Aerogels Fabricated from Wood-Derived Functional Cellulose Nanofibrils for Highly Efficient Separation of Microplastics

Microplastics pollution in the aquatic environment has been considered as a particular concern for global ecosystems in recent years. Herein, bleached eucalyptus pulp was chemically modified by 2,2,6,6-tetramethylpiperidine-1-oxyl and 2,3-epoxypropyltrimethylammonium chloride to produce modified cellulose nanofibrils (CNFs). Then, porous CNF-based aerogels were prepared by the freeze-drying process and selected as a matrix filter for highly efficient separation of polystyrene microplastics (PSMPs). Results showed that the modified CNF aerogels could efficiently separate different types of PSMPs with filtration efficiencies of 100 and 75% for carboxylate-modified polystyrene (PS–COOH) and amine-modified polystyrene (PS–NH2), respectively. Meanwhile, the hydrophilicity and porous structure of these materials endowed aerogels with high filtration flux. The excellent filtration performance of materials mainly relied on their microstructure and high surface charge, which could effectively capture and separate PSMPs from aqueous solution through the synergistic actions of physical entrapment, electrostatic interaction, and hydrogen bonding. In addition, the modified aerogels had good stability and reusability, and the filtration efficiency of PS–COOH remained at 100% after eight cycles. These findings provide a green and promising method for designing functional aerogel filters from sustainable resources to be used for applications in microplastics separation and water purification.