Iron nanoparticles 1,000 times thinner than a human hair have demonstrated an unprecedented ability to clean contaminated groundwater since they were invented 10 years ago at Lehigh.
The palladium-coated particles have remediated more than 50 toxic waste sites in the U.S. and other countries in one-tenth the time, and at a much greater economy of scale, than traditional “pump and treat” methods.
Now, thanks to Lehigh’s unrivaled electron microscopy and spectroscopy facilities, researchers have gained unmatched insights that could improve the efficiency and extend the applications of the powerful nanoparticles.
The researchers used scanning transmission electron microscopy (STEM) and X-ray energy dispersive spectroscopy (XEDS) to capture, for the first time, the evolution in the nanostructure of the bimetallic particles as they remove contaminants in water.
The advanced imaging instruments at Lehigh captured amazing details of the reactions within nanoparticles. As they react with pollutants such as trichloroethene (TCE), a toxic industrial solvent, the nanoparticles display huge structural changes. The particle core hollows out, the iron diffuses outward, and the palladium, a catalyst that makes up 1 percent of particle mass, migrates from the outer surface to the interior surface of the iron.
Writing earlier this month in Environmental Science and Technology (ES&T), the premier journal in its field, the Lehigh researchers reported that the nanoparticles’ ability to remove toxins decreases as the particles “age” and undergo structural change with exposure to water.
Their results, they wrote, suggest that the nanoparticles’ age and storage environment play a critical role in influencing their effectiveness as remediation agents.