Purification method of lithium chloride
Through the method of mixing solvents with ethanol and acetone and rotary evaporation, the problems of low purity and high cost in the existing lithium chloride purification are solved, and potassium and sodium ions are efficiently removed, and high-purity lithium chloride is obtained, which is suitable for lithium batteries and high-end materials fields.
Patent Information
- Application Number
- CN202510476843.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-16
- Publication Date
- 2025-07-18
AI Technical Summary
The existing lithium chloride purification methods have problems with low product purity and high cost, especially the difficulty in effectively removing potassium and sodium ion impurities, which affects the performance of lithium batteries and the quality and safety of other industrial applications.
The crude lithium chloride product is dissolved by a mixed organic solvent of ethanol and acetone, and crystallized by rotary evaporation. Combined with sonication, the purity is further improved, the lithium ions are selectively dissolved, and the solubility of sodium ions and potassium ions is reduced, thereby achieving efficient solid-liquid separation.
High-purity lithium chloride with a purity of more than 99.9 wt% is obtained, which significantly reduces energy consumption and costs, is suitable for industrial production, and meets the purity requirements of lithium batteries and other high-end materials.
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Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of lithium compound purification, and particularly to a method for purifying lithium chloride. Background Art
[0002] Lithium chloride (LiCl) occupies an extremely important position in many industrial fields, especially in the lithium industry and the preparation of related high-end materials. Lithium chloride is a key raw material for the production of metallic lithium, lithium alloys, and various lithium compounds, and has wide applications in industries such as lithium battery materials, ceramic materials, and pharmaceuticals.
[0003] In raw materials for extracting lithium resources, such as lithium ores and saline lake brines, a large amount of potassium salts and sodium salts are often associated. These potassium ions and sodium ions will enter the lithium chloride system along with the extraction process. In addition, in the scenario of recycling and reusing lithium chloride, such as recovering lithium from waste lithium battery electrolytes and treating lithium-containing wastewater from lithium battery factories, potassium ion and sodium ion impurities will also be mixed in. Sodium, potassium, and lithium are all alkali metals, and sodium ions and potassium ions have similar chemical properties to lithium ions. Therefore, the removal of potassium ions and sodium ions is extremely challenging and crucial during the production and purification of lithium chloride.
[0004] In the existing lithium chloride preparation process, preliminary treatment is usually first carried out to remove most other types of impurities to obtain crude lithium chloride. In the crude lithium chloride, non-alkali metal impurities have been effectively removed, but due to their similar chemical properties and similar ionic radii to lithium ions, potassium ions and sodium ions still exist in the system and are difficult to completely separate.
[0005] The presence of potassium ions and sodium ions will have a serious negative impact on the quality and performance of lithium chloride products. For example, in the field of lithium batteries, potassium ion and sodium ion impurities will interfere with the insertion and extraction processes of lithium ions between the positive and negative electrodes of the battery, reduce the charge and discharge efficiency of the battery, increase the internal resistance of the battery, and may even cause safety hazards, such as problems like dendrite growth leading to short circuits. In other industrial applications, potassium ions and sodium ions may also affect the activity, selectivity of chemical reactions involving lithium chloride, and the physical and chemical properties of the final products, reducing the added value and market competitiveness of the products.
[0006] In the prior art, methods for further purifying crude lithium chloride containing potassium ion and sodium ion impurities include thermal concentration crystallization method, cooling crystallization method, extraction method, etc. Among them, the thermal concentration crystallization method evaporates and concentrates the crude lithium chloride solution to a supersaturated state, and uses the common ion effect to make sodium chloride precipitate out prior to lithium chloride, so as to achieve the removal of sodium chloride. This method is extremely difficult to control the concentration of sodium chloride precipitation, and when the solution concentration is high, sodium chloride and lithium chloride will precipitate out simultaneously, resulting in poor removal effect of sodium chloride, and the obtained product cannot meet the requirements of industrial-grade lithium chloride standards.
[0007] In the cooling crystallization method, lithium hydroxide is added to the lithium chloride crude product solution concentrated to supersaturation, and sodium chloride crystallizes out under freezing conditions and then is separated. This method can make the precipitation of sodium chloride more complete, and thus industrial-grade lithium chloride is obtained. However, this method still has problems of high energy consumption and high cost of adding lithium hydroxide.
[0008] In the extraction method, an alcohol extractant is used to dissolve and extract lithium chloride, and then the lithium chloride product is separated by evaporating the solvent to dryness. This method can obtain high-purity lithium chloride products and can also be used to produce battery-grade lithium chloride products. However, a large amount of energy is consumed when the alcohol extractant is evaporated to dryness, the cost is high, and there is also a risk of environmental pollution.
[0009] Therefore, a method for purifying lithium chloride that can obtain high-purity lithium chloride and has a lower cost is needed. Summary of the Invention
[0010] (1) Technical Problems to be Solved
[0011] To solve the problems of low purity and high cost of lithium chloride products in the existing technology, the present invention provides a method for purifying lithium chloride.
[0012] (2) Technical Solutions
[0013] To achieve the above object, the main technical solutions adopted by the present invention include:
[0014] A method for purifying lithium chloride, comprising the following steps:
[0015] S1: Dissolve the lithium chloride crude product in a mixed organic solvent of ethanol and acetone, and then perform solid-liquid separation treatment to obtain a saturated lithium chloride organic solution; in the lithium chloride crude product, the purity of lithium chloride is ≥98.5 wt%.
[0016] S2: Perform rotary evaporation treatment on the saturated lithium chloride organic solution to crystallize lithium chloride, obtain high-purity lithium chloride, and recover the mixed organic solvent of ethanol and acetone.
[0017] For the method for purifying lithium chloride as described above, preferably, in step S1, in the mixed organic solvent of ethanol and acetone, the volume ratio of ethanol to acetone is 1:3 - 3:1, and the purity of ethanol and acetone is analytical pure or above.
[0018] For the method for purifying lithium chloride as described above, preferably, in step S1, add the lithium chloride crude product to the mixed organic solvent of ethanol and acetone, and after adding, perform ultrasonic treatment on the system composed of the mixed organic solvent and the lithium chloride crude product within 5 minutes. The frequency of ultrasonic treatment is 20 - 40 kHz, the power is 100 - 300 W, and the time is 30 - 40 minutes;
[0019] After the ultrasonic treatment, solid-liquid separation treatment is completed within 30 min.
[0020] For the lithium chloride purification method as described above, preferably, in step S1, a mixed organic solvent of ethanol and acetone is added to the crude lithium chloride, and after stirring for 30 - 120 min, solid-liquid separation is carried out.
[0021] For the lithium chloride purification method as described above, preferably, in step S1, the solid-liquid separation treatment is precipitation separation, centrifugal separation or filtration.
[0022] For the lithium chloride purification method as described above, preferably, in step S1, the solid-liquid separation treatment is carried out under the temperature condition of 0 - 30 °C.
[0023] For the lithium chloride purification method as described above, preferably, in step S1, the solid-liquid ratio of the crude lithium chloride to the mixed organic solvent is 1 g:(1 - 5) ml.
[0024] For the lithium chloride purification method as described above, preferably, in step S2, the saturated lithium chloride organic solution is added to a rotary evaporation device for rotary evaporation treatment; the vacuum degree during the rotary evaporation treatment is 20 - 200 mbar, the rotation speed is 10 - 60 r / min, and the heating temperature is 50 - 100 °C.
[0025] For the lithium chloride purification method as described above, preferably, in step S2, when 5 - 30% of the mixed organic solvent in the crystallization system remains, the crystallization system is agitated to separate lithium chloride from the inner wall of the rotary evaporation device, and then the rotary evaporation treatment is continued for 30 - 180 min to obtain high-purity lithium chloride.
[0026] For the lithium chloride purification method as described above, preferably, in step S2, the mixed organic solvent of ethanol and acetone distilled out is recovered by cooling water with a temperature ≤ 30 °C, and the recovered mixed organic solvent of ethanol and acetone is reused in step S1.
[0027] (III) Beneficial effects
[0028] The present invention uses a mixed organic solvent of ethanol and acetone as the purification medium for lithium chloride. The mixed organic solvent of ethanol and acetone has good solubility for lithium chloride, while the solubility for sodium ions and potassium ions is significantly reduced. This selectivity makes it difficult for sodium ions and potassium ions to dissolve in the mixed organic solvent, so that they can be effectively removed in the subsequent solid-liquid separation process, and high-purity lithium chloride with a purity greater than 99.9 wt% can be obtained. The rotary evaporation treatment is carried out under a certain vacuum condition, so lithium chloride crystallization can be achieved at a lower temperature, reducing the heat required for heating and significantly reducing the energy consumption. During the rotary evaporation treatment, the mixed organic solvent of ethanol and acetone can be efficiently recovered, and its quality is hardly affected and can be reused multiple times, thus reducing the input cost and the waste treatment cost, and realizing the maximum utilization of resources.
[0029] In addition, the crystallization method of lithium chloride in the present invention is more convenient, has strong operability, and is easy to realize industrial production. Specific embodiments
[0030] In order to better explain the present invention for easy understanding, the present invention will be described in detail below in conjunction with specific embodiments.
[0031] The present invention provides a method for purifying lithium chloride, which includes the following steps:
[0032] S1: Dissolve the crude lithium chloride in a mixed organic solvent of ethanol and acetone, and then carry out solid-liquid separation treatment to obtain a saturated lithium chloride organic solution. In the above-mentioned crude lithium chloride, the purity of lithium chloride is ≥98.5 wt%.
[0033] S2: Carry out rotary evaporation treatment on the saturated lithium chloride organic solution to crystallize lithium chloride, obtain high-purity lithium chloride, and recover the mixed organic solvent of ethanol and acetone. In the high-purity lithium chloride prepared by the present invention, the purity of lithium chloride is greater than 99.9 wt%.
[0034] The present invention uses a mixed organic solvent of ethanol and acetone as the purification medium for lithium chloride. The interaction between ethanol and acetone optimizes the overall properties of the mixed organic solvent. Compared with ethanol and acetone, the solubility of the mixed organic solvent of ethanol and acetone for lithium chloride is enhanced, while the solubility for sodium ions and potassium ions is significantly reduced. This selectivity makes it difficult for sodium ions and potassium ions to dissolve in the mixed organic solvent, so that they can be effectively removed in the subsequent solid-liquid separation process, and high-purity lithium chloride with a purity greater than 99.9 wt% can be obtained.
[0035] In addition, through measurement, the crude lithium chloride is purified by dissolving it in a mixed organic solvent and performing rotary evaporation crystallization. The removal efficiency of potassium ions in the finally obtained lithium chloride product can reach 70% or more, and the removal efficiency of sodium ions can reach more than 96%, and is further preferably 98% or more.
[0036] In step S2, the rotary evaporation treatment is carried out under a certain vacuum condition, and lithium chloride crystallization can be achieved at a lower temperature. Therefore, the heat required for heating crystallization can be reduced, and the energy consumption can be significantly reduced. During the rotary evaporation treatment, the mixed organic solvent of ethanol and acetone can be efficiently recovered, and its quality is hardly affected and can be reused multiple times, thereby reducing the input cost and the waste treatment cost, and realizing the maximum utilization of resources. In addition, the crystallization method of lithium chloride in the present invention is more convenient, has strong operability, and is easy to realize industrial production.
[0037] Preferably, in the above step S1, the crude lithium chloride is lithium chloride obtained after preliminary impurity removal treatment to remove non-alkali metal impurities. The impurities in the crude lithium chloride are difficult-to-separate sodium chloride and potassium chloride, and the purity of lithium chloride in the crude lithium chloride can be ≥98.5 wt%.
[0038] Preferably, in the above step S1, in the mixed organic solvent of ethanol and acetone, the volume ratio of ethanol to acetone is 1:3 - 3:1. Within this volume ratio range, the mixed organic solvent has strong selectivity for lithium ions, sodium ions and potassium ions. If it exceeds this volume ratio range, the purity of the lithium chloride product may be affected. In addition, the purity of ethanol and acetone needs to reach analytical purity or above to avoid introducing new impurities.
[0039] Further preferably, in the above step S1, a mixed organic solvent of ethanol and acetone can be added to the crude lithium chloride, and after mechanical stirring for 30 - 120 min, solid-liquid separation is carried out. Stirring can accelerate the dissolution of the crude lithium chloride to obtain a saturated solution.
[0040] Preferably, in the above step S1, the solid-liquid separation treatment can be precipitation separation, centrifugal separation or filtration, and is further preferably centrifugal separation. After the crude lithium chloride is dissolved, the mixed system has a certain viscosity. It takes a long time to carry out solid-liquid separation through precipitation separation and filtration treatment, and part of the lithium chloride organic solution will be lost, thereby reducing the recovery rate of lithium chloride. Centrifugal separation can minimize the loss of the lithium chloride organic solution and ensure that the recovery rate of lithium chloride remains in a high range. Further, the solid-liquid separation treatment can be carried out at a temperature condition of 0 - 30°C. It should be noted that the crude lithium chloride in step S1 cannot be completely dissolved. Therefore, the recovery rate of lithium chloride is the ratio of the mass of the lithium chloride product to the difference between the mass of the initial lithium chloride and the mass of the solid (after drying) obtained after the solid-liquid separation treatment.
[0041] Since lithium chloride has good solubility in the mixed organic solvent, while the solubility of sodium chloride and potassium chloride in the mixed organic solvent is very low. Therefore, after solid-liquid separation, the liquid phase is the lithium chloride organic solution, and the solid phase remains undissolved lithium chloride, as well as sodium chloride and potassium chloride impurities, and the content of sodium chloride and potassium chloride impurities in the solid phase is higher than that in the crude lithium chloride. Further, in order to ensure obtaining a saturated lithium chloride organic solution in step S1, an excessive amount of crude lithium chloride is required. Specifically, the solid-liquid ratio of crude lithium chloride to the mixed organic solvent can be 1 g:(1 - 5) ml.
[0042] Preferably, in the above step S2, the saturated lithium chloride organic solution is added to a rotary evaporation device for rotary evaporation treatment. The vacuum degree during the rotary evaporation treatment is 20 - 200 mbar, the rotation speed is 10 - 60 r / min, and the heating temperature is 50 - 100 °C.
[0043] Preferably, in the above step S2, when the volume of the mixed organic solvent in the crystallization system remains 5 - 30%, the crystallization system presents a relatively viscous state. The crystallization system can be stirred to separate lithium chloride from the inner wall of the rotary evaporation device, prevent lithium chloride from sticking to the wall, reduce losses, and improve the recovery rate of lithium chloride. Then continue the rotary evaporation treatment for 30 - 180 min to obtain high-purity lithium chloride with a water content ≤ 0.1 wt%. In the present invention, the rotary evaporation device can be a rotary evaporator, etc.
[0044] Further preferably, in step S2, the mixed organic solvent of ethanol and acetone distilled out can be recovered by cooling water with a temperature ≤ 30 °C, and the recovered mixed organic solvent of ethanol and acetone can be reused in step S1.
[0045] In addition, in some fields, such as the power battery field, the semiconductor field, and pharmaceutical synthesis, higher purity requirements for lithium chloride are needed. The sodium content usually needs to be ≤ 15 ppm, and the total content of sodium and potassium impurities needs to be ≤ 50 ppm. The above purification method cannot completely obtain lithium chloride within this purity range for the time being. Therefore, in order to further remove impurities and achieve the above purity, the present invention also provides another purification method for lithium chloride. The step S2 of this method is exactly the same as the above method and will not be elaborated. Step S1 specifically includes the following steps:
[0046] The crude lithium chloride is added to the mixed organic solvent of ethanol and acetone. After adding, the system composed of the mixed organic solvent and the crude lithium chloride is ultrasonically treated within 5 min. The frequency of the ultrasonic treatment is 20 - 40 kHz, the power is 100 - 300 W, and the time is 30 - 40 min. After the ultrasonic treatment is completed, the solid-liquid separation treatment is completed within 30 min.
[0047] The cavitation effect of ultrasonic treatment can destroy the crystal structure of crude lithium chloride, making it easier for solvent molecules to penetrate into the interior of the crystal, thereby accelerating the dissolution of lithium chloride. At the same time, ultrasonic treatment may also cause the formation of micro-defects on the surface of impurities (sodium chloride, potassium chloride) or change their morphology, making the surface of the impurities rougher or showing microscopic defects, reducing the affinity between the impurities and solvent molecules, reducing the solubility of the impurities in the ethanol-acetone mixed organic solvent, and making it easier to remove them in the subsequent solid-liquid separation process, further improving the purity of lithium chloride.
[0048] Through the above improved purification method, lithium chloride with a purity of 99.99% or more can be obtained.
[0049] In the above method, the crude lithium chloride is added to the ethanol-acetone mixed organic solvent, and after addition, the system composed of the ethanol-acetone mixed organic solvent and the crude lithium chloride needs to be ultrasonically treated within 3 - 5 minutes to prevent excessive dissolution of the impurities in the crude lithium chloride in the ethanol-acetone mixed organic solvent. Although ultrasonic treatment can temporarily put the impurities in a state of high surface energy, after the ultrasonic treatment stops, the impurities may gradually restore their surface structure due to the thermal motion of the solvent molecules, and the solubility may increase. Therefore, after the ultrasonic treatment is completed, the solid-liquid separation treatment needs to be completed within 30 minutes.
[0050] Similarly, in the above crude lithium chloride, the purity of lithium chloride ≥ 98.5 wt%, in the ethanol-acetone mixed organic solvent, the volume ratio of ethanol to acetone is 1:3 - 3:1, the solid-liquid separation treatment is preferably centrifugal separation, the centrifugal separation treatment can be carried out at a temperature of 0 - 30 °C, and the solid-liquid ratio of the crude lithium chloride to the mixed organic solvent can be 1 g:(1 - 5) ml.
[0051] To further clarify the solution of the present invention and its technical progressiveness, the following will be described in combination with specific examples and technical effects.
[0052] Example 1
[0053] This example provides a method for purifying lithium chloride, including the following steps:
[0054] S1: Add a mixed organic solvent with a volume ratio of ethanol to acetone of 2:1 to the crude lithium chloride, with a solid-liquid ratio of the crude lithium chloride to the mixed organic solvent of 1 g:3 ml, mechanically stir for 60 minutes, and then carry out centrifugal separation treatment at 20 °C to obtain a saturated lithium chloride organic solution.
[0055] S2: Add the saturated lithium chloride organic solution to a rotary evaporator for rotary evaporation. The vacuum degree during the rotary evaporation process is 200 mbar, the rotation speed of the flask is 60 r / min, and the heating temperature of the water bath is 60 °C to crystallize lithium chloride. When the volume of the mixed organic solvents in the crystallization system remains 15%, remove the flask, stir the crystallization system to detach lithium chloride from the inner wall of the flask, and then continue the rotary evaporation process for 60 min to obtain high-purity lithium chloride. During the rotary evaporation process, recover the mixed organic solvents of ethanol and acetone distilled out by cooling water at a temperature of 25 °C.
[0056] After calculation, the removal rate of potassium ions in this example is 70%, the removal rate of sodium ions is 96.94%, and the recovery rate of lithium chloride is 98.4%.
[0057] Example 2
[0058] This example provides a method for purifying lithium chloride, which includes the following steps:
[0059] S1: Add a mixed organic solvent with a volume ratio of ethanol to acetone of 3:1 to the crude lithium chloride. The solid-liquid ratio of the crude lithium chloride to the mixed organic solvent is 1 g:4 ml. After mechanical stirring for 60 min, perform centrifugal separation at 20 °C to obtain a saturated lithium chloride organic solution.
[0060] S2: Add the saturated lithium chloride organic solution to a rotary evaporator for rotary evaporation. The vacuum degree during the rotary evaporation process is 200 mbar, the rotation speed of the flask is 60 r / min, and the heating temperature of the water bath is 60 °C to crystallize lithium chloride. When the volume of the mixed organic solvents in the crystallization system remains 15%, remove the flask, stir the crystallization system to detach lithium chloride from the inner wall of the flask, and then continue the rotary evaporation process for 60 min to obtain high-purity lithium chloride. During the rotary evaporation process, recover the mixed organic solvents of ethanol and acetone distilled out by cooling water at a temperature of 20 °C.
[0061] After calculation, the removal rate of potassium ions in this example is 85.83%, the removal rate of sodium ions is 99.86%, and the recovery rate of lithium chloride is 97.3%.
[0062] Example 3
[0063] This example provides a method for purifying lithium chloride, which includes the following steps:
[0064] S1: Add the mixed organic solvent of ethanol and acetone obtained from the first recovery in Example 2 to the crude lithium chloride. The solid-liquid ratio of the crude lithium chloride to the mixed organic solvent is 1 g: 3 ml. After mechanical stirring for 60 min, perform centrifugal separation at 20 °C to obtain a saturated lithium chloride organic solution.
[0065] S2: Add the saturated lithium chloride organic solution to a rotary evaporator for rotary evaporation. The vacuum degree during the rotary evaporation process is 200 mbar, the rotation speed of the flask is 60 r / min, and the heating temperature of the water bath is 60 °C to crystallize lithium chloride. When the volume of the mixed organic solvent in the crystallization system remains 15%, remove the flask, stir the crystallization system to separate lithium chloride from the inner wall of the flask, and then continue rotary evaporation for 60 min to obtain high-purity lithium chloride. During the rotary evaporation process, recover the mixed organic solvent of ethanol and acetone distilled out with cooling water at 25 °C.
[0066] After calculation, the removal rate of potassium ions in this example is 99.17%, the removal rate of sodium ions is 99.86%, and the recovery rate of lithium chloride is 97.9%.
[0067] Example 4
[0068] This example provides a method for purifying lithium chloride, which is different from Example 3 in that the organic mixed solvent obtained from the fifth recovery in Example 2 is used in step S1.
[0069] After calculation, the removal rate of potassium ions in this example is 70%, the removal rate of sodium ions is 96.94%, and the recovery rate of lithium chloride is 96.1%.
[0070] Example 5
[0071] This example provides a method for purifying lithium chloride, including the following steps:
[0072] S1: Add the mixed organic solvent with a volume ratio of ethanol to acetone of 1:3 to the crude lithium chloride. The solid-liquid ratio of the crude lithium chloride to the mixed organic solvent is 1 g: 5 ml. After mechanical stirring for 120 min, perform centrifugal separation at 20 °C to obtain a saturated lithium chloride organic solution.
[0073] S2: Add the saturated lithium chloride organic solution into a rotary evaporator for rotary evaporation. The vacuum degree during the rotary evaporation process is 100 mbar, the rotation speed of the flask is 40 r / min, and the heating temperature of the water bath is 100 °C to crystallize lithium chloride. When the volume of the mixed organic solvents in the crystallization system remains 5%, remove the flask, stir the crystallization system to separate lithium chloride from the inner wall of the flask, and then continue the rotary evaporation process for 30 min to obtain high-purity lithium chloride. During the rotary evaporation process, recover the mixed organic solvents of ethanol and acetone distilled out through cooling water at 25 °C.
[0074] After calculation, the removal rate of potassium ions in this example is 85.3%, the removal rate of sodium ions is 98.66%, and the recovery rate of lithium chloride is 97.6%.
[0075] Example 6
[0076] This example provides a method for purifying lithium chloride, including the following steps:
[0077] S1: Add a mixed organic solvent with a volume ratio of ethanol to acetone of 1:2 to the crude lithium chloride. The solid-liquid ratio of the crude lithium chloride to the mixed organic solvent is 1 g:1 ml. After mechanical stirring for 30 min, perform centrifugal separation at 20 °C to obtain a saturated lithium chloride organic solution.
[0078] S2: Add the saturated lithium chloride organic solution into a rotary evaporator for rotary evaporation. The vacuum degree during the rotary evaporation process is 20 mbar, the rotation speed of the flask is 10 r / min, and the heating temperature of the water bath is 50 °C to crystallize lithium chloride. When the volume of the mixed organic solvents in the crystallization system remains 30%, remove the flask, stir the crystallization system to separate lithium chloride from the inner wall of the flask, and then continue the rotary evaporation process for 180 min to obtain high-purity lithium chloride. During the rotary evaporation process, recover the mixed organic solvents of ethanol and acetone distilled out through cooling water at 25 °C.
[0079] After calculation, the removal rate of potassium ions in this example is 83.3%, the removal rate of sodium ions is 98.95%, and the recovery rate of lithium chloride is 97.8%.
[0080] Example 7
[0081] This example provides a method for purifying lithium chloride. The difference from Example 1 is that step S1 includes the following steps:
[0082] Add the crude lithium chloride to a mixed organic solvent of ethanol and acetone. After adding, perform ultrasonic treatment on the system composed of the mixed organic solvent and the crude lithium chloride for 4 min. The frequency of the ultrasonic treatment is 30 kHz, the power is 200 W, and the time is 35 min. After the ultrasonic treatment is completed, perform centrifugal separation treatment in 10 min to obtain a saturated lithium chloride organic solution.
[0083] Among them, the volume ratio of ethanol to acetone, the solid-liquid ratio of the crude lithium chloride to the mixed organic solvent, and the centrifugal separation treatment are the same as those in Example 1.
[0084] Example 8
[0085] This example provides a method for purifying lithium chloride. The difference from Example 1 is that step S1 includes the following steps:
[0086] Add the crude lithium chloride to a mixed organic solvent of ethanol and acetone. After adding, perform ultrasonic treatment on the system composed of the mixed organic solvent and the crude lithium chloride for 3 min. The frequency of the ultrasonic treatment is 20 kHz, the power is 300 W, and the time is 30 min. After the ultrasonic treatment is completed, perform centrifugal separation treatment in 12 min to obtain a saturated lithium chloride organic solution.
[0087] Among them, the volume ratio of ethanol to acetone, the solid-liquid ratio of the crude lithium chloride to the mixed organic solvent, and the centrifugal separation treatment are the same as those in Example 1.
[0088] Example 9
[0089] This example provides a method for purifying lithium chloride. The difference from Example 1 is that step S1 includes the following steps:
[0090] Add the crude lithium chloride to a mixed organic solvent of ethanol and acetone. After adding, perform ultrasonic treatment on the system composed of the mixed organic solvent and the crude lithium chloride for 2 min. The frequency of the ultrasonic treatment is 40 kHz, the power is 100 W, and the time is 40 min. After the ultrasonic treatment is completed, perform centrifugal separation treatment in 14 min to obtain a saturated lithium chloride organic solution.
[0091] Among them, the volume ratio of ethanol to acetone, the solid-liquid ratio of the crude lithium chloride to the mixed organic solvent, and the centrifugal separation treatment are the same as those in Example 1.
[0092] Comparative Example 1
[0093] This comparative example provides a method for purifying lithium chloride. The difference from Example 5 is that the organic solvent used in step S1 is ethanol and does not contain acetone.
[0094] Comparative Example 2
[0095] This comparative example provides a method for purifying lithium chloride, which is different from Example 5 in that the organic solvent used in step S1 is acetone and does not contain ethanol.
[0096] Comparative Example 3
[0097] This comparative example provides a method for purifying lithium chloride, which is different from Example 1 in that the volume ratio of ethanol to acetone in the organic mixed solvent used in step S1 is 8:1.
[0098] Comparative Example 4
[0099] This comparative example provides a method for purifying lithium chloride, which is different from Example 1 in that the volume ratio of ethanol to acetone in the organic mixed solvent used in step S1 is 1:8.
[0100] Comparative Example 5
[0101] This comparative example provides a method for purifying lithium chloride, which is different from Example 1 in that the amount of the organic mixed solvent is small, and an unsaturated lithium chloride organic solution is obtained in step S1.
[0102] Comparative Example 6
[0103] This comparative example provides a method for purifying lithium chloride, which is different from Example 7 in that the crude lithium chloride is added to a mixed organic solvent of ethanol and acetone, and the system composed of the mixed organic solvent and the crude lithium chloride is ultrasonically treated 30 minutes after the addition.
[0104] Comparative Example 7
[0105] This comparative example provides a method for purifying lithium chloride, which is different from Example 7 in that the centrifugation separation treatment is carried out 80 minutes after the ultrasonic treatment ends.
[0106] The impurity content in the crude lithium chloride of Examples 1-6 and Comparative Examples 1-5, the sodium ion content, potassium ion content and purity of the obtained lithium chloride product are detected to obtain Table 1.
[0107] Table 1 Purity statistical table of crude lithium chloride and lithium chloride products in Examples 1-6 and Comparative Examples 1-5
[0108]
[0109]
[0110] As can be seen from Table 1, the purity of the lithium chloride products prepared in Examples 1-6 is higher than 99.9 wt%, and the purity of the lithium chloride products prepared in Examples 7-9 is higher than 99.99 wt%. In Comparative Examples 1-4, since the proportion of the organic solvent exceeds the range defined in the present invention, the purity of the lithium chloride product cannot reach 99.9 wt%. In Comparative Example 5, due to the excessive addition of the organic mixed solvent, an unsaturated lithium chloride organic solution is obtained, and the dissolved amounts of impurity sodium ions and potassium ions increase. Therefore, the purity of the lithium chloride product also fails to reach 99.9 wt%. In Comparative Example 6 and Comparative Example 7, since the ultrasonic treatment starts too late or the residence time after ultrasonic treatment is too long, the impurities are dissolved in advance or redissolved, and the purity of the prepared lithium chloride product fails to reach 99.99 wt%.
[0111] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for purifying lithium chloride, characterized in that, It includes the following steps: S1: Dissolve the crude lithium chloride in a mixed organic solvent of ethanol and acetone, and then perform solid-liquid separation to obtain a saturated lithium chloride organic solution; in the crude lithium chloride, the purity of lithium chloride is ≥98.5 wt%. S2: Perform rotary evaporation on the saturated lithium chloride organic solution to crystallize lithium chloride, obtain high-purity lithium chloride, and recover the mixed organic solvent of ethanol and acetone.
2. The purification method of lithium chloride according to claim 1, characterized in that, In step S1, in the mixed organic solvent of ethanol and acetone, the volume ratio of ethanol to acetone is 1:3 - 3:1, and the purity of ethanol and acetone is analytical pure or above.
3. The purification method of lithium chloride according to claim 1, characterized in that, In step S1, add the crude lithium chloride to the mixed organic solvent of ethanol and acetone, and perform ultrasonic treatment on the system composed of the mixed organic solvent and the crude lithium chloride within 5 minutes after adding. The frequency of ultrasonic treatment is 20 - 40 kHz, the power is 100 - 300 W, and the time is 30 - 40 minutes. After the ultrasonic treatment, complete the solid-liquid separation within 30 minutes.
4. The purification method of lithium chloride according to claim 1, wherein In step S1, add the mixed organic solvent of ethanol and acetone to the crude lithium chloride, stir for 30 - 120 minutes, and then perform solid-liquid separation.
5. The purification method of lithium chloride according to claim 1 or 4, characterized in that In step S1, the solid-liquid separation treatment is precipitation separation, centrifugal separation or filtration.
6. The purification method of lithium chloride according to claim 1 or 3, characterized in that, In step S1, the solid-liquid separation treatment is carried out under the temperature condition of 0 - 30°C.
7. The purification method of lithium chloride according to claim 1 or 3, characterized in that In step S1, the solid-liquid ratio of the crude lithium chloride to the mixed organic solvent is 1 g:(1 - 5) ml.
8. The purification method of lithium chloride according to claim 1 or 3, characterized in that, In step S2, add the saturated lithium chloride organic solution to a rotary evaporation device for rotary evaporation treatment; the vacuum degree during the rotary evaporation treatment is 20 - 200 mbar, the rotation speed is 10 - 60 r / min, and the heating temperature is 50 - 100°C.
9. The purification method of lithium chloride according to claim 1 or 3, characterized in that, In step S2, when 5 - 30% of the mixed organic solvent in the crystallization system remains, stir the crystallization system to separate lithium chloride from the inner wall of the rotary evaporation device, and then continue the rotary evaporation treatment for 30 - 180 minutes to obtain high-purity lithium chloride.
10. The purification method of lithium chloride according to claim 1 or 3, characterized in that, In step S2, recover the mixed organic solvent of ethanol and acetone distilled out by cooling water with a temperature ≤30°C, and reuse the recovered mixed organic solvent of ethanol and acetone in step S1.