Thermodynamic Data of Separating Yttrium from Heavy Rare Earths via a Phenoxypropionate-Based Ionic Liquid

Ion-adsorbed rare-earth minerals often contain high proportions of yttrium; it is a technical challenge to separate yttrium from rare-earth elements (REEs). For the purpose of separating yttrium effectively, a novel ionic liquid [trioctylmethylammonium][(2,6-dimethylheptyl propionate] ([N1888][POPA]) was prepared to separate Y from heavy rare-earth elements (HREEs). The thermodynamic data of the separation process was studied systematically. The extraction mechanism of [N1888][POPA] was demonstrated to be ion association, which conduces to avoid the saponification wastewater. [N1888][POPA] revealed better selectivities for Y and other HREEs (Ho–Lu); also, deionized water could be utilized for stripping the HREE-loaded organic phase. On this basis, the fractional extraction process based on [N1888][POPA] was carried out. This extraction system showed satisfying performance as shown by the fractional extraction, i.e., Y was purified from 85.2 to 99.1 wt % accompanying 85.37% yield by means of nine extraction stages and six scrubbing stages. The developed extraction process has shown application potential in the field of clean production of ion-adsorbed rare-earth minerals.