Method for effectively removing fluorine ions in lithium salt solution

Abstract

The invention discloses a method for effectively removing fluorine ions in a lithium salt solution, and belongs to the technical field of chemical engineering. The method comprises the following steps: placing a fluorine-containing lithium salt solution in a container, adding a seed crystal into the fluorine-containing lithium salt, simultaneously adding a lithium hydroxide solution and an aluminum salt solution into the lithium salt solution under a stirring condition, maintaining the stability of the whole reaction pH value in the feeding process, reacting, aging, and filtering to obtain the fluorine ions in the lithium salt solution. Filtering to obtain filter residues and filtrate subjected to deep defluorination; the filter residues are dried and then calcined, and calcined residues are obtained; and washing the calcined slag with a washing solvent to extract lithium so as to obtain a recycled lithium solution. The method is simple and convenient to operate, remarkable in fluorine removal effect, low in lithium loss, small in impurity introduction amount and high in slag recycling value, and the purity and quality of a lithium salt product can be effectively improved.

Description

Technical Field

[0001] This invention belongs to the field of chemical technology, specifically the field of high-purity lithium salt production technology, and specifically relates to a method for effectively removing fluoride ions from lithium salt solutions. Background Technology

[0002] Fluorine is a common harmful impurity in lithium salt production, affecting product quality and process stability. Therefore, developing an efficient and environmentally friendly deep defluorination technology is crucial for producing high-purity lithium salts. Existing defluorination methods include physical, chemical, and biological methods. Physical methods such as adsorption and membrane separation can remove some fluorides, but their effectiveness for deep defluorination is limited. Traditional chemical methods suffer from problems such as large reagent consumption, difficult solid waste treatment, and the introduction of numerous impurities. Aluminum salt chemical defluorination is simple to operate, requires no complex equipment, has high defluorination efficiency, and relatively low reagent costs. However, it generates a large amount of defluorination waste, increasing the difficulty and cost of environmental treatment. Furthermore, it easily forms amorphous aluminum hydroxide colloids during defluorination, which can adsorb large amounts of lithium, making filtration and washing difficult and resulting in high lithium loss after defluorination. Therefore, although aluminum salt defluorination technology is highly efficient and has low reagent costs, its practical application in lithium salt solutions for defluorination is limited in actual production operations.

[0003] Therefore, providing a method for defluorinating lithium salt solutions that can deeply remove fluoride with minimal lithium salt loss and simple operation has become a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0004] The purpose of this invention is to provide a method for defluorinating lithium salt solutions. This method is simple to operate, has a significant defluorination effect, low lithium loss, minimal impurity introduction, and high recycling value of the slag, which can effectively improve the purity and quality of lithium salt products.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] This invention discloses an effective method for removing fluoride ions from lithium salt solutions, comprising the following steps:

[0007] S1. Deep defluorination of fluorinated lithium salts

[0008] A fluorinated lithium salt solution is placed in a container, seed crystals are added to the fluorinated lithium salt, and lithium hydroxide solution and aluminum salt solution are added to the lithium salt solution simultaneously under stirring. During the addition process, the pH value of the entire reaction is kept stable. The reaction is carried out, aged, and filtered to obtain filter residue and filtrate with deep defluorination.

[0009] S2. Filter residue calcination transformation

[0010] The filter residue is dried and then calcined to obtain calcined residue;

[0011] S3. Lithium extraction through washing

[0012] The calcined residue was washed with a washing solvent to extract lithium, resulting in a recovered lithium solution.

[0013] This invention utilizes aluminum salts as a defluorination agent. During the aluminum salt flocculation defluorination process, amorphous aluminum hydroxide flocs with a large surface area are generated. Fluoride ions, with their small radius and high electronegativity, readily form hydrogen bonds with the aluminum hydroxide flocs, enabling the physical adsorption of fluoride ions onto the surface of the flocs, thus achieving deep removal of fluoride ions. However, the aluminum hydroxide flocs also have an adsorption effect on lithium ions. Therefore, the defluorination slag generated during the defluorination process undergoes high-temperature transformation and leaching for lithium recovery. The waste residue after lithium extraction is mainly alumina, which can be recycled for use as raw material in the preparation of adsorbents, ceramics, and electrolytic aluminum. This method has advantages such as simple operation, significant defluorination effect, low lithium loss, minimal impurity introduction, high slag recycling value, and the ability to effectively improve the purity and quality of lithium salt products. In lithium salt production, aluminum salt deep defluorination technology has significant application prospects and market competitiveness.

[0014] In some embodiments of the present invention, the fluorine content in the fluorinated lithium salt solution is 10 mg / L-1000 mg / L.

[0015] In some embodiments of the present invention, the concentration of the lithium hydroxide solution is 5-20 wt%, preferably 10 wt%.

[0016] In some embodiments of the present invention, the fluorinated lithium salt solution includes at least one of fluorinated lithium chloride, fluorinated lithium sulfate, and fluorinated lithium nitrate solutions.

[0017] In some embodiments of the present invention, the seed crystal is filter residue or dried filter residue;

[0018] Preferably, the amount of seed crystals added is 5%-15% of the mass of the filter residue.

[0019] In some embodiments of the present invention, the aluminum salt solution includes one or more of aluminum chloride solution, aluminum sulfate solution, and aluminum nitrate solution;

[0020] Preferably, in step S1, the aluminum salt solution is added in excess; more preferably, the mass ratio of aluminum in the added aluminum salt to fluorine in the fluorine-containing lithium salt solution is 0.1:1 to 20:1.

[0021] In some embodiments of the present invention, in step S1, the stirring speed is 200 r / min-500 r / min;

[0022] Preferably, in step S1, the pH value of the reaction system is 5-7;

[0023] Preferably, in step S1, the reaction temperature is 25℃-65℃;

[0024] Preferably, in step S1, the reaction time is 30 min to 120 min.

[0025] In some embodiments of the present invention, in step S2, the calcination temperature is 900℃-1200℃ and the calcination time is 30min-120min.

[0026] In some embodiments of the present invention, in step S3, the washing solvent includes at least one of water, dilute sulfuric acid, and dilute hydrochloric acid; the lithium adsorbed in the calcined slag dissolves in the washing solvent, thereby achieving the purpose of recovery.

[0027] Preferably, the amount of washing solvent used is 3-10 times the mass of the calcined slag.

[0028] In some embodiments of the present invention, in step S3, a three-stage countercurrent washing process is used to extract lithium.

[0029] Preferably, the temperature of the three-stage countercurrent washing is 25℃-60℃, and the washing time is 30min-120min.

[0030] In some embodiments of the present invention, step S3, the three-stage countercurrent washing for lithium extraction, includes the following steps:

[0031] S31. The calcined residue is subjected to primary countercurrent washing with secondary washing liquid to obtain tertiary washing liquid and primary washing residue; the tertiary washing liquid is recovered as the lithium recovery solution;

[0032] S32. The primary washing residue is subjected to secondary countercurrent washing with primary washing liquid to obtain secondary washing liquid and secondary washing residue;

[0033] S33. The secondary washing residue is subjected to primary countercurrent washing with a washing solvent to obtain primary washing liquid and tertiary washing residue; the tertiary washing residue is discharged from the system.

[0034] In some embodiments of the present invention, the recovered lithium solution is returned to step S1 and combined with the fluorinated lithium solution for deep defluorination.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] This invention is scientifically designed, ingeniously conceived, simple in method, easy to operate, and highly efficient in removing fluoride. The method of this invention can efficiently reduce the fluoride content in fluorinated lithium salts to below 3 mg / L, with minimal lithium loss and a lithium recovery rate of >99.5%.

[0037] The method of the present invention does not introduce any impurities other than aluminum, and the amount of aluminum introduced is less than 3 mg / L.

[0038] The technical solution of this invention produces less slag that is recyclable. The main component of the final slag is alumina, which can be recycled for the production of aluminum adsorbents, ceramics, abrasives, and electrolytic aluminum, thus achieving effective utilization of resources and making the process technology more environmentally friendly. Attached Figure Description

[0039] Appendix Figure 1 This is a process flow diagram of the present invention;

[0040] Appendix Figure 2 This is a schematic diagram of the three-stage countercurrent washing process of the present invention. Detailed Implementation

[0041] The following will provide a complete description of the concept, specific structure, and resulting technical effects of this application in conjunction with embodiments, so as to fully understand the purpose, features, and effects of this application. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them; the specification and embodiments of this application are merely exemplary.

[0042] In the embodiments of this invention, the excess aluminum-fluorine ratios are all mass ratios.

[0043] Example 1

[0044] This embodiment discloses an effective method for removing fluoride ions from lithium salt solutions, as shown in the attached figure. Figure 1 As shown, the specific steps include the following:

[0045] S1. Deep defluorination of fluorinated lithium salts

[0046] A 1.5L solution of fluorinated lithium chloride with a fluorine content of 169mg / L and a lithium content of 22.3g / L was placed in a stirrer, and 5% of the total amount of filter residue was added as seed crystals. The reaction temperature was set to 50℃ and the stirring speed to 200r / min.

[0047] Based on the fluorine content in the lithium salt solution, prepare 200 ml of aluminum chloride solution with an aluminum-fluorine excess ratio of 15:1; separately prepare 250 g of lithium hydroxide solution with a concentration of 10 wt%.

[0048] Lithium hydroxide solution and aluminum chloride solution were added simultaneously to a fluorinated lithium chloride solution under stirring conditions, maintaining the pH value of the entire reaction at 5.5. After reacting for 30 minutes, the solution was aged, filtered, and the filtrate and filter residue were obtained.

[0049] The filtrate was tested and found to contain lithium, fluorine, and aluminum at the following concentrations: lithium 19.9 g / L, fluorine 1 mg / L, and aluminum 1 mg / L.

[0050] S2. Filter residue calcination transformation

[0051] The filter residue obtained from S1 filtration was dried in an oven, and then calcined at a heating rate of 10℃ / min, a calcination temperature of 900℃, and a calcination time of 60min to obtain calcined residue.

[0052] Tests showed that the lithium content in the calcined slag was 9.54% by mass.

[0053] S3. Three-stage countercurrent washing for lithium extraction

[0054] Lithium extraction was performed on the calcined slag using a three-stage countercurrent washing process, as shown in the attached figure. Figure 2 As shown, the specific steps are as follows:

[0055] S31. Place the calcined slag in a container, perform primary countercurrent washing with secondary washing liquid, filter, and obtain tertiary washing liquid and primary washing slag; recover the tertiary washing liquid as the recovered lithium solution;

[0056] S32. Place the primary washing residue in a container, perform secondary countercurrent washing with the primary washing solution, filter, and obtain secondary washing solution and secondary washing residue;

[0057] S33. Place the secondary washing residue in a container, use pure water as the washing solvent for primary countercurrent washing, filter, and obtain primary washing liquid and tertiary washing residue; discharge the tertiary washing residue from the system; the solid-liquid mass ratio of pure water to secondary washing residue is 1:10;

[0058] The washing temperature for steps S31, S32, and S33 is 50℃, and the washing time is 30 minutes.

[0059] The final three washing residues were placed in an oven to dry and were then recovered, with a dried weight of 11g.

[0060] Tests showed that the lithium content in the three washing solutions was 7.5 g / L, and the lithium content in the three washing residues was 0.41% by mass.

[0061] Example 2

[0062] This embodiment discloses an effective method for removing fluoride ions from lithium salt solutions, as shown in the attached figure. Figure 1 As shown, the specific steps include the following:

[0063] S1. Deep defluorination of fluorinated lithium salts

[0064] A 1.5L solution of fluorinated lithium sulfate with a fluorine content of 431mg / L and a lithium content of 25.7g / L was placed in a stirrer, and 10% of the total amount of filter residue was added as seed crystals. The reaction temperature was set to 50℃ and the stirring speed to 200r / min.

[0065] Based on the fluorine content in the lithium salt solution, prepare 200 ml of aluminum sulfate solution with an aluminum-fluorine excess ratio of 10:1; separately prepare 200 g of lithium hydroxide solution with a concentration of 10 wt%.

[0066] Lithium hydroxide solution and aluminum sulfate solution were added simultaneously to a lithium chloride solution containing fluorine under stirring conditions. The pH value of the entire reaction was maintained at 5.5. After reacting for 60 minutes, the solution was aged, filtered, and the filtrate and residue were obtained.

[0067] The filtrate was tested and found to contain lithium, fluorine, and aluminum at the following concentrations: lithium 19.9 g / L, fluorine 2 mg / L, and aluminum 1 mg / L.

[0068] S2. Filter residue calcination transformation

[0069] The filter residue obtained from S1 filtration was dried in an oven, and then calcined at a heating rate of 10℃ / min, a calcination temperature of 1000℃, and a calcination time of 30min to obtain calcined residue.

[0070] Tests showed that the lithium content in the calcined slag was 10.09% by mass.

[0071] S3. Three-stage countercurrent washing for lithium extraction

[0072] Lithium extraction was performed on the calcined slag using a three-stage countercurrent washing process, as shown in the attached figure. Figure 2 As shown, the specific steps are as follows:

[0073] S31. Place the calcined slag in a container, perform primary countercurrent washing with secondary washing liquid, filter, and obtain tertiary washing liquid and primary washing slag; recover the tertiary washing liquid as the recovered lithium solution;

[0074] S32. Place the primary washing residue in a container, perform secondary countercurrent washing with the primary washing solution, filter, and obtain secondary washing solution and secondary washing residue;

[0075] S33. Place the secondary washing residue in a container, use pure water as the washing solvent for primary countercurrent washing, filter, and obtain primary washing liquid and tertiary washing residue; discharge the tertiary washing residue from the system; the solid-liquid mass ratio of pure water to secondary washing residue is 1:10;

[0076] The washing temperature for steps S31, S32, and S33 is 30°C, and the washing time is 30 minutes.

[0077] The final three washing residues were placed in an oven to dry and were then recovered, with a dried weight of 11.7g.

[0078] Tests showed that the lithium content in the three washing solutions was 7.9 g / L, and the lithium content in the three washing residues was 0.53% by mass.

[0079] Example 3

[0080] This embodiment discloses an effective method for removing fluoride ions from lithium salt solutions, as shown in the attached figure. Figure 1 As shown, the specific steps include the following:

[0081] S1. Deep defluorination of fluorinated lithium salts

[0082] A 1.5L solution of fluorinated lithium nitrate with a fluorine content of 256mg / L and a lithium content of 20.3g / L was placed in a heat-collecting constant-temperature magnetic stirrer. 5% of the total amount of filter residue was added as seed crystals. The reaction temperature was set to 40℃ and the stirring speed to 300r / min.

[0083] Based on the fluorine content in the lithium salt solution, prepare 200 ml of aluminum nitrate solution with an aluminum-fluorine excess ratio of 13:1; separately prepare 250 g of lithium hydroxide solution with a concentration of 10 wt%.

[0084] Lithium hydroxide solution and aluminum nitrate solution were added simultaneously to a lithium chloride solution containing fluorine under stirring conditions. The pH value of the entire reaction was maintained at 5.5. After reacting for 60 minutes, the solution was aged, filtered, and the filtrate and residue were obtained.

[0085] The filtrate was tested and found to contain lithium, fluorine, and aluminum at the following concentrations: lithium 19.8 g / L, fluorine 1 mg / L, and aluminum 1 mg / L.

[0086] S2. Filter residue calcination transformation

[0087] The filter residue obtained from S1 filtration was dried in an oven, and then calcined at a heating rate of 5℃ / min, a calcination temperature of 800℃, and a calcination time of 60min to obtain calcined residue.

[0088] Tests showed that the lithium content in the calcined slag was 8.53% by mass.

[0089] S3. Three-stage countercurrent washing for lithium extraction

[0090] Lithium extraction was performed on the calcined slag using a three-stage countercurrent washing process, as shown in the attached figure. Figure 2 As shown, the specific steps are as follows:

[0091] S31. Place the calcined slag in a container, perform primary countercurrent washing with secondary washing liquid, filter, and obtain tertiary washing liquid and primary washing slag; recover the tertiary washing liquid as the recovered lithium solution;

[0092] S32. Place the primary washing residue in a container, perform secondary countercurrent washing with the primary washing solution, filter, and obtain secondary washing solution and secondary washing residue;

[0093] S33. Place the secondary washing residue in a container, use pure water as the washing solvent for primary countercurrent washing, filter, and obtain primary washing liquid and tertiary washing residue; discharge the tertiary washing residue from the system; the solid-liquid mass ratio of pure water to secondary washing residue is 1:5;

[0094] The washing temperature for steps S31, S32, and S33 is 40℃, and the washing time is 60 minutes.

[0095] The final three washing residues were placed in an oven to dry and were then recovered, with a dried weight of 9.6g.

[0096] Tests showed that the lithium content in the three washing solutions was 7.8 g / L, and the lithium content in the three washing residues was 0.47% by mass.

[0097] Comparative Example 1

[0098] The difference between Comparative Example 1 and Example 1 lies in the reaction pH parameter in step S1; all other conditions are the same. The specific method for removing fluoride ions from the lithium salt solution in Comparative Example 1 is as follows:

[0099] S1. Deep defluorination of fluorinated lithium salts

[0100] A 1.5L solution of fluorinated lithium chloride with a fluorine content of 169mg / L and a lithium content of 22.3g / L was placed in a stirrer, and 5% of the total amount of filter residue was added as seed crystals. The reaction temperature was set to 50℃ and the stirring speed to 200r / min.

[0101] Based on the fluorine content in the lithium salt solution, prepare 200 ml of aluminum chloride solution with an aluminum-fluorine excess ratio of 15:1; separately prepare 250 g of lithium hydroxide solution with a concentration of 10 wt%.

[0102] Lithium hydroxide solution and aluminum chloride solution were added simultaneously to a fluorinated lithium chloride solution under stirring conditions, maintaining the pH value of the entire reaction at 4. After reacting for 30 minutes, the solution was aged, filtered, and the filtrate and filter residue were obtained.

[0103] The filtrate was tested and found to contain lithium, fluorine, and aluminum at the following concentrations: lithium 20.5 g / L, fluorine 71 mg / L, and aluminum 187 mg / L.

[0104] S2. Filter residue calcination transformation

[0105] The filter residue obtained from S1 filtration was placed in an oven to dry the moisture. After drying, it was calcined at a heating rate of 10℃ / min, a calcination temperature of 900℃, and a calcination time of 60min to obtain calcined residue.

[0106] The lithium content in the calcined slag was found to be 4.67% by mass.

[0107] S3. Three-stage countercurrent washing for lithium extraction

[0108] Lithium extraction was performed on the calcined slag using a three-stage countercurrent washing process, as shown in the attached figure. Figure 2 As shown, the specific steps are as follows:

[0109] S31. Place the calcined slag in a container, perform primary countercurrent washing with secondary washing liquid, filter, and obtain tertiary washing liquid and primary washing slag; recover the tertiary washing liquid as the recovered lithium solution;

[0110] S32. Place the primary washing residue in a container, perform secondary countercurrent washing with the primary washing solution, filter, and obtain secondary washing solution and secondary washing residue;

[0111] S33. Place the secondary washing residue in a container, use pure water as the washing solvent for primary countercurrent washing, filter, and obtain primary washing liquid and tertiary washing residue; discharge the tertiary washing residue from the system; the solid-liquid mass ratio of pure water to secondary washing residue is 1:10;

[0112] The washing temperature for steps S31, S32, and S33 is 50℃, and the washing time is 30 minutes.

[0113] The final three washing residues were placed in an oven to dry and were then recovered, with a dried weight of 13g.

[0114] Tests showed that the lithium content in the three washing solutions was 2.8 g / L, and the lithium content in the three washing residues was 0.31% by mass.

[0115] Comparative Example 2

[0116] The difference between Comparative Example 2 and Example 1 is that Steps S2 and S3 are omitted, and only Step S1 is used. The specific method for removing fluoride ions from the lithium salt solution in Comparative Example 2 is as follows:

[0117] S1. Deep defluorination of fluorinated lithium salts

[0118] A 1.5L solution of fluorinated lithium chloride with a fluorine content of 169mg / L and a lithium content of 22.3g / L was placed in a stirrer, and 5% of the total amount of filter residue was added as seed crystals. The reaction temperature was set to 50℃ and the stirring speed to 200r / min.

[0119] Based on the fluorine content in the lithium salt solution, prepare 200 ml of aluminum chloride solution with an aluminum-fluorine excess ratio of 15:1; separately prepare 250 g of lithium hydroxide solution with a concentration of 10 wt%.

[0120] Lithium hydroxide solution and aluminum chloride solution were added simultaneously to a fluorinated lithium chloride solution under stirring conditions, maintaining the pH value of the entire reaction at 5.5. After reacting for 30 minutes, the solution was aged, filtered, and the filtrate and filter residue were obtained.

[0121] The filter residue was dried in an oven, and the dried weight was 42.1g.

[0122] The filtrate was tested and found to contain lithium, fluorine, and aluminum at the following concentrations: lithium 19.9 g / L, fluorine 1 mg / L, and aluminum 1 mg / L. The lithium content in the filter residue was 10.4% by mass.

[0123] Comparative Example 3

[0124] The difference between Comparative Example 3 and Example 1 is that step S3 is omitted, and only steps S1 and S2 are present. The specific method for removing fluoride ions from the lithium salt solution in Comparative Example 3 is as follows:

[0125] S1. Deep defluorination of fluorinated lithium salts

[0126] A 1.5L solution of fluorinated lithium chloride with a fluorine content of 169mg / L and a lithium content of 22.3g / L was placed in a stirrer, and 5% of the total amount of filter residue was added as seed crystals. The reaction temperature was set to 50℃ and the stirring speed to 200r / min.

[0127] Based on the fluorine content in the lithium salt solution, prepare 200 ml of aluminum chloride solution with an aluminum-fluorine excess ratio of 15:1; separately prepare 250 g of lithium hydroxide solution with a concentration of 10 wt%.

[0128] Lithium hydroxide solution and aluminum chloride solution were added simultaneously to a fluorinated lithium chloride solution under stirring conditions, maintaining the pH value of the entire reaction at 5.5. After reacting for 30 minutes, the solution was aged, filtered, and the filtrate and filter residue were obtained.

[0129] The filtrate was tested and found to contain lithium, fluorine, and aluminum at the following concentrations: lithium 20.5 g / L, fluorine 9 mg / L, and aluminum 1 mg / L.

[0130] S2. Filter residue calcination transformation

[0131] The filter residue obtained from S1 filtration was placed in an oven to dry the moisture. After drying, it was calcined at a heating rate of 10℃ / min, a calcination temperature of 900℃, and a calcination time of 60min to obtain calcined residue with a mass of 45.3g.

[0132] Tests showed that the lithium content in the calcined slag was 9.68% by mass.

[0133] The experimental results of Examples 1-3 and Comparative Examples 1-3 were statistically analyzed, as shown in Table 1.

[0134] Table 1

[0135] Serial Number Defluorination rate Lithium loss rate Aluminum introduction amount (mg / L) Final slag alumina content Example 1 99.41％ 0.11％ 1 98.90％ Example 2 99.54％ 0.14％ 1 95.70％ Example 3 99.61％ 0.12％ 1 98.20％ Comparative Example 1 57.99％ 0.10％ 187 97.80％ Comparative Example 2 99.41％ 10.76％ 1 - Comparative Example 3 99.41％ 10.76％ 1 46.90％

[0136] As shown in the table above, the method of this invention has a high fluoride removal rate, low lithium loss, and a small amount of aluminum impurity introduced. The final slag material is mainly composed of alumina, which can be recycled for the production of aluminum adsorbents, ceramics, abrasives, and electrolytic aluminum, thus achieving effective utilization of resources.

[0137] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present application, and all such equivalent modifications or substitutions are included within the scope defined by the claims of the present application.

Claims

1. A method for effectively removing fluoride ions from a lithium salt solution, characterized in that, Includes the following steps: S1. Deep defluorination of fluorinated lithium salts A fluorinated lithium salt solution is placed in a container, seed crystals are added to the fluorinated lithium salt, and lithium hydroxide solution and aluminum salt solution are added to the lithium salt solution simultaneously under stirring. During the addition process, the pH value of the entire reaction is kept stable. The reaction is carried out, aged, and filtered to obtain filter residue and filtrate with deep defluorination. S2. Filter residue calcination transformation The filter residue is dried and then calcined to obtain calcined residue; S3. Lithium extraction through washing The calcined residue was washed with a washing solvent to extract lithium, resulting in a recovered lithium solution.

2. The method for effectively removing fluoride ions from lithium salt solution according to claim 1, characterized in that, The fluorinated lithium salt solution includes at least one of fluorinated lithium chloride, fluorinated lithium sulfate, and fluorinated lithium nitrate solutions.

3. A method for effectively removing fluoride ions from a lithium salt solution according to claim 1 or 2, characterized in that, The seed crystals are filter residue or dried filter residue; Preferably, the amount of seed crystals added is 5%-15% of the mass of the filter residue.

4. A method for effectively removing fluoride ions from a lithium salt solution according to claim 1 or 2, characterized in that, The aluminum salt solution includes one or more of aluminum chloride solution, aluminum sulfate solution, and aluminum nitrate solution; Preferably, in step S1, the aluminum salt solution is added in excess; more preferably, the mass ratio of aluminum in the added aluminum salt to fluorine in the fluorine-containing lithium salt solution is 0.1:1 to 20:

1.

5. A method for effectively removing fluoride ions from a lithium salt solution according to claim 1 or 2, characterized in that, In step S1, the stirring speed is 200 r / min-500 r / min; Preferably, in step S1, the pH value of the reaction system is 5-7; Preferably, in step S1, the reaction temperature is 25℃-65℃; Preferably, in step S1, the reaction time is 30 min to 120 min.

6. A method for effectively removing fluoride ions from a lithium salt solution according to claim 1 or 2, characterized in that, In step S2, the calcination temperature is 900℃-1200℃ and the calcination time is 30min-120min.

7. A method for effectively removing fluoride ions from a lithium salt solution according to claim 1 or 2, characterized in that, In step S3, the washing solvent includes at least one of water, dilute sulfuric acid, and dilute hydrochloric acid. Preferably, the amount of washing solvent used is 3-10 times the mass of the calcined slag.

8. A method for effectively removing fluoride ions from a lithium salt solution according to claim 1 or 2, characterized in that, In step S3, lithium extraction is performed using a three-stage countercurrent washing process. Preferably, the temperature of the three-stage countercurrent washing is 25℃-60℃, and the washing time is 30min-120min.

9. A method for effectively removing fluoride ions from a lithium salt solution according to claim 8, characterized in that, In step S3, the three-stage countercurrent washing lithium extraction includes the following steps: S31. The calcined residue is subjected to primary countercurrent washing with secondary washing liquid to obtain tertiary washing liquid and primary washing residue; the tertiary washing liquid is recovered as the lithium recovery solution; S32. The primary washing residue is subjected to secondary countercurrent washing with primary washing liquid to obtain secondary washing liquid and secondary washing residue; S33. The secondary washing residue is subjected to primary countercurrent washing with a washing solvent to obtain primary washing liquid and tertiary washing residue; the tertiary washing residue is discharged from the system.

10. The method for effectively removing fluoride ions from a lithium salt solution according to claim 9, characterized in that, The recovered lithium solution is returned to step S1 and combined with the fluorinated lithium solution for deep defluorination.

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