A method for removing silicon from a crude sodium tungstate solution

Abstract

The application belongs to the field of tungsten smelting, and particularly relates to a method for removing silicon from a crude sodium tungstate solution, comprising the following steps: S1, obtaining a crude sodium tungstate solution, adding sodium fluoride and sodium chloride into the crude sodium tungstate solution to obtain a first mixture; S2, adding an inorganic acid into the first mixture for stirring reaction to obtain a second mixture; and S3, performing solid-liquid separation on the second mixture to obtain a purified solution and a sodium hexafluorosilicate solid residue. The application proposes a sodium hexafluorosilicate precipitation method for purification process, which can effectively reduce the silicon content in the crude sodium tungstate solution to a qualified standard, has a good impurity removal effect, and simultaneously reduces the tungsten precipitation loss in the purification residue after solid-liquid separation.

Description

Technical Field

[0001] This application relates to the field of tungsten smelting, and more specifically, to a method for removing silicon from crude sodium tungstate solution. Background Technology

[0002] Tungsten is a rare and precious metallic element, widely used in cemented carbide, special steel, and electronic components. With the continuous development and utilization of tungsten resources, the grade of tungsten ore is declining, and its composition is becoming increasingly complex. The sodium tungstate solution produced by the pyrometallurgical process followed by alkaline decomposition of tungsten ore is called crude sodium tungstate solution. This crude sodium tungstate solution contains a large amount of silicon impurities, which interfere with subsequent processing steps. Current technologies for removing silicon from crude sodium tungstate solution mainly include magnesium salt precipitation, aluminum salt precipitation, and ammonium magnesium salt precipitation.

[0003] Magnesium salt precipitation, aluminum salt precipitation, and ammonium magnesium salt precipitation all produce hydroxide precipitates during silicon removal. These precipitates have strong adsorption properties and will adsorb tungsten after filtration, resulting in tungsten loss. Magnesium salt precipitation produces a large amount of slag, aluminum salt precipitation produces precipitates that are difficult to filter, and ammonium magnesium salt precipitation poses a risk of ammonia nitrogen pollution.

[0004] Therefore, there is an urgent need for a method to remove silicon from crude sodium tungstate solution without producing hydroxide precipitates, which is easy to filter and remove silicon with minimal tungsten loss. Summary of the Invention

[0005] To solve the above-mentioned technical problems, this application provides a method for removing silicon from crude sodium tungstate solution, comprising the following steps: S1, obtaining crude sodium tungstate solution, adding sodium fluoride and sodium chloride to the crude sodium tungstate solution to obtain a first mixture; S2, adding an inorganic acid to the first mixture and stirring to obtain a second mixture; S3, performing solid-liquid separation on the second mixture to obtain a purified liquid and sodium hexafluorosilicate solid residue.

[0006] In a preferred embodiment of the method for removing silicon from a crude sodium tungstate solution as described in this application, the crude sodium tungstate solution comprises the following components: WO3: 40-150 g / L, Si: 0.5-0.9 g / L, F: 1.0-2.0 g / L, Na: 20-35 g / L; and the pH of the crude sodium tungstate solution is ≥13.

[0007] As a preferred embodiment of the method for removing silicon from crude sodium tungstate solution described in this application, in step S1, the concentration of Na in the first mixture is 60-100 g / L.

[0008] As a preferred embodiment of the method for removing silicon from crude sodium tungstate solution described in this application, in step S1, the molar ratio of F to Si in the first mixture is (12-20):1.

[0009] In a preferred embodiment of the method for removing silicon from crude sodium tungstate solution described in this application, in step S2, the inorganic acid is one of hydrochloric acid, sulfuric acid, and nitric acid.

[0010] In a preferred embodiment of the method for removing silicon from crude sodium tungstate solution as described in this application, the pH of the stirring reaction in step S2 is 3-5.

[0011] As a preferred embodiment of the method for removing silicon from crude sodium tungstate solution described in this application, in step S2, the stirring speed of the stirring reaction is 180-220 r / min.

[0012] As a preferred embodiment of the method for removing silicon from crude sodium tungstate solution described in this application, the reaction time of the stirring reaction in step S2 is 1-2 hours.

[0013] As a preferred embodiment of the method for removing silicon from crude sodium tungstate solution described in this application, in step S3, the concentration of Si in the purified solution is ≤0.02g / L, and the mass fraction of WO3 in the sodium hexafluorosilicate solid slag is ≤0.5wt%.

[0014] As a preferred embodiment of the method for removing silicon from crude sodium tungstate solution described in this application, the loss rate of WO3 is ≤0.05%, and the removal rate of Si is ≥97.0%.

[0015] The beneficial effects of this application are as follows: This application provides a method for removing silicon from a crude sodium tungstate solution. The method involves adding a soluble sodium salt to the crude sodium tungstate solution to provide effective amounts of sodium and fluoride ions. An inorganic acid is used to adjust the pH of the solution to 3-5, resulting in sodium hexafluorosilicate precipitate, thereby removing silicon dioxide. Controlling the pH is to provide hydrogen ions, first forming hexafluorosilicic acid, which then reacts with sodium ions to form sodium hexafluorosilicate. If the pH is too low, tungstic acid precipitation occurs, significantly increasing the tungsten content in the residue and increasing tungsten loss; if the pH is too high, the reaction is incomplete, and the silicon removal efficiency decreases significantly. Sodium ions are used to better precipitate sodium hexafluorosilicate. If the sodium ion concentration is too low, the common ion effect decreases, reducing silicon removal efficiency; if the sodium ion concentration is too high, the silicon removal efficiency does not increase significantly, resulting in reagent waste. Controlling the amount of fluoride ions is because if the fluoride-silicon molar ratio is too low, a small amount of the generated silicic acid dissolves, reducing the silicon removal efficiency and increasing tungsten loss; if the fluoride-silicon molar ratio is too high, the silicon removal efficiency does not increase significantly, resulting in reagent waste and significantly reducing the adsorption capacity of the resin for tungsten in subsequent ion exchange processes.

[0016] This application proposes a sodium hexafluorosilicate precipitation purification process, which can effectively reduce the silicon content in crude sodium tungstate solution to the qualified standard, with good impurity removal effect, and at the same time reduce the precipitation loss of tungsten in the purification residue after solid-liquid separation. Detailed Implementation

[0017] 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.

[0018] This application provides a method for removing silicon from a crude sodium tungstate solution, comprising the following steps: S1. Obtain a crude sodium tungstate solution, and add sodium fluoride and sodium chloride to the crude sodium tungstate solution to obtain a first mixture; The crude sodium tungstate solution comprises: WO3: 40-150 g / L, Si: 0.5-0.9 g / L, F: 1.0-2.0 g / L, Na: 20-35 g / L; the pH of the crude sodium tungstate solution is ≥13; the concentration of Na in the first mixture is 60-100 g / L; the molar ratio of F to Si in the first mixture is (12-20):1. Specifically, the concentration of Na in the first mixture is any one of 60 g / L, 70 g / L, 80 g / L, 90 g / L, 100 g / L, or any two of these values; the molar ratio of F to Si in the first mixture is any one of 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, 20:1, or any two of these values. S2. Add an inorganic acid to the first mixture and stir to obtain a second mixture; The inorganic acid is one of hydrochloric acid, sulfuric acid, and nitric acid; the pH of the stirring reaction is 3-5; the stirring speed of the stirring reaction is 180-220 r / min; and the reaction time of the stirring reaction is 1-2 h. Specifically, the pH of the stirring reaction is any one of 3, 3.5, 4, 4.5, 5 and any range between any two; S3. The second mixture is subjected to solid-liquid separation to obtain purified liquid and sodium hexafluorosilicate solid residue; The concentration of Si in the purified liquid is ≤0.02g / L, the mass fraction of WO3 in the sodium hexafluorosilicate solid slag is ≤0.5wt%, the loss rate of WO3 is ≤0.05%, and the removal rate of Si is ≥97.0%.

[0019] The technical solution of this application will be further described below with reference to specific embodiments.

[0020] Example 1 This application provides a method for removing silicon from a crude sodium tungstate solution, comprising the following steps: S1. Obtain a crude sodium tungstate solution by adding sodium fluoride and sodium chloride to the crude sodium tungstate solution to obtain a first mixture; The crude sodium tungstate solution comprises: WO3: 100 g / L, Si: 0.7 g / L, F: 1.5 g / L, Na: 30 g / L; the pH of the crude sodium tungstate solution is 13; the concentration of Na in the first mixture is 80 g / L; the molar ratio of F to Si in the first mixture is 16:1. S2. Add the inorganic acid to the first mixture and stir to react to obtain the second mixture; The inorganic acid is hydrochloric acid; the pH of the reaction is 4; the stirring speed is 200 r / min; and the reaction time is 1.5 h. S3. The second mixture is subjected to solid-liquid separation to obtain purified liquid and sodium hexafluorosilicate solid residue; The test results showed that the concentration of Si in the purified liquid was 0.012 g / L, the mass fraction of WO3 in the sodium hexafluorosilicate solid residue was 0.22 wt%, the loss rate of WO3 was 0.011%, and the removal rate of Si was 98.29%.

[0021] Example 2 This application provides a method for removing silicon from a crude sodium tungstate solution, comprising the following steps: S1. Obtain a crude sodium tungstate solution by adding sodium fluoride and sodium chloride to the crude sodium tungstate solution to obtain a first mixture; The crude sodium tungstate solution comprises: WO3: 150 g / L, Si: 0.9 g / L, F: 2.0 g / L, Na: 35 g / L; the pH of the crude sodium tungstate solution is 13; the concentration of Na in the first mixture is 100 g / L; the molar ratio of F to Si in the first mixture is 20:1. S2. Add the inorganic acid to the first mixture and stir to react to obtain the second mixture; The inorganic acid is sulfuric acid; the pH of the reaction is 3; the stirring speed is 200 r / min; and the reaction time is 2 h. S3. The second mixture is subjected to solid-liquid separation to obtain purified liquid and sodium hexafluorosilicate solid residue; The test results showed that the concentration of Si in the purified liquid was 0.008 g / L, the mass fraction of WO3 in the sodium hexafluorosilicate solid residue was 0.13 wt%, the loss rate of WO3 was 0.006%, and the removal rate of Si was 99.11%.

[0022] Example 3 This application provides a method for removing silicon from a crude sodium tungstate solution, comprising the following steps: S1. Obtain a crude sodium tungstate solution by adding sodium fluoride and sodium chloride to the crude sodium tungstate solution to obtain a first mixture; The crude sodium tungstate solution comprises: WO3: 40 g / L, Si: 0.5 g / L, F: 1.0 g / L, Na: 20 g / L; the pH of the crude sodium tungstate solution is 13; the concentration of Na in the first mixture is 60 g / L; the molar ratio of F to Si in the first mixture is 12:1. S2. Add the inorganic acid to the first mixture and stir to react to obtain the second mixture; The inorganic acid is nitric acid; the pH of the reaction is 5; the stirring speed is 200 r / min; and the reaction time is 1 h. S3. The second mixture is subjected to solid-liquid separation to obtain purified liquid and sodium hexafluorosilicate solid residue; The test results showed that the concentration of Si in the purified liquid was 0.015 g / L, the mass fraction of WO3 in the sodium hexafluorosilicate solid residue was 0.45 wt%, the loss rate of WO3 was 0.043%, and the removal rate of Si was 97.0%.

[0023] Comparative Example 1 The difference between this comparative example and Example 1 is that the concentration of Na in the first mixture in step S1 is 40 g / L, while the other steps are the same as in Example 1.

[0024] The test results showed that the concentration of Si in the purified liquid was 0.031 g / L, the mass fraction of WO3 in the sodium hexafluorosilicate solid residue was 0.21 wt%, the loss rate of WO3 was 0.010%, and the removal rate of Si was 96.56%.

[0025] Comparative Example 2 The difference between this comparative example and Example 1 is that the concentration of Na in the first mixture in step S1 is 150 g / L, while the other steps are the same as in Example 1.

[0026] The test results showed that the concentration of Si in the purified liquid was 0.011 g / L, the mass fraction of WO3 in the sodium hexafluorosilicate solid residue was 0.21 wt%, the loss rate of WO3 was 0.012%, and the removal rate of Si was 98.3%.

[0027] Comparative Example 3 The difference between this comparative example and Example 1 is that the molar ratio of F to Si in the first mixture in step S1 is 5:1, while the other steps are the same as in Example 1.

[0028] The test results showed that the concentration of Si in the purified liquid was 0.053 g / L, the mass fraction of WO3 in the sodium hexafluorosilicate solid residue was 6.36 wt%, the loss rate of WO3 was 0.311%, and the removal rate of Si was 94.11%.

[0029] Comparative Example 4 The difference between this comparative example and Example 1 is that the molar ratio of F to Si in the first mixture in step S1 is 30:1, while the other steps are the same as in Example 1.

[0030] The test results showed that the concentration of Si in the purified liquid was 0.01 g / L, the mass fraction of WO3 in the sodium hexafluorosilicate solid residue was 0.2 wt%, the loss rate of WO3 was 0.01%, and the removal rate of Si was 98.33%.

[0031] Comparative Example 5 The difference between this comparative example and Example 1 is that the pH of the stirring reaction in step S2 is 1, while the other steps are the same as in Example 1.

[0032] The test results showed that the concentration of Si in the purified liquid was 0.014 g / L, the mass fraction of WO3 in the sodium hexafluorosilicate solid residue was 10.33 wt%, the loss rate of WO3 was 0.578%, and the removal rate of Si was 98.19%.

[0033] Comparative Example 6 The difference between this comparative example and Example 1 is that the pH of the stirring reaction in step S2 is 9, while the other steps are the same as in Example 1.

[0034] The test results showed that the concentration of Si in the purified liquid was 0.119 g / L, the mass fraction of WO3 in the sodium hexafluorosilicate solid residue was 0.19 wt%, the loss rate of WO3 was 0.006%, and the removal rate of Si was 86.78%.

[0035] As can be seen from the above examples and comparative examples: Example 1 combined with Comparative Example 1 shows that when the sodium ion concentration is too low, the common ion effect decreases, and the silicon removal efficiency decreases; Example 1 combined with Comparative Example 2 shows that when the sodium ion concentration is too high, the silicon removal efficiency does not increase significantly, resulting in reagent waste; Example 1 combined with Comparative Example 3 shows that when the fluorine-silicon molar ratio is too low, a small amount of the generated silicic acid dissolves, the silicon removal effect decreases, and the tungsten loss increases; Example 1 combined with Comparative Example 4 shows that when the fluorine-silicon molar ratio is too high, the silicon removal efficiency does not increase significantly, resulting in reagent waste and a significant reduction in the resin's adsorption capacity for tungsten in subsequent ion exchange processes; Example 1 combined with Comparative Example 5 shows that when the pH value is too low, tungstic acid precipitation occurs, the tungsten content in the residue increases significantly, and the tungsten loss increases; Example 1 combined with Comparative Example 6 shows that when the pH value is too high, the reaction is incomplete, and the silicon removal effect decreases significantly.

[0036] 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 silicon from a crude sodium tungstate solution, characterized in that, Includes the following steps: S1. Obtain a crude sodium tungstate solution by adding sodium fluoride and sodium chloride to the crude sodium tungstate solution to obtain a first mixture; S2. Add an inorganic acid to the first mixture and stir to obtain a second mixture; S3. The second mixture is subjected to solid-liquid separation to obtain purified liquid and sodium hexafluorosilicate solid residue; In step S2, the pH of the stirring reaction is 3-5.

2. The method for removing silicon from crude sodium tungstate solution according to claim 1, characterized in that, In step S1, the crude sodium tungstate solution comprises: WO3: 40-150 g / L, Si: 0.5-0.9 g / L, F: 1.0-2.0 g / L, Na: 20-35 g / L; and the pH of the crude sodium tungstate solution is ≥13.

3. The method for removing silicon from crude sodium tungstate solution according to claim 1, characterized in that, In step S1, the concentration of Na in the first mixture is 60-100 g / L.

4. The method for removing silicon from crude sodium tungstate solution according to claim 1, characterized in that, In step S1, the molar ratio of F to Si in the first mixture is (12-20):

1.

5. The method for removing silicon from crude sodium tungstate solution according to claim 1, characterized in that, In step S2, the inorganic acid is one of hydrochloric acid, sulfuric acid, and nitric acid.

6. The method for removing silicon from crude sodium tungstate solution according to claim 1, characterized in that, In step S2, the stirring speed of the stirring reaction is 180-220 r / min.

7. The method for removing silicon from crude sodium tungstate solution according to claim 1, characterized in that, In step S2, the reaction time of the stirring reaction is 1-2 hours.

8. The method for removing silicon from crude sodium tungstate solution according to claim 1, characterized in that, In step S3, the concentration of Si in the purified liquid is ≤0.02g / L, and the mass fraction of WO3 in the sodium hexafluorosilicate solid slag is ≤0.5wt%.

9. The method for removing silicon from crude sodium tungstate solution according to claim 1, characterized in that, The loss rate of WO3 is ≤0.05%, and the removal rate of Si is ≥97.0%.