An environmental-friendly electrostatically driven method for preparing graphene oxide composite membranes with amazing stability in aqueous solutions

Graphene oxide (GO) membranes are outstanding candidates for desalination and wastewater treatment thanks to the fast water permeation through two-dimensional nanocapillaries, combined with size and electrostatic ion exclusion mechanisms. However, their use for ionic and molecular separations is limited due to swelling phenomena which reduce both, selectivity and mechanical stability of GO laminates. This work focuses on the design and development of an environmental-friendly electrostatically driven method for preparing graphene oxide composite membranes with amazing stability in aqueous solutions. The experimental results highlight the key role of support chemistry, surface charge, and topography to obtain composite membranes free from swelling or delamination issues. A macroporous co-poly(amide-imide) membrane crosslinked with diamines (PAI_CL) results in an excellent support for the production of stable GO composite membranes. The GO composite membrane is stable for more than 30 days at 60 °C in water and saline solutions. On the contrary state-of-the-art GO membranes prepared by filtration through a porous support give almost immediate separation of the GO layer deposited from the support when in contact with water even at room temperature. An interlayer spacing of ~9 Å is maintained after long term storing of the composite membranes in water or saline solution. GO-PAI_CL membrane developed are able to reject organic dyes with water flux more than 1000 times higher than predicted for a viscous flux through such GO model membrane. Moreover, the composite membranes produced are also stable in organic solvents, opening the perspective of potential application in organic solvent nanofiltration.