Synergistic Extraction of Lanthanides(III) from Acidic Aqueous Solutions with Mixtures of Bis(Diphenylcarbamoylmethylphosphine Oxide) Ligands and Dinonylnaphtalene Sulfonic Acid

ABSTRACT The extraction of lanthanides(III) from aqueous nitric acid solutions with mixtures of bis(diphenylcarbamoylmethylphosphine oxides) (L) and dinonylnaphthalene sulfonic acid (HDNNS) in organic diluents is studied. It is established that the efficiency of extraction of Ln(III) ions increases significantly when HDNNS is added to the organic phase containing L. The synergistic effect arises due to the higher hydrophobicity of the extractable Ln(III) complexes formed by the L ligand and DNNS− anions compared to those containing NO3 − ions as counteranions. The stoichiometry of the extracted complexes is determined, and the influence of the composition of the aqueous phase, the nature of the organic solvent, and the structure of the bis-CMPO ligands on the efficiency of the extraction of metal ions into the organic phase is considered. The synergistic effect during the extraction of Ln(III) from aqueous nitric acid solutions with mixtures of L and HDNNS weakens with increasing the acidity of the aqueous phase; however, it also holds in acidic media.