Formation of Minimal Third Phase in Ionic Liquid Extraction System with Trioctylphosphine Oxide and Its Possible Application to Extraction Concentration

摘要

The third-phase formation behavior in ionic liquid (IL) extraction system using trioctylphosphine oxide (TOPO) was investigated. In the use of a relatively less-lipophilic IL, such as 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (C_(4)mimTf_(2)N), the third phase was formed between the aqueous phase and the IL phase. The third phase seems to have a relatively high lipophilicity compared to the IL phase. The main components of the third phase were suggested as being (H_(3)O)TOPO~(+), IL anion (Tf_(2)N~(?)), IL cation (C_(4)mim~(+)) and free TOPO. In addition, the third phase showed an extraction concentration ability for the Fe(III)-thiocyanato complex.