The availability of metals and rare earth elements is very important for our national security and economic growth since they are widely used in defense and energy applications including batteries and wind turbines as well as consumer electronics. Unfortunately, high grade ores have become scarce and their productions is dominated by only a few countries. Thus, there is a strong need to obtain these materials from domestic sources. Electronic wastes (e-wastes) are great candidates since they often contain significantly higher concentrations of metals even compared to high grade ores. Since the metals in e-wastes are not in the form found in natural ores and contain a wide range of impurities, conventional extraction and separation processes would not be effective. Thus, this study investigated the development of a greener solvent and innovative ligand design to enhance the extraction of various elements from complex feedstock (e.g., e-wastes, iron and steel slags and waste-to-energy plant ashes) and to separate target elements from high concentration of competing ions. A new hydrometallurgical system has been designed with supercritical CO2, and we have synthesized and studied the affinity of multidentate small molecule ligands for the separation of rare earth elements (e.g., cerium) from the other components found in the leachate. The target specific ligands are designed <i>in silico</i> before synthesis to confirm that the small molecule cerium complexes possess typical bond distances and angles. The synthesized ligands are incorporated into structured scaffolds to further improve the separation factors. This study has shown that innovative materials design and systems engineering can allow effective separations of different elements from complex feedstock while minimizing the environmental impacts.

CO<sub>2</sub>-facilitated hydrometallurgy and structured ligand chemistry for sustainable extraction and separation of critical elements from complex resources

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.

CO2-facilitated hydrometallurgy and structured ligand chemistry for sustainable extraction and separation of critical elements from complex resources

CO₂-facilitated hydrometallurgy and structured ligand chemistry for sustainable extraction and separation of critical elements from complex resources