Extraction of some metal cations from nitric acid solution by N,N'-substituted malonamides

The extraction of Am(III), Cm(III) and some trivalent lanthanides by two newly synthesised malonamides; N,N'-dimethyl-diphenyltetradecyl malonamide (DMDPHTD) and N,N'-dimethyl- dicyclohexyltetradecyl malonamide (DMDCHTD) has been investigated. A comparison of the extraction data for these malonamides for U(VI), Th(IV) and some trivalent lanthanide elements by N,N'-dimethyl-dibutyloctadecyl malonamide (DMDBOD) was also performed. The dependence on nitric acid concentration, diamide concentration and molecular structure of the extraction from nitric acid solution has been considered. It is possible that for nitric acid solutions (0. 1M to 1M), a coordinative mechanism dominates for the extraction of metal cations but at higher acid concentrations an ion-pair mechanism involving the mono- or diprotonated diamide and a metal nitrate anion appears to be more important. (authors)