High-purity vanadyl sulfate electrolyte, its preparation and use

Abstract

The application provides a method for preparing high-purity vanadyl sulfate electrolyte based on carbon slate type stone coal vanadium ore. The method is characterized by the following steps: soaking the ash residue obtained by decarburization and power generation of carbon slate type vanadium ore in mixed acid of 10% sulfuric acid and 10% hydrochloric acid, and obtaining leaching solution after solid-liquid separation; reducing the SO2 generated in the decarburization and power generation process to obtain tetravalent vanadium leaching solution with pH ranging from 1.8 to 2.6; using the P204 / P507 / Cyanex272:TBP:sulfonated kerosene system for multistage countercurrent extraction of the leaching solution; after two-phase separation, using 1-5 mol / L sulfuric acid solution for multistage countercurrent stripping of the vanadium-loaded organic phase to obtain high-purity vanadyl sulfate solution; and obtaining 3.5-valent vanadium electrolyte by electrolysis of the vanadyl sulfate solution. The application can achieve vanadium recovery rate of more than 90%, the prepared vanadium electrolyte has low impurity content, the process flow is short, and the emission of waste gas and waste water is reduced, thereby achieving energy saving and environmental protection.

Description

Technical Field

[0001] This invention belongs to the field of vanadium electrolyte processing and manufacturing technology, specifically relating to a method for preparing high-purity vanadium oxysulfate electrolyte using vanadium shale ore. Background Technology

[0002] Vanadium-ion flow batteries possess advantages such as cleanliness, high efficiency, safety, and long lifespan, and have already found some industrial applications in wind power, photovoltaic power generation, distributed power stations, communication base stations, electric buses, military energy storage, solar energy storage, and power station peak shaving. The concentration of vanadium in the electrolyte and the amount of electrolyte determine the battery capacity, while the quality of the vanadium electrolyte directly affects energy density, battery performance, and cycle life. Currently, the mainstream process for preparing vanadium electrolytes uses high-purity solid vanadium pentoxide as raw material, reducing V2O5 with chemical reducing agents such as SO2, oxalic acid, or V2O3, or through electrolysis to obtain vanadium oxysulfate. However, high-purity vanadium pentoxide leads to high production costs.

[0003] Vanadium resources are widely distributed across the Earth, mainly including magmatic vanadium-titanium magnetite and sedimentary vanadium deposits. Sedimentary vanadium deposits are primarily vanadium-bearing shale, also known as vanadium shale coal. my country's proven reserves of vanadium shale coal reach 6.188 × 10⁻⁶. 10 Vanadium ore deposits, with V₂O₅ grades mostly between 0.3% and 1.3%, account for 87% of my country's total vanadium reserves in ores, making them an important vanadium resource. Vanadium in shale coal vanadium deposits is primarily composed of V₂O₅. 3+ and V 4+ Composition: Currently, vanadium extraction from coal shale mostly involves oxidation to V. 5+ Subsequently, vanadium is extracted by leaching and then by extraction or by using ion exchange resin. The ammonia salts or ammonia water used for vanadium precipitation can easily generate ammonia nitrogen wastewater pollution.

[0004] Under the current conditions of vanadium redox flow battery technology, in order to ensure the overall performance of the battery, the vanadium concentration in the vanadium oxysulfate electrolyte must be ≥1.5mol / L, and the concentrations of sodium, potassium, and chlorine in the electrolyte must be <100mg / L, iron and aluminum <50mg / L, magnesium and calcium <30mg / L, chromium, nickel, and molybdenum <15mg / L, silicon and manganese <10mg / L, and copper, arsenic, lead, and gold <1mg / L.

[0005] Carbonaceous slate-type vanadium ore, an important vanadium source in China, exhibits a relict argillaceous texture, platy structure, and micro-layered structure. The main metallic mineral in the ore is pyrite, with trace amounts of magnetite; gangue minerals are mainly carbonaceous, argillaceous, quartz, and calcite, forming alteration minerals such as sericite and amphibole. The main chemical components of the ore are SiO2, C, Al2O3, Fe2O3, and FeS2, with a total content greater than 80%. Specifically, SiO2 typically contains 40%–80%, Al2O3 6%–10%, Fe2O3 6%–10%, and C 3%–22%. Direct acid leaching yields acidic vanadium-rich solutions dominated by V(IV), accompanied by the leaching and enrichment of impurities such as iron and aluminum, exhibiting high vanadium and high impurity content. This presents a significant challenge for the subsequent preparation of vanadium electrolytes, requiring deep impurity removal and enrichment. Currently, in the vanadium extraction process from vanadium-containing coal, the leaching, back-extraction, or resin eluent (vanadium content 1.0–10.0 g / L) has a vanadium oxysulfate to total metal impurities mass ratio (VOSO4 / ∑Me) < 80. This vanadium oxysulfate solution cannot meet the technical requirements for vanadium battery electrolytes.

[0006] In view of the structural composition characteristics of carbonaceous slate-type vanadium ore, this patent proposes a method for preparing vanadium electrolyte by extracting vanadium from carbonaceous slate-type vanadium ore through decarbonization power generation, leaching, reduction extraction, back extraction, and vanadium electrolyte mother liquor, while minimizing costs and protecting the environment. Summary of the Invention

[0007] The purpose of this invention is to provide a method for vanadium extraction from carbonaceous slate-type vanadium-bearing shale and the preparation of vanadium electrolyte, characterized by a short process, environmental friendliness, simple technology, low cost, and strong raw material adaptability. Carbonaceous slate-type vanadium-bearing shale is characterized by a Prototype hardness f = 4–6, with pyrite as the main metallic mineral and trace amounts of magnetite. The main chemical components of the ore are SiO2, C, Al2O3, Fe2O3, and FeS2, with SiO2 typically containing 40%–80%, Al2O3 6%–10%, Fe2O3 6%–10%, and C 3%–22%. The main mineral components of the ore consist of quartz, carbonaceous matter, and sericite, with an average V2O5 grade of 0.75%.

[0008] To achieve the above objectives, the specific technical solution adopted by the present invention is as follows:

[0009] Step 1: Ore pretreatment and decarbonization for power generation: To facilitate vanadium leaching, the ore is decarbonized and burned for 3 hours 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 vanadium ore leaching solution. The heat generated during decarbonization is used for power generation, which is then used in subsequent production processes, saving energy.

[0010] 2As2S3+9O2=2As2O3+6SO2↑ (1)

[0011] 2MeS + 3O2 = 2MeO + 2SO2↑ (2)

[0012] (Me represents metallic elements such as Fe, Ca, Mg, Cu, Ni, and Zn)

[0013] Specifically, the equipment used for coal decarbonization power generation is one of the following: tubular furnace, circulating fluidized bed, or fluidized bed furnace.

[0014] Step 2, Leaching: Using the coal ash residue from decarbonization power generation as the solid phase, with a liquid-to-solid ratio of 2:1, add 10% sulfuric acid + 10% hydrochloric acid. The leaching time is about 3 hours. Under normal temperature conditions, continuous leaching is carried out. The purpose is to transfer the vanadium in the ore into the aqueous solution, so as to separate the vanadium from most of the gangue impurities. Such leaching solution will not form silica gel and clump.

[0015] Specifically, in step (2), the vanadium leaching rate is greater than 90%, and the content of vanadium is 1.0-5 g / L, Al is 2.0-6 g / L, Fe is 0.5-5 g / L, Si is 0.5-1.5 g / L, and other metal impurities are less than 1.0 g / L.

[0016] Step 3, Reduction Extraction: The flue gas (containing SO2) generated during the decarbonization power generation in Step 1 is passed into the vanadium-containing leachate from Step 2 to reduce V(V) to V(IV), yielding the original extract with a pH of 1.8–2.6. The organic phase composition of the extractant is 15% P204 (bis(2-ethylhexyl) phosphate) / P507 (2-ethylhexylphosphonic acid mono-2-ethylhexyl ester) / Cyanex272 (bis(2,4,4-trimethylpentyl)phosphonic acid) + 5% TBP + 80% sulfonated kerosene, with an O / A ratio of 1–5:4. Extraction is performed at 25–50°C for 4–10 min, and the aqueous phase is subjected to 5–7 stages of countercurrent extraction to obtain the loaded organic phase and the raffinate.

[0017] Step 4, back-extraction: The concentration of the back-extraction agent H2SO4 solution is 1-5 mol / L, the back-extraction ratio O / A = 3:1-5, and the back-extraction time is 10-20 min. The loaded organic phase is subjected to 3-5 stages of countercurrent back-extraction at room temperature to obtain an empty organic phase and backwater.

[0018] Step 5: Electrolyze the vanadium-containing aqueous solution from step 4, and after electrolysis for a set time, obtain a vanadium electrolyte with 3.5 valence.

[0019] The beneficial effects of adopting the technical solution of this invention are: the overall preparation process is environmentally friendly and energy-saving, and the process is short. Step 1, decarbonization and power generation, makes full use of the thermal energy of the coal shale, and at the same time converts trivalent vanadium into tetravalent vanadium, which is beneficial to leaching; in step 2, adding dilute hydrochloric acid helps vanadium leaching, with a high vanadium leaching rate of 90-98%, containing 1.0-5.0 g / L of vanadium, with few other impurities and a concentration of other metals of 0.5-10 g / L; in step 3, the flue gas (containing SO2) released from the decarbonization of the coal shale vanadium ore is passed into the leaching solution to reduce pentavalent vanadium, reducing the emission of waste gas during the vanadium extraction process of carbonaceous coal vanadium ore; the added extractant can make the vanadium extraction rate 97-99%, while the impurity metal cations are not extracted; in step 4, sulfuric acid is used for back-extraction to obtain a high-purity vanadium-containing sulfuric acid solution, with a vanadium back-extraction rate of 93-99%. The vanadium-containing electrolyte prepared by the method of this invention meets the national standard (GB / T 37204-2018) for Grade I vanadium redox 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. Attached Figure Description

[0020] Figure 1 : Process diagram of the preparation of vanadium electrolyte mother liquor from carbonaceous slate-type vanadium ore coal through decarbonization power generation, leaching, reduction extraction, back extraction, electrolysis, and vanadium electrolyte. Detailed Implementation

[0021] This invention specifically describes a method for preparing vanadium battery electrolyte by vanadium extraction from coal shale, and a redox battery including the electrolyte. Those skilled in the art should understand that the following detailed description is for ease of understanding. The technical solution of this invention is not limited to the specific embodiments listed below, but also includes any combination of the various specific methods.

[0022] Example 1

[0023] A vanadium extraction electrolyte from coal shale and its preparation method. The specific steps of the preparation method described in this embodiment are as follows:

[0024] Carbonaceous slate-type vanadium ore was decarbonized and used for power generation in a fluidized bed furnace under a non-oxidizing atmosphere. Then, the ash residue from the decarbonization power generation of coal shale was used as the leaching ore. 10% sulfuric acid + 10% hydrochloric acid were added, with a liquid-to-solid ratio of 2:1. Flue gas (containing SO2) generated from the decarbonization combustion of vanadium ore was introduced. The pH value of the leaching mother liquor was 2.0, V was 2.62 g / L, Al was 4.62 g / L, Si was 1.48 g / L, Fe was 0.89 g / L, Mg was 0.92 g / L, K was 0.96 g / L, Na was 0.90 g / L, Ca was 0.87 g / L, Mn was 0.03 g / L, and As was 0.03 g / L.

[0025] Using 15% P₂O₄ + 5% TBP + 80% sulfonated kerosene as the extractant, with an O / A ratio of 1:4, extraction was performed at 25°C for 4 min. The aqueous phase was then subjected to 5 stages of countercurrent extraction to obtain the loaded organic phase and raffinate, with a vanadium extraction rate of 97.25%. Further back-extraction was performed using 5 mol / L H₂SO₄ as the back-extraction agent, with an O / A ratio of 3:5 and a back-extraction time of 10 min. The loaded organic phase was then subjected to 5 stages of countercurrent back-extraction at room temperature to obtain the unloaded organic phase and the back-extracted aqueous phase, with a vanadium back-extraction rate of 99.03%.

[0026] The above-mentioned back-extracted aqueous phase is passed into an electrolytic cell for electrolysis, and the reduction electrolysis is carried out for a certain period of time to obtain a vanadium electrolyte with 3,5 valence.

[0027] The vanadium electrolyte prepared in this embodiment was analyzed by ICP: V concentration approximately 2.0 mol / L; Al 21 mg / L; Si 3.3 mg / L; Fe 19 mg / L; Mg 2.2 mg / g / L; K 5.2 mg / L; Na 9.1 mg / L; Ca 4.3 mg / L; other metal ions less than 1 mg / L. The composition meets the requirements for Grade I vanadium redox flow battery electrolytes in the national standard (GB / T-37204-2018).

[0028] In this embodiment, the vanadium electrolyte is used at 40 mA / cm 2 The battery underwent 50-cycle charge-discharge testing at current density, resulting in an average coulombic efficiency of 93.12%, a voltage efficiency of 91.23%, and an energy efficiency of 87.37%.

[0029] Example 2

[0030] A vanadium extraction electrolyte from coal shale and its preparation method. The specific steps of the preparation method described in this embodiment are as follows:

[0031] Carbonaceous slate-type vanadium ore was decarbonized and used for power generation in a fluidized bed furnace under a non-oxidizing atmosphere. Then, the ash residue from the decarbonization power generation of coal shale was used as the leaching ore. 10% sulfuric acid + 10% hydrochloric acid were added, with a liquid-to-solid ratio of 2:1. Flue gas (containing SO2) generated from the decarbonization combustion of vanadium ore was introduced. The pH value of the leaching mother liquor was 1.8, V was 5.02 g / L, Al was 7.97 g / L, Si was 3.66 g / L, Fe was 1.46 g / L, Mg was 1.27 g / L, K was 2.32 g / L, Na was 1.38 g / L, Ca was 2.67 g / L, Mn was 0.05 g / L, and As was 0.05 g / L.

[0032] Using 15% P507 + 5% TBP + 80% sulfonated kerosene as the extractant, with an O / A ratio of 5:4, extraction was performed at 50℃ for 10 min. The aqueous phase was then subjected to 7 stages of countercurrent extraction to obtain the loaded organic phase and raffinate, with a vanadium extraction rate of 99.35%. Further back-extraction was performed using 2 mol / L H2SO4 as the back-extraction agent, with an O / A ratio of 3:1 and a back-extraction time of 20 min. The loaded organic phase was then subjected to 3 stages of countercurrent back-extraction at room temperature to obtain the unloaded organic phase and the back-extracted aqueous phase, with a vanadium back-extraction rate of 98.76%.

[0033] The above-mentioned back-extracted aqueous phase is passed into an electrolytic cell for electrolysis, and the reduction electrolysis is carried out for a certain period of time to obtain a vanadium electrolyte with 3,5 valence.

[0034] The vanadium electrolyte prepared in this embodiment was analyzed by ICP: V concentration approximately 1.7 mol / L; Al 26 mg / L; Si 3.0 mg / L; Fe 19 mg / L; Mg 1.0 mg / L; K 1.5 mg / L; Na 1.1 mg / L; Ca 1.6 mg / L; other metal ions less than 1 mg / L. The composition meets the requirements for Grade I vanadium redox flow battery electrolytes in the national standard (GB / T-37204-2018).

[0035] In this embodiment, the vanadium electrolyte is used at 40 mA / cm 2 The battery underwent 50-cycle charge-discharge testing at current density, resulting in an average coulombic efficiency of 90.46%, a voltage efficiency of 91.23%, and an energy efficiency of 86.07%.

[0036] Example 3

[0037] A vanadium extraction electrolyte from coal shale and its preparation method. The specific steps of the preparation method described in this embodiment are as follows:

[0038] Carbonaceous slate-type vanadium ore was decarbonized and used for power generation in a fluidized bed furnace under a non-oxidizing atmosphere. Then, the ash residue from the decarbonization power generation of coal shale was used as the leaching ore. 10% sulfuric acid + 10% hydrochloric acid were added, with a liquid-to-solid ratio of 2:1. Flue gas (containing SO2) generated from the decarbonization combustion of vanadium ore was introduced. The pH value of the leaching mother liquor was 2.6, V was 1.13 g / L, Al was 2.79 g / L, Si was 1.00 g / L, Fe was 0.98 g / L, Mg was 0.67 g / L, K was 0.90 g / L, Na was 0.75 g / L, Ca was 0.85 g / L, Mn was 0.01 g / L, and As was 0.01 g / L.

[0039] Using 15% Cyanex 272 + 5% TBP + 80% sulfonated kerosene as the extractant, with an O / A ratio of 3:4, extraction was performed at 40℃ for 4 min. The aqueous phase was then subjected to 7 stages of countercurrent extraction to obtain the loaded organic phase and raffinate, with a vanadium extraction rate of 99.43%. Further back-extraction was performed using 3 mol / L H₂SO₄ as the back-extraction agent, with an O / A ratio of 1:1 and a back-extraction time of 15 min. The loaded organic phase was then subjected to 4 stages of countercurrent back-extraction at room temperature to obtain the unloaded organic phase and the back-extracted aqueous phase, with a vanadium back-extraction rate of 99.06%.

[0040] The above-mentioned back-extracted aqueous phase is passed into an electrolytic cell for electrolysis, and the reduction electrolysis is carried out for a certain period of time to obtain a vanadium electrolyte with 3,5 valence.

[0041] The vanadium electrolyte prepared in this embodiment was analyzed by ICP: V concentration approximately 2.1 mol / L; Al 28 mg / L; Si 4.1 mg / L; Fe 20 mg / L; Mg 3.1 mg / L; K 4.5 mg / L; Na 7.1 mg / L; Ca 3.2 mg / L; other metal ions less than 1 mg / L. The composition meets the requirements for Grade I vanadium redox flow battery electrolytes in the national standard (GB / T-37204-2018).

[0042] In this embodiment, the vanadium electrolyte is used at 40 mA / cm 2 The battery underwent 50-cycle charge-discharge testing at current density, resulting in an average coulombic efficiency of 92.24%, a voltage efficiency of 91.67%, and an energy efficiency of 87.65%.

[0043] Example 4

[0044] A vanadium extraction electrolyte from coal shale and its preparation method. The specific steps of the preparation method described in this embodiment are as follows:

[0045] Carbonaceous slate-type vanadium ore was decarbonized and used for power generation in a fluidized bed furnace under a non-oxidizing atmosphere. Then, the ash residue from the decarbonization power generation of coal shale was used as the leaching ore. 10% sulfuric acid + 10% hydrochloric acid were added, with a liquid-to-solid ratio of 2:1. Flue gas (containing SO2) generated from the decarbonization combustion of vanadium ore was introduced. The pH of the leaching mother liquor was 2.0, and the following concentrations were obtained: V 3.62 g / L; Al 3.65 g / L; Si 1.65 g / L; Fe 1.79 g / L; Mg 1.23 g / L; K 1.08 g / L; Na 1.27 g / L; Ca 1.45 g / L; Mn 0.05 g / L; As 0.03 g / L.

[0046] Using 15% P507 + 5% TBP + 80% sulfonated kerosene as the extractant, with an O / A ratio of 1:2, extraction was performed at 25°C for 10 min. The aqueous phase was then subjected to 5 stages of countercurrent extraction to obtain the loaded organic phase and raffinate, with a vanadium extraction rate of 98.85%. Further back-extraction was performed using 4 mol / L H2SO4 as the back-extraction agent, with an O / A ratio of 1:1 and a back-extraction time of 20 min. The loaded organic phase was then subjected to 5 stages of countercurrent back-extraction at room temperature to obtain the unloaded organic phase and the back-extracted aqueous phase, with a vanadium back-extraction rate of 99.15%.

[0047] The above-mentioned back-extracted aqueous phase is passed into an electrolytic cell for electrolysis, and the reduction electrolysis is carried out for a certain period of time to obtain a vanadium electrolyte with 3,5 valence.

[0048] The vanadium electrolyte prepared in this embodiment was analyzed by ICP: V concentration approximately 1.8 mol / L; Al 21 mg / L; Si 2.8 mg / L; Fe 16 mg / L; Mg 1.3 mg / L; K 4.2 mg / L; Na 7.8 mg / L; Ca 3.1 mg / L; other metal ions less than 1 mg / L. The composition meets the requirements for Grade I vanadium redox flow battery electrolytes in the national standard (GB / T-37204-2018).

[0049] In this embodiment, the vanadium electrolyte is used at 40 mA / cm 2 The battery underwent 40-cycle charge-discharge testing at current density, resulting in an average coulombic efficiency of 92.35%, a voltage efficiency of 92.57%, and an energy efficiency of 88.27%.

[0050] Example 5

[0051] A vanadium extraction electrolyte from coal shale and its preparation method. The specific steps of the preparation method described in this embodiment are as follows:

[0052] Carbonaceous slate-type vanadium ore was decarbonized and used for power generation in a fluidized bed furnace under a non-oxidizing atmosphere. Then, the ash residue from the decarbonization power generation of coal shale was used as the leaching ore. 10% sulfuric acid + 10% hydrochloric acid were added, with a liquid-to-solid ratio of 2:1. Flue gas (containing SO2) generated from the decarbonization combustion of vanadium ore was introduced. The pH of the leaching mother liquor was 2.0, and the following concentrations were obtained: V 1.95 g / L; Al 4.73 g / L; Si 1.86 g / L; Fe 1.28 g / L; Mg 1.07 g / L; K 1.24 g / L; Na 0.84 g / L; Ca 0.57 g / L; Mn 0.03 g / L; As 0.03 g / L.

[0053] Using 15% P₂O₄ + 5% TBP + 80% sulfonated kerosene as the extractant, with an O / A ratio of 1:2, extraction was performed at 35°C for 4 min. The aqueous phase was then subjected to 7 stages of countercurrent extraction to obtain the loaded organic phase and raffinate, with a vanadium extraction rate of 99.45%. Further back-extraction was performed using 1 mol / L H₂SO₄ as the back-extraction agent, with an O / A ratio of 3:4 and a back-extraction time of 10 min. The loaded organic phase was then subjected to 3 stages of countercurrent back-extraction at room temperature to obtain the unloaded organic phase and the back-extracted aqueous phase, with a vanadium back-extraction rate of 97.65%.

[0054] The above-mentioned back-extracted aqueous phase is passed into an electrolytic cell for electrolysis, and the reduction electrolysis is carried out for a certain period of time to obtain a vanadium electrolyte with 3,5 valence.

[0055] The vanadium electrolyte prepared in this embodiment was analyzed by ICP: V concentration approximately 1.9 mol / L; Al 30 mg / L; Si 5.0 mg / L; Fe 19 mg / L; Mg 3.4 mg / L; K 3.6 mg / L; Na 9.0 mg / L; Ca 5.3 mg / L; other metal ions less than 1 mg / L. The composition meets the requirements for Grade I vanadium redox flow battery electrolytes in the national standard (GB / T-37204-2018).

[0056] In this embodiment, the vanadium electrolyte is used at 40 mA / cm 2 The battery underwent 50-cycle charge-discharge testing at current density, resulting in an average coulombic efficiency of 90.78%, a voltage efficiency of 89.85%, and an energy efficiency of 85.93%.

Claims

1. A process for the preparation of vanadyl sulfate electrolyte, characterized in that: The high-purity vanadyl sulfate electrolyte is obtained by decarburization power generation-leaching-reduction extraction-back extraction-electrolysis of carbonaceous slate type stone coal vanadium ore; specifically, the carbonaceous slate type stone coal vanadium ore is decarburized and combusted under a non-oxidizing atmosphere while the high-carbon stone coal heat energy is fully utilized, which also promotes the conversion of V(III) into V(IV) and facilitates the leaching of vanadium; the generated SO2 is used to reduce V(V) into V(IV); the ash obtained by decarburization power generation of the carbonaceous slate type stone coal vanadium ore is soaked in a mixed acid of 10% sulfuric acid and 10% hydrochloric acid as a leaching liquid, and the leaching liquid obtained after solid-liquid separation has a vanadium leaching rate of greater than 90%; the leaching liquid is reduced by SO2 generated in the decarburization power generation process to obtain a tetravalent vanadium leaching liquid with a pH ranging from 1.8 to 2.6; in the extraction process, the organic phase of the extractant is composed of 5% tributyl phosphate + 80% sulfonated kerosene + 15% bis(2-ethylhexyl) phosphate or 15% 2-ethylhexyl phosphonic acid mono 2-ethylhexyl ester or 15% bis(2,4,4-trimethylpentyl) phosphonic acid; the tetravalent vanadium leaching liquid is extracted by the extractant in multiple stages in countercurrent; after two-phase separation, the vanadium-loaded organic phase is subjected to multiple-stage countercurrent back extraction with 1-5 mol / L sulfuric acid solution to obtain a vanadium-containing aqueous solution; and the vanadium-containing aqueous solution is reduced by electrolysis to obtain a 3.5-valent vanadium electrolyte.

2. A process for the preparation of vanadyl sulphate electrolyte as claimed in claim 1, wherein: The main chemical components of the vanadium ore include SiO2, C, Al2O3, Fe2O3, and FeS2, and the total amount of the components is greater than 80%, wherein the content of SiO2 is 40%-80%, the content of Al2O3 is 6%-10%, the content of Fe2O3 is 6%-10%, and the content of C is 3%-22%.

3. The method for preparing a vanadium oxysulfate electrolyte according to claim 1, characterized in that: The liquid-solid ratio of the selected leaching liquid to the stone coal ash in the leaching process is 2:1, and the leaching time is about 3 h under normal temperature conditions, and the leaching is continuous.

4. The method for preparing vanadyl sulfate electrolyte according to claim 1, characterized in that: The tetravalent vanadium leaching liquid contains vanadium at 1.0-5 g / L, Al at 2.0-4 g / L, Fe at 0.5-5 g / L, Si at 0.5-1.5 g / L, and other metal impurities less than 1.0 g / L.

5. The method for preparing a vanadium oxysulfate electrolyte according to claim 1, characterized in that: In the extraction process, O / A = 1-5:4, the extraction is performed at 25-50°C for 4-10 min, the water phase is subjected to 5-7 stages of countercurrent extraction to obtain the vanadium-loaded organic phase and the raffinate.

6. The method for preparing a vanadium oxysulfate electrolyte according to claim 1, characterized in that: In the back extraction process, the back extraction phase ratio O / A = 3:1-5, the back extraction time is 10-20 min, the vanadium-loaded organic phase is subjected to 3-5 stages of countercurrent back extraction at room temperature to obtain the empty organic phase and the vanadium-containing aqueous solution obtained by back extraction.

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