(571f) Dynamic Microstructure and Compaction of Graphene Oxide Thin Film Membranes in Nanofiltration

Graphene-based materials has attracted a lot of interest for developing ultra-thin and high performance membranes due to their unique two dimensional structure, one atomic thickness and strong mechanical strength. Graphene oxide (GO) membranes made by assembling small GO flakes have shown excellent performance in nanofiltration due to their well-defined interlayer space. However, besides the interlayer distance, the microstructures of GO membranes such as the stacking of GO flakes and the defects within membranes may also affect the membrane performance [1-2]. In our study on GO membranes in nanofiltration, serious membrane compaction was observed, where water permeation flux decreased considerably over time. The compaction of GO membranes could be due to the change in microstructure, where highly order GO laminar microstructure was induced when pressure was applied during the permeation test. However, the disorder of microstructure was reversible and could be restored when GO membranes were dried in air, and compaction reoccurred every time when GO membranes were retested after drying. The change in microstructure was found in GO membranes prepared by most of the synthesis methods (pressure driven or surface tension driven) and can be affected by the conditions where the membranes were stored. Understanding of the dynamic of the microstructures is crucial as it could affect the performance of GO membranes/ thin films in applications where the microstructure is critical. The observation of the change in membrane microstructures also provided important information for the understanding of water transport phenomenon in GO membranes. Though the microstructure evolved over time, GO membranes still showed an excellent molecular cut off for nanofiltration, ~250 Dalton after repeated drying-wetting cycles.

[1] Aba, N.F.D., et al., Graphene oxide membranes on ceramic hollow fibers â?? Microstructural stability and nanofiltration performance. Journal of Membrane Science, 2015. 484: p. 87-94.

[2] Chong, J. Y., et al., UV-enhanced sacrificial layer stabilised graphene oxide hollow fibre membranes for nanofiltration. Scientific Reports, 2015. 5: 15799.