An Oleogel-Based Slippery Membrane via Green Solvent-Free Strategy for Paraffin Oil/Water Separation

Membranes with slippery liquid-infused porous surfaces (SLIPS) have emerged as highly promising candidates for oil/water separation owing to high separation efficiency and anti-fouling properties. However, the fabrication of SLIPS is complex and often involves organic solvents, posing environmental and cost concerns. This study developed an oleogel-based slippery membrane via a green solvent-free method. A beeswax/paraffin oil oleogel was hot-pressed onto the surface of polypropylene (PP) membrane. The obtained PP-OleG membrane exhibited self-lubricating property, enabling water droplets to slide on the surface. Further infusion of paraffin oil yielded a PP-OleG-oil membrane with enhanced slippery property and anti-protein adhesion. The oleogel and oil layers on the membrane surface demonstrated good stability. Both PP-OleG and PP-OleG-oil membranes outperformed unmodified PP in water-in-oil emulsion separation. Notably, the PP-OleG-oil membrane protected by oleogel and oil layers prevented direct contact between contaminants and the membrane substrate, resulting in excellent anti-fouling performance. After six cycles of filtration, the flux recovery rate reached 86%, and the separation efficiency remained above 98.5%. This oleogel-based membrane offers a feasible approach to enhancing anti-fouling performance in oil/water separation and also provides insights for wastewater treatment through green strategies.