Temperature and pH-responsive electrospun membrane with high flux recovery for emulsion separation

Stimuli-responsive wettability surfaces for oil-water separation have been receiving widespread attention. The introduction of responsive groups onto the surface usually requires complicated steps. In this study, poly(Nisopropyl acrylamide) (PNIPAm) and poly(N, N-dimethylaminoethyl methacrylate) (PDMAEMA) were blended with polyacrylonitrile (PAN) to fabricate pH and thermal dual-responsive PAN/PNIPAm/PDMAEMA nanofiber membranes through one-step electrospinning process. The introduction of a suitable proportion of responsive polymers provided the membrane with stimuli-responsive wettability to pH and temperature. Specifically, due to the protonation of tertiary amine groups and changes in membrane microstructure, the wettability of the membrane is hydrophilic at pH = 2.0 or T = 50 degrees C and presents hydrophobic at pH = 7.0 or T = 25 degrees C. The developed blend membrane performed excellently in separating various oil-water mixtures, with separation efficiency beyond 99.5% and 96.8% for immiscible oil-water mixture and surfactant-stabilized emulsions, respectively. More interestingly, the temperature and pH responsive wettability could effectively overcome the drawback of flux decline during the separation process. In particular, the membrane has achieved a superior resistance to contamination and a high flux recovery up to 98.9%, related to its greater affinity with water under pH = 2.0/T = 50 degrees C conditions. Therefore, the obtained dual-responsive blend membrane with tunable wettability could combine the merit of excellent separation efficiency and high flux recovery rate, showing the practical application for separating the emulsified oil-water mixtures.