Cellulose Nanofiber-Reinforced γ-AlOOH Aerogels for Enhanced Removal of Environmental Pollutants

In this study, we report the modification of a monolithic γ-aluminum oxy-hydroxide (γ-AlOOH) aerogel with cellulose nanofibers (CNFs) using the sol-gel method via supercritical drying. The optimized 2% CNF (w/w) results in a monolithic CNF-γ-AlOOH that is amorphous in nature, along with C-C and C-O-C functional groups. Transmission electron microscopy (TEM) images of the as-synthesized CNF-γ-AlOOH showed CNF embedded in the γ-AlOOH aerogel. The adsorption capacities were determined using azo dyes: methylene blue (MB) and crystal violet (CV), and heavy metal ions: lead [Pb(II)], uranium [U(VI)], and arsenic [As(III)] as models for environmental pollutants. The maximum adsorption capacities were 210 mg/g for CV, 204 mg/g for MB, 105 mg/g for As(III), and 339 mg/g for U(VI) at a pH of 7, whereas Pb(II) exhibited a maximum adsorption capacity of 100 mg/g at pH 5. This is attributed to the synergistic interactions between the CNF hydroxyl groups and γ-AlOOH active sites, facilitating electrostatic and coordination interactions. The as-synthesized aerogels demonstrated high recyclability, retaining over 94% adsorption efficiency after five cycles and offering a sustainable approach to environmental remediation. These findings establish CNF-γ-AlOOH aerogels as robust, eco-friendly materials for water treatment applications, with potential scalability for addressing diverse environmental pollutants. Future research should explore their application in the removal of emerging contaminants and optimize their synthesis for household and industrial-scale implementation.