Effective removal of Micro- and nanoplastics from water using Iron oxide nanoparticles: Mechanisms and optimization

Microplastics (MPs) and nano-plastics have emerged as critical environmental contaminants, with nano-plastics posing heightened risks due to their increased surface reactivity and ability to penetrate biological membranes. Consequently, there is a pressing need to develop efficient, rapid, and cost-effective technologies for their removal. This study introduces a facile magnetic separation approach utilizing iron oxide nanoparticles (IONPs), capitalizing on hydrophobic interactions between IONPs and plastic particles. Experimental results demonstrated that the removal efficiency for mixed micro- and nanoplastics reached up to 95 % within 20 min. The separation performance was enhanced for smaller plastic particles and larger IONP aggregates, with nano-plastics exhibiting higher removal rates compared to MPs. Mechanistic analysis confirmed that hydrophobic interactions serve as the dominant driving force for plastic adsorption onto IONPs. To evaluate real-world applicability, additional removal experiments were conducted using actual rainwater samples. In these tests, MPs smaller than 50 μm exhibited notably high removal efficiencies. Specifically, polypropylene and polyethylene particles achieved removal rates of up to 100 % and 79.2 %, respectively. These findings highlight the potential of IONPs as a stable, scalable, and environmentally benign material for the remediation of micro-nanoplastics, offering a viable alternative to conventional filtration or chemical degradation methods. • Iron oxide nanoparticles (IONPs) enable rapid magnetic removal of micro-nanoplastics. • Up to 95 % removal efficiency achieved within 20 min using IONP-based separation. • Smaller plastics and larger IONP aggregates enhance removal performance. • Hydrophobic interaction identified as the key mechanism in plastic adsorption. • Real rainwater tests show up to 100 % removal of polypropylene microplastics.