The synergistic extraction of heavy rare earth elements using EHEHP-type and BTMPP-type functional ionic liquids

As for the supply risk and application in clean energy, heavy rare earth elements (HREEs) are more important than light rare earth elements (LREEs). In this paper, the synergistic extraction based on 2-ethyl(hexyl) phosphate mono-2-ethylhexyl ester and the bis(2,4,4-trimethylpentyl) phosphate acid base coupling of bifunctional ionic liquids (ABC-BILs) for HREEs separation is reported. Extractabilities of the novel systems were better than those using mixed 2-ethyl(hexyl) phosphonic acid mono-2-ethylhexyl ester (HEH[EHP]) and bis(2,4,4-trimethylpentyl) phosphinic acid (HBTMPP). Also, the stripping property of the ABC-BIL based synergistic extraction system for HREE was better than that of mixed HEH[EHP] and HBTMPP. Advantages of the novel synergistic system based on ABC-BILs have revealed potential applications for the HREEs separation industry.