Development of an <i>f</i>-element separation chemistry using solid electrolytes

The f‒elements (lanthanides and actinides) have numerous applications and are critically important to many industries, including the energy, security, and medical industries. One of the barriers to increased use and availability of the f‒elements is the difficulty in separating them from each other due to their similar chemistries. This is especially true of the trivalent f‒elements (lanthanides and minor actinides). The development of separation techniques that maximize the differences in the physicochemical properties of the f‒elements is therefore an important area of research. For these reasons, an effort was undertaken to explore the use of solid electrolyte materials to accomplish separations of the f‒elements. The results of this work have led to the development of a novel separation method at Oak Ridge National Laboratory for accomplishing f‒element separations using inorganic solid electrolyte materials, specifically beta´´‒alumina. The use of beta´´‒alumina was both investigated both as an ion exchanger and selective membrane. Given the large dependence of superionic conductivity upon the valence of mobile ions, oxidation state control of the ions to be separated was explored. The high‒temperature regimes (greater than 300°C) required for superionic conduction of multivalent metal ions in beta´´‒alumina necessitated the use of molten salts as a medium to contain ions to interact with the solid electrolyte. These studies also included the development of Laser Induced Breakdown Spectroscopy for determining the concentrations of f‒elements in the alumina based materials.