Coprecipitation of Neptunium(IV) and Plutonium(IV) with Hydrolyzed Iron(III) in Carbonate Solutions

In regeneration of Np(IV)- and Pu(IV)-containing recycled solvent by treatment with aqueous sodium carbonate contaminated with iron, some portion of Np(IV) and Pu(IV) coprecipitates with hydrolyzed iron. The degree of coprecipitation of Np and Pu depends on both the iron and sodium carbonate concentrations. The presence of n-dibutyl hydrogen phosphate in the recycled solvent before its regeneration does not noticeably affect the coprecipitation of Np and Pu. The possible mechanisms of coprecipitation of actinides with hydrolyzed iron in carbonate solutions are discussed.