A method for removing phosphate from a system for the production of fluorinated salts using fluosilicic acid

Abstract

The present application relates to a kind of phosphorus removal in system when fluorosilicic acid is used to prepare fluorinated salt, belong to inorganic fluoride preparation technical field.The present application removes phosphorus in system when fluorosilicic acid is used to prepare fluorinated salt, first the solution containing ferrous fluorosilicate and fluorosilicic acid is ammoniated, obtain the ammoniated treatment liquid with pH 1.5~3, can avoid the precipitation of silicon dioxide when ammoniated and subsequent ammoniated treatment liquid and oxidant mixed reaction, then ammoniated treatment liquid and oxidant are mixed, divalent iron in ammoniated treatment liquid is oxidized into trivalent iron and reacts with phosphorus to generate iron phosphate precipitate, finally through solid-liquid separation, iron phosphate precipitate is dried and can be sold as iron phosphate product.The present application removes phosphorus in system when fluorosilicic acid is used to prepare fluorinated salt under the premise of not introducing impurity ion, can make each element in system be utilized to maximum limit, and wide application range.

Description

Technical Field

[0001] This invention relates to a method for removing phosphate ions from a system during the preparation of fluoride salts using fluorosilicic acid, belonging to the field of inorganic fluoride preparation technology. Background Technology

[0002] In current methods for preparing inorganic fluoride salts, hydrofluoric acid is commonly used as the fluorine source, and the primary source of hydrofluoric acid is fluorite. Due to the limited availability of fluorite resources, reducing the cost of fluoride preparation and finding alternatives to fluorite becomes crucial. The production processes of anhydrous hydrogen fluoride and phosphate fertilizers produce large quantities of fluorosilicic acid solutions of varying concentrations (15–40%) as byproducts. Therefore, using fluorosilicic acid solutions instead of hydrofluoric acid as the fluorine source for preparing inorganic fluoride salts has become an important approach.

[0003] Fluoride salts include ammonium fluoride salts (ammonium fluoride and ammonium hydrogen fluoride) and metal fluoride salts. Currently, there are two main methods for preparing metal fluoride salts from fluorosilicic acid solutions. The first is the direct reaction method, which involves reacting metal oxides or metal hydroxides with fluorosilicic acid to obtain metal fluoride salts and silicon dioxide. The second is the ammoniation treatment method, which involves mixing fluorosilicic acid with an ammonifying agent (ammonia water, pure ammonia, etc.) to undergo ammoniation and desilication, yielding ammonium fluoride and silicon dioxide precipitates. The ammonium fluoride or ammonium fluoride solution is then reacted with metal oxides or metal hydroxides to obtain the metal fluoride salt.

[0004] The fluorosilicic acid produced as a byproduct in the production of anhydrous hydrogen fluoride and phosphate fertilizers usually contains a certain concentration of impurity ions PO4. 3- In the process of preparing fluoride salts using these phosphorus-containing fluorosilicic acids, PO4 3- All of these phosphate ions will enter the fluoride salt solution and subsequently into the fluoride products, thus affecting product quality. Therefore, there is an urgent need to develop a method to effectively remove phosphate ions from the system used in the preparation of fluoride salts with fluorosilicic acid. For example, Chinese patent document CN101423238A discloses a method for removing phosphorus from aluminum fluoride solution. This method involves first reacting fluorosilicic acid solution with aluminum hydroxide to prepare an aqueous solution of aluminum fluoride containing phosphate ions and a silica precipitate. Then, the iron in the phosphorus removal agent (ferric hydroxide, ferric chloride, polyferric chloride, ferric sulfate, polyferric sulfate) reacts with the PO4 in the aluminum fluoride solution. 3- The reaction produces a precipitate, which then dephosphorizes the aluminum fluoride solution. The advantage of this method is that it removes phosphate ions by adding a dephosphorizing agent to the aluminum fluoride solution, and the process is simple and easy to operate. The disadvantage is that this method is not suitable for other fluoride solutions, and it introduces impurity ions (chloride or sulfate ions) during the preparation of other fluoride solutions, causing secondary pollution. Summary of the Invention

[0005] The purpose of this invention is to provide a method for removing phosphate ions from the system during the preparation of fluoride salts using fluorosilicic acid, which can solve the problem that current methods for removing phosphate ions from the system during the preparation of fluoride salts using fluorosilicic acid are prone to introducing impurity ions.

[0006] To achieve the above objectives, the technical solution adopted in the method for removing phosphate ions from the system during the preparation of fluoride salts using fluorosilicic acid of the present invention is as follows:

[0007] A method for removing phosphate ions from a system during the preparation of fluoride salts using fluorosilicic acid includes the following steps: ammonifying a solution containing ferrous fluorosilicate and fluorosilicic acid to obtain an ammonified solution with a pH of 1.5–3; then mixing the ammonified solution with an oxidant and reacting the mixture, followed by solid-liquid separation; wherein the molar ratio of phosphate ions in the solution containing ferrous fluorosilicate and fluorosilicic acid to the molar ratio of iron in the ferrous fluorosilicate is 1:1; and wherein the oxidant is selected from hydrogen peroxide, oxygen, ozone, or any combination thereof.

[0008] This invention relates to a method for removing phosphate ions from a system during the preparation of fluoride salts using fluorosilicic acid. First, a solution containing ferrous fluorosilicate and fluorosilicic acid is ammonified to maintain the pH of the ammonification solution between 1.5 and 3. This prevents silica precipitation during ammonification and subsequent mixing of the ammonification solution and the oxidant. Then, the ammonification solution and the oxidant are mixed to oxidize the ferrous iron in the ammonification solution to ferric iron. The ferric iron then reacts with phosphate ions in the ammonification solution to form ferric phosphate precipitate. The reaction equation is: Fe... 3+ +PO4 3- The reaction ⇌ FePO4·2H2O↓ with 2H2O, during which no silica precipitate is formed, is followed by solid-liquid separation to remove the ferric phosphate precipitate. After drying, it can be sold as a finished ferric phosphate product. This invention's method for removing phosphate ions from the system during the preparation of fluoride salts using fluorosilicic acid avoids the simultaneous precipitation of phosphate and silica during ammoniation desilication, which would otherwise cause silica byproduct pollution and phosphate waste. The liquid obtained from solid-liquid separation is the phosphorus-free mixture, which does not contain phosphorus and has not introduced other impurity ions. It can be used in existing ammoniation desilication methods to prepare ammonium fluoride and silica from the liquid obtained from solid-liquid separation, or it can be mixed with metal oxides or metal hydroxides to prepare metal fluoride and silica. This invention's method for removing phosphate ions from the system during the preparation of fluoride salts using fluorosilicic acid maximizes the utilization of each element in the system without introducing impurity ions, avoids material waste, and has a wide range of applications.

[0009] Preferably, the temperature of the mixing reaction is 50–80°C. When the temperature of the mixing reaction is below 50°C, the reaction time required for the mixing reaction of the ammonia treatment liquid and the oxidant is relatively long, which is not conducive to industrial production. When the temperature of the mixing reaction is above 80°C, hydrogen peroxide and fluorosilicic acid are prone to volatilization, which is also not conducive to production.

[0010] Preferably, the mixing reaction takes 0.5 to 2 hours. For example, the mixing reaction takes 1 hour.

[0011] Preferably, in the solution containing ferrous fluorosilicate and fluorosilicic acid, the mass fraction of phosphate is 0.5-4%.

[0012] Preferably, in the solution containing ferrous fluorosilicate and fluorosilicic acid, the mass fraction of fluorosilicic acid is 15-20%. When the mass fraction of fluorosilicic acid is less than 15%, excess water is introduced into the system, increasing energy consumption; when the mass fraction of fluorosilicic acid is greater than 20%, a mixture of ammonium fluorosilicate and ferric phosphate precipitates will be generated during operation, which is difficult to separate and results in waste.

[0013] It is understood that the solution containing ferrous fluorosilicate and fluorosilicic acid can be obtained by mixing ferrous fluorosilicate and fluorosilicic acid solutions, or by mixing ferrous fluorosilicate solution and fluorosilicic acid solution, or by mixing fluorosilicic acid solution containing dissolved ferrous fluorosilicate and fluorosilicic acid solution, or by dissolving iron in an excess of fluorosilicic acid solution. To fully utilize the raw material fluorosilicic acid solution and to reduce costs, preferably, the solution containing ferrous fluorosilicate and fluorosilicic acid is prepared by a method comprising the following steps: dissolving iron in a first fluorosilicic acid solution to obtain solution A, and then mixing solution A with a second fluorosilicic acid solution to obtain the final solution.

[0014] Preferably, the mass fraction of the first fluorosilicic acid solution is 10-25%. For example, the mass fraction of the first fluorosilicic acid solution is 20%. Preferably, the mass fraction of the second fluorosilicic acid solution is 15-20%. For example, the mass fraction of the second fluorosilicic acid solution is 20%.

[0015] For ease of operation and to avoid introducing impurities, the oxidant is preferably hydrogen peroxide. Preferably, the hydrogen peroxide has a mass fraction of 15-30%.

[0016] Preferably, the ammoniation treatment involves mixing and reacting an ammonifying agent with a solution containing ferrous fluorosilicate and fluorosilicic acid.

[0017] This invention does not limit the ammonifying agent used in the ammonification treatment. Any existing ammonifying agent used for ammonifying fluorosilicic acid solutions is suitable for this invention. For example, the ammonifying agent used in the ammonification treatment is selected from one or any combination of ammonia water, ammonia, ammonium carbonate, and ammonium bicarbonate. For ease of operation and to reduce costs, it is preferable that the ammonifying agent used in the ammonification treatment is ammonia water. Preferably, the mass fraction of the ammonia water is 5-20%. For example, the mass fraction of the ammonia water is 20%.

[0018] The present invention does not limit the specific implementation method of solid-liquid separation. It can be implemented by filtration or centrifugation. In order to reduce costs and meet the requirements of industrial production, the solid-liquid separation is preferably carried out by filtration.

[0019] The experimental principle of this invention is as follows: First, iron is dissolved in fluorosilicic acid to prepare ferrous fluorosilicate, and the reaction equation is as follows:

[0020] Fe + H₂SiF₆ = FeSiF₆ + H₂;

[0021] Then, ammonia water is added to a solution containing ferrous fluorosilicate and fluorosilicic acid for ammoniation treatment to obtain an ammoniation treatment solution with a pH of 1.5 to 3. The reaction equation is as follows: H2SiF6 + 2NH3 = (NH4)2SiF6. At this time, the fluorosilicic acid has not completely reacted (pH is less than 3).

[0022] Finally, the ammoniation solution and the oxidant (hydrogen peroxide) are mixed and reacted. The reaction equation is as follows:

[0023] 2FeSiF6+H2SiF6+H2O2=Fe2(SiF6)3+2H2O;

[0024] Fe2(SiF6)3+2NH4H2PO4=2FePO4+H2SiF6+(NH4)2SiF6;

[0025] Silica is only formed when ammonia reacts with fluorosilicic acid to form ammonium fluorosilicate and when ammonia is in excess. Therefore, when the ammoniation treatment solution and the oxidant (hydrogen peroxide) are mixed and reacted, only ferric phosphate precipitates out, and no silica precipitates out.

[0026] Preferably, the method for removing phosphate ions from the system when preparing fluoride salts using fluorosilicic acid further includes the following steps: after solid-liquid separation, the liquid obtained from solid-liquid separation undergoes a second ammoniation treatment to obtain a second ammoniation treatment liquid, and then the second ammoniation treatment liquid undergoes a second solid-liquid separation. The second ammoniation treatment of the liquid obtained from solid-liquid separation allows silicon to precipitate as silica. Since iron has already been removed as ferric phosphate, the silica obtained from the second solid-liquid separation is iron-free and has high purity. This invention employs a staged ammoniation process to precipitate iron and silicon as ferric phosphate and silica precipitates respectively, obtaining high-purity ferric phosphate and silica, achieving full and efficient utilization of each element and avoiding material waste. The liquid obtained from the second solid-liquid separation is an ammonium fluoride solution, which can be used to prepare ammonium fluoride or ammonium bifluoride, or other metal fluoride salts.

[0027] Preferably, the second ammonia treatment involves mixing and reacting the ammonia agent with the liquid obtained from solid-liquid separation. Preferably, the ammonia agent in the second ammonia treatment is ammonia water. Preferably, the mass fraction of the ammonia water in the second ammonia treatment is 18-23%. For example, the mass fraction of the ammonia water in the second ammonia treatment is 20%. Preferably, the temperature of the second ammonia treatment is 50-80°C.

[0028] The present invention does not limit the specific implementation method of the second solid-liquid separation. It can be carried out by filtration or centrifugation. In order to reduce costs and meet the requirements of industrial production, the second solid-liquid separation is preferably carried out by filtration. Detailed Implementation

[0029] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0030] Example 1

[0031] The method for removing phosphate ions from the system during the preparation of fluoride salts using fluorosilicic acid in this embodiment specifically includes the following steps:

[0032] (1) Elemental iron is dissolved in a 20% fluorosilicic acid solution. The elemental iron and fluorosilicic acid react to form ferrous fluorosilicate. After the dissolution reaction is completed, solution A is obtained.

[0033] (2) Mix solution A with the fluorosilicic acid solution to be treated (mass fraction of 20%) to obtain a solution containing ferrous fluorosilicate and fluorosilicic acid; the molar ratio of iron in ferrous fluorosilicate to the molar ratio of phosphate in the solution containing ferrous fluorosilicate and fluorosilicic acid is 1:1; in the solution containing ferrous fluorosilicate and fluorosilicic acid, the mass fraction of ferrous fluorosilicate is 4.27%, the mass fraction of fluorosilicic acid is 18.5%, and the mass fraction of phosphate (calculated as phosphorus) is 2.03%;

[0034] (3) Add a certain amount of ammonia water with a mass fraction of 20% to the solution containing ferrous fluorosilicate and fluorosilicic acid obtained in step (2), mix well, and obtain an ammonia treatment solution with a pH of 1.5.

[0035] (4) Heat the ammonification solution obtained in step (3) to 50°C, and slowly add a certain amount of hydrogen peroxide with a mass fraction of 20% under stirring (the amount of hydrogen peroxide is to ensure that all the divalent iron in the ammonification solution is converted into trivalent iron). Then mix and react at 50°C for 2 hours. After the mixing reaction is completed, filter the solution. After drying the filtered solid, ferric phosphate (purity is 92.39%, and the yield is 88.9% based on the iron element in the solution containing ferrous fluorosilicate and fluorosilicic acid) can be sold as a product. The filtered liquid is used to prepare ammonium fluoride and silicon dioxide.

[0036] The method for preparing ammonium fluoride and silicon dioxide using the filtered liquid includes the following steps: The filtered liquid and 20% ammonia water (the amount of ammonia water is determined to ensure that all fluorosilicic acid in the filtered liquid is converted into ammonium fluoride) are mixed and reacted at 50°C until no more precipitate is formed, at which point the reaction is complete. Then, the mixture is filtered, and the filtered solid is dried to obtain silicon dioxide (the purity of silicon dioxide can be adjusted according to the specific application through different processes). The filtered liquid is an ammonium fluoride solution (in the ammonium fluoride solution, the mass fraction of ammonium fluoride is 17.57%, the mass fraction of phosphate is 0.13%, and the mass fraction of iron is 0.001%), which is dried to obtain ammonium fluoride.

[0037] Example 2

[0038] The method for removing phosphate ions from the system during the preparation of fluoride salts using fluorosilicic acid in this embodiment specifically includes the following steps:

[0039] (1) Elemental iron is dissolved in a 20% fluorosilicic acid solution. Elemental iron and fluorosilicic acid react to form ferrous fluorosilicate. After the dissolution reaction is completed, solution A is obtained.

[0040] (2) Mix solution A with the fluorosilicic acid solution to be treated (mass fraction of 20%) to obtain a solution containing ferrous fluorosilicate and fluorosilicic acid; the molar ratio of iron in ferrous fluorosilicate to the molar ratio of phosphate in the solution containing ferrous fluorosilicate and fluorosilicic acid is 1:1; in the solution containing ferrous fluorosilicate and fluorosilicic acid, the mass fraction of ferrous fluorosilicate is 4.27%, the mass fraction of fluorosilicic acid is 18.5%, and the mass fraction of phosphate (calculated as phosphorus) is 2.03%;

[0041] (3) Add a certain amount of ammonia water with a mass fraction of 20% to the solution containing ferrous fluorosilicate and fluorosilicic acid obtained in step (2), mix well, and obtain an ammonia treatment solution with a pH of 2.5.

[0042] (4) Heat the ammonification solution obtained in step (3) to 65°C, and slowly add a certain amount of hydrogen peroxide with a mass fraction of 20% under stirring (the amount of hydrogen peroxide is to ensure that all the divalent iron in the ammonification solution is converted into trivalent iron). Then mix and react at 65°C for 1 hour. After the mixing reaction is completed, filter the solution. After drying the filtered solid, ferric phosphate (purity of 94.51%, yield calculated based on the iron element in the solution containing ferrous fluorosilicate and fluorosilicic acid) can be obtained and sold as a product. The filtered liquid is used to prepare ammonium fluoride and silicon dioxide.

[0043] The method for preparing ammonium fluoride and silicon dioxide using the filtered liquid includes the following steps: The filtered liquid and 20% ammonia water (the amount of ammonia water is determined to ensure that all fluorosilicic acid in the filtered liquid is converted into ammonium fluoride) are mixed and reacted at 50°C until no more precipitate is formed, at which point the reaction is complete. Then, the mixture is filtered, and the filtered solid is dried to obtain silicon dioxide (the purity of silicon dioxide can be adjusted according to the specific application through different processes). The filtered liquid is an ammonium fluoride solution (in the ammonium fluoride solution, the mass fraction of ammonium fluoride is 17.50%, the mass fraction of phosphate is 0.08%, and the mass fraction of iron is 0.001%), which is dried to obtain ammonium fluoride.

[0044] Example 3

[0045] The method for removing phosphate ions from the system during the preparation of fluoride salts using fluorosilicic acid in this embodiment specifically includes the following steps:

[0046] (1) Elemental iron is dissolved in a 20% fluorosilicic acid solution. Elemental iron and fluorosilicic acid react to form ferrous fluorosilicate. After the dissolution reaction is completed, solution A is obtained.

[0047] (2) Mix solution A with the fluorosilicic acid solution to be treated (mass fraction of 20%) to obtain a solution containing ferrous fluorosilicate and fluorosilicic acid; the molar ratio of iron in ferrous fluorosilicate to the molar ratio of phosphate in the solution containing ferrous fluorosilicate and fluorosilicic acid is 1:1; in the solution containing ferrous fluorosilicate and fluorosilicic acid, the mass fraction of ferrous fluorosilicate is 4.27%, the mass fraction of fluorosilicic acid is 18.5%, and the mass fraction of phosphate (calculated as phosphorus) is 2.03%;

[0048] (3) Add a certain amount of ammonia water with a mass fraction of 20% to the solution containing ferrous fluorosilicate and fluorosilicic acid obtained in step (2), mix well, and obtain an ammonia treatment solution with a pH of 3.0.

[0049] (4) Heat the ammonification solution obtained in step (3) to 80°C, and slowly add a certain amount of hydrogen peroxide with a mass fraction of 20% under stirring (the amount of hydrogen peroxide is to ensure that all the divalent iron in the ammonification solution is converted into trivalent iron). Then mix and react at 80°C for 0.5 h. After the mixing reaction is completed, filter the solution. After drying the filtered solid, ferric phosphate (purity of 85.62%, yield calculated based on the iron element in the solution containing ferrous fluorosilicate and fluorosilicic acid) can be sold as a product. The filtered liquid is used to prepare ammonium fluoride and silicon dioxide.

[0050] The method for preparing ammonium fluoride and silicon dioxide using the filtered liquid includes the following steps: The filtered liquid and 20% ammonia water (the amount of ammonia water is determined to ensure that all fluorosilicic acid in the filtered liquid is converted into ammonium fluoride) are mixed and reacted at 50°C until no more precipitate is formed, at which point the reaction is complete. Then, the mixture is filtered, and the solid obtained from the filtration is dried to obtain silicon dioxide (the purity of silicon dioxide can be adjusted according to the specific application through different processes). The filtered liquid is an ammonium fluoride solution (in the ammonium fluoride solution, the mass fraction of ammonium fluoride is 17.52%, the mass fraction of phosphate is 0.09%, and the mass fraction of iron is 0.001%), which is dried to obtain ammonium fluoride.

[0051] In other embodiments, other metal fluoride salts can be prepared directly using existing technology with ammonium fluoride solution.

[0052] Comparative Example 1

[0053] The difference between the method for removing phosphate from the system when preparing fluoride salts using fluorosilicic acid in this comparative example and the method for removing phosphate from the system when preparing fluoride salts using fluorosilicic acid in Example 2 is that the pH of the ammonia treatment solution is 1.2 in step (3) of the method for removing phosphate from the system when preparing fluoride salts using fluorosilicic acid in this comparative example.

[0054] Comparative Example 2

[0055] The difference between the method for removing phosphate from the system when preparing fluoride salts using fluorosilicic acid in this comparative example and the method for removing phosphate from the system when preparing fluoride salts using fluorosilicic acid in Example 2 is that the pH of the ammonia treatment solution is 3.2 in step (3) of the method for removing phosphate from the system when preparing fluoride salts using fluorosilicic acid in this comparative example.

[0056] Comparative Example 3

[0057] The difference between the method for removing phosphate from the system when preparing fluoride salts using fluorosilicic acid in this comparative example and the method for removing phosphate from the system when preparing fluoride salts using fluorosilicic acid in Example 2 is that in step (4) of the method for removing phosphate from the system when preparing fluoride salts using fluorosilicic acid in this comparative example, the temperature of the ammonia treatment solution and hydrogen peroxide for mixing and reaction is 45°C.

[0058] Comparative Example 4

[0059] The method for removing phosphate from the system when preparing fluoride salts using fluorosilicic acid in this comparative example differs from the method for removing phosphate from the system when preparing fluoride salts using fluorosilicic acid in Example 2 only in that, in step (4) of the method for removing phosphate from the system when preparing fluoride salts using fluorosilicic acid in this comparative example, the amount of hydrogen peroxide added is 0.

[0060] Experimental Example

[0061] To evaluate the effects of the pH of the ammoniation solution and the temperature of the reaction between the ammoniation solution and hydrogen peroxide in step (3) on the experimental results, the phosphate removal rate and the phosphate content in the ammonium fluoride solution obtained from the methods for removing phosphate from the system during the preparation of fluoride salts using fluorosilicic acid in Examples 1-3 and Comparative Examples 1-4 are listed in Table 1. The phosphate removal rate is calculated based on the phosphate content in the solution containing ferrous fluorosilicate and fluorosilicic acid; the phosphate content in the ammonium fluoride solution is calculated based on the total amount of the reaction solution.

[0062] Table 1. Phosphate removal rates and phosphate content in the prepared ammonium fluoride solutions of Examples 1-3 and Comparative Examples 1-4.

[0063] Methods for removing phosphate from the system Phosphate removal rate (%) Phosphate content (%) in ammonium fluoride solution Example 1 88.90 0.13 Example 2 93.17 0.08 Example 3 92.32 0.09 Comparative Example 1 0 1.20 Comparative Example 2 36.71 0.72 Comparative Example 3 9.51 1.06 Comparative Example 4 30.85 0.81

[0064] The results showed that phosphate could not be removed when the pH of the ammoniation solution was below 1.5; the phosphate removal rate was low when the pH of the ammoniation solution was above 3; the phosphate removal rate was slow and the removal rate was low when the reaction temperature was below 50℃; and the phosphate removal rate was very low when hydrogen peroxide was not added to the reaction.

Claims

1. A method for removing phosphate ions from a system during the preparation of fluoride salts using fluorosilicic acid, characterized in that, Includes the following steps: A solution containing ferrous fluorosilicate and fluorosilicic acid is ammonified to obtain an ammonified solution with a pH of 1.5-3. The ammonified solution is then mixed with an oxidant and reacted, followed by solid-liquid separation. The molar ratio of phosphate ions to iron in the solution containing ferrous fluorosilicate and fluorosilicic acid is 1:

1. The oxidant is selected from hydrogen peroxide, oxygen, ozone, or any combination thereof. The ammonification reaction is: H2SiF6 + 2NH3 = (NH4)2SiF6, and the fluorosilicic acid is not completely reacted.

2. The method for removing phosphate ions from the system during the preparation of fluoride salts using fluorosilicic acid as described in claim 1, characterized in that, The temperature of the mixing reaction is 50~80℃.

3. The method for removing phosphate ions from the system during the preparation of fluoride salts using fluorosilicic acid as described in claim 2, characterized in that, The mixing reaction takes 0.5 to 2 hours.

4. The method for removing phosphate ions from the system during the preparation of fluoride salts using fluorosilicic acid as described in claim 1, characterized in that, In a solution containing ferrous fluorosilicate and fluorosilicic acid, the mass fraction of the phosphate group is 0.5-4%.

5. The method for removing phosphate ions from the system during the preparation of fluoride salts using fluorosilicic acid as described in claim 1, characterized in that, In a solution containing ferrous fluorosilicate and fluorosilicic acid, the mass fraction of the fluorosilicic acid is 15-20%.

6. The method for removing phosphate ions from the system during the preparation of fluoride salts using fluorosilicic acid as described in any one of claims 1-5, characterized in that, The oxidant is hydrogen peroxide.

7. The method for removing phosphate ions from the system during the preparation of fluoride salts using fluorosilicic acid as described in any one of claims 1-5, characterized in that, The ammoniation treatment involves mixing and reacting an ammonifying agent with a solution containing ferrous fluorosilicate and fluorosilicic acid; the ammonifying agent used in the ammoniation treatment is selected from one or any combination of ammonia water, ammonia, ammonium carbonate, and ammonium bicarbonate.

8. The method for removing phosphate ions from the system during the preparation of fluoride salts using fluorosilicic acid as described in any one of claims 1-5, characterized in that, The solution containing ferrous fluorosilicate and fluorosilicic acid is prepared by a method comprising the following steps: dissolving iron in a first fluorosilicic acid solution to obtain solution A, and then mixing solution A with a second fluorosilicic acid solution to obtain the final solution.

9. The method for removing phosphate ions from the system during the preparation of fluoride salts using fluorosilicic acid as described in any one of claims 1-5, characterized in that, The method for removing phosphate ions from the system when preparing fluoride salts using fluorosilicic acid further includes the following steps: after solid-liquid separation, the liquid obtained from solid-liquid separation is subjected to a second ammoniation treatment to obtain a second ammoniation treatment liquid, and then the second ammoniation treatment liquid is subjected to a second solid-liquid separation.

10. The method for removing phosphate ions from the system during the preparation of fluoride salts using fluorosilicic acid as described in claim 9, characterized in that, The second ammonia treatment involves mixing and reacting the ammonia agent with the liquid obtained from solid-liquid separation; in the second ammonia treatment, the ammonia agent is ammonia water.