The binding properties of [1 n ]metacyclophanebased cation exchangers (n ϭ 5, 6, 7) towards trivalent lanthanides and americium were investigated by means of solvent extraction from water to chloroform and xylene. Extraction constants for four ligands were calculated for Ln(III) and Am(III). Three of the ligands lack Bu t groups in 4-position, giving them higher molecular flexibility compared with the corresponding t-butylcalixarenes. Due to this reason, changing the cavity size lead to small changes in metal extractabilities compared with series of Bu t analogue, while the metal extractabilities themselves are very high. The order of extractability, being Am 3ϩ Ͼ Nd 3ϩ Ͼ Eu 3ϩ Ͼ Tb 3ϩ Ͼ Dy 3ϩ Ͼ Er 3ϩ Ͼ Yb 3ϩ is not influenced by the molecular structure. In the series of tbutylcalix[n]arenes (n ϭ 4Ϫ7) the extraction of Am(III) improves with n, the improvement is significantly higher for CHCl 3 than for xylene as diluent. The crystal structure of one of these ligands (n ϭ 7) shows a distorted cone conformation. Dimerization in the crystal occurs due to the formation of 8 intermolecular and 4 intramolecular hydrogen bonds, two dimers form a cavity which contains 10 molecules of CDCl 3 .

No abstract

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 β-diketonates with trioctylphosphine oxide (TOPO) in synergistic extraction systems.

No abstract

Bringing social and cultural considerations into environmental management for vulnerable coastal communities: responses to environmental change in