Sodium vanadate single crystal, sodium vanadate composite metal single crystal, vanadium pentoxide and preparation method and application of sodium vanadate single crystal, sodium vanadate composite metal single crystal and vanadium pentoxide
By adjusting the pH and temperature of the sodium vanadium leaching solution, and combining low-temperature crystallization and ammonium salt precipitation, high-purity sodium vanadate single crystals and vanadium pentoxide were prepared. This solved the problems of high impurity content and high energy consumption in traditional processes, and achieved efficient and low-cost vanadium product preparation to meet the needs of aerospace and other fields.
Patent Information
- Application Number
- CN202511686265.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-18
- Publication Date
- 2026-02-10
AI Technical Summary
Existing technologies are insufficient for the efficient and low-cost preparation of high-purity vanadium products, especially vanadium pentoxide. Traditional vanadium precipitation processes suffer from problems such as high impurity content, complex processes, and high energy consumption, making it difficult to meet the needs of the fine chemical industry.
By adjusting the pH and temperature of the sodium vanadium leaching solution, sodium vanadate single crystals and composite metal single crystals were prepared using a low-temperature crystallization method, and vanadium pentoxide was prepared using an ammonium salt precipitation method. By controlling the form and solubility of vanadium, high-purity large-size single crystals were extracted.
The prepared vanadium pentoxide has a purity of 99.999%, meeting the high-purity vanadium product requirements of special industries such as aviation and aerospace. The process is simple, low-cost, and achieves efficient vanadium purification.
Smart Images
Figure CN121496547A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of vanadium compounds, specifically relating to a sodium vanadate single crystal, a sodium vanadate composite metal single crystal, and vanadium pentoxide, as well as their preparation methods and applications. Background Technology
[0002] Vanadium and its compounds possess excellent physicochemical properties and are widely used in catalysis, steel, bridges, shipbuilding, aerospace, chemical industry, energy storage, automotive, and pharmaceutical fields. Vanadium can react with oxygen to form various vanadium oxides, among which VO, V₂O₃, V₂O₄, and V₂O₅ are the most common. V₂O₅, as an amphoteric oxide, mainly exhibits acidity, is soluble in alkaline and strong acid solutions, slightly soluble in water, and has reducing properties, reacting with alkaline media in the presence of an oxidizing agent. V₂O₅ is an important vanadium-based catalyst commonly used in chemical production processes such as sulfuric acid production, petroleum refining, and organic oxidation. The vanadium ion in V₂O₅ is in the +5 valence state, is stable, and can be prepared by methods such as ammonium vanadate pyrolysis or low-valence vanadium oxidation.
[0003] Vanadium and its compounds are mostly prepared from vanadium slag. Vanadium is often found in nature as a byproduct of various metals such as iron, titanium, and aluminum, and new impurities are easily introduced during extraction and refining, making the purification process extremely complex. Traditional vanadium precipitation processes, due to their high impurity content, struggle to meet the stringent requirements of the fine chemical industry for high-purity vanadium products. Although some high-purity vanadium precipitation technologies can achieve high purity, these technologies generally suffer from high production costs, complex processes, and high energy consumption, severely limiting their industrial application. Therefore, developing a short-process, low-cost, and efficient production technology to achieve high-purity vanadium products with a purity of over 99.999% has become a pressing technical challenge. Summary of the Invention
[0004] In view of this, the present invention provides a sodium vanadate single crystal, a sodium vanadate composite metal single crystal, and vanadium pentoxide, as well as their preparation methods and applications; the preparation method provided by the present invention is simple and easy to operate, and the vanadium pentoxide prepared according to the preparation method provided by the present invention has a purity of over 99.999%, thus obtaining high-purity vanadium pentoxide.
[0005] To address the aforementioned technical problems, this invention provides a method for preparing sodium vanadate single crystals, comprising the following steps: Vanadium slag and sodium salt are first mixed and then roasted. The roasted product is then leached in water to obtain a vanadium-sodium leachate. After adjusting the pH of the sodium vanadate leaching solution to 5-6, low-temperature crystallization is carried out to obtain sodium vanadate single crystals. The low-temperature crystallization includes the following steps: cooling to -1-1℃ at a cooling rate of 0.8-1.2℃ / h and then holding at that temperature for 23-25h.
[0006] Preferably, the molar ratio of vanadium in the vanadium slag to sodium in the sodium salt is 1:0.3~0.5; The calcination includes sequential low-temperature calcination and high-temperature calcination. The low-temperature calcination temperature is 645~655℃, the heating rate to the required low-temperature calcination temperature is 1.8~2.2℃ / min, and the holding time for the low-temperature calcination is 0.48~0.52h. The high-temperature calcination temperature is 845~855℃, the heating rate to the required high-temperature calcination temperature is 4.8~5.2℃ / min, and the holding time for the high-temperature calcination is 1.8~2.2h.
[0007] The present invention also provides a sodium vanadate single crystal prepared by the method for preparing sodium vanadate single crystal according to the above technical solution, wherein the purity of the sodium vanadate single crystal is above 99.999%, and the size of the sodium vanadate single crystal is on the centimeter scale.
[0008] This invention also provides a method for preparing sodium vanadate composite metal single crystals, comprising the following steps: After mixing sodium vanadate leachate and soluble metal salt, the pH value was adjusted and crystallization was carried out sequentially to obtain sodium vanadate composite metal single crystals. The soluble metal salts include potassium salts, magnesium salts, or cobalt salts; After pH adjustment, the pH of the system is 5-6; When the soluble metal salt is a potassium salt, the crystallization temperature is 39~41℃, the heating rate to the required crystallization temperature is 1.8~2.2℃ / h, and the holding time for crystallization is 23~35h. When the soluble metal salt is a magnesium salt or a cobalt salt, the crystallization temperature is -1 to 1°C, the cooling rate to the required crystallization temperature is 0.8 to 1.2°C / h, and the crystallization holding time is 23 to 35h.
[0009] Preferably, the molar ratio of vanadium in the sodium vanadium leachate to the metal element in the soluble metal salt is 5:2.8~3.2.
[0010] The present invention also provides a sodium vanadate composite metal single crystal prepared by the preparation method described above, wherein the sodium vanadate composite metal single crystal has a purity of 99.99% or higher and a size in the centimeter range.
[0011] This invention also provides a method for preparing vanadium pentoxide, comprising the following steps: Sodium vanadate single crystal or sodium vanadate composite metal single crystal is dissolved in water to obtain a single crystal solution; the sodium vanadate single crystal is the sodium vanadate single crystal described in the above technical solution; the sodium vanadate composite metal single crystal is the sodium vanadate composite metal single crystal described in the above technical solution; The single crystal solution was mixed with a soluble ammonium salt to precipitate vanadium with ammonium salt, thus obtaining ammonium vanadate crystals; The ammonium vanadate crystals were calcined to obtain vanadium pentoxide.
[0012] Preferably, the mass concentration of the single crystal solution is 14~16 g / L; The soluble ammonium salt includes ammonium chloride or ammonium sulfate; the molar ratio of vanadate ions in the single crystal solution to ammonium ions in the soluble ammonium salt is 1:3.8~4.2; The pH of the system after mixing the single crystal solution and the soluble ammonium salt is adjusted to 1.8~2.2, and the ammonium salt vanadium precipitation temperature is 145~155℃ for 4.8~5.2h. The calcination includes a first calcination, a second calcination, and a third calcination performed sequentially. The temperature of the first calcination is 290~310℃, the heating rate to the temperature required for the first calcination is 0.8~1.2℃ / min, and the holding time of the first calcination is 1.8~2.2h; The second calcination temperature is 590~610℃, the heating rate to the second calcination temperature is 0.8~1.2℃ / min, and the holding time for the second calcination is 1.8~2.2h; The temperature of the third calcination is 440~460℃, the cooling rate to the required temperature of the third calcination is 0.8~1.2℃ / min, and the holding time of the third calcination is 0.8~1.2h.
[0013] The present invention also provides vanadium pentoxide prepared by the preparation method described above, wherein the purity of the vanadium pentoxide is above 99.999%.
[0014] The present invention also provides the application of vanadium pentoxide as described in the above technical solution in the aviation and aerospace fields.
[0015] This invention regulates the pH of sodium vanadium leaching solution and its mixture with potassium, magnesium, or cobalt salts to ensure that vanadium exists primarily in its pentavalent form, and directly obtains high-purity, large-sized single crystals from the leaching solution at a specific crystallization temperature. Using high-purity, large-sized single crystals as raw materials, this invention yields high-purity vanadium pentoxide through ammonium salt precipitation followed by calcination, meeting the demands of specialized industries such as aerospace for high-purity vanadium products. The preparation method provided by this invention has the advantages of simple process, low cost, and direct extraction of high-purity vanadium products from vanadium leaching solution. This invention controls the form and solubility of vanadium (V) by adjusting the pH and temperature of the solution system, thereby achieving efficient crystallization and purification of vanadium compounds. Attached Figure Description
[0016] Figure 1 This is a photograph of the system after low-temperature crystallization during the preparation of sodium vanadate single crystals in Example 1. Figure 2 A photograph of the sodium vanadate single crystal prepared in Example 1; Figure 3 This is a photograph of the system after crystallization during the preparation of potassium sodium vanadate single crystals in Example 2. Figure 4 This is a photograph of the system after crystallization during the preparation of sodium magnesium vanadate single crystals in Example 3; Figure 5 This is a photograph of the sodium cobalt vanadate single crystal prepared in Example 4. Figure 6 Sodium vanadate single crystals (Na6V) prepared in Example 1 10 O 28 Mapping diagram of ·10H2O; Figure 7 The sodium potassium vanadate single crystal (K4Na2V) prepared in Example 2 10 O 28 Mapping diagram of ·10H2O; Figure 8 The sodium magnesium vanadate single crystal (Mg2Na2V) prepared in Example 3 10 O 28 Mapping diagram of ·10H2O; Figure 9 Sodium cobalt vanadate single crystals (Co2Na2V) prepared in Example 4 10 O 28 Mapping diagram of ·10H2O; Figure 10 Mapping diagram of vanadium pentoxide (V2O5) prepared in Example 5; Figure 11 EDS energy dispersive spectra of the main elements, where (a) is the sodium vanadate single crystal (Na6V) prepared in Example 1. 10 O 28 EDS plot of ·10H2O, (b) is the sodium potassium vanadate single crystal (K4Na2V) prepared in Example 2. 10 O 28 EDS diagrams of vanadium pentoxide (V₂O₅) prepared in Example 5 are shown in (c) and (d) are EDS diagrams of sodium cobalt vanadate (Co₂Na₂V₅) prepared in Example 4. 10 O 28 EDS plot of ·10H2O, (e) is the sodium magnesium vanadate single crystal (Mg2Na2V) prepared in Example 3. 10 O 28EDS plot of ·10H2O; Figure 12 This is a photograph of the single crystal prepared in Comparative Example 1. Figure 13 This is a physical image of the system after crystallization during the preparation of single crystals for Comparative Example 2. Detailed Implementation
[0017] This invention provides a method for preparing sodium vanadate single crystals, comprising the following steps: Vanadium slag and sodium salt are first mixed and then roasted. The roasted product is then leached in water to obtain a vanadium-sodium leachate. After adjusting the pH of the sodium vanadate leaching solution to 5-6, low-temperature crystallization is carried out to obtain sodium vanadate single crystals. The low-temperature crystallization includes the following steps: cooling to -1-1℃ at a cooling rate of 0.8-1.2℃ / h and then holding at that temperature for 23-25h.
[0018] This invention involves first mixing vanadium slag and sodium salt, followed by roasting. The roasted product is then leached with water to obtain a vanadium-sodium leachate. In one specific embodiment, the vanadium content in the vanadium slag can be 10-25% by mass, specifically 13%, 15%, 20%, or 23%; the average particle size of the vanadium slag can be 48-75 μm, or 50-70 μm, or even 55-65 μm; the sodium salt can include sodium sulfate or sodium chloride, and the average particle size of the sodium salt can be 50-500 μm, or 70-400 μm, or even 100-300 μm; the molar ratio of vanadium in the vanadium slag to sodium in the sodium salt can be 1:0.3-0.5, specifically 1:0.4. In another specific embodiment, the first mixing can be carried out under stirring conditions. This invention does not have special requirements for the stirring, as long as the sodium salt is uniformly coated on the surface of the vanadium slag.
[0019] In one specific embodiment of the present invention, the calcination may include sequential low-temperature calcination and high-temperature calcination; the low-temperature calcination temperature may be 645~655℃, specifically 650℃; the heating rate to the required low-temperature calcination temperature may be 1.8~2.2℃ / min, specifically 2℃ / min; the holding time for the low-temperature calcination may be 0.48~0.52h, specifically 0.5h; the high-temperature calcination temperature may be 845~855℃, specifically 850℃; the heating rate to the required high-temperature calcination temperature may be 4.8~5.2℃ / min, specifically 5℃ / min; the holding time for the high-temperature calcination may be 1.8~2.2h, specifically 2h. In this invention, low-temperature roasting can fully oxidize low-valent vanadium, while high-temperature roasting can cause vanadium and sodium salt to react and generate sodium metavanadate. This invention can convert vanadium in vanadium slag into water-soluble sodium salt through roasting, which is beneficial for subsequent water leaching.
[0020] This invention does not have a specific limitation on the volume of water used for immersion, as long as it is sufficient to submerge the calcined product. In this invention, the immersion time can be 20-25 minutes. As a specific embodiment of this invention, the process after immersion further includes: performing solid-liquid separation on the immersion system to obtain the sodium vanadium leachate; the solid-liquid separation can be filtration.
[0021] After obtaining the sodium vanadium leaching solution, the present invention adjusts the pH value of the sodium vanadium leaching solution to 5-6 and then performs low-temperature crystallization to obtain sodium vanadate single crystals. The present invention adjusts the pH value of the sodium vanadium leaching solution to 5-6, specifically 5.95. As a specific embodiment of the present invention, the pH adjuster used to adjust the pH value of the sodium vanadium leaching solution includes sulfuric acid or hydrochloric acid; the present invention does not have a special limitation on the mass concentration of the sulfuric acid and hydrochloric acid, as long as the required pH value can be achieved. When the pH value of the system is too high (e.g., alkaline), vanadate ions are mainly monomers, but high supersaturation leads to more nucleation and smaller crystals; while a low pH value will form polymers or precipitates, making it difficult to control purity; the present invention limits the pH value of the system to the above range, allowing vanadium to exist in the form of decavanadate oligomers, where larger ionic forms are more readily reacted with Na+. + Aggregation with water results in a slower nucleation rate, more orderly growth, reduced defects, and improved purity of the single crystal.
[0022] In this invention, the temperature of the sodium vanadium leaching solution after pH adjustment can be room temperature, specifically 20-35°C, or more specifically 25-30°C. The low-temperature crystallization includes the following steps: cooling to -1-1°C at a cooling rate of 0.8-1.2°C / h and then holding at that temperature for 23-25 hours, specifically cooling to 0°C at a cooling rate of 1°C / h and then holding at that temperature for 24 hours. This invention limits the cooling rate during the low-temperature crystallization process to maintain a quasi-equilibrium state, ensuring the solution remains slightly supersaturated, preventing nucleation explosions while continuously supplying growth units.
[0023] This invention regulates the species morphology by controlling the pH value of the system (so that vanadium exists in the form of decavanadate ions); this invention affects the solubility and kinetics of crystals by controlling the crystallization temperature; this invention obtains large-sized (centimeter-scale) high-purity sodium vanadate single crystals under the combined effect of system pH value and crystallization conditions.
[0024] As a specific embodiment of the present invention, the low-temperature crystallization may further include: washing the product after low-temperature crystallization; the washing solvent may be frozen water, and the temperature of the frozen water may be -1~1℃, specifically 0℃.
[0025] The present invention also provides sodium vanadate single crystals prepared according to the preparation method of sodium vanadate single crystals described above, wherein the purity of the sodium vanadate single crystals is above 99.999%, and the size of the sodium vanadate single crystals is in the centimeter range, which can be 3.5~4.5cm, specifically 4cm.
[0026] This invention also provides a method for preparing sodium vanadate composite metal single crystals, comprising the following steps: The sodium vanadate leaching solution and the soluble metal salt were mixed and then subjected to pH adjustment and crystallization to obtain the sodium vanadate composite metal single crystal.
[0027] In this invention, the method for preparing the sodium vanadium leachate is the same as the method for obtaining the sodium vanadium leachate during the preparation of sodium vanadate single crystals, and will not be repeated here.
[0028] In this invention, the soluble metal salt includes potassium salt, magnesium salt, or cobalt salt; the potassium salt may include potassium sulfate or potassium chloride; the magnesium salt may include magnesium sulfate or magnesium chloride; and the cobalt salt may include cobalt nitrate or cobalt sulfate. As a specific embodiment of this invention, the molar ratio of vanadium in the sodium vanadium leaching solution to the metal element in the soluble metal salt can be 5:2.8~3.2, specifically 5:3.
[0029] The present invention does not have any special limitations on the second mixture, as long as it is mixed evenly.
[0030] In this invention, the pH value of the system after pH adjustment is 5-6, specifically 5.95. This invention can utilize sulfuric acid to adjust the pH value of the system. This invention does not have a specific limitation on the mass concentration of the sulfuric acid, as long as the desired pH value is achieved.
[0031] In this invention, the temperature of the system after pH adjustment can be room temperature, which can be 20~35℃ or 25~30℃; when the soluble metal salt is potassium salt, the crystallization temperature is 39~41℃, specifically 40℃; the heating rate to the required crystallization temperature is 1.8~2.2℃ / h, specifically 2℃ / h; the holding time for crystallization is 23~35h, specifically 25h, 28h, 30h or 33h; the obtained sodium vanadate composite metal single crystal is a sodium vanadate potassium single crystal.
[0032] In this invention, when the soluble metal salt is a magnesium salt or a cobalt salt, the crystallization temperature is -1 to 1°C, specifically 0°C; the cooling rate to the required crystallization temperature is 0.8 to 1.2°C / h, specifically 1°C / h; the crystallization holding time is 23 to 35 hours, specifically 25 hours, 28 hours, 30 hours, or 33 hours; and the obtained sodium vanadate composite metal single crystal is a sodium vanadate magnesium single crystal or a sodium vanadate cobalt single crystal.
[0033] This invention yielded large-sized (centimeter-scale) high-purity sodium vanadate composite metal single crystals under the combined effects of system pH and crystallization conditions.
[0034] In one specific embodiment of the present invention, the crystallization process may further include: washing the crystallized product; when the soluble metal salt is a potassium salt, the washing solvent may be ultrapure water, and the temperature of the ultrapure water may be room temperature, which may be 20~35℃, or even 25~30℃. When the soluble metal salt is a magnesium salt or a cobalt salt, the washing solvent may be chilled water, and the temperature of the chilled water may be -1~1℃, or specifically 0℃.
[0035] The present invention also provides a sodium vanadate composite metal single crystal prepared by the preparation method described above, wherein the purity of the sodium vanadate composite metal single crystal is above 99.99%, wherein the size of sodium magnesium vanadate is 1.5~1.8cm, and the size of sodium cobalt vanadate is 0.4cm.
[0036] This invention also provides a method for preparing vanadium pentoxide, comprising the following steps: Sodium vanadate single crystal or sodium vanadate composite metal single crystal is dissolved in water to obtain a single crystal solution; the sodium vanadate single crystal is the sodium vanadate single crystal described in the above technical solution; the sodium vanadate composite metal single crystal is the sodium vanadate composite metal single crystal described in the above technical solution; The single crystal solution was mixed with a soluble ammonium salt to precipitate vanadium with ammonium salt, thus obtaining ammonium vanadate crystals; The ammonium vanadate crystals were calcined to obtain vanadium pentoxide.
[0037] This invention involves dissolving sodium vanadate single crystals or sodium vanadate composite metal single crystals in water to obtain a single crystal solution. The dissolution process has no special requirements, as long as complete dissolution is achieved. In one specific embodiment, the water can be deionized water; the mass concentration of the single crystal solution can be 14-16 g / L, specifically 15 g / L.
[0038] After obtaining the single-crystal solution, the present invention mixes the single-crystal solution with a soluble ammonium salt to precipitate vanadium, thereby obtaining ammonium vanadate crystals. In one specific embodiment of the present invention, the soluble ammonium salt may include ammonium chloride or ammonium sulfate; the molar ratio of vanadate ions in the single-crystal solution to ammonium ions in the soluble ammonium salt may be 1:3.8~4.2, specifically 1:4. In one specific embodiment of the present invention, the mixing can be carried out under magnetic stirring conditions. The present invention has no special requirements for the magnetic stirring, as long as it can achieve uniform mixing. In one specific embodiment of the present invention, the mixing process may further include: adjusting the pH value of the system after mixing the single-crystal solution and the soluble ammonium salt to 1.8~2.2, specifically 2, using sulfuric acid.
[0039] In one specific embodiment of the present invention, the temperature for ammonium salt precipitation of vanadium can be 145~155℃, specifically 150℃; the precipitation time can be 4.8~5.2h, specifically 5h. In the vanadium salt precipitation process, a metathesis reaction occurs to form ammonium vanadate. The present invention uses high-purity single crystals as raw materials to obtain high-purity ammonium vanadate crystals by ammonium salt precipitation at specific pH values and temperatures, thereby improving the purity of vanadium pentoxide.
[0040] In one specific embodiment of the present invention, the ammonium salt vanadium precipitation process may further include: performing solid-liquid separation on the ammonium salt vanadium precipitation system, and sequentially washing and drying the solid obtained from the solid-liquid separation to obtain the ammonium vanadate crystals. In another specific embodiment of the present invention, the solid-liquid separation may be filtration; the washing solvent may be water, specifically deionized water; and the drying may be vacuum drying. The present invention does not have specific limitations on the vacuum drying process, as long as it can remove the solvent from the product surface.
[0041] After obtaining ammonium vanadate crystals, the present invention calcines the ammonium vanadate crystals to obtain vanadium pentoxide. In one specific embodiment of the present invention, the calcination may include a first calcination, a second calcination, and a third calcination performed sequentially; the temperature of the first calcination may be 290~310℃, specifically 295℃, 300℃, or 305℃; the heating rate to the temperature required for the first calcination may be 0.8~1.2℃ / min, specifically 1℃ / min; the holding time for the first calcination may be 1.8~2.2h, specifically 2h; the temperature of the second calcination may be 590~610℃, specifically 595℃, 600℃, or 6... The temperature of the third calcination can be 440-460℃, specifically 445℃, 450℃, or 455℃; the temperature of the second calcination can be 0.8-1.2℃ / min, specifically 1℃ / min; the holding time of the third calcination can be 0.8-1.2℃ / min, specifically 1℃ / min; the holding time of the third calcination can be 0.8-1.2h, specifically 1h. In one specific embodiment of the invention, the calcination can be carried out under a protective atmosphere, which can be nitrogen or argon; the calcination can be carried out in a muffle furnace.
[0042] The present invention also provides vanadium pentoxide prepared by the preparation method described above, wherein the purity of the vanadium pentoxide is above 99.999%.
[0043] The present invention also provides the application of vanadium pentoxide as described in the above technical solution in the aviation and aerospace fields.
[0044] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.
[0045] Example 1 Vanadium slag with an average particle size of 65 μm (vanadium mass percentage of 16%) and sodium sulfate were mixed under stirring and then calcined under the following conditions: the temperature was increased to 650℃ at a heating rate of 2℃ / min and held for 0.5 h; the temperature was increased to 850℃ at a heating rate of 5℃ / min and held for 2 h; the calcined product was soaked in deionized water for 25 min and then filtered to obtain vanadium sodium leachate. The pH of the sodium vanadate leaching solution was adjusted to 5.95 using sulfuric acid, and then the temperature was lowered from 25°C to 0°C at a rate of 1°C / h and held for 24 hours (low-temperature crystallization). The product after low-temperature crystallization was washed with 0°C chilled water to obtain sodium vanadate single crystals.
[0046] Figure 1 This is a physical image of the system after low-temperature crystallization during the preparation of sodium vanadate single crystals. Figure 2 The image shows a physical photograph of the prepared sodium vanadate single crystal. Figure 1 and Figure 2 It can be seen that sodium vanadate single crystals can be prepared according to the method provided by the present invention, and the prepared sodium vanadate single crystals have a large size, about 4 cm.
[0047] Example 2 A sodium vanadium leachate was prepared according to the method in Example 1; Potassium sulfate (vanadium to potassium molar ratio of 5:3) was added to the sodium vanadate leaching solution and mixed thoroughly. The pH of the system was then adjusted to 5.95 using sulfuric acid. The temperature was then increased from 25°C to 40°C at a rate of 2°C / h and held for 30 hours (crystallization). The crystallized product was washed with ultrapure water at room temperature (25°C) to obtain potassium sodium vanadate single crystals (K4Na2V). 10 O 28 ·10H2O).
[0048] Example 3 A sodium vanadium leachate was prepared according to the method in Example 1; Magnesium sulfate (molar ratio of vanadium to magnesium of 5:3) was added to the sodium vanadate leaching solution and mixed thoroughly. The pH of the system was then adjusted to 5.95 using sulfuric acid. The solution was then cooled from 25°C to 0°C at a rate of 1°C / h and held at this temperature for 30 hours (crystallization). The crystallized product was washed with 0°C chilled water to obtain magnesium sodium vanadate single crystals (Mg₂Na₂V₂). 10 O 28 ·10H2O).
[0049] Example 4 A sodium vanadium leachate was prepared according to the method in Example 1; Cobalt nitrate (molar ratio of vanadium to cobalt 5:3) was added to the sodium vanadium leaching solution and mixed thoroughly. The pH of the system was adjusted to 5.95 using sulfuric acid, and then the temperature was lowered from 25°C to 0°C at a rate of 1°C / h and held at this temperature for 30 hours (crystallization). The crystallized product was washed with 0°C chilled water to obtain sodium cobalt vanadate single crystals (Co₂Na₂V₂). 10 O 28 ·10H2O).
[0050] Figure 3 This is a photograph of the system after crystallization during the preparation of potassium sodium vanadate single crystals in Example 2. Figure 4 This is a photograph of the system after crystallization during the preparation of sodium magnesium vanadate single crystals in Example 3. Figure 5 This is a photograph of the sodium cobalt vanadate single crystal prepared in Example 4. Figures 3-5 It can be seen that the preparation method provided by the present invention can obtain sodium vanadate composite metal single crystals with larger sizes.
[0051] Comparative Example 1 Single crystals were prepared according to the method in Example 2, except that the pH of the system was adjusted to 3 using sulfuric acid.
[0052] At this pH, vanadate ions are protonated, and the ions aggregate to form larger vanadate ions. The charge of these aggregates is relatively reduced, which leads to a significant decrease in their solubility in water, reaching a saturated state. At this time, the crystal nuclei grow rapidly and form amorphous precipitates. The growth process is relatively chaotic, and eventually a "red cake" is formed macroscopically. It is difficult to form single crystals with high purity, and there are many defects.
[0053] Comparative Example 2 Single crystals were prepared according to the method in Example 2, except that sodium hydroxide was used to adjust the pH of the system to 10.
[0054] At this pH, vanadium exists as HV₂O₇. 3- In this form, the spatial structure of vanadium atoms gradually transforms from three-dimensional to planar and linear, and the volume of the vanadate anion also gradually decreases. This leads to a gradual decrease in the probability of collisions in solution, while the solubility continuously increases. At this point, the nucleation rate is extremely slow, and the yield is very low.
[0055] Comparative Example 3 Single crystals were prepared according to the methods of Examples 1, 3 and 4, respectively, except that the crystallization temperature was controlled at 25°C.
[0056] The final results showed that the crystal growth process was slow at 25℃, lacked growth momentum, had a low yield, and could not optimize the size distribution and internal quality of the crystals, failing to meet both quality and quantity requirements. This is because the solubility of sodium vanadate and sodium magnesium (cobalt) vanadate decreased with decreasing temperature, while the supersaturation increased, so cooling can drive crystallization.
[0057] Comparative Example 4 Single crystals were prepared according to the method in Example 2, except that the temperature was reduced from 25°C to 0°C at a rate of 1°C / h during the crystallization process.
[0058] The final results showed that very few crystals or even no crystals were formed at 0℃. This is because the solubility of potassium sodium vanadate is highest at this temperature. At 0℃, the supersaturation decreases sharply or even disappears completely, lacking the driving force for crystal growth, resulting in a very low yield.
[0059] Example 5 Sodium vanadate single crystals, potassium sodium vanadate single crystals, magnesium sodium vanadate single crystals, and cobalt sodium vanadate single crystals prepared in Examples 1-4 were dissolved in water to obtain single crystal solutions with a mass concentration of 15 g / L. Ammonium chloride (molar ratio of vanadate ions to ammonium ions is 1:4) was added to the single crystal solution and mixed evenly under magnetic stirring. The pH value was adjusted to 2 using sulfuric acid. After ammonium salt precipitation at 150℃ for 5 hours, the mixture was filtered. The solid obtained by filtration was washed with deionized water and then vacuum dried to obtain ammonium vanadate crystals. Ammonium vanadate crystals were placed in a muffle furnace and heated to 300℃ at a heating rate of 1℃ / min under a nitrogen protective atmosphere. The temperature was then held for 2 hours. The temperature was then increased to 600℃ at a heating rate of 1℃ / min and held for 2 hours. Finally, the temperature was decreased to 450℃ at a cooling rate of 1℃ / min and held for 1 hour to obtain vanadium pentoxide.
[0060] The products of Examples 1, 2, 3, 4 and 5 were analyzed by point analysis, surface scanning and elemental mapping using an energy dispersive spectrometer (EDS) with a scanning electron microscope. Figures 6-10 This is a mapping distribution diagram, where, Figure 6 Sodium vanadate single crystals (Na6V) prepared in Example 1 10 O 28 Mapping diagram of ·10H2O, Figure 7 The sodium potassium vanadate single crystal (K4Na2V) prepared in Example 2 10 O 28 Mapping diagram of ·10H2O, Figure 8 The sodium magnesium vanadate single crystal (Mg2Na2V) prepared in Example 3 10 O 28 Mapping diagram of ·10H2O, Figure 9 Sodium cobalt vanadate single crystals (Co2Na2V) prepared in Example 4 10 O 28 Mapping diagram of ·10H2O, Figure 10 This is a mapping diagram of vanadium pentoxide (V2O5) prepared in Example 5.
[0061] Figure 11 EDS energy dispersive spectra of the main elements, where (a) is the sodium vanadate single crystal (Na6V) prepared in Example 1. 10 O 28 EDS plot of ·10H2O, (b) is the sodium potassium vanadate single crystal (K4Na2V) prepared in Example 2. 10 O 28 EDS diagrams of vanadium pentoxide (V₂O₅) prepared in Example 5 are shown in (c) and (d) are EDS diagrams of sodium cobalt vanadate (Co₂Na₂V₅) prepared in Example 4. 10 O 28EDS plot of ·10H2O, (e) is the sodium magnesium vanadate single crystal (Mg2Na2V) prepared in Example 3. 10 O 28 EDS plot of ·10H2O.
[0062] As can be seen from the EDS spectrum, only characteristic X-ray peaks from the target elements V, O, Na, K, Mg, and Co were observed throughout the entire detection range; no characteristic peaks from any other elements were detected. This indicates that the product prepared by this invention has high chemical purity.
[0063] The surface distribution results of the elements provide direct visual evidence of phase purity. It can be clearly seen that the signals of the six elements, V, O, Na, K, Mg and Co, are all highly uniform and continuous in the scanning area. More importantly, the enrichment areas of all elements (bright areas in the figure) are completely co-located in space, which indicates that they together constitute a single, homogeneous phase, without element segregation or second-phase impurities.
[0064] The results of EDS energy dispersive spectroscopy and elemental surface distribution analysis jointly indicate that the prepared Na6V 10 O 28 ·10H2O, K4Na2V 10 O 28 ·10H2O, Mg2Na2V 10 O 28 ·10H2O, Co2Na2V 10 O 28 • 10H2O and V2O5 exhibit high chemical and phase purity. The elemental composition is as expected and uniformly distributed, with no obvious heterogeneous impurities observed.
[0065] Figure 12 This is a photograph of the single crystal prepared in Comparative Example 1. Figure 12 It can be seen that the single crystals obtained under the condition of pH 3 are small in size, making it difficult to form high-purity sodium potassium vanadate single crystals, and resulting in more defects.
[0066] Figure 13 The image shows the physical structure of the system after crystallization during the preparation of single crystals in Comparative Example 2. Figure 13 It can be seen that no obvious potassium sodium vanadate single crystals were formed under the condition of pH 10.
[0067] The purity of the single crystals prepared in Examples 1-4 and Comparative Examples 1-4 was detected by inductively coupled plasma atomic emission spectrometry (ICP), and the yield was calculated. The results are listed in Table 1.
[0068] Table 1. Purity and yield of the products prepared in Examples 1-4 and Comparative Examples 1-4
[0069] As shown in Table 1, the preparation method provided by this invention has a high yield for preparing sodium vanadate single crystals, and the prepared single crystals have high purity. Vanadium pentoxide prepared from sodium vanadate single crystals provided by this invention has high purity, all exceeding 99.999%.
[0070] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.
Claims
1. A method for preparing sodium vanadate single crystals, characterized in that, Includes the following steps: Vanadium slag and sodium salt are first mixed and then roasted. The roasted product is then leached in water to obtain a vanadium-sodium leachate. After adjusting the pH of the sodium vanadate leaching solution to 5-6, low-temperature crystallization is carried out to obtain sodium vanadate single crystals. The low-temperature crystallization includes the following steps: cooling to -1-1℃ at a cooling rate of 0.8-1.2℃ / h and then holding at that temperature for 23-25h.
2. The method for preparing sodium vanadate single crystals according to claim 1, characterized in that, The molar ratio of vanadium in the vanadium slag to sodium in the sodium salt is 1:0.3~0.5; The calcination includes sequential low-temperature calcination and high-temperature calcination. The low-temperature calcination temperature is 645~655℃, the heating rate to the required low-temperature calcination temperature is 1.8~2.2℃ / min, and the holding time for the low-temperature calcination is 0.48~0.52h. The high-temperature calcination temperature is 845~855℃, the heating rate to the required high-temperature calcination temperature is 4.8~5.2℃ / min, and the holding time for the high-temperature calcination is 1.8~2.2h.
3. The sodium vanadate single crystal prepared by the method of claim 1 or 2, characterized in that, The sodium vanadate single crystal has a purity of 99.999% or higher, and its size is on the order of centimeters.
4. A method for preparing sodium vanadate composite metal single crystals, characterized in that, Includes the following steps: After mixing sodium vanadate leachate and soluble metal salt, the pH value was adjusted and crystallization was carried out sequentially to obtain sodium vanadate composite metal single crystals. The soluble metal salts include potassium salts, magnesium salts, or cobalt salts; After pH adjustment, the pH of the system is 5-6; When the soluble metal salt is a potassium salt, the crystallization temperature is 39~41℃, the heating rate to the required crystallization temperature is 1.8~2.2℃ / h, and the holding time for crystallization is 23~35h. When the soluble metal salt is a magnesium salt or a cobalt salt, the crystallization temperature is -1 to 1°C, the cooling rate to the required crystallization temperature is 0.8 to 1.2°C / h, and the crystallization holding time is 23 to 35h.
5. The preparation method according to claim 4, characterized in that, The molar ratio of vanadium in the sodium vanadium leachate to the metal in the soluble metal salt is 5:2.8~3.
2.
6. The sodium vanadate composite metal single crystal prepared by the preparation method according to claim 4 or 5, characterized in that, The sodium vanadate composite metal single crystal has a purity of over 99.99% and a size in the centimeter range.
7. A method for preparing vanadium pentoxide, characterized in that, Includes the following steps: Sodium vanadate single crystal or sodium vanadate composite metal single crystal is dissolved in water to obtain a single crystal solution; the sodium vanadate single crystal is the sodium vanadate single crystal according to claim 3; the sodium vanadate composite metal single crystal is the sodium vanadate composite metal single crystal according to claim 6; The single crystal solution was mixed with a soluble ammonium salt to precipitate vanadium with ammonium salt, thus obtaining ammonium vanadate crystals; The ammonium vanadate crystals were calcined to obtain vanadium pentoxide.
8. The preparation method according to claim 7, characterized in that, The mass concentration of the single crystal solution is 14~16 g / L; The soluble ammonium salt includes ammonium chloride or ammonium sulfate; the molar ratio of vanadate ions in the single crystal solution to ammonium ions in the soluble ammonium salt is 1:3.8~4.2; The pH of the system after mixing the single crystal solution and the soluble ammonium salt is adjusted to 1.8~2.2, and the ammonium salt vanadium precipitation temperature is 145~155℃ for 4.8~5.2h. The calcination includes a first calcination, a second calcination, and a third calcination performed sequentially. The temperature of the first calcination is 290~310℃, the heating rate to the temperature required for the first calcination is 0.8~1.2℃ / min, and the holding time of the first calcination is 1.8~2.2h; The second calcination temperature is 590~610℃, the heating rate to the second calcination temperature is 0.8~1.2℃ / min, and the holding time for the second calcination is 1.8~2.2h; The temperature of the third calcination is 440~460℃, the cooling rate to the required temperature of the third calcination is 0.8~1.2℃ / min, and the holding time of the third calcination is 0.8~1.2h.
9. Vanadium pentoxide prepared by the preparation method according to claim 7 or 8, characterized in that, The purity of the vanadium pentoxide is above 99.999%.
10. The application of vanadium pentoxide as described in claim 9 in the aviation and aerospace fields.