Cellulose acetate-based composite fibrous membrane with asymmetric wettability for directional water transport and high-flux oil-water separation

The investigation of dual-layer fibrous membranes with asymmetric wettability is gaining growing interest. Here, we conceive a novel composite fibrous membrane base on cellulose acetate (CA), characterized by a hydrophobic-on-hydrophilic configuration, using a designed co-electrospinning system. A thin layer of hydrophobic thermoplastic polyurethane (TPU) side is overlaid onto a hydrophilic CA/TPU membrane to achieve directional water transport and oil-water separation. The core-shell CA/TPU bicomponent fibers exhibit a much higher tensile stress (3.6 MPa) and tensile strain (72.15%), when compared with CA fibrous membrane. The TPU membrane displays beads-on-string morphology, which promote the directional water transport capacity, and the possible mechanism is discussed. The measurements show that our composite membrane can effectively separate various oil-water mixtures, solely driven by gravity. Interestingly, the membrane shows high oil-water separation flux (up to 109,918 Lm-2 h-1). This study expands the range of potential applications for CA fibrous membranes.