JRP 06-02

Partners

FZK

PSI

FZD

Contact

Dr. Marie Marques Fernandes
Paul Scherrer Institut, 5232 Villigen, Switzerland
Phone +41-56-310-2310
E-mail e-mail

Influence of carbonate on actinides sorption on clay minerals

Status

 
Terminated - Planned from April 2007 till October 2008

Goals

This project is aimed at investigating the influence of carbonate on the sorption of trivalent actinides and uranyl onto clay minerals (montmorillonite and illite) under conditions relevant for nuclear waste disposal. Next to hydroxide ions, carbonate is the most important inorganic ligand for actinide ions in natural groundwaters and clay porewaters. Carbonate is known to decrease metal ion sorption through complexation. However, some studies have pointed out that the formation of ternary carbonate surface complexes might contribute to the surface sorption process.
In this project the sorption of Eu(III)/Cm(III)/Am(III) and U(VI) in the presence of carbonate will be studied by batch sorption experiments on purified and well characterized clay minerals (illite and montmorillonite) to measure sorption edges and isotherms.

Expected results

Molecular-level understanding of formation mechanisms and the structure of the main surface complexes will be obtained by spectroscopic techniques (X-ray Absorption Spectroscopy (XAS) and Time-Resolved Laser Fluorescence Spectroscopy (TRLFS)). XAS measurements will provide structural details of the sorbed species. TRLFS allows chemical information on the sorbed species at trace metal ion concentrations to be obtained. Measurements will be conducted on actinide loaded clay samples prepared in the presence and absence of carbonate.
Data obtained from all the experiments will be combined and included into a refined thermodynamic sorption model appropriate for performance assessment purposes, which will be able to take into account the influence of carbonate on actinide sorption.

Reports