Ultralight, hydrophobic, and reusable cattail fiber/cellulose cryogels for efficient oil spill remediation

Developing low-cost, high-efficiency, and reusable absorbents for oil spill remediation is critical yet challenging. In this work, an eco-friendly and facile approach was implemented to construct ultralight cattail fiber/cellulose composite cryogels (CF/CNF-CGs) through freeze-drying and silane-based functionalization. The resulting CF/CNF-CGs possessed a hierarchical porous architecture with ultralow density (5.84-6.47 mg/cm³) and ultrahigh porosity (99.55-99.58%). The hydrophobic cryogels (water contact angle up to 149.1°) demonstrated exceptional oil absorption capacities (109.2-121.4 g/g), retention (95.6%) capacity and excellent selective sorption property. Moreover, CF/CNF-CGs exhibited good reusability, retaining an oil absorption capacity of 82.0 g/g and oil-water separation efficiency of 99.6% after 10 cycles. The adsorption behavior of CF/CNF-CGs was quantitatively analyzed using quasi-first, quasi-secondary, and intraparticle diffusion models, which indicated that the adsorption of oil by cryogel was predominantly governed by physisorption driven by capillary action and pore filling, and involved both surface and internal diffusion mechanisms. These superior properties underscore the potential of CF/CNF-CGs as a promising and sustainable alternative for large-scale maritime oil cleanup.