Facile and scalable fabrication of hierarchically-structured and highly-wetting fibrous media for efficient oil/water coalescing separation

The development of efficient coalescing materials with fibrous structures remains a key focus for industrial oily wastewater treatment. In this study, we present a facile approach to create hierarchically-structured and highlywetting fibrous material with PVDF-decorated ZnO nanofibers on micro-glassfibers, via low-temperature hydrothermal and dip-coating techniques. These PVDF@ZnO nanofiber arrays, which vertically grow on the microglassfibers, exhibit high oil affinity and large surface area, offering numerous effective sites for capturing and colliding with small oil droplets, thereby enhancing oil coalescence efficiency in water. Simultaneously, the interconnected macropores of the micro-glassfiber substrate minimize fluid flow resistance, favorable for the easy release of coalesced oil without rupture. The synergy of a large surface area, high oil wetting property, and hierarchical porous structure yields exceptional oil/water separation performance, with a high separation efficiency of over 99 % for different oil types. Additionally, the durable PVDF skin layer ensures the new materials' long-term stability under various challenging environmental conditions. Given its simple and cost-effective fabrication, this innovative design shows significant potential to expand the practical use of hierarchicallystructured and highly-wetting fibrous materials for oily wastewater treatment.