Designing 3D fractal morphology of eco-friendly nanocellulose-based composite aerogels for water remediation

The renewable and economic aspects of cellulose nanofibril (CNF)-based aerogels are reviving interest in green adsorbents for water remediation. However, the combination of CNF chemical pre-treatment, fibrillation processes, and a solvent-free hydrophobization route to obtain structurally wet-resilient and eco-friendly porous adsorbent is lacking in the literature. Herein, the oxidation/fibrillation approaches to isolating CNF from sugarcane bagasse and producing CNF-based aerogels were investigated. These porous materials were designed through ice-templating, followed by a freeze-drying method. Oxidated CNF aerogels containing 3-times-microfluidization (TMI3) exhibited the most homogeneous interconnected regular structure, with micro- and nanoporous structures achieving robust compressive mechanical properties (Young's modulus ∼400 kPa). Natural rubber latex (NR) was combined with TMI3, yielding a water-resilient and hydrophobic composite aerogel (TMI/NR). The removal capacity of TMI/NR ranged from 108 to 420 mg·g−1 for Cu (II) and 159–334 mg·g−1 for methylene blue (MB) dye, with reuse performance ranging from 66 to 98 % over the reuse cycles. Furthermore, TMI/NR aerogel showed its effectiveness for Cu (II) removal from water in an environmentally relevant concentration (20 and 60 µg·L−1 Cu (II)) without posing additional toxicity to Daphnia similis aquatic model organisms. These findings indicate TMI/NR composite aerogels as promising and efficient green adsorbents of pollutants from contaminated water.