Controlling nanochannel dimensions in graphene oxide for the fabrication of graphene-based desalination membranes
The purpose of this research was to produce reduced graphene oxides for the fabrication of desalination membranes. Graphene has typically been considered a way to create more energy efficient desalination membranes. However, graphene is expensive and unstable, while graphene oxide has similar properties, but is less expensive and more stable. Graphene oxide membranes have the potential to perform above the permeability-selectivity tradeoff that is typical in membranes through size-based exclusion. Reduction through heat or Vitamin C reduces the size of graphene oxide nanochannels so salt and organic materials can be rejected in higher numbers. Both reduced and unreduced graphene oxide membranes were created and evaluated by their ability to filter dye and salt in a pressurized membrane cell. The permeability and rejection of the graphene oxide membrane is found to be dependent on the oxidation level of the graphene oxide material and the concentration on the graphene oxide on the membrane. Unreduced graphene oxide membranes were created in three concentrations: 7.37, 14.74, and 29.47 μg/cm2. As graphene oxide concentration increased, dye rejection and salt rejection increased, while water flux decreased. Graphene oxide was reduced in solution using Vitamin C and was used to create a 14.74 μg/cm2 membrane. The reduction resulted in an increase in salt rejection from 12.59% to 100%, an increase in dye rejection from 30.44% to 100%, and a decrease in water flux from 9.502 to 0.198 L/(hr*m2*bar). Future research should focus on creating membranes using different methods of synthesizing graphene oxide from graphene and creating a reduced graphene oxide membrane with a higher water flux.