TRLFS study on the complexation of Cm(III) with nitrate in the temperature range from 5 to 200 °C

Abstract

The formation of aqueous Cm(III) nitrate complexes is studied in the temperature range from 5 to 200 • C by time resolved laser fluorescence spectroscopy (TRLFS). The experiments are performed in a custom build high pressure and high temperature fluorescence cell. The complex formation is measured at nitrate concentrations ranging from 0.10 to 4.61 mol/kg H 2 O. The mono-and dinitrate complexes are quantified by peak deconvolution of the fluorescence spectra and the complexation constants are determined as a function of the temperature. The conditional equilibrium constants are extrapolated to zero ionic strength using the specific ion interaction theory (SIT) and the thermodynamic standard state data (Δ r H • m , Δ r S • m , Δ r G • m , Δ r C • p,m ) are determined from the temperature dependence of the equilibrium constants at I = 0. The equilibrium constants up to 75 • C are well described by the Van't Hoff equation (Δ r H • m independent of T and Δ r C • p,m = 0). Modelling of the data at higher temperatures requires an extended equation including a term for the heat capacity changes (Δ r C • p,m ).

Effect of Temperature on the Complexation of Uranium(VI) with Fluoride in Aqueous Solutions

“…Besides, the values of (∂ε/∂T) p for the reactants and products may balance out each other so that Δε for many reactions remains approximately constant up to 100 o C [28,29]. The calculated log β 0 are summarized in Table 1 (the error limits a The average coordination number of fluoride per uranium obtained by speciation calculation using the stability constants at 25 o C from the present work (Table 1).…”

A TRLFS Study on the Complexation of CmIII and EuIII with 2,6‐Bis(5,6‐dipropyl‐1,2,4‐triazin‐3‐yl)pyridine in Water/Methanol Mixture

“…[26] Inner sphere nitrate coordination is not expected under these conditions. [27] In the presence of increasing nPr-BTP concentration two Cm-BTP complex species are formed simultaneously, displaying emission maxima at 602.0 nm and 613.2 nm, respectively (species 1 and 2). Both exhibit bathochromic shifts compared to the solvated metal ion, indicating a larger ligand field splittings caused by stronger complexation of the metal ion.…”

Effect of temperature on the complexation of NpO2+ with benzoic acid: Spectrophotometric and calorimetric studies

“…The assumption that De remains constant in the temperature range of 283 to 343 K is valid because the temperature effect on the ion interaction parameters, (oe/oT) p , are usually 60.005 kg Á mol À1 Á K À1 for temperatures below 473 K [3][4][5]. Besides, the values of (oe/oT) p for the reactants and products may balance out each other so that De for many reactions remains approximately constant up to T = 373 K [20,21]. The calculated log b°for the Np(V)/benzoate complex at different temperatures are summarized in table 1 (the error limits were obtained by propagation of the uncertainties in the experimental values of log b and the uncertainty in De).…”