Selective extraction of scandium from yttrium and lanthanides with amic acid-type extractant containing alkylamide and glycine moieties

Abstract

The liquid–liquid extraction of rare earth metal ions (scandium (Sc³⁺), yttrium (Y³⁺) and the lanthanides (La³⁺, Nd³⁺, Eu³⁺ and Dy³⁺)) was investigated using N-[N,N-di(2-ethylhexyl)aminocarbonylmethyl]glycine (D2EHAG). Scandium was extracted selectively from lanthanides under highly acidic conditions (0 < pH ≤ 1.5), and stripped easily using a mild acidic solution such as 1 mol dm⁻³ H₂SO₄. By comparing the extraction behavior with N,N-dioctyldiglycol amic acid, which has a similar molecular structure to D2EHAG, or the commercial alkyl monocarboxylic acid extractant, Versatic 10, it was concluded that the affinity of D2EHAG to scandium was caused by a chelating effect and the size recognition ability of D2EHAG. The extraction mechanism was examined, and it was proven that the trivalent scandium ion is extracted by forming a stable metal complex with four D2EHAG molecules.