A sustainable nanocellulose-based superabsorbent from kapok fiber with advanced oil absorption and recyclability

Creating a low-cost, highly efficient, and recyclable superabsorbent for spilled-oil cleanup is of great significance but remains a big challenge. Herein, we report a facile strategy to produce economic, environmentally friendly, and reusable foam from agricultural waste kapok fibers. These kapok-derived cellulose nanofibrils foams (KNFs) demonstrate a hierarchically porous structure at micro-level with ultra-low density (2.7 mg·cm^-3). The superhydrophobic KNFs (150.5°) show outstanding oil absorption (126.8-320.4 g·g^-1) and oil-water separation performance. Notably, a facile approach is designed to reuse KNFs easily by a homemade oil release system. The release behavior of the KNFs is quantitatively analyzed and confirmed by the Rigter-Peppas model, indicating that the oil release followed the Fickian diffusion. The KNFs exhibit desirable reusability, and can be recycled for at least 50 times while keeping excellent oil absorption, and release performance. These advantages prove that the KNF is a desirable substitute for spilled-oil treatment.