A process for recovering lithium from a lithium-containing solution

Abstract

The present invention relates to a process for recovering lithium from a lithium-containing solution. S1: Sodium carbonate is added to the lithium-containing solution for lithium precipitation reaction, followed by solid-liquid separation. The solid is lithium carbonate, and the liquid is the mother liquor after lithium precipitation. S2: The mother liquor after lithium precipitation is subjected to evaporation crystallization to obtain a crystalline product. S3: The dissolution solution is mixed with the crystalline product to obtain a mixture. S4: The mixture is heated and stirred, and then filtered to obtain a filter cake and a filtrate. If the sodium sulfate content in the obtained filter cake is greater than 50%, it is further washed with the mother liquor after lithium precipitation; otherwise, the filter cake is returned to the lithium-containing solution in S1. S5: If the sodium sulfate in the filtrate is not close to saturation, the filtrate is used as the dissolution solution in S3; otherwise, the filtrate is subjected to freeze crystallization. The obtained freeze-crystallized product is sodium sulfate decahydrate, and the remaining solution after freeze crystallization is returned to the lithium-containing solution in S1. The beneficial effects are as follows: high-efficiency recovery of lithium can be achieved, and the process has the advantages of simplicity, low cost, and high freeze-crystallization efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of efficient utilization of lithium resources, and particularly to a process for recovering lithium from a lithium-containing solution. Background Art

[0002] With the continuous development of the global economy and technology, the demand for automobiles in China is gradually increasing. Therefore, the consumption of lithium resources will also become more and more. At present, lithium resources have become a hot spot of concern within the international mining industry. Although China is a large country of lithium resources with rich brine resources, there are indeed certain technical barriers in the process of use. In industrial production, a lithium-containing solution often contains some metal ions and sulfate ions, etc., which leads to the disadvantages of complex process and high recovery cost for the effective recovery of the lithium-containing solution. There is an urgent need for reasonable and feasible treatment and disposal technologies. Therefore, it is particularly important to study how to efficiently recover lithium from a lithium-containing solution.

[0003] Some scholars have carried out relevant research on the efficient recovery of lithium from a lithium-containing solution and have also made great progress. CN110451536 A discloses a method for recovering lithium from a battery-grade lithium carbonate mother liquor. The battery-grade lithium carbonate recovery mother liquor is prepared into battery-grade lithium carbonate by a combined process of freeze crystallization and evaporation concentration. At the same time, the sodium sulfate decahydrate generated by freeze crystallization is subjected to hot dissolution, evaporation concentration and other processes to prepare anhydrous sodium sulfate, and the filtrate is returned to freeze crystallization to recover lithium. Although this process can achieve high-efficiency recovery of lithium resources, the efficiency of sodium sulfate precipitation by freeze crystallization is low, and the efficiency of the filtration and washing process is also low. Moreover, using hot water for filtration and washing will increase the amount of water that needs to be evaporated in the whole system, thereby increasing the production cost.

[0004] CN 113896212 A discloses a method for recovering lithium carbonate by carbonizing and freezing sodium sulfate from a lithium precipitation mother liquor. Steps such as flash evaporation and cooling, carbonization and freezing crystallization, and thermal decomposition of lithium are used to treat the lithium precipitation mother liquor. By adding carbon dioxide and sodium sulfate to the lithium precipitation mother liquor, the carbonate ions in the lithium precipitation mother liquor are carbonized to avoid the loss of lithium ions during flash evaporation and freezing. Although the lithium carbonate obtained by this method has a high purity, the whole process flow is long and the recovery rate of the finally obtained lithium carbonate is not high.

[0005] CN 113912090 A discloses a method for recovering high-purity lithium carbonate by causticizing and freezing sodium sulfate from a lithium precipitation mother liquor. Steps such as lime causticization, evaporation concentration, freezing crystallization, and carbonization precipitation of lithium are used to treat the lithium precipitation mother liquor. Although this method can prepare high-purity lithium carbonate, the amount of water that needs to be evaporated during evaporation concentration is large, and lime and carbon dioxide need to be added, resulting in high costs and a relatively complex whole process.

[0006] In summary, certain achievements have been made in the research on the efficient recovery of lithium from lithium-containing solutions, but the problems of relatively complex processes, high costs, and low freezing crystallization efficiency cannot be solved simultaneously. Therefore, it is urgent to study a simple, efficient, and low-cost lithium extraction process from lithium-containing solutions. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a process for recovering lithium from a lithium-containing solution to overcome the deficiencies in the above-mentioned prior art.

[0008] The technical solution of the present invention to solve the above technical problems is as follows: A process for recovering lithium from a lithium-containing solution includes the following steps:

[0009] S1. Add sodium carbonate to the lithium-containing solution for lithium precipitation reaction, perform solid-liquid separation, the solid is lithium carbonate, and the liquid is the mother liquor after lithium precipitation;

[0010] S2. Perform evaporation crystallization on the mother liquor after lithium precipitation to obtain a crystalline product;

[0011] S3. Mix the dissolution solution with the crystalline product to obtain a mixture;

[0012] S4. Adjust the temperature, stir, and filter the mixture in sequence to obtain a filter cake and a filtrate. If the sodium sulfate content in the obtained filter cake is greater than 50%, wash it continuously with the mother liquor after lithium precipitation. If the sodium sulfate content in the obtained filter cake is not greater than 50%, return the filter cake to the lithium-containing solution in S1;

[0013] S5. If the sodium sulfate in the filtrate is not close to saturation, use the filtrate as the dissolution solution in S3. Otherwise, perform freezing crystallization on the filtrate. The obtained freezing crystalline product is sodium sulfate decahydrate, and the remaining liquid after freezing crystallization is returned to the lithium-containing solution in S1.

[0014] Based on the above technical solution, the present invention can also be improved as follows.

[0015] Further, the lithium-containing solution contains: sulfate ions, sodium ions, and lithium ions.

[0016] Further, the temperature of the lithium precipitation reaction is 70°C to 100°C, and the time is 0.5 h to 2 h.

[0017] Further, the molar ratio of carbonate ions to lithium ions in the solution after adding sodium carbonate to the lithium-containing solution in S1 is (0.5 - 0.7):1.

[0018] Further, the liquid-solid ratio of the dissolution solution to the crystalline product in S3 is (2 - 5):1 (ml / g).

[0019] Further, in S4, the temperature of the mixture is adjusted to 70°C to 100°C, and the stirring time is 0.5 min to 10 min.

[0020] Further, the temperature of freeze crystallization in S5 is -10°C to 10°C.

[0021] Further, sodium sulfate seeds are added during the freeze crystallization in S5.

[0022] The beneficial effects of the present invention are as follows: By treating the lithium-containing solution through processes such as lithium precipitation reaction, evaporation crystallization, heating and stirring, filtration, and freeze crystallization, and selectively dissolving the sodium salts in the evaporation crystallization product with the filtrate or / and the lithium precipitation mother liquor, the efficient separation of sodium salts and lithium carbonate is achieved. It has the advantages of simple process, high freeze crystallization efficiency, low cost, etc. All processes are easy to implement and control, with the advantage of simple operation, and finally the efficient recovery of lithium can be realized. In addition, the content of lithium and other impurities in the sodium sulfate decahydrate obtained by freeze crystallization is low, and the sodium carbonate in the freeze crystallization residual liquid can be returned to the lithium-containing solution for reuse, with good economic benefits. Description of the Drawings

[0023] Figure 1 It is a flowchart of the process for recovering lithium from the lithium-containing solution of the present invention. Detailed Embodiments

[0024] The principles and features of the present invention are described below in conjunction with the drawings. The examples given are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0025] Example 1

[0026] A process for recovering lithium from a lithium-containing solution includes the following steps:

[0027] First, an appropriate amount of sodium carbonate is added to the lithium-containing solution so that the molar ratio of carbonate ions to lithium ions in the solution is 0.7:1, and the lithium precipitation reaction is carried out at 100°C for 0.5 h, and then solid-liquid separation is performed. The solid obtained by separation is lithium carbonate, and the liquid is the lithium precipitation mother liquor;

[0028] Evaporation crystallization is carried out on the lithium precipitation mother liquor, and when the water is completely evaporated, a crystallization product is obtained;

[0029] The dissolution solution and the crystallization product are mixed at a liquid-solid ratio of 5:1 (ml / g), the temperature is adjusted to 100°C, and then stirred for 0.5 min, filtered to obtain a filter cake and a filtrate, and the filter cake is returned to the lithium-containing solution;

[0030] If the sodium sulfate in the filtrate is not close to saturation, this filtrate is used as the dissolution solution to dissolve the crystallization product. Otherwise, this filtrate is subjected to freeze crystallization at 10°C, and 2 g of sodium sulfate seeds are added. The obtained freeze crystallization product is dried and then analyzed. The obtained freeze crystallization residual liquid is returned to the lithium-containing solution, and the above steps are cycled 7 times under the above conditions according to the process of this example.

[0031] In the above embodiment, the contents of lithium ions, sodium ions, and sulfate ions in the initial lithium-containing solution are 15.8 g / L, 50.2 g / L, and 213.2 g / L respectively, and other ions are less, such as 0.0086 g / L of iron ions, 0.0035 g / L of cobalt ions, 0.0023 g / L of nickel ions, 0.0012 g / L of phosphate ions, etc. The purity of the finally obtained lithium carbonate is 99.36%, and the content of sodium sulfate in the dried freeze-crystallized product is 99.13% and the lithium content is 0.09%.

[0032] Example 2

[0033] A process for recovering lithium from a lithium-containing solution includes the following steps:

[0034] First, add an appropriate amount of sodium carbonate to the lithium-containing solution so that the molar ratio of carbonate ions to lithium ions in the solution is 0.5:1, and carry out a lithium precipitation reaction at 90 °C for 1 h, then perform solid-liquid separation. The separated solid is lithium carbonate, and the liquid is the lithium precipitation mother liquor;

[0035] Perform evaporation crystallization on the lithium precipitation mother liquor. Wait until the water is completely evaporated to obtain a crystallized product;

[0036] Mix the dissolution solution and the crystallized product at a liquid-solid ratio of 3:1 (ml / g), adjust the temperature to 90 °C, then stir for 5 min, filter to obtain a filter cake and a filtrate, then wash the obtained filter cake with the lithium precipitation mother liquor, and return the finally obtained filter cake to the lithium-containing solution;

[0037] If the sodium sulfate in the filtrate is not close to saturation, use this filtrate as the dissolution solution to dissolve the crystallized product, otherwise, perform freeze crystallization on this filtrate at 5 °C, add 1 g of sodium sulfate crystal seeds, dry the obtained freeze-crystallized product for testing, and return the obtained freeze-crystallized residual liquid to the lithium-containing solution. Perform the above steps 6 times in a cycle under the above conditions according to the process of this embodiment.

[0038] In the above embodiment, the contents of lithium ions, sodium ions, and sulfate ions in the initial lithium-containing solution are 20.1 g / L, 69.7 g / L, and 283.2 g / L respectively. Other ions are less, such as 0.0086 g / L of iron ions, 0.0155 g / L of carbonate ions, 0.0023 g / L of copper ions, 0.0012 g / L of phosphate ions, etc. The purity of the finally obtained lithium carbonate is 99.54%, and the content of sodium sulfate in the dried freeze-crystallized product is 99.23% and the lithium content is 0.08%.

[0039] Example 3

[0040] A process for recovering lithium from a lithium-containing solution includes the following steps:

[0041] First, add an appropriate amount of sodium carbonate to the lithium-containing solution so that the molar ratio of carbonate ions to lithium ions in the solution is 0.6:1, and carry out the lithium precipitation reaction at 70 °C for 2 h. Then, perform solid-liquid separation. The solid obtained by separation is lithium carbonate, and the liquid is the mother liquor after lithium precipitation;

[0042] Perform evaporation crystallization on the mother liquor after lithium precipitation. Wait until the water is completely evaporated to obtain a crystalline substance;

[0043] Mix the dissolution solution and the crystalline substance at a liquid-solid ratio of 2:1 (ml / g), adjust the temperature to 70 °C, then stir for 10 min, filter to obtain a filter cake and a filtrate, and return the filter cake to the lithium-containing solution;

[0044] If the sodium sulfate in the filtrate is not close to saturation, use this filtrate as the dissolution solution to dissolve the crystalline substance. Otherwise, perform freeze crystallization on this filtrate at -10 °C, add 0.5 g of sodium sulfate seed crystals, dry the obtained freeze-crystallized substance and then conduct chemical analysis, and return the obtained freeze-crystallized residual liquid to the lithium-containing solution. Carry out the above steps 8 times in a cycle under the above conditions according to the process of this embodiment.

[0045] In the above embodiment, the contents of lithium ions, sodium ions, and sulfate ions in the initial lithium-containing solution are 24.6 g / L, 85.4 g / L, and 347.1 g / L respectively, and the contents of other ions are relatively small, such as 0.016 g / L of aluminum ions, 0.0048 g / L of cobalt ions, 0.0021 g / L of iron ions, 0.0015 g / L of phosphate ions, etc. The purity of the finally obtained lithium carbonate is 99.63%, and the sodium sulfate content of the dried freeze-crystallized substance is 99.08% and the lithium content is 0.11%.

[0046] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A process for recovering lithium from a lithium-containing solution, characterized in that, It includes the following steps: S1. Add sodium carbonate to the lithium-containing solution for lithium precipitation reaction, perform solid-liquid separation, the solid is lithium carbonate, and the liquid is the mother liquor after lithium precipitation; S2. Evaporate and crystallize part of the mother liquor after lithium precipitation. After the water is completely evaporated, crystals are obtained; S3. Add water to a part of the mother liquor after lithium precipitation as a dissolving solution and mix it with the crystals. The liquid-solid ratio of the dissolving solution to the crystals is (2-5) mL: 1 g to obtain a mixture; S4. Adjust the temperature, stir, and filter the mixture in sequence to obtain a filter cake and a filtrate. The temperature adjustment range is 70°C to 100°C, and the stirring time is 0.5 min to 10 min. If the sodium sulfate content in the obtained filter cake is greater than 50%, wash it continuously with the mother liquor after lithium precipitation and return the finally obtained filter cake to the lithium-containing solution in S1. If the sodium sulfate content in the obtained filter cake is not greater than 50%, return the filter cake to the lithium-containing solution in S1; S5. If the sodium sulfate in the filtrate is not close to saturation, use the filtrate as the dissolving solution in S3. Otherwise, perform freeze crystallization on the filtrate. The obtained freeze crystallization product is sodium sulfate decahydrate, and the remaining liquid after freeze crystallization is returned to the lithium-containing solution in S1.

2. The process for recovering lithium from a lithium-containing solution according to claim 1, characterized in that: The lithium-containing solution contains: sulfate ion, sodium ion and lithium ion.

3. A process for recovering lithium from a lithium-containing solution according to claim 1 or 2, characterized in that: The temperature of the lithium precipitation reaction is 70°C to 100°C, and the time is 0.5 h to 2 h.

4. A process for recovering lithium from a lithium-containing solution according to claim 1, characterized in that: The molar ratio of carbonate substance to lithium ion substance in the lithium-containing solution after adding sodium carbonate in S1 is (0.5-0.7):

1.

5. A process for recovering lithium from a lithium-containing solution according to claim 1, characterized in that: The temperature of freeze crystallization in S5 is -10°C to 10°C.

6. The process for recovering lithium from a lithium-containing solution according to claim 1, characterized in that: Sodium sulfate crystal seeds are added during freeze crystallization in S5.

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