Extraction of Rare Earth Metals: The New Thermodynamic Considerations Toward Process Hydrometallurgy

Successful management of secondary waste resources is essential for the viable circular economy. E-waste could serve as the potential urban mining source for the alternative supply chain of critical metals such as rare earth elements (REEs). The hydrometallurgical processes for REEs aremainly designed for primary mining. Conventional approaches lack sustainability and the economic- and value chainbased aspects that are significant in the current era with its increasing focus and pressure to reduce environmental impact.We have performed thermodynamic calculations to simulate the solution chemistry behaviour of REEs, such as Neodymium (Nd), Dysprosium (Dy), and Praseodymium (Pr) present in NdFeB magnets. The results suggested that one could exploit the different solubility of these REE hydroxides by controlling the pH value and separating the REEs further using extractive processes. In contrast to primary mining, the use of appropriate wet chemistry, extractive conditions with selective ligands and supported liquid membrane methods with secondary (urban) mining could open up more sustainable and economic recycling of rare earth magnets with reduced environmental impact and direct scalability.