A method for recovering lithium fluoride to prepare high-purity lithium phosphate

Abstract

The present invention provides a method for recovering lithium fluoride to prepare high-purity lithium phosphate, belonging to the field of electrode material technology. The method uses the fallen lithium fluoride generated during the production and use of lithium fluoride as raw material, dissolves it in a solvent, and then reacts it with phosphate to obtain a filtrate containing lithium phosphate. The filtrate is then purified using a resin after adjusting the pH and filtering it twice to obtain a pure liquid. The pure liquid is then subjected to pH adjustment and filtering three times to obtain a high-purity lithium phosphate ointment. The method of the present invention has the advantages of simple process conditions, safe and easy operation, and high product purity. The prepared high-purity lithium phosphate ointment has an impurity ion content of less than 50 ppm and has extremely high economic value. It solves the problem that the fallen lithium fluoride is difficult to recover and the recovery process is highly dangerous.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrode materials, and in particular relates to a method for recovering lithium fluoride to prepare high-purity lithium phosphate. Background Art

[0002] In recent years, with the booming development of the new energy industry, the market demand for lithium fluoride has continued to rise. However, during the production and use of lithium fluoride, waste materials are inevitably generated. How to recycle and reuse these waste materials is a challenge that manufacturers need to face.

[0003] Currently, recycling lithium fluoride waste is difficult and costly, making it difficult to commercially apply. For economic reasons, manufacturers typically dump or bury unsatisfactory lithium fluoride products. However, this approach wastes resources and is prone to environmental pollution.

[0004] High-purity lithium phosphate is a raw material for the synthesis of lithium iron phosphate, a positive electrode material for batteries. The market demand is very large. Therefore, turning lithium fluoride waste into treasure and converting it into battery-grade lithium phosphate has certain economic value. However, there is currently no mature process to prepare lithium fluoride waste into lithium phosphate.

[0005] CN112340745A discloses a process for preparing lithium silicate using lithium fluoride waste material, and calcium chloride reaction is added after using hydrofluoric acid to dissolve lithium fluoride, and pH is adjusted to neutrality with sodium carbonate and filtered, and the filtrate adds an excess of sodium carbonate saturated solution, and lithium carbonate can be obtained by filtering after the reaction. The method can realize the reuse of lithium fluoride waste material, but it is necessary to use hydrofluoric acid with toxicity and strong corrosiveness, and it is dangerous and there is a large safety risk in the production process. In addition, the process cannot be used to prepare lithium phosphate.

[0006] Therefore, it is necessary to provide an improved technical solution to the above-mentioned deficiencies in the prior art. Summary of the Invention

[0007] The purpose of the present invention is to provide a method for recovering lithium fluoride to prepare high-purity lithium phosphate, which can convert lithium fluoride waste into high-purity lithium phosphate with high economic value, so as to solve the problem that lithium fluoride waste is difficult to utilize.

[0008] In order to achieve the above object, the present invention provides the following technical solutions:

[0009] A method for recovering lithium fluoride to prepare high-purity lithium phosphate comprises the following steps:

[0010] S1. Mix the lithium fluoride material with a certain amount of solvent, then add phosphate and stir evenly;

[0011] S2, using a strong acid to adjust the pH to between 0.5 and 1, then heating to a first preset temperature and reacting for a first preset time, and filtering while hot after the reaction is completed to obtain a first filtrate;

[0012] S3, adjusting the pH of the first filtrate to between 5 and 6, and keeping it at a second preset temperature for a second preset time, and then filtering to obtain a second filtrate;

[0013] S4, using resin to adsorb and purify the second filtrate to obtain a pure liquid;

[0014] S5. Adjust the pH of the purified solution to between 7 and 8, react for a third preset time, filter, and wash to obtain a high-purity lithium phosphate ointment.

[0015] Preferably, in step S1, the solvent is water, and the phosphate includes calcium and / or magnesium phosphate.

[0016] Preferably, in step S1, the solid-liquid ratio of lithium fluoride to solvent is 1:(10-20), unit: g / mL.

[0017] Preferably, the phosphate includes at least one of magnesium phosphate, magnesium hydrogen phosphate, magnesium dihydrogen phosphate, calcium phosphate, calcium hydrogen phosphate, and calcium dihydrogen phosphate.

[0018] Preferably, in step S2, the first preset temperature is 80-99° C., the first preset time is 2-8 hours, and the strong acid includes at least one of hydrochloric acid and nitric acid.

[0019] Preferably, in step S3, an alkaline substance is used to adjust the pH of the first filtrate to between 5 and 6, the second preset temperature is 25 to 60° C., and the second preset time is 0.5 to 1 h.

[0020] Preferably, in step S4, the resin includes at least one of D401 and D402.

[0021] Preferably, in step S5, the third preset time is 0.5 to 2 hours, an alkaline substance is added to the filtrate to adjust the pH to between 7 and 8, and washing is performed using hot water at 80 to 100°C.

[0022] Preferably, the alkaline substance includes at least one of lithium oxide, lithium hydroxide, sodium oxide, sodium hydroxide, lithium carbonate, lithium bicarbonate, sodium carbonate, and sodium bicarbonate.

[0023] Preferably, step S5 further includes drying the high-purity lithium phosphate paste to obtain a high-purity lithium phosphate finished product.

[0024] Beneficial effects:

[0025] The invention uses lithium fluoride waste as a raw material, utilizes calcium magnesium phosphate to react with the raw material under acidic conditions to generate a fluoride precipitate and a lithium liquid, removes high-valent metal ions in the lithium liquid by adjusting the pH value, and then utilizes a resin to deeply adsorb the high-valent metal ions in the lithium liquid to obtain a pure lithium liquid, and then precipitates lithium phosphate by controlling the pH value. After washing and drying, high-purity lithium phosphate is obtained. In the preparation process, no highly toxic and highly corrosive hydrofluoric acid is required, the process has high safety, mild reaction conditions, and a high product yield, which can stably reach more than 90%. The generated waste residue and waste liquid are easy to treat, and the process is environmentally friendly. In addition, the obtained lithium phosphate has extremely high purity, and the content of impurity elements is less than 50 ppm, thereby achieving the goal of recycling the lithium fluoride waste into high-purity lithium phosphate. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. Among them:

[0027] Figure 1 This is a process flow chart of a method for recovering lithium fluoride to prepare high-purity lithium phosphate provided by the present invention. DETAILED DESCRIPTION

[0028] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field are within the scope of protection of the present invention.

[0029] The present invention will be described in detail below with reference to the embodiments. It should be noted that the embodiments and features of the embodiments of the present invention can be combined with each other without conflict.

[0030] The present invention addresses the problem that unqualified products generated in the current lithium fluoride production process are difficult to recycle and utilize, and provides a method for recycling lithium fluoride to prepare high-purity lithium phosphate. According to the method, high-purity lithium phosphate can be obtained by processing lithium fluoride waste through a certain process. The obtained high-purity lithium phosphate can be used as a raw material for the production of lithium iron phosphate, has high economic value, and provides a new solution for the industrial application of the recycling and utilization of lithium fluoride.

[0031] like Figure 1 As shown, the present invention provides a method for recovering lithium fluoride to prepare high-purity lithium phosphate, comprising the following steps:

[0032] S1. Mix the lithium fluoride material with a certain amount of solvent, then add phosphate and stir evenly;

[0033] S2. Using a strong acid to adjust the pH to between 0.5 and 1 (e.g., 0.6, 0.7, 0.8, or 0.9), then heating to a first preset temperature and reacting for a first preset time to convert lithium fluoride into lithium phosphate. After the reaction is complete, filtering while hot to obtain a first filtrate;

[0034] S3, adjusting the pH of the first filtrate to between 5 and 6 (e.g., 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9), maintaining the first filtrate at a second preset temperature for a second preset time, and then filtering to obtain a second filtrate;

[0035] S4, using resin to perform adsorption purification on the second filtrate to obtain a pure liquid;

[0036] S5. Adjust the pH of the purified solution to between 7 and 8 (e.g., 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9), react for a third preset time, then filter and wash to obtain a high-purity lithium phosphate ointment.

[0037] The present invention dissolves lithium fluoride containing impurities in an acidic environment, reacts with phosphate to obtain a lithium phosphate solution, filters out most of the impurity ion salts, then fully precipitates the impurity ion salts by adjusting the pH and temperature, and then uses resin to continue purification. Finally, lithium phosphate is precipitated and filtered in a neutral or weakly alkaline environment, and high-purity lithium phosphate ointment is obtained after washing.

[0038] In a preferred embodiment of the present invention, in step S1, the solvent is water, and the phosphate includes calcium and / or magnesium phosphate.

[0039] In a preferred embodiment of the present invention, in step S1, the solid-liquid ratio of lithium fluoride to the solvent is 1:(10-20), for example, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19, unit: g / mL.

[0040] In a preferred embodiment of the present invention, the phosphate includes at least one of magnesium phosphate, magnesium hydrogen phosphate, magnesium dihydrogen phosphate, calcium phosphate, calcium hydrogen phosphate, and calcium dihydrogen phosphate.

[0041] In a preferred embodiment of the present invention, in step S2, the first preset temperature is 80-99°C (for example, 81°C, 83°C, 85°C, 87°C, 89°C, 91°C, 93°C, 95°C, 97°C, 98°C), the first preset time is 2-8h (for example, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5), and the strong acid includes at least one of hydrochloric acid and nitric acid.

[0042] In a preferred embodiment of the present invention, in step S3, an alkaline substance is used to adjust the pH of the first filtrate to between 5 and 6 (for example, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9), the second preset temperature is 25 to 60°C (for example, 26, 30, 35, 40, 45, 50, 55, 59), and the second preset time is 0.5 to 1h (for example, 0.6h, 0.7h, 0.8h, 0.9h).

[0043] In a preferred embodiment of the present invention, in step S4, the resin includes at least one of D401 and D402.

[0044] In a preferred embodiment of the present invention, in step S5, the third preset time is 0.5 to 2 h (for example, 0.6 h, 0.8 h, 1.0 h, 1.2 h, 1.4 h, 1.6 h, 1.8 h, 1.9 h), an alkaline substance is added to the filtrate to adjust the pH to between 7 and 8 (for example, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9), and washing is carried out using hot water at 80 to 100 ° C (for example, 81 ° C, 83 ° C, 85 ° C, 87 ° C, 89 ° C, 91 ° C, 93 ° C, 95 ° C, 97 ° C, 99 ° C).

[0045] In a preferred embodiment of the present invention, the alkaline substance includes at least one of lithium oxide, lithium hydroxide, sodium oxide, sodium hydroxide, lithium carbonate, lithium bicarbonate, sodium carbonate, and sodium bicarbonate.

[0046] In a preferred embodiment of the present invention, step S5 further includes drying the high-purity lithium phosphate paste to obtain a high-purity lithium phosphate finished product.

[0047] The following describes in detail a method for recovering lithium fluoride to prepare high-purity lithium phosphate according to the present invention through specific examples.

[0048] In the following embodiments:

[0049] Lithium fluoride is the lithium fluoride fallout generated during the production process of lithium fluoride, and its source is Baiyin Zhongtian Chemical Co., Ltd.

[0050] Resin D401: Manufacturer: Tianjin Bohong Resin Technology Co., Ltd.

[0051] Resin D402: Manufacturer: Tianjin Bohong Resin Technology Co., Ltd.

[0052] Example 1

[0053] This embodiment provides a method for preparing high-purity lithium phosphate by recycling lithium fluoride waste, and the specific steps are as follows:

[0054] S1. Mix 25.9 g of lithium fluoride with 259 mL of water, add 59.2 g of calcium phosphate (10% excess) while stirring, and continue stirring for 30 min at a stirrer speed of 200 rpm;

[0055] S2. Use 36% hydrochloric acid to adjust the pH to 1, then heat in a water bath to 95°C and keep the temperature for 2 hours. After the reaction is completed, filter while hot to obtain the first filtrate. The main component of the filter residue is calcium fluoride;

[0056] S3, adding sodium hydroxide to the first filtrate to adjust the pH value to 6, then reacting at 60° C. for 0.5 h, filtering to obtain a second filtrate, the main component of the filter residue being calcium phosphate;

[0057] S4, using D401 resin to perform adsorption purification on the second filtrate to adsorb trace calcium ions therein to obtain a pure solution;

[0058] S5. Add sodium hydroxide to the purified liquid, adjust the pH to 7, react for 1 hour, filter, and rinse with 90°C hot water to obtain high-purity lithium phosphate ointment. After drying the ointment at 120°C, 34.1g of high-purity lithium phosphate product is obtained.

[0059] The lithium content of the filtrate and filter residue in S2 was tested, and the lithium dissolution rate was calculated using the following formula:

[0060]

[0061] The calculated lithium dissolution rate was 92.3%.

[0062] The test results of metal impurities in lithium phosphate obtained from S5 are as follows: the total amount of impurity elements is less than 40ppm:

[0063]

[0064] Example 2

[0065] S1. Mix 25.9 g of lithium fluoride with 259 mL of water, add 95.6 g of calcium hydrogen phosphate (10% excess) while stirring, and continue stirring for 30 min at a stirrer speed of 200 rpm;

[0066] S2. Use 36% hydrochloric acid to adjust the pH to 0.5, then heat in a water bath to 95° C. and keep warm for 4 hours. After the reaction is completed, filter while hot to obtain a first filtrate and a first filter residue;

[0067] S3, adding sodium hydroxide to the first filtrate to adjust the pH value to 5.0, then reacting at 60° C. for 0.5 h, and filtering to obtain a second filtrate;

[0068] S4, using D402 resin to perform adsorption purification on the second filtrate to adsorb trace calcium ions therein to obtain a pure solution;

[0069] S5. Add sodium hydroxide to the purified liquid to adjust the pH to 7.0. After the reaction is completed, filter and rinse with 90°C hot water to obtain high-purity lithium phosphate ointment. After drying the ointment at 120°C, 34.9g of high-purity lithium phosphate product is obtained.

[0070] The lithium content of the filtrate and filter residue in S2 was tested, and the calculation formula was the same as that in Example 1. The calculated lithium dissolution rate was 93.6%.

[0071] The test results of metal impurities in the lithium phosphate obtained in S5 are as follows: the total amount of impurity elements is less than 40ppm:

[0072]

[0073] Example 3

[0074] S1. Mix 25.9 g of lithium fluoride with 518 mL of water, add 138.6 g of calcium dihydrogen phosphate (10% excess) while stirring, and continue stirring for 30 min at a stirrer speed of 200 rpm;

[0075] S2. Adjust the pH to 0.5 with 68% nitric acid, then heat to 95° C. in a water bath, and keep the temperature for 2 h. After the reaction is complete, filter while hot to obtain a first filtrate and a first filter residue;

[0076] S3, adding lithium hydroxide to the filtrate 1, adjusting the pH value to 5.5, then reacting at 60° C. for 0.5 h, and filtering to obtain a second filtrate;

[0077] S4, using D401 resin to perform adsorption purification on the second filtrate to adsorb trace calcium ions therein to obtain a pure solution;

[0078] S5. Sodium oxide is added to the purified solution to adjust the pH to 8.0. After the reaction is completed, the solution is filtered and rinsed with hot water at 90°C to obtain a high-purity lithium phosphate ointment. The ointment is dried at 120°C to obtain 35.2 g of a high-purity lithium phosphate product.

[0079] The lithium content of the filtrate and filter residue in S2 was tested, and the calculation formula was the same as that in Example 1. The calculated lithium dissolution rate was 94.0%.

[0080] The test results of metal impurities in the lithium phosphate obtained in S5 are as follows: the total amount of impurity elements is less than 50ppm:

[0081]

[0082] Example 4

[0083] S1. Mix 25.9 g of lithium fluoride with 388.5 mL of water, add 64.7 g of magnesium phosphate pentahydrate (10% excess) while stirring, and continue stirring for 30 min at 200 rpm;

[0084] S2. Adjust the pH to 1 with 68% nitric acid, then heat to 95° C. in a water bath, and keep the temperature for 2 h. After the reaction is complete, filter while hot to obtain a first filtrate and a first filter residue;

[0085] S3, adding sodium hydroxide to the filtrate 1 to adjust the pH to 6, then reacting at 60° C. for 0.5 h, and filtering to obtain a second filtrate;

[0086] S4, using D402 resin to perform adsorption purification on the second filtrate to adsorb trace magnesium ions therein to obtain a pure solution;

[0087] S5. Sodium oxide is added to the purified solution to adjust the pH to 7.5. After the reaction is completed, the solution is filtered and rinsed with hot water at 90°C to obtain a high-purity lithium phosphate ointment. The ointment is dried at 120°C to obtain 34.2 g of a high-purity lithium phosphate product.

[0088] The lithium content of the filtrate and filter residue in S2 was tested, and the calculation formula was the same as that in Example 1. The calculated lithium dissolution rate was 91.9%.

[0089] The test results of metal impurities in the lithium phosphate obtained in S5 are as follows: the total amount of impurity elements is less than 40ppm:

[0090]

[0091] Example 5

[0092] S1. Mix 25.9 g of lithium fluoride with 259 mL of water, add 95.9 g of magnesium hydrogen phosphate trihydrate (10% excess) while stirring, and continue stirring for 30 min at a stirrer speed of 200 rpm;

[0093] S2. Adjust the pH of the mixed solution to 1 with 36% hydrochloric acid, then heat the mixture to 95° C. in a water bath, and keep the mixture in this temperature for 2 h. After the reaction is complete, filter the mixture while hot to obtain a first filtrate and a first filter residue.

[0094] S3, adding sodium hydroxide to filtrate 1 to adjust the pH to 6, then reacting at 60°C for 0.5h, and filtering to obtain filtrate 2;

[0095] S4, using D402 resin to perform adsorption purification on the second filtrate to adsorb trace magnesium ions therein to obtain a pure solution;

[0096] S5. Sodium hydroxide is added to the purified liquid to adjust the pH to 7.5. After the reaction is completed, the solution is filtered and rinsed with hot water at 90°C to obtain a high-purity lithium phosphate ointment. The ointment is dried at 120°C to obtain 33.7 g of a high-purity lithium phosphate product.

[0097] The lithium content of the filtrate and filter residue in S2 was tested, and the calculation formula was the same as that in Example 1. The calculated lithium dissolution rate was 90.8%.

[0098] The test results of metal impurities in the lithium phosphate obtained in S5 are as follows: the total amount of impurity elements is less than 40ppm:

[0099]

[0100] Comparative Example 1

[0101] S1. Mix 25.9 g of lithium fluoride with 259 mL of water, add 59.2 g of calcium phosphate (10% excess) while stirring, and continue stirring for 30 min at a stirrer speed of 200 rpm;

[0102] S2, without adjusting the pH, then heating in a water bath to 95°C, keeping the temperature for reaction for 2 hours, filtering while hot after the reaction is completed to obtain the first filtrate;

[0103] After testing, the lithium content in the filtrate of step S2 is extremely low (285 ppm). The small amount of lithium contained in the obtained filtrate may be caused by the fact that lithium fluoride is slightly soluble in water, indicating that without adjusting the pH, it is impossible to use calcium phosphate to recover lithium fluoride to prepare lithium phosphate.

[0104] Comparative Example 2

[0105] S1. Mix 25.9 g of lithium fluoride with 259 mL of water, add 59.2 g of calcium phosphate (10% excess) while stirring, and continue stirring for 30 min at a stirrer speed of 200 rpm;

[0106] S2. Use 36% hydrochloric acid to adjust the pH to 0.5, react at room temperature at 25°C for 2 hours, and filter after the reaction to obtain the first filtrate;

[0107] After testing, the lithium content in the filtrate of step S2 was 371 ppm. A certain amount of lithium content may be caused by the fact that lithium fluoride is slightly soluble in water. Therefore, it is proved that lithium fluoride cannot be recovered by calcium phosphate to prepare lithium phosphate under room temperature reaction conditions by adjusting the pH value alone.

[0108] Comparative Example 3

[0109] S1. Mix 25.9 g of lithium fluoride with 259 mL of water, add 138.6 g of calcium dihydrogen phosphate (10% excess) while stirring, and continue stirring for 30 min at a stirrer speed of 200 rpm;

[0110] S2. Without adjusting the pH, heat the mixture to 95°C in a water bath and keep the mixture for 2 hours. After the reaction is complete, filter the mixture while it is hot to obtain filtrate 1.

[0111] S3, adding sodium hydroxide to filtrate 1 to adjust the pH to 6, then reacting at 60°C for 0.5h, and filtering to obtain filtrate 2;

[0112] S4, filtrate 2 is adsorbed by the tree to obtain the trace high-valent ions therein to obtain the pure liquid;

[0113] S5. Sodium hydroxide is added to the purified liquid to adjust the pH to 7.5. After the reaction is completed, the solution is filtered and rinsed with hot water at 90°C to obtain a high-purity lithium phosphate ointment. The ointment is dried at 120°C to obtain 18.3 g of a high-purity lithium phosphate product.

[0114] The lithium content of the filtrate and filter residue in S2 was tested, and the calculation formula was the same as that in Example 1. The calculated lithium dissolution rate was 48.9%.

[0115] The test results of metal impurities in the lithium phosphate obtained in S5 are as follows: the total amount of impurity elements is less than 40ppm:

[0116]

[0117]

[0118] In Comparative Example 1, when the phosphate added in step S1 did not contain hydrogen ions, the reaction could not proceed without adjusting the pH. In Comparative Example 2, the reaction in step S2 was almost impossible at room temperature. In Comparative Example 3, calcium dihydrogen phosphate containing hydrogen ions was used in step S1. Although finished lithium phosphate was obtained without adjusting the pH in step S2, the lack of pH adjustment in step S2 resulted in an incomplete reaction, resulting in a lithium dissolution rate of only 48.9%. In summary, the type of phosphate added and the reaction conditions (pH and temperature) have a significant impact on the recovery of lithium fluoride to produce high-purity lithium phosphate.

[0119] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for recovering lithium fluoride to prepare high-purity lithium phosphate, characterized in that: The steps include: S1. Mix the lithium fluoride material with a certain amount of solvent, then add phosphate and stir evenly; S2, using a strong acid to adjust the pH to between 0.5 and 1, then heating to a first preset temperature and reacting for a first preset time, and filtering while hot after the reaction is completed to obtain a first filtrate; S3, adjusting the pH of the first filtrate to between 5 and 6, and keeping it at a second preset temperature for a second preset time, and then filtering to obtain a second filtrate; S4, using resin to adsorb and purify the second filtrate to obtain a pure liquid; S5. Adjust the pH of the purified solution to between 7 and 8, react for a third preset time, filter, and wash to obtain a high-purity lithium phosphate ointment.

2. The method for recovering lithium fluoride to prepare high-purity lithium phosphate according to claim 1, wherein: In step S1, the solvent is water, and the phosphate includes calcium and / or magnesium phosphate.

3. A method for recovering lithium fluoride to prepare high-purity lithium phosphate according to claim 1 or 2, characterized in that: In step S1, the solid-liquid ratio of lithium fluoride to the solvent is 1:(10-20), unit: g / mL.

4. The method for recovering lithium fluoride to prepare high-purity lithium phosphate according to claim 2, wherein: The phosphate includes at least one of magnesium phosphate, magnesium hydrogen phosphate, magnesium dihydrogen phosphate, calcium phosphate, calcium hydrogen phosphate, and calcium dihydrogen phosphate.

5. The method for recovering lithium fluoride to prepare high-purity lithium phosphate according to claim 1, wherein: In step S2, the first preset temperature is 80-99°C, the first preset time is 2-8 hours, and the strong acid includes at least one of hydrochloric acid and nitric acid.

6. The method for recovering lithium fluoride to prepare high-purity lithium phosphate according to claim 1, wherein: In step S3, an alkaline substance is used to adjust the pH of the first filtrate to between 5 and 6, the second preset temperature is 25 to 60° C., and the second preset time is 0.5 to 1 hour.

7. The method for recovering lithium fluoride to prepare high-purity lithium phosphate according to claim 1, wherein: In step S4, the resin includes at least one of D401 and D402.

8. The method for recovering lithium fluoride to prepare high-purity lithium phosphate according to claim 1, wherein: In step S5, the third preset time is 0.5 to 2 hours, an alkaline substance is added to the filtrate to adjust the pH to between 7 and 8, and washing is performed with hot water at 80 to 100°C.

9. A method for recovering lithium fluoride to prepare high-purity lithium phosphate according to claim 6 or 8, characterized in that: The alkaline substance includes at least one of lithium oxide, lithium hydroxide, sodium oxide, sodium hydroxide, lithium carbonate, lithium bicarbonate, sodium carbonate, and sodium bicarbonate.

10. A method for recovering lithium fluoride to prepare high-purity lithium phosphate according to claim 1 or 8, characterized in that: Step S5 also includes drying the high-purity lithium phosphate paste to obtain a high-purity lithium phosphate finished product.

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