Extraction Behavior of Metal-Thiocyanato Complexes into Third Phase Formed in an Ionic Liquid Extraction System Using Trioctylphosphine Oxide

抄録

In 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (C₄mimTf₂N)–water biphasic extraction system, a tiny volume of third phase is formed under existing trioctylphosphine oxide (TOPO). To study possible use of the third phase as extraction concentration media, extraction behavior of several metal-thiocyanato complexes into the third phase was investigated. Fe(III) and Ga(III) complexes were quantitatively extracted into the third phase, and Co(II) and Cu(II) complexes were extracted to some extent. The extracted ternary complex species were indirectly estimated using 1-octyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (C₈mimTf₂N)–water biphasic system forming no third phase, and it was suggested that un- or smaller-charged complexes with high hydrophobicity have superiority for extraction into the third phase.