Cellulose- and Chitin-Based Polyethylenimine Sponges as Bio-Based Adsorbent Materials for the Remediation of Contaminated Water Environments

Bio-based adsorbent materials represent a sustainable alternative for the remediation of contaminated environments. In this work, two lightweight porous sponges derived from cellulose and chitin and functionalized with branched polyethylenimine were synthesized and comparatively investigated as adsorbents for organic compounds and heavy metals. The chitin-based material was obtained by adapting a synthetic platform originally developed for cellulose, demonstrating the transferability of the approach to a structurally distinct biopolymer derived from seafood-industry waste. Adsorbents were characterized by spectroscopy, scanning electron microscopy, and thermogravimetric analysis, confirming successful oxidation and polyethylenimine grafting as well as the formation of highly porous structures. Adsorption experiments with 4-nitrophenol, 4-nitrobenzaldehyde, methylene blue, and eosin B revealed comparable performance for both adsorbents, with adsorption strongly influenced by dye structure, pH, and speciation. Both materials exhibited efficient removal of 4-nitrobenzaldehyde and eosin B in deionized (>95%) and marine water (>75%); whereas 4-nitrophenol and methylene blue were only moderately adsorbed (<40%). Tests with inorganic contaminants (cadmium and chromium) showed maximum experimental Cd(II) uptakes of 38.88 mg/g for the cellulose- and 43.21 mg/g for the chitin-based material. Overall, surface functionalization dominates adsorption behavior over the polysaccharide backbone, identifying chitin-based material as a promising, sustainable adsorbent for environmental remediation.