Robust super-wetting biaxial polypropylene membrane with multi-scale roughness structures for highly efficient oil/water emulsion separation

Abstract

The severe toxicity of oily wastewater is considered extremely detrimental to both human health and the environment. Despite previous enormous efforts, it is still challenging to efficiently separate extremely stable micron-sized oils from wastewater emulsion. This study reports a highly mechanically stable biaxial polypropylene membrane with uniform nano-porous structures for excellent separating tiny oil droplets from emulsion. A facile and scalable two-step surface modification method has been developed by employing acrylic acid and sodium hydrogen carbonate monomer. This modification method ensures excellent hydrophilicity (0º) and underwater superoleophobicity (>160º) by constructing multiscale micro/nano rough surfaces with controllable membrane pores. The modified super-wetting membrane efficiently separates micron-sized oil droplets from surfactant-stabilized emulsions with more than 99.5% separation efficiency. Additionally, the membrane’s outstanding mechanical stability ensures excellent recyclability with remarkable wetting constancy to diverse harsh conditions. Inclusively, the simply modified biaxial polypropylene membrane shows noteworthy potential for usage in practical applications.