Abstract
Dioctahedral smectites are clay minerals that widely used as a crucial component for the edifice of natural barriers in industrial wastes and wastewater treatment. The hydration behaviours of these mineral types are very sensitive by environmental surroundings changes. The present work focuses the evolution of the interlayer water amount as a function of the relative humidity rates (RH), varied along a humidifying-drying cycle, in the case of two dioctahedral smectites with different charge location (i.e. Wyoming montmorillonite SWy-2 and Beidellite SbId-1). The CEC (i.e. cation exchange capacity) of the studied sample is saturated by two monovalent cations (i.e., Cs+ and Na+) characterized by a different ionic radius. The X-ray diffraction (XRD) profile modelling tools based on the indirect method that consist on the comparison of experimental 00l reflections with other calculated from structural models is used to perform these aims. The qualitative XRD profile investigation suggests heterogeneous hydration behaviour at different stage of the cycle for all studied samples. The water content fluctuation, confirmed by the appearance of a hydration hysteresis, within the interlamellar space of diverse complexes is an irreversible process during the shrinking–rewetting sequence. Comparing to Na+ cations, the presence of the Cs+ ions in exchangeable sites of both smectite structures is accompanied by more orderliness of systems, which retunes the lowest water molecules amount over the applied cycle.