Hexacarboxylate derivatives of p-t-butylcalixarene (2b) and p-hexylcalixarene (3b) extract uranyl ion (UO 22+) efficiently and selectively from water into organic media. This high selectivity can be attributed to the nature of calixarene; this is suitably structured for the binding of UO 22+, which requires a pseudo-planar hexaco-ordination. When trioctylmethylammonium cation (TMA+) is added to the organic phase, the stoicheiometry of the extraction species [UO 22+/(2b)] changes from 1:3 to 1:1-2. This implies that an additional 1-2 mol of UO 22+ are adsorbed to (2b) to form ‘neutral’ extraction species and can be displaced by added TMA+. UO 22+ is transported by (2b) across a liquid membrane from a neutral IN (source) aqueous phase (pH 8.5) to an acidic OUT (receiving) aqueous phase (0.1 mol dm-3 HCl) in an active transport manner. The rate-determining step is the release of UO 22+ from the membrane to the OUT aqueous phase. On the basis of these basic data, we have prepared polymer/liquid-crystal (N-4′-ethoxybenzylidene-4-butylaniline, EBBA/TMA+Cl−) composite membranes immobilising (2b) and have found that the rate of UO 22+ transport is efficiently controlled by the changes in pH and temperature. These are novel examples for the selective transport of UO 22+.
|Number of pages||5|
|Journal||Journal of the Chemical Society, Perkin Transactions 2|
|Publication status||Published - Jan 1 1989|
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