Conférence examinatrice externe Prof. Gisele Azimi (University of Toronto)

Titre: Advancing Green Chemistry in Rare Earth Extraction: A Study on Supercritical Fluid Extraction of Rare Earths from Ore Concentrate and Electronic Waste

Dr. Gisele Azimi

Canada Research chair in Urban Mining Innovations

Chemical Engineering and Applied Chemistry Department

University of Toronto

There is a significant global push towards recycling of waste electrical and electronic equipment (WEEE) to enable the circular economy. Conventional recycling processes rely on pyrometallurgy or hydrometallurgy. Pyrometallurgical recycling typically requires high energy consumption and reaction temperature and generates greenhouse gas emissions. Hydrometallurgical processes also face the drawback of being reagent intensive, often requiring the large consumption of strong acids and organic solvents as well as the production of secondary streams of potentially hazardous wastes. An emerging green separation technology is supercritical fluid extraction (SCFE) that can recycle secondary resources at a low cost, with low energy consumption and high recovery efficiency. Supercritical fluids are desirable for extraction processes because of their combination of gas-like and liquid-like properties, tuneable properties, and simple separation by phase transformation. Among supercritical fluids, supercritical carbon dioxide (sc-CO₂) has shown promising results for the extraction of rare earth elements (REEs) from synthetic feeds and as well as secondary feeds. In comparison with hydrometallurgical processes, SCFE does not generate hazardous wastewater and acid fumes. The CO₂ solvent can be easily separated from products through depressurization and recycled back to the process. In this talk, the application of sc-CO₂ for the recovery of REEs and battery materials from ores and electronic wastes such as magnets and lithium-ion batteries will be presented.