Process intensification in metal recovery from solid waste: Challenges, opportunities and recent advances

The increasing production of electric and electronic devices corresponds to the significant increase of e-waste. These solid wastes contain a great amount of metals, thus representing a secondary source of precious elements, within a circular economy context. The recovery of metals from waste thus provides a great opportunity to decrease the energy consumption and the environmental impact associated with the typical processes for metal extraction. Along with the conventional recovery methods (i.e., pyrometallurgy and hydrometallurgy), some emerging technologies are being developed with a particular emphasis on the process intensification (PI). Greener leaching agents, lower temperatures and the combination of different approaches are the most reported methods to obtain a more sustainable metal recovery. In this perspective article, the recent advances in metal recovery technologies are critically reviewed, focusing the attention PI strategies adopted to improve the recovery efficiency and reduce the environmental impact of the whole process. Some tolls, such as the design of experiments (DoE), life cycle assessment (LCA), and machine learning are proposed to address the challenges and improve the dissemination of innovative solutions.