The partition coefficients of nitratonitrosylruthenium complexes between nitric acid and TBP phases

Ruthenium Nitrosyl Structure in Solvent Extraction Systems: A Comparison of Tributyl Phosphate, Tetrabutyl Urea, N-Methyl, N-Octyl Ethylhexanamide, and N,N,N′,N′-Tetraoctyl Diglycolamide

“…The higher slope observed for TODGA may arise from a different number of extractants coordinating in the second coordination sphere of ruthenium complexes, or from the presence of n -octanol, which affects the water extraction. However, the relation between the ruthenium distribution ratio and water extraction confirms the former hypothesis of TBP–ruthenium interactions via water ligands, and generalizes this interaction for different solvent extraction systems. TBP extracts more ruthenium than TBU and MOEHA, since it better interacts with water molecules, and consequently, water ligands of ruthenium complexes.…”

“…Hence, the extractants are unlikely to interact in the inner sphere of ruthenium complexes. The bands ν 5 (NO 3 – ) at ∼1530 cm –1 are assigned to the asymmetric stretching of nitrate ligands in ruthenium complexes. , These vibrations are observed to have similar excitation energies in all applied solvents, as well as in the Raman spectra; as shown in Figure . However, the band ν 5 (NO 3 – ) is larger for the extraction with TBU, which could be explained by more nitrate ligands per ruthenium complex, or by overlapping vibrations.…”

“…During PUREX extraction cycles, extractable ruthenium appears in the form of numerous nitrosyl (RuNO) complexes. ,, These complexes have a pseudo-octahedral geometry, in which the Ru–NO bond is shorter than the ones to the other five ligands . Siczek and Steindler have published a general formula to summarize the general diversity of RuNO complexes in nitric acid solution: Nitrates, nitrites, and water ligands can occupy the equatorial position of the octahedral complexes, whereas one water or one hydroxide ligand occupies the axial position in opposite to the nitrosyl ligand .…”

The Solvent Extraction Behavior of Ruthenium I - The Nitric Acid-Tri-n-Butyl Phosphate System

“…Very recent work by MAYA [7] supports and refines mechanisms previously postulated by other investigators [8][9][10][11][12]. According to these mechanisms, labile TBP-ruthenium nitrosyl nitrato complexes, such as II and III, are formed and move into the organic phase where the TBP molecules slowly and reversibly displace the aquo or nitrato ligands to form an inner sphere complex I that cannot readily be stripped back into the aqueous phase.…”

“…Analytical data for 5 Μ acid are too scattered to form a useful plot, but give a value forZ) Ru near 0.01 and DRU near 0.2. The behavior of TBP-HN0 3 solvent extraction systems at high acid concentrations is not clearly understood, but is probably a function of changes in the activities of the many species in each phase, changes in the salting action of nitric acid, and formation of various higher H 2 0-HN0 3 -TBP complexes [1,9,18]. Some workers [8] have found a fourth-order dependence of the distribution coefficient on TBP.…”