Method for preparing ammonium metavanadate through rapid crystallization

Abstract

The invention provides a method for preparing ammonium metavanadate through rapid crystallization, and the method specifically comprises the following steps: step 1, weighing ammonium polyvanadate, dissolving the ammonium polyvanadate in diluted ammonia water to obtain an ammonium vanadate solution, and adjusting the pH value of the ammonium vanadate solution; step 2, slowly dropwise adding the ammonium vanadate solution in the step 1 into a poor solvent, and stirring while dropwise adding to obtain an ammonium metavanadate suspension; step 3, filtering the ammonium metavanadate suspension in the step 2 to obtain an ammonium metavanadate filter cake, and leaching the ammonium metavanadate filter cake by adopting a poor solvent which is the same as the poor solvent in the step 2; and 4, drying the ammonium metavanadate filter cake in the step 3 in a drying oven to obtain an ammonium metavanadate product. A mixed solvent method is adopted, ammonium polyvanadate is dissolved with 12.5 wt%-14 wt% of ammonia water to obtain an ammonium vanadate solution, the ammonium vanadate solution is poured into poor solvents such as methyl alcohol after pH is adjusted, ammonium metavanadate is separated out of a system instantly, and the technical problems that in the prior art, ammonium metavanadate is low in crystallization speed, low in crystallization rate and low in product purity are solved.

Description

Technical Field

[0001] This invention belongs to the field of compound preparation technology, and relates to ammonium metavanadate, specifically to a method for rapidly crystallizing ammonium metavanadate. Background Technology

[0002] Vanadium is widely used as an additive in the steel industry, aerospace, manufacturing, industrial catalysts, pigments, semiconductor materials, and lithium batteries. Ammonium vanadate, an important intermediate product in the vanadium industry, is not only a crucial raw material for producing V₂O₅ and metallic vanadium powder, but also, due to its unique crystal structure, is used as a cathode material in lithium-ion batteries. Furthermore, it holds broad research prospects in supercapacitors, gas-sensitive components, and catalysis. The main commercially available ammonium vanadate products are ammonium metavanadate (AMV) and ammonium polyvanadate (APV). Both utilize ammonium salt precipitation, i.e., adding ammonium salt precipitants such as ammonium chloride or ammonium sulfate to a vanadate solution to form ammonium metavanadate and ammonium polyvanadate precipitates. However, the pH values ​​for their formation differ; at pH = 8–9, vanadium in the solution mainly exists as VO₃⁻. - It exists in the form of ammonium vanadate, and upon the addition of ammonium salts, a metathesis reaction occurs, producing ammonium metavanadate with relatively low solubility. However, under weakly acidic conditions, VO3 in the solution... - Polymerization occurs, and after adding ammonium salt, the solution is acidified to a pH of 2–2.5, precipitating out ammonium polyvanadate. In the industrial production of ammonium metavanadate, heating to 80–90°C is required, the precipitation reaction is time-consuming, the crystallization rate is low, and energy consumption is high. After vanadium precipitation, the solution contains a large amount of inorganic salts, resulting in high recovery costs and low utilization. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention proposes a method for the rapid crystallization preparation of ammonium metavanadate, thereby solving the technical problems of slow crystallization rate, low crystallization rate, and high energy consumption in existing technologies.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A method for rapidly crystallizing ammonium metavanadate, the method specifically includes the following steps: Step 1: Weigh out ammonium polyvanadate and dissolve it in diluted ammonia water. Heat and stir to obtain an ammonium vanadate solution. Adjust the pH of the ammonium vanadate solution. Step 2: Slowly add the ammonium metavanadate solution from Step 1 to the unsuitable solvent while stirring, to obtain an ammonium metavanadate suspension; Step 3: Filter the ammonium metavanadate suspension from Step 2 to obtain an ammonium metavanadate filter cake. The ammonium metavanadate filter cake is washed with the same poor solvent as in Step 2. Step four: Place the ammonium metavanadate filter cake from step three in an oven for drying to obtain the ammonium metavanadate product.

[0005] The present invention also has the following technical features: Specifically, in step one, the average particle size of ammonium polyvanadate is 32 μm.

[0006] Specifically, in step one, the mass fraction of ammonia water is 12.5wt% to 14wt%.

[0007] Specifically, in step one, the pH of the ammonium vanadate solution is adjusted to 8-9.

[0008] Specifically, in step one, the concentration of the ammonium vanadate solution is 10 g / L to 200 g / L.

[0009] Specifically, in step two, the unsuitable solvents are methanol, ethanol, acetone, propanol, isopropanol, propylene glycol, DMF, or DMSO.

[0010] Specifically, in step two, the dropping rate of the ammonium vanadate solution is 0.25–25 mL / min.

[0011] Specifically, in step two, the stirring time is 5 to 30 minutes.

[0012] Specifically, in step two, the volume of the undesirable solvent is 1 to 20 times the volume of the ammonium vanadate solution.

[0013] Specifically, in step three, the ammonium metavanadate filter cake is rinsed 1 to 3 times with a poor solvent.

[0014] Specifically, in step four, the drying temperature is 60–90℃ and the drying time is 30–120 min.

[0015] Specifically, in step four, the particle size of the obtained ammonium metavanadate product is 10-30 μm.

[0016] Compared with the prior art, the present invention has the following beneficial technical effects: (I) The method for rapid crystallization preparation of ammonium metavanadate proposed in this invention adopts a mixed solvent method. Ammonium metavanadate is dissolved in ammonia water with a mass fraction of 12.5wt% to 14wt% to obtain an ammonium metavanadate solution. After adjusting the pH, it is poured into a poor solvent such as methanol. The system quickly reaches a supersaturated state and ammonium metavanadate is precipitated instantly. This solves the technical problems of slow crystallization speed, low crystallization rate and high energy consumption of ammonium metavanadate in the prior art.

[0017] (II) The method for preparing ammonium metavanadate by rapid crystallization proposed in this invention can control the precipitation rate. The prepared ammonium metavanadate is in the form of micron-sized particles, which are formed by the agglomeration of sheet-like particles with a length of 10-30 μm and a width of 5-10 μm into strip bundles. The particles are uniform, the formation rate is fast, and the purity is higher than that of the raw material ammonium metavanadate. Attached Figure Description

[0018] Figure 1 This is a process flow diagram for preparing ammonium metavanadate.

[0019] Figure 2 The image shows the XRD pattern of ammonium metavanadate.

[0020] Figure 3 This is the Fourier transform infrared (FTIR) spectrum of ammonium metavanadate.

[0021] Figure 4 This is a SEM image of ammonium metavanadate.

[0022] The specific content of the present invention will be further explained in detail below with reference to the embodiments. Detailed Implementation

[0023] It should be noted that, unless otherwise specified, all the equipment and materials used in this invention are those known in the prior art.

[0024] For example, the water used in this invention is pure water; The ammonia solution is a commercially available ammonia solution with a mass fraction of 25wt% to 28wt%. Ammonium polyvanadate is commercially available and has a chemical purity of 99%. Methanol, ethanol, and acetone were commercially available anhydrous methanol, anhydrous ethanol, and anhydrous acetone, all of analytical grade.

[0025] This invention utilizes the phenomenon that ammonium metavanadate is soluble in water and ammonia, but insoluble in organic solvents such as methanol, ethanol, and acetone. A mixed solvent method is employed, using water as the good solvent and methanol, ethanol, acetone, propanol, isopropanol, propylene glycol, DMF (N,N-dimethylformamide), or DMSO (dimethyl sulfoxide) as the poor solvent. The good and poor solvents can be miscible in any proportion. An ammonium metavanadate solution obtained by dissolving ammonium metavanadate in ammonia water with a mass fraction of 12.5 wt%–14 wt% is poured into a certain volume equivalent of methanol or other poor solvents, and the mixture is continuously stirred. This rapidly reduces the solubility of ammonium metavanadate in the good solvent, causing it to quickly reach a supersaturated state and precipitate as ammonium metavanadate. The precipitate is then filtered and dried to obtain the ammonium metavanadate product.

[0026] Following the above technical solutions, specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0027] Example 1: This embodiment provides a method for the rapid crystallization preparation of ammonium metavanadate, such as... Figure 1 As shown, the method specifically includes the following steps: Step 1: Weigh 4.3g of ammonium polyvanadate with an average particle size of 32μm and dissolve it in 50mL of ammonia water with a mass fraction of 12.5wt% to 14wt%. Heat and stir to obtain 52mL of ammonium polyvanadate solution with a concentration of 82.7g / L and a pH of 9. In this embodiment, the ammonia solution is commercially available ammonia solution with a mass fraction of 25wt% to 28wt% diluted with water to a mass fraction of 12.5wt% to 14wt%.

[0028] Step 2: Add 52 mL of ammonium vanadate solution from Step 1 to 52 mL of ethanol at a dropping rate of 20 mL / min. A large amount of white solid ammonium metavanadate will precipitate instantly. As the amount of ammonium vanadate solution added increases, the amount of ammonium metavanadate precipitated increases. Continue stirring for another 10 min to obtain an ammonium metavanadate suspension. Step 3: Filter the ammonium metavanadate suspension from Step 2 using a Buchner funnel to obtain an ammonium metavanadate filter cake. Rinse the ammonium metavanadate filter cake once with 10 mL of ethanol. Step 4: Place the ammonium metavanadate filter cake from Step 3 in an oven and dry it at 70℃ for 2 hours. Take it out and weigh it to obtain 4.3g of ammonium metavanadate product. The particle size of the ammonium metavanadate product is 10-30μm. The vanadium metal recovery rate is calculated to be 85.0%.

[0029] In this specific embodiment, the ammonium vanadate solution is slowly poured into ethanol (a poor solvent). Since the solubility of the ammonium vanadate solution decreases rapidly after contact with the poor solvent, the precipitation of solids is fast. Therefore, in the precipitation process, the ammonium vanadate solution needs to be added slowly and stirred quickly to ensure that the ammonium vanadate solution and ethanol are mixed evenly. This prevents the precipitated ammonium metavanadate solids from growing locally and becoming uneven in size. At the same time, it ensures that the ammonium vanadate solution and ethanol are mixed evenly so that the ammonium metavanadate is fully precipitated.

[0030] The XRD pattern of the ammonium metavanadate product is as follows: Figure 2 As shown, from Figure 2 As can be seen, distinct diffraction peaks appear at positions such as 2θ = 15.028°, 18.064°, 21.438°, 28.167°, 30.667°, and 34.081°. Comparing with the standard PDF card (JCPDS No. 04-010-2778), the peak positions perfectly match the characteristic peaks of ammonium metavanadate. No other impurity peaks were observed, indicating that the sample is pure-phase ammonium metavanadate. The diffraction peaks in the spectrum are sharp and have smooth baselines, without obvious broadening or diffuse peaks, indicating that the sample has high crystallinity. The intensity of each peak is consistent with the trend of the standard card, with the peak at 21.438° having the highest intensity and being the dominant diffraction peak.

[0031] Figure 3 This is the Fourier transform infrared (FTIR) spectrum of the ammonium dimolybdate and ammonium metavanadate prepared in this embodiment. Figure 3As can be seen, the infrared spectrum of ammonium metavanadate mainly consists of two parts: 1. Vibrations of the vanadium-oxygen anion group (VO) (400-1000 nm). ), of which: 884.43 The strong peak at 831.50 is the core characteristic peak of ammonium metavanadate, which belongs to the stretching vibration of the terminal oxygen bond at V=O; The strong peak at this point represents the antisymmetric stretching vibration of the VOV bridging bond, which is crucial for connecting vanadium-oxygen tetrahedra to form an infinite chain-like structure; 633.31 The medium-intensity peak at this point originates from the symmetrical stretching vibration of the VOV bridge bond or the bending vibration of VO; 495.84 The weak peak at that point represents the bending vibration mode of OVO or VO. 2. Ammonium ion Vibration (1300) -3200 ), of which: 2788.30 2926.51 3184.14 The multiple peaks at that point are due to the NH stretching vibration, because and Due to hydrogen bonding between them, this peak broadens into a multiplet; 1405.43 The very strong and sharp peak at 1732.38 is the most characteristic absorption peak of the ammonium ion, attributed to the in-plane bending vibration of NH; The weak peak at that point is an overtone peak of the NH bending vibration.

[0032] Figure 4 Here is a SEM image of the ammonium dimolybdate prepared in this embodiment, from... Figure 4 As can be seen, ammonium metavanadate exhibits a relatively regular geometric shape. Some particles are independently dispersed, while most show a certain degree of aggregation, presenting a clustered or piled distribution. Individual particles are approximately prismatic or needle-like structures with a certain crystal growth orientation, relatively smooth surfaces, and lengths between 10-30 μm.

[0033] Example 2: This embodiment provides a method for rapid crystallization to prepare ammonium metavanadate, which specifically includes the following steps: Step 1: Weigh 17g of ammonium polyvanadate with an average particle size of 32μm and dissolve it in 240mL of ammonia water with a mass fraction of 12.5wt% to 14wt%. Heat and stir to obtain 250mL of ammonium polyvanadate solution with a concentration of 68.0g / L and a pH of 8.7. In this embodiment, the ammonia solution is commercially available ammonia solution with a mass fraction of 25wt% to 28wt% diluted with water to a mass fraction of 12.5wt% to 14wt%.

[0034] Step 2: Take 50 mL of the ammonium vanadate solution from Step 1 and add it dropwise to 150 mL of methanol at a rate of 20 mL / min. A large amount of white solid ammonium metavanadate will precipitate instantly. As the amount of ammonium vanadate solution added increases, the amount of ammonium metavanadate precipitated increases. Continue stirring for another 10 min to obtain an ammonium metavanadate suspension. Step 3: Filter the ammonium metavanadate suspension from Step 2 using a Buchner funnel to obtain an ammonium metavanadate filter cake. Wash the ammonium metavanadate filter cake three times with 5 mL of methanol. Step 4: Place the ammonium metavanadate filter cake from Step 3 in an oven and dry it at 85°C for 1 hour. Take it out and weigh it to obtain 3.8g of ammonium metavanadate product. The particle size of the ammonium metavanadate product is 10-30μm. The calculated recovery rate of vanadium metal is 95%.

[0035] In this embodiment, the ammonium vanadate solution is slowly poured into methanol (a poor solvent). Since the solubility of the ammonium vanadate solution decreases rapidly after contact with the poor solvent, the precipitation of solids is fast. Therefore, in the precipitation process, the ammonium vanadate solution needs to be added slowly and stirred quickly to mix the ammonium vanadate solution and methanol evenly. This prevents the precipitated ammonium metavanadate solids from growing locally and becoming uneven in size. At the same time, it ensures that the ammonium vanadate solution and methanol are mixed evenly so that the ammonium metavanadate is fully precipitated.

[0036] Example 3: This embodiment provides a method for rapid crystallization to prepare ammonium metavanadate, which specifically includes the following steps: Step 1: Weigh 42.7g of ammonium polyvanadate with an average particle size of 32μm and dissolve it in 200mL of ammonia water with a mass fraction of 12.5wt% to 14wt%. Heat and stir to obtain 220mL of ammonium polyvanadate solution with a concentration of 194.0g / L and a pH of 8.4. In this embodiment, the ammonia solution is commercially available ammonia solution with a mass fraction of 25wt% to 28wt% diluted with water to a mass fraction of 12.5wt% to 14wt%.

[0037] Step 2: Take 50 mL of the ammonium vanadate solution from Step 1 and add it dropwise to 250 mL of acetone at a rate of 20 mL / min. A large amount of white solid ammonium metavanadate will precipitate instantly. As the amount of ammonium vanadate solution added increases, the amount of ammonium metavanadate precipitated increases. Continue stirring for another 10 min to obtain an ammonium metavanadate suspension. Step 3: Filter the ammonium metavanadate suspension from Step 2 using a Buchner funnel to obtain an ammonium metavanadate filter cake. Wash the ammonium metavanadate filter cake three times with 5 mL of acetone. Step 4: Place the ammonium metavanadate filter cake from Step 3 in an oven and dry it at 95°C for 2 hours. Take it out and weigh it to obtain 10.8g of ammonium metavanadate product. The particle size of the ammonium metavanadate product is 10-30μm. The calculated recovery rate of vanadium metal is 95%.

[0038] In this specific embodiment, the ammonium vanadate solution is slowly poured into acetone (a poor solvent). Since the solubility of the ammonium vanadate solution decreases rapidly after contact with the poor solvent, the precipitation of solids is fast. Therefore, in the precipitation process, the ammonium vanadate solution needs to be added slowly and stirred quickly to mix the ammonium vanadate solution and acetone evenly. This prevents the precipitated ammonium metavanadate solids from growing locally and becoming uneven in size. At the same time, it ensures that the ammonium vanadate solution and acetone are mixed evenly so that the ammonium metavanadate is fully precipitated.

Claims

1. A method for the rapid crystallization of ammonium metavanadate, characterized in that, The method specifically comprises the following steps: Step one, weigh the ammonium polyvanadate and dissolve it in ammonia water, heat and stir to obtain an ammonium vanadate solution, and adjust the pH of the ammonium vanadate solution; Step two, slowly drop the ammonium vanadate solution in step one into a poor solvent, stir while dropping, and obtain an ammonium metavanadate suspension; Step three, filter the ammonium metavanadate suspension in step two to obtain an ammonium metavanadate filter cake, and use the same poor solvent as in step two to leach the ammonium metavanadate filter cake; Step four, place the ammonium metavanadate filter cake in step three in an oven for drying to obtain an ammonium metavanadate product.

2. The process for the quick crystallization preparation of ammonium metavanadate as claimed in claim 1, wherein, In step one, the average particle size of the ammonium polyvanadate is 32 μm; In step one, the mass fraction of the ammonia water is 12.5wt%-14wt%; In step one, the pH of the ammonium vanadate solution is adjusted to 8-9; In step one, the concentration of the ammonium vanadate solution is 10g / L-200g / L.

3. The method of rapidly crystallizing ammonium metavanadate according to claim 1, wherein In step two, the poor solvent is methanol, ethanol, acetone, propanol, isopropanol, propylene glycol, DMF or DMSO; In step two, the dropping speed of the ammonium vanadate solution is 0.25-25mL / min; In step two, the stirring time is 5-30min; In step two, the volume of the poor solvent is 1-20 times the volume of the ammonium vanadate solution.

4. The method of rapidly crystallizing ammonium metavanadate according to claim 1, wherein In step three, the ammonium metavanadate filter cake is leached with the poor solvent for 1-3 times.

5. The method of rapidly crystallizing ammonium metavanadate according to claim 1, wherein In step four, the drying temperature is 60-95℃, and the drying time is 30-120min.

6. The process for the quick crystallization preparation of ammonium metavanadate as claimed in claim 1 wherein, In step four, the particle size of the obtained ammonium metavanadate product is 10-30μm.

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