Complexation of Eu(III) with a polymeric cement additive as a potential carrier of actinides

In the long term, cementitious materials in a final repository will be exposed to leaching processes generating highly alkaline solutions. Polymeric additives, so-called superplasticizers, are considered as potential mobilizing agents for released radionuclides, since it is uncertain whether complete degradation will take place under the evolving aqueous conditions. Regarding the complexing properties of superplasticizers, there are only indirect assessments so far. In this study, first systematic investigations on complexation with Eu(III) as an analogue of trivalent actinides were performed at variable pH and electrolyte content (NaCl, CaCl₂) using ultrafiltration as a separation method. A stability constant was derived according to the charge neutralization model. For this purpose, the proton exchange capacity was determined by potentiometric titration.