Advances in metal recovery from e-waste: Green solvent assessments with ionic liquids and deep eutectic solvents

The rising volume of electronic waste (e-waste) presents both environmental and resource sustainability challenges. Global e-waste production is estimated to reach 82 million tons by 2030. Untreated e-waste results in hazardous emissions and the loss of valuable metal resources. In contrast, e-waste recovery offers twin benefits of mitigating environmental hazards and enabling sustainable resource utilization. Conventional technologies such as hydrometallurgy, pyrometallurgy, biohydrometallurgy, and pyrolysis can be enhanced by green solvents such as ionic liquids (ILs) and deep eutectic solvents (DESs). These solvents provide favorable properties, including non-volatility, recyclability, and excellent thermal stability. DESs offer additional advantages of biodegradability, low toxicity, and affordability. This review covers the recent advancements in the utilization of ILs and DESs in metal extraction from e-waste. Assessments of ILs and DESs revealed high recoveries of critical metals, with recoveries of up to 100 % for Li, 99.6 % for Co, and over 95 % for Cu, Ni, and Au, under optimized conditions. However, challenges are in the recyclability and stability of ILs and DESs. Consequently, future research directions include pilot-scale validation, techno-economic assessments, and life-cycle analyses. Additionally, process integration and intensification are crucial for enhancing metal recovery from e-waste using these environmentally friendly solvents. These findings provide a basis for advancing green solvent-based metal recovery technologies.