Efficient microplastic removal from wastewater using Fe3O4 functionalized g-C3N4 and BNNS: A comprehensive study

The growing prevalence of microplastics (MPs) in water systems has outpaced the removal capabilities of conventional treatment plants, underscoring the urgent need for advanced remediation strategies. This study offers a novel investigation into the efficacy of two magnetic nanocomposites (MNCs), g-C₃N₄@Fe₃O₄ and BNNS@Fe₃O₄, for MP removal across synthetic and real water matrices. The materials were synthesized using thermochemical and co-precipitation techniques and characterized via FTIR , XRD , SEM-EDX, TEM, and BET analyses. Adsorption experiments, conducted under optimized conditions, revealed that g-C₃N₄@Fe₃O₄ achieved 96.16 % removal of polyethylene (PE, 125 μm) and 92.5 % of polystyrene (PS) in Milli-Q water, while BNNS@Fe₃O₄ achieved 94.44 % and 89.33 %, respectively. In filtered municipal wastewater, g-C₃N₄@Fe₃O₄ retained high performance with 91.91 % removal efficiency, compared to 83.78 % for BNNS@Fe₃O₄. A clear inverse relationship between particle size and removal was observed, with negligible adsorption of MPs ≥ 3 mm. Recyclability studies showed g-C₃N₄@Fe₃O₄ and BNNS@Fe₃O₄ retained 79.74 % and 69.18 % removal efficiency after three cycles, respectively. Phytotoxicity tests demonstrated that while raw MNCs exhibited toxicity toward Hordeum vulgare , Cicer arietinum , and Vigna radiata , their filtrates posed minimal to no risk, confirming environmental compatibility when used and recovered appropriately. This is the first report demonstrating real-world MP removal using these MNCs in treated municipal wastewater and drinking water , providing robust evidence of their scalability, reusability, and ecological safety. The results position g-C₃N₄@Fe₃O₄ and BNNS@Fe₃O₄ as promising candidates for next-generation point-of-use MP remediation systems.