Cross-Linked Cellulose Nanofibril Aerogel with Multiscaled Pores and Dual Wettability for Emulsion Separation

Filters with dual wettability are critically needed to meet the demand for both oil-in-water (O/W) and water-in-oil (W/O) emulsion separation. However, the smart filters reported in previous studies are challenged by conditional external stimuli, inadequate sensitivity, and poor scalability. In this study, an aerogel (CPM 600H) with dual wettability under normal condition was developed using superhydrophilic cellulose nanofibrils (CNFs) as the skeleton and dicarboxylated poly(ethylene glycol) as the cross-linker. By tuning the cross-linker length and CNF concentration, a robust aerogel with randomly stacked multiscale pores was obtained. The effect of surfactant types on the aerogel for O/W emulsion separation efficiency was investigated. Results showed that the aerogel exhibited excellent separation efficiency for the anionic surfactant (92.03%) and cationic surfactant (89.50%), but a lower efficiency for the nonionic surfactant (77.38%). The aerogel also demonstrated excellent separation efficiency (>97%) for different W/O emulsions, and it could remove trace amounts of water from diesel, showing potential application in biofuel purification.