A review of the application of deep eutectic solvents for metal recovery from diverse secondary sources

In recent years, the growing demand for critical, strategic, and precious metals across various industries has led to a worldwide shortage. The increasing disposal of metal-containing waste poses significant environmental and health risks while also accelerating the depletion of natural resources. Given the supply risks, environmental hazards, and challenges associated with extracting these metals from primary ores, it is vital to develop sustainable methods for recovering them from secondary sources. Metal recovery has garnered research interest due to its essential role in promoting a circular economy. Metallurgical processes, such as pyrometallurgy, bioleaching, and hydrometallurgy, often lead to secondary pollution and economic challenges. Methods based on solvometallurgy and green chemistry, such as the use of deep eutectic solvents (DESs), offer potential for separating metals from waste. DESs provide a sustainable approach for selective recovery, potentially replacing mineral acids while minimizing wastewater production. This paper provides a literature survey on the extraction of metals from sources including electrical and industrial waste, minerals, biological materials, and environmental samples using DESs. It discusses concepts, specifications, and characterization methods related to DESs. Additionally, the article classifies the techniques used for metal separation and recovery with DESs, along with key parameters that influence efficiency. The review emphasizes the selective and high-efficiency recovery of various metals using DESs. It highlights the necessity of designing DESs with low viscosity, strong coordination, and high reducibility for optimal separation. We hope that the challenges and opportunities for advancing metal recovery through DESs are clearly outlined, providing a roadmap for new applications of DES technology. • Deep eutectic solvents recover metals from electronic, industrial, and mineral waste. • Review covers extraction from batteries, magnets, solar panels, and biological sources. • Key solvent properties drive efficient and selective metal recovery. • Eco-friendly solvents reduce wastewater and replace harmful mineral acids. • Guidance provided for designing deep eutectic solvents for sustainability