New macrocyclic extractants for the processing of inorganic waste

The solvent extraction properties of 6 newly synthesized macrocycles and 3 reference compounds towards trivalent lanthanides and Am were investigated in order to determine the influence of structural characteristics such as the cavity size, hydrophobicity, the conformational freedom and the number of ligating groups. Eight of extractants are calix[n]arenes with a [1n] metacyclophane backbone and one is an rigid [1.0.1.0.1.0.1.]metacyclophane. They are bearing carboxylic acid and amide as ligating groups. The extracted metal ions include Am3+ and trivalent lanthanides. We observed an enhancement in extractability of Am3+ by the rigid cyclophane due to K+ co-extraction, an effect previously found for the system Na+/calix[4]arene only. A calix[4]arene with an alkylamide group can extract Am3+ from solutions of high acidity and ionic strength, in addition to extraction from weakly acidic solutions. (author)