Facile Fabrication of A Bioinspired Omniphobic-Slippery Membrane for Robust Membrane Distillation with Real Time Monitoring for Wetting, Fouling, and Scaling

Description

Increasing water scarcity and stringent discharge regulations necessitate the consideration of unconventional water resources such as seawater, hypersaline water, and wastewater, and call for emerging technologies to successfully augment water supplies. As a thermally driven membrane-based separation process, Membrane distillation (MD), is a promising technology for treating hypersaline waters from a variety of industries that cannot be treated by pressure driven reverse osmosis and traditional technologies. Despite MD’s practical benefits and increasing interest, MD has not yet reached the commercialization stage due to a number of technical obstacles that must be overcome. Specifically, when treating hypersaline brine, hydrophobic membrane’s pore wetting, mineral scaling, and fouling, could compromise an MD system’s performance or even lead to process failure. Therefore, a fundamental understanding and developing detection of these obstacles is of the utmost importance in driving commercialization. The application of membranes possessing high repellency of low surface liquid is one such mitigation strategy, which is driven by recent advances in material sciences. Over the past decade, various novel membranes with special wetting properties, such as hydrophobic, superhydrophobic, omniphobic, or Janus (asymmetric wettability) surface have been introduced as potential solutions. Most recently, omniphobic membranes have been gaining attention due to their superior wetting resistance against feedwaters with a wide range of surface tensions. However, high costs and complicated fabrication steps, as well as the use of environmentally polluting fluorine-containing materials, have limited their practical application. Thus, developing a novel MD membrane via simple and greener fabrication methods which is capable of prevent wetting, scaling, and fouling while maintaining high durability remains a challenge. In this study, we propose a facile and easily-scalable surface modification method that can fundamentally resolve the limitations encountered in the fabrication of conventional omniphobic membranes. Drawing inspiration from nature, particularly the springtail’s cuticle and pitcher plant, we intend to create a re-entrant structure by depositing concave polystyrene (PS) beads on a polyvinylidene difluoride (PVDF) substrate via electro-spraying to impart omniphobicity followed by a lubricant to impart superhydrophobicity and make it slippery. Successful completion of this project will deliver an omniphobic-slippery membrane by turning the originally easily-wet, smooth surface into one that has non-wetting properties and superior resistance to fouling, wetting, and scaling. Further, our novel detection and characterization methods will enable real time monitoring of wetting intrusion and the progression of fouling and scaling, providing early detection which will prolong MD operation, overcoming one of the main bottlenecks.