Direct Temperature-Swing Extraction of Rare-Earth Elements from Acidic Solution Using the Hydrophobic Interactions of Poly(N-isopropylacrylamide) with Diglycolamide-typed Ligands

Abstract

The phase transition-based gelification phenomenon of poly(N-isopropylacrylamide) [poly(NIPAAm)] has great potential in developing new waste-free extraction processes. In this study, we realized the direct and complete temperature-swing extraction of all trivalent rare-earth (RE) ions from a multi-component nitric acid solution onto a poly(NIPAAm) gel as chelate complexes with hydrophobic diglycolamide-typed ligands. Moreover, we elucidated that the extractabilities are affected by not only the coordination ability of the ligands with RE ions but also by the hydrophobic interaction between the poly(NIPAAm) and the ligands.