Nanofiltration of Water

Climate change reduced the precipitation rates, where water treatment infrastructure, such as reverse osmosis (RO) plants have been built to meet water demands. Although the RO process can separate 99% of salts from water, the process requires high operating pressures, which equates to high operational costs. Nanofiltration, which is also known as loose RO has lower operating pressure requirements, a molecular weight cutoff (MWCO) of 0.2 – 10 kDa, which allows the separation of divalent ions. The emergence of nanomaterials, such as graphene and graphene oxide (GO), has enabled the ability to tailor membrane properties, such as surface charge, hydrophilicity, and porosity, to enhance membrane performance, such as flux and rejection. The nanofiltration membranes were fabricated using GO that was cross-linked with chitosan (CS), an abundant biopolymer derived from shellfish, to prevent compaction of layers to create flow channels for increased water permeability. The solution was cast, and vacuum filtrated onto a polyethersulfone (PES) substrates and annealed at 80oC for 20 minutes. The membrane morphology was then characterized using scanning electron microscopy (SEM), and the membrane performance was tested by the separation of dye and divalent salt using a lab-made syringe dead-end cell.