Transport of Strontium Through a Ca-bentonite (Almería, Spain) and Comparison with MX-80 Na-bentonite: Experimental and Modelling

Abstract

In this work, the sorption of strontium on a Ca-bentonite (CGA) from Almeria (Spain) in column experiments was studied, and the results obtained were compared with the sorption onto the Na-bentonite (MX-80). The code CTXFIT (two site non-equilibrium sorption model) was used in order to fit the experimental data and to determine sorption and transport parameters. The effect of inlet Sr(II) initial concentration and the ionic strength were evaluated. The results obtained showed that the sorption capacities as well as the transport and sorption parameters of both bentonites were affected by the initial metal concentration. In experiments with higher inlet concentrations, columns were saturated faster, leading to shorter breakthrough and exhaustion times. On the other hand, a decrease of sorption and transport parameters was observed at higher ionic strengths, which would confirm ion exchange as the main mechanism of Sr(II) sorption onto both bentonites. The sorption parameters (sorption capacity and retardation factor) obtained indicated that the Ca-bentonite from Almeria (Spain) presented better sorption performance than the Na-bentonite, which was related to the physical properties of the Ca-bentonite.