Superhydrophilic PVDF nanofibrous membranes with hierarchical structure based on solution blow spinning for oil-water separation

Nanofibrous membranes (NFMs) are frequently used in oil-water separation thanks to their high porosity, controllable pore size, and convenience in modification to obtain super wettability. However, the low production rate and dense structure of NFMs have limited the industrial applications. In this work, zinc oxide (ZnO) seed loaded polyvinylidene fluoride (PVDF) NFMs with fluffy structure were prepared through solution blow spinning (SBS). Subsequently, ZnO nanowires (NWs) were synthesized based on the seeds through ultrasonic assisted hydrothermal reaction, constructing superhydrophilic surface with hierarchical structure. The u-ZnO-NWs/PVDF showed uniform morphology throughout the entire membrane with an average fiber diameter of 517.35 ± 158.72 nm and an average nanowire diameter of 72.55 ± 20.52 nm, which resulted in a low average pore size (4024.68 ± 393.40 nm), superhydrophilicity, and underwater oleophobicity. The nanowire equipped membrane revealed super high water flux (12960.77 ± 325.04 L·m−2·h−1·bar−1), which could be applied in the separation of oil-in-water emulsions with high separation efficiency (>97 %) and high flux (about 8000 L·m−2·h−1·bar−1) under gravity. Results indicated the potential of SBS u-ZnO-NWs/PVDF in the fields of oil-water separation, sewage treatment, as well as catalytic degradation.