GRAPHENE OXIDE MEMBRANES FOR WATER PURIFICATION

Abstract

Graphene oxide (GO) is a two-dimensional material with a single layer carbon lattice, which is decorated with oxygenated functional groups on the basal plane as well as on the edges. Due to its unique properties, GO has attracted many applications including electronics, energy, sensors, optics, etc. Recently, it has been demonstrated that the graphene surface of GO presents long slip lengths of water, thus allowing for an unimpeded water flow. It was anticipated that the ultrafast water transport would be translated into membrane separations, in order to address one of the major challenges for membrane technology—low performance. It was also expected that GO might provide solutions to other obstacles facing membrane technology, such as membrane fouling. These two overarching themes, the technical limitations for membrane technology and the potential of GO to overcome those restrictions, inspired the current study. The main objective of this dissertation was to develop highly efficient membranes for water purification based on GO. Also investigated were the transport mechanisms for the designed GO membranes, the potential of GO to mitigate membrane fouling, and the feasibility of GO membrane regeneration. Major achievements of the study include: (1) the development of high performance GO membranes for nanofiltration and forward osmosis by two facile and sustainable methods, (2) the elucidation of transport mechanisms to guide better GO membrane design, (3) the application of GO for fouling mitigation in pressure retarded osmosis processes, and (4) the validation for regenerable GO membranes. Collectively, not only do the findings provide the first experimental verification for the ultrafast water transport in GO membranes, they also suggest that the GO membrane could be a promising prototype of next generation membranes with high performance, low fouling propensity, and full regenerability. The work has already begun to show its profound impact in the membrane field, as seen in the publications it has prompted.