Malonamides as new extractants

Diamides of carboxylic acids could be an alternative to the mixture (carbamoylphosphonate, TBP) which is used nowadays in the TRUEX process to extract actinides from radioactive wastes. These solvents are economically interesting because they are easy to prepare and to purify. They are completely incinerable and don't create new wastes. First investigations have consisted in selecting the number of carbons between the two functional groups; it appeared that malonamides offer the best possibilities. As they act as chelating agents towards metallic cations steric effects are very important. It has been shown that a dissymetry between substituents has a favourable influence on extractive properties. Mechanisms of extraction have been investigated with dimethyl-dioctyl malonamide (noted as L) in t-butylbenzene. Extraction of metals peculiarly important in the nuclear wastes have been undertaken: U VI, Pu IV, VI and Np V are well extracted. They can be back extracted without chemical transformations (valence changes or complexation). Zr IV follows uranium and plutonium and must be separated by complexation in the aqueous phase