Method for extracting vanadium through electrochemical oxidation, vanadium-containing solution obtained through method and application of vanadium-containing solution in all-vanadium redox flow battery electrolyte

Abstract

The invention provides a method for extracting vanadium through electrochemical oxidation, a vanadium-containing solution obtained through the method and application of the vanadium-containing solution in an all-vanadium redox flow battery electrolyte. The method for extracting vanadium through electrochemical oxidation comprises the following steps that solid vanadium slag is subjected to alkaline leaching pretreatment in a hot alkaline solution, solid-liquid separation is conducted on a product system obtained through alkaline leaching pretreatment, and vanadium-containing tailings are obtained; and mixing the vanadium-containing tailings with a sulfuric acid solution, contacting with an anode of an electrolytic bath to carry out electrochemical oxidation treatment, and leaching vanadium ions from the vanadium-containing tailings to obtain a vanadium-containing solution. The solid vanadium slag is used as a raw material, and vanadium is extracted from the solid vanadium slag and can be subsequently applied to industrial scenes such as all-vanadium redox flow battery electrolyte.

Description

Technical Field

[0001] The present invention belongs to the technical field of vanadium resource recovery and utilization, and specifically relates to a method for extracting vanadium by electrochemical oxidation, a vanadium-containing solution obtained thereby, and application of the vanadium-containing solution in an all-vanadium liquid flow battery electrolyte. Background Art

[0002] With the current process of energy structure adjustment, problems such as discontinuity and volatility of renewable energy generation have become increasingly prominent. The emergence of large-scale energy storage technology can effectively alleviate this problem and is becoming an important part of the new power system. Among them, all-vanadium liquid flow batteries have the essential characteristics of large scale, long life, high efficiency, safety and reliability, and are gradually becoming an important equipment for new energy systems. As an important component of all-vanadium liquid flow batteries, the volume and concentration of electrolyte will directly determine the amount of energy that the battery system can store. However, due to factors such as the high price of vanadium in the market and the complex preparation process of electrolytes, coupled with the continuous reduction in the price of battery stacks, in medium and long-term energy storage systems, vanadium electrolytes can account for more than 50% of the cost, seriously restricting the development of this field.

[0003] Vanadium is widely used in metallurgy, chemical industry, materials, aerospace, defense cutting-edge technology and medicine. Vanadium resources are abundant and widely distributed, with high natural abundance and scattered distribution, mainly coexisting with metal minerals.

[0004] After years of research and development, different vanadium extraction methods have been realized using different raw materials and equipment. Generally speaking, it can be divided into two categories: pyrometallurgy and hydrometallurgy. Sodium roasting method, calcium roasting method, blank roasting method, sub-molten salt method, direct acid leaching method and other process technologies with different characteristics have been proposed.

[0005] Among them, the sodium salt added in sodium roasting is usually sodium carbonate, sodium chloride, sodium sulfate, etc., and the roasting temperature is usually 800-1000°C. The research results of Liu Baoyao et al. (The influence of roasting system on vanadium slag leaching behavior [J]. Comprehensive Utilization of Fly Ash, 2018 (01): 35-36.) show that the maximum vanadium leaching rate can reach 91% when the roasting temperature is 840-860°C and the roasting time is 30-60 minutes. This process produces toxic and harmful chlorine gas, which is prone to environmental pollution. Calcification roasting is a method of roasting a mixture of calcium compounds such as limestone and vanadium slag. The research results of Zhang Xiaogang et al. (Experimental study on vanadium extraction process by calcification roasting of stone coal vanadium ore [J]. Applied Chemical Industry, 2013, 42(06): 1026-1028+1032.) show that under the conditions of 5% CaCO3 additive, roasting temperature of 900℃, time of 2h, liquid-solid ratio of 3:1, sodium hydroxide weight fraction of 15%, alkali leaching temperature of 103℃ (slightly boiling), and alkali leaching time of 3h, the vanadium leaching rate can reach more than 90%. Blank roasting method refers to the process of roasting directly without adding any additives. The research results of Jiang Moufeng (Study on the mechanism of vanadium extraction by acid leaching of mica-type vanadium-containing stone coal by blank roasting [D]. Wuhan University of Technology, 2015.) show that the vanadium leaching rate can reach 91% after roasting at 850℃ for 1h and leaching with 20% sulfuric acid solution by weight for 12h. However, the traditional roasting process has high energy consumption, serious environmental pollution and poor application prospects.

[0006] In addition, process intensification is also one of the current technical research hotspots in the field of vanadium extraction, which promotes the improvement of vanadium extraction efficiency through electric field strengthening, mechanical strengthening, ultrasonic strengthening and other means.

[0007] Among them, invention patent CN104017988A discloses a process for extracting vanadium from vanadium-containing stone coal by slurry electrolysis. A water-soluble chloride salt is added to the slurry, stirred, and electrolyzed under the condition of passing oxygen-containing gas. The chlorine gas produced in the anode area is used as an oxidant for leaching vanadium, and the oxygen in the air passed into the cathode area reacts to generate OH - Ions provide an alkaline environment for vanadium leaching, while avoiding hydrogen evolution reaction in the cathode area and explosion of chlorine produced in the anode area. This method has the advantages of short process, high efficiency and low cost, but the generation of chlorine in the anode area will inevitably bring about environmental pollution and safety problems.

[0008] Invention patent CN113106494A discloses a slurry electrolysis vanadium extraction process for treating vanadium-containing solid waste. The pre-treated vanadium-containing solid waste is mixed with a certain concentration of HCl solution and evenly sent to the anode electrolytic cell. The electrolysis reaction is carried out under the premise of controlling the temperature and pH, and the metal vanadium can be continuously recovered from the cathode. This method can treat waste vanadium catalysts containing a large amount of impurities such as ammonium ions, and has a high vanadium extraction efficiency, but the scope of application is relatively limited, and the treatment effect on existing solid vanadium slag mineral resources such as vanadium-titanium magnetite is limited.

[0009] At present, there are related studies on the hydrometallurgical leaching process intensified by an electric field for converter vanadium slag in an alkaline environment (Hydrometallurgical leaching process intensified by an electric field for converter vanadium slag [J]. Hydrometallurgy, 2015, 155, 56-60.), but it is only applicable to converter vanadium slag obtained after sodium / calcification roasting. However, for mineral resources that have not been subjected to pyrometallurgical roasting, the actual application effect of this method is not good.

[0010] In general, the current vanadium extraction process still generally has problems such as high energy consumption, large amounts of toxic and harmful gas emissions, serious environmental pollution, and stringent requirements for raw materials, which seriously plague the development of the vanadium industry. It is difficult to achieve major breakthroughs by simply trying to optimize and improve the original process. Summary of the invention

[0011] In order to solve the problems of high energy consumption, toxic and harmful gas emissions, and serious environmental pollution in the existing vanadium extraction process, the purpose of the present invention is to provide a method for electrochemical oxidation extraction of vanadium, the vanadium-containing solution obtained thereby, and its application in the electrolyte of all-vanadium liquid flow batteries. The electrochemical oxidation method for vanadium extraction uses solid vanadium slag as a raw material to extract soluble vanadium ions, which can be used in industrial scenarios such as all-vanadium liquid flow battery electrolytes. The electrochemical oxidation method for vanadium extraction has the effect of green and efficient vanadium extraction, effectively reduces the cost of the vanadium extraction process, and promotes technological progress in the vanadium industry.

[0012] To achieve the above-mentioned purpose, the present invention provides a method for extracting vanadium by electrochemical oxidation, which comprises the following steps: subjecting solid vanadium slag to alkaline leaching pretreatment in a hot alkaline solution, and performing solid-liquid separation on the product system obtained by the alkaline leaching pretreatment to obtain vanadium-containing tailings; mixing the vanadium-containing tailings with a sulfuric acid solution, and then contacting the mixture with the anode of an electrolytic cell to perform an electrochemical oxidation treatment to leach vanadium ions from the vanadium-containing tailings to obtain a vanadium-containing solution.

[0013] The surrounding area of ​​solid vanadium slag usually contains crystalline structures such as silicates. Alkali leaching pretreatment can destroy the crystalline structures such as silicates in the surrounding area of ​​the mineral, exposing more vanadium iron spinel, providing a basis for subsequent electrochemical oxidation treatment and accelerating the electrochemical oxidation reaction of solid vanadium slag in acidic medium. At the same time, electrochemical oxidation treatment of solid vanadium slag that has been pretreated with alkaline leaching can greatly reduce the concentration of silicon ions in the solution and reduce the viscosity of the solution, which is conducive to the separation of vanadium-containing solution vanadium in the electrochemical oxidation treatment product.

[0014] During the electrochemical oxidation process, on the one hand, the anode products with strong oxidation ability such as O2 and OH generated by electrolysis will oxidize the vanadium-containing tailings; on the other hand, the vanadium-containing tailings will also be oxidized when they lose electrons in direct contact with the anode. These two oxidations will cause the low-valent vanadium in the vanadium-containing tailings to be oxidized into soluble high-valent vanadium ions, thereby leaching the vanadium in the vanadium-containing tailings into the sulfuric acid solution to obtain a vanadium-containing solution. Taking the above two oxidation modes as an example, considering that the anodic oxidation process mainly oxidizes +3-valent vanadium into +4 and +5-valent vanadium ion compounds, the main equations involved are as follows:

[0015] 4FeV2O4+28H + +3O2=4Fe 3+ +8VO 2+ +14H2O

[0016]

[0017] FeV2O4+4H + -3e - =Fe 3+ +2VO 2+ +2H2O

[0018]

[0019] In addition, the above method of the present invention does not require roasting, nor does it involve the problem of chlorine explosion. Under relatively mild conditions, vanadium in solid vanadium slag can be leached into sulfuric acid solution to obtain a vanadium-containing solution. The vanadium-containing solution can be further used to prepare vanadium products after subsequent purification, separation and enrichment operations, and is particularly used to prepare vanadium electrolytes for all-vanadium liquid flow batteries. The present invention avoids gaseous pollutants such as flue gas generated during the roasting process, and also greatly reduces the energy consumption required for roasting. It has the advantages of low energy consumption, low cost, high vanadium extraction rate, and green environmental protection, which significantly promotes the industrial technological progress in the field of vanadium extraction.

[0020] In some exemplary embodiments, the temperature of the electrochemical oxidation treatment is 50-90° C. For example, the temperature of the electrochemical oxidation treatment may be 50° C., 60° C., 70° C., 80° C., or 90° C.

[0021] In some exemplary embodiments, the electrochemical oxidation treatment time is 2 to 5 hours. For example, the electrochemical oxidation treatment time can be 2 hours, 3 hours, 4 hours or 5 hours.

[0022] In some optional embodiments, the current density of the electrochemical oxidation treatment is 100-300 mA / cm 2 For example, the current density of the electrochemical oxidation treatment can be 100 mA / cm 2 , 200mA / cm 2 、300mA / cm 2 .

[0023] In some exemplary embodiments, the anode is an inert electrode; for example, in an electrolytic cell, the anode is a graphite electrode, and the cathode is a graphite electrode or a nickel mesh electrode. Optionally, during the electrochemical oxidation treatment, a stirrer is installed in the electrolytic cell, and the stirring is continued at a speed of 400 to 500 r / min during the electrolysis process. Optionally, in the sulfuric acid solution, the molar concentration of sulfuric acid is 2 to 3 mol / L.

[0024] In some optional embodiments, the hot alkaline solution is selected from sodium hydroxide aqueous solution and / or potassium hydroxide aqueous solution. Optionally, in the hot alkaline solution, the weight fraction of the alkali is 20-30 wt %. Optionally, the temperature of the hot alkaline solution is 70-90° C.

[0025] In some exemplary embodiments, the weight ratio of the hot alkali solution to the solid vanadium slag is 5 to 10: 1. For example, the weight ratio of the hot alkali solution to the solid vanadium slag can be 5: 1, 6: 1, 7: 1, 8: 1, 9: 1, or 10: 1.

[0026] In some exemplary embodiments, the weight ratio of the sulfuric acid solution to the vanadium-containing tailings is 5 to 10: 1. For example, the weight ratio of the sulfuric acid solution to the vanadium-containing tailings may be 5: 1, 6: 1, 7: 1, 8: 1, 9: 1, or 10: 1.

[0027] In some exemplary embodiments, the temperature of the alkali leaching pretreatment is 70-90°C, and the time is 2-4 hours. For example, the temperature of the alkali leaching pretreatment is 70°C, 80°C, 90°C, and the time is 2 hours, 3 hours, 4 hours. Optionally, in the alkali leaching pretreatment, a stirrer is installed in the reactor used, and the stirring is continuously carried out at a speed of 400-500 r / min.

[0028] In some optional embodiments, the solid vanadium slag includes but is not limited to vanadium slag smelted from vanadium-titanium magnetite and / or vanadium-containing stone coal. The weight percentage of vanadium in the solid vanadium slag is greater than or equal to 1%, for example, 8-10%.

[0029] In some optional embodiments, the vanadium slag and / or vanadium-containing stone coal smelted from vanadium-titanium magnetite provided by the steel plant is first crushed and screened to obtain solid vanadium slag with a particle size of less than 0.5 μm, which is then subjected to alkaline leaching pretreatment.

[0030] The present invention also provides a vanadium-containing solution obtained by the aforementioned electrochemical oxidation vanadium extraction method. Based on the above reasons, such a vanadium-containing solution can be used for the preparation of vanadium electrolyte for all-vanadium liquid flow batteries and other vanadium-containing products after subsequent purification, separation and enrichment.

[0031] The present invention also provides an application of the aforementioned vanadium-containing solution in an all-vanadium liquid flow battery electrolyte. Based on the reasons mentioned above, the vanadium-containing solution extracted from the solid vanadium slag in the present invention can be used for the preparation of an all-vanadium liquid flow battery vanadium electrolyte after subsequent purification, separation and enrichment operations. The prepared all-vanadium liquid flow battery vanadium electrolyte can be used in large-scale electricity storage processes.

[0032] Based on the above scheme, the present invention achieves the following beneficial effects: it realizes the extraction of vanadium from solid vanadium slag under mild conditions, replaces the existing high-temperature roasting process, avoids the generation of flue gas and other gaseous pollutants during the roasting process, and also greatly reduces the energy consumption required for roasting, and has the advantages of low energy consumption, high extraction rate, and green environmental protection. The electrochemical oxidation process is used to extract V in vanadium iron spinel. 3+ Oxidized to V 4+ and V 5+ The vanadium compounds are further dissolved into the sulfuric acid aqueous solution, which is convenient for subsequent purification and impurity removal, and further preparation of vanadium products and electrolytes for all-vanadium redox flow batteries. The hot alkali impregnation pretreatment process is used to destroy the silicates and other substances that wrap the solid vanadium slag, so that the vanadium iron spinel is fully exposed, the electrochemical reaction of the vanadium oxide slag is strengthened, and it is conducive to the dissolution of high-valent vanadium ions into the sulfuric acid aqueous solution.

[0033] In summary, the electrochemical oxidation method for extracting vanadium of the present invention has the advantages of reducing energy consumption, reducing costs, improving vanadium leaching rate, and being green and environmentally friendly, which significantly promotes the progress of slag vanadium extraction technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A schematic diagram of the process of electrochemical oxidation vanadium extraction in one embodiment of the present invention is shown;

[0035] Figure 2 The XRD phase composition diagram of the solid vanadium slag used in Example 1 of the present invention is shown;

[0036] Figure 3 The FE-SEM morphology of the solid vanadium slag used in Example 1 of the present invention is shown;

[0037] Figure 4The FE-SEM morphology of the solid vanadium slag used in Example 1 of the present invention is shown;

[0038] Figure 5 The FE-SEM morphology of the vanadium-containing tailings obtained after alkali leaching pretreatment in Example 1 of the present invention is shown;

[0039] Figure 6 FE-SEM morphology images of different cross sections of vanadium-containing tailings obtained after alkali leaching pretreatment in Example 1 of the present invention are shown;

[0040] Figure 7 FE-SEM morphology images of different cross sections of vanadium-containing tailings obtained after alkali leaching pretreatment in Example 1 of the present invention are shown;

[0041] Figure 8 The FE-SEM morphology of the vanadium-containing tailings obtained after alkali leaching pretreatment in Example 1 of the present invention is shown. DETAILED DESCRIPTION

[0042] In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be construed as limiting the applicable scope of the present invention.

[0043] Example 1

[0044] This embodiment provides a method for electrochemical oxidation to extract vanadium, such as Figure 1 As shown, the following steps are included:

[0045] (1) preparing solid vanadium slag, which is obtained from vanadium-titanium magnetite smelting in a steel plant, and has a vanadium content of 9.86 wt %. After grinding, the solid vanadium slag is sieved with 200 mesh to obtain solid vanadium slag powder with a particle size of less than 0.5 μm; Figure 2 The XRD phase composition diagram of the solid vanadium slag used in Example 1 of the present invention is shown; Figure 3 The FE-SEM morphology of the solid vanadium slag used in Example 1 of the present invention is shown; Figure 4 The FE-SEM morphology of the solid vanadium slag used in Example 1 of the present invention is shown.

[0046] (2) the solid vanadium slag powder and the sodium hydroxide aqueous solution are mixed at a liquid-solid ratio of 5:1 (i.e., the weight ratio of the sodium hydroxide aqueous solution to the solid vanadium slag powder is 5:1), the weight fraction of sodium hydroxide in the sodium hydroxide aqueous solution is 30% (wt), the temperature is 80° C., the stirrer is continuously stirred at a speed of 450 r / min, and the alkaline leaching pretreatment is performed for 2 hours, the solid-liquid separation is performed, and the alkaline leaching solution and the vanadium-containing tailings are obtained after washing with deionized water and drying; Figure 5 The FE-SEM morphology of the vanadium-containing tailings obtained after alkali leaching pretreatment in Example 1 of the present invention is shown; Figure 6The FE-SEM morphology of the vanadium-containing tailings obtained after alkali leaching pretreatment in Example 1 of the present invention is shown; Figure 7 The FE-SEM morphology of the vanadium-containing tailings obtained after alkali leaching pretreatment in Example 1 of the present invention is shown; Figure 8 The FE-SEM morphology of the vanadium-containing tailings obtained after alkali leaching pretreatment in Example 1 of the present invention is shown;

[0047] (3) The vanadium-containing tailings after alkaline leaching pretreatment were mixed with sulfuric acid solution at a liquid-solid ratio of 10:1 (i.e., the weight ratio of sulfuric acid solution to vanadium-containing tailings was 10:1), the concentration of sulfuric acid in the sulfuric acid solution was 3 mol / L, the temperature was 80°C, the stirrer was continuously stirred at a speed of 450 r / min, and placed in an electrolytic cell for electrochemical oxidation treatment for 2 h, the anode was a graphite electrode, the cathode was a nickel mesh electrode, and the current density was 200 mA / cm 2 , solid-liquid separation to obtain vanadium-containing solution and tailings.

[0048] The concentration of vanadium ions in the solution was quantitatively determined by potassium permanganate-ammonium ferrous sulfate chemical titration. The vanadium leaching rate after the first step of alkaline leaching pretreatment was 1.39%, and after the second step of electrochemical oxidation treatment, the vanadium leaching rate calculated based on the vanadium-containing tailings used in the second step was 62.91%, and the vanadium leaching rate calculated based on the solid vanadium slag powder fed as the standard was 62.04%, and the total vanadium leaching rate was 63.43%.

[0049] Example 2

[0050] This embodiment provides a method for electrochemical oxidation to extract vanadium, such as Figure 1 As shown, the following steps are included:

[0051] (1) preparing solid vanadium slag, which is obtained from vanadium-titanium magnetite smelting in a steel plant, and has a vanadium content of 9.86 wt %. After grinding, the solid vanadium slag is sieved with 200 mesh to obtain solid vanadium slag powder with a particle size of less than 0.5 μm;

[0052] (2) the solid vanadium slag powder and the sodium hydroxide aqueous solution are mixed at a liquid-solid ratio of 5:1 (i.e., the weight ratio of the sodium hydroxide aqueous solution to the solid vanadium slag powder is 5:1), the weight fraction of sodium hydroxide in the sodium hydroxide aqueous solution is 30% (wt), the temperature is 90° C., the stirrer is continuously stirred at a speed of 450 r / min, and the alkaline leaching pretreatment is performed for 4 hours, the solid-liquid separation is performed, and the alkaline leaching solution and the vanadium-containing tailings are obtained after washing with deionized water and drying;

[0053] (3) The vanadium-containing tailings and the sulfuric acid solution were mixed at a liquid-to-solid ratio of 10:1 (i.e., the weight ratio of the sulfuric acid solution to the vanadium-containing tailings was 10:1), the concentration of sulfuric acid in the sulfuric acid solution was 3 mol / L, the temperature was 80°C, the stirrer was continuously stirred at a speed of 450 r / min, and the mixture was placed in an electrolytic cell for electrochemical oxidation treatment for 5 h, the anode was a graphite electrode, the cathode was a nickel mesh electrode, and the current density was 200 mA / cm 2 , solid-liquid separation to obtain vanadium-containing solution and tailings.

[0054] The concentration of vanadium ions in the solution was quantitatively determined by potassium permanganate-ammonium ferrous sulfate chemical titration. The vanadium leaching rate after the first step of alkaline leaching pretreatment was 1.79%, and after the second step of electrochemical oxidation treatment, the vanadium leaching rate calculated based on the vanadium-containing tailings used in the second step was 93.69%, and the vanadium leaching rate calculated based on the solid vanadium slag powder fed as the standard was 92.01%, and the total vanadium leaching rate was 93.80%.

[0055] It can be found from Example 1 and Example 2 that the leaching rate of vanadium in the first step of alkaline leaching pretreatment is very low, and vanadium is basically leached from the second step of electrochemical oxidation treatment, thereby eliminating the enrichment operation of vanadium in the two-step leaching solution, and the alkaline leaching solution obtained in the first step can be recycled after treatment, reducing resource waste.

[0056] Comparative Example 1

[0057] This comparative example provides a method for extracting vanadium, comprising the following steps:

[0058] (1) Prepare solid vanadium slag, which is obtained from the smelting of vanadium-titanium magnetite in a steel plant. The solid vanadium slag has a vanadium content of 9.86 wt %. After grinding, it is sieved with 200 mesh to obtain solid vanadium slag powder with a particle size of less than 0.5 μm.

[0059] (2) The solid vanadium slag powder and the sulfuric acid solution are mixed at a liquid-to-solid ratio of 10:1 (i.e., the weight ratio of the sulfuric acid solution to the solid vanadium slag powder is 10:1), the concentration of sulfuric acid in the sulfuric acid solution is 3 mol / L, the temperature is 80°C, the stirrer is continuously stirred at a speed of 450 r / min, and the mixture is placed in an electrolytic cell for electrochemical oxidation treatment for 4 hours, the anode is a graphite electrode, the cathode is a nickel mesh electrode, and the current density is 200 mA / cm 2 , solid-liquid separation to obtain vanadium-containing solution and tailings.

[0060] The concentration of vanadium ions in the solution was quantitatively determined by potassium permanganate-ammonium ferrous sulfate chemical titration. After electrochemical oxidation treatment, the vanadium leaching rate calculated based on the solid vanadium slag powder fed as the standard was 37.19%.

[0061] pass Figure 3-Figure 8It can be found that after the solid vanadium slag is pretreated by alkali leaching in Examples 1 and 2 of the present invention, the edges and corners of the obtained vanadium-containing tailings become rounded, and there are pit-shaped or lamellar structures that have been obviously corroded on the surface, and the structure around the mineral is greatly damaged, which creates better conditions for subsequent electrochemical oxidation and vanadium extraction, and the vanadium leaching rate can reach more than 62%. In Comparative Example 1, the solid vanadium slag is directly electrochemically oxidized, and the vanadium leaching rate is only 37.19%. Under the same treatment conditions, the vanadium leaching rate of the solid vanadium slag pretreated by alkali leaching is much higher than that of the sample directly electrochemically oxidized.

[0062] Comparative Example 2

[0063] This comparative example provides a method for extracting vanadium, comprising the following steps:

[0064] (1) preparing solid vanadium slag, which is obtained from vanadium-titanium magnetite smelting in a steel plant, and has a vanadium content of 9.86 wt %. After grinding, the solid vanadium slag is sieved with 200 mesh to obtain solid vanadium slag powder with a particle size of less than 0.5 μm;

[0065] (2) Sodium hydroxide solid and the above-mentioned solid vanadium slag powder were mixed at a mass ratio of 0.5:1 g / g, and then deionized water was added at a liquid-solid ratio of 4 mL / g (i.e., 4 mL of alkali solution for each gram of solid vanadium slag) to mix. The temperature was 90°C, and the stirrer was continuously stirred at a speed of 450 r / min. The mixture was placed in an electrolytic cell for electrolytic alkaline leaching for 2 h. Both the cathode and cathode were nickel mesh electrodes, and the current density was 100 mA / cm 2 , solid-liquid separation to obtain vanadium-containing solution and tailings.

[0066] The concentration of vanadium ions in the solution was quantitatively determined by potassium permanganate-ammonium ferrous sulfate chemical titration. After electrolytic alkali leaching treatment, the vanadium leaching rate calculated based on the solid vanadium slag powder fed as the standard was 2.61%.

[0067] The process in Comparative Example 2 adopts the existing related research on the selective leaching of vanadium from chromium residue intensified by electric field under alkaline environment (Selective leaching of vanadium from chromium residue intensified by electric field [J]. Journal of Environmental Chemical Engineering, 2015, 3 (2): 1252-7.), but it is only applicable to vanadium slag obtained by precipitation of wastewater treatment in steel plants. When it is used for mineral resources that have not been treated by pyrolysis, it can be found that the actual application effect of this method is not good, and the leaching rate of vanadium is only 2.61%. The electrochemical oxidation vanadium extraction method proposed in the present invention has a wider application range. In addition to being applicable to the residue obtained by wastewater treatment, it is also applicable to vanadium-containing slags such as vanadium-titanium magnetite with more stable structures, and adopts an acidic electrolytic leaching system instead of an alkaline system, which has a higher degree of damage to the mineral crystal structure and is more conducive to the subsequent purification and separation treatment for the production of vanadium electrolyte products for all-vanadium liquid flow batteries.

Claims

1. A method for extracting vanadium by electrochemical oxidation, wherein: The following steps are involved: The solid vanadium slag is subjected to an alkali leaching pretreatment in a hot alkali solution, and the product system obtained by the alkali leaching pretreatment is separated into a solid and a liquid to obtain a vanadium-containing tailing; The vanadium-containing tailings are mixed with a sulfuric acid solution and then brought into contact with an anode of an electrolytic cell for electrochemical oxidation treatment, thereby leaching vanadium ions from the vanadium-containing tailings to obtain a vanadium-containing solution.

2. The method for extracting vanadium by electrochemical oxidation according to claim 1, wherein: The electrochemical oxidation treatment time is 2 to 5 hours.

3. The method for extracting vanadium by electrochemical oxidation according to claim 1, wherein: The temperature of the electrochemical oxidation treatment is 50-90°C.

4. The method for extracting vanadium by electrochemical oxidation according to claim 1, wherein: The hot alkali solution is selected from a sodium hydroxide aqueous solution and / or a potassium hydroxide aqueous solution; in the hot alkali solution, the weight fraction of the alkali is 20-30wt%.

5. The method for extracting vanadium by electrochemical oxidation according to claim 1, wherein: The weight ratio of the hot alkali solution to the solid vanadium slag is 5 to 10:

1.

6. The method for extracting vanadium by electrochemical oxidation according to claim 1, wherein: In the sulfuric acid solution, the molar concentration of sulfuric acid is 2-3 mol / L.

7. The method for extracting vanadium by electrochemical oxidation according to claim 1, wherein: The particle size of the solid vanadium slag is below 0.5 μm.

8. The method for extracting vanadium by electrochemical oxidation according to claim 1, wherein: The anode is an inert electrode.

9. A vanadium-containing solution, wherein: The vanadium is obtained by the method for extracting vanadium by electrochemical oxidation according to any one of claims 1 to 8.

10. Use of the vanadium-containing solution according to claim 9 in an all-vanadium redox flow battery electrolyte.

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