'Smart rust' and magnets are used to remove harmful estrogen from the water.

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Access to safe, affordable and reliable drinking water  is an internationally recognized human right. However, anthropogenic molecular contaminants, such as hormones, are present in our groundwater. These contaminants can reach drinking water due to careless disposal and insufficient remediation, posing a significant risk to human health.

Natural and synthetic estrogens are one such group of hormones. The main sources of these contaminants include human and livestock waste. The amounts of estrogen in the environment are very low, so they are difficult to eliminate. However, even these levels have been shown to affect the metabolism and reproduction of some aquatic plants and animals.

Now, researchers at the University of Erlangen-Nuremberg in Germany have developed a new way to remove the hormone from water using what they call "smart oxide."

Smart rust takes the form of special iron oxide nanoparticles that can attract many substances, including oil, nanoplastics and microplastics, as well as the herbicide glyphosate, depending on the coating of the particles. Since nanoparticles are magnetic, they can be easily removed from water with a magnet along with contaminants.

Now, researchers have modified the particles to trap estrogen hormones that are potentially harmful to aquatic life. They coated the iron oxide nanoparticles with phosphonic acid molecules that stick out from the surface of the spheres like hairs. By changing what is attached to the other side of the phosphonic acids, researchers can tune the properties of the nanoparticle su  Special Data  rfaces to strongly adsorb different types of contaminants.



When removed from water simply by spinning a magnet, the smart oxide nanoparticles take the adsorbed contaminants with them. These contaminants can then be released from the particles so they can be safely removed and the smart rust can be reused.

Early versions of smart rust were able to trap crude oil from water collected from the Mediterranean Sea and glyphosate from pond water collected near the researchers' university. Even more impressive is that the team behind Smart Oxidation demonstrated that Smart Oxidation could remove nanoplastics and microplastics  from river and laboratory water samples.

Estrogen molecules have a bulky steroid body and parts with slight negative charges. To exploit both features, the researchers coated smart oxide particles with two types of molecules: one long and one positively charged.

When tested in water spiked with the most common estrogen, estradiol, the new form of smart oxide successfully removed the hormone from that water.

In the future, the team will test these particles in real-world water samples and determine the number of times they can be reused. Because each nanoparticle has a large surface area with many "pockets" that attract estradiol and trap it in place, the researchers say they should be able to remove estrogen from multiple water samples, thus reducing the cost per cleanup.