Effect of Phosphonium Ionic Liquids on the Extraction of Rare-Earth Elements(III) with 2,2′-Oxybis(N,N-dioctylacetamide) from Nitric Acid Solutions

New phosphonium ionic liquids, alkyldiphenylethylphosphonium bis[(trifluoromethyl)sulfonyl]imides (Alk = C 4 H 9 , C 8 H 17 , and C 12 H 25 ) have been synthesized. The effect of the obtained ionic liquids on the extraction of rare-earth elements(III) ions from nitric acid solutions of 2,2′-oxybis( N , N- dioctylacetamide) in 1,2-dichloroethane has been studied. The stoichiometry of the extracted complexes has been determined, and the effect of the size of alkyl substituents in the ionic liquid molecule and the concentration of HNO 3 in the aqueous phase on the efficiency of extraction of metal ions into the organic phase has been considered. The efficiency and selectivity of the extraction of ions of rare-earth elements(III) is significantly increased in the presence of a ionic liquid in the organic phase.