The extraction of microquantities of U, Th, Sc, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y from HNO3 solutions by bifunctional neutral organophosphorus compounds R2P(O)CH2P(O)Ph(OBu), R = Ph (II), R = Oct (IV), R = p‐Tol (V), R = p‐CH3OC6H4 (VI) in organic diluents has been studied. The effect of HNO3 concentration in the aqueous phase and that of the extractant concentration in the organic phase on the extraction of metal ions is considered. The stoichiometry of the extracted complexes has been determined and the extraction constants calculated. The replacement of phenyl radicals in the Ph2P(O)CH2‐fragment of compound II by p‐tolyl or p‐methoxy‐phenyl ones leads to an increase of metal ions extraction. The introduction of octyl substituents at the same part of molecule II instead of phenyl ones favors the extraction of Th(IV), Sc(III), and heavier Ln(III) ions. However, the extraction of La–Eu from HNO3 solutions decreases when octyl‐substituted compound IV is used as an extractant. All effects of substituent replacements were studied with 1,2‐dichloroethane as diluent. The extractive efficiency of compounds II, IV, V, and VI is compared with that of tetraphenylmethylene‐diphosphine dioxide (I) and dibutyl(diphenylphosphinylmethyl)phosphonate (III).
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