Selectivity of Na-Montmorillonite versus Concentration of Two Competitive Bivalent Cations (Cu 2+ , Pb 2+ ): Quantitative XRD Investigation

The goal of this paper is to examine, by quantitative XRD analysis, the effect of heavy metal cation concentrations (Pb 2+ , Cu 2+ ) on the selectivity phenomenon in the case of dioctahedral smectite (i.e., Na-montmorillonite). The quantitative XRD analysis is achieved using an indirect method based on the comparison of experimental XRD profiles to those calculated using structural models. The obtained results show that for strong metals concentrations (i.e., 10 −1 N), the host material presents heterogeneous structure characterized by interstratified hydration states between 1 W and 2 W (i.e., respectively, one and two water layer hydration state) attributed to Pb 2+ cation. For low concentration, the d 001 values investigation indicates that montmorillonite remains saturated with Na + characterized by homogeneous 1 W hydration state