| Abstract: |
In the field of nuclear waste storage, knowledge of the sorption behavior of radionuclides onto mineral surfaces is of fundamental importance in order to evaluate environmental impacts. We have studied uranyl ion sorption mechanisms onto zirconium silicate and zirconium oxide with a double approach, coupling both macroscopic and structural investigations. The spectroscopic results, reported in a previous paper, allowed a complete determination of the different species involved in the studied sorption reactions. This paper presents the results of the macroscopic part of the study. Surface characterizations of the solids were first carried out: determination of the pH of the point of zero charge, of the surface site densities and of the surface acidity constants. The experimental retention data were then interpreted in terms of a constant capacitance model using the FITEQL code. Results from structural investigation were used to constrain the modeling. This coupled approach led to accurate reactions stoichiometry and associated sorption constants values, since they were determined with respect to different experimental results, both macroscopic and microscopic. |
