Removal of AG 25 dye from aqueous solutions and treatment of real tannery wastewater by reusable magnetic iron oxide nanoparticles loaded with pomegranate pomace extract

This study developed reusable magnetite iron oxide nanoparticles (Fe₃O₄@PGP-NPs) coated with pomegranate pomace extract (PGP) for the removal of Acid Green 25 (AG 25) dye and treatment of real tannery wastewater. The nanoparticles were characterized using FTIR, UV–Vis, XRD, FESEM/EDX, VSM, and BET techniques, revealing spherical Fe₃O₄ NPs with an average diameter of 20.30 nm, a BET surface area of 69 m²/g, and a magnetization value of 42.41 emu/g. Optimization via RSM-CCD identified optimal adsorption conditions: Fe₃O₄@PGP-NPs dosage of 2.2 g/L, contact time of 88 min, and dye concentration of 200 mg/L, achieving 99 % removal efficiency. Adsorption followed the Langmuir model, with a monolayer capacity of 213 mg/g, and pseudo-second-order kinetics. Thermodynamic analysis confirmed the process was spontaneous and endothermic. When applied to tannery wastewater, Fe₃O₄@PGP-NPs achieved removal efficiencies of 98.87 % for BOD₅ and 97.40 % for COD across treatment stages. Additionally, the nanoparticles maintained efficiency for up to five reuse cycles, demonstrating significant potential as a nanoadsorbent for dye removal and industrial wastewater treatment.