XRD investigations of hydrated homoionic montmorillonite saturated by several heavy metal cations

► At 45%RH, (Na, Cu & Pb) saturated specimen present homogeneous”1W” phases. ► For RH> 45%, SWy-Pb complexes undergo a slow transition towards 2W hydration state. ► Brutal transition to 2W layer hydration state for SWy-Cu complex for RH>45%. ► (Co, Cd or Zn)-specimen present homogeneous hydration behavior for 35-55%RH range. ► SWy-Ni complex present homogeneous 3W layer hydration state for RH > 70%.