Comparison of water purification properties of Graphene Oxide (GO) membranes with tuned interlayer spacings

Worldwide researchers are actively engaged in developing materials that exhibit efficient water filtration and advanced contaminant separation properties. Graphene oxide (GO) is one such material that possesses well-defined nanosized pores. Literature reports indicate the advantageous property of GO nanosheets to be properly spaced and stacked into membranes allowing high speed water flow (low frictional) inside. Although precise sieving of ions and molecules is reported using GO membranes but tuning of interlayer spacing by varying the oxidation state during synthesis is yet to be investigated. In the current study three different GO samples have been synthesized by Hummer's method with different degrees of oxidation. XRD analysis is seen to confirm the decrease in interlayer spacing from 0.838 to 0.782 nm as processing temperature (in the last stage) is increased from 50 to 95 °C leading to different degree of oxidation. Water flux is noted to decrease for the GO membrane developed at higher temperature due to reduction in interlayer spacing. It is also observed that temperature of synthesis directly affects the degree of oxidation which in turn influences water purification application ability of the GO membranes. Membrane prepared at 95 °C is seen to exhibit highest dye rejection whilst it returns lowest pure water flux.