Impact of the solution ionic strength on strontium diffusion through the Callovo-Oxfordian clayrocks: An experimental and modeling study

摘要: Diffusion of cations in clayrocks is widely investigated, because deep clay-rich formations are currently considered as one the potential host rocks for radioactive waste repositories. However, several authors have already reported that sorbing seem to diffuse at rates larger than those predicted by a simple pore diffusion model from their sorption coefficients and diffusive flux non-sorbing water tracers. This process has been attributed migration within electrical double layer, next mineral surfaces, called surface phenomenon. The aim this work was verify whether “enhanced” cation compared neutral species observed strontium and, if so, what extent effect might vary with salinity synthetic solutions. These questions were addressed performing batch sorption, through-diffusion out-diffusion experiments on rock samples Callovo-Oxfordian claystone formation (France). The results showed there good agreement distribution ratios (RD) determined crushed intact methods RD decrease related increase sodium concentration, competitor. Such trend also well reproduced means geochemical modeling based multi-site ion exchange (MSIE) theory. Moreover, clearly study: Sr almost five times higher HTO cell lowest ionic strength, diminished less 1.5 highest strength. evolution strength qualitatively model, concept relative mobility or mobile fraction.