A method for recovering vanadium from a sulfuric acid-based vanadium-containing waste liquid and fully utilizing sulfuric acid

Abstract

The present application belongs to the technical field of hydrometallurgy and resource recovery, and particularly relates to a method for recovering vanadium from a vanadium-containing sulfuric acid waste solution and fully utilizing sulfuric acid. The present application utilizes the characteristic that only pentavalent vanadium ions can be precipitated in an acidic waste solution under heating conditions, and targeted vanadium precipitation can be achieved through simple constant temperature heating, without the need for complex extraction or adsorption equipment, and the operation is simple and easy to control. The vanadium product prepared by the present application has high purity, and the purity of vanadium pentoxide (V2O5) can reach 99.5%-99.8%.

Description

Technical Field

[0001] This invention belongs to the field of hydrometallurgy and resource recovery technology, and particularly relates to a method for recovering vanadium from vanadium-containing waste liquid in sulfuric acid system and making full use of sulfuric acid. Background Technology

[0002] Vanadium is an important resource with wide applications in steel, chemical, and energy industries (such as vanadium redox flow batteries). With the rapid development of the vanadium industry, the amount of vanadium-containing waste liquid generated is also increasing. Direct discharge of this waste liquid not only wastes resources but also seriously pollutes the environment.

[0003] Currently, methods for recovering vanadium from vanadium-containing wastewater mainly include resin adsorption / desorption, solvent extraction, acidic ammonium salt precipitation, and weakly basic ammonium salt precipitation. For example, Chinese patent applications CN 116875824 A and CN 109022828 B employ vanadium-loving resin adsorption / desorption; documents 1671-0460 (2024) 10-2428-06 and 0258-7076 (2019) 03-0303-09 also report the enrichment and recovery of vanadium using solvent extraction; ammonium salt precipitation is the most studied and currently the mainstream vanadium precipitation process. However, these existing technologies have the following significant drawbacks: 1. Resin adsorption and solvent extraction usually require multiple repeated operations, resulting in a long process flow, complicated operation, and large equipment investment; 2. The resin poses a risk of poisoning, and the waste liquid generated during resin regeneration is difficult to treat; the extractant in the extraction method is prone to emulsification, which leads to organic phase contamination of vanadium products and affects product quality. 3. Mainstream ammonium salt precipitation methods (such as acidic ammonium salt precipitation, weakly acidic ammonium salt precipitation, and weakly basic ammonium salt precipitation) are extremely sensitive to pH and temperature, and require high precision in process control. Otherwise, the phase and purity of the vanadium product will be affected. In addition, these methods usually require a large amount of acid, alkali and ammonium salt reagents, which not only increases the processing cost, but also easily introduces impurity ions, resulting in low purity of the final vanadium product and complex process control.

[0004] Therefore, developing a new vanadium extraction method that is simple to operate, consumes less reagents, produces high-purity products, and enables the recovery and utilization of acid resources in waste liquid is a technical problem that urgently needs to be solved. Summary of the Invention

[0005] The purpose of this invention is to provide a method for recovering vanadium from vanadium-containing wastewater in a sulfuric acid system and for fully utilizing sulfuric acid. This method utilizes the characteristic of pentavalent vanadium ions specifically precipitating from acidic vanadium-containing wastewater under heating conditions, combined with ion conversion technology, to achieve efficient vanadium recovery and full utilization of sulfuric acid resources.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for recovering vanadium from vanadium-containing waste liquid in sulfuric acid systems and making full use of sulfuric acid includes the following steps: S1. Filtration: The vanadium-containing sulfuric acid waste liquid is passed through a filter medium to remove any mud, sand, debris and other insoluble impurities that may be present, to obtain a clear filtrate 1; S2. Electro-oxidation: The filtrate 1 obtained in step S1 is transferred to an electrolytic cell for electro-oxidation treatment to ensure that all vanadium ions in the filtrate are oxidized to pentavalent vanadium ions, resulting in pentavalent vanadium waste liquid; S3. Salt Conversion: Add an appropriate amount of barium chloride (BaCl2) to the pentavalent vanadium waste liquid obtained in step S2, stir thoroughly to ensure complete reaction, and then filter. This step converts the sulfate ions in the waste liquid into barium sulfate (BaSO4) precipitate, and the filtrate is converted into hydrochloric acid-based pentavalent vanadium waste liquid. The barium sulfate precipitate is recovered after washing with pure water. S4. Heating to precipitate vanadium and recover hydrochloric acid: The hydrochloric acid-based pentavalent vanadium waste liquid obtained in step S3 is heated at a constant temperature. During this process, the volatilized HCl gas is passed into pure water through a condensation absorption device to generate hydrochloric acid for recovery (alternatively, alkaline solutions such as gas cylinders, ammonia, or sodium hydroxide can be used for collection and recovery as needed). As water and HCl evaporate, a wine-red precipitate continuously precipitates in the waste liquid until the solvent is almost evaporated. Heating is then stopped, and an appropriate amount of pure water is added to facilitate subsequent separation. S5. Filtration: The solid-liquid mixture obtained in step S4 is filtered and separated to obtain a wine-red precipitate and waste liquid (mainly containing residual acid, metal impurity ions from the original solution, and water). S6. Washing, drying and calcining: The wine-red precipitate obtained in step S5 is washed with pure water to remove impurity ions attached to the surface, dried at 60℃-90℃ and then calcined in a muffle furnace to obtain the final high-purity vanadium product.

[0007] As a preferred option, the pH value of the vanadium-containing sulfuric acid waste liquid in step S1 is not higher than 2.

[0008] As a preferred embodiment, the isothermal heating temperature in step S4 is controlled between 105°C and 115°C, more preferably 108°C. Within this temperature range, HCl volatilization efficiency is high and pentavalent vanadium precipitation effect is optimal.

[0009] As a preferred embodiment, the calcination temperature in step S6 is 500~550℃.

[0010] As a preferred embodiment, the vanadium product in step S6 is vanadium pentoxide with a purity of 99.5-99.8%.

[0011] Mechanism: In vanadium-containing sulfuric acid waste liquid, vanadium ions of different valence states are first completely oxidized to pentavalent vanadium ions, which are then precipitated by heating and recovered by filtration. Sulfuric acid and water are miscible and difficult to separate, but by adding an appropriate amount of barium chloride, the sulfuric acid is converted into barium sulfate precipitate and hydrochloric acid. The barium sulfate precipitate is recovered by filtration and washing with high purity, and the hydrochloric acid is recovered by volatilization and condensation with industrial-grade purity. Mud, sand, insoluble debris and other impurities can be directly removed by filtration. Finally, only impurity metal ions remain in the waste liquid. Almost all usable substances in the waste liquid are recovered with high purity.

[0012] The advantages of this invention are: 1. The process of this invention is simple and highly specific: it utilizes the characteristic that only pentavalent vanadium ions can be precipitated in acidic waste liquid under heating conditions, and can achieve targeted vanadium precipitation through simple constant temperature heating, without the need for complex extraction or adsorption equipment, and is easy to operate and control. 2. High product purity: By avoiding the introduction of organic reagents and complex chemical precipitation processes, and by removing sulfate interference through a pre-conversion step, the vanadium product obtained by this invention has high purity, with vanadium pentoxide (V2O5) purity reaching 99.5%-99.8%; 3. High resource utilization rate and good economic benefits: This invention creatively converts sulfuric acid, which is difficult to separate from water in waste liquid, into volatile hydrochloric acid and insoluble barium sulfate. Barium sulfate can be recovered as a by-product, and the volatile HCl gas is recovered as hydrochloric acid, realizing the full utilization of sulfuric acid and greatly improving the utilization rate of waste liquid. 4. Low cost and environmentally friendly: Compared with traditional methods, this invention does not require a large amount of ammonium salts, acids and bases, which reduces the processing cost and the risk of secondary pollution from chemical reagents. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the vanadium precipitation process of the present invention.

[0014] Figure 2 This is a photograph of the precipitate formed during the heating and crystallization step in the vanadium precipitation method described in this invention.

[0015] Figure 3 The image shows the XRD pattern of the final vanadium product in Example 1 of this invention. Detailed Implementation

[0016] The composition of the vanadium-containing sulfuric acid waste liquid in this invention includes: main components: sulfuric acid solvent; vanadium ions in different valence states; Minor impurities: insoluble matter such as mud, sand, and debris; minor metal ions: impurity metal ions such as iron, aluminum, sodium, magnesium, calcium, manganese, copper, and zinc.

[0017] Example 1 In this embodiment, a sulfuric acid-based electrolyte from a vanadium redox flow storage power station that had been in operation for a period of time was selected as the raw material. Testing revealed that the total vanadium ion concentration in this electrolyte was 1.6755 mol / L, and the hydrogen ion concentration was 6.74 mol / L.

[0018] The specific processing steps are as follows: 1. Filtration: Take 500 mL of the above sulfuric acid electrolyte and filter it using a filter membrane with a pore size of 0.5 micrometers to remove insoluble impurities from the filtrate, and obtain clear filtrate 1.

[0019] 2. Electro-oxidation: Place filtrate 1 into an electrolytic cell for oxidative electrolysis until it is confirmed that all vanadium ions in the filtrate have been converted to pentavalent oxidation. At this point, the filtrate appears as a yellow transparent or light red transparent solution, which is recorded as pentavalent vanadium electrolyte.

[0020] 3. Salt Conversion: The sulfate ion concentration in filtrate 1 was determined to be 3.1 mol / L. According to the stoichiometric ratio, 630 g of barium chloride solid was weighed and added to the pentavalent vanadium electrolyte. The mixture was stirred thoroughly until completely dissolved and reacted. After the reaction was complete, the precipitate was filtered to obtain a hydrochloric acid-based pentavalent electrolyte and barium sulfate precipitate. The barium sulfate precipitate was washed with pure water and then recovered.

[0021] 4. Heating to precipitate vanadium and recover hydrochloric acid: Transfer the filtrate obtained in step 3 (hydrochloric acid is a pentavalent electrolyte) to a distillation apparatus and heat it at a constant temperature of 108℃. The volatilized HCl gas is passed through a tube into an absorption bottle containing pure water to generate hydrochloric acid for storage. As heating proceeds, a wine-red precipitate continuously precipitates from the vanadium-containing waste liquid. After heating for approximately 2.5 hours, the solution is basically evaporated to dryness. The apparatus is then removed, and 100 mL of pure water is added to the residue.

[0022] 5. Filtration and separation: The solid-liquid mixture obtained in step 4 is filtered to separate the precipitate and waste liquid. Various impurity metal ions in the vanadium waste liquid remain in the waste liquid.

[0023] 6. Washing and drying: The above wine-red precipitate is washed with pure water, then dried in an oven at 60℃-90℃, and then calcined in a muffle furnace at 550℃ to obtain the final vanadium product.

[0024] Testing revealed that the vanadium pentoxide produced in this embodiment had a purity of 99.7%, and barium sulfate and industrial-grade hydrochloric acid were successfully recovered, achieving comprehensive utilization of resources.

[0025] Comparative Example A sulfuric acid-based electrolyte from a vanadium redox flow storage power station, after operating for a period of time, was selected as the raw material. Testing revealed that the total vanadium ion concentration in the electrolyte was 1.6755 mol / L, and the hydrogen ion concentration was 6.74 mol / L. Vanadium was recovered using an acidic ammonium salt precipitation method, with the following steps: 1. Filtration: Take 500 mL of the above sulfuric acid electrolyte and filter it using a filter membrane with a pore size of 0.5 micrometers to remove insoluble impurities from the filtrate, and obtain clear filtrate 1.

[0026] 2. Electro-oxidation: Place filtrate 1 into an electrolytic cell for oxidative electrolysis until it is confirmed that all vanadium ions in the filtrate have been converted to pentavalent oxidation. At this point, the filtrate appears as a yellow transparent or light red transparent solution, which is recorded as pentavalent vanadium electrolyte.

[0027] 3. Adjust pH value by adding alkali: Heat the pentavalent vanadium electrolyte and keep the temperature constant at 80-90℃, then add 134g of 3mol / L sodium hydroxide solution to adjust the pH value to 5.0.

[0028] 4. Add ammonium salt: Add 166g of ammonium sulfate solid at a constant temperature and stir thoroughly to dissolve.

[0029] 5. Adjust pH value with sulfuric acid: Add 4 mol / L sulfuric acid to the solution obtained in step 4 at a constant temperature to adjust the pH value to 1.0-2.0. A red precipitate will be generated. Stir the reaction for 2 hours and then let it stand overnight.

[0030] 6. Filtration: Filter the solid-liquid mixture obtained in step 5 while it is still hot to separate the red precipitate and waste liquid.

[0031] 7. Washing and drying: The red precipitate is washed with pure water, then dried in an oven at 60℃-90℃, and then calcined in a muffle furnace at 550℃ to obtain a final vanadium product with a purity of 98.5%-99.5%.

[0032] Mainstream ammonium salt precipitation methods (such as acidic ammonium salt precipitation, weakly acidic ammonium salt precipitation, and weakly basic ammonium salt precipitation) are extremely sensitive to pH and temperature. Different pH values ​​and precipitation temperatures can lead to significant differences in the phase composition and impurity content of the vanadium product. Furthermore, these methods require the consumption of large amounts of acid and alkali reagents to adjust the pH value and the use of excessive ammonium salts to precipitate vanadium, which not only increases processing costs but also easily introduces impurity ions, resulting in low purity of the final vanadium product. The method of this invention avoids the introduction of organic reagents and complex chemical precipitation processes, and removes sulfate interference through a pre-conversion step. It obtains a stable product with high vanadium purity while keeping processing costs low and the process simple and easy to control. The vanadium pentoxide (V2O5) prepared by the method of this invention can achieve a purity of 99.5%-99.8%.

Claims

1. A method for recovering vanadium from vanadium-containing waste liquid in a sulfuric acid system and fully utilizing sulfuric acid, characterized in that, Includes the following steps: S1. Filtration: The vanadium-containing sulfuric acid waste liquid is filtered to remove insoluble impurities and obtain a clear filtrate; S2. Electro-oxidation: The filtrate obtained in step S1 is transferred to an electrolytic cell for electro-oxidation treatment, so that all vanadium ions in the filtrate are oxidized to pentavalent vanadium ions to obtain pentavalent vanadium waste liquid; S3. Salting Conversion: Add barium chloride to the pentavalent vanadium waste liquid obtained in step S2, react and filter to obtain barium sulfate precipitate and hydrochloric acid-based pentavalent vanadium waste liquid. The barium sulfate precipitate is recovered after washing with pure water. S4. Heating to precipitate vanadium and recover hydrochloric acid: The hydrochloric acid-based pentavalent vanadium waste liquid obtained in step S3 is heated, and the volatilized HCl gas is passed into pure water through a condensation absorption device to generate hydrochloric acid for recovery. Wine-red precipitate continuously precipitates in the waste liquid until the solvent is about to evaporate and heating is stopped. Pure water is added to obtain a solid-liquid mixture. S5. Filtration: The solid-liquid mixture obtained in step S4 is filtered and separated to obtain a wine-red precipitate and waste liquid; S6. Washing, drying and calcining: The wine-red precipitate obtained in step S5 is washed with pure water, dried at 60-90℃ and then calcined in a muffle furnace to obtain the vanadium product.

2. The method as described in claim 1, characterized in that: In step S1, the pH value of the vanadium-containing sulfuric acid waste liquid is not higher than 2.

3. The method as described in claim 1, characterized in that: The heating temperature in step S4 is 105~115℃.

4. The method as described in claim 1, characterized in that: The calcination temperature in step S6 is 500~550℃.

5. The method as described in claim 1, characterized in that: In step S6, the vanadium product is vanadium pentoxide with a purity of 99.5-99.8%.

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