Method for separating potassium sulfate and sodium sulfate from lithium precipitation mother liquor

Abstract

The invention relates to the technical field of lithium salt recovery, in particular to a method for separating potassium sulfate and sodium sulfate from lithium precipitation mother liquor. The invention provides a method for separating potassium sulfate and sodium sulfate from lithium precipitation mother liquor, which achieves the purpose of improving the purity of sodium sulfate and potassium sulfate by adjusting the mass ratio of sodium sulfate and potassium sulfate in the lithium precipitation mother liquor and optimizing the temperature of evaporation and aging. According to the method, the high-purity potassium sulfate crystal and the high-purity sodium sulfate powder can be prepared by utilizing the byproduct lithium precipitation mother liquor of lithium carbonate smelting only through recrystallization without adding chemical agents, so that the cost and the operation difficulty are reduced, and the method has relatively good economic benefits.

Description

Technical Field

[0001] This invention relates to the field of lithium salt recovery technology, and in particular to a method for separating potassium sulfate and sodium sulfate from lithium precipitation mother liquor. Background Technology

[0002] Lithium, as the least dense metallic element in nature, is widely used in industries such as nuclear power, new energy, new materials, and pharmaceuticals due to its excellent properties. In recent years, with the rapid development of the lithium battery industry, research on the development and extraction of lithium resources has gradually gained attention. However, due to the limited solubility of lithium carbonate, the single-pass yield of lithium precipitation is only about 80%, with approximately 20% of lithium ions remaining in the mother liquor and unable to be recovered to produce lithium carbonate products.

[0003] Lithium precipitation mother liquor is Na + Li + K + and CO3 2- Li + The content is approximately 1–2 g / L, Na + The content is approximately 50–60 g / L, CO3 2- The brine system is a high-salinity alkaline brine system with a carbonate content of approximately 10–20 g / L, and also contains some B, Cl, and SO4.

[0004] Potassium sulfate is an important chemical widely used in agriculture, chemical industry, and medicine. As a high-quality, chlorine-free potassium fertilizer, its sulfur content has low hygroscopicity and is a necessary medium-nutrient element for plants. Industrially, potassium sulfate is used to manufacture glass, phosphates, dyes, pigments, and gunpowder. Furthermore, industrial potassium sulfate is used in the manufacture of electronic chemicals such as batteries, electrolytes, and electroplating solutions. Industrial potassium sulfate is also an important pharmaceutical raw material, used in the manufacture of drugs, cosmetics, and oral hygiene products. It can be used to treat hypertension, heart disease, and kidney disease, and is also used in oral hygiene and skin care. my country's potassium sulfate production is relatively low, relying mainly on imports, making it expensive.

[0005] Although some methods for separating mixed salts have been disclosed in the existing technology, they still have drawbacks such as high energy consumption, complex processes, and insufficient product purity. Therefore, it is still of great significance to develop a mixed salt separation method with a simple process, low cost, and high product purity. Summary of the Invention

[0006] The technical problem this invention aims to solve is to address the shortcomings of the prior art by providing a method for separating potassium sulfate and sodium sulfate from lithium precipitation mother liquor. This method improves the purity of sodium sulfate and potassium sulfate by adjusting the mass ratio of sodium sulfate to potassium sulfate in the lithium precipitation mother liquor and optimizing the evaporation and aging temperatures. This invention utilizes lithium precipitation mother liquor, a byproduct of lithium carbonate smelting, and produces high-purity potassium sulfate crystals and high-purity sodium sulfate powder solely through recrystallization without the addition of chemical reagents. This reduces costs and operational complexity, resulting in significant economic benefits.

[0007] This invention provides a method for separating potassium sulfate and sodium sulfate from lithium precipitation mother liquor, comprising the following steps: S1. Lithium carbonate and lithium precipitation mother liquor, a byproduct, are prepared by lithium extraction from ore. S2. The lithium precipitation mother liquor is first evaporated and centrifuged to obtain low potassium sodium sulfate salt, which is then recycled to the roasting process. This process also increases the mass ratio of potassium sulfate to sodium sulfate in the mother liquor. After a second evaporation, the mother liquor is cooled and aged to obtain high potassium sodium sulfate salt. The high potassium sodium sulfate salt is then recrystallized in two steps to separate potassium sulfate crystals and an intermediate solution. S3, Glauber's salt hot melt crystallization: Glauber's salt is added to the intermediate solution obtained in S2 to adjust the ratio of sodium sulfate and potassium sulfate. After hot melt crystallization of Glauber's salt, sodium sulfate crystals are obtained after separation and drying to obtain anhydrous sodium sulfate powder.

[0008] According to the method for separating potassium sulfate and sodium sulfate from lithium precipitation mother liquor provided by the present invention, the mass ratio of potassium sulfate to sodium sulfate in the evaporation mother liquor in step S2 is 0.8 to 2:1.

[0009] According to the method for separating potassium sulfate and sodium sulfate from lithium precipitation mother liquor provided by the present invention, the evaporation temperature in step S2 is 70-90 °C, the aging temperature is 15-35 °C, the evaporation time is 120 min, and the aging time is 30 min.

[0010] According to the present invention, a method for separating potassium sulfate and sodium sulfate from lithium precipitation mother liquor, the two-step recrystallization method in S2 is as follows: high potassium sodium sulfate is recrystallized in the first step to obtain potassium sulfate, and the potassium sulfate is recrystallized in the second step to obtain high-purity potassium sulfate crystals.

[0011] According to the method for separating potassium sulfate and sodium sulfate from lithium precipitation mother liquor provided by the present invention, the purity of the potassium sulfate crystals in S2 is 88-96.50%.

[0012] According to the method for separating potassium sulfate and sodium sulfate from lithium precipitation mother liquor provided by the present invention, after adding sodium sulfate in step S3, the mass ratio of sodium sulfate to potassium sulfate in the intermediate solution is 4 to 7:1.

[0013] According to the method for separating potassium sulfate and sodium sulfate from lithium precipitation mother liquor provided by the present invention, the hot melting temperature in S3 is 70-80°C, and the purity of the anhydrous sodium sulfate powder is 98-99.50%.

[0014] According to the method for separating potassium sulfate and sodium sulfate from lithium precipitation mother liquor provided by the present invention, the drying temperature in step S3 is 100°C.

[0015] Compared with the prior art, the present invention has the following advantages: This invention provides a method for separating potassium sulfate and sodium sulfate from lithium precipitation mother liquor. By adjusting the mass ratio of sodium sulfate to potassium sulfate in the lithium precipitation mother liquor and optimizing the evaporation and aging temperatures, the purity of sodium sulfate and potassium sulfate can be improved. This invention utilizes lithium precipitation mother liquor, a byproduct of lithium carbonate smelting, and can produce high-purity potassium sulfate crystals and high-purity sodium sulfate powder simply through recrystallization without adding chemical reagents. This reduces costs and operational difficulty, resulting in better economic benefits. Detailed Implementation

[0016] Example 1

[0017] This embodiment provides a method for separating potassium sulfate and sodium sulfate from lithium precipitation mother liquor, including the following steps: S1. Lithium carbonate and lithium precipitation mother liquor, a byproduct, are prepared by lithium extraction from ore. S2. The lithium precipitation mother liquor is first evaporated and centrifuged to obtain low potassium sodium sulfate salt, which is then recycled in the roasting process. The mass ratio of potassium sulfate to sodium sulfate in the evaporation mother liquor is increased to 2:1. The evaporation mother liquor is heated to 80 ℃ for evaporation and then cooled to 25 ℃ for aging to increase the potassium sulfate content in the crystals. The crystals are then recrystallized in the first step to obtain potassium sulfate (i.e., K3Na(SO4)2). The potassium sulfate is then recrystallized in the second step to obtain high-purity potassium sulfate crystals with a purity of 96.50%, and an intermediate solution with reduced potassium sulfate content. S3. Glauber's salt hot melt crystallization: Glauber's salt is added to the intermediate solution obtained in S2, and the mass ratio of sodium sulfate to potassium sulfate in the intermediate solution is adjusted to 6:1. The hot melt temperature is adjusted to 80℃, and recrystallization is carried out through solute supersaturation. After separation, sodium sulfate crystals are obtained. After drying and dehydration in a fluidized bed dryer at 100℃, sodium sulfate powder with increased sodium sulfate content is obtained, namely sodium sulfate powder, with a purity of 99.50%.

[0018] Example 2 This embodiment provides a method for separating potassium sulfate and sodium sulfate from lithium precipitation mother liquor, including the following steps: S1. Lithium carbonate and lithium precipitation mother liquor, a byproduct, are prepared by lithium extraction from ore. S2. The lithium precipitation mother liquor is first evaporated and centrifuged to obtain low-potassium sodium sulfate salt, which is then recycled in the roasting process. The mass ratio of potassium sulfate to sodium sulfate in the evaporation mother liquor is increased to 1.4:1. The evaporation mother liquor is heated to 75 ℃ for evaporation and then cooled to 30 ℃ for aging to increase the potassium sulfate content in the crystals. After the first recrystallization, potassium sulfate (i.e., K3Na(SO4)2) is obtained. The potassium sulfate is then recrystallized in the second step to obtain high-purity potassium sulfate crystals with a purity of 94.00%, and an intermediate solution with reduced potassium sulfate content. S3. Glauber's salt hot melt crystallization: Glauber's salt is added to the intermediate solution obtained in S2, the mass ratio of sodium sulfate to potassium sulfate in the intermediate solution is adjusted to 4:1, the hot melt temperature is adjusted to 75℃, and recrystallization is carried out by evaporation and concentration. After separation, sodium sulfate crystals are obtained. After drying and dehydration in a fluidized bed dryer at 100℃, sodium sulfate with increased sodium sulfate content is obtained with a purity of 99.00%.

[0019] Example 3 This embodiment provides a method for separating potassium sulfate and sodium sulfate from lithium precipitation mother liquor, including the following steps: S1. Lithium carbonate and lithium precipitation mother liquor, a byproduct, are prepared by lithium extraction from ore. S2. The lithium precipitation mother liquor is first evaporated and centrifuged to obtain low-potassium sodium sulfate salt, which is then recycled in the roasting process. The mass ratio of potassium sulfate to sodium sulfate in the evaporation mother liquor is increased to 1.1:1. The evaporation mother liquor is heated to 70 ℃ for evaporation and then cooled to 15 ℃ for aging to increase the potassium sulfate content in the crystals. The crystals are then recrystallized in the first step to obtain potassium sulfate (i.e., K3Na(SO4)2). The potassium sulfate is then recrystallized in the second step to obtain high-purity potassium sulfate crystals with a purity of 92.00%, and an intermediate solution with reduced potassium sulfate content. S3. Glauber's salt hot melt crystallization: Glauber's salt is added to the intermediate solution obtained in S2, the mass ratio of sodium sulfate to potassium sulfate in the intermediate solution is adjusted to 7:1, the hot melt temperature is adjusted to 70℃, recrystallization is carried out by evaporation and concentration, sodium sulfate crystals are obtained after separation, and after drying and dehydration in a fluidized bed dryer at 100℃, sodium sulfate with increased sodium sulfate content is obtained with a purity of 99.00%.

[0020] Example 4 This embodiment provides a method for separating potassium sulfate and sodium sulfate from lithium precipitation mother liquor, including the following steps: S1. Lithium carbonate and lithium precipitation mother liquor, a byproduct, are prepared by lithium extraction from ore. S2. The lithium precipitation mother liquor is first evaporated and centrifuged to obtain low-potassium sodium sulfate salt, which is then recycled in the roasting process. The mass ratio of potassium sulfate to sodium sulfate in the evaporation mother liquor is increased to 0.8:1. The evaporation mother liquor is heated to 80 ℃ for evaporation and then cooled to 35 ℃ for aging to increase the potassium sulfate content in the crystals. The crystals are then recrystallized in the first step to obtain potassium sulfate (i.e., K3Na(SO4)2). The potassium sulfate is then recrystallized in the second step to obtain high-purity potassium sulfate crystals with a purity of 88.00%, and an intermediate solution with reduced potassium sulfate content. S3, Glauber's salt hot melt crystallization: Glauber's salt is added to the intermediate solution obtained in S2, the mass ratio of sodium sulfate to potassium sulfate in the intermediate solution is adjusted to 5:1, the hot melt temperature is adjusted to 70℃, recrystallization is carried out by evaporation and concentration, sodium sulfate crystals are obtained after separation, and after drying and dehydration in a fluidized bed dryer at 100℃, sodium sulfate with increased sodium sulfate content is obtained with a purity of 98.00%.

[0021] In summary, when the mass ratio of potassium sulfate to sodium sulfate in the lithium precipitation mother liquor is (0.8–2):1, evaporation at 70–90 °C followed by aging at 15–35 °C is beneficial for the purification of potassium sulfate. The higher the mass ratio of potassium sulfate to sodium sulfate, the higher the purity of the potassium sulfate crystals. By utilizing the byproducts of lithium carbonate smelting, potassium sulfate crystals with a potassium sulfate content of 88–96.00% can be produced simply by recrystallization without the addition of chemical reagents. When the mass ratio of sodium sulfate to potassium sulfate in the lithium precipitation mother liquor is (4-7):1, Glauber's salt is added for hot melting and crystallization. After recrystallization at a suitable temperature of 70-80 ℃, sodium sulfate content of 98-99.50% can be obtained.

[0022] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A method for separating potassium sulfate and sodium sulfate from lithium precipitation mother liquor, characterized in that, Includes the following steps: S1. Lithium carbonate and lithium precipitation mother liquor, a byproduct, are prepared by lithium extraction from ore. S2. The lithium precipitation mother liquor is first evaporated and centrifuged to obtain low potassium sodium sulfate salt, which is then recycled to the roasting process. This process also increases the mass ratio of potassium sulfate to sodium sulfate in the mother liquor. After a second evaporation, the mother liquor is cooled and aged to obtain high potassium sodium sulfate salt. The high potassium sodium sulfate salt is then recrystallized in two steps to separate potassium sulfate crystals and an intermediate solution. S3, Glauber's salt hot melt crystallization: Glauber's salt is added to the intermediate solution obtained in S2 to adjust the ratio of sodium sulfate and potassium sulfate. After hot melt crystallization of Glauber's salt, sodium sulfate crystals are obtained after separation and drying to obtain anhydrous sodium sulfate powder.

2. The method for separating potassium sulfate and sodium sulfate from lithium precipitation mother liquor according to claim 1, characterized in that, The mass ratio of potassium sulfate to sodium sulfate in the evaporation mother liquor described in S2 is 0.8 to 2:

1.

3. The method for separating potassium sulfate and sodium sulfate from lithium precipitation mother liquor according to claim 1, characterized in that, The evaporation temperature in S2 is 70–90 °C, the aging temperature is 15–35 °C, the evaporation time is 120 min, and the aging time is 30 min.

4. The method for separating potassium sulfate and sodium sulfate from lithium precipitation mother liquor according to claim 1, characterized in that, The two-step recrystallization method described in S2 is as follows: high potassium sodium sulfate is recrystallized in the first step to obtain potassium mirabilite, and the potassium mirabilite is recrystallized in the second step to obtain high-purity potassium sulfate crystals.

5. The method for separating potassium sulfate and sodium sulfate from lithium precipitation mother liquor according to claim 1, characterized in that, The potassium sulfate crystals described in S2 have a purity of 88–96.50%.

6. The method for separating potassium sulfate and sodium sulfate from lithium precipitation mother liquor according to claim 1, characterized in that, After adding Glauber's salt as described in S3, the mass ratio of sodium sulfate to potassium sulfate in the intermediate solution is 4-7:

1.

7. The method for separating potassium sulfate and sodium sulfate from lithium precipitation mother liquor according to claim 1, characterized in that, The hot-melting temperature in S3 is 70-80 °C, and the purity of the anhydrous sodium sulfate powder is 98-99.50%.

8. The method for separating potassium sulfate and sodium sulfate from lithium precipitation mother liquor according to claim 1, characterized in that, The drying temperature described in S3 is 100°C.