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Extraction of U(VI) by functionalised calix[6]arenes

B. Boulet, C. Bouvier-Capely, C. Cossonnet and G. Cote, Atalante 2004, 21-25/06/2004, Nîmes(France).

Document type > *Congrès/colloque

Keywords >

Research Unit > IRSN/DRPH/SDI/LRC

Authors > BOUVIER-CAPELY Céline, COSSONNET Catherine

Publication Date > 21/06/2004


 This paper is focused on the solvent-extraction of U(VI) traces from weakly acidic media (3<pH<6) by functionalised calix[6]arenes. Calixarenes can selectively extract actinides depending on the size of their cavity, the functionalisation of their groups, their lipophilic or hydrophilic property and the geometry of their conformation.

A rapid review of the extraction of U(VI) by various types of functionalised calixarenes is presented. For example, the hexapseudoplanar conformation given by the calix[6]arene is the most suitable conformation for a selective extraction of the uranyl ion. Indeed, U(VI) has a higher affinity for the p-tert-butyl-calix[6]arene bearing six hydroxamic groups rather than for the one bearing six carboxylic groups and the extraction of U(VI) is more selective with a calix[6]arene bearing groups arranged in a C3 symmetry. From these literature data and from results obtained with the {1,3,5-O-trimethyl-2,4,6-tri-O-carboxylic acid p-tert-butyl-calix[6]arene} as an uranophile extractant, it is concluded that the {1,3,5-O-trimethyl-2,4,6-tri-O-hydroxamic acid p-tert-butyl-calix[6]arene} could be a powerful extractant of U(VI). In addition, it has been shown that U(VI) is not reduced by aceto and formo hydroxamic acids (AHA and FHA) in acidic media.

Then, a series of experimental results about the extraction of U(VI) by the {1,3,5-O-trimethyl-2,4,6-tri-O-hydroxamic acid p-tert-butyl-calix[6]arene} are presented. In particular, the effect of pH on the extraction of U(VI) is reported. The obtained results show that this ligand efficiently extracts U(VI) (10-9M) from NaNO3 (4.10-2M) at pH 5, and the stripping can be achieved in nitric acid solutions.

A comparison with the solvent-extraction results obtained with the {1,3,5-O-trimethyl-2,4,6-tri-O-carboxylic acid p-tert-butyl-calix[6]arene} and with the {1,3,5-O-trimethyl-2,4,6-tri-O-hydroxamic acid p-tert-butyl-calix[6]arene} shows that the hydroxamate function is a promising functional group to obtain an efficient calixarene-based uranophile extractant. 


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