A systematic review on sodium cation distributions in zeolites

Since the mid of 1990s, owing to the potential molecular sieving action, controlled host–guest interactions and high thermal and chemical stability, the preparations, characterizations and applications of membranes, films and coatings of zeolite and zeolite-like materials have been extensively investigated. The present paper, a historical survey, intends to review the present status of research activity on the ion exchange properties of different zeolites. Further for characterizing microstructures of zeolitic materials have been used X-ray diffraction (XRD), double-rotation (DOR) and magic angle spinning (MAS) nuclear magnetic resonance (NMR), powder and pulsed neutron diffraction and less often diffuse reflectance spectroscopy, infrared spectroscopy and near edge X-ray fine structure (NEXAFS). These analytical techniques are not further described in the present work, but the interested reader can consult the referenced works and reviews.