Method for directly preparing vanadium battery electrolyte from vanadium solution without organic participation

Abstract

The present application relates to the field of vanadium battery, and discloses a method for directly preparing vanadium battery electrolyte from vanadium solution without organic participation, comprising: adjusting the pH of the vanadium solution to 2-3, and adding inorganic reducing agent to convert V(V) in the vanadium solution into V(IV), to obtain pretreated vanadium solution; separating Fe impurities and Al impurities in the pretreated vanadium solution in the form of precipitation, and adsorbing Ti impurities in the pretreated vanadium solution by adsorbent, to obtain impurity-removed vanadium solution containing V(IV); performing electrodialysis treatment on the impurity-removed vanadium solution to concentrate the solution and remove alkali metal impurities in the solution, to obtain post-electrodialysis solution; performing electrolysis and blending on the post-electrodialysis solution, to obtain electrolyte with predetermined acid radical concentration and predetermined vanadium concentration, and V(III) / V(IV)=1:(0.95-1.05). The present application can shorten the process flow and avoid environmental pollution caused by the use of organic matter on the basis of ensuring the performance of the electrolyte.

Description

Technical Field

[0001] This invention relates to the field of vanadium battery technology, and specifically to a method for directly preparing vanadium battery electrolyte from vanadium liquid without the participation of organic matter. Background Technology

[0002] Vanadium redox flow batteries (VRFBs) have become a key technology for large-scale energy storage due to their advantages such as long lifespan, high safety, and deep charge / discharge capability. Their core electrolyte is vanadium electrolyte, but vanadium electrolytes have high requirements for their composition. For example, they need high purity, with impurity elements such as Fe, Al, and K content less than 50 ppm; they also need a stable valence ratio of V(III) / V(IV) ≈ 1:1; in addition, they need to maintain suitable acidity, with H2SO4 concentration of 2.0~4.0 mol / L.

[0003] Currently, vanadium electrolytes are mainly prepared in industry through the following two routes, but both have significant drawbacks. (1) Vanadium pentoxide dissolution method, the process flow is: vanadium leaching solution → precipitation of ammonium metavanadate → calcination of V2O5 → sulfuric acid dissolution → electrolytic reduction. This method has the following problems: the process is lengthy; energy consumption is high (calcination temperature > 550℃); NH4 is introduced. + Impurities require additional purification steps; vanadium pentoxide dissolves slowly and needs to be heated to above 80°C. (2) Solvent extraction method, the process flow is: vanadium leaching solution → organic extraction (such as P2O4 / TBP) → back-extraction → electrolysis to adjust the valence state. This method has the following problems: flammable and toxic organic substances (such as kerosene and phosphate esters) are used; the degradation of the extractant leads to excessive COD in the wastewater; the organic phase residue needs to be treated after back-extraction.

[0004] Therefore, existing technologies still need improvement. Summary of the Invention

[0005] The main objective of this invention is to provide a method for directly preparing vanadium battery electrolyte from vanadium liquid without the participation of organic matter, so as to solve the technical problems of existing methods for preparing vanadium electrolyte being lengthy and prone to environmental pollution due to the use of organic matter.

[0006] According to one aspect of the present invention, a method for directly preparing vanadium battery electrolyte from vanadium solution without the participation of organic matter is provided, comprising: adjusting the pH of the vanadium solution to 2-3, and adding an inorganic reducing agent to convert V(V) in the vanadium solution into V(IV), thereby obtaining a pretreated vanadium solution; separating Fe and Al impurities in the pretreated vanadium solution by precipitation, and adsorbing Ti impurities in the pretreated vanadium solution by an adsorbent, thereby obtaining a purified vanadium solution containing V(IV); subjecting the purified vanadium solution to electrodialysis to concentrate the solution and remove alkali metal impurities from the solution, thereby obtaining an electrodialysis solution; and electrolyzing and adjusting the electrodialysis solution to obtain an electrolyte having a predetermined anion concentration and a predetermined vanadium concentration, and V(III) / V(IV) = 1: (0.95-1.05).

[0007] According to one embodiment of the present invention, the inorganic reducing agent is one or more of the following: sulfur dioxide, sulfurous acid, iron powder, ferrous sulfate; when the inorganic reducing agent is sulfur dioxide and / or sulfurous acid, the amount of inorganic reducing agent used is 1.1 to 1.3 times the theoretical amount; when the inorganic reducing agent is iron powder and / or ferrous sulfate, the molar ratio of the amount of inorganic reducing agent used to V (V) is (1 to 1.15):1.

[0008] According to one embodiment of the present invention, after adding an inorganic reducing agent, the reaction is carried out at 60~70°C for 30~40 min.

[0009] According to one embodiment of the present invention, separating Fe and Al impurities in a pretreated vanadium solution by precipitation includes: adding thiosulfate at a concentration of 0.1~0.3 mol / L and heating to 80~90°C to precipitate Fe. 3+ Reduced to Fe 2+ The pH was adjusted to 4.5-5.0 using an inorganic base, which produced Al(OH)3 and Fe(OH)2 precipitates while V(IV) remained in the solution.

[0010] According to one embodiment of the present invention, the adsorption of Ti impurities in a pretreated vanadium solution by an adsorbent includes: allowing the pretreated vanadium solution to flow through an adsorption column containing a titanium-based adsorbent at a flow rate of 1~2 BV / h.

[0011] According to one embodiment of the present invention, the current density during electrodialysis is 20~50 mA / cm². 2 The concentration factor is 2 to 3 times.

[0012] According to one embodiment of the present invention, during electrolysis, the cathode potential is -0.7 to -0.9 V (vs. Ag / AgCl), the electrolysis time is 2.5 to 3 h, and a mixed valence solution with V(III) / V(IV) = 1: (0.95 to 1.05) is obtained after electrolysis.

[0013] According to one embodiment of the present invention, the blending process includes: supplementing H2SO4 to SO4. 2- The concentration is 3.0~3.5 mol / L, and the total vanadium concentration is 1.5~2.0 mol / L.

[0014] According to one embodiment of the present invention, the formulation includes adding an inorganic stabilizer to make its concentration in the electrolyte 0.05~0.15mol / L, wherein the inorganic stabilizer includes NaPO3 and / or Na2SiO3.

[0015] According to one embodiment of the present invention, before adsorbing Ti impurities by an adsorbent, the method further includes: adjusting the pH to 2.8-3.2 using an inorganic base, so that some of the titanium impurities form Ti(OH)4 precipitate and are separated.

[0016] In the technical solution of this invention, V(V) is converted to V(IV) under pH conditions of 2-3, so that V(IV) is retained in the solution. Then, Fe, Al, Ti and alkali metal impurities in the vanadium solution are removed by precipitation, adsorption and electrodialysis to obtain a pure vanadium electrolyte. Through electrodialysis concentration, electrolysis and adjustment, a vanadium electrolyte with a predetermined anion concentration, predetermined vanadium concentration and predetermined valence state ratio can be obtained. In the method of this invention, vanadium is always kept in the solution, eliminating the need for a process of first precipitating vanadium, then calcining and dissolving it, which helps to shorten the preparation process. Furthermore, the method of this invention does not use organic matter, which has the advantages of being green and environmentally friendly, and also helps to reduce costs. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A flowchart illustrating a method for directly preparing vanadium battery electrolyte from vanadium liquid without the participation of organic matter according to an embodiment of the present invention is shown. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to specific examples and the accompanying drawings.

[0020] It should be noted that all uses of "first" and "second" in the embodiments of the present invention are for the purpose of distinguishing two entities or parameters with the same name but different names. It is clear that "first" and "second" are only for the convenience of expression and should not be construed as limiting the embodiments of the present invention. Subsequent embodiments will not explain this in detail.

[0021] As mentioned in the background section above, some existing methods for preparing vanadium electrolytes require a lengthy process involving vanadium precipitation followed by calcination and dissolution; while other methods require extraction and back-extraction processes, the use of organic matter in these processes leading to environmental pollution. To address the problems in the prior art, this application proposes a method for directly preparing an all-vanadium redox flow battery electrolyte from vanadium leachate without using organic matter, the details of which are presented below.

[0022] refer to Figure 1 This invention proposes a method for directly preparing vanadium battery electrolyte from vanadium liquid without the participation of organic matter, comprising:

[0023] Pretreatment steps: Adjust the pH of the vanadium solution to 2-3, and add an inorganic reducing agent to convert V(V) in the vanadium solution into V(IV), to obtain the pretreated vanadium solution;

[0024] Selective impurity removal step: Fe and Al impurities in the pretreated vanadium solution are separated by precipitation, and Ti impurities in the pretreated vanadium solution are adsorbed by an adsorbent to obtain a purified vanadium solution containing V(IV).

[0025] Electrodialysis steps: The vanadium solution after impurity removal is subjected to electrodialysis to concentrate the solution and remove alkali metal impurities from the solution, resulting in an electrodialysis solution;

[0026] Electrolytic reduction step and final solution preparation step: Electrolyze and prepare the solution after electrodialysis to obtain an electrolyte with a predetermined anion concentration and a predetermined vanadium concentration and V(III) / V(IV)=1: (0.95~1.05).

[0027] In embodiments of the present invention, V(V) is converted to V(IV) at a pH of 2-3, allowing V(IV) to remain in the solution. Then, Fe, Al, Ti, and alkali metal impurities in the vanadium solution are removed by precipitation, adsorption, and electrodialysis to obtain a pure vanadium electrolyte. Through electrodialysis concentration, electrolysis, and adjustment, a vanadium electrolyte with predetermined anion concentration, predetermined vanadium concentration, and predetermined valence ratio can be obtained, ensuring the performance of the vanadium electrolyte. In the method of the present invention, vanadium remains in the solution throughout, eliminating the need for a process of vanadium precipitation followed by calcination and dissolution, thus shortening the preparation process. Furthermore, the method of the present invention does not use organic matter, offering advantages of being green and environmentally friendly, and also reducing costs.

[0028] Vanadium solution can be a vanadium-containing liquid obtained by processing various vanadium sources such as coal shale, vanadium-titanium magnetite, and spent catalysts. Vanadium solution can be, for example, a leaching solution. Vanadium solution contains V (V) and Fe. 3+ Al 3+ Ti 4+ Alkali metals (e.g., K) + Na + Impurities such as Fe can be present, and the pH of the vanadium solution can be acidic or alkaline. In some embodiments, the V (V) content in the vanadium solution is 35~45 g / L, and the Fe content is... 3+ Content is 5~15g / L, Al 3+ Content is 2~5g / L, Ti 4+ The content is 0.5~3g / L, and the alkali metal content is 1~5g / L.

[0029] In the pretreatment step, the pH of the vanadium solution can be adjusted using an inorganic acid (e.g., H₂SO₄) or an inorganic base (e.g., Na₂CO₃). By adjusting the pH to 2-3, it can be ensured that the obtained V(IV) exists in the solution under the reduction action of the inorganic reducing agent. The inorganic reducing agent can be used to completely convert V(V) to V(IV), so that the residual V(V) content in the solution is less than 0.1%. In some embodiments, the inorganic reducing agent is one or more of the following: sulfur dioxide, sulfurous acid, iron powder, and ferrous sulfate. When the inorganic reducing agent is sulfur dioxide and / or sulfurous acid, the amount of inorganic reducing agent used is 1.1-1.3 times the theoretical amount, and the amount can be controlled according to the detected redox potential (ORP) so that the detected ORP is ≤300mV. When the inorganic reducing agent is iron powder and / or ferrous sulfate, the molar ratio of the amount of inorganic reducing agent to V(V) is (1-1.15):1. A suitable dosage ensures complete conversion of V(V) to V(IV). Insufficient inorganic reducing agent will fail to achieve the desired effect, while excessive dosage will have side effects, affecting yield or wasting raw materials. The conversion of V(V) to V(IV) in the vanadium solution by adding the inorganic reducing agent includes reacting at 60-70°C for 30-40 minutes after adding the inorganic reducing agent.

[0030] In the selective impurity removal step, Fe and Al impurities in the pretreated vanadium solution are separated by precipitation. This includes adding a thiosulfate (e.g., one or more of sodium thiosulfate, potassium thiosulfate, and ammonium thiosulfate) at a concentration of 0.1–0.3 mol / L and heating to 80–90 °C for 30–60 min to separate the Fe impurities. 3+ Reduced to Fe 2+ The pH is adjusted to 4.5-5.0 using an inorganic base (such as NaOH), which generates Al(OH)3 precipitate and Fe(OH)2 precipitate, while V(IV) remains in the solution. After filtration, a solution with Al and Fe impurities removed can be obtained.

[0031] In the selective impurity removal step, Ti impurities in the pretreated vanadium solution are adsorbed by an adsorbent. This includes passing the pretreated vanadium solution through an adsorption column containing a titanium-based adsorbent at a flow rate of 1-2 BV / h. The titanium-based adsorbent may include TiO2·xH2O gel, which can adsorb not only Ti impurities but also heavy metal impurities such as Cu and Mn. Single-stage or multi-stage adsorption columns can be used as needed. When the Ti impurity content is high, before adsorbing the Ti impurities with the adsorbent, the method further includes adjusting the pH to 2.8-3.2 using an inorganic alkali, causing some of the titanium impurities to precipitate as Ti(OH)4 and be separated. By employing pH preprecipitation + two-stage titanium adsorption, ultra-low Ti impurity residue (residual amount <1 ppm) can be achieved.

[0032] In the electrodialysis step, the current density can be 20~50 mA / cm². 2 The concentration factor can be 2 to 3 times, and a bipolar membrane electrodialysis device can be used.

[0033] In the electrolytic reduction step, the cathode potential can be -0.7 to -0.9 V (vs. Ag / AgCl), and the electrolysis time can be 2.5 to 3 h. Through electrolysis, part of V(IV) is reduced to V(III), and a mixed valence solution with V(III) / V(IV) = 1: (0.95 to 1.05) is obtained after electrolysis.

[0034] In the final liquid preparation step, H2SO4 can be added to SO42-. 2- The concentration is 3.0~3.5 mol / L, the total vanadium concentration is 1.5~2.0 mol / L, and inorganic stabilizers can also be added to ensure the stability of the electrolyte. The concentration of inorganic stabilizers in the electrolyte can be 0.05~0.15 mol / L, and inorganic stabilizers can include NaPO3 and / or Na2SiO3.

[0035] In summary, this invention proposes a completely inorganic process for the direct purification of vanadium leaching solution and the preparation of electrolyte through stepwise precipitation-electrochemical coupling technology, without the use of any organic reagents. This stepwise precipitation-electrochemical coupling process completely avoids the use of organic reagents, reducing production costs by more than 30% compared to traditional methods, and achieving a wastewater COD of <30mg / L, meeting the strictest environmental standards. It is particularly suitable for various vanadium sources such as vanadium-titanium magnetite and coal shale, achieving excellent product purity (impurity content <10ppm) and cycle performance (capacity decay rate <0.5% after 100 cycles). With the global vanadium redox flow battery market growing at an annual rate exceeding 30%, this technology can be rapidly applied to large-scale energy storage power stations, off-grid systems, and other fields, promoting the resource utilization of vanadium slag in steel enterprises, thus possessing both economic and environmental value.

[0036] The all-inorganic method for preparing vanadium electrolyte proposed in this invention has significant application effects: 1) It has outstanding environmental advantages, as no organic reagents are used throughout the process, achieving zero organic pollutant emissions, and wastewater can be directly discharged for treatment; 2) The product has excellent performance, with the impurity content (Fe, Al, etc.) of the obtained electrolyte being <10ppm, the V(III) / V(IV) ratio being stable (1:1±0.05), and the capacity retention rate being >99% after 100 cycles; 3) It has significant economic benefits, reducing production costs by more than 20% compared to traditional processes, and increasing the vanadium recovery rate to 98.5%; 4) The process has strong adaptability and is suitable for different vanadium sources such as coal shale, vanadium-titanium magnetite, and spent catalysts.

[0037] The following description is based on specific embodiments.

[0038] Example 1

[0039] Treatment with high-concentration vanadium leaching solution; leaching solution composition: V (V) concentration 40.2 g / L, Fe... 3+ The concentration was 12.6 g / L, Al 3+ Concentration of 3.8 g / L, Ti 4+ Concentration of 1.2 g / L, K + The concentration is 2.5 g / L and the pH is 10.

[0040] Step 1: Leachate Pretreatment

[0041] The pH was adjusted to 2.2 ± 0.1 by adding H₂SO₄ solution. SO₂ gas (99.9% purity) was then introduced at a flow rate of 1.5 L / min·L, at a temperature of 65℃, and the ORP was controlled at 270 mV (1.2 times the theoretical amount). The test results showed that the residual V(V) was <0.05%.

[0042] Step 2: Selective Impurity Removal

[0043] Add a 0.3 mol / L Na₂S₂O₃ solution and react at 90°C for 50 min. Fe 3+ The reduction rate was 99.5%. The pH was controlled at 4.8±0.1 using NaOH, and the solution was aged for 2 hours before filtration. The filtrate composition was: V(IV) concentration 38.6 g / L, Fe concentration 0.002 g / L, and Al concentration 0.0015 g / L. Titanium adsorption was performed using a two-stage TiO2·xH2O column (300 m² / g) at a flow rate of 1.5 BV / h. 4+ The removal rate was 99.7%, and the final Ti concentration was <0.005 g / L.

[0044] Step 3: Electrochemical treatment

[0045] Bipolar membrane electrodialysis: current density 45 mA / cm², concentration factor 2.5 times, final V concentration 2.05 mol / L, K +Concentration < 0.002 mol / L.

[0046] Electrolytic reduction: Using a graphite electrode (purity 99.99%) as the cathode electrode, with a cathode potential of -0.85V (vs. Ag / AgCl) and an electrolysis time of 3h, a mixed solution with V(III) / V(IV) = 1:1.02 was obtained.

[0047] Step 4: Final Solution Preparation

[0048] Add 98% H2SO4 to adjust SO4 2- The concentration is 3.4 mol / L. NaPO3 stabilizer is added to make the content 0.1 mol / L. After aging for 24 hours, the solution is filtered to obtain the target vanadium electrolyte.

[0049] The final total V concentration was 2.03 mol / L, V(III) / V(IV) = 1:1.01, Fe impurity content was 2.5 ppm, Ti impurity content was 2 ppm, current efficiency was 95.6%, and retention rate after 100 cycles was 99.3%.

[0050] Example 2

[0051] High-speed rail low-titanium vanadium leaching solution treatment, leaching solution composition: V (V) concentration is 38.5 g / L, Fe 3+ The concentration was 15.2 g / L, Al 3+ Concentration of 4.5 g / L, Ti 4+ Concentration of 0.6 g / L, K + The concentration was 3.1 g / L and the pH was 1.8.

[0052] Step 1: Leachate Pretreatment

[0053] Adjust the pH to 2.0 ± 0.1 by adding Na2CO3, and use Fe powder (99.5% purity) as a reducing agent, according to VO2 + Fe was added at a molar ratio of 1:1.05, and stirred at 65°C for 40 min. Detection results: V(V) residue <0.1%.

[0054] Step 2: Selective Impurity Removal

[0055] Add 0.25 mol / L Na₂S₂O₃ and react at 85℃ for 60 min, Fe 3+ The reduction rate was 99.3%. The pH was adjusted to 4.6 ± 0.1 using NaOH, and the solution was aged for 2.5 hours before filtration. The filtrate composition was: V(IV) concentration 36.8 (g / L), Fe concentration 0.003 (g / L), and Al concentration 0.002 (g / L). Titanium adsorption was performed using a single-stage TiO2·xH2O column (250 m² / g) at a flow rate of 2 BV / h.4+ The removal rate was 99.5%, and the final Ti concentration was <0.005 g / L.

[0056] Step 3: Electrochemical treatment

[0057] Bipolar membrane electrodialysis: current density 40 mA / cm², concentration factor 2.2, final V concentration 1.92 mol / L, K + <0.003mol / L.

[0058] Electrolytic reduction: Using a graphite electrode (purity 99.9%), a cathode potential of -0.8V (vs. Ag / AgCl), and an electrolysis time of 2.5h, a mixed solution with V(III) / V(IV) = 1:1.03 was obtained.

[0059] Step 4: Final Solution Preparation

[0060] Add 98% H2SO4 to adjust SO4 2- The concentration was 3.2 mol / L. NaPO3 stabilizer was added to make the content 0.08 mol / L. After aging for 24 hours, the solution was filtered to obtain the target vanadium electrolyte.

[0061] The final total V concentration was 1.91 mol / L, V(III) / V(IV) = 1:1.03, Fe impurity content was 2.8 ppm, Ti impurity content was 0.6 ppm, current efficiency was 94.5%, and retention rate after 100 cycles was 99.1%.

[0062] Example 3

[0063] Treatment with low-iron, high-titanium vanadium leaching solution; leaching solution composition: V (V) concentration 42.0 g / L, Fe... 3+ Concentration of 8.3 g / L, Al 3+ The concentration was 2.9 g / L, Ti 4+ Concentration of 2.5 g / L, K + Concentration: 1.8 g / L, pH: 1.5

[0064] Step 1: Leachate Pretreatment

[0065] Add 10% Na2CO3 to adjust the pH to 2.5±0.1, then pass in 6% sulfurous acid (H2SO3) solution at 1.15 times the theoretical amount, react at 60℃ for 30 min, and the result is: V(V) residue <0.05%.

[0066] Step 2: Selective Impurity Removal

[0067] Pre-removal of titanium: The pH was adjusted to 3.0 using 6 mol / L NaOH, and the precipitated Ti(OH)4 was removed by filtration. Iron-aluminum co-precipitation: A 0.2 mol / L Na2S2O3 solution was added, and the reaction was carried out at 90℃ for 40 min. Fe... 3+ The reduction rate was 99.6%. The pH was adjusted to 4.7 ± 0.1 using NaOH, and the solution was kept at this temperature for 1.5 hours before filtration. The filtrate composition was: V(IV) concentration 40.1 g / L, Fe concentration 0.001 g / L, and Al concentration 0.001 g / L. Deep titanium removal was performed using a two-stage TiO2·xH2O column (350 m² / g) at a flow rate of 1.2 BV / h. 4+ The removal rate was 99.9%, and the final Ti concentration was <0.001 g / L.

[0068] Step 3: Electrochemical treatment

[0069] Bipolar membrane electrodialysis: current density 50 mA / cm², concentration factor 3.0, final V concentration 2.12 mol / L, K + Concentration < 0.001 mol / L.

[0070] Electrolytic reduction was performed using a graphite electrode (99.99% purity), a cathode potential of -0.9V (vs. Ag / AgCl), and an electrolysis time of 3.5h to obtain a mixture with V(III) / V(IV) = 1:1.01.

[0071] Step 4: Final Solution Preparation

[0072] Add 98% H2SO4 to adjust SO4 2- The concentration is 3.5 mol / L. Add NaPO3 and Na2SiO3 composite stabilizers to make the NaPO3 concentration 0.1 mol / L and the Na2SiO3 concentration 0.02 mol / L. After aging for 24 hours, filter to obtain the target vanadium electrolyte.

[0073] The final total V concentration was 2.11 mol / L, V(III) / V(IV) = 1:1.01, Fe impurity content was 1.2 ppm, Ti impurity content was 0.3 ppm, current efficiency was 96.8%, and retention rate was 99.5% after 100 cycles.

[0074] All the above embodiments achieve a completely inorganic process, with wastewater COD < 30 mg / L and no organic solvent residue. Example 2 uses Fe powder reduction, which is suitable for ultra-high ferric leachate and avoids the operational complexity associated with using SO2 gas.

[0075] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples. Within the framework of the invention, technical features of the above embodiments or different embodiments can be combined, and many other variations of the different aspects of the invention as described above exist, which are not provided in the details for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. A method for directly preparing vanadium battery electrolyte from vanadium leaching solution without the participation of organic matter, characterized in that, include: The pH of the vanadium leaching solution was adjusted to 2-3, and an inorganic reducing agent was added to convert V(V) in the vanadium leaching solution into V(IV), thus obtaining the pretreated vanadium leaching solution. Fe and Al impurities in the pretreated vanadium leaching solution are separated by precipitation, and Ti impurities in the pretreated vanadium leaching solution are adsorbed by an adsorbent to obtain a purified vanadium leaching solution containing V(IV). The vanadium leaching solution after impurity removal is subjected to electrodialysis to concentrate the solution and remove alkali metal impurities from the solution, resulting in an electrodialysis solution. The electrodialysis solution is electrolyzed and prepared to obtain an electrolyte with a predetermined anion concentration and a predetermined vanadium concentration and V(III) / V(IV)=1: (0.95~1.05); The process of separating Fe and Al impurities in the pretreated vanadium leaching solution by precipitation includes: Add 0.1~0.3 mol / L thiosulfate and heat to 80~90℃ to remove Fe. 3+ Reduced to Fe 2+ ; Adjusting the pH to 4.5-5.0 with an inorganic base generates Al(OH)3 and Fe(OH)2 precipitates, while V(IV) remains in the solution.

2. The method according to claim 1, characterized in that, The inorganic reducing agent is one or more of the following: sulfur dioxide, sulfurous acid, iron powder, ferrous sulfate; when the inorganic reducing agent is sulfur dioxide and / or sulfurous acid, the amount of the inorganic reducing agent is 1.1 to 1.3 times the theoretical amount; when the inorganic reducing agent is iron powder and / or ferrous sulfate, the molar ratio of the amount of the inorganic reducing agent to V (V) is (1 to 1.15):

1.

3. The method according to claim 1, characterized in that, After adding the inorganic reducing agent, react at 60-70℃ for 30-40 minutes.

4. The method according to claim 1, characterized in that, The adsorption of Ti impurities in the pretreated vanadium leaching solution by an adsorbent includes: passing the pretreated vanadium leaching solution through an adsorption column containing a titanium-based adsorbent at a flow rate of 1~2 BV / h.

5. The method according to claim 1, characterized in that, During the electrodialysis treatment, the current density is 20~50 mA / cm². 2 The concentration factor is 2 to 3 times.

6. The method according to claim 1, characterized in that, During the electrolysis, the cathode potential is -0.7 to -0.9 V, vs. Ag / AgCl, and the electrolysis time is 2.5 to 3 h. After electrolysis, a mixed valence solution with V(III) / V(IV) = 1: (0.95 to 1.05) is obtained.

7. The method according to claim 1, characterized in that, The aforementioned preparation includes: supplementing H2SO4 to SO4 2- The concentration is 3.0~3.5 mol / L, and the total vanadium concentration is 1.5~2.0 mol / L.

8. The method according to claim 1, characterized in that, The preparation includes adding an inorganic stabilizer to achieve a concentration of 0.05~0.15 mol / L in the electrolyte, wherein the inorganic stabilizer includes NaPO3 and / or Na2SiO3.

9. The method according to claim 1, characterized in that, Before adsorbing Ti impurities with an adsorbent, the method further includes adjusting the pH to 2.8-3.2 using an inorganic base, so that some of the titanium impurities form Ti(OH)4 precipitate and are separated.

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