Preparation of Polymeric Adsorbent Based on Schiff Base‐Chitosan‐Vanillin and Multi‐Walled Carbon Nanotubes for Methylene Blue Dye Adsorption Using Box–Behnken Design

A novel chitosan–vanillin Schiff base/multi‐walled carbon nanotube (CTS‐VAN/MWCNT) nanocomposite was developed in this study as an efficient adsorbent for removing the cationic dye methylene blue (MB) from aqueous solutions. Comprehensive characterization of the CTS‐VAN/MWCNT material was carried out using field emission scanning electron microscopy coupled with energy‐dispersive X‐ray spectroscopy (FESEM‐EDS), Brunauer–Emmett–Teller (BET) surface area analysis, X‐ray diffraction (XRD), and Fourier‐transform infrared spectroscopy (FTIR). The CTS‐VAN/MWCNT nanocomposite demonstrated a BET specific surface area of 50.43 m 2 /g, a Langmuir specific surface area of 77.44 m 2 /g, a total pore volume of 0.2943 cm 3 /g, and an average pore diameter of 23.34 nm. Process optimization for MB adsorption was carried out using the Box–Behnken design (BBD), focusing on key variables such as adsorbent dosage, solution pH, and contact time. Adsorption equilibrium data were best described by the Freundlich isotherm model, while kinetic analysis indicated that the pseudo‐second‐order model most accurately captured the adsorption dynamics. The CTS‐VAN/MWCNT nanocomposite achieved a maximum MB adsorption capacity of 209.58 mg/g. The proposed adsorption mechanism involves electrostatic interactions, nπ bonding, hydrogen bonding, and ππ stacking. Overall, the results suggest that the CTS‐VAN/MWCNT adsorbent is a promising multifunctional material for the treatment of complex industrial wastewater.