Large total area membrane of suspended single layer graphene for water desalination

Abstract

Among carbon nanomaterials, graphene has emerged as promising novel membrane material for enhancing desalination performance. However, realistic prospects for industrial-scale production of graphene membranes has been limited. Here we take steps forward in exploring methods to increase the size and enhance the mechanical stability of the single layer graphene membranes. Using Transmission Electron Microscopy (TEM) grids as porous mechanical support and oxygen plasma treatment for creating nanopores, freestanding graphene with large total area was fabricated. 1m column of salty water was used as the driving force for water desalination measurements in these membranes. High water permeation (1.64×107Lm−2h−1bar−1) and acceptable NaCl rejection rate (~76%) was achieved over an active area of 2.77×104μm2. Without an ideal porous support, large area freestanding graphene with significant number of cracks, wrinkles, pinholes and defects cannot withstand pressures (~50–80bar) required for water desalination. Fine mesh grids with small holes as inexpensive mechanical supports can be utilized to increase the rupture strength of large area suspended graphene for many purposes including desalination and filtration of multivalent ions or larger molecules.