Robust and Superhydrophobic PTFE Membranes with Crosshatched Nanofibers for Membrane Distillation and Carbon Dioxide Stripping

Abstract

AbstractPolytetrafluoroethylene (PTFE) nanofiber membranes with novel crosshatched structures are developed and applied to both water desalination by direct contact membrane distillation (MD) and CO2 separation by membrane gas absorption. Crosshatched structures are produced from a PTFE‐poly(ethylene oxide)(PEO) emulsion by depositing alternating layers of aligned fibers oriented in perpendicular directions. This is followed by sintering to remove the PEO and to stabilize the structure. The crosshatched structure allows for rapid gas and vapor transport due to the low tortuosity and high porosity, leading to fast and effective separation. PTFE nanofiber membranes with these novel structures are ideal for membrane CO2 stripping as this polymer is inherently strong and very hydrophobic. The mass transfer in both MD and CO2 stripping is greatly improved in the crosshatched nanofibers (CNF) as well as in composite membranes with microparticles (CNF‐MP), as compared with conventional random nanofibers. The membranes exhibit a MD flux up to 98.5 ± 1.2 kg m−2h−1, significantly greater than a standard PTFE membrane with asymmetric morphology, when tested with a 3.5 wt% sodium chloride feed solution at 80 °C in direct contact with water at 20 °C.