Hydration performance of dioctahedral smectite saturated with Ba2+ and Cs+ cations: Quantitative XRD investigation

The present paper aims at characterizing the hydration behavior in the case of dioctahedral smectite with different location charge (i.e. montmorillonite SWy-2 and beidellite SbId-1) exchanged by heavy metals cations characterized by different valence (Ba²⁺ and Cs⁺) generally coming from industrial waste and wastewater solution. The study was performed basing on the quantitative X-ray diffraction investigation. This method consists on the comparison between experimental patterns with a theoretical ones calculated from structural models and allows us to determine the relative proportions of different hydration states (dehydrated.0W, monohydrated.1W, or bihydrated.2W,) that can coexist within smectite structure. Furthermore, position and amount of both interlayer water molecules and heavy metals cations can be also, determined along the c* axis. Obtained qualitative and quantitative XRD analysis showed the possibility to distinguish diverse hydration behavior of each complex. The presence of the monovalent cation (i.e. Cs⁺) in the interlayer space of both smectite restricts the water molecule intercalation that structures are dominated by two principal hydration states: 1 W and 0W. Whereas in the case of the bivalent cation (i.e. Ba²⁺), the interlayer water amount retuned in the beidellite and montmorillonite structure is more important seen the presence of a major bihydrated layers types in their interlayer´s spaces.