Doped manganese-based lithium sorbents and methods of making same

Abstract

The application provides a doped manganese-based lithium adsorbent and a preparation method thereof, relates to the field of manganese-based adsorbents, and comprises the following steps: adding Li2CO3, manganese dioxide, MgO and TiO2 powders into a ball mill and uniformly mixing; adding into a muffle furnace and calcining under an air atmosphere; crushing, grinding and sieving; putting the precursor powder into a centrifugal granulator, continuously spraying a binder solution in an atomized form, and mutually adhering the precursor powder and the binder solution to obtain green granules; calcining the green granules in the muffle furnace under the air atmosphere; soaking, washing, and drying to obtain the adsorbent. The adsorbent has high strength, good stability, high mass transfer efficiency and long service life.

Description

Technical Field

[0001] This invention relates to the field of manganese-based adsorbents, and more specifically, to a doped manganese-based lithium adsorbent and its preparation method. Background Technology

[0002] Lithium, as an important strategic resource, is in increasing demand in fields such as new energy vehicles and energy storage batteries. Approximately 80% of the world's lithium resources are found in salt lake brines, but 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 technologies for lithium extraction from salt lakes.

[0003] Manganese-based lithium adsorbents (such as Li) 1.6 Mn 1.6 O4 has attracted widespread attention due to its high theoretical adsorption capacity and good lithium selectivity. Patent CN118558289A discloses Al-doped modified Li. 1.6 Mn 1.6 The O4 method, through Al 3+ Replace part of Mn 3+ This improves structural stability and adsorption capacity, but its ionic radius (0.535 Å) is similar to that of Mn. 3+ The difference in 0.645 Å is significant, and lattice distortion remains a problem. The mismatch in ionic radii leads to large internal stress in the lattice, changes in the lattice constant, and local lattice distortion. Long-term cycling stability is not ideal, with a capacity retention of approximately 83% after 5 cycles. In addition, excessive Al doping can block lithium-ion transport channels, thereby reducing adsorption kinetics performance. Summary of the Invention

[0004] The purpose of this invention is to provide a doped manganese-based lithium adsorbent with high strength, good stability, high mass transfer efficiency, and long service life.

[0005] Another objective of this invention is to provide a method for preparing a doped manganese-based lithium adsorbent, which involves two sintering processes. In the first sintering, a crystal structure is formed, and in the second low-temperature calcination, a pore-forming agent is removed, forming pores in the particles. Furthermore, the strength of the particles is enhanced through the second low-temperature sintering.

[0006] The technical problem solved by this invention is achieved by the following technical solution.

[0007] On one hand, embodiments of the present invention provide a doped manganese-based lithium adsorbent, comprising the following steps:

[0008] S1. Weigh out Li2CO3, manganese dioxide, MgO and TiO2 powders in a molar ratio of Li:Mn:Mg:Ti=1.6:1.6:0.05:0.10; add each powder to a ball mill and dry grind at 300-500 rpm for 2-3 hours until they are mixed evenly.

[0009] S2, add the mixture obtained in step S1 into a muffle furnace and calcine it in air atmosphere for 8-10 hours, then cool it naturally to room temperature to obtain the precursor;

[0010] S3, crush, grind and sieve the precursor from step S2 to obtain precursor powder;

[0011] S4, Sodium bicarbonate is added to the aqueous solution of hydroxypropyl methylcellulose and mixed evenly to obtain a binder solution; the precursor powder is put into a centrifugal granulator, the rotation is started, and the binder solution is continuously sprayed in the form of atomization, which adheres to the precursor powder in the rolling state to obtain green pellets.

[0012] S5, using the green pellets as the core, calcining the green pellets in an air atmosphere in a muffle furnace; soaking, washing, and drying to obtain the adsorbent.

[0013] In some embodiments of the present invention, in step S2, the calcination is: heating from room temperature to 300°C at a heating rate of 2°C / min;

[0014] Then, increase the temperature from 300℃ to 450℃ at a heating rate of 1℃ / min, and hold at 450℃ for 1-1.5 hours.

[0015] Then, raise the temperature from 450℃ to 680-720℃ at a heating rate of 2℃ / min, hold for 4-6 hours, cool with the furnace to 300℃, introduce a mixed gas containing oxygen, and then allow it to cool naturally.

[0016] In some embodiments of the present invention, the binder solution is composed of 3-5 wt% aqueous solution of hydroxypropyl methylcellulose and 10-20% sodium bicarbonate by mass of the precursor powder.

[0017] In some embodiments of the present invention, the aqueous solution of hydroxypropyl methylcellulose can also be replaced by polyvinyl alcohol, polyethylene glycol, silica sol, or aluminum sol; sodium bicarbonate can also be replaced by ammonium carbonate, ammonium bicarbonate, or ammonium oxalate.

[0018] In some embodiments of the present invention, step S5, the calcination includes the following steps:

[0019] The temperature is increased from room temperature to 250-300℃ at a rate of 1℃ / min and held at that temperature for 1-2 hours.

[0020] Increase the temperature to 600-800℃ at a rate of 2-3℃ / min, and hold for 1-2 hours;

[0021] After the furnace cools to 300°C, a mixture of oxygen-containing gas is introduced, and then the furnace is allowed to cool naturally.

[0022] In some embodiments of the present invention, the temperature of hot air drying is 60-80°C; the temperature of heat treatment is 400-450°C.

[0023] In some embodiments of the present invention, the method further includes pretreatment of manganese dioxide: manganese dioxide is mixed with Mg(NO3)2·6H2O and (NH4)2TiO(C2O4)2 and then dry-milled. The amount of Mg(NO3)2·6H2O added is 0.5-1.0 wt% of the mass of manganese dioxide, and the amount of (NH4)2TiO(C2O4)2 added is 0.5-1.0 wt% of the mass of manganese dioxide.

[0024] In some embodiments of the present invention, in step S4, the particle size of the precursor powder is less than 400 mesh.

[0025] Secondly, a doped manganese-based lithium adsorbent is provided, which is prepared by the above method.

[0026] Compared with the prior art, the embodiments of the present invention have at least the following advantages or beneficial effects:

[0027] The doped manganese-based lithium adsorbent provided by this invention has high strength, good stability, high mass transfer efficiency, and long service life. Mg 2+ The ionic radius (0.72 Å) of Li is similar to that of Li + (0.76 Å) similar, it can partially replace Li in the lithium manganese oxide lattice. + This creates sites for the formation of stable solid solutions. It can suppress lattice collapse during lithium-ion insertion / extraction, improve structural stability, and simultaneously regulate surface charge, enhancing the resistance to Li-ion degradation. + Selective adsorption of Ti. 4+ As a high-valence cation, TiO2 can enter the lithium manganese oxide lattice, occupy Mn sites, and form Ti-O-Mn bonds, enhancing the stability of the crystal structure. TiO2 can also reduce the redox reaction of manganese, inhibit manganese dissolution, and improve the resistance to Li+ through surface modification. + The affinity of Li. Doping with Mg and Ti makes the crystal structure of the adsorbent material more regular and forms selective sites on the surface, which enhances its affinity for Li. + It has a high affinity for other ions (such as Na+). + K + Mg 2+ The adsorption of ) is relatively weak.

[0028] During calcination, the pore-forming agent sodium bicarbonate forms abundant macropores within the particles, greatly reducing the Li content. + The reduced resistance to ion diffusion from the outside of the particle to the internal active sites shortens the adsorption / desorption cycle, resulting in higher lithium extraction per unit time. The organic binder hydroxypropyl methylcellulose and the pore-forming agent sodium bicarbonate are completely removed during heat treatment, leaving no residue; simultaneously, solid and liquid waste caused by pulverization and dissolution is significantly reduced.

[0029] This adsorbent uses a magnesium-titanium co-doped manganese-based adsorbent as its core, exhibiting high-capacity and highly selective chemisorption. Through two sintering processes, a crystalline structure is formed during the first sintering, and the pore-forming agent is removed during the second low-temperature calcination, creating pores within the particles. Furthermore, the second low-temperature sintering enhances the particle strength. 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] Prepare a doped manganese-based lithium adsorbent using the following steps:

[0034] S1, manganese dioxide, Mg(NO3)2·6H2O (1.0 wt% of manganese dioxide), and (NH4)2TiO(C2O4)2 (1.0 wt% of manganese dioxide) are mixed and dry-milled to obtain treated manganese dioxide; Li2CO3, treated manganese dioxide, MgO, and TiO2 powders are weighed in a molar ratio of Li:Mn:Mg:Ti=1.6:1.6:0.05:0.10; each powder is added to a ball mill and dry-milled at 300 rpm for 2 hours to mix evenly;

[0035] S2, the mixture obtained in step S1 is added to a muffle furnace and heated from room temperature to 300°C at a heating rate of 2°C / min under an air atmosphere; then heated from 300°C to 450°C at a heating rate of 1°C / min and held at 450°C for 1 hour; then heated from 450°C to 700°C at a heating rate of 2°C / min and held at 700°C for 5 hours. After cooling to 300°C in the furnace, a mixed gas containing oxygen (50 vol% oxygen and 50 vol% nitrogen) is introduced, and then the mixture is allowed to cool naturally to room temperature to obtain the precursor.

[0036] S3, crush, grind and pass the precursor from step S2 through a 400-mesh sieve to obtain precursor powder;

[0037] S4, add sodium bicarbonate (10% of the precursor powder mass) to a 5wt% aqueous solution of hydroxypropyl methylcellulose, mix evenly to obtain a binder solution; put the precursor powder into a centrifugal granulator, start the rotation, and continuously spray the binder solution in the form of atomization, so that it adheres to the precursor powder in the rolling state, and crush it into particles with a particle size of 0.3-0.5mm to obtain green pellets;

[0038] S5. In a muffle furnace under air atmosphere, the green pellets were calcined according to the following procedure: the temperature was increased from room temperature to 300°C at a rate of 1°C / min and held for 2 hours; the temperature was then increased to 700°C at a rate of 3°C / min and held for 2 hours; after cooling to 300°C in the furnace, an oxygen-containing mixed gas was introduced, followed by natural cooling. The pellets were then soaked and washed three times with a 0.2 mol / L LiOH solution at 60°C for 1 hour each time; and dried at 100°C to obtain the adsorbent.

[0039] Example 2

[0040] The difference from Example 1 is that in step S1, during the pretreatment of manganese dioxide, 0.5 wt% Mg(NO3)2·6H2O and 1.0 wt% (NH4)2TiO(C2O4)2 of manganese dioxide are added and mixed, followed by dry grinding. The remaining steps and raw material amounts are the same as in Example 1.

[0041] Example 3

[0042] The difference from Example 1 is that, in step S1, during the pretreatment of manganese dioxide, 1.0 wt% of Mg(NO3)2·6H2O and 0.5 wt% of (NH4)2TiO(C2O4)2 are added and mixed, followed by dry grinding. The remaining steps and raw material amounts are the same as in Example 1.

[0043] Example 4

[0044] The difference from Example 1 is that in step S1, during the pretreatment of manganese dioxide, 0.5 wt% of Mg(NO3)2·6H2O and 0.5 wt% of (NH4)2TiO(C2O4)2 are added and mixed, followed by dry grinding. The remaining steps and raw material amounts are the same as in Example 1.

[0045] Example 5

[0046] The difference from Example 1 lies in the following: in step S2, some parameters of the calcination process are different, specifically, the temperature is maintained at 450°C for 1.5 hours and at 720°C for 4 hours. The remaining steps and raw material amounts are the same as in Example 1.

[0047] Example 6

[0048] The difference from Example 1 is that some parameters of the calcination process are different in step S2, namely, holding at 450°C for 1 hour and holding at 680°C for 6 hours. The remaining steps and raw material amounts are the same as in Example 1.

[0049] Example 7

[0050] The difference from Example 1 is that the binder solution is composed of a 3 wt% aqueous solution of hydroxypropyl methylcellulose and 20% sodium bicarbonate by weight of the precursor powder. The remaining steps and raw material amounts are the same as in Example 1.

[0051] Example 8

[0052] The difference from Example 1 is that the binder solution is composed of a 4 wt% aqueous solution of hydroxypropyl methylcellulose and a 15% sodium bicarbonate solution by weight of the precursor powder. The remaining steps and raw material amounts are the same as in Example 1.

[0053] Example 9

[0054] The difference from Example 1 is that in step S5, the green pellets are calcined: the temperature is increased from room temperature to 250°C at a rate of 1°C / min and held for 1 hour; then increased to 450°C at a rate of 3°C / min and held for 1 hour; after cooling to 300°C in the furnace, an oxygen-containing mixed gas is introduced, followed by natural cooling. The remaining steps and raw material amounts are the same as in Example 1.

[0055] Example 10

[0056] The difference from Example 1 is that in step S5, the green pellets are calcined: the temperature is increased from room temperature to 250°C at a rate of 1°C / min and held for 2 hours; then increased to 450°C at a rate of 2°C / min and held for 2 hours; after cooling to 300°C in the furnace, an oxygen-containing mixed gas is introduced, followed by natural cooling. The remaining steps and raw material amounts are the same as in Example 1.

[0057] Comparative Example 1

[0058] The precursor powder was prepared according to steps S1-S3 of Example 1.

[0059] Comparative Example 2

[0060] Green pellets prepared according to steps S1-S4 of Example 1.

[0061] Experimental Example

[0062] The following tests were conducted using the adsorbents prepared in Examples 1-10, the precursor powder prepared in Comparative Example 1, and the green pellets prepared in Comparative Example 2 as test objects.

[0063] Adsorbent pretreatment: Rinse the adsorbent three times with deionized water, then dry it in an oven at 105°C until constant weight, and then cool it to room temperature in a desiccator for later use.

[0064] Adsorption capacity test solution: Prepared using analytical grade lithium chloride (LiCl) with an initial concentration (C0) of 100 mg / L (in Li...). + The solution was prepared. The pH was precisely adjusted to 12.0 using a 0.1 mol / L NaOH solution.

[0065] Selective test solution (simulated brine): The solution was prepared using analytical grade lithium chloride (LiCl) and magnesium chloride hexahydrate (MgCl2·6H2O), wherein Li... + The concentration is 20 mg / L, Mg 2+ The concentration was 1000 mg / L (i.e., Mg / Li mass ratio = 50:1). The pH was adjusted to 7.0 using dilute NaOH or HCl solution (to simulate the neutral environment of salt lake brine).

[0066] Desorption solution: Prepare a 0.5 mol / L hydrochloric acid (HCl) solution.

[0067] Adsorption capacity (Q, mg / g) test: 100 mL (V) of adsorption capacity test solution was accurately added to several 250 mL stoppered conical flasks. 0.1000 g (m) of the pretreated adsorbent was accurately weighed and added to each flask (i.e., solid-liquid ratio = 1 g / L). The flasks were placed in a constant-temperature shaker and shaken at 150 rpm at 25 ± 1 °C. At preset time points (0.5, 1, 2, 4, 6, 8, 12, 24 h), one flask was removed and immediately filtered through a 0.22 μm aqueous microporous membrane, and the filtrate was collected. The Li content in the filtrate was determined using inductively coupled plasma optical emission spectrometry (ICP-OES). + equilibrium concentration (C) e ). Calculate: Q e To balance the adsorption capacity (mg / g) = (C0 - C) e )*V / m, where: Q e To balance the adsorption capacity (mg / g); C0 and C e , where is the initial and equilibrium lithium concentration (mg / L); V is the solution volume (L); m is the adsorbent mass (g).

[0068] Separation factor (α) test: Add 100 mL of selective test solution (simulated brine) to a 250 mL stoppered conical flask. Accurately add 0.2000 g of adsorbent (solid-liquid ratio = 2 g / L). Shake at 25 ± 1 °C and 150 rpm for 8 hours (ensuring adsorption equilibrium is reached). Filter and collect the filtrate. Simultaneously determine the Li in the filtrate using ICP-OES. + and Mg 2+ equilibrium concentration (C) e,Li and C e,Mg ), and manganese ion (Mn) concentration (C Mn ).

[0069] First, calculate Li. + and Mg 2+ Adsorption capacity: q = (C0 - C e )* V / m, calculate Li + and Mg 2+ The amount of adsorption, and then according to α=(q Li / C e,Li ) / (q Mg / C e,Mg Calculate the separation factor α of Li / Mg. An α value much greater than 1 indicates that the adsorbent has a high affinity for Li. + It exhibits excellent selectivity. The manganese dissolution rate (%) is calculated as follows: = (C Mn * V) / m * 100%.

[0070] Cyclic adsorption-desorption experiment: 100 mL of simulated brine and 0.2000 g of fresh adsorbent were added to an Erlenmeyer flask, and adsorption was allowed to proceed for 8 hours. After filtration, the Li concentration in the filtrate was measured, and the adsorption capacity Q1 was calculated.

[0071] Washing: Rinse the adsorbent particles twice quickly with a small amount of deionized water.

[0072] Desorption: Transfer the adsorbed particles to a new conical flask containing 100 mL of 0.5 M HCl desorption solution and desorb for 4 h.

[0073] Washing and regeneration: Filter and wash with deionized water until neutral. Then dry the adsorbent at 105°C for 4 hours, which is considered as complete regeneration.

[0074] Repeat the adsorption-desorption steps for the next cycle. Record the adsorption capacity for each cycle. Using the adsorption capacity of the first cycle as 100%, calculate the adsorption capacity for the 5th cycle (Q5) and the 50th cycle (Q...). 50 The capacity retention rate after cycling is shown in Table 1.

[0075] Particle crushing resistance test: Ten intact adsorbent particles with no visible defects were randomly selected. Each particle was placed between two parallel plates of a particle strength tester, and pressure was applied until the particle broke. The instantaneous force value (in Newtons, N) at the moment of particle breakage was recorded. The average crushing resistance of the 10 particles was calculated.

[0076] Table 1

[0077]

[0078] Based on the experimental data in Table 1, we can conclude that:

[0079] 1. Adsorption capacity

[0080] The adsorption capacities of Examples 1-10 ranged from 23.1 to 25.5 mg / g, indicating that all examples possessed high lithium adsorption capacity. Example 9 exhibited the highest adsorption capacity (25.5 mg / g), but its other properties (such as selectivity for adsorption, cycle stability, and manganese dissolution rate) were poor. Example 10 had the lowest adsorption capacity (23.1 mg / g), but its other properties (such as selectivity for adsorption, cycle stability, and mechanical strength) were excellent. Comparative Examples 1 and 2 showed relatively low adsorption capacities (18.5 mg / g and 16.2 mg / g, respectively), indicating a significant decrease in adsorption capacity due to insufficient calcination and granulation.

[0081] 2. Select adsorption factors

[0082] The selective adsorption factors of Examples 1-10 ranged from 292 to 326, indicating that all examples exhibited high selectivity (much greater than 1) for lithium ions, effectively separating lithium from magnesium-rich brine. Examples 5 and 10 showed the highest selective adsorption factors (326 and 325), suggesting that optimizing the calcination parameters in steps S2 or S5 improved selectivity. Example 9 had a lower selective adsorption factor (292), which is related to the low-temperature calcination (450°C) in step S5, resulting in an incomplete material structure and decreased selectivity.

[0083] 3. Cyclic stability

[0084] Q5 (Capacity retention at 5th cycle): The Q5 of all examples was between 98.1% and 99.8%, indicating excellent short-term cycling stability. The Q5 of Comparative Examples 1 and 2 was lower (82.1% and 85.3%, respectively), indicating poor cycling performance of materials not treated in step S5.

[0085] Q50 (capacity retention after 50 cycles): The Q50 of the examples ranged from 95.3% to 98.5%, with Example 10 exhibiting the highest Q50 (98.5%), consistent with its low manganese dissolution rate and high mechanical strength. This indicates that the calcination procedure in step S5 (e.g., holding at 250°C for 2 hours and then at 450°C for 2 hours) significantly improves long-term stability. Example 9 showed a lower Q50 (95.3%), possibly due to the lower calcination temperature in step S5 (holding at 450°C for 1 hour), leading to material structural instability and faster capacity decay during cycling.

[0086] The Q50 values ​​of Comparative Examples 1 and 2 were significantly lower (55.3% and 67.4%, respectively), highlighting the crucial role of the S5 step calcination and washing in maintaining long-term stability.

[0087] 4. Manganese dissolution rate

[0088] The manganese dissolution rates in Examples 1-10 were all very low (0.02%-0.08%), indicating that the material structure was stable during the adsorption-desorption process and that manganese ion leaching was minimal. Example 10 exhibited the lowest manganese dissolution rate (0.02%), consistent with its high mechanical strength and cycle stability. Example 9 showed a relatively high manganese dissolution rate (0.08%), which is related to insufficient structural density caused by low-temperature calcination. Comparative Examples 1 and 2 showed very high manganese dissolution rates (2.5% and 1.2%, respectively), indicating that materials not treated in step S5 are prone to manganese dissolution, affecting their service life.

[0089] 5. Mechanical strength

[0090] The mechanical strength of Examples 1-10 ranged from 28.1 to 35.8 N, indicating that the granulation and calcination processes could form robust particles. Example 10 exhibited the highest mechanical strength (35.8 N), possibly related to the longer holding times in step S5 (250°C and 450°C for 2 hours each), which promoted particle sintering and strengthening. Example 9 had the lowest mechanical strength (28.1 N), possibly due to the lower calcination temperature and shorter time in step S5. Comparative Example 2 showed a low mechanical strength (10.2 N), indicating that the green particles not calcined in step S5 had poor strength and were easily broken.

[0091] In summary, in step S1 (Mg and Ti doping): In Examples 1-4, the variation in Mg and Ti doping amounts (0.5-1.0 wt%) had little effect on adsorption capacity, selectivity, cycle stability, and mechanical strength; all indicators were similar. This indicates that within this range, doping amount is not a key variable for performance.

[0092] Step S2 (Precursor Calcination): Compared with Example 1, Examples 5 and 6 adjusted the calcination temperature and time (e.g., 720℃ for 4 hours or 680℃ for 6 hours), resulting in a slight increase in adsorption capacity, but a slight decrease in cycle stability and mechanical strength. This indicates that a higher calcination temperature may increase adsorption capacity, but may sacrifice structural stability and strength.

[0093] Step S4 (Binder Solution): Compared to Example 1, Examples 7 and 8 showed changes in HPMC concentration and NaHCO3 content, resulting in a slight decrease in adsorption capacity, but improved cycling stability and manganese dissolution rate. This indicates that binder optimization can slightly affect performance, but is not a major factor.

[0094] Step S5 (Calcination of Green Particles): Examples 9 and 10 differed from Example 1 in that the calcination process was altered (e.g., low temperature for short time vs. low temperature for long time). Example 9 showed high adsorption capacity but low selectivity, cycling stability, and mechanical strength; Example 10 showed low adsorption capacity but high selectivity, cycling stability, and mechanical strength. This demonstrates that Step S5 is crucial for balancing various performance characteristics: appropriate calcination temperature and time can improve mechanical strength and stability, but may slightly reduce adsorption capacity.

[0095] Example 1 provides the best balance of overall performance, with high adsorption capacity (24.8 mg / g), excellent selectivity (312), cycling stability (Q50 98.2%) and mechanical strength (32.5 N), and low manganese dissolution rate (0.042%).

[0096] Example 10 demonstrates outstanding performance in terms of cycle stability, mechanical strength, and manganese dissolution rate, but has a low adsorption capacity, making it suitable for applications requiring high lifespan and strength. Example 9, while exhibiting a high adsorption capacity, has poorer performance in other areas and is not recommended for long-term cycling.

[0097] 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 doped manganese-based lithium adsorbent, characterized in that, It includes the following steps: S1. Manganese dioxide is mixed with Mg(NO3)2·6H2O and (NH4)2TiO(C2O4)2, and then dry-milled to obtain treated manganese dioxide. The amount of Mg(NO3)2·6H2O added is 0.5-1.0 wt% of the mass of manganese dioxide, and the amount of (NH4)2TiO(C2O4)2 added is 0.5-1.0 wt% of the mass of manganese dioxide. Weigh out Li2CO3, treated manganese dioxide, MgO and TiO2 powders in a molar ratio of Li:Mn:Mg:Ti=1.6:1.6:0.05:0.10; add each powder to a ball mill and dry grind at 300-500 rpm for 2-3 hours until they are mixed evenly. S2, add the mixture obtained in step S1 into a muffle furnace and calcine it in air atmosphere for 8-10 hours, then cool it naturally to room temperature to obtain the precursor; S3, crush, grind and sieve the precursor from step S2 to obtain precursor powder; S4, Sodium bicarbonate is added to the aqueous solution of hydroxypropyl methylcellulose and mixed evenly to obtain a binder solution; the precursor powder is put into a centrifugal granulator, the rotation is started, and the binder solution is continuously sprayed in the form of atomization, which adheres to the precursor powder in the rolling state to obtain green pellets. S5. The green pellets are calcined in a muffle furnace under an air atmosphere; then soaked, washed, and dried to obtain the adsorbent. In step S2, the calcination is as follows: the temperature is increased from room temperature to 300°C at a heating rate of 2°C / min; then the temperature is increased from 300°C to 450°C at a heating rate of 1°C / min, and held at 450°C for 1-1.5 hours; then the temperature is increased from 450°C to 680-720°C at a heating rate of 2°C / min, and held for 4-6 hours. After cooling to 300°C in the furnace, a mixed gas containing oxygen is introduced, and then the furnace is allowed to cool naturally. In step S5, the calcination includes the following steps: heating from room temperature to 250-300℃ at a heating rate of 1℃ / min and holding at that temperature for 1-2 hours; heating to 600-800℃ at a rate of 2-3℃ / min and holding at that temperature for 1-2 hours; cooling to 300℃ in the furnace, then introducing a mixed gas containing oxygen, and then allowing it to cool naturally.

2. The method for preparing the doped manganese-based lithium adsorbent according to claim 1, characterized in that, In step S4, the binder solution is composed of 3-5 wt% aqueous solution of hydroxypropyl methylcellulose and 10-20% sodium bicarbonate by mass of the precursor powder.

3. The method for preparing the doped manganese-based lithium adsorbent according to claim 1, characterized in that, In step S5, the soaking and washing process is as follows: soak and wash 2-3 times with 0.1-0.2 mol / L LiOH solution at 60-80℃, each time for 1 hour; the drying temperature is 100-120℃.

4. The method for preparing the doped manganese-based lithium adsorbent according to claim 1, characterized in that, In step S3, the particle size of the precursor powder is less than 400 mesh.

5. The method for preparing the doped manganese-based lithium adsorbent according to claim 1, characterized in that, In step S4, the particle size of the green pellets is 0.3-0.5 mm.

6. A doped manganese-based lithium adsorbent, characterized in that, It is prepared by the method described in any one of claims 1-5.

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