Molecular simulation of the diffusion of uranyl carbonate species in aqueous solution

Evaluation and application of Diffusive Gradients in Thin Films (DGT) technique using Chelex®-100, Metsorb™ and Diphonix® binding phases in uranium mining environments

“…Moreover, the D cell is very well correlated with D w for UO 2 2þ [42e47]. On the other hand, there is a significant discrepancy between the D cell and D w for UO 2 ðCO 3 Þ 2 2À , however this D w value is established based only on molecular dynamics simulations [45]. Up to date, no other experimental values for other U species than UO 2 2þ are determined due to co-occurring of various U species under most of experimental conditions (Fig.…”

Investigation of Reactive Transport and Coupled THMC Processes in the EBS

“…If the solute of interest is hydrated or solvated in any way, then the "diffusion-relevant" radius is represented by the solute-solvent complex, and not the solute itself (Cussler, 1997). For uranium, changes in chemical solution speciation and U(VI) complexation with inorganic ligands, such as carbonates, can change the molecular size of aqueous species, as well as their hydration properties and the water exchange kinetics with the hydration sphere (Kerisit and Liu, 2010). Current results from potentialbased molecular dynamics simulations suggest that these changes lead to differences in molecular diffusion coefficients for various U(VI) solution species, e.g., UO 2 2+ and UO 2 (CO 3 ) 3 4- (Kerisit and Liu, 2010).…”

“…For uranium, changes in chemical solution speciation and U(VI) complexation with inorganic ligands, such as carbonates, can change the molecular size of aqueous species, as well as their hydration properties and the water exchange kinetics with the hydration sphere (Kerisit and Liu, 2010). Current results from potentialbased molecular dynamics simulations suggest that these changes lead to differences in molecular diffusion coefficients for various U(VI) solution species, e.g., UO 2 2+ and UO 2 (CO 3 ) 3 4- (Kerisit and Liu, 2010). However, molecular diffusion rates of the fastest and slowest U(VI) species vary by less than a factor of 2, which will lead to only minor changes in overall U(VI) diffusion rates in porous media relative to other effects associated with metal-solid interactions.…”

“…In the first step, the dominant U(VI) solution species was determined individually for each set of chemical solution conditions to be simulated (Table 4.2), based on our previous results from speciation modeling with existing thermodynamic data (NEA database (Guillaumont et al, 2003); data not reported). Then, U(VI) diffusion coefficients in free aqueous solution ( 0 D ) were estimated for these species using literature values from molecular dynamics simulations (Kerisit and Liu, 2010 …”

Laboratory Experiments on Bentonite Samples: FY15 Progress

“…Furthermore, an understanding of diffusion rates is needed not only for relevant radionuclides but also predominant earth metals, because the latter elements can affect actinide solution speciation and compete with radionuclides for mineral surface sites. For instance, within engineered clay barriers containing minor amounts of calcite, Ca 2 UO 2 (CO 3 ) 3 0 is expected to dominate uranium(VI) solution speciation, and hence, control uranium(VI) sorption and diffusion behavior (Kerisit and Liu, 2010;Bradbury and Baeyens, 2011;Joseph et al, 2011). Hence, in an earlier part of this study, we also investigated calcium diffusion behavior in sodium-montmorillonite.…”