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Application of Surface-Modified Natural Magnetite as a Magnetic Carrier for Microplastic Removal from Water

Minerals 2025 1 citation ? Citation count from OpenAlex, updated daily. May differ slightly from the publisher's own count.
Palot Srichonphaisarn, Natatsawas Soonthornwiphat, Pongsiri Julapong, Thanakornkan Limlertchareonwanit, Thidarat Meekoch, Ilhwan Park, Mylah Villacorte-Tabelin, Onchanok Juntarasakul, Somsak Saisinchai, Carlito Baltazar Tabelin, Theerayut Phengsaart

Summary

Researchers modified natural magnetite — a common iron mineral — with a hydrophobic chemical coating so it would stick to plastic particles in water, then used magnets to pull everything out. When applied to six common plastic types including polyethylene and polystyrene, finely-ground treated magnetite removed over 90% of the microplastics. This low-cost, naturally-sourced approach could offer a scalable method for cleaning microplastics from water supplies.

This study investigates the modification and application of natural, micro-scale magnetite (Fe3O4)—an iron oxide mineral and one of the most abundant iron ores in the world—as a magnetic carrier for removing six common types of microplastics (MPs) from water: polypropylene (PP), polyethylene (PE), acrylonitrile butadiene styrene (ABS), polystyrene (PS), polyethylene terephthalate (PET), and polyvinyl chloride (PVC). Hexadecyltrimethoxysilane (HDTMS) was employed as a surfactant to modify the naturally hydrophilic magnetite, transforming it into a hydrophobic material. The characterization of magnetite treated with HDTMS for 0, 6, 12, 24, and 48 h was performed using a scanning electron microscope with energy-dispersive X-ray spectroscopy (SEM-EDS) and Fourier transform infrared spectroscopy (FT-IR). The results showed HDTMS sorption on the surface of natural magnetite, confirming successful surface modification. Carrier magnetic separation was then performed to remove PP, PE, ABS, PS, PET, and PVC using surface-modified, natural magnetite in two size fractions: +38–75 µm (fine-sized) and +75–150 µm (coarse-sized). Improved performance was observed with longer HDTMS treatment of magnetite, while greater than 90% MP removal was achieved using fine-sized, surface-modified, natural magnetite. These results suggest that surface modification enhanced the heterogenous interactions between magnetite and MPs via hydrophobic-hydrophobic interactions, leading to efficient MP removal via carrier magnetic separation.

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