Study On The Separation Of Sm,Gd And Dy By Electrolysis In Molten Salts

In this paper,the separation of rare earth?RE;RE=Sm,Gd and Dy?oxides and chlorides was studied by the methods of direct deposition,co-reduction and cathode alloying.The electrochemical behaviour of RE???ions were discussed by cyclic voltammetry,square wave voltammetry and open-circuit chronopotentiometry.Moreover,the electron transfer process and deposition potentials were researched.Potentiostatic electrolysis experiments were performed to separate rare earth oxides and chlorides.XRD pattern and SEM images with EDS were used to indicate the microstructure of deposits.In LiCl-KCl-MgCl₂ melts,the separation of Sm₂O₃,Dy₂O₃ and Gd₂O₃,was studied using inert electrodes by co-reduction methods.Because rare earth oxides were insoluble in chlorides,the chloration of MgCl₂ for Sm₂O₃,Dy₂O₃ and Gd₂O₃ was studied by the electrochemical measurement,XRD patterns of melts and non-dissolved residues,Gibbs energy of reaction.The research showed MgCl₂ could chloridize Sm₂O₃,Dy₂O₃ and Gd₂O₃.The electrochemical behaviour and separation of Sm₂O₃,Dy₂O₃ and Gd₂O₃ were studied in LiCl-KCl-MgCl₂ melts using inert electrodes.The order of separation was confirmed:firstly,Dy₂O₃ was extracted in a form of Mg-Dy alloys;secondly,Gd₂O₃ was extracted in a form of Mg-Gd alloys;meanwhile,Sm₂O₃ was kept in melts.The separation efficiency of Dy₂O₃ and Sm₂O₃/Gd₂O₃,Gd₂O₃ and Sm₂O₃ was calculated to be 95.6%and 98.0%,respectively.The separation was successfully finished by ICP-AES,XRD,SEM and EDS analyses of deposits.The electrochemical behaviour and separation of SmCl₃,DyCl₃ and GdCl₃ were studied in LiCl-KCl melts using inert electrodes.The order of separation was obtained:firstly,DyCl₃ was extracted in a form of Dy metal;secondly,GdCl₃ was extracted in a form of Gd metal;meanwhile,SmCl₃ was kept in melts.The separation was achieved at the inert electrodes due to the valence change of Sm???ions.The separation efficiency of DyCl₃ and SmCl₃/GdCl₃,SmCl₃ and GdCl₃ was calculated to be 98.0%and 99.7%,respectively.The electrochemical behaviour and separation of SmCl₃,DyCl₃ and GdCl₃ were studied in LiCl-KCl melts using Mg electrodes.The order of separation was determined:firstly,DyCl₃ was extracted in a form of Mg-Dy alloys;secondly,GdCl₃ was extracted in a form of Mg-Gd alloys;meanwhile,SmCl₃ was kept in melts.The separation efficiency of DyCl₃ and SmCl₃/GdCl₃,GdCl₃ and SmCl₃ was calculated to be 96.8%and 93.6%,respectively.The separation was completed by ICP-AES,XRD,SEM and EDS analyses of deposits.In the separation process by the cathode alloying method,the valence change of Sm?III?ions could be extracted in a form of alloys through long electrolysis,which could be controlled by the practical application.The results in this paper indicated the separation of valence change RE/valence constant RE,valence constant RE/valence constant RE could be achieved by electrolysis.It provided a method of the preparation or extraction of single rare earth.