Method for directly preparing vanadium battery electrolyte from vanadium liquid without participation of organic matters

Abstract

The invention relates to the field of vanadium batteries, and discloses a method for directly preparing vanadium battery electrolyte from vanadium liquid without participation of organic matters, which comprises the following steps: adjusting the pH value of the vanadium liquid to 2-3, and adding an inorganic reducing agent to convert V (V) in the vanadium liquid into V (IV) to obtain pretreated vanadium liquid; fe impurities and Al impurities in the pretreated vanadium liquid are separated in the form of precipitates, Ti impurities in the pretreated vanadium liquid are adsorbed through an adsorbent, and V (IV)-containing impurity-removed vanadium liquid is obtained; performing electrodialysis treatment on the impurity-removed vanadium liquid to concentrate the solution and remove alkali metal impurities in the solution to obtain an electrodialyzed solution; and electrolyzing and blending the solution after electrodialysis to obtain an electrolyte with a preset acid radical concentration and a preset vanadium concentration, wherein the ratio of V (III) to V (IV) is 1: (0.95-1.05). On the basis of ensuring the performance of the electrolyte, the process flow can be shortened, and the problem of environmental pollution caused by using organic matters can be avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of vanadium battery, and particularly relates to a method for directly preparing vanadium battery electrolyte from vanadium liquid without participation of organic matter. BACKGROUND

[0002] Vanadium redox flow battery (VRFB) becomes one of the key technologies for large-scale energy storage due to its long service life, high safety, deep charge and discharge and other advantages. The core electrolyte of the vanadium redox flow battery is vanadium electrolyte, but the vanadium electrolyte has high requirements for material composition, for example, the content of impurity elements such as Fe, Al and K is less than 50 ppm; at the same time, it also needs to have a stable valence ratio V(III) / V(IV)≈1:1; in addition, it also needs to maintain appropriate acidity, in which the concentration of H2SO4 is 2.0-4.0 mol / L.

[0003] Currently, the vanadium electrolyte is mainly prepared by the following two routes in the industry, but both have significant defects. (1) Vanadium pentoxide dissolution method, the process flow is: vanadium leaching solution -> precipitate ammonium metavanadate -> calcine V2O5 -> sulfuric acid dissolution -> electrolytic reduction, this method has the following problems: long process flow; high energy consumption (calcination temperature > 550℃); introduce NH4 + impurities, need additional purification steps; the dissolution speed of vanadium pentoxide is slow, which needs to be heated to more than 80℃. (2) Solvent extraction method, the process flow is: vanadium leaching solution -> organic extraction (such as P204 / TBP) -> back extraction -> electrolytic adjustment of valence, this method has the following problems: use of flammable, toxic organic matter (such as kerosene, phosphoric acid ester); extraction agent degradation leads to wastewater COD exceeding standard; need to handle organic phase residues after back extraction.

[0004] Therefore, the prior art still needs to be improved. SUMMARY

[0005] The main purpose of the present application is to provide a method for directly preparing vanadium battery electrolyte from vanadium liquid without participation of organic matter, so as to solve the technical problems of long process flow and environmental pollution caused by using organic matter in the existing preparation method of vanadium electrolyte.

[0006] According to one aspect of the present application, a method for directly preparing electrolyte of vanadium battery from vanadium electrolyte without organic participation is provided, comprising: adjusting pH of the vanadium electrolyte to 2-3 and adding inorganic reducing agent to convert V(V) in the vanadium electrolyte into V(IV) to obtain pretreated vanadium electrolyte; separating Fe impurities and Al impurities in the pretreated vanadium electrolyte in the form of precipitate and adsorbing Ti impurities in the pretreated vanadium electrolyte by adsorbent to obtain impurity-removed vanadium electrolyte containing V(IV); performing electrodialysis treatment on the impurity-removed vanadium electrolyte to concentrate the solution and remove alkali metal impurities in the solution to obtain post-electrodialysis solution; and 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).

[0007] According to one embodiment of the present application, 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 1.1-1.3 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 (1-1.15):1.

[0008] According to one embodiment of the present application, the inorganic reducing agent is reacted at 60-70℃ for 30-40min after being added.

[0009] According to one embodiment of the present application, the Fe impurities and Al impurities in the pretreated vanadium electrolyte are separated in the form of precipitate, comprising: adding thiosulfate with a concentration of 0.1-0.3mol / L and heating to 80-90℃ to reduce Fe 3+ to Fe 2+ ; adjusting pH to 4.5-5.0 using inorganic base to generate Al(OH)3 precipitate and Fe(OH)2 precipitate while V(IV) remains in the solution.

[0010] According to one embodiment of the present application, the Ti impurities in the pretreated vanadium electrolyte are adsorbed by adsorbent, comprising: making the pretreated vanadium electrolyte flow through an adsorption column containing titanium-based adsorbent at a flow rate of 1-2BV / h.

[0011] According to one embodiment of the present application, when performing electrodialysis treatment, the current density is 20-50mA / cm 2 and the concentration multiple is 2-3.

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

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

[0014] According to one embodiment of the present invention, the preparation includes: adding an inorganic stabilizer to a concentration in the electrolyte of 0.05-0.15 mol / L, wherein the inorganic stabilizer includes NaPO 3 and / or Na 2 SiO 3 .

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

[0016] In the technical solution of the present invention, V(V) is converted to V(IV) at a pH of 2-3, allowing V(IV) to remain in solution. Fe, Al, Ti, and alkali metal impurities in the vanadium solution are then removed through precipitation, adsorption, and electrodialysis to obtain a pure vanadium electrolyte. Through electrodialysis, concentration, electrolysis, and blending, a vanadium electrolyte with a predetermined acid radical concentration, a predetermined vanadium concentration, and a predetermined valence ratio can be obtained. In the method of the present invention, vanadium remains in solution throughout, eliminating the need for a vanadium precipitation, calcination, and dissolution process, which helps shorten the preparation process. Furthermore, the method of the present invention does not require the use of organic matter, making it environmentally friendly and cost-effective. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 A flow chart showing a method for directly preparing a vanadium battery electrolyte from a vanadium liquid without the participation of organic matter according to an embodiment of the present invention. DETAILED DESCRIPTION

[0019] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the embodiments of the present invention are further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0020] It should be noted that all the expressions of "first" and "second" in the embodiments of the present application are used to distinguish two entities with the same name or different parameters, and "first" and "second" are only for the convenience of description, and should not be understood as a limitation on the embodiments of the present application. The subsequent embodiments will not be described one by one.

[0021] As mentioned in the above background, some existing schemes for preparing vanadium electrolyte need to carry out the process of vanadium precipitation first, calcination and then dissolution, resulting in a long process; and some other schemes need to carry out extraction, stripping and other processes, in which the use of organic matter will cause environmental pollution. In order to solve the problems existing in the prior art, the present application proposes a method for directly preparing a vanadium battery electrolyte from a vanadium leaching solution without using organic matter, the details of which are presented below.

[0022] Reference Figure 1 The present application proposes a method for directly preparing a vanadium battery electrolyte from a vanadium solution without using organic matter, comprising: A pretreatment step: adjusting the pH of the vanadium solution to 2-3 and adding an inorganic reducing agent to convert V(V) in the vanadium solution to V(IV) to obtain a pretreated vanadium solution; A selective impurity removal step: separating Fe impurities and Al impurities in the pretreated vanadium solution in the form of precipitates, and adsorbing Ti impurities in the pretreated vanadium solution by an adsorbent to obtain a vanadium solution containing V(IV) after impurity removal; An electrodialysis step: treating the vanadium solution after impurity removal by electrodialysis to concentrate the solution and remove alkali metal impurities in the solution to obtain a solution after electrodialysis; An electrolytic reduction step and a final solution preparation step: electrolyzing and preparing the solution after electrodialysis to obtain an electrolyte with a predetermined acid radical concentration, a predetermined vanadium concentration and V(III) / V(IV)=1:(0.95-1.05).

[0023] In the embodiments of the present application, V(V) is converted to V(IV) at a pH of 2-3, which can keep V(IV) in the solution; then Fe, Al, Ti and alkali metal impurities in the vanadium solution are removed by precipitation, adsorption and electrodialysis, which can obtain a pure vanadium electrolyte; by electrodialysis concentration, electrolysis and preparation, a vanadium electrolyte with a predetermined acid radical concentration, a predetermined vanadium concentration and a predetermined valence ratio can be obtained, which ensures the performance of the vanadium electrolyte. In the method of the present application, vanadium is always kept in the solution, without the need for a process of vanadium precipitation first, calcination and then dissolution, which is beneficial to shorten the preparation process; and the method of the present application does not need to use organic matter, which has the advantages of green and environmental protection, and is also beneficial to reduce the cost.

[0024] The vanadium solution can be a vanadium-containing liquid obtained by treating various vanadium sources such as stone coal, vanadium-titanium magnetite, waste catalyst, etc. The vanadium solution can be, for example, a leaching solution. The vanadium solution contains V(V) and impurities such as Fe 3+ , Al 3+ , Ti 4+ , alkali metals (e.g., K + , Na + ), etc. 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, the Fe 3+ content is 5-15 g / L, the Al 3+ content is 2-5 g / L, the Ti 4+ content is 0.5-3 g / L, and the alkali metal content is 1-5 g / L.

[0025] 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 V(IV) obtained under the reduction of the inorganic reducing agent exists in the solution. 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, 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 oxidation-reduction potential ORP, so that the detected ORP is ≤300 mV. 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 amount ensures that V(V) is completely converted to V(IV), and too little inorganic reducing agent will result in failure to achieve the corresponding effect, and excessive amount will have side effects, affecting the yield or wasting raw materials. The addition of the inorganic reducing agent to convert V(V) in the vanadium solution to V(IV) includes: after the addition of the inorganic reducing agent, reacting at 60-70°C for 30-40 min.

[0026] In the selective impurity removal step, Fe impurities and Al impurities in the pretreated vanadium solution are separated in the form of precipitates, which includes: adding a thiosulfate salt (e.g., one or more of sodium thiosulfate, potassium thiosulfate, ammonium thiosulfate) with a concentration of 0.1-0.3 mol / L and heating to 80-90°C for 30-60 min to reduce Fe 3+ to Fe 2+ ; adjusting the pH to 4.5-5.0 using an inorganic base (e.g., NaOH) to generate Al(OH)3 precipitate and Fe(OH)2 precipitate while V(IV) remains in the solution, and after filtration, a solution from which Al impurities and Fe impurities have been removed can be obtained.

[0027] In the selective impurity removal step, the Ti impurities in the pretreated vanadium solution are adsorbed by the adsorbent, including: making the pretreated vanadium solution flow through the adsorption column containing the titanium adsorbent at a flow rate of 1-2 BV / h. The titanium adsorbent can include TiO2·xH2O gel, which can adsorb Cu, Mn and other heavy metal impurities in addition to Ti impurities. One or more stages of adsorption column can be used according to the situation. In the case of high Ti impurity content, the method further includes adjusting the pH to 2.8-3.2 using an inorganic base to make part of the titanium impurities form Ti(OH)4 precipitate and be separated. By using pH pre-precipitation and two-stage titanium adsorption, ultra-low residual Ti impurities (residual amount <1 ppm) can be achieved.

[0028] In the electrodialysis step, the current density can be 20-50 mA / cm 2 , the concentration ratio can be 2-3 times, and a bipolar membrane electrodialysis device can be used.

[0029] 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 2.5-3 h. Part of V(IV) is reduced to V(III) by electrolysis, and the mixed valence solution after electrolysis has V(III) / V(IV)=1:(0.95-1.05).

[0030] In the final liquid preparation step, H2SO4 can be added to the SO4 2- concentration is 3.0-3.5 mol / L, the total vanadium concentration is 1.5-2.0 mol / L, and an inorganic stabilizer can also be added to ensure the stability of the electrolyte. The concentration of the inorganic stabilizer in the electrolyte can be 0.05-0.15 mol / L, and the inorganic stabilizer can include NaPO3 and / or Na2SiO3.

[0031] In summary, the present application proposes a full inorganic process, which realizes the direct purification and electrolyte preparation of vanadium leaching solution by step-by-step precipitation-electrochemical coupling technology, and does not use any organic reagent throughout the process. The present application completely avoids the use of organic reagents by step-by-step precipitation-electrochemical coupling process, reduces the production cost by more than 30% compared with the traditional method, and the wastewater COD is less than 30 mg / L, which meets the most stringent environmental protection standards. It is especially suitable for different vanadium sources such as vanadium-titanium magnetite and stone coal, and can achieve excellent product purity (impurity content <10 ppm) and cycle performance (100 cycle capacity attenuation rate <0.5%). With the global all-vanadium redox flow battery market growing at an annual rate of over 30%, this technology can be quickly applied to large-scale energy storage power stations, off-grid systems and other fields, and can promote the resource utilization of vanadium slag in steel enterprises, with both economic benefits and environmental value.

[0032] The all-inorganic vanadium electrolyte prepared by the method has the following advantages: 1. The method is environmentally friendly, no organic reagent is used in the whole process, zero organic pollutant emission is achieved, and waste water can be directly discharged; 2. The product has excellent performance, the impurity content (Fe, Al and the like) of the obtained electrolyte is less than 10 ppm, the V(III) / V(IV) ratio is stable (1:1±0.05), and the 100-cycle capacity retention rate is greater than 99%; 3. The economic benefit is remarkable, the production cost is reduced by more than 20% compared with the traditional process, and the vanadium recovery rate is increased to 98.5%; and 4. The process has strong adaptability and is suitable for different vanadium sources such as stone coal, vanadium-titanium magnetite and waste catalyst.

[0033] The following is described according to specific examples.

[0034] Example 1 High-concentration vanadium leaching solution treatment, leaching solution composition: V(V) concentration is 40.2 g / L, Fe 3+ concentration is 12.6 g / L, Al 3+ concentration is 3.8 g / L, Ti 4+ concentration is 1.2 g / L, K + concentration is 2.5 g / L, pH=10.

[0035] Step one: leaching solution pretreatment H2SO4 solution is added to adjust the pH to 2.2±0.1, SO2 gas (purity 99.9%) is introduced, the flow rate is 1.5 L / min·L, the temperature is 65°C, and the ORP is controlled to be 270 mV (1.2 times the theoretical amount). The detection result is that the residual V(V) is less than 0.05%.

[0036] Step two: selective impurity removal Na2S2O3 solution with a concentration of 0.3 mol / L is added, and the reaction is carried out at 90°C for 50 min, the reduction rate of Fe 3+ is 99.5%; NaOH is used to control the pH to be 4.8±0.1, and the filter is obtained after heat aging for 2 h, the composition of the filtrate is that the V(IV) concentration is 38.6 g / L, the Fe concentration is 0.002 g / L, and the Al concentration is 0.0015 g / L. The titanium adsorption is carried out by using two-stage TiO2·xH2O columns (300 m² / g), the flow rate is 1.5 BV / h, and the Ti 4+ removal rate is 99.7%, and the final Ti concentration is less than 0.005 g / L.

[0037] Step three: electrochemical treatment Bipolar membrane electrodialysis: current density is 45 mA / cm², concentration multiple is 2.5 times, the final V concentration is 2.05 mol / L, and the K + concentration is less than 0.002 mol / L.

[0038] Electrolytic reduction: graphite electrode (purity 99.99%) as cathode electrode, cathode potential -0.85V (vs. Ag / AgCl), electrolysis time 3h, V(III) / V(IV)=1:1.02 mixed solution was obtained.

[0039] Step four: final solution preparation Adjust SO4 with H2SO4 of 98% concentration 2- The concentration is 3.4mol / L, and the NaPO3 stabilizer is added to make the content 0.1mol / L. After aging for 24 hours, filtration is performed to obtain the target vanadium electrolyte.

[0040] The final total V concentration is 2.03mol / L, V(III) / V(IV)=1:1.01, Fe impurity content is 2.5ppm, Ti impurity content is 2ppm, current efficiency is 95.6%, and 100 cycle retention rate is 99.3%.

[0041] Example 2 High-iron and low-titanium vanadium leaching solution treatment, leaching solution composition: V(V) concentration is 38.5g / L, Fe 3+ concentration is 15.2g / L, Al 3+ concentration is 4.5g / L, Ti 4+ concentration is 0.6g / L, K + concentration is 3.1(g / L), pH=1.8.

[0042] Step one: leaching solution pretreatment Add Na2CO3 to adjust pH to 2.0±0.1, use Fe powder (purity 99.5%) as reducing agent, add according to VO2 + :Fe=1:1.05 (molar ratio), stir at 65℃ for 40min. Test results: V(V) residue <0.1%.

[0043] Step two: selective impurity removal Add Na2S2O3 of 0.25mol / L concentration, react at 85℃ for 60min, Fe 3+ reduction rate 99.3%; adjust pH to 4.6±0.1 with NaOH, and filter after aging and curing for 2.5h, filtrate composition: V(IV) concentration is 36.8(g / L), Fe concentration is 0.003(g / L), Al concentration is 0.002(g / L). Ti adsorption uses single-stage TiO2·xH2O column (250m² / g), flow rate 2BV / h, Ti 4+ removal rate 99.5%, final Ti concentration <0.005g / L.

[0044] Step three: electrochemical treatment Bipolar membrane electrodialysis: current density 40 mA / cm2, concentration ratio 2.2, final V concentration 1.92 mol / L, K + <0.003 mol / L.

[0045] Electrolytic reduction: graphite electrode (purity 99.9%) was used, cathode potential -0.8 V (vs. Ag / AgCl), electrolysis time 2.5 h, V(III) / V(IV) = 1:1.03 mixture was obtained.

[0046] Step four: final solution preparation Adjust SO42by adding H2SO4 with concentration 98%. 2- The target vanadium electrolyte was obtained by filtering after aging for 24 h with V concentration 3.2 mol / L and NaPO3 stabilizer with concentration 0.08 mol / L.

[0047] 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 100 cycle retention rate was 99.1%.

[0048] Example 3 Low-iron high-titanium vanadium leaching solution treatment, leaching solution composition: V(V) concentration 42.0 g / L, Fe 3+ concentration 8.3 g / L, Al 3+ concentration 2.9 g / L, Ti 4+ concentration 2.5 g / L, K + concentration 1.8 g / L, pH = 1.5 Step one: leaching solution pretreatment Add 10% Na2CO3 to adjust pH to 2.5±0.1, and pass in sulfurous acid (H2SO3) solution (concentration 6%), add 1.15 times the theoretical amount, react at 60°C for 30 min, and the detection result is: V(V) residue <0.05%.

[0049] Step two: selective impurity removal Pre-titanium removal: adjust pH to 3.0 with 6 mol / L NaOH to precipitate part of Ti(OH)4, and remove by filtration. Iron and aluminum co-precipitation: add 0.2 mol / L Na2S2O3 solution, react at 90°C for 40 min, Fe 3+Reduction rate: 99.6%; pH adjusted to 4.7±0.1 with NaOH, kept warm for 1.5h and filtered. The filtrate composition: V(IV) concentration 40.1g / L, Fe concentration 0.001g / L, Al concentration 0.001g / L. Deep titanium removal: using a two-stage TiO2·xH2O column (350m² / g), flow rate 1.2BV / h, Ti 4+ The removal rate is 99.9%, and the final Ti concentration is less than 0.001g / L.

[0050] Step 3: Electrochemical treatment Bipolar membrane electrodialysis: current density 50mA / cm², concentration factor 3.0, final V concentration 2.12mol / L, K + Concentration <0.001mol / L.

[0051] Electrolytic reduction, graphite electrode (purity 99.99%), cathode potential -0.9 V (vs. Ag / AgCl), electrolysis time 3.5 h, to obtain a mixed solution with V(III) / V(IV)=1:1.01.

[0052] Step 4: Final solution preparation Supplement H2SO4 with a concentration of 98% to adjust SO4 2- The concentration is 3.5 mol / L, and NaPO3 and Na2SiO3 composite stabilizers are added to make the NaPO3 concentration 0.1 mol / L and the Na2SiO3 concentration 0.02 mol / L. After aging for 24 hours, filtration is performed to obtain the target vanadium electrolyte.

[0053] The final total V concentration was 2.11 mol / L, V(III) / V(IV)=1:1.01, the Fe impurity content was 1.2 ppm, the Ti impurity content was 0.3 ppm, the current efficiency was 96.8%, and the 100-cycle retention rate was 99.5%.

[0054] All the above examples realize a fully inorganic process, with wastewater COD less than 30 mg / L and no organic solvent residue. Example 2 uses Fe powder reduction, which is suitable for ultra-high iron leaching solution and avoids the problem of complex operation caused by using SO2 gas.

[0055] Those skilled in the art should understand that the above discussion of any embodiment is only exemplary, and is not intended to mean that the scope of the embodiments disclosed by the present application (including claims) is limited to these examples; under the idea of the embodiments of the present application, the above embodiments or technical features among different embodiments can also be combined, and there are many other changes of different aspects of the embodiments of the present application as described above, which are not provided in details for the sake of brevity. Therefore, any omission, modification, equivalent replacement, improvement, etc. made within the spirit and principle of the embodiments of the present application shall be included in the protection scope of the embodiments of the present application.

Claims

1. A method for directly preparing vanadium battery electrolyte from vanadium liquid without the participation of organic matter, characterized in that: include: The pH of the vanadium solution is adjusted to 2-3, and an inorganic reducing agent is added to convert V(V) in the vanadium solution into V(IV) to obtain a pretreated vanadium solution; Separating Fe and Al impurities in the pretreated vanadium solution in the form of precipitation, and adsorbing Ti impurities in the pretreated vanadium solution by an adsorbent to obtain a decontaminated vanadium solution containing V(IV); performing electrodialysis on the impurity-removed vanadium solution to concentrate the solution and remove alkali metal impurities in the solution to obtain an electrodialyzed solution; The electrodialysis solution is electrolyzed and prepared to obtain an electrolyte having a predetermined acid radical concentration and a predetermined vanadium concentration and a V(III) / V(IV) ratio of 1: (0.95-1.05).

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, and 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, the mixture is reacted at 60-70° C. for 30-40 minutes.

4. The method according to claim 1, wherein The Fe impurities and Al impurities in the pretreated vanadium solution are separated in the form of precipitation, comprising: Add 0.1~0.3mol / L thiosulfate and heat to 80~90℃ to remove Fe 3+ Reduction to Fe 2+ ; The pH is adjusted to 4.5-5.0 using an inorganic base, resulting in the formation of Al(OH)3 and Fe(OH)2 precipitates while V(IV) remains in the solution.

5. The method according to claim 1, wherein Adsorbing Ti impurities in the pretreated vanadium solution by an adsorbent comprises: 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.

6. The method according to claim 1, characterized in that During the electrodialysis treatment, the current density is 20-50 mA / cm 2 , the concentration multiple is 2~3 times.

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

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

9. The method according to claim 1, characterized in that The preparation includes: adding an inorganic stabilizer so that its concentration in the electrolyte is 0.05-0.15 mol / L, wherein the inorganic stabilizer includes NaPO3 and / or Na2SiO3.

10. The method according to claim 1, characterized in that Before adsorbing the Ti impurities by the adsorbent, the method further includes: using an inorganic base to adjust the pH to 2.8-3.2, so that part of the titanium impurities form Ti(OH)4 precipitates and are separated.

Images