From plastic that pollutes water to a tool that helps clean it up. Researchers at Madrid’s Institute of Materials Science (ICMM), part of the CSIC, have developed flower-shaped iron oxide nanoparticles capable of capturing nanoplastics, fragments a thousand times smaller than a microplastic, derived from PET, one of the most common materials used in bottles, packaging and polyester clothing. The study has been published in the Chemical Engineering Journal.
The secret lies in the shape. “Iron oxide is a magnetic material that allows many pollutants to be trapped at once. In addition, its nanoflower structure means that the particles have several cores that cooperate to enhance their magnetic properties,” explains Álvaro Gallo-Córdova, a researcher at ICMM-CSIC and one of the lead authors of the study, together with Rafael Herrera-Aquino and María del Puerto Morales.
From the microplastics in make-up to PET nanoplastics
It is not the first time these particles have proved their usefulness: in 2024 they already managed to extract and degrade microplastics measuring between 0.001 and 5 millimetres, originating from cosmetics. The step forward now is one of scale. Nanoplastics measure a billionth of a metre, a thousand times smaller than those microplastics.
“When they reach the end of their useful life, a large proportion of PET plastics ends up in the environment, where sunlight and physical wear act like sandpaper, grinding them down and turning them into nanoplastics, a kind of ultra-fine dust that contaminates our soils and water sources,” adds Gallo-Córdova.
Just one gram of these magnetic nanoflowers can capture up to 10,000 milligrams of nanoplastics, a figure the team itself describes as unprecedented until now.
The pollutant that helps clean up other pollutants
The work does not end with capture. Once the nanoplastic has been trapped, the team turns it into a magnetic material capable of extracting heavy metals or organic dyes from water, and can even take part in catalytic degradation processes.
“After capturing the nanoplastics thanks to our magnetic nanoparticles, we upcycle them into functional materials, turning a polluting waste into a new raw material within a circular economy approach,” the researcher sums up. In other words, they use the waste itself to remove other pollution, giving a second life to something that would normally end up in the bin.
The process uses barely any energy, because magnetic heating works locally, right on the surface of the nanoparticles, without the need to heat all the water.
And it stands up to repeated use: after five cycles, the nanoflowers retained 88% of their decontamination capacity and released into the water less than 0.82% of the iron they contained at the start, confirming that they are stable, reusable and safe. The ICMM-CSIC team is now looking towards advanced water treatment as the next field in which to apply this technology.