Magnetite–Chitosan–Alginate Nanocomposite (CS/Al@Fe ₃ O ₄ ) for Removal of Methylene Blue (MB) From Aquatic Environments: Preparation, Characterization, and Isotherms

Fe 3 O 4 magnetic nanoparticles (MNPs) and chitosan (CS) were combined to generate magnetic nanocomposites (MNCs), which were specially made to absorb methylene blue dye (MB) in a three‐dimensional (3D) cross‐linked alginate hydrogel (CS/Al@Fe 3 O 4 ) substrate. Different analytical techniques (XRD, FTIR, SEM, TEM, and TGA) were employed to confirm the structural characteristics of the MNCs. To ascertain the optimal conditions for adsorption, various factors affecting the adsorption capacity of MB were experimentally explored. The efficiency of MB removal reached a maximum adsorption efficiency of 526.32 mg/g under the ideal conditions of a duration time of 15 min, pH level of 10, adsorbent dosage of 0.003 g, dye concentration of 150 mg/L, and temperature of 298 K. The experimental equilibrium data were analyzed using the Langmuir, Freundlich, and Dubinin–Radushkevich isotherm models, demonstrating that the Langmuir isotherm comprehensively represents the adsorption process. Additionally, the pseudo‐first‐order (PFO), pseudo‐second‐order (PSO), and intraparticle diffusion kinetic models were utilized to interpret the experimental adsorption data, concluding that the PSO kinetic model exhibited the most favorable adaptation to the data. The prepared MNCs are unparalleled due to their reactive functional group, including a heteroatom and their porous, cross‐linked structure. This structure allows for the diffusion of MB dye and its interaction with the MNCs. The primary driving forces behind the adsorption process of the CS/Al@Fe 3 O 4 MNCs are electrostatic and hydrogen bonding interactions, resulting in a high adsorption efficiency. Meanwhile, the MNCs were used for three adsorption–desorption cycles without substantially decreasing their adsorption efficiency. This suggests they have great potential as an adsorption system for removing organic dyes due to their high removal efficiency.