Manganese dioxide-coated manganese-based lithium adsorbent and preparation method and application thereof

Abstract

This invention belongs to the field of lithium extraction technology from salt lakes, specifically relating to a manganese dioxide-coated manganese-based lithium adsorbent, its preparation method, and its application. This invention utilizes spherical manganese carbonate to prepare a precursor for the manganese-based lithium adsorbent, and then further achieves manganese dioxide coating modification through low-temperature redox technology to obtain a manganese dioxide-coated manganese-based lithium adsorbent. The resulting manganese dioxide-coated manganese-based lithium adsorbent can achieve highly efficient lithium extraction from salt lake brines with a high magnesium-to-lithium ratio, while also possessing advantages such as low manganese loss rate (<1.5%), strong recyclability, and low preparation cost, thus having broad application value.

Description

Technical Field

[0001] This invention belongs to the field of lithium extraction technology from salt lakes. More specifically, it relates to a manganese dioxide-coated manganese-based lithium adsorbent, its preparation method, and its application. Background Technology

[0002] Lithium is a crucial element in modern energy development. This lightest alkali metal is widely used in various fields, including new energy, and is an essential raw material for high-energy-density lithium batteries. Lithium batteries, in turn, are a vital power source for new energy vehicles, grid energy storage, portable electronic devices, and power tools. In recent years, with the rapid development of the new energy industry, the demand for lithium batteries has exploded, leading to a continuous increase in global market demand for lithium resources. Global lithium resources mainly exist in two forms: lithium-bearing ores, such as lepidolite, spodumene, and lithium saponite; and lithium-bearing water resources, such as salt lake brines and seawater. Surveys indicate that over 60% of the total lithium exists in salt lakes and seawater. Therefore, salt lake lithium resources have become an important source for the development of the lithium battery industry. Methods for extracting lithium from salt lakes include adsorption, electrodialysis, electrochemical deintercalation, and solvent extraction. However, apart from the high-quality salt lakes in South America with low magnesium-to-lithium ratios that have been extensively exploited, the extraction of lithium resources in most salt lakes with high magnesium-to-lithium ratios has encountered difficulties. Due to Mg... 2+ and Li + They have almost identical properties. For salt lake brines with a magnesium-to-lithium ratio exceeding 6, the application of conventional solar evaporation and precipitation methods is very limited, while adsorption methods offer a possibility for solving this problem.

[0003] The widespread application of lithium-ion batteries in power and energy storage fields has led to a continuous increase in global demand for lithium resources. Among the proven lithium resources on Earth, salt lake brines contain the largest reserves. However, the high total salt content, complex composition, and low lithium concentration of salt lake brines increase the technical difficulty of separating and extracting lithium from them. Therefore, methods for highly selective separation of lithium ions have attracted much attention, particularly research on the separation and extraction of lithium using inorganic materials such as manganese oxide-based, titanium oxide-based, and iron phosphate-based adsorbents, which have become a hot topic. Manganese oxide-based adsorbents include LiMn₂O₄ and Li₂O₃. 1.33 Mn l.67 O4 and Li 1.6 Mn 1.6 O4. They affect Li during the adsorption process. + It exhibits high selectivity and also demonstrates a high adsorption capacity. Li 1.6 Mn 1.6O4 is the most representative spinel material among all manganese oxide adsorbents due to its good stability and high theoretical adsorption capacity after multiple adsorption cycles. However, during the lithium intercalation and deintercalation process, especially during deintercalation, approximately 3.7% of the manganese in manganese oxide ion sieve adsorbents is lost. This loss of manganese not only reduces the adsorption capacity but also causes water pollution to both the raw water and the desorption solution in practical applications.

[0004] Therefore, it is essential to develop a novel lithium-ion adsorbent with lower manganese loss. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the defects and shortcomings of existing manganese oxide ion sieve adsorbents in the lithium intercalation and deintercalation process, especially in the deintercalation process, which have a high manganese dissolution rate (>1.5%), and to provide a method for preparing a manganese-based lithium adsorbent coated with manganese dioxide.

[0006] The purpose of this invention is to provide a manganese-based lithium adsorbent coated with manganese dioxide, wherein the manganese loss of the manganese-based lithium adsorbent coated with manganese dioxide is <1.5%.

[0007] Another object of the present invention is to provide the application of the manganese dioxide-coated manganese-based lithium adsorbent.

[0008] The above-mentioned objective of this invention is achieved through the following technical solution:

[0009] This invention protects a method for preparing a manganese dioxide-coated manganese-based lithium adsorbent, comprising the following steps:

[0010] S1. Mix the solution containing bicarbonate ions with the aqueous ethanol solution containing divalent manganese salt thoroughly and react completely. Filter the solution, dry the precipitate, and obtain spherical manganese carbonate.

[0011] S2. Grind the spherical manganese carbonate obtained in step S1 with lithium salt thoroughly, calcine at 240-270℃ for 150-180 min, then heat to 350-380℃ for full calcine, cool to obtain manganese-based lithium adsorbent precursor.

[0012] S3. The dispersion containing the manganese-based lithium adsorbent precursor obtained in step S2, the solution containing divalent manganese salt, and the potassium permanganate solution are thoroughly mixed and reacted. After the reaction is complete, the mixture is post-treated to obtain the manganese-based lithium adsorbent precursor coated with manganese dioxide.

[0013] S4. The manganese dioxide-coated manganese-based lithium adsorbent precursor obtained in step S3 is subjected to acid washing to remove lithium, and then dried to obtain the manganese dioxide-coated manganese-based lithium adsorbent.

[0014] To address the problem of high manganese loss (>1.5%) in existing manganese oxide-based ion sieve adsorbents during lithium insertion and extraction, especially during extraction, the present invention provides a manganese-based lithium adsorbent coated with manganese dioxide prepared by the above-mentioned method. This adsorbent does not significantly reduce the amount of lithium adsorbed (generally, the adsorption performance of the adsorbent is significantly reduced after coating), while effectively reducing the manganese loss rate (<1.5%) and exhibiting good recyclability.

[0015] Preferably, the manganese-lithium molar ratio of the spherical manganese carbonate to the lithium salt is 1:(0.8-1.2).

[0016] Preferably, the mass ratio of manganese dioxide in the manganese-based lithium adsorbent precursor and the manganese dioxide-coated manganese-based lithium adsorbent is (12-15):1.

[0017] Preferably, the divalent manganese salt is selected from manganese sulfate, manganese chloride, manganese nitrate, or a hydrate of any of the above divalent manganese salts.

[0018] Preferably, the bicarbonate ion is selected from sodium bicarbonate or potassium bicarbonate.

[0019] Preferably, the lithium salt is selected from lithium nitrate, lithium chloride, lithium sulfate, or lithium acetate, and more preferably lithium nitrate.

[0020] Furthermore, the reaction principle in step S1 is: 2HCO3 - +Mn 2+ =MnCO3↓+CO2↑+H2O.

[0021] Furthermore, the reaction principle in step S2 is: 1,6LiMnO2 + 0.4O2 → Li 1.6 Mn 1.6 O4.

[0022] Furthermore, the reaction principle in step S3: 3Mn 2+ +2MnO4 - +2H₂O=5MnO₂+2H + .

[0023] Preferably, the molar ratio of divalent manganese in the divalent manganese salt to bicarbonate in the solution containing bicarbonate is 1:(2-2.5). A slight excess of bicarbonate is beneficial for the reaction.

[0024] Preferably, the mixing ratio of divalent manganese salt, water and ethanol in the ethanol solution containing divalent manganese salt is 1 mol: (50-80) L: (4-10) L.

[0025] Further, in step S1, the solution containing bicarbonate is an aqueous solution containing bicarbonate, obtained by dissolving a reagent containing bicarbonate in water.

[0026] Preferably, the concentration of the bicarbonate-containing solution is 0.09–0.15 mol / L. In actual calculations, the results may differ slightly due to different decimal places. For example, a calculated concentration of 0.092 mol / L may round to 0.09 mol / L or 0.1 mol / L, both of which fall within the scope of this invention.

[0027] Further, in step S1, the method for preparing the ethanol aqueous solution of the divalent manganese salt includes the following steps: dissolving the divalent manganese salt in water first, then adding ethanol, and mixing well to obtain the solution.

[0028] Preferably, in step S1, the concentration of the ethanol aqueous solution containing divalent manganese salt is 0.02 to 0.024 mol / L.

[0029] Furthermore, in step S1, the reaction takes ≥10 hours to complete.

[0030] Furthermore, in step S1, the drying temperature is 60–80°C, and the drying time is 8–12 hours.

[0031] Preferably, in step S2, the heating rate of the calcination is 5-10 °C / min.

[0032] Preferably, in step S2, the calcination time is 540–720 min.

[0033] Further, in step S3, the manganese-based lithium adsorbent is obtained by dispersing a manganese-based lithium adsorbent precursor in water, and the preferred mixing ratio of the manganese-based lithium adsorbent precursor to water is 1 g: (80-100) mL.

[0034] Further, in step S3, the solution containing divalent manganese salt is an aqueous solution containing divalent manganese salt, obtained by dissolving divalent manganese salt in water, and the concentration of the divalent manganese salt is preferably 0.006 to 0.0084 mol / L.

[0035] Further, in step S3, the potassium permanganate solution is an aqueous solution of potassium permanganate, obtained by dissolving potassium permanganate in water, and the concentration of the potassium permanganate solution is preferably 0.0037 to 0.005 mol / L.

[0036] Furthermore, in step S3, the volume ratio of the dispersion of the manganese-based lithium adsorbent precursor, the manganese-based lithium adsorbent solution containing divalent manganese salt, and the potassium permanganate solution is preferably 1:1:1.

[0037] Furthermore, in step S3, the post-processing involves centrifugation and drying.

[0038] Furthermore, the drying temperature is 60–80°C, and the time is 8–12 hours.

[0039] Furthermore, in step S3, the time for thorough mixing is ≥2 hours.

[0040] Specifically, in step S4, the acid leaching for lithium removal involves fully leaching lithium elements with an acid solution, followed by filtration, drying of the precipitate, and obtaining a manganese dioxide-coated manganese-based lithium adsorbent. Further, the drying temperature is 60–80°C, and the drying time is 8–12 hours.

[0041] Furthermore, in step S4, the acid used for eluting lithium is selected from hydrochloric acid, and the concentration of the hydrochloric acid solution is 0.3-0.8 mol / L, more preferably 0.5 mol / L.

[0042] Furthermore, in step S4, the acid elution and delithiation time is 100-150 min.

[0043] This invention also protects the manganese dioxide-coated manganese-based lithium adsorbent prepared by the aforementioned preparation method.

[0044] The application of the manganese dioxide-coated manganese-based lithium adsorbent described in this invention in the extraction of lithium.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] This invention utilizes spherical manganese carbonate to prepare a precursor for a manganese-based lithium adsorbent, and then further achieves manganese dioxide coating modification through low-temperature oxidation-reduction technology to obtain a manganese dioxide-coated manganese-based lithium adsorbent. The resulting manganese dioxide-coated manganese-based lithium adsorbent can achieve efficient lithium extraction from high magnesium-to-lithium ratio salt lake brines, while also having advantages such as low manganese loss rate (<1.5%), strong recyclability, and low preparation cost, and has broad application value. Attached Figure Description

[0047] Figure 1 This is a SEM image of the spherical manganese carbonate prepared according to the present invention.

[0048] Figure 2 This is a schematic diagram of the process flow for the manganese dioxide-coated manganese-based lithium adsorbent of the present invention. Detailed Implementation

[0049] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in this technical field.

[0050] Unless otherwise specified, all reagents and materials used in the following examples are commercially available.

[0051] Example 1: Lithium extraction effect of manganese-based lithium adsorbents with different manganese-to-lithium ratios

[0052] A method for preparing a manganese-based lithium adsorbent includes the following steps:

[0053] (1) Preparation of manganese carbonate: 1.69 g of manganese sulfate (0.01 mol) was dissolved in 500 ml of water, and 40 mL of anhydrous ethanol was added under stirring to obtain solution A. 1.68 g of sodium bicarbonate (0.02 mol) was dissolved in 210 ml of water to obtain solution B. Solution B was slowly added to solution A under stirring, mixed, allowed to stand, and allowed to precipitate for 10 h. The supernatant was taken out, and the white precipitate was dried at 70 °C for 8 h to obtain white spherical manganese carbonate, the morphology of which is as follows. Figure 1 As shown, it has a near-spherical structure.

[0054] (2) Preparation of manganese-based lithium adsorbent precursors: The white spherical manganese carbonate and lithium nitrate obtained in step (1) were ground thoroughly in a mortar at molar ratios of 1:0.4, 1:0.6, 1:0.8, 1:1, and 1:1.2, respectively. The mixture was then placed in a tube furnace and the following program was set: First, the temperature was raised to 270℃ at 10℃ / min and held for 180 min. Then, the temperature was raised to 350℃ at 5℃ / min and held for 720 min. Finally, the temperature was allowed to drop naturally to obtain manganese-based lithium adsorbent precursor materials with different manganese-lithium molar ratios.

[0055] (3) Preparation of manganese-based lithium adsorbent: The manganese-based lithium adsorbent precursor materials prepared in step (2) with different manganese-lithium ratios were stirred thoroughly in 0.5M hydrochloric acid for 120 min to leach out the lithium element in the lithium-containing manganese-based lithium adsorbent precursor. After filtration, the precipitate was dried (70℃, 10 h) to obtain a manganese-based lithium adsorbent with specific lithium adsorption. The schematic diagram of the preparation process of the obtained manganese-based lithium adsorbent is shown below. Figure 2 As shown.

[0056] (4) Lithium extraction from simulated salt lake brine: 0.1g of the manganese-based lithium adsorbent prepared with different manganese-lithium ratios obtained in step (3) was placed in simulated brine with a magnesium-lithium ratio of 100:1 (100mL) for lithium extraction experiments. The results are shown in Table 1.

[0057] Table 1. Lithium extraction effect of manganese-based lithium adsorbents with different manganese-to-lithium ratios.

[0058]

[0059] As shown in Table 1, the lithium adsorption capacities for manganese-lithium ratios of 1:0.4, 1:0.6, 1:0.8, 1:1, and 1:1.2 are 6.5 mg / g, 8.4 mg / g, 14.1 mg / g, 12.3 mg / g, and 11.4 mg / g, respectively. This indicates that manganese-based lithium adsorbents with a manganese-lithium ratio of 1:(0.8–1.2) have better lithium extraction effects, with the manganese-lithium adsorbent having the best lithium extraction effect at a ratio of 1:0.8.

[0060] Example 2: Lithium extraction effect of manganese-based lithium adsorbent at different solid-liquid ratios

[0061] (1) Preparation of manganese carbonate: 1.69 g of manganese sulfate (0.01 mol) was dissolved in 500 ml of water, and 40 mL of anhydrous ethanol was added while stirring to obtain solution A. 1.68 g of sodium bicarbonate (0.02 mol) was dissolved in 210 ml of water to obtain solution B. Solution B was slowly added to solution A while stirring, mixed, allowed to stand, and allowed to precipitate for 10 h. The supernatant was taken out, and the white precipitate was dried at 70 °C for 8 h to obtain white spherical manganese carbonate.

[0062] (2) Preparation of manganese-based lithium adsorbent precursor: The white spherical manganese carbonate and lithium nitrate obtained in step (1) are ground thoroughly in a mortar at a molar ratio of 1:0.8, and placed in a tube furnace with the following program: First, the temperature is raised to 270℃ at 10℃ / min and held for 180min, then the temperature is raised to 350℃ at 5℃ / min and held for 720min, and finally the temperature is naturally cooled to obtain the manganese-based lithium adsorbent precursor.

[0063] (3) Preparation of manganese-based lithium adsorbent: The manganese-based lithium adsorbent obtained in step (2) is stirred in 0.5M hydrochloric acid for 120 min to leach out the lithium element in the lithium-containing manganese-based lithium adsorbent precursor. After filtration, the precipitate is dried (70℃, 10h) to obtain a manganese-based lithium adsorbent that can specifically adsorb lithium.

[0064] (4) Lithium extraction from simulated salt lake brine: 0.1g of the manganese-based lithium adsorbent obtained in step (3) was placed in 100mL, 150mL, 200mL and 250mL of simulated brine with a magnesium-to-lithium ratio of 100:1 for lithium extraction experiments. The results are shown in Table 2.

[0065] Table 2. Lithium extraction effect of manganese-based lithium adsorbent at different solid-liquid ratios.

[0066]

[0067] Table 2 shows that the lithium extraction amounts for solid-liquid ratios (g / L) of 1:1, 1:1.5, 1:2, and 1:2.5 are 14.1 mg / g, 16.75 mg / g, 22.1 mg / g, and 25.75 mg / g, respectively. This indicates that the adsorption effect increases continuously with the increase of the solid-liquid ratio, suggesting its strong potential for industrial applications.

[0068] Example 3: Lithium extraction effect of manganese-based lithium adsorbents coated with manganese dioxide at different coating ratios

[0069] (1) Preparation of manganese carbonate: 1.69 g of manganese sulfate (0.01 mol) was dissolved in 500 ml of water, and 40 mL of anhydrous ethanol was added while stirring to obtain solution A. 1.68 g of sodium bicarbonate (0.02 mol) was dissolved in 210 ml of water to obtain solution B. Solution B was slowly added to solution A while stirring, mixed, allowed to stand, and allowed to precipitate for 10 h. The supernatant was taken out, and the white precipitate was dried at 70 °C for 8 h to obtain white spherical manganese carbonate.

[0070] (2) Preparation of manganese-based lithium adsorbent precursor: The white spherical manganese carbonate and lithium nitrate obtained in step (1) are ground thoroughly in a mortar at a molar ratio of 1:0.8, and placed in a tube furnace with the following program: First, the temperature is raised to 270℃ at 10℃ / min and held for 180min, then the temperature is raised to 350℃ at 5℃ / min and held for 720min, and finally the temperature is naturally cooled to obtain the manganese-based lithium adsorbent precursor.

[0071] (3) Manganese dioxide coating modification using low-temperature redox technology: First, take 0.25g of the manganese-based lithium adsorbent precursor obtained in step (2) and disperse it in 20mL of water, labeling it as solutions A1, A2, A3, A4, and A5. Second, according to the chemical equation: 3Mn 2+ +2MnO4 - +2H₂O=5MnO₂+2H + Potassium permanganate (0.036 g, 0.023 g, 0.018 g, 0.015 g, and 0.012 g) was dispersed in 20 mL of water and labeled as solutions B1, B2, B3, B4, and B5, respectively. Manganese sulfate (0.058 g, 0.036 g, 0.029 g, 0.025 g, and 0.019 g) was dispersed in 20 mL of water and labeled as solutions C1, C2, C3, C4, and C5, respectively. The three solutions with the same serial number (A, B, C) were mixed separately, shaken for 2 h, centrifuged, and dried (70 °C, 10 h) to prepare manganese dioxide-coated modified manganese-based lithium adsorbent precursors with coating ratios (mass ratio of manganese-based lithium adsorbent precursor to manganese dioxide) of 5:1, 8:1, 10:1, 12:1, and 15:1.

[0072] (4) Preparation of manganese dioxide-coated manganese-based lithium adsorbent: The manganese dioxide-coated manganese-based lithium adsorbent precursor obtained in step (3) was stirred thoroughly in 0.5M hydrochloric acid for 120 min to leach out the lithium element in the manganese dioxide-coated manganese-based lithium adsorbent precursor. After filtration, the precipitate was dried (70℃, 10h) to obtain the manganese dioxide-coated manganese-based lithium adsorbent. The schematic diagram of the preparation process of the obtained manganese dioxide-coated manganese-based lithium adsorbent (also known as modified manganese-based lithium adsorbent) is shown below. Figure 2 As shown.

[0073] (5) Lithium extraction from simulated salt lake brine: 0.1g of the manganese-based lithium adsorbent coated with manganese dioxide obtained in step (4) was placed in simulated brine with a magnesium-to-lithium ratio of 100:1 (100mL) for lithium extraction experiment. The results are shown in Table 3.

[0074] Table 3. Lithium extraction efficiency of manganese-based lithium adsorbents coated with manganese dioxide at different coating ratios.

[0075]

[0076] Table 3 shows that the lithium extraction rates of manganese-based lithium adsorbents with mass ratios (manganese-based lithium adsorbent precursor: manganese dioxide) of 5:1, 8:1, 10:1, 12:1, and 15:1 were 6.1 mg / g, 8.2 mg / g, 9.1 mg / g, 12.6 mg / g, and 12.1 mg / g, respectively. The experimental data indicate that coating ratios (manganese-based lithium adsorbent precursor: manganese dioxide) of (12–15):1 exhibited better adsorption effects, with the best adsorption effect (12.6 mg / g) and the lowest manganese loss (1.31%) observed at a coating ratio of 12:1. Compared to the uncoated manganese-based lithium adsorbent, the manganese loss rate (2.48%) decreased by 1.17%, while the lithium extraction rate after coating (12.6 mg / g) decreased by only 1.5 mg / g compared to the uncoated adsorbent (14.1 mg / g). Manganese dioxide coating modification can effectively reduce the manganese loss rate without significantly reducing the adsorption amount.

[0077] Example 4: Lithium extraction effect of manganese dioxide-coated manganese-based lithium adsorbent at different solid-liquid ratios

[0078] (1) Preparation of manganese carbonate: 1.69 g of manganese sulfate (0.01 mol) was dissolved in 500 ml of water, and 40 mL of anhydrous ethanol was added while stirring to obtain solution A. 1.68 g of sodium bicarbonate (0.02 mol) was dissolved in 210 ml of water to obtain solution B. Solution B was slowly added to solution A while stirring, mixed, allowed to stand, and allowed to precipitate for 10 h. The supernatant was taken out, and the white precipitate was dried at 70 °C for 8 h to obtain white spherical manganese carbonate.

[0079] (2) Preparation of manganese-based lithium adsorbent precursor: The white spherical manganese carbonate and lithium nitrate obtained in step (1) are ground thoroughly in a mortar at a molar ratio of 1:0.8, and placed in a tube furnace with the following program: First, the temperature is raised to 270℃ at 10℃ / min and held for 180min, then the temperature is raised to 350℃ at 5℃ / min and held for 720min, and finally the temperature is naturally cooled to obtain the manganese-based lithium adsorbent precursor.

[0080] (3) Manganese dioxide coating modification using low-temperature redox technology: First, 0.25 g of the manganese-based lithium adsorbent precursor obtained in (2) was dispersed in 20 mL of water and labeled as solution A. Second, according to the chemical equation: 3Mn 2+ +2MnO4 - +2H₂O=5MnO₂+2H + 0.015 g of potassium permanganate was dispersed in 20 mL of water and labeled as solution B. 0.025 g of manganese sulfate was dispersed in 20 mL of water and labeled as solution C. The three solutions A, B, and C were mixed, shaken for 2 h, centrifuged, and dried (70 °C, 10 h) to prepare a manganese dioxide-coated modified manganese-based lithium adsorbent precursor with a coating ratio (manganese-based lithium adsorbent precursor: manganese dioxide) of 12:1.

[0081] (4) Preparation of manganese-based lithium adsorbent coated with manganese dioxide: The manganese-based lithium adsorbent precursor coated with manganese dioxide obtained in (3) was stirred in 0.5M hydrochloric acid for 120 min to leach out the lithium element in the manganese-based lithium adsorbent precursor coated with manganese dioxide. After filtration, the precipitate was dried (90℃, 10h) to obtain the manganese-based lithium adsorbent coated with manganese dioxide.

[0082] (5) Lithium extraction from simulated salt lake brine: 0.1g of the manganese-based lithium adsorbent modified by manganese dioxide coating obtained in (4) was placed in 100mL, 150mL, 200mL and 250mL of simulated brine with a magnesium-to-lithium ratio of 100:1 for lithium extraction experiments.

[0083] Table 4. Lithium extraction effect of manganese dioxide-coated manganese-based lithium adsorbent at different solid-liquid ratios.

[0084]

[0085] Table 4 shows that the lithium extraction amounts for solid-liquid ratios (g / L) of 1:1, 1:1.5, 1:2, and 1:2.5 were 12.6 mg / g, 18.3 mg / g, 21.8 mg / g, and 24.75 mg / g, respectively, with the best lithium extraction effect (24.75 mg / g) observed at a solid-liquid ratio of 1:2.5. This indicates that the adsorption effect increases continuously with the increase of the solid-liquid ratio, suggesting a promising industrial application prospect.

[0086] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A manganese dioxide-coated manganese-based lithium adsorbent, characterized in that, The preparation method of the manganese dioxide-coated manganese-based lithium adsorbent includes the following steps: S1. Mix the solution containing bicarbonate ions with the aqueous ethanol solution containing divalent manganese salt thoroughly and react completely. Filter the solution, dry the precipitate, and obtain spherical manganese carbonate. S2. Grind the spherical manganese carbonate obtained in step S1 with lithium salt thoroughly, calcine at 240-270℃ for 150-180 min, then heat to 350-380℃ for full calcine, cool to obtain manganese-based lithium adsorbent precursor. S3. The dispersion containing the manganese-based lithium adsorbent precursor obtained in step S2, the solution containing divalent manganese salt, and the potassium permanganate solution are thoroughly mixed and reacted. After the reaction is complete, the mixture is post-treated to obtain the manganese-based lithium adsorbent precursor coated with manganese dioxide. S4. The manganese-based lithium adsorbent precursor coated with manganese dioxide obtained in step S3 is subjected to acid washing to remove lithium, and then dried to obtain the manganese-based lithium adsorbent coated with manganese dioxide. In step S2, the molar ratio of manganese carbonate to lithium salt in the spherical manganese carbonate is 1:(0.8~1.2); The mass ratio of manganese dioxide in the manganese-based lithium adsorbent precursor and the manganese dioxide-coated manganese-based lithium adsorbent is (12-15):

1.

2. The manganese dioxide-coated manganese-based lithium adsorbent according to claim 1, characterized in that, The divalent manganese salt is selected from manganese sulfate, manganese chloride, manganese nitrate, or a hydrate of any of the above divalent manganese salts.

3. The manganese dioxide-coated manganese-based lithium adsorbent according to claim 1, characterized in that, The bicarbonate ion is selected from sodium bicarbonate or potassium bicarbonate.

4. The manganese dioxide-coated manganese-based lithium adsorbent according to claim 1, characterized in that, The lithium salt is selected from lithium nitrate, lithium chloride, lithium sulfate, or lithium acetate.

5. The manganese dioxide-coated manganese-based lithium adsorbent according to claim 1, characterized in that, The molar ratio of divalent manganese in the divalent manganese salt to bicarbonate in the solution containing bicarbonate is 1:(2-2.5).

6. The manganese dioxide-coated manganese-based lithium adsorbent according to claim 1, characterized in that, The mixing ratio of divalent manganese salt, water and ethanol in the ethanol solution containing divalent manganese salt is 1 mol: (50-80) L: (4-10) L.

7. The application of the manganese dioxide-coated manganese-based lithium adsorbent according to any one of claims 1 to 6 in the extraction of lithium.

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