Solvent Extraction of Europium(III) with 1-Naphthoic Acid into Chloroform in the Absence and Presence of Tetrabutylammonium Ions or Trioctylphosphine Oxide

Abstract

Abstract The solvent extraction of europium(III) in 0.1 mol dm−3 sodium nitrate solutions with 1-naphthoic acid (HA) into chloroform was studied in the absence and presence of tetrabutylammonium ions (tba+) or trioctylphosphine oxide (TOPO). In the absence of tba+ and TOPO the distribution ratio of europium(III) with 0.1 mol dm−3 1-naphthoic acid was higher when the initial concentration of the metal was higher under otherwise identical conditions. This could be explained in terms of the extraction of a polynuclear species, Eu2A6(HA)2, in addition to a mononuclear species, EuA3HA. Furthermore, by the addition of tba+ or TOPO, the extraction of europium(III) was greatly enhanced. This could be explained in terms of the extraction of the ternary complex, EuA4−tba+, or the adducts, EuA3TOPO and EuA3(TOPO)2, like that found in the extraction of this metal ion with β-diketones. In these systems the extracted anionic complex with tba+ or the adducts with TOPO were only mononuclear, even under conditions in which the polynuclear species were extracted in the absence of these.