氯化物体系中La的电化学提取及共沉积Zn-La合金

Electrochemical Extraction of La and Zn-La Alloy Codeposition in Chloride System

通过循环伏安、方波伏安和开路计时电位等方法研究了723 K时,La(Ⅲ)在LiCl-KCl和LiCl-KClZnCl_2熔盐体系中Mo电极上的电化学行为.结果表明,La(Ⅲ)还原为金属La是一步扩散控制的不可逆还原反应.在LiCl-KCl-ZnCl_2熔盐中,La(Ⅲ)在预先沉积的Zn阴极上欠电位沉积形成4种Zn-La金属间化合物.在923 K时通过恒电流电解获得Zn-La合金,通过X射线衍射(XRD)和扫描电子显微镜(SEM)以及附带的能谱仪(EDS)对合金的相组成和微观形貌进行了分析.采用恒电位电解提取La并用方波伏安曲线检测La(Ⅲ)离子浓度的变化,电解50 h后,La(Ⅲ)离子浓度接近于零,提取效率达到99.55%.

The electrochemical behavior of La（Ⅲ） ions was studied in LiCl-KCl and LiCl-KCl-ZnCl2 melts on the Mo electrode at 723 K by cyclic voltammetry, square-wave voltammetry and open-circuit chronopotentiometry. The results showed that the reduction of La（Ⅲ） to La（0） is a one-step irreversible reaction controlled by diffusion. In LiCl-KCl-ZnCl2 solutions,the underpotential deposition of La formed four kinds of Zn-La intermetallic compounds on pre-deposited Zn. Zn-La alloy was obtained by galvanostatic electrolysis at 923 K. The microstructure and micro-zone chemical analysis of Zn-La alloy were characterized by X-ray diffraction（XRD）,scanning electron microscopy（SEM） and energy dispersive spectrometry（EDS）.Based on the previous electrochemical results, square-wave voltammetry was used to determine the concentration changes of La during potentiostatic electrolysis,the concentration of La（Ⅲ） was close to zero,and the extraction efficiency was 99. 55% after potentiostatic electrolysis for 50 h.