Functional Polymer Nanocomposite of Chitosan‐Vanillin Schiff Base and <scp>NiO</scp> Nanoparticles for Acid Blue 93 Dye Removal: Physicochemical Analysis and Adsorption Optimization

ABSTRACT The development of functional polymer nanocomposites for efficient dye adsorption has become increasingly important. In this study, a functional polymer nanocomposite of chitosan‐vanillin Schiff base and nickel oxide nanoparticles (CS‐VAN/NiO) was synthesized for acid blue 93 (AB93) dye removal from aqueous systems. The CS‐VAN/NiO nanocomposite was thoroughly characterized using Brunauer–Emmett–Teller (BET) surface area analysis, X‐ray diffraction (XRD), Fourier‐transform infrared spectroscopy (FTIR), and scanning electron microscopy with energy‐dispersive X‐ray spectroscopy (SEM–EDX). The CS‐VAN/NiO nanocomposite exhibited a mean pore diameter of 14.08 nm, a BET surface area of 6.91 m 2 /g, and a total pore volume of 0.02436 cm 3 /g. The adsorption process was optimized using response surface methodology (RSM) with a Box–Behnken design (BBD), considering key parameters such as CS‐VAN/NiO dosage (0.01–0.07 g/L), pH (4–10), and contact time (10–40 min). The adsorption kinetics followed the pseudo‐first‐order model, while equilibrium data were best explained by the Freundlich model, suggesting multilayer adsorption. The CS‐VAN/NiO nanocomposite achieved a maximum adsorption capacity of 278.3 mg/g for AB93 dye. The adsorption mechanism was attributed to multiple interactions, including electrostatic forces, π–π stacking, n–π interactions, and hydrogen bonding interactions. The novelty of this work lies in the fabrication of a bio‐derived CS‐VAN Schiff base polymeric matrix embedded with NiO nanoparticles, offering a synergistic combination of biodegradability, functional surface groups, and enhanced adsorption performance. The results indicate that the CS‐VAN/NiO nanocomposite functions as an efficient adsorbent for the removal of organic dyes from aqueous solutions. The CS‐VAN/NiO nanocomposite, characterized by its high adsorption capacity and advantageous physicochemical properties, demonstrates strong potential as an effective material for wastewater treatment and environmental remediation.