Efficient removal of microplastics from aqueous environment by magnetic MOFs: Performance & mechanism

Addressing the urgent need for microplastic (MPs) removal technologies that combine high efficiency with easy recovery, this study designed a magnetic adsorbent by integrating Fe₃O₄ with the highly stable and porous MIL-101(Cr). The resulting Fe₃O₄/MIL-101(Cr) composite maintained a high specific surface area (977 m²/g) while gaining magnetic separability, effectively overcoming the pore-blocking issue common in conventional composites. It exhibited high adsorption performance toward polystyrene (PS, 1 μm and 10 μm) and polymethyl methacrylate (PMMA, 1 μm and 10 μm), as evidenced by experimentally determined adsorption capacities of 892, 10,285, 794, and 6616 mg/g, respectively. The adsorbent retained its efficacy across a broad pH range (2-8), in the presence of competing ions and humic acid, and could be regenerated and reused for five cycles in river water. However, when under alkaline conditions, structural degradation occurred, significantly restricting its potential for application in such environments. Mechanistic studies revealed that the removal process was governed by a synergy of hydrogen bonding, π-π interactions, electrostatic attraction, and van der Waals forces. This work provides a straightforward strategy for synthesizing an effective magnetic adsorbent with strong potential for MPs remediation in natural aquatic environments.