Synthesis and characterization of a high-performance magnetic nanocomposite adsorbent from pomegranate pomace waste for tannery wastewater treatment

Effective management of organic and chemical pollutants is crucial for the leather industry. In this study, a novel magnetic nanocomposite (AC/Fe₃O₄)PP) was synthesized from pomegranate juice processing waste, an agro-industrial byproduct, and used for treating real tannery wastewater from MEGA/EPE-Spa, a local leather industry in Batna, East Algeria (35°33′52.8"N 6°10′22.5"E), at three different stages. The pomace waste served as a precursor for activated carbon (AC-PP) production, while its extract functioned as a coating agent for synthesizing magnetic iron oxide nanoparticles (Fe₃O₄@PP-NPs). Combining these two adsorbents yielded the (AC/Fe₃O₄)PP nanocomposite, which demonstrated outstanding adsorption performance. The high surface area of AC (>1400 m²/g) enabled efficient pollutant removal, and the magnetic properties of the Fe₃O₄ component facilitated easy separation and recovery. Detailed characterization of the Fe₃O₄@PP-NPs, AC-PP, and (AC/Fe₃O₄)PP adsorbents was conducted. The optimal doses and contact times were 0.3 g/L for (AC/Fe₃O₄)PP with 30 minutes, 0.5 g/L for AC-PP with 40 minutes, and 0.8 g/L for Fe₃O₄@PP-NPs with 60 minutes, all at an initial concentration of 100 mg/L. The Langmuir isotherm showed high adsorption capacities, with values of 372.37 mg/g for AC, 827.6 mg/g for NPs, and 962.31 mg/g for the (AC/Fe₃O₄)PP nanocomposite. Adsorption mechanism studies revealed a mixed control process involving both external and intraparticle diffusion. The (AC/Fe₃O₄)PP nanocomposite effectively treated tannery wastewater, achieving high removal rates of COD, BOD₅, turbidity, and TDS across all treatment stages. These results position (AC/Fe₃O₄)PP as a promising, cost-effective solution for tannery wastewater treatment, addressing existing gaps in the current literature by offering a sustainable and efficient method for pollutant removal.