Study finds advantages to iron nanoparticles for environmental clean up

"The use of nano-sized particles of iron for cleaning up contaminants in groundwater, soil and sediments is one of the hottest new technologies to emerge in recent years," said Paul Tratnyek, Ph.D., an environmental chemist and professor of environmental and biomolecular systems at OHSU's OGI School of Science & Engineering, and a lead author of the study. "However, there are a lot of unanswered questions about the appropriate and optimal implementation of the nano-iron technology, and even some questions about its safety. We set out to answer some of the remaining questions that researchers have about the basic chemical processes that determine the fate and effects of metal nanoparticles in the environment."

The particles studies by Tratnyek and colleagues range in size from 10 to 100 nanometers. One nanometer is one-billionth of a meter. By comparison, many biomolecules are of similar size.

For the study, Tratnyek and his doctoral students James T. Nurmi and Vaishnavi Sarathy compared two leading types of nanoparticle-sized iron that are being promoted by others for groundwater remediation. They measured how fast these particles degrade carbon tetrachloride and they determined the major projects of the reaction.

Carbon tetrachloride is a manufactured chemical used mainly in cleaning fluids and degreasing agents. In a few locations, spills of these liquids infiltrated the soil and created very large areas of contaminated groundwater and soil. Carbon tetrachloride is a toxic chemical that has been shown to cause cancer in animals.

The research at OHSU was funded in part by a grant from the Department of Energy to the Pacific Northwest National Laboratory (PNL) in Richland, Wash. The interdisciplinary team includes 10 researchers from PNL, three from OHSU and two from the University of Minnesota.

The PNL researchers, led by Donald R. Baer, Ph.D., technical group leader at PNL's William R. Wiley Environmental Molecular Sciences Laboratory, first synthesized and characterized the nanoparticles using a variety of advanced microscopy and spectroscopy techniques. Once the nanoparticles were syntheisized and characterized, Tratnyek and his students studied their reactivity using electrochemical techniques they developed to help them systematically measure the microscopic particles. University of Minnesota scientists also helped with microscopy and some reactivity studies.

"Our team's study results show how the breakdown of carbon tetrachloride is influenced by some very subtle and transient differences between the two types of nano-iron," said Tratnyek.

One of the nano-irons studied, a commercially available product of iron oxide with a magnetite shell high in sulfur, quickly and effectively degraded carbon tetrachloride to a mixture of relatively harmless products. "This was an exciting find because it may provide the basis for effective remediation of real field sites with groundwater that is contaminated with carbon tetrachloride," said Tratnyek.

"Furthermore, since it may be possible to emplace nano-sized iron deep into the subsurface by injecting it through deep wells, this approach may be suitable for remediation of very deep plumes of carbon tetrachloride contaminated groundwater, such as the one at the Hanford site in Richland, Washington."

The other nano-iron studied by the OHSU-PNL-University Of Minnesota team had a shell, or coating, high in oxidized boron. While the oxide-coated iron also rapidly degraded the carbon tetrachloride, the primary product was chloroform, a toxic and persistent environmental contaminant.

"The idea of using nanosized particles of iron for cleanup of groundwater contaminants has been around since 1997 and has gained a lot of momentum in the past four years," noted Tratnyek. "Nanotech iron has shown promise for environmental remediation, but previous work has not been particularly rigorous or thorough.

"Our report is the most comprehensive and rigorous characterization of the reaction to date between carbon tetrachloride and two leading types of nano-sized iron. We have taken a careful, second look at the chemistry of nano-iron for environmental cleanup in hopes of providing better science on which to found this promising technology."

Tratnyek's nano iron research may also someday have medical applications, for instance, in the diagnosis of brain tumors.

Source: Oregon Health & Science University

Mouse studies suggest daily dose of ginkgo may prevent brain cell damage after a stroke
Working with genetically engineered mice, researchers at Johns Hopkins have shown that daily doses of a standardized extract from the leaves of the ginkgo tree can prevent or reduce brain damage after an induced stroke.
Deep biosphere research points to new methods for recovering petroleum
Miles below us, deep within Earth's crust, life is astir. Organisms there are not the large creatures typically envisioned when thinking of life. Instead, thriving there are microbes, the smallest and oldest form of life on Earth. Although the biological diversity of these deep biosphere microorganisms may surpass that of the more familiar surface biosphere, much about them is still unknown, including the origin of the organic compounds they consume. Arizona State University researchers are using a novel approach that integrates physical organic chemistry with organic geochemistry and biogeochemistry to uncover the source of these organic compounds.
'Little bang' triggered solar system formation
For several decades, scientists have thought that the Solar System formed as a result of a shock wave from an exploding star—a supernova—that triggered the collapse of a dense, dusty gas cloud that contracted to form the Sun and the planets. But detailed models of this formation process have only worked under the simplifying assumption that the temperatures during the violent events remained constant. Now, astrophysicists at the Carnegie Institution's Department of Terrestrial Magnetism (DTM) have shown for the first time that a supernova could indeed have triggered the Solar System's formation under the more likely conditions of rapid heating and cooling. The results, published in the October 20, 2008, issue of the Astrophysical Journal, have resolved this long-standing debate.
NASA to Explore 'Secret Layer' of the Sun
Next April, for a grand total of 8 minutes, NASA astronomers are going to glimpse a secret layer of the sun.
Scientists peel away the mystery behind gold's catalytic prowess
Few materials have exercised as much of a hold on the human imagination, or on human history, as has gold. But for all of its popular uses – money, medals, jewelry and more – gold's potential as a catalyst lay hidden until the 1980s, when Masatake Haruta and Graham Hutchings independently discovered that gold, which had long been considered inactive, could be an extraordinarily good catalyst. Haruta demonstrated the low-temperature oxidation of CO and Hutchings the hydrochlorination of acetylene to vinyl chloride.
Scientists Test 'Artificial Upwelling' to Learn More About Complex Ocean Ecosystem Behavior
(PhysOrg.com) -- A team of scientists is studying the complex ocean upwelling process by mimicking nature – pumping cold, nutrient-rich water from deep within the Pacific Ocean and releasing it into surface waters near Hawaii that lack the nitrogen and phosphorous necessary to support high biological production.
Complex ocean behavior studied with 'artificial upwelling'
A team of scientists is studying the complex ocean upwelling process by mimicking nature – pumping cold, nutrient-rich water from deep within the Pacific Ocean and releasing it into surface waters near Hawaii that lack the nitrogen and phosphorous necessary to support high biological production.
Finder of key hominid fossil disputes 7-million-year dating
A fresh storm has broken out over an ancient fossil presented by its defenders as a forebear of humanity and dismissed by its critics as the remains of a vulgar chimp. Controversy has swirled around Toumai, the name given to the nearly-complete skull, ever since it was found in the Chadian desert in 2001.

Study finds advantages to iron nanoparticles for environmental clean up

Related stories:

News discussion: