Monolithic and self-roughened Janus fibrous membrane with superhydrophilic/omniphobic surface for robust antifouling and antiwetting membrane distillation

The treatment of hypersaline wastewaters with membrane distillation (MD) is significant but challenging, owing to the critical limitations of severe membrane wetting and fouling. Herein, a monolithic and self-roughened Janus fibrous membrane (FM) with asymmetrical superwettability was developed via sequential electrospinning and electrospraying in combination with thermal treatment. We detailedly discussed the formation mechanism of the roughness on the fiber surface via electrospinning/electrospraying technique and explored the asymmetrical wettability and the monolithic performance of Janus FM for the synergistic resistance of membrane wetting and fouling. Benefiting from the high in-air water contact of 157° of the omniphobic surface, the high underwater oil contact angle of 156° of the superhydrophilic skin layer, as well as the monolithic performance of the resultant membrane, the newly developed Janus FM achieves a high water flux of over 27 L m⁻² h⁻¹ and high desalination efficiency of ~100% when desalination of the simulated hypersaline wastewater composed of 3.5 wt% of NaCl, 0.1 g of SDBS and 1.0 g of lubricating oil. The presented strategy on Janus FM fabrication is believed to open a new direction to prepare monolithic, self-roughened, and asymmetrically superwettable Janus FM and applied in a wide field of other selective separation applications.