Extraction of rare earths by undiluted [P666,14][NO_3] and DEHEHP,and the recovery of rare earths from lamp phosphors

摘要

Ionic liquids (ILs) have been extensively used for separation. However, most of the current reported undiluted IL-based extraction systems still suffer some issues, such as, the heavy loss and a slower extraction kinetic. In this work, the extraction of rare earths (REs) by IL mixture of trihexyl(tetradecyl)phosphonium nitrate ([P666,14][NO3]) and the commercial extractant di(2-ethylhexyl) 2-ethylhexyl phosphonate (DEHEHP), abbreviated as PND, has been investigated. The addition of DEHEHP into IL [P666,14][NO3] not only decreases the viscosity of IL phase, but also produces an obvious synergistic effect. The synergistic enhancement coefficients (R) and the separation factors (alpha(Lu/M)) between Lu(III) and non-REs for PND were compared with the other two systems: [A336][NO3] (tricaprylmethylammonium nitrate)-DEHEHP (AND) and [P666,14][Cl] (trihexyl(tetradecyl)phosphonium chloride)-DEHEHP (PClD). In addition, alpha(Lu/M) of PND has also been compared to the conventional P507-kerosene (2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester). Finally, PND was used to recover REs from the real feeding of fluorescent lamp phosphors and the extraction parameters have been optimized. It can be concluded that the prominent extraction ability of REs and higher alpha(Lu/M) of PND make it to be greatly suitable to recover REs from REs-containing secondary resources, such as the waste fluorescent lamp phosphors.