In-situ silica nanoparticle assembly technique to develop an omniphobic membrane for durable membrane distillation

Abstract This work reported that a novel omniphobic membrane distillation (MD) membrane was successfully fabricated by constructing a re-entrant microstructure via in-situ silica nanoparticle (SiNPs) growth on an electrospun polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP)/3-aminopropyl-triethoxysilane (APTES) nanofibrous membrane, and subsequent hydrophobization. Introducing APTES provided the nucleation sites for in situ SiNPs growth on the hydrophobic nanofibers for re-entrant structure construction. After hydrophobization, the final membrane exhibited outstanding omniphobicity with high contact angle values of 151.49°, 140.64°, 119.59°, and 107.5° to water, mineral oil, 4 mM sodium dodecyl sulfate (SDS) and ethanol, respectively. More importantly, the prepared omniphobic membrane showed satisfactory wetting resistance in a feed solution containing a 3.5 wt% NaCl and 0.4 mM SDS, and the salt rejection was ~100%. In addition, the omniphobic membrane also demonstrated robust scaling resistance, which was in sharp contrast to the PVDF-HFP membrane. Meanwhile, during treating a mineral oil-in-saline (3.5 wt% NaCl) water emulsion, the omniphobic membrane displayed outstanding anti-wetting and anti-fouling properties, indicated by a steady state permeate flux and ~100% stable salt rejection during the continuously 72 h tests. These overall findings indicated that the prepared omniphobic membranes have great potential in MD for challenging industrial wastewaters.