Lower-RIM Polyphosphorylated Calix[4]arenes. Their Use as Extracting Agents for Thorium (IV) and Europium (III) Ions

The extraction of thorium (IV) and europium (III) ions from aqueous nitrate media (1 M nitric acid and sodium nitrate) using six p-tert -butylcalix4]arene derivatives bearing phosphine oxide units (--CH 2 P(O)Ph 2 ) anchored at the lower rim has been investigated at 25°;C. All ligands display higher extracting properties toward thorium than europium ions. The number and position on the lower rim of the ligating groups play a crucial role in the extraction process, the highest extraction percentages being in each case achieved with the tetra-phosphorylated calixarene. In the presence of sodium nitrate the extraction percentages are considerably higher than those obtained in the presence of nitric acid.