A coated manganese-based lithium adsorbent and its preparation method
By using a TiO2-SiO2-C three-layer synergistic coating method, the problems of high manganese dissolution rate and insufficient mechanical strength of traditional manganese-based lithium adsorbents are solved, and a manganese-based lithium adsorbent with high adsorption capacity and stability is realized.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SICHUAN TAILI XINGKUN NEW MATERIAL CO LTD
- Filing Date
- 2025-11-06
- Publication Date
- 2026-06-30
Smart Images
Figure SMS_1
Abstract
Description
Technical Field
[0001] This invention relates to the field of manganese-based lithium adsorbents, and more specifically, to a coated manganese-based lithium adsorbent and its preparation method. Background Technology
[0002] Approximately 80% of the world's lithium resources are found in salt lake brines. However, these brines have a high magnesium-to-lithium ratio and low lithium concentration, making traditional lithium extraction methods costly and inefficient. Adsorption methods, due to their simplicity, environmental friendliness, and high selectivity, have become one of the most promising lithium extraction technologies from salt lakes.
[0003] Manganese-based lithium adsorbents exhibit significant advantages in the recovery of low-concentration lithium resources such as salt lake brines and gas field produced water due to their high selectivity, low cost, and environmental friendliness. Their core advantage lies in the fact that the crystal structure of manganese oxides can achieve lithium recovery through the ion sieving effect. + With Mg 2+ High-concentration coexisting ions can be efficiently separated. However, traditional manganese-based materials suffer from drawbacks such as high manganese dissolution rate (>5% after cycling) and insufficient mechanical strength. Furthermore, under complex water quality conditions, their adsorption capacity is easily affected by the magnesium-lithium ratio, leading to a decrease. In addition, the irreversible phase transition of manganese ions during adsorption-desorption can cause structural collapse, limiting their cycling stability.
[0004] Coated manganese-based lithium adsorbents can effectively address the aforementioned shortcomings of traditional manganese-based adsorbents through surface modification. For example, inert materials can be used for coating, such as silica or carbon layers, to encapsulate manganese particles. This physical barrier reduces manganese dissolution, lowering the dissolution rate from 5% to below 2%, while simultaneously enhancing the material's conductivity to improve adsorption kinetics. Furthermore, surface modification with metal oxides or polymers can modulate lithium-ion transport pathways and selectively enhance Li-ion adsorption. + Adsorption sites can also suppress side reactions through interfacial catalysis. Furthermore, manganese-based materials can be composited with two-dimensional materials, utilizing their high specific surface area and mechanical stability to buffer structural strain during cycling.
[0005] However, the coating layer on the surface of coated manganese-based adsorbents can hinder the exposure of active sites, reduce the specific surface area, and affect adsorption efficiency. Secondly, insufficient bonding strength between the coating layer and the matrix material can easily lead to interfacial failure. Summary of the Invention
[0006] The purpose of this invention is to provide a coated manganese-based lithium adsorbent, which has high adsorption capacity and high stability through a three-layer synergistic coating of TiO2-SiO2-C.
[0007] Another objective of this invention is to provide a method for preparing a coated manganese-based lithium adsorbent, which has high adsorption capacity and high stability through a three-layer synergistic coating of TiO2-SiO2-C.
[0008] The invention solves its technical problem by employing the following technical solutions.
[0009] On one hand, embodiments of the present invention provide a method for preparing a coated manganese-based lithium adsorbent, comprising the following steps:
[0010] S1: Silica nanoparticles were dispersed in a mixed solution of ethanol, water and ethylenediamine, and ultrasonically dispersed. Hexadecyltrimethylammonium bromide was added and ultrasonically dispersed again. Tetraethyl orthosilicate was then added dropwise, and the mixture was reacted under stirring for 10-12 hours. The mixture was then centrifuged, washed, dried, calcined, and cooled to obtain a silicon-based core.
[0011] S2: The silicon-based core was dispersed in anhydrous ethanol and ultrasonically dispersed. A mixed solution of tetrabutyl titanate and anhydrous ethanol was added dropwise at a rate of 1 mL / min at 0-5℃. Then a mixed solution of water and ethanol was added dropwise at a rate of 0.5 mL / min. After centrifugation, washing and drying, the titanium-silicon composite core was obtained.
[0012] S3: Add titanium-silicon composite core and glucose aqueous solution to a high-pressure reactor, and hydrothermally react at 160-180℃ for 10-12 hours. After cooling and centrifugation, an intermediate is obtained. The intermediate is mixed with solid potassium hydroxide, calcined, cooled, and washed to obtain a porous core.
[0013] S4: Lithium carbonate, electrolytic manganese dioxide, porous core, and an appropriate amount of anhydrous ethanol are mixed, milled in a ball mill for 4-5 hours, dried, calcined, and naturally cooled to room temperature before being ground to obtain precursor powder.
[0014] S5, the precursor powder is added to hydrochloric acid solution, shaken at 100-150 rpm for 24 hours at 25°C, centrifuged, washed and dried to obtain coated manganese-based lithium adsorbent.
[0015] In some embodiments of the present invention, in step S1, hexadecyltrimethylammonium bromide (CTAB) can be replaced by other cationic surfactants, such as hexadecyltrimethylammonium chloride (CTAC), or structure-directing agents such as Pluronic block copolymers (e.g., P123, F127); tetraethyl orthosilicate (TEOS) can be replaced by other silanes, such as methyl orthosilicate (TMOS); and ethylenediamine can be replaced by ammonia or other alkaline catalysts.
[0016] In step S2, tetrabutyl titanate can be replaced by titanium tetrachloride or titanium oxysulfate, etc.
[0017] In step S3, glucose can be replaced by other carbon-bearable biomass carbon sources, such as sucrose or starch.
[0018] In step S4, lithium carbonate can be replaced by lithium hydroxide or lithium nitrate; electrolytic manganese dioxide can be replaced by chemical manganese dioxide or manganese carbonate, manganese nitrate, etc.
[0019] In step S5, the hydrochloric acid used for pickling can be replaced by inorganic acids such as sulfuric acid or nitric acid.
[0020] In some embodiments of the present invention, in step S4, the calcination includes: heating to 480°C at a rate of 2°C / min in air atmosphere and holding at that temperature for 6 hours; then heating to 500°C at a rate of 2°C / min and calcining for 10-12 hours. The molar ratio of lithium to manganese is 1:2, and the mass ratio of the total mass of lithium carbonate and electrolytic manganese dioxide to the porous core is 2-2.5:1.
[0021] In some embodiments of the present invention, in step S2, the mass-to-volume ratio of the silicon-based core to tetrabutyl titanate is (2-2.5) g:1 mL. The rate of addition of the tetrabutyl titanate and anhydrous ethanol mixture is 1-2 mL / min, and the reaction is allowed to proceed for 1.5-2 h after the addition is complete; the rate of addition of the water and ethanol mixture is 0.3-0.5 mL / min, and the reaction is allowed to proceed for another 10-12 h after the addition is complete.
[0022] In some embodiments of the present invention, in step S3, the calcination is performed by heating from room temperature to 500-550°C at a heating rate of 1-1.5°C / min, holding at that temperature for 4 hours, and then cooling to room temperature. The mass ratio of the intermediate to solid potassium hydroxide is 3:1, and the mass ratio of glucose to the second particle is 1:2-1:3.
[0023] In some embodiments of the present invention, in step S1, the rate of adding tetraethyl orthosilicate is 0.5-1.0 mL / min. In step S1, the calcination is performed by heating to 500-550°C at a rate of 1-2°C / min under an inert atmosphere, holding at that temperature for 3.5-4 hours, and then cooling to room temperature.
[0024] On the other hand, embodiments of the present invention provide a coated manganese-based lithium adsorbent, which is prepared by the above method.
[0025] Compared with the prior art, the embodiments of the present invention have at least the following advantages or beneficial effects:
[0026] The adsorbent preparation method provided by the present invention synthesizes silica nanoparticles with good monodispersity and rich silanol groups on the surface in step S1. Hexadecyltrimethylammonium bromide (CTAB) is added as a template agent, and mesopores can be generated after calcination, which initially increases the specific surface area of the material and provides a uniform substrate for subsequent coating and modification.
[0027] In step S2, a titanium dioxide layer is coated onto the silicon-based core, forming a core-shell structure. Titanium dioxide (TiO2) itself has high chemical stability and good mechanical strength, which can significantly enhance the core's robustness. Secondly, titanium dioxide has a certain affinity for lithium ions, and its surface titanium hydroxyl groups can serve as secondary adsorption sites, helping to improve adsorption capacity or ion exchange kinetics. The entire coating process is carried out at a low temperature of 0-5℃, which can effectively control the hydrolysis rate of tetrabutyl titanate, avoid the aggregation of titanium dioxide nanoparticles, ensure the formation of a uniform coating layer, and at the same time, not damage the internal silicon sphere structure.
[0028] In step S3, through hydrothermal carbonization of glucose and subsequent activation with KOH, a carbon layer is formed on the surface of the silicon-titanium core. KOH reacts with the carbon at high temperature, causing vigorous etching and generating numerous micropores and mesopores. Simultaneously, KOH also has a corrosive effect on silicon dioxide, further enriching the pore structure. The synergistic effect of glucose and potassium hydroxide forms a porous shell with a large specific surface area, providing a large adhesion surface for subsequent loading of manganese-based active materials. Furthermore, the abundant pore structure provides pathways for rapid lithium-ion diffusion, which is beneficial for improving the adsorption rate.
[0029] In step S4, lithium carbonate, electrolytic manganese dioxide, and the porous core are mixed using ball milling. The mechanical force of ball milling ensures that the precursor of the active component is fully and uniformly embedded into the pores of the porous core and covers its surface, achieving close physical contact between the two. The subsequent step-by-step calcination process not only allows Li2CO3 and EMD to react to generate spinel-type LiMn2O4 active material, but more importantly, at high temperature, the newly formed LiMn2O4 crystals undergo a slight solid-phase reaction or form chemical bonds with the surface of the TiO2-SiO2 core, thereby firmly anchoring the active component to the core and reducing manganese dissolution. By controlling the mass ratio of the active material (lithium carbonate + electrolytic manganese dioxide) to the porous core to 2-2.5:1, it is ensured that the active component is the main body of the material, guaranteeing the final adsorption capacity, while providing a sufficient core as a supporting framework. Detailed Implementation
[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.
[0031] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to specific embodiments.
[0032] Example 1
[0033] The adsorbent of this embodiment is prepared according to the following steps:
[0034] S1. 5g of silica nanoparticles were dispersed in a mixed solution of 80mL ethanol, 20mL water and 1mL ethylenediamine, and ultrasonically dispersed. 0.5g of hexadecyltrimethylammonium bromide was added, and ultrasonic dispersion was carried out for 30min. Then, 1mL of tetraethyl orthosilicate was added dropwise at a rate of 0.5mL / min, and the reaction was carried out under stirring for 12h. After centrifugation, washing and drying, the temperature was raised to 550℃ at a rate of 1℃ / min under an inert atmosphere and held for 4h. After cooling to room temperature, a silicon-based core was obtained.
[0035] S2, 5g of silicon-based core was dispersed in 100mL of anhydrous ethanol and ultrasonically dispersed for 30min. At 0-5℃, a mixed solution of 2mL tetrabutyl titanate and 100mL anhydrous ethanol was added dropwise at a rate of 1mL / min. After the addition was completed, the reaction was allowed to proceed for 2h. Then, a mixed solution of 2mL water and 18mL ethanol was added dropwise at a rate of 0.5mL / min. After the addition was completed, the reaction was allowed to proceed for another 12h. After centrifugation, washing, and drying, the titanium-silicon composite core was obtained. The mass-volume ratio of silicon-based core to tetrabutyl titanate was 2.5g:1mL.
[0036] S3. 4g of titanium-silicon composite core and glucose aqueous solution (2g glucose, 20mL water) were added to a high-pressure reactor and hydrothermally reacted at 180℃ for 12h. After cooling and centrifugation, an intermediate was obtained. 6g of the intermediate was mixed with 2g of solid potassium hydroxide and heated from room temperature to 550℃ at a rate of 1.5℃ / min, held at that temperature for 4 hours, cooled to room temperature, and washed to obtain a porous core. The mass ratio of glucose to titanium-silicon composite core was 1:2, and the mass ratio of intermediate to solid potassium hydroxide was 3:1.
[0037] S4. Lithium carbonate, electrolytic manganese dioxide, and porous cores are mixed with an appropriate amount of anhydrous ethanol, milled in a ball mill for 4-5 hours, dried, heated to 480°C at a rate of 2°C / min in air atmosphere, and held at that temperature for 6 hours; then heated to 500°C at a rate of 2°C / min and calcined for 10-12 hours. After naturally cooling to room temperature, it is ground until the D50 is 10-20 μm to obtain the precursor powder; wherein, the molar ratio of lithium to manganese is 1:2, and the mass ratio of the total mass of lithium carbonate and electrolytic manganese dioxide to the mass of the porous cores is 2:1.
[0038] S5, the precursor powder is added to 100 mL of 0.5 M hydrochloric acid solution, shaken at 150 rpm for 24 h at 25 °C, centrifuged, washed and dried to obtain coated manganese-based lithium adsorbent.
[0039] Example 2
[0040] The difference from Example 1 is that in step S2, the mass-to-volume ratio of the silicon-based core to tetrabutyl titanate is 2g:1mL, while all other conditions are the same as in Example 1.
[0041] Example 3
[0042] The difference from Example 1 is that in step S2, the mass-to-volume ratio of silicon-based core to tetrabutyl titanate is 2.2 g: 1 mL, and all other conditions are the same as in Example 1.
[0043] Example 4
[0044] The difference from Example 1 is that the amount of tetraethyl orthosilicate used in step S1 is 0.5 mL, while all other conditions are the same as in Example 1.
[0045] Example 5
[0046] The difference from Example 1 is that the amount of tetraethyl orthosilicate used in step S1 is 1.5 mL, while all other conditions are the same as in Example 1.
[0047] Example 6
[0048] The difference from Example 1 is that in step S3, the mass ratio of glucose to titanium-silicon composite core is 1:2.5, while all other conditions are the same as in Example 1.
[0049] Example 7
[0050] The difference from Example 1 is that in step S3, the mass ratio of glucose to titanium-silicon composite core is 1:3, while all other conditions are the same as in Example 1.
[0051] Comparative Example 1
[0052] The difference from Example 1 is that step S3 is not performed, while the remaining steps and raw material amounts are the same as in Example 1.
[0053] Comparative Example 2
[0054] The difference from Example 1 is that step S2 is not performed, while the remaining steps and raw material amounts are the same as in Example 1.
[0055] Experimental Example
[0056] The adsorbents (powder, D50=10-20um) of Examples 1-7 and Comparative Examples 1-2 were used as test objects. The specific surface area, average pore size, lithium adsorption capacity, and manganese dissolution rate (%) of each adsorbent were tested. The results are shown in Table 1.
[0057] Specific surface area was measured using the low-temperature nitrogen adsorption-desorption method, in accordance with the national standard GB / T 19587-2017; lithium adsorption capacity was measured using the static adsorption method.
[0058] Table 1
[0059]
[0060] As can be seen from Table 1, the adsorbent of the embodiments, with its multilayer structure (silicon core-titanium layer-carbon layer-manganese base layer), provides a high specific surface area, suitable pore size, high adsorption capacity and low manganese dissolution rate.
[0061] Comparing Examples 1-3, as the proportion of tetrabutyl titanate increases (i.e., the titanium layer becomes thinner), the specific surface area and pore size increase slightly, and the adsorption capacity increases slightly, but the manganese dissolution rate also increases. A thinner titanium layer means more space for the subsequent carbon and manganese layers, thereby increasing the specific surface area and active sites, and improving the adsorption capacity. However, the thinner titanium layer weakens its protective effect, making manganese ions more easily dissolved during acid washing and subsequent use.
[0062] Comparing Examples 1, 4, and 5, a decrease in the amount of tetraethyl orthosilicate (TEOS) (thinner silicon shell) resulted in a slightly higher specific surface area and adsorption capacity, but slightly lower stability (slightly higher manganese dissolution loss). An increase in the amount of TEOS (thicker silicon shell) resulted in a denser structure, a slight decrease in specific surface area and capacity, but better protection (lowest manganese dissolution loss). The amount of TEOS directly affects the core size and surface smoothness. A moderate amount (Example 1) achieved a balance between providing a good template and maintaining a high specific surface area.
[0063] Compared with Examples 1, 6, and 7, reducing the amount of glucose (thinning the carbon layer) led to a significant decrease in specific surface area, an increase in average pore size, a decrease in adsorption capacity, and an increase in manganese dissolution rate. The carbon layer is key to creating a high specific surface area and conductive network. A thinner carbon layer reduces the micropores and mesopores generated by KOH activation, resulting in a decrease in specific surface area and adsorption sites. Simultaneously, the thinner carbon layer weakens the physical coating and conductive stabilization effect on manganese, leading to increased manganese dissolution.
[0064] Comparative Example 1 (without carbon layer): The specific surface area and pore size are significantly reduced due to the lack of numerous pores generated by the KOH-activated carbon. The low adsorption capacity is due to the lack of a conductive network, preventing the manganese oxide from fully utilizing its activity. The manganese dissolution rate is extremely high because the lack of physical protection from the carbon layer exposes manganese directly to the acid solution.
[0065] Comparative Example 2 (without titanium layer): The specific surface area and pore size are not significantly different from the examples, indicating that the pore structure is mainly determined by the carbon layer. However, the adsorption capacity is reduced, especially the manganese dissolution rate, which is significantly higher than in all examples. This demonstrates the importance of the titanium layer as an interfacial stabilizing layer, preventing outer layer peeling and loss of manganese active sites. Without the titanium layer, the core-shell structure is more unstable during heat treatment and use.
[0066] The embodiments described above are some, but not all, embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.
Claims
1. A method for preparing a coated manganese-based lithium adsorbent, characterized in that, Includes the following steps: S1: Disperse silica nanoparticles in a mixed solution of ethanol, water and ethylenediamine, sonicate, add hexadecyltrimethylammonium bromide, sonicate again, then add tetraethyl orthosilicate dropwise, and react under stirring for 10-12 hours. Centrifugation, washing, drying, calcination, and cooling yield silicon-based cores; S2: Disperse the silicon-based core in anhydrous ethanol, ultrasonically disperse it, and add a mixed solution of tetrabutyl titanate and anhydrous ethanol dropwise at 0-5℃; then add a mixed solution of water and ethanol dropwise. Centrifugation, washing, and drying yield the titanium-silicon composite core; S3: Add titanium-silicon composite core and glucose aqueous solution to a high-pressure reactor, and hydrothermally react at 160-180℃ for 10-12 hours. After cooling and centrifugation, an intermediate is obtained. The intermediate is mixed with solid potassium hydroxide, calcined, cooled, and washed to obtain a porous core. S4: Lithium carbonate, electrolytic manganese dioxide, porous core, and an appropriate amount of anhydrous ethanol are mixed, milled in a ball mill for 4-5 hours, dried, calcined, and naturally cooled to room temperature before being ground to obtain precursor powder. S5, the precursor powder is added to hydrochloric acid solution, shaken at 100-150 rpm for 24 hours at 25°C, centrifuged, washed and dried to obtain coated manganese-based lithium adsorbent.
2. The preparation method of the coated manganese-based lithium adsorbent according to claim 1, characterized in that, In step S4, the calcination includes: heating to 480°C at a rate of 2°C / min in air atmosphere and holding at that temperature for 6 hours; then heating to 500°C at a rate of 2°C / min and calcining for 10-12 hours.
3. The preparation method of the coated manganese-based lithium adsorbent according to claim 1, characterized in that, In step S2, the mass-to-volume ratio of the silicon-based core to tetrabutyl titanate is (2-2.5) g: 1 mL.
4. The method for preparing the coated manganese-based lithium adsorbent according to claim 1, characterized in that, In step S2, the rate of adding the tetrabutyl titanate and anhydrous ethanol mixture is 1-2 mL / min, and the reaction is allowed to proceed for 1.5-2 h after the addition is complete. The rate of adding the water and ethanol mixture was 0.3-0.5 mL / min. After the addition was completed, the mixture was allowed to react for another 10-12 hours.
5. The method for preparing the coated manganese-based lithium adsorbent according to claim 1, characterized in that, In step S1, the rate of adding tetraethyl orthosilicate is 0.5-1.0 mL / min.
6. The method for preparing the coated manganese-based lithium adsorbent according to claim 1, characterized in that, In step S3, the calcination is performed by heating from room temperature to 500-550°C at a heating rate of 1-1.5°C / min, holding at that temperature for 4 hours, and then cooling to room temperature.
7. The method for preparing the coated manganese-based lithium adsorbent according to claim 1, characterized in that, In step S1, the calcination is performed by heating the temperature to 500-550°C at a rate of 1-2°C / min under an inert atmosphere, holding the temperature for 3.5-4 hours, and then cooling to room temperature.
8. The method for preparing the coated manganese-based lithium adsorbent according to claim 1, characterized in that, In step S3, the mass ratio of the intermediate to solid potassium hydroxide is 3:1, and the mass ratio of glucose to the titanium-silicon composite core is 1:2-1:
3.
9. The method for preparing the coated manganese-based lithium adsorbent according to claim 1, characterized in that, In step S4, the molar ratio of lithium to manganese is 1:2, and the total mass ratio of lithium carbonate and electrolytic manganese dioxide to the porous core is 2-2.5:
1.
10. A coated manganese-based lithium adsorbent, characterized in that, It is prepared by the method described in any one of claims 1-9.