophilic fiber material is not placed in the core layer. This results in a large dissolution loss of the manganese ion sieve, thereby reducing the adsorption cycle performance. In addition, the high molecular weight polymer used in the formula and the two ion sieves may also affect the uniform distribution of the ion sieve or block the adsorption sites of the ion sieve, resulting in a decrease in adsorption energy.

[0124] In Comparative Example 2, the manganese ion sieve is placed in the fiber material coating layer, and the titanium ion sieve is placed in the fiber material core layer. The manganese ion sieve in the coating layer has a large dissolution loss, resulting in poor adsorption cycle performance.

[0125] In comparative example 3, the core layer spinning solution of Example 1 is used as the coating layer spinning solution, and the coating layer spinning solution is used as the core layer spinning solution. The fiber material coating layer obtained in comparative example 3 is more hydrophilic, which will increase the dissolution loss of the ion sieve and lead to a decrease in the adsorption cycle performance.

[0126] In Comparative Example 4, hydrophilic polyethersulfone is omitted in the core layer material, and polyhexamethylene adipamide and m-cresol are omitted in the coating layer material. At this time, the lack of modification of the core layer by hydrophilic polyethersulfone will significantly reduce the hydrophilicity, permeability and wettability of the fiber material. At the same time, since polyhexamethylene adipamide and poly(p-phenylene terephthalamide) can both provide strength for the skeleton material, the combination of the two is more effective. Omitting polyhexamethylene adipamide will lead to a decrease in the strength of the skeleton material. When the hydrophilicity and strength are affected, it will also affect the distribution of lithium ions in the material, resulting in a decrease in adsorption amount and a decrease in cycle performance.

[0127] Comparative Example 5 has a stronger hydrophilicity, which is beneficial to the wetting of the fiber membrane in water, thereby improving the adsorption. However, due to the increased water solubility, the adsorption cycle stability is poor.

[0128] In the fiber material of Comparative Example 6, the pore-forming agent of the core layer and the coating layer fiber materials is sodium carbonate. The speed and ability of the core layer fiber to generate bubbles during pore formation are weaker than those in Example 1, which will affect the pore formation of the fiber material, resulting in a decrease in adsorption capacity and adsorption cycle performance.

[0129] Experimental Example 2: Elongation at break test

[0130] At room temperature, the fiber materials obtained from Examples 1-6 and Comparative Examples 1-6 were subjected to elongation at break tests using an FL-8610A elongation testing machine. The elongation at break test method was performed according to the instrument's instruction manual. The results are shown in Table 3 below.

[0131] Table 3. Elongation at break test result record

[0132] As can be seen from Table 3, the double-layer lithium ion sieve fiber materials obtained in Examples 1-6 all have a large elongation at break, which shows that the fiber material has a large strength and is not prone to breakage, and is suitable for long-term use in brine. The fiber material of Comparative Example 1 is not a double-layer material, but a single-layer fiber formed by blending all materials. Its elongation at break is lower than that of the embodiment, and it is more prone to breakage. Comparative Example 3 uses the core layer spinning solution of Example 1 as the coating layer spinning solution, and the coating layer spinning solution as the core layer spinning solution, and obtains a fiber that is soft on the outside and hard on the inside. Its mechanical properties are weaker than those of Example 1 and it is easier to break. The composition of the core layer and the coating layer of the fiber materials of Comparative Examples 4 and 5 were adjusted, resulting in a decrease in elongation at break. The formation of pores in Comparative Example 6 is poor, resulting in its elongation at break being slightly lower than that of Example 1.

[0133] In summary, the double-layer lithium ion sieve fiber material provided by the present invention optimizes the formula of the core layer material and the coating layer material, and obtains a fiber material that is rigid on the outside and soft on the inside. The coating layer fiber has good rigidity, high strength, and is not easy to break, playing a good supporting role, and can resist water pressure well, and better maintain the structural integrity of the fiber material; the core layer fiber has good flexibility, which can further reduce the probability of the material breaking during use. The core layer material does not directly contact the brine during use, and the present invention modifies the core layer material by using hydrophilic polyethersulfone, thereby improving the inward penetration and infiltration of brine, thereby improving the adsorption performance of lithium ions.

[0134] The double-layer lithium ion sieve fiber material provided by the present invention places the manganese ion sieve, which is more easily dissolved, in the core layer of the fiber material, and the coating layer fiber material forms a protective layer for the manganese ion sieve, reducing the direct contact between the acid and the manganese ion sieve, inhibiting the corrosion of the acid on the manganese ion sieve, thereby reducing the dissolution of the manganese ion sieve and ensuring the circulation performance of the fiber material.

[0135] The double-layer lithium ion sieve fiber material provided by the present invention uses sodium carbonate as the coating layer fiber pore-forming agent and sodium bicarbonate as the core layer fiber pore-forming agent, so that the fiber can form more pores. At the same time, the bubbles generated when the core layer fiber is pore-formed are discharged from the inside to the outside, further promoting the formation of pores.

[0136] The preparation method of the double-layer lithium ion sieve fiber material provided in the present disclosure adopts a spinning process technology. The fiber material obtained by spinning has high porosity and large specific surface area. Pores are then formed by an acid leaching pore-forming process. During the acid leaching process, the precipitation of carbon dioxide further increases the porosity of the fiber material, so that the lithium ion sieve exposes more adsorption sites, thereby increasing the adsorption amount of lithium ions.

[0137] The disclosed method for preparing a double-layer lithium ion sieve fiber material can produce a fiber material in the form of a fiber membrane or fiber yarn. The specific form can be determined based on actual needs. Membrane-shaped fibers can be used directly for lithium extraction; linear fibers can be first filled into a column before lithium extraction. Alternatively, the linear fibers can be spun to form larger diameter fiber yarns, which can be assembled into fiber bundles for direct lithium extraction in brine.

[0138] The above describes in detail the optional embodiments of the present disclosure, but the present disclosure is not limited thereto. Within the technical concept of the present disclosure, various simple variations of the technical solution of the present disclosure can be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as the contents disclosed by the present disclosure and fall within the scope of protection of the present disclosure. Industrial Applicability

[0139] The double-layer lithium ion sieve fiber material provided by the present disclosure optimizes the formula of the core layer material and the coating layer material, and obtains a fiber material that is rigid on the outside and soft on the inside. The coating layer fiber has good rigidity, high strength, is not easy to break, plays a good supporting role, can well resist water pressure, and better maintain the structural integrity of the fiber material; the core layer fiber has good flexibility, which can further reduce the probability of the material breaking during use. The core layer material does not directly contact the brine during use, and the present disclosure improves the inward penetration and infiltration of the brine by using hydrophilic polyethersulfone to modify the core layer material, thereby improving the adsorption performance of lithium ions. The double-layer lithium ion sieve fiber material provided by the present disclosure places the manganese ion sieve, which is more easily dissolved, in the core layer of the fiber material, and the coating layer fiber material forms a protective layer for the manganese ion sieve, reducing the direct contact between the acid and the manganese ion sieve, inhibiting the corrosion of the acid on the manganese ion sieve, thereby reducing the dissolution of the manganese ion sieve and ensuring the circulation performance of the fiber material. The preparation method of the double-layer lithium ion sieve fiber material provided by the present disclosure is prepared by a spinning process technology. The fiber material obtained by spinning has a high porosity and a large specific surface area. Then, pores are formed by an acid leaching pore-forming process. Since the present disclosure adopts sodium carbonate as the coating layer fiber pore-forming agent and sodium bicarbonate as the core layer fiber pore-forming agent, the fiber can form more pores. At the same time, the bubbles generated when the core layer fiber is pore-formed are discharged from the inside to the outside, further promoting the formation of pores. During the acid leaching process, the precipitation of carbon dioxide further increases the porosity of the fiber material, so that the lithium ion sieve exposes more adsorption sites, thereby increasing the adsorption capacity of lithium ions. The prepared double-layer lithium ion sieve fiber material can be widely used in brine for lithium extraction.

Claims

1. A double-layer lithium-ion sieve fiber material, characterized in that, It successively includes a core layer and a coating layer from the inside to the outside; The core layer includes a flexible carrier and manganese ion sieves dispersed in the flexible carrier. The flexible carrier is composed of soft polyvinyl chloride and hydrophilic polyethersulfone, and a plurality of first holes are constructed on the flexible carrier; The coating layer includes a rigid carrier and titanium ion sieves dispersed in the rigid carrier. The rigid carrier is composed of poly(p-phenyleneterephthalamide) and poly(hexamethylene adipamide), and a plurality of second holes are constructed on the flexible carrier.

2. The double-layer lithium ion sieve fiber material according to claim 1, wherein, The thickness ratio of the core layer to the coating layer is 1:(1 - 3).

3. The double-layer lithium ion sieve fiber material according to any one of claims 1-2, characterized in that The specific surface area of the core layer is 5 m 2 / g - 12 m 2 / g.

4. The double-layer lithium-ion sieve fiber material according to any one of claims 1-3, characterized in that The specific surface area of the coating layer is 5 m 2 / g - 12 m 2 / g.

5. The double-layer lithium ion sieve fiber material according to any one of claims 1-4, characterized in that, The mass ratio of the manganese ion sieves, the soft polyvinyl chloride and the hydrophilic polyethersulfone is (25 - 40):(70 - 100):(25 - 50).

6. The double-layer lithium ion sieve fiber material according to any one of claims 1-5, characterized in that The mass ratio of the titanium ion sieves, the poly(p-phenyleneterephthalamide) and the poly(hexamethylene adipamide) is (25 - 40):(45 - 80):(25 - 50).

7. The double-layer lithium ion sieve fiber material according to any one of claims 1-6, characterized in that The density of the soft polyvinyl chloride is 1.2 g / cm 3 -1.3 g / cm 3 , and the yield strength is 15 MPa - 25 MPa.

8. The double-layer lithium ion sieve fiber material according to any one of claims 1-7, characterized in that The double-layer lithium ion sieve fiber material is a fiber membrane or a fiber thread.

9. The double-layer lithium ion sieve fiber material according to claim 8, wherein, The diameter of the fiber thread is 0.5μm - 100μm.

10. A preparation method of a double-layer lithium ion sieve fiber material, characterized in that, It includes: Mixing manganese ion sieves, soft polyvinyl chloride, hydrophilic polyethersulfone, a core layer solvent and sodium bicarbonate to form a core layer spinning solution; Mixing titanium ion sieves, poly(p-phenyleneterephthalamide), poly(hexamethylene adipamide), a coating layer solvent and sodium carbonate to form a coating layer spinning solution; Spinning the core layer spinning solution and the coating layer spinning solution to form a double-layer fiber intermediate product with the coating layer covering the core layer; Subjecting the double-layer fiber intermediate product to acid leaching for pore formation, and then drying to obtain the double-layer lithium ion sieve fiber material.

11. The preparation method of the double-layer lithium ion sieve fiber material according to claim 10, characterized in that, The mass ratio of the manganese ion sieves, the soft polyvinyl chloride, the hydrophilic polyethersulfone, the core layer solvent and the sodium bicarbonate is (25 - 40):(70 - 100):(25 - 50):(135 - 235):(15 - 30).

12. The preparation method of the double-layer lithium ion sieve fiber material according to any one of claims 10-11, characterized in that, The core layer solvent includes at least one of dimethylformamide and N-methylpyrrolidone.

13. The preparation method of the double-layer lithium ion sieve fiber material according to claim 12, characterized in that, The core layer solvent includes dimethylformamide and N-methylpyrrolidone with a mass ratio of (75 - 135):(60 - 100).

14. The preparation method of the double-layer lithium ion sieve fiber material according to any one of claims 10-12, characterized in that, The mass ratio of the titanium ion sieves, the poly(p-phenyleneterephthalamide), the poly(hexamethylene adipamide), the coating layer solvent and the sodium carbonate is (25 - 40):(45 - 80):(25 - 50):(140 - 250):(15 - 30).

15. The preparation method of the double-layer lithium ion sieve fiber material according to any one of claims 10-13, characterized in that, The coating layer solvent includes at least one of methanesulfonic acid and m-cresol.

16. The preparation method of the double-layer lithium ion sieve fiber material according to claim 15, characterized in that, The coating layer solvent includes methanesulfonic acid and m-cresol with a mass ratio of (90 - 150):(50 - 100).

17. The preparation method of the double-layer lithium ion sieve fiber material according to any one of claims 10-15, characterized in that, The spinning includes dry spinning, wet spinning or electrospinning.

18. The preparation method of the double-layer lithium ion sieve fiber material according to any one of claims 10-16, characterized in that, The spinning is coaxial electrospinning.

19. The preparation method of the double-layer lithium ion sieve fiber material according to claim 18, characterized in that, For the coaxial electrospinning, the spinning environment temperature is 15℃ - 25℃, the environmental humidity is less than 30%, and the spinning voltage is 15kv - 25kv.

20. The preparation method of the double-layer lithium ion sieve fiber material according to any one of claims 18-19, characterized in that, During the coaxial electrospinning, the advancing flow rate of the core layer spinning solution is 0.18 - 0.25mL / h, and the advancing flow rate of the coating layer spinning solution is 0.10mL / h - 0.15mL / h.

21. The preparation method of the double-layer lithium ion sieve fiber material according to any one of claims 10-20, characterized in that, The acid used for the acid leaching is hydrochloric acid.

22. The preparation method of the double-layer lithium ion sieve fiber material according to any one of claims 10-21, characterized in that, The time of the acid leaching is 0.5h - 1.5h.

23. The preparation method of the double-layer lithium ion sieve fiber material according to any one of claims 10-22, characterized in that, The preparation method of the core layer spinning solution comprises: mixing the core layer solvent with the soft polyvinyl chloride and the hydrophilic polyethersulfone, heating to 70°C - 85°C, stirring for 5h - 7h, cooling to room temperature, then adding the sodium bicarbonate, stirring evenly, and then adding the manganese ion sieve, stirring evenly to obtain the core layer spinning solution.

24. The preparation method of the double-layer lithium ion sieve fiber material according to any one of claims 10-23, characterized in that, The coating layer solvent comprises methanesulfonic acid and m-cresol. The preparation method of the coating layer spinning solution comprises: first mixing the methanesulfonic acid and the poly(p-phenyleneterephthalamide), heating to 70°C - 85°C, stirring for 5h - 6h to obtain a poly(p-phenyleneterephthalamide) solution; then mixing the m-cresol with the poly(hexamethylene adipamide), heating to 70°C - 85°C, stirring for 5h - 6h to obtain a poly(hexamethylene adipamide) solution; mixing the poly(p-phenyleneterephthalamide) solution and the poly(hexamethylene adipamide) solution, stirring evenly, cooling to room temperature, then adding the sodium carbonate, stirring evenly, and then adding the titanium ion sieve, stirring evenly to obtain the coating layer spinning solution.

25. Use of the double-layer lithium ion sieve fiber material as claimed in any one of claims 1 - 9 or the double-layer lithium ion sieve fiber material prepared by the preparation method of the double-layer lithium ion sieve fiber material as claimed in any one of claims 10 - 24 as an adsorbent in the extraction of lithium from salt lake brine.

26. The application according to claim 25, wherein The salt lake brine comprises at least one of raw brine and old brine.

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