Deep eutectic solvents for separation and purification applications in critical metals metallurgy: Recent Advances and Perspectives

As a separation and purification technology, solvent extraction is crucial in the field of critical metals metallurgy. At present, organic solvents mostly utilized in solvent extraction have the disadvantages of high volatility, high toxicity, and flammability, causing a spectrum of hazards for human health and environmental protection. Neoteric solvents are being recognized as preferable alternatives to these harmful organic solvents. In the past two decades, several neoteric solvents have been proposed involving ionic liquids (ILs) and deep eutectic solvents (DESs). DESs have gradually become the focus of green solvents owing to several advantages including low toxicity, degradability, and low cost. In this critical review, a systematic description on their classification, formation mechanisms, preparation methods, characterization technologies, and special physicochemical properties based on the most recent advancements in research. Afterwards, the major separation and purification applications of DESs in critical metals metallurgy and other fields were comprehensively summarized. Finally, the future opportunities and challenges about DESs were prospected in the current area of research. In conclusion, this review provides valuable insights for improving our overall understanding of deep eutectic solvents, and it has important significance for expanding separation and purification applications in critical metals metallurgy.