Polyethylenimine-grafted cellulose nanofibril composites: Adsorbents for anionic dye removal with thermodynamic insights.

Water pollution is a critical environmental issue that necessitates innovative approaches to water purification. This study presents the development of a novel cellulose-based adsorbent, DCNF/PEI, synthesized by grafting branched polyethyleneimine (PEI) onto dialdehyde cellulose nanofibers (DCNF) via a Schiff base reaction. This functionalization enhances the adsorption capacity of cellulose nanofibers for removing anionic dyes from aqueous solutions. The DCNF/PEI composite was characterized using Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), and Thermogravimetric Analysis (TGA), confirming successful modification and favorable structural and thermal properties. Batch adsorption experiments with methyl orange (MO) were conducted under various conditions, including pH, dye concentration, and contact time. The composite exhibited excellent dye removal efficiency, achieving a maximum adsorption capacity of 313 mg/g. The adsorption process followed the Langmuir isotherm and pseudo-second-order kinetic models, indicating monolayer chemisorption. These results highlight the DCNF/PEI composite as an efficient, sustainable, and scalable adsorbent for anionic dye removal, offering a promising solution for wastewater treatment.