A process for extracting vanadium from stone coal

Abstract

The invention discloses a process for extracting vanadium from stone coal, belonging to the technical field of vanadium extraction from stone coal. The process comprises the following steps: crushing the stone coal, spraying a strong oxidant such as peroxide or persulfate, and performing microwave activation; then acid leaching, heating, stirring, and solid-liquid separation to obtain a leachate; extracting a vanadium-rich phase through extraction-strip extraction, adjusting the pH value with alkali, adding polyacrylamide, and standing and separating to obtain a purified liquid; then adding ammonium salt, heating, and precipitation, and centrifugally drying to obtain ammonium metavanadate, which is finally calcined at high temperature to obtain vanadium pentoxide. The process can significantly reduce energy consumption and environmental pollution problems, and can also significantly improve the leaching efficiency of vanadium, thereby ultimately obtaining high-purity vanadium pentoxide.

Description

Technical Field

[0001] The invention belongs to the technical field of vanadium extraction from stone coal, and particularly relates to a process for extracting vanadium from stone coal. Background Art

[0002] Vanadium, a key strategic metal, plays an irreplaceable role in steel metallurgy, all-vanadium flow batteries, aerospace materials, and other fields. Approximately 20% of global vanadium resources are contained in anthracite. While anthracite vanadium reserves are abundant, their grade is generally low (V2O5 content 0.5%-1.5%). With the rapid development of new energy and high-end manufacturing industries, demand for vanadium continues to grow. Traditional vanadium extraction processes, due to their low efficiency and high pollution levels, are unable to meet the demands of green and low-carbon development. Therefore, the development of new, efficient, and clean anthracite vanadium extraction technologies is urgently needed.

[0003] Currently, the two most widely used industrial vanadium extraction processes include sodium roasting and calcium roasting. However, these processes all have significant technical limitations. The sodium roasting process, under high-temperature conditions (typically above 850°C), produces toxic gases such as Cl₂ and HCl, causing severe environmental pollution. Furthermore, this method requires the addition of large amounts of NaCl or Na₂CO₃, significantly increasing the sodium content in the tailings and making it difficult to meet resource utilization requirements. While the calcium roasting process avoids the environmental pollution issues associated with sodium roasting, it suffers from significant vanadium losses due to the reaction of calcium-based additives (such as CaO) with vanadium minerals to form insoluble calcium vanadate. Subsequent leaching requires high-concentration strong acid, which not only exacerbates equipment corrosion but also significantly increases acid consumption, further increasing process costs. For example, Chinese patent publication number CN115198116A discloses a process for direct deep impurity removal and vanadium extraction from enriched vanadium solution. This technology utilizes aging, impurity removal, and vanadium precipitation steps to produce high-purity vanadium pentoxide. However, the vanadium leaching rate of this process still needs to be further improved, and the roasting method requires high temperature reaction conditions, which increases energy consumption. Therefore, exploring a vanadium extraction process that can both improve the vanadium leaching rate and reduce energy consumption and environmental pollution has become an urgent problem to be solved. Summary of the Invention

[0004] The purpose of the present invention is to provide a low-energy-consumption, pollution-free process for extracting vanadium from stone coal, which can significantly improve the leaching rate of vanadium.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a process for extracting vanadium from stone coal, comprising the following steps:

[0007] (1) First, stone coal is crushed into fine powder, and then a strong oxidant aqueous solution is sprayed on the stone coal powder, and microwave irradiation is performed to obtain an activated sample, wherein the strong oxidant is peroxide or persulfate;

[0008] (2) Immerse the activated sample in a strong acid solution, heat and stir to obtain a suspension, separate the solid and liquid, and obtain a leachate;

[0009] (3) adding iron powder to the leachate, then extracting the leachate with a phosphoric acid extractant to obtain a vanadium-rich phase, and then stripping the vanadium-rich phase with dilute sulfuric acid to obtain a stripping solution;

[0010] (4) adding alkaline solution to the stripping solution to adjust the pH to 4-5, then adding polyacrylamide, stirring evenly and letting it stand for solid-liquid separation, then adjusting the pH of the liquid to 2-3, adding hydrogen peroxide, and obtaining a purified solution;

[0011] (5) adding ammonia water or ammonium salt to the purified liquid to adjust the pH to 7-8 to obtain a suspension; centrifuging, washing, and drying the suspension to obtain ammonium metavanadate;

[0012] (6) Ammonium metavanadate is calcined at high temperature in air to obtain vanadium pentoxide.

[0013] Preferably, in step (1), the strong oxidant is one of hydrogen peroxide, potassium persulfate, sodium persulfate, and potassium hydrogen persulfate; the mass concentration of the strong oxidant in the strong oxidant aqueous solution is 0.5-5.0%; the mass ratio of the strong oxidant aqueous solution to the stone coal powder is 5-12:1000; the size of the stone coal powder is 100-300 mesh; the microwave power is 500-1500 W; and the irradiation time is 5-15 min.

[0014] Preferably, the strong acid solution in step (2) is a mixture of phosphoric acid and an inorganic strong acid, the inorganic strong acid includes at least one of hydrochloric acid, nitric acid, and sulfuric acid, the concentration of the inorganic strong acid in the strong acid solution is 0.5-1 mol / L, and the molar ratio of phosphoric acid to the inorganic strong acid is 1-5:1; the volume mass ratio of the strong acid solution to the stone coal is 4-6 L:1 kg, the stirring temperature is 60-100° C., the stirring time is 1-5 h, and the stirring speed is 200-500 rpm.

[0015] Preferably, in step (3), the concentration of iron powder in the leaching solution is 3-6 g / L, the phosphoric acid extractant is one of P204+TBP+sulfonated kerosene and PC-88A+sulfonated kerosene; and the mass concentration of dilute sulfuric acid is 3-10%.

[0016] Preferably, in step (5), the ammonium salt is one of ammonium chloride and ammonium sulfate, the detergent is water or ethanol, the centrifugal speed is 4000-6000 rpm, the centrifugal time is 2-5 min; the drying temperature is 60-80° C., and the drying time is 6-8 h.

[0017] Preferably, the specific steps of high temperature calcination in step (6) are: controlling the heating rate to be 2-5°C / min to raise the temperature to 500-600°C, and keeping the temperature for 3-5h.

[0018] The beneficial effects of the present invention are as follows:

[0019] 1. The present invention proposes a process for extracting vanadium from stone coal. First, the stone coal is crushed to 100-300 mesh to increase the specific surface area of ​​the mineral and improve the exposure rate of the vanadium-containing phase. Then, a peroxide or persulfate strong oxidant aqueous solution is sprayed on the surface of the stone coal powder to oxidize the low-valent vanadium in the stone coal powder into high-valent vanadium. During the oxidation reaction, the stone coal powder is irradiated with microwaves. The selective heating effect of polar molecules is utilized to destroy the mineral lattice, triggering the decomposition of persulfate to produce sulfate radicals, greatly improving the efficiency of VO-Si bond breakage in the vanadium silicate lattice, further improving the exposure rate of the vanadium-containing phase, thereby improving the vanadium oxidation reaction efficiency, increasing the vanadium oxidation rate, and further improving the leaching rate of high-valent vanadium. The present invention converts the low-valent vanadium in the stone coal into high-valent vanadium through the synergistic effect of stone coal crushing, strong oxidant oxidation and microwave irradiation, replacing the high-temperature roasting process of traditional sodium roasting method and calcification roasting method, not only significantly reducing energy consumption, but also not generating toxic gases such as Cl2 and HCl; and also not generating insoluble calcium vanadate, reducing vanadium loss.

[0020] 2. The technical solution of the present invention adopts peroxide and persulfate as oxidants, which is mainly based on the following key factors: first, peroxide generates active free radicals (such as hydroxyl radical OH or sulfate radical SO4) under microwave irradiation conditions. - •. ), its oxidation potential is as high as 2.5~3.1V, which can effectively destroy the lattice structure of vanadium minerals in stone coal and oxidize low-valent vanadium into soluble V 5+ In contrast, the molecular structures of other oxidants are mainly ionic bonds or non-polar bonds, lacking microwave-sensitive polar functional groups and unable to achieve directional energy absorption through microwave fields. This efficient free radical generation mechanism not only significantly shortens the reaction time, but also reduces the decomposition products (H2O, SO4 2- ) Environmentally friendly, no need for complex post-processing, and no harmful by-products like other oxidants. For example, the Cr contained in potassium dichromate 6+ It is a strong carcinogen, and its residues pose a serious threat to the environment and human health. Subsequent treatment is complex and costly. During the oxidation process, sodium hypochlorite releases toxic gases such as Cl2 and ClO2, which not only pose a serious threat to the health of operators but also pollute the surrounding environment.

[0021] 3. The technical solution of the present invention uses a mixture of phosphoric acid and inorganic strong acid to dissolve and leach the activated sample. During the sample dissolution process, since the pH of the mixture of phosphoric acid and inorganic strong acid is less than 1, the phosphoric acid mainly exists in the form of undissociated H3PO4 molecules, which is difficult to react with Fe 3+ 、Al 3+ Combined to form iron phosphate and aluminum phosphate precipitation. In addition, phosphoric acid can form a stable complex with impurities such as iron and aluminum. This complex can form a protective film on the surface of stone coal powder, hindering the contact between inorganic strong acid and iron, aluminum and other impurities in the stone coal powder, thereby inhibiting the dissolution of impurities such as iron and aluminum, reducing the content of impurity ions such as iron and aluminum in the leachate, reducing the pressure of impurity removal in subsequent processes, saving the amount of impurity remover, shortening the standing time, and improving product purity.

[0022] 4. The technical solution of the present invention uses a mixture of phosphoric acid and inorganic strong acid to dissolve and leach the activated sample. Compared with the traditional acid leaching method using high-concentration strong acid for leaching, the acid concentration is low, the corrosion to the equipment is poor, the acid consumption is low, and the process cost is reduced.

[0023] 5. Because the main extractants P204 (di(2-ethylhexyl) phosphate) and PC-88A (2-ethylhexyl phosphate monoester) are mainly used to extract tetravalent vanadium, the present invention first adds iron powder to reduce the pentavalent vanadium in the leachate to tetravalent vanadium before extraction to ensure the extraction rate; then, the extractant is used in the leachate for extraction and separation, and back extraction is performed with 3-10% dilute sulfuric acid, which can achieve efficient and selective enrichment and purification of vanadium. Among them, the main extractant P204 or PC-88A can selectively enrich and purify vanadium through the phosphate group in its molecular structure. 4+ It exhibits high selective coordination ability and preferentially forms a hydrophobic complex with tetravalent vanadium under acidic conditions, thereby separating vanadium from the leachate containing impurity ions such as Fe, Al, and Si. After the co-extractant TBP (tributyl phosphate) is added as a neutral ligand, it enhances the binding ability of the main extractant with vanadium through synergistic coordination, while inhibiting Fe 2+ The diluent, acting as a solvent carrier, reduces the viscosity of the organic phase. Sulfonated kerosene further enhances the polarity and stability of the organic phase, making it more tolerant in acidic systems. Dilute sulfuric acid destroys the vanadium-extractant complex through a proton competition mechanism, rapidly dissociating the complex and achieving excellent stripping efficiency.

[0024] 6. During the impurity removal process, the present invention's technical solution combines the stripping solution with an alkaline solution and precisely adjusts the pH. This hydrolysis of residual impurity metal ions, such as Fe and Al, forms colloidal precipitates, such as Fe(OH)3 and Al(OH)3. Vanadium ions, however, remain soluble and stable in the liquid phase within this pH range, thereby achieving selective separation of impurities. Polyacrylamide (PAM), an anionic polymer flocculant, rapidly agglomerates dispersed colloidal particles into large flocs. After standing, the precipitate naturally settles, and the remaining suspended particles are then efficiently separated by centrifugal force for solid-liquid separation. DETAILED DESCRIPTION

[0025] The principles and features of the present invention are described below. The examples and comparative examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. In the examples, where specific conditions are not specified, conventional conditions or manufacturer-recommended conditions were used. Reagents or instruments used where the manufacturer is not specified are commercially available conventional products. Example 1

[0026] (1) 10 g of stone coal was crushed in a high-pressure roller mill to obtain fine powder, and the stone coal powder size was controlled to be 100-300 mesh. Subsequently, a 0.5% potassium persulfate aqueous solution was sprayed on the stone coal powder, and the stone coal powder was irradiated with microwaves at a power of 800 W for 5 min while maintaining constant stirring to obtain an activated sample. The mass ratio of potassium persulfate aqueous solution to stone coal powder was 5:1000.

[0027] (2) The activated sample was transferred to a leaching tank, and then a strong acid solution consisting of phosphoric acid and sulfuric acid in a molar ratio of 3:1 was added to the tank; the reaction was stirred to obtain a leaching solution; the stirring temperature was 70°C, the stirring speed was 400 rpm, and the stirring time was 5 h; the concentration of the phosphoric acid was 2.1 mol / L, the concentration of the sulfuric acid was 0.7 mol / L, and the volume mass ratio of the strong acid solution to the activated sample was 4 L:1 kg;

[0028] (3) Add iron powder to the leachate at a concentration of 3 g / L, then mix the leachate with an organic phase system consisting of P204+TBP+sulfonated kerosene (15%+5%+80%, volume fraction), and let it stand for 10 minutes to allow the two phases to separate, with the upper layer being a vanadium-rich phase and the lower layer being an aqueous phase; add 5% dilute sulfuric acid to the vanadium-rich phase for stripping, let it stand for 10 minutes to allow the two phases to separate, with the upper layer being an organic phase and the lower layer being a stripping solution containing vanadium;

[0029] (4) The stripping solution was mixed with a sodium hydroxide aqueous solution, and the pH value of the stripping solution was adjusted to 4.2. Subsequently, 5 mg / L of polyacrylamide flocculant was added, and the mixture was stirred evenly and allowed to stand for 1 hour to obtain a mixed solution. The mixed solution was poured into a centrifuge tube, and centrifuged at a speed of 3000 rpm for 10 minutes to separate the supernatant. The pH value of the supernatant was then adjusted to 2, and 2.5% concentration of hydrogen peroxide was added to obtain a purified solution.

[0030] (5) Mixing the purified liquid with ammonium chloride, adjusting the pH value of the purified liquid to 7, and obtaining a suspension; transferring the suspension to a centrifuge, and centrifuging at 4000 rpm for 5 min to obtain a lower layer of solid; washing the solid with deionized water, and drying at a constant temperature of 80°C for 6 h to obtain ammonium metavanadate;

[0031] (6) Ammonium metavanadate is placed in a tubular furnace and calcined at high temperature under air conditions. First, the heating rate is controlled to be 2°C / min to increase the temperature to 500°C, and the temperature is kept for 5 hours, and then cooled to room temperature to obtain vanadium pentoxide.

[0032] The vanadium content in the leachate was determined using an ultraviolet-visible spectrophotometer, and the vanadium content in the stone coal raw material was determined using X-ray fluorescence spectroscopy (XRF). The final calculated vanadium leaching rate was 90.3%.

[0033] The purity of the vanadium pentoxide product was tested using XRF, and the purity of the vanadium pentoxide was calculated to be 99.8%. Example 2

[0034] (1) 500 g of anthracite was crushed in a crusher to obtain fine powder, and the size of the anthracite powder was controlled to be 100-300 mesh. Subsequently, a 2.5% concentration of hydrogen peroxide aqueous solution was sprayed on the anthracite powder, and the anthracite powder was irradiated with microwaves at a power of 500 W for 15 minutes while maintaining constant stirring to obtain an activated sample; the mass ratio of hydrogen peroxide aqueous solution to anthracite powder was maintained at 8:1000;

[0035] (2) The activated sample was transferred to a leaching tank, and then a strong acid solution consisting of phosphoric acid and hydrochloric acid in a molar ratio of 1:1 was added to the tank; the reaction was stirred to obtain a leaching solution; the stirring temperature was 60°C, the stirring speed was 500 rpm, and the stirring time was 2 h; the concentration of the phosphoric acid was 0.5 mol / L, the concentration of the hydrochloric acid was 0.5 mol / L, and the volume mass ratio of the strong acid solution to the activated sample was 5 L:1 kg;

[0036] (3) Add iron powder to the leachate at a concentration of 6 g / L, then mix the leachate with an organic phase system consisting of P204+TBP+sulfonated kerosene (10%+10%+80%, volume fraction), and then let it stand for 20 minutes to allow the two phases to separate into layers. The upper layer is a vanadium-rich phase enriched in vanadium, and the lower layer is an aqueous phase. Add 10% dilute sulfuric acid to the vanadium-rich phase for stripping, let it stand for 15 minutes, and allow the two phases to separate into layers. The upper layer is the organic phase after stripping, and the lower layer is the stripping solution containing vanadium.

[0037] (4) Mix the stripping solution with ammonia water, adjust the pH value of the stripping solution to 4, then add 2 mg / L polyacrylamide flocculant, stir evenly and let it stand for 3 hours to obtain a mixed solution, pour the mixed solution into a centrifuge tube, centrifuge at 3000 rpm for 15 minutes, separate the supernatant, and then adjust the pH value of the supernatant to 2.5, add 2% concentration of hydrogen peroxide to obtain a purified solution;

[0038] (5) The purified liquid was mixed with ammonium sulfate, and the pH value of the purified liquid was adjusted to 7.5 to obtain a suspension; the suspension was transferred to a centrifuge and centrifuged at 5000 rpm for 4 minutes to obtain a lower layer of solid; the solid was washed with deionized water and dried at a constant temperature of 70°C for 8 hours to obtain ammonium metavanadate;

[0039] (6) Ammonium metavanadate is placed in a tubular furnace and calcined at high temperature under air conditions. First, the heating rate is controlled to be 3°C / min to increase the temperature to 600°C, and the temperature is kept for 3 hours, and then cooled to room temperature to obtain vanadium pentoxide.

[0040] The vanadium leaching rate in this embodiment is 87.7%, and the purity of vanadium pentoxide is 99.6%. Example 3

[0041] (1) 1 kg of stone coal was crushed in a high-pressure roller mill to obtain fine powder, and the size of the stone coal powder was controlled to be 100-300 mesh. Subsequently, a 5% sodium persulfate aqueous solution was sprayed on the stone coal powder, and the stone coal powder was irradiated with microwaves at a power of 1000 W for 10 minutes while maintaining constant stirring to obtain an activated sample. The mass ratio of hydrogen peroxide aqueous solution to stone coal powder was maintained at 10:1000.

[0042] (2) The activated sample was transferred to a leaching tank, and then a strong acid solution consisting of phosphoric acid, sulfuric acid, and hydrochloric acid in a molar ratio of 5:0.3:0.7 was added to the tank; the reaction was stirred to obtain a leaching solution; the stirring temperature was 100°C, the stirring speed was 200 rpm, and the stirring time was 3 h; the concentration of the phosphoric acid was 5 mol / L, the concentration of the sulfuric acid was 0.3 mol / L, and the concentration of the hydrochloric acid was 0.7 mol / L; the volume mass ratio of the strong acid solution to the activated sample was 6 L:1 kg;

[0043] (3) Add iron powder to the leachate at a concentration of 5 g / L, then mix the leachate with an organic phase system consisting of PC-88A + sulfonated kerosene (10% + 90%, volume fraction), and then let it stand for 15 minutes to allow the two phases to separate, with the upper layer being a vanadium-rich phase and the lower layer being an aqueous phase; add 3% dilute sulfuric acid to the vanadium-rich phase for stripping, let it stand for 20 minutes to allow the two phases to separate, with the upper layer being the organic phase after stripping and the lower layer being the stripping solution containing vanadium;

[0044] (4) Mix the stripping solution with ammonia water, adjust the pH value of the stripping solution to 5, then add 5 mg / L polyacrylamide flocculant, stir evenly and let it stand for 2 hours to obtain a mixed solution, pour the mixed solution into a centrifuge tube, centrifuge at 6000 rpm for 5 minutes, separate the supernatant, and then adjust the pH value of the supernatant to 3, add 2% concentration of hydrogen peroxide to obtain a purified solution;

[0045] (5) Mixing the purified liquid with ammonia water, adjusting the pH value of the purified liquid to 8, and obtaining a suspension; transferring the suspension to a centrifuge, and centrifuging at 5000 rpm for 3 min to obtain a lower layer of solid; washing the solid with deionized water, and drying at a constant temperature of 75°C for 6 h to obtain ammonium metavanadate;

[0046] (6) Ammonium metavanadate is placed in a tubular furnace and calcined at high temperature under air conditions. First, the heating rate is controlled to be 5°C / min to 500°C, and the temperature is kept for 4 hours, and then cooled to room temperature to obtain vanadium pentoxide.

[0047] The vanadium leaching rate in this embodiment is 89.5%, and the purity of vanadium pentoxide is 99.7%. Example 4

[0048] (1) 10 kg of stone coal was crushed in a ball mill to obtain fine powder, and the size of the stone coal powder was controlled to be 100-300 mesh. Subsequently, a 1% concentration of potassium persulfate aqueous solution was sprayed on the stone coal powder, and the stone coal powder was irradiated with microwaves at a power of 1500 W for 8 minutes while maintaining constant stirring to obtain an activated sample; the mass ratio of hydrogen peroxide aqueous solution to stone coal powder was maintained at 12:1000;

[0049] (2) The activated sample was transferred to a leaching tank, and then a strong acid solution consisting of phosphoric acid, sulfuric acid, hydrochloric acid, and nitric acid in a molar ratio of 1:0.3:0.5:0.2 was added to the tank; the reaction was stirred to obtain a leaching solution; the stirring temperature was 80°C, the stirring speed was 300 rpm, and the stirring time was 1 h; the concentration of the phosphoric acid was 1 mol / L, the concentration of the sulfuric acid was 0.3 mol / L, the concentration of the hydrochloric acid was 0.5 mol / L, and the concentration of the nitric acid was 0.2 mol / L; the volume mass ratio of the strong acid solution to the activated sample was 4 L:1 kg;

[0050] (3) Add iron powder to the leachate at a concentration of 4 g / L, then mix the leachate with an organic phase system consisting of PC-88A + sulfonated kerosene (20% + 80%, volume fraction), and then let it stand for 25 minutes to allow the two phases to separate, with the upper layer being a vanadium-rich phase and the lower layer being an aqueous phase; add 6% dilute sulfuric acid to the vanadium-rich phase for stripping, let it stand for 10 minutes, and allow the two phases to separate, with the upper layer being the organic phase after stripping and the lower layer being the stripping solution containing vanadium;

[0051] (4) The stripping solution was mixed with potassium hydroxide, and the pH value of the stripping solution was adjusted to 4.5. Subsequently, 3 mg / L of polyacrylamide flocculant was added, and the mixture was stirred evenly and allowed to stand for 1 hour to obtain a mixed solution. The mixed solution was poured into a centrifuge tube and centrifuged at 2000 rpm for 20 minutes to separate the supernatant. The pH value of the supernatant was then adjusted to 3, and 2.5% concentration of hydrogen peroxide was added to obtain a purified solution.

[0052] (5) The purified liquid was mixed with ammonium sulfate, and the pH value of the purified liquid was adjusted to 8 to obtain a suspension; the suspension was transferred to a centrifuge and centrifuged at 6000 rpm for 2 minutes to obtain a lower layer of solid; the solid was washed with deionized water and dried at a constant temperature of 60°C for 8 hours to obtain ammonium metavanadate;

[0053] (6) Ammonium metavanadate is placed in a tubular furnace and calcined at high temperature under air conditions. First, the heating rate is controlled to be 5°C / min to increase the temperature to 550°C, and the temperature is kept for 3 hours, and then cooled to room temperature to obtain vanadium pentoxide.

[0054] The vanadium leaching rate in this embodiment is 88.9%, and the purity of vanadium pentoxide is 99.7%. Comparative Example 1

[0055] The size of the stone coal powder in this comparative example is 10 mesh, and the other processes are the same as those in Example 1.

[0056] The vanadium leaching rate of this comparative example is 60.1%, and the purity of vanadium pentoxide is 99.3%. Comparative Example 2

[0057] The size of the stone coal powder in this comparative example is 50 mesh, and the other processes are the same as those in Example 1.

[0058] The vanadium leaching rate of this comparative example is 69.0%, and the purity of vanadium pentoxide is 99.1%. Comparative Example 3

[0059] The power of the microwave radiation in this comparative example is 300 W, and the other processes are the same as those in Example 1.

[0060] The vanadium leaching rate of this comparative example is 53.9%, and the purity of vanadium pentoxide is 99.7%. Comparative Example 4

[0061] The microwave irradiation time of this comparative example is 3 minutes, and the other processes are consistent with those of Example 1.

[0062] The vanadium leaching rate of this comparative example is 59.5%, and the purity of vanadium pentoxide is 99.2%. Comparative Example 5

[0063] The molar ratio of phosphoric acid to hydrochloric acid in this comparative example is 0.5:1, and the other procedures are consistent with those in Example 1.

[0064] The vanadium leaching rate of this comparative example is 89.3%, and the purity of vanadium pentoxide is 97.1%.

[0065]

[0066] In order to verify the process advantages of the present invention, we conducted a systematic control test on the key steps. The results show that different process conditions have a significant effect on the extraction rate of vanadium. The stone coal powder in Comparative Examples 1 and 2 is relatively large in size, resulting in a reduced exposure rate of the vanadium host phase, and it is difficult for the peroxide or persulfate strong oxidant aqueous solution and the strong acid solution to fully contact the vanadium phase, thereby reducing the vanadium leaching rate; secondly, the larger size is not conducive to the penetration of microwave irradiation, because the microwave energy is difficult to effectively transmit to the interior of the particles, thereby limiting the destructive effect of microwaves on the mineral lattice structure. These problems together lead to unsatisfactory leaching effects in Comparative Examples 1 and 2. The microwave radiation power and time caused by Comparative Examples 3 and 4 are respectively too low, resulting in insufficient microwave energy to effectively destroy the mineral lattice structure. This defect directly reduces the exposure rate of the vanadium host phase, resulting in poor vanadium leaching performance. The present invention converts low-valent vanadium in stone coal into high-valent vanadium through the synergistic effects of stone coal crushing, strong oxidant oxidation, and microwave irradiation. This replaces the high-temperature roasting process of traditional sodium roasting and calcium roasting methods, significantly reducing energy consumption and producing no toxic gases such as Cl2 and HCl. It also does not produce insoluble calcium vanadate, reducing vanadium loss. The product purity of Comparative Example 5 is lower than that of Example 1, indicating that an appropriate proportion of phosphoric acid can significantly inhibit the dissolution of impurities such as iron and aluminum. In the vanadium extraction process, impurities such as iron and aluminum are easily oxidized by strong oxidants and enter the leachate, increasing the difficulty of subsequent impurity removal. By controlling the amount of phosphoric acid used, the content of these impurity ions in the leachate can be reduced, thereby alleviating the pressure of impurity removal in subsequent steps and ultimately improving the purity of the product.

[0067] The above-described specific embodiments further illustrate the present invention in detail, but these descriptions should not be construed as limiting the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A process for extracting vanadium from stone coal, characterized in that: The steps include: (1) First, stone coal is crushed into fine powder, and then a strong oxidant aqueous solution is sprayed on the stone coal powder, and microwave irradiation is performed to obtain an activated sample, wherein the strong oxidant is peroxide or persulfate; (2) Immersing the activated sample in a strong acid solution, heating and stirring to obtain a suspension, and separating the solid and liquid to obtain a leachate; the strong acid solution is a mixture of phosphoric acid and an inorganic strong acid, the concentration of the inorganic strong acid in the strong acid solution is 0.5 to 1 mol / L, and the molar ratio of phosphoric acid to the inorganic strong acid is 1 to 5:1; (3) adding iron powder to the leachate, then extracting the leachate with a phosphoric acid extractant to obtain a vanadium-rich phase, and then stripping the vanadium-rich phase with dilute sulfuric acid to obtain a stripping solution; (4) The pH of the stripping solution is adjusted to 4-5, and then polyacrylamide is added. After stirring evenly, the solution is allowed to stand for solid-liquid separation. The pH of the solution is then adjusted to 2-3, and hydrogen peroxide is added to obtain a purified solution. (5) Adding ammonia water or ammonium salt to the purified liquid to adjust the pH to 7-8 to obtain a suspension; The suspension is centrifuged, washed, and dried to obtain ammonium metavanadate; (6) Ammonium metavanadate is calcined at high temperature in air to obtain vanadium pentoxide.

2. The process for extracting vanadium from stone coal according to claim 1, characterized in that: In the step (1), the strong oxidant is one of hydrogen peroxide, potassium persulfate, sodium persulfate, and potassium hydrogen persulfate; the mass concentration of the strong oxidant in the strong oxidant aqueous solution is 0.5-5.0%; the mass ratio of the strong oxidant aqueous solution to the stone coal powder is 5-12:1000; the size of the stone coal powder is 100-300 mesh; the microwave power is 500-1500W; and the irradiation time is 5-15 minutes.

3. The process for extracting vanadium from stone coal according to claim 1, characterized in that: In step (2), the inorganic strong acid includes at least one of hydrochloric acid, nitric acid, and sulfuric acid, the volume mass ratio of the strong acid solution to the stone coal is 4-6 L:1 kg, the stirring temperature is 60-100° C., the stirring time is 1-5 h, and the stirring speed is 200-500 rpm.

4. The process for extracting vanadium from stone coal according to claim 1, characterized in that: In the step (3), the concentration of iron powder in the leaching solution is 3-6 g / L, the phosphoric acid extractant is one of P204+TBP+sulfonated kerosene and PC-88A+sulfonated kerosene; and the mass concentration of dilute sulfuric acid is 3-10%.

5. The process for extracting vanadium from stone coal according to claim 1, characterized in that: In the step (5), the ammonium salt is one of ammonium chloride and ammonium sulfate, the detergent is water or ethanol, the centrifugal speed is 4000-6000 rpm, the centrifugal time is 2-5 minutes, and the drying temperature is 60-80°C, and the drying time is 6-8 hours.

6. The process for extracting vanadium from stone coal according to claim 1, characterized in that: In step (6), the specific steps of high-temperature calcination are: controlling the heating rate to be 2-5°C / min to raise the temperature to 500-600°C, and keeping the temperature for 3-5h.

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