Effect of organic compounds on the retention of radionuclides in clay rocks: Mechanisms and specificities of Eu(III), Th(IV), and U(VI)

The use of geological barriers is widely studied in the context hazardous waste management and pollution events. In near field sources, endure disturbances with concomitant release chemicals organic or saline plumes. this study, we investigate effect compounds on retention radionuclides contact a sedimentary rock, namely Callovo-Oxfordian clay rock (East Paris Basin). Eu(III), Th(IV), U(VI), was quantified at near-neutral pH, presence model released from wastes engineered barriers, e.g. ortho-phthalate, ?-isosaccharinate (?-ISA), succinate, as well high complexing (oxalate, citrate, EDTA). concentrations compounds, eventually higher than disposal conditions, aimed quantifying concentration ranges above which decreases, underlying mechanisms occurring. A simplified surface complexation model, assuming illite main sorbing phase, used for predictive modelling. comparison experimental results allowed evaluation robustness constants thermodynamic database “ThermoChimie” Andra-RWM-Ondraf/Niras consortium, to account speciation solution (ThermoChimie V10a, https://www.thermochimie-tdb.com). Specific are discussed, such Eu(III) by ?-ISA, Th(IV)/citrate complexes. U(VI) displayed unique behaviour because uranyl natural species under conditions. low solid liquid distribution ratio, Rd(U(VI)/COx) ~ 7.5 ± 1.6 L kg?1 decreases but without direct molecules. Indeed, plume induces disturbance chemical equilibria pore water leading additional calcium carbonates. Such highlights crucial role surfaces carbonate minerals. More generally, these provide insights geochemical buffers key parameters involved during near-field environmental media.