Carboxymethyl Chitosan Aerogels Reinforced with TEMPO-oxidized Cellulose Nanofibers for Efficient Adsorption of Pb(II) Ions in Aqueous Media

Abstract

A reinforced composite aerogel composed of carboxymethyl chitosan (CMCS) and cellulose nanofibers (CNFs) was synthesized via chemical crosslinking with epichlorohydrin (EH) for the efficient removal of Pb(II) ions from aqueous solutions. The CMCS, a chitosan derivative, was successfully prepared through a simple chemical reaction with a degree of substitution of 1.96. The incorporation of CNFs imparted enhanced mechanical stability to the aerogel matrix and increased the surface area, whereas carboxymethyl cellulose contributed functional carboxyl groups that facilitated efficient metal ion adsorption. In addition, crosslinking with EH significantly improved the structural integrity and water stability of the aerogels, rendering them suitable for application in aqueous environments. The composite aerogels exhibited a porous structure and good adsorption of lead ions (Pb²⁺) in water with a removal percentage of 98%. Upon the addition of 1 wt% CNF loading, the compression strength of the composite aerogels was enhanced 42% compared with the samples without CNF loading. The adsorption kinetics showed a high correlation with the pseudo-second-order model (R² = 0.99). The good structural stability and water absorption of the prepared CMCS aerogels make them an ideal candidate for eco-friendly heavy metal-ion treatment.