Study On Preparation And Mechanism Of High-purity Vanadium Sulphate Solution For Vanadium Battery Based On Solvent Extraction Method

All vanadium redox flow batteries show great application prospects in the field of energy storage due to their advantages such as large storage capacity,high efficiency,and long life.The active material vanadyl sulfate in the vanadium electrolyte is a key material that affects the comprehensive electrical performance of the all-vanadium redox flow battery.Increasing the concentration and purity of vanadium ions in the electrolyte can effectively improve the comprehensive electrical performance of the vanadium battery.Our country has rich resources of vanadium-titanium magnetite,which is the main mineral source for the preparation of vanadium products.Sulfuric acid leaching is the most important process for preparing high-purity vanadium products from vanadium-titanium magnetite steel-making vanadium slag after calcification,enrichment and purification.In industrial production,two-stage leaching is often used to increase the direct yield of vanadium.The acid leaching solution obtained from the second stage leaching has low vanadium concentration,high content of impurity elements,and various types,which restricts the direct application prospects.Usually,returning to the first stage leaching process to recover vanadium,increases the difficulty of removing impurities from the first stage leaching solution.Solvent extraction method for impurity removal and purification of target elements has the technical advantages of strong selectivity,large processing capacity,and high product purity.Aiming at the characteristics of low vanadium and high manganese in the second-stage leaching solution,this paper proposes a highly efficient,clean,short process,and vanadium ion concentration.The method for preparing high-purity vanadyl sulfate solution for vanadium batteries is to use solvent extraction to directly prepare high-purity vanadyl sulfate solution for vanadium battery electrolyte.The main research contents and results are as follows:（1）Study on the preparation of pentavalent vanadium-rich solution by removing impurities from the low-vanadium and high-impurity acid leaching solution obtained by calcification and roasting of steel-making vanadium slag.The results show that the optimal extraction process parameters are:the initial extraction p H=1.8,the extractant composition is25%N235（trioctyl decyl tertiary amine）+5%2-octanol+70%sulfonated kerosene,compared with O/A=1:3.Under the condition of extraction time of 5min,thesingle-stage extraction rate of each metal ion is 71.0%vanadium,1.0%manganese,1.0%magnesium,and 2.0%calcium;The extraction rates are respectively:99.4%for vanadium,3.2%for manganese,4.3%for magnesium,and 6.2%for calcium,which can effectively separate vanadium from impurity ions of manganese,magnesium and calcium.After the loaded organic phase is washed with water,the optimal stripping process parameters are:stripping agent Na₂CO₃concentration 1.0 mol/L,comparison O/A=3:1,stripping time 5 min,each metal ion single-stage stripping The rates are 95.2%for vanadium,21%for manganese,2%for magnesium,and 5%for calcium.The concentration of each metal ion in the pentavalent vanadium-rich liquid is respectively:vanadium 21.59 g/L,manganese 0.85 g/L,magnesium 21.9 mg/L,Calcium 6.99 mg/L.Among them,the concentration of vanadium was enriched from 3.4 g/L to 21.59 g/L,which realized the efficient separation and concentration of vanadium and impurity ions in the second-stage leachate.（2）Study on the enrichment and purification of pentavalent vanadium-rich liquid to prepare tetravalent vanadium-rich liquid.The results show that the pentavalent vanadium-rich liquid is reduced by Na₂SO₃,and the optimal extraction process parameters are:the initial p H of the aqueous phase is 2.0,and the composition of the organic phase is30%P507（2-ethylhexyl phosphate mono-2-ethylhexyl ester）+70%sulfonated kerosene,extraction ratio O/A=2:1,under the condition of extraction time of 5 min,the extraction rate of vanadium is 85.0%,and the extraction rate of manganese is 12.0%.After the loaded organic phase is washed with water and pickled,the optimal stripping process parameters are:stripping agent H₂SO₄concentration 2.5 mol/L,stripping ratio O/A=7:1,stripping time10min,vanadium stripping The extraction rate is 95.2%,and the manganese stripping rate is15.0%.The vanadium concentration in the obtained quadrivalent vanadium-rich solution is49.15 g/L,the manganese concentration is only 1.5 mg/L,and the total impurity ion content is 14.05 mg/L.Among them,the vanadium concentration is enriched from 21.59 g/L to 49.15g/L,Further realize the efficient separation and concentration of vanadium and impurity ions.（3）Research on preparing high-purity vanadyl sulfate solution for vanadium electrolyte by evaporation and concentration of tetravalent vanadium-rich solution.The results show that under the condition of heating at 95℃for 2.5 hours,a high-purity vanadium sulfate solution for vanadium electrolyte with a vanadium concentration of 100g/L and a total impurity ion content of 28.95 mg/L is obtained.All individual test items are in line with or excellent It is used in the national standard of electrolyte for all vanadium redox flow batteries（GB/T 37204-2018）.（4）Preliminary analysis of the mechanism,thermodynamics and kinetics of P507extracting vanadium.The results show that the extraction of vanadium by P507 is a cation exchange system,and the organic phase circulation performance is good;the saturated volume method,the equimolar series method,and the slope method can verify the reaction of P507 for extracting vanadium is VO²⁺+2（?）→（?）+2H⁺;thermodynamic analysis shows that the extraction of vanadium by P507 is an endothermic reaction.The enthalpy ofΔH=31.86 KJ/mol,the equilibrium constant of the extraction reaction K=10^-1.3934;kinetic analysis shows that the vanadium concentration,stirring intensity,and phase separation time of the extraction stock solution have a certain effect on vanadium extraction.P507 has a good extraction effect on vanadium.Selectivity,wide range of extraction concentration,fast extraction reaction rate.VO²⁺+2H₂R₂→VOR₂2（HR）+2H⁺...