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The extraction of europium­(III), dysprosium­(III), and gadolinium­(III) nitrates with di-(2-ethylhexyl) phosphoric acid (D2EHPA) in o-xylene was investigated at 298.15 K. Spectrophotometry and ICP-AES techniques were used for rare earth elements (REE) content determination. The content of nitric acid was measured by acid–base titration. The density of the equilibrium phases was determined. In the case of high content of rare earth element nitrates in the initial aqueous solutions, the third solid phase formation was observed during extraction experiments.

Densities of ternary solutions in the lanthanide di(2ethylhexyl)phosphate (LnA 3 , Ln = Nd, Sm, Eu, Gd, Tb, Dy)−D2EHPA−oxylene systems were measured by the vibrating tube densimeter at 298.15 K and atmospheric pressure. For the preparation of liquid mixtures under investigation, LnA 3 (Ln = Nd, Sm, Eu, Gd, Tb, Dy) were synthesized and characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), and chemical elemental analysis. Excess volumes of solutions were correlated by the Redlich−Kister equation. The maximum absolute deviation between experimental and calculated values of densities was found for the D2EHPA−o-xylene−TbA 3 system, and it was 6.3 × 10 −4 g• cm −3 . Densities of virtual liquid lanthanide di(2-ethylhexyl)phosphates were estimated as adjustable parameters. The impact of the impurities on the densities and excess volumes of solutions was investigated. The results obtained in this work may be of interest for extraction experiments where D2EHPA of different purity is usually used.

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