Radionuclide retention by portlandite in the presence of isosaccharinate and phthalate and possible role of ternary complexes.

This research evaluates the retention mechanisms for various radionuclides (RN) specifically, Ni, U, Eu and Pu, on portlandite, in the presence of two organic ligands (ORG): isosaccharinate (ISA) and phthalate (PHTH). The potential negative impact of ORG on RN uptake by the solid phase may arise from two main mechanisms that were analysed: (a) the competitive adsorption of ORG or (b) the formation of RN-ORG complexes in the aqueous phase. The sorption of ISA on portlandite exhibited a maximum log(K) value of 2.

Analysis of the effect of citrate on radionuclide retention on portlandite.

We analysed how citrate (CIT), a chelating agent potentially present in radioactive waste disposals, affects the mobility of four radionuclides (RN): Ni, U, Eu, Pu in portlandite, an important hydrated phase of cement, a commonly used material for waste isolation. Portlandite was synthetized in the laboratory and showed high purity and grain size of few μm. This solid, buffers the pH to 12.