| A series of electrochemical behaviors of rare earth ions Pr???and Dy???in liquid Pb electrode and Pb film electrode in LiCl-KCl molten salt system was studied,and the feasibility in active Pb electrode to extract earth ions of Pr and Dy and on-line detection of the concentration of rare earth ions in molten salt studied,the basic experimental datas and methods were prapared for the extraction of actinides in spent fuel.The research of this paper mainly includes the following aspects:?1?The electrochemical behavior of LiCl-KCl-PbCl2 system on inert W electrode has been studied by means of cyclic voltammetry at different termination potentials and square wave voltammetry and chronoptentimetry,it is known that there are five intermetallic compounds between Pb-Li,Through cyclic voltammetry at different sweep rates,and the diffusion coefficient is calculated to be 1.55×10-5 cm2 s-1.Through the cyclic voltammetry curves of different temperatures,the relation curve of temperature and diffusion coefficient is obtained,and the activation energy is calculated to be 39.4 kJ mol-1.In the range of 643-723K,the thermodynamic datas of Pb-Li intermetallic compounds were calculated through open circuit chronoptentimetry at different temperatures,and LiPb and Li3Pb alloys were prepared by galvanostatic electrolysis.?2?The electrochemical behavior of Pr???on the Pb film electrode was studied at 773K.Firstly,the cyclic voltammetry of Pr???on inert W electrode at different sweep speeds was studied,it is found that the reduction process is controlled by diffusion,and the diffusion coefficient is calculated to be 1.04×10-5 cm2 s-1.Then the kinetic datas were calculated by Tafel curve,and the activation energy is calculated to be 24.94 kJ mol-1.Through cyclic voltammetry,square wave voltammetry and open circuit chronoptentimetry,it was found that there are four intermetallic compounds of Pr???ions on Pb film electrode,and Pb3Pr alloy is obtained through galvanostatic electrolysis with XRD and SEM-EDS.The standard working curve of Pr???on the liquid Pb electrode was studied through square wave voltammetry at the temperature of 773 K and 823 K,and the corresponding relationship between the concentration and the peak height of square wave voltammetric was obtained.And then add a certain concentration of PrCl3 to extract each hour until that the peak height of square wave voltammetry was reduced constantly,and then the corresponding concentration was determined through the standard curve,concentration of rare earth Dy???ion in the electrochemical extraction process can be known.?3?The cyclic voltammetry at different sweep speeds curve of Dy???on liquid Pb electrode were studied,it was found that the reduction process of Dy???was controlled by diffusion,the diffusion coefficient was calculated to be 8.08×10-55 cm2 s-1.Through cyclic voltammetry,square wave voltammetry and open circuit chronoptentimetry,it is found that there are four intermetallic compounds of Dy???ions on Pb film electrode,which are consistent with the results obtained from phase diagram.The thermodynamic data of four kinds of intermetallic compounds were calculated and the Pb3Dy alloy was prepared by constant potential electrolysis.Meanwhile,the standard working curve of Dy???on the liquid Pb electrode was studied through square wave voltammetry at the temperature of 773 K and 823 K,and the corresponding relationship between the concentration and the peak height of square wave voltammetric was obtained.And then add a certain concentration of DyCl3 to extract each hour until that the peak height of square wave voltammetry was reduced constantly,and then the corresponding concentration was determined through the standard curve,concentration of rare earth Dy???ion in the electrochemical extraction process can be known. |
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