Hydratable Janus Membranes with Robust Antiwetting Pores for Stable Membrane Distillation of Saline Oily Wastewater

Abstract

Janus membranes, composed of a hydrophilic surface layer and a hydrophobic substrate, are potential candidates for membrane distillation (MD) to prevent organic substance induced wetting in saline oily wastewater treatments. However, owing to insufficient hydrophobicity of pore surfaces, traditional hydrophobic substrates suffer from pore wetting and limited MD performance stability when saline water penetrates through the hydrophilic layer. Herein, we present a Janus polyvinylidene fluoride (PVDF) nanocomposite membrane with robust pore surface antiwettability for stable MD desalination of saline oily wastewater. Hydrophobic silica (SiO₂) nanoparticles are used to build nanostructures on pore surfaces to significantly enhance their hydrophobicity for preventing pore wetting. The superhydrophilic tannic acid/Fe (TA/Fe) layer provides a hydratable surface to promote water molecule absorption, facilitate the evaporation rate, and effectively impede oil/surfactant/gypsum contaminants. As a result, the TA/Fe-PVDF/SiO₂ Janus membrane shows stable desalination (32 h) with a high flux of 25.2 kg m^–2 h^–1 and salt rejection (>99.9%) for saline oily solution. This work provides a promising approach to develop high-performance Janus membranes with antiwetting ability for stable saline oily wastewater treatment.