'Nanorust' Cleans Arsenic from Water

Photo: A nanoparticle that attracts arsenic molecules

"Arsenic contamination in drinking water is a global problem, and while there are ways to remove arsenic, they require extensive hardware and high-pressure pumps that run on electricity," said Rice University's Center for Biological and Environmental Nanotechnology (CBEN) director Vicki Colvin. "Our approach is simple and requires no electricity. While the nanoparticles used in the publication are expensive, we are working on new approaches to their production that use rust and olive oil, and require no more facilities than a kitchen with a gas cooktop."

CBEN's technology is based on a newly discovered magnetic interaction that takes place between particles of rust that are smaller than viruses. "Magnetic particles this small were thought to only interact with a strong magnetic field," Colvin said. "We decided to study just how big of magnetic field we needed to pull the particles out of suspension. We were surprised to find that we didn't need large electromagnets to move our nanoparticles, and that in some cases hand-held magnets could do the trick."

Colvin, professor of chemistry, said the experimental evidence with iron points to a magnetic interaction between the nanoparticles themselves. Doug Natelson explains, "As particle size is reduced the force on the particles does drop rapidly, and the old models were correct in predicting that very big magnetic fields would be needed to move these particles.”

"In this case, it turns out that the nanoparticles actually exert forces on each other," said Natelson, associate professor of physics and astronomy and in electrical and computer engineering. "So, once the hand-held magnets start gently pulling on a few nanoparticles and get things going, the nanoparticles effectively work together to pull themselves out of the water."

Because iron is well known for its ability to bind arsenic, Colvin's group repeated the experiments in arsenic-contaminated water and found that the particles would reduce the amount of arsenic in contaminated water to levels well below the EPA's threshold for U.S. drinking water.

COMPAMED.de; Source: Rice University