Temperature Dependent Solid-Liquid Extraction Behavior of Rare Earths Using N-Butyl Pyridinium Hexafluorophosphate with Benzoyl Acetone

Temperature dependent solid-liquid extraction (SLE) behavior of six rare earth elements (REs) was investigated using N-butyl pyridinium hexafluorophosphate ([BPy]PF 6 ) as an ionic liquid solvent and benzoyl acetone (HA) as an extractant at 80 °C. Parameters including the amount of [BPy]PF 6 , HA concentration, extraction time, extraction temperature and pH were investigated and optimized. The extracted species was neutral REA ( n -1) Cl ( n- 1 = 3 or 2) in the RE n + -[BPy]PF 6 -HA SLE system. The extraction percentage of RE n + could be 100% at stated pH and HA concentration. The recovery of RE n + extracted into [BPy]PF 6 can be achieved using the mixture of 0.1 mol·L -1 ClCH 2 CO 2 H and 0.2 mol·L -1 HCl as stripping agents. REs were extracted into solid ionic liquid phase with smaller volume and concentrated to some extent. Furthermore the temperature dependent SLE allows to recover [BPy]PF 6 after the extraction procedures. These results indicate that the proposed procedure can be used for the preconcentration and separation of REs using [BPy]PF 6 with high melting point.