Investigation of intermolecular interactions of mixed extractants of quaternary phosphonium or ammonium chlorides and bis(2,4,4-ethylhexyl)phosphoric acid for metal separation

Abstract

Mixed extractants composed of di(2-ethylhexyl)phosphoric acid (P204) and ionic liquids (trihexyl(tetradecyl)phosphonium chloride (IL101) or methyltrioctylammonium chloride (A336)) for Zn(II)/Cu(II) separation were investigated. An antagonistic effect can be found for the extraction of both zinc and copper when mixing ionic liquids with P204, especially for Cu(II), thus the Zn(II)/Cu(II) separation can be greatly improved by adjusting the kinds and mole fractions of ionic liquids in the mixed extractants. Attenuated total reflection infrared (ATR-IR) and nuclear magnetic resonance (NMR) spectroscopies elucidate that the diverse intermolecular interactions between P204 and ionic liquids can be tailored by changing their compositions. Two-dimensional correlation analysis on IR spectra further extracts the overlapped structural information of the mixed extractants. And the dependence of metal extraction on intermolecular interactions has been elucidated.