Super hydrophilic modified biaxially oriented polypropylene microporous membrane for excellent gravity-driven oil/water emulsion separation

Considering the protection of our natural environment from oily wastewater toxicity, the biaxially orientated polypropylene (PP) microporous membrane is taken as a suitable substrate to prepare a super hydrophilic and underwater superoleophobic membrane for oily wastewater separation. It is designed as a large-scale, cost-effective, and stable technology with the minimum possible environmental pollution to prepare the membrane for oily wastewater emulsion separation. The hydrophobic PP membrane is initially treated via corona discharge treatment followed by a grafting reaction with hydrophilic acrylamide monomer to generate rough micro-nano structures and polar functional groups. The permanent super hydrophilicity and underwater oleophobicity properties are accomplished by measuring the water contact angle (∼ 0°) and the underwater-oil contact angle (∼ 153°) over 10 weeks. Due to its excellent mechanical properties with a uniform modified micro-nano porous structure, significant separation flux with high efficiency is achieved for layered mixtures, surfactant-free, and surfactant-stabilized emulsions over 10 times reusability. Consequently, all separation processes are handled by the energy-saving gravity-driven separation method. Overall, this study demonstrated the super hydrophilic and underwater superoleophobic biaxially oriented polypropylene membrane, prepared in a stable and large-scale approach with outstanding separation performance, which can be widely used in emulsion separation and practically as an excellent solution for water separation from oily wastewater.