Solvent Extraction and Isolation Strategies for Uranium, Thorium, and Radium in Rare Earth Element Recovery from Ores: A Review

Review article, 2025

The process of recovering rare earth elements (REEs) from ores and secondary sources are often made difficult by the presence of radioactive elements such as uranium (U), thorium (Th), and their daughters, where radium (Ra) is especially troublesome. Effectively separating these radionuclides from REEs is essential for ensuring environmental safety and producing high-purity REE concentrates. This review thoroughly explores solvent extraction (SX) methods for the selective isolation of U, Th, and Ra during REE recovery, with a focus on Phosphorus, nitrogen, and sulfur-based extractants, as well as macromolecules and synergistic systems. Key extractants like TBP, the Cyanex series, and nitrogen-donor ligands are assessed for their extraction efficiency, selectivity, and environmental impact. The review also points out emerging green alternatives, such as ionic liquids and bio-based methods which offer potential for reducing the ecological footprint of traditional SX systems. Other separation techniques, including solid-phase extraction and cloud point extraction are also discussed for their role in enhancing selectivity and minimizing secondary waste. Challenges, including extractant degradation, third-phase formation, and the necessity for sustainable practices, are addressed. This work provides an overarching and practical approach to the SX processes with a special emphasis on addressing current environmental challenges and evolving regulatory frameworks, making it a valuable resource for both researchers and industry professionals.