A method for preparing potassium metavanadate

Abstract

The application discloses a method for preparing potassium metavanadate, and belongs to the field of vanadium chemical industry. The method comprises the following steps: dissolving potassium hydroxide in water or filtering return liquid by stirring to obtain solution L1; adding vanadium pentoxide into the solution L1, and stirring to dissolve the vanadium pentoxide to obtain solution L2; adjusting the pH value of the solution L2, and filtering after heat preservation and stirring to obtain filtrate L3; adding potassium metavanadate into the filtrate L3 to obtain solution L4, and stirring and standing to crystallize; obtaining crystals C and filtrate L5; and drying the crystals C to obtain potassium metavanadate. The method has high recovery rate, no wastewater is generated, and high-purity potassium metavanadate is obtained.

Description

Technical Field

[0001] This invention relates to the field of vanadium chemistry, and more particularly to a method for preparing potassium metavanadate. Background Technology

[0002] Potassium metavanadate is mainly used as a catalyst, mordant, and analytical reagent, and is an important fine chemical product of vanadium.

[0003] Patent CN201510626272.7 discloses a method for preparing potassium metavanadate. The method includes the following steps: a) according to the molar ratio VO3... - :K + The method involves: a) Adding ammonium metavanadate to water in a ratio of 1:1.01–1.05, along with potassium carbonate, potassium bicarbonate, or potassium hydroxide, to obtain a solution with a potassium ion concentration of 1.75–2.53 mol / L. The solution is then microwaved to 25–70°C while simultaneously undergoing a vacuum deammoniation reaction for 15–30 minutes. b) The deammoniation solution from step a is stirred and evaporated to crystallize. When the crystals occupy 1 / 3–1 / 2 of the solution volume, 1 / 2–1 volume of ethanol is added to precipitate the solid. c) The solid-liquid mixture obtained in step b is filtered and washed 2–3 times with ethanol to obtain solid potassium metavanadate. This solid is then vacuum dried at 50–70°C for 4–8 hours to obtain potassium metavanadate. This method uses ammonium metavanadate as raw material, generates wastewater during the preparation process, has a low recovery rate, and produces potassium metavanadate with low purity.

[0004] Therefore, the existing methods for preparing potassium metavanadate need to be improved. Summary of the Invention

[0005] To address the above problems, this invention provides a method for preparing potassium metavanadate.

[0006] According to one aspect of the present invention, a method for preparing potassium metavanadate is provided, comprising the following steps:

[0007] Step S1: Dissolve potassium hydroxide in water or by stirring in the filtered liquid to obtain solution L1;

[0008] Step S2: Add vanadium pentoxide to the solution L1, heat and stir to dissolve the vanadium pentoxide, and obtain solution L2;

[0009] Step S3: Adjust the pH value of solution L2, keep it warm and stir, then filter to obtain filtrate L3;

[0010] Step S4: Add potassium metavanadate to filtrate L3, stir and let it stand to crystallize, and obtain solution L4;

[0011] Step S5: Filter solution L4 to obtain crystals C and filtrate L5;

[0012] Step S6: Dry crystal C to obtain potassium metavanadate.

[0013] According to one embodiment of the present invention, in step S1, the purity of potassium hydroxide is above 96%, and the mass-to-volume ratio of potassium hydroxide to water or filtrate return liquid is 35-40 g: 100 ml.

[0014] According to one embodiment of the present invention, in step S2, the purity of vanadium pentoxide is ≥95%, and the mass ratio of the amount of vanadium pentoxide added to the mass of potassium hydroxide in solution L1 is 2.5 to 3:1.

[0015] According to one embodiment of the present invention, in step S2, the temperature is raised to 60-80°C and the stirring time is 30-60 min.

[0016] According to one embodiment of the present invention, potassium hydroxide is used in step S3 to adjust the pH value to pH = 8.0-9.

[0017] According to one embodiment of the present invention, the heat preservation temperature in step S3 is 60-80°C and the stirring time is 30-40 min.

[0018] According to one embodiment of the present invention, in step S4, the amount of potassium metavanadate is 0.2 to 1.5 g added to 100 ml of filtrate.

[0019] According to one embodiment of the present invention, the stirring speed in step S4 is 20-50 r / min, and the stirring time is 40-60 min.

[0020] According to one embodiment of the present invention, the settling time in step S4 is more than 24 hours.

[0021] According to one embodiment of the present invention, the method further includes recycling the filtrate L5 obtained in step S5 as the filtrate return liquid in step S1.

[0022] By adopting the above technical solutions, the method for preparing potassium metavanadate provided by the present invention has the following advantages compared with the prior art: the method has a high recovery rate, produces no wastewater, and yields potassium metavanadate with high purity. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0024] This invention provides a method for preparing potassium metavanadate, comprising the following steps:

[0025] Step S1: Dissolve potassium hydroxide in water or by stirring in the filtered liquid to obtain solution L1;

[0026] Step S2: Add vanadium pentoxide to solution L1, heat and stir to dissolve vanadium pentoxide, and obtain solution L2;

[0027] Step S3: Adjust the pH value of solution L2, keep it warm and stir, then filter to obtain filtrate L3;

[0028] Step S4: Add potassium metavanadate to filtrate L3, stir and let it stand to crystallize, and obtain solution L4;

[0029] Step S5: Filter solution L4 to obtain crystals C and filtrate L5;

[0030] Step S6: Dry crystal C to obtain potassium metavanadate.

[0031] This method uses vanadium pentoxide as raw material and potassium hydroxide as reagent. Vanadium pentoxide is used in excess, resulting in high recovery rate, no wastewater generation, and high purity potassium metavanadate.

[0032] The following provides a detailed explanation of each operational step using examples.

[0033] In step S1, potassium hydroxide is dissolved in water or by stirring to obtain solution L1. The potassium hydroxide has a purity of 96% or higher, and the mass-to-volume ratio of potassium hydroxide to water or by filtered liquid is 35-40 g: 100 ml. High-purity potassium hydroxide is used to reduce impurities in the product. The filtered liquid can be the filtrate obtained after filtering crystals in the previous preparation process, allowing for the recycling of the filtrate, saving resources and reducing water treatment costs.

[0034] In step S2, vanadium pentoxide is added to solution L1, and the mixture is heated and stirred to dissolve the vanadium pentoxide, yielding solution L2. The vanadium pentoxide purity is ≥95%. Using high-purity vanadium pentoxide reduces impurities in the product. The mass ratio of vanadium pentoxide added to potassium hydroxide in solution L1 is 2.5–3:1, with a relative excess of vanadium pentoxide to ensure maximum dissolution and efficient utilization. The excess vanadium pentoxide first forms potassium polyvanadate, which is then adjusted to a specific pH value with potassium hydroxide and converted into potassium metavanadate, resulting in efficient utilization and high preparation efficiency. The temperature is raised to 60–80°C, and the stirring time is 30–60 minutes.

[0035] In step S3, the pH of solution L2 is adjusted, and after incubation and stirring, it is filtered to obtain filtrate L3. Potassium hydroxide is used to adjust the pH of solution L2 to 8.0–9. The incubation temperature is 60–80°C, and the stirring time is 30–40 minutes. During this period, potassium polyvanadate, formed by vanadium pentoxide and potassium hydroxide under acidic conditions, slowly transforms into potassium metavanadate solution under the action of pH adjustment with potassium hydroxide, incubation, and stirring. Filtration removes excess vanadium pentoxide or entrained insoluble low-valence vanadium, ensuring the purity of the crystals. Maintaining the pH at 8.0–9 ensures the formation of potassium metavanadate, but further increasing the pH may lead to the formation of potassium orthovanadate or high water content in the crystals.

[0036] In step S4, potassium metavanadate is added to filtrate L3, stirred, and allowed to stand to crystallize, yielding solution L4. The amount of potassium metavanadate added is 0.2–1.5 g per 100 ml of filtrate, serving as a seed crystal. Stirring and allowing the solution to stand promotes the continuous crystal growth of potassium metavanadate, increasing its yield. Adding seed crystals also accelerates the crystallization rate and shortens the crystallization time. Therefore, the stirring speed is set to 20–50 r / min, and the stirring time is 40–60 min. Excessive stirring speed will generate a large number of potassium metavanadate nuclei, resulting in small-sized potassium metavanadate crystals and a low recovery rate. The standing time should be at least 24 hours.

[0037] In step S5, solution L4 is filtered to obtain crystals C and filtrate L5. Filtrate L5 can be recycled as the filtrate return liquid from step S1.

[0038] In step S6, crystal C is dried to obtain potassium metavanadate.

[0039] The following describes specific embodiments of the method for preparing potassium metavanadate according to the present invention. Unless otherwise stated, all contents mentioned below are mass percentages. Table 1 shows relevant information about the raw materials used in the following embodiments.

[0040] Table 1 Information on raw materials used in the embodiments.

[0041]

[0042] Example 1

[0043] First, weigh 70g of analytical grade potassium hydroxide and add 200ml of water to prepare a 35% aqueous solution. Then, add 175g of vanadium pentoxide at a mass ratio of 2.5-3:1 (vanadium pentoxide to potassium hydroxide). Stir and heat to 60-80℃, continuing stirring for 30-60 minutes. Measure the pH value to 7.5, and adjust the pH to 8.0-9.0 with potassium hydroxide. Continue stirring and maintaining the temperature for 30-40 minutes. Filter to obtain 196ml of filtrate. Add 0.2g of potassium metavanadate to 100ml of filtrate, then add 0.40g of potassium metavanadate. Stir at 20r / min for 40 minutes, let stand for 24 hours, and crystals will precipitate. Dry to obtain 162.15g of high-purity potassium metavanadate. Return the filtrate to the aqueous solvent of the first step for recycling. Analysis shows that the prepared potassium metavanadate contains 99.97% potassium metavanadate.

[0044] Weigh out 70g of potassium hydroxide. Return the filtrate to the container and add water to make a 35% aqueous solution (200ml). Add 175g of vanadium pentoxide (vanadium pentoxide to potassium hydroxide) at a ratio of 2.5–3:1. Stir and heat to 60–80℃, continuing stirring for 30–60 minutes. The pH is measured to be 7.5. Adjust the pH to 8.0–9.0 with potassium hydroxide, and continue stirring for another 30–40 minutes. Filter to obtain 197ml of filtrate. Add 0.2g of potassium metavanadate (0.40g) to 100ml of filtrate, stirring at 20 rpm for 40 minutes. Let stand for 24 hours to precipitate crystals. Dry to obtain 173.4g of high-purity potassium metavanadate. Return the filtrate to the aqueous solution used in the first step for recycling. Testing shows that the potassium metavanadate contains 99.98% potassium metavanadate.

[0045] Example 2

[0046] First, weigh 76g of analytical grade potassium hydroxide and add 200ml of water to prepare a 38% aqueous solution. Then, add 212.8g of vanadium pentoxide at a ratio of 2.5-2.8:1 (vanadium pentoxide to potassium hydroxide). Stir and heat to 60-80℃, continuing stirring for 30-60 minutes. Measure the pH to 7.0, and adjust the pH to 8.0-8.5 with potassium hydroxide. Continue stirring and maintaining the temperature for 30-40 minutes. Filter to obtain 194ml of filtrate. Add 1g of potassium metavanadate to 100ml of filtrate, then add 1.94g of potassium metavanadate. Stir at 40 rpm for 50 minutes, let stand for 24 hours, and crystals will precipitate. Dry to obtain 176.04g of high-purity potassium metavanadate. Return the filtrate to the aqueous solvent of the first step for recycling. Analysis shows that the prepared potassium metavanadate contains 99.97% potassium metavanadate.

[0047] Weigh out 76g of potassium hydroxide. Return the filtrate to the container and add water to make a final volume of 200ml to prepare a 38% aqueous solution. Then, add 212.8g of vanadium pentoxide at a ratio of 2.8:1 (vanadium pentoxide to potassium hydroxide). Stir and heat to 60–80℃, continuing stirring for 30–60 minutes. Measure the pH at 7.01. Adjust the pH to 8.0–9.0 with potassium hydroxide, and continue stirring for 30–40 minutes. Filter to obtain 196ml of filtrate. Add 1g of potassium metavanadate to 100ml of filtrate. Add 1.96g of potassium metavanadate, stirring at 40 rpm for 50 minutes. Let stand for 24 hours to precipitate crystals. Dry to obtain 189.24g of high-purity potassium metavanadate. Return the filtrate to the aqueous solution from the first step for recycling. Testing shows that the potassium metavanadate contains 99.98% potassium metavanadate.

[0048] Example 3

[0049] First, weigh 80g of analytical grade potassium hydroxide and add 200ml of water to prepare a 40% aqueous solution. Then, add vanadium pentoxide 240 at a ratio of vanadium pentoxide to potassium hydroxide of 2.5–3:1, stir and heat to 60–80℃, continue stirring for 30–60 minutes, measure the pH value to 6.5, adjust the pH value to 9.0 with potassium hydroxide, and continue stirring for 30–40 minutes. Filter to obtain 194ml of filtrate. Add 1.5g of potassium metavanadate to 100ml of filtrate, add 2.91g of potassium metavanadate, stir at 50 rpm for 40 minutes, let stand for 24 hours, crystals precipitate, dry to obtain 188.22g of high-purity potassium metavanadate. The filtrate is returned to be used as the aqueous solvent in the first step for recycling. Analysis shows that the potassium metavanadate contains 99.97% potassium metavanadate.

[0050] Weigh out 80g of potassium hydroxide. Return the filtrate to the container and add water to make a 40% aqueous solution (200ml). Add 240g of vanadium pentoxide (vanadium pentoxide to potassium hydroxide) at a ratio of 3:1. Stir and heat to 60-80℃, continuing stirring for 30-60 minutes. The pH is measured at 6.48. Adjust the pH to 8.0-9.0 with potassium hydroxide, and continue stirring for another 30-40 minutes. Filter to obtain 197ml of filtrate. Add 1.5g of potassium metavanadate to 100ml of filtrate. Add 2.96g of potassium metavanadate, stirring at 50 rpm for 40 minutes. Let stand for 24 hours to precipitate crystals. Dry to obtain 200.1g of high-purity potassium metavanadate. Return the filtrate to the aqueous solution used in the first step for recycling. Testing shows that the potassium metavanadate contains 99.98% potassium metavanadate.

[0051] The embodiments described above are merely illustrative of implementation methods of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for preparing potassium metavanadate, characterized in that, Includes the following steps: Step S1: Dissolve potassium hydroxide in water or by stirring in the filtered liquid to obtain solution L1, with potassium hydroxide purity above 96%; Step S2: Add vanadium pentoxide to solution L1, heat and stir to dissolve vanadium pentoxide, to obtain solution L2. The mass ratio of vanadium pentoxide added to potassium hydroxide in solution L1 is 2.5~3:1, and the purity of vanadium pentoxide is ≥95%. Step S3: Adjust the pH of solution L2 to pH=8.0~9 using potassium hydroxide, keep warm and stir, then filter to obtain filtrate L3; Step S4: Add potassium metavanadate to filtrate L3, stir and let it stand to crystallize, and obtain solution L4; Step S5: Filter solution L4 to obtain crystals C and filtrate L5; Step S6: Dry crystal C to obtain potassium metavanadate.

2. The method according to claim 1, characterized in that, Potassium hydroxide is prepared by mixing it with water or filtrate at a mass-to-volume ratio of 35-40g:100ml.

3. The method according to claim 1, characterized in that, In step S2, the temperature is raised to 60~80℃ and the stirring time is 30~60min.

4. The method according to claim 1, characterized in that, In step S3, the heat preservation temperature is 60~80℃ and the stirring time is 30~40min.

5. The method according to claim 1, characterized in that, In step S4, potassium metavanadate is added at a rate of 0.2-1.5g per 100ml of filtrate.

6. The method according to claim 1, characterized in that, In step S4, the stirring speed is 20~50 r / min and the stirring time is 40~60 min.

7. The method according to claim 1, characterized in that, In step S4, the settling time is more than 24 hours.

8. The method according to claim 1, characterized in that, It also includes recycling the filtrate L5 obtained in step S5 as the filtrate return liquid in step S1.

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