Fig. 1: Schematic illustration of surface charge and structure of NaX zeolite membrane.
From: Zeolite membrane with sub-nanofluidic channels for superior blue energy harvesting
a A demonstration of tetrahedrally coordinated silicon (SiO4) and aluminum (AlO4) alternatively connected by bridging oxygen. The negative charges caused by aluminum introduction are balanced by extra-framework sodium (Na+). These negative charges could also be compensated by other types of monovalent cations (M+) or divalent cations (M2+). b Tetrahedra SiO4 and AlO4 form sodalite cages which are then connected to form FAU supercages. There are three location sites (I, II, III) for charge balancing cations in the super cage49. c The top image demonstrates the cross-section of a zeolite membrane supported on a porous substrate with a certain thickness. The bottom image shows NaX zeolite sub-nanofluidic channels along [110] orientation. d The image shows the NaX zeolite selectively allows cations (e.g., Na+) to pass through the membrane and reject anions (Cl−), showing a visualized process for a cation/anion selective membrane process.
