The recovery of rare earth by a novel extraction and precipitation strategy using functional ionic liquids

A novel precipitation strategy grounded on [trihexyl(tetradecyl)phosphonium](2)[4,4'-isopropylidenebis (Phenoxyacetate)] (abbreviated as [P-66614](2)[IOPAA]) was put forward for rare earth element (REE) recovery. The H(2)IOPAA and [P-66614](2)[IOPAA] were synthesized and characterized by NMR, IR and elemental analysis. The factors in the precipitation process such as the equilibrium time, pH value of aqueous phase, concentration of salt-out agent and mole amount of IL were investigated. In addition, the precipitation mechanism of [P-66614](2)[IOPAA] for Pr(III) was proposed to be 2pr(aq)(3+) + 6Cl(aq)(-) + 3{[P-66614](2)[IOPAA]}(IL) = 6[P-66614]Cl-IL + Pr-2[IOPAA](3)down arrow. The process was successfully tested for the recovery of REE from simulated leaching solution of Nd-Fe-B scrap. After removing the iron ion with [P-66614]Cl, a high recovery rate (99.85%) of REE was obtained. Without saponification, organic diluent or oxalic acid, the proposed precipitation strategy has revealed the potential to be a sustainable process to the quantitatively recovery REE. (C) 2018 Elsevier B.V. All rights reserved.