Membrane distillation by novel Janus-enhanced membrane featuring hydrophobic-hydrophilic dual-surface for freshwater recovery

• The Janus-enhanced membrane with anti-wetting ability and high flux was prepared. • Double-side modification synergistically promoted membrane performance. • The crosslinked Polydimethylsiloxanes endowed the membrane anti-wetting property. • The crosslinked MXene sprayed on the permeate side can improve the permeate flux. Membrane distillation (MD) is a promising membrane process with nearly 100% salt rejection, which can can realize freshwater recovery and reuse. However, wetting and low permeate flux are major concern for the hydrophobic microporous membrane during MD operation. To address this concern, a simple and effective method to fabricate anti-wetting and high permeate flux Janus-enhanced membranes with double-sided spraying was developed. The spraying materials on both sides of the polytetrafluoroethylene (PTFE) membrane were prepared by crosslinking reactions. Sulfosuccinic acid (SSA) crosslinked MXene was used in the permeate side to construct hydrophilic nanochannels, consequently improving the permeate flux. Methyltriethoxysilane (MTES) crosslinked polydimethylsiloxanes (PDMS) was used in the feed side to reduce surface energy and enhance the anti-wetting ability of the membrane. The optimal water contact angles for the feed and permeate side were 135° and 71.8°, respectively. During direct contact membrane distillation (DCMD) experiments of seawater desalination, Janus-enhanced membrane proved to be stable after 60 hours with an average permeate flux as high as 33.5 kg/(m 2 ·h). Therefore, this study provided a novel insight on preparing a MD membrane with simultaneous enhanced permeability and wetting resistance for freshwater recovery.