Method for producing high-purity vanadium pentoxide by hydrolysis of vanadium precipitation

Abstract

The application relates to a method for producing high-purity vanadium pentoxide by hydrolysis of vanadium precipitation, which comprises the following steps: adding an ammonium salt into a vanadium-containing solution to obtain an ammonia (ammonium) vanadate solution; preparing a sulfuric acid solution with 1-2 times of the theoretical amount of acid required for converting vanadium in the ammonia (ammonium) vanadate solution into polyvanadic acid; adding the ammonia (ammonium) vanadate solution into the sulfuric acid solution to perform a hydrolysis reaction, controlling the temperature of the hydrolysis reaction system, and making the hydrolysis of vanadium always occur in a boiling acid solution environment to reduce or avoid the precipitation of sodium vanadate; stopping the feeding when the pH of the solution is greater than or equal to 0.5, continuing to stir, and then filtering to obtain red vanadium and a hydrolysis solution; and calcining the red vanadium after acid washing to obtain high-purity vanadium pentoxide products, and returning the acid washing solution to be used as the vanadium hydrolysis solution, so that the H + The ion plays a dual role of sodium washing and vanadium precipitation hydrolysis. The process flow is short, the reagent consumption is small, the product quality is good, the operation is simple, the consumption of the ammonium salt in the vanadium precipitation process and the ammonia nitrogen content in the solution after vanadium precipitation can be remarkably reduced, and the method is suitable for the industrial production and application of vanadium pentoxide.

Description

Technical Field

[0001] This invention relates to a method for producing high-purity vanadium pentoxide by hydrolysis and precipitation of vanadium, belonging to the field of chemical and metallurgical technology. Background Technology

[0002] Vanadium pentoxide is a major raw material for the production of vanadium metallurgical and chemical products. Vanadium pentoxide is obtained by the pyrolysis of vanadic acid, polyvanadic acid, ammonium metavanadate, and ammonium polyvanadate. Vanadic acid and polyvanadic acid are obtained by acid hydrolysis of vanadate solutions to precipitate vanadium, while ammonium metavanadate and ammonium polyvanadate are obtained by adding ammonium to vanadate solutions to crystallize and precipitate vanadium.

[0003] High-purity V₂O₅ refers to V₂O₅ products with a purity ≥ 99%. High-purity V₂O₅ is mainly used in vanadium redox flow batteries, aerospace-grade vanadium-aluminum alloys, vanadium-based catalysts, and the preparation of metallic vanadium. In recent years, the preparation of high-purity V₂O₅ has become a hot research topic. The main methods for preparing high-purity V₂O₅ include chemical precipitation purification-multi-stage crystallization, solvent extraction, and ion exchange. These methods all use vanadium-containing liquids, ammonium vanadate, or red vanadium obtained from existing processes as raw materials, and further process and purify them to obtain high-purity V₂O₅.

[0004] When ammonium salts are added to a vanadate solution under weakly alkaline conditions, ammonium metavanadate (NH4VO3) precipitates out. However, when ammonium salts are added under acidic conditions, ammonium polyvanadate ((NH4)2V6O) precipitates out. 16 Ammonium metavanadate and ammonium polyvanadate are then pyrolyzed to obtain vanadium pentoxide with a purity of 97%–99%, and the alkali metal (Na₂O + K₂O) content in the obtained vanadium pentoxide product is ≤1%. The advantage of ammonium salt precipitation of vanadium is the high product quality, but the disadvantage is the generation of a large amount of ammonia nitrogen wastewater during the process. This is because only when the ammonia addition coefficient is ≥1.5 can the alkali metal (Na₂O + K₂O) content in the obtained vanadium pentoxide product be ensured to be ≤1%. The resulting vanadium precipitation solution contains NH₄⁺. 4+ An ion concentration of ≥10g / L places a heavy burden on the ammonia removal process for vanadium precipitation wastewater.

[0005] To avoid the generation of ammonia nitrogen wastewater during vanadium precipitation, the book *Foreign Vanadium Metallurgy* describes a method for vanadium precipitation via acidification and hydrolysis using vanadate solution: First, add 25% vanadate solution to the acidification tank, start stirring, and then add all the sulfuric acid required for vanadium precipitation at once. Continue stirring and heating to boiling. Then, gradually add the remaining 75% vanadate solution to the tank. After the vanadate solution is completely added, take a sample to analyze the free acid in the solution. Based on the analysis results, adjust the pH of the solution to 1.8–2.0 by adding sulfuric acid or vanadate solution. When the supernatant contains V < 0.1 g / L, stop heating and stirring, let it stand for 15–20 minutes, and then filter to obtain red vanadium (red cake) containing polyvanadate. The obtained red cake contains 6.90–8.50% alkali metal (Na₂O + K₂O) in addition to hydrated vanadium pentoxide, and ~0.5% S and ~0.9% Fe. Because under the pH conditions of vanadium precipitation solution, the order of binding ability of vanadate and polyvanadate ions to alkali metal ions is: K... + >NH4 + >Na + >H + >Li + Directly mixing vanadate solution with sulfuric acid solution cannot provide the necessary environment for the precipitation of polyvanadate. The resulting red cake contains sodium polyvanadate throughout, requiring multiple washings with ammonium salt solution to reduce the alkali metal (Na₂O + K₂O) content to ≤1%. This process is cumbersome, consumes large amounts of reagents, and generates significant amounts of acidic waste liquid after vanadium precipitation. Therefore, almost all vanadium pentoxide production enterprises still use the traditional ammonium salt precipitation process. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a simple and convenient method for producing high-purity vanadium pentoxide by hydrolysis and precipitation of vanadium.

[0007] This invention discloses a method for producing high-purity vanadium pentoxide by hydrolysis and vanadium precipitation, comprising the following steps:

[0008] Step 1: Prepare an ammonia (ammonium) vanadate solution: Add ammonium salt to the vanadium-containing solution, and convert the vanadium in the solution into ammonium polyvanadate ((NH4)2V6O). 16 Add 10% to 90% of the required theoretical amount of ammonium salt, stir to dissolve, and set aside.

[0009] Step 2: Preparation of vanadium hydrolysate: Add sulfuric acid to water, and the vanadium in the ammonia (ammonium) vanadate solution prepared in Step 1) is converted into polyvanadate (H2V6O). 16 Add 1 to 2 times the theoretical amount of sulfuric acid; heat the resulting solution to 85 to 115°C for later use.

[0010] Step 3: Add the ammonia (ammonium) vanadate solution prepared in Step 1) dropwise to the hydrolysis solution prepared in Step 2 to carry out the hydrolysis reaction. Control the temperature of the hydrolysis reaction system at 85-115℃, so that the hydrolysis of vanadium always takes place in a boiling acidic solution environment to reduce or avoid the precipitation of sodium vanadate. When the pH of the solution is ≥0.5, stop adding the material, continue stirring for at least 15 minutes, and then filter to obtain red vanadium and the hydrolyzed solution. The obtained red vanadium is acid-washed and then calcined to obtain high-purity vanadium pentoxide product. The acid-washed solution is returned to be used as the hydrolysis solution for vanadium, so that H + The ions play a dual role in the process of washing sodium and hydrolyzing vanadium; the hydrolyzed liquid is further purified to separate and recover the residual vanadium and chromium.

[0011] This invention discloses a method for producing high-purity vanadium pentoxide by hydrolysis and precipitation of vanadium, wherein the vanadium-containing solution refers to an acidic vanadic acid and / or vanadate solution with a concentration of 5-35 g / L; and the pH of the vanadium-containing solution is 4-9.

[0012] This invention discloses a method for producing high-purity vanadium pentoxide by hydrolysis and precipitation of vanadium, wherein the concentration of H2SO4 in the hydrolysate is 0.5–5 mol / L.

[0013] This invention discloses a method for producing high-purity vanadium pentoxide by hydrolysis and precipitation of vanadium. When the hydrolysis reaction reaches a solution pH of 0.5 to 2.5, the feeding is stopped, stirring is continued for 0.25 to 0.5 hours, and the mixture is filtered to obtain red vanadium and the hydrolyzed solution.

[0014] This invention discloses a method for producing high-purity vanadium pentoxide by hydrolysis and precipitation of vanadium. The acid washing refers to adding the obtained red vanadium at a solid-liquid ratio of 1:0.5-10 g / mL to a solution with an H2SO4 concentration of 0.5-5 mol / L, stirring and washing at 65-105℃ for at least 15 minutes, followed by filtration to obtain refined red vanadium and a washing liquid. The refined red vanadium is then calcined at 380-580℃ for 1.5-2.5 hours to obtain the high-purity vanadium pentoxide product. The washing liquid is returned for use as a vanadium hydrolysis solution.

[0015] This invention discloses a method for producing high-purity vanadium pentoxide by hydrolysis and precipitation of vanadium. Red vanadium is stirred and added to an H₂SO₄ solution. After stirring and washing for 0.25–2.5 h, the mixture is filtered to obtain purified red vanadium and a washing solution. The concentration of H₂SO₄ in the washing solution is adjusted to 0.5–5 mol / L, and the concentration of V is ≤10 g / L. This solution is then returned for use as a vanadium hydrolysis solution. + The ions play a dual role in the process of washing sodium and hydrolyzing vanadium.

[0016] This invention discloses a method for producing high-purity vanadium pentoxide by hydrolysis and precipitation of vanadium. The purification treatment of the hydrolysis liquid refers to the process of reducing and neutralizing the hydrolysis liquid to separate and recover the residual V and Cr in the form of vanadium-chromium reduction slag, or adding lead salt to the hydrolysis liquid and stirring to precipitate and enrich the V and Cr.

[0017] This invention discloses a method for producing high-purity vanadium pentoxide by hydrolysis and precipitation of vanadium, wherein the high-purity vanadium pentoxide contains (Na2O+K2O) content ≤1% and V2O5 grade ≥99%; the high-purity vanadium pentoxide product is in powder or block form.

[0018] Compared with existing technologies, the present invention has the following advantages and effects:

[0019] This invention cleverly utilizes the characteristic that the initial acidity of polyvanadate, ammonium polyvanadate, and sodium polyvanadate in solution decreases sequentially upon initial precipitation. First, ammonium salt is added to the vanadate solution to dissolve it. Then, the resulting ammonium-containing vanadate solution is slowly added to a sulfuric acid solution and heated for hydrolysis (85-115℃). This ensures that the hydrolysis process of vanadium always takes place in a boiling acidic solution environment, thereby reducing or avoiding the precipitation of sodium vanadate. The result is a red vanadate precipitate with a polyvanadate core, polyvanadate and ammonium polyvanadate in the middle, and ammonium polyvanadate and sodium polyvanadate on the outermost layer. This also effectively prevents the hydrolysis of impurities such as Fe in the solution. After hydrolysis, the precipitate is filtered to obtain red vanadate containing a small amount of sodium vanadate and NH4+. 4+ The hydrolyzed solution with an ion concentration of only ~1 g / L was then added to a solution of H₂SO₄ with a concentration of 0.5–5 mol / L, and washed with heat and stirring. The H₂SO₄ solution was then used to further refine the vanadium. + Ions will bind Na in red vanadium + Ion displacement is performed, followed by filtration to obtain a washing solution and refined red vanadium. The refined red vanadium is then calcined to obtain high-purity vanadium pentoxide. The acid washing solution is returned for use as a vanadium hydrolysis solution. This process allows H... + The ions play a dual role in the process of sodium washing and vanadium hydrolysis precipitation, while also significantly reducing the consumption of ammonium salts and the ammonia nitrogen content (less than 1.2 g / L) in the vanadium precipitation solution. This invention has advantages such as a short process flow, low reagent consumption, high product quality, simple operation, and economic and environmental friendliness, making it suitable for industrial production of vanadium pentoxide. Detailed Implementation

[0020] The present invention will be further described below with reference to embodiments. These embodiments are intended to illustrate the present invention and not to further limit the present invention.

[0021] Example 1

[0022] Take 94.5 kg of a 1:1 H₂SO₄ solution, add 6 kg of ammonium sulfate to it, stir to dissolve and set aside. Separately, take a solution with pH 9.1 containing 18.45 g / L V, 1.04 g / L Cr, and NH₄⁺. 4+ 1.5m of vanadium slag clinker water leaching purification solution with a concentration of 0.29 g / L 3 The pH was adjusted to 4.5 using a 1:1 H₂SO₄ solution containing ammonium sulfate, and the remaining ammonium sulfate solution was then diluted with water to a concentration of 0.6 mg / L. 3The diluted sulfuric acid solution and the leaching purification solution with a pH of 4.5 were heated to 105℃ and 95℃ respectively. The leaching purification solution was then slowly added dropwise to the diluted sulfuric acid solution to force the vanadium to hydrolyze. The addition was carried out with stirring at 105–100℃, and after 0.75 hours, the mixture was boiled and stirred for another 0.5 hours. The solution was then filtered and washed to obtain 1.89 mg of the hydrolyzed solution with a pH of 1.61. 3 And 96.8 kg of vanadium hydrolysis precipitate filter cake, the hydrolysis solution contained 0.46 g / L V, 0.84 g / L Cr, and NH4+. 4+ 1.05 g / L, the resulting hydrolyzed precipitate filter cake was added to 0.6 mg / L. 3 Add 95 kg of a 1:1 H₂SO₄ solution to water, heat to boiling, stir and wash for 1 hour, filter and wash to obtain 0.67 ml of pickling solution. 3 The acid-washed filter cake was 152.7 kg, and then calcined at 580℃ for 2 h to obtain 42.6 kg of vanadium pentoxide with a purity of 99.02% and a Na2O content of 0.81%.

[0023] Example 2

[0024] Take 0.67 ml of the pickling solution from Example 1. 3 Add 8 kg of ammonium sulfate and dilute with water to approximately 1.2 ml. 3 For later use, separately prepare a solution with pH 9.1 containing 18.45 g / L V, 1.04 g / L Cr, and NH4+. 4+ 1.5m of vanadium slag clinker water leaching purification solution with a concentration of 0.29 g / L 3 The pH of the diluted pickling solution was adjusted to 5.1. The remaining diluted pickling solution and the leaching purification solution (pH 5.1) were then heated to 103°C and 97°C respectively. The leaching purification solution was then slowly added dropwise to the diluted pickling solution to force the vanadium to hydrolyze. The addition was carried out at 103–101°C with stirring. After the addition was completed in 0.5 hours, boiling and stirring continued for another 0.5 hours. The solution was then filtered and washed to obtain 1.83 ml of hydrolyzed solution with a pH of 1.75. 3 And 112.6 kg of vanadium hydrolysis precipitate filter cake, the hydrolysis solution contained 0.38 g / L V, 0.89 g / L Cr, and NH4+. 4+ 1.18 g / L, the resulting hydrolyzed precipitate filter cake was added to 0.8 mg / L. 3 96 kg of a 1:1 H₂SO₄ solution and 4 kg of ammonium sulfate were added to water, heated to boiling, and the mixture was stirred and washed for 0.5 h. After filtration and washing, 0.81 ml of pickling solution was obtained. 3 The pickled filter cake weighed 161.3 kg and was then calcined at 560°C for 2 hours to obtain 48.8 kg of vanadium pentoxide with a purity of 99.15% and a Na2O content of 0.35%.

Claims

1. A method for producing high-purity vanadium pentoxide by hydrolysis of vanadium sulfate, comprising the following steps: Step one, preparation of ammonium vanadate solution: add ammonium salt to vanadium-containing solution, add 10%~90% of the theoretical amount of ammonium salt required to convert vanadium in the solution to ammonium polyvanadate ((NH4)2V6O 16 ), stir and dissolve for standby; the vanadium-containing solution refers to an acidic vanadic acid and / or vanadate solution with a V concentration of 5~35g / L; Step two, preparation of vanadium hydrolysis solution: add sulfuric acid into water, and add 1-2 times of the theoretical amount of sulfuric acid required for the conversion of vanadium in the ammonium vanadate solution prepared in step one into polyvanadic acid (H2V6O 16 ). Step three, the prepared vanadate solution containing ammonium is added dropwise into the prepared hydrolysis solution in step two to carry out hydrolysis reaction, the temperature of the hydrolysis reaction system is controlled at 85-115℃, when the pH of the solution is greater than or equal to 0.5, the feeding is stopped, and the stirring is continued for at least 15 minutes before filtration, to obtain red vanadium and a post-hydrolysis solution, the obtained red vanadium is washed with acid and calcined to obtain high-purity vanadium pentoxide product, the post-washing solution is returned to be used as the hydrolysis solution of vanadium, and the post-hydrolysis solution is further purified to separate and recover the residual vanadium and chromium therein.

2. The method for producing high-purity vanadium pentoxide by hydrolysis and precipitation of vanadium according to claim 1, characterized in that: The pH of the vanadium-containing solution is 4-9.

3. The method for producing high-purity vanadium pentoxide by hydrolysis and precipitation of vanadium according to claim 1, characterized in that: The concentration of H2SO4 in the hydrolysis solution is 0.5-5 mol / L.

4. The method for producing high-purity vanadium pentoxide by hydrolysis and precipitation of vanadium according to claim 1, characterized in that: The hydrolysis reaction is stopped when the pH of the solution is increased to 0.5-2.5, the stirring is continued for 0.25-0.5 h, and then filtration is carried out to obtain red vanadium and a post-hydrolysis solution.

5. The method for producing high-purity vanadium pentoxide by hydrolysis and precipitation of vanadium according to claim 1, characterized in that: The washing with acid refers to that the obtained red vanadium is stirred and added into a solution with a H2SO4 concentration of 0.5-5 mol / L at a solid-liquid ratio of 1:0.5-10 g / mL, the stirring and washing are carried out at 65-105℃ for at least 15 minutes, and then filtration is carried out to obtain refined red vanadium and a post-washing solution, the refined red vanadium is calcined at 380-580℃ for 1.5-2.5 h to obtain high-purity vanadium pentoxide product, and the post-washing solution is returned to be used as the hydrolysis solution of vanadium.

6. The method for producing high-purity vanadium pentoxide by hydrolysis and precipitation of vanadium according to claim 5, characterized in that: The red vanadium is stirred and added into a H2SO4 solution, the stirring and washing are carried out for 0.25-2.5 h, and then filtration is carried out to obtain refined red vanadium and a post-washing solution.

7. The method for producing high-purity vanadium pentoxide by hydrolytic precipitation of vanadium according to claim 6, characterized in that: After the concentration of H2SO4 in the post-washing solution is adjusted to 0.5-5 mol / L and the concentration of V is adjusted to be less than or equal to 10 g / L, the post-washing solution is returned to be used as the hydrolysis solution of vanadium. 8.The method for producing high-purity vanadium pentoxide by hydrolysis and vanadium precipitation according to claim 1, characterized in that: The purification treatment of the post-hydrolysis solution refers to that the post-hydrolysis solution is reduced and neutralized, the residual V and Cr therein are separated and recovered in the form of vanadium-chromium reduction slag, or a lead salt is added into the post-hydrolysis solution, and the V and Cr therein are precipitated and enriched by stirring.

9. The method for producing high-purity vanadium pentoxide by hydrolysis and vanadium precipitation according to any one of claims 1-8, characterized in that: In the high-purity vanadium pentoxide, the content of (Na2O+K2O) is less than or equal to 1%, and the grade of V2O5 is greater than or equal to 99%.