Solvent Extraction of Lanthanoids(III) with N-Alkylcarbonyl-Substituted N-Phenylhydroxylamines

Abstract

Several N-alkylcarbonyl-substituted N-phenylhydroxylamines (R-PHAs) were synthesized for use in lanthanoids(III) extraction. They were N-octanoyl-, N-(3,5,5-trimethylhexanoyl)-, N-(4-butylcyclohexanoyl)-, N-(4-butylbenzoyl)-, N-(2-propylpentanoyl)-, and N-(2-hexyldecanoyl)-N-phenylhydroxylamines. The distribution ratio of a lanthanoid(III) ion between the carbon tetrachloride and aqueous phases was examined as functions of the pH and R-PHA concentration at 298 K and the ionic strength, 0.1 (NaNO₃). Sodium tartrate (1×l0⁻²mol dm⁻³) was present in the aqueous phase. Lanthanoids(III) were extracted as a self-adducted chelate, ML₃(HL)₂, with all the R-PHAs used. The conditional extraction constants and the separation factors of lanthanoids(III) with R-PHAs were evaluated. Among the R-PHAs, N-(2-hexyldecanoyl)-N-phenylhydroxylamine was most promising for the separation of heavy lanthanoids(III). Appropriate branching at the α-position of the carbonyl group seemed to transmit the R-PHAs different chemical properties with respect to the straight chain R-PHAs.