Facile Fabrication of Binary-Structured Fibrous Membranes with Antifouling and Flame-Retardant Properties for Durable Water/Oil Separation

Membrane fouling from dispersed droplets during water/oil separation undermines performance and limits long-term use. Additionally, there is an urgent need for flame-retardant fibrous membranes capable of purifying high-temperature polluted oils. Inspired by the binary structure of taro leaves, this study introduces a novel fibrous membrane with both antifouling and flame-retardant properties for water/oil treatment. Eco-friendly cellulose acetate (CA) and multifunctional thermoplastic polyurethane (TPU) were used to construct a microfiber-based substrate membrane via electrospinning. A TPU/ammonium polyphosphate (APP) nanofiber layer with a beads-on-string structure was then electrosprayed onto the substrate as a functional layer. This binary-structured composite membrane leverages the adhesive properties of TPU within both the base microfibers and the functional nanofibers, enhancing stability and structural integrity. The functional layer's re-entrant structure effectively prevents dispersed droplets from adhering under the continuous phase, enabling efficient separation performance in both oil-in-water and water-in-oil emulsions. The membrane demonstrated strong antifouling properties and excellent recyclability, maintaining stable flux and a consistently high separation efficiency (>99.6%) across multiple cycles. Additionally, its flame-retardant properties allowed the membrane to self-extinguish when removed from direct flame. This study presents a novel strategy for fabricating multifunctional separation membranes, with detailed analysis of the underlying mechanisms.