Hyper-Cross-linked Cellulose Nanofibrils with Spontaneous and Reversible Adsorption of Aromatic Pollutants from Water as a Valid Alternative to Fossil-Based Adsorbents.

In this work, a novel high surface area adsorbent based on cellulose and inspired by hyper-cross-linked polymers was designed. Cellulose nanofibrils (CNF) were functionalized with poly(vinylbenzyl chloride) and hyper-cross-linked through Friedel-Crafts alkylation, yielding a micro/mesoporous material characterized by a specific surface area of 409 m2/g, microporous fraction of 50%, and biobased content of about 70 wt %. The functionalized CNF, tested for the adsorption of 2,4-dichlorophenol (DCP) from water at 298 K, were able to remove 90% of the pollutant from a 62.5 mg/L DCP solution and adsorb 284 mg/g at a higher concentration (1000 mg/L). Thermodynamic studies demonstrated the multilayer adsorption of the hyper-cross-linked CNF, the exothermic nature of the process, and its spontaneity. The hyper-cross-linked cellulose nanofibrils were reusable with efficiency above 98% in 5 subsequent cycles. The adsorption performance was stable across varying pH levels, and interference from natural organic matter (e.g., humic acids) was minimal (<10%). This work marked a promising step toward more sustainable sorbent materials by demonstrating the potential of cellulose nanofibrils as functional scaffolds. The strategy could be extended to waste-derived cellulose sources and biobased aromatic compounds, paving the way for fully renewable porous adsorbents.