Highly Efficient and Flexible Electrospun Carbon–Silica Nanofibrous Membrane for Ultrafast Gravity-Driven Oil–Water Separation

A novel free-standing and flexible electrospun carbon–silica composite nanofibrous membrane is newly introduced. The characterization results suggest that the electrospun composite nanofibers are constructed by carbon chains interpenetrated through a linear network of 3-dimensional SiO₂. Thermogravimetric analysis indicates that the presence of insulating silica further improve the thermal resistance of the membrane. Additionally, the mechanical strength test shows that the membrane’s toughness and flexibility can be enhanced if the concentration of SiO₂ is maintained below 2.7 wt %. Thermal and chemical stability test show that the membrane’s wettability properties can be sustained at an elevated temperature up to 300 °C and no discernible change in wettability was observed under highly acidic and basic conditions. After surface-coating with silicone oil for 30 mins, the composite membrane exhibits ultra-hydrophobic and superoleophilic properties with water and oil contact angles being 144.2 ± 1.2° and 0°, respectively. The enhanced flexibility and selective wetting property enables the membrane to serve as an effective substrate for separating free oil from water. Lab-scale oil–water separation test indicates that the membrane possesses excellent oil–water separation efficiency. In addition, its inherent property of high porosity allows oil–water separation to be performed in a gravity-driven process with high-flux. We anticipate that this study will open up a new avenue for fabrication of free-standing carbonaceous composite membrane with tunable flexibility for energy efficient and high-throughput production of clean water.