Effect of the hydration sequence orientation on the structural properties of Hg exchanged montmorillonite: Quantitative XRD analysis

•A heterogeneous hydration behavior is observed over the studied RH.•The presence of several MLS involving 0W, 1W, 2W and 3W along RH range is observed.•A homogeneous hydration trend is noted after hydrous orientation switch.•The interlamellar water molecule abundance varied versus the RH rate.•The material history is affected by the first hydrous perturbation.

The use of montmorillonite for removing mercury is an effective technology for the treatment of industrial wastewaters and can become an effective tool for the remediation of ecosystems polluted with this metal. In order to assess the influence of hydration/dehydration orientation on the structural properties of the Hg exchanged montmorillonite a quantitative XRD analysis at room and under controlled atmosphere (variable RH rates) is conducted. This study is based on the modeling approach which consists in the comparison of experimental 00l reflections with the calculated ones deduced from structural models. This approach allows us to determine the amount of the interlayer water molecules, structural changes along the c* axis and reaches the relative layer types contributions. The obtained main results show that all experimental profiles are simulated using a mixed layer structure with various proportions of bihydrated (0W), mono-hydrated (1W), dehydrated (2W) and three-hydrated (3W) layer types, which demonstrate the heterogeneous hydration character over all RH rates. The hydrous perturbation is accompanied by an irreversible gradual growth of the interlayer water molecules content.