LiCl-KCl共晶熔盐的纯化

Purification of Lithium Chloride-Potassium Chloride Eutectic

氯化锂-氯化钾共晶熔盐是电解精炼干法后处理中最常用的电解质,其含有的杂质直接影响电流效率和产物纯度。本研究分别采用高温处理、HCl气体鼓泡和恒电位电解等方法依次去除了熔盐中的易挥发物质、氧离子和金属离子等杂质,获得了较高纯度的熔盐。采用热重分析(TGA)、电化学和电感耦合等离子体原子发射光谱(ICP-AES)等方法对比了纯化前后熔盐中各杂质的含量。研究结果表明:去除易挥发杂质的最佳处理温度范围为450～650℃;去除杂质金属离子时最佳电解电位为-2.3Vvs.Ag/AgCl(摩尔分数2%),恒电位电解800s后杂质金属离子总量低于1.5×10-6 g/g(盐)。以上研究结果表明,采用高温处理、HCl气体鼓入和恒电位电解可获得纯度较高的LiCl-KCl共晶熔盐。

Lithium chloride-potassium chloride eutectic is the most commonly used electrolyte in electrorefining dry reprocessing, and its impurities directly affect current efficiency and product purity. In this study, high-temperature calcination, HCl gas bubbling, and potentialstat electrolysis were used to remove the volatile, oxygen ions, and metal ions impurity in molten salt in sequence, and to obtain higher purity molten salt. Thermogravimetric analysis (TGA), electrochemical and inductively coupled plasma atomic emission spectrometry (ICP-AES) were used to compare the contents of impurities in molten salt before and after purification. The results show that the optimal calcining temperature range for removal of volatile impurities is 450-650 ℃; the optimal electrolytic potential for removing metal ions impurity is -2.3 V vs. Ag/AgCl( x =2%), and the total metal ion concentration after constant potential electrolysis for 800 s is less than 1.5×10^-6 g/g (salt). Based on the above results, higher purity LiCl-KCl eutectic can be obtained by high-temperature calcination, HCl gas bubbling, and constant potential electrolysis.