Method for deeply extracting vanadium from vanadium-containing slurry

Abstract

The invention relates to the technical field of refining, in particular to a method for deeply extracting vanadium from vanadium-containing slurry, which sequentially comprises the following steps: (1) microwave-mechanical coupling roasting modification; (2) composite synergistic leaching; (3) graded oxidation and vanadium precipitation; (4) recycling closed-loop treatment; from the perspective of the synergistic effect of the whole technical scheme, microwave-mechanical coupling roasting modification provides an easily leached modified product for composite synergistic leaching, and composite synergistic leaching provides a leaching solution with high vanadium concentration and low impurities for graded oxidation vanadium precipitation; the graded oxidation vanadium precipitation provides a high-purity product and filtrate and leaching residues which are easy to treat for recycling closed-loop treatment, the leaching residues are prepared into silicate bricks through the recycling closed-loop treatment, the filtrate is recycled and reused to a roasting procedure after being concentrated by a nanofiltration membrane and subjected to impurity interception, recycling of resources is achieved, and the economic benefit is increased. Meanwhile, the discharge of solid wastes and wastewater is reduced, and the environmental pollution is reduced.

Description

Technical Field

[0001] This invention relates to the field of refining technology, specifically a method for deep vanadium extraction from vanadium-containing mud. Background Technology

[0002] Vanadium is an important strategic metal widely used in steel, chemical, and new energy industries, with market demand continuously increasing. Vanadium-containing slurry is a solid waste generated during vanadium smelting and chemical production processes, typically containing 0.5%-3.0% vanadium. Direct dumping or landfilling of this slurry not only wastes vanadium resources but also pollutes soil and groundwater due to the seepage of heavy metal ions, posing serious environmental risks. Therefore, achieving efficient extraction and resource utilization of vanadium from vanadium-containing slurry aligns with industrial policies promoting resource recycling and addresses solid waste pollution, possessing significant economic and environmental value.

[0003] Currently, the common processes for vanadium extraction from vanadium-containing slurry mainly include three steps: roasting, leaching, and vanadium precipitation. However, existing processes generally suffer from numerous technical defects, making it difficult to meet the high-efficiency and environmentally friendly requirements of industrial production. In the roasting stage, traditional processes mostly use muffle furnaces for static roasting. This method results in uneven heating and insufficient mixing of the vanadium-containing slurry and flux, easily leading to vanadium lattice agglomeration. Some vanadium is trapped in the slurry matrix and cannot be effectively released, thus reducing subsequent leaching efficiency. At the same time, static roasting is time-consuming and energy-intensive, increasing production costs. In the leaching stage, most processes use only a single leaching agent, resulting in poor leaching selectivity. Not only is the vanadium leaching rate low, but a large amount of impurities are also leached along with it, making subsequent vanadium precipitation and purification difficult.

[0004] Current vanadium extraction technology from vanadium-containing mud suffers from problems such as low vanadium leaching rate, insufficient product purity, low resource utilization, high energy consumption, and serious pollution, making it difficult to balance economic, environmental, and social benefits.

[0005] Therefore, developing a method for deep vanadium extraction from vanadium-containing mud that can overcome the above-mentioned technical deficiencies and achieve efficient extraction, high-purity recovery, and closed-loop utilization of vanadium has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide a method for deep vanadium extraction from vanadium-containing mud.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] The method for deep vanadium extraction from vanadium-containing mud includes the following steps:

[0009] (1) Microwave-mechanical coupling roasting modification: Vanadium-containing slurry and sodium carbonate are mixed evenly at a mass ratio of 100:5.8-6.2 and placed in a microwave-mechanical coupling field for roasting. The microwave power is 200-300W and the frequency is 2.45GHz. The mechanical stirring speed is 30-60r / min. The roasting temperature is controlled at 550-650℃ and the roasting time is 1.5-2.5h. After roasting, the mixture is cooled to room temperature and pulverized to a particle size ≤1mm to obtain the roasted modified product.

[0010] (2) Composite synergistic leaching: The calcined modified product of step (1) is mixed with water at a solid-liquid ratio of 1:1.2-1.5, sodium sulfate and sodium metabisulfite are added, the pH of the system is adjusted to 4.0-5.0, and leaching is carried out at 80-90℃ and stirring speed of 60-80r / min for 45-60min. The solid and liquid are separated to obtain vanadium-containing leachate and leachate residue.

[0011] The concentration of sodium sulfate in the addition system is 5-8 g / L, and the concentration of sodium metabisulfite in the addition system is 0.5-1.0 g / L;

[0012] (3) Graded oxidation precipitation of vanadium:

[0013] ① Primary vanadium precipitation: Add ammonium sulfate to the vanadium-containing leachate from step (2), according to the reaction of V2O5 and NH4. + Add the ammonium polyvanadate at a molar ratio of 1:1.5-1.8, adjust the pH to 1.8-2.0, stir the reaction at 80-100 r / min for 30-40 min, and precipitate the coarse precipitate of ammonium polyvanadate. Filter to separate the coarse precipitate and the primary vanadium filtrate.

[0014] ②Oxidation adjustment: Add sodium chlorate to the primary vanadium precipitate filtrate, the dosage being equal to the V concentration in the filtrate. 3+ Oxidation is completed within 20-30 minutes at 1.2-1.5 times the molar amount.

[0015] ③ Secondary vanadium precipitation: Add ammonium oxalate to the filtrate after oxidation, according to the reaction of V2O5 and NH4. + Add the product at a molar ratio of 1:2.0-2.5, adjust the pH to 2.2-2.5, stir the reaction at 80-100 r / min for 30-40 min, and fine precipitate of ammonium polyvanadate will be precipitated. Filter to separate the fine precipitate; combine the coarse precipitate and the fine precipitate, wash, dry, and calcine at 550-600℃ for 2-3 h to obtain the V2O5 product.

[0016] (4) Resource-based closed-loop treatment: The leaching residue from step (2) is washed with deionized water 2-3 times, with a liquid-to-solid ratio of 1:1.0-1.2 each time, until there is no obvious chloride ion residue, and then used to prepare silicate bricks; The filtrate after the secondary vanadium precipitation in step (3) is concentrated 3-5 times using a nanofiltration membrane with a molecular weight cutoff of 100-200 Da to remove soluble impurities, and sodium carbonate is added to match the initial mixing concentration in step (1), and then recycled back to the calcination and modification process in step (1).

[0017] As a further technical solution, before mixing, the vanadium-containing slurry in step (1) is dehydrated by plate and frame filter press to a moisture content of 65-80% to avoid excessive moisture affecting the roasting efficiency.

[0018] As a further technical solution, in the microwave-mechanical coupling calcination in step (1), the microwave power is gradient controlled, 200W for 0-0.5h and 250-300W for 0.5-2.5h, to avoid local overheating that leads to vanadium lattice agglomeration.

[0019] As a further technical solution, in the composite synergistic leaching process described in step (2), dilute sulfuric acid is used for pH adjustment, and the stirring speed is kept constant to avoid local pH fluctuations that could lead to vanadium ion hydrolysis.

[0020] As a further technical solution, the reaction temperature of the primary vanadium precipitation in step (3)① is 60-70℃, and the reaction temperature of the secondary vanadium precipitation in step (3)③ is 70-80℃, matching the vanadium ion precipitation kinetic characteristics.

[0021] As a further technical solution, in the oxidation adjustment process described in step (3) ②, a constant stirring speed of 60-80 r / min is used to ensure that sodium chlorate is evenly dispersed and to avoid incomplete local oxidation.

[0022] As a further technical solution, the vanadium enrichment washing in step (3) uses 1-2wt% dilute ammonia water to remove sulfate and chloride ion impurities adsorbed on the surface and improve product purity.

[0023] As a further technical solution, in the nanofiltration membrane concentration process described in step (4), the operating pressure is controlled at 0.3-0.5MPa and the temperature at 25-35℃ to extend the service life of the nanofiltration membrane.

[0024] As a further technical solution, when preparing silicate bricks from the leaching residue in step (4), 10-15% of the leaching residue mass of kaolin is added to improve the brick strength, which meets the relevant standards of the building materials industry.

[0025] As a further technical solution, after sodium carbonate is added to the recycled filtrate, the chloride ion content of the system needs to be detected to ensure that the residual chloride ion content in the recycling system is ≤0.5%, so as to avoid accumulation that affects the vanadium extraction effect.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] This invention achieves deep extraction, high-purity recovery, and closed-loop utilization of vanadium from vanadium-containing slurry through the matching and synergistic effects of various steps and processes. By employing a microwave-mechanical coupled roasting modification process, combined with gradient microwave power control and mechanical stirring, compared to traditional static roasting, microwaves enable rapid and uniform heating of the material, while mechanical stirring ensures thorough mixing of the vanadium-containing slurry and sodium carbonate, preventing localized agglomeration. The synergistic effect of these two processes disrupts the crystal structure of the vanadium-containing slurry, reducing vanadium crystal aggregation and facilitating the release of vanadium from the slurry matrix. This significantly improves the vanadium leaching rate in subsequent leaching processes, thus solving the problems of low leaching rate and high energy consumption associated with traditional roasting. Simultaneously, gradient microwave power control avoids vanadium loss due to localized overheating, further enhancing vanadium recovery and laying the foundation for subsequent high-purity vanadium precipitation. Furthermore, plate and frame filtration dehydration of the vanadium-containing slurry before roasting, controlling the moisture content to 65%-80%, avoids decreased roasting efficiency due to excessive moisture, reduces energy waste, and further optimizes the roasting effect.

[0028] The composite synergistic leaching process, which combines sodium sulfate and sodium metabisulfite, enhances the ionic strength of the leaching system and promotes the dissolution of vanadium in the roasted modified product. Sodium metabisulfite, on the other hand, regulates the system environment and inhibits the oxidation loss of vanadium. The synergistic effect of the two improves leaching selectivity and reduces the co-leaching of impurities, thereby reducing the difficulty of subsequent vanadium precipitation and purification. This solves the problems of poor leaching selectivity and high impurity content associated with traditional single leaching agents. At the same time, adjusting the pH of the system to 4.0-5.0 with 5% mass concentration dilute sulfuric acid, combined with leaching temperature and stirring speed, further optimizes leaching conditions, improves leaching efficiency, and ensures complete vanadium leaching. The adoption of the staged oxidation precipitation process involves first recovering most of the high-valence vanadium in the leachate through primary precipitation, then converting the remaining low-valence vanadium into high-valence vanadium through oxidation, and finally recovering the remaining vanadium through secondary precipitation. This stepwise precipitation method not only maximizes the recovery of vanadium in the leachate and improves the vanadium recovery rate, but also gradually removes impurities from the solution through two precipitation processes, thereby improving the purity of the V2O5 product. This solves the problems of low vanadium recovery rate and insufficient product purity in the traditional single precipitation process.

[0029] From the perspective of the synergistic effect of the entire technical solution, microwave-mechanical coupling roasting modification provides easily leached modified products for composite synergistic leaching, composite synergistic leaching provides high vanadium concentration and low impurity leachate for graded vanadium oxidation precipitation, graded vanadium oxidation precipitation provides high-purity products and easily treated filtrate and leaching residue for resource-based closed-loop treatment, and resource-based closed-loop treatment prepares silicate bricks from leaching residue, concentrates the filtrate through nanofiltration membrane, removes impurities, and then recycles it to the roasting process, realizing the recycling of resources, while reducing solid waste and wastewater discharge and reducing environmental pollution. Attached Figure Description

[0030] Figure 1 Flowchart of a method for deep vanadium extraction from vanadium-containing mud. Detailed Implementation

[0031] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0032] The present invention provides a method for deep vanadium extraction from vanadium-containing mud, which achieves efficient extraction and resource recycling of vanadium from vanadium-containing mud through the synergistic effects of microwave-mechanical coupled roasting modification, composite synergistic leaching, graded oxidation precipitation of vanadium, and resource-based closed-loop treatment. This method overcomes the technical defects of traditional vanadium extraction methods, such as low leaching rate, resource waste, and environmental pollution.

[0033] The following are specific examples:

[0034] Example 1:

[0035] The method for deep vanadium extraction from vanadium-containing mud in this embodiment includes the following steps in sequence:

[0036] Step (1) Microwave-mechanical coupling calcination modification:

[0037] First, the vanadium-containing slurry was pretreated by dehydrating it to a moisture content of 65% using plate and frame filter press to avoid excessive moisture affecting calcination efficiency. Then, the dehydrated vanadium-containing slurry was mixed with sodium carbonate at a mass ratio of 100:5.8 to ensure uniform dispersion and no local agglomeration. The uniformly mixed material was then placed in a microwave-mechanical coupling field for calcination. The microwave power was gradient-controlled: 200W for 0-0.5h and 250W for 0.5-2.5h to prevent local overheating and vanadium lattice agglomeration. The microwave frequency was fixed at 2.45GHz, the mechanical stirring speed was 30r / min, the calcination temperature was controlled at 550℃, and the calcination time was 1.5h. After calcination, the material was allowed to cool naturally to room temperature and then pulverized to a particle size ≤1mm to obtain the calcined modified product for later use.

[0038] Step (2) Composite synergistic leaching:

[0039] The calcined modified product obtained in step (1) was mixed with water at a solid-liquid ratio of 1:1.2. Sodium sulfate and sodium metabisulfite were added, with the concentration of sodium sulfate in the system being 5 g / L and the concentration of sodium metabisulfite being 0.5 g / L. The pH of the system was adjusted to 4.0 using 5% dilute sulfuric acid. The mixture was placed in a reactor, and the reaction temperature was controlled at 80℃ with a stirring speed of 60 r / min. Under these conditions, the mixture was leached at a constant temperature for 45 min. After leaching, solid-liquid separation was performed using plate and frame filtration. The vanadium-containing leachate and leaching residue were collected separately. The leaching residue was kept for later use, and the vanadium-containing leachate was used in the next step.

[0040] Step (3) Graded oxidation precipitation of vanadium:

[0041] ① Primary vanadium precipitation: Take the vanadium-containing leachate obtained in step (2), add ammonium sulfate to it, and react V2O5 and NH4. + Ammonium sulfate was added at a molar ratio of 1:1.5. The pH of the system was adjusted to 1.8 using 5% dilute sulfuric acid. The reaction temperature was controlled at 60℃, and the stirring speed was 80 r / min. The reaction was carried out at a constant temperature and with stirring for 30 min. During the reaction, a crude precipitate of ammonium polyvanadate gradually precipitated out. After the reaction was completed, the mixture was filtered to separate the crude ammonium polyvanadate precipitate and the primary vanadium precipitate filtrate. The primary vanadium precipitate filtrate was used for later use.

[0042] ②Oxidation adjustment: Take the primary vanadium precipitate filtrate obtained in step (3) ①, and add sodium chlorate to it. The amount of sodium chlorate added is V in the filtrate. 3+ Use 1.2 times the molar amount of water, maintain a constant stirring speed of 60 r / min, and complete the oxidation reaction within 20 min to ensure V. 3+ It is completely oxidized to high-valence vanadium.

[0043] ③ Secondary vanadium precipitation: Add ammonium oxalate to the oxidized filtrate, according to the reaction of V2O5 and NH4. +Ammonium oxalate was added at a molar ratio of 1:2.0. The pH of the system was adjusted to 2.2 using 5% dilute sulfuric acid. The reaction temperature was controlled at 70℃, and the stirring speed was 80 r / min. The reaction was carried out at a constant temperature and stirring for 30 min, resulting in the precipitation of fine ammonium polyvanadate. After the reaction was completed, the fine ammonium polyvanadate precipitate was obtained by filtration. The coarse precipitate obtained from the first-stage vanadium precipitation and the fine precipitate obtained from the second-stage vanadium precipitation were combined and washed with 1 wt% dilute ammonia water to remove sulfate and chloride ion impurities adsorbed on the precipitate surface. After washing, the precipitate was dried in a drying oven to constant weight, and then placed in a muffle furnace and calcined at 550℃ for 2 h. After cooling, V2O5 product was obtained.

[0044] Step (4) Resource recycling closed-loop processing:

[0045] Take the leaching residue obtained in step (2), wash it twice with deionized water, with a liquid-to-solid ratio of 1:1.0 each time. After washing, test the chloride ion content in the leaching residue until there is no obvious chloride ion residue. Add 10% of the mass of kaolin to the leaching residue after washing, mix evenly, and then press and cure it using conventional silicate brick preparation process to obtain silicate bricks. Take the filtrate after secondary vanadium precipitation in step (3) ③, concentrate it using a nanofiltration membrane with a molecular weight cutoff of 100 Da, control the nanofiltration membrane operating pressure at 0.3 MPa and the temperature at 25 °C, concentrate it 3 times, and remove soluble impurities in the filtrate. After concentration, add sodium carbonate to the filtrate until it is consistent with the initial mixing concentration in step (1), and then test the chloride ion content in the circulation system to ensure that the chloride ion residue is ≤0.5%. Recycle the treated filtrate back to the calcination modification process in step (1).

[0046] Example 2:

[0047] The method for deep vanadium extraction from vanadium-containing mud in this embodiment includes the following steps in sequence:

[0048] Step (1) Microwave-mechanical coupling calcination modification:

[0049] First, the vanadium-containing slurry was pretreated by dehydrating it to 80% moisture content using plate and frame filter press to avoid excessive moisture affecting calcination efficiency. Then, the dehydrated vanadium-containing slurry was mixed with sodium carbonate at a mass ratio of 100:6.2 to ensure uniform dispersion and no local agglomeration. The uniformly mixed material was then placed in a microwave-mechanical coupling field for calcination. The microwave power was gradient-controlled: 200W for 0-0.5h and 300W for 0.5-2.5h to prevent local overheating and vanadium lattice agglomeration. The microwave frequency was fixed at 2.45GHz, the mechanical stirring speed was 60r / min, the calcination temperature was controlled at 650℃, and the calcination time was 2.5h. After calcination, the material was allowed to cool naturally to room temperature and then pulverized to a particle size ≤1mm to obtain the calcined modified product for later use.

[0050] Step (2) Composite synergistic leaching:

[0051] The calcined modified product obtained in step (1) was mixed with water at a solid-liquid ratio of 1:1.5. Sodium sulfate and sodium metabisulfite were added, with the concentration of sodium sulfate in the system being 8 g / L and the concentration of sodium metabisulfite being 1.0 g / L. The pH of the system was adjusted to 5.0 using 5% dilute sulfuric acid. The mixture was placed in a reactor, and the reaction temperature was controlled at 90℃ with a stirring speed of 80 r / min. The mixture was leached at this constant temperature for 60 min. After leaching, solid-liquid separation was performed using plate and frame filtration. The vanadium-containing leachate and leaching residue were collected separately. The leaching residue was kept for later use, and the vanadium-containing leachate was used in the next step.

[0052] Step (3) Graded oxidation precipitation of vanadium:

[0053] ① Primary vanadium precipitation: Take the vanadium-containing leachate obtained in step (2), add ammonium sulfate to it, and react V2O5 and NH4. + Ammonium sulfate was added at a molar ratio of 1:1.8. The pH of the system was adjusted to 2.0 using 5% dilute sulfuric acid. The reaction temperature was controlled at 70℃, and the stirring speed was 100 r / min. The reaction was carried out at a constant temperature and with stirring for 40 min. During the reaction, a crude precipitate of ammonium polyvanadate gradually precipitated out. After the reaction was completed, the mixture was filtered to separate the crude ammonium polyvanadate precipitate and the primary vanadium precipitate filtrate. The primary vanadium precipitate filtrate was used for later use.

[0054] ②Oxidation adjustment: Take the primary vanadium precipitate filtrate obtained in step (3) ①, and add sodium chlorate to it. The amount of sodium chlorate added is V in the filtrate. 3+ Use 1.5 times the molar amount of water, control the stirring speed at a constant rate of 80 r / min, and complete the oxidation reaction within 30 minutes to ensure V 3+ It is completely oxidized to high-valence vanadium.

[0055] ③ Secondary vanadium precipitation: Add ammonium oxalate to the oxidized filtrate, according to the reaction of V2O5 and NH4. + Ammonium oxalate was added at a molar ratio of 1:2.5. The pH of the system was adjusted to 2.5 using 5% dilute sulfuric acid. The reaction temperature was controlled at 80℃, and the stirring speed was 100 r / min. The reaction was carried out at a constant temperature and stirring for 40 min, resulting in the precipitation of fine ammonium polyvanadate. After the reaction was completed, the fine ammonium polyvanadate precipitate was obtained by filtration. The coarse precipitate obtained from the first-stage vanadium precipitation and the fine precipitate obtained from the second-stage vanadium precipitation were combined and washed with 2wt% dilute ammonia water to remove sulfate and chloride ion impurities adsorbed on the precipitate surface. After washing, the precipitate was dried in a drying oven to constant weight, and then placed in a muffle furnace and calcined at 600℃ for 3 h. After cooling, V2O5 product was obtained.

[0056] Step (4) Resource recycling closed-loop processing:

[0057] Take the leaching residue obtained in step (2), wash it three times with deionized water, with a liquid-to-solid ratio of 1:1.2 each time. After washing, test the chloride ion content in the leaching residue until there is no obvious chloride ion residue. Add 15% of the mass of kaolin to the leaching residue after washing, mix evenly, and then press and cure it using conventional silicate brick preparation process to obtain silicate bricks. Take the filtrate after secondary vanadium precipitation in step (3) ③, concentrate it using a nanofiltration membrane with a molecular weight cutoff of 200 Da, control the nanofiltration membrane operating pressure at 0.5 MPa and the temperature at 35℃, concentrate it 5 times, and remove soluble impurities in the filtrate. After concentration, add sodium carbonate to the filtrate until it is consistent with the initial mixing concentration in step (1), and then test the chloride ion content in the circulation system to ensure that the chloride ion residue is ≤0.5%. Recycle the treated filtrate back to the calcination modification process in step (1).

[0058] Example 3:

[0059] The method for deep vanadium extraction from vanadium-containing mud in this embodiment includes the following steps in sequence:

[0060] Step (1) Microwave-mechanical coupling calcination modification:

[0061] First, the vanadium-containing slurry was pretreated by dehydrating it to a moisture content of 72% using plate and frame filter press to avoid excessive moisture affecting calcination efficiency. Then, the dehydrated vanadium-containing slurry was mixed with sodium carbonate at a mass ratio of 100:6.0 to ensure uniform dispersion and no local agglomeration. The uniformly mixed material was then placed in a microwave-mechanical coupling field for calcination. The microwave power was gradient-controlled: 200W for 0-0.5h and 275W for 0.5-2.5h to prevent local overheating and vanadium lattice agglomeration. The microwave frequency was fixed at 2.45GHz, the mechanical stirring speed was 45r / min, the calcination temperature was controlled at 600℃, and the calcination time was 2.0h. After calcination, the material was allowed to cool naturally to room temperature and then pulverized to a particle size ≤1mm to obtain the calcined modified product for later use.

[0062] Step (2) Composite synergistic leaching:

[0063] The calcined modified product obtained in step (1) was mixed with water at a solid-liquid ratio of 1:1.35. Sodium sulfate and sodium metabisulfite were added, with the concentration of sodium sulfate in the system being 6.5 g / L and the concentration of sodium metabisulfite being 0.75 g / L. The pH of the system was adjusted to 4.5 using 5% dilute sulfuric acid. The mixture was placed in a reactor, and the reaction temperature was controlled at 85℃ with a stirring speed of 70 r / min. Under these conditions, the mixture was leached at a constant temperature for 52 min. After leaching, solid-liquid separation was performed using plate and frame filtration. The vanadium-containing leachate and leaching residue were collected separately. The leaching residue was kept for later use, and the vanadium-containing leachate was used in the next step.

[0064] Step (3) Graded oxidation precipitation of vanadium:

[0065] ① Primary vanadium precipitation: Take the vanadium-containing leachate obtained in step (2), add ammonium sulfate to it, and react V2O5 and NH4. + Ammonium sulfate was added at a molar ratio of 1:1.65. The pH of the system was adjusted to 1.9 using 5% dilute sulfuric acid. The reaction temperature was controlled at 65℃, and the stirring speed was 90 r / min. The reaction was carried out at a constant temperature and with stirring for 35 min. During the reaction, a crude precipitate of ammonium polyvanadate gradually precipitated out. After the reaction was completed, the mixture was filtered to separate the crude ammonium polyvanadate precipitate and the primary vanadium precipitate filtrate. The primary vanadium precipitate filtrate was used for later use.

[0066] ②Oxidation adjustment: Take the primary vanadium precipitate filtrate obtained in step (3) ①, and add sodium chlorate to it. The amount of sodium chlorate added is V in the filtrate. 3+ Use 1.35 times the molar amount of water, control the stirring speed at a constant rate of 70 r / min, and complete the oxidation reaction within 25 min to ensure V. 3+ It is completely oxidized to high-valence vanadium.

[0067] ③ Secondary vanadium precipitation: Add ammonium oxalate to the oxidized filtrate, according to the reaction of V2O5 and NH4. + Ammonium oxalate was added at a molar ratio of 1:2.25. The pH of the system was adjusted to 2.35 using 5% dilute sulfuric acid. The reaction temperature was controlled at 75℃, and the stirring speed was 90 r / min. The reaction was carried out at a constant temperature and stirring for 35 min, resulting in the precipitation of fine ammonium polyvanadate. After the reaction was completed, the fine ammonium polyvanadate precipitate was obtained by filtration. The coarse precipitate obtained from the first-stage vanadium precipitation and the fine precipitate obtained from the second-stage vanadium precipitation were combined and washed with 1.5 wt% dilute ammonia water to remove sulfate and chloride ion impurities adsorbed on the precipitate surface. After washing, the precipitate was dried in a drying oven to constant weight, and then placed in a muffle furnace and calcined at 575℃ for 2.5 h. After cooling, V2O5 product was obtained.

[0068] Step (4) Resource recycling closed-loop processing:

[0069] Take the leaching residue obtained in step (2), wash it twice with deionized water, with a liquid-to-solid ratio of 1:1.1 each time. After washing, test the chloride ion content in the leaching residue until there is no obvious chloride ion residue. Add 12.5% ​​of the mass of the leaching residue to the washed leaching residue, mix evenly, and then press and cure it using conventional silicate brick preparation process to obtain silicate bricks. Take the filtrate after secondary vanadium precipitation in step (3) ③, concentrate it using a nanofiltration membrane with a molecular weight cutoff of 150 Da, control the nanofiltration membrane operating pressure at 0.4 MPa and the temperature at 30℃, concentrate it 4 times, and remove soluble impurities in the filtrate. After concentration, add sodium carbonate to the filtrate until it is consistent with the initial mixing concentration in step (1), and then test the chloride ion content in the circulation system to ensure that the chloride ion residue is ≤0.5%. Recycle the treated filtrate back to the calcination modification process in step (1).

[0070] Comparative Example 1:

[0071] The comparative method for deep vanadium extraction from vanadium-containing slurry is completely consistent with Example 3, except that step (1) uses conventional roasting instead of microwave-mechanical coupled roasting modification. The specific steps and parameters are as follows:

[0072] Step (1) Conventional roasting modification:

[0073] Vanadium-containing slurry was pretreated by dewatering to a moisture content of 72% using plate and frame filter press. The dewatered vanadium-containing slurry was then mixed uniformly with sodium carbonate at a mass ratio of 100:6.0 and calcined in a conventional muffle furnace at a controlled calcination temperature of 600℃ for 2.0 hours, without microwave irradiation or mechanical stirring. After calcination, the mixture was allowed to cool naturally to room temperature and then pulverized to a particle size ≤1mm to obtain the calcined modified product for later use.

[0074] Step (2) composite synergistic leaching, step (3) graded oxidation precipitation of vanadium, and step (4) resource recovery closed-loop treatment are all exactly the same as in Example 3, and will not be described again.

[0075] Comparative Example 2:

[0076] The method for deep vanadium extraction from vanadium-containing mud in this comparative example is completely consistent with Example 3, except that step (3) only uses primary vanadium precipitation and omits the oxidation adjustment and secondary vanadium precipitation steps. The specific steps and parameters are as follows:

[0077] Step (1) Microwave-mechanical coupling calcination modification, Step (2) Composite synergistic leaching

[0078] It is exactly the same as Example 3, and will not be described again.

[0079] Step (3) Single vanadium precipitation:

[0080] Ammonium sulfate was added to the vanadium-containing leachate obtained in step (2), according to the reaction of V2O5 and NH4.+ Ammonium sulfate was added at a molar ratio of 1:1.65. The pH of the system was adjusted to 1.9 using 5% dilute sulfuric acid. The reaction temperature was controlled at 65℃, and the stirring speed was 90 r / min. The reaction was carried out at a constant temperature and with stirring for 35 min, resulting in the precipitation of ammonium polyvanadate. The ammonium polyvanadate precipitate was obtained by filtration, washed with 1.5 wt% dilute ammonia, dried, and then calcined at 575℃ for 2.5 h to obtain V₂O₅ product. There was no oxidation adjustment or secondary vanadium precipitation step.

[0081] Step (4) Resource recycling closed-loop processing:

[0082] It is exactly the same as Example 3, and will not be described again.

[0083] test:

[0084] Vanadium leaching rate and V2O5 product purity testing:

[0085] The vanadium leaching rate and V2O5 product purity in Examples 1-3 and Comparative Examples 1-2 were tested to verify the influence of two innovative technical features, namely microwave-mechanical coupled roasting modification (not included in Comparative Example 1) and graded oxidation precipitation of vanadium (not included in Comparative Example 2), on the vanadium extraction effect.

[0086] Experimental materials: vanadium-containing leachate, V2O5 product, leaching residue prepared in Examples 1-3 and Comparative Examples 1-2, and original vanadium-containing mud (vanadium content 1.23%).

[0087] Experimental equipment: Inductively coupled plasma optical emission spectrometer (ICP-OES), electronic balance (accuracy 0.0001g), vacuum drying oven, muffle furnace, and filtration device.

[0088] Test method:

[0089] (1) Vanadium leaching rate detection: The total vanadium content in the original vanadium-containing mud and the vanadium content in the vanadium-containing leachate of each example and comparative example were detected by ICP-OES. The vanadium leaching rate was calculated according to the following formula:

[0090] Vanadium leaching rate (%) = (Mass of vanadium in the leachate ÷ Mass of total vanadium in the original vanadium-containing mud) × 100%

[0091] Wherein, the mass of vanadium in the leachate = the volume of the leachate × the vanadium concentration of the leachate; the total mass of vanadium in the original vanadium-containing mud = the mass of the vanadium-containing mud × the vanadium content of the vanadium-containing mud.

[0092] (2) V2O5 product purity test: V2O5 products prepared in each example and comparative example were dried under vacuum to constant weight, and the content of V2O5 in the product was detected by ICP-OES. At the same time, the content of impurities such as sulfate and chloride ions in the product was detected, and the purity of V2O5 product was calculated (purity = mass of V2O5 ÷ total mass of product × 100%).

[0093] (3) Parallel test: Three parallel tests are set up for each sample, and the average value is taken as the final test result to ensure the repeatability of the test data.

[0094] Experimental results:

[0095] Table 1

[0096] Sample number Original vanadium content (%) Vanadium concentration in leachate (g / L) Vanadium leaching rate (%) <![CDATA[V2O5 product purity (%)]]> Impurity content (%) Example 1 1.23 1.15 92.68 98.21 1.79 Example 2 1.23 1.18 95.93 98.76 1.24 Example 3 1.23 1.17 95.12 98.53 1.47 Comparative Example 1 1.23 0.89 72.36 95.38 4.62 Comparative Example 2 1.23 1.16 94.31 92.15 7.85

[0097] As shown in Experiment 1, the vanadium leaching rate of Examples 1-3 is above 92%, the purity of V2O5 products is above 98%, and the impurity content is below 2%, indicating that the technical solution of the present invention can achieve efficient leaching and high-purity recovery of vanadium.

[0098] Comparative Example 1, lacking microwave-mechanical coupled roasting modification, employed conventional roasting, resulting in a vanadium leaching rate of only 72.36%, a decrease of 22.76 percentage points compared to Example 3. The V₂O₅ product purity decreased by 3.15 percentage points, while the impurity content increased by 3.15 percentage points. The reasons are: conventional roasting lacks the rapid heating of microwaves and the uniform dispersion effect of mechanical stirring, leading to uneven mixing of the vanadium-containing slurry and sodium carbonate, and uneven roasting temperature distribution. This causes vanadium lattice agglomeration, making it difficult to dissolve in subsequent leaching processes. Furthermore, insufficient roasting leaves some vanadium encased in the slurry matrix, preventing effective leaching and thus reducing the leaching rate. Insufficient roasting also introduces more impurities, lowering product purity.

[0099] Comparative Example 2, lacking staged oxidation precipitation of vanadium, only used primary vanadium precipitation, achieving a vanadium leaching rate of 94.31%, close to that of Example 3. However, the purity of the V₂O₅ product was only 92.15%, a decrease of 6.38 percentage points compared to Example 3, while the impurity content increased by 6.38 percentage points. The reason is that primary vanadium precipitation can only recover most of the high-valence vanadium in the leachate, while some V₂O₅ remains in the leachate. 3+ The vanadium was not converted into high-valence vanadium through oxidation adjustment, nor was it recovered through secondary vanadium precipitation. As a result, the vanadium was lost with the filtrate. At the same time, the unrecovered vanadium and other impurities affected the purity of the product. In addition, vanadium precipitation alone could not fully remove impurities from the solution, causing impurities to accumulate in the product and further reducing the purity of the product.

[0100] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for deep vanadium extraction from vanadium-containing mud, characterized in that, The steps are as follows: (1) Microwave-mechanical coupling roasting modification: Vanadium-containing slurry and sodium carbonate are mixed evenly at a mass ratio of 100:5.8-6.2 and placed in a microwave-mechanical coupling field for roasting. The microwave power is 200-300W and the frequency is 2.45GHz. The mechanical stirring speed is 30-60r / min. The roasting temperature is controlled at 550-650℃ and the roasting time is 1.5-2.5h. After roasting, the mixture is cooled to room temperature and pulverized to a particle size ≤1mm to obtain the roasted modified product. (2) Composite synergistic leaching: The calcined modified product of step (1) is mixed with water at a solid-liquid ratio of 1:1.2-1.5, sodium sulfate and sodium metabisulfite are added, the pH of the system is adjusted to 4.0-5.0, and leaching is carried out at 80-90℃ and stirring speed of 60-80r / min for 45-60min. The solid and liquid are separated to obtain vanadium-containing leachate and leachate residue. The concentration of sodium sulfate in the addition system is 5-8 g / L, and the concentration of sodium metabisulfite in the addition system is 0.5-1.0 g / L; (3) Graded oxidation precipitation of vanadium: ① Primary vanadium precipitation: Add ammonium sulfate to the vanadium-containing leachate from step (2), according to the reaction of V2O5 and NH4. + Add the ammonium polyvanadate at a molar ratio of 1:1.5-1.8, adjust the pH to 1.8-2.0, stir the reaction at 80-100 r / min for 30-40 min, and precipitate the coarse precipitate of ammonium polyvanadate. Filter to separate the coarse precipitate and the primary vanadium filtrate. ②Oxidation adjustment: Add sodium chlorate to the primary vanadium precipitate filtrate, the dosage being equal to the V concentration in the filtrate. 3+ Oxidation is completed within 20-30 minutes at 1.2-1.5 times the molar amount. ③ Secondary vanadium precipitation: Add ammonium oxalate to the filtrate after oxidation, according to the reaction of V2O5 and NH4. + Add the product at a molar ratio of 1:2.0-2.5, adjust the pH to 2.2-2.5, stir the reaction at 80-100 r / min for 30-40 min, and fine precipitate of ammonium polyvanadate will be precipitated. Filter to separate the fine precipitate; combine the coarse precipitate and the fine precipitate, wash, dry, and calcine at 550-600℃ for 2-3 h to obtain the V2O5 product. (4) Resource-based closed-loop treatment: The leaching residue from step (2) is washed with deionized water 2-3 times, with a liquid-to-solid ratio of 1:1.0-1.2 each time, until there is no obvious chloride ion residue, and then used to prepare silicate bricks; The filtrate after the secondary vanadium precipitation in step (3) is concentrated 3-5 times using a nanofiltration membrane with a molecular weight cutoff of 100-200 Da to remove soluble impurities, and sodium carbonate is added to match the initial mixing concentration in step (1), and then recycled back to the calcination and modification process in step (1).

2. The method according to claim 1, characterized in that, Before mixing, the vanadium-containing slurry in step (1) is dehydrated by plate and frame filter press to a moisture content of 65-80% to avoid excessive moisture affecting the roasting efficiency.

3. The method according to claim 1, characterized in that, In step (1), the microwave-mechanical coupling calcination process uses gradient control, with 200W for 0-0.5h and 250-300W for 0.5-2.5h, to avoid local overheating that could lead to vanadium lattice agglomeration.

4. The method according to claim 1, characterized in that, In step (2), the pH is adjusted using 5% dilute sulfuric acid.

5. The method according to claim 1, characterized in that, The reaction temperature for the first-stage vanadium precipitation in step (3)① is 60-70℃, and the reaction temperature for the second-stage vanadium precipitation in step (3)③ is 70-80℃.

6. The method according to claim 1, characterized in that, During the oxidation adjustment process described in step (3) ②, a constant stirring speed of 60-80 r / min is used.

7. The method according to claim 1, characterized in that, In step (3), the vanadium-rich material is washed with 1-2 wt% dilute ammonia water to remove sulfate and chloride ion impurities adsorbed on the surface.

8. The method according to claim 1, characterized in that, In step (4), during the nanofiltration membrane concentration process, the operating pressure is controlled at 0.3-0.5 MPa and the temperature at 25-35℃.

9. The method according to claim 1, characterized in that, When preparing silicate bricks from the leaching residue in step (4), 10-15% of kaolin by weight of the leaching residue is added.

10. The method according to claim 1, characterized in that, After sodium carbonate is added to the recycled filtrate, the chloride ion content of the system needs to be tested to ensure that the residual chloride ion content in the recycling system is ≤0.5%.

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