Hydrophobic cellulose nanofiber based aerogel for high-efficiency oil-water separation

Hydrophobic aerogel has emerged as an effective material for oil absorption. In this study, we fabricated four types of hydrophobic nanocellulose (NC)-based aerogels through a freeze-drying method with methyltrimethoxysilane (MTMS) surface modification for enhanced oil removal. It involved tuning the functional groups of NC (cellulose nanofibers (CNF) and TEMPO-oxidized cellulose nanofibers (TCNF)) and selection of crosslinkers (polyethyleneimine (PEI) and tannic acid (TA)). Among the developed aerogels, TCNF-PEI exhibited a homogeneous, hierarchical 3D scaffold with notably high porosity, as evidenced by SEM analysis. FTIR and XRD confirmed the formation of crosslinked networks through hydrogen bonds, electrostatic interactions, covalent bonds and physical entanglement. TCNF-PEI exhibited superior absorption capacity of 112.30 g/g, nearly twice of CNF-PEI (62.93 g/g), and three times in comparison with CNF-TA (44.67 g/g) and TCNF-TA (48.05 g/g), respectively. The absorption kinetics followed the pseudo-second-order model. Moreover, TCNF-PEI exhibited a wide temperature applicability and retained absorption capacity of above 74 % after five cycles. The developed TCNF-PEI aerogel also showed excellent sorption capacities (85.6-148.7 g/g) for a variety of oils and organic solvents. The significant enhancement in absorption capacity, superior reusability and applicability indicated that TCNF-PEI aerogel can be a candidate of emergency treatment for rapid oil spill recovery, particularly from port operations or maritime shipping.