Today, approximately 1,800,000 acres of land in the United States is used for landfill waste disposal. In terms of volume, the U.S alone generated over 290 million tons of solid waste in 2018, an amount equivalent to about 235,000 Olympic-size swimming pools, assuming an average solid waste density of a half ton per cubic meter.

Roughly 9% – about 26 million tons – of this waste is made up of iron and steel. These are resources with a stable market value used in various civil infrastructure projects. As a team of environmental engineers, we wanted to know whether we could use iron-rich waste to produce iron oxide nanoparticles – a useful tool for combating water pollution and building engineering hardware.

Iron oxide nanoparticles consist of iron and oxygen atoms and, because of their size, they exhibit unique physical and chemical properties. They are extremely small, typically at the nanoscale – one-billionth of a meter – in diameter.

The iron oxide nanoparticles we synthesized were a distinctive group called magnetite and maghemite. Initial studies have shown that nanoparticles in this group could help drugs get to the right part of the body, make batteries in electric vehicles more efficient and improve sensors for detecting toxic gas, as well as sound and motion.

Because these nanoparticles are made of iron, they’re both magnetic and stable. Their tiny size gives them a large surface area relative to their volume,........

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