Manganese adsorbent and preparation method thereof

Abstract

The invention discloses a manganese adsorbent and a preparation method thereof.The preparation method comprises the following preparation steps that S1, waste lithium manganate positive electrode powder reacts with reducing acid, and after metal impurities are removed, a Li-Mn mixed solution is obtained; s2, adding a structure-directing agent into the Li-Mn mixed solution to generate a lithium ion sieve precursor; and S3, etching the lithium ion sieve precursor, and acidifying to obtain the manganese adsorbent. According to the manganese adsorbent, the waste lithium manganate battery pole pieces are used as preparation raw materials, the problem of recycling of the waste lithium manganate batteries can be solved, meanwhile, the raw materials of the manganese adsorbent are saved, and a new solution thought is provided for green chemistry and a salt lake lithium extraction technology.

Description

Technical Field

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

[0002] With the rapid development of the global new energy industry, lithium-ion batteries, as the core components in fields such as electric vehicles and energy storage systems, have witnessed an explosive growth in market demand. However, the limited global lithium resource reserves and uneven distribution have led to an increasingly short supply of lithium ions, becoming a bottleneck restricting the sustainable development of the new energy industry. The existing lithium ore mining and processing capacities are difficult to meet such high-speed growth demands, and the contradiction between lithium resource supply and demand has become increasingly acute.

[0003] China is rich in lithium resources in salt lakes. 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 realizing lithium extraction from salt lakes include precipitation method, extraction method, electrochemical method, adsorption method, etc. Among them, the adsorption method has advantages such as good selectivity for lithium ions, being green and pollution-free, high adsorption capacity, and being economically recyclable, becoming a new trend in the current technical development of lithium extraction from salt lakes.

[0004] Manganese-based adsorbents have advantages such as fast adsorption and desorption rates, high adsorption capacity, good selectivity, non-toxicity, and low cost, and are ideal materials for lithium extraction from salt lakes. Currently, the commonly used methods for synthesizing lithium ion sieve precursors include high-temperature solid-phase method, sol-gel method, hydrothermal synthesis method, microwave sintering method, and coprecipitation method. Preparing manganese-based lithium ion sieves by the hydrothermal method is a commonly used synthesis method. This method can be carried out under high temperature and high pressure conditions, has the characteristics of simple process and low cost, and can control the particle size and crystal structure of manganese-based lithium ion sieves by adjusting the preparation parameters. Summary of the Invention

[0005] The purpose of the present application is to provide a manganese-based adsorbent, using the spent lithium manganese oxide battery electrode sheet as a raw material for preparation to save raw materials.

[0006] To achieve the above object, the technical solution adopted in the present application is as follows: providing a preparation method of a manganese-based adsorbent, including the following preparation steps: S1: Reacting the spent lithium manganese oxide positive electrode powder with a reducing acid, and obtaining a Li-Mn mixed solution after removing metal impurities; 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] As a preference, in the step S2, a lithium source is supplemented 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 preference, in the step S2, after the Li-Mn mixed solution is mixed with the structure guiding agent, it is synthesized by microwave-hydrothermal method and calcined at high temperature to obtain the lithium ion sieve precursor, and the lithium ion sieve precursor is Li4Mn5O 12 nanosheets.

[0010] As another preference, the reaction temperature of the microwave-hydrothermal method is 180-2�C.

[0011] As another preference, in the step S3, the lithium ion sieve precursor is etched and acidified with HNO3, and the etching time is 30-60 minutes to form a hierarchical pore structure, and the manganese-based adsorbent is obtained.

[0012] As another preference, in the step S1, after the waste lithium manganate cathode powder reacts with the reducing acid, a leaching solution is obtained, an alkali is added to the leaching solution, the pH of the solution is adjusted to 3-7, and metal impurities are precipitated.

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

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

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

[0016] Compared with the prior art, the beneficial effects of the present application are as follows: (1) For the manganese-based adsorbent of the present application, using the waste lithium manganate battery electrode as the preparation raw material can not only solve the problem of recycling waste lithium manganate batteries, but also save the raw materials of the manganese-based adsorbent, providing a new solution idea for green chemistry and lithium extraction technology from salt lakes; (2) For the manganese-based adsorbent of the present application, using the waste lithium manganate battery electrode as the preparation raw material, the preparation method is simple, the raw materials are easy to obtain, it is suitable for large-scale production, and the adsorbent is applicable to lithium extraction and lithium recovery fields such as salt lake brine, lithium precipitation mother liquor, and lithium-containing waste liquid, with wide applications. Description of the Drawings

[0017] Figure 1 It is the XRD test result of the manganese-based adsorbent in Examples 1-5 of the present application. Detailed Embodiments

[0018] Next, in combination with specific implementation manners, the present application will be further described. It should be noted that, on the premise of non-conflict, any combination of the following-described embodiments or technical features can form a new embodiment.

[0019] The terms "comprising" and "having" in the description and claims of the present application and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that comprises a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products, or devices.

[0020] The present application provides a preparation method of a manganese-based adsorbent, which is prepared from the spent lithium manganese oxide battery electrodes. The spent lithium manganese oxide battery electrodes contain metal elements such as manganese and lithium. Direct discarding will cause waste of resources. By preparing the adsorbent, it can be transformed into a functional material with practical value, realizing "turning waste into treasure", which conforms to the concept of circular economy.

[0021] In addition, manganese is an important strategic metal. The global manganese resource reserves are limited and unevenly distributed. Recycling manganese from waste batteries can reduce the dependence on primary mineral resources and ensure the security of resource supply.

[0022] The spent lithium manganese oxide battery electrodes belong to industrial waste, and the acquisition cost is much lower than that using metal salts or ores as raw materials, which can significantly reduce the preparation cost of the adsorbent and enhance the market competitiveness.

[0023] A preparation method of a manganese-based adsorbent comprises the following preparation steps: S1: React the spent lithium manganese oxide cathode powder with a reducing acid, and add a precipitant to precipitate metal impurities other than manganese and lithium to obtain a Li-Mn mixed solution; S2: Add a structure-directing agent to the Li-Mn mixed solution to generate a lithium ion sieve precursor; S3: Etch and acidify the lithium ion sieve precursor to obtain a manganese-based adsorbent.

[0024] In some embodiments, the reducing acid refers to an acid substance that can act as a reducing agent and has the ability of electron transfer in a chemical reaction, such as citric acid and ascorbic acid.

[0025] The present application uses citric acid / ascorbic acid as a green reducing acid. Compared with the traditional hydrochloric acid leaching process, it reduces the risk of heavy metal precipitation. Moreover, the by-products of the reaction of citric acid / ascorbic acid are biodegradable organic salts. The by-products precipitate heavy metal impurities through pH regulation, so that the heavy metal residual concentration in the wastewater is lower than 0.1 ppm, meeting the industrial discharge standard and reducing the wastewater treatment cost.

[0026] In some embodiments, in step S2, lithium ions are supplemented 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). During the preparation process of the present application, the Li-Mn molar ratio is adjusted to 1:(1-1.5) by supplementing the lithium source, enabling the full utilization of lithium elements in the raw materials, avoiding the additional input of a large amount of lithium salts in the preparation of traditional adsorbents, and further improving the resource utilization rate.

[0027] In some preferred embodiments, the lithium source can be lithium hydroxide or / and lithium nitrate.

[0028] In some embodiments, the structure-directing agent is cetyltrimethylammonium bromide (CTAB). After the Li-Mn mixed solution and the structure-directing agent are mixed in step S2, a lithium ion sieve precursor is synthesized by the microwave-hydrothermal method. The lithium ion sieve precursor is Li4Mn5O 12 nanosheets.

[0029] In some preferred embodiments, the reaction temperature of the microwave-hydrothermal method is 180-220 °C, the reaction time is 12-24 hours, and the heating rate is 1-10 °C. The process of synthesizing the precursor by the microwave-hydrothermal method further reduces energy consumption and reduces the emission of greenhouse gases such as carbon dioxide compared with the high-temperature solid-phase method, which is in line with the development concept of green chemistry.

[0030] In some embodiments, after the product of the microwave-hydrothermal method is filtered, washed, and dried, it is calcined at 400-450 °C for 1-10 h.

[0031] In some embodiments, the product is gently etched with HNO3 to form a hierarchical pore structure, which contains mesopores with a size of 2-5 nm and macropores with a size of 50-100 nm.

[0032] By precisely etching with nitric acid, a bimodal pore system with mesopores of 2-5 nm and macropores of 50-100 nm is formed. The mesoporous channels provide a high specific surface area of 120 m 2 / g, exposing the Mn 3+ / Mn 4+ active sites. In the high ionic strength environment of salt lake brine, the mesoporous surface electric field can enhance the polarization adsorption of Li + , increasing the lithium ion diffusion rate.

[0033] The 50-100 nm macropores are suitable for reducing the penetration time of the brine, 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 adsorption efficiency of the boundary layer.

[0034] In some preferred embodiments, the etching time is 30 to 60 minutes. The length of the etching time will affect the capacity and dissolution loss rate of the adsorbent.

[0035] In some embodiments, the specific surface area of the manganese-based adsorbent is 120 m 2 / g. The specific surface area of the adsorbent is closely related to its adsorption performance, ion diffusion rate, and cycle stability. The larger the specific surface area of the adsorbent, the more active sites are exposed on its surface, providing more sufficient adsorption positions for lithium ions, thus significantly enhancing the adsorption capacity of the adsorbent per unit mass for lithium ions.

[0036] In some embodiments, in step S1, after the spent lithium manganese oxide cathode powder reacts with the reducing acid and lithium ions are dissolved, an alkali is added to the leaching solution to adjust the pH of the solution to 3 to 7, so that other impurity metal ions in the leaching solution form precipitates, improving the purity of the Li-Mn mixed solution and reducing the influence of other metal impurities on the adsorbent.

[0037] In some embodiments, the spent lithium manganese oxide cathode powder reacts with the reducing acid at 60 to 80 °C to achieve the best leaching effect of lithium ions and inhibit the dissolution of manganese.

[0038] In a more preferred embodiment, the reducing acid selectively leaches lithium ions from the spent lithium manganese oxide cathode powder, so that the leaching rate of lithium ions is greater than 95%, and it can also reduce the subsequent addition amount of manganese source and inhibit the dissolution of manganese, so that the dissolution rate of manganese is less than 5%.

[0039] The preparation method of the present application uses the spent lithium manganese oxide battery electrode as the manganese source and lithium source. The raw materials are widely available and easy to obtain, and the price is low. The above preparation process steps are simple and easy to scale up for mass production.

[0040] The present application provides a manganese-based adsorbent prepared by the method of any one of the above embodiments. The manganese-based adsorbent provided by the present application, which is prepared from the spent lithium manganese oxide battery electrode, is an adsorbent suitable for extracting lithium from salt lakes, has strong stability, long life, good economic practicality, is suitable for the brine environment with a high magnesium-lithium ratio, and breaks through the bottleneck of traditional adsorbents.

[0041] In terms of industrial application value, the present application provides a low-cost and large-scale solution for the field of extracting lithium from salt lakes. First, the raw material cost advantage is significant. The acquisition cost of the spent lithium manganese oxide battery cathode powder is only 1 / 5 of that of traditional manganese salt raw materials. Second, the preparation process is simple and easy to scale up. The reaction equipment for the microwave-hydrothermal method can use a standardized hydrothermal synthesis kettle, combined with an automatic temperature control system to achieve continuous production. In addition, the application scenario of this adsorbent is wide. It is not only suitable for the brine environment with a high magnesium-lithium ratio such as Qinghai Salt Lake, but also can be used for lithium extraction and recovery from the lithium precipitation mother liquor and lithium-containing waste liquid, building a resource recycling bridge between the lithium battery recycling industry chain and the salt lake lithium extraction industry.

[0042] Example 1 Prepare a manganese-based adsorbent from the spent lithium manganese oxide battery electrode sheets according to the following preparation steps: S1: Disperse 200 g of spent lithium manganese oxide battery cathode sheet powder and 2 mmol of citric acid in 3 L of ultrapure water, and react at 60 °C to selectively leach Li + (leaching rate > 95%), dissolve Mn (dissolution rate < 5%). Subsequently, add Na2CO3 to the leaching solution to adjust the pH to 5 to precipitate residual Al and Fe impurities, and obtain a Li-Mn mixed solution; S2: Add 42 g of lithium hydroxide and 50 g of CTAB to the Li-Mn mixed solution, and react at 200 °C for 18 hours using the microwave-hydrothermal method to generate Li4Mn5O 12 nanosheets. After vacuum filtration, rinsing with deionized water and drying, heat-treat the precursor in a muffle furnace at 400 °C for 5 hours to obtain a lithium ion sieve precursor; S3: Mildly etch the lithium ion sieve precursor with 5M HNO3 for 30 minutes to form a hierarchical pore structure (mesopores 2 - 5 nm, macropores 50 - 100 nm), and increase the specific surface area to 120 m 2 / g to obtain a manganese-based adsorbent.

[0043] Example 2 Use 124 g of lithium nitrate to replace the lithium hydroxide in step S2, and keep other preparation steps the same as those in Example 1.

[0044] Example 3 Prolong the etching time in step S3 to 60 minutes, and keep other preparation steps the same as those in Example 1.

[0045] Example 4 Adjust the reaction temperature of the microwave-hydrothermal method in step S2 to 180 °C, and keep other preparation steps the same as those in Example 1.

[0046] Example 5 Adjust the reaction temperature of the microwave-hydrothermal method in step S2 to 220 °C, and keep other preparation steps the same as those in Example 1.

[0047] Material characterization: Perform XRD tests on the manganese-based adsorbent materials prepared in Examples 1 - 5, and plot the test results in Figure 1 .

[0048] As Figure 1 shown, Li4Mn5O was successfully prepared in Examples 1 - 5 12Materials, the preparation method of the present application can be implemented and the synthesized Li4Mn5O 12 The material has high purity and structural integrity, and the adsorbent material synthesized in Example 1 has higher crystallinity.

[0049] Adsorption performance test: Simulated brine was prepared according to the ion concentrations in Table 1. 20 g of the manganese-based adsorbent materials prepared in Examples 1 to 5 were weighed separately and placed in 2 L of simulated brine for adsorption for 2 h. The lithium ion content in the tail liquid after adsorption was measured.

[0050] Table 1 Composition of simulated brine

[0051] Desorption performance test: Using hydrochloric acid with a concentration of 0.05 mol / L, the adsorbed manganese-based adsorbent was dispersed in 500 mL of hydrochloric acid solution for 1 h. After desorption, the manganese-based adsorbent was separated from the hydrochloric acid to obtain the desorption solution, and the lithium and manganese contents in the desorption solution were measured.

[0052] Cycling performance test: The manganese-based adsorbent materials prepared in Examples 1 to 5 were repeatedly subjected to the adsorption-desorption steps 5 times. The lithium ion content in the adsorption solution of each cycle was measured, and the average dissolution loss rate was calculated.

[0053] The relevant calculation formulas involved are as follows: Adsorption capacity = (c 卤水Li - c 尾液Li ) × V 卤水 / m 吸附剂 Desorption capacity = c 解吸液Li × V 解吸液 / m 吸附剂 Dissolution loss rate = c解吸液Mn × V 解吸液 / (m 吸附剂 × 0.522) × 100% c 卤水Li ----Li concentration in brine, g / L c 尾液Li ----Li concentration in adsorption tail liquid, g / L V 卤水 ----Brine volume, L m 吸附剂 ----Adsorbent mass, g c 解吸液Li ----Li concentration in desorption solution, g / L V 解吸液 ----Desorption solution volume, L c 解吸液Mn----Mn concentration in desorbing solution, g / L Record the adsorption test results and the calculated results of the average dissolution loss rate of Examples 1 to 5 in Table 2 below.

[0054] Table 2 Performance test results of Examples 1 to 5

[0055] Analyze the performance test results of Examples 1 and 2 in Table 1 above. Supplement the lithium source to the Li-Mn mixed solution. Use lithium hydroxide or lithium nitrate as the lithium source. When using lithium hydroxide as the lithium source, the adsorption capacity and lithium-to-magnesium ratio of the manganese-based adsorbent are higher, and the average dissolution loss rate in 5 cycles is lower, and its adsorption effect and the stability of the adsorbent are better.

[0056] Analyze the performance test results of Examples 1 and 3. Extend the etching time of the lithium ion sieve precursor, and the adsorption capacity and lithium-to-magnesium ratio of the adsorbent decrease instead, and the average dissolution loss rate in 5 cycles increases. Therefore, the preferred etching time is 30 minutes.

[0057] Analyze the performance test results of Examples 1, 4, and 5. Adjust and optimize the reaction temperature of the microwave-hydrothermal method. From the test results of the adsorption capacity, lithium-to-magnesium ratio, and the average dissolution loss rate of the adsorbent, the optimal adsorption performance can be obtained when the reaction temperature is 200 °C.

[0058] In summary, the manganese-based adsorbent prepared by this application uses the waste lithium manganese oxide battery pole piece as the raw material, can be recycled 5 times in the hydrochloric acid system and still maintain a stable structure with less dissolution loss, significantly enhances the stability of the manganese-based adsorbent, improves the service life of the manganese-based adsorbent, and is suitable for popularization in the lithium extraction technology from salt lakes.

[0059] The above describes the basic principle, main features, and advantages of this application. Those skilled in the art should understand that this application is not limited by the above embodiments. What is described in the above embodiments and the specification is only the principle of this application. Without departing from the spirit and scope of this application, this application will have various changes and improvements, and these changes and improvements all fall within the scope of this application claimed. The scope of protection required by this application is defined by the appended claims and their equivalents.

Claims

1. A preparation method of a manganese-based adsorbent, characterized in that, It includes the following preparation steps: S1: React the waste lithium manganese oxide cathode powder with a reducing acid, and obtain a Li-Mn mixed solution after removing metal impurities; S2: Add a structure-directing agent to the Li-Mn mixed solution to generate a lithium ion sieve precursor; S3: Etch and acidify the lithium ion sieve precursor to obtain a manganese-based adsorbent.

2. The preparation method of the manganese-based adsorbent according to claim 1, characterized in that, 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 preparation method of the manganese-based adsorbent according to claim 2, wherein The lithium source is lithium hydroxide and / or lithium nitrate.

4. The preparation method of the manganese-based adsorbent according to claim 1, characterized in that, In the step S2, after the Li-Mn mixed solution is mixed with the structure directing agent, the lithium ion sieve precursor is obtained by microwave-hydrothermal synthesis and high-temperature calcination. The lithium ion sieve precursor is Li4Mn5O 12 nanosheets.

5. The preparation method of the manganese-based adsorbent according to claim 4, characterized in that, The reaction temperature of the microwave-hydrothermal method is 180~220 °C.

6. The preparation method of the manganese-based adsorbent according to claim 1, characterized in that, In the step S3, HNO3 is used to etch and acidify the lithium ion sieve precursor, and the etching time is 30~60 minutes to form a hierarchical pore structure and obtain the manganese-based adsorbent.

7. The preparation method of the manganese-based adsorbent according to claim 1, characterized in that, In the step S1, after the waste lithium manganese oxide cathode powder reacts with the reducing acid, a leaching solution is obtained. An alkali is added to the leaching solution to adjust the solution pH to 3~7 to precipitate metal impurities.

8. The preparation method of the manganese-based adsorbent according to claim 1, characterized in that, The reducing acid is citric acid and / or ascorbic acid, and the structure-directing agent is cetyltrimethylammonium bromide.

9. The preparation method of the manganese-based adsorbent according to claim 6, characterized in that, The manganese-based adsorbent has a hierarchical pore structure, containing mesopores of 2~5 nm and macropores of 50~100 nm.

10. A manganese-based adsorbent, characterized in that, It is prepared by using the preparation method according to any one of claims 1~9.

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