Nepenthes -inspired liquid-infused membranes with capillary-enhanced thermal efficiency anti-scaling, and anti-fouling for direct contact membrane distillation

Membrane distillation (MD) has emerged as a promising sustainable technology for desalination and the treatment of hypersaline or complex wastewater. However, the current MD membranes are susceptive to scaling and fouling and thus hamper their widespread application. Herein, we demonstrate a facile, general-applicable and robust approach inspired by the slippery surface of Nepenthes for fabricating anti-scaling and anti-fouling slippery liquid-infused membranes (LIMs) in MD process. The water vapor pressure plus an air pressure dynamically control opening and closing of the membrane pores to flexibly regulate the mass transfer. The simulation indicates that the LIMs effectively suppress the undesirable temperature polarization in MD. Compared to commercial membranes, the LIMs demonstrate superior salt rejection (>99.96 %), steady permeate flux within 12 h (22.5 L·m−2·h−1), and higher thermal efficiency (e.g., 61.4 % for a 3.5 wt% NaCl solution) under various complex water conditions. The slippery surface and low surface tension of LIMs reduce inorganic salt nucleation rates and oil adhesion forces, proving their excellent anti-scaling and anti-fouling properties. Our fabrication approach of the MD system with LIMs is general-applicable with excellent performance for diverse porous substrate membranes ranging from hydrophobic polytetrafluoroethylene and poly(vinylidene fluoride) to hydrophilic polyethersulfone. The general applicability of this approach overcomes conventional material limitations in MD while highlighting its potential for treating high-salinity and oily industrial wastewater.