A lithium ion separation membrane based on intercalated large-size graphene oxide and a preparation method and application thereof

Abstract

The application discloses an intercalation large-size graphene oxide-based lithium ion separation membrane and a preparation method and application thereof, and belongs to the technical field of membrane filtration and ion separation. The preparation method comprises the following steps: blending an oxidized graphene solution with an intercalation agent, standing to obtain a mixed solution, depositing the mixed solution on a base film, and drying to prepare a salt water lithium extraction membrane. The application also discloses the application of the graphene oxide-based salt water lithium extraction membrane prepared by the preparation method in the extraction of lithium ions from salt water. The interlayer spacing of the graphene oxide membrane can be adjusted by a specific intercalation agent to realize selective filtration of specific ions. With the increase of the size of the graphene oxide, the mechanical properties and film-forming properties of the large-size graphene oxide are improved, the stability of the membrane is improved, the membrane can be kept stable at a relatively thin thickness, and therefore, the lithium ions in salt lakes or brine can be stably extracted with high selectivity and high flux.

Description

Technical Field

[0001] This invention belongs to the field of membrane filtration and ion separation technology, specifically relating to a lithium-ion separation membrane based on intercalated large-size graphene oxide, its preparation method, and its application. Background Technology

[0002] Lithium metal, due to its light weight and high energy density, is widely recognized as an "energy metal driving global progress." With the widespread application of lithium in the manufacture of power batteries for new energy vehicles, the demand for lithium mining has increased significantly in recent years. Lithium exists partly in the form of solid lithium ore such as spodumene, and partly in the form of lithium from salt lakes. Due to the terrain and limited reserves of solid lithium ore, it can no longer meet the industry's ever-growing demand. Therefore, exploring the extraction of lithium from salt lakes with abundant reserves is an effective and necessary solution to address the lithium resource shortage.

[0003] Currently, commonly used methods for lithium extraction from salt lakes include solution extraction, adsorption, and membrane separation. However, extraction methods are complex and costly, while adsorption methods use resin-based lithium adsorbents, resulting in high costs, low adsorption rates, and low adsorbent recovery efficiency. In contrast, membrane separation methods are simple, low-cost, and efficient. Membrane separation primarily utilizes nanofiltration membranes to separate magnesium and lithium ions in salt lakes. Due to steric hindrance and the Donnan effect, nanofiltration membranes allow monovalent ions to pass through while retaining divalent or polyvalent ions. However, nanofiltration membranes suffer from low flux, low retention rates, and poor selectivity among monovalent ions, and often require combination with other adsorbents, leading to high costs. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the present invention aims to provide a lithium-ion separation membrane based on intercalated large-size graphene oxide, its preparation method, and its application, in order to solve the problems of low lithium extraction flux, low rejection rate, and poor membrane performance of membrane methods. The present invention utilizes the high mechanical strength and selective ion transport channels between the layers of large-size graphene, combined with the adjustment of the interlayer spacing by an intercalating agent, to ultimately achieve efficient lithium extraction from brine.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] This invention provides a method for preparing a lithium-ion separation membrane based on intercalated large-size graphene oxide, comprising the following steps:

[0007] A large-size graphene oxide solution was obtained by mixing large-size graphene oxide sheets with an average size of 5–150 μm with deionized water.

[0008] A large-size graphene oxide solution was mixed with an intercalating agent, and the mixture was allowed to stand to obtain a mixed solution. The mixed solution was then deposited on a base membrane and dried to prepare a lithium-ion separation membrane.

[0009] In the specific implementation process, the concentration of the large-size graphene oxide solution is 0.05-5 mg / ml; the concentration ratio of the large-size graphene oxide solution to the intercalating agent is 1:(0.1-50); and the thickness of the large-size graphene oxide sheet is 0.34-10 nm.

[0010] In specific implementation, the intercalating agent is one or a combination of several of the following: chloride salts and hydroxides containing metal ions, tetramethylammonium chloride, tetrabutylammonium chloride, dodecyltrimethylammonium chloride, tetradecyltrimethylammonium chloride, 12-crown-4 ether, 15-crown-5 ether, and 18-crown-6 ether.

[0011] In specific implementation, the intercalating agent is located between or on the surface of large-sized graphene oxide sheets inside the lithium-ion separation membrane.

[0012] In the specific implementation process, the mixed solution is deposited on the base membrane by any one of the following methods: scraping, spin coating, or vacuum filtration.

[0013] In specific implementation, the base membrane is any one of polyethersulfone membrane, nylon membrane, mixed cellulose membrane, and anodic aluminum oxide membrane.

[0014] In the specific implementation process, the drying temperature is 20℃~120℃, the drying humidity is 10%~80%, and the drying time is 30min~2d.

[0015] The present invention provides a lithium-ion separation membrane prepared according to any one of the methods for preparing lithium-ion separation membranes based on intercalated large-size graphene oxide.

[0016] In specific implementation, the interlayer spacing of the lithium-ion separation membrane is 0.4–5 nm; the thickness of the lithium-ion separation membrane is 20 nm–50 μm.

[0017] This invention provides a lithium-ion separation membrane based on intercalated large-size graphene oxide, which is applied to the selective filtration and separation of lithium ions in salt lake water or salt solution systems.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] This invention provides a method for preparing a lithium-ion separation membrane based on intercalated large-size graphene oxide. Large-size graphene oxide sheets, as an ideal two-dimensional material, can form regular nanoscale ion transport channels when stacked together. The large-size graphene oxide membrane fundamentally improves upon the problems of low lithium selectivity, small throughput, and membrane stability encountered by traditional polymer membranes during lithium extraction. By adjusting the interlayer spacing of the graphene oxide membrane with a specific intercalating agent, selective filtration of specific ions (such as lithium ions) can be achieved. Furthermore, as the size of the graphene oxide increases, the mechanical properties and film-forming properties of the large-size graphene oxide are further enhanced, improving the membrane's stability and allowing it to remain stable even at relatively thin membrane thicknesses. This enables highly selective, high-throughput, and stable extraction of lithium ions from salt lake water or salt solution systems.

[0020] The lithium-ion separation membrane prepared by this invention has the advantages of simple process, high lithium-ion selectivity, large processing throughput, low cost and no pollution.

[0021] The lithium-ion separation membrane prepared by this invention is used in the selective filtration and separation of lithium ions in salt lake water or salt solution systems. It has the advantages of high throughput, high rejection rate and no need to be used in combination with other adsorbents. The lithium-ion separation membrane prepared by this invention is different from commonly used polymer membranes. The two-dimensional space between the graphene oxide membrane layers is precisely adjustable, and it has good selectivity for monovalent ions, which is beneficial for selective lithium extraction in complex salt water environments. Attached Figure Description

[0022] Figure 1 An optical microscope image of the lithium-ion separation membrane based on intercalated large-size graphene oxide prepared according to the present invention;

[0023] Figure 2 A scanning electron microscope image of the lithium-ion separation membrane based on intercalated large-size graphene oxide prepared for this invention. Detailed Implementation

[0024] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0025] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0026] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0027] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0028] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0029] This invention provides a lithium-ion separation membrane based on intercalated large-size graphene oxide, its preparation method, and its application.

[0030] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0031] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0032] This invention provides a method for preparing a lithium-ion separation membrane based on intercalated large-size graphene oxide, comprising the following steps:

[0033] Step 1: Take a large-size graphene oxide solution with an average size of 5-150 μm and an intercalating agent and mix them at a concentration ratio of 1:(0.1-50). Let it stand for 10 min to 5 days to obtain a mixed solution. The concentration of large-size graphene oxide in the large-size graphene oxide solution is 0.05-5 mg / ml. The thickness of the large-size graphene oxide sheets is 0.34-10 nm. The intercalating agent is located between or on the surface of the large-size graphene oxide sheets inside the film.

[0034] The preparation process of large-size graphene oxide solution involves mixing large-size graphene oxide sheets with an average size of 5–150 μm with deionized water to obtain a large-size graphene oxide solution.

[0035] In the specific implementation process, blending refers to using physical methods such as stirring, ultrasound, or vibration to combine large-sized graphene oxide with intercalating agents, ensuring that the intercalating agent is located between or on the surface of large-sized graphene oxide sheets inside the lithium ion separation membrane, so that the intercalating agent is uniformly attached to the graphene surface.

[0036] Step 2: The mixed solution is deposited onto any one of the following substrate membranes: polyethersulfone membrane, nylon membrane, mixed cellulose membrane, or anodic aluminum oxide membrane, by means of scraping, spin coating, or negative pressure filtration; and dried under certain temperature and humidity to prepare a lithium-ion separation membrane based on large-size graphene oxide; the interlayer spacing of the lithium-ion separation membrane is 0.4–5 nm to ensure the sieving ability of different ions; and its thickness is 20 nm–50 μm.

[0037] As an alternative, intercalating agents include one or more combinations of chlorides and hydroxides of various metal ions (sodium, potassium, lithium, magnesium, calcium, aluminum ions), alkylammonium (tetramethylammonium chloride, tetrabutylammonium chloride, dodecyltrimethylammonium chloride, tetradecyltrimethylammonium chloride), and crown ethers (12-crown-4 ether, 15-crown-5 ether, 18-crown-6 ether).

[0038] The drying process is carried out at a temperature of 20℃ to 120℃, a humidity of 10% to 80%, and a drying time of 30 minutes to 2 days.

[0039] The lithium-ion separation membrane prepared by this invention has a simple process, high lithium-ion selectivity, large processing throughput, low cost, and no pollution when applied to lithium-ion extraction.

[0040] The lithium-ion separation membrane prepared by this invention can be used in the selective filtration and separation of lithium ions in salt lake water or salt solution systems. It has a large throughput, high rejection rate and stable membrane performance, and does not need to be used in combination with other adsorbents.

[0041] Large-size graphene oxide sheets, as an ideal two-dimensional material, can form regular nanoscale ion transport channels when stacked together. Large-size graphene oxide films fundamentally improve upon the problems of low lithium selectivity, small throughput, and poor film stability encountered by traditional polymer films during lithium extraction.

[0042] Specific intercalating agents can adjust the interlayer spacing of graphene oxide membranes, thereby enabling selective filtration of specific ions. As the size of graphene oxide increases, the migration channels for ions between graphene layers become longer and more uniform, which is beneficial for precise ion sieving through size effects and interlayer interactions. In addition, its mechanical properties and film-forming properties can improve membrane stability, allowing it to remain stable even at relatively thin membrane thicknesses, thus achieving highly selective, high-throughput, and stable extraction of lithium ions from salt lakes or brine.

[0043] Example 1:

[0044] A lithium-ion separation membrane based on intercalated large-size graphene oxide was prepared by the following steps: 100 ml of a 1 mg / ml graphene oxide solution was prepared using graphene oxide with an average size of 15 μm (sheet thickness of 1 nm). 500 mg of calcium chloride, an intercalating agent, was added and the mixture was allowed to stand for 2 days. The reacted graphene solution was then uniformly deposited onto a 10 cm × 20 cm polyethersulfone substrate membrane using a coating method. The membrane was then treated at 60 °C and 20% humidity for 12 hours to prepare the large-size graphene oxide lithium-ion separation membrane. The membrane interlayer spacing was 1.1 nm, and the thickness was 200 nm. Using this membrane to treat 1 L of a brine solution with a magnesium-to-lithium ratio of 20, a single filtration reduced the magnesium-to-lithium ratio to 2, and after 3–5 filtrations, the ratio was reduced to 0.1.

[0045] Example 2:

[0046] A lithium-ion separation membrane based on large-size graphene oxide from salt lakes or brine was prepared, comprising the following steps: 100 ml of a 1 mg / ml graphene oxide solution was prepared using graphene oxide with an average size of 50 μm (sheet thickness of 1 nm). 500 mg of lithium chloride (intercalating agent) was added and the solution was allowed to stand for 2 days. The resulting graphene mixture was then deposited onto a 10 cm × 20 cm polyethersulfone substrate membrane using negative pressure filtration. The filtered membrane was then treated at 50 °C and 30% humidity for 12 h to prepare a large-size graphene oxide lithium-ion separation membrane. The membrane interlayer spacing was 1.0 nm and the thickness was 100 nm. Using this membrane to treat 1 L of a brine solution with a magnesium-to-lithium ratio of 50, a single filtration reduced the magnesium-to-lithium ratio to 3.2, and after 3–5 filtrations, the ratio was reduced to below 0.2.

[0047] Example 3:

[0048] A lithium-ion separation membrane based on large-size graphene oxide from salt lakes or brine was prepared, comprising the following steps: 100 ml of a 0.5 mg / ml graphene oxide solution (average size 15 μm, sheet thickness 0.8 nm) was prepared, and 300 mg of intercalating agent 12-crown-4 ether was added and allowed to stand for 2 days. The reacted graphene mixture was then uniformly deposited onto a 10 cm × 20 cm polyethersulfone substrate membrane using a coating method. The membrane was then treated at 60 °C and 20% humidity for 12 h to prepare a large-size graphene oxide lithium-ion separation membrane. The membrane interlayer spacing was 0.4 nm and the thickness was 20 nm. Using this membrane to treat 1 L of a brine solution with a magnesium-to-lithium ratio of 20, a single filtration reduced the magnesium-to-lithium ratio to 1.8, and after 3–5 filtrations, the magnesium-to-lithium ratio was reduced to below 0.1.

[0049] Example 4:

[0050] A lithium-ion separation membrane based on large-size graphene oxide from salt lakes or brine was prepared, comprising the following steps: 100 ml of a 1 mg / ml graphene oxide solution was prepared using graphene oxide with an average size of 50 μm (sheet thickness of 0.9 nm). 500 mg of lithium chloride (intercalating agent) was added and the mixture was allowed to stand for 2 days. The resulting graphene mixture was then deposited onto a 10 cm × 20 cm polyethersulfone substrate membrane using negative pressure filtration. The membrane was then treated at 50 °C and 30% humidity for 12 h to prepare a large-size graphene oxide lithium-ion separation membrane. The membrane interlayer spacing was 0.9 nm and the thickness was 50 nm. Using this membrane to treat 1 L of a brine solution with a magnesium-to-lithium ratio of 50, a single filtration reduced the magnesium-to-lithium ratio to 3.2, and after 3–5 filtrations, the magnesium-to-lithium ratio was reduced to below 0.2.

[0051] Example 5:

[0052] A lithium-ion separation membrane based on large-size graphene oxide from salt lakes or brine was prepared by the following steps: 100 ml of a 5 mg / ml graphene oxide solution (with an average size of 5 μm and a sheet thickness of 10 nm) was prepared, and 500 mg of tetrabutylammonium chloride (an intercalating agent) was added and allowed to stand for 2 days. The reacted graphene mixture was then uniformly deposited onto a 10 cm × 20 cm polyethersulfone substrate membrane using a coating method. The membrane was then treated at 100 °C and 30% humidity for 24 h to prepare a large-size graphene oxide lithium-ion separation membrane. The membrane interlayer spacing was 5 nm and the thickness was 50 μm. Using this membrane to treat 1 L of a brine solution with a magnesium-to-lithium ratio of 50, a single filtration reduced the magnesium-to-lithium ratio to 1.5, and after 3–5 filtrations, the ratio was reduced to 0.45.

[0053] Example 6:

[0054] A lithium-ion separation membrane based on large-size graphene oxide from salt lakes or brine was prepared, comprising the following steps: 100 ml of a 0.05 mg / ml graphene oxide solution was prepared using graphene oxide with an average size of 5 μm (sheet thickness of 0.34 nm). 5 mg of intercalating agent 12-crown-4 ether was added, and the mixture was allowed to stand for 2 days. The resulting graphene mixture was then deposited onto a polyethersulfone substrate membrane using negative pressure filtration. The membrane was then treated at 60°C and 20% humidity for 12 hours to prepare a large-size graphene oxide lithium-ion separation membrane. Using this membrane to treat 1 L of a brine solution with a magnesium-to-lithium ratio of 10, a single filtration reduced the magnesium-to-lithium ratio to 1.8, and 3–5 filtrations reduced it to 0.5.

[0055] Example 7:

[0056] A lithium-ion separation membrane based on large-size graphene oxide from salt lakes or brine was prepared, comprising the following steps: 100 ml of a 5 mg / ml graphene oxide solution was prepared using graphene oxide with an average size of 150 μm. 50 mg of tetrabutylammonium chloride (Tetrabutylammonium chloride) was added as an intercalating agent and allowed to stand for 2 days. The reacted graphene mixture was then uniformly deposited onto a 10 cm × 20 cm nylon membrane using a coating method. The membrane was then treated at 60 °C and 20% humidity for 12 h to prepare a large-size graphene oxide lithium-ion separation membrane. Using this membrane to treat 1 L of a brine solution with a magnesium-to-lithium ratio of 10, a single filtration reduced the magnesium-to-lithium ratio to 0.9, and 3–5 filtrations reduced it to 0.2.

[0057] Example 8:

[0058] The method for lithium extraction from salt lakes or brine using large-size graphene oxide membranes includes the following steps: 100 ml of a 5 mg / ml graphene oxide solution was prepared using graphene oxide with an average size of 150 μm. 50 mg of tetramethylammonium chloride (TMC) was added as an intercalating agent and allowed to stand for 10 min. The reacted graphene mixture was then uniformly deposited onto a 10 cm × 20 cm mixed cellulose membrane using spin coating. The membrane was then treated at 20 °C and 10% humidity for 15 h to prepare a large-size graphene oxide lithium-ion separation membrane.

[0059] Example 9:

[0060] The method for lithium extraction from salt lakes or brine using large-size graphene oxide membranes includes the following steps: 100 ml of a 0.05 mg / ml graphene oxide solution with an average size of 50 μm was prepared, and 500 mg of dodecyltrimethylammonium chloride (DMC) intercalating agent was added and allowed to stand for 5 days. The resulting graphene mixture was then deposited onto a 10 cm × 20 cm anodic aluminum oxide membrane using negative pressure filtration. The filtered membrane was then treated at 120 °C and 30% humidity for 20 hours to prepare a large-size graphene oxide lithium-ion separation membrane.

[0061] Example 10:

[0062] The method for lithium extraction from salt lakes or brine using large-size graphene oxide membranes includes the following steps: 100 ml of a 0.5 mg / ml graphene oxide solution with an average size of 15 μm is prepared, and 300 mg of tetradecyltrimethylammonium chloride (a transdermal intercalating agent) is added and allowed to stand for 3 days. The reacted graphene mixture is then uniformly deposited onto a 10 cm × 20 cm polyethersulfone substrate membrane using a coating method. The membrane is then treated at 100 °C and 20% humidity for 30 min to prepare a large-size graphene oxide lithium-ion separation membrane.

[0063] Example 11:

[0064] A lithium-ion separation membrane based on large-size graphene oxide from salt lakes or brine was prepared by the following steps: 100 ml of a graphene oxide solution with an average size of 50 μm and a concentration of 1 mg / ml was prepared. 500 mg of intercalating agent 15-crown-5 ether was added, and the mixture was allowed to stand for 1 day. The resulting graphene mixture was then deposited onto a 10 cm × 20 cm polyethersulfone substrate membrane using negative pressure filtration. The membrane was then treated at 30°C and 30% humidity for 1 day to prepare a large-size graphene oxide lithium-ion separation membrane.

[0065] Example 12:

[0066] A lithium-ion extraction membrane based on large-size graphene oxide from salt lakes or brine includes the following steps: 100 ml of a graphene oxide solution with an average size of 50 μm and a concentration of 1 mg / ml was prepared. 500 mg of intercalating agent 18-crown-6 ether was added, and the mixture was allowed to stand for 5 days. The resulting graphene mixture was then deposited onto a 10 cm × 20 cm polyethersulfone substrate membrane using negative pressure filtration. The membrane was then treated at 40 °C and 80% humidity for 2 days to prepare a large-size graphene oxide lithium-ion separation membrane.

[0067] Comparative Example 1:

[0068] 100 ml of a 1 mg / ml graphene oxide solution (1 nm thick) with an average graphene size of 2 μm was prepared without intercalating agent. The resulting graphene mixture was then uniformly deposited onto a 10 cm × 20 cm polyethersulfone substrate using a coating method. The membrane was then treated at 60 °C and 20% humidity for 12 h to prepare a lithium extraction membrane. The separation membrane had a layer spacing of 0.35 nm and a thickness of 10 nm. When used to treat 1 L of a brine solution with a magnesium-to-lithium ratio of 20, the magnesium-to-lithium ratio decreased to 15 after approximately 1 h, but the membrane broke down after 2 h, making lithium extraction impossible.

[0069] Comparative Example 2:

[0070] A 100 ml solution of graphene oxide with an average size of 0.5 μm (sheet thickness of 15 nm) was prepared, containing 1 mg / ml of graphene oxide. 500 mg of calcium chloride, an intercalating agent, was added, and the mixture was allowed to stand for 2 days. The resulting graphene mixture was then uniformly deposited onto a 10 cm × 20 cm polyethersulfone substrate membrane using negative pressure filtration. The filtered membrane was then treated at 60 °C and 20% humidity for 12 hours to prepare a lithium extraction membrane. The membrane had a layer spacing of 8 nm and a thickness of 80 μm. When this membrane was used to treat 1 L of a brine solution with a magnesium-to-lithium ratio of 20, the membrane broke down, making lithium extraction impossible.

[0071] Comparative Example 3:

[0072] 100 ml of a 20 mg / ml graphene oxide solution was prepared using graphene oxide with an average size of 15 μm. 500 mg of calcium chloride, an intercalating agent, was added and the mixture was allowed to stand for 2 days. The resulting graphene mixture was then uniformly deposited onto a 10 cm × 20 cm polyethersulfone substrate membrane using a coating method. The membrane was then treated at 60 °C and 20% humidity for 12 hours to prepare a lithium extraction membrane. When used to treat 1 L of a brine solution with a magnesium-to-lithium ratio of 20, the magnesium-to-lithium ratio was 18.5 after one day of operation, indicating a low processing capacity.

[0073] Comparative Example 4:

[0074] 100 ml of a 2 mg / ml graphene oxide solution was prepared using graphene oxide with an average size of 15 μm. 20 g of excess calcium chloride intercalating agent was added, and the solution was allowed to stand for 2 days. The resulting graphene mixture was then uniformly deposited onto a 10 cm × 20 cm polyethersulfone substrate membrane using negative pressure filtration. The filtered membrane was then treated at 60 °C and 20% humidity for 12 hours to prepare a lithium extraction membrane. However, the membrane surface was very uneven. When treated with 1 L of a brine solution with a magnesium-to-lithium ratio of 20, the membrane ruptured within 1 hour.

[0075] Comparative Example 5:

[0076] 100 ml of a 0.1 mg / ml graphene oxide solution was prepared using graphene oxide with an average size of 0.8 μm. 500 mg of lithium chloride, an intercalating agent, was added and the mixture was allowed to stand for 2 days. The resulting graphene mixture was then uniformly deposited onto a 10 cm × 20 cm polyethersulfone substrate membrane using a coating method. The membrane was then treated at 220 °C and ~20% humidity for 20 h to prepare a large-size graphene oxide lithium extraction membrane. Using this membrane to treat 1 L of a brine solution with a magnesium-to-lithium ratio of 20, a single filtration reduced the magnesium-to-lithium ratio to 18, and after 3–5 filtrations, the ratio was reduced to 12, indicating poor performance.

[0077] like Figure 1 As shown in the optical microscope image of the large-size graphene oxide lithium-ion separation membrane prepared in Example 1, the membrane surface is intact and has a large number of wrinkles, which is conducive to the penetration of brine from the membrane surface.

[0078] like Figure 2 As shown in the scanning electron microscope image of the cross-section of the large-size graphene oxide lithium-ion separation membrane prepared in Example 2, the prepared membrane exhibits a layer-by-layer stacking morphology, which conforms to the face-to-face assembly structure of graphene sheets. This is beneficial for maintaining the mechanical stability of the membrane while ensuring selective transport of brine between layers.

[0079] Through comparisons of examples and comparative figures, this invention utilizes the high mechanical strength and selective ion transport channels between layers of large-size graphene, combined with the adjustment of membrane interlayer spacing by an intercalating agent, to ultimately achieve efficient lithium extraction from brine. This invention relates to a method for preparing a lithium-ion separation membrane for brine lake water or brine solution systems based on intercalated large-size graphene oxide. The method includes steps such as mixing large-size graphene with an intercalating agent, reactive intercalation, and drying to form a membrane. It utilizes the high mechanical strength and selective ion transport channels between layers of large-size graphene, combined with the adjustment of membrane interlayer spacing by an intercalating agent, to ultimately achieve efficient lithium extraction from brine lake water or brine solution systems.

[0080] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for preparing a lithium-ion separation membrane based on intercalated large-size graphene oxide, characterized in that, Includes the following steps: A large-size graphene oxide solution was obtained by mixing large-size graphene oxide sheets with an average size of 5-150 μm with deionized water; the concentration of the large-size graphene oxide solution was 0.05-5 mg / ml; the concentration ratio of the large-size graphene oxide solution to the intercalating agent was 1:(0.1-50); and the thickness of the large-size graphene oxide sheets was 0.34-10 nm. A large-size graphene oxide solution is mixed with an intercalating agent, and the mixture is allowed to stand to obtain a mixed solution. The mixed solution is deposited on a base membrane and then dried to prepare a lithium-ion separation membrane. The intercalating agent is one or a combination of several of the following: a chloride salt containing metal ions and a hydroxide containing metal ions; tetramethylammonium chloride; tetrabutylammonium chloride; dodecyltrimethylammonium chloride; tetradecyltrimethylammonium chloride; 12-crown-4 ether; 15-crown-5 ether; and 18-crown-6 ether. The drying process is carried out at a temperature of 20℃ to 120℃, with a humidity of 10% to 80%, and for a duration of 30 min to 2 days. The interlayer spacing of the lithium-ion separation membrane is 0.4~5nm; the thickness of the lithium-ion separation membrane is 20nm~50μm.

2. The method for preparing a lithium-ion separation membrane based on intercalated large-size graphene oxide according to claim 1, characterized in that, The intercalating agent is located between or on the surface of large graphene oxide sheets inside the lithium-ion separation membrane.

3. The method for preparing a lithium-ion separation membrane based on intercalated large-size graphene oxide according to claim 1, characterized in that, The mixed solution is deposited on the base membrane by any one of the following methods: blade coating, spin coating, or vacuum filtration.

4. The method for preparing a lithium-ion separation membrane based on intercalated large-size graphene oxide according to claim 1, characterized in that, The base membrane is any one of polyethersulfone membrane, nylon membrane, mixed cellulose membrane, and anodic aluminum oxide membrane.

5. A lithium-ion separation membrane prepared by the method for preparing a lithium-ion separation membrane based on intercalated large-size graphene oxide according to any one of claims 1 to 4.

6. A lithium-ion separation membrane based on intercalated large-size graphene oxide as described in claim 5, characterized in that, Lithium-ion separation membranes are used in the selective filtration and separation of lithium ions in salt lake water or salt solution systems.

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