Enhanced removal of microplastics from wastewater hydrological pathways using a magnetically recoverable Fe ₃ O ₄ /carbon black nanocomposite

Microplastic (MP) pollution is a major environmental concern, as particles are transported through interconnected hydrological pathways such as domestic wastewater systems, rivers, and coastal waters, where they accumulate in sediments and pose risks to aquatic ecosystems. Developing effective and affordable approaches to intercept microplastics before they enter natural water bodies is therefore essential. In this study, a magnetically recoverable Fe 3 O 4 /carbon black (Fe 3 O 4 /CB) nanocomposite was surface-modified using oleic acid and stearic acid to enhance its affinity for hydrophobic polyethylene (PE) microplastics. The modified nanocomposite showed a clear improvement in plastic removal compared to the unmodified Fe 3 O 4 /CB material, achieving near-complete removal under optimized conditions. Under optimized conditions (15 mg dosage, 50 r/min, 60 minutes), the modified nanocomposite removed 197.2 mg of PE from 200 mg in synthetic wastewater, corresponding to a removal efficiency of 98.6%. Application to real washing machine effluent further demonstrated its effectiveness, achieving a removal efficiency of 94.2%. The enhanced performance is attributed to increased surface hydrophobicity and the synergistic interaction between Fe 3 O 4 and carbon black. Overall, these findings highlight the potential of surface-modified magnetic nanocomposites as practical intervention tools at critical hydrological control points, such as wastewater discharge pathways, to reduce downstream transport of microplastics into freshwater and coastal environments.