Method for preparing vanadium oxide from high-sodium high-vanadium leaching solution

Abstract

This invention relates to the field of alloy smelting technology, specifically to a method for preparing vanadium oxide from a high-sodium, high-vanadium leaching solution, comprising the following steps: S1. Adjusting the pH of the high-sodium, high-vanadium leaching solution to 8.5–9.5, adding ammonium salt to obtain a vanadium precipitation mixture 1, and performing a primary vanadium precipitation to obtain a primary vanadium precipitation slurry; S2. Adjusting the pH of the primary vanadium precipitation slurry to 1.8–2.2, heating to 90–95°C for a secondary vanadium precipitation to obtain a secondary vanadium precipitation slurry; S3. Separating the secondary vanadium precipitation slurry to obtain an upper layer and ammonium polyvanadate precipitate; S4. Oxidizing and calcining the ammonium polyvanadate precipitate to obtain vanadium oxide. The method of this invention achieves stable control of the vanadium precipitation process without increasing the consumption of ammonium salts and sulfuric acid or the generation of vanadium precipitation wastewater, and reduces the sodium content of the vanadium product.

Description

Technical Field

[0001] This invention relates to the field of alloy smelting technology, specifically to a method for preparing vanadium oxide from a high-sodium, high-vanadium leachate. Background Technology

[0002] The traditional process for producing vanadium oxide from vanadium slag is "sodium roasting of vanadium slag - water leaching - acidic ammonium salt precipitation of vanadium - water treatment," which is also the mainstream process for vanadium oxide production both domestically and internationally. Acidic ammonium salt precipitation of vanadium has advantages such as high vanadium precipitation rate and low ammonium salt usage, which is the main reason for its widespread application. However, its application has certain limitations, mainly manifested in the need to control the vanadium concentration in the precipitation solution to below 35 g / L to ensure the stability and controllability of the acidic ammonium salt precipitation process and the qualified sodium content of the vanadium product. To ensure the normal production of the vanadium precipitation process, some vanadium oxide producers control the solid-liquid ratio of the leaching solution during the leaching process, directly obtaining a leaching solution with a TV of 10–20 g / L; some vanadium oxide producers obtain a high vanadium concentration leaching solution, then dilute it with water to TV–20 g / L before using it for vanadium precipitation; some vanadium oxide producers optimize the vanadium precipitation process and directly use a leaching solution with a TV of 30 g / L for vanadium precipitation, but the sodium content of the vanadium product is significantly higher than that of the vanadium product precipitated with a leaching solution with a TV of 20 g / L. While the above methods enabled normal production of the vanadium precipitation process, the low vanadium concentration in the precipitation solution led to a large volume of vanadium precipitation wastewater, increasing water treatment costs. Appropriately controlling the vanadium concentration at a higher level to reduce vanadium precipitation wastewater resulted in vanadium oxide products with high sodium content, significantly impacting the lifespan of vanadium-nitrogen alloy production equipment. Solving the technical challenge of vanadium precipitation from high-sodium, high-vanadium leaching solutions would help reduce the amount of vanadium precipitation wastewater and lower water treatment costs.

[0003] To address the issue of vanadium precipitation in high-sodium, high-vanadium leaching solutions, patent document CN116715267A, "Method for Preparing Vanadium Oxide from High-Concentration Sodium Vanadium Solution," employs a method of first hydrolyzing vanadium to precipitate sodium vanadate, then using ammonium salts to slurry under acidic conditions to convert the sodium vanadate into ammonium polyvanadate. While this method can yield qualified products, it still suffers from high sodium content in the vanadium product and increased wastewater generation. Patent document CN105603221A, "Method for Precipitating Vanadium from High-Vanadium, High-Sodium Solution," precipitates vanadium by mixing and diluting the high-concentration vanadium solution with water. This method also results in increased vanadium precipitation wastewater generation. Patent document CN106006732A, "Method for Preparing Ammonium Polyvanadate from High-Concentration Vanadium Solution," continuously and slowly adds high-concentration vanadium solution to the upper vanadium precipitate solution, using the upper solution to dilute the high-concentration vanadium solution to precipitate vanadium, thus producing a vanadium product with low sodium content. However, this method suffers from a narrow pH control range for vanadium precipitation and low precipitation efficiency. Patent document CN107119189A, "A method for vanadium precipitation from a high-vanadium, high-chromium, and high-sodium solution," describes a method for vanadium precipitation involving the addition of hydrolysis inhibitors and ammonium salts to a high-vanadium, high-chromium, and high-sodium solution at 40–80°C and pH 3.5–7.5. A second vanadium precipitation is then performed by adjusting the pH of the vanadium precipitation slurry to 1.5–2.5, maintaining the temperature at 90°C, and adding seed crystals for heat preservation. This method yields a vanadium product with a high sodium content, which is detrimental to the subsequent production of vanadium-nitrogen alloys. Patent document CN 106011469A discloses a method for continuous vanadium precipitation from a high-concentration vanadium solution, employing a two-stage vanadium precipitation process. Both vanadium precipitation stages utilize acidic ammonium salt precipitation. The first vanadium precipitation essentially involves diluting the high-concentration vanadium solution with the mother liquor from the acidic ammonium salt precipitation, reducing the vanadium concentration in the solution before the second acidic ammonium salt precipitation. During this process, the sodium concentration of the solution is not diluted. For the sodium vanadate solution acidic ammonium salt precipitation process, the hydrolysis of sodium vanadate into ammonium polyvanadate is unavoidable during the precipitation process. However, the degree of sodium vanadate hydrolysis can be controlled by adjusting the concentration of vanadium and sodium in the solution, and the sodium content of the vanadium product can be adjusted accordingly.

[0004] For vanadium precipitation from high-sodium, high-vanadium leaching solutions, the technical problem of how to stably produce low-sodium vanadium oxide without increasing or minimizing costs needs to be solved. Currently, there are no reports of relevant technologies that can effectively solve the above problems and have prospects for industrial application. Summary of the Invention

[0005] The problem this invention aims to solve is: to address the issues of flocculent precipitation caused by high sodium and vanadium concentrations in acidic ammonium salts during vanadium precipitation of high-sodium, high-vanadium leachates affecting the normal vanadium precipitation process, and the impact of sodium vanadate hydrolysis on the sodium content of vanadium products, without increasing the amount of vanadium ammonium salts used for vanadium precipitation or reducing the vanadium yield. This invention involves first precipitating vanadium in a weakly alkaline environment with a portion or all of the high-sodium, high-vanadium solution to reduce the vanadium concentration in the solution and obtain a vanadium product with extremely low sodium content. Then, another portion of the high-sodium, high-vanadium leachate is mixed with the vanadium slurry from the first vanadium precipitation, which is equivalent to diluting the vanadium concentration of the high-sodium, high-vanadium leachate before a second vanadium precipitation with acidic ammonium salts. After solid-liquid separation and calcination, vanadium oxide is obtained.

[0006] The technical solution adopted in this invention is as follows:

[0007] The first aspect of this invention provides a method for preparing vanadium oxide from a high-sodium, high-vanadium leachate, the method comprising the following steps: S1. Adjusting the pH of the high-sodium, high-vanadium leachate to 8.5–9.5, adding ammonium salt to obtain a vanadium precipitation mixture 1, and performing a first vanadium precipitation to obtain a first vanadium precipitation slurry; S2. Adjusting the pH of the first vanadium precipitation slurry to 1.8–2.2, heating to 90–95°C for a second vanadium precipitation to obtain a second vanadium precipitation slurry; S3. Separating the second vanadium precipitation slurry to obtain an upper layer and vanadium precipitate; S4. Oxidizing and calcining the vanadium precipitate to obtain vanadium oxide.

[0008] Furthermore, step S2 also includes: mixing the primary vanadium precipitation slurry with a high-sodium, high-vanadium leaching solution, adjusting the pH of the mixture to 1.8–2.2, and heating it to 90–95°C for secondary vanadium precipitation to obtain a secondary vanadium precipitation slurry.

[0009] Furthermore, in step S2, the high-sodium, high-vanadium leaching solution is mixed with the primary vanadium precipitation slurry at a volume ratio of 0:10 to 5:5, the pH of the mixture is adjusted to 1.8 to 2.2, and then heated to 90 to 95°C to precipitate vanadium, thereby obtaining a secondary vanadium precipitation slurry.

[0010] Furthermore, the sodium concentration in the high-sodium, high-vanadium leachate is selected from 35 to 50 g / L, and the total vanadium concentration is selected from 35 to 50 g / L.

[0011] Furthermore, when the ammonium salt in step S1 is an acidic ammonium salt, and when the acidic ammonium salt is selected from ammonium sulfate, ammonium sulfate is added at a mass ratio of ammonium sulfate / total vanadium = 1.2 to 2.4 to perform a vanadium precipitation.

[0012] Furthermore, in step S1, the primary vanadium precipitation temperature is selected from 30 to 60°C.

[0013] Furthermore, in step S1, the vanadium precipitation time is 40–120 min.

[0014] Furthermore, after heating to 90-95°C in step S2, the reaction is carried out at a constant temperature for 40-60 minutes.

[0015] Furthermore, in step S2, the vanadium concentration after mixing the primary vanadium slurry with the high-sodium, high-vanadium leaching solution is less than 25 g / L.

[0016] Furthermore, the primary vanadium precipitation slurry comprises solution 1 and precipitate 1, wherein the vanadium concentration in solution 1 is 1.3 to 15 g / L.

[0017] Furthermore, both S1 and S2 are adjusted using sulfuric acid.

[0018] The beneficial effects of this invention are:

[0019] This invention employs a two-stage vanadium precipitation design in the high-sodium, high-vanadium leaching process. First, a portion of the vanadium in the high-sodium, high-vanadium leaching solution is precipitated, addressing the issues of flocculent precipitation caused by high sodium and vanadium concentrations affecting the normal vanadium precipitation process and sodium vanadate hydrolysis impacting the sodium content of the vanadium product. This reduces the vanadium concentration in the solution and yields a vanadium product with extremely low sodium content. Then, another portion of the high-sodium, high-vanadium leaching solution is mixed with the primary vanadium precipitation slurry, effectively diluting the vanadium concentration of the high-sodium, high-vanadium leaching solution before acidic ammonium salt precipitation. This ensures the stability of the vanadium precipitation process and the vanadium precipitation rate. Compared to existing technologies, this invention achieves stable control of the vanadium precipitation process without increasing the consumption of ammonium salts and sulfuric acid or the generation of vanadium precipitation wastewater, while also reducing the sodium content of the vanadium product.

[0020] Specifically:

[0021] (1) The present invention uses weakly basic ammonium salt to precipitate vanadium in a primary precipitation process. The precipitated product is ammonium metavanadate, which avoids the hydrolysis problem of sodium vanadate in the primary precipitation process and the obtained vanadium product has extremely low sodium content.

[0022] (2) The secondary vanadium precipitation of the present invention is acidic ammonium salt precipitation, with low initial vanadium concentration, which provides a guarantee for stable control of the vanadium precipitation process and high vanadium precipitation rate. Correspondingly, the total amount of sodium vanadate hydrolyzed into the ammonium polyvanadate product is reduced, and the sodium content of the final vanadium product is reduced. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to specific examples.

[0024] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0025] Unless otherwise defined, all scientific and technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art.

[0026] In this invention, the term "TV" refers to the total vanadium content.

[0027] In this invention, the term "high sodium and high vanadium leachate" refers to a leachate with a sodium content of 20 g / L or higher and a vanadium content of 20 g / L or higher.

[0028] Unless otherwise specified, all percentages in this invention are expressed as mass percentages.

[0029] One or more embodiments of the present invention will now be described in detail.

[0030] In some embodiments of the present invention, the following steps are adopted: S1. Adjust the pH of the high-sodium, high-vanadium leaching solution to 8.5-9.5, add ammonium salt to obtain vanadium precipitation mixture 1, and perform primary vanadium precipitation to obtain primary vanadium precipitation slurry; S2. Adjust the pH of the primary vanadium precipitation slurry to 1.8-2.2, heat to 90-95°C for secondary vanadium precipitation to obtain secondary vanadium precipitation slurry; S3. Separate the secondary vanadium precipitation slurry to obtain the supernatant and vanadium precipitate; S4. Oxidize and calcine the vanadium precipitate to obtain vanadium oxide.

[0031] The vanadium oxide is selected from vanadium pentoxide.

[0032] This invention first precipitates vanadium in a portion of the high-sodium, high-vanadium leachate under weakly alkaline conditions to reduce the vanadium concentration in the solution and obtain a vanadium product with extremely low sodium content. Then, a second vanadium precipitation operation is performed to avoid flocculent precipitation caused by high sodium and vanadium concentrations in the acidic ammonium salt precipitation of the high-sodium, high-vanadium leachate. This is to solve the problem of sodium vanadate hydrolysis during the vanadium precipitation process of the high-sodium, high-vanadium leachate, and at the same time make the vanadium precipitation process stable and controllable.

[0033] Furthermore, the S1 pH includes, but is not limited to, 8.5, 8.6, 8.7, 8.8, 8.9, 9.0, 9.1, 9.2, 9.3, 9.4, or 9.5.

[0034] Furthermore, the S2 pH includes, but is not limited to, 1.8, 1.9, 2.0, 2.1 or 2.2.

[0035] In some embodiments of the present invention, based on the above embodiments, step S2 further includes: mixing the primary vanadium precipitation slurry with a high-sodium, high-vanadium leaching solution, adjusting the pH of the mixture to 1.8–2.2, and heating to 90–95°C for secondary vanadium precipitation to obtain a secondary vanadium precipitation slurry.

[0036] Since the sodium and vanadium concentrations in high-sodium, high-vanadium leachate do not affect the ammonium metavanadate precipitation process during vanadium precipitation, a partial or complete precipitation with high-sodium, high-vanadium leachate is first performed to precipitate ammonium metavanadate. Then, the supernatant is used to dilute the remaining high-sodium, high-vanadium leachate, reducing the vanadium concentration in the high-sodium, high-vanadium leachate and creating conditions for stable control of the acidic ammonium salt precipitation process. At the same time, the sodium content of the precipitated ammonium metavanadate is extremely low, and after mixing with the ammonium polyvanadate precipitate, the sodium content of the vanadium product can be further diluted and reduced. This is equivalent to diluting the vanadium concentration of the high-sodium, high-vanadium leachate before acidic ammonium salt precipitation, ensuring the stability of the vanadium precipitation process and the vanadium precipitation rate.

[0037] Furthermore, in step S2, the high-sodium, high-vanadium leaching solution is mixed with the primary vanadium precipitation slurry at a volume ratio of 0:10 to 5:5, the pH of the mixture is adjusted to 1.8 to 2.2, and then heated to 90 to 95°C to precipitate vanadium, thereby obtaining a secondary vanadium precipitation slurry.

[0038] In some embodiments of the present invention, based on the above embodiments, the sodium concentration in the high-sodium, high-vanadium leachate is selected from 35 to 50 g / L, including but not limited to 35 g / L, 40 g / L, 45 g / L or 50 g / L; the total vanadium concentration is selected from 35 to 50 g / L, including but not limited to 35 g / L, 40 g / L, 45 g / L or 50 g / L.

[0039] In this invention, the leachate obtained from the water leaching of vanadium from the sodium-roasted vanadium slag clinker during the production process, namely the high-sodium, high-vanadium leachate of this invention, generally has sodium and vanadium concentrations below 50 g / L. If the sodium and vanadium concentrations in the leachate are too high, it will affect the filtration performance of the leachate slurry produced by the water leaching of the sodium-roasted vanadium slag clinker and the residue washing effect. If the vanadium concentration in the high-sodium, high-vanadium leachate is too low, it will increase the amount of vanadium precipitation wastewater generated and the wastewater treatment cost, thereby increasing the production cost of vanadium oxide.

[0040] In some embodiments of the present invention, based on the above embodiments, the S1 ammonium salt is an acidic ammonium salt. When the acidic ammonium salt is selected from ammonium sulfate, in step S1, ammonium sulfate is added at a mass ratio of ammonium sulfate / total vanadium = 1.2 to 2.4 to perform a vanadium precipitation.

[0041] In this invention, the amount of ammonium salt added during the primary vanadium precipitation is controlled according to a mass ratio of ammonium sulfate / total vanadium of 1.2 to 2.4. This mass ratio includes, but is not limited to, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, or 2.4. On the one hand, adding ammonium salt within this range can control the vanadium precipitation rate of ammonium metavanadate to above 60%, achieving the goal of reducing the vanadium concentration in the vanadium precipitation solution; on the other hand, it achieves the effect of not increasing the amount of ammonium salt used in the vanadium precipitation process.

[0042] In some embodiments of the present invention, based on the above embodiments, in step S1, the primary vanadium precipitation temperature is selected from 30 to 60°C, for example, the temperature can be 30°C, 35°C, 40°C, 45°C, 50°C, 55°C or 60°C.

[0043] In this invention, the vanadium precipitation temperature is selected as 30-60℃ because the temperature of the vanadium precipitation solution used in industrial production is generally about 60℃. When precipitating ammonium metavanadate, a lower vanadium precipitation temperature is beneficial to increasing the vanadium precipitation rate and reducing the vanadium concentration in the upper layer of the solution.

[0044] In some embodiments of the present invention, based on the above embodiments, in step S1, the vanadium precipitation time is 40 to 120 minutes, including but not limited to 40 minutes, 45 minutes, 50 minutes, 55 minutes, 60 minutes, 65 minutes, 70 minutes, 75 minutes, 80 minutes, 85 minutes, 90 minutes, 95 minutes, 100 minutes, 110 minutes, or 120 minutes.

[0045] In this invention, the vanadium precipitation time of 40-120 min is selected to control the vanadium concentration in the upper layer of the vanadium precipitation solution. In this invention, a larger amount of ammonium salt is added, the vanadium precipitation speed is faster, and the time is correspondingly shorter; a smaller amount of ammonium salt is added, the vanadium precipitation speed is relatively slower, and the required vanadium precipitation time is longer.

[0046] In some embodiments of the present invention, based on the above embodiments, the S2 step is heated to 90-95°C and then reacted at a constant temperature for 40-60 minutes. The precipitation temperature and time of the secondary vanadium ammonium salt precipitation in the S2 step of the present invention are standard operating procedures for vanadium precipitation, but other more suitable parameters may also be used.

[0047] In some embodiments of the present invention, based on the above embodiments, the vanadium concentration after mixing the primary vanadium precipitation slurry and the high-sodium, high-vanadium leaching solution in step S2 is less than 25 g / L, that is, the initial vanadium concentration of the secondary vanadium precipitation in step S2 is less than 25 g / L.

[0048] The purpose of controlling the initial vanadium concentration of the vanadium precipitation solution in step S2 to be less than 25 g / L in this invention is that, since the initial vanadium concentration of the S2 vanadium precipitation solution is much lower than that of the high sodium and high vanadium leaching solution, the nucleation rate of the initial reaction of acidic ammonium salt vanadium precipitation is slower, the generation of short-chain crystals (forming flocculents) and the reduction of sodium vanadate hydrolysis products are reduced, making the vanadium precipitation process stable and controllable.

[0049] In some embodiments of the present invention, based on the above embodiments, the primary vanadium precipitation slurry includes solution 1 and precipitate 1, wherein the vanadium concentration in solution 1 is 1.3–15 g / L. This is to control the vanadium concentration, which is more conducive to secondary vanadium precipitation.

[0050] Furthermore, both S1 and S2 are adjusted using sulfuric acid.

[0051] The purpose of using sulfuric acid to adjust pH in this invention is that sulfuric acid is inexpensive, readily available, and easy to store, while also allowing for precise pH adjustment of the system.

[0052] The specific embodiments of the present invention will be further described below with reference to specific examples, but the present invention is not limited to the scope of the examples described herein.

[0053] Example 1

[0054] Take 800 mL of high-sodium, high-vanadium leachate (TV 39.42 g / L, Na 35.51 g / L), adjust the pH to 8.8 with sulfuric acid, maintain the temperature at 40℃ in a water bath, add 37.84 g of ammonium sulfate (mass ratio of ammonium sulfate / total vanadium = 1.2) to obtain vanadium precipitation mixture 1, stir the vanadium precipitation mixture 1 and react for 120 min to carry out the first vanadium precipitation; after the first vanadium precipitation is completed, the first vanadium precipitation slurry is obtained (wherein, the vanadium concentration of the supernatant of the first vanadium precipitation slurry is 13.75 g / L); adjust the pH of the first vanadium precipitation slurry to 1.8-2.2 with sulfuric acid, heat to 95℃ in a water bath, stir and react for 40 min to carry out the second vanadium precipitation. After the vanadium precipitation reaction was completed, a supernatant and vanadium precipitate were obtained. The solid and liquid were separated and the vanadium precipitate was washed to obtain 872 mL of supernatant. The TV in the supernatant was 0.28 g / L and the vanadium precipitation rate was 99.23%. The vanadium precipitate was oxidized and calcined to prepare vanadium pentoxide, which contained 99.26% V2O5 and 0.13% Na2O.

[0055] Example 2

[0056] Take 600 mL of high-sodium, high-vanadium leachate (TV 44.73 g / L, Na 42.18 g / L), adjust the pH to 9.0 with sulfuric acid, maintain the temperature at 30℃ in a water bath, add 53.68 g of ammonium sulfate (mass ratio of ammonium sulfate / total vanadium = 2) to obtain vanadium precipitation mixture 1. Stir vanadium precipitation mixture 1 and react for 60 min to perform the first vanadium precipitation. After the first vanadium precipitation, obtain the first vanadium precipitation slurry (wherein, the vanadium concentration of the supernatant of the first vanadium precipitation slurry is 4.17 g / L). Add 400 mL of high-sodium, high-vanadium leachate (TV 44.73 g / L, Na 42.18 g / L, at this time the vanadium concentration of the first vanadium precipitation slurry and the high-sodium, high-vanadium leachate mixture is about 20.39 g / L) to the first vanadium precipitation slurry, adjust the pH of the first vanadium precipitation slurry to 1.8-2.2 with sulfuric acid, heat to 95℃ in a water bath, stir and react for 50 min to perform the second vanadium precipitation. After the vanadium precipitation reaction was completed, a supernatant and vanadium precipitate were obtained. The solid and liquid were separated and the vanadium precipitate was washed to obtain 1120 mL of supernatant with a TV of 0.34 g / L and a vanadium precipitation rate of 99.15%. The vanadium precipitate was oxidized and calcined to prepare vanadium pentoxide, which contained 99.32% V2O5 and 0.17% Na2O.

[0057] Example 3

[0058] Take 500 mL of high-sodium, high-vanadium leachate (TV 48.22 g / L, Na 44.17 g / L), adjust the pH to 9.0 with sulfuric acid, maintain the temperature at 50℃ in a water bath, add 57.86 g of ammonium sulfate (mass ratio of ammonium sulfate / total vanadium = 2.4) to obtain vanadium precipitation mixture 1, stir the vanadium precipitation mixture 1 and react for 40 min to carry out the first vanadium precipitation; after the first vanadium precipitation, obtain the first vanadium precipitation slurry (wherein, the vanadium concentration of the supernatant of the first vanadium precipitation slurry is 1.33 g / L), add 500 mL of high-sodium, high-vanadium leachate (TV 48.22 g / L, Na 44.17 g / L, at this time the vanadium concentration of the first vanadium precipitation slurry and the high-sodium, high-vanadium leachate mixture is about 24.78 g / L), adjust the pH of the first vanadium precipitation slurry to 1.8-2.2 with sulfuric acid, heat to 95℃ in a water bath, stir and react for 50 min to carry out the second vanadium precipitation. After the vanadium precipitation reaction was completed, a supernatant and vanadium precipitate were obtained. The solid and liquid were separated and the vanadium precipitate was washed to obtain 1136 mL of supernatant with a TV of 0.35 g / L and a vanadium precipitation rate of 99.18%. The vanadium precipitate was oxidized and calcined to prepare vanadium pentoxide, which contained 99.22% V2O5 and 0.19% Na2O.

[0059] Comparative Example 1

[0060] Take 800 mL of high-sodium, high-vanadium leachate (TV 39.42 g / L, Na 35.51 g / L), adjust the pH to 8.8 with sulfuric acid, maintain a constant temperature of 40℃ in a water bath, add 37.84 g of ammonium sulfate (mass ratio of ammonium sulfate / total vanadium = 1.2), stir and react for 120 min to precipitate vanadium once. After the first precipitation, separate the solid and liquid to obtain a vanadium supernatant and a vanadium precipitate. The vanadium concentration of the vanadium supernatant is 13.75 g / L, and the precipitation rate is 65.12%. The vanadium precipitate is oxidized and calcined to prepare vanadium pentoxide, which contains 99.58% V₂O₅ and 0.03% Na₂O.

[0061] Comparative Example 2

[0062] Take 800 mL of high-sodium, high-vanadium leachate (TV 39.42 g / L, Na 35.51 g / L), adjust the pH to 1.82 with sulfuric acid, add 37.84 g of ammonium sulfate (mass ratio of ammonium sulfate / total vanadium = 1.2), heat in a water bath and maintain a constant temperature of 95 °C with stirring for vanadium precipitation reaction for 60 min; after vanadium precipitation, solid-liquid separation is performed to obtain vanadium supernatant and vanadium precipitate. The vanadium concentration of the vanadium supernatant is 0.35 g / L, and the vanadium precipitation rate is 99.11%. The vanadium precipitate is oxidized and calcined to prepare vanadium pentoxide, of which V₂O₅ is 98.07% and Na₂O is 1.58%.

[0063] Comparative Example 3

[0064] Take 500 mL of high-sodium, high-vanadium leachate (TV 48.22 g / L, Na 44.17 g / L), adjust the pH to 1.90 with sulfuric acid, add 28.93 g of ammonium sulfate (mass ratio of ammonium sulfate / total vanadium = 1.2), heat in a water bath and maintain a constant temperature of 95°C while stirring to precipitate vanadium. When the temperature of the vanadium precipitate rises above 80°C, a large amount of flocculent precipitate begins to appear. After stirring at 95°C for 5–10 minutes, it becomes a paste-like consistency and cannot be stirred normally. Separate the precipitate slurry from the solid to the liquid. The vanadium precipitate is large in volume (commonly known as "bubbly vanadium") and has a high water content. After washing, the vanadium precipitate is calcined to prepare vanadium pentoxide, containing 92.49% V₂O₅ and 4.54% Na₂O.

[0065] In summary, the method for preparing vanadium oxide from high-sodium, high-vanadium leachate of the present invention can first perform a vanadium precipitation under weakly alkaline conditions on a portion of the high-sodium, high-vanadium leachate to reduce the vanadium concentration in the solution and obtain a vanadium product with extremely low sodium content. Then, a second vanadium precipitation operation is performed, which can make the vanadium precipitation rate of the high-sodium, high-vanadium leachate greater than 99%, while ensuring that the mass fraction of V2O5 in the vanadium pentoxide prepared by oxidative calcination of the vanadium precipitate is greater than 98%, and at the same time reduce the sodium content. As calculated by Na2O, the sodium content in the vanadium pentoxide prepared by the present invention can be reduced to below 0.2%.

[0066] This invention document is intended to illustrate how to use the disclosed techniques and various embodiments, and is not intended to limit its true scope and equivalent spirit. Furthermore, the foregoing description is not exhaustive of all possibilities or to limit the scope of protection to the precise forms disclosed. Changes and variations are possible in accordance with the foregoing teachings. The selected and illustrated embodiments provide the best illustration of the principles of the technology and its practical application, and enable those skilled in the art to use the disclosed technology for various conceivable specific applications with various modifications. Therefore, various changes and modifications made to the above embodiments without substantially departing from the spirit and principles of the technology described herein are intended to be included within the scope of this invention.

Claims

1. A method for preparing vanadium oxide from a high-sodium, high-vanadium leachate, characterized in that, The method includes the following steps: S1. Take a high-sodium, high-vanadium leachate, adjust the pH of the high-sodium, high-vanadium leachate to 8.5-9.5, add ammonium salt to obtain vanadium precipitation mixture 1, and perform primary vanadium precipitation to obtain primary vanadium precipitation slurry; S2. Mix the high-sodium, high-vanadium leachate with the primary vanadium precipitation slurry at a volume ratio of 0:10-5:5, adjust the pH of the mixture to 1.8-2.2, heat to 90-95℃ to precipitate vanadium, and obtain secondary vanadium precipitation slurry; S3. Separate the secondary vanadium precipitation slurry to obtain the supernatant and vanadium precipitate; S4. Oxidize and calcine the vanadium precipitate to obtain vanadium oxide; In step S1, the ammonium salt is ammonium sulfate, which is added at a mass ratio of ammonium sulfate / total vanadium = 1.2~2.4 for primary vanadium precipitation. The primary vanadium precipitation slurry includes solution 1 and precipitate 1, wherein the vanadium concentration in solution 1 is 1.3~15 g / L, the sodium concentration in the high-sodium high-vanadium leaching solution is 35~50 g / L, and the total vanadium concentration is 35~50 g / L. In step S1, the primary vanadium precipitation temperature is 30~60℃. In step S2, the vanadium concentration after mixing the primary vanadium precipitation slurry with the high-sodium high-vanadium leaching solution is less than 25 g / L.

2. The method as described in claim 1, characterized in that, In step S1, the vanadium precipitation time is 40~120 minutes.

3. The method as described in claim 1, characterized in that, After heating to 90-95°C in step S2, the reaction is carried out at a constant temperature for 40-60 minutes.

4. The method as described in claim 1, characterized in that, The pH adjustment in both steps S1 and S2 is performed using sulfuric acid.