Separating Rare-Earth Elements with Ionic Liquids

Abstract

The rare-earth elements (REEs) are a group of 17 chemically similar metallic elements; this group consists of scandium, yttrium, and 15 lanthanides. Due to their essential role in permanent magnets, lamp phosphors, catalysts, and rechargeable batteries, the REEs have become an essential component of the global transition to a green economy. Currently, with China producing over 90 % of the global REE output and its increasingly tightening export quota, the rest of the world is confronted with the potential risk of REE shortage. As such, many countries will have to rely on recycling REEs from pre-consumer scrap, industrial residues, and REE-containing end-of-life products. Over the course of the last two decades, ionic liquids have been increasingly used to separate REEs in the recycling process. Ionic liquids (ILs) are a class of molten salts that are liquid at temperatures below 100 C. ILs are amenable to the recycling of REEs because the cation and anion components are readily tailored to a given process, and they offer numerous advantages over typical organic solvents, such as low volatility, low flammability, a broad temperature range of stability, the ability to dissolve both inorganic and organic compounds, high conductivity, and wide electrochemical windows. In this chapter, we discuss the performance of several IL-based extraction systems used to separate and recycle REEs.

Extraction of light, medium and heavy rare-earth elements using synergist extractants developed from ionic liquid and conventional extractants

“…In this sub-section, the performance of each extractants on the extraction of Gd, one of the medium REE, is evaluated and presented in Fig. 3 [22,61]. Therefore, one of the ways to reduce the loss of ionic liquid into the aqueous solution is through the formulation of a synergist extractant, which was carried out in this research.…”

Acceleration of Solvation Free Energy Calculation via Thermodynamic Integration Coupled with Gaussian Process Regression and Improved Gelman–Rubin Convergence Diagnostics

“…Characterized by their negligible vapor pressure, nonflammability, and exceptional chemical and electrochemical stability, ILs with solvent extractants offer a viable avenue to facilitate the efficient extraction of REEs from aqueous solutions. 4,5 Nonetheless, the process of identifying effective species from a wide variety of ILs, or devising taskspecific ILs, remains a time-intensive endeavor often plagued by laborious trial and error methodologies. 6 Molecular dynamics (MD) simulation is, in principle, a powerful method for expediting the screening process to achieve specific relative coordination selectivity for particular elements in the mixture of dissolved ionic species through the calculation of solvation free energies.…”

“…Among the potential solution chemistry environments, ionic liquids (ILs) emerge as a promising contender because, composed of charged species, they can introduce strong perturbations in the electronic state of ions in solution, altering their chemical interaction properties. Characterized by their negligible vapor pressure, nonflammability, and exceptional chemical and electrochemical stability, ILs with solvent extractants offer a viable avenue to facilitate the efficient extraction of REEs from aqueous solutions. , Nonetheless, the process of identifying effective species from a wide variety of ILs, or devising task-specific ILs, remains a time-intensive endeavor often plagued by laborious trial and error methodologies …”