Graphene Membranes for Water Nanofiltration and Desalination

Graphene, a single layer of graphite, has been considered as an ideal membrane material because it is extremely thin and thus can provide high permeation flux. However, currently there are no technologies available to fabricate large area, ultrathin (<5 nm), defect-free graphene-based membranes that can highly selectively separate mixtures. A scalable technique was developed to prepare low-cost, ultrathin (down to 2 nm) and defect-free, graphene-based membranes with tunable pore sizes (sub-nanometer – 20 nm). Tunable pore sizes, from sub-nanometer to > 10 nm, and ultrathin thickness (< 5 nm), allow ultrathin, graphene-based membranes for desalination and nanofiltration for water purification. We found that water flux and rejection for nanometer-sized organic molecules can be adjusted by tuning proe sizes on graphene. This tunability of membrane pore sizes may allow water treatment from ultrafiltration, nanofiltration, to reverse osmosis (RO) desalination. This completely new type of membranes has the great potential to revolutionize separation using membrane technology, because they can provide both high selectivity and high flux.