Preparation Of Vanadium Metal By Direct Electrochemical Reduction Of Solid Oxides

Due to its unique physical and chemical properties,vanadium plays an important role in modern industry.Because of having good density,hardness,corrosion resistance,etc.Metal vanadium is widely used in chemical industry,metallurgy,steel,medicine and so on.Vanadium is also an indispensable additive in specialty alloys,known as industrial "vitamins." The vanadium resource reserves of China rank third all over the world.With the development of industry,the application of vanadium is more and more widely,and the demand is also increasing.So the efficient development and utilization of vanadium resource have become the focus of attention.They are many methods in traditional of preparation vanadium metal including Calorific reduction,Magnesium reduction,Thermite reduction,Vacuum carbothermal reduction,Thermal decomposition of vanadium nitride,Silicon thermal reduction and Chloride metal thermal reduction.These methods are also relatively mature.Due to its long cycle,not being continuous production,complex technology,higher equipment requirements,and serious secondary pollution,highly cost of producing metal vanadium,and it is not conducive to industrial production.The experiment uses the green metallurgy method-FFC method(electrolysis in molten salt).The method is a new type of clean metallurgy method,which is considered a low energy consumption.This experiment focuses on the process of preparing vanadium from vanadium oxide by FFC method.The powder metallurgy method made a certain amount of vanadium oxide powder into a sheet under 135 Mpa pressure.After sintering for 1 h at vacuum hot-pressing furnace under1000℃.The sintering sheet is cathode,anode using graphite electrode.In an argon atmosphere,the LiCl-KCl eutectic system was used as the molten salt electrolyte for electrolysis.In the LiCl-KCl eutectic system,using different temperature(400-600℃),different electrolysis time,different voltage(2.7-3.2 V),adding different pore-forming agents to explore the impact on electrolysis.Studying the relevant current curve,observing the different process parameters,analyzing the XRD patterns and SEM images of the samples and combining with the actual reaction process.Results showed that the low oxidation of vanadate and lithium vanadium was formed in the middle of the electrolytic reaction.Then the metal vanadium was generated by further deoxygenation.It was found that the electrolysis process of vanadium was consistent with the three-phases interline theory.The particle size of the metal vanadium could reach the nanometer level according to the relevant particle size analysis.The experiments also obtained the optimum process conditions of preparation vanadium:25%of cathode porosity,600℃ of the reaction temperature,8 h electrolytic under voltage of 3.1 V.The mechanism of vanadium formation was also explored in this paper through the scanning and constant potential electrolysis of the molybdenum electrode of the V2O3 powder in LiCl-KCl high temperature molten salt.According to the time current and cyclic voltammetry curves as well as the analysis of phase composition and morphology of the product,the reduction process of vanadium oxide was further clarified.And the reaction process of vanadium metal was found to be in accordance with the thin film electrochemical theory by changing the scanning rate(50-200 mV/s).It was found that the peak current and the scanning rate were linear relation,and the peak potential and the scanning rate were in a logarithmic relationship,indicating that the reaction of vanadium was consistent with the film electrochemical theory.This paper further explored the vanadium flow battery using electro-deoxidation method.The cathode was made of compressed vanadium oxide and vanadium pentoxide tablets,respectively.In the low temperature ionic liquid(choline chloride-ethylene glycol)electrolysis 10 h at 100℃ and 3.5 V for preparing vanadium battery electrolyte.In addition,the preliminary study was conducted through the electrochemical workstation and found that the variation of the price was in accordance with the requirements of vanadium batteries.The feasibility of the electrolyte was further illustrated by making a small battery and the diode glow.The battery capacity of the battery has been preliminarily studied through charging and discharging test,which laid the foundation for further exploration of the all-vanadium flow battery in new energy.