Solvent Extraction of Neodymium(III) by Functionalized Ionic Liquid Trioctylmethylammonium Dioctyl Diglycolamate in Fluorine-free Ionic Liquid Diluent

The extraction behavior of neodymium and other rare earths from nitric acid media by the functionalized ionic liquid trioctylmethylammonium dioctyl diglycolamate, [A336][DGA], was investigated. The nonfluorinated ionic liquid trioctylmethylammonium nitrate, [A336][NO3], was used as diluent. The extraction behavior of neodymium(III) in this ionic liquid solution was carried out as a function of various parameters such as the pH, concentration of the extractant, type of acidic media, temperature, concentration of salting-out agent, and concentration of the aqueous feed. The extraction behavior of [A336][DGA] in [A336][NO3] was compared with that of [A336][DGA] in the chloride-containing ionic liquid diluent [A336][Cl] (Aliquat 336). The distribution ratios obtained in [A336][DGA] were compared with those observed in molecular extractant N,N-dioctyl diglycol amic acid (HDGA), from which the anion of the ionic liquid extractant was prepared. The distribution ratio for extraction of neodymium(III) by [A336][DGA] in [A336][NO3] was higher than that for extraction by HDGA in [A336][NO3], at pH values >2. The effects of thermodynamic parameters, the stripping of neodymium(III) from the ionic liquid, and the reusability of the functionalized ionic liquid were studied in detail. The general applicability of the extraction system was illustrated by the extraction of lanthanide(III) ions other than neodymium(III).