Electrolyte for extracting vanadium from stone coal as well as preparation method and application of electrolyte

Abstract

The invention provides an all-vanadium redox flow battery vanadium electrolyte based on carbonaceous slate type stone coal and a preparation method of the all-vanadium redox flow battery vanadium electrolyte. The method is characterized in that the carbonaceous slate type vanadium ore coal is subjected to decarburization, blank roasting, soaking in a mixed solution of 10% sulfuric acid and 0.1% sodium chlorate and solid-liquid separation to obtain a pentavalent vanadium leaching solution, the pH range is 1.8-2.6, the leaching solution is subjected to 3-5-stage multi-stage counter-current extraction by using an N235 / N1923: TBP: sulfonated kerosene system, after two-phase separation, a vanadium-loaded organic phase is subjected to multi-stage counter-current back extraction by using a 1-5mol / L sulfuric acid solution, and the vanadium-loaded organic phase is subjected to solid-liquid separation. Further reducing SO2 generated by a decarburization process to prepare a vanadyl sulfate solution; and the vanadyl sulfate solution is electrolyzed to obtain a 3.5-valence vanadium electrolyte. According to the method, the recovery rate of vanadium is increased, the prepared vanadium electrolyte is low in impurity content, the technological process is short, emission of waste gas and waste water is reduced, and energy conservation and environment protection are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of processing and manufacturing electrolyte for vanadium flow battery, and specifically relates to a method for preparing high-purity vanadyl sulfate electrolyte mother liquor by using stone coal vanadium ore. Background Art

[0002] All-vanadium ion flow battery is an emerging energy and energy storage technology that is green, environmentally friendly, and can be repeatedly charged and discharged. It has the advantages of being clean, efficient, safe, and having a long life. It has been partially industrially applied in wind energy, photovoltaic power generation, distributed power stations, communication base stations, electric buses, military power storage, solar energy storage, and power station peak regulation. All-vanadium ion flow battery has no solid-state reaction and does not change the structure and morphology of the electrode material. The functional components of the electrolyte of the all-vanadium battery are vanadium cations of various valence states, and the anions paired with them can be acid radicals such as sulfuric acid or hydrochloric acid. The concentration of vanadium in the electrolyte and the amount of electrolyte determine the capacity of the battery. The quality of the vanadium electrolyte has a direct impact on the energy density, battery performance, and cycle life.

[0003] Vanadium resources are widely distributed on the earth, mainly including magmatic vanadium-titanium magnetite and sedimentary vanadium ore. Sedimentary vanadium ore is mainly vanadium-containing stone coal, also known as stone coal vanadium ore. The proven reserves of stone coal in my country are 6.188×10 10 t, its V 2 O 5 The grade is mostly between 0.3% and 1.3%, and the total reserves are V 2 O 5 The calculation is about 1.18×10 8 t, accounting for 87% of the total vanadium reserves in my country's ores, is an important vanadium resource. 3+ and V 4+ Composition, currently vanadium is extracted from stone coal by oxidation to V 5+ Later, leaching and then extraction of vanadium precipitation process, the leaching operation of this process requires oxidation of vanadium to V 5+ , V 5+ Restore to V 4+ After stripping, vanadium precipitation needs to be oxidized to V 5+ The intermediate oxidation-reduction-oxidation causes a large consumption of reagents, and the precipitation of vanadium using ammonia salt or ammonia water easily produces ammonia nitrogen wastewater which is difficult to treat.

[0004] Under the existing technical conditions of all-vanadium liquid flow batteries, in order to ensure the comprehensive performance of the battery, the vanadium concentration in the vanadyl sulfate electrolyte is required to be ≥1.5 mol / L, the sodium, potassium, and chlorine in the electrolyte are required to be less than 100 mg / L, iron, aluminum <50 mg / L, magnesium, calcium <30 mg / L, chromium, nickel, and molybdenum <15 mg / L, silicon, manganese <10 mg / L, and copper, arsenic, lead, gold, etc. are required to be less than 1 mg / L respectively.

[0005] As an important vanadium source in China, carbonaceous slate-type vanadium ore has a metamorphic argillaceous structure, plate-like structure and micro-stratified structure. The metal minerals of the ore are mainly pyrite, containing trace magnetite; the gangue minerals are mainly carbonaceous, argillaceous, quartz, calcite, etc., and form altered minerals such as sericite and chalcanthite. The main chemical components of the ore are SiO 2 , C, Al 2 O 3 , Fe 2 O 3 , FeS 2 etc., the total amount is greater than 80%, of which SiO 2 The general content is 40% to 80%, Al 2 O 3 The content is 6% to 10%, Fe 2 O 3 The content is 6% to 10%, and the C content is 3% to 22%. The acidic vanadium-rich solution obtained by direct acid leaching is mainly V (IV), accompanied by the leaching and enrichment of impurities such as iron and aluminum. It has the characteristics of high vanadium and high impurities, which brings the difficulty of deep impurity removal and enrichment for the subsequent preparation of vanadium electrolyte. At present, the leaching, stripping or resin analysis liquid (vanadium content 1.0 to 10.0 g / L) in the process of vanadium extraction from vanadium-containing stone coal, the mass ratio of vanadyl sulfate to total metal impurities (VOSO 4 / ∑Me)<80, the vanadyl sulfate solution cannot meet the technical requirements of vanadium battery electrolyte.

[0006] In view of the characteristics of the structural composition of carbonaceous slate-type vanadium ore coal, vanadium in carbonaceous slate-type vanadium ore coal is extracted to prepare electrolyte under the premise of saving costs and protecting the environment as much as possible. This patent proposes a preparation method of vanadium ore through decarbonization-roasting-leaching-extraction-strip extraction-electrolyte mother liquor. Summary of the invention

[0007] The purpose of the present invention is to provide a method for extracting vanadium from stone coal and preparing vanadium electrolyte with low cost, environmental friendliness, wide pH range for extraction, simple process and strong raw material adaptability for carbonaceous slate-type stone coal vanadium ore. The characteristics of carbonaceous slate-type stone coal vanadium ore are Pu-type hardness f=4-6, and the metal minerals of the ore are mainly pyrite, containing trace magnetite. The main chemical components of the ore are SiO 2 , C, Al 2 O 3 , Fe 2 O 3 , FeS 2 etc., among which SiO 2 The general content is 40% to 80%, Al 2 O 3 The content is 6% to 10%, Fe 2 O 3The content of V is 6% to 10%, and the content of C is 3% to 22%. The main mineral components of the ore are quartz, carbonaceous, and sericite. 2 O 5 The average grade is 0.75%.

[0008] In order to achieve the above object, the specific technical solution adopted by the present invention is:

[0009] Step 1: Pretreatment of ore, decarburization: In order to facilitate the leaching of vanadium, the ore is decarburized and burned in a non-oxidizing atmosphere, which also promotes the conversion of V(III) to V(IV). The generated SO 2 (Equations 1 and 2) are used as reducing agents for preparing vanadium electrolyte by electrolysis. V(IV) is converted into V(V) by further blank roasting at 800-900°C for 3h.

[0010] 2As 2 S 3 +9O 2 =2As 2 O 3 +6SO 2 ↑ (1)

[0011] 2MeS+3O 2 =2MeO+2SO 2 ↑ (2)

[0012] (Me is a metal element such as Fe, Ca, Mg, Cu, Ni, Zn, etc.)

[0013] Step 2, leaching: the liquid-to-solid ratio is 2:1, 10% sulfuric acid + 0.1% sodium chlorate is added, the leaching time is about 2 hours, and continuous leaching is carried out at room temperature. The purpose is to transfer the vanadium in the ore into the aqueous solution to separate the vanadium from most of the gangue impurities. Such a leachate will not form silica gel and agglomerate. Sodium chlorate plays an oxidizing role, and the tetravalent vanadium is oxidized to pentavalent vanadium as the extraction stock solution.

[0014] Particularly, the vanadium leaching rate in step (2) is greater than 85%, the pH value of the leaching mother liquor obtained after filtration is 1.8-2.6, and it contains 1.0-5 g / L of vanadium, 2.0-4 g / L of Al, 0.5-5 g / L of Fe, 0.5-1.5 g / L of Si, and other metal impurities are less than 1.0 g / L.

[0015] Step 3, extraction: the pH value of the extraction solution is 1.8-2.6, the organic phase composition is 10% N235 / N1923+5% TBP+85% sulfonated kerosene, O / A=1-5:5, extraction is carried out at 25-50°C for 4-20 minutes, and the aqueous phase is subjected to three to five levels of countercurrent extraction to obtain a loaded organic phase and a raffinate.

[0016] Step 4: Stripping: Stripping agent H2 SO 4 The solution concentration is 1-5 mol / L, the stripping phase ratio O / A=5:1-5, the stripping time is 10-20 min, and the loaded organic phase is subjected to one to four stages of countercurrent stripping at room temperature to obtain an unloaded organic phase and stripping water.

[0017] Step 5: electrolyze the stripping solution from step 4 and pass it through decarbonization combustion to produce SO 2 After reduction and electrolysis for a set time, a 3.5-valent vanadium electrolyte is obtained.

[0018] The beneficial effects of the technical solution of the present invention are as follows: the vanadium leaching rate in steps 1 and 2 is high, which can reach 85-98%, and the vanadium content is 1.0-5.0 g / L, and other impurities are small, and the concentration of other metals is 0.5-10 g / L; the extractant added in step 3 can make the vanadium extraction rate 97-99%, and the impurity metal cations are not extracted; step 4 uses sulfuric acid to extract back to obtain a high-purity vanadium-containing sulfuric acid solution, and the vanadium stripping rate is 93-99%; step 5 passes the flue gas (containing SO 2 ) and electrolyze to obtain a 3.5-valent vanadium electrolyte, which reduces the emission of waste gas during the vanadium extraction process of carbonaceous stone coal vanadium ore; the vanadium-containing electrolyte prepared by the method of the present invention meets the national standard (GB / T 37204-2018) for first-grade all-vanadium liquid flow battery electrolyte, wherein the total vanadium concentration is above 1.5 mol / L, the aluminum concentration is less than 50 mg / L, the iron concentration is less than 30 mg / L, the Si concentration is less than 10 mg / L, and the concentrations of magnesium, manganese, molybdenum, nickel, etc. are below 1 mg / L. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 : Process diagram for preparing vanadium electrolyte mother liquor from carbonaceous slate-type vanadium ore coal through decarbonization - roasting - leaching - extraction - stripping - reduction electrolysis - vanadium electrolyte mother liquor. DETAILED DESCRIPTION

[0020] The present invention is specifically described for a stone coal vanadium extraction electrolyte and a preparation method thereof, as well as a redox battery comprising the electrolyte. Those skilled in the art should understand that the following specific description is for the purpose of facilitating the understanding of the present invention. The technical solution of the present invention is not limited to the specific implementation methods listed below, but also includes any combination of the specific methods.

[0021] Example 1

[0022] A vanadium-extracting electrolyte for stone coal and a preparation method thereof. The specific steps of the preparation method described in this embodiment are:

[0023] The ore was decarbonized and burned in a non-oxidizing atmosphere, and further blank roasted at 800°C for 3 hours. 10% sulfuric acid + 0.1% sodium chlorate were added, the liquid-to-solid ratio was 2:1, the pH value of the leaching mother liquor was 2.3, V was 2.32 g / L, Al was 3.62 g / L, Si was 1.42 g / L, Fe was 0.89 g / L, Mg was 0.92 g / L, K was 1.26 g / L, Na was 0.90 g / L, Ca was 0.47 g / L, Mn was 0.03 g / L, and As was 0.03 g / L.

[0024] 10% N235 + 5% TBP + 85% sulfonated kerosene was used as the extractant, O / A = 1:3, and the extraction was carried out at 25°C for 4 minutes. The aqueous phase was subjected to three-stage countercurrent extraction to obtain the loaded organic phase and the raffinate. The vanadium extraction rate was 98.65%. 2 SO 4 The stripping agent was used for stripping, the stripping phase ratio was O / A=2:1, the stripping time was 15min, and the loaded organic phase was subjected to secondary countercurrent stripping at room temperature to obtain an empty organic phase and a stripping water phase. The stripping rate of vanadium was 96.23%.

[0025] The stripping water phase is introduced into the electrolytic cell for electrolysis, and the flue gas (containing SO 2 ), and then reduction electrolysis is performed for a certain period of time to obtain a 3.5-valent vanadium electrolyte.

[0026] The vanadium electrolyte prepared in this embodiment is measured by ICP: V concentration is about 1.6 mol / L; Al is 26 mg / L; Si is 5.3 mg / L; Fe is 30 mg / L; Mg is 3.2 mg / L; K is 7.2 mg / L; Na is 8.9 mg / L; Ca is 4.7 mg / L; other metal ions are less than 1 mg / L. The composition meets the requirements of the first-grade product of all-vanadium redox flow battery electrolyte in the national standard (GB / T-37204-2018).

[0027] The vanadium electrolyte in this embodiment is 40 mA / cm 2 The battery was tested for 20 cycles of charge and discharge at the current density: the average coulomb efficiency was 90.58%; the voltage efficiency was 91.33%; and the energy efficiency was 86.37%.

[0028] Example 2

[0029] A vanadium-extracting electrolyte for stone coal and a preparation method thereof. The specific steps of the preparation method described in this embodiment are:

[0030] The ore was decarbonized and burned in a non-oxidizing atmosphere, and further blank roasted at 900°C for 3 hours. 10% sulfuric acid + 0.1% sodium chlorate were added, the liquid-to-solid ratio was 2:1, the pH value of the leaching mother liquor was 1.8, V was 4.89 g / L, Al was 7.27 g / L, Si was 2.66 g / L, Fe was 1.36 g / L, Mg was 1.24 g / L, K was 2.03 g / L, Na was 1.31 g / L, Ca was 1.67 g / L, Mn was 0.05 g / L, and As was 0.05 g / L.

[0031] 10% N1923 + 5% TBP + 85% sulfonated kerosene was used as the extractant, O / A = 1:1, and the extraction was carried out at 40°C for 10 minutes. The aqueous phase was subjected to five-stage countercurrent extraction to obtain the loaded organic phase and the raffinate. The vanadium extraction rate was 99.35%. 2 SO 4 The stripping agent was used for stripping, the stripping phase ratio was O / A=5:1, the stripping time was 20min, and the loaded organic phase was subjected to secondary countercurrent stripping at room temperature to obtain an empty organic phase and a stripping water phase. The stripping rate of vanadium was 99.03%.

[0032] The stripping water phase is introduced into the electrolytic cell for electrolysis, and the flue gas (containing SO 2 ), and then reduction electrolysis is performed for a certain period of time to obtain a 3.5-valent vanadium electrolyte.

[0033] The vanadium electrolyte prepared in this embodiment is measured by ICP: V concentration is about 2.3 mol / L; Al is 32 mg / L; Si is 3.8 mg / L; Fe is 17 mg / L; Mg is 1.2 mg / L; K is 1.8 mg / L; Na is 0.7 mg / L; Ca is 1.3 mg / L; other metal ions are less than 1 mg / L. The composition meets the requirements of the first-grade product of all-vanadium redox flow battery electrolyte in the national standard (GB / T-37204-2018).

[0034] The vanadium electrolyte in this embodiment is 40 mA / cm 2 The battery was charged and discharged for 20 cycles at the current density: the average coulomb efficiency was 93.17%; the voltage efficiency was 91.94%; and the energy efficiency was 87.85%.

[0035] Example 3

[0036] A vanadium-extracting electrolyte for stone coal and a preparation method thereof. The specific steps of the preparation method described in this embodiment are:

[0037] The ore was decarbonized and burned in a non-oxidizing atmosphere, and then blank roasted at 860°C for 3 hours. 10% sulfuric acid + 0.1% sodium chlorate was added, the liquid-to-solid ratio was 2:1, the pH value of the leaching mother liquor was 2.6, V was 1.35 g / L, Al was 2.97 g / L, Si was 1.03 g / L, Fe was 0.78 g / L, Mg was 0.61 g / L, K was 0.92 g / L, Na was 0.65 g / L, Ca was 0.47 g / L, Mn was 0.01 g / L, and As was 0.01 g / L. 。

[0038] 10% N235 + 5% TBP + 85% sulfonated kerosene was used as the extractant, O / A = 1:5, and the extraction was carried out at 50°C for 4 minutes. The aqueous phase was subjected to three-stage countercurrent extraction to obtain the loaded organic phase and the raffinate. The vanadium extraction rate was 95.63%. 2 SO 4 The stripping agent was used for stripping, the stripping phase ratio O / A=1:1, the stripping time was 15min, and the loaded organic phase was subjected to four-stage countercurrent stripping at room temperature to obtain an empty organic phase and a stripping water phase. The stripping rate of vanadium was 99.35%.

[0039] The stripping water phase is introduced into the electrolytic cell for electrolysis, and the flue gas (containing SO 2 ), and then reduction electrolysis is performed for a certain period of time to obtain a 3.5-valent vanadium electrolyte.

[0040] The vanadium electrolyte prepared in this embodiment is measured by ICP: V concentration is about 2.1 mol / L; Al is 32 mg / L; Si is 4.8 mg / L; Fe is 23 mg / L; Mg is 3.8 mg / L; K is 5.8 mg / L; Na is 8.3 mg / L; Ca is 3.9 mg / L; other metal ions are less than 1 mg / L. The composition meets the requirements of the first-grade product of all-vanadium redox flow battery electrolyte in the national standard (GB / T-37204-2018).

[0041] The vanadium electrolyte in this embodiment is 40 mA / cm 2 The battery was tested for 20 cycles of charge and discharge at the current density: the average coulomb efficiency was 89.24%; the voltage efficiency was 91.34%; and the energy efficiency was 85.55%.

[0042] Example 4

[0043] A vanadium-extracting electrolyte for stone coal and a preparation method thereof. The specific steps of the preparation method described in this embodiment are:

[0044] The ore was decarbonized and burned in a non-oxidizing atmosphere, and further blank roasted at 880°C for 3 hours. 10% sulfuric acid + 0.1% sodium chlorate were added, the liquid-to-solid ratio was 2:1, the pH value of the leaching mother liquor was 2.0, V was 3.43 g / L, Al was 3.99 g / L, Si was 1.78 g / L, Fe was 2.08 g / L, Mg was 0.92 g / L, K was 1.26 g / L, Na was 1.34 g / L, Ca was 1.58 g / L, Mn was 0.05 g / L, and As was 0.03 g / L.

[0045] 10% N235 + 5% TBP + 85% sulfonated kerosene was used as the extractant, O / A = 1:2, and the extraction was carried out at 25°C for 10 minutes. The aqueous phase was subjected to four-stage countercurrent extraction to obtain the loaded organic phase and the raffinate. The vanadium extraction rate was 99.05%. 2 SO 4 The stripping agent was used for stripping, the stripping phase ratio O / A=1:1, the stripping time was 20min, and the loaded organic phase was subjected to four-stage countercurrent stripping at room temperature to obtain an empty organic phase and a stripping water phase. The stripping rate of vanadium was 99.23%.

[0046] The stripping water phase is introduced into the electrolytic cell for electrolysis, and the flue gas (containing SO 2 ), and then reduction electrolysis is performed for a certain period of time to obtain a 3.5-valent vanadium electrolyte.

[0047] The vanadium electrolyte prepared in this embodiment is measured by ICP: V concentration is about 1.8 mol / L; Al is 22 mg / L; Si is 3.3 mg / L; Fe is 23 mg / L; Mg is 1.2 mg / L; K is 4.7 mg / L; Na is 8.2 mg / L; Ca is 3.6 mg / L; other metal ions are less than 1 mg / L. The composition meets the requirements of the first-grade product of all-vanadium redox flow battery electrolyte in the national standard (GB / T-37204-2018).

[0048] The vanadium electrolyte in this embodiment is 40 mA / cm 2 The battery was tested for 20 cycles of charge and discharge at the current density: the average coulomb efficiency was 92.24%; the voltage efficiency was 93.57%; and the energy efficiency was 87.60%.

[0049] Example 5

[0050] A vanadium-extracting electrolyte for stone coal and a preparation method thereof. The specific steps of the preparation method described in this embodiment are:

[0051] The ore was decarbonized and burned in a non-oxidizing atmosphere, and further blank roasted at 850°C for 3 hours. 10% sulfuric acid + 0.1% sodium chlorate were added, the liquid-to-solid ratio was 2:1, the pH value of the leaching mother liquor was 2.0, V was 2.47 g / L, Al was 3.93 g / L, Si was 1.46 g / L, Fe was 1.08 g / L, Mg was 1.21 g / L, K was 1.39 g / L, Na was 0.88 g / L, Ca was 0.63 g / L, Mn was 0.03 g / L, and As was 0.03 g / L.

[0052] 10% N1923 + 5% TBP + 85% sulfonated kerosene was used as the extractant, O / A = 1:2, and the extraction was carried out at 35°C for 4 minutes. The aqueous phase was subjected to three-stage countercurrent extraction to obtain the loaded organic phase and the raffinate. The vanadium extraction rate was 99.25%. 2 SO 4 The stripping agent was used for stripping, the stripping phase ratio was O / A=4:1, the stripping time was 10 min, and the loaded organic phase was subjected to primary countercurrent stripping at room temperature to obtain an empty organic phase and a stripping water phase. The stripping rate of vanadium was 94.02%.

[0053] The stripping water phase is introduced into the electrolytic cell for electrolysis, and the flue gas (containing SO 2 ), and then reduction electrolysis is performed for a certain period of time to obtain a 3.5-valent vanadium electrolyte.

[0054] The vanadium electrolyte prepared in this embodiment is measured by ICP: V concentration is about 1.5 mol / L; Al is 37 mg / L; Si is 5.8 mg / L; Fe is 24 mg / L; Mg is 5.2 mg / L; K is 7.4 mg / L; Na is 9.7 mg / L; Ca is 6.5 mg / L; other metal ions are less than 1 mg / L. The composition meets the requirements of the first-grade product of all-vanadium redox flow battery electrolyte in the national standard (GB / T-37204-2018).

[0055] The vanadium electrolyte in this embodiment is 40 mA / cm 2 The battery was charged and discharged for 20 cycles at the current density: the average coulomb efficiency was 87.93%; the voltage efficiency was 89.44%; and the energy efficiency was 84.03%.

Claims

1. A vanadium-extracted all-vanadium ion flow battery electrolyte and its preparation method and use, characterized in that: A high-purity all-vanadium liquid flow battery electrolyte is obtained from vanadium-containing stone coal ore through decarbonization-roasting-leaching-extraction-strip extraction-reduction electrolysis.

2. The method for preparing an all-vanadium ion flow battery electrolyte according to claim 1, characterized in that: The stone coal used is a carbonaceous slate-type vanadium ore. The main chemical components of the ore are SiO2, C, Al2O3, Fe2O3, FeS2, etc., and their total content is greater than 80%. Among them, the general content of SiO2 is 40% to 80%, the content of Al2O3 is 6% to 10%, the content of Fe2O3 is 6% to 10%, and the content of C is 3% to 22%.

3. The method for preparing an all-vanadium ion flow battery electrolyte according to claim 1, characterized in that: Pretreatment of ore, decarbonization: In order to facilitate the leaching of vanadium, the ore is decarbonized and burned in a non-oxidizing atmosphere, which also promotes the conversion of V(III) to V(IV). The generated SO2 (Equations 1 and 2) is used as a reducing agent for the electrolytic preparation of vanadium electrolyte. Further blank roasting at 800-900℃ for 3h converts V(IV) to V(V).

4. The method for preparing an all-vanadium ion flow battery electrolyte according to claim 1, characterized in that: The liquid-to-solid ratio selected for the leaching process is 2:1, 10% sulfuric acid + 0.1% sodium chlorate are added, the leaching time is about 2 hours, and the leaching is continuous at room temperature. The vanadium leaching rate is controlled to be greater than 85%. The pH value of the leaching mother liquor obtained after filtration is 1.8-2.6, containing 1.0-5g / L vanadium, 2.0-4g / L Al, 0.5-5g / L Fe, 0.5-1.5g / L Si, and other metal impurities are less than 1.0g / L.

5. The method for preparing an all-vanadium ion flow battery electrolyte according to claim 1, characterized in that: The extractant of the extraction process is trioctyl tertiary amine (N235) or dioctyl thiophosphate amide (N1923), the additive is tributyl phosphate (TBP), and the diluent is sulfonated kerosene; the stripping agent of the stripping process is sulfuric acid solution.

6. The method for preparing an all-vanadium ion flow battery electrolyte according to claim 5, characterized in that: In the extraction process, the pH value of the extract is 1.8-2.6, the composition of the organic phase is 10% N235 / N1923+5% TBP+85% sulfonated kerosene, O / A=1-5:5, and the extraction is carried out at 25-50°C for 4-20 minutes. The aqueous phase is subjected to three to five levels of countercurrent extraction to obtain a loaded organic phase and a raffinate.

7. The method for preparing an all-vanadium ion flow battery electrolyte according to claim 5, characterized in that: In the stripping process, the concentration of the stripping agent H2SO4 solution is 1-5 mol / L, the stripping phase ratio is O / A=5:1-5, and the stripping time is 10-20 min. The loaded organic phase is subjected to one to four stages of countercurrent stripping at room temperature to obtain an unloaded organic phase and stripping water.

8. The method for preparing an all-vanadium ion flow battery electrolyte according to claim 1, characterized in that: In the reduction electrolysis step, the reducing agent introduced is the flue gas (containing SO2) produced by decarbonization combustion, and 3.5-valent vanadium electrolyte is produced by electrolysis.

Images