Hierarchical selective membranes combining carbonaceous nanoparticles and commercial permeable substrates for oil/water separation

Abstract

Developing a simple and scalable method to create effective oil–water separation membranes and achieving optimal trade-off between its permeability and selectivity are current challenges in membrane technology for oil from water recovery. Herein, new highly hydrophobic/superoleophilic membranes (contact angles of ~143°/~0°) which meet these challenges have been obtained via a one-step process. Metallic meshes, polypropylene non-woven and cotton fabrics were exposed to low power RF-plasma of commercial grade acetylene at room temperature and medium vacuum. This way, plasma polymerized nanoparticles (NPs) were deposited over the substrates. The as-obtained membranes completely prevent the passage of water while allowing a maximum oil flux over 10,000 L m−2h−1 at 116 Pa, achieving an efficiency above 99% and reusability maintaining high performance. By controlling the mass surface density of the NPs deposit, it is possible to change both the membranes water breakthrough pressure and oil permeation speed. Membrane permeabilities were successfully obtained by fitting permeated oil volume vs time data with a Darcy-based model. The influence of surface density of NPs on the permeability and water pressure resistance was described with empirical equations. From the combination of these mathematical relations it is possible to design membranes with optimal trade-off between water pressure resistance and oil permeation speed according to the usage conditions.