Superhydrophobic cellulose-based aerogel derived from Phormium tenax (harakeke) for efficient oil sorption

Oil removal and recovery solutions are essential in our modern world, and discovering eco-friendly, highly efficient oil sorbents is of paramount importance. In this study, a straightforward method was designed to create reusable, superhydrophobic cellulose nanofiber-based aerogels derived from harakeke, a native New Zealand flax plant. By employing chemical purification and ultrasonication techniques, cellulose nanofibers (CNFs) were extracted from raw harakeke fibers, and nanocellulose-based aerogels were formed through freeze-drying. The resulting harakeke-derived cellulose nanofiber aerogels (HNAs) exhibited remarkable porosity (98.98–99.73%) and an ultralight density (3.91–15.13 mg/cm³). Among the various cellulose aerogels produced, the 1.2 wt% CNF aerogel demonstrated the highest Young's modulus of 39.45 kPa. Subsequent surface modification with methyltriethoxysilane (MTES) transformed the aerogels into superhydrophobic materials (s-HNA), with a water contact angle of 153°. The oil sorption capacity of s-HNA ranged from 90 to 146 g/g for various oils and solvents. The oil sorption of s-HNAs obeys the pseudo-second order kinetic model, with sorption constant rate of 0.00525 g∙g⁻¹∙s⁻¹.