Method for recovering lithium chloride

Abstract

The invention provides a method for recovering lithium chloride, and relates to the technical field of lithium salt recovery. The method for recovering lithium chloride comprises the following steps: adding calcium chloride or barium chloride into a solution containing lithium and sodium, carrying out solid-liquid separation after complete reaction, and collecting a first filtrate; and separating sodium chloride and lithium chloride in the first filtrate by adopting an alcohol solvent to obtain lithium chloride. According to the method, sulfate radicals in the solution are removed through calcium chloride or barium chloride precipitation, then high-purity lithium chloride is obtained through separation according to the solubility difference of sodium chloride and lithium chloride in the alcohol solvent, and the recovery rate of lithium is high.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium salt recovery and relates to a method for recovering lithium chloride. Background Art

[0002] In recent years, the demand for lithium products has been increasing day by day, and the effective development and extraction of lithium resources are imminent. At present, when utilizing lithium resources, some mixed solutions containing lithium and sodium are often generated. Economically and effectively recovering lithium from such mixed solutions is a major factor in improving the efficient utilization of lithium resources. At present, the methods for separating lithium and sodium in such mixed solutions mainly include extraction method, crystallization separation method, sodium phosphate precipitation method, etc., but these methods all have deficiencies: the extraction method has problems such as high price of the extractant, high acidity of the stripping solution, and large residual amount of the extractant in the stripping solution; the crystallization separation method has problems such as difficult control and high lithium content in the crystallized sodium salt product, which affects the lithium recovery rate; the sodium phosphate precipitation method has problems such as difficult treatment of phosphorus-containing wastewater, low purity of lithium phosphate products and small demand, etc.

[0003] Chinese Patent CN116040659A discloses a method for preparing battery-grade anhydrous lithium chloride, and the steps include: a. adding calcium chloride to a lithium sulfate solution or a sulfuric acid leaching solution of lithium concentrate, and adding NaOH to adjust the pH of the solution to 9 - 12. After full reaction, filter and wash. The obtained filter cake is CaSO4·2H2O, and the filtrate is a LiCl solution, that is, a conversion solution; b. measuring the Ca 2+ concentration, adding an appropriate amount of Na2CO3 to remove Ca 2+ , to obtain a calcium-removed solution; c. passing the calcium-removed solution through a nanofiltration membrane to remove sulfate radicals and then through an ion exchange resin to remove boron to obtain a purified solution; d. adding hydrochloric acid to the purified solution to adjust the pH value to 2 - 5, heating to remove CO3 2- , then adding NaOH to adjust the pH value to 8.0 - 11.0, and obtaining a lithium chloride neutralization solution after reaction; e. evaporating and concentrating the lithium chloride neutralization solution to obtain a lithium chloride concentrated solution with a Li2O concentration of 160 - 240 g / L calculated based on the Li2O concentration; f. cooling the lithium chloride concentrated solution to ≤15°C, filtering to remove NaCl, and the filtrate is a sodium-separating solution; g. adding a refining agent to the sodium-separating solution according to the Na + concentration, with the weight ratio of the refining agent:Na + = 30 - 35:1, reacting at a reaction temperature of 50 - 80°C for 4 - 6 hours, then filtering, and the filtrate is concentrated and dried to obtain battery-grade anhydrous lithium chloride. This technology has the following deficiencies: (1) long processing steps, (2) the need to use a nanofiltration membrane, ion exchange resin, etc., resulting in long processes and high costs, (3) the need to add a refining agent, high cost, etc.

[0004] Therefore, it is necessary to study a method for economically and efficiently recovering lithium from a mixed solution containing lithium and sodium. Summary of the Invention

[0005] To solve the above technical problems, the present invention provides a method for recovering lithium chloride.

[0006] The technical solution of the present invention is as follows:

[0007] A method for recovering lithium chloride, comprising the following steps:

[0008] Calcium chloride or barium chloride is added to the lithium-containing sodium solution. After the reaction is complete, solid-liquid separation is carried out, and the first filtrate is collected.

[0009] Sodium chloride and lithium chloride in the first filtrate are separated using an alcohol solvent to obtain lithium chloride.

[0010] Preferably, the concentration of lithium ions in the lithium-containing sodium solution is not less than 6 g / L, the concentration of sodium ions is not less than 50 g / L, the concentration of SO4 2- is not less than 120 g / L, the content of CO3 2- is not more than 0.1 g / L, and the pH of the lithium-containing sodium solution is 6.5 - 7.3.

[0011] Preferably, the molar ratio of SO4 2- in the lithium-containing sodium solution to calcium chloride or barium chloride is 1:0.95 - 1.

[0012] Preferably, the operation of separating sodium chloride and lithium chloride in the first filtrate using an alcohol solvent is selected from the following operation (1) or operation (2):

[0013] Operation (1):

[0014] The first filtrate is evaporated to crystallization to obtain a crystalline product;

[0015] The crystalline product is added to the alcohol solvent, stirred, and solid-liquid separation is carried out to collect the second filtrate;

[0016] The solvent is removed from the second filtrate;

[0017] Operation (2):

[0018] The alcohol solvent is added to the first filtrate, and the precipitated solid is separated to obtain a third filtrate;

[0019] The solvent is removed from the third filtrate.

[0020] More preferably, in operation (1), the weight ratio of the crystalline product to the alcohol solvent is 1:1 - 10.

[0021] More preferably, in operation (1), the stirring time of the stirring is not less than 20 min.

[0022] More preferably, in the operation (2), the weight ratio of the first filtrate to the alcohol solvent is 1:10 - 100.

[0023] More preferably, in the operations (1) and (2), the method for removing the solvent is independently heating and evaporation, and the solvent is condensed and recovered.

[0024] More preferably, in the operation (2), the solid separated by precipitation is separated from sodium chloride after sodium chloride is precipitated by azeotropic water removal.

[0025] More preferably, the alcohol solvent is an aqueous solution of an alcohol solvent, the volume percentage content of the alcohol solvent in the aqueous solution is not less than 70%, and the alcohol solvent is selected from one or more combinations of methanol, ethanol, isopropanol, and n-propanol.

[0026] The beneficial effects of the present invention are as follows:

[0027] (1) The present invention uses calcium chloride and / or barium chloride to remove sulfate ions from a lithium-containing and sodium-containing solution, and then uses an alcohol solvent to selectively dissolve lithium chloride from a mixture of sodium chloride and lithium chloride and separate and remove insoluble sodium chloride, so that a lithium chloride product with a purity of up to 99.5% or more can be obtained, and the recovery rate of lithium reaches 95% or more.

[0028] (2) The process flow of the present invention is simple, easy to operate, and no wastewater is generated, which is convenient for industrialization. Description of the Drawings

[0029] Attached Figure 1 is the process flow diagram for recovering lithium chloride of the present invention. Detailed Embodiments

[0030] The technical solutions of the present invention will be further described and described through the following detailed embodiments.

[0031] For the recovery of lithium ions in a mixed solution containing Li + and Na + and obtaining lithium chloride with a relatively high purity, the present invention provides a method for recovering lithium chloride. As shown in the attached Figure 1 figure, it includes the following steps:

[0032] Calcium chloride or barium chloride is added to the lithium-containing and sodium-containing solution. After the reaction is complete, solid-liquid separation is carried out, and the first filtrate is collected;

[0033] Sodium chloride and lithium chloride in the first filtrate are separated using an alcohol solvent to obtain lithium chloride.

[0034] Li + and Na +has relatively similar properties. During the process of extracting lithium from lithium resources (such as lithium ore, brine, etc.), NaOH and sulfuric acid are added, and Li + cannot be completely extracted during the extraction process, resulting in the mixed solution containing not only Li + , but also Na + , SO4 2- , etc., or also containing a certain concentration of CO3 2- , H + (or OH - ), etc. In the present invention, calcium chloride or barium chloride is first added, which can react with SO4 2- in the solution to generate a precipitate (at 25 °C, the solubility product parameter Ksp of calcium sulfate is 3.16×10 -7 , and the Ksp of barium sulfate is 1.1×10 -10 ), and SO4 2- is removed first. After removing the precipitate, the remaining filtrate mainly contains sodium chloride and lithium chloride. Then, taking advantage of the large difference in solubility between sodium chloride and lithium chloride in alcohol solvents (for example, at 25 °C, the solubility of sodium chloride in absolute ethanol is <0.1 g / 100 g, and the solubility of lithium chloride in absolute ethanol is about 3.4 g / 100 ml), the separation of sodium chloride and lithium chloride is achieved, thereby obtaining lithium chloride with high purity and high yield.

[0035] In some embodiments, the concentration of lithium ions in the lithium-containing sodium solution is not less than 6 g / L, the concentration of sodium ions is not less than 50 g / L, the concentration of SO4 2- is not less than 120 g / L, the content of CO3 2- does not exceed 0.1 g / L, and the pH of the lithium-containing sodium solution is 6.5 - 7.3. If the lithium-containing sodium solution is acidic or alkaline, an alkali (such as NaOH or LiOH) or an acid (such as sulfuric acid or hydrochloric acid) can be added respectively to adjust it to neutral. If the lithium-containing sodium solution contains a certain amount of CO3 2- , an acid (such as sulfuric acid or hydrochloric acid) can be added to react to remove CO3 2- , with the control end point being that no more CO2 gas is generated after adding the acid. Controlling the content of CO3 2- within a lower range can save the amount of calcium chloride and / or barium chloride added, and avoid more entrainment of lithium ions by the precipitate caused by the generation of more precipitates, thereby reducing the lithium recovery rate. A concentration of lithium ions in the lithium-containing sodium solution of not less than 6 g / L is more conducive to the recovery of lithium ions. If the concentration of lithium ions is much lower than 6 g / L (such as 2 g / L, 3 g / L, etc.), the solution can be pre-concentrated to increase the concentration of lithium ions, and the lithium ion concentration reaching 6 g / L or above is sufficient.

[0036] In some embodiments, SO4 2-The molar ratio to calcium chloride or barium chloride is 1:0.95 - 1. Using calcium chloride or barium chloride to precipitate sulfate radicals can remove sulfate radicals, and calcium chloride or barium chloride is not in excess relative to sulfate radicals, which can avoid introducing impurity metal ions (calcium ions or barium ions). For example, SO4 2- The molar ratio to calcium chloride or barium chloride can be any value among 1:0.95, 1:0.96, 1:0.97, 1:0.98, 1:0.99, 1:1, etc., without any particular limitation. Calcium chloride or barium chloride is insufficient relative to sulfate radicals. For example, SO4 2- The molar ratio to calcium chloride or barium chloride is 1:0.96. Since sodium sulfate and / or lithium sulfate has very low solubility in alcohol solvents, the remaining small amount of sulfate can also be separated by adding alcohol solvents. In the present invention, there is no particular limitation on the stirring temperature after adding calcium chloride or barium chloride, which can be 10 - 95 °C, and there is no particular limitation on the stirring time, which can be 0.5 - 3 h.

[0037] In some embodiments, the operation of separating sodium chloride and lithium chloride in the first filtrate using an alcohol solvent is selected from the following operation (1) or operation (2):

[0038] Operation (1):

[0039] The first filtrate is evaporated to crystallization to obtain a crystalline product;

[0040] The crystalline product is added to an alcohol solvent and stirred, followed by solid-liquid separation to collect the second filtrate;

[0041] The solvent is removed from the second filtrate;

[0042] Operation (2):

[0043] An alcohol solvent is added to the first filtrate, and the precipitated solid is separated to obtain a third filtrate;

[0044] The solvent is removed from the third filtrate.

[0045] For separating sodium chloride and lithium chloride in the first filtrate using an alcohol solvent, the present invention has two operation methods, as shown in operation (1) and operation (2) above. Operation (1) is: obtaining a crystalline product mainly composed of sodium chloride and lithium chloride from the first filtrate, and then adding the crystalline product to an alcohol solvent. Lithium chloride has a certain solubility in the alcohol solvent and can be dissolved in the alcohol solvent, while sodium chloride and other salts (such as sodium sulfate) are basically insoluble in the alcohol solvent, thus realizing the separation of lithium chloride in the crystalline product. Operation (2) is: directly adding an alcohol solvent to the first filtrate. Utilizing the solubility difference of sodium chloride and lithium chloride in the alcohol solvent, the added alcohol solvent changes the composition of the solvent in the first filtrate, and the solubility of sodium chloride and other salts (such as sodium sulfate) decreases significantly and is precipitated, thus realizing the separation of lithium chloride in the first filtrate.

[0046] In some embodiments, the weight ratio of the crystallized product to the alcohol solvent in operation (1) is 1:1 - 10. For example, the weight ratio can be 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, etc. Further, the weight ratio of the crystallized product to the alcohol solvent can be 1:2 - 8.

[0047] In some embodiments, the stirring time in operation (1) is not less than 20 min. Since lithium chloride in the crystallized product needs to be dissolved in the alcohol solvent, but sodium chloride, etc. is insoluble, in order to promote the dissolution of lithium chloride in the alcohol solvent as much as possible, the stirring time cannot be too short, otherwise it will lead to insufficient dissolution of lithium chloride and affect the recovery rate. For example, the stirring time can be 20 min, 30 min, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, etc. Considering the complete dissolution of lithium chloride and the stirring efficiency, the stirring time can be 1 - 3 h. For the stirring speed, there is no special limitation. It can be a relatively low stirring speed, such as 150 - 400 rpm, or a relatively high stirring speed, such as 800 - 1500 rpm, or other stirring speeds, such as 400 - 800 rpm.

[0048] In some embodiments, the weight ratio of the first filtrate to the alcohol solvent in operation (2) is 1:10 - 100. For adding the alcohol solvent to the first filtrate in operation (2), the first filtrate contains a certain amount of water. Adding the alcohol solvent can change the composition of the solvent, making the solubility of sodium chloride decrease rapidly and precipitate; while the content of lithium chloride in the first filtrate is not high. Although the solubility of lithium chloride also decreases with the addition of the alcohol solvent, it is still in a dissolved state. Therefore, the separation of lithium chloride from salts such as sodium chloride is achieved. For example, the weight ratio of the first filtrate to the alcohol solvent can be 1:10, 1:15, 1:20, 1:25, 1:30, 1:35, 1:40, 1:45, 1:50, 1:55, 1:60, 1:65, 1:70, 1:75, 1:80, 1:85, 1:90, 1:95, 1:100, etc. The more alcohol solvent, the greater the influence on the solubility of salts such as sodium chloride, and the easier and more complete the precipitation of salts such as sodium chloride; if the alcohol solvent is insufficient, the solubility of salts such as sodium chloride decreases little and the precipitation is incomplete, resulting in insufficient purity of the obtained lithium chloride.

[0049] In some embodiments, the method of removing the solvent in operations (1) and (2) is independently heating and evaporation, and condensing and recovering the solvent. By the method of removing the solvent through heating and condensing and recovering, the solvent (alcohol solvent) can be recycled and reused, which is beneficial to environmental protection and cost reduction.

[0050] In some embodiments, the solid separated by precipitation in operation (2) is obtained by separating sodium chloride after precipitation by azeotropic dehydration of water and then removing sodium chloride. Since the first filtrate contains a certain amount of water, alcohol solvents such as methanol, ethanol, and isopropyl alcohol can form azeotropes with water to remove part or all of the water, and the solvent in the solution changes from water to an alcohol solvent or a mixed solvent mainly composed of an alcohol solvent, reducing the solubility of salts such as sodium chloride. Moreover, the solubility of salts such as sodium chloride is very low, and lithium chloride has a certain solubility, which is more conducive to the separation of lithium chloride and sodium chloride and the obtaining of high-purity lithium chloride.

[0051] In some embodiments, the alcohol solvent is an aqueous solution of an alcohol solvent, and the volume percentage content of the alcohol solvent in the aqueous solution is not less than 70%. The alcohol solvent is selected from one or a combination of two or more of methanol, ethanol, isopropyl alcohol, and n-propyl alcohol. In the present invention, the alcohol solvent can be an aqueous solution composed of an alcohol solvent and water. The alcohol solvent can be methanol, ethanol, isopropyl alcohol, etc. The lower the polarity of the alcohol solvent (polarity: methanol > absolute ethanol > isopropyl alcohol), the lower the solubility of sodium chloride and lithium chloride, and the more conducive to the separation of sodium chloride and lithium chloride. If the polarity of the alcohol solvent is too low, the solubility of lithium chloride will also be too low, and a small amount or part of lithium chloride will also precipitate. Although the purity of the collected lithium chloride is relatively high (≥99.5%), the yield of lithium chloride is reduced. For example, the alcohol solvent can be absolute ethanol, 95% ethanol aqueous solution (ethanol volume percentage content is 95%), 90% ethanol aqueous solution, 95% isopropyl alcohol aqueous solution, 90% isopropyl alcohol aqueous solution, 85% isopropyl alcohol aqueous solution, etc. If the polarity of the alcohol solvent is relatively high, the solubility of sodium chloride and lithium chloride can also be reduced by lowering the temperature of the alcohol solvent, and the separation of lithium chloride can still be achieved.

[0052] The technical solution of the present invention will be further described and illustrated according to the following embodiments.

[0053] Example 1

[0054] The composition of the lithium- and sodium-containing solution is: the concentrations of Li + , Na + and SO4 2- are 3.0 g / L, 38.87 g / L, and 101.70 g / L respectively. The pH of the solution is 6.8.

[0055] Concentrate the above lithium- and sodium-containing solution to a Li + concentration of 6 g / L to obtain a pretreatment solution, and then add calcium chloride (calcium chloride and SO4 in the pretreatment solution 2-(with a molar ratio of 0.97:1), stirred and reacted at 50 °C for 1.5 h, then solid-liquid separation was carried out to obtain gypsum and the post-reaction liquid. The obtained post-reaction liquid was evaporated to dryness for crystallization to obtain the crystalline product. The obtained crystalline product was added to an ethanol aqueous solution with a volume percentage of 90% according to a liquid-solid weight ratio of 8:1, stirred for 3 h, and after solid-liquid separation, a solid (mainly sodium chloride) and a lithium chloride solution were obtained. The obtained lithium chloride solution was evaporated to dryness for crystallization to obtain a lithium chloride product with a purity of 99.6%, and the lithium recovery rate of the whole process was 97.4%. The steam from evaporation and crystallization was condensed and returned for reuse, and was used for the dissolution and separation of the crystalline product.

[0056] Example 2

[0057] The composition of the lithium- and sodium-containing solution is: Li + , Na + , SO4 2- and CO3 2- with concentrations of 2.50 g / L, 37.39 g / L, 67.61 g / L, and 17.23 g / L respectively. The pH of the solution is 8.9.

[0058] Dilute hydrochloric acid was added to the lithium- and sodium-containing solution until CO3 2- disappeared, then sodium hydroxide with a concentration of 10 wt% was added until the solution was neutral, and then it was concentrated until the concentration of Li + was 7 g / L to obtain a pretreated solution. Calcium chloride was added (the molar ratio of calcium chloride to SO4 2- in the pretreated solution was 0.95:1), and after stirring and reacting at 95 °C for 0.5 h, solid-liquid separation was carried out to obtain gypsum and the post-reaction liquid. The post-reaction liquid was evaporated to dryness for crystallization to obtain the crystalline product. The obtained crystalline product was added to an aqueous solution of n-propanol with a volume percentage of 85% according to a liquid-solid weight ratio of 5:1, stirred for 2 h, and after solid-liquid separation, a solid (mainly sodium chloride) and a lithium chloride solution were obtained. The obtained lithium chloride solution was evaporated to dryness for crystallization to obtain a lithium chloride product with a purity of 99.7%, and the lithium recovery rate of the whole process was 97.2%. The steam from evaporation and crystallization was condensed and returned for reuse, and was used for the dissolution and separation of the crystalline product.

[0059] Example 3

[0060] The composition of the lithium- and sodium-containing solution is: Li + , Na + , SO4 2- , CO3 2- and OH - with concentrations of 2.00 g / L, 37.80 g / L, 67.61 g / L, 15.09 g / L, and 0.30 g / L respectively. The pH of the solution is 10.3.

[0061] Sulfuric acid was added to the lithium- and sodium-containing solution until CO32- disappear, then add sodium hydroxide to adjust the pH of the solution to 7.0, and then concentrate to a Li + concentration of 7.8 g / L to obtain a pretreated solution. Add barium chloride (the molar ratio of barium chloride to SO4 2- in the pretreated solution is 0.99:1), stir and react at 10 °C for 3 h, then perform solid-liquid separation to obtain barium sulfate and the reacted solution. Evaporate and crystallize the reacted solution until it is completely dried to obtain a crystalline product. Add the obtained crystalline product to anhydrous methanol at a liquid-solid weight ratio of 8:1, stir for 1 h, and after solid-liquid separation, obtain a solid (mainly sodium chloride) and a lithium chloride solution. Evaporate and crystallize the obtained lithium chloride solution to obtain a lithium chloride product with a purity of 99.5%, and the lithium recovery rate of the entire process is 96.3%. The steam from evaporation and crystallization is condensed and returned for reuse, and is used for the dissolution and separation of the crystalline product.

[0062] Example 4

[0063] The composition of the lithium- and sodium-containing solution is: Li + , Na + , SO4 2- and Cl - with concentrations of 2.20 g / L, 38.87 g / L, 81.13 g / L, and 11.16 g / L respectively. The pH of the solution is 6.5.

[0064] Concentrate the lithium- and sodium-containing solution to a Li + concentration of 6.5 g / L to obtain a pretreated solution. Add calcium chloride (the molar ratio of calcium chloride to SO4 2- in the pretreated solution is 1:1), stir and react at 35 °C for 2 h, then perform solid-liquid separation to obtain gypsum and the reacted solution. Evaporate and crystallize the obtained reacted solution until it is completely dried to obtain a crystalline product. Add the obtained crystalline product to a mixed solvent composed of isopropyl alcohol and n-propyl alcohol in a volume ratio of 1:1 at a liquid-solid weight ratio of 2:1, stir for 2 h, and after solid-liquid separation, obtain a solid (mainly sodium chloride) and a lithium chloride solution. Evaporate and crystallize the obtained lithium chloride solution to obtain a lithium chloride product with a purity of 99.7%, and the lithium recovery rate of the entire process is 97.2%. The steam from evaporation and crystallization is condensed and returned for reuse, and is used for the dissolution and separation of the crystalline product.

[0065] Example 5

[0066] The composition of the lithium- and sodium-containing solution is: Li + , Na + and SO4 2- with concentrations of 2.50 g / L, 37.80 g / L, and 67.61 g / L respectively. Additionally, OH - , Cl - and CO3 2-The concentrations are 0.30 g / L, 12.68 g / L and 6.52 g / L respectively.

[0067] Hydrochloric acid is added to the solution containing lithium and sodium until CO3 2- disappears, then sodium hydroxide with a concentration of 15 wt% is added to adjust the pH of the solution to 6.7, and then it is concentrated until the Li + concentration is 6.3 g / L to obtain a pretreatment solution. Calcium chloride (the molar ratio of calcium chloride to SO4 2- in the pretreatment solution is 0.98:1) is added, and after stirring and reacting at 70 °C for 1.5 h, solid-liquid separation is carried out to obtain gypsum and the reacted solution. Absolute ethanol is added to the obtained reacted solution, and the weight ratio of absolute ethanol to the reacted solution is 16:1. After stirring for 1.5 h, solid-liquid separation is carried out to obtain sodium chloride solid and lithium chloride solution. The obtained lithium chloride solution is subjected to evaporation crystallization to obtain a lithium chloride product with a purity of 99.6%, and the lithium recovery rate of the whole process is 97.8%. The steam from evaporation crystallization is condensed and then recycled.

[0068] Example 6

[0069] The composition of the solution containing lithium and sodium is: Li + , Na + , SO4 2- and H + with concentrations of 1.50 g / L, 32.39 g / L, 77.95 g / L and 0.001 g / L respectively.

[0070] 15 wt% sodium hydroxide is added to the solution containing lithium and sodium until the pH is 7.0, and then it is concentrated until the Li + concentration is 7.5 g / L. Barium chloride (the molar ratio of barium chloride to SO4 2- in the pretreatment solution is 0.97:1) is added, and after stirring and reacting at 75 °C for 1.5 h, solid-liquid separation is carried out to obtain barium sulfate and the reacted solution. Isopropyl alcohol is added to the obtained reacted solution, and the weight ratio of isopropyl alcohol to the reacted solution is 10:1. Azeotropic distillation is carried out to remove half of the water, and after cooling to room temperature, solid-liquid separation is carried out to obtain sodium chloride and lithium chloride solution. The obtained lithium chloride solution is subjected to evaporation crystallization to obtain a lithium chloride product with a purity of 99.6%, and the lithium recovery rate of the whole process is 96.2%. The steam from evaporation crystallization is condensed and then reused.

[0071] The above examples prove that for the solution containing lithium and sodium, by using the process method of the present invention, high-purity and high-recovery lithium chloride can be obtained through simple treatment.

[0072] As described above, the basic principles, main features and advantages of the present invention have been shown and described. Those skilled in the art should understand that the present invention is not limited by the above embodiments, and the above embodiments are only preferred embodiments of the present invention. The scope of implementation of the present invention cannot be defined accordingly. That is, equivalent changes and modifications made according to the scope of the present invention patent and the content of the specification should still fall within the scope covered by the present invention. The scope of protection required by the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for recovering lithium chloride, characterized in that, It includes the following steps: Calcium chloride or barium chloride is added to the lithium-sodium solution. After the reaction is complete, solid-liquid separation is carried out, and the first filtrate is collected. Sodium chloride and lithium chloride in the first filtrate are separated using an alcohol solvent to obtain lithium chloride.

2. The method for recovering lithium chloride according to claim 1, wherein The concentration of lithium ions in the lithium-containing sodium solution is not less than 6 g / L, the concentration of sodium ions is not less than 50 g / L, the concentration of SO4 2- is not less than 120 g / L, the content of CO3 2- does not exceed 0.1 g / L, and the pH of the lithium-containing sodium solution is 6.5 - 7.

3.

3. The method for recovering lithium chloride according to claim 1, characterized in that, SO4 in the lithium-containing sodium solution 2- The molar ratio of 2- to calcium chloride or barium chloride is 1:0.95 - 1.

4. The method for recovering lithium chloride according to claim 1, wherein The operation of separating sodium chloride and lithium chloride in the first filtrate using an alcohol solvent is selected from the following operation (1) or operation (2): Operation (1): The first filtrate is evaporated to crystallization to obtain a crystalline substance. The crystalline substance is added to the alcohol solvent and stirred, followed by solid-liquid separation to collect the second filtrate. The solvent in the second filtrate is removed. Operation (2): The alcohol solvent is added to the first filtrate, and the solid precipitated is separated to obtain the third filtrate. The solvent in the third filtrate is removed.

5. The method for recovering lithium chloride according to claim 4, wherein In operation (1), the weight ratio of the crystalline substance to the alcohol solvent is 1:1 - 10.

6. The method for recovering lithium chloride according to claim 4, wherein In operation (1), the stirring time of the stirring is not less than 20 min.

7. The method for recovering lithium chloride according to claim 4, characterized in that, In operation (2), the weight ratio of the first filtrate to the alcohol solvent is 1:10 - 100.

8. The method for recovering lithium chloride according to claim 4, wherein, In operation (1) and operation (2), the method of removing the solvent is independently heating evaporation, and the solvent is condensed and recovered.

9. The method for recovering lithium chloride according to claim 4, wherein, In operation (2), the separation of the solid precipitated is to remove water by azeotropy, precipitate sodium chloride, and then separate and remove sodium chloride.

10. The method for recovering lithium chloride according to any one of claims 4-9, characterized in that, The alcohol solvent is an aqueous solution of an alcohol solvent, and the volume percentage content of the alcohol solvent in the aqueous solution is not less than 70%. The alcohol solvent is selected from one or a combination of two or more of methanol, ethanol, isopropyl alcohol, and n-propyl alcohol.

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