The complexation of Eu(III) and Cm(III) with polyacrylate as a model compound for complex polycarboxylates studied by laser fluorescence spectroscopy

The complexation of the trivalent heavy metals Eu(III) and Cm(III) with polyacrylate as a model ligand is investigated by time-resolved laser fluorescence spectroscopy (TRLFS) and subsequent thermodynamic modelling (charge neutralization model). The aqueous speciation of both metals is investigated as a function of temperature (20–60 °C) and ligand concentration (0–0.4 g/kg) in 0.1 mol/kg NaCl solution ([H⁺]_total ≈ 10⁻⁴ mol/kg). Only one complex species is observed at all experimental conditions. With increasing temperature the aqueous Eu(III) and Cm(III) speciation is slightly shifted towards the complexes species. This effect is attributed to the stronger deprotonation of the polymer, which is also reflected by an increase of its loading capacity. The complex stability constants, however, show no visible temperature dependency. Log β'(T) ranges between 5.8 and 5.9 for both Eu(III) and Cm(III) over the whole range of experimental conditions.