Size-Dependent Ion Adsorption in Graphene Oxide Membranes.

Graphene oxide (GO)-based materials have demonstrated promising potential for adsorption and purification applications. Due to its amphiphilic nature, GO offers the possibility of removing various kinds of contaminants, including heavy metal ions and organic pollutants from aqueous environments. Here, we present size-selective ion adsorption in GO-based laminates by directly measuring the weight uptake of slats. Adsorption studies were conducted in graphene oxide purchased from Nisina Materials Japan prepared using a controlled method. We tuned the interlayer spacing of GO membranes via cationic control solutions using intercalation of very small salts ions (i.e., K+, Na+, Cl-) very precisely to facilitate the adsorption of larger ions such as [Fe(CN)6]4- and [Fe(CN)6]3-. This study demonstrates that if the opening of nanocapillaries within the laminates is bigger than the hydrated diameter of ions, the adsorption occurs within the membranes while for smaller opening, with no ion entrance the sorption occurs on the surface of the membranes.