ION PERMEATION THROUGH GRAPHENE OXIDE MEMBRANES

Abstract

Graphene oxide (GO), a promising membrane material consisting of oxygenated graphene sheets, hosts a wealth of physicochemical properties such as exceptional chemical stability, flexibility, hygro-responsivity, ultrafast water permeation and exceptional molecular sieving properties, to list a few. However their use in desalination applications requires a stable sub nanometre channels, which are difficult to achieve in GO due to hydration mediated swelling of graphene capillaries. The work presented in this thesis mainly describes how to achieve tunable and swelling controlled sub nanometre capillaries in GO membranes by physical confinement, ion/water transport through such capillaries and the governing transport mechanism. GO membrane with interlayer spacing in the range of ̴ 6-10 Å was obtained by utilizing its hygro-responsive property and the subsequent physical confinement by epoxy resin limits the swelling. The epoxy resin acts as physical wall on both sides of the GO laminates, restricting the capillaries from hydration when exposed to water. Regardless of the steric effects, ions still pass through these channels even though the channel size is smaller than the hydrated ion diameter size. This unique observation of violation of steric effects in sub nanometre channel cases is explained by a phenomenon called dehydration. Beyond the sake of fundamental understanding of the transport mechanism in sub nanometre capillaries, our results open the door for developing GO membranes with dehydration mediated ion selectivity for water desalination and separation applications.

Date of Award	1 Aug 2018
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Irina Grigorieva (Supervisor) & Rahul Raveendran Nair (Supervisor)