Novel sandwich-like membrane with hydrophilic-omniphobic-hydrophilic structure for sustainable water recovery in membrane distillation

Membrane distillation (MD) is attractive for water recovery from surfactant-stabilized oil-in-water emulsion due to its unique characteristics. To address the membrane fouling and wetting issues, a novel hydrophilic-omniphobic-hydrophilic sandwich-like membrane (PFZP) was firstly developed. Top PDA skin layer induced the hydration shell facing feed, which endowed membrane with high energy barriers (0.12 kT) to limit free hexadecane deposition. Omniphobic substrate (FZP) effectively avoided the deposition of free sodium dodecyl sulfate (SDS) and hexadecane-SDS aggregate. Bottom PDA skin layer was beneficial to maintain transmembrane temperature difference and driving force. Besides, both PDA layers (similar to 4.1 mu m) partly intruded into FZP substrate to shorten water vapor transmembrane transfer path. Compared with pristine membrane, PFZP membrane displayed greatly improved anti-fouling, anti-wetting and water recovery performance with stable water flux (18.0 LMH) and high salt rejection (99.99%). Obtained findings further improved the understanding of robust MD membrane design, its anti-fouling, mass and heat transfer mechanism.