Dissociation of M(CO3)33- into M(CO3)2- for M3+ = Am3+ and Cm3+ at 10 to 70°C

Conférence du 18 au 23 Septembre 2005. Communication par affiche

Sulfate Complexation of Trivalent Lanthanides Probed by Nanoelectrospray Mass Spectrometry and Time-Resolved Laserinduced Fluorescence Spectroscopy

Conférence du 18 au 23 Septembre 2005. Communication par affiche

Sulfate Complexation of Trivalent Lanthanides Probed by Nanoelectrospray Mass Spectrometry and Time-Resolved Laser-Induced Luminescence

International audienceSulfate complexation of lanthanides is of great interest for predicting speciation of radionuclides in natural environments. The formation of LaSO4+(aq) in HNO3/H2SO4 aqueous solutions of low ionic strength (I) was studied by nanoelectrospray ionization mass spectrometry (nanoESI-MS). Several gaseous species containing LaSO4+ were detected. The formation constant of LaSO4+(aq) was determined and extrapolated to I = 0 (logβ°1 = 3.5 ± 0.3) by using a simple specific ion interaction theory (SIT) formula. This value supports the potential of nanoESI-MS for the study of kinetically labile species. The species La(SO4)2- was also detected. In addition, time-resolved laser-induced luminescence (TRLIL) was used to study Eu(III) speciation under ionic conditions of 0.02−0.05 M H+ (H2SO4/HClO4) and 0.4−2.0 M Na+ (Na2SO4/NaClO4). The data were interpreted with the species EuSO4+ (logβ°1 = 3.78 ± 0.1) and Eu(SO4)2- (logK°2= 1.5 ± 0.2). For extrapolating to I = 0, all of the major ions were taken into account through several SIT ion-pair parameters, ε. Most of the ε values were estimated by analogy to known parameters for similar ion-pair interactions using linear correlations, while εEu3+,SO42− = 0.86 ± 0.5 was fitted to the experimental data because, to date, SIT coefficients between multicharged species are not reported. The formation constants obtained here confirm some of those previously measured for Ln(III) and An(III) by various experimental techniques, and conversely do not give credit to the idea that in equilibrium conditions TRLIL and other spectroscopic techniques would provide stability constants of only inner-sphere complexes. The fluorescence lifetimes measured for EuSO4+ and Eu(SO4)2- were consistent with the replacement of one H2O molecule in the first coordination sphere of Eu3+ for each added SO42- ligand, suggesting a monodentate SO42- coordination

Stabilities of the Aqueous Complexes Cm(CO3)33_3)_3^3- and Am(CO3)33_3)_3^3- in the Temperature Range 10-70 \degres C

RADIOCHInternational audienceThe carbonate complexation of curium(III) in aqueous solutions with high ionic strength was investigated below solubility limits in the 10−70 °C temperature range using time-resolved laser-induced fluorescence spectroscopy (TRLFS). The equilibrium constant, K3, for the Cm(CO3)2- + CO32- ⇌ Cm(CO3)33- reaction was determined (log K3 = 2.01 ± 0.05 at 25°C, I = 3 M (NaClO4)) and compared to scattered previously published values. The log K3 value for Cm(III) was found to increase linearly with 1/T, reflecting a negligible temperature influence on the corresponding molar enthalpy change, ΔrH3 = 12.2 ± 4.4 kJ mol-1, and molar entropy change, ΔrS3 = 79 ± 16 J mol-1 K-1. These values were extrapolated to I = 0 with the SIT formula (ΔrH3° = 9.4 ± 4.8 kJ mol-1, ΔrS3° = 48 ± 23 J mol-1 K-1, log K3° = 0.88 ± 0.05 at 25°C). Virtually the same values were obtained from the solubility data for the analogous Am(III) complexes, which were reinterpreted considering the transformation of the solubility-controlling solid. The reaction studied was found to be driven by the entropy. This was interpreted as a result of hydration changes. As expected, excess energy changes of the reaction showed that the ionic strength had a greater influence on ΔrS3 than it did on ΔrH3

Real-time monitoring of a dynamic molecular system using H-1-C-13 HSQC NMR spectroscopy with an optimized C-13 window

The kinetic and thermodynamic parameters of an equilibrating network involving 8 molecules can be determined from a series of quick and highly resolved (1)H-(13)C HSQC NMR experiments obtained using a reduced carbon spectral window

Determination of the scavenging coefficients of gaseous and particulate chlorine 36 by rain

International audienc

Determination of the scavenging coefficients of gaseous and particulate chlorine 36 by rain

International audienc

Determination of the scavenging coefficients of gaseous and particulate chlorine 36 by rain

International audienc

Determination of the scavenging coefficients of gaseous and particulate chlorine 36 by rain

International audienc