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Cellulose nanomaterial (CNM) and polyethylenimine (PEI) composites have attracted growing attention due to their multifunctional characteristics, which have been applied in different fields. In this work, soybean hulls were valorized into carboxyl cellulose nanofibrils (COOH-CNFs), and composited into hydrogels with PEI by combining them with cationic chelating and physical adsorption strategies. Cellulose nanofibrils (CNFs) were produced from soybean hulls prior to oxidation by a TEMPO mediated reaction to obtain COOH–CNFs; then drops of zinc chloride were added to 1.5% aqueous COOH–CNF dispersions, which were left for 24 h to form COOH-CNF hydrogels. Finally, the hydrogels were functionalized using different concentration of PEI solutions over a range of pH values. Elemental analysis results showed that 20% aq. PEI at pH 11.6 is the optimum condition to synthesize the COOH–CNF/PEI hydrogels. Additionally, the adsorption efficiency for the removal of anionic methyl blue dyes and Cu(II) ions from water was tested, reaching 82.6% and 69.8%, respectively, after 24 h. These results demonstrate the great potential of COOH–CNF/PEI hydrogels as adsorbent materials for water remediation. 

Nano-porous aerogels are an advantageous approach to produce low-density materials with high surface area, particularly when using biobased materials. Frequently, most biobased aerogels are synthesized through a bottom-up approach, which requires high energy inputs to break and rebuild the raw materials, and for elimination of water. To curb this, this work focused on generating aerogels by a top-down approach through the delignification of a wood substrate while eliminating water by solvent exchange. To diversify the surface chemistry for use in water treatment, the delignified wood–nanowood-was coated with a chitosan–cyclodextrin co-polymer and tested in the capture of microcystin-LR. The generated nanowood structure had 75% porosity after coating, with up to 339% water swelling and an adsorption capacity of 0.12 mg g −1 of the microcystin. This top-down technique enables the generation of low-cost aerogels by reducing steps, using a biobased self-assembled coating with hydrophobic active sites, and avoiding costly energetic input.