A method for removing potassium from a vanadium-containing sodium molybdate solution

Abstract

The application provides a method for removing potassium from a vanadium-containing sodium molybdate solution, comprising the following steps: 1) adding sodium sulfate into the vanadium-containing sodium molybdate solution to obtain a sulfidation solution of sodium molybdate; 2) adding ferrous sulfate into the sulfidation solution, adjusting the pH to 7-7.5 when the pH is 5-5.5, until the ferrous sulfate is added completely, to obtain a final pH 7-7.5 emerald or dark green solution system; 3) adding hydrogen peroxide into the solution system obtained in the step 2) until the solution becomes colorless, then stopping adding the hydrogen peroxide, stirring and reacting for 0.5-1 h, and filtering to obtain a low-potassium sodium molybdate solution. The whole operation process is simple, the cost is low, the potassium removal efficiency is high, the removal rate of potassium reaches more than 90%, and the molybdenum content of the filter cake is less than or equal to 0.05%.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical technology and relates to a method for removing potassium from a sodium vanadate-containing solution. Background Technology

[0002] High-purity molybdenum compounds have a wide range of applications and demands, such as in catalysts and metal products. In recent years, some molybdenum consuming manufacturers have placed higher requirements on the potassium content of molybdenum. Potassium is an alkali metal in Group IA of the periodic table, with a melting point of 63.65℃ and a boiling point of 774℃. Due to its low melting and boiling points and extremely reactive chemical properties, potassium volatilizes in a gaseous state during the high-temperature sintering of molybdenum (above 1900℃) or when used as a material in electric light sources. It can adhere to heating or light-emitting components, or absorb moisture and affect the insulation performance of these components, or corrode components, refractory materials, and insulation materials as a strong alkali, contaminating product surfaces. Therefore, purification processes to further reduce potassium content are essential.

[0003] Currently available methods for potassium removal include membrane separation, ion exchange, potassium perchlorate precipitation, and potassium tartrate precipitation. However, membrane separation and ion exchange methods are cumbersome and have high equipment maintenance costs. Furthermore, both potassium perchlorate and potassium tartrate are soluble in sodium molybdate solution, making potassium removal from sodium molybdate solution impossible using these methods. Summary of the Invention

[0004] The purpose of this invention is to provide a method for removing potassium from a sodium vanadate solution, wherein the potassium-removed sodium molybdate solution can meet the requirements for preparing low-potassium molybdenum products.

[0005] The technical solution adopted by the present invention to achieve the above objectives is as follows:

[0006] A method for removing potassium from a sodium vanadate-containing solution includes:

[0007] 1) Add sodium sulfate to a sodium vanadate-containing solution to obtain a sulfidated sodium molybdate solution;

[0008] 2) Add ferrous sulfate to the sulfidation solution, and adjust the pH to 7-7.5 when the pH is 5-5.5, until all the ferrous sulfate is added, to obtain a dark green or deep green solution system with a final pH of 7-7.5;

[0009] 3) Add hydrogen peroxide to the solution system obtained in step 2) until the solution becomes colorless, then stop adding hydrogen peroxide, stir the reaction for 0.5 to 1 hour, and filter to obtain a low potassium sodium molybdate solution.

[0010] Preferably, in step 1), the amount of sodium sulfate added is calculated based on 50-60 g / L of sulfate.

[0011] Preferably, in step 2), the amount of ferrous sulfate to be added is calculated according to the molar ratio Fe:K = 3.1 to 3.3 (that is, the number of moles of ferrous ions in the solution is 3.1 to 3.3 times the number of moles of potassium ions), and the ferrous sulfate is added to the sodium molybdate sulfidation solution.

[0012] Preferably, in step 2), sodium hydroxide is added to adjust the pH to 7-7.5 when the pH reaches 5-5.5.

[0013] Preferably, during the addition of ferrous sulfate, the step of adjusting the pH to 7-7.5 is repeated until all the ferrous sulfate has been added.

[0014] Preferably, in step 3), 3μm filter paper is used for vacuum filtration.

[0015] Preferably, in step 3), after filtration, molybdenum-containing potassium iron vanadium is obtained, and the molybdenum-containing potassium iron vanadium is washed with salt water to obtain a low-potassium sodium molybdate solution and potassium iron vanadium.

[0016] More preferably, the potassium ion content in the anhydrous water is ≤10mg / L.

[0017] More preferably, the washing endpoint is defined as a molybdenum ion content in the effluent of <50 mg / L.

[0018] The beneficial effects of this invention are as follows:

[0019] This invention provides a method for removing potassium from a sodium molybdate solution containing vanadium. Sodium sulfide, alkali, and ferrous sulfate are added to the vanadium-containing sodium molybdate solution to maintain the pH within a specific range. After the ferrous sulfate is added, hydrogen peroxide is added for oxidation, causing potassium to precipitate as vanadium ferrophosphate. After filtration, a low-potassium sodium molybdate solution is obtained. The filter cake is washed to obtain vanadium ferrophosphate, and the washing liquid is returned to the low-potassium sodium molybdate solution for reuse. The entire operation is simple, low-cost, and highly efficient in removing potassium, achieving a potassium removal rate of over 90%, with the filter cake containing ≤0.05% molybdenum. Attached Figure Description

[0020] Figure 1 This is a flowchart of the method of the present invention. Detailed Implementation

[0021] To more clearly illustrate the present invention, the invention will be further described in detail below with reference to embodiments and accompanying drawings. Those skilled in the art should understand that the specific description below is illustrative rather than restrictive and should not be construed as limiting the scope of protection of the present invention.

[0022] Combination Figure 1The main process of this invention includes: adding sodium sulfate to a vanadium-containing sodium molybdate solution, adding alkali and ferrous sulfate to maintain the pH of the system within a certain range, adding hydrogen peroxide after the ferrous sulfate is added for oxidation, and precipitating potassium as vanadium ferrophosphate. After filtration, a low-potassium sodium molybdate solution is obtained, the filter cake is washed to obtain vanadium ferrophosphate, and the washing liquid is returned to the low-potassium sodium molybdate solution for reuse.

[0023] Example

[0024] This embodiment mainly includes the following steps:

[0025] 1. Sulfide solution

[0026] Take 1 L of sodium molybdate solution containing vanadium with a K content of 1.5 g / L, add 81 g of sodium sulfate (corresponding to 55 g / L of sulfate ions), stir thoroughly and dissolve to obtain a sulfidated solution of sodium molybdate.

[0027] 2. Adjust pH to precipitate potassium

[0028] According to the molar ratio Fe:K = 3.2, 18.7g of ferrous sulfate was added to the sodium molybdate solution. When the pH reached 5-5.5, sodium hydroxide was added to adjust the pH to 7-7.5. The above steps were repeated until all the ferrous sulfate was added, and the final pH reached 7-7.5.

[0029] After adding ferrous sulfate, the sodium molybdate solution turns dark green or deep green. Add hydrogen peroxide to oxidize it until the sodium molybdate solution becomes colorless. Then stop adding hydrogen peroxide and stir the reaction for 0.5 to 1 hour before proceeding to the next step.

[0030] 3. Filtering

[0031] After potassium precipitation, the molybdic acid solution was filtered using a vacuum filtration flask (using 3μm filter paper). The filter cake was dried under vacuum and then washed with anhydrous saline (10 mg / L K) until the effluent molybdenum concentration was less than 50 mg / L. The solution was then dried under vacuum to obtain a low-potassium sodium molybdate solution (containing 75–150 mg / L K) and vanadium ferrophosphate solid (containing ≤0.05% Mo). The potassium removal rate was 90–95%.

[0032] This application is particularly applicable to sodium vanadate solutions with potassium ion content of 0.5–2 g / L.

[0033] Obviously, the above embodiments of the present invention are merely examples to illustrate the present invention more clearly, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all implementation methods here. Any obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A method for removing potassium from a sodium vanadate-containing solution, comprising: 1) Add sodium sulfate to a sodium vanadate-containing solution to obtain a sodium molybdate sulfide solution. Calculate the amount of sodium sulfate to be added based on a sulfate concentration of 50-60 g / L. 2) Calculate the amount of ferrous sulfate to be added according to the molar ratio Fe:K = 3.1~3.

3. Add ferrous sulfate to the sulfidation solution. When the pH is 5~5.5, add sodium hydroxide to adjust the pH to 7~7.

5. During the process of adding ferrous sulfate, repeat the step of adjusting the pH to 7~7.5 until all the ferrous sulfate is added, and obtain a dark green or dark green solution system with a final pH of 7~7.

5. 3) Add hydrogen peroxide to the solution system obtained in step 2) until the solution becomes colorless, then stop adding hydrogen peroxide and stir the reaction for 0.5~1h. After filtration, a low-potassium sodium molybdate solution is obtained, and molybdenum-containing potassium iron vanadium is also obtained. The molybdenum-containing potassium iron vanadium is washed with salt water to remove molybdenum and obtain a low-potassium sodium molybdate solution and potassium iron vanadium.

2. The method for removing potassium from a vanadium-containing sodium molybdate solution according to claim 1, characterized in that, In step 3), 3μm filter paper is used for vacuum filtration.

3. The method for removing potassium from a sodium vanadium molybdate solution according to claim 1, characterized in that, The potassium ion content in the anhydrous water is ≤10mg / L.

4. The method for removing potassium from a sodium vanadate-containing solution according to claim 1, characterized in that, The washing endpoint was defined as a molybdenum ion content of <50 mg / L in the effluent.

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