Method for removing phosphate from a fluorosalt solution

Abstract

The present application relates to a kind of removal methods of phosphate in fluorine salt solution, belong to fluoride dephosphorization technical field.The removal method of phosphate in fluorine salt solution of the present application, it includes the following steps: mixing in fluorine salt solution metal Zn and / or Zn-containing compound is reacted, after reaction, if system pH is 5.0~8.0, then the system is carried out solid-liquid separation, if system pH <5.0 or >8.0, then add pH regulator to adjust the pH of system to 5.0~8.0 to carry out reaction, then carry out solid-liquid separation;The fluorine salt is ammonium hydrogen fluoride and / or ammonium fluoride, and the pH value of the fluorine salt solution is <5.0 or >8.0.The removal method of phosphate in fluorine salt solution of the present application, while removing phosphate, does not reduce the content of fluoride ion in fluorine salt solution, and the dephosphorization effect is good.

Description

Technical Field

[0001] This invention relates to a method for removing phosphate from fluoride salt solutions, belonging to the field of fluoride dephosphorization technology. Background Technology

[0002] Ammonium fluoride and ammonium bifluoride are widely used inorganic fluoride compounds. Their functions are essentially the same, such as glass etchants or corrosion inhibitors. The difference lies in the fact that ammonium bifluoride undergoes a more vigorous chemical reaction during application, while ammonium fluoride is relatively milder. They are often used together in many applications, such as glass frosting and aluminum profile surface treatment, where the pH of the mixture and the reaction intensity are adjusted by changing the ratio of ammonium bifluoride to ammonium fluoride.

[0003] Traditional production methods for ammonium fluoride and ammonium bifluoride use hydrogen fluoride as a raw material. However, with the increasingly tight supply of fluorite, technologies have emerged in recent years to produce ammonium fluoride and ammonium bifluoride using fluorosilicic acid, a byproduct of phosphate fertilizer production and anhydrous hydrogen fluoride production. The fluorosilicic acid produced as a byproduct of phosphate fertilizer production mainly comes from calcium fluorapatite (abbreviated as apatite), a raw material for phosphate fertilizer preparation. Pure apatite contains 42.26% P2O5, 55.56% CaO, and 3.77% by mass, respectively. However, natural apatite has a lower grade than pure apatite, with a maximum P2O5 content of 40.7% and an F content of 2.8%–3.4%. During the acidolysis of phosphate rock, 42%–46% of the fluorine in apatite is released in gaseous form (HF, SiF4). In the production of ordinary calcium carbonate, 18%–35% is converted into gaseous fluorides and discharged. These gaseous fluorides are absorbed by water to form a fluorosilicic acid solution (mass fraction 10–40%). Anhydrous hydrogen fluoride produces fluorosilicic acid as a byproduct, mainly from the reaction of fluorite powder (primarily calcium fluoride with a certain amount of phosphorus) with sulfuric acid to generate hydrogen fluoride and calcium sulfate. The SiO2 impurities in the fluorite powder participate in the reaction, generating SiF4, which is then absorbed by water to become fluorosilicic acid (mass fraction 35%–40%). Meanwhile, phosphorus in apatite is converted into PO4 during the phosphate fertilizer production process and in fluorite during the anhydrous hydrogen fluoride production process. 3- Inevitably, it ends up in the byproduct fluorosilicic acid. Currently, in the processes for preparing ammonium fluoride or ammonium hydrogen fluoride from fluorosilicic acid produced as a byproduct of phosphate fertilizer production or anhydrous hydrogen fluoride production, the fluorosilicic acid must first be ammonified to convert it into ammonium fluoride. This process reduces the PO4 content in the fluorosilicic acid. 3- Then it will all be transferred to the ammonium fluoride solution. The PO4 in the ammonium fluoride solution... 3- Whether the production of ammonium fluoride involves subsequent concentration, crystallization, and centrifugation, or the production of ammonium bifluoride involves subsequent concentration, hydrofluoric acid acidification, crystallization, and centrifugation, PO4 will be produced. 3-Phosphate accumulates in the mother liquor and continues to accumulate as the mother liquor circulates, reaching a concentration of over 10% and forming salts such as ammonium phosphate, ultimately affecting the content of the finished product. Therefore, it is necessary to remove phosphate from the system.

[0004] In the field of chemical production, methods for removing phosphorus from solutions mainly include biological methods, adsorption methods, crystallization methods, ion exchange methods, electrodialysis methods, and chemical precipitation methods. Among these, chemical precipitation is widely used for phosphorus removal from solutions due to its simplicity and low cost. Chemical precipitation removes phosphorus by utilizing the formation of insoluble phosphate precipitates from metal ions and phosphate groups. Traditional phosphorus removal agents include iron salts, calcium salts, and magnesium salts. However, these agents readily react with fluoride ions in fluoride-containing solutions, such as those used in the preparation of ammonium fluoride or ammonium bifluoride, to form insoluble fluoride salts, thus failing to achieve the desired phosphorus removal effect. Summary of the Invention

[0005] The purpose of this invention is to provide a method for removing phosphate from fluoride salt solutions, which can solve the problem that existing phosphate removal agents cannot effectively remove phosphate from fluoride salt solutions.

[0006] To achieve the above objectives, the technical solution adopted by this invention is as follows:

[0007] A method for removing phosphate from a fluoride salt solution includes the following steps: mixing metallic Zn and / or a Zn-containing compound into the fluoride salt solution for reaction; after the reaction, if the pH of the system is 5.0–8.0, then performing solid-liquid separation; if the pH of the system is <5.0 or >8.0, then adding a pH adjuster to adjust the pH of the system to 5.0–8.0 for further reaction, followed by solid-liquid separation; wherein the fluoride salt is ammonium hydrogen fluoride and / or ammonium fluoride, and the pH of the fluoride salt solution is <5.0 or >8.0; wherein the Zn-containing compound is one, two, or three of ZnO, Zn(OH)2, and water-soluble Zn salts.

[0008] The method for removing phosphate ions from fluoride salt solutions of the present invention utilizes the property that zinc, zinc oxide, zinc hydroxide, and water-soluble zinc salts are readily soluble in ammonium salt solutions. These are mixed into the system and rapidly react with phosphate ions in the fluoride salt solution to form zinc ammonium salts. In the early stage of the reaction, in fluoride salt solutions with pH < 5.0, phosphates exist in the form of monohydrogen phosphate and dihydrogen phosphate, which are readily soluble in the mixed solution. Therefore, the Zn entering the solution... 2+ In ammonium bifluoride solution, NH4ZnF3 is formed through reaction. However, with the addition of an alkaline pH adjuster, HF in the solution is converted to NH4F, and NH4ZnF3 dissociates. Since phosphates also exist as ammonium phosphate in the solution at pH values ​​of 5.0–8.0, adjusting the pH to 5–8 will reduce the amount of phosphate in the solution. 2+The zinc phosphate reacts with ammonium phosphate to form NH4ZnF3 precipitate, which is then removed from the fluoride solution via solid-liquid separation to remove the precipitate. In fluoride solutions with pH > 8.0, free ammonia readily complexes with zinc ions to form tetraamminezinc complex ions (Zn(NH3)4). 2+ When the pH of the solution is adjusted to 5.0-8.0 using a pH adjuster, free ammonia decreases or disappears, and the zinc ammonium complex ions dissociate into zinc ions, forming zinc ammonium phosphate precipitate. Phosphorus removal from the fluoride solution is achieved by removing the zinc ammonium phosphate precipitate through solid-liquid separation. The method for removing phosphate from the fluoride solution of this invention removes phosphate without reducing the fluoride ion content in the fluoride solution, resulting in excellent phosphorus removal.

[0009] It is understood that the solvent for the fluoride salt solution is water. When the pH value of the fluoride salt solution is <5.0, the pH adjuster is an alkaline pH adjuster; when the pH value of the fluoride salt solution is >8.0, the pH adjuster is an acidic pH adjuster. Further, when the pH value of the fluoride salt solution is <5.0, the fluoride salt in the fluoride salt solution is ammonium bifluoride or a combination of ammonium bifluoride and ammonium fluoride; when the pH value of the fluoride salt solution is >8.0, the fluoride salt in the fluoride salt solution is ammonium fluoride. When the pH value of the fluoride salt solution is <5.0, the reaction of metallic Zn and / or Zn-containing compounds in the fluoride salt solution generates NH4ZnF3; when the pH value of the fluoride salt solution is >8.0, the reaction of metallic Zn and / or Zn-containing compounds in the fluoride salt solution generates Zn(NH3)4. 2+ .

[0010] When zinc oxide / zinc hydroxide is added to a fluoride solution with pH < 5.0 to generate NH4ZnF3, the following reactions are involved:

[0011] ZnO+3F - +2H + +NH4 + =NH4ZnF3 + H2O;

[0012] Zn(OH)2+3F - +2H + +NH4 + =NH4ZnF3 + 2H2O.

[0013] Adding zinc oxide / zinc hydroxide to a fluoride solution with pH > 8.0 generates Zn(NH3)4. 2+ At that time, the reactions involved are:

[0014] ZnO + 2NH3 + 2NH4 + =Zn(NH3)4 2+ +H2O;

[0015] Zn(OH)₂ + 2NH₃ + 2NH₄ +=Zn(NH3)4 2+ +2H2O.

[0016] Then, adjust the pH of the solution, and add NH4ZnF3 or Zn(NH3)4 to the solution. 2+ Dissociation occurs, with zinc ions reacting with phosphate ions to form zinc ammonium phosphate precipitate, thus the following reaction takes place:

[0017] NH4ZnF3+PO4 3- =NH4ZnPO4↓+3F - ;

[0018] Zn(NH3)4 2+ +4H + +PO4 3- =NH4ZnPO4↓+3NH4 + .

[0019] The overall reaction equation is:

[0020] ZnO+PO4 3- +2H + +NH4 + =NH4ZnPO4↓+H2O;

[0021] Zn(OH)2+PO4 3- +2H + +NH4 + =NH4ZnPO4↓+2H2O.

[0022] It can be seen that the removal method of the present invention does not consume F as a whole. - After zinc ammonium phosphate precipitates, solid-liquid separation (filtration or centrifugation to remove the precipitate) achieves the removal of phosphate ions from the solution. The zinc ammonium phosphate product is obtained by washing and drying the solid obtained after solid-liquid separation. In chemical production, the precipitate after phosphorus removal is often stored as waste and cannot be used, which may cause secondary pollution. However, the zinc ammonium phosphate obtained by the solid-liquid separation method of this invention has high economic value and can be sold as a product.

[0023] It is understood that the pH adjuster and the water-soluble Zn salt do not directly or indirectly introduce phosphate ions into the fluoride salt solution. For example, the pH adjuster does not contain phosphate, monohydrogen phosphate, dihydrogen phosphate, or phosphoric acid, and the water-soluble Zn salt is any water-soluble Zn salt other than phosphate, monohydrogen phosphate, and dihydrogen phosphate. To avoid introducing new impurities during the removal of phosphate ions from the fluoride salt solution, further, when the pH of the fluoride salt solution is <5.0, the pH adjuster is liquid ammonia, ammonia gas, ammonia water, ammonium fluoride, or an aqueous solution of ammonium fluoride; when the pH of the fluoride salt solution is >8.0, the pH adjuster is hydrogen fluoride and / or hydrofluoric acid. The Zn-containing compound is ZnO and / or Zn(OH)₂.

[0024] It is understood that the removal method of the present invention can be used to remove phosphate ions from relatively complex fluoride salt solution systems. For example, the fluoride salt solution is the circulating mother liquor from the process of preparing ammonium fluoride or ammonium bifluoride from an ammonium fluoride solution obtained by ammoniation of ammonium fluoride solution produced by ammonium fluoride from phosphate fertilizer byproducts of fluorosilicic acid and / or anhydrous hydrogen fluoride byproducts of fluorosilicic acid, or ammonium fluoride solution obtained by ammoniation of ammonium fluoride solution produced by ammonium fluoride from phosphate fertilizer byproducts of fluorosilicic acid and / or anhydrous hydrogen fluoride byproducts of fluorosilicic acid. The circulating mother liquor is obtained after concentration, crystallization, and separation processes, or after concentration, acidification, crystallization, and separation processes, to separate ammonium fluoride or ammonium bifluoride. The main component of the circulating mother liquor in the preparation of ammonium bifluoride is ammonium bifluoride (it may also contain a certain amount of ammonium fluoride due to the volatilization of hydrogen fluoride after the decomposition of ammonium bifluoride), with a pH value less than 5.0, and the enriched phosphate ions can be as high as 5% or more. The main component of the circulating mother liquor in the preparation of ammonium fluoride is ammonium fluoride, with a pH value greater than 8.0, and the enriched phosphate ions can reach over 2%. In conventional production processes, this circulating mother liquor is directly mixed with the ammonium fluoride solution obtained from the ammoniation reaction before entering the aforementioned concentration, crystallization, and separation processes, or the aforementioned concentration, acidification, crystallization, and separation processes. This leads to phosphate enrichment, which in turn affects product quality. By using the phosphate removal method of this invention to remove phosphate from the circulating mother liquor before entering the aforementioned concentration, crystallization, and separation processes, or the aforementioned concentration, acidification, crystallization, and separation processes, phosphate enrichment can be avoided, ensuring stable and qualified product quality.

[0025] This invention can remove phosphate ions from the circulating mother liquor during the preparation of ammonium fluoride or ammonium bifluoride in the form of precipitation, reducing the content to below 0.1%, with significant effect and convenient industrial operation. It can be used for centralized treatment to remove phosphate ions after they have accumulated to a certain extent in the mother liquor, or it can be used as a routine operation, with flexible and versatile operation methods.

[0026] To better remove phosphate ions and reduce the phosphorus content in the solution, the molar ratio of Zn in the Zn and / or Zn-containing compounds mixed into the fluoride salt solution to P in the fluoride salt solution is further 0.5–2.0:1. Even further, the molar ratio of Zn in the Zn and / or Zn-containing compounds mixed into the fluoride salt solution to P in the fluoride salt solution is 1.5–2:1.

[0027] Furthermore, a pH adjuster is added to adjust the system pH to 5.0–7.0. Adjusting the pH to 5.0–7.0 has the beneficial effect of maximizing the utilization of zinc ions and ensuring the maximum conversion of zinc ammonium fluoride to zinc ammonium phosphate. Even further, a pH adjuster is added to adjust the system pH to 6.0–7.0.

[0028] Since adjusting the pH value is an acid-base reaction that releases heat, the system temperature is controlled at 40–60°C during the pH adjustment process using a pH adjuster. After adjusting the pH to 5.0–8.0, the system temperature is maintained at 40–60°C to continue the reaction; the preferred reaction time is 0.5–1.5 hours, for example, 1 hour. To reduce the cost of phosphate removal, industrial ammonia or industrial-grade hydrofluoric acid is preferred as the pH adjuster.

[0029] Furthermore, when the pH of the fluoride solution is < 5.0, the PO4 in the fluoride solution... 3- The content of fluoride is ≥5%; when the pH of the fluoride solution is >8.0, the PO4 content in the fluoride solution is ≥5%. 3- The content is ≥2%. Detailed Implementation

[0030] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0031] The conventional method for preparing ammonium bifluoride from fluorosilicic acid, a byproduct of phosphate fertilizer production, includes the following steps:

[0032] 1) After ammoniation of fluorosilicic acid, silica is separated to obtain ammonium fluoride solution;

[0033] 2) Concentrate the ammonium fluoride solution, then acidify it with hydrofluoric acid, then crystallize it, and then separate it by centrifugation to obtain the ammonium bifluoride product and the circulating mother liquor;

[0034] 3) Return the circulating mother liquor obtained in step 2) to the ammonium fluoride solution obtained in step 1), repeat steps 1) to 2), and collect the ammonium bifluoride product.

[0035] In Examples 1 and 2 below, the fluoride solution used to remove phosphate ions is the circulating mother liquor from the repeated steps 1) and 2) of the above-mentioned method for preparing ammonium bifluoride using fluorosilicic acid, a byproduct of phosphate fertilizer, as a raw material. The circulating mother liquor contains PO42-... 3-The content was 5.24%, and the pH value was 4.5.

[0036] In Example 3, the fluoride solution used to remove phosphate ions was prepared by ammoniation of fluorosilicic acid (a byproduct of phosphate fertilizer production), followed by concentration and crystallization to obtain ammonium fluoride mother liquor after separating out silica; the ammonium fluoride mother liquor contained PO4. 3- The content was 2.31%, and the pH value was 8.5.

[0037] Example 1

[0038] The method for removing phosphate ions from fluoride solutions in this embodiment includes the following steps:

[0039] 1) Take a quantitative amount of circulating mother liquor containing 5.42% phosphate for the preparation of ammonium bifluoride, take zinc oxide according to a molar ratio of Zn / P of 1.0, slowly add all the zinc oxide to the circulating mother liquor, stir and mix to obtain solution A.

[0040] 2) Slowly add ammonia to solution A to adjust the pH to 5. During the pH adjustment process, control the system temperature at 40℃. After the adjustment is complete, maintain the temperature at 40℃ and continue stirring for 1 hour to obtain solution B.

[0041] 3) Filter solution B to obtain a dephosphorization solution and a filter cake of zinc ammonium phosphate. Wash and dry the filter cake to obtain the finished zinc ammonium phosphate product. The phosphate content in the dephosphorization solution is reduced to 0.15%, which can be directly mixed with ammonium fluoride solution for concentration, hydrofluoric acid acidification, and crystallization to prepare the finished ammonium bifluoride product.

[0042] Example 2

[0043] The method for removing phosphate ions from fluoride solutions in this embodiment includes the following steps:

[0044] 1) Take a quantitative amount of circulating mother liquor containing 5.42% phosphate for the preparation of ammonium bifluoride, take zinc oxide according to a molar ratio of Zn / P of 1.5, slowly add all the zinc oxide to the circulating mother liquor, stir and mix to obtain solution A.

[0045] 2) Slowly add ammonia to solution A to adjust the pH to 6. During the pH adjustment process, control the system temperature at 50℃. After the adjustment is complete, maintain the temperature at 50℃ and continue stirring for 1 hour to obtain solution B.

[0046] 3) Filter solution B to obtain a dephosphorization solution and a filter cake of zinc ammonium phosphate. Wash and dry the filter cake to obtain the finished zinc ammonium phosphate product. The phosphate content in the dephosphorization solution is reduced to 0.08%, which can be directly mixed with ammonium fluoride solution for concentration, hydrofluoric acid acidification, and crystallization to prepare the finished ammonium bifluoride product.

[0047] Example 3

[0048] The method for removing phosphate ions from fluoride solutions in this embodiment includes the following steps:

[0049] 1) Take a quantitative amount of ammonium fluoride mother liquor containing 2.31% phosphate, take zinc oxide according to a molar ratio of Zn / P of 2.0, slowly add all the zinc oxide to the ammonium fluoride mother liquor, stir and mix to obtain solution A.

[0050] 2) Slowly add hydrofluoric acid to solution A to adjust the pH to 7. During the pH adjustment process, control the system temperature at 60℃. After the adjustment is completed, maintain the temperature at 60℃ and continue stirring for 1 hour to obtain solution B.

[0051] 3) Solution B was filtered, and the filtrate was the dephosphorization solution. The filter cake was zinc ammonium phosphate. The filter cake was washed and dried to obtain the finished zinc ammonium phosphate product. The phosphate content in the dephosphorization solution was reduced to 0.05%.

[0052] Example 4

[0053] The method for removing phosphate ions from fluoride solutions in this embodiment includes the following steps:

[0054] 1) Take a quantitative amount of circulating mother liquor containing 5.42% phosphate for the preparation of ammonium bifluoride, take zinc hydroxide according to a molar ratio of Zn / P of 1.5, slowly add all the zinc hydroxide to the circulating mother liquor, stir and mix to obtain solution A.

[0055] 2) Slowly add ammonia to solution A to adjust the pH to 7. During the pH adjustment process, control the system temperature at 50℃. After the adjustment is complete, maintain the temperature at 50℃ and continue stirring for 1 hour to obtain solution B.

[0056] 3) Filter solution B to obtain a dephosphorization solution and a filter cake of zinc ammonium phosphate. Wash and dry the filter cake to obtain the finished zinc ammonium phosphate product. The phosphate content in the dephosphorization solution is reduced to 0.07%, which can be directly mixed with ammonium fluoride solution for concentration, hydrofluoric acid acidification, and crystallization to prepare the finished ammonium bifluoride product.

[0057] Example 5

[0058] The method for removing phosphate ions from fluoride solutions in this embodiment includes the following steps:

[0059] 1) Take a quantitative amount of circulating mother liquor containing 5.42% phosphate for the preparation of ammonium bifluoride, take elemental zinc according to a molar ratio of Zn / P of 1.5, slowly add all the elemental zinc to the circulating mother liquor, stir and mix to obtain solution A.

[0060] 2) Slowly add ammonia to solution A to adjust the pH to 8. During the pH adjustment process, control the system temperature at 50℃. After the adjustment is complete, maintain the temperature at 50℃ and continue stirring for 1 hour to obtain solution B.

[0061] 3) Filter solution B to obtain a dephosphorization solution and a filter cake of zinc ammonium phosphate. Wash and dry the filter cake to obtain the finished zinc ammonium phosphate product. The phosphate content in the dephosphorization solution is reduced to 0.16%, which can be directly mixed with ammonium fluoride solution for concentration, hydrofluoric acid acidification, and crystallization to prepare the finished ammonium bifluoride product.

[0062] Comparative Example 1

[0063] The method for removing phosphate from the fluoride solution in this comparative example differs from that in Example 1 only in that the pH value of the ammonium bifluoride mother liquor in Example 1 is adjusted to 4.8, and the phosphate content in the final dephosphated solution is reduced to 2.97%.

[0064] Comparative Example 2

[0065] The method for removing phosphate from the fluoride solution in this comparative example differs from that in Example 1 only in that the reaction temperature of the ammonium bifluoride solution in Example 1 is adjusted to 70°C, and the phosphate content in the final dephosphated solution is reduced to 2.31%.

[0066] Comparative Example 3

[0067] The method for removing phosphate from the fluoride salt solution in this comparative example differs from that in Example 2 only in that: in this comparative example, during the reaction of the ammonium bifluoride solution in Example 2, the amount of zinc oxide added to the solution was in a molar ratio of Zn / P of 0.4, and the phosphate content in the final dephosphorized solution was reduced to 2.26%.

[0068] Table 1 summarizes the results of phosphate removal rate of fluoride salt solution and phosphate content in dephosphorization solution in Examples 1-5 and Comparative Examples 1-3.

[0069] Table 1. Phosphate removal rate of fluoride solutions and phosphate content in dephosphorization solutions in Examples 1-5 and Comparative Examples 1-3.

[0070]

[0071]

Claims

1. A method for removing phosphate ions from a fluoride salt solution, characterized in that: Includes the following steps: Metallic Zn and / or Zn-containing compounds are mixed into a fluoride salt solution for reaction. After the reaction is completed, if the pH of the system is 5.0~8.0, the system is separated into solid and liquid components. If the pH of the system is <5.0 or >8.0, a pH adjuster is added to adjust the pH of the system to 5.0~8.0, and the reaction is carried out again, followed by solid-liquid separation. The fluoride salt is ammonium hydrogen fluoride and / or ammonium fluoride, and the pH value of the fluoride salt solution is <5.0 or >8.0; the Zn-containing compound is one or both of ZnO and Zn(OH)2; the fluoride salt solution is the circulating mother liquor in the process of preparing ammonium fluoride or ammonium hydrogen fluoride from ammonium fluoride solution obtained by ammoniation reaction of fluorosilicic acid by-product of phosphate fertilizer and / or fluorosilicic acid by-product of anhydrous hydrogen fluoride, or it is ammonium fluoride solution obtained by ammoniation reaction of fluorosilicic acid by-product of phosphate fertilizer and / or fluorosilicic acid by-product of anhydrous hydrogen fluoride.

2. The method for removing phosphate ions from fluoride salt solutions according to claim 1, characterized in that: When the pH of the fluoride solution is <5.0, the pH adjuster is liquid ammonia, ammonia gas, ammonia water, ammonium fluoride, or an aqueous solution of ammonium fluoride; when the pH of the fluoride solution is >8.0, the pH adjuster is hydrogen fluoride and / or hydrofluoric acid.

3. The method for removing phosphate ions from a fluoride salt solution according to claim 1 or 2, characterized in that: When the pH of the fluoride solution is < 5.0, the PO4 in the fluoride solution... 3- The content of fluoride is ≥5%; when the pH of the fluoride solution is >8.0, the PO4 content in the fluoride solution is ≥5%. 3- The content is ≥2%.

4. The method for removing phosphate ions from a fluoride salt solution according to claim 1 or 2, characterized in that: The molar ratio of Zn in the fluoride salt solution and / or Zn-containing compounds to P in the fluoride salt solution is 0.5~2.0:

1.

5. The method for removing phosphate ions from fluoride salt solutions according to claim 4, characterized in that: The molar ratio of Zn in the fluoride salt solution and / or Zn-containing compounds to P in the fluoride salt solution is 1.5~2:

1.

6. The method for removing phosphate ions from a fluoride salt solution according to claim 1 or 2, characterized in that: Adjust the pH of the system to 5.0-7.0 by adding a pH adjuster.

7. The method for removing phosphate ions from fluoride salt solutions according to claim 6, characterized in that: Adjust the pH of the system to 6.0-7.0 by adding a pH adjuster.

8. The method for removing phosphate ions from fluoride salt solutions according to claim 1, characterized in that: During the process of adjusting the pH of the system by adding a pH adjuster, the temperature of the system should be controlled at 40~60℃.

9. The method for removing phosphate ions from a fluoride salt solution according to claim 1 or 8, characterized in that: After adjusting the pH of the system to 5.0-8.0 with a pH adjuster, the temperature of the system is controlled at 40-60℃ for the reaction.

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