Nanocellulose/Graphene Oxide layered membranes: Elucidating their behaviour during filtration of water and metal ions in real time
TThe deposition of a thin layer of Graphene Oxide (GO) onto Cellulose Nanofibrils (CNF) membranes, to form CNF-GO layered-composite membranes, dramatically enhances their wet-mechanical stability, water flux and adsorptive capacity of water pollutants (J. Hazar. Mat. 2019, 371, 484-493). In this work, we studied in real time the behavior of these layered membranes during filtration of water and metal ions solutions by means of small-angle X-ray scattering (SAXS) and reactive molecular dynamics (ReaxFF) computational simulations. In-situ SAXS confirms that the GO layers limit swelling and structural deformations of CNF during filtration of aqueous solutions. Moreover, during filtration of metal ions solutions, the connection of the CNF-GO network becomes highly complex mass-fractal like, with an increment in the correlation length. In addition, after ion adsorption, the SAXS data also evidence the apparent formation of nanoparticles during the drying stage where the particle size increases as a function of time. The molecular dynamics simulations, on the other hand, provides a deep insight into the assembly of both components, as well as elucidating the motion of the metal ions that potentially lead to the formation of metal clusters during adsorption, confirming the synergistic behavior of GO and CNF for water purification applications.