Atomistic Computer Modeling of Hydrocalumite As an Adsorbent for Radioactive Anions from Aqueous Solutions

International audienceResults are presented from atomistic computer modeling of hydrocalumite (cement AFm-phase) with Cl- and I- anions in the interlayer space as a potential adsorbent of radionuclides Cl-36, I-129, Cs-137. Properties of the crystals themselves and the interaction between aqueous solutions of CsCl and CsI and surfaces of crystalline phases are studied. It is shown the adsorption of Cl- is stronger than that of I- on surfaces of hydrocalumite, which can be explained by the difference in ionic radii of hydrated anions

Atomistic Modeling of the Structural and Dynamic Properties of Aqueous NaCl and Na2SO4 Solutions in the Interlayer Space of Ettringite

International audienceThe use of a new modification of the ClayFF force field for molecular dynamics modeling of ettringite crystals and interaction of aqueous NaCl and Na2SO4 solutions with their surface shows that the possibility of explicitly taking into account metal-O-H interactions in the system leads to the formation of stronger hydrogen bonds in the crystal structure and on the surface and to greater localization of the atoms of both the crystalline phase and solutions in the subsurface zone. The relative fractions of the inner- and outer-spheric adsorption of Na+, Cl-, and (SO4)(2-) ions and the mobility of H2O molecules in both solutions also change. The calculated crystal lattice parameters and the density of ettringite remained almost unchanged between the old and new versions of the ClayFF force field, but the accuracy of reproduction of the elastic characteristics of the crystal markedly increased

An EPR study of Cu adsorption by clinoptilolite from Cl-, NO3 and SO42- solutions

The concentration and the type of Cu2+ species adsorbed on a natural zeolite (Clinoptilolite) was measured and studied by using Electron Paramagnetic Resonance Spectroscopy (EPR). The EPR results together with macroscopic sorption data indicate that the solution ionic strength as well as, the type of electrolyte anion (Cl-, NO3- and SO42- ions were examined) affect the amount of Cu adsorbed and the type of Cu surface complexes. The increasing in solution pH affects Cu adsorption quantitatively whereas; the type of surface complexes formed depends mainly on solution ionic strength. For low solution ionic strength, when the inhibition from solution species is limited, the adsorbed Cu is characterized by more than one type of chemical environment. On the contrary, for high solution ionic strength the Cu adsorption is inhomogeneous and EPR spectra show only one type of surface complex. When the anions of the background electrolytes are different, but of equal normality, the results indicate that in the presence of SO42- discernible Cu surface complexes are formed whereas, for Cl- and NO3- these surface formations are obtained only for high Cu adsorbed concentrations