Abstract: The invention relates to a process for the selective extraction of (III) actinides by means of amides having a nitrogenous heterocyclic substituent of formula: ##STR1## in which R.sup.1 is an alkyl or alkoxy group or a hydrogen atom, R.sup.2 and R.sup.3, which can be the same or different, represent a hydrogen atom, an alkyl or an alkoxy group and R.sup.4 is a hydrogen atom or a group of formula: ##STR2## in which R.sup.5 and R.sup.6, which can be the same or different, represent a hydrogen atom or an alkyl or alkoxy group. This process makes it possible to separate (III) actinides from (III) lanthanides.

Abstract: The invention relates to a process for separating iron and/or zirconium from the actinides and/or lanthanides present in an aqueous acid solution by means of a propane diamide.According to the invention, use is made of a pentasubstituted propane diamide of formula: ##STR1## in which R.sup.1, R.sup.2 and R.sup.3, which can be the same or different, are alkyl radicals, which can have 1 or 2 oxygen atoms in their chain.To maintain the iron in aqueous solution, a choice is made of an appropriate propane diamide of formula (I) with R.sup.3 representing a C.sub.12 to C.sub.25 alkyl in order to have different extraction kinetics between Fe and the actinides or lanthanides, or an additive is added to the aqueous solution, e.g. oxalic acid or sodium nitrate.