Methods for synthesizing titanium-based lithium-ion sieves, titanium-based lithium-ion sieves and their applications

Abstract

This invention provides a method for synthesizing titanium-based lithium-ion sieves, the titanium-based lithium-ion sieves themselves, and their applications, specifically relating to the field of ion sieve preparation technology. The method for synthesizing titanium-based lithium-ion sieves includes the following steps: A) Activating a precursor β-Li₂TiO₃ slurry by adding an organic acid solution; separating the activated slurry into solid and liquid components to obtain titanium-based lithium-ion sieve β-H₂TiO₃ and an acidic activation solution; B) Adding lithium hydroxide solution to the acidic activation solution to adjust its pH to neutral, obtaining a neutral activation solution; C) Concentrating the neutral activation solution to 40-60% of its original volume, obtaining a concentrated activation solution and recycled water; D) Adding titanium dioxide to the concentrated activation solution and stirring until homogeneous, obtaining a mixed slurry; microwaving the mixed slurry to obtain a solid mixture; then calcining the solid mixture to obtain the precursor β-Li₂TiO₃, repeating steps A-D.

Description

Technical Field

[0001] This invention relates to the field of ion sieve preparation technology, and in particular to a method for synthesizing titanium-based lithium ion sieves, titanium-based lithium ion sieves, and their applications. Background Technology

[0002] Lithium metal is widely used in rechargeable batteries, glass, ceramics, alloys, lubricants, and pharmaceuticals. Rechargeable lithium batteries, in particular, have received widespread attention in recent years as a primary power source for hybrid and electric vehicles. Statistics show that lithium resources in salt lake brines account for approximately 70% to 80% of total lithium resources. Extracting lithium from salt lake brines is currently the main focus of lithium salt production. Domestic lithium resources are largely distributed in major salt lakes in Northwest my country, with a concentration in the Qinghai-Tibet Plateau region. Qinghai salt lakes generally exhibit a high magnesium-to-lithium ratio and low lithium content. Adsorption is a lithium extraction technology with significant advantages from both environmental and economic perspectives, especially for extracting lithium from low-grade, high-magnesium-to-lithium ratio brines and seawater. Adsorption offers high selectivity, can handle low-concentration brines, and enables clean production. Furthermore, the process is simple and has a high recovery rate, making it significantly more advantageous than other methods from both economic and environmental perspectives. It is particularly suitable for extracting lithium from salt lake water. The process involves first using a lithium adsorbent to adsorb and extract lithium ions from the brine, and then eluting the lithium ions to separate them from other ions.

[0003] Currently, lithium extraction adsorbents are mainly classified into four categories: manganese-based, titanium-based, aluminum-based, and doped adsorbents. At present, aluminum-based and titanium-based lithium adsorbents are the two main types that have achieved industrial application. Titanium-based lithium ion sieve β-H₂TiO₃ is obtained by activating the precursor β-Li₂TiO₃ with an acidic solution. The activation reaction is β-Li₂TiO₃ + 2H₂O. + =β-H2TiO3+2Li + The precursor β-Li₂TiO₃ is synthesized at high temperature using lithium sources (lithium carbonate, lithium hydroxide, lithium acetate, lithium citrate, etc.) and titanium sources (metatitanic acid, orthotitanic acid, titanium dioxide, etc.). Lithium sources account for over 90% of the raw material cost. To reduce the cost of synthesizing the precursor β-Li₂TiO₃, it is necessary to reduce the cost of obtaining lithium source raw materials. This involves addressing the high-purity lithium-containing acid solution (Li₂TiO₃) formed during the activation process of the precursor β-Li₂TiO₃. + and H + The current method for treating these lithium-containing acid solutions involves a cumbersome purification process (concentration, precipitation, separation, drying, and pulverization) to convert them into solid lithium hydroxide or lithium carbonate. This process is cumbersome, time-consuming, inefficient, and costly.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] One of the objectives of this invention is to provide a method for synthesizing titanium-based lithium-ion sieves, aiming to solve the technical problems of cumbersome, time-consuming, inefficient, and costly post-processing of high-purity lithium-containing acid solutions in the prior art.

[0006] The second objective of this invention is to provide a titanium-based lithium ion sieve.

[0007] The third objective of this invention is to provide an application of a titanium-based lithium ion sieve.

[0008] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0009] The first aspect of the present invention provides a method for synthesizing titanium-based lithium-ion sieves, comprising the following steps:

[0010] A. An organic acid solution is added to the precursor β-Li2TiO3 slurry at a flow rate of 50-100 L / h for activation; the activated slurry is then subjected to solid-liquid separation to obtain titanium-based lithium ion sieve β-H2TiO3 and acidic activation solution;

[0011] B. Add lithium hydroxide solution to the acidic activation solution to adjust the pH of the acidic activation solution to neutral to obtain a neutral activation solution;

[0012] C. Concentrate the volume of the neutral activating solution to 40-60% of its original volume to obtain concentrated activating solution and recycled water. The recycled water is reused in the preparation of precursor β-Li2TiO3 slurry or organic acid solution.

[0013] D. Add titanium dioxide to the concentrated activation solution and stir evenly to obtain a mixed slurry; microwave dry the mixed slurry to obtain a solid mixture; then keep the solid mixture at 400-500℃ for 3-5h, and finally raise the temperature to 800-900℃ and keep it for 0.5-1h to obtain the precursor β-Li2TiO3, and repeat steps A and D.

[0014] Furthermore, in step D, after adding titanium dioxide, the molar ratio of Li to Ti in the mixed slurry is 1.8-2.3.

[0015] Preferably, in step D, the water content of the solid mixture is 1-5%.

[0016] Furthermore, the organic acid in the organic acid solution includes at least one of formic acid, acetic acid, oxalic acid, malonic acid, fumaric acid, maleic acid, citric acid, malic acid, and tartaric acid, preferably citric acid.

[0017] Further, in step A, the content of precursor β-Li2TiO3 in the precursor β-Li2TiO3 slurry is 55-75 wt.%.

[0018] Preferably, the organic acid content in the organic acid solution is 50-62.5 wt.%.

[0019] Preferably, the temperature of the organic acid solution is 50-70°C.

[0020] Further, in step A, the amount of organic acid solution added is 1.4-3 times the mass of the precursor β-Li2TiO3 slurry.

[0021] Preferably, in step A, the activation time is 2-5 hours.

[0022] Furthermore, in step A, the solid-liquid separation method includes centrifugation, filtration, and sedimentation, with filtration being preferred.

[0023] Preferably, the filtration method is plate and frame filtration.

[0024] Furthermore, in step B, the pH of the acidic activation solution is adjusted to 6.5-7.

[0025] Furthermore, in step C, the concentration is achieved through evaporation.

[0026] A second aspect of the present invention provides a titanium-based lithium-ion sieve synthesized by the method described above.

[0027] A third aspect of the present invention provides the application of the aforementioned titanium-based lithium-ion sieve as a lithium extraction adsorbent in the production of lithium salts.

[0028] Compared with the prior art, the present invention has at least the following beneficial effects:

[0029] The method for synthesizing titanium-based lithium-ion sieves provided by this invention uses an organic acid solution to activate the precursor β-Li₂TiO₃, obtaining titanium-based lithium-ion sieve β-Li₂TiO₃ while simultaneously producing an activation solution (a mixed solution of organic acid and lithium organic acid). By neutralizing and concentrating the activation solution, the concentrated solution is then used as the lithium source raw material for synthesizing the titanium-based lithium-ion sieve precursor β-Li₂TiO₃. This method solves the technical problems of cumbersome, time-consuming, inefficient, and costly activation solution processing, as well as the high cost of the β-Li₂TiO₃ precursor lithium source. It achieves resource reuse, has a simple process, and is easy to industrialize, showing great promise for the large-scale production of titanium-based lithium-ion sieves.

[0030] The titanium-based lithium ion sieve β-H2TiO3 provided by this invention has a lower preparation cost, broadens the application field of titanium-based lithium ion sieve β-H2TiO3, and promotes the development of downstream industries.

[0031] The titanium-based lithium ion sieve β-H2TiO3 provided by this invention serves as a lithium extraction adsorbent, providing a lower-cost raw material for lithium salt production, reducing the production cost of lithium salts, and saving resources. Attached Figure Description

[0032] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0033] Figure 1 This is a schematic diagram of the process for synthesizing titanium-based lithium-ion sieves in Example 1 of the present invention;

[0034] Figure 2 SEM images of precursor A, titanium-based lithium ion sieve β-H2TiO3, and precursor B used in Example 1 of this invention;

[0035] Figure 3 XRD patterns of precursor A, titanium-based lithium ion sieve β-H2TiO3, and precursor B used in Example 1 of this invention;

[0036] Figure 4 SEM images of precursor A, titanium-based lithium ion sieve β-H2TiO3, and precursor B used in Example 2 of this invention;

[0037] Figure 5 XRD patterns of precursor A, titanium-based lithium ion sieve β-H2TiO3, and precursor B used in Example 2 of this invention;

[0038] Figure 6 This is a bar chart showing the adsorption capacity of the product obtained in 20 tests in brine, as a verification example of the present invention.

[0039] Figure 7 XRD pattern of titanium-based lithium ion sieve β-H2TiO3 provided in Example 3 of this invention;

[0040] Figure 8 XRD pattern of titanium-based lithium ion sieve β-H2TiO3 provided in Example 4 of this invention;

[0041] Figure 9 The XRD pattern of the titanium-based lithium ion sieve β-H2TiO3 provided in Example 5 of this invention. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0043] In the following, the terms “comprising,” “having,” and their cognates, which may be used in various embodiments of the invention, are intended only to indicate a particular feature, number, step, operation, element, component, or combination thereof, and should not be construed as excluding, firstly, the presence of one or more other features, numbers, steps, operations, elements, components, or combinations thereof, or adding the possibility of one or more features, numbers, steps, operations, elements, components, or combinations thereof.

[0044] Furthermore, the terms "first," "second," and "third" are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0045] The first aspect of the present invention provides a method for synthesizing titanium-based lithium-ion sieves, comprising the following steps:

[0046] A. An organic acid solution is added to the precursor β-Li2TiO3 slurry at a flow rate of 50-100 L / h for activation; the activated slurry is then subjected to solid-liquid separation to obtain titanium-based lithium ion sieve β-H2TiO3 and acidic activation solution;

[0047] B. Add lithium hydroxide solution to the acidic activation solution to adjust the pH of the acidic activation solution to neutral to obtain a neutral activation solution;

[0048] C. Concentrate the volume of the neutral activating solution to 40-60% of its original volume to obtain concentrated activating solution and recycled water. The recycled water is reused in the preparation of precursor β-Li2TiO3 slurry or organic acid solution.

[0049] D. Add titanium dioxide to the concentrated activation solution and stir evenly to obtain a mixed slurry; microwave dry the mixed slurry to obtain a solid mixture; then keep the solid mixture at 400-500℃ for 3-5h, and finally raise the temperature to 800-900℃ and keep it for 0.5-1h to obtain the precursor β-Li2TiO3, and repeat steps A and D.

[0050] The method for synthesizing titanium-based lithium-ion sieves provided by this invention uses an organic acid solution to activate the precursor β-Li₂TiO₃, obtaining titanium-based lithium-ion sieve β-Li₂TiO₃ while simultaneously producing an activation solution (a mixed solution of organic acid and lithium organic acid). By neutralizing and concentrating the activation solution, the concentrated solution is then used as the lithium source raw material for synthesizing the titanium-based lithium-ion sieve precursor β-Li₂TiO₃. This method solves the technical problems of cumbersome, time-consuming, inefficient, and costly activation solution processing, as well as the high cost of the β-Li₂TiO₃ precursor lithium source. It achieves resource reuse, has a simple process, and is easy to industrialize, showing great promise for the large-scale production of titanium-based lithium-ion sieves.

[0051] Specifically, an organic acid solution is used as the activating liquid instead of an HCl solution because the organic acid reacts with the precursor β-Li₂TiO₃ to form lithium organic acid. Lithium organic acid reacts with titanium dioxide at high temperatures to form the precursor β-Li₂TiO₃, carbon dioxide, and water. The reaction proceeds easily and does not produce corrosive gases. However, if an HCl solution is used as the activating liquid, the reaction between the HCl solution and the precursor β-Li₂TiO₃ will result in a side reaction to form LiCl. LiCl is difficult to react with titanium dioxide or metatitanic acid (H₂TiO₃) at high temperatures, and the activating liquid cannot be reused.

[0052] In step A, the β-Li₂TiO₃ precursor slurry is used to react with the organic acid solution, instead of the β-Li₂TiO₃ precursor powder being reacted directly with the organic acid solution. This is because the β-Li₂TiO₃ precursor powder, after being made into a slurry, helps to quickly reduce the acidity of the organic acid and avoids high concentrations of H₂. + Dissolution of the precursor β-Li2TiO3.

[0053] It should be noted that in step A, the titanium-based lithium ion sieve β-H2TiO3 obtained by solid-liquid separation is in a wet solid state. Before the product leaves the factory, the wet solid needs to be dried and crushed to obtain the final product.

[0054] In step B, the activation solution is neutralized with LiOH, mainly to treat the organic acid in the activation solution into lithium organic acid. On the one hand, this can increase the concentration of lithium in the solution, and on the other hand, the soluble lithium organic acid can be used as a lithium source to blend with the insoluble TiO2 to obtain a uniformly dispersed blend of lithium and titanium sources. During the high-temperature calcination process, the lithium organic acid generates the precursor β-Li2TiO3. The carbon dioxide and water vapor produced help prevent the agglomeration of the precursor β-Li2TiO3 crystals, resulting in smaller β-Li2TiO3 precursor crystals.

[0055] In step C, the neutral activation solution is evaporated to reduce its total volume by 40%-60%, rather than evaporating all the water. This is because the subsequent blending of the organic lithium acid as a lithium source with insoluble TiO2 also needs to be carried out in an aqueous solution. Therefore, it is not necessary to evaporate all the water from the neutral activation solution, which helps save evaporation costs, shortens evaporation time, and improves economic efficiency and production efficiency. The condensed pure water collected during the evaporation and concentration process is recycled to obtain recovered water, which is reused in the preparation of organic acid solutions and the precursor β-Li2TiO3 slurry, forming a closed-loop use of water resources, reducing water waste and improving economic efficiency.

[0056] In step D, low-temperature, long-time calcination is used to achieve material decomposition and crystal formation, while high-temperature, short-time calcination is used to perfect the growth of defective crystals. The solid mixture is transferred to a roller kiln and held at 400-500℃ for 3-5 hours, then heated to 800-900℃ and held for 0.5-1 hour. This segmented isothermal operation is to obtain a high-performance product. Using lithium organic acid as both the lithium source and the TiO2 titanium source, the reaction at a low temperature of 400-500℃ avoids carbonization caused by excessively rapid decomposition of lithium organic acid at high temperatures, which results in a black carbon layer in the product. This carbon layer reduces the β-Li2TiO3 crystals, thus reducing the Ti... 4+ Restored to Ti 3+ To disrupt the chemical structure of β-Li₂TiO₃ crystals, a prolonged holding time at a low temperature of 400-500℃ for 3-5 hours is beneficial for controlling the decomposition rate of lithium organic acid into carbon dioxide and water vapor, thereby improving the yield of β-Li₂TiO₃ crystals. Then, the temperature is raised to a high temperature of 800-900℃ and held for a short time of 0.5-1 hour. This operation is necessary because at low temperatures, due to the lower energy, the generated β-Li₂TiO₃ crystals have more defects. In the high-temperature region, these defective β-Li₂TiO₃ crystals will use high energy to repair these defects. The holding time should not be too long, because if the holding time is too long, the β-Li₂TiO₃ crystals will use high energy to grow, which is not conducive to improving the adsorption capacity.

[0057] Further, in step D, after adding titanium dioxide, the molar ratio of Li to Ti in the mixed slurry is 1.8-2.3. When the molar ratio of Li to Ti is greater than 2.3, due to the high activity of lithium ions, excessive lithium ions at high temperatures lead to an excessively fast reaction rate, which can easily cause the synthesized titanium-based lithium ion sieve to overheat and clump, resulting in larger crystal particles, a decrease in specific surface area, and a sharp drop in adsorption capacity. When the molar ratio of Li to Ti is less than 1.8, the synthesized titanium-based lithium ion sieve crystals are prone to being impure, containing many impurities, ultimately affecting the adsorption capacity and selectivity of the material.

[0058] In specific implementations of the present invention, typically but not limitingly, the molar ratio of Li to Ti in the mixed slurry can be, for example, 1.8, 1.9, 2.0, 2.1, 2.2 or 2.3.

[0059] Preferably, in step D, the moisture content of the solid mixture is 1-5%. Using microwave drying to dehydrate the lithium and titanium compound slurry can lead to significant cost increases if the moisture content of the dehydrated solid mixture is <1%, hindering cost control in production. Conversely, if the moisture content is >5%, a large amount of water vapor is generated during calcination in the roller kiln. This water vapor evaporates, carrying away significant heat and increasing calcination costs. Furthermore, it causes substantial temperature fluctuations in the roller kiln, making temperature control difficult and resulting in a large number of defective products. In specific implementations of this invention, typically but not limitingly, the moisture content of the solid mixture can be, for example, 1%, 2%, 3%, 4%, or 5%.

[0060] Furthermore, the organic acid in the organic acid solution includes at least one of formic acid, acetic acid, oxalic acid, malonic acid, fumaric acid, maleic acid, citric acid, malic acid, and tartaric acid, preferably citric acid.

[0061] Further, in step A, the content of precursor β-Li2TiO3 in the precursor β-Li2TiO3 slurry is 55-75 wt.%.

[0062] In specific implementations of the present invention, typically but not limitingly, the content of precursor β-Li2TiO3 in the precursor β-Li2TiO3 slurry can be, for example, 55 wt.%, 60 wt.%, 65 wt.%, 70 wt.%, or 75 wt.%.

[0063] Preferably, the organic acid content in the organic acid solution is 50-62.5 wt.%.

[0064] In specific implementations of the present invention, typically but not limitingly, the content of organic acid in the organic acid solution can be, for example, 50 wt.%, 52 wt.%, 54 wt.%, 58 wt.%, 60 wt.%, or 62.5 wt.%.

[0065] Preferably, the temperature of the organic acid solution is 50-70°C. The organic acid is dissolved in deionized water at a temperature of 50-70°C because the solubility of organic acids in water increases with increasing temperature. Therefore, deionized water at a temperature of 50-70°C is used to dissolve the organic acid in order to reduce the amount of deionized water used.

[0066] In specific implementations of the present invention, typically but not limitingly, the temperature of the organic acid solution can be, for example, 50°C, 55°C, 60°C, 65°C, or 70°C.

[0067] Further, in step A, the amount of organic acid solution added is 1.4-3 times the mass of the precursor β-Li2TiO3 slurry.

[0068] Preferably, in step A, the activation time is 2-5 hours.

[0069] Furthermore, in step A, the solid-liquid separation method includes centrifugation, filtration, and sedimentation, with filtration being preferred.

[0070] Preferably, the filtration method is plate and frame filtration.

[0071] Further, in step B, the pH of the acidic activation solution is adjusted to 6.5-7. This is because, in the precursor activation process, an excess of organic acid is added to improve activation efficiency. By adding a saturated lithium hydroxide solution, the pH of the acidic activation solution is adjusted from 2-4 to 6.5-7. This serves two purposes: firstly, to neutralize the residual organic acid, preventing waste and corrosion / pollution of the equipment and environment; and secondly, to obtain a higher concentration of organic lithium acid. Increasing the lithium source concentration is beneficial for improving the production efficiency of titanium-based lithium-ion sieves.

[0072] In step B, when adjusting the pH by adding lithium hydroxide solution to the acidic activation solution, it is preferable to use saturated lithium hydroxide to reduce the water content in the system and reduce the energy consumption of subsequent concentration.

[0073] Furthermore, in step C, the concentration is achieved through evaporation.

[0074] A second aspect of the present invention provides a titanium-based lithium-ion sieve synthesized by the method described above.

[0075] The titanium-based lithium ion sieve β-H2TiO3 provided by this invention has a lower preparation cost, broadens the application field of titanium-based lithium ion sieve β-H2TiO3, and promotes the development of downstream industries.

[0076] A third aspect of the present invention provides the application of the aforementioned titanium-based lithium-ion sieve as a lithium extraction adsorbent in the production of lithium salts.

[0077] The titanium-based lithium ion sieve β-H2TiO3 provided by this invention serves as a lithium extraction adsorbent, providing a lower-cost raw material for lithium salt production, reducing the production cost of lithium salts, and saving resources.

[0078] The present invention is further illustrated below with specific embodiments and comparative examples. However, it should be understood that these embodiments are merely for illustrative purposes and should not be construed as limiting the invention in any way. Unless otherwise specified, the raw materials used in the embodiments and comparative examples of the present invention were carried out under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0079] Example 1

[0080] This embodiment provides a method for synthesizing titanium-based lithium-ion sieves, and the flowchart of the method is shown below. Figure 1 As shown, the specific steps are as follows:

[0081] 1. Preparation of citric acid solution: Dissolve 400 kg of citric acid (C6H8O7) in 300 kg of deionized water at 50 °C to obtain a citric acid solution at 50 °C, which is then ready for use.

[0082] 2. Preparation of precursor β-Li2TiO3 slurry: [The following text appears to be incomplete and requires further context: "in 2m..."] 3 100 kg of deionized water was added to a mechanical mixing tank. Under stirring conditions, 250 kg of precursor β-Li2TiO3 (precursor A) powder was added to the mixing tank and stirred for 0.5 h to obtain a uniform precursor β-Li2TiO3 slurry for later use.

[0083] 3. Precursor activation: Under stirring conditions, the 50℃ citric acid solution prepared above is added to the β-Li2TiO3 precursor slurry at a flow rate of 50L / h. After all the citric acid solution is added, stirring continues for 2 hours. The precursor β-Li2TiO3 is converted into titanium-based lithium ion sieve β-H2TiO3 (β-Li2TiO3+C6H8O7=β-H2TiO3+C6H6O7Li2). The activated slurry in the stirring tank is transferred to a plate and frame filter press for solid-liquid separation to obtain wet solid titanium-based lithium ion sieve β-H2TiO3 and acidic activation solution (a mixture of lithium citrate and citric acid, pH about 4).

[0084] 4. Neutralization of the activation solution: Place the above acidic activation solution in a mechanically stirred tank, and adjust the pH of the acidic activation solution from 4 to 6.5 by adding saturated lithium hydroxide solution. The reaction C6H8O7 + 2LiOH = C6H6O7Li2 + 2H2O will occur, resulting in a neutral activation solution.

[0085] 5. Concentration of Activated Solution: A small triple-effect evaporator (model SJN-500, evaporation efficiency 500 kg / h, steam pressure 0.09 MPa, evaporation temperature 80℃ for the first effect, 70℃ for the second effect, and 60℃ for the third effect) is used to evaporate water from the neutral activated solution, reducing the total volume of the neutral activated solution by 40% to obtain a concentrated activated solution. The condensed pure water collected in this evaporation and concentration process is reused for the preparation of citric acid solution and the preparation of the precursor β-Li2TiO3 slurry (insufficient water will be added from outside the system), forming a closed-loop use of water resources, reducing water waste and improving economic efficiency.

[0086] 6. Reuse of concentrated activation solution: Take the concentrated activation solution and test the lithium ion concentration using an inductively coupled plasma (ICP) instrument. The concentration is 16.53 g / L. Calculate and add the corresponding mass of rutile titanium dioxide powder to the concentrated activation solution according to the elemental molar ratio of Li:Ti = 1.8. Stir for 3 hours, then microwave dry the mixture to obtain a solid mixture with a water content of 1%. Transfer the solid mixture to a roller kiln and keep it at 400℃ for 3 hours, then raise the temperature to 800℃ and keep it at 800℃ for 0.5 hours to obtain the titanium-based lithium ion sieve precursor β-Li2TiO3 (precursor B). The reaction is: 2C6H6O7Li2 + 2TiO2 + 9O2 = 2Li2TiO3 + 12CO2 + 6H2O.

[0087] Compared to directly purchasing lithium carbonate at 300,000 RMB / ton for the synthesis of the precursor β-Li₂TiO₃ without using activation solution recycling technology, Example 1 reduces raw material costs by 91.5% and total production costs (including lithium source recycling production costs) by 80.2%. These two cost reductions are substantial, resulting in significant economic benefits. The precursor β-Li₂TiO₃ is then activated to obtain titanium-based lithium-ion sieve β-H₂TiO₃, while simultaneously generating an activation solution (a mixed solution of citric acid and lithium citrate). By appropriately neutralizing and concentrating the activation solution, the concentrated solution can be used as the lithium source raw material for synthesizing the titanium-based lithium-ion sieve precursor β-Li₂TiO₃, recycling the entire process and enabling the economical and efficient recycling of lithium source raw materials.

[0088] Figure 2 In the image, 'a' represents the SEM image of precursor A (β-Li₂TiO₃) before activation with citric acid. Figure 2 In the image, b represents a SEM image of a titanium-based lithium-ion sieve β-H₂TiO₃ activated with citric acid. Figure 2 c in the image represents a SEM image of the novel precursor B (β-Li₂TiO₃) synthesized using the activated liquid as a lithium source. Figure 2 It can be seen that the surface morphology of the three powders is not significantly different, and the particle size is approximately 0.5-2 μm.

[0089] Figure 3 In this diagram, 'a' represents the XRD pattern of precursor A (β-Li₂TiO₃) before activation with citric acid. Figure 3 In the figure, b represents the XRD pattern of titanium-based lithium-ion sieve β-H2TiO3 activated with citric acid. Figure 3 In the figure, c represents the XRD pattern of the novel precursor B (β-Li₂TiO₃) synthesized using the activated liquid as a lithium source. Figure 3 The precursor A (β-Li2TiO3) and Figure 3 XRD analysis of the titanium-based lithium-ion sieve β-H2TiO3 showed that after activation of precursor A (β-Li2TiO3), the peaks at (-133), (-206), and (062) disappeared, proving that citric acid can efficiently activate precursor A (β-Li2TiO3), transforming the powder crystal form from β-Li2TiO3 to β-H2TiO3; Figure 3 The precursor A (β-Li2TiO3) and Figure 3 The XRD pattern of precursor B (β-Li2TiO3) shows that the XRD pattern of the new precursor B (β-Li2TiO3) synthesized by recycling the activated liquid as a lithium source is consistent with that of precursor A (β-Li2TiO3). This proves that the technology of this invention, which uses the activated liquid as a lithium source to synthesize the new precursor β-Li2TiO3, is feasible, scientific, and advanced.

[0090] Example 2

[0091] This embodiment provides a method for synthesizing titanium-based lithium-ion sieves, the specific steps of which are as follows:

[0092] 1. Preparation of citric acid solution: Dissolve 500 kg of citric acid (C6H8O7) in 400 kg of deionized water at 70 °C to obtain a citric acid solution at 70 °C, which is then ready for use.

[0093] 2. Preparation of precursor β-Li2TiO3 slurry: [The following text appears to be incomplete and requires further context: "in 2m..."] 3 200 kg of deionized water was added to a mechanical mixing tank. Under stirring conditions, 300 kg of precursor β-Li2TiO3 powder (precursor A) was added to the mixing tank and stirred for 1 h to obtain a uniform precursor β-Li2TiO3 slurry for later use.

[0094] 3. Precursor activation: Under stirring conditions, the 70℃ citric acid solution prepared above is added to the β-Li2TiO3 precursor slurry at a flow rate of 100L / h. After all the citric acid solution has been added, stirring continues for 5h. The precursor β-Li2TiO3 is converted into titanium-based lithium ion sieve β-H2TiO3 (β-Li2TiO3+C6H8O7=β-H2TiO3+C6H6O7Li2). The activated slurry in the stirred tank is transferred to a plate and frame filter press for solid-liquid separation to obtain wet solid titanium-based lithium ion sieve β-H2TiO3 and acidic activation solution (a mixture of lithium citrate and citric acid, pH about 2).

[0095] 4. Neutralization of the activation solution: Place the above acidic activation solution in a mechanically stirred tank, and adjust the pH of the acidic activation solution from 2 to 7 by adding saturated lithium hydroxide solution. The reaction C6H8O7 + 2LiOH = C6H6O7Li2 + 2H2O will occur to obtain a neutral activation solution.

[0096] 5. Concentration of Activated Solution: A small triple-effect evaporator (model SJN-500, evaporation efficiency 500 kg / h, steam pressure 0.20 MPa, evaporation temperature 80℃ for the first effect, 70℃ for the second effect, and 60℃ for the third effect) is used to evaporate water from the neutral activated solution, reducing the total volume of the neutral activated solution by 60% to obtain a concentrated activated solution. The condensed pure water collected during this evaporation and concentration process will be reused for the preparation of citric acid solution and the precursor β-Li2TiO3 slurry (insufficient water will be added from outside the system), forming a closed-loop use of water resources, reducing water waste and improving economic efficiency.

[0097] 6. Reuse of concentrated activation solution: Take the concentrated activation solution and test the lithium ion concentration using an inductively coupled plasma (ICP) instrument. The concentration is 22.56 g / L. Calculate and add the corresponding mass of rutile titanium dioxide powder to the concentrated activation solution according to the elemental molar ratio of Li:Ti = 2.3. Stir for 8 hours, then microwave dry the mixture to obtain a solid mixture with a water content of 5%. Transfer the solid mixture to a roller kiln and keep it at 500℃ for 5 hours, then raise the temperature to 900℃ and keep it at 900℃ for 1 hour to obtain the titanium-based lithium ion sieve precursor β-Li2TiO3 (precursor B). The reaction is 2C6H6O7Li2 + 2TiO2 + 9O2 = 2Li2TiO3 + 12CO2 + 6H2O.

[0098] Compared to directly purchasing lithium carbonate at 300,000 RMB / ton for the synthesis of the precursor β-Li₂TiO₃ without using activation solution recycling technology, the raw material cost decreases by 92.1%, and the total production cost (including lithium source recycling production costs) decreases by 81.4%. These two cost reductions are substantial, resulting in significant economic benefits. The precursor β-Li₂TiO₃ is then activated to obtain titanium-based lithium-ion sieve β-H₂TiO₃, while simultaneously generating an activation solution (a mixed solution of citric acid and lithium citrate). By appropriately neutralizing and concentrating the activation solution, the concentrated solution can be used as the lithium source raw material for synthesizing the titanium-based lithium-ion sieve precursor β-Li₂TiO₃, recycling the entire process and enabling the economical and efficient recycling of lithium source raw materials.

[0099] Figure 4 In the image, 'a' represents the SEM image of precursor A (β-Li₂TiO₃) before activation with citric acid. Figure 4 In the image, b represents a SEM image of a titanium-based lithium-ion sieve β-H₂TiO₃ activated with citric acid. Figure 4 c in the image represents a SEM image of the novel precursor B (β-Li₂TiO₃) synthesized using the activated liquid as a lithium source. Figure 4 It can be seen that the surface morphology of the three powders is not significantly different, and the particle size is approximately 0.5-2 μm.

[0100] Figure 5 In this diagram, 'a' represents the XRD pattern of precursor A (β-Li₂TiO₃) before activation with citric acid. Figure 5 In the figure, b represents the XRD pattern of titanium-based lithium-ion sieve β-H2TiO3 activated with citric acid. Figure 5 In the figure, c represents the XRD pattern of the novel precursor B (β-Li₂TiO₃) synthesized using the activated liquid as a lithium source. Figure 5 The precursor A (β-Li2TiO3) and Figure 5 XRD analysis of the titanium-based lithium-ion sieve β-H2TiO3 showed that after activation of precursor A (β-Li2TiO3), the peaks at (-133), (-206), and (062) disappeared, proving that citric acid can efficiently activate precursor A (β-Li2TiO3), transforming the powder crystal form from β-Li2TiO3 to β-H2TiO3; Figure 5 The precursor A (β-Li2TiO3) and Figure 5 The XRD pattern of precursor B (β-Li2TiO3) shows that the XRD pattern of the new precursor B (β-Li2TiO3) synthesized by recycling the activated liquid as a lithium source is consistent with that of precursor A (β-Li2TiO3). This proves that the technology of this invention, which uses the activated liquid as a lithium source to synthesize the new precursor β-Li2TiO3, is feasible, scientific, and advanced.

[0101] Example 3

[0102] This embodiment provides a method for synthesizing titanium-based lithium-ion sieves, and the flowchart of the method is shown below. Figure 1 As shown, the specific steps are as follows:

[0103] 1. Preparation of citric acid solution: Dissolve 450 kg of citric acid (C6H8O7) in 350 kg of deionized water at 60 °C to obtain a citric acid solution at 60 °C, which is then ready for use.

[0104] 2. Preparation of precursor β-Li2TiO3 slurry: [The following text appears to be incomplete and requires further context: "in 2m..."] 3 150 kg of deionized water was added to a mechanical mixing tank. Under stirring conditions, 280 kg of precursor β-Li2TiO3 powder was added to the mixing tank and stirred for 1 hour to obtain a uniform precursor β-Li2TiO3 slurry for later use.

[0105] 3. Precursor Activation: Under stirring conditions, the prepared 60℃ citric acid solution was added to the β-Li₂TiO₃ precursor slurry at a flow rate of 750 L / h. After all the citric acid solution was added, stirring continued for 2 hours, transforming the β-Li₂TiO₃ precursor into titanium-based lithium-ion sieve β-H₂TiO₃ (β-Li₂TiO₃ + C₆H₈O₇ = β-H₂TiO₃ + C₆H₆O₇Li₂). The activated slurry in the stirred tank was transferred to a plate and frame filter press for solid-liquid separation, yielding wet solid titanium-based lithium-ion sieve β-H₂TiO₃ and an acidic activation solution (a mixture of lithium citrate and citric acid, pH approximately 3). The XRD pattern of the titanium-based lithium-ion sieve β-H₂TiO₃ is as follows. Figure 7 As shown.

[0106] 4. Neutralization of the activation solution: Place the above acidic activation solution in a mechanically stirred tank, and adjust the pH of the acidic activation solution from 3 to 7 by adding saturated lithium hydroxide solution. The reaction C6H8O7 + 2LiOH = C6H6O7Li2 + 2H2O will occur, resulting in a neutral activation solution.

[0107] 5. Concentration of Activated Solution: A small triple-effect evaporator (model SJN-500, evaporation efficiency 500 kg / h, steam pressure 0.09 MPa, evaporation temperature 80℃ for the first effect, 70℃ for the second effect, and 60℃ for the third effect) is used to evaporate water from the neutral activated solution, reducing the total volume of the neutral activated solution by 40% to obtain a concentrated activated solution. The condensed pure water collected in this evaporation and concentration process is reused for the preparation of citric acid solution and the preparation of the precursor β-Li2TiO3 slurry (insufficient water will be added from outside the system), forming a closed-loop use of water resources, reducing water waste and improving economic efficiency.

[0108] 6. Reuse of concentrated activation solution: The concentrated activation solution was tested using an inductively coupled plasma (ICP) instrument, and the lithium ion concentration was found to be 18.37 g / L. Based on calculations, according to the elemental molar ratio of Li:Ti = 2, the corresponding mass of rutile titanium dioxide powder was added to the concentrated activation solution. The mixture was stirred for 3 hours, and then microwave-dried to obtain a solid mixture with a water content of 1%. The solid mixture was transferred to a roller kiln and kept at 400℃ for 3 hours, then heated to 800℃ and kept at 800℃ for 0.5 hours to obtain the titanium-based lithium ion sieve precursor β-Li₂TiO₃. The reaction that occurred was as follows:

[0109] C6H6O7Li2+2TiO2+9O2=2Li2TiO3+12CO2+6H2O.

[0110] Example 4

[0111] This embodiment provides a method for synthesizing titanium-based lithium-ion sieves. The difference from Example 1 is that acetic acid is used instead of citric acid; the remaining raw materials and methods are the same as in Example 1 and will not be repeated here. The XRD pattern of the titanium-based lithium-ion sieve β-H₂TiO₃ is as follows: Figure 8 As shown.

[0112] During production, it was discovered that the acetic acid solution was highly volatile, resulting in a strong odor in the operating area, which was detrimental to personnel operations.

[0113] Example 5

[0114] This embodiment provides a method for synthesizing titanium-based lithium-ion sieves. The difference from Example 1 is that oxalic acid is used instead of citric acid; the remaining raw materials and methods are the same as in Example 1 and will not be repeated here. The XRD pattern of the titanium-based lithium-ion sieve β-H₂TiO₃ is as follows: Figure 9 As shown.

[0115] During production, it was discovered that oxalic acid solution was mixed in with the concentrated activation solution. During the later heating process, a small amount of carbon monoxide was generated, which increased the safety risk.

[0116] Verification Example

[0117] The entire process was carried out according to the method in Example 1, that is, the precursor β-Li₂TiO₃ synthesized in the previous step was used to prepare the β-Li₂TiO₃ slurry in the next step, and the synthesis was carried out 20 times, 1-2 t each time. The adsorption capacity of the product (β-Li₂TiO₃) after 3 hours of adsorption using the brine water in Table 1 is as follows. Figure 6 As shown.

[0118] Table 1. Brine Water Quality

[0119]

[0120]

[0121] Depend on Figure 6 It can be seen that the adsorption capacity of the product synthesized in 20 batches is very stable with small fluctuations, proving that the entire process has production stability, and the adsorption capacity after 3 hours is greater than 35 mg / g, which can meet the process requirements for lithium extraction from salt lakes. This proves that the titanium-based lithium-ion sieve synthesized by this invention can significantly reduce production costs while meeting the high-performance requirements of the product.

[0122] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the technical scope disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for synthesizing titanium-based lithium-ion sieves, characterized in that, Includes the following steps: A. An organic acid solution is added to the precursor β-Li2TiO3 slurry at a flow rate of 50-100 L / h for activation; the activated slurry is then subjected to solid-liquid separation to obtain titanium-based lithium ion sieve β-H2TiO3 and acidic activation solution; B. Add lithium hydroxide solution to the acidic activation solution to adjust the pH of the acidic activation solution to neutral to obtain a neutral activation solution; C. Concentrate the volume of the neutral activating solution to 40-60% of its original volume to obtain concentrated activating solution and recycled water; D. Add titanium dioxide to the concentrated activation solution and stir evenly to obtain a mixed slurry; microwave dry the mixed slurry to obtain a solid mixture; then keep the solid mixture at 400-500℃ for 3-5h, and finally raise the temperature to 800-900℃ and keep it for 0.5-1h to obtain the precursor β-Li2TiO3, and repeat steps A and D.

2. The method according to claim 1, characterized in that, In step D, after adding titanium dioxide, the molar ratio of Li to Ti in the mixed slurry is 1.8-2.

3.

3. The method according to claim 1, characterized in that, In step D, the water content of the solid mixture is 1-5%.

4. The method according to claim 1, characterized in that, The organic acid in the organic acid solution includes at least one of formic acid, acetic acid, oxalic acid, malonic acid, fumaric acid, maleic acid, citric acid, malic acid, and tartaric acid.

5. The method according to claim 1, characterized in that, The organic acid in the organic acid solution is citric acid.

6. The method according to claim 1, characterized in that, In step A, the content of precursor β-Li2TiO3 in the precursor β-Li2TiO3 slurry is 55-75 wt.%.

7. The method according to claim 1, characterized in that, The organic acid solution contains 50-62.5 wt.% organic acid.

8. The method according to claim 1, characterized in that, The temperature of the organic acid solution is 50-70℃.

9. The method according to claim 1, characterized in that, In step A, the amount of organic acid solution added is 1.4-3 times the mass of the precursor β-Li2TiO3 slurry.

10. The method according to claim 1, characterized in that, In step A, the activation time is 2-5 hours.

11. The method according to any one of claims 1-10, characterized in that, In step A, the solid-liquid separation methods include centrifugation, filtration, and precipitation.

12. The method according to any one of claims 1-10, characterized in that, In step A, the solid-liquid separation method is filtration.

13. The method according to claim 12, characterized in that, The filtration method is plate and frame filtration.

14. The method according to any one of claims 1-10, characterized in that, In step B, the pH of the acidic activation solution is adjusted to 6.5-7.

15. The method according to any one of claims 1-10, characterized in that, In step C, the concentration method is evaporation.

Images