Pouring flecks of rust into water usually makes it dirtier. But researchers have developed special iron oxide nanoparticles they call “smart rust” that actually makes it cleaner. Smart rust can attract many substances, including oil, nano- and microplastics, as well as the herbicide glyphosate, depending on the particles’ coating. And because the nanoparticles are magnetic, they can easily be removed from water with a magnet along with the pollutants. Now, the team is reporting that they’ve tweaked the particles to trap estrogen hormones that are potentially harmful to aquatic life.

The researchers will present their results today at the fall meeting of the American Chemical Society (ACS).

“Our ‘smart rust’ is cheap, nontoxic and recyclable,” says Marcus Halik, Ph.D., the project’s principal investigator. “And we have demonstrated its use for all kinds of contaminants, showing the potential for this technique to improve water treatment dramatically.”

For many years, Halik’s research team has been investigating environmentally friendly ways to remove pollutants from water. The base materials they use are iron oxide nanoparticles in a superparamagnetic form, which means they are drawn to magnets, but not to each other, so the particles don’t clump.

To make them “smart,” the team developed a technique to attach phosphonic acid molecules onto the nanometer-sized spheres. “After we add a layer of the molecules to the iron oxide cores, they look like hairs sticking out of these particles’ surfaces,” says Halik, who is based at Friedrich-Alexander-Universi