Method for removing silicon impurities in lithium sulfate solution
By using sodium aluminate or ferric sulfate as a silicon remover, and combining it with an alkaline regulator to treat lithium sulfate solution, the problem of excessive silicon impurities in lithium sulfate solution was solved, achieving efficient and low-cost impurity removal.
Patent Information
- Application Number
- CN202511441904.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-10
- Publication Date
- 2026-01-09
AI Technical Summary
Existing technologies are insufficient to effectively remove silicon impurities from lithium sulfate solutions, leading to excessive silicon impurities during the preparation of lithium carbonate and affecting product quality.
Sodium aluminate or ferric sulfate was used as a silicon removal agent, and combined with an alkaline regulator, the lithium sulfate solution was treated under certain temperature and pH conditions. The purified lithium sulfate solution was obtained by filtration.
It can quickly and efficiently reduce the silicon content in lithium sulfate solution, with a removal rate of up to 90.8%, at a low cost and without introducing new impurities.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of solution impurity removal technology, specifically relating to a method for removing silicon impurities from lithium sulfate solutions. Background Technology
[0002] In the recycling of spent lithium batteries, the black powder from spent lithium-ion batteries can be leached using sulfuric acid and a reducing agent. The target metal enters the solution to form a leachate mainly composed of sulfates. After extraction, the raffinate is obtained, and then concentrated and crystallized using MVR (Medium-Volume Reduction) to obtain a lithium sulfate solution. This lithium sulfate solution is subsequently used for carbonation precipitation to obtain lithium carbonate, or converted into lithium hydroxide. However, lithium sulfate solution still contains impurities such as Si, Al, and Fe. The preparation of industrial-grade lithium carbonate requires certain requirements for the silicon impurity content in the lithium sulfate solution; excessively high levels will lead to excessive silicon impurities in the lithium carbonate crystals. Before preparing lithium carbonate, a process to remove silicon impurities is needed to reduce the silicon impurity content in the lithium sulfate solution. Therefore, providing a rapid, efficient, low-cost method for removing silicon impurities from lithium sulfate solution without introducing new impurities is of great significance for reducing the cost of recycling spent lithium batteries. Summary of the Invention
[0003] In view of this, the present invention provides a method for removing silicon impurities from lithium sulfate solution, which can effectively remove silicon impurities from lithium sulfate solution, reduce the silicon content of lithium sulfate solution, and is fast, efficient, low cost, and does not introduce new impurities.
[0004] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a method for removing silicon impurities from lithium sulfate solution, comprising the following steps: S1. Add a silicon remover to a lithium sulfate solution to obtain a mixture, wherein the silicon remover is at least one of sodium aluminate and ferric sulfate; S2. Add an alkaline regulator to the mixture to adjust the pH value, carry out the reaction, and obtain a reaction solution; S3. Filter the reaction solution to obtain a purified lithium sulfate solution.
[0005] It should be noted that in step S1, the lithium sulfate solution is the same lithium sulfate solution used in the waste lithium battery recycling process.
[0006] Preferably, in step S1, the mass-to-volume ratio of the silicon remover to the lithium sulfate solution is (2~10) g: 1 L.
[0007] Preferably, in step S2, the alkalinity regulator includes at least one of sodium carbonate and liquid alkali.
[0008] Preferably, in step S2, an alkaline regulator is added to the mixture to adjust the pH value to greater than or equal to 7.5.
[0009] Preferably, in step S2, the reaction temperature is 40℃~100℃.
[0010] Preferably, in step S2, the reaction time is 0.5 h to 2 h.
[0011] Preferably, before step S1, the method further includes: Step S01: Heat the lithium sulfate solution to obtain a heated lithium sulfate solution.
[0012] Preferably, in step S01, the temperature of the heated lithium sulfate solution is 40°C to 100°C.
[0013] Preferably, in step S1, the silicon remover is sodium aluminate.
[0014] Preferably, in step S1, the silicon remover is ferric sulfate.
[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention uses sodium aluminate and ferric sulfate as silicon removers, which can effectively remove silicon impurities in lithium sulfate solution, reduce the silicon content of lithium sulfate solution, and the method is fast, efficient, low cost (low consumption of auxiliary materials) and does not introduce new impurities. Detailed Implementation
[0016] The present invention will now be described in further detail with reference to specific embodiments, so that those skilled in the art can more clearly understand the present invention.
[0017] The process for obtaining lithium sulfate solution from recycled waste lithium batteries is as follows:
[0018] The lithium sulfate solution used in the following examples is a lithium sulfate solution from the recycling of waste lithium batteries. The lithium sulfate solution contains 0.130 g / L of Si, 0.005 g / L of Fe, 0.003 g / L of Al, and has a pH value of 7.54.
[0019] Example 1 A method for removing silicon impurities from a lithium sulfate solution includes the following steps: (1) Take 800 mL of lithium sulfate solution and place it in a beaker. Stir and heat it to 65°C in a water bath. (2) Add 3.2 g of sodium aluminate to the solution obtained in step (1), the concentration of sodium aluminate being 4.0 g / L; (3) Add liquid alkali to the solution obtained in step (2), control the pH value of the reaction to be ≥7.5, and react at 65℃ for 1 h; (4) Filter the solution obtained from the reaction in step (3) to obtain a purified lithium sulfate solution.
[0020] Example 2 A method for removing silicon impurities from a lithium sulfate solution includes the following steps: (1) Take 800 mL of lithium sulfate solution and place it in a beaker. Stir and heat it to 75°C in a water bath and keep it warm. (2) Add 3.2 g of sodium aluminate to the solution obtained in step (1), the concentration of sodium aluminate being 4.0 g / L; (3) Add liquid alkali to the solution obtained in step (2), control the reaction pH value to be ≥7.5, and react at 75℃ for 1 h; (4) Filter the solution obtained from the reaction in step (3) to obtain a purified lithium sulfate solution.
[0021] Example 3 A method for removing silicon impurities from a lithium sulfate solution includes the following steps: (1) Take 800 mL of lithium sulfate solution and place it in a beaker. Stir and heat it to 85°C in a water bath. (2) Add 3.2 g of sodium aluminate to the solution obtained in step (1), the concentration of sodium aluminate being 4.0 g / L; (3) Add liquid alkali to the solution obtained in step (2), control the pH value of the reaction to be ≥7.5, and react at 85℃ for 1 h; (4) Filter the solution obtained from the reaction in step (3) to obtain a purified lithium sulfate solution.
[0022] Example 4 A method for removing silicon impurities from a lithium sulfate solution includes the following steps: (1) Take 800 mL of lithium sulfate solution and place it in a beaker. Stir and heat it to 95°C in a water bath. (2) Add 3.2 g of sodium aluminate to the solution obtained in step (1), the concentration of sodium aluminate being 4.0 g / L; (3) Add liquid alkali to the solution obtained in step (2), control the pH value of the reaction to be ≥7.5, and react at 95℃ for 1 h; (4) Filter the solution obtained from the reaction in step (3) to obtain a purified lithium sulfate solution.
[0023] Example 5 A method for removing silicon impurities from a lithium sulfate solution includes the following steps: (1) Take 800 mL of lithium sulfate solution and place it in a beaker. Stir and heat it to 85°C in a water bath. (2) Add 1.6 g of sodium aluminate to the solution obtained in step (1), the concentration of sodium aluminate being 2.0 g / L; (3) Add liquid alkali to the solution obtained in step (2), control the pH value of the reaction to be ≥7.5, and react at 85℃ for 1 h; (4) Filter the solution obtained from the reaction in step (3) to obtain a purified lithium sulfate solution.
[0024] Example 6 A method for removing silicon impurities from a lithium sulfate solution includes the following steps: (1) Take 800 mL of lithium sulfate solution and place it in a beaker. Stir and heat it to 85°C in a water bath. (2) Add 8 g of ferric sulfate to the solution obtained in step (1), the concentration of ferric sulfate being 10.0 g / L; (3) Add liquid alkali to the solution obtained in step (2), control the pH value of the reaction to be ≥7.5, and react at 85℃ for 1 h; (4) Filter the solution obtained from the reaction in step (3) to obtain a purified lithium sulfate solution.
[0025] Example 7 A method for removing silicon impurities from a lithium sulfate solution includes the following steps: (1) Take 800 mL of lithium sulfate solution and place it in a beaker. Stir and heat it to 85°C in a water bath. (2) Add 6.4 g of ferric sulfate to the solution obtained in step (1), the concentration of ferric sulfate being 8.0 g / L; (3) Add liquid alkali to the solution obtained in step (2), control the pH value of the reaction to be ≥7.5, and react at 85℃ for 1 h; (4) Filter the solution obtained from the reaction in step (3) to obtain a purified lithium sulfate solution.
[0026] Example 8 A method for removing silicon impurities from a lithium sulfate solution includes the following steps: (1) Take 800 mL of lithium sulfate solution and place it in a beaker. Stir and heat it to 85°C in a water bath. (2) Add 4.8 g of ferric sulfate to the solution obtained in step (1), the concentration of ferric sulfate is 6.0 g / L; (3) Add liquid alkali to the solution obtained in step (2), control the pH value of the reaction to be ≥7.5, and react at 85℃ for 1 h; (4) Filter the solution obtained from the reaction in step (3) to obtain a purified lithium sulfate solution.
[0027] Example 9 A method for removing silicon impurities from a lithium sulfate solution includes the following steps: (1) Take 800 mL of lithium sulfate solution and place it in a beaker. Stir and heat it to 65°C in a water bath. (2) Add 8 g of ferric sulfate to the solution obtained in step (1), the concentration of ferric sulfate being 10.0 g / L; (3) Add liquid alkali to the solution obtained in step (2), control the pH value of the reaction to be ≥7.5, and react at 65℃ for 1 h; (4) Filter the solution obtained from the reaction in step (3) to obtain a purified lithium sulfate solution.
[0028] Performance Tests and Results The contents of Si, Al and Fe, as well as the pH value, of the purified lithium sulfate solutions obtained in Examples 1-9 were detected, and the results are shown in Table 1.
[0029] Table 1. Detection results of purified lithium sulfate solutions obtained in Examples 1-9
[0030] As shown in Table 1, Examples 1-9 effectively removed silicon impurities from the lithium sulfate solution, reducing its silicon content. Examples 1-5 showed that the best silicon impurity removal effect was achieved when the reaction temperature was controlled at 85°C and the amount of sodium aluminate added was 4.0 g / L, reducing the silicon content of the lithium sulfate solution to 0.010 g / L, with a removal rate of 92.3%. Examples 6-9 showed that the best silicon impurity removal effect was achieved when the reaction temperature was controlled at 85°C and the amount of ferric sulfate added was 8.0 g / L, reducing the silicon content of the lithium sulfate solution to 0.012 g / L, with a removal rate of 90.8%.
[0031] In summary, the method for removing silicon impurities from lithium sulfate solution provided by this invention can effectively remove silicon impurities from lithium sulfate solution, reduce the silicon content of lithium sulfate solution, and is fast, efficient, low-cost (with low consumption of auxiliary materials) and does not introduce new impurities.
[0032] Unless otherwise specified, all raw materials used in this invention are existing substances that can be purchased directly from the market.
[0033] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A method for removing silicon impurities from lithium sulfate solution, characterized in that, Includes the following steps: S1. Add a silicon remover to a lithium sulfate solution to obtain a mixture, wherein the silicon remover is at least one of sodium aluminate and ferric sulfate; S2. Add an alkaline regulator to the mixture to adjust the pH value, carry out the reaction, and obtain a reaction solution; S3. Filter the reaction solution to obtain a purified lithium sulfate solution.
2. The method for removing silicon impurities from lithium sulfate solution according to claim 1, characterized in that, In step S1, the mass-to-volume ratio of the silicon remover to the lithium sulfate solution is (2~10) g: 1 L.
3. The method for removing silicon impurities from lithium sulfate solution according to claim 1, characterized in that, In step S2, the alkalinity regulator includes at least one of sodium carbonate and liquid alkali.
4. The method for removing silicon impurities from lithium sulfate solution according to claim 1, characterized in that, In step S2, an alkaline regulator is added to the mixture to adjust the pH value to be greater than or equal to 7.
5.
5. The method for removing silicon impurities from lithium sulfate solution according to claim 1, characterized in that, In step S2, the reaction temperature is 40℃~100℃.
6. The method for removing silicon impurities from lithium sulfate solution according to claim 1, characterized in that, In step S2, the reaction time is 0.5 h to 2 h.
7. The method for removing silicon impurities from lithium sulfate solution according to claim 1, characterized in that, Before step S1, the following is also included: Step S01: Heat the lithium sulfate solution to obtain a heated lithium sulfate solution.
8. The method for removing silicon impurities from lithium sulfate solution according to claim 7, characterized in that, In step S01, the temperature of the heated lithium sulfate solution is 40℃~100℃.
9. The method for removing silicon impurities from lithium sulfate solution according to claim 1, characterized in that, In step S1, the silicon remover is sodium aluminate.
10. The method for removing silicon impurities from lithium sulfate solution according to claim 1, characterized in that, In step S1, the silicon remover is ferric sulfate.