Efficient Removal of Anionic Dyes From Water Using Fe ₃ O ₄ @PANI Magnetic Nanocomposites

Abstract Anionic dyes significantly threaten ecological environments and human beings. In this study, polyaniline was fabricated on the surface of Fe 3 O 4 nanoparticles by the co‐precipitation method for the removal of Methyl Orange (MO), Reactive Orange 16 (RO 16) and Naphthol Blue Black (NBB). The Fe 3 O 4 @PANI nanocomposite was characterized by XRD, FT‐IR, XPS, SEM, TEM, BET, TGA, VSM, and Zeta potential. These techniques confirm the surface morphology, structure, thermal stability, magnetization, and successful fabrication of polyaniline over Fe 3 O 4 . The adsorptive behavior of the Fe 3 O 4 @PANI nanocomposite was examined for its interaction with MO, RO 16, and NBB dyes, considering factors such as pH, contact time, initial concentration, temperature, and salinity. The adsorption mechanism was well ascribed by pseudo‐second‐order kinetics and the Langmuir model, having maximum adsorption capacity (Q max ) 231, 234, and 118 mg g −1 for MO, RO 16, and NBB, respectively. Thermodynamic studies revealed that the adsorption of MO and NBB dye is endothermic, while RO 16 is exothermic and spontaneous. The adsorption mechanism reveals that the chemical monolayer adsorption of anionic dyes onto the Fe 3 O 4 @PANI nanocomposite is by Van der Waals force, electrostatic interaction, π–π interaction, and hydrogen bonding. This study provides rapid kinetics, enhanced adsorption capacity at various pH and excellent reusability, showing more than 90% even after five cycles, making it an eco‐friendly and cost‐effective solution for the remediation of anionic dye‐contaminated water.