A method for preparing VOSO4 electrolyte by gas-enhanced reduction back-extraction

Abstract

This invention provides a method for preparing VOSO4 electrolyte by gas-enhanced reduction back-extraction, comprising the following steps: adding an extraction inhibitor to an acidic vanadium-containing solution and stirring to obtain a vanadium-containing solution, wherein the extraction inhibitor is phosphoric acid and / or a phosphoric acid compound; adjusting the pH of the solution to 0.5–3.0 with sulfuric acid, mixing with an organic phase for extraction, and separating the extract to obtain a vanadium-loaded organic phase; washing the vanadium-loaded organic phase with dilute sulfuric acid; mixing a back-extraction agent with the vanadium-loaded organic phase for back-extraction, while simultaneously introducing gas to enhance the back-extraction process, to obtain an empty organic phase and a vanadium electrolyte; adjusting the vanadium back-extraction solution through electrolysis in a fuel cell stack to obtain a vanadium electrolyte with a valence state conforming to the standard. This invention provides a novel gas-enhanced reduction process for directly preparing vanadium oxysulfate electrolyte, which has the advantages of simple process, easy operation, low cost, and environmental friendliness.

Description

Technical Field

[0001] This invention relates to vanadium electrolyte energy storage technology for all-vanadium redox flow batteries, and more particularly to a method for preparing VOSO4 electrolyte by gas-enhanced reduction back-extraction. Background Technology

[0002] Vanadium redox flow batteries, with their high energy conversion efficiency, long service life, adjustable capacity, safety, and environmental friendliness, can effectively solve the intermittency and instability problems of renewable energy sources, improve the stability and reliability of power systems, and have become the preferred technology for large-scale energy storage such as wind and solar power and peak shaving and valley filling. Furthermore, vanadium redox flow batteries have broad application prospects in emergency power supplies, municipal transportation, military energy storage, and communication base stations.

[0003] Compared to other chemical batteries, the vanadium redox flow battery (VanadiumRFB) is a redox flow battery based on the reversible conversion of vanadium ions between different oxidation states. Its active material, vanadium, is in the form of V... 2+ (II) and V 3+ (III), V 4+ (IV) and V 5+ Vanadium redox flow batteries exist in four forms, including (V), and utilize the reversible changes of vanadium ions between different oxidation states to store and release energy. Furthermore, the positive and negative electrode active materials of the vanadium redox flow battery are stored in two separate tanks. During charging and discharging, an external pump drives the electrolyte to flow through the positive and negative electrodes respectively, achieving separation of charging (energy storage) and discharging (energy release). This allows for independent optimization and control of the battery's energy density and power density, and provides good scalability. The most crucial component is the vanadium oxysulfate electrolyte; therefore, the discharge performance, discharge efficiency, and energy efficiency of the vanadium redox flow battery system all depend on the composition and performance of the vanadium electrolyte. Currently, the main methods for preparing the electrolyte for vanadium redox flow batteries are physical dissolution, chemical reduction, and extraction electrolysis.

[0004] The physical dissolution method involves preparing high-purity ammonium metavanadate from vanadium-containing raw materials, then reducing and roasting the ammonium metavanadate to V₂O₄ and V₂O₃ in a rotary kiln. Finally, V₂O₄ and V₂O₃ are dissolved sequentially in sulfuric acid solution in a specific ratio, and after subsequent adjustments, a vanadium energy storage medium meeting the standards is obtained. This method has the advantages of mature technology and high product stability, but the process is lengthy, cumbersome, and generates large amounts of ammonia nitrogen wastewater, resulting in high energy consumption and high costs. The chemical reduction method uses low-valent sulfur, oxalic acid, or organic carboxylic acids and alcohols as reducing agents to reduce the high-valent vanadium in V₂O₅ or vanadate prepared from vanadium-containing raw materials to trivalent or tetravalent vanadium under high-temperature conditions to prepare vanadium energy storage media. Because this method introduces organic matter, the final vanadium electrolyte has poor stability, is prone to crystallization and precipitation, and has a narrow temperature applicability.

[0005] The extraction electrolysis method generally uses pentavalent vanadium purified solution as raw material. The process flow varies depending on the extractant. Using phosphate ester cationic extractants such as P507 and P204, the process involves obtaining a qualified pentavalent vanadium solution, adjusting the pH to 2.0–3.0 with sulfuric acid, then adding a reducing agent to reduce it to tetravalent vanadium, followed by extraction enrichment, sulfuric acid back-extraction to obtain vanadium oxysulfate solution, and finally electrolysis to prepare vanadium electrolyte. This process suffers from high reducing agent consumption, low utilization rate, and the inability to recycle the raffinate wastewater generated during extraction. Conversely, using organic amine anionic extractants such as N235 and N1923, the process involves obtaining a qualified pentavalent vanadium solution, adjusting the pH to 1.0–2.0 with sulfuric acid, then extraction enrichment, sodium carbonate back-extraction to obtain sodium vanadate solution, adding ammonia or ammonium sulfate to prepare ammonium metavanadate solid, followed by solid calcination, reduction, and dissolution to prepare vanadium oxysulfate solution, and finally electrolysis to prepare vanadium electrolyte. Although the leaching wastewater can be recycled in this process, it generates ammonia nitrogen wastewater, and has disadvantages such as solid-liquid phase change, large acid and alkali consumption, cumbersome operation, long process flow, and high cost. Summary of the Invention

[0006] The purpose of this invention is to address the above-mentioned problems by proposing a gas-enhanced reduction back-extraction method for preparing VOSO4 electrolyte. This method provides a novel process for the direct preparation of vanadium oxysulfate electrolyte by gas-enhanced reduction, which not only solves the problem that existing processes cannot use high-concentration acid back-extraction with organic amine extractants to prepare VOSO4, but also has the advantages of simple process, easy operation, low cost, and environmental friendliness.

[0007] It should be noted that, in this invention, unless otherwise specified, the specific meaning of "comprising" in relation to composition and description includes both open-ended meanings such as "comprising," "including," etc., and closed-ended meanings such as "composed of," "consisting of," etc., and similar meanings.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is: a method for preparing VOSO4 electrolyte by gas-enhanced reduction back-extraction, comprising the following steps:

[0009] Step 1: Add an extraction inhibitor to an acidic vanadium-containing solution and stir to obtain a vanadium-containing solution. The extraction inhibitor is phosphoric acid and / or a phosphoric acid compound.

[0010] Step 2: Extraction. The pH of the vanadium-containing solution was adjusted to 0.5–3.0 using sulfuric acid. After mixing with the organic phase and extracting, the solution was separated to obtain the vanadium-loaded organic phase.

[0011] Step 3: Washing. Use dilute sulfuric acid to wash the vanadium-loaded organic phase to remove easily entrained metallic impurities such as Na, K, Ca, and Mn.

[0012] Step 4: Back-extraction. The back-extraction agent is mixed with the vanadium-loaded organic phase for back-extraction, and gas is introduced at the same time to enhance the back-extraction process, resulting in an empty organic phase and vanadium back-extraction solution.

[0013] Step 5: After adjusting the vanadium back-extraction solution, the valence state is adjusted by electrolysis of the battery stack (the vanadium valence state is adjusted to 3.5 by electrolysis of the battery stack) to obtain a vanadium electrolyte with a valence state that meets the standard.

[0014] Further, the acidic vanadium-containing solution in step 1 is obtained by acid leaching of vanadium slag from vanadium-titanium magnetite tailings or vanadium slag after calcification and roasting in shale mines using sulfuric acid. Before adding the extraction inhibitor, the acidic vanadium-containing solution in step 1 undergoes impurity removal. This impurity removal includes, but is not limited to, oxidizing manganese from divalent to trivalent manganese by adding a strong oxidizing agent (e.g., potassium permanganate). The trivalent manganese ions then undergo a disproportionation reaction, becoming MnO2 precipitate, which is then removed by filtration.

[0015] Furthermore, the pH value of the acidic vanadium-containing solution in step 1 is 1.0 to 3.0, preferably 2.0 to 3.0.

[0016] Furthermore, the vanadium concentration (calculated as V2O5) in the acidic vanadium-containing solution described in step 1 is 5 g / L to 55 g / L.

[0017] Furthermore, the iron concentration in the acidic vanadium-containing solution described in step 1 is 0.05 g / L to 0.5 g / L.

[0018] Furthermore, the aluminum concentration in the acidic vanadium-containing solution described in step 1 is 0.1 g / L to 3 g / L.

[0019] Furthermore, the chromium concentration in the acidic vanadium-containing solution described in step 1 is 0.1 g / L to 1 g / L.

[0020] Furthermore, the silicon concentration in the acidic vanadium-containing solution described in step 1 is 0.1 g to 2 g / L.

[0021] Furthermore, the manganese concentration in the acidic vanadium-containing solution described in step 1 is 0.1 g to 3 g / L.

[0022] Furthermore, the zinc concentration in the acidic vanadium-containing solution described in step 1 is 0.1 g / L to 2 g / L.

[0023] Furthermore, the titanium concentration in the acidic vanadium-containing solution described in step 1 is 0.05 g / L to 0.5 g / L.

[0024] Further, the extraction inhibitor mentioned in step 1 is one or more selected from phosphoric acid, trisodium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, ammonium phosphate, diammonium hydrogen phosphate, and ammonium dihydrogen phosphate, and the extraction inhibitor can release phosphate ions. Phosphoric acid is preferred as the extraction inhibitor because when phosphoric acid is used as the extraction inhibitor, impurities such as sodium and ammonium are not introduced into the solution.

[0025] The extraction inhibitor described in this invention has two functions: first, it can inhibit the co-extraction process of three metal impurities, iron, chromium, and titanium, during the extraction process; second, it can improve the stability of vanadium-containing solutions when pH ≤ 2.0.

[0026] Furthermore, the amount of the extraction inhibitor added is 0.02 mol / L to 0.05 mol / L (acidic vanadium-containing solution) based on the molar amount of phosphorus.

[0027] Furthermore, the stirring speed described in step 1 is 200 rpm to 500 rpm.

[0028] Furthermore, the stirring reaction (extraction inhibitor reaction) in step 1 takes 0.5 h to 2.0 h, followed by standing for 4 h to 20 h. The reaction is carried out at room temperature without the need for an external heat source.

[0029] a. When the reaction time of the extraction inhibitor is 4h to 6h, the subsequent extraction process will affect Fe. 3+ The co-extraction showed the best inhibitory effect;

[0030] b. When the reaction time of the extraction inhibitor is 4h to 16h, the subsequent extraction process for Cr... 3+ The co-extraction of [a specific material] showed the best inhibitory effect;

[0031] c. When the extraction inhibitor reaction time is 6h to 10h, the subsequent extraction process for Ti... 4+ Co-extraction showed the best inhibition.

[0032] Further, the organic phase extracted in step 2 includes an organic extractant, a co-solvent, and an organic diluent, wherein the volume percentage of the organic extractant is 1%–15%, the volume percentage of the co-solvent is 5%–10%, and the volume percentage of the organic diluent is 75%–94%. The organic extractant is an organic amine extractant, including but not limited to trioctylamine (N235); the co-solvent is a polyol, one of tributyl phosphate (TBP), n-octanol, and sec-octanol; and the organic diluent is sulfonated kerosene.

[0033] Furthermore, in step 2, the volume ratio of the extracted organic phase to the vanadium-containing solution is O:A = 0.2 to 5:1.

[0034] Furthermore, in step 2, the extraction stirring speed is 500 rpm to 800 rpm, the stirring temperature is 20℃ to 60℃, and the stirring time is 3 to 15 min.

[0035] Further, in step 2, sulfuric acid is used to adjust the pH of the solution to 0.5 to 3.0, preferably 1.0 to 2.0, wherein the sulfuric acid concentration is concentrated sulfuric acid of 94% to 98%.

[0036] Further, the concentration of dilute sulfuric acid in step 3 is 0.05 mol / L to 0.1 mol / L, and the washing conditions are as follows: the vanadium-loaded organic phase is mixed with dilute sulfuric acid at a volume ratio of O / A = 10 to 20:1, the number of countercurrent washing stages is 1 to 4, the washing temperature is 20℃ to 50℃, and the single-stage washing time is 3 min to 10 min.

[0037] Further, the back-extraction agent in step 4 is V 3+ Concentrations of 0.8 mol / L to 1.2 mol / L, SO4 2- Aqueous solutions with concentrations of 3.8 mol / L to 4.5 mol / L or SO4 2- An aqueous solution with a concentration of 3.5 mol / L to 4.2 mol / L and a sulfurous acid concentration of 0.2 mol / L to 0.6 mol / L. The SO4... 2- The aqueous solution with a concentration of 3.5 mol / L to 4.2 mol / L and a sulfurous acid concentration of 0.2 mol / L to 0.6 mol / L is prepared by passing SO2 gas into the sulfuric acid solution.

[0038] Furthermore, in step 4, when the stripping agent is mixed with the vanadium-supported organic phase for stripping, SO2 gas can also be introduced into the stripping agent. SO2 gas can act as a reducing agent, reducing pentavalent vanadium to tetravalent vanadium together with hydrogen ions, and sulfur dioxide is converted into sulfate ions.

[0039] Further, in step 4, the volume ratio of the back-extraction agent to the vanadium-supported organic phase is O / A = 1 to 10:1.

[0040] Furthermore, in step 4, the number of back-extraction stages is 2 to 6, the back-extraction temperature is 20℃ to 60℃, and the single-stage back-extraction time is 5 min to 20 min.

[0041] Furthermore, the gas introduced in step 4 is one or more of carbon dioxide, oxygen, nitrogen, air, and argon.

[0042] Furthermore, in step 4, the gas is dispersed using a gas disperser or a gas dispersion disc, and the gas flow rate is 100-500 mL / min·L (oil-water mixture), that is, the gas flow rate is 100-500 mL / min for every 1 L of liquid volume (volume of organic phase plus volume of aqueous phase).

[0043] Furthermore, the vanadium concentration (calculated as V2O5) in the vanadium electrolyte described in step 5 is 145 g / L-155 g / L.

[0044] Furthermore, the iron concentration in the vanadium electrolyte described in step 5 is ≤0.035g / L.

[0045] Furthermore, the aluminum concentration in the vanadium electrolyte described in step 5 is ≤0.035g / L.

[0046] Furthermore, the chromium concentration in the vanadium electrolyte described in step 5 is ≤0.005 g / L.

[0047] Furthermore, the silicon concentration in the vanadium electrolyte described in step 5 is ≤0.010 g / L.

[0048] Furthermore, the manganese concentration in the vanadium electrolyte described in step 5 is ≤0.005 g / L.

[0049] Furthermore, the zinc concentration in the vanadium electrolyte described in step 5 is ≤0.005 g / L.

[0050] Furthermore, the titanium concentration in the vanadium electrolyte described in step 5 is ≤0.010 g / L.

[0051] The gas-enhanced reduction back-extraction method for preparing VOSO4 electrolyte of the present invention has the following advantages compared with the prior art:

[0052] 1) This invention enhances the interfacial reaction by introducing gas during back-extraction, allowing the reduction reaction to occur smoothly, converting pentavalent vanadium to tetravalent vanadium, and transferring vanadium from the organic phase to the aqueous phase. This solves the limitation that amine anionic extractants can only be used with alkaline back-extraction; it also solves the problem of abnormal phase separation and the inability to regenerate the organic phase during back-extraction with high-concentration acids (sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, etc.) using amine anionic extractants.

[0053] 2) This invention utilizes the organic amine extractant N235 in the extraction of V 5+The high-extraction solution characteristics of this process allow for the extraction of vanadium from vanadium purification solution using an extractant and the direct preparation of vanadium oxysulfate electrolyte through gas reduction back-extraction. This process has a much lower raw material cost than that of preparing vanadium electrolyte using APV, AMV, or high-purity V2O5 as raw materials, significantly reducing the cost of preparing electrolyte from acidic vanadium-containing leachate and lowering the total cost by more than 20%.

[0054] 3) Compared with the traditional VOSO4 preparation process, the present invention has the advantages of being easy to operate, having a short process, extremely low organic phase loss throughout the process, and the organic phase after back-extraction can be directly used for the next extraction. The raffinate can be directly back-extracted into the leaching section after pH adjustment, and there is no wastewater discharge. It is easy to apply on a large scale in large-scale production such as extraction machines. Attached Figure Description

[0055] Figure 1 This is a process flow diagram of the gas-enhanced reduction back-extraction method for preparing VOSO4 electrolyte according to the present invention. Detailed Implementation

[0056] The present invention will be further described below with reference to embodiments. The description of the technical features described below is based on representative embodiments and specific examples of the present invention, but the present invention is not limited to these embodiments and specific examples. It should be noted that:

[0057] Unless otherwise stated, all units used in this specification are international standard units, and all numerical values ​​and ranges appearing in this invention should be understood to include systematic errors that are unavoidable in industrial production.

[0058] In this specification, the range of values ​​referred to as "value A to value B" refers to the range including the endpoint values ​​A and B.

[0059] In this specification, the numerical range indicated by "above" or "below" refers to the numerical range that includes the stated number.

[0060] In this specification, the word "may" has two meanings: to perform a certain process and not to perform a certain process.

[0061] In this specification, the terms "optional" or "optional" are used to indicate the use or omission of certain substances, components, procedures, application conditions, etc.

[0062] In this instruction manual, when "room temperature" or "room temperature" is used, the temperature can be 15-25℃.

[0063] Unless otherwise specified, all reagents or instruments used in this instruction manual are commercially available products.

[0064] Unless otherwise specified, % in this invention refers to mass percentage.

[0065] Example 1:

[0066] This embodiment discloses a method for preparing VOSO4 electrolyte using gas-enhanced reduction back-extraction, using vanadium purification solution as the vanadium extraction stock solution. The vanadium purification solution has a V2O5 concentration (equivalent concentration) of 52.14 g / L and a solution pH value between 2.5 and 3.0. The composition of the vanadium purification solution is shown in Table 1.

[0067] Table 1 Composition of Vanadium Purification Solution in Example 1

[0068] project <![CDATA[V2O5(g / L)]]> Fe(g / L) Al(g / L) Cr (g / L) Si(g / L) Mn(g / L) Zn(g / L) Ti(g / L) concentration 52.14 0.045 0.206 0.017 0.832 0.345 0.278 0.018

[0069] An equal volume of N235 was acidified with 1 mol / L dilute sulfuric acid to obtain acidified N235. 200 mL of an acidified N235 extractant with the following composition (by volume): 5% N235 + 90% No. 260 solvent oil + 5% 2-octanol was prepared. V 3+ A 0.98 mol / L aqueous solution with a sulfate concentration of 4.22 mol / L was used as the stripping agent in 60 mL.

[0070] The method for preparing VOSO4 electrolyte by gas-enhanced reduction back-extraction described in this embodiment is as follows: Figure 1 As shown, the specific steps include:

[0071] Step 1: Add 0.006 mol of phosphoric acid dropwise to 200 mL of vanadium purification solution, stir for 5 min, let stand for 6 h, and then adjust the pH of the vanadium purification solution to 1.47 using concentrated sulfuric acid to obtain the vanadium pre-extraction solution.

[0072] Step 2: Mix the prepared acidified N235 extractant with the vanadium pre-extraction solution, with a ratio of O / A = 200:200 = 1:1, and extract vanadium in a 50°C water bath at a stirring speed of 800 rpm for 5 min. Separate the phases to obtain the vanadium-loaded organic phase and the raffinate.

[0073] Step 3: The vanadium-loaded organic phase was washed in a three-stage countercurrent process with a ratio of O / A = 20:1 and 0.1 mol / L dilute sulfuric acid. The washing water bath temperature was 50℃, the stirring speed was 400 rpm, and the single-stage washing time was 5 min.

[0074] Step 4: Using the above back-extraction solution, with an O / A ratio of 10:1, vanadium is back-extracted in three stages at a CO2 gas flow rate of 100 mL / min, a back-extraction temperature of 60℃, a stirring speed of 600 rpm, and a single-stage back-extraction time of 20 min. After phase separation, a vanadium back-extraction solution with a V2O5 concentration of 268.64 g / L and a regenerated organic phase are obtained.

[0075] Testing revealed that the vanadium recovery rate was 98.75%, and the iron content in the back-extraction solution was 0.019 g / L, the aluminum content was 0.005 g / L, the chromium concentration was 0.004 g / L, the manganese content was 0.006 g / L, the zinc content was 0.001 g / L, and the titanium content was 0.009 g / L.

[0076] Step 5: After passing through a resin and activated carbon tower, the vanadium back-extraction solution is electrolyzed to obtain a vanadium electrolyte with a valence state (3.5 valence) that meets the specifications.

[0077] Example 2:

[0078] This embodiment discloses a method for preparing VOSO4 electrolyte using gas-enhanced reduction back-extraction, using vanadium purification solution as the vanadium extraction stock solution. The vanadium purification solution has a V2O5 concentration (equivalent concentration) of 23.85 g / L and a solution pH value between 2.5 and 3.0. The composition of the vanadium purification solution is shown in Table 2.

[0079] Table 2 Composition of Vanadium Purification Solution in Example 2

[0080] project <![CDATA[V2O5(g / L)]]> Fe(g / L) Al(g / L) Cr (g / L) Si(g / L) Mn(g / L) Zn(g / L) Ti(g / L) concentration 23.85 0.029 0.263 0.011 0.671 0.311 0.260 0.005

[0081] An equal volume of N235 was acidified with 1 mol / L dilute sulfuric acid to obtain acidified N235. 200 mL of an acidified N235 extractant with the following composition (by volume): 5% N235 + 90% No. 260 solvent oil + 5% 2-octanol was prepared. V 3+ A 1.0 mol / L aqueous solution with a sulfate concentration of 4.32 mol / L was used as the back-extraction reagent in 60 mL.

[0082] The method for preparing VOSO4 electrolyte by gas-enhanced reduction back-extraction as described in this embodiment specifically includes the following steps:

[0083] Step 1: Add 0.006 mol of phosphoric acid dropwise to 200 mL of vanadium purification solution, stir for 5 min, let stand for 6 h, and then adjust the pH of the vanadium purification solution to 1.48 with concentrated sulfuric acid to obtain the vanadium pre-extraction solution.

[0084] Step 2: Mix the prepared acidified N235 extractant with the vanadium pre-extraction solution, with a ratio of O / A = 200:200 = 1:1, and extract vanadium in a 50°C water bath at a stirring speed of 800 rpm for 5 min. Separate the phases to obtain the vanadium-loaded organic phase and the raffinate.

[0085] Step 3: The vanadium-loaded organic phase was washed in a three-stage countercurrent process with a ratio of O / A = 20:1 and 0.1 mol / L dilute sulfuric acid. The washing water bath temperature was 50℃, the stirring speed was 400 rpm, and the single-stage washing time was 5 min.

[0086] Step 4: Using the above back-extraction solution, with an O / A ratio of 10:1, vanadium is back-extracted in three stages at a CO2 gas flow rate of 100 mL / min, a back-extraction temperature of 60℃, a stirring speed of 600 rpm, and a single-stage back-extraction time of 20 min. After phase separation, a vanadium back-extraction solution with a V2O5 concentration of 206.75 g / L and a regenerated organic phase are obtained.

[0087] Testing revealed that the vanadium recovery rate was 98.39%, and the iron content in the back-extraction solution was 0.021 g / L, the aluminum content was 0.006 g / L, the chromium concentration was 0.002 g / L, the manganese content was 0.006 g / L, the zinc content was 0.0007 g / L, and the titanium content was 0.004 g / L.

[0088] Step 5: After passing through a resin and activated carbon tower, the vanadium back-extraction solution is electrolyzed to obtain a vanadium electrolyte with a valence state (3.5 valence) that meets the specifications.

[0089] Example 3:

[0090] This embodiment discloses a method for preparing VOSO4 electrolyte using gas-enhanced reduction back-extraction, using vanadium purification solution as the vanadium extraction stock solution. The vanadium purification solution has a V2O5 concentration (equivalent concentration) of 23.85 g / L and a solution pH value between 2.5 and 3.0. The composition of the vanadium purification solution is shown in Table 3.

[0091] Table 3 Composition of Vanadium Purification Solution in Example 3

[0092] project <![CDATA[V2O5(g / L)]]> Fe(g / L) Al(g / L) Cr (g / L) Si(g / L) Mn(g / L) Zn(g / L) Ti(g / L) concentration 20.63 0.021 0.144 0.018 0.159 0.595 0.018 0.014

[0093] An equal volume of N235 was acidified with 1 mol / L dilute sulfuric acid to obtain acidified N235. 200 mL of an acidified N235 extractant with the following composition (by volume): 5% N235 + 90% No. 260 solvent oil + 5% 2-octanol was prepared. V 3+ A 1.18 mol / L aqueous solution with a sulfate concentration of 4.51 mol / L was used as the back-extraction reagent in 60 mL.

[0094] The method for preparing VOSO4 electrolyte by gas-enhanced reduction back-extraction as described in this embodiment specifically includes the following steps:

[0095] Step 1: Add 0.006 mol of phosphoric acid dropwise to 200 mL of vanadium purification solution, stir for 5 min, let stand for 6 h, and then adjust the pH of the vanadium purification solution to 2.08 with concentrated sulfuric acid to obtain the vanadium pre-extraction solution.

[0096] Step 2: Mix the prepared acidified N235 extractant with the vanadium pre-extraction solution, with a ratio of O / A = 200:200 = 1:1, and extract vanadium in a 50°C water bath at a stirring speed of 800 rpm for 5 min. Separate the phases to obtain the vanadium-loaded organic phase and the raffinate.

[0097] Step 3: The vanadium-loaded organic phase was washed in a three-stage countercurrent process with 0.08 mol / L dilute sulfuric acid at a ratio of O / A = 20:1. The washing water bath temperature was 40℃, the stirring speed was 400 rpm, and the single-stage washing time was 5 min.

[0098] Step 4: Using the above back-extraction solution, with an O / A ratio of 8:1, vanadium is back-extracted in three stages at an air flow rate of 100 mL / min, a back-extraction temperature of 60℃, a stirring speed of 800 rpm, and a single-stage back-extraction time of 20 min. After phase separation, a vanadium back-extraction solution with a V2O5 concentration of 238.72 g / L and a regenerated organic phase are obtained.

[0099] Testing revealed that the vanadium recovery rate was 98.15%, and the iron content in the back-extraction solution was 0.011 g / L, the aluminum content was 0.006 g / L, the chromium concentration was 0.005 g / L, the manganese content was 0.004 g / L, the zinc content was 0.0004 g / L, and the titanium content was 0.008 g / L.

[0100] Step 5: After passing through a resin and activated carbon tower, the vanadium back-extraction solution is electrolyzed to obtain a vanadium electrolyte with a valence state (3.5 valence) that meets the specifications.

[0101] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing VOSO4 electrolyte by gas-enhanced reduction back-extraction, characterized in that, Includes the following steps: Step 1: Add an extraction inhibitor to an acidic vanadium-containing solution and stir to obtain a vanadium-containing solution. The extraction inhibitor is phosphoric acid and / or a phosphoric acid compound. Step 2: Extraction. Adjust the pH of the solution to 0.5-3.0 using sulfuric acid, mix with the extraction organic phase, and then separate the extract to obtain the vanadium-loaded organic phase. Step 3: Washing, using dilute sulfuric acid to wash the vanadium-supported organic phase; Step 4: Back-extraction. The back-extraction agent is mixed with the vanadium-loaded organic phase for back-extraction, and gas is introduced at the same time to enhance the back-extraction process, resulting in an empty organic phase and vanadium back-extraction solution. Step 5: After adjusting the vanadium back-extraction solution, the valence state is adjusted by electrolysis of the fuel cell stack to obtain a vanadium electrolyte with a valence state that meets the standard. The acidic vanadium-containing solution described in step 1 has a pH value of 1.0 to 3.0; The acidic vanadium-containing solution contains vanadium at a concentration of 5-55 g / L, and / or iron at a concentration of 0.05 g / L-0.5 g / L, and / or aluminum at a concentration of 0.1 g / L-3 g / L, and / or chromium at a concentration of 0.1 g / L-1 g / L, silicon at a concentration of 0.1 g-2 g / L, and / or manganese at a concentration of 0.1 g-3 g / L, and / or zinc at a concentration of 0.1 g / L-2 g / L, and / or titanium at a concentration of 0.05 g / L-0.5 g / L. The stripping agent in step 4 is V 3+ Concentration 0.8~1.2 mol / L, SO4 2- Aqueous solutions with a concentration of 3.8~4.5 mol / L or SO4 2- An aqueous solution with a concentration of 3.5~4.2 mol / L and a sulfurous acid concentration of 0.2~0.6 mol / L; the volume ratio of the stripping agent to the vanadium-supported organic phase is O / A = 1~10:

1.

2. The method for preparing VOSO4 electrolyte by gas-enhanced reduction back-extraction according to claim 1, characterized in that, The extraction inhibitor mentioned in step 1 is one or more of the following: phosphoric acid, trisodium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, ammonium phosphate, diammonium hydrogen phosphate, and ammonium dihydrogen phosphate.

3. The method for preparing VOSO4 electrolyte by gas-enhanced reduction back-extraction according to claim 1 or 2, characterized in that, The amount of the extraction inhibitor added is 0.02 mol / L to 0.05 mol / L based on the molar amount of phosphorus.

4. The method for preparing VOSO4 electrolyte by gas-enhanced reduction back-extraction according to claim 1, characterized in that, The organic phase extracted in step 2 includes an organic extractant, a co-solvent, and an organic diluent. The organic extractant is an organic amine extractant; the co-solvent is a polyol; and the organic diluent is sulfonated kerosene. And / or, the volume ratio of the extracted organic phase to the vanadium-containing solution is O:A = 0.2~5:

1.

5. The method for preparing VOSO4 electrolyte by gas-enhanced reduction back-extraction according to claim 1, characterized in that, The concentration of the dilute sulfuric acid mentioned in step 3 is 0.05 mol / L to 0.1 mol / L.

6. The method for preparing VOSO4 electrolyte by gas-enhanced reduction back-extraction according to claim 1, characterized in that, The gas introduced in step 4 is one or more of carbon dioxide, oxygen, nitrogen, air, and argon.

7. The method for preparing VOSO4 electrolyte by gas-enhanced reduction back-extraction according to claim 1 or 6, characterized in that, In step 4, the gas flow rate is 100 mL / min·L to 500 mL / min·L.

Images