Design of a superhydrophobic network layer for enhancing the stability and wetting resistance of membrane distillation

Membrane distillation (MD) is an advanced separation technology that combines principles of traditional distillation with membrane technology, offering significant potential for applications in desalination, high-salinity water treatment, and industrial wastewater management. Nevertheless, MD membranes encounter challenges such as low permeate flux and membrane pore wetting, which notably hinder their development and wider application. To address these issues, this study developed MD membranes with superhydrophobic network interlayer through a one-step impregnation method. The superhydrophobic network layer was fabricated using the hydrophobic polymer PDMS and ZnO nanoparticles (ZnNPs). Following the modification, the structural properties and MD performance were remarkably improved. Specifically, the water contact angle (WCA) of the membrane increased from 125.5° to 155.9°, accompanied by a sliding angle (SA) of 11.3°, while the liquid entry pressure (LEP) was enhanced from 0.85 bar to 1.55 bar, and the average pore size decreased from 0.88 μm to 0.61 μm—attributable to the constructed superhydrophobic network layer. Furthermore, the results of direct contact membrane distillation (DCMD) tests showed that the superhydrophobic membranes exhibited superior anti-wetting properties and more outstanding permeation fluxes compared to commercial PVDF membranes. Using a 3.5 wt% NaCl solution as feed solution, the superhydrophobic membrane exhibited a water flux of 35.47 ± 0.96 kg·m −2 ·h −1 in an 18 h DCMD test. In the 72-h-long DCMD test, the superhydrophobic membrane exhibited a stabilized water flux of 35.01 ± 1.83 kg·m −2 ·h −1 and a retention rate of 99.95 %, which proved its applicability in MD desalination.