Study On Preparation Of Vanadium From V₂O₃ By Direct Electrochemical Reduction In Molten Salt

Vanadium,a kind of important high melting metal,has a broad application prospect in the fields of hydrogen storage alloys,atomic energy industry,superconducting alloys,special alloys additives and electronic industry,etc.Due to the complex production process and expensive cost,the traditional preparation method of metal vanadium severely restricts the widespread use of vanadium.Because of the advantages of short process flow and low energy consumption,Direct Electrochemical Reduction in Molten Salt(FFC)is widely regarded as a promising method of high melting point metals,but with some sho’rtcomings,such as strict requirements for raw materials and low rate of electrolysis.Therefore,(NH4)2V6O16 was choose as the raw material to prepare V2O3 cathode by coal gas reduction and in-situ sintering,then deacidized in fluoride molten salt system in this paper.Thermodynamic analysis shows that,the preparation of V2O3 by reduction ammonium molybdate in coal gas atmosphere is feasible.The optimum sintering condition was at 750℃ for 30min with gas flow velocity of 0.4min/L,the thickness of tables was 3.42 to 4.24mm.With the vanadium content of 64.7wt%in V2O3,this reduction condition has reached the technology requirements for direct electrochemical reduction.The effects of sintering temperature,electrolysis time,forming pressure,fluoride molten salt composition on the preparation of vanadium by Direct Electrochemical Reduction were studied.The results show that the V2O3 tablets prepared at 1200℃with molding pressure 30MPa have an excellent electrochemical properties meeting the requirements of the electri deoxidization reaction.With nNaF:nAlF3 = 2.95 and reaction for 3h,the V2O3 cathode has been fast completed electri deoxidization process and converted to vanadium.The direct electrochemical reduction of V2O3 goes from outside to inside,step by step.The specific path is:V2O3→VO→V2O→V.The effects of the additives in V2O3 cathode preparation process,such as sulfur powder,carbon powder and ammonium hexafluoroaluminate,on the porosity,resistivity,microstructure and electrolytic products of the cathode tables after sintering were studied also.The results show that additives of sulfur powder,carbon powder,ammonium hexafluoroaluminate can effectively increase the porosity,the microstructure and the sizes of the particles of the cathode tables after sintering.V-Al alloy phases were found in the electrolytic reaction of 3h.It can be considered that the three additives can improve the electrochemical activity of V2O3 cathode,accelerate the electrolysis reaction.Considering the reaction,ammonium hexafluoroaluminate additive is selected an amount of 5wt%for V2O3 cathode.