MgCl2 and ZnCl2 assisted electrochemical extraction lanthanum by formation of Mg-Zn-La alloy in LiCl-KCl melts

In this work, Mg-Zn alloy film electrode was prepared by co-deposition of Mg(II) and Zn(II) on Mo electrode in LiCl-KCl melts for electrochemical extraction of La. The electrochemical behavior of La(III) in LiCl-KCl-ZnCl2-MgCl2 melts and the deposition mechanism of La(III) on Mg-Zn film electrode were investigated by different electrochemical methods. The results illustrated that two kinds of Zn-La intermetallic compounds and one kind of Mg-La intermetallic compound were formed under our experimental conditions. At 1073 K, Mg-Zn-La alloys were prepared by galvanostatic electrolysis with different concentration of LaCl3. La element was successfully extracted in the form of Mg-Zn-La alloys. X-ray diffraction (XRD) analysis confirmed that Mg-Zn-La alloys were mainly composed of Zn5La, La2Zn17 and Mg17La2 phases, and the phase composition could be adjusted by changing the concentration of LaCl3. Scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS) were used to analyze the microstructure and element distribution of the alloy. The results exhibited that La has good diffusion properties on the Mg-Zn matrix, indicating that it is feasible to extract La with the assistance of MgCl2 and ZnCl2.