Magnetically retrievable PANI-Fe3O4 nanocomposite for efficient dye removal from tannery wastewater: Mechanistic insights and performance assessment

Leather dyeing techniques create highly pigmented and toxic effluents that pose ecological problems due to synthetic azo dyes and organic loading. This study will create, investigate, and use a magnetically separable polyaniline-Fe 3 O 4 nanocomposite to remove mixed anionic pigments from tannery wastewater. The proposed material improves surface activity and simplifies post-treatment separation over polymer-supported composites by combining conductive polymer functionality with magnetic recovery. In situ oxidative polymerization generated the nanocomposite, which FT-IR, XRD, and SEM examinations confirmed successful synthesis, structural integrity, and many surface-active sites. Batch adsorption studies showed that pH, adsorbent dosage, contact duration, and settling time optimally removed dye at 89.45% at pH 5.6 and 0.30 g. In adsorption studies, the process followed the Langmuir isotherm (R 2 = 0.9954) and pseudo-second-order kinetics (R 2 = 0.9980). The Van’t Hoff plot (R 2 = 0.9916) shows endothermic adsorption (ΔH° = +33.931 kJ mol -1 ) with increased disorder (ΔS° = +28.582 J K -1 mol -1 ) and negative ΔG° at higher temperatures, indicating entropy-driven physisorption enhanced by diffusion and binding. FT-IR band shifts and surface morphology changes also confirm monolayer physisorption on a uniform surface, with electrostatic interactions, π-π stacking, and hydrogen bonding as the primary removal mechanisms. After optimal treatment, COD dropped 48.13%, BOD 18.99%, and salinity 28.65%. Thus, the produced nanocomposite improves effluent quality significantly. The adsorbent also exhibited above 70% regeneration effectiveness across multiple adsorption-desorption cycles. Therefore, this study uniquely combines structural characterization and adsorption mechanism investigation for a magnetically recoverable PANI-Fe 3 O 4 nanocomposite adsorbent in real tannery effluents. • PANI-Fe 3 O 4 nanocomposite developed via in situ oxidative polymerization • 89.45% dye removal from real tannery wastewater under optimized conditions • Reduction of COD, BOD, and salinity improved effluent quality • Endothermic physisorption confirmed by thermodynamic study • Electrostatic and π-π interactions with hydrogen bonding are found in the mechanism