Solvent Extraction of U(VI) by Calix[6]arenes

This paper focuses on the solvent extraction of U(VI) traces by 1,3,5‐OMe‐2,4,6‐OCH2CONHOH‐p‐tert‐butylcalix[6]arene (LH3). The global extraction equation of U(VI) has been established. The complex formed in the organic phase is (UO2)(LH) with an apparent extraction constant equal to 7.1×10−5 M (I=0.04 M). Distribution data show that LH3 efficiently extracts U(VI) from NaNO3 media at pH 5 and that the stripping of U(VI) can be achieved in nitric acid solutions. Finally a comparison with previous results obtained with the 1,3,5‐OMe‐2,4,6‐OCH2COOH‐p‐tert‐butylcalix[6]arene (L′H3) shows that the hydroxamate groups are as efficient as the carboxylate ones for uranyl extraction.