Extraction processes with ionic liquids and deep eutectic solvents: emerging trends in rare earth metal recovery

Ionic liquids (ILs) and deep eutectic solvents (DESs) are newly developed, designer solvents that provide a sustainable alternative to conventional processes in various applications. Among these approaches, the extraction and recovery of valuable components appear particularly promising, offering an alternative to traditional volatile and toxic organic solvents. The present review provides an overview of ILs and DESs, focusing on their recent applications in the extraction and recovery of rare earth metals. The review begins with a basic introduction, covering the main sources of water pollution and the importance of treating wastewater. Later, it discusses the importance of rare earth metals and their recovery, considering their limited natural availability and associated environmental and health concerns. Moreover, the review highlights the drawbacks associated with conventional rare earth element (REE) recovery processes and emphasizes the need for alternative methods. Then, it introduces ILs and DESs, followed by an overview of their properties and selected applications in the extraction and recovery of rare earth metals. The review concludes with a discussion of future perspectives in the field. Overall, we hope that this review will provide general readers with a clear and comprehensive understanding of ILs, DESs and their important applications in rare earth extraction. This article is part of the discussion meeting issue 'Ionic liquids and the future of soft materials'.