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

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 (0 degrees) and underwater superoleophobicity (>160 degrees) 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.

Automated summary

Despite previous efforts, separating stable micron-sized oils from wastewater emulsion remains challenging. This study presents a mechanically stable biaxial polypropylene membrane with nano-porous structures for efficient separation of tiny oil droplets. A two-step surface modification method using acrylic acid and sodium hydrogen carbonate monomer achieves excellent hydrophilicity and underwater superoleophobicity. The modified membrane demonstrates high separation efficiency (>99.5%) for micron-sized oil droplets and remarkable wetting constancy under harsh conditions. Overall, this simply modified biaxial polypropylene membrane shows significant potential for practical applications.