The optimization of an ionic liquid-based TALSPEAK-like process for rare earth ions separation

Five new functionalized ionic liquids (FILs), tetraethylammonium di(2-ethylhexyl)phosphate ([N-2222] [DEHPI), tetraethylammonium bis(2,4,4-trimethylpentyl)phosphinite ([N-2222][BTMPPD, tetraethylammonium bis(2,4,4-trimethylpentyl)dithiophosphinite ([N-2222][BTMPDTP]), tetrahexylammonium di(2-ethylhexyl)phosphate ([N-6666][DEHP]), and tetraoctylammonium di(2-ethylhexyl)phosphate ([N-8888][DEHP]) were synthesized and characterized. These ILs along with two previously synthesized FILs ([N-4444][DEHP] and [N-1888][DEHP]) were used as ionic extractants and investigated for rare earth elements (REEs) separation in 1-decyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide/bis(perfluoroethanesulfonyl)imide ([C(10)mim][NTf2]/[BETI]). These FILs as ionic extractants were miscible with [C(10)mim][NTf2]/[BETI]. We herein report the applications of these FILs in an IL-based TALSPEAK-like process and the optimization of the process by adjusting the cations and anions of the FILs, concentrations of the FILs as ionic extractants in the IL phase, concentrations of diethylenetriamine pentaacetic acid (DTPA) in the aqueous phase, and acidities of the aqueous phase. (C) 2013 Elsevier B.V. All rights reserved.