Superhydrophobic membranes with enhanced pore surface hydrophobicity for stable membrane distillation of hypersaline wastewater
Porous membranes with superhydrophobic surfaces are widely employed to prevent pore wetting during membrane distillation (MD) desalination of hypersaline wastewater. However, prolonged operation often leads to scaling and pore wetting due to depletion of surface-trapped air cushions, a degradation attributed to enhanced surface hydrophobicity rather than bulk hydrophobicity throughout the membrane. This work simultaneously enhances the hydrophobicity of both membrane surfaces and pore surfaces by constructing nanostructures using hydrophobic nanoparticles. The resulting membranes exhibit a 31.3% increase in specific liquid entry pressure of water (reaching 0.109 bar μm−1) compared to membranes with only surface superhydrophobicity, indicating improved resistance to pore wetting. Stable permeate flux (16.2 kg m−2 h−1) and high salt rejection (>99.9%) are maintained when treating 70 °C brines (105 g L−1) in MD. The high pore wetting resistance against gypsum-containing saline is further demonstrated through cyclic MD desalination over 30 h, indicating strong potential for high-performance MD membranes in hypersaline wastewater treatment.