Molten-salt Electrolysis And Vacuum Melting Refining High Purity Ce

As an important strategic metal,high purity Ce is mainly used in the new fields such as laser material,rare earth permanent magnetic material,hydrogen storage battery anode materials and so on.At present,the purification of metal cerium mainly include vacuum melting,vacuum distillation/sublimation,Zone melting,Solid state electranspor,light incentive refining,etc.Molten salt electrolysis is widely used in the refining of aluminum,which has the advantages of simple process,short flow,low equipment requirements,facilitate large-scale industrial production,etc.,,but the research on the preparation of high purity metallic Ce is still seldom,so the refining process of Ce by molten salt electrolysis and vacuum melting is studied in this paper.In this paper,the raw materials of high purity Ce2(CO3)3 were prepared for preparation of raw materials for electrolysis CeCl3 by dissolved-vacuum dehydration.The effect of dehydration temperature,dehydration time,dehydration vacuum degree and dosage of NH4Cl on dewatering effect was investigated by single factor experiment.The optimum dehydration conditions were determined:the dehydration temperature is 170℃,the dehydration time is 3h,the vacuum degree is 0.04 MPa,the dosage of NH4Cl(NH4Cl accounts for the mass fraction of CeCl3·7H20)is 30%.The purity of anhydrous CeC13 is 94%,and other impurities are mainly CeO2 and CeOCl,which can basically meet the requirements of the cerium in electrolytic refining.CeC13-KCl chloride molten salt system was used for electrolytic refining of Ce.the effects of molten salt ratio,cathode current density,electrolyte temperature,polar distance and the material of metal collector on the cathode product impurity content and current efficiency was systematically investigated and the analysis results of inductively coupled plasma mass spectrometry(ICP-MS)was combined to determine the best electrolysis refining conditions:molten salt ratio is n(CeCl3):n(KCl)＝1:7,cathode current density is 2.0A/cm2,the electrolysis temperature is 860℃,polar distance is 1.5-2cm,metal collector is boron nitride crucible,metallic Ce purity can be reached 99.90%,the current efficiency is up to 86%.At the same time,the molten salt system of CeF3-LiF fluoride is preliminarily explored.Through the calculation of the theoretical decomposition voltage of the material in the molten salt system,the theoretical decomposition voltage of LiF and CeF3 is very close.In the process of electrolysis,the Li and Ce are prone to be co-deposition.The vacuum melting refined metal Ce which was prepared by electrolytic refining in vacuum induction furnace,and the effect of smelting temperature,vacuum degree and smelting time on the metal purity was investigated.The optimum vacuum melting conditions were determined:the melting temperature is 1200℃ the vacuum degree of melting is 3.4 X 10-3Pa,the refining time is 30min,the purity of the metal cerium is 99.95%.