Access to clean water has become an increasing challenge due to the increased incidence of the worldwide oil spill, wastewater pollution, and hot island effect. Membranes that have selective oil/water wetting properties have received significant attentions recently. In particular, membranes with hierarchical architectures, which integrate different sizes of pores in tandem, are of great interests due to their potentials for achieving large flux, high selectivity, and mechanical durability. However, it remains challenging to manipulate the pore size of the top skin layer in the nanoscale without sacrificing the flux, thus limiting the size of the oil/water droplets that can be filtered. Meanwhile, oil will foul the membrane over time, thus, blocking the holes for oil/water separation. Here, I will discuss several strategies to control membrane architectures, including 1) Electrospin polymer fibers followed by stretching to create elongated pores. 2) Utilize photofluidization of the electrospun fiber network made from azobenzene-containing polymer to precisely control the pore size of hierarchical membranes ranging from micro- to nano-scale. 3) Create a superhydrophilic, hierarchically porous structures on fabric for high throughput and continuous removal and recovery of spilled oil from water. Superhydrophilic surfaces are underwater superoleophobic. Along the line, we synthesize and assemble polyelectrolyte (e.g. polyacrylic acid, PAA) grafted silica chain nanoparticles. When spray coated on surface, nanoporous membranes are obtained. While chain nanoparticles and their assembly provide control of surface topography, the hygroscopic nature of the grafted polyelectrolyte, the combination leads to an ultrastable superhydrophilic and anti-oil fouling coating. Even after the PAA-grafted nanochain coating is purposely fouled by oil, oil can be readily and completely expelled and lifted-off from the coating within 10 seconds when placed under water.<br/>

Design of hierarchical membranes for efficient oil/water separation and anti-oil fouling

2019 Fall National Meeting

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