Deep eutectic solvents and ionic liquids in hydrometallurgical recovery of metals - A review of recent advances and challenges

This review focuses on the hydrometallurgical recovery of metals via deep eutectic solvents (DESs) and ionic liquids (ILs), which are well known for their low toxicity, cost-effectiveness, and eco-friendliness, offering a promising route for sustainable metal extraction through leaching and solvent extraction (SX) processes. The focus is on assessing the efficacy of novel leaching liquids to produce leachates and the use of these unconventional solvents as extractants and diluents in the SX process for metal extraction. This review summarizes and discusses the characteristics of the ILs and DESs used for metal recovery, including their original introduction, synthesis, and classification. The DESs and ILs can be used as lixiviants for metal leaching and have significant potential to replace mineral acids. The selective and efficient leaching of metals from minerals or wastes has been proven in many experimental studies and is surveyed in this review. Solvometallurgy is a new branch of hydrometallurgy that uses DESs and ILs for leaching and SX of metals, and several studies in which both of these solvents are used as mixtures for the recovery and extraction of metals are also included in this review. Furthermore, IL-based and DES-assisted SX processes are discussed in detail, demonstrating that they are a credible alternative to traditional chemical solvents. This review also aims to explore the benefits, challenges, and environmental consequences of using DESs and ILs.