Effect of Chemical Properties of Ligand on the Solvent Extraction of Cobalt ( II ) with Several β-Diketones and Tetrabutylammonium Ions as Ternary Complexes

Abstract

The effect of tetrabutylammonium ion(TBA⁺) on the solvent extraction of cobalt (II)in aqueous 1 mol/dm³ sodium chloride solution with 5 different β-diketones (HA) was studied. The effect was found to be negligible on the extraction with acetylacetone and benzoylacetone while the addition of this bulky cation increased that with trifluoroacetylacetone and benzoyltrifluoroacetone. It also increased the extraction with hexafluoroacetylacetone more than that with these two β-diketones having one trifluoromethyl group. The increase was concluded to be due to an extraction of the CoA₃^-TBA⁺ species in addition to that of the uncharged CoA₂ species. The chemical equilibria of the extractions of these binary and ternary complexes were analyzed and the relation between the chemical properties of the β-diketone and the stability as well as the extractability of the ternary complex was considered.