Achieve a High-Selective Rare-Earth Elements Separation in Neutral-pH All-Aqueous System

Rare earth elements (REE) are strategic resources with their distinctive and versatile electronic properties and have been deeply involved in the development of modern technology. However, achieving a highly efficient rare earth elements (REE) separation remains challenging due to the chemical similarity among lanthanide elements. Nowadays most works focus on ligand design to optimize the separation. While the achieved good selectivity validates the efficacy of this approach, the relatively strong interaction between lanthanide ions (Ln³⁺) and ligands within the first coordination shell necessitates the use of acid for ligand regeneration. Here we report a new separation method by utilizing the confinement in the hydrated layered oxide. Our experiments and calculation show that the accommodated lanthanide ions in the hydrated layers keep their intact first hydration shell, which allows fast diffusion kinetics. Meanwhile, the layered framework exhibits two different structural responses (mixing and de-mixing) to leaching ions depending on the layer structural difference. Combining the fast exchange kinetics and mechanical squeezing effect, a two-step exchange method has been developed to achieve high-selective rare-earth element separation. Starting from neodymium (Nd) / dysprosium (Dy) mixed solution, 99.9% purity of Nd with a yield of over 80% can be achieved. This work highlights the possibility of green and sustainable REE separation in aqueous system.