Аннотация:The extraction of U(VI), Th(IV), Am(III), and lanthanide(III) ions and HNO3 from nitric acid solutions with 1,2-dichloroethane solutions of 3-oxapentane-1,5-diylbis(diphenylphosphine)dioxide and its structural analogues was studied. The stoichiometry of the extractable complexes was determined. The effects of the extractant structure and HNO3 concentration in the aqueous phase on the efficiency of the metal ions extraction into the organic phase were considered. The successive replacement of two methylene groups connecting the ether oxygen atom with Ph2P(O) groups in the podand molecule by o-phenylene groups leads to an increase in the efficiency of Th(IV) Am(III), and Ln(III) extraction from nitric acid solutions, but has little effect on the efficiency of U(VI) extraction.