(159av) Water Desalination through the Selective CVD Graphene-Based Membrane

One of the most important and recently studied candidates for Reverse Osmosis (RO) or nanofiltration (NF) membranes is graphene, which has excellent chemical and mechanical stability. Graphene is the thinnest possible membrane, with its one atom thickness acting as the membrane. Small thickness is desirable because it gives high flux. But high flux must be accompanied by high salt rejection. The application of plasma methods can make the graphene membrane and its substrate controllably nanoporous to give the desired high flux and high salt rejection. As a further benefit, graphene manifests greater resistance to chlorine than current polyamide membranes.

In the fabrication of an efficient graphene NF/RO membrane, it is critical to have a suitable flexible substrate (hydrogel) that can offer support to the one-atom-thick graphene membrane while still allowing rapid water transmission. In this project, the process of transferring CVD graphene onto a hydrogel-modified NF membrane will be discussed. CVD graphene is fragile and can easily be torn if it is directly transferred to a membrane support structure. To allow transference without damage, a hydrogel underlayer—polyvinyl alcohol (PVA)—has been synthesized and cross-linked and applied onto membrane support. The degree of crosslinking and the thickness of the PVA layer can affect a PVA / support membrane's permeability. The graphene is transferred onto the PVA support by a simple but unique approach to decreasing the chance that defects will form.

Making tunable nanometer pores by plasma: As reported by O'Hern et al., using plasma through the graphene can create sub-nanometer pores that make the graphene more selective. Consequently, the results of the plasma cleaner with the different condition that was used to apply nanometer pores on the graphene surface will be discussed.

Experimental work combined with membrane characterization methods (SEM, AFM, and FTIR) and filtration studies using a home-made RO system to examine the graphene as RO membrane will be presented. These results will be compared with the other synthesized membrane and different types of supports.

This research will provide insights into developing CVD graphene-based membranes with high water permeability and excellent size selectivity, membranes that will be highly attractive for water purification and desalination because of their high energy-efficiency.