The synergistic extraction by combined ammonium and phosphonium type ionic liquids for rare earth elements separation

A novel synergistic system of combined ammonium and phosphonium type ionic liquids is reported for the first time, which displays pronounced synergistic effect in the extraction of Lu(III). The synergistic enhancement coefficients from different mole fractions of [P66614][EHEHP] and [N1888][BTMPP] were calculated. Extraction mechanism of the combined functionalized ionic liquids for Lu(III) was shown to be ion association. Thermodynamic functions of the synergistic extraction system were obtained. The loaded Lu(III) in the synergistic system could be fully stripped using hydrochloric acid. The novel synergistic extraction provides the possibility of separating heavy lanthanides, which reveals theoretical and practical importance in REEs separation.