Praseodymium Nitrate and Neodymium Complexation with Organophosphorus Reagents in Supercritical Carbon Dioxide Solvent

Journal Article · Mon Nov 01 00:00:00 EST 2004 · Journal of Supercritical Fluids

DOI:https://doi.org/10.1016/j.supflu.2003.11.006· OSTI ID:912172

Fox, Robert V; Ball, R Duane; B Harrington, Peter de; Rollins, Harry W; Jolley, John G; Wai, Chien M

Complex formation reactions of praseodymium nitrate hexahydrate, and neodymium nitrate hexahydrate salts with tri-n-butyl phosphate (TBP) and several other neutral organophosphorus reagents were investigated in supercritical carbon dioxide. The concentration of the metal complexes in the supercritical fluid (SCF) phase was determined using UV-Vis and luminescence spectroscopies. The stoichiometry of the complexes was determined using the mole-ratio method. Extraction equilibrium constants were calculated from the spectral data using least-squares regression and hard-equilibria models. UV-Vis absorbance data indicate that praseodymium nitrate and neodymium nitrate both form 1:4 lanthanide–tributyl phosphate complexes in supercritical carbon dioxide at 308 K. The conditional extraction coefficients for those two systems were calculated to be log Kex=7.45±0.06 for the praseodymium system and log Kex=7.52±0.03 for the neodymium system. For comparison, neodymium nitrate complexation reactions with tri-n-butyl phosphate and tributyl phosphite (TBPO3) were studied in hexane under ambient conditions. UV-Vis data indicate that a 1:4 neodymium–tributyl phosphate complex is formed in hexane with a conditional extraction coefficient of log Kex=3.4±0.2. Tributyl phosphite forms a 1:8 complex with neodymium in hexane with a conditional extraction coefficient of log Kex=11.0±0.1. Neodymium nitrate was titrated with other organophosphorus reagents, tributyl phosphite and tributyl phosphine oxide (TBPO), in supercritical carbon dioxide to investigate differences between neutral oxygen donor ligands and neutral phosphorus donor ligands. UV-Vis and luminescence data indicate that neodymium nitrate forms a 1:8 complex with tributyl phosphite and a 1:5 complex with tributyl phosphine oxide, compared to a 1:4 complex with tri-n-butyl phosphate. The conditional extraction coefficient for the 1:8 neodymium–tributyl phosphite system was calculated as log Kex=21.4±0.2 from UV-Vis data, and log Kex=19.8±0.2 from luminescence data. The conditional extraction coefficient for the 1:5 neodymium–tributyl phosphine oxide complex was calculated as log Kex=7.83±0.05.

• Research Organization: Idaho National Lab. (INL), Idaho Falls, ID (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: DE-AC07-99ID-13727
• OSTI ID: 912172
• Report Number(s): INEEL/JOU-03-00155; JSFLEH; TRN: US200801%%625
• Journal Information: Journal of Supercritical Fluids, Vol. 31, Issue 3; ISSN 0896-8446
• Country of Publication: United States
• Language: English

Related Subjects

37 - INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CARBON DIOXIDE
HEXANE
LUMINESCENCE
NEODYMIUM
NEODYMIUM NITRATES
OXYGEN
PHOSPHATES
PHOSPHINE OXIDES
PHOSPHOROUS ACID
PHOSPHORUS
PRASEODYMIUM
PRASEODYMIUM NITRATES
SOLVENTS
STOICHIOMETRY
Lanthanides
Metal complexation
Multivariate hard equilibrium modeling
SIMPLISMA
Supercritical carbon dioxide