Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New pollutant cleanup technique puzzles, pleases chemists

10.09.2003


Scientists looking for ways to clean up a common, persistent type of organic pollutant have developed an approach that not only restores the power of a naturally occurring pollution buster but also boosts it to levels of effectiveness that they can’t currently explain.



"It’s safe to say that we don’t fully understand why this approach works so well, but we’ll take it and develop it and figure out the details as we go," Gerald Meyer, professor of chemistry in the Krieger School of Arts and Sciences at The Johns Hopkins University, said with a laugh.

The targets of the new technique, developed by Sherine Obare, a postdoctoral fellow in Meyer’s lab, are organohalides, a class of compounds used in pesticides, pharmaceuticals, and manufacturing. They pose health risks to humans and have been linked to environmental problems like ozone depletion and climate change.


Obare’s new approach combines an extremely thin film of titanium dioxide with a compound found in life known as hemin. After exposure to ultraviolet light, the hemin and titanium dioxide can break up organohalides at surprisingly high rates. Obare and Meyer will present results of tests of the new approach at 6 p.m. on Sept. 8 in the North Pavillion of the Javits Convention Center in New York at the 226th national meeting of the American Chemical Society.

Seventeen of the top 25 organic groundwater contaminants in urban areas are organohalides, according to a 1997 Environmental Protection Agency report. Organohalides are a class of organic compounds that include a halogen, a group of elements comprised of bromine, fluorine, iodine and chlorine. The compounds are very difficult to break down chemically. Some instances of organohalides in the environment today, for example, can be traced back to the dry cleaning industry of the 1920s and 1930s.

Meyer is director of the National Science Foundation-funded Collaborative Research Activities in Environmental Molecular Sciences (CRAEMS) Center at Johns Hopkins, which is dedicated to finding ways to deal with the environmental effects of organohalides. "These compounds play many important and beneficial roles in the chemical and pharmaceutical industries, so they’re not going away soon, and it’s important that we find ways to minimize their environmental effects," he said.

According to Meyer, scientists have known for decades that hemes, a naturally occurring group of compounds that contain iron atoms, can break up organohalides. The most well-known heme is hemoglobin, a compound in red blood cells that carries oxygen.

"There’s a lot of speculation that hemes in proteins are what cells use to defend themselves from organohalides," Meyer explained. "We can buy hemes – we don’t have to extract them from protein or anything – but when you remove them from their naturally occurring environment, you tend to oxidize them."

In their oxidized state, hemes are no longer useful for breaking down organohalides. Hemes can be re-activated using chemical or electrochemical techniques, but Obare wanted to try using a practical, easily available energy source to power the re-activation: sunlight. She decided to try to take advantage of titanium dioxide’s abilities as a photocatalyst, a substance that promotes chemical reactions in other nearby materials when exposed to light.

"I anchored hemin on porous thin films of nanocrystalline titanium dioxide, and when I exposed the system to light, the hemin was activated to a reduced state where it reacted rapidly with organohalides, producing much better results than I expected," Obare explained. "I’ve even been able to recycle and reactivate the thin films for further organohalide degradation."

Meyer noted that there’s still a lot of development work to be done, not the least of which is figuring out exactly how the chemistry of the new system works. But he speculated that scientists might someday be able to insert a similar system in drinking water – down a well, for example – and power the removal of organohalides with sunlight.


THE JOHNS HOPKINS UNIVERSITY
OFFICE OF NEWS AND INFORMATION
3003 N. Charles Street, Suite 100
Baltimore, Maryland 21218-3843
Phone: 410-516-7160; Fax: 410-516-5251
MEDIA CONTACT: Phil Sneiderman
410-516-7160
prs@jhu.edu

Phil Sneiderman | EurekAlert!
Further information:
http://www.jhu.edu/

More articles from Ecology, The Environment and Conservation:

nachricht Conservationists are sounding the alarm: parrots much more threatened than assumed
15.09.2017 | Justus-Liebig-Universität Gießen

nachricht A new indicator for marine ecosystem changes: the diatom/dinoflagellate index
21.08.2017 | Leibniz-Institut für Ostseeforschung Warnemünde

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: The pyrenoid is a carbon-fixing liquid droplet

Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.

A warming planet

Im Focus: Highly precise wiring in the Cerebral Cortex

Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.

The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

Im Focus: Ultrafast snapshots of relaxing electrons in solids

Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!

When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...

Im Focus: Quantum Sensors Decipher Magnetic Ordering in a New Semiconducting Material

For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.

Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

Rainbow colors reveal cell history: Uncovering β-cell heterogeneity

22.09.2017 | Life Sciences

Penn first in world to treat patient with new radiation technology

22.09.2017 | Medical Engineering

Calculating quietness

22.09.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>