Synthesis of vanillin‐grafted chitosan polymer/manganese oxide nanocomposite for organic dye removal: isotherm, adsorption kinetics, and statistical modeling
Ahmed Saud Abdulhameed, Rima Heider Al Omari, Samaa Abdullah, Abeer A. Altamimi, Mahmoud AbualhaijaAbstract
A vanillin‐grafted chitosan polymer/manganese oxide nanocomposite (CHA‐VN/MnO 2 ) was fabricated by functionalizing a chitosan polymer matrix with MnO 2 nanoparticles and subsequently chemically grafting vanillin onto the chitosan backbone to form a multifunctional adsorption system. CHA‐VN/MnO 2 was used for acid blue 93 (AB93) dye adsorption from aquatic environments. Detailed characterization using X‐ray diffraction, Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller surface area analysis, and scanning electron microscopy coupled with energy‐dispersive X‐ray spectroscopy confirmed the successful formation of a multifunctional adsorption surface with enhanced physicochemical properties. Nitrogen adsorption–desorption analysis revealed that the CHA‐VN/MnO 2 nanocomposite exhibits a specific surface area of 14.22 m 2 g −1 , a total pore volume of 0.051 cm 3 g −1 , and an average pore diameter of 14.35 nm, indicating a mesoporous structure. The adsorption behavior of AB93 was systematically optimized using a Box–Behnken design (BBD) to assess the combined effects of key operating variables. The BBD showed that the highest AB93 removal efficiency (96.68%) was achieved at a CHA‐VN/MnO 2 dosage of 0.075 g, a solution pH of approximately 9, and a contact time of 30 min. Adsorption equilibrium was well described by the Temkin isotherm model, suggesting the adsorption process involves a relatively uniform distribution of binding energies across the CHA‐VN/MnO 2 nanocomposite surface. Kinetic modeling demonstrated that the adsorption followed a pseudo‐second‐order mechanism, highlighting the involvement of chemical interactions. The observed adsorption capacity of 195.97 mg g −1 was mainly governed by electrostatic attractions, hydrogen bonding, n– π stacking and π – π interactions. Overall, CHA‐VN/MnO 2 significantly adsorbs anionic dyes, indicating strong applicability for wastewater remediation. © 2026 Society of Chemical Industry.