SOLVENT-EXTRACTION OF SEVERAL DIVALENT METAL-IONS WITH BENZOYLTRIFLUOROACETONE AND 2-THENOYLTRIFLUOROACETONE INTO CHLOROFORM IN THE PRESENCE OF TETRABUTYLAMMONIUM IONS

The solvent extractions of manganese(II), iron(II), cobalt(II), nickel(II), copper(II), zinc(II), and cadmium(II) (M2+) in 0.1 mol dm-3 sodium nitrate solutions with benzoyltrifluoroacetone and 2-thenoyltrifluoroacetone (HA) into chloroform were studied in the absence and presence of tetrabutylammonium ions (tba+). The addition of tba+ enhanced the extraction, except that of copper(II). This enhancement could be explained in terms of the extraction of the ternary complex, MA3-tba+, in addition to the neutral complex, MA2. The data were treated on the basis of the formation equilibrium of the ternary complex from the neutral complex, MA2, with the extracted ion-pairs of the reagents, A-tba+, in the organic phase. It was concluded that the association constants of MnA2, FeA2, CoA2, NiA2, and CdA2 with the ion-pair, A-tba+, are not very much different from each other. However, that of ZnA2 is lower than those of the five divalent metal complexes. This trend is similar to that found among the adduct metal complexes of beta-diketonates with trioctylphosphine oxide (TOPO) in synergistic extraction systems.