Sorption behaviour of caesium on a bentonite sample

Abstract

Sorption of elements like Cs on clay is one of the principal processes delaying their release from deep repositories of nuclear wastes into the environment. The sorption processes taking place between non-purified natural clay material (bentonite) and synthetic groundwater (containing Ca, Mg, Na, K and carbonates) were therefore studied experimentally and modelled for Cs to determine whether thermodynamic computer codes capable of predicting the behaviour of this element in natural systems might be developed. The model used, based on the properties of a pure montmorillonite phase, incorporates the surface reactions for natural major ions and sorbing cations but does not have any adjustable parameters. The weight of each parameters used in the model is assessed. Surface reactions are classified as either major or minor, and a simplified model of Cs sorption that considers only the major processes is proposed. This simplified model might correspond to the less sophisticated thermodynamic model included in coupled geochemistry-transport models.

Study of the Interaction of Ni2+and Cs+ on MX-80 Bentonite; Effect of Compaction Using the “Capillary Method”

“…Table 1 (11) performed under well-controlled conditions (simplified medium, purified Namontmorillonite) with Swy-1 and MX-80 Na-montmorillonite, respectively, were chosen as references for this study. For Cs, the lines in Figure 2 correspond to the calculation made considering an interaction governed by the exchange sites using only the published exchange constant (11). The prediction agrees to the experimental data for equilibrium solution concentrations (C L ) above 10 -6 M. At lower concentration, the prediction underestimates the sorption by a factor of about 0.6.…”

“…[5][6][7][8][9][10] kg/m 3 ). The results were modeled based on published models obtained with pure clay materials (11,12,13). The effect of secondary phases on the total retention was discussed.…”

Effect of temperature on the acid–base properties of the alumina surface: Microcalorimetry and acid–base titration experiments

“…Surface complexation models (SCMs) are among the most employed in the literature and were recently used to describe sorption on montmorillonite and bentonite surfaces [1,2]. Nevertheless, SCMs are applied only under ambient temperature conditions even if higher temperatures (up to 100 • C) could be expected when considering sorption reactions in the context of radioactive waste disposal, for example.…”

Mathematical Modeling of a Cs(I) – Sr(II) – Bentonite – Magnetite Sorption System, Simulating the Processes Taking Place in a Deep Geological Repository

“…l Between the surface charge, s, and the electrostatic potential, y, the following dependencies hold (2,3,4): where G is the so-called Helmholtz capacitance.…”

“…In our deep geological repository, we plan to use canisters made of stainless and carbon steel, with a compacted bentonite barrier. The use of bentonite as a backfill barrier in repositories for nuclear waste is based mainly on its low permeability, swelling properties and capability to significantly retard the migration of most radionuclides (RN) [1,2,3]. As a result of corrosion processes, the main corrosion product of steel canisters -magnetite -will also form an important part of the barrier.…”