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High-performance thin film composite polyamide (TFC-PA) membranes with controllable structure and transport properties are of great significance. However, TFC-PA membranes prepared by interfacial polymerization are far from ideal due to their quick and uncontrollable reaction process. In this study, we reported a novel strategy to fabricate TFC-PA membranes via an electrospray interface-less polymerization (EILP) technique with a miscible solvent system. The miscible solvent system facilitated both the stable and fine spraying of monomer solutions and the efficient polymerization of monomers, and thus resulting in the formation of a smooth and defect-free PA skin layer. Moreover, the crosslinking degree and thickness of the EILP membrane skin layer could be controlled easily by regulating the concentration and dose of sprayed monomers. Attenuated total reflectance-Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, zeta potential and mean effective pore size were employed to characterize the EILP membrane and clarify the separation mechanism. The optimum EILP membrane showed excellent filtration performance with a high water flux of up to 17.7 L m−2 h−1 bar−1, high salt rejection (98.2% of Na2SO4) and complete dye rejection for Congo red. This study provides new insights into the understanding of electrospray procedures and enlightens the design and manufacture of advanced membrane materials through electrospray.

Membrane distillation (MD) is an emerging water treatment technology suitable for hypersaline wastewater. However, membrane wetting is a primary obstacle to restrict its widespread industrial use. In this study, a superhydrophobic nanofibrous membrane (labeled as FZP) with high water contact angle of 162.3° and sliding angle of 9.8° was fabricated through fluorinating of zinc oxide (ZnO) blended electrospun polyvinylidene fluoride (PVDF) membrane. In comparison with neat and ZnO blended PVDF (ZP) nanofibrous membranes, FZP membrane has much better anti-wetting property due to its superhydrophobicity and higher liquid entry pressure (LEP) value when desalinating both pure NaCl solution and NaCl solutions with low-surface-tension sodium dodecyl sulfate (SDS) and sparingly soluble salt CaSO4. LEP values of membranes for SDS and CaSO4 contained feed solutions were calculated to be smaller than that for pure NaCl solution, accelerating the occurrence of membrane wetting. Temperature gradient across the membrane and Gibbs free energies of CaSO4 heterogeneous nucleation were further calculated to elucidate the wetting mechanism. Our results provide valuable insights for better developing superhydrophobic membrane and understanding its anti-wetting property in MD process.

This study introduced a facile approach for high-performance electrospinning-phase inversion composite membrane, aiming at solving the low mechanical property, low mass transfer and salt leakage in extractive membrane bioreactor (EMBR) for phenol saline wastewater treatment. Composite membrane was fabricated through coating polydimethylsiloxane (PDMS) on electrospun PDMS membrane via dry phase inversion. Its surface was similar to that of phase inversion membrane while the cross section was uniformly distributed electrospun fibers in phase inversion layer, forming interconnected pore. The loose porous structure and high porosity were suitable for phenol permeation, and hydrophobic surface could reject the salt invasion. The tensile strength and elongation at break of composite membrane (56.5 μm thickness) were 1.7 MPa and 60.0%, making it stably operated in EMBR. Effects of different process variables were investigated, including membrane thickness, phenol concentration and wastewater flow rate. Remarkable performance of phenol biodegradation and salt rejection was achieved during EMBR operation, where the maximal phenol removal rate and conductivity variation in microorganism side were 508.9 mg L−1 d−1 and