Membrane hydrophobicity enhanced by non-solvent induced separation strategy for improving membrane distillation performance

Development of high-performance hydrophobic layer using green and economic method is still urgently on demand for wide applications of membrane distillation (MD). In this study, a novel Janus membrane was prepared by electrospinning polystyrene with the water addition on the surface of hydrophilic electrospun nanofiber substrate. With increasing water content to 3 wt%, the hydrophobic layer is completely converted to be nanofiber-dominate morphology that could be beneficial for water vapor permeation during MD process. The surface roughness, water contact angle value and porosity of the hydrophobic layer are enhanced by the water addition, and the optimized Janus membrane with the hydrophobic layer prepared at the water content of 2 wt% could achieve a high water flux of 33.1 L/m²h and superior salt rejection of >99.9 % when 3.5 wt% NaCl solution was used as the feed solution. The as-prepared Janus membrane shows better performance stability and reusability than the control membrane (without the water addition) within the 24-h continuous operation duration. Our work demonstrates that the proper water addition could be used as a green strategy for fabricating efficient electrospun nanofiber membranes for the direct contact membrane distillation (DCMD) processes.