Method for developing lithium resources in salt lake brine by extraction

Abstract

This invention discloses an extraction method for developing lithium resources in salt lake brine. It primarily uses lithium-containing salt lake brine as raw material to selectively extract metallic lithium resources. A rapid, green, and circular extraction system for salt lake brine lithium resources is achieved using imidazole ionic liquid extractants, neutral washing solutions, and low-concentration hydrochloric acid extractants. Through a three-stage reflux circulation system involving the extractant, washing solution, and brine resources, efficient, low-emission, and low-pollution development of salt lake brine lithium resources is achieved. The final product is high-purity lithium carbonate. Using brine with a magnesium-to-lithium mass concentration ratio of 100:1 as raw material, this invention achieves a lithium extraction rate of 98.3% and a magnesium extraction rate of almost 0% after lithium precipitation, five-stage countercurrent extraction, washing, and back-extraction. The extracted liquid phase, accounting for 22% of the total liquid volume, is discharged after appropriate wastewater treatment and can be directly discharged with almost no waste gas generation. The waste residue can be used in construction and other fields. This invention enables efficient development of lithium resources in salt lake brine while achieving a green and circular process, which can effectively promote the development of lithium resources in salt lake brine and the development of green lithium extraction processes.

Description

Technical Field

[0001] This invention relates to the field of green extraction methods for salt lake resources, and more particularly to a green development method for extracting lithium resources from salt lake brine using an imidazole ionic liquid system to achieve magnesium-lithium separation and the production of high-purity lithium carbonate materials. It also relates to ionic liquid preparation and by-product utilization, as well as the recycling of liquids in the process flow. Background Technology

[0002] In recent years, the rapid development of the new energy field has led to the widespread application of lithium batteries in various fields due to their high energy density and long cycle life, increasing the demand for lithium resources. Lithium resource extraction mainly involves two methods: ore extraction and salt lake extraction. Due to its ease of extraction, lower cost, and 59% market share, salt lake lithium mines are currently the most important type of lithium resource development and utilization. Salt lakes are mainly distributed in the Qinghai-Tibet Plateau of China, the Andes Plateau of western South America, and the western plateau of North America. Compared to the low lithium-magnesium ratio conditions of other plateau salt lakes, most salt lakes on the Qinghai-Tibet Plateau have a high lithium-magnesium ratio. Therefore, how to efficiently utilize the lithium-ion resources of China's salt lake brine is an urgent scientific and technological problem that needs to be solved.

[0003] Extraction is a mature industrial separation method with advantages such as high efficiency, simple operation, and low fixed investment in lithium extraction from salt lakes. It typically involves selecting organic solvents with high selectivity for lithium ions to extract lithium from the brine into the organic phase. After separating impurities, back-extraction is used to obtain a high-concentration lithium solution. Following multi-stage extraction and back-extraction, the lithium-containing solution is purified and concentrated to obtain lithium carbonate. This lithium carbonate can then be used as a raw material for power battery plates. However, extraction of lithium resources from salt lake brine generates a large amount of industrial wastewater, placing a significant burden on the fragile salt lake ecosystem. Therefore, adhering to the concept of sustainable development, it is necessary to develop a highly efficient and low-emission extraction process for lithium resources from salt lake brine.

[0004] This invention proposes a method for developing lithium resources in salt lake brine using 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, tributyl phosphate, and kerosene as the extractant, sodium chloride and lithium chloride as the detergent, and dilute hydrochloric acid as the back-extraction agent. Battery-grade lithium carbonate products are prepared. my country has abundant lithium resources in salt lakes, which not only enables efficient utilization and conversion of resources but also reduces the damage to the salt lake ecosystem caused by resource extraction. Summary of the Invention

[0005] A method for developing lithium metal resources in salt lake brine, characterized by the following steps: Preparation steps: Prepare simulated salt lake brine with a magnesium-to-lithium mass ratio of 100:1. Produce 1-butyl-3-methylbis(trifluoromethanesulfonyl)imide using 1-butyl-3-methylimidazolium chloride and lithium bis(trifluoromethanesulfonyl)imide. Reaction steps: At room temperature, magnesium precipitation is performed on the simulated brine using sodium carbonate or ammonium carbonate solution. The treated brine with a magnesium-to-lithium mass ratio of approximately 30:1 is then mixed with the extract and subjected to five-stage countercurrent extraction. Precipitation step: After back-extraction, a certain amount of sodium carbonate is added to the liquid phase, and crystallization is carried out under high temperature conditions to obtain crude lithium carbonate product. Then, after vacuum filtration, washing and drying, lithium carbonate product is obtained. Circulation Steps: The washing liquid used in the washing process is recycled to the extraction step. After the back-extraction step is completed, a small amount of 1-butyl-3-methylbis(trifluoromethanesulfonyl)imide salt solution is added for repair and then recycled. After the elemental content of the extracted liquid phase is checked, it can enter the wastewater treatment step and is then recycled back to the natural water body.

[0006] According to the method for developing lithium resources from salt lake brine as described in claim 1, the simulated salt lake brine has the following composition as shown in the table below. Component Li Mg Na B Content (g / L) 2.13 71.31 3.15 6.28 .

[0007] According to the method for developing lithium resources in salt lake brine as described in claim 1, the extraction solution is characterized by a volume fraction of 10% 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, 40% TBP and 50% kerosene, the washing solution is characterized by a LiCl:NaCl ratio of 0.2M:2M, and the extraction solution is 1M hydrochloric acid.

[0008] According to the method for developing lithium resources in salt lake brine as described in claim 1, the extraction step is characterized by an extraction liquid to simulated brine liquid phase volume ratio of 2:1, an extraction time of 10 minutes for each stage, a total extraction time of 50 minutes, and an extraction temperature of room temperature.

[0009] The method for developing lithium resources in salt lake brine as described in claim 1 is characterized in that the volume ratio of organic phase to washing liquid phase in the washing step is 5:1, the washing time is 10 min, and the washing temperature is room temperature.

[0010] According to the method for developing lithium resources in salt lake brine as described in claim 1, the characteristic of the back-extraction step is that the volume ratio of organic phase to back-extraction liquid is 3:1, the back-extraction time is 10 min, and the back-extraction temperature is room temperature.

[0011] According to the method for developing lithium resources in salt lake brine as described in claim 1, the characteristic step is that in the recycling step, 5% by volume of 1-butyl-3-methylbis(trifluoromethanesulfonyl)imide salt is added to the organic extractant during reflux to repair the extractant before recycling. Attached Figure Description

[0012] Figure 1 Flowchart of the extraction method for developing lithium resources in salt lake brine.

[0013] Figure 2 This is a chart for determining product types. Detailed Implementation

[0014] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto: Example 1: A method for developing lithium resources in salt lake brine using extraction, comprising the following steps:

[0015] Using brine from a salt lake with a magnesium-to-lithium mass ratio of 100:1 as raw material, sodium carbonate was added to the raw material solution to precipitate magnesium carbonate from magnesium ions. After removing the precipitate, the magnesium-to-lithium mass ratio in the raw material solution was approximately 30:1. An ionic liquid extractant was prepared by mixing 1-butyl-3-methylbis(trifluoromethanesulfonyl)imide salt, tributyl phosphate (TBP), and kerosene as a diluent, with a volume ratio of 1:4:5. The raw material solution was subjected to five-stage extraction using the ionic liquid mixture system described above. The volume ratio of the ionic liquid extractant system to the raw material solution was 2:1 for each extraction, and the extraction time was 10 minutes per extraction. After each extraction, the solution was allowed to stand for separation. The upper organic phase was collected and stored, while the lower aqueous phase was used for further extraction until the fifth extraction was completed. The organic phase obtained from the five extractions was collected and mixed to form organic phase 1. Using the LiCl solution obtained from the production of 1-butyl-3-methylbis(trifluoromethanesulfonyl)imide salt in step 2 and NaCl solid as raw materials, a mixed solution of NaCl with a concentration of 1 mol / L and LiCl with a concentration of 0.2 mol / L was prepared as a washing solution. Example 2: A method for developing lithium resources in salt lake brine using extraction, comprising the following steps:

[0016] An ionic liquid extraction system was prepared by mixing 1-butyl-3-methylbis(trifluoromethanesulfonyl)imide salt, tributyl phosphate (TBP), and kerosene as a diluent. The volume ratio of 1-butyl-3-methylbis(trifluoromethanesulfonyl)imide salt, TBP, and kerosene in the mixture was 1:5:4. Using a 3:1 ratio, an extraction time of 10 min, and an extraction temperature of 25°C, a single extraction yielded 32.13% magnesium and 70.63% lithium. The ionic liquid mixture was then used for five-stage extraction (five-stage extraction). Each extraction used a 3:1 volume ratio of the ionic liquid extraction system to the raw material, with a single extraction time of 10 min. After each extraction, the mixture was allowed to stand for separation. The upper organic phase was collected and stored, while the lower aqueous phase was used for further extraction until the fifth extraction was completed. The organic phases obtained from the five extractions were collected and mixed to form organic phase 1. After five stages of extraction, the lithium extraction rate was 98.02% and the magnesium extraction rate was 6.54%. Example 3: A method for developing lithium resources in salt lake brine using extraction, comprising the following steps:

[0017] The organic phase 2 obtained in step 4 was back-extracted using 5 mol / L hydrochloric acid as the back-extraction agent. The volume ratio of organic phase 2 to hydrochloric acid during back-extraction was 3:1, and the extraction time was 10 min. After extraction, the mixture was allowed to stand and separated to obtain the upper organic phase 3 and the lower aqueous phase after back-extraction. The lithium extraction rate was greater than 98%, and the magnesium extraction rate was 1.34%.

[0018] The above embodiments merely illustrate the implementation of the present invention, and their descriptions are relatively specific and detailed. However, they should not be construed as limiting the scope of the present invention. Any technical solutions obtained by adopting equivalent substitutions or equivalent transformations should fall within the protection scope of the present invention.

Claims

1. A method for developing lithium metal resources in salt lake brine, characterized by the following: step: Preparation steps: Prepare simulated salt lake brine with a magnesium-to-lithium mass ratio of 100:

1. Produce 1-butyl-3-methylbis(trifluoromethanesulfonyl)imide using 1-butyl-3-methylimidazolium chloride and lithium bis(trifluoromethanesulfonyl)imide. Reaction steps: At room temperature, magnesium precipitation is performed on the simulated brine using sodium carbonate or ammonium carbonate solution. The treated brine with a magnesium-to-lithium mass ratio of approximately 30:1 is then mixed with the extract and subjected to five-stage countercurrent extraction. Precipitation step: After back-extraction, a certain amount of sodium carbonate is added to the liquid phase, and crystallization is carried out under high temperature conditions to obtain crude lithium carbonate product. Then, after vacuum filtration, washing and drying, lithium carbonate product is obtained. Circulation Steps: The washing liquid used in the washing process is recycled to the extraction step. After the back-extraction step is completed, a small amount of 1-butyl-3-methylbis(trifluoromethanesulfonyl)imide salt solution is added for repair and then recycled. After the elemental content of the extracted liquid phase is checked, it can enter the wastewater treatment step and is then recycled back to the natural water body.

2. The method for developing lithium resources from salt lake brine according to claim 1, wherein the simulated salt lake brine has the following composition as shown in the table below. 。 3. The method for developing lithium resources in salt lake brine as described in claim 1, characterized in that... The extract solution was prepared with a volume fraction of 10% 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, 40% TBP and 50% kerosene. The washing solution was prepared with a ratio of LiCl:NaCl = 0.2M:2M. The extract solution was 1M hydrochloric acid.

4. The method for developing lithium resources in salt lake brine as described in claim 1, characterized in that... In the extraction step, the volume ratio of the extract to the simulated brine liquid phase was 2:1; the extraction time was 10 minutes for each stage, with a total extraction time of 50 minutes; and the extraction temperature was room temperature.

5. The method for developing lithium resources in salt lake brine as described in claim 1, characterized in that... The volume ratio of organic phase to washing liquid phase in the washing step is 5:1, the washing time is 10 minutes, and the washing temperature is room temperature.

6. The method for developing lithium resources in salt lake brine as described in claim 1, characterized in that... In the back-extraction step, the volume ratio of organic phase to back-extraction liquid was 3:1, the back-extraction time was 10 min, and the back-extraction temperature was room temperature.

7. The method for developing lithium resources in salt lake brine as described in claim 1, characterized by the following steps: In the recycling step, 5% by volume of 1-butyl-3-methylbis(trifluoromethanesulfonyl)imide salt is added to the organic extractant during reflux to repair the extractant before recycling.

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