Green-solvent-processed amphiphobic polyurethane nanofiber membranes with mechanically stable hierarchical structures for seawater desalination by membrane distillation

Abstract

Seawater desalination which offers an abundant and reliable source of freshwater is a promising strategy to ensure water security; however, most present desalination membranes show low porosity and weak mechanical properties, and typically have an inevitable trade-off dilemma between permeate flux and salt rejection. Here, we present a unique strategy to create environmentally friendly polyurethane (PU) nanofiber membranes with desirable surface wettability, stable pore structures, and robust mechanical properties for desalination via green electrospinning technique and heat pressing treatment. The incorporation of polytetrafluoroethylene (PTFE) nanoparticles and heat pressing manipulation endow the nanofiber membranes with the integrated properties of robust hydrophobicity, small pore size, and hierarchical structures by constructing micro/nano surface roughness, low energy surface, and bonding points. Strikingly, the heat pressed PU/PTFE nanofiber membranes exhibit robust mechanical strength (23.5 MPa), remarkable liquid entry pressure (79.2 kPa), and exceptional vapor permeation (3395 g m−2 d−1), achieving high permeate flux of 44 kg m−2 h−1 and salt rejection of 99.96% for seawater desalination. This work provides a powerful platform for the design and development of the next-generation nanofiber materials for various filtration and separation applications.