Sunday, July 04, 2010

Can Iron Nano-Particles Save Shale Gas from Green Hysteria?

The shale gas bonanza has completely overturned mainstream peak oil / peak energy expectations. But recent sensationalist portrayals of shale gas environmental effects have revived hope among the true believers of the peak oil apocalypse. Knowing that no form of energy production is totally risk-free, and accepting that anti-fossil fuels crusaders have exaggerated harmful effects by a factor of at least 100, what can problem-solvers do in the real world to reduce risks to approximately zero?
Lehigh U. PDF

It looks as if nano-particles of Iron and Palladium may provide an answer. Researchers at Lehigh University in Pennsylvania have been studying groundwater remediation using iron nanoparticles for several years (PDF). This important research has led to at least 50 successful toxic waste site cleanups, and continues to advance the science of nano-remediation.
Researchers at Lehigh University have been utilising scanning transmission electron microscopy (STEM) and X-ray energy dispersive spectroscopy (XEDS) in order to extend and improve the applications of the powerful nanoparticles. They have captured, for the first time, the evolution in the nanostructure of the bimetallic particles as they remove contaminants in water. 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% 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 Lehigh researchers reported that the ability of the nanoparticles to remove toxins decreases as the particles ‘age' and undergo structural change with exposure to water. Their results, they wrote, suggest that the age and storage environment of the nanoparticles play a critical role in influencing their effectiveness as remediation agents. The nanoparticles, which were invented by co-author Zhang, average 50 nanometres in diameter (1 nm equals a billionth of a metre). Islands of palladium on the outer surface of the iron measure 2-5nm in diameter. The particles have removed pesticides, vinyl chloride, TCE and other contaminants in 10 states and in Europe and Asia. Treated sites include landfills, an electronics manufacturing plant, chemical plants and military facilities.
When injected into groundwater, the nanoparticles flow with the water and react with and detoxify contaminants. Their small size and greater proportional surface area give them more reactivity with toxins than larger quantities of the same catalyst. According to Harch Gill (president of Lehigh Nanotech LLC, a Bethlehem company which owns the commercial rights to the particles), this superior reactivity enables the particles to remediate a toxic site in less than a year; treating such a site with traditional pump-and-treat methods would take 10-20 years. According to the Association of University Technology Managers, which named Lehigh Nanotech one of the top 25 technology-collaboration stories in 2008, 'it takes only six ounces of the tiny nanomaterials, versus a ton of larger compounds, to make sweeping changes in cleaning up contaminated environments.' As a result, the nanoparticles are now one of the world's most widely used nanomaterials. _EnvironmentalExpert

For purposes of environmental remediation, few metals have been more thoroughly investigated than iron. In moist settings, including the ground, iron naturally corrodes to iron oxide—rust—by giving up electrons to water molecules. Environmental engineers have long sought to commandeer this trait by designing iron particles that donate electrons to toxic chemicals instead. As iron transforms into rust, many bad chemicals transform into benign products as well. For instance, the extra electrons strip all the chloride groups off TCE, converting the toxic compound into ethane.

Several years ago, Zhang developed a chemical technique for making nanoscale particles of iron. Since then, his team has tested, with approval from EPA, iron nanoparticles at several sites polluted with TCE and its toxic relatives perchloroethylene and dichloroethylene.

One of the first field tests took place in 2002 at an industrial site in Research Triangle Park, N.C. To enhance the particles' reactivity, the researchers coated the iron nanoparticles with a layer of palladium, a favorite metal for catalyzing the breakdown of chemicals. Then, Zhang's team mixed a total of 11.2 kg of the nanoparticles—enough to fill a coffee can—into about 6,000 liters of water and slowly injected the resulting slurry into contaminated groundwater running under the site. Within 6 weeks, the concentration of the target chemicals dropped by 99.9 percent in groundwater within 12 meters of the injection site.

Engineers with the consulting firm PARS Environmental in Robbinsville, N.J., have also seen promising outcomes from injecting iron nanoparticles at more than a dozen sites around the United States. "We haven't seen results [from other remediation strategies] as effective as those we've experienced with nanoiron," says Harch Gill, an engineer with the company.

In addition to being simple, the technology is relatively inexpensive, says Gill. He contrasts the price of injecting a slurry of nanoparticles with alternative strategies. The company recently calculated that the cost of using the pump-and-treat approach to clean up a small, polluted site owned by a New Jersey manufacturing firm would be about $4 million. An alternative, to intercept a plume of polluted groundwater with a permeable iron barrier, would cost about $2 million. The firm chose to experiment with iron nanoparticles, the cheapest option at $450,000.

Targeting the source
Although iron nanoparticles have already proved successful at cleaning up toxic chemicals that spread through groundwater, they don't go after the source, the polluted, saturated soil under the original dumping sites, says Chris Clausen, a chemist at the University of Central Florida in Orlando. Even after a plume is cleaned up, material from the source can continue leaching out of the soil, forming a new plume.

"Take a dry cleaning operation that dumped chlorinated solvents into the environment," he says. "If you had nothing more than 25 kg of solvents in that soil and your groundwater flow was relatively slow, you could have a contaminated plume that could last for hundreds of years."

Iron nanoparticles don't work very well for treating sources of chemicals because the particles are hydrophilic, or water attracting, says Clausen's colleague Cherie Geiger, also of the University of Central Florida. In contrast, the organic contaminants in a typical underground source are highly hydrophobic, or water repelling. Instead of penetrating the saturated soil, the iron particles float on top of the contaminated zone.

Clausen and Geiger have adapted iron nanoparticles to circumvent this problem. The researchers encapsulated clusters of particles in hydrophobic membranes of vegetable oil. "In order to get the particles to move to where the contamination is, we wanted to create something that would travel through the [contaminated] soil just like chlorinated solvents do," says Clausen.

To demonstrate the technology in the field, Clausen and Geiger teamed with researchers at NASA, EPA, and Geosyntec, an engineering firm based in Guelph, Ontario. Their maiden site was Launch Complex 34.

As reported in the March 1 Environmental Science & Technology, the group injected a half-ton of nanoparticles into a small area under one of the complex's engineering buildings. Within 90 days, soil tests showed that 85 percent of the contaminants—mainly TCE and dichloroethylene—had disappeared from the test site. Within that area, some sections of soil showed 100 percent removal while others showed very little, a disparity that Geiger blames on uneven distribution of the particles.

Environmental engineer Greg Lowry and chemist Krzysztof Matyjaszewski of Carnegie Mellon University in Pittsburgh are using another material to cover iron nanoparticles. The polymer coatings they're developing not only facilitate the nanoparticles' transport through contaminated soil but also enable the particles to selectively seek out chlorinated compounds. "If we can't get [the particles] to where they need to be, then they're no good to us," says Lowry.

The coatings consist of three polymer layers. The outside shell is hydrophilic, so that the particle can move easily through the groundwater. The next layer is hydrophobic, to have an affinity for chemicals such as TCE. The third and innermost layer anchors the entire polymer complex to the iron nanoparticle. _phschool

Interestingly, similar iron nanoparticles are also used to locate and kill malignant tumours in the human body. The nano-particles can be coated with sugars, peptides, or lipids for more effective penetration into tumours and tumour cells.

Iron is also combined with Palladium and Platinum in a new, nano-particle approach to fuel cells. This approach reduces the platinum requirement in the fuel cell appreciably, thus helping to reduce overall costs.

You are wondering how all of this can help with reducing groundwater pollution risks associated with shale gas drilling and fracking?

First, the level of risk needs to be established scientifically, without all the green mulch-for-brains hysteria which dominates the discussion in media, government, conspiracy theory, and political activist circles. Clearly the risk is much less than is being portrayed by sensationalist media.

Once the risk is quantified and clearly delineated, decisions can be made as to the timing and location of injection of nano-remediating particles for both prophylactic and rehabilitative purposes. The groundwater and soil can be remediated well in advance of any human contact.

In fact, nano-particles can be encapsulated in time-release polymers, and packed around the drill casings and groundwater barriers, as a just-in-case preventative measure.

Similarly, bio-remediative preventative measures can be utilised alongside the nano-particles, as an extra precaution.

But again, the first step is to move away from the typical hysteria, in order to scientifically quantify and qualify the actual risks involved.



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