Recovery of Rare Earth Elements (REEs) Using Ionic Solvents

Abstract

Rare earth elements (REEs) are becoming more and more significant as they play crucial roles in many advanced technologies. Therefore, the development of optimized processes for their recovery, whether from primary resources or from secondary sources, has become necessary, including recovery from mine tailings, recycling of end-of-life products and urban and industrial waste. Ionic solvents, including ionic liquids (ILs) and deep-eutectic solvents (DESs), have attracted much attention since they represent an alternative to conventional processes for metal recovery. These systems are used as reactive agents in leaching and extraction processes. The most significant studies reported in the last decade regarding the recovery of REEs are presented in this review.

Long-Range Organization Study of Piperidinium-Based Ionic Liquids by Polarizable Molecular Dynamics Simulations

“…This class of ILs is, however, very promising not only for various electrochemical applications 49 such as high-voltage supercapacitors, 50 electrolytes in lithium−metal batteries at room temperature, 50,51 and high capacity anodes for lithium-ion batteries 15 but also for applications in liquid−liquid extraction. 19,20 Most of molecular dynamics (MD) studies focusing on the nanoscale organization of ILs use the nonpolarizable force field developed by Canongia Lopes and Padua. 52−54 This force field allowed great advances in the understanding of the ILs structure.…”

“…They have many properties of interest such as good thermal and electrochemical stability and very low volatility. − The air stability of ILs makes them theoretically recyclable and therefore more advantageous from economic and environmental points of view. Associated with their performance versatility under slight modifications of the chemical architecture, these properties make them tunable and interesting for many applications in electrochemistry, catalysis, or extraction. − …”

“…To our best knowledge, only one study has been conducted to understand the long-range organization of piperidinium-based ILs and none via simulations. This class of ILs is, however, very promising not only for various electrochemical applications such as high-voltage supercapacitors, electrolytes in lithium–metal batteries at room temperature, , and high capacity anodes for lithium-ion batteries but also for applications in liquid–liquid extraction. , …”

Recycling REEs from the Waste Products of Silius Mine (SE Sardinia, Italy): A Preliminary Study

“…Quantitative extraction of REE from ores can be performed based on well-standardized procedures, deeply detailed in analytical protocols. In general, a suitable combination of mineral acids (in a single step or in a tailored sequence) is proposed (i.e., [8,14,[28][29][30]). However, leaching of REE from fluorite, calcite, and dolomite, which are the main ore minerals extracted at Silius, may require a somewhat different strategy [17], due to the risk to have high acid consumption.…”

Towards the Circular Economy of Rare Earth Elements: Lanthanum Leaching from Spent FCC Catalyst by Acids

“…Specifically, the counter-current separation with two immiscible phases, one aqueous containing the rare earths to be separated and the other organic containing the extractant, by using mixer-settler equipment, is an industrial technique used not only for rare earth recycling but also for their industrial production from the minerals. Given the massive environmental impact of hydrometallurgical techniques, numerous studies have been carried out to mitigate them, such as those in which the organic solvent is replaced with an ionic liquid [15][16][17][18][19].…”