Complexing power of hydro-soluble degradation products from γ-irradiated polyvinylchloride: influence on Eu(OH)3(s) solubility and Eu(III) speciation in neutral to alkaline environment

The complexing power of hydrosoluble degradation products (HDPs) from an alkaline hydrolysis of a 10 MGy gamma-irradiated polyvinylchloride is studied. The complexation of Eu(III), as an analogue of lanthanide and actinide radionuclides at their + III oxidation state for oxygen containing functions, is evidenced both from the increasing of Eu(OH)(3) (s) dissolution, and from a complexometric titration by time-resolved luminescence spectroscopy. The dissolution of Eu(OH)(3) (s) in a simplified alkaline solution (0.3 M KOH/0.1 M NaOH) increases moderately, but significantly, with the HDPs concentration. The luminescence signal of the supernatant clearly indicates the presence of several complexed Eu(III) species. Performing a complexometric titration of Eu(III) from pH 6 by alkaline HDPs shows the formation of two different species with increasing HDPs' concentration and pH. Operational complexation constants - based on dissolved carbon concentration - are proposed. The analyses of the spectra and luminescence decays seem to confirm the presence of two different species.