Directional Fluid Gating by Janus Membranes with Heterogeneous Wetting Properties for Selective Oil–Water Separation

Abstract

The rising oil seepage accidents evolved into a global issue necessitating immediate counter measure to abridge its catastrophic repercussions on sensitive marine ecosystem urging innovative techniques for effective oil/water separation. Here, we report surface tailored wettability modified superhydrophobic/superoleophilic Janus membrane by impregnating nonionic surfactant stabilized nanosized polytetrafluoroethylene (PTFE) dispersion polymerized via nonfluorinated processing aid onto cotton substrate using the Meyer rod-coating technique, exhibiting excellent separation efficiency up to 98% with various petroleum products and retaining its intrinsic properties for at least 30 recurrences. Morphological analysis revealed the generation of closely spaced irregularly patterned nanospindles on the microfibral cotton surface devising hierarchical dual-scale surface architecture, followed by superhydrophobicization (WCA 168° ± 3°) and low ice-adhesion, illustrating deviation from conventional Wenzel and Cassie-Baxter wetting theories. The developed membrane exhibited flame retardancy, anti-icing characteristic, and retained its superhydrophobic/superoleophilic characteristic of Janus membrane in hyper-saline solution, UV-irradiation of wavelenghth 254 nm, high temperature of 150 °C, and subzero temperature of -20 °C. Furthermore, we hypothesized the developed membranes as a directional fluid diode, allowing lower surface tension liquids (oil) to permeate while barring higher surface tension liquids (water) from penetrating, and the breakthrough pressure of 0.65 kPa for water permeation was also mathematically calculated. This study systematically exemplifies the reported fabric as a potentially competent alternative for cleaning massive marine oil seepages.