Cellulose nanofiber-reinforced carboxymethyl chitosan/polyvinyl alcohol composite gels: Physicochemical characterization and acid blue dye adsorption performance.

Composite gels of carboxymethyl chitosan (CMCS), polyvinyl alcohol (PVA), and cellulose nanofibers (CNF) are promising for environmental remediation and materials science. This study examines how varying CNF content affects the structural, thermal, and adsorption properties of CMCS/PVA/CNF gels. The results show that CNF enhances the storage modulus and thermal stability of the gels. The PCF composite gel with 0.4 % CNF content exhibited the highest thermal stability, maintaining stability up to 600 °C. The microstructure of the composite gels displayed a porous structure, favorable for dye adsorption. FTIR analysis revealed that the hydrogen bonding interactions between CNF, CMCS, and the PVA matrix increased with higher CNF content. XRD results indicated that these interactions reduced the crystallinity of the composite gels. As CNF content rose, the swelling ratio decreased from 1124.4 % to 973.3 %, and the gel fraction increased from 75.8 % to 83.5 %. Dye adsorption followed the pseudo-second-order kinetic model and the Langmuir isotherm. The maximum adsorption capacity for Acid Blue dye at 25 °C was 940.6 mg/g. The adsorption process was chemical, spontaneous, endothermic, and entropically favorable, indicating strong interactions between the gel and dye molecules. This study highlights the potential of CMCS/PVA/CNF gels for environmental applications and efficient dye removal.