Emulsified oil-water separation properties of superhydrophobic/superoleophilic surface by emulsion droplets impacting dynamic behavior

Abstract

Superhydrophobic/superoleophilic materials with excellent separation property are urgently needed for the clarification of water from oil-water emulsions, however, the lack of interfacial contact dynamics in the separation process is not beneficial to extensive application for them. Herein, a superhydrophobic/superoleophilic mesh was successfully prepared by spraying fluorinated polyurethane (FPU), silicon dioxide (SiO2) and carbon nanotubes (CNTs). The prepared mesh exhibited excellent superhydrophobic/superoleophilic performance, accomplishing a 1636.9 L m−2h−1 flux and a high separation efficiency above 99.8 % for water-in-oil (W/O) emulsions. The dynamic behavior of emulsion droplets impacting on the prepared mesh was innovatively investigated by experiment and simulation. As the oil content of emulsion droplets increased from 0 wt% to 2 wt%, the maximum spreading diameter (Ddmax) of emulsion droplets decreased from 5.57 mm to 5.28 mm, which can be attributed to the oil capture ability of the superhydrophobic/superoleophilic surface. Simultaneously, the maximum jet height (Hdamx) and the retraction velocity of the droplets firstly decreased and then increased. The results revealed that the oil film captured on the surface possessed good lubricity and water repellency, which could accelerate the dislodging of water from the surface and enhance separation performance. The separation mechanism of superhydrophobic/superoleophilic surface revealed by the contact dynamics study provided a novel path for the fabrication of emulsified oil-water separation materials.