Intrinsic microspheres structure of electrospun nanofibrous membrane with rational superhydrophobicity for desalination via membrane distillation

Electrospun nanofibrous membranes with superhydrophobicity are good candidates for membrane distillation (MD). In this study, we developed a facile one-step electrospinning method to prepare a superhydrophobic PVDF-HFP microsphere/nanofiber membrane in N-methyl-2-pyrrolidone (NMP). Then, the electrospun membrane was treated with ethanol-water solvent exchange. The fabricated membrane shows an interconnected microsphere-nanofiber structure with hierarchical micro-nano roughness. Due to the intrinsic microspheres on the nanofibers, the water contact angle of all microsphere/nanofiber membranes is higher than 150°. The optimal membrane exhibits superhydrophobicity, with a static contact angle of 156.6 ± 1.38° and a low sliding angle of 6.4 ± 0.2°. In a laboratory-scale direct contact membrane distillation (DCMD), the optimal membrane (with an effective membrane area of 9 cm2) shows a high permeate flux of 38.8 kg·m−2·h−1 and a salt rejection of 99.99% during a 40-h long-term desalination process. The superhydrophobic membrane exhibits excellent wetting and fouling resistance. Therefore, these properties will increase the water production of MD, thereby solving the problem of membrane wetting or fouling in wastewater treatment.