A manganese-based adsorbent and its preparation method

Abstract

This application discloses a manganese-based adsorbent and its preparation method, comprising the following preparation steps: S1: reacting waste lithium manganese oxide positive electrode powder with a reducing acid to remove metal impurities to obtain a Li-Mn mixed solution; S2: adding a structure-directing agent to the Li-Mn mixed solution to generate a lithium ion sieve precursor; S3: etching and acidifying the lithium ion sieve precursor to obtain the manganese-based adsorbent. The manganese-based adsorbent of this application uses waste lithium manganese oxide battery pole pieces as the preparation raw material, which not only solves the problem of recycling waste lithium manganese oxide batteries, but also saves manganese-based adsorbent raw materials, providing a new solution for green chemistry and salt lake lithium extraction technology.

Description

Technical Field

[0001] The present application relates to the field of lithium extraction from salt lakes, and specifically to a manganese-based adsorbent and a preparation method thereof. Background Art

[0002] With the rapid development of the global new energy industry, market demand for lithium-ion batteries, core components in electric vehicles and energy storage systems, has exploded. However, global lithium reserves are limited and unevenly distributed, leading to a growing lithium-ion supply shortage, a bottleneck hindering the sustainable development of the new energy industry. Existing lithium mining and processing capacity is unable to meet this rapidly growing demand, leading to an increasingly acute imbalance between lithium supply and demand.

[0003] my country's salt lakes are rich in lithium resources. Therefore, developing new salt lake lithium extraction technologies is an important measure to effectively alleviate the shortage of lithium resources. Currently, the main methods for extracting lithium from salt lakes include precipitation, extraction, electrochemical, and adsorption. Among them, adsorption has the advantages of good selectivity for lithium ions, environmental friendliness, high adsorption capacity, and economical recycling, making it a new trend in the development of salt lake lithium extraction technologies.

[0004] Manganese-based adsorbents offer advantages such as fast adsorption and desorption rates, high adsorption capacity, good selectivity, non-toxicity, and low cost, making them ideal materials for lithium extraction from salt lakes. Commonly used methods for synthesizing lithium ion sieve precursors include high-temperature solid-phase methods, sol-gel methods, hydrothermal synthesis, microwave sintering, and co-precipitation methods. The hydrothermal method for preparing manganese-based lithium ion sieves is a commonly used synthesis method. This method can be performed under high temperature and high pressure conditions, is simple to process, and is low-cost. Furthermore, the particle size and crystal structure of the manganese-based lithium ion sieve can be controlled by adjusting the preparation parameters. Summary of the Invention

[0005] The purpose of the present application is to provide a manganese-based adsorbent, which uses waste lithium manganese oxide battery pole pieces as raw materials for preparation, thereby saving raw materials.

[0006] To achieve the above objectives, the technical solution adopted in this application is: to provide a method for preparing a manganese-based adsorbent, comprising the following preparation steps: S1: reacting waste lithium manganate positive electrode powder with a reducing acid to remove metal impurities to obtain a Li-Mn mixed solution; S2: adding a structure directing agent to the Li-Mn mixed solution to generate a lithium ion sieve precursor; S3: etching and acidifying the lithium ion sieve precursor to obtain a manganese-based adsorbent.

[0007] Preferably, in step S2, a lithium source is added to the Li-Mn mixed solution so that the molar ratio of lithium ions to manganese ions in the Li-Mn mixed solution is 1:(1-1.5).

[0008] As another preference, the lithium source is lithium hydroxide and / or lithium nitrate.

[0009] As another preferred embodiment, in the step S2, the Li-Mn mixed solution is mixed with the structure directing agent, synthesized by microwave-hydrothermal method and calcined at high temperature to obtain the lithium ion sieve precursor, wherein the lithium ion sieve precursor is Li4Mn5O 12 Nanosheets.

[0010] As another preference, the reaction temperature of the microwave-hydrothermal method is 180-220°C.

[0011] As another preferred embodiment, in step S3, the lithium ion sieve precursor is etched and acidified using HNO3, and the etching time is 30 to 60 minutes to form a multi-level pore structure to obtain the manganese-based adsorbent.

[0012] As another preferred embodiment, in step S1, the waste lithium manganate positive electrode powder reacts with the reducing acid to obtain a leachate, and an alkali is added to the leachate to adjust the pH of the solution to 3-7 to precipitate the metal impurities.

[0013] As another preference, the reducing acid is citric acid and / or ascorbic acid, and the structure-directing agent is cetyltrimethylammonium bromide.

[0014] As another preference, the manganese-based adsorbent has a multi-level pore structure, containing 2-5 nm mesopores and 50-100 nm macropores.

[0015] The present application also provides a manganese-based adsorbent, which is prepared by any of the above preparation methods.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] (1) The manganese-based adsorbent of the present application uses waste lithium manganese oxide battery pole pieces as the preparation raw material, which not only solves the problem of recycling waste lithium manganese oxide batteries, but also saves manganese-based adsorbent raw materials, providing a new solution for green chemistry and salt lake lithium extraction technology;

[0018] (2) The manganese-based adsorbent of the present application uses waste lithium manganese oxide battery electrodes as raw materials for preparation. The preparation method is simple and the raw materials are easy to obtain, which is suitable for large-scale mass production. In addition, the adsorbent is suitable for lithium extraction and lithium recovery in salt lake brine, lithium precipitation mother liquor, lithium-containing waste liquid, etc., and has a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 These are the XRD test results of the manganese-based adsorbents in Examples 1 to 5 of this application. DETAILED DESCRIPTION

[0020] Below, the present application is further described in conjunction with specific implementation methods. It should be noted that, under the premise of no conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0021] The terms "comprises" and "having" and any variations thereof in the specification and claims of this application are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus that includes a series of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, product or apparatus.

[0022] The present application provides a method for preparing a manganese-based adsorbent, which is prepared from waste lithium manganese oxide battery pole pieces. Waste lithium manganese oxide battery pole pieces contain metal elements such as manganese and lithium, and directly discarding them will cause waste of resources. By preparing an adsorbent, they can be converted into functional materials with practical value, realizing "turning waste into treasure" and complying with the concept of a circular economy.

[0023] In addition, manganese is an important strategic metal. Global manganese reserves are limited and unevenly distributed. Recycling manganese from used batteries can reduce dependence on primary mineral resources and ensure resource supply security.

[0024] Waste lithium manganese oxide battery electrodes are industrial waste, and the cost of obtaining them is much lower than using metal salts or ores as raw materials. They can significantly reduce the preparation cost of adsorbents and enhance market competitiveness.

[0025] A method for preparing a manganese-based adsorbent comprises the following steps:

[0026] S1: reacting waste lithium manganate positive electrode powder with reducing acid, adding a precipitant to precipitate metal impurities other than manganese and lithium to obtain a Li-Mn mixed solution;

[0027] S2: adding a structure-directing agent to the Li-Mn mixed solution to generate a lithium ion sieve precursor;

[0028] S3: The lithium ion sieve precursor is etched and acidified to obtain a manganese-based adsorbent.

[0029] In some embodiments, the reducing acid refers to an acidic substance that can act as a reducing agent in a chemical reaction and has electron transfer capability, such as citric acid and ascorbic acid.

[0030] This application uses citric acid / ascorbic acid as a green reducing acid, which reduces the risk of heavy metal precipitation compared to the traditional hydrochloric acid leaching process. In addition, the by-products of the citric acid / ascorbic acid reaction are biodegradable organic salts. The by-products are precipitated to precipitate heavy metal impurities through pH control, so that the residual concentration of heavy metals in the wastewater is lower than 0.1 ppm, meeting the standard for industrial discharge and reducing wastewater treatment costs.

[0031] In some embodiments, step S2 adds lithium ions to the Li-Mn mixed solution so that the molar ratio of lithium ions to manganese ions in the Li-Mn mixed solution is 1:(1-1.5). In the preparation process of this application, the lithium source is added to adjust the Li-Mn molar ratio to 1:(1-1.5), so that the lithium element in the raw materials is fully utilized, avoiding the additional input of large amounts of lithium salts in traditional adsorbent preparation, and further improving resource utilization.

[0032] In some preferred embodiments, the lithium source may be lithium hydroxide and / or lithium nitrate.

[0033] In some embodiments, the structure directing agent is hexadecyltrimethylammonium bromide (CTAB). In step S2, the Li-Mn mixed solution is mixed with the structure directing agent and a lithium ion sieve precursor is synthesized by microwave-hydrothermal method. The lithium ion sieve precursor is Li4Mn5O 12 Nanosheets.

[0034] In some preferred embodiments, the microwave-hydrothermal method has a reaction temperature of 180-220°C, a reaction time of 12-24 hours, and a heating rate of 1-10°C. Compared to high-temperature solid-phase methods, the microwave-hydrothermal method for synthesizing precursors further reduces energy consumption and emissions of greenhouse gases such as carbon dioxide, aligning with the development of green chemistry.

[0035] In some embodiments, the product of the microwave-hydrothermal method is filtered, washed, dried, and then calcined at 400-450° C. for 1-10 h.

[0036] In some embodiments, the product is gently etched using HNO 3 to form a hierarchical pore structure containing 2-5 nm mesopores and 50-100 nm macropores.

[0037] By using nitric acid for precise etching, a dual-mode pore system of 2~5 nm mesopores and 50~100 nm macropores is formed. The mesoporous channel provides 120 m 2 / g high specific surface area, exposing Mn 3+ / Mn 4+ Active sites. In the high ionic strength environment of salt lake brine, the mesopore surface electric field can enhance the Li + Polarized adsorption increases the diffusion rate of lithium ions.

[0038] The 50-100 nm macropores are suitable for reducing the penetration time of brine and solving the problem of magnesium ions blocking micropores in high-magnesium brine. The capillary effect formed in the pores can directionally enrich low-concentration lithium and improve the boundary layer adsorption efficiency.

[0039] In some preferred embodiments, the etching time is 30 to 60 minutes. The length of the etching time will affect the capacity and dissolution rate of the adsorbent.

[0040] In some embodiments, the specific surface area of ​​the manganese-based adsorbent is 120 m 2 / g. The specific surface area of ​​an adsorbent is closely related to its adsorption performance, ion diffusion rate, and cyclic stability. The larger the specific surface area of ​​an adsorbent, the more active sites exposed on its surface, providing more adsorption sites for lithium ions, thereby significantly increasing the adsorption capacity of lithium ions per unit mass of the adsorbent.

[0041] In some embodiments, in step S1, the waste lithium manganese oxide positive electrode powder reacts with a reducing acid to dissolve the lithium ions, and then an alkali is added to the leachate to adjust the pH of the solution to 3-7, so that other impurity metal ions in the leachate form precipitation, thereby improving the purity of the Li-Mn mixed solution and reducing the impact of other metal impurities on the adsorbent.

[0042] In some embodiments, the waste lithium manganese oxide positive electrode powder reacts with a reducing acid at 60-80° C. to achieve the best leaching effect of lithium ions and inhibit the dissolution of manganese.

[0043] In a more preferred embodiment, the reducing acid selectively leach lithium ions from the waste lithium manganese oxide positive electrode powder so that the lithium ion leaching rate is greater than 95%, and can also reduce the subsequent addition amount of manganese source and inhibit the dissolution of manganese so that the manganese dissolution rate is less than 5%.

[0044] The preparation method of the present application uses waste lithium manganese oxide battery pole pieces as manganese sources and lithium sources. The raw materials are widely available and inexpensive. The above preparation process steps are simple and easy to scale up for mass production.

[0045] This application provides a manganese-based adsorbent, prepared by any of the methods described in the preceding examples. This application provides a manganese-based adsorbent prepared from spent lithium manganate battery electrodes. This adsorbent is suitable for lithium extraction from salt lakes and exhibits strong stability, long lifespan, and economical practicality. It is suitable for use in brine environments with high magnesium-to-lithium ratios, breaking through the bottleneck of traditional adsorbents.

[0046] In terms of industrial application value, this application provides a low-cost, large-scale solution for the field of lithium extraction from salt lakes. First, the raw material cost advantage is significant. The cost of obtaining the positive electrode powder of waste lithium manganese oxide batteries is only 1 / 5 of that of traditional manganese salt raw materials. Secondly, the preparation process is simple and easy to scale up. The microwave-hydrothermal reaction equipment can use a standardized hydrothermal synthesis kettle, combined with an automated temperature control system to achieve continuous production. In addition, the adsorbent has a wide range of application scenarios. It is not only suitable for brine environments with high magnesium-lithium ratios such as the Qinghai Salt Lake, but can also be used for lithium recovery from lithium-precipitated mother liquor and lithium-containing waste liquid, building a resource circulation bridge between the lithium battery recycling industry chain and the salt lake lithium extraction industry.

[0047] Example 1

[0048] Manganese-based adsorbents are prepared from waste lithium manganese oxide battery pole pieces according to the following preparation steps:

[0049] S1: 200 g of spent lithium manganese oxide battery cathode powder was dispersed with 2 mmol of citric acid in 3 L of ultrapure water and reacted at 60 °C to selectively leach Li + (leaching rate > 95%), Mn dissolution (dissolution rate < 5%)), then Na2CO3 was added to the leachate to adjust the pH to 5, precipitate the residual Al and Fe impurities, and obtain a Li-Mn mixed solution;

[0050] S2: 42 g lithium hydroxide and 50 g CTAB were added to the Li-Mn mixed solution and reacted at 200 °C for 18 h to generate Li4Mn5O 12 The nanosheets were vacuum filtered, rinsed with deionized water and dried, and then the precursor was heat treated at 400 °C in a muffle furnace for 5 hours to obtain a lithium ion sieve precursor;

[0051] S3: The lithium ion sieve precursor was gently etched with 5M HNO3 for 30 minutes to form a multi-level pore structure (mesopores 2-5 nm, macropores 50-100 nm), and the specific surface area was increased to 120 m 2 / g to obtain a manganese-based adsorbent.

[0052] Example 2

[0053] 124 g of lithium nitrate was used instead of the lithium hydroxide in step S2, and the other preparation steps were consistent with those in Example 1.

[0054] Example 3

[0055] The etching time in step S3 was extended to 60 minutes, and the other preparation steps were consistent with those in Example 1.

[0056] Example 4

[0057] The reaction temperature of the microwave-hydrothermal method in step S2 was adjusted to 180° C., and the other preparation steps were consistent with those in Example 1.

[0058] Example 5

[0059] The reaction temperature of the microwave-hydrothermal method in step S2 was adjusted to 220° C., and the other preparation steps were consistent with those in Example 1.

[0060] Material characterization: The manganese-based adsorbent materials prepared in Examples 1 to 5 were subjected to XRD tests, and the test results were plotted on Figure 1 middle.

[0061] like Figure 1 As shown in Figure 1, Examples 1 to 5 all successfully prepared Li4Mn5O 12 Materials, the preparation method of this application can be implemented and synthesized Li4Mn5O 12 The materials have high purity and structural integrity, and the adsorbent material synthesized in Example 1 has higher crystallinity.

[0062] Adsorption performance test: simulated brine was prepared according to the ion concentration in Table 1, and 20 g of the manganese-based adsorbent materials prepared in Examples 1 to 5 were weighed and placed in 2 L of simulated brine for adsorption for 2 h. The lithium ion content in the tail liquid after adsorption was tested.

[0063] Table 1 Composition of simulated brine

[0064]

[0065] Desorption performance test: Using hydrochloric acid with a concentration of 0.05 mol / L, the adsorbed manganese adsorbent was dispersed in 500 mL of hydrochloric acid solution. The desorption time was 1 h. After the desorption was completed, the manganese adsorbent and the hydrochloric acid were separated to obtain a desorption solution, and the lithium and manganese contents in the desorption solution were tested.

[0066] Cyclic performance test: The manganese-based adsorbent materials prepared in Examples 1 to 5 were subjected to repeated adsorption-desorption steps for 5 times. The lithium ion content in the adsorption solution was measured in each round, and the average dissolution loss rate was calculated.

[0067] The relevant calculation formulas involved are as follows:

[0068] Adsorption capacity = (c 卤水Li -c 尾液Li ) × V 卤水 / m 吸附剂

[0069] Desorption capacity = c 解吸液Li ×V 解吸液 / m 吸附剂

[0070] Dissolution rate = c 解吸液Mn ×V 解吸液 / (m 吸附剂 ×0.522)×100%

[0071] c 卤水Li ----Li concentration in brine, g / L

[0072] c 尾液Li ----Li concentration in adsorption tail liquid, g / L

[0073] V 卤水 ----Brine volume, L

[0074] m 吸附剂 ----Mass of adsorbent, g

[0075] c 解吸液Li ----Li concentration of desorption solution, g / L

[0076] V 解吸液 ----Desorption liquid volume, L

[0077] c 解吸液Mn ----Mn concentration in desorption solution, g / L

[0078] The adsorption test results and average dissolution rate calculation results of Examples 1 to 5 are recorded in Table 2 below.

[0079] Table 2 Performance test results of Examples 1 to 5

[0080]

[0081] Analysis of the performance test results of Example 1 and Example 2 in Table 1 above shows that when a lithium source is added to the Li-Mn mixed solution, lithium hydroxide or lithium nitrate is used as the lithium source, and lithium hydroxide is used as the lithium source, the adsorption capacity and lithium-magnesium ratio of the manganese-based adsorbent are higher, the average dissolution loss rate over five rounds is lower, and the adsorption effect and stability of the adsorbent are better.

[0082] Analysis of the performance test results of Examples 1 and 3 shows that prolonging the etching time of the lithium ion sieve precursor reduces the adsorption capacity and lithium-magnesium ratio of the adsorbent, while increasing the average dissolution rate over five rounds. Therefore, the preferred etching time is 30 minutes.

[0083] The performance test results of Examples 1, 4, and 5 were analyzed, and the reaction temperature of the microwave-hydrothermal method was adjusted and optimized. Based on the test results of adsorption capacity, lithium-magnesium ratio, and average dissolution rate of the adsorbent, the optimal adsorption performance was achieved when the reaction temperature was 200°C.

[0084] In summary, the manganese-based adsorbent prepared by the present application uses waste lithium manganese oxide battery electrodes as raw materials. It can be recycled in a hydrochloric acid system for 5 rounds while still maintaining structural stability and less dissolution loss, which significantly enhances the stability of the manganese-based adsorbent and improves the service life of the manganese-based adsorbent, making it suitable for promotion in salt lake lithium extraction technology.

[0085] The above describes the basic principles, main features, and advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above-described embodiments. The above-described embodiments and the specification merely illustrate the principles of the present application. Various changes and improvements may be made to the present application without departing from the spirit and scope of the present application. These changes and improvements fall within the scope of the present application for which protection is sought. The scope of protection claimed by the present application is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a manganese-based adsorbent, characterized in that: The method comprises the following preparation steps: S1: reacting waste lithium manganese oxide positive electrode powder with reducing acid to remove metal impurities to obtain a Li-Mn mixed solution; S2: adding a structure directing agent to the Li-Mn mixed solution to generate a lithium ion sieve precursor; S3: etching and acidifying the lithium ion sieve precursor to obtain a manganese-based adsorbent; In the step S2, the Li-Mn mixed solution is mixed with the structure directing agent, synthesized by microwave-hydrothermal method and calcined at high temperature to obtain the lithium ion sieve precursor, which is Li4Mn5O 12 nanosheets; In step S3, the lithium ion sieve precursor is etched and acidified using HNO3 for 30 to 60 minutes to form a multi-level pore structure to obtain the manganese-based adsorbent; The reducing acid is citric acid and / or ascorbic acid, and the structure-directing agent is hexadecyltrimethylammonium bromide. In step S1, the waste lithium manganate positive electrode powder reacts with the reducing acid to obtain a leachate, and an alkali is added to the leachate to adjust the solution pH to 3-7 to precipitate metal impurities.

2. The method for preparing a manganese-based adsorbent according to claim 1, wherein: In the step S2, a lithium source is added to the Li-Mn mixed solution so that the molar ratio of lithium ions to manganese ions in the Li-Mn mixed solution is 1:(1-1.5).

3. The method for preparing a manganese-based adsorbent according to claim 2, wherein: The lithium source is lithium hydroxide and / or lithium nitrate.

4. The method for preparing a manganese-based adsorbent according to claim 1, wherein: The reaction temperature of the microwave-hydrothermal method is 180-220°C.

5. The method for preparing a manganese-based adsorbent according to claim 1, wherein: The manganese-based adsorbent has a multi-level pore structure, containing 2-5 nm mesopores and 50-100 nm macropores.

6. A manganese-based adsorbent, characterized in that: The method is prepared by any one of claims 1 to 5.

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