Hierarchical Superhydrophilic Electrospun Membranes via Postfabrication Grafting of Polydopamine and Surface-Tailored Silica Nanoparticles for Efficient Oil/Water Emulsion Separation

The separation of surfactant-stabilized oil/water emulsions remains a critical challenge due to the inefficiency of conventional methods and the limitations of existing membranes, such as poor wettability, low porosity, and fouling susceptibility. In this study, we propose a novel strategy to fabricate hierarchically structured superhydrophilic and underwater superoleophobic electrospun membranes via postfabrication grafting of polydopamine (PDA) and surface-tailored silica (M-SiO₂) nanoparticles. This strategy enables the synergistic design of interfacial morphology and surface energy of membranes. At the microscale level, key parameters in the electrospinning process were first optimized to construct polyacrylonitrile (PAN) nanofiber membranes with high permeability and oil retention capability. Then, at the nanoscale level, a high-surface-energy layer was further constructed on the PAN nanofiber network via in situ dopamine polymerization and nanoparticle grafting, ultimately achieving a hierarchical superhydrophilic and underwater superoleophobic interface. The prepared SiO₂/PDA@PAN membrane exhibited highly efficient oil/water emulsion separation performance and exceptional oil fouling resistance, primarily owing to the synergistic effects of its superhydrophilicity and hierarchical micronano rough structure. Experimental results demonstrated that the membrane achieved a stable permeability of ∼15 L m^-1 h^-1 kPa^-1 and an oil retention rate exceeding 99% when treating oil/water emulsions. Furthermore, the SiO₂/PDA@PAN membrane maintained an oil retention rate of over 99% even after ten separation cycles, highlighting its remarkable regeneration capability and long-term stability. These findings underscored that the SiO₂/PDA@PAN membrane holds significant promise for practical applications in the field of oil/water separation, offering a sustainable and effective solution for addressing oil-contaminated wastewater.