A method for removing phosphorus and silicon from a sodium tungstate solution

Abstract

The application belongs to the technical field of hydrometallurgy of tungsten, and particularly relates to a method for removing phosphorus and silicon from a sodium tungstate solution, which comprises the following steps: adjusting the pH of the sodium tungstate solution containing phosphorus and silicon to 9-10, the temperature to 25-60 DEG C, adding an aluminum salt saturated solution, stirring to obtain a mixed solution, the mass ratio of aluminum in the aluminum salt saturated solution to the total mass of silicon and phosphorus in the sodium tungstate solution being (1.1-1.8):2; adjusting the pH of the mixed solution to 13-14, the temperature to 80-90 DEG C, adding a calcium salt, stirring, standing, and then filtering to obtain a purified sodium tungstate solution, the mass ratio of the calcium salt (calculated as CaO) to the aluminum salt (calculated as Al2O3) being 1:(1-2). The technical scheme finds that the adding sequence of the aluminum salt and the calcium salt has an influence on the effect of removing phosphorus and silicon, and develops a method for deeply removing phosphorus and silicon by adding the aluminum salt first and then adding the calcium salt; the optimal effect of removing phosphorus and silicon is determined by adjusting the adding time, adding amount and reaction conditions of the aluminum salt and the calcium salt; and the problem of difficult single aluminum salt precipitation and filtration is solved through the synergistic effect of aluminum-calcium-silicon.

Description

Technical Field

[0001] This application belongs to the field of hydrometallurgical technology of tungsten, specifically a method for removing phosphorus and silicon from sodium tungstate solution. Background Technology

[0002] Sodium tungstate, as an important chemical raw material, is widely used in cemented carbide, electronics industry, catalysts and other fields. However, the presence of impurities during the production process of sodium tungstate can seriously affect its purity and performance.

[0003] Currently, calcium salts are commonly used in industrial applications for phosphorus removal, and the dosage can be 30 to 80 times the theoretical amount, depending on the type of calcium salt. Furthermore, the phosphorus removal effect of sodium tungstate is also affected by silicon; when both phosphorus and silicon impurities are present, using a single removal agent is not only ineffective but also significantly increases the amount of calcium salt required. Patent CN112853123A mentions the use of sodium aluminate and magnesium oxide for silicon removal. Sodium aluminate and magnesium oxide do not react with other impurities to introduce new ones. Sodium aluminate also acts as a flocculant, causing the generated silicic acid and magnesium silicate to flocculate together, thus increasing the size of the insoluble precipitate particles and improving the silicon removal effect. However, despite the good silicon removal effect of aluminum salts, the aluminum salt precipitate also presents the problem of being difficult to filter.

[0004] In summary, existing technologies can remove phosphorus and silicon to a certain extent, but some problems and shortcomings remain. First, methods using aluminum or calcium salts alone cannot remove phosphorus and silicon simultaneously, requiring additional processing steps to improve removal efficiency. Second, these methods often require high chemical dosages, increasing processing costs. Furthermore, methods using aluminum or calcium salts alone have limitations in practical applications, making it difficult to meet removal requirements under different conditions. Therefore, developing a novel method for phosphorus and silicon removal using a combination of aluminum and calcium salts has significant practical importance and application value. Summary of the Invention

[0005] To address the aforementioned problems, this application provides a method for removing phosphorus and silicon from sodium tungstate solution. This method alters the morphology of the precipitate through pre-flocculation with aluminum salts, while utilizing the efficient phosphorus precipitation capacity of calcium salts and the synergistic effect between aluminum, calcium, and silicon. This solves the problem of difficult precipitation and filtration of single aluminum salts, achieving simultaneous deep removal of phosphorus and silicon.

[0006] This application discloses a method for removing phosphorus and silicon from a sodium tungstate solution, comprising the following steps:

[0007] S1. Obtain a sodium tungstate solution containing phosphorus and silicon, adjust the pH of the sodium tungstate solution to 9-10, control the temperature to 25-60℃, add a saturated aluminum salt solution to the sodium tungstate solution, and perform a first stirring to obtain a mixed solution. The ratio of the mass of aluminum in the saturated aluminum salt solution to the total mass of silicon and phosphorus in the sodium tungstate solution is (1.1-1.8):2.

[0008] S2. Adjust the pH of the mixed solution to 13-14, control the temperature to 80-90℃, add calcium salt to the mixed solution, stir for the second time, let it stand, and then filter to obtain sodium tungstate purified solution and filter residue. The mass ratio of the calcium salt (calculated as CaO) to the aluminum salt (calculated as Al2O3) is 1:(1-2).

[0009] Under alkaline conditions, adding aluminum salts to sodium tungstate solution allows the aluminum salts to hydrolyze and form positively charged, highly adsorbent and flocculating aluminum hydroxyl polymers and amorphous Al(OH)3 polymers. These polymers preferentially bind to or capture silicate and some phosphate ions, forming fine-particle flocs that provide nuclei for subsequent co-precipitation with calcium salts. Adding a saturated aluminum salt solution to the alkaline sodium tungstate solution ensures rapid supersaturation of the aluminum salt under alkaline conditions, promoting rapid polymer formation and enhancing its ability to capture silicon and phosphorus. While adding a non-saturated aluminum salt solution to the alkaline sodium tungstate solution can have some effect due to pH increase, it cannot guarantee that the aluminum salt will remain saturated in the system. Furthermore, if the pH of the sodium tungstate solution is too high, Al(OH)4 will immediately form upon the addition of aluminum salt. - Dissolution eliminates the flocculation effect. Therefore, in step S1, the pH of the sodium tungstate solution is adjusted to the range of 9-10 to ensure good flocculation by the aluminum salt. Temperature also affects the solubility of aluminum salt; therefore, controlling the temperature between 25-60℃ weakens its impact on solubility. The pH of the mixed solution is then adjusted to 13-14, and the temperature is controlled at 80-90℃ before adding calcium salt. Under high alkalinity and high temperature conditions, the calcium salt preferentially reacts with phosphorus and silicon bound in the flocs to form a stable precipitate mainly composed of calcium silicate phosphate (Ca-Si-P complex), achieving deep phosphorus removal. Excess calcium salt also reacts with residual aluminum and silicon to form insoluble calcium aluminosilicate, achieving deep silicon removal without binding with tungstate and causing tungsten loss. Furthermore, calcium aluminosilicate and calcium silicate phosphate particles are coarser than ordinary aluminum salt precipitates, with greater porosity between crystals, making them easier to filter. Simple filtration then simultaneously removes phosphorus and silicon, solving the problem of difficult filtration of ordinary aluminum salt precipitates.

[0010] If aluminum salt solution and calcium salt are added simultaneously, the calcium salt will have already reacted almost completely before the aluminum salt's capture and adsorption effect can be fully realized. Therefore, adding them simultaneously can only achieve the effect of removing silicon. Similarly, adding calcium salt first cannot simultaneously solve the problem of excessive phosphorus and silicon. On the other hand, adding aluminum salt alone to remove phosphorus and silicon easily forms colloids under alkaline conditions, resulting in limited efficiency. Adding calcium salt alone easily reacts with tungstate ions to form calcium tungstate precipitate under strongly alkaline conditions, causing tungsten loss. The "aluminum-calcium synergy" cleverly avoids the shortcomings of each: aluminum first "locks in" impurities, and calcium then "strengthens" the precipitate and promotes separation. The two complement each other, forming a purification effect of "1+1>2". This technical solution also has advantages in alkaline solutions such as sodium molybdate.

[0011] Furthermore, the concentration of the sodium tungstate solution, calculated as WO3, is 50~200g / L, and the phosphorus content and silicon content in the sodium tungstate solution are ≤1g / L and ≤1g / L, respectively.

[0012] Furthermore, the aluminum salt includes aluminum sulfate, and the calcium salt includes calcium carbonate.

[0013] Furthermore, in step S1, the first stirring rate is 200~400 r / min, and the time is 1~2 h.

[0014] Furthermore, in step S2, sodium hydroxide is used to adjust the pH of the mixed solution to 13-14.

[0015] Furthermore, in step S2, the second stirring rate is 200~400 r / min, and the time is 1~2 h.

[0016] Furthermore, in step S2, the settling time is 1 to 2 hours.

[0017] Furthermore, in step S2, a Buchner funnel with an outer diameter of 200 mm, an inner diameter of 190 mm, and a volume of 5 L, and double-ring filter paper with a diameter of 18 cm are used for filtration, and the filtration time for each liter of sodium tungstate purified solution is ≤2 min.

[0018] Furthermore, the filter residue includes calcium silicate phosphate and calcium aluminosilicate.

[0019] Furthermore, the phosphorus content and silicon content in the sodium tungstate purification solution are ≤0.05g / L and ≤0.05g / L, respectively.

[0020] This application proposes a method for removing phosphorus and silicon from sodium tungstate solution, which yields the following beneficial effects: it innovatively discovers that the order of addition of aluminum and calcium salts affects the phosphorus and silicon removal efficiency, and develops a method for deep phosphorus and silicon removal by adding aluminum salt first and then calcium salt; the optimal phosphorus and silicon removal efficiency is determined by adjusting the timing, amount, and reaction conditions of adding aluminum and calcium salts; and the problem of difficult precipitation and filtration of single aluminum salts is solved through the synergistic effect between aluminum, calcium, and silicon. Detailed Implementation

[0021] The technical solutions in the embodiments will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0022] This application discloses a method for removing phosphorus and silicon from a sodium tungstate solution, comprising the following steps:

[0023] S1. Obtain a sodium tungstate solution containing phosphorus and silicon. Adjust the pH of the sodium tungstate solution to 9-10 and control the temperature to 25-60℃. Add a saturated aluminum sulfate solution to the sodium tungstate solution and stir the reaction at a rate of 200-400 r / min for 1-2 h to obtain a mixed solution. The ratio of the mass of aluminum in the saturated aluminum sulfate solution to the total mass of silicon and phosphorus in the sodium tungstate solution is (1.1-1.8):2.

[0024] Specifically, the pH of the sodium tungstate solution can be adjusted to any one or a combination of 9, 9.2, 9.4, 9.6, 9.8, and 10; the temperature can be controlled to any one or a combination of 25℃, 35℃, 45℃, 55℃, and 60℃; the stirring speed can be any one or a combination of 200 r / min, 250 r / min, 300 r / min, 350 r / min, and 400 r / min; and the ratio of the mass of aluminum in the saturated aluminum sulfate solution to the total mass of silicon and phosphorus in the sodium tungstate solution can be any one or a combination of 1.1:2, 1.2:2, 1.3:2, 1.4:2, 1.5:2, 1.6:2, 1.7:2, and 1.8:2.

[0025] S2. Adjust the pH of the mixed solution to 13-14, control the temperature to 80-90℃, add calcium carbonate to the mixed solution, stir the reaction at a rate of 200-400 r / min for 1-2 h, let it stand for 1-2 h, and then filter to obtain sodium tungstate purified solution and filter residue. The mass ratio of calcium carbonate (calculated as CaO) to aluminum sulfate (calculated as Al2O3) is 1:(1-2).

[0026] Specifically, the pH of the mixed solution can be adjusted to any one or any two of 13, 13.2, 13.4, 13.6, 13.8, and 14; the temperature can be controlled to any one or any two of 80℃, 82℃, 84℃, 86℃, 88℃, and 90℃; the stirring speed can be any one or any two of 200r / min, 250r / min, 300r / min, 350r / min, and 400r / min; and the mass ratio of calcium carbonate (CaO) to aluminum sulfate (Al2O3) can be any one or any two of 1:1, 1:1.2, 1:1.4, 1:1.6, 1:1.8, and 1:2.

[0027] Preferably, the concentration of the sodium tungstate solution, calculated as WO3, is 50~200 g / L, and the phosphorus content and silicon content in the sodium tungstate solution are ≤1 g / L and ≤1 g / L, respectively.

[0028] Preferably, in step S2, sodium hydroxide is used to adjust the pH of the mixed solution to 13-14.

[0029] Preferably, in step S2, a Buchner funnel with an outer diameter of 200 mm, an inner diameter of 190 mm, and a volume of 5 L, and double-ring filter paper with a diameter of 18 cm are used to filter the mixed solution after the reaction with calcium salt, and the filtration time for each liter of sodium tungstate purified solution is ≤2 min.

[0030] Preferably, the filter residue includes calcium silicate phosphate and calcium aluminosilicate.

[0031] Preferably, the phosphorus content and silicon content in the sodium tungstate purification solution are ≤0.05g / L and ≤0.05g / L, respectively.

[0032] The technical solution of this application will be further described below with reference to specific embodiments. In all the following embodiments and comparative examples, the sodium tungstate solution containing phosphorus and silicon impurities has a phosphorus content of 1 g / L and a silicon content of 1 g / L. The concentration of the sodium tungstate solution as WO3 is 150 g / L. The saturated aluminum salt solution used is a saturated aluminum sulfate solution prepared at 20°C, wherein the mass fraction of Al is 57.08 g / L. The calcium salt used is calcium carbonate. During filtration, a Buchner funnel with an outer diameter of 200 mm, an inner diameter of 190 mm, and a volume of 5 L, and double-ring filter paper with a diameter of 18 cm are used.

[0033] Example 1

[0034] The pH of a sodium tungstate solution containing phosphorus and silicon impurities was adjusted to 9, and the temperature was set to 25°C. A saturated aluminum sulfate solution was added to the sodium tungstate solution, with the volume of the saturated aluminum sulfate solution being 2% of the volume of the sodium tungstate solution. The mixture was stirred at 200 r / min for 1 h to obtain a mixed solution. The pH of the mixed solution was adjusted to 14, and the temperature was set to 80°C. Calcium carbonate was added to the mixed solution, with the mass ratio of calcium carbonate (CaO) to aluminum sulfate (Al2O3) being 1:1. The mixture was stirred at 200 r / min for 1 h, and after standing for 1 h, it was filtered to obtain a purified sodium tungstate solution and filter residue. The filtration time for each liter of purified sodium tungstate solution was ≤2 min.

[0035] The sodium tungstate purified solution obtained in this embodiment was tested, and the phosphorus content was <0.05 g / L and the silicon content was <0.05 g / L.

[0036] Example 2

[0037] The pH of a sodium tungstate solution containing phosphorus and silicon impurities was adjusted to 10, and the temperature was set to 60°C. A saturated aluminum sulfate solution was added to the sodium tungstate solution, with the volume of the saturated aluminum sulfate solution being 3% of the volume of the sodium tungstate solution. The mixture was stirred at 400 r / min for 2 h to obtain a mixed solution. The pH of the mixed solution was adjusted to 13, and the temperature was set to 90°C. Calcium carbonate was added to the mixed solution, with the mass ratio of calcium carbonate (CaO) to aluminum sulfate (Al2O3) being 1:1. The mixture was stirred at 400 r / min for 2 h, and after standing for 2 h, it was filtered to obtain a purified sodium tungstate solution and filter residue. The filtration time for each liter of purified sodium tungstate solution was ≤2 min.

[0038] The sodium tungstate purified solution obtained in this embodiment was tested, and the phosphorus content was <0.05 g / L and the silicon content was <0.05 g / L.

[0039] Example 3

[0040] The pH of a sodium tungstate solution containing phosphorus and silicon impurities was adjusted to 10, and the temperature was set to 60°C. A saturated aluminum sulfate solution was added to the sodium tungstate solution, with the volume of the saturated aluminum sulfate solution being 3% of the volume of the sodium tungstate solution. The mixture was stirred at 400 r / min for 2 h to obtain a mixed solution. The pH of the mixed solution was adjusted to 13, and the temperature was set to 90°C. Calcium carbonate was added to the mixed solution, with the mass ratio of calcium carbonate (CaO) to aluminum sulfate (Al2O3) being 1:2. The mixture was stirred at 400 r / min for 2 h, and after standing for 2 h, it was filtered to obtain a purified sodium tungstate solution and filter residue. The filtration time for each liter of purified sodium tungstate solution was ≤2 min.

[0041] The sodium tungstate purified solution obtained in this embodiment was tested, and the phosphorus content was <0.05 g / L and the silicon content was <0.05 g / L.

[0042] Example 4

[0043] The pH of a sodium tungstate solution containing phosphorus and silicon impurities was adjusted to 9.5 and the temperature to 40℃. A saturated aluminum sulfate solution was added to the sodium tungstate solution, with the volume of the saturated aluminum sulfate solution being 2.5% of the volume of the sodium tungstate solution. The mixture was stirred at 300 r / min for 1.5 h to obtain a mixed solution. The pH of the mixed solution was adjusted to 13.5 and the temperature to 85℃. Calcium carbonate was added to the mixed solution, with the mass ratio of calcium carbonate (CaO) to aluminum sulfate (Al2O3) being 1:1.5. The mixture was stirred at 300 r / min for 1.5 h and allowed to stand for 1.5 h before filtration to obtain purified sodium tungstate solution and filter residue. The filtration time for each liter of purified sodium tungstate solution was ≤2 min.

[0044] The sodium tungstate purified solution obtained in this embodiment was tested, and the phosphorus content was <0.05 g / L and the silicon content was <0.05 g / L.

[0045] Comparative Example 1

[0046] The only difference between this comparative example and Example 1 is that: first, the pH of the sodium tungstate solution was adjusted to 14 and the temperature to 80°C, and calcium carbonate was added; then, the pH was adjusted to 9 and the temperature to 25°C, and a saturated aluminum sulfate solution was added.

[0047] The filtration time for each liter of sodium tungstate purified solution is ≥3h;

[0048] The sodium tungstate purification solution obtained in this comparative example was tested, and the phosphorus content was <0.05 g / L and the silicon content was 0.57 g / L.

[0049] Comparative Example 2

[0050] The only difference between this comparative example and Example 1 is that the pH of the sodium tungstate solution was adjusted to 9, the temperature was set to 25°C, and a saturated aluminum sulfate solution and calcium carbonate were added. The mixture was then stirred at a rate of 200 r / min for 1 h, allowed to stand for 1 h, and then filtered.

[0051] The filtration time for each liter of sodium tungstate purified solution is ≤2 min;

[0052] The sodium tungstate purified solution obtained in this comparative example was tested, and the phosphorus content was 0.64 g / L and the silicon content was <0.05 g / L.

[0053] Comparative Example 3

[0054] The only difference between this comparative example and Example 1 is that the mass ratio of calcium carbonate (calculated as CaO) to aluminum sulfate (calculated as Al2O3) is 1:3.

[0055] The filtration time for each liter of sodium tungstate purified solution is ≥5 min;

[0056] The sodium tungstate purification solution obtained in this comparative example was tested, and the phosphorus content was <0.05 g / L and the silicon content was 0.14 g / L.

[0057] Comparative Example 4

[0058] The only difference between this comparative example and Example 1 is that the volume of the added saturated aluminum sulfate solution is 1% of the volume of the sodium tungstate solution, and the ratio of the mass of added calcium carbonate (calculated as CaO) to the mass of aluminum sulfate (calculated as Al2O3) is 2:1.

[0059] The filtration time for each liter of sodium tungstate purified solution is ≥5 min;

[0060] The sodium tungstate purification solution obtained in this comparative example was tested, and the phosphorus content was <0.05 g / L and the silicon content was 0.71 g / L.

[0061] Comparative Example 5

[0062] The only difference between this comparative example and Example 1 is that calcium carbonate is not added, and the mixed solution obtained after reacting with saturated aluminum sulfate solution is allowed to stand for 1 hour and then filtered.

[0063] The filtration time for each liter of sodium tungstate purified solution is ≥3 hours;

[0064] The sodium tungstate purification solution obtained in this comparative example was tested, and the phosphorus content was 0.97 g / L and the silicon content was 0.28 g / L.

[0065] Comparative Example 6

[0066] The only difference between this comparative example and Example 1 is that: instead of adding a saturated aluminum sulfate solution, the pH of the sodium tungstate solution was directly adjusted to 14, the temperature was set to 80°C, calcium carbonate was added, and then the mixture was stirred, allowed to stand, and filtered.

[0067] The filtration time for each liter of sodium tungstate purified solution is ≥5 min;

[0068] The sodium tungstate purified solution obtained in this comparative example was tested, and the phosphorus content was 0.29 g / L and the silicon content was 0.99 g / L.

[0069] Comparative Example 7

[0070] The only difference between this comparative example and Example 1 is that ferric hydroxide is used instead of calcium carbonate, and the mass ratio of ferric hydroxide (Fe2O3) to aluminum sulfate (Al2O3) is 1:1.

[0071] The filtration time for each liter of sodium tungstate purified solution is ≥8 min;

[0072] The sodium tungstate purification solution obtained in this comparative example was tested, and the phosphorus content was 0.96 g / L and the silicon content was 0.23 g / L.

[0073] Comparative Example 8

[0074] The only difference between this comparative example and Example 1 is that the pH of the mixed solution was adjusted to 10 before adding calcium carbonate.

[0075] The filtration time for each liter of sodium tungstate purified solution is ≥7 min;

[0076] The sodium tungstate purified solution obtained in this comparative example was tested, and the phosphorus content was 0.44 g / L and the silicon content was <0.05 g / L.

[0077] Comparative Example 9

[0078] The only difference between this comparative example and Example 1 is that the pH of the mixed solution was adjusted to 13 before adding the saturated aluminum sulfate solution.

[0079] The filtration time for each liter of sodium tungstate purified solution is ≥7 min;

[0080] The sodium tungstate purification solution obtained in this comparative example was tested, and the phosphorus content was <0.05 g / L and the silicon content was 0.55 g / L.

[0081] Comparative Example 10

[0082] The only difference between this comparative example and Example 1 is that the temperature of the mixed solution was adjusted to 80°C before adding the saturated aluminum sulfate solution.

[0083] The filtration time for each liter of sodium tungstate purified solution is ≥7 min;

[0084] The sodium tungstate purification solution obtained in this comparative example was tested, and the phosphorus content was 0.35 g / L and the silicon content was <0.05 g / L.

[0085] Comparative Example 11

[0086] The only difference between this comparative example and Example 1 is that the temperature of the mixed solution was adjusted to 40°C before adding calcium carbonate.

[0087] The filtration time for each liter of sodium tungstate purified solution is ≥7 min;

[0088] The sodium tungstate purification solution obtained in this comparative example was tested, and the phosphorus content was <0.05 g / L and the silicon content was 0.38 g / L.

[0089] Comparative Example 12

[0090] The only difference between this comparative example and Example 3 is that the added aluminum sulfate is an unsaturated solution;

[0091] The filtration time for each liter of sodium tungstate purified solution is ≤2 min;

[0092] The sodium tungstate purification solution obtained in this comparative example was tested, and the phosphorus content was 0.43 g / L and the silicon content was 0.50 g / L.

[0093] This application proposes a method for removing phosphorus and silicon from sodium tungstate solution, which yields the following beneficial effects: it innovatively discovers that the order of addition of aluminum and calcium salts affects the phosphorus and silicon removal efficiency, and develops a method for deep phosphorus and silicon removal by adding aluminum salt first and then calcium salt; the optimal phosphorus and silicon removal efficiency is determined by adjusting the timing, amount, and reaction conditions of adding aluminum and calcium salts; and the problem of difficult precipitation and filtration of single aluminum salts is solved through the synergistic effect between aluminum, calcium, and silicon.

[0094] The above description is only a preferred embodiment of this application and does not limit the patent scope of this application. All equivalent structural transformations made using the content of this application's specification under the inventive concept of this application, or direct / indirect applications in other related technical fields, are included within the patent protection scope of this application.

Claims

1. A method for removing phosphorus and silicon from a sodium tungstate solution, characterized by, The method comprises the following steps: S1, obtaining a sodium tungstate solution containing phosphorus and silicon elements, adjusting the pH of the sodium tungstate solution to 9-10, controlling the temperature to be 25-60 DEG C, adding a saturated solution of aluminum salt to the sodium tungstate solution, carrying out first stirring to obtain a mixed solution, the mass ratio of aluminum element in the saturated solution of aluminum salt to the total mass of silicon and phosphorus elements in the sodium tungstate solution is (1.1-1.8):2; S2, adjusting the pH of the mixed solution to 13-14, controlling the temperature to be 80-90 DEG C, adding calcium salt to the mixed solution, carrying out second stirring, and filtering after standing to obtain a purified sodium tungstate solution and a filter residue, the mass ratio of the calcium salt calculated as CaO to the aluminum salt calculated as Al2O3 is 1:(1-2).

2. The method of removing phosphorus and silicon from a sodium tungstate solution according to claim 1, characterized in that, The concentration of the sodium tungstate solution calculated as WO3 is 50-200 g / L, the content of phosphorus element in the sodium tungstate solution is ≤1 g / L, and the content of silicon element is ≤1 g / L.

3. The method of removing phosphorus and silicon from a sodium tungstate solution according to claim 1, wherein The aluminum salt comprises aluminum sulfate, and the calcium salt comprises calcium carbonate.

4. The method of removing phosphorus and silicon from a sodium tungstate solution according to claim 1, wherein In the step S1, the first stirring rate is 200-400 r / min, and the time is 1-2 h.

5. The method of removing phosphorus and silicon from a sodium tungstate solution of claim 1, wherein, In the step S2, sodium hydroxide is used to adjust the pH of the mixed solution to 13-14.

6. The method of removing phosphorus and silicon from a sodium tungstate solution of claim 1, wherein, In the step S2, the second stirring rate is 200-400 r / min, and the time is 1-2 h.

7. The method of removing phosphorus and silicon from a sodium tungstate solution according to claim 1, wherein In the step S2, the standing time is 1-2 h.

8. The method of removing phosphorus and silicon from a sodium tungstate solution of claim 1, wherein, In the step S2, a Buchner funnel with an outer diameter of 200 mm, an inner diameter of 190 mm, a volume of 5 L, and a double-circle filter paper with a diameter of 18 cm are used for the filtering, and the filtering time per liter of the purified sodium tungstate solution is ≤2 min.

9. The method of removing phosphorus and silicon from a sodium tungstate solution of claim 1, wherein, The filter residue comprises calcium silicon phosphate and calcium aluminate.

10. The method of removing phosphorus and silicon from a sodium tungstate solution of claim 1, wherein, The content of phosphorus element in the purified sodium tungstate solution is ≤0.05 g / L, and the content of silicon element is ≤0.05 g / L.