Abstract

The formation of aqueous Cm(III) nitrate complexes is studied in the temperature range from 5 to 200 degrees 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 (Delta(r)H(m)degrees, Delta(r)S(m)degrees, Delta(r)G(m)degrees, Delta(r)C(p,m)degrees) are determined from the temperature dependence of the equilibrium constants at I = 0. The equilibrium constants up to 75 degrees C are well described by the Van't Hoff equation (Delta(r)H(m)degrees independent of T and Delta(r)C(p,m)degrees. = 0). Modelling of the data at higher temperatures requires an extended equation including a term for the heat capacity changes (Delta(r)C(p,m)degrees).

Keywords

Curium(III); Nitrate; Speciation; Complexation; Time resolved laser induced fluorescence spectroscopy; High temperature

Published in

Radiochimica Acta
2009, Volume: 97, number: 8, pages: 385-393
Publisher: OLDENBOURG VERLAG

UKÄ Subject classification

Inorganic Chemistry


Publication identifier

DOI: https://doi.org/10.1524/ract.2009.1631

Permanent link to this page (URI)

https://res.slu.se/id/publ/95520