'Nanorust' cleans arsenic from drinking water

Nov 09, 2006

The discovery of unexpected magnetic interactions between ultrasmall specks of rust is leading scientists at Rice University's Center for Biological and Environmental Nanotechnology (CBEN) to develop a revolutionary, low-cost technology for cleaning arsenic from drinking water. The technology holds promise for millions of people in India, Bangladesh and other developing countries where thousands of cases of arsenic poisoning each year are linked to poisoned wells.

The new technique is described in the Nov. 10 issue of Science magazine.

"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 center director and lead author 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. "Because we had just figured out how to make these particles in different sizes, 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."

The experiments involved suspending pure samples of uniform-sized iron oxide particles in water. A magnetic field was used to pull the particles to out of solution, leaving only the purified water. Colvin's team measured the tiny particles after they were removed from the water and ruled out the most obvious explanation: the particles were not clumping together after being tractored by the magnetic field.

Colvin, professor of chemistry, said the experimental evidence instead points to a magnetic interaction between the nanoparticles themselves.

Co-author 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."

Colvin said, "It's yet another example of the unique sorts of interactions we see at the nanoscale."

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.

Colvin's group has been collaborating with researchers from Rice Professor Mason Tomson's group in civil and environmental engineering to further develop the technology for arsenic remediation. Colvin said Tomson's preliminary calculations indicate the method could be practical for settings where traditional water treatment technologies are not possible. Because the starting materials for generating the nanorust are inexpensive, she said the cost of the materials could be quite low if manufacturing methods are scaled up. In addition, Colvin's graduate student, Cafer Yuvez, has been working for several months to refine a method that villagers in the developing world could use to prepare the iron oxide nanoparticles. The primary raw materials are rust and fatty acids, which can be obtained from olive oil or coconut oil, Colvin said.

Source: Rice University

Explore further: A quantum leap in nanoparticle efficiency

add to favorites email to friend print save as pdf

Related Stories

'Twisted rope' clue to dangerous solar storms

Oct 22, 2014

A "twisted rope" of magnetically-charged energy precedes solar storms that have the potential to damage satellites and electricity grids, French scientists said on Wednesday.

First light for MAVEN (w/ Video)

Oct 13, 2014

After 10-month voyage across more than 400 million miles of empty space, NASA's MAVEN spacecraft reached Mars on Sept. 21st 2014. Less than 8 hours later, the data started to flow.

Coronal mass ejections at Mars

Sep 24, 2014

Looking across the Mars landscape presents a bleak image: a barren, dry rocky view as far as the eye can see. But scientists think the vista might once have been quite different. It may have teemed with water ...

Recommended for you

A quantum leap in nanoparticle efficiency

12 hours ago

(Phys.org) —New research has unlocked the secrets of efficiency in nanomaterials, that is, materials with very tiny particles, which will improve the future development of chemical sensors used in chemical ...

Gold nanoparticle chains confine light to the nanoscale

Oct 29, 2014

A multidisciplinary team at the Centre d'Elaboration de Matériaux et d'Etudes Structurales (CEMES, CNRS), working in collaboration with physicists in Singapore and chemists in Bristol (UK), have shown that ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.