Preparation of Hydrophobic Functionalized Poly(vinyl alcohol) Formaldehyde-Based Composite Sponges for Highly Effective Water-in-Oil Emulsion Separation

Three-dimensional porous materials featuring unique pore structures and wettability properties have shown great potential for emulsion separation. However, their practical utilization in industrial settings is hampered by their inability to sustain a high separation flux and efficiency during the separation process. To address these challenges, we developed composite sponges based on poly(vinyl alcohol) formaldehyde (PVF) with a hierarchical pore structure. This was achieved through secondary chemical cross-linking of poly(vinyl alcohol) (PVA), followed by additional hydrophobic modification using grafting polymerization of various methacrylate monomers. Typically, the resultant typical PVF/PVA-Mac-PEMA sponge exhibits an average pore size of 24 μm and hydrophobic networks with a water contact angle of 133.3°. The intriguing sponges possess notable potential for effectively separating water-in-oil emulsions driven solely by gravity, achieving a maximum flux of 5.40 × 10⁵ L m^–2 h^–1 bar^–1 and separation efficiency exceeding 99.72%, respectively. The PVF-based composite sponges display remarkable reusability and long-term stability, which remain nearly unchanged even after undergoing 10 cycles and continuous use for 30 min. Furthermore, their ability to be easily restored through washing renders them suitable candidates for practical applications. These merits make them highly promising for applications requiring prolonged and repetitive operation.