(450c) Graphene Oxide Membranes with Hierarchical Roughness for High Flux, Anti-Fouling Oil/Water Separation

Underwater superoleophobic surfaces have shown increasing importance in a variety of applications among which oil/water separation is of great interest due to the increasing amount of oily wastewater from industries, a shortage of clean water, and frequent oil spill accidents. Despite recent advances in nano/ultrafiltration membranes in oil/water separation, fully recoverable oil/water separation performance has rarely been demonstrated, especially for stable, difficult-to-separate oil emulsions. A promising strategy of designing superoleophobic surfaces for underwater applications is to incorporate desirable hierarchical surface roughness, as inspired by the natural formation of fish scales. Mimicking the structure of fish scales has been attempted to for the preparation of superoleophobic surfaces and has been studied for oil/water separation. Compared with conventional antifouling coating agents, bio-inspired underwater superoleophobic materials have improved oil/water separation performance and enhanced fouling resistance. Most previous studies, however, focused merely on replicating the structure of fish scales. The function of the mucus layer on the surface of fish scales was usually neglected. In fact, the mucus layer replicates the hierarchical roughness of the fish scales underneath, and it preferentially attracts water molecules in oil/water mixtures, forming a superoleophobic oil/water/solid interface. To mimic the excellent anti-fouling and self-cleaning performance of fish scales, a combination of the hierarchical surface roughness and the conformal, underwater superoleophobic coating layer is apparently necessary. However, it is highly challenging to perfectly combine these two aspects, and little success has been reported to date. Graphene oxide (GO) is a promising two-dimensional (2-D) membrane/coating material, owing to its one carbon atom thickness, ease of conformation to substrates, excellent chemical stability, and mechanical strength. GO membranes have shown great potential for gas and liquid separations through size-sieving by either interlayer spacing or selective structural defects. Here, we report, for the first time, the utilization of mucus-mimicking GO for fabricating ultrafiltration membranes with desirable hierarchical surface roughness and their application for high flux, anti-fouling oil/water separation.