Method for preparing vanadium battery electrolyte from alkaline vanadium solution in short process

Abstract

The invention relates to the field of vanadium batteries, and discloses a method for preparing a vanadium battery electrolyte from an alkaline vanadium liquid in a short process, which comprises the following steps: adding an adsorbent into the alkaline vanadium liquid to remove impurities to obtain an impurity-removed vanadium liquid; wherein the adsorbent comprises sulfhydrylated chitosan microspheres; the impurity-removed vanadium liquid and a transforming agent are mixed and react, V (OH) 4 + in the impurity-removed vanadium liquid is transformed into VO < 2 + >, and transformed vanadium liquid is obtained; wherein the transforming agent comprises ascorbic acid and sulfite; and the converted vanadium liquid is adjusted to be acidic, a stabilizer is added to obtain a to-be-electrolyzed solution, the to-be-electrolyzed solution is electrolyzed, and an electrolyte containing V < 3 + > and VO < 2 + > is obtained. The preparation process of the electrolyte can be effectively shortened, impurity interference is avoided, and the current efficiency is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of vanadium battery, and particularly relates to a method for preparing vanadium battery electrolyte by short process of alkaline vanadium solution. BACKGROUND

[0002] The all-vanadium redox flow battery (VRFB) has become one of the preferred technologies for large-scale energy storage due to its excellent cycle stability and scalability. The commercial VRFB electrolyte usually adopts a sulfuric acid system (V 3+ / V 4+ / V 5+ ), and the pH value needs to be maintained in the range of 0-2 to obtain the best electrochemical performance. However, more than 90% of vanadium resources extraction processes currently use alkaline leaching methods (such as sodium roasting-water leaching), and the obtained leaching solution has a pH>10 and contains Fe, Al, Si and other impurities. The traditional process needs to be repeatedly adjusted by acid and alkali to convert it into an acidic electrolyte, resulting in a long process and high cost.

[0003] There are three major technical problems in the current conversion of alkaline vanadium solution: (1) Incomplete removal of impurities: step-by-step precipitation method is used, but Fe and Al residues still reach 20-50 ppm, which will form a colloidal blockage in the ion exchange membrane during the subsequent acidification process; (2) Large consumption of acid and alkali: first neutralize with sulfuric acid to pH=2 to precipitate silicon, then readjust to pH=7 to remove iron and aluminum, and finally acidify to pH=0, with acid and alkali consumption reaching 3 times the theoretical value; (3) Low current efficiency: in the acidic electrolysis, V 4+ / V 5+ conversion current efficiency is only 82-85%, and the electrode is easily passivated by silicon and aluminum deposits.

[0004] Recent improvement attempts have obvious shortcomings. The solvent extraction method uses P204 extractant, which can deeply remove impurities, but the loss of organic phase increases the cost by 30%; the biological adsorption method uses sulfate-reducing bacteria to remove heavy metals, but the bacteria are inactivated under strong acid conditions; the catalytic electrolysis method introduces Ce 3+ / Mn 2+ catalyst, but metal ions pollute the electrolyte and affect the battery life.

[0005] Therefore, the prior art needs to be improved. SUMMARY

[0006] The main purpose of the present application is to provide a method for preparing vanadium battery electrolyte by short process of alkaline vanadium solution, to at least solve the problem that the method for preparing vanadium battery electrolyte based on alkaline vanadium solution in the prior art has a long process and incomplete removal of impurities.

[0007] According to one aspect of the present application, a method for preparing vanadium battery electrolyte from alkaline vanadium solution in a short process is provided, comprising: adding an adsorbent to the alkaline vanadium solution to remove impurities, to obtain a vanadium solution after impurities removal; wherein the adsorbent comprises mercapto-chitosan microspheres; mixing and reacting the vanadium solution after impurities removal with a conversion agent, so that V(OH)4 in the vanadium solution after impurities removal is converted into VO + 2+ , to obtain a vanadium solution after conversion; wherein the conversion agent comprises ascorbic acid and sulfite; adjusting the vanadium solution after conversion to be acidic and adding a stabilizer to obtain an electrolyte to be electrolyzed, and electrolyzing the electrolyte to be electrolyzed to obtain an electrolyte containing V 3+ and VO 2+ .

[0008] According to one embodiment of the present application, the particle size of the mercapto-chitosan microspheres is 50-100 μm, and the mercapto content is 2.5-5 mmol / g.

[0009] According to one embodiment of the present application, the method further comprises preparing the mercapto-chitosan microspheres, which comprises: dissolving chitosan in an acid solution to obtain a dissolved solution; wherein the mass of chitosan is 2-10% of the mass of the acid solution; adding 2,3-dimercaptosuccinic acid sodium to the dissolved solution, and reacting at 50-90°C under an inert atmosphere for 3-6 h to obtain a reacted solution; wherein the mass of 2,3-dimercaptosuccinic acid sodium is 2-5% of the mass of the dissolved solution; dropping the reacted solution into a basic solution or performing spray drying to obtain the mercapto-chitosan microspheres.

[0010] According to one embodiment of the present application, the pH of the alkaline vanadium solution is 9-12 and the alkaline vanadium solution contains at least one impurity of Fe, Al and Si.

[0011] According to one embodiment of the present application, adding the adsorbent to the alkaline vanadium solution to remove impurities comprises: after adding the adsorbent to the alkaline vanadium solution, oscillating at 30-60°C for 1-3 h and then filtering, wherein the solid-liquid ratio of the adsorbent to the alkaline vanadium solution is 3-8 g / L.

[0012] According to one embodiment of the present application, in the conversion agent, the molar ratio of ascorbic acid to sulfite is (10-25):(2-5).

[0013] According to one embodiment of the present application, in the conversion agent, the concentration of ascorbic acid is 0.1-0.25 mol / L, and the concentration of sulfite is 0.02-0.05 mol / L; mixing and reacting the vanadium solution after impurities removal with the conversion agent comprises: mixing the vanadium solution after impurities removal with the conversion agent at a volume ratio of 1:(0.04-0.08), and reacting at 60-90°C for 20-40 min.

[0014] ​According to one embodiment of the present application, the pH of the to-be-electrolyzed solution is 1-1.5; the concentration of the stabilizer in the to-be-electrolyzed solution is 0.02-0.1 mol / L; the method further comprises adjusting the vanadium concentration of the to-be-electrolyzed solution to 1.5-2.5 mol / L.

[0015] According to one embodiment of the present application, the stabilizer comprises one or more of the following: inorganic stabilizer, organic acid, organic acid salt, alcohol, surfactant.

[0016] According to one embodiment of the present application, the electrolysis comprises: electrolyzing for 4-7 h at a current density of 70-90 mA / cm 2 .

[0017] In the technical solution of the present application, the thiolated chitosan is used as an adsorbent to remove impurities, which can effectively remove Fe, Al, Si and other impurities in the alkaline vanadium solution; the conversion agent containing ascorbic acid and sulfite can avoid the generation of V2O5 precipitate, and directly obtain VO 2+ with high electrolysis activity; the stabilizer is used to improve the stability of the to-be-electrolyzed acidic solution, which can directly electrolyze to generate V 3+ / VO 2+ , and the vanadium precipitation-calcination-dissolution step is omitted. Thus, the present application can effectively shorten the preparation process of the electrolyte, avoid the interference of impurities, and improve the current efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0019] Figure 1 A flow chart of a vanadium battery electrolyte preparation method according to an embodiment of the present application is shown. DETAILED DESCRIPTION

[0020] In order to make the objects, technical solutions and advantages of the present application more clear, the following will further illustrate the embodiments of the present application in combination with specific embodiments and with reference to the drawings.

[0021] It should be noted that all the expressions of "first" and "second" in the embodiments of the present application are used to distinguish two same name but different entities or different parameters. It can be seen that "first" and "second" are only for the convenience of description, and should not be understood as a limitation of the embodiments of the present application. The subsequent embodiments will not be described one by one.

[0022] As mentioned in the above background, the method process of preparing vanadium battery electrolyte from alkaline vanadium solution in the prior art is lengthy, cannot realize direct conversion from "alkaline leaching solution to acidic electrolyte", and needs to go through an intermediate pH value transition stage. To solve this problem, the present application proposes a short process method capable of directly preparing high-purity acidic electrolyte from alkaline vanadium solution, which adopts a three-stage process route of "alkaline deep impurity removal → vanadium form directional conversion → acidic efficient electrolysis".

[0023] Reference Figure 1 The present application proposes a method for preparing vanadium battery electrolyte from alkaline vanadium solution by a short process, comprising the following steps: S1, adding an adsorbent to the alkaline vanadium solution to remove impurities to obtain a vanadium solution after impurity removal; wherein the adsorbent comprises mercapto chitosan microspheres; S2, mixing and reacting the vanadium solution after impurity removal and a conversion agent to convert V(OH)4 + in the vanadium solution after impurity removal into VO 2+ (that is, to convert pentavalent vanadium into tetravalent vanadium) to obtain a vanadium solution after conversion; wherein the conversion agent comprises ascorbic acid and sulfite; S3, adjusting the vanadium solution after conversion to be acidic and adding an aminopolycarboxylic acid ligand to obtain an electrolyte to be electrolyzed, and electrolyzing the electrolyte to be electrolyzed to obtain an electrolyte containing V 3+ and VO 2+ .

[0024] In some embodiments, the alkaline vanadium solution has a pH of 9-12 and contains at least one impurity of Fe, Al and Si. The alkaline vanadium solution can be a leaching solution obtained by an alkaline leaching method (such as sodium roasting-water leaching). In some embodiments, the V concentration of the alkaline vanadium solution is 30-40 g / L, the Fe concentration is 1.5-3.0 g / L, the Al concentration is 1.0-2.0 g / L, and the Si concentration is 1.0-1.5 g / L.

[0025] Step S1 corresponds to the alkaline deep impurity removal stage. In this stage, the mercapto chitosan, a biological adsorbent, is used as the adsorbent to remove impurities, which can effectively adsorb and remove Fe, Al, Si and other impurities in the alkaline vanadium solution. The adsorption mechanism is: under alkaline conditions, the mercapto group forms stable coordination bonds with Fe 3+ , Al 3+ , and Si is electrostatically adsorbed in the form of SiO3 2- . The adsorption capacity of mercapto chitosan under strong alkaline conditions can be increased by 8 times compared with traditional resins, and can be simply regenerated and reused after elution with 0.1 mol / L HCl. In some embodiments, the impurity residual amount of the vanadium solution after impurity removal obtained by step S1 is: Fe <0.5 ppm, Al <0.3 ppm, and Si <2 ppm, and the impurity removal effect is obvious.

[0026] In some embodiments, the particle size of the thiolated chitosan microspheres is 50-100 μm, and the thiol content is 2.5-5 mmol / g, thereby ensuring good impurity removal effect. In some embodiments, the adsorbent is added to the basic vanadium solution to remove impurities, including: after adding the adsorbent to the basic vanadium solution, oscillating at 30-60°C for 1-3 h, and then filtering, wherein the solid-liquid ratio of the adsorbent and the basic vanadium solution is 3-8 g / L.

[0027] In some embodiments, the method of the present application further comprises preparing thiolated chitosan microspheres by crosslinking chitosan with 2,3-dimercaptosulfonic acid sodium (DMPS), and the preparation method specifically comprises: dissolving chitosan in an acid solution to obtain a dissolved solution; wherein the mass of chitosan is 2-10% of the mass of the acid solution; adding 2,3-dimercaptosulfonic acid sodium to the dissolved solution, and reacting at 50-90°C for 3-6 h under an inert atmosphere (such as nitrogen) to obtain a post-reaction solution; wherein the mass of 2,3-dimercaptosulfonic acid sodium is 2-5% of the mass of the dissolved solution; dropping the post-reaction solution into a basic solution or performing spray drying to obtain thiolated chitosan microspheres. The degree of deacetylation of chitosan can be ≥95%. The acid solution can be an acetic acid solution with a mass percentage concentration of 1-5% (such as 2%), or it can also be other dilute acids with a mass percentage concentration of 1-10%. The basic solution can be a NaOH solution with a mass percentage concentration of 3-8% (such as 5%). In some embodiments, the post-reaction solution is dropped into the basic solution to form microspheres, which are washed with ethanol after filtration, and then vacuum dried to obtain thiolated chitosan microspheres. In other embodiments, the post-reaction solution is spray dried at 130-180°C to obtain thiolated chitosan microspheres. It should be understood that although the present application proposes the preferred method for preparing thiolated chitosan microspheres as described above, the present application is not limited thereto, and thiolated chitosan microspheres prepared by other methods in the prior art can also be used where feasible.

[0028] Step S2 corresponds to the vanadium form directional conversion stage. In this stage, a composite system of ascorbic acid and sulfite is used, which can avoid the generation of V2O5 precipitate, and directly obtain VO 2+ , realize precise control of vanadium form, realize efficient conversion of V(OH)4 + → VO 2+ (the conversion rate is >99%). The reaction mechanism is: ascorbic acid provides reducing hydroxyl groups to promote the reduction of V(V) to V(IV), and SO3 2- inhibits the polymerization of vanadium to avoid the generation of V2O5 precipitate.

[0029] In some embodiments, the molar ratio of ascorbic acid to sulfite in the conversion agent is (10-25):(2-5). In some embodiments, the conversion agent is a composite solution comprising ascorbic acid and sulfite, wherein the concentration of ascorbic acid in the conversion agent is 0.1-0.25 mol / L and the concentration of sulfite is 0.02-0.05 mol / L. Mixing and reacting the decontaminated vanadium solution with the conversion agent comprises: mixing the decontaminated vanadium solution and the conversion agent at a volume ratio of 1:(0.04-0.08) and reacting at 60-90°C for 20-40 minutes. In some embodiments, the pH of the decontaminated vanadium solution is 9.5-11. The sulfite may be, for example, one or more of Na2SO3, K2SO3, NaHSO3, and (NH4)2SO3.

[0030] Step S3 corresponds to the acidic high-efficiency electrolysis stage. In this stage, a stabilizer is used to improve the stability of the acidic electrolyte to be electrolyzed, and V 3+ / VO 2+ , eliminating the vanadium precipitation-calcination-dissolution steps. In some embodiments, the pH of the electrolyte solution is adjusted by adding an acid (e.g., concentrated sulfuric acid) to the converted vanadium solution, ultimately bringing the pH of the electrolyte solution to 1-1.5. In some embodiments, the method further comprises adjusting the vanadium concentration of the electrolyte solution to 1.5-2.5 mol / L. In some embodiments, the concentration of the stabilizer in the electrolyte solution is 0.02-0.1 mol / L. The stabilizer may include one or more of the following: an inorganic stabilizer, an organic acid, an organic acid salt, an alcohol, and a surfactant. Inorganic stabilizers may include one or more of the following: phosphoric acid, phosphates, sulfates, and boric acid; organic acids may include one or more of the following: oxalic acid, citric acid, and aminopolycarboxylic acid ligands (e.g., EDTA (ethylenediaminetetraacetic acid) and HEDTA (N-hydroxyethylethylenediaminetriacetic acid)); alcohols may include methanol and / or ethylene glycol; and surfactants may include PEG and / or Tween 20. Of course, the present invention is not limited to these examples; other suitable stabilizers known in the art may be employed. In some embodiments, performing electrolysis comprises: 2 Electrolysis was performed at a current density of 4 to 7 hours. Graphene / carbon felt composite electrodes can be used for electrolysis. The electrolyte obtained contains V 3+ and VO 2+ The molar ratio is about 1:1, for example 1:(0.95~1.05).

[0031] In summary, the present application relates to a method for preparing high-purity acidic vanadium electrolyte from alkaline vanadium leaching solution by coupling biosorption, selective conversion and electrochemical catalysis technology. The method uses a two-stage pH control strategy, first uses a modified biosorbent to deeply remove impurities such as iron, aluminum and silicon, and then realizes efficient electrolysis of vanadium in acidic medium through directional conversion of vanadium oxy groups and composite electrocatalytic system, with a current efficiency of more than 95%. The present application solves the problems of traditional process such as repeated adjustment of acid and alkali, long process and impurity interference, and is suitable for high-performance vanadium flow battery energy storage system.

[0032] The following is described according to specific examples.

[0033] Example 1 Alkaline deep impurity removal stage: Step one: adsorbent preparation. Dissolve 5g of chitosan powder (degree of deacetylation ≥95%) in 100mL of 2% acetic acid solution, stir until completely dissolved; add 2,3-dimercaptosuccinic acid sodium (DMPS) 3.2g, react at 60°C for 6h under nitrogen protection; drop the reaction solution into a 5% NaOH solution to form microspheres, wash with ethanol after filtration, and vacuum dry to obtain mercapto chitosan microspheres (particle size 80±15μm, mercapto content 3.2mmol / g).

[0034] Step two: impurity removal process. Take 1L of alkaline vanadium leaching solution (pH=11.2, V content 35.3g / L, Fe content 2.8g / L, Al content 1.9g / L, Si content 1.4g / L); add the above adsorbent according to the solid-liquid ratio of 6g / L of adsorbent and vanadium leaching solution, constant temperature oscillation at 50°C for 2h (rotation speed 150rpm), after filtration, the Fe content is 0.4ppm, the Al content is 0.2ppm, the Si content is 1.6ppm, and the vanadium loss rate is <0.5%.

[0035] Vanadium form directional conversion stage: Step three: preparation of conversion agent, 0.1M ascorbic acid + 0.05M Na2SO3 (dissolved in deionized water); take 500mL of impurity-removed solution (pH=10.8), add 25mL of conversion agent (volume ratio 1:0.05); 75°C water bath reaction for 30min, sample detection: V(OH)4 + →VO 2+ Conversion rate 99.3%, solution blue (VO 2+ Characteristic color).

[0036] Acidic efficient electrolysis stage Step four: slowly add concentrated sulfuric acid to the post-conversion solution until pH = 1.3; add VOSO4to adjust the total vanadium concentration to 2.0 M and add HEDTA to make its concentration 0.05 M; use a graphene / carbon felt composite electrode (graphene loading 10 mg / cm2) to electrolyze at a current density of 80 mA / cm2for 6 h; the final electrolyte composition: V 3+ concentration 1.02 M, VO 2+ concentration 0.98 M (molar ratio 1:0.96), current efficiency 95.7%.

[0037] Example 2 Basic deep impurity removal stage: Step one: adsorbent preparation. Dissolve 6 g of medical-grade chitosan (degree of deacetylation 97%) in 100 mL of 2% acetic acid solution, stir until completely dissolved, add 2.5 g of 2,3-dimercaptopropane sulfonic acid sodium (DMPS), and react at 65°C for 4.5 h under nitrogen protection; use a syringe pump (flow rate 5 mL / min) to drop the reaction solution into a 5% NaOH coagulation bath, collect the microspheres and wash with 50% ethanol, and vacuum dry for 48 h to obtain microspheres with a particle size of 60 ± 10 μm and a thiol content of 3.8 mmol / g.

[0038] Step two: impurity removal process. Treat the vanadium leaching solution (pH = 10.7, V content 32.5 g / L, Fe content 2.5 g / L, Al content 1.8 g / L, Si content 1.2 g / L), add adsorbent according to a solid-liquid ratio of 6 g / L, oscillate at 45°C for 2 h, and after filtration, detect: V content 32.3 g / L (recovery rate 99.4%), Fe content 0.3 ppm, Al content 0.2 ppm, Si content 1.2 ppm. Adsorbent regeneration efficiency: after elution with 0.1 M HCl, it can be reused for 6 times.

[0039] Vanadium form directional conversion stage Step three: prepare the conversion agent, ascorbic acid with a concentration of 0.15 M and Na2SO3with a concentration of 0.02 M; take 500 mL of the post-impurity removal solution, add 20 mL of the conversion agent (volume ratio 1:0.04); react in a 90°C water bath for 30 min, and take a sample for detection: V(OH)4 + → VO 2+ conversion rate 99.7%, the solution is blue (VO 2+ characteristic color).

[0040] Acidic efficient electrolysis stage Step four: slowly add concentrated sulfuric acid to the converted solution until pH = 1.5; add VOSO4to adjust the total vanadium concentration to 1.8 M, and add HEDTA to make its concentration 0.08 M; use graphene / carbon felt composite electrode (graphene loading 10 mg / cm2), electrolyze for 5 h at a current density of 80 mA / cm2; the final electrolyte composition: V 3+ concentration 1.01 M, VO 2+ concentration 0.99 M (molar ratio 1.02:1), current efficiency 96.5%.

[0041] Example 3 Basic deep impurity removal stage: Step one: adsorbent preparation. Take 7 g of medical grade chitosan (deacetylation degree 97%) and dissolve it in 100 mL of 2% acetic acid solution, stir until completely dissolved, add 3.2 g of 2,3-dimercaptosuccinic acid sodium (DMPS), and react at 55°C for 3 h under nitrogen protection; directly spray dry at 160°C to obtain particles with a particle size of 80 ± 20 μm, and the mercapto content is 3.0 mmol / g.

[0042] Step two: impurity removal process. Treat the vanadium leaching solution (pH = 11.2, V content 37.7 g / L, Fe content 1.9 g / L, Al content 1.3 g / L, Si content 1.4 g / L), add adsorbent according to the solid-liquid ratio of adsorbent and vanadium leaching solution of 8 g / L, constant temperature oscillation at 35°C for 2 h, after filtration, test: V recovery rate 99.2%, Fe content 0.4 ppm, Al content 0.3 ppm, Si content 1 ppm; adsorbent regeneration efficiency: after elution with 0.1 M HCl, it can be reused for 6 times.

[0043] Vanadium form directional conversion stage Step three: prepare the conversion agent, ascorbic acid with a concentration of 0.2 M and Na2SO3with a concentration of 0.05 M; take 500 mL of impurity-removed solution and add 25 mL of conversion agent (volume ratio 1:0.05); 80°C water bath reaction for 20 min, sample test: V(OH)4 + → VO 2+ conversion rate 98.8%, the solution is blue (VO 2+ characteristic color).

[0044] Acidic efficient electrolysis stage Step four: slowly add concentrated sulfuric acid to the converted solution until pH = 1.3; add VOSO4to adjust the total vanadium concentration to 2.2 M, and add HEDTA to make its concentration 0.01 M; use graphene / carbon felt composite electrode (graphene loading 10 mg / cm2), electrolyze for 5 h at a current density of 75 mA / cm2; the final electrolyte composition: V 3+ concentration 1 M, VO 2+Concentration 1.01 M (molar ratio 1:1.01), current efficiency 95.2%.

[0045] Those skilled in the art will appreciate that the above discussion is by way of example only, and that the scope of the embodiments disclosed in this patent application (including the claims) is not intended to be limited to these examples; many modifications and variations of the embodiments described herein are possible and will occur to those skilled in the art. Any reference to claimant's patent application shall not be construed as a limitation on the generality of the disclosure [including the claims] or on the scope of protection sought for any patent application that may be filed by the claimant.

Claims

1. A method for preparing vanadium battery electrolyte using alkaline vanadium solution in a short process, characterized in that: include: adding an adsorbent to the alkaline vanadium solution to remove impurities, thereby obtaining a decontaminated vanadium solution; wherein the adsorbent comprises thiolated chitosan microspheres; The impurity-removed vanadium solution and the conversion agent are mixed and reacted to make the V(OH)4 + Convert to VO 2+ , obtaining the converted vanadium liquid; wherein the conversion agent comprises ascorbic acid and sulfite; The converted vanadium solution is adjusted to be acidic and a stabilizer is added to obtain a solution to be electrolyzed, and the solution to be electrolyzed is electrolyzed to obtain a solution containing V 3+ and VO 2+ of electrolyte.

2. The method according to claim 1, characterized in that The particle size of the thiolated chitosan microspheres is 50-100 μm, and the thiol content is 2.5-5 mmol / g.

3. The method according to claim 1, characterized in that The method also includes preparing the thiolated chitosan microspheres, which includes: Dissolving chitosan in an acid solution to obtain a solution, wherein the mass of the chitosan is 2-10% of the mass of the acid solution; Adding sodium 2,3-dimercaptopropanesulfonate to the dissolved solution, reacting at 50-90° C. for 3-6 hours under an inert atmosphere to obtain a reacted solution, wherein the mass of the sodium 2,3-dimercaptopropanesulfonate is 2-5% of the mass of the dissolved solution; The post-reaction solution is dropped into an alkaline solution or spray-dried to obtain the thiolated chitosan microspheres.

4. The method according to claim 1, wherein The alkaline vanadium solution has a pH of 9-12 and contains at least one impurity selected from the group consisting of Fe, Al, and Si.

5. The method according to claim 1, wherein Adding an adsorbent to the alkaline vanadium solution to remove impurities comprises: adding the adsorbent to the alkaline vanadium solution, shaking at 30-60° C. for 1-3 hours, and then filtering, wherein the solid-to-liquid ratio of the adsorbent to the alkaline vanadium solution is 3-8 g / L.

6. The method according to claim 1, characterized in that In the conversion agent, the molar ratio of ascorbic acid to sulfite is (10-25):(2-5).

7. The method according to claim 1, characterized in that In the conversion agent, the concentration of ascorbic acid is 0.1-0.25 mol / L, and the concentration of sulfite is 0.02-0.05 mol / L. The impurity-removed vanadium solution and the conversion agent are mixed and reacted, comprising: mixing the impurity-removed vanadium solution and the conversion agent in a volume ratio of 1:(0.04-0.08), and reacting at 60-90° C. for 20-40 minutes.

8. The method according to claim 1, characterized in that The pH of the electrolyte to be electrolyzed is 1-1.5; in the electrolyte to be electrolyzed, the concentration of the stabilizer is 0.02-0.1 mol / L; the method further comprises adjusting the vanadium concentration of the electrolyte to be electrolyzed to 1.5-2.5 mol / L.

9. The method according to claim 1, characterized in that The stabilizer comprises one or more of the following: an inorganic stabilizer, an organic acid, an organic acid salt, an alcohol, and a surfactant.

10. The method according to claim 1, characterized in that Electrolysis includes: 70~90mA / cm 2 Electrolysis was carried out at a current density of 4 to 7 h.

Images