Valorized soybean hulls as TEMPO-oxidized cellulose nanofibril and polyethylenimine composite hydrogels and their potential removal of water pollutants

Abstract

AbstractCellulose 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. Graphical abstract