A method for preparing a fluorine-doped spinel titanium-based lithium adsorbent

Abstract

The application relates to a preparation method of a fluorine-doped spinel titanium lithium adsorbent and relates to a preparation method of a titanium lithium adsorbent. The application aims to solve the technical problems of a large solution loss rate of an existing inorganic lithium adsorbent in an acid immersion process and a low adsorption capacity. The fluorine doping in the fluorine-doped titanium lithium adsorbent prepared by the application can enhance the targeted adsorption of lithium ions by the adsorbent, thereby improving the adsorption capacity and selectivity of the adsorbent; the fluorine doping is also beneficial to expanding the diffusion channel of internal lithium ions, increasing the specific surface area, improving the internal and external diffusion rates of the adsorbent, thereby improving the adsorption capacity and kinetic performance of the adsorbent. Meanwhile, the preparation method is simple in steps and convenient in operation, the prepared adsorption material product has excellent performance, the cost of manpower and equipment can be effectively reduced, and the performance of the adsorption material product synthesized in a large quantity is stable.

Description

Technical Field

[0001] This invention relates to a method for preparing a titanium-based lithium adsorbent. Background Technology

[0002] Lithium, as the lightest alkali metal, is widely used in batteries, ceramics, chemicals, nuclear energy, catalysis, and glass, playing a crucial role, especially in rechargeable batteries. The recent adoption of clean and renewable energy sources in many countries has accelerated the expansion of lithium batteries in electric vehicles and other electric devices. Lithium has become one of the most important elements in various industries this century. More than 60% of the world's lithium resources are located in brines. In recent years, due to the gradual depletion of lithium mineral ores, lithium extraction from brine and seawater has received increasing attention, thus creating an urgent need to develop liquid-phase lithium extraction technologies with excellent economic benefits.

[0003] Currently, several technologies have been developed for recovering lithium from brine, such as evaporation precipitation, electrochemical technology, calcination leaching, membrane separation, solvent extraction, and adsorption. However, most of these methods have their own limitations or involve complex preparation and application processes. Evaporation precipitation is only suitable for lithium extraction from brine with a low magnesium-to-lithium ratio due to the complexity of pretreatment to remove coexisting ions. Electrochemical technology relies on an external electric field, thus being limited by high cost and energy consumption. Calcination leaching is simple, but hydrated magnesium chloride is difficult to completely decompose, and the generated hydrogen chloride gas is highly corrosive to equipment. Membrane separation is difficult to industrialize due to issues with separation efficiency and membrane durability. Solvent extraction is suitable for lithium extraction from brine with a high magnesium-to-lithium ratio, but the process is long and involves equipment corrosion, significantly increasing costs. Adsorption offers advantages such as simple process, high recovery rate, and environmental friendliness. Clearly, for low-grade brine, adsorption is currently the most promising method. In recent years, manganese-based ion sieves, titanium-based ion sieves, and aluminum-based ion sieves have been the most studied inorganic lithium adsorbents. Manganese-based ion sieves offer high selectivity, low cost, and fast adsorption rates, but suffer from significant solubility loss during acid leaching. Aluminum-based ion sieves have lower adsorption capacities. In contrast, titanium-based ion sieves exhibit higher stability and greater adsorption capacity, demonstrating broad development and application prospects. Summary of the Invention

[0004] The present invention aims to solve the technical problems of high solubility and low adsorption capacity of existing inorganic lithium adsorbents during acid leaching, and provides a method for preparing a fluorine-doped spinel titanium-based lithium adsorbent.

[0005] The preparation method of the fluorine-doped spinel titanium-based lithium adsorbent of the present invention is as follows:

[0006] 1. Add the surfactant and titanium source together to deionized water, and then stir until homogeneous to obtain mixture a;

[0007] The surfactant is dodecyltrimethylammonium bromide, dodecyldimethylbenzylammonium chloride, dodecyldimethylbenzylammonium bromide, or dodecylpyridine chloride;

[0008] The titanium source is anatase titanium dioxide, rutile titanium dioxide, mixed-phase titanium dioxide, or hydrated titanium dioxide;

[0009] The concentration of surfactant in the mixture a is 0.083 mol / L to 0.166 mol / L;

[0010] The molar ratio of the surfactant to the titanium source is 1:(1-25);

[0011] 2. Add lithium source and fluorine source to mixture a, mix well to obtain mixture b;

[0012] The lithium source is lithium carbonate, lithium nitrate, lithium acetate, lithium hydroxide, or lithium hydroxide monohydrate;

[0013] The fluorine source is lithium fluoride or lithium hexafluorophosphate;

[0014] The molar ratio of the fluorine source to the lithium source is 1:(9-19);

[0015] The molar ratio of the sum of the lithium source and the fluorine source to the titanium source in step one is 1:(0.2~1);

[0016] 3. Place mixture b into a reaction vessel for hydrothermal reaction, cool naturally, wash with methanol or ethanol, then wash with deionized water and dry.

[0017] The hydrothermal reaction temperature is 160℃~200℃, and the heating time is 6h~24h;

[0018] 4. The product from step 3 is calcined at high temperature under a protective atmosphere to obtain the adsorbent precursor.

[0019] The calcination temperature is 600℃~800℃, the calcination time is 1h~6h, and the heating rate is 4℃ / min~5℃ / min;

[0020] 5. The adsorbent precursor from step 4 is acid-washed with hydrochloric acid, then washed with deionized water and dried to obtain fluorine-doped spinel titanium-based lithium adsorbent.

[0021] The beneficial effects of this invention are:

[0022] The fluorine doping in the fluorine-doped titanium-based lithium adsorbent prepared by this invention enhances the targeted adsorption of lithium ions by the adsorbent, thereby improving the adsorption capacity and selectivity of the adsorbent. Fluorine doping also helps to expand the internal lithium ion diffusion channels, increase the specific surface area, and improve the internal and external diffusion rates of the adsorbent, thereby improving the adsorption capacity and kinetic performance of the adsorbent.

[0023] Meanwhile, the preparation method of the present invention is simple and easy to operate. Not only does the prepared adsorbent material product have excellent performance, but it can also effectively reduce labor and equipment costs, and the adsorbent material products synthesized in large quantities have stable performance.

[0024] This invention, by controlling the types and amounts of lithium source, titanium source, surfactant, and dopant elements, first involves hydrothermal synthesis, followed by high-temperature calcination, and finally acid washing to remove lithium ions, resulting in a fluorine-doped spinel titanium-based lithium adsorbent. The amount of dopant elements is relatively small, thus avoiding adverse effects on the bulk structure of the titanium-based lithium adsorbent. This modification method can enhance the adsorption effect and selectivity of the adsorbent material. Attached Figure Description

[0025] Figure 1 Scanning electron microscope image of HTOF-0.2, a fluorine-doped spinel titanium-based lithium adsorbent prepared for Experiment 1;

[0026] Figure 2 The adsorption kinetics diagrams are for Comparative Example 1 and two adsorbents with different fluorine doping ratios (Experiment 1 and Experiment 2).

[0027] Figure 3 The graph shows the adsorption selectivity data for Comparative Example 1 and two adsorbents with different fluorine doping ratios (Experiment 1 and Experiment 2).

[0028] Figure 4 The graph shows the adsorption-desorption cycle performance of the adsorbent materials (Experiment 1) for Comparative Example 1 and the fluorine doping ratio. Detailed Implementation

[0029] Specific Implementation Method 1: This implementation method is a method for preparing a fluorine-doped spinel titanium-based lithium adsorbent, and the specific process is as follows:

[0030] 1. Add the surfactant and titanium source together to deionized water, and then stir until homogeneous to obtain mixture a;

[0031] The surfactant is dodecyltrimethylammonium bromide, dodecyldimethylbenzylammonium chloride, dodecyldimethylbenzylammonium bromide, or dodecylpyridine chloride;

[0032] The titanium source is anatase titanium dioxide, rutile titanium dioxide, mixed-phase titanium dioxide, or hydrated titanium dioxide;

[0033] The concentration of surfactant in the mixture a is 0.083 mol / L to 0.166 mol / L;

[0034] The molar ratio of the surfactant to the titanium source is 1:(1-25);

[0035] 2. Add lithium source and fluorine source to mixture a, mix well to obtain mixture b;

[0036] The lithium source is lithium carbonate, lithium nitrate, lithium acetate, lithium hydroxide, or lithium hydroxide monohydrate;

[0037] The fluorine source is lithium fluoride or lithium hexafluorophosphate;

[0038] The molar ratio of the fluorine source to the lithium source is 1:(9-19);

[0039] The molar ratio of the sum of the lithium source and the fluorine source to the titanium source in step one is 1:(0.2~1);

[0040] 3. Place mixture b into a reaction vessel for hydrothermal reaction, cool naturally, wash with methanol or ethanol, then wash with deionized water and dry.

[0041] The hydrothermal reaction temperature is 160℃~200℃, and the heating time is 6h~24h;

[0042] 4. The product from step 3 is calcined at high temperature under a protective atmosphere to obtain the adsorbent precursor.

[0043] The calcination temperature is 600℃~800℃, the calcination time is 1h~6h, and the heating rate is 4℃ / min~5℃ / min;

[0044] 5. The adsorbent precursor from step 4 is acid-washed with hydrochloric acid, then washed with deionized water and dried to obtain fluorine-doped spinel titanium-based lithium adsorbent.

[0045] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the titanium source mentioned in step one is anatase titanium dioxide. Everything else is the same as in Specific Implementation Method One.

[0046] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 1 or 2 in that the stirring time in step 1 is 0.5h to 1h. Everything else is the same as in Specific Implementation Method 1 or 2.

[0047] Specific Implementation Method Four: This implementation method differs from one of Specific Implementation Methods One to Three in that the lithium source mentioned in step two is lithium hydroxide monohydrate. Everything else is the same as in one of Specific Implementation Methods One to Three.

[0048] Specific Implementation Method Five: This implementation method differs from Specific Implementation Method Four in that: in step two, the mixture is stirred for 0.5 to 1 hour, followed by ultrasonic mixing for 20 to 30 minutes. Everything else is the same as in Specific Implementation Method Four.

[0049] Specific Implementation Method Six: This implementation method differs from Specific Implementation Method Five in that the protective gas mentioned in step four is argon. Everything else is the same as in Specific Implementation Method Five.

[0050] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Method Six in that the concentration of hydrochloric acid mentioned in step five is 0.1 mol / L to 0.5 mol / L. Everything else is the same as in Specific Implementation Method Six.

[0051] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Method Seven in that the acid washing process in step five involves soaking the adsorbent precursor in hydrochloric acid and stirring for 6 to 24 hours. Everything else is the same as in Specific Implementation Method Seven.

[0052] The invention was verified using the following experiments:

[0053] Experiment 1: This experiment demonstrates a method for preparing a fluorine-doped spinel titanium-based lithium adsorbent. The specific process is as follows:

[0054] 1. Add 1.82g of CTAB and 0.4g of titanium source to 60mL of deionized water, and stir for 0.5h to obtain mixture a;

[0055] The titanium source is anatase titanium dioxide;

[0056] 2. Add 0.957g of lithium source and 0.031g of lithium fluoride to mixture a, mix and stir for 0.5h, then sonicate for 30min to obtain mixture b;

[0057] The lithium source is lithium hydroxide monohydrate;

[0058] 3. Place the mixture b into a 100 mL reaction vessel for hydrothermal reaction, cool naturally, wash with ethanol, then wash with deionized water, and then dry at 60 °C.

[0059] The hydrothermal reaction was carried out at a temperature of 180°C for 24 hours.

[0060] 4. The product from step 3 is calcined at high temperature in an argon atmosphere to obtain the adsorbent precursor.

[0061] The calcination temperature is 600℃, the calcination time is 2h, and the heating rate is 4℃ / min;

[0062] 5. The adsorbent precursor from step 4 was acid-washed with 0.2 mol / L hydrochloric acid, then washed with deionized water, and then dried at 60℃ to obtain fluorine-doped spinel titanium-based lithium adsorbent HTOF-0.2; the acid washing process was to soak the adsorbent precursor in hydrochloric acid and stir for 12 h.

[0063] Figure 1 Scanning electron microscope (SEM) images of the fluorine-doped spinel titanium-based lithium adsorbent HTOF-0.2 prepared for Experiment 1, from... Figure 1 The spinel structure of the adsorbent material can be seen from the image.

[0064] Experiment 2: The difference between this experiment and Experiment 1 is that in step 2, 0.906g of lithium source and 0.062g of lithium fluoride were added to mixture a, mixed and stirred for 0.5h, and then sonicated for 30min to obtain mixture b; the lithium source was lithium hydroxide monohydrate. Everything else was the same as in Experiment 1, resulting in fluorine-doped spinel titanium-based lithium adsorbent HTOF-0.2.

[0065] Experiment 3: The difference between this experiment and Experiment 1 is as follows:

[0066] In step one, 3.65g of CTAB and 10g of titanium source were added together to 60mL of deionized water and stirred for 0.5h to obtain mixture a; the titanium source was anatase titanium dioxide.

[0067] In step two, 4.99 g of lithium source and 0.162 g of lithium fluoride were added to mixture a, stirred for 0.5 h, and then sonicated for 30 min to obtain mixture b; the lithium source was lithium hydroxide monohydrate. Everything else was the same as in experiment one.

[0068] Experiment 4: The difference between this experiment and Experiment 1 is as follows:

[0069] In step one, 14.6g of CTAB and 40g of titanium source were added to 120mL of deionized water and stirred for 0.5h to obtain mixture a; the titanium source was anatase titanium dioxide.

[0070] In step two, 19.96g of lithium source and 0.648g of lithium fluoride are added to mixture a, mixed and stirred for 0.5h, and then sonicated for 30min to obtain mixture b; the lithium source is lithium hydroxide monohydrate.

[0071] In step three, the mixture is placed in a 200 mL reactor for hydrothermal reaction. Everything else is the same as in experiment one.

[0072] Comparative Example 1: This comparative example did not use lithium fluoride for doping. The specific steps are as follows:

[0073] 1) Add 1.82g of CTAB and 0.4g of anatase titanium dioxide to 60mL of deionized water and stir vigorously for 0.5h;

[0074] 2) Add 1g of lithium hydroxide monohydrate to the solution in step (1), mix and stir for 0.5h and sonicate for 30min;

[0075] 3) Place the solution from step (2) into a 100mL hydrothermal reactor and hydrothermally heat it at 180℃ for 24 hours. After cooling, wash it with ethanol, then wash it with deionized water and dry it at 60℃.

[0076] 4) The product obtained in step (3) was calcined at 600℃ for 2 hours in an argon atmosphere to obtain the adsorbent precursor, with a heating rate of 4℃ / min.

[0077] 5) Soak and stir the precursor obtained in step (4) with 0.2 mol / L hydrochloric acid for 12 h, wash with deionized water and dry at 60 °C to obtain spinel titanium lithium adsorbent HTO.

[0078] Comparative Example 2: The difference between this comparative example and Comparative Example 1 is as follows:

[0079] 1) Add 3.65g of CTAB and 10g of anatase titanium dioxide to 60mL of deionized water and stir vigorously for 0.5h;

[0080] 2) Add 5.25g of lithium hydroxide monohydrate to the solution in step (1), mix and stir for 0.5h, and sonicate for 30min. The rest is the same as Comparative Example 1.

[0081] Experiment 5: The performance of the titanium-based lithium adsorbents obtained in the above experiments and comparative examples was tested. The specific method was as follows: 50 mg of the spinel titanium-based lithium adsorbent prepared above was added to 50 mL of LiOH solution (Li... + The concentration of the solution was 500 mg / L. The mixed solution was placed in a shaker for an adsorption batch experiment (conditions: 25℃, 180 rpm, 6 h). Samples were taken at different time points, diluted with deionized water, and measured by flame atomic absorption spectrometry. The equilibrium adsorption capacity and adsorption kinetics during the adsorption process were calculated and simulated. The final results are shown in Table 1.

[0082] Table 1

[0083]

[0084] As can be seen from the data in Table 1, the fluorine-doped spinel titanium-based lithium adsorbent described in this application can effectively improve the adsorption capacity and selectivity without affecting the adsorption rate. Furthermore, it still exhibits excellent capacity retention after multiple adsorption-desorption cycles, demonstrating that the fluorine-doped titanium-based lithium adsorbent described in this application can effectively improve the adsorption performance of the adsorbent. Moreover, after scaling up the synthesis and production, it was found that the adsorbent produced in large quantities still has good adsorption performance under different scaling-up synthesis and production ratios, proving that the material has the potential for practical industrial application.

[0085] Figure 2 The figure shows the adsorption kinetics of Comparative Example 1 and two adsorbents with different fluorine doping ratios (Experiment 1 and Experiment 2) in Experiment 5. It can be seen from the figure that all three adsorbents have a relatively fast adsorption rate and basically reach adsorption equilibrium in 4 hours. Among them, HTOF-0.2 prepared in Experiment 1 has the largest adsorption capacity, reaching 58.35 mg / g in 6 hours.

[0086] Experiment 6: Adsorption selectivity tests were conducted on Comparative Example 1 and two adsorbents with different fluorine doping ratios (Experiment 1 and Experiment 2). The tests were carried out under the condition that the molar concentrations of lithium, potassium, and sodium were all 0.05 mol / L. Figure 3 The figure shows the adsorption selectivity data for Experiment 6. It can be seen from the figure that all three materials have good adsorption selectivity in the environment where lithium, potassium and sodium coexist. The HTOF-0.2 prepared in Experiment 1 has the best adsorption selectivity and the largest separation coefficient, with separation coefficient α(Li / K) = 638.9 and separation coefficient α(Li / Na) = 2911.4.

[0087] Figure 4 The adsorption-desorption cycle performance diagrams for Comparative Example 1 and the fluorine-doped adsorbent (Experiment 1) are shown. The test procedure was as follows: the adsorbent material after adsorption in Experiment 5 was desorbed in 0.2 mol / L hydrochloric acid for 12 h. After desorption, the adsorbent material was collected and the adsorption experiment of Experiment 5 was repeated. This was repeated for 4 adsorption-desorption cycles. Figure 4 As can be seen, the material can still maintain a high adsorption capacity after four adsorption-desorption cycles. The adsorbent material HTOF-0.2 prepared in Experiment 1 had an adsorption capacity of 40.9 mg / g after four cycles, which proves that the material has excellent stability.

Claims

1. A method for preparing a fluorine-doped spinel titanium-based lithium adsorbent, characterized in that... The preparation method of fluorine-doped spinel titanium-based lithium adsorbent is as follows:

1. Add the surfactant and titanium source together to deionized water, and then stir until homogeneous to obtain mixture a; The surfactant is dodecyltrimethylammonium bromide, dodecyldimethylbenzylammonium chloride, dodecyldimethylbenzylammonium bromide, or dodecylpyridine chloride; The titanium source is anatase titanium dioxide, rutile titanium dioxide, mixed-phase titanium dioxide, or hydrated titanium dioxide; The concentration of surfactant in the mixture a is 0.083 mol / L to 0.166 mol / L; The molar ratio of the surfactant to the titanium source is 1:(1-25); 2. Add lithium source and fluorine source to mixture a, mix well to obtain mixture b; The lithium source is lithium carbonate, lithium nitrate, lithium acetate, lithium hydroxide, or lithium hydroxide monohydrate; The fluorine source is lithium fluoride or lithium hexafluorophosphate; The molar ratio of the fluorine source to the lithium source is 1:(9-19); The molar ratio of the sum of the lithium source and the fluorine source to the titanium source in step one is 1:(0.2~1); 3. Place mixture b into a reaction vessel for hydrothermal reaction, cool naturally, wash with methanol or ethanol, then wash with deionized water and dry. The hydrothermal reaction temperature is 160℃~200℃, and the heating time is 6h~24h; 4. The product from step 3 is calcined at high temperature under a protective atmosphere to obtain the adsorbent precursor. The calcination temperature is 600℃~800℃, the calcination time is 1h~6h, and the heating rate is 4℃ / min~5℃ / min; 5. The adsorbent precursor from step 4 is acid-washed with hydrochloric acid, then washed with deionized water and dried to obtain fluorine-doped spinel titanium-based lithium adsorbent.

2. The method for preparing a fluorine-doped spinel titanium-based lithium adsorbent according to claim 1, characterized in that... Stir for 0.5 to 1 hour in step one.

3. The method for preparing a fluorine-doped spinel titanium-based lithium adsorbent according to claim 1, characterized in that... In step two, mix and stir for 0.5 to 1 hour, then sonicate for 20 to 30 minutes to mix.

4. The method for preparing a fluorine-doped spinel titanium-based lithium adsorbent according to claim 1, characterized in that... The protective gas mentioned in step four is argon.

5. The method for preparing a fluorine-doped spinel titanium-based lithium adsorbent according to claim 1, characterized in that... The concentration of hydrochloric acid mentioned in step five is 0.1 mol / L to 0.5 mol / L.

6. The method for preparing a fluorine-doped spinel titanium-based lithium adsorbent according to claim 1, characterized in that... The acid washing process in step five involves soaking the adsorbent precursor in hydrochloric acid and stirring for 6 to 24 hours.

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