Titanium-based lithium adsorbent for low salinity water body and preparation method thereof

Abstract

The application provides a titanium-based lithium adsorbent for low-mineralization water bodies and a preparation method thereof, and relates to the technical field of adsorbents, and the preparation method comprises the following steps: precursor preparation, selecting a titanium source, a lithium source and a functional additive, and preparing a mixed solution, wherein the titanium source is tetrabutyl titanate, the lithium source is lithium carbonate, the molar ratio of titanium to lithium is 1:1.2 to 1:1.8, the functional additive is a crown ether or a derivative thereof, and the addition amount is 1% to 5% of the weight of the titanium source, hydrothermal synthesis, transferring the mixed solution into a high-pressure reaction kettle, reacting at 150-200 DEG C for 12-24 hours, controlling the temperature rising rate to be 2-5 DEG C / min during the reaction process, naturally cooling to room temperature after the reaction, ion exchange, constructing a stable crystal skeleton by using the process of hydrothermal synthesis combined with high-temperature calcination and activation, enhancing the physical and chemical stability of the adsorbent in mild to weak acidic water bodies, and improving the economy and reliability of the lithium extraction process.

Description

Technical Field

[0001] This invention relates to the field of adsorbent technology, and in particular to a titanium-based lithium adsorbent for low-mineralized water bodies and its preparation method. Background Technology

[0002] Adsorbents, also known as absorbents, are substances that allow active ingredients to adhere to the surface of their particles, transforming liquid trace compound additives into solid compounds. This facilitates uniform mixing. They are solid substances that can effectively adsorb certain components from gases or liquids, possessing a large specific surface area, suitable pore structure and surface structure, strong adsorption capacity for adsorbates, ease of manufacturing and regeneration, and excellent adsorption and mechanical properties.

[0003] Currently, due to the extremely low lithium-ion concentration and the coexistence of numerous competing cations in low-mineralized water bodies, the synthesized adsorbent framework structure is not stable enough in such waters during the development of lithium adsorbents for this type of water. It cannot maintain the structural integrity of the adsorbent in mild to weakly acidic waters for extended periods. Framework collapse or loss of active sites significantly shortens the adsorbent's cycle life, compromising the economic viability of lithium extraction. Furthermore, during selective lithium-ion adsorption, the competitive interference from numerous coexisting sodium, potassium, calcium, and magnesium cations cannot be effectively overcome, leading to a decrease in the adsorbent's selectivity for lithium-ions. Insufficient selectivity cannot be restored through simple regeneration. When extracting lithium from low-mineralized waters, the adsorption rate and capacity of traditional titanium-based adsorbents are not ideal at low concentrations. In developing high-performance adsorbents, the synergistic construction of high specific surface area and numerous dedicated lithium vacancies cannot be achieved, resulting in low dynamic adsorption efficiency in low-concentration lithium environments. This further affects the practical application value and extraction effect of lithium adsorbents.

[0004] Therefore, a titanium-based lithium adsorbent for low-mineralized water bodies and its preparation method are proposed to solve the above problems. Summary of the Invention

[0005] To address the technical problems of significantly shortened cycle life of existing adsorbents, which cannot guarantee the economic efficiency of the lithium extraction process, decreased selectivity of adsorbents for lithium ions, and low dynamic adsorption efficiency of adsorbents in low-concentration lithium environments, this invention provides a titanium-based lithium adsorbent for low-mineralized water bodies and its preparation method.

[0006] The technical solutions provided by the embodiments of the present invention are as follows:

[0007] This invention provides a titanium-based lithium adsorbent for low-mineralized water and its preparation method, comprising the following steps:

[0008] Step 1: Precursor preparation. Select a titanium source, a lithium source, and a functional additive to prepare a mixed solution. The titanium source is tetrabutyl titanate, and the lithium source is lithium carbonate. The molar ratio of titanium to lithium is 1:1.2 to 1:1.8. The functional additive is a crown ether or its derivative, and the amount added is 1%-5% of the weight of the titanium source.

[0009] Step 2: Hydrothermal synthesis. The mixed solution is transferred to a high-pressure reactor and reacted at 150-200℃ for 12-24 hours. During the reaction, the heating rate is controlled at 2-5℃ / min. After the reaction, the mixture is allowed to cool naturally to room temperature.

[0010] Step 3: Ion exchange. The hydrothermal products are treated with an acid solution, such as hydrochloric acid or sulfuric acid, with a concentration of 0.1-0.5 mol / L. The pH is adjusted to 2-4, and the mixture is stirred at 25-40℃ for 1-3 hours to complete the ion exchange.

[0011] Step 4: Post-treatment, including washing, drying and activation. First, wash with deionized water until neutral, then dry at 80-120℃ for 2-6 hours, and finally calcine at 300-500℃ for 2-4 hours to obtain titanium-based lithium adsorbent.

[0012] In step one, the mixed solution also includes a dispersant, which is polyvinylpyrrolidone or polyethylene glycol, and the amount added is 0.5%-2% of the weight of the titanium source.

[0013] Preferably, the precursor preparation in step one includes the following steps: Tetrabutyl titanate is slowly added to anhydrous ethanol at a mass ratio of 1:3 to 1:5, and stirred at 200-500 r / min for 10-20 minutes to form a homogeneous titanium source solution. Simultaneously, lithium carbonate is dissolved in deionized water at a mass ratio of 1:10 to 1:15, and stirred until completely dissolved. The titanium source solution and lithium source solution are then mixed, and functional additives and dispersants are added. The mixture is stirred at 300-600 r / min for 30-60 minutes to obtain a mixed solution. The pH of the mixed solution is controlled at 7-9, adjusted using ammonia or sodium hydroxide.

[0014] Preferably, the hydrothermal synthesis in step two includes the following steps: transferring the mixed solution into a high-pressure reactor lined with polytetrafluoroethylene, with a filling degree of 70%-80%, sealing it, and placing it in an oven, heating it to 150-200℃ at a rate of 2-5℃ / min, holding it at that temperature for 12-24 hours, and after the reaction is completed, cooling it to room temperature at a rate of 0.5-1℃ / min, taking out the reaction product, and centrifuging it at 3000-5000r / min for 5-10 minutes to separate a white precipitate.

[0015] Preferably, step three, ion exchange, includes the following steps: redispersing the precipitate obtained by hydrothermal synthesis in deionized water at a solid-liquid ratio of 1:10 to 1:20, adding an acid solution, slowly adjusting the pH to 2-4, stirring with a magnetic stirrer at 200-400 r / min for 1-3 hours, controlling the stirring temperature at 25-40℃, and then filtering with a vacuum filtration device to obtain the ion-exchanged product.

[0016] Preferably, the post-processing in step four includes the following steps: during washing, the product is repeatedly rinsed with deionized water 3-5 times until the pH of the filtrate is 6.5-7.5; during drying, the product is placed in a vacuum drying oven and dried at 80-120℃ for 2-6 hours, with the vacuum degree maintained at -0.08 to -0.1MPa; during activation, the dried product is placed in a muffle furnace and heated to 300-500℃ at 3-8℃ / min, calcined for 2-4 hours, and then naturally cooled to obtain the final titanium-based lithium adsorbent.

[0017] Preferably, the functional adjuvant crown ether or its derivative is 18-crown-6 or benzo-15-crown-5, and its pretreatment method includes: dissolving the crown ether in acetone at a concentration of 5%-10%, ultrasonically treating it at 40-60°C for 20-40 minutes with an ultrasonic power of 100-200W, then evaporating to remove the acetone to obtain purified crown ether, and then mixing it with a titanium source.

[0018] Preferably, during the activation process in step four, a structural stabilizer is also added. The structural stabilizer is a silane coupling agent or a titanate coupling agent, and the amount added is 0.1%-1% of the weight of the adsorbent. It is sprayed on the surface of the dried product before calcination, mixed evenly, and then calcined together.

[0019] Preferably, the method for adding the structural stabilizer includes: dissolving silane coupling agent KH-550 or titanate coupling agent NDZ-101 in ethanol at a concentration of 1%-5%, uniformly spraying it onto the dried product at a pressure of 0.1-0.3 MPa using a spraying device, with a spraying amount of 0.5-2 mL per gram of product, followed by aging at room temperature for 1-2 hours, and then calcining.

[0020] Preferably, the preparation method further includes step five: surface modification treatment, in which the activated adsorbent is immersed in a surface modification solution, the surface modification solution being composed of silica gel and lithium selective ligands, the mass ratio of silica gel to ligands being 1:1 to 1:3, the immersion time being 2-4 hours, the temperature being 50-70℃, and then the adsorbent is removed, washed and dried, wherein the lithium selective ligand is azacrown ether or phosphate ester compound.

[0021] Preferably, its composition is mainly lithium titanate, with crown ether groups and silane coating on the surface, and it has a nanoporous structure with a pore size distribution of 2-10 nm and a specific surface area of ​​150-400 m².2 / g, with an adsorption capacity of 25-60mg / g for lithium ions, and a selectivity coefficient of 50-100 for lithium in low-mineralized water bodies, wherein the low-mineralized water bodies refer to water bodies with a mineralization of less than 500mg / L, including river water, lake water or groundwater.

[0022] The beneficial effects of the technical solutions provided by the embodiments of the present invention include at least the following:

[0023] 1. In this invention, when preparing titanium-based lithium adsorbents for low-mineralized water, a stable crystal framework is constructed by using a process of hydrothermal synthesis combined with high-temperature calcination activation, and a structural stabilizer is introduced for surface reinforcement. This enhances the physicochemical stability of the adsorbent in mild to weakly acidic water, solves the problem of adsorbent framework collapse or loss of active sites due to long-term use, ensures the structural integrity and service life of the adsorbent for recycling in low-mineralized water, and thus improves the economy and reliability of the lithium extraction process.

[0024] 2. In the design and preparation of this titanium-based lithium adsorbent, by adding crown ether functional additives to the precursor and performing surface modification treatment in the later stage, the specific recognition and complexation ability of the crown ether group for lithium ions can be utilized to improve the selectivity of the adsorbent for lithium ions in low-mineralized water bodies rich in competitive cations of sodium, potassium, calcium and magnesium. This solves the problem of decreased selectivity caused by interference from coexisting ions, enabling the adsorbent to accurately capture lithium ions and improve the purity and efficiency of lithium extraction from complex water bodies.

[0025] 3. In this invention, when optimizing the performance of the titanium-based lithium adsorbent, a dedicated lithium vacancy is created through an ion exchange step, and the preparation process is synergistically controlled to obtain a high specific surface area and a nanoporous structure. This enables the adsorbent to rapidly adsorb lithium ions and achieve high capacity loading in low lithium concentration environments, solving the problems of slow kinetic rate and low adsorption capacity of traditional adsorbents in low-concentration water. This ensures that the adsorbent can maintain efficient dynamic adsorption performance even in low-mineralized water, enhancing the practical value and extraction effect of the titanium-based lithium adsorbent. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a flowchart illustrating a titanium-based lithium adsorbent for low-mineralized water bodies and its preparation method, according to the present invention. Detailed Implementation

[0028] The technical solutions of the present invention will now be described with reference to the accompanying drawings. It should be noted that, to make the embodiments more detailed, the following embodiments are the best and preferred embodiments, and those skilled in the art can use other alternative methods to implement some well-known technologies. Furthermore, the accompanying drawings are only for more specific description of the embodiments and are not intended to specifically limit the present invention.

[0029] Example 1: This embodiment of the invention provides a titanium-based lithium adsorbent for low-salinity water and its preparation method, comprising the following steps:

[0030] Step 1: Precursor preparation. Select a titanium source, a lithium source, and a functional additive to prepare a mixed solution. The titanium source is tetrabutyl titanate, the lithium source is lithium carbonate, the molar ratio of titanium to lithium is 1:1.2, and the functional additive is a crown ether or its derivative, added at 1% of the weight of the titanium source.

[0031] Step 2: Hydrothermal synthesis. The mixed solution is transferred to a high-pressure reactor and reacted at 150°C for 12 hours. During the reaction, the heating rate is controlled at 2°C / min. After the reaction, the mixture is allowed to cool naturally to room temperature.

[0032] Step 3: Ion exchange. The hydrothermal products are treated with an acid solution, such as hydrochloric acid or sulfuric acid, with a concentration of 0.1 mol / L. The pH is adjusted to 2, and the mixture is stirred at 25°C for 1 hour to complete the ion exchange.

[0033] Step 4: Post-treatment, including washing, drying and activation. First, wash with deionized water until neutral, then dry at 80℃ for 2 hours, and finally calcine at 300℃ for 2 hours to obtain titanium-based lithium adsorbent.

[0034] In step one, the mixed solution also includes a dispersant, which is polyvinylpyrrolidone or polyethylene glycol, and the amount added is 0.5% of the weight of the titanium source;

[0035] Step 1, the preparation of the precursor, includes the following steps: Tetrabutyl titanate is slowly added to anhydrous ethanol at a mass ratio of 1:3, and stirred at 200 r / min for 10 minutes to form a homogeneous titanium source solution. At the same time, lithium carbonate is dissolved in deionized water at a mass ratio of 1:10, and stirred until completely dissolved. Then, the titanium source solution and the lithium source solution are mixed, functional additives and dispersants are added, and the mixture is stirred at 300 r / min for 30 minutes to obtain a mixed solution. The pH of the mixed solution is controlled at 7 and adjusted using ammonia or sodium hydroxide.

[0036] Step 2 hydrothermal synthesis includes the following steps: the mixed solution is transferred to a high-pressure reactor lined with polytetrafluoroethylene, with a filling degree of 70%, sealed and placed in an oven, heated to 150°C at a rate of 2°C / min, and held at that temperature for 12 hours. After the reaction is completed, it is cooled to room temperature at a rate of 0.5°C / min, the reaction product is taken out, and centrifuged at 3000 r / min for 5 minutes to separate a white precipitate.

[0037] Step 3, ion exchange, includes the following steps: the precipitate obtained by hydrothermal synthesis is redispersed in deionized water at a solid-liquid ratio of 1:10, acid solution is added, the pH is slowly adjusted to 2, and the mixture is stirred at 200 r / min for 1 hour using a magnetic stirrer with the stirring temperature controlled at 25℃. After that, the mixture is filtered using a vacuum filtration device to obtain the ion-exchanged product.

[0038] Step four post-processing includes the following steps: During washing, the product is repeatedly rinsed with deionized water three times until the pH of the filtrate is 6.5. During drying, the product is placed in a vacuum drying oven and dried at 80°C for 2 hours while maintaining a vacuum of -0.08 MPa. During activation, the dried product is placed in a muffle furnace and heated to 300°C at a rate of 3°C / min. It is then calcined for 2 hours and then naturally cooled to obtain the final titanium-based lithium adsorbent.

[0039] The functional additive crown ether or its derivatives are 18-crown-6 or benzo-15-crown-5. The pretreatment method includes: dissolving the crown ether in acetone at a concentration of 5%, sonicating at 40°C for 20 minutes with an ultrasonic power of 100W, then evaporating to remove the acetone to obtain purified crown ether, and then mixing it with a titanium source.

[0040] In step four, during the activation process, a structural stabilizer is also added. The structural stabilizer is a silane coupling agent or a titanate coupling agent, and the amount added is 0.1% of the weight of the adsorbent. It is sprayed on the surface of the dried product before calcination, mixed evenly, and then calcined together.

[0041] The method for adding the structural stabilizer includes: dissolving silane coupling agent KH-550 or titanate coupling agent NDZ-101 in ethanol at a concentration of 1%, and uniformly spraying it onto the dried product at a pressure of 0.1 MPa using a spraying device, with a spraying amount of 0.5 mL per gram of product, followed by aging at room temperature for 1 hour, and then calcining.

[0042] The preparation method also includes step five: surface modification treatment, in which the activated adsorbent is immersed in a surface modification solution, which is composed of silica gel and lithium selective ligands, with a mass ratio of silica gel to ligand of 1:1, an immersion time of 2 hours, and a temperature of 50°C. After that, it is taken out, washed and dried. The lithium selective ligands are azacrown ethers or phosphate ester compounds.

[0043] Its composition is mainly lithium titanate, with crown ether groups and silane coating on the surface. It has a nanoporous structure with a pore size distribution of 2 nm and a specific surface area of ​​150 m². 2 / g, with an adsorption capacity of 25mg / g for lithium ions, and a selectivity coefficient of 50 for lithium in low-mineralized water bodies. Low-mineralized water bodies refer to water bodies with a mineralization of less than 500mg / L, including river water, lake water, or groundwater.

[0044] Example 2: An embodiment of the present invention provides a titanium-based lithium adsorbent for low-salinity water and its preparation method, comprising the following steps:

[0045] Step 1: Precursor preparation. Select a titanium source, a lithium source, and a functional additive to prepare a mixed solution. The titanium source is tetrabutyl titanate, the lithium source is lithium carbonate, the molar ratio of titanium to lithium is 1:1.5, and the functional additive is a crown ether or its derivative, added at 3% of the weight of the titanium source.

[0046] Step 2: Hydrothermal synthesis. The mixed solution is transferred to a high-pressure reactor and reacted at 170°C for 18 hours. During the reaction, the heating rate is controlled at 3°C / min. After the reaction, the mixture is allowed to cool naturally to room temperature.

[0047] Step 3: Ion exchange. The hydrothermal products are treated with an acid solution, such as hydrochloric acid or sulfuric acid, with a concentration of 0.3 mol / L. The pH is adjusted to 3, and the mixture is stirred at 30°C for 2 hours to complete the ion exchange.

[0048] Step 4: Post-treatment, including washing, drying and activation. First, wash with deionized water until neutral, then dry at 100℃ for 4 hours, and finally calcine at 400℃ for 3 hours to obtain titanium-based lithium adsorbent.

[0049] In step one, the mixed solution also includes a dispersant, which is polyvinylpyrrolidone or polyethylene glycol, and the amount added is 1% of the weight of the titanium source;

[0050] Step 1, the preparation of the precursor, includes the following steps: Tetrabutyl titanate is slowly added to anhydrous ethanol at a mass ratio of 1:4, and stirred at 300 r / min for 15 minutes to form a homogeneous titanium source solution. At the same time, lithium carbonate is dissolved in deionized water at a mass ratio of 1:13, and stirred until completely dissolved. Then, the titanium source solution and the lithium source solution are mixed, functional additives and dispersants are added, and the mixture is stirred at 400 r / min for 40 minutes to obtain a mixed solution. The pH of the mixed solution is controlled at 8, and adjusted using ammonia or sodium hydroxide.

[0051] Step 2 hydrothermal synthesis includes the following steps: the mixed solution is transferred to a high-pressure reactor lined with polytetrafluoroethylene, with a filling degree of 75%, sealed and placed in an oven, heated to 170°C at a rate of 4°C / min, and held at that temperature for 18 hours. After the reaction is completed, it is cooled to room temperature at a rate of 0.7°C / min, the reaction product is taken out, and centrifuged at 4000 r / min for 7 minutes to separate a white precipitate.

[0052] Step 3, ion exchange, includes the following steps: the precipitate obtained by hydrothermal synthesis is redispersed in deionized water at a solid-liquid ratio of 1:15, acid solution is added, the pH is slowly adjusted to 3, and the mixture is stirred at 300 r / min for 2 hours using a magnetic stirrer with the stirring temperature controlled at 30℃. After that, the mixture is filtered using a vacuum filtration device to obtain the ion-exchanged product.

[0053] Step four post-processing includes the following steps: During washing, the product is repeatedly rinsed with deionized water 4 times until the pH of the filtrate is 7.0. During drying, the product is placed in a vacuum drying oven and dried at 100°C for 4 hours while maintaining a vacuum of -0.09 MPa. During activation, the dried product is placed in a muffle furnace and heated to 400°C at a rate of 5°C / min. It is then calcined for 3 hours and then naturally cooled to obtain the final titanium-based lithium adsorbent.

[0054] The functional additive crown ether or its derivatives are 18-crown-6 or benzo-15-crown-5. The pretreatment method includes: dissolving the crown ether in acetone at a concentration of 7%, sonicating at 50°C for 30 minutes with an ultrasonic power of 150W, then evaporating to remove the acetone to obtain purified crown ether, and then mixing it with a titanium source.

[0055] In step four, during the activation process, a structural stabilizer is also added. The structural stabilizer is a silane coupling agent or a titanate coupling agent, and the amount added is 0.5% of the weight of the adsorbent. It is sprayed on the surface of the dried product before calcination, mixed evenly, and then calcined together.

[0056] The method for adding the structural stabilizer includes: dissolving silane coupling agent KH-550 or titanate coupling agent NDZ-101 in ethanol at a concentration of 3%, and uniformly spraying it onto the dried product at a pressure of 0.2 MPa using a spraying device, with a spraying amount of 1 mL per gram of product, followed by aging at room temperature for 1.5 hours, and then calcining.

[0057] The preparation method also includes step five: surface modification treatment, in which the activated adsorbent is immersed in a surface modification solution, which is composed of silica gel and lithium selective ligands, with a mass ratio of silica gel to ligand of 1:2, an immersion time of 3 hours, and a temperature of 60°C. After that, it is taken out, washed and dried. The lithium selective ligands are azacrown ethers or phosphate ester compounds.

[0058] Its composition is mainly lithium titanate, with crown ether groups and silane coating on the surface. It has a nanoporous structure with a pore size distribution of 6 nm and a specific surface area of ​​300 m². 2 / g, with an adsorption capacity of 40mg / g for lithium ions, and a selectivity coefficient of 70 for lithium in low-mineralized water bodies. Low-mineralized water bodies refer to water bodies with a mineralization of less than 500mg / L, including river water, lake water, or groundwater.

[0059] Example 3: An embodiment of the present invention provides a titanium-based lithium adsorbent for low-salinity water and its preparation method, comprising the following steps:

[0060] Step 1: Precursor preparation. Select a titanium source, a lithium source, and a functional additive to prepare a mixed solution. The titanium source is tetrabutyl titanate, the lithium source is lithium carbonate, the molar ratio of titanium to lithium is 1:1.8, and the functional additive is a crown ether or its derivative, added at 5% of the weight of the titanium source.

[0061] Step 2: Hydrothermal synthesis. The mixed solution is transferred to a high-pressure reactor and reacted at 200°C for 24 hours. During the reaction, the heating rate is controlled at 5°C / min. After the reaction, the mixture is allowed to cool naturally to room temperature.

[0062] Step 3: Ion exchange. The hydrothermal products are treated with an acid solution, such as hydrochloric acid or sulfuric acid, with a concentration of 0.5 mol / L. The pH is adjusted to 4, and the mixture is stirred at 40°C for 3 hours to complete the ion exchange.

[0063] Step 4: Post-treatment, including washing, drying and activation. First, wash with deionized water until neutral, then dry at 120℃ for 6 hours, and finally calcine at 500℃ for 4 hours to obtain titanium-based lithium adsorbent.

[0064] In step one, the mixed solution also includes a dispersant, which is polyvinylpyrrolidone or polyethylene glycol, and the amount added is 2% of the weight of the titanium source;

[0065] Step 1, the preparation of the precursor, includes the following steps: Tetrabutyl titanate is slowly added to anhydrous ethanol at a mass ratio of 1:5, and stirred at 500 r / min for 20 minutes to form a homogeneous titanium source solution. At the same time, lithium carbonate is dissolved in deionized water at a mass ratio of 1:15, and stirred until completely dissolved. Then, the titanium source solution and the lithium source solution are mixed, functional additives and dispersants are added, and the mixture is stirred at 600 r / min for 60 minutes to obtain a mixed solution. The pH of the mixed solution is controlled at 9 and adjusted using ammonia or sodium hydroxide.

[0066] Step 2 hydrothermal synthesis includes the following steps: the mixed solution is transferred to a high-pressure reactor lined with polytetrafluoroethylene, with a filling degree of 80%, and after sealing, it is placed in an oven and heated to 200°C at a rate of 5°C / min, and kept at that temperature for 24 hours. After the reaction is completed, it is cooled to room temperature at a rate of 1°C / min, the reaction product is taken out, and centrifuged at 5000r / min for 10 minutes to separate a white precipitate.

[0067] Step 3, ion exchange, includes the following steps: the precipitate obtained by hydrothermal synthesis is redispersed in deionized water at a solid-liquid ratio of 1:20, acid solution is added, the pH is slowly adjusted to 4, and the mixture is stirred at 400 r / min for 3 hours using a magnetic stirrer with the stirring temperature controlled at 40℃. After that, the mixture is filtered using a vacuum filtration device to obtain the ion-exchanged product.

[0068] Step four post-processing includes the following steps: During washing, rinse repeatedly with deionized water 3-5 times until the pH of the filtrate is 7.5. During drying, place the product in a vacuum drying oven and dry at 120℃ for 6 hours while maintaining the vacuum at -0.1MPa. During activation, place the dried product in a muffle furnace and calcine it at 8℃ / min to 500℃ for 4 hours, followed by natural cooling to obtain the final titanium-based lithium adsorbent.

[0069] The functional additive crown ether or its derivatives are 18-crown-6 or benzo-15-crown-5. The pretreatment method includes: dissolving the crown ether in acetone at a concentration of 10%, sonicating at 60°C for 40 minutes with an ultrasonic power of 200W, then evaporating to remove the acetone to obtain purified crown ether, and then mixing it with a titanium source.

[0070] In step four, during the activation process, a structural stabilizer is also added. The structural stabilizer is a silane coupling agent or a titanate coupling agent, and the amount added is 1% of the weight of the adsorbent. It is sprayed on the surface of the dried product before calcination, mixed evenly, and then calcined together.

[0071] The method of adding the structural stabilizer includes: dissolving silane coupling agent KH-550 or titanate coupling agent NDZ-101 in ethanol at a concentration of 5%, and uniformly spraying it onto the dried product at a pressure of 0.3 MPa using a spraying device, with a spraying amount of 2 mL per gram of product, followed by aging at room temperature for 2 hours, and then calcining.

[0072] The preparation method also includes step five: surface modification treatment, in which the activated adsorbent is immersed in a surface modification solution, which is composed of silica gel and lithium selective ligands, with a mass ratio of silica gel to ligand of 1:3, an immersion time of 4 hours, and a temperature of 70°C. After that, it is taken out, washed and dried. The lithium selective ligands are azacrown ethers or phosphate ester compounds.

[0073] Its composition is mainly lithium titanate, with crown ether groups and silane coating on the surface. It has a nanoporous structure with a pore size distribution of 10 nm and a specific surface area of ​​400 m². 2 / g, with an adsorption capacity of 60mg / g for lithium ions, and a selectivity coefficient of 100 for lithium in low-mineralized water bodies. Low-mineralized water bodies refer to water bodies with a mineralization of less than 500mg / L, including river water, lake water, or groundwater.

[0074] Comparative Example 1: The difference between this comparative example and Example 1 is that no crown ether functional additive was added when preparing the precursor in this comparative example.

[0075] Comparative Example 2: The difference between this comparative example and Example 2 is that no structural stabilizer was added during the post-processing of this comparative example.

[0076] Comparative Example 3: The difference between this comparative example and Example 3 is that this comparative example did not undergo surface modification treatment.

[0077] Comparative Example 4: The difference between this comparative example and Example 3 is that no dispersant was added when preparing the precursor in this comparative example.

[0078] The performance of the titanium-based lithium adsorbents prepared in Examples 1-3 and Comparative Examples 1-4 was tested. The test items and methods are as follows:

[0079] Lithium adsorption capacity test: A simulated low-mineralization water body was prepared with an initial lithium ion concentration of 20 mg / L and background ion Na+. + , K + Ca 2+ Mg 2+ The concentrations of all solutions were 10 times that of lithium ions. 100 mL of solution was taken, 0.1 g of adsorbent was added, and the solution was shaken at 25 °C and 150 r / min for 24 hours to reach adsorption equilibrium. After that, the solution was sampled and filtered. The lithium ion concentration in the filtrate was determined by atomic absorption spectrometry, and the equilibrium adsorption capacity was calculated.

[0080] Selectivity coefficient test: In the above adsorption equilibrium experiment, the Na content in the filtrate was simultaneously measured. + , K + Ca 2+ Mg 2+ The concentration of the adsorbent was calculated to determine the effect of the adsorbent on Li. + The selectivity coefficient relative to each interfering ion.

[0081] Cycle life test: The adsorbent after saturation adsorption was desorbed with 0.5 mol / L hydrochloric acid solution, washed with deionized water until neutral, and then dried. This is one cycle. The adsorption-desorption cycle experiment was repeated, and the number of cycles required to reduce the adsorption capacity to 80% of the initial capacity was recorded.

[0082] Specific surface area and pore size analysis: The nitrogen adsorption-desorption method was used to conduct the test at liquid nitrogen temperature. The specific surface area was calculated using the BET model and the pore size distribution was calculated using the BJH model.

[0083] The test data of the titanium-based lithium adsorbents prepared in Examples 1-3 and Comparative Examples 1-4 are recorded in the table below:

[0084]

[0085] Comparison and analysis of the data in the table show that the titanium-based lithium adsorbents prepared in Examples 1-3 exhibit significantly superior performance compared to those prepared in Comparative Examples 1-4. This indicates that by constructing a stable crystal framework using a hydrothermal synthesis combined with high-temperature calcination activation, and by introducing structural stabilizers for surface reinforcement, the physicochemical stability of the adsorbent in mild to weakly acidic water can be enhanced. This solves the problem of adsorbent framework collapse or loss of active sites due to long-term use, ensuring the structural integrity and lifespan of the adsorbent for recycling in low-mineralization water, thereby improving the economy and reliability of the lithium extraction process. Furthermore, by adding crown ether functional additives to the precursor and performing surface modification treatment in the later stage, the specific recognition of lithium ions by the crown ether groups is utilized... The complexing ability enhances the selectivity of the adsorbent for lithium ions in low-mineralized water bodies rich in competitive cations such as sodium, potassium, calcium, and magnesium. This solves the problem of decreased selectivity caused by interference from coexisting ions, enabling the adsorbent to accurately capture lithium ions and improving the purity and efficiency of lithium extraction from complex water bodies. By creating dedicated lithium vacancies through ion exchange and synergistically controlling the preparation process to obtain a high specific surface area and nanoporous structure, the adsorbent can achieve rapid adsorption and high capacity loading of lithium ions in low-lithium concentration environments. This solves the problems of slow kinetic rates and low adsorption capacity of traditional adsorbents in low-concentration water bodies, ensuring that the adsorbent can maintain efficient dynamic adsorption performance even in low-mineralized water bodies, thus enhancing the practical value and extraction effect of this titanium-based lithium adsorbent.

[0086] By comparing and analyzing the relevant data in the table, it can be seen that the titanium-based lithium adsorbent prepared by the present invention has a high lithium adsorption capacity and excellent selectivity when facing low-mineralized water bodies. At the same time, it exhibits good structural stability and recycling performance. This shows that the titanium-based lithium adsorbent and its preparation method for low-mineralized water bodies provided by the present invention have superior comprehensive performance.

[0087] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0088] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a titanium-based lithium adsorbent for low-mineralized water bodies, characterized in that, Includes the following steps: Step 1: Precursor preparation. Select a titanium source, a lithium source, and a functional additive to prepare a mixed solution. The titanium source is tetrabutyl titanate, and the lithium source is lithium carbonate. The molar ratio of titanium to lithium is 1:1.2 to 1:1.

8. The functional additive is a crown ether or its derivative, and the amount added is 1%-5% of the weight of the titanium source. Step 2: Hydrothermal synthesis. The mixed solution is transferred to a high-pressure reactor and reacted at 150-200℃ for 12-24 hours. During the reaction, the heating rate is controlled at 2-5℃ / min. After the reaction, the mixture is allowed to cool naturally to room temperature. Step 3: Ion exchange. The hydrothermal products are treated with an acid solution, such as hydrochloric acid or sulfuric acid, with a concentration of 0.1-0.5 mol / L. The pH is adjusted to 2-4, and the mixture is stirred at 25-40℃ for 1-3 hours to complete the ion exchange. Step 4: Post-treatment, including washing, drying and activation. First, wash with deionized water until neutral, then dry at 80-120℃ for 2-6 hours, and finally calcine at 300-500℃ for 2-4 hours to obtain titanium-based lithium adsorbent. Step 5: Surface modification treatment. The activated adsorbent is immersed in a surface modification solution, which is composed of silica gel and lithium selective ligands. The mass ratio of silica gel to ligands is 1:1 to 1:

3. The immersion time is 2-4 hours and the temperature is 50-70℃. After that, it is taken out, washed and dried. The lithium selective ligands are azacrown ethers or phosphate esters. In step one, the mixed solution also includes a dispersant, which is polyvinylpyrrolidone or polyethylene glycol, and the amount added is 0.5%-2% of the weight of the titanium source; In the activation process of step four, a structural stabilizer is also added. The structural stabilizer is a silane coupling agent or a titanate coupling agent, and the amount added is 0.1%-1% of the weight of the adsorbent. It is sprayed on the surface of the dried product before calcination, mixed evenly, and then calcined together.

2. The method for preparing a titanium-based lithium adsorbent for low-mineralized water bodies according to claim 1, characterized in that, The precursor preparation in step one includes the following steps: Tetrabutyl titanate is slowly added to anhydrous ethanol at a mass ratio of 1:3 to 1:5, and stirred at 200-500 r / min for 10-20 minutes to form a homogeneous titanium source solution. Simultaneously, lithium carbonate is dissolved in deionized water at a mass ratio of 1:10 to 1:15, and stirred until completely dissolved. Then, the titanium source solution and lithium source solution are mixed, functional additives and dispersants are added, and the mixture is stirred at 300-600 r / min for 30-60 minutes to obtain a mixed solution. The pH of the mixed solution is controlled at 7-9, and adjusted using ammonia or sodium hydroxide.

3. The method for preparing a titanium-based lithium adsorbent for low-mineralized water bodies according to claim 1, characterized in that, The hydrothermal synthesis in step two includes the following steps: the mixed solution is transferred to a high-pressure reactor lined with polytetrafluoroethylene, with a filling degree of 70%-80%, and after sealing, it is placed in an oven and heated to 150-200℃ at a rate of 2-5℃ / min, and kept at that temperature for 12-24 hours. After the reaction is completed, it is cooled to room temperature at a rate of 0.5-1℃ / min, the reaction product is taken out, and centrifuged at 3000-5000r / min for 5-10 minutes to separate a white precipitate.

4. The method for preparing a titanium-based lithium adsorbent for low-mineralization water bodies according to claim 1, characterized in that, Step three, ion exchange, includes the following steps: redispersing the precipitate obtained by hydrothermal synthesis in deionized water at a solid-liquid ratio of 1:10 to 1:20, adding acid solution, slowly adjusting the pH to 2-4, stirring with a magnetic stirrer at 200-400 r / min for 1-3 hours, controlling the stirring temperature at 25-40℃, and then filtering with a vacuum filtration device to obtain the ion-exchanged product.

5. The method for preparing a titanium-based lithium adsorbent for low-mineralization water bodies according to claim 1, characterized in that, The post-processing in step four includes the following steps: During washing, the product is repeatedly rinsed with deionized water 3-5 times until the pH of the filtrate is 6.5-7.5; during drying, the product is placed in a vacuum drying oven and dried at 80-120℃ for 2-6 hours, with the vacuum degree maintained at -0.08 to -0.1MPa; during activation, the dried product is placed in a muffle furnace and heated to 300-500℃ at 3-8℃ / min, calcined for 2-4 hours, and then naturally cooled to obtain the final titanium-based lithium adsorbent.

6. The method for preparing a titanium-based lithium adsorbent for low-mineralization water bodies according to claim 1, characterized in that, The functional adjuvant crown ether or its derivative is 18-crown-6 or benzo-15-crown-5. Its pretreatment method includes: dissolving the crown ether in acetone at a mass concentration of 5%-10%, ultrasonically treating it at 40-60°C for 20-40 minutes with an ultrasonic power of 100-200W, then evaporating to remove the acetone to obtain purified crown ether, and then mixing it with a titanium source.

7. The method for preparing a titanium-based lithium adsorbent for low-mineralization water bodies according to claim 1, characterized in that, The method for adding the structure stabilizer includes: dissolving silane coupling agent KH-550 or titanate coupling agent NDZ-101 in ethanol at a mass concentration of 1%-5%, and uniformly spraying it onto the dried product at a pressure of 0.1-0.3 MPa using a spraying device, with a spraying amount of 0.5-2 mL per gram of product, followed by aging at room temperature for 1-2 hours, and then calcining.

8. A titanium-based lithium adsorbent for low-mineralized water, prepared by the method described in any one of claims 1-7, characterized in that, Its composition is mainly lithium titanate, with crown ether groups and silane coating on the surface. It has a nanoporous structure with a pore size distribution of 2-10 nm and a specific surface area of ​​150-400 m². 2 / g, with an adsorption capacity of 25-60mg / g for lithium ions, and a selectivity coefficient of 50-100 for lithium in low-mineralized water bodies, wherein the low-mineralized water bodies refer to water bodies with a mineralization of less than 500mg / L, including river water, lake water or groundwater.

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